GB668186A - Improvements in or relating to variable resistances or potentiometers - Google Patents

Abstract

668,186. Variable resistances. EGEN ELECTRIC, Ltd.; and KING, A. E. May 12, 1950 [May 12, 1949], No. 12638/49. Class 37. [Also in Group XXIV] A variable resistance or potentiometer in which a slider is moved by a rotatable shaft with a helical groove is so arranged that when the slider reaches either extremity of the groove it becomes disengaged therefrom by continued turning of the shaft. Two end brackets 1, 2 of insulating material are rigidly connected by two metal brackets 3, 4, the latter of which has a terminal tag. Also supported by the end brackets is a resistance wire 5 wound on a former and connected to a terminal at each end. The end brackets have bearings for a shaft 6 rotatable by a knob 7. A nickel silver or other slider 8 is formed with a turned-up tag which engages a helical groove in the shaft 6. One end of the slider rests on the resistance wire 5 whilst the other end rests on the bracket 4, the resilience of the slider maintaining electrical contact and also holding the tag in the groove. On turning the knob 7 the slider 8 moves along the resistance wire 5 until it reaches the end of the groove in the shaft, whereupon continued rotation of the shaft causes the tag to ride out of the groove without causing any breakage of the parts. When the knob 7 is rotated in the opposite direction the tag again enters the groove. Alternatively the slider 8 may be arranged above the shaft 6 and be carried by a U-shaped member adapted partly to encircle the shaft, this member being provided with a protuberance extending into the groove.