WO1995024298A1

WO1995024298A1 - Paper and paperboard web slitting apparatus and method

Info

Publication number: WO1995024298A1
Application number: PCT/US1995/002827
Authority: WO
Inventors: Richard F. Paulson; Carl R. Marschke
Original assignee: Marquip, Inc.
Priority date: 1994-03-10
Filing date: 1995-03-07
Publication date: 1995-09-14
Also published as: AU1940295A

Abstract

A paper or paperboard web slitting apparatus of the type utilizing a thin high speed rotary slitting blade (24) extending through the web and into a slotted anvil or web supporting surface (34, 72) on the opposite side of the web is adapted to provide effective plunge slitting while maintaining a desirable narrow blade-receiving slot in the supporting surface. The web supporting surface (34, 72) may comprise either a slotted roller assembly (34) or a stationary slotted plate (72), either of which includes a mechanism (47, 78) for allowing the repositioned rotary cutting blade to plunge into an initially widened slot which is subsequently closed laterally toward the opposite faces of the cutting blade, resulting in a narrow blade-receiving slot, the edges of which are either closely spaced from or in light sliding contact with the opposite faces of the slitting blade.

Description

PAPER AND PAPERBOARD WEB SLITTING APPARATUS

AND METHOD

Background of the Invention

The present invention pertains to an apparatus and related method for slitting a continuous running web of paper or paperboard, including a web of corrugated paperboard, and more particularly to an apparatus and method for effecting accurate slitting and scoring of a paperboard web and rapid order change repositioning of the slitting and scoring tools.

Various types of apparatus for longitudinally slitting a continuous running web of corrugated paperboard are known in the art. Such apparatus often includes a related mechanism for simultaneously providing longitudinal score lines in the advancing web, which score lines facilitate subsequent folding in the construction of boxes or the like. Thus, a combined slitter-scorer utilizes pairs of rotatable cutting tools and scoring tools disposed in the path of the advancing web of corrugated paperboard, with one tool of each pair disposed on an opposite side of the web. Typically, multiple slitting tools are mounted coaxially and laterally spaced across the width of the web and, likewise, multiple scoring tools are also coaxially mounted and spaced across the width of the web.

A conventional prior art device is shown for example in U.S. Patent 4,627,214. Each pair of upper and lower slitting tools is disposed with overlapping radial cutting edges between which the advancing paperboard web is moved to provide a continuous slit. Although commonly referred to as a "slitting" operation, the cutting tools of this type of prior art device in fact shear the moving sheet, resulting in a relative vertical displacement of the adjacent cut edges. However, problems arise as the thickness of the web increases, resulting in cuts which tend to become more ragged, edges which tend to be crushed, and a general degradation in the slit quality. Prior art methods also generate significant amounts of dust, resulting in a wide variety of well known environmental, operational, maintenance and quality control problems.

U.S. Patent 5,090,281 discloses a slitting apparatus which represents a significant improvement in the above described prior art shear-type slitting apparatus. In this apparatus, the paperboard web is cut with a true slitting technique utilizing an apparatus in which the advancing web is directed through a thin circular blade rotating at high speed and running in the same direction as the web, with the board supported below the blade by rollers in contact with the underside of the web. This apparatus reduces significantly the generation of paperboard dust in the slitting operation and improves slit quality.

U.S. Patent 5,197,366 is directed to improvements in the supporting roller assembly for a slitting apparatus of the type described in U.S. Patent 5,090,281. The improvements minimize the build up of adhesive on the supporting rollers and the entry of adhesive, board dust and board scraps into the blade- receiving slot in the supporting rollers. The assembly also facilitates the discharge of board scrap which does enter the slot. Paperboard processing speed is also very important, but cannot be attained with a sacrifice in slit quality. Above identified patent 4,627,214 provides an apparatus for rapidly and accurately repositioning the slitting and scoring heads to effect an order change, but because the slitting blades remain in the path of web travel while they are shifted laterally for repositioning, the web must be laterally severed and a gap in the web created to accommodate tool repositioning. Apparatus has also been developed to move the upper and lower tool heads vertically away from the running web, adjust the tool head positions laterally while in the vertically displaced inoperative positions, and return the tool heads vertically into slitting and/or scoring contact with the running web without the necessity of having created a gap in the web. Such an apparatus utilizes so-called "plunger slitting" technique and is shown, for example, in U.S. Patent 4,380,945. However, such devices require significant additional mechanical equipment to effect vertical tool head movement which equipment, in conjunction with the conventional lateral tool repositioning mechanism, must be able to provide precise cutting blade and scoring head alignment as the repositioned tools are brought back into operating engagement with the running web.

Summary of the Invention In accordance with the present invention, the improved web slitting apparatus of U.S. Patent 5,090,281, identified above, has been modified to provide true plunge slitting in an effective and relatively simple manner. The apparatus of the present invention utilizes a thin annular rotary cutting blade which is positioned with its axis of rotation on one side of the web and has a peripheral cutting edge defined by opposite blade faces, which cutting edge extends through the path of the web to slit the web in the direction of travel. A supporting surface is positioned on the other side of the web to support the web at the point of slitting and includes a slot defined by opposed edges of web supporting surface portions on opposite sides of the blade for receiving the blade cutting edge.

The cutting blade and the web-supporting surface are mounted for relative movement with respect to one another in the plane of the blade between a slitting position, with the blade received in the slot, and a stand-by position, with the blade withdrawn from the slot and out of slitting engagement with the web. The web- supporting surface is mounted in a manner allowing the surface portions to be moved to vary the width of the slot in response to relative movement of the blade with respect to the supporting surface. Means for moving the surface portions is provided which is operable to vary the slot width between a closed slitting position and an open stand-by position. Means may also be provided for biasing the surface portions toward one another in the slitting position to cause the opposed edges to contact the blade faces. Means are preferably provided for moving the surface portions of the web supporting surface to establish the open stand-by position prior to blade movement to the slitting position and to move the surface portions to establish the closed slitting position after blade movement to the slitting position.

In a preferred embodiment, the supporting surface comprises a pair of rollers which are positioned in contact with the web, the rollers having adjacent radial outer edge portions which define the surface portions and provide the slot at the point of tangent contact. The means for moving the surface portions is operable to provide the closed slot position at the point of tangent contact. The mounting means preferably comprises a fixed lower support structure which includes a lower tool head mounting the cutting blade for lateral blade positioning movement transverse to the direction of web travel, a movable upper support structure which includes an upper tool head mounting the rollers for lateral positioning movement corresponding to the positioning movement of the cutting blade, means on the upper support structure for lifting the rollers upwardly to the stand-by position, and means for deflecting the running web upwardly to move the web out of slitting engagement with the rotary cutting blade. The upper and lower support structures may each be provided with a scoring tool head which mounts a rotary scoring tool for lateral positioning movement transverse to the direction of web travel. Means are also provided for moving the upper support structure vertically to move the upper scoring tool away from the lower scoring tool. In one embodiment, the pair of supporting rollers are mounted to rotate on mutually non-parallel axes with the outer edge portions of the rollers defining a variable width circumferential slot around the roller peripheries. The means for moving the surface portions includes means for translating the rollers vertically and horizontally with respect to the blade cutting edge to provide the slitting and stand-by positions. In a presently preferred embodiment, the axes of the web- supporting rollers are disposed in a substantially vertical plane normal to the cutting blade in the slitting position, and means are provided for rotating the rollers on a common horizontal axis lying in the vertical plane to vary the slot width. The web supporting surface may alternately comprise a generally flat, horizontal plate, including a generally Y-shaped slot which is positioned with the opposed edges of the supporting surface portions diverging laterally from the point of slitting. Means are provided for rotating the plate about a horizontal plate axis which is disposed generally parallel to the rotational axis of the slitting blade and at approximately the point of maximum divergence of the edges of the surface portions. In a preferred embodiment, the plate is oriented to position the plate axis downstream of the point of slitting. The supporting surface directly adjacent the edges of the surface portions may be constructed to comprise an air bearing. Means may also be provided for releasably biasing the surface portion edges into engagement with the blade faces in the slitting position.

Brief Description of the Drawings FIG. 1 is a side elevation of a slitting apparatus incorporating the preferred embodiment of the present invention and shown in its operative slitting position. FIG. 2 is a side elevation of the apparatus shown in FIG. 1 and further showing movement of the apparatus to its inoperative order change position.

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2.

FIGS. 4 and 5 are, respectively, a side elevation and an end elevation of the web-supporting roller assembly in the operative position of FIG. 1. FIGS. 6 and 7 are, respectively, a side elevation and an end elevation of the web-supporting roller assembly in an intermediate position.

FIGS. 8 and 9 are, respectively, a side elevation and an end elevation of the web-supporting roller assembly in the inoperative position of FIG. 2. FIG. 10 is a sectional view similar to FIG. 3 showing an alternate embodiment of the roller assembly.

FIG. 11 is a top plan view of a web supporting surface of an alternate embodiment of the present invention. FIG. 12 is a side elevation of the apparatus shown in FIG. 11.

Detailed Description of the Preferred Embodiments

Referring initially to FIG. 1, the slitting apparatus of the present invention is shown in an embodiment in which it is combined and operated in conjunction with a scoring apparatus, wherein the continuous web 12 of corrugated paperboard is simultaneously slit longitudinally and also provided with longitudinal score lines, all in a generally well known manner. The main supporting framework for the combined slitter-scorer includes a horizontal upper beam 10 and a parallel lower beam 11. The beams 10 and 11 extend across the width of the slitting apparatus and are somewhat longer than the maximum width of the continuous moving web 12 which moves between the beams and the attached components of the slitting apparatus and the companion scoring apparatus to be described hereinafter. Each slitting apparatus includes a plurality of lower tool heads 13 which are attached to the top side of the lower beam 11 for individual movement across the width of the web 12 on a pair of linear ways 14 attached to the beam 11. Each tool head 13 has a pair of linear bearing pads 15 attached to its lower edge, which bearing pads support the tool head 13 on the linear ways 14 for lateral sliding movement across the web to set the tool head in the position where a longitudinal slit in the web 12 is desired.

Referring also to FIGS. 3-5, a rotary tool holder 16 is attached to each tool head 13. The tool holder 16 includes an inner hub 17 which forms the inner race of a rotary bearing. The outer race of the rotary bearing is secured in an annular boss 20 in the tool head 13. The inner hub 17 of the tool holder has an axial through bore 21 having a non-circular cross section, such as the hexagonal shape shown in FIG. 1. The hexagonal through bores 21 of the tool holders 16 lie on a common axis and a driveshaft 22 having a hexagonal cross section is mounted to extend through the bores 21 in each of the plurality of co-axially mounted tool holders 16. The driveshaft 22 extends across the full width of the apparatus and is connected at one end to a suitable drive means, whereby it is driven to cause the tool holders 16 to rotate with respect to the tool heads 13. Also, the driveshaft 22 provides support for the commonly mounted tool holders 16 and tool heads 13 for movement along the linear ways 14. Each tool holder 16 includes an outer hub 23 to which a thin annular slitting blade 24 is demountably attached, as described in greater detail in U.S. Patent 5,090,281. However, in a manner inverted from the arrangement shown in that patent, each slitting blade 24 extends upwardly from its respective tool head 13 so that the circular cutting edge extends above the upper face 26 of the corrugated paperboard web 12 as the web travels through the slitting station. The circular slitting blade 24 has a smooth continuous peripheral cutting edge 25 which is defined by a pair of opposite beveled edge faces 27. Each blade may have a thickness, which increases radially inwardly from the edge faces 27, from a minimum of about .020 inch (0.5 mm) adjacent the edge faces to a maximum of about .040 inch (1.0 mm) adjacent the hub. Because the slitting blades 24 are operated at high speed, a substantial amount of heat is generated and, in addition, the blade edges eventually become dull and must be resharpened. When used to slit a corrugated paperboard web 12, particularly as it exits the wet end of a corrugating machine, the typical starch-based adhesive used to secure the multilayer paperboard web may not be completely dried and tends to stick to and build up on the cutting blades 24. Therefore, the slitting apparatus also preferably includes a sharpening device 28, whereby each blade edge may be sharpened on-the-fly. The sharpening device 28 is attached to the tool head 13 and may be periodically activated to touch each of the opposite blade edge faces 27 as required for sharpening. A lubricating device 30 is also attached to each tool head 13 to apply a thin coating of a lubricant or anti-stick liquid to the opposite faces of the blade 24 to prevent adhesive build- up thereon. The lubricating device 30 preferably includes a pair of wicks which are retained in constant light contact with the opposite faces of the blade to distribute the lubricant thereon.

A plurality of upper tool heads 31 are supported for individual sliding movement along a pair of upper linear ways 32 which are, in turn, attached to the underside of the upper beam 10. Each upper tool head 31 is supported for movement along the linear ways 32 by a pair of linear bearing pads 33 similar to the bearing pads 15 on the lower tool heads 13. A roller assembly 34 of the present invention is attached to each upper tool head 31 and is adapted to cooperate with a slitting blade 24 on an opposite lower tool head 13. Each roller assembly includes a pair of identical rollers 35 positioned to contact the upper face 26 of the web 12 and to receive the peripheral edge of the slitting blade 24 therebetween as the blade projects upwardly past the upper face of the web during slitting.

Each of the lower tool heads 13 and upper tool heads 31 is individually positionable in a lateral direction along its respective linear ways 14 and 32 by an electric servomotor 36 mounted on each tool head and carrying a driven pinion gear 37 positioned to engage a linear toothed rack 38 attached to the supporting face of the respective lower and upper beams 11 and 10. Each cooperating pair of lower and upper tool heads 13 and 31 is accurately positioned in operation to define a cutting nip between the slitting blade 24 and the slotted roller assembly 34. In order to change the lateral position of the tool heads 13 and 31 to effect a change in position of the slit in the web for an order change, the tool heads and attached slitting blade and roller assembly are moved vertically relative to one another and out of slitting engagement with the running web 12. With the slitting blade and roller assembly out of engagement with one another and with the web, the servomotors 36 are operated to reposition the respective heads laterally to the position of the desired new slit and then returned to their operative positions, so that the slitting blade 24 pierces the running web and enters the slot 40 between the rollers 35 of the roller assembly. The slitting blade and cooperating roller assembly are then locked against lateral movement in their operative positions by a mechanical or electromechanical locking device between the tool heads and the supporting beams. For example, a solenoid-operated locking bar 41 attached to the surface of each main beam 10 and 11 is adapted to engage cooperating locking pads 42 on each of the tool heads 13 and 31 to secure the tool heads against lateral displacement in their fixed operating positions.

Although the system of the servomotor tool head adjustment is ordinarily satisfactory to provide sufficiently accurate tool head positioning, the desire to maintain as narrow a width in the slot 40 requires extremely precise alignment between the upper and lower tool heads so that the repositioned slitting blade 24 which is caused to plunge through the web will enter the slot cleanly and not strike either of the rollers 35. In the supporting roller embodiment of U.S. Patent 5,197,366, the supporting rollers 35 are actually biased into light contact with the opposite faces of the slitting blade 24. Although the slitting blade may be withdrawn readily from the slot when it is desired to effect an order change, the repositioned blade and roller assembly may not be aligned accurately enough to assure smooth and unobstructed re-entry of the blade into the slot. FIGS. 1 and 2 show generally the type and degree of vertical displacement which take place between the lower slitting blade 24, upper roller assembly 34 and web 12 to allow the slitting blade to be withdrawn from the running web, the roller assembly moved out of supporting contact therewith, and the supporting tool heads adjusted laterally for repositioning. As is well known in the art, each of the supporting upper and lower beams 10 and 11 carries a plurality of upper and lower scoring heads 43 and 44 carrying, respectively, rotary ^• upper and lower scoring tools 45 and 46. The scoring tool heads 43 and 44 are mounted and laterally adjustable in the same manner as the lower and upper heads 13 and 31 for the previously described slitting assembly. In a general sense, the scoring tools 45 and 46 are cleared from engagement with the web for lateral repositioning in a manner similar to that described in U.S. Patent 4,627,214. Thus, the upper beam 10 is rotated in its lateral supporting side frame members (not shown) about a horizontal laterally-extending axis A as shown in FIGS. 1 and 2. Because the upper tool heads 31 carrying the roller assemblies 34 are mechanically less complex than the lower tool heads 13 carrying the slitting blades 24, rotation of the upper beam 10 is preferred over rotation of the lower beam. However, rotation of the lower beam 11 in a similar manner is also possible and, in addition, the entire assembly could be inverted to place the slitting blades 24 above the roller assemblies 34, as shown for example in U.S. Patent No. 5,197,366.

In any event, rotation of the upper beam 10 about the axis A to move the scoring tools 45 and 46 out of scoring engagement with the web results in little rotation of the roller assemblies 34 and no disengagement of the slitting blades with the web. The necessary additional vertical displacement of the roller assemblies 34 is provided by the roller mounting assembly 47 of the present invention by which the roller assemblies are adjustably mounted on the upper tool heads 31. In addition, movement of the web out of engagement with the slitting blades 24 is accomplished simultaneously by upward rotation of the free ends of the upstream and downstream web supporting pans 48 and 50. Upward rotation of the web supporting pans during order change, lifts the web 12 above the cutting edge 25 of the blades, thus allowing all of the tool heads to be laterally adjusted and repositioned without creation of a longitudinal gap in the web. Operation of the roller mounting assembly 47 of the present invention is detailed in FIGS. 3-9. This assembly utilizes a roller assembly 34 of the type disclosed in above identified patent 5,197,366, but other roller and non-roller board supporting assemblies may also be utilized in accordance with the concepts of the present invention, as will be described hereinafter. Each roller 35 is mounted on a separate rotational axis, which axis is defined by a short stub shaft 51. In the operative slitting position shown in FIGS. 1 and 3-5, the stub shaft axes are disposed in a common vertical plane, but are angled downwardly in opposite directions at a very small angle (such as 1°) so that, as viewed in FIGS. 3 and 5, the slot 40 between the rollers is downwardly convergent. In other words, the slot is widest at the top of the rollers and narrowest at the bottom thereof where the web 12 makes tangent contact and the slitting blade 24 enters. As the roller mounting assembly 47 is operated to pivot the rollers upwardly and out of engagement with the web 12, it also provides an opening of the slot 40 at the point of re-entry so that, when the rollers are subsequently returned to the operative slitting position, the slitting blade first enters the temporarily opened slot portion which is caused to close on the opposite blade faces once slitting position has been re-established. Each roller 35 is rotatably mounted on its stub shaft 51 which is, in turn, rotatably supported in the free end of one of a pair of spaced support arms 52. The opposite ends of the support arms 52 are attached to a common support arm pivot 53 on the upper tool head 31. A tension spring 54 mounted between the tool head and support arm, and spaced from the pivot 53, holds the roller assembly 34 in its operative down position. Each roller 35 is rotatably supported on its stub shaft 51 on a bearing 55. The bearing 55 for each roller 35 is separated from the roller support arm 52 by a Belleville washer assembly 56 mounted on the stub shaft 51. The Belleville washer assemblies press the interior edge faces 39 of the rollers 35 defining the slot 40 against the opposite faces of the slitting blade 24. As described in the prior art, the roller faces 39 are pressed against the blade faces with a light load just sufficient to help prevent a detrimental build up of starch and board dust on the blade faces.

One end of a short cam arm 57 is secured to the end of a stub shaft 51 on the outside face of one support arm 52, as with a pinned connection 58 shown in

FIG. 3. Further, the abutting ends of the stub shafts 51 are also secured together, such that rotation of the cam arm 57 causes rotation of the stub shafts despite the fact that their axes do not coincide as a result of their angled mounting described above. The opposite end of the cam arm 57 is attached to the end of a linear actuator, such as the rod 60 of a pneumatic cylinder 61. The cylinder is mounted to the upper tool head 31 such that retraction of the cylinder rod 60 from its fully extended position of FIGS. 1 and 4 results in upward rotation of the cam arm 57 and the interconnected stub shafts 51 to which the cam arm is rigidly attached. Rotation of the cam arm and stub shafts is limited to an angle of about 60° by engagement of the cam arm with a stop bar 62 mounted on the support arm 52, as best shown in FIG. 6. Because of the fixed angular relationship between the axes of the interconnected stub shafts 51, this initial rotation of the cam arm and stub shafts results in a rotation of the downwardly convergent slot 40 between the rollers (shown in FIG. 5) , resulting in the rollers opening slightly at their lower peripheral edges where they had been in contact with the opposite faces of the slitting blade 24 (this opening movement being best shown in FIG. 7) . With the cam arm 57 in engagement with the stop bar 62, further retraction of the cylinder rod 60 causes the support arms 52 and rollers 35 attached thereto to pivot upwardly about the support arm pivot 53 against the bias of tension springs 54 to the fully retracted position shown in FIGS. 2, 8 and 9. The vertical gap created between the roller assembly 34 and the upper edge of the slitting blade 24 in the fully retracted position must be sufficient so that upward deflection of the moving web 12 by upward rotation of the web supporting pans 48 and 50 can take place to lift the web out of slitting engagement by the blade, but without engaging any portion of the assembly on the upper beam, as shown in FIG. 2.

After the upper and lower tool heads have been laterally repositioned, the entire process just described is reversed to return the supporting pans, web, and roller and scoring tool assemblies on the upper beam 10 from their FIG. 2 positions to the FIG. 1 slitting position. As the cylinder 61 is initially extended to rotate the roller mounting assembly 47 downwardly about the support arm pivot 53, the gap 63 at the bottom of the roller assembly 34 remains open because the force of the tension springs 54 holds the stop bar 62 in contact with the cam arm 57. Thus, as the rollers move downwardly to receive the slitting blade 24 in the slot 40, the blade edge 25 will enter the widened gap 63 in the intermediate position of the rollers shown in FIGS. 6 and 7, so that any minor lateral misalignment between the blide and the rollers as a result of their independent repositioning will prevent the blade edge from striking the outer surfaces of the rollers 35. The correct vertical position of the rollers with respect to the slitting blade is established by a support arm stop 64 attached to the tool head 31 and engaged by the lower edge of the support arm 52 as the support arms rotate downwardly from the FIG. 8 to the FIG. 6 position. Continued extension of the cylinder rod 60 causes rotation of the cam arm 57 from the FIG. 6 to the FIG. 4 position, resulting in simultaneous rotation of the interconnected stub shafts 51, thereby causing effective rotation of the divergent slot 40 between the rollers and resultant light clamping contact of the lower inside edges 39 of the rollers 35 against the blade face, as best shown in FIGS. 3 and 5.

Suitable programmed movement under the control of a microprocessor may be utilized to provide simultaneous return rotation of the upper beam 10 about axis A, downward movement of the web supporting pans 48 and 50, and return movement of the roller assemblies 34 just described. Once the roller assemblies have been returned, allowing re-entry of the slitting blades 24 into each of the slots 40, the locking bars 41 are activated to clamp the upper and lower tool heads securely in their reset slitting positions. Should there be a slight misalignment between any upper roller assembly 34 and its lower slitting blade 24, as the roller assembly is returned to its operative position, one of the inner edges 39 of the rollers 35 defining the convergent slot 40 will contact the corresponding face of the slitting blade 24 and, as the cam arm 57 continues its downward rotation, the camming action of the roller edge against the slitting blade provides a self-aligning action between the rollers and the blade.

Referring to FIG. 10, a modified roller assembly 65 includes a pair of rollers 35 which are identical to those of the previously described embodiment and are mounted in a slightly skewed manner on angled stub shafts 51, as previously described. However, the stub shafts are held against rotation with respect to the support arms 52 to which they are attached and, as a result, the closed end of the convergent slot 40 between the rollers is always oriented near the bottom of the roller pair to bear lightly against the opposite faces of the slitting blade 24, as shown. In order to open the slot 40 and create an alignment gap to accommodate any misalignment between the repositioned roller pair and the slitting blade as the rollers are brought back into operative position (in a manner similar to that previously described) , one of the rollers 35 is mounted on a modified stub shaft 66 which also functions as the rod end of a small pneumatic cylinder 67 mounted on the outside face of one support arm 52 as shown in FIG. 10. The roller 35 is secured against axial movement along the free end of the modified stub shaft 66, as with a pair of snap rings 68. The opposite end of the stub shaft 66 is provided with a piston 69 which, when the cylinder 67 is pressurized, forces the roller 35 against its companion roller to close the slot 40 onto the slitting blade. A bias spring 70 positioned between the support arm 52 and the outside face of the piston 69 causes the roller and modified stub shaft 66 to move outwardly to open the slot 40 when pressure on the cylinder 67 is released. The rod end 60 of the lift cylinder 61, used to rotate the support arms 52 to lift the modified roller assembly 65 from the blade, is attached to the outside end of the small pneumatic cylinder 67 with a conventional connecting bolt 71. When it is desired to effect an order change requiring lateral repositioning of one or more of the slitting blades 24, the support arms 52 may be pivoted upwardly without the necessity of first releasing the pressure on the stub shaft cylinder 67 and allowing the slot 40 to open. The light pressure by which the cylinder 67 holds the roller edges in contact with the opposite blade faces is light enough to allow the roller assembly 65 to be slid easily out of contact with the blade. Thus, the slot 40 need only be opened at some point before the support arms 52 are rotated back to the active operating position after the roller assembly and cooperating blade have been repositioned. As with the preferred embodiment, the open slot allows some tolerance for possible misalignment as the modified roller assembly 65 is pivoted downwardly to receive the slitting blade 24 therein.

FIGS. 11 and 12 show a variation in the slotted support for the web in which the roller assembly of the two above described embodiments is replaced with a generally flat slotted plate 72. The plate is oriented in a manner similar to the supporting rollers of the previously described embodiments so as to present a lower backing surface 73 against which the moving web 12 is pressed by the action of the rotating slitting blade 24. The web is supported upstream and downstream of the slitting station by a pair of supporting pans 48 and 50, also as previously described. The plate surface 73 is provided with a generally Y-shaped slot 74 which diverges in a downstream direction from a pair of parallel closely spaced edge portions 75 where the slitting blade enters the slot to a widely spaced opening 76 at the downstream edge of the plate. The plate is hinged about its downstream edge on a plate pivot 77 and the opposite end is provided with an actuator 78 to lift the plate and pivot it upwardly and in a downstream direction to disengage the blade from the slot 74 when it is desired to reposition the slitting tools.

To accommodate a plunge-type slitting operation, means must also be provided for lifting the hinged downstream edge of the plate 72 and raising the running web 12 out of engagement by the slitting blade, as by raising the supporting pans 48 and 50. These features are not shown in the generally schematic presentation of the embodiment shown in FIGS. 11 and 12. The Y-shaped slot 74 in the anvil or backing plate 72 allows the plate to be pivoted downwardly about the plate pivot 77 from the upper dashed line position to which it is moved for lateral repositioning of the plate and its corresponding slitting blade to the solid line horizontal position without the danger of the plate engaging the blade edge in the event one or the other is slightly misaligned. As the plate 72 pivots downwardly to allow the slitting blade to enter the slot 74, the blade edge will initially enter a wider downstream portion of the Y-shaped slot and, as the plate continues its downward movement, the more closely spaced parallel edge portions 75 will receive the circular cutting edge of the blade. If there is any misalignment between the blade and the slot, the wider curved edge portion of the slot will engage one side face of the blade and ride therealong to self-align the blade in the slot.

Although a flat anvil plate or backing plate 72 is of a substantially simpler construction than a supporting roller assembly, the stationary flat surface has certain inherent deficiencies. First of all, the high speed of the moving paper web results in a substantial temperature build up in the plate as a result of sliding friction. In addition, the narrowly spaced edge portions 75 defining the slot are subject to rapid wear, even when the plate is made of steel. To help minimize these problems, the edges of the slot 74, particularly the edge portions 75 defining the narrow slot portion at the point of slitting, may be provided with an air bearing 80 to reduce sliding friction and wear of the slot edge portions. The air bearing may be defined by a pattern of orifices 81 arranged in any suitable pattern.

Provision may also be made to divide the plate 72 into two laterally spaced plate sections so that the closely spaced edge portions 75 may be brought into light contact with the opposite faces of the rotating slitting blade, as described with respect to the supporting roller assemblies of the preceding embodiments. For example, the plate 72 could be cut along the extended slot edges 82 to divide the plate in two, and suitable means provided to close the slot on the blade, as shown by the laterally extending arrows in FIG. 11. The slitting apparatus of the embodiment shown in FIGS. 11 and 12 could be adapted to a more conventional station by inverting the entire assembly so that the plate 72 supports the web 12 from the underside with the slitting blade 24 mounted above the web. In this orientation, the plate 72 would be positioned between the pans 48 and 50 with the backing surface 73 coplanar with the upper surfaces of the pans. Also, as with the other embodiments, plunge slitting could be effected by mounting the slitting blade for vertical movement out of the path of the moving web, rather than lifting the web to clear the blade edge. In either case, however, rotational movement of the supporting plate 72 would still be needed to present initially a wider portion of the Y-shaped slot to the slitting blade edge, thereby minimizing the chance of damaging blade engagement with a misaligned plate.

Claims

Various modes of carrying out the present invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.We claim:

1. In an apparatus for slitting a horizontal running web of paper, said apparatus including a thin annular rotary cutting blade positioned with its axis of rotation on one side of the web and having a peripheral cutting edge defined by opposite blade faces, said cutting edge extending through the path of the web to slit the web in the direction of web travel, and a supporting surface on the other side of the web for supporting the web at the point of slitting and including a slot defined by opposed edges of supporting surface portions on opposite sides of the blade for receiving the blade cutting edge, the improvement in said apparatus comprising: mounting means supporting the cutting blade and the supporting surface for relative movement with respect to one another in the plane of the blade between a slitting position with the blade recn.ived in the slot and a stand-by position with the blade withdrawn from the slot and out of slitting engagement with the web; and, said mounting means including means for moving said surface portions to vary the width of said slot in response to relative movement of said blade with respect to said supporting surface.

2. The apparatus as set forth in claim 1 wherein said moving means is operable to vary the slot width between a closed slitting position and an open stand-by position.

3. The apparatus as set forth in claim 1 wherein said moving means includes means for biasing said surface portions toward one another in the slitting position to cause the opposed edges to contact the blade faces.

4. The apparatus as set forth in claim 2 wherein said moving means is operable to move the surface portions of said web supporting surface to establish the open stand-by position prior to blade movement to the slitting position and to move said surface portions to establish the closed slitting position after blade movement to the slitting position.

5. The apparatus as set forth in claim 1 wherein the supporting surface comprises a pair of rollers in tangent contact with the web, said rollers having adjacent radial outer edge portions defining said surface portions and providing the slot at the point of said tangent contact; and, said moving means is operable to provide said closed slot position at said tangent contact point.

6. The apparatus as set forth in claim 5 wherein said mounting means comprises: a fixed lower support structure including a lower tool head mounting the cutting blade for lateral blade positioning movement transverse to the direction of web travel; a movable upper support structure including an upper tool head mounting said rollers for lateral positioning movement corresponding to the positioning movement of said cutting blade; means on the upper support structure for lifting said rollers upwardly to the stand-by position; and, means for deflecting the running web upwardly to move the web out of slitting engagement with said blade.

7. The apparatus as set forth in claim 6 wherein said upper and lower support structures each include a scoring tool head mounting a rotary scoring tool for lateral positioning movement transverse to the direction of web travel; and, including means for moving the upper support structure vertically to move the upper scoring tool away from the lower scoring tool.

8. The apparatus as set forth in claim 5 wherein said pair of rollers are mounted to rotate on mutually non-parallel axes with said outer edge portions defining a variable width circumferential slot around the roller peripheries, and wherein said means for moving the surface portions comprises means for translating said rollers vertically and horizontally with respect to the blade cutting edge to provide said slitting and stand-by positions.

9. The apparatus as set forth in claim 8 wherein said roller axes are disposed in a substantially vertical plane normal to the cutting blade in the slitting position, and further comprising means for rotating said rollers on a common horizontal axis lying in the vertical plane to vary the slot width.

10. The apparatus as set forth in claim 2 wherein said web supporting surface comprises a generally flat, horizontal plate, said slot is generally Y-shaped and positioned with the opposed edges of the supporting surface portions diverging laterally from the point of slitting, and including means for rotating said plate about a horizontal plate axis disposed generally parallel to the rotational axis of the slitting blade and at approximately the point of maximum divergence of said surface portion edges.

11. The apparatus as set forth in claim 10 wherein said plate is positioned to dispose the plate axis downstream of the point of slitting.

12. The apparatus as set forth in claim 10 wherein the supporting surface directly adjacent the edges of the supporting surface portions comprises an air bearing.

13. The apparatus as set forth in claim 10 including means for releasably biasing said surface portion edges into engagement with the blade faces in the slitting position.

14. A method for slitting a horizontal running web of paper in an apparatus including a thin annular rotary cutting blade positioned with its axis of rotation on one side of the web and having a peripheral cutting edge defined by opposite blade faces, said cutting edge extending through the path of the web to slit the web in the direction of web travel, and a supporting surface on the other side of the web for supporting the web at the point of slitting and including a slot defined by opposed edges of supporting surface portions on opposite sides of the blade for receiving the blade cutting edge, said method including the steps of:

(1) supporting the cutting blade and the supporting surface for relative movement with respect to one another in the plane of the blade between a slitting position with the blade received in the slot and a stand¬ by position with the blade withdrawn from the slot and out of slitting engagement with the web; and,

(2) moving said surface portions to vary the width of said slot in response to relative movement of said blade with respect to said supporting surface.

15. The method as set forth in claim 14 including the step of varying the slot width between a closed slitting position and an open stand-by position.

16. The method as set forth in claim 14 including the step of biasing said surface portions toward one another in the slitting position to cause the opposed edges to contact the blade faces.

17. The method as set forth in claim 15 including the steps of:

(1) moving the surface portions of said web supporting surface to establish the open stand-by position prior to blade movement to the slitting position; and, (2) moving said surface portions to establish the closed slitting position after blade movement to the slitting position.