Patent Application
20150298340
Rolled tissue products, as well as other rolled paper or nonwoven products, are typically perforated (“perfed”) in order to facilitate the tearing off of the desired length of product for the intended use in a neat and undamaged fashion. In tissue products, the perforations facilitate easy removal of the required number of sheets. The perforations are normally provided in transverse perforation lines across the roll width, which are uniformly spaced in the machine direction of the roll. The lines of perforations comprise alternating bonds and perfs which are of uniform length and spacing. The perfs are typically rectangular slits or round holes with transverse orientation.
Perforating devices are well known in the papermaking art and are incorporated into almost all bathroom tissue and towel winders as well as other converting equipment in a typical tissue manufacturing and converting plant. In the past, conventional devices typically comprised a perforator roll, which holds a number of perf blades, and a stationary anvil head.
In the converting process, a balance must be struck between having perforation lines that have sufficient bond strength to operate efficiently and without breaks on the converting equipment, and yet have low enough bond strength to provide easy and undamaged sheet detaching for the consumer. Nevertheless, in spite of efforts to achieve this proper balance, poor detaching has been the subject of various consumer complaints for rolled tissue products such as toilet tissue or kitchen towels.
The above problems become exacerbated when attempting to perforate thicker, heavier and multiple-ply tissue sheets. Thicker and heavier tissue sheets, for instance, are more difficult to perforate cleanly and efficiently. The tissue sheet tends to be grabbed by the perf blade or gets stuck in the perf blade which can create uneven perforations or tearing of the sheet.
In view of the above, a need exists for a new method and apparatus for perforating tissue sheets, especially thicker and heavier tissue sheets.
In general, the present disclosure is directed to an apparatus for perforating sheet materials, such as tissue sheets. In accordance with the present disclosure, the apparatus includes a perforation blade having specially shaped teeth. The specially designed perforation blade prevents snagging and picking of the sheet. Of particular advantage, the blade of the present disclosure has also been found to work well when installed in a stationary position as will be described in greater detail below.
The apparatus of the present disclosure is for perforating continuous sheet materials. The apparatus comprises an anvil and a perforation blade. In one embodiment, the perforation blade may rotate to strike the anvil. In an alternative embodiment, however, the anvil may rotate and strike the perforation blade. In this embodiment, the perforation blade remains stationary. Having the perforation blade be stationary in the apparatus can provide various advantages. For instance, the blade can easily be replaced, minimizing downtime of the process. Alternatively, the stationary member can have multiple blades installed requiring just a turn of the member to a new blade for a grade change to a different perforation pattern. It is generally more difficult, however, to perforate sheet materials cleanly and efficiently with a stationary blade. The blade design of the present disclosure, however, overcomes problems experienced in the past.
In accordance with the present disclosure, the perforation blade comprises a blade member that has a length along a longitudinal axis and terminates along an edge. The edge defines a plurality of teeth configured to contact a sheet material and form perforations. Each tooth includes a sheet contacting surface having a width for creating more than a point contact with a sheet material. Each tooth can include two opposing side walls located on opposite sides of the sheet contacting surface.
The teeth are spaced apart along the edge of the perforation blade and are separated by recesses. Each recess is bordered by two side walls of two adjacent teeth. Each recess has a width along the edge of the blade member and a depth that extends along the bordering side walls. In accordance with the present disclosure, each side wall within each recess is at a non-zero angle in relation to the longitudinal axis.
In one embodiment, for instance, the non-zero angles are all equivalent in relation to the longitudinal axis. The side walls can all extend in the same direction and be parallel to each other. In an alternative embodiment, the side walls may extend in divergent directions. For instance, a first group of side walls may extend in a first direction and be parallel with each other. A second group of side walls may extend in a different direction and be parallel with each other. In one embodiment, the recesses have a V-shape.
In one embodiment, the non-zero angle of the side walls can be from about 2° to about 40°, such as from about 5° to about 20°. All of the recesses on the perforation blade can have substantially the same shape. Further, all of the teeth can have substantially the same width so as to produce uniform perforations.
In one embodiment, each tooth includes a pair of opposing faces separated by the two opposing side walls. At least one of the faces includes a chamfer that extends along a portion of the recess and terminates at the edge of the perforation blade.
