Wrapping apparatus

Abstract

A wrapping apparatus for wrapping a product in a plastic film includes a conveyor system for moving the product, a wrapping assembly for spirally wrapping a continuous sheet of the film about the product and the conveyor system, and a cutting assembly for forming in the wrapped film a series of perforations defining a line of tearing weakness. The conveyor system includes a pair of spaced apart conveyors which cooperatively move a product through the wrapping assembly. The cutting assembly includes a cutting element which selectively engages the film at a location between the spaced apart conveyors to form the series of perforations.

Description

BACKGROUND OF THE INVENTION

The present invention pertains to a wrapping apparatus, and in particular to a rotary stretch wrapping apparatus that provides a continuous wrap about a product.

Stretch wrapping is primarily employed to package manufactured goods in a continuous plastic wrap for protection during shipping and storage. A rotary stretch wrapping apparatus operates by rotating a plastic wrapping film about a product passing axially through the apparatus. This procedure results in the plastic film being spirally wrapped tightly about the entire product. An example of one stretch wrapping apparatus is disclosed in U.S. Pat. No. 4,317,322 to Lancaster et al. and entitled ROTATABLE FILM WRAPPING APPARATUS WITH WRAP CARRYING MECHANISM.

Although the plastic wrap provides ample protection for the goods during shipping, problems have been experienced in removing the film from the products. To provide effective protection for the goods, the wrapping films are typically quite strong and tough to resist tearing or subsequent stretching. Hence, removal of the wrap has usually been accomplished by manually cutting the wrap with a knife or other sharp implement.

The manual removal of the wrap has proven to be unsatisfactory to many users. The products are often nicked, cut, or otherwise damaged during the removal of the wrap. The situation is especially acute in regard to finished products and products shaped such that the film contiguously lies against the entire periphery of the product (e.g., a table top). Moreover, the manual cutting procedure poses a risk of personal injury.

SUMMARY OF THE INVENTION

The aforementioned problems are overcome in the present invention, wherein a rotary wrapping machine provides the wrapped film with an easy-open line of tearing weakness. Accordingly, the wrapping machine of the present invention includes a cutting device that perforates the film after it has been spirally wrapped upon the product.

More specifically, the present system includes a pair of endless conveyors that are positioned to cooperatingly transport products to be wrapped through the rotary wrapping apparatus. During the wrapping procedure, the apparatus wraps not only the product but also the conveyors supporting the product. At this time, gaps between the film and the product exist due to the configuration and locations of the conveyors. The cutting device forms a series of perforations in the film after it has been spirally wrapped, but before the product and its corresponding wrap is fed off of the conveyors.

The perforation of the plastic film permits the wrap to be easily removed by manually tearing the film along the line of tearing weakness. The present invention greatly enhances the use of the stretch wrapping procedure as a packaging alternative by effectively eliminating the difficulties and hazards heretofore experienced during removal of the wrap.

These and other objects, advantages, and features of the present invention will be more fully understood and appreciated by reference to the written specification and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a rotary stretch wrapping apparatus of the present invention;

FIG. 2 is a side view of the apparatus;

FIG. 3 is a fragmentary perspective view of the apparatus showing a conveyor system of the present invention with the clamping assembly omitted for clarity;

FIG. 4 is a rear fragmentary view of the apparatus with the clamping assembly omitted for clarity;

FIG. 5 is a cross-sectional view taken along line V--V in FIG. 2 with the electric motor omitted for clarity;

FIG. 6 is a top fragmentary view of a portion of one end of one of the conveyors;

FIG. 7 is a side elevational view of a resilient lug of the conveyor system;

FIG. 8 is a top plan view of the lug;

FIG. 9 is a cross-sectional view taken along line IX--IX in FIG. 3;

FIG. 10 is a fragmentary perspective view of a portion of the air pressure system of the apparatus;

FIG. 11 is a cross-sectional view taken along line XI--XI in FIG. 2 with the wrapping assembly omitted for clarity;

FIG. 12 is a cross-sectional view taken along line XII--XII in FIG. 1;

FIG. 13 is a sectional view of a second embodiment of the conveyor system of the apparatus;

FIG. 14 is a sectional view of a third embodiment of the conveyor system of the apparatus;

FIG. 15 is a top fragmentary view thereof;

FIG. 16 is a fragmentary perspective view of one of the conveyors of the third embodiment;

FIG. 17 is an enlarged sectional view of one of the conveyors of the third embodiment;

FIG. 18 is a side elevational view of the clamping assembly, with the wrapping and driving assemblies omitted for clarity;

FIG. 19 is a cross-sectional view taken along the XIX--XIX in FIG. 18;

FIG. 20 is a top plan view of the movable jaw of the clamping assembly;

FIG. 21 is a fragmentary top plan view of the free end of the conveyors and the perforation assembly;

FIG. 22 is a cross-sectional view taken along line XXII--XXII in FIG. 21;

FIG. 23 is a cross-sectional view taken along line XXIII--XXIII in FIG. 22;

FIG. 24 is a fragmentary cross-sectional view taken along line XXIV--XXIV in FIG. 22;

FIG. 25 is a top plan view of the assembly for measuring the width of the product;

FIG. 26 is a cross-sectional view taken along line XXVI--XXVI in FIG. 25;

FIG. 27 is a cross-sectional view taken along line XXVII--XXVII in FIG. 26;

FIG. 28 is a side elevational view of the assembly for measuring the height of the product;

FIG. 29 is a top plan view of an alternate embodiment for measuring the width of the product; and

FIG. 30 is a side elevational view of an alternate embodiment for measuring the height of the product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the preferred embodiment, a rotary stretch wrapping apparatus 10 includes a base frame 12, a rotary cage or support structure 14, a wrapping assembly 16, a conveyor system 18, and a perforating or cutting assembly 19. These components cooperate with one another to wrap products with a protective plastic film having an easy-open line of tearing weakness 21.

