Abstrict By a load detector, a magnitude of a dynamic load, depending on
a downward-flow impact of a particulate material flowing through
a flow passage, is measured, and also a magnitude of a static load,
corresponding to a total amount of the particulate material flown
through a predetermined position for a predetermined time period,
is measured. A value of a dynamic load-type flow rate of the particulate
material, corresponding to a measured value of the dynamic load,
is calculated from the measured value of the dynamic load by a first
calculation formula, and also a value of an actual flow rate of
the particulate material is calculated from a measured value of
the static load during the predetermined time period by a second
calculation formula. A correction factor for bringing the dynamic
load-type flow rate value, depending on the difference of the particulate
materials, into agreement with the actual flow rate value is found.
The first calculation formula is corrected by the correction factor,
and a corrected dynamic load-type flow rate value is calculated
from the measured dynamic load value by the use of the corrected
first calculation formula. With this construction, there can be
obtained a flow meter in which the correction of the flow rate of
the flow meter or calibration of the flow meter can be effected
easily.
Claims What is claimed is:
1. A flow meter comprising:
a tubular member forming a flow passage for a particulate material;
an opening-closing valve member connected to the tubular member
so as to open and close a the downstream end of the tubular member,
the opening-closing valve member being adapted to receive a dynamic
load corresponding to a flow rate of the particulate material flowing
through the flow passage, when the opening-closing valve member
is in its open position to open the downstream end of the tubular
member; and
a load detector for detecting the load acting on the opening-closing
valve member;
wherein the flow meter further comprising:
an arithmetic and control unit including:
dynamic load flow rate calculation means for calculating a dynamic
load flow rate of the particulate material from a measured value
of the load detector when the opening-closing valve member allows
the flow of the particulate material, so that the particulate material
is flowing through the flow passage;
actual flow rate calculation means for calculating an actual flow
rate of the particulate material based on a measured value of the
load detector, representing the static load of the particulate material
accumulated within the tubular member for a predetermined time period
after the flow of the particulate material is interrupted by the
opening-closing valve member, and a value of the predetermined time
period; and
means for obtaining a correction factor for converting the dynamic
load flow rate value into the actual flow rate value.
2. A flow meter according to claim 1 in which the load detector
has a range for detecting the dynamic load of the particulate material,
and a range for detecting the static load of the particulate material.
3. A flow meter system comprising:
a plurality of flow meters as defined in claim 1
wherein the arithmetic and control unit of each of the plurality
of flow meters has a normal operating mode for obtaining the dynamic
load flow rate, and a correction mode for obtaining the correction
factor, and the arithmetic and control units are connected to a
centralized control unit which controls the arithmetic and control
units in a centralized manner, and when the particulate material
flowing through the flow passage in at least one of the flow meters
is changed to a different one, the centralized control unit supplies
to the at least one flow meter a control signal so as to change
the associated arithmetic and control unit from the normal operating
mode to the correction mode.
4. A flow meter comprising:
a load-receiving plate member disposed in an inclined or oblique
manner in a flow passage for a particulate material, the load-receiving
plate member being adapted to receive a dynamic load corresponding
to a flow rate of the particulate material flowing through the flow
passage;
a load detector for detecting a magnitude of the load acting on
the load-receiving plate member; and
a weir member movable between a block position where the weir member
blocks the flow of the particulate material at a position downstream
of the load-receiving plate member and an open position where the
weir member allows the flow of the particulate material; wherein
the flow meter further comprising:
an arithmetic and control unit including:
dynamic load flow rate calculation means for calculating a dynamic
load flow rate of the particulate material from a measured value
of the load detector when the weir member allows the flow of the
particulate material so that the particulate material is flowing
through the flow passage;
actual flow rate calculation means for calculating an actual flow
rate of the particulate material based on a measured value of the
load detector, representing the static load of the particulate material
accumulated on the load receiving plate member for a predetermined
time period after the weir member is set to the block position,
and a value of the predetermined time period; and
means for calculating a correction factor for converting the dynamic
load flow rate to the actual flow rate.
5. A flow meter according to claim 4 in which the load detector
has a range for detecting the dynamic load of the particulate material,
and a range for detecting the static load of the particulate material.
6. A flow meter system comprising:
a plurality of flow meters as defined in claim 4
wherein the arithmetic and control unit of each of the plurality
of flow meters has a normal operating mode for obtaining the dynamic
load flow rate, and a correction mode for obtaining the correction
factor, and the arithmetic and control units are connected to a
centralized control unit which controls the arithmetic and control
units in a centralized manner, and when the particulate material
flowing through the flow passage in at least one of the flow meters
is changed to a difference one, the centralized control unit supplies
to the at least one flow meter a control signal so as to change
the associated arithmetic and control unit from the normal operating
mode to the correction mode.
7. A method of calibrating a flow meter comprising the steps of:
measuring, by a load detector, a magnitude of a dynamic load, depending
on a downward-flow impact of a particulate material flowing through
a flow passage, and a magnitude of the static load corresponding
to a total amount of the particulate material having been accumulated
at a block position in a predetermined time period after the flow
of the particulate material is blocked;
calculating a value of a dynamic load flow rate of the particulate
material, corresponding to a measured value of the dynamic load,
from the measured value of the dynamic load by a first calculation
formula, and also calculating a value of an actual flow rate of
the particulate material from a measured value of the static load
in the predetermined time period by a second calculation formula;
obtaining a correction factor for bringing the dynamic load flow
rate value, depending on difference of the particulate materials,
into agreement with the actual flow rate value; and
converting the first calculation formula by the correction factor,
and calculating a corrected dynamic load flow rate value from the
measured dynamic load value by the converted first calculation formula.
8. A method according to claim 7 comprising the steps of:
forming the flow passage in a tubular member;
connecting an opening-closing valve member, which opens and closes
the downstream end of the tubular member, to the tubular member;
detecting, by the load detector, the dynamic load represented by
the downward-flow impact applied to the opening-closing valve member
from the particulate material flowing through the flow passage in
an open condition of the opening-closing valve member, the load
detector being coupled to the tubular member connected to the opening-closing
member; and
detecting, by the load detector, the static load represented by
the load corresponding to the total amount of particulate material
deposited within the tubular member during the predetermined time
period when the opening-closing valve member is set at its closing
position.
9. A method according to claim 7 comprising the steps of:
providing a load-receiving plate member in an inclined manner in
the flow passage;
providing a weir or block member at the downstream portion of the
load-receiving plate member, the weir member being movable between
a block position where the weir member blocks the flow of the particulate
material at a position downstream of the load-receiving plate member
and an open position where the weir member allows the flow of the
particulate material;
measuring, by the load detector, the static load representing the
weight of the particulate material having been deposited on the
load-receiving plate member in the predetermined time period after
the weir member is set to the block position; and
setting the weir member to the open position, and measuring, by
the load detector, the dynamic load during the time when the particulate
material is flowing through the flow passage.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a flow meter for measuring the flow rate
of a particulate material flowing continuously through a flow passage,
and also relates to a method of calibrating the flow meter.
The term "particulate material" means herein grains or
particles which can flow substantially continuously, and examples
thereof include not only grains of wheat and rice and grain powder
such as wheat powder or flour, but also particles which vary in
characteristics (such as a specific gravity), depending on external
conditions such as an environmental condition and a production condition,
and particles different in average size of the particles, and the
size of the particles or grains is not limited.
2.Description of the Related Art
In a plant for processing cereal such as rice and wheat, the amount
of processing of the grains is measured in terms of a flow rate.
Herein, "the flow rate of the particulate material" means
the weight of the particulate material flowing per unit period of
time. In order to continuously measure the flow rate of a continuously-flowing
particulate material, there is used an impact load detection-type
or impact-type flow meter in which the particulate material is received
by an impact-receiving detection plate (impact-receiving plate-like
member), and its impact load on the plate is measured, and this
impact load is converted into the flow rate.
