GB2362365A - Rope clamp/lowering device - Google Patents

Abstract

A rope clamp powering device includes a pulley 3 together with a clamping assembly comprising a tension roller 7 and a clamp element 9, the clamp assembly being mounted for rotation about an axis offset from the tension roller axis. In use the rope section to be tensioned passes into the rope clamp and is wrapped around the tension roller and pulley before passing between the pulley and clamp element so that the tension in the rope acts on the tension roller to apply a couple to the clamping assembly around its axis of rotation and so urge the clamp element against the pulley to clamp the rope between them. Preferably, the clamping element 9 is mounted via a pin 10 and has an arcuate slot 12 allowing movement of the assembly about limits defined by the slot and a pin 11. Preferably the pulley has a rack and is moved via a ratchet (14, Fig 2) and locking handle (16) allowing the pulley to move between, free, tensioned and locked positions. Preferably the pulley has a V-groove.

Description

2362365 I Rope Clamp This invention relates to a rope clamp and

particularly to a combined rope tensioner and clamp for use in height safety equipment.

Height safety equipment is intended to prevent fall injuries to personnel. One common arrangement for height safety equipment is for safety ropes or cables to be arranged between anchor points around the region to which access is required and for personnel to wear harnesses connected by lanyards to travellers which are attached to the safety ropes or cables. In such a system the travellers are arranged to normally be freely moveable along the ropes or cables so that they can follow the movements of the personnel but to automatically lock onto the rope or cable when a fall event occurs. An energy absorbing unit may be placed in line with the rope or cable to absorb the energy of the fall without applying dangerous loads to the falling person and to limit the loads applied to the anchor points.

Where such height safety equipment is a permanent installation steel cables are commonly used. However, the weight and bulk of steel cables and the difficulty of coiling and uncoiling them tightly makes the use of steel cables undesirable in temporary height safety equipment because of the inconvenience of setting up, dismantling and transporting the equipment. Accordingly, temporary height safety equipment commonly uses ropes.

As explained above, height safety equipment may employ energy absorbers in line with the ropes to absorb fall arrest energy. In order for such energy absorbers to function to their fall potential the amount of stretch or elastic deformation of the rope which occurs should be as low as possible. Further, whether energy absorbers are employed or not, in order to allow the length of fall before the fall is arrested to be controlled the ropes should be taut. Accordingly, height safety equipment employing ropes non-nally has the ropes taut, and where 2 the ropes are made of a relatively elastic material such as nylon the ropes may be placed under a high tension in order to take up most of their available range of elastic stretching and so minimise the amount of elastic stretch which occurs in the event of a fall arrest incident.

Rope based height safety equipment is commonly set up using winches to tension the ropes as necessary and rope gripping devices employing clamps to retain the tensioned ropes. This requirement for separate pieces of equipment to tension the rope and then to secure it is inconvenient. Further, the use of rope securing devices operating by clamping the rope can cause damage to the rope at the position where the clamping takes place. This is a problem because once the rope is damaged it must be disposed of and replaced in order toensure reliable and consistent operation of the height safety equipment. For similar safety reasons, a rope which has actually arrested a fall should be disposed of and replaced in any event. However, fall incidents are relatively rare and it would nonnally be expected that temporary height safety equipment would be erected and dismantled many times without a fall anest incident occurring. As a result the extra cost of replacing ropes damaged by clamps can significantly increase the cost of using the temporary height safety equipment.

Further, there is a risk that damage to the rope may not be noticed and a damaged rope re-used, which could prevent safe operation of the height safety equipment.

Ropes made of natural materials and some synthetic materials such as nylon are generally relatively elastic and as explained above elastic stretching of the rope is generally undesirable in height safety equipment, As a result, modem synthetic ropes having less elasticity, that is, a lower range of elastic stretching, are generally prefer-red. However, it has ID been found in practice that damage to such ropes of modem less elastic synthetic material is more common than with natural fibre or nylon ropes. This is because the coefficient of 4 1 ffiction of the more modem ropes 3 is generally lower than the earlier types of rope. As a result, in order to ensure that the rope is securely held even under the maximum loading. expected to be applied to the rope when a fall arrest occurs, the amount of clamping force which must be applied to the rope by the clamps must be increased and this increase in the clamping force results in a greater risk of damage to the rope.

