US 3246621 A
Description (OCR text may contain errors)
April 19, 1966 CQPELAND 3,246,621
WATERPROOF SEAM CONSTRUCTION Filed March 1, 1963 2. Sheets-Sheet 1 INVENTOR.
LYNN L. COPELAND April 19, 1966 L, L, C PELAND 3,246,621
WATERPROOF SEAM CONSTRUCTION Filed March 1, 1963 2 Sheets-Sheet 2 FIG. ll
FIG. l2 INVENTOR.
LYNN L. COPELAND United States Patent 3,246,621 WATERPRGOF SEAM CQNSTRUCTIGN Lynn L. Copeland, Philadelphia, Pa., assignor to Ruhco Products, Inc., a corporation of Pennsylvania Filed Mar. 1, 1963, Ser. No. 262,140 Claims. (Cl. 112413) The invention relates to seam for securing butt joints of elastomeric material, and more particularly to an improved method for joining the edges of foam or sponge rubber sheets of the type used in divers suits.
The present invention is a continuation-in-part of my application, Serial No. 173,223, filed February 14, 1962. In the above previously filed application I described a divers suit of the type customarily utilized by skin divers and in emergencies by aviators, naval personnel, etc. Prior to the invention described herein and in my copending application, joints for these suits had been made of an adhesive, with or without a lapped reinforcement. These have been found to be extremely unsatisfactory and particularly defective Where it is desired to join two pieces of material of different thicknesses. In developing the most satisfactory joint for a sponge type rubber, either natural or synthetic, it was found to my surprise that several factors are quite critical in obtaining proper results. It is important that extensibility in all directions be at a maximum. The needle size and number of stitches must be so controlled that the material is not dam-aged to the extent that it ruptures at the stitches when substantially stretched. It is also of considerable importance to maintain a condition of compression between the butted edges of the material after the seam has been made and in order to achieve this objective I run the seam with the edges in line and the sheets superimposed one on top of the other. They then can be opened up and with a quick stretch in direction at right angles to the joint, the edges will snap into place within the seam and remain under suflicient compression to prevent the seam from opening when the material is pulled in the same direction.
The present invention includes three types of seamed joints but all three stem from the basic stitch produced in accordance with the disclosure of the present invention. The joints may be seamed only, or they may be cemented and seamed, and either of the first two may have a reinforcing tape adhesively secured to the completed seam. The last is the strongest, but the most expensive and the first is the cheapest but the least strong.
A primary object of the invention, therefore, is to provide a method for joining two sheets of elastomeric ma terial.
A further object of the invention is to provide a method for seaming joints of two sheets of cellular sponge synthetic or natural rubber.
A further object of the invention is to provide an improved method -for joining two sheets of elastomeric material of different thicknesses.
A still further object of the invention is to provide an improved seamed joint for sheets of cellular sponge rubber.
Further objects will be apparent from the specification and drawings in which FIG. 1 is a fragmentary section showing two layers of elastomeric material seamed together prior to being expanded,
FIG. 2 shows the two sheets of FIG. 1 partly opened and ready to be stretched to form a compressed butt joint,
FIG. 3 shows the fully formed butt joint with the edges under compression; the seam being somewhat distorted to fully illustrate the compression of the material edges within the seam,
FIG. 4 shows a joint similar to FIG. 3 with the addition of an adhesive,
FIG. 5 shows a joint similar to FIG. 4 with the addition of an adhesively secured tape,
FIG. '6 is a view similar to FIG. 1 but showing sheets of elastomeric material of different thickness,
FIGS. 7, 8, 9, and 10 are views corresponding to FIGS. 2-5, respectively, but illustrating a joint constructed according to the present invention with sheets of different thickness,
FIG. 11 is an enlarged top view of the completed joint as seen in either FIG. 3 or FIG. 8, and
FIG. 12 is a view of the joint of FIG. 11 showing the action of the stitches when the joint is very substantially stretched along the line of the seam.
The invention comprises essentially the stitching of the superimposed edges of two layers of sponge rubber using an overedge lock stitch. Upon opening the layers and stretching them vigorously in a direction across the seam the butt edges of the sponge rubber layers will snap into place, facing each other to form a compressed and continuous contact between the edges within the seam.
Referring now more particularly to the drawings, two sheets, 15 and 16 of elastomeric material such as closed cell sponge neoprene, are positioned in super-imposed relationship as shown in FIG. 1. The edges 17 and 18 of the sheets are vertically aligned and the lock stitch 19 is run through the non-abutting but superimposed edges in a modified blind stitch sewing machine. After the seam 19 has been run the length of the edges to be joined, the sheets 15 and 16 are then opened out as shown in FIG. 2 to extend in opposite directions. The edges 17 and 18, however, are still superimposed within the seam. Additional tension in the direction shown in the arrows in FIG. 2 causes the edges 17 and 18 to snap into abutting relation as shown in FIG. 3 and when the tension is released the stitches compress at edges 17 and 18 so that they are in a tight butting relationship at all times except when the sheets 15 and 16 are very substantially stretched. With the seam 19 formed in accordance with the present invention it has been found that it is impossible to open the once formed seam of FIG. 3 by pulling on the sheets. The material will rupture before the joint will separate, even in the absence of adhesive. If it is desired to provide additional strength or sealing properties, an adhesive 25 may be applied to the exposed edges 17 and 18 prior to snapping them in place. FIG. 4 shows the joint of FIG. 3 with the addition of an adhesive material. In the event a somewhat smoother surface is desired and to increase the strength of the seam by adding to the strength at the puncture points of the stitches, a tape or strip of fabric or elastomeric material 26 may be secured over the seam as shown in FIG. 5.