In this impact flow meter, however, a downward-flow impact, applied
by the particulate material to the impact-receiving detection plate,
varies depending on the nature or characteristics of the particulate
material, such as its bulk specific gravity, water content and temperature.
When the flow rate is measured only for the raw grains of the same
kind in the same condition, this variation does not cause substantial
problem. Actually, however, it is seldom that the environment for
raw materials is in good order, and in most cases the flow rate
of various kinds of grains must be measured. And besides, even grains
of the same kind often varies in water content, depending on various
conditions the grains have been subjected to. Therefore, in a processing
plant or facility where various kinds of grains were processed,
much time was required for calibrating the flow meter or correcting
the indication of the flow rate in the flow meter. The term "correcting
the flow rate" and "correction of flow rate" in or
of the flow meter mean herein "correcting the indication of
the flow rate" and "correction of the indication of the
flow rate" in or of the flow meter, i.e. "calibrating
the flow meter" or "calibration of the flow meter".
In the correction (of the indication) of the flow rate in the impact
flow meter, usually, a certain amount of grains are extracted or
sampled from a flow of the grains (to be measured) for a predetermined
period of time, and an actual flow rate is calculated from the weight
of the grains thus extracted for the predetermined time period,
and the correction of the flow rate or calibration is effected according
to this actual flow rate value. Most of these correction or calibration
operations are carried out manually. If trying to accurately effect
the correction of the flow rate or calibration for each of many
flow meters installed in one processing facility, much time (for
example, one to two days) is often required for this correction
or calibration operation. If trying to keep the labor, required
for the correction or calibration operation, to a minimum, the correction
of the flow rate or the calibration is omitted when the raw grains
are similar to the grains of the preceding lot, and as a result
the accuracy of the value of the flow rate measured by the flow
meter is lowered.
There are known the type of flow meters which comprise a load-receiving
plate-like member provided in an inclined manner in a flow passage
of a particulate material--the term "particulate material",
here in the Description of the Related Art, is not limited to the
material with properties or nature easily changed or varied in specific
gravity etc. depending on environmental conditions, but means broadly
any particulate materials of a medium or a small particle size,
and powders--for receiving a dynamic load corresponding to the flow
rate of the particulate material flowing through the flow passage,
a load detector for detecting a magnitude of the load received by
the load-receiving plate-like member, and an arithmetic and control
unit having a dynamic load-type flow rate calculation means for
calculating a "dynamic load-type flow rate" (defined later
in this specification) from a measured value of the load detector
obtained during a period when the particulate material is flowing
through the flow passage. Such flow meters are disclosed, for example,
in Japanese Patent Unexamined Publication No. 1-105120 (A) (convention
priority of U. S. patent application Ser. No. 07/049666 filed May
13 1987 being claimed), Japanese Patent Unexamined Publication
No. 63-195524 (A), U.S. Pat. No. 5065632 Japanese Patent Unexamined
Publication Nos. 8-14962 (A) and 57-189013 (A), and WO-A-93-22633.
Among the above prior art references, Japanese Patent Unexamined
Publication No. 1-105120 (A), U.S. Pat. No. 5065632 and Japanese
Patent Unexamined Publication No. 8-14962 (A) disclose a typical
impact detection-type flow meter in which the load-receiving plate-like
member receives a downward-flow impact of the particulate material
falling a substantial distance.
On the other hand, among the above prior art references, Japanese
Patent Unexamined Publication No. 63-195524 (A) and Japanese Patent
Laid-Open Specification No. 6-511558 (A) corresponding to WO-A-93-22633
disclose a structure in which the load-receiving plate-like member
receives a relatively small downward-flow impact of the particulate
material falling a relatively small distance from an upstream-side
slanting surface, and also the load-receiving plate-like member
supports the particulate material so that the particulate material
can flow down over an upper surface of this plate-like member, and
the total load (hereinafter referred to as "dynamic load"),
which the plate-like member receives, is the sum of the two (that
is, the downward-flow impact and the load of the particulate material
flowing down over the upper surface of the plate-like member).
In this specification, the term "dynamic load" means
the total load including a load applied by the flowing particulate
material to the load detector, and it may include, as a part thereof,
a static load due to the weight of particulate material being flown
with proviso that the static load of the particulate material, deposited
or accumulated in a non-flowing condition on the plate-like member,
is not included in the dynamic load.
Japanese Patent Unexamined Publication No. 1-105120 corresponding
to U.S. patent application Ser. No. 07/049666 discloses an impact
flow meter in which a downward-flow impact is detected as the dynamic
load, and its output span is adjusted or corrected.
More specifically, Japanese Patent Unexamined Publication No. 1-105120
discloses an impact flow meter 120 as shown in FIG. 15. The impact
flow meter 120 comprises a cylindrical housing 123 having a downstream
end opening 121 at its lower end and a side opening in which a particulate
material inflow tube 122 is inserted, an impact-receiving plate
124 for receiving a downward-flow impact of a particulate material
flowing through the inflow tube 122 and a strain gauge unit (serving
as a load detector) 125 which is suspendedly mounted at its upper
end on an inner peripheral surface of the housing 123 and supports
the impact-receiving plate 124 at its lower end in a suspended manner.
The strain gauge unit 125 detects a horizontal component force of
the downward-flow impact, received by the impact-receiving plate
124 as an impact load. The impact flow meter 120 further comprises
a calibration weight 127 which is connected to an outer surface
of the impact-receiving plate 124 through a cable 126 if necessary.
This calibration weight 127 is used for adjusting the span of an
amplifier constituting the load detector.
However, in this case, also, in order to determine whether or not
the value of the actual flow rate, obtained by converting the detected
load of the impact-receiving plate 124 is correct, it is necessary
"to check the calibration by passing the flow material at a
known flow rate through the flow meter".
SUMMARY OF THE INVENTION
With the above problems in view, it is an object of this invention
to provide a flow meter in which a flow rate (indication) can be
easily corrected or calibrated, and also to provide a method of
or calibrating the flow meter or correcting (an indication of) the
flow rate measured by the flow meter.
Another object of the invention is to provide a flow meter in which
less time and labor are required for the correction thereof or for
the correction (of the indication) of the flow rate thereby, and
also to provide a method of or calibrating the flow meter or correcting
(the indication of) the flow rate measured by the flow meter.
A further object of the invention is to provide a flow meter capable
of accurately measuring a flow rate in accordance with a change
of raw particulate materials, and also to provide a method of calibrating
the flow meter or correcting (the indication of) the flow rate measured
by this flow meter.
A still further object of the invention is to provide a flow meter
in which each time before measurement of a flow rate of a particulate
material of different nature or characteristics is started, calibration
thereof or correction (of the indication) of the flow rate thereby
is substantially or automatically carried out, and also to provide
a method of correcting the flow meter or calibrating (the indication
of) the flow rate measured by the flow meter.
To achieve at least a part of the above objects, according to a
first aspect of the invention, there is provided a flow meter comprising:
a tubular member forming a flow passage for a particulate material;
an opening-closing valve member connected to the tubular member
so as to open and close a downstream end opening of the tubular
member, the opening-closing valve member being adapted to receive
a dynamic load corresponding to a flow rate of the particulate material,
flowing through the flow passage, when the opening-closing valve
member is in its open position to open the downstream end opening
of the tubular member; and
a load detector for detecting a load acting on the opening-closing
valve member; wherein the flow meter further comprising:
an arithmetic and control unit including:
dynamic load-type flow rate calculation means for finding or calculating
a dynamic load-type flow rate of the particulate material from a
measured value of the load detector when the opening-closing valve
member allows the flow of the particulate material, so that the
particulate material is flowing through the flow passage;
actual flow rate calculation means for finding or calculating an
actual flow rate of the particulate material based on a measured
value of the load detector, representing a static load of the particulate
material deposited or accumulated within the tubular member for
a predetermined time period after the flow of the particulate material
is interrupted or blocked by the opening-closing valve member, and
a value of the predetermined time period; and
means for finding or obtaining or calculating a correction factor
for correcting the dynamic loadtype flow rate value into the actual
flow rate value.
