Abstract: A method and apparatus are disclosed for determining airflow through a PAP device while applying PAP therapy. The actual speed of a blower 6 is measured. The desired motor current IDES required for the actual speed to approach or maintain a desired speed is used, together with the actual speed RPM ACT, in a flow estimation algorithm to determine flow through the PAP device. The estimation algorithm consists of a two-dimensional look-up table, where the inputs are the desired motor current and actual motor speed, and the output is the flow through the PAP device.

Abstract: A method for supplying compressed air for the operation of moving bed filters by way a compressor is characterized by controlling the pressure of compressed air from the compressor by controlling the rotational speed of the compressor. A system for supplying compressed air is also provided. By use of the described method and system, substantial energy savings of approximately 50 percent can be achieved.

Abstract: A fan control system includes first and second adjacent fans, first and second motors configured to rotate the first and second fans, and a control unit configured to control rotational speeds of the first and second motors in order to control rotational speeds of the first and second fans. The first and second motors are energized such that the rotational speeds of the first and second fans reach target rotational speeds prior to increasing the rotational speeds of the first and second fans to required rotational speeds. The target rotational speeds are lower than the required rotational speeds. The first and second motors are energized such that the rotational speeds of the first and second fans reach the required rotational speeds after the rotational speeds of the first and second fans reach the target rotational speeds.

Abstract: An electric motor control apparatus includes a phase correction portion that generates and outputs an amount of phase correction with which to correct a phase of a signal from a position sensor detecting a position of a magnetic pole of an electric motor. The phase correction portion generates and outputs an energization stop signal in a case where a rotation speed of the electric motor is within a predetermined range and stores an amount of phase correction generated therein according to a comparison between a signal from the position sensor or a first phase and an induced voltage of the electric motor to output the amount of phase correction.

Abstract: A sensor assembly for measuring movements of a fluid pump driven by an electric motor, the electric motor connectable to a feed voltage, the sensor assembly comprising an accelerometer electrically connected to a bias circuit, the latter comprising a feed terminal electrically connectable to the feed voltage of the motor and a signal terminal electrically connectable to an external measuring terminal. A fluid pump is also described, comprising a cylinder, a piston, a housing comprising a hermetic terminal and hermetically enclosing the cylinder and the piston, thus forming a hermetic assembly, the piston driven by an electric motor, the electric motor connected to an electric voltage by a pair of voltage terminals associated to the hermetic terminal, the fluid pump comprising a sensor assembly associated to the cylinder comprising a feed terminal connected to one of the voltage terminals and a signal terminal electrically connected to an external measuring circuit.

Abstract: A well watchman pumping and control system capable of operating in a wide range of ambient conditions is described. The system automatically maintains fluid level in a fluid storage vessel, while protecting the pump and generator from operating in conditions outside preset operating parameters to prevent premature failure and reduce repair. By operating to pump fluid only when preset operating conditions exist, e.g. low fluid level, ambient temperature, etc., the system reduces labor, fuel, and maintenance operating costs to the owner, improves well pumping reliability and production, reduces generator fuel consumption, reduces emissions, and conserves ground water or liquid hydrocarbons, whichever is being pumped into the fluid storage vessel by the system.

Abstract: A device for controlling the stroke of a piston 3 of a metering pump comprising an electromagnet 1 formed by a fixed part and a mobile part fixed with respect to said piston 3 in such a way that at each displacement of the piston there corresponds a different value of inductance of the electromagnet 1 and hence of the piston stroke itself.

Abstract: The present invention relates to a system and to a method of controlling a fluid pump, as well as to a linear compressor and a cooler configured to calibrate the respective functioning at the time of the first use or in cases of problems caused by electric or mechanical failures. According to the teachings of the present invention, the fluid pump is provided with a piston-position sensing assembly, the electronic controller monitoring the piston displacement within the respective cylinder by detecting an impact signal. The impact signal is transmitted by the sensing assembly upon occurrence of an impact of the piston with the stroke end, the electronic controller successively incrementing the piston displacement stroke upon a trigger signal as far as the occurrence of the impact to store a maximum value of piston displacement.

