Abstract: A hydraulic control circuit for a radial piston engine with two speeds. The changeover between the speeds takes place through the alteration of the absorption volume, the delivery side being connected to the discharge side with a bypass connection by a valve arrangement for a selected number of engine pistons. The control circuit provides a space-saving way of ensuring that the changeover between speeds occurs smoothly and in such a manner to preserve the individual components as far as possible. To this end, at least one intermediate switching position, in which the delivery side is throttled to the discharge side, i.e. connected by a diaphragm-type arrangement, is provided in front of valve arrangement between the two end switching positions. The valve arrangement is preferably driven such that a valve body can be moved through the intermediate switching position at a controlled speed.

Abstract: What is disclosed is a pilot apparatus whereby at least two mechanically operable control valves and two electrically or electro-hydraulically operable control valves may be driven. The pilot apparatus comprises a pivoted lever having two handles, on each of which a switching element for driving the electrically/electro-hydraulically operable control valves is provided.

Abstract: A free-piston engine directed to reduced throttling losses at minimum expenditure is provided. The free-piston engine has an engine piston, and a hydraulic piston co-operating with the engine piston. The engine piston may receive application of a force in the direction of compression via a hydraulic cylinder. A pressure in a high-pressure accumulator means or a low-pressure accumulator may be communicated to the hydraulic cylinder via a switchover valve. Between the hydraulic cylinder and the switchover valve is a valve assembly including a control piston. A connection to the high-pressure accumulator means may be controlled open with the aid of the control land of the control piston.

Abstract: A hydraulic distributor that has a regulating balance including a housing hollowed in the distributor body and containing coaxially a fixed central core. A tubular plunger is interposed sliding freely, coaxially, between the core and the housing and co-operates with a lateral orifice connected to a working orifice. The core and the plunger define between them an annular chamber. The plunger has a first radial annular surface subjected to the highest charge pressure (LS) and a second annular surface subjected to the pressure of the intake fluid. A central passage in the core constitutes a first orifice emerging at one end of the housing exposed to the highest charge pressure (LS). A second orifice emerges in the annular chamber and a third orifice is located opposite the other end of the housing and remains closed by the plunger as long as the charge pressure of the distributor is below the highest charge pressure (LS).

Abstract: The present invention relates to a hydro-transformer including a hydraulic machine, a switching valve and a control means. A work port of the switching valve, which may optionally be connected hydraulically with a pressure port of the switching valve or a drain port of the switching valve, is connected with a first port of the hydraulic machine. The second port of the hydraulic machine is in hydraulic connection with a drive member. The switching valve is driven by the control means in response to a signal characterizing the volume flow into the hydraulic machine. Where the driver member is a cylinder, its extension may be carried out at a constant velocity and independently of a load, and energy may be recovered upon retraction. Due to the provision of a further switching valve between the second part of the hydrostatic motor and the drive member, a higher pressure may be generated at the drive member in the presence of a low pressure at the pressure port of the switching valve.

Abstract: A hydraulic circuit for controlling a consumer of a mobile work tool, wherein the pressure in supply and outlet lines towards the consumer is limited by means of pilot-controlled pressure control valves. The pilot control stage of these pressure control valves may be adjusted in accordance with a pilot control pressure corresponding to the load of the work tool.

Abstract: The invention concerns a technically optimized radial piston engine comprising a cam ring and a cylinder block arranged so as to rotate about an axis of rotation relative to the cam ring and having a plurality of cylinders oriented in the radial direction of the cylinder block. A piston capable of being radially displaced is located in each cylinder, resting on the cam ring via a roller. Said roller is mounted on the piston so as to rotate about an axis parallel to that of the cylinder block and rests axially, relative to its axis of rotation in the cylinder, against roller guides arranged on its surfaces. Said radial piston engine is characterized in that the roller guides are integrally mobile with the roller associated with them, in the piston stroke direction, and thereby driven by the roller both when the piston performs a loaded stroke and an idle stroke, without any contact occurring between the roller guides and the cam ring.

Abstract: There is disclosed an inching braking system wherein a brake piston of a brake valve assembly initiates an actuation movement of the brake piston by way of an actuator only after a predetermined stroke of a driving member for an inching piston.

Abstract: The present invention relates to a drive mechanism for a pump (10) implemented by means of a drive motor (20), the rotational speed and torque of which are influenced by a frequency converter (30). The frequency converter (30) is arranged on a heat dissipator (40) confining a flow of the pressure liquid guided to the pump (10). It is advantageous to also arrange the drive motor (20) inside the said heat dissipator (40), for this makes it possible to perform intense forced air cooling of a pump-drive motor system without the necessity of an additional cooling liquid. The drive motor (20) preferably has a central arrangement inside a tubular heat dissipator and is exposed to the pressure liquid over its entire circumference. Baffles or offset connecting sleeves allow for uniform flow through the entire heat dissipator (40).

Abstract: A hydraulic steering system, which is used, in particular, for a mobile working machine, and has a steering unit that can be actuated by a first steering member, which is constructed as a steering wheel, that has a first fluid connection, which is connected to a pressure chamber of a steering motor, the pressure chamber being subjected to pressure for a steering movement to the left, and that has a second fluid connection, which is connected to a pressure chamber of the steering motor, the pressure chamber being subjected to pressure for a steering movement to the right, and which has a control valve that can be actuated by a second steering member, which is constructed in the manner of a joystick, and likewise has fluid connections that are connected to the pressure chambers of the steering motor.

