WO1991014122A1

WO1991014122A1 - A valve

Info

Publication number: WO1991014122A1
Application number: PCT/GB1991/000376
Authority: WO
Inventors: Charles Percival D'archambaud
Original assignee: Archambaud Charles Percival D
Priority date: 1990-03-09
Filing date: 1991-03-08
Publication date: 1991-09-19
Also published as: AU7342291A; GB9005348D0

Abstract

A valve (10) for controlling the flow of fluid from two alternative supplies in such a manner that reduction or cessation of one supply automatically causes the valve to switch to the other supply comprises a cylinder having a piston (26) slidable therein in a region between a first fluid inlet (17) and a second fluid inlet (20). The piston has working surfaces (27A, 27B, 28A) of differential area such that equal pressure on both sides of the piston biases the piston (26) to one end of the cylinder. The valve has a fluid outlet (16) from the valve, a first fluid flow path from the first fluid inlet to the fluid outlet, and a second fluid flow path from the second fluid inlet to the fluid outlet and including an axial outlet bore (29). The second fluid flow path is closable by an end (28) of the piston abutting against a seal (32) in the cylinder and is opened upon axial movement of the piston towards the first fluid inlet caused when the supply of fluid from the first fluid inlet fails, is arrested or falls below a predetermined limit. The first fluid flow path is closable by the other end (34) of the piston sealing abutting the cylinder. The first working area of the piston presents to the first fluid inlet, depending upon the axial position of the piston in the cylinder either a minor working area (27A) less than the second working area (28A) presented to the second fluid inlet or a major working area (27A, 27B) greater than the second working area (28A) presented to the second fluid inlet. Both fluid paths may include the piston axial bore (29) or they may be separate and parallel.

Description

A VALVE

This invention relates to a fluid flow control valve which controls the flow of fluid (air or other gas or liquid) from at least two alternative supplies in such a manner that reduction or cessation of one supply automatically causes the valve to switch to another of the alternative supplies.

Such a valve is hereinafter referred to, where required, as "a valve of the kind described", and an example of such is disclosed in my Patent Application PCT/GB 89/00390 (Publication No. WO89/09903).

The valve disclosed in my aforesaid Patent Application comprises a cylinder having a piston slidable therein in a region between a first fluid inlet and a second fluid inlet, the piston having working surfaces of differential area such that equal pressure on both sides of the piston biases the piston to one end of the cylinder, a fluid outlet from the valve, a first fluid flow path from the first fluid inlet to the fluid outlet, a second fluid flow path from the second fluid inlet to the fluid outlet and including an axial outlet bore, the second fluid flow path being closable by the piston and being opened upon axial movement of the piston towards the first fluid inlet caused when the supply of fluid from the first fluid inlet fails, is arrested or falls below a predetermined limit, the valve being characterised in that the first fluid flow path is permanently open thus rendering the valve fail safe, and in that the axial outlet bore of the second fluid flow path is formed through the piston and is closable by a seal in the cylinder against which an end of the piston is adapted to abut.

Such a valve has many applications including, inter alia:-

1. the provision of a secondary air supply to air breathing apparatus used by an operative working in a contaminated atmosphere, which apparatus is normally connected to a primary air supply, in case of failure of the latter.

2. the operation (standby or primary) of bulk fire extinguishers, such as halon extinguishers on ships, or other C02 or other inert gas media for fire-fighting purposes.

3. in hydraulic applications, to cut in a secondary supply or to operate as a sensing valve. 4. in air brake systems, to operate as a fail safe device is a mains supply fails, which systems may be used in any vehicle or machine requiring air braking or emergency braking systems.

5. as a control valve for use in operating a secondary function.

6. in the underwater diving industry to operate emergency gas supplies to divers.

7. in high pressure reduction systems.

8. in anti-skid braking systems.

It is an object of the present invention to provide alternative constructions of the valve of the kind described in my aforesaid Patent Application.

