GB2179887A

GB2179887A - Manufacturing plastic bags

Info

Publication number: GB2179887A
Application number: GB08620452A
Authority: GB
Inventors: Rene Francois Debin
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1983-09-02
Filing date: 1986-08-22
Publication date: 1987-03-18
Also published as: EP0215394A1; CA1225856A; BR8404370A; GB2145658B; ES535585A0; GB2179887B; GB2145658A; ES8505582A1; EP0215394B1; EP0134711A3; DE3470012D1; JPH0649346B2; GB8620452D0; EP0134711B1; AU570707B2; JPS6076331A; EP0134711A2; AU3147584A; GB8420542D0

Description

1 GB2179887A 1

SPECIFICATION

Twin wicketing bag machine This invention relates to equipment for converting thermoplastic films, for example to converting equipment and that produces thermoplastic bags.

The disclosure of the present application is related to and is an improvement to the subject matter disclosed in co-pending application No. 81.28656, publication No. 2089286.

This prior application discloses a bag making procedure in which the elongate strip of thermoplastic web is provided with lines of perforation located centrally of the web strip. Each segment produced by the action of the seal bar contains the centrally located lines of perforation. In transporting the web segment by a rotary transfer device, from the pickup station to the stacking station containing the upwardly projecting pins, partial or full separation along a line of perforati6n sometimes occurs. If full separation occurs while the web segment is in transit to the stacking station, stacking of that web segment cannot be achieved since registration with the stacking post is no longer possible. In the event partial separation occurs and stacking on the post is achieved a portion of that web segment may not lie in a position to produce a bag stack having the edges of each individual bag overlying each other.

According to the present invention there is provided bag-making apparatus operative to process a web of thermoplastic film material and to divide the web into segments of equal dimensions and provide each segment with at least two apertures located adjacent to and on either side of the median, considered in the longitudinal direction of the web, of each segment, the segments produced being transferred to a stacking device provided with stacking posts on which successive segments are stacked, the posts extending through aligned apertures of the stacked segments, the apparatus comprising means operative while a stack of segments is retained on said stacking device for producing lines of perfora- tion enabling subsequent division of each segment to define two bags, and means concurrently or subsequently operable for cutting the perforated stack of segments along a line between the stacking posts and between the lines of perforation to produce two discrete stacks, one line of perforations being included in each layer of thermoplastic web material of each discrete stack.

Further according to the present invention there is provided apparatus for perforating a plurality of web segments provided with holes received on stacking posts serving to retain the segments in a stack, said apparatus comprising a pair of simultaneously operable linear actuators mounted on a support located above the stack and through which support the output rods project, a crosshead fixed to the actuator rods, means carried by said crosshead for compressing the stack, and means also carried by said crosshead for perforating the stack, while compressed, to provide a line of weakness to facilitate separation of a portion of each web segment.

Still further according to the present inven- tion there is provided perforating apparatus for perforating a plurality layers of thermoplastic web material comprising means for supporting the layers of thermoplastic material, means for perforating the thermoplastic material, means mounting said perforating means, said mounting means including a holder carrying said perforating means, means connected to said holder for advancing said perforating means to penetrate all layers of the thermoplastic ma- terial to effect perforation thereof, said advancing means being operable to withdraw said perforating means after perforation is effected, means carried by said holder for heating said perforating means thereby to facilitate penetration of the thermoplastic material, said perforating means comprising an elongate, flat, blade-like member clamped to a recess formed in said holder and provided with series of slots interrupting the leading sharped edge to thereby produce a series of incisions and uncut bond portions being sufficiently weak to alloy easy separation of a layer of thermoplastic material.

Application No. 81.28656 discloses, in Figs.

9 and 10, a cutting station substantially simiJar to the cutting station disclosed herein.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:

Figures 1A and 1B, considered together, is a side elevation of a web processing machine constructed and operating in accordance with the present invention; Figure 2 is a perspective view illustrating a mechanism forming a part of the machine of Fig. 1 involved for transferring a web segment from a transfer station to the stacking station of the machine; Figure 3 is a perspective view illustrating a stack of web segments deposited on pins carried by a stacking plate; Figure 4 is similar to Fig. 3 but additionally shows perforating knives of the machine after perforation of the stacked web segments has occurred; Figure 5 illustrates the web segments being cut between the pins by a knife to produce two bag stacks; Figure 6 is a side elevation of the knife sup- porting and actuating means; Figure 7 is a section of Fig. 6 taken substantially along the line 7-7; Figure 8 is an elevation of the perforating mechanism; and Figure 9 is a side view of Fig. 8 as viewed 2 GB2179887A 2 along the line 9-9.

