1990-02-26
1991-07-02
Halvosa, George E. A.
Brakes
Rod
81 5718, 279 4, 279 71, 279114, 2941022, B23Q 5033
Patent
active
050279262
ABSTRACT:
An hydraulically operated slip assembly useful to grip pipe being run into or pulled from a well. This assembly has upper and lower plates, each having a passage for pipe. Wedges, carrying unique slip systems are positioned around the passages between the plates and are slidably mounted for guided radial movement inwardly to initially grip pipe in neutral position and outwardly to ungrip pipe as moved by an hydraulic cylinder pivotally mounted aside on the lower plate. The unique slip systems automatically increase gripping force on initially gripped pipe on more than about 0.7 inches up or down movement from neutral position caused by loads on the pipe. Forces resulting from increased pipe gripping force on pipe develop frictional forces within the slip assembly, which effectively prevent outward movement of the wedges after inadvertent or on purpose operation of the cylinder to ungrip the pipe. The gripped pipe must be moved to return the slip systems to neutral position where the slip systems are not automatically increasing gripping force on pipe before the cylinder can move the slip systems outwardly to ungrip pipe. The slip systems automatically return to neutral position on ungripping pipe.
REFERENCES:
patent: 1704057 (1929-03-01), Neilsen
patent: 2068217 (1937-01-01), Abegg
patent: 2887754 (1959-05-01), Johnson
patent: 3760469 (1973-09-01), Brown
patent: 4576254 (1986-03-01), Cox
Cox Roland O.
Halvosa George E. A.
Otis Engineering Corporation
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