WO2013019120A1

WO2013019120A1 - Improvements in cutting blades

Info

Publication number: WO2013019120A1
Application number: PCT/NZ2011/000147
Authority: WO
Inventors: Patrick Petrus Antonius Maria Van Berlo; Jason Paul Rogers
Original assignee: Corcel IP Ltd
Current assignee: Corcel IP Ltd
Priority date: 2011-07-30
Filing date: 2011-08-01
Publication date: 2013-02-07
Anticipated expiration: 2014-01-30

Abstract

This invention relates to a rotary blade, made from an at least partially resilient material, wherein the rotary blade has a thickness, which facilitates lateral flexing of at least a portion of the rotary blade, and wherein the rotary blade includes: " a body portion having a substantially central aperture, and " at least one cutting section extending from the body portion and defined by at least one transition edge and at least one cutting edge, and wherein the rotary blade is configured such that in use the transition edge(s) terminate(s) contact between the cutting edge(s) and a material being cut enabling the cutting section to if necessary laterally flex back toward the body portion.

Description

IMPROVEMENTS IN CUTTING BLADES

STATEMENT OF CORRESPONDING APPLICATIONS

This application is based on the Provisional specification filed in relation to New Zealand Patent Application Number 587122, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates to blades for a cutting apparatus.

In particular, the present invention relates to blades for use with automated cutting apparatus used to cut fibrous material such as corrugated cardboard. However, it should be appreciated that the present invention may be used for the cutting of other materials.

BACKGROUND ART

The blades of the present invention can be used to cut a variety of different materials including paper based products and timber. For ease of reference the present invention will now be described in relation to cutting paper based products.

The cutting of various materials such as fibreboard, corrugated paperboard/cardboard, and in particular thick layers of composite corrugated paperboard/cardboard, such as closed cell coreboard, can be a difficult task. The term 'closed cell coreboard' as used herein refers to composite paper board which has at least one first liner sheet and at least one second liner sheet which respectively sandwich a core having a plurality of cells there between. Thus, closed cell coreboard includes honeycomb paper board which has a honeycomb core, or X-board as is manufactured by Xanita of South Africa, or 3C™ board as manufactured by Corcel. X- board and 3C™ board are composite boards comprising a core manufactured from adjacent strips of single or double face corrugated paperboard sandwiched between two liner sheets so that the flutes run orthogonally (i.e. the flute channels extend from the top liner sheet to the bottom liner sheet).

These products will now, for ease of reference only, simply be termed composite board or simply board. In the packaging industry, it is often desired to cut the board into a number of strips as part of a continuous process. This usually involves lengths of continuous board being fed through a l cutting apparatus.

Typically, the cutting of these lengths of board is achieved with multiple blades. These blades can operate either together, or sometimes independently of each other.

Unfortunately, it is relatively easy for a blade edge to become deflected or otherwise laterally deformed relative to the path of the board and desired cut path which is parallel to the edge of the board. This wayward tracking typically leaves no opportunity for the blade to realign (as it remains embedded in the material being cut) this can cause the blade to gradually track further and further off line.

It should be appreciated that as many metres of board are being processed through the blades, what starts as an initially small misalignment at the commencement of a cutting operation can become very pronounced overtime, as once the blade starts tracking offline, it tends to stay offline on the same incorrect path, gradually exacerbating the problem. This deviation from the desired cut path can result in the significant wastage of material.

Tracking offline also places huge stresses not only on the board but also on the blade. Increased friction on the blade causes heat, which can eventually cause the blades to become warped. The lateral pressure on the blade can also cause damage to the portion of the machine holding the blades and the mechanism driving them.

It is well known in the art that any damage occurring to the blades or the machines driving the blades is not only costly to repair itself, but the downtime in disassembling the machine, in order to replace the blades, can cause considerably losses in terms of production.

It would therefore desirable if a cutting blade could be designed which avoids the problems of misaligned tracking of cutting blades as described above.

Another problem associated with the cutting of board (and other materials) is that of kerf. To prevent the body of the blade from "sticking" or otherwise binding with the material being cut, circular saw and band saw blades have offset teeth which create a kerf wider than the body of the blade. The creation of a wide kerf results in cuts that tear and rip at the paper edges, causing a bad finish and a large amount of dust. Dust contamination can be a considerable problem requiring measures to remove the dust from the floor and atmosphere.

