Method for embossing products using a rotary embossing device

Abstract

Method for embossing products (2) with a rotary embossing device (10), wherein the rotation of at least one embossing roller (13) is controlled depending on a sensory detection of marks (26) on the products (2), wherein the embossing roller (13) is alternately rotated in a first and a second direction in accordance with a pendulum motion, the embossing roller (13) does not perform a full revolution during the pendulum motion, and the embossing roller (13) is rotated in the first direction during each embossing operation and in the second direction between embossing operations.

Description

[0001] The present invention relates to a method for embossing products with a rotary embossing device.

[0002] Folding boxes are packaging made of cardboard or corrugated board, and to a lesser extent plastic, which, depending on their design, are glued in one or more places during the folding process. They are usually produced from a single blank. The blanks are usually punched out using a die cutter. The blank must be glued along at least one edge. The folded boxes emerge from the folding-gluing machine lying flat. The box can be erected and filled mechanically or manually.

[0003] In addition to the folds required to produce the folding boxes, additional creasing lines are also pre-folded in the folding box gluing machine in preparation for the subsequent production step. This facilitates the assembly of the box and subsequent filling.

[0004] If the folding boxes are used to package medicinal products, it is required by law to print the name of the medicinal product in Braille on the folding box (e.g. by embossing).

[0005] According to the state of the art, the embossing of the Braille takes place either during the die-cutting process in the sheet-cutting machine when producing the blanks. However, this is complex because a die-cutting sheet contains several blanks, and a tool pair consisting of a female and male die must be provided for each blank. Alternatively, rotary embossing devices with two rotating embossing tools are used, which can be part of a folding box gluing machine, for example, as described in US 7,794,379 B2. In order to apply the embossing to the folding box blank in the correct position, the rotating tools must be synchronized relative to the folding box blank. In particular, when embossing Braille into the folding box blank, the synchronization must be very precise.Due to the mass moment of inertia of the die, the punch, and the rotary drive, the required synchronization accuracy is difficult or even impossible to achieve. Furthermore, production output is limited by the fact that the rotary stamping device cannot be adjusted to the size of the product being processed.

[0006] DE 10 2007 060 581 A1 describes a rotary embossing device in which the duration of a so-called asynchronous phase is determined by the extent of the embossing to be created and the speeds of the male and female dies. The distance between the male and female dies during the asynchronous phase allows the embossing dies of the male die to be positioned relative to the position of a surface of the folding box blank to be embossed, thus synchronizing them.

[0007] DE 10 2007 060 613 A1 describes a rotary embossing device in which the male die rolls on the folding box blank in the area of ​​an embossing segment only during the embossing process, thus embossing the blank. Before and after the embossing process, the male die is not in contact with the folding box blank. During this time window, also referred to as the asynchronous phase, the male die can be accelerated and decelerated again in order to synchronize, i.e., align, the embossing segment provided with the embossing dies relative to the position of a surface of a folding box blank to be embossed.

[0008] State-of-the-art embossing machines, which operate in a simple start-stop mode, cannot achieve sufficiently high production output and accuracy.

[0009] The invention is based on the object of providing a stamping method by which higher production output and accuracy can be achieved.

[0010] This object is achieved by a method having the features of claim 1. In the method according to the invention for embossing products using a rotary embossing device, marks are detected by means of at least one sensor, at least one of which is arranged on each product to be embossed. Based on the sensor signals, the rotation of at least one embossing roller is controlled.

[0011] The method according to the invention enables the products to be embossed to be transported through the embossing device in very rapid succession, thus achieving a comparatively high production output. Despite the high speed, the embossing can be placed very precisely on the products.

[0012] A non-contact sensor, such as an optical sensor, can be used as the sensor. The marks can be printed on the products or can be existing features on the products, such as product edges, such as the product's leading edge.

[0013] The products can be printed sheets, such as cardboard sheets, or folding box blanks. Embossing can be used to add braille to the products. The rotation of the embossing roller can be controlled so that it rotates irregularly. The embossing roller can be equipped with a die or a male die.

[0014] Further training is mentioned in the subclaims.

[0015] In a further development, the rotation of the embossing roller is controlled so that it rotates alternately in a first direction, e.g., clockwise, and in a second direction, e.g., counterclockwise. In this case, the embossing roller does not perform a rotation extending over a rotation angle of 360°. The embossing roller therefore performs a pendulum motion, rotating in the first direction during each embossing process and in the second direction between embossing processes.

[0016] In a further development, the products are transported one after the other in a chain or row past the embossing roller, with each product being provided with at least one embossing by the embossing roller. The embossing does not extend over the entire length of the product, but only over an embossed section. When the embossed section is opposite the embossing roller or moves past it, the embossing roller is rotated in the first direction. When the section of the product not to be embossed and / or a product gap between the successive products moves past the embossing roller, the roller is rotated in the second direction. The section not to be embossed, together with the product gap, forms a so-called embossing gap.

