EP1563920B1 - Tube extrusion press - Google Patents

Description

The invention relates to a extrusion spinning press of a hollow body such as a tube and its object, in particular, to ensure perfect concentricity of the outer and inner profiles of the extruded tube.

It is known that an extrusion spinning machine generally comprises a fixed front and a rear crossmember, kept spaced apart by a constant distance by columns, a die mounted in a die holder fixed on the bed base and defining a spinning axis, a container provided with a housing centered on the spinning axis and into which is threaded a cylindrical billet of metal to be spun and an elongated follower able to penetrate into the housing of the container so that the metal of the billet compressed between the front of the follower and the die, passes into it by forming, by extrusion an elongated product.

In the so-called direct method, the front face of the container is supported on the bed that carries the die and the follower is mounted on a movable crosspiece moving, under the action of the main cylinder, between the fixed cross and the bed.

In the so-called reverse method, the die is mounted at the end of a tubular follower bearing on the fixed bed base and the container is supported, by its rear face, on the movable cross member so as to be slipped on the tubular follower by causing the extrusion of the billet metal.

For spinning a tube, the billet of metal introduced into the housing of the container is traversed axially by a needle consisting of a rigid rod having an end which has a diameter slightly smaller than that of the die and is placed substantially at level thereof, so as to limit an annular space in which is extruded the billet metal thereby forming a tubular hollow product having an outer face and an inner face whose dimensions are determined, respectively, by the die and by the front end of the needle.

This technique of spinning tubes is very old and described, for example, in the document DE-A-167,392 published in 1903 , which shows a tube spinning machine having a needle slidably mounted axially in a bore of the ram and connected by a control rod to the piston of a jack mounted at the rear of the main spinning jack. In this way, the needle can be returned completely to the gland for spinning profiles or extend cantilever from the gland crossing the billet, for spinning tubes. For this, the billet is first introduced into the housing of the container, then it is pierced by advancement of the needle under the action of the auxiliary cylinder placed at the rear of the press, until the nose of the needle reaches the level of the die. The main cylinder then controls the advancement of the follower to perform the spinning of a tube in the annular space between the die and the nose of the needle.

In the document technique DE-A-167,392 the so-called stopped needle method is used, in which the leading end or the nose of the needle is maintained, during spinning, at the level of the die. However, it is also possible to use the method of the accompanied needle, in which the needle is advanced with the follower and gradually enters the die during spinning.

To produce a tubular product having the desired thickness in all directions, it is necessary that the front end of the needle is perfectly centered with respect to the die.

On the other hand, the external profile of a raw billet of metal to be spun is not always regular and its dimensions must necessarily be a little lower than those of the housing of the container to allow its introduction therein. Since the length of the billet may vary, the length of the housing must correspond to the maximum length of the billet.

It is therefore necessary to proceed, before spinning, the bale stacking in the housing by advancing the follower that enters the housing by slightly crushing the billet compressed between the die and the gland. This results in a transverse expansion of the billet which is strongly applied to the side wall of the housing.

During this tamping operation, the needle has returned completely to the follower.

Then, the billet is pierced by advancing the needle forward of the follower, until its front end reaches the die in the desired position for spinning.

Since the needle extends cantilever from the follower and its diameter is necessarily small, it may tend to deviate and must be guided.

In the layout of the document DE-A-167,392 , the needle is slidably mounted inside the follower, that is to say on a length of the same order as that of a billet. In addition, the control rod is articulated at its ends, respectively on the needle and on the piston rod and is guided axially, along its length of displacement, in a fixed tube penetrating inside the piston of the main cylinder. It must therefore be slidably mounted, sealingly along the tube.

Such an arrangement has been used for a long time for spinning tubes but has the disadvantage of increasing the length of the press.

However, currently, an extrusion press must be capable of spinning very diverse profiles and the necessary billet length may be large enough for some products. However, the stroke of the main cylinder and the needle must correspond to the maximum length of the billet and the layout of the document DE-A-167,392 , with the drill cylinder placed behind the main cylinder, can lead to an excessive press length, of the order of 10 or 11 times the maximum billet length.

Therefore, in more recent presses, the thrust cylinder of the needle is usually placed inside the piston of the main cylinder which is itself the body of this drill cylinder. The needle must then be carried by a slidably mounted auxiliary cross member inside a front portion of the movable crosshead. This crossbar is guided by two lateral devices mounted on either side of the main cylinder to ensure, on the one hand, guiding the needle and, secondly the stop thereof in the spinning position , by means of two stops, which must be relatively spaced from each other, on both sides of the main cylinder. However, there may be a slight offset between these two lateral stops, likely to cause a parasitic force, perpendicular to the direction of spinning, may cause a shift of the needle relative to the container and the die.

In addition, the different parts of the machine can deform.

This results in a risk of misalignment of the needle during drilling and during spinning, which can cause a lack of concentricity between the internal profile and the external profile of the extruded product, but until now, such defects were judged acceptable.

For some time, however, customers have required a very low concentricity tolerance between the profiles, internal and external respectively of the product, and it has become apparent that the tube spinning presses currently in use do not respond well to this new need.

The object of the invention is to solve such problems by means of a press employing a set of characteristics which cooperate with each other so as to ensure, in all the phases of the process, a perfect alignment of the various members on the spinning axis. . This gives an excellent concentricity of the inner face and the outer face of the extruded product, to control the thickness of the tubular wall with a very low tolerance.

In order to solve these centering problems, the applicant company first of all advised that it might be preferable to go back to the old technique in which the drilling cylinder is placed outside the press, at the back of the machine. it. This results, as we have seen, an elongation of the press but this disadvantage can be offset by the use of a particular technique of loading the billet in which the container is first threaded, backwards on the follower to release, between the front face of the latter and the die, a space of length just necessary for the introduction of a new billet which can be perfectly centered on the spinning axis and then maintained tight between the die and the follower by advancing it to catch up games. The container can then be advanced so that its housing is put on the billet and kept well centered on its axis. This loading technique makes it possible to reduce the length of the press and the result is that the control cylinder of the needle can be placed at the rear of the press, without unduly increasing the overall size thereof.

