EP0298832A1 - Method and apparatus for forming a corrugated tube by hammering and its application to tubes for the automobile industry - Google Patents

Abstract

This device essentially comprises at least one radially expandable mandrel (10) whose body (11) is associated with at least one relatively elastic arm (12) which carries on its surface (13) an imprint (14) whose profile ( 15) corresponds to that of the wave to be obtained and a lock (20) movable axially for passing the mandrel from a retracted position to a deployed position where it immobilizes it and where these hammer, tube, mandrel-lock are suitable to be animated by relative relationships along the common longitudinal axis. Application in particular to tubes for automobile steering column.

Description

The invention relates to the manufacture of wave tubes and, more particularly, the shaping of such a tube by hammering. The invention more particularly relates to a method and a device for shaping by hammering a tube to give it in particular a wave configuration and the application of such a tube to the automotive industry for example.

As is known, wave tubes, whether their cross section is circular or not and whether these waves are helical or not, are used in different sectors of industry.

For example, such tubes are used which have a certain flexibility, both axial and transverse, to absorb differences in alignment or expansion of tubular conduits subjected to thermal or mechanical stresses, for example vibration. Such tubes make it possible to compensate for longitudinal expansions and / or to take account of axial alignment faults between different pipes situated on either side of the wave tube section.

Another application for the automotive sector consists in using it to absorb the energy developed by the driver thrown forward during a relatively violent frontal collision; the driver, by a shock in return, strikes the steering wheel and the latter risks causing significant thoracic lesions if it cannot be erased, at least partially, under the impact of the driver. This is why, for example, such wave tubes are located immediately behind the steering wheel, between it and the dashboard, or after the latter between two rigid sections of the upper part of the steering column. , placed between the fixing of the column to the dashboard and the steering box.

Such applications of wave tubes are common. It is therefore understood that the manufacture of such tubes is of great practical interest.

Currently, a commonly used solution for manufacturing a wave tube consists in deforming such a tube under the action of high hydraulic pressure; we perform what is usually called in the art a hydroprocessing. An oil pressure is developed inside the tube and, possibly, combined with an axial thrust, to deform the tube against a female part which has imprints of the waves to be obtained. Simultaneously with the swelling of the tube which expands, all the waves thus obtained approach each other so as to allow a thickness of the metal of the walls of the waves to be kept practically constant. The movement of each external female part which bears the imprint of a wave is controlled mechanically or hydraulically.

Such a manufacturing technique is not without its drawbacks; in fact, it requires a very complex specific machine, and such a machine allows only a few waves to be formed at each operating cycle of the machine. A pressure developed by oil is used and it is difficult subsequently to remove the residual oil which remains inside the wave tube thus obtained. In addition, the wave profile must be very progressive to obtain good results.

Another solution is that set out in patent application FR 2 176 707. This document proposes to manufacture wave tubes using a device which comprises a mandrel carrying at its periphery imprints of the waves to be obtained and a crown of toothed wheels placed radially around with their axes orthogonal to that of the mandrel, These wheels carry at their periphery imprints of the waves to be obtained complementary to those of the mandrel. The tube to be shaped is placed between wheels and mandrel, the imprints of which mesh with one another in the manner of pinion teeth, thus deforming the tube which progresses in a single axial translation with the mandrel through the crown of toothed wheels at the exclusion of any rotation that would be harmful.

Another technique consists in deforming the tube by hammering. This is obtained using hammers driven by reciprocating radial movements relative to the axis of the tube, which are applied periodically with more or less brutality on the outer periphery of the tube so as to obtain a constriction. This technique makes it possible to obtain local reductions in diameter, dishes, successions of necks. Sometimes, in certain cases, so that the tube does not collapse under the forces developed by the various hammers, it may be desirable to have therein a core whose profile corresponds to that of the configuration to be given to the tube; this is, for example, practiced to manufacture fluted tubes using a complementary fluted core. To implement this technique, equidistant hammers are used, arranged at the periphery of the tube to be shaped, which are successively periodically moved alternately, for example using rollers which circulate in a cage somewhat like a roller bearing.

Depending on the results to be obtained, the dimensions and the nature of the material of the tube to be shaped, a number of hammers which rarely exceeds twelve.

This complex hammering technique is well known, so we will not expand on its recall. We also know the numerous drawbacks, which we have summarily and briefly recalled previously of "hydraforming".

