GB2321431A - Fixing device for printing formes - Google Patents

Abstract

A fixing device is described for clamping printing formes on the forme cylinder of printing presses, particularly for clamping printing plates on the plate cylinder of offset sheet printing presses. It has a lower portion (5) movable swivellably radially which can be pressed for clamping a printing forme against a corresponding surface (e.g. groove (10)) in an upper portion (4). This is effected by an actuation device (6) for opening and closing the clamping device as well as spring elements (8) arranged between the movable lower portion (5) and the fixed upper portion (4). Such a constructionally simple clamping device can be matched to various printing formes to and can be remotely controlled both manually and also automatically. The lower part (5) is constructed as an L-shaped profile clamping rail, and can be pressed by the actuation device (6) in positively interlocked fashion against the corresponding surface (10) of the upper portion (4). Spring elements (8) bias the lower portion (5) into the opened position.

Description

2321431 - 1 FIXING DEVICE FOR PRINTING FORMES This invention relates to a

fixing device for printing formes on the forme cylinders of printing presses.

In offset sheet printing presses, the printing formes constructed as printing plates are installed on forme cylinders by means of fixing and clamping devices which engage the edges of the printing plate coordinated to the print start and the print end on corresponding fixing devices by clamping. The tensioning of the printing plate around the exterior periphery of the impression cylinder as a forme cylinder then takes place as a rule by corresponding shifting of the fixing device coordinated to the print end. With manually actuatable fixing devices for printing plates of the above briefly outlined type the approach to introduce a new printing forme first to open the corresponding fixing device, i.e. with a fixing device constructed as a clamping device it must be opened by means of an actuation device of the clamping mechanism. Then the edge of the used, or an edge of a newly to be fed in printing plate, is introduced into the clamping device, whereafter then the clamping of the corresponding printing plate edge takes is - 2 place.

With fixing devices for printing plates or printing formes constructed manually actuatable and as a clamping device, the actuation devices effecting the clamping and unclamping must be manually operated, which, as a rule, takes place by means of a corresponding tool (insertion key or lever). Especially in the case of devices serving for automated printing forme change, the clamping as well as the unclamping of the corresponding printing plate edges takes place in remotely actuatable fashion. The actuation devices can then be arranged relative to adjusting motors (electrical, pneumatic or hydraulic) integrated in the forme cylinder. Furthermore, it is also known to provide the actuation devices for automatic clamping/unclamping from an actuation device fixed with respect to the frame, for which purpose then the forme cylinder is moved into a suitable position and one which corresponds with the actuation device. Then the swivellable end of a lever actuated, for example, by a pneumatic cylinder engages on a corresponding support surface of the lever on the cylinder in order to effect the clamping or unclamping with application of the necessary force.

From DE 34 01 351 Al, a rapid tensioning bar for fixing a printing plate on printing presses is known which consists of a fixed upper portion as well as a radially movable lower portion. For clamping a printing plate edge which has been introduced, the radially movable lower portion is actuated via a specially shaped eccentric shaft so that the forces necessary for clamping a printing plate are provided by positively interlocked cooperation of the corresponding components. According - 3 to various embodiments of this rapid tensioning bar, it is furthermore also provided that the eccentric shaft, particularly in combination with a given profiling, cooperates directly with the printing plate and the fixed upper portion for clamping, which, however, as is explicitly provided with this device, brings with it a deformation of the printing plate edge. Because of the lasting deformation of the printing plate edge, used printing formes are accordingly no longer usable without further ado particularly in combination with automated printing plate in- feed mechanisms, since particularly on the introduction of a printing plate front edge deformed in this way, there is the danger of jamming or locking during the feed process, The same problem can arise during removal of a used printing plate.

From DE 26 06 773 B2, a device for fixing and tensioning a flexible printing plate on a forme cylinder of a rotary printing press is known wherein here likewise a radially movable lower part cooperates with a fixed upper part. The eccentric shaft constructed as actuation device acts in this case via, in particular, pre-tensioned spring elements on a corresponding pressure piece which is pressed against the fixed upper part for applying the clamping force via the spring elements. The extra spring elements provided here effect an evening out of the clamping force across the format width of the forme cylinder. Also an automatic matching to various printing plate thicknesses takes place in this way. However, disadvantageous is that because of the exclusively radial movability, the lower part must have a relatively precise guidance with respect to the fixed upper part in order, in particular, in the case of tension exerted laterally on the printing plate, to permit no movement in the tensioning force. Exactly with a clamping device constructed as a print start clamping rail, this is absolutely to be avoided, since on slight comovement of the printing plate on tension exerted on the clamping device, the register is lost and initial prints, particularly with multi-colour printed products, have register differences, which then have to be alleviated in turn by time-consuming and waste-generating corrections.