Base frame 12 includes a pair of upstanding large metal sheets 20, 22 and a plurality of horizontal interconnecting beams 24 (FIGS. 1, 2 and 4). Beams 24 are bolted or otherwise secured to the inner faces 26, 28 of sheets 20, 22 along their periphery, to provide a large stable base with which to effect the wrapping operation. Each sheet 20, 22 defines a large central opening 30, 32 through which the products to be wrapped are passed.

Rotary cage 14 is rotatably mounted to base frame 12 to achieve wrapping of the products as discussed below. Cage 14 is comprised of a framework including a pair of annular rings 34, 36 and a plurality of interconnecting brace members 38 (FIGS. 1-4). Braces 38 are bolted or otherwise fixedly secured to the inner faces 35, 37 of rings 34, 36 to form a uniform and stable rotary support structure. Rings 34, 36 further define a pair of aligned openings 39, 41 positioned concentrically within openings 30, 32 of base frame 12, to permit passage of the products.

Cage 14 is mounted for rotation about a substantially horizontal axis by a plurality of rollers 40, 42 journaled between sheets 20, 22 (FIGS. 1-2, 4, and 11). Preferably, eight support rollers are provided along the lower portions of base frame 12 to support cage 14. In particular, the rollers 40, 42 are paired upon rotatable shafts 44, 45 such that four rollers 40 engage the outer peripheral edge 46 of forward ring 34 and four rollers 42 engage the peripheral edge 48 of rearward ring 36. In the most preferred embodiment, the four lower-most rollers 40a, 42a are driven by an electric motor 50 and a conventional chain drive (not shown) to rotate cage 14. As a safety measure, motor 50 is preferably a fail-safe brake motor which will stop the rotation of cage 14 if the power is cut off. The four upper-most rollers 40b, 42b are idler rollers provided for support of the cage. Of course additional support rollers could be provided about the entire periphery of rings 34, 36 if needed or desired. Generally, the size and weight of cage 14 precludes it from lifting upwardly when rotated.

To further support and position cage 14, each sheet 20, 22 includes a plurality of lateral stops 52 positioned around openings 30, 32 (FIGS. 1 and 4). Stops 52 slidingly engage the outer surfaces 47, 49 of rings 34, 36 to prevent the cage from moving longitudinally. Each stop 52 includes a mounting tab 54 fixed to base frame 12 and a shoe 56 having a low-friction end surface 58 pressed against the cage rings 34, 36.

Wrapping assembly 16 includes a number of components secured to cage 14 for rotation therewith about the products (FIGS. 1-2, 4, and 5). Additionally, a cooperating counterweight (not shown) is also preferably secured to cage 14 to offset the weight of wrapping assembly 16 and thereby achieve greater balance. In short, wrapping assembly 16 functions to mount the rolls of plastic wrapping film, dispense the film as the cage is rotated, and effect prestretching of the film before it is wrapped about the product. Wrapping assembly 16 includes a film mounting structure 64, a roll driving assembly 66, a film prestretching arrangement 68, dancer roll assembly 69, and an electric motor 70.

Film mounting structure 64 is adapted to releasably mount a roll of the plastic film 72 for rotation about a substantially horizontal axis (FIG. 2). The film 74 is preferably a conventional plastic wrapping film (e.g. polyethene), such as one commercially available from Mobil Oil Corporation or Presto Corp. Of course, other suitable materials could be used. As is conventional, the film 74 is rolled upon a core 76 for easy storage, handling, and use. Film mounting structure 64 includes a pair of rotatable hubs 78, 80 each having a head which is received within the hollow core 76, and a shoulder abutment 82, 87 which flushly engages against the ends thereof. To effect installation and release of the rolls one hub 78 is longitudinally movable toward and away from core 76. More specifically, hub 80 is journaled for rotation to ring 34 by a support 84 which maintains the hub in a fixed longitudinal position. The other hub 78 is journaled for rotation by a longitudinally movable support 85 secured to ring 36 by a toggle or other type of clamp 86. Alternatively, both hubs 78, 80 could be mounted for longitudinal movement.

Film 74 is dispensed from roll 72 by a roll driving assembly 66 (FIGS. 1-2 and 5). Roll driving assembly 66 includes a driving roller 88 adapted to engage the outer periphery 89 of the roll of film 72 at all times during the wrapping operation. Driving roller 88 preferably includes a resilient outer pad 91 (preferably composed of urethane) fixedly secured upon a central, driven mounting pin 101. As can be readily appreciated, this arrangement will dispense film 74 at a substantially constant rate irrespective the diameter of the roll 72.

Driving roller 88 is pivotally mounted for arcuate movement about a drive shaft 90 secured between rings 34, 36. More specifically, an H-shaped connector 92 includes a pair of mounting segments 94 having bearings 96, 98 at each end thereof, and an interconnecting rod 99. Bearings 96 function to mount segments 94 on drive shaft 90 so that connector 92 is neither affected by nor inhibits the shaft's rotation. Bearings 98 rotatably secure segments 94 to the central mounting pin 101 of driving roller 88. Rod 99 is fixedly attached to and interconnects segments 94 to facilitate the coupling of a biasing cylinder 105 to roller 88.

Biasing cylinder 105 provides a constant force which presses driving roller 88 against the outer surface 89 of roll 72, so that no significant slippage occurs therebetween to disrupt the wrapping operation. Biasing cylinder 105 is a pneumatic cylinder having a casing 106, piston (not shown) movably positioned therein, and an extended piston rod 108. The distal end 110 of piston rod 108 is pivotally secured to connecting rod 99 by a bifurcated bracket 112 and cooperating bolt 114. Casing 106 is likewise pivotally secured to an adjacent brace 38' so that cylinder 105 can move to accommodate the variable extension of rod 108 as the film 74 is dispensed.

