Abstract:
A module is provided for attachment to the roof of a bus and includes all of the necessary components for conditioning the return air from the passenger compartment and delivering conditioned air thereto. Each module may include an evaporator section, a condenser section and a power section including a compressor and an inverter. The condenser section includes a condenser coil and a transverse fan with its axes disposed horizontally so as to draw air through a fresh air intake opening, through the coil and out a condenser discharge opening. The drain pan is shaped so as to form an air guiding wall around the fan, and a vortex wall is attached to the condenser coil support structure to separate low and high pressure sides of the fan. A rear wall and the fins of a discharge grill are angled with respect to the vertical plane so as to thereby prevent a recirculation of hot discharged air back into the air intake opening.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is related to the following pending applications being concurrently filed herewith and assigned to the assignee of the present invention: 
   
     
       
             
             
           
         
             
                 
             
             
                 
               Our Docket 
             
             
               Title 
               No.: 
             
             
                 
             
           
           
             
               Modular Rooftop Air Conditioner for a Bus 
               210 — 546 
             
             
               Modular Bus Air Conditioning System 
               210 — 545 
             
             
               Supply Air Blower Design in Bus Air Conditioning Units 
               210 — 549 
             
             
               Bus Rooftop Condenser Fan 
               210 — 550 
             
             
               Method and Apparatus for Refreshing Air in a Bustop Air 
               210 — 548 
             
             
               Conditioner 
             
             
               Coil Housing Design for a Bus Air Conditioning Unit 
               210 — 547 
             
             
               Integrated Air Conditioning Module for a Bus 
               210 — 558 
             
             
               Fresh Air Intake Filter and Multi Function Grill 
               210 — 554 
             
             
               Integrated Air Conditioning Module for a Bus 
               210 — 557 
             
             
               Modular Air Conditioner for a Bus 
               210 — 561 
             
             
               Modular Air Conditioner for a Bus Rooftop 
               210 — 562 
             
             
               Evaporator Section for a Modular Bus Air Conditioner 
               210 — 564 
             
             
               Wide Evaporator Section for a Modular Bus Air 
               210 — 565 
             
             
               Conditioner 
             
             
               Condensate Pump for Rooftop Air Conditioning Unit 
               210 — 568 
             
             
               Condensate Removal System Rooftop Air Conditioning 
               210 — 551 
             
             
               Modular Rooftop Unit Supply Air Ducting Arrangement 
               210 — 577 
             
             
               Configuration for Modular Bus Rooftop Air Conditioning 
               210 — 595 
             
             
               System 
             
             
               Unibody Modular Bus Air Conditioner 
               210 — 596 
             
             
                 
             
           
        
       
     
   
