GB1113084A - Variable resistance device - Google Patents

Abstract

1,113,084. Resistances. BECKMAN INSTRUMENT Inc. 30 Jan., 1967 [28 Feb., 1966]., No.4359/67. Heading HIS. To accurately position the resistance element 31 of a variable resistor during assembly in an open-ended housing 10 with respect to the movable contact 16b and the stops limiting its travel, a number of tabs (51, 52, 53, Fig. 9, not shown) are provided on the housing to cooperate with a number of grooves (54, 55, 56, Fig. 9, not shown) in the base assembly supporting the resistance element arranged so that the grooves and tabs may be engaged only when the base assembly and housing are in the precise relative position. The base assembly supporting the resistance element which may be of cermet or conductive plastics material and metal collector disc 33 comprises an insulating material wafer 32 in conjunction with an insulating material stand-off member 36 which carries the alignment grooves. Wafer 32 and stand-off member 36 are relatively aligned by means of slot 35 in the wafer surface into which shoulders (41, Fig. 4, not shown) on the stand-off member fit. After assembly the tabs (51, 52, 53) are bent over in the grooves (54, 55, 56) to retain the base assembly within the housing and the open space surrounding the terminals 34 is filled with an epoxy material 58 to seal the end of the device and help to support the terminals. The other end of the casing is sealed by resilient ring 28. Housing 10 may be formed of any suitable metallic material or plastics material, and the stops limiting the travel of the movable contact are formed by one or more depressions in the housing wall (Fig. 1, not shown) engaging a raised lug on the movable contact.