Abstrict A flow meter comprises a housing defining a fluid inlet passage
and a fluid outlet passage; a piston defining a jacket surface and
a base surface is arranged in the housing for reciprocating movement
between the two passages; a biasing spring urges the piston into
a zero flow position in which the piston interrupts the communication
between the two passages; the base surface of the piston faces the
inlet passage so that the fluid flow displaces the piston into a
flow position; flow distributing means in the form of a partition
arranged in the outlet passage has a plurality of slots shaped for
adjusting the flow rate between the two passages according to the
variation of the spring bias of the moving piston; and an electrical
position detector coupled to the piston to generate an electrical
signal proportional to the displacement of the piston.
Claims What is claimed as new and desired to be protected by Letters Patent
is set forth in the appended claims:
1. In a flow meter, a combination comprising: a housing defining
a fluid inlet passage and a fluid outlet passage; a piston arranged
in said housing for reciprocating movement between said passages,
said piston defining a jacket surface, a base surface and a control
edge between the two surfaces, said control edge and said jacket
surface being arranged for controlling the opening of said passages
during the movement of the piston; spring means biasing said piston
into a zero flow position in which the piston closes the communication
between said passages; flow distributing means arranged between
the passages for adjusting the flow rate of the fluid in response
to the movement of said piston, and including a sleeve attached
to said piston and projecting into said fluid inlet passage, said
sleeve being provided with a plurality of slots for passing the
fluid from said inlet passage into said outlet passage; and an electrical
position detector coupled with the piston to generate an electrical
signal proportional to the displacement of the piston.
2. A combination as defined in claim 1 wherein the width of each
slot viewed in the opening direction of movement of said piston
is inversely proportional to the spring bias of said piston.
3. In a flow meter, a combination comprising: a housing defining
a fluid inlet passage and a fluid outlet passage; a piston arranged
in said housing for reciprocating movement between said passages,
said piston defining a jacket surface, a base surface and a control
edge between the two surfaces, said control edge and said jacket
surface being arranged for controlling the opening of said passages
during the movement of the piston; spring means biasing said piston
into a zero flow position in which the piston closes the communication
between said passages; and flow distributing means arranged between
the passages for adjusting the flow rate of the fluid in response
to the movement of said piston, and including a partition inserted
into said housing between said outlet passage and said piston and
defining a plurality of slots cooperating with a control edge of
said piston to adjust the communication between said inlet and outlet
passages, the variation of the width of each slot corresponding
to the following conditions:
(a) the ratio of the piston circumference to the width of a control
slot is larger or equal to 2;
(b) the ratio of the base surface of the piston acted upon by the
inlet pressure fluid to the maximum open cross section of the combined
control slots is larger or equal to 23;
(c) the spring constant of the spring urging the piston in closing
direction has such a value that the square root of the ratio of
the fluid inlet pressure at the maximum open position of the piston
of the inlet fluid pressure at the minimum open position of the
piston is equal or smaller than 1 2; and an electrical position
detector coupled with the piston to generate an electrical signal
proportional to the displacement of the piston.
4. In a flow meter, a combination comprising: a housing defining
a fluid inlet passage and a fluid outlet passage; a piston arranged
in said housing for reciprocating movement between said passages,
said piston defining a jacket surface, a base surface and a control
edge between the two surfaces, said control edge and said jacket
surface being arranged for controlling the opening of said passages
during the movement of the piston; spring means biasing said piston
into a zero flow position in which the piston closes the communication
between said passages; a universal joint member for coupling said
spring means to said piston; flow distributing means arranged between
the passages for adjusting the flow rate of the fluid in response
to the movement of said piston; and an elecrrical position detector
with the piston to generate an electrical signal proportional to
the displacement of the piston.
5. The combination as defined in claim 4 wherein said spring means
includes a spring supported on a spring rest coupled to the piston
by said universal joint.
6. A combination as defined in claim 4 wherein said piston has
a cylindrical recess, and means disposed in said recess for supporting
a coupling member for said electrical position detector.
7. A combination as defined in claim 6 wherein the position detector
is in the form of an electrical signal generator including an induction
coil and a movable core secured to the free end of said coupling
member.
8. A combination as defined in claim 4 wherein said housing further
includes an electromagnetically controlled pressure control valve
for controlling the fluid pressure in said inlet passage, the electromagnet
of said pressure control valve being energized by a nominal value
signal corresponding to a predetermined pressure difference in the
valve and the output signal from said position detector being applied
to the electromagnet of said valve to produce a difference signal
for controlling the operation of said electromagnet.
