CA1265173A - Fall arrest device for pole climbers - Google Patents
Fall arrest device for pole climbersInfo
- Publication number
- CA1265173A CA1265173A CA000480478A CA480478A CA1265173A CA 1265173 A CA1265173 A CA 1265173A CA 000480478 A CA000480478 A CA 000480478A CA 480478 A CA480478 A CA 480478A CA 1265173 A CA1265173 A CA 1265173A
- Authority
- CA
- Canada
- Prior art keywords
- pole
- arms
- fall arrest
- arrest device
- yokes
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Emergency Lowering Means (AREA)
Abstract
ABSTRACT
A fall arrest device for a pole climber which has a main yoke with a respective spring biased arm at each end for partly encompassing a pole. The resiliently biased arms are movable in the same plane as the main yoke and also urge secondary yokes into contact with the pole to accomodate a range of pole diameters. Handles are attached to each arm for gripping by the pole climber to move the arms so that the fall arrest device can be raised or lowered, and each arm also has eyelets for receiving safety straps attached to the pole climber. In a preferred embodiment the arms have sharp projections 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 to bite tightly into the pole. Alternative embodiments are also described.
A fall arrest device for a pole climber which has a main yoke with a respective spring biased arm at each end for partly encompassing a pole. The resiliently biased arms are movable in the same plane as the main yoke and also urge secondary yokes into contact with the pole to accomodate a range of pole diameters. Handles are attached to each arm for gripping by the pole climber to move the arms so that the fall arrest device can be raised or lowered, and each arm also has eyelets for receiving safety straps attached to the pole climber. In a preferred embodiment the arms have sharp projections 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 to bite tightly into the pole. Alternative embodiments are also described.
Description
~26~
FALL ARREST DEVICE FOR POLE CLIMBERS
The present invention relates to a fall arrest device for pole climbers and particular:Ly, 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 reqairements of lightness, simplicity and, of course, ' ~
:~2i~ 3 electrical insulation. To prevent the climber from falling down the pole, a pole climber's fall arrest device should support the full weight of the climber; it should engage the pole by itself without needing the weight of the lineman and S 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 engag0 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 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.
FALL ARREST DEVICE FOR POLE CLIMBERS
The present invention relates to a fall arrest device for pole climbers and particular:Ly, 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 reqairements of lightness, simplicity and, of course, ' ~
:~2i~ 3 electrical insulation. To prevent the climber from falling down the pole, a pole climber's fall arrest device should support the full weight of the climber; it should engage the pole by itself without needing the weight of the lineman and S 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 engag0 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 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.
- 2 -:,.
7;3 U.S. Patent No: 869,382 to Newton, discloses a lineman's fall arrest device which has 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.
U.S. Patent No: 1,036,987 to Feinen relates to a fire escape and a travelling member for use therewith. The fire escape is formed by a series of rounded projections extending from the ground upwardly and the travelling member has a C-shaped frame, hinged in the middle of the "C-shape". Spring biased blades are provided which engage the projections and which deform due to the weight of a person hanging onto handles so that when a person hangs onto the travelling member it moves over the rounded projections. This member is not a pole safety device, nor could it be used as a pole climber's fall arrest device because as it is intended to slip down a pole in response to the weight of a person. It would therefore not support his weight. Also this device is not adjustable because once locked in position, it is held locked by a spring until it reaches the ground.
U.S. Patent Nos: 2,842,300 to Johnson; 2,879,830 to Rayner and 2,920,714 to Johnson all disclose pole climbing aids which encircle the pole and whlch have teeth for engaging the pole. None of these devices is resiliently
7;3 U.S. Patent No: 869,382 to Newton, discloses a lineman's fall arrest device which has 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.
U.S. Patent No: 1,036,987 to Feinen relates to a fire escape and a travelling member for use therewith. The fire escape is formed by a series of rounded projections extending from the ground upwardly and the travelling member has a C-shaped frame, hinged in the middle of the "C-shape". Spring biased blades are provided which engage the projections and which deform due to the weight of a person hanging onto handles so that when a person hangs onto the travelling member it moves over the rounded projections. This member is not a pole safety device, nor could it be used as a pole climber's fall arrest device because as it is intended to slip down a pole in response to the weight of a person. It would therefore not support his weight. Also this device is not adjustable because once locked in position, it is held locked by a spring until it reaches the ground.
U.S. Patent Nos: 2,842,300 to Johnson; 2,879,830 to Rayner and 2,920,714 to Johnson all disclose pole climbing aids which encircle the pole and whlch have teeth for engaging the pole. None of these devices is resiliently
- 3 -~ .:
'`' ~6S~7~
biased and adjustability is difficult in situ. In the event of slippage these devices may be insufficient to retard the lineman's fall because they do not automatically close on the pole.
U.S. Patent No: 4,407,391 to Greenway, et al discloses a pole climber's safety device having a closed yoke for encompassing a pole. The yoke consists of two half yo~es hingedly interconnected together and secured by a releasable fastening. Pole engaging blades are pivotally mounted on the underside of the yoke and, in use, the blades are normally biased, by weight or by springs, to a pole engaging position and are manually releasable. In practice, it has been found that this device is difficult and time-consuming to adjust, because first the pole blades have to be retained and held whilst the yoke is moved. The fixed closed yoke limits the size of poles it can be used with. Indeed with some poles the lineman could not climb to the top because the blades do not engage adequately the upper parts of the pole and on larger poles the blades do not engage the pole because they lie almost parallel to the pole. Also, the closed yoke can interfere with cables and/or cable sheathings especially laryer onesj and may cause restriction in movement of the device. This device has been found unsatisfactory in breaking the fall of a lineman whose feet have slipped and the lineman can fall quite a way before his fall is broken, if at all.
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.
:[n accordance with one aspect oE the present invention a pole climber's fall arrest device is provided which comprises, an arcuate yoke member for engaging a pole, and resiliently biased arms pivotally mounted at opposite ends of the arcuate member for further engaging the pole. Each arm is pivotable in a plane parallel to the arcuate yoke member and has attachment means for coupling the device via a lanyard to safety belt connectors and handle means on each arm adapted to be gripped by a pole climber. The yoke member and the arm each have a surface for engaging the pole and, in use, the resiliently biased arms retain these surfaces in contact with the pole. The arms are movable by the pole climber relative to the yoke member, away 15 from the pole against said resiliently biased means to permit movement of the fall arrest device lengthwise of the pole.
In a preferred embodiment of the invention, the arms include a sharp pro~ection for biting into the pole. Coil springs connected between each arm and the yoke provide the biasing force. The yoke is made using tubular metal and castings and the arms are castings. The device includes stop means for preventing each of the arms from being rotated too far about its pivotal axis. The yoke is tubular and by also making parts of the arms tubular the design of the preferred embodiment can be made in different sizes. The handles also serve as means for securing a lanyard to the device which, in turn, is secured to the linemans safety belt connectors.
~2~
In an alternative embodiment of the invention, the arms have pivotable jaws mounted thereon, each jaw having two surfaces for engaging a pole. The surfaces are at different distances from the pivotal axis of the jaw so that, by S rotating the jaws about the jaw axis, any one of the two surfaces can be brought into a pole-engaging position. This permits the device to accommodate a large range of pole diameters.
In a further embodiment of the invention the arcuate yoke i5 hinged midway between the ends to allow the device to be folded when not in use. Each arm is also connected to the yoke member by smaller secondary yoke elements, one end of which can be slid relative to the yoke member and the other end which is pivotable relative to the arm in the same plane as the yoke member. The smaller secondary yoke elements also have a pole engaging surface. The pole engaging surfaces are preferably serrated to facilitate gripping of the pole by the device.
These and other aspects of the invention will be readily understood with reference to the following description and drawings in which:-Fig. 1 is a diagrammatic view of a lineman using a preferred form of pole climber's fall arrest dèvice 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 o~ a pole climber's fall arrest device shown n Figs. 1 and 2 and ~6~'7;~
drawn to a larger scale;
Fig. 4 is a bird's eye view to the same scale as Fig. 2 of part of a pole climber's fall arrest device and showing the position of an arrn and jaw relative to the yoke for a large pole diameter;
Pig. 5 is a similar view to Fig. 4 to the same scale and showing the orientation of the jaw when the pole diameter is smaller;
Fig. 6 is view of a device shown in Fig. 1 and modified for use on larger diameter poles;
Fig. 7 is a diagrammatic view of a lineman using an alternative form of pole climber's fall arrest device in accordance with the invention;
Fig. 8 is a bird's eye view of the device in Fig. 7 in use with part of the pole broken away to show the device;
Fig. 9 is a partly exploded and perspective view of a pole climberls fall arrest device shown in Figs. 7 and 8 and drawn to a larger scale;
Fig. 10 is a bird's eye view to the same scale as Fig. 9 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. 11 is a similar view to Fig. 4 to the same scale and showing the orientation of the jaw when the pole diameter is smaller;
Fig 12 is a diagrammatic view similar to Fig. 1 of a lineman using an alternative form of pole climber's fall ~ ..
7~
arrest device in accordance with the invention;
Flg. 13 is a bird's eye view of the device of Fig. 12 in use with part of the pole broken away to show the device;
Fig. 14 is a partly exploded perspective view of a pole climber's ~all arrest device, shown in Figs. 12 and 13, drawn to a larger scale;
Fig. 15 is a view of part of one of the handles shown in Fig. 13, and drawn to a larger scale with part of the handle sectioned along 15-15 to better illustrate the handle mounting;
Fig. 16 is bird's eye view of the same scale as Fig. 14 of part of a pole climber's fall arrest device according to the alternative embodiment of the invention and showing the position of an arm relative to the yoke for two different pole diameters;
and Fig. 17 is a view to the same scale as Fig. 14 of part of an arm showing a part of an alternative arm structure for attachment to a safety belt strap.
