US 3695055 A
A temperature compensating refrigerant charging device and refrigeration servicing unit comprising a volumetric refrigerant flow establishing unit such as a volumetric charging pump controlled by a temperature-responsive timer assembly comprising a thermistor-controlled, pulser-actuated counter which may be pre-set for the desired weight of the refrigerant to be placed in a refrigeration unit. When the temperature of the refrigerant entering the pump is relatively low and its density correspondingly high, the thermistor resistance changes to increase the pulsing rate of the pulser and cause the counter to reach shutoff position in less time. When the temperature of the refrigerant is relatively high, the thermistor resistance change causes the pulser to discharge at a slower rate thereby increasing the time it takes the counter to reach shutoff position and allowing the pump to complete more cycles and to introduce a larger volume of the less dense refrigerant into the system.
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Description (OCR text may contain errors)
United States Patent 51 Bruce 1 Oct. 3, 1972  TEMPERATURE COMPENSATING  ABSTRACT REFRIGERANT CHARGING DEVICE  Inventor: Ralph E. Bruce, 6342 Seton Hill,
Dayton, Ohio 45459  Filed: July 15, 1970  App]. No.: 55,059
 US. Cl. ..62/157, 62/126, 62/292  Int. Cl. ..G05d 23/32  Field of Search ..62/157, 77, 216, 126, 222, 62/224, 225, 292, 227
 References Cited UNITED STATES PATENTS 1,744,287 l/l930 Tibbetts ..62/292 3,491,546 [/1970 Holzer ..62/227 X 3,282,063 11/1966 Klipping et al ..62/216 X 3,293,877 12/1966 Barnes ..62/224 X 3,400,552 9/1968 Johnson et al. ..62/292 X 3,478,534 11/1969 Matthies ..62/225 Primary Examiner-Meyer Perlin A temperature compensating refrigerant charging device and refrigeration servicing unit comprising a volumetric refrigerant flow establishing unit such as a volumetric charging pump controlled by a temperature-responsive timer assembly comprising a thermistor-controlled, pulser-actuated counter which may be pre-set for the desired weight of the refrigerant to be placed in a refrigeration unit. When the temperature of the refrigerant entering the pump is relatively low and its density correspondingly high, the thermistor resistance changes to increase the pulsing rate of the pulser and cause the counter to reach shutoff position in less time. When the temperature of the refrigerant is relatively high, the thermistor resistance change causes the pulser to discharge at a slower rate thereby increasing the time it takes the counter to reach shutoff position and allowing the pump to complete more cycles and to introduce a larger volume of the less dense refrigerant into the system.
Assistant ExaminerRonald C. Capossela V V H 7 W7 Drawing Figures Attorney-Norman R. Wissinger 90 PR v -v 46 SW Til REL 321 la 22 B PULSER CALIBRATION l8 cmcun CIRCUIT N LL mm 42 I5 30 44 U) cnARcmc A sun, POWER 1 if SUPPLY /2 4m /7 REFRIGERATION unn PRTENTEDUBH I972,
SHEET 1 BF 2 CALIBRATION CIRCUIT REFRIGERATION UNIT D 67 U PULSER D I as 94 CALIBRATION cmcun n I I L H 95 Lqfl 60 IIVVEWTOI? RALPH E. BRUCE ATTORNEY P'ATEN TED B I972 3.695.055
SHEET 2 0F 2 s. 7 65 TRANSFORMER '64 l 65 g J/ I -73 i I 83 a4 8586' a Ll T0 7 START T0 COUNTER BU4T;0N A J swn c 4 I c/-93 c A CI I I T0 RELAY 94 I OFF OFF i T0 COUNTER SWITCH 47 T0 THERMISTER 27 T0 PULSER 32 wy INVENTOR RALPH E. BRUCE A TTORNE Y TEMPERATURE COMPENSATING REFRIGERANT CHARGING DEVICE BACKGROUND OF INVENTION 1 Field of the Invention The within invention pertains to the art of refrigeration servicing devices and relates particularly to a refrigerant charging device consisting generally of a volumetric metering pump, a vacuum pump and a charging gun, the latter of which may be associated with a refrigeration unit such as an air-conditioner for selectively evacuating the refrigerant system and thereafter filling the same with a precisely controlled weight of refrigerant. The invention is particularly adaptable to such devices as are portable and can be used in the maintenance and repair of refrigeration units in the field such as automotive air-conditioners or home refrigerators and air-conditioners.
