A liquid flow meter comprises a housing having a cylindrical piston
chamber and a control chamber. A measuring piston is movable in
the piston chamber and a flow control slider is movable in the control
chamber and it has respective oppositely directed control surfaces
which are made effective, by the flow of liquid between the inlet
to the housing and a communication between the measuring piston
chamber and the control chamber to move the control slider in a
control direction. At each end position of the slider, there is
a magnetic holding device for holding the slider until a predetermined
control pressure is brought to bear against it to move it in an
opposite direction. At each limit of its movement, the piston engages
and charges an energy or power storage device operable to accelerate
its movement in the opposite direction. The control movements of
the slider for regulating the flow between the inlet and the outlet
are varied in accordance with the position of the measuring piston.
What is claimed is:
1. A liquid flow meter comprising, in combination, a measuring
chamber; a measuring member reciprocable in said measuring chamber
between two limit position; a control chamber having an inlet and
outlet for the liquid to be measured; a control slide reciprocable
in said control chamber and formed with control passages for the
measured liquid; passage means interconnecting said measuring and
control chambers so that the liquid to be measured flows, under
dynamic pressure, from said inlet through said control passages
and through said measuring chamber to reach said outlet; said control
slide being movable between two end positions in each of which said
control passages direct fluid under dynamic pressure to a different
respective end of said measuring member to reverse the movement
of said measuring piston; said control slide, when said measuring
piston is stopped in either of its limit positions with said control
slide in one of its end positions, being moved, under the effect
of the dynamic pressure of the measured liquid, to its opposite
end position to effect reverse movement of said measuring piston;
a counter operable responsive to reciprocation of one of said measuring
piston and said control slide; and respective power accumulators,
operable to store energy responsive to motion of said measuring
piston, in said measuring chamber at each limit position of said
measuring member, said power accumulators accelerating said measuring
member during initiation of reversal of its motion.
2. A liquid flow meter, according to claim 1 wherein said flow
control passage means are constructed so that during the rapid movement
of said control slider from one end position to the other, the supply
into and discharge from said flow meter are shut off.
3. A liquid flow meter, according to claim 1 including sensing
means arranged along the path of travel of said measuring piston
for indicating the partial volumes in accordance with the piston
4. A liquid flow meter, as claimed in claim 1 in which said power
accumulators comprise springs mounted in said measuring chamber
coaxially of said measuring piston and compressible by said measuring
piston at its respective limit positions.
5. A liquid flow meter, as claimed in claim 1 including respective
retaining means at each end position of said control slide releasably
operated to retain said control slide in the associated end position;
said retaining means being released responsive to an increase in
the value of the dynamic pressure of the measured fluid to a value
sufficient to overcome the retaining force of said retaining means,
whereupon said retaining means are released for unrestricted movement
of said control slide under the dynamic pressure to its opposite
6. A liquid flow meter, according to claim 5 wherein said control
slide comprises a rod member having a plurality of spaced axial
rings with grooves therebetween, the rings defining respective oppositely
directed control surfaces, said retaining means comprising a permanent
magnet on said slide and a ferromagnetic armature plate in said
control chamber engageable with said magnet.
7. A liquid flow meter, as claimed in claim 6 wherein said retaining
means includes an annular magnet on said control slide; and a counter
contact member disposed along the path of movement of said control
slide and operable by said annular magnet.
8. A liquid flow meter, according to claim 5 wherein said retaining
means comprises electromagnets which are actuated as a function
of the position of the measuring piston.
9. A liquid flow meter, as claimed in claim 5 wherein said control
slide has respective oppositely directed control surfaces and which
are subject to such dynamic pressure; said piston being a double-acting
piston; said flow passage means including a connection between the
respective pressurized sides of said measuring chamber with said
control chamber for delivering a control dynamic pressure to a respective
control surface of said control slide for moving said control slide
away from said retaining means.
10. A liquid flow meter, as claimed in claim 6 in which said measuring
chamber and said control chamber are co-axial cylinders arranged
in end-to-end axial alignment; said control slide and said piston
being also arranged in end-to-end axial alignment.
11. A liquid flow meter, according to claim 10 including an adjusting
device comprising a setscrew threadable in an end face of said measuring
chamber for limiting the stroke of said measuring piston.
12. A liquid flow meter, as claimed in claim 1 in which said measuring
chamber and said control chamber are arranged in co-axial end-to-end
axial alignment in a common housing; an apertured disc positioned
in said common housing; a bellows secured at one end to said measuring
piston and enclosing said measuring piston, said bellows being secured,
intermediate its ends, to said apertured disc, and having its opposite
end secured to said control slide beyond said apertured disc.
