AU2012202487A1 - Pressure relief valve - Google Patents

Abstract

A dual plunger valve having nested inner and outer plungers seated within a bore in the valve housing. The valve housing has an inlet port and an outlet port fluidly connected by 5 the bore and sealed from one another by the plungers which are biased towards respective sealing surfaces by a pair of nested biasing elements located between the inlet port and the outlet port. The outer plunger is slidable within the bore and has a lip extending inwardly therefrom. The inner plunger is slidable within the outer plunger between a sealed position and a second position wherein it is in contact with the lip. Pressure in the inlet port which is 10 high enough to overcome the force of the biasing elements causes the inner plunger to slide within the outer plunger to its second position wherein the outer plunger will then begin to slide within the bore to remove the seal between the inlet port and the outlet port.

Description

AUSTRALIA Patents Act COMPLETE SPECIFICATION (ORIGINAL) Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Stackpole Limited Actual Inventor(s): Paul Morton, Eric Cozens Address for Service and Correspondence: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: PRESSURE RELIEF VALVE Our Ref: 940575 POF Code: 455565/486060 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- PRESSURE RELIEF VALVE The present application is a divisional application from Australian Patent Application No.2006279207, the entire disclosure of which is incorporated herein by reference. 5 FIELD OF THE INVENTION [0001] The present invention relates to pressure relief valves used in fluid systems. DESCRIPTION OF THE PRIOR ART 10 [0001A] A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission or a suggestion that that document or matter was, known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims. 15 [0001 B] Throughout the description and claims of the specification, the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps. [0002] Pressure relief valves used in fluid systems are generally one-way valves 20 designed to open at a specific pressure to prevent damage to the system. For example, a pressure relief valve is used in an engine's lubrication system to relieve excessive pressure that may develop in the oil pump as the engine speed increases or downstream of the pump if an unpredictable restriction occurs. 25 [0003] Pumps used in fluid systems are susceptible to contamination. In the case of an engine the contamination generally originates in the engine and may comprise particles of iron, aluminum, sand etc. Although filters and inlet screens are provided, the system is designed on the assumption that some particles of contaminate will reach the pump, which therefore are designed to pass the contaminates through the pump without issue. 30 [0004] A conventional relief valve has a seat in a bore with a valve member biased into engagement with the seat. There is a nominal clearance between the bore and the valve member to maintain a seal when the valve is closed. An effective seal is necessary to ensure priming of the pump as the engine starts, particularly where the pump is mounted in an 35 elevated position and flow past the valve is re-circulated to the inlet. If a contaminate particle becomes lodged between the valve member and the bore, the relief valve will become 1a wedged into an open position. With the relief valve wedged open, the pump will drain when the engine is switched off and may not prime when the engine is initially started. This can lead to premature failure of the engine. The tendency for particles to become wedged is particularly evident when the pressure drops in the pump and the valve is closing, i e when 5 the engine is shut down, and thereby exacerbates the problem. [0005] U.S. patent 4,953,588 to Sands discloses a check valve assembly in which a pair of poppet valves is arranged to act independently of one another to seal a line. The purpose of this assembly is to inhibit reverse flow if one of the poppets fails. The Sands 10 patent is directed to check valves where only a nominal resistance to flow is envisaged rather than relief at an elevated pressure. As such the independent operation of the valves is of primary concern rather than the pressure/flow characteristics of a relief valve. If used as a relief valve, the independent nature of each of the valves would require each to function as a separate relief valve in series, causing significant difficulties in matching their operation to 15 regulate the pressure accurately. [0006] It would therefore be desirable to obviate or mitigate the above mentioned disadvantages. 