Reference is first made to Fig. l 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 whlch 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 hooks 24 at its outer ends, (one of which is shown) and which engage with D-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 by a combination of a pair of gaffs 28, " ,l ., . ~., .
(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 (Fig. 2), 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. ~n 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 6061 T6 aircraft grade aluminum (Atlas Alloys, Toronto, Ontario) and which is covered with a nylon insulating dielectric material Rilsan 11 (Trade Mark, Rilsan, U.K.). The yoke 30 has an inner surface 32 for engaging parts of the far sides of the pole from the lineman. Aluminum Alloy Tenzaloy (trademark Federated Genco, Burlington, Ontario, Canada) castings 31 and 59 (Fig. 3~ are honded by expoxy resin and riveted to the ends of the yoke and the castings, as best seen in Fig. 3 are coupled to arms 34.
Planar arms 34, which for convenience of description will be described as being generally L-shaped, are coupled to each casting 31 by pivotal connections or axes 40. The arms are allochiral and, for convenience of description, one arm will be described although the other arm will be numbered for ease of comparison The arm will also be described as s ~
~ t7 ~
having legs because it is generally L-shaped. A first longer leg 46 of the arm is connected to the casting 31. In a second shorter leg 44 the arm has a large generally circular aperture ~3 for receiving a lanyard or strap 22 to permit the fall arrest device to be ~astened to the belt as described above. The 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 forces generated during a fall cause the arm to pivot about pivotal connection 40 and generate suhstantial force against the pole. The second leg 44 is thicker than the first leg 42 and has sharp stainless (#304) steel projections 48 fastened to the bottom thereof. The sharp projections 48 facilitating 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 (5~ lbs force~ 50 which are connected between a spring anchor position 52, located on the yoke inboard of the pivotal connection 40 and a spring anchor position 54 on leg 42 and spaced from pivotal connec~ion 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 54 is moved towards the aperture 43 spring-biased moment acting about pivotal connection 40 ~ t7;~
would increase the ~orce 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 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.
Between the anchor 52 and an anchor pin 57 or portion 56 of leg 44 a stop wire 58 is connected which extends beneath the arms as best seen in Fig. 3. This wire acts as a stop to prevent the arm 34 from being rotated too far about the pivotal connection 40 so that the springs do not go over centre as will be explained. The construction of pivotal connections 40 will also be later explained.
Reference is now made to Fig. 3 of the drawings which shows a pole climberls fall arrest device according to the ;pre~erred embodiment in an enlarged and partly exploded view. It will be seen that the yoke 30 consists of two ;20 tubes which are connected together by an elbow casting 59 to provide, when assembled, the V-Shape. The casting and tubular portions are joined by epoxy resin and are also riveted together with steel rivets 60 through pre-drilled apertures 62 in the castings and tubes. Similarily castings 31 are riveted by steel rivets 70 to the other ends of the tubes through pre-dri1led apertures, as well as being bonded with expoxy resin to provide a very strong secure connection. It will also be seen that pivotal ~lZ~-j5'~'7~
connection 40 is provided by a grade 8 bolt 63 which passes through aperture 64 in the end leg and aperture 66 in the casting 31 for engagement wi,th a self locking Nylok (trademark) nut 67 which is provided with a nylon insert. Washers 68 are provided on the tOp and bottom parts of the casting to permit freely pivotal movement oE the arm.
The spring 50 and stop wire 58 are fastened to the yoke 30 by bolt 86 and nut 87 to provide the anchor 52. A washer 89 is provided to retain wire 58 and spring 50. The other end of the spriny 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. Aperture 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 leg portion 44 has a lower downwardly sloping surface 95 to which the stainless steel projection 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 sloping of the lower surface includes the projections 48 to the plane of the device and facilitates penetration of the pole.
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.
' ~
S~7~
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 C-shaped in plan. Because the projections do not rneet they define an opening 88 which provides 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 cables, or the cable safety sheath for the cables which run between the base and the top of the pole.
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 pole of smaller diameter.
In use, the lineman grips the handles or arms 34 and opens them sufficiently so that the pole fall arrest device can be located around the base of the pole. The lineman then pulls the handles away from each other and the spring forces produced by spring 50 force the projections 48 into contact with the pole, and also cause the inner surface 32 of the yoke to engage with the rear surface of the pole. The stop wires 58 tension and prevent the arms r ~ ~
~Z~5~
being rotated too far. The lineman then connects the device to the D-rings on his belt as previously described.
To climb the pole, the lineman firstly relieves his weight on the device by using his gaffs 28 to support his weight and then he grips the handles provided by the arm 34 and pulls the arms apart sufficiently to separate the projections 48 from the pole and the yoke surface 32 and then lifts the device to a higher position and releases the arms. Spring forces urge the arms with projections back into contact with the pole and the lineman then, using the device as a supportl climbs the pole using his gaffs.
The lineman continues to climb in this way until he reaches his desired working position at a level where the pole is of a different diameter such as 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 and he begins to fall, the strap 22, is pulled loading the arms 34 and pulling them inwardly towards the pole to reinforce the spring forces acting on the arms 34 and causing the projections 48 to bite tightly into the pole. Because of the spring forces and the weight of the lineman the device grips the pole so tightly that the device, and hence the lineman, are prevented from slipping down the pole, and the lineman's fall is arrested. The shape of the 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 tne event of slippage such that the projections will bite into oily, icy, soft, or hard poles.
This means that if slippage of the linernan 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. E`or example, Fig. 6 shows a modified device according to the preferred embodiment for use in climbing very large diameter poles, in which like numerals refer to like parts as ~igs. 1-5 but with the suffix "a". It will be seen that this is very similar to the device of Figs. 1-5 except that yoke 30a is made of ]onger tubular portions. Also, the arms have tubular leg portions inserted between arm casting 34a and a casting 31a coupled to pivotal connector 40a. It will be appreciated that this use of tubular portions permits the preferred device to be made of a size suitable for different ranges of pole diameters.
The device in Fig. 6 can be used with poles up to 60 inches in diameter, which covers almost all poles in use.
It will also be appreciated that all relevant parts of the device i.e., yoke, arms, projections etc. will be covered with nylon based Reslin (trademark) dielectric coating.
; Although only a single yoke is shown, it will be appreciated that two half yokes could be provided being hinged together about the center so that the device could either fold about an axis parallel to the pivotal axis 40 or about an axis perpendicular to the pivotal axis 40 to permit folding for :~, :
'' ~s~
storage and transport. In such a case it will be appreciated that stops would be requirecl to be located in the surfaces of the yoke opposite to the direction o~
folding, and locking pins would be required to secure the S yoke in its in-use position. It will be appreciated that although coil springs are shown connecting the ar~s to the yoke, any other resilient connection would be suitable. For example, an elastomer having a very strong resilient force could be used or torsion springs could be used.
Reference is now made to Fig. 7 o~ the drawings which shows a lineman working on a telephone pole using a fall arrest device 120 in accordance with an alternative embodiment of the invention and which is secured to the pole and to which he is connected by a safety crossed straps 122 hooked through the device. The safety strap 122 has respective hooks 124 at their outer ends, (one of which is shown) and which engage with D-rings 125 attached to the lineman's belt 126. The fall arrest device 120 is secured around the telephone pole, and as will be later explained, the lineman is supported by a combination of a pair of gaffs 128, tone of which is sbown) and by the device whi~h is biased to engage the pole. In the working position, a component of the lineman's weight acts on strap 122 to produce a force on the fall arrest device which acts~ in combination with a spring force on jaws 127, to pull the arms and jaws of the safety device towards the pole to increase engagement of the device on the pole as will be later explainecl.
7;~
To better illustrate how the safety device is mounted on the pole, reference is now made to Figs. 8 and 9 of the drawings. In Fig. 8 the pole is shown partly broken away to facilitate understanding. The fall arrest device comprises a generally V-shaped main yoke 130 which is essentially planar and which is made of a cast alluminum alloy, (Tenzaloy), and which is covered with an epoxy resin insulating dielectric material.
The yoke 130 has an inner surface 132 for engaging parts of the far sides of the pole from the lineman.
Two planar 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 136 of the yoke 130 by pivotal connections 140. The arms are allochiral and, for convenience of description, one arm will be described although the other arm will be numbered for ease of comparison.
The arm will also be described as having apices because it is generally diamond shaped. A first apex 142 of the arm is connected to the outer end 136 of the yoke. The arm has a large generally diamond-shaped 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 as described above.
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 during a fall cause the arm to pivot about pivotal connection 140 and ;. ~J~
generate substantial force against the pole. A second apex of the arm 148 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 closer to 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 is at the top of a pole, then the jaws 150 are rotated about the pivotal connection 149 to bring generally V-shaped surfaces 154 in contact with the pole, as shown in Fig. 8 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 postion 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 i 25 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 I" `
' ~'`
l73 accommodate pole diameters up to about 21 inches, i.e., is about 75% of the pole diameters used.
Between the pivotal connection lA0 and the an~hor 156 i5 located a stop pin 158 which ~xtends 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 and limits it to movement as shown in dotted outline in Fig. 10, as will be exp]ained. The construction of pivotal connections 140 and 149 will also be later explained.
Reference is now made to Fig. 9 of the drawings which shows a pole climber's Eall arrest device according to the preferred embodiment in an enlarged and partly exploded view. It will be seen that pivotal connection 140 is provided by a bolt 160 which passes through aper-ture 162 in the apex 142 of the arm and aperture 164 in the end 138 of the yoke 130 for engagement beneath the yoke with a self locking nut 166. Washers 168 are provided above the arm and below the yoke to permit freely pivotal movement of the arm.
Pivotal connection 149 is also provided by a bolt 170 2Q which passes through an aperture 172 in a second apex of the arm and through a corresponding aperture 174 in respective jaw 150 for engagement with a self locking nut 176 beneath the jaw. The bolt 170 also receives one end 178 of the spring and the bolt also has another lower nut 180 to sandwich the end of the spring 178 between nuts 176 and 180. Washers 182 are also provided in this pivotal connection to permit free pivotal movement of the ~aw '";,;`.
