GB2188246A - Fall arrest safety device for pole climbers - Google Patents

Abstract

A fall arrest device for a pole climber which has a main yoke (30) with resiliently biased arms (34) at each end for partly encompassing a pole. The resiliently biased arms (34) are movable in the same plane as the main yoke (30) and also urge the secondary yokes into contact with the pole to accommodate a range of pole diameters. Handles are attached to each arm (34) for gripping by the pole climber to move the arms (34) so that the fall arrest device can be raised or lowered, and each arm also has eyelets (43) for receiving safety straps attached to the pole climber. In a preferred embodiment the arms have sharp projections (48) for biting into the pole. A pull on the strap, due to slippage of the pole climber, causes the arms to move towards each other and the sharp projections (48) to bite tightly into the pole. <IMAGE>

Description

SPECIFICATION Fall arrest safety device The present invention relates to fall arrest devices for pole climbers and particularly, but not exclusively, for use by linemen and the like who have to climb poles in the course of their duties.

A pole climber normally wears lineman's gaffs strapped to each leg, which are designed to engage the pole when climbing to prevent slipping and provide purchase for his feet. The pole climber uses a pole climber's device in conjunction with the gaffs, which usually takes the form of a strap which can be looped around the pole and attached to the waist belt of the lineman. The strap is principally used for supporting the lineman as he works but can also be used to assist climbing the pole. In the latter case the strap is thrown up, and tensioned to support the lineman who then climbs up the pole using his gaffs.

If the lineman's gaffs slip or become disengaged from the pole, the strap would not normally prevent the climber from falling down the pole and serious injuries can result from such accidents.

There are many design criteria to be satisfied in designing a pole fall arrest device apart from the obvious requirements of lightness, simplicity and, of course, eiectrical insulation. To prevent the climber from falling down the pole, a pole climber's fall arrest device shouid support the full weight of the climber; it should engage the pole by itseif without needing the weight of the lineman and it should support the climber in any working position.

Also, the device should be easily movable to different heights and diameters on the pole without interfering with cables or cable sheathing running lengthwise on the pole, and further, during movement between heights the device should rapidly and effectively engage the pole in the event of the lineman slipping during such movement. If the lineman does slip the device should automatically close on the pole due to the weight of the lineman independently of any corrective measures taken by the lineman.

A number of such fall arrest devices for pole climbers have been proposed. For example, U.S.

Patent No: 213,715 to Mengden discloses pole climbing apparatus which required two frames; one for use by the hand and the other by the feet. The hand-operated frame encompasses the pole and is adjustable to accommodate poles of different diameters by means of pins which can be passed through registering openings in pairs of frame members at the front and at the rear of the apparatus. This device has a number of significant disadvantages. Firstly, it is complex to adjust because both the front and rear frames require adjustment. Also the pole engaging members are not resiliently biased into contact with the pole and some slippage could occur unless the weight of the lineman always acts on the members.

Another example is U.S. Patent No. 869,382 to Newton which discloses a lineman's fall arrest device having an adjustable belt looped around the lineman and the pole. The belt includes a curved plate with spurs for engaging the pole and an arm for moving the spurs between a pole engaging and a pole non-engaging position. In the event of slipping, the spurs are insufficient to retard the fall of the lineman. Climbing the pole is awkward with such a device.

It is therefore an object of the present invention is to provide an improved pole climber's fall arrest device and to obviate or mitigate the disadvantages associated with the above-mentioned safety devices.

In accordance with one aspect of the present invention a fall arrest device for a pole climber is provided and comprising: a main yoke member for engaging a pole and lying in a plane, two arms pivotally connected to respective opposite ends of the yoke member for further engaging said pole, each arm being rotatable relative to the yoke member about an axis generally perpendicular to the plane of the yoke member, the yoke member and the arms each having a pole-engaging means for engaging the pole, each arm having handle means which can be gripped by the pole climber and pulled to rotate the arms about their pivotal axis towards one another, and attachment means located on each arm and adapted to be coupled by lanyard means to safety belt connectors, each attachment means being spaced from its respective pivotal connection, whereby, in use, said attachment means, when coupled via said lanyard means to said safety belt connectors, constitutes means effective for providing, in the event of slippage of the pole climber, a force for moving each arm towards the other arm to increase the engagement between the pole-engaging means of each arm and the pole.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. lisa diagrammatic view of a lineman using a preferred form of pole climber's fall arrest device in accordance with the invention; Fig. 2 is a bird's eye view of the device in Fig. 1 in use with part of the pole broken away to show the device; Fig. 3 is a partly exploded and perspective view of a pole climber's fall arrest device shown in Figs. 1 and 2 and drawn to a larger scale; Fig. 4 is a bird's eye view to the same scale as Fig.

