Device for deep drawing cup-shaped workpieces

Abstract

Device for deep-drawing cup-shaped workpieces (10) in several deep-drawing processes to form cans, comprising several deep-drawing stations through which the workpieces (10) pass successively, wherein the deep-drawing stations each comprise a drawing core (14), an annular workpiece holder (16) surrounding the drawing core (14) and movable in the axial direction relative to the drawing core (14), and a drawing ring (18) surrounding the drawing core (14) and movable in the axial direction relative to the drawing core (14), so that the workpieces (10) are received in the deep-drawing stations with their opening facing downwards, wherein the outer cross-section, in particular the outer diameter, of the drawing core (14), the inner cross-section, in particular the inner diameter, of the workpiece holder (16), and the inner cross-section, in particular the inner diameter, of the drawing ring (18) decrease from one deep-drawing station to the next deep-drawing station, further comprising a drive device which is designed toin the deep-drawing stations, to displace the drawing ring (18) relative to the drawing core axially against the workpiece holder (16), so that the workpieces (10) experience a cross-sectional reduction, in particular a diameter reduction, and an increase in height during the deep-drawing draws in the deep-drawing stations, further comprising an ejection device which is designed to lift the workpieces upwards from the drawing core (14) after completion of a deep-drawing draw in a deep-drawing station, and comprising a transport device which is designed to transport the workpieces (10) successively from one deep-drawing station to the next deep-drawing station, wherein the transport device comprises grippers (22) which grip the workpieces (10) from the outside after ejection by the ejection device, characterized in that the ejection device is further designed toto lift the workpieces (10) upwards from the drawing core (14) after completion of a deep-drawing process so far that, after being gripped by the grippers (22), the edge of their opening is above a transport surface of the device arranged between the deep-drawing stations, so that the workpieces (10) are located at a distance above the transport surface during transport by the grippers (22).

Description

[0001] The invention relates to a device for deep-drawing cup-shaped workpieces in several deep-drawing lines to form cans, comprising several deep-drawing stations through which the workpieces pass successively, wherein the deep-drawing stations each comprise a drawing core, an annular workpiece holder surrounding the drawing core and movable in the axial direction relative to the drawing core, and a drawing ring surrounding the drawing core and movable in the axial direction relative to the drawing core, so that the workpieces are received in the deep-drawing stations with their opening facing downwards, wherein the outer cross-section, in particular the outer diameter, of the drawing core, the inner cross-section, in particular the inner diameter, of the workpiece holder and the inner cross-section, in particular the inner diameter, of the drawing ring decrease from one deep-drawing station to the next deep-drawing station, further comprising a drive device which is designed toin the deep-drawing stations, to displace the drawing ring relative to the drawing core axially against the workpiece holder, so that the workpieces undergo a cross-sectional reduction, in particular a diameter reduction, and an increase in height during the deep-drawing draws in the deep-drawing stations, further comprising an ejection device designed to lift the workpieces upwards from the drawing core after completion of a deep-drawing draw in a deep-drawing station, and comprising a transport device designed to transport the workpieces successively from one deep-drawing station to the next deep-drawing station and optionally to other stations, such as stations for base profile forming or trimming, wherein the transport device comprises grippers which grip the workpieces from the outside after ejection by the ejection device.

[0002] In deep-drawing presses, workpieces are formed into a predetermined shape using rigid tools. Frequently, several deep-drawing passes are carried out one after the other. In these passes, for example, starting from a round, flat sheet (round blank), successive cup-shaped workpieces of decreasing diameter and increasing height are drawn. The passes following the first deep-drawing pass are also referred to as re-drawing passes. If deep-drawing takes place in several deep-drawing passes, the device has several deep-drawing stations through which the workpieces pass successively. In the device in question here, the cup-shaped workpieces are placed with their opening facing downwards onto the upward-standing drawing core. The drawing core determines the cross-section of the workpiece after the deep-drawing pass has been completed. Before the deep-drawing pass, the cross-section of the workpiece is larger than that of the drawing core.By means of a workpiece holder which surrounds the drawing core in a ring and which can be flush with the top side of the drawing core before the start of the deep drawing, the workpiece is held securely in position on the drawing core and the workpiece holder surrounding it before the deep drawing begins. A drawing ring moves from above towards the drawing core and presses the workpiece holder downwards, deforming the workpiece accordingly. The workpiece is held between the drawing ring and the workpiece holder by an annular flange. After the deep drawing is complete, the drawing ring is lifted upwards away from the workpiece holder and the drawing core and the workpiece is also lifted upwards from the drawing core by means of an ejection device on the device. The ejection device can, for example, comprise the workpiece holder, which presses the workpiece upwards accordingly via the annular flange.

