Metal filter

• US 6,355,082 B1
• Filed: 07/19/2000
• Issued: 03/12/2002
• Est. Priority Date: 10/12/1998
• Status: Expired due to Term

• Current Assignee: Nippon Seisen Co., Ltd.
• Original Assignee: Nippon Seisen Co., Ltd.
• Inventors: Ishibe, Hideomi
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): PHAM, MINH CHAU THI
• Application Number:
  US09/554,658
• Time in Patent Office: 601 Days
• Field of Search: 553/851, 553/852, 555/23, 555/25, 555/28, 210/315, 210/342, 210/487, 210/493.1, 210/493.5, 210/494.2, 210/496, 210/499, 210/500.25, 210/510.1
• US Class Current: 55/528
• CPC Class Codes: B01D 2265/06 Details of supporting structures for filtering material, e.g. cores
• CPC Class Codes: B01D 39/2027 Metallic material
• CPC Class Codes: B01D 39/2044 sintered or bonded by inorganic agents
• CPC Class Codes: B01D 46/522 with specific folds, e.g. having different lengths
• CPC Class Codes: B01D 46/54 Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
• CPC Class Codes: B01D 69/00 Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
• CPC Class Codes: B01D 71/022 Metals
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 3/1103 with particular physical characteristics
• CPC Class Codes: B22F 7/002 of porous nature

Abstract

It is a metal filter 1 including a fine filtering layer 3 and a supporting member 2 sintered to be porous and having a covering surface 4 to integrate the fine filtering layer 3 into a laminate to maintain its shape. The average pore diameter of the fine filtering layer 3 is set to be smaller than an average pore diameter of the supporting member 2. The covering surface 4 is formed in an uneven shape so as to allow a filtering surface of the fine filtering layer 3 to be an undulating filtering surface 3A such that the area ratio S1/S0 of its real filtration area S1 to the standard filtration area S0 of the case where it is not formed in an uneven shape, is larger than or equal to 1.3. The average thickness of the fine filtering layer 3 at valley portions 6 of the uneven shape is set to be larger than the average thickness of the fine filtering layer 3 at the crest portions 5 of the uneven shape, and the undulating filtering surface 3A is formed in a smoothly curved surface shape.

Claims

1. A metal filter comprising:

a fine filtering layer, said fine filtering layer having a thickness that cannot, by itself, maintain its shape against filtration pressure, and

a supporting member sintered to be porous and having a covering surface which integrates with the fine filtering layer as a laminate to maintain its shape, wherein

an average pore diameter of pores of said fine filtering layer is set to be smaller than an average pore diameter of pores of said supporting member, and said covering surface of said supporting member is formed in an uneven shape having crest portions so as to allow a filtering surface of the fine filtering layer to be an undulating filtering surface such that an area ratio S1/S0, where S1 is the actual filtration area and S0 is the standard filtration area in the case where the supporting member is not formed in an uneven shape, is larger than or equal to 1.3, and wherein an average thickness of said fine filtering layer at valley portions between said crest portions is set to be larger than an average thickness of said fine filtering layer at the crest portions, and the filtering surface of said fine filtering layer is formed in a smoothly curved surface shape.

2. The metal filter according to claim 1, wherein the supporting member comprises a tubular body in which said crest portions are adjacent to one another in a circumferential direction and extend in an axial direction;

and a pitch of the crest portions in the circumferential direction is 2 to 4 times as large as an elevational height of the crest portions from said valley portions to said crest portions.

3. The metal filter according claim 1, wherein said fine filtering layer comprises a sintered body of a powdery substance containing short metal fibers having an average diameter d smaller than or equal to 3 μ

m and an average aspect ratio L/d of length L to diameter d of 2 to 20.

4. The metal filter according to claim 1, used for filtering a gas so that the number of particles having a size larger than or equal to 0.01 μ

m is substantially less than or equal to 10<sup>−

10</sup>; and

said gas is used for producing semiconductors.

5. The metal filter according to claim 2, wherein said fine filtering layer comprises a sintered body of a powdery substance containing short metal fibers having an average diameter d smaller than or equal to 3 μ

m and an average aspect ratio L/d of length L to diameter d of 2 to 20.

6. The metal filter according to claim 2, used for filtering a gas so that the number of particles having a size larger than or equal to 0.01 μ

m is substantially less than or equal to 10<sup>−

10</sup>; and

said gas is used for producing semiconductors.

7. The metal filter according to claim 3, used for filtering a gas so that number of particles having a size larger than or equal to 0.011 μ

m is substantially less than or equal to 10<sup>−

10</sup>; and

said gas is used for producing semiconductors.