This invention is intended to overcome these problems, at least in part.

This invention provides a rope clamp comprising a pulley, a tension roller and a clamp element mounted on a clamping assembly, the tension roller being mounted for rotation about a first axis relative to the assembly and the assembly being mounted for rotation relative to the pulley about a second axis offset from the first axis; the pulley, tension roller and clamp element being arranged such that when a rope passes between the tension roller and the pulley, around the pulley and between the pulley and the clamp element, tension in the rope will act on the tension roller to generate a couple on the assembly about the second axis which couple will urge the clamp element towards the pulley to clamp the rope between the clamp element and the pulley.

A rope clamp employing the invention will now be described by way of example only with reference to the accompanying diagrammatic figures in which:

Figure 1 shows the general arrangement of a rope clamp according to the invention; Figure 2 shows a cross section along the line A-A in Figure 1; Figure 3 shows a perspective view of a pulley for use in the rope clamp of Figure 1; Figure 4a shows a side view of an engagement element for use in the rope clamp of Figure 1; Figure 4b shows a plan view of the engagement element of Figure 4a; 4 Figure 4e shows a first perspective view of the engagement element of Figure 4a; Figure 4d shows a second perspective view of the engagement element of Figure 4a; Figure 4e shows a detail of an engaging part of the engaging element of Figure 4a; and Figure 5 shows a second side plate of the rope clamp of Figure 1.

Referring to the figures, a cable grip according to the invention is shown.

Referring to Figure 1 the general arrangement of the cable grip can be seen. Figure 1 shows the general arrangement of the cable grip with one side plate removed so that the internal mechanism of the cable grip can be seen.

The cable grip comprises a pair of parallel spaced apart side plates IA and IB. Only a first one of the side plates 1A is shown in Figure 1. Between the side plates 1 an attachment bolt 2 is provided, this links the side plates 1 and provides an attachment point for a lug, shank or similar link to allow the cable grip to be attached to a supporting structure. When used in height safety equipment it will usually be convenient for the cable grip to be attached to an energy absorbing unit by the attachment bolt 2 so that the cable grip is attached to the supporting structure through the energy absorbing unit.

A pulley 3 is located between the plates 1 and is arranged for rotational movement about a spindle 4 which passes through the plates 1.

Between the side plates 1 a pair of parallel spaced apart clamping plates 5 are located for rotational movement around a spindle 6 secured to the side plates 1. A tension roller 7 is located between the clamping plates 5 for rotation about an axle 8 attached to the clamping plates 5. It should be noted that the axle 8 is not attached to the side plates 1 so that the tension roller 7 and axle 8 are free to move with the clamping plates 5 relative to the side plates 1.

A clamping element 9 is also located between the clamping plates 5 and is fixedly located relative to the clamping plates 5 by a pair of spaced apart bolts 10 and 11. The bolts 10 and 11 are attached to the clamping plates 5 only and not to the side plates 1. However, the bolt 11 passes through a pair of arcuate slots 12 respectively formed in the side plates 1.

As a result of this construction, the clamping element 9 is fixed relative to the clamping plates 5 and the tension roller 7 has a fixed position relative to the clamping plates 5 but is able to rotate relative to the clamping plates 5, while the entire structure formed by the clamping plates 5, tension roller 7 and clamping element 9 is able to rotate about the spindle 6 relative to the side plates 1 through an arc limited by the range of movement of the bolt 11 along the arcuate slots 12.