[0003] To transport the workpieces from one deep-drawing station to the next deep-drawing station, grippers are provided which grip the workpieces from the outside as they are lifted upwards from the drawing core. By moving the grippers sideways, the workpieces are transported to the next deep-drawing station, where a drawing core with a correspondingly smaller cross-section but longer cross-section further reduces the cross-section and increases the height of the workpiece in the next deep-drawing train. Between the deep-drawing stations there is a transport surface which can in particular surround openings of the various deep-drawing stations. During transport from one deep-drawing station to the next deep-drawing station using the grippers, the workpieces slide with the flange over the transport surface.Even beforehand, problems can arise due to the flange shape, for example when leaving the retightening tool if a protruding ring makes it impossible to leave the station by moving sideways.

[0004] Such devices have proven themselves in practice. In some applications, however, an irregular shape of the flange can occur, for example a crown formation or a so-called earing. The diameter of the workpiece holder is determined by the inside diameter of the draw station in front of it. The so-called reduction, i.e. the change in diameter of the workpiece from one deep drawing station to the next, is determined by the material properties, the material thickness and the final workpiece dimensions. If crown formation occurs, e.g. due to severe earing (anisotropy of the material) or due to different stretching of the material due to tool temperature-dependent friction coefficients of coatings such as foils, the flange material can protrude downwards in the axial direction of the cup-shaped workpiece. This effect has been observed, for example, in metallic materials coated with a foil instead of a paint.This can lead to problems when transporting workpieces between deep-drawing stations. In particular, irregular flange geometry can cause jamming when leaving a deep-drawing station, or it can cause jamming on the transport surface or openings of deep-drawing stations. This, in turn, can lead to production interruptions and scrap.

[0005] Based on the prior art explained above, the object of the invention is to provide a device of the type mentioned at the outset which ensures problem-free transport of the workpieces between the deep-drawing stations and the following stations even in the case of irregular flange shapes, in particular a crown formation.

[0006] The invention solves the problem by independent claim 1. Advantageous embodiments can be found in the dependent claims, the description and the figures.

[0007] For a device of the type mentioned at the outset, the invention achieves the object in that the ejection device is further designed to lift the workpieces upwards from the drawing core and the workpiece holder after completion of a deep-drawing process to such an extent that, after being gripped by the grippers, the workpieces are located with the edge of their opening above a transport surface of the device arranged between the deep-drawing stations, so that the workpieces are located at a distance above the transport surface during transport by the grippers.

