GB2179970A - Sisal decorticator - Google Patents

Abstract

A mobile decorticator for decorticating leaves of sisal comprises a feed device which engages a medical portion of the leaves. The feed device comprises pairs of upper and lower rope conveyors (1,2) the upper conveyor being a multiple rope conveyor. The sisal leaves are held between the ropes of the upper and lower conveyors. Two rotatable drums (30, 50) carrying spaced apart blades (44) around the periphery are arranged to decorticate the leaves, the drums each decorticating one side of an individual leaf. The decorticator is mobile and may be towed by a tractor and operates without water. <IMAGE>

Description

SPECIFICATION Sisal decorticator This invention is concerned with improvements in and relating to decorticators particularly decorticators for use in extracting fibre from sisal leaves.

Decorticators have taken the form of a static plant set up on permanent foundations and comprising a feed device for carrying cut leaves in a layer, with their longitudinal axes generally parallel andtransverseto the direction offeed. The layer of leaves, held by the feed device af a mid region ofthe layer so that a portion of the layer extends each side of the feed device, is fed past a decorticator drum located to one side the feed device and rotating about an axis parallel to the direction of feed. The drum carries blades around its periphery to which the portion ofthe layer to that side of the feed device on which the drum is located, which strike that portion ofthe layer and strip the flesh from that portion of the layer.The layer is then carried past a second similar decorticator drum which is located to the other side ofthe feed device and the flesh is stripped bythe second drum from the portion ofthe leaves to that side of the feed device.

Each drum is of heavy construction and comprises circular side plates and a peripheral wall extending between the side plates so as to form a hollow closed drum, the blades being fixed to the exterior ofthe peripheral wall. Each drum is within a casing, having side plates and a peripheral wall, which with the drum defines an annular passage between the peripheral walls of the casing and drum, the blades extending into that passage. The peripheral wall ofthe casing is interrupted to allow the leaf layerto be exposed to the action of the blades and has an outlet for ejection of the flesh. A water inlet is provided to feed water into the casing which isthoughtto assistthe action ofthe blades on the flesh and to assist in ejection of the flesh from the casing.

Use ofsuch an installation requires leafto be broughtto it, removal of extracted flesh and substantial quantities of water. The fibre content of sisal leaf is about 5% by weight so that some 95% of leaf brought to the plant is waste from a fibre production view point. Howeverthe pulp makesfertiliser and if it is to be used as such it has again to be transported from the installationto the area where it isto be spread.

The quantity of water used is ofthe order of 8 to 10 thousand gallons per hour which limitsthe locations where installations can be economically located and is removed along flume channels eitherto rivers or reservoirs where the flesh represents a pollution hazard, seepage ponds being sometimes provided to reducethis hazard.

A sisal estate producing 100 tons offibre per month requires 2,000tons of leaf and produces 1,900 tons of flesh.

To improve the economics of sisal fibre a decorticator is provided according to this invention which is portable and comprises a feed device to engage a mid region of a layer of leaf with the individual leaves extending transverse to the direction of travel and extending to either ofthe feed device and decorticator drum located on each side ofthefeed device, each drum comprising a rotatable structure through which leaf flesh may pass, the structure carrying blades spaced aboutthe periphery ofthe structure and between which flesh may pass, the drum being located in a casing which includes an opening in a peripheral wall where the feed device will expose the layer extending to that side of thereof on which the drum is located, each drum casing including a flesh outlet.

The feed device preferably comprises conveyors located on either side of a longitudinal plane of the decorticator parallel with the direction of feed, a first conveyor located to engage the leaf layerto one side of said plane remote from the side on which the first drum is located and a second conveyor located to engage the leaf layer to the side ofthe plane remote from the second drum. Thereby the mid region ofthe leaflayercan be exposed in parttothefirstdrum and in part to the second drum so that substantially all the flesh will be removed.

In orderthatthe invention may be fully understood, an embodiment will now be described with reference to the accompanying drawings wherein: Figure lisa diagrammatic side elevation of a mobile sisal decorticator, Figure 2 is a schematic view ofthe rope conveyors, Figure 3 is a side view ofthe central part ofthe rope conveyors mounted on a frame, Figure4 is a plan view ofthe rope conveyors of Figure 1 showing the position ofthe decorticator drums, Figure 5 is a partly sectioned view of a decortication drum, and Figure 6 is a bottom view of a decortication drum.