However, it became apparent that, thanks to the use of such a technique, it was possible, during tamping, to achieve a regular expansion in all directions, the billet and that thus decreased the risk of misalignment of the needle during drilling, as will be described in more detail later.

In general, the invention therefore applies to a tube spinning press by the direct method, of the type described in the preamble of claim 1 (cf. US Patent 3345851 ).

According to the invention, the needle is slidably mounted axially in the follower between a rear position for which the needle is completely retracted into the follower and a forward position for which the needle extends cantilevered over a length corresponding to that of the housing, axially through the billet that said needle forms, with the control rod a sliding assembly which is guided axially, at least in the front in the follower and at the rear on the rear extension of the piston on a guide length at least equal to three times the length of the container housing, and that, in the rear position of the gland, the front face of the latter is separated from the die by a loading space of at least the length of the housing, the container being axially displaceable between a rear loading position of a billet in said space for which the housing is threaded on the follower and a position before bearing on the die after threading the housing on the billet held tight between the die and the front face of the crusher.

Thanks to this arrangement and to this method of loading, the billet is always perfectly centered with respect to the lateral wall of the housing and is subjected, during the packing in advance of the follower, to an expansion in all directions by regularly bearing on any the periphery of the housing, so that during the drilling of the billet by advancing the needle, it is subjected to any parasitic force may cause misalignment.

According to another particularly advantageous characteristic, the control rod is associated with an abutment centered on the spinning axis and coming to bear, in the forward position of the needle, on a fixed shim placed at the rear of the fixed crossbeam and providing at least two support points spaced apart on either side of the spinning axis, at a small distance therefrom.

Preferably, this stop comes to bear on an eclipsable shim having two positions, respectively a closed stop position of the stop and an open position of passage of the stop, allowing the advance of the needle with the follower, as and as the billet is spinning. According to another preferred feature, this shim is fixed on a rear portion of the body of the main cylinder, at a distance of the order of one time the length of the container housing.

In the case where the press is provided only for spinning with the needle stopped, the stroke of the control cylinder of the needle is of the order of one time the length of the housing.

Since the press is of the compact type, the main cylinder also has a stroke of the order of one time the length of the housing and the whole of the press, including the control cylinder of the needle, then extends over a total length of the order of 6 times said length of housing.

In another particularly advantageous embodiment, the fixed shim on which abuts the stop of the control rod, is eclipsable and can take two positions, respectively a closed stop position of the stop and an open position of passage of the stop, allowing the advancement of the needle with the follower, as and when spinning the billet.

The press according to the invention can then operate by the method of the accompanied needle, the stroke of the control cylinder of the needle being of the order of twice the length of the housing, respectively once for drilling and once for spinning.

In this case, the main cylinder also has a stroke of the order of one time the length of the housing and the entire press, including the control cylinder of the needle, then extends over a total length of the order of 7 times this length.

In a preferred embodiment, the eclipsable wedge consists of a fork-shaped plate provided with a notch width equal to that of the control rod of the needle and associated with a means of controlling its sliding between two positions, respectively an open position spaced apart from the control rod and allowing the axial sliding thereof, and a closed position for which the fork-shaped plate caps the control rod in order to oppose the sliding of the control rod in a stop position of the stop.

Particularly advantageously, the bearing position of the abutment on the fixed shim is axially adjustable so as to allow adjustment of the level of the front end of the needle relative to the die.

For this purpose, the stopping stop of the needle may consist of a nut screwed onto an external thread of the control rod and whose position along it can be adjusted by rotating the nut by compared to the control rod.

Furthermore, according to another advantageous characteristic, the press comprises means for controlling the rotation of the control rod with the needle around the spinning axis, for adjusting the orientation of the front end of the spindle. needle with respect to the die.

• La figure 1 est un schéma d'ensemble d'une presse de filage de tubes selon l'invention.
• La figure 2 montre schématiquement l'opération de tassage, respectivement dans une presse conventionnelle et dans une presse selon l'invention.
• La figure 3 montre schématiquement la mise en place d'une nouvelle billette dans l'axe de filage.
• La figure 4 montre l'enfilement de la billette à l'intérieur du conteneur.
• La figure 5 montre le tassage de la billette dans le logement.
• La figure 6 montre la mise en place du grain de poussée.
• La figure 7 est une vue en perspective, avec arraché partiel, de l'ensemble d'une presse selon l'invention.
• La figure 8 est une vue en coupe longitudinale de l'ensemble de commande du déplacement axial de l'aiguille.
• La figure 9 est une vue de détail, en coupe axiale, du dispositif de réglage de la butée.
• La figure 10 est une vue de face selon A-A de la figure 8.
• La figure 11 est vue de l'arrière, selon B-B de la figure 8.

Other advantageous features falling within the scope of protection of the invention will become apparent in the following description of certain embodiments given by way of nonlimiting example and illustrated by the accompanying drawings.

• Figure 1 is an overall diagram of a spinning press tubes according to the invention.
• Figure 2 schematically shows the tamping operation, respectively in a conventional press and in a press according to the invention.
• Figure 3 shows schematically the introduction of a new billet in the spinning axis.
• Figure 4 shows the threading of the billet inside the container.
• Figure 5 shows the beating of the billet in the housing.
• Figure 6 shows the placement of the push grain.
• Figure 7 is a perspective view, with partial cutaway, of the assembly of a press according to the invention.
• Figure 8 is a longitudinal sectional view of the control assembly of the axial displacement of the needle.
• Figure 9 is a detail view, in axial section, of the stop adjustment device.
• Figure 10 is a front view along AA of Figure 8.
• Figure 11 is seen from the rear, according to BB of Figure 8.

