US3738079A

US3738079A - Bag type shrink wrapping apparatus

Info

Publication number: US3738079A
Application number: US00114637A
Authority: US
Inventors: R Rudman; L Adams
Original assignee: AUBURN ENG Inc
Current assignee: AUBURN ENG Inc
Priority date: 1971-02-11
Filing date: 1971-02-11
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12

Abstract

In a machine for enclosing a palleted load in shrink-wrap film, a flattened tubular sheet of shrink-wrap film is fed downwardly between pinch rolls to a predetermined level where the leading end is in a plane disposed between two oppositely moving gripping bars that are carried on a vertically reciprocable carriage, the carriage being at its uppermost limit of travel. The two bars move toward each other and approach opposite faces of the leading end of the flattened tube. Gripping the opposite faces of the flattened tube, the bars move apart and the carriage starts its descent, opening the leading end of the film into a four-sided configuration while drawing the open end down over a load centered beneath the pinch rolls. When the required length of tube is so pulled down, the tube is sealed with a transverse seal and severed above the seal. The severed length, now a tubular bag sealed across the top continues to have its lead end, still gripped by the bars, is pulled the remainder of the distance down over the load until its lower end is below the deck of the pallet when the bars release the films and the carriage moves up to its uppermost position prepared to repeat the cycle. An electric eye mechanism is provided that determines the height of the load and determines when the transverse sealing and cut off is to take place so that the length of each successive length of film is automatically measured and cut to the height of the load.

Description

United States Patent Rudman et al.

[ June 12, 1973 BAG TYPE SHRINK WRAPPING APPARATUS [75] Inventors: Regis M. Rudman, Braddock;

' Lawrence D. Adams, Pittsburgh,

both of Pa.

[73] Assignee: Auburn Engineering, Inc.,

Pittsburgh, Pa.

[22] Filed: Feb. 11, 1971 [21] Appl. No.: 114,637

[52] U.S. Cl 53/66, 53/183, 53/386 [51] Int. Cl..... B65b 1/02, B65b 43/30, B65b 57/12 [58] Field of Search 53/30, 184, 183,

[56] References Cited UNITED STATES PATENTS 3,308,601 3/1967 Masters 53/256 3,429,095 2/1969 Huson 53/24 3,112,586 12/1963 Luetzow .53/256 X 3,029,571 4/1962 Douthit 53/66 3,676,980 7/1972 Engelhardt et al.

3,621,638 11/1971 Grocke 53/184 X FOREIGN PATENTS 0R APPLICATIONS 1,925,664 1l/l970 Germany 53/183 Primary Examiner-Robert C. Riordon Assistant Examiner-E. F. Desmond Attorney-Parmelee, Utzler & Welsh [57] ABSTRACT In a machine for enclosing a palleted load in shrinkwrap film, a flattened tubular sheet of shrink-wrap film is fed downwardly between pinch rolls to a predetermined level where the leading end is in a plane disposed between two oppositely moving gripping bars that are carried on a vertically reciprocable carriage, the carriage being at its uppermost limit of travel. The two bars move toward each other and approach opposite faces of the leading end of the flattened tube. Gripping the opposite faces of the flattened tube, the bars move apart and the carriage starts its descent, opening the leading end of the film into a four-sided configuration while drawing the open end down over a load centered beneath the pinch rolls. When the required length of tube is so pulled down, the tube is sealed with a transverse seal and severed above the seal. The severed length, now a tubular bag sealed across the top continues to have its lead end, still gripped by the bars, is pulled the remainder of the distance down over the load until its lower end is below the deck of the pallet when the bars release the films and the carriage moves up to its uppermost position prepared to repeat the cycle. An electric eye mechanism is provided that determines the height of the load and determines when the transverse sealing and cut off is to take place so that the length of each successive length of film is automatically measured and cut to the height of the load.

7 Claims, 8 Drawing Figures Futurism-12 V 3.138.019

IN VEN TORS REE/S M. RUDAM/V and LAWRENCE D. ADAMS "M, M 7 IZZX their Attorneys Pmmmmzma 3.738.079

m1 2 I s INVENTORS REG/5 M. RUDfiMN and LAWRENCE D. ADAMS Mew M M air Attorneys Pmmenm 3.736.079

sm 3 I 5 76 mcuuu INVENTORS REG/S AI. RUDMAN and LAWRENCE D. ADAMS Mair Allarnoys 1 BAG TYPE SHRINK WRAPPING APPARATUS This invention is for an apparatus which we term a bagger, the purpose of which is to surround a load supported on a pallet or the like with shrink-wrap film, and is for an improvement in apparatus for this purpose disclosed in pending application Ser. No. 68136, filed Aug. 6, 1968, and Ser. No. 7741, filed Feb. 2, 1970, and assigned to our assignee. i

The invention will be herein described specifically in connection with the enclosure in a shrink-wrap film of an article or a prearranged load of articles carried on a pallet but this is by way of illustration, and not by way of limitation, and the invention may apply to an article or load carried on a support other than a pallet.

