US3735557A

US3735557A - Machine for wrapping palletized loads in heat shrinkable plastic film

Info

Publication number: US3735557A
Application number: US00172163A
Authority: US
Inventors: O Hoffarth; T Schuette
Original assignee: Possis Machine Corp
Current assignee: Possis Machine Corp
Priority date: 1970-08-24
Filing date: 1971-08-16
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29
Also published as: DE2142284A1; CA955169A; FR2105927A5; GB1366881A

Abstract

A machine for forming bags of gussetted flat heat sealable web stock, opening the formed bags and drawing them down over palletized loads preparatory to conveying the same into an oven where the bags shrink into intimate contact with the load. The bags are opened by suction cup and claw assemblies mounted on the ends of arms that project from hinged carrier frames between which the palletized load is placed to be enwrapped. The frames swing towards and from one another, and in their innermost positions bring the suction cups into contact with the side panels of the pendently hanging web. This causes the suction cups to attach themselves to the side panels, and that attachment brings about initial retraction of the suction cups. With the side panels held by the suction cups, the claws are actuated to cause them to penetrate and grab the side panels. Outward swinging motion of the carrier frames and downward travel of the arms that carry the suction cup and claw assemblies opens the bag and draws it down over the load.

Description

tent 1 Hoftarth et al.

[ MACHINE FOR WRAPPING PALLETHZED LOADS EN HEAT SHRINKABLE PLASTIC FILM [75] Inventors: Odell H. Hotfarth, Brooklyn Center;

Thomas L. Schuette, Osseo, both of Minn.

[73] Assignee: Possis Machine Corporation, Minneapolis, Minn.

[22] Filed: Aug. 16, 119711 [21] Appl. No.: 172,163

[30] Foreign Application Priority Data Aug. 24, 1970 Great Britain ..40,587/70 [52] US. Cl .53/183, 53/386 [51] int. Cl. .BfiSb 43/30 [58] Field of Search ..53/29, 30, 33, 183,

[56] References Cited UNITED STATES PATENTS 3,62l,638 11/1971 Grocke ..53/386 [451 May 29, 1973 Primary Examiner-Robert L. Spruill Attorney-Ira Milton Jones [57] ABSTRAUH A machine for forming bags of gussetted flat heat sealable web stock, opening the formed bags and drawing them down over palletized loads preparatory to conveying the same into an oven where the bags shrink into intimate contact with the load. The bags are opened by suction cup and claw assemblies mounted on the ends of arms that project from hinged carrier frames between which the palletized load is placed to be enwrapped. The frames swing towards and from one another, and in their innermost positions bring the suction cups into contact with the side panels of the pendently hanging web. This causes the suction cups to attach themselves to the side panels, and that attachment brings about initial retraction of the suction cups. With the side panels held by the suction cups, the claws are actuated to cause them to penetrate and grab the side panels. Outward swinging motion of the carrier frames and downward travel of the arms that carry the suction cup and claw assemblies opens the bag and draws it down over the load.

17 Claims, 17 Drawing Figures PATENTED m29|975 3,735,557

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MACHINE FOR WRAPPING PALLETIZED LOADS IN HEAT SHRINKABLE PLASTIC FILM This invention relates to the shrink-wrapping art, and refers more particularly to a machine for wrapping a palletized load in heat-shrinkable plastic fihn by drawing a tube of such film down over the load.

It is not new to manually apply preformed plastic film bags onto a load piled on a pallet, and then subject the Same to heat to cause the plastic film to shrink into intimate contact with the load and with the edges of the pallet, so that the resulting enwrapment holds the load on the pallet and against derangement. Attempts have also been made to perform this operation by machine, but the machines heretofore available for this purpose left much to be desired. An example of such prior machines may be seen in British Pat. No. 974,529, published Nov. 4, 1964. Also, the article by Martin Siegel in the 1967 issue of Modem Packaging Encyclopedia" (Section 12) fairly well describes the machines then available.

The purpose and object of this invention is to provide an improved machine by which palletized loads can be efficiently and quickly wrapped in heat-shrinkable plastic film.

To that end, the invention provides a machine having conveyor means to advance a palletized load to a wrapping station, hold it there while the load is being wrapped, and then move it into and through an oven in which the plastic fihn enwrapment shrinks into intimate contact with the load and the edges of the pallet. The plastic film is supplied to the machine as a gussetted tubular web drawn from a roll thereof by a pair of nip rolls located above the wrapping station. The nip rolls are cyclically driven and with each cycle draw from the supply roll a length of web long enough to encompass the load to be wrapped.

