GB2029488A - Automatic float free release gear for lifeboats - Google Patents

Abstract

A cradle launched lifeboat is automatically released so as to float free should a ship sink while the lifeboat is still in the davits. The boat is suspended in the cradle 5 by hooks 12 closed by pivoted plates 15 retained by a shear pin 17 which is broken by the upward force on the pendants 14 due to the buoyancy of the boat. The boat may be retained in the cradle by means gripping the keel and operated by a line including a frangible link. <IMAGE>

Description

SPECIFICATION Automatic float free release gear for lifeboats This invention is concerned with gear for the automatic release of a lifeboat which is being dragged down by a ship sinking, so that it may float free from the ship to the surface.

It is especially though not essentially applicable to launching systems such as that known as the "Miranda" system in which the lifeboat is stowed in a cradle suspended from davits and resting in an inclined plane and is launched by sliding the cradle down the plane, over the ship side and into the water.

When the lifeboat is water bourne it is released from the cradle by a manually operated release gear from within the lifeboat, and is then free to go into operation.

If a ship sinks with the lifeboat still in the davits, the boat will be carried down with the ship and the manually operated release gear may be inaccessible so that the lifeboat is not available for rescue purposes.

It is an object of the present invention to provide release gear operated by the inherent buoyancy of the lifeboat whereby the lifeboat is automatically released from the cradle when the ship sinks and allowing to float free.

From one aspect, the invention provides release gear for a cradle launched lifeboat comprising a hook on the cradle engageable by suspension means supporting the lifeboat in the stowed position, the open end of the hook being closed by closure means including a frangible element designed to break and release the suspension means from the hook when the lifeboat moves upwardly relatively to the cradle due to its inherent buoyancy.

From another aspect, lifeboat launching gear according to the invention comprises a cradle suspended from davits and in which the boat is suspended by pendant links engaging in hooks carried by the cradle, closure means closing the open ends of the hooks and frangible means retaining the closure means in the closed position, said frangible means being designed to break and release said pendant links when force is exerted on said closure means by the pendant links due to the buoyant upward movement of the lifeboat in relation to the cradle.

Preferably the closure member comprises a pair of pivoted plates extending across the bight of the hook and held in closed position by a shear pin extending between the plates.

Upward force on the plates forces the shear pin against a fixed abutment, for example, the body of the hook and breaks it allowing the plates to rotate and release the pendant links, thereby allowing the lifeboat to float free.

When the lifeboat is in the stowed position, it is customarily held against the cradle by ties between the keel of the lifeboat and the cradle and such ties must be released before the lifeboat can float upwards relative to the cradle. According to a further aspect of the invention such retaining means comprises a releasable catch engaging the keel of the boat and retained closed by a frangible element connecting the catch to the ship. If and when the ship beins to sink, the lifeboats' inherent buoyancy will exert a tensile force on the frangible element to break it and release the catch from the keel. The frangible element preferably comprises a tension pin in the line connecting the catch to the ship designed to break when tension is exerted by the upward pull due to the lifeboat tending to rise in the cradle.

If a ship equipped with the launching gear of the present invention sinks whilst the cradle and lifeboat are still in the davits, the lifeboat will rise due to its buoyancy, first breaking the retaining means and eventually opening the hook members so that it is freed completely from the cradle and can rise to the surface.

Other parts of the invention are embodied in the preferred form which will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a side view of launching gear with a lifeboat in the stowed position; Figure 2 is a end view of the launching gear of Fig. 1; Figure 3 is a view on an enlarged scale of the part of Fig. 1 enclosed within the circle A; and Figure 4 is a view to an enlarged scale of the part of Fig. 2 enclosed within the circle B.

As shown in Figs. 1 and 2, launching gear for a lifeboat 1 from a ship indicated at 10 comprises a pair of davits 2 from which is suspended by cables 4 a cradle 5. The cradle 5 with the boat 1 can be raised and lowered by a winch 6. The cradle has curved portions 7 provided with rollers 8 which run on inclined planes 9 and which on launching are maintained in contact with the hull of the ship 1 0. After launching, the lifeboat is released from the cradle which can later be used to retrieve the lifeboat.

