GB2101915A - Method and apparatus for cutting layered material - Google Patents

Abstract

A machine for cutting tobacco leaf is provided in which the leaf is fed by two converging conveyor bands 15, 16 to be cut by cutter blades 10 arranged in a holder which rotates on an axis parallel to the axis of the throat, so that the cutting edge of the knives are caused to pass across the mouthpiece. Each cutter blade has an undulating cutting edge which is repeatedly sharpened by means of a rotating grinding wheel 30 extending over the whole length of the blade. The grinding wheel is substantially cylindrical with an undulating profile formed by a series of contiguous grooves and is so disposed in relation to the path of movement of said cutter blade that the cutting edge is sharpened at each pass thereof past the wheel. <IMAGE>

Description

SPECIFICATION Method and apparatus for cutting layered material This invention relates to a method and apparatus for cutting layered material and particularly but not solely for cutting tobacco.

Machines are known for cutting tobacco leaf, in which the leaf is fed into a convergent throat of rectangular cross section formed by two parallel plates and two converging conveyor bands or by two parallel plates and two converging roller conveyors. At the convergent end of the throat is a mouthpiece. The leaf is fed into the throat at the divergent end and the conveyor bands or rollers are driven through the mouthpiece, where the leaf is cut as it issues from the mouthpiece either by a single knife caused to reciprocate across the mouthpiece or by one or more knives arranged in a holder which rotates on an axis either at right-angles or parallel to the axis of the throat, so that the cutting edge of the knife or knives are caused to pass across the mouthpiece.The convergence of the throat compresses the leaf sufficiently so that it may be cut and not pulled from the mouthpiece. One of the two band or roller conveyors is free to move and pressure is applied to it so that the compression of the leaf can be regulated. The width of cut of the shreds can be adjusted by altering the conveyor speed and hence the distance the compressed leaf is fed through the mouthpiece between cuts by the knife or knives.

Such machines are disclosed for example in British Patents Nos 751 014, 1078843 and 1195163.

Furthermore, a machine is known (see German 0.5.1532051) which can cut the lamina material to give a wavy (crinkled) profile to the resulting strands.

The tobacco cut in this way improves the filling capability in the production of cigarettes.

A problem arising in such a machine for cutting the tobacco into wavy strands is that of sharpening the cutter blades and it is an object of the present invention to provide an improved method and apparatus ensuring more reliable sharpening with less complicated mechanism, compared with the known arrangement.

According to the invention, there is provided a method of cutting lamina material comprising feeding the material by divergent conveyor bands towards a cutting position, cutting the material by means of a rotary cutter including at least one cutter blade extending parallel to the axis of the rotary cutter, said blade having an undulating cutting edge and effecting repeated sharpening of said edge by means of a rotating grinding wheel extending over the whole length of the blade, said wheel being substantially cylindrical with an undulating profile formed by a series of contiguous grooves, said wheel being so disposed in relation to the path of movement of said cutter blade that the cutting edge is sharpened at each pass thereof past the wheel.

Further according to the invention there is provided a cutting machine comprising a rotatable cutting drum, one cutting blade on said drum, extending axially thereof, said blade having an undulating cutting edge, conveyor bands arranged so as to diverge towards the cutting drum, and a sharpening wheel disposed on an axis parallel to the axis of the drum and extending over the whole length of the cutting edge of said blade, said wheel being substantially cylindrical and having an un dulating profile formed by a series of contiguous annular grooves.

Another problem arising from the use of a wavy cutting edge, is the tendency for the tobacco strands to break into short lengths. This is caused by the tips of the blade twisting the strands at points at each side of the tips which, in certain circumstances, eg.

when the tobacco is slightly too dry, fractures the strands.

Accordingly, a further feature of the invention comprises a cutter blade of steel having an undulating cutting edge formed by grinding a series of grooves on one side of said sheet at said edge and a second series of grooves on the other side of the said sheet and, of which, second series the pitch is offset by half the pitch of the grooves of the first series, whereby the cutting edge, although undulating viewed in the plane of the sheet, is nearly or substantially straight when viewed at the normal to the plane of the sheet.

Constructional forms of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 3 shows an elevation in the direction of arrow A in Figure 5 of part of a knife having grooves of sinusoidal cross section, Figure 4 shows the knife viewed in the direction of arrow B in Figure 5, Figure 5 is a section taken along the line C-C in Figure 4.

Figure 1 is a side elevation of a rotary cutting machine with parts omitted for clarity, Figure 2 is an isometric end view of the machine showing the cutting drum and sharpening cylinder, various parts being omitted for clarity, Figure 6 is an elevation of a profiled grinding cylinder, Figure 7 is a schematic section through the knife mounted on the cutting cylinder of the rotary cutting machine in the region of the mouth of the conveyor mechanism, Figure 8 shows a portion of cut tobacco of the desired wavy form, Figure 9 is a part elevation of a modified cutting blade viewed in the direction of arrow X in Figure 10, and Figure 10 is a schematic view showing three sections, taken along the lines A, B and C of Figure 9, and groove profiles.

