Toroidal armature stereophonic pickup

Claim 2

In an electromagnetic cartridge having a moving stylus, a magnetic structure having a front magnetic member and including first and second pole pieces terminating in faces, said front magnetic member and said first and second pole piece faces defining first and second operating gaps, an armature disposed in said first and second operating gaps and means mounting said armature for movement in a direction substantially parallel to said first and second operating gaps in response to motion of said stylus, said armature and said pole piece faces defining first and second working gaps, first and second working gaps, first and second coils mounted on said first and second pole pieces, said first and second coils being of substantially identical configuration and connected in voltage adding and hum cancelling relation to each other, means in said magnetic structure providing first and second compensating gaps for said first working and first operating gaps and said second working and second operating gaps, respectively, said first and second compensating gaps being sized in relation to the corresponding operating and working gaps and said pole pieces being disposed in relation to said coils such that said mangnetic structure is substantially balanced and symmetrical with respect to said coils whereby stray fields will not produce hum-producing voltages in said cartridge.

Claim 3

An electromagnetic cartridge according to claim 1 including a rear magnetic member and respective non-magnetic spacers mounting said pole pieces on said rear magnetic member, said spacers being dimensioned to provide said first and second compensating gaps between said pole pieces and said rear magnetic member.

Claim 4

An electromagnetic cartridge according to claim 1, wherein said armature and stylus are removably mounted on said magnetic structure.

Claim 5

An electromagnetic cartridge according to claim 3 wherein said armature and stylus are removably mounted on a common non-magnetic carrier, said first and second pole pieces including first and second pole piece extensions mounted on said carrier and removably mounted thereon, said first and second pole piece extensions bearing against said first and second pole pieces respectively when said carrier is mounted on said magnetic structure and having free end faces providing said faces defining said first and second operating gaps and said first and second working gaps.

Claim 6

In a stereophonic electromagnetic cartridge having a moving stylus, a magnetic structure having a front magnetic member and including first and second pairs of pole pieces terminating in faces, said front magnetic member and said pole piece faces defining first and second pairs of operating gaps, an armature disposed in said first and second pairs of operating gaps and means mounting said armature for movement in a direction substantially parallel to said first and second operating gaps in response to motion of said stylus, said armature and said firsT and second pairs of pole piece faces defining first and second pairs of working gaps, first and second pairs of coils mounted on said first and second pairs of pole pieces and connected by pairs said first and second pairs of coils being of substantially identical configuration and connected respectively in voltage adding and hum cancelling relation to each other, means in said magnetic structure providing first and second pairs compensating gaps for said first pair of working gaps and first pair of operating gaps and second pair of working gaps and second pair of operating gaps, respectively, said first and second pairs of compensating gaps being sized in relation to the corresponding operating and fixed working gap pairs and said pole pieces being disposed in relation to said coils such that said magnetic structure is substantially balanced and symmetrical with respect to said coils whereby stray fields will not produce hum-producing voltages in said cartridge.

Claim 7

In a stereophonic electromagnetic cartridge having a moving stylus, a magnetic structure having a front magnetic member and including first and second pairs of pole pieces terminating in faces, said front magnetic member and said pole piece faces defining first and second pairs of operating gaps, an armature disposed in said first and second pairs of operating gaps and means mounting said armature for movement in a direction substantially parallel to said first and second operating gaps in response to motion of said stylus, said armature and said firsT and second pairs of pole piece faces defining first and second pairs of working gaps, first and second pairs of coils mounted on said first and second pairs of pole pieces and connected by pairs said first and second pairs of coils being of substantially identical configuration and connected respectively in voltage adding and hum cancelling relation to each other, means in said magnetic structure providing first and second pairs compensating gaps for said first pair of working gaps and first pair of operating gaps and second pair of working gaps and second pair of operating gaps, respectively, said first and second pairs of compensating gaps being sized in relation to the corresponding operating and fixed working gap pairs and said pole pieces being disposed in relation to said coils such that said magnetic structure is substantially balanced and symmetrical with respect to said coils whereby stray fields will not produce hum-producing voltages in said cartridge.

Claim 8

An electromagnetic cartridge according to claim 5 including a rear magnetic member and first and second pairs of non-magnetic spacers mounting said first and second pairs of pole pieces on said rear magnetic member, said spacers being dimensioned to provide said first and second pairs of compensating gaps between said pole pieces and said rear magnetic member.

Claim 9

An electromagnetic cartridge according to claim 6, wherein said armature and stylus are removably mounted on said magnetic structure.

