US3763335A - Pickup cartridge with magnet armature having opposite axial sides of like polarity and central portion of opposite polarity - Google Patents

Pickup cartridge with magnet armature having opposite axial sides of like polarity and central portion of opposite polarity Download PDF

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Publication number
US3763335A
US3763335A US00218983A US3763335DA US3763335A US 3763335 A US3763335 A US 3763335A US 00218983 A US00218983 A US 00218983A US 3763335D A US3763335D A US 3763335DA US 3763335 A US3763335 A US 3763335A
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United States
Prior art keywords
armature
pickup cartridge
yokes
cartridge according
stylus
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Expired - Lifetime
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US00218983A
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English (en)
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K Morita
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type
    • H04R11/08—Gramophone pick-ups using a stylus; Recorders using a stylus
    • H04R11/12—Gramophone pick-ups using a stylus; Recorders using a stylus signals being recorded or played back by vibration of a stylus in two orthogonal directions simultaneously

Definitions

  • ABSTRACT A small-sized light stylus pressure pickup cartridge with superior characteristics having an armature comprising a permanent magnet plate with both of its sides magnetized in opposite polarity from its central portion, a substantially inverted channel-shaped yoke or yokes arranged in the proximity of the outer sides of the mag net, a stylus arm fixed on the magnet and a reproducing stylus; characterized in that movement of the stylus is transmitted to the magnet thereby obtaining a corresponding electrical output from a coil or coils wound on a yoke or yokes.
  • the present invention relates to a pickup cartridge used for reproduction from a stereophonic disc record.
  • the conventional pickup cartridge of the kind employing a columnar magnet as shown in FIG. 1 is widely used.
  • This pickup cartridge comprises a stylus arm 2 with a reproducing stylus l fixed on its end, a columnar magnet 3 north (N) -south (S) polar magnetized in longitudinal direction of the stylus arm, a damper 4 for elastically supporting the central portion of the magnet 3 and a yoke 5.
  • N north
  • S -south
  • a reproducing pickup cartridge for use with a stereophonic disc record, which operates on the principle of efficient voltage generation by perfect magnetic flux alternation and which is characterized by an armature composed of a plate magnet with large coercive force and with a small moment of inertia as well as by a yoke having a simple construction, thereby obtaining a high output, reproduction over a wide range of frequencies, a low mechanical impedance and a high signal to noise ratio.
  • FIG. 1 is a diagram showing the construction of the essential parts of the conventional pickup cartridge
  • FIG. 2a is a diagram showing the construction of the essential parts of the pickup cartridge embodying the present invention.
  • FIG. 2b shows the construction of the essential parts of the stereo pickup cartridge of the 45-45 type according to the invention
  • FIGS. 3a, 3b and 3c are diagrams for explaining the operation of the device according to the invention.
  • FIGS. 40, 4b, 4c and 4d show front and side views of armatures embodying the present invention
  • FIG. 5 is a diagram showing the construction of the essential parts of another embodiment of the present invention.
  • FIG. 6 is an exploded perspective view of the essentinl parts of the pickup cartridge showing an actual construction of the embodiment of FIG. 5;
  • FIG. 7a is a diagram showing the construction of the essential parts of a monoral pickup cartridge according to another embodiment of the present invention.
  • FIG. 7b shows a perspective view of the device of FIG. 7a.
  • FIGS. 8a and 8b show respectively the construction and a perspective view of the essential parts of the stereo pickup cartridge of the 4545 type according to still another embodiment of th present invention.
  • FIG. 2 An example of the construction of the pickup cartridge according to the present invention is shown in FIG. 2.
  • the pickup cartridge is so constructed that a magnetic axis is set up in the transverse direction of a flat magnet plate with a small length-todiameter ratio.
  • the armature 7, comprising a permanent magnet which is magnetized in such a manner that north poles (or south poles) are set up on both sides and a south pole (or a north pole) is formed in the central portion thereof, is coupled with a stylus arm 26 with a reproducing stylus mounted on its end.
  • a support member 11 with a notch portion 10 is arranged as an axial extension of the stylus arm so that the armature 7 moves with a central portion thereof as a supporting point.
  • the yoke 15 which is made of an alloy with a high magnetic permeability has pole pieces 16 and 17 on its ends which are placed on either side of the armature 7 and in its proximity.
  • a coil 18 is wound on the yoke 15.
  • the pole end 8 of the armature 7 approaches the pole piece 16 of the yoke 15, while the other magnetic pole 9 of the armature 7 moves away from the pole piece 17 of the yoke 15.
  • magnetic fluxes flow in the yoke 15 in the direction of arrow B, thereby inducing an electromotive force e in the direction of arrow B in the coil 18.
  • the magnetic pole 9 of the armature 7 moves close to the pole piece 17 and the other magnet pole 8 moves further away from the pole piece 16, As a result, magnetic fluxes flow in the opposite direction from the case of FIG.
  • the armature 7 is magnetized in such a manner as is illustrated in FIG. 2a.
  • This armature magnet consists of the two magnet plates 8 and 9 which are magnetized individually and bonded to each other with sides of the same polarity fixed to each other.
  • a barium ferrite magnet or a platinum-cobalt alloy magnet with a large coercive force is more suitably used as the armature than a cast magnet with a small corecive force.
  • a magnet with anistropic magnetic properties it is desirable to employ a magnet with anistropic magnetic properties.
  • the barium ferrite magnet may be obtained in any desired shape by a pressing process. Also, its specific gravity is lower than that of a metallic magnet and less grinding processes are required, contributing to lower production cost.
  • Other advantages of a barium ferrite magnet include a large coercive force and a magnetic permeability which is almost equal to air, thus permitting it to be magnetized in any desirable manner.
  • the section of the armature 7 may take various forms including a simple circle as shown in FIG. 4, or a cross, V shape or semi-circle.
  • This armature is provided with a center hole 12 for receiving the stylus arm 26.
  • the stylus arm 26 may be coupled with the armature in a different manner.
  • the armature 7 may be magnetized partially only at the shadowed portion 13 in the proximity to the pole pieces 16 and 17.
