WO2010034070A1

WO2010034070A1 - Fibre processing mill

Info

Publication number: WO2010034070A1
Application number: PCT/AU2009/001277
Authority: WO
Inventors: Richard Bamford
Original assignee: Kingston Investment And Management Company Limited
Priority date: 2008-09-26
Filing date: 2009-09-25
Publication date: 2010-04-01

Abstract

A mill (20) is used to process and separate fibre and rubber from a fibre and vulcanised rubber composite, such as that obtained from tyre shredding operations and includes a rotor (50) having a plurality of discs (58) which are spaced along a rotation axis (XX). The rotor (50) includes guide channels (70) which are secured to V-shaped grooves formed in the circumferences of each of the discs (58). Flails (100) are pivotally mounted around the circumference of the rotor (50), within the channels (70) and have a stepping profile including two or more steps or serrations (106) which terminate at a cutting tip (108). The mill (20) includes a perforated screen (120) a discharge chamber (130), such that fibres liberated by the flails and the residual rubber granules pass through the perforations in the screen (120) and are directed to a central collection area (132).

Description

Fibre Processing Mill

Field of the Invention

The present invention relates to a fibre processing mill. In particular, the present invention relates to a mill for separating and treating fibre and rubber in a tyre recycling process. However, it will be appreciated that the invention may be used to process other materials.

Background of the Invention

The disposal of used car and truck tyres in a commercially viable and environmentally friendly manner poses an ever increasing global problem. Tyres generally end up being discarded as landfill on account of the difficulty presented in processing the used tyres into usable by-products. Tyres are generally made of rubber, fibre and steel. The steel can be sold as scrap metal, and the vulcanised rubber can be used in a number of different industries. However, the fibre is typically considered an unwanted by-product of the tyre recycling operation. Accordingly, the fibre is generally discarded at a significant expense to the recycling plant operator.

A further problem with existing tyre recycling processes is that sufficient separation of the vulcanised rubber and the fibre is generally difficult to achieve. Accordingly, it is common that the final processed vulcanised rubber product still contains a significant percentage of fibre, which may reduce the quality of the recycled rubber product.

A further disadvantage of existing fibre separation systems is that the resulting fibre is typically not released from the vulcanised rubber in a form which is readily usable in other manufacturing processes. Accordingly, the fibre is generally discarded.

Object of the Invention

It is an object of the present invention to substantially overcome, or at least ameliorate one or more of the above disadvantages, or to provide a useful alternative. Summary of the Invention

In a first aspect, the present invention provides a mill comprising: a housing; a rotor mounted within said housing and having a first disc mounted at a first end and a second disc mounted at an opposing second end, said rotor being rotatable on a shaft about a rotation axis extending between said first and second ends, said rotor having an inlet located at one or both of said first and second ends, which permits access to a cavity located between said first and second discs; one or more flails having a proximal end pivotally mounted to a radially outer portion of said rotor, and a distal free end, said flail having a flail axis extending between said proximal and distal ends, and a perforated screen mounted to said housing adjacent to said rotor, wherein a clearance is present between said screen and the distal end of said flail.

The distal end of the flail preferably has a serrated profile which terminates at a tip.

The rotor preferably includes a guide channel extending between the discs parallel to the rotation axis, and the guide channel limits an angle through which the flail is permitted to pivot.

The rotor preferably includes a plurality of secondary discs spaced along the rotation axis between the first and second discs, and supported on the shaft, and the guide channel is secured to a V-shaped groove formed in a circumferential region of each disc.

The guide channel preferably limits a range of pivoting of the flail to about 90 degrees.

The inlet is preferably defined by a plurality of apertures located on a common pitch circle diameter on one of the first and second discs.

The mill preferably includes six guide channels evenly radially spaced around the circumference of the discs.

A clearance between the screen and the distal end of the flail is preferably at least about 5mm. The screen preferably has an arcuate profile which extends parallel to the rotation axis.

The screen is preferably co-axial with the rotor.

The screen arcuate profile preferably extends through about 180°.

