Abstract:
The performance of a PCA unit associated with an airport gate is monitored by a temperature sensor in the stream of output air leaving the PCA unit, to produce a signal indicative of the temperature of the output air that may be compared to an acceptable range of values, or to the temperature of air input to the PCA unit (as measured by a second temperature sensor). An alert is generated to a human operator if the temperature measured does not compare favorably with the desired range.

Description:
RELATED APPLICATIONS 
       [0001]    The present invention claims priority to U.S. Ser. No. 61/236,656 filed Aug. 25, 2009, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]    The present invention generally relates to ground-based conditioned air systems for aircraft. 
       BACKGROUND 
       [0003]    It is generally known to supply commercial aircraft with conditioned air for heating and cooling when the aircraft is stationary at a gate. In this application, the term gate is meant to refer to any place that an aircraft receives or discharges passengers or cargo. This may be by way of a telescoping corridor (also referred to as a walkway, bridge way, jet bridge), stairs, or any other facility. Typically, conditioned air is supplied to the aircraft from a pre-conditioned air (PCA) unit associated with the gate that is a part of the airport terminal. The PCA unit may produce heated air or cooled air depending on the needs of the aircraft it is servicing. The PCA outputs its air into a duct that may be rigid or flexible, and then the air is delivered from the gate to the aircraft with a flexible and usually insulated air hose. When not in use, the hose is usually stored under the terminal. In some installations a branch of the same duct, or a separate one, may be used to supply preconditioned air to the enclosed walkway that passengers walk through to access the airplane. In such a case, there may also be a return air duct from the walkway to the PCA unit, or there may not be one. 
         [0004]    A problem arises if the PCA unit starts to malfunction and fails to supply the cooled air or the heated air of which it is capable. It is easy for this condition to go undetected, because a PCA unit is not used like a typical building heating, ventilation, and cooling (HVAC) unit. In the latter, the HVAC is permanently connected and typically running per the commands of a thermostat that is sensing room air temperature. The HVAC unit services a building of a given size, with a permanent ducting system that is never kinked, improperly connected, or torn. Usually there is a steady group of occupants, and a designated maintenance person to pay attention to the HVAC system. If the occupants become uncomfortable, it is quickly evident that the HVAC system is probably not cooling or heating to its usual ability, and corrective action is taken. But the situation with a PCA unit is different. For example, the PCA unit is called upon to service aircraft of different sizes. The flexible hose is often kinked because usually a single length hose is used to hook up aircraft with connections at varying distances from the PCA unit. The hose may be torn. There may be a delay in how quickly the PCA unit is hooked up to the aircraft and turned on. It may only be hooked up for a short time. Somebody may fail to turn the PCA unit on. The PCA unit may be switched off overnight even though an aircraft is parked at the gate, and the aircraft heats up in the sun the next morning, or cools down excessively overnight. For these and various other reasons a complaint of “too hot” or “too cold” by the people using the aircraft and the walkway may be considered of limited value by the ground based personnel who have to keep many PCA units operating. A decrease in operating performance by a PCA unit is likely to go unnoticed and unattended to by the people who could fix it before complete failure. 
       SUMMARY OF THE INVENTION 
       [0005]    Thus, there is a need for a device that measures the output temperatures of a PCA unit close to the aircraft, so the measurement provided is unaffected by the vagaries of aircraft changes, air hose installations, and other conditions. Further, the device should alert people of a problem so that corrective action can be taken. 
         [0006]    In accordance with principles of the present invention, the performance of a PCA unit associated with an airport gate is monitored by a temperature sensor in the stream of output air leaving the PCA unit, to produce a signal indicative of the temperature of the output air that may be compared to an acceptable range of values, or to the temperature of air input to the PCA unit (as measured by a second temperature sensor). An alert is generated to a human operator if the temperature measured does not compare favorably with the desired range. 
         [0007]    Particular aspects involve both the apparatus for monitoring and the monitoring method described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention. 
           [0009]      FIG. 1  is a perspective view illustrating an embodiment of the present invention installed at a PCA unit under an airport bridge way. 
           [0010]      FIG. 2  is a perspective detail view of the control unit of the embodiment of  FIG. 1 . 
           [0011]      FIG. 3  is a perspective detail view of the control unit of  FIG. 3  with an access door open. 
           [0012]      FIG. 4  is a perspective view illustrating a second embodiment of the present invention installed at a PCA unit under an airport bridge way. 
