EP1539393B1 - Press for tube notching provided with a mandrel which is arranged inside said tube and a piece corresponding to produced notch - Google Patents

Abstract

The invention relates to a press for tube notching provided with at least one tool which comprises the following elements: an internal fixed matrix in the form of a semishell whose inner cavity contours the external semicylindrical surface of a tube to be notched (2), a clamp frame device for suitably clamping the tube (2) or two tubes simultaneously, at least one upper punch (3) whose extremity (4) has a shape corresponding to the shape of a notch (5) to be produced, a mandrel (6) which is introduced into the tube to be notched in such a way that it can form in the inner cavity thereof a volume or volumes for material expansion resulting from stamping.

Description

The present invention relates to a tool according to the preamble of claim 1 (see for example JP-A-58218339) and a machine using such a tool for the notching of a tube, in particular a headrest reinforcement tube for motor vehicle.

The invention applies in particular, but not exclusively to height adjustable headrests whose armature is composed of two parallel branches, at least one of which has a plurality of notches each defining a position of adjustment of the support. while performing one of the following functions: anti-ejection in maximum-lift position, stroke adjustment, maximum low hold.

Different profiles of such notches are shown schematically in FIG. 1 and one of the end notches, with orthogonal profile, is drawn in detail in FIG.

For the maintenance of the headrest, these notches cooperate with latches integrated in guide bushes provided at the top of the seat back.

On solid metal rods these notches are easily made whatever their profile for example by machining, or by cold deformation (stamping).

For the sake of lightening and as for many components integrated in the automobile, the headrest frames gradually move from a rod or wire execution to a tube execution for which there are problems of realization of the notches.

The machining process of the notches remains applicable to the tubes by milling or broaching if the thickness of the tube allows it and if the weakening of section confers on the product a rigidity and a resistance corresponding to the requirements of rigidity. The major disadvantage of this process is therefore to be limited to certain dimensions of tubes.

• limiter l'effondrement de la paroi du tube estampé afin de conserver une arrête fonctionnelle efficace entre le flanc souvent vertical du cran et la génératrice du tube,
• faire en sorte que le métal déplacé n'augmente pas le diamètre externe. du tube et contribue le plus possible à la rigidité de la zone travaillée.

Moreover, to apply the stamping process to the tubes, several problems must be solved, namely:

• limit the collapse of the wall of the stamped tube in order to maintain an effective functional stop between the often vertical flank of the notch and the generatrix of the tube,
• to ensure that the displaced metal does not increase the outer diameter. of the tube and contributes as much as possible to the rigidity of the area worked.

A stamping solution of the tube is proposed in the document DE 29714315 and it consists in introducing a sleeve into the zone of the tube where the notches must be formed, to facilitate the formation of the notches, but this sleeve does not constitute a tool but an insert. residing in the room. Another solution described in document EP 97 4409 makes it possible to achieve a notch by hammering. but the operation time is relatively long and the implementation machine is complicated and expensive.

The invention aims to overcome the aforementioned drawbacks and to provide a machine capable of making several notches simultaneously in the wall of a tube, without restriction of shape.

This object is achieved by the invention by a tube detent tool, with the features of claim 1. Claims 2 and 3 define preferred embodiments of the invention. A notching machine comprising at least one tool according to the invention is defined in claim 4.

• figure 1 : représentation schématique d'une branche d'armature d'appui tête comportant une série de crans de différents profils,
• figure 2 : cran d'extrémité à profil orthogonal,
• figure 3 : schéma de principe de la partie innovante d'une machine selon l'invention,
• figure 4 : section verticale selon AA de la figure 3.

The invention will be better understood from the description given with reference to the following figures:

• FIG. 1: schematic representation of a head support armature branch comprising a series of notches of different profiles,
• FIG. 2: end notch with orthogonal profile,
• FIG. 3: block diagram of the innovative part of a machine according to the invention,
• FIG. 4: vertical section along AA in FIG.

• une matrice inférieur fixe non représentée et en forme de demi coquille dont la cavité interne est -apte à épouser la forme extérieure-demi cylindrique d'un tube à cranter (2),
• un dispositif serre flan du type à ressort ou à actionnement par vérins séparés, pour assurer un bridage approprié d'un tube (2) ou deux tubes simultanément,
• au moins un poinçon supérieur (3) mobile dont l'extrémité est conformée selon une forme complémentaire (4) inverse de celle d'un des crans (5) à réaliser, et apte à se déplacer perpendiculairement à l'axe longitudinal du tube,
• un mandrin (6) apte à être introduit à l'intérieur du tube à cranter et dont la section à été prévue pour résoudre les problèmes d'exécution tels qu'il sera expliqué plus loin.

