GB855348A - Flexible fluid sealing diaphragm and method of making same - Google Patents

Abstract

855,348. Stuffing-box substitutes; pistons. TAPLIN, J. F. Dec. 11, 1956 [Dec. 12, 1955], No. 37812/56. Classes 122 (1) and 122 (5). A method of making a cup-shaped diaphragm or rolling-sleeve type of seal which permits limited circumferential extension of the cylindrical portion whilst ensuring axial inextensibility comprises the steps of placing a blank of flat cross-weave fabric, e.g. nylon, in a die of the form shown in Fig. 3, clamping the blank within a countersunk portion 8 by a top-plate 10 so that the blank is held flat but is allowed to slide during the insertion of a heated cylindrical male die 22 into the cavity of the female portion. The clearance between the male and female portions of the die is made as large as possible while remaining insufficient to allow the quantity of fabric deformed therebetween to double upon itself. During the deformation of the fabric the warp and weft threads take up the relative positions shown diagrammatically in Fig. 6. As the fabric comprising the cylindrical portion has been circumferentially compressed and axially extended by rearrangement of the threads, the warp threads 34 at A are substantially straight having been axially dislodged to only a slight extent while the weft threads 36 at A are curved, having been rearranged by circumferential compression of the cylindrical part of the fabric, and thus lie at an oblique angle to the warp threads. The flange portion at A and the cylindrical portion at D is substantially non- stretchable in the direction of the warp but extensible in the direction of the weft. At B, substantially 90 degrees from A, the weft threads 36 have been maintained in their original linear relationship but in this case the warp threads 34 have been curved or rearranged by compression. The flange at B and the cylindrical part at E is extensible in the direction of the warp and substantially non-stretchable in the direction of the weft. At C both the warp and the weft threads have been rearranged from their normal mutually-perpendicular relationship to a mutually-oblique or biased arrangement, forming a diamond-shaped pattern. The cylindrical part at F is non-extensible radially and axially, but is expansible circumferentially. The fabric is rendered impervious to fluid by treating it with an elastomer which is, preferably, pre-formed to a shape similar to that of the diaphragm and is bonded to the fabric by heat and pressure in a common mould. Alternatively a slug or pellet of elastomeric material may be placed at the top of the mould and softened by heat so that it impregnates the fabric during moulding. A circular hole may be cut in the top surface of the diaphragm to provide an inwardly-extending annular flange. The wall portion may be cylindrical, slightly conical or of double frustoconical form, as shown in Fig. 13. The mould may be formed with fine axial corrugations to increase the circumferential extensibility. The diaphragm 52, Fig. 12, may be used to seal the piston 64 of a pressure-actuator unit, air or other fluid pressure entering the cylinder through an opening 73.