JP2011513091A - Method and apparatus for releasing a seal formed between a used printing plate and the surface of a printing plate cylinder - Google Patents

Abstract

  A method is disclosed for releasing a seal formed between a used printing plate and a surface of a printing plate cylinder prior to removal of the printing plate from the surface. The method includes the step of providing a jet of compressed air between adjacent printing plates toward the surface of the plate cylinder.

Description

  The present invention provides a seal formed between a used printing plate and the surface of a printing press plate cylinder prior to removal of the printing plate from the surface to facilitate removal of the printing plate. , How to release. The invention also relates to an apparatus for carrying out the method of the invention and a printing press comprising the apparatus.

  A web offset printing press has a number of printing units. Each unit is designed to print an image on a continuous paper web as it passes through the printing unit. The printed webs that run from each printing unit are collected in a folding unit that directs, folds and cuts each web, thereby producing a finished product such as a newspaper or magazine. Each unit includes at least a pair of cylinder groups including a rotatably mounted plate cylinder and a rotatably mounted blanket cylinder to which one or more printing plates are mounted for printing Have a print couple. The printing unit may have a shaftless drive system in which each cylinder group is driven by an individual drive motor, which drives the group cylinder via a belt or gear drive. One of the cylinders is directly driven, and the other cylinder in the group is mechanically coupled to the cylinder to be driven. The ink supply system associated with each printing couple serves to supply ink to the printing plate attached to the plate cylinder as the plate cylinder rotates. When the cylindrical surfaces of the plate cylinder and the blanket cylinder are in rolling contact, the inked image is transferred from the printing plate to the blanket cylinder and from the blanket cylinder to the printing medium.

  For example, in a large-scale large-capacity printing machine used in the manufacture of newspapers, a pair of paper webs stacked and attached to each other in the vertical direction so as to run vertically between each pair of print couples. Multi-color printing is performed by providing each printing unit with a number of printing couples arranged in an array. A pair of four print couples, ie a unit having eight print couples, can print up to four colors on each side of the paper web and is often referred to as a “four high” unit.

  When a printing press is prepared for a printing run, at least one printing plate having a print image to be printed must be attached to the plate cylinder of each printing couple. In general, each plate cylinder has at least one recess or lock-up slot extending longitudinally along the surface of the plate cylinder in which the leading and trailing edges of the printing plate are received. . A mechanism located in the recess engages the leading and trailing edges of the inserted plate and holds the plate firmly in place during the printing operation. The number of plates that must be attached to the plate cylinder of each printing couple depends on the width of the printing press and whether the plate cylinder has one plate or two plates along the circumference, ie " It is determined depending on whether it is a one-around “plate cylinder” or a “two-around” plate cylinder. For example, in a double-width one-around printing press, the plate cylinder supports four plates across the width and one plate that extends circumferentially along the cylindrical surface. Therefore, 8 printing plates can be provided in one printing couple pair, 32 printing plates can be provided in a four-high printing unit, and all printing plates must be loaded before starting a new printing operation. Must be replaced. If the plate cylinder is a “two-around” type, the number of plates is correspondingly doubled. Therefore, even when only one newspaper version is manufactured, a very large number of printing plates are required.

  In conventional printing presses, the printing press operator manually removes the used printing plate from the plate cylinder, but automatic printing plate removal systems are also known. One such system is known from the applicant's previous application WO 06/120171. One method for manually removing a printing plate from a plate cylinder is for a printing press operator to attach a printing plate gripping element such as a suction cup to the surface of the printing plate to be removed. The printing plate gripping element has a handle by which the printing plate is peeled off from the plate cylinder surface. Similarly, in an automatic plate removal system, the plate gripping element suspended from the plate removal head is removed to pull the plate away from the plate cylinder surface when the plate loading head is lifted from the plate cylinder surface. Grab the surface of the plate you want.

