Abstract:
A nip mechanism for a substrate transfer system allows the nip mechanism to be actuated such as opened and/or closed by the drive motor for the nip mechanism. As a result, the need to operate the nip mechanism pneumatically, for example, can be avoided. Essentially, the drive motor now performs a dual role, i.e., both driving the nip rollers and also opening and closing the nip mechanism. The nip mechanism comprises a roller separation mechanism and a one-way clutch for engaging the roller separation mechanism when the drive motor is driven in the second direction. In the present implementation, this roller separation mechanism comprises a cam that pushes the first nip roller and the second nip roller away from each other. A cam limiter can be used to prevent over-rotation of this cam.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Nip mechanisms typically, minimally comprise upper and lower nip rollers. These nip rollers extend parallel to each other and directly oppose each other. They are used to move substrates. In one typical mode of operation, the nip rollers are initially separated from each other, i.e., open, and a substrate is inserted between the nip rollers. The nip rollers are then brought together, i.e., closed, to engage the substrate between the two nip rollers. One or both of the nip rollers are then driven to transfer the substrate.  
           [0002]    One application for nip mechanisms is in platesetters. In this example, the substrates that the nip mechanisms manipulate are termed plates. Plates are typically large sheets that have been coated with photosensitive or thermally-sensitive material layers. The plates are usually used in commercial printing operations. For large run applications, the substrates are fabricated from aluminum, although organic substrates, such as polyester or paper, are also available for smaller runs. Computer-to-plate printing systems are used to render digitally stored print content onto these printing plates. Typically, a plate management system supplies individual plates to the platesetter. A computer system is used to drive an imaging engine of the platesetter. The engine selectively exposes the surfaces of these plates. After exposure, the plates are supplied to post exposure processing equipment.  
           [0003]    The nip mechanisms are used in the transfer systems that move the plate substrates between the management system and the platesetter. After exposure in the platesetter, another transfer system is used to move the substrate to the post processing equipment.  
           [0004]    Typically, the nip mechanisms are driven by electric motors. The motors can include encoders to monitor how far the substrates have been transferred. Further, especially in platesetter systems, the nip mechanisms are usually opened and closed using pneumatic cylinders that are operated by solenoids.  
         SUMMARY OF THE INVENTION  
         [0005]    Pneumatic operation in these platesetter systems is very common. Typically, there are many tubes for the routing of the pressurized air throughout the system in order to provide necessary actuation force to the various components of the machine.  
           [0006]    However, as these platesetter systems, for example, become more complex, offering higher levels of functionality, the routing of the pneumatic lines can become problematic. As a result, it is sometimes desirable to replace pneumatic with, for example, electrical or mechanical actuation, especially if such replacement will decrease the overall complexity of the system. Moreover, each pneumatically driven function requires a separate solenoid to control the airflow to an actuation mechanism, such as an air cylinder. These devices add incrementally to the overall cost of goods in the manufacture of these systems.  
           [0007]    The present invention is directed concerns a nip mechanism for a substrate transfer system. It allows the nip mechanism to be actuated, such as opened and/or closed, by a motor, such as the drive motor for the nip mechanism. As a result, when using the present invention, the need to operate the nip mechanism pneumatically can be avoided. Essentially, the drive motor now performs a dual role, i.e., both driving the nip rollers and also opening and closing the nip mechanism. Thus, for a slightly more complex mechanical system, a pneumatic operation can be avoided.  
           [0008]    In general, according to one aspect, the invention features a nip mechanism for a substrate transfer system. It comprises a first nip roller and a second nip roller. A drive motor is used to drive the first nip roller and a second nip roller to feed a substrate between the first nip roller and the second nip roller, when the drive motor is driven in a first direction. According to the present invention, the drive motor actuates, such as opens, the nip mechanism by separating the first nip roller from the second nip roller when the drive motor is driven in a second direction.  
           [0009]    According to the present embodiment, the inventive nip mechanism comprises a roller separation mechanism and a one-way clutch for engaging the roller separation mechanism when the drive motor is driven in the second direction. In the present implementation, this roller separation mechanism comprises a cam that pushes the first nip roller and the second nip roller away from each other. A cam limiter can be used to prevent over-rotation of this cam.  
           [0010]    According to the preferred embodiment, a floating bearing block is used on either side of the second nip roller. This allows the second nip roller to be urged out of engagement from the first nip roller. In the preferred embodiment, the second nip roller is an upper nip roller and the first nip roller is a lower nip roller. As a result, the second nip roller is biased toward the first nip roller by gravity.  
           [0011]    A downstream drive roller is preferably used for conveying the substrate downstream of the first nip roller and the second nip roller.  