To achieve at least a part of the above objects, according to a
second aspect of the invention, there is provided a flow meter comprising:
a load-receiving plate-like member provided or disposed in an inclined
or oblique manner in a flow passage for a particulate material,
the load-receiving plate-like member being adapted to receive a
dynamic load corresponding to a flow rate of the particulate material
flowing through the flow passage;
a load detector for detecting a magnitude of a load acting on the
load-receiving plate-like member; and
a weir or stop or block member movable between a block position
where the weir member blocks the flow of the particulate material
at a position downstream of the load-receiving plate-like member
and an open position where the weir member allows the flow of the
particulate material; wherein the flow meter further comprising:
an arithmetic and control unit including:
dynamic load-type flow rate calculation means for finding or calculating
a dynamic load-type flow rate of the particulate material from a
measured value of the load detector when the weir member allows
the flow of the particulate material so that the particulate material
is flowing through the flow passage;
actual flow rate calculation means for finding or calculating an
actual flow rate of the particulate material based on a measured
value of the load detector, representing a static load of the particulate
material deposited or accumulated on the load-receiving plate-like
member for a predetermined time period after the weir member is
set to the block position, and a value of the predetermined time
period; and
means for finding or calculating a correction factor for correcting
the dynamic load-type flow rate to the actual flow rate.
In either of the above two flow meters, preferably, the load detector
has a range for detecting the dynamic load of the particulate material,
and a range for detecting the static load or weight of the particulate
material.
In a flow meter system comprising a plurality of flow meters of
either or both of the above two types, preferably, the arithmetic
and control unit of each of the plurality of flow meters has a normal
operating mode for finding or obtaining the dynamic load-type flow
rate, and a correction or calibration mode for finding or obtaining
the correction factor, and the arithmetic and control units are
connected to a centralized control unit which controls the arithmetic
and control units in a centralized manner, and when raw material
of the particulate material flowing through the flow passage in
at least one of the flow meters is changed to a different one (for
example, the lot of particulate material is changed), the centralized
control unit feeds or supplies to the at least one flow meter a
control signal so as to change the associated arithmetic and control
unit from the normal operating mode to the correction mode.
To achieve at least a part of the above object, according to a
third aspect of the invention, there is provided a method of calibrating
a flow meter comprising the steps of:
measuring, by a load detector, a magnitude of a dynamic load, depending
on a downward-flow impact of a particulate material flowing through
a flow passage, and a magnitude of a static load corresponding to
a total amount of the particulate material having been deposited
or accumulated at a block position in a predetermined time period
after the flow of the particulate material is blocked;
finding or calculating a value of a dynamic load-type flow rate
of the particulate material, corresponding to a measured value of
the dynamic load, from the measured value of the dynamic load by
a first calculation formula, and also finding or calculating a value
of an actual flow rate of the particulate material from a measured
value of the static load in the pre-determined time period by a
second calculation formula;
finding or obtaining a correction factor for bringing the dynamic
load-type flow rate value, depending on difference of the particulate
materials, into agreement with the actual flow rate value; and
correcting the first calculation formula by the correction factor,
and finding or calculating a corrected dynamic load-type flow rate
value from the measured dynamic load value by the corrected first
calculation formula.
Preferably, the above flow meter calibration method comprises the
steps of:
forming the flow passage in a tubular member;
connecting an opening-closing valve member, which opens and closes
a downstream end opening of the tubular member, to the tubular member;
detecting, by the load detector, the dynamic load represented by
the downward-flow impact applied to the opening-closing valve member
from the particulate material flowing through the flow passage in
an open condition of the opening-closing valve member, the load
detector being coupled to the tubular member connected to the opening-closing
member; and
detecting, by the load detector, the static load represented by
the load corresponding to the total amount of the particulate material
deposited within the tubular member during the predetermined time
period when the opening-closing valve member is set at its closing
or blocking position.
Alternatively, the above flow meter correction method comprises
the steps of:
providing a load-receiving plate-like member in an inclined or
oblique manner in the flow passage;
providing a weir or block member at a downstream portion of the
load-receiving plate-like member, the weir member being movable
between a block position where the weir member blocks the flow of
the particulate material at a position downstream of the load-receiving
plate-like member and an open position where the weir member allows
the flow of the particulate material;
measuring, by the load detector, the static load representing the
weight of the particulate material having been deposited on the
load-receiving plate-like member in the predetermined time period
after the weir member is set to the block position; and
setting the weir member to the open position, and measuring, by
the load detector, the dynamic load during the time when the particulate
material is flowing through the flow passage.
Since, in the flow meter calibration method of the invention, by
the load detector, a magnitude of the dynamic load, depending on
the downward-flow impact of the particulate material flowing through
the flow passage, is measured, and also a magnitude of the static
load, corresponding to the total amount of the particulate material
having been flown through a predetermined position during a predetermined
time period, is measured, and since a value of the dynamic load-type
flow rate of the particulate material, corresponding to a measured
value of the dynamic load, is calculated from the measured value
of the dynamic load by the first calculation formula, and also a
value of an actual flow rate of the particulate material is calculated
from a measured value of the static load during the predetermined
time period by the second calculation formula, it is possible to
obtain, with respect to the actually-flowing particulate material,
both of the dynamic load-type flow rate value, based on the measured
value of the dynamic load depending on the downward-flow impact,
and the actual flow rate value, and therefore it can be easily judged,
whether or not the dynamic load-type flow rate value is accurate,
by comparing it with the actual flow rate value.
In the flow meter-calibration method of the invention, since the
correction factor for bringing the dynamic load-type flow rate value,
depending on the difference of the particulate materials, into agreement
with the actual flow rate value is calculated, and the first calculation
formula is corrected by the correction factor, and the corrected
dynamic load-type flow rate value is calculated from the measured
dynamic load value by the corrected first calculation formula, following
advantageous effects can be obtained; if the dynamic load-type flow
rate value deviates from the actual flow rate value, the first calculation
formula is corrected so as to give a dynamic load-type flow rate-indicating
value in agreement with the actual flow rate value, and by doing
so, the calibration of the flow meter can be effected easily. Therefore,
for example, when the lot of particulate material whose flow rate
is to be measured is changed, so that a new particulate material,
having a different nature, begins to flow through the flow passage,
the correction of the flow rate of the flow meter or calibration
thereof can be automatically effected in a short time. As a result,
it becomes substantially unnecessary the correcting operation, which
has been conventionally effected manually beforehand by the operator
for each flow meter.
As a matter of course, it is not necessary to measure or detect
the actual flow rate constantly, but this is effected only when
the correction of the flow rate or calibration becomes necessary.
For example, this is effected twice a day, or when the raw material
of the particulate material is changed, i.e. the particulate material
of different origin is flown. Therefore, although the flow of the
particulate material through the flow passage is interrupted when
measuring the actual flow rate by a kind of batch process for the
purpose of the correction, the time period of this interruption
is short, and only temporary, and therefore the overall processing
will not be affected significantly.
