Printing plate registration

An apparatus for registering a printing plate includes a support surface. A first registration member provides an electrical signal to the printing plate when contact is established between the first registration member and a first edge of the printing plate. Each registration member in a set of two or more registration members receives the electrical signal provided to the printing plate when contact is established between an edge of the printing plate and the registration member. A set of two or more sensors detects a presence of the electrical signal received by a registration member. A plurality of actuators is operable for moving the printing plate towards a registration member. A controller determines a presence or absence of contact between the printing plate and a selected registration member based on information provided by each sensor. The controller selectively operates at least one of the actuators to move the printing plate towards the selected registration member.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned U.S. patent application Ser. No. 12/700,785 (now U.S. Publication No. 2011/0192303), filed Feb. 5, 2010, entitled IMPROVED DETECTION OF A MISREGISTERED PRINTING PLATE, by Hines, the disclosure of which is incorporated herein.

FIELD OF THE INVENTION

The invention relates to printing, and in particular to registering printing plates in an apparatus such as a computer-to-plate system. Registration of the printing plate can be required prior to subjecting the printing plate to a subsequent process such as the formation of an image on the printing plate or the formation of a registration feature on the printing plate.

BACKGROUND OF THE INVENTION

Contact printing using high volume presses is commonly employed to print a large number of copies of an image. A contact printing press typically utilizes a printing plate to apply a colorant to a surface to form an image thereon. The surface can form part of a receiver media (e.g. paper) or can form part of an intermediate component adapted to transfer the colorant from its surface to the receiver media (e.g. a blanket cylinder of a press). In either case, a colorant pattern is transferred to the receiver media to form an image on the receiver medium.

Printing plates typically undergo various processes to render them in a suitable configuration for use in a printing press. For example, exposure processes are used to form images on an imageable surface of a printing plate that has been suitably treated so as to be sensitive to light or heat radiation. One type of exposure process employs masks. The masks are typically formed by exposing highly sensitive film media using a laser printer known as an “image-setter.” The film media can be additionally developed to form the mask. The mask is placed in area contact with a sensitized printing plate, which is in turn exposed through the mask. Printing plates exposed in this manner are typically referred to as “conventional printing plates.” Some conventional lithographic printing plates are sensitive to radiation in the ultraviolet region of the light spectrum.

Another conventional method directly forms images on printing plates through the use of a specialized imaging apparatus typically referred to as a plate-setter. A plate-setter in combination with a controller that receives and conditions image data for use by the plate-setter is commonly known as a “computer-to-plate” or “CTP” system. CTP systems offer a substantial advantage over image-setters in that they eliminate film masks and associated process variations associated therewith. Printing plates imaged by CTP systems are typically referred to as “digital” printing plates. Digital printing plates can include photopolymer coatings (i.e. visible light plates) or thermo-sensitive coatings (i.e. thermal plates).

In many printing processes, a plurality of printing plates is used to apply different colorants to a receiver media. Typically, each printing plate applies a different colorant to the receiver media. In this way, the printed image formed on the receiver media can contain different colors. Each of the printing plates must be registered with respect to one another to form a printed image having a desired visual quality. Regardless of the manner by which an image is formed on a printing plate, it must be accurately positioned on the printing plate to achieve a desired registration with the images formed on other associated printing plates.

In some cases, registration features are formed in a printing plate to help register the printing plate on a printing press. The registration features can be formed by various processes including processes adapted to form perforations in the printing plate. A set of perforations can be used to define registration features comprising locating holes or locating channels adapted for providing a desired alignment with a corresponding set of registration features on printing press. It is noted that accurate registration requires that the registration features formed on a printing plate also be registered with the images formed on the printing plate. In some cases, the image forming process and the registration feature forming process are conducted by different apparatus. In other cases, the image forming process and the registration feature forming process are conduced by the same apparatus. In some cases, the image forming process precedes the registration feature forming process while in other cases, the opposite occurs. In some cases, a registration feature formed on a printing plate is employed to assist in the accurate placement of an image on the printing plate. In other cases, an image formed on a printing plate is employed to assist in the accurate placement of a registration feature on the printing plate.

In many cases, one or more edges of a printing plate are used for registration purposes during a processing of the printing plate. For example, during some processes, a printing plate is aligned on a support surface of an apparatus by bringing one or more of the plate edges known as “registration edges” into contact with various registration members. Various groupings of registration members are often employed to register printing plates to the support surface. “Three-point” registration is especially advantageous for rectangular or square shaped printing plates. Once a required contact is established between the printing plate and the registration members, the printing plate is deemed to be in a required registration for a subsequent processing such as the forming of an image or registration feature. Failure to establish the necessary contact between the printing plate and the registration members can introduce registration errors during the subsequent processing. The failure to establish the necessary contact between the printing plate and the registration members is referred to as “misregistration.” Registration errors can lead to reduced quality in the finished printing plate and adversely impact the productivity of the plate making process.

