GB2183312A

GB2183312A - Inflation valves

Info

Publication number: GB2183312A
Application number: GB08627266A
Authority: GB
Inventors: Stanley Edgar Otter
Original assignee: Fawcett Engineering Ltd
Current assignee: Fawcett Engineering Ltd
Priority date: 1985-11-15
Filing date: 1986-11-14
Publication date: 1987-06-03
Anticipated expiration: 2006-11-14
Also published as: GB8627266D0; GB2183312B; GB8528231D0

Abstract

An inflation valve for an oleopneumatic hydraulic pressure accumulator has a valve body (9) formed with an inlet having a stepped bore (17, 18) in which a valve member (21) is slidable but captive. The valve member (21) has a cylindrical body portion (22) which is formed with a helical groove (30) defining a gas passage and is slidable in the larger diameter portion (17) of the bore. The valve member also has a stem (23) engaged in the smaller diameter portion (18) of the bore and an elastomeric sealing O-ring (24) engaged in a groove (25) in the stem. Axial movement of the valve member carries the O-ring into and out of the smaller diameter bore portion (18) to close and open the valve respectively. When the body (9) is screwed into accumulator fitting (8), an extension (31) of the valve member (21), Fig. 2, or a sleeve (26) extending from the body (9) (Fig. 4), opens a ball valve (32 or 52) downstream of the inflation valve. In a modification, Fig. 7, the ball valve (32) is not opened by the valve member extension (31A) until after the inflation valve has been opened. The inflation valve can be opened by a pressing element (27, Fig. 3) of an inflation connection or a pressure testing connection (28). <IMAGE>

Description

SPECIFICATION Inflation valves The present invention relates to inflation valves of the kind used as non-return valves for inflating a chamber with gas, the valve being openable from the exterior in order to test the pressure in the chamber.

According to one aspect of the invention, there is provided an inflation valve comprising a valve body having an inlet passage in the form of a stepped bore therethrough, a valve member captive in the stepped bore but slidable therein between open and closed positions, the valve member having a cylindrical body portion slidable in a larger diameter portion of the bore, and a stem of small diameter extending into a smaller diameter portion of the bore towards the outer end of the valve body, and an elastomeric O-ring engaged in a groove in the stem for movement between the larger and smaller diameter portions of the bore in the open and closed positions respectively of the valve member.

When the valve is in its open position, gas can pass from an external supply through the clearance between the valve member and the bore, the O;ring being then in the larger diameter part of the bore but out of contact therewith. When the external supply is removed and gas starts to return through the bore, both the pressure difference between the ends of the valve member and the drag exerted on the valve member by gas flowing through the clearance will act to return the valve member towards its closed position.As soon as the O-ring contacts the step or shoulder, it will effectively close the escape path for the gas and the full pressure of the gas in the chamber which has been inflated or pressurised will be applied to the inner end face of the body of the valve member to move the latter to its fully closed postion, carrying the O-ring fully into the smaller diameter portion of the bore. The inner edge of the step or shoulder should of course be chamfered or radiussed to prevent damage to the 0 ring.

Particularly where the inflation-pressure is low (for example 5 psi or .35 bar), it may be advantageous to ensure rapid closing of the valve by forming at least the major part of the clearance as one or more grooves in the cylindrical wall of the valve member body portion. These grooves are preferably non-straight, being for example helical.

According to a further aspect of the invention, there is provided an inflation valve assembly having an inlet duct controlled by an inflation valve (preferably in accordance with the first aspect of the invention) and a non-return valve downstream, in the inflation direction, of the inflation valve, the non return valve having a valve element which is held away from its seat by the valve member of the inflation valve in all positions of the latter for example by means of a rod-like extension of the latter. If, however, the inflation valve is removed from the duct, the non-return valve can close. Such an arrangement prevents any substantial loss of gas while enabling a suspect or faulty inflation valve to be replaced without loss of the main charge of air or other gas from the chamber.This is clearly of particular advantage where the gas is not air and/or where the pressure is high. The non-return valve may be of simple type having a metal ball as valve element and a spring biasing the ball towards contact with its valve seat.

The application of the invention to a hydraulic pressure accumulator will now be described byway of example with reference to the accompanying drawings, in which: Figure lisa view partly in section and partly in elevation of an oleopneumatic hydraulic pressure accumulator having one form of gas inflation valve in accordance with the present invention; Figure 2 is an axial sectional view of the inflation valve assembly of the pressure accumulator of Figure 1 on an enlarged scale; Figure 3 shows the inflation valve portion of Figure 2 during either inflation from an external source or testing of the inflation pressure; Figure 4 is an axial sectional view of another form of inflation valve; Figure 5 shows a detail of Figure 4 on a greatly enlarged scale;; Figure 6 shows the arrangement of Figure 4 with the gas inflation valve partly unscrewed; and Figure 7 shows part of a further inflation valve assembly.