Other features and aspects of the present disclosure are discussed in greater detail below.
A full and enabling disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.
It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present disclosure.
In general, the present disclosure is directed to an apparatus for perforating sheet materials and to a process for perforating sheet materials. More particularly, the present disclosure is directed to a specially designed perforation blade. The perforation blade includes a plurality of teeth. In accordance with the present disclosure, each tooth includes at least one angled side wall.
In the past, perforation blades typically included teeth with straight side walls. Angled side walls as taught according to the present disclosure, however can provide various advantages and benefits. The perforation blade of the present disclosure, for instance, has been found to perforate sheet materials more cleanly and efficiently than conventional perforation blades. Perforation blades according to the present disclosure also inhibit or prevent snagging or picking of the sheet material during the perforation process. Ultimately, due to less snagging and picking of the sheet, the perforation process can occur with less strength degradation or variability and at increased speeds.
In one embodiment, each tooth can be separated by a V-shaped recess area formed by two adjoining side walls. In this embodiment, each tooth has an expanding width as the tooth penetrates a sheet material. The expanding width of the tooth forms a perforation in the sheet material while further preventing the sheet material from being caught in the recess area of the blade.
As will be described in greater detail below, the perforation blades of the present disclosure are particularly well suited for use in systems where the perforation blade remains stationary and strikes against a moving anvil. It was discovered that the design of the perforation blade in accordance with the present disclosure allows for the blade to be used in a stationary position while still perforating sheet materials, including sheet materials that are thicker and have a heavier basis weight.
Sheet materials that may be perforated in accordance with the present disclosure can vary depending upon the particular application. The tissue product may have a single layer or may have a multi-layer construction. In one embodiment, the sheet material may comprise a tissue product. Tissue products that may be perforated in accordance with the present disclosure include facial tissues, bath tissues, paper towels, wipers, and the like.
In one embodiment, the sheet material may contain pulp fibers. Pulp fibers include natural cellulosic fiber sources such as softwood fibers, hardwood fibers, non-woody fibers, and mixtures thereof. In general, pulp fibers can be present in the sheet material in an amount of at least about 50% by weight, such as at least about 60% by weight, such as at least about 70% by weight, such as at least 80% by weight, such as at least 90% by weight, such as even 100% by weight. In addition to pulp fibers, the sheet material may contain other suitable fibers, such as synthetic fibers. Synthetic fibers include polymer fibers, such as polyester fibers, nylon fibers, or polyolefin fibers such as polypropylene fibers.
When perforating tissue products, the sheet material can have a relatively high bulk. For instance, the bulk of the sheet material can be greater than about 3 cc/g, such as greater than about 5 cc/g, such as greater than about 7 cc/g, such as greater than about 9 cc/g. In general, the bulk is less than about 20 cc/g, such as less than about 15 cc/g.
Especially when perforating tissue products, the basis weight of the sheet material can generally be greater than about 8 gsm, such as greater than about 10 gsm, such as greater than about 12 gsm. The basis weight is generally less than about 150 gsm, such as less than about 140 gsm, such as less than about 130 gsm, such as less than about 120 gsm, such as less than about 110 gsm, such as less than about 100 gsm, such as less than about 90 gsm. The present disclosure is particularly well suited to perforating thicker sheet materials and heavier sheet materials. In this regard, the present disclosure is well suited to perforating tissue products having a basis weight of greater than about 20 gsm, such as greater than about 25 gsm, such as greater than about 30 gsm. In one embodiment, for instance, the sheet material can have a basis weight of from about 20 gsm to about 100 gsm, such as from about 20 gsm to about 90 gsm. When perforating multi-ply tissue products, the basis weight can be calculated by adding together the basis weight of the different plies.
The manner in which the sheet material is formed can vary and is generally not critical to the present disclosure. For example, the sheet material, when comprised of a tissue product, may be formed through a wet lay process. In a wet lay process, the fiber furnish is combined with water to form an aqueous suspension. The aqueous suspension is then spread onto a wire or felt and dried to form the web. In one embodiment, the tissue web can be adhered to a creping surface and creped to the surface to form a creped web. Alternatively, an uncreped web may be formed, such as an uncreped, through-air dried web.
