Abstrict An impact type flow meter for a particulate material such as cereal
comprises a supply device for dropping the particulate material,
an inclined load detection plate for receiving the dropped particulate
material, and a load detector for detecting a load of the particulate
material exerted to the load detection plate. A bottom surface of
the supply device is inclined at substantially the same degree with
the load detection plate, and has at its lower end with a supply
opening for dropping the particulate material onto the load detection
plate. The bottom surface serves to guide the particulate material
to the load detection plate at substantially the same inclination
therewith. Thus, the flow meter has a buffer device for softening
a dropping impact of the particulate material integrally incorporated
in the particulate material supply device, and accordingly, the
height is low and the whole apparatus is compact. The particulate
material impinges upon the bottom surface of the supply device,
diverges widthwise thereof and reaches the supply opening. Accordingly,
the direction and position of dropping of the particulate material
onto the load detection plate are fixed. Further, the flow-down
speed of the particulate material is lessened, unevenness of the
speed is averaged or uniformed, thereby the flow meter is high in
measurement accuracy.
Claims What is claimed is:
1. An impact type flow meter for a particulate material, comprising:
a supply device having an inclined flat bottom surface and a supply
opening disposed proximate a lower end of said bottom surface as
viewed in a direction of inclination for dropping the particulate
material therethrough, said supply device being capable of changing
a flow rate of the particulate material flowing through said supply
opening, said supply device being arranged at a height relative
to a base of said meter and having a substantially trough-like shape
for defining a particulate material passage, the supply opening
being defined by a plate member slidable in parallel with said bottom
surface to close the supply opening, said plate member being substantially
planar with said bottom surface when the supply opening is closed;
an inclined load detection plate disposed to receive a load of
the particulate material dropping from said supply device, said
bottom surface, supply opening, and load detection plate being at
substantially the same inclination so that the particulate material
flows at an inclination substantially the same as the inclination
of said load detection plate to reduce a flowing-down speed of the
particulate material and reduce a dropping impact of the particulate
material onto said load detection plate;
a load detector detecting the load of the particulate material
exerted to said load detection plate and converting the same into
an electrical signal; and
computing means for computing a flow rate of the particulate material
based on the electrical signal from said load detector.
2. A flow meter according to claim 1 wherein said supply opening
of said supply device is rectangular and is positioned close to
said load detection plate to reduce a dropping impact of the particulate
material.
3. A flow meter according to claim 2 wherein a distance between
said supply opening of said supply device and said load detection
plate is about 40 mm.
4. A flow meter according to claim 1 further comprising an opening
and closing device for said supply opening of said supply device,
said opening and closing device including a plate member slidable
in parallel with said bottom surface for opening and closing said
supply opening, and drive means for moving said plate member.
5. A flow meter according to claim 4 wherein when the supply opening
is open, said plate member is disposed upstream of said supply opening
as viewed in a direction of inclination of said bottom surface and
is moved downward to close said supply opening.
6. A flow meter according to claim 4 wherein said plate member
is formed with a cut-out portion in a lower end edge thereof as
viewed in a direction of inclination of said bottom surface.
7. A flow meter according to claim 8 wherein said load detector
is arranged at a height substantially equal to the height of said
supply device and suspends said load detection plate.
8. An impact type flow meter for a particulate material, comprising:
a supply device having a supply opening for dropping the particulate
material therethrough, said supply device being capable of changing
a flow rate of the particulate material flowing through said supply
opening, said supply device having a substantially trough-like shape
for defining a particulate material passage and an inclined flat
bottom surface, the supply opening being disposed proximate a lower
end of said bottom surface as viewed in a direction of inclination
thereof;
a plate member slidable in parallel with said bottom surface to
close the supply opening, said plate member being substantially
planar with said bottom surface when the supply opening is closed;
an inclined load detection plate disposed to receive a load of
the particulate material dropping from said supply device, said
bottom surface, plate member, and load detection plate being at
substantially the same inclination;
a load detector detecting the load of the particulate material
exerted to said load detection plate and converting the same into
an electrical signal; and
computing means for computing a flow rate of the particulate material
based on the electrical signal from said load detector.
