Hydraulic interlock mechanism on back hoe

Claim 1

A FOLDABLE POWER OPERATED BOOM CONSTRUCTION COMPRISING IN COMBINATION A VEHICLE HAVING A CHASSIS, (A) A BOOM ASSEMBLY MOVABLE BETWEEN A LOADED, LIFTED AND INOPERATIVE POSITION IN WHICH IT IS LIFTED AND FOLDED BACK OVER SAID CHASSIS AND AN UNLOADED, LOWERED AND OPERATIVE POSITION, (B) A SUPPORT ASSEMBLY MOUNTED UPON THE REAR END OF SAID CHASSIS FOR SWINGING MOVEMENT ABOUT A HORIZONTAL AXIS EXTENDING TRANSVERSELY OF SAID CHASSIS, (C) ACTUATING MEANS CONNECTED TO SAID CHASSIS AND TO SAID SUPPORT ASSEMBLY FOR VERTICALLY TILTING THE LATTER ABOUT SAID HORIZONTAL AXIS, (D) A TURNTABLE PIVOTALLY MOUNTED UPON SAID SUPPORT MEANS FOR TURNING ABOUT A VERTICAL AXIS, (E) SAID BOOM ASSEMBLY BEING MOUNTED UPON AND CARRIED BY SAID TURNTABLE, (F) A HYDRAULICALLY OPERATED LOCK MEANS FOR MAINTAINING SAID TURNTABLE FIXED AGAINST ROTATION ABOUT SAID VERTICAL AXIS WITH SAID BOOM ASSEMBLY DISPOSED IN LONGITUDINAL ALINEMENT WITH SAID CHASSIS, (G) A SOURCE OF HYDRAULIC FLUID UNDER PRESSURE, (H) A CONTROL VALVE CONNECTING SAID SOURCE TO SAID TURNTABLE LOCK MEANS, (I) MEANS OPERABLE ONLY WHEN SAID LOCK MEANS IS LOCKING SAID TURNTABLE FOR CONNECTING SAID SOURCE TO SAID ACTUATING MEANS AND TO SELECTIVELY EFFECT RAISING AND LOWERING OF SAID SUPPORT MEANS, TURNTABLE AND BOOM ASSEMBLY.