WO1999026494A1

WO1999026494A1 - Improvements in or relating to cutting machines

Info

Publication number: WO1999026494A1
Application number: PCT/GB1998/003515
Authority: WO
Inventors: Alan Cobbold
Original assignee: Legg Limited
Priority date: 1997-11-24
Filing date: 1998-11-24
Publication date: 1999-06-03
Also published as: AU1250399A; GB9724776D0

Abstract

The present invention relates to improvements in or relating to cutting machines, particularly leaf cutting machines, especially machines for cutting leaf tobacco. There is described an upper conveyor unit for a leaf cutting machine, the unit comprising a conveyor belt or band (11) passing over a plurality of conveyor rollers (12, 13, 14), and providing a lower conveyor surface where the conveyor belt (11) passes over a bottom conveyor plate (20, 21) and which, in combination with a lower conveyor unit of a leaf cutting machine defines, in use, a duct along which leaves are conveyed towards a mouthpiece adjacent a cutter; wherein the bottom conveyor plate comprises two half-plates, a fixed half plate (20), remote from the mouthpiece, and a retractable half-plate (21) mounted transversely adjacent the mouthpiece for pivotal movement.

Description

IMPROVEMENTS IN OR RELATING TO CUTTING MACHINES

The present invention relates to improvements in or relating to cutting machines, particularly leaf cutting machines, especially machines for cutting leaf tobacco.

Smoking tobacco for cigarettes, pipes and so on is formed by shredding tobacco leaves. Conventionally, leaves are mechanically shredded by dropping the leaves through a feed area onto a moving conveyor belt or rollers. The conveyor carries the leaves along a tapering duct which becomes gradually shallower terminating at a mouthpiece. The conveyor is retained between two substantially vertical walls. Typically the roof of the duct is formed by a second conveyor which converges with the first conveyor at or near the mouthpiece. Thus the leaves are compressed into a dense mass or cheese at the mouthpiece. A cutter in the form of a transverse dram carrying one or more knives rotates adjacent the mouthpiece. The movement of the conveyors presses the cheese against the rotating cutter thereby shredding the compressed mass. It is important that the mass is adequately compressed to ensure satisfactory shredding. Such a machine is described in fuller detail in GB 980,935, to which further reference should be made.

In conventional machines, the angle of tapering of the duct is fixed. That is, the inclination of the second, upper, conveyor with respect to the lower conveyor is fixed. The rate at which compression occurs is a function of the convergent angle between the two conveyors. This angle is designed to suit the tobacco component, of which there .are principally two; the stem, including the midrib, and the lamina or blade of the leaf. A machine designed for cutting one component results in unsatisfactory cutting of the other component. This is simply because of the different compression characteristics of the two components.

Often, a cutting machine is only required to fulfil one purpose, cutting either stems or leaves. Nevertheless, there are occasions when a dual purpose machine would be required. It is possible to adjust the geometry of the two conveyors by insertion of a wedge section on the underside of the upper conveyor. Whilst this is an. adequate remedy during manufacture or refurbishment of the cutting machine, it is not suitable for performing on a machine which is in active production.

Accordingly, where a machine will be used for cutting both leaf and stem, in order to ensure that there is no compromise in either throughput or qu.ality, there is a need for a cutting machine having a variable geometry upper conveyor unit.

Accordingly, in its broadest sense, the present invention provides an upper conveyor unit for a leaf cutting machine, the unit comprising a conveyor belt or band passing over a plurality of conveyor rollers, .and providing a lower conveyor surface where the conveyor belt passes over a bottom conveyor plate and which, in combination with a lower conveyor unit of a leaf cutting machine defines, in use, a duct along which leaves are conveyed towards a mouthpiece adjacent a cutter; wherein the bottom conveyor plate comprises two half-plates, a fixed half plate, remote from the mouthpiece , and a retractable half-plate mounted transversely adj acent the mouthpiece for pivotal movement.

Adjustment of the retractable half-plate is preferably achieved by means of a link rod coupled between the inner surface of the half-plate and a cranksh-aft upon which one of the conveyor rollers of the unit is carried, in such a manner that adjustment of the half-plate causes an appropriate movement of the roller to adjust and maintain the correct tension in the conveyor belt or band.

