Web Cutter

Abstract

A paper cutter in the form of a knife mounted in a slot of a first roller closely spaced and parallel to a second roller. The knife protrudes from the first roller and engages the second roller when the first roller is rotated, the paper to be cut being fed between the rollers. An elastomeric material is pressed against the back edge of the knife to prestress the knife blade so that the force on the blade remains essentially constant during the cutting process.

Description

This invention relates to a web cutter, and is particularly useful in conjunction with, although not limited to, the cutting of paper to predetermined lengths from a paper roll in a xerographic copying apparatus.

Roller type web cutters, and particularly paper cutters are well known in the art, and generally comprise two adjacent cylindrical rollers, one of the rollers having a knife blade protruding therefrom which contacts or nearly contacts the other roller when the roller containing the knife is rotated, the web to be cut being disposed between the two rollers.

In order to reduce cutter wear, it has been attempted to space the rollers very precisely, so that the cutting edge of the knife blade penetrates the paper or other web to be cut, but does not contact the roller on the opposite side of the web. The critical adjustment required for such an arrangement, however, makes it impractical for equipment such as xerographic copying apparatus, which equipment must be capable of fabrication by mass production techniques, and exhibit a long operating life without requiring frequent adjustment.

Another technique which has been suggested involves the placing of a resilient member behind the cutting blade, so that the blade is inwardly deflected upon contacting the oppositely disposed roller. However, such a technique has proven to be unreliable, and has resulted in undesirable vibration of the cutting blade as well as considerable variation in the cutting force, so that the quality of the cut varies considerably with the particular characteristics of the web being cut.

As herein described, there is provided a cylindrical web cutting roller having a longitudinal slot therein. A resiliently mounted web cutting knife blade is disposed in the slot, the cutting edge of the blade protruding a predetermined distance beyond the periphery of the roller. Resilient biasing means is provided within the roller for prestressing the blade so that substantial initial force is required to deflect the blade into the slot.

Also described herein is a web cutter comprising first and second cylindrical rollers which are mounted for rotation about mutually parallel axes. The first roller has a longitudinal slot therein, with a resiliently mounted web cutting knife blade disposed in the slot. The cutting edge of the knife blade protrudes a predetermined distance beyond the periphery of the first roller.

The rollers are disposed in juxtaposition with the peripheries of the rollers spaced apart by a given distance which is less than the aforementioned predetermined distance which the cutting edge of the knife blade protrudes beyond the periphery of the roller in which it is mounted. As a result, the knife blade is deflected inwardly into the slot upon engagement of its cutting edge with the periphery of the second roller. Means is provided for feeding the web to be cut between the rollers, and means is also provided for rotating the first roller to bring the cutting edge of the knife blade into engagement with the web and with the periphery of the second roller to sever the web. Resilient biasing means within the first roller is provided for prestressing the knife so that substantial initial force is required to deflect the blade upon engagement of its cutting edge with the periphery of the second roller.

In the drawing:

FIG. 1 shows a cross sectional view of a web cutter according to an embodiment of the present invention.

FIG. 2 shows a cross sectional view of a web cutter according to an alternative and preferred embodiment of the present invention.

FIG. 3 shows a side view of the cutting roller shown in FIG. 2, and its adjacent web guide plate, taken in the direction A indicated by the arrow in FIG. 2, with the knife blade of the cutting roller aligned with the web guide plate.

The web cutter shown in FIG. 1 consists of a cylindrical rotatably mounted cutting roller 10 mounted in juxtaposition with and parallel to second roller or platen 11. The cutting roller 10 has a T-shaped longitudinal slot 12 therein, in which is disposed a T-shaped web cutting knife blade 13 having a cutting edge 14 which protrudes beyond the periphery 15 of the cutting roller 10. The knife blade 13 is retained within the roller 10 by abutment of the head portion 16 of the knife blade 13 with the shoulder 17 of the longitudinal slot 12.

A strip 18 of a suitable resilient material (preferably an elastomeric material such as neoprene or rubber) is disposed in the slot 12 adjacent the head portion 16 of the knife blade 13.

A pressure equalizing plate 19, preferably of a relatively rigid metal such as steel, is disposed in the slot 12 adjacent the surface of the resilient strip 18.

The T-shaped slot 12 runs the entire length of the cutting roller 10. A plurality of holes 20 are provided in the cutting roller 10, each hole communicating with the slot 12. Each of the holes 20 is internally threaded, and a set screw 21 is threaded into each hole to apply pressure to the pressure equalizing plate 19, thus compressing the resilient material 18 against the head of the knife blade 13.

The resultant force applied to the head 16 of the knife blade 13 acts to prestress the knife blade, so that when the cutting edge 14 of the knife blade 13 engages the platen roller 11, a substantial amount of force is required to deflect the knife blade 13 into the slot 12.

In order to prevent the set screws 21 from loosening during operation of the web cutter, Nylok set screws 22 are threaded into the holes 20 and tightened against the rear surfaces of the set screws 21. The set screws 22 are tightened sufficiently to retain the set screws 21 in proper position.

Preferably, the backing plate or pressure equalizing plate 19 should be of sufficient rigidity and thickness so as to distribute the force applied thereto by the set screws 21 equally across the length and width of the resilient strip 12.

The resilient strip 12 is preferably provided with a number of holes therethrough (not shown in FIG. 1) to permit expansion of the material as it is compressed in thickness by the set screw 21 and pressure equalizing plate 19. Preferably, the amount by which the thickness of the resilient material 12 is reduced due to the pressure applied thereto by the pressure equalizing plate 19 should be substantially greater than the deflection of the cutting edge 14 upon engagement thereof with the platen roller 11. This assures a constant cutting force when paper to be cut is passed between the two rollers and severed by interaction of the cutting edge 14 with the platen roller 11.

It has been found advisable, in order to provide a web cutter having extremely long life, to fabricate the knife blade 13 and the platen roller 11 of a material having a surface hardness on the order of at least 60 on the Rockwell C scale. The steel alloy known as 8620 (an American Iron and Steel Institute designation) has been found suitable for this purpose, this alloy being especially useful since it may be readily machined to the desired configuration, and subsequently surface hardened to the required hardness, then ground to the desired tolerance.

Excellent paper cutting results have been obtained by passing the paper to be cut between the two rollers, and rotating the cutting roller 10 (preferably at a peripheral speed equal to that of the paper and the platen roller 11) to bring the cutting edge 14 of the knife blade 13 into contact with the paper and the periphery of the platen roller 11. Since the "interference" between the cutting edge 14 of the knife blade 13 and the platen roller 11 is small compared to the initial deformation of the resilient strip 18 (as provided by the pressure equalizing plate 19 and set screws 21), an essentially constant cutting force is provided throughout the cutting operation. This cutting force can be set quite precisely by proper adjustment of the set screws 21 and, once set, is accurately maintained.

As a result, stresses at the tip of the knife blade are substantially reduced, the peak torque to which the cutting roller 10 is subjected during the cutting process is reduced (thereby reducing wear on the cutting roller drive mechanism), and vibration of the knife blade 13 is reduced, thus reducing blade wear and acoustical noise.

Excellent paper cutting results have been achieved with the arrangement shown in FIG. 1, with an "interference" between the knife blade 13 and the platen roller 11 on the order of 0.005 inch, and an initial compression of the thickness of the resilient strip 18 (neoprene being employed as the strip material) on the order of 0.050 inch, corresponding to a prestress force of 300 pounds per inch of knife length applied to the knife blade 13.

The diameters of the rollers 10 and 11, in the aforementioned example, were 2.5 inches, while the lengths of these rollers were 14.5 inches.

The alternative web cutter arrangement shown in FIGS. 2 and 3 provides improved cutting operation and ease of maintenance.

Whereas the cutting roller 10 shown in FIG. 1 is unitary, i.e., machined from a single piece of material, the cutting roller 23 shown in FIG. 2 is a three piece structure, consisting of a major portion 24 and two minor portions 25 and 26.

The minor portions 25 and 26 are secured to the major portion 24 by a plurality of threaded screws 27 and 28 respectively, the minor portions 25 and 26 being maintained in proper alignment with the major portion 24 by means of longitudinal bosses 29 and 30 on the major portion 24, which bosses engage corresponding longitudinal slots in the minor portions 25 and 26. The screws 27 and 28 are secured through the holes 31 and 32.

In fabricating the cutting roller 23, the interior surfaces of the cutting roller portions 24, 25 and 26 are first machined to the desired configuration, the exterior surfaces of these portions are approximately machined, the three portions are secured together by means of the screws 27 and 28, the roller is machined to provide a smooth exterior cylindrical surface, and the screws 27 and 28 are removed to separate the cutting roller portions to permit insertion of the various internal parts in the T-shaped slot 33 of the cutting roller 23.

The cutting roller 23 may be fabricated of any suitable relatively rigid material, steel being preferred.

Situated within the T-shaped slot 33 of the cutting roller 23 are a web cutting knife blade 34, a resilient strip 35, a relatively rigid pressure equalizing plate 36, and a plurality of resilient flailing fingers 37.

A plurality of set screws 38 are threaded into holes 39 which communicate with the T-shaped slot 33, the set screws 38 being adjusted to apply a predetermined force to the backing plate 36 to compress the resilient strip 35 and properly prestress the knife blade 34 by pressing the enlarged head portion 40 thereof against the adjacent shoulder 41 of the T-shaped slot 33.

Perferably, the enlarged portion of the T-shaped slot 33 has a width on the order of 0.50 inch, the pressure equalizing plate 36 comprises steel having a thickness on the order of 0.250 inch, the resilient strip 35 comprises neoprene (having a plurality of holes therein to permit material expansion) having an initial thickness of 0.375 inch and a compressed thickness of 0.325 inch due to the force applied thereto by the pressure equalizing plate 36. The knife blade 34 and the platen roller 42 preferably are formed of a machinable, hard material having a surface hardness on the order of at least 60 on the Rockwell C scale. As previously mentioned, the steel alloy known as 8620 is well suited for this purpose.

The flailing fingers 37 are formed of a resilient material such as phosphor bronze or hardened beryllium copper, and may typically have a thickness on the order of 0.005 inch and a width on the order of 0.5 inch, the edge 43 of the cutting roller portion 25 being relieved adjacent the flailing fingers 37.

The set screws 38 are preferably adjusted so that the prestress force applied to the enlarged head portion 40 of the web cutting knife blade 34 by way of the neoprene strip 35, is on the order of 300 pounds per inch of knife length. The length of the knife blade 34 and the configuration of the T-shaped slot 33 are so selected that the cutting edge 44 of the knife blade 34 protrudes beyond the periphery of the cutting roller 23 by a distance b on the order of 0.037 inch.

The cutting roller 23 is disposed in juxtaposition with the platen roller 42, both rollers being cylindrical and rotatably mounted on parallel shafts, the distance between the rollers being such that the "interference" a between the cutting edge 44 of the knife blade 34 and the adjacent periphery of the platen roller 42 is on the order of 0.005 inch.

Typically, the flailing fingers 37 may protrude from the periphery of the cutting roller 23 by a distance on the order of 0.093 inch.

A web guide plate 45 is provided to receive the cut portion of the paper or other web 46 after the cut portion is severed from the remainder of the web. In order to provide clearance for the knife blade 34, the web guide plate 45 must necessarily be spaced from the periphery of the cutting roller 23 by a distance c somewhat greater than the protrusion b of the cutting edge 44 of the knife blade 34.

In order to cut the web 46, the cutting roller 23 is rotated in the direction indicated by the arrow 47, the web 46 being severed when the cutting edge 44 of the knife blade 34 engages the periphery of the platen wheel 42, which rotates in the direction indicated by the arrow 48. The drive mechanism of the cutting roller 23 is so arranged that the roller makes a single rotation for each desired cut of the web 46, the cutting roller 23 being maintained in a predetermined angular orientation wherein the knife blade 34 is not in engagement with the platen roller 42 during the period between cuts of the web 46.

Thus a cut can be made at any desired time, and variable length cuts can be made by operating the cutting roller 23 under the supervision of a suitable control system. The minimum length that can be cut when the paper is continuously in motion is determined by the circumference of the cutting roller 23.

