WO2010029348A2

WO2010029348A2 - Cutting apparatus

Info

Publication number: WO2010029348A2
Application number: PCT/GB2009/051144
Authority: WO
Inventors: Thomas Henry White
Original assignee: Dickinson Legg Limited
Priority date: 2008-09-09
Filing date: 2009-09-09
Publication date: 2010-03-18
Also published as: PL2346363T3; HUE037314T2; JP5801198B2; WO2010029348A3; GB0816491D0; CN102196735B; EP2346363A2; JP2012501640A; EP2346363B1; CN102196735A

Abstract

A cutting apparatus for producing a controlled strand length effect using a tobacco cutting machine fitted with standard, non-profiled knives is disclosed. The cutting apparatus comprises a mouth defined by a jaw assembly for delivering the material to be cut to a cutting position at the mouth and a cutting drum. The cutting drum is provided with a least one knife the, or each, knife having a cutting edge. The cutting drum comprises drive means and is rotatable about an axis arranged substantially parallel to the mouth such that the cutting edge of the at least one knife is arranged substantially perpendicularly to the material to be cut. A grinder is provided for removing material from the cutting edge of the at least one knife, wherein the grinder is configured to be brought into contact with the cutting edge with a movement in a direction substantially parallel to the axis of rotation of the cutting drum and with a movement in a direction substantially perpendicular to the axis of rotation of the cutting drum. The cutting apparatus allows the maximum length of strands of cut tobacco to be limited, by employing standard plain knives combined with a special mode of operation of a cutting machine knife grinding system.

Description

Cutting Apparatus

The present invention relates to cutting apparatus and a method of cutting, particularly, but not exclusively to a cutting apparatus and method of cutting for cutting portions of a laminar product such as tobacco leaves.

Tobacco leaves are processed for cigarette manufacture in a primary tobacco process. The laminate portions of the tobacco leaves are compressed and then cut in a cutting machine to create tobacco particles suitable for cigarette manufacturers. In a typical cutting process, the width of cut is between 0.7 and 1.0mm. The length of the tobacco strands produced is highly variable, ranging from less than 1 mm to more than 200mm. The maximum length of particle depends on the sizes of the lamina portions being cut, and these ultimately depend on the dimensions of the leaves from which they came.

The presence of long particles in the cut tobacco was traditionally thought to be advantageous, and was considered to be an indicator of product quality.

However, it has been shown that long particles detract from the free- flowing nature of the product, and cause problems of process non-uniformity at all stages up to and including cigarette manufacture. To overcome these problems, various ways of limiting the maximum length of strands of cut tobacco have been devised. One characteristic of this controlled strand length cut tobacco is that it is much more free-flowing than conventionally cut material. This means that the product is more easily blended with other types of tobacco blend component during processing, and that a greater degree of process uniformity is achieved in drying processes, and in the application of flavours to the tobacco. It is also found that the variation of cigarette weights produced by cigarette making machines is significantly reduced when processing controlled strand length product.

An example of a technique limiting the maximum length of strands of cut tobacco by the use of castellated or ribbed knives is described in WO85/104616. By the application of such means, the maximum length of tobacco strands is limited to the distance between the ribs, or alternatively, the pitch of the castellations of the knives. Typically the maximum strand length would be limited to between 20 - 40 mm although other dimensions are feasible. The type of castellated or ribbed knife described in WO85/104616 can be expensive to produce due to the preparation and machining of the knives to the required shape or profile.

It is desirable to produce tobacco strands cut to a limited maximum length using an inexpensive apparatus and a simple and inexpensive process.

According to a first aspect, the present invention provides a means for producing a controlled strand length effect using a tobacco cutting machine fitted with standard, non-profiled knives.

The present invention allows the maximum length of the strands of cut tobacco to be limited as described above, but by employing standard plain knives combined with a special mode of operation of the cutting machine knife grinding system.

A disadvantage of the use of ribbed or castellated knives is that a large proportion of the knife material has to be removed by expensive and accurate machining operations during the manufacture of the knives. This results in a cost for these consumable items which is several times the cost of the equivalent standard knives.