20 SUMMARY OF THE INVENTION [0007] According to one aspect of the present invention, there is provided a valve for use in fluid systems including: (a) a housing, said housing having an inlet port, an outlet port, a bore fluidly connecting said inlet port to said outlet port; 25 (b) an inner sealing surface and an outer sealing surface at spaced locations between said inlet port and said outlet port; (c) an outer sealing member slidably located within said bore and having a sealing face biased into engagement with said outer sealing surface by an outer biasing element and a circumferential sealing surface that engages a portion of 30 the wall of said bore extending axially between said inlet and said outlet; and (d) an inner sealing member located within said outer sealing member and being sealingly engaged with said inner sealing surface by an inner biasing element; wherein said outer sealing member is moveable to an open position in which fluid flows between said inlet port and said outlet port; and 35 wherein said outer sealing surface is inclined with respect to the wall of said bore. 2 BRIEF DESCRIPTION OF THE DRAWINGS [0008] An embodiment of the invention will now be described by way of example only with reference made to the appended drawings wherein: [0009] Figure 1 is a schematic representation of a hydraulic pump with a pressure 5 relief valve. [0010] Figure 2 is a cross sectional view of the valve of Figure 1 along line II-II. [0011] Figure 3 is a series of views showing the operation of the valve of Figure 2 under different conditions. 2a 1 [00121 Figure 4 is a cross sectional view of an alternative embodiment of valve to that 2 shown in figure 2. 3 DETAILED DESCRIPTION OF THE INVENTION 4 100131 Referring therefore to Figures 1 and 2, an oil supply for an engine includes a 5 pump P having a vaned impeller V driven by the engine and rotating within a pump housing 6 H. Oil is drawn in to the housing H by an inlet I and delivered to a supply port S. A bypass 7 path B is provided between the supply port S and inlet I to permit oil to be re-circulated from 8 the supply port S to the inlet I. Flow through the bypass path B is controlled by a valve 10 9 which opens to permit flow when the pressure in the supply port S exceeds a predetermined 10 value and closes when the pressure of oil drops below that value. In many installations, the 11 pump P is mounted at an elevated location on the engine and draws oil through the inlet I into 12 the housing H from the sump below the engine. 13 [0014] Valve 10 generally comprises a valve housing 12 with an inlet pressure port 14 14 connected to the supply port S and an exhaust port 16 connected to the bypass path B. The 15 inlet port 14 and exhaust port 16 are axially spaced along a stepped bore 17. 16 (0015] The stepped bore 17 extends within the valve housing 1:2 from the inlet port 14 17 past the outlet port 16 to a recess 31 in the housing 12. A pair of radial seats 24, 28 are 18 formed in the bore 17 separated by an inner circumferential sealing surface 32. The radial 19 seat 24 is positioned adjacent the inlet port 14 and extends between the port and the inner 20 sealing surface 32. The radial seat 28 extends between the inner sealing surface 32 and an 21 outer circumferential sealing surface 34 defining a major extent of the bore 17 and which is 22 intersected by the exhaust port 16. A retainer provided by a retaining disc 30 and secured by a 23 pin (or other means), is located in the recess 31. 24 100161 An inner sealing member or plunger 18 and an outer sealing member or plunger 25 20 are nested within the bore 17 and are biased towards the inlet port 14 by respective inner 26 and outer springs 22, 26. The outer plunger 20 is formed as a cylindrical sleeve with a 27 sealing face 29 at one end and a radial lip 21 at the opposite end. The sealing face 29 is 28 biased into engagement with the outer radial sealing surface 28 by the outer spring 26 which 29 acts between the lip 21 and the retaining disc 30. The outer plunger 20 is sized to provide a 30 close sliding fit within the bore 17 between the radial face 29 and the outlet 16. This -3- I maintains a seal between its outer surface 23 and the outer circumferential sealing surface 34 2 whilst it slides within the bore 17 and thus provides a pair of separate sealing bands, one 3 radial and one circumferential (extending axially along bore), between the plunger 20 and 4 bore 17. 5 [0017] The inner plunger 18 is formed as a "cup shaped" member with a sealing face 25 6 at one end opposed to the inner sealing face 24 in the bore 17. The plunger 18 also is a close 7 sliding fit within the inner circumferential sealing surface 32 to provide seal between the 8 plunger 18 and bore 17. The sealing face 25 is biased into engagement with the inner radial 9 seat 24 by the inner spring 22 which is seated between the interior of the plunger 18 and the 10 retainer 30 and nested within the outer spring 26. The inner plunger 18 is a sliding fit within II the outer plunger 20 to maintain a seal between the two plungers 18, 20 over the axial extent 12 of their sliding engagement. The rear end of the inner plunger 18 abuts the lip 21 to limit 13 relative movement between the plungers 18, 20. The relationship between the plungers 18, 14 20 also helps to protect the spring 22 from hitting solid height or experiencing premature 15 fatigue failure. 