FR2880833A1 - DEVICE FOR CUTTING FILMS OF LOW THICKNESS - Google Patents

Abstract

Film cutting device, comprising a knife (1) and at least one counter knife (2), the knife (1) and the counter knife (2) being driven by a first relative movement against one another other in a cutting plane substantially perpendicular to the film to be cut so as to achieve a first shearing effect, characterized in that the knife (1) and the counter knife (2) are mounted with a degree of freedom allowing their respective movement in a second direction out of the cutting plane.

Description

Cutting device for thin films

  The invention relates to a device for cutting thin films, particularly suitable for cutting plastic films, paper or metal, in applications in the field of packaging.

  In the prior art, such a cutting device is based on a movable knife which descends against a counter-knife on which is placed the film to be cut so as to perform the cutting along the line of contact between the knife and the blade. against knife. In such a device, the counter knife is fixed and the knife descends in a direction perpendicular to the plane of the knife against, more or less rubbing against the edge of the counter knife to cause a shearing effect in a vertical plane. It is known in these devices that the clearance between the knife and the counter-knife must not exceed one-tenth of the thickness of the film, otherwise the latter is folded and uncut. For thin films, the cutting elements, knives and counterknives, are chosen from a relatively flexible metal to be able to operate with a very low clearance and very high friction forces. A first disadvantage of this solution is that it causes very rapid wear of the cutting elements which must be regularly changed. A second disadvantage of this solution is that it is not suitable for very thin films, below 35 micrometers thick for example because a game too weak and mechanically impossible would be necessary.

  An object of the present invention is to provide a thin film cutting device which does not have the disadvantages of the prior art.

  More specifically, a first object of the present invention is to provide a device for cutting thin films whose life of the cutting elements is elongated. SUMMARY OF THE INVENTION

  A second object of the invention is to provide a cutting device which is suitable for films of very small thickness.

  The invention is based on a film cutting device, comprising a knife and at least one against knife, the knife and the counter-blade being driven by a first relative movement against each other in a cutting plane substantially perpendicular to the film to be cut so as to achieve a first shearing effect, characterized in that the knife and the counter knife are mounted with a degree of freedom allowing their respective movement in a second direction out of the cutting plane.

  According to one embodiment, the film cutting device is characterized in that the knife is driven downward in a first direction in a vertical cutting plane and in that the counter knife has a degree of freedom in a second direction substantially perpendicular.

  According to a variant, the counter-blade is rotatably mounted on an axis and is forced against the knife by a spring.

  The film cutting device may comprise two counter-knives mounted rotatably on the same axis of rotation on a first end and connected by a spring at their second end. The two counter-knives can be placed in a slightly DA \ 1 plane. K282. 12FR.11 deposit.doc inclined, and the knife, substantially horizontal, can be animated by a descent movement in a substantially vertical direction.

  The spacing between the counter-knives may be less than the width of the knife, in the high position of the latter, and the counter-knives may gradually deviate during the descent of the knife between the two counter-knives, remaining in contact with its sharp edge. Thus, the knife and the counter knife have a second shearing effect in a plane substantially perpendicular to the cutting plane.

  According to an implementation of the invention, the knife and the counter knife are in a hard metal type tool steel.

  These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment made in a non-limiting manner in relation to the attached figures among which: FIG. 1 represents a sectional view of side of the device according to one embodiment of the invention; FIG. 2 represents a front view of the device according to the embodiment of the invention; FIG. 3 represents a rear view of the device according to the embodiment of the invention; FIG. 4 represents a view from above of the device according to the embodiment of the invention.

  The device comprises a knife 1, shown in the upper position in FIG. 1, which is guided by an arm 11 of the device in order to descend to reach a low position in which it enters between two counter-knives 2. Advantageously, the direction of descent of the knife has a slight inclination, a few degrees, relative to the direction perpendicular to the plane of the counter-knives, to create a first shearing effect in a vertical plane, said plan cutting, at the intersection between the knife and a counter knife, in the manner of scissors.

  According to this embodiment of the invention, the two counter knives 2 are rotatably mounted around a same vertical axis 3, in order to be able to move apart under the effect of the friction force exerted by the knife. 1 descendant.

  As is particularly visible in Figure 2, the device allows to laterally convey two films 4 to be cut. These two films are placed on the surface of the counter-knives in order to be sheared simultaneously along the line of contact 10 defined by the outline of the knife 1, visible in FIG. 4. The sharp end of the counter-knives 2 moves slightly away from the parallel to the contour or cutting edge 10 of the knife 1, as one moves away from the point of permanent contact 12 between the knife and the counter-knife, and the spacing between the two counter-knives 2 is in the upper position of the knife 1, slightly less than the width of the knife 1. Thus, during the lowering of the knife 1, its cutting edge 10 defines the line of contact with the counter-knives by exerting a pressing force on their blade. sharp edge that separates them progressively, by their rotation about the axis 3. This mechanism makes it possible to obtain a second shearing effect in the plane of the counter-knives 2, perpendicular to the vertical plane of the first DA \ I.K282.12EN . 1 1 deposit.doc shear. This principle makes it possible to obtain a better shearing effect by avoiding the problem of defining a game between the knife and the counter knife.

