Method and device for notching tubes and the tube thus obtained
The invention relates to a method of notching a tube. The inventive method is characterised in that it comprises the to-and-fro movement of at least one pressure roller. During said movement, the aforementioned roller applies pressure locally to the wall of the tube (1) and plastically deforms same. The movement of the pressure roller is produced by a combination of at least two other movements, namely: a first essentially rectilinear to-and-fro movement, during which the roller rolls against the wall of the tube (1); and a second forward movement, the resultant of which is essentially perpendicular to the direction of the first movement. In this way, the tube (1) is plastically deformed in at least two movements of the pressure roller.
The invention relates to a process and a device for the notching of tubes.
The word “tube” here indicates a hollow body, specifically cylindrical, which may be open or closed, and which is made of metallic material or any other similar material.
In many industrial areas, notches must be made in hollow tubes. This type of notching is done, for example, in support bars with a ratchet for a hand brake, pinion racks, or in structures for headrests in automotive vehicles.
In this last specific use, the notches in the tubes must have sharp, clean edges in order to get accurate adjustment of the height of the headrest, and in order to prevent the headrest from being easily shifted and disturbed when a slight pressure is applied, for example by a child.
Structures for headrests with the tube in the shape of a notched U are described, for example, in the following documents:
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- Requests for patent in France, published under numbers 2,755,915, 2,751,926, 2,734,612, 2,734,216, 2,721,267, 2,704,188, 2,666,771;
- Requests for European patents, published under numbers 1,108,607, 1,046,541, 953,477, 875,417, 743,222, 687,590, 412,307;
- American patents published under U.S. Pat. Nos. 5,478,136, 5,398,996, 5,257,853, 5,165,754, 4,390,209.
We already know, from prior practice, about various processes which allow a series of sharp-angle notches to be made in tubes, whether or not the material is removed.
Notching the tubes by machining, where the material is removed, presents numerous drawbacks and is no longer considered, because it makes the tube much too fragile.
In return, many processes for notching a tube that do not involve removing the material are proposed in prior practice.
Document EP-A-0 974 409 describes a notching process that implements an epicycloid train riveting machine, with a spherical cap, which is already known, and which, instead of its rivet-punch, consists of a punch that is adapted to the profile of the notching to be executed. This punch is engaged in a complex movement that breaks down into a translation movement and an orbital movement. The tube to be notched is placed in a groove in a fixed half-shell, a moveable half-shell or a blank-holder that has a groove located opposite the groove in the fixed half-shell.
The procedure described in document EP-A-0 974-409 has numerous drawbacks. In particular, the productivity achieved is very low, and not very compatible with the requirements of the automobile manufacturing sector. Moreover, as mentioned in this earlier document, the movement of the punch is complex and can prove difficult to control, so that the quality of the notches produced on the tube is subject to variations, and this in spite of a blockage in the rotation of the notching punch by an anti-diverter.
Document FR-A-2 805 481 describes a tube notching process that is done by press stamping. The process uses a matrix that consists of parts; a lower matrix, a right upper matrix and a left upper matrix. A groove is arranged in the lower part of the matrix to accept the tube to be notched. Then the parts of the left and right upper matrix are plated against the tube to be notched, and the matrix obtained features through-holes, through which the punches stamp the tube.
The process described in document FR-A-2 805 481 has numerous drawbacks. In particular, in order to minimize the amplitude of weakening by shear forces, it is necessary to adjust the dimensions of the indented part and the notch. If this is not done, the notches may have burrs: notching tubes by press deformation as described in document FR-A-2 805 481, involves sagging, which requires additional machining in order to obtain sharp angles. Productivity obtained by the stamping process is low.
In order to control the thickness and section of tubing during stamp notching, document EP-A-1 112 791 offers placement of a mandrel and pressing in multiple passes. This type of process does not allow assurance of high productivity and cannot, by its very nature, be implemented with closed tubes.
Document WO-A-01/15827 describes a notching device that comprises a sliding forming tool.
Other tube notching processes are described in documents DE-U-29717174, De-U-29714315, EP-A-0 867 334.
