Abstract:
A clamping device for firmly clamping a cylinder packing or covering on a printing machine cylinder, the clamping device having a clamping seat, a clamping jaw cooperating therewith, and an eccentric shaft, includes a support wherein the eccentric shaft and the clamping jaw are jointly mounted, the support being adjustable alternatively into a first support position and into a second support position relative to the clamping seat; and a printing machine having at least one clamping device with the foregoing construction.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a clamping device for firmly clamping a cylinder packing or covering on a printing machine cylinder, the clamping device including a clamping seat, a clamping jaw cooperating therewith, and an eccentric shaft. 
     Such a clamping device is described, for example, in the published Non-prosecuted Japanese Utility Model Specification No. 2-104235. The trailing-edge clamping device shown in FIG. 2 of the aforementioned published specification for clamping printing plates includes a winding rod extending in the direction of the cylinder axis and having a clamping plate articulatedly connected thereto, the winding rod bearing an eccentric shaft for operating the clamping plate. In this clamping device, a clamping seat or support is formed directly on the winding rod. Neither the eccentric shaft nor the clamping plate is mounted in a support that is adjustable with respect to the clamping seat. 
     A drawback with respect to the operating convenience of this clamping device of the Japanese utility model is the rather small width of the opening between the clamping plate and the clamping seat, the printing plate being insertable into the opening only with great difficulty so as to attain the clamping position thereof. 
     Furthermore, there is described in the published German Patent DE 195 15 843 C1, corresponding to U.S. Pat. No. 5,642,669 to Becker, a device for clamping a printing plate on a plate cylinder, which does not, however, belong to the general type of clamping device mentioned in the introduction hereto. 
     Although the width of the opening thereof is sufficiently large, this clamping device of the German patent document has a drawback from another point of view. In order to release the end of the plate, pneumatic cylinders are required, by which a clamping element is pivotable counter to the action of clamping springs. In the case of this heretofore known device, manual release by a tool is not possible for the operator, because the clamping force of the clamping springs that has to be overcome is too high. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a clamping device for firmly clamping a cylinder packing on a printing machine cylinder, the clamping device being operatable manually, and having a large opening width. 
     With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a clamping device for firmly clamping a cylinder packing or covering on a printing machine cylinder, the clamping device including a clamping seat, a clamping jaw cooperating therewith, and an eccentric shaft, comprising a support wherein the eccentric shaft and the clamping jaw are jointly mounted, the support being adjustable alternatively into a first support position and into a second support position relative to the clamping seat. 
     In accordance with another feature of the invention, the support is mounted in the printing machine cylinder so as to be pivotable about a support joint. 
     In accordance with a further feature of the invention, the clamping jaw is mounted in the support so as to be pivotable about a jaw joint. 
     In accordance with an added feature of the invention, the clamping device includes a spring borne by the support. 
     In accordance with an additional feature of the invention, the clamping jaw is returnable by the spring from a clamping position into a released position. 
     In accordance with yet another feature of the invention, the eccentric shaft has a safeguard against rotation assigned thereto for blocking rotation of the eccentric shaft when the support is in the first support position, and for enabling rotation of the eccentric shaft when the support is in the second support position. 
     In accordance with yet a further feature of the invention, the eccentric shaft is formed with a circumferential flat which, when the support is in the first support position, is located opposite a stop face on the outside of the support and formlockingly locks the rotation of the eccentric shaft. 
     In accordance with yet an added feature of the invention, the eccentric shaft, on at least one shaft end thereof, has a tapered shaft extension, a side face of the shaft extension forming the flat. 
     In accordance with yet an additional feature of the invention, the clamping device includes a coulisse assigned to the eccentric shaft, the coulisse being disposed on the printing machine cylinder and having a groove with an inner face forming the stop face, the coulisse having a widening of the groove which, when the support is in the second support position, enables the rotation of the eccentric shaft. 
     In accordance with another aspect of the invention, there is provided a printing machine having at least one clamping device with at least one of the foregoing features. 
     Thus, the clamping device according to the invention for firmly clamping a cylinder packing on a printing machine cylinder, having a clamping seat and a clamping jaw cooperating with the latter, and having an eccentric shaft, is distinguished by the fact that the eccentric shaft and the clamping jaw are jointly mounted in a support which can be adjusted alternatively into a first support position and a second support position relative to the clamping seat. 
