Abstract
A clamping device for clamping a die board onto a die holding cylinder of a rotary die cutting machine includes a fluid pressure cylinder with an axially displaceable piston. A clamping bolt is attached to the piston, the clamping bolt has a shank and a head extending radially from the shank. The fluid pressure cylinder is configured for displacing the piston axially outwards in response to injection of fluid into the fluid pressure cylinder. The clamping device further includes a clamping spring arranged to bias the piston axially inwards.
The clamping bolt has a threaded portion by which the clamping bolt is attached to the piston by a threaded connection. The head of the clamping bolt may be configured to facilitate the application of torque to the clamping bolt for releasing the clamping bolt from the piston by unscrewing.
Claims
1. A clamping device for clamping a die board onto a die holding cylinder of a rotary die cutting machine, the clamping device comprising a fluid pressure cylinder with an axially displaceable piston, a clamping bolt being attached to the piston, the clamping bolt comprising a shank and a head extending radially from the shank, wherein the fluid pressure cylinder is configured for displacing the piston axially outwards in response to injection of fluid into the fluid pressure cylinder, the clamping device further comprising a clamping spring arranged to bias the piston axially inwards, wherein the clamping bolt comprises a threaded portion by which the clamping bolt is attached to the piston by a threaded connection.
2. The clamping device according to claim 1, wherein the head of the clamping bolt is configured to facilitate the application of torque to the clamping bolt for releasing the clamping bolt from the piston by unscrewing.
3. The clamping device of claim 1, wherein a nut is provided in the piston, the threaded portion of the clamping bolt being engaged with an internal thread of the nut.
4. The clamping device of claim 3, wherein the nut is arranged within the piston in an axially displaceable manner, the nut being biased axially outwards by a nut supporting spring.
5. The clamping device of claim 3, wherein the nut is blocked against rotation, and wherein the nut has an external shape matching an internal shape of a portion of the piston, so that the nut can slide in the axial direction within the piston, but is blocked against rotation.
6. The clamping device of claim 1, wherein the piston is blocked against rotation in relation to the fluid pressure cylinder.
7. The clamping device of claim 1, wherein the head of the clamping bolt comprises a portion with a circumference having a non-circular cross section.
8. The clamping device of claim 1, wherein the head of the clamping bolt comprises a recessed portion adapted for insertion of a tool for unscrewing the clamping bolt.
9. An assembly comprising a clamping device according to claim 1, wherein the assembly further comprises an interface member configured to be coupled to a die board, the interface member comprising an opening having a wider portion shaped and dimensioned to allow the head of the clamping bolt to pass through the wider portion, and a narrower portion shaped and dimensioned so as not to allow the head of the clamping bolt to pass through the narrower portion, so as to allow the clamping bolt to apply a clamping force onto the interface member.
10. The assembly of claim 9, wherein the interface member is of metal.
11. The assembly of claim 9, wherein the interface member is an insert to be inserted into a through hole in a die board, the insert comprising a bottom with the opening.
12. The assembly of claim 11, wherein the insert comprises a laterally extending rim portion surrounding at least part of the upper end of the insert, the rim portion being configured for being supported on an upper surface of a die board when the insert is placed in a through hole in the die board.
13. The assembly of claim 9, wherein the interface member is configured to be attached to an inner surface of a die board, wherein the clamping device and/or the die holding cylinder optionally comprises a recess for receiving at least part of the interface member, and wherein the interface member optionally is arc-shaped.
14. A die cutting machine comprising a die holding-cylinder and a plurality of clamping devices and/or a plurality of assemblies according to claim 9, wherein the clamping devices are inserted in recesses in the die holding cylinder.
15. The die cutting machine according to claim 14, further comprising a plurality of die boards, wherein the die cutting machine comprises a plurality of assemblies, and wherein: each die board comprises a plurality of through holes, wherein the interface members of at least some of the assemblies are arranged in at least some of the through holes, or wherein the interface members of at least some of the assemblies are attached to an inner surface of at least one of the die boards, wherein the interface members are arranged to fit into recesses in the clamping device and/or into recesses in the die holding cylinder.
