Structural Element for Very Low Temperature Apparatus

摘要

1,165,800. Shafts. TOKYO SHIBAURA ELECTRIC CO. Ltd. 22 Dec., 1967 [22 Dec., 1966], No. 58499/67. Heading F2U. A reinforced body for a very low temperature apparatus, e.g. the driving shaft and hanging member for the expansion engine of helium liquefying apparatus, comprises a metal portion of stainless steel or a titanium alloy, and a synthetic resin portion bonded thereto and of a fluorine-containing resin or a linear polyamide resin, the metal portion being given a tensile stress (# sn ) before bonding of the resin portion thereto. As shown, the shaft comprises a perforated metal cylinder 22 embedded in a solid resin cylinder 21, the metal cylinder being initially stretched so that on subsequently applying a tensile stress to the shaft, the compressive stress in the resin cylinder, due to the initial tensile stress, e.g. at least 3 kg./mm.2, in the metal cylinder, must first be overcome, thus utilizing the compressive strength of the resin whilst protecting its low tensile strength. The surface of the metal portion may be roughened to improve bonding. The ratio of the cross-sectional area of the metal cylinder to that of the resin cylinder (#), is 0À01 to 0À2 to maintain low thermal conductivity along the shaft. Screw-threaded bores are provided in the ends of the shaft for attachment thereof to other parts of the apparatus (not further described). Again, Fig. 3 (not shown), the metal portion is a hollow cylinder having inturned flanges at its ends, and is filled with the resin. Alternatively, the metal portion may comprise a metal rod embedded in a resin cylinder, Fig. 1 (not shown), or two spaced parallel metal rods attached to circular end plates and embedded in a resin cylinder, Fig. 2 (not shown), the ends of the resin cylinder being foamed with a hexagonal nut and an externally screw-threaded portion respectively. Examples of metals to be used are AISI-304, AISI-316 and AISI-321 stainless steels and titanium alloys of 5% of Al, 2À5% of Sn and the remainder of Ti. Examples of fluorine-containing resins include P.T.F.E., polytrifluorochloroethylene, and polymers or copolymers of vinyl fluoride, vinylidene fluoride or dichlorodifluoro-ethylene. Examples of linear polyamide resins include all nylons including 6-nylon, 6,6-nylon, 11-nylon and 6,10-nylon. Graphs are provided, Figs. 5-8 (not shown), showing the relationship between thermal conductivity and temperature of specific metals and resins; between the mechanical strength and #; and the effect of # and # sn on the mechanical strength of the shaft and the stress on the resin portion.