From EP 0 492 138 Bl, a rapid clamping device is known which, as in the last-mentioned case, has a fixed upper part cooperating with a radially movable lower part.

Also here, the force necessary for clamping a printing plate, by means of which the lower part is pressed is against the fixed upper part, is applied via compression springs. At least a retraction element is provided, which is constructed as a rocker or lever and is supported swivellably on the cylinder housing or on a support surface which is firmly connected with the cylinder housing. The retraction element(s) are actuatable via at least one adjusting element which can be subjected to the actuation medium. In the various embodiments mentioned in this specification, it is provided that the radially movable underneath part especially is supported directly against the plate cylinder or on the front channel wall of the plate cylinder. Thereby with reference to the register or registration problems, the same disadvantages appear as in the case of the last-noted specification. On account of the direct support of the radially movable underpart on the corresponding channel wall of the plate cylinder, it is furthermore not possible with this rapid clamping device to construct the entire clamping device which is constructed as a clamping rail additionally still movable in the plate cylinder. The clamping devices on the forme or plate cylinders of sheet printing presses with not too high a degree of automation or the clamping devices for the printing formes on the forme cylinders of varnishing units or varnishing devices are generally constructed movably for register or matching corrections relative to the respective cylinder. To this extent, in simple fashion by corresponding correction of the position of the printing forme on the forme cylinder, register or matching differences can be compensated.

From DE 20 65 582 B2, a device for clamping printing plate ends which have not been bent off of flexible printing formes is known in which a radially movable and additionally swivellably mounted inner rail is pressed against an outer rail by the force of pretensioned springs in a position firmly clamping the printing plate. For opening this clamping device by means of a tool, the movable inner rail is actuated counter to the force of the pretensioned springs. The pretensioned springs cooperate, in this connection, with the movable inner rail in the fashion of a toggle lever. The entire clamping device fixed together on a rail can, in this connection, for the purpose of the above-noted register corrections additionally be moved with respect to the plate cylinder.

However disadvantageous with this device is that the forces to be applied for clamping a printing plate are applied by particularly pretensioned compression springs, which especially makes more difficult a manual actuation of this clamping device. Particularly with large format forme cylinders with correspondingly long clamping rails, a plurality of spring elements must accordingly be subjected to excess pressure in order to open the clamping rail, so that a device of this type can really only be used exclusively with small and very small format presses. Furthermore, it is to be seen as disadvantageous that because of the actuation force to be applied permanently for opening the clamping device, this device can only be opened with the cylinder stationary. Furthermore, disadvantageous with this previously known device is that a part of the inner clamping rail cooperates under sliding friction with corresponding surfaces of the outer clamping rail and on the other hand that the clamping force is not increased by corresponding pulling on the part of the printing plate in selfclamping fashion.

We have now found that a fixing device for printing formes on the forme cylinders of printing presses can be constructed in such a way that while avoiding the previously noted disadvantages, a more secure plate clamping is possible for a plurality of application areas with manually actuatable and also automated construction and with minimum constructional outlay.

According to the present invention, there is provided a fixing device for printing formes on the forme cylinders of printing presses, the device consisting of a clamping rail with a radially movable and swivellable lower part, an actuation device acting on the lower part and spring elements arranged between upper part and lower part, wherein the lower part is constructed as an L-shaped profiled clamping rail, the short leg of which cooperates with a correspondingly shaped surface in the upper part for clamping the printing forme and on the long leg of which the actuation device acts, and wherein for clamping the actuation device cooperates in positively interlocked fashion with the lower part and the spring elements arranged between lower part and upper part to maintain the lower part in the opened position.

