GB837462A - Improvements in or relating to waveguides and methods of bending waveguides - Google Patents

Abstract

837,462. Making waveguides; angular bending; flexible mandrels.GENERAL ELECTRIC CO. Ltd., and GILL, R. I. Nov. 27, 1958 [Dec. 2, 1957], No. 37541/57. Classes 83 (2) and 83 (4). A method of bending a waveguide comprises the steps of substantially filling the waveguide, at least over that length of the waveguide which is to be bent, with a mandrel, said mandrel comprising a stack of substantially flat metal strips slightly less wide than the waveguide, the said stack of strips including a first group of strips which are clamped together at a point beyond one end of the waveguide and a second group of strips which are clamped together at a point beyond the opposite.end of the waveguide, all the strips of the second group lying between two adjacent strips of said first group at least over that length of the waveguide which is to be bent, bending the waveguide, and removing the mandrel. The waveguide tube of copper alloy with 30% zinc is cut to length, deburred, and hung vertically in the furnace at 600‹ C. for 15 minutes, then quenched and dipped in an acid bath to remove scale. The mandrel is then drawn into a length of waveguide. The mandrel is formed of flat strips of spring steel, one single strip 2 being doubled to enclose a group of strips 3 which are doubled around the bobbin 9 at one end of the waveguide 1, the strips 3 enclosing a group of strips 4 doubled around a bobbin at the other end of the waveguide. Clamps 5 and 6 secure the strips adjacent the bobbins. The mandrel and waveguide are lubricated with tallow. The draw-bar 14, to which is secured the bobbin 9, pulls the mandrel into the waveguide until it fills it over the length which is to be bent, a shoe 16 at one end of the waveguide preventing scoring during loading of the mandrel. The waveguide 1 with the mandrel inside is bent by an hydraulic ram 17 into a die 19, strips of metal 23 being interposed between the ram 17 and the waveguide to prevent corrugation of the wall of the waveguide, the waveguide being bent to slightly more than the final bend to allow for spring-back. The mandrel is then removed and the waveguide deburred and degreased prior to stress relieving in an air circulating furnace for one hour at between 250‹ and 270 ‹ C., the waveguide then being allowed to cool. Forging.-The bent waveguide is returned to the press, and the ram 17 locked to the die 19, and is sized by forcing rollers in sequence therethrough, with the provision of a tallow lubricant. A first working roller, being 1-thousandth of an inch less in thickness than the cross-section of the waveguide, is followed by four slave rollers smaller than the first working roller, a second slightly larger working roller, followed by four slave rollers, then passes through and so on for the third, fourth and fifth working rollers, followed by slave rollers, the last working roller being of the required cross-section. The waveguide is then removed from the press, degreased and bright acid dipped. In a modification, Fig. 3, to bend the waveguide to an S-shape, one end of it is clamped to a shoe 25 on a base 26 and the other end to a shoe 29 slidable along a groove 37 on a carriage 33, in turn slidable along the base 26 in the guides 35. A screw shaft 31 is turned to move the carriage 33 along the guides 35 and thus bend the waveguide 1, the shoe 29 moving along the carriage 33. The waveguide may be of aluminium.