In Figure 1 which shows schematically the assembly of a tube spinning press by the direct method, it shows only the essential organs of the press which comprises, as usually, a main cylinder 1 mounted on a fixed rear cross member 10 , a die 2 mounted in a die holder 21 fixed on a fixed front bed base 20, a container 3 and a spin follower 4 carried by a movable cross member 40. All these members are centered on a x'x spinning axis passing through the center of the die 2 which is extended by an axial duct 22 formed in the bed base 20 for the evacuation of the spun product.

The rear crossmember 10 and the front beam 20 are fixed on a foundation and kept spaced apart from one another by a constant distance, by columns not shown in the diagram.

Similarly, the press comprises, as usual, various auxiliary members, such as two pairs of lateral cylinders acting respectively on a container cradle 30 for the independent movement thereof, and on the movable cross member 40 to optionally control the displacement. of the follower 4 without pressurization of the main cylinder 1.

As usual, the container 3 is provided with a cylindrical housing 31 centered on the x'x spinning axis and into which is introduced a billet 5 of metal to be spun. As shown in Figure 1, for a spinning operation, the container 3 is applied against the die 2 and the follower 4, pushed by the main jack 1, enters the housing 31 so as to force the metal of the billet 5 to go through the die 2 to form an extruded product 5 '.

For this, the follower 4 consists of a spindle-shaped piece of length l ₁ and having a front face of diameter a little smaller than that of the housing 31 of the container 3.

The clearance necessarily between the front of the gland and the housing causes the formation of a thin jacket along the side wall of the housing. Usually, the front face of the follower thus consists of a piece 42 in the form of a disc, called the pushing rod, which is removably mounted at the front end of a rod 4 'extending in door-to-door false from the movable crosshead.

At the end of the spinning, this pushing grain 42 is included in the jacket which is removed by scraping, with removal of the grain. This must be cleaned before it can be reused and, in the meantime, it is replaced by a new grain for spinning the next billet.

For spinning tubes, the rod 4 'and the grain 42 forming the follower 4 are pierced with an axial duct in which is slidably mounted an elongate rod 6 forming a needle capable of axially passing through the billet 5 of metal to be spun, until 1 to the position shown in FIG. 1, for which the front end 61 of the needle 6, which has a diameter smaller than that of the die 2, is substantially at the same level, so as to limit a space annular passage of the metal, the spun product 5 'thus having the shape of a tube having an outer face 51 and an inner face 52 whose dimensions are determined by those of the die 2 and the front end 61 of the needle 6.

For the reasons indicated above, the needle is slidably mounted axially in the follower and its position can be adjusted by means of a jack 7 placed at the rear of the press and connected to the needle by a control rod. passing through the bottom 14 and the piston 11 of the main spinning jack 1.

As we have seen, the profiles of the two faces, respectively outer 51 and inner 52 of the extruded tube 5 'depend on those of the die 2 and the front end 61 of the needle 6 whose position can be adjusted, for spinning, by means of the control cylinder 7. This position also depends on the spinning technique used and must be adjusted accurately. For example, it is preferable, in some cases, to keep the end 61 of the needle 6 slightly set back from the die 2.

In what follows, we will describe the spinning of a tube having an inner face and a cylindrical outer face, using, therefore, a die and a circular section needle.

In this case, the regularity of the thickness of the tubular wall 5 'depends on the concentricity of the needle 6 and the die 2. However, in conventional presses, concentricity defects can occur due to part of the existence of games in the guiding and alignment systems of the various members and, secondly, deformations of the machine that can generate stray forces resulting in misalignment of the needle.

For some time, however, the customer demands for some products a very low tolerance of concentricity between the inner 52 and outer 51 profiles of the extruded product 5 '.

The object of the invention is to solve this problem by means of a set of characteristics which combine their effects in such a way as to avoid play and parasitic forces, and thus to keep the needle perfectly centered on the spinning axis during the operations of piercing and spinning, to ensure perfect concentricity of the inner faces 52 and outer 51 of the extruded tube 5 '.

Firstly, the inventor observed that the parasitic forces tending to deflect the needle could be due to the initial decentering of the billet in conventional presses and that it was particularly advantageous, in order to avoid this defect, to use the loading mode described above, which ensures the centering of the billet in all phases of the process.

This appears in the comparative diagram of FIG. 2 which illustrates the compression process of the billet in the container housing, respectively on the left for a conventional press and on the right for a press according to the invention.

In the conventional process shown in the diagram on the left, the container 3 is applied on the bed base 20 carrying the die 2 and the billet 5 is placed by means of a loader in a space left between the rear face of the container 3 and the face before the follower 4 and then it is pushed back by the follower sliding axially on the loader, in order to get into the housing 31 of the container. It then rests along a generator on the underside of the housing 31 and the clearance between the side face 53 of the billet and the inner face of the housing 31 is not regular.

When the follower 4 is advanced to compress the billet 5, it expands upwardly to apply to the upper part of the inner face of the housing 31. This is not filled so symmetrical.

In contrast, for the loading of a billet in a press according to the invention, the container is first threaded onto the follower and applied to the movable crosshead. The billet is introduced into the space between the die and the follower and can be perfectly centered on the spinning axis by means of the loader.

The follower is then advanced so as to pinch the billet between its front face and the die, which allows to remove the loader and push the container forward to apply it on the bed base, by threading the housing 31 on the billet thus held tight between the die and the follower.

During all these operations, the billet 5 has remained centered on the spinning axis and is thus surrounded, over its entire periphery, with a clearance of approximately constant thickness between its lateral face 53 and the inner face of the housing. 31.

Therefore, as shown in the diagram on the right of Figure 2, when the follower 4 is advanced to compress the billet, it expands in all directions and fills the inner space of the housing 31 substantially symmetrically . This avoids the appearance, as in conventional presses, an asymmetrical filling defect capable of generating, during drilling and spinning, a displacement of material with the creation of parasitic forces which can cause misalignment of the needle.

