METHOD FOR MANUFACTURING A PRESSURE ACCUMULATOR

Abstract

A method for manufacturing a vehicle pressure accumulator, in which a thermoplastic parison is used to form an enclosure around a chamber by applying at least one portion, at least partially molten, of the parison onto at least one portion of the chamber, to attach the parison to the chamber.

Claims

1-14. (canceled)

15. A method of fabrication of a pressure accumulator for a vehicle, comprising: forming an enclosure around a chamber from a parison of thermoplastic material by applying at least one portion, at least partly molten, of the parison to at least one portion of the chamber to attach the parison to the chamber.

16. The method as claimed in claim 15, wherein the chamber comprises a bladder.

17. The method as claimed in claim 15, wherein the chamber comprises at least one piston assembly.

18. The method as claimed in claim 15, wherein the chamber is attached to an extrusion head of the parison, by a robot.

19. The method as claimed in claim 15, wherein the portion or each portion of the chamber is heated prior to applying of the parison to that portion.

20. The method as claimed in claim 15, wherein the applying is done by pressure.

21. The method as claimed in claim 15, wherein the applying is done by closing of a mold for a molding of the enclosure from the parison.

22. The method as claimed in claim 15, wherein the portion of the chamber or at least one of the portions of the chamber forms a lower or upper end of the chamber, or a valve, and the applying is performed at the lower and upper ends.

23. The method as claimed in claim 15, wherein the portion of the chamber or at least one of the portions of the chamber constitutes an assembly composed of elements which can only be separated by destruction of at least one of the elements.

24. The method as claimed in claim 15, wherein the portion of the chamber or at least one of the portions of the chamber has an external face formed by a thermoplastic material and the applying is performed by applying the parison to the external face.

25. A pressure accumulator for a vehicle, comprising: an enclosure of thermoplastic material; and a chamber housed in the enclosure, the enclosure being at least partly overmolded on at least one portion of the chamber.

26. The accumulator as claimed in claim 25, wherein the chamber comprises a bladder.

27. The accumulator for a vehicle as claimed in claim 25, wherein: the chamber comprises a piston assembly; and overmolding of the enclosure takes place on portions of the chamber forming at least one portion of a first nozzle for an inlet and outlet of a pressurized gas and at least one portion of a second nozzle for an inlet and outlet of a pressurized liquid.

28. The accumulator as claimed in claim 25, wherein: the chamber comprises a piston assembly; overmolding of the enclosure takes place on at least one portion of a first peripheral nozzle for an inlet and outlet of a pressurized gas; the chamber comprises a second central nozzle for an inlet and outlet of a pressurized liquid; and the first and second nozzles are placed on a same side of the accumulator.

Description

[0064] Embodiments of the invention will now be described by non-limiting examples and supported by the enclosed drawings, in which:

[0065] FIGS. 1 to 3 illustrate schematically and in axial section a method for fabrication of a pressure accumulator according to a first embodiment of the invention;

[0066] FIG. 4 illustrates an axial section view of the system for attaching the extrusion head to the bladder;

[0067] FIG. 5 is an axial section view of a lower end of a chamber secured to an enclosure of this accumulator; and

[0068] FIGS. 6 and 7 are axial section views of two other embodiments of an accumulator according to the invention.

FIRST EMBODIMENT

[0069] First of all a layout and a method for the realization of an accumulator according to a first embodiment of the invention shall be described making reference to FIGS. 1 to 3.

[0070] The fabrication layout 50 comprises an extrusion head 11 making it possible to extrude a parison of thermoplastic material 9. The layout comprises a mold to form an enclosure from the parison, having for example two mold portions 7 and 8, mounted so as to be movable with respect to each other, here in a horizontal direction, and with respect to the head 11. The head comprises means of supporting a bladder 3 such that the bladder extends between the mold portions, whether the mold is open or closed. The layout also comprises a lower blowpipe 6 extending vertically to the head 11 and making it possible to inject gas into the parison during the blow molding of the latter to form the enclosure. The layout also comprises a robot having an arm 2 able to secure a bladder to the extrusion head and to the blowpipe by the upper and lower ends of the bladder.

