CA1330753C

CA1330753C - Zippered film feed and stretcher for package forming

Info

Publication number: CA1330753C
Application number: CA000585314A
Authority: CA
Inventors: Hugo Boeckmann
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 1987-12-10
Filing date: 1988-12-08
Publication date: 1994-07-19
Anticipated expiration: 2011-07-19
Also published as: AU2584488A; EP0319995A3; AU608916B2; JPH01167007A; EP0319995A2

Abstract

ABSTRACT OF THE DISCLOSURE
A method and mechanism for advancing a continuous length of bag making plastic film having reclosable fastener strips extending therealong with a filling tube over which the film is formed, means for sealing the edges of the film over the filling tube, or for joining the fasteners to form bag tubing, opposed pairs of advancing belts for pressing the film against the tube and driving it incrementally downwardly. Opposed cam surfaces at each of the bag edges contact each other at a point just outside of the bag edges and progressively walk into the edge of the bag with the point of contact shifting in an outward direction while it progresses inwardly on the bag to apply the stretching force to the film of the bag for smoothing the entire width before a cross-seal is formed.

Description

S P E C I F I C A T I O N

T I T L E
"ZIPPERED FILM FEED AND STRETCHER FOR PACKAGE FORMING"

BACKGROUND OF THE INVENTION
The invention relates to reclosable bags and to methods and apparatus for the manufacture of such bags and more particularly to continuous formation of bags by a form fill and seal process with improved means for advancing the film, stretching the film laterally to remove the wrinkles and cross sealing and cutting the laterally stretch~d film to complete the closure of a filled bag and form a seal at the end of a tube for ;
filling a succeeding bag with contents.
Reclosable bags having male and female profile cooperating rec]osable zipper elements along the opening to the bag have been known Ifor;some considerable time. ~arious forms of manufacture have been employed with one method of making such a bag including extruding plastic film where the reclosable elements are integral therewith. Other forms of manufacture~;
attach the zipper elements to the surface of the film with both turning out a web with reclosable zipper profiles on the surface.
One method of forming bags has been known as the form fill and seal method wherein a continuous web of film is fed forwardly and downwardly over a forming tube with the edges of ` 1 330753 .

the sheet of film being joined to each other by a reclosable zipper to form a tubing. In another form, the zipper elements are already joined and a continuous seam joins the edges of the film to form a tubing. The thus formed tubing is cross-sealed at intervals and contents are filled into the bags down through the tubular filling tube over which the bag tubing is formed.
An improved form of bag made by the foregoing methods resulted from advancements in the development of reclosable fasteners. Thus, a bag formed in this manner can be openable and reclosable when film which is utilized has reclosable continuous fastener zipper elements extending along the film edge and the zipper elements joined to join the tube edges cross-sealing and cutting as the cross-seal forms bags at the lead end of the advancing tubing. ;
In the formation of such bags, it is necessary to intermittently advance a continuous sheet of film over a filling tube thereby forming the film into tubing shape. Between the intermittent advancements of film, the reclosable fastener or zipper which joins the film edges is ultrasonically spot welded at bag widths to maintain engagement of the male and female profiles. A cross-seal is formed at the end of the tubing and . .
contents are dropped gravitationall~ down through the filling tube to fill the tubular bag. The film is then advanced and another cross-seal formed to provide a finishing seal at the other edye of the bag.
The mechanism and method used for the advancement of the film is critical to form the bags of the proper width and it may be even more critical where printing on the bag must be kept in registry. It is also important that the film be advanced without rotating it on the filling tube so that the reclosable fastener

