Tubes having indentations formed therein

Abstract

A hollow metal tube having a sharp-angled indentation that is made without removing any material and without deforming the external diameter while conserving the fiber orientation of the metal and maintaining a constant thickness of the tube. The process of forming the sharp-angled indentation comprises the steps of, providing a riveting machine, the riveting machine having an epicycloid mechanism and a spherical joint and comprising a riveting head fitted to a spindle, operating in conjunction with pressing devices and a fixed half-clamp, replacing the spindle of riveting machine with a sharp angled former adapted to the profile of the indentation to be made and to the former's sharp angle, inserting the tube on which indentations are to be made between the former and the fixed half-clamp, and activating the pressing devices to cause movement of the spindle in order to form the sharp-angle indentation in the tube.

Description

RELATED APPLICATIONS

[0001] This is a divisional application of U.S. Ser. No. 09/314,279 filed on May 15, 1999 that claimed priority of European Patent Application No. 98 401 857.2 filed Jul. 27, 1998.

TECHNICAL FIELD

[0002] This invention relates to a process by which it is possible to make a sharp-angled indentation on hollow tubes without removing any material, maintaining a constant thickness of tube and also without deforming the external diameter and conserving the fiber orientation of the metal.

[0003] In many industrial fields, it is necessary to make a series of indentations in tubes for adjustment purposes.

[0004] As a non-exhaustive illustration, such indentations are used in the automobile industry when making “frames” for adjustable head restraints for motor vehicles.

[0005] In order to make indentations in tubes, processes have already been proposed that involve machining and removing material, a technique which is difficult to apply in the case of hollow tubes, or that use a press, which leads to deformation (caving in) of the tubes, making further machining necessary, and which does not enable sharp-angled indentations to be produced.

[0006] The presence of sharp-angled indentations is essential in order to ensure catches are properly engaged and that positions can be adjusted.

[0007] Consequently, the “frames” of head restraints for motor vehicles are, as a general rule, currently made from non-tubular, solid cylindrical metal bars, which to a great extent increases their weight and their cost price.

OBJECTS OF THE INVENTION

[0008] The purpose of this invention is to resolve these problems by offering a process that makes it possible to make sharp-angled indentations on hollow tubes, without removing any material.

[0009] According to this invention, it has been possible, surprisingly, to achieve this objective not by means of a press as has previously been proposed, but by means of a riveting machine which in itself is a well-known machine, comprising a riveting head fitted to a spindle operating in conjunction with pressing devices and a fixed half-clamp.

SUMMARY OF THE INVENTION

[0010] The process used in this invention is characterized by the fact that the riveting head of a riveting machine of this type is replaced by a former adapted to the profile of the indentation to be made and in particular to its sharp angle. The tube on which indentations are to be made is inserted between the former and the fixed half-clamp and the pressing devices are activated, causing movement of the spindle, in order to allow indentations to be made in the tube.

[0011] Thus by radial deformation it is possible to obtain indentations of various shapes, without removing any material, and to maintain a sharp angle in the side engaged by the catch, without deforming the external diameter of the tube.

[0012] One possible characteristic of the invention is that the riveting machine is a riveting machine with an epicycloid mechanism and a spherical joint.

[0013] When such a machine is used, the indentation former is subjected to a complex movement that can be broken down into a translational movement and an orbital movement.

[0014] It has thus been possible to make indentations in tubes with a depth one-and-a-half times their thickness, without perforating the deformed part.

[0015] Another possible characteristic of the invention is that the spindle of the riveting machine is fitted with a holding-down clamp, the front part of which secures the tube in which indentations are to be made and holds it tightly against the fixed half-clamp.

[0016] Another possible characteristic of the invention is that rotation movement of the indentation former is prevented by means of a stabilizing device.

[0017] There are no limits in terms of the maximum and minimum tube diameters that can be handled by the process. The depth and the surface area to be obtained determine the power of the riveting machine.

[0018] By way of example, tests have been carried out on steel tubes with an external diameter of 11.70 mm and an internal diameter of 7.80 mm. A force of 500 daN was required in order to obtain indentations 2 mm in depth with an area of 50 mm2.

[0019] The invention also relates to a hollow tube produced by means of the process described above.