Since the first type of flow meter of the invention comprises the
tubular member forming the flow passage for the particulate material,
the opening closing valve member, which is connected to the tubular
member so as to open and close the downstream end opening of the
tubular member, and receives a dynamic load corresponding to the
flow rate of the particulate material, flowing through the flow
passage, when the opening-closing valve member is in its open position
to open the downstream end opening of the tubular member, and the
load detector for detecting the total load acting on the tubular
member, it is possible to detect, by one load detector the dynamic
load and the static load or weight (of the particulate material
deposited within the tubular member for a predetermined time period
after the flow of the particulate material is interrupted by the
opening-closing valve member), in the same flow meter structure
having the opening-closing valve member at the tubular member. Therefore,
this flow meter can be simple in structure or construction although
it has the calibration function of correcting the flow rate value.
In the flow meter of the invention, a dynamic load-type flow rate
value, calculated by the dynamic load-type flow rate calculation
means from a value of the load detector measured when the opening-closing
valve member allows the flow of the particulate material so that
the particulate material is flowing through the flow passage, is
brought into agreement with the actual flow rate value which is
obtained by the actual flow rate calculation means based on a measured
value of the load detector, representing the static load or weight,
and a value of the predetermined time period. Namely, if there is
any difference between the two values, a correction factor for correcting
the dynamic load-type flow rate value in such a manner as to eliminate
the difference is obtained by the correction means, and the thus
obtained correction factor is used for correcting the calculation
of the dynamic load-type flow rate.
Here, if a term or a factor, to be corrected, of the calculation
formula of the dynamic load-type flow rate calculation means are
beforehand determined, the correction can be effected easily. Therefore,
when the actual flow rate or the static load or weight corresponding
to the actual flow rate is measured, the correction processing is
effected promptly. This correction can be processed by the arithmetic
and control unit without requiring any substantial manual labor
or operation, and therefore can be completed in a very short time.
It will be readily appreciated that, in the second type of flow
meter of the present invention, the calibration thereof or the correction
of the flow rate can be made similarly to that described above with
respect to the first type of flow meter.
In the flow meter of the invention, preferably, the load detector
has the range for detecting the dynamic load of the particulate
material, and the range for detecting the static load of the particulate
material. Therefore, in accordance with a magnitude of the load,
the load can be always measured with the full range, and hence the
accurate measurement can be effected.
For example, in the first type of flow meter, it has been experimentally
confirmed that the ratio between the dynamic load (composed mainly
of the impact load) and the batch load is about 1:100 and that
it is sufficient that the full range of the indication value of
the load detector is set to about 1:100 in view of a resolution
of the load cell etc. serving as the load detector. For example,
when the flow rate was 5 tons/hour (where 1 ton=1000 kilograms),
a dynamic load was about 150 g, whereas a static load or weight
of rice grains as the particulate material, deposited or accumulated
for 10 seconds (This will be hereinafter referred to as "batch
load for ten seconds"), was about 14 kg. Therefore, by switching
the range, the loads different in the ratio of 1:100 can be detected
with the same precision (in terms of the number of effective digits
or figures). It will be readily appreciated that by using the load
detector such as a load cell with the full range, the accurate measurement
can be achieved. In this example, actually, the dynamic load was
measured with a load detection range whose full range was 200 g,
and the batch load was measured with a load detection range whose
full range was 20 kg.
In the second type of flow meter of the invention, the magnitude
of the impact load is relatively small. In this case, however, the
ratio of the range may be, for example, about 1:100 if an additional
static load is considered.
In the flow meter system comprising a plurality of flow meters
of the invention, preferably, the arithmetic and control unit of
each of the plurality of flow meters has the normal operating mode
for obtaining or finding the dynamic load-type flow rate, and the
correction mode for obtaining or finding the correction factor,
and the arithmetic and control units are connected to the centralized
control unit which controls the arithmetic and control units in
a centralized manner, and when the particulate material to be flown
through the flow passage in at least one of the flow meters is changed
to a different one, the centralized control unit supplies to the
at least one flow meter a control signal so as to change the associated
arithmetic and control unit from the normal operating mode to the
correction mode. Therefore, there is no need to effect the correction
operation by manually operating the corresponding flow meter each
time the particulate material to be flown is changed to a different
one. And besides, since the correction can be effected easily in
a short time, the correction can be effected at least each time
the particulate material to be flown is changed to a different one,
and therefore the flow rate can always be measured correctly by
all the flow meters in the system. Even when the particulate material
to be flown is not changed to a different one, the flow rate (indication)
correction of the flow meter or calibration thereof may be periodically
effected in view of a change of environmental conditions and others.
The foregoing and other objects, features and advantages of the
invention will be made clearer hereafter from the description of
preferred embodiments of the invention referring to attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partly-broken, front-elevational view of a flow meter,
according to one preferred embodiment of the present invention,
in a state for measuring a dynamic load-type flow rate;
FIG. 2 is a partly-broken, front-elevational view of a portion
of the flow meter, shown in FIG. 1 in a state for measuring an
actual flow rate;
FIG. 3 is a block diagram of a flow rate measurement and correction
control system of the flow meter of FIG. 1;
FIG. 4 is a block diagram of a flow rate measurement system having
a plurality of flow meters of FIG. 1;
FIG. 5 is a graph generally showing the relation between a dynamic
load-type flow rate value and an actual flow rate value in the flow
meter of FIG. 1;
FIG. 6 is a time chart showing a variation, of a dynamic load and
a static weight load, with time in the flow meter of FIG. 1;
FIG. 7 is a flow chart or sheet showing a processing procedure
of measuring the flow rate by the measurement of the dynamic load
in the flow meter of FIG. 1 as well as a processing procedure of
correcting the flow rate;
FIG. 8 is a side view of a flow meter of a second preferred embodiment
according to the invention;
FIG. 9 is a front-elevational view of the flow meter of FIG. 8
as seen in a direction IX of FIG. 8;
FIG. 10 is a view of a modification of the flow meter of FIG. 8
showing a condition in which a particulate material is flowing through
the flow meter;
FIG. 11 is an explanatory view showing a condition in which the
flow of the particulate material is interrupted in the flow meter
of FIG. 10;
FIG. 12 is a partly-broken, plan view showing a detailed structure
of particulate material supply portion of the flow meter of FIG.
10;
FIG. 13 is a vertical cross-sectional view showing a detailed structure
of the particulate material supply portion of the flow meter of
FIG. 10;
FIG. 14 is a block diagram of a control system for controlling
the flow rate in the flow meter of FIG. 10; and
FIG. 15 an explanatory view of an example of the conventional flow
meters.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A flow meter according to a first preferred embodiment of the invention
will now be described with reference to FIGS. 1 to 7.
In FIG. 1 showing a main portion of the flow meter 30 a vertically-extending,
tubular member 3 of a desired length is supported, to be located
below a lower end or downstream end of a stationary conduit 2 forming
a flow passage 1 for a particulate material G, by a stationary frame
21 of the flow meter 30 through load cells 4 and 5 serving as a
load detector. A funnel-like reception portion 3a is formed at an
upper end or upstream end of the tubular member 3.
A movable valve device 10 in the form of a shut-off valve serving
as an opening-closing valve is provided at a downstream end or discharge-side
end 6 of the tubular member 3 and is operable to open and close
a downstream end opening 7 at the downstream end of the tubular
member 3. The movable valve device 10 includes an opening-closing
valve member 9 pivotally movable about a pivot shaft 11 in directions
D and E between a closing position B (see FIG. 2) where the valve
member 9 closes the downstream end opening 7 to shut off the flow
passage 1 and an open position A (see FIG. 1) where the valve member
9 opens the downstream end opening 7 to open the flow passage 1.