A badly finished edge is also not suitable for further processing. Typically, cardboard is formed by gluing a number of layers together. However, the dust caused by kerfing can contaminate the glue rollers and result in poor lamination between layers of cardboard.

A wide kerf is also wasteful. For example, a 300mm wide composite material may be cut into 9 mm strips with an array of circular saw blades. If the saw blades produce a typical kerf of 3 mm, then only 25 strips can be produced. This means that 75 mm of raw material is turned into dust, which contributes towards an overall loss of 25% of the original material. This loss can be attributed to the kerf created by the blade.

Yet another problem associated with a cutting apparatus is that of crushing. Rotary knives having a tapered cutting edge are commonly used in the paper industry to cut board up to triple wall thickness. The rotary knife rotates at the same speed as the board being cut while being sharpened by air operated stones.

This method functions well, especially for a single blade set up, or if the blades are set sufficiently far apart. If not, corrugated material and glue binds on the body of the knife which is thicker than the cutting edge. Unfortunately, the tapered cutting edge does not provide an accurate square edge - which is a critical requirement when making vertical flute board from layers of laminated corrugated material.

A rotary knife tends to crush and round the top edge of the laminated board upon entry. Thus when the strips of laminated board are reoriented so that the flutes are vertically aligned low spots are created by the rounded edge. As a result the rounded edge does not make contact with the liners being bonded to the strips thereby resulting in a weak composite board.

It would be desirable if there could be provided cutting apparatus which addresses the aforementioned problems.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF THE INVENTION

According to one aspect of the present invention, there is provided a rotary blade, made from an at least partially resilient material, wherein the rotary blade has a thickness, which facilitates lateral flexing of at least a portion of the rotary blade, and wherein the rotary blade includes:

• a body portion having a substantially central aperture, and

• at least one cutting section extending from the body portion and defined by at least one transition edge and at least one cutting edge, and wherein the rotary blade is configured such that in use the transition edge(s) terminate(s) contact between the cutting edge(s) and a material being cut enabling the cutting section to if necessary flex back toward the body portion.

It will be understood that the term 'lateral' as used herein refers to the sideways movement with respect to the plane of the blade and/or direction in which the cut is to be made.

In some preferred embodiments the transition edges and cutting edge also define a void between either: a) the start and finish of a cutting section; and /or b) the rotary blade and the material being cut effectively removing the rotary blade temporarily from any contact with the material being cut.

In a preferred embodiment the transition edge(s) may be configured to provide a bi-directional blade.

In a preferred embodiment of bi-directional blade there is at least one pair of transition edges which diverge from a common point of origin. Most preferably the pair of transition edges are symmetrical about a radial axis through the common point of origin. An advantage of such embodiments is that the blade can cut in both clockwise and anticlockwise directions, thereby removing the risk of being installed in the wrong cutting direction.

In embodiments where the pairs of transition edges are not symmetrical about the common point of origin the blade can have a different cutting characteristics such as the length of cut, or impact of initial cut, depending on the configuration of the respective transition edges.

Other possibilities to those mentioned above are of course envisaged. In embodiments where the transition edges define a specific direction (i.e. clockwise or anticlockwise) in which the blade will cut material the blade may include a marking on at least one surface thereof indicatina if the blade is correctlv installed on a SDindle in order to effect a desired cut.

According to a further aspect there is provided a rotary blade including a body portion and a cutting edge wherein the rotary blade has a uniform thickness as between the cutting edge and the body portion and wherein the cutting edge and body portion are aligned along the same plane.

Preferably, the rotary blade has a cutting edge including a plurality of teeth thereon, the teeth being aligned in the same plane as the body portion from which they directly or indirectly extend.

An advantage of this sort of blade is that the blade produces a kerf which is substantially the same width as the thickness of the blade resulting in a lot less wastage of valuable material than conventional saws.

In some preferred embodiments the single blade embodiment may have holes to help with reducing heat build up caused by friction.

The term 'body portion' as used herein refers to the inner portion of the blade from which the cutting sections peripherally extend.

