FR2656251A1 - METHOD FOR MANUFACTURING HOLLOW HANGED BODIES, PARTICULARLY IN THE FORM OF TUBES. - Google Patents

Abstract

Process for manufacturing bent hollow bodies, in particular in the form of tubes, characterized in that the hollow body is manufactured, in particular in an unbent mold, in an injection mold, then in a second step, the hollow body is molded on demand, and in particular it is bent.

Description

i "Process for manufacturing bent hollow bodies, in

particularly in the form of tubes ".

  The invention relates to a method for manufacturing curved hollow bodies, in particular in the form of tubes, such as, for example, suction pipes for internal combustion engines.

  of plastic in an injection mold.

  For the production of hollow bodies, such as

  for example tubes, there are many methods.

  Let us mention here, for example, the process of melting a nucleus, as it is mentioned in the "Automobiltechnisden Zeitschrift" (Automobile Technical Review) 89 (1987) 3, page 139 In this process, "lost" nuclei are used. cores constitute the mass of a hollow space inside the hollow body and are made, for example, of an alloy of metals with a low melting point but also of salts, or of plastics soluble in water. are for example placed in the mold of an injection press, and surrounded by extrusion with plastic material The finished product is then passed through a melting device, for example in a bath at a moderate temperature, and, by a strong inductance reinforcement, the core or nuclei are melted This process is expensive, since a "lost" nucleus must first be manufactured which, apart from the formation of a space

hollow, no longer fulfills any role.

  Another known method consists in manufacturing the suction pipe from two half-shells, which are then connected to one another with fastening elements.

sealing problems.

  The invention is characterized in that the hollow body is produced in particular in a non-bent mold in an injection mold, then then in a second step, the hollow body is molded with the

  ask, and in particular we bend it.

  In the process according to the invention, the hollow body is first of all manufactured so as to be demouldable, that is to say that it is manufactured in a mold which is not bent in the injection mold, then in a second step it is put in

  shape on demand, especially curved.

  All this means that the hollow body can be easily produced in a mold, by injection; the tool is therefore not complicated, since no manufacture of bodies which may not be demouldable, for example bodies

bent hollows cannot be made.

  The hollow body should preferably be reheated before molding Here it is necessary to examine the economic aspect of the process, to see if the heat of the injection molding process can be used In the second step, the hollow body is distorted to the corresponding shape, and the case

if necessary is also cooled.

  Compared to the method implementing the melting of the core, the present method has the particular advantage that it does not have to implement a step of casting the core, nor another step of melting, nor finally the handling of a difficult cast core Compared to the manufacturing process from two shells, the sealing problems do not arise, since the element is made in one piece Here we also expect fewer problems of

mechanical resistance.

  In the context of the invention, the hollow body must preferably undergo stiffening during manufacture. This can be done by inserting, for example, a spiral spring in the injection mold, and this spring remains in the envelope of the hollow body,

after the injection.

  Subsequently, it is intended that the hollow body, after injection, is filled with a substance, this substance possibly being for example compressed air. Thanks to the two measures which have just been mentioned, it is guaranteed that the tubing during its transformation will not be bent by compression

nor dented.

  According to another characteristic, the body

  hollow is heated again before deformation.

  According to another characteristic of the invention, the hollow body, after having been heated,

is deformed more cooled.

  According to another characteristic of the invention, the hollow body is hardened at the time of its manufacture. According to another characteristic of the invention, before injection, a spiral spring is placed in the injection mold and that this spring has an inside diameter larger than the diameter

  interior desired for the hollow body.

  According to another characteristic of the invention, a pressurized agent is maintained or

  brought inside the hollow body.

The advantages and particularities of

  the invention will become apparent from the following description,

  more particularly examples of embodiments and drawings in which: FIG. 1 shows a schematic representation of a hollow body produced in an injection mold; Figure 2 shows a top view of the hollow body corresponding to that of Figure 1 after its transformation; Figure 3 shows a partially broken top view on the hollow body corresponding to that of Figure 1, in a mold; Figure 4 shows a partial and enlarged longitudinal section of a hollow body provided with a flange; Figure 5 shows an enlarged partial longitudinal section of another example of the body

hollow according to the invention.

  A hollow body according to the invention R consists, according to FIG. 1, of an approximately cylindrical envelope and two flanges which are formed there on each side. A hollow body of this kind is produced in a plastic injection machine. o thanks to its linear mold, it is

easily demouldable.

  In the manufacturing example shown in Figure 1, the hollow body R has along the axis line A a central opening 4 This opening

central 4 has a diameter d.

  After the hollow body R has been produced in a corresponding injection mold, it is removed from the injection mold and shaped in a second manufacturing process. In accordance with FIG. 2, this is the forming process. with a simple bending However, we can also consider more complicated shaping processes,

  these being part of the spirit of the invention.

  After demolding, the hollow body R has acquired an axis

curved median.

  In Figure 3, there is a mold 5 which can be constituted for example by two half shells The hollow body R is inserted under this mold 5, bent and cooled Before bending, the hollow body R had to be put in the state plastic under

the effect of heat.

  The flanges 2 and 3, which are constituted for example by threaded flanges placed on a suction pipe, can be molded in one piece on the hollow body R, or alternatively can also be injected subsequently as seen in the Figure 4 In this figure, we can see the flange with the mark 6 which partially surrounds the end of a hollow body Rl In order to obtain a better hold of the hollow body Rl on the flange 6, the opening area 7 of the hollow body is curved towards the outside In addition, the holes 8 pass through the flange 6, and through them, if necessary, it is possible to

  pass the corresponding fixing parts.

  In FIG. 5 another example of the production of a hollow body R 2 is shown. There, there is in the cylindrical envelope 1 a spiral spring 9,

  thanks to which the envelope is reinforced.

  In accordance with the invention, the spiral spring 9 is surrounded by plastic during the injection phase, in the injection mold. In the next step of the molding, a bending is thus avoided.

  by compression or embossing of the hollow part R 2.

  (rotassure) We will also get a similar result, as follows: after the manufacture of the hollow body, it is filled with a pressurized agent, and a corresponding interior volume is maintained or enlarged This is avoided also a compression deflection or a bump in the

hollow part.

Claims (5)

R E V E N D I C A T I O N S   1) Method for manufacturing curved hollow bodies, in particular in the form of tubes, made of plastic in an injection mold, for example the suction pipes of internal combustion engines, being capable of being demouldable, characterized in that the hollow body is produced in particular in a non-bent mold, in an injection mold, then then in a second step, the hollow body is molded on demand, and in particular we bend it.   2) Method according to claim 1, characterized in that the hollow body is again heated before deformation.   3) Method according to claim 2, characterized in that the hollow body, after having been   heated, is deformed more cooled.   4) Process according to any one of   claims 1 to 3, characterized in that the body   hollow is hardened at the time of its manufacture.   ) Method according to claim 4, characterized in that before the injection, a spiral spring is placed in the injection mold and that this spring has an internal diameter larger than the   inner diameter desired for the hollow body.   6) Process according to any one of   Claims 1 to 5, characterized in that an agent   under pressure is maintained or brought inside the hollow body.