Background to the invention Release mechanisms are known for use in securing a life raft or the like to a ship or a boat in a manner that when the ship on which the life raft is installed, is in danger of submerging or accidentally submerges in water can be either automatically or manually activated to release the life raft from the ship. The release mechanism is generally included as part of the stowage system which secures the life raft to the vessel.

Two types of mechanisms are generally employed, the first being a remotely operated release mechanism generally known as a Manual Remote Release Unit (M. R. R. U. ) which is usually activated by, for instance, having a vacuum or an air pressure differentially applied to it or by electrically operated means, such as an integral solenoid.

Upon such application, the life raft or other article is released from its stowage and can be suitably deployed. The second type of mechanism is that known as a hydrostatic release mechanism. Such a mechanism is generally inserted as part of the stowage system for the life raft and is so constructed that if the vessel with the life raft submerges, then the water pressure exerted on the hydrostatic release mechanism by the submersion will automatically activate the release mechanism to release the life raft from its stowage on the vessel.

Prior art United States patent specification 4,065, 823 discloses a hydrostatic release mechanism which has a latching mechanism connected to buoyant seat cushions which when the vessel on which the cushions have been installed is submerged in water, the release mechanism will release the seat cushions to provide emergency floating gear. The mechanism includes a hollow body which houses a diaphragm one side of which is vented to the air. Water pressure will act on the diaphragm to move it against the spring pressure from a latched position to a release position to enable the mechanism to release the life raft container from the stowage.

United States Patent Specification 5573343 disclose a hydrostatic release mechanism which has a main body which houses a piston in a chamber filled with oil. A

diaphragm is mounted on the chamber behind which is a sealed internal chamber. The diaphragm can be moved by a pressure differential such as when the mechanism is submerged. The diaphragm includes a plunger with a spike so that when the diaphragm moves under a variation in ambient pressure, the spike will pierce a frangible disc to open a fluid filled chamber to the internal chamber which will release the piston and in turn release a link mechanism.

United States patent specification 5365873 discloses another hydrostatic pressure release unit which has an upper and lower casing having a centrally located aperture. The lower casing has a centrally located boss on the floor of the chamber and has a pressure sensing chamber sealed by a diaphragm assembly. A helical coil spring urges the diaphragm towards a rest position. If the release mechanism is submerged, water or trapped air will act on the upper surface of the diaphragm to deflect it against the pressure of the spring to activate a release mechanism. The stated advantage of this mechanism is that it can be manually actuated and re-set to test the action of the mechanism.

United States patent specification 5855450 also discloses a hydrostatic release mechanism which has a body with a cover housing a diaphragm which is normally maintained in a latched position by a compression spring. A cap which has shoulders is attached to the diaphragm and is locked in position by legs. Additional water pressure will flex the diaphragm to move the cap and separate the upper part of the cap from the shoulders to allow the legs to pass through a recess to disengage the release mechanism.

The mechanism can be manually tested and re-set.

The disadvantages with the known automatic release mechanisms is that they are excessively complicated thereby leading to high costs in manufacture and in assembly. In addition because of the generally complex nature of the mechanism, the likelihood of malfunction is greater than desirable.

A yet further disadvantage is that with prior known hydrostatic release mechanisms it is possible during transportation and storage for a substantial or sudden change in air pressure to prematurely trigger the release of the mechanism.

Object of the invention

It is therefore an object of this invention to provide an improved construction of a hydrostatic release mechanism which will minimise the above disadvantages and which is cost effective to construct, is reliable in operation and is robust and simple to assemble.

It is a still further object of the invention to provide an improved construction of a hydrostatic release mechanism which can be manually operated and which can be functionally tested.