  • the armature 7 consists of the two magnetized plates attached to each other with the sides of the same polarity inside, and therefore it is possible to increase the density of magnetic fluxes.
  • the armature 7 consists of a flat plate in shape, the moment of inertia can be greatly lessened, in comparison with the conventional device employing a bar magnet, by pivot-supporting the portion of the armature near its center of gravity. This leads to a smaller effective mass of the vibration system from the viewpoint of the reproducing stylus, thereby contributing greatly to the improvement in the performance of the pickup cartridge.
  • a notch portion is made of elastic, strong and thin metal wire such as phosphorus bronze or plastic material so that the end portions of the armature 7 which are opposed to the pole pieces of the yoke vibrate in response faithfully to the motion of the reproducing stylus in a given direction.
  • a damper 23 made of elastic material such as butyl rubber is interposed between the armature 7 and the support 11 as shown in FIG. 6, whereby the space between the support 11 and the armature 7 is regulated to obtain an appropriate compliance and damping of the reproducing stylus.
  • FIG. 2b A stereo pickup cartridge of the 4545 type embodying the present invention is shown in FIG. 2b.
  • the yokes 15R and 15L shown in FIG. 2b which are fundamentally of an inverted channeLshape and made of an alloy with high magnetic permeability such as permalloy are disposed in proximity to each other in such a manner that the pole pieces 16R and 17R; 16L and 17L of the yokes 15R and 15L are repectively astride the disc armature 7 at an angle of 45 to the plane which contains the axis of the tip of the reproducing stylus and the main axis of the stylus arm 26 and which is at right angles to the surface of the record disc 24, said yokes being placed at right angles to each other in the planes R and L respectively containing the supporting point 14.
  • the edges of the pole pieces 16R, 17R, 161.. and 17L come closest to the armature 7 when the pole pieces are in the above-mentioned local relationship with each other. In this case, however, other portions of the yokes than the edges thereof may be differently shaped.
  • the pole pieces 16R, 17R, 16L and 17L are so shaped at their ends that the magnetic resistance in them is the least when they are set at 45 as mentioned above.
  • the armature 7 may be either interposed between the pole pieces 16 and 17 or the pole pieces 16 and 17 may be located within the levels of both side surfaces of the magnet 7.
  • the pickup cartridge operates as described below.
  • the reproducing stylus 25 changes its position in the direction of arrow D (leftward at 45)
  • the coil 18L wound on the yoke 15L located to the right of the reproducing stylus 25 produces an output voltage on the same principle as in its relocation in vertical directions as described earlier.
  • no output voltage is produced in the coil 18R wound on the left yoke 15R since the armature 7 moves only around the R axis.
  • signals of the two channels are separated.
  • the reproducing stylus is relocated rightward at 45, by contrast, an output voltage is produced in coil 18R, while no voltage is generated in coil 18L.
  • output voltages proportionate to the vector components in the direction of the pole pieces are generated in the coils, thereby making it possible to reproduce stereo sound from the stereo rec'ord disc.
  • FIG. 5 Another embodiment of the invention is illustrated in FIG. 5.
  • the coils 18 are wound on both legs of the yoke 15 and are connected in series so that output voltages thereof are combined with each other.
  • This arrangement permits the output voltage e to be twice as high as the preceding embodiment, whereby it is possible to dampen the noise voltages due to externally leaked noise magnetic fluxes generated in the motor and transformer, thus improving the signal to noise ratio remarkably.
  • FIG. 6 shows an actual example of the construction of the stereophonic pickup cartridge which is obtained from the embodiment of FIG. 5.
  • the yokes 15L and 15R including the pole pieces 16L, 17L, 16R and 17R are injection-molded thereby putting them exactly into place and simplifying their assembly.
  • the yoke-coil unit is housed in the shield case 19 made of an alloy with high magnetic permeability, such as permalloy thereby protecting the unit from the external magnetic fields.
  • the shield case 19 is fixed on the housing 20 with the ends of the coils 18L and 18R connected with the terminals 21 respectively.
  • the parts of the vibration system are mounted on the stylus holder 22 and fitted replaceably in the housing 20, thereby securing them in place with respect to the pole pieces 16L, 17L, 16R and 17R and at the same time facilitating the replacement of the stylus 25.
  • the damper 23 which is interposed between the armature 7 and the support 11 controls the vibration system including the reproducing stylus 25, stylus arm 26 and armature 7.
  • the vibration system is attached to the cartridge from under the yokes 15R and 15L, which makes possible a small and accurate vertical tracking angle, while at the same time minimizing the occurrences of vertical tracking errors.
  • the armature 7 is displaced toward the pole piece 17 by a length corresponding to the static compliance of the supporting portion by the bias force due to the stylus pressure. To prevent this undesired displacement of the armature 7, it is recommended that the shape of the damper 23 should be deformed in the direction of the bias force or such other necessary steps should be taken to correct the dislocation in advance.
  • the output voltages generated in the coils 18R and 18L wound on the yokes R and 15L are proportional to the vibration velocity of the armature 7 with respect to the pole pieces 16 and 17 or the vibration displacement of the armature 7 under the same frequency. Therefore, in order to obtain a high output, the armature 7 may be enlarged in the direction perpendicular to its thickness, that is to say, the diameter of the armature 7 may be increased. By so doing, the shortcircuited magnetic fluxes as shown by arrow A in FIG. 3a are reduced thereby improving the magnetic efficiency.
  • FIGS. 7a and 7b respectively illustrate the construction of its essential parts and a perspective view.
  • the pickup is of the monaural type and the yokes 15a and 15b are disposed on both sides of the armature 7 in parallel with the surface of the record disc 24, the coils 18a and 18b being wound on the yokes 15a and 15b respectively.
  • the reproducing stylus 25 changes its position as shown in FIG.
  • the magnetic fluxes in the yokes 15a and 15b flow in the directions of arrows E and E respectively and the coils wound on the yokes are connected in series so that output voltages e and e induced in the coils 18a and 18b are added to each other. It is of course possible that the coils 18a and 18b are wound respectively in a pair on the yokes 15a and 15b to cancel external leakage magnetic flux.
  • This arrangement of the yokes 15a and 15b on both sides of the armature permits an output two or four times higher than the preceding embodiments to be produced, and excellent signal to noise ratio.
