GB2488363A

GB2488363A - Lock device for limiting chain slippage in a hoist system

Info

Publication number: GB2488363A
Application number: GB1103351.1A
Authority: GB
Inventors: Simon Neve; Andrew Pestana; Steve Waite
Original assignee: Balfour Beatty PLC
Current assignee: Balfour Beatty PLC
Priority date: 2011-02-28
Filing date: 2011-02-28
Publication date: 2012-08-29
Also published as: WO2012117237A1; GB201314523D0; GB201103351D0; GB2501848A; GB2501848B

Abstract

A chain lock or stopper for clamping to a roller chain 10 includes a handle 24 rotatable between lock and release positions and a locking arm 22 moved by the handle 24 between a lock position between adjacent roller surfaces of a roller chain and a release position spaced from the path of the roller chain. In a release mode, the chain lock can be slid along the chain 10 and in the lock mode it is fixed in position along the chain 10 and may abut the casing of a hoist (12 fig. 1) and limit slippage should the chain slip in the hoist. The locking arm 22 may be rotatable by the handle 24. Two locking arms 22 may be provided and may be positioned between different roller surfaces. The locking arm 22 may be curved. The chain lock may include a central body 26 for mounting on the chain by means of a slot 28. A spring 40 may bias the handle 24 to the locked position.

Description

DEVICE FOR LIMITING CHAIN SLIPPAGE AND HOIST SYSTEM USING THE

SAME

This invention relates to a device for limiting chain slippage by providing a stop which attaches to the chain. The invention is of particularly interest to a device for limiting chain slippage of a chain which forms part of a chain hoist system, although the invention can be used to provide a stop for chains in other pulley systems.

Chain hoists are used for raising, lowering and supporting heavy loads. A chain hoist uses a drum or lift-wheel around which the chain wraps. It may be manually operated, electrically or pneumatically driven. The load is attached to the hoist by means of a lifting hook.

is Slippage of the chain in a chain hoist system can of course have serious consequences. A number of methods have accordingly been looked at to provide a fail-safe safety device to prevent chain slippage. Indeed, there are a number of chain stop type devices available.

Such chain stop devices are typically for link chain type chain hoists (a link chain being a series of interlocked closed chain links, with one link orthogonal to the next). For example a chain stop device can comprise an orifice through which the chain passes. This orifice can have a plus ("+") shape so that the orthogonal chain links can all pass through. By changing the orifice shape to a slit ("-") shape for example by a sliding operation, the chain stop device will become locked on one chain link, because it cannot pass the junctions to the adjacent orthogonal chain links. Thus, it is relatively straightforward to design a locking device for link chains.

However, designing a locking device for roller chains (a roller chain being a series of pivotally articulated links, such as commonly used for bicycle chains) is less straightforward. The outer shape of the chain (in cross section along its length) is much more uniform from link to link, so this makes it difficult to define an orifice shape that will reliably lock around one chain link.

This invention relates particularly to a chain lock for roller chains. There remains a need for a chain lock for roller chains which is adjustable with the least amount of effort as well as providing a fail safe method of stopping a chain from running out should the chain hoist slip in operation.

According to the invention, there is provided a device for clamping to a roller chain comprising: a locking arm; a handle, attached to the locking arm, wherein the handle is rotatable between a lock position and a release position, wherein in the lock position, an end of the locking arm is adapted to be positioned in the space between adjacent roller surfaces of the roller chain, and in the release position, the locking arm is away from the path of the roller chain.

This device enables rotation of a handle to cause an arm to move into the space between chain rollers to block the movement of the chain, i.e. to clamp the device at a fixed position along the chain. This provides a simple to operate device.

The device can comprise two locking arms, wherein an end of each locking arm is adapted to be positioned in the space between a different pair of adjacent rollers. This provides improved safety.

Each locking arm can have a first end attached to the handle and a free end, wherein the first ends are diametrically opposite and the free ends are diametrically opposite. The rotation of the handle thus moves both free ends into engagement with their respective spaces.

The or each locking arm can be curved. This enables a compact design, for example with a cylindrical outer shape. The or each locking arm can for example comprise an arc of between 30 and 60 degrees.

The device can comprise: a central body for mounting on the chain; the handle; an end piece; and fixings, wherein the fixings are adapted to clamp the central body between the handle and the end piece so that the central body cannot be dismounted from the chain.

The device is mounted to the chain by fixing the handle and end piece together around the central body. The fixings can be screws. The end piece thus rotates with the handle, but the central body is mounted on the chain such that it cannot rotate relative to the chain.

A spring preferably acts between the handle the central body to rotationally bias the handle to the lock position.

The invention also provides a chain hoist system comprising: a chain; a chain hoist drum; and a device as claimed in any preceding claim for limiting slippage of the chain through the drum.

An example of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a chain hoist system of the invention; Figure 2 shows the device for limiting slip in more detail and in exploded view; Figure 3 shows the device for limiting slip in side view and cross section in the lock position; and Figure 4 shows the device in open cross sectional side view and in a view with hidden detail, in the release position.

The invention provides a chain lock for roller chains which is rotationally controlled between lock and release modes. In the release mode, the device can be slid along the chain, and in the lock mode, it is fixed in position along the chain.

The device comprises a locking arm which is rotatable by a handle so that in the lock mode, an end of the locking arm is seated in the space between adjacent rollers of the roller chain.

Figure 1 shows a chain hoist system of the invention.

The system comprises a chain 10, a chain hoist drum 12, and a locking device 14 of the invention for limiting slippage of the chain through the drum.

