CA1106273A

CA1106273A - Wrapping apparatus and method of wrapping

Info

Publication number: CA1106273A
Application number: CA289,522A
Authority: CA
Inventors: Alec Singer
Original assignee: STARPAK Pty Ltd
Current assignee: STARPAK Pty Ltd
Priority date: 1976-10-29
Filing date: 1977-10-26
Publication date: 1981-08-04
Also published as: JPS5356582A; GB1589778A; DE2748541A1; SE7712146L; IT1113782B; NL7711799A; FR2369161A1

Abstract

ABSTRACT OF THE DISCLOSURE

Wrapping apparatus in which shrink wrap material in web form is fed from a reel onto an apertured, rotating drum. The interior of the drum is maintained at a sub-atmospheric pressure to draw the web against the drum. An oscillating cutter is pressed against the web on the drum to sever the web into sheets, and the sheets are transferred to two apertured feed belts. Suction conditions maintained at the apertures in the belts holds the sheets against the belts.
These belts place the sheet curtain-like ahead of the article to be wrapped, and the article is fed by an infeed conveyor into engagement with the sheet. The sheet is draped over the article as it is fed forward onto a main conveyor, the leading edge portion of the sheet being between the article and the conveyor. The trailing edge portion is blown or pushed through a slot in the main conveyor so that it hangs down below the main conveyor. Movement of the article is then interrupted while the main conveyor continues to move.
This causes the trailing edge portion to be carried under the stationary article by the main conveyor so that the leading and trailing edge portions are overlapped. Thereafter, the article is allowed to move with the main conveyor and the overlapped portions are secured together to form a sheath around the article.

Description

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This invention relates to wrapping apparatus and to a method of wrapping.
Accor~ing to-one aspect of the present invention there is provide~ wrapping apparatus comprising a structure on which an article to be wrapped is supported and on which the article is fed along an in-feed path, means for suspending a succession of sheets of material across said path so that each sheet forms a curtain against which one of said articles is fed whereby said sheet is draped over the top of the respective article with leading and trailing portions thereof hanging down adjacent the leading and trailing faces of the article, the trailing portion having an end part, an article supporting conveyor onto which the article is fed from said structure for support and conveyance by the conveyor, a lower part of the leading, hanging portion of the sheet being tucked beneath the article as the article moves onto the conveyor and being held against the underface of the article by said conveyor, the conveyor having a transverse slot, means for urging said end part of the trailing portion of said sheet downwardly thr-ough said slot, and means far then temporarily preventing said article from moving with said conveyor which thus advances with respect to the article whereby said slot carries the said end part of said trailing portion beneath said article and overlaps the said end part of said trailing portion with said lower part of said leading portion.
Said conveyor means can be a roller conveyor including freely rotatable, spaced apart rollers, said slot being formed by the gap between two adjacent rollers.

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11~6~3 Means, such as an air blast or a tucking bar, can be provided for forcing said trailing portion downwardly through said slot. The tucking bar can be mounted on an endless conveyor having an operative run which converges with said conveyor.
Preferably, said bar is pivotally mounted on said endless con-veyor and hangin~ therefrom~
Said means for temporarily preventing the article from moving with the conveyor can comprise a clamp element arranged to move downwardly into contact with the article and prevent movement thereof.
~ ccording to a.further aspect of the present invention there is provided a method of wrapping a sheet of wrapping mat-erial around an article, the method comprising advancing the article along an in-feed path onto a conveyor for support by the conveyor and advance at the same speed as the conveyor, sus-pending a succession of discrete sheets of wrapping material across said in-feed path in advance of said conveyor, each sheet extending to below the article travelling along said in-feed path and each advancing article, when it contacts that one of XO the sheets which is suspended in front of it, causing the portion of the sheet which is hanging down below the article to be tucked between the underside of the article and the con-veyor, the remainder of the sheet being draped over the article with a portion hanging down behind the trailing face of the article, feeding the end part of the said portion of the sheet which is behind said trailing face downwardly through a slot in said conveyor to a level below said conveyor, and then temporarily preventing said article from moving with the con-C ~3~

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veyor so that the conveyor advances with respect to the articleand said end part of said sheet is carried beneath the article by the conveyor slot and overlaps said tucked portion.
In one form of the method the article is held stationary while said trailing part of said sheet is carried beneath the article~ In an alternative form of the method, movement of the article with the conveyor is temporarily inter-rupted by displacing it in the direction opposite to the direction of movement of the conveyor and then releasing it for further O
1 movement with the conveyor.