[0071] The method takes place as follows.

[0072] In an external station a heating of the portions of the bladder 3 to which a parison will be applied is performed. In this example, the bladder 3 has one end 5 and the opposite end 10 made of thermoplastic material. Thus, by heating these ends 5 and 10, the latter are placed in a partly molten state. In one particular embodiment, this heating can be of infrared type. Alternatively, this heating can be of laser type, or by hot air current, or a heating by a mirror. This heating at an external station advantageously allows a saving of cycle time. In fact, the heating occurs independently of the blow molding operations in the mold.

[0073] In another embodiment, the heating of all or a portion of the bladder can be accomplished in the area of the mold. For example, the extrusion head can be outfitted with heating means, such as hot air blow molding means. This embodiment has the advantage of enabling a compact layout.

[0074] Next, during a step inside the layout 50, the robot arm 2 attaches the upper rigid monoblock end 5 of the bladder 3 to a lower portion of the extrusion head 4. This bladder 3 is likewise attached by the arm to the blowpipe 6, at the opposite end 10. The bladder, outside of its rigid monoblock ends 5 and 10, comprises a deformable flexible bag 13 forming a gas-tight chamber. The two portions of the mold are situated on either side of the bladder, the head, and the blowpipe.

[0075] In one variant not illustrated, the end 10 of the bladder 3 is not attached to the blowpipe.

[0076] In a following step, shown in FIG. 1, a parison 9 of thermoplastic material, shown by dotted lines, is extruded and descends vertically from the extrusion head 11 so as to surround the bladder. Thus, the bladder is contained in the parison 9.

[0077] Once the extrusion is finished, a draping is performed to maintain the parison in position in the mold and a pre-blowing to stretch the parison and prevent contact between the parison and the bladder during the mold closure which will ensue. Then, in a further step illustrated in FIG. 2, the mold is closed: the two mold portions 7 and 8 are moved toward each other. The top and bottom ends of these two portions compress the parison at the two respective preheated ends of the bladder: in the area of the end 5 held by the extrusion head and in the area of the end 10 supported on the blowpipe 6.

[0078] In a following step, not illustrated, the blowpipe injects air into the parison, around the bladder. Thus, the walls of the parison are compressed against the walls 12 of the mold. The parison thus takes the shape of the mold to become the enclosure of the accumulator, and contains the bladder to which it is rigidly attached in the area of its ends 5 and 10.

[0079] During the next step, which can be seen in FIG. 3, the two mold portions 7 and 8 are withdrawn in opposite directions, and the unit comprising the enclosure produced and the bladder attached to the two upper and lower ends of the enclosure are obtained. The basic elements for a pressure accumulator 30 are thus obtained.

[0080] The upper end 5 of the bladder forms, for example, a valve in order to connect the bladder to the conduits of the vehicle in order to bring gas into the bladder, while the end 6 can form a valve and hold the bladder in place in the enclosure 9 of the pressure accumulator.

[0081] FIG. 4 illustrates the system for attaching the upper end 5 of the chamber to the extrusion head 11. The extrusion head 11 comprises a head body 13 which is fixed in relation to a frame of the layout and a movable portion such as a punch 14. The punch is mounted to slide in relation to the body in the vertical direction. In the top position, it is in contact with the body all around the punch 14, leaving no space between the punch and the body 13, so that any extrusion of material is prevented, the head being closed. In the bottom position, it leaves a symmetrical space of revolution about the vertical axis between the punch and the body in order to allow the extrusion of the thermoplastic material and the descending of a parison 9, the head then being open. The layout comprises a support 41 rigidly attached to the lower face of the punch 14, having a seat to receive the upper portion 5 of the bladder, which is open toward the bottom, in order to carry the latter in a movable manner. The movable connection between the bladder and the support can be done by various conventional means such as a holding magnet and/or a pressure ball. The overmolding of the enclosure 9 takes place at a lower portion 51 of the end of the chamber which extends beyond the bottom of the support.

[0082] The attachment of the lower end of the chamber 3 to the blowpipe 6 is done by conventional means, not shown.