Referring first to Fig. 1 A it will be seen that a web roll WR is mounted on a transverse shaft 20 rotatably supported by an unwind stand 22 carried by a frame structure 24. The web strip unwound from the web roll WR passes over a series of rolls collectively identified by the numeral 26 and then progresses over a serial of rolls rotatably mounted in a tower structure 28 which includes gusseting devices 30. Unreeling of the web strip from the web roll is accomplished by drive rolls 32 and thereafter the web is passed over a series of rolls comprising a web tensioning device 34. A turning roll 36 directs the web strip to 80 draw rolls 37 which are intermittently oper ated by the drive of a bag machine 38.

The thermoplastic film TF is advanced by the draw rolls to a severing and sealing sta- tion 40 and the portion of web advanced is momentarily retained on a series of belts 42 generally describing a triangular path and de fining a transfer station TS. On creation of a web segment WS located at the transfer sta tion (Fig. 2), a rotary transfer mechanism 44, 90 which includes a plurality of regularly spaced radially extending tubular bars 46, connected through a hub 48 to a source of vacuum, engages and retains a web segment at the transfer station and translates it through an arc for reception by one of a series of stack ing devices 50 located at a stacking station 52.

Reference to Fig. 2 will reveal one style of web segment in which each segment has a central media[ strip removed from one panel and the remaining panel is provided with four holes 54 through which project stacking pins or posts 56 projecting upwardly and fixed to a base plate of the stacking devices 50. The posts 56 are located to correspond to the spacing of the holes 54 so that each web segment is retained on the stacking devices by the posts 56. During machine operation a selected number of web segments are stacked on the stacking devices 50 and when the predetermined number of web segments has been stacked operation of the bag ma chine 38 is arrested and concurrently there with a successive stacking device 50 is posi tioned at the stacking station 52.

Reference to Fig. 113 will reveal the pro vision of a conveyor 58 that is intermittently driven by drive mechanism 60 such that the upper reach of the conveyor is incrementally advanced from right to left as viewed in Fig.

1B. Also, as revealed by this Figure, the stacking devices 50 are mounted on the con veyor and successive stacking devices are po sitioned at the stacking station 52 for a period of time required to accumulate a selected number of web segments.

In accordance with the principle feature of the preferred embodiment the problem of pre mature partial or complete detachment of a 130 portion of a web segment WS, along a line of perforation, does not arise since the web segments produced by the bag machine do not include perforations. Accordingly, forces created by air pressure in the course of transferring a web segment by the transfer device 44 from the transfer station TS to the stacking station 52 is easily tolerated by the web segment. As will be explained presently, the bag stacks produced include perforations but their creation occurs while a stack of web segments is retained on the stacking posts 56 carried by the stacking devices 50.

Further processing of the web segments WS to produce two perforated bag stacks from each group of web segments is achieved by perforating means 62 and cutting means 64 being carried by a frame structure 66 straddling and overlying the conveyor 58. The cutting means 64 are in substantial respects similar to the cutting means disclosed in the above referenced Application.

During the time when a stack of web segments is being accumulated on the stacking device 50 located at the stacking station 52 the conveyor 58 is inactive. During this time period the perforating means 62 and the cutting means 64 are rendered operative, sequentially or concurrently, to effect, respectively, perforation and separation of the accumulated web segments to produce two individual bag stacks each of which contain a line of perforation.

The preferred construction of the perforating means 62 comprises linear actuators 68 secures to a flat plate 70 which is in turn adjustably secured to horizontal supports 72 (Fig. 1 B) of the frame structure 66. The plate 70 is provided with bores through which extend the rods 74 of the linear actuator 68. The extremity of each rod 74 is fixed to a crosshead 76 carrying downwardly projecting perforating knife holders 78. The knife holders 78 are secured to the crossheads 76 by a series of bolts 80 passing through insulating spacer blocks 82 and threaded into the perforating knife holders 78. Perforating knives 84 are secured to the holders 78 by a series of fasteners 86 and the perforating knives 84 extend beyond the holders 78 sufficient to penetrate a stack of web segments. Fig. 8 shows the general configuration of each of the perforating knives, and it will be seen that each knife is provided with a series of slots 88 creating an interruption in the line of cut defined by a cutting edge 90 which may take the form of a jagged edge which experience has shown requires less force to penetrate each stack of web segments. To enhance penetration of the knife 84 each of the perforating knife holders 78 is provided with a slug heater 92 which can be energized to produce a given temperature to each of the knives 84. Heating of the knives 84 has been found to reduce the amount of force necessary to penetrate a 3 GB2179887A 3 1 stack of web segments and yet the tendency to form a blocked stack does not arise when a sufficiently low temperature level is selected.