16 [00181 The position shown in Figure 2 illustrates the valve under normal operating 17 conditions wherein the pressure of the fluid in the inlet port 14 is at or below the maximum 18 desired operating pressure of the particular component utilizing the valve 10. In this position, 19 a seal is provided between the plunger 18 and both the radial face 24 and circumferential seal 20 32 and a further pair of seals between the plunger 20 and the radial face 28 and 21 circumferential seal 34. In addition a sliding seal is provided between the plungers 18, 20. 22 100191 As the pressure in the inlet port 14 rises, the force imparted on the sealing face 25 23 will cause the inner plunger 18 to compress the inner spring 22 and begin to slide within the 24 outer plunger 20. During this movement, a seal is maintained between the plunger 18 and the 25 circumferential face 32. The biasing force of the inner spring 22 is chosen to respond to 26 changes in pressure such that at a predetermined value, below the crack or opening pressure, 27 it will have overcome the biasing force imparted by the inner spring 22 on the inner plunger 28 18 which then abuts the lip 21. -4- 1 100201 Upon abutment of the plunger 18 with the lip 21, further increase in the pressure 2 causes a corresponding conjoint movement of the plungers 18, 21 against the bias of both 3 springs 22, 26 with the pressure acting on the entire face of both plungers. 4 100211 A seal is maintained between the inlet port 14 and the exhaust port 16 until the 5 sealing face 29 of the outer plunger 20 uncovers the exhaust port 16. Upon exposure of the 6 port 16, fluid present in the inlet port 14 may pass through the exhaust port 16 to maintain 7 pressure in the supply port S at a predetermined value. 8 100221 It will be appreciated that the outer plunger 20 may also be designed to move 9 without requiring the inner plunger 18 to engage the lip 21. For eKample, the sealing face 29 10 may be designed to be partially exposed such that a predetermined pressure (and 11 corresponding spring) will also move the outer plunger 20. 12 [00231 The plungers 18, 20 will regain the position seen in Figure 2 when the pressure in 13 the inlet port 14 falls below the maximum desired pressure. The biasing forces imparted by 14 the springs 22, 26 will cause the plungers 18, 20 to slide back into position when these forces 15 are able to overcome the force imparted on the sealing faces 25, 29 by the fluid pressure in 16 the inlet port 14. Initially the inner and outer plungers 18, 20 move in unison until the outer 17 plunger 20 engages the radial face 29. Thereafter, the inner plunger 18 extends from the 18 outer plunger 20 until the end face 25 seats against the seat 24. It will be noted that the 19 plungers 18, 20 act in unison against a common bias during opening, thereby facilitating 20 control of relief pressure. 21 100241 As noted above, the oil in the sump of the engine may carry contaminants that 22 interfere with the normal operation of the valve. If the valve 10 is lodged in an open position, 23 a direct connection between the supply port s and inlet port 1 is provided that inhibits the 24 priming of the pump when the engine is restarted, The provision of the multiple sealing 25 surfaces and the independent operation of the plungers mitigates the impact on the operation 26 of the valve and permits priming of the pump in all but the most extreme situations. 27 100251 As shown in Figure 3a, contaminant 44 may become lodged between the plungers 28 18, 20 to inhibit relative sliding movement. If the inner plunger 18 is held within the plunger 29 20, the outer plunger 20 is operable to move to a closed position with a seal on the radial face -5 - 1 28 and circumferential seal 34. Thus an effective seal is provided that allows rejoining of the 2 pump. Moreover, the valve 10 will continue functioning to relieve pressure. 3 100261 If the plunger 18 is wedged so that it partially extends from the plunger 20, an 4 additional seal is provided between the plunger 18 and circumferential face 32. 5 100271 Alternatively, the plunger 18 may be wedged whilst partially extended as shown 6 in Figure 3b. In that position, the plunger 18 will seat against radial face 24 and seal against 7 inner circumferential seal 32 although the outer plunger 20 is held away from its sealing 8 position. The valve is therefore operable to seal the pump cavity and re-prime the pump. 9 (00281 Typically, the wedging by the contaminant is a transient condition and is freed at 10 the next operation of the pump by flow of fluid under pressure. 