A mobile sisal decorticator mounted on wheels W has an input conveyor A which feeds sisal leaves arranged transversely across the conveyor to a first pair of rope conveyors 1 (Fig. 2).The mid regions of the leaves are gripped in between upper and lower parts ofthe conveyors 1. The leaves are then fed by the first pair of conveyors 1 to a first decorticator drum 30 which strips the flesh from that part of the leaves to the same side ofthe conveyor as is the drum.The resultant pulp is expelled through an outlet chute 31.

The partly stripped leaves are then accepted by a second pair of rope conveyors 20 which convey the leaves pasta second decorticator drum 50 which stripstheflesh from that partofthe leaves as is on the same side of the second conveyors as is drum 50. The stripped pulp is ejected via a chute 33. Finally the resultant fibres are conveyed to a collection section B.

The mobile decorticator is conveniently tractor driven and powered, power being transmitted by any conventional means.

The input conveyorto feed the leaves to the first rope conveyors comprises firstly a disc conveyor 60 having parallel rows of discs, each row rotatable about axes parallel to the direction of feed which convey sisal leaves to a wire conveyor 65 having parallel endless wires which present the leaves to the first pair of rope conveyors 1. The leaves are arranged transversely across the disc and wire conveyors to form a continuous layerofleaves.

Referring now to Figures 1 to 4 in particular; The first pair of rope conveyors comprises an upper and a lowerconveyor,shown in Figure 2 by a broken line and solid line respectively.

The lower conveyor is a single rope conveyor comprising a single rope 3 extending in a loop beneath three-groove pulley 8 overthree-g roove pulley 5 beneath three-groove pulley 7, around single-groove pulley 6 and around single groove pulley 4. Throughoutthe description it should be noted that the rope of a single rope conveyor is always guided in the middle groove of anythree-groove pulley with which it is associated.

The upper rope conveyor is a double rope conveyor comprising two ropes 9, 10 extending in respective loops beneath three-groove pulley 8 overthreegroove pulley5 around three-groove pulley 7, under idler 16 and around respective single groove pulleys 11 and 12. All the pulleys rotate on shaftsjournalled in bearings attached to the main frame 15 ofthe decorticator. Single pulleys 11 and 12 are each mounted on an arm 70,71 (Fig. 1) which is pivotally mounted on the frame and biased by a spring 72,73 so that the tension in the ropes can be varied. Ropes 9 and 10 run in the outergrooves of all thethreegrooves pulleys. It can be seen from Figure 2 thatthe three ropes 3,9,10 have a common path for part of their length, the common path being under pulleyS and over pulley 5, the paths then separating beneath pulley 7.

Thefirst pair of rope conveyors 1 are located to that side of a mid plane of the decorticator indicated by broken line 18 in Figure4 remotefrom thefirstdrum 30. Itwill be appreciated thatthe arrangement of the second pair of rope conveyors 20 is the same as the first pair 1. No further description is therefore necessary. The second pair of rope conveyors 20 is j ocated on the side ofthe mid plane remote from the second drum 50.

With reference to Figure 3, the first decortication drum 30 is mounted for rotation on shaft 25 and the second drum 50 on shaft 26. Each drum is arranged so that it rotates about an axis parallel with the plane of rotation ofthe rope conveyors. The drums are each surrounded by a cover 55,56 having chutes 31,33 through which pulpisexpelled.Thecover55Ofthe second drum can be seen in Figure 3.

Referring nowto Figures 5 and 6; each decortication drum comprises two spaced apart plates 40,42 between which are arranged decorticating knives 44.

The shape ofthe knives is as shown in Figures 4 and 5.

This shape has been found to be the most effective.

The knives are arranged around the periphery of the drum sothatthe blades extend radiallyoutside plate 42. The periphery of the drum is open so that the flesh can be ejected without having to be flushed out by water. The drums are mounted to one side oftheir respective rope conveyors in such a mannerthatthe path ofthe knives extends across the central plane of the machine to the side on which the respective pair of conveyors is mounted. The second drum maybe of largerdiameterthanthefirst.

