GB1588726A

GB1588726A - Flow regulator

Info

Publication number: GB1588726A
Application number: GB3031677A
Authority: GB
Original assignee: Gould Inc
Current assignee: Gould Inc
Priority date: 1977-07-19
Filing date: 1977-07-19
Publication date: 1981-04-29
Also published as: FR2400230A1

Description

(54) FLOW REGULATOR (71) We, GOULD INC., a corporation organized and existing under the laws of the State of Delaware, United States of America, of 10 Gould Centre, Rolling Meadows, Illinois, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to flow regulators.

In the operation of fluid controlled devices it is desirable to have a fluid system which can cope with rapid movement of a load whilst keeping to a minimum undesirable effects such as chattering, overshooting and variable travel rate. One application where fluid controlled devices are of particular importance is for lifting mechanisms, for example in forklift trucks, where the load weight may vary considerably which aggravates the undesirable effects. In such devices pressures may vary for example over the range of approximately 0 to 4000 p.s.i. drop in the regulating system. Further aggravation of the control problem may also be caused by oscillations in the pressure which may occur typically with a frequency of two oscillations per second.

Flow regulators have been designed which utilise a fixed orifice to damp the oscillations, however, with a fixed orifice the flow rate varies with load, which presents a serious problem in the accurate control of the load in applications such as a fork-lift truck. Fixed orifice flow regulators permit damped oscillations which may have original substantial excursions causing a chattering effect. A more serious chattering problem is encountered however in known piston-type flow regulators where the pressure variation excursions may continue for a substantial period of time.

The present invention utilises a piston and is directed towards providing a flow regulator which may overcome these disadvantages and may therefore be suitable for use in fluid systems having a wide range of pressure changes.

Accordingly the invention provides a flow regulator comprising a biased piston which has a sensing orifice at its proximal end to the flow inlet and which is positionally responsive to the pressure drop over the sensing orifice to thereby control the flow passage to the outlet, and a perforate stabiliser element disposed between the inlet and the piston which has each perforation off-set relative to the sensing orifice so that when fluid flows from the inlet to the sensing orifice it is laterally diverted by the stabiliser element.

This stabiliser element may enable the sensing orifice to be more sensitive to pressure changes and thereby may enable more sensitive and accurate control of the hydraulic fluid.

The stabiliser element may minimise the effect of the viscosity of the fluid on the operation of the sensing orifice, as the single relatively large opening of the sensing orifice may function in the manner of a knife edge opening and may provide improved distribution of pressure on the piston face for improved flow regulation. Selection of the flow rate may be achieved by changing the stabiliser element, which may be removably disposed in the regulator.

Preferably the flow regulator also comprises two dashpots which damp movement of the piston caused by changes in fluid pressure across the sensing orifice. The dashpots may be arranged coaxially in series, a first one of the dashpots retarding the movement of the piston from an outermost position to a preselected inward position and further inward movement of the piston may be retarded by either the second or both dashpots.

Preferably the piston is contained in a sleeve the piston and sleeve having corresponding apertures which can be aligned to an extent determined by the position of the piston. These overlapping apertures may comprise the flow passage from the inlet via the sensing orifice to the outlet and may be arranged to partially overlap at all times.

Low pressure conditions may occur between the piston and sleeve due to the venturi action at the outlet ports comprised by the overlapping apertures. The piston may therefore be provided with a radial port adj acent its distal end to the inlet which serves to substantially equalise the pressure of the fluid in the piston and in the adjacent clearance space between the sleeve and the piston.