According to the present invention there is provided a valve of the kind described comprising a cylinder having a piston slidable therein in a region between a first fluid inlet and a second fluid inlet, the piston having first and second working surfaces of differential area such that equal pressure on both sides of the piston biases the piston to one end of the cylinder, a fluid outlet from the valve, a first fluid flow path from the first fluid inlet to the fluid outlet, a second fluid flow path from the second fluid inlet to the fluid outlet and including an axial bore through the piston, the second fluid flow path being closable by an end of the piston abutting against a seal in the cylinder and being opened upon axial movement of the piston towards the first fluid inlet caused when the supply of fluid from the first fluid inlet fails, is arrested or falls below a predetermined limit, the valve being characterised in that the first fluid flow path is closable by the other end of the piston sealing abutting the cylinder, and in that the first working area of the piston presents to the first fluid inlet, depending upon the axial position of the piston in the cylinder, either a minor working area less than the second working area presented to the second fluid inlet or a major working area greater than the second working area presented to the second fluid inlet.

As a result, supply of fluid from the first fluid inlet moves the piston axially to close the second fluid flow path when the piston presents to the first fluid inlet its greater working area until the supply of fluid to the first fluid inlet fails, is arrested, or falls below a predetermined limit whereupon the supply of fluid from the second fluid inlet moves the piston axially to close the first fluid flow path and to present the lesser working area of the piston to the first fluid inlet, the first fluid path remaining closed until the supply of fluid to the second fluid inlet fails, is arrested, or falls below a predetermined limit.

In the valve according to this invention the second fluid path, when operational, in effect, takes and retains the role of the primary fluid supply to the valve outlet even when a fresh primary air supply is provided at the first fluid inlet until the secondary fluid supply fails, is arrested or falls below a predetermined limit.

This distinguishes this valve from that disclosed in my aforesaid Patent Application where, with the secondary fluid path operational, re-establishment of the primary air supply immediately causes closure of the second fluid path even though the secondary fluid supply is still effective.

The aforesaid predetermined limits of fluid supply may be the same or different.

Preferably, the piston axial bore forms part of both fluid paths.

Preferably, the piston has at its second fluid inlet end a seal adapted to abut an end of the cylinder to close the second fluid flow path.

Preferably the piston has adjacent its first fluid inlet end a radial inlet communicating with the axial bore of the piston.

Preferably, the first working area of the piston is, in terms of outflow of fluid from the valve, upstream of the radial inlet.

Preferably, the piston at its first fluid end has a seal adapted to abut against a surface of the cylinder to close the first fluid path.

Preferably, the first flow path is constituted by one or more axial bores parallel with and spaced from the piston axial bore, the first flow path communicating with a fluid outlet chamber of the valve with which the second flow path also communicates via a non-return valve.

Preferably, the piston at its first fluid end has a seal adapted to abut an end of the axial bore or bores parallel with the piston axial bore to close the first fluid path.

Preferably, the first working area of the piston is of stepped configuration defining inner and outer peripheral (usually annular) working areas with the inner working area having a seal adapted to abut a surface of the cylinder to interrupt communication between the first fluid inlet and the radial inlet in the piston thereby to close the first fluid flow path, the outer working area still being exposed to the first fluid inlet.

The present invention can be applied to the valve disclosed in my aforesaid Patent Application by forming the piston 18 (see Fig 1 of said Patent Application) with a first stepped and sealed effective area as above defined and radially disposing the axial bores 46 in the cylinder body such that they will be closed by the sealed inner working area of the piston, the radial passages 51 being omitted.

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:-

Fig. 1 is a longitudinal sectional view through a valve of the kind described according to the present invention;

Fig. 2 is a longitudinal sectional view of a valve as disclosed in my aforesaid Patent Application modified in accordance with the present invention; and

Fig. 3 is an enlarged detail view of part of the valve of

Fig. 2.