The roll of gussetted tubular stock is supported in the lower rear portion of the machine, and the web drawn therefrom travels upwardly to the top of the machine and then forwardly over an idler roll to a point over the center of the wrapping station where the nip rolls are located so that the pendent end portion of the web hangs from the nip rolls with its gussets closed and its flat side panels vertical and contiguous to a plane bisecting the load and parallel with its opposite sides.

Lying athwart the path of the web upstream from the nip rolls and in fact between the nip rolls and the idler roll by which the path of the web is changed at the rear of the-machine from substantially vertical to horizontal, there-is a heat sealing device which acts upon the web tose'al at least a portion of each side panel to its adjacent gussets and thereby form at least a partial closure of the tubular stock. That closure limits the extent the tubular web can be pulled down over the load, and assures against having the film pulled away from the upper portion of the load during the heat shrink operation.

A cutoff knife located directly below the nip rolls operates cyclically to sever the web upstream of the heat sealed closure, except for narrow frangible necks that can be broken by a pull thereon. However, the cut-off arranged in opposing relationship and so spaced as to grip the side panels near their edges.

Front and back carrier frames pivotally mounted at their lower ends to swing inwardly towards and outwardly from one another, mount the suction cups. Each carrier frame comprises a pair of upright standards rigidly connected at the top. The groups of suction cups are mounted on the pivoted carrier frames by arms that extend inwardly from crossbars that span the distance between the upright standards of the frames and have their ends fixed to carriages that ride on tracks fixed to the standards, so that the carriages and all structure thereon can move up and down the carrier frames. Power actuated drive means connected with the carriages moves them along their tracks, and through suitable timing means, holds the carriages in their upper positions while the carrier frames are swung inwardly towards one another.

The instant the mouths of the suction cups are closed by the side panels, suction responsive bellows by which the groups of suction cups are connected with their respective supporting arms, contract and retract the suction cups from normally projected positions. This pulls the side panels away from one another and efiects initial opening of the tubular stock. It also enables the suction cups in coaction with the nip rolls to hold the side panels substantially taut. While the side panels are thus held, a group of sharp claws rockably mounted on the outer end of each of the supporting arms directly adjacent to the suction cups thereon, penetrates and grabs the side panels. Since it is only the side panels that are held by the suction cups, the claws do not penetrate the underlying gussets, even though the claws may strike the gussets.

The claws are an important feature of the invention, since it is they that positively engage the side panels and, in so doing, assure opening of the tubular stock and its placement about the load.

With the side panels held jointly by the suction cups and the claws, and especially the latter, the carrier frames swing away from one another and, in so doing, fully open the tubular web, permitting it to be pulled down over the load. Depending upon the height of the load, the cutoff knife acts either before descent of the tubular web past the top of the load or thereafter during such descent, to sever the web except for narrow uncut necks which enable the nip rolls to retain some control over the placement of the tubular web about the load.

The carriages are now moved down along the tracks on the carrier frames and, as they are, the tubular stock knife does not act until groups of front and back sucis drawn down over the load with its bottom end portion extending below the edges of the pallet. During descent of the carriages, the unsevered necks of the web ing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of the embodiment of the invention, and several modifications thereof, constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a perspective view of the wrapping machine of this invention, showing a palletized load in position to be enwrapped;

FIG. 2 is an end view of the machine, also showing a load in position to be enwrapped;

FIG. 3 is an end view similar to FIG. 2, but with the carrier frames that carry the suction cups and claws swung to their innermost positions;

FIG. 4 is an end view similar to FIGS. 2 and 3, but showing the carrier frames returned to their erect positions and the suction cups and claws holding the bottom of the tubular web open, and in light broken lines, showing the web drawn partially down onto the load;

FIG. 5 is a perspective view illustrating the positioned relationship of the heat sealing device, the nip rolls and the cutoff knife which has just acted to form the interrupted cut;

FIG. 6 is a top plan view of the machine;

FIG. 7 is a sectional view through FIG. 2 on the plane of the line 7-7;

. FIG. 8 is a perspective view of one of the suction cup and claw assemblies and of the arm and associated structure by which that assembly is mounted on its carrier frame;

FIG. 9 is a detail sectional view through FIG. 7 on the plane of the line 9-9;

FIGS. 10, 11 and 12 are cross sectional views through the nip rolls and the cutoff knife, illustrating the manner in which the suction cups and claws function to initially open the bottom end of the tubular web;

