Magnetic stereophonic phonograph pickup

Abstract

A magnetic stereophonic pickup having four coil carrying core members arranged symmetrically around the axis of an annular ceramic magnet against the inner pole and end face of which one end of said core members abut the opposite ends being magnetically interconnected. A magnetic armature connected to a stylus is so supported within and coaxial with the magnet that it can oscillate in any direction about a point adjacent the outer end thereof. The armature acts as a variable magnetic load converting stylus movements into variations of the magnetic potentials at the magnet abutting ends of the core members, said potential variations in turn causing flux variations in the coil carrying core members.

What we claim is: 
     
       1. A magnetic structure for a stereophonic pickup in the form of an electromechanical transducer, said structure comprising a hollow cylindrical magnet made of a magnetizable ceramic material and having magnetic poles of opposite polarity at the end faces thereof, four elongated core members abutting one end face of said magnet and extending therefrom in a direction parallel to the axis thereof, said core members being arranged symmetrically with respect to said axis, means for magnetically interconnecting said core members at the ends thereof remote from said magnet, further comprising a stylus carrying .Iadd.permanent magnet .Iaddend.armature, and means supporting said .Iadd.permanent magnet .Iaddend.armature within and coaxial with said hollow cylindrical magnet for pivotal movement in all directions about a point of said axis spaced from .[.the center point.]. .Iadd.any point located interiorly .Iaddend.of said magnet.Iadd., said permanent magnet poled oppositely to the polarity of said hollow cylindrical magnet.Iaddend.. 
     
     
       2. An electromagnetic transducer comprising in combination: a housing having a bore extending obliquely from one surface thereof, an annular permanent magnet of a ceramic material supported within said housing coaxially with and surrounding said bore a small distance from the outer end thereof, a ring of elastic material mounted within and engaging the walls of said bore adjacent .Iadd.to but outside .Iaddend.the outer end of said magnet, a tubular .Iadd.permanent magnet .Iaddend.armature supported by said ring and extending coaxially with said .Iadd.angular .Iaddend.bore and said magnet beyond the inner end of the latter, a stylus arm fixed to said .Iadd.permanent magnet .Iaddend.armature and carrying a stylus on its outer end extending beyond said surface of said housing, four rods of a high permeance material .[.and with circular cross-section.]. extending parallel to and equiangularly spaced around the axis of said bore, said rods abutting the inner end face of said magnet with their outer ends and extending beyond the inner end of said bore, a cross-piece of magnetizable material magnetically interconnecting the inner ends of said rods and fixedly held in said housing, and four coils mounted on the inner portions of said rods respectively between the inner end of said bore and said cross-piece, .[.sand.]. .Iadd.said .Iaddend.coils being series connected in pairs each consisting of oppositely disposed coils and connected to respective terminals.Iadd., said permanent magnet having a polarity opposite to that of said annular permanent magnet.Iaddend.. 
     
     
       3. An electromechanical transducer comprising a magnetic structure defining an airgap .[.and.]. symmetrically disposed with respect to an axis therein, a stylus carrying armature .Iadd.comprising a permanent magnet and .Iaddend.extending through said airgap and means pivotally mounting said armature around a pivot located on said axis adjacent .Iadd.to but outside .Iaddend.one end of the airgap, said magnetic structure comprising magnetic means surrounding the armature and having magnetic poles of one polarity adjacent one end of the armature and magnetic poles of the opposite polarity adjacent the other end of the armature, .Iadd.said permanent magnet poled opposite to the polarity of said magnetic means, .Iaddend.two pairs of core members symmetrically disposed with respect to the axis of the airgap and defining planes forming a right angle, said core members abutting magnetic pole faces of the same polarity at one end of said magnetic means, means for magnetically interconnecting the core members of each of said pairs at the ends thereof remote from said pole faces, and a coil mounted on each of said core members. 
     
     
       4. An electromechanical transducer as claimed in claim 3, in which the said magnetic means comprises a hollow cylindrical body made of a magnetizable ceramic material. .[.5. An electromechanical transducer as claimed in 
     
     
        claim 3 in which said armature comprises a permanent magnet..]. 6. An electromagnetic transducer comprising: a pair of permanent magnet means arranged in spaced parallel relationship;   magnetic conductor means magnetically connecting two pole faces of said permanent magnet means having the same polarity, said two pole faces being connected to said magnetic conductor means;   coil means surrounding a portion of said magnetic conductor means for generating an electrical current in response to a magnetic flux induced in said coil means by said permanent magnet means;   an armature .Iadd.comprising a further permanent magnet.Iaddend.;   a stylus connected to said armature; and   mounting means pivotally mounting said armature .Iadd.for pivoting about a point located outside said permanent magnet means but .Iaddend.magnetically in parallel with said permanent magnet means to vary a magnetic load imparted to said permanent magnet means by said armature.Iadd., said permanent magnet poled opposite to the polarity of   
     
     
        said annular cylindrical magnet.Iaddend.. 7. An electromagnetic transducer as defined in claim 6, further comprising: a further pair of permanent magnet means arranged in spaced parallel relationship about a commmon longitudinal axis with said pair of permanent magnet means;   further magnetic conductor means magnetically connecting further two pole faces of said further pair of permanent magnet means having the same polarity, said further two pole faces being connected to said further magnetic conductor means; and   further coil means surrounding a portion of said further magnetic conductor means for generating an electrical current in response to a magnetic flux induced in said further coil means by said further permanent magnet means;   wherein the respective planes defined by said pair of permanent magnet means and said further pair of permanent magnet means form substantially right angles with each other and said mounting means mounts said armature   
     
