Abstract: To prevent a tractor pulling a plow (P) from digging itself in, if the plow position, with respect to soil or tractor level, is controlled by an automatic control system which causes the plow to be lowered if the pulling force of the tractor decreases, slip of the drive wheels of the tractor is sensed and an overriding command signal given to the plow positioning system (S) tending to raise the plow, or, alternatively, a visual indication is given to the operator that the plough should be raised manually; the slip condition is sensed by differentiating a signal representative of plow position, with respect to time, and comparing the so differentiated plow positioning signal (or, in other words, plow dropping speed signal) with a reference which, preferably, includes such factors as tractor engine speed, tractor and/or implement weight, ground wheel adhesion, tractor gearing, and the like.

Abstract: An external gear type hydraulic pump or motor wherein the trunnions of gears in the chamber of the housing are surrounded by annular bearing members. The peripheral surface of each bearing member defines with the adjacent internal surface of the housing an arcuate gap whose width increases in a direction toward the respective end face of the corresponding gear. To this end, portions of or the entire peripheral surfaces of bearing members and/or portions of or the entire internal surfaces of the housing have a conical or spherical shape. The gaps are located in the low-pressure zone and reduce the likelihood of wear upon those end faces of bearing members which are adjacent to the end faces of the gears because the bearing members can tilt in response to increasing load without localized rubbing against the gears. Additional gaps can be provided between the end faces of the gears and the adjacent end faces of the bearing members to further reduce the likelihood of uneven wear upon the bearing members.

Abstract: An external gear pump wherein the gears are installed in an eight-shaped compartment of a central housing section which is flanked by two covers. The outlet port of the housing communicates with two arcuate recesses for metallic inserts which are biased against the adjacent gears by fluid pressure in the outlet port whereby the inserts urge the gears against those portions of the internal surface of the central housing section which are located opposite the recesses. Such portions of the internal surface are formed with narrow first cutouts which communicate with the outlet port. The internal surface is further formed with relatively wide additional cutouts which are located between the first cutouts and the recesses and communicate with the inlet port. The force which is produced by fluid in the cutouts opposes the force which urges the gears against the internal surface of the central housing section to thus reduce the force with which the stubs of the gear shafts are urged against the housing.

Abstract: A gear type hydraulic pump or motor wherein the stubs of the gears are surrounded by annular bearing members which are non-rotatably mounted in the housing. The forces which the stubs tend to transmit to the respective bearing members are counteracted by hydrostatic pressure fields produced by pressurized fluid which is entrapped in plenum chambers defined and completely surrounded by rectangular frame-like gaskets which are recessed into the surfaces surrounding the bores of the bearing members and are spaced apart from the nearest end faces of the respective gears. The gaskets may bear directly against the peripheral surfaces of the stubs or against the peripheral surfaces of cylindrical sleeves which are received in the bores of the bearing members and only the outer end portions of which are a tight fit in the respective bearing members.

Abstract: A gear pump wherein the trunnions of two or more mating gears are mounted directly in ring-shaped bearing members or in bearing sleeves which are fitted into the bearing members. The deformation of those surfaces of bearing members which are immediately adjacent to the end faces of the corresponding gears is prevented by enlarging the bores of the bearing members in close proximity to the end faces of the gears, by forming the internal surfaces of the bearing members with circumferentially complete or arcuate grooves, or by reducing the outer diameters of bearing sleeves in immediate proximity to the end faces of the gears. This insures that the deformation of bearing members in response to transmission of forces by the respective trunnions is not propagated all the way to those surfaces of the bearing members which are immediately adjacent to the end faces of the gears.