2. Description of the Prior Art In the maintenance of refrigeration systems such as automotive and residential air-conditioners and home refrigerators, the most recurrent failure is the loss from the system of the required amount of refrigerant. There is accordingly a need for portable means of introducing new refrigerant to such systems and an equally important need for introducing precisely the correct amount thereof. Because the volatile nature of the refrigerant and its performance in the unit are such that it experiences substantial density changes in cycling through the unit, alternately passing from a liquid to a gaseous phase, it is desirable that the amount of refrigerant be controlled as a function of its weight rather than its volume. On the other hand, prior art methods for installing a measured weight of the refrigerant are complicated and timeconsuming and are accordingly difficult to manipulate and to control with the necessary degree of precision, especially when used in the field under conditions and by operators which are not amenable to close control.
While the prior art has involved principally the use of volumetric pumps or metering devices for the actual introduction of the refrigerant into the refrigeration systems, it has either disregarded the effects of temperature-induced density changes or has resorted to elaborate means for maintaining a relatively constant temperature at that predetermined level for which the particular unit has been calibrated. In the former case it has, of course, been impossible to install the precise weight of the fluid that the machine requires and, especially in the servicing of field units where a wide range of ambient temperatures are encountered, the variations in the weight of the refrigerant charge has often been such as to render the unit inoperable. On the other hand, the time, attention and elaborate mechanism normally required to maintain a certain desired temperature in the face of widely varying ambient conditions have traditionally rendered this approach economically impractical.
It is accordingly an object of the present invention to provide an improved servicing device which is capable of charging a refrigeration unit with a precise weight of a refrigerant.
Another object of the invention is to provide such a device which is operable in environments of widely different or changing temperatures.
SUMMARY OF THE INVENTION To achieve these and other objects and advantages which will appear from the following disclosure, the present invention utilizes the known concept of a volumetric metering pump for transmitting a charge of refrigerant from a supply tank or reservoir to the individual unit with appropriate conduits and fittings. To provide a controlled weight of the refrigerant charge so supplied however, the present invention teaches the introduction into the volumetric pump operating circuit of a temperature-responsive timer assembly which comprises an electronic pulser controlled by a thermistor circuit for sensing the temperature of the refrigerant at the point where it enters the pump and a relay-activated mechanical counter switch wherein the switch, after the pre-selected number of pulses have been counted, stops the pump operation. The pump itself is made to operate at constant speed whereby it will induce a consistent volume of refrigerant for a given time of its operation. As the timer acts to reduce the time of such pump operation, it of course lessens the volume of refrigerant in the charge; whereas, if the timer allows for a longer pump operation, the volume of the charge is correspondingly increased. Where the changes in pump operation time and the resultant volume of the charge are calibrated in connection with the thermistor-pulser-counter assembly so that the changes in the volume are inversely proportional to the temperature-induced changes in the density of refrigerant, it follows that for any given setting of the counter, a constant weight of the fluid may be supplied to the unit, regardless of the ambient temperature in which the device is operating and, more precisely, regardless of the temperature of the fluid at the critical point at which it is introduced into the metering pump.
In a preferred modification of the invention, a separate calibration circuit is provided wherein the thermistor is replaced by a resistor or bank of resistors having known resistances corresponding to the design resistance of the thermistor for various temperatures in connection with which the time of pump operation for a given charge is known. The time during which the counter operates in response to any such resistance can then be read and compared with the known time to determine whatever adjustments are necessary to compensate for nominal variances in the actual resistance of the thermistor. The device of this invention is customarily used in combination with a vacuum pump which, along with the metering filling pump, is connected to a charging unit or gun for simultaneously connecting the vacuum pump with the low side and the filling pump with the high side of the unit to be serviced.
