Pressurised container valve

A valve for a pressurized fluid cylinder. The valve comprises a shut off valve biased against a seat to seal the cylinder. An actuation element is movable linearly to open the valve against the biasing force. A linkage element couples the actuation element to the shut off valve and comprises a first piston towards its top and a second piston towards its bottom. The valve also comprises a gas refill inlet between the pistons such that refill gas pressure biases the linkage element away from the valve. The actuation element is a depressed position pushes against the linkage element to hold the linkage element down and the valve open so that the cylinder can be refilled. When the actuation element is in a non-depressed position, the linkage element is free to move with the refill gas pressure so that it is spaced from the valve.

The present invention relates to a valve for use in pressurised containers or gas bottles.

Gas bottles are typically sealed by urging a sliding/moveable member against a gas valve seat. This moveable member may be located either within or without the gas bottle. In the event that it is located within the gas bottle, it is urged closed by the high gas pressure inside the bottle and opened, when required, using a handwheel or lever. Once the valve has been opened in this way, high pressure gas is then driven through the valve into the bottle. An example of such a system is shown in US 2005/0173007.

In some situations, during refill, the pressurised gas may be passed through the valve before the valve has been opened using either the handwheel or the lever. This might happen for instance if the operator is tired or distracted. In these situations, the high pressure gas may itself generate enough force to open the valve and enter the bottle. However, the valve in this situation may chatter against the valve seat (due to the biasing force on the valve and the irregular force coming from the incoming gas). When certain gases are used, for instance oxygen, such chattering may present a risk of ignition.

Thus the present invention is directed towards a gas bottle which cannot be filled when such a handwheel or lever has not been first depressed.

Accordingly, the present invention provides a valve for a pressurised fluid cylinder, with a bore containing a valve assembly. The valve assembly includes a shut off valve biased against a seat to seal the cylinder; an actuation element movable linearly to open the valve against the biasing force; and a linkage element coupling the actuation element to the shut off valve. A first piston located towards the top of the linkage element seals with a first portion of the bore having a first diameter, and a second piston towards the bottom of the linkage element seals in a first position with a second portion of the bore having a second diameter less than the first diameter. The linkage element is movable to a second position in which the second piston enters a third portion of the bore having a diameter greater than the second diameter, such that the second position is no longer sealed with the bore. A gas refill inlet communicates with the second portion of the bore. The first piston includes a face exposed to the gas refill inlet which is larger than a face of the second piston exposed to the gas refill inlet, such that refill gas pressure biases the linkage element away from the valve. When the actuation element is in a depressed position, it pushes against the linkage element to hold the linkage element down and the valve open so that the cylinder can be refilled. When the actuation element is in a non-depressed position, the linkage element is free to move with the refill gas pressure so that it is spaced from the valve.

When the actuation element is in its first, non-depressed, position the pressure of the incoming fluid acts on solely the first and second pistons. Since the diameter of the first piston is more than that of the second piston, the pressure from the gas creates a net force towards the first piston, forcing the linkage element away from the shut off valve. The seal between the second piston and the bore in this position prevents the refill gas from reaching the shut off valve. The valve therefore cannot be opened by the refill gas when the actuation element is not depressed, so that the problem of ‘chatter’ cannot arise.

Only when the linkage element is moved into its second position by the operator moving the actuation element can gas flow past the second position to refill the cylinder.

The valve10therein shown is formed of a body11having a valve bore12which has a generally cylindrical shape. The valve bore12has a longitudinal axis L-L. A refill inlet14delivers gas from a pressurised source (not shown) and comprises an inlet passage20which is fluidly connected to the valve bore12through the valve body11via an opening in the bore's side wall. A seat26leading to the gas cylinder is located at the bottom of the bore12, whilst a control port18forms an opening in the top of the valve bore12.

A shut off valve22is located below the seat26and is biased by a spring24into a closed position and into engagement with the valve seat26.

