Patent Publication Number: US-6698326-B2

Title: Lock-up system for cutting mat

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to a locking device for flexible, annular covers and in particular, to a lockup device for securing a cutting mat to a rotary anvil. 
     Rotary die cutting machines are used to cut a continuously moving workpiece by passing the workpiece through the nip of two generally cylindrical rotary components, a cutting roller and a rotary anvil. The cutting roller includes any combination of cutting blades or rules, and scoring elements projecting from the surface thereof. The rotary anvil provides a suitable surface to support the workpiece at the point where the work material is cut or scored by the cutting roller. Essentially, the rotary anvil serves as a backstop allowing the cutting blades to be urged against the work material to be cut or scored, without damaging the cutting blades themselves. Because of their speed of operation, rotary die cutting machines are used to perform cutting operations in numerous industries. For example, the corrugated industry utilizes such machines to cut and score corrugated paperboard materials for constructing packaging products such as boxes and shipping containers. 
     Typically, several cutting mats are axially aligned on a rotary anvil, such that a substantial portion of the rotary anvil is sleeved by the cutting mats. Each cutting mat is constructed of a deformable material such as a polymeric composition. The outer surface of the cutting mat is sufficiently rigid to give adequate support to the work material, yet soft enough so that the cutting blades will not wear or be damaged by impact with the rotary anvil. The rules or cutting blades on the cutting roller penetrate the cutting mats in operation. This leads to eventual fatigue and wear of the cutting mats, requiring periodic replacement. 
     At times, rotary die cutting machines are set up to feed a workpiece centrally, and as such, the full width of the rotary die cutting machine is not used. Under this circumstance, the cutting mats located generally in the central portion of the rotary anvil experience most of the wear. Likewise, the cutting mats located at the opposing end portions of the rotary anvil receive the least wear. To prolong the life of cutting mats, it is desirable to rotate the relative positions of the cutting mats on the rotary anvil, such that the cutting mats wear more evenly. Typically, a rotary anvil will hold between eight and fourteen cutting mats. Repositioning a number of cutting mats causes considerable downtime. The cutting mats wear continuously during cutting operations. As the cutting mats wear, the quality of the cutting operation deteriorates until the worn cutting mats are replaced. However, because of the considerable downtime in cutting mat rotation and changeover, the industry tendency is to prolong the time between cutting mat changeovers. This leads to a greater possibility of poor quality cuts. 
     Several techniques have been devised to secure the cutting mat to the rotary anvil. For example, several lockup devices comprise latching mechanisms built into flanged end portions of cutting mats. The flanged ends are interconnected and inserted into a channel of the rotary anvil itself, or in a slip bearing secured to the rotary anvil. In one device, a rotary anvil cover latching assembly includes a cutting mat having a female latch member, and an opposing flanged male latch member. The female latch member comprises a generally U-shaped metal frame having an upper segment, a side segment, and base segment. The rotary anvil includes a slip bearing having a channel extending longitudinally. A groove is provided along the intersection of each sidewall and the base of the channel, defining a pair of locking regions. The female latch member is inserted into the channel, such that the base segment rests on the base of the channel, and an angled end section of the base segment is received into one of the grooves. The mat is wrapped around the rotary anvil, and the flanged, male latch member is angled into the female latch member. However, cutting mats with this type of latch assembly have a tendency to pull away from the surface of the slip bearing and are difficult to mount because of the amount of compression required to force the male member into the final position within the female member. Difficulty in mounting such cutting mats leads to rotary die cutting machine downtime and infrequent cutting mat changeover. 
     Still other lockup devices comprise complimentary interlocking fingers cut into opposing ends of the cutting mat. Such devices attempt to eliminate the use of flanged end portions of a cutting mat and further eliminate the need for the channel in the rotary anvil. For example, one cutting mat construction comprises opposite ends having a plurality of complimentary fingers and receivers. The cutting mat is wrapped around the rotary anvil, and the ends are joined in puzzle like fashion. However, this construction may not provide suitable holding strength. Further, the ends of the cutting mat may pull away or slightly lift from engagement with each other causing one or more ridges or humps to be formed on the outer surface of the cutting mat. These ridges may interfere with the smooth operation of the rollers and as such, are detrimental to the rotary die cutting procedure. Cutting mats that incorporate interlocking fingers can also be difficult to install and mount leading to press downtime, and infrequent cutting mat changeover. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of previously known locking systems for cutting mats by providing a lockup device that allows for rapid cutting mat changeover, and installation. The lockup device comprises a base portion, one sidewall, and a wedge portion, and is inserted into a channel of a rotary anvil such that the sidewall of the lockup device is adjacent a wall of the channel. A cutting mat having opposing first and second flanged ends is wrapped around the rotary anvil. The first flange is compressed between the locking wedge and the sidewall of the lockup device. The second flange is compressed between the locking wedge and a channel wall. As such, the locking wedge and cutting mat are frictionally secured to the rotary anvil. Further, the cutting mat may be quickly repositioned by releasing the second flange from the channel. When the cutting mat is unwrapped from the rotary anvil, the lockup device remains secured to the first flange, allowing for quick repositioning. 
