Fluid pressure sensing releasing device

Technical field: The present invention relates to a fluid-pressure sensitive releasing device. Particulary in shipping, such devices are used for releasing mechanisms when the device in question is submerged under-water. These mechanisms are generally designed to retain objects such as life-rafts, emergency radio transmitters etc., which should be released from a vessel in the event of an accident. In other areas use is also made of devices which bring about the release of some mechanism when they are submerged or come into contact with water or possibly other fluids. Such mechanisms may be found in washing machines or dishwashers for shutting off the water supply and/or emitting an alarm signal in the event of the release of the washing fluid outside of the machine.

Background of the invention:

A device known fϊfom US-A-3 630 413 uses as a water sensitive element a body of a material which has certain strength in.a condition in which it is not affected by the fluid and whose strength is considerably reduced with exposure of the material to the fluid. A release member which abuts the body and retains it in a safety position is arranged to be displaced to a release position by the action of a spring force when the material of the body reduces its strength due to the influence of fluid. The body is sealingly enclosed in a space to which a valve is connected. The valve, upon being subjected to a predetermined pressure acting on the releasing device, is

arranged to connect the space to the surroundings. If the device is emersed in liquid the pressure of the liquid opens the valve and the liquid will flow in through the valve to the body so that release during displacement of the release member is achieved. The invention relates to a device of this type.

Technical problem:

Releasing devices of this type have the advantage of being simple in design and, through their simple performance, offer high reliability in terms of bringing about the releasing when the device comes into contact with the fluid. There is however a large risk that releasing accidently occurs if the valve which should protect the fluid-sensitive body leaks or "breathes" even at pressure changes which are so small that release should not occur. With conventional valves having a displaceable valve body it is difficult to fully ensure that this does not occur.

Solution:

According to the invention the valve arrangement consists of a member which is arranged to be displaced under the influence of said pressure and a sleeve separating the body from the surroundings, whereby the member is provided with parts which are arranged to penetrate the sleeve and expose the body in connection with movement of the member.

Advantages:

With the present invention a fluid sensitive releasing device is achieved which has a simple construction and reliable releasing function, though at the same time presents a high margin of safety against undesired releasing due to valve leakage and water vapour in the surrounding atmosphere. This is mainly achieved due to the fact that the member can be made with greater resistance to leakage than a valve of the conventional type.

Brief description of the figures:

An embodiment of the invention is shown in the attached drawing in a central cross-section, the device having a cylindrical shape.

Best mode of carrying out the invention:

As can be seen from the drawing the device comprises a housing 1 which is cylindrical and closed by a cover 2 which can be located by a ring of screws 3. The cover 2 presents a hole 4.

Clamped between the cover 2 and the housing 1 is the outer edge of a body of an elastomer which shall be referred to as the membrane 5 in the following. The membrane 5 has a disc-shaped region 6, the edge of which is clamped between the cover and the housing and which, by means of a radial groove 7 transcends to a substantially cylindrical part 8 with a bellow fold 9. Below the bellow fold the cylindrical part has a tighter region 10 which terminates the membrane 5.

The housing 1 is bowl-shaped with the open end covered by the cover 2 and has a base 11 opposite the opening. A central section 12 extends from the base and the upper part thereof is arranged in the hole 4 of the cover with a clearance within the hole whereby a chamber between the region 6 of the membrane and the cover is in communication with the surroundings. The central section 12 is provided with a corbelling which, on the s de remote from the cover, forms a seat 13 for the inner edge of the membrane's region 6. The membrane possesses such resilience that it maintains a sealing contact with an edge against the seat 13. The part 10 of the membrane is in sealing contact against the central section.

Within the central section 12 is a cavity with an upper narrower region 16 which, via a shoulder 17, opens into a wider region 18. A body 20 of the type mentioned in the introduction rests against the shoulder 17 under the influence of a release member 21. A plurality of holes 14 are located around the central section 12 below the membrane's sealing edge, which holes extend through the wall of the central section.

The release member 21 consists of an inner part 22 which rests against the body 20 and the member thereafter transcends via a outwardly protecting flange 23 to an outer part 24. The outer part projects through a hole in a disc¬ screw 26 threaded into a hole in the base 11 and which is sealed to the member 21 with the help of an O-ring 27. The threads between the disc-screw 26 and the housing 1 are also sealed to the surrounding atmosphere.