A linkage element28, generally cylindrical in shape, is located inside the valve bore12and is movable along axis L-L. At the top of the linkage element28is a first piston30which, in a first position, engages with the side wall of the valve bore12and has a top surface which contacts a shoulder32in the valve bore12. Connected to this top surface of the piston30is an actuation element31(for instance, a lever) which is operated by a user to depress the linkage element28. Towards the bottom of the linkage element28is a second piston34which in a first position engages with the side wall of the valve bore12. Located at the bottom of the linkage element28is a contact surface36which selectively bears against the shut off valve22.

As is shown inFIG. 1A, the first and second pistons straddle the refill inlet14.

The bottom surface of the first piston30and the top surface of the second piston34each define a respective gas contact area30A;34A which is defined by the cross sectional area of the piston30;34less the cross sectional area of the linkage element28between the pistons. In the closed position of the valve (FIG. 1A), pressurised gas coming from the refill inlet14acts on both these contact areas30A;34A. The first piston30has a larger gas contact area than that of the second piston34.

To prevent fluid leaking past the first and second pistons30;34when in the closed position, each piston has a circumferential o-ring seal38which engages with the side wall of the valve bore12.

The diameter of the bore12is stepped along its axis L-L as shown inFIGS. 1A and 1Band is generally formed of five portions. A first topmost portion12A of the bore has a first diameter which is sized to seal against the diameter of the first piston30. Beneath the first portion of the bore12is a second portion12B which has a second diameter which is less than that of the first portion12A and which is sized to seal against the diameter of the second piston34when the valve is in its closed position. Beneath the second portion12B is a third portion12C which has a larger diameter than that of the second portion12B. A fourth portion12D beneath the third portion12C of the bore is sized to accommodate the valve seat26whilst the fifth and bottommost portion12E is sized to accommodate the check valve22with clearance.

If a user attempts to refill the cylinder when the valve10and the actuation element31are in the closed position shown inFIG. 1A, pressurised gas which enters the valve bore12from the refill inlet14acts on the gas contact areas30A;34A. Since the gas contact area30A of the first piston30is larger than the gas contact area34A of the second piston34, the net force from the pressurised gas in the valve bore12forces the linkage element28upwards and the top surface of the first piston30into engagement with the shoulder32at the top of the bore12. This brings the second piston34into the second portion12B of the bore, thereby sealing the path to the shut off valve22. Thus in the closed position, the pressurised gas is contained between the two pistons30;34. Therefore the refill unit cannot supply fluid to the gas cylinder.

When a user requires refill gas to be delivered to a gas cylinder, they depress the linkage element28by using the actuation element31to exert a downward force F on the top surface of the first piston30which exceeds the net force applied by the pressurised gas on the linkage element28and the spring24. The downward force applied to the top surface of the first piston30forces the linkage element28and hence the check valve22downwards into the valve's second, open, position shown inFIG. 1B.

In this open position, whilst the first piston30is still sealed with the first portion12A and the side wall of the valve bore12, its top surface disengages from the shoulder32and a portion of its gas contact area30A lands on a second shoulder33in the valve bore12(which is defined by the interface between the first and second portions of the bore12). This shoulder33prevents the linkage element28from moving beyond its second position. Also in the open position, the second piston34moves beyond the side wall of the second portion12B of the valve bore12into the third portion12C of the bore12; and the contact surface36makes contact with the shut off valve22, forcing the shut off valve downwards and apart from its valve seat26. Thus in the open position the pressurised gas from the refill inlet14can pass around the second piston34, through the open shut off valve22, and into the gas cylinder.

When enough gas has been supplied to the gas cylinder, the gas supply from the refill unit (not shown) connected to the inlet14can be isolated, shutting off the supply of pressurised gas flowing through the bore12. The downward force F from the user applied using the actuation element31can then be removed. In so doing, the pressure from the gas cylinder and the force from the spring24closes the shut off valve22.

Although the above valve has been described with reference to pressurised gas being fed from the inlet14, past the check valve22and into a cylinder when the actuation element is depressed; it will be appreciated that in normal use (i.e. when the cylinder is not being refilled) the shut off valve22can be pushed down such to allow pressurised gas from a cylinder to pass around the check valve when the actuation element31is depressed and out through the refill inlet14(which becomes the outlet of the valve).