Cutting device

Abstract

 A cutting device for cutting flexible materials such as thin webs (11) wherein a cutting element (3) is mounted in a carrier (1) and during a cutting operation two working faces (2a, 2b) associated with the cutting element (3) and located one on either side of the cutting element (3) co-operate with reaction surfaces (8), the arrangement being such that the working faces (2a, 2b) will tend to move away from the cutting element (3) while the material (11) to be cut is clamped between the working faces (2a, 2b) and reaction surfaces (8) so as to tension the material (11) to be cut during a cutting operation. In one construction the working faces (2a, 2b) are supported on a carrier (1) which also supports the cutting element (3) and are resiliently deformable away from the cutting element (3) and they co-operate with rigid reaction surfaces (8) which may be formed in a single member which is relieved (at 10) where it co-operates with the cutting element (3).

Description

[0001] This invention is directed towards the cutting of laminar materials such as paper, film, foil or the like presented in sheet or reel form. The device can be adapted to make both straight and curved cuts but is limited to complete separation of the cut portion. It can be adapted to a rotary cutter or a flying cutter.

[0002] There are several known cutting devices for such materials. In one type, a moving blade co-operates with a fixed blade in a scissors action, a device commonly known as a Guillotine. This is very accurate but requires careful setting and maintenance and cannot easily be adapted to cut moving material. It is also noisy.

[0003] A second type has a moving blade co-operating with a fixed anvil. This requires very accurate setting and the blade requires very frequent sharpening. The whole device can be arranged to move either in a reciprocating linear motion, or as two tangentially touching rollers which allow -the cutting of a moving film or sheet.

[0004] Neither of these known devices are suitable for cutting very thin or very flexible materials as the Guillotine type relies on the rigidity of the material to be cut for its action and the blade and anvil cutter is limited to material thicker than the setting accuracy of the blade.

[0005] Our own Patent No.1592857 describes a modification to the blade and anvil device mentioned above wherein the fixed anvil is replaced by a bed of upstanding flexible pins which permit the cutting member to penetrate without damaging its cutting edge. Even this device relies on some degree of rigidity in the material to be cut.

[0006] Furthermore, that cutting device usually requires external tensioning means for the material to be cut. This can limit the minimum size of the cut portion in some cases.

[0007] In accordance with the present invention, we provide a web cutting device comprising two co-operating web tensioning means consisting of a pair of movable working faces and a reaction surface for co-operation with each working face together with a cutting element mounted so that at least during a cutting operation it is located between the working faces, the working faces being so arranged that when they are pressed against their respective reaction surfaces with the web to be cut located between the reaction surfaces and the working faces, the working faces will tend to move away from the cutting element thus tensioning the web and allowing the cutting element to come into contact with it.

[0008] According to one embodiment of the invention, the cutting element is mounted in a resilient carrier, spaced parts of which provide the working faces which tend to move away from the cutting element when they are pressed against the reaction surfaces with the web therebetween.

[0009] Preferably, the relaxed state of the resilient carrier is such that the working edge of the cutting element is within the perimeter of the carrier as defined by s surface joining the working faces and moves in the working direction through that perimeter when the carrier is pressed against the reaction surfaces. The reaction surfaces are preferably part of a rigid member which is preferably relieved to accommodate the working edge of the cutting element.

[0010] Preferably, the reaction surfaces.have a low coefficient of friction relative to the material to be cut.

[0011] Preferably, the resilient carrier is made of or coated with 'a material whose coefficient of friction with respect to the material to be cut is high at least on the surfaces which co-operate with the reaction surfaces.

[0012] In another embodiment of the invention the cutting element may be mounted between the reaction surfaces which are preferably rigid and preferably have a low coefficient of friction, and the working faces are mounted in another carrier, are resiliently deformable, and move away from the cutting element when the working faces are brought into engagement with them.

[0013] In yet another embodiment of the invention, both the reaction surfaces and the working faces are formed from resilient material.

[0014] It will thus be appreciated that a laminar sheet, if trapped between the working faces and the reaction surfaces will be tensioned by outward movement of the working faces and then cut by the cutting element.

[0015] The cutting element may be a blade or an array of pointed pins defining a straight or curved cutting edge which may be angled or serrated to allow a progressive cutting action.

[0016] The working faces may be part of a member formed from rubber or similar elastomeric material of appropriate hardness. The member should be so shaped as to cause a mutually-outward movement of the working faces in a direction perpendicular to the direction of movement of the cutting element and to the cutting axis.

[0017] Alternatively, the working faces could be part of a mechanism incorporating resilient members such as springs, together with swinging links and/or cam arrangements to achieve the same effect.