In both of the two applications for patent herein above referred to, there is disclosed an apparatus including a supporting frame structure through which a roller conveyor extends. The palleted load to be wrapped is moved along said roller conveyor to a position centered beneath the overhead structure. Flattened tubular shrink film sheeting feeding down between pinch rolls from the top of the structure well above the top of the load is first opened out by gripping means that moved opposed faces of the flattened tubular film strip in opposite directions to open the leading end of the tube into a substantially square or four-sided configuration tapering tent-like upwardly,. but with its leading end opened out enough to be freely pulled down over the load. At the proper time the flattened tube which has been transversely heat-sealed is cut off, so that the length which is cutoff and sealed across the top becomes a detached inverted bag or wrapper open at its lead end and closed at its trailing end. The means which open the flattened tube continues to pull it down around the load to a position where the lower end of the bar is below the deck of the pallet with the closed upper end then extending across the top of the load to be wrapped. With the wrapper thus pulled down over the load, the gripping means releases the film. The severed end of the tubular sheet extending down from the pinch rolls provides the lead end of the wrapper or enclosure for the next load.

It was originally proposed in said first-filed application that the flattened tubular wrapper be opened out by oppositely traveling endless belts with suction cups that gripped opposite faces of the flattened tubular film sheet, and after opening it to a generally square shape, would transfer it to vertically traveling suction belts that pulled the opened tube or bag down around the palleted load. This arrangement was thereafter changed by dispensing with suction belts, and in place thereof opposed carriages were provided to simultaneously move up and down in the frame at opposite sides of the load. These carriages are each provided with gripping means at the free end of a swinging side frame arrangement pivoted to the carriage so that it may swing in a vertical arc downwardly from a horizontal position when the carriages are at the upper limit of their travel in the frame to a depending vertical position alongside their respective carriages. There is a combined suction and mechanical pinching or gripping means on each such swinging frame arrangement. As the flattened tubular sheet is lowered by pinch rolls, it moves between the then confronting gripping means on the free ends of the swinging frame structures which are then outstretched horizontally toward each other.

The opposite faces of the leading end of the flat tubular sheet are pulled apart by suction and mechanically gripped by the respective gripping means, whereupon the pivoted side frames swing down, opening the tube out, and the carriages also move down, pulling the opened tube down over the load. As in the arrangement first described, the flattened tube is sealed and cut off to form an inverted bag, and when the leading end of the bag so formed is below the level of the deck of the pallet, the gripping means releases the bag, the carriages lift and the hinged side frames move up to a horizontal position ready for the next cycle.

The present invention relates generally to a further modification of this type of apparatus, but the mechanism is more positive in its operation but simpler and less cumbersome than the two mechanisms previously described. In the present apparatus the swinging side frame members and the endless suction belts are replaced in a machine having a generally similar frame and conveyor table, but in this case, there is one single carriage movable vertically in the supporting frame between upper and lower limits.

The carriage has two opposed bars extending horizontally thereacross, which are movable toward and away from each other between a closed position close to the plane of downward travel of the film strip to a separated position where they are near opposite sides of the supporting frame. Each of these bars has suction cups thereon at intervals therealong which initially suck the two opposite faces of the flattened tubular film strip against the bars so that as the bars start to move apart, the lead end of the film strip is slightly opened. Each bar also has a rotatable shaft thereon with gripping fingers therealong. As the lead end of the flat tubular film strip starts to open, this shaft is rotated, bringing the gripping fingers from a normally generally horizontally extending position to a vertical position inside the partially opened end of the tubular strip, thereby mechanically clamping the flattened sides of the strip against the respective bars. With this arrangement suction is required to only initially effect separation of the two faces of the flattened strip, after which these faces are mechanically clamped. As the bars move apart, the carriage starts to move down, and they are at the outermost limit of travel well before the carriage reaches the level of the top of the load to be wrapped. The carriage then continues to travel down, pulling the tube which has been opened to a square configuration, tapering, however, in a tent-like fashion toward the pinch rolls, down around the load. At the proper time the strip is heat-seamed and cut off just above the heat seam so that the cut-off portion is an inverted tubular bag. When the carriage has moved to a level where the bars are below the deck of the pallet, the respective shafts are rotated to return the gripping fingers to a normal position and release the two sides of the film. Thereupon the carriage returns to its uppermost limit of travel for the next cycle of operation.

In addition there is provided means for determining the level at which the film strip is to be sealed so that as loads of different height move into the apparatus, the inverted bag which is formed in the manner described will be longer or shorter, depending upon the height of the load. This mechansim includes an electric eye which is shaded from an energizing light source when a pallet moves between it and the light source. The electric eye is on an endless chain which travels up until the eye can see" the light over the top of the load. This will stop the upward movement automatically. The upward movement of the eye, however, moves a limit stop downwardly from an uppermost position to the level determined by the electric eye. This stop is engaged by a switch on the carriage. When the switch on the carriage engages the stop, the sealing and cut-off mechanism will operate. The lower the stop is moved by the electric eye, the longer will be the travel of the carriage before the sealing and cutting takes place, so that the inverted bag will be longer where a longer bag is required, and shorter where a shorter one is required.