A machine according to a preferred devicalization mode of the invention consists essentially of a press on which is mounted at least one notching tool (1) specific to the invention and which comprises the following elements:

• a fixed lower die which is not shown and which is in the form of a half-shell, the internal cavity of which is able to conform to the outer half-cylindrical shape of a craning tube (2),
• a spring-type flanged device or actuated by separate cylinders, to ensure proper clamping of a tube (2) or two tubes simultaneously,
• at least one movable upper punch (3) whose end is shaped in a complementary shape (4) opposite to that of one of the notches (5) to achieve, and able to move perpendicular to the longitudinal axis of the tube,
• a mandrel (6) adapted to be inserted inside the sleeve tube and whose section has been provided to solve the problems of execution as will be explained later.

If the machine is intended to notch U-shaped armatures with two parallel branches, it may comprise two notching tools (1) as described above.

Similarly, each notching tool can also be provided to include a plurality of upper punches (3) aligned, each intended for the realization of one of the notches of one and the same armature branch (2), and actuated simultaneously during a same stamping operation.

Referring now to Figure 4 showing the appropriate section of a mandrel according to the invention.

• un allongement du tube (2) concerné, car l'effort de bridage exercé par le serre flan est calculé de façon à s'opposer à tout gonflement diamétral dudit tube,
• une contrainte élevée appliquée au mandrin du fait des efforts de pliage du métal.

The problem to solve when executing a notch by stamping with a mandrel completely filling the cavity of a tube results from the displacement of a volume of metal causing:

• an elongation of the tube (2) concerned, because the clamping force exerted by the blank greenhouse is calculated so as to oppose any diametral swelling of said tube,
• a high stress applied to the mandrel due to the bending forces of the metal.

In order to avoid these drawbacks, the invention provides for the use of a mandrel the section of which does not fill the whole of the internal cavity of the tube, so as to reserve one or more volumes for the expansion of material, and to be able to be extracted of the tube after stamping.

At the level of the area to be stamped, the cylindrical mandrel comprises a modified area: the section of the mandrel (6) necessarily has on the one hand a flat area (7) in a plane parallel to the longitudinal direction (10) of the mandrel and making anvil function during stamping, and secondly two side blanks (8,9) for example (but not necessarily) arranged symmetrically with respect to the vertical median plane (11) of the mandrel so as to clear on each side mandrel an expansion volume (12, 13).

Preferably, but not exclusively, the two blanks are planar and determine between them a predetermined angle (α).

The width (d) of the anvil and the predetermined angle (α) are calculated according to the dimensions of the tube and the notch to be obtained while ensuring the desired rigidity and safety.

By way of example for a tube with an outside diameter of 12 mm and a thickness of 2 mm, the mandrel has an outside diameter of 7.9 mm in these cylindrical parts, and in the active parts an anvil of width (d) = 3 mm for an angle (α) of 60 °.

In addition, a machine using the invention is a press comprising at least one notching tool according to the invention and means for moving and positioning a mandrel in a cranberry tube, along its longitudinal axis, in one direction or in the other.

Claims (4)

1. Notching tool (1) for notching a tube (2), more especially but not limitingly for notching one or two tubes of a head support framework for a motor vehicle of the type comprising the following elements:

   - a lower matrix, fixed and in the shape of a half-shell, the internal cavity of which is capable of marrying-up with the semi-cylindrical exterior shape of a tube to be notched (2),

   - a tight blank device, to ensure an appropriate clamping of one tube (2) or two tubes simultaneously,

   - at least one upper punch (3), the end of which is shaped in a reverse complementary shape (4) to that of one of the notches (5) to be produced, and

   - a mandrel (6) capable of being introduced into the interior of the tube to be notched,

   characterised in that the cylindrical mandrel comprises a modified zone and has a planar zone (7) along a plane parallel to the longitudinal direction (10) of the mandrel and fulfilling the function of an anvil during the stamping on the one hand and, on the other hand, two lateral blanks (8, 9), so as to free on each side of the mandrel an expansion volume (12, 13).
2. Notching tool according to claim 1, characterised in that the tight blank device is of the spring type or the type actuated by separate jacks.
3. Notching tool according to claim 2, characterised in that the two blanks are planar and form therebetween a predetermined angle (α).
4. Notching machine (1) for notching a tube (2), more especially but not limitingly for notching one or two tubes of a head support framework for a motor vehicle, characterised in that it is made up of a press comprising at least one tool according to one of claims 1 to 3 for achieving the notches by stamping.

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