GB2398542A

GB2398542A - Creasing device

Info

Publication number: GB2398542A
Application number: GB0303775A
Authority: GB
Inventors: Graham Harris
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-02-19
Filing date: 2003-02-19
Publication date: 2004-08-25
Also published as: WO2004073966A1; GB0303775D0; AU2003295146A1

Abstract

The invention provides a device for creasing paper between a first drum 10 mounted for rotation on a first shaft 2 and a second drum 30 mounted for rotation on a second, parallel shaft 4. A creasing ring, which may be a resilient ring, projecting from an outer surface of the first drum 10 is received in a groove 26 extending around a circumference of the second drum 30. The first drum 10 is fixedly mounted on the first shaft 2 so that it must rotate with the first shaft 2 but the second drum 30 is freely mounted on the second shaft 4 so that it may rotate independently of the second shaft 4. Preferably, the second drum 30 is also free to move axially along the second shaft 4. The freely moving second drum 30 reduces tearing of the leading edge of the paper and facilitates the setting up of the device.

Description

TITLE

Creasing device

DESCRIPTION

s Technical Field

This invention relates to a creasing device for creasing paper or card before it is folded.

In the remainder of this specification, the term "paper" is used to denote the stock creased by the creasing device, whether it is paper or card.

Background

A high percentage of printed stock such as book covers or greetings cards needs to be creased before the next operation of folding can be carried out.

A known device for creasing paper is described in patent application WO 00/55080. The device consists of a first drum clamped on a first rotary shaft, the first drum having at least one groove for holding a resilient ring that protrudes from the groove. A second drum is clamped on a second, parallel rotary shaft and has at least one groove that is slightly wider and deeper than the corresponding groove of the first drum. When the resilient ring protruding from the first drum is aligned with the groove of the second drum, a sheet of paper fed between them will be creased by the pressure of the resilient ring forcing the paper into the groove of the second drum.

H097002 - 2 - The first and second parallel shafts may conveniently be the top and bottom shafts of a conventional folding machine. In the prior art, the first and second drums are clamped to the respective shafts for rotation with the shafts. The clamping is achieved either by a grub screw extending radially through the drum to grip the shaft or by securing the drum between a pair of bosses that are fixed to the shaft. The device needs to be set up with care in order to ensure that the drums are clamped to the shafts with their respective grooves perfectly aligned.

One problem found with the known creasing device is that the rotating resilient ring can sometimes tear the leading edge of the paper as the paper is fed between the drums. The problem occurs more often if the drums have a relatively small diameter and the paper is relatively thin.

Summarv of the invention The invention provides a device for creasing paper, comprising a first drum mounted for rotation on a first shaft; a second drum mounted for rotation on a second shaft that is parallel to the first shaft; a creasing ring extending around a circumference of the first drum and projecting from an outer surface of the first drum; and a receiving groove extending around a circumference of the second drum; wherein the first drum is fixedly mounted on the first shaft so that it must rotate with the first shaft; and wherein the second drum is freely mounted on the second shaft so that it may rotate independently of the second shaft.

H097002 - 3 - The inventor has found that by allowing the second drum, which has the receiving groove, to rotate freely on its shaft, the problem of tearing the leading edge of the paper is substantially reduced. This produces better results and makes possible the use of thinner paper

compared with the prior art. It also allows the

development of devices using smaller diameter drums.

Bearings may be provided between the second drum and the second shaft in order to facilitate the free rotation of the drum on the shaft.

Preferably! the second drum is free to move axially along the second shaft. It was expected that, as with the known creasing devices, the axial position of the second drum would have to be closely constrained in order to ensure alignment between the creasing ring of the first drum and the receiving groove of the second drum.

Without such constraint, and especially with a resilient creasing ring, it was expected that the drum would wander in the axial direction, resulting at least in an uneven crease and perhaps in complete misalignment between the ring and the groove. However, the inventor has made the surprising discovery that, if the second drum is free to move axially, the groove of the second drum tracks the creasing ring and aligns itself reliably with the ring to produce uniform creases.

Because the second drum is freely mounted both rotationally and axially on the second shaft, the setting H097002 - 4 up of the device is much simpler and careful alignment of the respective components is not necessary.

In a preferred embodiment, the creasing ring is a resilient ring. The resilient ring is preferably mounted in a circumferential groove around the outer surface of the first drum. However, other forms of creasing ring may be used, for example a resilient ring adhered to the surface of the first drum or a steel ring formed as an integral rib on the first drum or as a disc clamped between two halves of the first drum.

The drawings

Figure 1 illustrates a prior art creasing device,

partially in section.

Figure 2 illustrates a creasing device according to the invention, partially in section.