During a period of time when the opening-closing valve member 9
is held in the closing position B, the particulate material G is
continuously deposited or accumulated on the opening closing valve
member 9 within the tubular member 3. On the other hand, the opening-closing
valve member 9 when held in the open position A, is inclined, that
is, disposed obliquely generally across the flow passage 1 as shown
in FIG. 1 and therefore when the opening closing valve member 9
is in the open position A, a downward-flow impact load of the particulate
material G is continuously or constantly applied to the opening-closing
valve member 9. In so far as the opening-closing valve member 9
can be located in the open position A and the closing position B,
the manner of movement of this valve member 9 intermediate the two
positions A and B, as well as the manner of supporting this valve
member 9 may be different from the above manner. Further, in so
far as the downward-flow impact load, received by the opening-closing
valve member 9 in its open position A, can be detected by the load
cells 4 and 5 as the load detector, the tubular member 3 may be
inclined instead of extending in the vertical direction, and also
may be curved at its lower end portion instead of being straight.
In so far as the load detector (load cells 4 and 5) can detect the
total load applied to the tubular member 3 in the vertical direction,
their detection principle and structure may be any suitable ones.
The load detector may be constituted by the single load cell instead
of plural load cells if appropriate arrangement of the associated
members is taken for detecting the load thereon.
The opening-closing valve member 9 is driven by drive means 12
such as a pneumatic cylinder, to be moved or displaced in the directions
D and E between the open position A and the closing position B.
A stopper or spacer 13 supports the opening-closing valve member
9 at its open position A, and when the opening-closing valve member
9 is opened through a desired angle F to the open position A, the
stopper or spacer 13 supports the valve member 9 so that the valve
member 9 can be maintained in the open position A against the downward-flow
impact load of the particulate material G. The stopper or spacer
13 may be provided with a cushioning or shock-absorbing material.
A solenoid valve 14 controls to drive the pneumatic cylinder 12
by means of compressed or pressurized air. The solenoid valve 14
constituting a part of the movable valve device 10 is connected
to a drive control device 16 which delivers, in response to an output
signal of an arithmetic and control unit 15 such as a microprocessor,
a signal for controlling to drive the pneumatic cylinder 12 as
shown in FIG. 3. The load cells 4 and 5 serving as the load detector
are connected to the arithmetic and control unit 15. Where the load
detector is of such a type as the load cell for delivering an analog
signal, the load cells 4 and 5 as the load detector are connected
to the arithmetic and control unit 15 such as the microprocessor
through an A/D converter 17. An output range or span of each of
the load cells are adjusted appropriately by a so called "span
adjustment". A memory or storage device 18 is connected to
the arithmetic and control unit 15. The memory device or unit 18
stores therein programs, including calculation formulas necessary
for converting the magnitudes of the loads, represented by output
signal of the load detector (load cells 4 and 5), into flow rate
values, and constant values necessary for the calculation formulae,
a correction formula and a correction value etc. Detected data of
the load detector 4 and 5 and results of calculation in the arithmetic
and control unit 15 are also stored in a time series manner in the
memory device 18. The memory device 18 includes a RAM and a ROM.
Reference numeral 19 denotes a display unit capable of displaying
the calculation results in terms of a calculation degree.
Basically, the flow meter 30 according to the first preferred embodiment
of the invention has the above construction.
In an actual job site (processing plant) where the flow rate of
a particulate material, such as rice grains and wheat grains, is
continuously measured, a plurality of flow meters are often provided
or installed in one system. One example of such a system, forming
a modification of the first embodiment, is shown in FIG. 4. In the
system 31 of FIG. 4 for example, four arithmetic and control units
15a to 15d are connected to a centralized or central control unit
20 such as a microcomputer or a minicomputer. The data of flow meters
30a to 30d been given to the central control unit 20 the degree
of opening of an opening-closing valve member (not shown in FIG.
4 but has a function substantially the same as that of a flow rate
control gate mechanism described later in an embodiment of FIGS.
10 to 14), provided at an upstream portion of each of the flow meters
30a to 30d, is adjusted by the central control unit 20 thereby
controlling all the flow rates in the system 20.
Data of various kinds of raw particulate materials (that is, particulate
materials G to be treated or processed) upon arrival at the processing
plant are stored in the central control unit 20 and also information
of what kind of raw particulate material G is flowing through a
respective one of the flow meters is held by the central control
unit 20 and this information is used when processing each raw particulate
material G.
When the central control unit 20 supplies or delivers to any of
the arithmetic and control units 15a to 15d of the flow meters 30a
to 30d a signal indicating that the raw particulate material G is
changed to a new one, the arithmetic and control unit 15 of the
designated flow meter 30 confirms that the new particulate material
G has flown thereinto, and then effects a correction of the flow
rate or calibration of the flow meter in accordance with the invention.
Alternatively, the central control unit 20 may deliver a flow rate
correction or calibration operation initiation instruction signal
to the relevant arithmetic and control unit 15 so that this arithmetic
and control unit 15 can effect a correction of the flow rate or
a calibration in accordance with the invention. In the latter case,
regardless of whether or not the kind of particulate material G,
flowing through the flow passage 1 is changed, the correction of
the flow rate in the flow meter or calibration thereof is effected
at predetermined timings (for example, at predetermined time intervals).
Next, a load conversion operation, and principles of calculation
of a dynamic load-type flow rate and an actual flow rate, which
are necessary for the correction of the flow rate in the flow meter
30 shown in FIGS. 1 to 3 or the calibration thereof, will be described.
When the opening-closing valve member 9 of the movable valve device
10 is in its open position A as shown in FIG. 1 a downward-flow
impact load of the falling (or downwardly-flowing) particulate material
G acts on the opening-closing valve member 9. This downward-flow
impact load is detected by the load cells 4 and 5 in the form of
a sum of loads applied to the load cells 4 and 5 and this downward-flow
impact load, that is, the dynamic load, is converted into a flow
rate, by a predetermined calculation formula.
The mode or condition or state shown in FIG. 1 is a normal operating
mode or condition or state (that is, a normal mode or condition
or state of use) in which the flow rate of the particulate material
G is measured while the particulate material G is flowing or passing
through the flow meter 30 and this condition is a particulate material-flowing/flow
rate-measuring mode. Analog signals, delivered from the load cells
4 and 5 in accordance with the downward-flow impact load corresponding
to the flow rate of the particulate material G, are converted by
the A/D converter 17 (FIG. 3), and are supplied as an impact load
signal EA serving as the dynamic load signal to the arithmetic and
control unit 15 (FIG. 3) and is converted therein into a flow rate
value QA according to the impact load (dynamic load), by means of
the following calculation formula 1:
where a represents a conversion factor for converting the impact
load (dynamic load) into the flow rate.
In FIG. 6 in which the abscissa axis represents time t, and the
ordinate axis represents the dynamic load W acting on the load cells
4 and 5 regions indicated by "RA" are regions where the
dynamic load consists essentially of the impact load, and a region
indicated by "RB" is a region where the dynamic load consists
essentially of the static load or weight. When the flow rate of
the particulate material G is kept substantially constant, the dynamic
load signal W from the load cells 4 and 5 hardly varies with time.
Therefore, for example, if the output of the flow meter 30 is adjusted
such that a predetermined bias is beforehand applied to the output
W of the load cells 4 and 5 so that the output W (=EA) of the load
cells 4 and 5 can become zero in a condition where the opening-closing
valve member 9 is in the open position A, and where the particulate
material G is not flowing (that is, in a condition in which only
the constantly acting static loads or weights of the tubular member
3 the opening-closing valve member 9 the pneumatic cylinder 12
etc., act on the load cells 4 and 5), the output W coincides with
the impact load EA, and the flow rate value QA can be obtained merely
by multiplying the impact load signal EA (corresponding to the output
W representing the impact load (dynamic load)) by the conversion
factor a.
