Abstract: A positive displacement gear pump useful for pumping hydraulic fluid includes a drive gear and an idler gear. In a first embodiment, the drive gear has symmetrical teeth, whereas the idler gear has asymmetrical teeth. The asymmetrical teeth of the idler gear include working surfaces which have a profile corresponding to the profile of the working and non-working surfaces of the drive gear, but have a non-working surface which has been relieved so as to be substantially flat. Consequently, in the zone of the pump where the gears mesh, a large backlash is created which substantially prevents bubble formation. In a second embodiment, the drive gear, as well as the idler gear, have non-contact surfaces which are substantially flat to create even a larger backlash for relieving cavitation when the teeth are made wider in the axial direction. By preventing bubble formation, cavitation which occurs at high pump speeds is substantially eliminated, thus avoiding pump damage which results from cavitation.

Abstract: A hydraulic pressure system includes a pump and a dry valve situated in the inlet of the pump, the dry valve being actuated by a pilot valve capable of capturing the pressure differentials between inlet and outlet of the pump for shifting the dry valve between opened and closed positions. In the dry operational mode, the pump inlet operates at a pressure below atmospheric, thus providing a pressure differential substantial enough to move the dry valve to an opened position. In the preferred form, the pilot valve is a solenoid actuated two-position, four-way, spring loaded valve. The dry valve is a gate valve directly coupled to a fluid control motor.

Abstract: A gear pump which includes a pressure balancing structure to ensure balanced pressure within the pump chamber during low flow operation is disclosed. A groove is formed in the casing internal surface throughout the entire axial length of the gears and supplies high pressure fluid to positions within the pump chamber which are at a high pressure during normal flow operation. This groove thus ensures that high pressure fluid will be at all locations within the pump chamber which are expected to have high pressure during normal pumping operation. Forces on the gear are as expected during low flow operation, and that the gears will not be forced in an undesirable direction.

Abstract: A system for detecting when the pressure on a bi-directional hydraulic device, such as a motor or a pump, exceeds a predetermined pressure. The device is of the type having two meshing gears mounted to rotate in a housing. Fluid inlet and outlet ports are located in the housing on opposite sides of the meshing gear teeth. A pilot port is located in the housing to detect the fluid pressure between one gear and the housing at a location isolated from the inlet and outlet ports. The sensed pressure is a function of the maximum pressure at the inlet and outlet ports.

Abstract: An hydraulic steering system for a ground-engaging, self-powered vehicle, the system including an engine driven primary pump for pumping hydraulic fluid to the steering system when the vehicle engine is operating and a wheel-driven secondary pump for pumping hydraulic fluid to the steering system when the vehicle is in motion, even if the engine or the engine driven primary pump is inoperable, or if the output of the engine driven primary pump is inadequate. The wheel-driven secondary pump is an over-center, axial piston pump which is controlled so that it is unidirectional in its output regardless of any change in direction of its input power source and which, thus, avoids the need for check valves in the hydraulic lines of the secondary pumping system, regardless of whether the vehicle is moving forward or in reverse when the engine becomes inoperable.

Abstract: A dry valve for a gear pump includes a piston having a valve head and a piston head mounted on the opposite ends of a piston rod. The piston is selectively movable between an opened position, wherein hydraulic fluid is permitted to flow from a reservoir to a pumping chamber of the gear pump, and a closed position, wherein such flow is obstructed. A source of pressurized air exerts a biasing force against the piston head to selectively move the piston. An outlet port of the gear pump is connected through a feedback passageway to the dry valve. The feedback passageway communicates with the side of a chamber in which the piston rod of the dry valve reciprocates between the opened and closed positions. When the dry valve is in the opened position, the pressurized fluid from the outlet port of the gear pump exerts a side-loading pressure against the piston rod, causing a frictional force to be generated between the piston rod and the piston rod chamber which resists relative movement.

Abstract: The disclosure relates to improvements in pumps and motors of the gear type. The gear elements are arranged within the pump or motor housing so that the ends or the tips of the teeth are spaced out of fluid sealing relationship and not pressed into the surrounding chamber wall on the low pressure side of the housing. Rigid sealing members of limited circumferential extent having a curved sealing surface and planar support and side wall surfaces are seated in a recess in the housing at the high pressure side of the gears for the purpose of providing a fluid seal between the tips of the teeth in a limited region adjacent the opening in the housing which is at higher pressure. The sealing members are positioned in a recess in the housing and are configured to be resistant to bending and movement. The sole support for the shoes is provided by planar surfaces on the side pressure plates.

Abstract: The disclosure relates to improvements in pumps and motors of the gear type. The gear elements are arranged within the pump or motor housing so that the ends or the tips of the teeth are spaced out of fluid sealing relationship and not pressed into the surrounding chamber wall on the low pressure side of the housing. According to the disclosure, sealing members of limited circumferential extent are provided in the housing at the high pressure side of the gears for the purpose of providing a fluid seal between the tips of the teeth in a limited region adjacent the opening in the housing which is at higher pressure. The sealing members disclosed are a pair of separate shoes located adjacent the high pressure opening. The sole support for the shoes is provided by the side pressure plates.

Abstract: A control system for plural circuits having motor-driven hydraulic pumps. As disclosed, a pair of pumps is connected in a hydraulic actuating circuit individual to that pair and the circuit includes an hydraulically operated actuator to be advanced and retracted by fluid under pressure delivered from the pair of pumps of that circuit. A single prime mover drives the pair of pumps and pumps in other circuits, and each circuit has a pressure-responsive control valve which provides for unloading a pump of the first circuit in response to increases in pressure in the various other circuits to a predetermined value at which, in the absence of such unloading, the input horsepower requirement has risen toward a value which would stall the prime mover.Pumps in several of the circuits may be sequentially and selectively unloaded.

Abstract: An emergency hydraulic system for a hydraulically powered device such as the power steering mechanism used on large earth-moving vehicles and the like is disclosed. The emergency system includes an auxiliary pump connected to the wheels or some other part of the vehicle so that the pump is operated despite engine failure whenever the vehicle is in motion. An inlet valve for the pump is held in the closed position whenever the vehicle prime mover is in operation so that the pump is deprived of operating fluid when an emergency condition does not exist. If the prime mover stops running so that the main hydraulic system is not operating and the power steering system is deprived of its source of power, the inlet to the emergency pump is opened so that the pump supplies operating fluid to the steering system so long as the vehicle is in motion. Since the pump is deprived of operating fluid when an emergency does not exist very little power is consumed.

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: An Emergency or back-up Hydraulic System for use with a primary hydraulic system in motor operated equipment is disclosed. The system illustrated is a steering system for a vehicle and includes a motor driven pump and a wheel driven pump for supplying hydraulic fluid to the steering system of the vehicle. The motor driven pump and the wheel driven pump are connected in series so that the fluid discharged from the motor driven pump is supplied to the inlet of the wheel driven pump. The inlet of the wheel driven pump also communicates with the reservoir as for example through the anticavitation check for the engine driven pump. By-pass connections are provided around the wheel driven pump so that fluid in excess of the demands of that pump are channelled to the steering circuit when the engine driven pump is in operation.