Various conventional printing plate registration detection systems are known. For example, in commonly-assigned U.S. Pat. No. 6,510,793 (Kerr et al.), which is herein incorporated by reference, describe a electronic printing plate registration system in which registration is established when the edges of a printing plate contacts all of three electrically conductive members to create a short between the all of the three conductive members. In one embodiment, Kerr et al. teaches the use of a signal generator that generates an electrical signal at each of two of the three conductive members which act as “emitter” members. An electrical short detection system employs a short detector that senses both the electrical signals at the remaining third conductive member which acts a “receiver” member. In this regard, the electrical detector is adapted to detect both the electrical signals provided by the two “emitter” conductive members. Kerr et al. teaches the use of two signals having different characteristics (e.g. frequency) to determine whether a misregistration is created by an absence of contact between the printing plate and a particular one of the two emitter members. Although this electronic printing plate registration system can identify some misregistrations, it cannot identify others. In particular, this electronic printing plate registration system cannot distinguish between a first misregistration caused by an absence of contact between the printing plate and each of the two emitter members and a second misregistration caused by an absence of contact between the printing plate and the receiver member. In this regard, this uncertainty may hinder corrective actions in an automated system used to correct any misregistration.

There is a need for improved methods and apparatus for properly registering a printing plate during a printing plate processing operation.

There is a need for improved methods and apparatus for correcting a misregistration of a printing plate during a printing plate processing operation.

There is a need for improved methods and apparatus for accurately identifying which of a plurality of different printing plate misregistrations exist.

There is a need for automated methods for correcting an identified misregistration of printing plate during a printing plate processing operation.

There is a need for an imaging apparatus with improved printing plate registration abilities.

There is a need for a perforation apparatus with improved printing plate registration abilities.

SUMMARY OF THE INVENTION

Briefly, according to one aspect of the present invention an apparatus for registering a printing plate comprising an electrically conductive material including a support surface adapted for supporting the printing plate; a plurality of registration members comprising a first registration member adapted for providing an electrical signal to the printing plate when contact is established between the first registration member and a first edge of the printing plate, and a set of two or more registration members, each registration member in the set of two or more registration members adapted for receiving the electrical signal provided to the printing plate when contact is established between an edge of the printing plate and the registration member in the set of two or more registration members; a set of two or more sensors, each of the sensors adapted for detecting a presence of the electrical signal received by a registration member in the set of two or more registration members; a plurality of actuators, each of the actuators being individually operable for moving a portion of the printing plate towards a registration member of the plurality of registration members; and a controller configured for determining a presence or absence of contact between the printing plate and a selected registration member of the plurality of registration members based at least on information provided by each sensor in the set of two or more sensors, the controller being further configured for selectively operating at least one of the actuators to cause the printing plate to move towards the selected registration member in the event that an absence of the electrical signal is detected by at least one sensor in the set of two or more sensors.

The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following description specific details are presented to provide a more thorough understanding to persons skilled in the art. However, well-known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive sense.

FIGS. 1-4schematically illustrate a printing plate imaging apparatus10as per an example embodiment of the invention. In the embodiment ofFIGS. 1-4, imaging apparatus10is a computer-to-plate imaging apparatus. Imaging apparatus10comprises a frame12supporting an image recording system14, a staging support surface90, a plate exchange surface17, a transfer support surface60, a perforation system19, and a controller20.

Controller20can comprise a microprocessor such as a programmable general purpose microprocessor, a dedicated micro-processor or micro-controller, or any other system that can receive signals from various sensors, and from external and internal data sources and that can generate control signals to cause actuators and motors within imaging apparatus10to operate in a controlled manner to form imaged printing plates24. Controller20can comprise a plurality of controllers.

Image recording system14comprises an imaging head22adapted to take image-forming actions within an image forming area of an imaging support surface28so that an image can be formed on each of one or more printing plates24loaded within the image forming area on imaging support surface28. In the illustrated embodiment, a plurality of printing plates24including printing plate24A and printing plate24B is supported on imaging support surface28. However, this is not limiting and in other embodiments, imaging support surface28may be capable of supporting a different number of printing plates24in a manner that allows imaging head22to form images on each of printing plates24held thereby. Printing plates24A and24B can include different sizes or substantially the same size as shown in the illustrated embodiment. In this example embodiment, each of the printing plates24includes an electrically conductive material. In some example embodiments, each printing plate24is made from an electrically conductive substrate. In some example embodiments, each printing plate24is formed from a plastic or other substrate having an electrically conductive layer or coating.

Imaging head22generates one or more modulated light beams or channels that apply image modulated energy onto printing plates24A and24B. Imaging head22can move along a sub-scanning axis SSA while a motor36or other actuator moves the imaging support surface28along a main scanning axis MSA such that image forming actions can be taken over an image forming area of imaging support surface28on which printing plates24A and24B are supported.

