Hydraulic and earth engineering – Earth treatment or control – Shoring – bracing – or cave-in prevention
Patent
1987-05-20
1989-01-10
Corbin, David H.
Hydraulic and earth engineering
Earth treatment or control
Shoring, bracing, or cave-in prevention
405296, 405299, E21D 1544
Patent
active
047970235
ABSTRACT:
A mine roof support has a roof engaging canopy 23, a floor engaging base 12, and a hydraulic jack 24 acting between the canopy and the base for urging the canopy and the base apart. The hydraulic jack 24 is provided with at least two different locations, movement of the jack means 24 from one location to another location bringing about an alteration in the distance between the canopy and the base. The invention makes it possible to provide a hydraulic jack having a first working position in which the hydraulic jack is arranged in the optimum position to support a mine roof, and a second stowing position for transportation purposes.
REFERENCES:
patent: 3848928 (1974-11-01), Nakajima
patent: 3925995 (1975-12-01), Harmsma et al.
patent: 4056941 (1977-11-01), Watermann
patent: 4121426 (1978-10-01), Heyer
Corbin David H.
Gullick Dobson Limited
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