Abstract: A gear pump is disclosed having an integrated gear cavity and bearing receptacle that includes a fluid path for lubricating the bearings. The preferred embodiment includes a helical gear pump having a manifold with inlet and outlet ports. The integrated gear cavity and bearing receptacle are located in a one piece molded end cap. The bearing receptacle receives a coupled bearing assembly. Together, the coupled bearing assembly and the bearing receptacle define a supply path outside the bearings along the bearing receptacle and a return path through the bearings so that fluid can pass by, and lubricate, the bearing-axle interface.

Abstract: A pump motor controller for making pump motor speed independent of fluid pressure at the inlet and outlet of the pump. A first embodiment employs feedback to cause pump motor speed to converge to a desired speed established with a reference input signal. Based on this feedback, forward and reverse drive amplifiers in the first embodiment cause the pump motor speed to track the desired speed. A second embodiment employs a controller that produces drive signals to a stepper motor in proportion to a reference frequency. The controller and stepper motor in the second embodiment achieve speed control at low speeds without the use of a feedback control loop.

Abstract: A modified elliptical gear defined by a modified elliptical shape having perpendicularly disposed major and minor axes, and bulged portions projecting outwardly beyond the contour of a true ellipse in peripheral regions between the major and minor axes. A computer is preferably used to rotate a simulated hobbing rack having a row of hobbing teeth around the modified elliptical shape. The outline of the hobbing rack is traced at selected positions during the rack rotation to produce a profile of a modified elliptical gear with projecting gear teeth. A topping shape is superimposed upon the gear profile to selectively top the gear teeth. The modified elliptical gear profile is transmitted to a machining device operable to produce a modified elliptical gear.

Abstract: Pump heads comprising at least two gear-pump chambers are disclosed. Each chamber comprises a housing which defines a corresponding pump cavity. Each cavity contains a driving gear and at least one driven gear and has a separate inlet and outlet. The pump cavities are hydraulically interconnected by a fluid conduit allowing passage whenever the pump chambers are pumping a fluid so as to generate a higher pressure in one cavity relative to the other cavity, of the fluid from the higher-pressure cavity to the lower-pressure cavity sufficient to maintain hydraulic prime of both cavities. The invention is particularly useful for ink jet printing applications.