Abstract: A hydraulic control arrangement for a mobile working machine has at least one hydraulic cylinder with the aid of which a working tool is moved, a directional control valve for controlling pressure-fluid channels between chambers of the hydraulic cylinder, a pressure-fluid source and a tank, a hydraulic accumulator connected to the pressure-fluid source via a filling line, and a control valve to open and to close a connection between the hydraulic accumulator and a pressure chamber of the hydraulic cylinder. To achieve a damping of pitching movement of the machine, a pilot-operated shutoff valve is connected upstream of the pressure chamber of the hydraulic cylinder, and opens when the directional control valve is actuated to allow pressure fluid to flow off from the pressure chamber to the tank.

Abstract: An LUDV-circuit for controlling at least one of a lower-load consumer and a higher-load consumer is disclosed, wherein a metering orifice and a downstream pressure compensator for maintaining constant the pressure drop across the metering orifice constant are associated with each consumer. The pressure compensator of the lower-load consumer is associated with a bypass channel capable of being controlled open, whereby the pressure compensator of this consumer may be bypassed.

Abstract: A hydraulic control arrangement for a mobile working machine which serves for damping pitching vibrations and has a hydraulic accumulator which can be connected to a hydraulic fluid source via a filling valve and which can be connected to a pressure chamber of a hydraulic cylinder, and a shut off valve which, with a first condition fulfilled, can be moved into a through position in which hydraulic fluid can flow through it in the direction from the hydraulic accumulator to the pressure chamber of the hydraulic cylinder and vice versa. The shut off valve may, at the same time, also be the filling valve. A first condition may be that a certain traveling speed is exceeded. Limiting the accumulator pressure to a limit pressure is intended to keep the wear on the hydraulic accumulator low and to increase the safety.

Abstract: A drive device which has small dimensions an axial and radial directions. The small dimensions of the device are a result of a brake body of a friction brake provided in the drive device being located at least partially within an enclosure configured in a rotor.

Abstract: A PID controller has a parallel arrangement of a P-element, an I-element, and a D-element coupled to a first summation point for adding their respective output signals, a summation signal produced by the first summation point being employed for control of a variable. An actual value of the controlled variable is inputted to the parallel arrangement of the P-element, the I-element, and the D-element. The I-element is a series arrangement of a weighting section followed by an integrator, the I-element being coupled to the weighting section by a second summation point. The controller applies a time derivative of the actual value of the controlled variable to the second summation point, the second summation point subtracting the derivative from a signal outputted by the weighting section of the I-element.

Abstract: The supply of pressure medium to hydraulic or pneumatic cylinders is usually carried out by means of pressure medium lines which are connected to the heads of the cylinders by means of standardized connection threads. This method of supplying pressure medium requires a minimum wall thickness of the casing of the cylinder in the connection region. In order to permit secure attachment of the pressure medium lines even when the minimum thickness which is necessary for the use of the standardized connection thread is not present, the outside of the casing of the cylinder is flattened in the vicinity of the exit point of a duct provided for the supply of pressure medium. A connection plate which is provided with ducts for the pressure medium is secured to the flattened part of the casing, and the connection plate is provided with a port for a pressure medium line.

Abstract: The invention concerns a hydraulic control circuit in which the pressure medium conveyed by a hydraulic pump of variable delivery (10) is fed, in each case via a metering aperture (17, 31), as a priority to a first hydraulic consumer (14) and only secondly to a second hydraulic consumer (15). A priority control system is now produced without additional delivery losses and with sufficient amounts of pressure medium being conveyed in that the valve member (48) of the priority valve (45) can be acted upon in the closure direction of the connection between the first connection (46) and the second connection (47) by a pressure prevailing in a line section (13) upstream of the first metering aperture (17).

Abstract: A hydraulic directional control valve with a regulating balance comprising a plunger which can be displaced in a housing (13) under the action of a differential pressure (&Dgr;p) between the intake pressure (P) and the highest load pressure (LS), and which is designed to open, in proportion to this differential (&Dgr;p), a lateral orifice of the housing linked to a working orifice (A, B) of the directional control valve; the wall of the housing and/or the plunger is provided with a calibrated passage linking the intake of fluid at pressure (P) and the lateral orifice when the plunger is pushed back into an end position by the pressure (LS) exceeding the intake pressure (P); consequently, in spite of the excess value of the pressure (LS) intended to inhibit operation of the directional control valve, hydraulic fluid is delivered to the lateral orifice at a low rate and allows the hydraulic receiver controlled by the hydraulic directional control valve to be displaced at a low rate.

Abstract: An hydraulic control arrangement which is chiefly used for a mobile working machine, especially for a wheel loader, and has at least one hydraulic cylinder with the aid of which a working tool can be moved, a directional control valve for controlling the pressure-fluid channels between the hydraulic cylinder, a pressure-fluid source and a tank, a hydraulic accumulator which can be connected to the pressure-fluid source via a filling line, and a control valve with the aid of which a connection between the hydraulic accumulator and the hydraulic cylinder can be controlled to open and close. The aim of such a hydraulic control arrangement is to avoid undesired movements of the hydraulic cylinder. This is achieved wherein the fact that the hydraulic accumulator can be filled up only when the directional control valve is actuated.