Electrostatically enhanced HEPA filter

DETAILED DESCRIPTION OF THE INVENTION The HEPA filter utilized in the practice of the present invention is substantially conventional, except for those modifications to be enumerated hereinafter.
The HEPA filter is illustrated in FIGS.
1 and 2, and is generally indicated at 1.
The filter 1 comprises a frame, generally indicated at 2.
The frame may be made of any appropriate non-conductive material, such as wood, pressboard, molded plastic or the like.
For purposes of an exemplary showing, the frame is illustrated as comprising four side members 2a-2d.
Within the confines of the frame 2, there is located a non-conductive, fibrous filter medium sheet 3 of fiberglass or other appropriate material known in the art.
As can most clearly be seen in FIG.
2, the filter medium sheet 3 is folded in a zig-zag or accordian fold with one of its ends lying along frame side member 2c.
It will be appreciated that the other of its ends will similarly lie along frame side member 2a.
The filter medium sheet is of such width as to extend from frame side 2b to frame side 2d.
As can be seen from both FIGS.
1 and 2, the folds of the filter medium sheet 3 are substantially evenly spaced from each other and are held substantially parallel to each other by a plurality of spacer elements 4 and 5.
Spacer elements 4 and 5 are identical and are made of electrically conductive material.
Such spacers most frequently encountered in the industry are made of corrugated metallic foil such as aluminum foil and the spacers 4 and 5 are so illustrated in FIGS.
1 and 2.
The spacers 4 and 5 (as is true of filter medium sheet 3) extend from frame side member 2b to frame side member 2d with the corrugations extending in the direction of flow of the dust laden air.
This flow direction is indicated by arrow A in FIG.
2.
Although the spacers 4 and the spacers 5 are identical, they have been designated by different index numerals for the following reason.
It will be noted that by virtue of the accordian fold of the filter medium sheet 3, that longitudinal edge of each spacer 4 at the air inlet face of filter 1 is exposed, while that longitudinal edge of each spacer 4 at the air discharge face of filter 1 is covered by the filter medium sheet 3