Between the disc-screw 26 and the flange 23 there is a tensioned pressure spring 28 by means of whose force the release member 21 rests against the body 20. The body 20 is hereby formed of such material that in its condition in which it is not affected by fluid it retains the release member in the secure position as shown in the drawing. The purpose is that, upon contact with the fluid in which the device is intended to release, the body will lose its strength so that the release member 21 under the influence of the spring 28 is displaced upwardly with respect to the position shown in the drawing with its end within the space which the body in its unaffected condition otherwise occupies.

The outer part 24 of the release member 21 is connected in a not shown manner to the mechanism which is to be released. Thus, the member 21 can be introduced in a chain or link which is arranged to be broken when the member is

displaced in to the housing by the spring 28 so that, for example, a life-raft is released from the vessel to which it is secured.

The chamber in the housing 1 which surrounds the membrane should suitably be in communication with the surrounding atmosphere via an opening 29 within which a fine porous material is maintained. In this manner, normal slow pressure changes in the atmosphere can be balanced by flow through the fine porous material so that the membrane 5 always maintains a balanced bearing pressure whilst the pores at the same time do not allow ingress of fluid.

The region 8 of the membrane 5 is wider than the central section 12. A sleeve 32 of a thin sealing material, suitably an elastomer, is tightly held around the central section 12 within the region 8. Above the holes 14 and projecting in through the region 8 is arranged a number of knives 34 secured to a ring 33 and which are sealingly moulded in the material of the membrane 5.

The device functions in the following manner: provided that the device is not submerged in liquid the release member 21 is maintained in the shown position resting against the body 20. If the device is submerged in liquid, this will flow in through the gap between the hole 4 of the cover and the central section 12 and, at a certain depth, the region 6 of the membrane 5 will be acted upon such that it releases from the seat 13 and allows liquid to flow into the space within the region 8 of the membrane and into contact with the sleeve 32.

Even if the membrane 5 should move away from its seat there will not be a connection between the surrounding atmosphere and the body 20 for example through "breathing" as a result of pressure jolts or temperature variations. The sleeve 32 in fact protects the body 20 from contact with the atmosphere by covering the holes 14.

If on the other hand the device is subjected to a sufficiently high fluid pressure on the side of the membrane 5 facing the cover 2 such that the region 30 is displaced so far downwards that the knives 34, by cutting through the sleeve's 32 thin material, open up slits in the sleeve, the fluid can flow in through these slits, through the holes 14 and to the body 20. Accordingly a decisive fluid pressure on the membrane is required to actually achieve such a large knife movement that the sleeve 32 is opened. When the fluid flows in to the body 20 via the holes 14, the body loses its resistive effect and the spring 28 ensures that the release member 21 is projected inwardly and executes its releasing function. The said fine porous material prevents such a subpressure arising behind the membrane that it can be affected by the atmosphere so that it opens up. In addition, an overpressure in the chamber beneath the membrane is also avoided which would mean that it would not open at the intended depth of submergence. The device can be adapted for release at a certain pressure by adjusting the opening pressure of the membrane.

The invention's technical content is accordingly that use is made of a body of a fluid-sensitive material, as described, and encased in the device and sealed from the surroundings by a valve which is activated by surrounding fluid pressure. The actual releasing function remains of simple design which is known from this type of releasing

device and a further safety function is achieved by means of a device which is simple in itself, i.e. by the design of the sealing sleeve which is not affected by those pressure transients and inner underpressure which can cause the valve body in a conventional valve to "breath".

The element which internally protects the body from the effects of the surroundings has been shown here as a tube- shaped sleeve. Other forms, such as a membrane, are also conceivable. In this manner the penetration can occur by puncturing during the movement of the member.

This and other forms fall within the scope of the invention, in that a pressure activated member is arranged to penetrate a sealing element by means of, for example, cutting implements. The term "sleeve" hereby includes a large number of possibilities. The final phase of the process is not affected by if the membrane exercises any sealing valve function, accordingly if the space around the sleeve is air or fluid filled.