MX2008005725A - Mandrel used for digital printing on can members - Google Patents

Abstract

Disclosed is a mandrel for a rotationally symmetric hollow member embodied as a beverage can that is monolithically composed of a body and a bottom. The aim of the invention is to transmit accurate coupling and precise controlling of the movement of the mandrel to the hollow member. Said aim is achieved by providing several clamping segments (2;2a, 2b, 2c) that form an outward-facing cylindrical clamping area (16) so as to grip an internal surface of the hollow member. The clamping segments are guided in a radially movable manner. A force transmitting mechanism (10, 13) that is arranged inside the mandrel (1) is used for synchronously controlling the radial movement of the clamping segments (2) such that a hollow member which is clamped by the clamping device can be accurately moved in a controlled fashion.

Description

MANDRIL FOR DIGITAL PRINTING IN CAN BODIES DESCRIPTION OF THE INVENTION A method and a fixing device for precisely housing and fixing hollow bodies for the realization of controlled precision movements is proposed. It is sought to achieve that the position of the hollow body can be controlled with sufficient accuracy to allow a digital impression on the external surface of the hollow body wall with great precision. Digital printing (digital printing) replaces the application of color and decoration practiced, until now, by a screen printing method on the external face of the hollow body. The invention relates to a cylindrical fixing device for hollow bodies with rotational symmetry, in particular for cans consisting of a body and a floor, formed in one piece, generally with a dome-shaped domed floor. It is public knowledge that it is of extraordinary importance for processing (treatment), in particular the printing or decoration of the external surfaces of hollow bodies of this type an exactly controlled movement, generally step by step, in the manner of a rotation of the hollow body, for the precision and reliability of the "machining" of the external surface, cf. US-A 6,767,357 (Joe Finan) which relates to printing, but does not contain detailed information regarding a fixing device. US-A 3,960,073 (Rush) discloses a decorating device for cans consisting of a body and floor in one piece, which has a multiplicity of identical mandrels for the cans. Each mandrel has several fastening segments with a cylindrical outer surface which are guided in a radially movable manner synchronized, in each case, by radial guide pins and under preload by springs, disposed in the direction of the withdrawn radial position. Inside the mandrel there is provided a shaft that is axially displaceable in a controlled manner, whose axial movement is transformed through a first inclined surface in the shaft and second complementary inclined surfaces in a radial movement. The inclined surfaces are attached to the fastening segments. The axial displacement of the shaft is carried out by means of mechanical control elements which are located outside the mandrel and which are connected by means of intermediate elements corresponding to the shaft. On the front face of the mandrel, several conduit channels open, which can be connected at their other end to a source (pressure or vacuum) to hold the can in its precise axial position in the mandrel, or to eject the can from the mandrel. The fixing function of the mandrel is achieved and controlled separately in a purely mechanical way. For this purpose, many individual components are necessary that collaborate with each other and adjusted to each other; the pressure (overpressure or negative pressure) does not have a controlling role in this. To achieve the precision and reliability of the treatment of an external face of a fixed hollow body, in the sense of a machining, a coating, in particular also of a printing, and the above also at a high speed of rotation and treatment and / or change of the hollow body, is the technical objective of the claimed invention. This objective is achieved by means of a fixation device as "mandrel" having the features of claim 1, alternatively with each of the methods according to claim 11, 22 or claim 12. Additional mandrels are comprised by claim 20. The device Cylindrical fixing system is of a very simple construction. It consists of relatively few components that act together very quickly and accurately. The necessary travels of the displaced components are very small. Above all, a control of these components operates by means of overpressure or negative pressure in a very simple and reliable way. The hollow body is fastened in a large area and reliably, but also carefully, by the fixing segments of the cylindrical fixing device. This makes it possible to achieve a precisely controlled movement, generally step by step, in particular in a rotary mode, of the fixed hollow body. This is the basis of a reliable treatment of the external surface of the hollow body fixed, as an example, of its printing. The clamping and clamping forces act in a synchronized (uniform) fashion from inside the hollow body, in particular from the can, and in this way the mandrel and the can are combined in radial motion by a movement unit whose movement can be controlled with the maximum precision. It excludes any risk of permanent deformation of the can, as it occurs when holding it on the outside or only on the front face. The components and devices used for the controlled movement of the fastening elements are inside the mandrel. Particularly advantageous with regard to simplicity, time reversal and effectiveness are negative pressure and coupling on the hollow body (claim 2 and claim 3). On the one hand it is possible to apply and control negative pressure and overpressure inside the mandrel without great investment and with great precision and speed. On the other hand, the insertion, respectively, of ejection of the hollow body in the mandrel, respectively, from the mandrel without additional measures is achieved simultaneously. The floor of the hollow body is used in this connection in cooperation with the free front face of the mandrel in the manner of a valve element which automatically provides for the floor to rest on the front face of the mandrel when the can is inserted by negative pressure on the mandrel, the negative pressure begins to take effect to move the fixing segments radially outward, so that they rest under pressure on the inner wall of the can (claim 11, claim 12). The claimed method for the positioning in the precise position and for the precise controlled movement - preferably step by step - of hollow bodies with rotational symmetry "consisting of one piece" of body and floor (without joining by seaming in the floor region) , in particular beverage cans, also with a domed floor inwards, is made possible thanks to the exact fixing achieved. It is a fastening without risk of damage or deformation of the hollow body (claim 11, claim 12, claim 20).

