Fire escape – ladder – or scaffold – Torso harness – Strand-engaging – with descent retarder
Reexamination Certificate
1997-01-07
2001-07-24
Stodola, Daniel P. (Department: 3634)
Fire escape, ladder, or scaffold
Torso harness
Strand-engaging, with descent retarder
C188S065100, C254S405000
Reexamination Certificate
active
06263999
ABSTRACT:
The present invention relates to vertical fall arrest devices, and in particular to vertical fall arrest devices adapted for easy attachment to and detachment from a safety cable or the like.
Vertical fall arrest devices are an important accessory for maintenance personnel who climb tall structures since they enable the hazard of falls to be minimised. Vertical fall arrest systems which employ a safety line such as a flexible cable for engagement by the fall arrest device require intermediate support brackets to restrain the cable from buffeting against the tall structure while under wind loading. Such systems therefore present a practical problem of enabling the fall arrest device (and the user) to bypass the support brackets without increasing the fall hazard.
Certain known designs attempt to overcome this bypass problem by using a manually operated bracket lock. This requires the user to open and close the bracket when he traverses it. Other known designs require that the user should lean out from the normal climb/descend posture and pull the cable away from the bracket in order to move the fall arrest device past the bracket position. Both of these methods significantly add to the difficulty of the climb, are more tiring and hence possibly increase the fall hazard.
Another problem facing maintenance personnel on very tall structures such as telecommunication pylons, masts etc. is the provision of a number of discrete vertical fall arrest systems up the side of the structure. This is due to the fact that ladder placement is often along a number of different climbing axes. Such structures may therefore require the detachment and re-attachment of the fall arrest device at any point during the climb or descent, and the ease by which this can be achieved is an important factor in determining the overall safety of the manoeuvre.
It is therefore an object of the present invention to provide a vertical fall arrest device which is capable of negotiating all intermediate safety line support brackets without user input and which also allows access to and egress from the safety line at any point without the need for special entry/exit fittings on the vertical fall arrest system.
The invention is a vertical fall arrest device for use on an elongate safety line, said device comprising:
a body member;
a rotary member having at least one recess formed in its periphery;
safety line retaining means extending between the body member and the rotary member and being adapted to retain a safety line in a space defined between the body member and the rotary member;
biasing means to urge said locking means into locking engagement with a safety line accommodated in the safety line retaining means in response to a sudden change in load experienced by the device, and means for attaching a personnel safety cable to the device;
wherein said rotary member is rotatably mounted in relation to the retaining means and wherein the or each recess formed in the periphery of the rotary member is adapted to traverse support means used to support an elongate safety line without the need for user manipulation by rotation of the rotary member relative to the retaining means such that elements of said support means are successively received, guided and passed by a recess automatically;
characterised in that at least one of the rotary member, the body member and the retaining means is movable relative to the others of such parts to enable a safety line to be introduced into or removed from said space so as to allow the device to be attached to or detached from the safety line.
A device constructed in accordance with the invention is especially advantageous because it provides, for the first time in a single unit, the means to arrest a fall, the capability to automatically traverse intermediate support means provided along a safety line, and ease of attachment to or detachment from the safety line at any point throughout its length.
Conveniently, the relative movement between at least one of the rotary member, the body and the retaining means is movement in a direction away from the other parts. Alternatively, the parts may be slidable relative to one another, or they may be rotatable. The important feature is the ability to create a gap between them which allows a safety line to be introduced or removed from the space defined between the body member and the rotary member.
Advantageously, the device incorporates releasable means for maintaining the rotary member, the body and the retaining means in a closed condition in which introduction or removal of a safety line is prevented. This feature means that a conscious decision must be taken on the part of the user to open the device. Preferably, the releasable means includes a positive latching mechanism which retains the parts in the closed condition against accidental release. The latching mechanism may be biased to its non-release position for added safety.
In an especially preferred form, the device is converted to the attachment/detachment condition by operating a release mechanism against biasing pressure and at the same time pulling the rotary member against biasing pressure in a direction away from the body. This action creates an opening for insertion or removal of a safety line.
With no external forces applied, the internal biasing mechanisms ensure that the rotary member returns to its fully locked position and the release means returns, together with the latching mechanism, to the fully latched condition. Various designs of release means may be adopted, including push button, safety pin, pull-release or rotary mechanisms.
In a preferred form of the invention, a spindle upon which the rotary member is rotatably mounted is locked into the body. The spindle may not be pulled away from the body without first operating a release catch, and hence disengaging the locking mechanism, by an intentional action. In the closed and locked condition, it is not possible for the device to be removed from or attached to a safety line. When attached to a safety line, the device is always in a ready state to grip the safety line firmly in the event of a fall.
By virtue of the fact that the removable vertical fall arrest device of the present invention has a single rotary member in juxtaposition with the body member, it will be apparent to persons skilled in the art that the device is “handed”. In a working personnel safety system attached to a tall structure, it is also necessary for the intermediate brackets supporting the safety line to be consistently “handed” for correct traversing.
However, with a removable device, there is a remote possibility that the device could be inverted and incorrectly installed on the safety line. To avoid this, the invention may incorporate a safety mechanism which prevents the release means from being actuated. Only when the device is correctly oriented can the release means be moved to an unlatched position allowing the opening of the device and its attachment to a safety line.
In an especially preferred form of the invention, the release means for the latching mechanism incorporates a safety mechanism which alerts the user to the fact that the device is being attached in the wrong orientation.
The safety mechanism may be in the form of a detent member which is freely-movable under the influence of gravity between first and second positions, according to the orientation of the device. The direction of free movement is arranged to be substantially parallel to the suspension axis of the device.
In one of said first and second positions, the detent member engages with the release means and jams it against actuation, thereby discouraging attachment of the device in the wrong orientation. Then, if the device is inverted, the detent member moves to the other position which frees the release means and renders it operable. Only by crossing or changing hands can the user attach the device incorrectly.
The detent member may be a ball which rolls or a pin which slides in a channel provided in the body member or a cover member associated therewith. Alterna
Atkinson Geoffrey Fraser
Patterson David John
Klauber & Jackson
Latchways Limited
Stodola Daniel P.
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