US3924076A - Electromagnetic phono cartridge - Google Patents

Electromagnetic phono cartridge Download PDF

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Publication number
US3924076A
US3924076A US425852A US42585273A US3924076A US 3924076 A US3924076 A US 3924076A US 425852 A US425852 A US 425852A US 42585273 A US42585273 A US 42585273A US 3924076 A US3924076 A US 3924076A
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United States
Prior art keywords
permanent magnet
segment
stylus
armature
cantilever
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US425852A
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English (en)
Inventor
Roger Dubois
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HUBER AND CO
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HUBER AND CO
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Publication date
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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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/16—Mounting or connecting stylus to transducer with or without damping means
    • H04R1/18—Holders for styli; Mounting holders on transducers
    • 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

Definitions

  • ABSTRACT [30] Foreign Application Priority Data
  • a stylus for an electromagnetic phono cartridge which May 29 1973 Switzerland 7753/73 comprises a tubular ferromagnetic armature mounted on the flat side of a permanent magnet.
  • the armature 152 0.5. c1.
  • 179/100.41M* 179/100 41 14 extends axially from the Permanent mgne 51 1111.0.
  • H04R i1/12 cantilever the opposite direcmn-
  • the Permanent [58]
  • Field 61 Search 179/10041 .1 100.41 K magret is used inside "Onmagnetizable 179/100 274/37 which is located between a pair of pole pieces having coils in the phono cartridge.
  • a flexible sleeve covers [56] References Cited the entire circumference of the outer narrow side of the permanent magnet to hold the stylus in the non- UNITED STATES PATENTS magnetizable Shell. 3,349,194 10/1967 Shaper 179/100.41 1 3,356.795 12/1967 Shaper 179/10041 K 10 ClaImS- 4 Drawmg Flgures US. Patent Dec. 2, 1975 3,924,076
  • the present invention relates to a stylus for an electromagnetic phone cartridge, with an armature containing a lamellar permanent magnet magnetized in the axial direction, the magnet being connected to a cantilever provided with a stylus tip or needle.
  • Prior styli of the above type have as a armature a permanent magnet consisting of a flat plate, magnetized with the same polarity on both outer sides and with opposite polarity at the center. Furthermore, the cartridge is provided with at least one essentially inverted ring-shaped yoke, a pair of pole pieces mounted in the vicinity of the armature and a coil wound around the yoke.
  • the cantilever supporting the stylus tip has an axial extension as a mount, the extension being linked to the cantilever or to the permanentmagnetic plate by means of an elastic connection, in such fashion that the plate moves essentially with its central section as the working point.
  • An object of the present invention is to overcome the defects in the prior art, such as indicated above.
  • Another object is to provide for improved electromagnetic phone cartridges.
  • Another purpose of the present invention is to further reduce the inert mass of the armature which constitutes the moving part of a cartridge, and, simultaneously, to produce a mount for the stylus which is light, has low friction, and which results in a cartridge with a small cross section.
  • the stylus described below uses permanent magnetic materials with a high coercive force and high magnetic energy, for example Samarium-cobalt (Sm-Co), which has a coercive force H of 4 to kOe and a magnetic energy B.H. of approximately 18 kOe/g.
  • Sm-Co Samarium-cobalt
  • the stylus according to the instant invention is characterized by a tubular ferromagnetic armature which is mounted on one face of the permanent magnet.
  • the armature extends out coaxially from the permanent magnet to the abovementioned cantilever in the opposite direction.
  • the permanent magnet is provided on its outer narrow side over its entire circumference with a flexible sleeve to hold the stylus in a shell which is non-magnetizable and is located between the pole pieces of the cartridge, the pole pieces being provided with coils.
  • FIG. 1 is a lengthwise cross-sectional view through a stylus made according to the instant invention, without the stylus tip holding element.
  • FIG. 2 is a side elevational view of the stylus shown in FIG. 1.
  • FIG. 3 is a front elevational view of the stylus in FIG. 2 mounted in a housing located between a plurality of pole pieces.
  • FIG. 4 is a lengthwise cross sectional view of the arrangement shown in FIG. 3, including the magnetic lines of force.
  • the illustrated stylus has a disc-shaped permanent magnet l, which may consist, for example, of the initially mentioned samariumcobalt or a similar permanent magnetic material with high coercive force and high magnetic energy.
  • a tubular armature 2 is attached to one end face of the permanent magnet l, the armature 2 being made, for example, of Armco iron.
  • Armature 2 has a first segment 3, whose axial length is at least approximately equal to the thickness of permanent magnet 1 and whose outer diameter is equal to the outer diameter of permanent magnet l.
  • the end face of the first segment 3 of the armature 2 is fastened to the end face of permanent magnet 1 by means of a suitable adhesive layer 4, e.g., an
  • a second segment 5 of the armature 2 is connected to the first segment 3 of the tubular armature, the second segment having an outside diameter and wall thickness less than those of the first segment 3, but whose axial length is greater than that of the first segment.
  • the ratio of the diameter of the permanent magnet l to its thickness is in the range from 2 to 10, while the ratio of the axial length of the tubular armature section 2 to the thickness of the permanent magnet is in the range from 4 to 10.
  • the outside diameter of the permanent magnet 1 may be 25 mm and its thickness 0.5 mm, while the armature section 2 then may have a length of 2.5 mm.
  • the transition 6 from the first segment 3 with the larger outside diameter to the second segment 5 with the smaller outside diameter is advantageously continuous, as can be seen from FIG. 1 and 2.
  • the permanent magnet 1 has a central bore whose diameter is equal to that of the bore of the first segment 3 of tubular armature section 2.