Disclosure of the invention Accordingly one form of the invention comprises a release mechanism adapted to release an article from stowage, said mechanism including: an aneroid chamber having a floor surrounded by a chamber wall which terminates in an opening, an elastomeric substantially circular diaphragm having a periphery adapted to contact the chamber wall and to seal the opening to the aneroid chamber, said diaphragm having a portion between the axial centre of the diaphragm and the perimeter of the diaphragm of a lesser thickness than the remainder of the diaphragm to provide a frustum action to the diaphragm to normally maintain the diaphragm in an armed condition, a spigot plate located at and secured to the axial centre of the diaphragm and having a spigot which projects axially from a first face of the diaphragm, a body shackle plate adapted to be located on and secured to the opening of the chamber wall and to sandwich the diaphragm between the body shackle plate and the chamber wall to seal the interior of the chamber from ambient and to form the aneroid chamber, said body shackle plate having a hole through which the spigot of the spigot plate will project when the diaphragm is in an armed condition, a latching mechanism to prevent release of the article from stowage when in an armed condition, and wherein the action of the mechanism is such that when pressure on the first

face of the diaphragm is greater than the pressure of air within the aneroid chamber, the diaphragm will flex to retract the spigot of the spigot plate within the spigot hole in the body shackle plate to free to latching mechanism and to allow the article to be released from stowage.

Preferably the latching mechanism comprises a cam block and a top shackle plate, said top shackle plate having means to releasably lock to the body shackle plate and to be retained in that locked position by being engaged with the cam block when the mechanism is in the armed condition.

Preferably the cam block is maintained in an armed condition by means of the spigot of the spigot plate exerting pressure on the cam block to maintain the cam block in contact with a tongue formed as part of the body shackle plate.

Preferably the latching mechanism includes a manual release means.

Preferably the manual release means comprises a lever pivotally connected to the cam block in a manner that the lever may be pivoted to contact the spigot of the diaphragm and to depress the diaphragm to retract the spigot from contact with the cam block to release the cam block from the tongue formed as part of the body shackle plate Preferably the means to lock the top shackle plate with the body shackle plate includes: a stub on the body shackle plate which is adapted to engage within a spigot hole formed in the top shackle plate, and a ramp formed as part of the top shackle plate and adapted to enter a release slot formed in the body shackle plate, and shackle release catch tongues adapted to engage with the cam block when the cam block is in the armed condition to maintain the top shackle plate in an armed condition and wherein when the cam block is released, the top shackle plate can move and allow

the spigot hole to disengage from the stub of the body shackle plate and allow the ramp of the top shackle plate to disengage from the latching hole in the body shackle plate.

Preferably the cam block is provided with rebates to receive the shackle release catch tongues of the top shackle plate when the unit is in an armed condition Preferably the aneroid chamber includes a central boss extending upwardly from the floor and having an axial bore, and the elastomeric diaphragm has a stem which projects axially from the second face of the diaphragm, which stem is adapted to be engaged in sliding contact within the bore of the central boss.

Preferably the wall of the chamber is formed with arcuate extensions adapted to receive a portion of the rim of the body shackle plate, said arcuate extensions each having a recess into which the portion of the rim of the body shackle plate will engage to retain the body shackle plate on the opening of the chamber wall.

Preferably the body shackle plate includes two rebated portions which are adapted to enter into and be engaged in the said recesses.

Preferably the diaphragm is constructed in a manner that pressure exerted on the first face of the diaphragm through the unit being submerged in water will retract the diaphragm into the aneroid chamber when the unit is submerged below a predetermined depth.

Preferably the mechanism can be disarmed to release the top shackle plate by reducing the air pressure in the aneroid chamber to allow the diaphragm to partly retract into the aneroid chamber.

Preferably the diaphragm is formed in a manner that it will in conjunction with trapped air in the aneroid chamber inherently resist retraction into the aneroid chamber.

Preferably spring means are provided to spring urge the top shackle plate to

facilitate disengagement of the top shackle plate from the mechanism when the unit is disarmed.

Preferably means are provided to minimise the load on the release mechanism when the unit is applied to restrain heavy objects.

Brief description of the drawings.

Preferred forms of the invention will now be described with the aid of the accompanying drawings, wherein: Figure 1 is a plan view of one form of the assembled hydrostatic release unit.

Figure 2 is a sectional view along the line A-A of Figure 1.

Figure 3 is an isometric three quarter view from above of the first end of the assembled unit.

Figure 4 is an isometric three quarter view from above of the second end of the assembled unit.

Figure 5 is an exploded view of the component parts of the hydrostatic release unit.

