US3765309A

US3765309A - Bag bottom construction

Info

Publication number: US3765309A
Application number: US00172049A
Authority: US
Inventors: R Joice
Original assignee: UNIVERSAL MACHINERY CORP
Current assignee: FMC Corp; UNIVERSAL MACHINERY CORP
Priority date: 1971-08-16
Filing date: 1971-08-16
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16
Also published as: CA973001A; GB1405436A

Abstract

A machine and method for forming a single thickness bottom in a bag of heat-sealable sheet material such as polyethylene film from a folded strip of such material of indefinite length, the folded edge having an inwardly folded gusset therein forming a pair of double thickness marginal panel portions. The machine includes an anvil having longitudinally extending faces lying in planes symmetrically inclined above and below a central horizontal plane, each anvil face having a groove formed therein in the shape of two legs of an isosceles right triangle whose altitude lies in a vertical plane perpendicular to the direction of strip movement. During strip movement the panel portions are folded apart and are drawn along the anvil faces. The strip is momentarily stopped, and clamping means immediately upstream and downstream of the anvil grooves tightly retain the panels stationary on the anvil, with portions bridging the grooves. A pair of electrically heated cutting and sealing knives, each having an edge registering with one of the anvil grooves but of narrower width than the groove, are brought into sealing and cutting relation with the strip panel portions which bridge the grooves, sealing the perpendicular strip panel edges and cutting triangular chips from the panels. Upper and lower vacuum hoods immediately inwardly of the grooves communicate with a vacuum source for removal and disposal of the chips. The anvil is cooled to minimize film build-up, desirably by circulating cooling water through its hollow interior. After chip removal the vacuum supply is interrupted, the knives and clamping means are retracted, and the strip is then indexed downstream, with means being provided to support the strip panels in a common plane with the remaining portion of the strip. Individual bags are formed from the strip downstream of the present machine by conventional sealing and cutting transversely of the strip intersecting the apex of the triangular cut-outs in the strip panels.

Description

United States Patent i191 J oice BAG BOTTOM CONSTRUCTION [76] Inventor: Richard L. Joice, c/o Universal Machinery Corporation, 8955 Fullbright Ave., Chatsworth, Calif.

[22] Filed: Aug. 16, 1971 [21] App]. No.: 172,049

2,606,850 8/1952 Piazze..... 93/DlG. 1 3,023,679 3/1962 Piazze 93/35 R 3,395,622 8/1968 Kugler.... 93/DlG. l 3,537,360 11/1970 Farnam... 93/35 R X 3,646,856 3/1972 Worndl 93/35 R 3,460,441 8/1969 Davis, Jr. 93/35 R X Primary Examiner-Andrew R. Juhasz Assistant Examiner-James F. Coan Attorney-Allan M. Shapiro 57] ABSTRACT I A machine and method for forming a single thickness bottom in a bag of heat-scalable sheet material such as polyethylene film from a folded strip of such material of indefinite length, the folded edge having an in- Oct. 16, 11973 wardly folded gusset therein forming a pair of double thickness marginal panel portions. The machine includes an anvil having longitudinally extending faces lying in planes symmetrically inclined above and below a central horizontal plane, each anvil face having a groove formed therein in the shape of two legs of an isosceles right triangle whose altitude lies in a vertical plane perpendicular to the direction of strip movement. During strip movement the panel portions are folded apart and are drawn along the anvil faces. The strip is momentarily stopped, and clamping means immediately upstream and downstream of the anvil grooves tightly retain the panels stationary on the anvil, with portions bridging the grooves. A pair of electrically heated cutting and sealing knives, each having an edge registering with one of the anvil grooves but of narrower width than the groove, are brought into sealing and cutting relation with the strip panel portions which bridge the grooves, sealing the perpendicular strip panel edges and cutting triangular chips from the panels. Upper and lower vacuum hoods immediately inwardly of the grooves communicate with a vacuum source for removal'and disposal of the chips. The anvil is cooled to minimize film build-up, desirably by circulating cooling water through its hollow interior. After chip removal the vacuum supply is interrupted, the knives and clamping means are retracted, and the strip is then indexed downstream, with means being provided to support the strip panels in a common plane with the remaining portion of the strip. Individual bags are formed from the strip downstream of the present machine by conventional sealing and cutting transversely of the strip intersecting the apex of the triangular cut-outs in the strip panels.

11 Claims, 14 Drawing Figures Oct. 16, 1973 United States Patent [1 1 Joice PAIENTEDnm 16 um 3,765,309 sum u 0F 5 INVENTO/Q. R/CHQED L JO/CE wuzz 1 BAG BOTTOM CONSTRUCTION BACKGROUND AND SUMMARY OF THE INVENTION tus can subsequently form open-topped bags for packaging any of many commodities such as loaves of bread.