9. In a flow meter, a combination comprising
a housing defining fluid inlet and fluid outlet passages arranged
in said housing opposite each other, said housing further defining
a boring traversing said inlet and outlet passage and two opposite
control slots communicating with said boring;
a piston arranged in said housing for reciprocating movement between
said passages, said piston defining a jacket surface, a base surface
and a control edge between the two surfaces, said control edge and
said jacket surface being arranged for controlling the opening of
said passages during the movement of the piston, the latter having
an embossed central part closing said control slots; in a zero flow
position of the piston;
spring means including two springs acting in opposite directions
on said piston so as to hold the latter in said zero flow position
in which said piston closes the communication between said passages;
flow distributing means arranged between the passages for adjusting
the flow rate of the fluid in response to the movement of said piston;
and an electrical position detector coupled with the piston to generate
an electrical signal proportional to the displacement of the piston.
10. A combination as defined in claim 9 wherein a sleeve is attached
to said piston, said sleeve having a plurality of control slots
cooperating with a control edge defined between said boring and
said inlet and outlet passages.
Description BACKGROUND OF THE INVENTION
This invention relates generally to flow meters, and more specifically
it relates to a flow meter of the type where the pressure of inlet
fluid impinges in an opening direction against a movable member,
the position of which relative to a fixed point indicates the rate
of flow.
Conventional flow meters of this type consist of a conical tube
in which a suspended body is arranged for free movement. The conical
tube has to be installed perpendicularly whereby the instant position
of the suspended body is a measure of the rate of flow of the fluid.
The conical tube is made of a transparent material and is provided
with a scale for reading the vertical position of the suspended
body.
SUMMARY OF THE INVENTION
An object of this invention is to provide a flow meter that can
be installed in hydraulic devices in any desired position.
Another object of this invention is to provide a flow meter that
can be easily combined with and adjusted to different hydraulic
devices.
Still another object of this invention is to provide a flow meter
that can be readily calibrated.
In keeping with these objects, and others which will become apparent
hereafter, one feature of the invention resides, in a flow meter
having a suspended body impinged by the incoming fluid, in a combination
which comprises a housing defining a fluid inlet passage and a fluid
outlet passage, a piston arranged in the housing for reciprocating
movement between the two passages, the piston defining a jacket
surface and a base surface; a spring biasing the piston into a zero
flow position in which the base surface closes the inlet passage
and the jacket surface closes the outlet passage, and into a flow
position in which the control edge between the base surface and
the jacket surface opens the outlet passage; a partition having
a plurality of slots arranged in or insertable into the outlet passage
to regulate the communication between the two passages in response
to the position of the piston; and an electrical position detector
coupled to the piston to generate an electric signal proportional
to the displacement of the piston.
The flow controlling partition can be movably arranged within the
housing in connection with the piston or it can be fixedly arranged
in the outlet passage to cooperate with the jacket surface of the
piston.
In another modification, the piston can be profiled to define a
boss cooperating with the inlet passage, and at least one annular
recess between the base and the boss of the piston, the recess providing
a communication between the inlet passage and the outlet passage.
In this modification, counteracting tension springs urge the piston
in the zero flow position in which the boss is in alignment with
a control slot communicating with the inlet passage.
The novel features which are considered as characteristic for the
invention are set forth in particular in the appended claims. The
invention itself, however, both as to its instruction and its method
of operation, together with additional objects and advantages thereof,
will be best understood from the following description of specific
embodiments rendered in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a sectional view of an embodiment of the flow meter of
this invention having fixedly arranged flow control slots;
FIG. 2 is a sectional view of another embodiment of the flow meter
of this invention having movably arranged flow control slots;
FIG. 3 is a sectional view of still another embodiment of the flow
meter of this invention adapted for operation in either direction
of flow; and
FIG. 4 is a side view partly in section of a combination of the
flow meter of this invention with an electrically adjustable pressure
regulating valve.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring firstly to FIG. 1 a receptacle housing 1 defines a fluid
outlet passage 1a and, arranged at right angles thereto, a fluid
inlet passage 1b. Arranged in alignment with the inlet passage 1b
is a bore hole in which sleeve 2 is inserted. In the region of the
outlet passage 1a the sleeve 2 has two juxtaposed control slots
2a and 2b the combined widths of which are smaller or equal to half
the circumference of a piston 3 that is arranged for reciprocating
movement in the sleeve 2. In this manner the ratio of the piston
circumference to the total width of the control slots is equal or
larger than 2.