Figure 6 s a partly cross sectional view of an accessory for use with larger life saving equipment such as large life rafts.

Figure 7 is a cross sectional view of part of the body of the unit illustrating one method of connecting a means for remotely releasing the unit so the unit can be utilised as a manual remote release unit.

Figure 8 is a view illustrating the connection of a weak link that can be used to secure a life raft painter to the unit.

Description of a preferred embodiment.

As illustrated in the drawings, the hydrostatic release unit has an aneroid chamber 2 by an upstanding peripheral wall 4 (see Figure 2) which is preferably but not necessarily

formed from moulded plastic material that is resistant to corrosion and to the adverse conditions likely to be encountered during the service life of the unit. The interior of the body 4 forms an aneroid chamber 2 while the outside of the body can be covered by a bottom label 3 and a peripheral label 1. A central boss 5 extends upwardly from the floor of the body, the boss having a blind bore 6 into which one end of a diaphragm stem 7 is located in a manner that the end of the stem is supported by the boss, but has telescopic movement in the bore 6.

The open end of the chamber 2 is sealed by a diaphragm assembly which includes a diaphragm 10 formed of a suitable elastomeric material which is capable of flexing in a direction which is normal to the diameter of the diaphragm as will be further described. In the form illustrated (see particularly Figure 5), the diaphragm assembly also includes a circular plate 11 from which a diaphragm stem 7 (see Figure 2) projects in a manner that its axis will lie normal to the diameter of the diaphragm. The thickness of the diaphragm 10 varies so the portion 9 of the diaphragm between the circular plate 11 and the rim 8 of the diaphragm is reduced in thickness and a frustum geometry is provided to the diaphragm. The diameter of the diaphragm 10 is such that it will be a press fit within an enlarged portion 12 of the wall 4 of the chamber 2 and can seal against a shoulder of the enlarged portion 12 of the wall of the chamber 2. An O ring 13 (see Figure 5) may optionally be utilised to assist in the sealing of the diaphragm to the wall 4 of the chamber 2 in a manner that the diaphragm can flex axially as will be hereafter further described and yet form a seal to the wall of the chamber to complete the aneroid chamber 2.

A body shackle plate 15 is positioned to rest on the rim 8 of the diaphragm and to sandwich and seal the rim 8 of the diaphragm against the shoulder 14. The shackle plate 15 is located by two arcuate extensions 16 which extend upwardly from the wall 4 of the chamber 2 and which are provided with recesses 17. Because the body of the chamber 2 is formed of a plastic material, the body shackle plate 15 can be attached to the body of the chamber by forcing the perimeter of the shackle plate 15 downwardly past the lugs 16 which will be deformed outwardly to allow the perimeter of the body shackle plate to enter into the recesses 17 and so be located in place on the chamber as will be further described. It will be noted portions 18 of the perimeter of the shackle plate are rebated to assist in the correct location of the plate 15 on the body 2.

The upper portion of the circular plate 11 of the diaphragm assembly is preferably formed into a spigot 20 which when assembled will partly protrude through a hole 21 formed in the body shackle plate 15 and when the diaphragm in its rest position, the spigot 20 will protrude partly through the hole 21 to lie substantially flush with the upper surface of the body shackle plate 15.

A mandatory diaphragm drain hole 22 is formed in the body shackle plate 15 to enable water entrapped between the underside of the shackle plate and the diaphragm assembly to drain through the hole when the release unit is in position. Water and/or air can also bleed through other clearances in the unit as well as through the drain hole 22. A deck attachment hole 23 is formed adjacent one end of the body shackle plate 15 to enable the unit to be connected to a shackle (not shown in the drawings) to secure the unit either to the deck of a vessel or to a cradle for the life raft. The other end of the body shackle plate 15 includes a stub 19 (see particularly Figures 3 and 5).