When the opening-closing valve member 9 of the movable valve device
10 is set to the closing position B as shown in FIG. 2 the falling
(or downwardly-flowing) particulate material G is deposited or accumulated
on the opening-closing valve member 9 within the tubular member
3. The total weight of the thus deposited particulate material G
is sampled and detected at desired time intervals, and a change
of the weight per unit time is found or calculated to obtain the
actual flow rate. Namely, the condition or state shown in FIG. 2
is a condition or state in which the flow of the particulate material
G is temporarily blocked or intercepted within the flow meter 30
so as to effect the correction of the flow rate or calibration,
while keeping the flow rate of the particulate material G constant
at the upstream side of the flow meter 30. Thus, this mode or condition
or state is a flow rate correction or flow meter calibration mode.
As in the normal mode, the analog signals from the load cells 4
and 5 are converted by the A/D converter 17 (FIG. 3) into a static
load or weight signal EB, representing the total weight of the deposited
particulate material G, which signal is sent to the arithmetic and
control unit 15 (FIG. 3) where the signal EB is converted into a
weight Y by means of the following calculation formula 2:
where b represents a conversion factor for converting the output
in the static load or weight measurement range of the load cells
4 and 5 into the actual weight.
The actual flow rate QB is obtained from weight values Y1 and Y2
measured respectively at consecutive sampling times X1 and X2 by
means of the following calculation formula 3:
During the time period indicated by the region RB in FIG. 6 the
weight W (expressed by Y in terms of a scale) increases as the amount
of deposition or accumulation of the falling particulate material
G increases. Therefore, based on the information of the weight Y1
at time X1 and the information of the weight Y2 at time X2 the
actual flow rate QB is obtained by the calculation formula 3.
Before describing details of the correction of the flow rate in
the flow meter 30 or the calibration thereof, basic principles of
the correcting or calibrating operation will first be described
briefly.
Since the flow of the same particulate material G through the same
flow passage 1 is measured, the impact load flow rate value (dynamic
load-type flow rate value) QA should essentially or inherently coincide
with the actual flow rate value QB obtained from the static load
or weight. The actual flow rate value QB is obtained by the measurement
according to the definition of the weight flow rate or mass flow
rate, and therefore it is thought that in so far as the calibration
of each associated apparatus itself is effected properly, the actual
flow rate value QB is an accurate value independent of the material
to be measured. On the other hand, the dynamic load-type flow rate
value QA can vary depending on various factors, of the material
to be measured, such as bulk specific gravity and resiliency; however,
so far as the same material to be measured is concerned, the dynamic
load-type flow rate value QA increases as the actual flow rate increases.
Namely, the dynamic load-type flow rate value QA has a positive
correlation with to the actual flow rate QB, and also is virtually
proportional to the actual flow rate QB as shown in FIG. 5. Therefore,
the relation, indicated by the following equation or calculation
formula 4 can be established:
where k represents a correction factor.
A dynamic load-type or impact load-type flow rate value QAc after
the correction or calibration can be obtained from the following
calculation formula 5 derived from the calculation formulae 1 and
4:
where k represents the flow rate correction factor, a represents
the conversion factor, and EA represents the impact load signal,
as described above.
Therefore, if it is desired to provide a correction processing
loop to be continuously executed according to a computer program,
a is replaced by "a*ku".
Now, the flow rate correction or flow meter calibration operation
in the flow meter 30 will be described in detail with reference
to FIGS. 6 and 7.
Normally, the flow meter 30 is operating in the mode to continuously
detect the impact load as the dynamic load. Therefore, the impact
load signal EA is constantly inputted as shown in Step S1 and the
dynamic load-type flow rate QA is constantly calculated or found
by the calculation formula 1 as shown in Step S2.
In Step S3 it is always checked by the arithmetic and control
unit 15 of the flow meter 30 whether or not the raw particulate
material G is changed and also whether or not there is an instruction
that the correction calculation should be effected, and as long
as these events or situations do not occur, the program or processing
returns to Step 1 i.e. Step Sl and Step S2 are repeated. Where
the plurality of flow meters 30a, 30b,. . . are connected to the
central control unit 20 as described above with reference to FIG.
4 information indicating the occurrence of the above-mentioned
events or situations can be given from the central control unit
20 to corresponding one or ones of the flow meters 30a -30d. If
the signal representative of the change of the raw particulate material
G, or the flow rate correction calculation initiation instruction
signal is produced, the program proceeds to a flow rate correction
or calibration processing routine of infra Step S4.
When the program processing proceeds to the correction processing
routine, the detection of the dynamic load or impact load is not
effected, and therefore during a period of time (corresponding to
a time period T3 in FIG. 6) before the program exits from the correction
processing routine, that is, when the correction processing is being
effected, there is used the impact load signal EA obtained immediately
before the program enters the correction processing routine, whereby
even when the plurality of flow meters are monitored and controlled
by the central control unit 20 the central control unit 20 can
continue to control all of the flow rates in the system.
In a case where the flow meter 30 is so constructed that the ratio
of the impact load to the batch load is substantially 1:100 as described
above, and for example, if the impact load is about 150 g, i.e.
150 gram-force, with the flow rate of 5 tons/hour, then the batch
load amounts to about 14 kg for ten seconds. When trying to process
the signal of such a wide range by one amplifier, there is a possibility
that the precision of measurement of the impact load is lowered.
Therefore, in Step S5 the measurement range is switched from a
gram unit for the impact load to a kilogram unit for the batch load.
Namely, the measurement range is switched from the measurement range
for the region RA (FIG. 6) to the measurement range for the region
RB.
In Step S6 the opening-closing valve member 9 of the movable valve
member 10 is switched from the open position A to the closing position
B, and simultaneously with this switching operation, time T is reset
to 0 and time (time period) T after setting the opening-closing
valve member 9 to the closing position B is measured.
When the opening-closing valve member 9 is set to the closing position
B, the total load of the falling particulate material G acts on
the opening-closing valve member 9 and the output of the load detector
4 and 5 are not stable at first due to vibrations etc. In an example
in Step S7 it is estimated that stability time period or stabilizing
time period T1 required for extinction or elimination of the disturbance
such as the vibrations is 3 seconds.
In Step S8 based on a first point of time X1 for weight measurement,
after the elapse of time T1 and the output EB1 of the load cells
4 and 5 at the time point X1 the time point X1 and a weight value
Y1 at this time point X1 are obtained.
With the elapse of time T, the amount of deposited or accumulated
the particulate material G (having flown through the flow passage
1) on the opening-closing valve member 9 within the tubular member
3 increases, so that the load acting on the load cells 4 and 5 increases.
If the flow rate is constant, the flow rate can be found by measuring
the weight of the deposited or accumulated particulate material
G. In Step S9 it is judged whether or not the elapse of time T
is 8 seconds.
In Step S10 a time point X2 after time T elapses 8 seconds (X2=8
if X1 is set to 0 in Step S8), as well as a weight value Y2 derived
from the output EB2 of the load cells 4 and 5 at this time point
X2 is obtained.
In Step S11 the actual flow rate QB is derived or calculated from
the calculation formula 3. If desired, a zero or reference point
for the output EB1 EB2 of the load cells 4 and 5 from which the
actual flow rate QB is derived, may not be adjusted because only
the difference of therebetween is effective as apparent from the
calculation formula 3.
In Step S12 the flow rate correction factor k is derived or calculated
from one form of the calculation formula 5 and the dynamic load-type
flow rate QAc after the correction or calibration is derived or
calculated from another form of the calculation formula 5 by using
this flow rate correction factor k.
If the same flow rate correction is utilized until the next flow
rate correction operation is effected, the conversion factor a is
replaced by a*k in the program processing operation as shown in
Step S13.
