Abstract:
A web width adjusting device can adequately adjust the width of paper web which travels through at least two printing sections. The travelling web is sandwiched by a pair of wave forming devices including a plurality of fluid ejectors which are aligned in the width direction of the paper web. The fluid ejectors of one alignment face alternately the other alignment to alternately eject fluid to both sides of the web.

Description:
This application is a continuation of application, Ser. No. 08/041,195, is filed Apr. 1,1993 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a width adjusting device for a paper web, which adjusts the width of the paper web for a printing system prior to a printing section. More particularly, the present invention relates to a lithographic rotary press which is equipped with at least one of the width adjusting device and a plurality of printing sections through which the paper web is successively travelled to be printed. 
     2. Description of the Prior Art 
     A typical conventional lithographic rotary press adapted for a color printing system is, for example shown in FIG. 4 which is a schematically elevational view. This conventional lithographic printing system comprises a plurality of printing sections P each of which includes two pairs of a combination of a plate cylinder PC and a blanket cylinder BC. The blanket cylinders BC of each the printing section P are vertically arranged to be in contact with each other. In this conventional printing system, four sets of the printing sections P are horizontally arranged in parallel as shown in FIG. 4. A paper web W is also horizontally travelled through the printing sections in which the paper web W is successively passed between the pairs of the blanket cylinders BC, BC to print both sides of the paper web W. 
     Another conventional lithographic rotary press for a color printing system is shown in FIG. 5. In this drawing, four printing sets each of which is composed of a plate cylinder PC and a blanket cylinder BC are radially arranged about an impression cylinder IC as a common center cylinder. The blanket cylinders BC are respectively in contact with the impression cylinder IC to form printing sections P. A paper web W is roundly travelled along the circumference of the impression cylinder IC so that the paper web W is successively passed through the four printing sections P defined between the blanket cylinders BC and the impression cylinder IC to print one side of the paper web W. 
     In recent years, many newspaper publishers have progressed to print newspaper in color inks and thus demanded to perform such color printing on many pages at a high speed in a limited printing space. 
     In order to satisfy such demands, another conventional lithographic rotary press for a color printing system has been proposed as shown in FIG. 6. In this printing system, each printing section P includes two sets of a blanket cylinder BC and a plate cylinder PC which are symmetrically arranged so as to bring the blanket cylinders BC into contact with each other. A paper web W is vertically travelled through the four printing sections P to print both sides of the paper web W in the same manner as the above described systems. This type of printing system is for example shown in &#34;IFRA Newspaper Techniques English Edition&#34;, pp.64 to pp.73; April, 1988 published by INCA-FIEJ Research Association. 
     Paper webs used in various printing systems are generally produced in such manner that pulp fibers are mechanically cut and broken into fine particles; dispersed in water; dehydrated and dried; and finally adhered by hydrogen-bond to form paper in a web or sheet figure. Under moisture conditions, each of pulp fibers tends to extend a little less than 1 percent in its longitudinal direction and 20 to 30 percent in its radius direction. Thus, the paper web is extended in its longitudinal and width directions by dampening and/or watering operation. Most of the pulp fibers of general mechanically produced paper webs are orientated in the longitudinal direction of the paper web, so that paper webs are remarkably extended in their width direction. 
     In a specific lithographic printing system employing dampening or watering operation in printing a section, a paper web is swelled by the water supplied during the dampening operation. Therefore the image and lines printed on the paper web are also deformed in response to the swell of the paper web. In the printing systems including at least two lithographic printing sections each of which is associated with dampening means to successively print color images on the same paper web, the printed images or lines formed at the first printing section are not correctly coincided with the images or lines formed at the second and later printing sections. Accordingly, this will produce printed materials with poor quality. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is a primary object of the invention to provide an improved width adjusting device for a paper web, which can be associated with a lithographic color-printing system including at least two printing sections using dampening means to successively print image and lines on the same paper web, and which can adjust the width of the paper web to correctly agree the former printed image with the succeeding printed image. 
