Hepa filter

• US 6,428,610 B1
• Filed: 01/18/2000
• Issued: 08/06/2002
• Est. Priority Date: 01/18/2000
• Status: Expired due to Fees

• Current Assignee: The Tennessee University Research Corporation
• Original Assignee: The University Of Tennessee Research Corporation (University of Tennessee)
• Inventors: Tsai, Peter, Malkan, Sanjiv R.
• Primary Examiner(s): Chiesa, Richard L.
• Application Number:
  US09/484,864
• Time in Patent Office: 931 Days
• Field of Search: 555/28, 554/86, 554/87, 555/24, 555/27, 555/20, 555/21, 55D/IG.5, 55D/IG.39, 96/15, 96/67, 96/69, 96/66, 961/00, 264/466, 264/471, 264/441, 264/148, 264/151, 264/160, 264/DIG.48
• US Class Current: 96/15
• CPC Class Codes: B01D 2275/10 Multiple layers
• CPC Class Codes: B01D 2279/51 in clean rooms, e.g. production facilities for electronic devices, laboratories
• CPC Class Codes: B01D 39/163 sintered or bonded
• CPC Class Codes: B01D 46/0001 Making filtering elements
• CPC Class Codes: B01D 46/0028 provided with antibacterial or antifungal means
• CPC Class Codes: B01D 46/10 Particle separators, e.g. dust precipitators, using filter plates, sheets or pads having plane surfaces
• CPC Class Codes: B01D 46/521 using folded, pleated material
• CPC Class Codes: B03C 3/155 Filtration
• CPC Class Codes: B03C 3/28 Plant or installations without electricity supply, e.g. using electrets
• CPC Class Codes: Y10S 264/48 Processes of making filters
• CPC Class Codes: Y10S 55/05 Methods of making filter
• CPC Class Codes: Y10S 55/39 Electrets separator

Abstract

The present invention is directed toward a filter media for a high efficiency particulate air (“HEPA”) filter including a multiplicity of adjacent electrostatically charged piles of nonwoven fabric. The invention further includes a method of making a HEPA filter.

Claims

1. A particulate air filter media comprising:

a. a first pile of charged nonwoven fabric having a weight in the range of 5-40 grams per square meter and one or more fibers having a diameter in the range of 1.5-2.0 microns;

b. a second pile of nonwoven fabric having a weight in the range of 5-40 grams per square meter and one or more fibers having a diameter in the range of 1.5-2.0 microns, adjacent to said first pile;

c. a third pile of nonwoven fabric having a weight in the range of 5-40 grams per square meter and one or more fibers having a diameter in the range of 1.5-2.0 microns, adjacent to said second pile; and

d. a stiffening layer bonded to one of said piles.

2. The filter media of claim 1 further comprising a fourth pile adjacent to said third pile, and wherein the weight of each pile is less than or equal to 35 grams per square meter.

3. The filter media of claim 2 further comprising a fifth pile adjacent to said fourth pile and wherein the weight of each pile is less than or equal to 25 grams per square meter.

4. The filter media of claim 3 further comprising a sixth pile adjacent to said fifth pile, and wherein the weight of each pile is less than or equal to 20 grams per square meter.

5. The filter media of claim 1 wherein said nonwoven fabric is a meltblown fabric.

6. The filter media of claim 5 wherein said meltblown fabric comprises polypropelene.

7. The filter media of claim 1 wherein the bonding area of said stiffening layer is in the range of 0.1% to 30% of the surface area of the bonded pile.

8. The filter media of claim 7 wherein said bonding is ultrasonic bonding and said bonding area is greater than or equal to 1% of the surface area of the bonded pile.

9. The filter media of claim 7 wherein said stiffening layer comprises a spunbond fabric.

10. A particulate air filter comprising:

a. at least three adjacent piles of charged nonwoven fabric, each of said piles having a weight in the range of 5-40 grams per square meter and comprising one or more fibers having a diameter in the range of 1.5-2.0 microns, said piles comprising a first outer surface and a second outer surface; and

b. a first stiffening layer bonded to said first outer surface such that the bonding area is in the range of 0.1-30% of the surface area of said first outer surface.

11. The filter of claim 10, further comprising a second stiffening layer bonded to said second outer surface such that the bonding area is in the range of 0.1-30% of the surface area of said second outer surface.

12. The filter of claim 10, wherein said nonwoven fabric comprises meltblown polypropelene.

13. The filter of claim 10 further comprising a fourth pile adjacent to said second outer surface and wherein the weight of each pile is less than or equal to 35 grams per square meter.

14. The filter of claim 13 further comprising a fifth pile adjacent to said fourth pile and wherein the weight of each pile is less than or equal to 25 grams per square meter.

15. The filter of claim 14 further comprising a sixth pile adjacent to said fifth pile, and wherein the weight of each pile is less than or equal to 20 grams per square meter.

16. A method of making a particulate air filter comprising:

a. charging at least three adjacent piles of nonwoven fabric, each of said piles having a weight in the range of 5-40 grams per square meter, and each of said piles comprising one or more fibers having a diameter in the range of 1.5-2.0 microns;

b. collating a stiffening layer of fabric with said piles;

c. bonding the stiffening layer to one of said piles to form a stiffened filter media having a top side and a bottom side;

d. scoring said stiffened filter media;

e. folding said stiffened filter media into a multiplicity of adjacent layers; and

f. inserting a separator between two adjacent layers.

17. The method of claim 16 wherein said separator is made from aluminum.

18. The method of claim 16, wherein said bonding is ultrasonic bonding.

19. A method of making a particulate air filter comprising:

a. charging at least three adjacent piles of nonwoven fabric, each of said piles having a weight in the range of 5-40 grams per square meter, and each of said piles comprising one or more fibers having a diameter in the range of 1.5-2.0 microns;

b. collating a stiffening layer with said piles;

c. bonding the stiffening layer of fabric to one of said piles to form a stiffened filter media having a top side and a bottom side;

d. scoring said stiffened filter media;

e. applying glue to a side of said stiffened filter media;

f. folding said filter media into a series of V shaped pleats; and

g. cutting said pleated filter media into a multiplicity of pieces having a predetermined size.

20. The method of claim 19 wherein said bonding is ultrasonic bonding.