The object of the invention is to remedy most of the drawbacks of "hydraforming" by using a technique which uses conventional and no longer special machines but by using a particular tool implemented from a special way.

The invention relates to a device for shaping by hammering a tube to give it in particular a wave conformation using at least one hammer movable radially relative to the axis of the tube to be shaped; this device comprises a mandrel which has at least one hollow body with which is associated at least one arm which carries on its surface a partial imprint whose profile corresponds to that of the wave to be obtained and which is intended to cooperate with the tube and which is radially movable between a retracted position to allow the establishment and extraction of the tube and a deployed position to allow the hammering of the tube and a preferably full latch which cooperates with the mandrel and is axially movable between a first position to allow the mandrel to occupy its retracted position and a second position to allow the mandrel to occupy its deployed position and where these hammer, tube, mandrel-latch are capable of being driven by relative rotations according to the common axis.

The invention also relates to a method for shaping by hammering a tube to give it in particular a wave conformation using at least one hammer movable radially with respect to the axis of the tube to be shaped; this process consists in subjecting the tube, preferably internally, to a device which comprises a mandrel which has at least one hollow body with which is associated at least one arm which carries on its surface a partial imprint whose profile corresponds to that of the wave to be obtained and which is intended to cooperate with the tube and which is radially movable between a retracted position for its installation and its extraction relative to the tube and a deployed position to allow hammering of the tube, to axially move a preferably full latch cooperating with the mandrel enters a first position where the mandrel is in its retracted position and a second position to cause the mandrel to take its deployed position, to use the hammer to apply the tube against the impression and give it its wave conformation, s 'there is reason to animate these hammer, tube, mandrel-lock relative rotations along the common axis, to move the lock axially from its second to s in the first position and to release the shaped tube.

The invention also relates to the application of such a method and such a device for the shaping of wave tubes in particular of steel for automobiles.

• - les Fig. 1A, 1B et 1C illustrent la tech­nique classique de façonnage d'un tube par martelage ;
• - les Fig. 2A, 2B et 2C représentent un pre­mier mode de réalisation d'un dispositif selon l'invention en perspective démonté, en coupe méri­dienne et en section transversale, respectivement ;
• - les Fig. 3A, 3B et 3C sont des vues ana­logues à celles de la Fig. 2 d'un autre mode de réa­lisation de l'invention ; et
• - la Fig. 4 est une section méridienne par­tielle d'une tronçon de tube à ondes façonné suivant l'invention.

Other characteristics of the invention will emerge from reading the description and the claims which follow and from examining the appended drawing, given only by way of example, where:

• - Figs. 1A, 1B and 1C illustrate the conventional technique of shaping a tube by hammering;
• - Figs. 2A, 2B and 2C represent a first embodiment of a device according to the invention in disassembled perspective, in meridian section and in cross section, respectively;
• - Figs. 3A, 3B and 3C are views similar to those of FIG. 2 of another embodiment of the invention; and
• - Fig. 4 is a partial meridian section of a section of wave tube shaped according to the invention.

Hammering techniques being familiar to the specialist in shaping tubes, we will confine ourselves in the description which follows to relate what relates directly or indirectly to the invention. For the rest, the specialist in the technique under consideration will draw on the conventional solutions available to him adapted to the particular cases which he has to solve according to the objectives to be achieved and the constraints to be satisfied.

In Fig. 1, the conventional technique of shaping by hammering a tube has been schematically illustrated, FIG. 1A shows obtaining a constriction and FIG. 1B obtaining a local diameter shrinkage. Fig. 1C shows, in diagrammatic transverse view, the manner in which the hammers are driven to shape a tube by hammering. As can be seen in these figures, hammers 50 act on a tube 100 in which, if necessary, a core 53 of suitable shape can be engaged whose profile of the imprint corresponds to the configuration to be obtained. The hammers approach or move away periodically, simultaneously or in turn, from the tube to be shaped under the action of rollers 52 which move in a cage 51. It is therefore seen that each time a roller passes in the longitudinal axis of a hammer movable alternately radially, this roller pushes on the hammer to apply it against the tube possibly supported by the inner core. The number of hammers and rollers and the relative displacements of the rollers, the cage and the hammers as well as those of the tube, depend on the profile to be shaped on the tube, the nature of the material of the latter and its dimensions as well that of the characteristics of the machine; therefore, we will not go further on this technique.

As indicated, the invention aims to use a machine of this type by equipping it with the device according to the invention to make it suitable for manufacturing by hammering wave tubes. As has been recalled, when it is desired to use the hammering technique, it is sometimes necessary to use a support for the tube, preferably placed inside of it.

