GB2367048A

GB2367048A - Rope safety device

Info

Publication number: GB2367048A
Application number: GB0113484A
Authority: GB
Inventors: Keith Jones; Christopher Howard Ware
Original assignee: NAT ACCESS AND RESCUE CT; Heightec Group Ltd
Current assignee: NAT ACCESS AND RESCUE CT; Heightec Group Ltd
Priority date: 2000-09-21
Filing date: 2001-06-04
Publication date: 2002-03-27
Anticipated expiration: 2021-06-04
Also published as: GB2367048B; GB0113484D0; GB0023137D0

Abstract

A rope safety device provides a secondary independent braking mechanism comprising an eccentric pulley 2 and an associated bollard 11, that acts cumulatively with a primary braking mechanism comprising an eccentric pulley 1 and a bollard 10, the pulley 1 having a control handle 12 secured thereto for releasing the primary braking mechanism. The secondary braking mechanism can be added or removed while the device is under load. The action of the cumulative braking mechanisms means the restraining force does not diminish too quickly when the primary braking mechanism is released. Preferably, the control handle has a further protuberance 13 to coact with the bollard 10 to jam the rope. Preferably, the bollard 10 is rectangular. Preferably, the pulleys and bollards are mounted on a base 5 and a pivotally mounted cover (6, Fig 1) with slots can be moved to cover or expose the pulleys allowing roping or removal of the rope thereof. Instead of pulleys, cams can be used.

Description

ROPE SAFETY DEVICE The present invention relates to a rope safety device for controlling the lowering and/or raising a load, such as a person, on a rope, cable, web or other similar elongate load supporting member (collectively referred to hereinafter as"rope").

Rope safety devices are known for controlling or arresting the descent of a person or other load down a rope or for controlling or arresting the descent of a rope having a load thereon. Such devices can be used to rescue a trapped or injured person from a building or other high or inaccessible place or during leisure activities such as climbing, abseiling or pot holing.

A known rope safety device is shown in GB 2 044 414, which discloses a selflocking descender comprising a pair of pulleys 14,16 mounted between a pair of plates, the rope being wound in an S-shape around the pulleys, the top or fixed pulley 14 being a stationary member secured to the first side plate 20, the bottom or movable pulley 16 being pivotally mounted on the side plate and having a control lever attached thereto. In figure 3 the descender is shown attached to a users harness. The friction of the rope 12 on the movable pulley 16 effects clockwise rotation of the movable pulley 16 so that the rope is trapped between the protuberance 50 on the movable pulley 16 and a locking element 54, locking the descender onto the rope and preventing the downward movement of the user. By pressing the control lever the protuberance 50 of movable pulley 16 is moved away from the locking element 54, releasing the rope and allowing the person to descend the rope.

Release of the lever allows the descender to once again lock onto the rope.

To control the passage of a loaded rope through the device, either for descent of a fixed rope by a person or to allow a load to be lowered, the device must provide sufficient friction to allow passage of the loaded rope through the device to be controlled. The main disadvantage of the prior art descender is that, once the locking mechanism has been released, descent of the user can occur uncontrollably, especially where a large load is placed on the rope.

The present invention overcomes the above difficulties by providing an additional independent braking mechanism that acts cumulatively with a primary braking or self locking mechanism and can be connected or disconnected from the rope while the device is under load. The action of the cumulative braking mechanisms means the restraining force does not diminish too quickly when the primary braking mechanism is released.

