Abstract:
An apparatus for slitting a running paperboard web includes a thin high speed rotary slitting blade that is plunged through the moving web and into a slot between a pair of anvil surfaces supporting the web on the opposite side. Because the slitting blade and the anvil surfaces are vertically separated and pre-positioned before order change, an adjustment apparatus is provided to spread the anvil surfaces apart to provide an open gap with a large target for blade edge when it is plunged through the web and into the slot. The anvil surfaces are then closed to bring the edges of the surfaces against the opposite faces of the blade for running operation. Preferably, the anvil surfaces are mounted on brackets hinged together below the surfaces to move the edges of the surfaces defining the slot between the opened and closed positions in the manner of a clam shell. The anvil surface support assembly is also adjustable in the machine direction to compensate for reduction in rotary slitting blade diameter with blade wear.

Description:
This application is a continuation-in-part of application Ser. No. 10/152,501, entitled “Plunge Slitter with Clam Style Anvil Rollers” and filed on May 21, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for slitting a moving web of corrugated paperboard or the like and, more particularly, to a slotted anvil assembly for supporting the running web below and in cooperation with an upper rotary slitting blade. 
     Apparatus for longitudinally slitting a continuous running web of corrugated paperboard is well known in the art. Such apparatus typically also includes a related mechanism for simultaneously providing longitudinal score lines in the advancing web, which score lines facilitate subsequent folding in the construction of paperboard boxes. Thus, a combined slitter-scorer utilizes pairs of rotatable cutting tools and scoring tools disposed in the path of the running web with one tool of each pair disposed on each side of the web. Typically, multiple slitting tools are mounted coaxially and spaced laterally across the width of the web and, likewise, multiple scoring tools are also coaxially mounted and spaced laterally across the width of the web. 
     In accordance with the teaching of prior art U.S. Pat. No. 5,090,281, the moving web is directed through a thin circular blade rotating at high speed with the board supported below the blade by a roller assembly in contact with the underside of the web. Each such roller assembly includes a pair of rollers which are rotatably mounted to provide tangent contact with the underside of the web and to define therebetween a slot which is positioned to receive the lower edge of the high speed rotary cutting blade positioned over the web. These supporting rollers are also sometimes referred to as anvil rollers since they support the paperboard web against the cutting force of the thin, high speed slitting blade. 
     Prior art U.S. Pat. No. 5,197,366 discloses a roller assembly in which the rollers of each pair are mounted on separate rotational axes displaced from one another by a small angle to define a blade-receiving slot which is downwardly divergent. The rollers of each pair are also biased toward one another to cause the axially adjacent radial edge portions of the rollers at the point of supporting web contact to bear against the faces of the blade received in the slot. Contact between the anvil rollers and opposite blade faces also produces a sharp, high quality cut edge in the paperboard web. The angled anvil roller assembly also minimizes the build up of paperboard adhesive on the rollers. It also minimizes the entry of adhesive, board dust and board scraps into the blade-receiving slot between the rollers. Foreign material that enters the slot is also more readily discharged with roller rotation. 
     However, the foregoing anvil roller assembly is intended for use primarily in a corrugator in which an order change is facilitated by creating a machine direction gap in the web, thereby permitting repositioning of the slitting tools (and scoring tools) without disengaging or moving the tools from their operative cutting orientation. The split anvil roller assembly with the slitting blade positioned in the slot between the rollers permits the latter to be repositioned by driving the slitting blade tool head and carrying the anvil roller assembly therewith. Because the anvil rollers are always engaged with the rotary cutting blade, proper alignment between the blade and rollers is always maintained, even as their cross machine direction position is changed (as during presence of the gap in the web). 
     In another type of corrugator, order change is effected by moving the cutting tools out of operative slitting position, repositioning the tools in the cross machine direction to the new order position, and then plunging the tools back into the running web. Preferably, the slitter-scorer will have two separate slitting stations (and two separate scoring stations) whereby the inactive slitting station may be set for the new order such that, when the running order slitting tools are moved out of operative slitting engagement at order change, the already positioned slitting tools on the other axis may be simultaneously plunged into slitting contact with the web. A complicating factor in a no gap order change is that the slitting blade and the anvil roller assembly must be repositioned in the cross machine direction independently of one another, and the slitting blade must re-engage the gap in the anvil rollers as it is plunged back into slitting engagement. Because of this independent repositioning, there may be slight position errors between the slitting blade and the anvil roller slot which could interfere with proper re-engagement. 
