Abstract: An apparatus for damping the pressure increase of hydrostatic drives, especially axial piston pumps, with swash plate control and pre-biased oil circulation, wherein the pressurized oil compartment of an adjustment cylinder is connected with the low pressure side of the oil infeed of the pump via a check or nonreturn valve which opens in the direction of the low pressure conduit of the oil infeed. There is further provided a supply pump and a mechanical adjustment mechanism. The adjustment cylinder is rigidly connected with the mechanical adjustment and the bottom side of the adjustment cylinder is connected via a regulation throttle and a check valve means with the pressure side of the supply pump.

Abstract: An axial piston machine has a cylinder barrel mounted on a shaft and rotatable with respect to a portion of the casing. Between the cylinder block and the casing portion is a disc. The side of the disc adjacent the casing portion is concave and abutting casing portion is correspondingly convex. The disc is restrained against rotation and forms part of the valving means for the cylinder barrel. In one embodiment the casing and shaft are in two articulated sections. The shaft sections lie in a common plane and are pivotable with respect to each other about a point and the casing sections are pivotable about an axis normal to that plane and offset with respect to the shaft pivot point. In another embodiment the casing and shaft are each a single unit.

Abstract: A valve in the production flow line of an oil well closes a reed switch indicative of fluid being pumped through the line. The switch closure activates a first oscillator whose count is compared with a variable frequency oscillator having a frequency of approximately one-half that of the first oscillator. The comparison is made over a given period of time to ascertain the percentage of time the valve has been open and passing fluid. Theoretically, the valve should be open approximately fifty percent of the time because almost that much time is taken on the downstroke of the pumping assembly when no production is occurring. The integrated timer is adjusted to shut down the system when the percentage of time the valve is open drops to the preselected amount, usually equal to or less than around 50 percent. In response to the integration timer producing a signal, a shutdown timer is turned on which restarts the cycle after a preselected amount of time.