GB2242152A

GB2242152A - Preparation of box blanks of corrugated board

Info

Publication number: GB2242152A
Application number: GB9102474A
Authority: GB
Inventors: Colin Stutt; Paul Ronald Wiese
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1990-02-05
Filing date: 1991-02-05
Publication date: 1991-09-25
Anticipated expiration: 2011-02-05
Also published as: GB9102474D0; GB9002518D0; GB2242152B

Abstract

In preparing box blanks 10 of corrugated board, at least one edge portion which is to overlap with and adhere to the opposite edge is thinned by first acting on it with at least two narrow cutters arranged to produce respectively a groove delineating the inner boundary of the thinned area and a groove at the actual edge of the blank or inwardly spaced from the edge. Further removal of material is achieved by at least one milling cutter 20, 21 while guide members 17-19 extend into the grooves to hold the edge portion of the blank against or close to a guide surface 18. The speed of the blank is preferably reduced while the trailing portion of the blank is being acted upon by the cutters. <IMAGE>

Description

Box Manufacture from Corrugated Board This invention is concerned with improvements over our earlier patent application GB 2196286. That earlier application describes a number of ways of reducing the thickness of overlapping edge portions of a box blank to avoid the common situation in which the overlapping creates a locally thickened portion where the edges of the blank are overlapped so as to be glued together to form a flat-folded box.

This invention is in particular an improvement over the apparatus described with reference to the Figures 4 to 7 of our earlier application whereby each edge portion of the blank is thinned by a milling cutter 48, after the inner boundary of the thinned area has been delineated by a narrow milling cutter 44.

According to one aspect of the present invention, at least one edge portion of a corrugated board blank is thinned (reduced in thickness) by first acting on it with at least two narrow cutters arranged to produce respectively a groove delineating the inner boundary of the thinned area and a groove at the actual edge of the blank or inwardly spaced from the edge; and further removal of material is achieved by at least one milling cutter while guide members extend into the grooves to hold the edge portion of the blank against or close to a guide surface. Preferably, as described in our earlier application, suction is applied through apertures In the guide surface to assist in holding the edge portion of the blank against that surface while removal of material by milling is taking place.

In a preferred construction there are three narrow milling cutters arranged to produce initial grooves in the board respectively at the inner boundary of the area to be thinned, at the edge of the area to be thinned and at an intermediate position. Removal of the material lying between the grooves is achieved by means of two milling cutters while three guide plates or other guide members extend into all three grooves, engaging the bottoms of the grooves, to hold the edge portion of the blank against the guide surface.

A simplified alternative to this preferred construction could involve elimination of the central thin milling cutting. In this case, two guide plates would be used and the intermediate material could be removed by a single wide milling cutter.

We have found that operation of the wide milling cutters at the speed necessary to mill away the paper material in an appropriate manner tends to produce air currents which can tend to cause the edge portion of the blank to lift from the guide surface against the resistance of the holding suction; this occurs particularly if, as is preferred, the cutting teeth on the milling cutters are slightly helical, i.e. inclined to the cutter axis.

In order to counter this effect, one or more air jets may be directed onto the edge portion of the blank to assist in urging the edge portion onto the guide surface.

According to a second aspect of this invention, the means for moving each corrugated board blank past the milling cutter or cutters is arranged to reduce the speed of the blank while the trailing portion of the blank is being acted upon by the cutter or cutters. The purpose of this feature is to reduce the tendency for the trailing portion of the blank to be torn, which tendency can arise if the blank moves at a uniform speed past the cutters. It should be noted that this aspect of the invention is applicable to the apparatus described in Figures 4 to 7 of our above-mentioned earlier application, whether or not the feature according to the first aspect of the present invention is incorporated.