Preferably, the fixed and retractable half-plates have interconnecting teeth to form a substantially continuous surface.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a part cross-sectional, part schematic view through a first embodiment of a variable geometry upper conveyor unit in accordance with the present invention in a 'stem' compression configuration;

Figure 2 is a part cross-sectional, part schematic view of the embodiment of Figure 1 in a 'lamina' compression configuration;

Figure 3 is a perspective view of the fixed bottom plate of the embodiment of Figures 1 and 2; and

Figure 4 is a perspective view of the retractable bottom plate of the embodiment of Figures 1 and 2.

With reference to the Figures, an embodiment of an upper conveyor unit 10 in accordance with the present invention includes a conveyor band 11 carried by three rollers 12,13,14 in a triangular arrangement upon a carriage 15. Carriage 15 is mounted in a fixed spatial relationship with the lower conveyor unit (not shown). First roller 12 is adjacent the inlet to the duct formed between the upper conveyor unit 10 and the lower conveyor unit. Second roller 13 is adjacent the mouthpiece of the duct and third roller 14 is spaced between and, in use, vertically above the first and second rollers. One of the rollers is driven to provide movement to the conveyor and in practice it does not matter which. Conveniently, however, third roller 14 acts as an 'idle' roller. The conveyor band 11 passes over the bottom plate of the conveyor unit 10 which defines the upper surface of the duct into which the tobacco leaves are passed. Such an arrangement is generally conventional in the prior art. Whereas prior art machines have a unitary fixed bottom plate which, in use, acts as a support for the moving conveyor band against the pressure of the compressed leaves, that of the present invention is of a two part construction, comprising a fixed bottom half-plate 20 positioned towards the inlet end of the duct and fixed to the carriage 15 of the conveyor unit 10 and an adjustable or retractable bottom half-plate 21 positioned forward of the fixed plate 20 towards the mouthpiece of the duct.

In the embodiment shown, retractable plate 21 pivots about the axis 25 of second roller 13 adjacent the mouthpiece so as not to impair the conveyor band slat path. The pivoting movement of retractable plate 21 is actuated by means of a link rod 22 coupled at one end generally centrally upon the retractable plate 21 and coupled at the other end eccentrically to a rotatable disc adjacent the third roller 14 or, as shown, to a crankshaft 23 which also carries the third roller 14. The crankshaft 23 is coupled to the third roller 14 in such a way that adjustment of the crankshaft 23 through 180° to move the retractable plate 21 causes a corresponding adjustment of the third roller 14 with respect to the first and second rollers to maintain the correct tension in the conveyor band 11. In practice, there are two link rods 22, one on each side of the conveyor unit. There are numerous suitable mechanisms to allow adjustment of the crankshaft 23 and thus the retractable plate 21. The mechanism will include an indicator to indicate to the operator of the machine whether it is in the lamina or stem configuration.

The fixed and retractable bottom half-plates 20,21 are adapted to be able to pass one through the other to maintain a continuous bottom supporting surface to the conveyor band by including co-operating teeth or combs 30,31 on respective opposing edges. In addition, retractable plate 21 includes a slight bend such that good contact or support is maintained between the conveyor band 11 and the underside of the plate in both the lamina and stem configurations.

As shown, the surfaces of the half-plates 20,21 over which the conveyor band passes are provided with protective surfaces 35. Perplas (trade mark) is a suitable surface and provides a smooth resilient surface. Perplas is a high molecular weight polyethylene and is used in artificial limb joints.

Claims

1. An upper conveyor unit for a leaf cutting machine, the unit comprising a conveyor belt or band passing over a plurality of conveyor rollers, and providing a lower conveyor surface where the conveyor belt passes over a bottom conveyor plate and which, in combination with a lower conveyor unit of a leaf cutting machine defines, in use, a duct along which leaves are conveyed towards a mouthpiece adjacent a cutter; wherein the bottom conveyor plate comprises two half-plates, a fixed half plate, remote from the mouthpiece, .and a retractable half-plate mounted transversely adjacent the mouthpiece for pivotal movement.

2. An upper conveyor unit for a leaf cutting machine as claimed in claim 1, wherein adjustment of the retractable half-plate is achieved by means of a link rod coupled between the inner surface of the half-plate and a crankshaft upon which one of the conveyor rollers of the unit is carried, in such a manner that adjustment of the half-plate causes an appropriate movement of the roller to adjust and maintain the correct tension in the conveyor belt or band.

3. An upper conveyor for a leaf cutting machine as claimed in claim 1 or claim 2, wherein the fixed and retractable half-plates have interconnecting teeth to form a substantially continuous surface.