The invention may be more fully understood by reference to the accompanying drawings, in which:

FIG. 1 is a front elevation looking into the entrance end of the machine with the load-supporting conveyor being shown in section, the view .also indicating the load in broken lines, and the inverted bag is illustrated with the movable frame and gripping means indicated in phantom lines,

FIG. 2 is a side elevation view of FIG. 1 with certain control panels being shown in dotted lines;

FIG. 3 is a top plan view of the machine;

FIG. 4 is a fragmentary side elevation on a larger scale of one of the corner posts of the supporting frame with the electric eye indexing device for adjusting the machine to the wrapping of loads of different heights;

FIG. 5 is a transverse section view of the upper portion of the machine, the view being in substantially the plane of line VV of FIG. 1;

FIG. 6 is a fragmentary perspective view of a portion of one of the movable loads on the carriage with one of the suction cups and with the load with the gripping fingers and means for rotating the load;

FIG. 7 is a similar view showing the pinch rolls, the sealing and cut-off device, and the two oppositely movable bars which are on the carriage;

FIG. 8 is a diagrammatic view showing in section the typical way in which the flat tubular sheet is usually folded.

In the drawings, 2 designates the base of a flat arch type frame having four corner posts 3 and 3', corner posts 3 being at one side of the arch, and 3' at the other. A conveyor belt 4 passes through the arch and it is supported on a roller frame 5. The return flight of the belt is indicated at 6 in FIG. 3. The top of the frame comprises rigid structural members 7 connecting the tops of the corner posts 3, and 7 connecting the tops of the corner post 3. The members 7 and 7' are parallel with each other and with the longintudinal axis of the conveyor. Other

structural members

8 and 8 extend at right angles to members 7 and 7' and they extend crosswise above the top of the conveyor.

As seen in FIG. 1, there is ample clearance between the edges of the conveyor and the sides of the framework, and the conveyor is centered on a pass-line through the frame. This figure also shows that a load L on a conventional pallet P will be well clear of the sides of the frame. This view also shows that the conveyor is elevated above the base 2 of the frame and that a typical palleted load 1., which may be shorter or taller than that indicated, is well below the sturcture at the top.

There is a vertically movable carriage, designated generally as 10, guided in the frame for vertical up and down travel, and which is normally in a raised position at the top of the frame, but which may travel downward to a level below the top of the pallet P, or close to the level of the conveyor belt 4, the phantom lines showing parts of the carriage near its lowermost limit of travel.

As here shown, the carriage has four shoes or trolleys 11, one on each corner post. Each shoe has two spaced rollers 12 that roll on strips or rails 13 on confronting faces of the two corner posts 3'. Each shoe also has two other spaced rollers 14 positioned at right angles to rollers 12 that roll on strips or rails 15 on the confronting faces of each opposite pair of corner posts 33. As most clearly seen in FIG. 2, this carriage has parallel upper and lower bars 16 which connect each two of these shoes which are on the same side of the frame, and by reference to FIGS. 1 and 5, it may be seen that there is a transverse cross bar 17 at each side of the carriage extending crosswise over the conveyor between the shoes on each opposite pair of

corner posts

3 and 3.

For moving the carriage 10 up and down, there is an elongated loop type connector 20 on each side of the carriage which is secured to the upper and lower rails 16 (see FIG. 2.) There is a looped sprocket chain 21 on each side of the frame, having one end anchored to the top of this connector. It extends up over and idler sprocket 22 on one of the longitudinal top cross members, then over a sprocket 23 on a transversely extending driven shaft 24 in the upper part of the supporting frame. Then it passes down near a corner of the frame to an idler sprocket 25 on the bottom structure 2 and then laterally around a second idler sprocket 26 mounted on the base 2 at a position directly under the connector 20. The chain extends up from the sprocket 26 to the lower end of the elongated connector 20 to which it is anchored, providing in effect an endless loop.

FIGS. 1 and 3 indicate schematically a drive for shaft 25. There is a reversible fluid pressure motor 30 mounted on a supporting bracket fixed to the upper portion of the frame. This motor is coupled to a shaft 31 on which is fixed a sprocket wheel 32 and at 33 is a hydraulic brake. A sprocket chain 34 passes around sprocket wheel 32 and a sprocket wheel 35 fixed on the shaft 24. When the fluid pressure motor operates, shaft 24 is driven to drive the chain-loops 21 at each side of the frame to move the carriage 10 up or down, and when the motor is stopped, the brake 33 is set.

The purpose of the carriage is to open out a flat tubular sheet of shrink wrap film and pull it down around the load to be enclosed. The flattened tubular film is generally folded in the manner schematically indicated in FIG. 8. In this figure, W represents the flattened tube having two opposed flat faces W and two infolds W, each infold reaching almost to the center line of the flat tube so that when the flat faces W are pulled apart, the infolds W open out to a width almost equal to faces W, and the tube when opened in this way assumes a generally square configuration.

There are one or more rolls 40 of flattened tubular film rotatably mounted on the top of the frame structure, each roll having a core and a central shaft 41. The ends of each shaft 41 extend into notches in opposed bearing blocks 42 carried on the

cross members

8 and 8, the arrangement being such that an empty core and shaft can be lifted out of its bearings and a replacement roll with its core and shaft set in its place.

