Abstract: A method of starting a variable-speed pump turbine or a variable-speed pump driven by a variable-speed generator motor or a variable-speed motor connected to an electric power line in parallel therewith. The generator motor or the motor is first operated at low speed with the guide vanes or the delivery valve fully closed. The low speed is lower than a stable starting speed of the pump turbine or the motor but high enough to prevent backward flow of water into the pump turbine or the pump. After the operation is set at the low speed, the guide vanes or the delivery valve are opened and the opening degree is gradually opened until the speed is increased to a speed optimum for the steady operating condition of the pump turbine or pump. This method effectively suppresses abrupt increase in the pump input power required for the driving of the pump turbine or the pump, whereby unfavorable effect on the electric power line is avoided advantageously.

Abstract: A hydraulic servomechanism for controlling the pressure of ink supplied to an ink jet printer head includes a bellows located between an ink source and the head and arranged for expansion and contraction to decrease and increase the pressure of ink in the bellows.Pressure is sensed at the bellows output connected to the ink head and the sensed pressure is compared to a desired ink pressure to produce a driving signal which excites an electromagnetic driver coupled to the bellows. The driver applies a force to the bellows to adjust the pressure to the desired pressure. A position sensing switch is responsive to the volume of the bellows and controls a valve located between an ink source and the bellows input to maintain the volume of ink in the bellows within a predetermined volumetric range.

Abstract: A system for dispensing multiple discrete streams of a high viscosity liquid material, and particularly, systems such as those for applying sealants to the seams of an automobile body on a production line. The system is provided with a multi-speed pump for supplying the viscous liquid from a reservoir at high pressure to a distribution manifold from which it is distributed at regulated rates to a plurality of extrusion guns through drop lines from the manifold. A motor speed control which is settable to a number of predetermined motor operating speeds which selects the speed of the multi-speed pump in response to the combination of guns which is activated, so that the dispensing rate can remain the same regardless of which other guns are activated. Regulators which include volumetric metering pumps are included in the drop lines at each of the guns, with controls coordinated with the motor speed control.

Abstract: An accurately controllable two-stage pump assembly comprising two plunger pumps connected in series. The suction port of the outlet pump A is connected to the discharge port of the inlet pump B, so that the discharge port of the outlet pump A and the suction port of the inlet pump B act as the discharge port and the suction port, respectively, of the whole pump assembly. While the inlet pump B is delivering fluid from the whole pump assembly, the outlet pump A completes the filling stroke of the whole pump assembly and fully increases the pressure inside the chamber of the outlet pump A. While the inlet pump B is filling, the outlet pump A is in the stage of displacement stroke and delivers fluid from the whole pump assembly. The plungers of the pumps are moved via cams by stepper motors which swing or rotate back and forth within a certain angular range.

Abstract: Variable stroke pump apparatus includes a photovoltaic array for providing electrical current to motors, one of which provides for the pumping action of a walking beam, one of which provides for movement of a control unit which varies the length of stroke of the pumping apparatus from a minimum of zero to a maximum, and one of which operates a counterweight for moving the counterweight in response to the pumping load. The apparatus includes mechanical elements which adjust the length of the stroke of the pumping arm, and a control system which controls the length of the pumping stroke in response to the output of the photovoltaic array.

Abstract: A low volume submersible pump assembly has features to stabilize the operation. The pump assembly includes a centrifugal pump driven by a submerged electrical motor. The centrifugal pump has an impeller configuration that is designed for high specific head, but potentially unstable operation. At the design speed, the pump potentially could deliver an indeterminate flow rate for a given head. Also, at the design speed, the design flow rate will yield a design head that is very close to the maximum head at zero flow. The pump has the characteristic of requiring a significant increase in torque to produce higher flow rates. To stabilize the potentially unstable pump, a variable speed drive varies the speed of the motor to maintain constant torque. Maintaining a constant torque allows a considerable variance in head with only a small variance in flow rate resulting.

Abstract: An operation control system of a rotary displacement type vacuum pump capable of reducing a starting torque of the vacuum pump includes a suction regulating valve and a pressure sensor for monitoring suction pressure located in a suction passage of the vacuum pump, an inverter electrically coupled to a variable speed electric motor for driving the vacuum pump and a control unit. The control unit is operative, when the vacuum pump is started, to keep the suction regulating valve in a closed position until the value of suction pressure monitored by the pressure sensor reaches a predetermined upper limit value and to gradually increase the rpm. of the variable speed electric motor. The control unit is further operative to produce a signal for increasing or decreasing the rpm of the variable speed electric motor so as to bring the value of suction pressure monitored by the pressure sensor to the vicinity of a predetermined lower limit value.

