US 3660962 A
A plastic shrink film package formed of two peripherally heat-bonded films and at least one windowed backer sheet is produced at high speed by being formed of two separate sheets, rather than from a single folded sheet, at least one sheet having multiple windows, the pressure forming die having multiple recesses and the heating plate having multiple heat seal elements. A perforated line is formed inside the heat seal of each individual package during or after the heating step, each pocket is stretched to the full extent of the female die during the pressure step, and each pocket is punctured to form an air outlet orifice at the end of each pressure step.
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Description (OCR text may contain errors)
O United States Patent [151 3,660,962 Bliss et al. 51 May 9, 1972 [s41 SHRINK FILM PACKAGE, AND 3,497,059 2/1970 Watts ..53/30 x APPARATUS AND METHOD FOR 3,522,687 8/1970 Mahaffy MAKING E 3,577,700 5/1971 Bippus et al. ..53/30  Inventors: Richard T. Bliss; George L. Nason, both of Primary Examiner-Theron E. Condon Andover, Mass. Assistant Examiner-Eugene F. Desmond  Assignee: Bliss-Pack, lnc., Lawrence, Mass. Atmmey-pearson Pearson  Filed: Oct. 13, 1969  ABSTRACT  Appl. N 0.: 865,829 A plastic shrink film package formed of two peripherally heatbonded films and at least one windowed backer sheet is produced at high speed by being formed of two separate sheets, rather than from a single folded sheet, at least one  Fi Id 184 1 12 200/45 3 sheet having multiple windows, the pressure forming die have o 6 ing multiple recesses and the heating plate having multiple heat seal elements. A perforated line is formed inside the heat seal of each individual package during or after the heating  References cued step, each pocket is stretched to the full extent of the female UNITED STATES PATENTS die during the pressure step, and each pocket is punctured to 3 l 18 262 1/1964 M k 53/184 form an air outlet orifice at the end of each pressure step.
esslc 3,353,218 11/1967 Cloud et al ..53/l84 X 19 Claims, 9 Drawing Figures PATENTEDMAY same 3,660,962
sum 2 UP 2 Fig.3. 8
20 I In:
INVENTOR. RlCHARD T. BLISS GEORGE L. NASON 8 p ATTZ:NEYS
BACKGROUND OF THE INVENTION The art of shrink film packaging is well developed and such packaging. may be performed on intermittent turret type machines, as in U.S. Pat. No. 3,195,284 to Crane of July 20, 1965, or on straight line machines, as in US. Pat. No. 3,075,329 to Swezey ofJan. 29, I963.
In general, the machines actually being used in the art are of the type making one package at a time, so that production is relatively slow. It is believed that there are no practical, short length, low cost shrink film packaging machines on the market which superpose two separate windowed cards and simultaneously form multiple pockets, each having an article heat sealed therein whereby the multiple pocketed sheets may be severed into individual packages. One disadvantage of prior art machines has been the use of a separate station on an intermittent carrier for applying heat to the plastic film, so that it can be vacuum stretched at the next station. The heating station not only takes up fioor space, but, depending on the dwell at each station and the rapidity of the intermittent travel between stations, may cause the plastic film to unduly cool before reaching the pocket forming station. Another disadvantage has been the use of rather impositive holders for gripping the windowed sheets while permitting one portion to be raised by elongated folder bars into overfolded position, the folded sheets occasionally being out of registration and commercially unacceptable.
SUMMARY OF THE INVENTION In this invention, no such overfolding occurs, and, instead, two separate sheets are used, both having registration pin holes, the lower sheet being positively snapped onto the pins and the upper sheet being similarly snapped thereover, so that registration is positive and assured.
The invention relates to a straight line, intermittent advance, type machine, similar to that of the Swezey patent, but it is preferably characterized by having eliminated the preheating station in favor of a narrow pre-heat zone, so that the plastic film is heated as the sheets are moving from the sheet feed station into the pocket-forming station.
It also is characterized by eliminating the fold station, which takes up considerable floor space, as the folder bars turn an upper panel through a 180 overfold, in favor of a second, short, sheet feed station and apparatus which can be identical with the first feed station and apparatus and thus reduce cost.
It is also preferably characterized by two sidewise mounted sheet feed stations which reduce machine length, the magazine mechanism being top-feed, so that the stack is below the level of the paper line and thus does not bar the view of the operator.