Biasing cylinder 105 is supplied with a substantially constant pressure of air so that roller 88 engages roll 72 with sufficient pressure throughout the entire dispensation of film 74. The air pressure for cylinder 105 is maintained through a unique supply system 143 (FIGS. 4 and 10-12). Supply system 143 includes a central unit (not shown) which is of a conventional design and includes a pump, filter, lubricator, and regulator for supplying, controlling, and maintaining a constant air pressure source through supply hose 145. Supply hose 145 is fluidly coupled to an air shoe 147 adapted to transfer the pressurized air to cage 14.

Air shoe 147 includes a body 155 secured to the underside of a support structure 149 via bolting or the like, and a sealing ring 161 secured to body 151 via an adhesive or other securing means to form an integral air shoe unit (FIG. 12). Air shoe 147 defines a radial bore 159 and a cavity 157 extending at right angles thereto. Cavity 157 opens at one end through an end face 162 of ring 161, and is fluidly coupled at its opposite end to bore 159. Bore 159, in turn, is coupled to supply hose 145 so that the supply of pressurized air is passed through air shoe 147. Air shoe 147 is positioned such that end face 162 is firmly pressed against the outer face 49 of ring 36 to form an air-tight seal therewith. Preferably, sealing ring 161 is composed of conventional V-packing material, although other materials having a low-frictional characteristic and sealing qualities could be used. The pressurized air passed into cavity 157 is transferred to an air routing system 169 provided on rotating cage 14.

Routing system 169 includes a plurality of spaced apart holes 165 defined in and extending completing through ring 36. A check valve unit 167 is securely mounted along the inner surface 37 of ring 36 at each hole 165. As ring 36 rotates during the wrapping operation, holes 165 will be sequentially passed across cavity 157 of air shoe 147 and thereby given a shot of pressurized air. The air, then, passes through check valve 167 and into conduit 168 supported by ring 36.

Each of the braces 38 has a hollow air-tight construction (FIGS. 10 and 11). Braces 38 are interconnected with one another, and with check valves 167, by conduit 168 (flexible or otherwise) (FIGS. 4 and 10-12). Hence, the pressurized air is passed through check valves 167 and travels via conduit 168 to braces 38. As seen in FIG. 5, biasing cylinder 105 is then fluidly coupled with the brace 38' to which it is secured. In this way, the fluid pressure remains substantially the same despite the expansion of cylinder 105 and any loss of air due to leaks in the system.

In an alternative embodiment, supply system 143' is a closed system such that the air in braces 38 is pressurized before the operation begins (through a port not shown) and then pressurized again only upon need. This arrangement will be sufficient for most operations.

Driving roller 88 is preferably driven by an electric DC motor 70 through a series of chains and sprockets (FIG. 2). Of course, other driving arrangements could be used. Motor 70 is fixedly attached to one of the braces 38 of cage 14 for rotation therewith. In the preferred embodiment motor 70 is mounted to the same brace 38' as biasing cylinder 105, although such mounting is not necessary. The power for motor 70 is preferably supplied through a conventional arrangement of slip rings 170 secured to the outer surface of sheet 22 about opening 32. Slip rings 170 are well known tracks, such as commonly used to power overhead cranes and the like, positioned in a circular manner circumscribing opening 32. Annular ring 36 of cage 14 includes common mating elements (not shown) to electrically couple to the tracks. Motor 70 includes a motor sprocket 107 which provides the necessary output to dispense and prestretch the film.

Drive shaft 90 is journaled for rotation between rings 34, 36 by mounts 113. Drive shaft 90 functions to transfer the output power of motor 70 to the roll driving and prestretching components. More particularly, power sprocket 109 is keyed to drive shaft 90 opposite motor sprocket 107. The two sprockets 107, 109 are operably coupled by chain 111 to effect a driving rotation of drive shaft 90.

A first driving sprocket 115 is also keyed to drive shaft 90 for concurrent rotation therewith. Opposite sprocket 115, and coupled therewith by chain 119, is a driving roller sprocket 117 keyed to mounting pin 101. Driving roller sprocket 117, then, effects driving rotation of roller 88 upon activation of motor 70. The mounting of driving roller 88 directly on drive shaft 90 also permits the driving roller sprocket 117 to move arcuately about first driving sprocket 115, without disrupting the coupling therebetween.

Once film 74 is dispensed from roll 72 by driving roller 88, it passes through a pair of prestretching pinch rollers 123, 125 (FIGS. 1-2, and 5). Pinch rollers 123, 125 each include a resilient pad 124, 126 (preferably composed of urethane) fixedly mounted on axles 129, 131 which are each journaled between rings 34, 36 by mounts 127, 128. Each axle 129, 131 includes an axle sprocket 133, 135 which is aligned and coupled with a second driving sprocket 137 (keyed to drive shaft 90) by chain 139. This driving arrangement further includes an idler sprocket 141 rotatably attached to inner face 37 of ring 36. Idler sprocket 141 facilitates the proper routing of chain 139 to obtain the necessary opposite rotations of pinch rollers 123, 125. As best seen in FIGS. 1 and 5, chain 139 follows a serpentine path outwardly of idler sprocket 141, inwardly of axle sprocket 133, and outwardly of axle sprocket 135. This arrangement enables pinch rollers 123, 125 to cooperate with one another in moving the film 74 therebetween. Axle sprockets 133, 135 are of equal size so that the pinch rollers rotate at the same rate.

