发明名称 |
Hydraulic control arrangement for a roof support unit of a mineral mining installation |
摘要 |
A roof support unit for a longwall mineral mining installation has a roof shield supported above a floor sill. A first hydraulic ram is provided for advancing the roof support unit. The roof shield is provided with a forward extension which is advanceable by means of a second hydraulic advance ram. A hydraulic control arrangement, which includes the two hydraulic advance rams is provided for controlling the advance of the roof shield extension in dependence upon the working stroke of the first hydraulic advance ram. The control arrangement is such that the amount of hydraulic fluid supplied to one of the pressure chambers of the second hydraulic advance ram is dependent upon the amount of hydraulic fluid expelled from one of the pressure chambers of the first hydraulic advance ram during the working stroke of the first hydraulic advance ram.
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申请公布号 |
US4440522(A) |
申请公布日期 |
1984.04.03 |
申请号 |
US19800217968 |
申请日期 |
1980.12.19 |
申请人 |
GEWERKSCHAFT EISENHUTTE WESTFALIA |
发明人 |
DETTMERS, MICHAEL;WEIRICH, WALTER |
分类号 |
E21D23/06;E21D23/08;E21D23/16;(IPC1-7):E21D15/14;E21D23/00;F15B11/20 |
主分类号 |
E21D23/06 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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