Abstract:
A module is provided for attachment to the roof of a bus and includes all of necessary components for conditioning the return air from the passenger compartment and delivering conditioned air thereto. A module can be ganged in various relationships to collectively provide the total capacity required by the bus. Each module includes an evaporator section, a condenser section and a power section including a compressor and an inverter. The evaporator sections have a return air compartment that extends a substantial distance across the roof of the bus such that a single design can meet the needs of various return air duct installations of various types of buses. Provision is made for the selectively mixing of return air with fresh air, with the mixture then being passed by the evaporator blower through the evaporator coils and into the supply air ducts. The frames of the modules are attached to the roof of the bus by rails which are properly spaced to accommodate the modules frame and allow their selective longitudinal placement.

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: 
     
       
         
               
               
             
           
               
                   
               
               
                 Title 
                 Our 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 
                 210_549 
               
               
                 Units 
               
               
                 Bus Rooftop Condenser Fan 
                 210_550 
               
               
                 Method and Apparatus for Refreshing Air in a Bustop 
                 210_548 
               
               
                 Air 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 Condition- 
                 210_551 
               
               
                 ing 
               
               
                 Modular Rooftop Unit Supply Air Ducting Arrange- 
                 210_577 
               
               
                 ment 
               
               
                 Configuration for Modular Bus Rooftop Air Condition- 
                 210_595 
               
               
                 ing 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. 
     Also associated with the existing bus air conditioning systems is the problem of a component failure causing a complete loss of the air conditioning capacity. That is, with a single large unit as is now customary, failure of that unit such as, for example, a leaking hose causing loss of refrigerant, an electrical failure leading to inoperation of one of the components such as a fan, or a compressor failure, the entire unit is inoperable and no air conditioning can be provided to the unit. In such a situation, it would preferable if partial capacity could be maintained in order to provide a “limp home” capability. 
     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 engine 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. 
     Another object of the present invention is that of providing a “limp home” capability in the event of certain component failures. 
     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, rather than a large single air conditioning unit, a plurality of relatively small identical modules can be installed on the roof of a bus, with each being capable of operating independently of the others so as to allow for the relatively low cost mass production of identical standardized units and also provide for a limp home capability in the event of failure of one or more units. 
     In accordance with another aspect of the invention, each of a plurality of modules are installed in a centered relationship with respect to a longitudinal centerline of the bus and extend transversely across the width of the bus. The number and length of modules is dependent on the total air conditioning capacity requirement of the bus. 
     By yet another aspect of the invention, each of the identical modules includes all the necessary components with electrical power being provided to the electrical components by an inverter/controller that is powered by an engine driven generator. 
     By another aspect of the invention provision is made for mounting the frames of multiple modules in adjacent or longitudinally spaced positions on the bus rooftop by way of a pair of longitudinally extending rails. 
     By still another aspect of the invention the evaporator section of the modules has a return air compartment that spans a substantial width of the bus to thereby accommodate various sizes and types of return air interface requirements. 
     By yet another aspect of the invention the evaporator section of each module has three different vertical levels to accommodate the respective incoming flows of return air and replenishing fresh air, and includes a mixer for selectively varying the amount of each which passes to the fan and then to the evaporator coil. 
     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 spirit and scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a module as installed on the rooftop of a bus in accordance with a preferred embodiment of the invention. 
     FIG. 2 is a perspective view of a module with the top cover removed. 