The apparatus and method of the invention also includes a novel, female vacuum die in which there is a narrow peripheral suction slot around the bottom to fully stretch the film into the die and at least one sharp prong upstanding from the die bottom to automatically pierce the pocket for exhaust of air during subsequent heat shrinking.
The package of the invention includes a perforated line between a window edge and a heat seal line, so that when the perforated line is tornopen the contents of the package may be easily removed, and the package is reusable.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 is a plan view of a packaging machine constructed in accordance with the invention;
FIG. 2 is a side elevational view thereof;
FIG. 3 is an end elevational view thereof;
FIG. 4 is an enlarged side sectional view showing the preheater of the invention;
FIG. 5 is an enlarged, side sectional view showing the suction slot and pocket puncture apparatus of the invention;
FIG. 6 is a front view of a multiple, pocket sheet;
FIG. 7 is an enlarged front view of an individual pocket package severed from the multiple sheet;
FIG. 8 isa side elevation, of the package shown in FIG. 7; and
FIG. 9 is a view similar to FIG. 8 showing the package torn on the perforated line for easy opening.
DESCRIPTION OF THE PREFERRED EMBODIMENT INTERMITTENT BLANK CARRIER As shown in FIGS. 1-3, the high production rate, shrink film packaging machine 20 of this invention includes a suitable frame 21 supporting blank carrier 22, the carrier including a pair of laterally-spaced, longitudinally-extending register chains 23 and 24, trained around suitable sprockets 25 and 26 at opposite ends of the frame. The upper stretches of endless chains 23 and 24 establish a horizontal path, or paper line 27, at about the waist height of the operator, and sprockets 25 and 26 are driven intermittently by a suitable power train of known type from drive motor 28 under the control of cycle timer 29.
The chains 23 and 24 are provided with oppositely located, longitudinally spaced pairs of upstanding register pins such as 32 and 33, and the cycle timer 29 is so arranged that one pair of pins halts at each of the stations spaced along the path 27. The pins 32 or 33 are preferably tapered to diverge from tip to base whereby they will better enter the register holes in the blanks. The pairs of tapered pins on the upper stretches of the chains thus move in the direction of the arrows, with a dwell of about 6 seconds at each of the stations, to position the blanks individually and successively at blank feeding station 34,
MULTI-WINDOWED BLANKS The blanks 46 are preferably formed of stiff, but bendable, sheet material, such as cardboard 47, with four rows of three windows 48, there being a transparent plastic film 49 adhered to the upper face 52 by suitable means, such as adhesive layer 53. On each opposite side of each multiple windowed blank 46, near the leading edge 54, are registration holes 55 and 56, which fit over the registration pins 32 and 33 on the carrier chains. The plastic film 49 may be polyvinyl chloride adhered by layer 53 of polyvinyl acetate, and pre-formed so that a stack 57 of such sheets may be loaded into the automatic topfeed magazine means 58. The PVC film has a memory and after being heated to form a pocket and the pocket filled, the ambient or residual conductive heat of the edge heat sealing causes the PVC to shrink around the article without requiring a subsequent shrink tunnel operation. In the prior art, where dielectric, R.F. sealing has been used, there is insufficient ambient, or residual heat to shrink the film, thereby requiring a subsequent application of heat as a separate, costly step.
The cardboard 47 is preferably solid bleached sulphate, medium density, paperboard and the cover sheets 62, applied at the pocket-covering station 37, are preferably also of cardboard 47, having the PVC film 49 adhered to the underface 63, and having windows 64 and register holes 66 identical with the corresponding parts of blanks 46. The PVC film being on the mating faces of the blank and cover, adheres to itself under heat.
The windows of the blanks 46 may, if desired, be covered with a DuPont Company plastic film known as Surlyn" which not only adheres to itself but also adheres to the cardboard stock 47 without an adhesive, when heated. Thus with a Surlyn" film, rather than a PVC film 49, the cover sheets 62 need no layer of film but can be adhered directly to the film on the windowed blank, and similarly no adhesive is needed to preform the film on the windowed blanks.
