# US 5,710,745 A · Assembly having flux-directing return yoke for magneto-optical drive > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,745 A - Document ID: US5710745A - Status: Granted - Kind: A - Application number: 08/418,697 - Filed: 1995-04-07 - Granted: 1998-01-20 - Earliest claimed: 1995-04-07 - Assignees: Discovision Associates - Inventors: Kurt W. Getreuer - Web page: https://patentgrep.com/patent/US5710745A ## CPC - G11B 11/10534: {for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording} - G11B 25/043: {using rotating discs} - H01F 7/06: Electromagnets; Actuators including electromagnets {(electric coils H01F5/00; devices for holding workpieces using electric force B23Q3/15; load-engaging elements for lifting articles electromagnetically B66C1/06; electromagnetic couplings F16D27/00; magnetic brakes F16D63/002; electromagnetically operated valves F16K11/24, F16K31/00; analysing materials by magnetic means G01N27/72, G01N27/80; electromagnets for winding mechanical clocks G04C1/02; electromagnetic relays H01H51/00; windings for salient poles of dynamo-electric machines H02K3/18; electromagnets for telegraphic communication H04L; for arc lamps H05B31/28)} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES ## Abstract A bias coil assembly for use in combination with a magnetomotive generator such as employed in a magneto-optical disc drive. The assembly includes a return yoke having a body portion and a tip having a predetermined thickness and extending beyond the body portion. A winding for receiving electric current is wound around the body portion of the yoke so that the winding is contained below the tip. A first plate is disposed on the winding and includes at least one heat-radiating finger extending substantially around the winding without increasing the vertical height of the assembly. A second plate is disposed on the winding in a magnetic circuit with the first plate and the return yoke so that when the winding is connected to a source of power, the tip receives lines of magnetic flux that are channeled through the body portion while the at least one flange radiates thermal energy thereby produced. ## Claims ### Claim 1 A bias coil assembly for use in a magnetomotive generator, said assembly comprising: a return yoke having a body portion and a tip having a predetermined thickness and extending beyond said body portion substantially perpendicular thereto; a winding for receiving electric current, said winding being wound around said body portion of said return yoke so that said winding is contained below said tip; a first plate disposed on said winding, said first plate having at least one heat-radiating finger extending substantially around said winding to thereby maintain a minimum height of the bias coil assembly; a second plate disposed on said winding in a magnetic circuit with said first plate and said return yoke so that when said winding is connected to a source of power, said tip receives lines of magnetic flux that are channeled through said body portion while said at least one finger radiates thermal energy thereby produced. ### Claim 2 (depends on 1) The assembly according to claim 1 wherein said return yoke projects above an upper surface of said winding. ### Claim 3 (depends on 2) The assembly according to claim 2 wherein said first plate has an aperture having an inner edge, said aperture allowing said return yoke to project therethrough. ### Claim 4 (depends on 3) The assembly according to claim 3 wherein a top surface of said tip is substantially coplanar with a top surface of said first plate. ### Claim 5 (depends on 4) The assembly according to claim 4 wherein a gap is provided between said tip and said inner edge of said aperture so that lines of flux extend across said gap in an arc that intersects a field point having a maximized magnetic field intensity. ### Claim 6 (depends on 5) The assembly according to claim 5 wherein dimensions of said gap are optimized for maximized magnetic field intensity at a particular field point. ### Claim 7 (depends on 5) The assembly according to claim 5 wherein dimensions of said aperture are optimized for maximized magnetic field intensity at a particular field point. ### Claim 8 (depends on 1) The assembly according to claim 1 wherein at least one of said first plate and said second plate includes a plurality of side flanges. ### Claim 9 (depends on 8) The assembly according to claim 8 wherein said side flanges are blackened to increase heat radiation therefrom. ### Claim 10 (depends on 1) The assembly according to claim 1 wherein said at least one finger is blackened to increase heat radiation therefrom. ### Claim 11 (depends on 1) The assembly according to claim 1 including a plurality of heat-radiating fingers that fold around said winding. ### Claim 12 (depends on 1) The assembly according to claim 1 wherein said predetermined thickness of said tip is selected to maximize field intensity of said lines of magnetic flux channeled therethrough. ### Claim 13 A magnetic bias field generating apparatus for directing a magnetic field through a region of space, said apparatus comprising: a winding for carrying an electrical current; a return yoke having a body portion and a tip having a predetermined thickness, said winding being wound about said body portion, and said tip having an extension that extends beyond said body portion to overlap a surface of said winding; a first plate disposed on one side of said winding, said first plate having a plurality of fingers extending about said winding; a second plate disposed on another side of said winding, said vertical fingers formed without adding vertical height beyond said first and second plates; a first pole piece in magnetic flux communication with said first plate; and a second pole piece in magnetic flux communication with said second plate, a first end portion of said second pole piece opposing a first end portion of said first pole piece across a region of space to be subjected to a