Liquid charging devices for hydraulic pit props

Claim 1

A HYDRAULIC CHARGING DEVICE FOR INTERCONNECTION BETWEEN A SOURCE OF PRESSURIZED LIQUID AND A HYDRAULIC PIT PROP, COMPRISING A CASING DEFINING A CHAMBER HAVING A DISCHARGE OUTLET WHICH IS ADAPTED FOR CONNECTION WITH THE PROP, AND AN INLET PASSAGE WHICH IS ADAPTED FOR CONNECTION WITH THE SOURCE OF LIQUID AND IN COMMUNICATION WITH THE CHAMBER THROUGH AN OPENING IN THE CHAMBER, A VALVE DISPOSED IN THE INLET PASSAGE AT A LOCATION ADJACENT THE CHAMBER OPENING, A VALVE CONTROL MEMBER ASSOCIATED WITH THE VALVE, A VALVE CLOSURE MEMBER URGING THE CONTROL MEMBER TO CLOSE THE VALVE AGAINST FLOW INTO THE CHAMBER, A PISTON WHICH IS SLIDABLY ENGAGED IN THE CHAMBER TO PUMP THE LIQUID IN THE DIRECTION OF THE DISCHARGE OUTLET, FOR PURPOSES OF INCREASING THE PRESSURE IN THE PROP, MEANS OPERABLE YIELDABLY TO RETAIN THE PISTON IN A RETRACTED POSITION IN THE CHAMBER, MEANS OPERABLE TO RECIPROCATE THE PISTON THROUGH OPPOSITELY DIRECTED STROKES IN THE CHAMBER, IN ONE OF WHICH STROKES THE PISTON IS DISPLACED OUT OF ITS RETRACTED POSITION FOR THE PUMPING OPERATION, AND IN THE OTHER OF WHICH STROKES THE PISTON IS WITHDRAWN INTO SUCH POSITION, AND MEANS INCLUDING A MOVABLE DEACTUATOR MEMBER WHICH IS CONNECTED WITH THE VALVE CLOSURE MEMBER AND OPERABLE AFTER THE PISTON HAS BEEN WITHDRAWN INTO ITS RETRACTED POSITION TO DEACTUATE THE CLOSURE MEMBER SO THAT THE VALVE IS OPENED FOR FLOW OF THE LIQUID THROUGH THE PASSAGE AND INTO THE CHAMBER, UNDER THE PRESSURE OF THE SOURCE.