  • This common central opening contains a tube section 8, made of a light metal and fastened in place, such as by epoxy resin.
  • Tube section 8 serves, on the one hand, to accept a tubular cantilever 9 made of a light metal alloy (e.g. a magnesium alloy which is pushed onto tubular section 8 and fastened to the latter (see FIG. 2).
  • the free end of cantilever 9 is fitted with a stylus tip 10, preferably a diamond needle.
  • the tube section 8 serves, on the other hand, as a mount for a wire spring 11 whose function will be described below.
  • the spring 11 is fastened centrally in tube section 8 by means of a drop of adhesive 12.
  • the stylus described in FIG. 1 and 2 is pushed into a shell with a square cross section (shown in FIG. 3) when the phono cartridge is assembled, the shell being made of a nonmagnetizable material, e.g., brass.
  • the four points of support 14 of elastic sleeve 7 on the internal surface of shell 13 ensure a free movement, hindered only by extremely low frictional forces, of cantilever 9 supporting stylus tip 10 in a conical region whose apex is located at the center of the common plane of permanent magnet 1 and the first segment 3 of the tubular armature section 2.
  • this stylus is made so that this point is simultaneously the center of gravity of the stylus.
  • FIG. 3 also shows the pole discs and 16, each associated with the core of the magnet, arranged in pairs on the outside of the shell 13, said pole discs extending lengthwise along the shell 13 and connected together in known fashion by yokes, said yokes each carrying one coil in which voltages are induced when cantilever 9 is deflected.
  • stylus tip 10 moves in mutually perpendicular directions 17 and 18 in accordance with the two recording channels, so that, as will be described below, the magnetic flux in the pole pieces 15 and 16 changes.
  • the stylus tip moves in a horizontal direction 19, so that the same change in flux is caused in two mutually perpendicular pole pieces 15 and 16.
  • FIG. 4 shows a lengthwise cross-sectional view of the arrangement shown in FIG. 3 at a 45 angle.
  • FIG. 4 shows a portion of the stylus according to FIG. 1 and 2 with permanent magnet 1, the tubular ferromagnetic armature section 2 which consists of segments 3 and 5, flexible sleeve 7 and cantilever 9 are visible.
  • the stylus is held by means of the flexible sleeve 7 in the nonmagnetizable square shell 13 which is mounted in turn between a pair of pole pieces 15. It can also be seen from FIG. 4 that the free end of the wire spring 11 is connected to the shell.
  • the wire spring 11 is clamped firmly in place by means of plate 20 which is made of an insulating material that is pressed into shell 13.
  • Spring 11 serves to compensate for the weight of the tone arm when the stylus tip rests on the record.
  • the free end of the spring is fastened to the opposite side of the point of the stylus tip 10 with respect to the lengthwise axis of the stylus at shell 13.
  • FIG. 4 also shows that both pole pieces 15 constitute portions of a magnetic core which has a yoke 21 on which a coil 22 surrounding the yoke is fastened in known fashion.
  • a magnetic core arrangement mounted in the phono cartridge in the same fashion contains pole pieces 16 in FIG. 3.
  • the pattern of the magnetic field or magnetic flux is represented schematically by individual lines.
  • Permanent magnet l is magnetized in the axial direction so that armature section 2 is likewise magnetized in the axial direction.
  • the corresponding magnetic poles are represented by N and S.
  • the useful magnetic field represented by lines of force 24 runs from the indicated North pole of permanent magnet l with equal amplitude to each pole piece 15 and from the letter to the South pole of the free end of the tubular armature section 2.
  • the magnetic field is therefore completely symmetrical with respect to pole pieces 15 when the stylus is at rest.
  • the present stylus has a mass which is much less than that of known styli for electromagnetic phono cartridges, especially as far as the mass of the armature is concerned.
  • the permanent magnet 1 and the contiguous segment 3 of the tubular armature have circular or cylindrical shapes, while the nonmagnetizable shell 13 has a square internal cross section. It is naturally possible to reverse these shapes although it is less simple to do so.
  • An electromagnetic phono cartridge comprising:
  • a lamellar axially magnetized permanent magnet said permanent magnet having a flat side, an outer circumferential narrow side and an end face; non-magnetic cantilever provided with a stylus tip connected to said permanent magnet; ferromagnetic armature tube directly mounted on the end face of said permanent magnet, said armature extending coaxially from the permanent magnet to the cantilever in the opposite direction, and wherein said armature tube includes a first segment connected to the end face of said permanent magnet, said first segment having transverse dimensions approximately equal to those of said permanent magnet; flexible sleeve means for covering the entire circumference of the outer narrow side of said permanent magnet; nonmagnetizable shell means having an inner surface and housing said permanent magnet, said armature and a portion of said cantilever adjacent said permanent magnet; said flexible sleeve means being in contact with said inner surface of said shell means at a plurality of points for supporting said permanent magnet, armature and cantilever; and
  • pole pieces substantially enclosing said shell means, said pole pieces including coils in the phono cartridge.
  • said armature tube has a second segment, said second segment having external cross sectional dimensions and a wall thickness less than those of said first segment and having an axial length greater than that of said first segment, wherein the axial length of the first segment is approximately equal to the thickness of the permanent magnet.
  • said cantilever includes a tubular member of light metal and wherein said permanent magnet and said first segment of said armature tube each have a central bore, said tubular member being fastened within said bores.
  • the stylus of claim 7, comprising a spring having an outer end fastened to said tubular member, said outer end of said spring being connectable with said nonmagnetizable shell means.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electromagnetism (AREA)
  • Electromagnets (AREA)
US425852A 1973-05-29 1973-12-18 Electromagnetic phono cartridge Expired - Lifetime US3924076A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH775373A CH567856A5 (is") 1973-05-29 1973-05-29

