WO2002038487A1

WO2002038487A1 - Winch system

Info

Publication number: WO2002038487A1
Application number: PCT/GB2001/004823
Authority: WO
Inventors: Kenneth Hanson
Original assignee: Coflexip S.A.; Perry Slingsby Systems Ltd
Priority date: 2000-11-11
Filing date: 2001-10-31
Publication date: 2002-05-16
Also published as: AU2002212453A1; GB0027622D0

Abstract

A winch (10) comprising a spool (12) upon which a flexible elongate member (16) is wound, and a level wind mechanism (18) including a first diverter sheave assembly (24) upon which a first diverter sheave (26) is mounted, the first diverter sheave assembly (24) being mounted relative to the spool (12) and moveable parallel to an axis of rotation (14) of the spool (12), and a second diverter sheave (32) located at a distance from the spool (12), where the diverter sheaves (26, 32) are pivotable such that the parts of the sheaves (26, 32) that contact the elongate member (16) are aligned with the portion of the elongate member (16) that extends from the spool (12) between the first and second diverter sheaves (26, 32) at all times during motion of the first diverter sheave (26) and first diverter sheave assembly (24).

Description

Winch System

The present invention relates to winches and in particular to marine winch systems designed to lift loads to and from sea-going vessels., such as are used in the offshore oil industry for example.

Winch systems typically comprise a winch with a spool used to store a wound cable, umbilical or other flexible, elongate member (referred to hereinafter as a cable, for simplicity) , a first diverter sheave located above the winch and a second diverter sheave located above the position at which the load is to be lifted or lowered. The winch system is often also equipped with a level wind mechanism above the winch spool, upon which the first diverter sheave is mounted, designed to allow the first diverter sheave to travel back and forth parallel to the axis of rotation of the spool as the cable is wound off or on the spool. In such cases the first diverter sheave may be referred to as a "level wind sheave". Lateral bending stresses are applied to the cable between the first and second diverting sheaves as the level wind sheave travels back and forth on the spool. In order to avoid damage to the cable, the extent to which the cable is bent between these points must be kept within acceptable limits. Consequently, it is necessary to locate the first and second diverter sheaves a considerable distance apart so as to reduce the angles through which the cable is bent. This increases the deck space occupied by the winch system.

It is an object of the present invention to provide a winch system that allows cables and the like to be wound on and off a spool, whilst avoiding possible damage to the cable by lateral bending stresses and which minimises the distance between the first and second diverter sheaves .

In accordance with the present invention, there is provided a winch system comprising a winch including a spool rotatable about a first rotational axis and adapted to receive a flexible elongate member wound thereon, a level wind mechanism mounted relative to said spool and including a first diverter sheave rotatable about a second rotational axis, and a second diverter sheave located at a distance from the winch and rotatable about a third rotational axis; wherein said first and second diverter sheaves are mounted so as to be pivotable about respective first and second pivot axes such that planes of said first and second sheaves oriented substantially perpendicular to said second and third rotational axes may remain substantially aligned with the line of a portion of said elongate member extending from said spool between the first and second diverter sheaves as the first diverter sheave travels back and forth across the width of the spool .

Preferably, said first and second pivot axes are oriented substantially at right angles to said first rotational axis.

Preferably, said first rotational axis is substantially horizontal and said first and second pivot axes are substantially vertical .

Most preferably said first pivot axis is substantially co-linear with a nominal path defined by an elongate member extending between the spool 12 and the first diverter sheave.

Most preferably, the second pivot axis is substantially co-linear with a path defined by an elongate member as it leaves the second diverter sheave in the direction of unspooling.

^' Preferably, each of said first and second diverter sheaves is rotatably mounted in a corresponding yoke member pivotably mounted on the level wind mechanism and on a support structure respectively. Preferably, said yokes are configured to allow said elongate member to pass therethrough and said yoke members are pivotably mounted by means of respective pivot ring assembles such that said elongate member may pass through the centres of the pivot rings .

Most preferably, said first and second sheaves, yokes and pivot rings are arranged such that an elongate member passing therethrough follows a path which is substantially coincident with the first and second pivot axes.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a plan view of an embodiment of a winch system in accordance with the present invention;

Fig. 2 is a side perspective view of the first and second diverter sheaves of the winch system of Fig. 1;

Fig. 3 is a side perspective view of the winch system of Fig. 1; and

Fig. 4 shows a schematic side view illustrating the relative positions of a winch spool and first and second diverter sheaves of the winch system of Fig. 1. Referring now to the drawings, Fig. 1 shows a winch system comprising a winch 10 including a spool 12 which is rotatable about a first rotational axis 14 and upon which is wound a length of cable or the like 16. Mounted on the winch 10 is a level wind mechanism 18, including a pair of rails 20 and 22 extending parallel to the first rotational axis 14 and a first diverter sheave assembly 24, including a first diverter sheave 26 which rotates about a second rotational axis 28. By means of the level wind mechanism 18, the first diverter sheave assembly 24 travels back and forth across the width of the spool 12, parallel to the first rotational axis 14, with the cable 16 as the cable 16 is wound on or off the spool 12. The winch system further includes a second diverter sheave assembly 30, located at a distance from the winch 10, including a second diverter sheave 32 which rotates about a third rotational axis 34. The level wind mechanism 24 and diverter sheaves 26 and 32 thus serve to guide the cable 16 on and off the spool 12 and to and from the location at which, for example, the cable is overboarded from a marine vessel; e.g. over the side of the vessel or through a moonpool (not shown) . The second diverter sheave assembly 30 is mounted on a suitable supporting structure 36 -appropriate to the overboarding location.

