Abstract: A hydraulic pump assembly includes a housing having a bore, and a sump piston, a pump piston and an accumulator piston received coaxially within the bore. The pistons respectively define a sump chamber, a pump chamber, and an accumulator chamber within the housing. A motor reciprocates the pump piston to pump fluid fron the sump chamber into the accumulator chamber.

Abstract: A regulation system controls the print head pressures of a plurality of discrete ink jet printers of the continuous type to the same nominal pressure, while the printers use a common drive source to their own ink pumps. The regulation system includes bypass pressure detection passages extending from a tap in each printer's circulation system to a detection reservoir. Each bypass passage includes a bladder/valve portion whose exterior is in fluid communication with a detection fluid enclosed within the common reservoir. A transducer detects the pressure of the common reservoir and signals control of the common pump drive so as to regulate all print head pressures to the same nominal operating pressure.

Abstract: A probe is mounted on a water submersible pump housed within a transformer vault. The probe will extend into any water which accumulates in the bottom of the transformer vault enabling a conductive path to be established through an appropriate electric circuit to the pump motor to permit operation of the pump so that the water which is on the bottom of the vault can be safely pumped from the vault. As the water level falls as it is pumped, oily fluids, which are immiscible in the water and will normally rise to a level above the water level in the vault, will come in contact with the probe to form an electrical insulator to inactivate the circuit to disconnect a power source from the pump motor.

Abstract: The invention concerns a bilge pump control system. Sensing of water level in the bilge is accomplished by the conduction of current (on the order of one milliampere) between two stainless steel probes. The probes are mounted in a triangular package which is placed in the boat bilge. When immersed, a conduction path is provided between the probes. One edge of the package is aligned with the probes to enhance water run-off. An associated circuit is activated when the conduction path is present (when the probes are immersed) which operates the bilge pump in a time-hysteresis fashion.

Abstract: A rheostat of the kind that comprises a tank containing electrolyte and at least two electrodes, one electrode being connectable to an electric power supply and the other electrode being connectable to apparatus to be fed by the power supply. The electrodes define therebetween an electrolyte flow path and there is associated with the electrolyte flow path operational pumping apparatus providing for a controlled effective circulation of the electrolyte between the electrodes. The rheostat is particularly usable in conjunction with the starting of squirrel-cage motors.

Abstract: Alternator circuit arrangement (20) for controlling the electrical energization of multiple load devices such as two pump motors (41,42) on an alternating basis so as to maintain the level of a liquid (86) in a container (84) within a predetermined range. The alternator circuit arrangement (20) further including an RC circuit (54) having a capacitor (62) for discharging through a normally closed switch (50b) which is opened during energization of the pump motors (41,42) so as to energize a bi-stable relay (52) which in turn interconnects alternate ones of the pump motors (41,42) to the alternator circuit (20) such that upon detection of the liquid (86) at an intermediate level (96) alternate ones of the pumps (41,42) are energized.

Abstract: A sump pump assembly having a primary sump pump and a secondary sump pump and including a T-fitting for connecting together the outlets of the primary sump pump and the secondary sump pump to a common exhaust. The T-fitting contains a one-way valve on the secondary pump outlet connection and a fastening means for a water level sensing device.

Abstract: An apparatus for sensing the difference between a polar fluid and a non-polar fluid includes a control assembly, a probe assembly and a conduit electrically coupling the probe assembly to the control assembly at a remote location thereto. The probe assembly includes a float, at least one fluid sensor mounted beneath the float, a fluid sensor circuit for providing a signal indicative of the polar characteristics of the fluid, and a logic circuit having a first state when the signal indicates a polar fluid and a second state when the signal indicates a non-polar fluid. The control assembly includes circuitry responsive to the state of the logic circuit for controlling alarms, visual indicators, and machine operations. The probe assembly may also include a detector for detecting the state of the fluid. If the fluid has a non-liquid state then the logic circuit has a third state which indicates the non-liquid state of the fluid.

Abstract: A direct current operated bailer pump which utilizes battery power to winch up, while recovering the energy generated by the motor acting as a generator during the downward movement of the bailer to recharge the battery. A sensing circuit senses when the bailer contacts the surface of the oil by monitoring the generated voltage from the motor. A voltage drop corresponds to the sudden decrease in velocity as the bailer encounters the surface of the oil in the well. A dynamic brake is connected to the motor, after a set time period, to decrease the down speed of the bailer to a predetermined safe speed.