According to a second aspect, the present invention provides a cutting apparatus comprising, a mouth defined by a jaw assembly for delivering the material to be cut to a cutting position at the mouth; a cutting drum having; at least one knife the, or each, knife having a cutting edge, the cutting drum having drive means therefor and being rotatable about an axis arranged substantially parallel to the mouth such that the cutting edge of the at least one knife is arranged substantially perpendicular to the material to be cut; and a grinder for removing material from the cutting edge of the at least one knife, wherein the grinder is configured to be brought into contact with the cutting edge with a movement in a direction substantially parallel to the axis of rotation of the cutting drum and with a movement in a direction substantially perpendicular to the axis of rotation of the cutting drum.

By providing a cutting apparatus with a grinder operating with a combination of movements in the directions substantially parallel and substantially perpendicular to the axis of rotation of the cutting drum a controlled strand length cutting operation can be achieved with standard, non-profiled knife or knives. The knives used may be of a uniform thickness and do not need to be produced with an expensive machining operation. The overall cost of the apparatus is thus reduced and replacement parts more easily obtained. The, or each knife, may be configured to be to be fed in a direction away from the axis of rotation of the cutting drum and towards the cutting position at the mouth, with this arrangement the knives are moved towards the cutting position and can advantageously make repeatable, reliable cuts at the material to be cut. There may be a plurality of knives, for example a number of knives in the range from 8 to 10.

The grinder may be configured to be rotated about an axis arranged substantially parallel to the axis of rotation of the cutting drum at the cutting position allowing the grinder ease of access to the knives to be ground and such that the cutting edge is arranged to lie on an imaginary cylindrical surface.

The cutting apparatus may comprise a clamp assembly for compressing the material to be cut at the cutting position. By this arrangement the material to be cut can be presented at the cutting edge in an extruded and compressed manner and with a substantially uniform composition.

One or more conveyor bands or conveyor belts may form the jaw assembly.

Preferably, the cutting apparatus comprises a control assembly configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum. More preferably, the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum in a series of one or more discrete movements, such that the grinder moves in a substantially castellated motion. In an alternative arrangement, the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum in a series of one or more gradual movements, such that the grinder moves in an undulating motion. These configurations of cutting apparatus and control assembly are found to be particularly useful in providing the knives with a non-standard profile.

Preferably, the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum and is configured to control the movement in a direction substantially parallel to the axis of rotation of the cutting drum, wherein the speed of movement the grinder in the direction substantially perpendicular to the axis or rotation of the cutting drum is faster than the speed of movement of the grinder in the direction substantially parallel to the axis of rotation of the cutting apparatus. This configuration is found to be particularly useful for grinding a knife with a castellated profile. The control assembly may comprise a pivoted arm and a geared stepper. The control assembly may adjust the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum in the range from 0.2mm to 2.5mm and is found to be particularly useful for cutting controlled length sections of a material. Advantageously, the cutting edges of the at least one knife may be arranged such that the cutting edges correspond to the mouth. It is preferable to provide the mouth parts with a profile corresponding to the profile of the knives, so that the minimum clearance between the knives and the mouth parts is maintained at all points across the cutting width.

According to a third aspect, the present invention provides a method of manufacture of controlled strand length tobacco, configured with the aforementioned cutting apparatus.

According to a fourth aspect, the present invention provides a method of manufacture for controlled strand length tobacco, comprising the steps of: delivering the tobacco material to be cut to a cutting position at a mouth defined by a jaw assembly; rotating a cutting drum having a cutting edge about an axis arranged substantially parallel to the mouth such that the cutting edge is arranged substantially perpendicular to the material to be cut; and bringing a grinder into contact with the cutting edge with a movement in a direction substantially parallel to the axis of rotation of the cutting drum and with a movement in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with a cutting profile.

The step of moving the grinder may comprise the step of moving the grinder in a series of one or more discrete movements in a direction substantially parallel to the axis of rotation of the cutting drum and in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with a castellated profile.