FIG. 13 is a diagrammatic view in perspective, illustrating the drive means by which the carrier frames are swung in and out and the drive means by which the arms mounting the suction cups and claws are raised and lowered along the carrier frames;

FIG. 14 is a perspective detail view illustrating the manner in which a web consisting of a series of frangibly connected pre-made bags is handled by the machine of this invention and separated from one another by a pair of tear-off rolls coacting with the nip rolls;

FIG. 15 is a top plan view of the tear-off rolls shown in FIG. 14, with portions broken away to enable a larger scale illustration;

FIG. 16 is a perspective view of that portion of the tear-off rolls shown in FIG. 15; and

FIG. 17 is a perspective view of a modified form of suction cup and claw assembly.

Referring to the drawings, the numeral 5 designates generally the frame of the machine which, for convenience may be considered as having a front and a back, with spaced comer posts 6 at the front and spaced pedestals 7 at the rear. The comer posts and pedestals are fixed to and rise up from a base 8 and are connected at the top by a superstructure 9. The space between the front and rear of the machine constitutes the wrapping station into which palletized loads are brought by a conveyor 1 1. Roller tracks 12 and 13, respectively, lead to and from the conveyor, the former coming from a loading station and the latter leading to a shrink oven, neither of which is shown. The conveyor 11 may be of any suitable form, but in the present instance is shown as comprising a pair of side-by-side endless roller chains trained over sprockets and riding on rails, so that the palletized loads can be set directly on the chains, as seen in FIG. 1, which illustrates a palletized load in position to be enwrapped.

At the back of the machine, the pedestals 9 provide a roll stand upon which two rolls RR' of the plastic film stock are rotatably supported. As previously explained, the film stock is in the form of a gussetted tube with overlying side panels SP connected by gussets G, and as drawn from the supply roll is a flat web. Obviously, the stock is drawn from only one roll at a time, the provision for mounting two rolls simply enables maintaining substantially continuous operation of the machine by manually splicing the web drawn from the roll being depleted to the web from a fresh roll.

The nip rolls 14 by which the web of the gussetted tubular film stock is drawn from the supply roll are mounted on the superstructure 9 above the conveyor 11. The web travels along a defined path, which extends upwardly from the supply roll at the rear of the machine over the idler roll 15 and horizontally therefrom to the nip rolls. In the final stretch of its path, the web hangs pendently from the nip rolls which, as hereinbefore noted, are so located with respect to the conveyor that the plane of the pendent end portion of the web bisects the palletized load in position to be enwrapped and is parallel with the sides of the load.

The nip rolls are cyclically driven by drive means, indicated generally by the numeral 16, to iteratively advance the web and bring its open end portion to the aforesaid location hanging pendently from the nip rolls, with its side panels SP in close juxtaposition and its gussets G closed between the side panels.

Mounted on the superstructure 9 and positioned to lie athwart the horizontal stretch of the path of the web, is a heat sealing device 17 by which the overlying plies of the gusseted tubular web are joined to one another. The resulting heat-sealed junction forms the downstream portion of the web into a bag long enough to encompass the load and have its open bottom end extend below the floor of the pallet on which the load is piled. Obviously, by forming the web into a bag, assurance is provided against having the enwrapment pulled from the upper part of the load during subsequent shrinkage of the film.

The heat sealed closure of the web can extend continuously across the full width of the web, or if desired the sealing device can be arranged to seal only a portion of each gusset to its adjacent side panel, so that the top of the load can be left exposed. In some cases, this is an advantage, since it permits water or other fire fighting liquids to reach the load in the event of fire in a warehouse in which the enwrapped palletized loads are stored. The copending application, Ser. No. 46,692, filed June 16, 1970, which is assigned to the assignee of the instant invention, discloses and covers the concept of partially closing the tubular web.

A short distance below the nip rolls, a cutoff knife, indicated generally by the numeral 18, extends transversely across the path of the web. Actuation of this knife severs the pendent end portion of the web from the remainder thereof, except for narrow frangible necks NK (See FIG. 5) that are readily broken by a pull on the pendent portion of the web. Operation of the cutoff knife and of the sealing device is so timed with respect to the rate at which the nip rolls advance the web that the cutoff knife severs the web between the heat sealed closure and the nip rolls.

The details of the heat sealing device and of the cutofi knife will be dealt with later.