In a second aspect, the present invention provides a method of processing a fibre and rubber composite with a mill, said mill including a rotor mounted within a housing and having a first disc mounted at a first end and a second disc mounted at an opposing second end, said rotor having a cavity located between said first and second discs, and said rotor being rotatable on a shaft about a rotation axis extending between said first and second ends, said rotor having an inlet located at one or both of said first and second ends, said mill including one or more flails having a proximal end pivotally mounted to a radially outer portion of said rotor, and a distal free end, said mill also including a perforated screen mounted to said housing adjacent to said rotor; said method including the steps of: inserting said composite into said inlet, such that said composite enters said cavity; rotating the rotor about said rotation axis, to centrifugally drive the distal end of said flail radially outwardly; directing said composite radially outwardly from the cavity to a clearance between said screen and the distal end of said flail, wherein the composite is processed by impact with said flail, resulting in separation of the fibre from the rubber, and the processed rubber and fibre pass through the perforations into a discharge chamber.

The method preferably includes the step of providing a negative pressure in the discharge chamber to assist in drawing the processed fibre and rubber through the perforations.

The method preferably includes the step of rotating the rotor at about 960 revolutions per minute.

Brief Description of the Drawings

A preferred embodiment of the invention will now be described by way of specific example with reference to the accompanying drawings, in which:

Fig. 1 is a side view of a fibre processing mill with the cover in an open position; Hg. 2 is a further side view showing the fibre processing mill of Fig. 1 mounted on a support stand with the cover closed;

Hg. 3 is a top view of the mill of Rg. 1 with the cover open;

Fig. 4 is a front view of the mill with the cover in a dosed position;

Rg. 5 shows an end view of a rotor support hub;

Rg. 6 shows a rotor of the fibre processing mill;

Rg. 7 is an end view of the rotor of Fig. 6;

Fig. 8 is an end view of the rotor of Rg. 6 including flails;

Rg. 9 is a side view of a flail of the fibre processing mill;

Fig. 10 shows the flail of Rg. 9 mounted within a channel;

Rg. 11 is a schematic showing the channel of Rg. 10 located adjacent to the circumference of the rotor;

Rg. 12 shows a screen and discharge chamber of the mill; and

Hg. 13 is a top view of the screen.

Detailed Description of the Preferred Embodiment

A fibre processing mill 20 is shown in the accompanying drawings. The mill 20 can be used to process and separate fibre and rubber from a fibre and vulcanised rubber composite, such as that obtained from tyre shredding operations. As shown in Fig. 1, the mill 20 has an external housing 22 including a base frame 24 and a cover 26. The cover 26 is made of sheet metal supported on a structural frame and is mounted to the base frame 24 with a hinge 28 which permits the cover 26 to be pivotally opened when required for maintenance or inspection purposes. The cover 26 is also connected to the base frame 24 with a pneumatic cylinder 30 which regulates the speed of opening and lowering of the cover 26, ensuring that the cover 26 does not fall excessively quickly during closing.

As shown in Figs. 3 and 4, the base frame 24 includes one or more inspection doors 32, which permit an operator to inspect the interior mechanisms of the mill 20 if required.

The mill 20 includes a rotor 50. The rotor 50 is partially shown in Rg. 1 and is shown in plan view in Rg. 6. The rotor 50 has a first end 52 and an opposing second end 54. The rotor 50 is rotatable about a shaft 56 on a rotation axis XX extending between the first and second ends 52, 54. The shaft 56 is mounted to the base frame 24 on a bronze bush. The rotor 50 includes a plurality of discs 58 which are spaced along the rotation axis XX, and each of the discs 58 is supported by the shaft 56. The rotor 50 includes guide channels 70 which are secured to V-shaped grooves formed in the circumferences of each of the discs 58. The guide channels 70 are formed from sections of steel angle, which serve to reinforce the rotor 50, by providing lateral stability to each disc 58, and increase the overall rigidity of the rotor 50. The guide channels 70 are welded to the discs 58.