The invention uses a conventional machine by adding to it according to the invention an eclipsable device so as to be able to place it in the workpiece and to be able to extract the finished shaping therefrom. We will refer to FIG. 2 which illustrates a first embodiment of the device according to the invention.

The device for shaping by hammering a tube 100 to give it a wave conformation 110 (FIG. 4) using at least one hammer 50 movable radially with respect to the axis 101 of the tube to be shaped comprises a mandrel 10 which has a hollow body 11 with which is associated at least one arm 12 which carries on its surface 13 a partial imprint 14 whose profile 15 corresponds to that of the wave to be obtained. This mandrel is intended to cooperate with the tube and it is radially movable between a retracted position to allow the establishment and extraction of the tube and a deployed position to allow the hammering of the tube. The retracted position is shown in FIG. 2A and in broken lines in FIG. 2B; the deployed position is shown in solid lines in FIGS. 2B and 2C. This device also comprises a lock 20, preferably full, which cooperates with the mandrel 10; this lock is axially movable between a first position to allow the mandrel to occupy its retracted position and a second position to allow the mandrel to occupy its deployed position, as will be understood later.

Preferably, the arm 12 is integral with the body and has an inherent elasticity which naturally tends to urge the mandrel towards one of its two positions and preferably towards its retracted position, as illustrated in FIG. 2A. As can be seen, the lock 20 carries a cam 26 and the mandrel 10 a cam follower 16 cooperating with the cam of the lock. Preferably, the cam 26 comprises a cone 261 followed by a cylinder 262 of revolution; the cam follower 16 is preferably of circular and conical cross section in the retracted or cylindrical position 162 in the deployed position of the mandrel 10.

As can be seen in the drawing, the arm 12 carries on its surface 13 a partial imprint 14 whose profile corresponds to that of the wave to be obtained on the tube.

Fig. 2A illustrates this first embodiment in the disassembled position, outside the tube. Fig. 2B shows, in solid lines, the device according to the invention in its deployed position ready to support the tube 100 to be hammered and in broken lines in its retracted position allowing the assembly of the assembly in the machine; this view is a section along the offset plane identified in FIG. 2C.

Fig. 2C is a cross section illustrating the latch in its second position and the mandrel in its deployed position.

It is therefore understood that, the mandrel being in its retracted position, the imprints tend to be contiguous due to the inherent elasticity of the arms which carry them. If the lock 20 is pressed axially into the body of the mandrel 10, the cone 261 of the cam 26, by pushing on the cam follower 16 of the arms makes them protrude first then, continuing its translation places the mandrel in deployed position and finally locks him in this attitude.

The tube to be shaped is therefore supported internally and can be struck in the usual way using hammers which have been provided with impressions 54 of complementary profile, as illustrated.

The number of arms is not critical, in the illustrated embodiment there are shown six.

It can therefore be seen that when the lock moves axially from its first position relative to the mandrel to take its second position, it causes the arms of the mandrel to expand. These arms open practically to the dimension of the wave tube to be obtained. The tube to be deformed, initially cylindrical and of equal diameter or greater than the peripheral external diameter of the wave parts of the imprints of the arm in the deployed position, can be inserted on the mandrel when the lock is in either of its first or second positions or vice versa.

When the tube is in place and the lock occupies its second position, one or more hammers strike and radially deform the tube on the profile in the impression.

According to the invention, in order to obtain the formation of waves over the entire circumference of the tube using this embodiment of the device in question, it is necessary to rotate, along the common longitudinal axis and relatively to each other, tube , hammer and chuck-lock assembly. This chuck-latch assembly rotates at a synchronous speed with that of the hammers and depends on the number of bearing impressions carried by the chuck relative to the number of active hammers. The manner in which these hammer, tube, mandrel-latch are mounted and supported in order to be able to rotate along their common longitudinal axis and the manner in which they are made to rotate on themselves at distinct own speeds so that they have relative displacements between them, calls upon common solutions to be chosen, if necessary by adapting them, according to each specific case.

After forming and returning the hammers to a position radially distant from the axis of the tube, the lock is returned from its second to its first position; this allows the impressions to retreat centripetally due to the inherent elasticity of the arms of the mandrel which carry them. It can therefore be seen that the mandrel then spontaneously returns to its retracted position; when the mandrel occupies this position, it is possible to separate the tube from it since the imprints are released from the waves shaped on the tube.