Abstract: A hydropneumatic tank control for a water supply system having a closed water tank (10), an air compressor (17) and a water pump (21, 22). A plurality of pressure switches (PS18, PS23, PS25, PS26) at the air compressor detect air pressure threshholds in the tank and a plurality of water level detector electrodes (32, 33, 34, 35) detect water level threshholds in the tank. A control causes the water pump to fill the tank to a pressure level or a water level at the operator's option. A pressure switch (PS2) in a tank adapter assembly (20) shuts down the system if an over pressure condition is detected. The compressor is housed in a waterproof housing (41) and cooled by a blower (48) passing air through the housing with thermostats (TH14, TH15, TH16) functioning to protect the compressor from overheating. A baffle 52 prevents the cooling air from recirculating through the housing.

Abstract: A system for controlling production in an oil well comprises a controller for activating the means for causing reciprocation of the sucker-rods; a sensing means secured to the outer surface of the production tubing near the lower end thereof comprising a radioactive source spaced from a radioactivity detector such that oil at that level will fill the said space, means associated with said radioactivity detector for counting the output of the detector and establishing an "off signal" when the frequency of the output is indicative of no oil in the said space; means for converting the "off signal" into an acoustical signal directed up the borehole; and receiving means at the top of the borehole for detecting the acoustical representation of the "off signal" and transmitting it as an electric signal to said controller.

Abstract: A stepper for use between a transducer subjected to variable pressure, heat or liquid level for converting the continuous output signal of the transducer with all of its variations, both of significant magnitude and those of insignificant importance, into a continuous stepped output signal that increases or decreases the current to a transducer responsive control unit, particularly a servo amplifier, which stepped signal eliminates all minor and unimportant fluctuations from the output current from the transducer. The stepper also includes a sequence of voltage regulators such as potentiometers in the circuits between the stepper and the servo amplifier by means of which the magnitude of the current flow of each step to the servo amplifier may be adjusted or programmed with respect to one another. It is particularly useful in the regulation of flow control valves in water distribution and sewage disposal systems, but its application to steam boilers is also disclosed and described.

Abstract: A 100% solid state, liquid level control circuit which utilizes printed board construction with integrated circuits to control duplex pumps. Mercury switches provide information to the solid state, non-inductive input interface circuitry which relays this information to logic control circuitry and an alternator. The logic control circuitry and an alternator forward the information to solid state, non-inductive output circuitry for powering pump starters. The alternator selectively alternates the sequencing of the pumps for controlling the lead pump. Current limiting devices, light emitting diodes and logic control circuitry are combined to provide operation of pump starters for controlling the liquid level in a wet well, reservoir, bilge of a vessel, or the like.

Abstract: An in-ground control system to override an automatic sprinkling system during periods of excess rain or moisture, having a housing with a peripheral water collection trough connected to a collection chamber. Sensors are positioned in the chamber and upon a predetermined rise in the water level in the chamber will either operate a control to suspend operation of the watering system or to operate a pump to carry away excess water.

Abstract: A method and apparatus for controlling the amount of fluid (12) pumped to a using implement by a fluid distribution system (10) is the subject of this application. The apparatus includes a weir chamber (40) into which fluid diverted from a fluid supply line (22) into a return line (36) floods. A head is generated in the chamber (40), the height of the head depending upon the volumetric rate of residual flow through the return line (36). Sensing means (52, 54) are provided in the chamber (40) to sense the volumetric rate of flow of diverted fluid. The amount of fluid (12) pumped through the supply line (22) is controlled, in response to the head sensed in the weir chamber (40), by a controller unit (62) which governs operation of pumps (24) pumping fluid (12) through the supply line (22).

Abstract: A useful dry battery driven liquid pump for pumping liquid such as kerosene or the like into a tank for an oil heater or the like very conveniently includes a combination of a motor and a liquid pump disposed at the lower end part of a suction tube, a plurality of dry cells contained in a dry battery casing, a liquid surface level detector disposed at the lower end part of a delivery tube and a control circuit which controls operation of the liquid pump properly in response to an output from the liquid surface level detector. The liquid surface level detector includes a prism formed at the lower end of a cylindrical detector body, a light beam generating element and a light beam receiving element. The liquid pump is driven as long as the prism does not get wet with liquid and thus light is reflected from the inner optical surface of the prism toward the light beam receiving element.