It is well known that heat-sealable sheet materialsuch as polyethylene film has become increasingly popular for packaging various foods as well as many other products. Such film, in the form of a strip having a thickness of from about I to 3 or 4 mils and an indefinite length, is formed by heat-sealing and cutting machinery into containers such as open-topped bags for later filling with the desired product. When used to package loaves of bread, typical bag making, machines form the bottom from a folded strip of film by first forming a continuous gusset or infold in the already folded edge of the strip, thus creating a four-ply thick ness of film adjacent tothe strip edge; and by then heat sealing the side walls, transverselyof the strip length. The resulting bag, when filled as witha loaf of bread, presents an appearance at the bottom. end'which isobjectionable in that tucked-in ear or reentrant portion is formed at each end of the bottom. Moreover, most bags are made from film having a decorative pattern printed thereon, and'the region including the in-folded ears creates a clash of the patterns because much of that region is of double thickness, with portions-of the pattern on each sheet of film being visible.

Thus a bag having'abottom of single thickness film throughout is desirable, an'dattempts have beenmade to create machines for making such a bag, known' as a square bottom bag. It'has been proposed, for example, to make a square bottom for a bag by first forming a gusset in the folded edge of a strip, then heat-sealing and cutting chips from the four-thickness material, and subsequently separating the two folded portions from one another, breaking the seal between one pair of vided amachine andprocess for forming square bottoms for bags of heat sealable film material wherein no parting agent such as lacquer is needed on the film, since no separation of sealed or partially sealed edges is involved in the practice of the invention. The bottom forming machine of this invention receives, from a source of heat sealable film, a horizontally disposed strip of indefinite length having a fold along one longitudinal edge, and a gusset or in-foldin the folded edge, thus forming a pair of double thickness marginal panels bounded laterally by fold lines, one fold line being a common boundary of bothof the pair of panels. The

machine separates the two panels as they enter the machine during movement of the strip, so that the panels lie adjacent to angularly related faces of a water-colled anvil having formed in each of its faces a groove in the shape of the two legs of an isosceles right triangle, the apex pointing inwardly or transversely of the strip. The two grooves are in vertical alignment. The strip is momentarily halted, and the panels are tightly pressed to the anvil faces by clamping members upstream and downstream of the grooves, with portions of the panels thus bridging the grooves. Electrically heated knives having edges registering with the grooves are then moved into contact with the film, sealing the panel sheets along edges aligned with the grooves, and cutting free a part of each panel, or chip, in the form of a right isosceles triangle. A vacuum system removes the chips while the knives are in cutting positions, and the knives and clamping members are then retracted away from the anvil faces and the panels. The strip is then indexed downstream and the cycle is repeated. Subsequently complete bags are made from the strip in accordance with the conventional side seal process, by cutting and heat sealing the strip along transverse lines intersecting the apex of the cut-out portions of the panels.

Accordingly it is a principal object of the invention to provide and disclose novel improvements in the making of bag bottoms of heat-sealable sheet material such as polyethylene film. Other objects and purposes are to provide a machine and method for heat sealing edges of such film while a double thickness of the film is stretched taut acrossa groove formed in a back-up member such as an anvil; to provide in such an arrangement means for cooling the anvil, to thereby minimize build-up of film thereon and also accelerate cooling of sealed'edges; to provide means for evacuatingly removing cut-out portions of film; and for other and additional objects as will become clear from a study of the 4 following description of a preferred embodiment of the invention, taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the general path of movement of a strip of folded film in accordance with the present invention.

FIGS. 2, 3, 4 and 5 are sectional views taken on arrows II--II, IIIIII, IV-IV and V-V respectively of FIG. 1, looking in the direction of strip movement, i.e., downstream.

FIG. 6 is a vertical sectional view of the machine of the present invention, taken substantially on the plane of arrows VIVI of FIG. 1, but looking upstream, i.e., against the direction of strip movement; distal portions of the upstream clamping assemblies and the upstream halves of the knives are fragrrientarily shown in broken lines in their retracted or inoperative positionsjthose assemblies and knife halves are fully shown in their extended or operative positions in solid lines except where concealed by other parts.

FIG. 7 is an exploded perspective view of the machine; for clarity of presentation the upper shaft actuator means is omitted, and the upper shaft assembly, and the clamping assemblies and knife mounted thereon, are shown displaced upwardly from their true positions; for the same reason the upper vacuum duct and hood, as well as the upstream film guide plates, are shown in broken lines; and the lower shaft assembly and parts carried thereon are omitted, except that the shaft portion nearest the viewer, and the lower shaft actuator means, are shown.

FIGS. 8 and 9 are fragmentary sectional views taken on arrows VIII-VIII and IX-IX of FIG. 7, showing details of preferred construction by which to electrically insulate opposite shaft portions of the shaft assemblies.

FIG. 10 is a perspective view of a bag in flattened condition, as made in accordance with the present invention.

FIG. 11 is a perspective view like FIG. 10, with the gusseted bottom portions folded outwardly so that the bottom is planar.

FIG. 12 is a perspective view like FIGS. 10 and 11, with the bag expanded into content-receiving conditron.

FIG. 13 is a fragmentary sectional view, on an enlarged scale, similar to the corresponding portion of FIG. 6, but showing the parts at the instant when the clamps first make contact with the film strip to hold it in place, and before the cutting edge of the knife has contacted the panel portions of the film strip.

FIG. 14 is a fragmentary sectional view similar to the operative portion of FIG. 13, showing the cutting and sealing edges of the knives during the cutting and sealing operation.

