SHEET-FED ROTARY PRINTING PRESS

Abstract: A sheet-fed rotary printing press includes an abnormal sheet detecting unit. (30) This unit includes a double-diameter cylinder (33) or a support plate (54) which is in contact with a traveling printed sheet to keep the sheet taut. The unit further includes a detecting apparatus,(35) arranged above the double-diameter cylinder or the support plate, for detecting a printing density of the taut printed sheet.

Description: Background of the Invention The present invention relates to a sheet-fed rotary printing press according to the preamble of claim 1. In accordance with types of plates to be used sheet-fed rotary printing presses can be classified into lithographic presses, letterpress machines, and intaglio printing presses. In case of a multicolor lithographic press the same is arranged as shown schematically in Fig. 4. The particular printing press 1 consists of a paper sheet feeder 2, a plurality of printing units 3, and a delivery apparatus 4. The paper sheet feeder 2 comprises a stack board 6 which is automatically moved vertically while supporting paper sheets 5 thereon. Above the sheets 5 there is provided a paper pick-up device (not shown), for drawing the paper sheets 5 by suction one by one from the stack of sheets and feeding the same onto a feedboard 7. Each printing unit 3 comprises a plate cylinder 8, a blanket cylinder 9, and an impression cylinder 10, which are in contact with each other. Between the impression cylinders 10 of the adjacent printing units 3 there are provided two transfer cylinder 11 and 12 the transfer cylinder 12 having a diameter twice that of the transfer cylinder 11 , while their peripheral surfaces are in contact with each other. Above the impression cylinder 10 of the first color there are arranged swing grippers 13 while a delivery cylinder 14 is in contact with the last impression cylinder 10. Reference numerals 15 denote a pair of right and left sprockets which are coaxially supported on the delivery cylinder 14. A pair of right and left delivery chains 18 are looped between the sprockets 15 while a pair of right and left sprockets are disposed at the front end portions of a delivery frame 16 so as to be deviated by deviation sprockets 19. Between the right and left delivery chains 18 at equal intervals there are suspended a plurality of delivery grippers (not shown), mounted on a corresponding gripper rod equally not shown. Below a rear end portion of a convey path of the delivery chains 18 there is arranged a stack board 20 which is automatically moved vertically while supporting the sheets 5 thereon. These devices are driven by a motor 21, arranged at the side of the transfer cylinder 12 for the first color. The functioning of this printing press is as follows: The sheets 5 on the stack board 6 drawn by suction by the paper pick-up device are gripped one by one by the swing grippers 13 and from there transferred to the grippers of the impression cylinder 10. Whenever a sheet 5 conveyed by the grippers of the impression cylinders 10 and the transfer cylinders 11 and 12 pass between the blanket cylinder 9 and the impression cylinder 10 of a particular colorstation, an image present on the blanket surface of the blanket cylinder 9 is transferred onto the sheet 5, thus performing a printing operation. The sheet 5 on which an image of the final color is printed is transferred from the grippers of the impression cylinder 10 to the grippers of the delivery chains 18 in cooperation of the delivery cylinder 14. From there the sheet is conveyed by the delivery chains 18 which travel in a direction indicated by an arrow in Fig. 4. Thereafter, the sheet 5 is released from the grippers at the rear end portion of the convey path, and is stacked on a stack board 20. During the printing operation described above, misregistration, contamination with oil, offset, and the like may occur due to various causes. An abnormal sheet must therefore be removed so as not to be mixed with the normal sheets stacked together. For this purpose, an abnormal sheet detecting apparatus has been recently developed (see JP-A-61-12342) . In this apparatus, pixels from the leading edge to the trailing edge of printed products are detected sequentially thereby using a sensor or a camera. Thereby the difference between the detected density and the density of the pixels of a reference image is detected, so that in accordance with the appearance of a discrimination signal an abnormal sheet can be delivered onto a separate delivery tray or a special mark can be printed on the abnormal sheet. In order to accurately operate such an abnormal sheet detecting apparatus, additionally an apparatus for tensioning the printed product during the detection procedure must be provided. This abnormal sheet detecting apparatus must be provided on the downstream side of the final printing unit. However, if such an apparatus shall be provided to an existing printing press, this printing press must be modified to a large extend. Since most of the existing printing presses cannot be modified, the above detecting apparatus has not yet been used in practical applications although there is a great demand for it. Summary of the Invention It is therefore the object of the present invention to provide a sheet-fed rotary printing press in which an abnormal sheet detecting apparatus can be installed in an easy way, thereby reducing greatly the installation cost for such an apparatus. In order to achieve this object, the sheet-fed rotary printing press as stated in the preamble of claim 1, comprises features as stated in the characterizing clause of claim 1. Special improvements of the invention are stated within the subclaims 