Brakes – Operators – Speed-responsive
Reexamination Certificate
2000-03-07
2001-12-04
Graham, Matthew C. (Department: 3613)
Brakes
Operators
Speed-responsive
C187S214000, C187S366000
Reexamination Certificate
active
06325184
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to a device for stopping a load in a vertical shaft and more particularly to a gravity brake that stops a load being lowered or raised in a vertical shaft after failure of a suspending member.
2. Description of the Background Art
When loads are hoisted within a vertical shaft, the load is suspended from a support member, such as a cable, and moved in a slow ascent or descent within the shaft to a desired position by means of a manual or motor-driven hoist system. Certain catastrophic failures of the supporting members or hoist system can allow the load to free fall down the shaft. Obviously such a situation can be destructive for both the load and the shaft. Furthermore, under certain conditions the free falling load poses a danger to personnel.
Therefore a need exists for a device that can stop a load from rapidly descending down a shaft should the hoisting mechanism fail. The gravity brake in accordance with the present invention satisfies that need, as well as others, and overcomes deficiencies in previously known techniques.
BRIEF SUMMARY OF THE INVENTION
The present invention comprises a gravity brake which is positioned between a suspending member, such as a cable, and a load being hoisted up or down a shaft. Should a failure occur in the suspending member, or related hoist machinery, such that the supporting force of the suspending member is released, the gravity brake extends braking arms which contact the walls of the shaft, thereby applying a braking force which stops the load from a free-fall descent.
An object of the invention is to prevent loads from free-falling down a shaft.
Another object of the invention is to provide a system of gravity braking that is very reliable.
Another object of the invention is to provide a gravity braking device that is simple to manufacture, and does not rely on complex mechanisms or electronics for its proper operation.
Another object of the invention is to provide a gravity braking device to perform the gravity braking function while providing a secure connection between upper and lower support members, such that an inoperative gravity braking mechanism will not itself cause a hoisted load to fall.
Another object of the invention is to provide a gravity braking device which can operate within shafts of various shapes and sizes.
Another object of the invention is to provide a gravity brake with a compliant braking action whereby braking occurs even in shafts with slightly varying cross-sections and irregularities.
Another object of the invention is to provide a gravity braking device which employs the force differential between a lifting force and a loading force to extend a set of brakes.
Another object of the invention is to provide a gravity braking design that can be scaled for use in shafts of various sizes.
Another object of the invention is to provide a gravity braking device whose brake pad material and surface texture can be easily configured to suit the particular shaft material and environmental conditions.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.
REFERENCES:
patent: 1046609 (1912-12-01), Kosztura
patent: 4151981 (1979-05-01), Gennep
patent: 4359207 (1982-11-01), Maryonovich et al.
patent: 4552248 (1985-11-01), Payne
patent: 4797075 (1989-01-01), Edwards et al.
patent: 4809823 (1989-03-01), Fargier
patent: 4813493 (1989-03-01), Shaw et al.
patent: 5701972 (1997-12-01), Bloder
patent: 240722 (1925-10-01), None
Graham Matthew C.
O'Banion John P.
The Regents of the University of California
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