Abstrict A volume flow meter for the measurement of the flow quantity of
a liquid, which meter comprises a cylindrical flow channel (3),
which has an inlet point (10) and an outlet point (12) for passing
the liquid to be measured through the measurement channel. In the
measurement channel, there is an axially moving, spring-loaded indicator
piston (4), which is shifted by the liquid in the measurement channel
into different positions depending on the flow quantities. In the
wall of the measurement channel, there is an outflow slot (27) for
the liquid, which slot becomes deeper from the inlet point to the
outlet point. The meter is provided with a reversing valve (17),
so the flow of the liquid to be measured can be guided through the
by-passing channel (26) to the opposite side (3') of the indicator
piston (4), as seen from the inlet point (10), so as to shift the
indicator piston towards the inlet point. This movement of the indicator
piston wipes the wall of the measurement channel clean from impurities.
In the indicator piston, there is a flow connection from the opposite
side of the piston to the outflow slot of the measurement channel.
Claims What is claimed is:
1. A volume flow meter for the measurement of the flow quantity
of a flowing medium, especially of a liquid, which meter comprises
a cylindrical measurement channel, to which channel are connected
an inlet point and an outlet point for passing the medium to be
measured through the measurement channel, an indicator piston moving
axially in the measurement channel, which piston is shifted by the
medium flowing from an inlet channel to the measurement channel
into different axial positions depending on the flow quantities,
and an axial flow slot in communication along its length with the
measurement channel, the size of the said slot being affected by
the axial position of the indicator piston, characterized by means
for cleaning the measurement channel by forcing the indicator piston
toward the inlet point, said means including a reversing valve which
guides the medium to be measured optionally to the inlet point of
the measurement channel or, via a by-passing channel, to the opposite
side of the indicator piston in the measurement channel, as seen
from the inlet point, and the indicator piston having a flow connection
from said opposite side of the measurement channel to the inlet-point
side and to the flow slot of the measurement channel.
2. A meter as claimed in claim 1 characterized in that the reversing
valve is fitted in the inlet channel leading to the inlet point
of the measurement channel and that the by-passing channel runs
from the inlet channel by-passing the measurement channel to its
opposite side end, as seen from the inlet point.
3. A meter as claimed in claim 2 characterized in that the reversing
valve comprises a press-knob-operated, axially moving spindle, which,
in the measurement position, closes the connection of the inlet
channel to the by-passing channel, and opens the connection of the
inlet channel to the inlet point and, in a cleaning position, closes
the connection of the inlet channel to the inlet point and opens
the connection of the inlet channel to the by-passing channel.
4. A meter as claimed in claim 1 characterized in that the reversing
valve is fitted in the end of the measurement channel placed next
to the inlet point and that the by-passing channel runs from this
end of the measurement channel by-passing the measurement channel
to the opposite side of the measurement channel.
5. A meter as claimed in claim 4 characterized in that the reversing
valve comprises a press-knob-operated, axially moving spindle, which,
in the measurement position, opens the connection of the inlet point
to the measurement channel and closes the connection of the measurement
channel to the by-passing channel and, in a cleaning position, opens
the connection of the measurement channel to the by-passing channel
and closes the connection of the inlet point to the measurement
channel.
6. A meter as claimed in claim 1 characterized in that the indicator
piston is loaded by a spring, which presses the piston towards the
inlet point of the measurement channel.
7. A meter as claimed in claim 1 characterized in that the flow
slot is formed by at least one groove in the wall face of the measurement
channel, which groove passes from the inlet point of the measurement
channel to the outlet point and becomes constantly deeper towards
the outlet point.
8. A meter as claimed in claim 7 characterized in that the indicator
piston is fitted with gliding precision in the measurement channel
and that the piston is provided with a sleeve-shaped extension,
which, in the various positions of the piston, covers the portion
of the flow slot that is placed on the opposite side of the piston,
as seen from the inlet point.
Description The subject of the present invention is a volume flow meter for
the measurement of the flow quantity of a flowing medium, especially
of a liquid, which meter comprises a cylindrical flow channel, to
which channel are connected an inlet point and an outlet point for
passing the medium to be measured through the measurement channel,
an indicator piston moving axially in the measurement channel, which
piston is shifted by the medium flowing from the inlet channel in
the measurement channel into different axial positions depending
on the flow quantities, and an axial flow slot placed in the measurement
channel, the size of the said slot being affected by the axial position
of the indicator piston.
In prior art, similar volume flow meters are known for the measurement
of flow quantities of liquids by making use of the interaction between
the velocity pressure and the static pressure of the liquid in a
measurement channel of varying size. The state of pressure produced
in this way guides a piston moving in the measurement channel, the
position of the piston in the channel constituting the measure of
the volume flow quantity. In some prior-art meter constructions
the measurement channel is conically widening and as indicator member
is used a ball or any other float, whereby the variation of the
size of the flow slot available for the passage of the liquid takes
place so that the axially mobile ball or float changes its position
to a wider or narrower point in the measurement channel as the flow
quantity changes. In other prior-art meter constructions, the measurement
channel is cylindrical and as indicator means is used a piston gliding
against the inside face of the measurement channel, which piston
moves around a stationary conical spindle extending through the
piston. In such a case, the change in the size of the flow slot
available for the passage of the liquid takes place as the piston
changes its position to a thicker or narrower point of the conical
spindle as the flow quantity varies.