In preferred embodiments the cutting edges may present an orthogonally oriented surface with respect to the direction in which the material is being cut.

According to a further aspect of the present invention there is provided a rotary blade substantially as described above wherein the cutting sections extend along at least substantially 1/4 of the peripheral edges of the blade.

Preferably the transition edge(s) create a void of at least around 1/16 the circumference of the blade between the start and finish of a cutting section.

Most preferably the transition edge(s) create a void of at least around 1/12 the circumference of the blade between the start and finish of a cutting section. According to a further aspect of the present invention there is provided a cutting assembly which includes a rotary blade substantially as described above.

According to a yet still further aspect of the present invention there is provided a cutting assembly wherein there is provided a spindle including a plurality of rotary blades substantially as described above. Preferably the spindle has adjacent blades offset such that each cutting section on an adjacent blade is next to, or overlaps at least a portion of, a void on a neighbouring blade or vice versa. This acts to minimise friction on the material being processed (which can stress the material and the motor driving the shaft) as well as minimise the potential for trackina off line. In preferred embodiments the cutting assembly includes two plates which retain sheet material whilst being cut the plates including slots for receiving the rotary blades. Preferably, the plates are spaced apart a distance which can hold laminated sheet material in sufficient abutment to maintain bond formation between said sheets. Preferably, the material being processed or otherwise cut with the present invention is paperboard. However, this should not be seen as limiting and persons skilled in the art will appreciate that the present invention may be used to cut a variety of planar sheet materials, such as cardboard, thin medium density fibreboard (mdf), plastic and even thin sheets of metal or plastic. In preferred embodiments the body portion and blade sections are cut from spring steel, as this provides requisite strength, flex, and cutting ability. It should be appreciated however that the body portion and/or blade sections may be made from other materials having appropriate qualities, such as high tensile steel, titanium and any material that has high strength at thin thicknesses and flexibility. In preferred embodiments of the present invention, the thickness of the blade may range from 0.15 to 0.3 mm. In a most preferred embodiment the blade may have a thickness of 0.15mm.

A 'cutting section' as used herein should be understood to mean the portion of the blade which at least partially penetrates and cuts the material being processed. The cutting surface extends out radially from the body portion. In some preferred embodiments the cutting edge may have a plurality of teeth thereon. One advantage of a tooth cutting edge compared to a smooth cutting edge is the reduced contact with the material being cut, which allows the material to be fed through the cutting assembly at a faster rate, than that with a smooth cutting edge.

However, it will be appreciated by persons skilled in the art that other types of cutting edges may be employed depending on the requirements of the end application.

For example, the cutting surface may be configured as a flat edge. This edge configuration is preferred by the inventor for slow to medium throughput of material being cut. However, fast throughput of material can result in a crushing effect on the material proximate to the cut due to the flat edge of the cutting surface. It should be appreciated that in preferred embodiments of the present invention the cutting sections are formed integrally with the body portion.

However, in some embodiments of the present invention, each cutting sections may be provided as a segment or otherwise separate pieces which are secured to a suitably configured body portion. Thus, if one cutting section is damaged or otherwise worn, it can be replaced by removing the segment bearing the cutting section of concern and installing a replacement segment.

In one preferred embodiment, the blade of the present invention is configured with at least three cutting sections. However, persons skilled in the art will appreciate that more or less cutting sections may be provided for depending on the requirements of the user.

In another preferred embodiment the blade may include one or two cutting sections.

The configuration of the cutting sections and the transition surfaces are dependent on the nature of the material from which the blade is fabricated.

The purpose of the configuration of the present invention is to provide the separate cutting sections of the blade with sufficient flex to have the re-ability to realign with the body portion after cutting and exiting the cut material. For example, once the first cutting section has emerged from the material being cut, the transition surface of the blade provides a small window of time in which the first cutting section can laterally flex back into alignment prior to, or when, the cutting section, or an adjacent cutting section, on the rotary blade is penetrating the material being processed.

In the prior art, blades tend to be of greater thickness than the rotary blade of the present invention, in order to avoid distortion or deformation of the blade as it is cutting. Because of the width of the cut line, which is directly related to the thickness of the blade as well as the teeth being configured to create a kerf wider than the thickness of the body portion, there is a consequent loss of material. The thinness of the blade of the present invention and fact the cutting sections are aligned in the same plane as the body portion is important, as it ensures there is minimal wastage of the material being processed.

