Printing press having carriage mounted interchangeable plate cylinders

Abstract: A rotary offset printing press having a pair of carriage mounted interchangeable plate cylinders (32,34) is disclosed. The carriage (36) is slidably mounted to the press and reciprocates along a generally linear path. The pair of plate cylinders are rotatably mounted to the carriage, and each of the plate cylinders is selectively moveable into an operative position in contact with the blanket cylinder (22). Accordingly, while the press is operating using one of the plate cylinders, the other plate cylinder is idle, which permits the impression sleeve thereon to be removed and replaced without stopping the press. The plate cylinders, when in their respective operative positions, contact the blanket cylinder at the same point of tangency, thus simplifying registration.

Description: The present invention relates generally to a rotary offset printing press having a pair of carriage mounted plate cylinders, one of which is positioned to transfer images to a blanket cylinder while the other is idle. The carriage mounted plate cylinder arrangement allows the press operator to re-plate the idle plate cylinder while the press is running at full speed, and thus changeover can be effectuated very quickly. Background of the Invention Rotary offset double-sided printing presses are generally well known in the art. On rotary presses, a web of paper passes through one or more printing units or couples, with each couple having a pair of blanket cylinders in contact with the opposite sides of the paper web. Each blanket cylinder is in contact with a plate cylinder which transfers images to the blanket cylinder for printing onto the web in a manner well known in the art. In order to change the printed material, the plate or impression sleeve on one or both of the plate cylinders must be separated from its adjacent blanket cylinder and changed. Typically, when a rotary offset printing press is operated for short runs or when editorial changes must be made in newspaper production, the printing press is stopped, the plate cylinders are removed form the printing press, the impression sleeves on the plate cylinders are changed, the plate cylinders are re-installed in the printing press, and the machine is then re-started. Each time the press is started, stopped, and re-started a tremendous amount of paper is wasted as the machine slows to a stop and is subsequently brought back up to operating speed after the changeover has been completed. Moreover, a tremendous amount of valuable time is lost as the impression sleeves are changed and the ink settings are adjusted while the press sits idle. Accordingly, there exists a need for a rotary offset printing press having interchangeable plate cylinders, each having a different impression sleeve, so that changeovers can be made quickly and efficiently without stopping and re-starting the printing press. There also exists a need for a printing press on which the impression sleeve on the inactive plate cylinder can be changed safely while the press is still operating using the other plate cylinder. EP-A-0 895 857 which forms part of the prior art according to Art. 54(3) EPC describes a printing apparatus in which a plate cylinder and an ink roller assembly are duplicated. The plate cylinders are moveable together with their respectice ink roller assembly between a position in which the first plate cylinder with the first ink roller assembly is in contact with a blanket cylinder, and a second position in which the second plate cylinder with the second ink roller assembly is in contact with the blanket cylinder. Document US-A-5 063 844, according to which the preamble of claim 1 has been drafted, discloses a printing press in which two plate cylinders are moveable in unison between a first and a second position. In the first position, the first plate cylinder is in contact with a blanket cylinder at a first point of tangency. In the second position, the second plate cylinder is in contact with the blanket cylinder at a second point of tangency, which is distinct from the first point of tangency. A similar printing press is known from DE-A-33 13 219. US-A-5,463,950 discloses a printing machine with two plate cylinders which are moveable between a first and a second position. In the first position, the first plate cylinder is in contact with a blanket cylinder, and in the second position, the second plate cylinder is in contact with the blanket cylinder. The point of tangency is the same in both positions. In order to go from the first to the second position, the first plate cylinder has to be shifted upwardly and then moved laterally to a rest position. Then, the second plate cylinder has to be moved laterally out of his rest position and, finally, downwardly to the blanket cylinder. Summary of the Invention The present invention provides a printing press which comprises a frame, a blanket cylinder rotatably supported by said frame being