  A spring 5 exerts a permanent restoring force on the cutters 2, tending to cause them to rotate towards each other about the axis 3 and inducing their permanent support against the knife 1, a lower part 12 of which is still supported on the counter knives 2.

  The counter-knives 2 are fixed on lateral support arms 7 by means of fixing screws 8 enabling their position to be adjusted as illustrated in FIGS. 3 and 4. These two support arms 7 are connected to each other. a part to the same central axis of rotation 3, placed at the rear of the device, by two connecting arms 9 and secondly by the return spring 5 at the front of the device.

  As illustrated in FIG. 4, the contact between the knife 1 and the counter knives 2 defines a cutting line 10 whose shape is chosen as a function of the chosen application. In this embodiment, the device allows the cutting of a plastic film of very small thickness and very thin width, to form a tear strip to be welded on a film for the manufacture of a food package, to form an easy opening device of the package. For this particular application, the knife can be placed in a horizontal plane, animated by a descent movement in a direction having a slight angle with respect to the vertical direction, the counter-knives being placed in an inclined plane, allowing with the knife to have the second transport function of the torn strip in order to place it on the film which would be placed horizontally just below the cutting device.

  According to the concept of the invention, during the descent of the knife 1 towards the counter-knife 2 according to a first relative movement in a first placed direction, to achieve the function of scissors by a first shearing effect in a vertical plane, the knife 1 and its counter-blade 2 are furthermore animated by a second relative movement in a second direction, in a plane parallel to the counter-knives 2, thanks to a degree of additional freedom provided on at least one of these elements, to obtain a second shear effect in a perpendicular plane. This principle makes it possible to obtain the following technical effects: the counter-knife 2 is constantly forced to bear against the knife 1 during the cutting operation, which makes it possible to avoid precise control of a certain clearance between these two cutting elements as in the prior art. This solution also makes it possible to cut very thin films, even less than 35 micrometers thick, the counter-knife 2 has a degree of freedom in a second direction substantially perpendicular to the cutting direction, which allows it to move slightly away from the knife 1 during the descent of the latter when the friction force between the two elements exceeds a predefined value, inducing a reduction of this friction force. Thus, the wear of the cutting elements is reduced. This solution thus indirectly makes it possible to use metal materials of greater hardness, which further increases their service life.

  The restoring force exerted by the spring 5, the dimensions of the cutting elements and their respective nominal position will be defined case by case according to the characteristics of the film to be cut.

  DA \ 1.K282.12FR. This solution makes it possible to achieve the objects of the invention, the cutting of films of any size and in particular of very small thickness while greatly reducing the wear of the cutting elements.

  In the embodiment described, the relative movements of the cutting elements have been chosen by way of example, but the concept of the invention also covers embodiments in which the counter-knife may be driven by a movement of translation and not of rotation, or in which the counter-knife would remain fixed but for which the knife would have an additional degree of freedom to fulfill an equivalent function.

DA \ 1.K282.12EN.1 I filing.doc

Claims (8)

claims:   1. Device for cutting films, comprising a knife (1) and at least one knife (2), the knife (1) and the counter-knife (2) being driven by a first relative movement against each other. other in a cutting plane substantially perpendicular to the film to be cut so as to achieve a first shearing effect, characterized in that the knife (1) and the counter knife (2) are mounted with a degree of freedom allowing their movement respective in a second direction outside the cutting plane.   Film cutting device according to claim 1, characterized in that the knife (1) is driven downwardly in a first direction in a vertical cutting plane and in that the counter knife (2) has a degree of freedom in a second substantially perpendicular direction.   3. A film cutting device according to claim 1 or 2, characterized in that the counter-knife (2) is rotatably mounted on an axis (3) and is forced in abutment against the knife (1) by a spring (5).   4. Device for cutting films according to claim 3, characterized in that it comprises two counter-knives (2) rotatably mounted on the same axis of rotation (3) on a first end and connected by a spring (5). ) at their second end.   5. A film cutting device according to claim 4, characterized in that the two counter-knives (2) are placed in a slightly inclined plane, in that the knife (1) is DA \ t.K282.12FR. 1 1 deposition substantially horizontal and animated by a descent movement in a direction close to the vertical, and in that the counter-knives (2) are mounted mobile in rotation about an axis (3).   6. film cutting device according to one of claims 4 or 5, characterized in that the distance between the counter-knives (2) is less than the width of the knife (1) in the upper position of the latter , and in that the counter-knives (2) are progressively spaced during the descent of the knife (1) between the two counter-knives (2), while remaining in contact with its cutting edge (10).   7. A film cutting device according to claim 6, characterized in that the knife (1) and the counter knife (2) have a second shearing effect in a plane substantially perpendicular to the cutting plane.   8. film cutting device according to one of the preceding claims, characterized in that the knife (1) and the counter-knife (2) are in a hard metal type tool steel. DA \ 1.K282.12EN.11 filing.doc