According to the present invention there is provided a safety device for controlling the lowering and/or raising of a load on a rope, the device comprising a first mounting plate, a first cam or eccentrically mounted pulley pivotably mounted on the mounting plate and pivotal about a rotational axis extending perpendicular thereto, a first abutment means extending from the mounting plate adjacent the first pulley, a second cam or eccentrically mounted pulley, spaced from said first pulley, pivotably mounted on the mounting plate and pivotal about a rotational axis extending perpendicular to the mounting plate, a second abutment means extending from the mounting plate adjacent the second pulley, said first and second pulleys and first and second abutment means defining a substantially S-shaped rope path with the rope passing around the first pulley, between the first pulley and the first abutment means, between the second pulley and the second abutment means and around the second pulley, the first and second pulleys each being movable between a respective rope jamming position wherein the rope is pressed between the respective pulley and the respective adjacent abutment means and a release position wherein the respective pulley is spaced from the respective abutment means to allow the rope to move freely therebetween, a second mounting plate being provided to cover the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device, attachment means being provided on the first and/or second mounting plates for anchoring purposes, the device being such that, when a load is applied to a downstream end of the rope, both the first and second pulleys are urged to their respective jamming position by the moment applied thereto by the rope passing around the pulleys, control handle means being secured to or formed integrally with the first pulley for moving the first pulley from its rope jamming position to its release position.

The control handle may comprise an elongate substantially flat plate parallel to and adjacent the first and second supporting plates. Preferably the second pulley comprises a substantially circular eccentrically mounted pulley or sheave, the rotational axis of the second pulley being positioned between the central axis of the second pulley and the first abutment means when the second pulley is in its rope jamming position. Preferably the first pulley comprises a substantially circular eccentrically mounted pulley or sheave, the central axis of the first pulley being between the rotational axis of the first pulley and the first abutment means when the first pulley is in its rope jamming position. The outer circumferential surface of the first pulley may comprise a substantially circular region and a substantially planar region extending tangentially to the pulley, the intersection between the planar region and the circular region defining a rope engaging point, the first pulley, the rotational axis of the first pulley and the first abutment means being arranged such that the rope engaging point presses the rope against the first abutment means when the first pulley is in its rope jamming position.

Preferably the first abutment means comprises a substantially rectangular post mounted on a side of the first supporting plate adjacent the control handle, the first abutment means having a first planar rope engaging surface adjacent the first pulley. When the first pulley is in its release position the first planar rope engaging surface of the first abutment means is preferably parallel with the planar portion of the first pulley, allowing the rope to pass freely between the first pulley and the first abutment means.

The second abutment means may comprise a cylindrical peg or post mounted on the first supporting plate adjacent the second pulley on the opposite side of the first supporting plate to the first abutment means.

Preferably a third abutment means is mounted on the control handle, the third abutment means being movable between a rope jamming position wherein the rope is pressed between the third abutment means and the first abutment means and/or the second pulley and a release position wherein the third abutment means is spaced from the first abutment means and/or the second pulley to allow the rope to pass freely therebetween, the control handle having three operative positions, a first position wherein the first pulley is in its rope jamming position and the third abutment means is in its release position, a third position wherein the first pulley is in its release position and the third abutment means is in its rope jamming position and an intermediate second position wherein both the first pulley and the third abutment means are in their respective release positions. The third abutment means may comprise a portion of the inner side surface of the control handle or may comprise a peg or post mounted on the control handle.

At least a portion of the circumferential surface of each of the first and second pulleys may be recessed or grooved to increase the surface area of the pulley in contact with the rope.

Preferably the second mounting plate is moveable between a rope loading/removing position and a closed position wherein the second mounting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device retains the rope within the device. The second mounting plate may be pivotally mounted on the first plate and may be pivotal about the rotational axis of the first pulley. A notch may be provided in a side surface of the second mounting plate for guiding the rope between the first pulley and the first abutment means as the second mounting plate is moved between its rope loading/removing position and its closed position.

The attachment means may comprise a first aperture provided adjacent one end of the first mounting plate and a second aperture provided adjacent one end of the second mounting plate, said first and second apertures being aligned with one another when the second supporting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device to allow a connector, such as a karabiner or screw link, to be inserted through both apertures to connect the device to a person or secure anchorage point.

Alternatively, the first and second apertures may be offset with respect to one another when the second supporting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment such that the second supporting plate is urged in a closing direction by a connector inserted through both apertures.