FIELD AND BACKGROUND OF THE INVENTION
This invention relates in general to the construction of devices
for controlling the flow of fluids and, in particular, to a new
and useful device for continuously measuring the rate of flow of
a liquid flowing from a supply tank to a consuming device.
DESCRIPTION OF THE PRIOR ART
With the increasing scarcity of mineral oil products and the high
prices therefor, it becomes necessary to effect the exact monitoring
of the fuel consumption in consuming devices, such as motor vehicles,
heating devices and similar operating devices in order to effect
an economy of consumption and the elimination of waste. For this
purpose, flow meters are needed which indicate the rate of flow
accurately even at very low consumption rates and which are responsive
to small differences in hydraulic pressure between the inlet and
outlet of such devices. The standard values to be assumed for the
required measuring performance may be a rate of flow of approximately
1 liter per hour with a response pressure of about 30 cm water column,
and an accuracy of measurement of at least .+-. 2%. Numerous types
of flow meters are known which are based on various principles.
They do not, however, comply with the requirements as to minimum
pressure of response, accuracy of measurement and measurable minimum
rate of flow mentioned above.
SUMMARY OF THE INVENTION
The present invention provides a flow meter having satisfactory
operating characteristics, and it includes a housing having a measuring
chamber in which is movable a measuring piston. The measuring piston
influences the position of a reversing control member for regulating
the flow through the device and which advantageously includes means
for counting the piston strokes.
In accordance with the invention, a high precision of measurement
is obtained primarily by a high accuracy provided at the reversal
of the measuring piston at the end of its stroke. For this purpose,
the reversing control member is equipped with a retaining device
by which the control member is retained in its end position up to
the accomplishment of the full stroke of the measuring piston and
then it is suddenly released so that it can move instantly into
its opposite end position. During the reversing operation, the supply
and discharge of the liquid to be measured are shut off.
The retaining device may advantageously comprise a locking mechanism
with a linkage, an electrically actuated arrest, or, preferably,
a magnetic device, which is engageable with the control slider in
each end position. A particularly satisfactory solution with respect
to simplicity, reliability and service life is the use of permanent
magnets for retaining the control member in the respective end positions.
According to a feature of the invention, in order to release the
retaining device of the control member for initiating the reversal,
there is a means for accumulating potential energy mounted at each
end of the stroke path of the measuring piston. Preferably, this
means comprises springs against which the measuring piston or a
part connected thereto is pushed at each end position at the end
of the stroke. In this manner, the spring or other element is increased
in tension until the measuring piston abuts against a stop. Thereby,
a back pressure builds up in the piston chamber which is actively
effective during the respective strokes and which increases rapidly
as the measuring piston abuts against the stop. This pressure acts
on the retained end of the control slider until the holding force
of the permanent magnet is overcome or it releases a similar locking
device. Thereupon, because of the accumulated potential energy,
the reversing control member is pushed back toward its other end
position where it is retained again by another magnet or similar
Instead of springs, a small pressure accumulator with an air cushion
or similar arrangement may be employed. In addition, a similar effect
may be obtained by replacing the springs by permanent magnets of
suitable polarity or by use of electromagnets. For example, one
of the magnets may be provided on the front face of the measuring
piston and one on the front face of the measuring cylinder.
A construction particularly favorable from the hydraulic point
of view is obtained by designing the reversing control member as
a control slide valve which comprises a cylindrical piston with
annular grooves defining respective oppositely directed control
surfaces which may be operated on by the circulating liquid. The
control member slides in a control chamber which has walls which
define with the control slide valve, flow control passage means
between the inlet and outlet to the housing. A concentrically positioned
annular retaining magnet provided in one of the front faces of the
control slider makes it possible to provide a magnetically actuable
contact concentrically projecting into the slider control chamber
and which is actuated by the stroke of the slider to count the number
of strokes, for example, by use of an electromagnetic counter.
A particular advantage of the hydraulic reversal of the control
slider is that, at the start of the slider motion, and inlet and
outlet passageways are closed and, during the further reversing
motion, no leakage can occur and a high measuring accuracy is ensured
even with very small rates of flow. In addition, it is sufficient
to connect the control part and the measuring part to each other
only hydraulically and they may be arranged in any mutual spacial
relationship for this purpose.
In a preferred embodiment, the measuring cylinder and the control
member are aligned along a common rotational axis so that a compact
design is obtained which frequently permits the mounting of the
flow meter at any desired location.
