GB2388331A

GB2388331A - A punch-shredding machine

Info

Publication number: GB2388331A
Application number: GB0210599A
Authority: GB
Inventors: Paul Arthur Aries; David Mead
Original assignee: Acco UK Ltd
Current assignee: Acco UK Ltd
Priority date: 2002-05-09
Filing date: 2002-05-09
Publication date: 2003-11-12
Anticipated expiration: 2022-05-09
Also published as: GB2388331B; GB0210599D0

Abstract

A punch-shredding machine 10 comprises a housing/die 28, defining a passageway 40 through which material (such as paper and other sheet material intended for punch-shredding) may pass, and a punching mechanism 14 having a plurality of punch members 22, 24 and means 16, 34 to move the punch members from a retracted position (as in figure 1) in which they are spaced away from the passageway 40 to an advanced position in which they extend through the passageway; movement between the mentioned retracted and advanced positions effectively punch-shredding the material. In operation, paper and the like is fed in to passageway 40 via a plurality of spring-biassed 42 in-feed rollers 12. Cam 32 acts upon push plate 36 and consequently finger plate 38, forcing a first punch member 22 to an advanced position, thereby partially perforating the paper. As the paper continues through passageway 40, a second punch plate member 24 acts upon it in a similar way to the first, this time completely piercing the paper. Punch members 22, 24, which are arranged in rows, are of different sizes (as shown in figure 3); the first having a diameter range of 3 to 5mm and the second a range of 5 to 7mm. The punch-shredded material produced has dimensions of 1x4mm. A method of shredding sheet material, comprising repeated punching, is also disclosed.

Description

238833 1

Title: Shredding Machines Description of Invention

This invention relates to shredding machines of the kind which are used to shred a sheet of material, typically documentary material, into many small pieces so that the information contained on the material cannot be read. The machines will be described hereinafter in relation to paper, but it will of course be appreciated that many types of sheet material could be so shredded.

A conventional shredding machine comprises a cutting mechanism which comprises two shafts mounted for rotation about respective parallel axes, and cutting discs arranged at spaced intervals on each shaft, the cutting discs intermeshing and the shafts being rotated in opposite directions so as to provide a nip into which documentary material (such as paper) may be fed. The engagement between the circumferential edges of adjacent discs subjects the documentary material to a plurality of longitudinal cuts and the discs may be provided with transverse cutting edges by which the material is subjected to a transverse severing.

These shredding machines produce particles having a certain size. The size of the particle produced determines the security level at which the shredding machine can operate, with smaller particle sizes being necessary for higher security levels. As reconstruction techniques grow more sophisticated there is a continuing demand for shredding machines which can produce smaller particle sizes. Indeed, changes in print technology, such as scaleable fonts and landscape style formats, have led to a requirement for a smaller particle simply to maintain current levels of security. A new standard of security has therefore been proposed, having a maximum particle size of 1 mm by 4 mm.

Typical conventional shredding machines are able to shred material into reasonably small particle sizes, but the smallest sizes typically achievable are 1 mm by 5 mm. It has proved difficult to reach smaller sizes than this for two main reasons. First, to achieve a good quality of cut using conventional shredding machines of the kind described above it is necessary to precisely intermesh the cutting discs on the two shafts so that the paper can be held taut as it is pierced by the transverse cutting edges. For example, for particle lengths of 4 mm the discs must be aligned to within a tolerance of approximately 2 mm and currently such precision cannot be reliably achieved.

Second, at such small particle sizes the power required to drive the cutting discs increases disproportionately, which means that such shredding machines tend to have a low sheet capacity.

There is, therefore, a need for a shredding machine which can reliably and economically achieve small particle sizes.

According to this invention there is provided a shredding machine comprising: a) a housing which defines a passageway through which material to be shredded may pass, and b) a punching mechanism comprising a plurality of punch members, and means to move the punch members from retracted positions in which the punch members are spaced from the passageway to advanced positions in which the punch members extend through the passageway' movement of the punch members between the retracted and the advanced positions effecting shredding of the material.