positioned for contacting and transferring images to a substrate, a first and a second plate cylinder adapted to transfer images to said blanket cylinder, and an ink roller assembly for transferring ink from an ink supply to the first or the second plate cylinder. Said plate cylinders are moveable in unison between a first and a second position, one of said plate cylinders being in contact with said blanket cylinder at a point of tangency and with said ink roller assembly when the plate cylinders are in said first position, the other one of said plate cylinders being in contact with said blanket cylinder at a point of tangency and with said ink roller assembly when the plate cylinders are in said second position. The point of tangency in said first position is the same as in said second position. The pair of interchangeable plate cylinders is preferably mounted on a moveable carriage so that each plate cylinder can be selectively brought into contact with its adjacent blanket cylinder. The carriage is supported by linear bearings enabling the carriage to move back and forth along a generally linear path, thus enabling one of the plate cylinders to be brought into contact with the blanket cylinder while the other plate cylinder is shifted away from the blanket cylinder to an inoperative position. Thus, while one of the plate cylinders is in operation the other plate cylinder is idle, which permits the impression sleeve on the idle plate cylinder to be installed or replaced while the printing press is operating at full speed. Accordingly, downtime is greatly reduced. Furthermore, because the plate cylinders are paired and move in unison, only one of the plate cylinders can contact the blanket cylinder at a time, and consequently the plate cylinders never interfere with each other. An embodiment of the present invention also incorporates a pair of retractable form or inking rollers which are thrown out of position prior to movement of the carriage and which permit generally linear movement of the carriage, thereby enabling each of the plate cylinders, when in their respective operative positions, to contact the blanket cylinder at the same point of tangency. Consequently, it is much easier to keep the plate cylinders in proper register, which is especially important in multi-color and verso-printing processes. Moreover, the linear travel of each plate cylinder away from the blanket cylinder is far enough that no axial movement (i.e. movement of the plate cylinder in a direction parallel to the axis of the blanket cylinder) is required. Preferably, each of the plate cylinders are rotated by separate drive motors. When the idle cylinder has been plated up and is ready for use, the cylinder can be pre-driven to match the speed of the press, registered, and brought into contact with the blanket cylinder upon movement of the carriage. The other cylinder can then be stopped and re-sleeved in preparation for the next changeover. Ideally, the changeover process can take place very quickly, and changeover times being as short as five (5) seconds or less are contemplated. Thus, down time and wasted paper are effectively eliminated. Accordingly, it is an object of this invention to provide a rotary offset printing press having interchangeable mounted plate cylinders which virtually eliminate wasted paper and downtime. Another object of this invention is to provide a rotary printing press having a pair of interchangeable plate cylinders and which is more cost effective for short printing runs and editorial zone changes than are prior art presses. A still further object of this invention is to provide a paired plate cylinder arrangement which eliminates the possibility of interference between the plate cylinders. These and other objects of the invention will become readily apparent to those skilled in the art upon a reading of the following description with reference being had to the accompanying drawings. Brief Description of the Drawings Figure 1 is an elevational view of a rotary offset printing press incorporating the features of the present invention; Figure 2 is an enlarged fragmentary elevational view of the printing press shown in Figure 1 and illustrating one of the plate cylinders in the middle or operative position in contact with the blanket cylinder; Figure 3 is a schematic diagram of one of the paired plate cylinder assemblies shown in Figures 1 and 2 illustrating the linear movement of the carriage mounted plate cylinders and the movement of the retractable inking rollers; and Figure 4 is an enlarged fragmentary elevational view similar to that shown in Figure 2, but illustrating the other of the plate cylinders in the operative position. Detailed Description of the Invention Referring now to the drawings, a rotary offset printing press incorporating the features of the present invention is generally referred to by the reference numeral 10. Press 10 includes a housing or frame 6 and a synchronized drive system 8 as is commonly employed in the