Hydraulic crowd and retarding control systems for trench hoe attachments or the like

Claim 1

A CONTROL SYSTEM FOR A TRENCH HOE OR THE LIKE HAVING A BOOM MOUNTED FOR MOVEMENT ABOUT A HORIZONTAL PIVOT, MEANS FOR HOISTING AND LOWERING SAID BOOM ABOUT SAID PIVOT, AND MEANS FOR CONTROLLING THE OPERATION OF SAID BOOM HOISTING AND LOWERING MEANS; SAID SYSTEM COMPRISING A CLOSED HYDRAULIC CIRCUIT, MEANS CONNECTED IN SAID CIRCUIT AND COUPLED TO SAID BOOM TO INDUCE A FLOW OF FLUID IN SAID CIRCUIT IN A FIRST DIRECTION UPON HOISTING MOVEMENT OF SAID BOOM ABOUT SAID PIVOT, VALVE MEANS CONNECTED IN SAID CIRCUIT TO PREVENT FLUID FROM FLOWING THROUGH SAID CIRCUIT IN SAID FIRST DIRECTION PRIOR TO THE DEVELOPMENT OF A PRESELECTED MINIMUM PRESSURE IN SAID CIRCUIT, SAID VALVE MEANS YIELDING TO PERMIT FLUID TO FLOW THROUGH SAID CIRCUIT IN SAID FIRST DIRECTION IF PRESSURE IS DEVELOPED IN SAID CIRCUIT WHICH EXCEEDS SAID PRESELECTED MINIMUM, AND MEANS COUPLING SAID VALVE MEANS TO SAID HOISTING AND LOWERING OPERATION CONTROLLING MEANS TO CONDITION SAID VALVE MEANS TO PERMIT FLUID TO FLOW THROUGH SAID CIRCUIT IN SAID FIRST DIRECTION AT PRESSURES BELOW SAID PRESELECTED MINIMUM PRESSURE WHEN SAID HOISTING AND LOWERING MEANS IS ACTUATED TO HOIST SAID BOOM.