Description BACKGROUND OF THE INVENTION
The present invention relates to an impact type flow meter for
measuring and controlling a flow rate of a particulate material
such as cereal, and in particular to a flow meter utilizing a slanting
or inclined detection plate.
The term "particulate material" used herein means not
only a granular or particulate material but also a powdery or pulverulent
material.
A conventional impact type flow meter is so constructed as to cause
particulate material to drop onto an impact plate or detection plate
and to calculate a flow rate thereof from its impact force. The
detection plate is mounted with an inclination or descent so that
the particulate material impinging thereupon can slide down at once
with no stagnation. Such a flow meter is seen in, for example, U.S.
Pat. No. 3611803 Japanese Patent Application Laid-Open Publication
No. 60-122324 International Application Publication Nos. W081/00312
and W093/22652.
It has also been known to, instead of dropping particulate material
directly onto the detection plate from a vertically above position,
guide the same along inclined chutes to the detection plate. Such
a flow meter is seen in International Application Publication No.
W093/22633 and Japanese Patent Publication No. H8-12091
FIG. 8 shows the arrangement proposed by Japanese Patent Publication
No. H8-12091. The arrangement is such that one or more inclined
buffer plates are provided between a discharge opening 103 in the
lower portion of a particulate material supply device 102 which
is below a hopper 101 and a detection plate 104. The particulate
material dropping from the supply device 102 impinges upon the first
one of the buffer plates, then slides down along the subsequent
buffer plates, slides along the last buffer plate 105 and is finally
dropped onto the detection plate 104. FIG. 8 illustrates only the
final buffer plate 105 which is inclined in the same direction with
the detection plate 104. The detection plate 104 is installed with
its upper end located right below the lower end of the final buffer
plate 105 and it has a detecting system or load cell 100 for detecting
the vertical component of a force exerted to the detection plate
104.
The flow meter thus constructed functions as follows. (1) Thanks
to the provision of the buffer plate 105 the particulate material
is substantially constant in its position of dropping, indicated
by an arrow 106 and direction of dropping, indicated by an arrow
107 with respect to the detection plate 104 even though the flow
rate varies. That is, unevenness of the speed of the particulate
material dropped from the supply device 102 is uniform. (2) The
buffer plate 105 and the detection plate 104 have only a small difference
between their inclining angles. Accordingly, the particulate material
impinges onto the detection plate 104 with less impact, and then
moves while it slides on the detection plate 104. When setting the
inclining angle .theta.D of the detection plate 104 less than the
inclining angle .theta.B of the buffer plate 105 a quasi-static
force can be applied to the detection plate 104 according as the
particulate material is moving thereon.
By the way, many conventional impact type flow meters use a cut-gate
type particulate material supply device as shown in FIG. 9. The
supply device is provided in its lower portion with a cut-gate 102
and opens and closes the discharge opening through rotary movement
of the cut-gate. Therefore, there are caused a part A in which the
material tends to stagnate, and a part C in which the material smoothly
flows, depending on a degree of opening of the cut-gate 102. A boundary
layer B is formed between the part A and the part C, and the thickness
of the boundary layer B varies with the opening degree of the cut-gate
102. Change in the thickness of the boundary layer B causes the
angle of repose of the stagnating part A to vary and provides a
possibility that the stagnating part A will crumble at once. Thus,
with the supply device of this type, the opening degree of the cut-gate
102 does not always coincide with the flow rate of the material,
and there are cases where the accuracy in measuring the flow rate
of the material is subject to detrimental affection.
Further, the flow meter shown in FIG. 8 because of its construction
in which the plurality of buffer plates are arranged in a stair-like
manner and the load cell 100 is situated below the detection plate
104 is large in the height h of the apparatus, thereby becoming
large in its overall size.