The invention thus generally described may be more clearly understood by reference to the following detailed description of a preferred embodiment thereof in connection with which reference may be had to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings FIG. 1 is a schematic representation of the components of a refrigeration unit servicing device embodying the features of the present invention.
FIG. 2 is an electrical diagram of the circuitry to be associated with the components of the unit illustrated in FIG. 1.
FIG. 3 is a wiring diagram of the pulser circuit for automatically adjusting the time of pump operation and the resultant weight of the refrigerant to be pumped during one operation cycle of the device illustrated in FIGS. 1 and 2.
FIG. 4 is a wiring diagram of the calibration circuit to be used in checking the accuracy of the temperature response of the thermistor-pulser-timer circuit.
DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1, the present invention involves a system whereby a refrigerant supply source such as the bottle is associated with a charging gun 11 which is in turn associated with the high pressure side 12 of a refrigeration unit 13 via a sequence of conduits and auxiliary units including a volumetric metering pump 14. The complete servicing unit also comprises a vacuum pump 15 which is itself associated with the charging gun I1 and a vacuum line 16 which is associated with the low side 17 of the refrigeration unit 13. To insure that the refrigerant leaving the supply bottle 10 will be under sufficient pressure to be in liquid form, regardless of the amount thereof within the bottle and regardless of the ambient temperature, the bottle may be associated with a heating unit such as the electrical resistant heating coils 18. The supply line from the bottle may then be provided with a pressure gauge 19 capable of measuring pressures of from 0 to 400 pounds per square inch and a pressure switch 20 which opens only after a sufficient pressure to insure liquidity of the refrigerant is present. Downstream from the pressure switch may then be a check valve 21 to prevent reverse flow of the refrigerant and a float sight glass 22 for a visual confirmation of the presence of liquid in the system at this point. As a safeguard against excessive pressure, a pressure relief valve 23 may be then placed in the system. The refrigerant liquid, in response to the action of the pump 14 is pulled through the heat exchanger 24 which in combination with the fan 46; cools the liquid before it enters the pump through the pump inlet line 25 which itself includes the ball valve 26 and the temperature sensing thermistor 27. The pump discharge line 28 may also be provided with a pressure relief valve set or designed to open at approximately 750 pounds per square inch. The vacuum pump 15 is associated with the charging gun 11 by the conduit 29 which may also include a ball valve 30 to be closed upon sufficient evacuation of the refrigeration unit. The thermistor 27 is mechanically fixed to or actually placed within the pump inlet line in heat transfer relationship therewith and is electrically connected to the pulser 32 which drives the counter 47 as hereinafter described. The term thermistor is meant to include any electrical device which changes its electrical resistance in response to changes in its temperature.
Referring now to FIG. 2, the vacuum pump motor 40 is energized and driven by closing the disconnect switch 41 which closes the circuit between the vacuum pump motor 40 and the power supply 41a such as 440 volts, three-Phase 60-cycle electrical current. The connection between the vacuum pump circuit and the rest of the circuit to be hereinafier explained is via the transformer 42 which induces a reduced voltage on the order of l 15 volts in the balance of the circuit.
The closing of the valve handle switch 43 completes the circuit to the vacuum gauge meter 44 which reads the degree of vacuum when a sufficient vacuum has been drawn on the unit to justify the commencement of the filling operation. Closing of the switch 43 also energizes the electrical circuit to the heaters 18. This also energizes and drives the fan motor 46 which operates over the heat exchanger unit 24. After switch 43 has remained closed a sufficient length of time to allow the desired vacuum to be drawn and the heaters 18 to bring the temperature of the refrigerant to the operable level the device is ready to charge a refrigeration unit. This may be accomplished by the automatic operation of the pressure switch 20 and the closing of the starter switch 49.