There are opposed pinch rolls 45 and 46 supported in bearings on the cross beams 8 and 8 and they extend in the same direction as the conveyor belt above the center line of which they are located, on each side of the central plane. One of these pinch rolls 45 has a pinion 47 on its shaft at one end, the pinion having a ratchet (not shown) so arranged that when the gear rotates counterclockwise as viewed in FIG. 5, the roll 45 will be rotated, but on reverse rotation the pinion will not rotate the roll. Also this ratchet arrangement allows the roll 45 to rotate or free-wheel relative to the pinion in a counterclockwise direction. There is a fluid pressure cylinder and piston unit 49 fixed to the beam 8 with its piston rod comprising a rack 50 that engages pinion 47. In FIG. 5, the piston rod is retracted, but when it is extended, it rotates the pinion 47 to drive the roll 47 a predetermined distance. Limit switches or limit

valves

51 and 52 may adjustably limit the travel of the rack. Because of the confronting engagement of

rolls

45 and 46, the roll 46 which is an idle roll is driven by rotation of roll 45.

There is a bracket 55 on each of the cross beams 8 and 8', and these support an idler roller 56 positioned to quite the flattened tubular sheet from one of the rolls 40 vertically into the bight of the pinch rolls 45 and 46 (See FIG. 5.) The bearings for the pinch roll 46 are carried on arms 57, one of which is pivoted at 58 to bracket 55. A fluid pressure cylinder and piston unit 59 has the cylinder anchored to the cross bar 8, and its piston rod connected at 60 with one of the arms 57. With this arrangement the pinch roll 46 can be pulled away from roll 45 to open them or pressed into cooperative contact with roll 45. This enables the easy threading of the flat tubular film strip between the rolls when a new roll is being started, and it also enables the film strip to be freely pulled between these rolls when the film strip is being pulled down by the carriage, as hereinafter described.

Fixed to the upper part of the frame structure just below the pinch rolls is a combined cut-off and heatsealing unit designated generally as 65. It comprises a fixed channel-like bar structure 66 under pinch roll 46. There is a knife 67 on one reach of an endless cord 68 that passes around pulleys (not shown) at each end of the member 69. By operating this unit, the bar 69 may be oscillated through an arc to clamp and fuse the film sheet.

As hereinafter described, at some interval after the sealed end of the flat tubular film has been released and drops away, the fluid pressure cylinder and piston unit is operated to move the rack 50 to drive the pinch rolls and feed a predetermined length of film down toward the carriage l0.

At each side of the carriage the upper longitudinally extending frame members for a shaft 76 near each end thereof providing bearings for a shaft 76 along each side of the frame (See FIG. 3). Each shaft has a sprocket wheel 77 near each end. There is a sprocket bar structure 66 so that the knife may be drawn alternately in one direction to make one cut, and in the opposite direction to make the next cut in a manner well known in the art and as more fully explained in the said copending applications, and particularly the secondfiled one. One common mechanism for this purposes utilizes a fluid pressure cylinder with a piston and a piston rod that extends from each end of the cylinder and opposite ends of the cord are connected to the ends of the piston so that travel of the piston in one direction moves the knife on the first cut and the opposite direction it reverses the travel of the knife for the second cut. As viewed in FIG. 5, the channel 65 faces toward the right and there is a confronting channel-shaped element 69 carried on a cross shaft so that it may be oscillated about the axis of the shaft from the open position shown in FIG. 5 to a closed position where it flanges will clamp the tubular film sheet above the below the knife 67 to keep the film taut while it is being cut by the transverse travel of the knife. The lower flange 70 of this channel is electrically heated so that it will fuse a transverse seam across the tubular sheet just below the plane of the cut. For oscillating the channel-like bar structures 69, there is a cylinder and piston unit 71 with the cylinder pivotallyanchored to the frame and the free end of the piston rod is pivotally attached at 72 to chain 78 extending crosswise of the carriage between each of the aligned sprocket wheels on these two shafts. The sprocket chains 76 extend crosswise of the conveyor, and they have upper and lower reaches, see FIG. 8, and, of course, the upper reach moves in a direction opposite to the lower one when the shafts 76 are rotated. A reversible hydraulic motor 79 is indicated in FIG. 3 for rotating one shaft 76.

There are two

rigid bars

80 and 81 extending lengthwise of the carriage. As most clearly seen in FIG. 5, bar 80 is attached at its opposite ends to the lower reaches of the sprocket chain 78 and the bar 81 has its opposite ends attached to the upper reaches of the cahins 78 through vertically elongated connectors 82, the arrangement being such that the two

bars

80 and 81 travel in the same horizontal plane at the same rate, but in opposite directions when the chains 78 are driven. Each bar has a supporting trolley 83 at its opposite ends that rides on a narrow strip or track 84 at each end of the frame, so that the bars travel in a common horizontal plane. Their range of travel is between a mid position where they are in close confronting relation at each side of the path of travel of the descending flattened tubular film strip to a spread or open position where they are near opposite sides of the fixed frame structure.

As shown in FIGS. 3, 5, and 6, bars 80 and 81 have a plurality of suction ports or suction cups 85 on the confronting faces thereof, the cups being at spaced iritervals, three such cups being shown on each bar, one at the center and one at each side of the center at a location near the edges of the flat tubular strip that extends down between the two bars. Each cup has a flexible suction tube 86 connected thereto, these tubes leading to a common hose or duct (not shown) that connects with the inlet of a motor-driven suction pump unit 87, this unit being also mounted on the carriage 10.