Directly after the nip rolls stop and advance of the web is interrupted, the bottom of the pendent end portion of the tubular web is opened. This is done by the two groups of suction cups that are mounted at each side of the pendent web for in and out movement to wards and from the web. The suction cups are mounted on upright carrier frames 21 each of which consists of a pair of spaced standards 22 rigidly connected at the top by a crossbar 23, and pivoted at the bottom to the base as at 24 to swing towards one another from the erect vertical positions shown in FIGS. 1 and 2 to inclined positions depending upon the girth of the load to be enwrapped.

The pivots 24 are spaced from the conveyor 11 a distance sufficient to assure that with the carrier frames in their erect positions, they are far enough apart to accommodate the widest palletized load the machine can handle, as it is moved to and from the wrapping station, and since the standards 22 of each carrier frame are spaced sufficiently far to swing in planes forward and rearward of any load in position to be enwrapped, they clear the load when the frames are in their inclined positions, regardless of height of the load.

Arms 25 that project inwardly from the pivoted carrier frames have the suction cups 20 attached thereto and so locate the same with respect to the carrier frames that when the frames reach their inwardly inclined positions (FIG. 3) the rims of the cups lie in vertical planes to assure full contact thereof with the side panels SP of the pendent web.

The instant the mouths of the suction cups are closed by the side panels SP, suction responsive bellows 26 by which the groups of suction cups are attached to their respective arms 25, contract and retract the suction cups from normally projected positions. This pulls the side panels away from one another and effects initial opening of the tubular web. It is at this time that the suction cups and nip rolls coact to hold-the side panels substantially taut and against any substantial flatwise displacement, so that the groups of the downwardly facing claws 27 can penetrate and grab the side panels as the claws are rocked downwardly and outwardly.

With the side panels positively held by the claws and also held by the suction cups, the carrier frames are swung to their erect vertical positions to fully open the tubular web; and then by lowering the arms the tubular web is pulled down over the load; the unsevered frangible necks NK being torn during the descent.

The machine can be adjusted to handle loads of different girth and can accommodate loads of any height within the capacity of the machine. Quite obviously, for loads of large girth the width of the side panels and of the gussets of the tubular web must be greater than for loads of smaller girth. To accommodate this difference in web dimensions, the distance between the arms 25 on each carrier frame must be adjustable. Also, to open a large sized web (required for loads of maximum girth) the suction cups and claws with the side panels in their grasp must move farther than they do in opening a smaller sized web. Accordingly, the carrier frames must swing through a larger angle for large girth loads than they do for small girth loads; but in all instances the suctioncups must be brought into contact with the pendent web. To enable this to occur regardless of the angle through which the carrier frames swing, the length of the arms 25 must be adjustable; and to assure that the mouths of the suction cups are always vertical when they contact the pendent side panels, the angular disposition of the arms with respect to the carrier frames must be adjustable.

FIGS. 7, 8 and 9 best illustrate the manner in which the several needed adjustments can be made. As there shown, the arms 25 are slidably mounted on a pair of

parallel rods

30 and 31 that span the distance between the standards 21 of the carrier frames and have their ends secured to carriages 32 that travel up and down the standards. That travel is guided by

rollers

34, 35, 36 and 37 on the carriages riding on tracks 38 that are fixed to the standards.

Endless sprocket chains 3 trained about axially aligned sprockets 40 at the top and axially aligned sprockets 41 at the bottom of the standards have the carriages attached thereto so that upon simultaneous powered rotation of the sprockets the carriages are moved up or down in unison depending upon the direction of that rotation.

FIG. 13 illustrates the manner in which the sprockets are driven. As there shown, the sprockets 41 at the bottom of each carrier frame are mounted on a common shaft 42 which also has a driven sprocket 43 fixed thereon. A drive chain 44 trained over the driven sprockets 43, over a drive sprocket 45 and over a plurality of idler sprockets 46 imparts opposite rotation to the driven sprockets whenever a motor 47 that is drivingly connected with the drive sprocket is energized. This motor is reversible and its energization and direction of rotation is governed by a suitable control system (not shown) that includes appropriate sensors responsive to such conditions as the presence or absence of the web at certain locations.

FIG. 13 also illustrates the manner in which the carrier frames are swung in and out. For this purpose the top of each carrier frame is attached at each end thereof to one stretch of an endless sprocket chain 48 trained over horizontally spaced sprockets 4 and 50. The two sprockets associated with each of the carrier frames are mounted on a common shaft 51 and when driven turn in opposite directions by virtue of meshing gears 52 fixed to the shafts 51. To drive the sprockets 49 one stretch 48 of one of the chains is trained over a drive sprocket 53 that is drivingly connected with a reversible motor 54. This motor provides the power source for the drive unit 16 mounted on the superstructure 9. An idler sprocket 55 holds the stretch 48' taut.