The accuracy of the fixing can be illustrated in the sense that an equivalent accuracy of the motion transmission, which can be called "suitable for digital printing", is also achieved in this way. A rest position of the fixing device is achieved by a return force (claim 14). She returns the force transmission device to a resting position. This is appropriate, in any case, to compensate also fluctuating diameters of the hollow bodies that can be inserted in the mandrel with their fluctuating diameters. The coupling of the force in the can sucked and clamped, as an example of a thin-walled hollow body, is preferably improved in such a way that the mandrel has a front face which is adapted at least in the region of the mouth of the mouth. axial perforation to the shape of the floor of the can. A bulge in the form of a dome inwards (in the can) is domed in the form of a dome in the axial direction (in the mandrel). The mandrel has a shaft that is supported outside the mandrel together with a multiplicity of identical mandrels in a rotary head in indexed passages. At the end of the tree a controllable own drive is provided which works step by step. Axial drilling of the shaft can be connected to a source for higher or lower pressure. Both pressures are measured in relation to the normal pressure of the environment. The invention is described (explained and supplemented) below in more detail by means of the schematic figures 1 to 4 in several exemplary embodiments: Figure 1 shows a perspective view of a fixing device 1 as a mandrel according to a first example of the invention. Figure 2 schematically shows a side view of the mandrel at an enlarged scale. Figure 3 shows a schematic longitudinal section through the mandrel. Figure 4 shows a mandrel in section similar to figure 3, but listed rather in functional sense and on a larger scale. A can floor supported on the front face 7b is shown schematically. A fixing surface 16 itself of the fixing device as a mandrel 1 is formed by several segments 2a, 2b, 2c, etc. (briefly: 2), preferably configured in an identical manner, each having an external surface of a partial cylinder as fixing surface elements and which together form a cylindrical fixing surface 16. The fastening segments extend over the entire length of the fastening device 1 and are guided in a radial direction in a basic body of the fastening device. An example is the fixing surface element 2a 'which is associated with the fixing segment 2a. The analogous is true for the fixing segment 2c and the fixing surface element 2c '. The basic body consists of a central shaft 3 extending along the entire length of the fixing device and beyond one of its front ends, in which two front wall elements 6 and 7 are mounted at a corresponding axial distance, between which the fixing elements 2 extend. The front wall element 7 at the free front end f of the mandrel 1 has a cylindrical wall 11 which extends very deep into the mandrel. The shaft 100 clarifies the axis direction and the center of the fixing device. The shaft 3 has a through axial opening, for example, as a bore 4, which ends flush with the free end 5 of the shaft 3 and the external face 7a of the front wall element 7. At an axial distance from this end 5 and in the region of the cylindrical wall 11 the shaft 3 has a radial opening, for example, a hole 21, which is connected to the axial bore 4. A little further, in the axial direction, towards the inside of the mandrel is arranged, axially displaceable in a limited manner in the shaft 3, a disc-shaped wall 10 which is guided by an annular element 12 so as to seal and slide in the cylindrical wall 11. With the disc-shaped wall element 10, a control element or actuator with rotational symmetry is firmly attached. The wall has a sliding bearing in an opening, central cylindrical which can slide axially in the shaft 3. The mandrel 1 is carried by the tree 3 that is housed, on the outside of the mandrel, together with a multiplicity of equal mandrels in a rotary head in indexed steps (indicated on the right). in figure 1). At the end of the tree there is a controllable own drive that works step by step and is not shown. The axial bore 4 of the shaft can be connected in a controllable manner with a source for greater or lesser pressure that is also not shown. Both pressures are measured in comparison with the normal pressure of the environment. The overpressure is used to release a fixed can. The negative pressure, to suck and fix the can. The front wall element 7 of the basic body of the mandrel forms, together with the cylindrical wall 11 and the disk-shaped wall 10, a chamber 9 for a pressure or a vacuum (against ambient pressure). The control element 13 is located axially outside the pressure chamber 9, but forms together with the disk-shaped wall 10 a force transmission device which is explained in more detail below. The control element 13 (also referred to as the drive element) has an axial opening, v. gr. in the manner of a perforation 13a, whose diameter 14 is visibly greater than the external diameter d3 of the shaft 3. By means of bearing bushes 20 and 20 'the control element 13 is guided axially displaceable in the shaft and can carry and guide in this way, in