[0008] The basic structure of the device according to the invention was explained at the beginning, so reference can be made to it. As also explained, a bowl-shaped workpiece, a so-called cup, can already be fed to the first deep-drawing station. So-called redraws then take place in the deep-drawing stations. The drawing core can also be referred to as a punch and the drawing ring as a drawing bell. The workpiece holder can also be referred to as a pleat holder, particularly since it prevents the workpiece from developing wrinkles during deep drawing and the associated reduction of the material. The inner cross-section or inner diameter of the workpiece holder almost corresponds to the outer cross-section or outer diameter of the drawing core. The outer cross-section or outer diameter of the workpiece holder corresponds to the inner cross-section or inner diameter of the workpiece before the deep-drawing process in the respective deep-drawing station.The workpiece holder and the drawing ring surround the drawing core at least temporarily during operation of the respective deep-drawing station. The relative mobility of the components of the device in the axial direction is understood in relation to the longitudinal axis of the annular workpiece holder or the drawing ring. The axial direction generally also corresponds to the longitudinal axis of the cylindrical, in particular circular-cylindrical, drawing core. During the deep-drawing process, the workpiece is placed downwards onto the workpiece holder and the drawing core, as explained at the beginning. The drawing ring is then pushed downwards against the workpiece holder, holding the workpiece between itself and the drawing ring in the area of ​​the workpiece flange. The drawing ring pushes the workpiece onto the drawing core. This results in the explained reduction in the cross-section or diameter and the increase in the height of the cup.In this way, the cross-section or diameter is successively reduced and the height increased in the deep-drawing stations through which the workpiece passes one after the other. The inner cross-section or inner diameter of the drawing ring therefore corresponds to the outer cross-section or outer diameter of the workpiece after the deep-drawing process in the respective deep-drawing station. Between an inner surface of the drawing ring and an outer surface of the drawing core, there is a small distance corresponding to the material thickness of the workpiece being machined. As already explained, the workpiece is held by the flange between the workpiece holder and the drawing ring during the deep-drawing process.

[0009] The deep-drawing stations of the device, as well as other stations such as stations for base profile forming and trimming, are arranged one behind the other. A transport surface is arranged between the stations and, if applicable, enclosing the stations or openings of the stations. In particular, it forms a horizontal plane. As already explained, in the devices concerned here, in which the workpieces are processed with their opening facing downwards, in the prior art the workpieces slide with their underside, in particular the flange surrounding their opening, over the transport surface from station to station. For this purpose, for example, two grippers each grip a workpiece from opposite sides. The grippers can be mechanically controlled, for example by a mechanical cam control. The device can also comprise a control device that controls the components of the device as described above and below.The workpieces finished in the device according to the invention can be used as cans, in particular food cans, such as beverage cans or canned goods.

[0010] In order to solve the problems of the prior art explained above, the ejection device is designed according to the invention to lift the workpieces upwards from the drawing core after completion of a deep-drawing draw so far that, after being gripped by the grippers, the edge of their opening, in particular the flange surrounding the opening, is located above the transport surface arranged between the deep-drawing stations. Accordingly, the workpieces are then located at a distance above the transport surface during transport by the grippers from one deep-drawing station to the next deep-drawing station. The sliding of the workpieces over the transport surface provided for in the prior art is avoided according to the invention. The workpiece is therefore lifted for transport before the grippers firmly grasp the respective workpiece for further transport.This reliably prevents any shape irregularities on the underside of the workpieces, particularly the flange, from causing problems when moving the workpiece out of a deep-drawing station and during transport from one deep-drawing station to the next deep-drawing station and to other stations. In particular, the jamming of the workpieces described above and the associated production interruptions are reliably avoided. In the next deep-drawing station, the workpieces can then be released from the grippers, as before, for example above an opening in the deep-drawing station, so that the workpieces fall downwards, for example due to gravity and guided by the grippers, which are initially slightly open.

[0011] According to the invention, it was recognized that as the temperature in the device increases during workpiece processing, the friction coefficient of the workpiece material, particularly of any foil applied thereto, changes. This, in turn, can be considered the cause of an irregular shape of the flange, for example, a downwardly protruding rim or so-called earing. This problem is solved in a simple manner according to the invention without the need for complex temperature control in the device.

[0012] According to one embodiment, the workpiece holder can be pre-tensioned upwards, in particular by spring means, so that the workpiece holder pushes the workpieces upwards after completion of a deep-drawing process and lifting of the drawing ring. The pre-tension also holds the workpiece securely between the workpiece holder and the drawing ring during the deep-drawing process. The pre-tensioning means, for example the spring means, of the workpiece holder can be part of the ejection device. For example, a main lift of the workpieces can be effected in this way after completion of the deep-drawing process. A further lifting of the workpieces can then also be effected by at least one other component of the ejection device. In particular, a combined effect of the pre-tensioning means and at least one other component of the ejection device takes place.

