EP0029380B1 - Method of forming a bead in the wall of a metallic tube - Google Patents

Abstract

1. A process for forming a collar (11, 11') on the wal of a metal tube (1, 1'), preferably of small thickness, said process being characterized in that the tube (1, 1') being empty of any filling a circular groove (6, 6', 17) delimited by two adjacent sides (7, 8) is formed in per se known manner at the periphery of the tube (1, 1') and on the face opposite to that where the collar is to be produced, by an operation of displacing the metal such as knurling, and that a an axial compression is then applied to the ends of the tube (1, 1') until the two adjacent sides (7, 8) formed in the course of the first phase are brought into contact.

Description

The present invention relates to a method of forming a flange, which can in particular serve as a stop, on the internal or external wall of a metal tube and, in particular, of a thin tube.

Usually, to achieve a stop on a tube, one proceeds by removing metal, for example by making a recess. However, this solution can hardly be used except in the case of tubes having a sufficient thickness.

In the case of thin tubes, it is often preferred, in order to avoid weakening the product, to use means which avoid the need for material removal and rather involve deformation techniques, such as, for example, knurling. .

In processes of this type, the material is made to flow so as to form a circular groove on one side and, consequently, an annular bulge forming a stop on the other side. The flanks of the stops thus produced are inclined relative to the cross section of the tube, which is incompatible with applications requiring free stops.

FR-A-1 051 547 has also proposed a process for the manufacture of an external flange on a metal tube, this process consisting, in a first phase, in repressing a tube filled with a repressing material between two dies, the tube being, during this operation, hermetically closed at its two ends and retained externally on all sides, except at the location of the flange to be formed, then, in a second phase, after having removed the filling material, to compress the bulge formed during the first phase between the two matrices. This process is relatively complex, due to the use, in one of the phases, of a filling material, and the use of dies. In addition, it does not allow an internal collar to be produced.

The present invention aims to remedy these drawbacks by making it possible to obtain flanges constituting frank stops, both on the internal face and on the external face of metal tubes, by simple deformation of the metal.

To this end, it relates to a method of forming a flange on the wall of a tube, preferably of small thickness, this method being characterized in that, the tube being empty of any filling, we form, in a manner known per se, by a metal pushing operation, such as knurling, at the periphery of the tube and on the face opposite to that where it is desired to obtain the flange, a circular groove limited by two adjacent flanks, and in which is then exerted on the ends of the tube axial compression, until bringing into contact the two adjacent flanks formed during the first phase.

It is certainly known from US-A-2,147,032 a method of deformation of a metal tube according to which a tool having a cutting edge is brought into contact with the external face of the tube so as to form an external groove there.

Likewise, US Pat. No. 3,031,904 describes a tool capable of being engaged inside a tube with a view to imparting a deformation which results in the formation of an annular groove on the outside of this tube.

None of these methods of the prior art however contemplates compressing the tube by exerting an axial compression on its ends in order to bring into contact the adjacent sides of the groove produced on the tube, as proposed by the method in accordance with the present invention.

It goes without saying, therefore, that the method according to the invention is limited to the combination of a preliminary phase of deformation of a tube capable of producing on this tube an external or internal groove and of an axial compression phase subsequent of said tube exerted on its two ends, with a view to bringing the two sides of said groove into contact. On the other hand, the invention does not encompass each of these phases, considered in isolation.

The method according to the invention has the advantage of providing flanges whose planes are substantially perpendicular to the wall of the tube. They thus constitute frank stops, capable of constituting a non-deformable blocking means.

Another advantage of the invention, of a decorative order, resides in the fact that in the case of an internal stop, the usual external groove, which attracted the eye, is replaced by a simple circular line.

• La figure 1 est une coupe axiale d'un tube représenté à la fin de la première phase du procédé suivant l'invention, dans son application à la formation d'une butée interne;
• La figure 2 est une coupe axiale du tube de la figure 1 représenté à la fin de la seconde phase du procédé;
• La figure 3 est une vue en perspective du tube montré à la figure 2;
• Les figures 4, 5 et 6 sont des vues analogues aux figures 1,2 et 3 dans le cas de l'application du procédé selon l'invention à la formation d'une butée interne;
• La figure 7 est une coupe axiale partielle d'une variante de réalisation.

Modes of implementing the invention will be described below, by way of nonlimiting example, with reference to the appended drawings, in which:

• Figure 1 is an axial section of a tube shown at the end of the first phase of the method according to the invention, in its application to the formation of an internal stop;
• Figure 2 is an axial section of the tube of Figure 1 shown at the end of the second phase of the process;
• Figure 3 is a perspective view of the tube shown in Figure 2;
• Figures 4, 5 and 6 are views similar to Figures 1,2 and 3 in the case of the application of the method according to the invention to the formation of an internal stop;
• Figure 7 is a partial axial section of an alternative embodiment.

As indicated above, in a first phase of the process which is the subject of the invention, an annular groove is formed on a tube 1.

To do this, and in a known manner, the tube being held by rollers shown by arrows 2 and 3, a wheel shown by arrow 4 is applied to it, while a rotational movement shown by the arrow 5. Under the combined action of the radial force and the rotational movement, the metal creeps and a circular groove 6 limited by the sides 7 and 8, is formed.

In a second phase, an axial compression force, shown by arrows 9 and 10, is applied to the tube. This force must be sufficient to bring the two sides 7 and 8 of the groove 6 into contact. Thus, the flange 11 formed by the sides 7 and 8 is substantially located in a cross section of the tube and, therefore, constitutes a frank and non-deformable stop.

Figures 4, 5 and 6 show an alternative embodiment of the invention in which the flange is formed not inside the tube, but outside of the latter.

In these figures, the bodies already described retain the same references assigned to the index.

An advantageous implementation of the method according to the invention consists, during the first deformation phase and as shown in FIG. 7, in pushing the bottom 15 of the circular groove 17 until it is in the alignment of the wall 19 (alignment shown by the line 1-1) on which the flange will be formed.

This removes any area of material directly connecting, in a straight line, part 23 to part 25 of the tube. Therefore it eliminates a resistance zone directly opposing the axial compression force exerted on the tube during the second phase and it makes it easier to form the flange.

It is obvious that, without departing from the scope of the invention, this process could be adapted to specific cases, for example by making the circular groove by a process other than knurling.

It should be noted that, since the process according to the invention does not require removal of material, it is possible to considerably reduce the thickness of the tubes to which it is applied, thereby achieving appreciable savings, of up to 50%. , of the material of said tube.

Claims (2)

1. A process for forming a collar (11, 11') on the wall of a metal tube (1, 1'), preferably of small thickness, said process being characterised in that, the tube (1, 1') being empty of any filling, a circular groove (6, 6', 17) delimited by two adjacent sides (7, 8) is formed in per se known manner at the periphery of the tube (1, 1') and on the face opposite to that where the collar is to be produced, by an operation of displacing the metal such as knurling, and that an axial compression is then applied to the ends of the tube (1, 1') until the two adjacent sides (7, 8) formed in the course of the first phase are brought into contact.

2. A process for forming a collar on a tube according to claim 1 characterised in that deformation of the tube which is produced in the course of the first phase is such that the bottom (15) of said groove (17) reaches at least a position of alignment with the wall surface (19) on which the collar is formed.

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