The sizes of the first and second driving sprockets 115, 137, the driving roller sprocket 117, the axle sprockets 133, 134, the pinch rollers 123, 125, and the driving roller 88 are all selected such that the pinch rollers 123, 125 operate to pass the film 74 therethrough at a quicker rate than driving roller 88 dispenses the film 74 from roll 72. In this way, then, film 74 is stretched a predetermined amount prior to being wrapped about the product. Preferably, the film is to be elongated approximately 50 percent, although other amounts could be chosen. Of course, the speeds of the pinch rollers and driving roller are also coordinated with the rotation rate of cage 14.

After the film passes through pinch rollers 123, 125 it is directed through dancer roll assembly 69 (FIGS. 1 and 5). More specifically dancer roll assembly 69 includes a dancer roller 171 pivotally mounted between rings 34, 36 by a pair of pivot arms 172. The dancer roller is preferably a tubular aluminum member so as to be light weight and yet still sufficiently rigid. Of course other types of rollers could be used. Each pivot arm 172 includes a mounted end 182 and a free end 184, wherein the mounted end 182 is pivotally attached for movement about a substantially horizontal axis 186 and the free end rotatably mounts roller 171. In particular, at least one of the pivot arms 172 (and preferably both) is pivotally secured to a rotary actuator 187. The rotary actuator is a conventional device utilizing a pressurized rack and pinion arrangement designed to apply a substantially constant torque on the pivot arms 172, to thereby bias the dancer roller 171 away from pinch rollers 123, 125. Dancer roll assembly 69 further includes a guide roller 188 which is secured between rings 34, 36 to guide the film around the rotary actuator 187.

Dancer roll assembly 69 is used to partially compensate for irregularities in the shape of the product. For example, referring to FIG. 1, it can be readily seen that the lower surface of the product P is closer to the rings 34, 36 than its upper surface. Hence, wrapping assembly 16 will tend to dispense a greater amount of film when it traverses above the product than it will when it traverses below the product. To accommodate this inconsistency, the dancer roller is adapted to take up the slack when too much film is dispensed and permit extra film to be used when too little film is being dispensed. For example, as the wrapping assembly 16 rotates about the top of the product P dancer roller 171 will be biased in a counterclockwise direction (as shown in FIG. 5) so that it moves gradually away from pinch rollers 123, 125 and takes up the accumulating slack being otherwise generated. Thereafter, as the roll of film and dispensing means rotate around to the lower end of the product P, more film than is being dispensed will be required, and the tension on the film will tend to pull the dancer roller 171 back toward the pinch rollers 123, 125 to use the film accumulated as it traveled across the top of the product P. A limit switch (not shown) is included on the dancer roll assembly 69 to activate the roll driving assembly 66 by way of a pneumatic clutch and brake (now shown) in a fashion well known to those having skill in the control art.

The products to be wrapped are passed through cage 14 on a unique conveyor system 18 (FIGS. 1, 3-4, 6 and 9). Conveyor system 18 generally comprises two horizontally adjacent endless conveyors 173. Conveyors 173 are mounted on a support stand 175 in a cantilever manner such that their free ends 176 extend well within and substantially through cage 14. In a rotary stretch wrapping process, the conveyors 173 along with the product are tightly wrapped with a plastic film. To facilitate effective operation of the device, the portions of the conveyors 173 contacted by the plastic film 74 must be moving in the same direction as the product to be wrapped; otherwise the conveyors and the product will be fighting against one another and a proper wrap will not be achieved.

In the present invention, the two conveyors 173 are substantially arranged about vertical axes in a horizontal plane such that the forward, carrying path portions 178 of the conveyors are positioned along the outer paths and the rearward, return path portions 180 of the conveyors oppose one another along the interior paths. Each of the conveyors 173 includes a plurality of resilient lugs 177 which are positioned adjacent to one another in end-to-end relationship along the entire conveyor. To obviate the resistance generated by the return path, lugs 177 are expanded along the forward supporting paths so that along the top of the conveyors the product to be wrapped is supported above the return path, and along the bottom of the conveyors the plastic film 74 wrapped around the conveyors is held off the return path. Each lug 177 is preferably formed as a resilient, reinforced plastic member, preferably composed of urethane molded over a metallic core 174 for additional durability (FIGS. 7 and 9). Core 174 is a thin, C-shaped, unitary metallic member composed of spring steel or other similarly resilient material. Of course other materials and constructions possessing the requisite strength and resiliency could be used to form the lugs.

Each of the lugs 177 includes a pair of outer arms 179, 181 which are positioned along the top and bottom of the conveyors 173, respectively (FIGS. 6-9 and 21). Each arm 179, 181 is bent along its mid-section such that its natural shape is contracted with the distal ends of the arms 183, 185 directed toward one another at an inclination of approximately 30.degree.. The width of each arm further narrows toward its distal end 183, 185 to facilitate its travel around the ends of the conveyors.

Arms 179, 181 define a gap 191 which receives a portion of an endless driving chain 193. An L-shaped connector 189 (FIGS. 9 and 21) couples each lug 177 to chain 193 for movement therewith. More particularly, connector 189 includes a first segment 189a that overlies and engages a portion of chain 193; and a second segment 189b that engages the inner surface of base 192 of lug 177. Segments 189a and 189b each define a pair of spaced apart holes 194a, 194b. Holes 194a, 194b function to secure connector 189 to chain 193 and lug 177, as discussed below. In the preferred embodiment, holes 194a are spaced further apart than holes 194b, to correspond to the spacing of the chain links 195. Further, holes 194b are preferably screw threaded bores.

Chain links 195 of each chain 193 are interconnected by hollow pins 197. First segment 189a of connector 189 is secured to chain 193 by passing rivets, screws, or other securing means through holes 194a and into pins 197. The connectors are mounted to chain 193 before being secured to lugs 177 because of the limited access after attachment of lug 177 to connector 189.

Base 192 of each lug 177 defines a pair of spaced apart apertures 196 which extend through the urethane outer layer and the steel core. Lugs 177 are positioned over connectors 189 so that apertures 196 are aligned with the threaded bores 194b. Bolts 198 are passed through openings 194b, 196 and threaded in place to securely attach lugs 177 to connector 189.