In fixing devices in accordance with the invention, the radially movable simultaneously swivellable lower clamping rail is moved by an actuation device, in particular constructed as an eccentric shaft cooperating in positively interlocked fashion with this rail, into the plate clamping position. The radially movable simultaneously swivellable mounted lower clamping rail is held by means of one or more spring elements arranged spaced from one another across the format width of the is forme cylinder in the position for introduction of a new printing forme front edge. The actuation device, constructed in particular as an eccentric shaft, which cooperates in positively interlocked fashion with a corresponding surface of the lower clamping rail can, in this connection, be remotely controlled either via a tool by hand, or by using an automatically operating construction with adjusting members arranged in the forme cylinder or outside the forme cylinder, and which are actuated electrically, pneumatically or hydraulically.

The invention has, in this connection, the advantage that both in the opened and also in the closed (clamped) position, no permanently applied forces are necessary with respect to the actuation device. This means, in other words, that both the opened and also the closed clamping device can be turned with the cylinder without permanent application of force or power. This in particular brings the advantage with an automatic plate change that, for example, for feeding out a used printing forme from the forme cylinder, the fixing device constructed, for example, as print start clamping rail is first opened and then the forme cylinder can be turned backwards further for feeding the printing forme into a receiving container. If, in the receiving container, holding devices are installed for the used printing forme then by subsequent forward turning of the forme cylinder, the edge of the printing forme coordinated to the print start can be pulled out of the opened print forme. Such a procedure is, in the case of fixing devices clamping via the force of pre-tensioned springs, only possible if the corresponding adjusting members for the actuation device of the clamping device are arranged within the cylinder.

In accordance with the invention, it is provided that the radially movable and simultaneously swivellable lower clamping rail part is constructed as an L-shaped formed profiled part, wherein the long leg of this L-profile cooperates with the actuation device constructed in particular as an eccentric shaft and the short leg of this L-profile serves for clamping the printing forme edge with respect to the fixed part. In this connection, use is made of the fact that this sort of an L- shaped component acts as a bow spring wherein thereby certain tolerances in the thickness of the printing forme to be fixed in place are evened out. According to a preferred variant embodiment of the invention, the Lshaped profiled lower clamping rail part is guided by coordinated rollers or shafts of the type of roller bearings for carrying out the combined swivelling and radial movement. A shaft or roller of this bearing carrying the lower clamping rail part is, in this connection, still additionally adjustable, whereby matching to a wide range of printing forme thicknesses may be achieved.

The invention is illustrated, by way of example, with reference to a specific embodiment illustrated in the accompanying drawings, in which Figure 1 shows a fixing device in accordance with the invention in section in a plane perpendicular to the axis of the forme cylinder, diagrammatically, and in opened position, and Figure 2 shows the device of Figure 1 in a position clamping the printing plate.

Referring to Figures 1 and 2, these show only part of the cross-section of a forme cylinder 1 having a channel 2 extending across the format width of the forme cylinder 1. A clamping rail 3 is arranged adjacent one wall of the channel 2 and consists of an upper portion 4 which, on its underside as indicated in Figure 1 and 2, is connected directly with the floor of channel 2. Alternatively thereto, for making possible register corrections, rail 3 can be mounted movably by a predetermined amount relative to the forme cylinder 1.

The upper part 4 as well as the entire clamping rail 3 can be constructed either in one piece extending all the way together across the format width of the forme cylinder 1 or it can be divided into sections across the format width. In both cases, it can be provided that the devices for clamping or unclamping or releasing a printing forme are constructed in such a fashion so that this can be loosened by only one actuation process.

- As illustrated in Figures 1 and 2, the upper portion 4 has, in an upper region for receiving a printing forme a V-shaped profiled groove 10 with a flat floor at the base of the "V". Supported on the floor of this groove 10 is a shaft 9 forming a rolling contact joint or alternatively thereto several rollers lying adjacent one another are let in across the length of the upper part 4 which cooperate with a correspondingly shaped support surface of an L-shaped profiled lower part 5. The short leg of this L-shaped profiled lower part 5 is, in this connection, seated in the V-shaped groove 10 of the upper part 4. Swivellably seated in a correspondingly shaped recess 6.1 of the upper part 4, in an actuation device 6 constructed as an eccentric shaft, or as a shaft with a flat. Device 6 cooperates with a correspondingly shaped support surface on the long leg of the L-shaped profiled lower part 5. At the lower end of the long leg of the Lshaped lower part 5, there is likewise arranged a shaft 11 or several adjacently lying rollers, which cooperate with support surfaces on the longer leg of the lower part 5, and on the other side, are supported on an inclined part of a pressure piece 12. The or the several adjacently lying pressure pieces 12 can, in this connection, be adjustable by one or several adjusting screws 13 inserted through the upper part 4 for matching the clamping rail 3 to differing thicknesses of printing formes.