An example of the relevant part of a machine according to this invention is shown in the accompanying diagrammatic drawings. In these drawings, which are cross-sections at successive positions spaced in the direction of movement of the blanks: Figure 1 shows one edge portion of the box blank being machined by three narrow milling cutters; Figure 2 shows the entry of guide plates into the grooves formed by the narrow cutters; Figure 3 shows the milling of the material between the three grooves; and Figure 4 is a section on the line IV-IV in Figure 3.

In Figure 1 a blank 10 is shown having its edge portion 11 operated on by three narrow milling cutters 12, 13 and 14 while the blank is being supported by a guide surface 15 of a member 16. Each of the milling cutters 12 is mounted on a common drive shaft (not shown).

Figure 2 is a cross-sectional view at a location downstream of Figure 1 at which three finger-like plates 17, 18 and 19 are shown entering the grooves formed by the milling cutters 12 to 14 so as to engage the bottoms of the grooves. These plates extend in the direction of the movement of the blank so as to hold the edge portion of the blank against the guide surface 15 while two wider milling cutters 20 and 21 (Figure 3) remove the material lying between the three grooves. The milling cutters 20 and 21 are mounted on a common drive shaft (not shown).

It will be appreciated that a similar set of milling cutters may be arranged to act upon the opposite edge of the blank from below, as described in our earlier application.

Figure 4 shows a milling cutter 20 about to remove material from the trailing portion 10A of the edge portion of the blank 10, movement of the blank being from left to right as shown. In view of the absence of further material behind the portion 10A, movement of the blank 10 at full speed (i.e. at a speed appropriate for most of the milling operation) tends to tear off the portion 10A. This tendency is compensated, in accordance wlth this invention, by temporarily reducing the speed with which each blank 10 is moved past the cutter 20 at this point, and indeed until the blank has entirely passed the cutter 20.

The speed of rotation of the cutter 20 may remain constant or may alternatively be temporarily altered while the trailing portion 10A is being milled away. For example, the speed of the cutter may be increased so as to further increase the number of cuts per unit length of the blank as the trailing portion 10A is being milled by the cutter, the speed being returned to normal by the time the next blank 22 arrives at the milling cutter.

Claims

1. A method of preparing box blanks of corrugated board, in which at least one edge portion which is to overlap with and adhere to the opposite edge is thinned by first acting on it with at least two narrow cutters arranged to produce respectively a groove delineating the inner boundary of the thinned area and a groove at the actual edge of the blank or inwardly spaced from the edge; and further removal of material is achieved by at least one milling cutter while guide members extend into the grooves to hold the edge portion of the blank against or close to a guide surface.

2. A method according to claim 1 in which suction is applied through apertures in the guide surface to assist in holding the edge portion of the blank against that surface while removal of material by milling is taking place.

3. A method according to claim 1 or claim 2 in which the narrow cutters are arranged to produce initial grooves in the board respectively at the inner boundary of the area to be thinned, at the edge of the area to be thinned and at an intermediate position, removal of the material lying between the grooves being achieved by means of two milling cutters while three guide plates or other guide members extend into all three grooves, engaging the bottoms of the grooves, to hold the edge portion of the blank against or close to the guide surface.

4. Apparatus for carrying out the method according to claim 1, comprising means for conveying successive box blanks along a guide surface, a number of cutters arranged to produce a number of narrow grooves in an edge portion of each blank, a number of guides positioned so as to extend into the grooves to hold the edge portion of the blank against or close to the guide surface while at least one milling cutter is arranged to mill away the material of the blank lying between the grooves as the blank moves along the guide surface.

5. Apparatus for preparing box blanks of corrugated board by milling away part of the thickness of an edge portion of each blank, in which the means for moving each corrugated board blank past the milling cutter or cutters is arranged to reduce the speed of the blank while the trailing portion of the blank is being acted upon by the cutter or cutters.

6. A method according to claim 1 and substantially as described with reference to the accompanying drawings.

7. Apparatus according to claim 4 or claim 5 and substantially as described with reference to the accompanying drawings.