When the flow rate correction calculation is completed, the opening-closing
valve member 9 of the movable valve device 10 is returned to the
open position A as shown in Step S14. As a result, the particulate
material G, having been deposited or accumulated on the opening-closing
valve member 9 within the tubular member 3 drops, so that the flow
meter 30 is returned to the condition in which the opening-closing
valve member 9 receives the normal impact load. In this case, also,
the output of the load cells 4 and 5 becomes unstable at first because
of an abrupt load change, and therefore although not shown in the
flow chart of FIG. 7 preferably stability time or stabilizing time
T2 as shown in FIG. 6 is preserved.
After the output of the load cells 4 and 5 becomes stable, the
load detection range is returned from the measurement region RB,
corresponding to the kg-unit range, to the measurement region RA
corresponding to the gram-unit range, and the operation control
is returned to the normal mode or routine (that is, to Step S1)
in which the impact load (dynamic load) is detected.
In the above arithmetic and control unit 15 such as a microprocessor,
the processing Step S2 of the program therein corresponds to a function
of dynamic load flow rate calculation means of the flow meter 30
and the processing Steps S5 to Sll of the program correspond as
a whole to a function of actual flow rate calculation means of the
flow meter 30 and the processing Step S12 of the program corresponds
to a function of means for calculating the correction factor of
the flow meter 30. These are quantitative calculations of physical
quantities, and therefore in so far as mathematically- or algebraically-equivalent
quantities can be derived, their specific calculation procedures
may be changed as desired.
In the flow meter 30 of the above construction and the system 31
including the plurality of flow meters 30 when correction of the
dynamic load-type flow rate value QA in the impact load detection-type
flow meter, i.e. flow meter 30 in the normal mode, to make it equal
to the actual flow rate OB determined from the measured weight can
be effected automatically without requiring any manual labor or
operation. And besides, when it becomes necessary to correct the
flow rate indication or calibrate the flow meter as a result of
change of the raw particulate material G, this correction or calibration
can be effected substantially promptly. Therefore, the more precise
flow rate measurement can be made constantly as compared with the
conventional impact load detection-type flow meters. Moreover, in
the flow meter 30 the movable valve device 10 having the opening-closing
valve member 9 the load detector constituted by the load cell 4
and 5 and the arithmetic and control unit 15 are combined together
as if an impact load detection-type flow meter and an actual flow
rate meter are formed on the common tubular member 3 and the construction
of the flow meter is relatively simple.
In addition, as the measurement ranges for the load cells 4 and
5 as a load detector, there are provided two ranges, that is, the
larger range for the detection of the static load or weight and
the smaller range for the detection of the impact load, and therefore
the detection of the load can be always effected over substantially
the full range or span of the load cells 4 and 5 so that the accurate
load output can be obtained.
Furthermore, the plurality of arithmetic and control units 15a,
15b, . . ., of the plurality of flow meters 30a, 30b, . . . installed
in a processing plant, are connected to the central control unit
20 and the flow rate of each of the flow meters is automatically
corrected in response to the signal from the central control unit
20. Therefore, in accordance with the change of the raw particulate
material G or with a predetermined condition (for example, at predetermined
time intervals), the correction operation initiation instruction
signal etc. can be delivered to a respective one of the flow meters
30a, 30b, . . ., and therefore there is no need to control the flow
meters 30a, 30b, . . . individually of one another by a manual labor
or operation, and the continuous detection of the flow rate by the
detection of the dynamic load can be constantly made accurately.
Next, a flow meter according to a second preferred embodiment of
the invention will be described with reference to FIGS. 8 and 9.
In FIGS. 8 and 9 the flow meter 60 comprises a particulate material
supply portion 41 a particulate material flow rate detection portion
42 a particulate material flow rate calculation and correction
control portion 43 and a particulate material discharge portion
44. A flow passage 45 for a particulate material G is formed in
the flow meter 60 to extend from the supply portion 41 through the
particulate material detection portion 42 down to the particulate
material discharge portion 44.
A first inclined flow passage portion 46 for guiding the particulate
material G supplied from a hopper etc. (not shown) is provided in
the particulate material supply portion 41 and also a second inclined
flow passage portion 48 is formed in the supply portion 41. The
second inclined flow passage portion 48 extending in a direction
substantially perpendicular to the first inclined flow passage portion
46 is connected to the first inclined flow passage portion 46 by
a gently-curved flow passage portion 47. An inclined guide plate
or flow-down plate 49 is mounted in a stationary manner on a flow
meter frame 59 to form the second inclined flow passage portion
48.
The flow rate detection portion 42 comprises a load-receiving plate-like
member 50 which is provided in an inclined manner in the flow passage
45 for the particulate material G so as to receive a dynamic load
corresponding to the flow rate of the particulate material G passing
through the flow passage 45 a load cell 51 serving as a load detector
for detecting a magnitude of the load received by or applied to
the load-receiving plate-like member 50 and a weir member 52 movable
between a block position H where the weir member 52 intercepts or
blocks the flow of the particulate material G at a downstream region
of the load-receiving plate-like member 50 and an open position
J where the weir member 52 allows the particulate material G to
flow or pass.
The load-receiving plate-like member 50 is supported by the load
cell 51 in such a manner that the plate-like member 50 is spaced
by a predetermined distance or height L vertically downwardly from
the inclined guide plate 49 of the supply portion 41 in generally
or substantially parallel relation thereto. Therefore, the particulate
material G, flowing over the inclined guide plate 49 along the second
inclined flow passage portion 48 of the flow passage 45 falls a
distance not smaller than L from a downstream end 49a of the guide
plate 49 to the plate-like member 50 so that the plate-like member
50 is subjected to a drop impact corresponding to the flow rate
of the particulate material G.
When the weir member 52 is disposed in the open position J indicated
by phantom lines in FIG. 8 the particulate material G, having dropped
on the load-receiving plate-like member 50 flows down over the
plate-like member 50 along a flow passage 53 defined by the plate-like
member 50 and is discharged to the exterior through the discharge
portion 44 at a bottom portion of the frame 59 of the flow meter
60 constituted by a discharge tube and a bellows 58 for preventing
the particulate material G from dissipation. At this time, similarly
to the load cells 4 and 5 of the flow meter 30 of the first embodiment
as described above, the load cell 51 serving as the load detector
receives not only an impact load EAf1 proportional to the flow rate
of the particulate material G dropping on the plate-like member
50 but also a substantially static load EAf2 corresponding to the
amount of the particulate material G present on the plate-like member
50 upon flowing down thereover. Therefore, when the particulate
material G is flowing continuously, the load cell 51 receives a
total load EAf of a magnitude equal to (EAf1+EAf2). The magnitude
of the dynamic impact load EAf1 depends on various factors such
as the weight flow rate (mass flow rate) of the particulate material
G, the height L and the angle M of inclination of the load-receiving
plate-like member 50. On the other hand, the magnitude of the static
load EAf2 depends not only on an inclined angle T of the load-receiving
plate-like member 50 but also on the weight of the particulate material
G present on the plate-like member 50 upon flowing thereover. This
weight of the particulate material G, in turn, depends on a length
of the plate-like member 50 and a thickness of a layer of the particulate
material G on the plate-like member 50 (in other words, a stacked
height of the particulate material G at the flow passage portion
48) etc. The ratio between magnitudes of these two kinds of loads
EAf1 and EAf2 is determined appropriately, and may be determined
in view of the technique disclosed in Japanese Patent Unexamined
Publication No. 63-195524 described above as the prior art and incorporated
herein by reference thereto, if necessary. If a suitable zero point
adjustment is made for the dynamic load EAf, this dynamic load EAf
can be treated in the similar manner to the dynamic load EA (impact
load) in the flow meter 30 according to the first embodiment. The
inclination angle T of the plate-like member 50 is about 45 degrees
in the example illustrated in FIG. 8 while this angle T may be
selected freely as desired so long as the particulate material G
can flow down thereover or therealong, i.e. this angle T may be
greater or smaller than 45 degrees, and may be greater or smaller
than the angle of inclination of the flow-down plate 49.
