Abstract:
A flow control system allows sampling of refrigerant from a refrigerant recovery inlet of the system or, alternatively, the refrigerant recovery tank. Refrigerant selected from either source is metered and oil is filtered therefrom to provide a clean vapor refrigerant sample to a refrigerant identification detector. Oil separated from the refrigerant is returned to the oil drain of the main system for collection. In a preferred embodiment, a first conduit having a pressure control valve is coupled from a refrigerant inlet to the refrigerant recovery and recharging system. A check valve, a metering orifice, and an oil separator is coupled in the first conduit and to a refrigerant identification detector. The system includes a second conduit coupled to the main refrigerant recovery tank through a solenoid valve also communicating with the orifice and oil separator, with the valves being selectively operable for sampling either incoming refrigerant to the recovery and recharging system from the refrigerant circuit under service or from the recovery tank of the servicing instrument itself. A third conduit couples the collected oil from the oil separator through a check valve and control solenoid to the oil recovery system of the recovery and recharging unit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/273,212, entitled REFRIGERANT RECOVERY AND RECHARGING SYSTEM WITH AUTOMATIC OIL DRAIN, filed on Mar. 19, 1999, now U.S. Pat. No. 6,138,462. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for servicing refrigeration systems and particularly to a system which integrally includes a flow control for the sampling of refrigerant type. 
     When vehicles are brought to a service center for professional servicing of the air conditioning system, frequently the system has had refrigerant leaks and losses in the past and either the vehicle owner or service center that does not have the proper equipment or refrigerant has mixed different types of refrigerant or added the wrong refrigerant to the system. The preferred refrigerant now in use is the environmentally approved R-134. Still available, however, is the previously used R-12 refrigerant and R-22 refrigerant is used in home air conditioning systems. Frequently, a vehicle owner will mix the wrong types of refrigerant or purchase a blend of refrigerants from a retail store in an attempt to recharge the system, which, having needed to be recharged, leaks refrigerant and does not operate satisfactorily with the wrong or blended refrigerant. Thus, when a vehicle finally reaches a service center with proper equipment for professional maintenance of the air conditioning system, frequently refrigerant contained in the system is a mix and of an unknown nature. Thus, it is necessary and desirable to identify whether this problem exists and, if so, completely new refrigerant of the proper type is employed for charging the system. 
     In order to detect the refrigerant in a vehicle refrigerant circuit, a sample is taken directly from the vehicle coupled to the servicing instrument. Also, it is useful to periodically monitor the recovery tank of the system to make certain it has not become contaminated. In the past, a stand-alone flow control system has been provided which provides a metered orifice and pressure control switch to allow the sampling of refrigerant from the servicing unit to a refrigerant identification instrument, such as a Neutronics ACR2KID, through an oil separator. The oil separator protects the instrument from damage due to oil in the refrigerant being sampled from entering the instrument. The disadvantages of this prior art system is that it is an add-on, stand-alone unit requiring its own power source and is somewhat prone to incorrect installation by the service technician to protect the refrigerant identification unit. Further, this only permits testing of refrigerant on the low side (vapor) of the air conditioning servicing unit. 
     There remains a need, therefore, for a protection system for refrigerant identification detectors and one which is integrated with the refrigerant recovery and recharging system and one which allows sampling of refrigerant, either from the high or low pressure sides of the recovery system and also from the main refrigerant tank. 
     SUMMARY OF THE PRESENT INVENTION 
     The system and method of the present invention provides a refrigerant recovery system which evacuates and recovers refrigerant from a refrigeration circuit, such as a vehicle air conditioning system, filters and removes oil therefrom, and recharges the refrigerant to the proper pressure, adding new oil as required. Integrally included within the recovery and recharging system is a flow control system allowing for the sampling of refrigerant from a refrigerant recovery inlet of the system or, alternatively, the refrigerant recovery main tank as well as metering refrigerant selected from either source, filtering oil therefrom to provide a clean vapor refrigerant sample to the refrigerant identification detector. Oil separated from the refrigerant is returned to the oil drain of the main system for collection. 
     In a preferred embodiment of the invention, an orifice of about 0.016″ to 0.025″ is provided to limit the flow rate. A pressure operated sensor allows sensing of refrigerant only when the pressure is below a predetermined level, thereby protecting the oil separator and refrigerant identification detector from excessive pressures and oil blow by. Systems embodying the present invention include a first conduit having a pressure control valve coupled thereto and a check valve permitting refrigerant coupled from the refrigerant inlet to the refrigerant recovery and recharging system to a check valve, a metering orifice, an oil separator, and having an outlet for coupling to a refrigerant identification detector. The system includes a second conduit coupled to the main refrigerant recovery tank through a solenoid valve communicating also with the orifice and oil separator, with a valve being selectively operable for sampling either incoming refrigerant to the recovery and recharging system from the refrigerant circuit under service or from the recovery tank of the servicing instrument itself. A third conduit couples the collected oil from the oil separator through a check valve and control solenoid to the oil recovery system of the recovery and recharging unit. 
