ADHESIVE APPLICATOR FOR PLASTIC FILM WRAPPING MATERIAL AND METHOD

Abstract: Method and apparatus for printing plastic film such as polyvinyl chloride stretchable wrapping film including multi-colored printing apparatus (11), with multiple cylinders (26), supply roll apparatus (61), take-up roll apparatus (113), a transport web (23) for carrying the film through the printing cylinders (77) is adapted to apply an adhesive in a pattern in register with the multi-colored printing pattern: the adhesive printing cylinder (77) has a drier section (53) downstream thereof. The adhesive printing cylinder (77) preferably is located upstream of the multi-color printing cylinders (26); and downstream of such cylinders, immediately before the film take-up roll (113) is a chill roller (121) for cooling the film prior to its being rolled onto the take-up roll (113). The pressure of the take-up driver roll (113) is controlled by a fluid pressure cylinder (115) to prevent adhesion of adjacent film layers on the take-up roll (113).

Description: ADHESIVE APPLICATOR FOR PLASTIC FILM WRAPPING MATERIAL AND METHOD The present invention relates to an improvement to machines and methods for printing thin stretchable film such as polyvinyl chloride or the like which makes it particularly suitable for wrapping for trays of food products such as meat, poultry, fish or the like. Machines are known for multi-color printing of such plastic film material as exemplified in U.S. Patent Number 4,218,973 issued August 26, 1980 to Alphee J. Bouffard et al. entitled, "MATERIAL HANDLING APPARATUS FOR PRINTING PLASTIC FILM". Rolls of printed stretchable film-wrapping material produced by such apparatus (or in some cases unprinted wrapping material) are utilized in packaging apparatus particularly adapted to wrap trays containing food products such as meat or poultry with the stretchable plastic film material, as exemplified by Hamilton, U.S. Pat. No. 4,522,013, U.S. Pat. No. 4,388,796, and U.S. Pat. No. 3,662,513. Such machines have utilized various procedures such as heat-sealing and heat-shrinking and combinations thereof to produce a sanitary package in which the product is displayed to the ultimate consumer. A large portion of the stretchable film material is normally left unprinted so that the product is visible through the transparent stretchable film. Use of the stretchable transparent film- wrapped trays has many advantages and has found wide us:e, but the packages so formed have suffered some dis¬ advantages. The primary disadvantage has been that while the package is sufficiently secure to prevent contamination of the product, liquids which are 5 generally released from the product will often leak through imperfections in the seal between the wrapping material and itself or between the wrapping material and the tray in which the product is contained. Such leaky packages are obviously undesirable since they result in ICT soiling the customer's clothing, automobile upholstery or otherwise producing customer dissatisfaction. According to the present invention the process of printing, advertising and identification of material on the stretchable film wrapping material is enhanced by 15 also printing on the material a pattern of heat- activated adhesive. The adhesive pattern is in register with the printed matter so that when the printed matter is properly located on the tray package the adhesive will be on the wrapping on the other side of the tray. 20 Thus when the stretchable film material is utilized to form the wrapped tray package a conventional heat-sealer wrapping machine or a specially adapted heat-sealer wrapping machine will cause the adhesive to be activated and form a substantially liquid-tight seal for the ' 25 wrapped package which is difficult or impossible to obtain by heat-fusing the plastic film to itself or to the tray. Once the stretchable film-wrapping material has been imprinted with the adhesive according to the 30 apparatus and method of the invention it may be utilized in the final tray wrapping operation in substantially the same manner as previously available film-wrapping material without adhesive coated portions, but it results in a seal of far greater integrity and virtually 35 eliminates the problem of leaky packages. The apparatus and method according to the present invention overcomes the problem that would be expected when the stretchable plastic material having freshly laid down adhesive layers thereon is rolled tightly on a take-up roll in contact with other layers of the stretchable plastic with which it is designed to make sealing engagement. Clearly, if the adhesive coated portion of the plastic wrapping material prematurely becomes sealed to the adjacent layer of the film material it will become impossible or impractical to feed the stretchable film