The pressure accumulator shown in Figure 1 follows conventional practice in that it comprises a hollow cylindrical metal shell 1 having hemispherical upper and lower ends 2 and 3, an elastomeric bladder 4 dividing the interior of the container 1 into a gas chamber 5 within the bladder and a liquid chamber 6 outside the bladder and communicating with a liquid port assembly 7 connected in use for example to a hydraulic installation (not shown).

The upper end of the bladder 4 is anchored to the upper end 2 of the shell by means of a fitting 8 incorporating a gas valve assembly comprising an inflation valve 9 and a non-return valve 10 (Figure 2).

The fitting 8 is externally screw-threaded and at its lower end is of enlarged diameter at 11 and terminates in a still further enlarged diameter flange 12 embedded in the bladder 4. A nut 13 on the screw threaded exterior of the fitting 8 clamps the enlarged portion 11 against the internal wall surface of the upper end 2 of the container both to secure the bladder in position and to form an effective seal by compressing material of the bladder 4 against the container wall.

The fitting 8 has a central duct 14 which at its upper end opens into an internally screw-threaded bore 15 into which the lower, screw threaded end of the inflation valve 9 is engaged. An elastomeric sealing washer 16 is deformed and compressed when the inflation valve 9 is tightened, the components being shown in Figure 2 just prior to such tightening, whereby to form a gas seal.

The body of the inflation valve 9 is formed with a stepped bore comprising a larger diameter, lower portion 17 and a smaller diameter upper portion 18, the upper end of which opens into a countersink which makes sealing engagement with an insert 19 in a conventional valve cap 20 screwed onto the upper end of the inflation valve 9.

An inflation valve member 21 has a cylindrical body portion 22 slidable in the larger bore 17 and a cylindrical stem 23 slidable in the bore 18 (with a small clearance). A rubber O-ring 24 is located in a groove formed by a smaller diameter portion 25 of the valve stem 23. In the closed position of the valve as shown in Figure 2, the O-ring 24 is compressed between the stem portion 25 and the bore wall 18, thereby sealing the gas duct against escape of gas.

As shown, however, in Figure 3, the inflation valve can be opened by means of an element 27 of an inflation connection or pressure testing connection 28 when the latter is screwed onto the inflation valve body 9 after removal of the cap 20. The element 27 presses the valve member 21 downwards, moving the O-ring into the larger diameter bore 17 where the O-ring 24 expands to its natural free dimensions with clearance between it and the wall of the bore 17. The lowermost position for the valve member is determined by an externally screw-threaded sleeve 26 screwed into the lower end of the body of the inflation valve.

When the connection 28 is removed, the valve member returns to its closed, upper position carrying the O-ring 24 past a rounded shoulder 29 at the junction of the bores 17 and 18, thereby closing the inflation valve. Movement of the valve member is effected both by the pressure of the gas beneath the valve member and by drag exerted on the valve member by gas flowing between the valve member and the bore wall 17. This drag may be increased by forming a shallow helical groove 30 in the cylindrical surface of the portion 22. In the closed position, the valve member body 22 abuts the step 29.

In the valve assembly shown in Figures 2 and 3, the inflation valve member has an integral rod-like extension 31, the free end of which, in the assembled condition, holds a ball 32 away from a valve seat 33 formed a shoulder in the duct 14. The ball 32 is biassed towards the seat 33 by a spring 34, the opposite end of which is supported on a porous sintered metal block 35 secured in the fitting 8. This block registers with an aperture 36 in the bladder 4, thereby connecting the duct 14 with the gas chamber 5. With this arrangement, the rod-like extension 31 holds the non-return valve formed by the ball 32, spring 34 and seat 33 in the open position so that any pressure reading taken in the normal manner through the inflation valve represents a full pressure in the chamber 5.If, however, the inflation valve 9 or the sealing member 16 is considered to be faulty, either can be replaced without substantial loss of gas from the chamber 5 simply by unscrewing the complete inflation valve 9, the withdrawal of the rod-like extension 31 allowing the non-return valve to close.

In the inflation valve assembly shown in Figures 4 to 6, the construction is generally similar to that shown in Figures 2 and 3. The inflation valve member 41 here has the upper part of its stem 43 tapered, for example at an angle of 3 to its axis, to provide an annular clearance between it and the lower or inner end of the bore 18 when the valve member 41 is in its open position.

Figure 5 shows the region of the junction between the bores 17 and 18 on a greatly enlarged scale with the O-ring 24 omitted. The shoulder 29 at the step forming the junction between the bores 17 and 18 is again rounded to avoid damage to the O-ring. In addition to its tapered surface 43, the stem of the valve member 41 has a short parallel sided portion 44 which is a free sliding fit in the bore 18. The side walls 45 and 46 of the groove to accommodate the O-ring diverge slightly from each other with increasing radius.