   BACKGROUND OF THE INVENTION 
   This invention relates generally to air conditioning systems and, more particularly, to an air conditioning system for the rooftop of a bus. 
   The most common approach for air conditioning a bus is to locate the air conditioning components on the rooftop thereof. Inasmuch as power is available from the engine that drives the bus, it has become common practice to locate the air conditioning compressor near the drive engine such that the drive engine is drivingly connected to the compressor, with the compressor then being fluidly interconnected to the air conditioning system on a rooftop of a bus. 
   In the condenser section of a bus rooftop air conditioner, it has been common practice to use one or more propeller fans for circulating outdoor air through the condenser coil. This is normally accomplished by installing the condenser fan(s) with its axis oriented vertically, and with the fan then drawing air through the condenser coil and discharging it upwardly. This approach has been recognized by the applicants as problematic for a number of reasons. First, the vertical orientation of the fan, together with its drive motor, severely limits the degree in which the vertical height can be reduced. Secondly, the fan drive motor is necessarily within the hot condenser air stream, thereby reducing it reliability. Further, such condenser fan motor installations are difficult to reach for purposes of serviceability. Also the propeller fans tend to be noisy. Finally, because of the relatively low profile unit aspect ratio, there tends be an unequal air flow distribution to the condenser coil. 
   It is therefore an object of the present invention to provide an improved bustop air conditioning system. 
   Another object of the present invention is the provision in a bus air conditioner for condenser section that is relatively quiet and has a pleasing profile to an observer. 
   Yet another object of the present invention is the provision for reducing the manufacturing, installation, and maintenance costs of a bus air conditioning system. 
   Still another object of the present invention is the provision in a bustop air conditioner for limiting the vertical height of the condenser section thereof. 
   Another object of the present invention is the provision in a bustop air conditioner for a condenser fan motor installation that is reliable in service and easily accessed for purposes of serviceability. 
   Still another object of the present invention is the provision in a bustop air conditioner for providing uniform air flow distribution through the condenser coil. 
   Yet another object of the present invention is the provision for a bus rooftop air conditioning system which is economical to manufacture and effective in use. 
   These objects and other features and advantages become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings. 
   SUMMARY OF THE INVENTION 
   Briefly, in accordance with one aspect of the invention, an air conditioning module is assembled with its condenser coil, evaporator coil and respective blowers located within the module and so situated that a standard module can accommodate various installation interfaces with different types and locations of return air supply air ducts on a bus. 
   In accordance with another aspect of the invention, a plurality of modules can be installed on the roof of a bus, with each pair being in back-to-back relationship near the longitudinal center line of the bus. 
   By yet another aspect of the invention, the modules may include a compressor, such that all the necessary refrigerant piping is located entirely on the module, with electrical power being provided to the electrical components on the module from a motor driven generator. 
   As still another aspect of the invention, a transverse fan is disposed downstream of the condenser coil, with its axis oriented horizontally so as to draw air through the condenser coil and discharge it upwardly through the unit. 
   By yet another aspect of the invention, the structure surrounding the transverse fan is installed such that the flow exiting the transverse fan is orientated in a direction away from the condenser fresh air intake to avoid recirculation. 
   In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true sprit and scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a module in accordance with a preferred embodiment of the invention. 
       FIG. 2  is an alternative embodiment of the invention to include a compressor. 
       FIG. 3  is a schematic illustration of both a refrigeration circuit and an electrical circuit within a module in accordance with the present invention. 
       FIG. 4  is a cut away perspective view of a module in accordance with a preferred embodiment of the invention. 
       FIG. 5A–5C  are sectional views of modules as applied to various types of bus installations in accordance with a preferred embodiment of the invention. 
       FIG. 6  is a partial side view of the module showing the condenser fan portion thereof. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a module  11  with the cover removed to show the various components including an evaporator coil  12 , a condenser coil  13 , a plurality of evaporator blowers  14  and associated drive motor  16 , and a condenser fan motor  17  for driving a condenser fan. 
   Outside the module  11  is a compressor  18  which is driven by a motor drive  19  to pump refrigerant from the compressor  18  through refrigerant line  21  to the condenser coil  13  and eventually to the evaporator coil  12  by way of an expansion valve  22  (not shown). The refrigerant vapor then passes back to the compressor  18  by way of refrigerant line  23 . 
