DE2007469A1 - Magnetic stereo pickup - Google Patents

Description

i-; ijji. ~ ing. Heinz L-: .'ν λ. -

Patent attorney

D-8 Munich 26, P.O. Box 4
Phone 0811/292555

69,151
/

2007460

Munich, February 18, 1970

My reference: P 902

F0H0FILM IHDUSTRI A / S

Drumstick 5

1614 Copenhagen / Denmark

Magnetic stereo pickup

The invention relates to a magnetic stereo pickup with a magnetic unit that has at least two magnetic Conductor as well as one or more permanent magnets, and in which unit one with a needle arm fixed armature is arranged movably in such a way that its movements are dependent on the plane of movement Bring out flux changes in the two magnetic conductors. The two magnetic conductors generally exist from four plate or strip-shaped legs, which in cross-section form the sides of a square, and between the free ends of the anchor arranged in this way is that the two channels in the sound groove on a stereo record scanned by the ladel the anchor in the Level of each pair of opposing legs

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let it oscillate, whereby the fluxes in the legs change, so that one in each of the windings Signal voltages representing the sound channel are induced.

In the first pickups of the type mentioned existed the anchor itself made of a permanent magnet; the increasing demands on the reproduction of signals at the top However, the end of the audio frequency spectrum has to develop guided by pickups in which the effective needle mass is reduced by the fact that the magnetizing Force is generated by a permanent magnet arranged outside the oscillating needle system. The armature can consist of a very light tube made of magnetically conductive material, for example soft iron. at A known construction of this type uses a rod-shaped permanent magnet, one end of which is sealed is attached to the outer end of the anchor, which thus is magnetized by the lines of force of the permanent magnet and thereby acts itself as a magnet from which distribute the lines of force between the legs depending on the needle position so that flow changes occur in the legs in time with the needle movements. Since all lines of force have to end at the other pole of the bar magnet facing away from the four legs, they have to travel relatively long airways. As a result, the pickup is surrounded by a magnetic stray field that prevents it from being present in the environment.

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send magnetic objects sensitive. Due to the asymmetrical position of the bar magnet in the In relation to the armature or to the legs, the magnet will continue to have a certain force of attraction on the armature exercise, which is thus biased in a certain direction, and the ratio between the needle deflection and the resulting changes in flow in the limbs will depend on the plane in which the rash occurs. As a result, the signal amplitudes are not in the correct ratio unless specific corrective hate statements are made.

The object of the invention to provide a stereo pickup of the kind in which the Hagnet or Hagnete arranged iin-t, aaäs egg or they nictn enter into the vibrating needle ground, thereby but a symmetrical construction of the magnetic unit and thus also more symmetrical magnetic fields that do not bias the armature are made possible.

This purpose is achieved in that the permanent magnet or the permanent magnets are designed and converted in this way the armature are arranged that four magnet parts magnetized parallel to the armature each on one side of the Anchors are opposite each other in pairs and that the magnetic conductor is the connection between the same named Make poles from one pair of magnet parts each. With this construction, the anchor also forms

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one way with relatively little resistance for the magnetic lines of force, so that the stray field from the magnet or magnets is correspondingly weak will. The armature will, so to speak, cause a magnetic short circuit of the permanent magnet or permanent magnets. When the armature is in its neutral center position, it becomes all four magnet parts mainly load the same amount. The pole faces of the magnet parts therefore have essentially the same magnetic properties Potential. This means that in this state no flux will pass through the magnetic conductors. When the armature oscillates in the plane determined by two opposing magnetic parts, the one becomes magnetic Resistance in the armature flux path against the flux from one magnet part is reduced and the resistance against the Flux from the other magnetic part can be increased. The short circuit flow through the armature from one magnetic part will thus rise, with the result that the magnetic The potential of the pole face of this magnet falls, while the short-circuit flux from the other magnet part decreases which increases the magnetic potential of the pole face of this magnet. There is thus a of the magnetic potential difference dependent on the Vadel movement between the two ends of the magnetic conductor connected to the relevant magnet parts, whereby a flux is produced in this conductor which generates an electromotive force in the conductor winding

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induced, which represents the signal corresponding to the needle movement.

A structurally simple embodiment of the pickup according to the invention is present if the magnetic conductors consist of four legs, mainly parallel to the armature axis, which on one side End are connected in pairs and at the other end of the armature is attached, the permanent magnet or the permanent magnets are arranged at the free ends of the legs that the mentioned magnetic Parts are in extension of these. A bar magnet can be conveniently attached to the free 1 "Ad e of each leg arrange.