A conveyor sprocket 204 is rotatably mounted at each end of the two conveyors 173 for engagement with the chain 193. Drive sprockets 204a, positioned above support stand 175, are driven by a conventional electric motor (not shown). Idler sprockets 204b are secured to plates 201, 202 at the free ends 176 of the conveyors.

To facilitate the expansion of lugs 177 as they travel along the forward carrying paths 178, a pair of elongated cams 208, 210 are fixedly attached to the upper and lower conveyor plates 201, 202 of each conveyor 173. These cams 208, 210 push arms 179, 181 outwardly along the forward paths, such that they expand beyond the arms of the lugs 177 traveling along return paths 180 (FIG. 9). These cams 208, 210 extend the entire length of the conveyors and are tapered at each end 211 to provide an easy and gradual expansion and contraction of the lugs 177.

In an alternative embodiment 215, a pair of spaced apart vertically aligned conveyor systems 18a, 18b are provided to lend additional support to a particularly tall or off-balanced product P' (FIG. 13). In this arrangement, the apparatus operates in the same manner as discussed above, except that the product is fed and sandwiched between a lower conveyor system 18a and an upper conveyor system 18b. The conveyor systems 18a, 18b, are identical to the conveyor system 18 described above; with the possible exception that the central clamping jaw may be eliminated from the top conveyor system. The plastic film 74 is wrapped about both conveyor systems 18a, 18b and engages the lugs 177a, 177b traveling the four forward path portions 178a, 178b of the conveyors 173a, 173b. Further, the products may be sequentially fed and separated downstream by a cutter, or may be individually wrapped as needed.

In a third embodiment 220, an alternative conveyor system 221 is provided to support cylindrical products P" for passage through cage 14 (FIGS. 14-16). Conveyor system 221 is similar to conveyor system 18 in that it includes a pair of horizontal adjacent conveyors 225, each having forward conveying paths 227 along the outer sides thereof and return paths 229 along the interior sides thereof.

More specifically, each conveyor 225 includes a elongated base 231, a pair of sprockets 233 positioned at each end of base 231, a plurality of spaced apart resilient lugs 237, and an endless chain 239. Lugs 237 are preferably composed of urethan molded over a spring steal core, although other constructions and materials could be used. Similar to conveyors 173, chain 239 is driven by sprockets 233a coupled to a motor at a support stand 175. Lugs 237, in turn, are attached to links of the chain 239 for movement therewith along the forward and return paths 227, 229.

Each lug 237 is preferably of a unitary construction and includes a supporting portion 242, a mounting portion 244, and a resilient hinge portion 246. Mounting portion 244 is preferably a block-shaped section positioned adjacent endless chain 239 for attachment thereto. L-shaped brackets 247 are used to secure lugs 237 to chain links 240. In particular, a horizontal leg 248 of bracket 247 is fixedly attached to links 240 by screws or the like similar to the attachment of lugs 177, and a vertical leg 249 of bracket 247 is attached to portion 244 by screws or the like. Preferably, the mounting portion 244 of each lug further includes a metal backing plate 251 for additional support. Mounting portion 244 also includes an outer corner 245 which is adapted to engage and tautly hold the plastic film 74 in place. Supporting portion 242 is also preferably a block-like member having a distal, engaging surface 252, a lower guiding surface 253, and an opposite bracing surface 254 for adequately supporting product P" as discussed below. Supporting portion 242 and mounting portion 244 are coupled together by a relatively thin hinge portion 246 along the upper surfaces thereof to facilitate the requisite pivotal movement of supporting portion 242. Hinge portion 246 defines a recess 256 between supporting portion 242 and mounting portion 244.

Each base 231 includes a top surface 258 having a return portion 260 along the interior side thereof and a cam bracket 262 attached along the exterior side. Cam bracket 262 is preferably comprised of a pair of metal frames 263, 265 fixed by welding or the like into a integral structure. Bottom frame 263 is preferably an elongated metal plate extending entirely across the length of the conveyors and having longitudinal bend 267 along a medial section thereof. Bend 267 defines a mounting segment 268 adapted to be secured to top surface 258 by bolting or the like and a supporting segment 269 projecting upwardly and outwardly therefrom so as to define an angle of approximately 120.degree. with mounting segment 268. Of course this angle could be varied. Upper frame 265 has a substantially inverted V-shaped segment 271 having first and second outer flanges 273, 275. The outer flanges 273, 275 lie flushly against mounting segment 268 and supporting segment 269, respectively, for mounting thereto (preferably by welding).

Bracket 262, then, functions to expand lug 237 and move supporting portion 242 upward to support the cylindrical product P" thereon. Second outer flange 275 and bearing face 277 of segment 271 cooperatively define a channel 270 adapted to receive and lift the supporting portion 242 of lug 237. Flange 275 and bearing face 277 then slidingly engage against bracing surface 254 and guiding surface 253 to receive and support the weight imposed on the lug by the product P". Also, as with cams 308, 210, brackets 262 are tapered downwardly to the top surface 258, to accommodate a gradual expansion and contraction of the lugs 237.

The return portion 260 is defined by the top surface 258 along which the lower guiding surface 253 of supporting portion 242 is slidingly engaged when traversing the inner return portions of conveyors 225. Lugs 237 are shaped and oriented such that supporting portions 242 naturally, without additional biasing means, assume the shape in the return mode.

In the third embodiment 220, the bottom faces 282 of mounting portions 244 are adapted to lie along the inner sides of the film 74. Nevertheless, film 74 is so tautly wrapped about the outer lugs that the inner lugs merely slide along without impairing the wrapping operation. Moreover, the overlap of the film strips further eliminates any possible impairment. More specifically, the trailing edge 284 of the prior strip of film 74a overlaps the forward edge 285 of the trailing strip of film 74b along the inside surfaces over which the return lugs pass, so that easy sliding therebetween is achieved.

