Abstract: Methods and systems pertaining to generating a startup or other operating order of pumps of a pumping system for performing a subterranean formation fracturing operation, and/or another pumping operation, and for coordinating distribution of flow rates to the pumps for performing the pumping operation.

Abstract: A fan array is provided having a frame including a plurality of frame members. The frame members are joined to define a plurality of chambers. Each of a plurality of fan units is configured to be positioned in one of the plurality of chambers. Each fan unit has a motor. A plurality of local motor controllers are joined to corresponding motors. The local motor controllers are configured to control an operation of the corresponding fan unit. A master controller is configured to communicate with the local motor controllers. The master controller is configured to provide the local motor controllers with target operating parameters for the corresponding fan units.

Abstract: Examples described herein relate to fan control. For example, operating a computing device includes storing data on a data storage device of the computing device and controlling a fan of the computing device based on throughput of the data storage device.

Abstract: According to some embodiments, system and methods are provided, comprising providing a dual-mode model for a reciprocating compressor, wherein the model includes a measurement mode and a tuning mode; receiving one or more inputs to the model from an operating reciprocating compressor; and in response to receipt of the one or more inputs, executing the model in at least one of the measurement mode and the tuning mode, wherein: in a measurement mode, execution of the model further comprises calculating an actual flow rate of gas in the compressor based on the one or more inputs; and in a tuning mode, execution of the model further comprises calculating one of an unloader setting and a speed set point of a physical element of the compressor for a given flow rate of gas. Numerous other aspects are provided.

Abstract: A pressure control device for controlling a compressor includes a pressure sensor configured to measure pressure of a pressure line and a processing circuit. The processing circuit is configured to receive the measured pressure of the pressure line from the pressure sensor and control the compressor based on a set-point and the measured pressure. The pressure control device includes a mechanical switch sensitive to the pressure of the pressure line and configured to move between an open position and a closed position responsive to the pressure of the pressure line. Movement of the mechanical switch into one of the open position or the closed position causes the compressor to turn off and overrides the control of the compressor by the processing circuit.

Abstract: The bilge pump safety system comprises a bilge pump, a primary switch, a monitor switch, and a control system. The primary switch is a first float switch that controls the operation of the bilge pump based on the level of liquid accumulated in the bilge that is protected by the bilge pump. The monitor switch is a second float switch installed within the bilge such that the monitor switch mimics the operation of the primary switch. By mimic is meant that: 1) when the primary switch is closed the monitor switch is closed; and, 2) when the primary switch is open the monitor switch is open. The control system simultaneously monitors the status of both the primary switch and the monitor switch. In situations where the operation of the monitor switch does not mimic the primary switch, the control system generates a message to an appropriate authority.

Abstract: An electro-mechanical actuation system for a piston-driven fluid pump. The electro-mechanical actuation system includes a plurality of electro-mechanical actuators, and a control system electrically connected to the plurality of electro-mechanical actuators. Each electro-mechanical actuator is configured to operatively couple with a piston of the fluid pump. The control system is configured to determine a target output of fluid to be pumped by the fluid pump, individually control a speed and a phase at which each electro-mechanical actuator actuates the piston, such that the plurality of cylinders collectively pump fluid at an actual output that corresponds to the target output, and in response to detecting an operating condition, individually adjust the speed and/or the phase at which one or more of the electro-mechanical actuators actuates the piston based on the operating condition to thereby cause the actual output of the fluid pump to correspond to an updated target output.

Abstract: Apparatus features a signal processor or processing module configured to respond to signaling containing information about a set point and a speed related to one or more pumps in a pump system, e.g., including a variable speed multiple pump booster system, operating at a substantially constant discharge pressure; and determine an adjustment to the set point to compensate for system friction loss and maintain the substantially constant discharge pressure of the variable speed multiple pump booster system for flow variation, based at least partly on the signaling received. The signal processor or processing module 10a provides corresponding signaling containing information to control the one or more pumps in the variable speed multiple pump booster system.

Abstract: The safety apparatus for a brake of a vehicle includes a first line and a second line. The first line includes an exhaust manifold, an engine, an intake manifold, a check valve, a vacuum hose, a vacuum switch, a booster, a check valve, a vacuum hose, a negative connection portion, a vacuum switch and a brake booster, and the second line includes a vacuum hose, a check valve, a booster, a check value, a vacuum hose and a vacuum pump, which are connected to the negative connection portion. The apparatus can isolate a supply of electric power to a fuel motor to stop starting of the engine when the brake booster lacks a vacuum because of a deterioration of a performance of an auxiliary vacuum pump, and enable the brake to normally operate so as to prevent an accident even though a sudden acceleration occurs or the engine suddenly stops.