As will no doubt be obvious, the various sprockets and shafts involved in the drive system just described, are suitably journaled in bearings mounted on the frame of the machine and on the carrier frames.

To slidably mount the arms 25 on the

rods

30 and 31, each arm has a crosshead 57 with a bore through which the lower rod 30 passes, and a saddle 58 adjustably fixed to the crosshead and embracing the upper rod 31. By sliding the saddle back and forth on the crosshead (lengthwise of the arm) the arm can be tilted up or down so that its angular disposition with respect to the carrier frame can be coordinated with the angle through which the carrier frames swing and the consequent length of the arms, to insure that the mouths of the suction cups will be correctly oriented at the instant they contact the pendent side panels of the web.

Guidance for the relative motion between the saddle 58 and the crosshead is effected by a guideway 59 in the top of the crosshead in which a tongue 60 on the underside of the saddle rides; and to secure the saddle in its selected position of adjustment on the crosshead, slotted rails 61 are fixed to the opposite sides of the crosshead and clamped to the underside of the saddle by screws 62 passing through the slotted rails and threaded into the saddle.

Each arm consists of a pair of parallel flat bars 63 connected at one end by a crosspiece 64 and at the other end by a stamped metal bracket 65. The bars 63 slidably embrace the crosshead and are confined between upwardly facing ledges 66 formed on the sides of the crosshead and the underside of the slotted rails 61, and releasable clamps 66' on the crosshead grip the bars 63 and thereby hold the arms in selected positions of lengthwise adjustment.

The ends of the bars 63 that are connected by the bracket 65 are bifurcated to provide parallel fingers 67 between which a block 68 is slidably received for movement lengthwise of the arms. The block 68 is hollow and forms a manifold through which the suction cups are connected with a source of suction, the cups being mounted on the front face of the block and, of course, in communication with the interior thereof. Secured to the rear of the manifold block, also in communication with the interior thereof is a collapsible bellows 69.

The bellows which forms part of the connection between the manifold block and the source of suction, has a front half 70 and a back half 71, each with a tubular hub. The front half is secured to the manifold block by means of its hub and has a tube 72 fixed thereto and projecting rearwardly therefrom. This tube extends slidably through the hub of the back half 71 and is telescopingly received in a larger diameter tube 73 which is connected by a coupling 74 with the hub of the back half of the bellows. The tube 73 passes slidably through a hole in the crosshead 57 to have its rear end anchored in the crosspiece 64 and there connected with a flexible hose 75 which leads to a stationary suction line and accommodates the motions of the suction cup assembly during operation of the machine.

A spring 76 in the tube 73 bearing against the end of the tube 72 yieldingly maintains the bellows in its expanded condition as defined by the abutment of a stop collar 77 on the tube 72 against the end of the hub of the back half of the bellows; and a port 78 through the wall of the tube 72 inside the bellows enables suction to collapse the bellows when the mouths of the suction cups are sealed by their attachment to a side panel of the web. The collapse of the bellows pulls back the manifold block and since this operation takes place simultaneously at each of the arms 25, the resulting retraction of all of the suction cups effects initial opening of the bottom of the web.

The suction cups carried by each arm are arranged in a horizontal row side-by-side. Such side-by-side disposition of the suction cups results in that portion of the gripped material between adjacent suction cups to be so held that penetration of the claws 27 through the material is assured as the claws are actuated.

Although the specific design of the claws is not critical, the design and construction herein disclosed has been found to be entirely practical. It comprises a U- shaped stamping 80 one flange of which is shaped to provide four sharp sideby-side prongs 81 so spaced that each of the two middle prongs is located between two of the suction cups. The other flange of the stamping is secured to an arm 82 that spans the distance between the bars 63 and is pivoted thereto by a pin 83. An air cylinder 84 is connected between the pivoted arm 82 and the bracket 65 which, as stated hereinbefore, connects the adjacent ends of the bars 63. For this purpose the bracket 65 has a pair of cars 85 formed thereon to lie flat against and be secured to the inner faces of the bars 63.