[0013] According to a further embodiment, the ejection device can comprise a compressed gas device that introduces compressed gas between the top of the drawing core and the bottom of the respective workpiece to eject the workpieces. The ejection device can be designed to lift the workpieces upwards from the drawing core by introducing the compressed gas so far that, after being gripped by the grippers, the edge of their opening is above the transport surface. In a particularly practical manner, the compressed gas can be compressed air. The compressed gas device can accordingly be a compressed air device. Due to the aforementioned embodiment, the ejection of the workpieces above the transport surface can be achieved in a particularly simple manner.

[0014] Alternatively or in addition to a compressed gas device, the ejection device can also comprise other devices for ejecting the workpieces. Examples include devices for generating a negative pressure or vacuum and / or for generating an air control, particularly in the drawing ring, and / or devices comprising a controlled ejector, particularly a mechanical ejector. Regardless of the type of ejection device, the workpiece flange, together with the transport device, particularly the grippers, ensures a defined vertical position of the workpiece.

[0015] According to a further embodiment, the grippers can be designed to initially grip the workpieces with some play after they have been lifted off the drawing core, and only grip them firmly after they have been lifted off the drawing core to the extent that the edge of the workpiece opening is above the transport surface. The grippers therefore do not initially grip the workpieces firmly, but rather only with some play such that the workpieces can still be moved within the grippers, in particular upwards. Only when the grippers have been raised sufficiently far above the transport surface do the grippers grip them firmly, thus preventing the workpieces from resting on the transport surface and sliding during further transport to the next deep-drawing station. The initial gripping with play secures the workpieces against unintentional lateral movement during further lifting.The flange of the workpiece can be forced to a defined height by the grippers through positive locking.

[0016] According to a further embodiment, the deep-drawing stations can be provided with a vacuum device designed to hold the workpieces in the deep-drawing stations to the drawing core and the workpiece holder surrounding it using vacuum. This achieves even better positional fixation of the workpieces for processing.

[0017] The workpieces may have a flange surrounding the opening of the workpiece, at least after the last deep-drawing pass. As already explained, this flange may exhibit shape deviations, such as a crown or so-called earing. Such shape deviations may extend downward from the flange plane, i.e., away from the workpiece body.

[0018] The workpieces can be made of a metal, especially sheet metal. Common metals for can production, for example, are aluminum or tinplate. The cans produced can be, for example, food cans, such as beverage cans or canned goods.

[0019] The workpieces can be coated with a film. As already explained, this advantageously eliminates the need for subsequent painting. The film is migration-resistant, meaning that plasticizers do not diffuse into the contents of the can. At the same time, the above-mentioned problems associated with such films regarding the flange geometry can be overcome by the invention.

[0020] The device according to the invention can comprise at least one workpiece, for example a plurality of workpieces.

[0021] The invention also relates to a method for deep-drawing cup-shaped workpieces in several deep-drawing processes to form cans, in particular beverage cans or food cans, in particular using a device according to the invention.

[0022] An embodiment of the invention is explained in more detail below with reference to the figures. They show schematically: Fig. 1 shows a part of a device according to the invention in a first operating position in a sectional view, Fig. 2 the representation from Fig. 1 in a second operating position, Fig. 3 the representation from Fig. 1 in a third operating position, Fig. 4 a cup-shaped workpiece machined in the device according to the invention in a perspective view from below.

[0023] Unless otherwise stated, the same reference symbols in the figures refer to the same objects.

[0024] In the Fig. 1 to 3, the function for deep-drawing a cup-shaped workpiece 10 (cup) is shown by way of example for a deep-drawing station of a device according to the invention. The device according to the invention has a plurality of such deep-drawing stations, which are arranged one after the other and through which the workpiece 10 passes successively. As explained above, during the deep-drawing operations in the individual deep-drawing stations, a cross-sectional reduction and an increase in the height of the workpiece 10 takes place, as will be explained below with reference to the Fig. 1 to 3 for one of the deep drawing stations.

