GB2027362A

GB2027362A - Document Comminuting Apparatus

Info

Publication number: GB2027362A
Application number: GB7832772A
Authority: GB
Original assignee: Ofrex Group Ltd
Current assignee: Ofrex Group Ltd
Priority date: 1978-08-09
Filing date: 1978-08-09
Publication date: 1980-02-20
Also published as: GB2027362B

Abstract

A machine for comminuting documentary material, and a method of comminuting documentary material involving the use of the machine. The machine comprises a frame (6) affording a housing, which provides a chamber (8), a lower surface of the chamber being defined by a reticulated sheet (10). One or more fixed blades (12) provide cutting edges (14) which extend into the chamber and longitudinally thereof. A rotor assembly (16) is mounted for rotation about an axis substantially co-incident with the axis of the cylindrical surface of the chamber, and comprises rotor blades (20) having cutting edges (22) which extend longitudinally of the chamber, and which engage the fixed blades (14) in a cutting action as the rotor assembly is rotated. Sheet documentary material is fed into the chamber, preferably along a chute (24), preferably being fed into the chamber, by a feeding device (30). Advantageously the feeding device (30) comprises a number of intermeshing cutter discs, which sever the documentary material into long strips in a pre-cutting operation. <IMAGE>

Description

SPECIFICATION Improvements Relating to the Comminution of Documentary Material This invention is concerned with improvements in or relating to the communication of documentary material.

A known machine for comminuting scrap thermoplastics material, to allow the scrap material to be re-used in a thermoplastics moulding operation, comprises a housing, a chamber in the housing, a lower surface of the chamber being defined by a part-cylindrical reticulated sheet, there being one or more fixed blades extending into the chamber, generally parallel to the axis of the cylinder. Within the chamber there is mounted for rotation about an axis substantially co-axial with the axis of the cylinder a rotor assembly, comprising one or more blades also extending generally parallel to the axis of the cylinder.

A machine of this kind will hereinafter be referred to as "a machine of the kind specified".

In the use of the machine, scrap thermoplastics material is deposited into a hopper mounted above the chamber, and falls from the hopper into the chamber through an opening in the housing.

The scrap plastics material is maintained in motion within the chamber by rotation of the rotor assembly, particles of the material being continually cut between the fixed blades and the blades of the rotor assembly. In due course, as material is reduced to the desired chip size, it passes through the openings of the reticulated sheet into a bin beneath.

If desired, in a machine of the kind specified, either the fixed blades or the blades of the rotor assembly or both may extend in the longitudinal direction and may also be provided with a slow helix (in a manner somewhat akin to the rotor assembly of a conventional cylinder lawn-mower) to provide a smoother cutting action.

A conventional machine of the kind specified is usually large (i.e. has a height greater than 5 foot) and usually, the chamber is greater than 1 foot in diameter. Additionally, the sizes of the openings in the reticulated sheet are relatively large, typically having an area greater than 0.005 sq.inches, and usually about 0.01 sq.inches.

A conventional document shredding machine comprises two rows of cutter discs mounted for rotation in opposite directions about respective parallel axis, the discs of one row being arranged to enter gaps between the discs of the other row with little or no clearance so that a shearing action is performed between each pair of adjacent cutter discs, and a sheet of documentary material fed into the nip of the machine is cut into narrow Strips.

It has also been proposed to sever the strips of material, thus formed into shorter lengths by forming in the periphery of each disc a plurality of angularly-spaced cut-outs or notches so arranged that the notches in any pair of adjacent overlapping discs, one in each row, do not register with one another as the discs rotate. The depth of the notches in less than the extent of overlap between the discs so that the shearing action performed between each pair of adjacent discs is uninterrupted, whilst the notches effect a transverse cutting or tearing action across the strips to cut the material into smaller pieces.

However, it is a requirement that the size of the pieces into which the material is shredded be no greater than a small, specified size, and increasingly it is required that the size of the pieces be smaller. This requirement is particularly encountered in the destruction of film material, upon which classified information is reproduced photographically, in view of the continually increasing miniaturisation of the information upon such film material.

Whereas the size of the pieces into which documentary material (including documentary material upon which classified information is reproduced photographically) is shredded may be decreased by decreasing the width of the cutter discs, and increasing the number of notches, this reduces the strength of the machine, and simultaneously requires a greater power input in view of the increased work load. This significantly reduces the capacity of the machine.

It will be appreciated;that it is a disadvantage to reduce the size into which documentary material is comminuted to a greater degree than is required, both for reasons of time and power consumption. It will further be appreciated that using a conventional document shredding machine, the size into which the documentary material is shredded cannot readily be varied. This in effect means that (for example) when it is desired to comminute documentary material to a smaller size, either a different machine must be used, or an existing machine must be substantially re-built.

It is one of the various objects of this invention to provide a document shredding machine which is more versatile than existing machines.

In its broader aspect this invention consists of a method of comminution of documentary material, involving the use of a machine of the kind specified.