     FIG. 3 is a schematic illustration of the electrical and refrigerant circuits within the module in accordance with the preferred embodiment of the invention. 
     FIG. 4 is a front elevational view of the condenser section of the module. 
     FIG. 5 is a front elevational view of the evaporator section of the module. 
     FIGS. 6-8 are front elevational views of the evaporator section as applied to different types of bus rooftops. 
     FIG. 9 is a perspective view of the evaporator section with its fan and mixer. 
     FIG. 10 is a bottom perspective view thereof. 
     FIG. 11 is a perspective view of the evaporator section showing the fresh air flap in the fully opened position. 
     FIG. 12 is a perspective view thereof with the flap in an intermediate position. 
     FIG. 13 is a perspective view thereof with the fresh air flap in the closed position. 
     FIG. 14 is a perspective view of a pair of modules in adjacent relationship. 
     FIG. 15 is a perspective view of three modules in adjacent relationship. 
     FIG. 16 is a perspective view of four modules in adjacent relationship. 
     FIG. 17 is a perspective view of the modules frames and related mounting rails. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The inventive module is shown generally at  10  in FIG. 1 as applied to the rooftop top  11  of a bus in accordance with the present invention. Electrical power is provided to the module  10  by way of line  12 , which in turn receives its power from a generator  13  driven by the bus engine  14  as shown. 
     The module  10  interfaces with openings in the bus top so that fans within the module  10  cause the return air from the passenger compartment to flow upward into the module  10  where it is conditioned, and the conditioned air to then flow downwardly into supply air ducts that carry the conditioned air to the passenger compartment. The various structures and the manner in which they interface with the bus rooftop  11  will more fully described hereinafter. 
     In FIG. 2, the module  10  is shown with its cover removed to include a frame  16  with an evaporator section  17  attached to one end thereof and a condenser section  18  attached to the other end thereof. Adjacent the condenser section  18  is a power section  19  which includes a compressor  21  and an inverter/controller  22 . The manner in which they provided motive power to the refrigerant circuit and electrical power to the electrical components of the module  10  will be more fully described hereinafter. 
     The evaporator section  17  comprises a pair of identical units in abutting end-to-end relationship with each unit including an evaporator blower  23  with its evaporator blower motor  24 , and an evaporator coil  26 . Briefly, the evaporator blower  23  draws in return air from the passenger compartment of the bus, and fresh air from outside and passes a mixture of the two through the evaporator coil  26  to be conditioned, after which it flows back to the passenger compartment by way of the supply air ducts. This will be more fully described hereinafter. 
     Within the condenser section  18 , there is provided a condenser fan  27  driven by an electric motor, and a pair of condenser coils  28  and  29 . Briefly, the condenser fan draws air upwardly to create a vacuum below, which in turn causes fresh air to be drawn through the condenser coils  28  and  29  to condense the refrigerant flowing through the coils  28  and  29 . The resulting warm air is then discharged upwardly to the atmosphere by the fan  27 . 
     Referring now to FIG. 3, the module  10  is shown with its electrical connection by way of line  12  to the generator  13  and driving vehicle engine  14 . The inverter/controller  22  receives AC power from the generator, or alternator, and, in turn provides discretely controlled AC power to the evaporator blower motor  24 , the drive motor  31  of the condenser fan  27  and the drive motor  32  of the compressor  21 . A plurality of control sensors, shown generally at  33  provide feedback to the inverter/controller  22  as necessary for it to control the AC power being delivered to the various drive motors. 
     As will be seen, the refrigeration circuit is a closed circuit through which the refrigerant flows from the compressor  21  to the condenser  29 , an expansion valve  34 , the evaporator  26  and finally back to the compressor  21 . This is accomplished in a conventional manner. 
     It will be seen that the module  10  is self-contained with all of the necessary components, with the only input thereto being the electrical power by way of the electrical line  12 . Other modules, indicated as numbers  2 - 6  are identically configured and are powered and controlled in the same manner. 
     Returning now to the condenser section  18  as shown in FIG. 4, the flow of air as caused by the condenser fan  27  is shown by the arrows. Fresh air is drawn in through the fresh air intake openings  36  and  37 , passes through the respective condenser coils  28  and  29  and then flows upwardly through the condenser fan  27  and the condenser outlet air opening  38  as shown. 
