Filtre perfectionné pour séparer des particules des gaz

768,634. Gas filters. HERSEY, H. J. April 27, 1955 [May 7, 1954], No. 12131/55. Class 8(2) The duration and volume of a reverse jet of filter cleaning air under positive pressure are respectively automatically controlled by a relay device responsive to the pressure difference between both sides of an inward flow filter sleeve 20 Fig. 1 and serving to start and stop a motor 80 driving a, blower 72 feeding a revolving nozzle 50. and by a device for controlling the speed of the blower motor 80 and which is also responsive to said pressure differences. The cleansing nozzle 50 is rotated between the sleeve 20 and a supporting frame 30 by a hollow shaft 40 geared to a motor 66 and having supply arms 52, 54. Starting of motors 64, 80 is effected when a pivoted lever 120 Fig. 3 of a pressure switch box 102 is swung to the left by expansion of a bellows 114 connected by a duct 110 to the high pressure side of the sleeve 20 to contact a point 124 whereupon a double-pole singlethrow normally open relay 128 is energized by a source of e.m.f. applied to lines 134, 136 thereby closing contacts 140, 142 in lines 132, 134 leading to a starter box 94 for said motors 64, 80. A locking switch 164 maintains the relay energized even though contact between point 124 and lever 120 may be broken. Stopping of the motors 64, 80 is effected when the lever 120 is swung to the right by expansion of a bellows 116 connected by a duct 106 to the low pressure side of the sleeve 20 to contact a point 126 whereupon a singlepole single-throw normally closed relay 130 is energized by the e.m.f. across lines 134, 136 and thus breaks a normally closed switch 156, 158 in line 134. The speed of the blower motor 80 is controlled by a lever 174 connected by links 176, 192 and a bell crank 180 to the free end of a bellows 186 connected by a duct 202 to the high pressure side of the sleeve 20 whereby as the cleaning thereof proceeds and the back pressure diminishes the volume of cleaning air is gradually reduced. In a modification the blower motor runs at constant speed and the bellows 230 Fig. 4 (not shown) controls an air bleed valve in the blower outlet. Specification 682,217 is referred to.