NZ585246A - A piston valve where the movement of the valve has reduced friction due to a change in a seals compression - Google Patents

Abstract

A piston valve (100) that minimises friction during movement of the valve piston (140) is disclosed. The valve (100) has a hollow valve body (110) having an inlet port (111) and an outlet port (112), a piston chamber (130) within an interior of the body (110) and a piston (140) reciprocally moveable within the chamber (130). The piston (140) moves between a closed position where the piston (140) closes the valve (100) to fluid flow, and an open position. Within a groove (145) around an outer wall of the piston (140) a sealing element (150) is used to seal between the piston (140) and the chamber (130) wall when the piston is in the closed position. The sealing element (150) has a smaller cross-sectional width than that of the groove (145) with allows the sealing element (150) to roll as the piston (140) moves between the open and closed positions, thus assisting in breaking the initial sticking between the sealing element (150)and the chamber (130) wall. The groove (145) or the inner wall of the chamber (130) has a varying diameter such that when the piston (140) is in the closed position the sealing element (150) is compressed between the groove (145) and the chamber and when the piston (140) moves from the closed towards the open position, the sealing element (150) moves to a position adjacent a smaller diameter that causes a reduction in compression of the sealing element (150). The sealing element (150) may be an o-ring.

Description

NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION PISTON VALVE No: 585246/585472/591800 Date: 10 May 2010/19 May 2010/18 March 2011 We, HANSEN DEVELOPMENTS LIMITED, a New Zealand company whose registered office is located at 16 Union Street East, Whangarei 0114, New Zealand, do hereby declare this invention to be described in the following statement: FIELD OF THE INVENTION The invention relates to a piston valve and in particular to a sealing arrangement for a piston valve.

BACKGROUND OF THE INVENTION Piston valves are used to control the flow of fluid by linear motion of a piston within a cylinder of the valve opening or closing a fluid path through the valve. Typically, such valves incorporate a sealing element, such as an O-ring, between the piston and the cylinder.

Valves of this type therefore often have a lubricant applied to the O-ring to reduce friction and ensure free movement of the piston. The lubricant however tends to wash away over time which can cause the seal to stick and prevent the valve from working effectively.

It is an object of the invention to provide a piston valve having a sealing arrangement with 15 reduced friction against piston movement or to at least provide the public with a useful choice.

SUMMARY OF THE INVENTION In one aspect the invention may broadly be said to consist of a piston valve comprising: a hollow valve body having an inlet port and an outlet port, a piston chamber within an interior of the body, a piston reciprocally moveable within the chamber between a closed position where the piston closes the valve to fluid flow, and an open position, the piston having a groove around an outer wall of the piston, and a sealing element in the groove for sealing between the piston and the chamber and 25 having a smaller cross-sectional width than that of the groove, the groove or an inner wall of the chamber having a varying diameter such that when the piston is in the closed position the sealing element is compressed between the groove and the chamber and when the piston moves from the closed towards the open position, the sealing element moves to a position adjacent a diameter that causes at least a reduction in compression of the sealing element.

In one embodiment, the groove comprises of a first diameter section and a second diameter section and movement of the piston towards the closed position causes the seal to move at least partially within the first section of larger diameter where the seal contacts a base of the groove and the chamber wall, and movement of the piston towards the open position causes the seal to move into the second section of smaller diameter where the seal is no longer in contact with the base of the groove.

The connection between the first and second diameter sections may be tapered or alternatively 5 stepped. In the stepped form, movement of the piston towards the closed position causes the seal to contact a corner section of the stepped connection and the chamber wall.

In an alternative embodiment, the inner wall of the chamber comprises a first diameter section and a second diameter section, and movement of the piston to the closed position causes the 10 groove and the seal to move along the chamber into a position adjacent the first section of smaller diameter where the seal contacts the chamber and a base of the groove, and movement of the piston to the open position causes the groove and the seal to move along the chamber into a position adjacent the second section of larger diameter where the seal no longer contacts the base of the groove or the chamber wall.

The valve may be a float valve and further comprise a float arm pivotally coupled to the body of the valve, the float arm being coupled to the piston at one end of the arm and adaptable to be coupled to a float at the other end of the arm, so that pivotal movement of the arm due to movement of the float causes the end of the arm coupled to the piston to act on the piston to 20 open and close the valve.

Preferably the sealing element is an O-ring type seal.