On the other hand, when the weir member 52 is disposed in the closing
position H indicated by solid lines in FIG. 8 the particulate material
G, having fallen on the load-receiving plate-like member 50 is
blocked or intercepted by the weir member 52 and is therefore deposited
or accumulated on the plate-like member 52. A change of a load EBf,
acting on the load cell 51 in accordance with this deposition or
accumulation, is substantially similar to a change of the load EB
acting on the load cells 4 and 5 in the closing position of the
opening-closing valve member 9 of the flow meter 30 according to
the first embodiment.
Reference numeral 54 denotes guide members, such as rollers, for
guiding the vertical (upward and downward) movement or displacement
of the weir member 52 between the open position J and the closing
position H. Similarly to the opening-closing valve member 9 of the
flow meter 30 according to the first embodiment, the weir member
52 is connected to drive means 55 (which comprises a solenoid valve
and a pneumatic cylinder) driven under the control of the arithmetic
and control unit 43 and the weir member 52 is moved upward or downward
when a piston rod of the pneumatic cylinder of the drive means 55
is contracted or extended. In the flow meter 60 according to this
embodiment, so long as the opening and closing of the flow passage
is concerned, the weir member 52 replaces the opening-closing valve
member 9 of the flow meter 30 according to the first embodiment.
The pneumatic cylinder drive means 55 may be replaced by any other
appropriate drive means such as an electric motor which drives and
rotates at least one of the guide rollers 54.
The arithmetic and control portion 43 constituted by a microprocessor
etc., serving as the arithmetic and control unit is designed substantially
similarly to the arithmetic and control unit 15 of the flow meter
30 according to the first embodiment, and utilizing the relations
and characteristics shown in FIGS. 5 and 6 a dynamic load-type
flow rate QA, an actual flow rate QB and a flow rate correction
factor k are calculated or obtained from the dynamic load EAf (corresponding
to EA) and the static load or weight EBf (corresponding to EB) in
accordance with a procedure similar to that shown in FIG. 7. Therefore,
this flow meter 60 can be also configured as in FIG. 3 and can
support a system including a plurality of flow meters as in FIG.
4. In FIGS. 8 and 9 reference numeral 56 denotes a display portion
corresponding to the display unit 19 of the flow meter 30.
The flow meter 60 may be provided with a supply control portion
for adjusting or controlling the flow rate of the particulate material
G to be supplied or fed to the flow rate detection portion 42.
Next, with reference to FIGS. 10 to 13 description will be made
of a flow meter 90 in which a particulate material flow rate-adjusting
gate is further provided in the particulate material supply portion
of the flow meter shown in FIGS. 8 and 9.
The flow meter 90 schematically shown in FIGS. 10 and 11 includes
a flow rate-adjusting gate mechanism 63 in a particulate material
supply portion 61 corresponding to the particulate material supply
portion 41 of the flow meter 60 and this gate mechanism 63 controls
the flow or supply of a particulate material G into a flow passage
portion 62 corresponding to the flow passage portion 48. The flow
meter 90 is substantially identical in construction or structure
to the flow meter 60 except that the particulate material supply
portion 61 with the flow rate-adjusting gate mechanism 63 replaces
the particulate material supply portion 41 and that an arithmetic
and control unit 43 has a control processing function of controlling
the supply of the particulate material G by the flow rate-adjusting
gate mechanism 63. Therefore, only these differences will be described
below in detail.
As schematically shown in FIGS. 10 and 11 the flow rate-adjusting
gate mechanism 63 comprises an electric motor 64 and a pivotally
movable gate member 67 which is pivotally moved or displaced in
directions M and N by the electric motor 64 to change a degree S
of opening (or flow area) of a flow passage portion 66 so as to
adjust the flow rate of the particulate material G from a particulate
material reservoir 65 to the flow passage portion 62.
More specifically, the flow rate-adjusting gate mechanism 63 has,
for example, a construction or structure shown in FIGS. 12 and 13.
In FIGS. 12 and 13 a frame 68 of the flow rate-adjusting gate
mechanism 63 is fixedly mounted on the frame 59 of the flow meter
90 and has a lower end 70 open to the flow passage portion 62.
A particulate material-supplying, tubular portion 71 having a square
cross-section, decreasing in cross-sectional area progressively
toward a lower end thereof, is fixedly secured to the frame 68.
An outlet opening 73 is formed at the lower end of the particulate
material-supplying, square tubular portion 71 and has an arcuate
lower edge 72 forming a part of a circle around a center P (FIG.
13). The gate member 67 having a generally sector-shape as viewed
from the side thereof and U-shaped bridge-like configuration, is
mounted to be outside of the lower edge or end portion 72 and an
outer side edge portion 75 of the square tubular portion 71 so that
the gate member 67 can be pivotally moved in the directions M and
N about a shaft 74 with an axis passing through the center point
(or center line) P. The gate member 67 has a gate plate portion
77 at a generally partially cylindrical portion 76 having an arcuate
shape as seen in FIG. 13. Radially extending portions 78 and 79
at upper and lower edges, of the gate member 67 are opened. Link
members 80 and 81 are adapted to displace the gate member 67 pivotally
in the directions M and N around the shaft 74 in response to forward
and backward rotation of an output shat of the motor 64. When the
gate member 67 is fully displaced in the direction N to be disposed
to a position Q shown by solid lines in FIG. 13 the opening 73
is completely closed by the gate plate portion 77 of the gate member
67 so that the particulate material G will not flow out of the
supply portion 61. On the other hand, when the gate member 67 is
fully displaced in the direction M to be disposed in a position
R shown by phantom lines in FIG. 13 the opening 73 is completely
opened, so that the flow rate of the particulate material G through
the opening 73 becomes maximal. A magnitude S of the opening or
aperture 73 which is not closed or blocked by the gate member 67
can be changed, according to the position, of the gate member 67
between the positions Q and P to be defined in response to forward
(normal)/backward (reverse) rotation of the motor 64 to thereby
change or adjust the flow rate of the particulate material G from
the not-closed or blocked part of the opening 73.
The flow rate adjustment gate mechanism 63 may be of any shape
other than that shown in FIGS. 10 to 13 so long as the flow rate
of the particulate material G from the supply portion can be adjusted
or controlled.
It will be apparent that the flow meter 90 with the supply gate
can be operated in the similar manner to the flow meter 60 shown
in FIGS. 8 and 9 in a case where the degree S of opening at the
opening or aperture 73 to be defined by the gate member 67 of the
gate mechanism is set to a fixed level or magnitude.
In this flow meter 90 the following control may be employed. As
shown in FIG. 14 a flow rate QA in accordance with a dynamic load,
i.e., dynamic load-type flow rate QA, detected by a load cell 51
serving as the load detector, is corrected in accordance with the
procedure shown in FIG. 7 and then the opening degree S at the
opening 73 of the flow rate-adjusting gate mechanism 63 in the open
condition of this flow rate-adjusting gate mechanism 63 is controlled,
so that the corrected dynamic load-type flow rate QAc can coincide
with a predetermined target flow rate value Qt. by a flow rate-setting
control portion 85 additionally provided in the arithmetic and control
unit 43 in association with a corrected flow rate calculation portion
84.
The flow rate-adjusting gate mechanism 63 may be also provided
in the flow meter 30 of the first embodiment shown in FIGS. 1 and
2 as having described above with reference to FIG. 4 so that the
flow rate (opening degree S) can be controlled as described with
reference to FIG. 14. |