GB684832A - Improvements in or relating to self-locking screw threaded sealing devices - Google Patents

Abstract

684,832. Seals. THOMAS, R. E. Dec. 3, 1948. [Dec. 10, 1947] No. 32614/47. Class 146 (ii). [Also in Group XXV] Relates to sealing devices in the form of nuts comprising a resilient helix mounted in an unthreaded casing and consists in anchoring one end of the helix to the casing in such manner that a visible trace is left if the nut be unscrewed. The nut comprises a sleeve 5, Figures 1 and 2 bored to a close fit for the screw at each end but chambered out to receive a spring wire helix 7 the outer end 10 of which extends through a hole in the sleeve so as to be visible from the outside. This end may be secured by lightly brazing. On forcible removal of the nut the anchorage is broken and the end of the wire drawn in through the hole and deformed thus providing a visible indication. The inner end of the helix then engages an abutment 13 and further unscrewing of the nut becomes easy. In modifications employing fewer turns of the wire the inner turn may be of polygonal form. The inner end of the wire may be bent to be parallel to the axis and may pass under the adjacent turn which may be cranked or offset to facilitate this. The wire instead of being of thread form may be such as to permit tapping after coiling and in this case the pitch of the helix need not be the same as that of the thread. The casing 5, Fig. 4 may be a press fit in a hole in a lug 15 and in this case a hole 16 is drilled through the lug in line with the hole 10 so that the anchored end of the helix may be inspected. Helices for use with square threads are of round or triangular section of wire of size too great to enter completely into the threads. The Provisional Specification denotes other constructions, in one of which a nut tapped to fit the bolt at one end is hollowed out to receive therein helix at the other. In a further form in which flat strip is employed for the helix the outer turn may be of less width than the inner turn. The strip may be sufficiently thin so that the turns may be side by side in the worm thread and part of the strip is joggled and cut away beneath it to pass over the cuts of a thread into the adjacent groove. A helix of wound wire may be applied to the reduced end of a bolt the leading end being anchored in a transverse hole. The helix may be formed from flat strip, wide enough when corrugated to engage more than one thread.