US5230800A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Scrim inserted electrostatic fibrous filter web
Assignee: 3M Co
•
Filing: 1992-02-20
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Granted: 1993-07-27
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Expires: 2012-02-20
Abstract
Abstract Provided is a nonwoven web of electrically charged fibers needle-punched to a scrim support. This web provides a filter medium having increased uniformity in pressure-drop, basis weight and filtration performance.
Inventors
- 👤 David L. Nelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 20:38
CPC Classifications
B; B01; B01D; B01D35/00; B01D35/06; B01D39/00; B01D39/14; B01D39/16; B01D39/1607; B01D39/1623; D; D04; D04H; D04H1/00; D04H1/40; D04H1/44; D04H1/46; D04H1/498; D04H13/00; D04H13/02; D04H3/00; D04H3/02; D04H3/04; D04H3/045; B01D2239/00; B01D2239/04; B01D2239/0435; B01D2239/06; B01D2239/0604; B01D2239/0613; B01D2239/0627; B01D2239/065; B01D2239/0654; B01D2239/0659
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
92 words
A method for forming an electret nonwoven filter web comprising the steps of a) providing electrostatically charged, dielectric, fibrillated discontinuous fibers formed by fibrillating an electrostatically charged film, b) forming the electrostatically charged discontinuous fibers into at least one nonwoven filter web, c) joining the at least one filter web to a reinforcement scrim, and d) consolidating the at least one filter web by needle punching the at least one filter web and reinforcement scrim to form a filter web with substantially uniform basis weight and filter performance properties across the web.
Claim 2
Independent Claim
92 words
A method for forming an electret nonwoven filter web comprising the steps of a) providing electrostatically charged, dielectric, fibrillated discontinuous fibers formed by fibrillating an electrostatically charged film, b) forming the electrostatically charged discontinuous fibers into at least one nonwoven filter web, c) joining the at least one filter web to a reinforcement scrim, and d) consolidating the at least one filter web by needle punching the at least one filter web and reinforcement scrim to form a filter web with substantially uniform basis weight and filter performance properties across the web.
Claim 3
Dependent Claim
12 words
The method of claim 1 wherein the fibers have substantially rectangular cross-sections.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein the reinforcement scrim is an inner layer between two outer filter web layers.
Claim 5
Dependent Claim
17 words
The method of claim 1 wherein the at least one nonwoven filter web is formed by carding.
Claim 6
Dependent Claim
19 words
The method of claim 4 further comprising randomizing the carded filter web prior to joining with the scrim reinforcement.
Claim 7
Dependent Claim
27 words
The method of claim 1 wherein the fiber is a polypropylene polymer or copolymer fiber and the scrim reinforcement is a spunbond polypropylene polymer or copolymer nonwoven.
Claim 8
Dependent Claim
34 words
A uniform electret nonwoven filter comprising at least one nonwoven filter web of electrostatically charged dielectric fibrillated fibers formed by fibrillation of an electrostatically charged film joined to a reinforcement scrim by needle punching.
Claim 9
Dependent Claim
34 words
A uniform electret nonwoven filter comprising at least one nonwoven filter web of electrostatically charged dielectric fibrillated fibers formed by fibrillation of an electrostatically charged film joined to a reinforcement scrim by needle punching.
Claim 10
Dependent Claim
15 words
The electret nonwoven filter of claim 7 wherein the fibers are polypropylene polymers or copolymers.
Claim 11
Dependent Claim
24 words
The electret nonwoven filter of claim 7 wherein the reinforcement scrim is a center layer between two outer layers of the nonwoven filter web.
Claim 12
Dependent Claim
16 words
The electret nonwoven filter of claim 7 wherein the nonwoven filter web is a carded web.
Claim 13
Dependent Claim
14 words
The electret nonwoven filter of claim 10 wherein the nonwoven filter web is randomized.
Claim 14
Dependent Claim
24 words
The electret nonwoven filter of claim 7 wherein the nonwoven web material has a total basis weight of less than 120 gm/m 2 .
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-07-26 | 1997-01-25 | 1997-07-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-07-26 | 2001-01-25 | 2001-07-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-07-26 | 2005-01-25 | 2005-07-27 | $7700.00 | Window Closed / Lapsed |