Pipe for a vehicle fuel tank suitable for welding

Abstract

This method for manufacturing a pipe (2) for a vehicle fuel tank involves—molding a wall, comprising an inner layer (6) made from ethylene vinyl alcohol (EVOH) and an outer layer (8) made from a polymer suitable for welding, in a mold comprising at least one female shoulder that creates at least one male shoulder on an outer surface of an end portion of the wall during molding, then—cutting off the end portion of the wall.

Claims

1. A pipe for a vehicle fuel tank, comprising a wall having an inner layer made of ethylene vinyl alcohol (EVOH) and an outer layer made of a polymer suitable for welding, an axial end portion of the pipe being formed of the polymer suitable for welding so as to allow welding in a main direction of the pipe, the outer diameter of the pipe in the region of the end portion being less than or equal to the outer diameter of a center part of the pipe.

2. The pipe according to claim 1, wherein the outer diameter of the end portion is less than or equal to the outer diameter of a portion of the pipe adjoining the end portion.

Description

(1) An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 is a longitudinal section of a pipe for a vehicle fuel tank according to a first embodiment of the invention,

(3) FIG. 2 shows a cutting step of a method for manufacturing the pipe in FIG. 1,

(4) FIG. 3 shows an end portion of the pipe in FIG. 1 following a cutting step,

(5) FIG. 4 shows an end portion of a pipe for a vehicle fuel tank according to a second embodiment of the invention,

(6) FIG. 5 is a schematic view showing a mold comprising a female shoulder, said mold being suitable for implementing a manufacturing method according to the invention,

(7) FIG. 6 is a schematic view showing the welding of the pipe in FIG. 1 to a fuel tank, and

(8) FIG. 7 is a sectional view of the welding of the pipe to the tank as shown in FIG. 6.

(9) FIG. 1 shows a pipe 2 according to a first embodiment of the invention. The pipe 2 has a main axis 4. In the present case, the pipe 2 at least locally has a cylindrical shape, but the pipe may also have any other shape.

(10) The pipe 2 comprises a wall having a plurality of layers. In the present case, said wall comprises an inner layer 6 and an outer layer 8, which radially overlap over a large part of the pipe 2.

(11) The inner layer 6 is made of a “barrier” layer that allows the permeability of the pipe 2 to be reduced. In this case, said inner layer is made of ethylene vinyl alcohol (EVOH). However, a completely different barrier material having properties similar to those of EVOH could be selected.

(12) The outer layer 8 is made of a polymer suitable for the later welding of the pipe 2 to a fuel tank. Polymers of this kind are well known to a person skilled in the art. Said polymer may be, for example, high-density polyethylene (HDPE).

(13) The inner layer 6 is understood to mean the layer located radially below the outer layer 8. In other words, the inner layer 6 does not face the radially outer surface of the pipe 2. The inner layer 6 may be formed of a plurality of layers comprising different materials. For example, a wall structure having six or seven layers may be provided, said structure comprising, from the interior to the exterior of the pipe, a conductive layer of conductive HPDE, optionally an intermediate HDPE layer, an adhesive layer, an EVOH barrier layer, an adhesive layer, an intermediate layer and lastly a black HDPE decorative layer. In this case, the black HDPE decorative layer forms the outer layer, and the entirety of the five or six other layers forms the inner layer within the meaning of the invention. Part of the inner layer is thus made of EVOH.

(14) In the following, the wall will be considered to comprise only two layers, i.e. the inner layer 6, made entirely of EVOH, and the outer layer 8, to make it easier to illustrate the invention.

(15) The pipe 2 has an axial end 10 suitable for welding the pipe 2. The other end of the pipe 2 is not shown and will not be described because it is not necessary to describe said end for the invention to be understood. As can be seen in FIG. 1, the end portion 10 of the pipe is formed of the polymer suitable for welding. The pipe 2 can thus be readily welded in the region of said end 10 because EVOH, a material incompatible with welding, is not present in the end portion 10.

(16) As can also be seen in FIG. 1, the outer diameter of the pipe 2 in the region of the end portion 10 is less than or equal to the outer diameter of a center part 11 of the pipe 2. In this case, the outer diameter of the end portion 10 is less than or equal to the outer diameter of a portion of the pipe adjoining the end portion 10. The inner layer 6 and the outer layer 8 radially overlap over the entirety of the center part 11 of the pipe 2. In this case, the outer diameter of the pipe 2 in the region of the end portion 10 is roughly equal to the diameter of the center part 11. The center part 11 of the pipe 2 is located outside of the two axial end portions of said pipe.

(17) These properties of the pipe are valuable for reasons that will be described further on in the application.

(18) A method for manufacturing the pipe according to a first embodiment will now be described.

(19) With reference to FIG. 5, the wall comprising the EVOH layer and the polymer layer suitable for welding are firstly molded in a mold 14 that allows blow molding.

(20) The mold 14 comprises two mold parts 14a and 14b, each having part of an insert 16. In the mold, said insert forms a female shoulder 18 arranged so as to create at least one male shoulder 12 on an outer surface of the end portion of the wall during molding. Once the molding is complete, the wall takes the form of the pipe 2.

(21) After molding, the end portion 10 of the pipe 2 is cut off. As can be seen in FIG. 2, this cut is made in parallel with the axis 4, along the arrow 20. In this way, the part of the end portion 10 having the male shoulder 12 is taken away from the pipe 2. It is this cut that allows the remaining part of the end portion 10 of the pipe 2 to be formed, entirely, of the polymer suitable for welding. This can be seen at a larger scale in FIG. 3.

(22) According to a second embodiment of the invention shown in FIG. 4, the end portion 10 is not cut off in parallel with the axis 4, but at a non-zero angle α in relation to the axis 4, along the cutting line 22. Said angle α is less than 60°; in FIG. 4, it is roughly 45°. However, it is preferable for said angle α to be less than 30°. In exactly the same way as the first embodiment, the remaining part of the end portion 10 of the pipe 2 is formed of the polymer suitable for welding.

(23) FIG. 6 shows a fuel tank 24 that belongs to a vehicle fuel storage system according to the invention. Said storage system is manufactured according to the following method: manufacturing the pipe 2 according to a method corresponding to the above, according to either of the two outlined embodiments, and then welding the end portion 10 of the pipe 2 to the tank 24.

(24) Since the end portion 10 of the pipe 2 is formed of the polymer suitable for welding, it is possible to perform the weld directly without having to prepare the pipe 2 or the tank 24 for this purpose.

(25) Furthermore, this allows the end portion 10 of the pipe 2 to maintain a shape similar to an identical filling pipe that does not comprise an EVOH layer, the end portion of said filling pipe not having to be adapted in any particular way and having a constant outer diameter.

(26) Furthermore, the fact that the diameter of the wall of the pipe 2 in the region of the end portion 10 is less than or equal to the outer diameter of the center part 11 of the wall makes it possible to weld the pipe 2 in an opening or spout 26 provided on a wall of the tank 24. As can be seen in FIG. 7, the outer diameter of the pipe 2, which is constant or decreases towards the end 10, allows said pipe to conform to the shape of the spout 26. This also makes it possible not to hinder the functioning of an intake valve 28 located in the spout 26. Said valve 28 is commonly referred to as an “inlet check valve” (ICV).

(27) Of course, it is also possible to modify the invention in many ways without going beyond the scope thereof.

(28) The invention can also be applied to the welding of the pipe to a filler neck head. In practice, the second end of the pipe may be welded to a filler neck head of this kind. The embodiments of the invention outlined above can still be applied if the tank 24 and the spout 26 thereof are replaced with a filler neck head.