WO2010100119A1

WO2010100119A1 - Method and device for embossing a cylindrical hollow body

Info

Publication number: WO2010100119A1
Application number: PCT/EP2010/052573
Authority: WO
Inventors: Andre Wichelhaus
Original assignee: Imv Innovation Marketing Und Vertriebs Gmbh
Priority date: 2009-03-02
Filing date: 2010-03-01
Publication date: 2010-09-10
Also published as: DE102009011231B3

Abstract

Method and device for embossing a peripheral wall (1) of a cylindrical hollow body (2), especially of a beverage can. On the outer side of the rotating peripheral wall (1), at least one embossing projection (3A, 3B) is rolled in a predetermined region, preferably in incremental repetition, so that the embossing projection penetrates the predetermined region with a predetermined penetration depth, and thereby a recess (10) is formed into the outer side of the peripheral wall and an elevation (11) is formed on the inner side of the peripheral wall, the elevation being pressed into a filling material (5) made of an elastically compressible material which is pressed against the inner side of the peripheral wall (1) with a contact pressure.

Description

METHOD AND DEVICE FOR EMBOSSING A CYLINDRICAL HOLLOW BODY

The invention relates to a method and. device for embossing a circular-cylindrical peripheral wall of a hollow body, especially of a beverage can.

In the state of the art, two embossing rollers are used for embossing a thin web of material, interacting with each other on both sides of the material web and driven in opposite directions, one embossing roller of which comprising on its roller surface a plurality of embossing projections, whereas the other embossing roller being provided on its roller surface with recesses complementary to the embossing projections. When the web of material passes through the roller gap between the embossing rollers, the embossing projections are rolled on the web of material, so that the web of material is locally pressed into the respectively relating recesses of the other embossing roller.

Both embossing rollers which have the same diameter must be driven synchronously, so as to ensure that the projections on one embossing roller are capable of entering the related recesses of the other embossing roller exactly even after several revolutions of the embossing rollers. Moreover, the embossing recesses must be adapted precisely to the shape of the embossing projections if enlarged by the stretch thickness of the web of material, so as to be able to achieve a clear embossed pattern without too strong squeezings and without ruptures and cracks in the web of material. In addition, the achievable stretching degree or degree of deformation is limited. According to GB 339 346, opposed edges of material portions pre-embossed in such a manner can be connected to each other, so that a cylindrical hollow body with the pre- embossed embossed pattern is produced. In addition, several circumferential beads can be rolled into the peripheral wall of the hollow body. However, embossing methods of that type on pre-embossed material portions are not suitable for cylindrical hollow bodies, such as beverage cans, which are seamlessly brought from a planar material portion to a cylindrical shape in a deep-drawing process.

However, it is also known from US 3,452,695 to provide two interacting embossing rollers for embossing cylindrical hollow bodies, which have a smaller diameter than the internal diameter of the hollow body, one embossing roller of which being introduced eccentrically into the hollow body. For example, a pattern of longitudinal beads is to be embossed in the peripheral wall of the hollow body. For this purpose, the embossing rollers are formed as toothed wheels which are rolled on the inner side and on the outer side of the rotating peripheral wall in such a manner that each tooth of the outer toothed wheel penetrates the peripheral wall and locally forms it into a gap between the teeth of the internal toothed wheel. Even in such a case, the rotational speeds of the embossing rollers as well as the teeth and the tooth gaps have to fit each other closely, so as to avoid undesired squeezings and cracks especially in the case of a thin wall thickness of the peripheral wall. Moreover, such a method is limited in respect of the configuration possibilities of the patterns to be embossed, and the equipment effort for inserting and removing the internal embossing roller as well as for controlling and synchronizing the embossing rollers is high.

EP 0852972 Bl discloses methods and devices for embossing a hollow cylindrical peripheral wall of a can body of metal, wherein the peripheral wall includes alternating projecting portions and recessed portions on the outer side of the peripheral wall that are formed by introducing a radially expandable rubber cylinder into the can body and expanding the same into contact with the inner side of the can body, the expanded rubber cylinder including a plurality of recessed portions and projecting portions, wherein an outer embossing member with embossing projections is used to emboss respective peripheral portions of the peripheral wall into the recessed portions of the rubber cylinder.