Imaging head22is illustrated as providing two light emission channel sources30and32which can each comprise, for example, a source of laser light and laser modulation systems (not illustrated) of a kind known to those of skill in the art each capable of taking image forming actions on printing plates24located within the image forming area. In some embodiments, light emission channel sources30and32can be independently controlled, each source applying modulated energy to printing plates24A and24B. In yet other embodiments of this type, a single light emission channel source can be used to generate a modulated light beam that can be directed across the entire image forming area.

In various embodiments, not illustrated, various types of imaging technology can be used in imaging head22to form an image pattern on printing plates24A and24B. For example, and without limitation, thermal printing plate image forming techniques known to those of skill in the art can be used. The choice of a suitable light emission source can be motivated by the type of printing plate24that is to be imaged.

In the embodiment ofFIGS. 1-4, imaging support surface28illustrates an external drum-type of imaging support surface having a generally cylindrical exterior surface34. Accordingly, in the embodiment ofFIG. 2, main scanning axis MSA is illustrated as extending along an axis that is parallel to a direction of rotation of exterior surface34. However, in other embodiments imaging support surface28can comprise an internal drum or a flatbed support surface. In the external drum embodiment illustrated, printing plates24A and24B are held on exterior surface34by clamping forces, electrostatic attraction, vacuum force or other attractive forces supplied respectively by plate clamps, electrostatic systems, vacuum systems or other plate attracting systems (not illustrated).

During imaging operations, controller20causes image modulated beams of light from imaging head22to be scanned over the imaging forming area by a combination of operating a main scanning motor36to rotate imaging support surface28along main scanning axis MSA and translating imaging head22in the sub-scanning direction by causing rotation of a threaded screw38to which light emission channel sources30and32are attached in a manner that causes them to advance in a linear fashion down the length of threaded screw38as threaded screw38is rotated. It is understood that other mechanical translation systems known in the art can be used for this purpose. In some embodiments, light emission channel sources30and32can be controlled to move independently of one another along sub-scanning axis SSA. In other example embodiments, other well-known light beam scanning systems, such as those that employ rotating mirrors, can be used to scan image modulated light across the image forming area of imaging support surface28.

As is shown in greater detail inFIG. 2, exterior surface34has various groupings of registration members including a first registration member40A and a second registration member40B associated with printing plate24A, and a first registration member40C and a second registration member40D associated with printing plate24B. In this example embodiment, printing plates24A and24B are positioned in contact with their associated registration members during an imaging operation to locate the printing plates along the main-scanning axis MSA.

First and second registration members40A and40B are arranged to help control the position of registration edge52of printing plate24A along main scanning axis MSA. Similarly, registration members40C and40D are arranged to help control the position of registration edge54of printing plate24B along main scanning axis MSA.

Alignment of the first and second printing plates24A and24B along sub-scanning axis SSA can be provided in various ways. In a preferred embodiment, imaging head22has an integral edge detector (not illustrated) that is adapted to sense lateral edges25A and25B of respective printing plates24A and24B as imaging head22is moved past the printing plates during imaging operations. In this example embodiment, each of lateral edges25A and25B has a substantially perpendicular orientation to respective registration edges52and54. Controller20receives signals from the edge detector and adjusts imaging operations so that images are formed on printing plates24A and24B in precise relation to the sensed lateral edges25A and25B of printing plates24A and24B respectively. Typically, integral edge detectors include an optical sensor that detects an edge based upon differences in an amount of light reflected thereby. However, integral edge detectors can take other forms known to those of skill in the art including magnetic field detectors, electrical sensors, and contact detectors.

Alternatively, alignment along the sub-scanning axis SSA during imaging can be provided by additional third registration members40E and40F as illustrated in broken lines inFIG. 2. When employed, third registration members40E and40F are positioned for respective contact with lateral edges25A and25B to help accurately position printing plate24A and printing plate24B along sub-scanning axis SSA. In this regard, registration members40A,40B, and40E define a three-point registration system for printing plate24A during imaging, and registration members40C,40D, and40F define a three point registration system for printing plate24B during imaging.

In the embodiment illustrated, a staging support surface90is provided and is adapted to exchange various printing plates24(e.g. printing plates24A and24B) with imaging support surface28. Printing plates24can be provided to staging support surface90for subsequent transfer to imaging support surface28in various ways. For example, plate handling mechanism33can be used to pick each printing plate24from one or more printing plate stacks35and transfer each printing plate24to staging support surface90by various methods as are well known in the art. Printing plate stacks35can be arranged or grouped in various manners, including by plate size, type, etc. Cassettes, pallets and other containing members are regularly employed to group a plurality of printing plates24. The printing plates24in printing plate stack35are shown separated from one another for clarity. Interleave or slip-sheets can be employed to separate adjacent printing plates24from one another in printing plate stack35.

