Patent Publication Number: US-7900542-B2

Title: Knife assembly for rotary cutting system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application which claims priority of provisional application Ser. No. 60/513,083, filed Oct. 20, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates generally to rotary cutters for cutting web or sheet material, and more particularly to a knife holder apparatus which may be attached to a knife cylinder and employed with an associated anvil cylinder to transversely cut or score a moving web or sheet. 
     It is conventional practice to use a rotary cutter to transversely cut web material received from a printing press. In general, rotary cutters have an anvil cylinder and a knife cylinder which are rotatable in timed relation. One or more knife holders, which hold the cutting knives, are attached to the knife cylinder. The knife and anvil cylinders normally rotate at the same speed and the moving paper or web material is transversely cut or scored as the cutting knife moves into and out of engagement with the anvil surface. The cutting knives may be spaced apart to create the desired cut. 
     In the conventional rotary cutter, knife replacement is a time-consuming operation. Moreover, because of the increased use of recycled paper and its negative effect on the life of the cutting knife, reducing the time required for the knife replacement operation has become even more important. 
     To reduce down time due to blade replacement, unitary epoxy knife holder and blade assemblies have been employed. An example of a unitary epoxy knife holder and blade assembly  112  is shown in  FIG. 10 . Replacement of a worn cutting knife of this type, however, requires that the entire assembly be removed from the knife cylinder, which requires stripping away the cushioning and rubber material which is placed over the knife cylinder and portions of the holder. The installer must then realign and remount the replacement holder on the knife cylinder. 
     To avoid the above-mentioned problems associated with unitary knife holder and blade assemblies, the knife holder assembly as shown in  FIG. 11  has been developed. This knife holder assembly includes a metal holder  116  and a backing member  110 , which locks a cutting rule  114  to the holder  116  with holding screws  118 . Although this knife holder assembly does not require the complete removal of the holder  116  from the knife cylinder, it does require some of the cushioning material to be stripped back because the release screws  118  are located on the side of the holder. This requires the person changing the cutting rule  114  to loosen the holding screws  118  from the side of the holder, which is both awkward and time consuming. 
     U.S. Pat. No. 5,893,314 discloses an improved knife holder assembly that overcomes some of the problems associated with the knife holder assembly shown in  FIG. 11 . An example of this type of improved knife holder assembly is shown in  FIG. 12 . This knife holder assembly  200  includes a holder  202 , and an adjusting member  204  that allows the operator to replace the knife  206  by loosening the fasteners  208  from the top portion of the holder. This eliminates the need to pull back or remove the cushioning material to get at side mounted fasteners  212 . However, this apparatus requires a significant number of screws to adequately secure the multiple adjusting members. This apparatus is also expensive to manufacture. 
     It would be desirable to have an uncomplicated and inexpensive knife holder assembly that would allow the user to quickly and efficiently remove the worn cutting knife and replace it without removing the holder from the knife cylinder. 
     BRIEF SUMMARY 
     The invention provides a knife holder apparatus and method of operating the same. The knife holder apparatus includes a holder, a backing bar and an adjusting member. The holder includes a slot opening through its top portion and an opening through its side portion. The backing bar includes an opening through its side portion. The adjusting member includes a tapered side portion substantially parallel to the inner side portion of the holder, and a body portion which includes a top portion opening to allow a fastener to be inserted through the top portion thereby moving the adjusting member up and away from the outer side portion of the holder. The backing bar, connected to the adjusting member, is drawn toward the side portion of the holder to clamp an inserted knife between the backing portion and an outer side portion of the holder, and to allow a fastener to be retracted to allow the backing portion to be moved away from the outer side portion of the holder to release the knife. 
     This design allows the operator to replace the knife by simply loosening or removing the fastener or fasteners from the top portion of the holder. This eliminates the need to pull back or remove the cushioning material to get at side mounted fasteners or screws and thereby reduces downtime. This design also reduces the number of screws and adjusting members required to secure the knife. 
     The invention further provides other features which include the following: the slot opening formed through the top portion of the holder allows the holder to be fastened to a knife cylinder; the fastener being screwably attached to the top portion of the adjusting member; the above apparatus further including a knife for inserting between the backing member and the outer side portion of the holder; the above apparatus further including a fastener for inserting through the top portion opening of the holder; and the fastener being a screw and the top portion opening of the adjusting member having threaded sidewalls for receiving the screw. 
