Patent GB-573822-A (GB)
Title: Method of forming wire coils
IPC: B21F3/04
Filed: 1943-06-22
Abstract: 573,822. Making wire coils for screw connections. AIRCRAFT SCREW PRODUCTS CO., Inc. June 22, 1943, No. 10090. Convention date, Dec. 24, 1942. [Classes 83 (iii) and 83 (iv)] In making wire coils, particularly for use as an insert in the screw connection of a male to a female member, as described in Specification 497,309, [Group XXV], from wire of a cross-section such that a portion diminishes in width with the distance from the axis of the cross-section which is the neutral axis in the coiling operation, the wire is first provided with a cross-section in which the portion corresponding to that of the desired shape is of a width diminishing at a smaller rate and is of height larger than in the finished coil if the portion is located on the outside of the coil with respect to the neutral axis, and is of width diminishing at a larger rate and is of smaller height than in the finished coil of the portion is on the inside of the coil with respect to the neutral axis and coiling is effected while guiding the wire to prevent tilting of the cross-section. Round wires are used as the starting material and are shaped to the required initial cross-section by drawing. In forming a coil with the final cross-section of the wire of diamond form 21-24 with pointed or with truncated ends 25, 26, the wire is first shaped to produce a cross-section which is larger above the neutral axis 27, where it is subjected to tensile stress in the bending, and smaller in the portion below the neutral axis, where it is subjected to compression, than in the finished coil.' Thus, it is shaped to an angle 30 included by the sides 31, 32 as much smaller than the angle 28 as the angle 35 included by the sides 33, 34 is greater than the angle 29, or in the case of a truncated section, the border lines 45, 46 are located above the desired lines 25, 26 and are respectively longer and shorter than the latter. The sides of the upper triangle are slightly convex at 41, 42 and the sides of the lower triangle are concave at 43, 44. If a final pear-shaped cross-section 50, Fig. 5, is desired with converging sides 53, 54 and a portion 55 forming a circular arc, the wire is shaped originally with two slightly convex sides 51, 52 converging at an angle 47 somewhat smaller than the angle 48 and the lower portion 56 is a curve in which the radius of curvature of any point is larger than that of the arc 55, the radius of the middle part of curve 56 being shorter than the radii of laterally located points. If a final circular cross-section is desired, the wire is first shaped so that the lower portion is smaller than a semicircle and of a form similar to 56, Fig. 5, whereas the upper portion is larger than a semicircle and has the radius of curvature of the middle part larger than the radii of points laterally thereof, but less than that of the final section. Fig. 6 shows a wire cross-section 58 of asymmetric shape produced in a coil from wire of crosssection 59. A tang 13 which may be formed on an end turn of smaller diameter and which may be provided with a notch 14 to facilitate subsequent removal thereof, is gripped and rotated to form the coil and is cut off at the other end at a slant with respect to the wire axis to produce a sharp edge which may engage the boss or nut to increase the resistance of the coil to a force which might tend to screw the coil backward. The wire is guided during coiling flanks, as described in Specification 564,057, to prevent wire from tilting. The Specification as open to inspection under Sect. 91 states that the wires may be of chromium-nickel stainless steel or of bronze, the steel wire being first annealed, pickled, cleaned and then oxide coated, and the bronze wire being cleaned. The wire may be first reduced by drawing through a carbide die. After forming the wire to the initial crosssection it is passed through straightening rolls to remove any cast caused by the original winding on a small reel and the wire is then wound on a large reel. The wire is guided during cooling into a thread groove of desired pitch and root diameter on a mandrel, the outer part being guided along stationary flanks. The groove in the mandrel and that in the outer guide may be of a shape complementary to the desired shape of the wire of the finished coil. The mandrel and die. may be of sufficiently hard material to serve for coiling and consequential shaping of the wire. The mandrel 60, Fig. 7 (Cancelled), may be formed with a groove 62 shaped similarly to the inner portion of the desired wire cross-section, but with the flanks continued to a sharp edge to obtain a clearance for the wire should it be slightly oversized. The die 63 has a groove with sides of the desired shape and a sharp edge at the bottom and has a recess at 65 through which the wire 66 may be fed. This subject-matter does not appear in the Specification as accepted.