The term "comprising" as used in this means "consisting at least in part of'. When interpreting 25 each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

This invention may also be said broadly to consist in the parts, elements and features referred to 30 or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described by way of example only and with reference to the drawings, in which: Figure la is a cross-sectional view of a first embodiment of a piston valve of the invention shown in the closed position, Figure lb is an enlarged view of the sealing arrangement of the piston valve of figure la when it is in the closed position, Figure 2a is a cross-sectional view of the piston valve of figure la shown in the open position, Figure 2b is an enlarged view of the sealing arrangement of the piston valve of figure la when it is in the open position, Figure 3a is a cross-sectional view of a second embodiment of a piston valve of the invention shown in the closed position, Figure 3b is an enlarged view of the sealing arrangement of the piston valve of figure 3a when it 20 is in the closed position, Figure 4a is a cross-sectional view of the piston valve of figure 3a shown in the open position, and Figure 4b is an enlarged view of the sealing arrangement of the piston valve of figure 3a when it is in the open position, Figure 5a is cross-sectional view of the valve of the second embodiment employing a smaller sealing element, Figure 5b is an enlarged view of the sealing arrangement of the piston valve of figure 5a.

Figure 6a is a cross-sectional view of a third embodiment of a piston valve of the invention shown in the closed position, Figure 6b is an enlarged view of the sealing arrangement of the piston valve of figure 6a when it is in the closed position, Figure 7a is a cross-sectional view of the piston valve of figure 6a shown in the open position, 5 and Figure 7b is an enlarged view of the sealing arrangement of the piston valve of figure 7a when it is in the open position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A first embodiment of a piston valve 100 is shown in figures la and 2a. The valve is shown in the closed state in figure la and in the open state in figure 2a. The valve 100 comprises a main body component 110 having an inlet port 111 for connection to a fluid supply under pressure, which 15 when the valve is open will flow through the interior of the valve 100 as indicated by arrow A. Inlet port 111 may threadably engage a pipe system for example to receive the flow of fluid A. An outlet port 112 is provided for the exit stream of fluid (arrow B) from the interior of the body 110. Fluid will enter through inlet port 111 and flow through the interior of the valve, exiting via outlet port 112 only when the valve is open (as shown in figure 2a). When the valve is closed, the 20 fluid path is obstructed and the outlet port 112 is closed so no fluid exits the valve.

The valve 100 comprises a piston 140 which is reciprocally moveable within a chamber or hollow cylinder 130. Movement of the piston 140 in the cylinder 130 opens and closes the valve 100. A valve seat 120 is provided adjacent the outlet port 112 onto which the under surface 121 of 25 piston 140 engages to close the valve 100 and block fluid (from the interior of the body 110) from exiting through outlet port 112. Figure la shows the valve 100 closed with the piston 140 in the closed position and against the valve seat 120. Figure 2a shows the valve 100 open with the piston 140 in the open position clear of the valve seat 120, allowing fluid entering through inlet port 111 to flow through the interior of the body of the valve and exit through outlet port 112 30 (stream C).

An O-ring 150 is employed between the outer wall 141 of the piston 140 and the inner wall 131 of the cylinder 130. The O-ring 150 is retained within a groove 145 on the outer wall 141 of the piston 140. The groove 145 is wide enough to enable the O-ring 150 to move within the groove 35 145 and be retained within either an upper 145a or lower 145b section of the groove 145 depending on whether the valve is closed or open, as shown in figures la/lb and 2a/2b respectively.

Figure lb shows the position of the O-ring 150 when the piston 140 is in the closed position. In 5 this first embodiment, the groove 145 is formed with a base 146 of varying diameters. Mainly, the base 146 of the groove 145 has a larger diameter section 146a and a smaller diameter section 146b. The connection 146c between these two sections 146a and 146b is tapered and smooth but not stepped, to facilitate movement of the O-ring 150 between the sections. The cylinder bore/diameter in this embodiment is substantially constant at least along the length of the 10 cylinder 130 adjacent the groove 145 during operation of the valve 100.

The distance dl between section 146a and die cylinder wall 131 is less than or equal to the cross-sectional width of the O-ring 150. In conjunction with the cylinder wall 131, section 146a of the base of the groove forms a region for retaining the O-ring 150 that enables the O-ring 150 to 15 make contact with both the cylinder wall 131 and the base 146 of the groove 145. This effectively seals the hollow cylinder 130 and prevents fluid from entering through gap 160 when the piston 140 is in the closed position as shown in figure lb. Preferably the distance dl is less than the cross-sectional width of the O-ring 150 to cause the O-ring 150 to compress upon entering the associated region shown in figure lb.