According to a further aspect of the invention, a safety device for controlling the lowering and/or raising of a load on a rope comprises first and second substantially circular, movable pulleys, mounted eccentrically with relation to their centres on pivots fixed normally on a first flat supporting plate, a second supporting plate being mounted parallel to the first, the second supporting plate being movable to allow a rope to be inserted and then retained in the device, a hole in the first supporting plate corresponding with a similar hole in the second supporting plate when the second supporting plate is in its closed position, the holes allowing a connector to be inserted to connect the device to a person or secure anchoring point, first and second bollards being positioned normally on the first supporting plate, one adjacent each moveable pulley such that a rope can pass between each pulley and its corresponding bollard, a control handling comprising an elongate flat plate being mounted on the first pulley parallel to and adjacent to the first supporting plate, a third bollard being mounted on the control handle, normally to the plate, such that a rope leaving the device after the second pulley passes between the third bollard and the first bollard.

The present invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front elevation of a safety device according to the invention; Fig. 2 is a side elevation of the safety device of Fig. 1; Fig. 3 is a front elevation of the safety device of Fig. 1 with the cover plate removed and with the primary braking mechanism in a first operative position to lock the device onto a rope; Fig. 4 is a front elevation of the safety device of Fig. 1 with the cover plate removed and with the primary braking mechanism in a second operative position; Fig. 5 is a front elevation of the safety device of Fig. 1 with the cover plate removed and with the primary braking mechanism in a third operative position; Fig. 6 is a front elevation of the safety device of Fig. 1 with the cover plate removed and with the rope removed from the secondary braking mechanism and; Fig. 7 is a front elevation of the safety device of Fig. 1 with the cover plate moved to its rope loading/removing position.

As shown in the drawings, the safety device comprises first and second predominantly circular movable sheaves or pulleys 1,2, pivotally mounted eccentrically with relation to their centres on spindles 3,4 secured normally on a flat portion of a first supporting plate 5. A second supporting plate 6 or cover plate is mounted parallel to the first supporting plate 5, the second supporting plate 6 being pivotally movable between a rope loading/removing position and a closed position to allow a rope 7 to be inserted and then retained in the device. The outer circumferential surfaces of the first and second pulleys 1,2 are provided with grooves (as shown in Fig. 2) to increase the surface area of the pulleys 1,2 in contact with the rope 7 and hence increase frictional relationship of the pulleys with the rope and to retain the rope around the circumferential surface of the pulleys 1,2.

An aperture 8 adjacent one end of the first supporting plate 5 corresponds with a similar aperture 9 in the second supporting plate 6 when in the closed position to allow a connector, such as a karabiner or screw link, to be inserted to connect the device to a person or secure anchorage point. Apertures 8,9 may be slightly offset with respect to each other when the second supporting plate 6 is in the closed position such that the second supporting plate 6 is urged towards its closed position by a connector passing through the apertures 8,9.

First and second abutment members or bollards 10,11 are mounted normally on the first supporting plate 5, one adjacent to each of the first and second pulleys 1,2.

As shown in Figs. 3 to 5, the first and second pulleys 1,2 and the first and second bollards 10,11 define between them a substantially S-shaped rope path with the rope 7 passing around the first pulley 1, between the first pulley 1 and the first bollard 10, between the second pulley 2 and the second bollard 11 and around the second pulley 2. In an alternative arrangement, shown in Fig. 6, the rope 7 only passes around the first pulley 1. Each of the above arrangements provides different modes of operation as will be described later.

A control handle 12 comprising an elongate flat plate is secured to the first pulley 1 parallel to and adjacent to the first supporting plate 5. A third abutment member or bollard 13 is mounted on the control handle 12, normally to the control handle 12 so that the rope 7 leaving the second pulley 2 passes between the third bollard 13 and the first bollard 10.

The first pulley 1, first bollard 10 and control handle 12 together constitute a primary braking mechanism, while the second pulley 2 and second bollard 11 constitute a secondary braking mechanism.