The dimensions and shape of the U-shaped stamping 80, the length of the pivoted arm 82 and the location of the pivot pin 83 with respect to the suction cups is such that with the suction cups retracted, the prongs 81 (which form the claws) swing downward and rearward from their normal retracted position when the air cylinder is actuated to extend its length, and in doing so readily penetrate the material held by the suction cups. At the completion of the operative stroke of the claws (prongs 81) each of the points thereof digs into an anvil 86 in the form of a rubber block fixed to the front face of the manifold block 68 to clamp the gripped material thereto.

If desired, the individual claws can be provided with shoulders 87 flanking their points, as shown in FIG. 17, to assure a better clamping coaction with the anvils.

The drive unit 16, which as noted hereinbefore, drives the sprocket chains by which the carrier frames are swung in and out, also drives the nip rolls 14 and the cutoff knife 18. To swing the carrier frames in and out the motor of the drive unit is reversible, but no such reversal is needed in the drive for the nip rolls and the cutoff knife, instead it must be intermittent. For this purpose an electric clutch 90 of any suitable conventional design connects one of the nip roll shafts with a driven pulley 91 whenever nip roll rotation is required, and similarly an electric clutch 90 connects the rotatable cutoff knife with a driven pulley 91 when cutoff action is to take place. Both pulleys 90-90 are continually driven by the drive unit through timing belts 91-91. Since no advance of the web is to take place during the interval the carrier frames are swung inward and also no cutoff action takes place during that interval, the reversal in rotation of the drive motor does not interfere with use of the same drive unit for all three functions.

Only one of the pair of nip rolls is driven. It has a solid metal surface and coacts with a series of rubber rings 95 on the other nip roll to maintain good tractive engagement with the plastic web so that by controlling the time and duration for which the electric clutch 90 is engaged the length of web advanced by each operation of the nip rolls can be accurately predetermined.

The cutoff knife consists of a rubber covered roll 96 and a bar 97 to which the knife per se is secured to slightly enter the surface of the roll upon simultaneous rotation of the bar and roll. Obviously only one revolution is involved in a cutoff action, and to assure against difiiculties in drawing the severed length of web down over the load, the edge of the knife has interruptions along its length so that the cut made thereby is not continuous but interrupted to leave the frangible necks NK by which the severed length of web is connected to the remainder of the web.

The heat sealing device 17 employed in the machine illustrated is of conventional form and consists simply of a pair of electrically heated hinged jaws 98-99 that are long enough to span the full width of the widest web and when open have the web pass unscathed therebetween. An air cylinder 100 closes the jaws when a seal is to be made, at which time there is, of course, no advance of the web.

A modified embodiment of the invention, illustrated in FIGS. 14-46, adapts the machine to use with a web consisting of a series of pre-made bags. In this case the machine has no heat sealing device and no cutoff knife. Instead, a pair of tear-off rolls 101 coacting with the nip rolls, tears each bag from the web at the right instant. To facilitate this action, the bags are connected with one another by readily torn connections similar to the frangible necks NK, and to make the tearing action easier, the tear-off rolls function progressively along the length of the tear. To this end one of the rolls has friction pads 102 arranged helically thereon. During advance of the web the tear-off rolls are stationary and the pads 102 thereof are so oriented that they are spaced from the companion smooth surfaced roll and thus do not interfere with advance of the web. However, when the tear is to take place, the tear-off rolls make one revolution while the nip rolls are stationary.

Whether the machine is operating with pre-made bags or the leading portion of a tubular web is successively formed into a bag preparatory to being drawn down over the load, elevation of the arms 25 far enough from their lowermost positions to disengage the claws from the bottom of the bag takes place, before motion of the enwrapped load out of the wrapping station and towards the shrink oven begins.

The operation of the machine will no doubt be readily understood from the foregoing description so that no need for further discussion thereof is needed, except to point out that the required sequential functioning of the various components of the machine is governed by a suitable electro-pneumatic control system. This control system includes suction type sensors 103 mounted on or near the manifolds 68 of the four groups of suction cups 20 to detect whether or not all of the suction cups have properly attached themselves to their respective portions of the web. In the event any one of these sensors detects failure of its respective group of suction cups to attach itself to the web, the control system acts to stop the machine.

The control system also includes other sensors located to be responsive to the arrival of the web at predetermined locations and to the completion of operations performed by the various components of the machine.