     Within the evaporator section  17  as shown in FIG. 5, the relatively warm return air flows upwardly from a return air duct communicating with the passenger compartment and enters a return air compartment  39  of the evaporator section  17  as shown by the arrows. The evaporator blower  23  causes the return air to flow upwardly to its inlet at the top, and at the same time, fresh air may be brought in by way of a fresh air flap in a manner to be described hereinafter. A mixture of the two airflow streams is thus admitted at the intake of the evaporator blower  23  and caused to flow downwardly and outwardly as indicated by the arrows to the evaporator coils  26 . After passing through the evaporator coil  26  it is then caused by a curved cowling  41  to flow downwardly to a supply air duct leading to the passenger compartment. Thus, while the module is operating, there is a constant circuitous flow of return air out of the passenger compartment and of conditioned air back into the passenger compartment. The amount of return air that is discharged to the outside, and also the amount of fresh air that is brought into the circuit from the outside is controlled by the selective movement of the fresh air flaps as will be described hereinafter. There are shown in FIGS. 6-8 installations of the module  10  with various types of buses and associated return air and supply air ducts. In FIG. 6, for example, a wide bus installation is shown wherein the existing duct work within the bus includes supply air ducts  43  and  44  near the lateral sides of the bus, and return air ducts  46  and  47  that are closer to the center line of the bus, but are substantially spaced apart. Here it will be seen that the return air ducts  46  and  47  communicate directly with the return air compartment  39  of the module  10 , but at a position at near the outer end thereof. 
     In FIG. 7, which shows a narrow bus installation, again the supply air ducts  48  and  49  are near the transverse sides of the bus. But the return air ducts  51  and  52  are abutting each other at the center line of the bus. Again, the return air ducts  51  and  52  fluidly communicate with the return air compartment  39 , but at the other end thereof. 
     Finally, in FIG. 8 there is shown a curved top bus wherein the supply air ducts  53  and  54  are again near the transverse sides of the bus, but the return air ducts  56  and  57  are in intermediate positions, relatively close to the center line but substantially spaced apart. Again, the return air ducts  56  and  57  fluidly communicate with the return air compartment  39 , but at a position intermediate the two ends thereof 
     It will thus be seen that the same identical module is so constructed and designed that it can accommodate any of these various installation requirements without modification of the module itself. That is, the conditioned air discharge opening  40  is sufficiently large and the transverse direction to accommodate the various supply air duct orientations, and, more importantly, the return air compartment  39  is relatively large in the transverse direction so as to accommodate each of the various types of return air duct configuration as shown. 
     In order to describe the evaporator section  17 , and the manner in which the flow of return air is mixed with the flow of fresh air, reference is made to FIGS. 9-13. In FIG. 9, the evaporator blower  23  is shown with its blower inlet  58  receiving the air to be cooled, which flows downwardly and then outwardly toward and through the evaporator coil  26  as shown by the arrows. The cold air then flows further outwardly and downwardly to the supply air duct as shown by the arrow at the left. The air passing into the blower inlet  58  is a mixture of return air that flows upwardly through the channel  59  and the fresh air that flows in through the fresh intake window  41  as shown by the arrows. That is, referring to FIG. 10, the return air which has come into the return air compartment  39  below the evaporator blower  23  flows into an opening  61  and upwardly through the channel  59  as shown by the arrows. When the return air flow reaches the top of the channel  59  the amount of return air, and also the amount of fresh air passing through the fresh air intake window  41  will depend on the position of the fresh air flap  42 . 
     In FIG. 11, the fresh air flap  42  is shown as attached to a linkage  62 , which in turn is attached to a rotatable lever  63  for selectively rotating the fresh air flap on its axis to thereby vary the size of the opening at the fresh air intake window  41 . The position of the fresh air flap  42  is the fully opened position wherein there is no restriction of the flow of fresh air that is coming into the fresh air intake window  41 . When in this position, the fresh air flap also closes off the exit side of the flow channel  59  in which the return air is flowing upwardly. Thus, when the fresh air flap  42  is in the fully opened position, none of the return air passes upwardly into the evaporator blower  23  and the only, and the only air passing into the evaporator blower  23  and on to the evaporator coil  26  is the fresh air coming in through the fresh air intake window  41 . The return air in the channel  59  is thus caused to flow out into the atmosphere by way of an opening to be described hereinafter. 