. For a better understanding of the present invention, :, and to show how the same may be carried into effect, : reference will now be made, by way of example, to:the ,~
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ti2~3 accompanying drawings in which:-Figure 1 is a side elevation of wrapping apparatus;
Figure 2 is a section on the line II-II of Figure l;
Figure 3 is a view taken in the same direction as Figure 1 and showing a modified form of one section of the apparatus;
Figure 4 is a top plan view of the section shown in Figure 3;
Figure S is a detail of a modified form of a part of the apparatus; and Figures 6 to 10 diagrammatically illustrate the wrapping method of the apparatus of Figure 1.

The apparatus illustrated comprises a machine frame 10 including transverse members 12 and two side plates 14. One side plate has been omitted to show the portion of the apparatus between the side plates and a number of transverse members 12 have also been omitted from the drawings to avoid such detail obscuring the working parts of the apparatus.

The apparatus includes a section 16 for severing wrapping material in web form into sheets, a vertical feed structure 18 for feeding sheets of wrapping material down-wardly from the section 16, an article infeed conveyor 20, a main conveyor 22 and a sheet manipulating arrangement 24.

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The framework for supporting these components has largely been omitted from the drawings. The arrangement 24 is mounted between two upward extensions 26 of the side plates 14.

The section 16 comprises a drum generally in-dicated at 28. The drum comprises a cylinder 30 of a material which resists build-up of static electricity.
Nylon is a suitable material and it has been found that a sheet of this can be bent to cylindrical form, transversely welded and then skimmed so as to provide an outer surface which is cylindrical. The ends of the cylinder 30 are closed by discs 32 and 34 (see particularly Figures 3 and 4). A solid shaft 36 protrudes from the disc 32, this shaf*
being rotatably supported in a bearing (not shown) carried by a portion of said framework which projects upwardly from the side plates 14. A hollow, stationary shaft 38 passes through the disc 34, there being a bearing diagrammatically illustrated at 40 (see Figure 4) between the shaft 38 and the disc 34. The shaft 38 forms part of a fan 42. The fan 42 includes a casing 44 in which there is a rotor (not shown) the rotor being driven by a motor contained within a sub-casing 46. The fan outlet is diagrammatically shown at 48. The shaft 38 is supported by a further part of said framework.

The section 16 further includes a cutter unit 50 which is shown in Figures 3 and 4. Only the cutter 52 of the unit has been shown in Figure 1.

The unit 50 is mounted on a pair of radially extending arms 54 which are themselves mounted one on each of the shafts 36 and 38. A cross-bar 56 links the two arms 54 and a wire support arranged parallel to the cross-bar 56 is shown at 58. A wire 60 is carried by the wire support 58, the wire support and wire 60 together forming the cutter 52. Air cylinders 62 have their bodies mounted on the cross-bar 56 and their rods connected to the wire support 58. The cylinders 62 can be double acting. Alternatively, the cylinders can be single acting and return springs can be provided for retracting the wire support 58 after operation of the air cylinders 62.
.' A further air cylinder 64 has its body mounted on a cross member 66 of the machine framework. A flexible wire 64.1 connects the piston of the air cylinder to the cross-bar 56. A spring 68 is connected between the cross-bar 56 and a further cross member 70 of the machine framework.
Further air cylinders, or solenoids, can be mounted on the arms 54. When actuated, these engage the discs 32 or 34 to ensure that the cutter unit moves in an arc with the drum.

A reel 72 (Figure 1) of wrapping material in web form is mounted adjacent the drum 28. The web feeding off the reel 72 is shown at W and it will be seen that this passes between a guide roller 74 and the drum 28 before passing upwardly over the drum and thence, on the remote side of the drum, downwardly between the drum 28 and the vertical feed structure 18.

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2~3 ~ A drive roller 76 is provided beneath the drum 28, this roller being in face-to-face contact with the drum 28 and driving it by frictional contact.

The cylinder 30 is formed with a plurality of apertures 78 (see particularly Figure 4) which pass through the cylinder 30 and thus place the interior of the drum in communication with the exterior.

The vertical feed structure 18 comprises upper and lower shafts 80 and 82 at least one of which is driven. The shafts 80 and 82 carry toothed sprockets 84 and two parallel belts 86 and 88, each toothed on one of their faces, are entrained around the sprockets 84.

Vertically extending vacuum chambers 90 and 92 are provided between the runs of the belts 86 and 88 respectively.
The chambers 90 and 92 are linked by a plenum chamber 94 and a fan 96 is connected to the chamber 94. The downward run of each belt 86 and 88 is in contact with the adjacent face of the respective vacuum chamber 90 and 92.