The cutting machine as shown in Figure 1 comprises conveyors 15,16 driven by a motor 17 towards a mouth M through which the tobacco lamina T is compressed. The pressure at the mouth is adjustable by means of a jack 18 arranged between a fixed part of the machine and a frame 19 which carries sprockets 20 to supporting the conveyor 16.

Adjacent the mouth is a cutter drum 21 on which is mounted a plurality of the knives 10 described below. The drum, which is driven by means not shown, may be rotated at a speed selected in relation to the tobacco feed speed to determine the width of cut (or vice versa). The cut tobacco is collected in a hopper 22.

The plate knife 10 shown in Figures 3 to 5 is ground along one edge with sinusoidal section grooves 11 obliquely to the plane of the knife at a pitch of approximatey 1 cm and repeated so as to cover the entire cutting edge. The angle of inclina tion of the grooves to the plane of the knife may be conveniently 10-30".

The effect of the grooves is to produce an undulating cutting edge 12 of sinusoided shape. If desired, the knife which may be typically 45cm in length may be formed with interruptions such as slots or steps in its cutting edge, so that predeter mined lengths of cut tobacco are produced.

Whilst a regular sinusoidal shaped edge gives a suitable wavy shape to the tobacco it it possible to form irregular undulations. However, it is necessary that the portions of the edge producing the predeter mined lengths of tobacco required be continuous.

The knife of the example may be used in a reciprocating single knife cutting machine of a known kind described in Patent No 1195163 or in the rotary cutter as shown in Figures 1 and 7.

The bottoms and tops of the undulating cutting edges of the knives 10 lie on concentric pitch circles 23,24, (see Figures 5 and 7). The mouth M of the cutting machine is formed by a top lining strip 25 and a bottom strip or anvil 26 which are profiled over the lateral extent of the mouth to complement the profile of the cutting edges of the knives.

The knives may be fixed to the drum by clamps or guides 27. However, unless specially hard wearing material is used for the knives it is preferred to provide an arrangement for feeding the knives outwardly to maintain a pitch determined by the fixed position of the lining strips and anvil with means for continuously sharpening the cutting edges.

Such a feed arrangement comprises a mechanism forfeeding a knife stepwise in the direction of its own plane as the knife edge is ground away by a grinding device, the mechanism including a ratchet wheel, means for rotating the ratchet wheel step wise in one direction only and a hollow shaft carried by the ratchet wheel, a sliding shaft linked to the I knife, threaded externally to the inside surface of said hollow shaft and prevented from rotating, whereby step-wise rotation of said ratchet wheel imparts a sliding motion to said sliding shaft to feed the knife. On rotation of the drum the knives are sharpened over their entire width by a grinding wheel 30 (see Figure 1) driven by a motor 31 and mounted on arms 32 pivoted on a fixed post 33.The arms 32 are supported on adjusting screws 34 engaging a fixed part of the machine. The motor 31 is mounted on a yoke 29 fixed to rotate with said arms and is coupled to the wheel 30 by a belt 35. The arm 32 is connected to a fluid activator 36 which serves to pivot the grinding wheel into an inopera tive position for the purpose of replacement of the knives and the grinding wheel.

The grinding wheel 30 is shown enlarged in Figure 6 and comprises a tubular mild steel member having grooves 37 on the periphery thereof to provide a sinusoidal profile.

The surface of the grinding wheel is coated with boron nitride (Borozon, Registered Trade Mark), by electro-deposition or by fine diamond particles secured by adhesive and binders in a known manner.

Cleaning means may be provided adjacent the grinding cylinder to remove tobacco and moisture which might otherwise render the grinding cylinder ineffective.

Alternatively, the cylinder may be made of an abrasive material (eg. aluminium oxide) which may be dressed with a traversing dresser mechanism and feed system to retain the profile of the cylinder due to wear.

The lamina tobacco is fed into the mouth M between the two conveying conveyors 15, 16 and compressed so that it is driven through the mouth as a plug (cheese). As the plug emerges it is shredded by the knives 10 into strands 40 having a wavy configuration such as that shown in Figure 8 having preferably a width X from 1 to 0.2mm.

By providing full width sharpening of the knives 10, in which the entire edge of the knife is sharpened at one pass by the sharpening cylinder, the construction of the cutting machine is considerably simplified over known arrangement with resulting economy.

The knife shown in Figures 3,4 and 5 is adequate for cutting tobacco which has been conditioned to contain the correct amount of moisture. However, in certain circumstances, especially if the tobacco is a little dry, the strands may break. This is because as the tips of the 'teeth' of the knife edge enter the tobacco and progressive cutting take place from the tip of the root, the tobacco engaged by the tip moves down and distorts (twists) the cut portion of the strand(s) in relation to the adjacent uncut regions.

To overcome this, a modified knife, as shown in Figures 9 and 10, has been produced in which grooves have been provided on both sides of the plate, one series of grooves being offset by half the pitch of the other series.

