FIBER DENSIFICATION KNIFE

This invention relates to a knife for cutting fibrous material. More particularly, the invention relates to a knife for cutting fibrous material such as paperboard and the like and densifying the material in an area adjacent to the cut.

Advances in fiber based, e.g., paperboard, technology enable the use of paperboard for liquid food packaging materials. Paperboard based materials are now recognized as a preferred container material for many types of liquid foods. For example, juice, milk and the like, are commonly packaged in paperboard based materials. Non-food items such as laundry detergent, laundry softeners and the like are also commonly found packaged in paperboard packaging.

It has been observed that paperboard packaging can be problematic for liquid products. One known problem is that the liquid product can be absorbed into the packaging material by a wicking phenomena which occurs at the edges of the material which come into contact with the liquid. Liquid wicks, or.is transported from the edges of the packaging material into the paperboard body of the container material Wicking can compromise the structural integrity of the package, and can cause contamination of the food product packaged in the container.

Wicking can be reduced or eliminated by sufficiently increasing the density of the packaging material. This is typically effected by increasing the density and thus the weight of the entirety of the material package. While this is a somewhat effective solution, the material and manufacturing costs increase commensurately with increased material weight.

Accordingly, there continues to be a need for a cost effective densified packaging material which effectively reduces or eliminates wicking of the liquid product into the packaging material. Preferably, such a packaging material has selectively densified areas to maintain the low cost advantages and other benefits of paperboard packaging. In this respect, reference is directed to US Patent US 4 596 541A and European Patent Application EP 0 318 659A.

The present invention is directed at a cutting device for effecting a cut in a board-like fibrous material and comprising a main body portion; and a blade portion extending from the main body portion and having a cutting edge having first and second angled surfaces extending divergingly therefrom. According to the invention, the device includes a densifying member which extends outwardly from only one of the first and second angled surfaces, and has a compression surface for contacting a said board-like material and densify an adjacent area thereof during use of the device. In use, the device is positioned with the blade portion in contact with and impressed into the fibrous material. The blade is then moved to effect a crush cut of the material, while the densifying member compresses and densifies an area of the material adjacent to the cut. Typically, the densifying member extends outwardly from a line substantially halfway between the cutting edge and the main body portion.

The compression surface in a device of the invention can be flat and generally parallel to the plane of the material to be cut. However, it may be configured other than parallel to the material plane to selectively, variably densify the area under the compression surface to produce a desired effect. An additional densifying member may extend outwardly from the other angled, diverging surface of the blade, but at a spacing from the cutting edge different from that of the first mentioned densifying member.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings wherein:

• FIG. 1 is a side elevational view of a cutting device embodying the principles of the present invention, the device being illustrated pressed into an exemplary laminated paperboard sheet;
• FIG. 2 is a side elevational view of the cutting device of FIG. 1, without the paperboard sheet;
• FIG 3 is a side elevational view of an alternative embodiment of the invention with a non-planar compression surface and a riser surface parallel to the centreline of the cutting device blade portion; and
• FIG. 4 is a side elevational view of another alternative embodiment of the invention with offset densifying members showing the device being impressed into a paperboard sheet.

As shown in FIGS. 1 and 2, the cutting device 10 includes generally a main body portion 12 and a blade portion 14. The blade portion 14 has a cutting edge 16 and includes first and second adjacent, angled surfaces 18, 20. The surfaces 18,20 extend upwardly, diverging from the cutting edge 16.

The cutting device 10 is configured for use with most types of fibrous materials. The device is particularly useful for cutting fibrous material, such as paperboard, formed as a blank or sheet, which is used for manufacturing packing for liquid products.

The packaging material can be formed of, for example, a plurality of layers, or a laminate of various materials, one of more of which layers is a fibrous material. One typical laminate L, as illustrated in FIG. 1, includes an inner layer of thermoplastic material I, such as low density polyethylene (LDPE), a barrier material B such as metal foil, a paperboard layer P, and an outer layer. O of thermoplastic material, such as LDPE.