In preferred embodiments of the present invention, the end of the transition surface of the blade coincides with the beginning of the cutting edge. In preferred embodiments of the present invention, the beginning of the transition surface of the blade and the end of the cutting edge form an arc. The beginning of the arc (and the transition surface of the blade) being closer to the centre of the axis of rotation than the cutting edge.

In addition to the ability of the cutting sections to flex, the timing of the cutting operation also needs to be taken into account when designing a blade and cutting assembly. For example, if the blade is spinning at high speed (say 3000 rpm) then a cutting section needs sufficient time to spring back into alignment before it contacts again the material to be cut. Thus, if the transition edge(s) of the blade is/are are not long enough then there will be insufficient time for the cutting section to spring back before the cutting section contacts the material being processed. In a preferred use of the present invention, there is provided a cutting assembly that includes a number of rotary blades, substantially as described above, that are positioned on a single rotatable shaft.

In this embodiment of the invention, the blades of the cutting assembly can be sandwiched between spacers on the shaft securing the blades and providing much of the stability required.

In some embodiments of the present invention, the cutting assembly may be in the form of a removable blade cartridge. This has a number of advantages, including being relatively easy to maintain.

A further advantage of the blade cartridge embodiment is that the spacers between the adjacent blades may be of different sizes on different cartridges. This enables different blade cartridges to be used to produce different widths from the sheet material being cut without the need to individually reconfigure spacers and blades on a shaft.

A shaft spinning at 3000rpm and above in a preferred embodiment provides sufficient production speed for each blade to cut a metre of board of vertical flute composite paperboard every three seconds. Further, it should be appreciated that increasing the radius of the cutting section from the axis of rotation can increase production speed for a rotary blade while at the same time reducing the number of revolutions per minute.

In preferred embodiments the spacers are configured to firmly hold the blade on both sides thereof to minimise flexing of the body portion of the blade. In preferred embodiments of the present invention there is provided a cutting apparatus which incorporates at least two cutting assemblies each of which comprises a spindle including a plurality of rotary blades thereon, wherein the spindle of each cutting assembly is vertically and horizontally offset with respect to the other, wherein the spindles are positioned so that material to be cut can be fed between the blades on respective spindles such that each assembly cuts half way through the material from opposing sides thereof.

Therefore, as a consequence of this arrangement each blade on a respective shaft does not have to penetrate as far into the board, as would be required, if cutting through the entire thickness of the material. Consequently, thinner blade sections can be used without risking breakage. By using two blades, each cutting half of the material, the cutting sections of the blade extend radially a smaller distance out from the outer circumferential surface of the spacers. The cutting sections may therefore radially extend in the order of 1 mm to 50mm out (which defines the maximum cut depth) from the outer circumferential surface of a spacer, depending on the depth of cut required. Generally, trying to keep the maximum cut depth to a minimum distance helps ensure there is less force on the cutting sections to facilitate a thin blade construction which is less prone to undue lateral flexing and hence less prone to breakage.

In other embodiments, there may be provided multiple shafts (say four) each of which make a partial cut (say a quarter of the material depth) to speed up throughput of the card through the cutting apparatus.

It is envisaged that the blade sections could be extremely thin if they are to be used in relation to corrugated paperboard/cardboard and other similar fibrous or composite materials. For example, the blade sections could be as thin as 0.15 to 0.3 mm. This thickness is sufficiently thin to cut material of those types and also not require sharpening. It will be appreciated that generally the material being cut is carried along a conveyor belt or similar transportation means towards the cartridge. During cutting, there is a possibility that there may be some slight vertical movement of the material due to the cutting action of the blades.

To reduce this possibility, the material being processed may be held during the cutting process. In such embodiments, the material may pass between slotted metal plates located between the shaft(s) and material being cut. In this embodiment of the invention, the plates have slots substantially aligning with the blades on a shaft. The cutting sections pass through the slots and penetrate the material an appropriate depth.

The plates effectively sandwich the material being processed against any substantially vertical forces imparted via the cutting action of the blades. Alternatively, the plates may be located just before and just after the blades. Obviously, in this embodiment, there is no need for apertures in the plates to allow passage of the blades.

