GB2051212A - Hydrostatic release device - Google Patents

Abstract

Entry of water through inlet 28 into chamber 20 urges diaphragms 14 against spring 26 into sealed chamber 18. This pulls rod 30 to the left and removes elements 34 from the illustrated blocking position. Lever arms 36 are thus free to pivot under the influence of a force tending to remove attachment 46, which is thus released. <IMAGE>

Description

SPECIFICATION Hydrostatic release device This invention relates two a securing device which is intended to release when immersed in water to a predetermined depth. Such devices are used on ships for automatically releasing iifesaving equipment if the vessel sinks.

Conventionally such a device comprises a housing which is partitioned internally by a flexible.

diaphragm to provide two chambers, one chamber having an inlet for the entry of water on submersion and the other chamber being essentially.sealed so that increasing water pressure in said one chamber flexes the diaphragm against a spring, causing a stepped rod to move axially, a pair of spring-loaded lever arms following the step in the rod so that they move out of a position in which they retain an attachment pin projecting from one end of the housing, whereby the pin can detach from the housing and release the equipment secured thereby. The rod is arranged along an axis normal to the plane of the diaphragm and is slidably mounted in one part of the housing. A separate second part of the housing,defines one of the chambers and the two parts are secured together with the diaphragm between them.The attachment pin projects from said one part of the housing, and said other part of the housing is adapted for attachment to a fixed part of the vessel or the like.

Such design of release device is rather complicated, and hence expensive, to manufacture and assemble. Also the internal mechanism is subject to appreciable friction so that it is difficult to ensure its operation at an accurately predetermined depth of submersion.

The hydrostatic release device of the present invention comprises a housing containing a flexible. diaphragm which separates first and second chambers in the housing, one chamber having inlet for the entry of water, the other chamber being essentiaily sealed against the entry of water, a spring urging the central portion of the diaphragm towards said one chamber, a rod movable with the diaphragm extending therefrom at right angles to the plane of the diaphragm, a lever arm pivotally mounted in the housing and having an abutment portion which normally engages and retains the inner end of a detachable attachment member the outer end of which projects from the housing for securing equipment to the device, another portion of the lever arm being normally engaged by an element movable with said rod to keep the lever arm in its retaining position, axial movement of the rod produced by the entry of water above a predetermined pressure in said one chamber causing movement of said element relative to the lever arm so that the arm can pivot into a position in which it releases said attachment member The element movable with the rod is preferably a rollable element such as a ball or disk rotatably located in a lateral recess in the rod and projecting therefrom.The lever arm is preferably freely pivotable between the retaining and release positions, and the abutment portion of the lever arm and the part of the attachment member engaged thereby are arranged so that when the rod moves to its release position withdrawal force on the attachment member cams the released lever arm out of its retaining position. By these means frictional resistance to release of the device is kept low.

The housing is preferably in two parts with the diaphragm between them. The sealed chamber is preferably on the side of the diaphragm remote from the rod with the spring disposed therein. The sealed chamber may have a port suitably closed, for example by a porous disc, so as to allow passage of air to keep the chamber at atmospheric pressure but prevent the entry of water.

Alternatively a porous element of such a type may be provided between the first and second chambers so as to allow slow equalisation of pressure between them. Preferably a pair of lever arms are provided on opposite sides of the rod, each acted on by a respective rollable element projecting from a recess in the rod, the two arms co-operating to retain the attachment member.

The part of the housing from which the attachment member projects preferably has on its side remote from the attachment member means for securing the device to a fixed Support The housing preferably has an aperture coaxial with the rod to allow the rod to be moved manually against the spring to manualiy-release the attachment member. The rod may project through the aperture, but preferably it is wholly contained within the housing and accessible to an instrument inserted through said aperture. The direction of withdrawal of the attachment member is preferably radial to the axis of the rod, and the lever arm is pivoted on an axis parallel to the axis of the rod.

In order that the invention may be more clearly understood, two embodiments will now be described with reference to the accompanying drawings, wherein: Fig. 1 is a cross-section of a first embodiment on the line I-I of Fig. 2; Fig. 2 is a cross-sectional side view of the device; Fig. 3 is a fragmentary cross-sectional plan view in the region of engagement of the balls and lever arms; Fig. 4 is a fragmentary cross-sectional end view in the region of engagement of the lever arms with discs instead of balls; Fig. 5 is a fragmentary cross-sectional side view of an alternative form of pressure equalising arrangement; Fig. 6 is a cross-sectional view of a second embodiment on the line X-X of Fig. 7; and Fig. 7 is a cross-sectional view on the line Z-Z of Fig. 6.