The unit also includes a latching mechanism which comprises the components more particularly illustrated in Figure 5. In a highly preferred form the latching mechanism includes a cam block 27, a manual release lever 28, and a top shackle plate 30 all of which act in conjunction with the body shackle plate 15 and the diaphragm 10. The component parts of the latching mechanism are all preferably formed of stainless steel or appropriate corrosion resistant material. The top shackle plate 30 is a pressing having a floor 31, strengthening ribs 32, a latching hole 33 which as illustrated is formed with a ramp 37 to engage in a release slot 44. The top shackle plate 30 also includes shackle release catch tongues 34 and a shackle attachment hole 35 at the opposite end of the top shackle plate 30 to enable a life raft lashing to be attached to the shackle plate 30. The area 35a surrounding the shackle attachment hole is preferably shaped as illustrated more particularly in Figure 5.

The portion of the top shackle plate surrounding the shackle attachment hole is preferably dished as illustrated to form a tongue 38 which as illustrated particularly in Figure 3 includes a stub lock 39, the tongue being deformed during manufacture so that when assembled, the stub lock 39 can engage over and on the stub 19 extending from the body shackle plate 15.

A manual release lever 28 (see particularly Figure 5) comprises a body 40 having pivot pins 41 adjacent a first end and finger grips 42 adjacent the second end. A hole 51 is formed in the manual release lever to enable a cable tie or similar to be passed through the hole to enable the unit to be secured against inadvertent activation.

The pivot pins 41 of the manual release lever 28 are engaged in pivot holes 43 formed in the cam block 27 which also has a ramp 47 adapted to engage under a tongue 48 which may conveniently be formed during the pressing or stamping of the body shackle plate 15. As can be seen particularly in Figure 4, the tongue 48 projects from the body shackle plate 15 in a manner that the free end of the tongue 48 will slope upwardly in relation to the body shackle plate 15 and can engage over the ramp 47.

The cam block 27 also includes stepped portions 45 which are so formed that when the unit is assembled, the cam block will retain the shackle release catch tongues 34 of the top shackle plate 30 between the stepped portions 45 and the top surface of the body shackle plate 15.

In its restrained, assembled condition the underside of the cam block 27 will contact and engage the spigot 20 of the diaphragm which partly protrudes through the opening 21 in the body shackle plate 15. Because of the resilient nature and frustum geometry of the diaphragm, the plate 11 will normally maintain an upward pressure on the underside of the cam block 27. This upward pressure will maintain the component parts of the latching mechanism in a latched condition.

To ensure satisfactory release of the mechanism independent of any external buoyancy load, a serpentine spring 55 is associated with the top shackle plate and in the form illustrated, the spring includes legs 56 which are engaged in locating holes 57 in the top shackle plate with the spring being so formed that the nose 58 will bear on the upper surface of the tongue 48 to thereby exert spring pressure on the top shackle plate so the end of the top shackle plate 30 comprising the shackle release tongues 34 will be spring assisted away from the body shackle plate.

To manually release the mechanism, the finger grips 42 are pulled away from the body shackle plate 15 by inserting a finger or fingers between the finger grips 42 and the

body shackle plate 15 and lifting and pulling the finger grips away from the body shackle plate in the direction of the arrow B in Figure 4. This will cause the manual release lever 28 to pivot about the pivot pins 41 and the nose 36 of the manual release lever will bear against the spigot 20 to depress the diaphragm which will free the cam block 27 and allow the ramp 47 of the cam block 27 to slide out of engagement with the tongue 48 and thereby free the shackle release catch tongues 34 of the top shackle plate 30. Since the shackle release catch tongues 34 are released, the top shackle plate 30 can move and the spigot hole 38 will in turn disengage from the stub 19. This movement is facilitated by the action of the spring 55 so the top shackle plate will be released from the unit.

To assemble the unit, the diaphragm assembly, that is the diaphragm 10 which includes the plate 11 and the diaphragm stem 7 are offered up to the chamber 2 so the stem 7 will engage in the bore 6 of the boss 5 and the periphery of the diaphragm will contact the shoulder 14 of the wall 4. If the O ring 13 is being utilised, this will first have been placed on the shoulder 14 of the wall so it will be sandwiched between the periphery of the diaphragm and the body 4 of the chamber 2. The body shackle plate 15 is next positioned above the body of the unit so the rebates 18 of the plate will register with the extensions 16. By exerting downward pressure on the plate 15, the rebates 18 will be forced against the extensions 16 which will deform slightly and allow the body shackle plate to move downwardly to enable the rebates 18 to enter into the recesses 17. The natural resilience of the lugs will ensure the lugs return to their rest position and so retain the body shackle plate between the recesses 17 with a snap action assembly.