Once a printing plate24is transferred to staging support surface90, a plate positioning system64is operated to engage with a surface of the printing plate24and move it at least in part from staging support surface90onto imaging support surface28in this example embodiment. In this regard, it is desired that the printing plate24be transferred to imaging support surface28such that one of its edges is in contact and aligned with each of an associated set of registration members.

In this example embodiment, imaging apparatus10has a transfer support surface60and a positioning system62. In this example embodiment, transfer support surface60is sized to receive, hold and/or deliver a plurality of printing plates24at the same time. In this example embodiment, positioning system62is connected between frame12and transfer support surface60and defines a movement path for transfer support surface60between a transfer position shown inFIG. 3and a perforation position shown inFIG. 4.

When transfer support surface60is in the transfer position, printing plates24A and24B can be transferred between imaging support surface28and transfer support surface60. Depending on the desired flow of the printing plates24through the apparatus10, printing plates24A and24B can be transferred from transfer support surface60to imaging support surface28, or from imaging support surface28to transfer support surface60when transfer support surface60is in the transfer position.

In this illustrated embodiment, printing plates24are transferred after they are imaged by imaging head22. In this illustrated embodiment, transferred printing plates24can be perforated at the second position by perforation system19. In this example embodiment, perforation system19perforates printing plates24with various punches and is herein referred to as punching system19. While it is common in the industry for punches to be used to perforate printing plates, it will be appreciated that there are a variety of other ways in which the perforations can be formed. For example, and without limitation, laser cutting, thermal cutting, drilling, chemical etching, ablation, and other well known mechanical, chemical, and electrical processes can be employed. In some embodiments of the invention, printing plates24can be transferred to other systems for other forms of processing.

When transfer support surface60is in the perforation position, registration edges52and54of respective printing plates24A and24B are positioned proximate to various punches73(not shown InFIGS. 1-4) in punching system19. In this example embodiment, punches73are employed to punch holes or detents or other forms in the printing plates24that can be used to form registration features. These registration features can be employed for various reasons including to align the printing plates24on a printing press.

FIG. 5schematically shows a portion of apparatus10including a plan view of a portion of transfer support surface60with a printing plate24(i.e. first printing plate24A) supported thereupon, and punch system19. In this example embodiment, a plurality of registration members are arranged so that various edges of printing plate24A can be positioned against various ones of registration members. Registration members are positioned so that when various edges of printing plate24A are positioned in contact with various ones of the registration members, the printing plate24A will be accurately positioned so that registration features can be formed at desired locations on printing plate24A by punches73.

In this example embodiment, registration members include a first registration member50A, a second registration member SOB, and a third registration member50C. In this example embodiment, first and second registration members50A and SOB assume fixed locations relative to transfer support surface60. In this example embodiment, first and second registration members50A and50B are affixed to transfer support surface60. In this example embodiment, it is desired that first and second registration members50A and50B be positioned for contact with a first edge of printing plate24A. In this example embodiment, the first edge is registration edge52. In this example embodiment, a mechanism is provided to permit movement of third registration member50C relative to transfer support surface60. In this example embodiment, third registration member50C can be positioned at various locations under the influence of a drive70which can include a motor and transmission arrangement (not illustrated) or pneumatic or hydraulic cylinder (not illustrated) by way of non-limiting example. In operation, third registration member50C is positioned against a second edge of printing plate24A that is oriented substantially perpendicular to the first edge of printing plate24A. In this example embodiment, the second edge is lateral edge25A. In this example embodiment, drive70and third registration member50C can be employed to laterally position printing plate24A at a desired location relative to punches73used to form the registration features in printing plate24A. In this example embodiment, the positioning of printing plate24A relative to the first and second registration members50A and50B employed during the punching operation corresponds to the positioning of printing plate24A relative to first and second registration members40A and40B during the imaging operation. In this regard, a spacing between first and second registration members50A and50B is selected to match a spacing between first and second registration members40A and40B. In some example embodiments, registration members50A and50B are selected from a plurality of sets of registrations members, each set being positioned to engage a different sized printing plate as described in commonly-assigned U.S. Pat. No. 6,755,132 (Cummings). Various members of the plurality of registration members can be positioned for contact with various printing plates24of a select size. In some example embodiments, one or both of registration members50A and50B are repositioned to various locations suitable for achieving a desired spacing there between. The repositioning of a registration member can include moving the registration member to a location suitable for contact with an edge of a printing plate24. For example, a registration member can be repositionable between a first position which is recessed below transfer support surface60and a second position where the registration member protrudes from the transfer support surface60sufficiently to accommodate the desired contact with an edge of a printing plate24. The repositioning of a registration member can include moving a surface of the registration member to a location suitable for contact with an edge of a printing plate24. For example, a registration member can includes a cam-like surface wherein a portion of the surface is positioned for contact with an edge of a printing plate24when the registration member is rotated about an axis.