: ~ ' ~lZ~ ;'3 relative to the arm and to the pole~
The other end of the spring 155 is anchored to the yoke 130 via bolt 186 and nut 187 to provide a respective anchor position 156 for the arm 134. It will be seen from this figure that arm 134 and yoke 130 lie in parallel planes to the jaws 150. The overall thickness of the fall arrest device is a combination of the thickness of the arm and the jaw and also the depth of the springs. In practice it is about 2 inches.
When the device is assembled as shown in Figs. 8, 10 and 11 the periphery of the arm permits the sides to be used as handles by the lineman, and the pivotal connections 1~0 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. 8, appears generally C-shaped in plan. Because the jaws of the arms do not meet they define an opening 188 which provides clearance for the cables but the fall arrest device must be adjusted to pass over the telephone pole. This clearance is convenient because it means that the fall arrest device does not interfere with cables 190, or the cable safe-ty sheath 192 for the cables which run between the base and the top of the pole.
The operation of the fall arrest device will now be described with reference to Figs. 8, 10, ll of the drawings. In Fig. 10 one half of the fall arrest device is shown mounted (in solid lines) on the pole, at a larger diameter and Fig. 11 shows the same fall arrest device when moved up the pole to accommodate a pole of smaller .~ !
, .
~Z~5~3 diameter. In the case of Figure 11 it will be seen that the jaw has been rotated about pivotal axis 149 to present V-shaped surface 154 with the pole instead of surface 152.
In use, the lineman grips the handles 134 and opens them sufficiently so that the pole fall arrest device can be located around the base of the pole. The lineman then pulls the handles towards each other after pivoting the jaws so that the V-shaped surfaces 152 engage the surface of the pole and the spring force produced by spring 155 then forces the arms and pivotal jaws into contact with the pole, and also causes the inner surface 132 of the yoke to engage with the rear surface of the pole.
The lineman then connects the device to the D-rings on his belt as previously described.
To climb the pole, the lineman firstly relieves his weight in the device by using his gaffs 128 to support his weight and then he grips the handles provided by the arm 134 and pulls the arms apart sufficiently to separate the V-shaped ; surface 154 from the pole and the yoke surface 132 and then lifts the device to a higher position and releases the arms.
2Q Spring forces urge the arms and the jaws 150 back into contact with the pole and the lineman then, using the device as a support, climbs the pole using his gaffs.
The lineman continues to climb in this way until he reaches his desired working position at a level where the pole is of a different diameter such as shown in Fig. 11. At some level before this the lineman will have pivoted the jaws 50 so that the V-shaped surface 154 abutts the pole .3 ; . ~, and, at the desired level as shown in Fig. 11, the springs urge the arms and the jaws so that surfaces 154 and the yoke surface 132 engage the pole. In this position, the pole fall arrest device is secure and the lineman can lean back as shown in Fig.
7 to be supported by the straps 122 and gaffs 128. In the event that his feet should slip because the gaffs are not properly engaged and he begins to fall, each of the straps 122, are pulled loading the opposite arm 134 and pulling him inwardly towards the pole to reinforce the spring force actiny on the jaws 150 and cause the jaw surfaces 154 to bite tightly against the pole. secause of the spring forces and the weight of the lineman the device grips the pole so tightly that the device, and hence the lineman, are prevented from slipping down the pole, and the lineman's fall is arrested. The shape of the jaw contact surfaces 152 and 154 and the yoke contact surface 132 are such that they present a maximum surface contact area to engage the surface of the pole throughout its height. 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, although only two jaw contact surfaces are shown, it will be appreciated that more than two could be used depending upon the specific requirements of the pole climber's fall arrest device. In addition, although a single piece yoke is shown, it will be appreciated that the yoke could be provided with a hinge at ~S~7;~
the centre so that the device could either fold about an axis parallel to the pivotal axis 140 or about an axis perpendicular to the pivotal axis 140 to permit folding for storage and transport. In such a case it will be appreciated that stops would be required to be located in the surfaces of the yoke opposite to the direction oE folding and locking pins would be required to secure the yoke in its in-use position. In addition, it will be appreciated that the slots 146 need not be positioned exactly as shown on the arms, for example, they could be located on the section of the arm parallel to the spring, or on the section of the arm nearest to the jaws 150. The slot must be outside the pivotal connections 140 so that the straps 122 create a moment of the arm about the pivotal axis 140 to pull the arms and jaws towards the pole in the event of slippage. It will be appreciated that although coil springs are shown connecting the arms and jaws to the yoke, any other resilient connection would be suitable. For example, an elastomer having a very strong resilient force could be used.
Although it is indicated in this embodiment that serrated surfaces are not used on surfaces 152 and 154 nor on yoke inner surface 132, it will be appreciated that such surfaces could in fact be serrated if so required.
Reference is now made to Fig. 12 of the drawings which shows a lineman working on a telephone pole using a fall arrest device 220 in accordance with another alternative embodiment of the invention which is secured to the pole and to which he is connected by safety straps 222. The straps 12~5~73 222 have respective hooks 224 at their outer ends, (one of which is shown) and which engage with D-shaped buckles 225 or "D-rings" attached to the lineman's belt 226. The fall arrest device 220 is secured around the telephone pole and, as will be later explained, the lineman is supported by a combination of pair of gaffs 228 (one of which is shown) and by the device which is biased to engage the pole~ In the working position, a component of the linemans weight acts throuyh straps 222 to produce an outwardly acting force on the fall arrest device 220 and this increases engagement of the device to the pole as will be explained.
To better illustrate how the fall arrest device is mounted on the pole, reference is now made to Figs. 13 and 14 of the drawing. In Fig. 13 the pole is shown partly broken away to facilitate understanding. The fall arrest device comprises an arcuate main yoke 230 which consists of two half yokes 231, made of an electrically insulating synthetic plastic material. The yoke 230 has an inner curved serrated surface 232 for engaging the far side of the pole from the lineman, and the yoke 230 has a hinge 234 connecting the half-yokes to permit the fall arrest device to be folded for transport and storage. Also, the half-yokes 231 are adjustable relative to one another by using a locking pin 235 to engage one of the respective aligned apertures 237, selected according to the diameter of the pole to be climbed.
Two planar arms 236 which for convenience of description will be described as having three apices because - 2~ -. .
., . ~4 of their generally triangular shape, are mounted on the upper surface of each outer end 238 of the half-yokes 231 by pivotal connections 240. The arms are allochiral and for convenience of description one arm will be described although the other will be 5 numbered for ease of comparison. The arm will also be described as having apices because of its generally triangular shape.
Pivotal connections 240 connect a first apex 242 of the arm to the outer ends 238 of the yoke. A second apex 244 of the arm defines a slot 246 through which straps 222 pass to permit the fall arrest device to fasten to the linesman's belt as described above. The slot 246 is located outside the pivotal connection 240 so that when the lineman leans back a component of force also acts to force the arms to pivot about connections 240 towards the pole. The arm has an inner curved surface 248 extending between the first and second apices for engaging the pole near the front as shown in ~igure 13 and as will be seen in broken outline in Fiyure 14 the curved surface has serrations 249 for engaging the pole. A smaller secondary yoke 250 is connected between the underside of the arm and the underside of the main yoke 230. The secondary yoke is connected to the arm 236 by a pivotal connection 252 at the second apex 254 of the arm and the secondary yoke is connected to each yoke halve 231 by a sliding connection 256. The pivotal connections 240, 252 and the sliding connection 256 will be explained later. As best shown in Fig. 14 the secondary yoke 250 has an inwardly facing serrated curved surface 258 for engaging the sides of the 3l~6~
telephone pole.
One pivotal connection 240 is best illustrated in Fig.
14 and is provided by a pin 262 which passes through aligned apertures 264 and 266 in the end of the half-yoke 231 and in the apex 242 of the arm. The pin 262 has a circular groove 265 at its upper end and is of such a length that when it is passed through aperatures 264,266 it receives a washer 268 and then a spring clip 270 which engages with the groove. Inserted into the top surface of the outer end 238 of the half-yoke 231 and the arm in the vicinity of the first apex 242 are plns 272 which have apertures 273 for receiving the ends 274 of a torsion spring 276.
As best seen in the assembled portion of Fig. 14 and Fig. 13 the torsion spring 276 urges the arms 236 and secondary yokes towards each other to engage the sides of the pole as will be explained. Pivotal connection 252 is provided by pin 278 which passes through apertures 282 in the secondary yoke 250 and 280 in the second apex 254 of the arm 236 respectively. Pin 278 is shorter than the pin 262 but when assembled receives a washe~
284 and spring clip 286 to fasten the arm 236 to the secondary yoke 250 in the same way as with pivotal connection 240. The ; secondary yoke 250 is spaced from the arm 236 by an annular spacer 288 so that the secondary yoke 250, the main yoke 230, and the arm 236 all lie in parallel planes as seen in Fig. 12.
Still referring to Fig. 14 the sliding connection 256 at the end 251 of secondary yoke 250 is a pin 290 sliding in elongate arcuate slots 292 in the main yoke 230 between the :~L2~
hinge 234 and each end 238 of the half-yoke 231. The elongate slot 292 has a step 294 in its wall above the lower surface of the yoke to define a narrower slot opening to the yoke lower surface. The pin 290 causes a circular bush 296 and washer 297 to be held by a spring clip 298 in the same way as with the pins 262 and 278 such that the bush 296 is supported by the step 294 to permit relative sliding movement between the secondary yokes 250 and the main yoke 230. The length and location of the slot partially dictates the pole diameters which the device can accommodate with the secondary yokes 250 engaging the pole. The location of the slots is determined by an arc on the radius of the centxe point of the largest pole diameter to receive the fall arrest device.
