EP0781631A1

EP0781631A1 - Rotating cutter particularly suitable for cutting ribbon-like materials

Info

Publication number: EP0781631A1
Application number: EP96108721A
Authority: EP
Inventors: Davide Viola; Marco Viola
Original assignee: VIOLA GIORGIO Srl
Current assignee: VIOLA GIORGIO Srl
Priority date: 1995-12-27
Filing date: 1996-05-31
Publication date: 1997-07-02
Also published as: ITMI952765A0; ITMI952765A1; IT1279250B1

Abstract

A rotating cutter (30) for cutting ribbon-like materials, obtained along the surface of a metal roller (10) or fastened to the same, formed by a cutting profile having a substantially trapezoid section whose opposite inclined sides (34, 34') are connected to the surface of the roller (10) through a vertical wall (36, 36') and converge at the top in a plane (38). The width of angle alpha formed internally between each of the inclined sides (34, 34') and said plane is at least equal to 95°.

Description

This invention relates to a rotating cutter particularly suitable for cutting ribbon-shaped materials.
More particularly, this invention refers to a cutter as defined above, obtained along the surface of a cylinder or roller from metal and shaped in function of the shape of the cut to be obtained on ribbon-shaped materials.
The term "ribbon-shaped materials" as is used in this description and the claims, comprises plastic, coupled, non-woven films generally utilized for the realization of disposable products, such as for instance napkins and sanitary towels for incontinent people and women, and the like.
As is known, the stages of fabrication of these disposable products, especially of napkins, include a cutting operation which gives said products a particular profile, in correspondence of given parts. This happens, for instance in the portions relative to the passage of the legs, which must be hollow, to allow the napking, once folded on itself, to assume the wrapping conformation typical of pants. These cuts are generally made by means of cutters or blades obtained along the surface of a roller. The form of the cutter corresponds to the shape of the cut to be obtained. The cutters or blades are generally realized by removing material from a metal block forming the roller or cylinder, and subject to thermal treatment for hardening the surface. Along the surface of the roller two specular cutters or blades are formed, spaced from one another of a given length to obtain as many hollowed opposite portions which correspond to the passage of the legs; said cutters define therefore as many cutting profiles, formed integrally with the roller.
The frame on which said roller is mounted supports a dragging counter-roller or counter-cutter having a smooth surface, locaded below the roller carrying the blades and aligned with the same.
In the blades or cutter utilized by the known art for cutting the above listed disposable products, the cutting profile has a substantially pointed conformation which defines an angle of a width comprised between 55° and 70°, while the dimensions in width and height of the same blades are respectively comprised between 5-7 mm and 8-10 mm. The point of the blades is provided with a slight flattening which defines a plane whose width is generally comprised between 0.15 and 0.25 mm, forming the so-called cusp.
These cutters can perform a number of cuts which, in function of the quality of the materials utilized for their working, the speed and precision of work required, generally oscillate between 3 and 6 millions, after which they must be sharpened. The blades wear especially along the edges formed between said cusp and the opposite inclined sides. Along said edges, after a certain number of cuts, microfractures form due to the cutting strain. To carry out this sharpening operation, which, depending on the aforementioned variables, is performed each 15-30 days, the roller carrying the blades or cutters must be removed fron the frame of the machine and replaced by another one carrying already sharpened blades. Such replacement, while requiring rather short times, involves all the same the standstill of the whole production line, with the obvious drawbacks associated.
Object of this invention is to obviate the aforementioned drawback.
More particularly, object of this invention is to provide a cutter for cutting ribbon-like materials having characteristics of duration and cutting effectiveness higher than the conventional blades used in this field.
A further object of the invention is to provide users with an improved cutter, suitable to ensure a high degree of resistance and reliability in the time, and also such as to be easily and economically realizable.
According to this invention, these and still other objects are achieved by a cutter obtained along the surface of a metal roller or fastened to the same and formed by a sharp profile having a substantially trapezoid section, wherein the opposite inclined sides are connected to the roller surfaces through a vertical wall and converge on the top in a plane of limited width, the width of the angle formed internally between each of the inclined sides and said plane being at least equal to 95°.
The constructive and functional characteristics of the improved cutter subject matter of this invention may be better understood from the description hereunder, wherein reference is made to the attached drawings, which represent a preferred embodiment of the same, illustrated by way of non limitative example, and wherein:

Fig. 1 is a schematic front view of the frame carrying the roller with the blades or cutters of this invention, and the underlying counter-roller or counter-cutter;
Fig. 2 is a perspective schematic view of the roller with the blades and the underlying counter-roller or counter-cutter, between which the ribbon-like material to be cut is caused to pass;
Fig. 3 is the schematic view of a cross-section of one of the blades or cutters of this invention;
Fig. 4 is an enlarged schematic view of the top part or cusp of the blade or cutter of Fig. 3.