The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 is a diametric section of a portion of a fork-lift truck hydraulic mechanism housing provided with a flow regulator embodying the invention; Figure 2 is a diametric section of the flow regulator of Figure 1; Figure 3 is an enlarged exploded elevation of the flow regulator shown in Figure 2; Figure 4 is an enlarged diametric section illustrating the arrangement of the flow regulator of Figures 1 to 3 with minimum pressure differential thereacross; Figure 5 is an enlarged diametric section illustrating the arrangement of the flow regulator of Figures 1 to 3 with maximum pressure differential thereacross; Figure 6 is a transverse section taken substantially along the line 6-6 of Figure 4;; Figure 7 is a transverse section taken substantially along the line 7-7 of Figure 4; Figure 8 is a transverse section taken substantially along the line 8-8 of Figure 4; Figure 9 is a transverse section taken substantially along the line 9-9 of Figure 4; Figure 10 is a transverse section taken substantially along the line 10-10 of Figure 4; Figure 11 is a graph illustrating the pressure variation upon a sudden change in the load conditions provided by the flow regulator of the present invention; Figure 12 is a graph illustrating the pressure variation upon a sudden change in the load conditions provided by a piston-type flow regulator of the prior art; Figure 13 is a graph illustrating the pressure variation upon a sudden change in the load conditions provided by a fixed orifice flow regulator of the prior art;; Figure 14 is an enlarged diametric section illustrating another embodiment of flow regulator with minimum pressure differential thereacross; Figure 15 is a transverse section taken substantially along the line 15-15 of Figure 14; Figure 16 is a transverse section taken substantially along the line 16-16 of Figure 14; Figure 17 is a graph illustrating the pressure variation upon sudden change in the load conditions provided by the flow regulator of Figure 14 without the spring means for biasing the check valve and the outlet aperture in the lower dashpot; and Figure 18 is a graph illustrating the pressure variation upon a sudden change in the load conditions provided by the flow regulator of Figure 14.

In the exemplary embodiment of the invention as disclosed in Figures 1-13 of the drawing, a flow regulator generally designated 10 is provided for regulating fluid flow in fluid systems having a wide range and sudden changes in fluid conditions thereof. In the illustrated embodiment, the flow regulator is installed in a housing 11 of a fork lift truck for controlling fluid flow between an inlet 12 and and outlet 13 thereof. Conventionally, the fluid utilized in such truck lifting mechanisms is hydraulic fluid and is subject to wide and sudden changes in pressure in the operation of the truck, such as in the range of from 0 to 4000 p.s.i., substantially instantaneously. The flow regulator may be received in a chamber 14 disposed intermediate the inlet 12 and outlet 13 and defines an inlet end portion 15 and an outlet end portion 16.

As best seen in Figure 3, the flow regulator includes a tubular shell 17 coaxially receiving a piston sleeve 18. The piston sleeve defines a closed inner end portion 19 and an open outer end portion 20.

A cup-shaped dashpot housing 21 is received in the inner end 19 of the piston sleeve 18 and slidably receives a cylindrical dashpot plunger 22 provided at its outer end with a head 23. The dashpot plunger is urged axially outwardly by a helical spring 24 extending between a spring retainer flange 25 on the inner end of the dashpot housing and the head 23 of the dashpot plunger.

A piston 26 is slidably received in the outer end 20 of the sleeve and is provided with an inner end 27 receiving a check valve body 28 in which is movably received a check valve disc 29.

The outer end 30 of the piston defines an axial sensing orifice 31 (Fig. 4). A stabilizing disc 32 is disposed outwardly of the piston end 30 for stabilizing flow of hydraulic fluid through sensing orifice 31. Disc 32 may comprise any one of a plurality of stabilizing disc elements having different flow capacities for selectively controlling the flow rate of the regulator.

A split retaining ring 33 may be provided for retaining the elements of the flow regulator within the shell 17 by the removable reception of the ring 33 in an annular groove 34 in the outer end 35 of the shell.

Piston 26 is provided adjacent inner end 27 with a plurality of radial ports 36 adapted to pass the hydraulic fluid outwardly through a corresponding plurality of ports 37 in piston sleeve 18 adjacent outer end 20. A plurality of small pressure relief ports 38 may be provided in piston sleeve 18 inwardly adjacent ports 37.

Inward movement of piston sleeve 18 through shell 17 is limited by a shoulder 39 at the inner end of piston sleeve portion 20 abutting an outwardly facing shoulder 40 at the inner end of shell portion 35.

Dashpot plunger head 23 may be provided with an axial passage 41 extending partially into plunger portion 22, as shown in Figure 4.

A plurality of radial ports 42 may be provided opening outwardly from passage 41 into dashpot chamber 43 defined by the inner end 19 of piston sleeve 18.

A plurality of pressure relief ports 44 may be provided in piston 26 inwardly of outer end 30, and a plurality of annular grooves 45 may be provided in the piston between outer end 30 and ports 36.

The piston defines an annular channel 46 through which ports 36 open. A groove 47 may be provided in the inner end 27 of the piston through which may open a plurality of radial pressure relief ports 48.