Above the actuation device 6, formed as an eccentric shaft or as a shaft with a flattening are arranged screws 7 preferably lying adjacent one another over the length of the clamping rail 3, the ends of which are screwed into corresponding threaded bores of the lower part 5 in the in each case long leg of the L-shaped profiled lower 11 - part 5. Surrounding the shafts of the screws 7 are pretensioned spring elements 8 constructed as compression springs which on the one side are supported on a corresponding support surface of the upper part 4 and on the other side on the surfaces of the heads of screws 7 lying opposite these support surfaces. By these spring elements 8, the lower part 5, drawn in Figure 1 in the opened position for introduction of a new printing forme or for taking out a used printing forme after corresponding swivelling of the actuation device 6, is pulled towards upper part 4. The shafts 9. 11 (or set of corresponding adjacently lying rollers act as roller bearings effect in this connection as likewise illustrated in Figure 1 that the L-shaped profiled lower part 5 takes up a lowermost position in the radial direction. The shaft 11 (or several rollers) accordingly are located at the lowermost part of the inclined surface of the pressure piece 12. This movement is additionally supported by the corresponding incline of the ends of the short leg of the L-shaped profiled lower part 5 which cooperates with the shaft 9 (or several adjacently lying rollers) of the upper bearing with respect to the upper part or in the shaped groove 10.

With the device in the position shown in Figure 1, a printing forme to be fixed on a forme cylinder 1 can now be introduced into the slot between the upper surface of the short leg of the L-formed profiled lower portion 5 and the downwardly facing surface of the V-formed groove 10, whereafter, for clamping, a swivelling of the actuation device 6 (eccentric shaft or shaft with a flat) takes place. As indicated in Figure 2, there takes place in this connection both a swivelling and also an upwards movement in the radial direction of the L-shaped profiled 12 - lower part 5, whereby this is supported against the lower side on the long leg via the shaft 11 (or the several rollers) against the inclined surface of the pressure piece 12 in the radial direction. The short leg of the L-shaped profiled lower part 5 can, in this connection, spring somewhat for force limitation so that overall a self-clamping effect between the eccentric or the shaft with flats of the actuation device 6 and the corresponding leg of the lower part 5 arises.

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Claims (7)

1. A fixing device for printing formes on the forme cylinders of printing presses, the device consisting of a clamping rail with a radially movable and swivellable lower part, an actuation device acting on the lower part and spring elements arranged between upper part and lower part, wherein the lower part is constructed as an Lshaped profiled clamping rail, the short leg of which cooperates with a correspondingly shaped surface in the upper part for clamping the printing forme and on the long leg of which the actuation device acts, and wherein for clamping the actuation device cooperates in positively interlocked fashion with the lower part and the spring elements arranged between lower part and upper part to maintain the lower part in the opened position.

2. A fixing device according to Claim 1 wherein a shaft or several adjacently lying rollers are let into a groove in the upper part which cooperate(s) with a correspondingly shaped support surface at the end of the short leg of the lower part.

3. A fixing device according to Claim 1 or 2 wherein the lower part is supported with a corresponding surface on the end of the long leg on a shaft or several adjacently lying rollers which, for their part, are supported on a surface running obliquely relative to the direction of action of the actuation device.

4. A fixing device according to Claim 3 wherein the oblique surfaces coordinated to the shaft or the several adjacently lying rollers are constructed as one or more movable pressure pieces movable with respect to the upper part by means of adjusting screws.

5. A fixing device for clamping a printing forme on to a forme cylinder in a printing press substantially as hereinbefore described with reference to the accompanying drawings.

6. A printing press forme cylinder including a fixing device according to any one of Claims 1 to 5 set in a channel thereof.

7. An of f set printing press including one or more f orme cylinders according to Claim 6.