     In accordance with one embodiment of the present invention, a lockup device for securing a cutting mat to a rotary anvil is sized and dimensioned to fit within an axially extending channel along the surface of the rotary anvil. The lockup device comprises a base portion having first and second axially extending edges, and first and second transverse edges that correspond generally to the width of the axially extending channel. A sidewall projects from the first axial edge of the base. The height of the sidewall corresponds generally to the depth of the channel. The locking wedge further includes a locking wedge projecting from the base. The lockup device is insertable into the channel of the rotary anvil and is arranged to receive opposing first and second flanges of a cutting mat such that when the lockup device is inserted within the channel, and the opposing first and second flanges are received by the lockup device, the lockup device and the cutting mat are frictionally secured to the rotary anvil. 
     The locking wedge comprises a leg portion extending from the base. A pair of opposite, angularly outward extending locking surfaces project from the leg portion, and a pair of guide surfaces extend from their respective locking surfaces. The pair of guide surfaces are substantially inverted “V” shaped, each guide surface joining together at a common point. The locking surfaces frictionally hold the flanges of the cutting mat. As such, the locking surfaces may comprise any geometry that is disposed towards holding. For example, the locking surfaces may be arcuate, and comprise surface conditioning such as a knurled surface. 
     A first locking area is defined between the sidewall and the locking wedge, and a second locking area is defined between the locking wedge and the second axial edge of the base portion. When the lockup device is inserted within the channel, and a cutting mat is installed around the rotary anvil, the first flange of the cutting mat is frictionally held within the first locking area, and the second flange of the cutting mat is frictionally held within the second locking area. To improve the frictional fit of the first flange in the first locking area, the sidewall may comprise a non-uniform thickness, for example by tapering out as the sidewall extends out from the base portion. Further, the second flange is releasable from the second locking area such that when the cutting mat is unwrapped from the rotary anvil, the lockup device releases from the channel with the first flange remaining at least partially secured within the first locking area. This allows rapid replacement and moving of the cutting mats because only the second flange of the cutting mat need be released from the locking wedge in order to remove the cutting mat and the locking wedge from the channel. 
     The lockup device maintains the cutting mat securely fixed to the rotary anvil by frictional forces only. As such, there are no screws, bolts, or the like to slow down cutting mat changeover. The frictional forces are divided between the cutting mat and the lockup device so that relieving the frictional forces contributed by the cutting mat allows the lockup device to release easily from the channel. Specifically, when the lockup device is inserted within the channel, and the opposing first and second flange are received by the lockup device, the lockup device and the cutting mat are secured to the rotary anvil by frictional forces between the base portion and the channel floor, the side wall of the lockup device and the first channel wall, and the second flange and the second channel wall. By releasing the second flange from the second locking area, the friction retaining the cutting mat and the lockup device is partially relieved, allowing the lockup device to be easily removable from the channel. 
     In accordance with another embodiment of the present invention, a rotary anvil construction comprises a rotary anvil having a generally cylindrical surface and a channel axially disposed on the cylindrical surface, the channel comprising first and second channel walls projecting inward from the cylindrical surface. A lockup device is insertable into the channel and held therein by frictional forces only. The lockup device comprises a base portion having first and second axial edges, and first and second transverse edges. A sidewall projects from the first axial edge of the base, and a locking wedge projects from the base between the first and second axial edges. 
     The lockup device is insertable within the channel. A cutting mat has a first end terminating in a first flange, and a second end opposite the first end terminating in a second flange. The cutting mat is wrappable around the cylindrical surface of the rotary anvil such that the first flange is received in, and secured between, the locking wedge and the sidewall, and the second flange is received in, and secured between, the locking wedge and the second channel wall. As such, the lockup device and the cutting mat are frictionally secured to the rotary anvil. Further, upon removing the cutting mat from the rotary anvil by releasing the second flange from the channel and unwrapping the cutting mat, the lockup device releases from the channel, and the first flange remains at least partially secured between the locking wedge and the sidewall. 