Abstract: An inverter-integrated electric compressor has a control device. The control device estimates a compressor suction pressure based on the temperature of the power element of the inverter, or directly measures the compressor suction pressure by a sensor, or estimates the compressor suction pressure based on a compressor suction temperature or on a compressor housing temperature. Further, the control device calculates a motor torque based on a motor rotational speed, a motor phase current, and a motor phase voltage, estimates a compressor discharge pressure based on the compressor suction pressure and the motor torque, and estimates a compressor discharge temperature based on the compressor suction pressure and the compressor discharge pressure. The electric compressor has a discharge temperature detection device in place of a conventional thermal protector.

Abstract: A hydraulic fan circuit includes a primary pump, a motor fluidly connected to the primary pump, and a fan operably connected to and driven by the motor. The circuit also includes a supply passage extending from the primary pump to the motor, a return passage extending from the motor to the primary pump, and a pressure limiting valve configured to selectively reduce pressure of a flow of pilot fluid directed to the primary pump. The circuit further includes an override valve configured to selectively connect the supply passage to the pressure limiting valve.

Abstract: Disclosed herein is an approach that uses a wattmeter to obtain diagnostics of a hydraulic system during transient-state start-up operation. In one aspect, a controller uses the electric power measured by the wattmeter during the transient-state start-up operation to determine fluid flow parameters. In another aspect, the controller determines diagnostics for the hydraulic fluid consuming device and the hydraulic pump unit as a function of the fluid flow parameters.

Abstract: An apparatus for controlling a compressor is provided. When grounding the apparatus for controlling a compressor, an analogue circuit ground and a digital circuit ground may be insulated from each other to protect the apparatus. A ground of an analogue circuit driven by commercial alternating current (AC) power, and a ground of a digital circuit driven by a voltage which has been converted from commercial AC power, may also be insulated from each other by a simple circuit device to protect a controller inside the digital circuit.

Abstract: Embodiments of the invention provide a pump control circuit for use with a pump. The circuit includes a pressure sensor capable of sensing a pressure in the pump and a microcontroller coupled to the pressure sensor and to the pump. The microcontroller switches operation of the pump between a high-flow mode and a low-flow mode. When in the high flow mode, the microcontroller limits a current provided to the pump to a high-flow current limit value that is not dependent on the sensed pressure. When in the low flow mode, the microcontroller limits the current provided to the pump to a low-flow current limit value that is less than the high-flow current limit value and that changes depending on the sensed pressure.

Abstract: A medical pump with a closed loop stroke feedback system and method, for use with a pumping chamber, for example in a cassette, is disclosed. The pump includes a pumping element that intermittently pressurizes a pumping chamber during a pumping cycle. A pressure sensor detects the pressure exerted by the pumping element on the pumping chamber. A position sensor detects the position of the pumping element. A processing unit processes pressure data from the pressure sensor and position data from the position sensor to determine a calculated stroke volume of the pump for a pump cycle, and to adjust a stroke frequency of the pump to compensate for variation in the stroke volume.

Abstract: In an inverter control apparatus in which a control circuit board is fixed by use of pin-like terminals provided in a power board, the breakage of the pin-like terminals is prevented. The power board 160 is provided with a plurality of signal transmission terminals 210a, 210b, 220a, 220b for signal transmission to and from the control circuit board 150 and for grounding along each of a pair of opposed sides, the control circuit board 150 is electrically connected to the plurality of signal transmission terminals 210a etc. and is fixed by soldering to the plurality of signal transmission terminals 210a etc., and the plurality of signal transmission terminals 210a etc. are arranged along each of the pair of sides in a plurality of rows.

Abstract: There is provided an integrated electric compressor having a circuit configuration capable of decreasing the size thereof while restraining current ripples. In an inverter of the electric compressor, by providing a capacitor 13 and a reactor 14 between a power source and an inverter board 12, the ripples of a driving voltage is restrained, and a motor can be driven with high efficiency and the size of a housing can be decreased. Further, by connecting the capacitor 13 and the reactor 14 to a power board 16 by using a bus bar 23, the voltage ripple restraining effect is further increased, and the capacitor 13 and the reactor 14 are unitized integrally by the bus bar 23 to improve the assembling workability of the power board 16.

Abstract: When controlling an air compressor (13) for a pneumatic braking system on a large hybrid commercial vehicle (e.g., a bus, a package delivery truck, etc.), PID control of an air compressor motor (12) is employed during normal system operation such as when the motor shaft is spinning, and state machine control is employed during startup or upon a system disturbance such as a shaft seizure or stall. In this manner, stalling events that occurs due to PID control inability to correct for unexpected disturbances are mitigated by employing state machine control.

