GB2170145A

GB2170145A - Attaching elements to a web

Info

Publication number: GB2170145A
Application number: GB08602199A
Authority: GB
Inventors: Trevor James Dimond
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-01-29
Filing date: 1986-01-29
Publication date: 1986-07-30
Also published as: GB8602199D0; GB2170145B; GB8502175D0

Abstract

Apparatus for attaching elements to a web, e.g. handle reinforcements for a web of carrier bags, is adapted to operate independently of a web producing machine, by having its own power source 22 and being synchronised to the web producing machine by an electrical signal. A preferred apparatus has a pair of rotary carrier drums 18 with a gap 14 between them through which a web is passed to receive elements from each drum on respective faces. Each drum has multiple carrier faces 20 which are indexed past a supply station 40,52 to pick up an element, and carry it to the gap 14 where it is applied to the web. Each drum 18 is braked (104). A control pulse releases the brake and urges rotation for a fixed interval. Completion of an indexing step is detected and braking is reapplied. <IMAGE>

Description

SPECIFICATION Attaching elements to a web The present invention relates to apparatus for attaching elements to a web. It is particularly concerned with apparatus for adhering elements such as handle reinforcements in the production of carrier bags.

Carrier bags, particularly plastics ones, often fail by rupturing of a handle, especially where this is merely a portion of the bag material defined by a cut-out. It is known to provide reinforcing patches.

These are portions of material attached to the handle area, e.g. by gluing. Machinery for applying such portions has been provided as an inseparable part of a bag producing machine. That is, it is permanently coupled to the rest of the machine, and is driven by the main drive thereof. If it is desired to produce bags without patches, this may not be possible. Even if it is, the patch applying machinery will nevertheless continue to go through its motions. Known machinery is complex and expensive.

According to the present invention, an apparatus for attaching elements to a web, and particularly for attaching reinforcements for carrier bags, is provided with its own drive, and means for synchronising its operation to an electrical control pulse. Control pulses may be obtained from associated machinery earlier in a production line, e.g.

from part of a bag making machine whose bags are to be reinforced by the present apparatus.

The apparatus may employ a carrier (e.g. a rotary drum) which is indexed cyclically between a station at which it receives an element, and a station at which it applies the element to the web.

The carrier may be held immobile except after receipt of a control pulse. Suitably, a pulse releases a brake and causes motive power to be applied to the carrier for a fixed time. Completion of a predetermined displacement of the carrier may be detected, and used to reapply the brake. There may be a further delay before the element is transferred to the web.

The carrier may employ an element applicator comprising a displaceable transfer plate and a pin plate having pins extending through openings in the transfer plate. Thus an element can be held on the transfer plate by the pins until that plate is displaced to carry the element to the web and to shield the pins in the openings.

Elements may be cut from a supply web. This supply web may be connected to the carrier and subsequently cut, possibly simultaneously with the transfer of an earlier element.

The apparatus may be a self-contained unit, which can be fitted to the vast majority of bag making machines. It can employ sealed bearings and a virtually sealed gearbox, so that lubrication and maintenance requirements are minimal. Operations such as transfer of an element and/or cutting of elements from a supply web may be powered by air cylinders.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a front elevation of an embodiment of the invention which is an apparatus for attaching handle reinforcements to carrier bags; Figure 2 is a side elevation on a larger scale of one drum assembly of the apparatus; Figure 3 shows a vane of the drum assembly; Figure 4 shows suitable control circuitry; and Figure 5 is an operational flow diagram.

The illustrated apparatus is intended for applying pairs of patches to respective carrier bags (or to respective portions of a continuous web which will subsequently be separated into individual carrier bags), one patch on either side. Thus as can be seen in Figure 1, a framework 10 supports a casing 12 having a through slot 14, through which, in use, a web of carrier bags is fed. Above and beneath the slot 14 is a respective one of a pair of drum assemblies 16. Each includes a many-sided drum 18 (here twelve-sided). Each drum 18 is mounted for rotation about an axis parallel to the direction of travel of the carrier bags through the slot 14. The drums 18 are indexed between positions wherein successive faces 20 are adjacent (and parallel to) the slot 14 by means of a motor 22 which drives a belt 24 via a gearbox 26 and a clutch 28.Thus the belt 24 passes round an intermittently driven shaft 30 and round a respective pulley 32 on each drum 18. It also passes around a pair of guide rollers 34, 36, one of which (36) is displaceabie for tensioning.

Each drum assembly 16 has an associated patch supply assembly 40. In this, a web of polyethylene from a reel R is first fed through a gluing station 42. Here it passes through a nip between a pair of rollers 44, 46, the lower one of which is partly immersed in a glue pot 48. The web 50 thereby receives a coating of adhesive on one side, the upper side in Figure 1. It is then guided to its drum 18, where it passes through a nip between a pressure roller 52 and the drum 18, and successive portions of the web 50 are releasably secured to successive faces of the drum 18. The successive portions are mutually separated by operation of a knife 54.