material off the roll at the subsequent tray-wrapping operation. The apparatus and method according to the present invention overcome such problems by the use of drying steps and cooling steps and control of the pressure applied in rolling the film material onto the take-up roll, as will later by more fully described. In addition to providing the above-described features and advantages it is an object of the present invention to provide an improved printing apparatus and method for stretchable film-wrapping material by which a pattern of heat-activated adhesive may be imprinted in a predetermined controlled pattern on the stretchable film-wrap material and rolled onto a take-up roll without causing adhesion between layers of stretchable film on the take-up roll. It is another object of the present invention to provide an apparatus and method for printing adhesive on stretchable plastic film wherein the adhesive layer is dried immediately subsequent to being laid down and is thereafter subjected to a cooling surface which reduces the temperature of the film to about room temperature or less. It is still another object of the present invention to provide apparatus for printing an adhesive on stretchable film-wrapping material including a hot- air drier following the printing cylinder and a chill- roller located just upstream of the take-off roll for - said film. Other objects and advantages of the present invention will be apparent from consideration of the following description in conjunction with the appended drawings in which: FIGURE 1 is an elevational partially schematic view from the right side of printing apparatus incorporating the improvement of the present invention; FIGURE 2 is an enlarged elevational view partially in section including the portion of the apparatus in FIG. 1 associated with imprinting an adhesive pattern on the film; FIGURE 3 is an enlarged perspective view of the apparatus shown in FIG. 2 taken from the left side of the apparatus; FIGURE 4 is a perspective view of the portion of the apparatus in FIG. 1 including the chill-roller for reducing the temperature of the adhesive imprinted film; and FIGURE 5 is a developed view of an exemplary print pattern of adhesive. Referring now to the drawings and particularly to FIG. 1, multi-color printing apparatus 11 for printing transparent polyvinyl chloride film or other similar film is shown. Printing stations 13-18 for printing respective colors on the film are mounted on a frame 19 which also supports a plurality of inside idler rolls 21 partially defining a loop for a transport web 23. The transport web 23 supports and transports the film while it is being printed, dried, or otherwise processed. Transport web 23 may be formed of polyethylene or other suitable flexible plastic material of a thickness between 7 and 10 mils. It is joined at its free ends into a loop by suitable means such as pressure-sensitive or heat-sensitive adhesive tape. Outside idler rolls 25 are also provided in conventional fashion to guide the transport web. The transport web drive apparatus and the apparatus for feeding the stretchable film onto the web and for taking it off the web are generally conventional and will not be described in detail. These aspects of the apparatus which do not form a part of the present invention may be found in the literature and are, for example, described in detail in previously cited U.S. Patent No. 4,218,973. Rolls 21 and 25 are stationary whereas roll 45 is arranged for vertical translation under a force applied by air cylinders 46. Transport web 23 is preferably placed under substantial tension by air cylinders 46 acting on roll 45. The force on the web may typically be from 1/4 to 4 pounds per inch or about 100 pounds for a 52-inch-wide transport web. Roll 28 serves to drive the transport web and is driven from the same mechanical drive mechanism as that of printing cylinders in the printing apparatus. Rolls 21, 25 and 45 are shown as free-running rolls, but of course the apparatus may be arranged to have different ones of the rolls driven or free-running as may be desired. Also, some of the rolls shown may be omitted or it may be desired to add additional rolls for guiding the transport web. As seen in FIG. 1 there are six decks 13-18 giving the illustrated apparatus a capability for printing six different colors simultaneously. The invention is also applicable to multi-color printing presses with a capability for printing more than six colors or less than six colors. Even in an apparatus adapted for or set up to print only a single color the present invention would be advantageous in registering the pattern of adhesive applied to the stretchable film with the pattern printed on the film. This is particularly the case when the printed film is to be later used on automated