16. A method of preparing a die cutting machine, comprising the steps of: providing a die holding cylinder with a plurality of recesses; providing a plurality of die boards; arranging the clamping device of an assembly according to claim 9 in each of at least some of the recesses; and: arranging an insert to be inserted into a through hole in a die board, the insert comprising a bottom with the opening, in each of at least some through holes in at least one of the die boards; or attaching at least one interface member configured to be attached to an inner surface of a die board, wherein the clamping device and/or the die holding cylinder optionally comprises a recess for receiving at least part of the interface member, and wherein the interface member optionally is arc-shaped, to an inner surface of at least one of the die boards.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as examples of how the disclosure can be carried out. The drawings comprise the following figures:
[0044] FIG. 1 is a schematic exploded view of part of a die cutting machine (that is, a so-called die cutter) according to a first embodiment of the disclosure.
[0045] FIG. 2 is a perspective view of a clamping device of an assembly according to this embodiment of the disclosure.
[0046] FIG. 3 is a perspective exploded view of the clamping device.
[0047] FIGS. 4A-4D are a perspective top view, a perspective bottom view, a top view and a cross sectional side view of an interface member of the assembly according to this embodiment of the disclosure.
[0048] FIGS. 5A-5D are cross sectional side views of part of the die cutting machine according to this embodiment of the disclosure.
[0049] FIG. 6 is a cross sectional side view of part of the die cutting machine according to this embodiment of the disclosure.
[0050] FIG. 7 is a cross sectional side view of part of the die cutting machine of the same embodiment, but from a different angle.
[0051] FIGS. 8A-8C are a perspective exploded view and sectional side views, respectively, of part of the die cutting machine according to another embodiment of the disclosure.
[0052] FIGS. 9A-9C are a perspective exploded view and sectional side views, respectively, of part of the die cutting machine according to yet another embodiment of the disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 schematically illustrates a portion of a die cutting machine comprising a die holding cylinder 3 and a plurality of die boards, a part of one die board 4 being shown in the figure. For example, the die holding cylinder 3 can support two or more die boards 4, each die board having a curved shape adapted to the external shape of the die holding cylinder 3, as known in the art. The die holding cylinder is typically a metallic cylinder, provided with a plurality of recesses 31 distributed over its surface. One of these recesses 31 is shown in FIG. 1. Each die board 4 typically comprises a plurality of through holes 41, one of which is shown in FIG. 1. Interface members in the form of a metallic inserts 2 are arranged in at least some of these through holes 41, the inserts comprising rims that rest on the upper surface of the respective die board 4.
[0054] A clamping device 1 is arranged in each one of at least some of the recesses 31 in the die holding cylinder 3. The clamping device comprises a substantially disc-shaped cover 17 provided with a plurality of bores 171 distributed around its circumference, for receiving screws or bolts (not shown in FIG. 1; see FIG. 7 for one of these bolts 173) for attaching the clamping device 1 to the die holding cylinder 3, so that it will be securely retained in the respective recess 31. The clamping device 1, better shown in FIGS. 2 and 3, includes a fluid pressure cylinder 11, such as a pneumatic or hydraulic cylinder, with a piston 12 incorporating a nut 15 to which a clamping bolt 13 is attached by screwing. The fluid pressure cylinder 11 is configured to displace the piston 12 with the nut 15 axially outwards (radially outwards if the axis of the die holding cylinder is taken as the reference) when the fluid pressure cylinder is activated by the introduction of fluid in a chamber of the fluid pressure cylinder. The piston 12 (and, with it, the nut 15) is biased axially inwards by a clamping spring 14. The clamping bolt 13 comprises a shank 13B and a head 13A that extends radially outwards from the shank 13B. The bottom surface of part of the head is intended to contact the surface of the insert 2 so as to apply a clamping force onto the insert 2, for clamping the die board to the die holding cylinder 3. The clamping force is exerted by the clamping spring 14. As shown in FIG. 3, the nut 15 has externally a hexagonal cross section, and the nut is slidably arranged within a bore 122 in a central shaft portion 121 of the piston 12. The central shaft portion 121 is surrounded by the helicoidal clamping spring 14. The bore 122 has a hexagonal cross section that matches the external shape of the nut 15, so that the nut is blocked against rotation, whereas it is capable of sliding in the axial direction, as will be described more in detail below. The nut is biased axially outwards by a nut supporting spring 16 arranged within the piston 12.