[0017] In a further development, the circumference of the embossing roller is divided into a first and a second circumferential section. Only the first circumferential section is equipped with tools, e.g., with punches or holes for embossing. The first circumferential section can also be referred to as the synchronous region or section. The second circumferential section is tool-free and can be referred to as the asynchronous region. If the first circumferential section extends over an angle of 120°, the second circumferential section extends over the remaining 240°. When passing through each embossing gap, the embossing roller rotates in the second direction up to a maximum limit angle. The limit angle corresponds to half the circumferential section length of the second circumferential section. If the circumferential section length of the second circumferential section is 240°, as in the example given above, the limit angle is 120°.Several synchronous areas and several asynchronous areas, which together amount to 360°, can also be distributed over this total circumferential length.

[0018] In a further development, a product gap is always present in the chain or row of products between the trailing edge of the leading product and the leading edge of the immediately following product. The size of this distance—the product gap—varies from product gap to product gap in the row.

[0019] In a further development, the rotation of the embossing roller is controlled by a control device in which motion curves or motion functions are stored or calculated. The motion functions differ from one another. The motion functions can differ from one another, for example, in terms of their function type.

[0020] In a further development advantageous for automation, a program running in a control device selects, e.g., calculates, the appropriate motion function for each product gap. Depending on the sensor signals, the control device or the program running within it selects a different motion function for the subsequent product gap than for the previous product gap.

[0021] Depending on the selected movement functions, the control device controls the rotation of the embossing roller during the passage of the previous product gap according to one movement function and during the passage of the subsequent product gap according to the other movement function.

[0022] In a further development advantageous for harmonic motion, the motion functions are polynomial functions of different orders, and the rotation of the embossing roller is controlled according to a lower-order polynomial function when passing through a product gap and according to a higher-order polynomial function when passing through another product gap. For example, the rotation of the embossing roller is controlled according to a fifth-order polynomial function when passing through the previous product gap and according to a seventh-order polynomial function when passing through the subsequent product gap.

[0023] In a further development, the aforementioned embossing roller cooperates with another embossing roller when embossing the products. According to one variant, the embossing roller can be a male roller and the other embossing roller a female roller, and according to another variant, the embossing roller can be a female roller and the other embossing roller a male roller. The synchronization of the rotations of the two embossing rollers with each other takes priority over the synchronization of the rotation of the embossing rollers with a transport movement of the products. When controlling the rotation of the embossing rollers, the control device takes into account that the synchronous running of the embossing rollers with each other is more important than the synchronous running of the embossing rollers relative to the transport movement of the products or product transport device. This means, for example:that during synchronisation, deviations in the position of the punches of the male roller and / or the holes of the female roller relative to the front edge of the product to be embossed are accepted if this is necessary to ensure that the punches fit or engage with the holes with sufficient precision.

[0024] The invention also includes a rotary embossing device with an electronic control device which contains a program for carrying out the method according to the invention or one of its further developments, as well as a folding box gluing machine equipped with such a rotary embossing device.

[0025] Further constructively and functionally advantageous developments of the invention will also become apparent from the following description of an embodiment and the associated drawings.

[0026] In this shows: Fig. 1 a folding box gluing machine, Fig. 2 a rotary embossing device of the folding box gluing machine in Fig. 1 and Fig. 3a+ Fig. 3b Diagrams of various motion functions for controlling the rotary embossing device in Fig. 2.

[0027] Fig. 1 shows a folding box gluing machine 1 with a rotary embossing device 10. Folding box blanks 2 forming products to be embossed are transported from a feeder in the transport direction T through the folding box gluing machine 1 and through the rotary embossing device 10 to a delivery unit. The rotary embossing device 10 has a first embossing roller 13 with a male die 11 and a second embossing roller 14 with a female die 12 for imparting embossing to the folding box blanks 2. The folding box blanks 2 are transported at a speed vF.

[0028] In the line of contact between male die 11 and folding box blank 2 during the embossing process, male die 11 has a speed vP. In the line of contact between female die 12 and folding box blank 2 during the embossing process, female die 12 has a speed vM. During the embossing process, the speeds of female die vM, male die vP, and folding box blank vF are the same, so that there are no relative movements between tools 11, 12 and folding box blank 2, thus avoiding markings on the folding box blank. For this purpose, male die 11 and female die 12 must be synchronized relative to one another with regard to their speed. Furthermore, the two embossing tools - male die 11 and female die 12 - must be synchronized relative to one another with regard to their angular position, i.e. it must be ensured that the punches 18 (cf. Fig. 2) the patrix 11 in holes 19 (cf. Fig. 2) of the die 12. If the male die 11 and the female die 12 each have their own stamping tool drive 20, 21, synchronization is electronic.