Abstract: Method for controlling a turbocompressor, whereby a compressed air line (5) is connected to this turbocompressor (1) with a non-return valve (6) provided therein, characterised in that, when one or several process parameters exceed a predetermined limit, the rotational speed of the turbocompressor (1) will be reduced very suddenly to a predetermined minimum rotational speed and the above-mentioned non-return valve (6) will be closed and in that, after the above-mentioned reduction of the rotational speed, when one or several gear-down conditions are fulfilled, the rotational speed of the compressor (1) will be increased again and the non-return valve (6) will be opened.

Abstract: A fan control system for a fan on a motherboard includes an I/O controller installed on the motherboard and a control circuit electrically connected to the I/O controller. The fan includes a motor and a rotation speed detecting chip. The I/O controller outputs a rotation speed control signal and a pulse width modulation (PWM) signal. The rotation speed detecting chip detects a rotation speed of the fan, and outputs a rotation speed feedback signal according to the rotation speed of the fan. The I/O controller receives the rotation speed feedback signal, and adjusts a duty cycle of the PWM signal accordingly to change the rotation speed of the fan. The control circuit receives the rotation speed control signal, and outputs a fan driving signal accordingly. The motor receives the fan driving signal, and drives the fan to rotate in a direction according to the fan driving signal.

Abstract: Compact, lightweight, battery operated, self-priming, positive displacement pump for storing in a toolbox or tool belt includes an elongated housing having a longitudinal axis, and an inline configuration including a positive displacement pump assembly to respond to a motor assembly drive torque, self-prime, and pump fluid from an input port to an output port, a motor assembly to respond to signaling and provide the motor assembly drive torque, a pump control interconnect assembly to provide the signaling to control the operation of the motor assembly by current based on run dry mode or over current, by time based on a timer set to run for an amount of time, or voltage based on over/under voltage; and a rechargeable battery housing/assembly to respond to recharging signaling and with a rechargeable DC power supply and power control module for providing some combination of inrush, overcharging, over-discharging, short circuit, over current protection.

Abstract: The invention relates to a method for starting at least one asynchronous electric motor of a large hydraulic excavator having a service weight >100 t and having an electrohydraulic drive, in that the particular electric motor is transferred from an idle position to an operating position by using a three-stage motor starting process, wherein the volumetric flow rate of at least one hydraulic pump operatively connected to the electric motor is set to the delivery rate V=0 during all starting stages of the electric motor and the delivery rate V of the hydraulic pump is controlled to a value >0 only after the last starting stage of the electric motor by activating an actuator.

Abstract: A drive device (2) for the oil pump (6) of a motor vehicle automatic transmission, in which the oil pump (6) on the one hand can be coupled to the drive motor by way of an overrunning clutch (34) and on the other hand is drivingly connected to an auxiliary electric motor (22), which is powered by the on-board power supply of the motor vehicle. The electric motor (22) is arranged outside of the pump housing (8) and is drivingly connected to a driven pump impeller wheel (ring gear 10) that is arranged in the pump housing via a non-rotatable connection.

Abstract: Apparatus for maintaining differential internal fluid pressure in a dual fluid chamber object where it is desired for one chamber to have greater internal pressure than the other includes a sensor for generating a differential signal indicating the difference in pressure between the chambers, a pressure sensor for generating a pressure signal indicating the pressure inside the chamber desired to have less pressure, a comparator for generating a first output when the differential signal is less than a predetermined minimum differential value, a second comparator for generating a second output when the pressure signal is less than a predetermined minimum pressure value, where the predetermined minimum pressure value biased by the first output, and blowers coupled to the respective chambers and responsive to said first and second outputs respectively.

Abstract: The invention relates to an electronic driving device (20) for turning on and off a synchronous pump, that is a pump (15) comprising a synchronous electric motor (1) with a permanent-magnet rotor (8), comprising:—at least a static power switch (17) inserted in series between the motor (1) and an AC electric power supply source (Vp); and—a processing unit (16) having at least an input receiving a synchronism signal (V) and a control output connected to said switch (17); characterized in that it is enabled by a signal emitted by a float level sensor (40) and includes an input receiving a signal (a) by a position sensor (21) detecting the rotor (8) polarity and position; the pump turn-on and off being regulated according to the signal emitted by said level sensor (40) and to a measured difference between a critical load angle (8) and a current load angle computed during different working conditions of the pump.

