Gas filter

Claim 1

A gas filter, comprising: a. a set of rectangular container trays formed of sheet metal material, each including a perforated bottom plate bordered on three sides by imperforate upwardly directed major walls of the same height and the fourth side by an imperforate upwardly directed minor wall of less height than its major walls; b. a set of rectangular cover trays formed of sheet metal material, each including a perforated bottom plate bordered on three sides by imperforate upwardly directed major walls of the same height and on the fourth side by an imperforate upwardly directed minor wall of less height than its major walls; c. all of the major and minor walls of each cover tray nesting within the corresponding major and minor walls of a corresponding container tray and substantially flush therewith at their upper edges; said container and cover trays forming a filter unit defining a filter cell between their perforated plates; d. said filter units being stacked in end-for-end reversal wherein the minor walls of the container and cover trays forming a lower filter underlie a major wall of the filter unit next above; e. the lower portions of said minor wall and adjacent major walls of each upper filter unit being inwardly offset to nest within the major walls of the cover tray of each filter unit next below and defining a shoulder seated on the flush upper edges of the major walls of the unit next below; f. means sealing the junctures between said shoulders and the contiguous upper edges of the major walls of the unit next below; g. adjacent filter units forming therebetween plenums closed and sealed on three sides and open above the minor wall side of the lower filter unit, the open ends of adjacent plenums facing in opposite directions to form a set of inlet openings and a set of outlet openings separated by the filter cells; h. and a filter medium filling each cell.