Abstract:
An image-carrying plate such as a printing plate, an embossing plate, a die-cutting plate or the like for reproducing the image on a suitable media is mounted on a rotatable cylinder or drum by attaching a removable clamp to each end of the plate and removably attaching the plate clamps respectively to clamp carriers which are circumferentially spaced from one another on the cylinder with the plate at least partially wrapped around the outer surface of the cylinder. At least one clamp carrier on the cylinder can be adjusted to move the associated plate clamp so that the plate is pulled taut against the outer surface of the cylinder.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is in the field of curved latches or holding devices in the form of a cylinder or drum in combination with an image-carrying plate removably mounted on the outer surface of the cylinder or drum for reproducing the image on a suitable media. More particularly, the invention is directed toward removably coupling the image-carrying plate to the cylinder by removably attaching clamps which are attached to each end of the image-carrying plate to clamp carriers which are circumferentially spaced from one another on the cylinder. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    U.S. Pat. No. 6,454,686 by McEachern describes a magnetic cylinder or drum which firmly holds in place a magnetically permeable image-carrying plate such as a printing plate, an embossing plate, a die-cutting plate or the like and the cylinder or drum is rotatably driven, usually at fairly high speeds, to reproduce or transfer the image on the image-carrying plate repeatedly to suitable image-receiving media. The magnetic holding field of the cylinder armatures with the magnetically permeable image-carrying plate to securely hold the plate in place as the cylinder is rotated and the plate repeatedly contacts the media to transfer the image. There are also machines used in the industry for printing, embossing or die-cutting or similar which do not use a magnetic cylinder and use mechanical clamps to secure the image-carrying plater onto the cylinder. It is not uncommon that in some applications it is necessary to repeatedly change the image-carrying plate especially when the system is being used to produce what is called short runs. Typically and conventionally it has been found that in those instances, instead of stopping the machine then removing the cylinder, then replacing the plate and then placing the same cylinder with the new plate back in the machine, it is more efficient to have a second cylinder on hand with the replacement plate mounted on the cylinder, then stopping the machine and removing the cylinder with its attached plate and replacing it with the second cylinder with its attached replacement plate. Some operators change plates by turning off the equipment and attaching the replacement plate onto the same cylinder without removing the cylinder. This can result in a significant amount of down time for the equipment. 
         [0003]    In any event, it appears that it is simpler to attach and/or replace a magnetically permeable plate on a magnetic cylinder and locate and align it in proper registration than it is to attach a plate to a nonmagnetic cylinder. In the case of the latter, the normal and past practice has been to attach the ends of the plate onto respective clamps which are integral parts of the cylinder and then adjust the plate while mounted on the cylinder and the cylinder itself to bring the image into register with the previously imprinted or transferred image from a previously used plate. Even when first mounting the plate on a nonmagnetic cylinder generally a significant amount of handling of the plate is necessary just to attach it and to adjust it so that it is properly located on the cylinder. This often has resulted in smudging or even damaging the image-carrying surface of the plate so that it has to be cleaned or replaced or repaired. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides for having a clamp at each end, sometimes hereinafter referred to as the leading or trailing edge, of an image-carrying plate. Correspondingly, a plate cylinder has a pair of respective clamp carriers which are spaced circumferentially on the cylinder to accommodate the length of the plate. Registration or indexing apertures or openings at the leading and trailing edges of the plate are provided to mate with corresponding registration or indexing pins in the respective clamps. To attach the plate to a cylinder the plate is indexed and clamped at each end and then the plate clamps are grasped and attached to the respective clamp carriers on the cylinder so that the plate is virtually untouched in the area of the image-carrying surface in the process. As with present day equipment, means are provided on the cylinder to adjust one or both ends of the mounted plate circumferentially to pull the plate taut so it rests firmly against the surface of the rotatable cylinder. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is an end perspective view of a cylinder illustrating an embodiment of the invention in use; 
           [0006]      FIG. 2A  is a top view of a jaw of a plate clamp as an element of an embodiment of the invention; 
           [0007]      FIG. 2B  is a top view of the other jaw of a plate clamp; 
           [0008]      FIG. 2C  is a side view of the plate clamp jaw illustrated in  FIG. 2B ; 
           [0009]      FIG. 2D  is an end view of  FIG. 2B ; 
           [0010]      FIG. 3A  is a top view of a clamp carrier utilized in an embodiment of the invention; 
           [0011]      FIG. 3B  is a front edge view of  FIG. 3A ; 
           [0012]      FIG. 3C  is an end view of  FIG. 3A ; 
           [0013]      FIG. 4A  is a plan view of a portion of an image-carrying plate; 
           [0014]      FIG. 4B  is a side edge view of  FIG. 4A ; and 
           [0015]      FIG. 5  is a blow-apart illustration of an embodiment of the invention as attached to a cylinder. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    As illustrated in  FIG. 1 , an image-carrying plate  10  is wrapped at least partly around the outer surface of a cylinder  11  and attached to cylinder  11  by plate clamps  12  which are attached to the ends of plate  10 . Clamps  12  are coupled to clamp carriers  13  which are located in grooves or recesses  32  ( FIG. 5 ) in the outer surface of cylinder  11 . Conventionally, cylinder  11  has a hollow core for mounting the cylinder onto a rotatably driven shaft, not shown. Conventionally the shaft is cantilevered and the cylinder is removed by sliding the cylinder off the end of the cantilevered shaft and then replaced with a substitute cylinder. Typically and conventionally the equipment has features, not shown, which allow for minor adjustment for registration of the cylinder with attached plate when the cylinder is placed on and attached to its shaft. The. cylinder is usually made of a metal and may be a magnetic or nonmagnetic cylinder. Usually if a magnetic cylinder is used then a magnetically permeable plate is used and held in place by the magnetic holding field of the cylinder armaturing with the magnetically peremeable plate without the need for clamps  12  or clamp carriers  13 . However, there are occasions when a user might want to attach a nonmagnetically permeable plate to a magnetic cylinder and, as mentioned earlier, many machines use a nonmagnetic plate with a nonmagnetic cylinder. The present invention serves either or both of the latter arrangements. Cylinder  11  has outer access openings  15  to permit adjustment of the clamp carriers  13  to pull the plate taut against the outer surface of cylinder  11 . U.S. Pat. No. 6,443,064 by McEachern illustrates and describes mechanisms and method for adjusting a cylinder mounted on a shaft for accurate registration. 
