Abstract:
A compressor assembly comprises a compressor, a motor protector, and a signaling device. Upon an overload condition, the motor protector activates. The signaling device also activates to serve as an alert that the compressor is not malfunctioning but instead is in an overload condition.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This application discloses and claims an overload status indicator for a compressor that signals an overload condition following the shut down of the compressor.  
           [0002]    Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor a pair of scroll members each have a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two scroll members is caused to orbit relative to the other. As the wraps orbit relative to each other, the size of the compression chambers decreases and an entrapped refrigerant is compressed.  
           [0003]    There are many challenges with scroll compressor design. One of the challenges relates to the mass flow through the compressor. The compressors are typically incorporated into a refrigerant cycle, and there is the possibility of loss of charge in the refrigerant from several spots in the cycle. During a loss of charge situation, the mass of refrigerant flowing through the compressor decreases. Continued operation at loss of charge situations can have undesirable side effects. Thus, there is an effort to identify loss of charge situations.  
           [0004]    One protection element incorporated into compressors is a motor protector. A motor protector senses several variables within the compressor housing and stops operation of the electric motor driving the compressor should conditions indicate some problem with the compressor or its associated refrigerant cycle. Typically, the protector is actuated by an anomaly in the power supply to the electric motor (i.e., a spike in voltage or current) or, due to excessive heat. Motor protectors have been typically incorporated into the windings of the motor stator.  
           [0005]    Individuals servicing these compressors frequently mistake a compressor in which a motor protector has been activated to be a malfunctioning compressor. Consequently, these compressors may be wrongly sent in for repair rather than allowing the overload condition to pass or the compressor to reset. Indeed, in some cases, the compressor may be replaced by another unit, resulting in further unnecessary cost and expense. Moreover, the activation of the motor protector may indicate a system wide problem such as loss of refrigerant charge or failed condenser fan motor. Accordingly, a technician may forego troubleshooting the refrigerant system, mistakenly believing a faulty compressor motor to be the problem.  
           [0006]    Currently, to determine whether the compressor is in a temporary overload condition, a technician must measure the resistance between the motor common winding and run/start of the winding because of the motor protector&#39;s incorporation into the motor&#39;s windings. This analysis permits the technician to determine if the circuit has been broken as a consequence of activation of the motor protector. Due to the difficulty of performing this task, the technician may not take the time to conduct this analysis.  
           [0007]    A need therefore exists for a simple and inexpensive device to signal that the compressor is in an overload condition.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a convenient and inexpensive signaling device that serves as an alert that an overload switch has been activated. The compressor assembly comprises a compressor, a motor, a motor protector, and a signaling device. The motor protector limits operation of the motor and activates upon a predetermined condition. Additionally, the signaling device also activates upon the meeting of the predetermined condition. The signaling device is positioned outside of the compressor housing. In this way, when the compressor reaches the predetermined condition, the signaling device serves as a signal that the compressor has met the predetermined condition and is not necessarily in need of repair, but rather the overload condition must be removed.  
           [0009]    The motor protector is preferably a switch, such as an overload switch, in which activation of the switch activates the signaling device. The switch and signaling device may comprise a simple circuit, for example, a bi-metal switch and light circuit, such that when the switch shuts down the compressor, the switch diverts power from the motor to the light. The signal device could also be a simple terminal block with one or two blunt terminal posts. This type of signal could be used to measure continuity across the overload protector. Additionally, blunt posts, when applied correctly, would prevent the service technician from bypassing the overload protector with a jumper wire.  
           [0010]    The predetermined condition may relate to an overload condition of the compressor. Accordingly, a compressor may have a limited range of operation. When the limited range of operation is reached, its operation is limited by a motor protector such as a shutoff switch. In contrast to the prior art, a signal is issued when the compressor is shut down to advise a technician of the correct condition of the compressor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
         [0012]    [0012]FIG. 1 shows an embodiment of the invention.  
         [0013]    [0013]FIG. 2A shows a motor protector with the present invention.  