Methods and devices for embossing a hollow-cylindrical peripheral wall of a hollow body are provided by the invention. The invention is preferably suited for embossing the peripheral wall of a beverage can. According to the invention, shaped elements consisting of recesses of different sizes and with variable, even extensive patterns can be embossed into the outer side of the hollow- cylindrical peripheral wall by means of an embossing roller. In this respect, the shaped elements can be made of font and/or figures and/or of other signs and symbols. In addition or as an alternative, it is, however, also possible to form differently configured recesses in the thin, circular-cylindrical peripheral wall, which may widely vary in size and/or shape, for example for stiffening the same. The total height of the hollow body may be occupied by the hollow-cylindrical peripheral wall. However, the invention may also be applied in an advantageous manner if the hollow-cylindrical peripheral wall extends along a partial portion of the height dimension of the hollow body.

According to the invention, an embossing roller is used on the roller surface of which at least one embossing projection is formed. Depending on the pattern to be generated, several embossing projections may be provided on the roller surface as well, which may be equal or different in shape and size. The peripheral wall is rotated around its circular cylinder axis. The at least one embossing projection of the rotatably driven embossing roller is rolled across a predetermined region of the outer side of the peripheral wall, so that the embossing projection penetrates the peripheral wall with a predetermined penetration depth and thereby deforms the same locally in the predetermined region in accordance with the shape and the radial height of the embossing projection. Thereby, a radial recess is formed in the outer side of the peripheral wall configured to be complementary to the penetrating portion of the embossing projection, and a corresponding radial elevation is formed on the inner side of the peripheral wall.

According to the invention, the predetermined region of the peripheral wall to be deformed by the embossing projection is not depressed into a pre-recessed portion of a supporting body within the hollow body. Instead, according to the present invention, the embossing pressure is received by a filling material of the hollow body made of an at least largely elastically compressible material which is pressed against the inner side of the peripheral wall with a predetermined contact pressure, so that the elevation which is formed on the inner side of the peripheral wall is reproduced complementarily as a recess in the elastically compressible material by elastically deforming the same. The elastically compressible material has a high compression degree, so that the local deformation of the predetermined wall region, which is created by the rolling of the embossing projection, results in a corresponding local deformation of the compressible material even in a case that it is already in a substantially compressed and elastically pre-tensioned state due to the contact pressure onto the peripheral wall.

The predetermined contact pressure is such that the peripheral wall of the hollow body is supported by the compressible material without a substantial co-deformation in the next adjacent surrounding portions of the peripheral wall around the recess formed by the embossing projection, and that thereby the local deformation of the peripheral wall complementary to the embossing projection is accompanied by a corresponding local reduction of the wall thickness of the peripheral wall as in the case of a conventional stretch drawing deformation process. In doing so, the wall of the generated recess is progressively supported by the elastically compressible material during the entire penetration process while the embossing projection is penetrating and is supported across the entire inner side of the wall of the recess depending on the progress of the deformation process. At the same time, the elastic material allows, due to its elastic compressibility, the formation of the recess in the peripheral wall by elastically forming a corresponding recess in the elastic material as a complementary reproduction of the elevation created on the inner side of the peripheral wall as long as it penetrates the material and remains penetrated. With the emersion of the elevation from the material, the local deformation thereof is undone due to the elasticity of the material.

Suitable materials for the elastically compressible material are at the skilled person's disposal. For example, a material used for damping springs may be used, such as a porous polyurethane material . The degree of compressibility of the material can be chosen by the person skilled in the art to suit the desired deformation degree of the peripheral wall .

By the invention, the penetration region of the peripheral wall which is increasingly deformed upon the rolling of the embossing projection due to the increasing penetration thereof into the peripheral wall is continuously supported by the elastic material during the entire deformation process and across the entire deformation region. This cannot be achieved by a counter- roller that includes pre-shaped recesses complementary to the embossing projections of the embossing roller, because in that case the complete counter-support of the deformation region can only take place once the embossing projection has entirely and complementarily penetrated the complementary recess of the counter-roller.

Hence, a continuously progressing deformation process can be achieved by the invention following the principle of a stretch formation without the substantial risk of local squeezings and ruptures of the material of the peripheral wall. It goes without saying that corners and edges of the embossing projection should be rounded. By the invention it is, in addition, not required to provide for a close adaptation of counter recesses in a counter-roller interacting complementarily with the embossing projections, and for an exact synchronization of the embossing roller with a counter-roller. Nevertheless it is possible to achieve by the invention that sufficiently contour-sharp embossings, such as those of letters and numbers and other signs are created even in the case of comparably flat embossing projections.

