GB2294004A

GB2294004A - Apparatus for cutting perforations into moving webs

Info

Publication number: GB2294004A
Application number: GB9519760A
Authority: GB
Inventors: Ulrich Eckelt
Original assignee: Windmoeller and Hoelscher KG
Current assignee: Windmoeller and Hoelscher KG
Priority date: 1994-10-13
Filing date: 1995-09-28
Publication date: 1996-04-17
Also published as: ITBZ950062A0; ES2130010A1; DE4436679A1; FR2725653A1; ITBZ950062A1; GB9519760D0; JPH08174494A; ES2130010B1; IT1282442B1; CA2160275A1

Description

1 2294004 APPARATUS FOR CUTTING PERFORATIONS IN MOVING WEBS The present

invention relates to an apparatus for cutting perforations in moving webs, having a perforating cutter drivable in rotation, and a grooved cylinder into whose peripheral grooves the perforating cutter parts penetrate.

Such an apparatus is known, for example, from DE-C-14 79 858. Such apparatuses are usually designed in such a way that the tips of the perforating cutter that provide the web with transverse perforations rotate at a peripheral speed which corresponds to the speed of the web running over the grooved cylinder. The web may, for example, consist of paper or a plastic material. This arrangement has the result that the speeds of (i) the web and of (ii) the tips of the transverse perforating cutter substantially coincide when the transverse perforating cutter comes into contact with the web at the start of the cutting of the transverse perforations. However, during the subsequent increasing penetration of the tips or points of the transverse perforating cutter into the grooves of the grooved cylinder, the effective radius of the perforating cutter becomes shortened relative to the contact zone of the perforating cutter with the web, so that the speed of the web becomes higher than that of the perforating cutter, and this may lead to ripping or incipient tearing of the 2 perforations cut into the web. Such an incipient tearing of the cut perforations is particularly undesirable and is harmful in the case of paper webs which are subjected to certain tensile stresses during their further processing, for example in machines for manufacturing sacks or bags. Such sack or bag machines may possibly be incapable of taking up the web if it has an incipient tear at the perforations, since such incipient tears are subject to the risk of further tearing which may result in the webs tearing off and thereby to malfunctions and downtimes during the manufacture of bags or sacks.

It is therefore an object of the invention to create an apparatus of the kind indicated at the outset which prevents any undesirable tearing of the perforations being cut into the webs.

In accordance with the invention, there is provided an apparatus for cutting perforations in a moving web, having a rotatably drivable perforating cutter and a grooved cylinder, into whose peripheral grooves the perforating cutter parts penetrate, wherein a support is rigidly connected to a cutter shaft, which support is provided with a pivotably mounted cutter bar disposed parallel to the cutter shaft and carrying the perforating cutter.

In the perforating apparatus according to the invention as - 3 soon as the tips or points of the perforating cutter perforating the web have come into contact with the web they penetrate during their further rotation into the grooves of the grooved cylinder, so that the radius of the perforating cutter is reduced at the point of contact with the web, the perforating cutter is entrained by the web in a leading or overrun mode for rotating the cutter shaft, so that a tearing of the cut perforations is reliably avoided. In this arrangement, the limited scope for the rotation of the perforating cutter relative to the support is of such a magnitude that it is possible to compensate for the speed differential between (i) the contact points of the perforating cutter with the web and (ii) the web.

To allow the perforating cutter to be brought into contact with the web at the start of the transverse perforation cut in a precisely defined way, in a preferred embodiment of the invention, provision is made for the cutter bar to be held, by a resilient element, against a stop of the support in such a way that, starting from the position into which it has penetrated in the web and which is defined by the stop, the perforating cutter can be entrained by the web in a leading or overrun mode by being swung out in order to rotate the support.

An embodiment of the invention will now be explained in greater detail below, with reference to the accompanying drawings, in which:- Fig. 1 is a side view showing the perforating apparatus, partly sectioned and in a schematic representation, in a state where the perforating cutter has just touched the web at the start of the perforating cut; and Fig. 2 is a representation, corresponding to Figure 1, wherein the points of the perforating cutter have penetrated into the grooves of the grooved cylinder.

is The perforating apparatus consists of a shaft 1 mounted in a machine frame, not shown, and provided with a drive, not shown, on which shaft there is mounted a radially projecting support 2. This support has, at its axially opposite ends, lateral parts 3 to which is secured a pin 4 on which a cutter bar 5 is pivotably mounted. For this mounting the pin 4 passes through a bore of the cutter bar 5. For the purpose of providing a low friction mounting, it is of course also possible to make provision for roller bearings.

The cutter bar 5 may instead be provided with journals which are mounted in appropriate bores of the lateral parts 3.

The cutter bar 5 and the perforating cutter 6 are bolted - 5 together in the usual manner, or they may be connected in some different way. On both sides of the cutter bar 5 the support 2 is connected to angle pieces 7, 8. The cutter bar 5 has a widened portion 9 wherein there are arranged blind bores 10 which extend in a direction substantially radially of the shaft 1. Compression springs 11 in these blind bores 10 bear at one end on the bottom of the blind bore 10 and at the other end on the inside of the bent arm of the angle piece 7. The compression springs 11 thus tend to hold the stop edge 12, formed by a step in the bar 5, against the outer side of the bent arm of the angle piece 7.

The web 13 to be perforated passes between the rotating perforating cutter 6 and the grooved cylinder 15, in the direction of the arrow head A. The grooved cylinder 15 is in the usual way provided with grooves 16 extending over its circumference.

It will be seen from the Figures that the enveloping circle 14 described by the tips of the perforating cutter intersects the passing web 13.

In Figure 1 there is designated the point B at which the points or tips of the perforating cutter 6 first touch the web 13 to be perforated. At this contact point B, the peripheral speed of the tips of the perforating cutter 6 is 6 equal to the speed of the web 13. When, during the further rotation of the perforating cutter 6, its points or tips penetrate into the grooves 16 with an increasing depth in the way shown in Figure 2, the web 13 entrains the perforating cutter in a leading or overrun mode relative to the rotation of the cutter shaft 1, so that the cutter bar 5 performs a small rotation in the clockwise direction relative to the support 2 as may be seen in Figure 2.

Claims

1. An apparatus for cutting perforations in a moving web, having a rotatably drivable perforating cutter and a grooved cylinder into whose peripheral grooves the perforating cutter parts penetrate, wherein a support is rigidly connected to a cutter shaft, which support is provided with a pivotably mounted cutter bar disposed parallel to the cutter shaft and carrying the perforating cutter.

2. An apparatus according to claim 1, wherein the cutter bar is held by a resilient element against a stop of the support, in such a way that, starting from its position is into which it has penetrated in the web and which is defined by the stop, the perforating cutter can be entrained by the web to swing in a leading or overrun mode relative to the rotation of the support.

3. An apparatus according to claim 1 or 2, wherein the cutter bar is pivotably mounted on a pin carried by the support.

4. An apparatus for cutting perforations in a moving web, constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.