AUTOMATIC MAGAZINE MEANS It will be understood that while the blanks 46 are windowed and therefore have cutout lateral edges which might normally be used for positive feeding, the magazine means 58 is preferably a "top-feed," so that the uppermost blank 70 has its upper face 52 covered with the taut, smooth, film 49, and its lower face resting on the stack 57. The advantage of a topfeed magazine, with the stack below the level of paper line 27 is that the operator can view the operation of the machine, and a top-feed magazine is more easily loaded than other types of magazines.
A positive, high speed feed is obtained with magazine means 58, there being vertical guides 67 for an elevator platform 68 which is raised by the piston rod 69 and cylinder 72 to continually urge stack 57 upward so that each successive topmost blank 66 is at about the level of paper line 27. The magazine means 58 is mounted alongside frame 21 of machine at blank feeding station 34, to reduce floor length and enable an operator to supervise the machine without undue travel therearound.
Means 58 includes a reciprocable friction foot 73, having a pair of sharp prongs 74 at the terminal end of piston rod 75 slidable in air cylinder 76, the cylinder valve being synchronized in known manner with cycle timer 29.
Means 58 also includes the pair of feed rolls 77 and 78, having a feed nip 79 and rotated at high speed in the direction of feeding by the motor 82. Extending over blank feeding station 34 is a cantilevered catch plate 83 and a hinged, liftable cover guide 84, with a blank receiving space 85 therebetween.
In operation, cycle timer 29 actuates the valve of friction foot cylinder 76 to cause the prongs 74 to engage the plastic film on the upper face of the topmost blank in a parting line area of the blank, and to advance the blank several inches sufficiently to be engaged in feed nip 79. The nip rolls throw the blank at high speed laterally across station 34, in space 85, over catch plate 83 and under cover guide 84 to position the blank with its registration holes 55 and 56, in the path of an oncoming pair of register pins 32 and 33. The tapered pins ride along the lower face of the blank which is held down and slightly bowed, or distorted, by the advancing pins until the blank snaps down onto the pins for positive registration and advance.
Cycle timer 29 causes the next successive blank to feed immediately, so that it is in position to receive the next set of register pins.
PRE-HEATER MEANS AND ZONE The plastic windowed blanks first pass through a heater to soften the plastic. Preferably the heater is located between blank feeding station 34 and pocket forming station 35 and is a short two or three inch space forming a preheat zone 86 and occupied by the pre-heater 87, which operates as the blanks advance through the zone on the register chains. As best shown in FIG. 4, pre-heater 87 extends transversely across path 27 with a hollow shell 88, partitioned at 89 to form a positive air pressure inlet slot 92, and a negative air pressure outlet slot 93. An electric resistance unit 94, or any other suitable heating means is mounted in air pressure slot 92, and a deflector 95 is mounted above path 27 to deflect hot air down into slot 93 when there is no blank across the slots to so guide the hot air. It will be seen that the hot air blown upwardly against the underface of each successive blank moving through the zone, softens the plastic film in each window ready for the subsequent pocket-forming step at station 35, and it is then removed from the ambient atmosphere through suction slot 93. Slots 92 and 93 are in parallelism and each is connected to a suitable source of positive or negative air pressure, not shown, for example, to mill air or vacuum supply.
POCKET-FORMING STATION The pocket-forming means 96 at pocket-forming station 35 includes a multiple female die plate 97, mounted below the level of path 27, so that the multiple windowed blanks 46 are pulled thereover by the carrier chains 23 and 24. A limit switch 98, in the path of the leading edge 54 and connected to timer 29, is actuated to halt the carrier with each film-covered window 48 exactly over, and in registration with, one of a plurality of female dies 99, in plate 97.
As best shown in FIG. 5, each female die recess 99 is formed by a substantially vertical side wall 102, which is spaced entirely around the lower periphery thereof from a bottom wall 103 to form a narrow suction slot 104 of minute height. The die plate 97 includes a plenum 105, encircling the multiple recesses and connected to a source of suction at 106 so that application thereof draws the heat-softened plastic down to entirely fill the recess in the furthest comers thereof as defined by the peripheral bottom slot 104. There is usually considerable talc, or other powder, lint, dust, and the like, in stacks of paperboard, the particles thereof sometimes plugging small diameter suction orifices. The elongated slot 104 cannot be so plugged, due to its extent.