     Thus, with the system of the present invention, refrigerant can be safely sampled by either the circuit under servicing or the recovery tank of the servicing unit, protecting the refrigerant identification detector from damage due to oil blow by or excessive flow rates of refrigerant. These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view, partly broken away, of a refrigerant maintenance system for a vehicle which incorporates the present invention; 
     FIG. 2 is a flow diagram of the refrigerant recovery, flushing, evacuation, and recharging system incorporated in the system shown in FIG. 1; and 
     FIG. 3 is a flow diagram of the program for the microprocessor employed to control the protection system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, there is shown a maintenance unit  10  for coupling to a refrigerant circuit such as a vehicle&#39;s air conditioning system for its maintenance. The unit  10  comprises a portable machine mounted within a cabinet  12  supported by a pair of wheels  14 , such that it can be conveniently moved to the situs of a vehicle. Unit  10  includes a high pressure hose  16 , typically color coded red, with a coupling  17  for coupling to the vehicle&#39;s high pressure port and a low pressure hose  18 , typically color coded blue, having a coupling  19  for coupling to the low pressure port of the vehicle&#39;s refrigerant circuit. The front panel of the cabinet is shown broken away in FIG. 1 to show the major elements of the system which are also identified by similar numbers in the flow diagram of FIG.  2 . 
     The maintenance unit  10  includes an electronic module  20  integrally including a microprocessor  21  on a circuit board  22  for controlling the electromechanical solenoid valves shown in the flow diagram of FIG.  2  and for receiving input information from the pressure sensors and control switches included on the control panel  30  shown in FIG.  1 . The control panel  30  includes an on/off switch  31  and a display  32  for displaying the operational status of the machine operation, which display may be an LCD display or other suitable electronic display coupled to the microprocessor via a conventional input/output circuit. The display panel  30  further includes a switch panel  34  having a conventional keyboard  35  and a plurality of push-button switches  36  for controlling the operation of the machine through its various phases of operation and/or for selecting parameters for display. Thus, the keyboard  35  in conjunction with the operational switches  36  and display  32  allow the operator to enter the desired operational parameters for the machine according to manufacturer specifications for the servicing of an air conditioner unit in a particular vehicle. 
     The input hoses  16  and  18  are coupled to mechanical pressure gauges  13  and  15 , respectively, which are mounted on the front panel of the service unit  10 , as seen in FIG.  1 . In addition, electrical pressure transducers  13 ′ and  15 ′ are coupled to the hoses  16  and  18 , as shown in FIG. 2, and are coupled to the microprocessor through conventional input/output circuits to provide the microprocessor with information as to the current pressure in the hoses during operation of the unit. Gauges  13  and  15  additionally provide the operator with a conventional analog display of the pressure. Mounted to the top surface  33  of cabinet  12  is a sight gauge  50  which also includes an integral replaceable filter cartridge  52  mounted to the cabinet for filtering particulate material from the refrigerant during the flushing cycle as described in greater detail below. 
     Mounted to the floor  35  of cabinet  12  is a compressor  60  and a vacuum pump  70 . A main tank  80  and a supply tank  90  (FIG. 2) of refrigerant for the supply of refrigerant to the system are mounted behind the front of cabinet  12  on an extension of floor  35 . The supply tank  90  supplies make-up refrigerant to the main tank  80  as described in connection with U.S. patent application entitled BACKGROUND TANK FILL, filed Mar. 19, 1999, Ser. No. 09/272,789, the disclosure of which is incorporated herein by reference. Mounted to the rear wall  36  of cabinet  12  is an oil accumulator tank  100 , a compressor oil separator filter  110 , a manifold  120  (shown as a node in FIG.  2 ), and a condenser  130 . In addition, a fresh oil canister  140  is mounted within a side compartment of cabinet  12 . A recovery oil container  142  is mounted on the lower part of the cabinet to receive oil drained from the accumulator  100  and from drain  113  coupled to oil separator  210  as described below. Having briefly described the major components of the refrigerant servicing unit  10  shown in FIGS. 1 and 2, a more detailed description of the system follows in connection with the FIG. 2 diagram. 