The rotor 50 has one or more inlets 80 located at one or both of the first and second ends 52, 54. The inlets 80 are defined by a plurality of apertures located on a common pitch circle diameter on a central hub 82 secured to the shaft 56. The hub 82 is shown in Fig. 5. As shown in the plan view of the rotor 50 in Fig. 6, the two hubs 82 which are located at either end 52, 54 of the rotor 50 are reinforced with stiffening ribs 84.

Fig. 9 shows a flail 100 which has a proximal end 102 which is pivotally mounted with a screw, pin or other suitable fastener to a radially outer portion of the rotor 50. The flail 100 has a distal, free end 104, and a flail axis YY extends between the proximal and distal ends 102, 104. The flails 100 are pivotally mounted around the circumference of the rotor 50, within the channels 70. The mounting of one flail 100 within the channel 70 is shown in Fig. 10. The channel 70 includes two arms 72 projecting at approximately 90° relative to each other. Accordingly, the flail 100 is restricted to pivot through a range of motion of approximately 90°. Fig. 11 shows an end view of the channel 70 at the flail 100 mounting location. The channel 70 has a triangular steel web 74 welded to it, and the web 74 has a hole formed in it which receives a flail 100 fastener.

As shown in Figs 9 and 10, the flails 100 have a stepping profile including two or more steps or serrations 106 which terminate at a cutting tip 108.

Fig. 8 shows an end view of the rotor 50 when stationary. When stationary, the flails 100 each tend to hang downwardly under the influence of gravity. However, when the rotor 50 is rotating at a sufficiently high rotational speed, the flails 100 extend outwardly under centrifugal force, such that the flail axis YY of each flail 100 extends generally perpendicular to the circumference of the rotor 50. The mill 20 includes a perforated screen 120 which is manufactured from 6mm steel and is mounted adjacent to the rotor 50. The size of the perforations is approximately 9mm. The perforations are plasma cut through the screen. There is a clearance between the screen 120 and the distal end 104 of the flails 100. When the flail axis YY is extending perpendicular relative to the circumference of the rotor 50, the clearance is approximately 5mm between the cutting tip 108 and the screen 120. As shown in Fig. 12, the screen 120 has an arcuate surface which is co-axial with the rotor 50. Accordingly the clearance is generally constant around the radius of the screen. As shown in Fig. 12, the screen 120 is generally semi-circular in profile, such that the screen 120 extends around the lower half of the circumference of the rotor 50.

The mill 20 includes a discharge chamber 130 located in the housing 22 beneath the screen 120. The walls of the discharge chamber 130 slope downwardly and inwardly, such that any material that passes through the perforations in the screen 120 is directed to a central collection area 132.

The operation of the mill 20 will now be described. A fibre and vulcanised crumb rubber composite produced from tyre shredding is blown, or otherwise introduced by force through an inlet conduit toward the inlet 80, during rotation of the rotor 50. The rotor 50 is typically operated at a speed of approximately 960 RPM. As the rotor 50 spins around the axis XX, the hub 82 also turns, and the crumb rubber and fibre composite passes through the inlet apertures 80 in the hub 82, into the centre of the rotor 50.

The high rotation speed of the rotor 50 causes the discs 58 to act as impellers, which assist to fan the composite material outwardly. Given that the rotor 50 has no circumferential shell, the composite material is directed either upwardly into the space 90 between the rotor 50 and the outer cover 26, or downwardly to the clearance between the flails 100 and the screen 120. In the clearance, the majority of the composite particles are initially too large to fit through the perforations. However, the rotating flails 100 impact with the composite material, and this impact force assists to separate the fibre from the rubber. Given that the there are many flails 100 mounted both radially and longitudinally around the circumference of the rotor 50, the composite material is impacted by many flails 100 in a given period of time. Fibre is initially contained in the shredded tyre as pieces of fibre cloth, or woven material which is bonded to the vulcanised rubber. During flailing of the composite material, the size of the composite shreds become smaller, and the fibre pieces are liberated from the vulcanised rubber as separate, non-woven strands. The serrations on the flails 100 assist in separating the fibre cloth or woven material and tearing it into separate strands. The high rotation speed of the rotor 50 generates static electricity. The presence of the static electricity assists in gathering the fibre strands in clusters similar to cotton wool in overall texture, and the fibre strands are at this stage substantially separated from the vulcanised rubber.

