Abstract:
A filler neck for a fuel tank used on busses achieves higher filling rates by varying the geometry and cross sectional size of the filler neck depending on local slope of the neck and available space to fit the neck, particularly between a bus chassis frame rail and the bus body floor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The invention relates to a fuel tank filler neck and more particularly to a filler neck for a between the rail (BTR) fuel tank which fits between a vehicle body floor and the vehicle chassis while admitting a high fuel flow rate on filling of the BTR fuel tank.  
         [0003]     2. Description of the Problem  
         [0004]     Filler necks connecting a fuel inlet on the side of a vehicle and a BTR fuel tank commonly found on busses have been unduly restrictive of fuel flow in certain applications. Fuel flow restriction has occurred due to the increasingly horizontal slope of the filler neck and the restricted diameter of the circular pipes sized to fit between the bus floor and the vehicle&#39;s frame rails. This has resulted in the back up of fuel as the fuel moves toward the fuel tank on filling.  
       SUMMARY OF THE INVENTION  
       [0005]     According to the invention there is provided a fuel tank assembly for a motor vehicle. The vehicle is conventionally a school bus having a body, a body floor and a pair of parallel chassis frame rails which support the body. The fuel tank assembly comprises a fuel tank supported between the frame rails under the body floor. Fuel is added to the fuel tank through a filler neck having an inlet on a side of the motor vehicle. The filler neck connects the inlet to the fuel tank. The filler neck passes between the floor of the body and one of the frame rails. In order to assure a high rate of fuel flow the filler neck increases in cross sectional area as it comes closer to the fuel tank and the slope of the neck becomes more horizontal. The cross sectional profile of the neck varies from the inlet to the fuel tank between the vehicle floor body and the frame rails to allow a first increase in sectional area while still fitting between floor and frame rail. The filler neck has a circular cross sectional profile adjacent the inlet, flattens to an oblong cross sectional shape where the neck passes over one of the frame rails and returns to a circular cross sectional shape, of increased diameter, proximate to the fuel tank inlet.  
         [0006]     Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     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:  
         [0008]      FIG. 1  is a perspective view of a bus.  
         [0009]      FIG. 2  is a top plan view of a bus chassis incorporating a between the rails fuel tank and its filler neck.  
         [0010]      FIGS. 3A and 3B  are perspective view of a fuel tank assembly in accord with the present invention.  
         [0011]      FIG. 4  is a front section of the fuel tank assembly.  
         [0012]      FIG. 5  is a top plan of a portion of the filler neck of the fuel tank assembly of  FIG. 4 .  
         [0013]      FIG. 6  is a cross sectional view taken along section line  6 - 6  of  FIG. 4 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Referring now to the figures and in particular to  FIG. 1 , a school bus  10 , which incorporates a fuel system in accordance with the present invention, is illustrated. Along one side of school bus  10 , here driver&#39;s side  12 , a fuel inlet cover  14  is visible. Although fuel inlet cover  14  is illustrated as installed on the driver&#39;s side  12  of the vehicle, it is often located on the vehicle&#39;s opposite side. Fuel inlet cover  12  may be moved to allow access to a filler neck inlet behind the cover, by which fuel is added to a between the rails (BTR) fuel tank located under the bus body and between the front  86  and rear wheels  90 .  
         [0015]     The location of a fuel tank system  20  is best illustrated with reference to  FIG. 2  which shows fuel tank system  20  as positioned on a vehicle chassis  80 . Vehicle chassis  80  is based on two longitudinally aligned, mutually parallel frame rails  81 ,  82 . Frame rails  81 ,  82  are held in parallel, and chassis  80  stiffened, by a plurality of cross members  83  which are located at mutually spaced locations running from the front to the back of the vehicle. Fuel tank system  20  comprises a fuel tank  26  held in a cradle  22  which is suspended from the outside faces of frame rails  81 ,  82 . Fuel tank  24  is located about midway between the front and the back of chassis  80  and between frame rails  81  and  82 . Fuel is added to fuel tank  24  through a filler neck  26  which is disposed between the top of the fuel tank running to the side of the chassis  80  over right hand side frame rail  82 .  
