Severing by tearing or breaking – Methods – With preliminary weakening
Reexamination Certificate
1998-08-13
2002-05-28
Vo, Peter (Department: 3729)
Severing by tearing or breaking
Methods
With preliminary weakening
C225S003000, C225S096000, C083S649000, C083S023000, C083S027000
Reexamination Certificate
active
06394330
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to web processing apparatus and methods for slitting a wide web of material into plural web portions and subsequently winding the web portions into separate rolls. In particular, the web material is initially slit while leaving connections between the web portions and breaking the connections prior to winding.
BACKGROUND OF THE INVENTION
In some situations, it is desirable to split a single, relatively wide web of material into a plurality of relatively narrow web portions and wind the web portions into several rolls (or otherwise convert the web portions into use supply forms). It is generally more efficient to produce and/or process material in wider webs but often more convenient to package, ship, sell, and/or use the material in narrower rolls. Also, the narrower web portions are preferred or required for some applications. Common examples of web materials that are often split into web portions include paper (for example, toilet paper, computer paper, paper towels, etc.) and tape (for example, adhesive tape, magnetic tape, etc.). Slitting can be done on single webs (for example, films), structured webs (for example, webs with structured features), multilayer laminates, or coated webs (for example, adhesive coated webs for making adhesive tape).
A plurality of web portions can be formed from a web by slitting (or otherwise cutting) the web in the lengthwise direction so that the individual web portions are separated from one another. U.S. Pat. No. 3,695,131 issued to Zimmermann relates to one such approach wherein a web is carried by a traveling support surface across razor sharp cutting edges of circular slitting blades, wherein the web is held on the traveling support to reduce longitudinal or transverse shifting of the web portions. The slitter blades are rotated so as to distribute wear uniformly about the circumferences of the slitter blades. After slitting, the various web portions are directionally separated by directing adjacent web portions through different guide means that thread the web portions to different winding reels.
U.S. Pat. No. 2,897,893 issued to Rockstrom et al. relates to another slitting mechanism in which a continuous web of material is taken from a mill roll and passed over a compensating roll in a rewind machine and under a cutter roll against which the web is slit into web portions before winding into a rewind roll. Slitting wheels bear against a hardened sleeve of the cutter roll at any desired position along the sleeve and they bear with sufficient pressure to sever the web into web portions. The slitting wheels are softer than the hardened sleeve and, although preferably not given a sharp edge, they divide the web. Immediately after the web is cut by the slitting wheels, an angular-faced spreader having a vertical, forward-extending center with backswept sides bears against the web with the forward center of the spreader bearing on the line of the cut to push the web portions apart and to assure their complete separation along the cutting line. U.S. Pat. No. 1,465,967 issued to Cameron et al. relates to a somewhat similar slitting and rewinding machine that also includes a secondary separating device having a knife blade for severing any stray fibers connecting adjacent web portions that have not been severed by the slitting action. The secondary separating device severs the stray fibers after slitting and before winding of the web portions.
After the plural web portions are split and separated, they typically pass individually through guiding and tensioning rollers and then are ultimately wound about a core to form a roll of web material. Each web portion may be individually guided to a distinct core, or plural cores can be supported in axial alignment on a single shaft. Often, adjacent web portions are divided to different winding shafts supporting such plural cores so that they can be guided without interfering with one another. Alternatively, the plural web portions can ultimately be folded, cut, or otherwise processed to form a stack (or other form) of web material. The roll or stack of web material is the use supply form that is used by the consumer of the web portions. To process the split, separated web portions to create use supply forms, each web portion must be individually guided, which requires accurate control to prevent each web portion from wandering. Tension control is an important aspect of web guiding, and web properties (such as the thickness of the web across the web) can cause slight variations in guiding and tensioning each web portion. Variations in guiding and tensioning can cause the web portions to wander and be wound with uneven edges and, where several rolls are wound side by side about a common winding shaft, to be wound with overlapping and interweaved edges that cause the several rolls to become intermeshed.
It is also known to perforate web or web portions prior to forming the use supply forms in order to provide a perforation or tear line so that someone or something provided with the web material in use supply form can split the web material by tearing along the perforations. The perforation or tear line is formed by cutting a plurality of small, spaced slits in the web material. The connections of the web material that remain between the slits maintain the structural integrity of the web material until the connections are torn to further separate the web or web portion along the perforation line. A number of different configurations of perforations lines have been developed.
Perforations can be created in the machine direction of a web or web portion by a perforating wheel having a beveled cutting edge in which one or more notches are formed at angularly spaced intervals so as to define cutting and non-cutting portions of the cutting edge. Typically, several perforating wheels are spaced and rotatably mounted along a bar so that the perforating wheels tangentially contact the outer surface of a back-pressure roll, which is rotated by a motor or the like. The rotation of the back-pressure roll causes the perforating wheels to rotate. The web is run between the perforating wheel and the back-pressure roll and, as the perforating wheels rotate and the cutting portions of the cutting edges come into contact with the web, the cutting portions of the cutting edges penetrate and cut the web to form the perforations. When the perforating wheels further rotate and the non-cutting portions move over the web, the notches formed in the cutting edges prevent the web from being cut, which forms the connections in the perforation line. A perforating wheel of this general type is disclosed in U.S. Pat. No. 3,978,753 issued to Meaden et al. Thus, perforations can be provided in the longitudinal direction so as to define two or more connected web subportions that are wound or stacked into the use supply form.
Perforations can be provided across the transverse width of the web or web portion so as to define individual sheets of the web material. Examples include paper towels and toilet paper, which are typically perforated so that individual sheets can be separated from the roll by the consumer. Many techniques have been developed to make transverse perforation as a web is moved in a machine direction. Most rely on a perforating roll that creates the perforation lines at spaced intervals on the web based upon a notched cutting edge extended transversely on the roll. Whether longitudinally or transversely perforated, such connected web subportions are designed to be separated by a consumer as the web material is converted from its use supply form.
One noteworthy application of perforations in web or web strands is in continuous paper of the type commonly used in computer printers, especially contact or dot matrix type computer printers. Continuous paper of this type is commonly sold as a stack or roll of paper having rows of perforations across the width of the paper. The spacing of the these rows determines the length of the page. Typically, the paper is folded along th
3M Innovative Properties Company
Bond William J.
Griswold Gary L.
Sprague Robert W.
Trinh Minh
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