The desired stroke volumes may be adjusted in a simple manner during
operation and very accurately by means of an adjusting device projecting
centrally into the measuring cylinder and limiting the stroke of
the measuring piston. This makes it unnecessary to work the length
and diameter of the measuring cylinder with highest precision.
The invention also makes it possible to effect measurement of partial
quantities of the stroke volume. For such a purpose, switching means,
such as contacts, radiation paths, sensors or the like, are provided
along the stroke path of the measuring piston and these are made
responsive to the particular location of the piston to actuate certain
control circuits for indications or recording devices.
Accordingly, it is an object of the invention to provide a liquid
flow meter which includes a housing having a cylindrical piston
chamber, and a control chamber with a measuring piston movable in
the piston chamber and a flow control slider movable in the control
chamber and which has control surfaces which are influenced to move
the slider in either of two directions in accordance with the position
of the piston so as to control the flow of liquid through the device
and through the piston chamber and the control chamber and which
also includes retaining means, such as a magnet, at each end position
of the control member so as to retain the control member in the
end positions until a predetermined control pressure acts thereon
to move it in a reversing direction.
A further object of the invention is to provide a liquid flow meter
which is simple in design, rugged in construction and economical
The various features of novelty which characterize the invention
are pointed out with particularity in the claims annexed to and
forming a part of this disclosure. For a better understanding of
the invention, its operating advantages and specific objects attained
by its uses, reference should be had to the accompanying drawing
and descriptive matter in which there are illustrated preferred
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a longitudinal sectional view of a liquid flow meter
constructed in accordance with the invention;
FIG. 2 is a view similar to FIG. 1 but at a right angle to the
section shown therein; and
FIG. 3 is a view similar to FIG. 1 of another embodiment of the
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in particular, the invention embodied
therein in FIGS. 1 and 2 comprises a flow meter which has a housing
2 forming a cylinder with a piston chamber having a measuring piston
1 slidable therein. The stroke of the piston may be controlled by
an adjusting device 4. During movement of piston 1 toward each end
position, it engages with a compressible coil spring 3 to pretension
this coil spring and, thereafter, it engages against a stop 40.
Housing 2 also includes a cylindrical portion 5 defining a control
chamber in which a control slider 6 is movable. Slider 6 is provided
with annular grooves so as to define control surfaces which face
in respective opposite directions and which may be acted upon by
the fluid which is brought in through an inlet 10 to the housing
and circulated through the housing between the measuring chamber
and the control chamber and flow passage control means to an outlet
25. A permanent magnet 7 is associated with each end of the control
slider and it cooperates with a ferromagnetic armature plate 8 to
retain the slider in each end position of its movement until a fluid
pressure force acting on the control surfaces overcomes this retention
force and moves it rapidly in an opposite direction. The housing
portion 5 includes a tubular part 5a which accommodates a guard
tube contact 9 which may be actuated during the movement of the
control slider to the various reverse operating positions in order
to provide a counting or other control signal associated with operating
A liquid to be measured, such as gasoline, oil or a similar material,
flows from a pump, which has not been shown, through the inlet connection
10 into a bore 11 defined in the housing and, therefrom, it flows
through passageways or annular grooves 12 13 and 14 into a bore
15 as seen in FIG. 2 from where it passes through the channel
16 into the righthand chamber portion 22 of measuring cylinder 2.
In consequence, piston 1 is driven to the lefthand side. The bores
and passageways 11 15 21 and 18 are offset relative to each other
by about 90.degree.. During the motion of piston 1 to the left side,
the liquid to be measured flows from the left cylinder chamber 23
through passages 34 18 19 33 20 and 21 to the outlet 25. All
of these passages and control grooves define flow control passage
means in the housing.
At the end of the travel of the measuring piston to the lefthand
side, it will engage the left spring 3 and tension the spring and
compress it until it abuts against the stop 40. This causes a back
pressure in chamber 22 which increases, at first gradually, and
then suddenly. The back pressure becomes effective also in channel
17 where it acts on the left end face of the control slider 6 in
a direction opposite to the retaining force which is effective between
the left magnet 7 and the associated armature plate 8. As soon as
the back pressure exceeds the retaining force of the magnet 7 slider
6 is torn loose and moved in the direction of its opposite end position.
During this travel, the control slider 6 shuts off the communication
between groove 13 and channel 14 on the one hand, and outlet passages
33 20 on the other hand.
The left spring 3 pushes measuring piston 1 to the right while
the control slider 6 is also further pushed to its righthand end
position hydraulically. The slider is again retained magnetically.