         [0016]     Referring now to  FIGS. 3A and 3B , the manner of supporting fuel tank  24  using cradle  22  and the routing of filler neck  24  from a side of the vehicle body to the fuel tank is more completely illustrated. In  FIG. 3B  all features other than filler neck  26  and a protective shield  46  are shown in phantom to allow complete illustration of the filler neck. Cradle  22  comprises a plurality of slats  30  which run from side to side of the chassis  80 , under frame rails  81 ,  82  and which support fuel tank  24  from underneath the fuel tank between the frame rails and which position the fuel tank at least partly at the level of the frame rails. The details of construction of cradle  22  are not important to understanding the invention and are in any event conventional. At least a pair of braces  34  depend from each of the outside faces of frame rails  81 ,  82 , extending below the frame rails and carrying longitudinal supports  32  which are parallel to and below their respective frame rails. Slats  30  are connected between longitudinal supports  32 . The bottom surface of fuel tank  24  may be indented to conform to the shape of slats  30 . At least a pair of steal bands  36  are mounted around fuel tank  24 , connecting at opposite ends to one of slats  30  using an appropriate, adjustable connector  38 .  
         [0017]     Filler neck  26  extends from an inlet  49  accessible from port  40  in body sidewall  17  to the upper exterior surface of fuel tank  24 , passing over frame rail  82 . Port  40  is located in sidewall  17  just above the level of floor  28 . A housing  42  (with roof removed to allow viewing of the filler neck) protecting filler neck  26  is constructed around the portion of the filler neck which extends above the level of the floor. Filler neck  26  is slanted to pass though an opening  44  in floor  28  thus passing below the level the floor outside of frame rail  82 . The downward slant promotes the flow of fuel toward fuel tank  24 . Filler neck  26  passes between floor  28  and the upper surface of frame rail  82  between its inlet and its point of connection to fuel tank  24 . Filler neck  26  is protected outside of frame rail  82  by a protective cover or shield is constructed of a half cylinder  46  which is placed below floor  28  under filler neck  26 .  
         [0018]     Referring to  FIG. 4 , the changes in slope of filler neck  26  moving from inlet section  50  adjacent the outside wall of the bus toward tank  24  are better illustrated. Filler neck  26  comprises three sections of distinct shapes and sizes. The sections are an inlet section  50  closest to the side wall of the bus, which is downwardly sloped, a mid-section  51  which lies essentially horizontally and which passes over frame rail  82  but under floor  28 , and an outlet section  52  which connects to fuel tank  26  through an outlet  53 . Referring briefly to  FIG. 6  it may be seen the mid-section  51  fits between the bottom of floor  28 , the top of frame rail  82  and between a pair of cross supports  60 , on which floor  28  rest and which are supported from the frame rails. Mid-section  51 , unlike inlet section  50  and outlet section  52  which have circular cross sectional shapes, has an oblong cross-sectional shape, being flattened from top to bottom.  
         [0019]     Referring to  FIG. 5 , a portion of filler neck  26  is isolated to emphasize the oblong character of mid-section  51 . Inlet section  50  and outlet section  52  both have circular cross-sections, however, the diameters A and B of these sections differ, with diameter B being greater than diameter A to assure that the outlet section does not become a choke point for fuel flow.  
         [0020]     The invention provides a fuel tank filler neck for BTR fuel tanks commonly found on busses which is not unduly restrictive of fuel flow at some point along the neck. Fuel flow restriction resulting from horizontally sloped sections of the filler neck is compensated for by increasing the cross sectional area of the neck. The restricted diameter the conventionally circular pipes used between the vehicle floor and vehicle side rails has been negated by using a pipe having a section in the effected area that is other than round.  
         [0021]     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.