     With this clamping device, a two-stage clamping operation may be implemented. In a first stage, the clamping jaw can be adjusted by a manual adjustment of the support from a wide-open jaw position with good accessibility for the insertion of one edge of a cylinder packing into a less-open jaw position. In the less-open jaw position, the clamping jaw does not yet exert full clamping action on the cylinder packing. However, the latter is secured against slipping out of the clamping position thereof. In a second stage, the clamping jaw is adjustable by a manually performable rotation of the eccentric shaft from the less-open jaw position into a completely closed jaw position with full clamping effect. The clamping device permits distortion-free and in-register firm clamping even of cylinder packings without a bent-over edge, which provides a precondition for subsequent uniform tensioning of the cylinder packing in the circumferential direction of the printing machine cylinder. 
     The following embodiments constitute developments of the clamping device according to the invention which are particularly advantageous in construction terms and ensure high operating security. 
     One embodiment is distinguished by the fact that the support is mounted in the printing machine cylinder so that it can be pivoted about a support joint. 
     A further embodiment is distinguished by the fact that the clamping jaw is mounted in the support so that it can be pivoted about a jaw joint. 
     A further embodiment is distinguished by the fact that the support bears a spring. 
     A further embodiment is distinguished by the fact that the clamping jaw can be returned by the spring from a clamping position into a released position. 
     A further embodiment is distinguished by the fact that the eccentric shaft has a rotation safeguard assigned thereto, which blocks rotation of the eccentric shaft when the support is in the first support position, and which enables rotation of the eccentric shaft when the support is in the second support position. 
     A further embodiment is distinguished by the fact that the eccentric shaft has a circumferential flat which, when the support is in the first support position, is located opposite a stop face on the outside of the support. 
     A further embodiment is distinguished by the fact that, on at least one shaft end, the eccentric shaft has a tapered shaft extension, a side face of the shaft extension forming the flat. 
     A further embodiment is distinguished by the fact that the eccentric shaft has a coulisse assigned thereto that is disposed on the printing machine cylinder and has a groove with an inner face forming the stop face, the coulisse having a widening of the groove which, when the support is in the second support position, enables the rotation of the eccentric shaft. 
     The clamping device according to the invention is suitable for firmly clamping various types of cylinder packings, for example, foil or film-like cylinder packings or those formed as flexible plates, on printing machine cylinders of rotary printing machines. For example, with the clamping device, it is optionally possible for plates based on an aluminum carrier, plates formed of polyester material, as well as rubber blankets for varnishing or coating the whole area, to be clamped onto a coating cylinder. 
     The clamping device permits a reliable, frictional and/or formlocking firm clamping of the cylinder packings to be effected, without requiring the edges thereof to be bent over for this purpose. A good frictional connection can be achieved by a directly clamping contact surface on the clamping seat, and/or the clamping jaw being roughened. In addition or as an alternative to these measures, a good formlocking clamping action can be achieved by the contact surface of the clamping seat and/or the contact surface of the clamping jaw being provided with knob-like formlocking elements which press into the cylinder packing. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a clamping device for firmly clamping a cylinder packing on a printing machine cylinder, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side elevational view of a printing machine having a cylinder carrying a packing or covering on the outer cylindrical surface thereof, the packing being held at a trailing edge thereof by a clamping device; 
     FIG. 2 is an enlarged fragmentary view of FIG. 1 showing the clamping device in a clamping position; 
     FIG. 3 is a view like that of FIG. 2 in a different operative phase of the clamping device wherein it is in a released position; 
     FIG. 4 is a view like those of FIGS. 2 and 3 in yet a further operative phase of the clamping device wherein it is in a wide open position; 
     FIG. 5 is a view similar to those of FIGS. 2 to  4 , showing another embodiment of the clamping device having a clamping jaw mounting that differs from the clamping jaw mounting shown in FIGS. 2 to  4 ; and 
     FIG. 6 is a top plan view, rotated 90° clockwise, of the clamping device illustrated in FIGS. 2 to  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and, first, particularly to FIG. 1 thereof, there is shown therein a printing machine  1  represented as a rotary printing machine having a sheet feeder  2 , a sheet delivery  3 , a number of offset printing units, namely four printing units  4  to  7  in the illustrated embodiment, and a coating unit  8  disposed downline of the offset printing units  4  to  7  in a direction of transport of the printed material. The coating unit  8  includes a cylinder  9  carrying the printed material and having assigned thereto, at the circumference thereof, a cylinder  10  covered by a cylinder packing  11 . The cylinder  9  is an impression cylinder assigned to the cylinder  10 , and the cylinder  10  is a coating cylinder  10  for applying a printing ink, a varnish or a coating liquid to the printed sheet resting at that time on the cylinder  9 . 