- 2 -will always remain at the right location on the side or top of the bag~ Also, the bag must be advanced such that the sealing apparatus will always engage ~he edges of the bag to form a satisfactory seal between the film edges.
It is also important in the formation of bags from thin lightweight plastic film in a form, fill and seal process, to cross-seal the formed tube in a moisture and air-tight manner.
The cross-seal is usually formed by the application of heated sealing bars clamping and flattening the tube to form a cross-seam. With methods and structures heretofore available, it was almost impossible to form this cross-seal without inclusion of some wrinkles in the tubular film. Such wrinkles detract from the attractive appearance of the bag and can easily result in leakage through the seam.
It is accordingly an object of the-present invention to provide an improved structure and method for advancement of the film in a form fill and seal apparatus wherein film with a reclosable fastener is used.
Another object of the invention is to provide an improved apparatus for advancement of the film in a form fill and seal mechanism wherein relatively delicate film can be handled, and can be accurately and reliably advanced so that the functions of forming the cross-seal, the filling and forming the longitudinal seal can be carried out accurately and reliably.
A further object of the invention is to provide an improved film advancing mechanism which is capable of advancing the film without wrinkling or stressing and wherein accurate control of the increment of advance can be effected.
A still further object of the invention is to provide an improved method and apparatus for forming bags from a continuous ~ .

1 33075;~

layer of film wherein the film is shaped into a tube and the tube is cross-sealed, with an object of the invention particularly dealing with flattening the tube in a manner such that cross-seals can be made without wrinkles.
SUMMARY OF THE INVENTION
In accordance with the present invention, thin plastic film for forming bags is advanced in a form fill and seal operation by the flat plastic film being wrapped around a tubular filling tube through which contents are filled into the finished bag. The film is advanced uniquely by driving it downwardly through engagement of the outer surface by frictional or vacuum -belts. The belts are preferably in the form of two pairs of ~-belts with one pair straddling the longitudinal fastener. The pairs are placed diametrically opposite and are of essentially identical construction so that equal and opposite forces are applied to the film so that even very fragile soft film material subject to wrinkling or stretching will be handled and advanced uniformly in a manner so that the longitudinal seam can be formed. Means are provided in advance of one pair of belts to guide the reclosable fastener accurately and reliably between two of the belts.
The fragile film, having been formed into a tube and drawn down by the unique belt drivers, is cross-sealed but first laterally stretched in a manner so that all wrinkles are pulled out of the flattened tube. This is accomplished by opposed uniquely shaped and mounted cams which press against each other and are automatically moved in an outward direction so that they waIk onto the edge of the film pulling it outwardly and removing the wrinkles. The cam arrangements are such that they start on the very outer edge of the film so that no wrinkles are introduced by the fact that surfaces must contact the film to pull it outwardly.
Other objects, advantages and features will become more apparent with the teaching of the principles o the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings in which:

DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of apparatus constructed and operated in accordance with the principles of the present invention;
FIG. la is a perspective view similar to Fig. 1 but illustrating the structure for forming cross-seams in the film tubing as it is drawn down over the filling tube, with Fig. 1 illustrating in greater detail the structure for drawing the tube down over the filling tube.
FIG. 2 is a fragmentary elevational view of a portion of the structure of Fig. l;
; FIG. 3 is a fragmentary vertical view taken substantiall~ along line III-III of Fig. 2;
FIG. 4 is a fragmentary vertical sectional view taken substantially along line IV-IV of Fig. 2;
FIG. 5 is a vertical sectional view taken substantially along line V-V of Fig. l; and FIG. 6 is a plan view taken substantially along lines VI-VI of Fig. 1, but partially in section showing the mechanism or laterally stretching the wrinkles from the tubing.