     Another object of the present invention is to provide an improved width adjusting method for a paper web to successively print image and lines on the same paper web without any shears. 
     To accomplish the above described objects, a web width adjusting device according to the present invention comprises a pair of wave forming means between which a paper web is travelled. Each of the wave forming means includes a plurality of fluid ejectors which are aligned in the width direction of the paper web. The fluid ejectors of one alignment face alternately that of the other alignment. 
     Another aspect according to the present invention is characterized that a web width adjusting method comprises a wave forming step by alternately ejecting fluid to one side and the other side of the paper web so that a wave is formed in the longitudinal direction of the web. 
     In the width adjusting device according to the present invention, the paper web is subjected to fluid pressure alternately applied from the fluid ejectors aligned along the width of the paper web. Thus the fluid pressure causes the paper web to form a wave in the longitudinal direction of the web as the paper web is travelled toward a succeeding printing section. This wave-forming results in shortening the width of the paper web. The width shortened web reaches the to succeeding printing section and is subjected to a printing operation at the succeeding printing section. The paper web is kept in the width shortened state without any wrinkles and rucks during the succeeding printing operation. 
     Although the reason why the paper web can pass the printing section with keeping the width in shortened state and without any wrinkles and rucks is not clear, it may be considered that fibers of wave formed portions are gathered, not shown with the naked eye, and pressed by printing pressure. Thus the gatherd and pressed fibers may allow the width of the paper web to be stable. 
     In this width adjusting method according to the present invention, width of the paper web expanded owing to water supplied from the preceding printing section can be cancelled by wave-forming which permits the width to shorten. Therefore, the image and lines printed at the preceding printing section can coincide with that of the succeeding printing section. 
     Other objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematically perspective view showing the first embodiment of a web width adjusting device according to the present invention; 
     FIG. 2 is a schematically perspective view showing the second embodiment of a web width adjusting device according to the present invention; 
     FIG. 3 is a schematic illustration showing an overall construction of a lithographic rotary press which is associated with a plurality of web width adjusting devices according to the present invention; 
     FIG. 4 is a schematic illustration showing one conventional configuration of a commonly used lithographic rotary press; 
     FIG. 5 is a schematic illustration showing another conventional configuration of a commonly used lithographic rotary press; and 
     FIG. 6 is a schematic illustration showing another conventional configuration of a commonly used lithographic rotary press. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One preferred embodiment, as the first embodiment, of the present invention will be described in detail with referring to the accompanying drawings FIG. 1 and FIG. 3. 
     In FIG. 3, there is shown an overall constitution of a lithographic rotary press which comprises first to fourth printing sections P1, P2, P3 and P4 vertically arranged in the same manner as the above described conventional color-printing lithographic rotary press shown in FIG. 6. Each printing section includes two sets of a blanket cylinder BC and a plate cylinder PC which are symmetrically arranged so as to bring the blanket cylinders BC into contact with each other. A paper web W is vertically travelled from the first printing section P1 to the fourth printing section P4. Further, the rotary press shown in FIG. 3 comprises a plurality of web width adjusting devices 20, described later in detail. 
     In FIG. 3, IN and DP represent an inking unit and a dampening unit, respectively. 
     The web width adjusting device 20 is typically shown in FIG. 1, wherein the device 20 comprises a pair of wave forming means between which the paper web W is travelled. Each of the wave forming means includes a first fluid feeding pipe 2 and a first series of fluid ejectors 1a, 1b, 1c, 1d, 1e and 1f; and a second fluid feeding pipe 2 and a second series of fluid ejectors 1g, 1h, 1i, 1j, and 1k. In the first series of the fluid ejectors 1a to 1f, they are isolated from each other at a regular interval. In the second series of the fluid ejectors 1g to 1k, they are also isolated from each other at a regular interval. The fluid ejectors 1g to 1k of the second series are respectively shifted half of the interval between the fluid ejectors of the first series, so that each fluid ejector of the second series is positioned at the center of two fluid ejectors of the first series as shown in FIG. 1. 