   Also shown in  FIG. 1  is an electrical resistance heater  24  which is downstream of the evaporator coil  12  such that, for periods of heating, the air is drawn by the evaporator blower  14  through the evaporator coil  12  and the heater  24  such that the air being delivered to the passenger compartment of the bus is heated. The electrical power to the heater  24 , as well as to the evaporator blower motor  16  and the condenser fan motor  17 , are provided by way of an electrical line receiving electrical power from a generator or the like, which in turn is driven by the drive motor  19 . The heater  24  can be powered by either DC or AC currents with the heat output being independent of the speed of the drive engine. With the module as shown in  FIG. 1 , DC power is available to power all of the motor components and is therefore preferred for the heater  24 . 
   Referring now to  FIG. 2 , a modified module  26  is shown to include all of the components as described hereinabove. Further, it includes a horizontal rotary compressor  27  which is operatively interconnected between the evaporator coil  12  and the condenser coil  13  so as to circulate refrigerant in a manner similar as described hereinabove. The difference over the earlier described system, however, is that the hermetic compressor  27  is driven by an internal electric motor  20 , with the power being provided by way of the generator  29 , driven by the main engine  19 , and an invertor/controller  28  as shown in  FIG. 3 . The invertor/controller  28 , which receives inputs from various control sensors  30  and which includes a rectifier and an inverter, receivers AC power from a generator or alternator  29  and provides, by way of the inverter, controlled AC power to the evaporator blower motor  16 , the condenser blower motor  17 , the compressor drive motor  20  and the heater  24  or, alternatively the heater may be powered by the generator shown by the dotted line of  FIG. 3 . Since the invertor/controller  28  is capable of providing controlled AC power, each of the motors are AC motors, thereby ensuring a more maintenance free system. 
   With the inverter/controller providing controlled AC power, a preferred type of heat  24  is a positive temperature coefficient (PTC) heater wherein electrical resistance increases relatively fast as the temperature increases. Whereas this type of heater is relatively expensive in it initial installation, it acts as a self limiter and does not require a thermostat to maintain a safe temperature limit. 
   Referring now to  FIG. 4 , the module is shown with the various components as described hereinabove enclosed within a housing  29  and including a condenser fan  31 . Also shown are various openings in the housing  29 , including a return air opening  32 , a condenser outlet opening  33  and a condenser/fresh air intake opening  34 . A fresh/return/exhaust air flap  36  is provided between the condenser coil  13  and the evaporator coil  12  to control the mix of air passing to the evaporator coil  12 , depending on the particular demands of the system, as well as the existing ambient conditions. The air flow pattern, as indicated by the arrows, is thus controlled by the condenser fan  31 , the evaporator fan  14  and the position of the air flap  36 . As the return air enters the return air opening  32 , it is caused to flow out the condenser outlet air opening and/or through the evaporator coil  12  depending on the position of the air flap  36 . Similarly, the fresh air coming in the intake opening  34  passes through the condenser coil  13  and then out the condenser outlet air opening  33  and/or, depending on the position of the air flap  36 , it is allowed to pass through the evaporator coil  12 . Thus, with the use of the air flap  36  it is possible to have all of the return air pass through the condenser air outlet opening  33 , with all fresh air passing into the air intake opening  34  and then through the evaporator coil  12 , or when the flap  36  is placed in the other extreme position, all the return air passes through the evaporator coil  12  and all of the fresh air entering the air intake opening  34  passes through the condenser coil  13  and out the condenser outlet air opening  33 . A more likely operating condition, however, is an intermediate position of the air flap  36  wherein a selective mix of return air and fresh air are passed through the evaporator coil  12 . 
   As will be seen, a filter  37  is positioned in the air flow stream which enters the fresh air intake opening  34  and passes through the evaporator coil  12 . Its purposes is to filter out any debris that may be in the air stream entering the air intake opening  34 . After passing through the evaporator coil  12 , the conditioned air is caused to flow by the evaporator blower  14  out a supply air opening  38  as shown. 
   Considering now the manner in which the module  11  is positioned on the rooftop in such a way as to interface with the existing air path openings on the rooftop, reference is made to  FIGS. 5   a – 5   c . As will be seen, the position of the various openings on a bus can vary substantially from application to application. For example, in a wide bus application as shown in  FIG. 5   a , the supply air duct  39  is located near the outer side of the bus, whereas the return air duct  41  is disposed at a substantial distance from the longitudinal center line thereof. In a narrow bus application as shown in  FIG. 5   b , the supply air duct  42  is moved a small distance inwardly from the outer side of the bus, and the return air duct is located adjacent the longitudinal centerline as shown. In a curved-roof bus as shown in  FIG. 5   c , the supply air duct  44  is moved slightly more inwardly from the outer side of the bus, and the return air duct  46  is located in an intermediate position, somewhat outwardly of the longitudinal centerline, but not as far as for a wide bus application. 