, Beneath the belts 86 and 88 the walling of each vacuum chamber 90 and 92 has a vertically extending slot 98 (Figure 2) therein, the belts 86 and 88 overlying these slots. The edge regions of the belts 86 and 88, by engaging the longitudinally extending portions of the walling of the vacuum chambers 90 and 92 which lie on each longitudinal g --X~'---:

11~6~73 side of the slots 98, form seals which minimise ingress of atmospheric air into the chambers 90 and 92. Each belt 86 and 88 is formed, throughout its length, with apertures 100 which register with the slots 98.

Simply by way of example, the slots 98 can be approximately 5mm wide and the apertures in the belts 86 and 88 can have a 5mm diameter and be spaced at 25mm centres.

.: ' In Figure 1 the return runs of the belts 86 and 88 are shown as being close to the non-operative faces of the chambers 90 and 92. In Figure 3 an additional pair of guide sprockets 102 are provided, these holding the return runs of the belt away from the chambers 90 and 92. In this form the lower sprockets 84 are somewhat larger than the upper sprockets 84.

The infeed conveyor 20 comprises a pair of chains 104 carrying flight bars 106. The chains 104 are entrained around - sprockets 108. `

A support 110 is provided for the series of articles A which are to be wrapped. The articles A feed from a somewhat raised support 112 onto the support 110 and are moved forward in timed relationship on this latter support by the flight bars 106. It will be seen that the support 110 passes between the belts 86 and 88 (see particularly Figure 2). The left hand end of the support 112 is cyclically tilted upwardly during operation to halt the next article of the incoming series.

~`?~, ~, . ' ~l~tiZ'73 The main conveyor 22 is a roller conveyor and comprises two laterally spaced chains 114 entrained around a series of sprockets 116. The rollers of the conveyor are referenced 118 and these are freely rotatable about their own longitudinal axes with respect to mounting bosses (not shown) carried by the chains.

The main conveyor 22 has a horizontal upper run which is in substantially the same plane as the upper face of the support 110. Chain supports, not shown, can be provided for preventing sagging of the upper run. This upper run passes beneath the sheet manipulating arrangement 24, beneath a brake 120 provided for temporarily interrupting movement of the articles in the feed direction, and into a heat shrink tunnel 122 only the inlet end portion of which has been shown.

The sheet manipulating arrangement 24 comprises two endless chains 124 which are entrained around three sprockets 126, the chains 124 forming an endless conveyor.
The sprockets 126 guide the chains 124 along a triangular path which includes a horizontal return run 128 and an operative run 130 which slopes downwardly and converges with the upper horizontal run of the main conveyor 22. A plurality of tucking bars 132 are pivotally mounted on the chains 124 and hang downwardly therefrom.

b , , 11~6273 The brake 120 is mounted on a cross bar 134 of the machine framework and comprises an air cylinder 136 mounted in a vertical position on the bar 134. The rod 138 of the air cylinder extends downwardly through the bar 134 and carries a plate 140 at the lower end thereof. The plate 140 may be in the form of a disc.

An alternative form of brake is shown in Figure 5.
In this form, the cross-bar 134 carries a rotatable cam 142.
The cam 142 acts on the plate 140 which is guided for vertical movements by means of a stem 144. A slot 146 is provided in this stem and a fixed element 148 passes through the slot. A spring 150 acts between the stem 144 and the fixed element 148 to hold the plate 140 against the peri-phery of the cam 142.

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In use of the apparatus, the drum 28 and the belts 86 and 88 are driven continuously. As the linear speed of the downward run of the belts 86 and 88 must equal the peripheral speed of the drum 28, the driven sprockets 84 and the roller 76 are driven in timed relationship to ensure that this requirement is met.

~ he web W is fed from the reel 72, beneath the guide roller 74 and thence o~er the periphery of the drum 28. The fan 42 creates a sub-atmospheric pressure within the drum 28 so that the air impervious web W is drawn against the periphery of the drum.

1~6Z73 The cutter unit 50 is operated in timed relationship with infeed of articles A by the infeed conveyor 20. For example, a photoelectric cell can be provided, the succession of articles A interrupting the light beam to the photoelectric cell and thereby actuating a solenoid valve (not shown) which feeds air to the air cylinders 62 and 64.

Upon air being fed to the air cylinders 62, the cutter 52 comprised by the wire support 58 and the wire 60 is displaced radially inwardly into engagement with the web W. ~he wire 60 can carry a continuous heating current or, alternatively, a heating current circuit can be completed at the same time as said solenoid operated valve is actuated.
The wire 60 serves to sever a sheet of wrapping material from the web. The sheets are referenced S in Figures 1, 2, 6 etc.