The portion of the composite material which was initially directed upwardly eventually falls downwardly under gravity and reaches the clearance between the rotor 50 and the screen 120 where it is also flailed and treated as described above.

The processed rubber has a reduced size and is permitted to pass through the perforations in the screen 120 into the discharge chamber 130.

A negative pressure is applied to the outlet of the discharge chamber 130 which assists the liberated fluffy fibre to be sucked through the perforations in the screen 120 into the discharge chamber 130.

An advantage of the mill 20 is that the fibre is liberated from the rubber in a form that is readily used as a filler in plastics recycling.

Advantageously, the flails 100 are easy to remove for maintenance or replacement.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

CLAIMS:

1. A mill comprising: a housing; a rotor mounted within said housing and having a first disc mounted at a first end and a second disc mounted at an opposing second end, said rotor being rotatable on a shaft about a rotation axis extending between said first and second ends, said rotor having an inlet located at one or both of said first and second ends, which permits access to a cavity located between said first and second discs; one or more flails having a proximal end pivotally mounted to a radially outer portion of said rotor, and a distal free end, said flail having a flail axis extending between said proximal and distal ends, and a perforated screen mounted to said housing adjacent to said rotor, wherein a clearance is present between said screen and the distal end of said flail.

2. The mill of claim 1, wherein said distal end of said flail has a serrated profile which terminates at a tip.

3. The mill of claim 2, wherein said rotor includes a guide channel extending between said discs parallel to said rotation axis, and said guide channel limits an angle through which said flail is permitted to pivot.

4. The mill of claim 3, wherein said rotor includes a plurality of secondary discs spaced along said rotation axis between said first and second discs, and supported on said shaft, and said guide channel is secured to a V-shaped groove formed in a circumferential region of each disc.

5. The mill of claim 3, wherein said guide channel limits a range of pivoting of said flail to about 90 degrees.

6. The mill of claim 4, wherein said inlet is defined by a plurality of apertures located on a common pitch circle diameter on one of said first and second discs.

7. The mill of claim 4 including six said guide channels evenly radially spaced around the circumference of said discs.

8. The mill of claim 1, wherein a clearance between said screen and said distal end of said flail is at least 5mm.

9. The mill of claim 1, wherein said screen has an arcuate profile which extends parallel to the rotation axis.

10. The mill of claim 9, wherein said screen is co-axial with said rotor.

11. The mill of claim 9, wherein said screen arcuate profile extends through about 180°.

12. A method of processing a fibre and rubber composite with a mill, said mill including a rotor mounted within a housing and having a first disc mounted at a first end and a second disc mounted at an opposing second end, said rotor having a cavity located between said first and second discs and said rotor being rotatable on a shaft about a rotation axis extending between said first and second ends, said rotor having an inlet located at one or both of said first and second ends, said mill including one or more flails having a proximal end pivotally mounted to a radially outer portion of said rotor, and a distal free end, said mill also including a perforated screen mounted to said housing adjacent to said rotor; said method including the steps of: inserting said composite into said inlet, such that said composite enters said cavity; rotating the rotor about said rotation axis, to centrifugally drive the distal end of said flail radially outwardly; directing said composite radially outwardly from the cavity to a clearance between said screen and the distal end of said flail, wherein the composite is processed by impact with said flail, resulting in separation of the fibre from the rubber, and the processed rubber and fibre pass through the perforations into a discharge chamber.

13. The method of claim 12, including the step of providing a negative pressure in said discharge chamber to assist in drawing the processed fibre and rubber through the perforations.

14. The method of claim 13, including the step of rotating the rotor at about 960 revolutions per minute.