As best shown in FIG. 5, pocket-forming means 96 may include at least one set of detachable insert fillers 150, each shaped to fill a portion of the volume of each recess 99 to a desired amount, and each configured to conform to the shape of an article to be packaged, so that the die plate 97 is usable for many different shapes and sizes of articles. Each filler 150 is spaced from the walls 102 to permit connection with pressure orifice 104, and each filler includes at least one prong 107 in the leading upper portion thereof.
Pocket-forming means 96 also includes at least one sharp, upstanding pin, or prong, 107, which may be fixed in the center of the bottom wall 103 of each female die recess 99, to puncture the pocket 108 as it is vacuum drawn into the recess. A small orifice 109 is thereby formed in each pocket, which serves as an air exhaust outlet when the plastic shrinks around an article, to prevent the trapping of an air bubble in the package. Preferably several such pins are used, fixed near the leading wall of the recess, for ease of removal of the plastic from the pins.
Preferably also, a positive back pressure of air is applied through the slots 104 after the puncturing to assure the release of the pockets from the recesses, the air being supplied through valve 100, from source 101, under control of timer 29.
ARTICLE-LOADING STATION At least one article-loading station 36 is provided along path 27, so that an article may be manually, or automatically, deposited in each pocket 108 of the blank 46, halted at the station. It will be seen that the female die plate 97 may be immovable because the pockets 108 are yieldable and ride over the edges of the plate to move into station 36 while flattened and then fall downwardly into pocket configuration. Preferably there are two loading stations, depending on the nature of the articles 111 and the rate of production desired. With twelve pocket blanks 46, and a dwell of 6 seconds at each station, 120 packages are completed each minute, or two packages per second, this being well above the production rate of conventional, prior art machines.
POCKET-COVERING STATION A second, automatic, top-feed blank magazine means 112, substantially identical with magazine means 58, is mounted alongside paper line, or path 27, at station 37, to feed cover sheets 62 individually and successively across the path 27. The register holes 66 are guided onto register pins 32 and 33 so that each cover sheet is superposed on a filled, muIti-pocketed blank 46 with the plastic film 113 on the underface 63 of cover sheet 62 lying flatwise on the plastic film 49 of blank 46 surrounding each window of the blank. The vertical guides 114, elevator platform 115, friction foot 116, nip rolls 117, catch plate 118, cover 119, and piston and cylinder system 122, all correspond to similar parts in means 58, foot 116 being actuated by timer 29 at the appropriate time in the cycle.
HEAT-SEALlNG STATION Heat-sealing means 123 is mounted to move in a vertical path at station 38, and preferably comprises an immovable upper heating, or backer plate, 124, and a movable heating plate 125. Plate 125 is supported on piston rod 126 in cylinder 127 valve-connected to cycle timer 29 to cause plate 125 to move upwardly and clamp each successive multi-pocketed filled card 128 against upper plate 124. Both plates are preferably provided with linear electric resistance units 129 of well known type, arranged to heat-seal at least one line along each side of each window as at 132, 133, 134, and 135 in FIGS. 6 and 7.
The mating faces of the plastic films 49 and 113 of each blank 46 and cover 62 are thus heat-bonded to each other to enclose each article 1 11 in the space 136 within a pocket 108, and the lines of bond are so arranged that the multi-pocketed card 128 of FIG. 6 may be cut along the lines 137 to separate the card into individual shrink film cards 138.
As shown in H0. 7, each package 138 preferably includes a die-cut aperture 142 by which it may be suspended on display, a line of perforations 143 located between the peripheral edge 144 of a window and an adjacent outer edge 145, within and inside, and in parallelism with, the adjacent heat-seal line, such as 133, and another die-cut aperture 146 may also be provided. It will be seen that unlike prior art packages which are most difficult to tear for access to the article therein, the package 138 may be easily torn along perforated line 143 to create an opening 147 (FIG. 9), and the opening may be enlarged by squeezing the edges of the package. After being opened, the package may be suspended by aperture 146 on a hook, for example, when several articles are packed therein and only one has been used.
The dies 152, 153, and 154 for forming the apertures and perforations may, if desired, be mounted on lower clamp 125 of heat-seal means 123, opposite any necessary female elements on upper plate 124, so that heat-sealing and cutting are simultaneous. Suitable cutting dies 155 may also be so mounted on plates 124 and 125 for severing the multi-cards 128 into individual packages 138. it will be understood that the cards 128 are commercially useful in uncut condition, and the dies 155 may be omitted if desired. However, it has been found preferable to accomplish the perforation line step and the sheet-severing step subsequent to the heat-sealing step, for example, at station 39, or in a separate machine. This is for the reason that more adequate severing pressure can be applied, the cutting waste can be better handled, one cutting machine can handle the output of several packaging machines, and the severing time can be longer or shorter than the packaging dwell, as desired.