Abstract: An HV-ECU performs a step of detecting an atmospheric pressure, a step of calculating a maximum value of a boost voltage corresponding to the atmospheric pressure by using a map, and a step of setting the maximum value as a system voltage value and controlling a DC/DC converter. Moreover, the HV-ECU may calculate a resistance value of a gate resistance of a switching element corresponding to the atmospheric pressure by using the map and control the gate resistance to achieve the set resistance value.

Abstract: A miniature fan, particularly an axial fan, has a space-conserving structure which permits sophisticated electronic control circuits within a limited amount of space. It features an electronically commutated motor (ECM) including an internal stator 68, an external rotor 27 on a shaft 62, and a fan wheel 28 mounted on the rotor and bearing fan blades 26. The motor flange 40? supports a bearing tube 60 which rotatably journals the rotor shaft 62 and is formed with a cavity 84 which receives a first circuit board 86 devoted to control of motor speed and/or voltage, and a second circuit board 96 which supports a galvanometric sensor 100 which senses the rotational position of the rotor, for purposes of triggering commutation of the motor stator windings 68 at appropriate times.

Abstract: A dispenser includes a pump that, upon actuation, progresses through a discrete dispense cycle to dispense a discrete dose of product. The dispenser further includes an actuating mechanism serving to actuate the pump, and a dispenser controller that controls operation of the actuation mechanism. The discrete dose is less than a desired dose. When the dispenser controller receives a single dispense request, the dispenser controller causes the actuating mechanism to actuate the pump through multiple discrete dispense cycles so as to dispense multiple discrete doses to achieve a dispensing of the desired dose.

Abstract: A self-priming diaphragm pump is connected to a circuit board which activates the self-priming diaphragm pump at predetermined intervals, e.g., for 1-3 seconds. When the self-priming diaphragm pump is activated, the circuit board senses the amperage draw from the pump's motor and either continues to run the pump or stops the pump depending on the different amperage levels read. If there is water present in the bilge, the motor is working harder, requiring more amperage and circuit board keeps the pump running. If there is no water present for the pump to draw, the amperage load is very low and the circuit board shuts the pump off, retesting it in the predetermined interval.

Abstract: A fan (20) has: a motor having a stator (40) and having a rotor (60) with at least one fan blade; at least one air inlet having an air entrance opening (102) for the inlet of air; at least one air outlet having an air exit opening (32) for the outlet of air; a circuit board (80) having at least one recess, which circuit board (80) is arranged in the region of the air inlet in such a way that air can enter the fan (20) through the recess, motor electronics (88) being arranged on the circuit board (80). In a preferred embodiment, a Negative Temperature Coefficient (NTC) resistor (84) is surface-mounted on a PC board portion (83) extending into the air passage, to thereby sense air temperature. This facilitates compact, automated construction.

Abstract: A fluid pumping system for a vehicle having an internal combustion engine includes a housing, an electric motor, a controller to control the speed of the electric motor, a planetary gearset including a first member adapted to be driven by the internal combustion engine, a second member driven by the electric motor and a third member. A pump is driven by the third member of the planetary gearset. The housing contains the electric motor, the pump and the controller.

Abstract: A system and method of spread-spectrum fan control for an air-cooled system is provided for reducing the vibrational and acoustical noise associated with the air-cooled system. The method includes generating a first control signal that controls a blade-passing frequency of a first cooling fan and a second control signal that controls a blade-passing frequency of a second cooling fan, wherein the first and second control signals may be pulse width modulated (“PWM”) signals. One or more noise generators independently vary duty cycles for the first and second PWM signals within a range around respective first and second blade-passing frequency set points. As a result, the blade-passing frequencies for the first and second cooling fans are independently and randomly modulated within a range around the respective first and second blade-passing frequency set points.

Abstract: A system is provided for transmitting control signals to the internal devices of a compressor. The compressor includes a housing, a hermetic power terminal and a motor for powering the compressor. The system includes a frequency converter that is located external to the compressor housing and a frequency decoder that is positioned inside the compressor housing. The frequency converter can convert a control signal from a controller to a high frequency signal. The frequency decoder decodes and converts the high frequency signal to a control signal for an internal device of the compressor. An AC input power source provides electrical power to the motor, and power transmission lines connect the AC input power source to the hermetic power terminal. The frequency converter is electrically coupled to the frequency decoder by two power transmission lines.