However, the machine used in the method will be significantly smaller than a conventional machine of the kind specified (i.e. conveniently having a rotor assembly of less than 4.inches in diameter) and the size of the apertures in the sheet of reticulate material will be significantly smaller than a conventional machine of the kind specified. It is envisaged that the aperture size will be less than 0.005 sq.inches, and desirably less than 0.001 sq.inches. Additionally, provision may be made for the convenient removal of the reticulated sheet, and its replacement by a similar reticulated sheet having apertures of different size.

In view of the small size into which the documentary material is shredded, compared with the size into which a conventional machine of the kind specified comminutes scrap plastics material, advantageously means is provided to restrict exit of the small particles through the opening through which material enters the chamber. Advantageoulsy such means additionally affords means to constrain sheet documentary material for movement towards the chamber in a plane, such as a plane extending radially or tangentially to the longitudinal axis of the cylinder. Such means may be static, and may be afforded by a narrow chute through which one or more sheets of documentary material may be fed into the chamber, or may be active, for example provided by a feeding device constituted by a pair of rollers.Such rollers advantageously provide a preliminary cutting operation on the documentary material, and may conveniently be of the kind described in the specification of our co-pending application number 4/76 or 38160/76.

There will now be given a detaiied description to be read with reference to the accompanying drawings, of a method of comminution of documentary material, and a machine for carrying out said method, both the method and machine being illustrative of certain inventive aspects of this invention.

In the accompanying drawings: Figure 1 is a schemataic vertical sectional view of the machine which is the preferred embodiment; Figures 2 is a schematic side elevation of part of a modified machine.

The machine shown in Figure 1 comprises a frame 6 affording a housing, which provides a chamber 8. A lower side of the chamber 8 is defined by a reticulated member 10, end portions of which are secured to the frame 6 by bolts, and a central portion of which is formed into a generally semi-cylindrical shape. Conveniently the reticulated member is provided by a sheet of perforated material, formed into the shape shown in Figure 1 by a pressing operation.

Extending into the chamber 8 are three fixed blades 12a, 12b, 12c, each comprising a cutting edge 14. The blades 122 and 1 2b are generally on diametrically opposite sides of the longitudinal axis A of the part-cylinder afforded by the reticulated member 10, and the blade 1 2c is vertically above the axis A.

Mounted within the chamber 8, for rotation about an axis substantially co-incident with the axis A is a rotor assembly 16 comprising a spindle 18 and two blades 20a, 20b adjustably secured thereto. The length of the two blades 20a and 20b is such that, on rotation of the rotor assembly 16, cutting edges 22 of said blades pass through a cutting relationship with each of the blades 12a, 1 2b and 1 2c in turn. Additionally, the cutting edges of the two blades 20a, 20b pass very close to the inner surface of the part-cylindrical portion of the reticulated member 10.

Mounted above the chamber 8, and opening there into is a chute 24, through which documentary material may be fed into the chamber. The chute is narrow, but is sufficiently wide to allow a whole sheet of documentary material (e.g. 7" width) to be fed into the chamber. Desirably a pair of feed rollers 30 is used, to positively feed the material along the chute into the chamber. The chute constrains the documentary material for movement towards the chamber in a plane extending generally tangentially to a portion of the rotor assembly, said plane lying at right angles to a plane which extends normal to the axis A.However, as documentary material enters the chamber 8, it is diverted by the blade 12c, and passes across the cutting edge 1 4 thereof, ensuring an immediate initial comminution of the documentary material as it is fed into the chamber.

Additionally, the opening into the chamber afforded by the chute 24 is sufficiently small as to restrain small pieces of documentary material within the chamber passing outwardly therefrom.

In the use of the machine, the relatively small particles of the documentary material produced by the initial cutting operation will be retained mobile in the chamber, falling towards the surface of the cylindrical portion of the reticulated member 10, and being continually subjected to a cutting action between the cutting edges of the fixed and moving blades. When material has been comminuted to a sufficiently small size, it falls through the apertures of the reticulated member into a bin 28 mounted therebeneath.

Advantageously during rotation of the assembly 16, the cutting edges 22 of the blades 20a and 20b engage the inner surface of the cylindrical portion of the reticulated member 10.

This assists the passage through the reticulated member of material which has been comminuted to a sufficiently small size, and ensures that material which has fallen onto the member 10 which has been insufficiently comminuted is picked up, and subjected to a further cutting operation.

Preferably the machine illustrated in Figure 1 is no more than 4 foot high (e.g. 3 foot high) allowing the machine to be mounted on or alongside a desk in an office premises.

Advantageously the motor is arranged to drive the rotor assembly at a speed of between 700 and 800 revs. per minute, and the apertures of the reticulated member 10 are less than 1/10" diameter, preferably being about 1/32" diameter.

Additionally, either the fixed blades 12a, 12b and 12c, and/or the blades 20a, 20b of the rotor assembly, in addition to extending generally lengthwise in a direction parallel to the axis A, may be formed with a slow helix to provide smooth, semi-continuous engagement between the rotor assembly and the fixed blades.