The top shackle plate 30 complete with the assembled serpentine spring 55 is then positioned on the body shackle plate 15 and pressed downwards in a manner that the stub lock 39 will engage over the stub 19 and the ramp 37 will engage in the release slot 44 and the shackle release catch tongues will straddle the tongue 48. The cam block 27 with the assembled manual release lever 28 is then positioned above the plate 11 of the diaphragm 10 and by depressing the spigot 20 of the diaphragm, the ramp 47 of the cam block can be slid under the tongue 48 until it is in position with the rebated portions 45 of the cam block lying over the shackle released catch tongues 34 of the top shackle plate 30. When in this position, the diaphragm will snap upwards thereby locking and maintaining the cam block 27 in position which will in turn retain the top shackle plate in a latched position.

In operation, the hydrostatic release unit is installed as part of the stowage system for the life raft or other device to be deployed. To effect this a shackle (not shown in the drawings) is passed though the deck attachment hole 23 and the shackle is fastened to the deck of the vessel or to the cradle for the life raft. A life raft painter (not shown in the drawings) is secured to the unit by a shackle attached by a weak link. This weak link may be a cord or other component having a specific breaking load, but more preferably the weak link is of the form illustrated at 46 in Figure 5 and may conveniently be formed of a plastic material through an injection moulding process. In this form, the weak link 46 which is preferably of a dumb bell shape with suitable holes or the like formed adjacent each end, has a predetermined breaking tensile strength typically between 1.8 and 2.6 kN.

Preferably a control hole 49 or similar aperture is formed in the weak link to enable the breaking load of the weak link to be adjusted.

If a vessel has installed the hydrostatic release unit as herein described to stow a life raft and if the vessel capsizes or sinks, and if the life raft has not been launched in the usual manner, the life raft will be taken down with the sinking vessel. When the life raft submerges, water or air pressure generated by the submersion will act on the outside face of the diaphragm. When the life raft has submerged beyond a predetermined depth, which is typically between 1.5 to 4 metres, the water or air pressure will act on the outside surface of the diaphragm and when the pressure is sufficient to overcome the resistance of the frustum diaphragm assembly and the pressure of air in the aneroid chamber below the diaphragm, the diaphragm assembly will retract towards the floor of the chamber. This will retract the spigot 20 on the underside of the cam block 27 and in conjunction with the forces exerted by the serpentine spring 55, will allow the cam block to slide away from the top shackle plate 30 and will release the top shackle plate. This in turn will release the lashings of the life raft container allowing the container to float free of the cradle or storage position on the vessel. Once released, the life raft container will float free of the sinking vessel and will rise towards the surface with the painter line continuing to pay out as the vessel continues to sink. When the free length of the painter line is paid out, the inflation mechanism of the life raft will be automatically activated and the life raft will inflate thus bursting open the container. The life raft will continue to rise towards the surface and because of the high buoyancy of the inflated life raft, the load on the painter will be sufficient to break the weak link 46. This will allow the life raft to float to the surface, free of the vessel.

It will be understood that in the embodiment illustrated, the depth of submersion at which the device activates is dependent upon the differential pressure of the water compared with the pressure necessary to overcome the deformation of the frustum diaphragm and the compression of the air in the aneroid chamber 2 to allow the diaphragm assembly to retract and withdraw the spigot away from cam block 27 and allow the top shackle plate to release from the unit. Consequently it is a simple matter to manufacture the diaphragm to provide the desired geometry in conjunction with the air in the aneroid chamber 2 to determine the depth to which the unit has to be submerged for it to activate.

In addition, the unit is designed such that the contact angle of the tongue 37 with the front surface of the release slot 44 is just reliably below the angle of repose to ensure a reliable release of the component parts when the unit is activated.

