Abstract:
A gauge manifold is connectable to the suction and liquid lines of an air conditioning refrigerant circuit and has a built-in charge level calculator into Which system manufacturing and capacity data is enterable. Charging data corresponding to the input data is stored within the calculator and automatically utilized in conjunction with ambient temperature and refrigerant pressure levels sensed by the calculator to generate a visual display indicating whether the circuit&#39;s refrigerant charge level is acceptable, high or low for the particular unit or system being checked. If the displayed charge level is high or low, the gauge manifold is additionally connected to a pressurized refrigerant canister or recycling drum and a valve portion of the manifold is operated to add or remove refrigerant to the circuit, via the gauge manifold, as necessary until the calculator display indicates that the circuit is properly charged.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to air conditioning apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed refrigerant gauge manifold having a built-in refrigerant charging calculator.  
           [0002]    AS is well known in the air conditioning industry, for an air conditioning system to properly perform at its designed-for capacity the charge level of its refrigerant circuit must be neither too high nor too low. It is accordingly desirable to periodically check the amount of refrigerant which the refrigerant circuit contains. In direct expansion type refrigerant circuits this is typically done by taking refrigerant pressure readings at service ports on the liquid and suction sides of the circuit, determining the ambient temperature adjacent the service ports, and comparing these ambient temperature and refrigerant pressure readings to data contained on a system charge chart which is provided by the manufacturer of the air conditioning system.  
           [0003]    A charge chart of this type typically has outdoor ambient dry bulb temperature lines plotted on a liquid pressure vs. suction pressure graph. To check the system&#39;s refrigerant charge level, the service technician determines the outdoor ambient temperature, and the liquid and suction line pressures, and marks on the chart the point of intersection of the determined liquid and suction pressures. If this intersection point falls below the determined ambient dry bulb temperature line, the technician adds refrigerant to the circuit, and if the intersection point falls above the determined ambient dry bulb temperature line, the technician removes refrigerant from the circuit The new liquid line/suction line pressure intersection point is then checked against the determined ambient temperature line, and the refrigerant addition or removal step is repeated until the pressure intersection point falls on the ambient pressure line on the charging chart. AS an alternative to this charge chart in graph form, the manufacturer may provide this data in tabular form.  
           [0004]    Several well known problems, limitations and disadvantages are typically associated with this conventional method of checking and adjusting the refrigerant charge level of an air conditioning system. For example, not every service technician has appropriate instruments, sensors and the like to efficiently carry out this process. Additionally, as conventionally carried out, this process is an iterative one which can be a time consuming and laborious one. Further, a given portion of the air conditioning system may have a number of independent circuits and associated charge charts. This presents the possibility that the technician could utilize the wrong chart, thereby providing a refrigerant circuit with an incorrect charge level. And, of course, the charging chart(s) initially provided by the manufacturer could be lost.  
           [0005]    AS can readily be seen from the foregoing, a need exists for an improved technique for measuring and adjusting the charge level of an air conditioning system refrigerant circuit that eliminates or at least substantially reduces the above-mentioned problems, limitations and disadvantages commonly associated with conventional techniques for performing these tasks. It is to this need that the present invention is directed.  
         SUMMARY OF THE INVENTION  
         [0006]    In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, apparatus is provided for determining and, if necessary, adjusting the charge level of an air conditioning system refrigerant circuit.  
           [0007]    Representatively, the apparatus comprises a porting portion interconnectable between the circuit and a refrigerant vessel, the porting portion being operative to selectively transfer refrigerant in a variable direction between the circuit and the refrigerant vessel which may be, for example, a refrigerant charging canister or a refrigerant recovery drum. The apparatus further comprises a valve portion for operating the porting structure, and a sensing portion for sensing ambient temperature and circuit refrigerant pressure levels and responsively generating output signals.  
           [0008]    The apparatus also comprises a calculator portion for storing identifying and charging data for a plurality of air conditioning systems, receiving the output signals and system identifying data input by an operator indicative of the circuit being tested, and responsively creating a display indicative of whether the circuit being tested is adequately charged, undercharged or overcharged, the display being automatically changeable in response to variation of at least one of the output signals caused by a flow of refrigerant into or out of the circuit via the refrigerant transfer port.  
           [0009]    In a preferred embodiment of the present invention, the apparatus is a refrigerant gauge manifold with a built-in charging calculator, and may be easily and quickly used to both determine the sufficiency of the refrigerant charge in the circuit being tested, and to adjust the refrigerant charge, via the manifold, if necessary.  
           [0010]    According to various features of the invention, in a preferred embodiment thereof, the porting portion includes a suction port communicatable with a suction line portion of the circuit, a liquid port communicatable with a liquid line portion of the circuit, and a refrigerant transfer port communicatable with a refrigerant canister or a refrigerant recovery drum. The valve portion representatively includes a first valve operative to selectively permit and preclude communication between the suction and refrigerant transfer ports, and a second valve operative to selectively permit and preclude communication between the liquid and refrigerant transfer ports.  