Those skilled in the art will appreciate that the inven tion can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims:

1. In a machine for wrapping a load presented to the machine on movable load supporting means, in plastic film wherein the film in the form of a flattened gussetted web is drawn from a roll thereof and fed along a defined path which includes a vertical stretch in which the web moves downward towards the load with its gussets closed and its side panels in close juxtaposition and pendently vertical, and which path passes through a cutoff station and a heat sealing station at which, respectively, a length of the leading portion of the vertical stretch of the web is severed from the rest of the web and overlying portions of the trailing end of the severed length are heat sealed to form at least a partially closed upper end for said severed length, said machine being characterized by improved means for opening the gussetted web and pulling it down over the load, and which improvement comprises:

A. nip rolls located downstream from the cutoff and heat sealing stations by which the gussetted web is iteratively advanced and by which the trailing upper end portion of the severed length of web is held from dropping down onto the load until its bottom end has been opened;

13. a plurality of suction cups, each operable to attach itself to a side panel of the web;

C. movable mounting means mounting certain of said suction cups at each of the opposite sides of the pendent portion of the web, and operable to move the same inwardly towards the pendent portion of the web to positions at which the suction cups do attach themselves to the side panels of the web and outwardly to draw the side panels apart and in so doing coact with the nip rolls to hold the side panels against any substantial flatwisedisplacement, there being at least one pair of suction cups to engage each of the opposite side portions of each side panel; and

D. movable claw means located between the suction cups of each pair thereof operable to penetrate and grasp the held side panels.

2. The machine of claim 1, wherein said movable mounting means mounts the claw means as well as the suction cups for inward movement towards and outward movement from said vertical stretch of the web in defined paths sufficiently above the load supporting means as to be above a load thereon, the suction cups and claw means when in their outer positions being horizontally spaced apart sufficiently to clear a load on the load supporting means and in their inner positions being contiguous to the pendent side panels.

3. The machine of claim 2, further characterized in that said movable mounting means further provides for vertical movement of the suction cups and claw means to draw the tubular web down around a load on the load supporting means; and means for actuating said movable mounting means to effect said defined movements of the suction cups and claw means.

4. The machine of claim 3, wherein said movable mounting means for the suction cups and the claw means comprises:

A. an upright carrier frame at each of two opposite sides of the load supporting means;

B. pivot means at the bottom end of each of said carrier frames, mounting the same for swinging motion about a horizontal axis towards and from said vertical stretch of the path of the web; and

C. arm means on said upright carrier frames projecting inwardly therefrom and having the suction cups and the claw means mounted on the free ends thereof.

5. The machine of claim 4, wherein the suction cups are mounted on the arm means by collapsible bellows which, upon being collapsed, draw the suction cups towards the carrier frames.

6. The machine of claim 4, further characterized by:

A. a pair of endless sprocket chains trained over spaced apart axially aligned upper and lower sprocket pinions at the upper and lower ends of each carrier frame; and

B. cross bars attached to their ends to the same stretch of each of said endless sprocket chains, said arm means being mounted on the cross bars so that rotation in unison of one of the sprocket pinions for each chain moves the arm means up or down depending upon the direction of such rotation.

7. The machine of claim 6, wherein said crossbars hold the arm means so oriented when the pivoted carrier frames are in their innermost positions that the mouths of the suction cups have their edges lying in vertical planes and hence parallel to the pendent side panels of the web.

8. The machine of claim 6, wherein the mounting of the arm means on the crossbars provides for adjustment of the location of the arm means lengthwise of the crossbars to accommodate webs of different widths.

9. The machine of claim 8, wherein the length of the arm means is adjustable, to enable the distance the suction cups and claw means are spaced from the carrier frames to be coordinated with the girth of the load to be enwrapped.

10. The machine of claim 1, wherein the suction cups of each pair thereof are spaced horizontally, wherein the suction cups are mounted on the arm means by collapsible bellows which, upon being collapsed, draw the suction cups toward the carrier frames,

whereby the stretch of the side panel between each pair of suction cups is pulled outwardly and the portion thereof directly above said stretch assumes a partially horizontal disposition, and

wherein the claw means move with a downward motion to penetrate said portion of the side panel.

11. The machine of claim 10, wherein the claw means move with an outward as well as a downward motion, and further characterized by anvil means between each pair of the suction cups, and against which the claw means clamps the adjacent portion of the side panels.

12. The machine of claim 11, further characterized in that each claw means has a sharp claw projecting from a shoulder, the latter forming a clamping surface to coact with the anvil.

13. The machine of claim 1, wherein said web of gusseted tubular stock is in the form of a series of premade bags joined to one another by frangible connections, and further characterized by a pair of tear-off rolls beneath the nip rolls, operable to grip the web and coact with the nip rolls to tear the frangible connections.