turn, the wall 10 as the first disk control element 10. The second control element 13 has an external surface 19 with a slightly conical contour in the axial direction. As shown in Figure 3, the fixing segments 2 have on their internal face a conical surface 17, complementary, ie parallel to the surface 19, as an internal surface. This can also be provided in separate elements 15, but fixedly connected with the fastening elements. Each of these fixing wedges 15 is associated with a respective fixing segment. That is, the fixing wedge 15a with the fixing segment 2a, the fixing wedge 15c with the segment 2c. 15 designates all the fixing wedges (fastening elements), just as 2 designates all fastening segments 2a, 2b, 2c (and additional). In the conical gap between the opposing surfaces 17 and 19 there are disposed corresponding support and force transmission elements 18 which are fixedly connected to one of both elements 2 or 13. If the surface 19 has no interruption in its circumference, then the surface 17 is arranged in segments, as predetermined by the segments 2a, 2b, 2c, or the fixing wedges 15a, 15c. The fixing wedge 15c has, by way of example, the tapered segment segment surfaces 15c 'forming a section of the conical internal surface 17. The radial movement of the tension segments 2 is caused by negative pressure to fix and by overpressure to release the fixation. Both types of pressure act through the axial bore 4 of the shaft 3 (supplied, respectively, removed). The generating device for the respective pressure is not represented. Both pressures are used to place a hollow body with rotational symmetry, consisting of floor and body in one piece, for example, a beverage can (beverage can), axially above the mandrel and expel it from it. The floor of the can is used in this together with the external surface of the front wall element 7 to automatically drive the fixing movement of the fixing segments 2 only until the can has been properly inserted axially into the mandrel (completely) and start the ejection event only when the fixing segments have released the can correspondingly. An anterior external surface 7a of the front wall element 7 is configured in such a way that it has an annular contact in the form of a line or an area with the can of the can resting on it, that for the suction of air from outside through the vacuum applied from outside through the perforation 4, so that now the vacuum acts through the radial perforations 21 and the chamber 9 on the disc-shaped wall 10 and it moves this together with the control element 13 to the left in FIG. 3. By means of the jointly acting conical surfaces, all the control segments 2 are moved radially outwards in the event of an axial advance of the control element 13. The control element, therefore, drives the clamping segments 2a, 2b, 2c (and additional) together and outwardly synchronized. That is why it is also called drive element 13. A good coupling is achieved if the shape of the dome-shaped floor of the hollow body -which is not represented, but is public knowledge- is adjusted to the shape of the front face of the mandrel. This front face is the anterior external surface of the front front wall element. A concave / convex adaptation is appropriate. FIG. 3 shows, as an example, a flat frontal surface 7a having a phase 7b in the front wall element 7 on the circumference of its edge. The perforation 4 in the shaft 3 has a smaller diameter than a central section covering it in the front face of the domed internal domed floor of the hollow body, so that a seal is achieved in at least the circular edge anterior of the through hole, elongated in axial direction, when sucking the hollow body in the mandrel. The convex / concave adaptation referred to at least one inner region of the front wall 7a (domed internal to the right) and the external domed floor to the right of the hollow body is not shown separately in Figure 3, but the skilled person You can detach it from the explanation. The peripheral bevel 7b serves in this for a better adaptation of the initial insertion of the hollow body in the fixing device and to avoid a sharp edge in the cavity of the fixed can. When the hollow body is to be released from the mandrel 1, compressed air is then carried through the axial bore 4 to the chamber 9. This displaces the first / second control element 10 and 13 as an adjustment device axially towards the end of the shaft. (to the right) and releases the clamping force of the fixing segments 2. If this clamping force ends, then the compressed air acts through the front end of the hole 4 on the floor of the hollow body and thereby ejects it from the mandrel. A return movement of the adjusting device 10/13 can be achieved by means of a spring 40. This is disposed between the control element 13 and the front wall element 6. He achieves that the control element 13 is placed in a rest position, after ejecting the hollow body from the mandrel, the so-called zero position, and that it does not remain in a state of undefined axial position as an axial intermediate position. Thanks to this, the next hollow body can be inserted axially without problem. Fluctuations in the diameter of the hollow body due to tolerance are compensated.