SUMMARY OF THE INVENTION
The present invention has an object of, in view of the above-mentioned
problems, providing an impact type flow meter which is small in
height and compact and which is high in the accuracy of measurement
of a flow rate.
Another object of the invention is to provide an impact type flow
meter which can always make the opening degree of a particulate
material supply device coincident with the conveying flow rate of
particulate material to improve the accuracy of flow rate measurement.
The impact type flow meter for particulate material according to
the invention comprises a supply device having a supply opening
for dropping the particulate material, which can change the flow
rate of the particulate material flowing through the supply opening,
an inclined load detection plate provided at a position for receiving
a load of the particulate material dropping from the supply device,
a load detector for detecting the load of the particulate material
exerted on the load detection plate and for converting the load
into an electrical signal, and a computing device for computing
the flow rate of the particulate material from the electrical signal
delivered from the load detector. The supply device is in a trough-like
shape defining a passage for the particulate material, and has a
flat bottom surface of substantially the same inclination with the
detection plate, and the supply opening is provided in the lower
end of the bottom surface as viewed in the direction of inclination.
With the above arrangement, the inclined bottom surface of the
supply device guides the particulate material at substantially the
same inclination with the load detection plate, and accordingly,
serves as the conventional buffer plate which has been described
above. Thus, the flow meter is of the construction that the particulate
material supply device is integrally incorporated with the buffer
plate, and it is possible to reduce the height and make the whole
apparatus compact. The particulate material flowing into the supply
device always impinges on the bottom surface, diverges in the widthwise
direction of the bottom surface and reaches the supply opening.
Accordingly, the direction and position of dropping of the particulate
material onto the load detection plate come to be constant or fixed.
Even though the speed of the particulate material flowing into the
supply device is uneven, at the time when flowing down through the
supply opening, the flow-down speed has been reduced, so that the
flow meter is high in the measurement accuracy.
The supply opening of the supply device is preferably rectangular
and located close to the load detection plate so as to lessen the
dropping impact of the particulate material. More specifically,
it is preferable to set the space or distance between the supply
opening and the load detection plate in such a manner that a quasi-static
load on the inclined surface is detected to be larger than an impact
load caused by dropping of the particulate material. The distance
is, for example, about 40 mm for a flow meter which has the maximum
measuring range of about 5 tons per hour. In this case, the flow
meter can measure the particulate material in a manner like weighing
measurement and is improved in the measurement accuracy. Incidentally,
in order to improve the measurement accuracy of an impact type flow
meter, it is desirable to calculate a flow rate based on a quasi-static
load while eliminating an impact load.
Further, the flow meter is preferably provided with an opening
and closing device for the supply opening of the supply device.
The opening and closing device includes a plate member which is
slidable in a direction parallel with the bottom surface so as to
open and close the supply opening, and a drive source for moving
the plate member. It is preferable for the plate member to be situated
at a higher level than the supply opening with respect to the direction
of inclination of the bottom surface, and to be moved downward for
closing the supply opening. In this case, at whatever position the
plate member lies, the particulate material by its all part slides
down along the bottom surface and the plate member not to cause
stagnation. Accordingly, the opening degree of the supply opening
corresponds to the flow rate of the particulate material, and thereby
the accuracy in measurement of a flow rate is further improved.
The plate member is preferably formed with a cut-out portion in
the lower end edge thereof as viewed in the direction of inclination
of the bottom surface. In this case, the plate member, even when
being near its close position, can control the particulate material
to the region of a small flow rate and does not cause the material
to stagnate.