In order to provide sufficient support for the cylindrical products P" and lift the products adequately so as to avoid contact with the return path lugs, support portions 242 are of increased length in comparison to the arms 179, 181 of lugs 177 in conveyor system 18. To accommodate this increased length, lugs 237 are spaced apart so that they are able to traverse the turns around sprockets 233 without interfering with one another.

To begin the wrapping operation, the leading end of the film must be held in place until one or two subsequent wraps overlap it to hold it in place. In the preferred embodiment, the leading end of the film is clamped into place by a clamping assembly 290. Clamping assembly 290 includes a reciprocal clamping element 292 which has a fluid cylinder 294, a guiding rod 296, and a movable jaw 298. The movable jaw 298 is adapted to cooperate with a fixed elongate jaw 300 mounted between the two horizontal conveyors 173 or 225 irrespective of the particular embodiment of conveyor system. In short, the movable jaw 298 is reciprocally movable so that it is adapted to clamp or release the film between itself and the fixed jaw 300.

More specifically, the reciprocal clamping element 292 includes a supporting beam 302 mounted beneath support stand 175. Supporting beam 302 is mounted at an inclination to the horizontal at an angle of approximately 20.degree.. This angle of course could be varied a great deal. Fluid cylinder 294 is fixedly secured to the lower end 304 of beam 302 with piston rod 306 positioned for reciprocal movement toward and away from the upper end 308 of beam 302.

Guiding rod 296 is attached to the free end of piston rod 306 and is positioned directly above beam 302 in a substantially parallel relationship therewith. Guiding rod 296 is preferably comprised of a tubular core 310 having a pair of elongated ears 312 attached along opposite sides thereof. Ears 312 are preferably angle members which have been welded in place. Attached to beam 302 and projecting upwardly along each side of guiding rod 296 are a plurality of guiding rollers 314. Rollers 314 are mounted for rotation about substantially vertical axles 316 (they are actually inclined to the vertical approximately 20.degree.) and have a V-shaped outer periphery 318 adapted to engage and mate with ears 312. Hence, as piston rod 306 is reciprocated back and forth, guide rod 296 with ears 312 are guidingly moved in a longitudinal direction by guiding rollers 314.

Movable jaw 298 is fixedly attached to distal end 320 of guiding rod 296. Movable jaw 298 essentially comprises a planar plate member having a pair of tapering outer sides 322. The tapering of sides 322 permit the jaw 298 to be withdrawn more easily after the wrap has been begun, as discussed below. To mount movable jaw 298 in place tubular core 310 is preferably cut to form a horizontal edge 324 to which jaw 298 is firmly secured by welding or the like.

Fixed jaw 300 is essentially an elongated block member adapted to fit between horizontal conveyors 173 (or 225). The lower face 326 of jaw 300 is adapted to be positioned just slightly above the point at which the film is stretched across the lower portions of the conveyors. The lower movable jaw 298 then is able to securely clamp the film between its upper face 328 and the lower face of fixed jaw 300.

In use, when beginning a new roll of film, the film is manually fed beneath the conveyors with the movable jaw in its lower release position (not shown), wherein the jaw is retracted beneath support stand 175. Once the film is so positioned, the fluid cylinder 294 is actuated so that the guiding rod 296 and movable jaw 298 are moved upwardly along supporting beam 302, until upper face 328 of jaw 298 engages and presses the film against lower face 326 of jaw 300. Cage 14 is then rotated once or twice about the product P (already positioned above movable jaw 298) to overlap the leading end of the film clamped by the jaws 298, 300. These first two rotations, are performed without actuating the conveyor system 18 so that the leading end of the film will be securely held by the overlying strips when movable jaw releases it, and so that the jaws 298, 300 do not interfere with the forward movement of the film with the lugs. Once the leading end has been overlapped with the subsequent strips, fluid cylinder 294 is actuated in the reverse direction so that guiding rod 296 and movable jaw 298 move downwardly along the supporting beam 302 to release the film from its grip. Thereafter, the operation can continue so the product is spirally wrapped with the film. At the end of the wrapping of the product, the fluid cylinder 294 may once again be actuated so that movable jaw 298 engages the trailing end of the film between itself and fixed jaw 300. The film is then severed and the wrapped product removed for shipment. Conventional sensors (not shown) coupled to a central processing unit (not shown) may be used to automate the above discussed process.

The perforating assembly 19 creates a tearing line of weakness 21 in the wrapped plastic film 74. More specifically, perforation assembly 19 (FIGS. 1, 3, 18, and 21-24) is positioned adjacent the free ends 176 of conveyors 173. In this location, the line of tearing weakness 21 may be formed in the plastic film 74 after it has been wrapped about conveyors 173 and product P, but before the product and the corresponding wrapped film is fed off of the conveyors 173 and onto downstream conveyor 356. Although the cutting assembly 19 is discussed with regard to the first embodiment (FIG. 3), it is equally applicable to the second and third embodiments (FIGS. 13 and 17).

Perforation assembly 19 (FIGS. 18 and 21-24) includes a cutting wheel 401 and a backing wheel 403. The cutting and backing wheels 401, 403 are located between conveyors 173 adjacent their free ends 176. In use, cutting wheel 401 and backing wheel 403 are positioned on opposite sides of the wrapping film 74 as it is moved along with conveyors 173.

