Patent US4528099A successfully refreshed from Google Patents.
US4528099A
Expired / Lapsed
US
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Filter medium for filtering molten metals
Assignee: Rio Tinto Switzerland AG
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Filing: 1983-06-06
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Granted: 1985-07-09
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Expires: 2003-06-06
Abstract
Abstract Filter medium in the form of a stable body made of ceramic material and employed for filtering molten metals. The filter medium is made up of at least two effective filter layers such that a relatively thick layer of large pore diameter lies on a relatively thin layer of small pore diameter. This arrangement aims at attaining the maximum possible wetting of the interior of the filter medium.
Inventors
- 👤 Wolfhart Rieger
- 👤 Lugwig Gauckler
- 👤 Konrad Kampfer
- 👤 Albert Mauer
- 👤 Marco Dellapina
- 👤 Volker Nobbe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 21:48
CPC Classifications
B; B32; B32B; B32B18/00; B01; B01D; B01D39/00; B01D39/14; B01D39/20; B01D39/2068; B01D39/2072; B01D39/2075; C; C04; C04B; C04B38/00; C04B38/007; C04B2111/00; C04B2111/00474; C04B2111/00793; C04B2235/00; C04B2235/65; C04B2235/656; C04B2235/6562; C04B2235/6565; C04B2235/6567; C04B2237/00; C04B2237/30; C04B2237/32; C04B2237/34; C04B2237/341; C04B2237/343; C04B2237/345; C04B2237/348; C04B2237/36; C04B2237/363; C04B2237/365; C04B2237/368; C04B2237/38; C04B2237/50; C04B2237/58; C04B2237/586; C04B2237/588
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
201 words
A filter medium in the form of a stable body of ceramic material for filtering molten metal comprising at least a first filtering layer A and a second filtering layer B arranged one after the other in the direction of filtration, said at least first filtering layer A having a thickness d A of between 9-91 mm, porosity f A of between 0.25-0.8 and pore diameter λ A of between 0.5-2 mm wherein the parameter H SA of layer A which is proportional to the filtering resistance of layer A is equal to ##EQU4## and has values of between 28-14,560 cm -1 , said at least second filtering layer B having a thickness d B of between 1-33 mm, porosity f B of between 0.25-0.5 and pore diameter λ B of between 0.2-1 mm wherein the parameter H SB of layer B which is proportional to the filtering resistance of layer B is equal to ##EQU5## and has values of between 20-33,000 cm -1 , and wherein the ratio of thickness d A to thickness d B lies between 9:1 and 3:1, and the ratio of the numerical values of parameters H SA and H SB lies between 1:1.2 and 1:30.
Claim 2
Dependent Claim
201 words
A filter medium in the form of a stable body of ceramic material for filtering molten metal comprising at least a first filtering layer A and a second filtering layer B arranged one after the other in the direction of filtration, said at least first filtering layer A having a thickness d A of between 9-91 mm, porosity f A of between 0.25-0.8 and pore diameter λ A of between 0.5-2 mm wherein the parameter H SA of layer A which is proportional to the filtering resistance of layer A is equal to ##EQU4## and has values of between 28-14,560 cm -1 , said at least second filtering layer B having a thickness d B of between 1-33 mm, porosity f B of between 0.25-0.5 and pore diameter λ B of between 0.2-1 mm wherein the parameter H SB of layer B which is proportional to the filtering resistance of layer B is equal to ##EQU5## and has values of between 20-33,000 cm -1 , and wherein the ratio of thickness d A to thickness d B lies between 9:1 and 3:1, and the ratio of the numerical values of parameters H SA and H SB lies between 1:1.2 and 1:30.
Claim 3
Dependent Claim
22 words
A filter medium according to claim 1 wherein said first filtering layer A is positioned upstream of said second filtering layer B.
Claim 4
Dependent Claim
33 words
A filter medium according to claim 1 wherein said first filtering layer A and said second filtering layer B are made up of refractory material in the form of spherical grains bonded together.
Claim 5
Dependent Claim
13 words
A filter medium according to claim 3 wherein said spherical grains are hollow.
Claim 6
Dependent Claim
17 words
A filter medium according to claim 4 wherein said refractory material comprises hollow, spherical grains of corundum.
Claim 7
Dependent Claim
45 words
A filter medium according to claim 5 wherein said hollow corundum grains are employed with close control on grain size distribution such that the minimum grain diameter in a range of particle sizes is greater than 65% of the size of the maximum particle size.
Claim 8
Dependent Claim
33 words
A filter medium according to claim 3 wherein said grains are strongly bonded together with a glassy type binder, the amount of binder accounting for 20-40 wt. % of the final filter medium.
Claim 9
Dependent Claim
18 words
A filter medium according to claim 3 wherein said grains are bonded strongly together by a crystalline substance.
Claim 10
Dependent Claim
29 words
A filter medium according to claim 1 wherein the filter medium is built up of three layers wherein at least one of the layers contains a fluoride bearing compound.
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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) | 1988-07-08 | 1989-01-07 | 1989-07-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-08 | 1993-01-07 | 1993-07-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-08 | 1997-01-07 | 1997-07-09 | $7700.00 | Window Closed / Lapsed |