[0025] The workpiece 10 consists, for example, of a metal such as aluminum or tinplate and can be coated with a foil. In the example shown, the workpiece 10 has a circular-cylindrical shape with a circular flange 12 surrounding the opening of the workpiece 10. Fig. 1 shows a circular cylindrical drawing core 14 of the deep drawing station, which is surrounded by a ring-shaped workpiece holder 16. The upper side of the workpiece holder 16 is flush with the upper side of the drawing core 14. The workpiece holder 16 can be clamped into the Fig. 1. The upper side formed jointly by the drawing core 14 and the workpiece holder 16 corresponds approximately to the inner surface of the bottom of the workpiece 10, so that the workpiece 10 can be clamped as shown in Fig. 1 is held in a fixed position by the drawing core 14 and the workpiece holder 16.

[0026] In Fig. 2, a drawing ring 18 can also be seen, which is used to achieve the Fig. 2 was pressed from above against the spring holder 16 by means of a drive device of the device and in the operating position shown in Fig. 2, also surrounds the drawing core 14. The workpiece holder 16 has been pressed downward against the preload during machining. During this deep-drawing process, the diameter of the workpiece 10 has been reduced and the height has been increased. Furthermore, it can be seen that the flange 12 of the workpiece 10, held between the workpiece holder 16 and the drawing ring 18, has a downwardly projecting material section 20 on its outer edge. This section may be irregularly shaped and was created during the deep-drawing process, in particular due to a change in the friction coefficient of the material of the workpiece 10.

[0027] In Fig. 4 shows an example of a correspondingly deep-drawn workpiece 10, wherein the downwardly projecting material section 20 can be seen on the flange 12. It is understood that the material section 20 in Fig. 4 is shown circumferentially and regularly for illustrative purposes. In practice, this can be irregularly shaped and / or only formed in sections over the circumference of the flange 12. In the prior art, the shape of the flange 12 makes it difficult to transport the workpiece 10 from one deep-drawing station to the next deep-drawing station or other stations, such as stations for base profile forming or trimming. For example, the openings of the deep-drawing stations that receive the drawing cores 14 and workpiece holders 16 are surrounded by a flat and horizontal transport surface over which the workpieces 10 slide in the prior art for transport from one deep-drawing station to the next deep-drawing station. The shape of the flange 12, in particular the downwardly projecting material section 20, makes this sliding more difficult and can lead to the workpieces 10 becoming caught and to a consequent production interruption.

[0028] In Fig. 3 shows the state of the workpiece 10 ejected from the deep-drawing station. After completion of the deep-drawing process, the workpiece 10 was lifted upwards from the drawing core 14. After the deep-drawing process has ended, the drawing ring 18 is first moved upwards, whereby the workpiece holder 16, driven by the pre-tensioning means, also moves upwards and thus, as part of the ejection device according to the invention, already largely lifts the workpiece 10 from the drawing core 14. In this case, the workpiece holder 16 again reaches the Fig. 1 shown position, as in Fig. 3 can be recognized.

[0029] Without further measures, the flange 12 would now rest on the workpiece holder 16, as in Fig. 3 for a flange without downwardly projecting material section 20 or rim at the reference number 12'. In order to avoid problems due to the downwardly projecting material section 20, the ejection device according to the invention further comprises a compressed air device which lifts the workpiece 10 further away from the drawing core 14 into the Fig. 3. The pneumatic device supplies compressed air into the opening of the workpiece 10, so that it is driven further upwards. At the same time, two grippers 22 from opposite sides of the workpiece 10 grip the workpiece 10 in the upwardly lifted position, as shown in Fig. 3. The workpiece 10 is then gripped by the grippers 22 in the Fig. 3 and can be transported to the next deep-drawing station by moving the grippers 22 above the transport surface. During this transport, the workpiece 10 is located with the flange 12 and in particular the downwardly projecting material section 20 at a distance above the transport surface. After reaching the next deep-drawing station, in particular a corresponding opening of the deep-drawing station, the grippers 22 can be released from the workpiece 10 so that the workpiece falls downwards, for example due to gravity, onto the drawing core and workpiece holder of the next deep-drawing station. The next deep-drawing draw can then be carried out in the next deep-drawing station.

