METHOD FOR MANUFACTURING A PLASTIC CONDUIT SUBJECTED TO AN INNER RELATIVE PRESSURE AND ASSOCIATED CONDUIT

Abstract

A method for manufacturing an injection rail subjected to an inner relative pressure, comprises the following steps: providing an injection rail body, comprising at least one end to be closed, providing a plug shaped so as to close the end of the body, assembling the plug into the end of the body, positioning the assembly within a mold cavity in which an overmolding area is at least contiguous with a contact area defined by a portion of the plug and a portion of the end of the conduit body are in contact with each other, the overmolding area being shaped so as to delimit the shape of a junction part configured to fixedly attach the plug into the end of the conduit body, filling the overmolding area by matter injection in order to form the junction part, the overmolding area comprising a matter injection inlet opening into the contact area.

Claims

1. A method for manufacturing an injection rail subjected to an inner relative pressure, wherein the method comprises the following steps of: Providing a conduit body, comprising at least one end to be closed, Providing a plug shaped so as to close the end of the conduit body, Assembling the plug into the end of the body, Positioning the assembly within a mold cavity in which an overmolding area is at least contiguous with a contact area defined by a portion of the plug and a portion of the end of the conduit body which are in contact with each other, the overmolding area being shaped so as to delimit the shape of a junction part configured to fixedly attach the plug into the end of the conduit body, Filling the overmolding area by matter injection in order to form the junction part, the overmolding area comprising a matter injection inlet opening into the contact area.

2. The manufacturing method according to claim 1, wherein the assembly of the plug with the conduit body is achieved by interlocking the plug into the end of the conduit body.

3. The manufacturing method according to claim 1, wherein the assembly is held laterally by a first mold metallic portion and by a second mold metallic portion each being arranged at one side of the assembly.

4. The manufacturing method according to claim 3, wherein the assembly is further held by a third mold metallic portion engaged at least partially into the plug.

5. The manufacturing method according to claim 1, wherein the overmolding area further extends at least partially out of the contact area to form a matter excess.

6. The manufacturing method according to claim 1, wherein the matter used for overmolding the junction part is a thermoplastic material.

7. The manufacturing method according to claim 1, wherein the overmolding area presents a generally annular, cylindrical, or helical shape.

8. A plastic injection rail subjected to an inner relative pressure for an engine obtained by the manufacturing method according to claim 1, wherein the injection rail comprises at least: a conduit body having an end to be closed, a plug closing the end of the conduit body, a junction part overmolded within a contact area defined by a portion of the plug and a portion of the end of the conduit body which are in contact with each other, the junction part being configured to fixedly attach the plug into the end of the body, the junction part comprising at least one first portion arranged around the contact area of the plug and of the conduit body and one second portion included within at least one space created between the conduit body and the plug.

9. The injection rail according to claim 8, wherein the conduit body comprises an application surface on which a fluid pressure may be applied, the application surface is a circular surface whose center is arranged on the middle longitudinal axis X-X of the conduit body within the inner volume of the conduit body and whose perimeter corresponds to a diameter of the conduit body.

10. The injection rail according to claim 8, wherein the plug comprises a plug body comprising an end on which a plug head is formed.

11. The injection rail according to claim 10, wherein the plug body comprises at least one crenellation.

12. The injection rail according to claim 10, wherein the plug body comprises at least one projection having at least one hollow ring such as a circumferential groove.

13. The injection rail according to claim 12, wherein the body comprises at least one recess positioned at least partially opposite the projection formed on the plug.

