Mannesmann Rexroth Corporation

G. L. Rexroth Gmbh

Norbert Mucheyer

Heinz Schulte

Wolfgang Kauss

Hubertus Schmidt

Kurt Wittich

Ludwig Muncke

Norbert Kreth

Peter Buttner

Wolfgang Krausse

A hydraulic system having an axial piston pump as a control pump which is regulated by a regulating device as a function of the demands with respect to volumetric flow and pressure of a load circuit supplied by it. On the suction side, the control pump is optionally provided with a partial amount of its maximum delivery volume by a feed pump, while the remaining part of the corresponding delivery quantity is drawn in directly from a storage container, bypassing the feed pump. Possibly impermissibly high vacuums on the suction side of the control pump are detected by a suction safety device which acts on the control pump via its regulating device so that the control pump delivers smaller quantities of hydraulic fluid unitl permissible operating conditions are reached.

Hydraulic system with suction maintenance of its control pump

The invention concerns a hydraulic system for supplying a hydrostatic steering system. A central variable capacity hydraulic fluid pump supplies the steering system and a secondary consuming device via separate respective compensated pressure maintaining valves. The steering system and secondary consuming device are controlled by respective load report lines which are brought together at a changeover valve which is operative to permit the higher reported pressure to be delivered to a volume governor for the pump. Upon the secondary consuming device entering a neutral condition or a fluid loss condition, the changeover valve moves to block the load report line to the secondary consuming device; and a control circuit, including a branch line from the feed line to the steering system, maintains a higher pressure in the load report line of the steering hydraulic circuit than in the line of the secondary consuming device.

Hydraulic system for the supplying of hydrostatic steering system

In the supply of priority and lower-ranking consumers the flow to the priority consumer must be maintained even when there is a leak in the hydraulic system of the lower-ranking consumers. For this purpose the priority consumer is connected via in each case a check valve to a pump and an auxiliary pump. If the pressure generated by the pump drops for example due to a leak a valve opening the pressure line to the discharge is shut-off and the priority consumer thereby supplied with fluid delivered by the auxiliary pump.

Safety device for priority hydraulic consumer

A fluid operated positioning apparatus includes a multi-position valve operated in response to differential pressure in a fluid control circuit. The control circuit includes two adjustable throttles in series, the junction between the throttles being connected to a control device at one end of the valve. Particular relationships for the throttles are disclosed. Other embodiments include additional throttles for improved control with low pressures.

Apparatus for controlling an adjustable member

A vehicle, such as a tractor, has an attachment implement, such as a plow. An automatic controller acts upon a power lift of the plow, which moves the plow during operation in trenching position. In a first control, this motion of the plow ensues relative to the tractor, so that the vertical absolute velocity component of the plow becomes approximately zero. The plow is so moved relative to the vehicle that it moves upward during a downward motion of the plow-tractor joint and downward during an upward motion of such joint. The tractor is this completely disconnected dynamically from the plow, so that the pitching vibration behavior of the tractor is not subjected to a negative change due to the moments resulting from the forces of acceleration of the plow and affecting the plow, as is the case with a vehicle having a rigidly connected attachment implement. In a second control, the plow is moved in opposite phase to the tractor to counteract a change of its pitching angle coordinate. This results in a pitching angle behavior having an amplitude which is less than that of a tractor without an attachment implement.

Vehicle with hinged attachment implement

In a priority control device the supply flow to the lower-ranking consumer is set by a flow control valve (pressure balance) whose control chamber subjected to the control pressure of the lower-ranking consumer can be relieved of pressure via a proportional valve. The proportional valve is adjusted in dependence upon the load pressure of the priority consumer so that the flow of fluid to the lower-ranking consumer is throttled by the pressure balance when the pressure difference at the priority consumer drops on increased volume flow requirement. The priority control device thus consists of two simply constructed power valves and a small-dimensioned pilot valve.

Priority control for hydraulic consumers

A pressure responsive flow divider valve for servo-powered steering devices comprises a flow control valve having three ports to divide the fluid flow delivered by a pump between a pair of partial volumes, one flowing to the steering valve and the other flowing to a further hydraulic load. When the steering device is not operated, the further load is primarily supplied with fluid, while the flow to the load is reduced, but the steering valve is fully supplied when the steering device is actuated. The valve comprises a valve member which is actuated in response to pressure to change the cross section of the throttle in the flow control valve so that the steering valve is supplied with a relatively small volume of fluid when the steering device is not operated, whereas the valve member is shifted by a pressure increase when the steering device is actuated to supply an increased fluid flow to the steering valve as required. The valve according to the invention allows to reduce energy to drive the pump.

Pressure responsive flow divider valve for servo-powered steering devices

In the supply of a power-assisted steering and an additional hydraulic system with fluid the power-assisted steering has priority so that when the steering is actuated the influx of fluid to the hydraulic system is correspondingly throttled by a priority valve. When a leak occurs in the hydraulic system, the influx of fluid to the hydraulic system is completely shut off when the oil level in the reservoir drops to a lower limit value. The closure of the priority valve is effected by a switch valve which is disposed in one of the control pressure lines of the priority valve and which is rendered currentless on response of the sensor for the fluid level.