In use, the second supporting plate 6 is moved to its rope loading/removing position and a rope 7 is threaded anti-clockwise in a U-shape around the first pulley 1, moving away from the downstream end 14 of the rope 7 (i. e. the end of the rope to which the load is to be applied or which is to be attached to an anchor point). The rope 7 is then passed between the first pulley 1 and the first bollard 10. Next the rope 7 is threaded clockwise around the second pulley 2, passing between the second pulley 2 and the second bollard 11, to describe an S-shape before passing between the third bollard 13 and the first bollard 10 and leaving the device (as shown in Figs. 3 to 5).

When a load is applied to the downstream end 14 of the rope 7 (or to the apertures 8,9 or the supporting plates 5,6 with the downstream end of the rope fastened to an anchor point), the frictional force created by the rope 7 around the first pulley 1 will cause the first pulley 1 of the primary braking mechanism to pivot in a clockwise direction, thus locking the rope 7 securely between point surfaces on the first pulley 1 and first bollard 10, as shown in Fig. 3.

In order to release the rope 7 the control handle 12 is pressed towards the first and second supporting plates 5,6, as shown in Fig. 4, moving the first pulley 1 in an anti-clockwise direction. Once the control handle 12 has been pressed to release the rope 7 the secondary braking mechanism will activate to control the movement of the rope 7 through the device. As the rope 7 moves through the device the frictional force between the rope 7 and the second pulley 2 will cause the second pulley 2 to pivot in an anticlockwise direction, thus clamping the rope 7 between point surfaces on the second pulley 2 and the second bollard 11, providing an increased frictional braking force to prevent uncontrolled movement of the rope 7 through the device. As such, the secondary braking mechanism dampens the effect of releasing the primary braking mechanism.

Pulling on the free end 15 of the rope 7 will increase the frictional force applied to the second pulley as the rope passes therearound, increasing the braking force applied to the rope 7 by the second pulley 2 and the second bollard 11.

During release of the primary braking mechanism, further movement of the control handle 12 towards and between the first and second plates 5,6 moves the third bollard 13 towards the first bollard 10, clamping the rope 7 securely therebetween, as shown in Fig. 5. Thus, the third bollard 13 will allow the device to brake the rope 7 to a complete halt if the control handle 12 is operated in panic, or will allow a heavily loaded rope to be controlled smoothly.

In an alternative embodiment (not shown) the third bollard 13 may be positioned to clamp the rope 7 between itself and the second pulley 2 when the control handle 12 is moved towards the first and second supporting plates 5,6. This arrangement would provide even greater braking force since the force applied to the first pulley 2 by the third bollard 13 via the rope would push the second pulley towards the second bollard 11, increasing the braking force applied to the rope by the secondary braking mechanism. It is also envisaged that the bollard 13 might be omitted, a portion of the control handle 12 acting directly on the rope to push the rope against the second pulley and push the second pulley towards the bollard 11 when the handle is moved towards and between the first and second supporting plates 5,6.

In a further alternative embodiment, the third bollard 13 may be positioned on the control handle 12 such that it engages the rope between the first bollard 10 and the second pulley 2 when the control handle is moved towards the first and second supporting plates 5,6, pushing the rope against three surfaces (i. e. the first bollard 10, the second pulley 2 and the third bollard itself 13).

The device may be used purely as a rope locking device utilising only the primary braking mechanism by feeding the rope 7 through the device so that it only passes around the first pulley 1 in a U-shape, as shown in Fig. 6. It should be noted that, from the arrangement shown in Fig. 6, the free end 15 of the rope 7 can be passed around the second pulley 2 and between the third bollard 13 and the first bollard 10, in order to utilise the secondary braking mechanism, while the rope 7 is clamped between the first pulley 1 and the first bollard 10 and the device is under load, without unfastening the supporting plates 5,6 or unthreading the rope. The relative positions of the second pulley 2 and the second bollard 11 on the first supporting plate are such that they do not interfere with the movement of the rope through the device when only the primary braking mechanism used. Where the device is being used to arrest the fall of a person attached to either the rope or the device this feature can allow the free end of the rope to be wound around the second pulley 2 while the persons weight is being supported by the device with the first pulley 1 in its locking position, allowing the person to be lowered or to descend safely.