Each cable 4 is secured to the cradle 5 by a head member 11 which is formed with a hook 1 2 and the lifeboat is suspended from these hooks by the links 1 3 of pendant lines 14.

Plates 15, one on each side of the head member 11, are pivoted to the head member by a pivot pin 1 6 and extend across the bight of the hook 1 2 to prevent escape of the link 1 3. The plates 1 5 also extend in the opposite direction from the pivot pin 1 6 and protrude beyond the head member 11. A shear pin 1 7 passes through these protruding portions of the plates 15, spanning the head member, and preventing rotation of the plates 1 5 in the counter clockwise direction shown in Fig. 3.

The shear pin 1 7 is designed so that it will shear under the force applied to it through the plates 1 5 by the upward buoyancy of the lifeboat.

In the stowed position, the boat 1 is held against the cradle 5 by a line 1 8 connected to the keel 1 9 and to the davit 2. Keel gripping mechanism 20 comprising a pair of hook members 21, 22 pivoted together by a pin 23, grips the sides of plate 24, secured to the keel. The line 1 8 is attached to the hook member 21 so that tension in this line draws the two hook members 21, 22 together into engagement with the plate 24. The line 18 includes a frangible member 25 such as a tension pin so that when additionai tension is applied to the line 18, this member 25 beaks and releases the tension and the keel gripping mechanism opens and drops free of the boat.

If the ship sinks with the lifeboat still in the davits, the cradle and the lifeboat will be carried down with the ship. As the ship sinks, the inherent buoyancy of the boat will cause the boat to tend to rise relatively to the ship.

This will exert an additional tension on the line 1 8 causing the frangible member 25 to break and release the keel gripping mechanism 20.

The boat is then free to float upwards causing the launching pendants 14 to move from the position P1 shown in full lines to the position P2 shown in dotted lines in Fig. 3.

The launching pendants 14 then exert a force on the plates 1 5 to rotate then in the counterclockwise direction as shown in Fig. 3, forcing the shear pin 1 7 against the body of the head member 11 and thus shearing it. The plates 1 5 are then free to rotate further, opening the hook 1 2 and releasing the link 1 3 so that the boat is freed from the cradle and can float up to the surface.

It will be understood that the invention is not restricted to the details of the preferred form described by way of example, which may be modified without departure from the scope of the accompanying claims.

Claims (6)

1. Release gear for a cradle launched lifeboat comprising a hook on the cradle engageable by suspension means supporting the lifeboat in the stowed position, the open end of the hook being closed by closure means including a frangible element designed to break and release the suspension means from the hook when the lifeboat moves upwardly relatively to the cradle due to its inherent buoyancy.

2. Lifeboat launching gear comprising a cradle suspended from davits and in which the lifeboat is suspended by pendant links engaging in hooks carried by the cradle, closure means closing the open ends of the hooks and frangible means retaining the closure means in the closed position, said frangible means being designed to break and release said pendant links when force is exerted on said closure means by the pendant links due to the buoyant upward movement of the boat in relation to the cradle.

3. Lifeboat launching gear as claimed in Claim 2, in which the closure member comprises a pair of pivoted plates extending across the bight of the hook and held in closed position by a shear pin extending between the plates.

4. Lifeboat launching gear in which the lifeboat is supported in a cradle and is held against the cradle by retaining means comprising a releasable catch engaging the keel of the lifeboat and retained closed by a frangible element connecting the catch to the ship.

5. Lifeboat launching gear as claimed in Claim 4, in which the frangible element comprises a tension pin in the line connecting the catch to the ship designed to break when tension is exerted by the upward pull due to the lifeboat rising in the cradle.

6. Lifeboat launching gear substantially as described with reference to the accompanying drawings.