GB2283227A

GB2283227A - Launching and recovery apparatus

Info

Publication number: GB2283227A
Application number: GB9322247A
Authority: GB
Inventors: David Michael Bradley; Ronald Lynch
Original assignee: SCHAT WATERCRAFT Ltd
Current assignee: SCHAT WATERCRAFT Ltd
Priority date: 1993-10-28
Filing date: 1993-10-28
Publication date: 1995-05-03
Anticipated expiration: 2013-10-28
Also published as: GB9322247D0; GB2283227B

Abstract

A lifeboat (4) to be launched from a vessel is carried by a cradle (3) supported by fall wires (23, 24) passing over sheaves (25, 26) on a fixed davit structure (9, 5, 6) and has at its lower end roller assemblies that run over inclined trackways (7). A third fall wire (33) incorporating chain (34) hooked on the boat runs over a third sheave (32) on said structure. This fall wire (33), which attaches to one middle horn (42) on the cradle, is substantially untensioned during the launch and recovery. All three fall wires are preferably wound onto and off a single winch drum. Preferably the third sheave is spring mounted. <IMAGE>

Description

LAUNCHING AND RECOVERY APPARATUS This invention relates to launching and recovery apparatus for use on ships and other floating vessels as well as floating or fixed marine platforms, its purpose being to enable boats such as lifeboats and rescue launches and the like to be launched from and recovered onto the vessel or platform.

In patent specification No. GB2054517 there is described a launching and recovery apparatus having a davit structure rising from parallel trackways to support a single sheave over which a single fall wire passes to carry a cradle incorporating roller assemblies that run on the trackways as the cradle, while carrying the boat to be launched, run, the trackways being so positioned that they are inclined downwards to portions thereof that are curved over the edge of the vessel or platform.

On reaching the water the boat can float away from the cradle when manually released from the fall wire.

In a more simple version of the above apparatus that has also proved to be satisfactory in the conditions for which it is designed, the trackways are eliminated and the davit structure is brought to the edge of the vessel so that the cradle carrying the boat can be lowered and raised directly from and to its stowed position on a single fall wire.

While the above described form of apparatus is simple and is satisfactory in appropriate conditions, the single fall wire limits its use to quite small boats and during recovery, when the boat is clear of the water, the combined boat and cradle have pendulum stability which can render stowing of the boat as by the engagement of the roller assemblies with the trackways problematical, particularly as the fall wire is under tension. It is, therefore, an object of the present invention to provide apparatus such that the above disadvantages are considerably reduced.

According to the present invention there is provided a launching and recovery apparatus for a boat such as a lifeboat or rescue launch, the apparatus being arranged to be fixed to a ship or other floating vessel or a floating marine or fixed platform and comprising a davit structure and a launching and recovery cradle arranged to be hung on two parallel fall wires passing over two sheaves mounted on the davit structure, characterised in that a third sheave is mounted between said two sheaves and a third fall wire passes over the third sheave to be secured to a central horn on the cradle which bears the weight of the boat when being lowered or raised on the cradle for launch or recovery, the arrangement being such that the third fall wire remains under substantially negligible tension throughout launching and recovery operations, while the said two parallel fall wires maintain the full weight of the cradle and boat when mounted thereon.

The third fall wire engages a guide which enables a snap on hook to be easily attached and guided onto a central cradle horn. Thus boat recovery is reasonably easy and moreover it provides control when the cradle is being recovered, for example loaded onto trackways, and the tension in the two fall wires, when lifting, acts to centre the cradle.

The use of three fall wires in no way complicates the winch mechanism because all three wires can be coiled on a simple common drum.

In order that the invention may be clearly understood and readily carried into effect launching and recovery apparatus in accordance therewith will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of the apparatus with a boat and launching cradle in a stowed position denoted by solid lines and in a launching/recovery position denoted by chain dotted lines; and Figure 2 is a side elevation of the apparatus shown in Figure 1.

Referring to Figures 1 and 2 a pair of rigid davit members 1 fixed to a ship 2 from which a launching and recovery cradle 3 carrying, in this example, a rescue or survival boat 4, can be raised. The boat 4 is stowed in a raised position in the cradle 3 for embarkation.

Each of the davit members 1 has an upper portion 5 inclining towards the side of the ship as it extends upwards from a lower portion 6 in which is formed a trackway 7 that is radiused at its lowest extremity 8 and extends inwardly and upwardly from the side of the ship at an angle of about 35 degrees to the horizontal. The tops of the davit members 1 are joined by a transverse beam 9 carrying three sheaves as described below. The davit members 1 are mounted on deck support legs 10.

Further cross beams 30 and 31 are provided.

