Mine roof prop and advancing arrangement

Claim 1

IN A MINE ROOF PROP AND ADVANCING ARRANGEMENT FOR USE WITH AN ELONGATED MINING CONVEYOR, INCLUDING A PAIR OF PRESSURE FLUID MEDIUM ENERGIZED EXTENSIBLE AND RETRACTABLE MINING PROP FRAMES, PRESSURE FLUID MEDIUM ENERGIZED FRAME ADVANCING MOTIVE MEANS HAVING A FIRST MOTIVE PART AND A SECOND MOTIVE PART OPERATIVELY INTERCONNECTED FOR RELATIVE LINEAR MOVEMENT ALTERNATELY TOWARD AND AWAY FROM EACH OTHER, ONE SAID FRAME BEING CONNECTED WITH ONE SAID MOTIVE PART FOR LINEAR MOVEMENT THEREWITH AND THE OTHER SAID FRAME BEING CONNECTED WITH THE OTHER SAID MOTIVE PART FOR LINEAR MOVEMENT THEREWITH WHEREBY TO ACHIEVE ALTERNATE ADVANCEMENT OF SAID FRAMES WITH THE RESPECTIVE MOTIVE PART UPON CORRESPONDING ALTERNATE HIGH AND LOW FORCE RESULTANT PRESSURE FLUID MEDIUM ENERGIZING OF SAID FRAMES AND SAID MOTIVE MEANS, AND AUXILIARY PRESSURE FLUID MEDIUM ENERGIZED CONVEYOR URGING PISTON-CYLINDER MEANS INCLUDING A DOUBLE ACTING PISTON MEMBER AND A CYLINDER MEMBER OPERATIVELY INTERCONNECTED FOR RELATIVE LINEAR MOVEMENT IN A DIRECTION ALTERNATELY TOWARD AND AWAY FROM ONE ANOTHER, ONE SAID MEMBER BEING CONNECTED TO SAID ONE FRAME AND THE OTHER SAID MEMBER BEING ADAPTED TO ENGAGE OPERATIVELY SUCH MINING CONVEYOR TO URGE SUCH CONVEYOR IN A GIVEN OPERATIVE LINEAR DIRECTION IN DEPENDENCE UPON SUCH RELATIVE LINEAR MOVEMENT BETWEEN SAID MEMBERS, THE IMPROVEMENT WHICH COMPRISES CONTROL VALVE MEANS FOR CONTROLLING AUTOMATICALLY THE AUXILIARY PRESSURE FLUID MEDIUM FOR SAID URGING PISTON-CYLINDER MEANS AND HAVING A BIASING COUNTER FORCE NORMAL POSITION AND A PRESSURE FLUID MEDIUM RESPONSIVE ENERGIZED POSITION, SAID VALVE MEANS IN ONE OF SAID POSITIONS PERMITTING POSITIVE FLOW OF AUXILIARY PRESSURE FLUID MEDIUM TO URGE SAID URGING PISTONCYLINDER MEANS IN ONE OF SAID ALTERNATE DIRECTIONS AND SAID VALVE MEANS IN THE OTHER OF SAID POSITIONS PREVENTING SUCH POSITIVE FLOW, SAID VALVE MEANS BEING IN COUPLED OPERATIVE FLOW COMMUNICATION WITH THE PRESSURE FLUID MEDIUM USED FOR ACHIEVING SAID ALTERNATE ADVANCEMENT OF SAID FRAMES, WHEREBY WHEN THE FORCE OF SAID PRESSURE FLUID MEDIUM USED FOR ADVANCEMENT OF SAID FRAMES EXCEEDS THE COUNTER FORCE OF THE NORMAL POSITION OF SAID VALVE MEANS SAID VALVE MEANS WILL CHANGE TO SAID ENERGIZED POSITION AND WHEN SAID COUNTER FORCE EXCEEDS THE FORCE OF SAID PRESSURE FLUID MEDIUM USED FOR ADVANCEMENT OF SAID FRAMES SAID VALVE MEANS WILL CHANGE TO SAID NORMAL POSITION, TO CONTROL AUTOMATICALLY THE FLOW OF PRESSURE FLUID MEDIUM FOR URGING SAID PISTON-CYLINDER MEANS IN DEPENDENCE UPON THE DIFFERENCE BETWEEN SAID COUNTER FORCE AND THE FORCE OF SAID PRESSURE FLUID MEDIUM USED FOR ADVANCEMENT OF SAID FRAMES AND IN TURN IN DEPENDENCE UPON THE POSITIVE AND NON-POSITIVE FLOW POSITIONS OF SAID VALVE MEANS.