DETAILED DESCRIPTION Referring now to the drawings, there is shown in FIG. 1 a diagrammatic representation of the general path of movement of a folded strip of film or web material in accordance with the present invention. The direction of strip movement is generally upwardly and to the left in the perspective showing of FIG. 1. Thus the double thickness strip is indicated generally at 20, in which the upper sheet 21 is folded upon lower sheet 22 along a folded edge 23. Desirably the lower sheet 22 extends somewhat beyond the upper sheet 21, producing a singlethickness lip 29, as seen in detail in FIGS. 2 and 3. Although not shown in the present illustrative form of the invention, and forming no part thereof, perforations may be formed in lip 29 for ease of handling ofindividual bags during later operations, as is well known in the art.

As shown in FIG. 1, folded strip from a source, not shown, of indefinite length is passed successively through a gusseting station 30, a dancer station 40, bottom forming station 70 of the present invention, a driving station 80, a bag forming station 85, and a receiving station 95 for receiving individual bags 90 and deliverv ing them, as by conveyor means, for eventual stacking,

wicketing or other packaging as may be desired. Driving station 80 includes a pair of drive rolls 81, 82 and drive means here shown as including a drive motor 83 and a power train such as gears 84. Bag forming station 85 includes a vertically reciprocatable heated sealing and cutting knife 86 cooperating with back-up roll 87.

With the exception of the bottom forming machine 70, the other elements and procedures just mentioned are all conventional and well known in the art, and form no part of the present invention as such. Briefly stated, gusseting means 30 may include a disk 31 mounted for rotation about a shaft 32 on a vertical axis, and serving to form a gusset in the folded edge portion of strip 20 by folding inwardly the folded edge 23,

thereby forming two additional folded edges, upper and lower folded

edges

24 and 25 respectively, as best seen in FIGS. 3 and 4, defining upper and lower

double thickness panels

26 and 27.

' As will be later understood as the description progresses, strip 20 moves through the bottom forming portion of the machine 70 in intermittent fashion, means being provided to cyclically stop the longitudinal movement of the film during certain sealing and cutting operations to be later described. As a consequence, and in order to permit continuous strip movement at and upstream of gusseting station 30, the dancer station 40 permits intermittent motion at its output or downstream end 41, while maintaining substantially constant speed of strip movement at its input or upstream end 42. This constant movement thereby permits the gusseter 30 to form the gusset in the strip while the strip is moving at substantially constant speed. Dancer station 40 thus includes a number of upper idler rollers 43 mounted for free rotation about fixed horizontal axes, and a number of lower idler rollers 44 mounted for rotation about horizontal axes on a pair of

arms

45 and 46 joined at their distal ends by cross-member 49, the arms being pivotally mounted at 47 and 48 respectively for pivotal swinging about a common horizontal axis. Dancer station 40 also includes a pair of drive rolls 50 and 51 which are driven in synchronism by motor means indicated generally at 52 and suitable gears forming a power train indicated generally at 53.

Means are provided in dancer station 40 for making fine variations in speed of the driving motor 52, in response to excessive pivotal movement of

support arms

45 and 46 of the dancer assembly, such movement being caused by intermittent motion of strip 20 at the output end 41 of the dancer station. Thus electrical control means schematically shown as including upper and lower contact terminals 54 and 55 are connected to suitable control means indicated generally at 56 through leads 57 and 58 respectively. The output of control means 56 in line 59 serves to make fine variations in the speed of rotation of motor 52 driving the rollers 50 and 51. A member 60 fixed to the outer end of arm 45 contacts one or the other of terminals 54, 55 if arm 45 swings beyond predetermined limits.

Thus dancer means 40 serves to draw strip 20 through rollers 50, 51 at a substantially constant speed, with only slight variations from time to time when the pivoted

support arms

45, 46 and idler rollers 44 supported thereon are caused to swing beyond their designed limits. For example, if the pivoted assembly of

arms

45, 46 and rollers 44 is drawn upwardly far enough so that member 60 actuates contact 54, then control means 56 serves to increase slightly the speed of driving motor 52. Conversely, if the pivoted assembly swings downwardly far enough to actuate contact 55, then control means 56 serves to slightly decrease the speed of driving motor 52. In either event, the speed of rolls 50, 51 is slightly changed in the proper sense until equilibrium is restored and continued.

In the bag bottom forming machine of the present

invention strip panels

26, 27 are separated from one another, as seen in FIG. 4. As will be later understood, portions are cut from

panels

26, 27, the cut portions being in the form of right isosceles triangles, with the strip edges forming the legs of the right triangle being sealed together. Such cutout portions are shown at 71,

and the apex 72 will be the point at which the final sealing and cutting operation by sealing and knife means 85 will be performed, extending transversely of strip 20.

The general construction of the present machine will be best understood by reference of FIGS. 6. and 7, showing the detailed components by which the right isosceles triangular portions or chips are cut from the side edges portions of the strip, and the adjacent edges of the remaining portions of the strip are sealed together. A vacuum exhaust system is provided in order to remove the chips from the machine at the time of cutting.

The general arrangement of cooperating parts will be best understood by reference first to FIG. 7. In this perspective showing, the upper actuating shaft, together with the upper cutting and sealing blade and the upper pair of clamp members mounted on the shaft, has been exploded upwardly from their true locations, in order to better show the parts of the machine otherwise concealed. The machine also includes a lower actuating shaft and clamping means and blade mounted thereon, disposed symmetrically relative to a central horizontal plane. These lower parts are shown only fragmentarily in order not to obscure important parts of the machine.