     A plurality of lockup devices and corresponding cutting mats may be axially disposed within the channel, the plurality of lockup devices and cutting mats arranged such that any one of the cutting mats may be released from the rotary anvil without disturbing the remainder of the plurality of cutting mats. 
     According to yet another embodiment of the present invention, a lockup device for a rotary anvil comprises a base portion having first and second axial edges, and first and second transverse edges. A sidewall having non-uniform thickness projects from the first axial edge of the base, and a locking wedge projects from the base, and is positioned between the first and second axial edges, and spaced closer to the first axial edge than the second axial edge. A first locking area is defined between the sidewall and the locking wedge, and a second locking area is defined between the locking wedge and the second axial edge of the base. 
     The locking wedge has a cross section comprising a leg portion extending from the base, a pair of opposite, angularly outward extending arcuate, knurled locking surfaces projecting from the leg portion, and, a pair of guide surfaces substantially forming an inverted “V” shape, each guide surface extending from a respective one of the locking surfaces to join together at a common point. 
     The lockup device is arranged to fit into a channel of a rotary anvil. A first flange of a cutting mat is compressed into the first locking area, and a second flange of the cutting mat is compressed into the second locking area. As such, the lockup device secures the cutting mat to the rotary anvil by frictional forces only. 
     Accordingly, it is a feature of the present invention to provide a lockup device for securing a cutting mat to a rotary anvil, which is simple in construction and easy to use. 
     It is further a feature of the present invention to provide a lockup device that is insertable within a channel of a rotary anvil and that can secure a cutting mat to the cylinder portion of a rotary anvil using frictional forces only. 
     It is still another feature of the present invention to provide a lockup device that allows for quick cutting mat changeover and replacement without disturbing adjacent cutting mats. 
     Other feature of the present invention will be apparent in light of the description of the invention embodied herein. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The following detailed description of the preferred embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals, and in which: 
     FIG. 1 is a perspective view of a rotary anvil having a plurality of cutting mats wrapped around a cylindrical portion and locked into an axially extending channel; 
     FIG. 2 is a perspective view of the lockup device of FIG. 1; 
     FIG. 3 is an end view of the lockup device of FIG. 1, and opposite flanged ends of a cutting mat according to an embodiment of the present invention; 
     FIG. 4 is an enlarged fragmentary end view of the rotary anvil of FIG. 1 showing the lockup device of FIG. 2 and a cutting mat installed in the axially extending channel. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced. It will be appreciated that these are diagrammatic figures, and that the illustrated embodiments are not shown to scale. Further, like structure in the drawings is indicated with like reference numerals. 
     Reference is made to FIG. 1 of the drawings that illustrates an exemplary rotary anvil  100 . The rotary anvil  100  comprises a generally cylindrical anvil portion  102 . A shaft  104  extends from opposite end faces  106 ,  108  of the anvil portion  102 , and is particularly adapted to support the rotary anvil  100  for rotation on associated support bearings (not shown) as is known in the art. A channel  110  extends axially along the surface  112  of the anvil portion  102 . Any number of cutting mats  114  are wrapped around the surface  112  of the anvil portion  102  and secured thereto, by engaging opposing first and second flanges  116 ,  118  of the cutting mat  114  in a lockup device  120  located in the channel  110 . The cutting mat  114  comprises a compressible resilient elastomeric material such as a synthetic plastic material, and may include a backing material (not shown). Preferably, the cutting mat  114  comprises polyurethane. The backing material may be any suitable material employed in the art for this purpose such as a woven or non-woven fabric. Lockup device  120  frictionally secures the first and second flanges  116 ,  118  in the channel  110  thereby securing the cutting mat  114  to the rotary anvil  100  as more fully described herein. 
     As best illustrated in FIG. 2, the lockup device  120  comprises a base portion  122  having first and second axial edges  124 ,  126  and first and second transverse edges  128 ,  130 . A sidewall  132  projects from the base portion  122 , disposed along the first axial edge  124 . The thickness of the sidewall  132  is preferably non-uniform. As illustrated, the sidewall  132  has a sidewall thickness TI located proximate to the base portion  122 , and a second sidewall thickness T 2  distal to the base portion  122  such that the thickness T 2  is greater than the thickness T 1 . For example, the sidewall  132  comprises a first surface  132 A exterior to the lockup device  120 , and a second surface  132 B interior to the lockup device  120 . The first surface  132 A projects normal to the base portion  122 . The second surface  132 B projects from the base portion  122  at an acute angle A 1 . The angle A 1  is preferably in the range of 80-88 degrees, however, the angle may be adjusted to any angle required to suit the particular application. 