3 of part of a pole climber's fall arrest device and showing the position of an arm and jaw relative to the yoke for a large pole diameter; Fig. 5 is a similarviewto Fig. 4to the same scale and showing the orientation of the jaw when the pole diameter is smaller; Fig. 6 is a bird's eye view of an alternative embodiment of the device shown in Fig. 7 in use with part of the pole broken away to better illustrate the device; Reference is first made to Fig. 1 of the drawings which shows a lineman working on a telephone pole using a fall arrest device 20 in accordance with the preferred embodiment of the invention and which is secured to the pole and to which he is connected by a safety strap 22 looped through the device.The safety strap 22 has respective snap-hooks 24 at its outer ends, (one of which is shown) and which engage with rings 25 attached to the lineman's belt 26. The fall arrest device 20 is secured around the telephone pole, and as will be later explained, the lineman is supported buy a combination of a pair of gaffs 28, (one of which is shown) and by the device which is biased to engage the pole. In the working position, a component of the lineman's weight acts on strap 22 to produce a force on the fall arrest device which acts, in combination with a spring force on arms 34, to pull the arms of the device towards the pole to increase engagement of the device on the pole as will be later explained.

To better illustrate how the safety device is mounted on the pole, reference is now made to Figs.

2 and 3 of the drawings. In Fig. 2 the pole is shown partly broken away to facilitate understanding. The fall arrest device comprises a generally V-shaped main yoke 30 which is tubular and lies in a plane.

The tubing is preferably 6061 T6 aircraft grade aluminum and which is covered with an nylon insulating dielectric material Rilsan 11 (Trade mark Dupont). The yoke 30 has an inner surface 32 for engaging parts of the pole remote from the lineman.

Aluminum castings 31 and 59 (Fig. 3) are bonded by epoxy resin and riveted to the ends of the tubing forming yoke 30.

Arms 34, which for convenience of description will be described as being generally L-shaped, are coupled to each casting 31 by pivotal connections 40. The arms are mirror images of one another (i.e.

allochiral) and, for convenience of description, one arm will be described and the other arm will also be numbered for ease of comparison. The arm will also be described as having portions because it is generally L-shaped. A first longer portion 42 of the arm is connected to the casting 31. In a second shorter portion 44 the arm has a large generally circular aperture 43 for receiving the lanyard or strap 22 to permit the fall arrest device to be fastened to the belt as described above. A portion 46 of the arm between the aperture and the edge permits the arm to be grasped and constitutes handle means. It will be seen that the straps loop through the apertures of each arm and thus provide means for attaching the lanyard to the fall arrest device to be attached on opposite sides of the lineman's belt.The reason for this is that the lines of action of the forces in the belt operate outside the pivot points 40 of the arms causing them to pivot and generate substantial forces against the pole.

The second portion 44 is thicker than the first portion 42 and has a stainless (&num;304) steel projection 48 fastened to the bottom thereof. The sharp projections 48 facilitate the arms biting into the pole for better penetration and grip.

The arms 34 are biased into engagement with the pole by steel coil springs (58 Ibs force) 50 which are connected between a spring anchor position 52, located on the yoke inboardbf the pivotal connection 40 and a spring anchor position 54 on portion 42 and spaced from pivotal connection 40.

The relative location of these anchor positions is important because it varies the location of the spring with respect to the pole surface and hence the spring force. For example, if the anchor portion 54 is moved towards the aperture 43 the springbiased moment acting about pivotal connection 40 would increase the force of the arms acting on the pole surface. However, the further the anchor pins are moved towards the aperture 43 the smaller the diameter of pole which can be accommodated by the pole climber fall arrest device. It has been found in practice that by locating the anchor pins as shown, the fall arrest device according to this embodiment will accommodate pole diameters up to about 21 inches, i.e., about 75% of the pole diameters used.

A stop wire 48 is connected between the anchor portion 52 and an anchor pin 57 on portion 56 of arm portion 44.

The wire extends beneath the arms as best seen in Fig. 3 to prevent the arm 34 from being rotated too far about the pivotal connection 40. Without this wire the springs could go over centre as will be explained. The construction of pivotal connections 40 will also be explained later.

Reference is now made to Fig. 3 of the drawings which shows a pole climber's fall arrest device according to the preferred embodiment in an enlarged and partly exploded view. It will be seen that the yoke 30 consists of two tubes which are connected together by the elbow casting 59 mentioned previously. The casting is shaped to provide, when assembled, a V-Shape and the tubular portions are joined by epoxy resin to the casting and then riveted using steel rivets 60 through pre-drilled apertures 62 in the castings and tubes. Similarily castings 31 are riveted using steel rivets 70 to the other ends of the tubes through predrilled apertures, as well as being bonded with epoxy resin to provide a very strong secure connection.It will also be seen that pivotal connection 40 is provided by a grade 8 bolt 63 which passes through aperture 64 and aperture 66 in the casting 31 for engagement with a self locking Nylok (trademark) nut 67. Washers 68 are provided on the top and bottom parts of the casting to permit freely pivotal movement of the arm.