Abstract: A cartridge (2) with a fill level detection system (10, 10?, 10?), the cartridge comprising a substantially rigid containing wall (4) having a tubular wall portion (12) surrounding a chamber (18) for receiving liquid therein, a plunger or piston (8) mounted inside the chamber and configured to seal one side of the chamber, the plunger or piston being displaceable in the chamber towards an outlet end (14) of the cartridge, characterized in that the fill level detection system comprises a plurality of discrete fixed electrodes (24, 24?) positioned along the tubular wall portion in a juxtaposed manner in a direction of displacement D of the plunger or piston (8), and a mobile electrode member (28) fixed to the plunger or piston and displaceable therewith.

Abstract: A ceiling fan controller using a DIP switch to set a rotation speed comprises a rectifying filter circuit, a CPU, a motor driving module, a voltage lowering circuit, an automatic balancing circuit, and a sensing circuit for a DC non carbon brush motor. A DIP switch electrically connects to the CPU to set different maximum rotation speeds for the DC non carbon brush motor.

Abstract: An autonomous sump (ASP) system is designed to remove water from a sump using a source of power other than commercial electrical power or battery power. The ASP system can be a stand-alone unit or, alternatively, can be used along with a preexisting sump pump system. In some embodiments, the ASP system can provide an alert to a building owner of the ASP system failure.

Abstract: A control system for a fan includes a control housing that is external to a fan housing for the fan. At least one fan control module is within the control housing and communicates remotely with terminals within the fan housing via at least one wire. The at least one fan control module includes a detection module. The detection module detects induced voltages in at least one of a plurality of stator coils within the fan housing via the at least one wire without receiving signals from a sensor in the fan housing.

Abstract: A secondary air system comprising a variable speed air pump and a gated check valve connected between the variable speed air pump and an IC engine. The gated check valve has two ports, and generally, a first of the two ports is connected to a first bank of engine cylinders, and a second of the two ports is connected to a second bank of engine cylinders. The system further comprises a controller for controlling the speed of the variable speed air pump, and the positioning of the gated check valve. The gated check valve is operable to fully close air flow to both ports, fully open air flow to one of the two ports, or variably split air flow between the two ports.

Abstract: A system includes a housing; a first fan having a first inlet and a second fan having a second inlet, the first fan and the second fan mounted in a wall of the housing, the first fan and the second fan oriented to draw air into the housing; a device in the housing, the device positioned to receive airflow from the first fan and the second fan; and a controller for controlling the first fan and the second fan, wherein the controller is configured to initiate a cleaning cycle during which the first fan is on and the second fan is off to cause backpressure airflow to flow through the second inlet in a reverse direction for a first time period and the first fan is off and the second fan is on to cause backpressure airflow to flow through the first inlet in a reverse direction for a second time period.

Abstract: A magnetic drive metering pump in which a movable thrust member is fixed to a diaphragm and is axially movable in a magnet shroud. The thrust member, on electrically actuating the magnet shroud, is drawn into the magnet shroud against the force of a recuperating spring, and after deactivating the magnet shroud, is returned to a starting position. The diaphragm cooperates alternately with an outlet and an inlet valve to produce a pump stroke in a pump metering head. The magnetic drive metering pump has a reference element associated with the thrust member and diaphragm, the position of which reference element is detected by a positional sensor. The positional sensor provides a signal which has a fixed relationship to the position of the reference element, and the motion of the thrust member is controlled by a control circuit such that it follows a predetermined nominal profile.

Abstract: An apparatus and method for pumping fluids, such as water and/or hydrocarbons, from a subterranean formation or reservoir, include a linear rod pump having a mechanical rack and pinion drive arrangement, adapted for attachment to a pumping mechanism, such as the polished rod at the top of a rod string in a hydrocarbon well. The rack gear, of the rack and pinion drive arrangement, is adapted for connection to a cable and pulley arrangement for imparting motion to the polished rod. The pinion gear does not translate with the rack gear, and is driven by a reversible motor for affecting up and down reciprocating motion of the rack gear and pumping mechanism. Some forms of the invention include a compressible gas counter-balance arrangement. Some forms of the invention include an electronic drive configured for dealing with electric power generated by the motor during a portion of the pumping cycle.

Abstract: An apparatus for adjusting the pressure in a tire of a vehicle comprises a compressed gas source, a coupling which can be fastened on a valve of the tire, and control means for selective action upon the coupling with compressed gas from the compressed gas source, said control means comprising an interface for communication with a TPM system.