     A locking wedge  134  projects from the base portion  122 , extending axially and generally parallel to the sidewall  132 . The locking wedge  134  includes a leg portion  136  extending from the base portion  122  and substantially normal thereto. Opposite, angularly outwardly extending first and second locking surfaces  138 A,  138 B extend outwardly from opposite sides of the leg portion  136 . The first and second locking surfaces  138 A,  138 B provide additional holding strength and, while illustrated as being substantially planar, may incorporate any geometry conducive to such task. First and second guide surfaces  140 A,  140 B extend from their respective first and second locking surfaces  138 A,  138 B and join together defining a substantially inverted “V” shape, joining at a common point  142 . The lockup device  120  is preferably constructed from a metal such as aluminum; however other suitable materials may be used such as plastics or composite materials. 
     Referring to FIG. 3, as illustrated, the first and second locking surfaces  138 A,  138 B and first and second guide surfaces  140 A and  140 B appear generally symmetrical about axis  144 . However, it shall be appreciated by those skilled in the art, that such surfaces may each have unique geometries and need not be symmetrical. Further, as an alternative to substantially planar first and second locking surfaces  138 A,  138 B as illustrated in FIG. 2, the first and second locking surfaces  138 A,  138 B are arcuate in shape and may optionally include surface textures  139 , such as knurls or similar features for improved grip on first and second flanges  116 ,  118  of cutting mat  114 . 
     The locking wedge  134  projects from the base portion  122  off-center between the first and second axial edges  124 ,  126 . As illustrated, the locking wedge  134  is positioned a distance L 1  from the first axial edge  124  and a distance L 2  from the second axial edge. Preferably, the distance L 2  is greater than the distance L 1 . For example, the distance L 1  may be 60% of L 2 . The exact amount of the difference between L 1  and L 2  may vary depending upon the application, and may include ratios of L 1  to L 2  greater than or less than 60%. The area generally between the lockup device  120  and the sidewall  132  defines a first locking area  146 , and the area generally between the lockup device  120  and the second axial edge  126  of the base portion  122  defines a second locking area  148 . 
     The cutting mat  114  in FIG. 3 illustrates opposing first and second flanges  116 ,  118 . The entirety of the cutting mat  114  is not shown. The first flange  116  includes a first aligning surface  150 . The first aligning surface  150  is oriented such that when the first flange  116  is being snap fitted into the lockup device  120 , the first aligning surface  150  engages the first guide surface  140 A to direct and guide the first flange  116  into the first locking area  146 . As the first flange  116  recesses into the first locking area  146 , the first holding surface  152  engages the first locking surface  138 A of the lockup device  120 . Surface  154  is contoured to generally receive the first guiding surface  140 A of the lockup device  120  when the first flange  116  is seated in the first locking area  146 . A relief channel  156  is provided in the cutting mat  114  to aid in flexibility of the cutting mat  114  and first flange  116 . Further, the first flange  116  has a length L 3 , which is proportional to distance L 1  such that when the first flange  116  is compressed into the first locking area  146 , the first holding surface  152  engages the first locking surface  138 A, and the back surface  157  of the first flange  116  presses against the second surface  132 B of the sidewall  132 . As such, the first flange  116  is frictionally secured within the first locking area  142 . 
     Likewise, the second flange  118  includes a second aligning surface  158 . The second aligning surface  158  is oriented such that when the second flange  118  is being snap fitted into the lockup device  120 , the second aligning surface  158  engages the second guide surface  140 B to direct and guide the second flange  118  into the second locking area  148 . As the second flange  118  recesses into the second locking area  148 , the second holding surface  160  engages the second locking surface  138 B of the lockup device  120 . Surface  162  is contoured to generally receive the second guiding surface  140 B of the lockup device  120  when the second flange  118  is seated in the second locking area  148 . A relief channel  164  is provided in the cutting mat  114  to aid in flexibility of the cutting mat  114  and second flange  118 . Further, the second flange  118  has a length L 4  which is proportional to the distance L 2  such that when the lockup device  120  is inserted into the channel (not shown in FIG.  3 ), the second flange  118  is compressed into the second locking area  148 , the second holding surface  160  engages the second locking surface  138 B, and the back surface  165  of the second flange  118  presses against the channel wall (not shown in FIG.  3 ). 
