Hydraulic and earth engineering – Earth treatment or control – Shoring – bracing – or cave-in prevention
Patent
1989-11-16
1991-06-25
Corbin, David H.
Hydraulic and earth engineering
Earth treatment or control
Shoring, bracing, or cave-in prevention
405302, 405291, E21D 1544
Patent
active
050262181
ABSTRACT:
A hydraulic temporary mine roof support cylinder is disclosed. The support cylinder includes an outer housing and a coaxial intermediate housing member and inner cylinder. A downwardly extending piston is provided between the outer housing and intermediate housing member. In addition, a sleeve piston is provided within the inner cylinder while an inner piston rod is extensible from the sleeve piston. Controls are provided for independently operating the lower cylinder and the upper cylinders. Additionally, a sequence/check valve ensures the timed operation of the upper cylinders. Due to the present design, each of the cylinders may be collapsed within the outer housing.
REFERENCES:
patent: 3371901 (1968-03-01), Groetschel
patent: 4252475 (1981-02-01), Cobb et al.
Corbin David H.
Joy Technologies Inc.
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