  Whether the operator manually removes the plate from the plate cylinder or uses an automatic plate removal process, it is often difficult to remove the used plate from the plate cylinder quickly and easily. This substantially increases the time taken to perform the plate change operation before the printing press or at least the individual printing units can be brought back into operation, thereby increasing the overall productivity of the printing press. Significantly adversely affect

  In particular, when the printing plate is fixed to the plate cylinder by the printing pressure applied to the printing plate during the printing operation, the printing plate tends to adhere to the plate cylinder. This is mainly because a solution of water and gum arabic is provided on the front surface (printing surface) and back surface of the printing plate in order to form a protective film that remains in place after moisture evaporates. Gum arabic prevents the oxidation of the aluminum plate between the processing of the plate and the use of the plate in the printing press. The gum arabic film remaining on the back side of the printing plate acts as a mild adhesive that adheres or seals the printing plate to the surface of the plate cylinder. This effect is exacerbated by the printing pressure and heat generated during the printing run, making the gum arabic film even more tacky and effectively "baking" the printing plate in place on the plate cylinder. This problem is exacerbated by the presence of gum arabic residue deposited in the lock-up slot.

  Even if there is no problem caused by the gum arabic film, the printing force also acts to push air out between the printing plate and the plate cylinder during printing, which creates a vacuum seal between the printing plate and the plate cylinder. Arise. The effect of this seal and the seal produced by the presence of the gum arabic membrane is necessary to overcome the lock-up clamping or friction spring force that holds the leading and trailing edges of the plate in the individual lock-up slots. When combined with the forces assumed, the difficulty experienced when removing a used printing plate from a printing press cylinder is increased.

  Due to the aforementioned problems, the force that the press operator must exert on the plate gripping element to pull the plate away from the plate cylinder may be excessive and / or beyond the operator's capabilities. Alternatively, the required force may exceed the force created between the plate gripping element and the surface of the plate cylinder, which may cause the gripping element to break without lifting the plate. . Even when an automatic plate loading system is used, the gripping force applied must be large, otherwise the plate loading system simply leaves the plate when the plate loading head is lifted.

  The present invention provides a method and apparatus that substantially overcomes or alleviates the above problems and allows for easier and faster removal of a printing plate from the surface of a printing press cylinder.

  According to the present invention, there is provided a method of releasing a seal formed between a used printing plate and a curved surface of a printing drum of a printing press in order to facilitate removal of the printing plate from the surface. Provided, the method includes providing a jet of compressed air toward the surface of the plate cylinder adjacent to the edge of the plate attached to the cylinder.

  The edge of the printing plate is preferably the longer edge extending circumferentially around the curved surface of the plate cylinder.

  In a preferred embodiment, the method comprises the step of providing a jet of the compressed air toward the surface of the plate cylinder between the edges of the adjacent printing plates.

  The plate cylinder may have a trailing edge lockup slot in which the trailing edge of the printing plate is received, and the method is preferably adjacent to each other at a location circumferentially away from the trailing edge lockup slot. Providing a jet of the compressed air toward the surface of the plate cylinder during the printing plate.

  In one embodiment, the method includes providing a jet of compressed air toward the plate cylinder at an angle substantially perpendicular to the axis of the plate cylinder. However, in an alternative embodiment, the method comprises providing a jet of compressed air toward the plate cylinder at an angle of 0 to 90 degrees with respect to the axis of the plate cylinder.

  The invention may provide multiple pulses of compressed air towards the surface of the plate cylinder.

  In one embodiment, the printing press has a plate remover and at least one nozzle attached to the plate remover connected to a compressed air supply, through which the jet is jetted. Is released. In this case, the method includes the step of moving the plate removal device to a position where each nozzle is positioned above the surface of the plate cylinder between adjacent plates.

  The plate removal apparatus may have a plurality of plate gripping elements that are movable to contact the surface of the plate to be removed from the plate cylinder. If so, the method preferably includes a flow of compressed air toward the surface of the plate cylinder between adjacent plates before moving the plate gripping element into contact with the surface of the plate. Providing a jet.

  A plurality of nozzles attached to the plate removal apparatus can be provided. Thus, the method may comprise the step of operating the nozzles sequentially or simultaneously.

  The method may include providing a jet of compressed air toward the surface of the plate cylinder for a controlled time of 1 second or less.

