Method for making permanent magnet type demagnetizing head

• US 5,078,944 A
• Filed: 06/06/1990
• Issued: 01/07/1992
• Est. Priority Date: 11/02/1987
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yoshino, Tuyoshi
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US07/533,959
• Time in Patent Office: 580 Days
• Field of Search: 29/603, 360/66, 360/118, 360/122, 360/129, 264/250, 264/254, 264/272.16, 425/359-361, 425/185, 425/588
• US Class Current: 264/254
• CPC Class Codes: G11B 5/325 Erasing heads using permanent magnets general details therefor G11B5/133 - G11B5/255
• CPC Class Codes: Y10T 29/49041 with significant slider/housing shaping or treating
• CPC Class Codes: Y10T 29/49043 Depositing magnetic layer or coating

Abstract

A permanent magnet type demagnetizing head is made by successively molding a resin-magnet which forms a body having a magnetic member forming a part of a tape contact surface and a resin which forms protection member forming a remainder part of the tape contact surface, and therefore a manufacturing process is simplified, and further quality of the demagnetizing head is improved, since size precision is enhanced.

Claims

1. A method for making a permanent magnet type erasing head having

a body formed from a resin-magnet material, said body including

means for mounting the body to audio equipment and

a unitary magnet member having an end face defining a first tape contact surface and at least one side face defined in a plane substantially perpendicular to a plane of said first tape contact surface, said unitary magnet member having a protrusion extending from said side face in a direction substantially perpendicular to said plane of said at least one side face, said protrusion including a relatively large portion and a relatively small portion, said relatively small portion being spaced from said plane of said first tape contact surface a distance greater than a predetermined length;

and

a protection member formed from a non-magnetic resin material around said magnetic member with said protrusion, said protection member having an end face defining a second tape contact surface coplanar with and surrounding said first tape contact surface, said protection member interlocking with said protrusion so as to fix said protection member with respect to said magnet member;

comprising the steps of

first injecting said resin-magnet material from a first injection nozzle to a space formed by a first movable metal mold and a first fixed metal mold for forming said body,

decoupling a metal mold table having said first movable metal mold and a second movable metal mold from an injection block having said first fixed metal mold and a second fixed metal mold,

rotating said metal mold table to align said first movable metal mold and said second fixed metal mold,

coupling said metal mold table to said injection block, and

secondly injecting said non-magnetic resin material from a second injection nozzle into space formed by said first movable metal mold and said second fixed metal mold for forming said protection member.

2. A method for making a permanent type erasing head in accordance with claim 1, wherein said first injecting step comprises the step of

forming an erasing head body having a magnetic member which forms a first part of a tape contact surface by molding a resin-magnet, and

wherein said second injecting step comprises the step of

forming a protection member around said magnetic member by molding a non-magnetic resin in a manner such that said protection member forms a second part of said tape contact surface.

3. A method for making a permanent magnet type erasing head in accordance with claim 2 wherein;

resin-magnet made of 87-91% by weight of magnetic powder and 9-13% by weight of resin is used for forming said erasing head body.

4. A method for making a permanent magnet type erasing head in accordance with claim 3 wherein;

said resin is thermoplastic resin.