In this example embodiment, third registration member50C is positioned to locate printing plate24C such that substantially similar points on registration edge52are contacted by respective registration members during each of the imaging and punching operations thereby ensuring a substantially precise geometric relationship between the punched registration features and the image formed on printing plate24A. In this example embodiment, third registration member50C is positioned to move printing plate24A to a desired location after printing plate24A has been moved towards first and second registration members50A and50B. In this example embodiment, the position of third registration member50C at the time of punching is determined by controller20. In this example embodiment, when contact is established between registration edge52and each of first and second registration members50A and50B and between lateral edge25A and third registration member50C, printing plate24A is said to be in registration and can be punched by punches73.

In many cases, registration of a printing plate24is not achieved when the desired contact between the printing plate and an associated set of registration members is not established. For exampleFIGS. 6A,6B, and6C show different misregistrations caused by an absence of contact between printing plate24A and various ones of first, second and third registration members50A,50B and50C. In particular,FIG. 6Ashows a skewed misregistration caused by an absence of contact between registration edge52and first registration member50A.FIG. 6Bshows a skewed misregistration caused an absence of contact between registration edge52and second registration member50B.FIG. 6Cshows an offset or lateral misregistration cause by an absence of contact between lateral edge25A and third registration member50C.

Referring back toFIG. 5, elements of apparatus10employed for detecting a misregistration between a printing plate (i.e. printing plate24A in this embodiment) and a set of registration members50and correcting for the detected misregistration is schematically shown. In this example embodiment, signal generator72is adapted for providing an electrical signal65to first registration member50A. In this example embodiment, first registration member50A includes an electrically conductive portion55A adapted for contacting a first edge of printing plate24A. In this example embodiment, the first edge is registration edge52. Electrical signal65received by first registration member50A from signal generator72is in turn provided to the supported printing plate24A when contact is made between the first registration member50A and registration edge52. In this example embodiment, electrical signal65can be provided to printing plate24A when contact is established between electrically conductive portion55A and registration edge52. In this example embodiment, first registration member50A is referred to as the “signal emitter member”.

In this example embodiment, second registration member50B and third registration member50C are part of the registration members adapted to receive electrical signal65when electrical signal65is conveyed through the supported printing plate24A along a path away from first registration member50A. In this example embodiment, electrical signal65will be received by at least one of the second registration member50B and the third registration member50C when contact is established between the first registration member50A and the registration edge52and contact is established between each of the at least one of the second registration member50B and the third registration member50C and an edge of printing plate24A. In this example embodiment, second registration member50B will receive electrical signal65through printing plate24A when contact is established between registration edge52and an electrically conductive portion55B of the second registration member50B. In this example embodiment, third registration member50C will receive electrical signal65through printing plate24A when contact is established between an electrically conductive portion55C of the third registration member50C and a second edge of printing plate24A (i.e. lateral edge25A in this example embodiment). In this example embodiment, each of second registration member50B and third registration member50C is referred to as a “signal receiver member.” In this example embodiment, electrical signal65can travel through a portion of printing plate24A comprising an electrically conductive material. In this example embodiment, each of the first, second, and third registration members50A,50B, and50C are electrically isolated from each other. In this example embodiment, electrical signal65can only flow from the signal emitter member to a signal receiver member via a path through printing plate24A.

Apparatus10includes a set of two or more sensors including a first sensor80A corresponding to second registration member50B and a second sensor80B corresponding to third registration member50C. Each of the sensors is adapted for detecting a presence or absence of electrical signal65received by a respective one of second and third registration members50B and50C. In this example embodiment, a presence or absence of electrical signal65at either second registration member50B or third registration member50C is communicated to a respective one sensors via respective conductors66A and66B. In this example embodiment each of conductors66A and66B are respectively coupled to electrically conductive portions55B and55C. Various sensors known in the art can be employed in embodiments of the present invention. For example, various touch sensors can be employed. In some example embodiments, electrical continuity sensors have been employed by the present inventors. The selection of a particular sensor may be motivated by a particular characteristic of electrical signal65. Electrical signal65can include various types of signals including voltage signals and current signals.

Because even a small separation between printing plate24A and any of first, second, and third registration members50A,50B, and50C can, cause significant registration errors during a processing of printing plate24A, apparatus10is adapted to electronically determine when an absence of contact between printing plate24A and any one of the first, second and third registration members50A,50B, and50C occurs. Unlike other prior art printing plate registration detection systems, apparatus10is further adapted to identify the particular ones of the plurality of registration members which are not contacted by an edge of a printing plate24and initiate an automated response to reestablish contact between the printing plate24and the identified ones of the plurality of registration members. The accurate identification occurs regardless if the non-contacted registration member acts as a signal emitter member or acts as a signal receiver member.

