Smart controller for reverse pulse air filter

#Present air filter controllers used on self-cleaning reverse pulse air filters and dust collectors initiate a cleaning cycle on either a fixed or adjustable time interval. Such operation does not take into account various conditions experienced by such filters or dust collectors, resulting in less than optimum performance.

#Self-cleaning air filters and dust collectors of the reverse pulse type, such as that shown in U.S. Letters Pat. No. 4,319,897, the teachings of which are incorporated herein by reference, perform a filter cleaning operation by opening a compressed air valve for a short period of time. The resulting blast of compressed air is normally directed into a venturi or eductor tube to entrain a much larger volume of secondary air and develop the static pressure required to force this air back through the filter in a direction opposite to the normal air flow therethrough. It is normal practice to clean or pulse no more then 10% of the filters at one time. This leads to the use of 4 to 26 valves depending on the air flow capacity or size of the air filter or dust collector. Thus, to perform a cleaning cycle it is necessary to provide a means to turn on each compressed air valve in sequence for a prescribed period of time and with a prescribed time interval between pulses.

#Currently available controllers do nothing more than turn valves on and off in sequence. The basic timer-type controller operates either continuously or is initiated on the closure of an adjustable pressure switch. Since the pressure loss across the filters increases continuously over the life of the filters, even the pressure switch controlled timer will revert to continuous cleaning unless the set point is frequently increased. These devices require continuous manual attention to fully utilize the life expectancy of a filter.

#FIG. 1 is a partial section view of a reverse pulse type dust collector assembly,

#FIG. 2 is an enlarged sectional view of an ejector tube shown mounted over a filter element and illustrating the air flow there through during back pulsing,

#FIG. 3 is a block diagram of the present invention showing the major functional components of the electronic controller for controlling the cleaning system,

#Referring now in detail to the drawings, a filter assembly 10 using a ejector tube jet pump 20 is illustrated in FIG. 1. As seen therein, the filter assembly is comprised of a large housing 14, a lower hopper 16 for collecting the filtered dust or other foreign matter, a plurality of cylindrical pleated filter elements 18, a corresponding plurality of ejector tubes 20 and back pulsing nozzles 22. The filter housing 14 has a lower air inlet 23, an upper air outlet 24, and the interior thereof is partitioned by horizontal diaphragm plate 26 into a lower dirty air chamber 28 and upper clean air chamber 30. The filter assembly has doors 31 therein providing access to the lower chamber 28 and the filter elements 18 mounted therein. The lower chamber 28 is opened at its lower end so that foreign matter filtered from the air can fall freely into the hopper 16. The lower chamber communicates with the upper chamber through a plurality of apertures 32 (see FIG. 2) in the diaphragm plate 26. The filter elements 18 are removably mounted within the lower chamber 28 and held against the diaphragm plate 26 by a locking mechanism 12 such that they depend from the diaphragm plate.

#Each element, as shown in FIG. 2, is comprised of pleated paper filter medium 34 which is formed into a cylindrical configuration to define a hollow interior 35. The medium can be supported in this configuration by a helical wrap 36 around the outer surface of the medium with twine which has been pre-coated with a suitable adhesive. Of course, other means of supporting the pleated filter medium could also be employed. The lower ends of the filter elements are sealed by end plates 40 and a mounting plate 42 is secured about the open upper end of the filter elements. A suitable gasket 46 is secured to the mounting plate about the open upper end of the filter elements for effectuating an air tight seal with the diaphragm plate 26 when the filter element is pressed there-against by the locking mechanism 12.

#A plurality of ejector tubes 20 are secured to the diaphragm plate 26 directly above the apertures 32 therein so that air passing through the pleated walls of the filter elements 18 flows upwardly through the interior of the filter element, through the apertures 32 in the diaphragm plate, through the ejector tubes and into the clean air chamber or plenum 30. Disposed directly above the open ends of the ejector tubes are a plurality of air nozzles 22. These nozzles depend from flow pipes 50 (FIG. 1) which are in fluid communication through manifolds 52 with a source of air pressurized at about 70-100 psig.