The filling material made of an elastically compressible material which is pressed against the inner side of the peripheral wall of the hollow body with a predetermined contact pressure may be provided by a cylindrical support body having a smaller diameter than the internal diameter of the hollow body. For this purpose, the support body may, for example, comprise a thick sheath made of an elastically compressible material and a radially extendible core, by which the sheath is radially and elastically pressed against the inner side of the peripheral wall continuously across the entire circumference of the peripheral wall or at least across the peripheral region which is to be deformed by the embossing process. The pressing surface of the filling material that is pressed against the inner side of the peripheral wall is un-profiled. The filling material shows a continuous and un-profiled pressing surface that is pressed against the inner surface of the peripheral wall so that the filling material becomes locally and progressively displaced in an elastic manner by the elevation of the peripheral wall that is progressively growing in the course of and corresponding to the penetration of the outer embossing projection into the outer surface of the peripheral wall.

Preferably, the contact pressure of the elastically compressible material is created by compressing the filling material in the axial direction of the hollow body, so that the material is bulged radially until a sufficient pressure against the inner side of the peripheral wall is achieved. Thereby, the power of the contact pressure can be set individually depending on the level of axial compression of the filling to suit, for example, the deformation degree when embossing is performed.

The invention also opens up the possibility to perform embossing in an incrementally progressive manner in several successive steps. This is especially achieved by the use of the elastically compressible material for supporting the peripheral wall to be embossed. Due to its elastic properties, the elastically compressible material adapts its deformation behavior to the progress of the respective deformation of the elevation created on the inner side of the wall, and hence to the deformation itself. Therefore, it is intended in an embodiment of the invention that, according to a first embodiment, the embossing projection is repeatedly rolled in several steps in and across the predetermined region of the peripheral wall for an incremental formation of the recess in and across the predetermined region of the peripheral wall, or that, according to a second embodiment, several embossing projections are rolled one after the other in and across the predetermined region of the peripheral wall.

By the repeated rolling of the embossing projection or by the rolling of several embossing projections one after the other, a change in the size and/or the shape of the respective recess can be achieved according to the invention from one step to the other. In particular, the respective recess which is formed by the embossing projection or by the embossing projections into the peripheral wall of the hollow body is formed into the predetermined region of the peripheral wall in several embossing steps in an incrementally progressive manner with a size increasing from one step to the other. Thereby, the stretching process in the wall of the recess can be adapted to the deformation ability of the material of the peripheral wall even in case of a comparably high degree of deformation, as in the case of stretch-drawing.

According to the first embodiment, the incremental increase in size of the recess can be realized by radially moving the embossing projection which is repeatedly rolled in the predetermined area in several steps closer towards the peripheral wall from step to step, so that the embossing projection radially penetrates the peripheral wall with a penetration depth increasing from one step to the other. In this regard, the embossing projection has a radial height that corresponds at least to the maximum penetration depth.

In this first embodiment of the invention, the embossing projection is pressed at most only across a partial height into the peripheral wall in a first embossing step by rolling it in the predetermined region of the peripheral wall, so that first a recess of a depth smaller than the final depth is formed into the peripheral wall, and so that there is a gap outside the embossing projection between the embossing roller and the peripheral wall of the hollow body which are provided with the same diameters. Then, in a second embossing step, the embossing roller is advanced radially towards the hollow body after the smaller recess has been formed, so that the distance between the embossing roller on which the embossing projection is formed and the peripheral wall of the hollow body is reduced, and thereby the embossing projection enters the smaller recess with an increased penetration depth following a full revolution of the embossing roller and further deepens the same.

If in this case the embossing projection is configured to taper in a direction radially outwards in its axial sections, the volume of the recess formed into the predetermined region increases from one step to the other as the penetration depth of the embossing projection increases from one step to the other.

In addition, the embossing projection may be rolled in the predetermined region of the peripheral wall to be offset by a circumferential dimension of the peripheral wall being predetermined from step to step, so that the recesses formed from step to step into the outer side of the peripheral wall intersect each other. Therefore, the recess formed in the first step is increased by the embossing projection only unilaterally in a second step. At the same time, the form of the recess which is now composed of two partial recesses offset with respect to each other changes as well. In the second step, the penetration depth of the embossing projection can be greater or smaller than in the first step or can remain constant in both steps.