A drawback of meters of these types is that impurities in the liquid,
e.g. humus substances in water, form sediments on the inside face
of the measurement channel. This makes the assuming of the right
position by the mobile piston more difficult and, also, makes the
inside face of the measurement channel dark so that it is difficult
to see the position of the piston. In order that it should be possible
to avoid disassembling of the meter for cleaning, it is suggested
in the Finnish Pat. No. 53042 that a brush be mounted in the measurement
channel which can be moved from the outside and by means of which
the inside face of the measurement channel can be cleaned. True
enough, the patent relates to a meter with a conically widening
measurement channel, but a similar brush cleaning would also be
conceivable in a meter with a cylindrical measurement channel and
an indicator piston. The use of the brush is, however, relatively
slow, for which reason one may neglect to use it. Moreover, the
brush shaft projecting from the meter is readily damaged and increases
the space requirement of the meter considerably.
The object of the present invention is to provide a volume flow
meter which eliminates the problem resulting from contamination
and thereby increases the reliability of operation and the dependability
of the meters. This objective is achieved by means of a volume flow
meter in accordance with the invention, which is characterized by
a reversing valve, which guides the medium to be measured optionally
to the inlet point of the measurement channel or, via a by-passing
channel, to the opposite side of the indicator piston in the measurement
channel, as seen from the inlet point, and that the indicator piston
has a flow connection from the said side of the measurement channel
to the inlet-point side and to the flow slot of the measurement
channel.
The invention is based on the idea that the cleaning of the measurement
channel is performed by means of the indicator piston itself by
making the piston to move by a sudden strike to its initial position
and back to its measurement position by momentarily reversing the
flow of the liquid by means of a particular reversing valve. This
movement of the indicator piston wipes the inside face of the measurement
channel clean of impurities. The wiping movement of the indicator
piston is started simply by pressing a knob, whereby the liquid
to be measured takes care of the moving of the piston. During the
wiping stroke of the indicator piston, the flow of the liquid to
the outlet point of the meter is not interrupted, which is important,
e.g. when the meter is used for controlling the seal liquid of a
two-sided slide-ring seal.
The invention will be described in more detail below with reference
to the attached drawings, wherein
FIG. 1 shows a preferred embodiment of the flow meter in accordance
with the invention as a front view,
FIG. 2 shows the meter as a side view as a section along line II--II
in FIG. 1
FIG. 3 shows the meter as a front view as a section along line
III--III in FIG. 2
FIG. 4 shows the meter as a side view as a section along line IV--IV
in FIG. 3
FIG. 5 shows the meter as a front view as a section along line
V--V in FIG. 4
FIG. 6 shows the meter as a side view as a section along line VI--VI
in FIG. 3
FIG. 7 shows the meter as viewed from the bottom,
FIG. 8 shows the meter as viewed from above as a section along
line VIII--VIII in FIG. 1 and
FIGS. 9 and 10 show an alternative embodiment of the meter as a
front view and as a vertical section in the flow-measurement position
and in the cleaning position, respectively.
The volume flow meter illustrated in FIGS. 1 to 8 of the drawings
consists of an installation part 1 of steel and of a transparent
measurement part 2 of plastic, fixed onto the installation part.
The measurement part comprises a cylindrical measurement channel
3 which includes an axially moving indicator piston 4 which is
pressed by a spring 5 towards the inlet end of the measurement channel.
The installation part 1 has an inlet connection opening 6 for the
liquid to be measured, the said inlet opening being connected over
channels 7 8 9 and 10 to the inlet end of the measurement channel
3. The installation part further includes a outlet connection opening
11 which is connected over channel 12 to the measurement channel
and over channel 13 to the pressure meter 14. A choke means 16 adjustable
by means of an adjusting screw 15 is mounted in the channel 8 the
said means 16 forming a choking point in the channel for the adjustment
of the volumetric flow coming into the measurement channel to the
desired magnitude in connection with the calibration.
According to the invention, a reversing valve 17 is mounted in
the channel 7 FIG. 8 which reversing valve includes an operating
spindle 18 moving axially in the valve body, a closing disk 19 being
fixed to the inner end of the spindle and a press knob 20 being
fixed to the outer end of the spindle. A spring 21 fitted between
the press knob and the body pushes the spindle to the measurement
position shown in FIG. 8 in which position the closing disk is
pressed against the tubular extension 22 of the valve body. When
the press knob is in the pressed-in position, the closing disk closes
the connection opening 23 between the channels 7 and 8 as is shown
in FIG. 5. A bore 24 has been made into the tubular extension 22
to connect the interior space of the extension to the channel 25
made into the installation part, which channel 25 is again connected
by means of the channel 26 FIG. 5 to the spring-side end of the
measurement channel 3.