     Initially, the hoses  16  and  18  are coupled to the vehicle and the refrigerant is sampled as described in detail below. After the refrigerant is sampled, the recovery cycle is initiated by the opening of the dual back-to-back high pressure and low pressure solenoids  150 ,  152 , respectively. This allows the refrigerant within the vehicle to flow through conduits  154  through check valve  156  and recovery valve  158  into the manifold  120 . A low pressure switch  160  senses the pressure and provides an output signal coupled to the microprocessor through a suitable interface circuit which is programmed to detect when the pressure has recovered refrigerant down to  13 ″ of mercury. The refrigerant then flows through valve  162  and unit  164  via conduit  166  into the accumulator  100  where it travels through an output conduit  168  through a water separating molecular sieve  170  to the input of compressor  60 . Compressor  60  draws the refrigerant through the compressor through a valve  172  and through the oil separating filter  110  for the compressor which circulates oil back to the compressor through conduit  174  and oil return valve  176 . A pressure transducer  178  is coupled to the microprocessor which is programmed to determine the upper pressure limit of, for example, 435 psi to shut down the compressor in the event the pressure becomes excessive. The compressed refrigerant exits the oil separator through conduit  180 , through check valve  182  and through a heating coil  102  in accumulator  100  via conduit  184 . The heated compressed refrigerant flowing through coil  102  assists in maintaining the temperature in accumulator  100  within a working range. The refrigerant then flows through conduit  186  to the condenser  130  which cools the compressed refrigerant which next flows through check valve  188  and into the main tank  80 . 
     During the recovery and flushing processes, oil is separated from the recovered refrigerant into the accumulator/oil separator  100 , which comprises a generally cylindrical tank as seen in FIG. 1, having a drain  104  at the bottom thereof (FIGS. 1 and 2) which communicates with a conduit  105  coupled to an orifice  106  for restricting oil flow. Orifice  105  is an inline fitting which is hidden in FIG. 1 but which is shown in FIG. 2 in block form. Orifice  106  has a diameter of from about 0.035″ to about 0.050″ and preferably about 0.042″ selected to limit the flow rate of oil from accumulator  100  to tank  142  preventing, in connection with the control of valve  109 , the loss of refrigerant. A pressure sensing switch  107  is coupled to the junction of orifice  106  and a check valve  108 . An electrically actuated solenoid  109  is coupled to collection bottle  142  through conduit  111 . Suitable conductors  112  (FIG. 1) couple the pressure sensing switch  107  and electrically actuated solenoid  109  to the microprocessor carried on circuit board  22  by means of conventional interface circuits. The oil drain  104  is also coupled by conduit  113  to an oil separator  210  coupled to a refrigerant identifier instrument  220 , such as a Neutronics ACR2KID which, with the present invention, can be integrated into the maintenance unit  10 . The protection system for the sampling of refrigerant from either the high or low pressure sides  16  or  18  of the vehicle refrigerant circuit or from the main recovery tank  80  is also shown in FIG.  2 . 
     The protection system of the present invention includes a first conduit  212  (FIG. 2) coupled to a common port  213  at the input side of the system coupled by hoses  16  and  18  to service unit  10  for sampling refrigerant from a vehicle&#39;s air conditioner. Conduit  212  is coupled to a normally closed inlet test solenoid valve  214 , in turn, serially coupled to a check valve  216  and to node  218 . A second conduit  230  is coupled to the main tank  80 , a pressure regulator  232  to maintain the pressure at about 30 p.s.i. and to a tank test solenoid valve  234 . A metering orifice  240  couples node  218  to oil separator  210 . Metering orifice  240  has a diameter of from about 0.016″ to 0.025″ and limits the flow of refrigerant sampled either from the tank via conduit  230  or from the vehicle system via conduit  212 . A pressure detecting switch  242  is positioned upstream of orifice  240  and selectively controls sampling valves  214  and  234  between a pressure range of 27 p.s.i. (opening pressure) and 40 p.s.i. (closing pressure) to prevent excessive vapor pressure during sampling by instrument  220 . Oil separator  210  is coupled to the output of orifice  240  and drains through conduit  113  and check valve  211  and a normally open oil drain  215  to container  142  as described above. Valve  215  is normally open, except during sampling, to allow the oil separator  210  to drain and clear, preventing over filling of the separator. The check valve prevents oil and/or refrigerant from being forced from the accumulator  100  into the oil separator  210 . 
     Separator  210  is a latex saturated Grade 5 coalescing element part number 701551, available from the Finite Filter Division of Parker Filtration, and filters undesired oil from the flow path from either of conduits  212  or  230  being sampled by instrument  220 . The operation of the refrigeration protection circuit during its sampling is controlled by the microprocessor  21  which also controls the operation of the servicing unit  10  as described in U.S. patent application Ser. No. 09/273,212, entitled REFRIGERANT RECOVERY AND RECHARGING SYSTEM WITH AUTOMATIC OIL DRAIN, filed on Mar. 19, 1999, the disclosure of which is incorporated herein by reference, as well as the BACKGROUND TANK FILL application identified above. The refrigerant sampling subroutine for the microprocessor  21  is now described in connection with FIG.  3 . 