If the embossing projection is to be rolled in the predetermined region of the peripheral wall to be offset by a circumferential dimension of the peripheral wall predetermined from step to step, the diameter of the embossing roller comprising the embossing projection may in a second step correspondingly be greater or smaller than the diameter of the hollow body. According to the second embodiment, in which several embossing projections are rolled in succession in the predetermined region of the peripheral wall, the same configuration possibilities exist for the incremental embossing of the corresponding recess as in the first embodiment, so that insofar reference can be made to the explanations made in respect of the first embodiment in this regard. However, it is not required in the second embodiment to perform, for example, the increase in the penetration depth of the projections by radially advancing the embossing roller, because the embossing projections can be formed in a different manner in the second embodiment. Therefore, the embossing projections may be configured for the incremental embossing in such a manner that the size of the embossing projections measured in the axial direction and/or in the circumferential direction of the peripheral wall increases from one step to the other. In this respect, their radial height may also increase from one step to the other, so that the penetration depth of the projections and preferably also their penetration volume increase from step to step as well. However, by a different configuration of the embossing projections it is also possible that the penetration volume of the embossing projections is gradually increased from one step to the other, although the radial height of the embossing projections remains equal or decreases from one step to the other.

Moreover, according to the second embodiment, the embossing projections may be configured to have a gradually varying shape in addition or as an alternative to their change in size. Furthermore, according to the second embodiment, the embossing projections may be rolled in the predetermined region of the peripheral wall to be offset by a predetermined circumferential dimension of the peripheral wall as illustrated above with respect to the first embodiment, so that the recesses formed into the peripheral wall by successive embossing projections intersect each other.

The embossing projections which are rolled one after the other in the predetermined region may be arranged on one or on several embossing rollers according to the second embodiment .

A device according to the invention for embossing a peripheral wall of a cylindrical hollow body, especially of a beverage can, can be provided with at least one rotatably driven first embossing roller comprising at least one first embossing projection on its roller surface, and with a rotatable clamping device in which the hollow body is clampable with its axis oriented in parallel to the axis of the embossing roller, so that it is co-rotated by the clamping device. The embossing roller is positioned radially outside the clamping device and may be adjustable in the radial direction, so that the embossing roller can be rolled on the peripheral wall of the clamped and rotating hollow body, and so that preferably the center distance between the rotational axis of the clamping device and thus of the hollow body on the one hand, and of the rotational axis of the embossing roller on the other hand, can be adjusted. Optionally or as an alternative, this adjustability of the center distance can be implemented by the clamping device being adjustable in the radial direction. In addition, a filling body made of an elastically compressible material is provided which can be inserted in the hollow body prior to or following the clamping of the hollow body in such a manner that the filling body is held to be pressed against the inner side of the peripheral wall of the hollow body with a predetermined radial contact pressure.

The hollow body clamped in the clamping device can be counter-supported in the embossing operation by a support roller rotatable in a driven or freewheeling manner, which is diametrically opposed to the embossing roller and supportingly engages with the outer side of the peripheral wall of the hollow body after the hollow body has been clamped.

An insertion device may be provided for inserting the filling body into the hollow body. A radially acting pressing device may be provided for pressing the filling body against the inner side of the peripheral wall, which is arranged on the insertion device or the clamping device and from which the for example annular filling body is radially extendible. Preferably, a compression device for axially compressing the filling body after insertion thereof in the interior space of the hollow body as well as a holding device are provided, by which the filling body is held in the compressed state. By axially compressing the filling body, the filling body is radially bulged and thereby pressed against the inner side of the hollow body with a predetermined contact pressure.

The clamping device and the embossing roller can be driven by means of a transmission and/or a control device in such a manner that the peripheral speeds of the clamped hollow body and of the embossing roller comply with each other in operation. By means of a control device it is also possible to control that the embossing roller is advanced radially towards the hollow body following the clamping thereof and is radially moved away by the clamping device after the embossing operation.

An incremental advancing of the embossing roller towards the clamping device may be provided for the above- described incremental embossing, which is controlled by the control device, so as to be able to gradually increase the penetration depth of the embossing projection into the peripheral wall .