The mode of attachment of the portions will now be described in greater detail, primarily with reference to Figure 2.

Each face 20 of each drum is provided by a respective patch applicator 60. (Only one of these is shown schematically in Figure 1; Figure 2 contains more detailed views of one in side view and one in plan.) Each applicator 60 includes a fixed pin plate 62, bearing an array of (here ten) pins 64 projecting outwardly. The pins 64 are in two rows. Between them is a central aperture containing a resilient pad 66, suitably of rubber. In the centre at either lateral side, there is an aperture 68 through which a bolt 70 extends slidably. Each bolt 70 has a spring 72 braced between its head and the underside of the plate 62. On the outer side of the pin plate 62 there is a transfer plate 74. This has apertures in register with the pins 64. It is fast with the outer ends of the bolts 70, so that the force of the springs 72 pulls the plate 74 down against the pin plate 62.In this configuration, the pins 64 project outwardly of it.

The pressure roller 52 has main portions 76 for urging the patch web 50 against the transfer plate 74, and recessed portions 78 for accommodating the pins 64. It should be fairly hard but with some resilience. PTFE is a suitable material, particularly since it has non-stick properties. The roller 52 is journalled so as to be rotated by contact with the drum 18. Since the drum has a facetted surface rather than being truly cylindrical, the spacing of the roller 52 from the centre of the drum 18 varies cyclically. To facilitate this, the drum has at one side a steel cam 80. This is followed by a ball race 82 which is fast with the axle of the roller 52, which is mounted to allow the necessary displacement while being urged into contact with the drum.

Within each drum 18 adjacent the slot 14, there is a hammer 84 arranged for delivering a blow to the resilient pad 66 in the pin plate 62 located adjacent the slot 14, so as to displace the transfer plate 74 outwardly. One such hammer is shown schematically in the lower drum 18 in Figure 1. It may be driven by an air cylinder, as may the knives 54.

The general operation of the parts so far described is as follows. The patching webs 50 from the reels R have glue applied to one side, and are fed to the drums 18. A respective roller 52 presses each web onto the transfer plates 74, where it is held spiked by the pins 64. The roller 52 contacts the glued side of the web 50 but, being made of PTFE, has little tendency to stick. The drums are indexed round clockwise, and about 75" after the roller 52 there is a knife 54 which is operated to cut the web 50 into separate patches. A further four indexing steps brings the severed patch to the position adjacent the slot 14. Each indexing step of the drums 18 corresponds to the introduction of a fresh carrier bag blank into the slot 14.Actuation of the hammers 84 displaces the transfer plates 74, so that in effect the pins 64 are withdrawn into the apertures 75 of the plate 74. The plate 74 is momentarily urged against the carrier bag or blank, so that the two transfer plates 74 squeeze it, and the patches adhere to it.

The means for controlling the indexing of the drums will now be described. The motive power is the electric motor 22. In an actual working embodiment, this works constantly at 960 rpm, and is permanently coupled to a gearbox 26 giving a 25:1 reduction. The gearbox drives a clutch plate 92.

When actuated, by means of an armature 94, the clutch engages a hub 96 which is fast with a toothed pulley 98 (having twenty teeth). This is coupled by a belt 24 (which is toothed, and of pitch 0.5 in., 12 mm.) to a toothed pulley 32 which is rotationally fast with the drum. (In this example, this pulley has thirty teeth.) Axially adjacent the drum pulley 32 is the brake assembly 104. A shaft 106 of the drum extends through this, and has mounted on or about it brake blocks 108, 110; a brake hub 112; a brake coil 114; an armature 116; and a toothed vane 118 (which is shown in more detail in Figure 3). The operation of the brake assembly 104 can be generally conventional, the coil 114 being actuable to control brak ing.

The vane 118 has a mounting hub 120 and a web 122 formed with the same number of teeth 124 as there are sides to each drum 18. The brake assembly 104 includes a Hall effect detector 126 arranged to embrace a sector of the periphery of the web 124, so as to detect whether that sector is a tooth 124 or a gap between teeth. Thus the detector 126 can provide an output signal that indicates when a drum has rotated through one indexing step. Other forms of detector might be used, but the Hall detector is preferred because there is no danger of a spark which might cause a fire, e.g. by igniting vapour from the glue.

The operation of the drum assemblies 16 must be controlled in two ways: firstly to ensure that the indexing steps are correct (since even a tiny cumulative error would soon become serious); and secondly to ensure synchronisation with the supply of carrier bags or bag blanks. The first form of control makes use of the Hall detector 126. The second makes use of an electrical pulse signal obtained from the bag making machine. Most such machines use pulses for controlling their own operations, so that it is easy to obtain a suitable input for the present apparatus. However, if this is not the case it is easy to provide a suitable transducer, e.g. employing a non-contact switch device for counting the revolutions of some rotary element of the bag making machine.Thus by some such means, an input is arranged which provides one pulse each time a carrier bag is fed into the present apparatus. (Of course, a different type of pulse signal could also be used.) When the present apparatus is standing by, the motor 22 is running, the clutch is not engaged, and the brake of each drum assembly is preventing rotation. Receipt of an input pulse causes release of the brake and engagement of the clutch. Thus the drums rotate. After a preset time, the clutch is caused to disengage. This time is sufficiently short that the drums have not yet indexed by one step; but the inertia of the system keeps the drums moving. When one indexing step is complete, a tooth 124 of the vane 118 enters the Hall detector 126.