Abstract: There is disclosed a microprocessor-controlled peristaltic pump for use in a portable continuous insulin infusion device. The peristaltic pump is configured with a removable cover comprising a part of the pump housing surrounding a pump rotor, and holding a delivery tube between the cover and the rotor. The removable cover combines with a reservoir and the delivery tube to constitute a pre-filled disposable package facilitating installation and removal of the insulin in the device. A microprocessor controls the number of times the rotor turns during a cycle. This operation allows the microprocessor to automatically compensate for different diameter delivery tubes, as well as to allow the physician to vary the on/off time of the pump to administer different dosages.

Abstract: An outdoor water holding and pumping system comprising a water tank into which is recessed a pump housing such that water in the tank surrounds and insulates the housing. A pump is disposed in the pump housing for pumping water from the tank to a desired location. The pump housing has a door providing access to the pump from outside the tank. The system preferably includes a housing conduit which extends from the housing to the base of the tank so that conduits to and from the tank can extend underground, through the tank, and to the pump without being exposed. Reserve conduit means are also preferably provided to provide a reserve supply of water to the pump. The system elements are preferably connected for transporting as a unit.

Abstract: An apparatus for controlling the operation of a pump, especially a submersible pump, and particularly for controlling a water level in connection with cellar drainage pumps, comprises at least one level detector using the principle of acoustic impedance for detecting the presence or absence of liquid to be pumped, said level detector being electrically connected to a control circuit controlling a switching device for the pump.

Abstract: A liquefied gas transfer apparatus having a recirculation passage for recirculating the liquefied gas sucked into a glandless pump back into the closed tank, and a device for changing the speed of the pump driving motor by suitable measures such as pole change, Y-.DELTA. switching, frequency control, primary voltage control or the like. In operation, the pump is driven at a high speed during the transfer of the liquefied gas from the tank to the containers or the like, whereas, in the period in which the transfer of the gas in not necessary, the pump is continuously operated at a low speed while recirculating the liquefied gas through the recirculation passage, thereby to prevent the evaporation of the liquefied gas in the pump to ensure smooth and safe intermittent operation of the pump, as well as prolonged life of the bearing.

Abstract: A control system (10) is provided for maintaining a constant fluid level in a mixing container of a delivery and metering device. Structure (12) is provided for monitoring the fluid level in the mixing container and for generating a level signal (14) representing the fluid level present in the mixing container. Structure (18) is further provided for establishing a desired amount of fluid entering the mixing container and for generating a first control signal (20). Structure (22) is provided for establishing a desired amount of fluid discharged from the mixing container and for generating a second control signal (24). Measuring devices (30, 34) are utilized for measuring the amount of fluid discharged from the mixing container and for generating a discharge signal (36) representing the amount of fluid discharged from the mixing container.

Abstract: A circuit for controlling a pump for pumping a column of gasoline floating on a column of water. A first probe is positioned at the level of the pump intake and a second probe is positioned beneath the first probe. A float switch is positioned adjacent the pump intake for providing a signal when the pump is immersed in liquid. The float switch and the probes are operatively connected to an AND gate circuit which generates a preselected signal when both probes are immersed in a nonconducting liquid. A time delay is operatively connected to the AND gate and begins a timing period responsive to the preselected signal. At the end of the timing period, the time delay provides a signal which energizes the pump. A latch circuit maintains the pump in an energized condition until both probes are again immersed in water.

Abstract: This is a digital solid state control system for pumping liquid to regulate the condition of the liquid in a container, such as the liquid level. One pump is turned on when the liquid rises to one level, and another pump is turned on when the liquid rises to a higher level. An alarm is activated if the liquid rises to a still higher level or if a leak occurs in either pump. The control system alternates which pump turns on first in successive operating cycles. If a power failure occurs while both pumps are on, when power is restored only one pump comes on immediately; the other comes on only after a time delay.

Abstract: A submersible pump adapted to pump out the liquid in a reservoir has a built-in control unit for alternate pump operation. The control unit includes step memory means which provides a signal to permit the starting of pump operation every other time a high liquid level sensor senses the liquid. Once started, the pump continues its operation until the liquid level drops below a low liquid level sensor. The submersible pump can be combined with an additional pump having a conventional control unit in which case the two pumps are alternately operated.

Abstract: A sump pump includes a submersible electric motor for driving an impeller which discharges water radially outward into a volute oriented in a horizontal plane at the bottom of the device. An optical sensor located at a predetermined pump-operating level utilizes the light reflecting and refracting properties of the sensor-chamber interface to sense the presence or absence of water at such level. In a first embodiment, the pump includes a supplementary water level-sensing chamber which has a first leg ascending from an inlet near its lower end to an overflow point at the top of a vertical barrier separating the first leg from a second leg which descends to the low pressure area of the impeller.