     The present invention is directed to a method and apparatus for opening the slot or gap between the anvil rollers to accept the plunging slitting blade, closing the anvil rollers on the blade with an appropriate force, and permitting the anvil rollers to float in the cross machine direction to self-align with the blade. 
     In an alternate embodiment, the anvil rollers are replaced by a pair of anvil plates that are mounted to define the slot between adjacent plate edges. Opening and closing the slot is effected in the same manner as in the preferred anvil roller embodiment. 
     SUMMARY OF THE INVENTION 
     Each anvil roller assembly is supported on linear ways extending in the cross machine direction. Each anvil assembly carries a drive motor to move the roller assembly to a commanded position, dictated by the order to be run, and then locked in place. Alternate means for positioning the anvil roller assembly and the cooperating tool head for the slitting blade, such as robotic placement, could also be used. The anvil roller assembly is also supported on a short linear bearing extending in the machine direction that allows adjustment of the position of the anvil rollers to compensate for blade wear. Directly supporting the anvil roller pair is a pivot mechanism having a horizontal pivot axis extending in the machine direction and positioned on the roller assembly center line. This pivot mechanism supports both halves of the roller assembly in a sort of clam shell manner. The two halves of the roller assembly are independently pivotable on the pivot axis and a separate air cylinder joins the two halves to draw them together on cylinder retraction, thereby closing the gap and bringing the upper edges of rollers into contact with the opposite faces of the slitting blade. As the cylinder is retracted and the rollers pinch on the blade, they automatically align themselves with the blade. The clamping air cylinder imposes equal forces on both sides of the blade, as determined by air pressure and the positioning of the cylinder. 
     When the anvil roller assembly is repositioned in the cross machine direction and in preparation to receive a slitting blade plunged through the running web and into the slot between the rollers, the air cylinder extends to separate the rollers at the blade entry slot. Adjustable stops on the supporting structure limit the gap between the rollers and precisely center the gap to provide an optimum target for the thin rotary cutting blade as it is plunged into the slot. 
     In accordance with the alternate embodiment, the anvil rollers are replaced by a pair of anvil plates which together define a web supporting surface and have adjacent edges that define the blade receiving slot. Preferably, the anvil plates and the mounting brackets comprise a pair of channel sections each having a lower flange and an upper flange connected by an intermediate web. The pivot joint connects adjacent edges of the lower flanges, and the upper flanges form the anvil plates. The first actuator is mounted to interconnect the webs of the channel sections. The entire lower support arrangement is carried on a base plate to which it is connected by the pivot joint. A stop is provided that extends between each mounting bracket and the base plate to limit movement of the first actuator to open the slot. The stops are preferably adjustable. The base plate is also preferably mounted for movement along a linear track that extends parallel to the direction of web travel. An adjustable lock is provided for selectively adjusting the position of the lower support arrangement along the track and for locking the support arrangement in a selected position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an upper tool head carrying a rotary slitting blade and a lower tool head carrying an anvil roller assembly with the upper slitting blade raised and withdrawn from operative slitting engagement. 
     FIG. 2 is a front view of the assembly shown in FIG.  1 . 
     FIG. 3 is a side view of the assembly shown in FIG.  1 . 
     FIG. 4 is an isometric view similar to FIG. 1, but showing the upper rotary slitting tool lowered and plunged into the slot in the lower anvil roll assembly. 
     FIG. 5 is a front view of the assembly shown in FIG. 4 with the slot in the anvil roll pair opened for receipt of the slitting blade. 
     FIG. 6 is a front view similar to FIG. 5, but showing the anvil roll pair closed against the opposite faces of the slitting blade. 
     FIG. 7 is a side elevation view of FIGS. 4-6. 
     FIG. 8 is an enlarged isometric view of the anvil roller assembly. 
     FIG. 9 is an isometric view similar to FIG. 8 showing an alternate embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIGS. 1-3, a web slitting apparatus  10 , particularly suited for slitting a moving corrugated paperboard web  11 , includes an upper tool head  12  carrying a rotary slitting blade  13  and a lower counterhead  14  carrying an anvil roll assembly  15 . The upper tool head  12  is supported for lateral movement in the cross machine direction on a pair of linear bearing ways  17  attached to the underside of an upper box beam  16 . Similarly, the lower counterhead  14  is supported for lateral movement in the cross machine direction on a single lower linear way  20  mounted on the upper face of a lower box beam  21 . 