A significant aspect of the present invention is the transition surface between the cutting sections of the blades. The inventor has recognised that previous problems with tracking can be solved if there is a loss of contact between the cutting sections of a blade for a period of time.

Therefore, the inventor prefers that the space/void between adjacent cutting sections is such that the following cutting sections which cuts the material is not so close that it is compelled to follow in the track made by the previous cutting sections. For example, each blade is capable of having sufficient resilience such that when a first cutting section leaves contact with the board, the cutting section can spring back into its normal alignment. Thus when the blade rotates around and contacts the board again with the following cutting section, any previous misalignment or tracking will not be present. Indeed, as soon as the first cutting section leaves the board, the following cutting section already in the correct alignment so that any tracking that occurs would only be present for the duration that the first cutting section was in contact with the material being processed. It should be appreciated that this tracking would be minimal given the high velocity at which the blades are spinning.

A further advantage by having a transition surface between the cutting sections of the blade is that there is less friction on the blade as a whole due to the reduced cutting contact between the blade and the board. With less friction, there are less stresses on the blade and the shaft to which it is attached. Further, less friction means less heat and less likelihood of the blades warping as a consequence of that heat.

The blades mostly break the paper fibres apart thus producing almost no dust in the cutting action. The broken fibres get pushed out of the way and bend into the material being cut. Thus, the body of the blade has little to bind on further ensuring low friction between the blades and the material being cut. It should be appreciated that preferred embodiments of the present invention may address one or more of the problems in the prior art, namely:

• little or no tracking;

• minimises dust;

• minimises product damage; · increased yield;

• minimises friction;

• minimises warping of cutting blades;

• produces a square cut edge;

• produces sharper board edges; · minimises or eliminates the need for sharpening of the blades;

• is easily dismantled.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a side view of a single blade in accordance with one embodiment of the present invention;

Figure 2 is a perspective view of a cartridge in accordance with one preferred embodiment of the present invention;

Figure 3 is a cross sectional view showing a cutting apparatus in accordance with one preferred embodiment of the present invention; and

Figure 4 is a perspective view of the cutting apparatus shown in Figure 3;

Figure 5 is a side view of a single blade in accordance with a further preferred embodiment of the present invention;

Figure 6 is a side view of a single blade in accordance with a further preferred embodiment of the present invention; and

Figure 7 is a side view of a single blade in accordance with still further embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Figure 1 illustrates a rotary blade generally indicated by arrow (1 ) in accordance with one preferred embodiment of the present invention.

The rotary blade (1 ) has a body portion (2) and a central aperture (3) which fits onto a shaft (7) shown in Figure 2. The body portion (2) has three cutting sections (4) which are defined by cutting edges (5) and transition edges (6).

In this embodiment, the cutting sections (4) are integral with the body portion (2) and radially extend therefrom. However, it should be appreciated that in other embodiments, the cutting sections (4) may be provided as separate pieces or segments which are secured to a suitable configured body portion (not shown).

The transition edges (6) are separated from each other by the cutting edges (5).

In the illustrated embodiment, the cutting edges (5) are toothed. The cutting direction is indicated by arrow.

Figure 2 illustrates a number of the blades (1 ) on a shaft (7) to form a blade cartridge (100). In this embodiment the blades (1 ) are separated by spacers (8). The spacers (8) have a wider diameter than the central aperture (not shown but indicated in Figure 1 ) of the blades (1 ). This means that the blades (1 ) are at least partially supported through being sandwiched between the adjacent spacers (8).

It can be seen that the transition edges (6) of the blades (1 ) extend to at least the outer circumference of the spacers (8) as seen in Figure 1. This enables the cutting sections (4) to have the flex required to re-align with the body portion (2). The blades (1 ) are arranged on shaft (7) so that adjacent blades have their cutting sections (4) at least slightly offset. This results in cutting sections on adjacent blades being adjacent to a void formed by the transition edges (6) of a neighbouring blade.

Figures 3 and 4 illustrate how the blades (1a) and (1 b) can act to cut a strip of laminated corrugated paper board (9).

Each of the blades (1a) and (1 b) are on opposite sides of the paper board (9) to each other, as well as being offset with respect to each other.