     The reference numeral 3 denotes a driving unit for a shifting means 15. In this embodiment, the driving unit is an electric motor whose drive shaft is secured with a driving gear 4. This driving gear 4 is meshingly engaged with a driven gear 5 which is secured to one end of a guide shaft 6 formed with a screw section. The guide shaft 6 penetrates through a base member 7a for supporting the fluid feeding pipe 2 near to the driven gear 5, and the screw section of the guide shaft 6 is meshingly engaged with a female screw, not shown, formed in another base member 7b for supporting the fluid feeding pipe 2 far from the driven gear 5. The reference numeral 8 shown in FIG. 1 denotes a regulator unit for regulating flow amount and rate of the fluid fed to the fluid ejectors 1a to 1k. In this embodiment, the regulator unit 8 includes a regulator 8a and a valve 8b. 
     The reference numeral 9 denotes an automatic control means which is electrically operated by an input means 10 such as a key board and a detecting means 11 which detects various operation information such as speed of a main motor 12 representing travelling speed of the paper web W. The control means 9 is electrically connected to a first detecting means 13a for detecting the distance between the fluid ejectors 1a to 1k and the paper web W. Since this distance corresponds to rotational phase of the guide shaft 6, the first detecting means 13a counts the number of rotations of the guide shaft 6. Further the control means 9 is connected to a second detector 13b which detects the fluid pressure and ejecting rate of the fluid ejected by the fluid ejectors 1a to 1k. In this embodiment, the second detector 13b detects the regulation rate of the regulator 8a and the valve 8b. On the other hand, the control unit 9 is electrically communicated with the driving unit 3 for the shifting means 15 and adjusting units 8aa and 8bb for the regulator 8a and the valve 8b. 
     Additionally, the control means 9 is electrically connected to the similar means and members belonging to the other web width adjusting devices, not shown, to perform the width adjusting operation in the whole printing system. 
     Alternatively, the control means 9 may be communicated with these detecting means and driving means by any conventional radio means. 
     FIG. 1 shows the preceding printing section P and the succeeding printing section P&#39; which include two blanket cylinders BC, respectively. 
     FIG. 2 shows the second embodiment of a web width adjusting device according to the present invention, wherein the automatic control means 9 is omitted and the shifting mean 15 includes fluid pressure activating cylinders 3&#39; as the driving unit and guide shafts 6&#39;. 
     A typical operation of the printing system using the web width adjusting devices will be described in detail. 
     The paper web W is set in the printing system shown in FIG. 3 such that the web W is successively travelled through the printing sections P1, P2, P3, and P4 with passing through between the first series of the fluid ejectors 1a to if and the second series of the fluid ejectors 1g to 1k of the web width adjusting devices 20. 
     After or prior to the above described work, required information on the paper web such as width, material, thickness, and the like are input into the control means 9 through the input means 10. The control means 9 outputs an actuating signal from the detecting means 13a so that the fluid ejectors 1a to 1k are set at their initial positions predetermined in response to the web information. Additionally, the control means 9 outputs a control signal to the regulator unit 8 with referring to the detected signal from the detecting means 13b so that the fluid ejectors 1a to 1k are set in their initial fluid pressure and ejecting rate predetermined in response to the web information. 
     Then a start switch, not shown, for the printing system is turned on to start travelling the paper web W and printing operation of the printing sections P1, P2, P3, and P4. 
     As the printing sections begin their rotational work, the detecting means 11 detects the rotating speed of the main motor 12, representing the travelling speed of the paper web W, and inputs the detected information to the control means 9. According to the information on the travelling speed of the paper web W corresponding to the rotating speed of the main motor 12, the control means 9 outputs an adjusting signal to shift the fluid ejectors 1a to 1k from their initial positions to predetermined adjusting positions, and/or the control means 9 outputs an actuating signal to actuate the regulator unit 8 to adjust the fluid pressure and ejecting rate of the fluid ejected from the fluid ejectors 1a to 1k. 