At the time that the air cylinders 62 are actuated to thrust the wire support 58 radially inwardly, the rear chamber of the air cylinder 64 is also subjected to pressure.
Its piston moves faster than does the cutter 52 so that the wire 64.1 goes slack. Under the influence of the spring 68 and the rotation of the drum 28, the cutter 52 swings on the arms 54 in an arc about the common axis of the shafts 36 and 38.

After a timed interval, supply of air to the rear chambers of the air cylinders 62 ceases. If double acting aix cylinders are used, air is immediately thereafter supplied ' ' , 11~6~73 to the front chambers to retract the wire support 58.
Alternatively, if single acting cylinders are employed, then the return springs are effective to withdraw the wire support 58. The cutter unit, however, continues to move with the drum under the influence of the spring 68, and the slack in the wire 64.1 is taken-up. Air is supplied to the front chamber of the cylinder 64 shortly after the wire support is withdrawn from the drum 28 so that the cutter unit 50 is returned to its initial position to commence the next cycle of operations.

Motion of the unit 50 with the drum 28 provides the requisite cutting time without displacing the web on the drum.
Furthermore, as the cutter unit continues to move with the drum while the cutting wire is being withdrawn, there is no tendency for the cutter unit to displace the web. Because suction is constantly applied via the apertures 78 to the radially inner face of the web, the web remains firmly in position on the periphery of the drum.

The vacuum effect created at those apertures 100 which register with the slots 98 is greater than the vacuum effect created at the apertures 78. Consequently, at the region where the belts 86 and 88 run tangentially to the drum 28, the sheets S are transferred from the drum 28 to the belts 86 and 88 and are conveyed downwardly therewith. To assist with this transfer, the drum 28 can be provided with fixed internal partitions such as are shown at 152 in Figure 3. In this form the drum must include a fixed shaft which passes axially therethrough and on which the partitions 152 are mounted.

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Seals are provided between the cylinder 30, discs 32 and 34 and the partitions 152. Between the partitions atmospheric pressure conditions are permitted to prevail. This construc-tion ensures that, at the region where the sheet comes under the influence of suction at the apertures 100, it is not drawn onto the drum 28.

The sheets S are held along their peripheries (see particularly Figure 2) by the belts 86 and 88 and are fed downwardly with the belts.

The leading edge portion L of each sheet passes to a level which is below the upper surface of the support 110. At this stage the sheet forms a curtain ahead of the incoming article A which, at this moment, is fed forward by the flight bar 106 behind it into engagement with the sheet S. As each article is fed forward by one of the flight bars 106, the support 112 tilts downwardly to permit another article to be urged into it. This article in turn feeds onto the support 110 the article already on the support 112.

~, The rate of feed of the article into engagement with the sheet S equals or exceeds the rate of downward feed of the sheet so that, as the article moves onto the upper run of the main conveyor 22, the sheet S is stripped from the belts 86 and 88 without being crumpled and is draped over the article. The configuration of the sheet S immediately after being stripped from the belts 86 and 88 can be seen by referring to Figure 6 and to the centre article of the seven illustrated in Figure 1.

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11~62~73 The portion L is between the article and the rollers 118 of the conveyor 22.

The article moves to the right with the main conveyor and as it does so that one of the tucking bars 132 which is moving down the operative run 130 enters the space between that article and the following article in close proximity to the trailing face of the article.

The tucking bar reaches its lowest position as it passes around the lowermost sprocket 126 and in this condition its lower portion has passed through the transverse slot between two adjacent rollers 118 of the main conveyor 22. It will be seen that the trailing edge portion T of the sheet S, before bein~ encountered by a tucking bar 132, lies on the rollers 118 of the main conveyor 22. As the tucking bar passes between the rollers, it carries the trailing edge portion T of the sheet S through the inter-roller slot with it. This is illustrated in Figure 7 which shows the trailing edge portion T
in its positions before and after being manipulated by the bar 132.
' ' ' As each article passes beneath the brake 120, air is fed to the air cylinder 136. The plate 140, which forms a clamp element, is thus thrust downwardly into engagement with the article. The frictional restraint applied is sufficient to haIt progress of the article in the feed direction. While the article is so held, the rollers 118 rotate as they pass beneath it.

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' The roller 118.1 (Figure 8) which is behind the slot through which the trailing edge portion T of the sheet S hangs, commences to over-run the portion T immediately the article A
ceases to move in the feed direction. This condition is illustrated in Figure 8 from which it will be seen that said slot has moved in the feed direction with respect to the article and the roller 118.1 has commenced to press the portion T against the underside of the article A. An air blower diagrammatically shown at 154 directs a continuous flow of air against the leading edge portion L to hold it against the underside of the article. Any inherent stiffness of the material of sheet S assists in this regard.