The distance d2 between section 146b and the cylinder wall 131 is greater than the distance dl. In conjunction with the cylinder wall 131, section 146b of the base of the groove 146 forms a region for retaining the O-ring 150 that enables the O-ring 150 to decompress as the piston moves towards the open position shown in figure 2b. This decompression of the O-ring 150 effectively 25 reduces the friction against movement of the piston 140 along the cylinder 130 to aid in opening the valve. Preferably the distance d2 is greater than the cross-sectional width of the O-ring 150 such that when the piston 140 moves to open the valve, the O-ring no longer contacts at least one of the surfaces 146/131 and completely decompresses as shown in figure 2b.

In operation, as the piston 140 moves down the cylinder 130 to close the valve 100, the O-ring 150 moves with the piston 140 and up the groove 145 into the larger diameter section 146a where it becomes squeezed/compressed between the base of the groove 146 and the cylinder wall 131. This forms an effective seal when the valve 100 is closed and prevents fluid from entering the cylinder 130 through gap 160. When the valve is caused to open, the piston 140 then 35 moves up the cylinder 130 to open the valve 100, the O-ring 150 moving with the piston 140 will roll/slide down the groove 145 and into the smaller diameter section 146b of the groove 145, thereby reducing or eliminating friction between the O-ring 150 and the groove 145/cylinder 130. It can be seen from figures la/b, the groove 145 is shaped such that when the piston 140 is in the closed position, the O-ring 150 is in contact with both the base of the groove 146 and the 5 cylinder wall 131 and when the piston 140 is caused to open (figures 2a/b), the O-ring 150 no longer makes contact with the base of the groove 146 to reduce friction.

This sealing arrangement is particularly useful in low pressure applications where the opening force on the piston 140 is low (due to low pressure fluid stream C). If the O-ring 150 sticks to 10 one or both of the surfaces 146 and 131, it can prevent the valve 100 from opening. Thus, by increasing the size of the region in which the seal lies and providing relief in the piston groove 145, the O-ring effectively becomes free of one surface during opening, thereby eliminating much of the friction and allowing the piston 140 to move freely. In some high pressure applications, the pressure of the fluid helps push the piston open against any O-ring 150 friction. The O-ring 15 150 will also be pushed up against die upper surface of the groove 145 (i.e. into section 145a) by fluid pressure as the piston 140 moves.

The cross-sectional width, w, of the groove 145 is greater than the cross-sectional width of the O-ring 150 to enable the O-ring 150 to roll between the sections/regions of the groove 145. This 20 enables the O-ring 150 to roll slightly during the initial movement of the piston 140 which assists in breaking the sticking between the O-ring 150 and the cylinder wall 131.

A second embodiment of the invention is shown in figures 3a/b and figure 4a/b. In this embodiment, the structure of the valve 200 is very much the same as that of the valve 100 in the 25 first embodiment. The sealing arrangement is however slightly different but achieves the same result. As shown in figures 3b and 4b, the groove 245 has a base 246 of substantially constant diameter, but the inner wall of the cylinder 231 is formed of two sections 231a and 231b of varying diameters. Section 231a having a larger diameter than section 231b. It is preferred that these two sections are connected 231c via a smooth connection to facilitate movement of the O-30 ring 250 up and down the cylinder wall 231 and between these two sections 231a and 231b.

Referring to figures 3a and 3b, as the piston 240 moves down the cylinder 230 and towards the closed position, the O-ring 250 also moving down the cylinder 230 with the piston 240 will move up the groove 245 and into the upper section 245a of the groove. As the piston 240 then 35 approaches the closed position, the groove 245 will approach the smaller diameter section 231b of the cylinder wall 231. In the closed position therefore, the groove 245 will be adjacent and the upper section 245a (where the O-ring 250 now lies) at least partially bridged by the smaller diameter section 231b of the cylinder wall 231 which will cause the O-ring 250 to contact both the cylinder wall 231 and the base of the groove 246 and preferably be squeezed/compressed in 5 between the two to form an effective seal.

