GB2188667A - Ships' access ladder system - Google Patents

Abstract

An accommodation ladder system suitable for providing access to and from a deck of a ship comprises an elongated lower platform 1, a ladder support carriage 7 mounted for linear movement generally parallel to the length of said lower platform, a ladder 9 pivotally mounted at or adjacent to its lower end upon said support carriage, in upper platform 13 pivotally mounted at or adjacent to the upper end of said ladder, means 15 for securing said upper platform to the ship and cable means 3 for raising and lowering the whole assembly with the lower platform generally level. The system provides, in a single unit simply operated, a ladder assembly including a lower platform from which access to a boat is readily gained. <IMAGE>

Description

SPECIFICATION Access ladder system The present invention relates to ladder systems designed to afford access to and from a deck of a ship, which ladders are usually known as accommodation ladders. It is particularly concerned with such ladders for providing access to boats.

While accommodation ladders are now well developed which provide a secure link between the deck of a ship and an adjacent quayside, there remain difficulties in the use of accommodation ladders for access to and from a boat alongside the ship. Transferring directly from the ladder to a small boat in any but the calmest of conditions is a difficult, and even hazardous, exercise but the provision of a pontoon to assist the transfer introduces other problems. Firstly it is necessary to stow the pontoon in some convenient, reasonably nearby location and secondly it has to be manoeuvred into a working position at the foot of the ladder.

The present invention is devised to reduce or eliminate these difficulties and provides an accommodation ladder system which is readily operable to afford access to and from a boat alongside a ship.

The accommodation ladder system according to the present invention comprises an elongated lower platform, a ladder support carriage mounted for linear movement generally parallel to the length of said lower platform, a ladder pivotally mounted at or adjacent to its lower end upon said support carriage, an upper platform pivotally mounted at or adjacent to the upper end of said ladder, means for securing said upper platform to the ship and cable means for raising and lowering the whole assembly with the lower platform generally level. Thus the system provides, in a single unit simply operated, a ladder assembly including a lower platform from which access to a boat is readily gained.

The lower platform may be buoyant in the manner of a pontoon and may then be lowered until it is floating at the foot of the ladder alongside the ship. However a stable arrangement may be satisfactorily achieved if the lower platform remains suspended on the lowering cables at or slightly above the waterline. Thus it is not necessary for the lower platform to be buoyant.

Upon the lower platform, the ladder support carriage is mounted. The carriage may be carried by wheels and/or rails and is mounted for linear movement along the platform. The lower end of the accommodation ladder is pivoted to the carriage so that the angle of inclination of the ladder to the carriage may vary as the carriage moves along the platform.

In the raised position of the assembly, the ladder rests upon the platform and is supported by it. For that purpose, the extent of linear movement of the carriage along the platform is preferably at least sufficient for the ladder to be able to adopt a generally horizontal position with its centre of gravity lying above the lower platform. Preferably the carriage can move far enough for the ladder to lie substantially wholly above the platform.

The ladder itself may have fixed treads but stowage of the ladder is easier if the treads can pivot into a position in which they lie more-or-less flat within the thickness of the ladder sides. It is particularly preferred that the treads be made self-levelling by means of a parallel-motion mechanism running the length of the ladder.

The upper platform is pivoted to the upper end of the ladder and, in use, is intended to be secured to the ship's side at an upper or intermediate deck level, especially adjacent to a shell door in the ship's side opening on to an intermediate deck. The means for securing the platform to the ship may be upon the platform and/or upon the ship. Thus projecting hooks or brackets upon the platform may engage either the edge of the doorway itself or lugs projecting from the ship's side; alternatively, upwardly-projecting hooks on the ship may engage eyes on the platform.

The whole assembly is raised and lowered by a cable system which is able to maintain the lower platform generally level during the raising and lowering. Preferably, the cable system comprises four cables linked with the four corners of the lower platform in such a way that uniform paying-out or winding-in of the cables lowers or raises the platform levelly.

Thus the two cables at each end of the platform may be controlled by divided drums, the drums in turn either being separately driven by two winches running in parallel or preferably being together driven by a single double-spindle winch.

The ladder assembly may advantageously be suspended from a pair of davits, by means of which the assembly may be swung inboard from its fully raised position and stowed compactly upon its side at the edge of the deck from which it is operated.

The invention will now be further described with reference to the accompanying drawing, which illustrates, in perspective view, one preferred embodiment of the accommodation ladder system according to the present invention.