2 to 7. Brief Description of the Drawings Figs. 1 to 3 show a sheet-fed rotary printing press according to an embodiment of the present invention, in which Fig. 1 is a schematic side view of a multicolor lithographic sheet-fed rotary printing press to which the present invention is applied, and Figs. 2 and 3 are schematic side views of a multicolor lithographic sheet-fed rotary printing press according to other embodiments of the present invention; and Fig. 4 is a schematic side view of a conventional multicolor lithographic sheet-fed rotary printing press. Description of the Preferred Embodiments An embodiment of the present invention will be described hereinafter. Fig. 1 shows a multicolor lithographic sheet-fed rotary printing press to which the present invention is applied. Since the arrangement of most of the paper sheet feeder, the printing units, and the delivery apparatus of this embodiment are the same as that of the printing press having no abnormal sheet detecting apparatus, shown in Fig. 4, the same reference numerals in Fig. 4 denote the same parts as in Fig. 1, and a detailed description thereof will be omitted. An abnormal sheet detecting unit 30 is provided between a final printing unit 3 and a delivery apparatus 4. The abnormal sheet detecting unit 30 comprises a pair of right and left frames 32 for coupling a frame 31 of the printing unit 3 and a delivery frame 16. A double-diameter transfer cylinder 33 serving as both a convey means and a printed sheet stabilizing means is axially supported between the frames 32. A transfer cylinder 34 is axially supported by bearings which axially support a delivery cylinder 14 in Fig. 4, so that its peripheral surface is in contact with those of an impression cylinder 10 and a double-diameter transfer cylinder 33. The delivery cylinder 14 which is in contact with the impression cylinder 10 in Fig. 4 is axially supported by the right and left frames 32 so as to be in contact with the double-diameter cylinder 33 in the unit 30. Delivery chains 18 are looped around the same sprockets 15 as those in Fig. 4 and coaxially mounted on the impression cylinder 14. A printed paper sheet 5 is regripped from grippers of the impression cylinder 10 to grippers of the transfer cylinder 34, and is then regripped and conveyed by grippers of the double-diameter transfer cylinder 33 while being in contact with the peripheral surface of the cylinder 33. Thereafter, the sheet 5 is regripped by grippers of the delivery chains 18 and is conveyed thereby. A detecting apparatus 35 is arranged above the double-diameter transfer cylinder 33 so as to detect a printing density of pixels from one end to the other end of the sheet 5 which is conveyed to be in contact with the double-diameter transfer cylinder 33. Then, the detecting apparatus 35 discriminates a difference between the detected density and a printing density of pixels of a reference image. If a difference is detected, the detecting apparatus 35 generates a signal. Note that beds 36 and 37 on which the printing units 3 and the delivery apparatus 4 are placed are extended by a length corresponding to the frames 32 and coupled to each other. With the above structure, when the printed sheets 5 are conveyed while being in contact with the double-diameter transfer cylinder 33, the printed densities of the sheets are detected by the detecting apparatus 35 one by one. If a difference between the detected density and the density of the reference image is found due to contamination with oil, offset, misregistration, or the like, i.e., if an abnormal sheet is detected, the detecting apparatus 35 generates a signal. This signal is sent to the delivery apparatus 4 through, e.g., a timer. When the abnormal sheet arrives the gripper release portion of the delivery apparatus 4, it is delivered to another path separated from the stacker board 20, or a tape is inserted on the abnormal sheet to easily distinguish the abnormal sheet from the normal sheets. In this case, since the sheet 5 is in contact with the double-diameter transfer cylinder 33 and is kept taut, stable and precise detection can be realized. In order to additionally dispose the abnormal sheet detecting apparatus, the printing press need only be modified such that the frames 32, the double-diameter cylinder 33, and the transfer cylinder 34 are additionally provided, and the delivery cylinder 14 is shifted. The existing bearings of the transfer cylinder 34 can be used without modification as well as the printing units 3 and the delivery apparatus 4, thus allowing easy modification. Fig. 2 shows a multicolor lithographic rotary printing press according to another embodiment of the present invention. Only a modified portion will be described below. An abnormal sheet detection unit 40 comprises right and left frames 42 which couple a frame 31 of a printing unit 3 and a frame 16 of a delivery apparatus 4 and are placed and fixed on an additional bed 41. A double-diameter transfer cylinder 43 is axially supported between the frames 42. A transfer cylinder 44 and a delivery cylinder 45 are axially supported to face each other on the upstream and downstream sides of the double-diameter transfer cylinder 43. A pair of right and left convey chains 47 comprising grippers are looped between sprockets 46 coaxially mounted on the transfer cylinder 44 and existing sprockets 14. Existing delivery chains 18 are extended on sprockets 48 coaxially provided on the delivery cylinder 45. Reference numeral 49 denotes the same detecting apparatus as in Fig. 1. With the above structure, a printed sheet 5 is conveyed to be regripped from grippers of an impression cylinder 10 to grippers of the convey chains 47, and is then