COMPOSITE FERRITE SHEET, METHOD OF FABRICATING THE COMPOSITE FERRITE SHEET, AND ARRAY OF SINTERED FERRITE SEGMENTS USED TO FORM THE COMPOSITE FERRITE SHEET

• US 20120088070A1
• Filed: 12/13/2011
• Published: 04/12/2012
• Est. Priority Date: 04/08/2011
• Status: Active Grant

• Current Assignee: Maruwa Co., Ltd.
• Original Assignee: Maruwa Co., Ltd.
• Inventors: NISHI, Ikuo
• Granted Patent: US 8,323,776 B2
• Time in Patent Office: Days
• US Class Current: 428/141
• CPC Class Codes: C04B 35/26 based on ferrites
• CPC Class Codes: C04B 35/2633 containing barium, strontium or calcium
• CPC Class Codes: C04B 35/265 Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt
• CPC Class Codes: C04B 35/2658 Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites
• CPC Class Codes: C04B 35/2666 Other ferrites containing nickel, copper or cobalt
• CPC Class Codes: C04B 35/2691 Other ferrites containing alkaline metals
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/2457 Parallel ribs and/or grooves
• CPC Class Codes: Y10T 428/24612 Composite web or sheet

Abstract

A method of fabricating a composite ferrite sheet including the steps of: (a) forming a grooved green ferrite sheet having a non-intersecting grid pattern by pressing a groove forming die including a plurality of first protrusions and a plurality of second protrusions having a triangular cross sectional shape, each protrusion of at least one of the plurality of first protrusions and the plurality of second protrusions being discontinuous at each imaginary intersecting portion at which extension lines of the respective first and second protrusions intersect each other, (b) firing the grooved ferrite green sheet to obtain a sintered ferrite sheet, (c) bonding at least one supporting sheet to at least one of opposite major surfaces of the sintered ferrite sheet, and (d) rupturing the sintered ferrite sheet along the grooves into a multiplicity of separate and independent rectangular planar ferrite segments which are bonded to the supporting sheet.

Claims

1. A method of fabricating a composite ferrite sheet, comprising the steps of:

providing a ferrite green sheet having a predetermined thickness;

providing a groove forming die having a pressing surface to be pressed onto the ferrite green sheet, the groove forming die including a plurality of first protrusions having a triangular cross sectional shape and a plurality of second protrusions having a triangular cross sectional shape that are formed on the pressing surface such that the first protrusions and the second protrusions extend in respective two directions perpendicular to each other so as to cooperate with each other to form a grid pattern, each protrusion of at least one of the plurality of first protrusions and the plurality of second protrusions being discontinuous at each imaginary intersecting portion at which an extension line of the first protrusions and an extension line of the second protrusions intersect each other;

forming a grooved ferrite green sheet by pressing the pressing surface of the groove forming die onto at least one of opposite major surfaces of the ferrite green sheet, the grooved ferrite green sheet including a plurality of first grooves having V-shaped cross section that correspond to the first protrusions and a plurality of second grooves having V-shaped cross, section that correspond to the second protrusions, the first and second grooves cooperating with each other to form a grid pattern, each groove of at least one of the plurality of first grooves and the plurality of second grooves being discontinuous at each imaginary intersecting portion at which an extension line of the first grooves and an extension line of the second grooves intersect each other;

obtaining a sintered ferrite sheet by firing the grooved ferrite green sheet, the sintered ferrite sheet having a plurality of first dividing grooves corresponding to the first grooves, and a plurality of second dividing grooves corresponding to the second grooves, the first and second dividing grooves cooperating with each other to form a grid pattern, each dividing groove of at least one of the plurality of first dividing grooves and the plurality of second dividing grooves being discontinuous at each imaginary intersecting portion at which an extension line of the first dividing grooves and an extension line of the second dividing grooves intersect each other;

forming a laminated sheet by bonding at least one supporting sheet to at least one of opposite major surfaces of the sintered ferrite sheet; and

bending the laminated sheet to rupture the sintered ferrite sheet along the first dividing grooves and the second dividing grooves, into a multiplicity of mutually separate and independent rectangular and planar segments of sintered ferrite which are bonded to the at least one supporting sheet.

2. The method according to claim 1, wherein each protrusion of the at least one of the plurality of first protrusions and the plurality of second protrusions of the groove forming die is made discontinuous at the each imaginary intersecting portion of the first and second protrusions, by dividing the each protrusion into a plurality of divisions which are spaced apart from each other in an extending direction of the each protrusion at the each imaginary intersecting portion, each of the plurality of divisions having a slant end face adjacent to a corresponding imaginary intersecting portion, the slant end face being inclined such that a distance between the end face and the corresponding imaginary intersecting portion increases as the end face extends in a height direction of the each division from its root toward its top.

3. The method according to claim 2, wherein a lower edge of the slant end face is spaced apart from the corresponding imaginary intersecting portion in the extending direction of the each protrusion.

4. The method according to claim 2, wherein a spacing distance of the plurality of divisions in the extending direction of the each protrusion at the each imaginary intersecting portion is not longer than 0.2 times a grid interval between the protrusions of the grid pattern.