Indeed, as shown in Figure 2, after the compression phase, the metal fills the housing symmetrically by exerting on its inner side a pressure evenly distributed in all directions.

This regularity of the internal stresses in the billet makes it possible to ensure the centering of the needle 6 during its advance inside the billet and to its spinning position at the level of the die 2. Similarly, the expansion symmetrical billet avoids parasitic vertical movement likely to decenter the needle 6.

Moreover, as indicated above, because of the loading mode chosen, by clamping the billet between the follower and the die, the length of the press between the bed base and the fixed crossbar is relatively small and it is therefore possible without unduly increasing the size of the press to control the sliding of the needle for drilling and to adjust its axial position by means of a cylinder centered on the x'x spinning axis and placed on the back of the fixed transom. The body 72 of the drilling cylinder 7 can thus be fixed directly to the foundation and / or connected by columns 81 to the body 12 of the main cylinder 1. As a result, the piston 71 of the drilling cylinder 7 exerts on the rod 62 control a force that always remains centered on the axis x'x spinning.

On the other hand, in this arrangement, the control rod 62 is extended rearwardly to the piercing cylinder 7 and must therefore axially cross the bottom 14 of the main cylinder 1. Advantageously, to ensure the seal and, in same time, guide the axial movements of the control rod and the needle 6, the piston 1 of the main cylinder is extended rearwardly by a portion 13 in the form of cylindrical sheath which passes through the bottom 14 of the body 12 of the jack , an annular seal of known type, sealing against the pressure in the main cylinder. This rear extension 13 of the piston 11 extends over a length I ₂ at least equal to the stroke C of the jack which, as will be seen later, may be of the order of the length L of the housing 31 corresponding to the maximum length of a billet to spin.

In addition, the length l ₁ of the follower must also be at least equal to the maximum length L of a billet.

Thus, the control rod 62 and the needle 6 are guided in a central duct pierced axially in the piston of the main cylinder extended forwards by the follower 4 and towards the rear by the sealing sheath 13. guide length is, at any time, at least equal to three times the length L of the housing 31 of the container.

Indeed, the needle 6 must be replaceable and is normally screwed by its rear portion on the front end of the control rod 62, so as to form a sliding assembly which is guided axially, at least to the before on the follower 4 and rear on the extension 13 of the piston 11. These two guide zones, which may also be formed by axial bearings, are separated by a distance of at least 3L and is move with the main cylinder, when spinning.

Furthermore, the control rod 62 can be sized to withstand buckling during drilling and transverse forces possibly applied by the needle 6 on its front end.

This guiding over a large length of the assembly of the needle 6 and its control rod 62 thus makes it possible to ensure at all times the centering of the needle on the spinning axis and to avoid the risks of misalignment. during drilling and spinning.

In addition, as indicated above, the advancement of the needle 6 for piercing the billet must be stopped in the spinning position shown in FIG. 1, for which the front or nose end 61 of the needle 6 is substantially at the die 2. However, this position must be adjusted accurately according to the spinning process, because it influences the extrusion process and, therefore, the profile of the spun tube 5 '.

According to another particular characteristic of the invention, the advance of the piston 71 of the piercing cylinder 7 can be stopped in a precise position by a stop 74 mounted on the control rod 62 of the needle 6, this stop 74 coming to take support on a fixed shim 8 secured to the rear part of the body 12 of the main cylinder 1.

In the example shown diagrammatically in FIG. 1, the abutment 74 is placed at the junction 62b with the piston rod 73 and has an annular shape, the wedge 8 consisting of a bearing circular formed at the end of a rear extension 15 of the body 12 of the cylinder 1 which surrounds the sealing sheath 13 at a small distance from it and extends over a length I ₃ which is also of the order the maximum length L of a billet to spin.

All of these characteristics ensure excellent centering of the needle 6 on the x'x spinning axis because the guiding of the needle takes place only in front of the abutment 74 and over a very long length equal to minus 3L, the shim 8 being furthermore placed at a short distance from the x'x axis and centered thereon.

On the other hand, when the drill cylinder is placed inside the main piston, the guide length is rather reduced and the stops stop the advance then act on a crossbar placed at the follower, in front of the system. and must be spaced from each other by a distance at least equal to the width of the main cylinder. A slight misalignment of the shims may then cause a deflection torque on the nose of the needle. Such a risk is avoided thanks to the provisions according to the invention.

In addition, as indicated above, the centering of the needle is further promoted, according to the invention, by the use of the loading technique by clamping the billet, which allows for compact presses having a reduced length.

The successive stages of loading have been schematically represented in FIGS. 3 to 6.

FIG. 3 shows the step of placing, in the spinning axis, a billet 5 of spinning metal having a diameter d and a length that can vary slightly but is at most L.

To allow the loading of a billet, the length of the housing 31 of the container 3 must be at least equal to this maximum length L and its diameter d1 must be a little greater than the diameter d of the raw billet 5 whose profile is not not always regular. The follower 4 which penetrates inside the housing 31 of the container 3 must have a length l ₁ a little greater than L and carries a push grain of diameter slightly smaller than the diameter d ₁ of the housing 31 so as to leave a gap simply allowing the penetration of the follower 4 in the housing 31 reducing as much as possible the thickness of the liner which forms, during spinning, along the wall of the housing 31.

As noted above, this push grain is removed with the jacket at the end of the previous spinning operation. The follower is then constituted only of the rod 4 'support grain.

In the position of introduction of a new billet shown in Figure 3, the movable cross member 40 can be retracted to the maximum, the main piston 11 is fully retracted. The container 3 is also moved back as far as the stop on the movable cross member, so that its housing 31 is threaded onto the follower rod 4 '.

