GB2171028A

GB2171028A - Apparatus for comminuting material in sheet form

Info

Publication number: GB2171028A
Application number: GB08603568A
Authority: GB
Inventors: Otto Arweiler; Ernst Jordan
Original assignee: Alois Zettler Elektrotechnische Fabrik GmbH
Current assignee: Alois Zettler Elektrotechnische Fabrik GmbH
Priority date: 1985-02-14
Filing date: 1986-02-13
Publication date: 1986-08-20
Also published as: DE3505075A1; FR2577443A1; DE3505075C2; GB8603568D0; IT1187913B; GB2171028B; FR2577443B1; IT8652991V0; IT8667112A0

Abstract

The cutting mechanism of the document disposal unit has two cutter cylinders driven in rotation in opposite directions, each of which comprises a shaft and a plurality of cutter discs 13 which are sheet metal stamping and pushed on to the shaft to lie against one another in pairs. The cutter disc pairs of each cutter cylinder are held axially spaced from one another by fixed distance washers 11 pushed on to the shaft and engage between cutter disc pairs of the other cutter cylinder in each case. The cutter disc pairs lie against one another with their sides provided on the circumference with stamping restriction radii 21 due to the stamping working. The cutter discs 13 and the distance washers 11 are pushed with axial play axially loosely on to the shafts so that tolerances can be taken up automatically. <IMAGE>

Description

SPECIFICATION Apparatus for comminuting material in sheet form The invention relates to an apparatus for com- minuting material in sheet form into shreds or shavings.

Apparatuses of this kind are known as document disposal units which comminute papers, films, cards, etc. in order to make writings thereon illegible. The cutting mechanisms of such document disposal units consist in the ordinary way of two parallel cutter cylinders having a plurality of cutter discs which stand opposite one another in staggered manner and interengage over a part of their circumferences to form cutting areas. The cutter discs have recesses on their circumference and comminute the material in sheet form introduced between them into shreds or shavings.

It is known to produce the cutter cylinders by turning or grinding from one single piece.

The disadvantage of this method is that the cutter discs and their interspaces must be manufactured with high precision. In view of the relatively high number of cutter discs necessary, for example of 130 discs for a sheet width of DIN A 4, this is relatively expensive.

It is known from Fed. German Publ. Spec.

No. 2,526,109 to assemble the cutter cylinders of a document disposal unit from a plurality of separate cutter discs which are pushed on to a shaft and secured in shapelocking manner against rotation. The interspaces between the cutter discs are fixed by separately pushed-on axially resilient distance rings. The cutter discs are axially stressed on both sides and must be ground for the formation of their cutting surfaces, which increases the manufacturing. expense.

From Fed. German Pub. Sp. No. 3,200,372 cutter cylinders of a document disposal unit are known where the cutter discs are fitted in pairs on a shaft and the cutter disc pairs are held opposite to interspaces by distance pieces. The cutter discs of each pair are con cavely domed towards one another and axially clamped fast on the shaft by exploitation of the springing properties of the doming. While it permits a slight taking up of tolerances, the resilient doming impairs the cutting properties, since cutter disc pairs associated with one another lie with convex side faces opposite to one another. The cutter discs of these cutter cylinders too must be ground on the circum ference. The shaping of the doming requires an additional operation.

It is the problem of the invention to produce an apparatus for the comminution of material in sheet form (document disposal unit) the cutter cylinders of which can be produced with relatively low production expense.

Within the scope of the invention the cutter cylinders of the document disposal unit, which have parallel axes and are driven in rotation in opposite directions, consist of a shaft and a plurality of cutter discs pushed on to the shaft, lying against one another in pairs. The cutter disc pairs for their part consist of two like sheet metal stampings which lie against one another with their sides which are provided at the circumference with stamping restriction radii due to the stamping working.

