GB2412113A

GB2412113A - Perforator

Info

Publication number: GB2412113A
Application number: GB0406018A
Authority: GB
Inventors: Richard John Truscott
Original assignee: PFE International Ltd
Current assignee: PFE International Ltd
Priority date: 2004-03-17
Filing date: 2004-03-17
Publication date: 2005-09-21
Anticipated expiration: 2024-03-17
Also published as: GB0406018D0; GB2412113B

Abstract

A perforator for perforating a continuous web includes a perforating roller 2 having a blade 3 on its surface, an anvil roller 2 cooperating with the perforating roller and means for moving one roller away from the other, said means preferably including a cam 7 on one roller and a cam member 21 movable into engagement with the cam, the cam being asymmetric with respect to the axis 9 of the roller and having two sections and the cam member moving tangentially to the roller. The cam may be mounted at each end of the perforating roller (7, 8 figure 1) and the cam member may be a roller mounted on a translationally movable control member 30. The control member may be driven by motor 20 to run on support wheels 22 and 23 engaging with guide track 31. A sensor may be provided to read control marks on the web, which may in turn control movement of the translationally movable member. The rollers may be driven by gear wheels (4, 5 figure 1).

Description

241211 3 Perforator

Description

5The present invention relates to a perforator for a continuous web.

A continuous web may typically comprise paper formed onto a large roll. The web is perforated to form individual sheets of paper, for example for printing and publications such as newspapers and continuous form or listing paper for computer printers.

Traditionally such perforation is accomplished by unwinding the web and passing it between rotating rollers one of which has a blade mounted on its surface. A perforating force is applied to urge the rollers together and the perforation is effected at intervals corresponding to the circumference of the roller with the blade. Of course more than one blade may be mounted on the roller to effect more than one perforation in each rotation of the roller. The perforating force can result from the gravitational force on the upper roller, but additional force may also be used either continuously or intermittently.

The perforating force is generally a high force to ensure a clean perforation. A problem arises in disengaging the perforator, i.e. separating the rollers at times when perforating is not required, because a relatively large amount of energy is necessary to separate the rollers sufficiently to withdraw the blade from the line of the web. Perforation may need to be suspended, for example, if a double length sheet of paper is required, or for feeding a new web.

According to the present invention there is provided a perforator for a continuous web, comprising a perforating roller having a perforating blade mounted on its surface, an anvil roller arranged to selectively cooperate with the blade to perforate the web, and means for selectively moving one roller away from the other roller, the separating means comprising a first cam member movable tangentially to the two rollers, and a cooperating second cam member mounted on the side of one of the rollers, wherein one of the cam members is asymmetrical with respect to the axis of rotation of said one roller.

Preferably the first cam member comprises a cam follower and the second cam member comprises a cam surface which traces a path which has a first section which is a first distance from the axis in a segment which includes the blade, and has a second section which is a second, smaller, distance from the axis in a segment which does not include the blade. Thus the cam surface is closer to the axis of the roller in a region which is generally angularly spaced from the blade and is further from the axis of the roller in a region generally angularly aligned with the blade.

According to a preferred embodiment sensors may be used to detect control marks on the web to control the operation of the roller separating means to control the size of paper which is cut.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawings, in which: Figure 1 is a cross sectional view of a perforator according to the present invention through the axes of rotation of the rollers; Figures 2-5 are end views of the perforator of figure 1 showing an operating sequence.

In figure 1 a lower anvil roller 1 is shown adjacent an upper perforating roller 2. A perforating blade 3 is mounted on the surface of the upper perforating roller 2. The rollers 1 and 2 rotate under action of a driven gear 4 acting on the anvil roller 1 which is connected by gear wheels 5 to the perforating roller 2 to synchronize their rotation speeds. A paper web (not shown) passes through the nip 6 between the two rollers 1 and 2 and is perforated on every rotation of the roller 2 when the blade 3 passes through the nip 6.

The perforating roller 2 has a camming member 7 and 8 extending from each of its ends, each having a circumferential cam surface which is asymmetrically arranged about the axis of rotation 9 of the roller 2, such that the cam surfaces pass closer to the axis 9 in respective regions 10, 11, which are opposite, i.e. 180 angle of rotation, from the blade 3.

