WO1989001364A1

WO1989001364A1 - Shredder unit

Info

Publication number: WO1989001364A1
Application number: PCT/GB1988/000647
Authority: WO
Inventors: Gordon Grasby Sowden
Original assignee: Sowden, Roger, Frank
Priority date: 1987-08-11
Filing date: 1988-08-05
Publication date: 1989-02-23
Also published as: GB8718952D0

Abstract

There is disclosed a shredder unit (10) which is especially suitable for shredding scrap tyres, and which comprises a base (11), a pair of drive shafts (12) mounted on the base (11) with their axes of rotation extending substantially horizontal, and material-shredding rotary cutters (13) mounted on the shafts (12) for rotation therewith. The shafts (12) are laterally spaced from each other to define a space (14) for receiving material to be shredded, and bearing housings (15) rotatably mount the ends of the shafts (12) by means of bearing assemblies which include fabric bearings. The bearing housings (15), the shafts (12) and the cutters mounted thereon form a unit which is bodily mountable in, and removable from a mounting (16) provided for the unit in the base frame (11), whereby the unit effectively takes the form of a cartridge unit which can be removed entirely in the event of a fault or undue wear developing in any of the components, and a replacement unit can then be mounted in place in a relatively short period.

Description

SHREDDER UNIT

This invention relates to a shredder unit for treating waste or scrap material. The invention has been developed primarily, though not exclusively, in relation to a shredder unit for rubber tyres, in which tyres are fed between two sets of cutters, which cut-up the tyres into small fragments which renders them usable for certain markets, or makes them more readily disposable.

Tyre shredders have a difficult task in carrying out a satisfactory shredding operation, in view of the nature of the product which is being shredded. Thus, while tyres are predominently made of rubber, there are other constituents, and particularly wire reinforcements, which cause particular problems in the shredding operation.

Since the tyres are made mainly of rubber, the cutters are primarily designed to cut-up or shred rubber satisfactorily, but are not well able to deal with the wire reinforcement. There are, in fact, two different types of wire usually present within the construction of a vehicle tyre. The first type comprises a relatively thick assembly of wires which is located within the tyre "bead", and the shredding of this is not a big problem. However, the further type of wire within a tyre comprises very narrow guage reinforcing wire which is located in the wall and cover of the tyre. This very fine wire tends to become wrapped around the cutters and the shafts on which they are mounted, and more seriously small fragments of cut wire tend to be driven into the bearing housings at the end of ^■ the shafts.

It is normal for roller bearings to be used in the bearing- housings, which are expensive items, and which rapidly deteriorate when fine wire fragments come into contact with the moving parts. When it becomes necessary to replace a worn bearing, it is a major operation which involves removal of the shaft-mounted cutter assembly, and the down time involved is a severe economic disadvantage to the shut tyre shredding operation. In addition, with existing tyre shredders, when cutter wear becomes such that replacement cutters are required, this also involves major down time in the removal of the cutter assembly, and withdrawal of worn cutters from their shafts on which they are mounted, so that replacement cutters can be mounted and then installed in the shredder. Replacement also can become necessary when a build-up of bonded-on rubber tends to form on the surfaces of the cutter blades. A typical down time for cutter replacement can be at least four hours, which severely interrupts the tyre shredding operation.

There is therefore a clear need to provide an improved design of tyre shredder which is able more readily to have replacement parts installed.

According to one aspect of the invention there is provided a shredder unit for shredding waste material and which comprises: a base; a pair of drive shafts mounted on said base with their axes of rotation extending substantially horizontally; material-shredding cutters mounted on said shafts for rotation therewith, the shafts being laterally spaced from each other to define a space for receiving material to be shredded; and a pair of axially spaced bearing housings in which said shafts are rotatably mounted: in which the bearing housings, the shafts and the cutters form a unit which is bodily mountable in, and removable from a mounting provided for the unit in the base frame. Thus, in the event of any fault or undue wear developing in any of the components of the unit, such as bearing wear or faulty operation of a cutter, the entire unit can readily be removed in a simple operation and a replacement unit mounted in its place in a relatively short period, say up to quarter of an hour.

Preferably, each bearing housing (which receives the ends of two shafts) includes so-called fabric bearings in which the shaft ends are rotatably mounted. Fabric bearings are made of a suitable fabric material, such as cotton fabric (impregnated with a molybdenum lubricant or graphite), which is shaped into cylindrical form to receive the respective shaft end, and can be readily installed and supplied much more cheaply than roller bearings.

A major advantage over roller bearings is that, in the event of ingress of fine metal wire to the housing, there is less risk of damage to the shaft end and to the bores of the housing receiving the shaft ends, since the wire tends to become entrapped at least partly into the material of the fabric bearing. To lubricate the rotation of the shaft ends in the fabric bearing, it is preferred that means is provided for routing water lubricant around and through the fabric ' bearing. Advantageously, the water is also directed over the fabric bearings and outwardly in a direction along the respective shaft. This water flow also acts to resist ingress of fine metal wire fragments, and at least some water may also come into contact with the material to be shredded which, in the case of at least rubber tyres, also promotes the feeding and shredding action. A shredder according to the invention is particularly applicable to the shredding of rubber tyres, but other waste material may be treated.