More specifically, the machine as seen in FIG. 6 includes a pair of spaced vertical structural members in the form of L-beams indicated generally at 100 and 101 providing support for the major components of the machine. An anvil assembly indicated generally at 110 includes a pair of rearwardly extendingmounting

plates

102, 103 attached to

brackets

104, 105 respectively, which are in turn mounted upon the parallel faces of

structural members

100, 101. The anvil assembly includes upper andilower walls or plates 11-1, 112 which may be formed integrally as shown. Their respective outer surfaces 113 and 114are smooth to permit portions of strip 20 to slide thereon without damage to the strip. Each of the surfaces 113, 1 14 has formed therein a groove having the form of the two equal legs of aright isosceles triangle, the groove on the upper plate 111 being indicated generally at 120 and including

legs

121 and 122 intersecting at a right angle at the apex 123. Anvil assembly 110 includes a rear wall'or plate 115, forming with plates 111 and 112 a hollow interior for flow of cooling liquid therethrough.

Means are provided in accordance with the invention for cooperating with anvil 110 for clampingly retaining the panel portions of strip 20 momentarily in fixed relation with anvil 1 10, and for sealingand cutting from the two separated

panel portions

26 and 27 triangular chips each defined generally by the anvil groove and the respective outer folded

edge

24 and 25. In the present embodiment of the invention, such means in the upper part of the machine are mounted upon a shaft assembly indicated generally at 130, and including a pair of metal shafts 131, l32and a central shaft portion of non-conductive material 133.

Means are provided in the present invention for mounting shaft assembly 130 relative to vertical structural members 100, 1.02, and in the present illustrative form of the invention such mounting means include a pair of

blocks

140, 141, mounted on the face of structural member 100, and a similar block 142 mounted on the corresponding face of structural member 101. Each of the

blocks

140, 141, 142 has formed therein a semicylindrical recess, and a cap is provided forv each of the blocks, the cap similarly having a semi-cylindrical recess and adapted .to be fastened to its respective block, in order to provide, by the mating of the two semicylindrical surfaces, a support for a non-conductive bushing which constitutes a bearing for the shaft. In FIG. 7 such a cap and bushing are shown for block 142, but are omitted for

blocks

140, 141, in order not to obscure other parts of the machine. It may be noted also that the machine of the present invention is basically symmetrical about a horizontal plane. Thus, although not shown in detail in FIG. 6, a shaft assembly similar to shaft assembly is mounted on

structural members

100, 101 beneath the anvil assembly 110. Portions of the lower shaft assembly, together with the bearing blocks and caps for supporting the lower shaft assembly, are fragmentarily shown in FIG. 7, together with the actuating motor for periodically partially rotating the shaft assembly.

Inorder to provide the necessary electrical insulation of

shafts

131 and 132 from the other parts of the rims ent machine, each of the bearing formed by blocks, 140, 141 and 142 and their respective caps is provided with a bushing of suitable non-conductive material such as nylon. A complete bearing assembly is shown in exploded form in connection with mounting block 142, including a nylon bushing 146 and a bearing cap member retained in position by fastening means such as machine screws received in threaded bores 147 of the bearing blocks. The corresponding parts of one of the lower bearings are shown assembled in FIG. 9.

The semi-cylindrical portions of bearing

blocks

140, 141 and 142 establish a common center line 150, which is of course also the center line of shaft assembly 130.

Mounted upon shaft assembly 130 are means in accordance with the present invention for cyclically clamping marginal panel portions of strip 20 fixedly relative to anvil assembly 110, together with means for sealing and cutting a chip from the panel portions of the momentarily stationary strip.

More particularly, and with continued reference to FIG. 7, the clamping means mounted upon shaft assembly 130 include a pair of clamp assemblies indicated generally at and 162. They are identical to one another except that one is the mirror image of the other, and they are symmetrically disposed relative to the central vertical plane of the machine. Clamping assembly 160 includes a base plate attached by fastening elements 164 to a mounting block 163, which is in turn fixedly mounted upon shaft 131. A clamping foot 166 is resiliently supported below base plate 165 and is connected thereto by upwardly extending studs or bolts 161 (see FIG. 13) whose upper ends are fixed to collars 167. Means are provided between the base plate 165 and the clamping foot 166 for resiliently supporting the foot, such means being here shown as including compression coil springs 168 surrounding the upstanding studs or bolts 161. The'lowermost face of foot 166 is provided with a layer or pad 169 of resilient rubber-like material having a high coeficient of friction when clamped on strip panel portion 26 holding the panel absolutely stationary on the upper surface 1 13 of anvil assembly 110 during the cutting and sealing operation to be described hereinafter.

Also mounted upon shaft assembly 130 is a cutting and sealing knife indicated generally at having a pair of integrally formed

legs

181 and 182, intersecting at a right angle at apex 183. Cutting blade 180 and its

legs

181, 182 are shaped to exactly register with groove 120 on anvil assembly 110, but, as will be later understood, the lower cutting edge of the blade 180 is smaller in dimension that the width of the groove 120.