Abstract: An aircraft engine fuel system is provided and includes a pump, including an inlet and an outlet, from which pressurized output is produced, a valve disposed downstream from the pump outlet to receive and to direct the pump output flow toward the engine and to provide a leak tight seal when the pump is not operating, a sensor configured to issue a signal reflective of a state of the valve at first and second conditions and a controller, operably coupled to the pump and the sensor, which is receptive of the signal and which modifies performance models of the pump and engine to control pump speed to modify pump flow accordingly.

Abstract: An auxiliary oil pumping system for an automatic transmission includes an auxiliary oil pump, the auxiliary oil pump being separate from an internal oil pump of the transmission but connected to an oil circuit of the automatic transmission to circulate oil in the system. An oil pump motor is connected to the auxiliary oil pump and selectively connectable to a power source for driving the auxiliary oil pump when a vehicle engine is off and the internal oil pump is not operating.

Abstract: A method and apparatus for operating a vehicle HVAC system includes detecting an elevated risk of water splash expulsion from an evaporator through a vent outlet and controlling a voltage supplied to at least one blower of the vehicle HVAC system to reduce a risk of water splash expulsion if the elevated risk is detected. Water splash risk is determined in view of a voltage supplied to a subject blower, a vehicle tilt angle, and a condensation risk or value. The condensation risk or value is determined in view of a window open/close value, a temperature value, and a humidity value. Each of these factors are, either independently or in combination, compared with a corresponding threshold value to determine if the water splash risk warrants voltage control.

Abstract: A system and method are provided for reducing the energy consumed by a pump jack electric motor by reducing the supply voltage to the motor when the motor would be generating energy in open loop mode. By substantially eliminating the energy generation mode, the braking action of the utility grid in limiting the acceleration of the motor and system that would otherwise occur is substantially removed. The motor and system will speed up, allowing the natural kinetic energy of the cyclic motion to perform part of the pumping action.

Abstract: A medical device system comprises a reservoir configured to store a therapeutic fluid and a medical pump configured to deliver the therapeutic fluid from the reservoir to a patient. The system also comprises a sensor that can detect a characteristic associated with the pump and a processor to determine if the characteristic detected indicates the reservoir is empty or near empty. The characteristic may comprise a property associated with the energization of an actuation mechanism configured to be energized to provide a pump stroke. The characteristic may also comprise a characteristic of a noise made by an actuator within the pump at the end of a pump stroke.

Abstract: A method of operating an oil well comprises applying through a regenerative variable frequency drive AC electrical energy from a power grid to an AC electric motor to operate a drive mechanism of an oil well pump. The motor speed is regulated in a manner to optimize fluid production and maximize the operational life of the drive mechanism, decreasing motor speed by transferring the electrical energy to the power grid and increasing motor speed by transferring the electrical energy from the power grid to the motor. The drive mechanism has a predetermined stroke cycle and, over the course of each stroke cycle, the motor is operated at different regulated speeds initiated when the drive mechanism is at a predetermined position.

Abstract: One embodiment relates to a hybrid vehicle drive system for a vehicle including a first prime mover, a first prime mover driven transmission, a rechargeable power source, and a PTO. The hybrid vehicle drive system further includes a hydraulic motor in direct or indirect mechanical communication with the PTO and an electric motor in direct or indirect mechanical communication with the hydraulic motor. The electric motor can provide power to the prime mover driven transmission and receive power from the prime mover driven transmission through the PTO. The hydraulic motor can provide power to the prime mover driven transmission and receive power from the prime mover driven transmission through the PTO.

Abstract: A cooling fan includes a sidewall coupled to a base of a housing and defining a compartment. The housing includes an air inlet, an air outlet, and a dust channel. The air inlet, the air outlet, and the dust channel are in communication with the compartment. An impeller is rotatably coupled to a stator coupled to the base. A control element includes a driving circuit electrically connected to the stator and a rotating direction control circuit electrically connected to the driving circuit. The air outlet and the dust channel separate an inner periphery of the sidewall into first and second guiding wall sections. The first guiding wall section has a guiding portion contiguous to the dust channel. A first spacing between the guiding portion and a center of the impeller is not larger than a second spacing between the second guiding wall section and the center of the impeller.

