WO2005070628A1

WO2005070628A1 - Male knives

Info

Publication number: WO2005070628A1
Application number: PCT/GB2005/000289
Authority: WO
Inventors: Dennis Gallagher
Original assignee: Dennis Gallagher
Priority date: 2004-01-27
Filing date: 2005-01-27
Publication date: 2005-08-04
Also published as: GB0401672D0

Abstract

There is provided a male knife (18, 19) for mounting on a roll of a slotting device. In one embodiment the male knife (18) has an arcuate outer cutting edge (20) with a tapered leading end (47) and a trailing end having a cutting tip (21) projecting radially beyond the cutting edge (20) and circumferentially inside the trailing end face (43). In another embodiment the male knife (19) has an arcuate cutting edge (20), the leading end of which is undercut (36) to produce a leading cutting edge (37).

Description

Male Knives

The present invention relates to male knives utilised in a rolling machine for cutting slots in a succession of advancing sheets or boards made of, for example, corrugated sheet or paperboard. This type of rolling machine is comrnonly used in the production of corrugated boxes or cartons to form linear slots in flat board blanks. The blanks can then be assembled into boxes by later folding and gluing. These rolling machines, or slotting devices, often incorporate creasing mechanisms to establish the folds in the finished boxes. Generally, each slot has parallel sides, one end of the slot opening to a free transverse edge of the board stock and the other end being closed by a transverse cut edge. The slots are formed by male knife/female knife combinations, the female knife comprising an annular straight sided groove formed in a roll. Each male knife is secured to an opposed second roll and projects outwardly therefrom in a radial direction and is closely engagable in the female groove during a particular portion of the rotation of the rolls to perform a cutting action. According to one aspect of the present invention there is provided a male knife for mounting on a roll of a slotting device, the male knife having an arcuate outer cutting edge section which has a leading end and a trailing end, said leading end having an inwardly tapered portion extending in an outward direction. According to another aspect of the present invention there is provided a male knife for mounting on a roll of a slotting device, the male knife having an arcuate outer cutting edge section which has a leading end and a trailing end, said leading end being undercut such that the leading end of the cutting edge section provides a cutting edge with an acute angle less than 90°. According to a further aspect of the present invention there is provided a male knife for mounting on a roll of a slotting device, the male knife having an arcuate outer cutting edge section which has a leading end and a trailing end, the trailing end terminating in a cutting tip which projects radially outwardly beyond the arcuate outer cutting edge section and which is circumferentially inside the circumferential extremity of the trailing end. In preferred arrangements the male knife has opposed axial faces which are substantially parallel to each other. Usually the tapered portion at the leading end is up to 1 mm maximum on each axial face but preferably the tapered portion at the leading end is in the region of 0.25 mm on each axial face. Normally said outward direction is between a radial and a circumferential direction, between 30° and 60° to the radial direction. With some arrangements holes are provided remote from the cutting edge section for securing the knife to the roll of the slotting device. In some embodiments the arcuate outer cutting edge section comprises two parallel arcuate cutting edges and/or said two cuttmg edges are serrated. Often, the male knife has an arcuate inner face, a radial leading end face and a radial trailing end face. A further preferred feature is that the leading end face is undercut at its outer radial extremity such that the leading end of the cutting edge section provides a transverse cutting edge with an acute angle less than 90°. Conveniently the undercut is part-circular in radial cross section. In preferred arrangements the knife has a radial leading end face and a radial trailing end face which includes the trailing end of the outer cutting edge section and also there is an arcuate inner face spaced from and parallel to the arcuate cutting edge section. Embodiments of the present invention will now be described in more detail making reference to the accompanying drawings in which: Figure 1 is a cross-section through part of a known rolling slotting machine, Figure 2 is a view of a blank of the type produced using a machine, as shown in figure 1, Figure 3 is a simplified section through interengaged male and female knives from the figure 1 machine, Figure 4 shows an axial side view of a male knife according to one aspect of the present invention, Figure 5 is a circumferential end view of the male knife shown in figure 4, Figure 6 is an opposite circumferential end view of the male knife shown in figure 4, Figure 7 is an axial side view of a male knife according to another aspect of the present invention, Figure 8 is a circumferential end view of the male knife shown in figure 7, and Figure 9 is an axial side view similar to figure 7 of a modified male knife according to the present invention. In figures 1 to 3 there is shown a basic slotting machine 10 for producing slots in a succession of blanks 12 advancing through the machine. The cutting station shown in figure 1 will commonly be repeated at intervals along the width of the machine in order to cut a number of slots simultaneously at various locations across the width of the machine. Typically the blanks 12 will be in sheet form made from corrugated board or paperboard. The fluting of the corrugated board can be parallel to the lengthwise direction of the machine or transverse to the lengthwise direction of the machine (reverse flute). The basic slotting machine 10 comprises two main rolls 13, 14 adapted to rotate in opposite directions as indicated by the arrows. For each cutting station as illustrated, the first roll 13 has a circumferential groove 15 which is the female part of a male/female knife arrangement. Ideally the groove 15 has substantially parallel, radially extending side walls 16 which can be seen more clearly in figure 3. The groove 15 can either be a machined groove or may be the result of another method of creation such as a spacer element of smaller diameter between two larger diameter sections of roll. The second roll 14 has removably attached to it, by means of bolts 17, for example a pair of angularly spaced male knives 18, 19 which are circumferentially aligned with each other. The two rolls 13, 14 are located accurately relative to one another so that