[0018] _"The cutting element can be arranged to move into and out of cutting positions in any suitable known manner. For example, a reciprocating motion perpendicular to the plane of the material to be cut can be used. Otherwise a rotary motion can be used for one part while a second rotary motion can be used for the second.

[0019] Either or both rotary motions can be replaced by a partly linear motion such as would be achieved by mounting the cutting element on a chain or a conveyor. In this case means would have to be provided to ensure that the pitch of the cutting element matches the pitch of the reaction members or, if the latter are mounted on the same carrier as the cutting element, of the working faces.

[0020] In yet another embodiment, instead of using a reciprocating motion perpendicular to the plane of the material, two reciprocating motions set at a shallow angle to the plane of the material could be used for cutting the material, e.g. a moving film or sheet while in motion.

[0021] In order that the invention may be better understood, various embodiments of its will now be described, by way of example with reference to the accompanying drawings, in which:-

FIGURE 1 is a transverse section through one embodiment of the invention;

FIGURE 2 is a view similar to Figure 1, but of an alternative embodiment of the invention wherein the reaction surfaces are part of a second resilient member, and the mechanism is shown in a relaxed state;

FIGURE 2a shows the apparatus shown in Figure 2 at the completion of the cutting stroke;

FIGURES 3 and 3a are transverse sections through a third embodiment of the invention wherein the cutting element projects from the surface of a rigid roller which co-operates with a resilient roller with an axially extending groove therein.

[0022] In the various Figures of the drawings, like parts are identified with common reference numerals.

[0023] Referring to Figure 1, a cutting assembly 1 consists of two resilient members 2a and 2b mounted on either side and secured to a cutting element 3 which may be a blade or an array of pins which can be secured by known means to a carrier plate 4 or to a pair of plates 4 and 4a. The cutting assembly 1 is secured to a part 5 of a cutting machine (not shown in detail) adapted to impart a reciprocal up and down motion to the cutting assembly 1 in the sense of the double arrow 6. The resilient members 2a and 2b are so shaped that their working faces 7a and 7b remain substantially parallel to the surface 8 of a rigid reaction member 9 when the cutting assembly 1 is moved into co-operation with it. The shape of the resilient members 2a and 2b is such that the working faces 7a and 7b move away from each other along the face of the surface 8 of the reaction member 9 when the cutting assembly 1 is moved against the reaction member 9. The surface 8 of the reaction member 9 may be split into two reaction surfaces by a groove 10 to avoid the edge of the cutting element 3 being damaged by contact with the reaction member 9.

[0024] The working faces 7a and 7b of the cutting assembly 1 are made of or coated with a material which has a higher coefficient of friction with respect to the material to be cut than the surface 8 of the reaction member 9 so as to ensure that the outward movement of the working faces 7a and 7b of the cutting assembly 1 induces sufficient tension in the material to be cut (not shown in Figure 1).

[0025] In an alternative arrangement, it is envisaged that the cutting element 3 may be secured directly or indirectly in a one piece "bifurcated" resilient member 2a, 2b formed integral with or secured to the part 5, the resilient member being formed of a relatively rigid elastomeric material but having working faces 7a, 7b, or working face portions formed of a softer, more resilient elastomeric material, e.g. by a dual durometer extrusion process, so that, in use, they will still tension the material to be cut.

[0026] Figures 2 and 2a show a different embodiment of the invention wherein the reaction member 9 is also formed of resilient material shaped so that distortion by the resilient cutting assembly 1 causes the two reaction surfaces 8 of the reaction member 9 to stretch or move in the same sense as the working faces 7a and 7b of the cutting assembly 1. The reaction member 9 may be set in a second part 14 of a cutting machine (not shown). A laminar sheet of material 11 to be cut is placed between the cutting assembly 1 and the reaction member 9 by external means (not shown) and is gripped between the working faces 7a. and 7b of the cutting assembly 1 on one side and the surface 8 of the reaction member 9 on the other side as the cutting assembly 1 and the reaction member 9 move towards each other (as occurs in the construction shown in Figure 1).

[0027] Figure 2a shows that as the cutting assembly 1 is moved towards the reaction member 9 in the sense of the arrows 12a and 12b the consequent movement of the working face 7a of the resilient member 2a in the direction of the arrow 13a and the movement of the working face 7b of the resilient member 2b in the direction of the arrow 13b tensions the laminar material 11 , where it is trapped between the working faces 7a and 7b and the reaction surfaces 8 of the reaction member 9, while the cutting element 3 effects the required separation of the material to be cut.