In use, a rope 13 passes around the tension roller 7 between the tension roller 7 and the clamping element 9 and then passes between the tension roller 7 and the pulley 3. The rope 13 then passes around the pulley 3 through substantially a single turn and passes between the pulley 3 and the clamping element 9. The rope 13 then passes around an arcuate surface of the clamping element 9 back between the clamping element 9 and the tension roller 7 and then finally out of the rope clamp. In use, the tensioned section of rope 13 is the section passing into the rope clamp and into contact with the tension roller 7 while the untensioned free end or free section of the rope 13 is the section of rope 13 contacting the clamping element 9 and passing out of the rope clamp.

In order to allow the length of rope 13 to be fed through the rope clamp as necessary to allow the correct amount of rope 13 to be deployed, to allow the rope 13 to be tensioned 6 and to securely clamp the rope 13, the movement of the pulley 3 can be controlled to operate in three different modes. In a first, feed through, mode the pulley 3 can rotate freely allowing the rope 13 to be fed into and through the rope clamp in either direction as desired. In a second, ratchet, mode the pulley 3 is able to rotate only in a direction corresponding to increasing tension in the tension section of the rope 13, clockwise in Figure 1, under control of 4 ratchet in order to allow the rope 13 to be tensioned as desired. In a third, lock off, mode, no movement of the pulley 3 is possible.

In order to allow this controlled movement of the pulley 3 a pulley movement control mechanism is employed as shown in Figure 2 which shows a cross-section through the clamp along the line A-A in Figure 1.

In Figure 2 the rope clamp is shown with the pulley 3 in the second, ratchet, mode.

Rotation of the pulley 3 is controlled by an engaging element 14. The pulley 3 has a peripheral V groove 3a around its circumference and the rope 13 is partially retained within this V groove 3a when it passes around the pulley 3. Around the circumference of the face of the pulley 3 opposing the engagement element 14 twelve ratchet elements 3b are formed in a continuous ring. Each ratchet element 3b comprises a first inclined wedging surface 3c and a second step surface 3d, the step surfaces 3d all laying on planes passing radially through the axis of symmetry of the pulley 3, which is co-axial with its axis of rotation relative to the side plates 1. The face of the pulley 3 opposed to the engagement element 14 further comprises a first flat annular section 3e located inward from the ring of ratchet elements 3c and a central flat annular surface 3f, the two flat annular surfaces being separated by a circular recess 3g. The central annular surface 3f bears against the second side plate lb in use and projects further in an annular direction than the other parts of the pulley 3 so that the other parts of the 7 pulley 3 do not contact the second side plate lb. This minimises the ffictional resistence to rotation of the pulley 3. A similar arrangement is formed on the other face of the pulley 3 to locate the pulley 3 relative to the first side plate 1 a.

Finally, the pulley 3 has a central cylindrical bore 3h.

The engaging element 14 comprises a circular body 14a having a flat inner surface 14b,. Around the circumference of the inner surface 14b a circle of twelve projecting engagement pegs 14c are arranged, equally spaced around the circumference of the surface 14b.

The second side plate lb has a circle of twelve equally spaced apertures. 1 c passing through it, the apertures 1 c being spaced and sized to correspond to the engagement pegs 14c.

The engagement pegs 14c have sloping faces and flat sides and are arranged so that each of the engagement pegs 14c can cooperate with one of the ratchet elements 3c of the pulley 3 to provide a single ratchet so that the pulley 3 and engaging element 14 can cooperate to form a ratchet mechanism made up of twelve separate individual ratchets.

The face of the engaging element 14 remote from the pulley 3 extends outwardly in a substantially conical arrangement leaving a central circular recess 14d and a central bore 14e. It should be noted that the central bore 14e of the engaging element 14 is smaller than the central bore 3h of the pulley 3.

The spindle 4 passes through both side plates I a and l b, the pulley 3 and the engagement element 14. The spindle 4 has a cylindrical main body section 4a passing through the side plate 1 and the pulley 3 and a second cylindrical portion 4b having a smaller radius which passes through the engagement element 14. An outwardly projecting flange 8 section 4c is formed at the end of the spindle 4 adjacent the second reduced radius cylindrical section 4b.