Means are provided in accordance with the present invention for supplying current to the ends of

legs

181 and 182 of knife 180, whereby to heat the blade. In the present illustrative form of the invention, such means include connector blocks 185 and 186 made of conductive material and serving both to mechanically support the outer ends of

blade arms

181 and 182 respectively, as well as to furnish electrical contact with such outer ends.

Blocks

185 and 186 terminate upwardly in

connectors

187 and 188 to which are connected the ends of

cables

189 and 190, of high current carrying capacity, such as welding cable, connected to a source of electric power not shown. It will be observed that connector blocks 185 and 186 are mounted upon inner ends of

shafts

131 and 132 respectively, and are not in electrical contact with one another, by reason of the fact that the central shaft portion 133 is made of non-. conductive material such as fiberglass.

In the sectional view of FIG. 8, there is shown the central portion of shaft assembly 130, including

operative shafts

131 and 132, and the central shaft portion 133 made of non-conductive material. Thus, the inner ends of

shafts

131 and 132 are fixed to the central shaft portion 133 by means, here shown as including drive pins 136, locking the several shaft components into a rigid unitary assembly. It will be noted that the inner ends of

shafts

131 and 132 are spaced apart and thus not in electrical contact.

A preferred construction of the bearing assembly for insulatingly supporting the upper and lower shaft assemblies, will be understood by reference to FIG. 9. Thus, bearing block 200 is one of the bearing blocks for the lower shaft assembly and is the counterpart of bearing block 140 in the upper part of the machine. The non-conductive bushing 146 is mounted upon shaft 203, the lower counterpart of shaft 131, and bushing 146 is received in the semi-cylindrical portion of bearing block 200, being retained in that position by bearing cap 204, the latter being held in assembled relation by fastening elements 205.

With further reference to FIG. 7, motor means for cyclically actuating the lower shaft assembly of which shaft 203 is a part, indicated generally at 210, and includes a cylinder 211 having a lower extension 212 which is pivotally mounted upon a pivot pin 213 extending between and mounted on a pair of

cars

214 and 215 projecting forwardly from and being mounted upon a mounting plate 216, which is fixed by suitable attachment elements 217 to the front surface of vertical structural member 100.

Projecting upwardly from cylinder 211 is a piston rod 220 having an upper extension 221 pivotably connected between a pair of ears 222 which project forwardly from and are fixedly mounted on shaft 203. It will thus be seen that vertical motion of piston rod 220 will impart rotational motion to the lower shaft assembly of which shaft 203 is a part. Similarly, as shown in FIG. 6, an upper actuating motor indicated generally at 233 serves to actuate by partial rotation the upper shaft assembly 130. Thus, with continuing reference to FIG. 6, the upper actuating motor 233 has projecting downwardly therefrom an actuator piston rod 234 terminating downwardly and connected to an attachment block 235 which in turn is pivotably connected between a pair of forwardly projecting ears, one of which is shown at 236 in FIG. 6, the ears being fixed at their rear ends to shaft 131 of the upper shaft assembly 130. It will be seen that vertical longitudinal movement of actuator piston rod 234 will cause rotational movement through a small arc of shaft 131, and thus of the entire upper shaft assembly 130.

Vacuum means are provided in accordance with the present invention for evacuatingly removing the cutout portions, or chips, of the

panel portions

26, 27 of the strip. In FIG. 7, such vacuum means are shown as including a vacuum conduit indicated generally at 230, leading to a source of vacuum not shown, and at its upper end being connected to a vacuum control valve indicated generally at 232. The latter valve may include a slidable plate 234, longitudinally movable between an inner or vacuum-blocking position and an outer or open position.

Means are provided for selectively moving slidable plate 234 between its inner and outer position, including in the present form of the invention an actuator rod 235 attached to the outer end of plate 234 by a bifurcated connector 236, the actuator rod 235 being longitudinally moved by power means 237 which may be, for example, an air-operated piston device, a solenoid or the like.

From vacuum control valve 232, a conduit 240 extends upwardly and is divided at its upper end 241 into front and rear upwardly extending

conduits

242 and 243 respectively. The rear vacuum conduit 243 continues upwardly, the upper portion. thereof being also shown in dotted outline. Said upper portion of the rear vacuum conduit extends arcuately forwardly and thence downwardly, terminating in an upper vacuum hood indicated generally at 245 and having V-shaped

sidewalls

246 and 247, which terminate slightly above and inwardly of the

grooves

121 and 122 of the anvil assembly 110. The

sidewalls

246, 247 of the vacuum hood meet forwardly along a vertical apex or edge 248, which itself lies slightly inwardly of apex 123 of groove 120. The lower vacuum hood 242 is similarly shaped, having a pair of V-shaped sidewalls 251 and 252, meeting forwardly in a forwardly directed apex or edge 253. Although not shown in FIG. 7, it will be understood that sidewalls 251 and 252 of the lower vacuum hood lie immediately inwardly of the legs of the groove formed on the lower face 114 of the anvil assembly, and the forwardly directed front edge 253 lies immediately inwardly of the apex of that groove. Walls 251 and 252 terminate upwardly slightly downwardly of the lower face of anvil assembly 110.