In the illustrated embodiment of the present invention, when contact is established between various edges of print plate24A and each of the first, second and third registration members50A,50B, and50C, electrical signal65can be conveyed through printing plate24A from first registration member50A to each of second registration member50B and third registration member50C. A lack of contact between a printing plate edge and various ones of the first, second and third registration members50A,50B, and50C will have a bearing on whether or not electrical signal65is detected by a given one of first sensor80A and second sensor80B. In this example embodiment, a detection circuit95is employed to condition information provided by each first sensor80A and second sensor80B for use by controller20. In this example embodiment, each of first sensor80A and second sensor80B provides electrical continuity information to detector circuit95. In this example embodiment, detector circuit95provides this information to controller20in a suitable format for use in controller20. In this example embodiment, detector circuit95provides a first signal96corresponding to second registration member50B and a second signal98corresponding to third registration member50C. Each of the signals96and98comprises digital state information associated with a respective one of the second registration member508and the third registration member50C. In this example embodiment, an ON digital state corresponds to a condition corresponding to a presence of the electrical signal65at an associated one of the second and third registration members50B and50C. In this example embodiment, an OFF digital state corresponds to a condition corresponding to an absence of the electrical signal65at an associated one of the second and third registration members50B and50C.

In this example embodiment, a plate positioning system82is employed to position against printing plate24A in a desired orientation. Plate positioning system82includes a plurality of actuators including a first actuator85A and a second actuator85B. Actuators are employed to establish relative movement between printing plate24A and first and second registration members50A and50B so as to position printing plate24A such that registration edge52contacts each of these two registration members. In some example embodiments, each of the first and second actuators85A and85B are adapted to engage an edge which is opposite to registration edge52. In this example embodiment, first and second actuators85A and85B are coupled to an intermediate or gripping member86adapted to grip a surface of printing plate24A. In this example embodiment, gripping member86includes various gripping elements87(i.e. some shown in broken lines) adapted to grip printing plate24A. Suitable gripping elements87can include suction/vacuum cups or mechanical grippers or clamps by way of non-limiting example. In various example embodiments of the invention, each of the first and second actuators85A and85B is selectively operable for moving a portion of printing plate24A towards a registration member positioned to intercept registration edge52.

Actuators can include various suitable actuators to establish the required positioning. In this example embodiment, variable force actuators85are employed. Although positional actuators can be employed to position printing plate24A to various selected positions, additional sensing elements are required to avoid potential damage to printing plate during the positioning. Potential damage can include deformations in registration edge52created by excessive contact stresses that can be created between registration edge52and a registration member when a positional actuator is controlled to position registration edge52to a target location that does not accurately reflect the desired location of contact. Accordingly, when positional actuators are employed, additional sensing elements such as contact sensors or positional sensors are typically required.

In this example embodiment, each of first actuator85A and second actuator85B are variable force actuators. Each of the variable force actuators85is adapted to apply a selected force to a portion of printing plate24A to move that portion towards one of the first registration member50A and the second registration member50B. In this example embodiment, each of the variable force actuators includes a pneumatic double acting pneumatic cylinder88and variable pressure regulator89adapted for varying a fluid pressure applied to the pneumatic cylinder88. It is understood that other forms of variable force actuators can be employed in other example embodiments of the invention. In this example embodiment, the force applied by each of the actuators to a respective portion of printing plate24A is selected to be sufficient to overcome inertial and frictional forces associated with printing plate24A. In this example embodiment, the force applied by each of the actuators to a respective portion of printing plate24A is sufficient to overcome inertial and frictional forces associated with gripping member86. In this example embodiment, the force applied by each of the actuators to a respective portion of printing plate24A is selected to reduce occurrences of damage to printing plate24A created by excessive contact stresses generated between registration edge52and a registration member. Accordingly, the forces that are applied to printing plate24A are sufficient to move it towards first and second registration members50A and50B while being insufficient to impart contact stress deformations on registration edge52.

In this example embodiment, after first and second actuators85A and85B are operated to move printing plate24A towards first and second registration members50A and50B, drive70is operated to move registration member50C towards printing plate24A to establish contact between registration member50C and lateral edge25A. Once registration member50C is finally positioned, one may expect that contact between printing plate24A and each of first, second and third registration members50A,50B, and50C has been established and that an initial registration has been achieved. However, this is not always the case since misregistrations between a printing plate24and a set of registration members can occur for various reasons. For example, some misregistrations can occur as a printing plate24is moved onto a support surface associated with a subsequent processing step. Some misregistrations can occur when a printing plate24is secured to a support surface in preparation for a subsequent processing. Some misregistrations can occur when a printing plate24undergoes the process itself such as imaging or punching. In this case, even the act of moving third registration member50C to a final position can cause printing plate24A to pivot at a point in the vicinity of one of the first and second registration members50A and50B or at some other point and lead to a misregistration.

