Protective frame structure for a motor vehicle fuel tank
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to safety devices for motor vehicles and more particularly for means for protecting a fuel tank during a collision. 
     2. Description of the Prior Art 
     In the event of an accident, the motor vehicle fuel tank is liable to suffer damage thereby resulting in fuel leakage which could lead to a fire. To prevent this, means such as those illustrated in FIGS. 1 and 2 have been employed. In FIGS. 1 and 2, fuel tank 1 has a pair of frame members 2 extending along the sides thereof. In front of the fuel tank 1, frame members 2 are provided with kicked up portions 3. Behind fuel tank 1 is provided a cross member 5 between the frame members 2 and in front of fuel tank 1 and before kicked up portions 3 is provided a cross member 4. Between cross members 4 and 5, fuel tank mounting brackets 6 are fastened to the frames 2 by means of fastening nuts 7 and bolts 8. Forward of kick-up portions 3, frame members 2 are reinforced by inner metal channels 9 coupled to the inside of frame member 2. 
     In the event of a collision from the rear with the above described frame structure, the entire frame structure supporting the tank receives the collision energy which deforms the frame structure, as shown in FIG. 3, resulting in deformation extending to the fuel tank supported by the frame. As a consequence, the fuel tank is frequently ruptured and a leakage of fuel can result. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is the general object of the present invention to provide a protective structure for a fuel tank which absorbs the energy of collision without deforming that portion of the frame adjacent the fuel tank. 
     In keeping with the principles of the present invention, the objects are accomplished by a unique protective structure for protecting a fuel tank which is mounted at the rear of a motor vehicle and between two parallel frame members extending along the side of the fuel tank. The structure includes reinforcing members coupled to the frame members for at least the length of the fuel tank. In this way, the frame is composed of a reinforced section extending along the length of the tank and nonreinforced sections before and behind the tank so that the nonreinforced sections absorb the energy of impact without deforming the fuel tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features and objects of the present invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein like referenced numerals denote like elements, and in which: 
     FIG. 1 is a top view illustrating a fuel tank protective frame structure for a motor vehicle of the prior art; 
     FIG. 2 is a side view of the prior art structure of FIG. 1; 
     FIG. 3 is a side view of the structure of FIG. 1 illustrating the results of a rear-end collision; 
     FIG. 4 is a top view of a protective structure for a motor vehicle fuel tank in accordance with the teachings of the present invention; 
     FIG. 5 is a side view of the embodiment of FIG. 4; 
     FIG. 6 is a side view of the principal parts of the embodiment of FIG. 4 illustrating the fit of the inner channels; 
     FIG. 7 is a side view of a protective structure in accordance with the teachings of the present invention showing the results of a rear-end collision; 
     FIG. 8 is a top view of a second embodiment of the present invention; 
     FIG. 9 is a side view of the embodiment of FIG. 8; 
     FIG. 10 is a partial side view showing a portion of the frame structure at the side where the inner channels meet; 
     FIG. 11 is a partial side view showing a portion of the frame structure at the site where the inner channels meet; and 
     FIG. 12 is an enlarged inner view showing a part of the frame structure at the portion where the inner channels meet. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 4, shown therein is a top view of a fuel tank protective frame structure in accordance with the teachings of the present invention and FIG. 5 is a side view of the embodiment of FIG. 4. 
     In FIGS. 4 and 5, the fuel tank 11 is supported on the frame 12 by fuel tank mounting brackets 16 and fastened to the mounting brackets by nuts and bolts 17 and 18. An inner channel 20 is coupled to the interior of frame 12 along the length of the fuel tank 11 and reinforces the frame 12 from the rear of inner channel 19 through kick-up portion 13 to a position near the front of cross-member 15. Inner channel 19 is provided on the inside of frame 12 forward of kick-up portion 13. 
     As shown in FIG. 6, the inner channel 20 is fitted and welded into frame 12 forming a closed cross-section with the frame which has a cross-section resembling a square. The anterior portion of inner channel 20 is provided so that it does not contact the edge of inner channel 19 within kick-up portion 13. Furthermore, the posterior edge of inner channel 20 is provided so that there is a suitable gap between it and the rear cross-member 15. This portion 22 between the end of inner channel 20 and rear cross-member 15 is designed so as to be not reinforced. 
     As shown in FIG. 7, in the event of a rear end collision occurring to a motor vehicle with a protective frame structure of the above composition, the impact energy would concentrate at the posterior nonreinforced section 22 as well as the point 21. As shown in FIG. 7, the posterior nonreinforced section 22 would be deformed and the point 21 would bend and open during deformation. Accordingly, the portions of the frame 12 supporting the fuel tank 11 would be reinforced by inner channel 20 so that deformation arising due to impact energy would be prevented or moderated thereby leading to a prevention of rupture of the fuel tank 11. 
     FIGS. 8 and 9 illustrate a second example of a protective structure in accordance with the teachings of the present invention. In this second embodiment, the inner channel 20 is united with the posterior cross-member 15 so as to form a strengthened area surrounding the fuel tank 11. Since this embodiment is similar to that previously described, like elements will be given like referenced numerals and a description of their interconnection in operation will be omitted. 
     In this embodiment, the impact energy concentrates at the point 21 where the two channels meet in front of the fuel tank and also at the area behind the rear cross-member 15. Furthermore, at the point 21, the inner channel 20 and the inner channel 19 forward of the kick-up portion 13 are adjoined at right angles to the axial direction of the inner channels. As shown in FIGS. 10 and 11, the edges of the inner channels 19 and 20 may be fitted together. In this case, the two inner channels 19 and 20 may be fitted together but they are not fastened together. In addition, a suitable space may be established between the edges of inner channels 19 and 20. 
     In this embodiment, a closed cross-section is formed by the inner channel 20 together with frame 12. However, as shown in FIG. 12, the inner channel 20 may be superimposed onto the frame 12 and fastened thereto, thereby forming an open cross-section. Furthermore, for the interconnection shown in FIG. 12, the edges of inner channels 19 and 20 may be angular to the axis of the inner channels so that they may overlap at the adjoining point 21. 
     In practice, the inner channels 19 and 20 may be metal channels such as channel steel or the like. 
     The above described device comprises a pair of frames which extend along the length of a motor vehicle, such as an automobile, forming a protective frame structure for the fuel tank situated at the rear of the motor vehicle. The frame must extend at least the length of the fuel tank and is composed of a reinforced section with nonreinforced sections before and behind the fuel tank so that when the automobile is struck from behind, the impact energy would be concentrated at the nonreinforced sections and absorbed there. Since this structure would prevent or moderate the deformation resulting from a collision from reaching the fuel tank, the effect of prevention of fuel leakage from a ruptured tank would be achieved. 
     In all cases, it is understood that the above described embodiments are merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Numerous and varied other arrangements can be readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.