Patent Publication Number: US-2003226431-A1

Title: Paper perforation system

Description:
TECHNICAL FIELD  
       [0001] The present invention relates generally to a perforation forming system of a printing press, and more particularly to a perforation forming system having a perforator cylinder that can be disengaged and precisely re-engaged with a mating anvil cylinder during press operation.  
       BACKGROUND OF THE INVENTION  
       [0002] Offset printing presses are well known in the art, as are various types of perforation systems employed in printing presses to produce transverse perforations in a continuous paper web. For certain applications, it is desirable to be able to temporarily suspend the perforation of the web without requiring the entire press to be stopped and then be able to accurately re-start the web perforation, all at press full operating speed.  
       [0003] U.S. Pat. No. 5,048,387 issued Sep. 17, 1991 to Niitsuma et al. discloses a horizontal perforation forming apparatus for a rotary press which includes an interaxial distance adjusting unit for adjusting the distance between the axes of a perforation cylinder and a mating cylinder. The interaxial distance adjusting means has eccentrically mounted roller bearings rotatably supporting the perforation cylinder and the mating cylinder, such that the distance adjusting means rotates both the first and second eccentric bearing housings to provide adjustment of the distance between the cylinders. The perforation system used by Niitsuma et al. is of a male/female type, wherein the axial blades protruding from the outer surface of the perforation cylinder mate with blade seats in blade receiving grooves extending in the axial direction of the mating cylinder. As there is a certain amount of penetration of the blades into the blade seats, bearing tolerances are less important in order to ensure complete perforation of the paper web. However, as the blades of the perforation cylinder and the blade seats of the mating cylinder must align perfectly, circumferential timing is of prime importance.  
       [0004] Perforation systems which alternately employ a perforation cylinder with blades that hit a hardened solid anvil cylinder, require much greater bearing tolerances in order to ensure that the gap between the blade and the anvil is exact. The blade must pass completely through the paper web in order to create an acceptable perforation. However, too deep a cut will result in a web break, and too shallow a cut will result in a final product rejection for insufficient perforation. Regular roller bearings such as those used by Niitsuma et al. always have approximately 0.001 inch of internal clearance, and therefore the total play between the two perforation cylinders could be as much as about 0.002 inches. For a common paper web of about 0.003 inches, this could result in two-thirds of the web material not being perforated.  
       [0005] A solution to this problem is to use pre-loaded roller bearings, which have no internal clearance and therefore do not cause unacceptable play in the distance between the blades and the anvil cylinder. However, as a result of their pre-load they create significantly more rolling resistance, and as such generate much more heat at high speeds. This extra heat generated by the bearings can make the supporting frame expand, changing the distance between the cylinders which will also result in an unacceptable product. Some attempts have been made to eliminate the thermal expansion of the frame caused by heat generated by the bearings, by, for example, pre-heating the entire frame supporting the perforation assembly. This is impractical, and both time and cost inefficient.  
       [0006] Certain printing applications are also more demanding than others in terms of perforation requirements. In equipment for commercial web printing, for example, perforation is often considered as an optional extra, but is not the feature of primary import. For business form applications, in contrast, accurate through-perforation is of vital importance, as the perforation is used as the base for the registration of all other press operations, such as printing and punching.  
       [0007] U.S. Pat. No. 4,793,229 issued Dec. 27, 1988 to Kleber discloses a multipurpose commercial web printing apparatus for performing die cutting, perforating, embossing and scoring functions, and having a die cylinder and an anvil cylinder supported by pre-loaded tapered roller bearings in eccentric housings. The center distance between the die cylinder and the anvil cylinder is adjustable by a manually controlled micro adjustment mechanism, which requires the operator to constantly monitor the apparatus, and regularly adjust the cylinder center distance as the product gradually creeps outside of the acceptable tolerances. This micro-adjustability is intended to permit minute adjustment of the cylinder center distance when required, and is not optimized for full disengagement and re-engagement of the perforation forming cylinders. If completely disengaged, the tolerance of the die cylinder with respect to the anvil cylinder would have to be manually reset by the operator for the resumption of perforation to occur. This would be a time consuming task, required every time perforation was completely disengaged and re-engaged again. This operation would also require significant operator skill, and leaves open the possibility of operator error that could result in insufficient perforation or web break.  