The cutting device 10 overcomes the problems associated with edge wicking by providing a packaging material that is selectively densified at cut edges which may be exposed to the liquid material in the package. Essentially, the present cutting device 10 is configured to density predetermined portions of the packaging material to reduce wicking and thus absorption.

As best seen in FIG. 2, the blade portion 14 of the cutting device 10 extends from the main body portion 12. In a typical container manufacturing process, the paperboard material, illustrated in FIG. 1 as a laminate L, is crush cut at its edges by the cutting edge 16 of the blade 14. The angled surfaces 18, 20 facilitate cutting the material L. A densifying member 22 extends outwardly from one of the angled surfaces 18 in a step-like manner. The densifying member 22 has a compression surface 24 which is configured to engage and compress the packaging material L, as the cutting device 10 and blade 14 are pressed into the material L. Essentially, the densifying member 22 produces an anvil-like effect which compresses and densifies the material in an area A under the compression surface 24 adjacent to the cut location C. The densifying member 22 has a riser. surface 26 which extends from the compression surface 24 to the main body portion 12.

In a typical configuration, the cutting edge 16 is a flat surface having a width W of about 2 to about 4 thousands of an inch (2 to 4 mils). The cutting edge 16 is in spaced relation to the main body portion 12. The force of the blade 12 into the material L effects a crush cut of the material L by the cutting edge 16.f The densifying member 22 is configured to densify the material in an area A under the member 22, adjacent to the cut C. Typical, the packaging material L is a flat, planar material having a consistent thickness t. In a current embodiment, the compression surface 24 is flat, and is configured to be generally parallel to the plane P of the material. Thus, a substantially consistent densification of the material L in the area A adjacent to the cut C occurs. It will be recognized that the compression surface 24' can be configured other than parallel to the material plane P such that the material L in area A can be selectively, variably densified to produce a desired effect (FIG. 3).

Referring to FIGS. 1 and 2, the angled surfaces 18,20 extend upwardly from the cutting edge 16 at a predetermined angle. In a current embodiment, each of the surfaces forms an angle α with a centerline of the blade portion, as illustrated by the arrow at 28, of about 30°. In one embodiment, the riser surface 26' is parallel to the centerline 28, i.e., perpendicular to the plane P of the material L (FIG. 3). Alternatively, as illustrated in FIGS. 1 and 2, the riser surface 26 can be formed an angle β relative to the blade centerline 28.

In a current embodiment, the densifying member 22 extends outward from the angled surface 18, at about a midpoint of the surface 18 between the cutting edge 16 and the main body portion 12. That is, the surface 18 has a length S, and the member 22 extends from the surface 18 at about a distance of S/2 from the edge 16. Alternatively, the member 22 can extend from the surface 18 from other than the midpoint to achieve a specific, desired densification characteristic and result.

An alternative embodiment 110 of the cutting device is iilustrated in FIG. 4. Similar to the embodiment 10 illustrated in FIGS. 1-3, it includes a main body 112 portion having a blade portion 114 extending therefrom. The blade 114 includes a cutting edge 116 having first and second angled surfaces 118, 120 extending from the edge 116. The alternate embodiment 110 includes first and second densifying members 122, 124 extending respectively from the first and second angled surfaces 118, 120.

The densifying members 122, 124 are formed differently from one another in order to achieve specific desired results at the opposing areas A₁, A₂ adjacent to the cut.

The densifying member 122 extends from a surface 118 at a point lower than the midpoint of the cutting edge 116. The densifying member 124 extending from a surface 120 at a point higher than the midpoint of the cutting edge 116 and the main body 112. Additionally, and similar to FIG. 3, the densifying member 122 has a non-parallel compression surface 123. Areas A₁ and A₂ are compressed differently due to the different positioning of densifying members 122 and 124.

Notwithstanding the linear appearance of the cutting device embodiments illustrated, it will be recognized by those skilled in the art that both embodiments can be configured in circular, as well as other desired arrangements.