The spring 50 and stop wire 58 are fastened to the yoke 30 by bolt 86 and nut 87. A washer 88 is provided to retain wire 58 and spring 50. The other end of the spring 50 is anchored at position 54 by a nut 90 and bolt 92. The other end of the stop wire 58 is fastened by bolt 57 and nut 93 to the portion 56 via aperture 94. Anchor portion 54 is located inboard of aperture 94 so that when the handles of the arms are opened, they are prevented from being opened to an over-centered position of the arm-yoke pivot point by the stop wire 58.

The shorter portion 44 of the L-shaped arm has a lower downwardly sloping surface 95 to which each of the stainless steel projections 48 is connected by a countersunk screw 96 threaded in aperture 97 of the arm. The projection is prevented from rotating by a stainless steel dowel pin 98 which passes through an aperture in the projection to engage with a mating aperture 99 in the arm.

The overall thickness of the fall arrest device is a combination of the thickness of the arms and also the depth of the springs. In practice it is about 3 inches.

When the device is assembled as shown in Figs. 2, 4 and 5 the periphery of the arm permits the sides to be used as handles by the lineman, and the pivotal connections 40 permit the handles to be folded towards each other to occupy less space during transit or storage.

The device when assembled and positioned on the pole, as shown in Fig. 2, appears generally Cshaped in plan. Because the projections do not meet they provide clearance for the cables when the fall arrest device is adjusted to pass over the telephone pole. This clearance is convenient because it means that the fall arrest device does not interfere with these cables, or with the cable safety sheath over the cables.

The operation of the fall arrest device will now be described with reference to Figs. 2,4 and 5 of the drawings. In Fig. 4 one half of the fall arrest device is shown mounted (in solid lines) on the pole, at a larger diameter and Fig. 5 shows the same fall arrest device when moved up the pole to accommodate a smaller diameter.

In use, the lineman grips the handles or arms 34 and opens them sufficiently to place the device around the base of the pole. The lineman then pulls the handles away from each other and the spring force produced by spring 50 forces the projections 48 into contact with the pole. This portion also causes the inner surface 32 of the yoke to engage with the rear surface of the pole. The stop wire 58 tensions and prevents the arms being rotated too far. The lineman then connects the device to the rings on his belt as previously described.

To climb the pole, the lineman firstly uses his gaffs 28 to support his weight on the pole and then he grips the handles provided by the arms 34 and pulls the arms apart sufficiently to separate the projections 48 from the pole, and lifts the device to a higher position before releasing the arms. The spring forces urge the arms back into contact with the pole and the lineman then, using the device as a support, moves up the pole using his gaffs.

The lineman continues to climb by alternately moving his feet and hands in this way until he reaches his desired working position. At this level the pole will be of a smaller diameter such as that shown in Fig. 5. In this position, the pole fall arrest device is secure and the lineman can lean back as shown in Fig.1 to be supported by the strap 22 and gaffs 28. In the event that his feet should slip because the gaffs are not properly engaged, the strap 22 is pulled automatically loading the arms 34 and pulling them inwardly towards the pole to reinforce the spring force acting on the arms 34. As a result the sharp projections 48 bite more tightly into the pole so that the lineman may be supported only by the device momentarily until he again engages the gaffs.

In general, the spring forces combine with the weight of the lineman to cause the device to grip the pole so tightly that the device, and hence the lineman, are prevented from slipping down the pole.

The shape of the sharp projections and their orientation on the yoke in combination with the fact that the device is weight activated, cause the device to close automatically in the event of slippage such that the projections will bite into oily, ice, soft, or hard poles. This means that if slippage of the lineman should occur at any level, the fall arrest device would be effective.

Various modifications may be made to the embodiment hereinbefore described without departing from the scope of the invention. For example, the proportions of the device can be changed to fit different sizes of poles. Also, and if found preferable, the main yoke can be made with telescopic legs so that a variety of sizes of device can be provided simply by adjustment of the yoke.

Reference is now made to Fig. 6 which illustrates an alternative embodiment of the safety device mounted on a pole, this view being similar to Fig. 2.

This fall arrest device comprises a generally Vshaped main yoke 130 which is essentially planar and which is made of a cast aluminum alloy. The yoke is covered with an epoxy resin insulating dielectric material and has an inner surface 132 for engaging parts of the pole from the lineman.