A spring 15 is located within the recess 14d between the flange 4c and the base of the recess 14b. It should be noted that the recess 14d has an upper section and a lower section with the radius of the upper section being higher than the radius of the lower section, the upper and lower sections of the recess 14d being separated by a step in the outer wall of the recess 14d which forms an annular abutment surface 14E Thus, the range of possible axial movement of the engagement element 14 along the spindle 4 is bounded at one end by the spindle 4 reaching the end of the second reduced radius cylindrical portion 4b and at the other end by contact of the annular surface 14f with the flange 4c.

The end of the spindle 4 remote from the engagement element 14 and adjacent to the side plate 1 a has a mode setting handle 16 secured to it for rotational movement relative to the spindle 4 about a pin 17 perpendicular to the axis of the spindle 4. The handle 16 is shaped to form a crank so that as the handle 16 rotates around the pin 17 the varying distance between the pin 17 and the bearing surface of the handle 16 against the first side plate I a will cause the spindle 4 to move axially relative to the side plates.

When the handle 16 is in a first, free, position, pointing vertically upwards in Figure 2, the spindle 4 can move in the direction of the engagement element 14 sufficiently to disengage the engagement pegs 14c completely from the ratchet elements 3b of the pulley 3. The pulley 3 can then rotate freely allowing the rope 13 to pass freely through the rope clamp in either direction.

If the handle 16 is then moved to a second, ratchet, position shown in Figure 2 where the handle 16 projects perpendicularly away from the first side plate 1 a, the contact surface 9 between the handle 16 and the first side plate l a is further from the pin 17, resulting in a caming action which moves the spindle 4 so that the end flange 4c moves closer to the second side plate lb, that is, to the right in Figure 2. When the spindle 4 is in its ratchet position the spring 15 located between the flange 4c and the base of the recess 14d urges the engagement element 14 towards the pulley 3 so that the engagement pegs 14c are urged into engagement with the ratchet elements 3c. In this position, further rotation of the pulley 3 in the tension direction is possible because the sloping faces of the engagement pegs 14c and the inclined surfaces 3c will cooperate to produce a wedging action which will urge the engagement element 14 away from the pulley 3 against the force of the spring 15 until each inclined surface 3c moves out of contact with the respective peg 14c allowing the engagement element 14 to move back inwards towards the pulley 3 under the force of the spring.

Movement of the pulley 3 in the opposite direction to release the tension on the rope 13 is impossible because the flat sides of the engagement pegs 14c will be brought in abutment with the step surfaces 3d of the ratchet elements 3c, locking the pulley 3 and engagement element 14 against the further relative rotation. Of course, rotation of the engagement element 14 around the spindle 4 is impossible because the pegs 13c pass through their respective apertures l c in the second side plate lb.

The handle 16 is moved into the third, lock off, position, vertically downwards in Figure 2, the caming action of the contact surface of the handle 16 with the first side plate 1 a moves the flange 4c of the spindle 4 even closer to the second side plate lb so that the engagement element 14 is held in contact with the pulley 3 by the flange 4c bearing against the annular abutment surface 14f.

Accordingly, with the handle 16 in the lock off position the pulley 3 cannot rotate relative to the engaging element 14 because movement of the engagement element 14 away from the pulley 3 due to the wedging action of the engagement pegs 14c and ratchet element 3b is not possible. As explained above, rotation of the engagement element 14 around the spindle 4 is also possible and as a result the pulley 3 cannot rotate about the spindle 4.

The engagement element 14 also has four pins 14g projecting from its flat inner surface 14b. There are four pins 14g arranged symmetrically about the central bore 14e and the pins 14g are circular in cross section and project flirther than the engagement pegs 14c.

The pins 14g extend through four corresponding circular apertures l d arranged in a circle in the second side plate lb and project into the circular recess 3g of the pulley 3.

The pins 14g act to prevent rotational movement of the engagement element 14 relative to the second side plate 1 b by engaging with the holes 1 d in the second side plate lb.