The load detector is preferably arranged at a height substantially
equal to that of the supply device for particulate material to suspend
the load detection plate. With this arrangement, it is possible
to reduce the height of the apparatus and make the same compact
as compared with the conventional flow meter in which the load detector
is situated under the detection plate.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and advantages of the present invention
will be more apparent from the description which will be made hereinbelow
with reference to the accompanying drawings, in which:
FIG. 1 is a longitudinal section view illustrating an essential
part of the impact type flow meter according to an embodiment of
the invention;
FIG. 2 is a section view of a particulate material supply device
in the flow meter of FIG. 1 illustrating a state that an opening
and closing device for the supply device is closed;
FIG. 3 is a section view showing the opening and closing device
in its opened state;
FIG. 4 is a perspective view illustrating the essential part of
the flow meter of FIG. 1;
FIG. 5 is a block diagram illustrating a control section of the
flow meter of FIG. 1;
FIG. 6 is a plan view of the opening and closing device as viewed
along the VI--VI line of FIG. 3;
FIG. 7 is a graph showing the relationship between opening degrees
of the opening and closing device and detection values by a load
detector in the flow meter of FIG. 1;
FIG. 8 is a schematic view illustrating the arrangement of a detection
plate and a buffer plate in a conventional impact type flow meter;
and
FIG. 9 is a section view of a particulate material supply device
for use in conventional impact flow meters.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Description will be made on the impact type flow meter according
to an embodiment of the invention with reference to the accompanying
drawings.
Referring to FIGS. 1 and 4 which show the essential part of the
flow meter, the flow meter 1 has a machine base 2 and a machine
frame 4 provided on the machine base 2 supports a particulate material
supply device 3 and a load detection plate 6. The supply device
3 which can change the flow rate of a particulate material, is
in a trough-like or pipe-like shape for defining a particulate material
passage, and is situated in an upper part of the machine frame 4.
The supply device 3 is connected with a reservoir hopper above the
supply device, not shown in the figures, via a pipe-like member
5. The load detection plate 6 is positioned below the supply device
3 to receive a load of the particulate material F dropping from
the supply device 3.
The load detection plate 6 is in a flat shape which is inclined
with respect to the horizontal plane, so that the particulate material
F slides along the inclined surface of the load detection plate
6 to exert a quasi-static load thereon. As shown in FIG. 4 support
members 7A,7B of a substantially triangular shape are attached to
widthwise opposite sides of the load detection plate 6 respectively.
The support members 7A,7B are formed in their upper portions with
grip parts 8A,8B, respectively, between which a support member 9
is spanned or bridged. A load cell 10 serving as a load detecting
means is attached at one end thereof to the support member 9. The
load cell 10 is supported at its other end by the machine frame
4 through a support member 11. Thus, the load cell 10 is configured
to suspend the load detection plate 6 therefrom.
The particulate material supply device 3 has at its lower end a
flat bottom surface 12 and the bottom surface 12 is inclined to
a degree substantially equal to the load detection plate 6. The
bottom surface 12 has, in its lower end as viewed in the direction
inclination, a rectangular supply opening 13 of a constant width
for dropping the particulate material F onto the load detection
plate 6. With this arrangement, the particulate material F having
flown into the particulate material supply device 3 diverges widthwise,
as indicated by reference letter M in FIG. 6 while sliding along
the bottom surface 12 and comes to the supply opening 13. The supply
opening 13 is arranged preferably close to the load detection plate
6 so as to reduce the dropping shock or impact of the particulate
material thereon. For example, in a case that the flow meter has
a measuring range of about 5 tons per hour, the space or distance
L between the supply opening 13 and the load detection plate 6 is
set to 40 mm, see FIG. 2. The distance L is set in a manner that
the quasi-static load of the particulate material F exerted on the
inclined surface of the load detection plate 6 that is, a load
close to that measured through weighing measurement, is larger than
an impact load caused by dropping of the particulate material F.
Further, the size of the supply opening 13 is set so that it can
feed the particulate material at a desired maximum flow rate.
The particulate material supply device 3 is provided with an opening
and closing device 16 for the supply opening 13. The opening and
closing device 16 is composed of a plate member 14 which is adapted
to slide in parallel with the bottom surface 12 to open and close
the supply opening 13 and a drive device 15 for moving the plate
member 14 which is a control motor in this embodiment. Alternatively,
the drive device 15 may comprise an air cylinder or the like which
can stop at desired positions. The plate member 14 is located in
a position higher than the supply opening 13 as viewed in the direction
of inclination of the bottom surface 12 and is moved downward to
close the supply opening 13.
