GB188517A - Improvements in apparatus for automatically regulating the draught in steam generator furnaces - Google Patents

Abstract

188,517. Dehn, F. B., (Thermogen Equipment Co., Inc.). Oct. 31, 1921. Switches, partly electromagnetic; pneumatic and other actuation.-Relates to automatic pressure-controlled switches for draught regulating in steam-generator furnaces. A rod 12 serves as an impelling device for a switch 20 of an electric blower 21, as shown in Fig. 1, or operates directly a damper 23 through a stiff spring 22<1>. The rod 12, guided by a sleeve 13 and rod 14, carries a screwed nut 16 rotated by a motor 19, controlled by a series of circuit-makers 82 and a reversing switch. These, in turn, are operated by the upper and lower ends of a pivoted lever 25, moved about its fulcrum in accordance with variations in steam-pressure in the boiler 10 by a diaphragm 34, lever 31 and rod 30. Motion of the rod 12 is completed in definite steps, circuit breakers 73 - - 79, adjustably arranged along a bar 80, being opened successively by the roller 81 mounted on the rod 12. As shown in Fig. 3, each circuit-maker 82 comprises a freely-mounted conducting rod 43 permanently in contact with a mercury-cup 44 and placed in contact with the cup 47 by one end or the other of a curved wire 46 as the finger 49 on the lever 25 engages a vertical pin 49 on the rod 43. The reversing switch, Fig. 4, comprises an insulated rod carrying at its ends plates 53, 60 connected respectively to wires 56, 57 and 63, 64. A quadrant 68 on the lower end of the lever 25 carries fingers 67 corresponding to the number of switches 82, and these successively engage the vertical pin 69 on the rod 52. Contact is thus made at one end of the rod between the cup 55 and one or the other of the cups 58, 59, and at the other between the cup 62 and one or the other of the cups 65, 66. The cups are connected in the circuit as shown in Fig. 2. The reversing switch is maintained closed by the electromagnets 71, 72 attracting an iron or steel piece 70 mounted on the underside of the rod 52. On the closing of a switch 82, current passes from the main 85 by the circuit 79, 71, 66, 62, armature 86, 87, starting resistance 88, 89, 90, 91, 82, 92, 76, 93, 55, 59, 94, 65, 95 to the main 85. This lowresistance current operates the temporary coil 90 of one of a series of relays 50 to close the maincurrent switch 96 and short-circuit the starting- resistance 88 and switch 82. By these means, arcing at the mercury cups on the opening of the circuit is prevented.