A more advantageous one in terms of production technology Construction is achieved, however, that the pickup has an annular, in the axial direction magnetize magnet made of ceramic, magnetic possesses anisotropic material. Such an annular magnet has a relatively high permeability in the axial direction, special a very low permeability in a right-angled direction on it and becomes therefore act as a separate magnet on each leg in relation to the pole legs.

Since, as I said, no river passes through the thighs, when the armature is in its neutral position, the magnetic working point is for these legs around the zero point of the hysteresis loop

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move, and the legs can therefore be made of thin rods made of highly permeable material, for example Permalloy, be produced without the risk that the working point is outside the straight part the very steep magnetization curve, what a Distortion of the signal reproduction. This means that the windings have small dimensions and a relatively short wire length obtained with resulting low resistance and low capacitance.

A particularly simple and inexpensive construction can be achieved by making the legs cylindrical. This construction is a break with the technical tradition that the use of plane-parallel or has prescribed pole faces conforming to the armature.

The total magnetomotive force in the short-circuit or load flux path can be increased by that the armature of the pickup according to the invention consists of one, the surrounding fixed magnet parts opposite oriented permanent magnet exists or contains such. It is true that at the same time the reluctance of the armature increases, but since the entire reluctance in the circuit comes mainly from the air gaps, plays the increased anchor reluctance plays a relatively minor role. As a net profit is also a certain increased Pickup sensitivity guaranteed.

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The invention is explained in more detail below with reference to the drawing. Show it

Pig. 1 shows a longitudinal section through an embodiment of the pickup according to the invention)

Mg. 2 a section along the line II-II in Fig. 1,

Pig. 3 shows in perspective the front end of the magnetic system and that therein arranged needle unit and

Pig. 4 half of the

magnetic system with the armature in neutral position.

The one in Pig. Pickup shown 1-3 has a molded of a suitable plastic material casing 1. At one end of the housing is a recess 7 provided in which a Kontaktst "r> 2 with four pin connectors. 3 - of which only two in Pig 1 shown siiv. At the other end of the housing a replaceable needle unit is arranged, which has a cast plastic support body 4 which engages with a protruding, hollow control pin 5 of non-circular cross-section in a recess 6 of the same cross-section in the housing 1.

A continuous one extends between the bottom of the recess 7 and the front of the housing 1 Recess which has a rear part 8 of mainly square cross-section and a front part 9, its cross-section as in Pig. 2 shown the shape of a

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Center circle and four along its circumference evenly distributed edge circles tangent to the center circle.

This continuous recess 8, 9 is used to accommodate the magnetic system, which consists of four cylindrical legs made of permalloy, the front parts of which each lie in a cylindrical edge part of the recess and extend backwards through the recess 8. The rear ends of the legs 10 are fastened to one another by a cross piece 11, which is also made of permalloy, and are magnetically connected to one another. A coil 12 located in the recess 8 is arranged on each leg 10. All diametrically opposite coil pairs are connected to one another and to two of the pin plugs 3 by lines 13. At the front end of the legs 10 and in extension of these, an annular permanent magnet 14, magnetized in the axial direction and made of ceramic, magnetically anisotropic material, is provided. The magnet 14 lies in an extension of the recess 9 on the front side of the housing 1. λ ■

In the lower part of the support body 4 of the needle assembly is an inclined, cylindrical, continuous channel formed, which opens out on the underside of the body and an extension of the recess 9 of the housing 1 forms. In this channel 15 is a non-magnetic Material, such as aluminum, attached to the existing pipe that protrudes from the support body 4 and when

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Attachment of the needle assembly in the housing 1 in the cylindrical Middle part of the recess 9 is introduced.

In the tube 16 is made of soft iron, tubular anchor 17 by means of an annular, elastic Cushion 18 made of, for example, rubber or neoprene mounted in such a way that it is in all directions around an in or point near the center of the pillow. The anchor 17 is much longer than the ring magnet 14 and is coaxial and symmetrical in relation to it. At the anchor, one end is one tubular, thin-walled needle arm 19 made of aluminum, which goes through the channel 15. That The free end of the needle arm 19 lying outside the support body 4 is pressed flat and bears a rebuke

On the underside of the housing 1 is a magnetic one Screen 21 attached, which extends between the housing and the support body 4 of the needle unit over the front of the housing extends.