This arrangement allows to leave, between the front end of the rod 4 'and the die a free space 50 whose length must be only sufficient to allow the introduction of the new billet 5 by means of a loading device 55 , for example a shovel. In this rear position of the mobile crosspiece 40, the front end 41 of the follower rod 4 'must therefore be separated from the die 2 by a distance a little greater than the maximum length L of the billet 5 so as to leave , before and back the games necessary to the establishment of this one.

In this loading position, the distance between the die 2 and the movable cross member 40 must therefore be only slightly greater than twice the maximum length L of a billet. The spacing between the bed 20 carrying the die 2 and the fixed crosspiece 10 carrying the main cylinder 1 can be reduced to the maximum, which also reduces the possibility of deformation and misalignment of the various organs and, consequently, to favor their perfect centering on the x'x spinning axis.

FIG. 4 illustrates the step of threading the new billet 5 inside the container 3. The movable cross member 40 is first advanced so as to catch up by pinching the billet 5 between the die 2 and the front end 41 of the follower rod 4 '. For this, one can use either the main cylinder 1, or the auxiliary cylinders not shown operating the movable cross member 40, the main piston 11 simply following the movements thereof.

The billet 5 thus held tight between the rod 4 'and the die 2, remains perfectly centered on the x'x spinning axis and can be removed. loading then advance the container 3 by means of its auxiliary cylinders, to put on the billet 5.

To allow this threading, a certain clearance must exist between the side face 53 of the billet 5 and the inner face of the housing 31. The spinning only begins after removal of this game.

Therefore, before spinning, it must first compress the billet between the front face 41 of the follower rod 4 'and the die to completely fill the housing of the container.

On the other hand, it is also necessary, before spinning, to place the push grain on the follower rod 4 'without risk of off-centering the billet.

The compression of it is therefore done in two stages.

Firstly, the billet being pinched between the end 41 of the rod 4 'and the die 2, a first tamping is carried out by advancing the moving crosspiece 40, as shown in FIG. 5.

The thrust exerted must be simply sufficient to achieve an expansion of the billet which can be exerted symmetrically in all directions, as shown in Figure 5. After this first compression time, the side wall 53 of the billet therefore applies. regularly on the entire inner face of the housing 31.

The billet which has always remained perfectly centered on the spinning axis, is then maintained by the inner wall of the housing 31 and it is therefore possible to eliminate the clamping force by moving the moving crosspiece back into the position shown in FIG. 6 to remove the rod 4 'of the housing 31 leaving, between its end 41 and the rear face 32 of the container 3, sufficient space for the introduction of the thrust 42.

The moving crosspiece 40 is then advanced again to apply the thrust 42 on the billet and perform the second stage of the compression phase. With the push grain, the compression force exerted by the main cylinder 1 can be of the same order as that required for extrusion.

After this compression, the follower 4 is moved back a little to leave, behind the billet, a space necessary for its elongation during the drilling which is then carried out by means of the needle 6 pushed back by the cylinder 7. It can then proceed to spinning, the needle being stopped at the desired level by the stop 74.

In addition, since the piercing jack 7 is placed behind the main jack 1, the needle 6 and its control rod 62 form a guided assembly over a large length, of at least 3L in the central duct 60 and subjected only to forces applied behind the guide duct and in the axis thereof.

Finally, as we have seen, the advance of the needle 6 is stopped by the stop 74 and the shim 8 comprises at least two parts placed symmetrically and close to the x'x spinning axis, this makes it possible to avoid any parasitic effort on the needle at the moment of the stop.

Thus, the press according to the invention gathers a set of characteristics which cooperate with each other to ensure the centering of the needle on the axis of the die 2 during drilling and during spinning and thus obtain a perfect concentricity of the faces. internal 52 and external 51 of the 5 'spun product.

Of course, the arrangements which have just been described schematically can be subject to modifications or variations without departing from the scope of protection of the invention, in particular to adapt to the type of the press or the method spinning used.

Thus, in the embodiment shown in Figure 1, the control rod 62 of the needle abuts, in the forward position, on a support surface 15 which can be formed on a part integral with body of the main cylinder or attached directly to the foundation.

As we have seen, it is essential to provide a support face orthogonal to the x'x axis, at a distance as small as possible thereof and this bearing surface could therefore consist of just two shims 8 spaced symmetrically on both sides of the axis x'x.

Furthermore, the stop position of the abutment relative to the fixed bed 20 and the die 2 could be modified by easy to design means to adjust the exact position of the nose 61 of the needle 6 relative to the die 2.

In this case, however, the so-called stopped needle technique is used since the leading end 61 thereof remains at the die 2 during spinning. However, it is sometimes necessary to use the so-called needle technique in which it controls a advancement of the needle which enters the die as and when the progress of the 4 and the flow of the metal of the billet 5. To allow this advance, the wedges 8 can be eclipsable so as to have two positions, respectively a closed position of stopping the needle 6 in the start position of spinning shown in Figure 1 and an open position allowing the passage of the stop 74 to advance the needle 6 during spinning. For example, the abutment 74 and the bearing surface 8 could be provided with notches allowing, by rotation about the x'x spinning axis to pass from a closed stop position of the abutment 74 to a position open passage of it.

It should be noted that such an arrangement is particularly advantageous because it makes it possible to operate the same press, either with a stopped needle or with a needle.

Moreover, by allowing, during spinning, an advancement of the needle 6 pushed by the piercing cylinder 7, the force exerted by the latter is added to the extrusion force exerted by the main cylinder 1. Such an effect is not negligible since the effort required for drilling can be of the order of 500 tons, which can represent 10 to 15% of the extrusion force.

To allow the advancement of the needle during spinning, the piercing cylinder 7 must have a stroke of the order of 2 times the length of the billet after tamping since it must first control the drilling of the piercing. billet with an advance of the same length of the needle 6 relative to the follower 4 which is stopped, then a simultaneous advance of the follower 4 and the needle 6, substantially the same length.