When the device is assembled as shown in assembled portion Fig. 14 and Fig. 12, it is relatively thin and the arms, the secondary yokes and the main yoke are all in parallel planes, which facilitate operation of the device as will be later described. Each arm has a handle, 300, connected thereto to facilitate operation of the device by the lineman. Each handle is pivotally mounted to the arm by pivotal connection 302 to permit the handles to be folded up during transit or storage.
As best seen in Fig. 15 this is achieved by using a thumbwheel 304 which is fastened by screw threads onto a threaded bolt 305 which in turn is attached to arm 236. By adjusting the thumbwheel the handles can be ~et in a fixed position or slackened to permit them to be folded.
~265~ 3 The device when asse~bled and positioned on the pole, as shown in Fig. 13, appears generally C shaped in plan.
Because the third apices of the arms do not meet they define an opening 306 which provides clearance for the cables but the fall arrest device must be adjusted to pass over the telephone pole. This clearance is convenient because it means that the fall arrest device does not interfere with cables 308 or the cable safety sheath 310 for the cables which runs between the base and top of the pole.
The operation of the fall arrest device will now be explained with reference to Fig. 13 and 16 of the drawings.
In Fig. 16 one half of the fall arrest device is shown mounted (in solid lines) on a pole at a large diameter 312 and ghost outline at a small diameter 314.
; 15 Because, the lineman removes pin 235 from hinge 234 and adjusts each half-yoke 231 until opening 306 is large enough that the device can be mounted on the base 312 of the pole.
The pin 235 is then inserted in an appropriate aperture 237 to lock the half-yokes relative to each otherO The lineman then locates *he device around the base of the pole. By gripping the handles 300, and pulling the arms 236 apart such that the arms pivot relative to the yoke against the torsion ~pring force produced as the pins 272 move towards each other. When the opening 306 is sufficiently large the lineman will then pull the fall arrest device towards himself and let the torsion force push the arms towards each other such tbat the surfaces 232, 249 and 258 of the yoke ' 230, arms 236 and secondary yokes 250 engage the pole at :~ :
~Z~ 73 diameter 312. The lineman will then connect the device to the D-rings on his belt as previou~ly described.
To climb the pole the lineman firstly relieves his weight on the device by using his gaffs to support his weight and then he grips the handles 300 and pulls the arms 236 apart ~ufficiently to separate arms 236 and yokes 250 from contacting the pole and then lifts the device to a higher position and xeleases the arms. The spring forces urge the arms and the secondary yokes back into contact with the pole and the lineman then using the device as a support climbs the pole using his gaffs 228.
The lineman continues to climb in this way until he reaches his desired working position i.e. at a level where pole diameter 314 is present. At this level the torsion lS spring has urged the arms 236 and secondary yokas 250 into contact as shown in ghosted outline in Fig. 16 and the sliding connection 256 has moved along the elongate slot 292 toward hinge 234 and the surface contact area of the device is reduced compared to that at diameter 312 level. In this position the serrated surfaces engage the surface of the pole and the lineman leans back as shown in Fig. 12 to be supported by the straps and gaffs. In the event that his feet should slip because the gaffs are not properly engaged, e~ch of the straps 222, are pulled down loading the arms 236 and pulling them inwardly to tightly grip the pole surface.
Because of the torsion force and weight of the lineman, the device grips the pole so tightly that the device and hence ; the lineman does not slip down the pole. The sliding - .
connection 256 permits the arrns and the yokes to move in such a manner that they present a maximum surface contact area to engage the surface of the pole throughout its height. This means that if slippage by the lineman should occur at any level, the fall arrest device will be effective.
Various modifications may be made to the embodiment described herein without departing from the scope of the invention in which like numerals denote like parts but with the suffix "a" added. For example, although a hinge 23~ connects two half yokes the connection may be replaced by an integral portion such that there is a single main yoke 230 designed for a single pole size at the base. Also, the half-yokes can be connected so that the device folds about a horizontal axis in such as arrangement. A stop would be located on the surface opposite to the direction of folding, and a locking pin would be required to secure the yoke in its in-use position. The slots 246 need not be in the same plane as the arm 236. As also shown in Fig. 17 the arm portion containing the slot 246a is bent over substantially perpendicular to the plane of the arm to faciliate compact storage of the fall arrest device. Also~ thè handles 300 need not be pivotally connected to the arms. As shown in Fig. 17, the handles 300a could be made integral with the arms, for example by welding or other suitable method. The torsion spring is one means of resiliently biasing the arms so that they tend to close around the pole with the secondary yokes 250. Any other suitable resiliently biased means which biases the arms and ~;~6Si~3 the secondary yokes into contact with the pole surace would be suitable such as a leaf spring or resilient material mounted between the main yoke and the secondary yoke. Also all the contact surfaces of the pole need not be serrated, and it ha~ been found that if the half-yoke 231, the arm 236 and the secondary yokes 25C are not serrated sufficient friction is still provided between the contact ~urfaces o~
the device and the pole to arrest the fall.
Although in the described embodiment, materials of the fall arrest device are preferahly plastic, this is not essential; the components could be made out by forging or stamping, and they can be suitably treated with other electrically insulating coatings, such as nylon, PTFE etc.
Also the fall arrest devices could be made of wood or ; 15 plastic.
It will also be appreciated that the fall arrest d~evice could be used on trees and on wooden, concrete and metal poles of non-circular cross-section, such as oval. Also, in the case of the alternative embodiment the position of the slots may be varied slightly to accommodate poles of different standard base diameters ~or most effective operation.
Other modifications may be made to the description and drawings disclosed which are exemplary without departing from the scope of the invention which is defined by the appended claims.
'`' ~6S~7~
biased and adjustability is difficult in situ. In the event of slippage these devices may be insufficient to retard the lineman's fall because they do not automatically close on the pole.
U.S. Patent No: 4,407,391 to Greenway, et al discloses a pole climber's safety device having a closed yoke for encompassing a pole. The yoke consists of two half yo~es hingedly interconnected together and secured by a releasable fastening. Pole engaging blades are pivotally mounted on the underside of the yoke and, in use, the blades are normally biased, by weight or by springs, to a pole engaging position and are manually releasable. In practice, it has been found that this device is difficult and time-consuming to adjust, because first the pole blades have to be retained and held whilst the yoke is moved. The fixed closed yoke limits the size of poles it can be used with. Indeed with some poles the lineman could not climb to the top because the blades do not engage adequately the upper parts of the pole and on larger poles the blades do not engage the pole because they lie almost parallel to the pole. Also, the closed yoke can interfere with cables and/or cable sheathings especially laryer onesj and may cause restriction in movement of the device. This device has been found unsatisfactory in breaking the fall of a lineman whose feet have slipped and the lineman can fall quite a way before his fall is broken, if at all.
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.
:[n accordance with one aspect oE the present invention a pole climber's fall arrest device is provided which comprises, an arcuate yoke member for engaging a pole, and resiliently biased arms pivotally mounted at opposite ends of the arcuate member for further engaging the pole. Each arm is pivotable in a plane parallel to the arcuate yoke member and has attachment means for coupling the device via a lanyard to safety belt connectors and handle means on each arm adapted to be gripped by a pole climber. The yoke member and the arm each have a surface for engaging the pole and, in use, the resiliently biased arms retain these surfaces in contact with the pole. The arms are movable by the pole climber relative to the yoke member, away 15 from the pole against said resiliently biased means to permit movement of the fall arrest device lengthwise of the pole.
In a preferred embodiment of the invention, the arms include a sharp pro~ection for biting into the pole. Coil springs connected between each arm and the yoke provide the biasing force. The yoke is made using tubular metal and castings and the arms are castings. The device includes stop means for preventing each of the arms from being rotated too far about its pivotal axis. The yoke is tubular and by also making parts of the arms tubular the design of the preferred embodiment can be made in different sizes. The handles also serve as means for securing a lanyard to the device which, in turn, is secured to the linemans safety belt connectors.
~2~
In an alternative embodiment of the invention, the arms have pivotable jaws mounted thereon, each jaw having two surfaces for engaging a pole. The surfaces are at different distances from the pivotal axis of the jaw so that, by S rotating the jaws about the jaw axis, any one of the two surfaces can be brought into a pole-engaging position. This permits the device to accommodate a large range of pole diameters.
In a further embodiment of the invention the arcuate yoke i5 hinged midway between the ends to allow the device to be folded when not in use. Each arm is also connected to the yoke member by smaller secondary yoke elements, one end of which can be slid relative to the yoke member and the other end which is pivotable relative to the arm in the same plane as the yoke member. The smaller secondary yoke elements also have a pole engaging surface. The pole engaging surfaces are preferably serrated to facilitate gripping of the pole by the device.
These and other aspects of the invention will be readily understood with reference to the following description and drawings in which:-Fig. 1 is a diagrammatic view of a lineman using a preferred form of pole climber's fall arrest dèvice 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 o~ a pole climber's fall arrest device shown n Figs. 1 and 2 and ~6~'7;~
drawn to a larger scale;
Fig. 4 is a bird's eye view to the same scale as Fig. 2 of part of a pole climber's fall arrest device and showing the position of an arrn and jaw relative to the yoke for a large pole diameter;
Pig. 5 is a similar view to Fig. 4 to the same scale and showing the orientation of the jaw when the pole diameter is smaller;
Fig. 6 is view of a device shown in Fig. 1 and modified for use on larger diameter poles;
Fig. 7 is a diagrammatic view of a lineman using an alternative form of pole climber's fall arrest device in accordance with the invention;
Fig. 8 is a bird's eye view of the device in Fig. 7 in use with part of the pole broken away to show the device;
Fig. 9 is a partly exploded and perspective view of a pole climberls fall arrest device shown in Figs. 7 and 8 and drawn to a larger scale;
Fig. 10 is a bird's eye view to the same scale as Fig. 9 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. 11 is a similar view to Fig. 4 to the same scale and showing the orientation of the jaw when the pole diameter is smaller;
Fig 12 is a diagrammatic view similar to Fig. 1 of a lineman using an alternative form of pole climber's fall ~ ..
