AU746568B2 - Pressure control valve - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT oo o* Invention Title: PRESSURE CONTROL VALVE Applicant: GSA INDUSTRIES (AUST.) PTY LTD The following statement is a full description of this invention, including the best method of performing it known to me: 1 CAWNWORDSHAROANDREWOENERAKLCAP1ODOC PRESSURE CONTROL VALVE This invention relates to valves for controlling pressure in a fluid flow system. The invention has particular relevance to pressure limiting or reducing valves and it will be convenient to describe the invention with respect to that type of valve. However, it should be appreciated that the invention could have application to other kinds of valves and therefore the description which follows is not exhaustive of the application of the invention.

Pressure control valves can take a variety of forms and these are often of a highly complex nature. The complexity of such control valves is such as to demand a high level of manufacturing tolerance, in order to ensure that the valve. operates correctly under working conditions in which it may experience extremes of both pressure and temperature, and type of fluid which it is .ooooi required to control. The precise operation of control valves in these conditions S° 15 is necessary, because failure to correctly control fluid pressure could lead to machinery or equipment failure and potentially endanger lives as a result of that failure.

One known method of manufacturing a control valve combines casting and machining to produce the valve housing. The housing is first cast, following which various surfaces are machined, generally for the purpose of providing mating sections threaded or otherwise as necessary for connection purposes and to ensure a high grade surface finish at sections of the housing as required. The manufacture of control valves in this manner is both time consuming and expensive, however the necessity for such high tolerancing discussed above generally excludes the adoption of less complex techniques.

In one form of control valve, a piston is axially movable within a cylindrical housing, between an open position in which the inlet and outlet ends of the valve are in fluid communication, and a closed position in which that communication is closed. In this form of valve, a piston guide may be provided to axially guide the piston in the housing between the open and closed positions. Such a control valve is disclosed in Australian Patent No. 581536 and in Figure 1 of that patent, a support member 21 is provided and that C:%WINWORD\SHAROMANDREWVAODELETEP281OCAP.DOC r 3 includes a cylindrical cavity 24 within which an end portion 29 of a valve member 20 is suitably guided in an axial direction. In one form of that type of valve, the support member 21 is integrally connected to the inside wall of the valve housing by a pair of webs which are cast in the valve in that manner.

That integral connection fixedly positions the support member 21 to the housing and necessarily requires extremely accurate concentricity tolerances with respect to the axial movement of the valve member 20. Without such tolerancing, it has been found in practice that the piston may jam against axial movement within the piston guide if it is not axially aligned to the degree required and will thus compromise the operation and safety of the valve.

It is an object of the invention to provide a control valve of the foregoing kind which has relatively simplified construction and in particular, which requires a reduced level of concentricity tolerancing compared to known valves.

•According to the present invention there is provided a pressure control valve including a hollow body, two chambers formed within said body, two parts each of which communicates with a respective said chamber and through which fluid can move into and out of that chamber and through which fluid can move into and out of that chamber, an orifice within said body thorough which said chambers can communicate, a valve member mounted within said body for movement relative thereto towards and away from a position at which it closes said communication through said orifice, movement of said valve member being guided by guide means and said guide means being mounted within said body for movement laterally relative to the direction of movement of the valve member.

The aforedescribed lateral movement of the guide piston facilitates a reduced level of manufacturing tolerance for the control valve, as the level of concentricity tolerance required between the valve piston apd the piston guide is lowered. That is, the limited lateral movement of the piston guide facilitates self alignment of the guide with respect to the valve piston during assembly thereof so that minor alignment deviations between the piston guide and the valve piston can be accommodated by lateral movement of the piston guide without the valve becoming inoperational. The laterally movable piston guide CA\WINWORD\SHAROWNDREW\ODELETEP210CAP.DOC 4 can advantageously also accommodate minor lateral deviation which may occur in the axial travel of the valve piston by shifting laterally as required.