The configuration of the component parts of the vacuum system permits the upper shaft assembly 130, and particularly the central non-conductive shaft portion 133, to extend between the vacuum conduit 243 and the vacuum hood 245. Thus, the upper vacuum hood 245 includes a rear wall 255 (see FIG. 6), which is spaced forwardly from the forward wall 256 by a distance sufficient to freely accommodate the nonconductive shaft element 133.

Walls

255 and 256 are joined at their upper ends by a semi-circular portion 257. Similarly, space is provided in the lower portion of the vacuum system, below anvil assembly 110, for permitting the lower shaft assembly, and particularly the non-conductive central portion thereof, to extend between the front and rear ducts of the vacuum system. Thus, with reference to FIGS. 6 and 7, lower vacuum hood 242 is bounded rearwardly by a vertical rear wall 258, which is spaced forwardly from the forward wall 256 of the rear duct. These two walls, 256 and 258, are joined at their lower ends by a semi-cylindrical portion. 259, and the lower non-conductive shaft component 333 (corresponding to shaft component 133 in the upper shaft assembly) is freely received in the space between

walls

256 and 258 of the conduit system.

As further shown in FIG. 7, means are provided in accordance with the invention for facilitating the separation of the gusset formed in marginal panel portions of the strip 20, and for guiding the panels 26 and 2-7 of the strip during their movement along the anvil assembly 1 10, so that the panels will be in close relationship with the respective faces of 113, 114 of the anvil assembly.

At its left end as seen in FIG. 7, anvil assembly 110 has a rearwardly extending mounting plate 106, formed integrally with the anvil assembly, and desirably there may be mounted thereon means for separating and guiding the gusseted panel portionsof strip 20 during travel of the strip through the present machine. Separator means indicated generally at 280 includes a foot portion 281 attached to the mounting plate 106 and a leg 282 terminating in a transverse portion 283 extending forwardly to an edge 284 in alignment with the forwardly projecting V-shaped edge of the anvil. Guide means, shown in dotted outline in FIG. 7, include upper and lower guide plates indicated generally at 287 and 288 respectively. The upper guide plate 287 includes an inclined portion 289 foxed to a bracket 290 which in turn is attached to mounting plate 106. The inclined portion 289 for guide plate 287 is spaced only slightly from the adjacent inclined face 113 of the anvil assembly. The lower guide plate 288 is symmetrically shaped and mounted.

Means may also desirably be provided in the present invention for supporting the lower panel portion 27 after the cutting and sealing operation has been performed. As shown in FIGS. 5 and 7, such means may include a plate indicated generally at 293 located below the anvil assembly and extending substantially parallel to the lower face of that assembly. Plate 293 has an inclined forward edge 194 so configured and located as to avoid interference with the adjacent clamping assembly in the lower portion of the machine (symmetrical to clamping assembly 162 previously described), so that the plate 293 serves to slidingly support thereon the marginal panel 27 portion of the strip. Plate 293 may be supported by any suitable means; in the present form of the invention (see FIG. 6), plate 293 is attached to a mounting block projecting rearwardly from the rear face of the anvil assembly and provided with a support bracket 295 attached to a mounting block 296 on the rear of anvil assembly 110. Panel 27 of the strip will under some. conditions tend to cling to the lower surface of 114, of the anvil, but under other conditions panel 27 may fall downwardly, and plate 293 limits such fall and prevents the possibility that panel 27 might fold itself downwardly and inwardly toward the major portion of the strip 20. Equivalent support means downstream or the anvil assembly 110 may be provided, in the form of

guide plates

297 and 298. Such plates may extend the entire width of strip 20, underlying and supporting the strip, although under typical conditions the tension in the strip is sufficient to support the major portion of the strip.

With further reference to FIG. 7, means are desirably provided in accordance with the invention for continuously cooling the anvil assembly 110. In the present form of the invention, such means include an inlet fitting 300 connected to a source of cooling liquid such as water and, at the near end of anvil assembly as seen in FIG. 7, an outlet fitting 301. As seen in FIG. 1, the inlet fitting 300 may enter the anvil assembly through the anvil rear wall 115, while outlet fitting 301 may be mounted in the end wall 106 of the anvil assembly. Both fittings communicate with the hollow interior of the anvil assembly, and water circulated thereby and through the anvil assembly serves to cool the anvil assembly and thereby minimize the build-up of deposits of film which would otherwise be likely to occur as a result of the sealing and cutting process during operation.

BOTTOM FORMING OPERATION With strip 20 momentarily stationary, the successive steps in the formation of a bag bottom will be understood by reference to FIGS. 6, 13 and 14. With reference first to FIG. 6, upper clamping assembly and its lower counterpart clamping assembly 360 are shown in their operative positions, with their

respective feet

166 and 366 in their clamping positions, so that their respective resilient frictional layers or

pads

169, 369 press the

strip panel portions

26 and 27 against upper and lower anvil surfaces 113 and 114. To assist visual orientation, fragmentary portions of the upper and lower clamps, and of the upper and lower knives, are shown in their retracted positions in dotted outline, and are indicated at 160A, A, 360A and 380A in FIG. 6.