Piston 3 defines a base surface 3b and a jacket surface that in
the initial zero flow condition covers the outlet passage 1a. The
edge 3a of the base surface 3b determines during the movement of
the piston the effective opening of the slots 2a and 2b and therefore
the displacement of the piston 3 controls also the rate of flow
between the inlet passage 1b and the outlet passage 1a. As shown
in FIG. 1 piston 3 is urged by means of a pressure spring 14 into
the zero-flow position in which the jacket surface of the piston
fully closes the control slots 2a and 2b of the outlet passage 1a
and in which the base surface 3b abuts against projections 4 of
a stop ring 5. Ring 5 is held in position in the lower portion of
the sleeve 2 by means of a collet 6 having an exterior thread in
engagement with a corresponding interior thread in the sleeve 2
to urge the ring 5 against a stop flange 2d in the sleeve 2. Piston
3 on its other end has a cylindrical recess 3c the bottom of which
has a hub-like projection 3d with a threaded boring 3e for receiving
an end portion of a rod 8. The free end 8a of the rod 8 supports
an iron core 9 cooperating with a coil 10 as it will be explained
below, to form an inductive pick-up or detector of the movement
or position of the piston 3. The threaded portion of rod 8 is secured
in the projection 3d by means of a lock nut 11 and above the lock
nut is provided a spherical supporting member 12 that supports a
cap-shaped spring washer 13 upon which one end of spring 14 is seated.
The other end of the tension spring 14 rests on a supporting member
15 that is inserted into a boring 16a in a cover plate 17 covering
the receptacle housing 1. Due to the spherical shape of the supporting
surface for the spring washer 13 any misalignment of the pressure
spring 14 can be minimized and consequently the hysteresis effect
of the spring can also be held at minimum. The cylindrical recess
3c of the piston 3 communicates via a radial boring 3f with an annular
groove 3g provided in the jacket surface 3h of the piston. The annular
groove 3g is, via an oblique boring 2d' through the insert sleeve
2 in communication with an annular space 19 in the range of the
control slots 2a and 2b and with the outlet passage 1a in the receptacle
housing 1. Consequently, the cylindrical recess 3c of piston 3 as
well as the guiding space 20 for the piston 3 is under the influence
of the outlet fluid pressure passing through the passages 1b and
1a. In this manner the piston 3 in addition to the force of the
pressure spring 14 is also acted upon in the closing direction by
the pressure of the fluid.
The guide space 20 for the piston 3 is closed from the outside
by cover plate 17 and cap 22 passing through the boring 16a in the
cover plate. The cap 22 acts at the same time as a support for coil
10 and its hollow interior accommodates the end of the rod 8 together
with the iron core 9 that is movable within the range of coil 10.
A threaded collar 23 holds the cap 22 in position in the cover plate
17 and the whole assembly forms an electrical pick-up unit for detecting
the movement of the piston. The pressure spring 14 has preferably
such a characteristic line that the square root of the ratio of
fluid pressure against piston 3 when the latter is in its uppermost
position rendering the outlet passage 1a fully open, to the fluid
pressure in the low position of the piston when the edge 3a has
just permitted the flow, is equal or smaller than 12. Moreover,
the ratio of the base surface 3b of the piston 3 that is acted upon
by the flowing fluid to the maximum combined opening area of both
control slots is larger or equal to 23. If these two conditions
as well as the previously mentioned condition according to which
the ratio of the piston circumference to the total width of the
control slits is equal or larger than 2 are fulfilled, the width
of the control slots over their entire length can be held constant
without necessity of modifying the measured values in the flow rate
of the fluid. In the case when the aforementioned conditions are
not fulfilled, the width of the control slots, viewed in the opening
direction of movement of the piston, has to be gradually reduced
in response to the changing pressure difference between the inlet
fluid pressure and the outlet fluid pressure and also in response
to the increasing force of spring 14 when the piston is being displaced
into its opening position. The accurate width variation of each
control slot can be computed from the following equation: ##EQU1##
wherein: b=the width of a control slot [cm]
x=the effective length of the slot measured from the base edge
of the piston
f.sub.1 =the bias of the pressure spring [cm]
c=spring constant [Kp/cm]
.rho.=the density [Kg/dm.sup.3 ]
.alpha.=the rate of contraction or throughflow
D=the diameter of the piston [cm] ##EQU2##
Any opening position of the piston 3 is transferred via the rod
8 to the iron core 9 and the position of the core 9 causes a corresponding
change in the inductivity of the coil 10 resulting in an electrical
signal that is applied to an electrical indicator for indicating
the amount of flow whereby the electrical signal is in a linear
proportion to the movement of the piston in the opening or closing
direction.