  According to another aspect of the invention, the seal formed between the used printing plate and the surface of the printing plate cylinder is released in order to facilitate removal of the printing plate from the surface. There is provided an apparatus for providing a nozzle for providing a jet of compressed air toward the surface of the plate cylinder adjacent to the edge of the plate.

  Preferably, the edge of the printing plate is an edge extending in the circumferential direction around the curved surface of the plate cylinder.

  In a preferred embodiment, the nozzle is configured to provide a jet of said compressed air toward the surface of the plate cylinder between the edges of the adjacent printing plates.

  In one embodiment, the plate cylinder has a trailing edge lockup slot in which the trailing edge of the printing plate is received, and the nozzles are adjacent to each other at a location circumferentially spaced from the trailing edge lockup slot. Is positioned relative to the plate cylinder so as to provide a jet of compressed air between the printing plates to be directed toward the surface of the plate cylinder.

  The nozzle may be configured to provide a jet of compressed air toward the plate cylinder at a predetermined angle, the angle being substantially perpendicular to the axis of the plate cylinder.

  The apparatus may have means for controlling the nozzle to provide multiple pulses of compressed air toward the surface of the plate cylinder.

  According to another aspect of the invention, there is provided a printing press having an apparatus for releasing a printing plate according to the present invention. The printing press may have a plate cylinder and a device for removing the printing plate from the plate cylinder, and the nozzle was moved to a printing plate removal position adjacent to the printing press plate cylinder. Sometimes, each nozzle is attached to a plate remover so that it can be moved to a position positioned above the surface of the plate cylinder between adjacent plates.

  In one embodiment, the plate removal device is in contact with the surface of the plate that is to be removed from the plate cylinder after a jet of compressed air is provided between the adjacent printing plates toward the surface of the plate cylinder. And a plurality of movable plate gripping elements.

  The printing press may have a plurality of nozzles attached to the plate removal device, each nozzle adjacent to each other when the plate removal head is moved to the plate removal position above the plate cylinder. Located between the plates above the plate cylinder.

  In a modified embodiment, the plate cylinder has a groove or scalloped surface extending from the underside of one printing plate toward an adjacent printing plate attached to the plate cylinder, and the groove Is configured to provide a jet of compressed air from the nozzle below a printing plate extending over the groove.

  Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings.

It is sectional drawing which looked at the printing plate removal head arrange | positioned above the surface of the plate cylinder of the printing machine with which the printing plate was attached from the side. FIG. 2 is a top view of the plate cylinder shown in FIG. 1, which has four printing plates mounted in juxtaposition to the plate cylinder, and a printing plate mounting head is omitted. It is sectional drawing along the XX line in FIG. It is sectional drawing which shows the changed printing cylinder along the XX line in FIG. FIG. 3 is a cross-sectional view along the line XX of FIG. 2 using an angled compressed air nozzle.

  While embodiments of the invention will be described primarily with respect to plate removal using an automatic plate removal system, it will be appreciated that the invention is equally applicable to manual plate removal.

  Referring now to the drawings, FIG. 1 shows a plate cylinder 1 forming one printing couple of a printing unit, equipped with an automatic plate removal device having a plate removal head 3 extending across the width of the plate cylinder 1. And a part of the blanket cylinder 2 is shown. The plate removal head 3 may be used in an automatic or semi-automatic plate loading operation to attach an unused plate at a predetermined position on the plate cylinder of the printing machine before starting a printing operation. The printing plate removal head 3 includes a rising position where the printing plate removal head is arranged away from the plate cylinder 1 when the printing unit is in use without performing the plate removal or mounting operation, It is possible to move between the lowered positions for performing the removal work using compressed air.

  The plate removal head 3 has an elongated support frame 5 extending substantially over the entire width of the plate cylinder 1. The arrangement of the plate gripping elements 6 is attached to the support frame 5 so as to face the curved cylindrical surface of the plate cylinder 1 and is suspended from the support frame 5. When the printing plate gripping element 6 is actuated, the printing plate gripping element 6 spans the width of one printing plate 7 or the plate cylinder 1 so that the printing plate 7 can be operated by the printing plate removal head 3. It works to engage with the surfaces of a plurality of juxtaposed printing plates 7 (see FIG. 2). The printing plate removal head also has a pressing element 8 that is movable independently of the support frame 5 and the printing plate gripping element 6 in a direction approaching and moving away from the surface 1 a of the plate cylinder 1. Since the pressing element 8 is generally used only in the plate mounting operation, the pressing element 8 will not be further described here.