package machinery and the interval between patterns in the film is required to be accurate and uniform for trouble-free operation of the automated packaging machinery. Cylinder 26 of deck 13 is a typical printing plate cylinder and is responsible for impressing the printing pattern for a respective one of the colors on the plastic film. The registration of the respective colors of the multi-color pattern is assured by the printing apparatus in a conventional fashion by reason of the fact that each plate cylinder 26 and impression cylinder 39 associated therewith are directly driven by one inter-linked drive mechanism connected to drive gear train 67 and being driven by electric motor 61 (shown in dashed lines in FIG. 1) . A conventional web lateral control mechanism is indicated at 47 having an edge-sensing device 49 with rolls 31 and 32 which are pivoted in response to edge- sensing device 49 to keep the transport web 23 in accurate alignment as it passes through the printing and adhesive applying mechanism. The nature of the mechanical drive which coordinates the motion of the various cylinders and drive rolls for the transport web 23 may be varied, for example, by substituting other known mechanical drive mechanisms for the shafts, belts, spockets, chains, etc. shown in the specific embodiment. The outer loop of the transport web 23 passes through a drying chamber 53 of conventional form. A large volume of air is provided by a blower 55 which feeds chamber 53 through an air duct 54. The air is optionally heated in a heater 59 with energy supplied by electricity, gaseous fuel or other means. The air and vapors exiting from chamber 53 are conducted away from the work area, preferably by an exhaust system not shown. The plastic film is supplied to the apparatus in a conventional manner similar to that shown in U.S. Patent No. 4,218,973; for example, a supply roll 61 may be driven at a peripheral speed very slightly less than the speed of web 23 by a friction drive roller 63 as shown schematically in FIG. 1. It should be noted that two or more supply rolls 61 may be placed side by side and a corresponding number of take-up rolls may be provided to accomplish the printing process in parallel. Thus, when a supply roll or a take-up roll is referred to it may be understood that two or more rolls may be processed simultaneously. Referring now to the adhesive imprinting apparatus better seen in FIGS. 2-4, an imprinting station 71 is mounted on frame 19 and includes an impression roller 73, a plate roller 75, and adhesive transfer roller 77 and a spreading and stirring roller 79. Impression cylinder 73 and plate cylinder 75 are driven at a peripheral speed synchronized with that of belt 23 through the drive linkage including drive sprocket 81, chain belt 83, driven sprocket 85 and idler 86. Sprocket 81 is connected to shaft 82 which in turn connects to the main drive mechanism through horizontal shaft 87, vertical shaft 91 and gear boxes 93. As seen in FIG. 2, a sprocket 101 driven by shaft 87 engages a chain belt 103 running on idler sprockets 102 and connected to drive double sprocket 105. A further chain belt 107 drives take-off roller 33 through sprocket 109. Sprocket 109 and the take-off roller 33 are mounted on a pivot bar 111 which pivots about a common axis with sprocket 105 and presses roller 33 with adjustably controlled force against take-up roller 113 powered by a fluid pressure cylinder 115. The pressure of air or other fluid supplied to cylinder 115 (and hence the force applied by roller 33) may be monitored and controlled by conventional guages and valves (not shown) . The above-described take-off mechanism for removing the plastic film from web 23 to be rolled on take-up roll 113 differs from previous such mechanisms in that it provides for controlled, substantially constant pressure between contact roll 33 and take-up roll 113 so that roll 113 is effectively friction driven and rotated at the proper speed but at the same time excessive pressure which could cause bonding of the adhesive to seal adjacent layers of the film together is avoided. An important part of the apparatus is the chill roll mechanism including chill roll 121 best seen in FIGS. 2 and 4. Chill roll 121 as shown in FIG. 4 is at least partially hollow and is mounted on a hollow shaft 122. Adjacent to roll 121 is an idler roll 123 arranged to cause web 23 and plastic film 100 to wrap around most of the periphery of roll 121; this provides a longer dwell time and better cooling of the plastic film. Chilled water from a conventional chiller (not shown) is supplied through pipe 125 and is returned through pipe 127. Pipes 125 and 127 connect to a concentric tubing assembly 129 with pipe 125 connected to a central tube 131 and pipe 127 connected to an outer conduit surrounding tube 