The piston guide is preferably located in one of the two adjacent chambers and is preferably mounted to the internal wall of the chamber in a laterally movable manner. That mounting might be facilitated in part by way of a shoulder provided in the internal wall of the chamber, which forms a mounting surface for mounting means, such as a flange, or a web or plurality of webs depending from the piston guide. Such a supporting surface can be arranged to restrain the piston guide against axial movement in at least one direction and can allow for sliding engagement with the relevant mounting means of the piston guide, so that the piston guide can move laterally by sliding against the supporting surface. The extent of lateral movement of the piston guide can be restrained to within a predetermined limit in any direction by having the mounting means abut the internal wall surface of the chamber, adjacent the S 15 shoulder, when the maximum lateral movement has occurred, or by other S. means as may be adopted.

The piston guide is preferably formed as an open-ended cup, which in cross-section includes an internal annular straight walled section for at least a ~portion of its axial extent from the open end. The inside surface of the cup along the straight walled section can form a sealing surface against which an end portion of the valve piston seals by appropriate sealing means. In operation of the valve, axial movement of the valve piston results in axial movement of that end portion relative to the piston guide and it is necessary to prevent the same movement from occurring in the piston guide. In the arrangement described, the piston guide is restrained against axial movement in the opening direction of valve piston, by the mounting means adopted, and is restrained, or substantially restrained from movement in the opposite direction by exposure to pressure in the other of the two chambers. That exposure can be facilitated by an opening in the valve piston that enables communication of pressure from that chamber to within the cup of the piston guide. Thus, under normal working conditions, movement of the piston guide is substantially or C.'IWINWORDZHARONVANDREMNODELETEXP2610CAP.DOC exclusively restricted to lateral movement relative to the axial movement of the valve piston.

A valve according to the invention can be manufactured with reduced effort and cost. Additionally, tests completed on prototype models have shown enhanced valve performance, by way of accuracy of pressure control and speed of valve response and this is thought to be due to reduced friction losses as a result of the arrangement of the laterally movable piston guide.

The invention further provides a pressure control valve including a hollow body, two chambers formed within said body, two parts each of which communicates with a respective said chamber and through which fluid can move into and out of that chamber and through which fluid can move into and out of that chamber, an orifice within said body through which said chambers can communicate, a valve member mounted within said body for movement relative thereto towards and away from a position at which it closes said communication through said orifice, said valve member being acted on by biasing means to urge it toward the open position, and by fluid pressure within one of said chambers to urge it toward the closed position, a passage permits fluid pressure in the other of said chambers to impinge on each of two oppositely facing sides of the valve member each said side faces generally in a respective one of the two directions of movement of said valve member and is arranged such that the area of each said side against which said pressure *°-*impinges is substantially the same when the valve member is in said communication closed portion and is different when the valve member is not in that position, the other said chamber is formed at least in part by the bore of a tubular barrel section, said orifice is located at one end of said barrel section, said spring is a coil compression spring which acts between said valve member and said body and which is arranged substantially coaxial with said barrel section, and at least part of said spring is located around said barrel section movement of said valve member being guided by guide means and said guide means being mounted within said body for movement laterally relative to the direction of movement of the valve member.

C:%WINWORMHARONkANDREWINODELETE\P2510CAP.DOC 6 The extent of available lateral movement is dependent on a variety of factors, such as the size of control valve and the amount of valve movement.

The attached drawings show an example embodiment of the invention included in an assembly of the foregoing kind. The particularity of those drawings and the associated description does not supersede the generality of the preceding broad description of the invention.

Figure 1 is a cross-sectional view of a valve according to a preferred embodiment of the invention. The valve 10 is a pressure control valve and includes an inlet port 11 and an outlet port 12. The designation of an inlet port and an outlet port is used for convenience and is not intended to be restrictive in relation to a particular construction or direction of fluid flow. The inlet and i outlet ports are in-line, although they could be arranged to have a different configuration as required in use. The valve 10 further includes a valve body 13, which is formed of an inlet part 14 and an outlet part 15. The outlet part 15 is of tubular form and is formed with connecting means 16 on an outer end surface thereof for releasably securing the outlet part 15 to the inlet part 14. The connecting means 16 may take any suitable form and conveniently may comprise a screw threaded connection.