[0055] The shank 13B of the clamping bolt 13 has a threaded end section 13C at the end opposite to the head 13A, that is, at the axially innermost end. This end section 13C is threadedly engaged with the threaded bore 151 of the nut 15. The head 13A of the clamping bolt has an upper portion that externally has a hexagonal cross section, thus facilitating the application of torque using a wrench or other suitable tool. In the case of jamming of the mechanism, for example, in the clamped state thereof, the bolt 13 can be removed by unscrewing it from the nut 15. This operation is facilitated by the fact that the head has a shape that facilitates the application of torque using a wrench, while the nut 15 is blocked against rotation in relation to the piston 12 as described above. Additionally, as shown in FIG. 3, the external wall 123 of the piston 12 that extends angularly around the piston includes a vertically extending slot 123A. In the mounted state, this slot receives a projection 172 (see FIG. 7) of the cover 17. Thus, also the piston is blocked against rotation around its axis.
[0056] The fluid pressure cylinder 11 is provided with a circumferential flange 110 at its upper end, the flange 110 being provided with a first set of bores 111 for receiving the screws or bolts 173 inserted via the bores 171 in the cover (one of these bolts is shown in FIG. 7), and a second set of bores 112 for receiving screws or bolts 174 for attaching the fluid pressure cylinder 11 to the cover 17 (one of these screws or bolts 174 is shown in FIG. 7).
[0057] FIGS. 4A-4D schematically illustrate an insert 2 forming part of an assembly according to an embodiment of the disclosure. The insert can be of any suitable material, for example, of metal. The insert as shown in FIG. 4A is open at its top end. The bottom end is partially closed by a bottom featuring an opening 20 comprising a wider portion 21 and a narrower portion 22. The wider portion is dimensioned and shaped so as to allow the head 13A of the clamping bolt 13 to pass through it, whereas the narrower portion is shaped and dimensioned so as not to allow the head 13A of the clamping bolt to pass through it, but it is wide enough to house the shank 13B of the clamping bolt. Thus, in operation, the clamping bolt can be moved axially outwards, by displacement of the piston 12 caused by actuation of the fluid pressure cylinder 11, so that the head enters into the insert 2 via the wider portion 21 of the opening 20, whereafter the insert 2 is laterally or angularly shifted (for example, in the circumferential direction of the die holding cylinder) so that the shank 13B enters into the narrower portion 22 of the opening, whereafter the fluid pressure cylinder can be operated to let fluid out of the chamber to allow the piston 12 to descend axially inwards, pushed by the clamping spring 14, until the head 13A of the clamping bolt 13 abuts against the inner surface 23 of the insert surrounding part of the narrower portion 22 of the opening 20. Thus, the clamping bolt 13 transmits the clamping force exerted by the clamping spring 14 onto the insert 2. The clamping forces applied in this way by several clamping bolts pertaining to different assemblies thus serve to securely clamp the die board 4 provided with the inserts 2 to the die holding cylinder 3.
[0058] As shown, the insert 2 is partially wedge-shaped so that it narrows towards its bottom end. It is also provided with laterally extending rim or flange portions 24 around part of its circumference, to allow for reliable retention when placed in the corresponding through hole in a die board.
[0059] FIGS. 5A-5D schematically illustrate some of the above described components at different moments of the operation of the clamping mechanism of a rotary die cutter according to an embodiment of the disclosure.
[0060] FIG. 5A illustrates the clamping device with the piston 12 in an axially retracted position and the helicoidal clamping spring 14 in its maximally expanded state. The clamping bolt 13 is attached to the nut 15 which is retained within the piston by a circumferentially projecting rim or bulge 152 which abuts against the upper part of the inner surface of the piston, adjacent to the lower end of the hexagonal bore 122. The nut 15 is biased upwards (that is, axially outwards) by the nut supporting spring 16, likewise housed within the piston 12. A die board 4 has been applied onto the cylinder, and an insert 2 placed in a through hole in the die board is placed with the wider portion 21 of the opening 20 in the insert positioned axially above the head 13A of the clamping bolt.
[0061] In FIG. 5B the fluid pressure cylinder has been activated by injection of a fluid into the chamber 113 in part delimited by the lower surface of the piston, so that the piston has been displaced axially outwards (upwards in FIG. 5B), compressing the clamping spring 14 and pushing the head 13A of the clamping bolt through the wider portion 21 of the opening in the insert 2.
[0062] In FIG. 5C the die board 4 and the insert 2 have been shifted in relation to the clamping bolt so that the shank 13B of the clamping bolt has entered into the narrower portion 22 of the opening.