Each of the

bars

80 and 81 also has a rock-shaft 90 supported thereon in spaced parallel relation thereto.

.Each rock shaft 90 has a gripping finger 91 thereon in front of each suction cup 85 that normally extends at a slightly downwardly and outwardly sloping angle from the rock-shaft, and which has an enlarged disklike pad 92 at its free end. When the rock-shaft is rotated through an arc of about 90, the pad 92 will cover and press against the suction cup adjacent to which it is located.

Each of these rock-shafts 90 may have a torsion spring, as indicated at 93, which biases the rock-shaft to turn to the position shown in FIG. 6, but each has its own means for rotating it through an arc of 90 or so. This means comprises a non-rotatable sleeve 94 slidable lengthwise on the rock-shaft. It has a helical slot 95 extending therealong. The rock shaft has a pin 96 thereon which has a sliding fit in the slot 95 so that as the sleeve slides back and forth along the rock-shaft, the rock-shaft will be turned one way or the other. The sleeve is reciprocated relatively to the rock-shaft and held against rotation by being fixed at one end to an arm 97 fixed to the piston rod 98 of a fluid pressure cylinder and piston unit 99, which unit is secured to the

bar

80 or 81 on which it is carried. By operating these fluid pressure units simultaneously, both rock-shafts will be rotated in unison.

In the operation of the gripping means, it may be assumed that lead end of the flat tubular film strip has been lowered to a level where the end is in the plane of travel of the

bars

80 and 81. The chains 78 are operated to bring the

bars

80 and 81 to their mid position substantially against the lead end of the film strip. The suction cups of the opposed bars will then be close to opposed faces of the flat tubular strip and these faces of the strip will be sucked against the suction cups of the respective bars which will then move slightly away from each other, opening out the end of the strip as shown in FIG. 7, and then the rock-shafts will be rotated in the manner described to bring the gripping fingers 91 to a position where the single thickness of plastic film is clamped by the pad 92 tightly against the suction cups and the two faces of the flattened tube then firmly clamped to the

bars

80 and 81. These bars continue to move away from each other until the lead end of the tubular film is opened to a four-sided configuration, tapering, however, to the flat configuration at the exit from the pinch rolls. While FIG. 7 for purpose of illustration shows the seal and cut arrangement 65 in the closed sealing and cut-of position, these parts at this time are actually in the open position shown in FIG. 5.

As the tube is being opened out, the carriage 10 begins to move down. The central area of the carriage itself is an open square that can be lowered around the palleted load centered beneath it without an obstruction that will strike the top of the load. As the downward travel of the carriage continues and the

bars

80 and 81 reach their full open position, the open end of the film will be pulled down around the load. The pinch rolls 45 and 46 are desirably spread apart at this time so that the tubular film strip will unwind easily from the roll as it is pulled down by the travel of the carriage.

When sufficient film has unwound, the cylinder 71 of the heat-sealing and cut-off unit will operate to bring the flange elements of the channel element 70 against the flanges of the member 66 to transversely heat scam the film, and the cutter knife 67 will be operated to sever the film strip just above the seal. The severed length of film is then an inverted bag with its lower end starting to envelop the load to be wrapped. The downward travel of the carriage, which is momentarily halted during the heat sealing and cutting operation, its resumed until the gripping means is below the top of the pallet or other load support. At this level the carriage stops, the sleeve 94 on each

shaft

80 and 81 will be moved by its cylinder-piston unit 99 to effect the movement of the gripping fingers 91 back to their normal position, after which the travel of the carriage reverses and it returns to its elevated position.

Generally the apparatus will operate on a succession of palleted loads of a uniform size, but it will adjust to loads of different heights. Tall loads, of course, require longer wrappers than short ones. The present invention provides an automatic means to index the operation of the machine to the height of the load to be wrapped. This is best seen by reference FIGS. 1 and 4.

One of the corner posts 3 has an upper sprocket wheel 100 near the top thereof, and a lower sprocket 101 near the bottom at a level below the top flight 4 of the conveyor. An endless sprocket chain 102 passes around these two sprockets and a reversing motor and reducing gear unit 103 drives the lower sprocket. While we have referred to other motors as being hydraulic or fluid pressure motors, they could be electric motors. We prefer that the motor in unit 103 be an electric motor, but it could be fluid pressure motor. The two vertical reaches of the sprocket chain 102 are partially enclosed in channel-like safety guards 104. The chain has a photosensitive unit, i.e., electric eye 105 on one reach thereof, and there is a switch operating abutment 106 on the othe reach, so that as one does up the other goes down.

There is an elongated light source such as a fluorsecent tube 107 on the opposite corner post 3. At the start of the operation, the electric eye is at a level opposite the bottom of the tube 107. When a palleted load is carried past the electric eye it interrupts the light path between 106 and 107. This initiates operation of the motor of unit 103 to operate the sprocket chain 102 and raise the electric eye to a level where it again sees the tube 107. At this level the drive unit 103 is de-energized. As the electric eye moves up, abutment 106, of course, moves down.