It is also possible that the embossing roller comprises a second embossing projection which is greater than the first embossing projection and arranged on the first embossing roller at the same axial height as the first embossing projection and offset with respect to said embossing projection along the circumference of the embossing roller by a circumferential dimension which corresponds at least approximately to one circumferential length of the peripheral wall of the hollow body or an integral multiple of the circumferential length. In such a case, the embossing roller has a diameter which is at least twice as great as the circumferential length of the circular-cylindrical hollow body. Thereby, the embossing projections can gradually penetrate the same deformation site one after the other upon rotation of the embossing roller and of the hollow body, so as to gradually increase the penetration depth and/or the width and/or the shape of the recess depending on the difference in size of the embossing projections.

In addition or as an alternative to the above-described embodiment, at least one driven second embossing roller may be provided, comprising at least a first embossing projection which is greater than the first embossing projection of the first embossing roller and which is arranged at the same axial height on the second embossing roller as the first embossing projection of the first embossing roller is arranged thereon. In this respect, the first embossing roller and the second embossing roller are driven with such a phase shift that the first embossing projection of the second embossing roller can be rolled in the recess that has been formed by the first embossing projection of the first embossing roller into the peripheral wall of the hollow body.

In this embodiment, it is possible that the first and second embossing rollers simultaneously engage with different peripheral sites of the clamped hollow body. For this purpose, the support roller can, for example, be provided as a second embossing roller. It is, however, also possible to arrange the embossing rollers in a distributed manner on the circumference of a rotatable rotary table having several rotatable clamping devices for clamping several hollow bodies, so that the respective hollow body is transferred by the rotary table to the following embossing roller for incrementally increasing the recess after having embossed a first recess in the peripheral wall of the hollow body.

By means of a rotatable rotary table it is also possible to achieve that several hollow bodies being arranged to be distributed around the rotary table are processed simultaneously or one after the other by means of several embossing rollers, wherein the support roller can be allocated jointly to several embossing rollers.

Although the invention is mainly described and illustrated using the example of embossing one recess, several recesses of different size and extension may also be formed in one or several operation steps into the peripheral wall of the hollow body in a circumferential direction and/or an axial direction of the peripheral wall of the hollow body according to the invention, with a distribution that is regular or irregular; in this regard, it is also possible to apply the invention correspondingly to hollow bodies other than circular-cylindrical hollow bodies .

According to the invention, it is also possible to emboss annular recesses into the peripheral wall by using an annular embossing projection, whereby elevated regions might be obtained which are entirely or in part enclosed in an annular manner. Furthermore, a symbol recognizable as being elevated can, for example, be formed in the gap between two successive recesses.

It may also be advantageous in the embossing methods operating in an incrementally progressive manner with several embossing projections, to perform the successive steps in several processes and to exchange the embossing roller used in a first process with another embossing roller used in a successive second process.

The invention will hereinafter be explained by means of preferred embodiments which can be derived from the drawings at least schematically, in which:

Figure IA and Figure IB show a longitudinal section and a top view of an embodiment of a device according to the invention prior to the radial advancing of the embossing roller 3,

Figure 2A and Figure 2B show a longitudinal section and a top view of a device according to the invention during embossing, Figure 2C shows the detail C from Figure 2A in larger scale,

Figure 3A and Figure 3B show two details according to detail C in Figure 2A according to two incremental embossing steps,

Figure 4A to Figure 4D show a preparation stage and three successive incremental embossing steps by incrementally advancing the embossing roller 3 , and

Figure 5 shows a top view of a second embodiment of a device according to the invention with a rotary table 9 and several embossing rollers 3 arranged thereon in a distributed manner.

The device for embossing the peripheral wall of a cylindrical hollow body 2 in the form of a beverage can, shown in Figure 1 and in Figure 2, comprises a rotatably driven embossing roller 3 and a clamping device 4 rotatably driven in a rotation direction opposed to that of the embossing roller 3 for the hollow body 2. The hollow body 2 is clamped on the clamping device 4 with its axis by which at the same time the rotational axis of the clamping device 4 is formed to be oriented in parallel to the rotational axis of the embossing roller 3. The embossing roller 3 is positioned radially outside the clamping device 4 and is adjustable in its radial direction, so that the center distance between the rotational axis of the embossing roller 3 and the clamping device 4 and hence of the hollow body 2 is adjustable.