Before the unit or product is charged and in most instances while the vacuum is being drawn on the same, the counter charge selector 47 can be set to establish the predetermined desired amount of refrigerant to be used in the charge. The counter charge selector is a solenoid-driven digital counter involving one or more wheels with consecutive numbers inscribed on the outer perimeter thereof, the wheels being so interrelated that they may be set to establish a counting period of from 0 through 9 in the case of one wheel or from 0 through 99 in the case of two wheels or from 0 through 999 in the case of three wheels. The solenoid actuation of such a counter is triggered or in response to the discharge of the thermistor-controlled pulser 32. The counter then is actually a switch, which in the case of the preferred embodyment illustrated, is closed by adjusting the wheels so that a reading of at least 1" is present thereon. In response to the pulser actuation, the counter counts downwardly to the zero position at which point the switch is opened. So long as a number appears on the digital counter the switch 47 will be closed position thereby completing the circuit to be hereinafter described. When the digital reading on the counter switch reaches zero the switch 47 opens thereby breaking the circuit and discontinuing the charge. While the counter switch is counting down and the switch is closed, electrical energy is supplied to the circuit driving the charging pump motor 48 which causes the discharge of a given volume of the refrigerant with each cycle of the pump. Before the filling of the refrigeration unit 13 can take place, the start button 49 is depressed to energize the pump motor 48 and simultaneously to bring the pulser into activating association with the counter as described.
thereby interrupting the short across the secondary output of the transformer 62. At the same time power is supplied to the pulser circuit via the terminal 63 and 64 from the secondary output of the transformer 65 in FIG. 2. The secondary output of the transformer 66 passes through the rectifiers 67 and 68 to convert the current to direct current. The output from the rectifier 67 passes through the dropping resistor 69 and is regulated by the voltage regulator 70 to the design voltage which reduces the voltage to an intermediate figure which is then carried through an additional dropping resistor 71 which reduces the voltage to the designed voltage at which the electronic components involved in the pulser are operable. The current operating at this designed voltage is then carried by the conductor 71 through the resistor network consisting of the resistors 73, the variable resistor or rheostat 74, and resistors 75, 76 and 77. Across the portion of the circuit including the resistor 77 is the thermistor 27 connected at the terminals 78 and 79.
The complex of the resistors 73, 74, 75, 76 and 77 and the thermistor 27 allows the capacitor 80 to charge at a rate which is determined by the change in resistance of the thermistor 27 which is in turn determined by changes in the temperature of the refrigerant at the point of its entering the pump 14. As the voltage in the capacitor reaches a certain level it will cause the unijunction transistor 72 to become conductive allowing the current to flow from the secondary of transformer 66 through the primary of transformer 62 which induces the voltage across the secondary coil of the transformer 62 which, in turn, triggers the thryotron glow discharge tube 81. The resultant firing of this glow discharge tube 81 actuates the coil 82 of the relay switch closing the contacts 83 and 84 which are mechanically adjusted so that the contacts 84 close a very small fraction of a second before the contacts 83. Contact 84 closes the circuit consisting of the conductors 85 and 86 which are connected respectively to the terminals 87 and 88 of the circuit in FIG. 2 thereby energizing the solenoid of the counter switch 47 causing the digital counter to reduce 1 count. The resultant nominally delayed closing of the contact 83 extinguishes the glow discharge tube thereby placing it in condition to receive the current for the next pulse. As the current continues to cycle in its buildup at the capacitor 80 and to fire the unijunction transistor 72, repeated pulses are generated actuating the contacts 83 and 84 thereby continuing to reduce the counter reading one value for each pulse. This pulsing continues so long as the circuit is closed and the counter switch has a reading other than zero.