         [0014]    [0014]FIG. 2B shows a motor protector actuated to stop operation of the motor.  
         [0015]    [0015]FIG. 3 shows terminal posts for a signaling device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    [0016]FIG. 1 shows a scroll compressor  20  incorporating a non-orbiting scroll  22  interfitting with an orbiting scroll  24 . As is known, a shaft  26  drives the orbiting scroll  24 . The shaft  26  is driven by a motor rotor  28  that is driven by a motor stator  30 . As known, windings  32  on the stator  30  are associated with a motor protector  34 . The motor protector  34  is shown schematically. Refrigerant enters a chamber surrounding the motor and protector through the suction tube  36 . During operation of the scroll compressor shown in FIG. 1, the suction refrigerant entering the compressor through the suction tube  36  will pass over the protector  34  and its holder  35 , cooling the protector. The purpose is to cool the motor. However, should the mass flow of refrigerant decrease, as would be the case in a loss of charge situation, then heat transfer will also decrease. At that time, the motor protector is likely to reach its trigger temperature—a predetermined condition that may be settable to the overload parameters of the motor. Reaching this condition stops operation of the motor. At this point, signaling device  40  activates, signaling the motor to be in an overload condition. As can be seen, the motor, scroll element and motor protector are all within a housing  41  whereas the signaling device  40  is positioned outwardly of the housing  41 . Although not shown in this figure, there would need to be appropriate sealing to insure that the connection of the signaling device  40  is fluid type. The invention thereby serves as an alert that protector  34  has triggered, preventing the misdiagnosis of the motor or compressor as a malfunctioning unit. As shown in FIG. 1, signaling device  40  may be a lighting element  44  that illuminates upon the meeting of the predetermined condition, such as a trigger temperature. It could also be a terminal post or posts  41  where the service technician could check the circuit continuity of the overload protector, as shown in FIG. 3.  
         [0017]    Signaling device  40  may be activated and controlled by motor protector  34 . FIG. 2A illustrates an embodiment of the invention. A single-phase motor (shown schematically), is wired to have start ( 50 ) and run ( 52 ) windings. A common line  54  supplies current to windings  50  and  52 .  
         [0018]    A common line  54  leads to a power supply  56  passing through the motor protector  34 . A start winding and a run winding  50  and  52  respectively communicate with line  60  downstream of protector  34 . As shown, a switch  58  within the motor protector  34  selectively is opened should conditions within the compressor indicate that motor operation should stop. In such an event, there is a short circuit between lines  56  and  60 . This will cause current to flow through lines  62  and  64 , and power the lamp  44 . As mentioned, the lamp  44  will be mounted in some form of sealed connection such that the passage of the illuminating signal and device  40  through housing  41  will not cause any fluid leak.  
         [0019]    As shown in FIG. 2B, the switch  58  has opened. Thus, the light  44  will now be illuminated. If the switch  58  is closed, the path through the switch  58  is of less resistance then passing through the light  44 . In such cases, the light  44  will not be illuminated. However, should the switch  58  open, as would be the case should temperatures within the compressor increase above a predetermined maximum, or should there be electrical anomalies in the power supply, then the switch  58  will open and the light  44  will become illuminated. Under such conditions, the light will stay illuminated until conditions change, such as by cooling of the temperature within a compressor, and such that the switch  58  can then re-close.  
         [0020]    The present invention thus provides a way of indicating to a service repair person that the motor protector switch has opened to stop motor operation. This will provide a good indication to the repair person that a particular type of condition may have stopped compressor motor operation. Thus, the problems as mentioned above will be overcome.  
         [0021]    While the motor protector is shown as triggering the signaling device, other “trigger” events could be utilized. As an example, compressors are often provided with valves which will open under certain conditions to allow hot refrigerant to contact a protector switch. The operation of such a valve could be utilized as a “trigger” for a signaling device. Moreover, while a scroll compressor is illustrated and disclosed, other types of compressors may benefit from this invention. Also, signaling devices other than a visual device, such as a light, may be utilized.  
         [0022]    The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.