Improvements in or relating to relief valves

Abstract: An in-line relief valve is described having a tubular member (1) for location in a bore (2), so that compressed gas can flow from the bore (2) and through the tubular member (1), in which at higher fluid pressures gas can vent through a gap (5) provided between the bore (2) and the tubular member, whilst at lower pressures the gap is closed by a seal (8). The seal (8) may be urged by a spring (9) against a shoulder (7) in the bore.

Description: This invention relates to a relief valve and more particularly is concerned with an in-line relief valve. Generally, when using pipes or hoses to convey compressed gas or other fluid, it is necessary to ensure that the pressure does not exceed a certain level. DE-A-2165179, which forms a basis for the preamble of claim 1, describes a safety valve suitable for connection to a pressure line, and having an inlet which can be connected to the pressure line, an outlet leading to an exterior, and an interposed valve seat which is closeable by a pre-stressed valve plate. It is an object of the present invention to provide a valve having a novel pressure relief mechanism. According to the present invention there is provided an in-line relief valve for use with a fluid, such as compressed breathable gas, characterised in that it comprises a tubular member fixed in a bore provided in a body, so that fluid can flow from the bore and through the tubular member, wherein the bore has a cross-sectional dimension greater than the cross-sectional dimension of the tubular member so that a gap is provided between the outer surface of the tubular member and the inner surface of the bore and a seal is provided downstream of said gap adapted to close said gap at lower fluid pressures and to allow fluid to vent through said gap at higher fluid pressures. For a better understanding of the invention and to show the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:- Figure 1 is a sectional view of a first embodiment of a relief valve in accordance with the present invention, and Figure 2 is a sectional view through a second embodiment of a relief valve in accordance with the present invention. Referring to Figure 1, there is shown a valve comprising a tubular member 1 for location in a bore 2 in a body 3. The bore 2 includes a portion 4 having a cross section which includes a dimension greater than the corresponding dimension of the tubular member 1. Thus, in the embodiment shown, the outer diameter of the tubular member 1 is somewhat less than the diameter of the bore portion 4 so that a gap 5 is provided between the wall of the bore portion 4 and the outer surface of the tubular member 1. The bore 2 includes, adjacent to and downstream of bore portion 4, another bore portion 6 of increased diameter with a stepped shoulder 7 provided between the two bore portions. An O-ring 8 is mounted on the outer surface of the tubular member 1 adjacent to the stepped shoulder 7. The O-ring 8 is longitudinally displaceable with respect to the tubular member 1 between a first position adjacent to the stepped shoulder 7 in which it closes said gap and a second position in which it is spaced from said gap. The O-ring 8 is urged into contact with the stepped shoulder 7 by a spring 9. Thus the O-ring 8 is downstream of the gap 5. The O-ring 8 is nested in a cup washer 10 loosely fitted to the outer surface of the tubular member 1. One end of the spring 9 acts on the cup washer 10 and the other end of the spring 9 acts on a flange portion 11 on the outer surface of the tubular member 1. The sealing face 7 is stepped so as to minimise the opening tolerances and the opening pressure. The tubular member is retained in the bore 2 by means of a staple pin comprising a pair of limbs 12 linked together at one of their ends to form a generally U-shaped member. The limbs 12 pass through holes 14 in the body 3 and lie in a circumferential groove 13 provided in the outer surface of the flange portion 11. In this way, the valve can be rapidly connected to, and disconnected from, the bore in the body 3. A chamber 15 is thus defined by the bore portion 6 and the outer surface of the tubular member 1 and a channel 16 is provided to link the chamber 15 with the atmosphere. The tubular member 1 terminates in a tail piece including an enlarged portion 17 to facilitate the connection of a hose or pipe (not shown). Tension can be applied to the hose or pipe without loss of pressure or of flow. In use, compressed air or other fluid under pressure flows along bore 2, through the tubular member 1 and thence along the hose or pipe connected thereto. The force exerted by the spring 9 is such that, at normal working pressures, the O-ring 8 is sealingly seated against the stepped shoulder 7 and prevents fluid passing through the gap 4 and into the chamber 15 and thence to the atmosphere. However, if the fluid in bore 2 is at a higher pressure exceeding a predetermined pressure (determined by the area between the step of shoulder 7 and the outer surface of the tubular member 1 and the force exerted by the spring 9) the O-ring 8 is caused to lift off the stepped shoulder 7 against the action of spring 9 whereby a part of the fluid can pass into chamber 15 via gap 4 and vent to the atmosphere via channel 16, whilst the remaining fluid can continue to flow through the tubular member 1. Instead of or additional to the channel 16, fluid can vent from the chamber 15 via a slot (not shown) provided in the flange portion 11 or by ensuring that a clearance is provided between the tubular member 1 and the wall of the bore portion 6. Referring now to Figure 2, parts corresponding to parts of Figure 1 are denoted by the same reference numerals. In this case, the bore portion 6 is defined by a cylindrical protrusion on the body 3 and an external screw thread is provided on the outer surface of the protrusion. The valve is retained on the body 3 by means of a cap 20 which includes an internal screw thread threadingly engaged with the external screw thread of the protrusion and which bears on the flange portion 11. Also, in this case, the cap 20 assists in retaining the pipe or hose (not shown) on the tail piece of the tubular member 1. As in the previous embodiment a substantial pulling force can be exerted on the hose or pipe without loss of pressure or of fluid flow.

Claims: An in-line relief valve for use with a fluid, such as compressed breathable gas, characterised in that it comprises a tubular member (1) fixed in a bore (2) provided in a body (3), so that fluid can flow from the bore (2) and through the tubular member (1), wherein the bore (2) has a cross-sectional dimension greater than the cross-sectional dimension of the tubular member (1) so that a gap (5) is provided between the outer surface of the tubular member (1) and the inner surface of the bore (2) and a seal (8) is provided downstream of said gap (5) adapted to close said gap (5) at lower fluid pressures and to allow fluid to vent through said gap (5) at higher fluid pressures. An in-line relief valve according to claim 1, in which the seal (8) is longitudinally displaceable with respect to the tubular member (1) between a first position in which it closes said gap and a second position in which it is spaced from said gap, the seal being resiliently biased towards the first position. An in-line relief valve according to claim 1 or 2, in which the bore has a first bore portion (4), a second bore portion (6) of larger cross-sectional dimension than the first bore portion and a stepped shoulder (7) between the first and second portions (4,6), said seal (8) being in contact with the stepped shoulder (7) at lower fluid pressures to close said gap (5) . An in-line relief valve according to claim 3, in which the seal (8) is urged against the stepped shoulder (7) by a spring (9). An in-line relief valve according to claim 3 or 4, in which said gap (5) is provided between said first bore portion (4) and said tubular member (1). An in-line relief valve according to any preceding claim, in which the tubular member (1) is fixed inside the bore (2) by means of a U-shaped staple pin (12) passing through holes (1) provided in the body (3) and engaging with a flange (13) provided on the tubular member (1). An in-line relief valve according to any preceding claim in which a channel (16) is provided in the body (3), such that at said higher pressures fluid passes through said gap (5) and vents through said channel (16).

Inventors: VAN HALL MAURICE, VAN HALL, MAURICE
Applicants: DRAEGER LTD, DRAEGER LIMITED
Application year: 1996
Main classification: F16K17
IPC codes: F16K17, F16L55, B63C11, A62B9, F16K24