The pins 14g are required for the following reason. When the engaging element 14 is in the third, free, position so that the engagement pegs 14c are fully disengaged from the ratchet elements 3c, rotation of the engagement element 14 on the spindle 4 is prevented by the continued location of the engagement pegs 14c in the holes 1 c in the second side plate lb. However, the engagement pegs 14c are only held in the holes 1 c by the biassing force of the spring 15. It is possible that the engaging element could be inadvertently moved against the urging of the spring 15 to remove the engagement pegs 14c from the apertures l c. Any subsequent rotational movement of the engagement element 14 would then move the engagement pegs 14c out of line with the apertures 1 c so that it would not be possible to move the engagement element back into the second, ratchet position or third, lock off, position.

t> 11 In order to prevent this happening the pins 14g prevent rotation of the engagement element 14 so that even if the engagement pegs 14c are removed from the apertures 1 c they will remain in line with the apertures 1 c and return back through the apertures 1 c when the mode of operation of the rope clamp is to be changed.

It should be noted that when the handle 16 is moved from the second, ratchet, position to the first, free, position there is no automatic mechanism which will cause the engagement element 14 to move out of engagement with the pulley 3. The engagement element 14 can be moved out of engagement with the pulley 3 by increasing the tension on the rope 13 so that the pulley 3 rotates slightly in the tension increasing direction so that the wedging action of the sloping faces of the engagement pegs 14c and the inclined surfaces 3c of the ratchet elements 3b moves the engagement element 14 out of engagement with the pulley. Alternatively the user can push the handle 16 into contact with the first side plate 1 a. The resulting movement of the spindle 4, to the left in Figure 2, will cause the engagement element 14 to be pushed out of engagement with the pulley 3 by the end of the larger radius cylindrical section 4a of the spindle 4 bearing against the surface 14b of the engagement element 14.

It would of course be possible to provide an automatic mechanism to disengage the engagement element from the pulley 3 when the handle 16 is moved to the first free position. However, it is believed to be a useful safety feature that farther positive action is required beyond movement of the handle 16 to release the tension in the rope 13 as this will make inadvertent release of tension in the rope 13 less likely. Further, the provision of an automatic disengagement mechanism would increase the weight and cost of the rope clamp.

12 As discussed above, the tension roller 7 and clamping element 9 are attached between the pair of spaced apart clamping plates 5 which are in turn retained between the side plates 1 for rotation about an axis 6.

The rope 13 passes between the tension roller 7 and clamping element 9, in between the tension roller 7 and pulley 3, around the pulley 3, between the pulley 3 and clamping element 9 and then between the clamping element 9 and tension roller 7 again. The tension roller 7, clamping element 9, pulley 3 and spindle 6 are arranged so that when the clamping plates 5 are in the correct position, the position shown in Figure 1, the rope 13 just passes between the tension roller 7 and the pulley 3 and between the clamping element 9 and the pulley 3. The rope 13 passes around the pulley 3 within the v-groove 3a. Conveniently, the arcuate slots 12 are positioned so that the bolt 11 is at one end of the arcuate slots 12 when the clamping plates 5 are in this position, although this is not essential.

In use the rope clamp can be attached using attachment 2 to a supporting structure through an energy absorbing unit, the handle 16 is moved into the first, free, position, and the rope 13 can be fed through the rope clamp as required in either direction until the end of the rope 13 remote from the rope clamp is attached to another supporting structure. Then, the handle 16 is moved to the second, ratchet, position and the loose end of the rope 13 can be pulled to remove slack from the rope 13 and then to apply tension to it. As tension is applied to the rope 13 this tension is prevented from being released by the ratchet mechanism on the pulley 3.