[0083] FIG. 5 illustrates a detail of the first embodiment in the area of the lower end 10 of the bladder, forming an insert. The insert 10 is a monoblock, that is, it can only be separated into several elements by the destruction of at least one of these elements. The enclosure 29 of the accumulator and the thermoplastic layer 21 of this insert onto which the enclosure is overmolded are seen, this layer being applied to the metallic part 20. Alternatively, the application of the layer 21 to the part 20 can be eliminated, the layer 21 can be dispensed with and the overmolding of the enclosure 29 can be performed directly on the metallic part 20 in grooves, orifices or other types of reliefs and cavities provided for this purpose on the surface of the part 20 to assist with this overmolding. The insert likewise has a seal 24 which enables tightness between the part 20 and the enclosure 29 or the part 20 and the layer 21. This seal can be made of rubber.

[0084] Two other embodiments of pressure accumulators making reference to FIGS. 6 and 7 and produced by means of the method according to the invention shall now be described. Unlike the accumulator of the first embodiment, this one is a piston accumulator.

SECOND EMBODIMENT

[0085] FIG. 6 illustrates schematically a pressure accumulator according to the second embodiment of the invention.

[0086] The pressure accumulator 130 comprises an enclosure 101 inside which is placed a piston chamber 102 comprising a piston assembly 103 mounted to slide in the chamber 102, and placed in a first position in the figure. Reference 103 illustrates the same piston assembly in a second position. The chamber 102 is equipped with a first nozzle 104 for the inlet and outlet of a pressurized gas and a second nozzle 105 for the inlet and outlet of a pressurized liquid. These two nozzles extend at opposite axial ends of the accumulator. The accumulator comprises an enclosure 101 covered by an exterior reinforcement layer 106. In one particular embodiment, this layer 106 can be a winding of carbon fibers. The enclosure 101 is made of thermoplastic material.

[0087] As illustrated in the example of FIG. 5, the enclosure 101 is overmolded onto the first nozzle 104 and onto the second nozzle 105. The zone of overmolding of the first nozzle 104 is referenced as S1 and that of the second nozzle 105 as S2. These so-called overmolding operations have been performed by means of the method of the invention as implemented in the first embodiment described above. Thus, the piston chamber 102 has been attached in the area of the nozzle 104 to the bottom of the extrusion head. Likewise, the nozzle 105 of the chamber has been attached to the blowpipe. The steps of the method also make it possible here to produce the accumulator in a faster and easier manner and with less risk than in the prior art.

[0088] Spaces 107, 108 are formed between the enclosure 101 and the piston chamber 102. The space 107 extends in the axial direction between these two elements, while the space 108 extends between them in the radial circumferential direction. Advantageously, the dimensions of the enclosure 101 and of the piston chamber 102 can be chosen so as to contain a desired quantity of gas in these spaces 107, 108. The piston chamber 102 has orifices 109, 110 configured to allow a circulation of the pressurized gas between the chamber 102 and the spaces 107, 108.

THIRD EMBODIMENT

[0089] In a third embodiment of an accumulator produced by means of the method according to the invention and illustrated in FIG. 7, the accumulator is identical to that of the second embodiment except for the following characteristics. Similar elements carry number references increased by 100, where necessary.

[0090] The first nozzle 204 for the inlet and outlet of a pressurized gas, such as nitrogen, is peripheral, and the second nozzle 205 for the inlet and outlet of a pressurized liquid is central, the first and second nozzles being placed this time on the same side of the accumulator. Furthermore, in this case, they are concentric.

[0091] As illustrated in the example of FIG. 7, the enclosure 201 is overmolded on the first peripheral nozzle 204. The zone of overmolding of the first peripheral nozzle 204 is referenced as S3. As in the preceding embodiment, the piston chamber 202 comprises an orifice 209 configured to allow a circulation of the pressurized gas between the chamber 202 and the spaces 207, 208. It may be possible, in certain configurations, to eliminate this second support for the piston chamber.

[0092] Of course, numerous modifications will be able to be made to the invention without leaving its scope.