As illustrated in Fig. 1, a sheet of film 10 is fed from a suitable supply to the eq~ipment illustrated in a form fill and seal operation. The sheet of fil~ is fed over a shaped guide having sides 16 so that it envelops a vertical hollow filling tube 14. Edges 11 and 12 of the sheet of film are brought together to be sealed. Where the film is of a material such as polyethylene, the sealing is a heat seal process and it will be understood that various forms of single layer or multiple layer film may be employed. Along the length of the film is a continuous reclosable fastener 13. This will provide an openable and reclosable fastener for the finished package which is shown at 22.
In operation, the film must be brought forward incrementally, and as it is brought forward, the edges are sealed together to form a side seam 18. As the film is stopped, a bottom cross-seam 21 is formed and the finished bag is cut to form bag 15a as shown. When the bottom seal 21 is formed, contents are filled into the bag through the hollow filling tube 14, and then the film is again advanced so that the next filled bag can be sealed at the top and cut off.
The film must be fed forwardly in a manner so that it does not wrinkle or tear and the reclosable fastener strip 13 must be maintained in its oriented position so that it will be located at the top front of the completed bag. The incremental feed can be measured such as by an electric eye, not shown, orienting with marks on the film and this method is used where printing is on the film which must be oriented on the finished bag. Alternately, the film may be advanced a predetermined distance but with either arrangement for advancement, the advancement must be uniform and done without damage to the film. This must be accomplished with sufficient force so that the edges of the film can be brought together and formed over the filling tube and a pull must be applied to the film in such a manner without losing the orientation or damaging or wrinkling the film.
In accordance with the principles of the present inventionl the film is pulled down frictionally by means having frictional engagement with the outer surface of the bag film.
As illustrated in the figures, the outer surface of the bag is engaged by first and second pairs of belts shown at 23 and 24 with the belts extending in the direction of the film advancement and having contact with the film over a substantial length.
One pair of belts shown at 25 and 26 is positioned at one edge of the bag in a location so as to straddle the reclosable fastener and hold it in orientation essentially bracketing the fastener 13 therebetween in the manner shown in the enlarged sectional drawing of Fig. 6. Diametrically opposite the frictional advancement mechanism 23, is located the other frictional advancement member 24 having belts 27 and 28. The sets of belts on opposite sides of the film must have essentially the same frictional engagement with the film so as to pull it down evenly. The smooth outer surface of the filling tube 14 provides a support for the film as the belts engage the outer surface. ;The belts have a polyurethane or other frictional plastic surface which engages the film and other forms of rubber or other outer belt surfaces may be employed depending upon the film used.
In advance of the fixst of belts 23, a fastener guide assembly 60 is provided. A fastener guide assembly has a vertical guiding slot for receiving the joined rib and groove elements which provide the reclosable fastener 13.

As will be understood, in another type of plastic film, as shown in Fig. la, a continuous web is supplied with rib elements at one edge and groove elements at the other edge r and these elements are joined and interlocked as they are brought together over a forming shoulder outside of the tube. In other words, Fig. 1 shows a film 10 which already has interlocked rib and grooves along the surface and the raw edges of the film are brought together and heat sealed. In another form, Fig. la, fastener ele~ents will be at the very edge of the film, and these fastener elements will be brought together to be interlocked and no vertical heat seaming will occur.
In the form which is shown in Fig. 1, the side seam which is continually formed as the film is advanced is formed by a heated bar 15 supported on an arm 17. If relatively low temperatures are used, the bar 15 can stay in contact with the seam, or the bar may be lifted each time the advance of the film i S 5 topped.
The frictional drive belts are carried on support mechanisms 32 and 33. The belts are of essentially identical construction, and therefore only the belts and support 32 need be described in detail as shown in Fig. 2.
Fixed frame members 39, shown on the right and left of Fig. 1, support the frictional drive assemblies and the assembly 32 is supported on horizontal rods 40 and 41 for the lefthand frictional drive, and rods 40a and 41a support the righthand frictional drive. The ends of the frame piece 39 are split so that bolts 42 and 43 can be tightened to lock the rods 40 and 41 in their adjusted position.
The rods support the dual sheaves 29 and 30 for the belts 25 and 26, and the dual sheaves 31 and 32 for the belts 27 ~ 1 3~075~