The step of moving the grinder may comprise the step of moving the grinder in a series of one or more gradual movements in a direction substantially parallel to the axis of rotation of the cutting drum and in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with an undulating profile. The method may comprise a step of compressing the extruded tobacco material at the jaw assembly.

In the description of the preferred embodiment of the invention the following terms are used and are set out below.

A first longitudinal dimension and a second longitudinal dimension are described. A first longitudinal dimension is a dimension measured substantially along the axis of rotation of the cutting drum and hereinafter referred to also as length (of, for example, cut strands) and width (of, for example, cutting drum). The length of the cut strands of tobacco is therefore a measurement of the dimension of the strand substantially in the direction of the axis of rotation of the cutting drum. The width of the cutting drum is therefore a measurement of the dimension of the cutting drum substantially in the direction parallel to its axis of rotation, and the width of the mouth is therefore a measurement of the dimension of the mouth opening in a direction substantially parallel to the axis of rotation of the cutting drum.

By movement in a transverse direction we mean in a direction substantially parallel to the axis of rotation of the cutting drum and thus along a length dimension.

A second longitudinal dimension is a dimension measured substantially perpendicular to the axis of rotation of the cutting drum hereinafter referred to also as width or depth or thickness. The width or depth of a cut is therefore the dimension of a cut in the plane substantially perpendicular to the axis of rotation of the cutting drum. The width or thickness of a cut strand of tobacco is therefore the dimension of a cut strand measured in the plane substantially perpendicular to the axis of rotation of the cutting drum.

By movement in a radial direction we mean in a direction substantially perpendicular to the axis of rotation of the cutting drum. By profile we mean the cutting edge on a knife blade and impinging on a material to be cut, a profile may also be the shape of the ground surface produced at a knife tip by the action of a grinder. By discrete we mean a change, substantially a step change, in a parameter, for example, a dimension, a state or an operation condition.

The present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a cross sectional view of a tobacco cutter of a conventional design suitable for adaptation to form the cutting apparatus of the present invention;

Figure 2 is a side view of the cutting drum of the tobacco cutter of Figure 1 , in further detail;

Figure 3 is a side view of a portion of the cutting apparatus of the present invention;

Figure 4 is a schematic view of the cutting apparatus of the present invention showing a range of movement the grinder;

Figure 5 is a schematic view of the shape of the knife tip produced by the present invention; and

Figure 6 is a side view of the knife tip of Figure 5.

A type of typical conventional tobacco cutter and the cutter adapted to form the cutting apparatus of the present invention will now be described with reference to the apparatus of Figure 1 and Figure 2. The cutting apparatus comprises a vibrating feeder 1 , monitor 2 and two converging feed bands 3, 4 which compress and convey the incoming low density tobacco lamina through the mouth 5 towards the cutting drum 6. In the preferred embodiment each feed band 3, 4 is in the form of a conveyor belt provided with compression weighting features. The feed bands 3, 4 form a jaw assembly of the mouth 5 and together define a plenum through which the tobacco lamina passes and is compressed. The cutting drum 6 is supported between bearings and is driven by a motor (not shown) such that the drum rotates at a speed between 200 and 600 rpm.

The cutting drum 6 can be fitted with 8 or 10 knives 12 equally disposed around its circumference, although other numbers of knives 12 may be used. Fig 2 shows the cutting drum in more detail. In the preferred embodiment the knives 12 are flat pieces of alloy steel approximately 1 -1.5 mm thick, extending over the full width of the mouth 5. The cutting drum 6 is located adjacent the mouth 5, through which a compressed 'cheese' or 'cake' of tobacco is extruded against the rotating cutting drum 6. The cutting drum 6 is positioned such that the axis of rotation of the cutting drum 6 is substantially parallel to the mouth 5. The action of the sharp knives 12 passing from top to bottom, from a location above the feed band 4 to a location below the feed band 3, of the extruded 'cheese' of material to be cut results in strands of tobacco being cut whose thickness is a function of the speed of extrusion relative to the rotational speed of the cutting drum 6.

