Abstract:
In accordance with the present invention, these and other problems in the prior art are addressed by providing a valve which comprises a valve body which includes an passage that extends at least partially therethrough, a valve seat which is formed in the passage, a valve member which is movably positioned in the passage proximate the valve seat, a first sealing element which is supported on the valve member and which in a closed position of the valve engages the valve seat to block fluid flow through the passage, and a protective member which is movable relative to the valve member between a first position in which the protective member substantially covers the first sealing element when the valve is in the open position and a second position in which the protective member is retracted from the first sealing element when the valve is in the closed position.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a device for protecting the seal element of a valve. More particularly, the invention relates to such a device which prevents the seal element from being displaced and damaged under the influence of a large pressure differential existing across the valve. 
   Many hydraulic systems comprise component parts, such as valves, which in use are subjected to large pressure differentials. Since these valves are often required to open and close against these large pressure differentials, they must include seals which are able to withstand the large pressure differentials. One problem with existing valves is that high pressure differentials may cause the seal to be displaced from its normal position within the valve, and this may necessitate removing the valve so that the seal can be replaced. 
   Valves which are used in high pressure applications often comprise hard seals, such as metallic or hard plastic seals. However, such seals will usually not seal properly unless they are energized, i.e., forced against their corresponding sealing surfaces, and this energizing force can sometimes be very high. Moreover, such seals commonly require smaller tolerances and relatively precise machining of their corresponding sealing surfaces. Also, hard seals are usually static and therefore do not withstand being moved, such as when the valve is opened and closed. Consequently, such seals must often be replaced after only a few operations of the valve. However, in many instances this is not always possible or convenient, such as when the valve is located hundreds of meters below the surface of the water. 
   Another kind of seal which is often used in valves is a soft elastomeric seal, such as an O-ring seal. Elastomeric seals will usually seal much better than hard seals since they will deform against their sealing surfaces. However, these seals tend to be extruded out of their grooves when the valve is opened, a tendency which becomes more pronounced when the pressure differential across the seal increases. Also, when the valve is being opened and the valve member is moving away from the valve seat, ambient pressure will tend to force the seal towards the valve seat and thereby obstruct the passage between the valve member and the valve seat. 
   Elastomeric seals are commonly used in poppet valves, such as those that exist in the male and female parts of undersea hydraulic couplings. These poppet valves are opened by inserting the male part into the female part. Before the valves are opened, the fluid in one of the parts will be at operational pressure and the fluid in the other part will be at ambient pressure or even zero pressure. Consequently, when the poppet valves first start to open, a large pressure differential may exist which can force the seals out of their corresponding grooves. This pressure differential can also cause the seals to become deformed, and if the seals are thereby neutralized, water may pour through the poppet valves at high speed and tear the seals partially or completely out of their grooves. If this happens, the coupling may have to be brought to the surface for repair. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, these and other problems in the prior art are addressed by providing a valve which comprises a valve body which includes a passage that extends at least partially therethrough, a valve seat which is positioned in the passage, a valve member which is movably positioned in the passage proximate the valve seat, a first sealing element which is supported on the valve member and which in a closed position of the valve engages the valve seat to block fluid flow through the passage, and a seal protective member which is movably positioned in the passage. The seal protective member is movable relative to the valve member between a first position in which the protective member is engaged with the first sealing element when the valve is in the open position and a second position in which the protective member is retracted from the first sealing element when the valve is in the closed position. 
   Thus, the valve of the present invention includes a seal protective member which protects the sealing element when the valve is opened but which retracts to allow the sealing element to engage the valve seat when the valve is closed. In this manner, the seal protective member will prevent the sealing element from extruding from its corresponding groove as the valve is being opened. Accordingly, the sealing element is able to withstand large pressure differentials without being damaged. 