[0020] Such a tube is characterized by the fact that it has sharp-angled indentations which have been made without removing material, maintaining constant tube thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The characteristics of the process and the tubes covered by the invention will be described in greater detail by referring to the appended drawings, in which:

[0022] FIG. 1 is a perspective view of a tube as according to the invention;

[0023] FIG. 2 is a section through this tube;

[0024] FIG. 3 is a schematic section of the riveting machine used in this process;

[0025] FIG. 3a is a schematic section of FIG. 3 along axis A-A;

[0026] FIGS. 4 and 4a, 5 and 5a, 6 and 6a show three examples of indentation formers as sections and views from below, respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0027] According to FIG. 1, the surface of the tube (1) has a series of indentations (2) of a determined profile.

[0028] According to FIG. 2, the indentations (2) have sharp angles (3) and are made without removing material so that the thickness of the tube remains constant.

[0029] According to FIG. 3, the riveting machine (4) used to make indentations in the tubes (1) is a machine with an epicycloid mechanism and a spherical joint, which is a well-known type of machine and which, for this reason, will not be described in detail in the context of this statement.

[0030] This machine is equipped, firstly, with a fixed half-clamp (5) and secondly a moving half-clamp or holding-down device (6) fixed to the head of the machine (4) by means of a screw (7) in conjunction with sleeves or springs made of rubber.

[0031] According to FIG. 3a, the two parts (5, 6) have grooves (8, 8′) located opposite each other in order to hold the tube (1) in which indentations are to be made.

[0032] Furthermore, and as shown in FIG. 3, the machine (4) is also fitted with a former (9) fitted to the nose of the same.

[0033] FIGS. 4, 4a, 5, 5a, 6 and 6a show examples of former profiles (9) which can be used according to the type of indentation to be produced.

Claims

1. A hollow metal tube having a sharp-angled indentation that is made without removing any material and without deforming the external diameter while conserving the fiber orientation of the metal and maintaining a constant thickness of the tube, where the process of forming the sharp-angled indentation comprises the steps of, providing a riveting machine, the riveting machine having an epicycloid mechanism and a spherical joint and comprising a riveting head fitted to a spindle, operating in conjunction with pressing devices and a fixed half-clamp, replacing the spindle of riveting machine with a sharp angled former adapted to the profile of the indentation to be made and to the former's sharp angle, inserting the tube on which indentations are to be made between the former and the fixed half-clamp, and activating the pressing devices to cause movement of the spindle in order to form the sharp-angle indentation in the tube.

2. A hollow metal tube as described in

claim 1, characterized in that the spindle of the riveting machine is fitted with a holding-down clamp, the front part of which secures the tube in which indentations are to be made and holds it tightly against the fixed half-clamp.

3. A hollow metal tube as described in

claim 1, characterized in that the riveting machine effects riveting by a rotational movement and the rotational movement of the indentation former is prevented by means of a stabilizing device.

4. A hollow metal tube as described in

claim 2, characterized in that the riveting machine effects riveting by a rotational movement and rotational movement of the indentation former is prevented by means of a stabilizing device.

5. A process for making a hollow metal tube having a sharp-angled indentation formed without removing any material and without deforming the external diameter while conserving the fiber orientation of the metal and maintaining a constant thickness of the tube, where the sharp-angled indentation is formed by a process comprising the steps of, providing a riveting machine, the riveting machine effecting riveting by a rotational movement and comprising a riveting head fitted to a spindle, operating in conjunction with pressing devices and a fixed half-clamp, replacing the spindle of the riveting machine with a sharp angled former adapted to the profile of the indentation to be made and the former's sharp angle, inserting the tube on which indentations are to be made between the former and the fixed half-clamp and activating the pressing devices causing movement of the spindle in order to allow indentations to be made in the tube and preventing rotational movement of the indentation former by means of a stabilizing device.

6. A process for making a hollow metal tube having a sharp-angled indentation formed without removing any material and without deforming the external diameter while conserving the fiber orientation of the metal and maintaining a constant thickness of the tube, where the sharp-angled indentation is formed by a process comprising the steps of, providing a riveting machine, the riveting machine effecting riveting by a rotational movement and comprising a riveting head fitted to a spindle, operating in conjunction with pressing devices and a fixed half-clamp, replacing the spindle of the riveting machine with a sharp angled former adapted to the profile of the indentation to be made and the former's sharp angle, inserting the tube on which indentations are to be made between the former and the fixed half-clamp and fitting the spindle of the riveting machine with a holding-down clamp, the front part of which secures the tube in which indentations are to be made and holds it tightly against the fixed half-clamp, and activating the pressing devices causing movement of the spindle in order to allow indentations to be made in the tube and preventing rotational movement of the indentation former by means of a stabilizing device.