       [0008] During web printing of products such as business forms, presses often run at high throughput speeds of as much as 1800 foot per minute. High press speeds results in high final product output, but also requires frequent blank web feed roll replacement. At these press speeds, a new feed roll is often required every twenty minutes. Splicing the start of a new roll with the existing web going through the press is well known in the art in order to avoid stopping the entire press to start the feed of the new web roll. However, this spliced web portion comprised of two layers of paper, can cause problems when it passes through a blade and anvil type perforation forming apparatus. If a perforation blade happens to strike the paper along such an overlapped spliced portion, there is a strong possibility of resulting web break.  
       [0009] The tension put on the paper feed roll to ensure that the web is taught and well aligned as it is fed into the press, tends to further increase the chance that a perforation occurring along the splice will cause a web break. A web break results in an entire press shutdown, and can mean a downtime of up to half-an-hour to re-spool the entire press. Such a downtime can mean significant losses for the press operator. For example, when a new paper roll is started to be rewound after perforation, the tension on the web is set as high as possible, in order to obtain a hard roll core. If the starting tension is not high enough, the center of the roll will start to slip and a roll having an axially unaligned stacking will result as the roll increases in diameter. This phenomenon is often termed roll “dish out”. The high starting tension, however, will often break the web at its weakest point, namely at the perforations. Therefore, perforations at the beginning of a new roll can often cause web breaks.  
       [0010] As a result, there is a need for a mating perforation and anvil cylinder type perforation forming apparatus that can be disengaged and accurately re-engaged anytime at press full operating speed, for example at the beginning and the end of a paper roll, and that does not require regular micro-adjustability and constant monitoring in order to maintain acceptable cylinder inter-axial distance tolerances.  
       SUMMARY OF THE INVENTION  
       [0011] It is an object of the present invention to provide an improved perforation forming apparatus for a printing press.  
       [0012] It is another object of the present invention to provide a perforation forming apparatus that does not require constant fine adjustment of the cylinder center distance, but is capable of accurate perforation throw-off and re-engagement at full press operating speed.  
       [0013] It is a further object of the present invention to provide a perforation forming apparatus having a blade cylinder and a mating anvil cylinder supported by pre-loaded bearings in eccentric housings.  
       [0014] It is a further object of the present invention to provide a perforation forming apparatus that prevents cylinder center distance movement due to thermal expansion by having oil cooled bearings.  
       [0015] Therefore, in accordance with the present invention, there is provided a perforation forming apparatus for a web fed paper processor comprising: a rotatable perforator cylinder comprising a longitudinal axis, and having at least a blade protruding radially from the perforator cylinder, extending axially therealong and being substantially parallel to the longitudinal axis; a rotatable anvil cylinder being adjacent the perforator cylinder and contiguously engageable therewith, the anvil cylinder having a longitudinal axis of rotation parallel to the longitudinal axis of the perforator cylinder; one of the perforator cylinder and the anvil cylinder being supported by eccentric bearing assemblies; the eccentric bearing assemblies comprising fluid cooled bearings eccentrically mounted in bearing housings; the eccentric bearing assemblies being adapted for rotation such that the one of the perforator cylinder and the anvil cylinder can be pivotally displaced between a first and a second position; the first position defining a perforation position wherein the blade just contacts the anvil cylinder, and the second position defining a non-perforation position wherein a radial clearance gap between the blade and the anvil cylinder is at least equal to twice a thickness of a paper web adapted to be fed through the perforation forming apparatus; whereby the one of the perforator cylinder and the anvil cylinder is displaceable to the second position during operation in order to temporarily suspend perforation of the paper web, and is returnable to the first position during operation in order to resume perforation of the paper web.  
