GB2253892A

GB2253892A - Valve for sudden rapid transfer of gas

Info

Publication number: GB2253892A
Application number: GB9106032A
Authority: GB
Inventors: Thomas Baker
Original assignee: CALOR ENGINEERING Ltd
Current assignee: CALOR ENGINEERING Ltd
Priority date: 1991-03-21
Filing date: 1991-03-21
Publication date: 1992-09-23
Also published as: GB9106032D0

Abstract

A valve (10) for sudden rapid transfer of helium from a gas cylinder to a flotation bag comprises a piston (12) in a cylinder housing (11) having an inlet (22) and an outlet (25). Above the piston head (15), the housing (11) forms a closed chamber (18). Within the piston (12) is a rod (38) of a servo device (37). The rod (38) is acted upon by high pressure helium and bears against housing cover (17) to hold piston (12) in its normal closed position. The housing (11) has actuation ports for supplying compressed air to a chamber (35) to actuate the valve (10). The valve (10) has a number of gas-tight seals (30, 31, 56), all of which vent on their downstream sides either to the actuation ports or to the outlet (25). <IMAGE>

Description

VALVE FOR SUDDEN RAPID TRANSFER OF GAS This invention relates to a valve for sudden rapid transfer of a gas from a high pressure gas container to a low pressure receiver. A preferred application of the invention is to a valve for sudden rapid inflation of a gas-fillable flotation bag from a high pressure gas cylinder.

A sea-going vessel may advantageously be equipped with several rapidly inflatable gas-fillable flotation bags, each provided with its own high pressure gas cylinder, for keeping the sea-going vessel afloat in the event of a disaster. Valves for these should preferably be completely sealed, apart from connections to the gas cylinder and to the flotation bag, and apart from a connection via an actuation port to a source of an actuating pressure. One particular problem which such a valve is likely to suffer is freezing of the valve due to adiabatic expansion of the gas as it rushes from the gas cylinder to the flotation bag through the valve.

As seen from one aspect of the invention, there is provided a valve according to claim 1, to which reference is directed.

The invention will be described by way of example with reference to the accompanying drawings, which illustrate a valve embodying the invention. In the drawings: Fig. 1 is a side elevation and Fig. 2 is an end elevation of the valve embodying the invention; Fig. 3 is a section on B-B of Fig. 1; Fig. 4 is a scrap section on C-C of Fig. 1; and Fig. 5 is a section on D-D of Fig. 2.

Referring to the drawings, the illustrated valve 10 comprises a housing 11 and a piston 12. The housing 11 comprises a housing body 13 which is formed with a cylindrical bore 14, in which a piston-head 15 is axially slidable, with a substantially gas-tight seal between piston rings 16 of piston-head 15 on the one hand and the wall of the bore 14 on the other hand. A piston cover 17, forming part of housing 11, is screwed tightly into the housing body 13, at what it is convenient to call "the top end" of the bore 14, with an O-ring seal 17a therebetween as shown, to form a closed chamber 18 between the cover 17 itself, the wall of the bore 14 and the upper side 20 of the piston-head 15.A helical compression spring 21 is housed within the chamber 18 as shown, and acts between the cover 17 on the one hand and the piston-head 15 on the other hand, to bias the piston 12 away from cover 17.

The housing body 13 has an inlet 22 for connection to a high pressure helium gas cylinder (not shown). The housing 11 further comprises a sleeve 23, forming an outlet adaptor, screwed into an opening 24 at what is called "the bottom end" of housing body 13, with an O-ring seal 19 therebetween, to form a helium gas outlet 25 for connection to an inflatable flotation bag (not shown).

Co-axially with, and "below", the bore 14, the housing body 13 and sleeve 23 together form a narrower bore 26, into which there projects an axial shaft 27 of piston 12, projecting from the piston-head 15.

The housing body 13 also comprises two diametrically opposite actuation ports 28, Fig. 3, for connection to an actuating gas pressure source (not shown), such as compressed air, whereby actuating gas pressure can be selectively applied to the actuation ports 28, to operate the valve 10 and cause the sudden rapid transfer of gas through the valve 10. Two nipples 29 are screwed into the housing body 13 at the actuation ports 28, for the connection to the actuating gas pressure source (not shown). Actuating gas pressure is not applied until operation of the valve is required, that is, until rapid gas transfer is required.