Figure 1 shows a first shaft 2 and a second shaft 4 that form part of a folding machine (not shown). The first shaft 2 rotates about a first axis 6 and the second shaft 4 rotates about a second axis 8, which is parallel to the first axis 6. The first and second shafts 2,4 rotate in opposite directions so as to draw a sheet of paper between them.

A first drum 10 is fixed to the first shaft 2 so as to rotate with the shaft. The first drum 10 has a series of grooves 12 around its circumference. Resilient rings (not shown) may be seated in the grooves 12 so as to project from the cylindrical outer surface 14 of the first drum 10 and form creasing rings. The grooves 12 H097002 differ in width so as to accommodate creasing rings of different widths. The grooves 12 also differ in depth in order that a single creasing ring may project from the surface 14 of the drum by differing amounts, depending on the groove 14 in which it is placed. The first drum 10 also comprises two circumferential channels 16, in which the resilient creasing rings can be stored when they are not in use.

In this known creasing device, a second drum 20 is fixed to the second shaft 4 so as to rotate with the shaft.

The second drum 20 comprises a radial threaded bore 22, into which a grub screw (not shown) is screwed to secure the second drum 20 to the second shaft 4 such that it is not free to move axially relative to the shaft 4 or to rotate relative to the shaft 4.

The second drum 20 has a series of grooves 24 around its circumference, the axial positions of which correspond to the axial positions of the grooves 12 in the first drum 10. Each groove 24 in the second drum 20 is slightly wider than the corresponding groove 12 in the first drum 10. The grooves 24 in the second drum 20 may all be of the same depth. 2s

The first and second drums 10,20 must be carefully positioned and secured on their respective shafts 2,4 to ensure that they are axially aligned. When the drums 10,20 are aligned and are counter-rotating on their respective shafts 2,4, the outer surface 14 of the first drum 10 and the outer surface 26 of the second drum 20 are close together and moving in parallel so they can H097002 6 - draw a sheet of paper (not shown) between them. A creasing ring located in one of the grooves 12 of the first drum 10 exerts pressure on the paper and the corresponding groove 24 in the second drum 20 allows the paper to deform, whereby the paper is creased along a line parallel to its direction of movement. It is found that as the paper is fed into the device, the leading edge of the paper tends to become torn where it first contacts the creasing ring.

Figure 2 is a view similar to Figure 1, showing a creasing device according to the present invention.

Corresponding parts are given the same reference numerals

as in Figure 1 and their description will not be

repeated. The device in Figure 2 differs from that in Figure 1 in relation to the means for mounting the second drum on the second shaft.

In Figure 2, the second drum 30 is mounted on the second shaft 4 but not secured to it. Thus there is no radial bore in the second drum 30. Instead, the axial bore 32 of the second drum 30 is enlarged at each end to accommodate a pair of bearings 34. The bearings allow the second drum 30 to slide axially and to rotate freely with respect to the second shaft 4.

During the paper creasing operation, only the rotation of the first drum 10 is driven by rotation of the first shaft 2. The second drum 30 may or may not rotate about the second shaft 4. When a sheet of paper is fed into the device, it will be drawn through the device by frictional contact between its upper surface and the H097002 - 7 - rotating surface 14 of the first drum 10. The second drum 30 may be caused to rotate by frictional contact between the lower surface of the paper and the surface 26 of the second drum 30.

It is found that with this arrangement, there is a much smaller tendency for the leading edge of the paper to be torn by the creasing ring. That may be because the movement of the paper controls the rotation of the second drum instead of the rotation of the second drum driving the movement of the paper. It is also found that, although the second drum 30 is free to wander along the second shaft 4, it does not do so but the groove 26 of the second drum 30 reliably aligns itself with the IS creasing ring on the first drum 10. Thus set-up and adjustment of the device is greatly facilitated.

H097002 - 8 -

Claims

l. A device for creasing paper/ comprising: a first drum mounted for rotation on a first shaft) a second drum mounted for rotation on a second shaft s that is parallel to the first shaft; a creasing ring extending around a circumference of the first drum and projecting from an outer surface of the first drum; and a receiving groove extending around a circumference of the second drum; wherein the first drum is fixedly mounted on the first shaft so that it must rotate with the first shaft; and.

wherein the second drum is freely mounted on the second shaft so that it may rotate independently of the second shaft.
2. A device according to claim l, wherein bearings are provided between the second drum and the second shaft.
3. A device according to claim l or claim 2, wherein the second drum is free to move axially along the second shaft.
4. A device according to any preceding claim, wherein the creasing ring is a resilient ring.
5. A device according to claim 4, wherein the resilient creasing ring is mounted in a circumferential groove around the outer surface of the first drum.

H097002 - 9
6. A device according to any preceding claim, wherein the width of the receiving groove is greater than the width of the creasing ring.
7. A device substantially as described herein, with reference to the drawings.

H097002