       [0016] There is also provided, according to the present invention, a method for controlling perforation of a paper web comprising the steps of: providing a first rotatable cylinder having a longitudinal axis and comprising at least a blade, protruding radially from an outer axially extending circumferential surface of the first cylinder and extending axially therealong; providing a second rotatable cylinder having a smooth outer axially extending circumferential surface and comprising a longitudinal axis of rotation parallel to the longitudinal axis of the first cylinder, the second cylinder being contiguously engageable with the first cylinder; providing eccentric bearing All assemblies for supporting one of the first and second cylinders, the bearing assemblies comprising fluid cooled bearings eccentrically mounted in rotatable bearing housings; displacing the one of the first and second cylinders from a first to a second position, the first position defining a perforation position wherein the blade contacts the second cylinder and the second position defining a non-perforation position wherein a radial clearance gap between the blade and the smooth outer axially extending circumferential surface of the second cylinder is at least equal to twice a thickness of the paper web; whereby displacing the one of the first and second cylinders to the second position suspends perforation of the paper web. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:  
     [0018]FIG. 1 is a side elevation view of a perforation forming apparatus according to the present invention.  
     [0019]FIG. 2 is a partial cross-sectional view taken along line  2 - 2  of FIG. 1.  
     [0020]FIG. 3 is an enlarged side elevation view of the perforation cylinder mounting of the perforation forming apparatus as shown in FIG. 1.  
     [0021]FIG. 4 is an enlarged view of the perforation cylinder bearing assemblies shown in FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0022] Referring to FIG. 1, a perforation forming apparatus  10  is adapted for use with a printing press, such as a web-fed offset printing press well known in the art. The perforation forming apparatus  10  generally comprises a perforation cylinder  12  and an anvil cylinder  14 , each rotatably mounted between vertical main frame members  15  of the frame assembly  16 , on perforation cylinder end shafts  18  and anvil cylinder end shafts  20 . The shafts  18  and  20 , and therefore the perforation cylinder  12  and the anvil cylinder  14 , have central longitudinal axes  22  and  24 , respectively, about which they rotate. The shafts can be integrally formed with the cylinder, or can be individual elements, to which the cylinder members are permanently fixed. The perforation cylinder  12  comprises a plurality of perforation blades  13  radially extending from the cylinder, and extending axially along its length. The anvil cylinder  14  is preferably a solid, hardened cylinder having a highly toleranced, smooth outer surface.  
     [0023] The paper web  26  enters the perforating apparatus  10  from the adjacent printing press, and is fed between the perforation and anvil cylinders. During operation of the perforating apparatus, the rotating blades of the perforation cylinder strike the paper web overlaid on the anvil cylinder, piercing the web at predetermined regular intervals. The interchangeable blades can have any one of a variety of blade profiles, such that different types of perforations can be created to suit the particular printing application.  
     [0024] The blades  13  are removably fastened to the cylinder  12 , and can be removed for replacement, maintenance, interchanging perforation style and set-up, and the like. Preferably, a plurality of threaded fasteners are used to fix the blades  13  into axial slots in the outer surface of the perforation cylinder. This can also be used for small height adjustment of the blades, to ensure that all the blades are uniformly protruding from the cylinder, such that the blade edges are precisely and uniformly located with respect to the central longitudinal axis  22  of the perforation cylinder  12 .  
     [0025] The perforation cylinder  12  is mounted on either end in an eccentric bearing assembly  30 , generally adapted to permit the perforation cylinder to be disengaged from contact with the anvil cylinder  14  during the operation of the printing press in order to temporarily suspend the perforation of the through-going paper web  26 . The eccentric bearing assembly  30  also allows accurate repositioning of the perforation roller when re-engaged with the anvil cylinder to resume perforation of the paper. Therefore, perforations can be started and stopped while the paper continues to be fed through the press and the perforating apparatus at full operating speed.  
     [0026] The eccentric bearing assembly preferably permits only either an on or off perforation position, and is not intended to allow running adjustment of the inter-axial distance between the perforation cylinder and the anvil cylinder. This permits a simplified perforation “throw-on/off” mechanism that, while requiring close tolerances of the cylinders, eccentric bearing assemblies and actuating mechanism, does not require a skilled operator to continuously monitor the perforation apparatus to ensure that the correct cylinder inter-axial distance is varied to maintain an acceptable perforation of the paper web.  
