Abstract:
A liquid proof seam construction is provided. A double needle flat-felled seam is constructed having a melt adhesive polymer film disposed within the seam. The seam is then passed through a hot air/pressure device which melts the film and compresses the seam. This forms a liquid, e.g. waterproof, bond between adjacent layers of material and also fills up any area around the stitching formed by needle holes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates, generally, to fabric seams and more particularly, to a liquid proof (e.g. waterproof) seam and method of manufacture. 
     1. Prior Art 
     Many attempts have been made to make liquid proof, particularly waterproof, articles such as raincoats, jackets, and similar outerwear as well as tents, outdoor equipment, tarpaulins and the like. Accordingly, the technology has developed to the point where reusable woven or knit fabric materials offer varying degrees of liquid proofing depending upon the characteristics of the material utilized and the use to which the material will be put. 
     Of recent date, a new class of garments have become important. This class relates to surgical, medical, laboratory and other types of garments, worn by personnel that have interaction with patients; as well as laundry bags, containers and the like for such medical uses. More particularly, with the attention of the clinical community focusing on the transmission of infectious diseases by blood and body fluids, the use of personal protective clothing has increased significantly. Comfort of such clothing has also become an important consideration. 
     While some materials are totally impervious to fluids and the like, they are generally unsuitable in that they do not breathe and/or are difficult or generally uncomfortable to wear. Furthermore, since materials of this nature cannot be sterilized by traditional methods, their use is prohibited. As a result, a number of materials have been developed which offer excellent comfort and performance characteristics. Examples of these fabrics are FASHION-BLOC and FASHION-SHIELD manufactured and produced by Superior Surgical Mfg. Co., Inc. of Seminole, Fla. These materials are very effective when worn as protective apparel by a health care worker during a procedure. 
     Protective apparel is also used to reduce the risk or exposure of a worker&#39;s skin or mucous membranes to blood and body fluids containing visible blood and other fluids to which universal precautions for the transmission of HIV (&#34;Universal Precautions&#34;) apply. Such precautions are relatively standard in the health care industry for a variety of reasons, the most recent and perhaps most important being the potential contraction of Acquired Immunity Deficiency Syndrome. i.e., AIDS. 
     However, while fabric construction has advanced greatly, the liquid proofing, e.g., waterproofing, of seams in these items has continued to present problems. Moreover, these types of items are generally only cost effective when repeated usage is possible. Therefore, they must be able to withstand the rigors of numerous institutional type processing cycles (laundering, drying and ironing), sterilizations and the like. Therefore, seam makeup including thread, overall construction and other fluid-resisting materials must similarly be able to withstand such abuse. 
     Many attempts have been made to produce waterproof, water resistant or liquid proof seams. For example, U.S. Pat. No. 4,604,152, &#34;Method of Making a Stitched and Bonded Seam&#34; to Liukko describes a liquid proof seam formed by interposing a thermal adhesive between overlapping edges of material. However, this has a significant drawback in that the joint is formed solely by the thermal adhesive. Once a portion of this type seam separates, for any one of a variety of reasons, a zippering effect will result, i.e. the entire seam will fail as stress is placed on it. 
     U.S. Pat. No. 4,593,418, &#34;Method and Seam Construction to Significantly Reduce Seam Leakage&#34; to Simon describes an elastomeric strip interposed between sheets of material. The elastomeric material is sewn to the seam, and surrounds and seals the thread as it passes through the seam. However, this is also somewhat unsatisfactory in that, since no bonding occurs between the elastomer and fabric, the integrity of the liquid proof seam is entirely dependent upon the structural integrity of the sewing. Therefore, should the thread become loosened or broken, fluids may wick or pass by or through the seam itself. 
     U.S. Pat. No. 4,561,128 &#34;Fusing Apparel Seams&#34; to Zimmerman is directed to a method for fusing seams for the purpose of providing aesthetically pleasing, i.e. straight and flat, seams. This patent does not teach or suggest waterproofing or the problems associated therewith. 