as they rotate, the radial extremities of the male knives 18, 19 engage closely within the groove 15 at appropriate times during the rotation of the rolls 13, 14 to effect a cutting action at each side wall 16. Each male knife 18, 19 has an arcuate outer cutting edge section 20 which may be serrated or otherwise enhanced to improve the cutting action. The cutting edge section may be solid in the axial direction or there may be a recessed area between axially extreme cutting edges. This will be illustrated in more detail later. The first knife 18 or 'front' knife has a projection 21 at the frailing end of its cutting edge section 20, which projection 21 terminates in a transverse cutting edge 22. The front knife 18 starts its cut at the leading edge 23 of the blank 12 and forms a parallel sided front slot 24 in the blank 12. The transverse cutting edge 22, which is usually perpendicular to the direction of the front slot 24, closes the slot 24 and the removed board drops away from the front slot 24. The second knife 19 or 'back' knife provides only the arcuate outer cutting edge section 20. The leading end of this meets the blank 12 and punches through the board and into the groove 15 of the first roll 13, with the cutting edge section 20 following on to form a parallel sided back slot 25 in the blank 12. A typical result is shown in the blank 12 of figure 2 in which there are three front slots 24 and three back slots 25. The blank 12 can be folded and glued to form a standard rectangular box with foldable top and bottom flaps defined by the slots 24, 25, and the free edges. hi practise, there are a number of problems associated with this type of machine. Usually, the end user of the box requires clean-cut slots 24, 25. This is especially the case with boxes intended for the food or pharmaceutical/medical industries. The standard knives will blunten through use and do have to be replaced. However, as the knives blunten the quality of the slots deteriorates. Also, to obtain cleaner cut slots requires very close tolerances between the male knives 18, 19 and the female knives 15. This in turn requires precise location of the rolls 13, 14 otherwise there can be a tendency to damage both knife sets if the male knives 18, 19 do not accurately engage the groove 15. This results in chipping of the edges of the knives 18, 19, 15. Known attempts to improve the quality of the cut have included serrations to the male knife cutting edges. In addition, in some arrangements the space between the axially spaced cutting edges of a male knife has been relieved. In figures 4 and 5 there is shown a back knife 19 according to the present invention. The back knife 19 has spaced axial facing surfaces 30, 31 which are parallel to each other and generally radial leading and trailing end faces 32, 33. The back knife 19 also has an inner arcuate face 34 and a radially outer, arcuate cutting edge section 20. Also provided are two spaced holes 35 for receiving bolts 17 for securing the back knife to the main roll 14. The leading end of the back knife 19 is provided with an undercut 36 adjacent the cutting edge section 20. The undercut 36 is shown as a part circular machining as this is simple and cheap to form. The result is a cutting edge 37 having an arcuate angle of less than 90° at the leading end of the back knife. The actual angle will depend on the size of the machine and the quality required. This cutting edge 37 makes a clean cut at the beginning of the formation of the back slot 25 even when difficult types of board are being used, such as reverse flute corrugated board. Not only does the edge 37 result in a cleaner cut but it also increases the longevity of the knives, both male and female, as a result of the cleaner cutting. Another modification shown in figures 4 and 5 is that the radially outer part 38 of the leading end tapers slightly inwardly in the outward direction. The taper on each side may be a maximum of 0.25 mm relative to both the axial face 30, 31 and to the radial leading end face 32 but the precise amount of the taper and the angle thereof will vary from machine to machine. The effect of the chamfered leading end is that the male knife engages more easily within the female groove 14 in the first roller 12. The chamfered edge acts as a lead-in and substantially reduces damage to the male and female knives 18, 19. This in turn results in increased quality for a longer period of time and allows for some play in the mountings of the rolls 13, 14. Figure 6 shows the trailing end face 33 of the back knife 19. This shows more clearly the recessed area 38 between the axially opposed cutting edges 39 of the cutting edge section 20. This optional feature is, however, one of a number of known modifications to the basic form of the back knife 19. Figures 7 and 8 illustrate a front knife 18 has an arcuate cutting edge section 20, spaced axial facing surfaces 40, 41 which are generally parallel to each other and generally radially leading and trailing end faces 42, 43. The front knife 18 also has an inner arcuate face 44 and two spaced holes 45 for receiving bolts 17 for securing the front knife to the main roll 14. Normally the transverse cutting edge 22 at the trailing end of the front knife 18 is formed at the trailing radial end face 43 but in the present arrangement the cutting edge is moved circumferentially forwards towards the leading end face 42 by a couple of millimetres. This enables better alignment with any cross cut blades which are provided to cut the ends from the glue panel 46 of the blank 12. Also, the radially outer part 47 of the leading end of the front knife 18 is chamfered such that it tapers slightly inwardly in the outward direction. The taper on each side may be a maximum of 0.25 mm but the precise amount of the taper and the angle thereof both to the axial face end and to the radial leading end face 42 will vary from machine to machine and will depend on the size of the knife 18. The chamfered section 47 gives rise to the same effects and advantages as discussed above in relation to the back knife 19. Figure 9 shows a modified front knife similar to that shown in figure 7. Like features have, therefore, been given like reference numerals. In figure 9, the front knife 18 has a relief undercut 50 in the trailing radial end face 43. In this embodiment the undercut is part- circular, semi-circular in fact, and begins about one fifth the way down the end face 43 from the projection or tip 21 and ends about three fifths the way down. The precise shape and location of the undercut 50 are, however, a matter of design choice and will vary depending on the machine and products being cut. It will be appreciated that the illustrated arrangements are examples and that modifications will be possible whilst remaining within the scope of the attached claims.