   Of course, in all of the bus applications, a balanced arrangement is provided wherein each side of the bus is provided with both a supply air duct and a return air duct, in a substantially mirror image arrangement as shown. Thus, the modules are usually placed in back-to-back relationship, with the space therebetween being varied to accommodate the individual application requirements. For example, for the wide bus application of  FIG. 5   a , there is a substantial space between the two modules wherein for the narrow bus application of  FIG. 5   b , they are substantially in an abutting relationship. For the curved roof bus application, they are somewhat angled from a true horizontal position, with the spacing therebetween being at an intermediate degree as shown. It should be understood that the three types of installations shown are presented as a sampling of the possible installation requirements, and there are also others that have heretofore required unique designs in order to meet the particular requirements. The present design, on the other hand, provides a single module which will meet the needs of all of the various applications of rooftop air conditioners. 
   As will be seen, the supply air opening is relatively small, and in each of the three cases described above, the module  11  is placed in such a position that the supply air opening  38  is located substantially over the individual supply air ducts  39 ,  42  and  44 . The return air opening  32 , on the other hand in relatively large and therefore can accommodate the various positions of the return air ducts  41 ,  43  and  46  as shown. 
   Referring now to  FIG. 6 , the condenser coil  13  is shown in its upstream position from the transverse fan  31 , which is driven by an electrical drive motor  17  as previously described. The transverse fan  31  is operated to cause the air flow in the direction indicated by the arrows. That is, outside air is brought in through the fresh air inlet opening  34 , while at the same time a portion of the air may be diverted by way of the flap  36  to include some of the return air that passes through the coil  13 . A mixture of the outdoor air and the return air passing through the condenser coil  13  is drawn into the transverse fan  31  and is discharged from the condenser discharge opening  33 . Thus, in operation, the transverse fan receives the air mixture coming in substantially horizontally at the left and turns it around 90° to be discharged from the condenser discharge opening  33 . This occurs in a relatively quiet and efficient manner, with the drive motor  17  being outside the air flow stream. 
   The transverse, or tangential, or cross flow fan is forward curved and made to operate in a counterclockwise direction. A suitable fan is a model Q.90×470 RAIU which is commercially available from Puncker Co., Puncker GmBh. A suitable drive motor is a Daewoo Electric Motor Industries Ltd, Model A2931ZA 010–020. 
   In order for the transverse fan  31  to properly operate, the surrounding structure is provided with certain desirable features. As will be seen, the drain pan  46  located below the condenser coil  13 , extends substantially horizontal until it reaches the edge of the transverse fan  31 , after which it curves down and around the 
   fan  31  to act as an air guiding wall  47  which approximates the shape of the typical fan housing  31  in the industry. 
   On the other side of the fan, near the condenser discharge opening  33 , a vortex wall  48  is mounted to the coil support structure  49 . The purpose of the vortex wall  48  is to divide the low pressure side at the left of the transverse fan from the high pressure side on the right side thereof. 
   In the applicants early designs of the present invention, the transverse fan  31  and its surrounding structure were so oriented that the discharge flow from the opening  33  was substantially in the vertical direction as indicated by the line. Because of a close proximity of the fresh air inlet opening  34 , some of the discharge flow from the opening  33  tended to be drawn over into the opening  34  to thereby be recirculated, which resulted in a loss of efficiency. It was therefore recognized that certain design changes needed to be made. 
   One design feature that was changed was that of tilting the back wall  51  of the fan housing such that it is not disposed vertically but is at an angle of which is preferably 2 degrees with respect to the vertical plane. Secondly, the fins of the outlet grill were rotated slightly in the clockwise direction in order to change the direction of the air flow therethrough. The result is that the main discharge flow streamline (indicated by the arrow), is tilted backward several degrees to avoid recirculation of the hot air back into the inlet of the condenser. 
   In addition to the improved features as discussed hereinabove, the present design is aesthetical more pleasing then the large round profiles that are seen with prop fans since the top view of the present design shows only a rather narrow slit, and the fan  31  is essentially hidden from view. Further, because of the relatively small height of the fan  31 , the vertical profile is much lower then can be achieved with a propeller fan. 
   While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes and detail may be effected therein without departing from the true sprit and scope of the invention as defined by the claims.