Patent GB-464578-A (GB)
Title: Improvements in and relating to rotating contact electric current rectifiers
IPC: H02M1/22
Filed: 1936-12-11
Abstract: 464,578. Rotary distributers. SIEMENS - SCHUCKERTWERKE AKT.- GES. Dec. 11, 1936, No. 34098. Convention date, Dec. 11, 1935. [Class 38 (v)] A rotating contact electric current rectifier in which conduction is established between the rotating and fixed contacts during the greater part of each current transmission period and in which open gaps are present at the ends of the arcuate rotating contact or contacts has the parts of the stationary counter contacts and/or of the rotating contact which are exposed to the arc arranged to be automatically adjustable in such a manner that the portions of electrode material which are burnt or worn away are continuously and automatically replaced during working by fresh material. As shown in Fig. 1, the rectifier comprises a rotary contact 16 engaging in turn a series of fixed contacts 12 mounted in the wall of a casing 11. Compressed gas enters the chamber 11 through an inlet 17 and passes across the arcs formed between the rotary contact and the fixed contacts, flowing upwardly through the fixed contact casings and exhausting through outlet pipes 18. Each of the relatively fixed contacts as shown in Fig. 2, consists of a rod 20 of carbon mounted in a sleeve 21 and having its lower end pressed against a lateral extension 22 of the sleeve by means of a piston 24 acted upon at its upper side by the compressed gas and bearing on the upper end of the rod 20 at its lower side through a ball-bearing 23. Both the lower face of the conducting rod 20 and the engaging face S of the rotary contact are formed with a spherical contour the centre of generation of which is the point of intersection M between the axis of rotation of the shaft 19 and the axis of the carbon rod 20 so that contact is established over a substantial surface area. As shown in Figs. 3 and 4, however, the contact path, as indicated in parallel dotted lines is unsymmetrically disposed with respect to the central axis of the rod 20 so that a torque is exerted on the rod causing its intermittent rotation during the operation of the rectifier. Thus different portions of the end surface of the rod are successively brought into exposure to the current arc and a uniform burning away of the rod is ensured. The rotating contact surface may be roughened to grind away any prominent portions on the end of the rod, which particles are carried away in the gas stream, from which they may subsequently be separated. The sleeve 21 is formed with radial arms 29 connected to curved members 30 rotatable in an outer fixed sleeve 27 which is extended at its lower end to form a screening electrode. The rotating contact member may be provided with an arcing tip 32 which is similarly screened. Alternatively, an automatically displaceable contact part may be provided on the rotating contact member which is operable in a manner similar to that already described. As an alternative method of producing automatic rotation of the rod 20 it may be driven through worm gearing by an air screw situated in the compressed gas exhaust pipe 18, Figs. 5 and 6 (not shown). In this arrangement the contact path may be arranged symmetrically with respect to the axis of the carbon rod so that no torque is exerted by the frictional engagement of the rotating contact, the rotation of the rod by the air screw occurring only during the period when the contacts are not in engagement.