The embossing roller 3 can thereby be advanced towards the adjusting device 4 from its starting position which is shown in Figure IA and Figure IB and in which the embossing roller is arranged with its circumferential surface at a distance from the external circumferential surface of the hollow body 2, until the embossing roller 3 contacts the circumference of the hollow body with its circumference and is pressed against the circumference of the hollow body 2. This arrangement of the embossing roller 3 following the advancing thereof is shown in Figure 2A and in Figure 2B. The radial displacement of the embossing roller 3 can take place during rotation thereof. The rotational speeds of the embossing roller 3 and of the clamping device 4 are such or can be adjusted in such a manner that the peripheral speed of the embossing roller and that of the hollow body 2 are opposingly equal, and hence the embossing roller 3 with its embossing projections and the peripheral wall of the hollow body are rolled on each other with the required contact pressure.

In the hollow body 2, a filling body 5 is arranged which is made of an elastically compressible material. The arrow 8 in Figure IA and in Figure 2B represents a pressing device in the form of a compression device, by which the filling body 5 is axially compressed in the hollow body 2. Thereby, the filling body 5 is radially bulged out in the hollow body 2, whereby the filling body 5 is pressed against the inner side of the peripheral wall of the hollow body 2 with a radial contact pressure.

On the radial side of the clamped hollow body 2 opposed to the embossing roller 3 diametrically to the hollow body 2, a support roller 7 is disposed rotatably, by which the embossing pressure of the embossing roller 3 is counteracted. The support roller 7 is rolled by the rotation of the hollow body on the outside of the peripheral wall thereof; in this regard, it is possible to pivot-mount the support roller 7 in a freewheeling manner or to rotatably drive the same synchronously to the embossing roller 3 and the clamping device 4.

The embossing roller 3 comprises a pattern of embossing projections, one of which is shown in Figure 2C according to the detail indicated in Figure 2A. By rolling the embossing projection 3A on the peripheral wall 1 of the hollow body, a recess is formed into the peripheral wall 1, complementarily reproducing the embossing projection 3A. Depending on the deformation degree of the material of the peripheral wall 1, an elevation 11 is thereby formed on the inner side of the peripheral wall 1, which is pressed into the elastically compressible material of the filling body 5 in such a manner that the elevation 11 itself is reproduced complementarily in the elastically resilient material of the filling body 5 as a recess .

Figure 3A and Figure 3B serve to illustrate a method according to the invention, wherein the embossing of the peripheral wall 1 of the hollow body is carried out in an incrementally progressive way by rolling several embossing projections one after the other in the same predetermined region of the peripheral wall 1. According to Figure 3A, first an embossing projection 3A of a small size is rolled in this region, so that a small recess 10 is embossed in the peripheral wall 1 reproducing the embossing projection 3A, and so that a small elevation HA is correspondingly formed on the inner side of the peripheral wall 1, which is reproduced in the material of the filling body 5. Then, an axially larger embossing projection 3B is rolled in the same region according to Figure 3B, whereby the recess 10A is enlarged axially correspondingly, so that an axially larger recess 1OB is formed on the outer side of the peripheral wall, and a correspondingly axially larger elevation llB is formed on the inner side of the peripheral wall. Due to the fact that the material of the filling body 5 pressed against the inner side is elastically compressible, the deformed region of the peripheral wall 1 is continuously supported during the deformation according to its progress across the region of the elevation 11 and in its surroundings.

The embossing projections 3A and 3B can be provided to be offset on the same embossing roller 3 according to the circumferential length of the hollow body. However, it is also possible to form the embossing projections 3A and 3B on different embossing rollers 3 which are rolled off, offset in the circumferential direction of the hollow body on the peripheral wall 1 thereof. For example, the support roller 7 shown in Figure 1 and in Figure 2 may also be provided as embossing roller on which the second embossing projection 3B is formed.

Instead of providing several projections with a size differing in the axial direction and/or the circumferential direction, the projections may in addition or as an alternative even be different in their radial height, so that their penetration depth into the peripheral wall 1 is correspondingly different.

According to Figure 2C and Figure 3A and Figure 3B, the peripheral wall 1 is supported not only in the deformation region in which the embossing projection 3A penetrates the peripheral wall, but also outside said deformation region inside on the filling body 5 and outside on the embossing roller 3. However, due to the fact that the peripheral wall 1 is, due to the invention, supported on its inner side also outside the region by the elastically compressible material of the filling body 5, it is also possible to keep free a gap between the outside of the peripheral wall 1 and the circumferential surface of the embossing roller 3 in the region outside the embossing projection 3A, so that the penetration depth of the embossing projection 3A into the peripheral wall 1 is smaller than the radial height of the embossing projection. This can be used to carry out the embossing incrementally with a penetration depth of the embossing projection increasing from one step to the other, and hence with a stretch draw deformation of the wall of the embossed recess 10 increasing from one step to the other.