One embodiment of a perforated tissue web in accordance with the present disclosure is shown in
Referring to
As shown in
Referring to
The apparatus further includes a blade head 36 for holding a perforation blade 40 made in accordance with the present disclosure. The blade 40 includes an edge that defines a plurality of teeth 42. The perforation blade 40 is disposed adjacent to the anvil roll such that the teeth 42 interfere with the path of travel of the anvils 34 as the anvil roll 32 rotates. This interference can range from about 0.003 inches to about 0.02 inches, such as from about 0.005 inches to about 0.01 inches.
A sheet material 10 is conveyed between the perforation blade 40 and the anvil roll 32. As the sheet material 10 passes between the blade head 36 and the anvil roll 32, one of the anvils 34 strikes the perforation blade 40 and forms a perforation line 14 into the sheet material 10. The spacing of the anvils 34 on the anvil roll 32 and the speed at which the anvil roll 32 rotates relative to the sheet material 10 as it is conveyed determines the distance between transverse perforation lines 14.
In one embodiment, the anvils 34 include an incline surface that contacts the teeth 42 of the perforation blade 40. As the anvil 34 contacts the perforation blade 40, the impact force between the teeth and the anvil increases until the anvil passes by the perforation blade. As the anvil moves past the perforation blade, an edge on the teeth forms perforations into the sheet material 10. During this process, the perforation blade 40 strikes the moving anvil and is deflected as the anvil rotates beyond the blade. The roll blade is typically mounted at a 45 degree angle relative to the roll surface, while the stationary blade is mounted with a slightly greater angle of approximately 60 degrees.
In the embodiment illustrated in
Having the capability to use the perforation blade in a stationary system as shown in
In general, perforation blades in accordance with the present disclosure include teeth that have at least one and preferably two angled side walls. One embodiment of a perforation blade made in accordance with the present disclosure is illustrated in
As shown in
In accordance with the present disclosure, the side walls 46 form a non-zero angle in relation to the longitudinal axis L. In the embodiment illustrated in
In the embodiment illustrated in
The blade design as shown in
In general, the angle of each side wall can be the same or different. In one embodiment, all of the angles have the same measurement with respect to the longitudinal axis L, albeit a first group of side walls extend in a divergent direction from a second set of side walls. The angle of the side walls is generally greater than about 2°, such as greater than about 5°, such as greater than about 7°, such as greater than about 10°, such as greater than about 12°, such as greater than about 15°. The angle is generally less than about 60°, such as less than about 40°, such as less than about 35°, such as less than about 30°, such as less than about 25°.
Along the edge 44 of the perforation blade 40, the width of each tooth 42 can be from about 0.050″ to about 0.200″, while the width of each recess can be from about 0.010″ to about 0.050″.
Referring to
The side walls 146 of the teeth 142 form a non-zero angle with a longitudinal axis L. In the embodiment illustrated in
In the embodiment illustrated in
In general, the side walls 146 of the perforation blade 140 can form an angle with the longitudinal axis L generally similar to the angles described above with respect to
In the embodiment illustrated in
Referring to
The perforation blade 140 as shown in
In the embodiment illustrated in
The chamfer 160 forms an inclined angle along the face 152 of each tooth 142. The angle extends to the edge 144 of the blade 140. The chamfer can have an angle of generally greater than about 3°, such as greater than about 5°, such as greater than about 7°. The chamfer generally has an angle less than about 20°, such as less than about 15°, such as less than about 12°.
In
Referring to
The perforation blade 140 as shown in
Similar to the embodiment illustrated in
The slanted side walls illustrated in
Perforation blades made in accordance with the present disclosure can be made from various materials. For instance, the perforation blade can be made from hardened steel. Each perforation blade can have a width that is generally the same or larger than the width of the sheet material being perforated. In one embodiment, for instance, the perforation blade can have a width of greater than about 70 inches, such as greater than about 80 inches, such as greater than about 90 inches. The width of the perforation blade is generally less than about 200 inches, such as less than about 160 inches, such as less than about 140 inches, such as less than about 120 inches. The dimensions of the perforation blade, however, depend upon various factors including the type of material being perforated and the dimensions of the processing line into which the blade is installed.
These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.