and 28. As shown in Fig. 4, suitable drive mechanisms are provided for driving the shaft of the sheaves and motor 34 i5 illustrated intermittently operated by a control mechanism, not shown, so that the motor is driven for the appropriate period of time to give the advancement necessary to provide the correct length of bag 22.
The belts at each side of the filling tube are driven concurrently and for the same distance.
The belts are pressed against the plastic film with a predetermined force and for this purpose, backing rollers engage the inner surface of the belts. As illustrated in Figs. 2 and 4, the backing rollers are arranged in tandem along behind the belts. As shown in Fig. 4, a series of rollers as illustrated at 46 and 47, back up belt 25 and a series of rollers 48 and 49 back up belt 26. These rollers are supported on their shafts in side plates 44 and 45. For purposes of assemblage of the rollers, the side plates have alternate holes to receive the roller shafts.
For example, roller 46 is assembled by having its shaft inserted ln a hole 50 in the frame plate 44. The adjacent roller for the belt 26 is assembled by having its shaft slid into a slot 52.
Similarly, the roller 49 below roller 48 is installed by having , , , . . , i , . ~
its shaft in~erted into a hole 53 in the side plate 45, while the opposite roller 47 h~s its shaft slid into the slot 51. In other words, the side plates 44 and 45 have alternate holes and slots which are staggered relative to the two plates 44 and 45 to permit assemblage of the rollers in the side plates.
The side plates 44 and 45 are part of a U-shaped support as shown in Fig. 6 which is mounted on shafts 54 and 55, Fig. 2, which shafts are supported on a base plate 56. The base plate is pushed inwardly to control th& force that the rollers apply to the belts by threaded shaft 57 which threads into the frame 39.
By turning a knob 58 on the shaft 57, the amount of force applied to the plate 56 will be determined and when the plate 56 is adjusted for the proper pressure between the rollers and the belts, it is locked in place by a locking nut 59. The belt assembly ~4 on the right of Fig. 1 is adjusted in the same manner so that the belts at each side of the filling tube engage the film with equal force~
Another manner of obtaining frictional engagement between the belts and the film to advance the material is by applying a vacuum to the film through the belts. By placing a vacuum gland behind the belts and providing belts with holes extending therethrough, a low vacuum will draw the film tightly to the surface of the belts so that the film will advance with travel of the belts due to the friction between the belts and film. With the vacuum arrangement, the belts can be situated so that they do not press the film against the filling tube, but instead draw the film downwardly in light engagement with the filling tube or the belts can be spaced slightly from the filling tube. A very light vacuum will be all that is needed to firmly grip the film to the belts and the belts can be shortened so that " , I , . . .
the extent of contact between the film and belt may be less than that shown in the drawing. The vacuum will be released at the lower end of the contact between the belts and the film so that the film will be freed from the belt at the lower end of belt travel. Thus, actually the film is drawn down due to frictional engagement between the belt and film, but the frictional engagement is obtained due to vacuum rather than having the belt pressed against the film as it is slidably backed by the filling tube. Control of the frictional engagement between the film and belts can be controlled by increasing or decreasing the vacuum so as to accommodate more or less slippery film and to accommodate film which requires more or less pressure to be pulled down.
Where the backing rollers are used to obtain the frictional engagement between the belt and film, the pressure of the rollers against the belt can be adjusted.
Fig. la illustrates a form, fill and seal machine wherein a continuous sheet of bag making plastic film 10' is fed and ~haped over a filling tube 14. The material 10 may be plastic film or plastic laminate and the edges of the film are brought together to join interlocking profile fasteners lOa and lOb which are on the surface of the film 10. In arrangement, the film has been formed with the interlocking profile fasteners such as the rib and groove type, and these fasteners are on the edges of the film and are aligned and pressed together to be interlocked between opposed rollers as the film is formed into tubing. In another form, the film has the profiles interlocked and edges of the film are joined as shown in Fig. 1.
Fig. 1 is used primarily to show the unique structure and method for drawing down the tube of film over the forming tube 14. Fig. 1 does not show in detail mechanism for forming the cross-seam 21 at the bottom of the tubing, and this mechanism is shown in Fig. la. Figs. 1 and la also differ in that Fig. 1 shows an arrangement wherein the locking profiles which will eventually be at the top of the bags which are formed are on the surface of the tubing and are joined to each other. The film 10 is fed forward and a vertical seam 18 is formed to complete the tubing of Fig. 1. In Fig. la the film 10' has profiles lOa and lOb at the outer edges thereof, and these profiles are guided together and pressed together to be joined by opposed rollers ;~