We will refer to FIG. 3 in which an improvement of the embodiment of FIG. 2.

As can be seen, in particular in FIG. 2C, when the mandrel is in the deployed position, there is a gap between each arm and with each strike of the hammers only a wave arc is obtained. To eliminate this drawback, another mandrel is used, the arms of which, when in the deployed position, fill the vacant gaps which exist between the arms of a first mandrel. When these two mandrels are then in the deployed position, the arms of one occupy the interstices between the arms of the other mandrel. It can therefore be seen that in this embodiment, the two mandrels are mounted head to tail and their respective arms are nested with one another.

To shorten the description, the homologous elements have the same reference numbers but assigned the sign "prime".

The operation of this second improved embodiment is as follows:

The tube 100 to be formed is slid over the first mandrel 10 whose arms 12 are deployed by the latch 20 which occupies its second position. The second mandrel 10 ′ is put in place by translation in the first mandrel 10, or vice versa, and the bolt continues its translation so as to cause the arms 12 ′ of the second mandrel to expand, which then fill the gaps left vacant by the arms of the first mandrel, as indicated previously and illustrated in FIGS. 3B and 3C.

After blocking in the deployed position of the two mandrels, the hammers strike the tube and the distort on the waveforms, as indicated above.

The hammer, tube and device assembly are rotated relative to each other.

To unlock the device, the lock 20 is made to slide axially which, during its movement, passes from its second position to its first position, which makes it possible to successively release each of the mandrels 10 ′, 10 which, as indicated, have arms 12 ′, 12 which have an inherent elasticity which tends to urge them towards their retracted position. As can be seen, the wave tube thus formed is released from the device by operating in the reverse order to what was done at the start of the process.

This being done, the tube can then be removed manually or ejected by the recoil from the mandrel; or one can also grasp the tube thus obtained using a robot or an automaton.

Reading the above description has clearly highlighted the interest of the invention and its characteristics.

As is clear, thanks to the invention, it is possible, by giving the imprint a suitably suitable shape, simultaneously by hammering the waves and a conical or cylindrical shrinkage.

Furthermore, as illustrated schematically in FIG. 4, the thickness of the tube wave can be varied locally by giving the imprints the appropriate profiles. This makes it possible to refine the configuration of the wave profile obtained to give the tube thus fashioned the desired mechanical characteristics, for example so that it satisfies well defined conditions of radial and / or axial behavior as a function of the displacements which it undergoes. In Fig. 4, these are the vertices 111 of the waves which are locally thinned.

It will also be observed that the invention makes it possible to obtain a large number of profiles and in particular to produce non-circular waves or any other profile which is known to be made by hammering, for example hexagonal waves. You can also get helical waves.

The prints form an integral part of, or are attached to, the arms and / or hammers. The choice of materials from which they are made depends on the dimensions and the nature, for example steel, of the tube to be worked. Tubes with a wall thickness of between 0.1 and 10 mm can be formed, for example, by adapting the equipment and tools accordingly. Thanks to the invention, it is easy to shape, for example steel tubes, the outside diameter of which is on the order of 60 mm and the thickness on the order of 2 mm, and to form waves over a length which can, at less, reach twice the diameter for example.

It will further be observed that, in addition to the technical advantages, the invention provides significant economic advantages since the cost of producing a tube obtained according to the invention is less than that resulting from hydraforming; indeed the work is faster by hammering and the tooling is of a lower cost price. In addition, it is no longer necessary to degrease the shaped tube to rid it of traces of hydroprocessing oil.

The invention makes it possible to obtain wave tubes which are particularly suitable for automotive technical applications; these wave tubes are especially suitable for the upper part of automobile steering columns that can be deformed in the event of impact, either directly at the time of a collision or immediately after the impact of the driver striking the steering wheel.

However, the applications are not limited to the automotive sector alone and are also suitable, for example, for pipelines when it is a question of taking account of misalignments or dilations.