As the load to be wrapped moves along on the conveyor, it strikes a limit switch 108 (FIG. 2). There is a fluid pressure pump and pressure regulator schematically indicated at 109. When the limit switch 108 is operated, the conveyor stops with the load centered under the carriage 10. At the same time, the cylinder 49 is energized to drive rack 50 to the left as viewed in FIG. 5. This will operate the pinch rolls 45-46 to feed enough flattened tubular film down for the leading end (which has been severed by knife 67 in the previous operation) to be in the plane of travel of the cross bars and 81 of the carriage. As the rack 50 reaches its limit of travel in a film feeding direction, it contacts limit switch 110 and initiates the operation of motor 79 to effect the movement of the

bars

80 and 81 toward each other and the intervening leading end of the tubular film strip.

As the

bars

80 and 81 approach the film strip, their suction cups will draw the two flat sides of the sheet in opposite directions, as previously described. Limit switch means (not shown) then energizes the cylinder 99 to turn the gripping fingers up inside the folds of the tube and clamp the opposite side faces thereof to the

respective bars

80 and 81. The operation of cylinder 99 to rotate and bring the fingers into gripping position will signal the operation of cylinder 59 to separate the pinch rolls. Also it will signal the reversal of motor 79 to effect the reverse travel of the

bars

80 and 81, causing them to move apart, spreading the leading end of the tubular film to a four-sided configuration, as earlier described.

As bars 80-81 approach the limit of their travel in the film tube opening direction, they operate a limit switch (not shown) to effect the operation of motor 30 to lower the carriage 10, pulling the non-open tubular strip down over the palleted load. As the carriage moves down, an arm of a limit switch 110 on the carriage schematically indicated in FIG. 5, strikes the element 106 to effect the operation of cylinder 71 to move the heat seal bar 70 into contact with the film and at the same time operate the power driven knife 67 to sever the strip. The controls are set to momentarily stop the down travel of the carriage for the few seconds that the sealing and cut-off takes place Switch means (not shown) operated by the travel of the knife to its limit of travel in one direction or the other operates cylinder to retract the heat sealing bar and energize cylinder 59 to move pinch roll 46 back to its operating position.

It will be appreciated that the higher the load, the further will be the upward travel of the electric eye before it sees the lamp or flourescent tube 107, so the lower will be the abutment element 106 and the longer will be the downward travel of the carriage before the sealing and cut-off takes place. In this manner the electric eye arrangement automatically provides for lengthening or shortening the film strip for higher or lower loads.

After the cut-off takes place and the carriage resumes its downward travel, it will move to the dotted line position shown in FIG. 1 or slightly below it where the

bars

80 and 81 with their gripping means are below the deck of the pallet. A limit switch (not shown) at this level momentarily stops the carriage, effects the reverse operation of cylinders 99 to rotate their respective shafts 90 to the position shown in FIG. 6 where the gripping fingers 92 release the opposite sides of the film sheet, which as explained has taken the form of an inverted bag and the carriage returns to its uppermost limit of travel. The electric eye length-gauging apparatus may be de-energized to stay at one level where a succession of loads of the same height are to follow, or limit switch means operated by the upward movement of the carriage may cause motor 105 to operate in the reverse direction to lower the electric eye to its starting level at or near the level of the pallet after each cycle.

In FIG. 1 we have indicated a fluid reservoir at 120 with a pump I21, a pressure diverting valve 122 and a control panel 123. While fluid pressure systems have been described, electric motors may be used. Reference to limit switches may refer either to valves or electric switches. Equipmentof this kind is well known, and their use to effect as the sequencing of operation is a common expedient and for this reason the fluid circuits and all switches have not been shown. Moreover, the switches could merely effect the operation of signal lights, so that an operator may manually operate push buttons or turn valves to then sequence the various operations.

In case where, for one reason or another, it is not convenient to have the rolls of tubular film strip at the top of the machine, a roll may be mounted at the side of the machine frame, as shown in FIG. 1, and carried up to the pinch rolls over an idler roll 130.

We claim:

1. Apparatus for enveloping a load carried by a pallet or other supporting base by opening out the lead end of a continuous roll of flat-folded tubular shrink-wrap film at a level above the load to be wrapped to a substantially four-sided configuration and then pulling the open end down over the load and heat-seaming and severing the folded film after a length sufficient to envelop the load comprising:

a. a supporting frame having a top and vertical sides defining an open passageway therethrough with a load-supporting conveyor extending through the passageway centered between and spaced from the two sides,

b. a four-sided carriage having sides and end members defining an area larger than the load to be wrapped mounted in the frame below the top and guided in the frame for vertical movement from an upper limit of travel below the top of the frame downwardly to about the level of the conveyor and constructed to clear a load to be wrapped which is positioned on the conveyor and centered under the carriage,

c. the carriage being characterized by having two sheet-gripping bars movable sideways in opposite directions between a closed position where they are in spaced side-by-side position over substantially the center line of the conveyor to an open position where they are close to opposite sides of the frame, the said sheet-gripping bars being supported for such movement on the end members, and means on the carriage for effecting such movement of the gripping bars,