  When removing one printing plate 7 or a plurality of printing plates 7 as shown side by side in FIG. 2 from the plate cylinder 1, the plate 7 has a trailing edge 7 a of the printing plate removal head 3. Indexed to a nearby location. This preferred position is shown in FIG.

  In a conventional plate removal operation as described in the applicant's previous PCT application issued as WO 06/120171, the plate removal head 3 is lowered and the plate gripping element 6 is removed. Is brought into contact with the surface of the plate 7 adjacent to the trailing edge 7a, and then the plate gripping element 6 is actuated to grip the plate 7. Next, the plate removal head 3 is lifted to lift or lift the plate 7 from the surface 1 a of the plate cylinder 1 and pull the trailing edge 7 a of the plate 7 from the lock-up slot 9 provided in the plate cylinder 1. (The direction of the arrow “X” in FIG. 1). Instead of lifting the entire plate removal head 3, the plate gripping element 6 is retracted relative to the plate removal head 3 to lift the trailing edge 7 a of the plate 7 from the lock-up slot 9. 6 can also be removably attached to the plate removal head 3.

  When the removal of the trailing edge 7a of the printing plate is achieved, the plate cylinder 1 is moved so that the leading edge (not shown) is used for the removal of the leading edge or at least a partial removal using the suction element 6. It is rotated (in the direction of the arrow “Y” in FIG. 1) until it is located below the plate removal head 3. If the leading edge is only partially removed from the lockup slot, the plate cylinder 1 is rotated again so that the leading edge is completely removed from the lockup slot by a printing plate extraction element (not shown). The plate extraction element contacts the partially removed leading edge while the plate cylinder 1 rotates, leaving the plate 7 hanging from the extraction element at the leading edge.

  As described above, due to the presence of gum arabic that effectively attaches the printing plate 7 to the surface of the plate cylinder 1 during the printing operation, and the vacuum generated as a result of the plate 7 being fixed to the plate cylinder 1. A complicated situation arises because it is difficult to first lift the plate 7 from the surface of the plate cylinder 1 in order to slide the trailing edge 7a out of the lock-up slot 9. However, Applicants have invented a method to overcome this problem. This method will be described below.

  The plate removing head 3 is provided with a number of compressed air nozzles 10 arranged at intervals along the length of the plate removing head 3 (only one compressed air nozzle 10 is shown in FIG. 1). It is shown). These nozzles 10 are located in the plate removal head 3 and when the plate cylinder 10 is indexed to the trailing edge mounting position as shown in FIG. 9, but preferably not directly above the trailing edge lockup slot 9, and is positioned directly above the circumferentially extending long edge 7 b of two adjacent printing plates 7. ing. Ideally, the nozzle is arranged away from the rear edge 7a of the printing plate 7 in the circumferential direction by a short distance of 30 to 200 mm.

  During the plate removal operation, before the plate removal head 3 is lowered and the plate gripping element 6 is actuated, a compressed air jet (indicated by “J” in FIG. 1) is applied from the nozzle 10 to the plate 7. To the surface 1a of the plate cylinder 1 between the long edges 7b of the printing plate 7. The short jet of compressed air provided towards the plate cylinder 1 in this way was caused by, for example, the vacuum produced by the presence of gum arabic and / or the fixing of the printing plate 7 to the surface 1a of the plate cylinder 1. , It has the effect of breaking the seal between each adjacent printing plate 7 and the surface 1a of the plate cylinder. The compressed air jet need only last a fraction of a second to serve the purpose of releasing the plate 7 so that when the plate gripping element 6 is subsequently activated, the plate gripping element 6 Can easily lift the plate 7 from the surface 1 a of the plate cylinder 1 and pull the trailing edge 7 a out of the lock-up slot 9. Although it is assumed that compressed air is used, several other compressed gases can alternatively be injected from the nozzle. Rather than providing the plate cylinder from a position spaced from the lockup slot, it is also possible to provide a jet of compressed air to the lockup slot.