           [0011]    The sensing portion is representatively operative to sense ambient dry bulb temperature and the liquid and suction line refrigerant pressures in the circuit, and illustratively includes a first pressure-to-electric transducer operatively coupled between the suction port and the calculator portion, and a second pressure-to-electric transducer operatively coupled between the liquid port and the calculator portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic diagram of a representative air conditioning refrigerant circuit to which is operatively attached a specially designed refrigerant gauge manifold having a built-in charging calculator and embodying principles of the present invention; and  
         [0013]    [0013]FIG. 2 is a schematic flow diagram illustrating the use and operation of the refrigerant gauge manifold schematically depicted in FIG. 1.  
     
    
     DETAILED DESCRIPTION  
       [0014]    Schematically depicted in FIG. 1 is a representative direct expansion type refrigerant circuit  10  used in an air conditioning system. Circuit  10  has an outside portion including a compressor  12  and a condenser  14 , and an inside portion including an expansion valve  16  and an evaporator  18 . These four components of the circuit  10  are operatively connected in a conventional manner by refrigerant-filled piping  20  including a suction or low pressure line portion  20   a  extending between the outlet side of the evaporator  18  and the inlet of the compressor  12 , and a liquid or high pressure line portion  20   b  extending between the outlet of the condenser  14  and the expansion valve  16 .  
         [0015]    The direction of refrigerant flow through the piping  20  during operation of the circuit  10  is indicated by the arrows on the piping  20 . A service valve  22  and a low side pressure tap or service fitting  24  are disposed in the suction line portion  20   a , and a service valve  26  and a high side pressure tap or service fitting  28  are disposed in the liquid line portion  20   b.    
         [0016]    With continuing reference to FIG. 1, to check and adjust the refrigerant charge level of the circuit  10 , a specially designed refrigerant gauge manifold  30  is provided in accordance with principles of the present invention. The refrigerant gauge manifold  30  includes a tubular body portion  32  having disposed on a longitudinally central portion thereof a suction port  34 , a liquid port  36  and a refrigerant transfer port  38 . Respectively mounted on the opposite ends of the manifold body  32  are conventional manifold valves  40 ,  42  having disc-shaped handles  44 ,  46  that may be rotated about the axis of the body  32  to selectively place their associated valves  40 ,  42  in open and closed positions.  
         [0017]    When valve  40  is in its open position it communicates the ports  34  and  38 , and when valve  40  is in its closed position it prevents communication between the ports  34  and  38 . When valve  42  is in its open position it communicates the ports  36  and  38 , and when valve  42  is in its closed position it prevents communication between the ports  36  and  38 .  
         [0018]    According to a key aspect of the present invention, a specially designed battery operated charging calculator  48  is mounted on the body  32  and includes a microprocessor  50 , a keyboard  52  useable to input data to the microprocessor  50 , and a display window  54 . Stored in the microprocessor  50  are sets of charging data for a preselected set of air conditioning systems with which the refrigerant gauge manifold  30  may be used, such data sets containing (for each system) desired relationships among the liquid pressure, suction pressure, and ambient dry bulb temperature for each system.  
         [0019]    Pressure-to-electric transducers  56 ,  58  are mounted on the body  32  and are operative to transmit to the microprocessor  50  electric signals respectively indicative of the refrigerant pressures at the suction and liquid ports  34 ,  36 . An ambient dry bulb temperature sensor  60  is incorporated in the gauge manifold  30  and is operative to transmit to the microprocessor  50  an electrical signal indicative of the ambient dry bulb temperature adjacent the gauge manifold  30 . For convenience, a hook member  64  is provided for supporting the gauge manifold  30  on a pipe or other structure while the gauge manifold is being used.  
         [0020]    Flexible refrigerant hoses  66 ,  68 ,  70  are respectively connected to the manifold ports  34 ,  36 ,  38 . Hose  66  is removably connectable to the suction line service port  24 , hose  68  is removably connectable to the liquid line service port  28 , and hose  70  is selectively connectable to either a pressurized refrigerant charging canister  72  (as indicated by the solid line position of the hose  70  in FIG. 1), or a refrigerant recovery drum  74  (as indicated by the dotted line position of the hose  70  in FIG. 1). TO use the refrigerant gauge manifold  30 , the manifold valves  44 ,  46  are first closed, so that neither of the ports  34 ,  36  communicates with the port  38 , and the hoses  66 ,  68  are respectively connected to the suction and liquid line service ports  24 ,  28  as indicated in FIG. 1.  
         [0021]    Referring now to FIG. 1, and to FIG. 2 which illustrates in flow chart form the use of the refrigerant gauge manifold  30 , the service technician, after connecting the gauge manifold  30  to the suction and liquid line portions  20   a ,  20   b  as just described carries out step  76  by using the keyboard  52  to input system identifying data to the microprocessor  50 . This identifying data representatively includes the manufacturer, model number, system number and electrical power frequency for the air conditioning system being tested from a refrigerant charging level standpoint.  