Referring to Fig. 1, the valve 10 comprises a body 11 to which is secured, preferably by screwing, an end cap 12, an O-ring seal 12A being interposed between the body 11 and the end cap 12.

The body 11 and end cap 12 define a chamber 13 which has an extension 14 of reduced diameter within the body 11 and a chamber 15 again of reduced diameter within the end cap 12.

The chamber extension 15 is of blind construction while the chamber extension 14 opens to an axially outlet passage 16 traversing the body 11. The passage 16 is of lesser diameter than the chamber extension 14. The outlet passage 16 of the valve 10 is connected directly or via hosing or piping to an operational mechanism or device such for example as a breathing mask.

A primary air inlet 17 is formed in the body 11 and communicates with the chamber 13. In this example, an air tank (not shown) is connected to the inlet 17 via a hose 18 incorporating a one-way valve 19. A secondary air inlet 20 is formed in the end cap 12 and communicates with the chamber extension 15 through a hole 21. Again an air tank (not shown) is connected to the air inlet 20 by a hose 22 incorporating a one-way valve 23.

There is thus provided for the valve a primary air supply indicated by the black arrows and a secondary air supply indicated by the hatched arrows.

Pressure indicators 24 and 25 are connected respectively with the chamber 13 and the chamber extension 25 via holes 24A and 25A respectively. These can be closed by plugs 24B, 25B respectively if the pressure indicators 24 and 25 are not required.

A piston 26 is slideably mounted within the chamber 13.

The piston 26 is provided on opposite sides with axial extensions 27 and 28 and an axial bore 29 traverses the length of the piston 26 and its extensions 27 and 28. There is thus communication between the axial chamber extension 15 and axial chamber extension 14 via the piston bore 29.

O-rings seals 30 and 31 are respective provided between the piston 26 and the valve body 11 and the piston axial extension 28 and the end cap 12.

The end of the blind bore chamber extension 15 has fitted thereto an O-ring seal 32 against which, in one position, the piston extension 28 abuts to close the communication between the secondary air inlet 20 and the piston axial bore 29.

The piston axial extension 27 is formed with a plurality of radial holes 33 which provides the communication between the primary air inlet 17 and the piston axial bore 29.

The piston 26 is formed, as can be seen, with two differential working areas defined by the end of the piston axial extension 28 constituting a secondary working area 28A and by surfaces 27A and 27B constituting a minor primary working area 27B and a major primary working area 27A and 27B combined.

The major primary working area 27A and 27B is greater than the secondary working area 28A while the minor primary working area 27B is less than the secondary working area 28A.

The working areas 27A and 27B are annular in configuration with the working area 27A being within the working area 27B. The sealing disc 34 overlies the inner working area 27A.

Assuming the piston 26 is in the position shown in Fig 1 and the primary and secondary air supplies are both open to the valve, the primary air supply will act on the major primary working area 27A and 27B to hold the piston 26 in the position shown which means that the secondary flow path from the secondary air inlet 20 to the outlet passage 16 is closed, the primary air flowing into the chamber 13, through the radial holes 33 and the axial bore 29 into the air outlet passage 16 and thence to the breathing mask.

If the primary air supply becomes exhausted i.e. the air in the air tank is used or substantially so (or for what ever reason the primary air supply is arrested) the secondary air supply will immediately act on the secondary working area 28A and cause the piston 26 to move axially so that the secondary air flow passage opens via the passages 21 and the axial bore 29 to the outlet passage 16 and the axial extension 27 of the piston 26 is driven into the chamber extension 14 until the sealing disc 34 contacts the valve body 11 thus closing off the primary air flow passage 17, 13, 33 and 29 from the outlet passage 16.

A fresh air tank can then be fitted to the primary air supply hose 18, the breathing mask now being supplied from the secondary air supply tank. The change over from the primary air supply to the secondary air supply is thus effected automatically and instantaneously.

