GB1578568A

GB1578568A - Apparatus for perforating synthetic plastics film

Info

Publication number: GB1578568A
Application number: GB21555/79A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-16
Filing date: 1977-07-05
Publication date: 1980-11-05
Also published as: PT66818B; NZ184632A; AU512009B2; JPS5311974A; GR63747B; GB1578567A; FR2358252A1; AU2697177A; CA1104783A; DE2732137C2; PT66818A; DE2732137A1; FR2358252B1; ZA764252B

Description

PATENT SPECIFICATION

( 11) 1 578 568 ( 21) Application No 21555/79 ( 22) Filed 5 Jul 1977 ( 62) Divided Out Of No 1578567 ( 31) Convention Application No 764252 ( 32) Filed 16 Jul 1976 in ( 33) South Africa (ZA) ( 44) Complete Specification Published 5 Nov 1980 ( 51) INT CL 3 B 26 F 1/00 ( 52) Index at Acceptance B 5 A l Al A 1 M 1 R 314 C 1 C 1 R 314 C 1 E T 20 P B 5 K 3 ( 54) APPARATUS FOR PERFORATING SYNTHETIC PLASTICS FILM ( 71) I, THOMAS GOUGH HUTT, a Citizen of the Republic of South Africa of 134 Perseus Street, Waterkloof Ridge, Pretoria, Transvaal Province, Republic of South Africa, do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed, to be particularly de-

scribed in and by the following statement:-

This invention relates to apparatus for perforating synthetic plastics film It relates more particularly to apparatus for the making of bags from synthetic plastics film.

In my copending application 28118/77 (Serial No 1578567), there is described a method of making bags in a continuous web of synthetic plastics film comprising a series of bags separated by a series of longitudinally spaced transverse zones of weakness, the method including providing a double layer web of synthetic plastics film; displacing the web in a longitudinal direction; and causing a transverse hot cutting edge having a series of interruptions spaced along its length to perforate the web and to seal the layers of the web together at longitudinally spaced intervals, thereby leaving unsealed lands at interruptions between the perforations in the zone of weakness for holding adjacent bags together.

The perforations may be made by the hot cutting edge intersecting the web and entering a transverse slot moving with the web.

The perforations may be long and the unsealed holding lands which lie between perforations and which hold adjacent panels together, may be short The length of a perforation may be between ten and one hundred and fifty times the length of an adjacent land.

The double layer may be open along one longitudinal edge and the longitudinal edge of the one layer may project transversely beyond the longitudinal edge of the other layer.

The web may be rolled into a roll at a position downstream from the perforating zone.

Accordingly the invention provides apparatus which includes (a) a slot-defining means defining at least one slot, and being adapted to receive a double layer of web of synthetic plastics material, the web being adapted in operation to seat on the slot-defining means and to span the slot; (b) displacing means adapted to displace both the slot-defining means and the web in contact therewith in unison in a direction transverse to the length of the slot; (c) a heat cutter member spaced from the slot defining means to permit the web to pass between them and having a heatable elongated cutting edge extending in a direction parallel to the length of the slot and having spaced interruptions along the length of its heatable cutting edge; and (d) a heat cutter member displacing means adapted in operation to displace the heat cutter member operatively to cause its heated cutting edge to intersect the web and to enter the slot and to move in unison with and in the same direction as the web and slot and thereafter to disengage from the web and the slot.

The slot-defining means may define a spaced series of transverse slots and the heat cutter member displacing means may be arranged to displace the heat cutter member operatively in cyclic to and fro fashion The slot-defining means may comprise a drum mounted to rotate about its axis, the drum having the series of slots spaced circumferentially in its periphery.

The product of the apparatus is a continuous double layer web of synthetic plastics film in roll form and comprising a series of panels in the form of bags separated by a v) ( 19) 1 578 568 series of longitudinally spaced transverse zones of weakness extending across the width of the web, each zone of weakness comprising a series of heat-produced elongate perforations in the web separated by transversely spaced holding lands holding adjacent panels together the two layers of film being sealed together along the lengths of the perforations, but being unsealed and separate at the holding lands between perforations.

At least one of the outermost lands may be spaced inwardly from the edge of the web.

The invention will now be described by way of example with references to the accompanying diagrammatic drawings.

In the drawings Figure 1 shows an oblique end view of apparatus according to the invention; Figure 2 shows a cross-sectional end elevation of the apparatus shown in Figure 1; Figure 3 shows a fragmentary front elevation of one end of the drum of the apparatus shown in Figures 1 and 2 of the drawings; Figure 4 shows a fragmentary section taken at IV-IV in Figure 3 of the drawings; Figure 5 shows a fragmentary front elevation of a heat cutter member of the apparatus shown in Figures 1 and 2 of the drawings.