Of course, because the drill cylinder 7 is placed behind the main cylinder 12 which is itself extended rearward, the length of the press is increased but, insofar as a compact press is used with loading by clamping the billet, the overall size of the press remains of the order of 7 times the maximum length L of a billet, since it is necessary to count, from the die 2, a length L for the loading space 50, 3L for the whole of the follower 4, the main cylinder 1 and its rear extension 13, once L for the displacement of the stop 74 during drilling and twice L for the stroke of the drilling cylinder 7.

Moreover, if one uses only the method of spinning with the needle stopped, the stroke of the piercing jack 7 can be reduced to once the length of the housing 31 and the size of the press from the bed base is then of the order of 6 times this length.

By way of example, FIG. 7 shows the assembly of a spinning press capable of operating, as required, as a stopped needle or a needle accompanied and provided, for this purpose, with means for adjusting the stop position and means for eclipsing the stop shown in greater detail in FIGS. 8, 9, 10.

FIG. 7 shows in perspective, with partial tearing, the assembly of a press according to the invention comprising, in a conventional manner a main jack 1 mounted on a fixed rear crossmember 10, a die 2 mounted on a front bed base 20, a container 3 mounted on a cross member 30 whose position can be adjusted by cylinders 35 and a movable cross member 40 carrying a spin follower 4 and actuated by auxiliary cylinders 45.

The piston 11 of the main cylinder 1 is extended rearwardly by a cylindrical sleeve 13 which passes through the bottom 14 of the body 12 of the cylinder.

Inside the assembly formed by the follower 4, the movable crosspiece 40, the piston 11 and its rear extension 13, is provided a passage duct centered on the spinning axis and in which is slidably mounted a rod of control 62 fixed, by its front end 62a, on a needle 6 of tube spinning, and its rear end 62b, on the rod 73 of the cylinder 7 for controlling the axial sliding of the needle 6.

In the embodiment shown in FIG. 7, the control rod comprises a rear part fixed on the rod 73 of the jack 7 and a front part forming a mandrel on which the needle 6 is screwed, the assembly being guided axially, at the front in the follower 4 and at the rear in the extension 13 of the piston 11.

According to the invention, the control cylinder 7 is placed at the rear of the main cylinder 1, in the spinning axis and, as shown in FIG. 8, it can be mounted on the rear part of a support frame 80, comprising two vertical uprights fixed to the foundation but, in addition, connected to the body of the main cylinder 1 by preloaded rods 81. The body 72 of the drilling cylinder 7 is thus maintained at a strictly constant distance from the die 2 , behind the main cylinder 1.

As has been indicated, the press shown in FIG. 7 is intended to function, either as a stopped needle or as an accompanied needle. Therefore, the stroke of the piercing cylinder 7 must be about 2L and the stop 74 mounted on the control rod 62 must be able to move at least the length L inside the frame 80, before to be stopped by the shim 8 which, in this arrangement, is mounted at the front of the frame 80.

In the preferred embodiment shown in FIGS. 7 to 11, the abutment 74 has the shape of a tubular sleeve internally threaded so as to constitute a nut which, by rotation about the x'x axis, is screwed onto a thread Conjugate 63 formed on the outer face of the control rod 62. As a result, a rotation about its axis of the nut 74 allows it to move axially along the rod 62 which is locked in rotation.

For this purpose, the outer face 75 of the nut 74 is provided along its entire length, with a toothing 75 parallel to the axis x'x, on which meshes with a pinion 82 rotated in one direction or in one direction. the other, by a motor 83 fixed on a corresponding platform of the auxiliary frame 9 and the latter is slidably mounted parallel to the x'x axis of spinning, inside the fixed frame 80, and is connected to the control rod 62 so as to move therewith under the action of the cylinder 7.

Thus, the rotation of the pinion 82 which meshes with the toothing 75 with the possibility of axial sliding, controls the rotation around its axis of the nut 74 which moves axially, in one direction or the other, along the rod. 62 locked in rotation.

Of course, other means for controlling the axial adjustment of the stop 74 could be imagined.

Figures 7 and 8 show the relative positions of the different organs before drilling. Drilling cylinder 7 is fully retracted. The billet 5 is inside the housing of the container 3 and has undergone a first tamping to allow the recoil of the movable cross member 40 and the installation of the new thrust 42.

It is then possible to drill the billet by advancing the needle 6, by means of the cylinder 7, until the stop 74 rests on the shim 8 mounted on the front portion of the frame 81 and maintained, therefore , at a constant distance from the bottom 14 of the main cylinder 1, by the tie rods 81.

In the embodiment shown in FIGS. 8 to 11, this wedge is constituted by a fork-shaped plate 8 mounted vertically sliding along the front upright of frame 80 and provided with an indentation 84 facing downwards and having a width equal to the diameter of the control rod 62. By vertical displacement of the fork 8 by means of a jack 85, the notch 84 is to cap the control rod 62 and then opposes the passage of the stop 74 whose axial position along the rod 62, can be adjusted by means of the motor 83, as indicated above. This stopping position on the wedge 8 thus determines the level of the end 61 of the needle 6 relative to the die 2, at the time of stopping.

The spinning can then begin by actuating the main jack 1 which pushes the follower 4.

In the so-called stopped needle technique, the needle 6 is held in this position by the wedge 8, the jack 7 being locked so as to maintain the position of the stop 74 and, therefore, of the nose 61 of the needle 6 compared to die 2.

On the other hand, in the technique known as the accompanied needle, the shim 8 is raised by the jack 85 and allows the passage of the nut-shaped stop 74. The jack 7 is then fed to advance the needle 6 same time as the follower 4 and its effect is added, thus, to that of the main cylinder 1.

Of course, the invention is not limited to the details of the embodiment which has just been described as a simple example but also covers the modifications and variants remaining in the same protective frame.