Referring to Figs. 1 to 3 of the drawings; the hydrostatic release device comprises a housing having two parts 10, 12 bolted together on a common plane through a flexible diaphragm 14 and an insert disc 1 6. The part 10 provides a chamber. 1 8 on one side of the diaphragm, while the insert disc 16 provides a chamber 20 on the other side of the diaphragm. The chamber 1 8 is sealed against the entry of water. A compression spring 26 in the chamber 1 8 bears upon the central portion of the diaphragm and urges it towards the chamber 20. The insert disc 1 6 has a port 28 which allows water into the chamber 20.

A rod 30 is attached at one end to the centre of the diaphragm and projects therefrom, at rightangles to the plane of the diaphragm, in the direction away from the spring, passing slidably through an aperture in the centre of the insert disk 16 and into a third chamber 32 in the housing part 12. Here the rod is provided with a transverse through passage containing a pair of steel balls 34 whose combined diameters are greater than the diameter of the rod, so that they project laterally from the rnd A pair of lever arms 36 are pivoted at 38 to the housing part 12 within the chamber 32 on either side of the rod 30. They are provided with tail portions 40 which are normally engaged by the balls and thereby kept apart.The lever arms are provided at their other end with mutually inwardly directed nose portions 42 which, when the rails are separated by the balls 34, co-operate to engage in a rebate 44 in the stem 46 of a detachable attachment member 48, thereby retaining it in the housing part 12. In this position the attachment member projects from an opening at the top of the housing part 12 and is provided with a hook part 50 which co-operates with a shoulder 52 on the housing part to retain a ring (not shown) attached to a line (also not shown) which is used to secure lifesaving equipment on board a vessel. The housing part 12 is provided on the side opposite the hook 50 with a fixed ring 54 for use in securing the device to the deck or other fixed support.

In operation, when the device is submerged to a predetermined depth, for example when the vessel sinks, the water pressure acting in the chamber 20 flexes the diaphragm 14 into the chamber 1 8 against the spring 26, thereby withdrawing the rod 30 somewhat from the chamber 32. This brings the balls 34 out of engagement with the lever arms 36, and into a retaining annular recess 56 in the wall of the insert disc 1 6. With their tail portions 40 thus released, the- lever arms 36 are free to pivot so as to bring their nose portions 42 out of engagement with the rebate 44.Either or both of the contacting surfaces of the nose portions and rebate are shaped, for example by a 50 inclination from the normal to the axis of the stem 46, so that a withdrawing force applied to the attachment member will cam the nose portions out of engagement with the rebate and allow the attachment member to be detached.

The device can be manually released if desired by inserting a suitable tool 60 through an aperture 58 in the wall of the housing part 1 2 concentric with the rod 30, and depressing the rod against the spring 26. As shown, the end of the rod 30 facing the aperture 58 is hollow and is closed by a plastics plug 62 having a peripheral rim 64 which normally engages an O-ring 66 to seal against the entry of water into the chamber 32. When the attachment member 48 has been withdrawn and the rod 30 allowed back to its normal position, the lever arms could close together at their nose portions 42, preventing the reinsertion of the attachment member.To avoid this, pins 69 are provided projecting from the insert disc 1 6 into the chamber 32 on either side of the tail portions 40 of the lever arms to limit the movement apart of the tail portions so that the nose portions cannot close.

Also as shown, the rod 30 is attached to the diaphragm 14 by a nut 68 which retains a porous p.t.f.e. sleeve 70 and washers 72. These porous p.t.f.e. elements allow very slow passage of air, but not water, between chambers 1 8 and 20 to equalise pressure resulting from atmospheric pressure or temperature changes. Fig. 5 shows an alternative arrangement in which the part 10 has a port 22 closed by an air-permeable but waterimpermeable disc 24 whereby air can pass through the port to keep the chamber 1 8 at atmospheric pressure.

Fig. 4 shows an arrangement in which, instead of balls 34, a pair of discs 35 (shown here edgeon) are rotatably located in a slot in the rod 30 and engage the tail portions 40 of the lever arms. The discs will make line contact with these tail portions if the latter have flat surfaces, or will make point contact with the tail portions if the latter have somewhat convex surfaces engaging the discs.

