GB760318A - Improvements relating to variable resistance electrical resistance boxes and variable inductance electrical inductance boxes - Google Patents

Abstract

760,318. Regulating switches. GRIFFIN & GEORGE, Ltd. Feb. 2, 1954 [Jan. 1, 1953], No. 11/53. Class 38(5) [Also in Group XXXVI] A dial-type decade resistance box has a smaller number of resistance elements (e.g. 4 or 5), than switch steps (10 or 11). In Fig. 4, with R1 equal to 1/9th and R2-R5 each equal to 2/9th of the resistance stage value and the wiring as shown then as contact pairs E0-E9 are successively bridged the resistance in circuit increases in steps from 0-9 units and four Fig. 4 decade units as represented in Fig. 2 produce the range 0-9999 ohms. A modification, Fig. 3 (not shown), uses four resist ances R1-R4 only, evaluated 1/9th, 2/9th, 2/9th and 3/9th respectively of the resistance stage value. In the construction of Figs. 7 and 8 (based on Fig. 4), as knob 221 is turned to select the value required (e.g. as in Fig. 5), wiper 24 bridges face-to-face annular contacts 141 (E0-E9), carried by coaxial mounting discs 13, 16 and to define each resistance step rollers 223, Fig. 9, on moving arm 223 also carried by spindle 22, occupy recesses 231 in locating disc 232. As shown in Fig. 10, the disc 16 is adjustably spring-urged by four screws 18 towards fixed disc 13 so that the distance between the faces of contacts 141 may be slightly varied to ensure good contact with wiper 24.