The device 14 is positioned a small distance below the drum 12 (which is the main body of the chain hoist), for example at a maximum distance of 3 links. If there is slippage of the chain through the drum, movement of the chain is limited when the device 14 butts against the casing of the drum 12. The device is mounted so that it is moved towards the drum in the event of slippage, i.e. when the direction of movement of the chain is the direction of movement induced by the load (not shown) supported by the chain hoist system.

The chain is a roller chain. The example shown is a bush roller chain. This has two types of links which alternate. The first type is inner links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. The inner links alternate with the second type, the outer links, consisting of two outer plates held together by pins passing through the bushings of the inner links.

is There is also a bushing-less roller chain design which is similar in operation, but instead of separate bushings or sleeves holding the inner plates together, the plate has a tube stamped into it protruding from the hole which serves the same purpose.

In both cases, there are rollers or at least roller surfaces around the pivot axes between adjacent chain links. Between adjacent roller surfaces are spaces, and the slippage limiting device of the invention is designed to insert one or more arms into the spaces to lock the movement of the chain relative to the device itself.

Figure 2 shows the device for limiting slip in more detail and in exploded view.

The chain design can be seen more clearly, with the rollers 20 around the pivot axes between adjacent links.

The device comprises a pair of locking arms 22 (although only one is needed) which are inserted into the spacing between rollers. A handle 24 is attached to the locking arms 22, and the handle is rotatable between a lock position and a release position.

The handle is generally circular and rotatable about a central axis 23.

Each locking arm 22 has a first end attached to the handle and a free end 22a. The first ends are diametrically opposite and the free ends are diametrically opposite, with respect to the central axis 23.

The locking arms are curved (with a constant radius to the central axis 23), S so that as the handle is rotated, they follow an arc. This movement along an arc allows them to be inserted into and removed from the space between rollers. Each locking arm can comprise an arc of between 30 and 60 degrees, for example 45 degrees.

The device has a central body 26 for mounting on the chain. This can comprise a metal or plastics body, such as an acetal body. This comprises a cylinder with a slot 28 into which the chain fits, with the chain butted against the inner end surface of the slot, to prevent rotation of the central body relative to the chain. The central body thus engages around the chain, but the chain is free to slide in the direction of its length up and down the slot.

The handle 24 is attached to an end piece 30 by fixings such as screws 32 and dowels 33. The end piece 30 has projections 34 which connect to the fixed ends of the locking arms 22. When connected, a cage is formed so that the central member 26 cannot slide away from the chain. For this purpose, the handle and the end piece each have a circular recess into which the ends of the central body 26 are fitted (seen more clearly in the cross section of Figure 3).

A torsion spring 40 acts between the handle 24 the central body 26 to rotationally bias the handle to the lock position.

In use, in the lock position, an end of each locking arm is positioned in the space between adjacent rollers of the roller chain, and in the release position, the locking arms are away from the path of the roller chain. Thus, there is a straight path through the device between the arms which is wide enough for the chain.

Figure 3 shows the device in side view and cross section in the lock position.

The two locking arms are not in adjacent spaces, but are spaced by one space, as shown. Figure 3 also shows more clearly the way the spring engages with the handle, in a dedicated recess 42, as well as engaging with a recess in the central body as can be seen in Figure 2.

Figure 4 shows the device in open cross sectional side view and in a view with hidden detail, in the release position. The angular rotation between the positions is shown as 45 degrees, although this may be more or less, for example between 30 and 60 degrees.

By way of example, the width of the device (from the handle to the end piece) may be around 85n-im and the diameter of the circular handle around 75mm. Of course, the device is sized to correspond to the chain to be used with the device.

As mentioned above, a single locking arm is enough for the device to work, but two arms give added security and symmetry.

The particular three-piece structure described above is not essential. A two piece arrangement could be used, with one piece rotating relatively to the other, and one fixed so that it cannot rotate relative to the chain. Various materials can be used.

The device can be used with any type of hoist. In a specifically designed system, the stopping device may be designed to butt against the hoist body in a certain way when slippage occurs, but the device can be used with hoists with no special design. The device can be used in other pulley systems, again to provide a stop which prevents a chain moving through another device by more than a desired amount (corresponding to an allowed amount of slippage).

The device is designed to be assembled around the chain as is clear from the above description. However, it can be pre-assembled and fed along the chain from an end of the chain.

Various other modifications will be apparent to those skilled in the art.

Claims

CLAIMS1. A device for clamping to a roller chain comprising: a locking arm; a handle, attached to the locking arm, wherein the handle is rotatable between a lock position and a release position, wherein in the lock position, an end of the locking arm is adapted to be positioned in the space between adjacent roller surfaces of the roller chain, and in the release position, the locking arm is away from the path of the roller chain.
2. A device as claimed in claim 1, comprising two locking arms, wherein an end of each locking arm is adapted to be positioned in the space between a different pair of adjacent roller surfaces.
3. A device as claimed in claim 2, wherein each locking arm has a first end attached to the handle and a free end, wherein the first end are diametrically opposite and the free ends are diametrically opposite.
4. A device as claimed in any preceding claim, wherein the or each locking arm is curved.
5. A device as claimed in claim 4, wherein the or each locking arm comprises an arc of between 30 and 60 degrees.
6. A device as claimed in any preceding claim, comprising: a central body for mounting on the chain; the handle; an end piece; and fixings, wherein the fixings are adapted to clamp the central body between the handle and the end piece so that the central body cannot be dismounted from the chain.
7. A device as claimed in claim 6, wherein the central body comprises a slot into which the chain fits, with the chain butted against the end of the slot to prevent rotation of the central body relative to the chain.
8. A device as claimed in claim 6 or 7, further comprising a spring which acts between the handle the central body to rotationally bias the handle to the lock position.
9. A chain hoist system comprising: a chain; a chain hoist drum; and a device as claimed in any preceding claim for limiting slippage of the chain through the drum.