The invention is intended to provide a process and a tube notching device that does not have the drawbacks that the processes and devices present up to now.
The invention is intended, specifically, to provide a process which assures an increased productivity, a greater regularity in shape for the notches, absence of burrs and repeated machining, because the notches are formed without removing the material and without significant weakening in the tube's resistance.
To this end, the invention relates, first of all, to a notching process for a tube, where this process consists of a back-and-forth motion of a least one pressing roller; during this movement the roller presses locally and plastically deforms the wall of the tube, where the movement of the pressing roller is formed by the combination of at least two motions, namely:
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- a first motion, largely rectilinear, back-and-forth, during which the roller rolls against the wall of the tube;
- a second motion, known as “forward”, whose result is largely perpendicular to the direction of the first motion, where the plastic deformation is also obtained in at least two passes of the pressing roller.
According to one characteristic, the process consists of an inspection step of one parameter selected from among the group consisting of: pressing force of the pressing roller on the tube, the position of the roller while it is in contact with the tube.
Secondly, the invention relates to a machine for the implementation of a process defined above, where this machine comprises a means for temporarily holding a tube in a predetermined position and a means of motorized driving of the pressing rollers following their first motion.
According to various methods of embodiment, the machine features the following characteristics, which may or may not be combined:
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- it comprises a means for causing the second motion, called the forward motion, of the pressing roller, in a controlled manner, where these means consists of a means chosen from among the group comprising springs, activators such as jacks;
- it consists of a motorized roller carrier trolley, where this trolley is driven back and forth following the first motion, and where it is mounted mobile in rotation around an axis that is largely perpendicular to the direction of this first motion;
- it consists of three pressing rollers whose diameters are largely identical and whose rotational axes are largely aligned following the direction of said first back-and-forth motion;
- it consists of a means of servo-system for moving the pressing rollers as a function of at least one parameter chosen from among the group consisting of: the support force of the pressing roller on the tube, the position of the roller during its contact with the tube;
- the servo-system is of the electro-hydraulic type.
Thirdly, the invention relates to a headrest tube obtained by implementing a process ad defined above.
Other subjects and advantages of the invention will become apparent during the following description of means of production and description which will be performed by referring to the attached drawings, in which:
The following description will be carried out in relation to the notching of a U-shaped tube of the type used in conventional headrest frames. As the skilled craftsman will understand, the process and the device in the invention also allow notches to be produced in other types of tubes, such as, for example, those used for pinion racks or support bars with ratchet for hand brake.
In the figures, a U-shaped tube 1 is held in position by a means 2 such as a groove matrix, in the work volume of a machine 3.
In the manner of embodiment shown, tube 1 is introduced into volume V, by a movement according to arrow F, where the two largely parallel branches 4 and 5 of tube 1 extend following direction D1.
This direction D1 shall be considered to be vertical, in the remainder of this description. It shall nevertheless be understood that this arrangement is being used only arbitrarily, for purposes of simplicity. In effect, as the craftsman will understand, functioning of the machine is in no way influenced by the assignment of direction D1.
Maintaining the position of the tube in its receptacle grooves may be achieved using means such as tightening clamps, for example.
In the manner of embodiment show, the tube is of a largely circular section. It shall nevertheless be understood that the process according to the invention may be implemented for tubes of oval or polygonal section.
Machine 3 is equipped with three profiled rollers 6, 7, and 8, mounted in rotation following direction D1.
In one manner of embodiment, these three rollers 6, 7, and 8 are mounted on a sliding trolley following direction D2, where this trolley is itself mounted jointed according to direction D1 relative to the machine 3's frame, where this frame is held on tube 1 to be notched. A means for controlled pressurizing ensures the support of rollers 6, 7 and 8 on tube 1 to be notched.
In a first specific implementation, these means comprise a torsion spring mounted on axle 10.
In a second specific implementation, these means consist of a compression spring mounted between a support bearing 11 and sliding chassis 12 which supports rollers 6, 7 and 8, this spring is drawn by reference 13 in
The first and second methods of embodiment indicated above produce a motion of the roller-mount trolley that is largely rectilinear, following direction D2.