d. the frame being characterized by having means thereon separate from said gripping bar moving means on the carriage for controllably moving the carriage up and down between its limits of travel, by having feed rolls at the top positioned to feed the flat-folded film from a supply source to the level of the sheet-gripping bars on the carriage when the carriage is in its uppermost position, means under the feed rolls and above the uppermost limit to which said gripping bars are raised when the carriage is at the upper limit of travel in the frame arranged to form a heat seam across the width of the film and cut-off means arranged to sever the film above the heat seam so formed, and a drive means arranged to rotate the feed rolls an amount only sufficient to advance the film in increments from the level of the cut-off means to the level where it may be engaged by the sheetgripping bars when the carriage is at its uppermost limit of travel whereby the sheet-gripping bars may be moved to their closed position and engage opposite sides of the flat-folded film and then move to their open position to open the lead end of the film into a four-sided configuration and hold it open as the carriage is then moved from its upper limit of travel to its lowermost limit of travel 2. Apparatus as defined in claim 1 wherein the gripping bars are arranged to grasp and clamp the surfaces of the film which they engage to pull the film through said rolls when the carriage travels downwardly, and means arranged to separate said feed rolls and provide free rotation thereof independently of said drive means when the film is pulled in this manner, and means for effecting release of the film from said gripping bars when the carriage reaches its lowermost limit of travel.

3. Apparatus as defined in claim 1 wherein said opposed film sheet-gripping bars each comprises a bar having spaced suction cups therealong together with fingers movable from an open position below the suction cups upwardly in an are into the interior of the tubular film to a closed position to clamp a single thickness of the film against the bar after its end has been drawn to the bars and partially opened by the suction cups, and operating means arranged to selectively move the fingers to grip the film and to release it.

4. Apparatus as defined in claim 3 in which said fingers are carried on a common rock shaft which is mounted on and extends along the bar parallel therewith, there being one finger on the bar positioned to cooperate with each suction cup when it is in sheetgripping position, and means for rotating the shaft through a vertical arc of about 90 to move the fingers between the film-gripping and the open position.

5. Apparatus as defined in claim 4 wherein each of said bars has a means mounted thereon for effecting said rotation of the rock shaft associated with it.

6. Apparatus as defined in claim 1 wherein there is means on the frame comprising a vertically movable electric eye at one side of the conveyor past which the load moves to a position in the frame where it will be wrapped and a vertically elongated light source directed toward said electric eye for gauging the height of the load, and contact means movable vertically with the electric eye but in the opposite direction, aid contact means being arranged to be engaged by the carriage as it moves downwardly to determine a level between the top and bottom limits of the movement of the carriage to momentarily stop its continued downward pull on the continuous film while the said means for heat-seaming and severing the film operates to cut off a length of film required to envelop the load and provide a closed seam to eventually be positioned along the top of the load.

7. In an apparatus for enveloping a load which is carried on a pallet with a length of tubular shrink-wrap film by first opening out of the lead end of a flat-folded tubular wrapper at a level above the load to be wrapped and then pulling it down over the load,

a. a supporting frame having a top and sides,

b. means below the top of the frame positioned between but spaced from the sides thereof on which the load to be wrapped along with its pallet or other base is supported,

c. power-driven means for feeding the lead end of a continuous flat-folded tubular film from a roll which is supported for rotation downwardly from the top of the frame in a vertical plane which is centered over the load-supporting means and termining such downward feed at a level above the top of a load positioned on said load-supporting means,

d. a pair of opposed tube-gripping bars movable horizontally between an open position near the sides of the frame to a tube-gripping position where they confront each other with said lead end of the flatfolded tubular film sheet intervening, said bars having means for drawing the opposite faces of the flat-folded tubular sheet apart and releasably gripping them comprising suction means and a plurality of movable film-pinching fingers with operating means for said fingers.

e. means for simultaneously moving both of said bars from the open position to said tube-gripping position and then moving them apart to the open position while the film is gripped thereby to open said lead end of the sheet film to a four-sided configuration, carriage means movable vertically in the frame and in which said bars are moved and guided for movement toward and away from each other and means for effecting movement of said carriage means between an upper limit at a level above the load to be wrapped to a lower limit ofttravel at a level where the bars in the open position, but still gripping the film, have drawn the film down around the load which is positioned on the load support,

g. means for operating the tube-gripping means on said bars to grip the opposed faces of the flattened film when the bars are in tube-gripping position and releasing them when said bars have been moved to the lower limit of their travel,

h. means on the frame adjacent the conveyor where it enters the frame for gauging the height of each load as it moves toward said central position wherein the load height-gauging means comprises an elongated vertical light source at one side of the conveyor and an electric eye at the other side with means for raising the eye when a load is carried by the conveyor between the eye and the light source and which is controlled by the eye to stop the upward travel of the eye when the light strikes the eye over the top of the load, the carriage having a switch thereon and means in the path of downward travel of the carriage that is moved down with the upward movement of the eye arranged to engage said switch to stop the downward travel of the carriage at the level where the transverse seal and severing of the film sheet should be made for the height of the load to which the operation of the eye is related.

