GB625514A - Improvements in high voltage switches suitable for electric signs - Google Patents

Abstract

625,514. Changing signs. BALDWIN, E. F. Aug. 5, 1947, No. 21245. Convention date, Sept. 26, 1938. [Class 3(i)] [Also in Group XXXVII] A motor - driven rotary switch illuminates step-by-step a multiple-electrode neon sign until it is fully lit whereupon the sign is switched off for a short period before being re-illuminated. The switch comprises an insulating plate 14 carrying five circular rows of staggered contact studs 33, and having a blank segment 32 extending through about 40 degrees containing no contacts. The two outer rows of studs 33 of studs 33 are incomplete and have continuous arcuate contacts 36, 40. The fifty studs 33 of the first stud group 34 are connected in order to the intermediate electrodes 72 of neon tube bank 1, one end electrode of the tube bank 1 being connected to the arcuate contact 36 and the other to the secondary 74 of transformer IT. Similarly, the thirty-nine studs of the second group 37 are connected to the intermediate electrodes of tube bank 2, the end electrodes of which are connected respectively to the arcuate contact 40 and the secondary of transformer 2T; likewise the intermediate electrodes of the third tube bank 3 are connected to the twenty-seven studs of the third group 41, the end electrodes of the tube bank 3 being connected respectively to the stud 42 and the secondary of transformer 3T. The other ends of the transformer secondaries 74 are connected together at 15T and to a slip ring 44. One line 81 of the A.C. supply is connected to a slip ring 49 and the other 80 to the transformer primaries 75, the other ends of the primaries being connected through resistors 1R, 2R, 3R to segments of contact rings 48, 47, 46, respectively. These segments vary in length depending on the arcuate extent of the contact stud groups 34, 37, 41, ring 48 having the shortest segment and ring 46 the longest. The remaining portions of the rings 48, 47, 46 are connected by further leads directly to the transformer primaries 75. Two groups of contact brushes 51, 53 are carried by an insulating arm 22 on a shaft 24 which is rotated by a motor, mounted on the switch, seven times per minute, group 51 comprising six brushes connected together and group 53 four brushes connected together. Each brush comprises a metal strip 59 bent in the form of a V and adjustable by a screw 60, Fig. 6. As the arm rotates counter-clockwise, Fig. 9, beginning at the first stud group 34, the electrodes of the tube bank 1 are progressively energized until the arcuate contact 36 is reached and the whole tube bank 1 illuminated. During this period the secondaries of the transformers 2T, 3T are open, but since, in this period, the respective contacts of the group 53 engage those segments of rings 47, 46 which are connected to the transformer primaries through resistors 2R, 3R, the open-circuit secondary voltage is prevented from rising. As the arm 22 continues to rotate the tube bank 1 remains alight and the tube bank 2 becomes progressively illuminated, and only resistor 3R is in circuit. When arcuate contact 40 is reached both tube banks 1, 2 are fully illuminated and resistor 3R is short-circuited, and then continued rotation of the arm 2 progressively illuminates the tube bank 3 until the stud 42 is reached when all three tube banks are energised. Further rotation de-energizes all the tube banks and inserts the resistors 1R, 2R, 3R in the primary circuit, and after about one second while the arm moves over the blank segment 32, the cycle recommences. Connection to the contacts on the plate 14 is made by inserting flexible leads 90 into socket contacts 15 which extend from the contacts to the outer side of the plate, the arrangement permitting variation in the manner of connection. The switch is enclosed by a cover 20 which engages the plate 14 to form a chamber which may be filled with oil through an inlet 29, and sparking is further eliminated by ridges 33<SP>1</SP>, 45 formed on the plate 14 between the rows of contacts.