The embodiment as shown in FIG. 2 differs from the embodiment according
to FIG. 1 only in the different arrangement of the control slots
200a and 200b and an additional control slot 200ab, arranged opposite
to another slot (not shown in the drawing). The slots are provided
in a cylindrical sleeve 3i that projects from the base of the piston
3. In this modification, the control edge 300a is formed by an edge
of the outlet passage in housing 1. A guide boring 200c is also
provided in the housing 1 for guiding the piston 3 so that an additional
sleeve insertable into the housing 1 is no longer necessary.
In the embodiment shown in FIG. 3 piston 3 has an embossed intermediate
part defining two control edges 3aa and 3ab spaced apart about the
distance of control slots 2a and 2b provided in the housing 1. In
a zero flow position, the jacket surface of the embossed part of
the piston 3 is held in alignment with the control slots 2a and
2b by means of two counteracting springs 114a and 114b. By this
arrangement the possibility arises that the flow meter according
to FIG. 3 is applicable for operation in either direction of flow
of the measured fluid. Of course, to measure the fluid flow in both
directions requires also a corresponding modification of the inductive
movement detector 9 and 10. In the position shown in FIG. 3 the
iron core 9 is situated approximately in the middle of the coil
10 and this position corresponds to the zero flow. In displacing
the core 9 in one direction, a position signal is generated whereas
the movement in opposite direction generates a negative electrical
signal. Consequently the sign of the electrical signal makes it
possible to determine the direction of flow. For example, if the
fluid flows through the flow meter from passage 50 in the direction
to passage 51 a base surface 54 of piston 3 is acted upon by the
incoming fluid via a bypass channel 58 and moves in the direction
of spring 114b. Due to the resulting movement of the piston 3 against
the force of spring 114b, the jacket surface of the embossed central
part of the piston 3 is displaced into the pressure space 55. As
a result, the control edge 3aa opens the control slots 2a and 2d
whereby the resulting cross section of the open area corresponds
to the rate of flow of the fluid. The fluid also flows through the
space 56 between the embossed central part of the piston and the
base part 54 into the outlet passage 51. The outgoing fluid in the
outlet passage 51 enters via a bypass channel 59 the pressure space
55 and acts against the base surface of the embossed central part
of the piston 3 and this pressure is added to the pressure of the
spring 114b in the closing direction of movement of the piston.
When the direction of flow is changed and the fluid streams through
the flow meter from the passage 51 in the direction to the passage
50 the fluid enters via the bypass channel 59 the pressure space
55 impinges against the base surface of the embossed central part
of the piston and moves the piston against the force of pressure
spring 114a in the direction of pressure space 60 whereby the displacement
corresponds to the rate of fluid flow. The control edge 3ab of the
embossed central part uncovers a proportionally large free opening
in the control slots 2a and 2b. The outgoing fluid in the passage
50 enters via a bypass channel 58 the pressure space 60 and impinges
against the base surface of the end section 54 of the piston 3 and
contributes to the pressure of spring 114a in the closing direction.
The incoming fluid or alternatively the outcoming fluid applied
into the interspace 56 between the embossed section of the piston
has no effect upon the movement of the piston because the annular
end surfaces 54a and 30 are equal and therefore no net force occurs
in the direction of pressure space 65. The embodiment as illustrated
in FIG. 3 can be modified according to FIG. 2 inasmuch as the piston
3 can be provided with a cylindrical sleeve having corresponding
control slots whereby the control edges 2c in the guide space 55
can cooperate with the cylindrical attachment sleeve to control
the size of effective openings through the control slots.
In FIG. 4 DM indicates a flow meter according to this invention
whereby a throttle or pressure control valve D is arranged in common
housing G in operative connection with the flow meter DM. The throttle
D is controlled by an electromagnet (not shown) that in turn is
controlled by the signal from the position detector of the flow
meter of this invention. A nominal value signal adjusts the throttle
D to a position corresponding to a predetermined pressure difference.
The actual signal received from the flow meter DM is compared to
the nominal signal for the control electromagnet of the throttle
D and the resulting difference signal is employed as a control signal
for the control electromagnet of the throttle D. In this manner,
a simple electrically controllable fluid stream regulator is created
which by virtue of avoiding the current balance of conventional
throttle regulators achieves an increased control speed as well
as a higher accuracy.
It will be understood that each of the elements described above,
or two or more together, may also find a useful application in other
types of constructions of flow meters differing from the types described
above.
While the invention has been illustrated and described as embodied
in a flow meter for use with induction type displacement detector,
it is not intended to be limited to the details shown, since various
modifications and structural changes may be made without departing
in any way from the spirit of the present invention.
|