| CPC A62B 23/02 (2013.01) [B29C 51/02 (2013.01); B29C 51/145 (2013.01); B29C 51/264 (2013.01); B29C 51/268 (2013.01); B29K 2023/12 (2013.01); B29K 2105/251 (2013.01); B29K 2507/04 (2013.01); B29L 2031/14 (2013.01)] | 30 Claims |
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1. A method of making a filter for mounting to a face piece or respirator, the method comprising:
providing a layer of flexible plastic netting material having a plurality of perforations allowing free passage of air through the perforations of the flexible plastic netting material;
providing a layer of polymeric filter media for filtering impurities in air passing through the filter;
positioning the layer of flexible plastic netting material and the layer of polymeric filter media to lie one on top of the other to form a multilayer of flexible plastic netting material and polymeric filter media;
moving the multilayer of flexible plastic netting material and polymeric filter media to a pleater;
pleating the multilayer of flexible plastic netting material and polymeric filter media to form a pleated composite layer of flexible plastic netting material and polymeric filter media having an overall structure of continuous and adjacent pleated folds;
moving a length of the pleated composite layer to a filter forming, assembly and sealing unit;
at the filter forming, assembly and sealing unit, combining the length of the pleated composite layer with a preformed filter mounting element, the preformed filter mounting element being semi-rigid and molded from a plastic material, the preformed filter mounting element comprising
a mounting connector for mounting the filter to the face piece or respirator; and
a plenum devoid of the pleated composite layer, the plenum defining a free volume between the mounting connector and the pleated composite layer allowing passage of unrestricted inhaled air into the face piece or respirator after the inhaled air has passed through the polymeric filter media of the filter,
the filter forming, assembly and sealing unit having a thermoforming tool including a mold configuration conforming generally to contours of the preformed filter mounting element, the mold configuration having an upper mold and a lower mold; and
by the upper mold and the lower mold, melting and pressing together an edge region including plastic material of the pleated composite layer and a flange formed by the plastic material of the preformed filter mounting element thereby to join and bond together, by the melting of the plastic material of the pleated composite layer and the plastic material of the preformed filter mounting element, the edge region of the pleated composite layer and the flange of the preformed filter mounting element to form an air impermeable seal extending around a periphery of the filter.
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