Spring devices – Elastic extension devices – Compression spring
Reexamination Certificate
2000-01-21
2001-07-17
Oberleitner, Robert J. (Department: 3613)
Spring devices
Elastic extension devices
Compression spring
C267S169000, C267S179000
Reexamination Certificate
active
06260833
ABSTRACT:
BACKGROUND OF THE INVENTION
The present disclosure is directed to a coil spring mounting mechanism which accommodates catastrophic failure of the coil spring. It is especially directed to coil springs which are used in taut cables or other load bearing conditions. Consider a cable having a specific load placed on it, such as 1,000 pounds. When the cable is pulled taut, equipment which is connected to the cable is subjected to severe shock loading in the event of unintended jerking on the cable. This is especially true with cables that anchor elevators, i.e., the dead end of the cable. Also, it can be used to support heavy equipment which is subject to periodic bumping. For instance, in a mechanism moving on a track to the dead end, it is desirable that a bumper intercept the load at the end of the track. If the bumper itself is suspended by a cable, one or many, then the shock of the load on the cable creates shock loading damage. In other instances, where a device is being towed, there may be a constant variation in tow bar load which periodically places shock in the towing equipment, just as in the bumpers noted above.
There are many situations where this shock load is relieved by installing a shock absorber in the cable. For instance, at a dead end connection of a cable in a drilling rig, it is highly desirable to smooth out shock loading. This can be done by installing a coil spring to be compressed with load. If, however, the coil spring and the support mechanism which connects the coil spring in the dead end connection were to fail and thereby separate failed components, then the dead end might break free, a highly undesirable result. There are devices available for the moment which accomplish this. By and large, they have the form of a coil spring which is mounted in a heavy gauge, durable cage of forged or cast construction. Such a cage, while effective for the purpose, is difficult to install and is rather costly to fabricate. Therefore, the present disclosure sets forth a cable dead end connection system (to pick just one application among many) to thereby enable the cable dead end to be spring mounted and yet provides assurance that it is a fail safe connection, i.e., even on catastrophic failure of the spring and other equipment, it does not “let go” of the cable dead end. The cable will remain intact and its desired connection will survive even the prospective catastrophic failure of the equipment of this disclosure.
Assume for purposes of explanation that the dead end of a cable is clamped or otherwise connected to an immovable object, i.e., through an eyelet looped around a bolt. Assume further that the free end of the cable is subjected to shock loading. While the stroke may not be great, the shock loading can cumulatively wear the cable so that the cable requires replacement. By the incorporation of a coil spring serially compressed by cable motion, to a major extent, shock loading can be reduced, cable life can be extended, and shock can be absorbed so that the loads supported by the cable are handled more smoothly both in dynamic and static situations. This equipment is a device which guides the spring so that it is regularly compressed.
Spring compression normally contemplates that an axial load is applied to the spring and that the multiple turns of the spring are compressed with a relatively even application. So to speak, the spring ends are compressed in parallel, and extend in parallel, and are maintained parallel at all points in operation. This parallel position of the two ends prevents the spring from bowing out to the side. The spring will tend to bow to the side when loaded unevenly. The equipment of this disclosure sets forth a spring loading safety link which is a fail safe mechanism that assures that the spring is hooked and held for compressive loading without bowing to the side. The value of this tension load compressing the spring without bowing will be noted in careful detail below.
SUMMARY OF THE INVENTION
This disclosure sets out a compressively loaded coil spring which is constructed with a number of turns and which terminates at each end of the spring with protruding tangs. The position of the tangs with respect to each other will be noted in careful detail below. The coil spring is held by a pair of mated hooks. The two hooks are essentially identical and differ only in positioning. One will be labeled the top hook and the other will be defined as the bottom hook. The top and bottom hooks are U-shaped bars which are inserted into each other on the interior of the coil spring. The respective hooks terminate in outwardly bent partial eyelets which encircle the respective tangs. There is one tang at the top end and one at the bottom end of the coil spring, and each hook is constructed so that the eyelet grabs the tang at one end. The hooks are deployed at approximate right angles to each other so that the two hooks position protruding cable eyelets suitable for cable connection. Under load, the hooks are pulled apart, but because they connect at the opposite ends of the coil spring, the two hooks apply equal and opposite compressive loads. One valuable feature of the disclosed mechanism is that the hooks are in planes approximately at right angles with respect to each other, and this in turn alignment is maintained so that the hooks do not apply forces that bow, buckle or bend the coil spring. This alignment of the respective hooks assures that parallel loading is applied to the two ends of the coil spring. In the absence of this equipment, the coil spring would tend to bow and fail much more rapidly as a result of bowing to the side.
REFERENCES:
patent: 1194417 (1916-08-01), Pelham
patent: 1388241 (1921-08-01), Dierking
patent: 2120528 (1938-06-01), Purweet
patent: 4057235 (1977-11-01), Halopoff
patent: 5624321 (1997-04-01), Snyder
patent: 5810339 (1998-09-01), Kuspert et al.
patent: 6098970 (2000-08-01), Lowe
Bracewell & Patterson L.L.P.
Nguyen Xuan Lan
Oberleitner Robert J.
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