The knife 50 shown in Figures 9 and 10, is formed with a first series of grooves 51 on one surface 52, (ie. the side facing away from the tobacco cake when in use). These grooves extend from the surface of the knife to a depth of between 0.5 and 0.75 the thickness of the plate (preferably 0.7), and have a sinusoidal profile as shown in the projection 53 within the elevation. The grooves havetheirvalleys and hills parallel to the surface 52,54 and extend parallel to the sides of the plate. A second series of grooves 55 is formed at the knife edges obliquely of the surface 54 with the grooves offset from the grooves of the first series by an amount equal to half the groove pitch. The profile of the second series (see projection 56) is identical to that of the first series. The 'valleys' 60 and 'hills' 61 are disposed at about 20" to the plate surface 52.

A cutting edge 57 is formed by the two series of grooves at the juncture thereof. As seen in Figure 9 the edge 57 is substantially straight when compared with the first example (Figure 4) whereby in use, the tobacco is cut substantially along one straight line.

As a result, no distortion of the strands occurs likely to break the strands.

Claims (17)

1. A method of cutting layered material comprising feeding the material by divergent conveyor bands, cutting the material by means of a rotary cutter including at least one cutter blade extending parallel to the axis of the rotary cutter, said blade having an undulating cutting edge, and effecting repeated sharpening of said edge by means of a rotating grinding wheel extending over the whole length of the blade, said wheel being substantially cylindrical with an undulating profile formed by a series of contiguous grooves, said wheel being so disposed in relation to the path of movement of said cutter blade that the cutting edge is sharpened at each pass thereof past the wheel.

2. A method is claimed in claim 1, wherein said blade is moved progressively outwardly of the rotary cutter whereby the cutting edge is repeatedly sharpened as it passes the wheel and is thereby maintained at a predetermined cylinder of revolution.

3. A cutting machine comprising a rotatable cutting drum, at least one cutting blade on said drum extending axially thereof, said blade having an undulating cutting edge, conveyor bands arranged so as to diverge towards the cutting drum, and a sharpening wheel disposed on an axis parallel to the axis of the drum and extending over the whole length of the cutting edge of said blade, said wheel having an undulating profiled surface formed by a series of contiguous annular grooves.

4. A cutting machine as claimed in claim 3, wherein said sharpening wheel comprises a steel body having said undulating profiled surface and a coating of boron nitride on said surface.

5. A cutting machine as claimed in claim 3, wherein said sharpening wheel comprises a body of aluminium oxide means being provided to traverse and dress said surface to maintain the undulating profile.

6. A cutting machine as claimed in claim 3, wherein said sharpening wheel comprises a steel body having said undulating profiled surface and a coating of diamond particles on said surface secured thereto by suitable binders.

7. A cutting machine as claimed in any one of the preceding claims 3 - 6, wherein said sharpening wheel is carried by an assembly comprising a pair of arms pivotally mounted to a fixed part of the machine at one end, and carrying said wheel at the other end, a yoke fixed to rotate with said arms, a motor carried by said yoke, and a transmission driven between said motor and said wheel.

8. A cutting machine as claimed in claim 7, wherein adjusting screws are provided on said arms and serve to hold said assembly in a predetermined position so that the surface of said wheel is maintained in the path of movement of said cutting edge.

9. A cutting machine as claimed in claim 7 or 8, wherein said assembly includes a fluid actuator by which said assembly can be pivoted to a position whereby the wheel can be exchanged.

10. A cutting machine as claimed in any one of the claims 3 - 9, wherein said cutting blade comprises a flat plate ground from one side thereof along one edge with grooves of sinusoidal section obliquely to the plane of the plate.

11. A cutting machine as claimed in claim 10, wherein the angle of inclination of the grooves to the plane of the plate is from 10 - 30 .

12. A cutting machine as claimed in claim 10 or 11, wherein further grooves are formed in said flat plate on the other side thereof, with the bottoms thereof parallel to the plane of the plate, said further grooves having the same profile on the first grooves and the same pitch, said further grooves being displaced laterally of the first grooves by half the pitch of the latter.

13. A cutter blade comprising a flat steel plate ground from one side thereof along one edge with a first series of contiguous grooves obliquely to the plane of the plate and having a second series of contiguous grooves having the same profile as the grooves in the first series formed on the other side of said plate wherein said second series of grooves is disposed with the bottoms parallel to the plane of the plate, said second series of grooves having the same profile and pitch as the first grooves and being displaced laterally of the first grooves by half the pitch of the latter.

14. A cutter blade as claimed in claim 13, wherein the grooves have identical sinusoidal profiles, said first series of grooves being disposed at 200 to the plane of the plate, said cutting edge being sinusoidal in shape and lying in a substantially flat plane.

15.A method of cutting layered material substantially as described herein by way of example.

16. A cutting machine substantially as described with reference to the accompanying drawings.

17. A cutter blade substantially as described by way of example with reference to the Figures 9 and 10 of the accompanying drawings.