GB1095107A - Conducting-liquid electric switch - Google Patents

Abstract

1,095,107. Conducting liquid switches; retractive switches. DELMAN CO. April 27, 1966, No. 18540/66. Heading H2B. A conducting liquid switch comprises a housing 53, Fig. 3, of insulating material and containing a rotary actuating member 62 having enlarged arcuate sections as at 102, Fig. 9, which engage the conductive fluid such as a mercury, causing it to rise or fall into or out of contact with conductors as at 94, 96, 99 mounted in the housing. Annular ribs as at 67, 69 separate the body into separate switch compartments having one or more downwardly projecting conductors and other conductors as at 91, 92, 93 permanently immersed in the mercury and which may bridge between the separate compartments. An inert fluid such as oil or glycerine may be arranged to cover the mercury to prevent oxidation and cavitation. A current limiting circuit breaker arrangement comprises a ceramic bush 79 arranged in a dividing wall 74 between two compartments and having a narrow bore 79 below the level of the mercury and arranged so that excessive current vaporizes the mercury to break the connection. The switch is used for controlling the windscreen wiper motor of a motor vehicle and has three positions as determined by a spring-loaded ball 111 engaged in notches 107- 109 of the actuating member 62. The multiple contact circuit, Fig. 12 (not shown), is arranged so that the motor armature (114) and field coils (115) and (116) are selectively connected for low- or high-speed operation or for the parked position in which the rotation is reversed and the current directed via a limit switch (123) opened when the wiper element reaches the correct position. A mechanical switch 47, Fig. 4, for separate actuation by a push rod 52, Fig. 3, is mounted on a threaded projection 124 of the housing 53. The rod 52 passes centrally through the hollow rotary control shaft 51 on which the rotor 62 of the liquid switch is mounted. The switch comprises a slider 127 carrying a bridging contact 132 engageable with a pair of flush contacts 129, 131 coupled to the electric motor (36), Fig. 1 (not shown), for driving the pump (34) of windscreen washing system (38).