Abstract: In a Stirling cryogenic refrigerator, the movement of the displacer is monitored by sensing the back EMF in the displacer drive coil throughout displacer stroke. The back EMF signal is applied through a feedback circuit to control the phase relationship of displacer movement with a reference signal related to the pressure wave.

Abstract: A closed loop control is provided to control pressure and/or temperature in a system where one or more liquid ring vacuum pumps evacuate a recipient. The suction ability of the liquid ring vacuum pumps is controlled either by speed control, operating water temperature, switching-on and -off of pumps or bypass-air. Simultaneous control of all operating characteristics is achieved with a programmable electronic controller.

Abstract: An oil-sealed rotary vacuum pump includes a pump system and an electric drive motor connected by a drive shaft and located within a housing. The housing is divided by a partition into two separate compartments with the pump system in one compartment and the drive motor in the other compartment. The drive shaft extends through a passage in the partition between the two compartments and the passage is arranged so that any leakage flow is directed from the motor compartment into the pump system compartment.

Abstract: A liquid pump motor control for a liquid chromatograph. The control detects when the pump needs to be refilled. Then, the pump motor is accelerated at a first rate for a given number of pulses. Then the motor is accelerated at substantially its maximum rate until a selected maximum speed is reached. Thereafter the speed is maintained at its maximum until the time calculated to begin deceleration. The motor is then decelerated substantially at its maximum deceleration rate until the speed is close to the final desired speed. Then deceleration occurs at a slower rate for a fixed number of pulses. The number of pulses applied to the stepping motor from the beginning of acceleration until the end of deceleration is constant regardless of the beginning or ending pulse rates.

Abstract: The invention relates to an arrangement in plant equipment for directly supplying to a building element a binder comprising, for example, mortar of pumpable consistency and containing water. The plant equipment includes a vessel for ready-mixed binder, a motor-driven pump and a pump conduit (3) for supplying binder under pressure to a nozzle (4). In order to prevent liquid from being expelled from the binder when the pump is stopped, so as to leave a dry plug in the nozzle, means (18) are provided for maintaining the pressure in and adjacent the nozzle (4) at a level which coincides at least substantially to atmospheric pressure.

Abstract: A torque control apparatus for enclosed compressors wherein a load torque, applied to an enclosed compressor, is detected by a position detector provided on the rotating portion of the compressor and a temperature detector provided in a refrigeration cycle. A voltage or current supplied to the compressor is controlled in accordance with the load torque to control the motor output torque of the compressor.

Abstract: An arrangement for controlling the pressure of a fluid being pumped by a pump driven by a drive means. The pump pressure is measured by a pressure sensor and transformed into an electrical signal which acts on a regulator for the drive means.

Abstract: An improved pulsation-free reciprocating volumetric pump is disclosed, which comprises two reciprocating plungers, a cam for driving said plungers, a driving motor connected to said cam, a circuit connected to said driving motor for controlling rotational rate, and another circuit for detecting a pressure of combined volume discharged by the two plungers and for correcting a control signal of said rotation controlling circuit through the detected signal.

Abstract: A novel refrigerator control system is disclosed which comprises an inverter for driving a motor for a compressor, and a change-over device for driving the compressor directly with a commercial power supply when the compressor motor is not driven by the inverter.

Abstract: Apparatus and process is disclosed for heat treating of material in a furnace comprising a fan driven by an electric motor, a load sensor which senses the motor load and a speed controller responsive to the load sensor signal for controlling the speed of the electric motor.

Abstract: An axial flow helical screw type compressor has a slide valve member and slide stop member mounted end to end beneath the intermeshing rotors such that the slide valve member controls communication between the work chamber defined by the rotors and the casing to the outlet port and the slide stop member and the valve member together control the working fluid inlet to the bores of the rotors, the slide valve member and the slide stop being independently movable. Control means for the slide valve member and slide stop include position sensing means for these two members, inlet and outlet pressure sensing means, and means for feeding these inputs into programmable circuitry to control the positions of the slide member and slide stop.