  • FIGS. 80 and 8b Still another embodiment of the invention in the form of a stereo pickup cartridge of the 45-45 type is shown in FIGS. 80 and 8b.
  • a pair of yokes 15L are disposed on both sides of the armature 7 along the L axis, and coils 18L which are wound on the yokes are connected in series to produce an output voltage eL.
  • a pair of yokes 15R are placed opposite to each other with the armature 7 interposed therebetween on the R axis at right angles to the L axis, and coils 18R which are wound on the yokes 15R are connected in series so that the output voltages eR in both coils are superimposed on each other.
  • each yoke may be wound with a pair of coils for the total number of 8 coils.
  • the vibration system comprising the reproducing stylus 25, stylus arm 26 and armature 7 should preferably be inserted into the gap among the oppositely placed yokes 15R and 15L.
  • the pickup cartridge according to the present invention comprises a permanent armature of a flat plate magnetized such that the same pole is set up on both sides in the direction of thickness while the opposite pole is formed in the central portion thereof and 'a stylus arm with a reproducing stylus attached to its end, wherein the vibration system is so constructed that the main axis of the stylus arm is connected to and pivotally supported in the neighborhood of the center of gravity of the armature in the direction of its magnetic axis so as to vibrate the peripheral portions of the armature in response to the vibration of the reproducing stylus in accordance with the contour of the grooves of the record disc.
  • the two pole pieces at the ends of the inverted channel-shaped yokes of magnetic material are placed in the proximity of the armature, the legs of the yokes being wound each with at least one coil, thereby making up at least one magnetic circuit.
  • output voltage is generated by alternation of magnetic fluxes supplied by the inverted channel-shaped yokes in combination with the armature which is magnetized in the transverse direction of the flat plate so as to set up magnetic fields of the same polarity on both sides thereof, resulting not only in a high transducing efficiency but in a high output voltage and reduced distortion thereof.
  • the stylus arm with the reproducing stylus attached to it is pivot-supported at a fulcrum located at or in the neighborhood of the center of gravity of the armature, both moment of inertia and the effective mass of the vibration system are decreased. This results in a higher limit of frequency range and in a lower mechanical impedance, whereby it is possible to obtain a pickup cartridge of such a superior quality that vibration transmitted from the disc grooves by a low stylus pressure is used for voltage generation. Furthermore, the advantage that two coils may be wound on a single yoke permits external leakage magnetic field to be cancelled, while at the same time increasing an output voltage and reducing noise voltages, resulting in a high signal to noise ratio.
  • the arrangement of the invention allows the vibration system or stylus assembly to be mounted from under the yoke assembly, which makes possible a smaller vertical tracking angle as well as an appropriate value thereof, minimizing the tracking error in the vertical direction and facilitating the replacement of the reproducing stylus.
  • the magnetic circuit incorporated in the invention is so simple that the cartridge can be assembled at low cost and with high precision.
  • a pickup cartridge comprising an armature comprising a permanent magnet of a flat plate magnetized in the axial direction in the same polarity on both outer sides and in the opposite polarity at the central portion boundary plane, a stylus arm coupled to said armature, a stylus mounted on the end of said stylus arm, a yoke of the substantially inverted channel shape and a coil wound on said yoke, said armature being supported approximately at its center of gravity, said stylus arm being movable in all angular directions, said yoke having a pair of pole pieces disposed in the proximity of said armature.
  • a pickup cartridge according to claim 1, wherein said armature in the form of a flat plate consists of two flat magnet plates which are bonded with each other 7 and magnetized in the axial direction in such a manner that portions of one polarity of the respective magnet plates are brought into contact with each other.
  • a pickup cartridge comprising a pair of substantially inverted-channel shaped yokes disposed in the proximity of the outer periphery of said armature, said yokes being wound with coils connected in series with each other.
  • a pickup cartridge according to claim I comprising a pair of substantially inverted channel-shaped yokes disposed at right angles to each, other in the proximity of the outer periphery of said armature.
  • a pickup cartridge according to claim 1 in which said armature is provided with a section in the shape of a semicircle,
  • a stereophonic pickup cartridge comprising an armature of a flat disc-shaped magnet magnetized in its axial direction and having magnetic poles of the same polarity set up on both outer sides and magnetic poles of the opposite polarity formed in its central portion at the boundary plane, a stylus arm coupled to said armature, a stylus mounted on the end of said stylus arm, a support member with a notch portion for supporting said armature approximately at its center of gravity, a damper of elastic material interposed between said armature and said support member for allowing said stylus arm and said armature to vibrate around said center of gravity, a pair of substantially inverted channelshaped yokes disposed at right angles to each other for effecting stereophonic reproduction from a stereophonic grooved sound record and coils wound on said yokes, said yokes being provided with pole pieces at their ends disposed in the proximity of the outer periphery of said armature.
  • a stereo pickup cartridge comprising four inverted channel-shaped yokes placed at right angles to each other in the proximity of the outer periphery of said armature, wherein coils wound on each of pairs of said yokes arranged at to each other are connected in series.
  • a pickup cartridge according to claim 8 in which said armature is provided with a section in the shape of a semicircle.
  • a pickup cartridge according to claim 8 in which said armature is provided with a section in the shape of a V.
  • a pickup cartridge according to claim 8 in which said armature is provided with a section in the shape of a 13.
  • said disc-shaped magnet comprises two disc-shaped axially magnetized plates, said plates being bonded to each other at surfaces of like polarity.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Moving Of Heads (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
US00218983A 1971-02-23 1972-01-19 Pickup cartridge with magnet armature having opposite axial sides of like polarity and central portion of opposite polarity Expired - Lifetime US3763335A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP46008791A JPS4937527B1 (ja) 1971-02-23 1971-02-23