5. The method according to claim 1, wherein each protrusion of both of the plurality of first protrusions and the plurality of second protrusions of the groove forming die is discontinuous at the each imaginary intersecting portion of the first and second protrusions, and each groove of both of the plurality of first grooves and the plurality of second grooves formed in the grooved ferrite green sheet is discontinuous at the each imaginary intersecting portion of the first and second grooves.

6. The method according to claim 1, wherein each protrusion of both of the plurality of first protrusions and the plurality of second protrusions of the groove forming die is discontinuous at the each imaginary intersecting portion of the first and second protrusions, and means for forming a rupture assisting portion which is in the form of a protrusion is provided at the each imaginary intersecting portion of the first and second protrusions, so that each groove of both of the plurality of first grooves and the plurality of second grooves formed in the grooved ferrite green sheet is made discontinuous at the each imaginary intersecting portion of the first and second grooves, and a recess corresponding to the means for forming a rupture assisting portion is formed at the each imaginary intersecting portion of the first and second grooves, independently of the first and second grooves.

7. The method according to claim 6, wherein the means for forming a rupture assisting portion is a pyramidal protrusion, and the recess formed at the each imaginary intersecting portion of the first and second grooves in the grooved ferrite green sheet has an inverted quadrangular pyramid shape.

8. The method according to claim 1, wherein the at least one supporting sheet comprises a single-coated adhesive sheet and a flexible double-coated adhesive sheet, and the single-coated adhesive sheet is bonded to one of the opposite major surfaces of the sintered ferrite sheet and the flexible double-coated adhesive sheet is bonded to the other of the opposite major surfaces, while a release paper is bonded to an outer surface of the double-coated adhesive sheet, whereby the laminated sheet is formed.

9. The method according to claim 1, wherein the at least one supporting sheet is bonded to the at least one of the opposite major surfaces of the sintered ferrite sheet such that peripheral portions of the supporting sheet extend outwardly from side faces of the sintered ferrite sheet, the peripheral portions being folded to be bonded to the side faces to cover at least the side faces.

10. The method according to claim 1, wherein the laminated sheet is first bent in an extending direction of the plurality of first dividing grooves, and is then bent in an extending direction of the plurality of second dividing grooves after the laminated sheet is turned by 90°

.

11. The method according to claim 1, wherein the laminated sheet is bent by at least one roller.

12. The method according to claim 1, wherein the step of bending the laminated sheet comprises a first bending operation to roll a first roller in pressing contact with the laminated sheet for bending the laminated sheet, and a second bending operation to roll a second roller having an axis of rotation perpendicular to an axis of rotation of the first roller, in pressing contact with the laminated sheet for bending the laminated sheet.

13. An array of sintered ferrite segments each having a rectangular and planar shape that is obtained from a sintered ferrite sheet including a plurality of first dividing grooves having V-shaped cross section and a plurality of second dividing grooves having V-shaped cross section, which first and second dividing grooves cooperate with each other to form a grid pattern, each dividing groove of at least one of the plurality of first dividing grooves and the plurality of second dividing grooves being discontinuous at each imaginary intersecting portion at which an extension line of the first dividing grooves and an extension line of the second dividing grooves intersect each other, the sintered ferrite sheet being ruptured along the first dividing grooves and the second dividing grooves, into the sintered ferrite segments,

wherein at least one side face of each of the sintered ferrite segments includes at least one ruptured section that is ruptured over an entire thickness of the sintered ferrite segment at at least one end portion in an extending direction of one of the first dividing groove and the second dividing groove.

15. A composite ferrite sheet comprising an array of sintered ferrite segments as defined in claim 13 and at least one flexible supporting sheet, wherein the sintered ferrite segments are arranged in mutually perpendicular two directions, and the at least one flexible supporting sheet is bonded to at least one of opposite major surfaces of each of the sintered ferrite segments such that adjacent ones of the sintered ferrite segments are butted together so as to form a grid pattern.

14. An array of sintered ferrite segments having rectangular and planar shape that is obtained from a sintered ferrite sheet having a plurality of first dividing grooves having V-shaped cross section and a plurality of second dividing grooves having V-shaped cross section, which first and second dividing grooves cooperate with each other to form a grid pattern, each dividing groove of both of the plurality of first dividing grooves and the plurality of second dividing grooves being discontinuous at each imaginary intersecting portion at which an extension line of the first dividing grooves and an extension line of the second dividing grooves intersect each other, the sintered ferrite sheet further having a rupture assisting portion at the imaginary intersecting portion, the sintered ferrite sheet being ruptured along the first dividing grooves and the second dividing grooves, into the sintered ferrite segments,

wherein at least one side face of each of the sintered ferrite segments includes at least one ruptured section that is ruptured over an entire thickness of the sintered ferrite segment, except for a portion corresponding to the rupture assisting portion, at at least one end portion in an extending direction of one of the first dividing groove and the second dividing groove.

16. A composite ferrite sheet comprising an array of sintered ferrite segments as defined in claim 14 and at least one flexible supporting sheet, wherein the sintered ferrite segments are arranged in mutually perpendicular two directions, and the at least one flexible supporting sheet is bonded to at least one of opposite major surfaces of each of the sintered ferrite segments such that adjacent ones of the sintered ferrite segments are butted together so as to form a grid pattern.