In orderto ensure that the sisal leaves are presented to the decorticating knives at the optim um height and orientation, a pairofcurved guides 80,82 are provided. The guides 80,82 are arranged so that the leaves pass between them to present the laves to the path of the drum knives. Guides are provided in respectofthe second drum forthe same purpose.

In orderto appreciate the cycle of operation sisal decorticator, the passage of leaf will now be described. The machine is normally used to treat layer of leaf made up of individual leaves placed transversely across the disc conveyor, conveyed thereby to the wire conveyor and thence to the first rope conveyors 1. The leaf is gripped by ropes 3,9 and 10. The upper, outer ropes 9,10 are above the leaf and the middle lower rope 3 is below the leaf.

The leaf layer is conveyed towards the first decortication drum via the guides 80,82 which bend the leaf as described. The knives on the rotating drum decorticate that part ofthe leafthat is to the same side ofthe conveyor as is the drum and flesh removed is expelled tjirnugh the chute. The partly stripped leaf is then conveyed towards the second pair of rope conveyors. It can be seen from Figures 1 and 3 that at the lower most point on pulley 7 the leaf is picked up bythe second pair of rope conveyors so that atthe changeover point the leaf is gripped by all six ropes.

The second pair of conveyors 20 convey the leafto the second decortication drum where the remaining flesh is tripped away and expelled, leaving bare sisal fibres.

The fibres are carried to the end ofthe conveyor to a collecting station for removal.

Due to the off-centre arrangement ofthe rope conveyors the path ofthe cutting knives can extend over the centre of the leaf so ensuring that the leaf is completely decorticated.

A mobile decorticator as described has the advantage that it runs without the need for water. The total weight may be a quarter of the weight of a static plant and it is very simple in construction. The pulp may be expelled straight onto the field when the decorticator is working where it may be collected for use as fertiliser. This operation is much more efficient than the prior art plants which require the leaves to be broughtfrom the fields and the pulpto betransported backtothefields.

Claims (9)

1. A decorticatorfor removing flesh from leaves, the decorticator being mobile and comprising a feed device to engage a medial portion of a layer of leaf with the individual leaves extending transverse to the direction oftravel of the layer on the feed device and extending to either side ofthe feed device, and rotatable decorticator means locates on each side of the feed device and each carrying peripheral spaced apart blades, each decorticator means being located in a casing which includes an opening in a peripheral wall where the feed device will expose the layer extending to that side thereof on which the decorticatormeans is located, each casing including a flesh outlet four decorticated leaf flesh.

2. A decorticator according to claim 1 wherein the feed device comprises conveyor means located on eithersideofa longitudinal plane of the decorticator parallel with the direction of feed, and the decorticator means comprising first and second drums, a first conveyor means being located to engage the leaf layer to one side of said plane remotefrom the side on which the first drum is located, and a second conveyor means being located to engage the leaf layerto the side of the plane remote from the second drum.

3. Adecorticatoraccordingtoclaim2whereinthe first and second conveyor means each comprise a pair of rope conveyors.

4. A decorticator according to claim 3 wherein each pair of rope conveyors comprises an upper conveyor and a lower conveyor, one of said conveyors being a multiple rope conveyor, said upperand lower conveyors having a common path over a portion of their length whereby medial portions of the leaves are held between the upper and lower conveyor ropes.

5. A decorticator according to any one of claims 2, 3or4whereinthefeeddeviceincludesadiscconveyor having parallel rows of discs, each row being rotatable about an axis normal to the direction offeed and a wire conveyor having parallel endless wires, said disc conveyor presenting leaves to said wire conveyor which in turn presents the leaves to said first conveyor means.

6. Adecorticatoraccording to any one ofthe preceding claimswherein each decorticator means comprises two spaced apart plates between which the blades are arranged, the blades extending radially outwards ofthe upstream plate in the feed direction,

7. A deco rticator according to any one of claims 2 to 6 wherein the path ofrotation of said knives intersects said longitudinal plane.

8. A decorticator according to any preceding claim wherein guide means are provided for presenting the leaves to the knives.

9. A decorticator substantially as herein described with reference to the accompanying drawings.