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4140321A (en) * 1978-04-04 1979-02-20 Pickering & Company, Inc. Phonograph cartridge replaceable stylus assembly
US4494227A (en) * 1981-04-13 1985-01-15 U.S. Philips Corporation Stereo phono pick-up and/or cutter
US20040196775A1 (en) * 2001-05-21 2004-10-07 Frank Schroder Spring-suspension magnetically stabilized pick-up arm
US20050141358A1 (en) * 2003-12-29 2005-06-30 Lg Electronics Inc. Optical pick-up actuator

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3964751A (en) * 1975-07-31 1976-06-22 Pickering & Company, Inc. Phonograph cartridge replaceable stylus assembly

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3349194A (en) * 1962-12-31 1967-10-24 Dyna Empire Inc Magnetic phonograph pickup utilizing off center mounting of armature
US3356795A (en) * 1964-11-05 1967-12-05 Dyna Empire Inc Stereophonic magnetic phonograph pickup cartridge
US3463889A (en) * 1957-10-30 1969-08-26 Shure Bros Moving magnet stereophonic pickup
US3538266A (en) * 1967-10-06 1970-11-03 Micro Seiki Co Ltd Magnetic pickup with inducing magnet axially aligned with the armature
US3576955A (en) * 1967-08-22 1971-05-04 Matsushita Electric Ind Co Ltd Armature assembly for magnetic-type phonograph pickup
US3761647A (en) * 1968-08-14 1973-09-25 Audio Technica Kk Cartridge for detecting vibrations representing stereophonic sound

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3463889A (en) * 1957-10-30 1969-08-26 Shure Bros Moving magnet stereophonic pickup
US3349194A (en) * 1962-12-31 1967-10-24 Dyna Empire Inc Magnetic phonograph pickup utilizing off center mounting of armature
US3356795A (en) * 1964-11-05 1967-12-05 Dyna Empire Inc Stereophonic magnetic phonograph pickup cartridge
US3576955A (en) * 1967-08-22 1971-05-04 Matsushita Electric Ind Co Ltd Armature assembly for magnetic-type phonograph pickup
US3538266A (en) * 1967-10-06 1970-11-03 Micro Seiki Co Ltd Magnetic pickup with inducing magnet axially aligned with the armature
US3761647A (en) * 1968-08-14 1973-09-25 Audio Technica Kk Cartridge for detecting vibrations representing stereophonic sound

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4140321A (en) * 1978-04-04 1979-02-20 Pickering & Company, Inc. Phonograph cartridge replaceable stylus assembly
US4494227A (en) * 1981-04-13 1985-01-15 U.S. Philips Corporation Stereo phono pick-up and/or cutter
US20040196775A1 (en) * 2001-05-21 2004-10-07 Frank Schroder Spring-suspension magnetically stabilized pick-up arm
US7086071B2 (en) * 2001-05-21 2006-08-01 Schroeder Frank Spring-suspension magnetically stabilized pick-up arm
US20050141358A1 (en) * 2003-12-29 2005-06-30 Lg Electronics Inc. Optical pick-up actuator
US7558164B2 (en) * 2003-12-29 2009-07-07 Lg Electronics Inc. Optical pick-up actuator

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CH567856A5 (is") 1975-10-15

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