-- 11 _ 12. The result in each case will be substantially the same with a bag formed where the bottom is formed of the doubled film, and the side seams are formed by cross-seams such as 21 formed across the tubing, and at the top of the bags, they are closed by the joined profiles which are 13 in Fig. 1 and which are at lOa and lOb in Fig. laO Additional rollers 13 and 13' further press the aligned profiles lOa and lOb together as the tubing descends in Fig. la. It will be understood that the tubing is drawn downwardly in the arrangement of Fig. la by a belt such as that shown in Fig. 1.
With reference to either Fig. 1 or Fig. la, with the cross-seal 21 formed at the base of the tubing, contents are fed into the bag tube through the filling tube 14. A subsequent cross-seal is formed above the contents and a finished bag is severed from the bag tube. This is illustrated by the completed bag where an ~arlier seam 16'a has been formed. A fully completed bag is shown severed from the tubing with the fully completed bag shown at 15' having a bottom 15a formed of the doubled film, and side seams 15b and 15c. At the top of the bag 15d are pull flanges with the closed zipper elements lOa and lOb `~
inside at the top of the bag holding the top edges closed.
An important feature of the present invention is the stretching of the flattened bag tube in a way that all wrinkles are removed from the plastic film so that the cross-seal can be made without any wrinkles thereby preventing the formation of any leaks and presenting a more attractive bag. In efforts heretofore made to flatten the bag tube and stretch it, flattening forces were applied by clamping the tube and pulling it laterally, but the layers of the film were not pulled in such a way to remove the wrinkles from both layers of films, and - 12 ~

~rinkles were not removed at the sides of the bag so wrinkles were left beneath the clamping pads. Prior efforts to flatten the tube to remove wrinkles when a cross-seal is made have not resulted in satisfactory operations in that efforts were made to stretch the bag from inside of the film, other efforts were made to pull the bag laterally e~ternally, but these resulted in wrinkles in that such devices usually utilized surface contact or contact starting inside of the edges, whereas in the instant arrangementt point contact is utilized which walks inwardly starting outside of the lateral edges of the bag and moving gently inwardly to stretch the material laterally and completely remove the wrinkles.
In accordance with the present invention, the equipment shown in Fig~ la includes a lateral stretching mechanism which stretches to the very edges of the bag. The stretching mechanism can be positioned directly adjacent sealing bars which cross-seal `
film tubing such as above the bars or below the bars. The stretching mechanism is such that it applies a stretching force at the very distal edges of the flattened bag and the stretching force is gently applied to both layers of the film at point contact continuing to stretch the film until it is completely flat just prior to the application of the séaling barsO The sealing bars are heated so that as khey are pressed against the outer surface of the film, the thermoplastic film is joined to form the cross-seam.
Shown better in Figs. la, 5 and 6, the mechanism includes the stretching eguipment 17', holding bars 18' and sealing and cutting mechanism at 19'. The three pieces of equipment for stretching, clamping and sealing and cutting are carried on laterally movable carriages ~3' and 24', Fig. 6, shown overall at 25' and 26', Fig. la, which slide horizontal guide bars 21' and 22'. The carriages are pushed inwardly to effect the operations on the bag tube 16' by operating mechanism not shown. Such operating mechanism may be in the form of a hydraulic or pneumatically operated cylinder which pushes the -carriages together and again separates them after the bag tube has been laterally stretched, clamped, and cross-sealed and cut.
The stretching equipment includes opposed cam pads 27' and 28' at one edge of the bag tube 16' and opposed cam pads 29' and 30' at the other edge.
To begin the formation of the cross-seams, the carriages 23' and 29' are pushed toward each other and the stretching cam pads 27' and 28' first contact each other in point contact just outside of the lateral edge of the bag tube 16'. Simultaneously, the cam pads 29' and 30' contact each other at point contact just outside the outer edge of the bag tube 16' and this point contact is shown in detail in Fig. 5. Actually, the cams engage in line contact when viewed vertically, but engage the film in point co~tact in a horizontal plane.
The cam pads are mounted on pivotal support arms with the pivot;point oflsaid support arms being laterally offset~ifrom the surfaces of the cam pads such that when the cam pads are pressed against each other, their point contact rolls inwardly to roll over the edges of the bag tube 16' and simultaneously begin pulling outwardly to pull the bag tube flat and remove all wrinkles. The point contact pressure will be applied at substantially uniform force as it moves inwardly~
As to the construction of the support for the cam pads, pads 27' and 28' are supported on pivotal arms 35' and 39'. The cam pads 29' and 30' are supported on pivotal arms 37' and 41'.