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US (1) US3763335A (ja)
JP (1) JPS4937527B1 (ja)
CA (1) CA952823A (ja)
FR (1) FR2126218B1 (ja)
GB (1) GB1381888A (ja)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USB365841I5 (ja) * 1972-07-20 1975-01-28
US3878342A (en) * 1972-08-18 1975-04-15 Fonofilm Ind A S Replaceable stylus for stereophonic phonograph pickup
US3983335A (en) * 1973-11-27 1976-09-28 Kabushiki Kaisha Audio-Technica Stylus assembly and transducer using same
US3991284A (en) * 1973-01-25 1976-11-09 Karl Braun Gramaphone pickup
US4004108A (en) * 1974-06-11 1977-01-18 Pioneer Electronic Corporation Armature for sound pick-up cartridge
US4031336A (en) * 1975-02-10 1977-06-21 Grado Joseph F Electromagnetic pickup with magnetic gap displacement generator
US4072823A (en) * 1975-06-06 1978-02-07 Kabushiki Kaisha Mitachi Onkyo Seisakusho Moving magnet pickup cartridge
US4209669A (en) * 1977-12-23 1980-06-24 Nippon Columbia Kabushikikaisha Pick-up cartridge
US4320487A (en) * 1980-09-23 1982-03-16 Rca Corporation Video disc stylus control apparatus
US4524439A (en) * 1980-04-08 1985-06-18 Victor Company Of Japan, Limited Electromagnetic pickup cartridge with flux sensors mounted above moving magnet

