CLAMPING SHAFT, PRINTING CYLINDER UNIT AND METHOD FOR OPERATING A CLAMPING SHAFT

Abstract

A clamping shaft (12) for a rotationally driven part (14) is described. It comprises at least one fluid chamber (28a, 28b) being located inside a shaft body (16) and being delimited by a piston (30a, 30b) and a cylinder part (32a. 32b). Additionally, the fluid chamber (28a, 28b) is delimited by an elastic clamping region (24a, 24b) having a first diameter if the piston (30a, 30b) and the cylinder part (32a, 32b) are in a first relative position, and a second diameter if the piston (30a, 30b) and the cylinder part (32a, 32b) are in a second relative position. Furthermore, a preloading unit (38) is provided, biasing the piston (30a, 30b) and the cylinder part (32a, 32b) towards the second relative position. Moreover, a printing cylinder unit (10) of a printing machine is presented comprising such a clamping shaft (12). Also, a method for operating a clamping shaft (12) is explained.

Claims

1. A clamping shaft for a rotationally driven part, the clamping shaft comprising: a shaft body being rotatable about a shaft axis; at least one fluid chamber being located inside the shaft body and being filled with a predetermined amount of fluid, wherein the fluid chamber is delimited by a piston surface of at least one piston being located inside the shaft body and a cylinder part, being movable relative to each other such that a volume of the fluid chamber is adjustable by moving the piston relative to the cylinder part, wherein the shaft body comprises at least one elastic clamping region delimiting the fluid chamber, wherein the clamping region has a first diameter when the piston and the cylinder part are in a first relative position, and a second diameter when the piston and the cylinder part are in a second relative position, the second diameter being bigger than the first diameter, wherein the clamping shaft further comprises at least one preloading unit, and wherein the preloading unit applies a preloading force on the piston and/or the cylinder part such that the piston and the cylinder part are biased towards the second relative position.

2. The clamping shaft according to claim 1, further comprising: two fluid chambers, each being located inside the shaft body and each being filled with a predetermined amount of fluid, wherein each of the two fluid chambers is delimited by a piston surface of a piston being located inside the shaft body and a cylinder part, being movable relative to each other such that a volume of the fluid chamber is adjustable by moving the piston relative to the cylinder part, wherein the shaft body comprises two elastic clamping regions each delimiting one of the fluid chambers, wherein the two elastic clamping regions have a first diameter when the corresponding piston and the corresponding cylinder part are in a first relative position, and a second diameter when the corresponding piston and the corresponding cylinder part are in a second relative position, the second diameter being bigger than the first diameter, and wherein the preloading unit is located between the pistons or between the cylinder parts and applies a preloading force on the pistons or the cylinder parts such that each of the pistons and the corresponding cylinder parts are biased towards the second relative position.

3. The clamping shaft according to claim 2, wherein the fluid chambers are fluidically connected via a fluid connection line located inside the shaft body.

4. The clamping shaft according to any claim 1, wherein an abutment surface associated with each piston is provided in the shaft body, each piston abutting against the respective abutment surface when the piston and the cylinder part are in the second relative position.

5. The clamping shaft according to any claim 1, wherein the preloading unit comprises a spring assembly.

6. The clamping shaft according to claim 2, wherein each of the two elastic clamping regions is formed integrally with the shaft body or wherein each clamping region is provided by an elastically deformable sleeve provided on the shaft body.

7. The clamping shaft according to claim 1, wherein the shaft body comprises at least one bearing interface, by which the clamping shaft is rotatably supportable, the shaft body preferably comprising two bearing interfaces.

8. The clamping shaft according to claim 1, wherein the shaft body comprises at least one drive interface by which the clamping shaft is rotationally drivable.

9. The clamping shaft according to claim 2, wherein at least one of the pistons and/or the cylinder part cooperating with the piston comprises an actuation interface by which an external force may be applied to the piston and/or the cylinder part counteracting the preloading force such that at least one of the pistons and the corresponding cylinder part are in the first relative position.

10. The clamping shaft according to claim 9, wherein the actuation interface is provided in proximity to an axial end of the shaft body.

11. A printing cylinder unit of a printing machine, the printing cylinder unit comprising: the clamping shaft according to claim 1.