Cutting wheel 401 is a metallic disc having a serrated outer perimeter edge 405. The serrated edge 405 defines spaced apart cutting edges 407 which are adapted to cut through the plastic film 74 to create a tearing line of weakness 21. Cutting wheel 401 is rotatably mounted on a horizontal axle 409 which is oriented substantially perpendicular to the direction of movement of the product and wrapped film. Axle 409 is attached to take-off table 411 by a pair of mounting bars 413. The take-off table 411 movingly supports the downstream conveyor 356. Downstream conveyor 356 is a split belt comprised of a pair of parallel, spaced apart endless belts that define a gap (not shown) therebetween. Mounting bars 413 project outwardly through the gap in conveyor 356 to mount axle 409 and cutting wheel 401.

Cutting wheel 401 is rotatably driven in part by the moving film 74 and in part by a flexible shaft driving mechanism 414. Driving mechanism 414 includes a power source 415, a flexible shaft 417, and a coupler 418 of conventional design which transfers the rotative motion of the flexible shaft 417 to cutting wheel 401. The power source 415 is preferably an adjustable-frequency AC drive, although DC drives may also be used. Of course a rigid shaft may be used in place of the flexible shaft 417. Preferably a pulse generator is used to match, or slightly mismatch, the speed of the master drive 66 and the slave drive 414. Preferably, friction rings (not shown) are provided between the coupler and the cutting wheel 401, so that no damage is incurred if the film speed varies or stops relative to the driving mechanism.

Backing wheel 403 is rotatably mounted on an extension of fixed jaw 300. Free end 419 of fix jaw 300 defines an opening 421 dimensioned to receive backing wheel 403. In particular, backing wheel 403 is mounted in a freely rotatable manner on a pin 423 extending across opening 421. Backing wheel 403 is preferably composed of urethane or other plastic material, but could of course be composed of other materials. Backing wheel 403 is positioned to extend below the lower face 326 of fixed jaw 30, in order to engage the film 74 in direct opposition to cutting wheel 401. Further, backing wheel 403 is sufficiently small to avoid contact with the products supported by conveyors 173.

In operation, the wrapping film 74 is wrapped tightly about product P and conveyors 173 (or product P' and conveyors 173a, 173b or product p" and conveyors 225), as discussed above. As the conveyors move the film 74 forwardly with the product, the film is passed between backing wheel 403 and cutting wheel 401. The cutting edges 407 of cutting wheel 401 cut the film and form an aligned series of perforations 21 therein. The perforation line 21 is made in both the single layers of film 74a and the overlapped layers of film 74b so that a single continuous line of tearing weakness 21 is created across the plastic wrap. After the perforation is completed, the wrap and the product rides off of conveyor 173 and onto downstream conveyor 356 as discussed below.

Product P is advanced toward conveyors 173 on a feed conveyor 330. Feed conveyor 330 is preferably of a typical endless conveyor design having a pair of horizontal axles 332 designed to rotate a supporting belt loop 334. As the product is advanced along feed conveyor 330, it is preferable to measure the width and height of the product so that its irregularities may be accounted for in the wrapping operation. As discussed above, the dancer roll assembly 69 is provided to accommodate certain irregularities. However, the dancer roll assembly 69 is capable of accommodating irregularities only up to a certain level. If the products have substantial irregularities (e.g. a wide, flat product or a tall, thin product), the dancer roll assembly 69 will not have sufficient leeway to make up the needed difference. Therefore, a preliminary measuring assembly 336 is provided along feed conveyor 330.

Preliminary measuring system 336 includes a width measuring component 338 (FIGS. 25-26) and a height measuring component 340 (FIGS. 26-28). Once these measurements have been taken, the results are transmitted to the central processing unit (not shown) which then determines the desired rate for dispensing the film for that particular product. More particularly, the rotation rate of cage 14 is always held at a constant rate. The adjustment then, is made at motor 70 which controls the speed of dispensing roller 88 and pinch rollers 123, 125. The adjustment is preferably made by adjusting the voltage supplied to the DC motor 70 so that it runs at a faster or slower rate as needed. Depending on the product, the adjustment may be made so that an average speed is chosen which will accommodate complete wrapping of the product. Alternatively the adjustment may be made during the wrapping operation so that the dispensing rate increases and decreases as needed during the rotation of the cage about the product P.

The width measuring component (FIGS. 25-26) includes a pair of opposing lateral assemblies 342 each of which includes an elongated engaging plate 344 connected to a pair of pivot bars 346 for lateral, reciprocal movement toward and away from the product P. More specifically, each pivot bar 346 is pivotally mounted to an upstanding support 348 at one end and to plate 344 at its opposite end. Moreover, the pivot bars 346 on each side, are arranged in a substantially parallel relationship, so that engaging plate 344 is kept in a substantially parallel relationship with the longitudinal axis of feed conveyor 330.

To effect movement of the assemblies 342, a band fluid cylinder 350 is provided beneath the belt 334. The cylinder 350 is fixedly mounted along the longitudinal axis of the belt 334. The piston (not shown) of cylinder 350 is attached to a transverse coupling bar 351 for imparting longitudinal movement thereto. Coupling bar 351 includes a pair of transverse slots 352 which are adapted to pivotally receive a pin 353 fixed to a coupling arm 355. The opposite ends of the arms 355 are fixedly secured to pivot bars 346 by a vertical rod 357. Vertical rod 357 is approximately a foot long and facilitates the spacing necessary to position pivot bars 346 above belt 334 and coupling arms 355 below belt 334.

In operation, a product P is stopped momentarily on feed conveyor 330 between lateral assemblies 342. Fluid cylinders 350 are then actuated such that coupling bar 350 is moved longitudinally such that coupling arms 355 and pivot bars 346 are arcuately swung outward from upstanding supports 348, until engaging plates 344 engage the opposite sides of the product P. This movement will be typically controlled by a pair of coordinating sensors on each engaging plate or by pressure sensors coupled with the fluid cylinders. Furthermore, conventional measuring devices 399 will be coupled to at least one of the pivot bars 346 to determine the width dimension of the product P. Also, as with the clamping assembly, conventional sensors (not shown) coupled to the central processing unit (not shown) may be used to automate the system.

