Mine door installation

DETAILED DESCRIPTION Among the several objects of the invention may be noted the provision of a mine door system having a door-operating hydraulic instrumentality (such as a hydraulic cylinder) for a door thereof (or two such instrumentalities for a pair of doors) which is safely operable in a dangerous environment down in a mine (e.
g.
in a passageway where there may be explosive gas); the provision of a system such as described which eliminates the need for electrical empowerment (e.
g.
eliminates the need for an electric motor) and thus avoids arcing and sparking which might set off an explosion; the provision of such a system taking advantage of a power source in the mine for other purposes; and the provision of such a system which is relatively economical to install and reliable in operation.
The invention takes advantage of the compressed air system conventionally available in a mine, generally comprising the provision of an air motor for driving a pump for supplying hydraulic fluid under pressure to a hydraulic instrumentality for operating a door in the mine, and a compressed air circuit for supplying the air motor with compressed air from said compressed air system in the mine.
Other objects and features will be in part apparent and in part pointed out hereinafter.