12. A method for operating a clamping shaft for a rotationally driven part, the method comprising: providing the clamping shaft in a clamping state when the clamping shaft is not actuated; and providing the clamping shaft in a release state when the clamping shaft is actuated.

13. The method according to claim 12, wherein the clamping shaft is actuated by pulling an actuation interface along an axial direction of the clamping shaft, by pushing an actuation interface along an axial direction of the clamping shaft, or by turning an actuation interface around an axial direction of the clamping shaft.

Description

[0028] The invention will now be explained with reference to two embodiments which are shown in the attached drawings. In the drawings,

[0029] FIG. 1 shows a printing cylinder unit according to the invention comprising a clamping shaft according to the invention being operable by a method for operating a clamping shaft according to the invention,

[0030] FIG. 2 the printing cylinder of FIG. 1 in an enlarged representation, wherein a middle section of the printing cylinder is cut out,

[0031] FIG. 3 the printing cylinder of FIGS. 1 and 2 in a further enlarged representation, wherein a middle section of the printing cylinder is cut out, and

[0032] FIG. 4 an alternative embodiment of the printing cylinder unit according to the invention in a schematic representation.

[0033] FIG. 1 shows a printing cylinder unit 10 of a printing machine, which comprises a clamping shaft 12 and a rotationally driven part 14.

[0034] In the examples shown the rotationally driven part 14 is a printing cylinder, e.g. a cliché cylinder of a flexographic printing machine or an adapter for such a printing cylinder.

[0035] The clamping shaft 12 comprises a shaft body 16 being rotatable about a shaft axis 18.

[0036] It may be rotatably supported inside a printing machine via two bearing interfaces 20a, 20b which are located at respective axial ends 16a, 16b of the shaft body 16. The bearing interfaces are formed as cone sections in the example shown.

[0037] In order to rotatably drive the clamping shaft 12, the shaft body 16 is equipped with a drive interface 22, which his only shown schematically.

[0038] The part 14 is clamped to the clamping shaft 12 via two clamping regions 24a, 24b. In the clamping regions 24a, 24b elastically deformable sleeves 26a, 26b are provided, which delimit a fluid chamber 28a, 28b respectively.

[0039] The fluid chambers 28a, 28b are located inside the shaft body 16 and both are filled with a predetermined amount of fluid, e.g. hydraulic oil.

[0040] Depending on the pressure of the fluid in the respective fluid chambers 28a, 28b, the sleeves 26a, 26b are deformed to have a first diameter or a second diameter, the second diameter being bigger than the first diameter.

[0041] Consequently, the part 14 is clamped to the clamping shaft 12 if the clamping regions 24a, 24b have a second diameter and may be axially and/or rotationally moved with respect to the clamping shaft 12 if the clamping regions 24a, 24b have a first diameter.

[0042] This change in diameter is achieved by altering the pressure inside the respective fluid chamber 28a, 28b. Thus, the first diameter is achieved if the fluid chambers 28a, 28b are pressurized and the second diameter is achieved if the fluid chambers 28a, 28b are de-pressurized, i.e. are substantially at ambient pressure.

[0043] In order to pressurize the fluid chambers 28a, 28b each of them is also delimited by a piston surface of a respective piston 30a, 30b being located inside the shaft body 16 and by a corresponding cylinder part 32a, 32b. Each piston 30a, 30b is movable relative to the corresponding cylinder part 32a, 32b, wherein in the example shown, the pistons are movable along a piston axis, which corresponds to the shaft axis 18. The cylinder parts 32a, 32b are formed as separate parts in the examples shown, but are axially and rotationally fixed inside the shaft body 16. Alternatively, the cylinder parts 32a, 32b may be formed as sections of the shaft body 16.

[0044] Thus, in the de-pressurized state of one of the fluid chambers 28a, 28b, the corresponding piston 30a, 30b and cylinder part 32a, 32b are in a first relative position.

[0045] In the pressurized state of one of the fluid chambers 28a, 28b, the corresponding piston 30a, 30b and cylinder part 32a, 32b are in a second relative position.

[0046] Additionally, an abutment surface 34a, 34b is formed on each of the cylinder parts 32a, 32b, wherein each of the abutment surfaces 34a, 34b is associated with one of the pistons 30a, 30b and the respective piston 30a, 30b abuts against the associated abutment surface 34a, 34b when the corresponding piston 30a, 30b and cylinder part 32a, 32b are in the second relative position.