The opening and closing device 16 moves the plate member 14 to
a position S for closing the supply opening 13 see FIG. 2 to another
position 0 for opening the supply opening 13 see FIG. 3 or to
any position between these two positions to control the degree of
opening of the particulate material supply device 3. More specifically,
the control motor 15 is adapted to stop at any rotating angle, and
has a motor shaft 17 attached thereto with a rotary plate 18. The
rotary plate 18 is coupled to the plate member 14 through a drive
arm 19. When the control motor 15 is rotated for a predetermined
angle, the drive arm 19 is pulled up obliquely in the direction
of inclination to open the supply opening 13 or to the contrary,
the drive arm 19 is pulled down obliquely in the direction of inclination
to close the supply opening 13.
The flow meter 1 has a control section, and FIG. 5 shows the control
section. As described above, the load cell 10 serving as the load
detector outputs an analog signal in accordance with a load exerted
to the load detection plate by the particulate material, and is
connected to a computing and controlling device 21 such as a microprocessor,
through an A/D converter 20. The computing and controlling device
21 computes a flow rate of the particulate material going along
the detection plate, on the basis of the input signal from the load
cell 10. Connected to the computing and controlling device 21 are
the control motor 15 for the particulate material supply device
3 and a display device 22 for indicating a flow rate as a result
of the computation.
The operation of the flow meter 1 will be now described.
Before starting the operation of the flow meter 1 the particulate
material supply device 3 closes its supply opening 13 as shown in
FIG. 2 and is in a state of being filled with the particulate material
F from the reservoir hopper. When the flow meter 1 is energized,
the computing and controlling device 21 outputs a drive signal to
the control motor 15. The control motor 15 rotates the rotary plate
18 for a predetermined angle and moves the plate member 14 upward
in the direction of inclination through the drive arm 19 to open
the supply opening 13. See FIG. 3. The particulate material F therefore
flows downward along the bottom surface 12 of the supply device
3 and then drops from the supply opening 13 which is on the lower
side as viewed in the inclination, onto the load detection plate
6.
Upon dropping of the particulate material F onto the load detection
plate 6 the load cell 10 detects the load of the particulate material
F, and delivers an analog signal in accordance with the result of
detection. The analog signal is A/D-converted by the A/D converter
20 and is then introduced into the computing and controlling device
21. The computing and controlling device 21 computes a quasi-static
load from the detection signal, and further converts the same into
a flow rate with the use of a predetermined arithmetic formula.
The computing and controlling device 21 when judging necessary
from the result of computation, drives the control motor 15 for
the opening and closing device 16 to adjust the opening degree of
the plate member 14. Further, the flow rate calculated by the computing
and controlling device 21 is indicated on the display device 22.
The primary feature of the invention resides in the provision of
the bottom surface 12 which is inclined to a degree similar to
the load detection plate 6 in the lower portion of the particulate
material supply device 3 as shown in FIG. 1 differently from the
conventional example shown in FIG. 8 wherein the plurality of buffer
plates are provided separately from the particulate material supply
device 102. More specifically, the particulate material supply device
and the buffer plate are integrally formed to simplify the construction,
thereby making the height of the apparatus lower and the whole apparatus
compact. In this supply device, the particulate material F flowing
down from the pipe-like member 5 always impinges upon the bottom
surface 12 diverges widthwise and reaches the supply opening 13.
Accordingly, the direction and position of dropping of the particulate
material F onto the load detection plate 6 are substantially fixed,
and therefor, even though the speed of the particulate material
flowing into the supply opening 13 is uneven, the flow-down speed
is lessened and the unevenness of speed is averaged or uniformed
when it flows out from the supply opening 13.
