A method for controlling a hydraulic pumping system that includes a centrifugal pump operating at a functional point. The method uses parameters of the centrifugal pump at the functional point and end-of-lines characteristics of the centrifugal pump to determine an updated Net Positive Suction Head Required, NPSH.sub.r, value.

A method and computer program product for defining a PWM drive signal having a defined voltage potential. The PWM drive signal has a plurality of “on” portions and a plurality of “off” portions that define a first duty cycle for regulating, at least in part, a flow rate of a pump assembly. At least a portion of the “on” portions of the PWM drive signal are pulse width modulated to define a second duty cycle for the at least a portion of the “on” portions of the PWM drive signal. The second duty cycle regulates, at least in part, the percentage of the defined voltage potential applied to the pump assembly.

A method and computer program product for defining a PWM drive signal having a defined voltage potential. The PWM drive signal has a plurality of “on” portions and a plurality of “off” portions that define a first duty cycle for regulating, at least in part, a flow rate of a pump assembly. At least a portion of the “on” portions of the PWM drive signal are pulse width modulated to define a second duty cycle for the at least a portion of the “on” portions of the PWM drive signal. The second duty cycle regulates, at least in part, the percentage of the defined voltage potential applied to the pump assembly.

The subject matter of the present invention is a variable-delivery pump device comprising a pump body (2), an impeller (5) and a shut-off element (8) capable of translational movement and adjustably covering at least part of the outer periphery of the impeller (5), as well as a cam element (9) which is rotationally driven and engages with said shut-off element (8) for effecting the translational movement thereof. The pump device (1) is characterized in that the shut-off element (8) and the cam element (9) have cylindrical walls (8′) and are arranged concentrically around the housing (7) that accepts the shaft (6) of the impeller (5), and in that the rotary cam element (9) is situated on the inside of the sliding shut-off element (8) and, on the external face of its wall, has at least one helical guideway (11) on which there runs at least one corresponding follower element (12) secured to the internal face of the wall (8′) of the shut-off element (8).

A method and computer program product for defining a PWM drive signal having a defined voltage potential. The PWM drive signal has a plurality of “on” portions and a plurality of “off” portions that define a first duty cycle for regulating, at least in part, a flow rate of a pump assembly. At least a portion of the “on” portions of the PWM drive signal are pulse width modulated to define a second duty cycle for the at least a portion of the “on” portions of the PWM drive signal. The second duty cycle regulates, at least in part, the percentage of the defined voltage potential applied to the pump assembly.

A pump front chamber automatic compensation device for improving closed impeller backflow is provided. The automatic compensation device is mounted on the inner wall surface of the pump body front chamber, extending from the inner wall surface of the pump body front chamber to the impeller front cover plate, stopping the flow of fluid from the impeller outlet to the pump front chamber. The automatic compensation device includes a spacer plate and a compensation feedback device. One end of the spacer plate extends into the pump front chamber, and the other end is connected to the automatic compensation assembly, through which the length of the spacer extension is automatically compensated. The pump front chamber automatic compensation device can prevent the fluid flowing out of the impeller outlet from entering the front chamber of the centrifugal pump, thus improving the operating efficiency and stability of the centrifugal pump.

A vacuum pumping apparatus may include: a common pumping line having a plurality of pumping line inlets and a pumping line outlet, each pumping line inlet being configured to couple with an outlet of an associated plurality of vacuum processing chambers; at least one primary vacuum pump in fluid communication with the pumping line outlet to pump gas from each vacuum processing chamber; and control logic operable to control operation of the primary vacuum pump in response to an indication of an operating state of the plurality of vacuum processing chambers. In this way, the performance of the primary vacuum pump can be adjusted to match the load provided by the processing chambers and when there is an excess capacity, the performance of the primary vacuum pumps can be reduced, which can lead to significant energy savings and reduce wear on the pump.

A method of controlling a delivery pressure of an aircraft engine fuel system includes operating a rotodynamic fuel pump hydraulically connected to the fuel system to pump a fluid from an inlet of the rotodynamic pump and out of an outlet of the rotodynamic pump for delivery to the fuel system. The method further includes varying an angular relationship between the inlet and the outlet of the pump to control the delivery pressure. An aircraft engine fuel system and a rotodynamic pump are also described.

A hydraulically powered rotary actuator is described including: a hydraulic linear actuator which is moveable in both directions between a retracted position and an extended position; a clutch device which is operable between an engaged condition and a disengaged condition; and a rotary output member; wherein the linear actuator is coupled to the rotary output member by way of the clutch.

A bypass mechanism for automatic swimming pool cleaners (APCs) is detailed herein. The bypass mechanism may be a valve or other mechanical device that limits operation of the APC by diverting water away from the APC or otherwise ceasing operation of the APC after a predetermined period of time (e.g., after the desired run-time for the APC has been reached). In this way, the bypass mechanism limits the time the APC operates, even if the pump that otherwise would drive the APC remains energized.