There are two annular gas-tight seals 30 and 31, "upper" and "lower", between the housing 11 and the piston 12.

The "upper" seal 30 is arranged above the inlet 22, and acts between the housing body 13 and the axial piston shaft 27 to seal the closed chamber 18 off from the high pressure helium at the inlet 22: The seal 30 is seated on top of an internal annular ledge 32 forming an integral part of housing body 13. The seal 30 is retained in place by an annular housing ring 33 screwed gas-tightly into an upwardly projecting annular flange 34 of housing body 13.

The "lower" seal 31 is held in place by sleeve 23 and acts between the housing body 13 and the axial piston shaft 27, well below the inlet 22, when the piston 12 is as shown in its normal, lowermost position to seal the inlet 22 from the outlet 25.

The actuation ports 28 communicate with an annular cavity 35 between the flange 34 and the bore wall, below the piston-head 15, for actuating gas pressure selectively to raise the piston 12 from the position shown.

The downstream side of the "upper" seal 30 is vented to the actuation ports 28, in the sense that any high pressure helium which may seep past the seal 30, from the inlet 22, will pass through housing ring 33 and then outwardly over the underside 36 of piston-head 1-5, into the cavity 35 and then out through the actuation ports 28, assuming that no actuating pressure is being applied.

The valve 10 comprises a servo device 37 for biasing the piston 12 downwardly when the piston 11 is in its most downward (closed) position. The servo device 37 comprises a rod 38, slidably arranged in a bore 39 in the piston 12. The bore 39 is open at the top of piston 12, but not at the bottom of the piston 12. The bore 39 is long enough to accomodate the rod 38 when the piston 12 is caused to move fully to the top of its travel in housing 11 by actuation gas pressure applied to ports 28.

The bottom end 43 of bore 39 communicates indirectly, through one or more of three, equi-angularly spaced, lateral passages 44 (only one of which is shown) in the piston shaft 27, via a recess 46 (see below) with the high pressure gas inlet 22, so that the rod is subjected at its bottom end 40 to high pressure helium from the inlet 22 and bears at its top end 41 against a frusto-conical downward projection 42 forming an integral part of the cover 17.

The housing body 13 is formed with two annular recesses 45, 46 in the wall of the bore 26, between seals 31, 32, both recesses 45, 46 communicating directly with the high pressure helium inlet 22.

The recess 45 is long and shallow and is centrally positioned, being axially level with (and opening into) the inlet 22, connecting through a radial passage 47 (Fig. 5) with a relief valve 48, which can vent the inlet 22 to atmosphere through an axially-extending passage 49 in the event of excessive pressure build-up, for example during filling. The passage 49 is normally closed off from atmosphere by a plug 50 which can be blown out in the event of operation of relief valve 48.

Relief valve 48 is conventional, having Belleville spring washers 51 acting between a valve member 52 and a screw-threaded pressure adjuster 53. A thread protector 54 keeps out dust and dirt.

The other recess 46 is nearer the lower seal 31 and is connected to the "open" side of the U-shaped cross-section of seal 31 through small axially-extending holes 55, to open out the seal 31 and keep the seal 31 in sealing engagement with the wall of bore 26 on the one hand and the piston shaft 27 on the other hand.

The "lower" seal 31 is always below the lateral passages 44, even with piston 12 in its lowermost position, and seals the chambers 45 and 46 (as well as inlet 22) from the outlet 25 when the piston 12 is in its closed position as shown.

A further gas-tight seal 56 acts between rod 38 and bore 39, being retained in bore 39 at the top thereof by a retainer 57 which is screwed as shown into a scew-threaded recess 58 in the piston 12 at the top of the bore 39.

For filling helium into the gas cylinder (not shown) which is connected to the inlet 22, the housing body 13 is provided with a port 59, fitted with a one-way valve 60, so that the valve 10 does not have to be disconnected from the gas cylinder when filling the gas cylinder. The port 59 communicates directly with chamber 45. A further port 61 is provided, specifically for connecting a pressure gauge 62 to the valve 10, to measure the pressure of the gas in the high pressure cylinder (not shown). For rotating the pressure gauge 62, there is provided a union 63.