Referring to figures 4a and 4b, as the piston 240 moves up the cylinder 230 and towards the open position, the O-ring 250 also moving up the cylinder 230 with the piston 240 will start to move down the groove 245 into the lower section 245b of the groove. The piston 240 and the groove 245 will then approach the larger diameter section 231a of the cylinder wall 231. The groove 245 will become adjacent and the lower section 245b (where the O-ring 250 now lies) will be at least partially bridged by the larger diameter section 231a of the cylinder wall 231 which will relieve the O-ring 250/cause it to decompress as it no longer contacts the base of the groove 246 and only the cylinder wall 231, thereby reducing the friction produced by the seal as the valve opens up.

The distance d3 between the base 246 of the groove and section 231b of the cylinder wall 231 is less than or equal to the cross-sectional width of the O-ring 250. In conjunction with the base 246 of the groove 245, section 231b forms a region for retaining the O-ring 250 that enables the O-ring 250 to make contact with both the cylinder wall 231 and the base of the groove 246 to effectively seal the hollow cylinder 230 and prevent fluid from entering through gap 260 when the piston 240 is in the closed position as shown in figure 3b. Preferably the distance d3 is less than the cross sectional width of the O-ring 250 to cause the O-ring 250 to compress upon entering the associated region shown in figure 3b.

The distance d4 between the base of the groove 246 and section 231a of the cylinder wall 231 is greater than the distance d3. In conjunction with the base 246 of the groove 245, section 231a of the cylinder wall 231 forms a region for retaining the O-ring 250 that enables the O-ring 250 to decompress as the piston 240 moves towards the open position shown in figure 4b. This decompression of the O-ring 250 effectively reduces the friction against movement of the piston 30 240 along the cylinder 230 to aid in opening the valve. Preferably the distance d4 is greater than the cross-sectional width of the O-ring 250 such that when the piston 240 moves to open the valve, the O-ring no longer contacts at least one of the surfaces 246/231a and completely decompresses as shown in figure 4b.

In the embodiment above, the sealing arrangement may be such that the O-ring makes contact with the base of the groove 246 but not the cylinder wall 231 when the valve 200 is caused to open. This is dependent on O-ring tolerances and/or dimensions. Figures 5a and 5b show such an arrangement where the valve 200 (shown in the open position) comprises a smaller O-ring 5 350. The O-ring 350 is shown clear of the cylinder wall 231 and contacting the base of the groove 246 when the valve 200 is in the open state. Friction between the O-ring 350 and the wall 231 is eliminated in this case.

A third embodiment of the invention is shown in figures 6a/b and figures 7a/b. In this 10 embodiment, the structure of the valve 400 is very much the same as that of the valve 100 in the first embodiment. The groove 445 in this embodiment is also formed with a base 446 of varying diameters, except that the connection between the two different diameter regions 446a and 446b of the groove 445 is stepped rather than tapered (146c). As shown in figure 6b, when the valve 400 is in the closed position, a corner section 446c of the base 446 of the groove 445 contacts the 15 inside of the O-ring 450 which provides a point contact seal.

The corner section 446c of this embodiment is preferably provided adjacent the upper half 450a of the O-ring 450 when the valve is in the closed position. When the piston 440 moves to open the valve 400, the corner section 446c moves up the O-ring 450, where the cross-sectional 20 diameter of the O-ring 450 decreases to immediately reduce the amount of compression imposed by the corner section 446c on the O-ring 450 and hence the level of friction against the cylinder 430. This allows the valve 400 to open quickly. When the piston 440 moves to close the valve, the O-ring 450 moves into the upper section 446a which causes contact between the corner section 446c of the stepped groove base 446 and the O-ring 450 to seal the cylinder 430 from 25 external fluid entering through gap 460.

The first and third embodiments may be used in conjunction with the arrangement of the second embodiment. In other words, the valve may be constructed such that both the piston groove and cylinder wall comprise varying diameter sections to create two regions of different cross-sectional 30 widths in which the seal is retained when the valve is in the open and closed positions respectively.

In the embodiments described above the sealing arrangement causes the O-ring to be free of one surface during opening of the valve. In an alternative embodiment however, the O-ring may still 35 be in contact with both the cylinder wall and the base of the groove as the valve is opened, but the diameter (of either the cylinder wall or the groove to which the O-ring becomes adjacent) would cause a reduction in compression of the O-ring, thereby achieving the reduction in friction required.

It will be appreciated as in the embodiments above the O-ring need not necessarily move entirely within the associated regions of the groove when the valve opens and closes. The O-ring needs to at least partially move within these regions to enable the reduction and increase in compression respectively.