Focused more on the functional aspect is figure 4. Its description can be derived from figure 3, with a tin floor being insulated with sealing effect in the anterior opening of the long perforation 4 of the tree 3. As the surface 7a The external front of the front wall element 7 makes a sealing effect on the floor of the wall that rests on it and stops the suction of air from outside through the perforation 4 of the negative pressure that prevails there, the pressure Negative Px now acts through the marginal perforations 21 to the chamber 9 and the adjustment device 10/13, which moves to the left. By means of the reciprocating conical surfaces 17/19, all of the fastening segments 2 synchronized radially outwardly move in an axial feed of the adjusting device 10/13. The mechanical fixation of the hollow body begins, therefore, only when the axial suction displacement has been completed. This is done by itself in a staggered manner and does not include critical dead times or needs that should be measured. A form of self-regulation of the fixing process is carried out, and this is controlled pneumatically. When the hollow body is to be separated from the mandrel 1 also in FIG. 4, then compressed air is introduced into the chamber 9. This displaces the adjustment device 10/13 axially towards the end of the shaft (to the right) and releases the force for securing the fixing segments 2 thanks to their synchronized radial inward movement. At the end of this radial clamping force on the wall of the can (not shown), then the compressed air also acts on itself on the floor, indicated schematically, and ejects it from the mandrel. The course of the fixation is designated in figure 4 with numbers enclosed in circles (1) to (3). (0) Suction / seal (1) Evacuate the chamber 9 (2) Axial adjustment of the adjustment device 10/13. (3) Radial displacement of the segments 2/15. The arrangement has a very simple structure and work, however, with great precision. The hollow bodies are grasped and held by the fixing segments from the inside over a large and reliable area, but also carefully. The necessary travels of the mandrel moving elements are small. The control by negative pressure and overpressure is simple and reliable, particularly in the automatic coupling of the conclusion of the event of axial suction of the hollow body and the beginning of the radial fixation of the fixing segments.