In a conventional arrangement of a tobacco cutter, the knives are fed outwards from a cutting drum by small amounts at frequent intervals. A grinder in the form of a rotating grindstone continually traverses across the width of the cutting drum, sharpening the knives and maintaining a sharp bevelled profile on the knives. The movement of the grindstone ensures that the radius of the knife tips from the mouth and from the centre of the cutting drum remains constant. After a small number of traverses, the grindstone is fed radially, in other words in a radial direction, towards the axis of the cutting drum, and its contact position is kept constant by the action of a fixed diamond which 'dresses' the stone as it passes over it at one end of its stroke. The speed of conveyor belts or feed bands is controlled in a ratio to the speed of the drum so as to produce the required width of cut.

The improvement to the operation of the conventional tobacco cutter of the present invention will now be described with reference to Figures 1 and 3. In the preferred embodiment of the invention, the grinder takes the form of a grindstone wheel 7 mounted on an axis parallel to the axis of the cutting drum 6. The grindstone assembly is arranged so that it can be accurately positioned closer to, or further away from, the periphery or outer circumference of the cutting drum 6. The grindstone 7 is driven by a motor and can be rotated. The grindstone 7 and its motor are carried on a pivoted arm 15. The pivoted arm, and thus the grindstone and motor are raised or lowered by means of a geared stepper motor 16 and screw 17. The grindstone assembly is mounted on location apparatus for movement in the transverse direction, in a direction parallel to the axis of rotation of the cutting drum 6. In the preferred embodiment the location apparatus is a traversing trolley 13 supported by linear bearings 14 so that it can move across the width of the cutting drum 6. The position of the grindstone 7 is determined by a leadscrew driven by a motor and provided with positioning apparatus such as a position encoder.

In order to achieve the desired castellated knife profile, the grinder is controlled as follows, with the motions as shown in Figure 4.

The grindstone 7 makes one or more traverses of the cutting drum 6, to establish the outer periphery of the knives 12.

The grindstone 7 then makes one or more 'plunging' traverses, during which it is moved by a controlled distance towards the centre of the drum at predetermined positions across the traverse. These plunging movements in the radial direction may be abrupt, in which case a castellated effect is produced, or alternatively more gradual, in which case a wavy or undulating effect is produced.

In the preferred embodiment, the depth of the plunge movement is equal to or greater than the width (or depth) of the cut dimension. In order to ensure that the individual strands will be fully cut through at the edges of the castellations or undulating shaped portions, and the strand lengths will be limited to the desired maximum. If the plunge movement in the radial direction is significantly less than the width (or depth) of the cut dimension then the strands may not be fully cut through at the edges of the castellations. The shape of the ground surface of the knife tip is shown in Figure 5 and Figure 6.

Various modifications may be made to the described embodiment without departing from the scope of the present invention. There may be a different number of knives and grinders. There may be more than one cutting drum and more than one apparatus for delivery of the material to be cut, for example there could be more than one conveyor or compressing line. In an alternative embodiment the orientation of the axis of rotation or the configuration of the grinding wheel could be set at an angle or along a different axis to that of the cutting drum. In addition other speeds of rotation of the cutting drum and the grinder wheel can be envisaged.

Claims

1. A cutting apparatus for producing a controlled strand length effect using a tobacco cutting machine fitted with standard, non-profiled knives.

2. A cutting apparatus comprising, a mouth defined by a jaw assembly for delivering the material to be cut to a cutting position at the mouth; a cutting drum having; at least one knife the, or each, knife having a cutting edge, the cutting drum having drive means therefor and being rotatable about an axis arranged substantially parallel to the mouth such that the cutting edge of the at least one knife is arranged substantially perpendicular to the material to be cut; and a grinder for removing material from the cutting edge of the at least one knife, wherein the grinder is configured to be brought into contact with the cutting edge with a movement in a direction substantially parallel to the axis of rotation of the cutting drum and with a movement in a direction substantially perpendicular to the axis of rotation of the cutting drum.