[0028] In a yet further alternative, not illustrated, the two reaction surfaces could be supported on the part 5 on either side of the cutting element 3, and the working surfaces could be as illustrated in Figures 2 and 2a.

[0029] Figures 3 and 3a show a further embodiment of the invention wherein the cutting element 3 is rigidly set in a reaction member in the form of a roller 15, with the reaction surfaces located on either side of the cutting element 3. The working faces 7a and 7b are formed on a resilient member 2 which is also in the form of a roller 16 relieved by a groove 10. The radii of the two rollers are so arranged that the circumference of the rigid roller 15 is greater than the length formed by the distance between the working faces 7a and 7b of the roller :16 added to the circumferential distance around the roller from the working faces 7a abd 7b. The coefficient of friction of the material forming the surface of the roller 16 and the working faces 7a and 7b must be higher with respect to the material to be cut than the material forming the surface of the roller 15.

[0030] The two rollers must be so set that the distance between the centres of rotation is less than the sum of the radius 17 of the rigid roller 15 and the radius 18 of the resilient roller 16. The two rollers must be so driven as to move in opposite senses shown by the arrows 19 and 20 and at an angular rate such that the cutting element 3 always matches with the groove 10.

[0031] In an alternative arrangement, the cutting element could be supported in the base of the groove 10 instead of on the roller 15, in which case a relieving groove to receive the tip of the cutting element would preferably be provided in the roller 15. As a yet further alternative, it is envisaged that the roller 16 would have a small cutter element receiving groove therein in place of the groove 10, and the clement 3 would be mounted in a groove formed in the surface of the roller 16.

[0032] In other words, the various reciprocating constructions described with reference to Figures 1, 2 and 2a could also be applied to the rotary construction described with reference to Figures 3 and 3a, and vice versa.

[0033] It will also be appreciated that the various modifications described, for example, in relation to Figure 1 could be applied to at least some of the other embodiments.

Claims

1. A web cutting device characterised in that it comprises two co-operating web tensioning means consisting of a pair of movable working faces (2a,2b) and a reaction surface (8) for co-operation with each working face (2a,2b) together with a cutting element (3) mounted so that at least during a cutting operation it is located between the working faces (2a,2b), the working faces (2a,2b) being so arranged that when they are pressed against their respective reaction surfaces (8) with the web (11) to be cut located between the reaction surfaces (8).and the working faces (2a,2b), the working faces (2a,2b) will tend to move away from the cutting element (3) thus tensioning the web (11) and allowing the cutting element (3) to come into contact with it.

2. A cutting device according to claim 1 characterised in that the working faces (2a,2b) are part of a member formed from elastomeric material so shaped as to cause movement of the working faces (2a,2b) in the direction perpendicular to the direction of movement of the cutting element (3) and perpendicular to the cutting axis.

3. A cutting device according to claim 1 characterised in that the working faces (2a,2b) are part of a mechanism incorporating springs, swinging links and/or cam arrangements (not shown).

4. A cutting device according to claim 1, 2 or 3 characterised in that the cutting element (3) is mounted in a resilient carrier (1) spaced parts of which provide the working faces (2a,2b) which tend to move away from the cutting element (3) when they are pressed against the reaction surfaces (8), the relaxed state of the resilient carrier being such that the working edge of the cutting element (3) is within the perimeter of the carrier as defined by a surface joining the working faces (2a,2b) and moves in the working direction through that perimeter when the carrier is pressed against the reaction surfaces (8).

5. A cutting device according to any one of claims 1-4 characterised in that the reaction surfaces (8) are part of a rigid member (9) which is relieved (at 10) to accommodate the working edge of the cutting element (3).

6. A cutting device according to claim 1, 2 or 3 characterised in that the cutting element (3) is mounted between the reaction surfaces and the working faces are mounted in another carrier (not illustrated).

7. A cutting device according to any preceding claim, characterised in that the reaction surfaces (8) are rigid and have a low coefficient of friction and the working faces (2a,2b) are resiliently deformable and move away from the cutting element (3) when the working faces (2a,2b) are brought into engagement with them.

8. A cutting device according to any one of claims 1-7 characterised in that the cutting element (3) is formed by an array of closely adjacent pointed pins.

9. A cutting device according to any one of the preceding claims characterised in that the cutting element (3) is mounted for reciprocating movement perpendicular to the plane of the material (11) to be cut.

10. A cutting device according to any one of claims 1-8 characterised in that the cutting element (3) is mounted for rotary motion and co-operates with a second member also mounted for rotary motion in a sense opposite that of the first member.

Drawing