Since such a shredding machine uses a punching mechanism to shred sheet material different alignment considerations are present than with conventional shredding machines and, in particular, the alignment does not deteriorate as rapidly with use.

Preferably the shredding machine further comprises means by which a sheet of paper to be shredded may be fed into the passageway. The means may comprise a plurality of in-feed rollers located adjacent the passageway.

( Preferably the shredding machine further comprises a die member provided with apertures to receive the punch members in their advanced position. Conveniently the punch members are moved rectilinearly. Alternatively, however, they may be moved rotationally. Preferably the shredding machine comprises a plurality of rows of punch members. This enables smaller particle sizes to be obtained easily. For example, for rotational shredding machines the punch members may be arranged in rows on a drum. Preferably each row of punch members is staggered with respect to its adjacent row or rows. This enables the paper to be more efficiently shredded.

In one embodiment the shredding machine comprises only two rows of punch members, the diameter of one row of the punch members being from 3 mm to 5 mm and the diameter of the other row of punch members being from 5 mm to 7 mm Preferably the diameter of the smaller row of punch members is substantially 4 mm and the diameter of the larger row of punch members is substantially 6mm. It has been found that such an arrangement is convenient for producing small particles and thus meeting the new security standard.

Preferably one row is disposed, in the retracted position of the punch members, on each side of the passageway, and the means to move the punch members is operative to move the punch members in a reciprocating motion.

This not only provides the shredding machine with a balanced action, but also enables the punch members themselves to control the movement of the last part of a sheet of paper through the passageway. If desired the reciprocating motion of the punch members may be controlled such that, in use, one or more rows of punch members will be in engagement with the material to be shredded. This means that the material to be shredded can be supported by the punch members even when the edge of the material has passed the feed rollers.

Alternatively, the punch members may be reciprocated at such a speed, that the

distance which the sheet of paper falls in the time between the sheet being engaged by successive punch members is within the required size parameters.

Alternatively the shredding machine may comprise a support means on which the paper to be shredded may be located. Conveniently the support means comprises a plurality of fingers which extend between the punch members of at least one row of punch members. This provides a convenient way of locating the paper to be punched.

According to this invention there is also provided a method of shredding sheet material comprising repeatedly punching the sheet material. Preferably the material is punched by an array of punch members which conveniently are moved rectilinearly and the punch members are preferably moved reciprocably.

Alternatively the punch members may be rotated.

The method preferably further comprises feeding a sheet of material to be shredded past the punch members. Preferably the punch members themselves control the rate of movement of the material. The method may further comprise supporting the material to be shredded.

Preferably the method further comprises shredding the sheet material length-wise from one edge, the material being moved past the punch members between two punch movements by an amount smaller than the diameter of the punch members. This generates small particles.

A preferred embodiment of this invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view showing the shredding machine which is the preferred embodiment of this invention; Figure 2 is a side section showing details of the punching mechanism; Figure 3 is a front section through the punching mechanism showing details of the support means; Figure 4A is a top view of the shredding machine showing details of the drive mechanism;

Figure 4B is a section on the line A-A through Figure 4A; and Figure 5 shows schematically an exploded perspective view of the punch assembly of Figure 1.

The shredding machine 10, which is the preferred embodiment of this invention, comprises a pair of in-feed rollers 12, a punch assembly 14, and a drive / transmission mechanism 16. The punch assembly 14 is shown in more detail in Figures 2 and 5. It comprises two punch plates 18, 20 each of which carries a row of punch members 22, 24, and two die blocks 28, 30.

The mechanism by which the punch plates 18, 20 are moved is best seen in Figure 2. A toothed belt 34, driven by a motor via a number of gear wheels, drives an eccentric cam 32 which moves a push plate 36 to advance the punch plate 18, 20 into the shredder. The push plate 36 is attached to a finger plate 38 which pulls the punch plate 18, 20 away from the shredder as the cam revolves.