     U.S. Pat. No. 2,115,368 &#34;Seam&#34; to Lustberg describes a waterproof seam by interposing a water repellant material between two layers of waterproof material. A water repellant thread is utilized to sew the seam. The integrity of this seam is dependent upon the mechanical integrity produced by thread. Therefore, should the thread become loose or ripped, passage for fluids is made possible. 
     While all of the above offer solutions to the problem of enhancing the integrity of seams, they are all lacking in one respect or another. 
     OBJECTS AND SUMMARY OF INVENTION 
     It is an object of the present invention to produce a seam suitable for use in protective apparel which satisfies the &#34;Universal Precautions&#34; used in the clinical field. 
     It is yet another object of the present invention to produce a seam which is capable of enduring repeated rigorous institutional launderings, sterilizations and usage. 
     A further object of the present invention is to produce a seam which will not zipper, that is, tear in the seam and migrate along the entire length of the seam. 
     Still a further object of the present invention is to produce a seam which has strong mechanical properties which will resist failure during normal usage or wearing. 
     Another object of the present invention is to produce a seam which is simple and inexpensive to manufacture. 
     Yet another object of the present invention is to produce a seam which prevents wicking of fluids, particularly aqueous fluids, through the thread or apertures in the seam produced by the thread. 
     Still another object of the present invention is to produce a seam which bonds adjacent layers of fabric material together to thereby form a liquid-tight seam. 
     Yet another object of the present invention is to produce a seam whereby a thermo-adhesive material seals any apertures in the seam surrounding the thread sewn in the seam. 
     The foregoing objects are achieved by providing a liquid proof, e.g. waterproof, garment seam. The garment seam comprises a first liquid proof fabric material and a second liquid proof fabric material having portions thereof overlapping each other, the portions being bonded together by a melt adhesive film disposed therebetween, and a liquid proof thread extending through the overlapping portions and film for fixedly securing the overlapping portions and film to form a liquid proof seam. 
     The method for forming the liquid proof seal comprises: 
     (a) providing a melt adhesive polymer film between over-lapping portions of two sheets of liquid proof fabric material to form a seam area; 
     (b) stitching the seam area with a liquid proof thread through the overlapping portions and film; 
     (c) heating the seam area to melt-bond the film to the overlapping portions of fabric material to thereby form a liquid proof seam. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Reference may be had to the accompanying drawings in which: 
     FIG. 1 is a perspective view of the seam of the present invention; 
     FIG. 1A is a cross-section of the seam of the present invention taken along line 1A--1A of FIG. 1; 
     FIG. 2 is an illustration of a representative garment utilizing the seam of the present invention; 
     FIG. 3 is a schematic representation of the method of this invention by which the seam is rendered liquid proof; and 
     FIG. 4 is a schematic end view of the seam of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1, 1A and 4 there is shown a perspective and end views, respectively of the seam of the present invention. More particularly, the preferred seam construction is shown generally at 10 and is comprised of a first fabric material 12 in overlapping relationship with a second fabric material 14. A melt adhesive film 16 is disposed between first and second edges 22,24 respectively of the first and second materials 12,14. In the preferred embodiment of the present invention, film 16 is a polyester film of an appropriate thickness, as for example, approximately 3-7 mils thick having a melting point of from about 250° F. to about 270° F. Two rows of waterproof, preferably thermoplastic polymer thread 18,20 are stitched through the fabric materials and film, the entire seam being a double needle flat-felled seam. Preferably the threads are a polyester treated with a fluorocarbon finish. Preferably the thermoplastic threads have a higher melting point, than the film to maintain the integrity of the seam after heating, (e.g. 450° F. melting point). Thus, upon heating of the seam to a sufficiently high temperature to melt the film, the thread is at most only partially melted or softened. The coating of fluorocarbon on the thread prevents wicking of aqueous fluids through the seams by virtue of the thread acting as a conduit or wick. 
     In the preferred embodiment of the present invention the first and second fabric materials 12,14 are preferably a yarn such as a polyester texturized yarn or a continuous filament polyester yarn such as FASHION BLOC or FASHION SHIELD, products of Superior Surgical Mfg. Co. of Seminole, Fla. However, it is to be understood that any suitable fabric material having a relatively dense weave and/or hydrophobic properties which prevent penetration of the liquid, and can withstand the heat and pressure to which the seam is subjected, may be utilized without departing from the spirit and scope of the present invention. 
