Power assisted feed for a kelly bar

Claim 1

A POWER-ASSISTED FEED FOR A KELLY BAR COMPRISING A FRAME STRUCTURE, AT LEAST ONE FLUID-PRESSURE RAM MOUNTED ON SAID FRAME STRUCTURE AND INCLUDING A MOVABLE MEMBER, SAID RAM BEING ADAPTED TO EXERT A DOWNWARD THRUST, THRUST BEARING MEANS CARRIED BY THE MOVABLE MEMBER OF SAID FLUID-PRESSURE RAM, A ROTATABLE MEMBER ROTATABLY SUPPORTED BY SAID THRUST BEARING MEANS AND HAVING AN AXIAL OPENING ADAPTED FOR THE PASSAGE THERETHROUGH OF A VERTICAL KELLY BAR, AT LEAST TWO TOGGLE MEMBERS SYMMETRICALLY DISPOSED ABOUT THE CENTRAL OPENING AND HAVING MUTUALLY REMOTE EDGES LOOSELY SUPPORTED IN THE ROTATABLE MEMBER AND MUTUALLY PROXIMATE EDGES FORMED TO COOPERATE IN GRIPPING THE KELLY BAR WHEN THE TOGGLE MEMBERS ARE DOWNWARDLY INCLINED AND DOWNWARD THRUST IS APPLIED TO THE RAMS, RESILIENT MEANS, TOGGLE ENGAGEMENT MEANS CARRIED IN VERTICALLY MOVABLE MANNER ON SAID ROTATABLE MEMBER AND UPWARDLY BIASED BY SAID RESILIENT MEANS, AND HAVING A FIRST ABUTMENT SURFACE ARRANGED TO ENGAGE SAID TOGGLE MEMBERS TO LIFT THE PROXIMATE EDGES OF SAID TOGGLE MEMBERS INTO CONTACT WITH SAID KELLY BAR WHEN SAID RAM IS DISPLACED FROM THE TOP OF ITS STROKE, AND A SECOND ABUTMENT SURFACE ARRANGED TO ENGAGE SAID TOGGLE MEMBERS, AND A STOP MEMBER MOUNTED ON SAID FRAME STRUCTURE WHERE IT CAN BE ENGAGED BY SAID TOGGLE ENGAGEMENT MEANS WHEN SAID RAM IS SUBSTANTIALLY AT THE TOP OF ITS STROKE TO DEPRESS SAID TOGGLE ENGAGEMENT MEANS AGAINST THE ACTION OF SAID RESILIENT MEANS TO CAUSE SAID SECOND ABUTMENT SURFACE TO ENGAGE AND DEPRESS SAID TOGGLE MEMBERS.