HK40003675A - Stress balancing mount for a knife on a cutter roll in a web processing machine - Google Patents

Description

Stress-balancing seat for tools on cutter rolls in web-processing machines

Technical Field

The present invention relates to machines for converting large rolls (bulk rolls) of web material (web material) into smaller rolls suitable for consumers, commonly known as rewinders, and more particularly to an improved mounting arrangement of a web cutting device for cutting or perforating the web in such a rewinder.

Background

Continuous webs of fabric, paper and the like are typically severed by feeding the web through a cutting apparatus having at least one rotating roll carrying one or more knives engageable with an anvil (anvil) secured or mounted to the opposite roll. The continuous web is fed along a conveying means, passing between a knife roll and an anvil, where it can be cut into a number of sections or perforations. The cutting section or the perforated web is conveyed away from the cutting device. By changing the knife and the interface with the anvil, the web can be perforated using a similar roll arrangement rather than cut. U.S. patent numbers 5,363,728 and 8,540,181 show roll-to-roll machines (rolls) of the type on which the present invention can be used.

The thickness of most webs requires precise control of the spacing between the knife and the anvil. Insufficient space can result in severing the web when perforation is desired and increase the rate of edge degradation. Too much space can result in the web not being cut or perforated by the knives. Large rolls of web material can be up to 6 feet wide, requiring a rotating knife to span the width of the roll. Maintaining a separation tolerance of approximately 0.0005 inches between the knife and anvil on a roll that can span 6 feet requires that the knife roll be robust and the connection between the knife and the roll be stable, but allow the knife to be removed to be sharp with reasonable ease. Furthermore, any deflection in the roll will result in a non-uniform cutting behaviour across the width of the web.

Web speeds in modern rewinding machines can approach 700 feet per minute. The rolls in the web path can thus be subjected to correspondingly high rotational speeds, which generate heat in the bearings and the connection to the machine structure. As the rewinding machine continues to operate, thermal expansion can affect the spatial relationship of critical interfaces in the machine, including the knife-anvil interface and the roll centerline of the cutter roll device, which results in inconsistent performance of the rotary cutting apparatus.

Disclosure of Invention

Accordingly, the present invention, in any of the embodiments described herein, may provide one or more of the following advantages:

it is an object of the present invention to provide an improved cutting device for a web converting machine that maintains the spatial tolerance between the knife and the anvil in the cutting device when the machine experiences thermal expansion. The cutting device includes a cutter roll having a knife attached thereto, the cutter roll being rotatably mounted to the machine by bearings disposed on opposite ends of the roll supported by bearing blocks connected to the machine so that the cutter roll spans the width of the web. The connection with the bearing support of the machine is oriented to manage thermal growth therein to an axis substantially parallel to the direction of travel of the moving web.

It is another object of the present invention to provide an improved rotary cutting apparatus for a web converting machine that maintains the spatial tolerances between the knife and anvil in the cutting apparatus by minimizing stress induced deflection in the knife roll. The rotary cutting apparatus comprises a roll having at least one cutter attached thereto, typically helically, and the roll is rotatably mounted to the machine by bearings disposed on opposite ends of the roll and supported by bearing housings connected to the machine. In a coil with a single cutter, the stresses caused by the slightly screw-mounted connection connecting the generally planar cutter to the coil can cause the coil to deviate slightly from its axis of rotation. To counteract these stresses, a second knife position is provided that is symmetrically positioned about the first knife, and a second knife without a cutting edge (cutting edge) is mounted to produce symmetrical stresses in the roll, thereby minimizing any deflection in the roll.

It is yet another object of the present invention to provide an improved rotary cutting apparatus for a web converting machine that maintains the spatial tolerances between the knife and anvil in the cutting apparatus by managing the heat and stress induced deflection in the rotary cutting apparatus, which is durable in construction, inexpensive to manufacture, convenient to maintain, easy to assemble, and simple and effective to use.

These and other objects are achieved according to the present invention by providing a rotary cutting apparatus comprising a roll having at least one cutter attached thereto, the roll being rotatably mounted to a machine by bearings disposed on opposite ends of the roll and supported by bearing housings connected to the machine. A thermal isolator is disposed between the bearing block and the machine to inhibit heat transfer from the bearing into the machine structure, and the bearing block is oriented so that thermal growth in the seat is aligned perpendicular to the plane in which the cutter and anvil are interfaced. The coil is further provided with at least two tool mounting locations symmetrically arranged on the coil so as to balance the stresses caused by the connection of the tool to the coil and thus not to cause asymmetric deflection of the coil.