In the modified form illustrated in Figure 2, the feeding device 30, comprising co-operating rollers mounted for rotation in opposite directions about parallel axis, replaces the chute 24. This enables the gap through which comminuted material may exit from the chamber to be almost entirely eliminated, and is particularly useful if the material being comminuted is such as may cause blockage of the chute 24.

Preferably however, the feeding device of the modified machine is itself such as will cause comminution of the material fed there through, preferably being constructed in accordance with the device illustrated in the specification of our co-pending application number 38160/76. In this manner, the documentary material is quickly reduced in size by means of a preliminary cutting operation, and the cutting effected within the chamber 8 is effective to reduce the precomminuted material further to the required size.

Additionally, in the modified construction, a rotor assembly 1 6 comprising three blades 20a, 20b and 20c is used.

In both constructions, the reticulated member 10 is mounted on the frame of the machine for easy removal and replacement by a similar reticulated member comprising apertures of a different size. This enables the machine to be readily modified, in accordance with the degree of comminution demanded.

The machines illustrated in the drawings are particularly suitable for use in comminution of documentary material in the form of paper, but are equally suitable for use in the comminution of documentary material upon which classified information is reproduced photographically.

Desirably, the machines illustrated in the drawings are used in conjuction with a delivery mechanism (not shown) adapted to pick up a sheet of documentary material, or a sheet upon which classified information is contained from a stack thereof, and to deliver the sheets one at a time to the feeding device 30.

Claims

1. A method of comminuting documentary material, involving the use of a machine comprising a housing, a chamber in the housing, a lower surface of the chamber being defined by a part-cylindrical reticulated sheet, one or more fixed blades extending into the chamber providing cutting edges which extend longitudinally of the chamber, and a rotor assembly mounted within the chamber for rotation about an axis substantially co-axial with the axis of the lower surface of the chamber, said rotor assembly comprising one or more blades adapted on rotation of the rotor assembly to engage with the fixed blades in a cutting action.

2. A method according to claim 1, wherein the rotor assembly of the machine used is less than four inches in diameter.

3. A method according to one of claims 1 and 2 wherein the aperture size of the reticulated sheet is less than 0.005 sq inches.

4. A method according to claim 3 wherein the aperture size of the reticulated sheet is less than 0.001 sq inches.

5. A machine for the comminution of documentary material, comprising a housing, a chamber in the housing, a lower surface of the chamber being defined by a part-cylindrical reticulated sheet, one or more fixed blades extending into the chamber providing cutting edges which extend longitudinally of the chamber, and a rotor assembly mounted within the chamber for rotation about an axis substantially co-axial with the axis of the lower surface of the chamber, said rotor assembly comprising one or more blades adapted on rotation of the rotor assembly to engage with the fixed blades in a cutting action.

6. A machine according to claim 5 wherein the diameter of the rotor assembly is less than four inches.

7. A machine according to one of claims 5 and 6 wherein the size of the apertures of the reticulated sheet is less than 0.005 sq inches.

8. A machine according to claim 7 wherein the aperture size of the reticulated sheet is less than 0.001 sq inches.

9. A machine according to any one of claims 5 to 8 wherein the machine comprises an opening through which material to be comminuted may be fed into the chamber.

10. A machine according to claim 9 comprising means to restrict exit of particles of comminuted material through the opening.

11. A machine according to claim 10 wherein said means additionally affords means to constrain sheet documentary material for movement towards the chamber in a plane.

12. A machine according to claim 11 wherein the plane in which sheet documentary material is constrained extends radially or tangentially to the longitudinal axis of the rotor assembly.

13. A machine according to any one of claims 10, 11 and 12 wherein said means is afforded by a narrow chute through which one or more sheets of documentary material may be fed into the chamber.

14. A machine according to any one of claims 10, 11 and 12 wherein said means is provided by a feeding device constituted by a pair of rollers.

15. A machine according to claim 14 wherein said rollers are operative to effect a preliminary comminution of the documentary material.

1 6. A machine according to claim 5, comprising additionally a feeding device adapted to feed sheet documentary material through an opening into the chamber.

1 7. A machine according to claim 1 6 wherein the feeding device comprises co-operating roller assemblies, each being mounted for movement about a respective axis which extends parallel to the longitudinal axis of the rotor assembly, in opposite directions.

18. A machine according to claim 17 wherein each roller assembly comprises a plurality of inter-meshing cutter discs, adapted to sever sheet documentary material fed through the feeding device into the chamber into a number of strips.

1 9. A machine according to any one of claims 16, 1 7 and 18 comprising a funnel into which documentary material is fed to the feeding device.

20. A method of comminuting documentary material, when carried out substantially as hereinbefore described with reference to the accompanying drawings.

21. A machine for comminuting documentary material, constructed and arranged substantially as hereinbefore described with reference to figure 1 or to figure 2 of the accompanying drawings.