GB684066A - Improvements in or relating to electromagnetic rapping devices and systems - Google Patents

Abstract

684,066. Electromagnetic vibrators. RESEARCH CORPORATION. April 16, 1951 [May 26, 1950], No. 8807/51. Class 35. An electromagnetic vibrator for cleaning an electrode of an electric precipitator comprises a magnetic plunger sliding in a sealed tubular casing attached to the electrode, so that, on energization with impulses of current, the plunger strikes the sealed ends of the tube which transmits the shock to the electrode. In the form shown, a magnetic plunger 33 having slots 34 to reduce losses slides in a non-magnetic tube 25 under the action of a coil 27. The casing 21 and the ends 18 and 36 are of mild steel so that when a pulse of current passes through the coil, the plunger jumps up, and striking the top member 36, rebounds to strike the bottom end 18. The end members are faced with non-magnetic material 24 and 35 to prevent sticking. The impulses are generated by the discharge circuit shown in Fig. 2, in which a condenser 40 is charged through a resistance 39 from a D.C. supply, and discharged through vibrator coils 27a-27e energized in turn by a selector switch 42. The thyratron 44 is normally biased negative by battery 45, but momentary closure of switch 49 charges the grid positive and initiates the discharge. The impulse shape may be modified by connecting a parallel resonant circuit in series with the condenser 40. In the form shown in Fig. 1, the shock is transmitted by a rod 15, but the device may be secured directly above or below the electrode so that the plunger strikes it directly. The vibrator body may be mounted horizontally on the electrode, in which case the return motion is produced either by a spring or by a second coil energized continuously or with alternate impulses. When it is desired to vibrate electrodes at elevated potentials, the vibrator, which is attached to the electrode, may be separated from the pulse generating circuit by means of a transformer having a highly insulated secondary winding. Instead of using a transformer, the coil itself may be insulated from the plunger and electrode by means of an insulating tube as shown in Fig. 13, in which the device is mounted on an earthed base 117 which supports the coil 126 while the plunger 125 travels in a tubular insulator 118 joined to the electrode 116 by an elastic metal bellows 123. In a modification, the part of the tube carrying the coil is of insulating material, while the rest is metal.