When the rope 13 is under tension, because the rope 13 leaves the pulley 3 and then curves around the tension roller 7, the tension forces in the rope 13 will apply a rotational couple to the tension roller 7, and through it to the entire assembly attached to the clamping 13 plates 5, around the spindle 6 and this couple will be such that the clamping element 9 will be urged towards the pulley 3, thus clamping the rope 13 between the clamping element 9 and the pulley 3. The frictional force produced is maximised by the V-groove 3a because the clamping element 9 is urging the rope 13 into the V-groove 3a. This will produce a higher ffictional force than if the pulley 3 had a flat circumferential surface. The rope 13 travels through almost a complete revolution around the pulley 3 within the v-groove 3a and accordingly the well known capstan effect or winch effect will cause the frictional force applied to the rope 13 by the clamping between the clamp element 9 and the pulley 3 to be greatly amplified so that the tension in the rope 13 which can be held by the clamp 3 is many times greater than the actual ffictional force generated at the clamping point between the clamp element 9 and the pulley 3. In order to allow for the necessary rotational movement of the clamping plates 5 and attachment elements around the spindle 6 to compensate for compression of the rope 13 between the clamping element 9 and the pulley 3, the arcuate slots 12 are provided and as a greater and greater clamping force is applied the bolts 11 will move further along the arcuate slots 12.

When the tension in the rope 13 is to be increased further, the free end or section of the rope 13 can be pulled away from the rope clamp and when the tension in the free section of the rope 13 is sufficiently high this force will generate a couple rotating the clamping element 9, and thus all of the elements linked to the clamping plates 5, around the spindle 6 in the opposite direction to the couple generated by the tension on the tensioned section of the rope 13. This will rotate the clamping plates 5 and associated elements until the clamping of the rope 13 between the clamping elements 9 and the pulley 3 is released. The rope 13 can then be pulled around the pulley 3 as it rotates in the direction allowed by the ratchet 14 mechanism to increase the tension in the rope 13. In order to ensure that when the loose section of the rope 13 is released the clamping action is immediately restored, the maximum movement of the clamping element 9 away from the pulley 3 is limited to be only just sufficient to allow the clamping force to be released by the bolt 11 bearing on one end of the arcuate slots 12.

Where the rope clamp is to be used in rope based height safety equipment employing low stretch ropes of modem synthetic materials, it is expected that the required degree of tension in the rope 13 will be such that they can be achieved by direct manual pulling on the loose end or section of rope 13. The application of the necessary tension forces manually will be the most convenient arrangement, but if higher tensions were required the rope clamp would be equally applicable to systems in which pulleys, levers or winches either manually or power operated were used to apply the necessary tension.

Once the required tension has been reached the handle 16 is moved into the third, locked, position and the pulley 3 then cannot move.

The rope grip will then hold the tension on the rope 13 until such time as the height safety equipment is to be dismantled or a fall arrest incident occurs.

In order to release the tension in the rope 13 the handle 16 must be moved through 180' from the third, locked, position through the second, ratchet, position, and into the first, free, position. Then, the free end of rope 13 should be pulled until sufficient tension is applied to pull the gripping element 9 away from the pulley 3 and release the gripping of the rope 13 and then to slightly further increase the tension of the rope 13 by rotating the pulley 3 in the tension direction until the ratchet mechanism disengages. The tension in the rope 13 is can then be released in a controlled manner and the rope 13 can then be pulled through the rope clamp in either direction as required to disassemble the height safety equipment.

Alternatively, it would be possible to release the tension in the rope 13 by pushing the handle 16 into contact with the surface of the first side plate 1 a after placing the handle 16 in the first, free, position. This procedure will result in an immediate uncontrolled release of all of the tension energy in the rope 13 and this could pose a risk to anyone in the path of or close to the free section of the rope 13. Accordingly, the procedure of releasing the ratchet by increasing the tension of the rope 13 will normally be preferred.

In the event of a fall arrest situation, the falling person will fall freely until they reach the end of the extension of their lanyard and harness and the traveller locks to the rope 13. The tension of the rope 13 will then increase rapidly. As the tension in the rope 13 increases the couple generated by the tension force on the tension pulley 7 urging the assembly attached to the clamping means 5 around the spindle 6 will increase and accordingly the force with which the rope is clamped between the clamping element 9 and the pulley 3 will increase. Because of the windlass or winch effect amplifying the friction produced by the clamping of the rope 13 between the clamping element 9 and the pulley 3 due to the length of the rope 13 held in the v-groove 3a of the pulley 3, the restraining force applied to the rope 13 by the rope clamp will increasewith the tension in the rope 13 so that the rope 13 will always be securely clamped.

