Abstract: Disclosed herein is a drive and swing control system for an excavator wherein the swing pump may selectively direct fluid to the drive motors of the vehicle when the swing motor of the vehicle is not in use.

Abstract: A fluid system for work elements of a work vehicle has first and second fluid circuits each having a pump connected to a work element through a control valve assembly that is operated by a pilot pump. A control means is provided for controllably passing fluid between the first and second fluid circuits in response to power demands of said circuits.

Abstract: A closed recirculating hydrostatic transmission system suitable for driving a traction vehicle. The system includes a pair of hydrostatic engine driven variable displacement pumps either of different displacements or engine driven at different speed ratios and each pump being operative to drive hydrostatic motors at the various wheels and in separate closed loop drive circuits such that accurate flow division as between the circuits is effected for driving the vehicle in four-wheel drive or, at the operator's selection, for driving the motors in the one closed loop circuit at a higher speed in two-wheel drive by means of the pump of larger discharge volume. An operator's control operates both pumps together within the limits of the smaller discharge pump in four-wheel drive, and operates the larger discharge pump within the limits thereof while rendering ineffective the smaller discharge pump in two-wheel drive. Valve means enables smooth transition and shifting between two and four-wheel drive at any time.

Abstract: The disclosure relates to plural, motor driven hydraulic pump circuits, including circuits having the pumps in at least one circuit operated in pairs with all pumps being driven by a single prime mover. A speed responsive control device unloads one pump in one circuit when engine speed drops below a predetermined value without regard to the source of the condition causing the slowdown. Also included is a crossover means for sensing the pressure in aother circuit for preventing reloading of the unloaded pump when speed rises above the predetermined value unless and until the pressure including the pressure sensed in the other circuit is below a predetermined pressure.

Abstract: A hydraulic system for pipelayers includes a first circuit with a pump and a motor for controlling a boom and a second pump and motor for controlling a hoist with pressure-responsive control means responsive to a first pressure for permitting combining of fluid for operation of the hoist and responsive to a second pressure for preventing combining of said fluid.

Abstract: The present invention is directed to a supply circuit for a hydraulic jack employing two pumps in which a valve is positioned in a pipe which is branched to the delivery pipe of the first pump and is controlled by two jacks supplied by the fluid delivered by the second pump. A constrictor is positioned in the supply system for one of the jacks and another constrictor is placed in the discharge system for the two jacks with the invention being particularly applicable to achieving a stable control circuit for the load relief of the first pump.

Abstract: A hydraulic backhoe utilizes two pairs of hydraulic pumps to power independent crawler track drives in any forward or reverse direction, and high or low speed ranges; allowing, for example, a wide arc turn either left or right, forward or backward. Through a novel hydraulic circuit, these pumps also power other functions such as boom, bucket and stick drives in high speed or low speed modes. This flexibility is accomplished by the use of a manually controlled track speed selector valve, an unloading valve and check valve between a track function valve and another function valve in each of the two hydraulic circuits. Full hydraulic pressure is available to all functions at all times except when a track drive is in high speed range. Conventional high-low or unloading operation of the other functions is had when the related track drive is not operating.

Abstract: A fluid pressure system having a plurality of pumps, valves, and fluid-pressure responsive units. These items are interconnected by fluid lines, and check valves are arranged to control the fluid in only certain directions in some portions of the lines. The entire arrangement permits the utilization of one pump for a respective fluid-pressure responsive unit, or all of the pumps can be directed to one of the fluid-pressure responsive units.

Abstract: A hydrostatic transmission control for a hydrostatic transmission having a variable displacement pump and a variable displacement motor including pressure-responsive displacement control means for the pump and motor with a displacement control valve for each of the pump and motor and positionable by a control pressure to set the displacement of the pump or motor with which it is associated. In dual path control of two hydrostatic transmissions, a master circuit has a first valve for setting a control pressure to determine the speed of operation of the transmissions and a second valve for determining the direction of operation of the transmissions, with operation of both valves by a single control handle. The master circuit connects into two branch circuits, each leading to the displacement controls for one of the hydrostatic transmissions and with each branch circuit having its own steering control valve.

Abstract: A fixed platen is supported in the machine frame, and a movable platen is connected to two parallel rods which project rearwardly through the fixed platen. Each rod carries a first piston and each piston is slidably received in a first cylinder. These cylinders are slidably received on the rods and each cylinder has a forward end defining a second larger piston slidably received in a fixed second cylinder. The front and rear faces of the smaller pistons are selectively connected to fluid from a first pump through a synchronizing valve, and a paralleling pump supplements the flow from the first pump during synchronization, that is during the major part of the mold opening and closing movement. Slower movement is provided for just prior to the platen reaching the mold open and closed positions.