   These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIG. is a cross sectional view of a male coupling member which comprises the seal protective member of the present invention, with the upper half of the figure showing the male coupling member in its closed position and the lower half of the figure showing the male coupling member in its open position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The seal protective member of the present invention will be described herein in the context of an exemplary underwater hydraulic coupling. However, it should be understood that the person of ordinary skill in the art will readily appreciate how to modify the seal protective member for use in other kinds of valves. 
   Referring to the Figure, a hydraulic coupling which comprises the seal protective member of the present invention is shown to include a male part  1  which is arranged to be interconnected with a corresponding female part (not shown) in a manner that is well understood in the art. The male part  1  comprises a tubular body  2  which includes a rear portion  4 , a number of external threads  6  which are disposed on the rear portion and via which the body may be attached to a fluid line (not shown), and a suitably shaped gripping portion  10  by which the body may be gripped and screwed into a manifold or the like using an appropriate tool, such as a spanner. The body  2  also comprises a front probe section  12  which includes a cylindrical outer surface  14 , a thickened end section  8 , and a radially extending front face  50 . 
   The male part  1  also comprises a passage  16  which extends axially through the body  2  and includes an enlarged passage portion  18  which is formed in the probe section  12  and a reduced front passage portion  24  which is formed in the end section  8 . The front passage portion  24  is defined by a first section  52  which comprises a first diameter, a second section  54  which comprises a second, larger diameter, and a third section  56  whose diameter diverges towards the enlarged passage portion  18 . The front passage portion  24  also includes a first backwards-facing shoulder  53  between the first and second sections  52 ,  54 , and a second backwards-facing shoulder  55  between the second and third sections  54 ,  56 . The surface of the second section  54  forms a valve seat surface, as will be explained in more detail later. 
   In accordance with the present invention, the male part  1  also comprises a valve retainer  20  which, as will be made apparent below, comprises the seal protective member of the present invention. The valve retainer  20  is axially movable within the passage  16  and is biased toward the front passage portion  24  by a preferably helical spring  32 . The spring  32  engages a first spring retaining sleeve  28  which is axially supported in the passage  16  by a spring retainer ring  26 . The first spring retaining sleeve  28  includes a radially inward projecting rear support shoulder  30  that forms a rear abutment for the spring  32 . The valve retainer  20  comprises a second spring retaining sleeve  34  which includes a radially inward projecting front support shoulder  38  that forms a front abutment for the spring  32 . The valve retainer  20  further comprises a number of radial holes or perforations  44  which allow fluid to flow from the passage  16  to the enlarged passage portion  18  and out through the front passage portion  24  when the valve is open. 
   The front part of the valve retainer  20  comprises a rear end  84  and a forward projecting cylindrical sleeve  22 . The sleeve  22  includes a front end  78 , a radially extending rear wall  82 , a rear inner surface  74 , and a front inner surface  72 . The front inner surface  72  comprises a larger diameter than the rear inner surface  74  and is separated from the rear inner surface by a radial shoulder  75 . 
   The male part  1  further comprises a valve member  40  which is axially movable within the sleeve  22 . The valve member  40  has a rear outer surface  76  and a front outer surface  79  which are separated by a rearward facing shoulder  77 . The rear outer surface  76  forms a sliding fit with the rear inner surface  74  of the sleeve  22 , and the front outer surface  79  forms a sliding fit with the front inner surface  72  of the sleeve. Furthermore, the shoulder  77  of the valve member  40  engages the shoulder  75  of the sleeve  22  to limit the backward travel of the valve member within the sleeve. 
   The front end of the valve member  40  comprises an actuator pin  42  that projects through the front passage portion  24  and past the front face  50  of the body  2 . An annular spring  70  is positioned in the space between the rear wall  82  of the valve retainer  20  and a rear end  69  of the valve member  40 . The spring  70 , which is designed to be weaker than the spring  32 , exerts a force to keep valve member  40  in its forward position, as shown in the top half of the FIGURE. 