Stabilizing disc 32 defines an inwardly opening cylindrical axial recess 49 and a plurality of longitudinally opening ports 50 spaced concentrically about the center portion 51 of the disc. Thus, the stabilizing disc element effectively comprises a perforate disc having an annular turned flange 49a defining stop means for limiting the movement of the piston toward the inlet. As best seen in Figure 4, the radially inner portion of the ports 50 may be axially aligned with the outer edge 52 of the sensing orifice 31.

As further shown in Figure 4, the piston sleeve outer portion 20 further defines an inner annular radial shoulder 53 which, as shown in Figure 5, limits the inward movement of piston 26 by the abutment of outer end 30 therewith at the extreme innermost position of the piston in the piston sleeve.

Check valve body 28 is provided with an outer annular groove 54 and a plurality of radial ports 55 opening outwardly through an annular edge portion 56 thereof to a corresponding plurality of ports 48 of piston 26.

The operation of the flow regulator is extremely simple. Hydraulic fluid may flow inwardly through inlet end portion 15 of the regulator through the ports 50 of the stabilizing disc 32. The fluid then flows through the recess 49 generally radially and angularly inwardly to sensing orifice 31 and into the hollow interior 57 of the piston. Ports 44 equalize the pressure radially outwardly of the piston axially outwardly of shoulder 53.

The pressure differential acting across orifice 31 causes the piston to move in piston sleeve 18, thereby adjustably positioning the piston ports 36 relative to the piston sleeve ports 37 and maintaining a constant flow rate of the hydraulic fluid through the regulator.

The piston is biased outwardly by the coil spring 24 which acts against dashpot plunger head 23 and, in turn, against the inner end 27 of the piston. Thus, the piston is selectively adjusted by the joint action of the fluid pressure differential across the sensing orifice 31 and the force of spring 24.

The stabilizing disc 32 limits the outward movement of the piston by the engagement of the disc with retainer 33. Retainer 33 comprises a removable split retainer permitting the substitution of any one of a plurality of different stabilizing discs having different size ports 50 to provide any one of a different number of flow rates in the regulator, as desired.

As seen in Figure 2, the hydraulic fluid leaving port 37 may flow through the annular space 58 to the outlet end portion 16 of the flow regulator. The flow regulator may be retained in outlet end 13 of housing 11 by a removable retaining ring 59.

The operation- of flow regulator 10 is damped by a plurality of dashpot means. A first dashpot means generally designated 60 is defined by the dashpot housing 21 and dashpot plunger 22. As seen in Figure 4, inward movement of the piston urges the dashpot plunger head 23 downwardly to correspondingly urge the dashpot plunger 22 into the dashpot chamber 61 of the housing 21. As hydraulic fluid is contained in chamber 61, this downward movement is resisted by the fluid which may escape from chamber 61 solely through the clearance space 62 between plunger 22 and housing wall 63. The fluid escaping therefrom flows into chamber 43 and is conducted therefrom through ports 42 and dashpot passage 41 through a plurality of ports 64 in check valve body 28 to the piston chamber 57 for flow outwardly therefrom through ports 36 and 37.When the piston is moving downwardly, as seen in Figure 4, the check valve disc 29 is raised by the upwardly moving fluid escaping from chamber 43 to permit this flow to the outlet ports 36 and 37.

This action may continue until the piston moves downwardly to the position of Figure 5 wherein the ports 42 are fully received within the dashpot housing wall 63, whereupon flow of fluid outwardly from chamber 43 through ports 42 is substantially restricted. Further downward movement of the piston 26 is now primarily accommodated by the flow of fluid from chamber 43 through the clearance space 65 between dashpot head 23 and piston end 27, and piston sleeve 18, permitting this escaping fluid to be discharged through ports 36 and 37 to the discharge chamber 58. Concurrently, fluid in chamber 61 displaced by the continuing downward movement of the dashpot plunger 22 passes through the clearance space 62 to the ports 42 to be discharged through the check valve ports 64 to the outlet ports 36 and 37.

Thus, during this phase of the operation of the flow regulator, the entrapped fluid is discharged through two dashpot clearance spaces in parallel to the outlet ports. As indicated above, the downward movement of the piston is limited by the engagement of piston end 30 with shoulder 53 to limit the flow regulator to a maximum inward disposition, as shown in Figure 5. As seen therein, a small portion of the ports 36 remains overlying the inner portion of the ports 37 so that the outlet from piston chamber 57 remains open to the outlet of the flow regulator at all times.