The unit is also designed to enable it to operate manually by remote means. This is effected by including a pressure tapping 50 (see particularly Figure 7) which provides communication into the aneroid chamber 2. The tapping is connected via suitable tubing such as a small diameter capillary tube (not shown in the drawings) to a remote source of vacuum which for instance can be a hand vacuum pump or the like (not shown in the drawings). The pressure tapping is connected to the chamber 2 by means of an elastomeric bush 52. A plug may be provided to seal the bush when the tapping is not connected to the chamber 2 when the unit is configured as hydrostatic release unit and is disassembled during air cargo transportation to prevent premature actuation of the unit. In addition or alternatively Upon operation of the pump or application of vacuum to the pressure tapping 50, this lowering of the air pressure in the aneroid chamber will retract the diaphragm into the chamber and with it the spigot of the diaphragm thereby initiating the release mechanism.

The advantage of the manual release embodiment is that it may be installed as part of the life raft stowage system on the outboard side of the life raft or other life saving equipment can be launched from a remote hand operated vacuum pump that may be positioned on the bridge or at any other convenient location. The system can be configured to operate more than one remote release unit thereby enabling the launching of more than one life raft or other life saving equipment at the same time. Consequently space can be conserved on the vessel because the life rafts can be placed out of the way and yet be readily accessible by

remote launching. After manual release and the launching of the life raft container and when all the free length of the painter line is paid out, the inflation mechanism will be automatically activated and the life raft will inflate, bursting open the container and leaving the life raft tethered to the vessel via the weak link and ready for boarding.

Another method of remotely activating the unit is to incorporate an electrical solenoid or equivalent with the unit so the unit can be activated either by passing electrical current to the solenoid or by interrupting electrical current to the solenoid.

The release unit can also be utilised in conjunction with stowage for a large object such as a very large life raft. However, because of the high tension load that can be exerted by such a stowage, it is desirable to minimise the load on the release mechanism of the unit as much as possible. One preferred method of minimizing the load on the release mechanism is illustrated in Figure 6. As depicted in this Figure, the load reducer includes a base plate 70 which is formed from a strong corrosion resistant material and is provided adjacent one end with a suitable mounting hole to receive a shackle 71 and at the other end, a strong shackle plate 77 and shackle 76 or the like, to enable the stowage lashings to be connected to the device. A stepped post 72 is fastened to the base plate 70 such as by a nut 73 to enable the unit to be attached to the post by passing the post through the attachment hole 23 in the body shackle plate 15 and fastening the plate to the post by a nut 74. A release post 75 having a central portion 78 of greater diameter than the two ends 79 has one end 79 engaged in a slot cavity 80 in the shackle plate 77 and also into a slot cavity 81 in the base plate 70. The top shackle plate 30 is engaged over an end 79 of the post 75 which passes through the shackle attachment hole 35 in the shackle plate 30 thereby restraining the shackle plate 77 and its associated shackle 76.

Because of the configuration of the component parts most of the tension exerted on the shackles 71 and 76 will be transmitted through the shackle plate 77 to the base plate 70. However when the release mechanism is activated to release the shackle plate 30, the release mechanism will immediately disintegrate to free the release post 75 from the top shackle plate 30 to in turn release the shackle 76 with the shackle plate 77 from the base 70 to thereby enable the unit which is to be deployed to break free of the stowage.

An advantage of the release unit hereinbefore described is that during its service

life, the unit can be functionally tested, reused, and if necessary disassembled and reconditioned or re-cycled. In addition the design of the unit is such that it can be functionally tested during production and assembly, thereby augmenting the quality control of the unit.

A yet further advantage of the unit, is that it is composed of a minimum number of component parts which can be simply and easily assembled from the top down. In particular, the unit can be assembled without the necessity of using fastening means, such as screws requiring complex orientation and lends itself to automated assembly.

A still further advantage is that load between the retaining strops of the life raft and the deck attachment acts on the unit in such a manner that the retaining load is not carried directly upon the release mechanism until the release action takes place. Upon actuation, the whole of the retaining mechanism comes apart with only the shackle plate 30 being attached to the retaining lashings of the life raft, thereby effecting release without jamming.

Having disclosed various preferred embodiments of the invention it will be apparent to those skilled in the art that variations and modifications can be made to certain aspects and yet still come within the general concept of the invention. All such variations and modifications are intended to be included within the scope of the present invention.