Such a method according to the invention, wherein the embossing of the peripheral wall 1 is also carried out in an incrementally progressive manner, wherein, however, the embossing projection 3A of the embossing roller 3 is rolled repeatedly and, in doing so, penetrates the peripheral wall 1 with a penetration depth increasing from one step to the other, is explained in Figures 4A to 4D. In this embodiment of the method, the embossing projection 3A is rolled on the peripheral wall 1 several times by several revolutions of the embossing roller 3, wherein the center distance between the rotational axis of the embossing roller 3 and the rotational axis of the hollow body is gradually reduced from revolution to revolution by an incrementally increasing advancement of the embossing roller.

In Figure 4A it is shown that the embossing roller 3 with its embossing projection 3A is initially arranged at a distance from the peripheral wall 1 of the hollow body, and that therefore, there is a gap 12 between the peripheral wall and the embossing roller 3 in the region outside the embossing projection 3A. Then, the embossing roller 3 is advanced towards the peripheral wall to such an extent that the embossing projection 3A first only penetrates the peripheral wall 1 by a small part of its radial height, and the gap between the peripheral wall 1 and the embossing roller 3 has decreased in the region outside the embossing projection to the gap 12A, as can be seen in Figure 4B. In the embodiment shown, said gap is reduced in a third step according to Figure 4C further to the gap 12B, until it has entirely disappeared in a fourth step according to Figure 4D. Therefore, the embossing projection 3A is rolled on the peripheral wall 1 during the steps according to Figures 4B to 4D with a penetration depth increasing from one step to the other.

The comparison of Figures 4B to 4D also reveals that the wall thickness of the peripheral wall 1 gradually decreases from one step to the other in the region of the embossed recess 10 and of the elevation 11 generated thereby due to the stretch draw deformation. This also results in that the radial height of the elevation 11 formed on the inner side of the peripheral wall is smaller than the depth of the recess 10 on the outer side of the peripheral wall 1 in accordance with the wall thickness of the peripheral wall 1 and the degree of the stretch draw deformation.

In the embodiment of the device shown in Figure 5, several embossing rollers 3 are arranged to be distributed on the circumference of a gradually rotatable rotary table 9. On the rotary table 9, several clamping devices 4 for hollow bodies 2 to be embossed are arranged to be driven rotatably, so that the hollow bodies 2 supplied to the rotary table 9 are processed by the embossing rollers 3 one after the other depending on the rotational position of the rotary table 9. A support roller 7 is rotatably arranged in the center of the round table, the diameter of which is so large that all hollow bodies 2 clamped on the clamping devices 4 are simultaneously supported by said support roller against the embossing pressures which are generated by each of the embossing rollers 3.

The embossing rollers 3 can be adjustable in their center distance with respect to the respective clamping device 4 individually or together, as indicated by the arrows allocated to the embossing rollers 3 on the right- hand side of Figure 5.

By means of the rotary table, it is therefore possible to emboss several hollow bodies 2 at the same time, for which purpose different embossing patterns may be embossed in the hollow bodies 2 as well, which are generated successively by several embossing rollers 3 following a corresponding rotational displacement of the rotary table 9.

Claims

1. Method for embossing a peripheral wall (1) of a cylindrical hollow body (2), especially of a beverage can, wherein the peripheral wall comprises a cylindrical outer side and a hollow-cylindrical inner side, in which method at least one embossing projection (3A, 3B) is rolled on the outer side of the rotating peripheral wall (1) in a predetermined region, so that the embossing projection penetrates the predetermined region with a predetermined penetration depth and a recess (10) is thereby formed in the outer side of the peripheral wall and an elevation (11) is formed on the inner side of the peripheral wall, wherein the elevation is pressed into a filling material (5) made of an elastically compressible material which is pressed against the inner side of the peripheral wall (1) by a predetermined contact pressure, so that a recessed portion is elastically formed into the filling material by the elevation as a complementary reproduction of the elevation during the formation of the same.

2. Method according to claim 1, wherein the contact pressure of the elastically compressible material is generated by compressing the filling material (5) of the elastically compressible material in the axial direction of the hollow body (2) until the filling material is pressed against the inner side of the peripheral wall (1) .