Claims

1. A male knife for mounting on a roll of a slotting device, the male knife havmg .an arcuate outer cutting edge section which has a leading end and a trailing end, said leading end being undercut such that the leading end of the cutting edge section provides a cutting edge with an acute angle less than 90°.

2. A male knife as claimed in claim 1 wherein the undercut is part-circular in radial cross-section.

3. A male knife as claimed in claim 1 or claim 2 wherein the male knife has opposed axial faces which are substantially parallel to each other.

4. A male knife as claimed in claim 3 wherein the arcuate outer cutting edge section comprises two parallel arcuate cutting edges.

5. A male knife as claimed in claim 4 wherein said two cuttmg edges are serrated.

6. A male knife as claimed in any one of claims 1 to 5 wherein the male knife has an arcuate inner face, a radial leading end face and a radial trailing end face.

7. . A male knife as claimed in any one of claims 1 to 6 wherein holes are provided remote from the arcuate cutting edge section for securing the knife to the roll of the slotting device.

8. A male knife as claimed in any one of claims 1 to 7 wherein the leading end has an inwardly tapering portion extending in an outward direction.

9. A male knife for mounting on a roll of a slotting device, the male knife having an arcuate outer cutting edge section which has a leading end and a trailing end, the trailing end terminating in a cutting tip which projects radially outwardly beyond the arcuate outer cutting edge section and which is circumferentially inside the circumferential extremity of the trailing end.

10. A male knife as claimed in claim 9 wherein the knife has a radial leading end face and a radial trailing end face which includes the trailing end of the outer cutting edge section.

11. A male knife as claimed in claim 10 wherein the radial trailing end face incorporates a cut away section.

12. A male knife as claimed in claim 11 wherein the cut away section is part-circular.

13 A male knife as claimed in any one of claims 9 to 12 wherein there is an arcuate inner face spaced from and parallel to the arcuate cutting edge section.

14. A male knife for mounting on a roll of a slotting device, the male knife having an arcuate outer cutting edge section which has a leading end and a trailing end, said leading end having an inwardly tapered portion extending in an outward direction.

15. A male knife as claimed in claim 14 wherein the male knife has opposed axial faces which are substantially parallel to each other.

16. A male knife as claimed in claim 15 wherein the tapered portion at the leading end is up to 1 mm maximum on each axial face.

17. A male knife as claimed in claim 16 wherein the tapered portion at the leading end is in the region of 0.25 mm on each axial face.

18. A male knife as claimed in any one of claims 14 to 17 wherein said outward direction is between a radial and a circumferential direction, between 30° and 60° to the radial direction.

19. A male knife as claimed in any one of claims 14 to 18 wherein holes are provided remote from the cutting edge section for securing the knife to the roll of the slotting device.

20. A male knife as claimed in any one of claims 14 to 19 wherein the arcuate outer cutting edge section comprises two parallel arcuate cutting edges.

21. A male knife as claimed in claim 20 wherein said two cutting edges are serrated.

22. A male knife as claimed in any one of claims 14 to 21 wherein the male knife has an arcuate inner face, a radial leading end face and a radial trailing end face.

23. A male knife as claimed in claim 22 wherein the leading end face is undercut at its outer radial extremity such that the leading end of the cutting edge section provides a transverse cutting edge with an acute angle less than 90°. ^■

24. A male knife as claimed in claim 23 wherein the undercut is part-circular in radial cross section.

25. A slotting device including one or more male knives as claimed in any one of claims 1 to 24.