GB2451232A

GB2451232A - Creasing ring

Info

Publication number: GB2451232A
Application number: GB0714297A
Authority: GB
Inventors: Graham Harris; Paul Graham Barrett
Original assignee: Tech ni Fold Ltd
Current assignee: Tech ni Fold Ltd
Priority date: 2007-07-21
Filing date: 2007-07-21
Publication date: 2009-01-28
Anticipated expiration: 2027-07-21
Also published as: GB2451232B; GB0714297D0

Abstract

A resilient creasing ring 8 for location in a channel (6, Figure 2) in the rotary drum 2 of a creasing device is split to form mutually abutting ends 30, whereby the ring 8 can be installed in the channel (6) without removal of the drum 2 from the shaft 4 on which it is mounted. Each of the ends 30 comprises a projecting lug 32 for engagement with at least one recess 34 in the channel (6) to hold the ends in abutment despite possible shrinkage of the ring 8. The ring 8 may be moulded as a continuous ring with a single precursor lug, through which a cut is then made to form the two ends 30 and two lugs 32. The recess is preferably formed by a continuation of an axially extending keyway (19, Figure 1) for a grub screw (17) used to secure a part of the drum. The creasing ring is used in apparatus for creasing paper, card, film, foil or other sheet material.

Description

TITLE

Creasing rings

DESCRIPTION

Technical Field

This invention relates to devices for creasing stock such as paper, card, film, foil or other sheet material to enable it to be easily folded. Such devices are especially well suited for fitting to the output of printing machines or the input of folding machines but can also be used in a stand-alone creasing machines or in other contexts. In particular, the invention relates to the manner in which resilient creasing rings are mounted on rotary drums for use in such devices.

Background

A known device for creasing paper or other stock is described in international patent application WO 2007/023258. The device consists of a first drum mounted on a first rotary shaft, the first drum having at least one channel for holding a resilient ring that protrudes from the channel. A second drum is mounted on a second, parallel rotary shaft and has at least one groove of appropriate width at a corresponding axial position. When the resilient ring protruding from the first drum is aligned with the groove of the second drum, a sheet of the paper fed between the two rotating drums will be creased by the pressure of the resilient ring deforming the paper into the groove of the second drum. Preferably, the resilient ring is moulded to have a body of sufficient thickness (as measured in the axial direction) to provide strength, with a narrower creasing rib projecting radially outwards therefrom. The groove of the second drum should be slightly wider than the projecting or protruding part of the creasing ring.

As also seen in WO 2007/023258, the resilient creasing ring may be split at a point around its circumference so that the two ends of the split ring are in abutment with one another. This allows the ring to be deformed and opened up at the split, in order to install the ring on the drum or to remove it, without the time-consuming task of removing the drum from the rotary shaft on which it is mounted. Because the ring is split, it can no longer be held in the channel by its own tension. Instead, the ring is formed with a cross section that engages with a corresponding channel cross section in such a way that the ring cannot be withdrawn radially from the channel. In particular, the ring may be formed with at least one laterally (i.e. axially) extending securing rib around its circumference, which engages with a corresponding undercut in the sidewall of the channel to secure the ring in the channel.

One problem with the prior art device is that the creasing ring is formed from rubber, which is liable to shrink during manufacture or use. The amount of shrinkage during curing of the rubber is typically around 5 or 6% and allowance is made for this in the size of the mould. However, the amount is variable and subsequent shrinkage can also occur, depending on the conditions of curing, cutting and using the ring. The effect is that the ring may not reach fully around the circumference of the channel and a gap opens up between the ends that should be in abutment. In turn, this can lead to an unacceptable gap in the crease that is fonned by the device.

Summary of the invention

The invention provides a resilient creasing ring, a drum for a creasing device on which a resilient creasing ring is mounted, and a method of making a resilient creasing ring; as defined in the respective independent claims. Preferred features of the invention are defined in the dependent claims.

By forming the ends of the split ring to have projecting lugs, which can engage in a recess of the creasing drum, the ends of the ring can be held in abutment even in the event of shrinkage of the resilient creasing ring.

For the avoidance of doubt, when this specification refers to the ends of the split ring being in abutment, it is not essential that they should be physically touching but that term is intended to include the practical case where the ends are in sufficiently close proximity to avoid an undesirable gap in the crease that is formed by the creasing ring.

The drawings Figure 1 illustrates a creasing device that incorporates a creasing ring and a drum according to the invention, the upper half being shown in longitudinal section as indicated by line A-A in Figure 3.

Figure 2 is a part of Figure 1, omitting the creasing ring to show details of the drum.

Figure 3 illustrates the creasing device of Figure 1 in cross section as indicated by line B-B in Figure!.