     The upper tool head  12  is moved along the upper linear ways  17  to position the slitting blade  13  by an upper servomotor  22  driving a pinion  23  that engages a linear rack  24  attached to the upper box beam  16  and extending parallel to the linear ways  17 . In a similar manner, lateral positioning of the anvil roll assembly  15  on the lower counterhead  14  utilizes a lower servomotor  25  driving a pinion  26  that engages a lower linear rack  27  attached to the lower box beam  21  and extending parallel to the lower linear way  20 . In a typical slitter-scorer, multiple pairs of an upper tool head  12  and lower counterhead  14  are positioned along their respective box beams  16  and  21  and, utilizing appropriate microprocessor control, each pair of heads may be driven to a selected position for slitting. Furthermore, the system may include another axis of slitting tools and corresponding anvil roller assemblies spaced in the machine direction from the first axis such that, when the tools of one slitting station are in an inoperative position as shown in FIG. 1, the slitting tools and anvil roller assemblies of the other axis are in their operative slitting positions as shown in FIG.  4 . 
     Each of the upper tool heads  12  carries a rotatable drive sprocket assembly  28  that includes a center drive hub  30  having a hexagonal through bore that receives a hexagonal drive shaft  31  extending the full width of the machine. The drive shaft  31  is supported at one end in a suitable bearing assembly and at the other end in a drive (not shown) in a manner known in the prior art. Rotary slitting blade  13  includes a driven sprocket assembly  32  connected with a suitable drive belt (not shown) to the drive sprocket  28 . The hexagonal drive shaft  31  is thus operative to simultaneously drive all of the rotary slitting blades  13  mounted on the common axis. In a manner known in the prior art, the upper tool head  12  may also carry a blade sharpener  33  for on-the-fly sharpening, as well as a contact blade lubricator  34 . The entire rotary slitting blade and driven sprocket assembly  32  is carried on a rotatable collar  35  centered on and rotatable about the drive shaft  31 . Rotation of the collar  35  and thus the slitting blade  13  about the axis of the drive shaft  31  is provided by a plunge cylinder  36  secured by its cylinder end to the upper tool head  12  by a mounting clevis  37  and having its rod end attached to a collar clevis  38 . In FIG. 3, the plunge cylinder  36  is extended causing the collar  35  to rotate in a clockwise direction thereby carrying the slitting blade  13  upwardly away from the web  11 . When the plunge cylinder  36  is retracted, the collar  35  rotates about the drive shaft  31  in a counterclockwise direction, causing the rotary slitting blade  13  to plunge through the moving paperboard web  11  and to be received in a slot in the anvil roller assembly  15  (see FIG.  7 ), in a manner to be described in greater detail below. 
     Referring again to FIGS. 1-3, the anvil roller assembly  15  mounted on the lower counterhead  14  includes a pair of anvil rollers  40  each of which is rotatably mounted by its laterally outside face to a roller mounting bracket  41 . As best seen in FIGS. 1,  2  and  8 , each mounting bracket  41  is generally L-shaped and positioned such that lower horizontal legs of the brackets  41  are joined by a horizontal hinge-like pivot  42  carried on a horizontal base plate  43 . The anvil rollers  40  are spaced axially apart to define therebetween a blade entry slot  44 . The slot  44  is shown in its fully open position in FIG.  2 . The mounting brackets  41  are also interconnected near their upper edges by a small air cylinder  45  which is operative to cause the brackets and anvil rollers mounted thereon to rotate about the pivot  42  such that the upper portion of the slot  44  can be closed against the opposite faces of the slitting blade  13 , as shown in FIG.  6 . The benefits accruing from operating the anvil rollers  40  in slight contact with the faces of the slitting blade  13  are known from U.S. Pat. No. 5,197,366, identified above, and described in greater detail therein and the description of which is incorporated by reference herein. In that prior art patent, however, the anvil roller pair is maintained in continuous contact with the faces of the slitting blade and the blade is maintained in the slot such that, at order change, a gap must be created in the web to allow simultaneous repositioning of each slitting blade/anvil roller assembly. 
     In accordance with the present invention, the upper tool head  12  and the lower counterhead  14  are separately repositioned while the web  11  continues to run therebetween. Because the repositioning of each tool head is independent of the other, there may be slight position errors between the blade edge and the center of the pair of rollers  40 . In accordance with the present invention, therefore, the rollers  40  mounted on the roller brackets  41  are pivoted to open the slot  44  by pivoting about the hinge-like pivot  42  in a manner similar to opening a clam shell. The open slot provides a larger target such that when the plunge cylinder  36  is retracted, the rotary slitting blade  13  will rotate downwardly and readily enter the open slot  44  after plunging through the running web  11 , as best seen in FIG.  5 . When the small air cylinder  45  is retracted the upper edges of the mounting brackets  41  and anvil rollers  40  mounted thereon are drawn together to close on the opposite faces of the slitting blade  13 , as best seen in FIG.  6 . Because of the pivotal mounting of the brackets  41  on the pivot  42 , the anvil rollers  40  automatically align themselves with the blade and equal force is applied to both sides of the blade. The force is determined by the air pressure and the geometry of the system. 