     
        for pivotal movement in all directions. 8. An electromagnetic transducer as claimed in claim 7, wherein: said permanent magnet means comprises four bar magnets arranged symmetrically and equiangularly spaced around said common longitudinal axis;   said magnetic conductor means comprises four rod-shaped members of a high permeance material and a common cross-piece magnetically interconnecting respective one ends of said four rod-shaped members, said four bar magnets connected to and forming extensions of the opposite ends of respective ones of said rod-shaped members; and   said coil means and further coil means together comprise two pairs of series connected coil pairs oppositely disposed on portions of said   
     
     
        rod-shaped members. 9. An electromagnetic transducer having a magnetic structure comprising an annular cylindrical magnet of a ceramic material magnetized in an axial direction and having a plurality of angularly spaced portions, magnetic conductor means, portions of which are surrounded by a coil, interconnecting a first pair of said angularly spaced portions, a stylus carrying armature .Iadd.comprising a further permanent magnet.Iaddend., means mounting said armature between said first pair of angularly spaced portions for pivotal movement .Iadd.about a point external of said annular cylindrical magnet .Iaddend.in response to stylus movements in the plane of said first pair of spaced portions to cause variations in the magnetic load imparted to said spaced portions by said armature, said magnetic conductor means interconnecting two pole faces of 
     
     
        the same polarity of said first pair of angularly spaced portions. 10. An electromagnetic transducer as defined in claim 9, further comprising a second magnetic structure having a second pair of angularly spaced portions arranged in spaced parallel relationship and interconnected by a second magnetic conductor, portions of which are surrounded by a second coil, wherein the planes of said first and second pairs of spaced portions form substantially right angles with respect to each other and wherein said first and second magnetic structures have a common longitudinal axis, said armature being mounted for pivotal movement in all direction between 
     
     
        said first and second pairs of spaced portions. 11. An electromagnetic transducer as claimed in claim 10 in which said first and second magnetic conductors comprise four parallel rods of a high permeance material arranged symmetrically and equiangularly spaced around the axis of said cylindrical magnet with one end of said rods abutting one end face thereof, the opposite ends of said rods being magnetically interconnected 
     
     
        by a common cross piece. 12. An electromagnetic transducer as claimed in 
     
     
        claim 11 in which said rods are circular in cross-section. 13. An electromechanical transducer, comprising: a pair of permanent magnet portions having an airgap between them and providing respective components of magnetic flux similarly directed in said airgap;   yoke means magnetically connecting pole faces of like polarity of each said pair of permanent magnet portions together, said pole faces being connected to said yoke means;   electrical output coil means surrounding portions of said yoke means for generating electrical output signals induced by magnetic flux changes in said yoke means;   an armature .Iadd.including a further permanent magnet.Iaddend.; and   mounting means pivotally mounting said armature .Iadd.for pivoting about a pivot point external of said permanent magnet portions and .Iaddend.magnetically in parallel with said pair of permanent magnet portions to provide a path for said respective .[.components of magnetic flux, to vary the magnetic.].  potentials of said pole faces and to   
     
     
        thereby produce said flux changes in said yoke means. 14. An electromechanical transducer as defined in claim 13, further comprising: a further pair of permanent magnet portions arranged on opposite sides of said airgap and angularly spaced substantially 90° from said pair of permanent magnet portions;   wherein said yoke means magnetically connects further pole faces of like polarity of said further pair of permanent magnet portions;   further electrical output coil means surrounding further portions of said yoke means for generating further electrical output signals induced by magnetic flux changes in said further portions of said yoke means;   said mounting means mounting said armature for pivotal movement in all directions about .[.a.]. .Iadd.said .Iaddend.pivot point on the central axis of said airgap and spaced therealong from a central point of symmetry   
     
     
        of said pair and further pair of permanent magnet portions. 15. An electromechanical transducer as defined in claim 14, wherein said permanent magnetic portions comprise respective angularly spaced integral parts of a hollow cylindrical body of a magnetizable anisotropic material and having its direction of maximum permeability substantially parallel to its axis, said body being permanently magnetized in said direction, and 
     
     
        surrounding said airgap. .[.16.  An electromechanical transducer as defined in claim 14, wherein said armature is made of a high permeance magnetic material..]. .[.17. An electromechanical transducer as defined in 
     
     
        claim 14, wherein said armature comprises a permanent magnet..]. 18. An electromechanical transducer as defined in claim 14, wherein said armature 
     
     
        is tubular. 19. An electromechanical transducer as defined in claim 14, wherein said means for mounting said armature comprises a ring of resilient material supported along its outer periphery and engaging the 
     
     
        armature along its inner periphery. 20. An electromechanical transducer as defined in claim 14, wherein said yoke means comprises four rods of a high permeance magnetic material extending substantially parallel to the central axis of the airgap, which rods at one end abut against their respective magnetic portions and at the opposite end are magnetically 
     
     
        interconnected by means of a common cross-piece. 21. An electromagnetic transducer as defined in claim 13, wherein said pair of permanent magnet portions comprise portions of a cylindrical magnet having a hollow central axial portion, said armature being mounted for movement within said hollow central axial portion.