Abstract: A fluid pumping system including a variable-volume, fluid-reception chamber having an inlet conduit leading from a fluid supply site and an outlet conduit leading to a fluid delivery site. An elongated plunger body is drivingly coupled with the chamber and linearly reciprocable along its longitudinal axis so as to alternately expand and contract the volume of the chamber, thereby alternately drawing a fluid into the chamber through the inlet conduit from the fluid supply site and pumping the fluid through the outlet conduit towards the delivery site. The linear reciprocation of the plunger body is effected by an electromagnetically operated drive, preferably a linear motor drive, at a rate of reciprocation in the range of 0.01 to 10 Hz.

Abstract: A compressor arrangement for a heat pump installation in which an electric motor is provided as the drive means for the compressor is disclosed. In order to make possible operation of the compressor without unpermissibly large surge currents in the electric network supplying power to the electric motor, the compressor is driven by a permanent magnet-excited d-c motor which is provided with an electronic commutating device. The starting current drawn by the d-c motor can be controlled by means of a d-c voltage control element coupled to the electric network by a rectifier so as to prevent unpermissibly large starting surge currents.

Abstract: The invention relates to a method and apparatus for driving the impeller (5) in a turbo-type liquid pump operating at relatively low power and relatively high delivery head by means of an a.c. motor (2). The invention is mainly characterized in that the motor (2) is driven from a static inverter (6) which operates at an operating frequency of 100-1000 Hz. This enables high specific speed impellers to be used, and therewith provides a considerable increase in the efficiency and capacity of the pump at unchanged motor sizes.

Abstract: Method and apparatus for matching the power output of a high slip motor to the demand requirement of a pumpjack unit. The stators of the high slip motor are automatically connected in various different configurations to provide the optimum torque as required by the pumpjack unit due to the downhole pumping conditions. A novel control circuitry is connected between the motor starter and the motor stators. The control measures the power drawn by the stators and selects the most optimum configuration thereof for the load required by the pumpjack. This selection operates the motor in the lowest possible torque mode, which is considered the best electrical and mechanical operation of the pumpjack apparatus.

Abstract: A swash plate assembly converts rotary motion to reciprocatory motion to reciprocate a diaphragm in a high frequency medical ventilator; the motor which drives the assembly is pivotally mounted for variation of the stroke of reciprocation thereby varying the tidal volume displaced by the diaphragm.

Abstract: An oil pump assembly having an adjustable production rate and capable of long stroke, low stroke per minute pumping rates, comprising a reciprocating pumping rod in a well hole, a counterbalancing mechanism for reducing the power needed to pump oil by the pumping rod, a driving mechanism to drive the reciprocating pumping rod and the counterbalancing mechanism, including a first cable and a second cable, to drive the reciprocating pumping rod and the counterbalancing mechanism, respectively, a speed control for the driving mechanism, and a dwell mechanism for the driving mechanism.

Abstract: A compressor drive system for controlling the gas pressure in a pressure gas volume (106) connected to the compressor (101). A brushless alternating current motor (23) is directly coupled to the compressor, which is driven with the same speed as the motor. The pressure in the gas volume (106) is sensed by pressure sensing means (109) connected to a converter (114). The converter simultaneously changes the amplitude and frequency of the drive voltage supplied to the motor (23). This is done in response to pressure changes in volume (106). The motor is stopped if the pressure exceeds a preset maximum value. A pressure gas container (104) is depressurized at motor stop to allow restarting without counter pressure on the compressor. Means (44) for controlling the amplitude and frequency of the drive voltage is provided so that the normal speed maximum load current is never exceeded during motor start.

Abstract: Disclosed is a method for controlling the volume of a fluid, e.g., air, moving through a duct system, e.g., a ventilating system for a vehicle, comprising the steps of moving the fluid through an inlet of the duct system under dynamic pressure; conducting the fluid through the duct system by means of propulsion system driven by an electric motor, wherein the electric current drawn by said motor varies with changes in the dynamic pressure; and adjusting the amount of fluid admitted into the duct system in response to the current drawn by the motor and thus, also responsive to the dynamic pressure, this adjusting step thereby maintaining a constant volume of fluid moving through the air duct system. Also disclosed is an apparatus for carrying out this method.