Furthermore, the position of the third bollard 13 on the control handle 12 is such that it is not possible to pass the rope between the third bollard 13 and the supporting plates 5,6, in order to remove the rope from the second pulley 2, unless the first pulley 1 is in its locking position.

The use of independent, cumulatively acting braking mechanisms allows precise control of loaded ropes, over a large range of possible loads.

The secondary braking mechanism allows the total braking force of the device to be released more gradually than if only a single braking mechanism were used. The severity of the secondary braking mechanism is inversely related to the braking force of the primary braking mechanism, causing a servo effect.

As the primary braking mechanism releases the effect of the secondary braking mechanism increases. This permits even control of a wide range of loads and rope diameters.

The use of a movable, eccentrically mounted, substantially circular second pulley 2 provides a multiplying effect on the braking force exerted on the free end 15 of the rope 7 by the user. This cannot occur with a fixed frictional surface.

The device has been designed to provide four functions: 1. To allow controlled lowering of a load attached to a rope (i. e. the device is attached to a fixed anchor point); 2. To allow controlled descent of a rope fastened to a fixed anchor point; 3. To function as a locking pulley in hauling systems; 4. To control a safety rope (allow paying out and taking in of a slack rope, in the event of tension being applied to the rope (i. e. a fall occuring) the device will lock the rope).

For the first and second functions the device is used as shown in Figs. 3 to 5 with the rope wound around both the first and second pulleys 1,2. When a load is applied via the downstream end 14 of the rope 7, the first pulley 1 pivots and locks the rope. As the handle 12 is moved towards the body of the device, the first pulley is moved away from the first bollard 10 gradually releasing the rope. As the rope begins to move through the device, the second pulley pivots towards the second bollard 11 due to the frictional force of the rope sliding around the pulley 2 and provides a clamping force. The relative positions and shape of the second pulley 2 and second bollard 11 are such that the clamping force is not sufficient to lock the rope. Whilst lowering, tension may be applied to the free end 15 of the rope by the user. Applying such tension increases the frictional force between the rope and the second pulley 2 thus increasing the clamping force on the rope between the second pulley 2 and the second bollard 11. In this way the user can obtain very fine control of the friction and therefore the rate of the movement of the rope through the device.

For the third and fourth functions the device is used as shown in Fig. 6 with the rope wound around only the first pulley 1. Applying a load via the downstream end 14 of the rope causes the first pulley 1 to pivot towards the first bollard 10 and lock the rope therebetween. When used for the third function, a hauling force applied to free end 15 of the rope causes the first pulley 1 to pivot in the opposite direction, releasing the rope and allowing the load to be raised. If the hauling force is removed the load once again causes the first pulley to rotate and lock the rope, thus holding the load.

When used for the fourth function, the downstream end 14 of the rope 7 is attached to a person and the device is secured to a fixed anchor point (or alternatively the downstream end 14 of the rope 7 is secured to a fixed anchor point and the device is attached to the person) and the first pulley 1 rotates to lock the rope in the device in the event of a fall.

The second pulley 2 is positioned and shaped so that its total braking force is less than that of the first pulley 1. The use of eccentrically mounted, substantially circular pulleys 1,2 allows the device to be used with ropes having a wide variety of diameters.

The positioning of the control handle 12 adjacent to the exit point of the free end 15 of the rope 7 allows the control handle 12 and the rope 7 to be controlled at the same time by one hand.

