Apparatus and method for forming an adhesively bonded seam...

Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor

Reexamination Certificate

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C156S073600, C156S304100, C156S304600, C156S502000, C156S507000, C156S580100

Reexamination Certificate

active

06375770

ABSTRACT:

TECHNICAL FIELD
The present invention relates, in general, to the formation of seams between two opposed edges of fabric sheets, and more particularly, relates to apparatus and methods for the formation of adhesively bonded butt seams between foamed, fully cured, elastomeric, resiliently compressible and flexible sheets of material of the type used in wet suits, dry suits and the like.
BACKGROUND OF THE INVENTION
Wet suits and dry suits of the type used in aquatic sports, such as wind surfing, board surfing, water skiing and scuba diving typically are fabricated from pieces of fully cured or set (no longer thermoplastic), foamed, neoprene rubber. The suits are comprised of various fabric pieces which are cut into shapes that accommodate the user's anatomy, provide desired elongation, and produce a variety of aesthetic effects. The wet suit pieces are joined together in seams which are either stitched or adhesively bonded, or a combination of both.
When a wet suit is fabricated using a seam stitching technique, the cost of manufacturing the wet suit is reasonable since conventional fabric seaming equipment, such as overlock sewing machines, can be employed. Thus, wet suits having stitched seams are good candidates for production sewing and semi-automated fabrication.
Unfortunately, wet suits having overlock-type stitched seams inherently leak water at the seams, which is tolerable for a wet suit, in that it is contemplated that water will enter the wet suit. Water leakage, however, is unacceptable for dry suits and should be minimized for wet suits which are intended for use in relatively cool or cold water locations.
Accordingly, dry suits and wet suits which are designed for use in cold water are formed from pieces of neoprene rubber material which are adhesively bonded together in butt seams so as not to leak water at the seams. Sometimes these suits are also blind stitched to reinforce the seam, but using current adhesive bonding techniques, the glued seams typically have a strength which is at least as great as the foamed neoprene rubber itself.
Adhesively bonding or gluing together of two foamed, fully cured or vulcanized, neoprene sheets, however, is a very labor intensive process. Conventional garment-industry fabrication techniques cannot be used because the resiliently compressible neoprene pieces are very difficult to manipulate, and the vulcanized or cured neoprene requires the application and/or activation of an adhesive bonding material on the edges of the pieces to be joined together.
Wet suits and dry suits are formed from fully cured neoprene sheets which have a thickness in the range of about 1 to about 6 millimeters, and the foamed neoprene fabric is both resiliently stretchy and flexible. In some instances, pieces of different thicknesses are bonded together, and often the neoprene will have a nylon fabric facing bonded to one or both sides of the sheet.
Currently, neoprene adhesive bonding is accomplished by applying a neoprene adhesive to the edges of the sheets to be bonded together. Usually the adhesive is applied to a plurality of similarly shaped pieces that are stacked with their edges exposed so that the adhesive can be applied with a brush to the edges only. The adhesive is then allowed to dry. After the adhesive has dried, a solvent is used to reactivate the adhesive when two pieces are to be seamed together. The pieces to be joined have their adhesive-coated edges painted with solvent, and then the edges are pressed together by hand. Finally, a pair of pneumatic pliers must be used to positively press or squeeze the edges of the pieces together to uniform bonding. The pliers are pushed down into the neoprene foam adjacent and inwardly of the edges and the jaws are closed to press the abutting edges of adjacent pieces together. This is repeated along the length of the seam by using a series of side-by-side, longitudinally adjacent pinching, releasing and moving steps.
While this technique produces a strong seam, the application of solvent using a brush, pressing together of the fabric pieces by hand and pneumatic squeezing with pliers of the pieces to bonding, all are labor intensive and undesirably costly. Moreover, the pneumatic pliers clamp the pieces together in a manner which appears to result in residual stresses in the seam. Additionally, there are significant health and safety hazards to the wet suit fabricator in connection with the application of solvent and the repeated, rapid use of pneumatic pliers.
An example of a stitched and bonded seam construction suitable for use in wet suits or the like is shown in U.S. Pat. No. 4,416,027 to Perla. This seam also includes a reinforcing insert, but as will be apparent, the hand labor required to create such a seam, and therefore the cost of forming the same, is substantial.
Adhesively bonded butt seams have been formed between sheets of plastic and rubber for various other applications. In U.S. Pat. No. 3,615,994 to MacLaine, laminated sheets, which include foamed layers, are joined together in a butt seam. In the process and apparatus of the MacLaine patent, however, the two edges which are joined at the seam are not urged toward each other, but instead are merely held in registration and overlapped on the front and back sides by a reinforcing tape.
In U.S. Pat. No. 4,231,836 to Ljungqvist, et al. and U.S. Pat. No. 4,867,823 to Pizzorno apparatus and processes for joining together unvulcanized rubber strips of material of the type used in automobile tires are disclosed. In both patents, cord strips, which are comprised of fiber or metallic cords that are oriented in a predetermined direction and surrounded by unvulcanized rubber, are joined in edge-to-edge abutting relationship. The apparatus in both patents includes bevelled wheel or roller assemblies which progressively urge the two opposed cord strip pieces toward each other during formation of the seam. The cord strips are held together initially by reason of the inherent stickiness of the unvulcanized rubber, and a separate vulcanization process is required to permanently bond the sheets together.
In both Ljungqvist, et al. and Pizzorno, the sheets being joined are not resilient, but instead are deformable or capable of plastic flow. Moreover, unlike wet suit neoprene fabric which is fully cured or vulcanized, the cord strips joined by Ljungqvist, et al. and Pizzorno are unvulcanized rubber sheets (with reinforcing cords or fibers). Since the unvulcanized rubber cord strips are plastic, application of substantial pressure to the cord strips during the joining process will permanently deform the strips. Thus, in Ljungqvist, et al. grooved wheels engage the cords to urge the strips together with minimal rubber deformation. In Pizzorno the rubber sheets are urged together by wide bevelled roller elements which are skewed and have peripheral surfaces oriented parallel to the sticky top and bottom rubber sheet surfaces. Additionally, in Pizzorno a guide wing structure is provided to direct the sheets toward each other. Thus, the wide rollers engage the top, and preferably the bottom, sticky surfaces of the sheets, and urge the sheets together.
While the Ljungqvist, et al. and Pizzorno patents disclose seam forming apparatus which is suitable for moving plastic, sticky, unvulcanized, reinforced rubber cord strips together to form a butt joint, which is subsequently bonded in a separate operation by vulcanization, they do not suggest or attempt to solve the problem of forming a butt seam between resilient, compressible, flexible, vulcanized foamed fabric sheets to which adhesive must be added. The flexible and compressible nature of foamed neoprene rubber, plus the inherent need to employ an adhesive agent, makes the formation of adhesively bonded butt seams very difficult. The neoprene material must be compressed positively together proximate the edges to uniform adhesive bonding, and the entire process must be capable of semi-automation so as to be economically comparable to sewn seams such as those made by overlock-type sewing machines. I

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