GB527511A - Improvements in or relating to electric liquid heaters - Google Patents

Abstract

527,511. Electric liquid heaters ; electric switches. McDOWELL, O. A., and DONE, J. P. C. April 6, 1939, No. 10830. [Class 39 (iii)] [Also in Group XXXVII] In an electric liquid heater of the flow type provided with means, actuated by the pressure of the liquid, for completing the circuits of a plurality of heating elements in succession, the control member is impervious to liquid. Inlet and outlet headers 14, 16 are connected by three flattened tubes 18 of sheet metal of the same width as the headers. Heating elements 20, of resistance wire between mica sheets, are placed between the tubes, which are lagged at 24, and clamped by bars 28 to a panel 12. The inlet pipe 32 is restricted at 36 to build up fluid pressure which acts on a diaphragm 38 connected to an insulated switch bar 56 which is adapted to make contact in succession with two contacts 66. 68. These contacts are connected to relays 70, 72 which control the circuits of two groups of heaters 20, so that these are energized in succession when the water is turned on. Successive energizing of the heaters may be effected by a mercury switch, Fig. 5. An iron plunger 112 normally floats on mercury 108, but when drawn down by a magnetizing coil 110, mercury is displaced into the tube 106 and reaches the contacts 114 of the heater circuits in succession. In an alternative form of pressure actuated switch, Fig 6, a diaphragm 116 subject to the flowing water, moves a lever 126, 127 carrying a magnet 142 which actuates an armature 140 normally held out of contact with mercury 134 by an insulated float 136 but completing a circuit with the mercury when the magnet 142 is moved down. This switch may control the magnetizing coil 110, Fig. 5.