Abstract: This invention relates to a safety system for an electrically driven medical delivery device for delivering a dose of medication, wherein the safety system is configured for preventing delivery of an erroneous dose of the medicament and comprising detector means for registering mechanical movement, the system comprising at least two detector means (10, 11) for detecting a mechanical parameter and for emitting signals to control circuits (14, 15) configured for controlling the rower supply to driving means (12) for the delivery device. Further, this invention relates to a computer-readable medium comprising a program for controlling a delivery device etc. This allows providing a system that works very quickly, accurately and reliable as to preventing an erroneous dose of medication.

Abstract: The present disclosure provides a method and system to supply pumping capabilities to a wet and dry vacuum cleaner. A single motor can operate a vacuum unit and the pump distinct from the vacuum unit. A port in the vacuum flow path can act as a vacuum tap to prime the pump when necessary. The pump can directly pump the fluids without having to flow first into the drum container of the vacuum cleaner. The system can allow independent operation of the vacuum unit and the pump and at different, more optimal speeds for each, allowing a higher performance on each of the vacuum unit and the pump, since maximum power for the system can be provided to either the operating device while the other one is not operating. Accordingly, the disclosure further provides a system and method for separately engaging and disengaging the vacuum unit and the pump.

Abstract: Methods and systems for improving the efficiency of a pumping process by controlling the operation of the pumps involved based on certain parameters characterizing the pump. A pump unit is coupled to a pump controller which is in turn, coupled to a pump modulator. A master controller drives the pump modulator based on a desired output parameter for the system. The pump modulator then drives each pump unit through its corresponding pump controller in a manner for the system to achieve optimal performance.

Abstract: A respiration system is provided with an electrically driven rotary compressor as a gas delivery unit. The system makes a low-noise mounting of the gas delivery wheel possible. The gas delivery wheel can also be washed and sterilized and ensures a reliable separation of the breathing gas from the electric components. The respiration system rotary compressor is mounted magnetically axially and radially during operation.

Abstract: A method of calculating the position of the rotor of a motor (1) in for example an electrical power assisted steering assembly is disclosed. The method comprises the steps of measuring the output shaft (2) (i.e. steering column) position, and scaling the measured value to produce an estimated motor rotor position value. This estimated value will be relative to an arbitrary datum point, and so the method further includes steps of adding an offset value derived from low resolution measurements of rotor position obtained using Hall effect sensors provided on the motor. Offsets for compensating for backlash and (in a second embodiment) compliance can also be included. Thus, the method allows high resolution information from an output shaft sensor (e.g. a torque sensor with a position dependent output) to be combined with the low resolution output from the Hall effect sensors to produce a high resolution rotor position signal.

Abstract: A power system for an implantable heart pump is provided. The system includes two batteries, a microprocessor controller, two motor drivers, a multiplexer, two stators and a TET coil. During normal operation, only one battery and one motor driver are in use at a time to drive both stators.

Abstract: Disclosed is a method and apparatus for controlling multistage systems where the relative capacities (process gains) of each stage are known. The method uses a split-range control concept in order to control multiple stages with a single feedback controller, such as PID. Stage combinations are generated automatically and sequenced to provide contiguous control and optimum control resolution across the overall range of the multistage system. The control method incorporates hysteretic deadzones to improve robustness around stage transition points. The assumption of a tuned PI feedback controller allows the size of the deadzone to be related to general control performance requirements applicable across classes of similar systems. A simulated HVAC&R system is used to evaluate the method and it is compared an alternative approach.

Abstract: A liquid pump and controller with separate pump activation and deactivation mechanisms that are both closed detector devices is provided. The pump activation mechanism includes a float device that activates a pump motor when water within a housing of the pump reaches a high water level. The pump deactivation mechanism includes a sensor that detects the load on the pump motor and deactivates it when the sensed load indicates that the water within the pump housing has reached a low water level.

