| 摘要 |
<p>A unitary hydraulic control device, especially for use with mining apparatus, has a main housing carrying replaceable individual valves arranged in bores. The valves are operated by tappets which engage on cams provided on one of three relatively rotatable coaxial parts forming a multi-part cam shaft. The rotatable parts have hand levers external to the housing permitting the parts to be partly-rotated in either direction, together or separately, to operate selected groups of valves. Each rotatable part has its own "dead man's" handle safety or restoring system which automatically return the rotatable part to a neutral position upon release of its hand lever and after part-rotation in either direction. Each such system is composed of a pair of spring-loaded plungers guided in casings fitted in the housing and engaging on diametrically-opposed cam surfaces of an additional cam on the associated rotatable cam shaft part.</p> |
