Improvements in or relating to electric current switches with magnetically controlled contacts

摘要

686,839. Magnetic switches. HOLLISTER, F. L. March 30, 1951 (Dec. 30, 1949], No. 33341/49. Class 38 (v) In a thermal or other switch, contacts 14, 16 are closed when an armature 17 is sufficiently attracted by poles 18 and are opened by springs 19 when the attraction diminishes sufficiently; the variation of attraction is produced by the movement of a magnetic member connected to the thermal or other device. In the form shown, a permanent magnet 11 supplies flux to the poles 18 but the flux may be shunted to a variable degree through an alternative path comprising pole pieces 12, pole shoes 13 and a diverter 24 mounted on a rod 25 connected to the thermal element and having projections 27 which shunt the flux most effectively when they are opposite projections 30 on the pole shoes. Assuming the switch is for controlling an electric cooker, the latter is switched on and a control knob connected to a shaft 41 rotates gears 40, 39 which slide the pole shoes 13 along the pole pieces 12 to a selected position corresponding to the temperature desired. As the temperature rises the diverter 24 moves down till its projections 27 are sufficiently near the projections 30 to cause it to be suddenly attracted downwards to bring the projections in line, the diverter sliding on the rod 25 and compressing a spring 34. This sudden movement diverts the flux from the poles 18 and releases the armature 17 and opens the contacts 14, 16. In modifications the permanent magnet may be replaced by an electromagnet, or a magnet may replace the member 24, and the magnet 11 be dispensed with so that there is no shunt magnetic path.