The inlet part 14 includes a barrel portion 18 which defines an inner cylindrical surface 19 and an outer cylindrical surface 20. The inner surface 19 :includes abutment means in the form of a projection 21 which extends radially inwardly about the full cylindrical extent of that surface. The projection 21 forms an abutment surface 22 against which one end of a valve seat 23 abuts. The abutment means could alternatively be provided by a stepped portion of the inner surface 19, or by other means, such as a circlip ring. The valve seat 23 shown is cylindrical and is a friction fit within the barrel portion 18 against the inner surface 19, although other configurations and means to fit the valve seat can be adopted. Alternatively, the valve seat 23 could be formed as an integral part of the barrel portion 18 such as by casting or machining the relevant portion of the valve 10. The valve seat 23 is typically formed from a stainless steel, while the parts 14 and 15 are typically formed of brass, although each of CAWNWORD SHAROANDREWNODELETE)P2e1OCAP.fOC 7 valve seat and the respective inlet and outlet parts can be formed of other metals, or alternatively plastics or ceramics, or a combination thereof.

The valve seat 23 includes an annular seating ring 24 that has a leading face 25 for sealing engagement with a valve piston 26. The seating ring 24 extends radially outwardly from the inner surface 19 of the barrel portion 18 and is spaced axially from the barrel end 27 to create a gap 29 therebetween. An O-ring 28 is placed within the gap 29 for sealing purposes relative to the valve piston 26.

The valve piston 26 includes an annular ring portion 30 which is positioned between the outer surface 20 of the barrel end 27 and an inner surface 31 of the outlet part 15. A groove 32 is provided in the inner surface i 31, so that an O-ring 33 can be located therein. The O-rings 28 (as previously described) and 33 seal against the annular ring 30. The annular ring :includes an end face 34 which is acted on by biasing means, which in the form shown, is a coil spring 35 which is in compression. The spring 35 is located at one end within an annular slot 36 formed between the outer surface 20 of the barrel portion 18 and an inner surface 37 of the tubular section 17 and at the other end between the outer surface 20 and the inner surface 31 of the outlet part The valve piston 26 includes a base 38 which is connected to the :annular ring 30 by a plurality of webs which, in the cross-sectional view of Figure 1, are not shown. Gaps extend between adjacent webs to allow communication between a chamber 39 of the inlet part 14 and a chamber 40 of the outlet part 15 when the leading face 25 of the seating ring 24 is displaced from engagement with the valve piston 26. The base 38 includes a recess 41 into which is received an annular seating member 42 of resilient material. The resilient material could be a rubber compound or a syntheticrubber compound for example. The seating member 42 is sealingly engaged with the leading face 25 when fluid communication between the respective chambers 39 and is to be closed. The member 42 is maintained in the recess 41 by engagement with the head 43 of a plug 44a which is received within a bore 45 in the base 38. The stem 46 of the plug 44a is received within the bore 45 in a manner C:.\WINWORDSMAROVAANDREWNOOELETEP2e10CAP.DOC 8 which secures the plug therewithin and that may be as a result of an interference or friction fit within the bore. Alternatively, an adhesive could be used to secure the plug 44a within the bore 45, or a threaded or other type connection could be made. The bore 45 extends completely through the base 38 and a second plug 44b is secured in opposed relationship to the plug 44a.

The plug 44b also includes a head designated by the reference numeral 47 and the head 47 is stepped to define a gap to receive a sealing ring 48.

A piston guide 49 is seated within the outlet part 15 against a shoulder in the chamber 40. A perspective view of the piston guide 49 is illustrated in Figure 2 and that shows a central cup 51 and locating means in the form of four locating webs 52, which are arranged for seating on the shoulder 50. The piston guide 49 could equally take various other configurations of cup shape and locating means and is not restricted to the shape and form illustrated. The ooo°° S: piston guide 49 is straight walled for a substantial portion of its depth, so that the sealing ring 48 can seal against the inside surface 53 of the straight wall S"and the sleeve portion 54 of the valve piston 26 can move axially within the guide 49.