The hollow bodies and the mandrel form in the fastening position a functional unit that can be moved reliably by the controlled movement of the shaft 3 in any direction and with any amplitude of pitch and speed of passage. This relates in particular to the rotational movement for a treatment of the external surface of the hollow body, for example, printing or coating in the sense of an application process which must be controlled with high precision in terms of its position.

Claims (29)

1. Mandrel for a hollow body with rotational symmetry, in particular a beverage can consisting of body and floor in one piece, - having several fixing segments forming (together) a cylindrical fixing surface that shows out to contact an internal surface of the hollow body; the fixing elements being guided in this in a synchronized radial displaceable manner; - having a force transmission device disposed inside the mandrel for controlling a radial displacement of the fastening segments; -for a precise controlled movement of the fixed hollow body.

Mandrel according to claim 1, characterized in that the force transfer device for fixing can be operated by a negative pressure and to release by an overpressure.

Mandrel according to claim 2, characterized in that the two different types of pressure used for the control are simultaneously active in each case for positioning the hollow body on the mandrel, respectively, to eject the hollow body from the mandrel.

Mandrel according to one of the preceding claims, characterized in that a basic body is provided which has a rotatable rotary shaft, an axial bore opening into the free front face of the shaft and two front wall elements fixedly arranged at a distance axial in the tree, and possessing in this one of the front wall elements that is oriented in the operation of the mandrel towards the floor of the hollow body an axial external surface that ends flush with the front surface of the shaft.

Mandrel according to claim 1 or 4, characterized in that the force transmission device has a control element which is guided in an axially displaceable drive shaft.

6. Mandrel according to claim 5, characterized in that the control element is connected with one of its front faces fixedly with a disk-shaped wall that is guided in an axially displaceable manner as a basic body in the force transmission device, being able to apply compressed air to the wall in the form of a disc, controlled by a source of compressed air or a pressure in the axial perforation.

7. Mandrel according to claim 6, characterized in that the disk-shaped wall forms a limiting wall of a chamber that receives overpressure or negative pressure that is limited on the other side by a front wall element enlarged as a chamber.

8. Mandrel according to one of claims 2 to 7, characterized in that the shaft is housed outside the mandrel together with a multiplicity of equal mandrels in a head-rotary drive with indexed steps- and equipped at the end of each shaft with a controllable drive that works step by step, and each axial bore it can be connected in a controlled way to a source for increased or reduced pressure.

9. Mandrel according to one of claims 5 to 8, characterized in that the control element is guided in the shaft axially displaceable by means of sliding elements.

Mandrel according to one of claims 5 to 9, characterized in that each fastening segment has a conical inner surface in its axial direction or is fixedly connected to a fastening element having such an internal surface, the inner surface extending therein. conical parallel to a conical external surface of the control element, but at a distance from it.

11. Method for position-accurate positioning and for the precise controlled movement - preferably step by step - of hollow bodies with rotational symmetry, in particular of cans in a piece consisting of body and floor, with a respective hollow body being held in place its internal face with rotational symmetry essentially over its entire area, in particular by associated fastening surfaces by synchronized impulse by radially acting clamping forces or / and released by synchronized shutdown.

12. Method for positioning with precision of position and for the displacement of controlled precision - preferably step by step - of hollow bodies with rotation symmetry, formed in a piece of body and floor, with the help of a respective rotating mandrel for each hollow body, characterized in that according to the method - the respective hollow body is placed in the mandrel and positioned axially in this; - the hollow body is fixed constituting a unit of movement by a pressure force caused by the same negative pressure and acting radially inside out, this pressure force being applied in a synchronized manner by fixing segments moved by the same pressure negative out.

Method according to claim 12, characterized in that the mandrel and hollow body movement unit is separated with the aid of compressed air.