In the bottom portion of the cylindrical wall of the measurement
channel 3 an inclined bore, i.e. a U-shaped flow slot 27 is formed,
which is inclined at an angle of about 5.degree. passing from the
inlet end of the measurement channel down to the outlet channel
12. At the closed end of the indicator piston 4 there is a circumferential
groove, which is connected by means of a radial opening 28 and an
axial center opening 29 to the interior space of the piston and
further to the spring-side space 3' of the measurement channel 3.
The piston is provided with a sleeve-shaped extension 4a, which
covers the portion of the flow slot 27 that at each particular time
remains between the closed end of the piston and the outlet opening
12.
The volume flow meter operates as follows:
The liquid to be measured flows into the meter through the inlet
opening 6 and via the channels 7 8 9 and 10 into the measurement
channel 3. The liquid flowing into the measurement channel directs
at the indicator piston 4 a force that tends to move the piston
against the effect of the spring 5. The position of the indicator
piston in the measurement channel depends on variations in the velocity
pressure and static pressure of the liquid and constitutes the measure
of the volumetric flow quantity of the liquid. The position of the
indicator piston can be observed readily from the outside owing
to the transparent material of the measurement part. When the volumetric
flow increases, the piston moves against the spring as pressed by
the liquid. At the same time, a wider outflow opening is opened
for the liquid because of the inclined flow slot 27. Thereby part
of the velocity pressure of the liquid is converted into static
pressure, whereby the piston moves into the position required by
the situation and by the flow quantity. On the outside face of the
measurement part there is a scale out of which the volumetric flow
concerned can be read directly. The openings 28 29 in the piston
balance the liquid pressures in the measurement channel at opposite
sides of the piston.
When it is desirable to cleanse the meter, the press knob 20 of
the reversing valve 17 is pressed. Then the closing disk 19 closes
the connecting opening 23 between the channels 7 and 8 so that the
flow of liquid from the inlet opening 6 through the channel 10 into
the measurement channel is prevented. However, at the same time
a connection is opened from the channel 7 through the tubular extension
22 of the reversing valve and through the bore 24 into the channel
25 and further through the channel 26 into the spring-side space
3' of the measurement space. By the joint force effect of the liquid
pressure and the spring 5 the piston moves to its basic position
at the inlet channel 10. Owing to its precise gliding fitting, the
piston at the same time wipes any slime and impurities possibly
adhering to the inside face of the measurement channel off, thereby
cleaning the display area of the meter. The liquid flow into the
outlet channel 12 of the measurement channel is, however, not interrupted,
for the liquid has access through the openings 28 and 29 in the
indicator piston 4 into the inlet-side space 3" of the measurement
channel and from there further through the flow slot 27 into the
outlet channel 12. In the opening 28 a strong pressure loss is produced,
whereby the pressure in the space 3' of the measurement channel
is higher than in the space 3", so that the piston is instantaneously
shifted into its basic position. When the press knob 20 is released,
the spring 21 returns the operating spindle to its initial position,
whereby the connecting opening 23 is opened and the tubular extension
22 is again closed. Owing to this, the liquid flow is restored through
the channels 7 8 9 and 10 to the inlet side of the measurement
channel, so that the indicator piston again indicates the liquid
flow. The cleaning operation can be repeated in this way by pressing
the press knob the desired number of times.
It is noticed that the meter can be cleaned in a simple way by
means of the indicator piston itself and that the cleaning operation
does not interrupt the liquid flow to the outlet connection of the
meter. Since the meter has been designed so as to be installed in
such a position that the measurement channel is horizontal and the
indicator piston operates in the lying position, the weight of the
piston itself does not have to be compensated, but the entire pressure
energy obtained from the liquid can be charged in the spring 5
whereby the cleaning stroke becomes faster. Detached impurities
heavier than the liquid can sink into the outflow opening in the
lower part of the measurement channel and be removed through the
opening unprevented from the meter without blocking the meter.
The alternative embodiment of volume flow meter illustrated in
FIGS. 9 and 10 differs from that illustrated in FIGS. 1 to 8 only
in the respect that the reversing valve 17 installed in the liquid
inlet channel system 7 to 10 has been substituted for by a reversing
valve 37 installed in the measurement channel 3. In this case the
arrangement is such that the closing disk 39 of the valve is positioned,
in the measurement position shown in FIG. 9 on the right side of
the inlet channel 10 where there is a direct connection from the
inlet channel to the measurement channel and from there to the outflow
slot 27 and, in the cleaning position shown in FIG. 10 on the
left side of the inlet channel 10 where the inlet channel is isolated
from the measurement channel and from the outflow slot. The channel
26 which passes to the spring-side end of the measurement channel
3 is opened at such a point in the wall of the measurement channel
that the inlet opening of the channel is, in the measurement position
of the closing disk (FIG. 9), closed by the closing disk but, in
the cleaning position of the closing disk (FIG. 10), opened into
the space between the closing disk and the body of the reversing
valve. Thus, in the cleaning position, the liquid flow can be guided
to the opposite side of the indicator piston and the piston be forced
to perform the cleaning stroke described above.
The drawings and the related description are only supposed to illustrate
the idea of the invention. In its details, the meter in accordance
with the invention may show even considerable variation within the
scope of the patent claims. |