     The terms &#34;melt-adhesive film&#34; and &#34;thermoplastic polymer&#34; as used in describing the film 16 and thread 18,20 respectively means the ability of the film or thread to deform or melt when an appropriate temperature and/or pressure is applied to enable conformation and/or adherence of the film or thread to the surface it is in contact with. Such terms are not to be considered to limit the chemical structure of the film or thread but only its physical properties under the conditions of use described herein. 
     Referring to FIGS. 1A and 4, seam 10 is preferably constructed so that the ends of fabric materials 12,14 are folded in overlapping U-shaped fashion so that first and second edges 22,24 meet the inside of the U-shaped seam for the second and first materials 14,12 respectively, with the film 16, therebetween. In this manner, the &#34;A&#34; and &#34;B&#34; sides of material 12 are in contact with the &#34;A&#34; and &#34;B&#34; side of material 14 and the &#34;B&#34; side of material 14 is in contact with film 16 while the &#34;B&#34; side of material 12 is in contact with the opposing surface of film 16. 
     Referring to FIG. 3, in the preferred embodiment of the present invention the seam 10 is passed through a hot air blower 26 and pressure rollers 34 after the seam 10 is constructed and sewn. This process consists of a controlled balance of air temperature, roller pressure and speed of the rollers applied to the seam area 10 so as to minimize distortion, puckering and damage to the base fabric and accomplish the final seaming operation. This operation melts and bonds the film 16 to the &#34;B&#34; sides of materials 12,14 along the seam length and additionally fills up the needle holes surrounding threads 18,20. Additionally, there may be a partial melting or softening of threads 18 and 20 to assist in closure of these holes and melt with the film 16. Accordingly, the seam produced has excellent mechanical strength and is waterproof. An important aspect of this invention is that the film, when melted, fills the needle holes thereby preventing any wicking or migration of fluids therethrough, without destruction of the integrity of the thread. Preferably the polyester film and fiber, after heating, create an integral waterproof structure. 
     Once the seam 10 is physically constructed, that is, the first and second materials have been overlapped and film 16 has been sewn into the seam area, it is passed through a press 28. It is to be understood that any suitable type of heat/pressure device may be utilized as long as it exhibits the appropriate heating characteristics commensurate with the particular film and thread being utilized (i.e. temperature, pressure and speed). The device 28 is comprised of upper and lower rollers 34. The function of rollers 34 are to advance and compress the seam as it passes between the rollers 34. In the preferred embodiment of the present invention the rollers exert an appropriate amount of pressure precisely at the point of temperature application thereby providing optimum heating and fusing characteristics. Preferably, the rollers apply a pressure of about 50 to 80 psi and are rotated at a speed sufficient to cause the material to be fed at about 20 to 40 feet per minute, preferably 30 feet per minute. The fabric is preferably heated by hot air jet 26, preferably at a volume of 80 ft 3  /min. having a temperature of about 650° C. to 800° C. for about 2 to 3 seconds. Obviously, these parameters are highly dependent on the specific structure of the device, the structure of the seam and the type fabric, thread and film used. 
     Referring to FIG. 2 there is shown a sketch of protective gown 40 utilizing the seam 10 of the present invention. Although it has been found that it is possible to produce garments having a minimal number of seams, some seams must be used for comfort, to maximize yield of material, facilitate manufacture and minimize costs. It is to be understood however that the present invention may be practiced with respect to any fabric structure, including garments, laundry bags and the like without departing from the spirit and scope of the present invention. The present invention produces a seam which is extraordinarily resistant to stress and which is also highly resistant to laundering processing cycles and the like. It has been found that a garment or bag or the like, although initially more expensive to manufacture, is actually cost effective when the overall life of the product is taken into account. 
     It is to be understood that many variations of the present invention may be practiced without departing from the spirit and scope of the present invention. For example, the number of folds in the material may be increased or decreased or a plurality of films may be interspaced throughout the seam. Further, other types of thread may be used or different fabric materials may be utilized and the seams may be used in any fabric structure.