Mine roof supports
US4473324A · kind A · utility
3Cited by
2References
4Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Feb 23, 1983 |
| Grant date | Sep 25, 1984 |
| Priority date | — |
| Expiry date | Feb 23, 2003 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21D23/16
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A mine roof support includes a first liquid supply means having a first control valve for connecting a source of liquid under pressure to the legs of the support. The support is also provided with a second control valve which is actuatable, when the pressure of the liquid being supplied to the legs attains a value below the setting pressure for the legs, to connect the legs to a source of liquid under pressure by way of a second liquid supply means. Time-delay means is operable on the second control valve to cause it to close when a predetermined time has elapsed after the pressure in the legs has reached the setting pressure.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.