Figure 1 shows a drum 2 rotatably mounted on a shaft 4 which forms part of a creasing device. The drum 2 defmes a channel 6 in which is received a resilient creasing ring 8 such that a creasing rib 10 of the ring 8 projects above a cylindrical outer surface 12 of the drum 2. In use, the illustrated drum 2 is placed adjacent to another, female drum (not shown) mounted on a second, parallel shaft (not shown), as is well known from the prior art. The female drum has at least one circumferential groove around its cylindrical outer surface, which receives the creasing rib 10. As the male drum 2 of this invention rotates and the female drum counter-rotates, a sheet of paper, card or other stock fed between the creasing rib 10 of the male drum and the circumferential groove of the female drum is deformed and creased. Because the creasing ring 8 is made from a resilient material such as rubber, it avoids damage to the surface coating of the paper that would otherwise lead to cracking of the coating when the paper is folded along the crease.

The drum 2 comprises a first drum part 14 and a second drum part 15. The first drum part 14 is annular in shape with a central bore that fits closely around the shaft 4. A first grub screw 16 can be tightened to clamp the first drum part 14 to the shaft 4 or loosened to allow the first drum part 14 to slide along the shaft 4. In this embodiment the first drum part 14 extends over the whole axial length of the drum 2; and the second drum part 15 does not contact the shaft but takes the form of a collar sliding solely on an outwardly facing, cylindrical guide surface 22 of the first drum part 14.

A second grub screw 17 can be tightened to clamp the second drum part 15 to the first drum part 14 or loosened to allow the second drum part 15 to slide on the guide surface 22 of the first drum part 14. Preferably the second grub screw 17 acts in a keyway 19 formed as an axial channel in the guide surface 22 of the first drum part 14. The keyway 19 stops short of the end of the drum 2 so that when second grub screw 17 is only slightly loosened the movement of the second drum part 15 is constrained by the engagement between the second grub screw 17 and the walls of the keyway 19. Thus the second drum part 15 can slide axially along the guide surface 22 of the first drum part 14 until the grub screw 17 reaches the end of the keyway 19, which prevents the second drum part 15 from becoming detached from the first drum part 14 without unscrewing the second grub screw 17 further.

It is known in the prior art for each of the first and second drum parts 14,15 to slide directly on the shaft 4 and the present invention would be equally applicable to such an arrangement (not illustrated).

In an alternative embodiment of the invention (not illustrated), instead of the second drum part 15 sliding axially on the first drum part 14, the two drum parts 14,15 may be threaded together so that the desired axial movement between them is a component of relative helical movement along the screw thread.

As seen best in Figure 2, the channel 6 for retaining the creasing ring 8 is located in the outer surface 12 of the drum 2 at the junction between the two drum parts 14,15.

The first drum part 14 defines the base 18 and a first side wall 20 of the channel 6, while the second drum part defines a second side wall 21 of the channel 6. The base 18 of the channel is formed by part of the guide surface 22 of the first drum part 14, except at the location of the recess described below.

The channel 6 has a generally rectangular cross section but each side wall 20,21 has an undercut 26, whereby the channel 6 is wider at its base 18 than at its mouth. The resilient creasing ring 8 has a corresponding cross section (seen in Figure 1), with a body of generally rectangular cross section having lateral ribs 27 extending into the undercuts 26 of the side walls 20,21 of the channel 6. The engagement between the -5.-lateral ribs 27 of the creasing ring 8 and the undercuts 26 of the channel 6 prevents the ring 8 being withdrawn radially from the channel 6. The undercuts do not have to have the triangular shape shown; nor do they need to be formed at the base of the channel: other forms of circumferentially extending recess in one or both sidewalls 20,21 of the channel can serve the same purpose.

As seen in Figure 1, the creasing ring 8 is split at a point around its circumference to form two adjacent ends 30. The ends 30 are in abutment or are sufficiently close to one another that the creasing rib 10 is substantially continuous across the junction. To hold the ends 30 in that arrangement, despite possible tension around the creasing ring 8 caused by shrinkage, each of the ends is provided with a projecting lug 32, which engages with a recess 34 in the drum 2 to anchor the respective end 30 of the creasing ring 8 in position. Preferably, as shown in the drawings, each lug 32 projects radially inwards from the ring 8 to engage in a recess 34 formed in the base 18 of the channel 6. However, the lugs 32 could be made to project laterally from the ring 8 to engage recesses in one or both sidewalls 20,21 of the channel. In either case, the recess 34 must be of limited circumferential extent to maintain the well-defined circumferential position of each lug 32 and hence the relative position of the ends 30 of the ring 8.

Preferably, as shown, the two lugs 32 both engage in a single recess 34 but it would be possible for the lugs 32 to engage in separate recesses, formed adjacent to the respective ends 30 of the ring 8.

In the preferred embodiment of the invention shown in the drawings, the recess 34 is formed by a continuation of the keyway 19 that intersects the base 18 of the channel 6. However, the recess 34 could be formed as a discrete pit in the base 18 of the channel 6.

The creasing device shown in the drawings is assembled in the following manner.