Due to the fact that only the minor primary working area 27B is now exposed to the primary air inlet, the secondary air supply system becomes, in effect, the primary air system even if a fresh primary air supply is coupled to the inlet 17 until the air in the secondary air tank in exhausted, or substantially so, or is arrested for what ever reason at which time the primary air supply acting on the minor primary working area 27B drives the piston 26 back to the position shown in Fig 1, the primary air supply acting also on working area 27A, i.e. the major primary working area, when the sealing disc 34 moves away from the valve body 11.

The primary air supply system thus once again takes up its primary role, it having, in effect, been the secondary air supply system when only minor primary working area 27B was exposed to the primary air inlet 17.

The piston 26 consequently effectively "shuttles" to-and-fro between the two air supplies, each of which plays the role, at different times, of primary air supply and secondary air supply.

Suitable sensors may be connected to the air supply hoses 18 and 22 to indicate to the user which air supply he is currently being fed.

While reference has been made to air supply tanks it will be manifest that other air supply means can be employed.

Referring now to Fig 2 , this is a modification of the valve which is disclosed with reference to Fig. 1 our aforesaid Patent Application and the primary air path to the valve outlet is via the axial bores 46.

The modified valve comprises, in screw-engaging relationship, a main body 50 and two end caps 51 and 52.

O-ring seals 53 and 54 are provided between the main body 50 and the end cap 51 and the main body 50 and the end cap 52 respectively.

The main body 10 constitutes a cylinder within the chamber 55 of which is accommodated an axially-movable piston 56, an O-ring seal 57 being fitted between the piston 56 and the wall of the cylinder 50.

The piston 56 is formed with two oppositely-directed axial extensions 58 and 59.

The piston 50 with its axial extensions 58 and 59 define respectively differential working areas at opposite ends of the piston 50 like piston 10.

There is a secondary working area 59A and a major primary working area 58A and 58B and a minor primary working area 58B constituted by the stepped end of the piston 50 and the axial extension 58.

A sealing ring 60 overlies the inner working area 58A.

An axial open-ended bore 61 extends through the piston 50 and its oppositely-directed axial extensions 58 and 59.

The axial extension 59 extends into a blind bore 62 of the end cap 51, an O-ring seal 63 being fitted between the axial extension 59 and the wall of the blind bore 62. The end of the axial extension 59 is adapted to abut against an O-ring seal 63 in the closed end of the blind bore 62 thereby to close" the axial bore 61 at said end.

The axial extension 58 extends into a bore 64 open to the chamber 55 but of reduced diameter.

The chamber bore 64 communicates with a bore 65 of reduced diameter which terminates in a valve seat 66.

A non-return valve 67 engages with the valve seat 66 and comprises a disc-like body 68 having an inset sealing element 69 on its side adjacent the valve seat 66. The disc-like body 68 is formed with a ring of holes 70 around and radially outwards of the sealing element 69 (see Fig. 3).

The non-return valve 67 is urged against the valve seat 66 by a spring 71 which abuts a cap 72 screw-engaging an end boss 73 of the body 50. The cap 72 is open to an air outlet chamber 74 of the valve 67 via holes 75 in the cap 72.

The air outlet chamber 74 communicates with an axially-bored fluid outlet spigot 76 of the valve onto which can be engaged, by screwing for example, a coupling of an air hose (not shown) connected to a breathing mask (also not shown).

The main body 50 of the valve is formed with a primary air inlet 77, air being delivered via a hose 78 and a coupling 79 screw-engaging, or otherwise engaging, the air inlet 77. The coupling 79 incorporates a one-way valve 80.

The primary air inlet 77 delivers primary air into the chamber 55 at the upper surface of the piston 58, and the chamber 55 communicates with the air outlet chamber 74 via a plurality of bores 81 parallel with and surrounding the bores 64, 65. There may only be one bore 81 provided.