The cradle 3 comprises a pair of parallel arms 11 joined by a horizontal member 12 which carries a centre load bearing horn 42 and is supported by oblique members 13. The arms 11 carry at their lower ends respectively support frames 14 each provided with a multiplicity of rollers 15 pivoted for rotation about horizontal axes which lie on a curve and when the cradle 3 is lowered and raised as described below they run along surfaces of the trackways 7. The frames 14 carry respective guide wheels 16 pivoted about axes normal to the axes of the rollers 15 and which during raising or lowering of the cradle 3 run on the inner faces of walls 17 of the trackways 7.

When the boat 4 is stowed in the raised position shown in Figures 1 and 2, it is constrained by webbing straps 18 held between points 19 on beam 9 and 20 on the lower davit portions 6. The cradle 3 is held at points 21 and 22 by respective fall wires 23 and 24 that pass over sheaves 25 and 26 on the transverse beam 9 and thence over guide sheaves 27 and 28 to a winch 29. To lower the craft 4 the winch 29 is conditioned to enable the weight of the cradle 3 and boat 4 to pull the fall wires 23 and 24 from the winch 29 until the cradle 3 has moved to the lowered position, shown by broken lines in Figure 1. The webbing straps 18 can then be disconnected from the cradle 3. These straps are fixed on main structure and released from deck level prior to launch.

Centrally mounted on the transverse beam 9 is a third sheave 32 over which a third fall wire 33 passes.

The third sheave is spring loaded. The third fall wire terminates at a central horn position 42 on the cradle 3.

Due to the action of the spring loaded sheave 32 the tension in this wire is minimal.

The boat is supported from the location of the central horn 42 via a suspension chain assembly comprising the chain 34 and a snap-on hook 37. The suspension chain is connected to the boat by an off-load release hook 35 which is bolted at 36 to the inboard section of a boat's lift frame.

To launch the boat, a winch brake is lifted and the cradle and boat together run down the trackways 7 under gravity. Lowering on the fall wires 23 and 24 continues until the boat is waterborne, when the release hook 35 is actuated, leaving the suspension chain 34 attached to the central horn 42 of the cradle via the snap-on hook 37.

The cradle 3 is recovered to the deck level where the suepsnion chain assembly 35, 37 is removed.

The cradle is then lowered to a submerged position, its position maintained by a lateral painter.

To recover the boat, an identical suspension chain with its snap-on hook 37 is fitted to the boat's release hook 35 and the snap-on hook 37 is connected some way above the horn 42 around the third fall wire 33. The cradle 3 is then raised by the fall wires 23 and 24 allowing the snap-on hook to run down the third fall wire 33 and engage onto the central horn 42 on the cradle, thus locating the craft conveniently in relation to the cradle. The two outer wires 23 and 24 carry the weight of the cradle and boat and their action under load automatically centres the cradle in relation to the trackways 7.

The winch 29 comprises a rotary drum furnished with peripheral annular flanges that define annular spaces for the respective coils of fall wires 23, 33, 24.

For raising the cradle and boat the cradle is raised by a unidirectional hydraulic motor through a sequence of reduction gearing. A centrifugal brake is provided for limiting the speed of fall. A hydraulic brake is provided for the motor shaft and a hand brake is also provided. Referring to Figure 1, dual electrically driven pumps 40 supply hydraulic pressure to the motor from a hydraulic reservoir 41. A ratchet lever is provided for manual hoisting.

Claims

CLAIMS:

1. A launching and recovery apparatus for a boat such as a lifeboat or rescue launch, the apparatus being arranged to be fixed to a ship or other floating vessel or a floating marine or fixed platform and comprising a davit structure and a launching and recovery cradle arranged to be hung on two parallel fall wires passing over twd sheaves mounted on the davit structure, characterised in that a third sheave is mounted between said two sheaves and a third fall wire passes over the third sheave to be secured to a central horn on the cradle which bears the weight of the boat when being lowered or raised on the cradle for launch or recovery, the arrangement being such that the third fall wire remains under substantially negligible tension throughout launching and recovery operations, while the said two parallel fall wires maintain the full weight of the cradle and boat when mounted thereon.

2. Apparatus according to Claim 1, in which the davit structure has upper portions rising from parallel trackways for mounting on the vessel or platform and supporting the three sheaves, the trackways being inclined to extend downward from upper positions to positions curved over the side of the vessel or platform and in which the cradle is furnished at a lower portion thereof with parallel roller assemblies arranged to run on the trackways while the cradle is lowered from a fully hoisted position to a partly lowered position whereat the roller assembles descend from the trackways.

3. Apparatus according to Claim 1 or Claim 2, in which the third sheave is spring mounted to enable the third fall wire to operate under substantially negligible tension.

4. Apparatus according to Claim 3, in which the third fall wire includes a terminal flexible extension detachable both from the central horn and from the boat.

5. Apparatus according to Claim 4,. in which the terminal flexible extension is a chain formed at one end to be received by a release hook on the boat and at the other end provided with a snap-on hook for attachment to the central horn.

6. Apparatus according to any one of the preceding claims, in which the three said fall wires are arranged to be wound onto and unwound from a single common winch drum.

7. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.