In particular, the press may be provided with certain auxiliary devices such as, for example, a cooling circuit 64 formed in the axis of the needle 6 and the control rod 62 and, if appropriate, a rotation device of the needle around its axis for the extrusion of products having a particular section.

Indeed, as indicated above, the die 2 and the needle 6 usually have concentric circular profiles but it is also possible to spin products having an external profile and / or a non-circular internal profile. In this case, it is often necessary to have the possibility of adjusting the orientation of the internal profile relative to the external profile. It is why, in the embodiment shown in Figures 6 to 9, the sliding carriage 9 for supporting the motor 83 for adjusting the stop 74 carries a bearing 90 of centering of the front end of the piston rod 73 of the cylinder of drilling 17, allowing rotation, around the axis x'x, of the assembly of the piston 73, the rod 62 and the needle 6.

The carriage 9 carries, on the other hand, a motor 91 for controlling the orientation of the piston 73 and the needle 6 by means of a pinion 92 connected by a chain 93 to a toothed wheel 94 integral in rotation of the piston rod 73.

The motor 91 thus makes it possible to accurately adjust, before drilling, the orientation of the needle 6 around the x'x spinning axis.

In addition, the orientation device being mounted on the sliding carriage 9, it is possible, if necessary, to change the orientation of the needle 6 during spinning.

In addition, other means could be used for adjusting the axial position of the stop.

For example, the rotation thereof could be controlled by an axially displaceable finger under the action of a jack and engaging in a helical groove formed on the outer face of the nut.

The reference signs inserted after the technical features mentioned in the claims, are intended only to facilitate the understanding of the latter and in no way limit the scope.

Claims (18)

