Control for rock drill mounting

Claim 1

A TRANSMISSION MECHANISM FOR A ROCK DRILL MOUNTING HAVING A DRILL SUPPORT MEMBER MOUNTED ON A BOOM FOR MOVEMENT RELATIVE TO THE LATTER, SAID TRANSMISSION MECHANISM COMPRISING: (A) A PINION RIGIDLY CONNECTED TO THE BOOM MEMBER AND AXIALLY ALIGNED THEREWITH, (B) A CASING CONNECTED TO THE ROCK DRILL SUPPORT MEMBER AND ROTATABLY MOUNTED ON SAID BOOM MEMBER TO ROTATE ABOUT SAID PINION, (C) A FIRST RACK POSITIONED IN SAID CASING AND CONNECTED TO TWO OPPOSING PISTONS, (D) SAID FIRST RACK BEING IN MESH WITH SAID PINION, (E) A FIRST PAIR OF OPPOSING CYLINDERS FOR THE PISTONS OF SAID FIRST RACK FORMED IN SAID CASING, (F) A SECOND RACK POSITIONED IN SAID CASING IN MESHING RELATIONSHIP WITH SAID PINION AND MOUNTED BETWEEN AND CONNECTED TO TWO OPPOSITE PISTONS, BOTH OF SAID RACKS BEING LOCATED TO SIMULTANEOUSLY ENGAGE THE SAME TEETH ON SAID PINION, (G) EACH OF SAID PISTONS ASSOCIATED WITH SAID FIRST RACK HAVING A COAXIAL BORE TO FORM OPPOSING CYLINDERS FOR SAID PISTONS ASSOCIATED WITH SAID SECOND RACK, (H) A GROOVE FORMED IN SAID FIRST RACK TO RECEIVE SAID SECOND RACK, AND (I) MEANS FOR CONTROLLING THE FLOW OF THE PRESSURE FLUID TO SAID CYLINDERS AND FOR CAUSING SAID FIRST RACK TO URGE SAID PINION IN ONE DIRECTION AND EFFECT ROTATION OF SAID CASING AND SAID ROCK DRILL SUPPORT MEMBER IN THE OPPOSITE DIRECTION, AND FOR CAUSING SAID SECOND RACK TO URGE SAID PINION IN SAID OPPOSITE DIRECTION TO PREVENT THE BACKLASH OF SAID RACKS RELATIVE TO SAID PINION.