WO2002007543A1

WO2002007543A1 - Lamina separator

Info

Publication number: WO2002007543A1
Application number: PCT/GB2000/002860
Authority: WO
Inventors: Shmuel Levy
Original assignee: Dickinson Legg Limited
Priority date: 2000-07-25
Filing date: 2000-07-25
Publication date: 2002-01-31
Also published as: AU2000261716A1

Abstract

Apparatus for separating the lamina portion of a leaf or bundle of leaves from the stem or mid-rib, comprising conveyor means including upper (50) and lower (25) runs which engage the leaves between them, and stripping means comprising mutually opposed pairs of teeth (15, 17) carried on a pair of drive chains set at an acute angle to the leaf conveyor. The drive chains are arranged so that the successive mutually opposed pairs of teeth come into engagement with successive leaves or bundles moving along the conveyor, and the teeth then move away from the conveyor so as to tear the leaves.

Description

LAMINA SEPARATOR

When processing organic leaf material it is common practice to separate the fleshy lamina portion of the leaf from the stem or mid-rib. This may be achieved manually, or by mechanical means such as a "cleaning and classifying" plant. In a cleaning conventional and classifying plant, the leaf material is introduced into a rotary mill, which randomly tears the leaf into smaller pieces. This tearing action frees a large proportion of the leaf from the stem, and the mixed lamina and stems can then be physically separated by pneumatic classification, winnowing or other means. The disadvantage of this process is that the lamina portion of the leaf is randomly torn into smaller fragments due to the action of the mill, which results in a significant reduction in particle size, and causes a total loss of some of the lamina by turning it to dust.

Accordingly the present invention seeks to provide apparatus for separating mechanically, the lamina from the stem in a continuous motion, whilst maximising the fragment sizes of the separated materials by means of a controlled, rather than a random, tearing action. The larger sizes of lamina particles which result will have a greater commercial value, and the overall process yield will be improved. For example, in a typical conventional leaf processing plant, it is normal to achieve 40 - 50% of lamina product in the size range above 1inch, as defined by sieving tests. By applying the techniques described in the present invention it is possible to achieve in excess of 70 - 80% of product in the size range above 1 inch. The functions which need to be performed in order to process the leaf material in this way are carried out by subsystems or mechanical assemblies which convey, restrain and process the leaf through the system. The leaf material may be fed to the process in the form of individual leaves, or as 'tied hands'. A 'tied hand' consists of a bundle of several leaves oriented in the same direction and held together by a tie leaf which is wrapped and knotted around the base of the bundle.

Accordingly the present invention provides apparatus for separating the lamina portion of a leaf or bundle of leaves from the stem or mid-rib comprising: conveyor means including means for gripping the stem or mid-rib of the leaf or bundle so as to transport it in a first direction, and stripping means, including means for engaging the lamina and moving it in a second direction at an angle to the first direction so as to separate it from the stem.

Preferably the conveyor means apparatus according to claim 1 in which the conveyor means comprises a first flexible belt onto which the leaf or leaves are fed, a second flexible belt or chain which is arranged above the first belt so as to engage the leaves, and means for applying pressure to the second belt so as to grip the leaves and to transport them with the major portion of the leaves projecting from the side of the conveyor means for engagement by the stripping means.

Preferably the stripping means comprises a series of pairs of synchronised teeth carried on a pair of mutually opposed upper and lower drive chains, the path of travel of the drive chains being arranged at an acute angle to the path of the conveyor means, whereby corresponding pairs of teeth are brought into convergence at a predetermined position of travel of the leaves along the conveyor means.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a front elevation of a lamina separating apparatus according to the invention;

Figure 2 is a plan view;

Figure 3 is an end elevation;

Figure 4 is a partial perspective view; Figures 5, 6 and 7 are schematic and views of a pressurizing arrangement;

Figure 8 is a schematic cross-sectional view along the line A-A of Figure 2 showing a leaf engaged for stripping;

Figure 9 is an enlarged partial view of part of the arrangement of Figure 8;

Figure 10 shows a leaf bundle in the process of stripping;

Figure 1 1 is a schematic cross-sectional view along the line B-B of figure 2 showing a leaf after stripping;

Figure 12 is a perspective view of a set of leaf-agitating rollers; and

Figure 13 is an enlarged view of the tooth guide-chain system.

Figs 1 , 2 and 3 show the front, plan and end elevations of the machine. The main elements are the hold-down system 12, the de-sanding rolls 16, the stripping system 18, and product take off conveyors 21-24.