, The arms 35' and 39' are pivotally supported at 36' and 40'.
The cam pad supporting arms 37' and 41' are pivotally supported respectively at 38' and 42'. As will be observed, these pivotal support points are lateral of the point of first contact of the cam pads. Thus, the reactant for~es between the cam pads will cause the arms to pivot laterally o~twardly.
The cam pads are preferably formed of a rubber material so that their outer surfaces will frictionally grip the film of the bag tube to pull it laterally. The faces are also logarithmically shaped so that as the point of contact between opposing pads shifts, it rolls inwardly over the bag tube to get a better grip and simultaneously travels laterally outwardly to apply a stretching force to the bag tube. The logarithmic contact surfaces for pads 27' and 28' are shown at 31' and 32'.
Logarithmic contact surEaces for the pads 29' and 30' are shown at 33' and 34'.
After the cam pads have contacted and after they have rolled inwardly applying their stretching force, first beginning at the very outer edges 16a and 16b of the tube, the tube is clamped by clamping bars 51' and 52', Figs. 5 and 6, and the bag tube is then heat sealed by the sealing bar surfaces 57' and 58'. At the same time, a knife 59', Fig. 5, in the recess of the bars, cuts the lower bag 15', Fig. la, from the bag tube.
When this has been completed, the carriages 22' and 24' are withdrawn from the bag tube, and the arms holding the stretch cams are spring loaded so that the stretch cams are pivoted back to the position shown in Fig. 6. As shown in Fig. 6, arm 35' is biased by a coil compression spring 43' which tends to urge it to the neutral non-stretch position shown in Fig. 6. An adjustable stop 43a' limits the return pivotal movement of the cam arm 35'. Similar springs are provided for the other cam arms with spring 44' serving the cam arm 37'.
~ he lateral position of the cams is also adjustable by mechanism not shown in detail. The position of the stretch cams toward each other is adjustable such as by bolts 45' and 46', Fig. 6.
Turning again to the relative position of the parts after the bag tube 16 has been stretched, the clamping bars 51' and 52' clamp the stretched bag tube. The clamping bars have soft noses so as to not damage the film and are mounted on plunger rods 55' and 56' as shown in Fig. 5. These rods are spring biased by springs such as 53' and 54' to urge the clamping bars 51' and 52' in a direction to clamp the bag tube material 16'. With the material so clamped, the sealing bar faces 57 and 58 engage the film and being heated, cross-seal the film to form a cross-seal across the tubing. The knife 59 severs the tubing so that the bag 15' can be separated from the tubing.
An optional arrangement is possible wherein stretch cams may be employed below the sealing bars as well as above the sealing bars.
After the tubing has been cross-stretched and a cross-seal formed with the bottom cut off, the heads which carry the cams and the sealing equipment move away from the tubing. A new length of material is indexed downwardly pulled down by the belts. In some instances, it may be desirable to additionally apply a force aiding in pulling the film downwardly by moving the heads downwardly while retaining the film tubing clamped. If this form is used, the heads will remain clamped~ pull the tubing downwardly, and then separate and move upwardly to their ready :` 1 330753 position as shown in Fig. la to again cross-seal and clamp a new length of tubing.
In operation, as an endless supply of film is fed forwardly such as the film 10 in Fig. 1, advancing belt assemblies 23 and 24 on opposite cides of the surface forming tube 14 pull the film forwardly over a forming shoulder to form a tube. In the arrangement of Fig. 1, a side seam 18 is formed, and in the arrangement of Fig. la, zipper fastener profiles lOa and lOb are joined and in each case, a closed length of tubing is ~ormed over the filling tube 14.
A cross-seal 21 is formed at the lower end af the tubing and contents are dropped through the filling tube 1~ into the base of the tube. The belt assemblies 23 and 24 then pull the film down further and the bag is completed by another cross-seal formed and the finished bag is cut from the end to drop downwardly such as illustrated by the completed bag 15' in Fig.
la. The cross-sealing equipment shown generally at 25' and 26' in Fig. la, moves against the tubing, flattening it and the uniquely mounted and shaped smoothing and stretching cams 27 and 28, at one side of the bag, and 29 and 30 at the other side of the bag move together in point contact and walk onto the edge of the bag film gently pulling it outwardly until all of the wrinkles are removed. At that point, the bag film is clamped by the clamping noses 18' to stabilize the bag and cross-seams are formed by heated jaws 57 and 58, Fig. 5, which seal the top end of the filled bag and form a new seal at the bottom end of the tubing. Complete clamping of the heads as they move inwardly causes the knife 59 to sever the finished bag so that it can drop downwardly in the manner shown by the bag 15' in Fig. la. The wrinkle smoothing cams operate automatically having uniquely shaped outer faces and unique mounts as illustrated in detail in Figs. la, 5 and 6.
Thus, it will be seen that there has been provided an apparatus and method for advancing film and forming bags which meets the advantages and objectives above set forth and which is capable of operating with a variety of materials and is capable of reliably forming bags at a suitable high rate of manufacturing speed.