The first drum parts 14 is mounted on the shaft 4 and the second drum part 15 is mounted on the guide surface 22 of the first drum part 14. The first grub screw 16 is tightened to lock the first drum part 14 in the correct axial position for a creasing ring 8 located in the channel 6 to form a crease at the desired point. The second grub screw 17 is tightened sufficiently to locate in the keyway 19 but not so fully that it prevents movement of the second drum part 15. The second drum part 15 is retracted so that the second channel wall 21 moves apart from the first channel wall 20, opening up the channel 6 for insertion of a resilient creasing ring 8, A resilient creasing ring 8 is installed on the device by deforining the ring 8 to separate its ends 30, which are passed around opposite sides of the shaft 4. The base of the ring 8 is then wrapped around the base 18 of the channel 6 in the circumferential position that allows the respective projecting lugs 32 to engage in the recess 34 and anchor the ends 30 in abutment with one another. The ring 8 should be slid axially until it engages the first side wall 20 of the channel 6 with a first lateral rib 27 located in the undercut 26 of the first wall 20. Next, the second drum part 15 is slid axially along the guide surface 22 of the first drum part 14 until the second channel wall 21 formed by the second drum part 15 engages the ring 8, at which point the second lateral rib 27 of the creasing ring 8 is located in the undercut 26 of the second side wall 21 of the channel 6. The second grub screw 17 is then tightened to lock the second drum part 15 in position and prevent radial withdrawal of the creasing ring 8 from the channel 6. The sequence may be reversed to remove a creasing ring 8 for replacement or to change the configuration of the device, noting that this can be achieved without removal of either drum part from the shaft.

The split creasing ring 8 can be formed by moulding the ring 8 with the split in place but it is preferred to mould a continuous ring, including a single precursor lug projecting inwardly therefrom. A single cut is then made through the ring and the precursor lug to form the two ends 30 and the two respective lugs 32. If the two lugs 32 are to be anchored in a single recess 34, then provided the precursor lug matches the shape of the recess 34 the position of the cut is not critical because when the two lugs 32 are brought together they effectively re-form the shape of the precursor lug.

Claims

1. A resilient creasing ring that is split to form mutually abutting ends, wherein each of the ends comprises a projecting lug for engagement with at least one recess of a creasing drum to hold the ends in abutment.

2. A creasing ring according to claim 1, wherein each of the lugs projects radially inwards from the ring.

3. A creasing ring according to claim 1 or claim 2, further comprising a securing rib that projects laterally from the ring around its circumference for engagement with an undercut in a sidewall of a channel of the creasing drum to hold the ring in the channel.

4. A creasing ring according to any preceding claim, further comprising a creasing rib that projects radially outwards from the ring around its circumference.

5. A drum for a creasing device, the drum comprising a circumferential channel and at least one recess formed at a location on the circumference of the channel for receiving Jugs that project from the ends of a split creasing ring.

6. A drum according to claim 5, comprising a single recess for receiving a pair of Jugs that project from respective ends of the split creasing ring.

7. A drum according to claim 6, wherein the recess extends radially inwards from the channel.

8. A drum according to claim 7, wherein the recess is a pit formed in a base of the channel.

9. A drum according to claim 7, wherein the recess is an axially extending channel that intersects a base of the circumferential channel.

10. A drum according to any of claims 5 to 9, further comprising an undercut that extends circumferentially around at least one sidewall of the channel for receiving a securing rib that projects laterally from the creasing ring, the channel being formed between two drum parts that can be moved axially apart to widen the channel for insertion or removal of a creasing ring.

II. A method of making a resilient creasing ring, comprising the steps of: moulding a continuous ring with a projecting precursor lug; and making a cut through the ring and the precursor lug to form mutually abutting ends, each of the ends comprising a projecting lug formed from part of the precursor lug.

12. A resilient creasing ring substantially as described herein with reference to Figures 1 and 3.

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13. A drum for a creasing device substantially as described herein with reference :::::: 20 to the drawings. * ** * .** S..

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13. A drum for a creasing device substantially as described herein with reference to the drawings.

Amendments to the claims have been filed as follows

1. A resilient creasing ring for mounting in a channel of a creasing drum such that it cannot be withdrawn radially from the channel, the ring being split to form mutually abutting ends, wherein each of the ends comprises a projecting lug for engagement with at least one recess of the creasing drum to hold the ends in abutment.

3. A creasing ring according to claim 1 or claim 2, further comprising a securing rib that projects laterally from the ring around its circumference for engagement with an undercut in a sidewall of the channel of the creasing drum to prevent the ring being withdrawn radially from the channel.

5. A drum for a creasing device, the drum comprising a circumferential channel :.:: 20 and at least one recess formed at a location on the circumference of the channel for receiving lugs that project from the ends of a split creasing ring. * . * ***

6. A drum according to claim 5, comprising a single recess for receiving a pair of lugs that project from respective ends of the split creasing ring.

* S S*S * * 25 *:* 7. A drum according to claim 6, wherein the recess extends radially inwards from the channel.

io 11. A method of making a resilient creasing ring, comprising the steps of: moulding a continuous ring with a projecting precursor lug; and making a cut through the ring and the precursor lug to form mutually abutting ends, each of the ends comprising a projecting lug formed from part of the precursor lug.