Abstract: An apparatus for the continuous flow fractionation of whole blood incorporates motor driven whole blood, anticoagulant and replacement pumps, negative and positive pressure monitors, and a dual bubble detector which function in conjunction with a disposable single-use flow system and a hollow fiber filter to separate and collect plasma from whole blood. Operation of the pump motors, pressure monitors and bubble detector is controlled by a control circuit within the apparatus to provide one of several operator-selected operating modes, including run, prime and reinfuse modes. The control circuit provides an alarm which can be cancelled by the operator when certain system parameters fall outside of normal operating limits, and interrupts operation of the pumps when the parameters exceed maximum limits. A failsafe circuit independent of the control circuits interrupts power to the pump motors in the event the motors do not stop upon detection of a bubble or fluid absence in the flow system.

Abstract: An improved occulsion detection apparatus and method for use in a pumping apparatus wherein a motor control sequencer provides signals adapted to rotate the shaft of a motor and a pump mechanism through a pumping cycle. The motor is advantageouly initially operated at a first higher torque to insure proper starting of the pumping cycle and is subsequently operated at a second lower torque through the remainder of the pumping cycle, the motor stalling if an occlusion within a fluid delivery system causes the back pressure within the delivery system to exceed the torque capabilities of the motor. An occulsion detector times the pumping cycle and if the cycle exceeds a first predetermined time period, an occulsion alarm is generated. The occlusion detector may further cause the motor control sequencer to increase motor torque to attempt to complete the pumping cycle or may de-energize the motor after a second predetermined period to prevent damage to the pumping apparatus.

Abstract: A control circuit for a liquid fuel combustion apparatus which employs a differential amplifier and square-wave generator to maintain a strong constant combustion in the burner until the differential amplifier senses that room temperature has approached a preselected target temperature, at which point the differential amplifier operates to alter the square-wave generator output to gradually reduce the combustion rate in an inverse proportion to room temperature as the target temperature is being reached. The differential amplifier subsequentially controls the square-wave generator in a manner which causes fuel to be available at a rate necessary and sufficient for maintaining the target temperature.

Abstract: A circulating pump unit comprising a pump and a motor for heating and service water installations, in which the motor is settable to at least two different speeds of rotation by means of a rotation speed switch. According to the invention the motor (1) couples automatically and independently of the operational speed (n) set on the rotation speed switch (3), after switching off or switching on of the unit by means of a start-up switch (5) overriding the rotation speed switch to the rotation speed (n3) with maximum start-up moment (M3) and starts at this rotation speed and after a pre-determined time switches over to the operational rotation speed set on the rotation speed switch. Thereby the circulating pump unit will give a reliable start of the pump also after a standstill for a long time.

Abstract: The present invention relates to an improved air-purifying device for respirators of the positive pressure type.The device comprises an expandable chamber having an outlet for connection to a facepiece, for example, a face mask, and an inlet connected to a pump for drawing ambient air into the device through a filter and pumping it into the chamber. In use, the wearer of the face mask draws air from the chamber and that air is replenished by operation of the pump.Apparatus is provided for sensing the degree of expansion of the expandable chamber and is coupled with a device for varying the power supplied to the pump so that the pump means supplies only sufficient filtered air to maintain the chamber inflated. A bias is provided on the chamber, advantageously coupled with the sensing apparatus for maintaining a positive pressure in the chamber.

Abstract: A water pump protector which includes electrical circuitry through which an electric motor is energized. The electric motor operates a water pump. The circuitry senses the phase angle between the voltage and the current applied to the electric motor. When the phase angle indicates that the motor is operating without a load, the circuitry deenergizes the electric motor. Thus, the water pump is protected against damage which may occur when the water pump is operated without pumping water.

Abstract: Method and apparatus for matching the power output of a multitorque motor with the torque requirement of a connected load device. The stator windings of the motor are automatically connected in various different configurations to provide the optimum motor torque demanded by a connected load device which imposes varying load conditions on the motor. A novel control circuitry is connected between the motor starter and the motor stators. The control measures the power drawn by the motor stators and selects the most optimum configuration thereof which meets the changing torque requirements of the connected load device. This selection of optimum stator winding configurations commensurate with torque demand operates the motor in the lowest possible torque mode, which is considered the best electrical and mechanical operation of the motor and connected load device.

Abstract: A protection device and circuit for a fluid pump or the like including a motor control relay MS for actuating relay contacts MS-1, MS-2, MS-3 that control the communication of power to a drive motor 10a, and a manual reset motor protection device 24 that deenergizes the control relay in response to sensed malfunctions. The motor protection device comprises a manual reset motor protector 40 having switch contacts 42 connected in series with the motor control relay and a tripping coil 44 which, when energized, opens the switch contacts. A current shunt path 46 including serially connected pump assembly mounted sensors 48, 50, normally shunts current around the tripping coil and is interrupted in the event of a sensed malfunction, causing the energization of the tripping coil which opens the switch contacts and deenergizes the drive motor. The switch contacts must be manually reclosed to reactivate the pump assembly.