14. The machine of claim 13, wherein said tear-off rolls have means to cause the frangible connections to be progressively torn along the length thereof.

15. The machine of claim 14, further characterized in that said means to effect progressive tearing of the frangible connections comprises:

gripping pads on one of said tear-off rolls arranged helically thereon and adapted to successively clamp the web against the other of said tear-off rolls.

16. The machine of claim 1,

further characterized by sensor means located to sense attachment of the claw means to the side edge portions of both side panels, and operable to effect stoppage of the machine in the event either side edge portion of either side panel is not held by claw means.

17. The machine of claim 4, wherein the cut-off station has cutoff means operable to sever the web downstream of the nip rolls; and further characterized by powered drive means; and motion transmitting means connecting said powered drive means with the nip rolls, the cutoff means and the carrier frames, to effect swinging motion of the latter to carry the suction cups and claw means towards and from said vertical stretch of the path of the web in timed relation with the functioning of the nip rolls and the cutoff means.

Claims

1. In a machine for wrapping a load presented to the machine on movable load supporting means, in plastic film wherein the film in the form of a flattened gussetted web is drawn from a roll thereof and fed along a defined path which includes a vertical stretch in which the web moves downward towards the load with its gussets closed and its side panels in close juxtaposition and pendently vertical, and which path passes through a cutoff station and a heat sealing station at which, respectively, a length of the leading portion of the vertical stretch of the web is severed from the rest of the web and overlying portions of the trailing end of the severed length are heat sealed to form at least a partially closed upper end for said severed length, said machine being characterized by improved means for opening the gussetted web and pulling it down over the load, and which improvement comprises: A. nip rolls located downstream from the cutoff and heat sealing stations by which the gussetted web is iteratively advanced and by which the trailing upper end portion of the severed length of web is held from dropping down onto the load until its bottom end has been opened; B. a plurality of suction cups, each operable to attach itself to a side panel of the web; C. movable mounting means mounting certain of said suction cups at each of the opposite sides of the pendent portion of the web, and operable to move the same inwardly towards the pendent portion of the web to positions at which the suction cups do attach themselves to the side panels of the web and outwardly to draw the side panels apart and in so doing coact with the nip rolls to hold the side panels against any substantial flatwise displacement, there being at least one pair of suction cups to engage each of the opposite side portions of each side panel; and D. movable claw means located between the suction cups of each pair thereof operable to penetrate and grasp the held side panels.

4. The machine of claim 3, wherein said movable mounting means for the suction cups and the claw means comprises: A. an upright carrier frame at each of two opposite sides of the load supporting means; B. pivot means at the bottom end of each of said carrier frames, mounting the same for swinging motion about a horizontal axis towards and from said vertical stretch of the path of the web; and C. arm means on said upright carrier frames projecting inwardly therefrom and having the suction cups and the claw means mounted on the free ends thereof.

6. The machine of claim 4, further characterized by: A. a pair of endless sprocket chaIns trained over spaced apart axially aligned upper and lower sprocket pinions at the upper and lower ends of each carrier frame; and B. cross bars attached to their ends to the same stretch of each of said endless sprocket chains, said arm means being mounted on the cross bars so that rotation in unison of one of the sprocket pinions for each chain moves the arm means up or down depending upon the direction of such rotation.

10. The machine of claim 1, wherein the suction cups of each pair thereof are spaced horizontally, wherein the suction cups are mounted on the arm means by collapsible bellows which, upon being collapsed, draw the suction cups toward the carrier frames, whereby the stretch of the side panel between each pair of suction cups is pulled outwardly and the portion thereof directly above said stretch assumes a partially horizontal disposition, and wherein the claw means move with a downward motion to penetrate said portion of the side panel.

13. The machine of claim 1, wherein said web of gusseted tubular stock is in the form of a series of pre-made bags joined to one another by frangible connections, and further characterized by a pair of tear-off rolls beneath the nip rolls, operable to grip the web and coact with the nip rolls to tear the frangible connections.

15. The machine of claim 14, further characterized in that said means to effect progressive tearing of the frangible connections comprises: gripping pads on one of said tear-off rolls arranged helically thereon and adapted to successively clamp the web against the other of said tear-off rolls.

16. The machine of claim 1, further characterized by sensor means located to sense attachment of the claw means to the side edge portions of both side panels, and operable to effect stoppage of the machine in the event either side edge portion of either side panel is not held by claw means.