Cutting – With means to deform work temporarily
Reexamination Certificate
1999-10-06
2001-05-08
Rachuba, M. (Department: 3724)
Cutting
With means to deform work temporarily
C083S402000, C083S471000, C083S477000, C493S025000, C162S286000, C162S363000
Reexamination Certificate
active
06227089
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a method and apparatus for penetrating a sheet material web, and in particular, to a method and apparatus for penetrating a sheet material web, such as by slitting, cutting, puncturing or perforating, while the web is being carried on a fabric.
It is well known in the field of paper making, and particularly in the field of manufacturing tissue products such as facial tissues, bath tissues and paper towels, to provide an apparatus for longitudinally slitting a continuous running sheet material web into two or more strips. Typically, the sheet material web is slit either as it traverses an “open draw” before being wound into rolls, before it is dried or after it is wound onto the roll. In the first instance, the area of open draw, where the dried sheet is momentarily unsupported before being wound, provides an ideal place to slit the web. In particular, the slitting device, often configured as a rotary saw blade, can be applied to the web without concern about cutting or otherwise damaging an underlying fabric, which otherwise carries the sheet material web throughout the forming process. Fabrics of this nature can be expensive and difficult to replace.
However, as described in U.S. Pat. No. 5,591,309, issued Jan. 7, 1997 to Rugowski et al., and assigned to Kimberly-Clark Corporation, the same assignee as the present application, open draws are a frequent source of sheet breaks and associated production delays. As a result, tissue sheets often are designed to have high machine direction strengths in order to remain intact as they are pulled through the open draw. However, high machine direction strengths can adversely affect the quality of the web in terms of its desired softness. Therefore, as explained in U.S. Pat. No. 5,591,309, the elimination of open draws in tissue manufacturing can result in a sheet material being made more efficiently at less cost and with more desirable properties.
When the open draw is eliminated, the sheet material web is typically slit using a water jet prior to drying the web. However, such “wet slitting” can result in a degradation of the throughdrying fabric as it is exposed to hot air passing through the slit in the sheet material during the drying stage of the process. Moreover, the slit edges of the sheet material web may not dry evenly due to the pile up of fibers along the slit. Additionally, when the sheet material web is slit prior to drying, the various strips of sheet material web are difficult to control and can become inadvertently interwoven, or overlapped, as they are further carried towards the wind-up reel. Interwoven strips can be more easily damaged and can make the winding process particularly difficult. Moreover, adjacent rolls having interwoven webs can be particularly difficult to separate. Accordingly, the strips of sheet material web are typically required to be spread apart so as to prevent interweaving.
In contrast to slitting the web prior to drying, it is also known in the art to slit the sheet material web as it is wound onto the roll, as mentioned above. Slitting apparatuses of this nature typically apply a pressure or guide roller, or like device, to the outermost surface of the roll so as to thereby control the penetration of the slitting device. However, facial and bath tissues typically have low densities. Accordingly, it usually is not desirable, or even possible, to allow such a guide roller to contact the roll as it builds so as to thereby control the position of the slitter, and the penetration thereof Moreover, the various strips are necessarily wound onto the same roll and must be rewound onto separate rolls after slitting in another manufacturing step if desired.
Alternatively, the sheet material web can be carried on two or more belts aligned side-by-side, wherein a slitting blade protrudes through the gap between the belts. The sheet material web can become caught or torn in the gap, however, and it is not possible to change the lateral position of the slitting device without reconfiguring the belts, which can be very expensive and time consuming. Moreover, the control of the belts, and the alignment thereof, can be difficult to maintain.
SUMMARY OF THE INVENTION
Briefly stated, the invention is directed to an apparatus for penetrating a sheet material web, such as by slitting, cutting, puncturing or perforating, while being carried on a fabric. In a preferred embodiment, the apparatus includes a penetrating device positioned above the fabric and an air flow, which is applied to a portion of the sheet material web adjacent the penetrating device so as to separate the web from the fabric and thereby bring the web into contact with the penetrating device above the fabric.
In a preferred embodiment, the apparatus includes a housing disposed around a slitting member, preferably configured as a rotary saw blade. The housing preferably includes a shoe member attached to a bottom of the housing and having an opening forming a mouth of the housing which opens towards the sheet material web carried on the fabric. The shoe member preferably includes a rearwardly facing nose portion shaped to strip the boundary layer of air from the sheet material web as it passes beneath the housing. Preferably, a curved plate is mounted to the shoe member at the mouth of the housing. The plate has a plurality of apertures and a slot formed therein. A vacuum is connected to the housing to apply an air flow such that a portion of the sheet material web is separated from the fabric at the mouth of the housing and thereby brought into contact with the slitting member.
In an alternative embodiment, an air hose is provided below the fabric. The air hose applies a pressurized air stream to a portion of the bottom of the web so as to lift it off of the fabric and into contact with the penetrating device, preferably including a slitting member. The air hose is used with air permeable fabrics, while the vacuum is employed with impermeable fabrics. Alternatively, the air hose can be used in combination with the vacuum so as to obtain the desired separation of the sheet material web when used with an air permeable fabric.
In one aspect of the invention, a sensor is provided below the fabric. The sensor monitors the position of the fabric and signals the retraction or stoppage of the penetrating device if the fabric inadvertently approaches the penetrating device. Preferably, the penetrating device is made height adjustable so as to allow the distance between the blade and fabric to be automatically adjusted according to the input from the sensor.
In yet another aspect, a method is provided for penetrating the sheet material web carried on the fabric. The method includes carrying the sheet material web on a fabric in a longitudinal direction, applying either a vacuum or a pressurized air stream, or both, to the sheet material web so as to separate at least a portion of the web from the fabric, penetrating the sheet material web as it is separated from the fabric and reapplying the separated portion of the sheet material web to the fabric.
The present invention provides significant advantages over other slitting or penetrating devices. Importantly, the apparatus allows for slitting the sheet material web while it is being carried by a fabric prior to winding the web onto rolls. In this way, the open draw of the forming process can be eliminated so as to reduce waste and costs, but without having to slit the sheet material web prior to the drying process, wherein the problems of fabric degradation, fiber build-up at the slit edges and loss of sheet control can be encountered. Moreover, since the apparatus can be positioned relatively close to the winding reel, as opposed to wet slitting, which is typically performed up stream in the process, the problem of interweaving can be greatly reduced.
In addition, the present invention provides an improved method and apparatus for slitting the sheet material web prior to winding the web onto rolls. In this way, the various strips of s
Hada Frank S.
Thoms Lowell E.
Brinks Hofer Gilson & Lione
Kimberly--Clark Worldwide, Inc.
Rachuba M.
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