This leads to instant actuation of the brake, and thus the drum is stopped. After a predertermined time interval, to make sure the drum is stationary, the hammer 84 and the knife 54 are actuated. The brake remains on until a further input pulse is received from the bag making machine, whereupon the sequence is repeated.

The operation of the apparatus is controlled by control circuitry as shown in the circuit diagram of Figure 4 and the operational flow diagram of Figure 5. Plainly there is much scope for variation in the control circuitry. In that shown in Figure 4, pulses from the bag making machine are converted to light pulses by a neon 200. These are converted to electrical signals by means of an LDR 202. These are used to drive the brake solenoid 204 and the clutch solenoid 206, after amplification. The circuitry also provides a pulse output from terminal 208 for operating the solenoids for each knife 54 and hammer 84. The delay of this pulse after the actuation of the brake is variable by the variable resistor 210. The pulse length is variable by the resistor 212. The length of time for which the clutch remains engaged is controllable by means of the resistor 214.The brake is reapplied in response to a signal provided by the Hall switch 216 (of detector 126). It will be seen that various lamps are provided to show the operation of the apparatus and its various components, for example there is a yellow LED 218 in parallel with the brake solenoid 204.

The illustrated apparatus is intended for applying pairs of patches to the external faces of carrier bags. The invention can also be embodied in apparatus which applies patches to the inside of bags.

This has the advantage that the patch material does not show externally, so that it does not matter if it is a different colour. Such apparatus could involve preliminary means for folding back one or other sides of a bag to expose the inner surfaces. If only one side is folded back, so that both inner surfaces face in the same direction, a pair of reinforcements could be applied using a single drum, in two steps.

Claims

1. Apparatus for attaching elements to a travelling web whose displacement is controlled by web displacement means separate from the apparatus; the apparatus comprising an attachment station arranged so that a web is displaceable through it; and attachment means for attaching elements to web portions at the attachment station; there being synchronisation means for receiving an input signal related to the displacement of the web and synchronising the operation of the attachment means thereto so that elements are attachable to the web at controlled spacings.

2. Apparatus according to claim 1 wherein the attachment means includes feed means for supplying elements to the attachment station.

3. Apparatus according to claim 2 wherein the feed means includes a carrier which is displaceable between a receiving station and the attachment station, and which is arranged to receive an element at the receiving station, and carry it to the attachment station where it is attachable to the web.

4. Apparatus according to claim 3, wherein there are brake/release means arranged to prevent said displacement of the carrier except when actuated in response to the input signal.

5. Apparatus according to claim 4, wherein said input signal is arranged to release the braking of the carrier and to cause the displacement of the carrier to be driven for a predetermined time.

6. Apparatus according to claim 5 including means for detecting a predetermined displacement of the carrier to the attachment station and actuating the brake/release means to reapply braking in response thereto.

7. Apparatus according to claim 6 arranged to effect attachment a predetermined time after the reapplication of braking.

8. Apparatus according to any of claim 3 to 7 having a multiplicity of carriers which are cyclically displaceable between the receiving station and the attachment station.

9. Apparatus according to claim 8 wherein the feed means comprises a polygonal drum and carriers are provided at the faces thereof; the drum being rotatable to effect said displacement.

10. Apparatus according to any of claims 3 to 9 wherein the carrier includes a displaceable transfer plate for carrying an element, and there are means at the attachment station for displacing the transfer plate so that the element is urged against the web.

11. Apparatus according to claim 10 wherein the carrier includes a pin plate having pins that can project through the transfer plate to retain an element thereon, and relative to which the transfer plate is displaceable so that the pins are relatively retracted to facilitate transfer of an element to the web.

12. Apparatus according to any of claims 3 to 11 including two said carriers arranged to carry elements for attachment to opposed faces of the web at the attachment station.

13. Apparatus according to claim 12 as appendant on claim 10 or 11 wherein the transfer plates of the two carriers are displaceable simultaneously to clamp the web between them momentarily.

14. Apparatus according to any preceding claim including a source of motive power for the operation of the attachment means.

15. Apparatus according to any preceding claim constructed and arranged for attaching handle reinforcing elements to a web of carrier bags or blanks thereof.

16. Apparatus for attaching elements to a web substantially as any herein described with reference to and as illustrated in the accompanying drawings.

17. Apparatus for producing a web optionally bearing attachment elements, including a web producing and displacing means and an apparatus according to any preceding claim which is selectively operable to attach elements to a web output from the web producing and displacing means.