magnetic field so that when said winding is connected to a source of power, said tip receives lines of magnetic flux that are channeled through said body portion and directed across the end portions of the pole pieces while said fingers radiate thermal energy thereby produced. ### Claim 14 (depends on 13) The apparatus according to claim 13 wherein said first plate and said second plate contact second end portions of said first pole piece and said second pole piece respectively, so that said winding, said return yoke, said first plate, and said second plate are remote from said region of space. ### Claim 15 (depends on 13) The apparatus according to claim 13, wherein said return yoke projects above said surface of said winding. ### Claim 16 (depends on 15) The apparatus according to claim 15 wherein said first plate has an aperture having an inner edge, said aperture allowing said return yoke to project therethrough. ### Claim 17 (depends on 16) The apparatus according to claim 16 wherein a top surface of said tip is substantially coplanar with said top surface of said first plate. ### Claim 18 (depends on 17) The apparatus according to claim 17 wherein a gap is provided between said tip and said inner edge of said aperture so that lines of flux extend across said gap in an arc that intersects a field point having a maximized magnetic field intensity. ### Claim 19 (depends on 18) The apparatus according to claim 18 wherein dimensions of said gap are optimized for maximized magnetic field intensity at a particular field point. ### Claim 20 (depends on 18) The assembly according to claim 18 wherein dimensions of said aperture are optimized for maximized magnetic field intensity at a particular field point. ### Claim 21 (depends on 13) The apparatus according to claim 13 wherein said first plate further includes a plurality of side flanges. ### Claim 22 The apparatus according to 21 wherein said side flanges of said first plate align with said side flanges said second plate. ### Claim 23 (depends on 13) The apparatus according to claim 13 wherein said return yoke includes an elongated bar, and said tip includes a first end extension attached to a first end of said bar, and a second end extension attached to a second end of said bar. ### Claim 24 (depends on 13) The apparatus according to claim 13 wherein said predetermined thickness of said tip is selected to maximize field intensity of said lines of magnetic flux channeled therethrough. ### Claim 25 In combination with a magneto-optical disc drive, a bias coil field generator for producing a magnetic field in a data storage area of an optical disc disposed in the disc drive, said bias coil field generator comprising: a first plate, a second plate, and a bias coil winding caged therebetween, at least one of said first plate and said second plate having a heat-radiating finger directed generally toward the other of said first plate and said second plate while contained therebetween to maintain a minimum height defined by said first plate and said second plate; an elongated return yoke disposed in said winding, said return yoke having a body portion, a tip that projects beyond said winding, and two thin end extensions extending from said tip, said extensions having a predetermined thickness and overlapping a portion of said winding; and a first pole piece and a second pole piece, said pole pieces and said return yoke being disclosed in a magnetic circuit, respective end is of said pole pieces forming an opening therebetween so that said magnetic circuit traverses said opening to thereby allow an information storage area of an optical disc residing in said opening to be exposed to a magnetic field when said winding is connected to a source of power, said tip thereby receiving lines of magnetic flux that are channeled through said body portion and directed across said ends of the pole pieces while said heat radiating finger radiates resulting thermal energy. ### Claim 26 (depends on 25) The combination according to claim 25 wherein said first plate includes side flanges aligned with corresponding side flanges of said second plate. ### Claim 27 (depends on 26) The combination according to claim 26 wherein said side flanges of said first plate are in contact with said side flanges of said second plate and said, side flanges of said first plate and said side flanges of said second plate have mounting holes bored therethrough. ### Claim 28 (depends on 25) The combination according to claim 25 wherein said heat radiating finger is disposed external of said winding and spaced apart therefrom. ### Claim 29 (depends on 25) The combination according to claim 25 wherein at least one of said heat radiating finger and said side flanges are blackened to increase heat radiation therefrom. ### Claim 30 (depends on 25) The combination according to claim 25 wherein said first plate includes an aperture having an inner edge, said aperture allowing said tip of said return yoke to project therethrough. ### Claim 31 (depends on 30) The combination according to claim 30 wherein a top surface of said tip is substantially coplanar with a top surface of said first plate. ### Claim 32 (depends on 31) The combination according to claim 31 wherein a gap is provided between said tip and said inner edge of said aperture so that lines of flux, extend across said gap in an arc that intersects a field point having a maximized magnetic field intensity. ### Claim 33 (depends on 32) The combination according to claim 32 wherein dimensions of said gap are optimized for maximized magnetic field intensity at a particular field point. ### Claim 34 (depends on 32) The combination according to claim 32 wherein dimensions of said aperture are optimized for maximized magnetic field intensity at a particular field point. ### Claim 35 (depends on 25) The combination according to claim 25 wherein said predetermined thickness of said tip is selected to maximize field intensity of said lines of magnetic flux channeled therethrough.