Description

[0063] The invention will be better understood, thanks to the description hereinafter, which relates to embodiments of an injection rail considered for illustrating the plastic conduit according to the present invention. The embodiments are provided as non-limiting examples and explained with reference to the appended schematic figures. The appended schematic figures are listed herein below:

[0064] FIG. 1 is a perspective view of the injection rail according to a first embodiment according to the invention,

[0065] FIG. 2 is an exploded perspective view of the end of the rail illustrated in FIG. 1,

[0066] FIG. 3 is a sectional view of the end of the rail according to the first embodiment,

[0067] FIGS. 4 and 5 are schematic illustrations of steps of the method for manufacturing the injection rail according to the first embodiment,

[0068] FIG. 6 is a perspective view of the end of the injection rail according to a second embodiment,

[0069] FIG. 7 is a sectional view according to the axis A-A of the end of the injection rail according to a second embodiment,

[0070] FIG. 8 is a sectional view of the end of the injection rail according to a third embodiment,

[0071] FIG. 9 is a perspective view of the junction part according to the third embodiment of the injection rail according to the invention,

[0072] FIG. 10 is an exploded perspective view of the end of the injection rail according to the third embodiment,

[0073] FIG. 11 is a perspective view of the junction rail according to the fourth embodiment of the injection rail according to the invention,

[0074] FIG. 12 is a perspective view of the end of the injection rail according to the fourth embodiment.

[0075] Regardless of the embodiment, the method for manufacturing the injection rail 1 comprises at least one step of providing a rail body or conduit body 2, comprising at least one end 2a to be closed, a step of providing a plug 3 shaped so as to close the end 2a of the rail body 2, a step of assembling the plug 3 into the end 2a of the rail 2, and a step of overmolding a junction part 5 configured to fixedly attach the plug 3 into the end 2a of the rail body 2.

[0076] More specifically and regardless of the embodiment, in this method, the assembly consists in interlocking the plug 3 into the end 2a of the rail body 2. Furthermore, subsequently to the assembly of the plug 3 with the rail body 2, said assembly is positioned in a mold, said assembly being held laterally on the one side by a first metallic portion and on the other side by a second metallic portion. In addition, a third metallic portion is engaged at least partially into the plug 3 in order to avoid the assembly collapsing during the overmolding of the junction part 5.

[0077] Regardless of the embodiment, the injection rail 1 according to the invention comprises at least one rail body 2 having an end 2a to be closed, a plug 3 closing said end 2a of the rail body 2 and a junction part 5 overmolded in the contact area 4 of the assembly of the rail body 2 and of the plug 3 so as to fixedly attach the assembly. This injection rail 1 is illustrated in FIGS. 1 and 2, the junction part 5 and the plug 3 represented in these figures corresponding to the first embodiment.

[0078] Regardless of the embodiment and as illustrated in FIG. 4 as example, the rail body 2 comprises an application surface S, S, on which a fuel pressure may be applied, said application surface S, S, is a circular surface whose center is arranged on the middle longitudinal axis X-X of the rail body within the inner volume of the rail body. As shown in FIG. 4, when the perimeter of the application surface corresponds to the external diameter of the rail body, the application surface is referred to as S and when the perimeter of the application surface corresponds to the internal diameter of the rail body, the application surface is referred to as S.

[0079] The first embodiment will now be described with reference to FIGS. 1 to 5.

[0080] According to the first embodiment, the overmolding area 100 extends around the contact area 4. Furthermore, the overmolding area 100 extends through the contact area 4 via recesses 13 formed on the end 2a of the rail body 2 and the recesses 14 formed on the plug head 3a, as illustrated in FIG. 2. Hence, the junction part 5 is formed only at the outside of the injection rail 1 as illustrated in FIG. 4 and in detail in FIG. 5. The overmolding area 100 is annular.

[0081] More specifically and as shown in particular in FIG. 3, the junction part 5 comprises an upper portion 5a lying against the plug head 3a and a lower portion 5b covering the end 2a of the rail body 2 clasping the contact area 4 at the level of which the plug head 3a and a flange of the end 2a of the rail body 2 are in contact. The matter of the junction part 5 crosses the contact area 4 via the recesses 13, 14.

[0082] Furthermore, the end 2a of the rail body 2 has a circumferential protruding lug 2b serving as a stop against which bears the lower portion 5b of the junction part 5.

[0083] According to the first embodiment, the junction part 5 presents an annular shape.

[0084] According to the invention and as illustrated in FIGS. 4 and 5, before injection of the matter of the junction part 5, the plug 3 and the rail body 2 are assembled together. This assembly is held laterally by a first mold metallic portion 201 and by a second mold metallic portion 202 each being arranged at one side of the assembly. Furthermore, the assembly is further held by a third mold metallic portion 203 engaged at least partially into the plug 3. Advantageously, the third metallic portion fits into the plug 3 so as to support the assembly during the overmolding of the junction part 5 in order to avoid the collapse of the assembly under the overmolding pressure.