     The invention further provides other features which include the following: an opening formed through the outer side portion of the holder to allow a fastener to pass through the backing bar to the adjusting member; the fastener being a screw and the side portion opening of the adjusting member having threaded sidewalls for receiving the screw; and a threaded insert for receiving the screw when it extends through the adjusting member. The invention further provides for a resilient strip, for example, a urethane strip adapted to be positioned adjacent a knife and clamped between the backing member and side portion of the holder. The urethane has been shown to increase the blade life. 
     The features of the invention are aimed at providing a knife holder assembly that is inexpensive, easy to manufacture, easy to maintain, and overcomes one or more of the problems stated in the “Background of the Invention”. The adjusting member and the holder openings are designed to allow one knife or two knives to be easily inserted and removed from the holder assembly. By use of the additional knife and spacer, or by positioning two separate holders back to back on the knife cylinder, any desired distance between the knives can be achieved. 
     The invention further provides for a method of operating a knife holder. A knife or cutting rule is inserted between a side portion of a holder and a backing bar. A fastener is then inserted through an opening formed in a top portion of the holder to contact with a top portion opening in the adjusting member. This contact moves the adjusting member in a direction away from the outer side portion of the holder, drawing the backing bar toward the outer side portion of the holder. The knife is thereby clamped between the outer side portion of the holder and the backing bar. Alternatively, prior to inserting or tightening the fastener, a urethane strip may be inserted on both sides of said knife. A spacer and a second knife may also be inserted adjacent the first knife. And, again, a urethane strip may be inserted on both sides of each knife. 
     These and other features and advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description of the presently preferred embodiments of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a rotary cutter with an embodiment of the knife holders according to the invention mounted on the knife cylinder. 
         FIG. 2  is a sectional view of an embodiment of the knife holder assembly mounted on the knife cylinder. 
         FIG. 3  is an exploded perspective view of a single knife embodiment of the invention. 
         FIG. 4  is a perspective view of the embodiment of  FIG. 3  in the assembled position. 
         FIG. 5  is a sectional view of the knife holder assembly of  FIG. 3 . 
         FIG. 6  is a side view of the knife holder assembly of  FIG. 3 . 
         FIG. 7  is a bottom view of the knife holder assembly of  FIG. 3 . 
         FIG. 8  is a top view of the knife holder assembly of  FIG. 3 . 
         FIG. 9  is a sectional view of a double knife holder embodiment of the invention. 
         FIG. 10  is a perspective view of an existing epoxy knife holder assembly. 
         FIG. 11  is a perspective area of an existing knife holder assembly with side mounted screws. 
         FIG. 12  is a perspective area of an existing knife holder assembly of the type described in U.S. Pat. No. 5,893,314. 
         FIG. 13  is a bottom perspective view of a knife holder assembly with three separate backing bars. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a schematic diagram of a rotary cutter having a knife cylinder  1 , and anvil cylinder  2 . The web material  3  is shown passing between the nip formed between the two cylinders. A pair of the single knife holder assemblies  4  are shown in  FIG. 1  attached to the knife cylinder  1 . The knife holder assembly  4  is preferably sized for use on a discrete section of the knife cylinder. Alternatively, the knife holder assembly  4  may be sized to cover greater portions of the knife cylinder  1 , and numerous individual knife holder assemblies  4  may be mounted on the knife cylinder. Rubber cushioning (not shown) may also be employed on the surface of either cylinder to facilitate the driving of the web through the cylinders and to keep the web taut while it is cut. The knife cylinder has a plurality of receiving holes  8  (see  FIG. 2 ), which are preferably threaded holes, positioned in a uniform matrix or array about its outer surface.  FIG. 2  shows single-knife holder assembly  4  mounted on the knife cylinder  1 . A long screw  7  (shown partially in phantom) is screwed into one of the threaded holes  8  to secure the holder to the knife cylinder  1 . 
     Referring to  FIGS. 3 and 4 , aid an exploded perspective view and an assembled view of the single-knife holder assembly  4 , respectively, is shown. The knife holder assembly  4  includes a holder  10 , backing bar  20 , adjusting member  30 , screws  31 - 36 , fasteners  21 - 26 , and cutting rule or knife  40 . The embodiment of the holder  10  shown in the figures is made of a 0.44×1.50 inch steel channel member having a 13.38 inch length. The top portion  70  of the holder  10  also has attachment slots  71 - 76  for allowing the holder  10  to be positioned upon or fastened to a knife cylinder  1 , as shown in  FIG. 2 . The attachment slots  71 - 76  also allow screws  31 - 36  to pass through to adjusting member  30 . 
     Referring to  FIG. 7 , a bottom view of the top portion  70  of the holder  10  is shown. The slots  71 - 76  preferably have an inner opening with a 0.206 inch width and an outer opening with a 0.436 inch width. 
