Ready clamp

A system and clamp for supporting a load such as an elevator in which the clamp is mounted on a cable above the load which is normally supported by and otherwise attached to the cable. The clamp supports the load in the event of failure of structure normally supporting the load between the clamp and load. The clamp includes two members defining between them an extending passage for the cable with one of the members being mounted for movement toward and away from the cable. A cam member is pivotably mounted with a cam surface at a variable radius from the pivot axis in engagement with the one member and attached by cable to the load to pivot and apply a force to the one member to frictionally lock the clamp to the cable and support the load in the event of failure.

BACKGROUND OF THE INVENTION 
The invention relates to a system and clamp for supporting a load in the 
event of failure of the normal supporting structure between the clamp and 
the load. 
For construction and other purposes, it is often useful to raise a load by 
means of a cable attached to a cage or some other load supporting 
structure. Particularly in a life supporting system in which personnel 
ride in the cage, it is desirable to provide some back-up system which 
will support the load in the event of failure of the cable or the 
attachment of the cable to the personnel cage. Such a failure can be due 
to errors of installing a main clamp, faulty materials, fatigue of the 
clamp or the cable, or damage to the cable caused by the main termination. 
Cable fatigue in particular happens almost always within three feet of the 
main termination. 
According to the present invention, a clamp is provided on the cable above 
the point of attachment to the load supporting structure. The clamp 
includes first and second members having opposed curved surfaces defining 
therebetween an extending passage for the cable. One of the members is 
mounted for movement toward and away from the cable, for example, in a 
U-shaped channel provided by another member. A cam member is mounted 
outward from the cable for pivotable movement about an axis in a vertical 
plane. The cam member engages the one member which is movable toward and 
away from the cable, and also includes structure for attaching the cam 
member to the load remote from the axis of rotation, for example, by a 
chain. Failure of the cable or attachment thus causes the cam member to 
pivot about its axis, so that its surface applies an increasing force to 
the one member to frictionally lock the clamp to the cable and support the 
load. 
The present invention has a number of advantages. It can be made of readily 
available materials such as steel, and is simple in construction. Its 
installation is simple, and it does not restrain the working of the cable. 
It does not preload the clamp or restrain the cable until failure and it 
lends itself to visual inspection. Readily available materials can be used 
to fabricate the clamp in a normal machine and fabricating shop. Location 
of the back-up clamp can be such that it will protect against almost all 
foreseeable failures. 
Others in the past have sought to provide automatic safety catches. For 
example, the U.S. patent to Wallace No. 1,002,947, and the U.S. patent to 
Metheen No. 1,080,648, both show safety catch structure for elevators in 
which a wedge is used to lock the elevator to the cable in the event of 
failure. The present invention utilizes both friction and leverage with 
the advantages described above. The U.S. patent to Eck No. 498,161 
describes eccentric cams which engage a safety cable and the U.S. Pat. to 
Wakefield No. 473,275 describes an elevator which may be secured for 
loading by a pair of tooth dogs. Other U.S. patents showing clamping to 
ropes include the patent to DeWit No. 92,837, the patent to Wilson No. 
1,334,925, the patent to Hecker No. 1,947,603, the patent to Swager No. 
4,077,094, the patent to Hubert No. 2,993,157, the patent to Thompson No. 
3,386,530, and the patent to Christiensen No. 3,967,349. 
Other objects and purposes of the invention will be clear from the 
following detailed description of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
Reference is now made to FIGS. 1 and 2 which show the system and clamp of 
the present invention in use. A conventional elevator cage 20 supports a 
load, for example, one or more people who are to be raised and lowered. A 
conventional cable 22 of appropriate strength and size is attached to the 
top of case 20 by a conventional clamp arrangement generally indicated as 
26. Above the point of attachment of cable 24 to cage 20, the clamp 28 of 
the present invention is provided. Clamp 28 is attached to cage 20 by 
respective chains 30 and 32, which cross as shown and which exert a force 
on clamp 28 to lock the clamp against cable 24 in the event of failure as 
described below. 
Reference is now made to FIGS. 3 and 4 which illustrate the clamp of the 
present invention in detail. First and second members 40 and 42 are 
provided with opposing surfaces 44 and 46 which define between them an 
extending passage for cable 24. Member 40 has an extending portion 50 
provided with a bore 52 to which the cable chain 30 can be conventionally 
attached. A further U-shaped channel member 54 is welded or otherwise 
permanently affixed to member 40 and mounts member 42 for movement in a 
vertical plane toward and away from cable 24. More particularly, a strut 
member 56 and a clamp indicated at 58 hold member 42 so that it is movable 
only in the vertical plane. Clamp 58 can be a simple double saddle cable 
clamp. A cam member 60 is pivotably mounted about axis 62 by means of pin 
64 extending through matching bores in cam member 60 and channel member 
54. A further bore 66 is provided remote from the point of pivoting for 
attachment of cable chain 32 so that in the event of failure of structure 
between clamp 28 and cage 20, cam member 60 is pivoted in the direction of 
the arrow. Since the radius of cam surface 70 from axis 62 increases in 
the opposite direction an increasing force is applied to member 42 forcing 
that member against cable 24 and frictionally locking clamp 28 to cable 
24. 
The structure is preferably made of heavy steel in an appropriate size to 
support whatever load is required. 
Many changes and modifications in the above described embodiment of the 
invention can, of course, be made without departing from the scope 
thereof. Accordingly, that scope is intended to be limited only by the 
scope of the appended claims.