Abstract: Disclosed is a liquid level controller that uses a pair of vertically spaced thermistors to control a switching means to turn a pump on when a sufficient depth of liquid is present and to turn the pump off before the pump runs dry. Such a device is ideally suited for applications such as "stripper" oil wells. The present invention uses thermistors in the self heat mode and senses the changes in the resistance between a thermistor exposed to air and one submerged in liquid, the latter increasing resistance because it is far more efficient in transferring away heat generated by the thermistor. The change of resistance when the liquid level covers the higher of the thermistors is detected by the use of comparators which selectively turn on a driving transistor. Turning the transistor on activates a coil which throws a relay switch and activates the control circuitry of the pump motor.

Abstract: A source of acoustic pressure pulses is coupled to the surface casing of a well so that they are transmitted down the well and reflected by the gas-liquid interface. A transducer is also coupled to the well to produce an electrical signal in response to direct and reflected acoustic pulses occurring in the well. Gating circuitry responds to the transducer for starting and stopping the counting of clock pulses by a digital counter. The digital count controls a pump so that the liquid level in the well is precisely controlled between desired levels.

Abstract: Device for activating or inactivating a liquid pump on the basis of the electrical conductivity of a liquid. Device comprises, in combination, a housing having a passageway through which a liquid can flow, a pair of conductivity-sensing electrodes disposed near or in the passageway, means for connecting the passageway to a liquid pump, and means for connecting the electrodes to a conductivity-dependent pump activator connected to the pump. Device provides through-the-probe pumping and is adaptable for manual operation or in-line liquid control.

Abstract: A sensor utilizes the opposition of a fluid to physical displacement to provide information about the fluid itself, such as its quality as measured by its density or viscosity, or about the state of a fluid system which contains it, such as the fluid pressure existing at some point in the system. The sensor includes a fluid displacement device or element physically adapted to displace the fluid and repetitively urged into displacement by the application of a known impetus or urging force. The resulting motion of the element is then analyzed to obtain the information desired. The fluid displacement element may additionally perform a pumping function, or it may operate in a fluid stream externally powered. When employed as a pump, the sensor may provide information on the fluid pumped or on the state of the fluid system.

Abstract: A suction pump has a suction pipe extending into a tank for receiving liquid. A detector, connected to a control circuit for the pump, is arranged to initiate operation of the pump when the liquid in the tank rises above a predetermined level. The detector comprises a hollow member of insulating material connected to the free end of the suction pipe. The member has a transverse dimension which is greater than that of the suction pipe whereby a shoulder is defined which connects the member to the pipe. Two or more electrodes are mounted on the member and the pump is operated when the liquid completes a circuit between the two electrodes. The electrodes are protected by the shoulder from liquid running backwardly within the suction pipe when the pump has stopped. In addition, a time delay means is included in the control circuit to delay restarting of the pump once it has stopped.

Abstract: An apparatus for dispensing material from a container comprising a plate having an aperture therein through which material is caused to flow out of the container when the plate is caused to move vertically within the container. A scraper member is spaced from and coupled to such plate to engage the inside walls of such container to scrape material from the walls as the plate moves vertically relative to the container. A space is formed between the scraper member and the plate to form a cavity which communicates with the aperture and which includes a material entering opening, the level of material in the cavity being controlled during operation of the apparatus.

Abstract: A source of acoustic pressure pulses is coupled to the surface casing of a well so that they are transmitted down the well and reflected by the gas-liquid interface. A transducer is also coupled to the well to produce an electrical signal in response to direct and reflected acoustic pulses occurring in the well. Gating circuitry responds to the transducer for starting and stopping the counting of clock pulses by a digital counter. The digital count controls a pump so that the liquid level in the well is precisely controlled between desired levels.

Abstract: In this solar steam driven water pump steam is periodically generated and then condensed within a cavity to produce first a period of pressure over a column of water and then a period of vacuum to thereby first expell water from the cavity through one check valve and to subsequently fill the cavity with water through another check valve at the time of the vacuum, the generation of said steam pressure within said cavity being effected by a separate small pump within the cavity when this pump moves a small quantity of water in the cavity to a solar heated chamber in the cavity and the subsequent effecting of the vacuum within said cavity being accomplished when the water pumping chamber is cooled by condensation of the steam on the column of water against which it is acting, the periodic cessation of the small pump causing steam generation to cease when thermostats contacted by hot steam as water is expelled from the water chamber open a circuit stopping the small pump.