^' The basic winch system described thus far is substantially conventional. Winches, spools, level wind mechanisms and diverter sheaves of this general type are well known and will not be described in detail herein. The diverter sheaves generally comprise pulley-type wheels having side flanges for retaining the cable or the like thereon and defining a plane substantially at right angles to the rotational axis of the sheave. In a conventional winch system, the first and second diverter sheaves would be mounted in fixed orientations relative to the spool, typically with their respective rotational axes oriented substantially parallel to the rotational axis of the spool. For this reason, the cable would be subject to lateral bending stresses about the side flanges of the sheaves as the first sheave travels back and forth across the width of the spool . In order to keep such lateral bending stresses within acceptable limits, the maximum angles through which the cable is bent about the flanges of the sheaves must be limited. Conventionally, this is achieved by locating the second diverter sheave at a sufficient distance from the winch, thereby increasing the deck space occupied by the winch system as a whole.

In accordance with the present invention, the first and second diverter sheaves 26 and 32 are mounted so as to be pivotable relative to the level wind mechanism 18 and to the supporting structure 36, respectively, about respective first and second pivot axes 38 and 40, such that the planes of the sheaves 26 and 32 may remain substantially aligned with the line of the portion of cable 16 extending between the sheaves 26 and 32 as the first sheave 26 travels back and forth across the width of the spool 12. This avoids any bending of the cable 16 about^" the flanges of the sheaves, completely or substantially eliminating any lateral bending stresses . This in turn allows the second diverter sheave 32 to be located at substantially any arbitrary distance from the winch 10, thereby minimising the deck area occupied by the winch system. The sheaves may be freely pivotable about the pivot axes 38 and 40, or the pivoting movement of the sheaves about the axes 38 and 40 may be driven by a motor or motors in synchronism with the level wind movement.

In general, the pivot axes 38 and 40 will be oriented at right angles to the rotational axis 14 of the spool 12. Typically, the rotational axis 14 of the spool 12 will be substantially horizontal, in which case the pivot axes 38 and 40 may suitably be substantially vertical. Preferably, the first pivot axis 38 is substantially co-linear with the nominal path taken by the cable 16 between the spool 12 and the first diverter sheave 26 and the second pivot axis 40 is substantially co-linear with the path of the cable 16 as it leaves the second diverter sheave 32 in the direction of unspooling. It will be appreciated that a small amount variance in the co- linearity of the cable path 16 and the first pivot axis 38 will occur where multiple layers of cable 16a (Fig. ) are wound on the spool 12 because the effective diameter of the spool will decrease as the cable is unwound. Depending on the arrangement of the winch system, the relevant cable paths may be other than vertical and the system may include more than two diverter sheaves, in which case each of the sheaves may be pivotable about an appropriate axis .

The pivoting movement of the sheaves 26 and 32 means that the cable 16 is subject to torsional stresses, rather than lateral bending stresses. Such torsional stresses are dependent on the length of the level wind path and will not normally be significant for typical winches and cables. Torsional stresses are minimised by making the pivot axes 38 and 40 coincident with the cable paths.

The sheave assemblies 24 and 30 typically each comprise the sheave 26 and 32 rotatably mounted in a yoke member 42, 44. In order to allow the sheaves 26 and 28 to pivot about their respective axes 38 and 40, the yoke members 42 and 44 are pivotably mounted on the level wind mechanism 18 and support structure 36 respectively. In this embodiment, the ^' relevant cable paths pass through the yokes 42 and 44, which are pivotably mounted on pivot ring assembles 46 and 48, so that the cable paths also pass through the centres of the pivot rings 46 and 48, coincident with the pivot axes 38 and 40.

Improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

1. A winch system comprising a winch including a spool rotatable about a first rotational axis and adapted to receive a flexible elongate member wound thereon, a level wind mechanism mounted relative to said spool and including a first diverter sheave rotatable about a second rotational axis, and a second diverter sheave located at a distance from the winch and rotatable about a third rotational axis; wherein said first and second diverter sheaves are mounted so as to be pivotable about respective first and second pivot axes such that planes of said first and second sheaves oriented substantially perpendicular to said second and third rotational axes may remain substantially aligned with the line of a portion of said elongate member extending from said spool between the first and second diverter sheaves as the first diverter sheave travels back and forth across the width of the spool.

2. A winch system as claimed Claim 1, wherein said first pivot axis is substantially co-linear with a nominal path defined by an elongate member extending between the spool 12 and the first diverter sheave.

3. A winch system as claimed Claim 1 or Claim 2, wherein the second pivot axis is substantially co- linear with a path define by an elongate member as it leaves the second diverter sheave in the direction of unspooling.

4. A winch system as claimed in any preceding Claim, wherein said first and second pivot axes are oriented substantially at right angles to said first rotational axis.

5. A winch system as claimed in any preceding Claim, wherein said first rotational axis is substantially horizontal and said first and second pivot axes are substantially vertical.

6. A winch system as claimed in any preceding claim, wherein each of said first and second diverter sheaves is rotatably mounted in a corresponding yoke member pivotably mounted on the level wind mechanism and a support structure respectively.

7. A winch system as claimed in Claim 6, wherein said yokes are configured to allow said elongate member to pass therethrough and said yoke members are pivotably mounted by means of respective pivot ring assembles such that said elongate member may pass through the centres of the pivot rings.

8. A winch system as claimed in claim 7, wherein said first and second sheaves, yokes and pivot rings are arranged such that an elongate member passing therethrough follows a path which is substantially coincident with the first and second pivot axes.