[0030] It is possible that the grippers 22 grip the workpiece 10 with play after it has been lifted from the drawing core 14 by the workpiece holder 16, so that the workpiece 10 is guided laterally by the grippers 22 during the subsequent introduction of compressed air for further upward lifting. The grippers 22 are controlled, for example, by a mechanical cam control such that they only grip the workpiece 10 after reaching the Fig. 3 firmly in the position shown. List of reference symbols 10 Workpiece 12 Flange 12' flange without crown formation 14 drawing core 16 workpiece holders 18 drawing ring 20 Material section 22 grippers

Claims

[1] Device for deep-drawing cup-shaped workpieces (10) in several deep-drawing processes to form cans, comprising several deep-drawing stations through which the workpieces (10) pass successively, wherein the deep-drawing stations each comprise a drawing core (14), an annular workpiece holder (16) surrounding the drawing core (14) and movable in the axial direction relative to the drawing core (14), and a drawing ring (18) surrounding the drawing core (14) and movable in the axial direction relative to the drawing core (14), so that the workpieces (10) are received in the deep-drawing stations with their opening facing downwards, wherein the outer cross-section, in particular the outer diameter, of the drawing core (14), the inner cross-section, in particular the inner diameter, of the workpiece holder (16) and the inner cross-section, in particular the inner diameter, of the drawing ring (18) decrease from one deep-drawing station to the next deep-drawing station, further comprising a drive device which is designed toin the deep-drawing stations, to displace the drawing ring (18) relative to the drawing core axially against the workpiece holder (16), so that the workpieces (10) experience a cross-sectional reduction, in particular a diameter reduction, and an increase in height during the deep-drawing draws in the deep-drawing stations, further comprising an ejection device which is designed to lift the workpieces upwards from the drawing core (14) after completion of a deep-drawing draw in a deep-drawing station, and comprising a transport device which is designed to transport the workpieces (10) successively from one deep-drawing station to the next deep-drawing station, wherein the transport device comprises grippers (22) which grip the workpieces (10) from the outside after ejection by the ejection device, characterized bythat the ejection device is further designed to lift the workpieces (10) upwards from the drawing core (14) after completion of a deep-drawing process to such an extent that, after being gripped by the grippers (22), the edge of their opening is located above a transport surface of the device arranged between the deep-drawing stations, so that the workpieces (10) are located at a distance above the transport surface during transport by the grippers (22). [2] Device according to claim 1, characterized by that the workpiece holder (16) is pre-tensioned upwards, in particular by spring means, so that the workpiece holder (16) presses the workpieces (10) upwards after completion of a deep-drawing process. [3] Device according to one of the preceding claims, characterized bythat the ejection device comprises a compressed gas device which introduces compressed gas between the top of the drawing core (14) and the bottom of the workpieces (10) in order to eject the workpieces (10). [4] Device according to claim 3, characterized by that the ejection device is designed to lift the workpieces (10) upwards from the drawing core (14) by introducing the compressed gas so far that, after being gripped by the grippers (22), they are located with the edge of their opening above the transport surface. [5] Device according to one of claims 3 or 4, characterized by that the compressed gas is compressed air. [6] Device according to one of the preceding claims, characterized bythat the grippers are designed to initially grip workpieces (10) with play after they have been lifted off the drawing core (14), and only after they have been lifted off the drawing core (14) to grip them firmly to such an extent that the workpieces (10) are located with the edge of their opening above the transport surface. [7] Device according to one of the preceding claims, characterized by that the deep-drawing stations have a vacuum device which is designed to hold the workpieces in the deep-drawing stations by means of vacuum on the drawing core (14) and the workpiece holder (16) surrounding it. [8] Device according to one of the preceding claims, characterized by that the workpieces have a flange (12) surrounding the opening of the workpieces, at least after the last deep-drawing pull. [9] Device according to one of the preceding claims, characterized by that the workpieces (10) consist of a metal, in particular of a sheet metal. [10] Device according to one of the preceding claims, characterized by that the workpieces (10) have a film coating. [11] Device according to one of the preceding claims, characterized by that it further comprises at least one workpiece (10).

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