7~
arrest device in accordance with the invention;
Flg. 13 is a bird's eye view of the device of Fig. 12 in use with part of the pole broken away to show the device;
Fig. 14 is a partly exploded perspective view of a pole climber's ~all arrest device, shown in Figs. 12 and 13, drawn to a larger scale;
Fig. 15 is a view of part of one of the handles shown in Fig. 13, and drawn to a larger scale with part of the handle sectioned along 15-15 to better illustrate the handle mounting;
Fig. 16 is bird's eye view of the same scale as Fig. 14 of part of a pole climber's fall arrest device according to the alternative embodiment of the invention and showing the position of an arm relative to the yoke for two different pole diameters;
and Fig. 17 is a view to the same scale as Fig. 14 of part of an arm showing a part of an alternative arm structure for attachment to a safety belt strap.
Reference is first made to Fig. l 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 whlch 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 hooks 24 at its outer ends, (one of which is shown) and which engage with D-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 by a combination of a pair of gaffs 28, " ,l ., . ~., .
(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 (Fig. 2), 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. ~n 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 6061 T6 aircraft grade aluminum (Atlas Alloys, Toronto, Ontario) and which is covered with a nylon insulating dielectric material Rilsan 11 (Trade Mark, Rilsan, U.K.). The yoke 30 has an inner surface 32 for engaging parts of the far sides of the pole from the lineman. Aluminum Alloy Tenzaloy (trademark Federated Genco, Burlington, Ontario, Canada) castings 31 and 59 (Fig. 3~ are honded by expoxy resin and riveted to the ends of the yoke and the castings, as best seen in Fig. 3 are coupled to arms 34.
Planar arms 34, which for convenience of description will be described as being generally L-shaped, are coupled to each casting 31 by pivotal connections or axes 40. The arms are allochiral and, for convenience of description, one arm will be described although the other arm will be numbered for ease of comparison The arm will also be described as s ~
~ t7 ~
having legs because it is generally L-shaped. A first longer leg 46 of the arm is connected to the casting 31. In a second shorter leg 44 the arm has a large generally circular aperture ~3 for receiving a lanyard or strap 22 to permit the fall arrest device to be ~astened to the belt as described above. The 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 forces generated during a fall cause the arm to pivot about pivotal connection 40 and generate suhstantial force against the pole. The second leg 44 is thicker than the first leg 42 and has sharp stainless (#304) steel projections 48 fastened to the bottom thereof. The sharp projections 48 facilitating 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 (5~ lbs force~ 50 which are connected between a spring anchor position 52, located on the yoke inboard of the pivotal connection 40 and a spring anchor position 54 on leg 42 and spaced from pivotal connec~ion 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 54 is moved towards the aperture 43 spring-biased moment acting about pivotal connection 40 ~ t7;~
would increase the ~orce 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 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.
Between the anchor 52 and an anchor pin 57 or portion 56 of leg 44 a stop wire 58 is connected which extends beneath the arms as best seen in Fig. 3. This wire acts as a stop to prevent the arm 34 from being rotated too far about the pivotal connection 40 so that the springs do not go over centre as will be explained. The construction of pivotal connections 40 will also be later explained.
Reference is now made to Fig. 3 of the drawings which shows a pole climberls fall arrest device according to the ;pre~erred embodiment in an enlarged and partly exploded view. It will be seen that the yoke 30 consists of two ;20 tubes which are connected together by an elbow casting 59 to provide, when assembled, the V-Shape. The casting and tubular portions are joined by epoxy resin and are also riveted together with steel rivets 60 through pre-drilled apertures 62 in the castings and tubes. Similarily castings 31 are riveted by steel rivets 70 to the other ends of the tubes through pre-dri1led apertures, as well as being bonded with expoxy resin to provide a very strong secure connection. It will also be seen that pivotal ~lZ~-j5'~'7~
connection 40 is provided by a grade 8 bolt 63 which passes through aperture 64 in the end leg and aperture 66 in the casting 31 for engagement wi,th a self locking Nylok (trademark) nut 67 which is provided with a nylon insert. Washers 68 are provided on the tOp and bottom parts of the casting to permit freely pivotal movement oE the arm.
The spring 50 and stop wire 58 are fastened to the yoke 30 by bolt 86 and nut 87 to provide the anchor 52. A washer 89 is provided to retain wire 58 and spring 50. The other end of the spriny 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. Aperture 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 leg portion 44 has a lower downwardly sloping surface 95 to which the stainless steel projection 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 sloping of the lower surface includes the projections 48 to the plane of the device and facilitates penetration of the pole.
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.
' ~
S~7~
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 C-shaped in plan. Because the projections do not rneet they define an opening 88 which provides 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 cables, or the cable safety sheath for the cables which run between the base and the top of the pole.
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 pole of smaller diameter.
In use, the lineman grips the handles or arms 34 and opens them sufficiently so that the pole fall arrest device can be located around the base of the pole. The lineman then pulls the handles away from each other and the spring forces produced by spring 50 force the projections 48 into contact with the pole, and also cause the inner surface 32 of the yoke to engage with the rear surface of the pole. The stop wires 58 tension and prevent the arms r ~ ~
~Z~5~
being rotated too far. The lineman then connects the device to the D-rings on his belt as previously described.
To climb the pole, the lineman firstly relieves his weight on the device by using his gaffs 28 to support his weight and then he grips the handles provided by the arm 34 and pulls the arms apart sufficiently to separate the projections 48 from the pole and the yoke surface 32 and then lifts the device to a higher position and releases the arms. Spring forces urge the arms with projections back into contact with the pole and the lineman then, using the device as a supportl climbs the pole using his gaffs.
The lineman continues to climb in this way until he reaches his desired working position at a level where the pole is of a different diameter such as 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 and he begins to fall, the strap 22, is pulled loading the arms 34 and pulling them inwardly towards the pole to reinforce the spring forces acting on the arms 34 and causing the projections 48 to bite tightly into the pole. Because of the spring forces and the weight of the lineman the device grips the pole so tightly that the device, and hence the lineman, are prevented from slipping down the pole, and the lineman's fall is arrested. The shape of the 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 tne event of slippage such that the projections will bite into oily, icy, soft, or hard poles.
This means that if slippage of the linernan 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. E`or example, Fig. 6 shows a modified device according to the preferred embodiment for use in climbing very large diameter poles, in which like numerals refer to like parts as ~igs. 1-5 but with the suffix "a". It will be seen that this is very similar to the device of Figs. 1-5 except that yoke 30a is made of ]onger tubular portions. Also, the arms have tubular leg portions inserted between arm casting 34a and a casting 31a coupled to pivotal connector 40a. It will be appreciated that this use of tubular portions permits the preferred device to be made of a size suitable for different ranges of pole diameters.
The device in Fig. 6 can be used with poles up to 60 inches in diameter, which covers almost all poles in use.
It will also be appreciated that all relevant parts of the device i.e., yoke, arms, projections etc. will be covered with nylon based Reslin (trademark) dielectric coating.
; Although only a single yoke is shown, it will be appreciated that two half yokes could be provided being hinged together about the center so that the device could either fold about an axis parallel to the pivotal axis 40 or about an axis perpendicular to the pivotal axis 40 to permit folding for :~, :
'' ~s~
storage and transport. In such a case it will be appreciated that stops would be requirecl to be located in the surfaces of the yoke opposite to the direction o~
folding, and locking pins would be required to secure the S yoke in its in-use position. It will be appreciated that although coil springs are shown connecting the ar~s to the yoke, any other resilient connection would be suitable. For example, an elastomer having a very strong resilient force could be used or torsion springs could be used.
Reference is now made to Fig. 7 o~ the drawings which shows a lineman working on a telephone pole using a fall arrest device 120 in accordance with an alternative embodiment of the invention and which is secured to the pole and to which he is connected by a safety crossed straps 122 hooked through the device. The safety strap 122 has respective hooks 124 at their outer ends, (one of which is shown) and which engage with D-rings 125 attached to the lineman's belt 126. The fall arrest device 120 is secured around the telephone pole, and as will be later explained, the lineman is supported by a combination of a pair of gaffs 128, tone of which is sbown) and by the device whi~h is biased to engage the pole. In the working position, a component of the lineman's weight acts on strap 122 to produce a force on the fall arrest device which acts~ in combination with a spring force on jaws 127, to pull the arms and jaws of the safety device towards the pole to increase engagement of the device on the pole as will be later explainecl.
7;~
To better illustrate how the safety device is mounted on the pole, reference is now made to Figs. 8 and 9 of the drawings. In Fig. 8 the pole is shown partly broken away to facilitate understanding. The fall arrest device comprises a generally V-shaped main yoke 130 which is essentially planar and which is made of a cast alluminum alloy, (Tenzaloy), and which is covered with an epoxy resin insulating dielectric material.
The yoke 130 has an inner surface 132 for engaging parts of the far sides of the pole from the lineman.
Two planar 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 136 of the yoke 130 by pivotal connections 140. The arms are allochiral and, for convenience of description, one arm will be described although the other arm will be numbered for ease of comparison.
The arm will also be described as having apices because it is generally diamond shaped. A first apex 142 of the arm is connected to the outer end 136 of the yoke. The arm has a large generally diamond-shaped 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 as described above.
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 during a fall cause the arm to pivot about pivotal connection 140 and ;. ~J~
generate substantial force against the pole. A second apex of the arm 148 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 closer to 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 is at the top of a pole, then the jaws 150 are rotated about the pivotal connection 149 to bring generally V-shaped surfaces 154 in contact with the pole, as shown in Fig. 8 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 postion 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 i 25 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 I" `
' ~'`
l73 accommodate pole diameters up to about 21 inches, i.e., is about 75% of the pole diameters used.
