724,179. Suction cleaners. ELECTROLUX CORPORATION. Nov. 27, 1950. No. 28922/50. Classes 8 (1) and 8 (2). In a device for separating dust from gas e.g., a suction cleaner comprising a housing 10 Fig. 4 defining a filter compartment 23 partitioned by a filter element 30 into intake and discharge sides having an inlet 14 and an outlet 74 within the housing and through which dust-laden gas is drawn and clean gas is discharged respectively by suitable means e.g., a fan 71, a cover 16 giving access to the compartment 23 for replacement or renewal of the filter 30 is opened automatically by means e.g., a pneumaticallyoperated triggering device 250, Fig. 14, on a predetermined pressure difference between opposite sides of the filter 30 acting on a control device 200. The control device 200 comprises an upwardly biased pressure responsive diaphragm 203 open at the lower and upper sides to the dirty and clean sides of the filter bag 30 through ducts 210, 230 respectively. A duct 231 also connects the clean side of the filter 30 to the lower side of an upwardly biased diaphragm 252 through a normally closed valve 240 which is opened to allow access of vacuum to the diaphragm 252 by a solenoid armature 350 on closing of a switch 327 by movement of the diaphragm 203 on clogging of the filter 30. The diaphragm 252 acts through linkages 254 255, 89, 87, 83 and link 81, Fig. 12, to release the first of two latches 63, 62 restraining a filter ejector plate 52 subject to spring-loaded lazy tongs 53, Fig. 5, and simultaneously the diaphragm 252 acts through linkages 254, 131 to trip a latch 100 to allow the cover 16 to be opened by a spring 18 and thereon release a rocker arm 96 to open an on-off switch 310 in the fan motor circuit. On the cover 16 being fully opened, a cam 94 on parallel linkages 115 by which an inlet 15 is pivoted to the cover 16, draws a bar 92 which actuates levers 88, 84 and a link 82 to release the second latch 62 to allow the plate 52 under the influence of the tongs 53 to eject the bag 30 which is of readily disposable material e.g., porous paper; the open end thereof having been closed by a' flap valve on the withdrawal of a duct 21 secured to the inlet 15. The switch 310 may be opened and closed manually as may the cover 16 without both the bag ejector plate latches being released. In a modification using a non-disposable cloth bag, ejection is prevented on automatic opening of the cover by a projection of the bag supporting ring pushing against the upper end of a bell crank 197 Fig. 13 thereby opening a normally closed shutoff switch 321 to stop the fan motor 72. Specifications 712,233 and 724,252 are referred to.