3. A cutting apparatus as claimed in Claim 2, wherein the knives are configured to be fed in a direction away from the axis of rotation of the cutting drum and towards the cutting position at the mouth.

4. A cutting apparatus as claimed in Claim 2 or Claim 3, wherein the grinder is configured to be rotated about an axis arranged substantially parallel to the axis of rotation of the cutting drum.

5. A cutting apparatus as claimed in any one of Claim 2, Claim 3 or Claim 4, wherein material is removed from the or each knife such that the cutting surface is ground and the cutting edge is arranged to lie on an imaginary cylindrical surface.

6. A cutting apparatus as claimed in any of Claims 2 to 5, further comprising a clamp assembly for compressing the material to be cut at the cutting position.

7. A cutting apparatus as claimed in any of Claims 2 to 6, wherein the jaw assembly comprises at least two conveyor bands.

8. A cutting apparatus as claimed in Claims 2 to 7, further comprising a control assembly for controlling the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum.

9. A cutting apparatus as claimed in Claim 8, wherein the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum in a series of one or more discrete movements, such that the grinder moves in a substantially castellated motion.

10. A cutting apparatus as claimed in Claim 8, wherein the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum in a series of one or more gradual movements, such that the grinder moves in an undulating motion.

11. A cutting apparatus as claimed in Claim 8, Claim 9 or Claim 10, wherein the control assembly is configured to control the movement of the grinder in a direction substantially perpendicular to the axis of rotation of the cutting drum and is configured to control the movement in a direction substantially parallel to the axis of rotation of the cutting drum, wherein the speed of movement of the grinder in the direction substantially perpendicular to the axis of rotation of the cutting drum is faster than the speed of movement of the grinder in the direction substantially parallel to the axis of rotation of the cutting drum.

12. A cutting apparatus as claimed in any one of Claims 8 to 11 , wherein the control assembly comprises a pivoted arm and a geared stepper motor.

13. A cutting apparatus as claimed in any one of Claims 8 to 12, wherein the control assembly is configured to adjust movement in a direction substantially perpendicular to the axis of rotation of the cutting drum in the range from 0.2mm to 2.5mm.

14. A cutting apparatus as claimed in any of Claims 2 to 13, wherein the cutting edges of the at least one knife are arranged such that the cutting edges correspond to the mouth.

15. A method of manufacture for controlled strand length tobacco, using the cutting apparatus of any preceding claim.

16. A method of manufacture for controlled strand length tobacco, comprising the steps of: delivering the tobacco material to be cut to a cutting position at a mouth defined by a jaw assembly; rotating a cutting drum having a cutting edge about an axis arranged substantially parallel to the mouth such that the cutting edge is arranged substantially perpendicular to the material to be cut; and bringing a grinder into contact with the cutting edge with a movement in a direction substantially parallel to the axis of rotation of the cutting drum and with a movement in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with a cutting profile.

17. The method as claimed in Claim 16, wherein the axis of rotation of the cutting drum is the longitudinal axis, further comprising the step of moving the grinder in a series of one or more discrete movements in a direction substantially parallel to the axis of rotation of the cutting drum and in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with a castellated profile

18. The method as claimed in Claim 16, wherein the axis of rotation of the cutting drum is the longitudinal axis, further comprising the step of moving the grinder in a series of one or more gradual movements in a direction substantially parallel to the axis of rotation of the cutting drum and in a direction substantially perpendicular to the axis of rotation of the cutting drum, thereby grinding the cutting edge with an undulating profile.

19. A method as claimed in any of Claims 16 to 18, wherein the profiled cutting edge is adjacent to the mouth, thereby cutting tobacco material at the cutting position.

20. A method, as claimed in any one of Claims 16 to 19, further comprising the step of compressing the extruded tobacco material at the jaw assembly.

21. A cutting method substantially as herein described and with reference to the accompanying drawings.

22. A cutting apparatus, substantially as herein described and with reference to the accompanying drawings.