Pipes and tubular conduits – Structure
Reexamination Certificate
2000-05-19
2001-09-11
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Structure
C138S178000, C138S037000
Reexamination Certificate
active
06286559
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a filling pipe for a fuel tank of a motor vehicle having a fuel vapor absorbing system, wherein the filling pipe has a reduced cross section over part of its length. By fuel vapor absorbing system is meant a system which absorbs fuel vapors which are displaced out of the fuel tank during refueling and feeds them to a regenerable filter. Such a system is known by experts as an ORVR system (Onboard Refueling Vapor Recovery).
In order to carry out this recovery function properly, it must be ensured that during refueling the fuel vapors do not flow out through the filling pipe, but rather flow in their entirety through the filter. For this purpose, the fuel which flows through the filling pipe during the refueling procedure has to build up a sealing liquid column which forms a liquid seal and thereby prevents fuel vapors from escaping through the filling pipe.
According to the prior art, the liquid seal is achieved by a circular symmetrical constriction of the filling pipe over part of its length. A venturi nozzle-like effect is therefore produced. However, this liquid seal fails if a turbulent flow forms in the filling pipe, whether due to a fuel nozzle inserted crookedly or due to the Coriolis force similar to drainage from a bathtub. In case of a helical flow being produced in this manner, the liquid is pressed by the centrifugal force against the pipe wall, and in the vicinity of the longitudinal axis a space is formed which is not filled with liquid and through which fuel vapors escape to the outside. This known design also has the disadvantage that the reduction in diameter of a pipe made of metal is costly in terms of manufacturing because it is normally done by expanding the adjacent parts.
SUMMARY OF THE INVENTION
It is the principal object of the present invention to design a filling pipe wherein the formation and maintaining of a sealing liquid column are ensured under all circumstances. According to the invention, this is achieved by the filling pipe having at least one longitudinally directed bead. It is a further object to provide such a filling pipe at a low manufacturing cost.
The provision of at least one bead prevents the formation of a turbulent flow by means of an air-permeable hole in the center of the pipe. In addition the bead permits reduction of the cross section in a cost effective manner. When a bead is pressed in the pipe there is no expansion of the pipe in the circumferential direction.
Further advantages of the filling pipe of the invention are as follows: The gentle transition between the bead and the cylindrical parts of the filling pipe reduces the flow resistance. The bead can be produced without the strength of the filling pipe being reduced. When two or three beads are provided, the beneficial turbulence-preventing action can be obtained with a small depth of deformation for the bead and the beneficial action is improved.
Two advantageous embodiments consist in the beads either being pressed in from the diameter of the cylindrical parts or in them originating from a smaller diameter portion of the pipe. In the first form, no change at all to the pipe diameter is required. In the second form the change, and the press-in depth of the bead, remain small, which, in certain cases (for example, if the pipe is made of plastic) is advantageous in terms of manufacturing. The length of the beads is optimal if it amounts to two to three times the diameter of the filling pipe.
REFERENCES:
patent: 1025568 (1912-05-01), Higgin
patent: 2731830 (1956-01-01), Eichenberger et al.
patent: 3358749 (1967-12-01), Chisholm et al.
patent: 5664606 (1997-09-01), Anderson
patent: 6098668 (2000-08-01), Siwinski et al.
patent: 6125891 (2000-10-01), Witmer et al.
Bachman & LaPointe P.C.
Brinson Patrick
Tesma Motoren und Getriebetechnik Ges.m.b.H
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