[0029] Fig. 2 shows that the rotary embossing device 10 comprises an electronic control device 28, which controls the first embossing tool drive 20 and the second embossing tool drive 21. A mark 26, e.g., a cross, is printed on each folding box blank 2, which can be detected by a sensor 27 of the control device 28. Based on the detected marks 26, the control device 28 can calculate the size of product gaps 22 between the folding box blanks 2. The first embossing roller 13 has a first circumferential section 29 and a second circumferential section 30. The embossing tools of the first embossing roller 13 are punches 18 and are arranged only within the first circumferential section 29. The development of the first circumferential section 29 corresponds to an embossing section 16 of the respective folding box blank 2. The embossing or embossings 23 are only introduced within the embossing section 16, the length of which is to be measured in the transport direction T.Embossing gaps 17 are located between the embossing sections 16 of the folding box blanks 2. The respective embossing gap 17 is the distance between the rear end of the embossing section 16 of the leading folding box blank 2 and the front end of the embossing section 16 of the trailing folding box blank 2. It is system-related that the size of the product gaps 22 varies from product gap 22 to subsequent product gap 22. For example, in . Fig. 2 the product gap 22 between the left folding box blank 2 and the middle folding box blank 2 is larger than the product gap 22 between the middle folding box blank 2 and the right folding box blank 2. Due to the system-related variation in the size of the product gaps 22, the size of the embossing gaps 17 also varies. In order to take this circumstance, the variation in the embossing gaps, into account and to ensure that the punches 18 cooperate with the holes 19 of the second embossing roller 14 at an exact angular position, the control device 28 controls the first embossing tool drive 20 in such a way that, in certain situations, when compensating between the movement of the second circumferential section 30 and the movement of the embossing gap 17, the first embossing roller drive 20 even moves the first embossing roller 13 back and forth in a pendulum movement 15. The second embossing tool drive 21 is also controlled accordingly, so that the second embossing roller 14 also executes a pendulum movement.A program P is stored in the control device 28, which carries out different movement functions 24, 25 (cf. . Fig. 3a and Fig. 3b), with the help of which the pendulum movement 15 is realized.

[0030] The Fig. 3a and Fig. The diagrams shown in Figure 3b show the angle of rotation of the first embossing roller 13 as a function of the so-called machine angle of the folding box gluing machine 1 or of the transport movement T of the transport device transporting the folding box blanks 2, which is not shown in detail. The two movement functions 24, 25, which are shown highly schematically, are polynomial functions, with polynomial function 24 having a different order than polynomial function 25. Polynomial function 24 can be a fifth-order polynomial function, and polynomial function 25 can be a seventh-order polynomial function.

[0031] The illustrated rotary embossing device 10 functions as follows: When setting up the machine, the embossing position and length are specified for each product. The distance between the front edge of the respective folding box blank 2 and the front end of the embossing section 16, as well as the length of the embossing section 16, is set. During operation, the embossing position is maintained with an accuracy of ± 1 millimeter by means of control via the marks 26. In control terms, the products (folding box blanks 2) form a so-called "master," and the embossing rollers 13, 14 form so-called "slaves." The control device 28 uses master-slave technology to precisely synchronize the embossing rollers 13, 14 - the slaves - to the passing product - the master - with mark control. After each embossing phase, the slaves move or rotate to their waiting position, preferably based on the master distance and not based on time.If, due to the rapid product sequence, the wait position is not reached until the arrival of the next product, the embossing rollers 13, 14 are resynchronized to the next product while in motion. The product sequence is variable, whereby the product length remains constant. Thus, the size of the product gap 22 is variable. The machine is highly productive and, with a production output of 100,000 folding box blanks per hour and a maximum production speed of 5 millimeters per millisecond, results in a cycle time of just 36 milliseconds. This cycle time can only be achieved with a certain ratio of the synchronous phase to the asynchronous phase. In this case, the slaves do not come to a standstill and immediately start resynchronizing after each synchronous phase. Synchronization takes place at the starting point of the synchronous operation without jerk.A control-related decoupling of the slaves after the synchronization phase of the last product to be embossed follows the same motion law as the coupling of the slaves to the master from a standstill of the slaves for the first product to be embossed. During decoupling, the motion profile for approaching the waiting position is defined via the master path using a polynomial calculation, with the polynomial calculation being executed by the control device 28 according to program P. If polynomial calculations are used as the motion functions 24, 25, particularly large product gaps 22 above a critical length may result in a backward rotation of the embossing rollers 13, 14, resulting in the pendulum movement 15 (reversing operation). This backward rotation is permissible up to a selectable limit value or critical angle.The limit value is half the difference between the circumferential length of the respective embossing roller 13, 14 and the length of the embossing section 16. The reverse rotation advantageously causes a lengthening of the path for the subsequent movement of the embossing rollers 13, 14 in the original direction. It is also possible that if product gaps 22 occur that exceed the critical length, the respective embossing roller 13, 14 temporarily remains in its waiting position.