Claim 10

An electromagnetic cartridge according to claim 7 wherein said armature and stylus are removably mounted on a common non-magnetic carrier, said first and second pairs of pole pieces including first and second pairs of pole piece extensions mounted on said carrier and removably mounted thereon, said first and second pairs of pole piece extensions bearing against said first and second pole pieces respectively when said carrier is mounted on said magnetic structure.

Claim 11

In an electromagnetic cartridge, a magnetic structure having a front magnetic member and including first and second diametrically opposed pairs of pole pieces having pole piece faces, said pole piece faces and said front magnetic member defining first and second pairs of operating gaps, said first pair of pole pieces having their longitudinal center lines in a substantially common first plane at 45* to the horizontal and said second pair of pole pieces having their longitudinal center lines in a substantially common second plane at right angles to said first plane and a toroidal armature in said first and second pairs of operating gaps, means mounting said armature for movement in a direction substantially parallel to said first and second operating gaps, said toroidal armature being of substantially triangular cross-section with one side thereof providing an armature face substantially parallel to said pole piece faces, said armature being arranged to provide a progressively decreasing cross-section and corresponding mass at increasing radii from the center thereof.

Claim 12

In an electromagnetic cartridge, a magnetic structure having a front magnetic member and including first and second diametrically opposed pairs of pole pieces having pole piece faces, said pole piece faces and said front magnetic member defining first and second pairs of operating gaps, said first pair of pole pieces having their longitudinal center lines in a substantially common first plane at 45* to the horizontal and said second pair of pole pieces having their longitudinal center lines in a substantially common second plane at right angles to said first plane and a toroidal armature in said first and second pairs of operating gaps, means mounting said armature for movement in a direction substantially parallel to said first and second operating gaps, said toroidal armature being of substantially triangular cross-section with one side thereof providing an armature face substantially parallel to said pole piece faces, said armature being arranged to provide a progressively decreasing cross-section and corresponding mass at increasing radii from the center thereof.

Claim 13

An electromagnetic cartridge according to claim 9 including a non-magnetic support for said armature.

Claim 14

An electromagnetic cartridge according to claim 10 wherein said support is conical.

Claim 15

An electromagnetic cartridge according to claim 11 wherein the cross-section of said armature is a right triangle with the base leg thereof being mounted on said conical support.

Claim 16

An electromagnetic cartridge comprising a support, a stylus-armature assembly mounted on said support and including a stylus lever pivotally mounted on said support and being uniformly compliant in all directions and a toroidal armature mounted on said stylus lever, a magnetic structure including a permanent magnet, a front magnetic member defining one side of first and second pairs of operating gaps and first and second diametrically opposed pairs of pole pieces having pole piece faces disposed in a substantially common plane and defining another side of said first and second pairs of operating gaps, said first pair of pole pieces having their longitudinal center lines coplanar at 45* to the horizontal and said second pair of pole pieces having their longitudinal center lines coplanar and at right angles to said first pair, said toroidal armature being disposed in said first and second pairs of operating gaps and being of a cross-section such that one side thereof provides a single armature face substantially parallel to said pole piece faces, means mounting said toroidal armature for movement in a direction substantially parallel to said first and second operating gap pairs, said toroidal armature being arranged to provide a progressively decreasing cross-section and corresponding mass at increasing radii from the center thereof.

Claim 17

An electromagnetic cartridge comprising a support, a stylus-armature assembly mounted on said support and including a stylus lever pivotally mounted on said support and being uniformly compliant in all directions and a toroidal armature mounted on said stylus lever, a magnetic structure including a permanent magnet, a front magnetic member defining one side of first and second pairs of operating gaps and first and second diametrically opposed pairs of pole pieces having pole piece faces disposed in a substantially common plane and defining another side of said first and second pairs of operating gaps, said first pair of pole pieces having their longitudinal center lines coplanar at 45* to the horizontal and said second pair of pole pieces having their longitudinal center lines coplanar and at right angles to said first pair, said toroidal armature being disposed in said first and second pairs of operating gaps and being of a cross-section such that one side thereof provides a single armature face substantially parallel to said pole piece faces, means mounting said toroidal armature for movement in a direction substantially parallel to said first and second operating gap pairs, said toroidal armature being arranged to provide a progressively decreasing cross-section and corresponding mass at increasing radii from the center thereof.

Claim 18

An electromagnetic cartridge according to claim 13 including a non-magnetic armature support for said toroidal armature.

Claim 19

An electromagnetic cartridge according to claim 14 wherein said armature support is conical.

Claim 20

An electromagnetic cartridge according to claim 15 wherein the cross-section of said armature is a right triangle with the base leg thereof being mounted on said conical support.