     [0027] The anvil cylinder is preferably permanently rotatably mounted in fixed bearing elements located within the frame members  15 .  
     [0028] Referring to FIG. 2 and FIG. 4, the eccentric bearing assembly  30  generally comprises pre-loaded tapered roller bearings  32  eccentrically mounted in cylindrical bearing housings  34 , located within holes  35  in the frame members  15  such that the bearing housings can rotate therewithin. The outer annular surface  46  of the housings  34  slides within corresponding inner annular surface of the holes  35 . The outer race of each roller bearing is rotatably fixed with respect to the bearing housing, and can be engaged therewith by press fitting or other otherwise fixing to prevent relative rotation therebetween. Outer and inner axial retention plates  36  and  37  maintain the bearing housings within the frame members, prevent any axial displacement, and are engaged to the bearing housings  34  by fasteners  38 , which can be pins or threaded fasteners. The retention plates therefore rotate with the bearing housings. The inner retention plates  37  comprise a toothed gear portion  39 , adapted to be driven by the actuating mechanism described in further detail below, in order to rotate the entire bearing housing within the holes  35  in the frame. As the bearing  32  is eccentrically located within the housing  34 , rotation of the housing about its own central axis of rotation  57  results in the vertical displacement of the central longitudinal axis  22 , common to the bearings  32  and the perforation cylinder  12 . In this manner, by rotating the bearing housing  34  within the frame, the perforation cylinder  12  can be raised or lowered with respect to the vertical elevation of the anvil cylinder.  
     [0029] Specifically, by rotating the bearing housings between two pre-determined, radially spaced positions, the perforation cylinder  12  can be moved from a position where the blades  13  of the perforation cylinder contact the anvil cylinder, to a position where the blades are raised sufficiently away from the anvil cylinder to prevent any contact with the through-running paper web. Perforation of the paper web can therefore be started and stopped during full speed operation of the printing press.  
     [0030] The tapered roller bearings  32  must be pre-loaded bearings. In comparison with other types of perforation systems, using a perforation cylinder and a mating hardened anvil cylinder such as is employed in the present invention necessitates close radial tolerances, and the internal clearance of the cylinder bearings is also of prime importance. Any play in one or the other cylinder can produce a gap between the perforation cylinder blades and the anvil cylinder, resulting in a final paper product that is insufficiently perforated. As the paper webs are relatively thin, even a very small play of 0.001 inch in each cylinder bearing can result in the blades only partially perforating the web. Pre-loaded bearings are used because they have substantially no internal clearance, and therefore will not cause any variations between the blades and the anvil cylinder. The side effect, however, is that they generate significant heat at high speeds, which can cause the supporting frame to expand, thereby changing the distance between the cylinders and resulting in an unacceptable final product. Therefore, to prevent such inter-axial cylinder movement due to thermal expansion, the pre-loaded bearings must be fluid cooled.  
     [0031] The pre-loaded tapered roller bearings  32  are preferably oil cooled, being fed oil through inlet passages  42  in the bearing housings  34 , which correspond to inlet feed holes  40  in the outer race of the bearings  32 . Cooling oil entering the bearings at the center thereof is dispersed axially by the rotation of the roller elements and into outer and inner annular passages  41  surrounding Art the bearing. The oil then continues to circulate under low pressure, which can be provided by a low pressure pump integral with an oil cooler for example, through passages  43  in the bearing housing  34  into circumferential annular groves  44  in the outer surface  46  of the housing. The annular grooves  44  ensure that cooling oil flow is maintained when the bearing housing  34  is rotated within the frame to engage or disengage the perforation cylinder. The grooves  44  correspond to and are in fluid flow communication with oil drain passages  48  in the frame members  15 . The drain passages  48  open into larger horizontal oil outlet passages  50 , also within the frame members, which can return the now heated oil to a standard oil cooler to be cooled and re-circulated. Preferably, the oil is cooled to a temperature of approximately 80° F. (26.67° C.) ±2° F. (1.11° C.) such that thermal expansion of the frame and all bearing assembly members is prevented. In order to ensure that the oil is adequately retained within the eccentric bearing assemblies  30 , annular oil seal rings  52  on the inside and outside edges of the outer surface  46  of the bearing housing  34 , prevents oil from leaking out between the bearing housing and the frame. Annular oil seal rings  54  located between the bearing housings  34  and the outer and inner axial retention plates  36  and  37 , additionally prevent cooling oil leakage.  