         [0017]    As illustrated more clearly in  FIG. 4 , typically an image-carrying plate  10  may be made out of a suitable material, such as aluminum for a non-magnetic plate or suitable metal for a magnetic plate, and thin enough so that it can be at least partially wrapped around the outside of the cylinder. The plate  10  has at least a pair of registration apertures or openings  16  at each end for engaging corresponding registration or indexing pins  17  ( FIG. 2C ) in plate clamps  12 . The underside of plate  10 , which rests against the cylinder surface, is usually smooth and unadorned and the upper or outer side carries an image  18  which is to be reproduced on or transferred to a suitable media, not shown. For illustration purposes only the image is shown as the letter “A” in block form. 
         [0018]    Plate clamp  12 , as illustrated in  FIG. 2 , comprises a pair of jaw members  12 A and  12 B. An end of plate  10  is clamped between the two jaw members with pins  17  engaging registration or indexing apertures  16 . Jaw member  12 A rests over jaw member  12 B with the plate clamped therebetween and openings  20  on upper jaw member  12 A are provided to accept threaded members  21 A ( FIG. 5 ) to engage threaded openings  21  on jaw member  12 B to removably bring the two jaw members together firmly with an end of plate member  10  grasped firmly therebetween. Cutouts  22  in jaw member  12 A are provided for access to threaded members  23  which extend through counter sunk openings  24  to engage threaded openings  25  for releasably attaching plate clamp  12  to clamp carrier  13 . The underside of jaw  12 B has a transverse recess or slot  27  for engaging a transverse raised section or rail  28  on clamp carrier  13 . Also, pins  17  extend through jaw member  12 B for engaging corresponding registration or indexing openings or recesses in clamp carrier  13 . 
         [0019]    As illustrated in  FIG. 5 , a pair of parallel T bars  30  are attached to cylinder  11  by threaded members  31  in the recess area generally designated by reference numeral  32 . T bars  30  are engaged with T slots  33  on the underside of clamp carrier  13  so that clamp carrier  13  is movably engaged with cylinder  11  to permit circumferential adjustment, if needed, of plate  10  when mounted on the cylinder to permit the plate to be pulled taut so that it rests firmly against the outer surface of cylinder  11 . As mentioned earlier and in conventional fashion, openings  15  are formed in cylinder  11  so that threaded adjustment members, not shown, can be inserted to engage threaded openings  35  located in the side of clamp carrier  13  and the adjustment members can be operated to move clamp carrier  13  circumferentially when plate clamps  12  with attached plate are coupled to clamp carrier  13  to ensure that plate  10  is pulled taut to rest firmly against the outside circumferential surface of cylinder  11 . 
         [0020]    In practice while one cylinder with attached image-carrying plate is in operation for transferring the image onto a media, another similar cylinder can be prepared to replace the cylinder in use with an image-carrying plate whose image likely must be registered with respect to the earlier transferred image. Each end of an image-carrying plate  10  is placed suitably between the clamping members or jaws  12 A and  12 B with the registration holes  16  engaged with the registration pins  17  and the clamp members secured together with threaded members  21 A engaged in threaded openings  21 . 
         [0021]    Clamp carriers  13  are mounted in their respective recesses  32  on cylinder  11  with T bars  30  attached to the cylinder by threaded members  31  engaged in the tracks  33  on the underside of the clamp carrier  13 . 
         [0022]    The plate clamps  12  with plate  10  attached are then each placed on a corresponding clamp carrier  13  with the slot  27  engaging rail  28  and the underside of pins  17  engaging openings  19  in clamp carrier  13 . Each plate clamp  12  is secured to its respective clamp carrier  13  with the respective threaded members  23  engaged in their respectively corresponding threaded openings  25 . Only the plate clamps need be handled when mounting the plate onto the cylinder. Once mounted, if necessary, threaded adjustment members in openings  15  are engaged with threaded openings  35  on clamp carriers  13  and adjusted as necessary to move clamp carrier  13  to the degree necessary to pull the plate taut against the outer surface of the cylinder. Pins  17  and corresponding mating openings and/or recesses are machined or formed to quite close tolerances so that indexing or registration is very accurate. 
         [0023]    The general practice is that when a plate is first mounted onto a cylinder as described hereinabove, the clamp carrier at one edge of the plate, usually the leading edge, locates that edge of the plate at an indexing location using conventional means and procedures, not shown or described. When the plate is replaced with another plate, as described hereinabove, the one clamp carrier locates that edge of the replacement plate at the indexing location and only the other clamp carrier is adjusted to pull the plate taut against the cylinder surface thereby insuring correct registration between the reproduced images of the respective plates. As mentioned earlier, generally the equipment is provided with features which allow for some minor adjustments if needed for more precise registration.