Abstract: An electronic control system is disclosed to control and to prevent damage to a standalone or a network of oil free, two stage compressor packages. The electronic control system uses pressure and temperature sensors to detect actual shutdown conditions or predict shutdown conditions based on the operating state of the compressor package and the current temperatures or pressures of the air at strategic locations in the compressor package. It has been determined through experimentation that, if the pressure at the inlet of the stage two compressor is less than the discharge pressure of the stage two compressor by more than an allowable value, then a high temperature condition will occur in the stage two compressor and cause the compressor to seize.

Abstract: A liquid pump and controller with separate pump activation and deactivation mechanisms that are both closed detector devices is provided. The pump activation mechanism includes a float device that activates a pump motor when water within a housing of the pump reaches a high water level. The pump deactivation mechanism includes a sensor that detects the load on the pump motor and deactivates it when the sensed load indicates that the water within the pump housing has reached a low water level.

Abstract: An intelligent fan system includes a microcontroller having memory and an interface which provides a connection to a host computer system. The host computer system dynamically provides a plurality of controlled instructions to the microcontroller which are stored in the memory of the microcontroller. The system also includes a temperature sensing device which is connected to the microcontroller. A fan responsive to the communication signal provided by the microcontroller adjusts the speed of the fan in accordance with the plurality of control instructions.

Abstract: A gear pump having two meshing gears which are each assigned to a shaft and which are each driven by a driving unit. The driving units are controllable by a control unit such that the shafts rotate at a definable angular velocity. The control units having a symmetrical construction, and a control device provided in each control unit, each control device being connected to the other by way of a data line.

Abstract: A multi-stage blowdown valve is provided that uses a single control signal to simultaneously decompress the interstage and the second stage in a compressor system. The valve uses a series of sliding spools located linearly within a single bore to either prevent or allow fluid communication between two isolated passageways each having an inlet port and a discharge port. The valve, when used as a two stage blowdown valve in a multi-stage compressor system, can prevent compressor failure from occurring by ensuring that both the interstage and the second stages are decompressed, not only the interstage.

Abstract: A redundant, modular pump system includes a plurality of substantially identical pump modules. Each module includes constant speed drive circuitry, variable speed drive circuitry and a pump. Expansion is accomplished by adding modules. Reliability is enhanced by being able to operate each pump at constant or variable speed irrespective of whether other modules are being operated at different variable or constant speeds. A common, software driven control element activates drives and other devices in the modules to provide fluid on demand at a pre-selected pressure.

Abstract: A liquid chemical delivery system (20) has a pump (27) driven by an electric motor (28) to draw a liquid from a bottle (21) and dispenses the liquid into a septic system (12). Separate independent controls (36,37) connect the electric motor (28) with a source of electric power (34). One of the controls (253) has a wireless remote switch (273) operable to trigger an electronic control unit (268) to activate the electric motor (228) that drives the pump (227) to deliver liquid to the septic system (212).

Abstract: An electronic control system is disclosed to control and to prevent damage to a standalone or a network of oil free, two stage compressor packages. The electronic control system uses pressure and temperature sensors to detect actual shutdown conditions or predict shutdown conditions based on the operating state of the compressor package and the current temperatures or pressures of the air at strategic locations in the compressor package. It has been determined through experimentation that, if the pressure at the inlet of the stage two compressor is less than the discharge pressure of the stage two compressor by more than an allowable value, then a high temperature condition will occur in the stage two compressor and cause the compressor to seize.

Abstract: A d.c. controller pump includes electronic control mechanisms that permit regulated control within a fluid flow system. A pump head is coupled to a housing allowing the fluid to infiltrate the region surrounding a permanent magnet rotor. Stator windings and control electronics fixed to a plurality of printed circuit boards are isolated from the fluid by means of a solid body that encapsulates the stator windings and seals the rear of the cavity. Hall effect sensor-generators and other assemblies are fixed within the solid body to enhance integrity and reduce parts count. Associated electronics includes a readily-removable circuit board for housing auxiliary electronic functions. The board is mounted in parallel at the rear of the pump housing with boards of sensor and controller electronics. The auxiliary function electronics pump configurations enable both fixed and variable speed operation in accordance with fluid flow system design and parameters.