The forces applied by the tension in the rope 13 during a fall arrest incident will be transmitted from the pulley 3 into the side plates 1 and from the tension roller 7 through the axle 8, side plates 5 and spindle 6 also into the side plates 1. These tension forces will then 16 pass through the side plates 1 to the attachment bolt 2 to be passed on further to the energy absorber and supporting structure.

It will be realised that because the clamping force applied to the rope 13 by the rope clamp is derived from and related to the tension in the rope 13, in normal use the clamping forces are only sufficient to reliably resist the tension in the rope 13 required for safe operation of the height safety apparatus. The much higher clamping forces required to resist the much greater rope tensions produced during a fall arrest incident are applied only when a fall arrest incident occurs. As a result, the forces applied to the rope 13 in use of the clamp are minimised so that the rope clamp reduces the risk of damage to the rope 13 in setting up and dismantling the height safety apparatus, reducing the rate of rope replacement and thus the operating costs of the height safety apparatus and improving safety.

Further, the use of a pulley and V-groove both further reduce the clamping forces which need to be applied to the rope 13, minimising the risk of damage to the rope 13 and so reducing operating costs and improving safety.

As explained above the ability of the rope grip to allow selective clamping, ratchet movement or free movement of the rope through the rope clamp simplifies the setting and dismantling of height safety apparatus.

As noted above, the clamping element 9 does not rotate relative to the clamping plates 5 to which it is attached. Accordingly, although the clamping element 9 is shown as a circular element in the illustrated embodiment this is not essential. It is necessary for the section of the clamping element which contacts the rope 13 to have a smooth surface with a sufficiently high radius of curvature to avoid damage to the rope when it is pulled across the clamping element 9 under tension, but the profile of the other parts of the clamping element 9 17 which do not contact the rope 13 is unimportant. In the illustrated embodiment the clamping element 9 is a circular wheel solely for ease and convenience of manufacture.

The described embodiment is discussed in terms of the use of the rope clamp in height safety equipment where an energy absorbing unit is placed in line with the rope. In such equipment the rope clamp and energy absorber could be formed as a single integral unit. The rope clamp can also be used in height safety equipment which employ other forms of energy absorbers or which do not employ an energy absorber at all. Further, the rope clamp can be used in situations where ropes need to be held under tension other than height safety equipment.

The embodiment described herein is purely exemplary and the person skilled in the art will realise that other arrangements of the invention will be possible.

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Claims (3)

Claims:

1. A rope clamp comprising a pulley, a tension roller and a clamp element mounted on a clamping assembly, the tension roller being mounted for rotation about a first axis relative to the assembly and the assembly being mounted for rotation relative to the pulley about a second axis offset from the first axis; the pulley, tension roller and clamp element being arranged such that when a rope passes between the tension roller and the pulley, around the pulley and between the pulley and the clamp element, tension in the rope will act on the tension roller to generate a couple on the assembly about the second axis which couple will urge the clamp element towards the pulley to clamp the rope between the clamp element and the pulley.

2. A rope clamp according to claim 1, in which the pulley is controllable by a ratchet to allow rotation only in a direction corresponding to increasing tension in a rope held in the rope clamp.

3. A rope clamp according to claim 2, in which the pulley is selectively controllable to operate in a first mode allowing free rotation of the pulley, a second mode in which the pulley is controlled by a ratchet to allow rotation only in a direction corresponding to increasing tension in a rope held in the rope clamp and a third mode in which the pulley cannot rotate.

4 A rope clamp according to any preceding claim in which the pulley has a Vgroove in its circumferential surface.

19 5. A rope clamp according to claim 4, in which the clamp element is arranged to urge the rope into the V-groove.

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