The supply to and the discharge from the cylinder chambers is open
again and a new supply is directed through passages 10 11 12
13 30 18 and 34 into chamber 23 and the back pressure builds
up at 31. The discharge follows the path from chamber 22 through
16 15 14 33 20 and 21 to the outlet 25. As soon as the measuring
piston 1 reaches its righthand end position, the cycle of increasing
the spring tension and the hydraulic pressure in the flow passage
control means is repeated to effect a tearing loose of the magnetic
connection and reversal of the control slider once again. The stroke
of measuring piston 1 is adjusted very accurately by the adjusting
means including the setscrew 4.
Left hand permanent magnet 7 may have, in addition, another function,
that is, it may be used for actuating a counter contact. For this
purpose, the guard tube contact 9 is provided which projects through
left hand magnet 7 into the interior of control slider 6 so that
each time the magnet moves past the contact, the contact is actuated.
The number of contact actuations is an exact measure, therefore,
of the liquid volume which has passed through the measuring cylinder.
Should it be desired to measure partial quantities of the stroke
volume of the piston, index cards, contacts, passages for light
paths, pulse transmitters or the like may be provided in the stroke
path of the measuring piston, such as the light passages 28 which
are defined in the cylinder 2 along the length of piston 1.
The measuring piston may also be designed as a diaphragm piston.
In such a case, the diaphragm divides the piston cylinder into two
chambers and its deflection from the central position acts in the
same manner as the reciprocating piston.
In the embodiment shown in FIG. 3 there is a closed housing 102
and a piston 101 is mounted for reciprocating motion within the
housing. In this embodiment, the righthand end of the piston 101
is sealed off relative to the housing by a means of a diaphragm
or bellows 150. Diaphragm 150 is held in position by means of an
apertured disc 151 by which a portion of the diaphram is clamped
into a support 152. Diaphragm 150 extends up to a circular groove
type control slider 106 to which the diaphragm is secured at the
side remote from piston 101 and disc 151. The lefthand pressure
chamber of piston 101 is limited by housing 102.
In the indicated position, the fluid flows into housing 102 at
inlet 110 and it passes into a circular channel 153 and into a groove
154 of slider 106 and it flows to the inside space 155 of the housing
and into bores 156 and 157 as well as into the space 158 where the
fluid acts on a lefthand surface of the piston 101 and moves the
piston to the right until piston 101 abuts, first by a spring 103
and then, by a stop surface 140 against the disc 151 which is firmly
positioned in the housing. The fluid present in the righthand pressure
chamber of piston 101 passes through apertured disc 151 and bores
159 and 160 into grooves 161 and 162 and, therefrom, through a bore
125 to the outside of the housing 102 where it is delivered to a
location of use.
As soon as piston 101 reaches the right hand end of its stroke
and cannot move any further, the fluid pressure increases and the
differential pressure acts on the front surface 163 of the slider
106 and urges the slider to the left. At the same time, the fluid
pressure acts on a circular surface 164 in the same direction. Initially,
however, the slider is still retained by a permanent magnet 107
until the pressure in space 155 increases to the desired value and
tears the slider loose and moves it to the left.
Consequently slider 106 is moved to the left and, thereby reversed,
so that now the fluid can act through passages 110 153 154 160
and 159 on the righthand surface of the piston. There is no creeping
transition at the reversal and the piston is torn loose and immediately
moves quickly in the new direction which is thus to the left until
it abuts against a spring 173 and then, by its surface 174 against
a fixed surface 175. A spring 103 which has been tensioned while
butting against disc 151 accelerates the motion of the piston 101.
The fluid present in the pressure chamber at the righthand side
of the piston passes through circular slot 176 into the grooves
161 and 162 and, therefrom, through bore 125 to the outside. The
pressure in spaces 155 and 158 drops. As soon as piston 101 attains
the left hand end of its stroke, the pressure increases in the space
enclosed by the diaphragm. Slider 106 is moved to the right and
reverses the flow of the fluid and the position shown in the drawing
is restored once again and a new operational cycle starts.
A permanent magnet 177 retains the slider 106 initially again in
its left hand end position until the desired pressure is attained
so that, similar to the first embodiment, a sudden reversal is obtained,
while any creeping transition is eliminated. In this embodiment,
the stroke of piston 101 can be very accurately adjusted by means
of a screw 104 comprising stop surface 175. Screw 104 accommodates
a switch 109 which is connected to a counter (not shown) by which
the number of strokes is counted and, thereby, the rate of flow
of the fluid is measured.
While specific embodiments of the invention have been shown and
described in detail to illustrate the application of the principles
of the invention, it will be understood that the invention may be
embodied otherwise without departing from such principles.