Claims (20)

1. Device for shaping by hammering a tube (100) to give it in particular a wave conformation (110) using at least one hammer (50) movable radially with respect to the axis (101) of the tube to be shaped, characterized in that it comprises at least one mandrel (10) which has a hollow body (11) with which is associated at least one arm (12) which carries on its surface (13) an imprint (14) partial whose profile (15) corresponds to that of the wave to be obtained and is intended to cooperate with the tube and which is radially movable between a retracted position to allow the establishment and extraction of the tube and a deployed position for allow hammering of the tube and a lock (20) preferably full which cooperates with the mandrel and is axially movable between a first position to allow the mandrel to occupy its retracted position and a second position to allow the mandrel to occupy its position deployed and where these hammer, tube, mandrel-latch are able to be be driven by relative rotations along the common axis. 2. Device according to claim 1, characterized in that the arm (12) is integral with the body (11) and has an inherent elasticity which naturally tends to urge the mandrel (10) towards one of its positions. 3. Device according to claim 1 or 2, characterized in that the inherent elasticity biases the mandrel (10) towards its retracted position. 4. Device according to any one of claims 1 to 3, characterized in that, when it passes from its retracted position to its deployed position, the mandrel (10) undergoes centrifugal radial expansion. 5. Device according to any one of Claims 1 to 4, characterized in that the lock (20) carries a cam (26) and the mandrel (10) a cam follower (16) cooperating with the cam (26) of the lock (20) and in that the latch (20) is axially movable. 6. Device according to claim 5, characterized in that the cam follower (16) is a cylinder (162) of constant circular cross section in the deployed position of the mandrel, in that the cam (26) is a cone (261) followed by a cylinder (262) of revolution and in that the latch (20) moves in the mandrel (10). 7. Device according to any one of claims 1 to 6, characterized in that it comprises a second mandrel (10 ′) which has a body (11 ′) with at least one associated arm (12 ′) bearing on its surface (13 ′) a partial imprint (14 ′) with a profile (15 ′) and in that the arms and imprints of a mandrel are interposed between those of the other at least in the deployed position. 8. Device according to claim 7, characterized in that the mandrels (10, 10 ′) are coaxial and in that each body with its arms (12, 12 ′) and imprints (14, 14 ′) is oriented head to tail relatively to each other. 9. Device according to any one of claims 1 to 8, characterized in that the lock (20) when it moves from its first to its second position and vice versa, successively causes the positioning of the mandrel (10, 10 ′) In its deployed position and the locking of the mandrel (10, 10 ′) in this deployed position. 10. Device according to any one of claims 1 to 9, characterized in that the hammer (50) carries an imprint (54) whose profile (55) is complementary to the other profiles (15, 15 ′). 11. Device according to any one of claims 1 to 10, characterized in that the imprints (14, 14 ′; 54) are attached. 12. Device according to any one of claims 1 to 10, characterized in that the imprints (14, 14 ′; 54) are at least for some of them an integral part of what carries them. 13. Device according to any one of claims 10 to 12, characterized in that the profiles (15, 15 ′; 55) of the indentations (14, 14 ′; 54) cooperating on the mandrel (10, 10 ′) and on the hammer (50) are chosen to locally modify the thickness of the finished shaping tube (100). 14. Device according to claim 13, characterized in that the complementary profiles (15, 15 ′; 55) are chosen to modify the thickness of at least one of the vertices (111) of the wave (110) of the tube ( 100). 15. Device according to any one of claims 1 to 14, characterized in that the impression (14, 14 ′) is carried by the surface (13, 13 ′) outside of the arm (12, 12 ′) of the mandrel ( 10, 10 ′). 16. Device according to any one of claims 1 to 15, characterized in that the profile (15, 15 ′; 55) is in accordion fold. 17. Device according to any one of claims 1 to 15, characterized in that the profile (15, 15 ′; 55) is helical. 18. Application of the device according to any one of claims 1 to 17 to the shaping of wave tubes in particular of steel for automobiles. 19. A method for shaping by hammering a tube to give it in particular a wave conformation using at least one hammer movable radially relative to the axis of the tube to be shaped, characterized in that it subjects to the tube a device in particular according to any one of claims 1 to 17, which comprises at least one mandrel which has a hollow body with which is associated at least one arm which carries on its surface a partial imprint whose profile corresponds to that of the wave to be obtained and which is intended to cooperate with the tube and which is radially movable between a retracted position for its installation and its extraction relative to the tube and a deployed position to allow the hammering of the tube, a bolt cooperating with the mandrel is moved axially a first position where the mandrel is in its retracted position and a second position to make the mandrel take its deployed position, the hammer is used to apply the tube against the impression and give it its wave conformation, we do it is necessary to rotate along the common axis relatively to each other these hammer, tube, mandrel-bolt, the bolt is moved axially from its second to its first position and the shaped tube. 20. A method according to claim 19, characterized in that the device is relatively placed in the tube.

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