Fire escape – ladder – or scaffold – Torso harness – Strand-engaging – with descent retarder
Patent
1997-03-18
1999-08-10
Chin-Shue, Alvin
Fire escape, ladder, or scaffold
Torso harness
Strand-engaging, with descent retarder
182192, A62B 114
Patent
active
059344083
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to fall arrest devices, and in particular to fall arrest devices for use on vertical or generally vertical safety cables or the like.
Fall arrest devices are an important feature for maintenance personnel who climb tall structures since they enable the hazard of falls to be eliminated.
In FIGS. 1 and 2 of European Patent Application No. 0 272 782, a self-locking fall arrest device is illustrated having a locking cam which is spring biased to a locking condition in which it firmly grips a safety line to lock the device to the safety line. In use, the device is connected to a lanyard of a personnel safety harness so that the loading applied to the locking cam by the lanyard is such as to maintain the locking cam in an unlocked condition, until such loading is released, for example in a fall arrest situation, whereupon the locking cam is then pivoted by its biasing spring to its locking condition.
Safety standards now require that the distance between the safety harness and the fall arrest device should be as short as possible. In some arrangements, the harness attachment can be at chest level and with a short connection to the fall arrest device, this device can be located at about the level of the stomach of the user.
This arrangement can present a problem in a situation in which substantial loading is then applied to the fall arrest device in a direction towards safety cable. This could occur, for example, if the fall arrest device became entangled in bulky clothing worn by the user and if the user leaned heavily towards the cable, perhaps in an unconscious condition.
The effect of a substantial weight applied to the device in such a situation, is that the body part becomes pressed against the cable before the locking cam is pivoted by its biasing spring to its locking condition. The force of the spring is insufficient to overcome the applied loading so that the device remains in an unlocked condition whereby the device is free to slide down the cable without providing the required fall arrest action.
The present invention seeks to provide a fall arrest device which is capable of minimizing the risk of ineffective locking action of the device when a loading is applied tending to force the device against a safety cable or the like with which it is engaged in use.
The invention provides a fall arrest device for use on an elongate safety line or track, said device comprising: line or track whilst allowing movement of the body part therealong; track in a fall arrest situation; safety line or track accommodated in the safety line retaining means in response to a sudden change in load experienced by the device, and of the body part on which said attaching means are situated, to receive loading applied to the device in a direction generally towards an elongate safety line or track engaged in the device in use, said cover means being pivotally or rockably connected to the body part and being in a force transmitting relationship with said locking cam means to apply said loading to said locking cam means so as to urge the locking cam means into locking engagement with a safety line or track accommodated, in use, in the safety line retaining means.
The addition of the cover means which, when loaded towards the safety wire, will by the nature of its construction, override any direct loading against the locking cam means that prevents locking operation thereof, but rather applies the loading to the locking cam means to urge it into its locking condition.
According to a feature of the invention, the locking cam means may comprise a pivotally mounted cam member having a grip portion formed on a part thereof for making said locking engagement with said elongate safety line or track. The attaching means may conveniently be provided on the cam member on the opposite side of the pivotal axis thereof to said grip portion.
In embodiments of the invention for use on safety cables or tracks having intermediate support brackets, the device may include at least one rotary member having at least one re
REFERENCES:
patent: 589541 (1897-09-01), Wilson
patent: 4265179 (1981-05-01), Tupper et al.
patent: 5029669 (1991-07-01), Lew
Chin-Shue Alvin
Latchways Limited
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