11 [0029] Contaminants may also become lodged against the radial seats 24, 28 as illustrated 12 in Figures 3c and 3d respectively. The independent movement of the plungers 18, 20 permits 13 an effective seal to be obtained to provide priming. Where the contaminant to present against 14 the radial seat 24, as shown in figure 3c a seal will be established on the circumferential wells 15 32, 34 and the radial seat 28. 16 [00301 Similarly, where a contaminant is present on the radial seat 28, a seal will be 17 established at the circumferential walls 32, 34 and the radial seat 24. 18 [00311 In both cases the pump will be able to re-prime and the valve will function as a 19 relief valve upon restarting of the pump. 20 [00321 A further potential failure made is shown in Figure 3e where contaminant is 21 lodged at the outlet 16 and prevents the outer plunger 20 from reseating. In this condition, 22 the inner plunger is free to move to a sealing position under the bias of the spring so that a 23 seal is established at the radial face 24 and the circumferential seal 32. Again therefore, 24 repriming of the pump is facilitated and pressure can be built up in the hydraulic circuit once 25 the pump is re-primed. 26 100331 Should one of the springs fail, the independent operation of the plunger will again 27 ensure effective sealing and continued operation under the influence of the remaining spring. -6- 1 100341 Accordingly, it can be seen that a redundancy is integrated in the valve to 2 accommodate potential failure modes. 3 100351 A further embodiment of the valve 10 is shown in Figure 4 where like reference 4 numerals will be used to denote like components with a suffix a added for clarity. In the 5 embodiment of figure 4, the outer plunger 20a is modified to provide a pair of part spherical 6 seats 50, 52 at axially spaced locations within the plunger 20a. A cross port 54 is provide in 7 the plunger 22a between the seats 50, 52. the cross port 54 is located on the plunger 22a such 8 that it is not aligned with the exhaust port 16a when the plunger 22a is against the seat 24a 9 but will be moved in to alignment as the plunger 22a slides away from the seat 24a. 10 100361 Inner plunger 18 is replaced with a ball 56 of a diameter corresponding to the 11 diameter of the seats 50, 52. A spring 22a acts against the ball 56 to hold it against the seat 50 12 and inhibit flow from the supply port S to the inlet I. When the pressure in the supply port S 13 exceeds the bias of spring 22a, the ball 56 is moved towards the seat 52, and, as the pressure 14 increases, the entire face of the plunger 20a and ball 56 is subjected to hydraulic pressure. 15 The plunger 20a acts against the bias of the spring 26a and moves axially within bore 17a 16 until the cross port 54 is aligned with exhaust port 16a. Re-circulating flow can then occur 17 through the seat 50 and the cross port 54, If the pressure drops, th-e ball 54 is held against the 18 seat 52 until the plunger 22a has again closed the exhaust port 16a, and, as the pressure 19 continues to drop, the ball 54 will be moved in to engagement with the seat 50. 20 100371 It will be apparent that if the ball 54 is held off the seat 50 due to contaminants, 21 the outer plunger 22a will again provide a seal at the radial seat 24a and the circumferential 22 seal 34a to permit re-priming of the pump P. If the plunger 22a is held open, the ball 54 will 23 seat against the seat 50 and close the flow path through the seat 50 to the exhaust port 16a. 24 Again therefore redundancy is provided to mitigate the potential for the valve 10 to be held in 25 an open position and inhibit re-priming of the pump P. Although the two "cracking" 26 pressures, namely for the ball 54 and plunger 22a, are typically different, this would still 27 protect the engine from a "no prime" condition. 28 10038] If a chip or contaminate particle becomes stuck between the ball 54 and the face 29 of the plunger 22a, the ball 54 will re-align itself and still provide a partial circumferential 30 seal. This will aid in engine priming since the leak path is smaller. -7- 1 [00391 The ball 54 also provides the advantage of a smoother flow path as fluid passes 2 over the face of the ball 54 and exits the valve 10. This encourages contaminate particles to 3 exit the system. 4 100401 Although the invention has been described with reference to certain specific 5 embodiments, various modifications thereof will be apparent to those skilled in the art 6 without departing from the spirit and scope of the invention as outlined in the claims 7 appended hereto. -B8-