     In FIG. 12, the lever  63  and attached rod  62  are selectively moved to adjust the fresh air flow  32  to an intermediate position wherein the exit opening at the top of the channel  59  is uncovered, while at the same time the fresh air flap  42  tends to offer some restriction to the flow of fresh air coming into the fresh air intake window  41 . The air being taken into the blower inlet  58  is thus a mixture of return air and fresh air, with only a portion of the return air being discharged to the outside. 
     FIG. 13 shows the fresh air flap in the closed position wherein it completely blocks off the fresh air intake window  41  and completely uncovers the channel  59 . Thus, when in this position, all of the return air, and no fresh air, passes into the blower inlet  58 , through the evaporator coil  26  and to the supply air ducts of the bus. It should, of course, be understood that the fresh air flap  42  maybe placed in any intermediate position not shown in order to obtain the desired mix as appropriate to meet the cooling needs as determined by the load in the passenger compartment of the bus, as well as the environmental conditions outside. 
     Of a structure of the evaporator section  17  as described hereinabove will be recognized as providing three levels within the evaporator section in which the flow of air occurs. At a lower level, the return air compartment  39  provides for a flow of return air from the return air duct to the evaporator section  17 . At an intermediate level, there is a channel to guide the flow of return air upwardly, and in a parallel route, to provide the flow of mixed air downwardly through the evaporator blower  23 . At a third, upper, level, there is a space provided for the flow of fresh air through the fresh air intake window  41 , for the mixture of that fresh air with the return air blowing upwardly, and for the mixture to flow into the intake  58  of the blower  58 . 
     While a single unit is shown in its installed position on the bus in FIG. 1, the present module is designed to be “ganged” with one or more other modules to provide a collective air conditioning capacity as necessary to meet the needs of the bus. In FIG. 14, a pair of modules are stacked together, with one being turned, end to end, as shown. In this configuration, the two condensing sections are at the forward and rear ends of the combination, and the two evaporator sections are abutted up against one another. The grill openings are shown at  64  in one unit and at  66  in the other unit, to conduct the flow of fresh air to the evaporator section when the fresh air flap is opened, and for the outflow of returned air when the fresh air flap  42  is fully opened or partially opened. An opening  67  can be provided to augment the flow of fresh air to the evaporator. 
     In FIG. 15, a pair of modules  68  and  69  are placed in ganged relationship in the manner as described hereinabove. A third module  71  is placed at the other end of module  69 , so that it is parallel to the module  69 , and not turned end for end as described hereinabove. Thus, the evaporator section of module  71  is adjacent the condenser section of module  69 , and in particular, the grill opening  72  are disposed adjacent to the condenser fan of module  69 . 
     In FIG. 16, there are shown four modules  72 ,  73 ,  74  and  76 , with modules  72  and  73  being parallel with each other and with modules  74  and  76  being parallel with respect to each other but being rotated end for end with respect to the modules  72  and  73 . 
     It should be recognized that the individual modules can be ganged in any combination in order to meet the required capacity for the bus, while also being positioned so that the return air openings in the bus are registerable with the respective inlet and outlet openings in the evaporator sections. While not shown, it should be understood that the modules can also be installed in positions so that they are longitudinally spaced and not necessarily abutted up against each other as shown. 
     In order to mount the modules, either as a single unit or in combinations as shown, it is desirable to have a method and apparatus for easily attaching the modules to the rooftop of the bus. A preferred approach is to have a pair of transversely spaced, longitudinally extending rails  77  and  78  which are attached to a bus by appropriate fasteners or the like. The framework of the individual modules can then, in turn, be attached to the rails  77  and  78  by appropriate fasteners such as screws or the like. In FIG. 17, a pair of module frames  79  and  81  are shown, with the frame  81  being turned end for end in a manner as described hereinabove. This arrangement allows for the modules to be easily attached to the rails such that they are all centered with respect to the center line of the bus, and can be attached to the rails  77  and  78  at any longitudinal position that is desired. 
     While this invention has been described with reference to a particular structure disclosed herein, it should be understood that it is not confined to the details set forth in this application, but is rather intended to cover any modifications and changes may come within the scope of the following claims.