Abstract:
A bustop air conditioning module is provided with an evaporator section having a return air opening and a condenser section having a fresh air opening. A mixer opening is provided between the fresh air opening and the evaporator coil, and a flap is selectively positionable to cover or uncover the mixer opening to allow a selective amount of fresh air to be passed to the evaporator coil. Simultaneously, the flap also to selectively block a portion of the return air flowing to the evaporator coil and at the same allow a portion of the return air to be exhausted from the system.

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 
               
               
                 Title 
                 Docket 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. This, of course, requires rather extensive piping between the engine compartment and the air conditioning unit, thereby increasing installation and maintenance costs. 
     Another problem with such existing systems is that the speed that the compressor is driven is dependent on the speed in which the drive engine is running. Thus, when the drive engine is idling in a parking lot, for example, the compressor is running at a relatively slow speed which may not be sufficient to provide the desired degree of air conditioning. It is therefore generally necessary to oversize the compressor in order to obtain the performance needed under these conditions. 
     Others problems associated with such a motor driven compressor system is that the open drive compressor needs a shaft seal and a mechanical clutch, both of which are subject to maintenance problems. Further, since DC power is available on a bus, DC motors have been used for the air conditioning system. In general, DC motors are not as reliable as AC motors since they have brushes that wear out, and brushless motors are relatively expensive. 
     In addition to the problems discussed hereinabove, it is recognized, that because the wide variety of bus types and application requirements, it has been necessary to provide many different types and variations of air conditioning systems in order to meet these different requirements and vehicle interfaces. As a result, the manufacturing and installation costs, and sustaining engineering resources that are necessary in order to properly maintain and service these units, are relatively high. 
     Conventionally, bus air conditioning systems have relied on the general leakiness of a bus for purposes of replenishing the air therein. That is, because buses generally have many areas where outside air can leak into the bus and inside air can leak out of the bus, there has been no need to deliberately circulate fresh air into the bus and stale return air out of the bus. However, as buses have become tighter in construction, it has been found that the recirculated air can eventually become stale. 
     It is therefore an object of the present invention to provide an improved bus top air conditioning system. 
     Another object of the present invention is the provision for a bus air conditioning system which is effective at all operating speeds of the bus, while at the same time does not require an oversized compressor. 
     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 rooftop air conditioner for a systemic replenishment of air within the bus. 
     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 and 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. 
     By still another aspect of the invention, an air mixing flap is adjustably positioned between the condenser coil and evaporator coil such that fresh air can be introduced into the flow to the evaporator coil, while at the same time, a portion of the return air is routed to the condenser discharge opening by way of the flap. 
     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. 
     FIGS. 5A-5C are sectional views of modules as applied to various types of bus installations in accordance with a preferred embodiment of the invention. 
     FIGS. 6A-6C are sectional views of a module with an air mixing flaps in various positions. 
    
    
     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 , an evaporator blower  14  and 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 electric 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. 
     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 compressor  18  is driven by an 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 includes a rectifier and an invertor, receives AC power from a generator or alternator  29  and provides, by way of the invertor, 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 (PIC) 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 the 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 of 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 may be 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 is relatively large and therefore can accommodate the various positions of the return air ducts  41 ,  43  and  46  as shown. 
     Considering the now the need to refresh the air in the air conditioner system by bringing in fresh air from the outside, the various positions of the fresh air/exhaust air flap  36  are shown in FIGS. 6 a - 6   c . The flap  36  is made up of blades  47  and  48  integrally attached to a pivot point  49 , with the angular orientation therebetween, θ, being about 135°. A related structure is a divider  51  with curvilinear portion  52  protrusion portion  53 , which is mounted at its end and extends transversely across (i.e., into the drawing) the opening  54  between the evaporator coil  12  and condenser coil  13  and a baffle portion  55 . 
     In FIG. 6 a , the flap  36  is placed in such a position that its blade  47  engages the evaporator coil support structure  56 , while its blade  48  engages the condenser coil support structure  57 . In this position, the opening  54  is closed such that no fresh air can flow from the fresh air inlet  34  into the evaporator coil  12 . Thus, all of the return air coming into the return air opening  32  passes through the evaporator coil  12  as shown, and all of the fresh air entering the fresh air intake opening  34  passes through the condenser coil  13  and out the outlet air opening  33 . 
     In FIG. 6 b , the flap  36  is rotated clockwise until the blade  47  engages protrusion portion  53  and the blade  48  engages the evaporator coil bottom support  60 . In this position, the flap  36  completely blocks off the flow of return air to the evaporator coil  12 , and at the same time, the opening  54  is completely opened such that some of the fresh air passing into the fresh air intake opening  34  passes through the opening  54  and through the evaporator coil  12 . 
     In FIG. 6 c , the flap  36  is placed in an intermediate position wherein the blade  47  is between the structure  56  and the curvilinear portion  52  and the blade  48  is suspended downwardly and not engaging any surface. In this position, the upper part of the opening  54 , between the structure  56  and the blade  47 , is open to the flow of fresh air from the fresh air opening  34 , through the opening  54  and to the evaporator  12 . At the same time, there is an open area to the left of the blade  48  wherein the return air may also flow through the evaporator coil  12 . However, the blade  48  does offer some blockage to the flow of the return air and it also acts to divert its flow to the right, between the divider  51  and the condenser coil  13 . This air then passes through the coil  13  and is caused by the fan  31  to exhaust through the opening  33 . In this way, as the return air becomes stale, some of it may be exhausted out of the system and replaced with fresh air. 
     Of course, it will be understood that the flap  36  can be placed in any other desirable position between those described hereinabove so as to obtain the desired mixture of fresh air with the return air. 
     It is the intermediate positions of the flap  36  wherein the divider  51  comes into play. For example in the FIG. 6 c  position, the divider  51  forms a boundary between the flow of fresh air coming into the opening  54  and the return air being exhausted through the opening between the divider and the condenser coil  13 . The protrusion  53  assists in preventing the exhaust air from being drawn into the flow of fresh air passing through the evaporator coil  12 . 
     While the present invention has been particularly shown and described with reference to a preferred mode as illustrated in the drawings, it will be understood by one skilled in 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.