Claims (12)

1. A valve for use in fluid systems including: (a) a housing, said housing having an inlet port, an outlet port, a bore fluidly 5 connecting said inlet port to said outlet port; (b) an inner sealing surface and an outer sealing surface at spaced locations between said inlet port and said outlet port; (c) an outer sealing member slidably located within said bore and having a sealing face biased into engagement with said outer sealing surface by an outer 10 biasing element and a circumferential sealing surface that engages a portion of the wall of said bore extending axially between said inlet and said outlet; and (d) an inner sealing member located within said outer sealing member and being sealingly engaged with said inner sealing surface by an inner biasing element; wherein said outer sealing member is moveable to an open position in which fluid 15 flows between said inlet port and said outlet port; and wherein said outer sealing surface is inclined with respect to the wall of said bore.

2. A valve according to claim 1 wherein said inner sealing member includes a ball and said inner sealing surface is provided by said outer sealing member whereby said ball is 20 slidable within said outer sealing member between said abutment and said inner sealing surface.

3. A valve according to any one of the preceding claims wherein said biasing elements are springs. 25

4. A valve according to claim 3 wherein said springs are nested.

5. A valve according to any one of the preceding claims wherein said outer sealing member includes an opening separating said circumferential sealing surface and said outer 30 sealing surface for aligning with said outlet in said open position.

6. A valve according to any one of the preceding claims, said outer sealing member having an open end for receiving said inner sealing member, said inner sealing member including a closed end for sealing said inlet, said bore being stepped inwardly toward said 35 inlet to provide said outer sealing surface and to provide an inner bore extending between 9 said outer sealing surface and said inlet for receiving a portion of said inner sealing member to engage said inner sealing member.

7. A valve according to claim 6 wherein said inner sealing surface is inclined with respect to said inner bore. 5

8. A valve according to claim 6 or 7 wherein during said conjoint movement, said outer sealing member slides away from said inlet to provide said open position upon said outer sealing surface aligning with said outlet. 10

9. A valve according to claim 6, 7 or 8 wherein said sealing members and said biasing elements are arranged concentrically within said bore.

10. A valve according to any one of the preceding claims wherein said valve provides pressure relief to an oil pump in an engine lubrication system. 15

11. A valve according to any one of the preceding claims further including an abutment between said inner sealing member and said outer sealing member to limit relative movement therebetween and to cause conjoint movement of said plungers to said open position. 20

12. A valve according to any preceding claim, substantially as herein described and illustrated. 10