Referring to the drawing, a lower platform 1 is suspended from two davits 2 by four wire cables 3, running ontwo divided drums 4 driven from a single twin-spindle winch 5 which is mounted with the davits upon an open deck 6 of the ship. A ladder support carriage 7 is mounted upon rails 8 on the platform 1 to enable it to run smoothly on a linear track foreward and aft along the platform in the directions indicated by arrows.

An accommodation ladder 9 with self levelling treads 10 is pivoted at 11 at its lower end upon the carriage 7. Pivoted to the upper end of the ladder 9 at 12 is a platform 13, which is removably secured in the doorway of a shell door 14 in the ship's side by two hooked brackets 15.

When the ladder assembly is stowed in its inoperative position the carriage 7 is in its furthermost leftward position (as viewed in the drawing) and the ladder is collapsed flat against the platform 1, with the various handrails collapsed (or in the case of the upper platform removed), the whole assembly being flush up against the davits 2 and swung inboard into an edge-on upright position.

When it is desired to install the accommodation ladder in its position of use, the winch 5 is operated to rotate the divided drums 4 and allow the cables 3 to pay out and permit the davits 2 to swing into the outboard position illustrated in the drawing. Further extension of the cables 3 allows the assembly, collapsed on the lower platform 1, to lower in a level manner down the side of the ship. In this collapsed condition, the upper platform 13 projects over the right-hand end of the lower platform 1 and, when the assembly reaches a level opposite the shell door 14, the hooked brackets 15 are engaged over the lower edge of the doorway.

As the cables 3 are payed out further, the platform 13 remains in position at the shell door 14 and the ladder 9 swings downward about the pivot 12. Movement of the carriage 7 along the rails 8 allows the lower end of the ladder to move to the right while the platform 1 continues to move vertically downwards into a position at water level. At this point the ladder 9 is in the position illustrated and provides a secure access link between the shell door 14 and the lower platform at sea level.

It will be recognised that the whole operation of installing the ladder in its position of use can be readily carried out by just two seamen, one at the winch on deck 6 and one at the shell door 14. The reverse operation, to stow the assembly on deck, requires only one operator at the winch.

Claims (13)

1. An accommodation ladder system suitable for providing access to and from a ship, comprising an elongated lower platform, a ladder support carriage mounted for linear movement generally parallel to the length of said lower platform, a ladder pivotally mounted at or adjacent to its lower end upon said support carriage, an upper platform pivotally mounted at or adjacent to the upper end of said ladder, means for securing said upper platform to the ship, and cable means for raising and lowering the whole assembly with the lower platform generally level.

2. An accommodation ladder system as claimed in Claim 1, wherein the lower platform is buoyant.

3. An accommodation ladder system as claimed in claim 1 or 2, wherein the ladder support carriage is carried by wheels and/or rails for linear movement along the lower platform.

4. An accommodation ladder system as claimed in any of the preceding claims, wherein the extent of linear movement of the ladder support carriage is at least sufficient to permit the ladder to adopt a generally horizontal position with its centre of gravity lying above the lower platform.

5. An accommodation ladder system as claimed in claim 4, wherein said extent of linear movement is sufficient to permit the ladder to lie substantially wholly above the lower platform.

6. An accommodation ladder system as claimed in any of the preceding claims, wherein the treads of the ladder are selflevelling an may pivot into a generally flat position biiehin the thickness of the ladder sides.! "...

7.. An accommodation ladder system as claimed in any of the preceding claims, wherein the means for securing the upper platform to the ship comprise hooks or brackets on the platform to engage a doorway in the ship's side or lugs projecting from the ship.

8. An accommodation ladder system as claimed in any of claims 1 to 6, wherein the means for securing the upper platform to the ship comprise upwardly-projecting hooks on the ship to engage eyes on the platform.

9. An accommodation ladder system as claimed in any of the preceding claims, wherein the cable means comprise four cables linked with the four corners of the lower platform and means to wind-in or pay-out the cables uniformly.

10. An accommodation ladder system as claimed in claim 9, wherein the two cables at each end of the lower platform are controlled by divided drums.

11. An accommodation ladder system as claimed in claim 10, wherein said two divided drums are driven by a single double-spindle winch.

12. An accommodation ladder system as claimed in any of the preceding claims, which is suspended from a pair of davits whereby it may be swung inboard from its fully raised position.

13. An accommodation ladder system substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.