Between the pivotal connection lA0 and the an~hor 156 i5 located a stop pin 158 which ~xtends 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 and limits it to movement as shown in dotted outline in Fig. 10, as will be exp]ained. The construction of pivotal connections 140 and 149 will also be later explained.
Reference is now made to Fig. 9 of the drawings which shows a pole climber's Eall arrest device according to the preferred embodiment in an enlarged and partly exploded view. It will be seen that pivotal connection 140 is provided by a bolt 160 which passes through aper-ture 162 in the apex 142 of the arm and aperture 164 in the end 138 of the yoke 130 for engagement beneath the yoke with a self locking nut 166. Washers 168 are provided above the arm and below the yoke to permit freely pivotal movement of the arm.
Pivotal connection 149 is also provided by a bolt 170 2Q which passes through an aperture 172 in a second apex of the arm and through a corresponding aperture 174 in respective jaw 150 for engagement with a self locking nut 176 beneath the jaw. The bolt 170 also receives one end 178 of the spring and the bolt also has another lower nut 180 to sandwich the end of the spring 178 between nuts 176 and 180. Washers 182 are also provided in this pivotal connection to permit free pivotal movement of the ~aw '";,;`.
: ~ ' ~lZ~ ;'3 relative to the arm and to the pole~
The other end of the spring 155 is anchored to the yoke 130 via bolt 186 and nut 187 to provide a respective anchor position 156 for the arm 134. It will be seen from this figure that arm 134 and yoke 130 lie in parallel planes to the jaws 150. The overall thickness of the fall arrest device is a combination of the thickness of the arm and the jaw and also the depth of the springs. In practice it is about 2 inches.
When the device is assembled as shown in Figs. 8, 10 and 11 the periphery of the arm permits the sides to be used as handles by the lineman, and the pivotal connections 1~0 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. 8, appears generally C-shaped in plan. Because the jaws of the arms do not meet they define an opening 188 which provides clearance for the cables but the fall arrest device must be adjusted to pass over the telephone pole. This clearance is convenient because it means that the fall arrest device does not interfere with cables 190, or the cable safe-ty sheath 192 for the cables which run between the base and the top of the pole.
The operation of the fall arrest device will now be described with reference to Figs. 8, 10, ll of the drawings. In Fig. 10 one half of the fall arrest device is shown mounted (in solid lines) on the pole, at a larger diameter and Fig. 11 shows the same fall arrest device when moved up the pole to accommodate a pole of smaller .~ !
, .
~Z~5~3 diameter. In the case of Figure 11 it will be seen that the jaw has been rotated about pivotal axis 149 to present V-shaped surface 154 with the pole instead of surface 152.
In use, the lineman grips the handles 134 and opens them sufficiently so that the pole fall arrest device can be located around the base of the pole. The lineman then pulls the handles towards each other after pivoting the jaws so that the V-shaped surfaces 152 engage the surface of the pole and the spring force produced by spring 155 then forces the arms and pivotal jaws into contact with the pole, and also causes the inner surface 132 of the yoke to engage with the rear surface of the pole.
The lineman then connects the device to the D-rings on his belt as previously described.
To climb the pole, the lineman firstly relieves his weight in the device by using his gaffs 128 to support his weight and then he grips the handles provided by the arm 134 and pulls the arms apart sufficiently to separate the V-shaped ; surface 154 from the pole and the yoke surface 132 and then lifts the device to a higher position and releases the arms.
2Q Spring forces urge the arms and the jaws 150 back into contact with the pole and the lineman then, using the device as a support, climbs the pole using his gaffs.
The lineman continues to climb in this way until he reaches his desired working position at a level where the pole is of a different diameter such as shown in Fig. 11. At some level before this the lineman will have pivoted the jaws 50 so that the V-shaped surface 154 abutts the pole .3 ; . ~, and, at the desired level as shown in Fig. 11, the springs urge the arms and the jaws so that surfaces 154 and the yoke surface 132 engage the pole. In this position, the pole fall arrest device is secure and the lineman can lean back as shown in Fig.
7 to be supported by the straps 122 and gaffs 128. In the event that his feet should slip because the gaffs are not properly engaged and he begins to fall, each of the straps 122, are pulled loading the opposite arm 134 and pulling him inwardly towards the pole to reinforce the spring force actiny on the jaws 150 and cause the jaw surfaces 154 to bite tightly against the pole. secause of the spring forces and the weight of the lineman the device grips the pole so tightly that the device, and hence the lineman, are prevented from slipping down the pole, and the lineman's fall is arrested. The shape of the jaw contact surfaces 152 and 154 and the yoke contact surface 132 are such that they present a maximum surface contact area to engage the surface of the pole throughout its height. 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, although only two jaw contact surfaces are shown, it will be appreciated that more than two could be used depending upon the specific requirements of the pole climber's fall arrest device. In addition, although a single piece yoke is shown, it will be appreciated that the yoke could be provided with a hinge at ~S~7;~
the centre so that the device could either fold about an axis parallel to the pivotal axis 140 or about an axis perpendicular to the pivotal axis 140 to permit folding for storage and transport. In such a case it will be appreciated that stops would be required to be located in the surfaces of the yoke opposite to the direction oE folding and locking pins would be required to secure the yoke in its in-use position. In addition, it will be appreciated that the slots 146 need not be positioned exactly as shown on the arms, for example, they could be located on the section of the arm parallel to the spring, or on the section of the arm nearest to the jaws 150. The slot must be outside the pivotal connections 140 so that the straps 122 create a moment of the arm about the pivotal axis 140 to pull the arms and jaws towards the pole in the event of slippage. It will be appreciated that although coil springs are shown connecting the arms and jaws to the yoke, any other resilient connection would be suitable. For example, an elastomer having a very strong resilient force could be used.
Although it is indicated in this embodiment that serrated surfaces are not used on surfaces 152 and 154 nor on yoke inner surface 132, it will be appreciated that such surfaces could in fact be serrated if so required.
Reference is now made to Fig. 12 of the drawings which shows a lineman working on a telephone pole using a fall arrest device 220 in accordance with another alternative embodiment of the invention which is secured to the pole and to which he is connected by safety straps 222. The straps 12~5~73 222 have respective hooks 224 at their outer ends, (one of which is shown) and which engage with D-shaped buckles 225 or "D-rings" attached to the lineman's belt 226. The fall arrest device 220 is secured around the telephone pole and, as will be later explained, the lineman is supported by a combination of pair of gaffs 228 (one of which is shown) and by the device which is biased to engage the pole~ In the working position, a component of the linemans weight acts throuyh straps 222 to produce an outwardly acting force on the fall arrest device 220 and this increases engagement of the device to the pole as will be explained.
To better illustrate how the fall arrest device is mounted on the pole, reference is now made to Figs. 13 and 14 of the drawing. In Fig. 13 the pole is shown partly broken away to facilitate understanding. The fall arrest device comprises an arcuate main yoke 230 which consists of two half yokes 231, made of an electrically insulating synthetic plastic material. The yoke 230 has an inner curved serrated surface 232 for engaging the far side of the pole from the lineman, and the yoke 230 has a hinge 234 connecting the half-yokes to permit the fall arrest device to be folded for transport and storage. Also, the half-yokes 231 are adjustable relative to one another by using a locking pin 235 to engage one of the respective aligned apertures 237, selected according to the diameter of the pole to be climbed.
Two planar arms 236 which for convenience of description will be described as having three apices because - 2~ -. .
., . ~4 of their generally triangular shape, are mounted on the upper surface of each outer end 238 of the half-yokes 231 by pivotal connections 240. The arms are allochiral and for convenience of description one arm will be described although the other will be 5 numbered for ease of comparison. The arm will also be described as having apices because of its generally triangular shape.
Pivotal connections 240 connect a first apex 242 of the arm to the outer ends 238 of the yoke. A second apex 244 of the arm defines a slot 246 through which straps 222 pass to permit the fall arrest device to fasten to the linesman's belt as described above. The slot 246 is located outside the pivotal connection 240 so that when the lineman leans back a component of force also acts to force the arms to pivot about connections 240 towards the pole. The arm has an inner curved surface 248 extending between the first and second apices for engaging the pole near the front as shown in ~igure 13 and as will be seen in broken outline in Fiyure 14 the curved surface has serrations 249 for engaging the pole. A smaller secondary yoke 250 is connected between the underside of the arm and the underside of the main yoke 230. The secondary yoke is connected to the arm 236 by a pivotal connection 252 at the second apex 254 of the arm and the secondary yoke is connected to each yoke halve 231 by a sliding connection 256. The pivotal connections 240, 252 and the sliding connection 256 will be explained later. As best shown in Fig. 14 the secondary yoke 250 has an inwardly facing serrated curved surface 258 for engaging the sides of the 3l~6~
telephone pole.
One pivotal connection 240 is best illustrated in Fig.
14 and is provided by a pin 262 which passes through aligned apertures 264 and 266 in the end of the half-yoke 231 and in the apex 242 of the arm. The pin 262 has a circular groove 265 at its upper end and is of such a length that when it is passed through aperatures 264,266 it receives a washer 268 and then a spring clip 270 which engages with the groove. Inserted into the top surface of the outer end 238 of the half-yoke 231 and the arm in the vicinity of the first apex 242 are plns 272 which have apertures 273 for receiving the ends 274 of a torsion spring 276.
As best seen in the assembled portion of Fig. 14 and Fig. 13 the torsion spring 276 urges the arms 236 and secondary yokes towards each other to engage the sides of the pole as will be explained. Pivotal connection 252 is provided by pin 278 which passes through apertures 282 in the secondary yoke 250 and 280 in the second apex 254 of the arm 236 respectively. Pin 278 is shorter than the pin 262 but when assembled receives a washe~
284 and spring clip 286 to fasten the arm 236 to the secondary yoke 250 in the same way as with pivotal connection 240. The ; secondary yoke 250 is spaced from the arm 236 by an annular spacer 288 so that the secondary yoke 250, the main yoke 230, and the arm 236 all lie in parallel planes as seen in Fig. 12.
