Mine vehicle safety apparatus
US4340920A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 30, 1981 |
| Grant date | Jul 20, 1982 |
| Priority date | — |
| Expiry date | Mar 30, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H3/17
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A mine safety system for use with a direct current power supply delivering power via a pair of conductors to the direct current load components of mining apparatus which includes a conductive frame electrically isolated from ground and at least one of the conductors. In the safety system, an alternating current generator transmits a predetermined frequency signal over the pair of conductors to the mining apparatus. A filter which passes the predetermined frequency signal is disposed at the mining apparatus in a shunt circuit with the load components, the filter thereby being connected to the generator. Circuitry monitors the impedance of the electrical load on the generator at the predetermined frequency and a contactor responsive thereto stops the delivery of power from the power supply to the mining apparatus upon the impedance of the electrical load on the generator at the predetermined frequency exceeding a predetermined level which exceeds the impedance of the shunt combination of the filter and load components. Switching circuitry disconnects the filter from the generator in response to the flow of significant current from one of the conductors to the mining apparatus frame, …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.