GB664257A - Electrical switch and variable resistor for miniature electrical apparatus - Google Patents

Abstract

664,257. Electric switches. DEHN, S. G. (Globe-Union, Inc.). Dec. 14, 1948. No. 32346/48. Class 38 (v). [Also in Group XL (c)] An electrical switch and variable resistor assembly comprises an operating shaft rotatably mounted in a base, a variable resistor mounted on one side of the base, a switch mounted on the other side of the base within the periphery thereof, the switch including a switch blade pivotally mounted directly to the said other side, a cam carried by the shaft and directly reacting with the blade in one position of the shaft to operate the blade, and a knob mounted on a shaft rotatable with respect to said base to regulate said variable resistor and operate said switch. A base-plate 10 of insulating material has a variable resistor 8 mounted on one side within the control knob 11. On the other side of the base 10 are mounted the resistor terminals 12, and two switch terminals 18, 19, these latter being mounted on fixed contact plates 14, 15 respectively. The hexagonal bases of the threaded terminals 18, 19 are held against rotation by lugs 23 so that nuts can be screwed on to the terminals. The contact plates 14, 15 are located against a semi-circular raised portion 16 of the base and fixed with rivets 17. On the plate 15 a movable contact blade 26 is pivoted at 20. An insulated cam 34 is loosely mounted on the rectangular end of the control shaft 13 and a cam follower 32 on the movable blade 26 normally rests in a notch 36 between the two cam teeth 37, 38 being retained therein by a spring 30 which also serves to keep the movable blade 26 in contact with the fixed plate 15. When the control shaft 13 is turned clockwise by the knob 11 the lost motion due to the loose fit of the cam 34 on the shaft 13 is first taken up and then the follower 32 rides up the inner arcuate face of the cam tooth 37, being forced with a snap action down the other side of the tooth by the spring 30 to bring contacts 26 and 14 together with a rubbing, self-cleaning action. For the remainder of the rotation of the resistor shaft 13 and its cam 34 the contacts 26, 14 are undisturbed since the follower 32 is held clear of the cam 34 by the engagement of the heel 33 of the movable contact 26 with a lug 24 on the fixed plate 15. When the resistor shaft 13 is returned to its normal off position the follower 32 rides up the face of tooth 37 to open the switch contacts 14, 26 and drops into the notch 36, the contacts remaining open. If it is desired to rotate the resistor control shaft in the opposite direction, the operation is similar but cam tooth 38 is brought into play instead of tooth 37. The fixed contact plates 14 and 15 may if desired be extended as at 21, 22 to form mounting lugs.