Such mechanisms are common in conventional automatic punching devices and will not be described further herein.

The two die blocks 28, 30 have two rows of bores 26 which correspond to the rows of punch members 22, 24. The bores 26 maintain the alignment of the punch members 22, 24 and act as die apertures through which the punch members 22, 24 may extend.

The die blocks are horizontally aligned and arranged spaced from each other by a small gap 40 which defines a passageway through which paper to be shredded may pass. One row of punch members 22, 24 is mounted on each side of this passageway 40, the smaller row 22 being disposed above the larger row 24. The rows of punch members are staggered as shown for example by the aperture plate 26 in Figure 5 so that the centre of each smaller punch member lies between the centres of two larger punch members. The larger row of punch members 24 are spaced apart from each other by a distance less than the diameter of the smaller row of punch members 24, as shown in Figure 3.

Each of the rows of punch members 24, 26 has a retracted position (shown in Figure 1) in which the punch members 24, 26 are spaced from the passageway 40 and an advanced position in which the punch members extend through the passageway 40. The alignment of the punch members is maintained throughout their travel by the bores 26 in the die blocks 28, 30.

The in-feed rollers 12 comprise two horizontally spaced, rubber coated cylinders, which are mounted for rotation about respective parallel axes, and between which paper to be shredded may be fed. One of the cylinders is attached to its mount via a spring 42. This enables multiple sheets of paper to be fed through the rollers 12 whilst tension is maintained on the paper.

Both the in-feed rollers 12 and the punching mechanism 14 are driven via a belt and gear system 16 from the same motor. This ensures that the drive to the in-feed rollers 12 and to the punching mechanism 14 is synchronised.

The paper is supported by the in-feed rollers 12 whilst being shredded.

A further support means is shown in Figure 3. This comprises a row of fingers 44 which extend between the lower row of punch members 24 to closely abut the upper row of punch members 22, there being a clearance of only . approximately 0.2 trim between the punch members 22 and the fingers 44.

The punch shredder 10 may be operated as follows. The user positions the edge of the paper between the in-feed rollers 12, and turns on the shredder 10. A motor (not shown) begins to drive the in-feed rollers and the punch mechanism 14. Paper is thus drawn through the in-feed rollers 12 with the tension on the paper being maintained by spring 42.

The in-feed rollers 12 feed the paper into the passageway 40 between the die blocks 28, 30 and the paper is propelled downwards until it meets the punch mechanism 14. The drive to the punch mechanism 14 is controlled so that the two rows of punch members 22, 24 are driven in a reciprocating motion so that both are in the advanced position substantially simultaneously, and both are in

( the retracted position substantially simultaneously. This produces a balanced shredding action.

As the leading edge of the paper approaches the first row of punch members 22, the punch members 22 will remove a circle up to 4 rnrn in diameter from the paper, depending upon the feed rate of the paper. In practice, the feed rate is controlled so that only a small proportion of the circle is punched by each forward motion of punch members 22. As the paper continues to be fed through it is punched by punch members 24. These may remove a circle up to 6 mrn in diameter. More usually, however, the feed rate is controlled so that the paper is shredded into extremely small crescent shapes.

The size of the shapes is determined by the feed rate of the feed rollers 12.

When the trailing edge of the paper leaves the in-feed rollers 12 the paper falls until it rests on the support means, the fingers 44. The upper row of punch members 22 then punches out a row of 4 mrn holes in the paper. The paper between the punch members 22 and the fingers 24 is also removed, usually being sheared off at the die aperture, since the clearance between the punch members 22 and the fingers 44 is so small. The paper then falls until the top of the punched out hole rests upon the fingers 44 and the lower row of punch members 24 is operated, shredding the paper further. This process is then repeated until the entire sheet of paper has been shredded.