According to a further aspect of the invention there is provided a shredder unit for shredding waste material and which comprises: a base; a pair of drive shafts mounted on said base with their axes of rotation extending substantially horizontally; material-shredding cutters mounted on said shafts for rotation therewith, the shafts being laterally spaced from each other to define a space for receiving material to be shredded; and a pair of axially spaced bearing housings in which said shafts are rotatably mounted; in which the bearing housings include fabric bearings in which the shaft ends are rotatably mounted.

Preferably, means is provided for routing a pumped supply of water lubricant into the bearing housings and around the fabric bearings, to lubricate the rotation of the shaft ends.

One embodiment of shredder unit according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an exploded and perspective illustration of a shredder unit according to the invention, for treating waste or scrap material;

Figure 2 is a schematic plan view of a pair of shaft mounted rotary cutters of the shredder unit; and, Figure 3 is a schematic side view of a rotary cutter.

Referring now to the drawings, there will be described an embodiment of shredder unit according to the invention, which has been particularly designed for shredding scrap tyres. However, it should be understood that a shredder unit according to the invention may be used for treating other waste or scrap material, which is required to be shredded into small shredded particles.

The shredder unit is designated generally by reference 10, and comprises a base 11, and a pair of drive shafts 12 mounted on the base 11 with their axes of rotation extending substantially horizontally. Material-shredding rotary cutters 13 (see Figures 2 and 3) are mounted on the shafts 12 for rotation therewith, the shafts 12 being laterally spaced from each other, as shown in Figure 1, to define a space 14 for receiving material to be shredded. Between each rotary cutter 13 there will be located a spacer collar 14 which co-operates with a cutter 13 on the adjacent shaft so as to define a very small space through which the tyre must be forced to pass -during the shredding operation. The construction of the cutters 13 and the spacers 14 may be of standard construction employed in existing constructions of tyre shredders.

A pair of axially spaced bearing housings 15 rotatably mount the ends of the shafts 12 by means of bearing assemblies which will be described in more detail below.

As can be seen particularly from Figure 1, the bearing housings 15, the shafts 12 and the cutters mounted thereon form a unit which is bodily moutable in, and removable from a mounting 16 provided for the unit in the base frame 11. The unit therefore may take the form of a cartridge unit which can readily be removed in the event of any fault or undue wear developing in any of the components of the unit, such as bearing wear or faulty operation of a cutter. A replacement unit can then be mounted in place in a relatively short period.

The bearing housings 15 include shaft bores 17 into which the shaft ends are received, and fabric bearings (not shown) are fixed in position within the bores 17 so as to rotatably receive the respective shaft ends. The fabric bearings are made of any suitable fabric, such as cotton fabric, impregnated with a molybdenum based lubricant or graphite, for lubrication purposes.

In the event of any fine wire fragments being formed during the tyre shredding operation, which become forced along the shafts 12 and into the bores 17, the fabric bearings can cause the wire fragments to become entrapped or at least partly embedded in the material of the fabric, thereby minimising the risk of damage to the shaft end and the wall of the bore 17. Although not shown, means is provided to lubricate the rotation of the shaft ends in the fabric bearings, by providing a pressure supply of water lubricant to the bearing housing, which is caused to flow into the bores 17 and around and through the fabric bearings, and then to - flow in a direction parallel to the axes of the shafts 12. This flow of water under pressure, axially of the shafts, will issue from the inner annular entrance to the bores 17, thereby tending to resist ingress of fine wire fragments. In addition, at least some of this water may come into contact with the rubber tyre which is being shredded, and this also promotes the feeding and shredding action.

The use of fabric bearings provides a much cheaper item than conventional roller bearings, and yet which can operate entirely satisfactorily. The water lubrication also has a dual function, in that it provides lubricating properties to the running of the shaft end in the fabric bearing, and also resist ingress of fine wire fragments into the bearing housing.

Claims

CLA I MS

1. A shredder unit for shredding waste material and which comprises: a base; a pair of drive shafts mounted on said base with their axes of rotation extending substantially horizontally; material-shredding cutters mounted on said shaft for rotation therewith, the shafts being laterally spaced from each other to define a space for receiving material to be shredded; and, a pair of axially spaced bearing housings in which said shafts are rotatably mounted; in which the bearing housings, the shafts and the cutters form a unit which is bodily mountable in, and removable from a mounting provided for the unit in the base.

2. A shredder unit according to-Claim 1, in which each bearing housing includes fabric bearings in which the shaft ends are rotatably mounted.

3. A shredder unit according to Claim 2, in which each fabric bearing comprises fabric material impregnated with a lubricant.

4. A shredder unit according to Claim 2, including means for routing water lubricant around and through each fabric bearing.

5. A shredder unit according to Claim 4, in which said means is arranged also to direct water over the fabric bearings and outwardly in a direction along each respective shaft .

6. A shredder unit for shredding waste material and which comprises: a base; a pair of drive shafts mounted on said base with their axes of rotation extending substan ially horizontally; material-shredding cutters mounted on said shafts for rotation therewith, the shafts be ^: ng laterally spaced from each other to define a space for receiving material to be shredded; and, a pair of axially spaced bearing housings in which said shafts are rotatably mounted; in which the bearing housings include fabric bearings in which the shaft ends are rotatably mounted.

7. A shredder unit according to Claim 6, in which means is provided for routing a pumped supply of water lubricant into the bearing housings and around the fabric bearings, to lubricate the rotation of the shaft ends.