Abstract: A motor control circuit for submersible pumps has features to prevent restarting while the electric motor is backspinning. The circuit includes a sensor for sensing the voltage produced by the residual magnetism in the rotor of the motor while it backspins. The voltage sensed is amplified, then rectified and compared with a reference voltage that is preset. The reference voltage corresponds to a voltage produced during backspinning at a selected maximum amount tolerable when restarting. The DC pulses are filtered to provide a corresponding voltage, then compared to the reference voltage. The control circuit is disabled from allowing a restart, either manual or automatic, when the corresponding voltage is greater than the reference voltage.

Abstract: A portable battery powered pump providing constant mass flow of air sample through a particular filter or vapor trap in which the pump drive motor speed is controlled by an amplifier having a reference voltage input and an inverse feedback signal related to sensed motor speed. Compensation for increased resistance to air sample flow is made by a motor current feedback signal applied to the amplifier to cause motor speed to increase with increased flow resistance.

Abstract: Disclosed are a method and system for monitoring and controlling the normally inaccessible dynamic operating conditions, such as well fluid head and motor terminal voltage, of a well pumping operation, in response to monitored conditions at the top of the well. At the heart of the system is a computer having, stored therein, coded data representative of the fixed well, motor, and pump characteristics and programs defining the mathematical relationship between the stored fixed data, dynamic operating conditions of interest, and the monitored conditions. Feedback control for regulating the well fluid head and motor terminal voltage include the computer and uniquely designed frequency converter and line drop compensator apparatus.

Abstract: A method and apparatus for controlling a resonant piston compressor of the type comprising an electrodynamic linear reciprocating motor adapted to be driven cyclically by an alternating current power source and having at least one piston coupled to and adapted to be driven within a selectively valved working cylinder by the linear reciprocating motor in synchronism with the frequency of the alternating current power source. Enclosed volumes of gas act as resilient gas springs coacting with the piston and with the linear reciprocating motor to form a mechanical resonant system having a resonant frequency substantially centered on the frequency of the alternating current power source. A midstroke porting arrangement is responsive to the position of the resonant piston for selectively communicating a gas spring control valve with said gas springs.

Abstract: A pump for producing a substantially smooth and continuous outflow of liquid at relatively high pressure has two piston assemblies flow connected in series. The first piston assembly includes a pressure piston having a long suction stroke and a relatively short and abrupt expulsion stroke. A valve at the inlet of the pressurization piston allows flow to enter (but not exit), and a valve at the outlet of the pressurization piston allows flow to exit (but not enter). The second piston assembly includes a damper piston which functions as a mechanically driven damper to smooth the outflow from the pressure piston. This smoothing is accomplished by storing of the liquid displaced by the expulsion stroke of the pressure piston and then delivering the stored pressurized liquid to the pump outlet during the suction stroke of the pressure piston.

Abstract: A bubbler tube is used to sense the liquid level in a wet well. Controls provide a constant flow of air, approximately 11/2 to 1 cubic foot per hour, through the bubbler tube which extends to about 6 inches above the top of the pump suction pipe. The pressure in the pipe is proportional to the height of the liquid above the bottom of the bubbler pipe. A transducer connected in the bubbler system responds to pressure changes in the pipe which are transformed to electrical signals used to control the speed of the pump driving motor. The motor will always drive the pump at a speed which corresponds to the flow coming into the wet well.

Abstract: The compression type refrigerating device having a compressor defining a pressure space and being driven by an asynchronous motor comprises a pressure sensitive switch arranged in a sealed housing communicating with the pressure space of the compressor and connecting in response to a predetermined pressure level in the housing an additional field coil in series with a main field coil of stator of the electromotor. In this manner the efficiency of the intermittently operating asynchronous driving motor is improved.

Abstract: An automatic speed-control actuator for variable speed pumps. A rotary or near actuator changes the pump speed to prevent unacceptably low pressures on the pump inlet or unacceptably high pressures on the pump outlet; pressure switches at these locations control the actuator to produce maximum flow rates through the pump.