         [0022]    In addition to this system identifying data input to the calculator  48  by the service technician, the pressure-to-electric transducers  56 ,  58  and the temperature sensor  60 , as indicated at step  78 , continuously transmit to the microprocessor  50  input signals respectively indicative of the sensed suction line pressure, the sensed liquid line pressure, and the sensed ambient dry bulb temperature. In response, as indicated at step  80 , the microprocessor  50  calculates (for the particular system entered by the technician) a calculated value P cal,liquid  as a function of the sensed suction line pressure P vapor  and sensed ambient dry bulb temperature T a .  
         [0023]    Next, at step  82 , the microprocessor  50  compares the sensed liquid line refrigerant pressure P liquid  to the calculated liquid line refrigerant pressure P cal,liquid  and determines whether the sensed liquid line refrigerant pressure P liquid  is equal to, greater than or less than the calculated liquid line refrigerant pressure P cal,liquid .  
         [0024]    If the microprocessor determines at step  82  that P liquid  is equal to P cal,liquid , the microprocessor  50 , at step  84 , causes the calculator  48  to create in the display window  54  a message (such as “DONE”) indicating that the circuit charge level is correct, and the charging process is completed without the necessity of adding refrigerant to or removing refrigerant from the circuit  10 .  
         [0025]    If the microprocessor  50  determines at step  82  that P liquid  is less than P cal,liquid , the microprocessor  50 , at step  86 , causes the calculator  48  to create in the display window  54  a message (such as “ADD IN”) which informs the technician that the charge level in the circuit  10  is low. The technician then connects the flexible hose  70  to the pressurized refrigerant charging canister  72  (see FIG. 1) and opens the manifold valve  44  to begin to flow pressurized refrigerant into the suction line portion  20   a  of the circuit  10  sequentially through the hose  70 , the ports  38  and  34 , the hose  66 , and the service fitting  24 .  
         [0026]    During this addition of refrigerant to the circuit  10 , the microprocessor  50  cycles the program through steps  78 ,  80 ,  82  and  86  so that the calculator  48  continues to display the “ADD IN” message which indicates to the technician that the circuit  10  is still undercharged. When the circuit charge level is increased to the proper level the program automatically transfers to step  84 , thereby causing the calculator  48  to display “DONE”. The technician then closes the manifold valve  44  and disconnects the refrigerant gauge manifold from the circuit  10  and the refrigerant recharging canister  72 .  
         [0027]    If the microprocessor  50  determines at step  82  that P liquid  is greater than P cal,liquid , the microprocessor  50 , at step  88 , causes the calculator  48  to create in the display window  54  a message (such as “PULL OUT”) which informs the technician that the charge level in the circuit  10  is too high.  
         [0028]    The technician then connects the flexible hose  70  to the recovery drum  74  (see FIG. 1) and opens the manifold valve  46  to begin to flow pressurized refrigerant into the recovery drum  74  sequentially via the liquid line service fitting  28 , the hose  68 , the ports  36  and  38 , and the hose  70 .  
         [0029]    During this removal of refrigerant from the circuit  10 , the microprocessor  50  cycles the program through steps  78 ,  80 ,  82  and  88  so that the calculator  48  continues to display the “PULL OUT” message which indicates to the technician that the circuit  10  is still overcharged. When the circuit charge level is decreased to the proper level the program automatically transfers to step  84 , thereby causing the calculator  48  to display “DONE”. The technician then closes the manifold valve  46  and disconnects the refrigerant gauge manifold from the circuit  10  and the refrigerant recovery drum  74 .  
         [0030]    The use of the refrigerant gauge manifold  30  provides a variety of advantages over conventional techniques for checking and adjusting the charge level of the circuit  10 . For example, the use of its valves  44 ,  46  and the manner in which the gauge manifold  30  is connected to and removed from the service fittings  24  and  28 , the refrigerant canister  72  and the recovery drum  74  are substantially identical to the valve use and connection techniques in conventionally constructed refrigerant gauge manifolds. Additionally, the refrigerant gauge manifold  30 , when programmed with the necessary identifying and charging data from various air conditioning systems and units, permits a service technician to very accurately check and adjust the charge levels of a corresponding variety of refrigerant circuits without the cumbersome location of their charging charts or tables, and with no related interpolation which can dramatically slow down the refrigerant charging level checking and adjustment task. Additionally, the usefulness of the refrigerant gauge manifold  30  may be expanded, if desired, by simply downloading identifying data and corresponding charging data into the microprocessor  50  from various additional air conditioning system manufacturers&#39; websites.  
         [0031]    In short, the refrigerant gauge manifold  30  substantially eliminates the guesswork in the refrigerant charging process, increases the accuracy and efficiency of the overall process, is easy and intuitive to use, and renders the entire field service process less costly. While the gauge manifold  30  has been representatively illustrated herein as being utilized in conjunction with a direct expansion type refrigerant circuit  10 , it will be readily appreciated by those of skill in the refrigeration and air conditioning art that it could also be used to advantage in other types of refrigerant circuits, such as capillary type refrigerant circuits.  
         [0032]    The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.