When it is desired to avoid perforation, the blade 3 must be lifted clear of the anvil roller 1. This is accomplished by a cam follower comprising a control roller 21 at each end of the arrangement. This will be described in more detail with respect to figures 2 to 5 in which a motor 20 is arranged to control the position of a mounting member 30 to which the control roller 21 is rotatably attached. The control roller 21 can thus be driven into and out of engagement with the cam surface 7. An identical arrangement is used at the opposite end of the rollers to engage the surface of camming member 8.

The control member 30 has a guide track 31 which rests on two pulley support wheels 22 and 23. It is driven by the motor 20 S in the direction of arrow 24; generally tangential to the cam surface 7 at a region 10 opposite to the blade 3. This region is sufficiently close to the axis 9 of the roller 2 to provide full clearance for the control roller 21 and very little or no force is needed to counter the gravitational and/or perforating forces 32 applied to the perforating roller 2.

As the perforating roller 2 turns, the cam surface 7 turns with it and the depressed region 10 rotates away from the control roller 21. The part of the cam surface 7 facing toward control roller 21 thus effectively moves further from the axis 9 as the perforating roller 2 turns, and the perforating roller thus rides up on the control roller 21 and moves up away from anvil roller 1. This can be seen in figure 3 in which the cam follower is fully engaged and there is a clearance gap between the blade 3 and the anvil roller 1 so that no perforation will be made.

In this manner less force is required to achieve the clearance gap and suspend perforation since the cam follower on control roller 21 is driven between the large rollers 1 and 2 only when the cam surfaces 7 and 8 are furthest from the respective outward facing surface of the large rollers 1, 2 providing full clearance for the control roller 21 to be inserted. The blade 3 is uppermost at this time.

Figure 4 and 5 illustrates the cam follower control roller 21 being withdrawn away from the rollers 1 and 2 in the direction of arrow 25. This is done when a perforation is required and the withdrawal is again effected when the blade 3 is uppermost on the perforating roller 2 so that the depressed region 10 of cam surface 7 is facing the control roller 21. At this point in the cycle the force on the control roller 21 is at a minimum and it requires a relatively small amount of energy to withdraw control roller 21 and thus the cam follower from engagement with the cam surface 7.

As the perforating roller 2 continues to rotate, the blade 3 turns and, as shown in figure 5, at the lowermost part of its path, engages with the anvil roller 1 to effect perforation of a web (not shown) in the nip between the rollers 1 and 2, since they are no longer held apart from each other by interaction of the control roller 21.

Control marks may be put on the paper web which are readable by sensors and used to control the motion of the control roller depending upon the size of a required sheet of paper to be cut. Thus control of web perforation is effected relatively easily and using a minimum of energy. l

Claims

Claims 1. A perforator for a continuous web, comprising a perforating

roller having a perforating blade mounted on its surface, an anvil roller arranged to cooperate selectively with the blade to perforate the web, and means for selectively moving one roller away from the other roller, the separating means comprising a first cam member movable tangentially to the two rollers, and a cooperating second cam member mounted on the side of one of the rollers, wherein one of the cam members is asymmetrical with respect to the axis of rotation of said one roller.
2. A perforator according to claim 1 wherein the first cam member comprises a cam follower and the second cam member comprises a cam surface.
3. A perforator according to claim 2 wherein the cam surface traces a path which has a first section located a first distance from the axis of rotation of the roller in a segment which includes the blade, and has a second section which is a second, smaller distance from the axis of rotation in a segment which does not include the blade.
4. A perforator according to claim 2 or 3 wherein the cam surface is mounted on the perforating roller.
5. A perforator according to claim 4 comprising a cam surface at each end of the perforating roller.
6. A perforator according to any one of the preceding claims wherein the first cam member comprises a control roller rotatably mounted to a translationally movable mounting member.
7. A perforator according to claim 6 comprising a sensor arranged to read control marks on the web and control means arranged to receive an output from the sensor to control the translational movement of the mounting member.
8. A perforator according to substantially as hereinbefore described with reference to figures 1 to 5 of the accompanying drawings.