Abstract: A precision-delivery and precision-pressure piston pump is actuated by a cam controlled by a finestep stepping motor. The initial delivery pressure is precisely regulated by fixing the commencement of the delivery stroke at the cam with the aid of the stepping motor, as well as the time required for this delivery. Delivery is also regulated very precisely, for example in a ratio of 1 to 1000 by controlling the delivery stroke with the aid of the stepping motor. The pump is of use in particular in high-pressure liquid-phase chromatography.

Abstract: Apparatus for measuring fluid pressure and velocity, and in particular for maintaining an aspirator air velocity constant under varying atmospheric conditions. A precisely controlled air velocity is provided by a reference air source whose frequency is derived from a crystal oscillator. The total air pressure from the aspirator wind tunnel is compared with the total air pressure from the reference air source using a matched thermistor pair technique to convert the pressure difference into an electrical error signal which is used to control the main air source for the aspirator wind tunnel such that the error signal is maintained at zero, thereby maintaining the air velocity in the aspirator constant.

Abstract: Renewed starting of an intermittently operating pump is controlled in that the running time of the pump from the last start thereof is measured by means of a running time gauge the measuring value of which is maximized, and in that the pause time commencing at the end of the running time is controlled by start delaying means in dependence on the duration, measured by the running time gauge, of the preceding running time such that a long running time gives a short pause time and a short running time gives a long pause time.

Abstract: Liquid flow sensing apparatus which in the illustrative embodiment is used to sense an occluded vein (cessation of blood flow). A flexible pressure pillow is connected in the blood flow line and is inserted into a housing in contact with a metallic leaf spring. The position of the leaf spring is adjusted relative to an eddy current proximity sensor so that the sensing apparatus is calibrated to a no-alarm position during proper blood flow. If blood flow ceases, the flexible pressure pillow contracts thereby moving the leaf spring away from the eddy current proximity sensor and an alarm condition is thereby detected.

Abstract: A method and an apparatus for operating a fuel supply system, in particular a fuel injection system, in which a fuel supply pump continuously supplies fuel and wherein the excess fuel not required for injection is returned to the fuel reservoir. In order to reduce the average operating power of the pump and thus reduce the average amount of fuel returned to the tank, thereby reducing undesirable temperature increases of the fuel in the reservoir, the system fuel pressure is monitored and maintained at a value substantially equal to a reference value. The electrical power of the fuel supply pump is altered continuously so as to maintain the fuel system pressure at the reference level.

Abstract: An improved dosimeter having a low air flow rate for monitoring working areas in which air is pumped through the dosimeter at a controlled constant low rate of flow and any particles or vapors in the air are collected on a filter, a variable drive pump having an inlet and an outlet is connected to the filter and is driven by an electric motor and controlled by a feed back circuit of an integrator and an amplifier and the pump maintains a constant flow of air through the dosimeter; in operation of the dosimeter the integrator receives a signal from a pressure switch that detects changes in the flow of the air stream through the dosimeter by a change in a pressure drop of the air which is being pumped through an orifice;The improvement is the use of an adjustable by-pass valve connected in parallel with the variable drive pump in such a manner that regulated quantities of air from the outlet of the pump are recycled to the inlet of the pump thereby allowing the pump to provide a constant low flow rate of air;In

Abstract: A peristaltic infusion pump is disclosed herein and includes a continuous tubular arrangement adapted to pass intravenous fluids therethrough and a peristaltic pump head mounted for rotation about a fixed axis. This pump head includes a plurality of innerconnected, circumferentially spaced tube engaging members adapted to successively engage the tubular arrangement during rotation for peristaltically pumping fluid therethrough. In a preferred embodiment, the pump includes a stepping motor which is energized in a particular way for rotating the pump head and which is also used to sense occlusion in the tubular arrangement. This preferred pump also includes a particular arrangement for detecting the index of refraction of the intravenous fluid for detecting the presence of air bubbles or the like.

Abstract: A fluid pump mechanism for delivering a smooth output of fluids to a system utilizing at least one piston in a chamber reciprocative therewithin. The piston has strokes that fill and empty the chamber in conjunction with the action of valve means located at the inlet and outlet of the chamber. Motive means causes reciprocation of the piston within the chamber. Control means is also included for minimizing the time during the piston cycle in which the piston is not emptying the chamber. The invention's scope also encompasses a pressure metering device for a fluid forcing means motivated by an electrical motor.