Two stage filter system for vacuum cleaners

Abstract

In a vacuum cleaner, a two stage filter system includes a primary inner filter such as a conventional vacuum cleaner filter, and a secondary outer filter with an enhanced surface area that is a self-cleaning, flexible interlocking knitted fabric having a rest position at atmospheric pressure, and a stretched position when under vacuum of a vacuum cleaner, the fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position. When the vacuum cleaner is operating, the secondary filter is in its stretched position and collects dust and debris, and when the vacuum cleaner is off, the secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, and a portion of the dust and debris to fall from the filter.

What is claimed is: 
     
         1 . In a vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and a canister outlet connected thereto, a two stage filter system, being positioned within said canister at said canister outlet, wherein, when said vacuum cleaner is operating, there is a vacuum at said canister inlet and in said canister, said two stage filter system comprising:
 (a) a primary filter, being an inner filter, connected to said canister outlet; and   (b) a secondary filter positioned over said primary filter and attached to at least one of said canister outlet and said primary filter, said secondary filter being an outer filter, said secondary filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, said fabric having a rest position at atmospheric pressure, and a stretched position when under said vacuum of said operating vacuum cleaner, said knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position; and,   such that when said primary filter and said secondary filter are in said vacuum cleaner and said vacuum is operating, said secondary filter is in its stretched position and collects dust and debris, and when said vacuum cleaner is subsequently not operating, said secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, said contracting causing a portion of said dust and debris to fall from said secondary filter.   
     
     
         2 . In a vacuum cleaner, the two stage filter system of  claim 1 , wherein said secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric. 
     
     
         3 . In a vacuum cleaner, the two stage filter system of  claim 1 , wherein said secondary filter is a fabric selected from the group consisting of knitted fabric, woven fabric and combinations thereof. 
     
     
         4 . In a vacuum cleaner, the two stage filter system of  claim 1 , wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position. 
     
     
         5 . In a vacuum cleaner, the two stage filter system of  claim 1 , wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position. 
     
     
         6 . In a vacuum cleaner, the two stage filter system of  claim 1 , wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard. 
     
     
         7 . In a vacuum cleaner, the two stage filter system of  claim 3  wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard. 
     
     
         8 . In a vacuum cleaner, the two stage filter system of  claim 1  wherein said cage includes a clasping mechanism for holding said secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener. 
     
     
         9 . In a vacuum cleaner, the two stage filter system of  claim 1  wherein said secondary filter is a washable, reusable filter. 
     
     
         10 . In a vacuum cleaner, the two stage filter system of  claim 4  wherein said secondary filter is a washable, reusable filter. 
     
     
         11 . A vacuum cleaner filter kit to create a two stage filter system, for retrofitting a secondary filter with an enhanced surface area over a primary existing filter of an electric power vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and canister outlet connected thereto, said filter kit comprising:
 (a) a fabric filter for positioning over said primary filter and attaching to at least one of said canister outlet and said primary filter, said fabric filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, said fabric having a rest position at atmospheric pressure, and a stretched position when under said vacuum of said operating vacuum cleaner, said knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position; and,   (b) an attachment mechanism for attachment of said fabric filter to at least one of said canister outlet and said primary filter;   such that when said primary filter and said fabric filter are in said vacuum cleaner said fabric filter is an outer filter that is a secondary filter, and when said vacuum is operating, is in its stretched position and collects dust and debris, and when said vacuum cleaner is subsequently not operating, said secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, said contracting causing a portion of said dust and debris to fall from said secondary filter.   
     
     
         12 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11 , wherein said secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric. 
     
     
         13 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11 , wherein said secondary filter is a fabric selected from the group consisting of knitted fabric, woven fabric and combinations thereof. 
     
     
         14 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11 , wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position. 
     
     
         15 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11 , wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position. 
     
     
         16 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11 , wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard. 
     
     
         17 . The vacuum cleaner filter kit to create a two stage filter system of  claim 13  wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard. 
     
     
         18 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11  wherein said attachment mechanism is a clasping mechanism for holding said secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener. 
     
     
         19 . The vacuum cleaner filter kit to create a two stage filter system of  claim 11  wherein said secondary filter is a washable, reusable filter. 
     
     
         20 . The vacuum cleaner filter kit to create a two stage filter system of  claim 14  wherein said secondary filter is a washable, reusable filter.