To ensure positive feeding of the paper into the passageway in the shredding operation, preferably the in-feed rollers extend as close to the punching zone as possible. However, in the event that a trailing edge of paper, after leaving the in-feed rollers, fails to pass through the punching zone, it has been found that entry of the next batch of paper between the in-feed rollers in a further punching operation will clear any residual paper from the previous batch remaining in the passageway.

It will, of course, be appreciated that such a shredding machine could be used for many types of documentary material as well as paper. The size of the

particles produced can be varied easily by changing the in-feed rate of the shredder, or the size or arrangement of the punch members. Furthermore, compared to conventional shredders, the machine can accept a relatively large number of sheets of paper without excessive power consumption.

In the present specification "comprises" means "includes or consists of"

and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following

claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

( CLAIMS

1. A shredding machine comprising: a) a housing which defines a passageway through which material to be shredded may pass, and b) a punching mechanism comprising: a plurality of punch members; and means to move the punch members from retracted positions in which the punch members are spaced Tom the passageway to advanced positions in which the punch members extend through the passageway, movement of the punch members between the retracted and the advanced positions effecting shredding of the material.

2. A shredding machine according to Claim 1 further comprising means by

which a sheet of material to be shredded may be fed into the passageway.

3. A shredding machine according to Claim 2 in which the means comprises a plurality of in-feed rollers.

4. A shredding machine according to any preceding claim further comprising a die member provided with apertures to receive the punch members in their advanced position.

5. A shredding machine according to any preceding claim in which the punch members are moved rectilinearly.

6. A shredding machine according to any of Claims 1 to 4 in which the punch members are moved rotationally.

7. A shredding machine according to any preceding claim comprising a plurality of rows of punch members.

8. A shredding machine according to Claim 7 in which each row of punch members is staggered with respect to its adjacent row or rows.

9. A shredding machine according to Claim 7 or Claim 8 comprising only two rows of punch members, the diameter of one row of punch members being between 3 mm and 5 mm and the diameter of the other row of punch members being between 5 trim and 7 mm.

10. A shredding machine according to Claim 9 in which the diameter of the smaller punch members is substantially 4 mm and the diameter of the larger punch members is substantially 6 mm.

11. A shredding machine according to any of Claims 7 to 10 in which the rows are arranged in a pair or pairs, one row of the or each pair being disposed, in the retracted position of the punch members, on each side of the passageway, and in which the means to move the punch members is operative to move the or each pair of punch members in a reciprocating motion so that both OF all are retracted or extended simultaneously.

12. A shredding machine according to Claim l l in which the reciprocating motion of the punch members is controlled so that all are in their advanced positions substantially simultaneously and all are in their retracted positions substantially simultaneously.

(

13. A shredding machine according to any preceding claim further comprising a support means on which the material to be shredded may be located.

14. A shredding machine according to Claim 13 in which the support means comprises a plurality of fingers which extend between the punch members of at least one row of punch members.

IS. A method of shredding sheet material comprising repeatedly punching the sheet material.

16. A method according to Claim 15 in which the material is punched by an array of punch members.

17. A method according to Claim 16 in which the punch members are moved rectilinearly.

18. A method according to Claim 17 in which the punch members are moved reciprocably.

19. A method according to Claim 16 in which the punch members are moved rotationally.

20. A method according to any of Claims 16 to 19 farther comprising feeding a sheet of material to be shredded past the punch members.

21. A method according to Claim 20 in which movement of the punch members controls the rate of movement of the material.

22. A method according to any of Claims 16 to 21 further comprising supporting the material to be shredded.

23. A method according to any of Claims 16 to 22 further comprising shredding the sheet material length-wise from one edge, the material being moved past the punch members between two punch movements by an amount smaller than the diameter of the punch members

24. A shredding machine substantially as hereinbefore described and as illustrated in the accompanying drawings.

25. A method of shredding sheet material substantially as hereinbefore described.

26. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.