Abstract: The present invention is provided to remove dust that adhered to a cooling fan. A plurality of comparators are disposed for each of a plurality of coils, respectively, and generates a back electromotive force sensing signal denoting a comparison result by comparing a back electromotive force appearing at one end of each corresponding coil with a neutral-point voltage of the coils. A driving signal synthesis circuit generates a driving control signal used to enable the fan motor to proceed the following actions: (i) enabling the fan motor to rotate toward the opposite direction as a normal operation within a specific reverse rotation period after a driving of the fan motor is started, (ii) applying a brake to the fan motor within a braking period, and (iii) enabling the fan motor to rotate toward a direction of normal operation in a normal driving period. A driving circuit drives the fan motor.

Abstract: A motor controlling method and apparatus of an air conditioner are disclosed. It is checked whether or not an operation frequency of a compressor motor is the same as or greater than a certain frequency and it is also checked whether or not a detected velocity of a fan motor is the same as or lower than a certain velocity during a certain time period. If the operation frequency is the same as or greater than the certain frequency and the detected velocity is the same as or lower than the certain velocity during a certain time period, the compressor motor is temporarily stopped. Because the compressor motor operates according to operational conditions of the fan motor, an overload can be prevented.

Abstract: A control system is provided with an electric water pump that has a sensorless-type brushless motor including a rotor that rotates so as to circulate a coolant between an internal combustion engine and a radiator, and a control device that issues an instruction to stop the brushless motor and prohibits a start of the brushless motor till the rotor stops rotating.

Abstract: A free piston gas compressor has a cylinder, a piston, the piston reciprocable within the cylinder in alternating compression and expansion strokes. A reciprocating linear electric motor is drivably coupled to the piston. A controller is programmed to control or adjust power input to the linear motor on the basis of a relationship including at least one of the present compression stroke or expansion stroke durations, the relationship being indicative of the top dead center (TDC) position of the piston, including in the absence of any collision. In the preferred embodiment the controller obtains a measure reflecting the difference between the compression stroke duration and the expansion stroke duration and adjusts the power input in response to the obtained measure.

Abstract: A compressor includes a motor driven by a controller and having a rotor and a stator, a compressing unit driven by the motor in a hermetic container in which refrigerant is filled. Driving the motor at a low rpm, the controller practices a feedback control which determines a timing of turning on/off switching elements based on a signal detecting a position of the rotor, and when the motor is driven at a high rpm, the controller practices an open-loop control which outputs a given frequency and drives the motor synchronizing with the given frequency. This structure achieves a compressor working with a fewer noises in PWM driving.

Abstract: A control for a linear compressor energises the linear motor in harmony with the present natural frequency of the compressor. The controller monitors the present operating frequency and compares the frequency with one or more outer limit thresholds. The control may remove power from the linear motor if the running frequency drops below a lower threshold. The control may reduce power to the linear motor if the running frequency rises above an upper threshold. The control uses compressor running frequency to operate the comperssor within safe operating limits.

Abstract: The present invention is a magnetic pump assembly for integration with a mechanically flexible thermal spreader. The assembly may include a casing which may be connectable to a mechanically flexible substrate of the thermal spreader. The assembly may further include a plurality of magnets which may be integrated with and enclosed by the casing. The magnets may be suitable for applying a magnetic field to an electrically-conductive liquid, and may be implemented in combination with electrodes, which may be integrated with the substrate and may be suitable for generating an electrical current flow through the liquid. The magnets and electrodes may combine to provide a pumping force for circulating the liquid within an internal channel of an electrically-conductive cooling loop of the substrate. The assembly may further include a thermally-conductive rigid metal insert integrated with the casing. The assembly may promote local thermal conductivity of the thermal spreader.

Abstract: An apparatus and method for pumping fluids, such as water and/or hydrocarbons, from a subterranean formation or reservoir, include a linear rod pump having a mechanical rack and pinion drive arrangement, adapted for attachment to a pumping mechanism, such as the polished rod at the top of a rod string in a hydrocarbon well. The rack gear, of the rack and pinion drive arrangement, is adapted for connection to, and movement with, the polished rod. The pinion gear does not translate with the rack gear, and is driven by a reversible motor for affecting up and down reciprocating motion of the rack gear and pumping mechanism. Some forms of the invention include a compressible gas counter-balance arrangement. Some forms of the invention include an electronic drive configured for dealing with electric power generated by the motor during a portion of the pumping cycle.