Abstract: A safety device for use in a fluid transfer system for a swimming pool or similiar application, having a pump which draws water from a reservoir through one or more intake lines each extending from an open end at the reservoir to the pump intake. The device analyzes negative pressure levels in the system and, upon detecting a negative pressure level being outside of a selected operational range, the device deactivates the pump and triggers a vacuum breaker device to eliminate negative pressure in the system, by introducing air from atmosphere into the intake lines thereby removing suction at the open ends of the intake lines. The safety device may further activate warning devices including audible and visible alarms to indicate that the system has been deactivated.

Abstract: An infusion apparatus includes a pump powered by a source of battery power and capable of operating in a plurality of infusion modes and operating in a power savings mode. The infusion apparatus further includes sensors which sense various conditions of the pump. A controller is programmed to periodically operate in a power-savings mode of operation and also selectively causes each sensor to be connected to the battery power only when the sensor is to detect a condition, thus further conserving battery power.

Abstract: An automated control system for an engine-powered pump system. The pump system includes an engine with a battery and a pump. A control unit includes: a display, engine sensors, pump sensors, fluid level sensors, engine controllers, pump controllers, strobe light status display, and a battery recharge system.

Abstract: An electric pump is turned ON and OFF by a main drive circuit including a negative pressure sensor for detecting a negative pressure in an accumulator, a first relay and a control device, and also turned ON and OFF by a back-up drive circuit including a negative pressure switch for detecting a negative pressure in an accumulator, and a second relay. For a period from the starting of the electric pump by the back-up drive circuit to the stopping of the electric pump by the main drive circuit, there is a period during which the electric pump is being driven only by the back-up drive circuit and a period during which the electric pump is being driven only by the main drive circuit. For each of these periods, a trouble of the main drive circuit and/or the back-up drive circuit can be determined by reference to a check signal indicative of the operational state of the electric pump. Thus, it is possible to reliably detect a trouble with the driving of the electric pump connected to the accumulator.

Abstract: A sensor can detect the difference in potential between a probe and the fluid into which it is immersed, and a signal generated by the probe representing this difference in potential is used to activate an oscillator circuit. By varying the conditions at which current in the oscillator circuit begins to oscillate, various liquids can be detected and identified.

Abstract: An oil pump driving device drives an oil pump combined with a transmission coupled to an engine for supplying working oil to lubricate the transmission and enable the transmission to make gear shifts. The transmission includes a first power transmitting mechanism for connecting the output shaft of an electric motor to the drive shaft of the oil pump, and a second power transmitting path for connecting the output shaft of the engine to the drive shaft of the oil pump. A controller for selecting one of the first and second power transmitting mechanisms at a time selects the first power transmitting mechanism to drive the oil pump with the electric motor when the rotational speed of the output shaft of the engine is lower than a predetermined speed, and selects the second power transmitting mechanism to drive the oil pump with the engine when the rotational speed of the output shaft of the engine exceeds the predetermined speed.

Abstract: A synchronous rotating apparatus synchronously rotates a plurality of rotary shafts independently driven by corresponding driving devices. The apparatus includes: a mechanical regulating member, arranged on the shafts, for maintaining relative rotating positions of the shafts at a predetermined angular difference; a rotation velocity and phase-detecting member, arranged on each shaft, for detecting rotation velocities of the shafts and phases within a regulated angular difference of the regulating member, and a driving control device for controlling the driving devices of the shafts so as to synchronously rotate the shafts based on a phase difference detected by the detecting member. The apparatus is applied to a fluid rotary apparatus.

Abstract: A fluid rotating apparatus includes non-circular rotors accommodated in a housing, rotary shafts having the rotors, bearings for rotatably supporting the shafts, a fluid suction and a fluid discharge ports formed in the housing, a positive displacement pump section formed of combination of the housing and rotors, and gears connected with the shafts having backlash set smaller than backlash between the rotors.

Abstract: A pump control controls the rate at which liquid is pumped through a tube. The pump has a variable speed shaft with a roller thereon engaged with the tube between the tube inlet the tube outlet for pumping liquid from a supply toward the tube outlet when the pump shaft operates. A first sensor senses liquid at a first location in the tube and a second sensor senses liquid at a second location in the tube between the first location and the tube outlet. A vibratory beam is coupled with the tube between the first location and the second location. An electric circuit transfers energy to a magnet on the beam and induces a natural response in the beam and the tube.

Abstract: In the operation of an A.C. motor by switching the number of poles of the motor or the power sources of different frequencies, switching operating circuit is constructed to automatically switch so that the motor does not overheat by the above-described switching. Thus, the energy of the power sources can be saved.