Abstract: An electrically operated device such as a duplicating machine has a recptacle for accommodating a fluid for the chemical treatment of sheet material and like objects. The receptacle may be in the form of a dip tank designed for passing sheet material therethrough. This dip tank is connected via a supply conduit to a storage tank and the supply conduit includes a pump controlled by an automatic charging and metering unit for supplying fluid to the dip tank. A drain conduit leading to the storage tank is connected to the dip tank. This drain conduit includes a solenoid valve for stopping or allowing the flow of fluid through the drain conduit.

Abstract: An electronic controller maintains the level of fluid in a container between an upper level and a lower level defined by the location of two probes in the container. Each probe actuates a first light source-photosensor pair used for controlling a device capable of changing the fluid level in the container. In some embodiments of this invention, a second photosensor-light source pair latches the first pair to provide system hysteresis. In other embodiments, the same pair both controls the fluid level device and latches itself to provide system hysteresis.

Abstract: A system for sensing and controlling the level of fluent material in a reservoir or other receptacle. In electrically conducting materials levels are sensed by low voltage direct current conduction between electrode pairs placed at desired "high" and "low" control levels which send D.C. digital logic sensing signals over connecting wires to very high resistance "high" and "low" inputs of a digital logic signal processing circuit, while nonconducting material levels are sensed by suitable transducers which upon immersion can send D.C. digital logic signals. The digital signal processing circuit receives the sensor signals and provides a digital output signal or absence thereof, depending on the relative state and sequence of the sensing signals and transmits a digital output signal to a solid state relay which controls the power of flow control means to maintain desired levels of the fluent material.

Abstract: An improved system for sensing and controlling the level of fluent material in two reservoirs when material is transferred from one reservoir to the other. In electrically conducting materials, levels are sensed by direct current conduction between electrode pairs placed in each reservoir at desired "high" and "low" control levels which send D.C. digital logic sensing signals from these four sensors over connecting wires to four high resistance input circuits of a digital signal processing circuit; in electrically nonconducting materials, levels are sensed by suitable transducers which upon immersion send D.C. digital logic sensing signals to the digital signal processing circuit.

Abstract: A method and apparatus for regulating electrolyte solution level in a liquid rheostat. The liquid rheostat is used to control the motor speed of a primary pump which is operable for pumping liquid from a well. The liquid rheostat includes an electrode compartment mounted above an electrolyte solution reservoir and solution from the compartment may drain into the reservoir. A conduit interconnects the reservoir with the compartment and a circulating pump, driven by a variable speed electric motor, is operable for delivering solution from the reservoir to the compartment. A sensor is immersed in the well and develops a signal proportional to the amount of liquid in the well. The signal is received by a motor control which operates to vary the speed of the circulating pump motor, and thus the solution level in the compartment, reflective of liquid level in the well.

Abstract: An AC driven pump and a DC driven pump are positioned in a sump and respectively energized as the liquid in the sump reaches two different levels, the DC driven pump being automatically tested for operation after every predetermined number of pumping cycles of the AC driven pump.

Abstract: A sewage pump assembly includes a sewage pump having an inlet port; and a substantially vertical pipe connected to the inlet port of the sewage pump, and extending up to a predetermined level relative to the sewage pump. The vertical pipe has a first inlet opening directed upwardly at its top end, and a second inlet opening extending in a predetermined length from the top end along the vertical pipe. The vertical pipe is connected through a long vertical suction pipe to the inlet port of the sewage pump. Floating materials on the filthy water can be sucked into the first and then second inlet openings of the vertical pipe for a long time required for the water level of the filthy water to change from a level slightly higher than the first inlet opening to another level adjacent to the lower end of the second inlet opening.

Abstract: A governor for a steam operated engine by which the steam valve opening for any selected engine speed can be varied to accommodate different steam pressures, or conversely with a constant steam pressure, the steam value opening may be varied to produce any selected engine speed.

Abstract: A method and an apparatus for liquid supply use a pressure tank and a plurality of pumps. When the pressure or liquid quantity in the pressure tank has decreased below a predetermined level, a preceding or regular pump starts. When the demand is too large for this pump, another pump in standby position starts, too. The regular pump continues running for a predetermined period of time after the start, even if the pressure or liquid quantity in the pressure tank has returned to a predetermined level, whereas the standby comes to a stop upon such recovery. In this manner the frequency of starting the pumps is minimized so as to avoid overheating of pump-driving motors and reduce the power consumption.