Drawings

The advantages of the present invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings, wherein:

fig. 1 shows a conventional web cutting apparatus on which the present invention may be used;

FIG. 2 shows the web cutting apparatus of FIG. 1 with the present invention shown incorporated therein;

fig. 3 is a plan view of the web cutting device of fig. 2;

FIG. 4 is an elevational view of the web cutting apparatus of FIG. 3;

FIG. 5 is a cross-sectional view of the web cutting apparatus of FIG. 4 taken along cut line 5-5; and

FIG. 6 is a second view of FIG. 5 showing thermal displacement and effect on knife alignment in a reel cutter seat in the present invention;

FIG. 7 is a partial elevational view of the prior art web cutting apparatus of FIG. 1, showing stress induced deflection in the cutter roll that may occur without the present invention; and

figures 8 and 9 illustrate the effect of the present invention on cutter roll deflection and on the quality of the slitter perforation.

Detailed Description

Many of the fastening, connecting, handling and other devices and means used in the present invention are widely known and used in the field of the described invention, and their exact nature or type is not essential to understanding and using the present invention by those skilled in the art, and therefore they will not be discussed in great detail. Additionally, any references herein to the terms "upper" or "lower" or "top" or "bottom" are used for convenience only and are intended to identify that the machine will typically rest on a horizontal surface. Moreover, the various components shown or described herein for any particular application of the present invention may be varied or modified as envisioned by the present invention, and the implementation of a particular application of any element is widely known or used in the art by those skilled in the art, and each is therefore likewise not discussed in great detail. When referring to the drawings, like parts are numbered the same throughout the figures.

Referring to fig. 1 and 2, a web cutting apparatus 10 of the type commonly used in roll-to-roll machines is shown, wherein the continuous web 5 is moved to the web cutting apparatus 10, severed or perforated by interaction with a knife 30 on the reel knife 20, and removed from the cutting apparatus 10 (if severed) by a discharge conveyor. A conventional frame 100 is provided for rotatably supporting the cutting means and suitable device(s) 105 for rotating the slitting reel 20 at the speed required to cut/perforate the web to a sheet of desired length. The reel knife 20 is supported at its opposite ends by bearings (not shown) to allow the reel knife to rotate about a reel axis 200 that is substantially transverse to the web 5. The bearings are connected to the frame 100 of the roll converting machine by bearing support blocks 40 and are supported by the frame 100. The cutting anvil 50 is also connected to the frame 100 of the reel change machine, preferably sharing a common anchor with the bearing support block 40 to preclude relative movement between the cutting anvil 50 and the reel knife 20 during operation. Alternatively, the anvil 50 may comprise a roll similar to a roll cutter having a peripherally disposed anvil surface that interacts with the knife as the adjacent roll rotates, with the rotations synchronized to allow knife and anvil interaction.

The winding knife 20 and the cutting anvil 50 extend at least the width of the web 5. In practice, web widths in the range of 36 to 72 inches are common.

The desired production rates in modern web converting machines require web travel speeds ranging from 200 to 700 feet per minute. The upward pressure for production efficiency improvement has driven the development of machines using higher web speeds. As web speeds increase, increased heat generation in bearings and other frictional interfaces occurs.

Maintaining tight spatial tolerances in the gap between the knife 30 and the anvil 50 of the web cutting device 10 is essential for high production efficiency, especially for perforation of the web. The web converting machine 10 may be required to handle web thicknesses ranging from 0.005 to 0.100 inches. This gap "G" (see fig. 5 and 6) must be maintained within close tolerances throughout the operating temperature range of the machine because movement on the order of the thickness of the web being processed will adversely affect the slitter performance.

Thermal displacement in the frame 100 caused by heat transfer from the slitter bearings may cause the slitter centerline 200 to move away from the anvil 50 (as shown by arrow "a" in fig. 1), causing the gap G (best shown in fig. 5 and 6) to increase. This is illustrated in fig. 1, where thermal expansion of the bearing support block 40 displaces the roller centerline upward, opening up the gap spacing between the knife 30 and the anvil 50. The first aspect of the present invention solves this problem shown in fig. 2 by reorienting the connection interface 101 between the bearing support block 40 and the frame 100 to be substantially perpendicular to the web passing tangentially through the knife roll. The orientation of the bearing block seat causes thermal expansion in the bearing support block, causing displacement of the slitter centerline 200 primarily along an axis generally parallel to the web (shown as arrow "B" in fig. 2). Note that, as best shown in fig. 5 and 6, the axis parallel to the web 5 is also substantially perpendicular to the cutting plane 120, in which cutting plane 120 the knife 30 and anvil 50 interact. The cutting plane 120 is defined by the edge of the anvil 50 and the slitter centerline 200, and thus may vary slightly from perpendicular to the web. The thermal effect therefore does not greatly change the vertical spacing between the anvil and the reel knife centerline, but simply causes the cutting plane 120 to be slightly angled as thermal expansion occurs.