The embodiment of Figs. 6 and 7 is suitable for a smaller scale device, for example for use on small yachts. For the most part the construction is similar to that of Figs. i to 3, and like parts given the same reference numerals. In this case, however, the rollable elements are omitted, and the rod 30 is provided with a frustoconical surface 31 leading to a region 33 of reduced diameter which, when the rod is moved axially by the increase of pressure in the chamber 20 allows the tail portions 40 of the lever arms to move closer together and release the attachment member 48.

The lever arms 36 are still freely pivotally mounted on pivot pins 38. The nose portions 42 being offset as shown results in a withdrawal force on the attachment member applying a turning movement to the lever arms tending to release them. Apart from this, there is no force appiied by the tail portions of the lever arms on the rod 30, so that frictional resistance to movement of the rod is normally low. In this embodiment also the pivot pins 38 are supported at both ends. At one end they are securely mounted to the wall of the housing part 12, and at their other end they have portions 39 of reduced diameter which locate in apertures in a support plate 41 which is fitted within the opening of the housing part 12 adjacent the insert disc 16 prior to assembly of the insert disc, the diaphragm 14 and the housing part 10.

The support plate 41 is also located on a third pin 43 projecting from the wall of the housing part 1 2.

In this embodiment, in place of the separate stop pins 69 there are provided integral moulded projections 69' on the inside wall of the housing part 12.

In both of the foregoing embodiments the device is a simple construction from relatively few parts. Relatively little machining is required, and that is confined to circular machining which can be done for example on a lathe rather than requiring more expensive milling processes. The housing between the attachment member and the securing.ring 54 is a single integral part 12, rather than two or more housing parts secured together and hence subject to the possibility of coming apart.

Claims (10)

1. A hydrostatic release device comprising a housing having a first part and a second part secured together with a flexible diaphragm between them separating first and second chambers in the housing, and a detachable attachment member the outer end of which projects from the first part of the housing for securing equipment to the device, one said chamber having an inlet for the entry of water, the other chamber being essentially sealed against the entry of water, a spring urging the central portion of the diaphragm towards said one chamber, a rod movable with the diaphragm extending therefrom an right angles to the plane of the diaphragm and into the first housing part, a lever arm freely pivotally mounted in the first housing part and having an abutment portion which normally engages and retains the inner end of the detachable attachment member, another portion of the lever arm being normally engaged by an element movable with said rod to keep the lever arm in its retaining position, axial movement of the rod produced by the entry of water above a predetermined pressure in said one chamber causing movement of the rod relative to the lever arm so that the arm disengages from said element and can pivot into a position in which it releases said attachment member, the first housing part having means for securing the device to a fixed support.

2. A hydrostatic release device according to claim 1 wherein said element movable with the rod is a rollable element rotatably located in a lateral recess in the rod and projecting therefrom.

3. A hydrostatic release device according to claim 1 wherein said element movable with the rod is a portion of the rod itself.

4. A hydrostatic release device according to any one of claims 1 to 3 wherein a pair of lever arms are provided on opposite sides of the rod, engaging respective element movable with the rod, the two arms co-operating to retain the attachment member.

5. A hydrostatic release device according to any one of the preceding claims wherein the housing has an aperture coaxial with the rod to allow the rod to be moved manually against the spring to manually release the attachment member.

6. A hydrostatic release device according to any one of the preceding claims wherein the abutment portion of the lever arm and the part of the attachment member engaged thereby are arranged so that when the rod moves to its release position withdrawal force on the attachment members cams the released lever arm out of its retaining position.

7. A hydrostatic release device according to any one of the preceding claims wherein the direction of withdrawal of the detachable.

attachment member from the housing is radial to the axis of said rod, and said lever arm being pivotally mounted on a pivot axis parallel to the axis of the rod.

8. A hydrostatic release device according to any one of the preceding claims wherein the sealed chamber is on the side of the diaphragm remote from the rod with the spring disposed therein.

9. A hydrostatic release device according to any one of the preceding claims wherein the sealed chamber has a port suitably closed so as to allow passage of air to keep the chamber at atmospheric pressure but prevent the entry of water.

10. A hydrostatic release device substantially as described herein with reference to the drawings.