[0085] The second embodiment will now be described with reference to FIGS. 6 and 7.

[0086] The second embodiment differs from the first embodiment in that the overmolding area 100 is out of the contact area 4 thereby forming a matter excess or bead 6 on the periphery of the plug 3 and at the same time it is included at the level of the contact area 4 and more specifically between a portion of the end 2a of the rail body 2 and of the plug head 3a as shown in particular in FIG. 7. Thus, the junction part 5 has less contact with the mold portions 201, 202, 203, schematically represented in FIG. 4, which allows preserving the heat of the matter forming the junction part in order to promote the melting of the contact area 4.

[0087] In the second embodiment, the injection inlet 101 is formed between the rail body 2 and the plug 3 via at least one recess 10 formed on the rail body 2. Preferably and as shown in FIG. 6, the rail body comprises several recesses 10 so as to enable an inclusion of the matter of the junction part 5 at several places of the assembly.

[0088] According to a variant of the second embodiment, the plug body 3b comprises a plurality of crenellations 7 configured to improve the mechanical strength of the assembly. These crenellations 7 are shown in FIG. 7.

[0089] According to the second embodiment, the matter excess 6 should be removed by a subsequent mechanical operation at the overmolding step.

[0090] According to the second embodiment, the junction part 5 presents a generally annular shape.

[0091] The third embodiment will now be described with reference to FIGS. 8 to 10.

[0092] The third embodiment differs from the first embodiment in that in order to increase the filling duration, we no longer act on the filling volume as is the case for the first two embodiments but rather on the flow length. Thus, as is the case for the first two embodiments, the injection inlet is located at the level of the contact area 4, but, unlike the first two embodiments, the contact area is located mainly at the level of the internal diameter of the rail body 2.

[0093] As shown in FIG. 10, the plug 3 has a hollow projection 8 formed at least partially on the plug body 3b and which extends from a free end of the plug body 3b toward the plug head 3a. In the third embodiment, the projection 8 comprises a plurality of hollow rings 8a, 8b including a primary ring 8a arranged at the level of the free end of the plug body 3b and secondary rings 8b arranged between the primary ring 8a and the plug head 3a. Thus, after overmolding, the junction part presents a generally cylindrical shape formed by rings 12a, 12b including the primary ring 12a the closest to the contact area 4, and secondary rings 12b between the primary ring 12a and the end of the junction part 5, as illustrated in FIGS. 9 and 10.

[0094] Furthermore, the rail body 2 comprises a plurality of recesses 9 positioned at least partially opposite the projection 8 formed on the plug.

[0095] More particularly, recesses 9 are arranged between two rings 8b of the projection 8 having a plurality of rings. Once filled, the recesses form a junction 11 between said rings 8b.

[0096] Advantageously, the more rings there are, the larger is the volume to fill and therefore the time of circulation of the hot matter within the first ring 8a increases. In addition, the longer the length of the flow, the more the pressure within the first ring 8a increases during filling. The pressure tends to promote the heat exchanges with the walls. Hence, the first ring 8a has all the characteristics for melting the contact surfaces: a hot fluid coming directly from the injection screw during the filling period with high pressures which increase the transmission of heat to the walls to melt.

[0097] The fourth embodiment will now be described with reference to FIGS. 11 and 12. The fourth embodiment differs from the third embodiment in that the secondary rings form a continuous helix 12c rather than rings 12b connected by junction elements 11. The helix allows having a longer flow than is the case with several rings and for the same bulk and the same mass of injected matter.

[0098] Of course, the invention is not limited to the embodiments described and represented in the appended figures and illustrating an injection rail, these embodiments may be applied to any plastic conduit subjected to a high inner relative pressure as explained hereinabove in the description. Modifications are still possible, in particular concerning the constitution of the various elements or by substitution with technical equivalents, yet without departing from the scope of the invention.