     The flow chart of FIG. 3 shows the subroutine  300  for controlling the flow of refrigerant to be sampled by instrument  220  from either the vehicle&#39;s high or low pressure side coupled by hoses  16  and  18  through conduit  212  or from the recovery tank  80  through conduit  230 . The subroutine is begun by a command from an RS232 port coupled by microprocessor  21  to the instrument  220  initializing the refrigerant identification sequence. The first test is to determine whether 25 pounds of refrigerant is available, as indicated by block  304 , which is accomplished by monitoring pressure gauges  13 ′ and  15 ′ inasmuch as that is the level necessary for providing a sample to the analyzer  220 . If 25 p.s.i. is unavailable, the subroutine returns to the normal recovery routine  306  for the recovery and recharging system. If 25 pounds of refrigerant power is available, a command is sent by the microprocessor to the instrument  220  to start the identification sequence, as indicated by block  308 . Neutronic system includes a self-test which is monitored by the microprocessor as indicated in block  310  to determine whether it is calibrated and ready to test the refrigerant. If not, as indicated by block  312 , calibration, elevation, purge, flow, or stabilization routines within the instrument  220  are performed, as indicated by block  312 , and the subroutine cycled through a loop including block  308  and  310  until such time as the Neutronic&#39;s instrument is ready to analyze refrigerant. 
     Next, the subroutine checks to determine whether the sample is from the vehicle or the recovery tank  80  as indicated by block  314 . This can be set by the operator and typically the vehicle will be under test, and the subroutine moves to block  316  where valves  152  are initially opened on the low pressure side to determine whether to provide refrigerant for sampling. If the low side has less than 25 p.s.i., valves  150  are opened to determine whether sufficient pressure exists on the high side. At the same time the program at block  316  closes, oil recovery valve  215  opens sampling solenoid valve  214  to allow a sample to be introduced through orifice  240  to oil separator  210  into analyzer  220 . The Neutronic system then samples the refrigerant as indicated by block  318  and, after approximately 10 seconds, determines whether a sufficient amount of refrigerant has been introduced to provide an analysis. If not, the valves remain open as indicated by loop  317  of the subroutine  300  until a sufficient sample has been introduced to the instrument. When this occurs, as indicated by block  320 , the solenoid valves  150  or  152  are closed, as is valve  214 , and the oil drain valve  215  again opened. The analyzer  220  then provides information to the microprocessor as to whether or not greater than 98% of refrigerant is R134A, as indicated by block  322 , and, if it is, the analyzer  220  provides a signal to microprocessor  21 , as indicated by block  324 , to provide a display of the information on the display panel  32  (FIG. 1) of the instrument displaying the results of the analysis. If, however, the test indicates that the refrigerant is at less than 98% of R134A, it loops through the sequence including blocks  308  through  322  again, and, if less than 98% a second time, the test results are reported to the user and completed. 
     If in block  314  the test source is the internal recovery tank  80 , the subroutine moves to block  328  to open valve  234  associated with the tank  80 , closing at the same time the oil recovery valve  215 . The instrument tests the sample, as indicated at block  318 ′, for ten seconds to determine if a sufficient sample has been taken. If so, the valve  234  is closed and valve  215  opened, as indicated by block  330 . Again, the analyzer  220  tests to determine whether at least 98% of the refrigerant detected is R134A, as indicated by block  332 . The results of the test at block  332  are reported to the user, as indicated by block  324 , and, at the same time, the sample is tested for air, as indicated by block  334 , to determine whether or not there is more than 6% of air in the sample. If the sample includes more than  6 % of air, an air purge solenoid  235  (FIG. 2) is opened, as indicated by subroutine block  336 , to purge air from the main tank  80  through an outlet orifice  237  to the atmosphere for approximately thirty seconds. The program then returns through the loop including blocks  308 ,  310 ,  314 ,  328  through  334  and, assuming the air is less than  6 %, the program returns to block  306  for normal operation of the servicing unit. If at block  332  the R134A is less than 98%, as indicated by block  338 , the subroutine cycles through a second test, as indicated by block  338 , and, if on the second pass the R134A is less than 98%, it reports the results to the user, indicating that the tank needs with fresh refrigerant from supply tank  90  as described in the above-identified copending application entitled BACKGROUND TANK FILL. 
     Thus, with the system of the present invention, an integrated refrigerant identification system for identifing the refrigerant in either the vehicle under service or in the recovery tank can be automatically achieved without the need for the attachment of separate equipment which must be separately controlled. 
     It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.