In this example embodiment, controller20is employed to determine if a lack of contact exists between printing plate24A and any of first, second and third registration members50A,50B, and50C. If a lack of contact with any of the first, second and third registration member50A,50B, and50C is determined, actions are then initiated to establish contact with the relevant registration member. In this example embodiment, controller20compares the digital state information provided by signals96and98to make this determination. In this regard, signal96will either include information comprising an ON state or an OFF state which reflects the presence or absence of electrical signal65at second registration member50B. In a similar manner, signal98will include information comprising and ON state or OFF state which reflects the presence or absence of the electrical signal65at the third registration member50C.

Controller20compares the digital information provided by each of signals96and98to determine if contact is established between printing plate24A and various ones of the first, second, and third registration members50A,50B, and50C. In this example embodiment, the following LOGIC TABLE I is employed to make the determination:

LOGIC TABLE ISignalSignal9698DeterminationOFFOFFAbsence of Printing Plate Contactwith First Registration Member 50AOFFONAbsence of Printing Plate Contactwith Second Registration Member 50BONOFFAbsence of Printing Plate Contactwith Third Registration Member 50CONONRegistration Achieved

According to LOGIC TABLE I, if each of signals96and98comprises OFF states, controller20determines that an absence of contact exists between printing plate24A and first registration member50A. In this regard, an absence of contact between printing plate24A and first registration member50A does not allow first registration member to act as a signal emitter member for electrical signal65, and thus electrical signal65would not be detected by either of second registration member50B and third registration member50C. It is to be noted that although this condition could also be interpreted as an absence of contact between printing plate24A and both of second registration member50B and third member50C, this condition is unlikely since a plurality of signal receiver members (i.e. second and third registration members50A and50B) are employed thereby reducing occurrences in which an absence of contact with all of the signal receiver members exists.

In the second case where first signal96comprises an OFF state and second signal98comprises and ON state, controller20determines that an absence of contact exists between printing plate24A and second registration member50B. This particular determination is made on the basis that second signal98indicates that electrical signal65was received by third registration member50C thereby indicating that contact between printing plate24A and the registration members50is such an electrical path exists only between first registration member50A and third registration member50C but not between first registration member50A and second registration member50B. Conversely, in the third case where first signal96comprises an ON state and second signal98comprises an OFF state, controller20determines that an absence of contact exists between printing plane24A and third registration member50C. This particular determination is made on the basis that first signal96indicates that electrical signal65was received by second registration member50B thereby indicating that contact between printing plate24A and the registration members50is such that an electrical path exists only between first registration member50A and second registration member50B but not between first registration member50A and third registration member50C.

In the fourth case, where each of the signals96and98comprise an ON state, controller20determines that contact exists between each of the first, second and third registration members50A,50B, and50C since the two ON states indicate that an electrical path exists between first registration member50A and second registration member50B and between first registration member50A and third registration member50C. In this regard, controller20determines that registration has been achieved.

In various example embodiments, controller20is employed to determine if printing plate24A is registered by a process that includes selecting one of the first, second and third registration members50A,50B, and50C and determining if contact exists between the selected registration member50and printing plate24A. This analysis is made for each of the first, second and third registration members50A,50B, and50C. In some example embodiments, a presence or absence of contact between printing plate24A and any selected one of the first, second and third registration members50A,50B, and50C is determined based at least on the detected presence or absence of electrical signal65at each of at least two of the registration members. In this example embodiment, a presence or absence of contact between printing plate24A and any selected one of the first, second and third registration members50A,50B, and50C is determined based at least on the detected presence or absence of the electrical signal65at each of the second registration member50B and the third registration member50C. In some example embodiments, a presence or absence of contact between printing plate24A and a selected one of the first, second and third registration members50A,50B, and50C is determined based at least on the detected presence or absence of the electrical signal65at another of the registration members.

In this example embodiment, when the first registration member50A is selected, a presence or absence of contact between the printing plate24A and the first registration member50A is determined based at least on the detected presence or absence of the electrical signal65at each of two of the registration members, each of the two registration members being other than the first registration member50A. In this particular embodiment, the two registration members include the second registration member50B and the third registration member50C. In this example embodiment, when one of the second registration member50B and the third registration member50C is selected, a presence or absence of contact between the selected registration member is determined based at least on the detected presence or absence of the electrical signal65at the selected one of the second and third registration members50B and50C as well as the detected presence or absence of the electrical signal65at the other of the second and third registration members50B and50C that has not been selected.