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5487504A (en) * 1977-12-23 1979-07-12 Alps Electric Co Ltd Electromagnetic pickup cartridge

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610259A (en) * 1946-06-21 1952-09-09 Int Standard Electric Corp Electromagnetic vibratory device
CH478502A (de) * 1967-06-20 1969-09-15 Audio Technica Kk Tonabnehmerkopf für stereophonische Schallplattenwiedergabe
US3627931A (en) * 1968-01-23 1971-12-14 Nippon Columbia Moving magnet type stereo pickup

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2610259A (en) * 1946-06-21 1952-09-09 Int Standard Electric Corp Electromagnetic vibratory device
CH478502A (de) * 1967-06-20 1969-09-15 Audio Technica Kk Tonabnehmerkopf für stereophonische Schallplattenwiedergabe
US3627931A (en) * 1968-01-23 1971-12-14 Nippon Columbia Moving magnet type stereo pickup

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USB365841I5 (ja) * 1972-07-20 1975-01-28
US3925628A (en) * 1972-07-20 1975-12-09 Electroacustic Gmbh Electromagnetic sound pick-up
US3878342A (en) * 1972-08-18 1975-04-15 Fonofilm Ind A S Replaceable stylus for stereophonic phonograph pickup
US3991284A (en) * 1973-01-25 1976-11-09 Karl Braun Gramaphone pickup
US3983335A (en) * 1973-11-27 1976-09-28 Kabushiki Kaisha Audio-Technica Stylus assembly and transducer using same
US4004108A (en) * 1974-06-11 1977-01-18 Pioneer Electronic Corporation Armature for sound pick-up cartridge
US4031336A (en) * 1975-02-10 1977-06-21 Grado Joseph F Electromagnetic pickup with magnetic gap displacement generator
US4072823A (en) * 1975-06-06 1978-02-07 Kabushiki Kaisha Mitachi Onkyo Seisakusho Moving magnet pickup cartridge
US4209669A (en) * 1977-12-23 1980-06-24 Nippon Columbia Kabushikikaisha Pick-up cartridge
US4524439A (en) * 1980-04-08 1985-06-18 Victor Company Of Japan, Limited Electromagnetic pickup cartridge with flux sensors mounted above moving magnet
US4320487A (en) * 1980-09-23 1982-03-16 Rca Corporation Video disc stylus control apparatus
FR2490906A1 (fr) * 1980-09-23 1982-03-26 Rca Corp Dispositif de controle de l'aiguille d'un videodisque

Also Published As

Publication number Publication date
JPS4937527B1 (ja) 1974-10-09
FR2126218A1 (ja) 1972-10-06
DE2208292B2 (de) 1976-05-26
DE2208292A1 (de) 1972-09-07
FR2126218B1 (ja) 1976-01-16
CA952823A (en) 1974-08-13
GB1381888A (en) 1975-01-29

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