The end cap 51 is formed with a secondary air inlet 82, air being delivered from an air cylinder (not shown) for example via a hose 83 and a coupling 84 screw-engaging, or otherwise engaging, the air inlet 82. The coupling 84 includes a one-way valve 85. The latter delivers air to the blind bore 62 at the end of the axial extension 59.

It is to be noted that in this valve the axial bore 61 through the piston 50 is not common to both the primary and secondary air flow paths, the primary air flow path being via the chamber 55, the axial bores 81 into the chamber 74 and then out of the valve via the bore 86 of the spigot 76 while the secondary flow path is via the axial bore 61 into the bore 64, 65 through the non-return valve 67 into the chamber 74 and out of the bore 86, the bores 81, when air flow from the secondary air inlet 82 is operational, being closed by the sealing ring 60.

It will manifest from Fig. 2 that when the piston extension 58 is driven into the bore 64 the sealing ring 60 abuts the valve body 50 and closes the axial bore 81 as aforesaid leaving only the minor primary working area 58A exposed to the primary air inlet 77.

This modified valve thus operates in exactly the same way as that described with reference to Fig 1 save that the primary and secondary flow paths are different.

Claims

1. A valve of the kind described comprising a cylinder having a piston slidable therein in a region between a first fluid inlet and a second fluid inlet, the piston having first and second working surfaces of differential area such that equal pressure on both sides of the piston biases the piston to one end of the cylinder, a fluid outlet from the valve, a first fluid flow path from the first fluid inlet to the fluid outlet, a second fluid flow path from the second fluid inlet to the fluid outlet and including an axial bore through the piston, the second fluid flow path being closable by an end of the piston abutting against a seal in the cylinder and being opened upon axial movement of the piston towards the first fluid inlet caused when the supply of fluid from the first fluid inlet fails, is arrested or falls below a predetermined limit, the valve being characterised in that the first fluid flow path is closable by the other end of the piston sealing abutting the cylinder, and in that the first working area of the piston presents to the first fluid inlet, depending upon the axial position of the piston in the cylinder, either a minor working area less than the second working area presented to the second fluid inlet or a major working area greater than the second working area presented to the second fluid inlet.

2. A valve as claimed in claim 1, in which the piston axial bore forms part of both fluid paths.

3. A valve as claimed in claim 2, in which the piston has at its second fluid inlet end a seal adapted to abut an end of the cylinder to close the second fluid flow path.

4. A valve as claimed in claim 3, in which the piston has adjacent its first fluid inlet end a radial inlet communicating with the axial bore of the piston.

5. A valve as claimed in claim 4, in which the first working area of the piston is, in terms of outflow of fluid from the valve, upstream of the radial inlet.

6. A valve as claimed in any one of claims 2 to 4, in which the piston at its first fluid inlet end has a seal adapted to abut against a surface of the cylinder to close the first fluid path.

7. A valve as claimed in claim 1, in which the first flow path is constituted by one or more axial bores parallel with and spaced from the piston axial bore, the first flow path communicating with a fluid outlet chamber of the valve with which the second flow path also communicates via a non-return valve.

8. A valve as claimed in claim 6, in which the piston at its first fluid end has a seal adapted to abut an end of the axial bore or bores parallel with the piston axial bore to close the first fluid path.

9. A valve as claimed in any one of claims 3 to 5, in which the first working area of the piston is of stepped configuration defining inner and outer peripheral (usually annular) working areas with the inner working area having a seal adapted to abut a surface of the cylinder to interrupt communication between the first fluid inlet and the radial inlet in the piston thereby to close the first fluid flow path, the outer working area still being exposed to the first fluid inlet.

10. A valve as claimed in claim 7, in which the first working area of the piston is of stepped configuration defining inner and outer peripheral (usually annular working areas with the inner working area supporting the seal adapted to abut the end of the axial bore or bores parallel with the piston axial bore to close the first fluid flow path, the outer working area still being exposed to the first fluid inlet.