For an explanation of how the pickup works, see Pig. 4 schematically one half of the electromagnetic System corresponding to the one sound channel shown in a stereo recording. The point of oscillation of the armature is denoted by 22 here. Since the anisotropic ceramic ring magnet 14 has a high magnetic resistance perpendicular to the axial direction in all directions, it is in magnetic relationship with two Rod permanent magnets equivalent, which as shown in Fig. 4

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shows are arranged at the end and in extension of each leg IO, it being assumed that the north poles of these magnets are facing the thighs. By assuming that the two magnets are the same are strong, in the shown neutral position of the armature 17, the magnetic potential of the two end faces of the existing of the legs 10 and the cross piece 11 magnetic conductor be the same, and it will therefore no river can pass through this ladder. In contrast, a relatively high flow from the North Pole becomes each Magnet go through the armature to the south pole of the magnet, as indicated by the dash-dotted lines. Because the armature has a much lower magnetic resistance than the ceramic magnets and because they are implied Air gaps are very small in practice, this flow can be seen as a short-circuit flow are designated.

If the anchor is now due to the needle movement, for example upwards in the plane of the paper around point 22 vibrates, it will approach the upper magnet, reducing the resistance in its short-circuit path, and at the same time move away from the lower magnet, whose short-circuit flux thus encounters increased resistance In other words, the upper short-circuit flux is increased and the lower one is decreased. Because of the proportional high internal resistance of the magnets will do this

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result in the magnetic potential at the north pole of the upper magnet falls, while the magnetic potential at the north pole of the lower magnet rises. Bs arises thus a magnetic potential difference between the two ends that is dependent on the armature movement of the magnetic conductor 10, 11, 10, which is why a flux is produced in this conductor, which in the windings 12 electrical voltages are induced, which are added and represent the sampled sound signal.

Armature vibrations originating from the other sound channel occur in the plane which is perpendicular to the paper and become electrical in the other half of the electromagnetic system lying in this plane Tensions converted.

Since the magnetic conductor 10, 11, 10 is only intended to carry the useful signal flow that is associated with the armature deflections changes direction, the legs 10 can be made very thin without the magnetic Working point outside the straight line part of the magnetization curve device.

The structural details of the cartridge shown and described can be included within the scope of the invention change many times. Thus, the legs 10 can, for example, instead of the circular cross-section shown have a square or rectangular cross-section. The anchor can also have other cross-sectional shapes have and can possibly from one, the surrounding solid

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Permanent magnet parts oppositely oriented permanent magnet exist or contain such, the north pole of the permanent magnet thus opposite the south pole of the mentioned parts lies or vice versa.

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Claims (7)

- 13 patent application. O3ae Magnetic stereo pickup with a magnetic unit that contains at least two magnetic conductors each enclosed by a winding and one or more permanent magnets, and in which unit an armature firmly connected to a needle arm is movably arranged in such a way that its movements are dependent on the plane of movement in the flux changes produce two magnetic conductors, characterized in that the permanent magnet or the permanent magnets are designed and arranged around the armature sis-d that four magnet parts magnetized parallel to the armature are opposite each other in pairs on one side of the armature and that the magnetic conductors establish the connection between make the pole of the same name from each pair of magnet parts. 2. Magnetic stereo pickup according to claim 1, in which the magnetic conductors consist of four legs mainly parallel to the armature axis, which are connected in pairs at one end and the armature is attached to the other end, characterized in that the permanent magnet or magnets are arranged at the free ends of the legs that the mentioned magnetic parts are in extension of these. 009841/1091 2007460 3. Magnetic stereo pickup according to claim 2, characterized in that a rod magnet is arranged at the free end of each leg. 4. Magnetic stereo pickup according to claim 2, characterized in that it has an annular, magnetized in the axial direction magnet made of ceramic, magnetically anisotropic material. 5. Magnetic stereo pickup according to claim 2, 3 or 4 » characterized in that the legs consist of thin rods made of highly permeable material, such as permalloy. 6. Magnetic stereo pickup according to any one of claims 2-5 » characterized in that the legs are cylindrical. 7. Magnetic stereo pickup according to any one of the preceding claims, characterized in that the armature consists of a permanent magnet oriented in opposite directions to the surrounding, fixed magnet parts or contains such a magnet. 0 09841/1091