industry for driving the rotatable components described below. As shown in Figure 1, press 10 typically includes four printing units or couples 12, 14, 16 and 18 that are arranged in progression such that a paper web or substrate 5 moves along a path 4 between the contact nip of each couple. Substrate 5 is typically a continuous web of paper as is well known in the art. In four color offset lithographic printing, the image to be printed on the substrate 5 is decomposed into four color "separations" which are combined to facilitate the printing of the final image. The four separations are comprised of the primary or black separation, and three secondary separations, typically cyan, magenta and yellow. Each of the printing couples 12, 14, 16, 18 applies one of the separations, with each separation being superimposed over the preceding separation(s) to form the final image, all of which is well known in the art. Although Figure 1 illustrates four printing couples 12, 14, 16, 18 arranged in progression, it will be understood that, except for the different color being applied, the structure, function and operation of each printing couple is the same. Accordingly, only printing couple 14 will be described in detail. Referring now to Figure 2, couple 14 includes a pair of blanket cylinders 20, 22 which converge along the substrate path 4 such that the substrate 5 passes between the blanket cylinders 20, 22, thereby imparting an image to both sides of the substrate 5. Each of the blanket cylinders 20, 22 has associated therewith a plate cylinder assembly 24, 26, respectively. Each plate cylinder assembly 24, 26 in turn includes a pair of plate cylinders 28, 30 and 32, 34, respectively. The diameters of blanket cylinders 20, 22 and plate cylinders 28, 30, 32 and 34 are all identical. It will be understood that the structure, function and operation of blanket cylinder 20 and its associated plate cylinder assembly 24 is the same as the structure, function and operation of blanket cylinder 22 and its associated plate cylinder assembly 26. Accordingly, only the blanket cylinder 22 and its associated plate cylinder assembly 26, which is shown to the right of Figure 1, will be described in detail. Blanket cylinder 22 is rotatably mounted to frame 6 on a set of bearings or sleeves (not shown) in a well known manner. As shown in Figure 2, cylinder 22 is mounted on an eccentric shaft (not shown) which includes a lever arm 28, and an actuator 30 connects lever arm 28 to frame 6, which permits cylinder 22 to be drawn away from the substrate path 4 and cylinder 20 in order to permit the removal of the substrate 5 in the event of a tear. Blanket cylinder 22 is operatively connected to drive system 8 for rotating cylinder 22. Plate cylinders 32, 34 of plate cylinder assembly 26 are mounted to a slide assembly or carriage 36 and supported for axial rotation on a set of sleeves or bearings (not shown) in a well known manner. Carriage 36 is slidably mounted to frame 6 by a plurality of linear bearings 38 slidably supported on a pair of tracks or rails 40, 42. A rotatable threaded shaft 44 and a drive motor 46 are mounted to frame 6 adjacent track 42, and an arm 48 extending from carriage 36 and having a threaded follower 49 attached thereto engages rod 44. Accordingly, rotation of rod 44 upon the actuation of drive motor 46 causes carriage 36 to reciprocate back and forth along tracks 40, 42 in a generally linear path as indicated by the reference arrow A between the position shown in Figures 2 and 3 and the position shown in Figure 4. Plate cylinders 32 and 34 move in unison by virtue of their attachment to carriage 36. As such, one of the plate cylinders 32, 34 may be selectively brought into contact with the blanket cylinder 22 depending on the location of carriage 36 along path A. For example, Figure 2 illustrates plate cylinder 34 in the middle or operative position designated by reference arrow B in contact with blanket cylinder 22 at a point of contact or tangency 35. It will be noted that point of tangency 35 intersects a radius 39 extending from the axis 41 of blanket cylinder 22. It will also be noted that radius 39 lies generally perpendicular to the path A of carriage 36. With carriage 36 in the position shown, plate cylinder 32 is in its inoperative position designated by reference arrow C located towards one end of path A, which is towards the upper right when viewing Figure 2, and is more than one cylinder diameter removed from the middle or operative position occupied by plate cylinder 34. By comparison, Figure 4 illustrates the carriage 36 at the other end of path A, with plate cylinder 32 in the operative position in contact with blanket cylinder 22 at the point of tangency 35. Plate cylinder 34 is now in its inoperative position designated by reference arrow D located at the other end of path A, which is towards the lower left when viewing Figure 4, and is likewise more than one cylinder diameter removed from the middle or operative position B