           [0012]    In general, according to another aspect, the invention also features a method for operating a nip mechanism of a substrate transfer system. This method comprises opening the nip mechanism by translating a first nip roller and a second nip roller away from each by driving a drive motor for the nip mechanism in one direction. A substrate can then be received between the first nip roller and the second nip roller. Then, nip mechanism is closed to bring the first nip roller and the second nip roller together to engage the substrate. The substrate is then advanced by driving the drive motor in the other direction.  
           [0013]    The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings:  
         [0015]    [0015]FIG. 1 is a block diagram illustrating the components of a platesetter system to which the present invention is applicable in one example;  
         [0016]    [0016]FIG. 2 is a perspective view of a substrate transfer system according to the present invention;  
         [0017]    [0017]FIG. 3 is a reverse angle perspective view of the inventive substrate transfer system;  
         [0018]    [0018]FIG. 4 is a close-up view showing the linkage between the drive motor and the first nip roller in the preferred embodiment of the present invention;  
         [0019]    [0019]FIG. 5 is a close-up perspective view showing the linkage between the first nip roller and the drive roller according to the preferred embodiment of the present invention;  
         [0020]    [0020]FIG. 6 is a close-up view showing the roller separation mechanism according to the present invention when the nip mechanism is closed; and  
         [0021]    [0021]FIG. 7 is a close-up perspective view of the roller separation mechanism when the nip mechanism is in an open position according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 illustrates the overall components of a typical substrate processing system, such as a platesetter system, to which the present invention is applicable.  
         [0023]    Specifically, substrates or plates are stored in plate storage  10 . In the example of a platesetter, this storage can be a plate management system. A transfer system  12  is used to transfer individual substrates to an imaging system  14 . In the example of a platesetter system, this imaging system can be an external drum platesetter. After the substrates have been exposed, another transfer system  12 , or the previous transfer system in some configurations, moves the individual substrates to post processing systems  16  for development, for example, in the example of a platesetter system.  
         [0024]    [0024]FIG. 2 shows a transfer system  12 , which has been constructed according to the principles of the present invention. Specifically, substrate  5 , such as a plate, is fed in the direction of arrow  6  to a nip mechanism  100 . The nip mechanism  100  generally comprises a first, or lower, nip roller  110 , and a second, or upper, nip roller  112 .  
         [0025]    Each nip roller  110 ,  112  has a series of friction drive wheels  130  distributed along their lengths. These drive wheels  130  are typically made of rubber or another high friction, yet soft material. As a result, the drive rollers  130  allow the nip rollers  110  and  112  to feed the substrate  5  in the direction of arrow  6 , while not damaging that substrate, so that the substrate is advanced to position  5 ′.  
         [0026]    The substrate  5 ′ is supported and transferred on an array of travel rollers  132  that allow the substrate to be further moved to the next sub-system in the platesetter system, for example.  
         [0027]    Structurally, the transfer system  12  comprises a transfer frame  50 . The frame  50  comprises a right frame member  52  and a left frame member  54 . A cross frame member  56  is bolted to the right frame member  52  and the left frame member  54  to extend between the right and left frame members to improve the overall rigidity to the frame  50 .  
         [0028]    The transfer system  12  is powered or actuated by a drive motor  114 . It is bolted to the inside face of the right frame member  52  in the illustrated implementation. Its spindle extends through the right frame member  52 . A drive motor pulley  134  is press-fit onto the motor&#39;s spindle and is located adjacent to the outer side of the right frame member  52 . A drive motor belt  136  extends over the motor pulley  134  and a right roller pulley  138 , which is press-fit onto the axle of the first nip roller  110 . As a result, this motor belt  134  allows the drive motor  114  to rotate and thereby drive the first nip roller  110 .  
         [0029]    [0029]FIG. 3 shows the other end of the axle of the first nip roller  110 . This axle extends through the left frame member  54  and terminates in a left roller pulley  140 . A drive roller belt  142  extends over the left roller pulley  140  and a drive roller pulley  144 . The drive roller pulley  144  is fit on the axle  146  of a drive roller  116 .  
         [0030]    With reference back to FIG. 2, the rotation of the drive roller  116  is used to operate or drive the travel rollers  132 . Specifically, a transfer roller belt  148  wraps in a serpentine fashion over a series of tension pulleys  150  and the intervening travel rollers  132 . In this way, the progress of the transfer roller belt  148 , as driven by the drive roller  116 , in turn drives all of the travel rollers  132  in tandem. A terminal tension pulley  152  returns the transfer roller belt  148  to form a complete circuit. Each one of the tension pulleys  150  is bolted and journaled to the inner wall to the left frame member  54 . Each of the transfer rollers  132  is journaled to both the right and left frame members  52 ,  54 .  
         [0031]    [0031]FIG. 4 shows the connection of the second nip roller  112  to the right frame member  52 .  
