Miniature substrate mounted potentiometer for radio circuits - has compressed, confined spiral spring serving as moving wiper contact and mounted radially w.r.t. support plane

摘要

A central metal zone (6) forms the common terminal and two metal pads (7,8) are joined by a circular resistive track (5) to form the potentiometer structure. The metal layers and resistive track are deposited on an insulating substrate (1). The wiper (2) is of cylindrical shape and is turned by a shaft (10) by a screwdriver or other tool. A radial cavity (13) in the cylindrical wiper contains a spiral spring (14a). The spring is trapped between the walls of the cavity and the layers on the substrate. The dimensions are such that the coils are slightly compressed and the spring is inserted with the coils inclined at angle between 35 and 60 degrees. The coils of the spring short the resistive track and the central pad together. The inclination of the coils helps to facilitate their movement over the tracks. The edges of the cavity have inward pointing lips to hold the spring in place.