Before the perforating knives 84 make con- tact with the uppermost web segment of the stack of segments, means 94 are provided for compressing the stack to prevent upward bulging of the stack when the knives 84 come into pressure engagement with the stack. As shown in Figs. 8 and 9 the compressing means 94 include elongate offset bars 96 which are subsequently equal in length to the perforating knives 84 and make contact with the stack adjacent the fine of perforation established by the knives 84. The bars 96 are connected to the crosshead 76 by spring biased rods 98 which slidably extend through bushings 100 mounted to the crosshead 76. A stop member 102 is secured to the upper end of the rod 98 by a fastener 104 to limit and retain the rods 98 in the bushings 100.

According to the above described arrangement when the actuator 68 is energized to effect operation of the perforating means 62 the elongate bars 96 come in contact with the stack of web segments forcing them downwardly onto the stacking devices 50 and immediately thereafter the perforating knives 84 penetrate and accordingly perforate the stack of web segments.

In order to enhance the longevity of the knives 84 the stacking devices 50 are provided with inserts 106 which can be made of wood or plastic material which will allow pen- etration of the knives 84 and yet have a minimal effect in rendering the cutting edge of the knives dull.

As shown in Fig. 2 the cutting means 64 is located downstream and adjacent the perforat- ing means 62 and if desired the perforating means and the cutting means can be actuated simultaneously or sequentially at the option of the user, Figs. 6 and 7 illustrate the cutting means 64 in greater detail and it will be seen to comprise linear actuators 108 also mounted 110 on the flat plate 70 being suitably bored to accommodate reciprocating movement of rods having their lower ends threaded to re ceive a nut 112 fastening the rods to a cros shead 114. A knife holder 116 is in turn con115 nected to the crosshead 114 by bolts 118 extending through _insulating spacers 120. In similar respect the cutting means is provided with stack compressing means 122 which in clude presser bars 124 rigidly connected to 120 rods 126 having their upper ends slidably dis posed, by means of bushings 128, to the crosshead 114. Tension springs 130 are as sociated with each of the rods and serve to A bias the presser bars 124 downwardly. 125 The knife holder 116 is formed to receive and retain a cutting knife 132 and rod heaters 134 serving to heat the knife 132 to a de-- sired temperature to facilitate cutting of the web segments, while they are retained on the pins 56, into two bag stacks each of which include a line of perforation previously made by the perforating means 62. As with the perforating means, cutting means 64 includes, in the stack device 50, an insert 136 selected of a material such as previously indicated to prevent dulling of the cutting edge of the knife 132. The knife 132 is retained in the holder 116 by a plurality of fasteners 138.

Reference to Figs. 3, 4 and 5 shows the condition of a stack of web segments at the stacking station 52, the perforating station 62 and the cutting station 64. When the conveyor positions a stack of web segments WS at the perforating station 62 and the actuators 68 are operated to drive the perforating knives 84 to cut the web segments, lines of perforation 85 are produced adjacent the stacking posts 56. As previously mentioned, the cutting station 64, operating the parting knife 132 may be concurrently or subse quently operated to produce two bag stacks BS by cutting the web segments along a line PS, located between the stacking posts 56.

In view of the above described construction of the mode of operation of the over-all ma chine, and more particularly the perforating means 62 and the cutting means 64, it should be evident that performing the perforating and cutting function after a selected number of web segments have been stacked the problem of the prior art of premature separation along one or more lines of perforation formed in the web segment before stacking does not arise.

Claims

1. Bag-making apparatus operative to process a web of thermoplastic film material and to divide the web into segments of equal di- mensions and provide each segment with at least two apertures located adjacent to and on either side of the median, considered in the longitudinal direction of the web, of each segment, the segments produced being transferred to a stacking device provided with stacking posts on which successive segments are stacked, the posts extending through aligned apertures of the stacked segments, the apparatus comprising means operative while a stack of segments is retained on said stacking device for producing lines of perforation enabling subsequent division of each segment to define two bags, and means concurrently or subsequently operable for cutting the perforated stack of segments along a line between the stacking posts and between the lines of perforation to produce two discrete stacks, one line of perforations being included in each layer of thermoplastic web material of each discrete stack.

