Abstract: An improved hydraulic swing mechanism is disclosed for operation of the boom assembly of a backhoe or similar implement. The swing mechanism includes a pair of double-acting hydraulic motors pivotally interconnected between the backhoe frame and the backhoe boom assembly. A novel multi-position sequencing spool valve is disposed in fluid communication between the head ends of the hydraulic motors and a manually operated directional control valve which directs swinging movement of the boom assembly. A straight-forward valve control linkage operatively connects the sequencing spool valve with the boom assembly so that the spool valve is selectively operated as the boom assembly is pivoted through its arc of travel. An improved hydraulic cushioning circuit is provided in association with the sequencing spool valve, with the entire system providing improved operation of the boom assembly, with significant improvement in the hydraulic cushioning and torque characteristics of the system.

Abstract: An improved hydraulic control system is disclosed for operating the swing tower and boom of a backhoe. The system includes a pair of hydraulic motors interconnected between the backhoe frame and swing tower. A sequencing valve is hydraulically associated with respective ends of the hydraulic motors and operates to direct the flow of pressurized hydraulic fluid to the motors for improved performance as they rotate the swing tower and boom. A hydraulic cushioning circuit associated with the sequencing valve provides an improved arrangement for cushioning of the swing mechanism as the swing tower and boom are moved toward either of their travel stops without the use of conventional cushioning devices.

Abstract: An improved hydraulic swing mechanism for a material handling implement, such as a backhoe, includes a multi-position, hydraulic sequencing valve for directing the flow of hydraulic fluid to hydraulic motors which rotate the swing tower and boom of the implement. A unique valve operating mechanism is provided for selectively repositioning the sequencing valve as the boom and swing tower are rotated in order to improve the operating characteristics of the swing mechanism. The valve operating mechanism includes a pivoted, frame mounted actuating arm connected with the sequencing valve by a lost-motion linkage, and flexible linkages connecting the actuating arm with the hydraulic motors of the swing mechanism.

Abstract: An improved hydraulic system is disclosed for a backhoe having a rotating boom operated by a hydraulic swing mechanism. The system includes a hydraulic rotary sequencing valve which is operatively connected with the swing tower which supports the rotating boom. During rotation of the swing tower and boom by the hydraulic motors of the backhoe, the rotary valve is operated to selectively direct pressurized fluid to the motors for improved torque characteristics. A hydraulic cushioning circuit is provided in association with the rotary sequencing valve so that hydraulic cushioning of the motors, and thus the boom, is effected during the approach of the boom toward its travel stops, eliminating the need for conventional cushioning mechanisms in the motors themselves, and improving overall performance of the machine.

Abstract: A unique hydraulic circuit is provided for converting rectilinear motion to rotational motion about an axis through the use of two pivotally mounted hydraulic motors. The hydraulic motors are pivotally interconnected between a pivoting member and a fixed member. A source of hydraulic fluid under pressure is directed to each hydraulic motor by a conduit system incorporating a flow control valve and a sequencing valve. The flow control valve selectively delivers fluid power to the hydraulic motors to rotate the pivoting member in one direction or the other. The sequencing valve senses the angular position of the two hydraulic motors and redirects the flow of fluid to the hydraulic motors in such a manner as to maintain the torque applied to the pivoting member relatively constant. The sequencing valve acts to redirect the flow of hydraulic fluid to the hydraulic motors so that only one of the hydraulic motors is pressurized at the end of the arc of swing of the pivoting member.

Abstract: A hydraulic fluid flow network, utilizing the fluid returned from by an open center hydraulic system, to augment the charging system of a hydrostatic transmission. The augmented charging system provides oil under pressure to flow into the charging system in the event that charging system pressure flow falls below normal. A back pressure is maintained in the return line header of an open center hydraulic system by a relief valve. Flow is diverted to the charging system by a line containing a non return valve.

Abstract: An automatic hydraulic shut-off system for use with a hydraulic valve and a work apparatus which is retained under hydraulic pressure even when the hydraulic line is broken inadvertently. A lock valve is connected in the line and senses the loss of hydraulic pressure, and the valve is actuated in response to the pressure drop and retains the work apparatus in a pressurized condition to thereby avoid undesired movement in response to the loss of pressure.

Abstract: A control system for connecting a manually actuated lever to an arm of a fluid translating device that forms part of the drive transmission for a skid steer vehicle is disclosed herein. The connection between the lever and the arm is in the form of a hydraulic fluid connection that includes master and slave cylinder and piston assemblies with the master cylinder and piston assembly connected to the lever and the slave cylinder and piston assembly connected to the control arm. The opposite ends of the respective cylinders on opposite sides of the respective pistons are interconnected by fluid conduits to define first and second chambers and both pistons are biased to a centered neutral position.

Abstract: An automatic control system for a backhoe utilizing a bucket at the end of a rigid boom is disclosed herein. The automatic control system includes an actuator cooperating with a control valve that controls the flow of fluid to hydraulic rams that pivot the boom. The control system also includes position indicating means between the boom and the frame and a manually settable control element both of which produce output signals that are combined and activate the actuator so that the implement is moved at a rate which corresponds to the differences between the respective signals.

Abstract: A self-leveling system for a material handling unit on a pivoted boom is disclosed herein. The self-leveling system consists of a separate valve which is automatically controlled by the actuation of a material handling valve to produce the leveling function in either the raising or lowering condition for the boom.