The outward flow through ports 36 and 37 may tend to produce a low pressure condition thereat by the venturi action of the flowing hydraulic fluid. Such venturi action produces a decrease in the static pressure and, thus, would tend to provide a spurious retarding force on the piston if it were not for the provision of the vent ports 55 and 48 in the check valve body 28 and piston end 27, respectively. Thus, these ports provide fluid pressure to the clearance space 65 substantially equal to the fluid pressure in chamber 57, preventing the undesirable pressure drop caused by the flowing discharging fluid and assuring maximum accuracy in the flow regulation of the regulator.

Upon a reduction in the fluid pressure delivered to the regulator inlet 12, spring 24 urges the dashpot head 23 outwardly, urging dashpot plunger 22 outwardly in chamber 61 and moving piston 26 upwardly to cause ports 36 to more fully overlie ports 37 and thereby provide an effectively maintained constant flow rate to the outlet chamber 58.

During such outward movement of the piston, the check valve disc 29 is caused to seat on the dashpot head 23, thereby preventing fluid flow outwardly through passage 41 and requiring that all replenishment fluid in chamber 43 and chamber 61 be delivered from chamber 57 through the clearance space 65. Outward movement of the plunger 22 is controlled by the clearance space 62, thereby providing further control in the permissible outward movement of the piston by the spring 24 at this time.

The use of the two dashpots provides a fail-safe functioning affording improved safety in the use of the hydraulic system, thereby providing further advantage in the use of the improved flow regulator hereof.

As best seen in Figures 11, 12 and 13, the functioning of flow regulator 10 provides a relatively small transient condition upon a sudden change in the pressure from a maximum to a minimum condition and effectively damps the oscillations so as to provide an improved constant flow rate regulation of the hydraulic fluid flow. This functioning is seen in Figure 11 and may be compared with the functioning of a fixed orifice regulator, as shown in Figure 13, and the prior art pistontype flow regulator illustrated in Figure 12, not provided with the improved features of regulator 10.

In the illustrated embodiment of Figures 1-13, the radial clearance 62 may be in the range of approximately .0005" to .0010" and the radial clearance 65 may be in the range of .0015" to .00025". The outer diameter of the shell may be approximately .79" and the length thereof may be approximately 1.98".

The diameter of the ports 50 in stabilizing disc 32 may be approximately .187" with five such ports being provided therein centered approximately .204" from the center of the disc. The sensing orifice effective diameter may be approximately .275" for a flow rate of approximately 13 gallons per minute, .295" for a flow rate of approximately 15 gallons per minute, and .315" for a flow rate of approximately 17 gallons per minute. The outlet ports 36 may have a diameter of approximately .140" and the outlet ports 37 may be similar thereto.

Referring now to Figures 14-18, a modified form of flow regulator generally designated 110 is shown to be similar to flow regulator 10 but provided with a helical spring 166 received in a spring retainer housing 167 attached to check valve body 128.

Spring 166 biases the check valve disc 129 to the closed position closing dashpot passage 141.

Further, regulator 110 distinguishes from regulator 10 in being provided with a small discharge port 168 in the lower portion of dashpot housing wall 163. The lower end of the dashpot plunger 122 is provided with a radially outwardly opening annular groove 169 in which is received a sealing O-ring 170.

Thus, control of the movement of dashpot plunger 122 is effected by the permissible flow through port 168 rather than the clearance between the dashpot plunger and the dashpot housing wall 163. Other than for these differences in structure, flow regulator 110 is similar to and functions similarly to flow regulator 10. All elements of regulator 110 similar to elements of regulator 10 are identified by similar reference numerals except 100 higher.

The difference in the functioning of the flow regulator 110 from the similar structure without the biasing spring 166 and the modified fluid port means 168 is illustrated in Figure 17 wherein the pressure condition curve is shown for the unmodified regulator and in Figure 18 for the regulator 110. As can be seen, a substantially iniproved damping and smooth transition operation is obtained by the provision of the biasing spring 166 and flow control port 168, providing further improved operation of the flow regulator.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

The flow regulator described herein is also described in British Patent Application No.