Still referring to Fig. 14 the sliding connection 256 at the end 251 of secondary yoke 250 is a pin 290 sliding in elongate arcuate slots 292 in the main yoke 230 between the :~L2~
hinge 234 and each end 238 of the half-yoke 231. The elongate slot 292 has a step 294 in its wall above the lower surface of the yoke to define a narrower slot opening to the yoke lower surface. The pin 290 causes a circular bush 296 and washer 297 to be held by a spring clip 298 in the same way as with the pins 262 and 278 such that the bush 296 is supported by the step 294 to permit relative sliding movement between the secondary yokes 250 and the main yoke 230. The length and location of the slot partially dictates the pole diameters which the device can accommodate with the secondary yokes 250 engaging the pole. The location of the slots is determined by an arc on the radius of the centxe point of the largest pole diameter to receive the fall arrest device.
When the device is assembled as shown in assembled portion Fig. 14 and Fig. 12, it is relatively thin and the arms, the secondary yokes and the main yoke are all in parallel planes, which facilitate operation of the device as will be later described. Each arm has a handle, 300, connected thereto to facilitate operation of the device by the lineman. Each handle is pivotally mounted to the arm by pivotal connection 302 to permit the handles to be folded up during transit or storage.
As best seen in Fig. 15 this is achieved by using a thumbwheel 304 which is fastened by screw threads onto a threaded bolt 305 which in turn is attached to arm 236. By adjusting the thumbwheel the handles can be ~et in a fixed position or slackened to permit them to be folded.
~265~ 3 The device when asse~bled and positioned on the pole, as shown in Fig. 13, appears generally C shaped in plan.
Because the third apices of the arms do not meet they define an opening 306 which provides clearance for the cables but the fall arrest device must be adjusted to pass over the telephone pole. This clearance is convenient because it means that the fall arrest device does not interfere with cables 308 or the cable safety sheath 310 for the cables which runs between the base and top of the pole.
The operation of the fall arrest device will now be explained with reference to Fig. 13 and 16 of the drawings.
In Fig. 16 one half of the fall arrest device is shown mounted (in solid lines) on a pole at a large diameter 312 and ghost outline at a small diameter 314.
; 15 Because, the lineman removes pin 235 from hinge 234 and adjusts each half-yoke 231 until opening 306 is large enough that the device can be mounted on the base 312 of the pole.
The pin 235 is then inserted in an appropriate aperture 237 to lock the half-yokes relative to each otherO The lineman then locates *he device around the base of the pole. By gripping the handles 300, and pulling the arms 236 apart such that the arms pivot relative to the yoke against the torsion ~pring force produced as the pins 272 move towards each other. When the opening 306 is sufficiently large the lineman will then pull the fall arrest device towards himself and let the torsion force push the arms towards each other such tbat the surfaces 232, 249 and 258 of the yoke ' 230, arms 236 and secondary yokes 250 engage the pole at :~ :
~Z~ 73 diameter 312. The lineman will then connect the device to the D-rings on his belt as previou~ly described.
To climb the pole the lineman firstly relieves his weight on the device by using his gaffs to support his weight and then he grips the handles 300 and pulls the arms 236 apart ~ufficiently to separate arms 236 and yokes 250 from contacting the pole and then lifts the device to a higher position and xeleases the arms. The spring forces urge the arms and the secondary yokes back into contact with the pole and the lineman then using the device as a support climbs the pole using his gaffs 228.
The lineman continues to climb in this way until he reaches his desired working position i.e. at a level where pole diameter 314 is present. At this level the torsion lS spring has urged the arms 236 and secondary yokas 250 into contact as shown in ghosted outline in Fig. 16 and the sliding connection 256 has moved along the elongate slot 292 toward hinge 234 and the surface contact area of the device is reduced compared to that at diameter 312 level. In this position the serrated surfaces engage the surface of the pole and the lineman leans back as shown in Fig. 12 to be supported by the straps and gaffs. In the event that his feet should slip because the gaffs are not properly engaged, e~ch of the straps 222, are pulled down loading the arms 236 and pulling them inwardly to tightly grip the pole surface.
Because of the torsion force and weight of the lineman, the device grips the pole so tightly that the device and hence ; the lineman does not slip down the pole. The sliding - .
connection 256 permits the arrns and the yokes to move in such a manner that they present a maximum surface contact area to engage the surface of the pole throughout its height. This means that if slippage by the lineman should occur at any level, the fall arrest device will be effective.
Various modifications may be made to the embodiment described herein without departing from the scope of the invention in which like numerals denote like parts but with the suffix "a" added. For example, although a hinge 23~ connects two half yokes the connection may be replaced by an integral portion such that there is a single main yoke 230 designed for a single pole size at the base. Also, the half-yokes can be connected so that the device folds about a horizontal axis in such as arrangement. A stop would be located on the surface opposite to the direction of folding, and a locking pin would be required to secure the yoke in its in-use position. The slots 246 need not be in the same plane as the arm 236. As also shown in Fig. 17 the arm portion containing the slot 246a is bent over substantially perpendicular to the plane of the arm to faciliate compact storage of the fall arrest device. Also~ thè handles 300 need not be pivotally connected to the arms. As shown in Fig. 17, the handles 300a could be made integral with the arms, for example by welding or other suitable method. The torsion spring is one means of resiliently biasing the arms so that they tend to close around the pole with the secondary yokes 250. Any other suitable resiliently biased means which biases the arms and ~;~6Si~3 the secondary yokes into contact with the pole surace would be suitable such as a leaf spring or resilient material mounted between the main yoke and the secondary yoke. Also all the contact surfaces of the pole need not be serrated, and it ha~ been found that if the half-yoke 231, the arm 236 and the secondary yokes 25C are not serrated sufficient friction is still provided between the contact ~urfaces o~
the device and the pole to arrest the fall.
Although in the described embodiment, materials of the fall arrest device are preferahly plastic, this is not essential; the components could be made out by forging or stamping, and they can be suitably treated with other electrically insulating coatings, such as nylon, PTFE etc.
Also the fall arrest devices could be made of wood or ; 15 plastic.
It will also be appreciated that the fall arrest d~evice could be used on trees and on wooden, concrete and metal poles of non-circular cross-section, such as oval. Also, in the case of the alternative embodiment the position of the slots may be varied slightly to accommodate poles of different standard base diameters ~or most effective operation.
Other modifications may be made to the description and drawings disclosed which are exemplary without departing from the scope of the invention which is defined by the appended claims.
Claims (18)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A fall arrest device for a pole climber comprising;
a main yoke member for engaging a pole and lying in a plane;
two arms pivotally connected one to each of the ends of the yoke member for further engaging said pole, the arms being rotatable relative to the yoke member about respective ones of a pair of axes arranged generally perpendicularly with respect to the plane of the yoke member;
resilient biasing means coupled to the yoke and to the arms and biasing the arms about the respective axes toward one another;
pole-engaging means coupled to the arms for engaging the pole;
handle means on the arms to be gripped by the pole climber and pulled to rotate the arms about said axes;
attachment means located on each arm and adapted to receive lanyard means, the attachment means being spaced from said axes whereby, in the event of the user slipping on the pole a force is created through the lanyard means to move the arms towards one another thereby increasing the engagement forces between the pole-engaging means and the pole.
a main yoke member for engaging a pole and lying in a plane;
two arms pivotally connected one to each of the ends of the yoke member for further engaging said pole, the arms being rotatable relative to the yoke member about respective ones of a pair of axes arranged generally perpendicularly with respect to the plane of the yoke member;
resilient biasing means coupled to the yoke and to the arms and biasing the arms about the respective axes toward one another;
pole-engaging means coupled to the arms for engaging the pole;
handle means on the arms to be gripped by the pole climber and pulled to rotate the arms about said axes;
attachment means located on each arm and adapted to receive lanyard means, the attachment means being spaced from said axes whereby, in the event of the user slipping on the pole a force is created through the lanyard means to move the arms towards one another thereby increasing the engagement forces between the pole-engaging means and the pole.
2. A fall arrest device as claimed in claim 1 whereby the pole-engaging means consist of sharp projections for biting into the pole surface.
3. A fall arrest device as claimed in claim 1 wherein the pole engaging means includes a pair of jaw means pivotally mounted one on each of the arms and pivotal about respective pivot points, the jaws means having at least one pole-contacting surface.
4. A fall arrest device as claimed in claim 3 wherein each of the jaw means includes two pole contacting surfaces located at different distances from the respective pivot points.
5. A fall arrest device as claimed in claim 1 or 3 wherein said resilient biasing means are coil springs.
6. A fall arrest device as claimed in claim 1 wherein said attachment means comprises means defining apertures through the arms to receive the lanyard means.
7. A fall arrest device as claimed in claim 1 wherein a pair of secondary yokes are connected one between each of the arms and the main yoke member, the secondary yokes being connected by pivotal connections to the arms and by sliding connections to the yoke member; and pole engaging surfaces located on each secondary yoke whereby, in user as the fall arrest device is moved along a pole, sliding and pivotal connections of said secondary yokes permit the secondary yoke pole engaging surfaces and the pole engaging means of the arms to contact the pole.
8. A fall arrest device as claimed in claim 1 wherein the main yoke member comprises;
two half-yokes;
adjustable hinge means joining the half-yokes to one another for pivotal movement; and locking means for locking the hinge means to hold the half-yokes in one of a plurality of positions relative to each other to accommodate poles of different base diameters.
two half-yokes;
adjustable hinge means joining the half-yokes to one another for pivotal movement; and locking means for locking the hinge means to hold the half-yokes in one of a plurality of positions relative to each other to accommodate poles of different base diameters.
9. A fall arrest device as claimed in claim 1 wherein the resilient biasing means includes at least one torsion spring.
10. A fall arrest device as claimed in claim 7 wherein the resilient biasing means includes at least one torsion spring.
11. A fall arrest device as claimed in claim 1 wherein the main yoke member, the arms and the handle means are of an electrically insulating material.