As previously mentioned in conjunction with the web cutter shown in FIG. 1, the prestress force applied to the knife blade 34 reduces stresses in the blade, reduces the instantaneous peak torque to which the drive mechanism of the cutting roller 23 is subjected (thereby reducing wear on the drive mechanism), and reduces vibration of the knife blade 34, thus prolonging blade life and reducing acoustical noise.

In addition, the constant cutting force provides clean cuts of uniform quality of the web 46.

It has been found that there is a tendency for the cut portion of the web 46 (which travels in the direction indicated by the arrow 49) to wrap around the periphery of the cutting roller 23, and thus bind within the space 50 between the edge of the guide plate 45 and the adjacent periphery of the cutting roller 23.

In order to prevent such binding of the cut portion of the web 46, the flailing fingers 37 are provided. As the knife blade 34 engages the platen roller 42 to cut the web 46, the flailing fingers 37 follow, and are bent back to the position indicated by the dashed line 51, by interaction with the periphery of the platen roller 42. After the flailing fingers 37 traverse the platen roller 42, they spring back to their initial positions, pushing the leading edge of the uncut portion of the web 46 away from the periphery of the cutting roller 23, and preventing binding of said leading edge in the space 50.

Suitable slots 52 (see FIG. 3) are provided in the edge of the web guide plate 45 adjacent the periphery of the cutting roller 23, in order to allow passage of the flailing fingers 37.

Claims

I claim:

1. A web cutter, comprising:

first and second cylindrical rollers mounted for rotation about mutually parallel axes,

said first roller having a T-shaped longitudinal slot therein, said slot having a relatively narrow portion extending to the periphery of said first roller, a relatively wide portion adjacent said relatively narrow portion, and a shoulder portion providing the transition between said relatively narrow and relatively wide portions;

an elongated T-shaped web cutting knife blade disposed in said slot, said blade having an enlarged head portion and a relatively narrow portion having a cutting edge disposed opposite said head portion,

the relatively narrow portion of said blade being disposed within the relatively narrow portion of said slot with the cutting edge of said blade protruding a predetermined distance beyond the periphery of said first roller,

the enlarged head portion of said blade being disposed in the relatively wide portion of said slot with the part of said head portion adjacent to and extending beyond the relatively narrow portion of said blade abutting against the shoulder portion of said slot;

an elongated relatively compliant strip of resilient material having a given initial thickness disposed within the relatively wide portion of said T-shaped slot in contact with the enlarged head portion of said knife blade;

a relatively rigid elongated load equalizing strip disposed within the relatively wide portion of said T-shaped slot in contact with said resilient strip;

said first roller having a plurality of threaded holes therein disposed opposite said knife blade and communicating with the relatively wide portion of said slot;

a corresponding plurality of set screws threadably mounted in said holes and abutting said load equalizing strip to urge said load equalizing strip toward the enlarged head portion of said knife blade, thereby compressing said resilient strip and prestressing said knife blade,

the force exerted by said set screws and load equalizing strip on said resilient strip being sufficient to reduce the thickness of said resilient strip from said given initial thickness to a second prestress thickness, the difference between said thicknesses having a desired value;

said rollers being disposed in juxtaposition with the peripheries thereof being spaced apart by a given distance slightly less than said predetermined distance, so that said blade is deflected a given distance into said slot upon engagement of said cutting edge with the periphery of said second roller, thus further compressing said resilient strip between the enlarged head of said knife blade and said load equalizing strip by an additional amount equal to the inward deflection of said blade,

the additional compression of said resilient strip, i.e., said given distance, being substantially less than the initial compression thereof, i.e., said desired value, so that substantial force is required to initially deflect said blade upon engagement of said cutting edge with the periphery of said second roller, the force between said cutting edge and said second roller being substantially constant during the engagement thereof; and

means for rotating said first roller to bring said cutting edge into engagement with a web disposed between said rollers and the periphery of said second roller to sever said web.

2. The web cutter according to claim 1, wherein the surface hardness of said knife blade and said second roller has a value on the order of at least 60 on the Rockwell C scale.

3. The web cutter according to claim 1, further including a plurality of resilient flailing fingers on said first roller adjacent said blade, said fingers extending beyond said cutting edge to deflect the leading edge of the uncut portion of said web away from said first roller after said web has been severed.

4. The web cutter according to claim 3, wherein said flailing fingers are disposed in said slot.