Abstract: A hydrostatic servo assembly unit (1) for being arranged inside, outside or distant from a variable displacement hydrostatic unit (100) and for controlling the displacement of the variable displacement hydrostatic unit (100). The servo assembly unit (1) includes a servo housing (10) in which at least one servo piston (40) is arranged. The piston head (42) of the servo piston (40) can be pressurized such that the servo piston (40) can move linear relative to a servo cylinder (12) formed in the servo housing (10). The servo assembly unit (100) further includes a movable output element (49) protruding outside of the servo housing (10), which can be mechanically coupled to a displacement element (102) of a variable displacement hydrostatic unit (100).

Abstract: The invention relates to a hydraulic axial piston machine (1) of dry case type of construction, whose case (2) is provided for connection to a gearing case (21) so as to form a fluid-tight overall case. The case (2) has openings (10) which permit the passage of leakage hydraulic fluid or of lubricant into the gearing case (21). By means of this design, splashing losses of the axial piston machine (1) are eliminated, and the leakage hydraulic fluid or the lubricant serve for the lubrication both of the axial piston machine (1) and of the gearing (20).

Abstract: The invention relates to a hydraulic axial piston machine (1) of dry case type of construction, whose case (2) is provided for connection to a gearing case (21) so as to form a fluid-tight overall case. The case (2) has openings (10) which permit the passage of leakage hydraulic fluid or of lubricant into the gearing case (21). By means of this design, splashing losses of the axial piston machine (1) are eliminated, and the leakage hydraulic fluid or the lubricant serve for the lubrication both of the axial piston machine (1) and of the gearing (20).

Abstract: The output speed of a hydrostatic unit in a transmission is determined using a pair of variable reluctance sensors, one on a gear driven by the hydrostatic unit output and the other on the carrier of the planetary system. One of the two sensors will always be measuring a relatively high speed from which the hydro output is directly determined or indirectly determined using the current engine speed. Thus the frequency of the speed sensor used to determine the hydrostatic unit output speed is not decreased at slow hydrostatic unit output speeds.

Abstract: A loop flushing arrangement for controlling a closed circuit hydraulic propulsion drive. The variable displacement pump 12 is driven by a combustion engine 11. A flush valve 21 is used to clean and cool the hydraulic fluid in the closed hydraulic circuit. The flush valve is electrically operated and, as a result, permits novel and varied control options. The flush valve is controlled automatically, for example by a digital computer 1 as a function of the vehicle speed, the rotational speed of the combustion engine 11, or the temperature of the hydraulic fluid in the variable displacement pump 12. This results in the flushing procedure only being triggered and carried out if the operating state of the vehicle requires and permits it, i.e. when traveling at high speeds, for example.

Abstract: A description is given of an adjustable hydrostatic axial piston machine whose angle can be varied by means of a servo-piston (9) to which actuating pressure can be applied and which is connected to an electrohydraulic control valve. The control valve has a control piston (15) and a control sleeve (22) which can be moved axially relative to one another. The control piston (15) can be axially adjusted with a stepper motor (10), and the control sleeve (22) is coupled mechanically or hydraulically to an adjusting mechanism (9, 7) for the angle for the purpose of feeding back the angle.

Abstract: A variable displacement bent axis hydraulic unit includes a control mechanism having a control housing with a displacement feedback sleeve and spool connected by a spring. A computer controls a proportional solenoid fluid valve that is in operative fluid engagement with the end of the spool opposite its spring connection with the displacement feedback sleeve. The displacement feedback sleeve is urged by the spring into engagement with a cam member on the yoke of the bent axis unit.

Abstract: A special ball joint for servo piston actuation in a bent axis unit includes an elongated actuator rod having a substantially spherical external surface on a first end and a servo piston on a second end. Also included is a single-piece yoke adapted to carry a cylinder block and rotate about an axis of rotation. A socket having a substantially spherical surface is interposed between the yoke and the spherical surface on the rod such that the actuator rod rotates the yoke with forces residing in at least two planes when hydraulic pressure is applied to the servo piston. Two servo pistons and two such ball joints can be applied to the yoke to obtain rotation of the yoke which is up to greater than plus or minus 45° from a neutral position. The external surface on the first end of the actuator rod and the socket must be mating so as to provide freedom of movement. The socket can be incorporated into the yoke itself. The foregoing servo pistons are received in servo bores of a one-piece control housing.

Abstract: A vehicle having a hydrostatic drive and a hydraulic control apparatus, in which the hydrostatic drive has a variable displacement hydraulic pump and a hydraulic motor in a closed circuit, an internal combustion engine for driving the hydraulic pump and a variable displacement pump, producing a volumetric output flow, of an open circuit, and a retarder valve arranged in the open circuit and intended for the hydraulic absorption of braking energy. The retarder valve has a valve and a pressure-limiting valve, connected thereto, for throttling the volumetric output flow of the variable displacement pump. The variable displacement hydraulic pump, the variable displacement pump and the retarder valve are controlled by a digital electronic unit for the respective driving and working functions.