In the past, much effort has been devoted to development of fall prevention devices known as rope grips. The desirable qualities of such a device fall into several categories including safety, reliability, versatility and convenience of use. Dodge Machine Company, Inc. commonly offers a rope grip with a number of desirable qualities, for example the rope grip is manufactured from large pieces of material which distributes the impact of a fall to relatively massive pieces of metal providing strength, reliability and safety.
Another commercially available rope grip is the Barrow-Hepburn-Everest Rope Grip, patented in the U.K. with Pat. No. 1,077,068. This rope grip operates by means of three small steel balls through which a rope is passed. When the rope grip begins to fall rapidly down a rope, the friction of the rope against the balls draws them into a conical shaped housing which jams the rope between the three balls. While this device offers advantages over many others in fail safe operation, it too has practical drawbacks. For example, this device can only be used with a very narrow tolerance in rope diameter. Moreover, the rope must be threaded through the grip, as it can not be opened for placing the grip on the rope.
In U.S. application Ser. No. 501,623 filed on June 6, 1983, a removable double action rope grip is disclosed. This rope grip takes care of many of the practical disadvantages of the prior art, however many problems still remain. In particular, it is often desirable to anchor vertical safety lines on the surface of a nearby structure. According to existing specifications issued by OSHA and other such safety organizations, a safety line should be held in place at least every thirty feet so that it does not blow and flap around in the wind. Whatever means are used to anchor the safety line will, of course, present an obstacle to a rope grip. Conventional safety devices for use on inclined lines cannot pass such an anchor, and therefor the rope grip must be removed from the line and reattached at the desired position.
The Latchway.RTM. Cliprider System manufactured and marketed by Barrow-Hepburn Equipment, Ltd. of London, England discloses a safety system that allows workers to move past clips holding horizontal line in place. In addition, this system has special fittings which allow a safety device to be put on or removed from a cable anywhere in the system.
U.S. Pat. No. 4,265,179 to Tupper describes in detail various aspects of the Cliprider system. By way of summary, the Latchway System is merely a means for protecting a worker by use of a horizontal safety line, and does not provide for arresting movement along the line. That is to say, the worker is protected by a horizontal line while he is working on more or less the same level. This, of course, would not be suitable for use by workers who are climbing long ladders such as found on water storage tanks, television transmitting towers, smokestacks or the like, where a vertical safety line is needed. While the Latchway System does provide a way of bypassing anchors which secure a line, it simply does not act as a safety device for use on an inclined line.