131. Thus, cold inlet water is directed toward the left end of the interior of chill roll 121 and passes back toward the right to exit from roll 121 into assembly 129 and pipe 127 thereby absorbing heat from the chill roll 121 and cooling the film which is in intimate contact with the smooth surface of roll 121. If desired, the exit for chilling water may be provided at the opposite end to pipe 125 and water agitating baffle means may be included in roll 121. The chilling water may be caused to have a lowered freezing point by the addition of antifreeze solution so that chill roll 121 may be operated below 32° fahrenheit. It should be noted, however, that the thin plastic film is in direct contact with roll 121 so that it receives maximum cooling effect and it is not necessary for chill roll 121 to cool the entire thickness of transport web 23. The film is removed from transport web 23 very soon after passing over roll 121 so there is little opportunity for heat to be transferred through web 23 to the film before it is taken up on roll 113. Chill roll 121 and the associated apparatus is of conventional construction and other commercially available chill roll apparatus, such as that supplied from the Carl iklander Company, Elk Grove Village, IL 60007, may be utilized to perform the function of the above means specifically illustrated. A hot air drier is provided to dry the adhesive printed film immediately after it leaves adhesive imprinting deck 71. As best seen in FIG. 3, drier 132 is provided with heated air through flexible duct 133 causing the plastic film on web 23 to have its adhesive imprinted side exposed to hot dry air, thereby accelerating the vaporization of solvent in the adhesive. Hot air supplied to heater 132 passes outwardly through openings in baffle plate 135 into exhaust chamber 137. The air and vapors in exhaust chamber 137 are drawn off by an exhaust system through flexible duct 139. As illustrated in FIG. 3, vapors are also drawn from the adhesive printing station into exhaust chamber 137 and out through duct 139 by virtue of the connection of flexible duct 141 from exhaust chamber 137 to print roller hood 143. Also shown in FIG. 3 is hydraulic motor 151 continuously driving mixer and spreader roll 179 thus avoiding congealing or setting of the adhesive while the main drive mechanism for the printing operation is stopped. This is a conventional apparatus and technique also employed with the color printing stations. FIGURE 5 is a developed view of the rubber composition plate utilized for imprinting a typical adhesive pattern on the plastic film. It should be noted that the illustrated adhesive pattern occupies only half the width of the transport web in the illustrated embodiment of the invention and normally the adhesive imprinting as well as the color printing would be done "two across". As shown in FIG. 5 where lines 161 and 163 indicate the edges of the elongated strip of plastic film, one portion 165 of the adhesive imprinting plate pattern extends transversely to the film wrap material edges 161 and 163. Also, portions of the imprinting plate pattern as indicated at 167 and 169 run parallel to edges 161 and.163. Portion 167 is about 1/4 inch from the film edge 161, and portion 169 is spaced slightly more than one inch from edge 163 to allow space for functional index marks printed on the film. The color printed pattern 171 applied to the plastic film is printed on some portion of the film not imprinted with the adhesive pattern shown in FIG 5. The design and location of the color printed material will, of course, depend upon the effect that is to be produced on the final wrapped package. The package wrapping equipment will be set up to cut the film wrap for successive packages through the pattern portion numbered 165 and the film wrap portions folded under the tray will thus have adhesive imprinted portions along at least two of their edges. The imprinted longitudinal strip 169 as shown in FIG. 5 is optional and may be omitted for some wrap designs. Of course, a pattern for adhesive printing could be arranged to completely surround the area to be color printed, but it has been found that this is not necessary. The adhesive used for the pattern of FIG. 5 is preferably of the class described as liquid thermal setting rapid response, moderate to long shelf life, non-toxic adhesive. An adhesive setting temperature range of 150°F. to 250°F. is preferred. Various resinous or polymeric adhesives may be used in the process including by way of example, Crodacoat 313-05600 made by Croda Inks Corporation, Niles, IL. The adhesive may be combined with 1/2 to 5% of a wax or other release substance. As shown in FIGS. 1 and 2, an optional air cooler 119 may be arranged to direct cooling air onto take-up roll 113 for further cooling the film 100.

