Abstract:
This invention relates to the method of producing a laminated vinyl thermoplastic stationery article from thermoplastic film material which simultaneously seals and tear/cuts the material leaving the article with a finished edge running parallel and adjacent to the seal applied to the margin of the article; and this invention also includes the article manufactured by the method set out.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and article produced thereby from laminated thermoplastic material having a uniform and an attractive marginal edge adjacent to seal by simultaneous sealing and tears/cutting of the marginal edge of the material thereby producing an attractive and finely finished article. 
     HISTORY AND BACKGROUND OF THE INVENTION 
     Stationery articles such as folders, portfolios and pocket document binders have long been produced such as illustrated in U.S. Pat. Nos. 5,876,143; 5,059,052; 5,752,721 and 5,417,509, including paper folders such as U.S. Pat. Nos. 4,934,584 and 3,516,599. Vinyl folios and folders are illustrated in U.S. Pat. Nos. 5,873,513 and 4,629,349. More specifically, polyethylene, polypropylene and polyvinyl chloride articles are illustrated in patents U.S. Pat. Nos. 5,275,438; 5,445,417 and 5,266,140. 
     Today, paper materials are less likely to be used in stationery paper products having pockets because of the durability factor. They do not stand up under heavy service necessating more durable materials. Problems have developed with the use of folders made of certain thermoplastic materials which tend to pick up the ink from inserted letters or the like leaving the transferred ink on the folders in an unsightly manner, and often where the folders are transparent, causing interference with subsequent articles placed in the folders because of ink transferred thereon at an earlier date. 
     Polypropylene has been found to be a thermoplastic material which when made into folders does not pick up ink from the papers inserted therein; whereas polyethylene and polyvinyl chloride tend to pick up ink. 
     Metallic polyethylene, polypropylene and polyvinyl chloride thermoplastic films are found to produce exceptional fine finished articles when used with this process probably due to the heat transfer of the metallic particles in the thermoplastic films. These metallic thermoplastics consist of aluminum powders, giving a special sheen to the folder as for example in silver, gold, red, green, blue, purple, etc. The metallic thermoplastics are available from American Profil of Cedar, Rapids, Iowa. 
     Where heat sealing is used in the manufacture of stationery articles such as folders and the like, it has been found necessary to use a two-stage system for producing the folders. This two-stage involves sealing the marginal edges followed by a cutting operation to remove the waste of flash materials adjacent the sealed edge. Unfortunately, it has been found that the cutting operation, being subsequent, often leaves marginal strips adjacent to seal which are uneven and unsightly. Further, the subsequent cutting and squaring off of the edges produces sharp corners which often injured or at least cause annoyance to the individual using such articles. In particular, polypropylene is ordinarily difficult to tear. 
     In most instances where a heat sealed is used, the attempt is to make the seal even in length, height and width. Depending on material, it has been found that if the seal is made having serrations, there is less likelihood of leakage or opening up of the seal. To some extent this is dependent upon the type of thermoplastic material used. 
     OBJECT AND SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a method and the article produced thereby which results from the simultaneous sealing and tear/cutting of the marginal edge of the article. 
     Another object of this invention is to provide a method and article produced thereby which uses ultrasound to vibrate the die having both the cutting and sealing edges to simultaneously seal and tear/cut the margin of the article produced. 
     A further object of this invention is to provide a method and the article produced thereby which utilizes polypropylene film such as sheet or role material. 
     Still further object of this invention is to provide a method and the article produced thereby which provides an even bead along the marginal edge of the article produced. 
     And a further object of this invention is to provide a method and the article produced thereby which has a uniform serrated seal and a marginal edge parallel to the serrated seal. 
     A still further object of this invention is to provide a method and the article produced thereby in which the corners of the article are rounded rather than pointed. 
     A further object of this invention is to provide a method and the article produced thereby which eliminates prior two step operation of sealing and subsequent cutting thereby reducing cost of operation. 
     Another object of this invention is to provide a method and the article produced thereby which gives the article a finished look by producing a uniform bead along the marginal edge. 
     Yet object of this invention is to provide a method and the article produced thereby which provides a die bar which by special machining eliminates distortion of the die bar providing a distortion factor of not over 0.001″. 
     A still further object of this invention is to provide a method and the article produced thereby which utilizes a step arrangement in the seal edge of the die to allow for even flow of the plastic material depending upon of the number of laminating sheets to be sealed by the seal operation. 
     A further object of this invention is to provide a method and the article produced thereby which relieves the stresses produced during the seal and tear/cut operation by relieving overflow material produced thereby producing a finer finished article. 
     Another object of this invention is to provide a method and the article produced thereby which enables the manufacture to tear or strip the article from the excess waste material around the margin which was earlier not possible due to the difficulty to tear polypropylene material. 
     Yet another object of this invention is to provide a method and the article produced thereby which utilizes ultrasound in order to seal and tear/cut the material in a manner to provide uniform edges to the article. 
     In summary, this invention relates to the method and article produced thereby which provides an attractive uniform marginal edge with a strong leak proof seal. 
     These and other objects will be apparent from the following description and the drawings which are described as follows: 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the die bar stock prior to machining; 
     FIG. 2 is cross-sectional view taking along the line of  2 — 2  of FIG.  1  and viewed in the direction of the arrows. 
     FIG. 3 is a side elevational view of the die bar stock after rough machining showing distortion upwardly; 
     FIG. 4 is cross-sectional taken along the line  4 — 4  of FIG.  3  and viewed in the direction of the arrows. 