Method or mandrel according to one of the preceding claims, characterized in that a control element of the force transmission device is loaded by a return device which applies an axial force of a front face of the mandrel back axially.

Method or mandrel according to one of the preceding claims, characterized in that the return device is a spring which is under preload, preferably in the rest position withdrawn from the control element.

Method or mandrel according to one of the preceding claims 14 or 15, characterized in that the control element is returned by the axial force load after removing a hollow body from a mandrel in each case to a neutral rest position, which is positioned in such a way that hollow bodies with fluctuating diameter can be axially accommodated in the rest position in the mandrel.

17. Mandrel according to claim 1, characterized in that the force transmission device has an adjustment device that can be pneumatically operated.

18. Mandrel according to claim 4, characterized in that at least the front face of the shaft is curved inwardly, so that it adopts the shape of the hollow body floor.

19. Mandrel according to claim 7, characterized in that the chamber is connected to the axial bore of the shaft through at least one essentially radial bore in the shaft.

20. Fastening device for a hollow body with rotational symmetry that is closed at one end, comprising several fastening segments guided in a radially displaceable manner forming a cylindrical fixing surface facing outwards to make contact on an internal surface of the hollow body, -as well as, arranged in the fixing device, a force transmission device having a control element, guided in a pulsed shaft of the fixing device so that it can move in the axial direction, having a conical peripheral surface in the direction external axial for the transformation of an axial displacement of the control element in the shaft in a corresponding synchronized radial adjustment movement of the fastening segments equipped with corresponding conical internal surfaces, all fastening segments being moved in a synchronized manner; the control element being connected with one of its front surfaces fixedly with a disc-shaped wall, guided axially displaceable in the shaft of a pressure chamber arranged in the mandrel which can be controlled in a controlled manner with a source of compressed air or a source of negative pressure.

Method or mandrel according to one of the preceding claims, characterized in that they are suitable for fixing cans consisting of body and floor in one piece.

22. Method for the positioning with exact position and for the precision movement controlled preferably step by step- of hollow bodies with symmetry of rotation, formed of body and adjacent floor in one piece with the help of a mandrel moved in a controlled manner for each one of the hollow bodies, characterized in that in this method - the respective hollow body is placed by negative pressure in the mandrel and positioned axially thereon; - the hollow body is fixed by the same negative pressure in a synchronized manner by a pressure force that is radially current from the inside out, to form a unit of movement with the mandrel.

23. Mandrel according to claim 1 or 4, characterized in that a control element of the force transmission device is guided axially displaceable in the pulsed shaft, and an outer peripheral surface of the control element extends conically in the axial direction to cause , as a function of a relative axial displacement of the control element in the shaft, a corresponding radial synchronized adjustment movement of all the fastening segments, whereby the axial displacement is converted into a radial adjustment.

24. Mandrel according to claim 23, characterized in that the control element has rotational symmetry.

25. Mandrel according to claim 5 or 6, characterized in that the control element is fixedly connected with one of its front faces to a disk-shaped wall which is guided in an axially displaceable manner as the basic body in the force transmission device, the disc-shaped wall being able to load with negative pressure, controlled by a termination flush with the floor of the hollow body on a front surface of a tree.

Mandrel according to one of claims 1 or 5, characterized in that one or the control element is fixedly connected with one of its front sides to a disk-shaped wall which is axially displaceable as a basic body in the transmission device of the vehicle. force.

27. Mandrel according to one of claims 5 to 9, characterized in that each fastening segment is coupled in the region of its conical internal surface with sliding elements, slidably displaceable, the sliding elements being displaceable or with respect to the outer conical surface or in relation to the conical internal surface, and being fixedly connected with the respective other surface.

Method according to claim 11, characterized in that the fixing forces are released or / and applied by an overpressure and / or negative pressure caused by air flow.

29. Method according to claim 13, characterized in that the hollow body is withdrawn axially from the mandrel with the same compressed air.