With reference to Figg. 1 and 2, the cutter for cutting ribbon-like materials of this invention is obtained integral with a roller o cylinder (10) supported by a frame formed by a base (12) (12) and two opposite shoulders or sides (16, 16').
Said sides or shoulders (16, 16') are provided with seats (18, 18') with the possibility of adjusting the shaft (20) of the roller (10) and/or the underlying smooth roller (24) which form the counter-cutter.
Conventional ball bearings (26) or the like are located in said seats (18, 18'), and an end of shaft (20) of roller (10) has connection or adjustment means (28) known in the art. In the embodiment of the aforementioned drawings, roller (10) is provided with two cutting blades or cutters (30), obtained along the surface of roller (10), near the transversal axis. The configuration of said blades (30), substantially semicircular with the concavity looking towards said axis, is strictly correlated to the shape of the cuts (32') to be obtained on the ribbon-like material (32) of Fig. 2. The ribbon-like material (32) illustrated in Fig. 2 is formed, by way of example and not critically, by coupled plastic films to form napkins. Said plastic films (32) are fed to the cutting machine provided with the upper roller (10) carrying blades (30) and the underlying matching roller (24), with known means, sliding along the direction defined by arrow "F".
Each of the shaped blades or cutters (30) constitute a sharp profile protruding from the surface of roller (10), and during the rotation of the latter, it acts on the ribbon-like material (32), cutting correspondingly shaped portions (32'). Said cutter (30) has a substantially trapezoid cross-section, as shown in Fig. 3, being defined by two opposite inclined sides (34, 34'), each of which is connected to the surface of roller (10) through a vertical wall (36, 36'). The inclined sides converge on the top in a plane (38) of reduced width, to form the so-called cusp, as shown in the enlarged schematic view of Fig. 4.
According to the invention, the width of the angle (alpha) formed internally between each of sides (34, 34') and plane (38) is comprised between 95° and 179° and preferably equal to 120°. This involves a remarkable resistance to wear of the cutting edges (40), the section of material engaged by the cutting being of markedly large size. As a consequence, the width "L" of cutter (30), i.e. the portion existing between the opposite vertical walls (36, 36') protruding from the surface of roller (10) is comprised between 10 and 25 mm and is preferably equal to 20 mm.
With this sizing of the cross-section, blade (10) is particularly resistant to dead and live loads to which it is subject during the cutting and at the same time it is subject to a minimum risk of overtemperature due to heating during the thermal treatment to which it is subject. The overall height of the blade, i.e. the "H" level between the surface of roller (10) and the upper plane (38) or cusp, changes in function of the type of product to be cut and is originally comprised between 10 and 14 mm; said level, obviously, reduces following the sharpening operation. The width "L1" of said upper plane 38 is preferably comprised between 0.15 and 0.25 mm and corresponds to that of the known blades utilized in this field. The duration tests have allowed to notice that a blade or cutter having a profile defined by the above indicated values can effectively operate on the ribbon-like material, giving it the wished profile, for a very long period of time, corresponding to a number of cut and shaped units comprised between 10 and 12 millions.
As can be inferred from the above, the advantages achieved by the invention are evident.
The improved cutter of this invention is particular resistant to wear, live and dead loads, and shows no problems of local brittleness as a consequence of the thermal treatments to which it is submitted.
The Figures show a particular embodiment of this invention, wherein cutter (30) has been obtained directly on the surface of roller (10). Alternatively, the cutter may be produced separately from the roller and fastened to the same by screws, bolts or any like means.
Besides, the cutter of this invention has been described with reference to its utilization as a cutter of ribbon-like materials to form napkins and sanitary towels, but obviously it can be utilized for cutting and profiling absorbant products of any kind, even in the paper and cardboard-field on materials other than the ribbon-like ones.
The form and the position of cutter (30) on roller (10) may change in function of the shape and type of cut required. Lastly, cutter (30) may be located or obtained on the counter-roller (24) or the roller (10) and the counter-roller (24), or the same roller may be provided with cutters (30) having different shapes and sizes.
Although the invention has been described in conjunction with specific embodiments, offered for illustrative purpose only, it is evident that many alternatives and variations will be apparent to those skilled in the art, in the light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims.

Claims

A rotating cutter (30) for cutting ribbon-like materials, obtained along the surface of a metal roller (10) or fastened to it, formed by a cutting profile having a substantially trapezoid section, wherein each opposite inclined side (34, 34') is connected to the surface of roller (10) through a vertical wall (36, 36'), orthogonal to the surface of roller (10), and said inclined sides (34, 34') converge at the top in a plane (38) wherein the width of the angle (alpha) formed internally between each of the inclined sides (34, 34') and said upper plane (38) is at least equal to 95°.
The rotating cutter according to claim 1, characterized in that the width of said angle (alpha) formed internaly between sides (34, 34') is comprised between 95° and 179°.
The rotating cutter according to claim 1 or 2, characterized in that the width of the angle (alpha) is of 120°.
The rotating cutter according to any of the preceding claims, characterized in that the distance (L) between the opposite vertical walls (36, 36') protruding orthogonally from the surface of roller (10) is comprised between 10 and 22 mm.
The rotating cutter according to any of the preceding claims, characterized in that said distance (L) is equal to 20 mm.
The rotating cutter according to any of the preceding claims, characterized in that the portion (H) existing between the surface of roller (10) and the upper plan (38) corresponding to the height od said cutter is comprised between 10 and 14 mm.
The rotating cutter according to any of the preceding claims, characterized in that the width (L1) of the upper plane (38) is comprised between 0.15 and 0.25 mm.
The rotating cutter according to any of the preceding claims, characterized in that said cutter is produced separately from the metal roller and fastened to said roller.
The rotating cutter according to any of the preceding claims, characterized in that it has a semicircular configuration.