1. Field of the Invention
This invention relates generally to hazardous environmental suits used to protect workers in contaminated areas, and particularly to a throw-away type such suit.
2. Description of Related Prior Art
Goldstein U.S. Pat. No. 4,272,851 is perhaps best illustrative of the prior art. It discloses a protective suit or garment constructed of a non-woven, spun bonded olefin manufactured under the trademark Tyvek.TM., a trademark of DuPont de Nemours & Company, which is coated on one side by a polyethylene film. The olefin provides tear resistance, and the film prevents chemical penetration. While the patent does not discuss the arrangement of adjacent surfaces of a seam of two pieces of the material, it is believed implicit that film side-to-film side is employed. First, examining the arrangement in FIG. 4, it is noted that each of the two thicknesses are turned 180.degree. to form facing surfaces, thus indicating that identical surfaces are mated. Second, normally, and as illustrated by Bibby U.S. Pat. No. 4,190,010, the film, less porous, side of a protective garment (waterproof) forms the outside of such a garment and, three, Tyvek.TM. is not directly heat bondable to another layer of Tyvek.TM., this being indicated by its manufacturer.
The Goldstein patent acknowledges the desirability of providing additional seam strength, accomplishing this by the addition of a binding around the external edge region of the seam and securing this region by stitching. The patent asserts that by this technique, since the needle holes are outside of the ultrasonic welded portion, the latter provides an unbroken barrier to the introduction of any contaminant, it being presumed that this means that even if a contaminant would pass through the stitching holes that it could not reach the interior because of the welded portion.
There are, however, two problems with the structure of Goldstein. First, while it is true that there is a seal between the two turned-back layers of material which is inboard of the stitching, there are two unsealed paths on the outside of these sealed layers which extend from the inside of the garment to the stitches. This, of course, can provide a leakage path. Second, even if one can effect a seal of all three surfaces of the material at a weld or welded seam, by the vary mechanical arrangement of the seam, it is particularly vulnerable to stretching forces which can and are frequently applied by natural movements of the wearer of the garment. The stresses are very concentrated, being first on the inside edge of a weld. In view of the small area to which the forces are initially directed, they can readily be hundreds of pounds per square inch just by the manipulation of one's arms, assuming a sleeve member is involved. As will be noted, initially, the sewn seam is not involved, and thus it provides no reinforcing pressure to hold the material together, with the result that with continued stretching forces, the weld is broken back to the point of sewing where sufficient resistance will probably be met to stop the tearing away process. Unfortunately, however, at this point, the seal of the weld no longer exists, and the remaining barrier, a sewn seam, is not liquid-proof.
Accordingly, it is the object of this invention to provide a significantly stronger seam and yet one which does not require sewing.