Figure 6 shows an underside plan view of the heat cutter member of Figure 5; Figure 7 shows a fragmentary crosssection at VII-VII of thile liheat cutter member of Figure 5, when in position intersecting the web on a slotted drum; Figlure 8 shows a fragmentary crosssection at VIII-VIII of a web shown in Figure 9; Figure 9 shows a fragmentary plan view of a web in the region of its zone of weakness.

Figure 10 shows a fragmentary longitudinal section at X-X in Figure 9; Figure 11 shows a front elevation of a web in roll form when mounted about a horizontal axis; an(l Figure 12 shows a front elevation of a web in roll form when mounted about a vertical axis.

Referring to Figures 1 and 2 of the drawings, there is shown apparatus according to the invention generally indicated by reference numeral 10 The apparatus comprises a frame 12 rotatably supporting slotdefining nl Ieans in the form of a slotted drum having a series of slots 16 spaced circumferentially in the periphery of the drum The drum 14 is mounted to rotate in the direction of arrow 17 about the axis of the shaft 18 It receives its drive from a drive wheel 20 which engages also with a take-up roller 22 engaging with an idler 24 which meshes in turn with a take-up roller 26.

A web 28 of synthetic plastics film unwound from roll 30, is caused to pass over deflecting rollers 32, thence over the drum 14 under a heat cutter sealing member 34 extending between a pair of opposed forks 36 provided at opposite ends of the drum 14.

The heat cutter sealing member 34 is provided with displacing means partly shown by reference numeral 38, and which is adapted to displace the heat cutter sealing member 34 in a to and fro and up and down direction in a closed loop as the drum 14 rotates in the direction of arrow 17 In so doing, the web 28 passes longitudinally through the machine from left to right The heat cutter sealing member 34, intersects the web cyclically at longitudinally spaced zones In doing so, the heat cutter member 34 provides a series of longitudinally spaced zones of weakness in the web 28 The various zones of weakness separate panels in the web, and the web having these zones of weakness, is then taken up in roll form as indicated at 40 carried on arms 42 slidable in guides 44 The roll 40 is caused to rotate in the direction of arrow 40 1 by means of the rollers 22 and 26 rotating in the direction of the arrow as indicated in Figure 2.

The heat cutter member, has a cutting edge 34 1 The heat cutter member and its operation will be described more fully hereafter.

Referring now to Figures 3 and 4 of the drawings, there are shown fragmentary details of the end of the drum 14 At the end of the drum 14, and closely axially spaced therefrom, there is provided a gear wheel 50, having a number of teeth corresponding to the number of slots 16 in the drum 14, the spaces between the teeth, being axially aligned with the slots 16 in the drum 14.

Furthermore, the fork 36 is provided with a tooth 52 axially aligned with the heat cutter member 34 supported between the axially spaced opposing forks 36 straddling the shaft 18 of the drum 14 The tooth 52 is adapted to engage cyclically between the teeth of the gear wheel 50 thereby ensuring that the heat cutter member 34 will enter accurately into the slots aligned with the spaces engaged by the tooth 52 The tooth 52, and hence the heat cutter member 34, being displaced by the displacing means, follow a closed loop path when viewed in the direction of Figure 4 of the drawings.

Referring to Figures 5, 6 and 7 of the drawings, the heat cutter member, is shown in greater detail It has a heating cutting edge 34 1 which, when hot, will intersect and seal web 28 as it lies on the drum 14.

The hot cutting edge 34 1 will pass through the web 28, and enter the slot 16 The cutting edge 34 1 is provided with interruptions 34 2 The length of an interruption 34.2 in the cutting edge 34 1 may be of the 1 578 568 order of a few millimetres say one or two millimetres The distance between interruptions, may vary from about 20 mm to about or 150 mm The total length of the interruptions may be of the order of 2/3 % to % of the total length of the heating cutting edge of the heat cutter member 34.

Referring now to Figures 8, 9, and 10 of the drawings, there are shown details of a double layer web of synthetic plastics material, after a zone of weakness has been provided in it The hot cutting edge 34 1 of the heat cutter 34, when it intersects the web 28, provides a zone of weakness 60-extending transversely to the direction of movement of the web through the machine 10.

The zone of weakness 60 is constituted by a plurality of perforations 60 1 separated by lands 60 2 holding adjacent panels 28 1 and 28 2 together These panels, are separated by the zone of weakness 60 The lands 60 2 are provided by the interruptions 34 2 in the cutting edge of the heat cutter member 34.

The cutting edge of the heat cutter member 34, at the interruptions 34 2, are provided with sharp edges, so as to ensure that the lands 60 2 between adjacent perforations 60.1, will have waists This will ensure that the panels will separate at the waists, along the zone of weakness, when pulled apart.