2. Apparatus for perforating a plurality of web segments provided with holes received on stacking posts serving to retain the segments in a stack, said apparatus comprising a pair of simultaneously operable linear actuators 4 GB2179887A 4 mounted on a support located above the stack and through which support the output rods project, a crosshead fixed to the actuator rods, means carried by said crosshead for compressing the stack, and means also carried by said crosshead for perforating the stack, while compressed, to provide a line of weakness to facilitate separation of a portion of each web segment.

3. Perforating apparatus for perforating a plurality layers of thermoplastic web material comprising means for supporting the layers of thermoplastic material, means for perforating the thermoplastic material, means mounting said perforating means, said mounting means including a holder carrying said perforating means, means connected to said holder for advancing said perforating means to penetrate all layers of the thermoplastic material to ef fect perforation thereof, said advancing means 85 being operable to withdraw said perforating means after perforation is effected, means carried by said holder for heating said perfor ating means thereby to facilitate penetration of the thermoplastic material, said perforating means comprising an elongate flat blade-like member clamped to a recess formed in said holder and provided with series of slots inter rupting the leading sharped edge to thereby produce a series of incisions and uncut bond 95 portions being sufficiently weak to allow easy separation of a layer of thermoplastic material.

4. Apparatus according to claim 3 further comprising means carried by said mounting means for compressing said layers of thermo- 100 plastic material along a line adjacent the line of perforations, said compressing means oper ating to engage the thermoplastic material be fore it is engaged by said perforating means.

5. Apparatus according to claim 1 wherein 105 each said stacking device has mounted ther eon a pair of said stacking posts located on each side of the said median and said web segments are each provided with apertures conforming in number and spacing to said pair 110 of stacking posts, said perforating means being positioned to produce perforations along lines adjacent said posts.

6. Bag-making apparatus for producing plastics bags from segments, each segment being dimensioned to produce two bags, said apparatus comprising elongate upstanding members arranged to hold the segments as a stack, perforating, means movable into the stack to produce two parallel, spaced lines of perforations enabling subsequent production of individual bags and cutter means operable to sever and seal the segments of the stack so that the divided segment elements each in- clude a line of perforations. 7. Bag-making apparatus substantially as hereinbefore described with reference to the accompanying drawings.

CLAIMS Amendments to the claims have been filed, and have the following effect:- Claims 1 to 1 above have been deleted.

New or textually amended claims have been filed as follows- 1. A method of preparing a stack of substantially similarly-shaped twin layered web segments, accumulated on a stacking device mounting upwardly projecting pins penetrating the central medial strip of web segments as they are successively placed on the stacking device to define, from each web segment, two bags, said method comprising transferring a succession of individual said web segments in a substantially planar condition over an arcuate path so that the segments are substantially normal to the projecting pins when penetration occurs, arresting transfer of the web segments after accumulation of a predetermined number of web segments on the pins, displacing the stacking device carrying the predetermined number of web segments to a perforating device, and perforating the web segments along lines located adjacent to and on either side of the projecting pins thereby to define two bags from each segment in the stack.

2. A method according to claim 1 including the further step of severing the stack of web segments along a line between said projecting pins to provide two part segments, each of which part segments has a said perforation line therein, individual bags being produced by rupturing the line of perforation in the corresponding sub-segment.

3. A method according to claim 1 or claim 2 including the further step of heating said perforating device.

4. Bag making apparatus comprising means for processing an elongate web of twin layered thermoplastic material to produce web segments each of equal dimensions, means for transferring the segments over an arcuate path to a stacking plate mounting upwardly projecting pins which penetrate through a medial region of successive segments, until a predetermined quantity of overlapping segments is stacked, and means, operable after displacing the stacking plate carrying the desired quantity of accumulated web segments from the arcuate path, for producing two spaced lines of perforations in the medial region of the stacked segments, said means for producing the lines of perforation dividing each segment such that on rupture of said lines two separate bags are produced.

