Patent GB-775577-A (GB)
Title: Pressure vessel and method of making the same
IPC: B29C70/86
Filed: 1954-05-26
Abstract: 775,577. Winding glass fibres on containers. APEX ELECTRICAL MANUFACTURING CO. May 26, 1954 [June 19, 1953], No. 15515/54. Class 109. [Also in Groups V and XXVIII] A vessel for storing high-pressure fluid comprises a wound shell corresponding to a surface of revolution and at least one fitting for the entry and/or discharge of fluid, the shell being formed of successive wrap windings with a resinous bonding agent (see Group V). In the described embodiment there are two fittings 12, 18, Fig. 5, for entry and discharge respectively, and the windings are formed from fibrous glass filaments coated by being drawn through a bath of thermosetting resin. According to the invention, to provide substantially uniform expansion of the shell under internal pressure, each of the inner wrap wind. ings starts from outside (in an axial sense) a flange formed on one of the fittings, as shown in Fig. 5, follows the shortest path along the surface of revolution, passes axially outside a similar flange formed on the other fitting and returns along the shortest path along the surface of revolution. For rotating the core during winding the arbor has a keyway to receive a key 34 in a winding adaptor 32, Fig. 3, and the fitting 18 has a polygonal flange to engage a complementary socket in the winding adaptor, and the fitting 18 must therefore be in the correct rotational position in relation to the keyway in the arbor, for which purpose it is rotated (with its rubber 15) by a wrench 20 until a spring- pressed detent in the wrench drops into the keyway. The wrench is removed and a forked arm 27 is operated by an air cylinder 26 to press down the hemisphere 14 into snug engagement with the hemisphere 6 where it holds it while a collar 19 is screwed into the internal thread of the outlet fitting 18, over a reduced section of the arbor, which is kept vertical by a pivoted aligning bracket 28. The winding adaptor 32 is then fitted, and locked by a nut 36, the arbor having a vent groove 8a to equalize pressure changes. The fitting 12 also has a polygonal flange and this is engaged by a complementary socket in an adaptor 38 which is splined to fit the driving member of the winding machine. Winding.-The coated fibres are wound on the core first at a fast speed, then at a slow speed. The fibres are made by extruding molten glass to form a large number of filaments which are brought together and cooled and wound on a spool. A number of spools are mounted on the inside wall of a casing and the glass filaments are drawn from them, through the casing, and through an eyelet in the opposite wall of the casing, to which they converge, heat lamps being fitted in the casing to remove condensed moisture from the filaments. About sixty filaments are drawn through the eyelet during the fast speed and about thirty during the slow speed. The glass fibres are coated by being drawn through a bath of resin, which is thermosetting so that the finished container is suited for use at high temperatures, epoxylene resin being preferred. The fast winding is in three stages, designed to build up the wall structure of the container round the outlet pipe and at the corresponding opposite end. A winding guide 132 comprising two semi-cylindrical sections is clamped. to the adaptor 32 and a similar winding guide 133 is clamped to the adaptor at the opposite end. The sections are flanged at their ends nearest the core to provide a pair of female part-spherical surfaces which leave a space into which the fibres skid when they are being wound on, piling on one another to form a local thickening 137. The strands are traversed backwards and forwards as the core rotates, crossing each other at points between the ends and the equator of the sphere in a basket-type weave, as described in detail in the Specification. For the second stage the winding guides are replaced by two more which leave a space further round the circumference of the sphere so that the end thickness is exteuded when the second fast winding stage proceeds, with a slightly smaller length of traverse which, however, remains constant during the winding. Similarly for the third stage, when the constant traverse stroke is less still. The three fast windings are followed by one slow winding in which the traverse stroke is progressively varied within limits which keep this outermost winding. axially. inside the fittings 12, 18, resulting in a spherical container with a wall section thinnest at its equator and progressively thinning from the ends whereby sharp changes are avoided and uniform deflection of the wall results when the sphere is subjected to pressure. The machine for effecting the winding is shown in Figs. 11 and 12, where the rubber-coated metallic core, mounted for rotation by means of its adaptors, is indicated at 57. After being drawn through the resin bath 356, in which it passes round a series of staggered studs 357 to equalize tension. and so ensure an even coating of resin, the strand 106 passes through wiping means comprising a slit in a resiliently mounted felt pad 110 and proceeds to a needle 66. The temperature of the resin bath is controlled by. cooling coils. The needle is mounted at the top of a traverse arm 74 in a pivotal manner as in Fig. 15a. The arbor shaft 56.is rotated from the motor 51 through a chain drive 113. For. the high-speed windings the chain is driven from a gear 110 through a smaller gear 111 and at its other end, drives a gear 117 through. a larger gear 116. For the low-speed windings, the gears 111, 116 are exchanged for two gears of equal size. The lower end of the traverse arm 74 carries a roller 78 which is engaged by a cam track 79 in the cylindrical surface of a drum 52 which is driven through a shaft 65. The arm 74 pivots about a latch 82 at the end of a pair of spaced bars 68, 69 which, for a fixed winding traverse, are stationary. As the traverse arm is oscillated by the cam track the needle 66 traverses to and fro and the strand is wound on the rotating core. The needle is guided to follow the curvature of the sphere by a cam, track 100 on which rolls a roller 103 on the end of the pivoted arm carrying the needle, Fig. 15a. The top of the traverse arm is guided in a channel 107. and the bottom by horizontal, tracks 80 in which runs a disc 80a on the;pin of: the roller 78, which pin enters a fork in the end of the arm to compensate for its arcuate travel. The length of the fixed fast winding traverse is governed by which one of a series of apertures 83-86 in the traverse arm the spring-pressed latch 82 occupies. When it is required to effect a variable traverse a jaw clutch 93 is engaged and the drive is transmitted through a gear-box 55 to a chain 91 which gradually rotates a cam 90. The connection of the bars 68, 69 with the traverse arm 74 is then between a pair of rollers which are supported in a pivoted frame to prevent binding, and at the other end the bars 68, 69 are slotted to slide on a pin 71 so enabling a pivoted link 75 to guide the roller connection in an approximately vertical path. When the core is completely wound with the coated glass fibre it is transferred to an oven in which, at a temperature too low to melt the core, the resin is polymerized. After curing, the arbor is removed and steam is admitted to the wound core. The pressure is at first such that the temperature of the steam is not high enough to melt the core but is high enough to vulcanize together two rubber hemispheres 11, 15 previously fitted on the metal hemispheres 6, 14 and now subjected to the pressure of the winding. The pressure of the steam is then raised until the temperature is high enough to melt the alloy of the core. The result is a spherical container of resinous bonded glass fibres with a wall section thinnest at its equator and progressively thinning from the ends, whereby sharp changes are avoided and uniform deflection of the wall results when the sphere is subjected to pressure.