CARD DISCHARGE STATION A station 39 is provided, at the end of the path 27, for either die cutting and perforating the cards, or for stripping of the multi-pocketed cards 128, there being a plurality of inclined parallel bars, such as 158, extending along the path in extension of the piano wire support tapes 45, for lifting the cards off the register pins for removal or deposit in a suitable hopper. It will be seen that, if the cards 128 are cut into individual cards 138, as part of the heat-sealing step in zone 38, or as a separate step in zone 39, the individual cards 138 will also ride along the tapes and bars and be lifted from the register pins.
It will be understood that while top feed magazines alongside and'below the level of the paper line are preferred for the reasons stated herein, other types of blank magazines may be used if desired to cooperate with the register pin carriers in permitting a windowed blank to have a cover sheet of the Lil same, or of different characteristics, registered thereon. Similarly while the short pre-heat zone of the invention saves floor space, a pre-heat station of the prior art may be used if desired. Similarly while the invention is intended for multiplepocket cards to be separated into individual cards, it is applicable not only to small, heavy articles, but to large, light or heavy articles in a single pocket such as an engine head gasket or the like.
What is claimed is:
1. in automatic, shrink film packaging apparatus of the type having a blank carrier intermittently advancing along a path and positioning a plurality of blanks, individually and successively at a blank-feeding station, a pocket-forming station, an article-loading station, a pocket-covering station, a heat-sealing station, and a card-discharge station, the combination of:
a pair of laterally-spaced register chains forming said carrier, said chains having upstanding pins spaced there-along for registering said blanks, and said carrier including a plurality of blank support elements extending along said path, in the space between said chains, for preventing sagging of said blanks;
automatic feed blank magazine means, mounted at said blank-feeding station, said magazine supporting a stack of plastic windowed blanks, each having register pin holes, and feeding each successive blank into engagement of said register pin holes on a pair of said pins;
pre-heating means mounted along said path between said blank-feeding station and said pocket-forming station for heating the plastic windows of each said windowed blank to soften the plastic thereof;
pocket-forming means at said pocket-forming station, said means including means for applying fluid pressure to stretch each said pre-heated plastic window of said sheet to form a plastic pocket; pocket-covering means at said pocket-covering station for applying a separate cover sheet, each having register pin holes over the filled pocketed blank at said station; and
heat-sealing means at said heat-sealing station for thermally bonding said cover sheet to said plastic pocketed blank, around the edge of each pocket thereof while simultaneously heat shrinking said plastic to form a pocketed card shrink film package.
2. An automatic shrink film packaging apparatus as specified in claim 1, wherein:
said automatic feed blank magazine means is a top feed type, alongside, and below the level of said path and includes a reciprocating presser foot engaging each successive topmost blank, and a pair of high-speed feed rolls in the rear of the leading edge of each said topmost blank, said foot advancing each blank into the nip of said rolls for high-speed advance across said path.
3. An automatic shrink film packaging apparatus as specified in claim 1, wherein:
said automatic feed blank magazine means includes a guide mounted over said path at said blank feed station, said guide urging each successive blank down on said carrier while said register pins enter the register holes in said blank.
4. An automatic shrink film packaging apparatus as specified in claim 1, wherein:
said magazine means includes a hold-down guide, mounted above said path at said feeding station, and said register pins are tapered to locate, and enter, the register holes in said blanks, said blanks being distorted by the approaching register pins, and then snapping down onto said pins.
5. An automatic shrink film packaging apparatus, as
specified in claim 1, wherein:
whereby said cover sheets may be of difierent longitudinal dimensions from said blanks or of limp sheet material and still be registered.
19. Apparatus as specified in claim 18 characterized by:
pocket forming means at said pocket forming station including at least one vacuum forming female die having a side wall and a bottom wall with a minute peripheral space therebetween forming a narrow suction withdrawal slot for decreasing the possibility of plugging by dust, talc or lint, and for serving as a positive back pressure air slot.