     As shown in FIG. 4, the channel  110  of the rotary anvil  100  comprises first and second channel walls  166 ,  168  and a channel floor  170 . The lockup device  120  is compression fit into the channel  110  such that the base portion  122  of the lockup device  120  rests on the channel floor  170  and the sidewall  132  lies juxtaposed the first channel wall  166 . The lockup device  120  is releasably held in the channel  110  by frictional forces only. That is, there are no latching strips, no bolting or gluing. As such, a quick cutting mat changeover time is realized. 
     The first flange  116  is press fit or snapped into the first locking area  146  as described above, the cutting mat  114  is wrapped around the anvil portion  102  of the rotary anvil  100 , and the second flange  118  is press fit or snapped into the second locking area  148 . The cutting mat  114  and lockup device  120  are securely held to the rotary anvil  100  by the combination of frictional forces derived from compression fitting the lockup device  120  into the channel  110 , and from the frictional forces of the second flange  118  compression fit into the second locking area  148 , wherein the back surface  165  of the second flange  118  pushes against the second channel wall  168 . 
     During use, several cutting mats  114  may be axially aligned on the rotary anvil  100  as shown in FIG.  1 . Where excess wear is evidenced on one of several cutting mats  114 , there is now, no longer a need to grind down or rotate the whole set of cutting mats  114 . A user may simply release the worn cutting mat by grasping and pulling on the flanges to release the mat from the lockup device, rotate the mat end for end, and reposition it back in place without disturbing the remainder of the cutting mats. Referring to FIG. 4, a user may pull the second flange  118  from the second locking area  148  thereby partially relieving the frictional forces holding the cutting mat  114  and lockup device  120  in the channel  110 . When the second flange  118  is pulled from the second locking area  148 , the back surface  165  of the second flange  118  no longer exerts a force against the second channel wall  168 . The cutting mat  114  is unwrapped from the rotary anvil  100 . The lockup device  120  releases from the channel  110  with the first flange  116  of the cutting mat  114  at least partially held in the first locking area  146 . The cutting mat  114  is repositioned as desired, the locking wedge is compression fit back into the channel  110 , the cutting mat is wrapped once again around the anvil portion  102  and the second flange  118  is snapped back into the second locking area  148 . Alternatively, both the first and second flanges  116 ,  118  may be released from the lockup device  120 , leaving the lockup device  120  positioned within the channel  110 . 
     Referring back to FIG. 3, as can now be seen, the second flange  118  is typically the end of the cutting mat  114  snap fitted into the channel  110  after the first flange  116  has been fit into place. As such, the length L 4  of the second flange  118  preferably exceeds the length L 3  of the first flange  116 , to provide a large surface to snap into place while the cutting mat  114  is under pressure from being wrapped around the rotary anvil  100 . Further, there is no sidewall on the lockup device  120  extending from the second axial edge  126  of the base portion  122 . Referring again to FIG. 4, it should be appreciated that when the lockup device  120  is compression fit into the channel  110 , the second channel wall  168  serves as a holding surface. Further, when the second flange  118  is released from the channel  110 , and the cutting mat  114  is unwrapped, the sidewall  132  of the lockup device  120  and the first locking surface  138 A maintain a secure hold on the first flange  114 . This allows the lockup device  120  to release from the channel  110  while still attached to the cutting mat  114 . 
     Further, as described above, the second flange  118  provides additional compressive force securing the lockup device  120  and the cutting mat  114  to the rotary anvil  100 . When the second flange  118  is released from the channel  110 , the component of compressive force generated by the second flange  118  pressing against the second channel wall  168  is relieved. This allows the lockup device  120  itself to provide some amount of compressive force less than the total amount of compressive force required to secure both the lockup device  120  and the cutting mat  114  to the rotary anvil  100 . As a result, when the second flange  118  is released from the channel  110 , the lockup device  120  may release from the channel  110 , while still secured to the first flange more easily. 
     Frequent rotation of cutting mats is known to extend the life of the mat. This is now feasible in a production environment due to the quick and effortless changeover time. Further, because there are no bolts, glue or other fasteners holding the cutting mats  114  in place, it is possible to locate the cutting mats  114  to cover only the area being used for cutting. That is, any one cutting mat  114  is infinitely repositionable within the channel  110 . As such, there is no longer a need to cover the entire rotary cylinder  100 . Further, a single cutting mat  114  may now be easily removed without disturbing adjacent cutting mats  114 . 
     Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.