   The male member  1  also includes a number of soft resilient seal rings, such as O-rings  66  and  68 , which are positioned in corresponding grooves  62  and  64 , respectively, that are formed in the valve member  40 . The O-ring  68  seals against the rear inner surface  74  of the sleeve  22  when the valve is in both the open and closed positions. The O-ring  66  seals against the front inner surface  72  of the sleeve  22  when the valve is in the open position and against the valve seat surface  54  when the valve is in the closed position. A number of holes  73  may be formed through the wall of the sleeve  22  to vent any fluid which may be trapped between the O-rings  66  and  68 . 
   The helical spring  32  is designed to exert a continuous forwardly directed force against the valve retainer  20 , and thus the valve member  40 , which urges the front end of the valve member  40  into abutment against the shoulder  53 . In this position the O-ring  66  seals against the valve seat surface  54  to close the valve. To open the valve, a force is directed against the actuator pin  42  which, since the spring  70  is weaker than spring  32 , causes the valve member  40  to move backwards and compress the spring  70  until the shoulder  77  of the valve member  40  engages the shoulder  75  of the sleeve  22 . In this regard, since the area of the rear end  84  of the valve retainer  20  is many times larger than the combined areas of the front end  78  and the shoulder  75 , the fluid pressure within the passage  16  will help to hold the retainer in place as the valve member  40  is moved. 
   During movement of the valve member  40 , the O-ring  66  will disengage from the valve seat surface  54  and move into contact with the front inner surface  72  of the retaining sleeve  22 . However, since the front end  78  of the sleeve  22  remains against the shoulder  55  as the valve member  40  is moving, only a limited amount of fluid can flow past the sleeve. Consequently, the O-ring  66  is protected against the pressure differential which otherwise would try to force the O-ring out of its groove  62  as the valve is opened. 
   Continued backward movement of the actuator pin  42  will now cause both the valve member  40  and the retainer  20  to move against the force of the spring  32 . This movement will cause the front end  78  of the sleeve  22  to move away from the shoulder  55  and thereby establish fluid communication between the passage  16  and the female part of the coupling via the rear retaining sleeve  28 , the front retaining sleeve  34 , the holes  44 , the enlarged passage portion  18  and the front passage portion  24 . 
   The invention presents a pressure assisted closing mechanism comprising the rear end  84  of the valve retainer  20 , which is influenced by fluid pressure within the passage  16  to assist in moving the valve retainer toward the closed position of the valve. 
   As mentioned above, the hydraulic coupling of the present invention also includes a complementary female coupling part which is designed to receive the probe section  12  of the male part  1 . The valve member of the female coupling part is otherwise identical to the male part as described above. 
   As the male and female coupling parts are disconnected from each other, the actuator pins  42  will remain in contact for a period of time. The spring  70  will be kept compressed due to the higher strength of the spring  32  until the front end  78  of the sleeve  22  abuts against the shoulder  55 . This stops the forward movement of the valve retainer  20  and closes the fluid path through the coupling. Further disconnecting of the male and female coupling parts will cause movement of only the valve member  40  because of the spring  70 . This will cause the O-ring  66  to move into contact with the seat  54 , thus forming the desired fluid-tight seal. 
   Fluid pressure working against the rear of rear spring retaining sleeve  28  will also aid in maintaining this fluid-tight seal. Since the spring  32  is much stronger than the spring  70 , the valve retainer  20  and the valve member  40  will move together until the front end  78  of the valve retainer engages the shoulder  55 . This will cause the valve retainer  20  to stop while the valve member  40  will be forced further forward by the spring  70 . The O-ring  66  will thus move out from under the sleeve  22  and into contact with seal surface  54 , thus closing fluid flow through the valve. 
   The invention will find use in any valve where a valve member must be moved to open a passage between lines with different pressures, where the danger exists that the seal may be forced out of its groove. 
   It should be recognized that, while the present invention has been described in relation to the preferred embodiments thereof, those skilled in the art may develop a wide variation of structural and operational details without departing from the principles of the invention. Therefore, the appended claims are to be construed to cover all equivalents falling within the true scope and spirit of the invention.