[0032] More important than the synchronicity of the slaves relative to the master, and thus the placement of the embossing 23 on the respective folding box blank 2, is the synchronicity of the two slaves with each other. For example, if the two embossing rollers 13, 14 each have a diameter of 130 millimeters, they must be synchronized to within ± 0.2 millimeters, with this measurement being measurable along the roller circumference. Due to the different dynamic forces of the two embossing rollers 13, 14, a control-related cross-coupling of these two slaves or their embossing tool drives 20, 21 is required. The synchronous running deviation of one slave relative to the master is transmitted to the other slave by the control device 28, so that the latter follows said synchronous running deviation.For example, in extreme cases, the control device 28 controls one embossing tool drive 20, 21 relative to the other in such a way that when the rotation of one embossing roller is stopped, the rotation of the other embossing roller is also stopped with synchronous movement.

[0033] The advantages of the invention lie in a harmonious motion due to the asynchronous phase, which is adapted online to the measured product distance. A product-by-product recalculation of the applied curves (motion functions 24, 25) with high-order polynomials can preferably be performed in real time. A pendulum motion 15 of the embossing rollers 13, 14 occurs with a variable pendulum angle, which leads to a further reduction in dynamics. List of reference symbols 1 folding box gluing machine 2 folding box blanks 10 Rotary embossing device 11 male part 12 die 13 first embossing roller 14 second embossing roller 15 Pendulum movement 16 embossing section 17 embossing gap 18 stamps 19 holes 20 first stamping tool drive 21 second stamping tool drive 22 Product gap 23 Embossing 24 Movement function 25 Movement function 26 brand 27 Sensor 28 Control device 29 first circumferential section 30 second circumferential section vP speed male part vM speed matrix vF speed folding box cutting T Transport direction and movement P Program

Claims

[1] Method for embossing products (2) with a rotary embossing device (10), wherein the rotation of at least one embossing roller (13) is controlled as a function of a sensory detection of marks (26) on the products (2), wherein the embossing roller (13) is rotated alternately in a first and a second direction in accordance with a pendulum movement, the embossing roller (13) does not perform a full revolution during the pendulum movement and the embossing roller (13) is rotated in the first direction during each embossing process and in the second direction between the embossing processes. [2] Method according to claim 1, wherein the products (2) are transported one after the other past the embossing roller (13) and are provided with embossings (23) within embossing sections (16), the embossing roller (13) is rotated in the first direction when passing each embossing section (16), an embossing gap (17) is formed between the embossing section (16) of a leading product (2) and the embossing section (16) of a trailing product (2) and the embossing roller (13) is rotated in the second direction when passing each embossing gap (17). [3] Method according to claim 1 or 2, wherein the embossing roller (13) has a total circumferential length with a first (29) and a second (30) circumferential section, all embossing tools (11) of the embossing roller (13) are located only in the first circumferential section (29) and each rotation of the embossing roller (13) in the second direction takes place at most up to a limit angle which corresponds to half a circumferential section length (30) of the second circumferential section. [4] Method according to one of claims 1 to 3, wherein the products (2) are transported past the embossing roller (13) in a row with product gaps (22) of different sizes between the products (2). [5] Method according to claim 4, wherein the rotation of the embossing roller (13) is controlled according to movement functions (24, 25) which differ from one product gap (22) to another. [6] Method according to claim 5, wherein for each product gap (22) the appropriate movement function (24, 25) is automatically selected. [7] Method according to claim 6, wherein the movement functions (24, 25) are polynomial functions (24, 25) of different orders and the rotation of the embossing roller (13) is controlled according to a lower order polynomial function (24) when passing through a product gap (22) and according to a higher order polynomial function when passing through another product gap (22). [8] Method according to one of claims 1 to 7, wherein during embossing a further embossing roller (14) cooperates with the embossing roller (13), the two embossing rollers (13, 14) are a matrix roller (14) and a male roller (13) and a synchronization of the rotation of the further embossing roller (14) with the rotation of the embossing roller (13) takes priority over a synchronization of the rotation of the further embossing roller (14) with a transport movement (T) of the products (2). [9] Folding box gluing machine (1) with a rotary embossing device (10) and a programmable control device (28) which has a program controlling the rotary embossing device (10) used in a method according to one of claims 1 to 8.

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