  FIG. 2 shows a plan view of the plate cylinder 1 shown in FIG. 1, but the plate mounting head 3 is omitted for the sake of clarity. The nozzle 10 is arranged so as to collide with the plate cylinder 1 between the printing plates 7 adjacent to each other at a place where the air jet “J” is indicated by “A”. In a printing machine having four printing plates 7 extending side by side across the width of the plate cylinder 1, as shown in FIG. 2, one is between the two printing plates on the left and the other is the two on the right. Two nozzles 10 positioned between two printing plates have been found to be sufficient to break the seal between each printing plate 7 and plate cylinder 1, but any number of nozzles 10 can be used. It will be appreciated that it may be done.

  As more clearly shown in FIG. 3, the jet of compressed air emitted by each nozzle 10 impinges on the plate cylinder 1 in a circumferential gap 11 between the printing plates. Most of this air jet is redirected out of the gap 1 as indicated by the arrow “C”, but at least a portion of this air is under the plate 7 (in the direction of the arrow “D”). Get into. This air flows under the printing plate 7, thereby releasing the adhesion of the printing plate 7 to the plate cylinder 1.

  Referring to FIG. 4, small grooves or scallops 12 are formed in the surface of the plate cylinder 1 to redirect the air jet toward the underside of the plate 7 as indicated by the arrow “E” in FIG. If formed, the effect of the air jet can be enhanced. However, it has been found that the air jet sufficiently releases the plate even when no changes are made to the plate cylinder 1. The air jet positioned as described above so as to be located near one corner of each of two adjacent printing plates 7 in order to achieve the desired release of the printing plate 7 from the surface of the plate cylinder 1. Enough.

  It is assumed that only one pulse of compressed air from the nozzle 10 is required to release the plate 7. However, it is also possible to cause each nozzle 10 to provide a series of pulses of compressed air and / or to rotate the plate cylinder 1 while the jet is operating. It is also possible to supply compressed air to all the nozzles 10 simultaneously, or to supply the printing plate 7 or a plurality of pairs of printing plates one after the other in order to release them sequentially.

  As described above, the present invention is also applicable to manual plate removal. In manual operation, the operator simply releases from the nozzle 10 attached to the plate removal head 3 before placing the plate gripping element 6 on each plate 7 and pulling the plate away from the surface of the plate cylinder 1. The compressed air hose is moved along the surface of the plate 7 so that a compressed air jet is provided at approximately the same location as the air jet.

  As shown in FIGS. 3 and 4, the jet of compressed air is substantially radially toward the surface of the plate cylinder and the plate, ie, the air jet is in the plate cylinder 1 just below the nozzle 10. It is envisioned that it will be injected to impact at a substantially 90 degree angle to the surface, but as shown in FIG. 5, the air jet is at an angle of less than 90 degrees to the surface. It is also possible that the nozzle 10 is angled so as to collide. When the nozzle 10 is angled in this way, the jet is provided closer to the edge of the plate 7 where the plate contacts the surface of the plate cylinder 1. However, it will be appreciated that if an automatic plate remover is used, a second nozzle 10 that is angled toward the edge of the adjacent plate 7 is required.

  Many modifications to the invention within the scope of the appended claims will be apparent to those skilled in the art. The above description should be regarded only as a description of the preferred embodiments.

Claims (23)