Claims: C L I M S 1. A method of making a heat-sealable printed trans¬ parent film wrap material in a continuous roll having a longitudinal axis comprising the steps of unrolling the film wrap material from a stock roll, passing the wrap material through a printing roll set to imprint a heat activated adhesive thereon in a predetermined pattern of segments substantially transverse to said axis, leaving an unimprinted area, applying heat to the wrap material, passing the wrap material through at least one further printing roll set adapted to print on said wrap material in registration with the first said printing roll set, printing a design on said wrap material in said unimprinted area, and rolling said material on a takeup roll. 2. A method according to claim 1, which includes cooling the material subsequent to printing a design thereon. 3. A method according to claim 2, which cooling is effected by passing the material over a chilled surface. 4. A method of making a heat-sealable printed trans¬ parent film wrap material in a continuous roll having a longi¬ tudinal axis comprising the steps of unrolling the film wrap ' material from a stock roll, passing the wrap material through a printing roll set to imprint a heat activated adhesive thereon in a predetermined pattern of elongated first segments substan¬ tially parallel to said axis and second segments substan¬ tially transverse to said axis, leaving an unimprinted area, applying heat to the wrap material, passing said wrap material over a chilled surface to lower the temperature thereof, and rolling said material on a takeup roll. 5. A method according to claim 3 or 4, in which the chilled surface is a chill roller. 6. A method of making a heat-sealable printed transparent film wrap material in a continuous roll having a longitudinal axis comprising the steps of unrolling the film wrap material from a stock roll, passing the wrap material through a printing roll set to imprint a heat activated adhesive -thereon in a predetermined pattern of elongated first segments substan¬ tially parallel to said axis and second segments substantially transverse to said axis, leaving an unimprinted area, applying heat to the wrap material, passing the wrap material through at least one further printing roll set adapted to print on said wrap material in registration with the first said printing roll set, printing a design on said wrap material in said un¬ imprinted area, passing said wrap material over a chill roller to lower the temperature thereof, and rolling said material on a takeup roll. 7. A method according to claim 6, which includes further cooling the material subsequent to its passing over the chill roller. 8. A method according to any one of the preceding claims, in which the step of applying heat includes directing air heated above ambient temperature on the adhesive imprinted side of said material. 9. A multicolor printing apparatus having multiple cylinders for placing a printed pattern on transparent plastic film wrap material and a film takeup roll receiving the imprinted material, and means for applying an adhesive pattern in registration with said printed pattern comprising a plate cylinder having a pattern thereon corresponding to the desired adhesive pattern, means for rotating said plate cylinder in synchro¬ nism with the multiple cylinder of said printing apparatus in contact with said film, means for supplying liquid adhesive to said plate cylinder, a drier adjacent said plate cylinder and in a -In ¬ direction downstream thereof relative to motion of said trans¬ parent plastic wrap material, and cooling means arranged along the path of said film near the exit point to said film takeup roll. 10. Apparatus according to claim 9, in which the cylinder pattern has at least a portion extending transversely of the film wrap material. 11. Apparatus according to claim 9 or 10, in which the means: for rotating the plate cylinder includes a mechanical coupling between the multiple cylinders and said plate cylinder. 12. Apparatus according to any one of claims 9 to 11, in which the drier includes means for directing air heated above ambient temperature on the adhesive imprinted side of film wrap material exiting from the impression cylinder. 13. Apparatus according to any one of claims 9 to 12, in which the multicolor printing apparatus has a transport web for carrying the film through the multiple cylinders and to the takeup roll and the plate cylinder is adjacent said transport web upstream of said multiple cylinders. 14. Apparatus according to any one of claims 9 to 13, in which the means for supplying liquid adhesive include a reservoir adjacent the plate cylinder, means for maintaining the adhesive level in said reservoir, at least one stirring and spreading roll arranged to uniformly wet said plate cylinder with said adhesive and means for continuously rotating said roll. 15. Apparatus according to any one of claims 9 to 14, in which the cooling means comprises a chill roll arranged to be partially encircled by the transport web at a position just upstream of the exit position to the film takeup roll.

Inventors: BIGGS M HAYS, BIGGS, M., HAYS
Applicants: PACKAGING SPECIALTIES INC, PACKAGING SPECIALTIES, INC.
Application year: 1986
Main classification: B05D3
IPC codes: B41F17, B41F23, B41M1, B65H37