5. A plastics bag making machine comprising means mounting a web of thermoplastics film having twin layers, means for converting the web into segments by transverse severing and sealing, means for conveying successive said segments over an arcuate path to stacking means including two pairs of upstanding pins on which the segments are engaged, 1 e GB2179887A 5 L means operative while the segments are on the stacking means to perforate in two parallel lines the stacked segments and simultaneously to sever the segments to form two separate stacks, the perforating and severing means in- cluding a pair of spaced, parallel, knives with interrupted edges and an uninterrupted knife to sever the stack, individual bags being made available by rupture of the perforations.

6. A bag making machine for manufactur- 75 ing bags from a thermoplastic web material comprising a rotary transfer device for use in grasping and transferring non-perforate web segments successively from a pickup station on to a stacking station, the stacking station 80 including an intermittently operating endless conveyor carrying a plurality of longitudinally spaced stacking devices having sets of stack ing pins for use in impaling successive non perforate web segments deposited thereon through complementary holes provided in a median strip of each non-perforate web seg ment, the conveyor intermittently positioning each successive empty stacking device in the path of the rotary transfer device and concur rently moving the filled stacking device con tainig a predetermined number of stacked non perforate web segments impaled on the stack ing pins upstream out of the path of the ro tary transfer pins upstream out of the path of 95 the rotary transfer device to a perforating sta tion, the perforating station including a perfor ating apparatus having a pair of perforating knives positioned above the stacking device filled with non-perforate segments impaled on 100 the stacking pins moved by the conveyor from the stacking station to the perforating station, and means for moving the pair of per forating knives downwardly and piercing the layer of stacked web segments and forming 105 two parallel lines of perforations extending longitudinally with respect to the movement of the conveyor and spaced laterally outwardly from the stacking pins and defining a stack of segments impaled on the stacking pins.

7. A machine according to claim 6 wherein the perforating station further includes cutting apparatus having cutting blade means extend ing along a median line laterally inwardly of the stacking pins and parallel to the parallel lines of perforations for use in separating the segment stack into two stacks of bags with each stack of bags being impaled on respec tive stacking pins with the respective lines of perforations of each stack of bags spaced laterally outwardly from the respective stack ing pins.

8. A machine according to claim 6, further comprising a cutting station downstream of the perforating station, the cutting station in- 125 cluding cutting apparatus positioned above a stack of perforated segments impaled on the stacking pins delivered thereunder by the con veyor from the perforating station, the cutting apparatus having a cutting knife for use in 1 separating stacks along a median line laterally inwardly of the stacking pins into two stacks of bags with each stack of bags impaled on respective stacking pins and each line of per- foration extending parallel to and spaced laterally outwardly from the respective stacking pins.

9. A machine according to claim 7 or claim 8, wherein the perforating knives are parallel to one another, have interrupted cutting edges and are positioned laterally outwardly of the stacking pins, and means for heating the perforating knives to a temperature below the melting temperature of the thermoplastic web material for facilitating penetration of the interrupted cutting edges through the thermoplastic web material without melting and joining the layer of stacked web segments impaled on the stacking pins.

10. A machine according to claim 7 or claim 8, further comprising a resilient pad mounted to each of the stacking devices vertically aligned below the cutting edge of each of the knives for use in protecting the cutting edges of the knives following the penetration of the stacked web material.

11. Bag making apparatus for producing plastics bags from web segments, each web segment being of a predetermined size dimensioned to produce two bags, said apparatus comprising elongate upstanding members arranged to hold a layer of unperforated web segments as a stack, and perforating means for producing two parallel, spaced lines of perforations in the stack of web segments, the perforating mean being so located that a perforation operation is effected on the stack of web segments while the stack of segments are held in registry by said upstanding members, thereby producing a stack of segments held by said upstanding members.

12. Apparatus according to claim 11, comprising means operable on each unperforated web segment for providing each unperforated web segment with at least two apertures located adjacent to and on either side of the median, considered in the longitudinal direction of the web, of each unperforated web segment, the unperforated web segments pro- duced being transferred successively to a stacking device incorporatng the said upstanding members on which the successive unperforated web segments are stacked, the upstanding members extending through the aligned apertures of the stacked unperforated web segments.

13. Apparatus according to claim 11 or claim 12, wherein the perforating means are operative while the stack of unperforated web segments is retained on said stacking device for producing parallel lines of perforation enabling subsequent division of each web segment along the lines of perforation to define two bags.

6 GB2179887A 6 Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8817356, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.

5,