GB1190959A - Air Filter with Filter Cleaning Apparatus - Google Patents

Abstract

1,190,959. Gas filter. MICROTRON CORP. 31 July, 1967 [1 Sept., 1966], No. 35142/67. Heading B1T. In a rotary drum ventilation air filter (Fig. 1, not shown), the drum 20 is rotated by an electric motor (23) at timed intervals or when clogging is detected, and during rotation a suction nozzle 24 is moved stepwise across the outer, upstream filtering surface of the drum by a self-acting or manually controlled doubleacting pneumatic ram. The nozzle remains in each of a series of overlapping positions during one drum revolution, then moves a step to the left, and on reaching the leftmost position causes the drum rotation to cease and initiates a repetative stepwise motion back to the right-hand starting position. Nozzle 24 is mounted on a carriage (30) running on a track 31 in a housing 32 and mounting cylinder 35 of the ram. Piston (39) of the ram has a piston rod 40 extending from one or both (as shown) ends of the cylinder to carry latch assemblies 41. A pneumatically actuated valve 55 delivers compressed air in turn to each end of cylinder 35, whereupon the cylinder moves while the piston is fixed by one of its latches 44, 45 bearing on the housing and or engaging one of respective notches R1, R2, R3, or (L1, L2, L3) depending on direction of movement. When cylinder 35 reaches the end of its rod 40 a plunger 80 or 81 engages latch post 42 or 43 to reverse valve 55, whereupon the other end of cylinder 35 is pressurised and the weight of the carriage, and its adjustable frictional engagement with a bar (115) (Fig. 11, not shown), causes it to remain stationary while the piston and latches are moved forward, notches R1 &c. being shaped to allow this (Fig. 6, not shown). When the nozzle is moving to the left, each step is initiated by a cam 50 on the rotating drum engaging a lever 51, which pivots actuator 72 (Fig. 2 not shown) to effect the first movement of valve 55. When the carriage reaches the leftmost position, drum motor (23) is automatically stopped by switch (5), latch rod 100 and reversing rod 84 strike the end of housing 32, whereby the latch 45 is rendered inoperative and the latch 44 operative, while the connections between valve 55 and its alternative sets of actuators are adjusted, whereafter both plungers 80 and 81 are effective instead of 81 alone. The carriage then moves rightwards in steps without cam 50 doing anything. Plunger 71 is accessible for manual operation of valve actuator 72, if desired. Alternatively valve 55 is controlled by a short period timer under control of a long period timer which also controls the drum movement and nozzle suction means (26). Suction means (26) could alternatively be controlled by downstream pressure switch (141) which controls restart of drum motor (23).