A particularly desirable feature of the invention resides in the fact that it is now possible to obtain an extremely strong joint between two sheets of elastomeric material such as sponge rubber which vary quite substantially in thickness. Such a joint is shown in FIGS. 6-10 in which the steps are the same as those previously described in connection with FIGS. 1-5. Attention is directed to FIGS. 8, 9 and 10 which show how the edge 30 of the thinner sheet 31 assumes a convex shape and actually fits within the edge 32 of the thicker sheet 33. This feature provides an added seal where normally one would expect decreased sealing efficiency.
The seam or stitches 34 of FIGS. 6-10 are the same as the seam 19 of FIGS. l-5. The adhesive 35 is shown in FIG. 9, and the additional reinforcing tape 36 is shown in FIG. 10. The overedge lock stitch shown in FIGS. 11 and 12 is similar to that in my co-pending application referred to above, and is capable of very substantial elongation in a direction parallel to the seam. This feature is of great importance in the manufacture of wearing apparel, otherwise the divers or wearers arm 3 and leg movements are severely hampered. In previous suits the life of the joints has been so short at the knees, elbows and shoulders that new suits are frequently required afterfeach use. FIG. 12 illustrates a sample joint which is shown stretched by means of a pair of clamps 37 and 38.
I have found that the present invention takes its preferred form when used with a closed cell sponge neoprene of thickness from A1 to A. The needles for this material may vary from 0.020" to 0.080" in diameter but most satisfactory results are obtained with a 0.020" diameter needle. In view of the method for butting the edges of the sheet material after seaming, the distance from the center of the seam to the edges is important. For sheet thicknesses of /s%", the permissible dimension is to 4''; W gives optimum results. With regard to the number of stitches per inch, stitches is found to behest, but more than stitches per inch reduces the strength of the material, and fewer than 4 stitches per inch will not give adequate joint strength. The sheet material preferably should be compressed on the order of 5% to in the seam. This naturally depends to some extent on the thickness of the sheet material, but the above is adequate to give a good tight joint. The thicker the sheet material the less-compression is required to produce the desired results. For example, for a sheet material /2 thick, the compression should be on the order of 20% whereas for material, a compression of only 5% gives satisfactory results. The thread material is not critical but depending upon the type of usage and whether rotting is a factor, a synthetic thread of nylon or an acrylic is preferable.
The following table illustrates the surprisingly strong joints that can be produced with the present invention. The joint is far superior toany previously known purely cemented joint and when taped, approaches the breaking strength of the sponge rubber itself.
provides for the first time, an extremely satisfactory seamed joint between sheets of foam and/or sponge rubber. The joint, of course, has general application Wherever sheets of this or similar material need to be secured to each other, but the particular features of the seam lend themselves to underwater swimming equipment. The joints may be made waterproof or not as may be desired but in the preferred form the butt joint between the sheet materials is sufiiciently tight even under stretching to prevent substantial leakage. In the absence of the tape on the seam, slight leakage may occur when the needle punctures are sufiiciently stretched to permit passage of water or other liquid. If this condition is not desired the tape may be used as shown in FIGS. 510.
Having thus described my invention, I claim:
1. As an article of manufacture, a substantially waterproof seam construction comprising two sheets of rubber having edges united in butt joint relationship with one another in the same plane along said seam, said abutting edges being compressed substantially within said seam, said seam including extensible overedge lock stitches whereby the seam can expand and contract only in a direction substantially parallel to the line of direction of the seam thereby allowing said seam to expand and at the same time maintain its waterproof condition.
2. The article of claim 1 in which the stitches are applied to the sheets at a distance of A from the aligned edges.
3. The article of claim 1 in which the seam comprises from 4 to 15 stitches per inch.
4. The article of claim 1 in which the seam contains 10 stitches per inch.
5. The article of claim 1 in which the sheets are of different thicknesses.
References Cited by the Examiner UNITED STATES PATENTS 265,497 10/1882 Hawley 156-93 1,129,853 3/1915 Dahl 1l2-269 1,219,023 3/ 19 17 Merritt 112434 1,220,524 3/1917 McNeil 2262 1,293,576 2/1919 Tate 1 12-434 1,989,140 1/1935 Lefkowitz 287 X 2,592,463 4/1952 Phillips.
2,749,551 6/1956 Ga rbellano 282 2,962,082 11/ 1960 Lenney 156-93 3,079,882 3/1963 \Vashburn 112-260 JORDAN FRANKLIN, Primary Examiner.
DAVID J. WILLIAMOWSKY, Examiner.