The piston valves 100 and 200 of the first, second and third embodiments respectively are float type valves as shown in the figures. A float arm 170/270/470 is shown coupled at one end 171/271/471 to an upper part of the piston 140/240/440. The end 171/271/471 of the float arm is shown coupled within a hollow portion 147/247/447 of the piston 140/240/440 between the head 148/248/448 and base 149/249/449 of the piston 140/240/440, The float arm is 15 pivotally coupled to the body 110/210/410 of the valve at 172/272/472. Pivotal movement of the float arm 170/270/470 therefore results in reciprocal movement of the piston 140/240/440. As is known, the other end 173/273/473 of the float arm is generally connected to a float element (not shown) arranged to float within a fluid reservoir such as a water trough for example. As the level of fluid in the reservoir lowers, the float element pulls on end 173/273/473 of the 20 float arm 170/270/470 which causes the piston 140/240/440 to move up and open the valve 100/200/400. Water can then flow from an external source through inlet 111/211/411 and out port 112/212/412 into the trough. Once the desired level is reached, the weight of the float element no longer forces end 173/273/473 of the float arm 170/270/470 down which then causes the float arm 170/270/470 to pivot back and return the piston 140/240/440 to the closed 25 position.

The piston valve of the invention does not need to be employed in a float type valve as described above and can be used in any other type valve/suitable application that requires a reduction in friction caused by the sealing element. Furthermore, the valve components (mainly the body and 30 the piston) can be from any suitable material such as a plastics material. The cylinder is preferably integrally formed within the valve body (using a plastic mould for instance). Alternatively the cylinder can be formed as a separate component and coupled to the interior of the valve body. The sealing element is preferably an O-ring type seal formed from a rubber material.

The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention.

Claims (11)

1. A piston valve comprising: a hollow valve body having an inlet port and an outlet port, 5 a piston chamber within an interior of the body, a piston reciprocally moveable within the chamber between a closed position where the piston closes the valve to fluid flow, and an open position, the piston having a groove around an outer wall of the piston, and a sealing element in the groove for sealing between the piston and the chamber and 10 having a smaller cross-sectional width than that of the groove, the groove or an inner wall of the chamber having a varying diameter such that when the piston is in the closed position the sealing element is compressed between the groove and the chamber and when the piston moves from the closed towards the open position, the sealing element moves to a position adjacent a diameter that causes at least a reduction in compression of the sealing element. 15

2. A piston valve as claimed in claim 1 wherein the groove comprises of a first diameter section and a second diameter section and movement of the piston towards the closed position causes the seal to move at least partially within the Erst section of larger diameter where the seal contacts a base of die groove and the chamber wall, and movement of the piston towards the 20 open position causes the seal to move at least partially within the second section of smaller diameter where the seal is no longer in contact with the base of the groove.

3. A piston valve as claimed in claim 2 comprising a tapered connecting portion between the first and second diameter sections of the groove. 25

4. A piston valve as claimed in claim 2 comprising a stepped connecting portion between the first and second diameter sections of the groove, and movement of the piston towards the closed position causes the seal to move over a corner section of the stepped portion to create a point contact seal with the base of the groove. 30

5. A piston valve as claimed in claim 1 wherein the inner wall of the chamber comprises a first diameter section and a second diameter section, and movement of the piston to the closed position causes the groove and the seal to move along the chamber into a position adjacent the first section of smaller diameter where the seal contacts the chamber and a base of the groove, 35 and movement of the piston to the open position causes the groove and the seal to move along -13 - the chamber into a position adjacent the second section of larger diameter where the seal no longer contacts the base of the groove or the chamber wall.

6. A piston valve as claimed in any one of the preceding claims further comprising a float 5 arm pivotally coupled to the body of the valve, the float arm being coupled to the piston at one end of the arm and adaptable to be coupled to a float at the other end of the arm, so that pivotal movement of the arm due to movement of the float causes the end of the arm coupled to the piston to act on the piston to open and close the valve. 10

7. A piston valve as claimed in any one of the preceding claims wherein the sealing element is an O-ring type seal.

8. A piston valve substantially as described herein with reference to accompanying figures la, lb, 2a and 2b. 15

9. A piston valve substantially as described herein with reference to accompanying figures 3 a, 3b, 4a and 4b.

10. A piston valve substantially as described herein with reference to accompanying figures 20 5a and 5b.

11. A piston valve substantially as described herein with reference to accompanying figures 6a, 6b, 7a and 7b,