     To limit the opening movement of the mounting brackets  41  and thus limit the gap created between the upper edges of the anvil rollers  40 , adjustable stops  46  are provided between each mounting bracket  41  and the base plate  43 . Each stop  46  includes a pin  47  threadably mounted in a nut  48  secured to the outside face of the mounting bracket  41 . The pin has a hardened lower end  50  that engages a hardened bearing pad  51  on the base plate  43 . In addition to limiting the amount of opening movement between the anvil rollers  40 , the adjustable stops also act the precisely center the gap to provide the best target for the slitting blade to enter. 
     As the rotary slitting blade  13  wears in use, the blade OD defining the cutting edge is gradually reduced. However, it is imperative that the blade edge be retained within the slot  44  between the anvil rollers  40  in order to maintain proper alignment and good slit quality. If adjustment is not made, reduction in the cutting blade edge diameter will result in the blade edge being slowly withdrawn from the slot. To compensate for blade wear and to maintain a consistent depth of penetration of the blade edge into the slot, the base plate  43  supporting the anvil roller assembly  15  is mounted on a short machine direction linear way  52  for slidable movement along the linear way such that, with blade edge wear, the vertical centerline of the anvil rollers  40  may be moved in the downstream direction to approach the vertical centerline of the rotary slitting blade  13 , thereby maintaining a consistent amount of blade penetration into the anvil slot  44 . Adjustment is accomplished easily by providing a spring steel tab  53  attached at one end to a stationary back plate  54  of the lower counterhead  14 . The spring tab  53  has a series of horizontally spaced holes that engage a fixed pin  55  extending from the base plate  43 . An offset end  56  on the opposite end of the spring tab  53  is engaged by the operator to bend the tab outwardly and disengage the spring tab from the fixed pin  55 . With the spring tab deflected, the base plate and attached anvil roller assembly  15  may be slid along the short linear way  52  to a position in which the desired amount of slitting blade edge within the slot is restored. The spring tab  53  is then released to allow the alignment pin  55  to enter the hole closest to the desired position. 
     Although the location of the horizontal pivot  42  for the roller mounting brackets  41  centered vertically below the anvil rollers  40  is preferred, the pivot point could be located elsewhere and at other than a horizontal orientation with appropriate adjustment in the construction of the mounting brackets  41 . The adjustable stops  46  are preferably set to provide a maximum gap in the blade entry slot  44  of about ¼ inch (about 6 mm). At this point, anvil rollers  40  are oriented with their rotational axes substantially horizontal and coaxial. When the air cylinder  45  is retracted to close the gap, the axes of the anvil rollers are each moved about 1° to 2° from the horizontal to close upon the opposite faces of the annular rotary slitting blade  13  which may have a thickness, for example, in the range of 0.035 to 0.045 inch (0.9 to 1.1 mm). 
     In FIG. 9, there is shown an alternate embodiment of the invention in which the anvil rollers  40  of the preferred embodiment have been replaced by stationary anvil plates  57 . The anvil plates  57  are formed as an integral part of modified mounting brackets  58 . Otherwise, the elements of the modified support assembly  59  of FIG. 9 are the same as those of the preferred embodiment and are numbered identically. 
     Each of the mounting brackets  58  is made from a channel section  60 , each of which sections includes a lower flange  61  and an upper flange  62  interconnected by an intermediate web  63 . Adjacent edges  64  of the lower flange  61  are interconnected by the pivot joint  42 . The adjacent edges  65  of the upper flange  62  define a blade receiving slot  66 . An air cylinder  45  of the type described with respect to the preferred embodiment interconnects the webs  63  of the mounting brackets  58 . In a manner the same as described with respect to the preferred embodiment, operation of the air cylinder  45  will cause the mounting brackets  58  and the integral anvil plates  57  to rotate about the lower pivot joint  42  to open the slot  66  for receipt of the slitting blade  13  and to close the slot after receipt of the slitting blade such that the anvil plate edges  65  are brought to bear against the opposite blade faces. 
     The upper surfaces of the anvil plates  57  provide support for the running paperboard web  11  or web of other material. Although it is preferable to support the web with moving rollers, as in the preferred embodiment, the anvil plates  57  provide adequate web support and, more importantly, by being able to close the plate edges  65  against the slitting blade, the quality of the slit paperboard edges is substantially improved.