     A first clamping device  12 . 1  serves for firmly clamping a trailing edge of the cylinder packing  11 , as viewed in the circumferential direction of the cylinder  10 , and a second clamping device  12 . 2  serves for firmly clamping, or another fastening device serves for holding, a leading edge of the cylinder packing  11 . 
     The construction of the clamping device  12 . 1  is illustrated in FIG.  2 . The clamping device  12 . 1  includes a bearing block  13  that is fixed to the cylinder  10  and, for example, to a non-illustrated tensioning or tautening lever that is assigned to the cylinder  10  and tensions or tautens the cylinder packing  11  in the circumferential direction of the cylinder  10 . The cylinder packing  11  is clamped between the bearing block  13  and a clamping jaw  15  mounted in the bearing block  13  so as to be pivotable via a plurality of articulated shafts  22  and  23 . 
     The clamping jaw  15  is mounted on a support  14  so that it is pivotable relative to the latter via the first articulated shaft or jaw joint  22 , and the support  14  is, in turn, mounted, via the second articulated shaft or support joint  23 , so that it is pivotable relative to the cylinder  10  and to the bearing block  13 . The clamping jaw  15  forms a rocker having a first lever arm, at the underside of which there is formed a clamping surface  30  (FIG. 4) that presses the cylinder packing  11  against a clamping seat  31  on the bearing block  13 . Formed on the underside of a second lever arm of the clamping jaw  15  is a supporting bale or hoof ball  37 , with which the clamping jaw  15  rests on a curved circumferential surface of an eccentric shaft  16 . 
     The eccentric shaft  16  is rotatably mounted in the support  14 , being inserted into a bearing groove  40  therefor that is shaped like a prismatic guide open at the top, so that the eccentric shaft  16  rests in a hollow extending along two parallel contact lines  41  and  42 . The articulated axes  24  and  25 , the clamping jaw  15  shaped like a profiled bar, the circumferentially flattened eccentric shaft  16 , and the bearing groove  40  extend in an axially parallel direction relative to one another and to the axis of rotation  26  (FIG. 1) of the cylinder  10 . 
     In addition to the clamping jaw  15  and the eccentric shaft  16 , the support  14  further bears at least one spring  21 , which is arranged to urge the clamping jaw  15  and the support  14  towards one another. The spring  21  is constructed as a helical spring that is inserted into an accommodating borehole  20  formed in the support  14  and presses against the first lever arm of the clamping jaw  15  at the underside thereof. It is preferable for a plurality of such springs  21  to be arranged in an axially parallel row, i.e., perpendicularly to the plane of FIG. 2, in the aforedescribed manner. 
     As a result of adjusting the support  14  by pivoting it about the second articulated shaft  23  from a first support position  14   a  (FIG. 4) into a second support position  14   b  (FIGS. 2 and 3) about axis  25 , the clamping jaw  15  and, simultaneously, the eccentric shaft  16 , on the one hand, and eccentric axes  19 . 1  and  19 . 2  thereof, respectively, on the other hand, are displaceable, relative to the clamping seat  31  that forms a counterpart to the clamping jaw  15  and that is fixed to the printing machine cylinder  10 , from a first axial position (FIG. 4) into a second axial position (FIGS. 2 and 3) that is axially parallel to the first axial position. The clamping jaw  15  is pivotable, relative to the support  14  about axis  24 , alternatively into a first jaw position  15   a  (FIGS. 3 and 4) and into a second jaw position  15   b  (FIG.  2 ), so that, in addition to the adjustment of the clamping jaw  15  relative to the cylinder  10 , which is effected by the adjustment of the support  14  towards the cylinder  10 , an additional ability to adjust the clamping jaw  15  relative to the support  14  is provided. 
