GB2120327A - Automatic release mechanism - Google Patents

Abstract

This invention relates to a hydraulic means to release a safety catch, and is particularly suitable for use on lifeboats carried on ships. The hydraulic means suitably has a hydraulic master cylinder 8 actuable by hydrostatic force and a hydraulic slave cylinder 10 responsive to the actuation of the master cylinder and connected to the safety catch whereby actuation of the slave cylinder by the master cylinder releases the safety catch. The actuation of the master cylinder by hydrostatic force is achieved by means of a diaphragm 3 or a float 6 or a combination thereof. One of the principal features of the present invention is that the use of a hydraulic means enables a significant mechanical advantage to be achieved by varying the relative diameters of the master and slave cylinders. <IMAGE>

Description

SPECIFICATION Automatic release mechanism This invention relates to an automatic release mechanism, particularly suitable for use on lifeboats carried on ships.

Lifeboats in service are usually slung from davits on a ship, the cables from the davits being attached to the lifeboat by means incorporating a release mechanism which can be released by operating a handle. In order to prevent accidental release of the lifeboat, for example when still suspended in the air, the handle is itself locked by a safety catch which is automatically released when the lifeboat makes contact with the surface of the water.

A typical device comprises a diaphragm fitted across a standpipe rising from the bottom of the lifeboat. When the hull of the lifeboat comes into contact with water, the hydrostatic force causes a movement in the diaphragm which is transmitted via a Bowden cable to the safety catch thereby unlocking the catch. The unlocked catch in turn enabels the handle to be operated thereby releasing the lifeboat. Unfortunately, however, the Bowden cable and associated components can become corroded and inoperable and the standpipe may fill with water which freezes at low temperatures. These defects make the mechanism, which must stand for long periods without use, unreliable and potentially dangerous.

We have now devised an improved means for releasing a safety catch without the use of Bowden cables.

Accordingly, the present invention is a hydraulic means for releasing a safety catch actuated by hydrostatic pressure.

The hydraulic means suitably comprises a hydraulic master cylinder actuable by hydrostatic force and a hydraulic slave cylinder responsive to the actuation of the master cylinder and connected to the safety catch whereby actuation of the slave cylinder by the master cylinder releases the safety catch.

The actuation of the master cylinder by hydrostatic force is suitably achieved by means of a diaphragm or a float or a combination thereof.

The master cylinder may be actuated directly or indirectly by the hydrostatic force.

The hydraulic means for releasing a safety catch is particularly suitably for use in conjunction with lifeboats carried on ships. In this case, the diaphragm and/or the float is preferably located in a self-draining chamber in the hull of the lifeboat, the chamber being open at the bottom and closed at the top thereby enabling the master cylinder to be actuated by the diaphragm and/or the float which convert the hydrostatic head into a hydrostatic force.

The chamber is fitted with a vent pipe rising to above the waterline of the lifeboat. This allows full use of hydrostatic force when the boat is in the water.

One of the principal features of the present invenition is that the use of a hydraulic means enables a significant mechanical advantage to be achieved by varying the relative diameters of the master and slave cylinders.

The invention is illustrated with reference to the accompanying drawing which is a schematic diagram.

A lifeboat hull 1 is fitted with a well 2 near the keel across which a slack diaphragm 3 is clamped by means of a lid 4.

The diaphragm 3 and lid 4 form a chamber 5 filled with air which contains a float 6 and a hydraulic master cylinder 7 fitted with a rolling diaphgram 8. The float 6 bears against the rolling diaphragm 8 when it rises in the chamber as a result of hydrostatic pressure. A hydraulic line 9 leads from the master cylinder to a slave cylinder 10 also containing a rolling diaphragm 11 which moves the releasable catch (not shown) connected at 12.

A vent pipe 13 leads from the chamber 5 to a point above the waterline in the hull 1.

The diaphragms are constructed from an elastomer such as neoprene. Other parts should be constructed from robust materials such as GRP, stainless steel or gun-metai. The lid 4 may be made of transparent material for ease of inspection. A mixture of glycol and water forms a suitable hydraulic fluid.

Claims

1. A hydraulic means for releasing a safety catch actuated by hydrostatic pressure.

2. A hydraulic means according to claim 1 said means comprising a hydraulic master cylinder actuable by hydrostatic force and a hydraulic slave cylinder responsive to the actuation of the master cylinder and being connected to the safety catch whereby actuation of the slave cylinder by the master cylinder releases the safety catch.

3. A hydraulic means according to claim 2 wherein the actuation of the master cylinder by hydrostatic force is achieved by means of a diaphgram or a float or a combination thereof.