     [0032] The perforation cylinder  12  is engaged and disengaged from contact with the anvil cylinder by rotating the eccentric bearing assembly  30 . The inner axial retention plates  37 , which are fixed to the bearing housing  34 , comprise a toothed gear portion  39 . The gears  39  are driven by throw-off gears  70 , fixed to a throw-off shaft  66  that is rotatably mounted to the frame members  15  in bushings  67 . The throw-off shaft  66  is rotated about its longitudinal axis  68  by linking member  62 . A first end  61  of the linking member  62  is fixed to an end  69  of the shaft  66  extending outwards from one frame member  15 . The linking member  62  also comprises, at an opposing second end  63 , a pivotal joint  64  with a displaceable piston end  71  of a hydraulic cylinder  60 . The opposing end of the hydraulic cylinder  60  is rotatably engaged with the frame by pivotal joint  65 . Therefore, when the entire mechanism is actuated, the piston of the hydraulic cylinder extends upwards, imparting rotational motion to the linking member  62  about the axis  68  of the throw-off shaft  66 . This results, through meshing gears  70  and  39 , in a corresponding rotation of the bearing housing  34  in an opposite direction, thereby raising the perforation cylinder  12  away from contact with the anvil cylinder  14 , as a result of the eccentric mounting of the perforation cylinder supporting bearings  32  within the bearing housing.  
     [0033] Referring to FIG. 3, visual indication of the position of the perforation cylinder is provided, namely indicating whether the perforation cylinder is in the lower position where the perforation blades are in contact with the anvil cylinder or whether the perforation cylinder is in the raised position where no perforation is being performed. A position identifying mark  84  is located on the exterior of at least one of the rotatable outer retention plates  36 . Two radially spaced apart indicating marks  82  are located on the frame member  15 , adjacent the outer retention plate  36 , in pre-determined positions representative of the maximum travel points of the perforation cylinder  12 .  
     [0034] Stops, either mechanical, hydraulic, or computer controlled, can be provided to limit the travel of the perforation cylinder, and to establish the precise pre-determined positions of the perforation cylinder for both perforation and thrown-off positions. Additionally, while the perforation throw-off mechanism actuation means is described above with respect to a hydraulic cylinder, it is equally possible to use other actuation means to rotate the throw-off shaft  66 . These can include, but are not limited to, a manually operated lever mechanism, a pneumatic cylinder, an electric motor driven mechanism, and an electromagnetic driven system. Furthermore, it is also envisionable to use a combination of several such throw-off mechanism actuation means, in order to provide a fail-safe system, or to also permit the option of a manual override for example. All such systems can also be linked to a computer control system, either stand alone or integrated with a control system of the associated printing press, in order to control and monitor the perforation system as required. These can include a single touch screen control console, whereby the operator can remotely activate or disable the perforation system.  
     [0035] The activation of the perforation apparatus can also be automated, such that the computer controlled system can precisely engage and disengage the perforation cylinder at appropriate times, such as for example, during splicing of a new paper web roll. As creating perforations in a spliced portion of the paper web can cause a web tear and result in significant press downtime, the present perforation system permits suspension of the perforations until such time as the spliced portion of paper web has passed through the press. As such, it is possible for the operation of the present perforating apparatus to be automated by a computer controlled system to disengage, or “de-perf”, when an automatic splice detector senses a paper web splice, and be re-engaged when the splice detector indicates that the paper splice has passed through the apparatus. As the paper through speeds can be very high, such an automated system improves accuracy by eliminating the need for manual engagement and disengagement of the perforation system at precise times, and reduces the possibility of web tears which cause significant time and financial losses for the press operator.