     As the eccentric shaft  16  is rotated in a counterclockwise direction, the oval cross-sectional shape thereof has the effect of continuously increasing the clamping force of the clamping jaw  15 , and permits the setting of the clamping force necessary for the respective cylinder packing  11  as a function of the thickness and compressibility of the latter. The oval cross-sectional shape of the eccentric shaft  16  results from two semicircles having radii R 1  and R 2  of equal size of, for example, 7 millimeters, respectively, the centers  19 . 1  and  19 . 2  of the semicircles being displaced an offset distance A in opposite directions, and the semicircles accordingly being displaced into one another. 
     The eccentric shaft  16  is formed with a circumferential flat  36  that extends over the entire axial length of the eccentric shaft  16 , and is slightly concavely curved, as can be seen from the cross-sectional view of the eccentric shaft  16 . With reference to the same cross-sectional plane (image plane), the flat  36  extends approximately perpendicularly to that direction in which the two semicircles are pushed together the offset distance A to form the oval shape of the eccentric shaft  16 . The radius of curvature of the circumferential concave flat  36  is greater than the radius of curvature of the convex supporting bale or hoof ball  37 , so that the situation wherein the convex supporting bale or hoof ball  37  rests in the hollow of the concave flat  36  is avoided, and the supporting hoof ball or bale  37  rests on the flat  36  along a supporting line that is perpendicular to the plane of the figure or image plane, as shown in FIG.  3 . 
     Formed on each end of the eccentric shaft  16  is a shaft extension  17 , the shaft extensions  17  serving to guide the eccentric shaft  16  on both sides (note FIG.  6 ). Each shaft extension  17  slides in the manner of a groove block in a respective slotted guide or coulisse  27 . The coulisses  27  are formed on the cylinder  10  on both sides of the eccentric shaft  16 , and, for example, on the bearing block  13  thereof or side walls  44  of the cylinder  10 . The end shaft extensions  17  can be produced, for example, by milling the eccentric shaft  16  a milling depth down to the flat  18  and, for example, a milling width of 5 millimeters, by which the shaft extension  17  projects, the shaft extension  17  appearing to be approximately semicircular in a cross-sectional view, and the flat  18  on the shaft extension  17  extending at an oblique angle to the circumferential flat  36 . 
     A dimension, measured perpendicularly to the flat  18 , up to the external rounding of the shaft extension  17  is smaller than a maximum dimension of the shaft extension  17 , that extends parallel to the flat  18 , so that a narrow cross-sectional extent and a broad cross-sectional extent of the shaft extension  17  result. The narrow cross-sectional extent is smaller than a nonwidened region of the coulisse  27  having a groove width N. In the longitudinal position thereof, the shaft extension  17  can be inserted into this nonwidened region of the coulisse  27 , as is illustrated in FIG.  4 . The broad cross-sectional extent of the shaft extension  17  is greater than the groove width N, so that rotation of the eccentric shaft  16  is blocked when the shaft extension  17  is located in the nonwidened region. 
     The coulisse  27  that extends in the manner of a circular arc about the axis  25  of the articulated shaft  23 , has a groove widening  29  that permits rotation of the shaft extension  17  within the groove in the coulisse  27 , from the longitudinal position of the shaft extension  17  into the tranverse position thereof. 
     FIG. 5 illustrates an alternative construction of the articulated shaft or pivot joint  22  of the embodiment of FIGS. 2 to  4 , which is particularly beneficial in production terms. In this case, at least one screw  33  is screwed into the support  14 , the underside of the head of the screw being rounded in an approximately hemispherical shape. The clamping jaw  32  that is used instead of the clamping jaw  15  in this alternative embodiment has a bore through which the screw  33  passes, the bore being formed with an inner annular chamfer  35  that is set at an angle to the axis of the screw and that, together with the rounding  34  of the screw head which rests on the inner chamfer  35 , forms a swivel joint of the clamping jaw  32 . It is preferable for a plurality of swivel joints of this type to be formed on the clamping jaw  32  in an axially parallel row perpendicular to the plane of the figure. 