           [0013]      FIG. 5  is a partial electrical schematic of the embodiment of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates a preconditioned air (PCA) temperature monitor  10  having a main box  11  (see  FIG. 2 ) mounted near a PCA unit  12  on an airport bridge way  14 . The PCA unit  12  blows preconditioned air into a duct  16  that runs to a PCA hose and airplane  18 . A smaller duct  20  supplies air to the bridge way  14 , although in many installations this smaller duct  20  may not exist or may be separate from the duct  16 . Not all bridge ways  14  are supplied with air by a PCA unit  12 . The PCA unit  12  has a temperature sensor  22  in the duct  16  to measure the temperature of air leaving the PCA unit  12 . In one embodiment the temperature sensor  22  is a thermistor, although it could be another type of device. As illustrated, the temperature sensor  22  is remote from the main box  11 , but it could be integral, depending on the specific design and mounting location. An electrical connection  24  from the PCA unit  12  provides a signal  26  to the PCA monitor  10  whenever the PCA unit  12  turns on. In some embodiments, the signal  26  may include information as to whether the PCA unit  12  is running in heating mode or cooling mode. A signaling device  28  in the form of a rotating or flashing light beacon is located in the operator&#39;s station of the bridge way  14 . The signaling device  28  could be located in other places and take other forms. It may be wireless. 
         [0015]      FIGS. 2 and 3  schematically illustrate various portions of the main box  11 . The front panel  30  has a cool cycle indicator  32 , a heat cycle indicator  34 , an over temperature indicator  36  an under temperature indicator  38 , and a light test button  39 . A display window  40  is aligned with a heat cycle display  42  and a cool cycle display  44 . Fittings along the bottom accept connections to the temperature sensor  22 , the PCA unit  12 , and the signaling device  28 . A timing circuit  46  determines when the PCA unit  12  has been on long enough that it and the path to the temperature sensor  22  should be at a steady state, rather than significantly changing. Alternatively, the timing circuit  46  used to predict steady state could be external to the PCA unit  12 , or, steady state could be determined by the rate of change at the temperature sensor  22  and not be estimated by the elapsed time. Because an electrician of ordinary skill in the art could wire the PCA monitor  10  to the circuitry of the PCA unit  12 , the wiring will not be further described here. What is important is that the PCA monitor  10  determine when the PCA unit  12  is operating and at steady state. 
         [0016]    At least one settable memory device  48  has a value for an appropriate cooling cycle high temperature limit  50  and an appropriate heating cycle cold temperature limit  52 . Heat cycle display  42  and cool cycle display  44 , visible through the display window  40 , show the limit values, and if desired the actual values. The limits are input either by inputting them into the box directly or remotely. 
         [0017]    The PCA monitor  10  further comprises processing circuitry  54  and comparison circuitry  56  to compare the signal from the temperature sensor  22  to the temperature limits. Values that do not meet the limits will trigger the over temperature indicator  36  or the under temperature indicator  38  and the signaling device  28 . 
         [0018]    In use, a person, usually in a maintenance department, will set the cooling cycle high temperature limit  50  and the heating cycle cold temperature limit  52  to values based on the PCA unit&#39;s manufacturing specifications, or experience. Ordinarily the over temperature indicator  36  and the under temperature indicator  38  will remain off. Only if the PCA unit  12  is unable to precondition the air to the limits do the lights illuminate. The test button  39  activates test circuitry to confirm the lights are in working order. 
         [0019]    If desired, the circuitry could be arranged differently. For example the indicator  36  and indicator  38  could be set to illuminate when things are working properly, and extinguish if they are not. 
         [0020]      FIG. 4  illustrates a second embodiment of a PCA monitor  210  that may enhance the ability to choose the cooling cycle high temperature limit  50  and the heating cycle cold temperature limit  52  that are more exact and work under a greater variety of conditions without giving false alarms. 
         [0021]    One consideration when measuring only the temperature of the output air, as in  FIG. 1 , is that the temperature of air that PCA unit  12  outputs is affected by the temperature of the air it is receiving to heat or cool. For example, the output temperature of a PCA unit  12  in cooling mode when cooling one hundred ten degree outside air is different than when cooling seventy-five degree outside air. In general, a PCA unit  12  should be able to change the air temperature a given amount, often referred to as a “ΔT” (Δ meaning difference, and T meaning temperature), the difference in output air temperature verses input air temperature. 
         [0022]    To that end PCA monitor  210  comprises an ambient air sensor  58  located away from any influences such as sunlight or thermal exhausts. It may be put directly in an entrance  60  to the PCA unit  12 , although it is not shown that way in this illustration. If a bridge way  14  has a return duct  62  to the PCA unit  12 , it may have a return temperature sensor  64 . The PCA monitor  210  has a main box  211  that includes processing circuitry  54  to determine a value indicative of delta T, and the memory device  48  similarly contains acceptable limits for delta T. 
         [0023]    Although the main box  211  is illustrated as different from the main box  11 , it is contemplated that a single main box  211  may be manufactured, and the features either not used or fully used, depending upon the actual installation. 
         [0024]      FIG. 5  is an electrical schematic of the embodiment  10 , with numerals corresponding to those described with reference to previous figures. 
         [0025]    The invention has been described herein with reference to specific embodiments, and those embodiments have been explained in substantial detail. However, the principles of the present invention are not limited to such details which have been provided for exemplary purposes. Further, the monitoring system although specifically described in terms relevant to a PCA unit  12  at an airport, may apply to other devices heating and cooling air or another gas or liquid.