now occupied by plate cylinder 32. As shown schematically in Figure 3, carriage 36 preferably includes a pair of position sensors 43, 45. A limit switch 47 is operatively connected to drive motor 46. As such, position sensor 43 indicates the presence of plate cylinder 32 in the operative position B, while position sensor 45 indicates the presence of plate cylinder 34 in the operative position B. When either position sensor 43, 45 approaches limit switch 47, the limit switch 47 signals drive motor 46 to stop with carriage 36 at a predetermined location in order to optimize the contact between plate cylinder 32 (Figure 4) or plate cylinder 34 (Figure 2) and the adjacent blanket cylinder 22. As shown in Figures 2 through 4, and ink roller assembly 50 is mounted to frame 6 adjacent plate cylinder assembly 26, which transfers ink from an ink supply 52 to either of plate cylinders 32, 34 via a pair of retractable rollers 54, 56. Retractable rollers 54, 56 are shiftable between the extended position as shown by the solid lines in Figures 2 through 4, and the retracted position as shown by the dotted lines in Figures 2 through 4. When in the extended position the retractable rollers 54, 56 contact either plate cylinder 34 as shown in Figures 2 and 3, or plate cylinder 32 as shown in Figure 4. When in the retracted position, plate cylinder assembly 26 is free to shift between the position shown in Figure 2 in which plate cylinder 34 abuts blanket cylinder 22, and the position shown in Figure 4, in which plate cylinder 32 abuts blanket cylinder 22. Retractable rollers 54, 56 are preferably mounted to frame 6 using eccentric shafts (not shown) in a manner well known in the art. A dampening assembly 58 is also mounted adjacent plate cylinder assembly 26 as shown in Figure 3. Dampening assembly 58 applies a dampening solution from a supply source 60 to either of the plate cylinders 32, 34 via a retractable dampening roller 62. As shown in Figure 3, dampening roller 62 is shiftable between the extended position shown in solid lines in Figure 3 and a retracted position illustrated in dotted lines. In operation, the four printing couples 12, 14, 16 and 18 are arranged in progression as shown in Figure 1 such that the continuous substrate 5 running along substrate path 4 will pass between the blanket cylinders of each printing couple, including the blanket cylinders 20, 22 of printing couple 14. All of the cylinders in the system are rotated at a common peripheral speed by drive system 8 in a manner well known in the art. As shown in Figures 1 through 3, printing couple 14 during normal operations is positioned such that blanket cylinder 22 abuts blanket cylinder 20 such that the cylinders impart an image on each of the opposite sides of the substrate 5 passing between the blanket cylinders along substrate path 4. When the plate cylinder assembly 26 is in the position shown in Figures 1 and 2, plate cylinder 34 abuts blanket cylinder 22, thus transferring images from plate cylinder 34 to blanket cylinder 22 for subsequent transference to the substrate 5 in a manner well known in the art. When it is desired to change editions or shift to a different print run, the retractable ink rollers 54 and 56 are retracted to the positions illustrated by the dotted lines in Figure 3, and the retractable dampening roller 62 is likewise retracted to the position illustrated by the dotted lines in Figure 3. With the rollers 54, 56 and 62 retracted, carriage 36 is free to move in the linear direction as indicated by reference arrow A in Figure 2 upon the rotation of threaded rod 44 by drive motor 46. After the plate cylinder assembly 26 has been shifted to the position shown in Figure 4, the retractable rollers 54, 56 and 62 are returned to their contact positions abutting plate cylinder 32, and plate cylinder 32 in turn abuts blanket cylinder 22. The press 10 can now be operated using plate cylinder 32 in place of plate cylinder 34, with plate cylinder 34 now being idle and spaced away from blanket cylinder 22. Furthermore, the surface of plate cylinder 34 can now be prepared for the next print job, which is typically accomplished by removing an impression sleeve (not shown) from the plate cylinder in a conventional manner. Meanwhile, the press 10 can be operated while the impression sleeve on plate cylinder 34 is being changed. Subsequently, when it is again desired to change the edition being printed or to start an entirely new job, the plate cylinder assembly 26 is again shifted back into the position shown in Figures 1 through 3, and the press is operated using the plate cylinder 34. In this position, the impression sleeve on the surface of plate cylinder 32 can now be changed while the press 10 is operating using plate cylinder 34. It will be understood that the above description does not limit the invention to the above-given details. It is contemplated that various modifications and substitutions can be made without departing from the scope of the following claims.

