Abstract:
A pressure limiting valve for the fuel return line connected to a tank of a motor vehicle is positioned in a flange which connects the fuel return line to the tank. The pressure limiting valve closes an outlet opening which branches off from a fuel passage of the flange.

Description:
The present invention relates to a tank for a motor vehicle and to a flange for connecting a fuel return line to a tank of a motor vehicle. 
     PRIOR ART 
     From German Patent Disclosure DE-A 44 26 667, a tank for a motor vehicle is known in which excess fuel is returned from and engine via a return line. The return line ends in the tank at a jet pump, which is disposed in the vicinity of the bottom of the tank and serves, with the aid of the returned fuel as a propellant, to feed fuel from a main portion of the tank into an impoundment container disposed in the tank, from this container it is drawn off by a delivery unit and resupplied to the engine. For proper jet pump operation, the pressure of the propellant must be regulated. In the known tank, this is done by means of a branch line, which originates at the jet pump; a spring-loaded ball presses against the end of this branch line that discharges into the impoundment container. If the pressure in the branch line exceeds a predetermined value, the ball is lifted from its seat at the end of the branch line, and fuel flows through the branch line into the impoundment container. 
     Because of its disposition on the bottom of the impoundment container, the valve is difficult to install and can sometimes be hard to clean. In addition, a certain minimum installation height must be provided, for the sake of proper functioning of the valve. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to optimize the disposition of the pressure limiting valve. 
     This object is attained according to the invention by a flange as defined by claim  1  and a tank as defined by claim  9 . 
     Mounting the pressure limiting valve on the flange makes it readily accessible for maintenance purposes. The structural height of a tank can also be kept low as a result. 
     Advantageous features of the flange and tank according to the invention are defined in claims  2 - 8  and  10  and  11 , respectively. 
     For instance, it is thus possible for a portion of the passage to be aligned with an outlet opening of the branch line, so that through the opening a check valve, such as a duckbill valve, can be disposed in the passage. 
     If the pressure limiting valve is held detachably in front of the outlet opening, then the check valve is easily accessible via the outlet opening and can be replaced easily as needed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become apparent from the ensuing description of an exemplary embodiment in conjunction with the drawings. Shown are: 
     FIG. 1, greatly simplified, a tank of a motor vehicle with a flange according to the invention; 
     FIG. 2, a section through a flange according to the invention; and 
     FIG. 3, an exploded view of the flange and its components. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a simplified view of a tank  10  of a motor vehicle and of an engine  12  connected to it. An impoundment container  14  is disposed in the tank  10 ; a fuel delivery unit  16  disposed in the impoundment container  14  aspirates from this container. A pressure line  20  is connected to a pressure neck  18  of the fuel delivery unit  16  and leads to the engine  12 . From the engine  12 , a return line  22  also leads through a flange  26  in the wall of the tank  10 , and through it excess fuel not used by the engine  12  flows back into the tank  10 . A jet pump  24  disposed inside the tank  10  communicates with the return line  22  and feeds fuel into the impoundment container  14 . During operation of the engine  12 , the fuel delivery unit  16  feeds fuel from the impoundment container  14  to the engine  12 , and the fuel flowing back through the return line  22  drives the jet pump  24 . 
     FIG. 2 shows a section through the flange  26 . It includes a shallow disk  28 , with a riblike edge  30  encompassing an underside of the disk  28  that faces toward the tank; this edge is provided for engagement with an opening of the tank, thus defining the position of the flange  26  at the opening. 
     A fuel passage includes an outer neck  32 , provided so that the return line  22  can be secured to it, and also includes a portion  36 , extending parallel to the plane of the disk, and an inner neck  46 , which is intended for connecting a line to the jet pump. 
     The portion  36  is disposed on a cufflike feature  34  of the side of the disk  28  facing toward the tank, and it includes two coaxial cylindrical chambers  38  and  44 . The height of the cufflike feature  34  is dimensioned such that when the flange is manufactured, for instance by plastic injection molding, a molding tool can be passed in the direction of the axis of the portion  36 , so that this feature can be formed without hindrance from the riblike edge  30 . 
     The outer neck  32  is connected to the first chamber  38 , and the inner neck  46  is connected to the second chamber  44 . The diameter of the second chamber  44  is slightly less than that of the first; the chambers merge with one another at an annular shoulder  42 . 
     The first chamber  38  forms a branch line from the fuel passage, having an outlet opening  39  which occupies a face end, opposite the shoulder, of the first chamber  38 . This outlet opening  39  is closed by a pressure limiting valve  40 . If desired, the portion  36  can also receive a check valve, such as a duckbill valve  50 . 
     The disposition of the valves  40 ,  50  in and on the fuel passage can be seen better in FIG.  3 . The duckbill valve  50  includes a tubular portion  51 , which in a wide-open end has an outward-protruding rim  52  and which is closed on the opposite end, except for a narrow slit, by two plane faces  54  extending obliquely to the axis of the tubular portion  51 ; of these faces, only one is visible in the drawing. The duckbill valve  50  is introduced through the opening  39  into the portion  36  far enough that the rim  52  rests on the shoulder  42 . In this arrangement, fuel returning from the engine can easily flow through this valve, yet this valve still prevents fuel from escaping if because of an accident the pressure at the outer neck  32  of the flange becomes less than inside the tank. 
     The pressure limiting valve  40  includes a shallow valve shield  60 , with a concave side facing toward the opening  39  and with a convex outer side. A mandrel  62  beginning at the convex outer side extends, in the assembled state of the valve (see FIG.  2 ), through a guide opening in a central portion of a U-shaped flexible metal clamp  64 . A shallow spiral spring  66  (see FIG. 2) mounted on the mandrel  62  acts on the valve shield  60  from the central portion of the clamp  64  in the form of the opening  39  and thus presses the edge of the valve shield  60  against a peripheral region of the opening  39  that acts as a valve seat, and thus keeps the opening  39  closed in the state of repose. 
     With the aid of openings  68  in its legs  70 , the clamp  64  can be locked to detent protrusions  72  on an outer wall of the portion  36 , and it can be disconnected from this portion by spreading the legs  70  apart. 
     If the pressure in the portion  36  exceeds a predetermined value, the valve shield  60  is lifted from the edge of the opening  39 , counter to the action of the spring  66 , and fuel exits through the opening  39 . As shown in FIG. 1, the flange  26  is disposed above the impoundment container  14 , so that fuel exiting through the valve flow back into the impoundment container  14 .