The piston guide 49 is located to be generally coaxial of the valve 10, but the radial extent of the webs 52 is such as to allow the piston guide 49 a limited amount of movement laterally of the central axis XX of the valve 10. The lateral movement is available in the valve shown, by sliding movement of the webs 52 against the shoulder 50. However, lateral movement of the piston guide 49 may be facilitated by other arrangements which provide for different mounting of the piston guide. The amount of lateral movement may be from a fraction of a millimeter, such as a tenth of a millimeter, to amounts such as several millimeters or more depending on the type of valve.

The valve as described above, operates in the following manner. For this, it will be assumed that the pressure to be controlled is the fluid pressure on the outlet side of the valve 10 and that the valve is in a stable condition, such that the valve seat 23 is in sealing engagement with the annular seating member 42, and there is no fluid communication between the respective chambers 39 and 40. Under those circumstances, the inlet fluid pressure acts C:%WINWORDSHAROMNANDREW0ODELETE281OCAP-DC 9 against the surfaces of the annular seating member 42 and the plug 44a which are exposed to pressure within the chamber 39 and that pressure also acts against the rear surface of the head 47 because the plugs 44a and 44b are centrally bored. The pressure acting against the respective surfaces just described is substantially equal so as not to cause axial movement of the valve piston 26, because the area over which the pressure acts is substantially the same. That is, the internal diameter of the seating ring 24 is substantially the same as the internal diameter of the straight-walled section of the piston guide 49 so that the surface area exposed to the inlet pressure is substantially the same.

The pressure existing in the outlet chamber 40 imports a closing force on the valve piston 26. That outlet pressure acts on the annular ring 30 so that the valve piston 26 is urged in a direction C toward the inlet port 11. That urging force acts against the spring 35 and the spring force can be chosen to have a S 15 particular value, to suit the pressure rating of the valve so that the valve can be caused to open or close at a given outlet pressure. When the outlet pressure falls below a certain level, the spring 35 pushes the valve piston 26 in a direction O so that sealing engagement between the annular seating member 42 and the leading face 25 of the valve seat 23 is interrupted and fluid communication between the chambers 39 and 40 commences through the o: gaps provided between the piston guide webs 52. The flange or web arrangement preferably provides no resistance to pressure flow through its mounting to the inside wall of the first chamber. The outlet pressure in the chamber 40 is consequently increased by the ingress of fluid under higher pressure from the chamber 39, until it reaches a level at which the annular ring is moved under the influence of that outlet pressure in the direction C so as to engage the leading face 25 against the annular seating member 42, so that fluid communication between the respective chambers 39 and 40 is interrupted and the valve is again closed.

The movement of the valve piston 26 in either of the direction C or O, results in sliding axial movement of the sleeve portion 54 within the piston guide 49. In prior art valves, the radial alignment of the piston guide 49 relative to the C:WMNWOROXSHARONANDREWWODELETEP2IOCAP.DOC valve piston 26 was critical, to ensure that the valve piston 26 did not jam during axial movement thereof. Thus, these components of the valve were required to be manufactured and assembled to extremely high levels of tolerances to ensure proper working of the valve. However, in a valve according to the invention, the level of tolerancing in relation to these components can be reduced by the adoption of an arrangement in which the piston guide 49 and the valve piston 26 become radially aligned automatically upon insertion of the sleeve portion 54 into the piston guide 49 during assembly of the valve 10, by providing for lateral movement of the piston guide 49 relative to the direction of axial movement of the valve piston 26. Thus, minor axial misalignment of the valve piston 26 will not necessarily result in failure of the i valve 10 during operation, or in excessive wear of the sealing ring 48, the sleeve 54 or the inside surface 53 of the piston guide 49, because lateral movement of the piston guide can compensate for that misalignment.

Accordingly, lateral movement of the piston guide 49 to accommodate any misalignment of the valve piston 26 can occur without adversely affecting the performance of the valve 10, and without requiring major structural change to the components of the valve.

Additionally, the present invention facilitates the manufacture of the valve 10 from solid bar by machining operations only, so that the valve body 13 need not be cast. Thus, only one kind of machining operation is necessary and the costs and difficulties associated with casting are eliminated. Furthermore, valves can be made from materials not previously employed because they were not suitable for casting.

The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description.