8 004 357 (Serial No. 1 588 727) and in British Patent Application No. 8 004 358 (Serial No. 1 588 728) which were divided out of the present application.

WHAT WE CLAIM IS: 1. A flow regulator comprising a biased piston which has a sensing orifice at its proximal end to the flow inlet and which is positionally responsive to the pressure drop over the sensing orifice to thereby control the flow passage to the outlet, and a perforate stabiliser element disposed between the inlet and the piston which has each perforation off-set relative to the sensing orifice so that when fluid flows from the inlet to the sensing orifice it is laterally diverted by the stabiliser element.

2. A flow regulator according to claim 1 in which the sensing orifice is centrally disposed on said proximal end of the piston and the stabiliser element comprises a disc with a plurality of radially distributed perforations.

3. A flow regulator according to claim 1 or claim 2, in which the sensing orifice functions as a knife edge fluid flow control means.

4. A flow regulator according to any preceding claim, in which the stabiliser element diverts the flow radially inwardly.

5. A flow regulator according to any preceding claim, in which the proximal end surface of the piston is planar.

6. A flow regulator according to any preceding claim, in which the stabiliser element comprises a stop which limits the movement of the piston towards the flow inlet.

7. A flow regulator according to any preceding claim, in which the stop comprises an annular flange on the stabiliser element.

8. A flow regulator according to claim 2 in which the perforation of the stabiliser element overlies the periphery of the sensing orifice.

9. A flow regulator according to any preceding claim, in which the stabiliser element is interchangeable.

10. A flow regulator according to any preceding claim, further comprising two dashpots which damp movement of the piston caused by changes in fluid pressure across the sensing orifice.

11. A flow regulator according to claim 10 in which a first one of the dashpots retards the movement of the piston from an outermost position to a preselected inward position and further inward movement of the piston is retarded by either the second or both dashpots.

12. A flow regulator according to claim 10 or claim 11 in which the dashpots are disposed in series.

t3. A flow regulator according to any one of claims 10 to 12 in which a check valve is associated with the first dashpot which operates to restrict inward axial movement of the piston away from the inlet after a predetermined displacement.

14. A flow regulator according to claim 13 in which upon closure of the check valve further inward movement of the piston is controlled by the second dashpot.

15. A flow regulator according to claim 13 in which upon closure of the check valve further inward movement of the piston is controlled by both dashpots.

16. A flow regulator according to any one of claims 10 to 15 in which one dashpot is disposed within the other, the inner dashpot comprising a cup which receives a plunger which moves with the piston and there is a preselected radial clearance between the cup and the plunger through which fluid can restrictedly pass and damp movement of the piston.

17. A flow regulator according to claim 16 in which the outer dashpot comprises a cylindrical piston sleeve.

18. A flow regulator according to claim 17 in which the piston acts as a plunger for the outer dashpot.

19. A flow regulator according to claim 18 in which the piston and plunger of the inner dashpot are interconnected.

20. A flow regulator according to any of claims 16 to 19 in which the inner dashpot is the first dashpot and the outer dashpot is the second dashpot.

21. A flow regulator according to any of claims 16 to 20 in which the cup is provided with a small port which permits restricted flow of fluid into and out from the cup upon movement of the plunger.

22. A flow regulator according to any preceding claim in which the piston is contained in a sleeve, and the piston and sleeve have corresponding apertures which can be aligned to an extent determined by the position of the piston in response to the pressure drop across the sensing orifice, and the overlapping portions of these apertures comprise the flow passage from the sensing orifice to the outlet.

23. A flow regulator substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 11 or 14 to 18 of the accompanying drawings.

24. A hydraulic lifting mechanism including a flow regulator according to any preceding claim.

25. A fork-lift truck including a hydraulic lifting mechanism with a flow regulator according to any preceding claim.~

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. (Serial No. 1 588 728) which were divided out of the present application. WHAT WE CLAIM IS:

1. A flow regulator comprising a biased piston which has a sensing orifice at its proximal end to the flow inlet and which is positionally responsive to the pressure drop over the sensing orifice to thereby control the flow passage to the outlet, and a perforate stabiliser element disposed between the inlet and the piston which has each perforation off-set relative to the sensing orifice so that when fluid flows from the inlet to the sensing orifice it is laterally diverted by the stabiliser element.