With the panel portions of the strip thus tightly held, and bridging the

upper anvil grooves

121, 122 and the corresponding lower anvil grooves, the cutting and sealing knives are then moved into their operative positions as seen in solid lines in FIG. 6, and in the enlarged fragmentary view FIG. 14. As will be understood, these movements of the clamping assemblies and knives are the result of partial rotation of the upper actuating shaft 130 and of its lower counterpart, of which the central portion 333 and one end shaft 203 are shown.

FIG. 13 shows the parts after the clamping feet have made initial contact with the

strip panels

26, 27, and before the

knives

180, 380 have arrived at their operative positions. At this point in the cycle vacuum is applied preparatory to removal of the chips when cut as in FIG. 14. After the chips are so cut and the side edges of the panels are sealed, the clamps and knives are withdrawn to their inoperative positions by counterrotation of the upper and lower shaft assemblies under the control of

motors

210 and 233.

In recapitulation, the cycle of operation includes the I following steps:

4. Opening of vacuum control valve 232 by actuating motor 237 to withdraw closure plate 234, thereby applying vacuum to the hoods above the central portion of strip panel 26 and below the central portion of strip panel 27.

5. Arrival of the cutting and sealing knives in their operative positions, as seen in FIG. 14, and concurrent increase of clamping force on the panel strips by reason of the resilient mounting of the clamping feet, including compression springs 168.

6. Vacuum removal of the triangular chips cut from the

panel portions

26 and 27, through upper and

lower ducts

245 and 242 respectively.

7. Closing of vacuum control valve 232 by actuating motor 237 to force closure plate 234 inwardly of the valve, thereby removing vacuum from the vacuum hoods.

8. Actuating lower and

upper motors

210 and 233 to withdraw the upper and lower clamping assemblies and knives to their inoperative positions, by counterrotation of

shafts

203 and 131.

9. Starting strip movement by energizing the drive motor 83.

The machine and method of the present invention from square bottoms at a cyclic rate of upwards of 120 per minute, and the present invention is hence compatible with production speeds of conventional sidesealing bag machines.

As seen in FIG. 6, the plates or

walls

111 and 112 of the anvil assembly 110 are perpendicular to one another, each lying in a plane 45 from the horizontal Downstream of the operating parts of the machine the walls taper gradually together, thus guiding the notched panels together. FIG. illustrates a typical section near the downstream end of the anvil assembly.

It will be observed that each of the inclined faces of the anvil assembly has a dimension such that the diverging arms of the groove formed therein extend beyond the outer folded edge of the strip panel received on the anvil face, since the present invention contemplates that the notches formed in the panels, or the chips cut out to form the notches, shall be bounded by the grooves and the outer folded edge of the panel.

It will also be observed that the apex of each of the grooves formed in the anvil faces should be as close as is reasonably feasible to the transversely directed apex of the anvil faces themselves. As will be seen, if the groove apex is spaced substantially from the anvil apex, the panels will not properly form a flat bottom when the completed bag is opened and filled with its intended contents.

No specific materials are necessarily contemplated except that the parts described as electrically conductive are typically made of metal, the cutting and sealing knives themselves being made of copper. The major structural members of the machine are advantageously made of steel.

It will accordingly be seen that there is here provided method and apparatus for heat sealing two or more plies or thicknesses of heat-scalable film material along a desired line by forming a groove having the shape of the desired line in the otherwise smooth face of a backup member, clamping the plies of material to the face with portions bridging the groove, and applying sealing heat to the plies immediately above the groove, as by a heated knife blade whose sealing edge has a shape congruent to that of the groove. When, as in the disclosed form of the invention, the groove is so shaped as to intersect an edge of the plies at spaced points, the chips of film cut from the plies concurrently with the sealing operation may be removed by vacuum means as here disclosed. In a bag bottom making operation from upper and lower panel portions of a gusseted strip of polyethylene film, the grooves forming the legs of a right isosceles triangle, and with means for cooling the back-up anvil to prevent film build-up, the present machine provides an efficient attachment for a conventional side-seal bag making machine.

Modifications and changes from the illustrative form of the invention herein disclosed are within the contemplation of the invention and all such modifications and changes not substantially departing from such disclosed form are intended to be embraced within the scope of the appended claims.

I claim:

1. The method of forming a bag bottom in a strip of indefinite length having a marginally folded edge, said marginal portion including a two ply panel of heatsealable sheet material, comprising the steps of:

inwardly folding a gusset at the marginally folded edge to form a pair of facing double thickness marginal edge portions;

separating the pair of facing marginal edge portions by separating them over an anvil;

separately clamping the edge portions against opposite sides of the anvil, which has a groove recessed on each side, with a portion of each of the edge portions bridging the groove; and

applying sealing heat to said bridging panel portion.

2. The invention as defined in claim 1 wherein the groove intersects the folded panel edge at two spaced points, and including the step of removing the portion bounded by the edge and groove by applying vacuum to the surface of the panel opposite the surface in contact with the back-up member.

3. Apparatus for forming a bag bottom construction in a two ply panel of heat-sealable sheet material which is folded and gusseted to form a pair of double thickness marginal panels comprising:

an anvil having opposite faces for separating said marginal panels;

means for clamping each of said panels against an opposite anvil face; and

means for cutting notches and applying sealing heat to the marginal panels on opposite sides of said anvil to form a bag bottom in the material.