In operation, the valve 10 is normally closed. That is, the piston 12 is in its lowermost position as shown, held there by the combined effect of spring 21 and servo device 37. A high pressure gas cylinder (not shown) is connected to inlet 22, whilst an empty, gas-fillable flotation bag (also not shown) is connected to outlet 25. The actuation ports 28 are connected to a source of actuation pressure (not shown), which does not apply pressure thereto until required. The piston 12 and the seals 30, 31 and 46 operate to prevent leakage of gas as described above. Any leakage of gas past these seals is vented to the actuation ports 28 as described above.

If sudden rapid inflation of the flotation bag is required, actuating pressure is applied from the actuating pressure source (not shown) to ports 28, and is transferred to chamber 35 so as to apply pressure to the underside of piston head 15 and lift piston 12 towards the top end (cover 17) of the housing 11.

This causes the piston shaft 27 to unblock the inlet 22, so that the high pressure gas from the gas cylinder (not shown) rushes past the end of the piston shaft 27 to the outlet 25 and into the inflatable flotation bag (not shown). With eventual equalisation of pressure, at a low value, in the flotation bag and the abovementioned (formerly high-pressure) cylinder, the pressure on the bottom end 40 of rod 38 of servo device 37 is substantially reduced, assisting the upward movement of piston 12, which is cushioned by the gas and/or air trapped in the closed chamber 18 above the piston-head 15. The spring 21 and the air/gas cushion in closed chamber 18 eventually together return the piston 12 downwardly to its closed position, shutting off inlet 22 and outlet 25.

In a modification, the piston shaft 27 is provided with an integral rounded extension 64, indicated by chain-dot lines in Figs. 3 and 5, so that the width of the piston shaft 27 is reduced gradually and progressively from the base of extension 64, where it adjoins the rest of piston shaft 27, to the tip of extension 64, remote from the piston-head 15. This regulates the speed of the gas rushing from the high pressure cylinder to the flotation bag when the valve is operated, that is, opened, and may help to reduce freezing of the valve.

Claims

Claims: -

1. A valve for sudden rapid transfer of a gas from a high pressure gas container to a low pressure receiver, the valve comprising a housing and a piston, a piston-head of the piston being axially movable in a cylindrical bore of the housing with a substantially gas-tight seal between the piston-head and the bore, the housing having an inlet for connection to the high pressure gas container, an outlet for connection to the receiver and at least one actuation port for connection to an actuating gas pressure source, whereby actuating gas pressure can be selectively applied to said actuation port to cause displacement of the piston and hence sudden rapid transfer of gas from said high pressure gas container to said low pressure receiver, a compression spring being arranged in a closed chamber, formed in a part of the cylindrical bore between the housing and one side of the piston-head, the spring acting between the piston-head and the housing to bias the piston-head and hence the piston towards a closed position, an axially-extending portion of the piston projecting from the piston head, away from the spring, said axially-extending piston portion closing, when the piston is in its closed position, the inlet off from the outlet, the actuation port communicating with said bore in the housing on the far side of the piston-head from the spring, whereby pressure from the actuating pressure source can move the piston-head, against the spring and against a cushion of air or gas(es) in said closed chamber, towards an open position, so that the inlet then becomes connected to the outlet past the piston, a first seal acting between the housing and said axially-extending portion of the piston to seal the inlet from said cylindrical bore, a second seal acting between the housing and said axially-extending portion of the piston at said opening, to seal the outlet from the inlet when the piston is in its closed position, the valve also comprising a servo device to convert pressure at the inlet from the high pressure gas container to a force upon the piston when the piston is in its closed position, the force being in a direction such as to tend to hold the piston in its closed position, a third seal acting between the piston and the servo device, at least said first and second seals being vented to said actuation port on their downstream sides, said outlet also being vented to said actuation port.

2. A valve as claimed in claim 1 wherein said servo device comprises a longitudinally-extending member slidably arranged with a gas-tight seal in an axial passage through the piston, one end of said member bearing upon said housing, the other end of said member being subjected to pressure via said inlet from said high pressure gas container to produce a force and reaction between the housing and the piston.

3. A valve as claimed in claim 1 or 2 wherein the end of the piston is formed as a rounded portion of gradually and progreesively reducing width away from the piston-head, whereby interconnection of the inlet and the outlet upon the displacement of the piston is gradual and progressive.