Abstract: A plurality of probes are situated as to experience being touched by the liquid being monitored; when at least one of such probes is touched by the liquid related electrical circuit means becomes energized as to cause related pumping means to be activated thereby pumping some of the monitored liquid to, in turn, reduce the level of such monitored liquid; when the level of the monitored liquid decreases to a predetermined level, the pumping means is automatically de-activated; during periods wherein there might occur a momentary splashing or sloshing of the monitored liquid, time delay means serves to correspondingly delay activation of said pumping means thereby preventing unnecessary activation of the pumping means.

Abstract: Pump off conditions of an oil well are determined by listening to the sonic clicks of the traveling valve and bottom hole valve. If the clicks do not occur within a certain period after top dead center for successive pump cycles, the well is assumed to be pumped off and is shut down. If, upon being restarted for a successive number of times, the valves do not click within the proper time frame it is assumed that there has been a pump failure and the well is shut down until manually restarted.

Abstract: The disclosure is a system for increasing the reliability of systems for keeping auxiliary liquid-holding tanks filled and reliably functional. A float-operated switch cycles an electric pump to maintain the liquid level between full and nearly full, and a back-flow-preventing check valve is employed and modified (apertured and/or bypassed) to permit slow back leakage to "exercise" the system. The pump, its input to the tank, and the check valve are all located below the pump-turn-on level so that they never lose their prime. One arrangement for testing liquid-level control has a float on a lever arm that operates both the pump-motor-cycling switch and also a low-level switch to energize an alarm. The lever arm also rotates a shaft carrying an indicator dial and/or pointer. The shaft has a manually engageable knob or lever for submerging the float to test the operability of the pump, the alarm, and other parts.

Abstract: A rain activated control system which shuts off an irrigation pump when a predetermined amount of rainfall occurs. A receptacle for catching rain is mounted in a manner to provide adjustment of the distance between its bottom and a pair of electrodes which extend into the receptacle. When rain is collected in the receptacle in sufficient quantity to immerse the electrodes, a control circuit is completed to operate a relay. The energized relay then activates the shut down system of the engine or motor which drives the irrigation pump. Ater a time delay sufficient to assure complete shut down of the pump, a timing circuit causes deenergization of the relay and closes a reset circuit. When the irrigation pump is to be restarted, the rain receptacle is emptied and a reset switch is opened to reset the control circuitry.

Abstract: An electronic system for determining, indicating and regulating the level of semi-solid matter, such as sludge, in a fluid medium. The system produces and directs ultrasonic signals toward the matter, and the reflected signals are used to compute signal transit time and thus indicate incremental sludge levels. An output signal is produced when the matter reaches a preset level, to activate a pump and thus regulate the sludge level.

Abstract: A device is described which comprises in combination at least one resistor means placed at a determined level on the inner wall surface of the vat, said resistor means having a resistance which is variable in response to the presence or absence of the liquid at the level thereof; switching means responsive to a control signal for causing the feed pump means for the liquid to be stopped, and control means for producing the control signal for the switching means, said control means comprising impedance means which includes the resistance of the said at least one resistor means, whereby the said resistance being varied by the presence or absence of the liquid in the vat at the level thereof causes the control means to operate the switching means thereby to stop or restart the feed pump means.

Abstract: A circuit for sensing and controlling the level of fluid within a reservoir includes a pump for controlling the level of fluid. The circuit further includes two sub-circuits each including a probe adapted to contact the fluid. Each sub-circuit further includes an SCR and an oppositely poled diode. Also included is a relay coupled to the sub-circuits for operating the pump. The relay is designed to energize the pump only upon submersion of both of the probes. The circuit is coupled to an AC transformer having, in one embodiment, an off-set center tap such that upon submersion of the first probe the first sub-circuit conducts a first magnitude of energy that is insufficient to pull in the relay but is sufficient to hold in the relay once it is actuated. In an alternative embodiment, the transformer includes first and second resistors coupled between the relay and the first and second sub-circuits, respectively.

Abstract: A pump control for a pipeline milking system in which milk collects in a receiver and is pumped out periodically. The control has a liquid level sensing circuit connected with an electrode in the receiver. The sensing circuit includes a transistor amplifier, a source of alternating signal, a circuit connecting the source through the electrode and liquid with the base of the transistor and a sensitivity resistor connected in shunt with the transistor base. A timer actuated by conduction of the transistor controls the pump operation. The circuit has provision for control of the pump operation during washing with a switch selecting the milk or wash control electrode and selecting the appropriate time period for the timer.