Fig.4 shows leaves fed individually or in the form of 'tied hands' onto an endless belt 25 which transports them in a direction perpendicular to the stems or mid-ribs of the leaves, along the axis of the machine. An endless chain or flexible belt 50 is positioned above the belt 25 and is driven at the same speed as belt 25, so that the leaves are trapped between this chain 50 and the conveyor 25. A series of pivoted fingers 30 provided with pads of low friction material at their ends 32 apply pressure to the chain 50 via a strip of flexible low friction material 35. The pressure applied to the chain results from the weight of each finger combined with the force from a pressurised flexible tube 20, which is located in a fixed position above the fingers 30 and extends in the direction of the belts. The pressure applied to the fingers 30, and hence the force between the chain 50 and the conveyor 25, can be varied by adjusting the pressure of the compressed air or other fluid contained within the flexible tube 20. The leaves are thus gripped positively between the chain 50 and the conveyor 25, so that they are driven through the rest of the process without slippage, and transverse movement is positively resisted. The force applied to the leaves by this hold-down system can be adjusted so that it is sufficient to grip the leaves without damaging them due to excessive crushing. Because they are free to pivot on a horizontal axis 34, the hold-down fingers can accommodate varying thickness of product. The flexible pressurised tube 20 acts on each finger with a constant force which is independent of the height of each finger. Thus the fingers maintain a positive grip at all points along the leaf's passage through the machine. After the leaves have been positively gripped by the hold-down system, they are transported so that their free ends are passed above a series of de-sanding rollers, 16. These rollers consist of cylinders 60, supported on rotating shafts 62, and are provided with projections 61 which agitate the leaves mechanically, and induce sand and other foreign particulate matter to be separated from the surfaces of the leaves. In situations where the product has been fed in the form of tied hands, and the tie leaves have been cut, the de-sanding rollers also perform a loosening function and separate the tightly compressed leaves where they were previously tied together.

While the leaves are still clamped by the hold-down system 12, and are travelling in the direction of the machine axis, they enter between two synchronised sets of teeth. These are shown in side elevation in fig 13, and in section in fig. 8. The upper and lower sets of teeth, 15 and 17 are carried on endless chains which are guided on tracks 14 and 18 extending at an acute angle to the machine axis (Figure 2). As the upper and lower sets of teeth converge together, they pierce the leaves which are being carried through the teeth by the hold-down conveyor system. The speed of the hold-down conveyor 25 and chain 50 is equal to the velocity component of the teeth along the machine axis. The upper and lower surfaces of the leaves are pierced by the teeth 15 and 17 simultaneously (Figure 8). The position and height of the opening between the upper and lower sets of teeth is adjustable to accommodate different types of leaf product. The upper tooth guidance assembly (14) is also suspended so that it is free to move upwards if a solid piece of foreign material is engaged by the system.

The teeth mate with each other and close together in the vertical plane, piercing through and trapping the lamina portion of the leaves (Figure 8), while the stems or midribs lie in the gaps formed between the upper and lower sets of teeth. Thus the stems or mid-ribs are neither cut nor pierced by the teeth. Because the teeth are driven along the track 14 at an angle to the machine axis, they have a component of velocity perpendicular to the machine axis, and therefore travel away from the ends of the leaves which are gripped by the hold-down system 12 tearing the lamina 42a away as shown in Figure 10. In fig 11 it can be seen that the lamina 43 has been peeled away from the stem 40a, and the tips of the leaves 41 together with the stems remain gripped by the hold-down system. The lamina falls away to be collected on take-off conveyor 23, thus achieving the desired mechanical separation of lamina from stem.

Towards the end of the tooth-guidance track (14,18), the upper and lower teeth separate from each other in a vertical direction, causing them to release the stems, lamina and remaining portions of leaf which are removed from the teeth by the combined action of gravity and mechanical stripping guides.

Consequently, the product released from the machine at the end of the hold- down system contains a high proportion of st=ems while product released at the end of the tooth-guidance track contains a high proportion of separated lamina. Chutes and conveyors transport these product components away for subsequent processing. This will typically include a cutting process to separate the lamina tip from the stripped portion of stem, and an air classification system to separate the stripped lamina from portions of leaf which still contain some stem.

Claims

(1 ) Apparatus for separating the lamina portion of a leaf or bundle of leaves from the stem or mid-rib comprising: conveyor means including means for gripping the stem or mid-rib of the leaf or bundle so as to transport it in a first direction, and stripping means, including means for engaging the lamina and moving it in a second direction at an angle to the first direction so as to separate it from the stem.

(2) Apparatus according to claim 1 in which the conveyor means comprises a first flexible belt onto which the leaf or leaves are fed, a second flexible belt or chain which is arranged above the first belt so as to engage the leaves, and means for applying pressure to the second belt so as to grip the leaves and to transport them with the major portion of the leaves projecting from the side of the conveyor means for engagement by the stripping means.

(3) Apparatus according to claim 2 in which the means for applying pressure to the second belt includes a plurality of pivoted fingers having their free ends resting on the belt.

(4) Apparatus according to claim 3 in which the means for applying pressure to the second belt further comprises a pressurised flexible tube which is positioned above the fingers, and means for varying the pressure in the tube so as to control the pressure applied to the fingers.

(5) Apparatus according to any of claims 2 to 4 further comprising a plurality of driven rollers positioned beneath the transport path of the leaves so as to agitate them mechanically as they pass over the rollers.

(6) Apparatus according to any preceding claim in which the stripping means comprises a series of pairs of synchronised teeth carried on a pair of mutually opposed upper and lower drive chains, the path of travel of the drive chains being arranged at an acute angle to the path of the conveyor means, whereby corresponding pairs of teeth are brought into convergence at a predetermined position of travel of the leaves along the conveyor means.

(7) Apparatus according to claim 6 in which the opening between the teeth is adjustable to accommodate different types of leaf product.

(8) Apparatus according to claim 6 or claim 7 in which the upper guide chain is freely suspended so as to move upwards if a solid piece of foreign matter is engaged between the teeth.