conveyed to be regripped by the grippers of the double-diameter transfer cylinder 43 while being in contact with the surface of the cylinder 43. Thereafter, the sheet 5 is conveyed to be regripped by the grippers of the delivery chains 18. The sheet 5 is detected while being in contact with the double-diameter transfer cylinder 43, i.e., in a taut state, precise detection can be performed. Components which are added for reconstruction are the bed 41, the frames 42, the double-diameter transfer cylinder 43, the transfer cylinder 44, the delivery cylinder 45, the sprockets 46 and 48, and the chains 47. Other existing components can be utilized, resulting in easy modification. Fig. 3 shows a multicolor lithographic rotary printing press according to still another embodiment of the present invention. Only a modified portion will be described below. An abnormal sheet detecting unit 50 comprises right and left frames 52 which couple a printing unit 3 and a frame 16 of a delivery apparatus 4, and are placed and fixed on an additional bed 51. Delivery chains 18 are extended by a length corresponding to the frames 52. A detecting apparatus 53 is arranged within a convey path of the delivery chains 18, and a support plate 54 as a printed sheet stabilizing means contacting a conveyed sheet 5 is provided below the detecting apparatus 53. With the above structure, since the sheet 5 conveyed by the delivery chains 18 is detected by the detecting apparatus 53 while being in contact with the support plate 54, i.e., in a taut state, precise detection is allowed. In order to additionally dispose the abnormal sheet detecting apparatus, the bed 51 and the frames 52 are added, and the delivery chains 18 are extended, resulting in easy modification. In each of the above embodiments, a printing density detected by the detecting apparatus 35, 49, or 53 can be displayed on a display unit. In the above embodiments, the present invention is applied to the multicolor lithographic rotary printing press, but can be applied to a monochromatic printing press, a letterpress machine, and an intaglio printing press. As can be understood from the above description, according to the present invention, an abnormal sheet detecting unit comprising a printed sheet stabilizing means which is in contact with a traveling printed sheet to keep the sheet taut and a detecting apparatus for detecting a printing density of the tensed printed sheet is arranged between a printing unit and a delivery apparatus, so that the conveyed sheet is detected while being in contact with the printed sheet stabilizing means, i.e., in a taut state. Therefore, an abnormal sheet can be precisely detected, and quality of a printed produce can be improved. In addition, when an existing printing press is modified to be one comprising an abnormal sheet detecting apparatus, most of the existing portion is utilized without modification, and some components need only be added. Therefore, the cost of equipment can be reduced, and the abnormal sheet detecting apparatus can be easily added. Thus, the detecting apparatus gains popularity, thus further improving quality of printed products.

Claims: A sheet-fed rotary printing press, whereby behind the last printing unit (3) there is installed an abnormal sheet detecting unit (30, 40, 50) with printed sheet stabilizing means (33, 43, 54) being in contact with the traveling printed sheets so as to keep the sheets taut and whereby there is provided further a detecting apparatus (35, 49, 53) arranged above said printed sheet stabilizing means (33, 43, 54) for detecting the printing density of the taut printed sheets, characterized by the fact that the bearings of the delivery cylinder (14) of the last printing unit (3) are used for supporting the transfer cylinder (44) resp. a special delivery cylinder (14). A printing press according to claim 1, characterized in that there are provided right and left frames (31, 32; 41, 42; 51, 52) for connecting the frame of a printing unit (1) and the frame (16) of the delivery apparatus (4). A printing press according to claim 2, characterized in that said printed sheet stabilizing means comprises a double-diameter transfer cylinder (33, 43) mounted between said right and left frames (31, 32; 41, 42; 51, 52). A printing press according to claim 3, characterized in that downstream to said double-diameter cylinder (33) and in contact therewith there is provided a sprocket (15) coaxial with a delivery cylinder (14) said sprocket (15) being looped by a delivery chain (18), while upstream to said doublediameter cylinder and in contact therewith there is provided a transfer cylinder (34). A printing press according to claim 3, characterized in that upstream to said double-diameter cylinder (43) and in contact therewith there are provided a transfer cylinder (44) and a sprocket (46) mounted coaxially to said transfer cylinder (44) and coupled by means of a chain (47) to a cylinder (15) of said printing unit (1), a delivery cylinder and that downstream of said double-diameter cylinder (43) and in contact therewith there is provided another sprocket (48) being mounted coaxially to said a delivery cylinder (45). A printing press according to claim 2, characterized in that said printed sheet stabilizing means comprises a support plate (54) being in contact which the printed sheet. A printing press according to claim 6, characterized in that the delivery chain (18) of the delivery apparatus (4) is modified to such an extend, that it is lenght is increased by a length of the right and left frames (51, 52).

Inventors: NOZAWA, KENJI C/O TORIDE WORKS
Applicants: KOMORI CORPORATION
Application year: 1987
Main classification: B41F33
IPC codes: B41F33