Patent ID: 8276376
Filing Date: 2012-10-02
Classification: F03C,F15B

Abstract:
1. A hydraulic circuit comprising: at least one hydraulic motor, said motor defining a motor cavity and including at least one piston at least partially disposed within a piston bore and movable between an extended position and a retracted position, said piston permitting free rotation of said motor when in said retracted position; a first hydraulic pump having a selectively variable discharge; a first loop within said circuit, hydraulic fluid being recirculateable through said first loop and said first loop comprises in serial order, said first hydraulic pump, a first hydraulic line, said hydraulic motor and a second hydraulic line; a third hydraulic line providing fluid communication between said first hydraulic line and a first valve; a fourth hydraulic line providing fluid communication between said second hydraulic line and a second valve; a fifth hydraulic line providing fluid communication between said first and second valves wherein said first valve has an open position permitting bi-directional fluid communication between said third and fifth hydraulic lines and a closed position preventing fluid communication from said third hydraulic line to said fifth hydraulic line; and wherein said second valve has an open position permitting bi-directional fluid communication between said fourth and fifth hydraulic lines and a closed position preventing fluid communication from said fourth hydraulic line to said fifth hydraulic line; a second hydraulic pump; a sixth hydraulic line receiving a hydraulic fluid from said second hydraulic pump and providing fluid communication between said second hydraulic pump and a third valve; a seventh hydraulic line providing fluid communication between said third valve and said motor cavity wherein said third valve has a first position providing fluid communication from said sixth hydraulic line to said seventh hydraulic line and a second position preventing fluid communication from said sixth hydraulic line to said seventh hydraulic line; and wherein, when said first hydraulic pump is discharging at no greater than a minimal discharge rate and said third valve is in said first position, hydraulic fluid pressure within said motor cavity moves said at least one piston into said retracted position; and wherein said at least one piston is movable into said extended position by moving said third valve into said second position and positioning each of said first and second valves in said open position and operating said second pump; and wherein said motor is actuable after extending said at least one piston by moving each of said first and second valves into said closed position and operating said first hydraulic pump at an elevated discharge rate.