The applicant has nevertheless stated that such a largely rectilinear movement could lead to significant residual constraints on the nicks, i.e. slight flaws in shape in these nicks following significant plastic deformation of the material comprising tube 1.
Also, in a third embodiment, roller mount trolley 12 is controlled, in its rotational movement about axis of rotation 10, by a means such as a double-effect actuator.
The control of the movements of the actuator shaft is enacted, in one variation, as a function of trolley motion. In another variation, controlling the movement of the actuator shaft is enacted as a function of the strain borne by the trolley as the roller passes over tube 1, where this strain reflects the force of plastic deformation borne by the tube material 1 during notching.
Thus it is possible to use variable pressure to work rollers on tube 1, for example increasing, then largely constant, then decreasing. The craftsman will know, for a specific tube material, how to experimentally adapt the pressure profile that offers the compromise that is most adapted to his fabrication time and residual constrain requirements.
The forward and backwards movements of the trolley that carries rollers 6, 7 and 8 are motorized, and rapid, on an order of several tens to several hundreds of back-and-forth motions per minute.
The applicant has stated that the process as it was just described allows extremely significant gains in productivity, relative to previously known processes, all the while ensuring a great regularity in the shape of the notches, where the material the tube is made of has not thinned out at the end of the notch.
Machine 3 can consist of one, two or more than two notches. The notches may be profiled for the production of one or more notches in the tube.
The notches may be arranged with their axes of rotation largely parallel, as shown.
In other manners of embodiment, not shown, axes of roller rotation are not aligned, for example for the formation of negative notches. The position of axes of rotation of the rollers is, in one manner of embodiment, subject to the position or the force of the roller on the tube being notched.
In this case, the rollers can be arranged according to several rows that are largely parallel, so that the make two or more than two notches at the same time.
As the craftsman will easily understand, by clamping tube 1 according to an angle determined relative to direction D3 in
The process according to the invention allows notching of headrest frame tubes to be done in a very short time, on an order of a few seconds.
Claims
1. Process for notching a tube, comprising a back and forth motion of at least one pressing roller, movement during which this roller locally presses and plastically deforms the tube wall, and where the movement of the pressing roller consists of a combination of at least two displacements, namely:
- a first motion, largely rectilinear, back and forth, during which the roller rolls against the tube wall;
- a second motion, called a forward motion, whose result is largely perpendicular to the direction of the first motion, the plastic deformation of the tube thus being obtained in at least two passes of the pressing roller.
2. Notching process according to claim 1, further comprising an inspection stage where a selected parameter is chosen from the group consisting of: the force of the pressing roller on the tube, the position of the roller during its contact with the tube.
3. Machine for the implementation of the process according to claim 1 comprising a means of temporarily holding at least one tube in a predetermined position, and a means of motorized drive of the pressure rollers following their first motion.
4. Machine according to claim 3, comprising a means to cause the second motion, known as the forward motion, of the pressing roller, in a controlled manner, these means comprising a means chosen from the group consisting of springs, activators such as jacks.
5. Machine according to claim 3, comprising a motorized roller-mount trolley, the trolley being driven back and forth following said first motion and being mounted mobile in rotation around an axle that is largely perpendicular to the direction of this first motion.
6. Machine according to claim 3, comprising three pressure rollers of diameters that are largely identical, and whose rotational axes are largely aligned according to the direction of the first back and forth motion.
7. Machine according to claims 3, comprising a means of servo-system for the pressure roller displacement, as a function of at least one parameter selected from among the group consisting of: the force of the pressure roller on the tube, the position of the roller upon contact with the tube.
8. Machine according to claim 7, wherein the servo-system is of the electro-hydraulic type.
9. Tube obtained by the implementation of the process according to claim 1, wherein the tube for a headrest support.
Type: Application
Filed: Dec 4, 2002
Publication Date: Feb 24, 2005
Inventor: Marc Lefevere (Croix)
Application Number: 10/497,561