     Referring to  FIG. 6 , a side view of the knife holder  10  is shown. The side portion of the knife holder  10  has a length that is preferably 13.38 inches and a width of 0.44 inches. The side portion openings  61 - 66 , into fasteners screws  21 - 26  are disposed (see  FIG. 3 ), are centered at 0.278 inches from the top edge of the side portion  61 - 66  and are spaced 2.23 inches from their centers. 
     Referring to  FIGS. 3 and 5 , the side portion of the knife holder  10  has an outer side portion  50  which is preferably angled 7° degrees from the vertical to position the knife  40  for optimum cutting on knife cylinders with diameters ranging between 24 and 50 inches. The backing bar  20 , shown in  FIG. 3 , has a length of 13.38 inches, a width of 0.44 inches and a depth of 0.125 inch. The openings  51 - 56  are aligned with the side portion openings  61 - 66 . As shown in  FIG. 5 , the backing bar openings  51 - 56  have recessed area  121  surrounding the openings, and both the opening and recessed area are angled at 7° degrees to allow the backing bar  20  to uniformly hold the knife  40  to the angled outer side portion  50 . The fastener  26  has a cap portion  131  and screw portion  141 . The cap portion  131  fits in the recessed area  121  around the backing bar member openings  51 - 56 . The screw portion  141  fits through these openings  51 - 56 . The knife  40  has notches  41 - 46  which maintain the 7° degree alignment of the knife with the outer side portion  50 . 
     As shown in  FIG. 3 , the adjusting member  30  has a length of 13.38 inches, a width of 0.375 inch and a thickness of 0.25 inch. The top side  30   a  of the adjusting member  30  includes a set of adjusting member openings  81 - 86  have 0.19 inch diameters (10-24 threaded holes) and generally aligned with the slots  71 - 76  when the knife holder assembly is in the closed position as shown in  FIG. 4 . The side face  30   b  of the adjusting member  30  also has screw holes  91 - 96  that are designed to receive the screw portion  141  of the fasteners  21 - 26 . 
     Referring to  FIG. 9 , a double knife embodiment  4 ′ is shown. A spacer  80  is inserted between the first knife  40  and a second knife  90 . The spacer  80  has a length of 13.38 inches, a width of 0.44 inch and a thickness that may be varied to achieve a desired distance between the knives. The spacer  80  includes notched openings  82  that are angled at 7° degrees to the horizontal to allow the spaced knives  40 ,  90  to be uniformly clamped between the backing bar  20  and the outer side portion  50 . 
     The inner side portion  68  of the holder  10  and the side face  30   b  of the adjusting member  30  are both angled and substantially parallel to each other. When the rotary cutting machine is shut down for maintenance, the operator would typically uses a hex wrench to loosen or remove the screws  31 - 36  from, for example, the openings  71 - 76 , as shown in  FIGS. 3-5 . This, in turn, allows the adjusting member  30  with attached fasteners  21 - 26  to translate or move toward the outer side portion  50  to thereby loosen the clamped knife  40 . The operator may then replace the worn knife  40  with a new knife by aligning the notches  41 - 46  of the knife with the screw portion  141  of the fasteners  21 - 26  and setting the knife onto the screw  141  of each of the fasteners. The operator may then easily and rapidly tighten the screws  31 - 36  using the hex wrench which moves the adjusting member  30  and attached fasteners  21 - 26  away from the outer side portion  50 . The cap portion  131  of the  21 - 26  fasteners retains the backing bar against the knife and clamps it to the outer side portion. The rotary cutting operation can then be resumed. 
     Alternatively, as shown in the embodiment of  FIG. 9 , the operator may place a spacer  80  and a second knife  90  onto the screw portion  141  of the fasteners  21 - 26 . The spacer  80  may have a desired thickness to achieve the desired spacing between knifes  40  and  90 . The embodiments described herein may be used for a  24 - 50  inch diameter knife cylinder. 
     In addition, urethane strips (not shown) with a 3/16 inch thickness, for example, may be inserted on either side of the knives  40 ,  90  to decrease the wear on the knife blade. The urethane strips preferably have openings formed therein to fit onto the screw of the fasteners  21 - 26 , and are placed on both sides of the knife or knives. 
     In addition, as shown in the embodiment in  FIG. 13 , cavities  170  may be milled or formed in the bottom of the knife holder assembly  160  to accommodate separate backing bars  180 . Separate backing bars are helpful for making more precise adjustments to the position of the cutting rule  190 . 
     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.