[0047] On the pistons 30a, 30b counter abutment surfaces 36a, 36b are formed.

[0048] The clamping shaft 12 further comprises a preloading unit 38, which is formed such that it applies a preloading force on both pistons 30a, 30b such that the pistons 30a, 30b are biased towards the second relative position.

[0049] In the example shown in FIGS. 1 to 3, the preloading unit 38 is used for both pistons 30a, 30b and is located between them.

[0050] The preloading unit 38 comprises a spring assembly 40, which is an arrangement of disk springs in the example shown.

[0051] In order to be able to use the functioning principle of the clamping shaft 12 for different lengths of the clamping shaft 12, piston 30b is connected to the preloading unit via a bar 42. Consequently, the length of the clamping shaft 12 may be adapted by changing the length of the bar 42. The remaining parts of the clamping shaft 12, especially the pistons 30a, 30b and the fluid chambers 28a, 28b do not need to be altered.

[0052] Moreover, the fluid chambers 28a, 28b are fluidically connected via a fluid connection line 44.

[0053] In the example shown the fluid connection line 44 is an axial bore located inside the shaft body 16.

[0054] As will be explained in the following, the fluid connection line 44 makes is possible to put both combinations of a piston 30a, 30b and a cylinder part 32a, 32b in the first relative position by just actuating one of the pistons 30a, 30b. This means that the clamping shaft 12 can be put into the release state by just actuating one single pistons 30a, 30b.

[0055] To this end, both pistons 30a, 30b comprise an actuation interface 46a, 46b, which is a realized as an axial end face of the respective piston 30a, 30b. This end face is provided at an axial end of the shaft body 16 and thus is well accessible for actuation.

[0056] Thus, if one of the actuation interfaces 46a, 46b is pushed either manually or automatically, the pressure in both fluid chambers 28a, 28b is reduced.

[0057] Since the forces resulting from the pressure of the fluid are counterbalanced by the preload forces resulting from the preloading unit 38, both the piston 30a, 30b actually actuated and also the piston 30a, 30b not directly actuated move towards an axial middle of the clamping shaft 12, thereby attaining the first relative position.

[0058] In summary, the clamping shaft 12 is in a clamping state, if it is not actuated and it is in a release state if it is actuated by pushing against at least one of the actuation interfaces 46a, 46b. Of course, the release state can also be achieved by pushing on both actuation interfaces 46a, 46b.

[0059] FIG. 4 shows a second embodiment of the printing cylinder unit 10, which differs from the embodiment of FIGS. 1 to 3 in that a different clamping shaft is used. In the following, only the differences with respect to this first embodiment will be explained. Corresponding parts will be designated with the same references signs that already have been used in FIGS. 1 to 3, where appropriate the suffixes are omitted in FIG. 4.

[0060] Essentially, the embodiment of FIG. 4 differs from the embodiment of FIGS. 1 to 3 in that there is only one single piston 30 and one single cylinder part 32 cooperating with the piston 30. Both delimit a single fluid chamber 28 and are movable inside the shaft body 16.

[0061] In contrast to the example of FIGS. 1 to 3, the single fluid chamber 28 is associated with two clamping regions 24a, 24b. More precisely, the single fluid chamber 28 is delimited by two elastically deformable sleeves 26a, 26b. To this end, the fluid chamber 28 comprises an axial bore 48 in the shaft body 16.

[0062] The preloading unit 38 biases the piston 30 against the cylinder part 32.

[0063] The clamping shaft 12 according to FIG. 4 may be operated as follows.

[0064] If the clamping shaft 12 is actuated by pushing on either actuation interface 46a of the piston 30 or actuation interface 46b of the cylinder part 32, the piston 30 and the cylinder part 32 will move relative to each other against the preloading force of the preloading unit 38.

[0065] In doing so, the fluid inside the fluid chamber 28 will be de-pressurized and the diameter of the sleeves 26a, 26b will be elastically decreased. Consequently, the clamping shaft 12 will attain a release state.

[0066] If none of the actuation interfaces 46a, 46b is pushed, the clamping shaft 12 is in its clamping state.