As shown in Fig. 7, the second supporting plate 6 or cover plate is pivotably mounted on the spindle 3 of the first pulley so that it can be moved from a rope loading/removing position to a closed position (shown in Fig. 1). A notch 16 is provided in a side of the second supporting plate 6 to allow the rope 7 to be guided between the first pulley 1 and the first bollard 10 as the second supporting plate 6 is moved between its rope loading/removing position and its closed position when loading a rope in to or removing a rope from the device. An extension 17, 17' of each of the first and second supporting plates 5,6 provides a grip for a users fingers when operating the control handle 12.

Claims

CLAIMS 1. A safety device for controlling the lowering and/or raising of a load on a rope or other elongate load supporting member, the device comprising a first mounting plate, a first cam or eccentrically mounted pulley pivotably mounted on the mounting plate and pivotal about a rotational axis extending perpendicular thereto, a first abutment means extending from the mounting plate adjacent the first pulley, a second cam or eccentrically mounted pulley, spaced from said first pulley, pivotably mounted on the mounting plate and pivotal about a rotational axis extending perpendicular to the mounting plate, a second abutment means extending from the mounting plate adjacent the second pulley, said first and second pulleys and first and second abutment means defining a substantially S-shaped rope path with the rope passe around the first pulley, between the first pulley and the first abutment means, between the second pulley and the second abutment means and around the second pulley, the first and second pulleys each being movable between a respective rope jamming position wherein the rope is pressed between the respective pulley and the respective adjacent abutment means and a release position wherein the respective pulley is spaced from the respective abutment means to allow the rope to move freely therebetween, a second mounting plate being provided to cover the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device, attachment means being provided on the first and/or second mounting plates for anchoring purposes, the device being such that, when a load is applied to a downstream end of the rope, both the first and second pulleys are urged to their respective jamming position by the moment applied thereto by the rope passing around the pulleys, control handle means being secured to or formed integrally with the first pulley for moving the first pulley from its rope jamming position to its release position.
2. A device as claimed in claim 1, wherein the control handle comprises an elongate substantially flat plate parallel to and adjacent the first and second supporting plates.
3. A device as claimed in any preceding claim, wherein the second pulley comprises a substantially circular eccentrically mounted pulley or sheave, the rotational axis of the second pulley being positioned between the central axis of the second pulley and the first abutment means when the second pulley is in its rope jamming position.
4. A device as claimed in any preceding claim, wherein the first pulley comprises a substantially circular eccentrically mounted pulley or sheave, the central axis of the first pulley being between the rotational axis of the first pulley and the first abutment means when the first pulley is in its rope jamming position.
5. A device as claimed in any preceding claim wherein the outer circumferential surface of the first pulley comprises a substantially circular region and a substantially planar region extending tangentially to the pulley, the intersection between the planar region and the circular region defining a rope engaging point, the first pulley, rotational axis of the first pulley and the first abutment means being arranged such that the rope engaging point presses the rope against the first abutment means when the first pulley is in its rope jamming position.
6. A device as claimed in any preceding claim, wherein the first abutment means comprises a substantially rectangular post extending perpendicularly from the first supporting plate and mounted adjacent the side of the first supporting plate adjacent the control handle, the first abutment means having a first planar rope engaging surface adjacent the first pulley.
7. A device as claimed in claim 6 when dependent on claim 5, wherein, when the first pulley is in its release position, the first planar rope engaging surface of the first abutment means is parallel with the planar portion of the first pulley, allowing the rope to pass freely between the first pulley and the first abutment means.
8. A device as claimed in any preceding claim, wherein the second abutment means comprises a cylindrical peg or post extending perpendicularly from the first supporting plate and mounted on the first supporting plate adjacent the second pulley adjacent the opposite side of the first supporting plate to the first abutment means.
9. A device as claimed in any preceding claim, wherein the device can be used in a first mode of operation wherein the rope passes around both the first and second pulleys and a second mode of operation wherein the rope passes around only the first pulley, the device being such that the free end of the rope can be passed around the second pulley in order to change from the second mode of operation to the first mode of operation while the rope is clamped between the first pulley and the first abutment means and the device is under load, without moving or unfastening the first and second mounting plates, the relative positions of the second pulley and the second abutment means on the first mounting plate being such that they do not interfere with the movement of the rope through the device during the second mode of operation.