The upper and lower layers 28 11 and 28.12 of a panel 28 1 will become fused together at the zone 62 in the perforation 60.1 When in operation, the heat cutter member 34 will be maintained at a suitable temperature in order to ensure effective cutting of the web, and effective welding of the upper and lower layers 28 11 and 28 12, and of corresponding layers of other panels.

The heat cutter sealing member 34 will be electrically heated The displacing means 38 will be driven in synchronism with the drum 14, and the remaining rollers 20, 22, 24 and 26.

Referring now to Figures 11 and 12 of the drawings after the web has been taken up in roll form 40, as indicated in Figures 1 and 2 of the drawings, the rolls are removed and mounted as shown in Figures 11 and 12 of the drawings, for use The roll 40 may be mounted to be rotatable about the axis of a horizontal shaft 70, the various panels 28 1, 28.2 and 28 3, being separated by zones of weakness 60 The zones of weakness are provided by a series of perforations 60 1, spaced across the width of the web 28 The perforations are separated by the lands 60 2.

The web in roll form 30 is in double layer folded over at the longitudinal edge 40 11 and is open at the longitudinal edge 40 2.

The edge 40 21 of one layer extends transversely beyond the longitudinal edge 40 22 of the other layer of the roll 40.

Figure 12 shows an alternative way of mounting the roll 40 In this embodiment, the roll 40 is mounted about the axis of a rod 72 fast with a base 74 resting on a support 76.

In practice, where a machine is of substantial width, it will be possible to have a plurality of rolls 30 processed at the same time, for the production of rolls 40 The rolls 40 will then be produced side by side, as shown in Figure 1.

Furthermore, the apparatus can also form part of an inline installation having a printing machine and a extruder upstream of the apparatus according to the invention, the drum 14 and its associated rollers, will be driven in synchronism with the upstream printing installation and the extruder.

The applicant has found that side sealed plastic bags have adequate strength for most purposes, for example, for packing of merchandise in shops The applicant has also found that for most purposes the bags do not have to be airtight Indeed, for some purposes it is advantageous if they are not airtight.

Accordingly, bags made in accordance with the invention can be utilized in roll form, adjacent bags being held together by holding lands 60 2 Bags can easily be torn from the roll, separation between bags taking place along the zones of weakness.

The film used is conveniently low density polyethylene film The bags are easily opened by having one lip 40 22 longer than the other lip 40 21.

Film having a thickness of between 5 microns and 100 microns can be processed in accordance with the invention Besides, low density polyethylene film, film of other materials, can also be processed in the manner according to the invention Thus, polypropylene film, high density polyethylene film, rigid polyvinylchloride film, ie without plasticiser, can all be processed in the manner of the invention.

Claims

WHAT I CLAIM IS:-

1 Apparatus which includes (a) slot defining means defining at least one slot, and being adapted to receive a double layer web of synthetic plastic material, the web being adapted in operation to seat on the slot-defining means and to span the slot; (b) displacing means adapted to displace both the slot-defining means and the web in contact therewith in unison in a direction transverse to the length of the slot; (c) a heat cutter spaced from the slot defining means to permit the web to pass between them and having a heatable elongated cutting edge extending in one direction parallel to the length of the slot and having spaced interruptions along the length of its heatable cutting edge; and (d) a heat cutter member displacing means adapted in operation to displace the 1 578 568 heat cutter member operatively to cause its heated cutting edge to intersect the web and to enter the slot and to move in unison with and in the same direction as the web and slot and thereafter to disengage from the web and the slot.

2 Apparatus as claimed in Claim 1, in which the slot defining means defines a spaced series of transverse slots and in which the heat cutter member displacing means is arranged to displace the heat cutter member operatively in cyclic to and fro fashion.

3 Apparatus as claimed in Claim 1 or Claim 2, in which the slot-defining means comprises a drum mounted to rotate about its axis and having the series of slots spaced circumferentially in its periphery.

4 Apparatus as claimed in any one of the preceding claims and which includes roll up rollers downstream of the slot-defining means for rolling up the web in roll form.

Apparatus as claimed in any one of the preceding claims, in which the total length of the interruption is from 2/3 % to % of the total length of the heatable elongated cutting edge.

6 Apparatus for providing a continuous web of synthetic plastics film having a series of longitudinally spaced transverse zones of weakness, substantially as described and illustrated herein.

STEVENS, HEWLETF & PERKINS, Chartered Patent Agents, 5, Quality Court, Chancery Lane, London WC 2 A 1 HZ Printed for ller Majesty's Stalioncry Office, by Croydon Printing Company Limited, Cro)don, Surrey, 1980 Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A IAY, frorn which copies may be obtained.