  A method of releasing a seal formed between a used printing plate and a curved surface of a printing plate cylinder to facilitate removal of the printing plate from the surface, the method comprising: Providing a jet of compressed air toward the surface of the plate cylinder adjacent to the edge of the plate attached to the plate.   The method of claim 1, wherein the edge of the printing plate is an edge extending circumferentially around the curved surface of the plate cylinder.   3. A method according to claim 1 or 2, wherein the method comprises the step of providing the jet of compressed air toward the surface of the plate cylinder between the edges of the plates adjacent to each other.   The plate cylinder has a trailing edge lockup slot in which a trailing edge of the printing plate is received, and the method includes the steps of the plates adjacent to each other at a position circumferentially spaced from the trailing edge lockup slot; 4. A method according to any one of the preceding claims, comprising providing the jet of compressed air toward the surface of the plate cylinder in between.   5. A method according to any one of the preceding claims, comprising the step of providing a jet of compressed air towards the plate cylinder at an angle substantially perpendicular to the axis of the plate cylinder.   5. A method according to any one of the preceding claims, comprising providing a jet of compressed air toward the plate cylinder at an angle of 0 to 90 degrees with respect to the axis of the plate cylinder.   7. A method according to any one of the preceding claims, comprising providing a plurality of pulses of compressed air towards the surface of the plate cylinder.   The printing press has a plate removal device and at least one nozzle attached to the plate removal device connected to a source of compressed air so that a jet is emitted through the nozzle. And the method includes the step of moving the plate removal device to a position where each nozzle is to be positioned above the surface of the plate cylinder between adjacent plates. The method according to any one of 1 to 7.   The plate removing apparatus has a plurality of plate gripping elements movable so as to come into contact with the surface of the plate to be removed from the plate cylinder, and the method is arranged so that the method comes into contact with the surface of the plate. 9. A method according to claim 8, comprising the step of providing a jet of compressed air toward the surface of the plate cylinder between adjacent plates before moving the gripping element.   The method according to claim 8 or 9, wherein a plurality of nozzles attached to the plate removing apparatus are provided, and the method includes the step of sequentially operating the nozzles.   11. A method according to any one of the preceding claims, comprising the step of providing a jet of compressed air toward the surface of the plate cylinder for a controlled time of typically less than 1 second.   An apparatus for releasing a seal formed between a used printing plate and a plate cylinder surface of a printing press to facilitate removal of the printing plate from the surface, the device comprising: An apparatus comprising a nozzle for providing a jet of compressed air toward the surface of the plate cylinder adjacent to the edge of the plate.   The apparatus of claim 12, wherein the edge of the printing plate is an edge extending circumferentially around the curved surface of the plate cylinder.   The apparatus of claim 13, wherein the nozzle is configured to provide a jet of the compressed air toward the surface of the plate cylinder between the edges of the adjacent printing plates.   The plate cylinder has a trailing edge lockup slot in which a trailing edge of the plate cylinder is received, and the nozzle is positioned between the adjacent printing plates at a position spaced circumferentially from the trailing edge lockup slot. The apparatus of claim 14, wherein the apparatus is positioned relative to the plate cylinder to provide a jet of compressed air toward the surface of the plate cylinder at.   15. The nozzle is configured to provide a jet of compressed air toward a plate cylinder at a predetermined angle, the angle being substantially perpendicular to the axis of the plate cylinder. 15. The device according to 15.   17. An apparatus according to any one of claims 14 to 16, comprising means for controlling the nozzle to provide a plurality of pulses of compressed air towards the surface of the plate cylinder.   18. A printing press comprising the apparatus according to any one of claims 14 to 17, wherein a plate cylinder and a device for removing the printing plate from the plate cylinder are provided, adjacent to the plate cylinder of the printing press. When the plate removing device is moved to the plate removing position, the nozzles are moved so that the nozzles are moved to positions where the nozzles are positioned above the surface of the plate cylinder between adjacent plates. A printing machine, wherein the printing machine is attached to a plate removing device.   The plate removal apparatus has a plurality of plate gripping elements, the plurality of plate gripping elements being provided toward the surface of the plate cylinder between the adjacent printing plates. 19. A printing press according to claim 18, which is movable so as to contact the surface of the plate that is to be removed from the plate cylinder later.   A plurality of nozzles attached to the plate removing device are provided, and each nozzle is moved between adjacent plates when the plate removing head is moved to the plate removing position above the plate cylinder. The printing press according to claim 18 or 19, wherein the printing press is arranged above the plate cylinder.   The plate cylinder has a groove or scalloped surface extending from the lower side of the printing plate toward an adjacent printing plate attached to the plate cylinder, and the groove has a jet of compressed air, 21. A printing press according to any one of claims 18 to 20, configured to provide from a nozzle to the underside of a printing plate extending above the groove.   A method substantially as described above.   Apparatus substantially as hereinbefore described with reference to the accompanying drawings.

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