Claims: A printing press (10) comprising: a frame (6); a blanket cylinder (22) rotatably supported by said frame (6) being positioned for contacting and transferring images to a substrate (5); a first and a second plate cylinder (32, 34) adapted to transfer images to said blanket cylinder (22); an ink roller assembly (50) for transferring ink from an ink supply (52) to the first or the second plate cylinder (32, 34); wherein said plate cylinders (32, 34) are moveable in unison between a first and a second position, one of said plate cylinders (32) being in contact with said blanket cylinder (22) at a point of tangency (35) and with said ink roller assembly (50) when the plate cylinders (32, 34) are in said first position, the other one of said plate cylinders (32, 34) being in contact with said blanket cylinder (22) at a point of tangency (35) and with said ink roller assembly (50) when the plate cylinders (32, 34) are in said second position; characterised in that the point of tangency (35) in said first position is the same as in said second position. The printing press as claimed in claim 1, wherein said substrate (5) is a web of paper passing through the printing press (10). The printing press as claimed in claim 1 or 2, wherein said plate cylinders (32, 34) are movable in unison along a linear path. The printing press as claimed in anyone of claims 1 to 3, wherein the first and second plate cylinders (32, 34) are rotatably mounted to a carriage (36), said carriage (36) being slidably mounted to said frame (6). The printing press as claimed in anyone of claims 1 to 4, wherein the path of movement of said plate cylinders (32, 34) is generally perpendicular to a radius extending from the axis of said blanket cylinder (20, 22) through said point of tangency (35). The printing press as claimed in claim 4 or 5, wherein said carriage (36) is slidably mounted to said frame (6) by linear bearings (38). The printing press as claimed in anyone of claims 1 to 6, including a linear actuator engaging said plate cylinders (32, 34) for moving said plate cylinders (32, 34) along their path between said first and second positions. The printing press as claimed in claim 7, wherein the actuator engages said carriage (36) for moving said carriage (36) along said path. The printing press as claimed in claim 7 or 8, including an axially rotatable threaded rod (44) mounted to said frame (6), said rod (44) being disposed generally parallel to the carriage path, said carriage (36) including a thread follower (49) engaging said rod (44), whereby said carriage (36) is moved along said path in response to rotation of said rod (44). The printing press as claimed in claim 9, including a reversible drive motor (46) engaging said rod (44) for rotating said rod (44). The printing press as claimed in claim 10 including a position sensor (43, 45) operatively connected to said carriage (36) for sensing the position of said carriage (36) relative to said frame (6), and further including a limit switch (47) carried by said motor (46) and operatively connected to said position sensor (43, 45). The printing press as claimed in anyone of claims 1 to 11, wherein the ink roller assembly (50) includes an inking roller (54, 56) rotatably mounted to said frame (6) for applying ink to one of said plate cylinders (32, 34) when said one plate cylinder (32, 34) is in contact with said blanket cylinder (22), said inking roller (54, 56) being shiftable between a contact position in contact with said one plate cylinder (32, 34) when said one plate cylinder (32, 34) is in contact with said blanket cylinder (22) and a retracted position. The printing press as claimed in anyone of claims 4 to 12, wherein said blanket cylinder (22) and said plate cylinders (32, 34) have the same diameter, and further wherein said carriage (36) is adapted to move along a path a distance greater than said diameter. The printing press as claimed in anyone of claims 1 to 13, wherein said linear path of movement of the plate cylinders (32, 34) includes opposite ends, each of said opposite ends defining an inoperative position for one of said plate cylinders (32, 34) said inoperative positions being spaced away from said blanket cylinder (22). The printing press as claimed in anyone of claims 1 to 13, wherein the path of the movement of the plate cylinders (32, 34) includes a path mid-portion and a pair of path ends, each of said plate cylinders (32, 34) being selectively movable to an operable position defined by said path mid-portion, one of said plate cylinders (32, 34) further being moveable to an inoperable position defined by one of said path ends and the other of said plate cylinders being moveable to an inoperable position defined by the other of said path ends.

Inventors: NIEMIRO THADDEUS A, ORZECHOWSKI THOMAS W, NIEMIRO, THADDEUS A., ORZECHOWSKI, THOMAS W.
Applicants: GOSS GRAPHIC SYST INC, GOSS GRAPHIC SYSTEMS, INC.
Application year: 1998
Main classification: B41F13
IPC codes: B41F7, B41F13