Two arms 134, which for convenience of description will be described as being generally diamond shaped, are mounted on the upper surface of each outer end 138 of the yoke 130 by pivotal connections 140. The arms are mirror images of one another (i.e. allochiral) and, for convenience of description, one arm will be described and the other arm will also be numbered for ease of comparison.

The arm will also be described as having apices because it is generally diamond shaped. Afirst apex 142 of the arm is connected to the outer end 138 of the yoke. The arm has a large generally diamondshaped aperture 143 for reasons of lightness and has in one section 144 an elongate slot 146 for receiving straps 122 to permit the fall arrest device to be fastened to the belt of the lineman.

It will be seen that the straps cross over to be attached on opposite sides of the lineman's belt.

The reason for this is that the forces generated by belt tension create a larger turning moment about connection 140 so that during a fall, the arm pivots about pivotal connection 140 and substantial forces are generated against the pole. A second apex 148 of the arm has a pivotal connection 149 to a jaw 150.

The jaw 150 has two generally V-shaped surfaces 152, 154 at different distances from the pivot point and which can be rotated as desired into engagement with the pole surface. The pole engaging surface 152 of the jaw 150 is at a further distance from the pivotal connection 149 and the jaws are generally pivoted to this position when the pole diameter is larger. When the pole diameter is smaller, for instance when the lineman starts to climb the pole, then the jaws 150 are rotated about the pivotal connection 149 to bring generally Vshaped surfaces 154 in contact with the pole, as shown in Fig. 6 for purposes of illustration only.

The arms 134 and jaws 150 are biased into engagement with the pole by steel coil springs 155 which are connected between the pivotal connections 149 and a spring anchor position 156, located on the yoke inboard of the pivotal connection 140. The location of this anchor is important because it varies the location of the spring with respect to the pole surface. For example, if the anchor is moved towards the apex 131 of the yoke 130 the spring-biased moment acting about pivotal connection 140 would increase the force of the jaws acting on the pole surface. However, the further the anchor pins are moved towards the apex 131 the smaller the diameter of pole which can be accommodated by the pole climbers fall arrest device.It has been found in practice that by locating the anchor pins as shown, the fall arrest device according to this embodiment will accommodate pole diameters up to about 21 inches, i.e., is about 75% of the pole diameters used. Again, this embodiment could include an adjustable yoke to accommodate all sizes of pole.

Between the pivotal connection 140 and the anchor 156 is located a stop pin 158 which extends above the surface of the yoke 130 as best seen in Fig. 9. This pin acts as a stop to prevent the arm 134 from being rotated too far about the pivotal connection 140.

The materials of the fall arrest device can be metal, wood or plastic. They can be made by forging or stamping, and they can be suitably treated with electrically insulating coatings, such as nylon, PTFE etc.

It will also be appreciated that the fall arrest device could be used on trees and on wooden, concrete and metal poles of non-circular crosssection, such as oval.

Claims (7)

1. A fall arrest device for a pole climber comprising: a main yoke memberfor engaging a pole and lying in a plane, two arms pivotally connected to respective opposite ends of the yoke member for further engaging said pole, each arm being rotatable relative to the yoke member about an axis generally perpendicular to the plane of the yoke member, the yoke member and the arms each having a pole-engaging means for engaging the pole, each arm having handle means which can be gripped by the pole climber and pulled to rotate the arms about their pivotal axis towards one another, and attachment means located on each arm and adapted to be coupled by lanyard means to safety belt connectors, each attachment means being spaced from its respective pivotal connection, whereby, in use, said attachment means, when coupled via said lanyard means to said safety belt connectors, constitutes means effective for providing, in the event of slippage of the pole climber, a force for moving each arm towards the other arm to increase the engagement between the pole-engaging means of each arm and the pole.

2. A fall arrest device as claimed in claim 1 in which the pole-engaging means of each arm consists of sharp projections for biting into the pole surface.

3. A fall arrest device as claimed in claim 1, wherein said pole-engaging means of said arms are constructed by jeaw means pivotably mounted to each arm, each jaw means having at least one polecontacting surface for engaging the pole.

4. A fall arrest device as claimed in any of claims 1 to 3, in which each arm is biased resiliently toward the other arm.

5. A fall arrest device as claimed in claim 4 wherein each jaw has two pole contacting surfaces, said pole-contacting surfaces being located at different distances from the pivotable axis of the jaw, and said different pole-contacting surfaces constituting means effective to permit said fall arrest device to be mounted on a wide range of pole diameters.

6. A fall arrest device as claimed in any preceding claim, in which the yoke is adjustable to permit use on a variety of different sizes of pole.

7. A fall arrest device substantially as hereinbefore described with reference to Figs. 1 to 5 or Fig. 6 of the accompanying drawings.