Further limitation of the knife positioning and thermally induced effects on the gap G is provided by incorporating thermal insulation 60 between the bearing support block 40 and the frame 100 to limit heat transfer from the support block 40 to the machine frame 100, which could otherwise result in thermal expansion of the frame components along an axis perpendicular to the web feed path.

In fig. 5, the edges of the knife 30 and anvil 50 are aligned on the cutting plane 120, creating a clean cut or perforation. Fig. 6 illustrates the thermal movement of the roll cutting centerline 200 due to thermal expansion of the support block 40. Although shown exaggerated for purposes of illustration, due to thermal expansion, move (T)₂-T₁) Which may be about 0.001 to 0.005 inches, rather than directly increasing the gap between the knife 30 and anvil 50, the movement causes the cutting plane 120 to be slightly angled relative to the web while minimizing the effect on the vertical spacing between the knife 30 and anvil 50. The altered orientation of the main axis of thermal growth reduces the adverse effect on the cut quality due to thermal growth. The initial orientation of the cutting plane 120 may also be adjusted so that the knife 30 and anvil 50 are aligned on a preferred vertical cutting plane when the machine is at operating temperature so that a greater proportion of the web cut may be at optimum conditions.

The thermal isolator 60 is preferably constructed of a material that is thermally stable and has a low thermal conductivity, is significantly lower, and preferably reduced by one or more orders of magnitude, than the ferrous material comprising the frame and bearing blocks. In one embodiment, thermal insulator 60 is made of mica, which has a thermal conductivity about two orders of magnitude lower than iron or steel, which has proven acceptable results.

In addition to generally stabilizing the relative position between the knife and anvil, a second aspect of the invention is directed to improving the spatial relationship between the knife 30 and anvil 50 along the extent of their transverse span across the web. Fig. 7 shows a cutter roll 20 equipped with only a single knife 30, a preferred cutter roll arrangement, in which the web is cut or perforated with each revolution of the cutter roll. The rotational speed of the knife is determined based on the desired sheet length or the desired perforation spacing so that the knife interfaces with the web at the desired spacing interval. For example, if a one foot web length is desired and the web travels at 500 feet per minute, the knife roll needs to be rotated at 500rpm to achieve the desired sheet length. The knife roll must be dimensioned so that the peripheral speed is greater than the web speed, preferably at least 15% greater.

The preferred knife arrangement on the knife roll aligns the knives on a slight spiral of the knife roll so that the knives and anvil interact to produce a "scissor-type" web shear. The knife is typically formed from a flat metal blank, which must then be twisted when attached to the knife roll. The stress caused by attaching a cutter formed from a two inch wide strip of quarter inch thick plate to a helical seat on the cutter roll is significant and results in bending of the cutter roll.

The individual knives 30 are secured to the cutter drum using a connector arrangement 70, which connector arrangement 70 includes a plurality of fasteners 72 that are evenly spaced along the knife-cutter drum interface for substantially the entire length of the cutter drum to create a secure connection of the knives to the roll. The fasteners 72 are preferably positioned at a spacing of about two to three inches for the entire width of the slitting reel 20. Multiple fasteners (e.g., pairs) may be used at each lateral position. As a result, the fasteners 72 can easily amount to eight or more for every twelve inches of cutter roll width. The stresses caused by bending the cutter to secure it to the cutter roll 20 result in an imbalance of static mechanical stresses in the cutter roll that can cause a slight deflection from its roll centerline 200. Cutter roll deflection caused by cutter mounting stresses may recombine as cutter roll temperature increases during operation.

Any deflection may cause the edge (edge)32 of the knife 30 to bend slightly from the straight interface with the anvil 50, which is typically greatest at mid-span of the cutter roller. Even though the maximum displacement may be only about a few thousandths of an inch, the result is that the web is not cut or perforated sufficiently by the knives, usually in the middle of the web width, where the knife edges will be closer to the anvil than desired, and contact between the knife edges and the anvil may result, which may damage the knives. This is best shown in fig. 8, where the peripheral path 150A defined by the knife edge 32 is shown on the cutter drum, which is deflected by the mounting of the knife 30. Instead of the desired cylindrical profile, an eccentricity may be introduced in the cutter roll, displacing the perimetral path 150 further away from the roll axis 200 at the midspan of the cutter roll than at displacements closer to the bearing support ends. In extreme cases, the blade 32 may even contact the anvil 50. More commonly, the eccentricity causes the knife edge to move away from the anvil in a mid-span position of the cutter roller, best shown as gap "P" in fig. 7. In this case, the edge displacement may even result in the cutter not being able to contact the web at mid-span.