     FIG. 6 illustrates the clamping device  12 . 1  in a plan view, some of the parts thereof having been omitted in the interest of better clarity. FIG. 6 shows that the eccentric shaft  16  has a number of clamping jaws  15  assigned thereto, and that the eccentric shaft  16  is provided with an annular bead located between the clamping jaws  15  and having one or more transverse bores  39  formed therein for the insertion of a handle  38  serving to rotate the eccentric shaft  16 . Instead of the handle  38  and the insertion bore  39 , other tools which can also be brought into formlocking connection with the eccentric shaft  16  can be used to rotate the eccentric shaft  16 . In this regard, it is noted that a formlocking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a forcelocking connection, which locks the elements together by force external to the elements. 
     The functioning and operation of the clamping device  12 . 1  is described hereinbelow with reference to FIGS. 2 to  4 : 
     In FIG. 4, the clamping device  12 . 1  is illustrated with the support  14  in the first support position  14   a  and with the clamping jaw  15  in the first jaw position  15   a , the clamping jaw  15  being wide open, and the clamping surface  30  thereof being retracted from a position opposite the clamping seat  31 , so that the edge of the cylinder packing  11  can be placed without difficulty onto the clamping seat  31 . If the operator pulls the handle  38  upwards in order to rotate the eccentric shaft  16  in the counterclockwise direction, as indicated in FIG. 4, rotation of the eccentric shaft  16  in relation to a groove inner surface  28  forming a stop face  28  is blocked at times by the latter striking the flat  18 , as long as the shaft extension  17  is located in the nonwidened region of the coulisse  27 , and thus the flat  18  is located opposite the stop face  28 . 
     The result, initially, is an adjustment of the support  14  without any rotation of the eccentric shaft  16  and thus without any adjustment of the clamping jaw  15 , the support  14  being pivoted in the counterclockwise direction about the articulating shaft or joint  23  until the side surface or flat  18  has been displaced out of the position opposite the stop face  28 , and the shaft extension  17  has been displaced into a groove widening  29  (note FIG. 2) which enables rotation of the eccentric shaft  16 , whereafter, the clamping device  12 . 1  is in the position illustrated in FIG.  3 . In this so-called released position, the clamping jaw  15  has already been pushed over the clamping seat  31  and the cylinder packing  11  resting on the latter, but has not yet been completely closed, so that any necessary fine corrections to the position of the cylinder packing  11  remain possible. 
     Pulling the handle  38  farther up effects a rotation of the eccentric shaft  16  in the counterclockwise direction against the restoring action of the spring  21 , further pivoting of the support  14  being blocked by a striking of the bearing block  13  against a stop face  43 . Due to the rotation of the eccentric shaft  16 , the clamping jaw  15  is pivoted in a counterclockwise direction about the articulating shaft or swivel joint  22  until it firmly clamps the cylinder packing  11 , and the clamping device  12 . 1  is adjusted from the slightly open position thereof illustrated in FIG. 3 into the fully closed clamped position thereof illustrated in FIG.  2 . 
     An advantage with regard to the clamping device  12 . 1  is that the entire clamping operation is executed with a single operating movement, i.e., by pulling the handle  38  upwards, the clamping movement being subdivided into two stages. In the first stage, the clamping eccentric  16  is blocked by the coulisse  27  and, guided by the coulisse  27 , covers a comparatively great travel distance. In the second stage, the coulisse  27  enables the clamping eccentric  16  and thereby permits the actual clamping movement. Consequently, very good accessibility is provided for the insertion of the cylinder packing  11 . 
     When the cylinder packing  11  is being clamped onto the cylinder  10 , the clamping device  12 . 1  holding the leading edge can be closed first and, either before or after the latter, the clamping device  12 . 2  holding the trailing edge of the cylinder packing  11  can be closed. When both clamping devices  12 . 1  and  12 . 2  have been closed, they can be moved towards one another approximately in the circumferential direction, so that the cylinder packing  11  wrapping around the cylinder  10  is tautly tensioned.