Abstract:
Heating, ventilation and air conditioning systems for busses achieve improved air distribution by the use of ducts to distribute the air throughout the passenger compartment. The ducts have a varying cross sectional area so that the impedance to air flow appears constant at all points along the duct. The quantity of air distributed from each of a plurality of vents is substantially even is effectively equalized.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to ventilation systems for busses, and, more particularly, to a duct system for delivering heated and air conditioned air evenly to all of the seating areas in a bus. 
     2. Description of the Problem 
     Busses, particularly school busses, have often been equipped with primitive heating, ventilation and air conditioning systems. Typically free air systems have been used which result in highly uneven temperatures through the vehicle&#39;s passenger compartment. In some applications overhead ducts have been used which provide better air distribution, but this results in reduced head room. Aircraft type high pressure systems have also been employed in busses with good results, but these can entail such expense as to be difficult to justify for school busses. 
     Under floor duct and vent systems have been proposed for smaller vehicles such as vans and cars as disclosed in U.S. Pat. Nos. 4,413,550 to Piano and 6,068,046 to Pommier et al. These systems do not however deal with the extensive lengths encountered in constructing a duct system for a bus fed from one or more air treatment units. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided an air distribution mechanism for a bus comprising an air blower and ducts connected to the air blower which extend along the interior side of the body side walls of the bus for transporting the air from the blower to various parts of the bus. Distributed along the length of the body side ducts and mutually spaced from one another are a plurality of underseat ducts connected to and extending from the body side ducts into the interior of the vehicle. Vents release air from the underseat ducts into the passenger compartment of the vehicle. The body side ducts expand in cross sectional area as distance from point of the connection each body side duct with the air blower increases. Reducing resistance to air flow in the primary air channel as a function of distance from the air blower results in the amount of air released from each vent being about the same. 
     Additional effects, features and advantages will be apparent in the written description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a school bus of a type with which the invention is advantageously employed. 
     FIG. 2 is a perspective view of a ventilation system in accordance with the invention for installation on a bus of the type illustrated in FIG.  1 . 
     FIG. 3 is a perspective view of a bench seat illustrating positioning of an underseat duct of the ventilation system. 
     FIG. 4 is a cross sectional view of a bus illustrating location of body side ducts of a ventilation system with respect to wheel wells. 
     FIG. 5 is a cross sectional view of a bus illustrating connection of underseat ducts to body side ducts. 
     FIG. 6 is a schematic view of the ventilation system in accord with a preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures, FIG. 1 shows a school bus  10  having an elongated body  12  enclosing a passenger compartment. As illustrated in FIG. 2, the passenger compartment has a plurality of bench seats  14  which typically are arranged in rows, facing forward and running substantially the length of the compartment. Bench seats  14  are oriented transverse to the direction of elongation of the passenger compartment. The invention provides for the distribution of air from the air treatment and blower unit  18  of a heating, ventilation and air conditioning system  16  through a duct system including a body side duct  20 . While the duct system for only one side of the vehicle is illustrated a second duct system, modified as required to accommodate doors and the like, is provided for the second side of the vehicle. 
     Body side duct  20  runs along a side of elongated body  12  at approximately the height of a floor to the passenger compartment (shown in FIGS.  4  and  5 ). Body side duct  20  comprises four sections in the preferred embodiment. Here an air treatment and blower unit  18  is located under the floor and centrally with respect to the horizontal extent of the passenger compartment. A transition duct section  24  is located centrally along the side of the vehicle connected directly to air treatment and blower unit  18 . Transition duct section  24  is a Y junction, dividing the flow into two streams, one to be directed into forward duct section  22 , which runs toward the front part of the vehicle, and the second directed into the rear duct section  26 , which carries air to the rear portion of the passenger compartment. A wheel well duct section  28  connects to the rear duct section distal from its point of attachment to the transition duct section  24 . Wheel well duct section  28  comprises a subsection flattened relative to the vertical and formed into a semicircle to accommodate the vehicle&#39;s wheels. 
     To promote the even distribution of air through the ducts, body side duct  20 , in each of its component sections, is characterized by an increasing cross sectional area of the flow channel  21  defined by the component sections as distance from the air treatment and blower unit  18  increases. The increasing cross sectional area of flow channel  21  results in reduced impedance to flow through the channel at each junction of the body side duct  20  with an underseat duct  30 . The same quantity of air should escape from the vents from each underseat duct  30 . Dimensions of the ducting may be increased in the vertical, horizontal or a combination of both directions. Adjustment in the dimensions of the venting may be stepped or gradual. 
     Air is released from the ducting system through vents from a plurality of underseat ducts  30 A-F. FIG. 3 better illustrates one underseat duct  30 , which attaches at one end to body side duct  20  and terminates at point distal to the body side duct inside the passenger compartment but under bench seat  14  (from which cushions have been removed to improve illustration of the underseat duct). Underseat ducts  30  are oriented perpendicular to body side duct  20  and include a riser section  32  which attaches to duct  20  at a point just above the floor  34  and extends upwardly to a point just under the bottom of the seat of bench seat  14 . An underseat section  36  extends along the bottom of seat  14  from the upper end of riser section  32  toward the longitudinal center line of the vehicle, before terminating at a point still under the seat. Vents  42  (illustrated in FIG. 5) direct air outward behind seat  14 . Vents  42  are illustrated as comprising a single outlet, however, they may be divided into two or more outlets, corresponding to the number of intended occupants of the trailing bench, and each outlet fitted with an independently directable nozzle. 
     FIGS. 4 and 5 are cross sectional views taken at different points along the length of elongated body  12 , looking forward from the rear of the vehicle from the wheel wells  38  in FIG.  4  and taken at a point along the forward duct section  22  in FIG.  5 . Duct sections  22  and  28  are positioned snug against the interior face of body side walls  50  of elongated body  12 . Duct sections  22  and  28  are embedded into floor  34 , although in other embodiments they may be located entirely under the floor, over the floor, form a portion of the floor, or be partly under the floor. In the area of wheel wells  38  duct section  28  is flattened in the vertical direction and spreads in the horizontal direction as it bends around the well. In this way wheels  40  are accommodated without loss of cross-sectional areas. 
     In FIG. 5 the projection of underseat ducts  30  into passenger compartment  19  is again illustrated. Vents  42  in underseat sections  36  release forced air into passenger compartment  19 , with each vent having approximately equal flow. 
     Referring now to FIG. 6, a schematic view of ventilation system  16  illustrates the centered position of air treatment and blower unit  18  and the flow of air (indicated by arrows) out of unit  18  into transition duct  24 , through the transition duct to the forward and rear body side duct sections  22  and  26  to the underseat ducts  30  and finally escape from the underseat ducts into the vehicle passenger compartment  19 . Downstream along flow channel  21  from the junction of each underseat duct  30  with body side duct  20 , body side duct  20  widens to control the amount of air which will pass into each underseat duct. Underseat ducts  30  are stepped up in terms of cross-sectional area as a function of the distance of the underseat ducts&#39; junction with body side duct  20  from blower  18 . More than one air treatment and blower unit  18  may be provided, each typically being used for a different zone of the vehicle. 
     The invention provides a cost advantageous system for achieving even distribution of air through a bus by use of ducts exhibiting reduced air flow resistance with distance from a blower. 
     While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.