Safety arrangement for power assisted steerings

An apparatus for controlling the movement of a movable element as a working circuit (10) with a directional control valve (3) equipped to control devices (11, 12) which can be pressure activated in two directions. A control circuit (29) which can be connected to a fluid source (19) is used to activate the directional control valve for which the control circuit is connected to the two control devices and has an adjustable first choke (24) connected to one of the two control devices (12), a second choke (22) which is similarly adjustable and connectable to the same control device, and third and fourth adjustable chokes (27, 28) which are connectable to the other of the two control devices (11). The first and third chokes are connectable further to a storage tank (7) and the second and fourth chokes are further connectable to a pressure source. A proportioning pressure valve (45) can be connected to the other of the two control devices (11). The first and third chokes are connected to a pilot valve (38). To form a simple device with which the chokes connected in series as reference and current value elements, respectively, with as little line as possible, the proportioning pressure valve and the first and third chokes are separately connected to ports of the pilot valve. In one control position, the pilot valve interconnects the first and second chokes and connects the proportioning pressure valve to the third choke. In the other control position, the first and second chokes are interconnected through a fifth choke and the third and fourth chokes are connected directly. The proportioning pressure valve is designed as a leak-proof valve.

Apparatus for positioning a movable member

The position control and force control of a device mounted to a tractor, in particular for controlling the depth penetration of a plough, is supplemented by a lowering speed-responsive control to limit the lowering speed to a predetermined maximum value in order to increase safety of operation. Activating and disabling the lowering speed signal takes place in response to operating a mode select switch provided for the position control and force control as well as in response to a high-speed actuation of the mounted device. Furthermore, the lifting and lowering function of the hydraulic jack of the mounted device may be locked to prevent undesired motions of the mounted device when the system is put in operation.

Electric circuit for controlling a tractor-pulled mounted device

A hydraulically unblockable non-return valve has a control piston (21), the control side of which can be connected with a control pressure medium source (35) and the other side of which can be connected with a supply container (33). In order to create a hydraulically unblockable non-return valve, in which the control side of the control piston does not need to be relieved of pressure, the other side of the control piston is perpetually connected with the supply container. Also provided is a throttle bore (27) which connects the two sides of the control piston with each other.

Hydraulically unblockable non-return valve

A pressure fluid operated limit switch, particularly for a device for controlling an adjusting element in dependence upon a control value and a reference value. The limit switch includes a housing formed with a recess in which a spring-biased valve member is positioned. The valve member normally abuts against a valve seat formed by a shoulder in the switch housing is at times moved away from that seat against the force of the spring in response to a condition of the adjusting element with which the limit switch is mechanically connected. In order to ensure rapid movement of the valve member away from its seat and thus preventing throttling of the pressure fluid when the switch is in its open position the valve member is provided with the actuating element rigidly connected thereto and carrying at its free end an axially slidable sleeve biased by a spring which is clamped between that sleeve and the valve member.

Pressure-fluid operated limit switch

A suction container for two hydraulic circuits, particularly for a steering circuit and a control circuit has a housing lower portion closed with a cover. A suction tube is inserted into the housing lower portion, which tube is connected to a first consumer line. The container also includes connections which are in communication with a second consumer line and with a fluid supply container. During operation the suction container is under predetermined pressure. A filter device is disposed in the cover before the connection to the second consumer line. A pressure-limiting valve and a reverse valve openable into the container housing are also mounted in the cover.

Pressure container for two hydraulic circuits

A device for the positioning of an adjustment element dependent upon a desired level and the actual level, particularly for the adjustment of a hoist gear train of a tractor, a combine or the like, has an operating circuit 10, which has a multi-way valve 3 pressure-operated in two directions, and a control circuit 29 for the operation of the multi-way valve, connected to a pressure source 19, which is connected to two control devices 11, 12 of the multi-way valve. Circuit 29 has two adjustable series-connected throttles 22, 24, connected to one of the two control devices. The first throttle 24 is also connected to a tank 7 and the second throttle 22 is also connected to pressure source 19. Both throttles have the same maximum flow-through cross section, and are adjustable in the same manner. Third and fourth throttles 27, 28 are provided, one being between the pressure source and control device 11, and the other between the control device and tank 7. The third and fourth throttles 27, 28 are each adjustable throttles, so that both control devices of the multi-way valve can be influenced as desired. The throttles are mounted in series and have the same flow-through cross section and are adjustable in the same manner. The maximum flow-through cross section of the third and fourth throttles is selected in the same manner as the flow-through cross section of the first and second throttles.

Apparatus for adjusting the position of an adjustable element

A device for controlling the connection between a pressure medium source and a medium supply container is provided in a pressure medium operated system. The device includes a control valve with a housing formed with a longitudinal bore, in which a valve member is axially displaced between two end positions by pressure of the pressure medium. The valve member includes a piston and a seat portion facing a valve seat formed in the valve housing. The piston is of the diameter larger than that of the valve seat. A bore connected to the medium supply container is provided in the valve housing which is controlled by displacement of the piston.

Growing community of inventors

Rechtenbach, Germany

Norbert Mucheyer