         [0032]    Specifically, a bearing block  154 -R is bolted to a top surface  156  of the right frame member  52 . The right bearing block  154 -R has an inner bore  156 -R. An axle  158  of the second nip roller  112  extends into this bore  156 -R. A bearing cartridge  160 -R is housed within this inner bore  156 -R. This allows the second nip roller  112  to freely rotate relative to the bearing block  154 -R, yet translate up and down along the direction of arrow  162 .  
         [0033]    [0033]FIG. 5 shows a similar arrangement relative to the second nip roller  112  on its left end. Specifically, a left bearing block  154 -L is bolted to the left frame member  54 . The left bearing block  154 -L has an inner bore  156 -L. A left bearing cartridge  160 -L of the second nip roller  112  extends into this inner bore  156 -L to allow the second nip roller  112  to rotate relative to the left bearing block  154 -L, yet move up and down in the direction of arrow  162 .  
         [0034]    [0034]FIG. 6 illustrates the roller separate mechanism  200  of the nip mechanism  100 . Specifically, the nip roller  110  is rotated in the direction of arrow ( 1 ), when the drive motor  114  is rotated in the direction (a), see FIG. 4. A substrate between the first nip roller  110  and the second nip roller  112  will be fed to the drive roller  116 . The first nip roller  110  is allowed to rotate in this direction by the slippage in a one-way roller clutch  210 . This one-way clutch  210  allows the first nip roller  110  to rotate freely in the direction of arrow ( 1 ). With reference to FIG. 4, this corresponds with rotation in the direction of arrow (a) of the drive motor  114 .  
         [0035]    [0035]FIG. 7 illustrates the opening of the nip mechanism  100  by the roller separation mechanism  200 . Specifically, when the first nip roller  110  is rotated in the direction of arrow ( 2 ) by the drive motor  114  rotating in the direction of arrow (b), the one-way roller clutch  210  converts to a locked state. As a result, the rotation of the nip roller  110  in the direction of arrow ( 2 ) causes a cam  212  to rotate with the first nip roller  110 . The outer cam surface  222  of the cam  212  comes into engagement with a nip wheel  224  that is rigidly secured to and co-axial with second nip roller  112 . As the cam  212  is fully rotated, it urges the second nip roller  112  upwards in the direction of arrow  226 , thereby opening a space S between the first nip roller  110  and the second nip roller  112  and specifically, the drive wheels  130  of each nip roller  110 ,  112 .  
         [0036]    According to the preferred embodiment, the motor  114  comprises an encoder  115  that allows for software control of the angular movement of the motor  114 . Specifically, during the opening of the nip mechanism  100 , the motor  114  is driven through the angular rotation required to rotate the cam  212  approximately 90 to 120 degrees to thereby open the nip mechanism  100 .  
         [0037]    The action of the cam  212  pushing on the nip wheel  224  to separate the first nip roller  110  from the second nip roller  112  has the result of the opening the nip mechanism  100  so that it can receive the substrate  5 .  
         [0038]    When the cam  212  has been sufficiently rotated, the drive motor  114  remains energized to hold its position. In a current implementation, if it were de-energized and the roller  110  allowed to freewheel, the force of gravity on the second nip roller  112  would cause the cam  212  to rotate back.  
         [0039]    In typical operation, the substrate  5  is inserted between the first nip roller  110  and the second nip roller  112 . Its position is detected by a detector system that detects the leading edge of the substrate after it has been fully inserted into the nip mechanism  100  between the first and the second nip rollers  110 ,  112 .  
         [0040]    The drive motor  114  is then reversed from rotating in the direction of arrow (b) to the direction of arrow (a) to thereby rotate the cam  212  in the direction of arrow ( 1 ), thereby rotating the cam  212  to allow the second nip roller  112  to close down onto the first nip roller  110 , and with further rotation, advance the substrate  5  to the drive roller  116  and the travel rollers  132 .  
         [0041]    According to the preferred embodiment, a cam limiter pin  214  is provided that projects from the left frame member  54  into an arcuate bore  230  formed in the cam  212 . This cam limiter pin  214  prevents over-rotation of the cam  212  when the first nip roller  110  is driven in the direction of ( 2 ) to open the nip mechanism  110  and also prevents over-rotation of the cam  212  when the first nip roller  110  is advanced in the direction of ( 1 ) to initially close the nip mechanism  100 , and then restricts the further progress of the cam  212 , so that the cam  212  is in a known angular position during a subsequent nip opening operation.  
         [0042]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. For example, a separate motor is used in some implementations to operate the cam. In this implementation, a motor system is provided that comprises a drive motor for driving the first nip roller and the second nip roller to feed the substrate and a separate roller separation motor for operating the roller separation mechanism.