Further, as the particulate material supply device 3 has the supply
opening 13 situated close to the load detection plate 6 the fall
L between the supply opening 13 and the load detection plate 6
see FIG. 2 is small so as to be 40 mm. Accordingly, the dropping
impact of the particulate material is less, and in the load exerted
on the load detection plate 6 the quasistatic load caused when
the particulate material F slides along the load detection plate
6 becomes larger in rate than the impact load upon dropping of the
particulate material. It is thus possible to detect the flow rate
of the particulate material F in a condition of almost weighing
measurement.
Moreover, the particulate material supply device 3 has the supply
opening 13 in the bottom surface 12 on the lower side thereof as
viewed in the inclination, and performs opening and closing of the
supply opening 13 by means of the plate member 14 which slides in
parallel with the bottom surface 12. The particulate material F
in the supply device 3 flows down in its entirety into the supply
opening 13 along the bottom surface part 12 and there is no possibility
that the plate member 14 causes a stagnating part of the material
due to its position, which corresponds to the part A shown in FIG.
9. Accordingly, the opening degree of the supply device 3 or the
plate member 14 is consistent with the flow rate of the material,
so that the accuracy in measuring the flow rate of the material
is improved and the control of opening and closing of the supply
opening 13 can also be carried out precisely. In addition, the distance
between the supply opening 13 and the load detection plate 6 is
fixed, and the distance of dripping of the particulate material
F is constant wherever the plate member 14 lies. That is, the magnitude
of the impact load exerted by the particulate material F is proportional
to the opening degree of the plate member 14 and thereby conversion
to the flow rate can be made with high accuracy. This will be explained
with reference to FIG. 7.
FIG. 7 is a graph showing the relationship between opening degrees
of the plate member 14 and detection values of the load cell 10
in which the abscissa denotes the opening degree and the ordinate
denotes the detection value. The solid line M in FIG. 7 represents
an actually detected value including the impact load which the load
detection plate 6 receives due to the particulate material F dropping
from the supply opening 13 and the quasi-static load of the particulate
material F together. Since the impact load varies in proportion
to the opening degree of the plate member 14 it is predicted that
the quasi-static load will change as a broken line N with respect
to the detection values of the solid line M. For instance, according
to the graph of FIG. 7 the impact load can be obtained from M-N,
and it will be appreciated that the impact load M-N is proportional
to the opening degree of the plate member 14. Therefore, by calculating
an impact load from, for instance, the flow rate at the maximum
opening degree of the supply opening 13 the ration of impact load
over all the region of opening of the supply opening can be predicted.
Accordingly, when knowing an opening degree of the plate member
14 a predicted value of impact load is known, and calculation of
a quasi-static load and conversion to a flow rate can be carried
out with high accuracy.
Meanwhile, the plate member 14 for opening and closing the supply
opening 13 is preferably formed, as shown in FIG. 6 in its leading
end edge, that
is, in the lower end edge as viewed in the direction of inclination
of the bottom surface 12 with a cut-out portion 14i a. The cut-out
portion 14a is generally in a chevron shape which become larger
in opening as it comes near the widthwise center of the plate member
14. In an example of dimensions of the cut-out portion, an opening
width is about 100 mm and the maximum height or depth of the chevron
shape at its center is about 10 mm for the plate member 14 of a
130 mm width. The cut-out portion 14a, however, may take another
shape than that described above and have other dimensions depending
on the volume to be handled.
In the case that the cut-out portion 14a is formed, the closing
position of the plate member 14 is set to a position where the cut-out
portion 14a passes over the supply opening 13. With this arrangement,
the plate member 14 even when lying near its close position, can
control the particulate material flow to the extent of a small flow
rate and does not allow the same to stagnate.
In the embodiment, the load cell 10 as the load detector is situated
at a height substantially equal to the particulate material supply
device 3 and suspends the load detection plate 6. Accordingly, the
height h of the flow meter 1 can be decreased to make the apparatus
compact as compared with the conventional example of FIG. 8 wherein
the load cell 100 is disposed below the detection plate 104.
Although the invention has been described with reference to the
embodiment, the invention is not limited solely to such a specific
form, and the specific form may be modified variously, or the invention
may take another form without departing from the scope of appended
claims. |