This construction of the valve element as shown in Figures 4 and 5 may of course be applied to the arrangement shown in Figures 2 and 3.

The valve member is formed without an extension corresponding to the extension 31 of Figures 2 and 3. To prevent loss of gas when the inflation valve fitting 9 is unscrewed, a ball 52 is urged onto a seat 53 both by a spring 54 and the gas pressure in the accumulator. The seat 53 is formed by a shoulder or step between a larger bore 55 (accommodating the ball 52 and spring 54) and a smaller diameter bore accommodating the unthreaded portion of the sleeve 26. The seat 53 may include an elastomeric sealing washer 57, the inner surface of which is frusto-conical to provide a clearance gap for gas to flow into the pressure accumulator during charging, the ball 52 being then held away from its seat by the sleeve 26.To permit gas to flow from the interior of the sleeve 26 past the ring of contact of the latter with the ball, one or more notches 58 are formed in the end surface of the sleeve 26.

When the fitting 9 is unscrewed, the ball 52 follows the outward movement of the sleeve 26 until it engages the sealing washer 57 (if the latter is present) and compresses the lattertoform a gas tight seal. Compression of the sealing washer 57 is limited by engagement of the ball 52 with the shoulder forming the step between the bores 55 and 56, in the position shown in Figure 6. If the sealing washer 57 is not used, the ball 52 seats directly on this seat and forms a metal-to-metal seal.

At higher pressures, for example above 3MPa, it may be found that it is difficult to complete the installation of a new inflation valve in view of the force required to open the non-return valve by forcing the ball 32 or 52 off its seat while screwing the valve body 9 into stem 8. Further, under such circumstances, there is a possibility of gas escaping between the screw threads on the body 9 and the stem 8 until the body 9 is fully screwed home. To avoid these problems, the modification shown in Figure 7 may be used. Here, the construction is similarto that shown in Figures 2 and 3 but the rodlike stem 31A is of reduced length so as just to allow the ball 32 to seat on the seat 33A even in the fully closed position of the inflation valve element 21.

However, the clearance between the end of the rodlike stem 31A and the ball 32 is sufficiently small to ensure that after initial opening movement of the valve element 21 by means of the element 27, the stem 31 engages the ball 32 and lifts it from its seat.

With this arrangement, the entire inflation valve carried by the fittings 9 may be removed and replaced without encountering the high pressure of the gas within the gas chamber 5. Further, any sudden rise in the measured pressure during the initial movement of the valve element 21 before the ball 32 is lifted from its seat will indicate that the ball has not been completing a gas-tight seal and that accordingly the accumulator must be depressurised and the valve seat member 33A and the ball 32A must be removed for replacement. A sealing washer 51 of synthetic rubber may be interposed between the seat member 33A and the stepped bore in the stem 8 and may have a frustoconical inner face to make sealing contact with the ball 32A.

Claims

1.An inflation valve comprising a valve body having an inlet passage in the form of a stepped bore therethrough, a valve member captive in the stepped bore but slidable therein between open and closed positions, the valve member having a cylindrical body portion slidable in a larger diameter portion of the bore and a stem of small diameter extending into a smaller diameter portion of the bore towards the outer end of the valve body, and an elastomeric O-ring engaged in a groove in the stem for movement between the larger and smaller diameter portions of the bore in the open and closed positions respectively of the valve member.

2. An inflation valve according to claim 1, wherein the inner edge of the step or shoulder is chamfered or radiussed to prevent damage to the O-ring.

3. An inflation valve according to claim 1 or 2, wherein, to ensure rapid closing of the valve, at least the major part of the clearance is formed by one or move grooves in the cylindrical wall of the valve member body portion.

4. An inflation valve according to claim 3 wherein the or each groove is helical.

5. An inflation valve assembly having an inlet duct controlled by an inflation valve and a non-return valve downstream, in the inflation direction, of the inflation valve, the non-return valve having a valve element which is held away from its seat by a part of the inflation valve at least when the inflation valve is opened but when the inflation valve is removed from the duct, the non-return valve is closed.

6. An assembly according to claim 5 wherein a valve member of the inflation valve has a rod-like extension to hold the valve element away from its seat in the open positions of the non-return valve.

7. An assembly according to claim 5, wherein the valve element of the non-return valve is held away from its seat by an extension of a housing portion of the inflation valve.

8. An assembly according to any of claims 5 to 7 wherein the non-return valve has a metal ball as valve element and a spring biasing the ball towards contact with its valve seat.

9. An assembly according to any of claims 5 to 7, wherein the inflation valve is an inflation valve according to any of claims 1 to 4.

10. An inflation valve substantially as described with reference to Figures 2 and 3 or Figures 4 to 6 of the drawings.

11. An inflation valve assembly substantially as described with reference to Figures 2 and 3 or Figures 4 to 6 or Figure 7 of the drawings.