     At the first printing section P1, the first image is printed on the paper web W and simultaneously blank sections of the printed web are supplied with dampening water through the blanket surface of the blanket cylinder BC. Thus wetted fibers of the paper web W become gradually extending in the width direction of the web W during travelling from the preceding printing section P (P1, P2, P3) to the succeeding printing section P&#39; (P2, P3, P4). When the web W is passed through the web width adjusting device 20 prior to the secceeding printing section P&#39;, the web W is subjected to the pressurized air alternately ejected by the fluid ejectors 1a to 1k so that the web surface is formed in wave WA. The wavy surface WA allows the primary width of the paper wave W to be decreased 11, l2. Thus, on this stage, the actual width of the paper web W is represented by &#34;l&#34;. 
     Although the wavy surface WA gradually returns to its primary shape after passing the web width adjusting device 20, the web width can not be completely returned to its primary width at the succeeding printing section P&#39; (P2, P3, P4) and thus the paper web W is slightly smaller than its primary width when it enters into the succeeding printing section P&#39; (P2, P3, P4). Therefore the extended width due to the dampening water at the preceding printing section P (P1, P2, P3) is cancelled by this shortened width. As a result, the paper web W without any faults such as visible wrinkels and rucks is printed at the succeeding printing section P&#39; (P2, P3, P4) so that the succeeding image and lines can be printed consistent with the preceding image. On the same occasion, the blank section of the paper web is supplied with dampening water through the blanket surface of the blanket cylinder BC in the same manner as the preceding printing section P(P1, P2, P3). 
     Next, the paper web W is successively travelled to the succeeding printing section (the third or fourth printing section P3 or P4) through another web width adjusting device 20 arranged prior to the third or fourth printing section P3 or P4. In this web width adjusting device 20, the paper web W is also subjected to the same adjusting operation as the former adjusting means. 
     In each of the web width adjusting devices 20, the positions of the fluid ejectors 1a to 1k against the paper web W and the ejecting pressure and ejecting rate of the fluid ejected by the fluid ejectors should be adequately adjusted in response to the travelling speed of the paper web W because the wetted fibers will expand in propotion to time. In other words, the fluid ejectors 1a to 1k should be largely shifted when the paper web W is travelled at a slow speed. 
     According to the web width adjusting device 20, the web width at the succeeding printing section P&#39; (P2, P3, P4) can be adjusted consinstent with that of the preceding printing section P (P1, P2, P3). Thus the image and lines printed at the first to fourth printing sections P1 to P4 can be formed consistent with each other. 
     In an experimental test executed by the present applicant, a rolled newspaper type A (width 1626 mm) was used to clarify the difference between the effect obtained by the web width adjusting devices 20 arranged between P1 and P2, P2 and P3, and P3 and P4 as shown in FIG. 3 and that of a conventional constitution without any web width adjusting means. This experimental test evidenced that shears (about 2 mm) generated in the width direction between the first printed image and lines and the fourth printed image and lines by conventional constituton can be wholly corrected by the web width adjusting device 20 according to the present invention. Although the expanding ratio in the web width depends on the type of paper web, the web width adjusting device according to the present invention can adequately compensate such shears in printing. 
     The automatic control means 9 may be replaced by manual control means. 
     The present invention is not limited to only the above described embodiments, and therefore for example the fluid ejectors 1a to 1k of the web width adjusting device 20 may be modified in any adequate shapes and numbers. Further the control means 9 may be input with the information on the dampening water fed onto the web paper W at the printing sections P1 to P3; i.e., ratio between image area and blank area to be printed at the printing sections P1 to P3. Various changes and modifications are possible without departing from the spirit and scope of the invention. 
     As disclosed in the above description, since expansion in web width due to dampening can be adequately corrected by the web width adjusting device arranged between the preceding printing section and the succeeding printing section, the image and lines printed at the succeeding printing section can be completely accorded with the former image and lines, thereby producing high quality printed matters without any shears or unclearness.