3. Method according to claim 1 or 2 , wherein the embossing is effected in an incrementally progressive manner by repeatedly rolling the embossing projection (3A) in the predetermined region of the peripheral wall (1) in several steps.

4. Method according to claim 3, wherein the embossing projection (3A) is provided to penetrate the predetermined region of the peripheral wall with a penetration depth increasing from one step to the other.

5. Method according to claim 3 or 4, wherein the embossing projection (3A) is rolled in the predetermined region to be offset by a circumferential dimension of the peripheral wall (1) predetermined from one step to the other, so that the recesses formed into the outer side of the peripheral wall from one step to the other intersect each other.

6. Method according to any of claims 1 to 5, wherein the embossing is effected in an incrementally progressive manner by rolling several embossing projections (3A, 3B) successively in several steps in the predetermined region.

7. Method according to claim 6, wherein the embossing projections (3A, 3B) are provided to have a different shape .

8. Method according to claim 6 or 7 , wherein the embossing projections (3A, 3B) are provided to have a different size.

9. Method according to any of claims 6 to 8, wherein the embossing projections (3A, 3B) are provided to penetrate the peripheral wall with a penetration depth increasing from one step to the other.

10. Method according to any of claims 6 to 9 , wherein the embossing projections {3A, 3B) are rolled in the predetermined region of the peripheral wall (1) to be offset by a circumferential dimension of the peripheral wall predetermined from one step to the other, so that the recesses formed into the outer side of the peripheral wall from one step to the other intersect each other.

11. Device for embossing a peripheral wall (1) of a cylindrical hollow body (2), especially of a beverage can, for carrying out the method according to claim 1, comprising at least one first rotatably driven embossing roller (3) having at least a first embossing projection

(3A) on its roller surface, a rotatable clamping device (4) in which the hollow body is clampable with its axis oriented in parallel to the axis of the embossing roller (3), the embossing roller (3) being arranged radially outside the clamping device (4) and is capable to be rolled on the cylindrical outer side of the clamped hollow body, so that the embossing projection penetrates into the peripheral wall with a predetermined penetration depth and a radial elevation is formed on the inner side of the peripheral wall, a filling body (5) made of an elastically compressible material and having an un-profiled outer pressing surface, a device (8) for radially pressing the un-profiled outer pressing surface of filling body against the inner side of the hollow body (2) , and a rotatable support roller (7) arranged on the side of the clamping device (4) which is diametrically opposed to the embossing roller (3) and engages with the outer side of the peripheral wall (1) of the hollow body following the clamping thereof, wherein the elastically compressible material is selected in such a manner that a recessed portion is elastically formed by the elevation into the outer pressing surface of the filling body as a complementary reproduction of the elevation during the formation of the same.

12. Device according to claim 11, wherein the pressing device (8) is formed as a compression device for axially compressing the filling body (5) following insertion thereof in the interior space of the filling body (2), the filling body being radially bulgeable by the axial compression and thereby pressable against the inner side of the hollow body with a predetermined contact pressure.

13. Device according to claim 11 or 12, wherein the first embossing roller (3) comprises a second embossing projection (3B) arranged on the first embossing roller at the same axial height as the first embossing projection (3A) and offset with respect to said embossing projection by a circumferential dimension corresponding at least approximately to one circumferential length of the peripheral wall (1) of the hollow body (2) or to an integral multiple of the circumferential length.

14. Device according to claim 13, wherein the second embossing projection (3B) is greater than the first embossing projection (3A) .

15. Device according to any of claims 11 to 14, wherein at least one driven second embossing roller (3) is provided comprising at least a first embossing projection (3B) which is greater than the first embossing projection (3A) of the first embossing roller and is arranged at the same axial height on the second embossing roller as the first embossing projection of the first embossing roll is arranged thereon, the first embossing roller and the second embossing roller being driven with such a phase shift that the first embossing projection of the second, embossing roller can be rolled in the recess (10) that has been formed in the peripheral wall of the hollow body by the first embossing projection of the first embossing roller.

16. Device according to claim 15, wherein the embossing rollers are arranged to be distributed on the circumference of a rotatable rotary table (9) with several rotatable clamping devices (4) for clamping several hollow bodies.

17. Device according to claim 16, wherein the support roller (7) is assigned jointly to the several embossing rollers (3) .

18. Device according to any of claims 11 to 17, wherein the support roller (7) itself is formed as an embossing roller.