4. A hydraulic means according to claim 3 wherein the diaphragm and/or the float is located in a self-draining chamber in the hull of a lifeboat, the chamber being open at the bottom and closed at the top thereby enabling the master cylinder to be actuated by the diaphragm and/or the float which convert the hydrostatic head into a hydrostatic force.

5. A hydraulic means according to any one of the preceding claims as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Automatic release mechanism This invention relates to an automatic release mechanism, particularly suitable for use on lifeboats carried on ships. Lifeboats in service are usually slung from davits on a ship, the cables from the davits being attached to the lifeboat by means incorporating a release mechanism which can be released by operating a handle. In order to prevent accidental release of the lifeboat, for example when still suspended in the air, the handle is itself locked by a safety catch which is automatically released when the lifeboat makes contact with the surface of the water. A typical device comprises a diaphragm fitted across a standpipe rising from the bottom of the lifeboat. When the hull of the lifeboat comes into contact with water, the hydrostatic force causes a movement in the diaphragm which is transmitted via a Bowden cable to the safety catch thereby unlocking the catch. The unlocked catch in turn enabels the handle to be operated thereby releasing the lifeboat. Unfortunately, however, the Bowden cable and associated components can become corroded and inoperable and the standpipe may fill with water which freezes at low temperatures. These defects make the mechanism, which must stand for long periods without use, unreliable and potentially dangerous. We have now devised an improved means for releasing a safety catch without the use of Bowden cables. Accordingly, the present invention is a hydraulic means for releasing a safety catch actuated by hydrostatic pressure. The hydraulic means suitably comprises a hydraulic master cylinder actuable by hydrostatic force and a hydraulic slave cylinder responsive to the actuation of the master cylinder and connected to the safety catch whereby actuation of the slave cylinder by the master cylinder releases the safety catch. The actuation of the master cylinder by hydrostatic force is suitably achieved by means of a diaphragm or a float or a combination thereof. The master cylinder may be actuated directly or indirectly by the hydrostatic force. The hydraulic means for releasing a safety catch is particularly suitably for use in conjunction with lifeboats carried on ships. In this case, the diaphragm and/or the float is preferably located in a self-draining chamber in the hull of the lifeboat, the chamber being open at the bottom and closed at the top thereby enabling the master cylinder to be actuated by the diaphragm and/or the float which convert the hydrostatic head into a hydrostatic force. The chamber is fitted with a vent pipe rising to above the waterline of the lifeboat. This allows full use of hydrostatic force when the boat is in the water. One of the principal features of the present invenition is that the use of a hydraulic means enables a significant mechanical advantage to be achieved by varying the relative diameters of the master and slave cylinders. The invention is illustrated with reference to the accompanying drawing which is a schematic diagram. A lifeboat hull 1 is fitted with a well 2 near the keel across which a slack diaphragm 3 is clamped by means of a lid 4. The diaphragm 3 and lid 4 form a chamber 5 filled with air which contains a float 6 and a hydraulic master cylinder 7 fitted with a rolling diaphgram 8. The float 6 bears against the rolling diaphragm 8 when it rises in the chamber as a result of hydrostatic pressure. A hydraulic line 9 leads from the master cylinder to a slave cylinder 10 also containing a rolling diaphragm 11 which moves the releasable catch (not shown) connected at 12. A vent pipe 13 leads from the chamber 5 to a point above the waterline in the hull 1. The diaphragms are constructed from an elastomer such as neoprene. Other parts should be constructed from robust materials such as GRP, stainless steel or gun-metai. The lid 4 may be made of transparent material for ease of inspection. A mixture of glycol and water forms a suitable hydraulic fluid. Claims

1. A hydraulic means for releasing a safety catch actuated by hydrostatic pressure.

2. A hydraulic means according to claim 1 said means comprising a hydraulic master cylinder actuable by hydrostatic force and a hydraulic slave cylinder responsive to the actuation of the master cylinder and being connected to the safety catch whereby actuation of the slave cylinder by the master cylinder releases the safety catch.

3. A hydraulic means according to claim 2 wherein the actuation of the master cylinder by hydrostatic force is achieved by means of a diaphgram or a float or a combination thereof.

4. A hydraulic means according to claim 3 wherein the diaphragm and/or the float is located in a self-draining chamber in the hull of a lifeboat, the chamber being open at the bottom and closed at the top thereby enabling the master cylinder to be actuated by the diaphragm and/or the float which convert the hydrostatic head into a hydrostatic force.

5. A hydraulic means according to any one of the preceding claims as hereinbefore described with reference to the accompanying drawing.