1. A press for extruding tubes by the direct method from a metal billet 5, comprising, along an extruding axis x'x, a fixed rear crossbeam (10) and a front girder (20) spaced from one another by a constant distance, a die (2) mounted on the girder (20) and centred on the extruding axis (x'x), a container (3) fitted with a cylindrical housing (31) centred on the extruding axis (x'x) and having a diameter and a length (L) corresponding to the diameter and to the maximum length of a billet to be extruded, an extruding plunger (4) centred on the extruding axis, and formed of a rod having a front face (41) of diameter corresponding to that of the housing (31) of the container, a main actuator (1) having a body (12) and a piston (11) resting, respectively, backwards on the fixed crossbeam (10) and forwards on the plunger (4), for axial moving the plunger (4) between a rear position for inserting a metal billet (5) into the housing (31) of the container (3) and a front position wherein the extrusion is completed, after threading the plunger (4) into said housing, a tube extruding needle (6), centred on the extruding axis (x', x), a control actuator (7), being situated behind the main actuator (1) and centred on the extruding axis (x', x), with a fixed body (72) and a piston (71) connected to the needle (6) by a control rod (62) running axially through the body (12) and the piston (11) of the main actuator (1), the said piston (11) being extended to the rear, over a length at least equal to its travel, by a tubular portion (13) running tightly through the bottom (14) of the body (12) of the main actuator (1) characterised in that the needle (6) is mounted slindingly axially in the plunger (4) between a rear position for which the needle (6) is retracted completely inside the plunger (4) and a forward position for which the needle (6) extends cantilever over a length corresponding to that of the housing (31) running axially through the billet (5), in that said needle (6) makes with the control rod (62) a sliding assembly which is guided axially at least forwards on the plunger (4) and backwards on the rear extension of the piston (11) over a guiding length at least equal to three times the length of the housing (31) of the container (3) and in that, in the rear position of the plunger (4), the front face (41) of the latter is separated from the die (2) by a loading space (50) of length at least equal to that of the housing (31), the container (3) being shiftable axially between a rear position for loading a billet into said space (50), for which the housing (31) is threaded on the plunger (4) and a forward resting position on the die (2) after threading the housing (31) on the billet (5) clamped between the die (2) and the front face (41) of the plunger (4).
2. An extruding press according to claim 1, characterised in that the body (72) of the actuator (7) controlling the needle (6) has a length corresponding to a travel of the main actuator (1) of the order of one time the length (L) of the housing (31) of the container (3).
3. An extruding press according to claim 2, characterised in that the whole press, including the actuator (7) controlling the needle (6), extends over a total length of the order of six times the length (L) of the housing (31).
4. An extruding press according to claim 1, characterised in that the body (72) of the actuator (7) controlling the needle (6) has a length corresponding to a travel of the main actuator (1) of the order of twice the length (L) of the housing (31) of the container (3).
5. An extruding press according to claim 4, characterised in that the whole press, including the actuator (7) controlling the needle (6), extends over a total length of the order of seven times the length (L) of the housing (31).
6. An extruding press according to any one of the previous claims, characterised in that the control rod (62) is associated with a stop (74) centred on the extruding axis (x',x) and bearing, in the front position of the needle (6), on a fixed chock (8) situated at the rear of the fixed crossbeam (1) and providing at least two resting points spaced from one another from the extruding axis (x',x), at a short distance therefrom.
7. An extruding press according to claim 6, characterised in that the stop (74) associated with the control rod (62) of the needle (6) bears, in the front position of the needle (6), on a fixed chock (8) situated at a distance of the order one time of the length (L) of the housing (31) of the container (3), behind the body (12) of the main actuator (1).
8. An extruding press according to one of claims 6 and 7, characterised in that the stop (74) associated with the rod (62) controlling the needle (6) has an annular shape and bears on a fixed chock (8) formed of a circular supporting surface surrounding at least partially the extruding axis (x',x), at a short distance therefrom.
9. An extruding press according to one of claims 6 to 8, characterised in that the stop (74) associated with the control rod (62) of the needle (6) bears on a retractable chock (8) having two positions, respectively a closed, latching position of the stop (74) and an open, let-through position of the stop (74), enable to advance the needle (6) with the plunger (4), as the billet (5) is being extruded.
10. An extruding press according to claim 9, characterised in that the retractable chock is formed of a plate (8) in the form of a fork, fitted with a recess (84) of the same width as that of the control rod (62) of the needle (6) and associated with a means (85) controlling the sliding motion thereof between two positions, respectively an opening position, spaced from the control rod (62) and enabling the axial sliding motion thereof, and a closing position for which the plate (8) in the form of a fork caps the control rod (62) in order to oppose the sliding motion thereof in a latching position of the stop (74).
11. An extruding press according to one of claims 6 to 10, characterised in that the actuator (7) controlling the needle (6) and the latching chock (8) thereof are mounted on a fixed chassis (80) situated behind the body (12) of the main actuator (1) and interconnected axially therewith.
12. An extruding press according to one of claims 6 to 11, characterised in that the bearing position of the stop (74) on the fixed chock (8) is adjustable axially to enable adjustment of the level of the front end (61) of the needle (6) with respect to the die (2).
13. An extruding press according to claim 12, characterised in that the latching stop (74) is formed of a nut screwed on an external thread (63) of the control rod (62) and whereof the position along thereof may be adjusted by rotating the nut (75) with respect to the control rod (62) locked in rotation.
14. An extruding press according to claim 13, characterised in that the latching stop is formed of a nut (74) in the form of a tubular sheath having a length at least equal to the axial adjustment margin of the stop (74).
15. An extruding press according to claim 14, characterised in that the stop (74) in the form of a nut is fitted with an external toothing (75) with teeth parallel to the axis x'x of the control rod, meshed with a toothed pinion (82) driven into rotation by a motor (83) carried by an auxiliary chassis (9) mounted slidingly parallel to the extruding axis x'x and connected to the control rod (62) in order to move axially therewith under the action of the piercing actuator (7).
16. An extruding press according to one of the previous claims, characterised in that it includes a means (94) controlling the rotation of the control rod (62) with the needle (6) around the extruding axis x'x, for adjusting the orientation of the front end (61) of the needle with respect to the die (2).
17. A method for extruding tubes by the direct method from a metal billet (5), in an extruding press comprising, along an extruding axis x'x, a fixed rear crossbeam (10) and a front girder (20) spaced from one another by a constant distance, a die (2) mounted on the girder (20) and centred on the extruding axis (x'x), a container (3) fitted with a cylindrical housing (31) centred on the extruding axis (x'x) and having a diameter and a length (L) corresponding to the diameter and to the maximum length of a billet to be extruded, an extruding plunger (4) centred on the extruding axis, and formed of a rod having a front face (41) of diameter corresponding to that of the housing (31) of the container, a main actuator (1) having a body (12) and a piston (11) resting, respectively, backwards on the fixed crossbeam (10) and forwards on the plunger (4) for axial moving the latter between a rear position for inserting a metal billet (5) in the housing (31) of the container (3) and a front position wherein the extrusion is completed, after threading the plunger (4) into said housing, a tube extruding needle (6), centred on the extruding axis (x', x) and mounted slidingly axially in the plunger (4) and an actuator (7) controlling the sliding motion of the needle (6) between a rear position for which the needle (6) is retracted completely in the plunger (4) and a forward position for which the needle (6) running axially through the billet (5), extends cantilever over a length corresponding to that of the housing, said control actuator (7) being situated behind the main actuator (1) and centred on the extruding axis (x',x), with a fixed body (72) and a piston (71) connected to the needle (6) by a control rod (62), running axially through, the body (12) and the piston (11) of the main actuator (1), said piston (11) being extended backwards by a tubular portion (13) running tightly through the bottom (14) of the body (12) of the main actuator (1), characterised in that the control rod (62) is guided axially, over a length at least equal to twice the length (L) of the housing (31) in a conduit provided inside the main piston (11) and the tubular extension thereof (13), in that in the rear position of the plunger (4) for inserting a billet (5), the front face (41) of the plunger (4) is separated from the die (2) by a loading space (50) of length at least equal to that of a billet (5), the container (3) being shiftable axially between a rear position for loading a billet into said space (50), for which the housing (31) is threaded on the plunger (4) and a forward resting position on the die (2) after threading the housing (31) on the billet (5) clamped between the die (2) and the front face (41) of the plunger (4) by advancing the latter and, in that in said front position of the container (5), the plunger (4) is fed forward in order to cause a shrink with expansion in all directions of the billet (5) which fills the housing (31) completely while resting evenly over its whole periphery, so that, when piercing the billet (5) by feeding the needle (6) until it stops in its front, extruding position, the needle (6) is guided axially, at least at the front by the plunger (4) and at the rear by the extension (13) of the piston (11), over a length of at least three times the length (L) of the housing (31) and thus remains perfectly centred on the extruding axis (x'x).
18. A method for extruding tubes according to claim 17, wherein the plunger (4) includes a rod (4') carrying a dummy block (42) which is placed before extruding a billet, characterised in that it includes the following steps:

    - placing a billet (5) between the die (2) and the front face of the rod (4') of the plunger whereon the container (3) is threaded, and centring the billet (5) on the extruding axis (x'x);

    - clamping the billet (5) between the die (2) and the rod (4') of the plunger;

    - feeding the container (3) for threading the housing (31) on the billet (5),

    - first compression phase of the billet (5) with expansion and symmetrical application of its lateral face (53) on the internal wall of the housing (31) ;

    - retracting the rod (4') of the plunger outside the housing (31) and placing a dummy block (42);

    - feeding the plunger (4) for a second compression phase of the billet (5) between the die (2) and the dummy block (42);

    - retracting the plunger (4) for leaving an extension space between the dummy block (42) and the rear face of the billet (5);

    - feeding the needle (6) for piercing the billet;

    - feeding the plunger (4) for extruding the billet (5).

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