The "burr sides" lying axially opposite to the restriction radii of the sheet metal stampings face outwards and without subsequent working, especially by grinding, form sharp cutting edges between circumference and end face of the sheet metal stampings as prerequisite for good cutting properties. The sheet metal stampings are precision stamped parts, so that machining of the "burr side" is also eliminated. It is also essential for the precision stamping operation that the metal hardness, within specific limits, can be the higher the thinner is the utilised sheet metal. Thus for the same overall thickness cutters built up from two sheet metal stampings can be made from harder sheet metal than can a one-piece stamped cutter.

Forms of embodiment in which the cutter disc pairs and the distance washers are guided loosely displaceably with axial play on the shaft of the cutter cylinder are of substantial importance. The cutter discs and distance washers lie against one another, independently of their individual thickness, and form a pack which oscillates freely in the axial direction of the shaft within the axial play between two abutments. The abutments can be cotters of the shaft or its axial bearings. If the material to be shredded is introduced between the cutter cylinders, then in the cutting operation ax ial forces occur between the interengaging cutter disc pairs which axially separate the cutter disc pairs from one another.Since all the cutter disc pairs and distance washers are individually freely displaceable, the clearance of cutter disc pairs in engagement with one another automatically adjusts itself. The axial thickness of the distance washers is expediently less than the axial thickness of the cutter disc pairs.

The distance washers, which for the sake of production at more favourable cost are expediently made as injection-moulded synthetic plastics parts, are preferably also used as hand guards and protrude beyond the cutter discs radially substantially on all sides except for the region of mutual engagement of the cutter cylinders. In the region of engagement of the cutter cylinders they form a material guide slot which both feeds the material to be comminuted to the cutter cylinders and also conducts the material in shredded form away from the cylinders. Distance washers of loz enge form which are guided displaceably for securing against rotation on a guide rod pass ing through the distance washers in the region of one corner of the lozenge have proved themselves favourable in this connection.

The cutter discs have on their circumference several axial grooves symmetrical of the radial direction, which widen preferably by way of oblique groove walls to the groove bottom.

This has the advantage that the material for cutting can be comminuted in two running directions of the cutter cylinders, since the cutting angle is the same in each running direction.

An example of embodiment of the invention will be explained in greater detail below by reference to a drawing, wherein: Figure 1 shows a diagrammatic front view, partially in section, of a document disposal unit; Figure 2 shows a sectional view of the cutting mechanism perpendicularly of its cutter cylinders, and Figure 3 shows a lateral elevation of a distance washer.

Figs. 1 and 2 show in partially diagrammatic form a cutting mechanism of a document disposal unit having two cutter cylinders 3 driven in rotation in opposite directions about mutually parallel rotation axes 1, each of which cylinders comprises a shaft 9 mounted at both ends in side walls 5 of a housing 7. A plurality of pairs of cutter discs 13 axially separated from one another by distance washers 11 is seated on each of the shafts 9, which disc pairs extend between mutually adjacent cutter disc pairs 13 of the other shaft 9 in each case. As Fig. 2 discloses, the cutter discs 13 are held fast in rotation by shape engagement on the shafts 3.However the cutter discs 13 and the distance washers 11 are merely fitted on to the shafts 9 and are displaceabie between two abutment 15 on the ends of the shafts 9, loosely with axial play both individually and as a pack in common. Since the thickness of the distance washers 11, which are alike and formed each as injectionmoulded synthetic plastics part, is less than the total thickness of the likewise alike pairs of cutter discs 13, the cutter discs 13 of the two cutter cylinders 3 can interengage without tilting and align themselves in relation to one another to take up dimensional tolerances.

Material in sheet form for comminuting which is introduced through an entry slot 17 of the housing 7 between the cutter cylinders 3 is comminuted between the edges of adjacent cutter discs 13. The consequent shreds and shavings drop through bottom openings 19 of the housing 7 into a waste paper basket standing therebeneath.

The cutter discs 13 are made as sheet metal stampings and lie against one another in pairs with their sides having the restriction radii 21 produced by the stamping operation.