Claims

1. Apparatus for enveloping a load carried by a pallet or other supporting base by opening out the lead end of a continuous roll of flat-folded tubular shrink-wrap film at a level above the load to be wrapped to a substantially four-sided configuration and then pulling the open end down over the load and heat-seaming and severing the folded film after a length sufficient to envelop the load comprising: a. a supporting frame having a top and vertical sides defining an open passageway therethrough with a load-supporting conveyor extending through the passageway centered between and spaced from the two sides, b. a four-sided carriage having sides and end members defining an area larger than the load to be wrapped mounted in the frame below the top and guided in the frame for vertical movement from an upper limit of travel below the top of the frame downwardly to about the level of the conveyor and constructed to clear a load to be wrapped which is positioned on the conveyor and centered under the carriage, c. the carriage being characterized by having two sheet-gripping bars movable sideways in opposite directions between a closed position where they are in spaced side-by-side position over substantially the center line of the conveyor to an open position where they are close to opposite sides of the frame, the said sheet-gripping bars being supported for such movement on the end members, and means on the carriage for effecting such movement of the gripping bars, d. the frame being characterized by having means thereon separate from said gripping bar moving means on the carriage for controllably moving the carriage up and down between its limits of travel, by having feed rolls at the top positioned to feed the flat-folded film from a supply source to the level of the sheet-gripping bars on the carriage when the carriage is in its uppermost position, means under the feed rolls and above the uppermost limit to which said gripping bars are raised when the carriage is at the upper limit of travel in the frame arranged to form a heat seam across the width of the film and cut-off means arranged to sever the film above the heat seam so formed, and a drive means arranged to rotate the feed rolls an amount only sufficient to advance the film in increments from the level of the cut-off means to the level where it may be engaged by the sheet-gripping bars when the carriage is at its uppermost limit of travel whereby the sheet-gripping bars may be moved to their closed position and engage opposite sides of the flat-folded film and then move to their open position to open the lead end of the film into a four-sided configuration and hold it open as the carriage is then moved from its upper limit of travel to its lowermost limit of travel

2. Apparatus as defined in claim 1 wherein the gripping bars are arranged to grasp and clamp the surfaces of the film which they engage to pull the film through said rolls when the carriage travels downwardly, and means arranged to separate said feed rolls and provide free rotation thereof independently of said drive means when the film is pulled in this manner, and means for effecting release of the film from said gripping bars when the carriage reaches its lowermost limit of travel.

3. Apparatus as defined in claim 1 wherein said opposed film sheet-gripping bars each comprises a bar having spaced suction cups therealong together with fingers movable from an open position below the suction cups upwardly in an arc into the interior of the tubular film to a closed position to clamp a single thickness of the film against the bar after its end has been drawn to the bars and partially opened by the suction cups, and operating means arranged to selectively move the fingers to grip the film and to release it.

4. Apparatus as defined in claim 3 in which said fingers are carried on a common rock shaft which is mounted on and extends along the bar parallel therewith, there being one finger on the bar positioned to cooperate with each suction cup when it is in sheet-gripping position, and means for rotating the shaft through a vertical arc of about 90* to move the fingers between the film-gripping and the open position.

7. In an apparatus for enveloping a load which is carried on a pallet with a length of tubular shrink-wrap film by first opening out of the lead end of a flat-folded tubular wrapper at a level above the load to be wrapped and then pulling it down over the load, a. a supporting frame having a top and sides, b. means below the top of the frame positioned between but spaced from the sides thereof on which the load to be wrapped along with its pallet or other base is supported, c. power-driven means for feeding the lead end of a continuous flat-folded tubular film from a roll which is supported for rotation downwardly from the top of the frame in a vertical plane which is centered over the load-supporting means and termining such downward feed at a level above the top of a load positioned on said load-supporting means, d. a pair of opposed tube-gripping bars movable horizontally between an open position near the sides of the frame to a tube-gripping position where they confront each other with Said lead end of the flat-folded tubular film sheet intervening, said bars having means for drawing the opposite faces of the flat-folded tubular sheet apart and releasably gripping them comprising suction means and a plurality of movable film-pinching fingers with operating means for said fingers. e. means for simultaneously moving both of said bars from the open position to said tube-gripping position and then moving them apart to the open position while the film is gripped thereby to open said lead end of the sheet film to a four-sided configuration, f. carriage means movable vertically in the frame and in which said bars are moved and guided for movement toward and away from each other and means for effecting movement of said carriage means between an upper limit at a level above the load to be wrapped to a lower limit ofttravel at a level where the bars in the open position, but still gripping the film, have drawn the film down around the load which is positioned on the load support, g. means for operating the tube-gripping means on said bars to grip the opposed faces of the flattened film when the bars are in tube-gripping position and releasing them when said bars have been moved to the lower limit of their travel, h. means on the frame adjacent the conveyor where it enters the frame for gauging the height of each load as it moves toward said central position wherein the load height-gauging means comprises an elongated vertical light source at one side of the conveyor and an electric eye at the other side with means for raising the eye when a load is carried by the conveyor between the eye and the light source and which is controlled by the eye to stop the upward travel of the eye when the light strikes the eye over the top of the load, the carriage having a switch thereon and means in the path of downward travel of the carriage that is moved down with the upward movement of the eye arranged to engage said switch to stop the downward travel of the carriage at the level where the transverse seal and severing of the film sheet should be made for the height of the load to which the operation of the eye is related.