4. The invention as defined in claim 3 including:

means for removing the notched-out portion of the panel by applying vacuum to the face of the panel opposite the face adjacent to the face of the anvil.

5. The invention as defined in claim 3 including means for cooling said anvil.

6. A machine for simultaneously forming congruent triangular notches, defined by sealed edges, in a pair of two ply marginal panels of a horizontally disposed gusseted strip of heat-scalable sheet material of indefinite length, the strip being intermittently stationary and being cyclically indexed downstream to space successive notches by a predetermined distance, comprising:

an elongated anvil provided with a pair of generally smooth inclined faces symmetrical to a reference plane and meeting at an apex directed transversely of strip movement, each face having formed therein a groove having a shape of the legs of a right isosceles triangle meeting at a groove apex close to the first named apex, said grooves being aligned normal to said reference plane and the legs being symmetrical relative to a plane normal to said reference plane passing through the groove apexes;

means, operative while the strip is stationary, for clamping each panel fixedly relative to an anvil face along upstream and downstream lines with intermediate panel portions bridging said grooves, the groove legs extending outwardly of the panel edges; 1 r

heat sealing and cutting means including a pair of heated knives having operative edges congruent with said grooves, said knives being disposed symmetrically above and below said reference plane through the first named apex, said knives being movable between operative positions wherein their edges are in heat sealing relation with said bridging panel portions, and retracted positions spaced substantially from the anvil faces; and

means for cyclically actuating said clamping means and for moving the knives from retracted to operative positions, and for subsequently retracting the knives and releasing the clamping means.

7. The invention as defined in claim 6 including means for cooling the anvil.

8. The invention as defined in claim 7 wherein the anvil is hollow and said cooling means includes means for circulating cooling liquid through the hollow intenor.

9. The invention as defined in claim 6 including,

means for applying vacuum to the panel portions between the grooves and thereby removing said portions as cut when the clamped panel edges are sealed.

10. The invention as defined in claim 6 wherein said clamping means include upper and lower pairs of clamping assemblies, each assembly including a base of the anvil.

Claims

1. The method of forming a bag bottom in a strip of indefinite length having a marginally folded edge, said marginal portion including a two ply panel of heat-sealable sheet material, comprising the steps of: inwardly folding a gusset at the marginally folded edge to form a pair of facing double thickness marginal edge portions; separating the pair of facing marginal edge portions by separating them over an anvil; separately clamping the edge portions against opposite sides of the anvil, which has a groove recessed on each side, with a portion of each of the edge portions bridging the groove; and applying sealing heat to said bridging panel portion.

3. Apparatus for forming a bag bottom construction in a two ply panel of heat-sealable sheet material which is folded and gusseted to form a pair of double thickness marginal panels comprising: an anvil having opposite faces for separating said marginal panels; means for clamping each of said panels against an opposite anvil face; and means for cutting notches and applying sealing heat to the marginal panels on opposite sides of said anvil to form a bag bottom in the material.

4. The invention as defined in claim 3 including: means for removing the notched-out portion of the panel by applying vacuum to the face of the panel opposite the face adjacent to the face of the anvil.

5. The invention as defined in claim 3 including means for cooling said anvil.

6. A machine for simultaneously forming congruent triangular notches, defined by sealed edges, in a pair of two ply marginal panels of a horizontally disposed gusseted strip of heat-sealable sheet material of indefinite length, the strip being intermittently stationary and being cyclically indexed downstream to space successive notches by a predetermined distance, comprising: an elongated anvil provided with a pair of generally smooth inclined faces symmetrical to a reference plane and meeting at an apex directed transversely of strip movement, each face having formed therein a groove having a shape of the legs of a right isosceles triangle meeting at a groove apex close to the first named apex, said grooves being aligned normal to said reference plane and the legs being symmetrical relative to a plane normal to said reference plane passing through the groove apexes; means, Operative while the strip is stationary, for clamping each panel fixedly relative to an anvil face along upstream and downstream lines with intermediate panel portions bridging said grooves, the groove legs extending outwardly of the panel edges; heat sealing and cutting means including a pair of heated knives having operative edges congruent with said grooves, said knives being disposed symmetrically above and below said reference plane through the first named apex, said knives being movable between operative positions wherein their edges are in heat sealing relation with said bridging panel portions, and retracted positions spaced substantially from the anvil faces; and means for cyclically actuating said clamping means and for moving the knives from retracted to operative positions, and for subsequently retracting the knives and releasing the clamping means.

7. The invention as defined in claim 6 including means for cooling the anvil.

8. The invention as defined in claim 7 wherein the anvil is hollow and said cooling means includes means for circulating cooling liquid through the hollow interior.

9. The invention as defined in claim 6 including means for applying vacuum to the panel portions between the grooves and thereby removing said portions as cut when the clamped panel edges are sealed.

10. The invention as defined in claim 6 wherein said clamping means include upper and lower pairs of clamping assemblies, each assembly including a base member and a clamping foot resiliently biased away from the base member, and wherein the actuating means force the clamping feet into clamping relation with the panels prior to the arrival of the knife edges at their operative positions.

11. The invention as defined in claim 6 wherein said anvil faces gradually converge in the downstream part of the anvil.