The circumferential edge of their "burr sides" forms a sharp cutting edge in the overlapping region of the two cutter cylinders. In this connection the term "burr side" is used only for the distinction of the stamping side. The cutter discs 13 are produced by precision stamping and are substantially free from burr without finishing work.

On the circumference of each of the cutter discs 13 there are formed several axially through-extending recesses or grooves 23 distributed in the circumferential direction. The grooves 23 are symmetrical in relation to the radial direction and widen by oblique groove walls towards the groove bottom. Thus the cutter discs 13 can be operated equally in both directions of rotation.

As Fig. 3 shows, the distance washers are of substantially lozenge form and protrude, as may be seen from Fig. 2, with three of their lozenge sides beyond the cutter discs 13, excepting the region of overlap of the cutter cylinders 3. The fourth lozenge side 25 forms a continuation of the housing entry slot 17 in the region of engagement of the cutter cylinders 3. To secure the distance washers 11 against rotation, guide rods 27 are secured to the side walls 5 with axes parallel to those of the shafts 9. The guide rods 27 pass through openings 29 of the distance washers 11, without hindering the displaceability of the distance washers 11. The lozenge corners of the distance washers 11 facing the entry slot 17 are provided with an entry facette 31 facilitating the introduction of the material to be com- minuted. Due to the fact that the distance washers 11 protrude beyond the cutter discs 13 of the cutter cylinders 3 except for their region of engagement, the distance washers 11 form a hand guard for the cutting mechanism.

The cutter discs 13 are connected fast in rotation with their respective shafts 9 by way of a flattened portion 33, with the flattened portion 33 winding in helical form about the shaft 9. This has the effect that the grooves 23 of axially adjacent cutter discs 13 are likewise staggered in helical form, so that the cutting effect is staggered along the whole cutting width and the drive of the cutting mechanism is uniformly loaded.

Claims

1. Apparatus for comminuting material in sheet form into shreds or shavings, having two axially parallel cutter cylinders (3) driven in rotation in opposite directions, each of which comprises a shaft (9) and a plurality of cutter discs (13) resting in pairs against one another and pushed on to the shaft (9), where the pairs (13) of cutter discs of each cutter cylinder (3) are held axially spaced from one another by distance washers (11) pushed on to the shaft (9) and engage between cutter disc pairs (13) of the other cutter cylinder (3) in each case, characterised in that the cutter disc pairs (13) consist of two like sheet metal stampings which lie against one another with their sides provided with stamping restriction radii (21) on the circumference due to the stamping working.

2. Apparatus according to Claim 1, characterised in that the cutter disc pairs (13) and the distance washers (11) are guided loosely displaceably on the shaft (9) with axial play, between two abutments (15).

3. Apparatus according to Claim 1 or 2, characterised in that the axial thickness of the distance washers (11) is less than the axial thickness of the cutter disc pairs (13).

4. Apparatus according to one of Claims 1 to 3, characterised in that the distance washers (11) protrude essentially as hand guard radially beyond the cutter discs (13), except for the region of mutual engagement of the cutter cylinders (3), and form a material guide slot in the region of engagement.

5. Apparatus according to Claim 4, characterised in that the distance washers (11) are of approximately lozenge form and for securing against rotation are guided on a rod (27) parallel to the shaft and passing through the distance washers (11) in the region of one lozenge corner, as well as on the shaft (9).

6. Apparatus according to Claim 5, characterised in that the lozenge corners of the distance washers (11) which form the intake end of the material guide slot possess an entry facette (31).

7. Apparatus according to one of Claims 1 to 6, characterised in that the washers (11) consist of synthetic plastics material.

8. Apparatus according to one of Claims 1 to 7, characterised in that the cutter discs (13) have on their circumference a plurality of axial grooves (23) symmetrical in relation to the radial direction and widening towards the groove bottom.

9. Apparatus for comminuting material in sheet form as claimed in claim 1, substantially as described herein with reference to and as illustrated by the example shown in the accompanying drawing.