Abstract: To control with precision and repeatability the amount of fluid dispensed or aspirated by a pumping system, a volume disk rotates with the output shaft of a DC motor that drives a reciprocating dispensing pump. A sensor detects indicia on the disk and provides periodic signals spaced-apart in time by an amount: (1) an amount proportional to the volume of fluid pumped; (2) proportional to the angle between indicia; (3) less than one-third of the length of the total stroke of the piston as the piston moves linearly in its working portion of a cycle; (4) necessary for the piston to sweep out a volume of less than five milliliters. The speed of the pump is controlled by a second disk having equally spaced indicia that are sensed to provide signals proportional to the motor speed. During dispensing or aspirating large volumes, the motor speed is increased to a high speed, run at the high speed and then decreased before stopping and during dispensing smaller volumes, it is maintained at a constant lower speed.

Abstract: A cleaner has in a tank a vacuum pump protected by a float valve above the maximum possible water level and a submersible pump at the bottom and both of these in the tank produce a vacuum for the suction of water against the vacuum, the submersible pump moving the filtered water collected in the lower region of the tank out of the tank past a check valve. The vacuum pump is constructionally combined with a tank cover, so that it can be mounted on differently constructed tanks for different cleaning functions. For wet suction purposes, the associated paper filter bag has a passage opening for the suction connecting pieces, so that the water to be filtered passes through the filter from the inside to the outside.

Abstract: To protect the pump of a whirlpool bath against running dry and against blockage at the inlet, a pressure (or flow) sensor 14 senses pump pressure and generates a signal to keep a switch S2 in the pump motor electrical supply circuit closed. If the pressure signal ceases owing to blockage or running dry, the switch S2 opens. A manual override button 15 is held ON to close switches S1a and S1b in the power circuit for start-up. The sensor 14 and manual button 15 are preferably air pressure devices. Switch S1a is preferably an air-signal-operated latching switch whereby with the pump operating, the button 15 can be operated to switch the pump off. Relays RLA 1 and 2 may be used in conjunction with the electrical switches. A bleed hole may be provided between the button 15 and switch S1b to limit the period of time for which the motor could be run, with the bath empty, by prolonged inadvertent actuation of the button 15.

Abstract: The electro-hydraulic actuator for turbine valves essentially includes a control valve, a rapid action stop valve, a hydraulic supply and an oil supply unit. In order to create a hydraulic actuator for turbine valves which, on the one hand, satisfies the stringent requirements with regard to adjustment force and adjustment speed and, on the other hand, avoids the problems associated with the transmission of hydraulic energy, at least one adjustment valve and at least one rapid action stop valve are allocated per turbine inlet valve. The actuators of these two valves are of the same design and are mutually interchangeable and integrated into a compact actuator unit located on the valve housing. The actuators are connected in pairs to a hydraulic supply located immediately adjacent to the actuators.

Abstract: A microprocessor based control system for establishing the optimum points of motor turn on and turn off for an oscillatory pumping system. The power to the motor is disabled at a point calculated to return the maximum stored mechanical energy to the system after turn-around. The motor is restarted at either a predetermined motor speed which may be different in the up and down stroke directions, or when the speed peaks. Safeguards are also provided under control of the microprocessor for disabling pump operation in the event of pump overtravel, overload or pump off. The control permits dynamic changes to the operating parameters of the pumping system in order to optimize the power required by the motor over a wide range of operating conditions.

Abstract: Methods and means for economically compressing low volume, low pressure natural gas at the wellhead are provided. The means include an electrically operated, self starting compressor responsive to a low pressure inlet shut-off switch and a high pressure discharge shut-off switch. The means may also include a scrubber for separating liquid and condensate from the gas and means for automatically transporting such to a remote liquid storage tank. The compressor itself is an air compressor modified by the provision of natural gas crankcase purging and venting, suction port oil injection, and increase lubrication capacity.

Abstract: A yo-yo variety reciprocating drive for long stroke, well pumping units, which employ a flexible element as the operative link between the winding drum and the polish rod of the well pump. Reversal from an upstroke to a downstroke is cushioned by mechanism which provides a power source off dwell period of predetermined duration during the aforesaid stroke exchange and is adjustable to control the length of stroke of the pumping unit. A velocity control senses the velocity of the polish rod during such dwell period and re-energizes the power source when a predetermined velocity is achieved following reversal of direction.