[0063] In FIG. 5D fluid has been allowed to flow out of the chamber 113 so as to reduce the pressure within the chamber, allowing the piston 12 to move axially inwards (downwards in FIG. 5D), under the pressure exerted by the expanding clamping spring 14. FIG. 5D shows the arrangement at the end of this movement, namely, with the head 13A of the clamping bolt abutting against the inner surface 23 of the insert 2, and the circumferential bulge 152 of the nut abutting against the internal top surface of the piston 12 adjacent to the bore 122, thereby preventing further expansion of the clamping spring. The pressure exerted by the clamping spring 14 at this stage thus represents the clamping force exerted by the head 13A of the clamping bolt onto the insert 2. Due to the use of the inserts 2, substantial clamping forces, such as clamping forces of more than 2000 N, such as more than 2500 N, can be applied without any substantial risk of damage to the die board.
[0064] Often, when applying die boards onto a die holding cylinder, it is difficult or impossible to provide axial alignment between all of the clamping bolts and a corresponding insert. This means that if all the fluid pressure cylinders are activated for axial displacement outwards of the pistons, some of the clamping bolts will not be able to exit through a corresponding through hole in the die board. FIG. 6 illustrates an example of a clamping device according to an embodiment of the disclosure in which the head 13A of the clamping bolt is not facing an opening in the die board 4. When the fluid pressure cylinder 11 is activated and the piston 12 is pushed upwards, the head 13A of the clamping bolt will abut against the inner surface of the die board 4. When the piston continues to move upwards, the nut supporting spring 16 will be compressed. In this way, it is possible to avoid that the clamping bolt causes damage to or displacement of the die board 4.
[0065] FIGS. 8A-8C illustrate another embodiment of the disclosure in which, instead of using an insert 2 as described above, the interface member 2A is a rib-like member with arcuate shape, which can be attached to the corresponding die board 4 by any suitable means, for example, by screws 42, as schematically illustrated in FIG. 8B. The arcuate shape of the interface member 2A corresponds to the arcuate shape of the radially external part of the die holding cylinder 3. The cover 17 of the clamping device 1 is provided with a recess 17A and the die holding cylinder 3 is likewise provided with recesses 3A. These recesses 17A and 3A form a continuous recess 3A+17A+3A extending in the circumferential direction of the die holding cylinder and arranged to receive the interface member 20A, thereby ensuring that the opening 20A thereof will be correctly positioned in relation to the head 13A of the clamping bolt in the axial direction of the die holding cylinder 3. By shifting the die board 4 in the circumferential direction of the die holding cylinder, the shank 13B of the clamping bolt 13 can be shifted from the wider portion 21A to the narrower portion 22A of the opening 20A in the interface member 2A, and vice-versa. What has been explained in relation to the insert 2 applies also to the arcuate interface member 2A, mutatis mutandis. The head 13A of the clamping bolt can be accessed from above (that is, from radially outside the die board 4) via the opening 41 in the die board 3. One advantage of this embodiment is that the interface member 2A does not have to be adapted to the opening 41 in the die board, as it does not fit into that opening: the interface member 2A is simply attached to the radially inner surface of the die board, for example, with screws.
[0066] FIGS. 9A-9C illustrate an embodiment somewhat similar to the one of FIGS. 8A-8C, but which does not feature the opening 41 in the die board of the embodiment of FIGS. 8A-8C. On the other hand, the opening 20B intended to receive the clamping bolt 13 has, in the interface member 2B of the embodiment of FIGS. 9A-9C, a configuration that is different from the configuration of the corresponding opening 20A of the embodiment of FIGS. 8A-8C: whereas the opening 20A of the embodiment of FIGS. 8A-8C has the same cross section all throughout its radial extension (taking the die holding cylinder 3 as the reference), that is, whereas the opening 20A has the same shape at its radially outer or upper end as at its radially inner or lower end, the opening 20B of the embodiment of FIGS. 9A-9C has a different shape at its radially outer end than at its radially inner end. More specifically, the wider portion 21B and the narrower portion 22B of the opening are formed in a bottom 23B of the opening 20B that is recessed from its radially outer end, thereby providing for a space that can accommodate the head 13A of the clamping bolt between said bottom 23A and the die board 4, as best shown in FIGS. 9A and 9B. To access the head 13A of the clamping bolt from above, it is first necessary to remove the die board 4. An advantage of this embodiment is that it does not require any opening in the die board above the clamping bolt 13.
[0067] In this text, the term comprises and its derivations (such as comprising, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.
[0068] The disclosure is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the disclosure as defined in the claims.