CA\WINWORD'SHARON NDREWI4OOELETEP2610CAP.DOC

Claims (14)

1. A pressure control valve including a hollow body, two chambers formed within said body, two ports each of which communicates with a respective said chamber and through which fluid can move into and out of that chamber, an orifice within said body through which said chambers can communicate, a valve member mounted within said body for movement relative thereto towards and away from a position at which it closes said communication through said orifice, movement of said valve member being guided by guide means and said guide means being mounted within said body for movement laterally relative to the °.°direction of movement of the valve member.

2. A valve according to claim 1, said valve having a longitudinal axis and S: said chambers being spaced apart coaxially along said axis and movement of said valve member being along that axis, said guide means being mounted within said body for movement laterally to said longitudinal axis.

3. A valve according to claim 1 or 2, said guide means being located in one 0 of said chambers.

4. A valve according to claim 3, wherein said one of said chambers includes a shoulder formed in a wall thereof, that forms a mounting surface for said guide means.

5. A valve according to any preceding claim,-said guide means including a plurality of webs extending outwardly from a body portion thereof to slidingly engage a mounting surface within said body.

6. A valve according to any preceoing claim, said guide means including an open-ended cup, including an internal annular straight walled section extending longitudinally from the open end of the cup, said straight walled section providing a sealing surface for sealing engagement with said valve member. C:%W1NWORDISHAROMANREW.NOOELETE\P2610CAP.DC 12

7. A valve according to claim 6, wherein said valve member is a valve piston and a cylindrical end of said piston is arranged for sliding engagement against said straight walled section of said cup.

8. A valve according to claim 6 or 7, said guide means being restrained against movement in the direction of movement of said valve member.

9. A valve according to claim 8, said guide means being located in one of said chambers and being restrained in one axial direction by the manner of its mounting within that chamber and in the opposite axial direction by exposure to fluid pressure with the other of said chambers.

A valve according to claim 9, wherein said guide means is exposed to :fluid pressure from the said other of said chambers through an opening in said S valve member.

*11. A pressure control valve including a hollow body, two chambers formed within said body, two ports each of which communicates with a respective said chamber and through which fluid can move into and out of that chamber, an orifice within said body through which said chambers can communicate, a valve :member mounted within said body for movement relative thereto towards and away from a position at which it closes said communication through said orifice, said valve member being acted on by biasing means to urge it away from the communication closed position, and by fluid pressure within one of said chambers to urge it toward the communication closed position, a passage permitting fluid pressure in the other of said chambers to impinge on each of two oppositely facing sides of the valve member, each of said side faces being generally in a respective one of the two directions of movement of said valve member and being arranged such that the area of each said side against which said pressure impinges is substantially the same when the valve member is in said communication closed position and is different when the valve member is not in that position, the other said chamber is formed at least in part by the bore i 13 of a tubular barrel section, said orifice being located at one end of said barrel section, said spring is a coil compression spring which acts between said valve member and said body and which is arranged substantially coaxial with said barrel section, and at least part of said spring is located around said barrel section, movement of said valve member being guided by guide means and said guide means being mounted within said body for movement laterally relative to the direction of movement of said valve member.

12. A valve according to claim 11, said guide means being mounted for sliding movement against a mounting surface on which it is mounted, said mounting surface being located in said one of said chambers.

13. A valve according to claim 12, said mounting surface being an annular, radially extending shoulder and said guide means including a plurality of webs 15 extending outwardly from a body portion thereof, into engagement with said mounting surface.

14. A valve according to any one of claims 11 to 13, said guide means being formed as an open-ended cup, including an internal annular straight walled section extending longitudinally from the open end of the cup, said straight walled section providing a sealing surface for sealing engagement with a cylindrical end section of said valve member, said cup being closed at an opposite end to said open end and said passage means extending through said end section and permitting communication between said other chamber and a space between said closed end of said cup and a free end surface of said end section. A valve substantially as herein described with reference to Figures 1 and 2. DATED: 22 March 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: GSA INDUSTRIES (AUST.) PTY LTD CAW1NWORDLSHAROArNDREW.NODELETEVP281OCAPOOC