     FIG. 5 is a side elevational view of the rough machine bar stock inverted and showing the bottom machined flat and showing in phantom lines the portion removed by the machining; 
     FIG. 6 is a cross-sectional view taken along the line  6 — 6  of FIG. 5; 
     FIG. 7 is the finished bar stock with the knife edge and serrated seal edges shown inside elevation with the machined portion shown in phantom lines; 
     FIG. 8 is a cross-sectional view along the line  8 — 8  of FIG.  7  and viewed in the direction of the arrows; 
     FIG. 9 is a fragmentary perspective view of the finished die mounted on the base support; 
     FIG. 10 is a fragmentary perspective view of a modification of the die bar stock; 
     FIG. 11 is a cross-sectional view showing in schematic the manner in which the die comes down on the laminations which are shown broken away; 
     FIG. 12 is an exploded perspective view outlined generally by phantom lines to show in somewhat schematic arrangement the positioning of the sheets of material relative to the ultrasound platen and the die; 
     FIG. 13 is a schematic showing in general the operation of the creasing dies; 
     FIG. 14 is a cross-sectional fragmentary view of the material positioned for creasing; 
     FIG. 15 is a schematic showing in general a typical folder showing a pocket across the folder on the inside of the folder and a pocket on the outside shown in phantom lines; 
     FIG. 16 is a fragmentary top plan view illustrating a corner of the folder produced. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-12 
     In the drawings of FIGS. 1-12 the bar stock B can be of metal such as brass or steel. This is first rough machined to produce side cuts  2  and  4 , leaving a die kerf  6 , as best shown in FIG.  4 . As best illustrated in FIG. 3, the rough machining of the bar stock B produces an upward curve to the bar stock. In order to provide a stable die accurate for the subsequent sealing and tear/cutting, the bar stock B is inverted, as shown in FIGS. 5 and 6, and the bottom  8  is now machined flat, as best shown in FIGS. 5 and 6. 
     The rough machined bar stock B is now inverted again so that the rough machined bar stock B can be precisioned machined producing the finished die having the cutting edge  12  and the sealing edge  14 . The cutting edge  12  is provided with a champfer  16 . The sealing edge  14  is provided with inner champfers  18 , outer champfers  20 , and where shown, side champfers  22 . Between the cutting or knife edge  12  and the sealing edge  14  is a flow relief pocket or groove  24 , as best shown in FIGS. 7 and 8 which forms a uniform bead  25 . 
     FIG. 9 shows one version of the die  10  mounted to a support plate  26  by screws  28 . The die  10  has the sealing edge comprised of serrations  30 . It is to be noted that the corner seal edge  32  is not serrated. To provide for different thicknesses of material or forming pockets or the like, the serrated edge  14  is step downwardly as at  34  and  36 . It should be noted that the actual die size is enlarge substantially in the drawings and that the height of the sealing edge  14  is only 0.03 inches. The distance between the serrations is about 0.009 inches with the width of the serration being about 0.05 inches. Dimensions may vary depending upon the number of materials layers and material thicknesses but still the dimensional size of the die bar  10  is going to be very small and require extremely accurate machining to eliminate distortion. 
     FIG. 10 shows a slight modification in which the seal edge  14  is non-serrated providing a uniform edge  38  having lower step edges  39  and  40 . 
     FIG. 11 shows the knife edge  12  and the sealing edge  14  with the flow relief pocket or groove engaging the materials layers  41 ,  42  and  44 . 
     FIG. 12 shows an exploded view with the each of the films  41 ,  42 , and  44  as they would be positioned prior to cut on the ultrasonic platen US. The ultrasound platen US consist of a series of a titanium bars  46 . The platen US is covered by MYLAR®  48 . 
     It should be noted that the vibrating ultrasound platen US generates friction and heat to the die  10  enabling the die to seal and tear/cut in one step which were before was not possible. 
     FIGS. 13,  14  and  15   
     In FIG. 13, the folder F is shown positioned between the top and bottom dies  50  and  52 , as best shown in FIG. 14 which forms a crease for the folder F. Steps  54  and  56  are provided to take care of the additional thickness of material forming the pocket P of the folder F, shown in FIG.  15 . 
     FIG. 16 
     FIG. 16 shows enclosed how a corner of the folder F appears with a serrated and evenly cut edge. 
     Operation 
     In the operation of the method, a first film of thermoplastic material is positioned on an ultrasonic platen US with the film having a length and breath sufficient to encompass the entire length and breadth of the article to be produced while providing excess material outside of the margin of the stationery article to be produced. At least a second film of thermoplastic material bondable to the first film is positioned overlying the first film encompassing only a portion of the length and breadth of the first film and a portion of the length and breadth of the article to be produced and providing excess material outside of that portion of the length and breadth of the stationery article to be produced. After the two films have been positioned, the die  10  having the knife and seal edges  12  and  14  is applied to the first and second thermoplastic films while activating the ultrasonic platen US causing the platen US and the die  10  to vibrate generating frictional heat and simultaneously sealing and tear/cutting the margin of the article to be produced with the seal just inside the margin of the article to be produced and the tear/cut on the margin of the article to be produced laminate the first and the second thermoplastic films together producing an airtight leak-proof seal. If third or fourth films are used, step dies are required. The thermoplastic materials, polyethylene, polypropylene, polyvinyl chloride and metallic polyethylene, polypropylene, polyvinyl chloride may be used in the process with polypropylene and metallic polypropylene being preferred. 
     Subsequent to the sealing and tear/cutting, the excess material is removed from the margin of the article produced leaving the article with a uniform margin bead  25  adjacent and parallel to the seal. It is to be noted that the volume of the relief area is based upon the thickness of thermoplastic material positioned at the time of sealing and tear/cutting and that this volume is based on 40-60% of the thickness of the thermoplastic material. Although 50% of the thickness is preferred. 
     While this invention has been described as having preferred design, it is understood that it is capable of further modification, uses and/or adaptations following in general the principle of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features set forth, and fall within the scope of the invention or the limits of the appended claims.