12. A fall arrest device as claimed in claim 1 wherein the main yoke member, the arms and the handle means are of a material coated with an electrically insulating material.
13. A fall arrest device for a pole climber comprising;
a main yoke member being generally V-shaped and lying in a plane;
a pair of arms pivotally connected one to each end of the main yoke member, each of the arms being rotatable relative to the main yoke member about a respective one of a pair of axes for movement towards and away from one another generally in said plane;
biasing means connected between the yoke member and the arms, the biasing means including at least one coil spring;
pole engaging means attached to the arms and having sharp projections for biting into the pole;
a pole engaging surface on the main yoke member for engaging the opposite side of the pole from the sharp projections;
handle means attached to the arms to be gripped by the pole climber to rotate the arms about said axes;
attachment means on the arms and adapted to be coupled to lanyard means, the attachment means being spaced on the respective arms from the respective pivotal axes of the arms whereby, in the event of a the user slipping on the pole, a force is created through the lanyard means to move the arms towards one another to thereby increase the engagement forces between the sharp projections and the pole.
a main yoke member being generally V-shaped and lying in a plane;
a pair of arms pivotally connected one to each end of the main yoke member, each of the arms being rotatable relative to the main yoke member about a respective one of a pair of axes for movement towards and away from one another generally in said plane;
biasing means connected between the yoke member and the arms, the biasing means including at least one coil spring;
pole engaging means attached to the arms and having sharp projections for biting into the pole;
a pole engaging surface on the main yoke member for engaging the opposite side of the pole from the sharp projections;
handle means attached to the arms to be gripped by the pole climber to rotate the arms about said axes;
attachment means on the arms and adapted to be coupled to lanyard means, the attachment means being spaced on the respective arms from the respective pivotal axes of the arms whereby, in the event of a the user slipping on the pole, a force is created through the lanyard means to move the arms towards one another to thereby increase the engagement forces between the sharp projections and the pole.
14. A fall arrest device as claimed in claim 13 wherein stop means are provided between the yoke member and the arms to limit the movement of the arms, the arms and the main yoke member forming a C-shape in plan and defining an opening between the arms to receive the pole, and the main yoke member and arms being electrically insulated.
15. A fall arrest device for a pole climber comprising;
a main yoke member being generally V-shaped and lyiny in a plane;
two arms pivotably connected one to each end of the yoke member, each arm being rotatable relative to the yoke member about a respective one of a pair of axes for movement towards and away from one another generally in said plane;
biasing means including spring means for resiliently biasing the arms towards one another;
pole engaging means mounted on each arm and including a pair of jaws connected thereto, each jaw being pivotable relative to one of the arms about a pivot point generally perpendicular to the plane of the yoke member;
a pole-engaging surface mounted on the yoke member;
two pole-engaging surfaces on each of the jaws and located at different distances from a pivot point on each jaw, whereby said fall arrest device may be mounted on a wide range of pole diameters;
handle means mounted on each arm for grasping by a pole climber to rotate the arm about its axis;
attachment means located on each arm outside said axis by which the fall arrest device can be coupled by lanyard means to a safety belt.
a main yoke member being generally V-shaped and lyiny in a plane;
two arms pivotably connected one to each end of the yoke member, each arm being rotatable relative to the yoke member about a respective one of a pair of axes for movement towards and away from one another generally in said plane;
biasing means including spring means for resiliently biasing the arms towards one another;
pole engaging means mounted on each arm and including a pair of jaws connected thereto, each jaw being pivotable relative to one of the arms about a pivot point generally perpendicular to the plane of the yoke member;
a pole-engaging surface mounted on the yoke member;
two pole-engaging surfaces on each of the jaws and located at different distances from a pivot point on each jaw, whereby said fall arrest device may be mounted on a wide range of pole diameters;
handle means mounted on each arm for grasping by a pole climber to rotate the arm about its axis;
attachment means located on each arm outside said axis by which the fall arrest device can be coupled by lanyard means to a safety belt.
16. A fall arrest device for a pole climber comprising;
a main yoke member made up of a pair of planar acruate half-yokes and lying in respective planes;
adjustable hinge means joining the half-yokes and permitting rotary movement of the half-yokes about an axis generally perpendicular to said planes;
locking means for locking the adjustable hinge means to hold the half-yokes in one of a plurality of positions relative to one another to accommodate poles of different base diameters;
a pair of generally planar arms parallel with the planes of the half-yokes, each of the planar arms being connected to a respective one of the half-yokes by a respective axisand each arm being rotatable relative to its respective half-yoke, said axis being perpendicular to the plane of the arm;
a pair of arcuate planar secondary yokes one connected between each and the arm connected thereto, half-yoke and lying in a plane parallel thereto;
a pair of pivotal connections one between each secondary yoke and the arm connected thereto;
a pair of sliding connections, one between each secondary yoke and the half-yoke connected thereto;
resilient biasing means for biasing the arms towards one another, the arms, half-yokes and secondary yokes forming a C-shape in plan and defining an opening between the arms to receive the pole;
pole engaging means located on both arms, for engaging part of the surface of the pole;
pole engaging surfaces located on both secondary yokes and both half-yokes for engaging part of the surface of the pole; and a pivotable handle mounted on each arm for gripping by the pole climber to move the arms about said axes and to cause the secondary yokes to move in their planes, attachment means located on the arms outside said axes by which the fall arrest device can be coupled by lanyard means to a safety belt whereby, in use, said fall arrest device is located on the pole such that the arms and secondary yokes are resiliently biased into contact with the pole and the pole is contacted by pole engaging surfaces on the half-yokes, said fall arrest device being movable up or down the pole by said climber gripping said handles and moving them against the resilient biasing means away from the pole and then moving the device up or down the pole.
a main yoke member made up of a pair of planar acruate half-yokes and lying in respective planes;
adjustable hinge means joining the half-yokes and permitting rotary movement of the half-yokes about an axis generally perpendicular to said planes;
locking means for locking the adjustable hinge means to hold the half-yokes in one of a plurality of positions relative to one another to accommodate poles of different base diameters;
a pair of generally planar arms parallel with the planes of the half-yokes, each of the planar arms being connected to a respective one of the half-yokes by a respective axisand each arm being rotatable relative to its respective half-yoke, said axis being perpendicular to the plane of the arm;
a pair of arcuate planar secondary yokes one connected between each and the arm connected thereto, half-yoke and lying in a plane parallel thereto;
a pair of pivotal connections one between each secondary yoke and the arm connected thereto;
a pair of sliding connections, one between each secondary yoke and the half-yoke connected thereto;
resilient biasing means for biasing the arms towards one another, the arms, half-yokes and secondary yokes forming a C-shape in plan and defining an opening between the arms to receive the pole;
pole engaging means located on both arms, for engaging part of the surface of the pole;
pole engaging surfaces located on both secondary yokes and both half-yokes for engaging part of the surface of the pole; and a pivotable handle mounted on each arm for gripping by the pole climber to move the arms about said axes and to cause the secondary yokes to move in their planes, attachment means located on the arms outside said axes by which the fall arrest device can be coupled by lanyard means to a safety belt whereby, in use, said fall arrest device is located on the pole such that the arms and secondary yokes are resiliently biased into contact with the pole and the pole is contacted by pole engaging surfaces on the half-yokes, said fall arrest device being movable up or down the pole by said climber gripping said handles and moving them against the resilient biasing means away from the pole and then moving the device up or down the pole.
17. A fall arrest device as claimed in claim 1, wherein the arms and the main yoke member form a C-shape in plan and define an opening between the arms for receiving a pole.
18. A fall arrest device as claimed in claim 16, wherein the main yoke member, the arms, secondary yokes and handles are all electrically insulated.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US61123984A | 1984-05-17 | 1984-05-17 | |
| US06/611,239 | 1984-05-17 | ||
| US66914184A | 1984-11-07 | 1984-11-07 | |
| US06/669,141 | 1984-11-07 | ||
| US06/703,851 US4595078A (en) | 1984-11-07 | 1985-02-21 | Fall arrest device for pole climbers |
| US06/703,851 | 1985-02-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1265173A true CA1265173A (en) | 1990-01-30 |
Family
ID=27417047
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000480478A Expired CA1265173A (en) | 1984-05-17 | 1985-04-30 | Fall arrest device for pole climbers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1265173A (en) |
-
1985
- 1985-04-30 CA CA000480478A patent/CA1265173A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4595078A (en) | Fall arrest device for pole climbers | |
| CA1165349A (en) | Pole climber's safety device | |
| EP0092317B1 (en) | Exercise device | |
| US3840091A (en) | Lineman{40 s safety belt | |
| US5505433A (en) | Sheet removal apparatus and method | |
| US4712646A (en) | Lineman's safety strap assembly | |
| US4263983A (en) | Single stile ladder | |
| US5638916A (en) | Ladder safety attachment | |
| US20020108811A1 (en) | Ladder stabilization apparatus | |
| US6752242B1 (en) | Wood pole fall protection device | |
| US8863900B1 (en) | Tree step | |
| US11125292B1 (en) | Rigid friction brake tether | |
| US5234074A (en) | Lanyard with pole gripping means | |
| US5222991A (en) | Lanyard with pole gripping means | |
| US4776503A (en) | Hunting, backpacking and camping accessory | |
| GB2229102A (en) | Pole climbing aid | |
| US4906323A (en) | Carpet stripping assembly | |
| US4886143A (en) | Hunter's tree stand | |
| US5417306A (en) | Tree climbing apparatus | |
| US4921069A (en) | Climbing device | |
| US8235172B2 (en) | Combination ascender/descender | |
| US5484036A (en) | Safety device for ladders | |
| CA1265173A (en) | Fall arrest device for pole climbers | |
| US20080314684A1 (en) | Foothold for climbing tree stands | |
| US6286625B1 (en) | Rope climbing device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |