GB2132076A - Knife for use in tobacco shredding machines - Google Patents

Abstract

A plate-like knife 4 for subdividing the leaves of a cake of compacted tobacco leaves in a tobacco shredding machine into elongated shreds has an elongated undulate cutting edge 8. The distance H between successive anti- nodes 8a of the cutting edge, as considered at right angles to the longitudinal direction of the cutting edge, does not exceed one millimeter and the distance L between alternate antinodes 8a, as considered in the longitudinal direction of the cutting edge, is not in excess of ten millimeters. The shreds which are obtained by resorting to such knife have a superior filling power. <IMAGE>

Description

SPECIFICATION Knife for use in tobacco shredding machines The present invention relates to tobacco comminuting machines in general, and more particularly to improvements in tobacco shredding machines. Still more particularly, the invention relates to improvements in knives which can be used in such machines to convert a continuously formed cake of condensed tobacco leaves into discrete shreds. The invention also relates to tobacco shreds which are obtained by resorting to the improved knife.

Tobacco shreds are the preferred form of constituents of tobacco fillers, i.e., of the rod-like tobaccocontaining portions of cigarettes or analogous smokers' products. This is due to the fact that the shreds can enhance the filling power of the filler, i.e., the resistance of the filler to deformation, as well as that the shreds are less likely to escape at the ends of a plain cigarette, or at both ends of a filter cigarette, than smaller tobacco particles. Moreover, the shreds are sufficiently pliable to reduce the likelihood of puncturing of cigarette paper which constitutes the wrapper of a plain cigarette or of the tobaccocontaining portion of a filter cigarette.

It is known to subject a cake of compacted tobacco leaves or tobacco leaf laminae to the action of a succession of orbiting knives having straight cutting edges which subdivide the leaves or laminae into elongated straight shreds. If the filler of a cigarette rod consists of straight or staightened (stretched) tobacco shreds, such filler must contain a relatively large quantity of tobacco particles in order to exhibit a satisfactory filling power which is appreciated by a large majority of smokers. The utilization of large quantities of tobacco is undesirable to the manufacturer due to increased cost of cigarettes and is likely to unduly enhance the resistance of the filler to the flow of tobacco smoke therethrough, i.e., the smoker must draw tobacco smoke with a pronounced effort which detracts from the enjoyment of cigarettes and analogous smokers' products.

Early attempts to solve the aforediscussed (in part contradictory) problems involve the shredding of tobacco leaves in such a way that the leaves yield shreds exhibiting very pronounced waves. This was considered to enhance the filling power of a filler consisting of or containing pronouncedly undulate shreds because the shreds were presumed to interlink and to thereby exhibit a certain resistance to deformation while simultaneously offering a relatively low resistance to the flow of tobacco smoke through the filler. Reference may be had to U.S. Pat.

No. 1,647,694 and to German Offenlegungsschrift No. 1,532,051. These prior publications propose to sever tobacco leaves in such a way that the distance between successive antinodes, as considered at right angles to the longitudinal direction of the shred, is as pronounced as possible. The just discussed proposals failed to gain acceptance in the industry because the improvement was insubstantial or non-existent. In fact, the teachings of the aforementioned references were never adopted by the makers of tobacco shredding or analogous machines.

One feature of the invention resides in the provision of a knife for use in tobacco shredding machines. The knife comprises an elongated undulate cutting edge having alternating nodes and antinodes. In accordance with a presently preferred embodiment of the improved knife, the distance between successive antinodes (as considered at right angles to the longitudinal direction of the cutting edge) is at most one millimeter and the distance between alternate antinodes (as considered in the longitudinal direction of the cutting edge) is at most ten millimeters.

The knife can resemble a thin plate or blade having two side faces or major surfaces and a preferably undulate edge face which makes an oblique angle with each of the side faces. The cutting edge is disposed at the junction of the edge face with one of the two side faces.

Another feature of the invention resides in the provision of elongated shreds which can be obtained by resorting to one or more knives of the above outlines character. The shreds have pairs of spacedapart edge faces with alternating nodes and antinodes. The distance between successive antinodes (as considered at right angles to the longitudinal direction of the respective shred) at most equals one millimeter, and the distance between alternate antinodes of each edge face (as considered in the longitudinal direction of the respective shred) at most equals ten millimeters.The distance between the two edge faces of a shred (i.e., the width of a shred), as considered at right angles to the longitudinal direction of the respective shred, is preferably less than the distance between alternate antinodes of the edge faces, as considered in the longitudinal direction of the shred, and such width is preferably in excess of the distance between successive antinodes, as considered at right angles to the longitudinal direction of the respective shred. For example, the width of each shred can be in the range of 0.75 millimeter (the distance between successive antinodes, as considered at right angles to the iongitudinal directions of the edge faces of the shred, is then preferably less than 0.75 millimeter).

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved knife itself, however, both as to its construction and mode of using the same, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

Figure 1 is a fragmentary perspective view of a tobacco shredding machine, showing one of the knives which are constructed in accordance with the invention; Figure 2 is an enlarged fragmentary plan view of the knife, substantially as seen in the direction of arrow II in Figure 1; and Figure 3 is a fragmentary elevational view of a tobacco shred which is obtained by resorting to knives of the type shown in Figures 1 and 2.

Referring to Figure 1, there is shown a portion of a tobacco shredding machine wherein the upper reach of an endless belt conveyor 2 supports and advances a continuously formed cake 3 of compacted tobacco leaves or laminae in the direction of arrowS. The comminuting station is adjacent to the driven front pulley 1 for the conveyor 2. The manner in which the pulley 1 is driven by a variable-speed or constantspeed motor forms no part of the invention. The same holds true for the making of cake 3. Reference may be had to commonly owned U.S. Pat. No.

4,244,382 granted January 13, 1981 to Thiele et al.

and/or to commonly owned U.S. Pat. No.4,401,205 granted August 1983 to Komossa et al. The compacting of tobacco leaves or laminae to form the cake 3 takes place between the upper reach of the illustrated conveyor 2 and the lower reach of a second conveyor (not shown in Figure 1) which preferably slopes downwardly toward the conveyor 2 so that the two conveyors define a substantially wedge-like path for the cake 3.

The severing station of the machine which embodies the structure of Figure 1 accommodates a rotary drum-shaped holder (not shown) for an annulus of circumferentially spaced-apart plate-like or bladelike knives 4 (only one shown in Figure 1). The path of orbital movement of the elongated cutting edges 8 of successive knives 4 is indicated by the arrow 6.

During travel past the driven pulley 1, successive knives 4 cooperate with a stationary counterknife 9 to sever successive increments of the advancing cake 3 at predetermined intervals so that the cake yields stacks of elongated tobacco shreds 11 of the type shown in Figure 3. The knives 4 extend or can extend substantially tangentially of the drum-shaped holder and are sharpened by a suitable dressing device which is not specifically shown in the drawing.

In accordance with a feature of the invention, each knife 4 has an elongated undulate edge face 7 (see Figure 2) which makes obtuse angles with the two side faces 4a, 4b and defines with the side face 4b an elongated cutting edge 8 whose undulate (sinusoidal) shape can be clearly seen in Figure 2. Each knife 4, as well as the counterknife 9, extends across the full width of the cake 3.

The distance H (namely, the amplitude of the curve represented by the cutting edge 8) between successive antinodes 8a of the undulate cutting edge 8 (as considered at right angles to the longitudinal direction of the cutting edge) is not in excess of one millimeter, and the distance L between alternate antinodes 8a (which is the same as the distance between alternate nodes 8b and represents the wavelength of the aforementioned curve) is not in excess of ten millimeters.In contrast to the aforediscussed prior proposals, a knife having a cutting edge of the just outlined type is capable of subdividing tobacco leaves or laminae into elongated shreds 11 each of which has a wave height H (i.e., the distance between successive antinodes 12a, which alternate with the nodes 1 2b of its edge faces 12, as considered at right angles to the edge faces 12) which is not in excess of one millimeter, and a wavelength L (i.e., the distance between alternate antinodes 12a of the edge faces 12) which is not in excess of ten millimeters. The width B of each lamination is preferably more than H but less than L.

In accordance with a presently preferred embodiment, the configuration of the cutting edge 8 shown in Figure 2 is selected (for a particular tobacco brand) in such a way that H equals 0.3 millimeter and L equals 2.5 millimeters. Also, the speed of the conveyor 2 (i.e., of the cake 3) and the speed of orbital movement of the cutting edges on the knives 4 in the machine shown in Figure 1 is selected in such a way that B equals 0.75 millimeter. Such configuration of the shreds 11 ensures a highly satisfactory filling power of the filler and further ensures that the filler which exhibits such satisfactory filling power does not offer an undesirably high resistance to axial flow of tobacco smoke therethrough. The values of H, Land B will vary from tobacco type to tobacco type; however, H should not exceed one millimeter and L should not exceed ten millimeters.

The superior qualities of tobacco shreds 11 are attributable to their (undulate) shape as well as to the fact that the undulations are not pronounced, i.e., that the distances H and L do not exceed the aforediscussed maximum values. This ensures that the elasticity of the tobacco stream which consists of or contains such shreds is highly satisfactory so that the stream can be converted into a filler (this normally involves trimming and condensing) which exhibits the aforediscussed superior characteristics as regards its filling power and resistance to the flow of tobacco smoke therethrough. Moreover, the shreds at the ends of a plain cigarette or at one end of a filter cigarette are not likely to escape; this is another highly desirable characteristic of a satisfactory filler. Still further, such highly desirable characteristics are achieved without resorting to substantial quantities of tobacco which is a feature that is highly appreciated by the makers of cigarettes since tobacco constitutes the most expensive ingredient of cigarettes or analogous rod-shaped smokers' products. It has been found that the just discussed highly desirable characteristics of shreds 11 are attributable to their slightly undulate shape, i.e., to the aforediscussed configuration and dimensioning of the cutting edges 8 of knives which are used for the making of such shreds.

A machine which can be used for conversion of tobacco shreds into a stream and for conversion of such stream into a continuous filler is disclosed, for example, in commonly owned U.S. Pat. No.

4,009,722 granted March 1, 1977 to Wahle et al.

Claims (10)

1. A knife for use in tobacco shredding machines, comprising an elongated undulate cutting edge having alternating nodes and antinodes, the distance between successive antinodes, as considered at right angles to the longitudinal direction of the cutting edge, being at most equal to one millimeter.

2. The knife of claim 1, wherein the distance between alternate antinodes, as considered in the longitudinal direction of the cutting edge, at most equals ten millimeters.

3. The knife of claim 1, further comprising two side faces and an edge face disposed between and making oblique angles with said side faces, said cutting edge being disposed at the junction of said edge face with one of said side faces.

4. The knife of claim 3, wherein said edge face is an undulate surface.

5. An elongated tobacco shred having two spaced-apart undulate edge faces with alternating nodes and anti nodes, the distance between successive anti nodes, as considered in the longitudinal direction of the shred, being at most equal to one millimeter.

6. The tobacco shred of claim 5, wherein the distance between alternate antinodes of each of said edge faces, as considered in the longitudinal direction of the shred, at most equals ten millimeters.

7. The tobacco shred of claim 6, wherein the distance between said edge faces, as considered at right angles to the longitudinal direction of the shred, is less than the distance between alternate antinodes of said edge faces.

8. The tobacco shred of claim 6, wherein the distance between successive anti nodes of each of said edge faces, as considered at right angles to the longitudinal direction of the shred, is less than the distance between said edge faces.

9. A knife for use in tobacco shredding machines, substantially as herein described with reference to the accompanying drawings.

10. An elongated tobacco shred, substantially as herein described with reference to the accompanying drawings.