10. A device as claimed in any preceding claim, wherein a third abutment means is mounted on the control handle, the third abutment means being movable between a rope jamming position wherein the rope is pressed between the third abutment means and the first abutment means and/or the second pulley and a release position wherein the third abutment means is spaced from the first abutment means and/or the second pulley to allow the rope to pass freely therebetween, the control handle having three operative positions, a first position wherein the first pulley is in its rope jamming position and the third abutment means is in its release position, a third position wherein the first pulley is in its release position and the third abutment means is in its rope jamming position and an intermediate second position wherein both the first pulley and the third abutment means are in their respective release positions.
11. A device as claimed in claim 10, wherein the third abutment means comprises a portion of the inner side surface of the control handle.
12. A device as claimed in claim 10, wherein the third abutment means comprises a peg or post mounted on the control handle.
13. A device as claimed in any preceding claim, wherein at least a portion of the circumferential surface of each of the first and second pulleys is recessed or grooved to increase the surface area of the pulley in contact with the rope.
14. A device as claimed in any preceding claim wherein the second mounting plate is moveable between a rope loading/removing position and a closed position wherein the second mounting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device retains the rope within the device.
15. A device as claimed in claim 14, wherein the second mounting plate is pivotally mounted on the first plate and is pivotal about the rotational axis of the first pulley.
16. A device as claimed in claims 14 or 15, wherein a notch is provided in a side surface of the second mounting plate for guiding the rope between the first pulley and the first abutment means as the second mounting plate is moved between its rope loading/removing position and its closed position.
17. A device as claimed in any preceding claim, wherein the attachment means comprises a first aperture provided adjacent one end of the first mounting plate and a second aperture provided adjacent one end of the second mounting plate, said first and second apertures being aligned with one another when the second supporting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device to allow a connector, such as a karabiner or screw link, to be inserted through both apertures to connect the device to a person or secure anchorage point.
18. A device as claimed in any of claims 1 to 16, wherein the attachment means comprises a first aperture provided adjacent one end of the first mounting plate and a second aperture provided adjacent one end of the second mounting plate, said first and second apertures being offset with respect to one another when the second supporting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment to retain the rope within the device such that, when a connector, such as a karabiner or screw link, is inserted through both apertures to connect the device to a person or secure anchorage point, the second supporting plate is urged towards the position wherein the second supporting plate covers the gaps between the first pulley and first abutment and second pulley and second abutment.
19. A device as claimed in any preceding claim, wherein at least a portion of the control handle passes between the first and second supporting plates when the control handle is pushed towards the first and second supporting plates.
20. A safety device for controlling the lowering and/or raising of a load on a rope, the device comprising first and second substantially circular, movable pulleys, mounted eccentrically with relation to their centres on pivots fixed normally on a first flat supporting plate, a second supporting plate being mounted parallel to the first, the second supporting plate being movable to allow a rope to be inserted and then retained in the device, a hole in the first supporting plate corresponding with a similar hole in the second supporting plate when the second supporting plate is in its closed position, the holes allowing a connector to be inserted to connect the device to a person or secure anchoring point, first and second bollards being positioned normally on the first supporting plate, one adjacent each moveable pulley such that a rope can pass between each pulley and its corresponding bollard, a control handling comprising an elongate flat plate being mounted on the first pulley parallel to and adjacent to the first supporting plate, a third bollard being mounted on the control handle, normally to the plate, such that a rope leaving the device after the second pulley passes between the third bollard and the first bollard, the device being such that, when rope is moving through the device under the influence of a load applied to the rope, frictional forces acting between the rope and the first and second pulleys will cause the pulleys to pivot respectively towards the first and second bollards, thus clamping the rope between point surfaces on the pulleys and the respective bollards.
21. A safety device substantially as herein described with reference to the accompanying drawings.