As best shown in fig. 5 and 6, the second aspect of the present invention addresses this deficiency by attaching a stress-balancing member 35 on the cutter drum 20 diametrically opposite the knife 30. The cutter drum 20 is configured such that the cutter 30 and the stress-balancing member 35 are in a physically and dimensionally symmetric configuration about the roll axis 200. Without attachment, the symmetrical cutter roll is balanced to minimize deflection when rotating. Basically, the stress-equalizing member 35 is a knife without a cutting edge, so that it does not interact with the web when positioned in the vicinity of the web. The stress-balancing component 35 is similar in physical construction (e.g., mass, size) to the cutter 30, except that it does not have a cutting edge 32 to maintain the rotational balance of the cutter roller. The symmetrical positioning of the stress-balancing member 35, the similarity in physical configuration, and the use of the same connector arrangement 70 to attach the cutter 30 to the cutter roll rotationally balances the cutter roll, and also balances the static stress imposed on the cutter roll through the connection of the cutter and balancing member to minimize stress-induced deflection (eccentricity) of the peripheral path 150B of the cutter roll 20, resulting in minimal variation in the spacing between the blade edge 32 and the spool wire 200 along the length of the cutter roll. This is best shown in fig. 9, which shows a generally cylindrical peripheral path 150B that results in a uniform spacing "S" along the entire length of the cutter 30. This improvement still exists when the cutter roll reaches operating temperature. The result is a more uniform cutting interaction between the knife 30 and the anvil 50 across the width of the web.

Naturally, the invention is not limited to the embodiments described above, but it can also be modified in many ways without departing from the basic idea. Variations in the details, materials, steps, and arrangements of parts, which have been described and illustrated in order to explain the nature of this invention, may be conceived and made by those skilled in the art upon reading this disclosure within the principles and scope of the present invention. The foregoing description illustrates preferred embodiments of the invention; however, concepts based on the description may be employed in other embodiments without departing from the scope of the invention.

Claims (8)

1. A web cutting roll for use in a web processing machine, comprising:

an elongated cutter roll disposed on a roll centerline and rotatably connected to the web handling machine and spanning the moving web;

a knife connected to the cutter roller by a first connector arrangement at a first location such that the knife rotates with the cutter roller to define a peripheral path in which lateral contact with the web occurs upon each revolution of the cutter roller; and

a stress-balancing member connected to the cutter drum in a position opposite the cutter about the drum centerline, the stress-balancing member being connected by a second connector arrangement, the first and second connector arrangements being substantially similar so that the static mechanical stresses imposed on the cutter drum by the connection of the cutter and the stress-balancing member are substantially the same, thereby balancing the static mechanical stresses in the cutter drum.

2. The web cutting roll of claim 1, wherein the cutter roll is symmetrically configured about the roll centerline.

3. Web cutting roll according to claim 2, characterized in that the knife and the stress-balancing member are substantially similar in dimensional configuration.

4. A web cutting roll according to claim 3, wherein the first connector arrangement and the second connector arrangement each comprise a plurality of fasteners uniformly spanning the length of the blade and the stress-balancing member.

5. In a web processing machine having a frame supporting a plurality of transverse rolls defining a feed path along which web material moves and across which web cutting means traverses the web, the web cutting means configured to perforate the web as it moves along the feed path, the improvement in the web cutting apparatus comprising:

an elongated cutter roll rotatably connected to the web-handling machine;

a knife connected by a first connector arrangement at a first location on the cutter roller such that the knife rotates with the cutter roller to define a generally cylindrical perimeter path in which lateral contact with the web occurs upon each revolution of the cutter roller; and

a stress-balancing member connected to the cutter roller diametrically opposite the cutter, the stress-balancing member connected by a second connector arrangement, the first and second connector arrangements being substantially similar to balance static mechanical stresses imposed on the cutter roller by the connection of the cutter and the stress-balancing member and to minimize eccentricity of the peripheral path as the cutter roller rotates.

6. The improvement of claim 5, wherein the cutter roller is symmetrically configured about the roller centerline.

7. The improvement of claim 6, wherein the cutter and the stress-balancing member are substantially identical in physical construction.

8. The improvement of claim 7, wherein the first and second connector arrangements each include a plurality of fasteners uniformly spanning the length of the cutter and the stress-balancing member.