It can be seen that the board (9) is positioned relative to the blades (1a) and (1 b) such that each blade cuts half or just over half way through the width of the board (9). The board (9) is supported on its outer faces by plates (10, 1 1 ) which ensure the board (9) remains firmly in contact with the cutting edges. The plates (10, 11 ) have slots (1 1 ,12) through which the blades pass and penetrate the board.

Figure 5 shows a uni-directional cutting blade 5000 which has a single cutting section (5001 ) and cutting edge (5002) which terminates at transition edge (5003) and starts at transition edge (5004). The cutting blade (5000) has a marking in the form of arrow (5005) which indicates the cutting direction of the blade. In some embodiments a colour may be used, such as green painted on one side of the blade, to indicate which side of the blade should be facing a person installing a blade on a shaft.

Figure 6 shows a cutting blade 9000 which has a cutting section (9001 ) transition edges (9002) and (9003) which are symmetrical about radial axis (9004). The cutting blade (9000) is bidirectional and has an identical cutting action in both directions.

Figure 7 shows a cutting blade 10000 which has a cutting section (10001 ) transition edges (10002) and (10003) which are non-symmetrical about radial axis (10004). The cutting blade (10000) is bi-directional and has a different cutting action in the clockwise direction (10005) to that in the anti-clockwise direction (10006) due to the non-symmetrical configuration of the transition edges.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims

WHAT WE CLAIM IS:

1. A rotary blade, made from an at least partially resilient material, wherein the rotary blade has a thickness, which facilitates lateral flexing of at least a portion of the rotary blade, and wherein the rotary blade includes:

• a body portion having a substantially central aperture, and

• at least one cutting section extending from the body portion and defined by at least one transition edge and at least one cutting edge, and wherein the rotary blade is configured such that in use the transition edge(s) terminate(s) contact between the cutting edge(s) and a material being cut enabling the cutting section to if necessary laterally flex back toward the body portion.

2. A rotary blade as claimed in claim 1 wherein the transition edges and cutting edge also define a void between either: a) the start and finish of a cutting section; and /or b) the rotary blade and the material being cut effectively removing the rotary blade temporarily from any contact with the material being cut.

3. A rotary blade as claimed in claim 1 which is in the form of a bi-directional blade there is at least one pair of transition edges which diverge from a common point of origin.

4. A rotary blade as claimed in claim 3 wherein the pair of transition edges are symmetrical about a radial axis through the common point of origin.

5. A rotary blade as claimed in any one of the preceding claims including a body portion and a cutting edge wherein the rotary blade has a uniform thickness as between the cutting edge and the body portion and wherein the cutting edge and body portion are aligned along the same plane.

6. A rotary blade as claimed in claim 5 wherein the rotary blade has a cutting edge including a plurality of teeth thereon, the teeth being aligned in the same plane as the body portion from which they directly or indirectly extend.

7. A rotary blade as claimed in any one of the preceding claims wherein the cutting sections extend along at least substantially 1/4 of the peripheral edges of the blade.

8. A rotary blade as claimed in any one of the preceding claims wherein the transition edge(s) create a void of at least around 1/16 the circumference of the blade between the start and finish of a cutting section.

9. A rotary blade as claimed in as claimed in claim 8 wherein the transition edge(s) create a void of at least around 1/12 the circumference of the blade between the start and finish of a cutting section.

10. A rotary blade as claimed in any one of the preceding claims wherein the thickness of the blade may range from 0.15 to 0.3 mm.

1 1. A cutting assembly which includes a rotary blade as claimed in any one of the preceding claims.

12. A cutting assembly as claimed in claim 1 1 wherein the cutting assembly comprises a

spindle including a plurality of rotary blades thereon.

13. A cutting assembly as claimed in claim 12 wherein the cutting assembly is in the form of a removable blade cartridge.

14. A cutting apparatus which incorporates at least two cutting assemblies each of which comprises a spindle including a plurality of rotary blades thereon, wherein the spindle of each cutting assembly is vertically and horizontally offset with respect to the other, wherein the spindles are positioned so that material to be cut can be fed between the blades on respective spindles such that each assembly cuts half way through the material from opposing sides thereof.