Referring to FIG. 4 and the operation of the calibration circuit, the calibration sequence is instituted by movement of the rotary switch 90 from the off position as shown to contact with either of the switch contacts 91, 92, or 93. As soon as the switch is rotated from the off position, the pump motor circuit and the thermistor circuit are electrically locked out by the resultant de-energization of the relay 94 which keeps the contacts 95 from closing and thereby prevents the motor pump 48 from operating. At the same time, the opening of the rotary switch 90 eliminates the thermistor from the circuit and replaces it by either of the resistors 96, 97 or 98 which respectively control the rate of buildup of the voltage in the capacitor 80 at a known rate, regardless of ambient temperature (since the thermistor is out of the circuit). To check the accuracy of the machine, it is then only necessary to establish the time interval required for the pre-set counter to return to a zero position. As a means for measuring this time interval visually, an alternating current timing motor 99 having a read-out dial is made to operate as long as the counter switch is closed. By comparing the position of the dial at the opening of the counter switch upon its reaching the zero position with the position on the dial that the timing motor should have reached if the counter switch had remained open for the previously determined length of time, the machine can be checked to see whether or not the pulser-timer mechanism is operating accurately.
While the invention has been described in considerable detail in connection with a preferred embodyment thereof, it is to be understood that the foregoing particularization has been for the purpose of illustration only and does not limit the scope of the invention as it is defined in the subjoined claims.
1. A temperature compensating refrigerant charging device comprising a volumetric refrigerant charging pump controlled by a temperature-responsive timer assembly comprising a thermistor-controlled, pulser-actuated counter wherein the thermistor is in heattransfer communication with the refrigerant the rate of pulsing of the pulser is responsive to the temperature induced changes in the resistance of the thermistor whereby an increase in the temperature of the refrigerant causes a reduction in the rate of pulsing and a decrease in the temperature of the refrigerant causes an increase in the rate of pulsing and wherein the counter counts the number of pulses of the pulser whereby a pie-determined setting of the counter allows the volumetric pump to discharge a constant weight of the refrigerant by controlling the time interval of the operation of the pump in inverse proportion to the temperature-induced changes in the density of the refrigerant being pumped.
2. A device according to claim 1 wherein the counter is an adjustable digital counter in combination with a switch wherein the switch is closed when the counter has a reading other than zero, the counter upon actuation by the pulser counts down to zero at which point the switch opens, and said switch controls the electrical energization of the refrigerant charging pump.
3. A temperature compensating refrigerant device comprising a refrigerant supply reservoir, a charging gun for fluid transmitting connection to the high and low sides of a refrigeration unit and a fluid transmission system between said reservoir and said gun comprising a volumetric refrigerant charging pump and an electrical circuit for selectively energizing said charging pump which circuit comprises an adjustable counter switch, an electronic pulser in electrical association with the counter switch whereby the counter counts down in response to the pulses of the pulser, and a temperatureresponsive resistor unit in heat transfer association with the refrigerant being pumped and electrically connected to said pulser whereby an increase in the temperature of the refrigerant decreases he rate of pulsing and the corresponding countdown of the counter and a decrease in temperature of the refrigerant increases the rate of pulsing and corresponding rate of countdown of the counter and wherein the counter switch opens when the counter has counted to zero, whereby for any pre-determined counter setting, a constant weight of refrigerant will be pumped not withstanding temperature-induced changes in the density of the refrigerant.
4. A temperature compensating refrigerant device according to claim 3 wherein an electrical heating unit is in heat transfer communication with said refrigerant reservoir, said fluid transmission system includes pressure responsive means for preventing movement of the refrigerant from said reservoir towards said gun until the refrigerant, in response to said heating unit, has attained a pressure at which it will be in a liquid phase throughout said fluid transmission system.
5. A device according to claim 4 wherein a heat exchange unit is positioned in said system between said pressure responsive means and said charging pump.
6. A device according to claim 3 comprising as an additional system in communication with said charging gun a vacuum pump, a conduit connecting the low pressure part of said pump with said charging gun and connector means associating said pump with said electrical circuit for operating said vacuum pump at least during the initial connection of said gun to said refrigeration unit until the latter is evacuated.
7. A device according to claim 6 wherein said additional system includes valve means for maintaining the association between said vacuum pump and the high