. ~ :

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED
AS FOLLOWS:

1. In a form, fill and seal machine for making and filling bags from a continuous plastic film comprising in combination:
a vertical filler tube over which film is formed into a general cylindrically shaped bag tube for filling with contents through the filler tube; means for advancing and shaping film in a downward direction over the filler tube to form a bag tube;
cross-sealing means located at a sealing station below the filler tube for forming seams across the bag tube at spaced intervals to make bags between the seams; and a lateral smoothing stretcher means located generally at said sealing station applying a lateral stretching force at a point location to the tube withsaid point location moving inwardly from the tube edge preventing wrinkles at the location of said seam, said smoothing means applying stretching force at the extreme lateral edge of the film for smoothing the entire width of the film from the outer edges inwardly.

2. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 1:
wherein said stretcher means engages the bag tube at a point beginning at the extreme edge of the tube in contact applying a force at said point contact beginning at the extreme lateral edge of the bag tube and moving inwardly.

3. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 1:
wherein said stretcher means engages the film in a progressively inwardly moving contact moving inwardly from the edge of the bag tube while applying the stretching force at uniform pressure while moving inwardly.

4. In a form, and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 1:
wherein said stretcher means includes opposed curved faces engaging the bag tube edge from opposite surfaces thereof.

5. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 4:
wherein said curved faces engage the film with point contact with said point contact moving progressively inwardly.

6. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 4:
wherein said faces are logarithmically shaped so that they move progressively inwardly from the edge of the film.

7. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 1:
the lateral edges of the film applying a separating force thereto smoothing the film between said stretcher means.

8. In a form, fill and seal machine for making and filling bags from a continuous plastic film comprising in combination:
means for advancing and shaping a continuous supply of plastic film to form a downwardly descending bag tube;
means for spreading the tube at spaced cross-sealing stations including opposed pivotal cams at each edge of the bag tube with said cams having curved faces for engaging the surface of the tube; and means for moving the pivotal cams toward each other at each edge of the bag to engage the extreme outer edges of the bag tube and pull the edges laterally to smooth the bag material therebetween.

9. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
wherein said cams are pivotally mounted at a point off-center from the point of engagement of the cam with the bag tube so that said cams pivot upon engagement with the bag film.

10. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
wherein the pivotal movement of said cams causes them to move progressively inwardly while applying a lateral stretching force.

11. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
including sealing bars positioned to engage the bag tube substantially immediately after the cams have stretched the bag material

12. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 11:
including cutting means for cross-severing the bag tube to separate a bag from the bag tube.

13. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 11:
wherein the sealing bars are located above the cams and holding bars are provided for engaging the tubular film above the sealing bars and flattening the bag tube.

14. In. a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
wherein the cams are shaped with a logarithmic face for progressively moving inwardly from the edge of the bag tube.

15. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
wherein said cams have a resilient soft face engaging the bag tube.

16. In a form, fill and seal machine for making and filling bags from a continuous plastic film in accordance with the structure of claim 8:
wherein the cams are shaped to engage the bag tube to lie in contact in inward movement from the tube edge.

17. The method of forming bags in a form, fill and seal process comprising the steps:
advancing film incrementally over a filling tube to shape a bag tube and deposit contents through the filling tube;
joining the vertical edges of the film to close the bag tube;
cross-sealing the bag tube beneath the filling tube at a sealing station top to form a cross-bag seam with the bag contents dropped into the tube above the seam; and stretching the bag tube laterally prior to cross-sealing applying a lateral stretching force at the extreme edge of the bag tube and gradually applying the force at a point location moving inwardly from the edge to flatten and stretch the complete width of the tube preventing wrinkles therein at the seam.

18. The method of forming bags in a form, fill and seal process in accordance with the steps of claim 17:
including first flattening the bag tube at the sealing station and thereafter stretching the bag tube laterally.

19. The method of forming bags in a form, fill and seal process in accordance with the steps of claim 17:
including applying said lateral stretching force by engaging the bag tube at point contact at the extreme edge.

20. The method of forming bags in a form, fill and seal process in accordance with the steps of claim 17:
including applying the lateral stretching force at the extreme edge and moving progressively laterally inwardly from the edge while continuing to apply the stretching force at a point location at a substantially uniform force.

21. The method of forming bags in a form, fill and seal process in accordance with the steps of claim 19:
including moving said point contact progressively inwardly on the tube while concurrently moving the location of the point contact outwardly to continue to apply the stretching force.

22. The method of forming bags in a continuous process from a supply of plastic film formed into a tube comprising the cross-sealing the tube at spaced increments to form successive bags; and stretching the bags at the general location of the cross-seal by applying a lateral force at the extreme edge of the bag and gradually applying the same amount of force moving inwardly preventing wrinkles throughout the entire width of the tube.

23. The method of forming bags in a continuous process from a supply of plastic film formed into a tube in accordance with the steps of claim 22:
including applying a rolling stretching force beginning at the extreme edges of the tube and progressively moving inwardly from the edge while continuing to stretch the tube laterally.

24. In a form/fill/seal packaging machine for making product-containing bags from a continuous length of sheet material having lengthwise directed male and female reclosable fastener strips, said machine having means for effecting intermittent advancement of said sheet material, means for sealing free edges of said bags, and means for interlocking said male and female fastener strips during formation of said bags, improvement comprising:
two pairs of pivotal arm means respectively disposed on a pair of carriers between which said sheet material passes, said carriers disposed for movement towards and away from each other, each arm means of each pair facing across said sheet material with one arm means of the other pair, and each said arm means being biased towards said sheet material, such that said facing arm means together engage said sheet material and actuate each other on contact with said sheet material to stretch said sheet material transversely in preparation for application of a transverse seal of bag free edges, said arm means having convex material engaging faces to have rolling contact with the material.

25. The improvement of claim 24:
wherein said carriers include heat sealing means for effecting said transverse seal.