In various example embodiments of the invention, controller20is configured for selecting and operating at least one of first actuator85A and second actuator85B to move a portion of printing plate24A towards a selected registration member in the event that an absence of the electrical signal65is detected by at least one sensor in the set of sensors. In various example embodiments, one of the actuators is selectively operated to move a portion of printing plate24A towards a selected registration member in the event that an absence of the electrical signal65is detected at each of a plurality of registration members other than the selected registration member. For example, when first registration member50A is selected, controller20is configured to cause first actuator85A to reduce a spacing between printing plate24A and first registration member50A in the event that an absence of electrical signal65is detected at each of the second and third registration members50B and50C. In some example embodiments, one of the actuators is selectively operated to move a portion of the printing plate24A towards a selected registration member in the event that an absence of the electrical signal65is detected at one of a set of two or more of the registration members and a presence of the electrical signal65is detected at another registration member of the set of two or more registration members50. For example, when the second registration member50B is selected, controller20is configured to cause second actuator85B to reduce a spacing between printing plate24A and second registration member50B in the event that an absence of electrical signal65is detected at the selected second registration50B and a presence of the electrical signal65is detected at the third registration member50C. In this example embodiment, when the third registration member50C is selected, controller20is configured to cause drive70to create relative movement between the between printing plate24A and third registration member50C to reduce a spacing between the two in the event that an absence of electrical signal65is detected at the selected third registration50C and a presence of electrical signal is detected at second registration member50B. In some example embodiments, relative movement between printing plate24A and the third registration member50C can include cycling the registration member50C so that it moves both away and towards lateral edge25A.

In various example embodiments, selective ones of first actuator85A, second actuator85B and drive70are operated to correct for a determined absence of contact between printing plate24A and a particular one of the registration members. The particular one of the registration members can be identified based on the detected presence of the electrical signal65at another of the registration members. In this manner, various example embodiments of the invention can include automated systems for identifying a particular misregistration of printing plate24A as well as automated systems for correcting the identified misregistration. In some example embodiments, once actions to correct an absence of contact between a printing plate24and a particular one of registration members has been initiated, additional steps can be undertaken to determine if the presence of contact subsequently exists at the particular registration member and/or whether a presence of contact between the printing plate24and another of the registration members exists, or has been maintained.

In this example embodiment, when an absence of contact is detected between printing plate24A and one of the first registration member50A and the second registration member50B, the actuator in the closest proximity to the non-contacted registration member is controlled to establish the required contact. Since each of the actuators are variable force actuators in this example embodiment, controller20controls the relevant actuator to increase its output force to move printing plate24A into contact with the non-contacted registration member. In some example embodiments, controller20can cause the relevant actuator force to increase by 10% or less of the nominal force used to initially position printing plate24A. In other example embodiments, controller20can cause the relevant actuator force to increase by 5% or less of the nominal force used to initially position printing plate24A. In yet other example embodiments, controller20can cause the relevant actuator force to increase by 2% or less of the nominal force used to initially position printing plate24A. The amount of increase in the actuator force employed may be motivated by various factors including the ability of printing plate24A to withstand potential damage as it makes contact with a registration member. In some example embodiments, after the relevant actuator has been operated to establish contact with a non-contacted registration member, the presence of contact with this registration member is re-checked. If an absence of contact is still present, the relevant actuator can be again operated to increase the force by a predetermined amount. In some embodiments, the predetermined amount of force increase is the same as that employed in a previous operation of the relevant actuator while in other embodiments, it is different. In some example embodiments this process is repeated a number of times until contact is established or until a predetermined number of cycles has been reached.

It is to be notated that the nominal force employed by each of the actuators85during an initial attempt to position the printing plate24A against various one registration members can vary among the actuators. For example, this force can vary in accordance with a positioning of each actuator relative to an associated one of the registration members. In this manner, reaction forces associated with any moments arising from the application of the actuator forces can be compensated for. In this example embodiment, the force provided by each of first actuator85A and second actuator85B is altered by an associated pressure regulator89under the influence of controller20.

Once a presence of contact between printing plate24A and each of the first, second and third registration members50A,50B, and50C has been determined to exist, printing plate24A is deemed to be registered and a subsequent processing of the printing plate24A can be undertaken. In this example embodiment, controller20operates punch system19to perforate printing plate24A. In other example embodiments, controller20can be operated to form one or more images on a surface of printing plate24A once it has been registered. It is understood that other forms of processing can be undertaken in other example embodiments of the invention.

Various example embodiments of the invention have been described in terms of registering a printing plate24on a punching support surface (i.e. transfer support surface60). It is to be noted however, that any suitable support surface adapted to receive and support a printing plate24can be employed by the present invention. One such example of a suitable support surface is imaging support surface28.

In the described example embodiments, image recording system14and punch system19were part of a common apparatus10. In other example embodiments, different apparatus may be employed.

In the described example embodiments, a combination of three registration members has been described. However, consistent with the principles of the present invention, additional registration members can be incorporated in other embodiments. It will be appreciated that a printing plate24may have other edge features that can require different arrangements of registration members.