As the roller 118.1 moves forwardly with respect to the article A (see Figure 9) more and more of the trailing edge portion T is placed in juxtaposition to the underside of the article A. Eventually the condition of Figure 10 is reached where the trailing and leading edge portions have been overlapped with respect to one another. Once this condition has been reached, the brake 120 is released and the article is free to move once more with the conveyor 22.

As the article enters the tunnel 122, the overlapped trailing and leading edge portions of the sheet S are subjected either to radiant heat from a heating element diagrammatically shown at 156 or are subjected to a heated air blast. This seals the overlapped portions to one another.

Thereafter the entire article is subjected to general heating to shrink the sheet tightly around the article A.

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~' '-' ' When the brake of Figure 5 is employed, timing is achieved by means of the drive arrangement of the cam 142. The configuration of this cam is such that there is a dwell period during which the plate 140 is held in contact with the article.

The céntre-to-centre distance of the series of articles on the conveyor 22 is determined by the spacing of the flight bars 106. The pitch of the bars 132 equals that of the articles.
The brake 120 can be operated in timed relationship with the bars 106. Alternatively there can be a photoelectric cell for detecting the presence at the brake 120 of each article. This cell actuates the brake.

The length of each sheet S depends on the rate of rotation of the drum 28. It will be understood that by changing this rate of rotation without increasing the rate of motion of any other part of the apparatus, or the pitch spacing or size of the articles, a greater or lesser degree of overlap between the trailing and leading edge portions can be obtained. Drum rotational speed can be varied by replacing one of the sprockets (not shown) in the drive to the roller 76 by a sprocket with a different number of teeth.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Wrapping apparatus comprising a structure on which an article to be wrapped is supported and on which the article is fed along an in-feed path, means for suspending a succession of sheets of material across said path so that each sheet forms a curtain against which one of said articles is fed whereby said sheet is draped over the top of the respective article with leading and trailing portions thereof hanging down adjacent the leading and trailing faces of the article, the trailing por-tion having an end part, an article supporting conveyor onto which the article is fed from said structure for support and conveyance by the conveyor, a lower part of the leading, hanging portion of the sheet being tucked beneath the article as the article moves onto the conveyor and being held against the under-face of the article by said conveyor, the conveyor having a trans-verse slot, means for urging said end part of the trailing por-tion of said sheet downwardly through said slot, and means for then temporarily preventing said article from moving with said con-veyor which thus advances with respect to the article whereby said slot carries the said end part of said trailing portion beneath said article and overlaps the said end part of said trailing portion with said lower part of said leading portion.

2. Wrapping apparatus according to claim 1, in which said conveyor comprises a roller conveyor including freely rotatable, spaced apart rollers, said slot being formed by the gap be-tween two adjacent rollers.

3. Wrapping apparatus according to claim 1 and including a tucking bar for forcing the end part of said trailing portion downwardly through said slot.

4. Wrapping apparatus according to claim 3, in which said tucking bar is mounted on an endless conveyor having an operative run which converges with said conveyor.

5. Wrapping apparatus according to claim 4, in which said bar is pivotally mounted on said endless conveyor and hangs therefrom.

6. Wrapping apparatus according to claim 5, and including a series of tucking bars on said endless conveyor, and means for driving said endless conveyor.

7. Wrapping apparatus according to claim 1, in which said means for temporarily preventing the article from moving with the conveyor comprises a clamp element arranged to move downwardly into contact with the article.

8. A method of wrapping a sheet of wrapping material around an article, the method comprising advancing the article along an in-feed path onto a conveyor for support by the conveyor and advance at the same speed as the conveyor, sus-pending a succession of discrete sheets of wrapping material across said in-feed path in advance of said conveyor, each sheet extending to below the article travelling along said in-feed path and each advancing article, when it contacts that one of the sheets which is suspended in front of it, causing the portion of the sheet which is hanging down below the article to be tucked between the underside of the article and the con-veyor, the remainder of the sheet being draped over the article with a portion hanging down behind the trailing face of the article, feeding the end part of the said portion of the sheet which is behind said trailing face downwardly through a slot in said conveyor to a level below said conveyor, and then temporarily preventing said article from moving with the conveyor so that the conveyor advances with respect to the article and said end part of said sheet is carried beneath the article by the conveyor slot and overlaps said truck portion.

9. The method defined in claim 8, in which said article is held stationary while said end part of said sheet is carried beneath the article.

10. The method defined in claim 8, in which movement of the article with the conveyor is temporarily interrupted by dis-placing it in the direction opposite to the direction of move-ment of the conveyor and then releasing it for further move-ment with the conveyor.