Moreover, lateral assemblies 342 also act to center the product on feed conveyor 330 which, in turn is aligned with conveyors 173. Hence, assemblies 342 effect substantial centering of the products on conveyors 173. This arrangement then helps reduce irregularities in the wrapping procedure.

The height measuring device (FIGS. 26-28) is designed to be similar to the lateral assemblies in that it utilizes pivot bars 346, engaging plate 348 and a fluid cylinder 358. Engaging plate 344 is mounted to an upper assembly 361, fixedly mounted over feed conveyor 330, for vertical movement so as to press the product between itself and the conveyor belt 334. As can be readily appreciated, the actuation of the cylinder 358 will move engagement plate 348 toward or away from the top of the product.

In an alternate embodiment (FIGS. 29-30), either or both of the horizontal and height measuring components, may be mounted with engagement rollers 354 which are each mounted to a single pivot bar 346 pivotally mounted to an upstanding support 348. As in the previous embodiment, a fluid cylinder 350 or 358 is used to arcuately move pivot bars 346 so that the engagement roller 354 is moved toward and away from the product P. This embodiment can be used to avoid stoppage of the product along the feed conveyor, which may be desirable if a continuous series of products are being wrapped. Further, the vertical height adjustment may alternatively also be a series of vertical photoeyes (not shown) which would optically measure the height of the product in a known manner. Conventional sensors (not shown) coupled to the central processing unit may also be used for automatic operation of the machine.

In the operation of the apparatus 10, a product P (or P' or P" if different embodiments are utilized) is first placed upon a feed conveyor 330 for advancement toward conveyors 173. When the product is positioned between the lateral assemblies 342, it is stopped temporarily, (or not, depending on the embodiment) so that the height and width may be measured, and so that the product may be centered. These measurements are transmitted to the central processing unit (not shown) which determines the needed film dispensing rate and makes any necessary changes in the voltage to be supplied to motor 70. Subsequently, the product is advanced and fed onto conveyors 173.

The product rests upon conveyors 173 such that it is supported upon the expanded lugs 177 moving along the forward paths 178. The product P, if it is the first product to be wrapped, is advanced until its front edge is substantially aligned with the forward edge of the film 74. At this point, the film 74 may be placed in the clamping assembly 290. Cage 14 is then rotated once or twice to provide a plurality of overlapping strips which will tightly hold the leading end in place. Thereafter, the movable jaw 298 is retracted to release the film and the conveyors 173 are again actuated such that the product will be completely wrapped in a spiral wrap of the film. Due to the tension on the film, the overlying strips will clamp down and hold the leading end in place after the movable jaw 298 is released.

Once the film 74 has been tightly wrapped about the product P and conveyors 173, it is moved forwardly such that it passes between cutting wheel 401 and backing wheel 403. As cutting wheel 401 moves with film 74, cutting edges 407 create a series of openings in the film. This line of tearing weakness 21 extends the entire length of the plastic wrap. This arrangement, as discussed above, provides a plastic wrap with sufficient strength to undergo the rigors of shipping, but additionally provides an easy-open means by which the products may be unwrapped without the risk of personal injury or damage to the goods.

Subsequently, a series of products may follow in a continual manner without stopping conveyors 173 or cage 14. These products are then separated by a conventional cutting apparatus downstream from apparatus 10. The film 74 is wrapped tightly about the product P and conveyors 173 such that it will tend to contract toward the product when the product is fed off free ends 176 of conveyors 173. The space 357 provided between conveyors 173 and downstream conveyor 356 will permit this contraction to take place so that the film is easily fed on to the downstream conveyor. As time progresses, the film will tend to contract further against the product to provide an even tighter wrap. Of course, the apparatus can also be used to individually wrap products by using the clamping assembly 290 after each product has been wrapped.

The above description is that of preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as set forth in the appended claims, which are to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.

Claims

1. An apparatus for wrapping a product comprising:

a pair of laterally spaced apart conveyors each defining a continuous loop movable about a plurality of substantially vertical axes, said conveyors disposed substantially in a single horizontal plane in longitudinally parallel relationship on either lateral side of a longitudinal center line therebetween, each loop including a rearwardly moving portion disposed adjacent said center line and a forwardly moving portion disposed laterally outwardly of said rearwardly moving portion, said forwardly moving portions each having an upper surface for moving a product supported thereupon and a lower surface spaced apart from said upper surface for contacting a sheet of wrapping material wrapped about the product and said conveyors and spanning across said lower surfaces, said rearwardly moving portions each having an upper surface disposed spaced apart from the product and a lower surface disposed spaced apart from the wrapping material;

wrapping means for wrapping a sheet of wrapping material about the product and said conveyors while the product is moved by said conveyors along said path; and

forming means for forming a line of tearing weakness in the sheet of wrapping material wrapped about the product and said conveyors, said forming means disposed adjacent said center line substantially between said conveyor rearwardly moving portions.

2. The apparatus of claim 1 wherein said forming means comprises a cutting wheel mounted for rotation about a horizontal, laterally extending axis and having its circumference in cutting engagement with the wrapping material.

3. The apparatus of claim 2 further comprising a backing element positioned substantially between said rearwardly moving portions of said conveyors on the side of the wrapping material opposite said cutting wheel, said backing element in cooperative engagement with the circumference of said cutting wheel.

4. The apparatus of claim 3 wherein said backing element comprises a backing wheel mounted for rotation about an axis parallel to and spaced apart from the axis of said cutting wheel.

5. The apparatus of claim 4 wherein said backing wheel is vertically positioned between the product and the wrapping material, the circumference of said backing wheel spaced apart from the product and in rolling contact with the wrapping material and the cutter wheel.