US2553715A - Segmented magnetic armature for phonograph pickups - Google Patents

Description

May 22, 1951 2,553,715

SEGMENTED MAGNETIC ARMATURE FOR PHONOGRAPH PICKUPS Filed Aug. 12, 1947 G. L. MII LER 2 Sheets-Sheet 1 INVENTOR v ATTORNEYS May '22, 1951 Filed Aug. 12, 1947 G. L. MILLER 2,553,715

SEGMENTED MAGNETIC ARMATURE FOR PHONOGRAPH PICKUPS 2 Sheet-Sheet 2 azjlzizzer" INVENTOR 1 t BY f I I I 0 ATTORNEYS Patented May 22, 1951 UNITED STATES 1+ PATENT OFFICE SEGMENTED MAGNETIC ARMATURE FOR PHONO GRAPH PICKUPS George L. Miller, Hackensack, N. J.

Application August 12, 1947, Serial No. 768,173

This invention relates to an audio frequency unit which is designed with a novel magnetic circuit for use in recording, or reproducing, phonograph pick-ups but which is easily adaptable for incorporation in earphones, speakers, and other similar actuator equipment.

The primary object of this invention resides in the provision of an improved magnetic circuit unit which will permit a wide variation in armature design.

Another object of this invention lies in the provision of various designed armatures for use with the improved magnetic circuit which extend the resonance of the unit to new limits thereby tending to completely eliminate note distortion and greatly increase the value of all notes especially the higher and lower notes which are greatly distorted and depreciated in value by present day units which cannot handle or control the wide differences in frequency and vibration rates which are encountered by the needle when tracking the average recording. This unit is capable of reproducing very wide ranges at their true tonal qualities with the additional reproduction of the heretofore completely lost overtones.

Still another object of this invention lies in the provision of an audio frequency unit provided with an improved supporting pick-up arm and flexible base therefor which improves the action of the unit and dampens any record noise which would be transmitted to the cabinet.

Still further improvements and objects of this invention will readily appear to those skilled in the art and science when the following description is read in the light of the accompanying,

drawings in which:

Fig. 1 is a side elevation of the pick-up unit.

Fig. 2 is an enlarged vertical section of the magnetic pick-up unit.

Fig. 3 is a vertical section of the arm supporting base.

Fig. 4 is a vertical section taken on line 4-4 of Fig. 2.

Fig. 5 is a horizontal section taken on line 5-5 of Fig. 2.

Fig. 6 is a perspective plan View of the preferred armature construction.

Figs. 7 and 8 are perspective views of modifications -of the armature shown in Fig. 6.

I wish it to be understood that I contemplate any and all modifications of the magnetic circuit and of the flexible armature, which are to be hereinafter set forth, which fall within the scope of the appended claims, together with other 3 Claims. (Cl. 179100.41)

2 structural modifications directed to materials, sizes and general characteristics.

Referring now to the accompanying drawings which are merely illustrative of the invention and in which like characters indicate similar parts throughout, A designates the supporting base for the pick-up arm B which carries at its outer extended end the audio frequency, magnetic, pickup unit 0.

The pick-up arm supporting base A comprises a housing I flanged at its base as at 2 to permit it to be' firmly secured in a phonograph unit. The top of the housing I is provided with a circular opening 3 centrally formed therein and a felt, sponge rubber, or like bushing 4 secured, by a split ring 5, or the like, within said housing beneath and underlapping the opening 3. A tube 6 is vertically seated in the bushing 5 and secured by a flat flange l, resting on the bushing top, and a lock collar 8, secured thereabout beneath the bushing, within the housing.

lhe tube 6 is universally coupled to the'pickup arm B by an extension 9 which'permits the circuit wires 10, from the magnetic pick-up C which are carried within the arm B, to be passed downwardly through the tube 6 into the housing where they are led to the speaker circuit.

The pick-up unit C, which comprises the principal embodiment of this invention, is composed of a hollow rectangular unit housing 20, with one enlarged face thereof being open, which is rigidly affixed to the extended end of the pick-up arm B by a Welded joining of the closed enlarged face vertically with an angularly formed termination of the arm, substantially as illustrated in Fig. 5.

a This arrangement places the open face of the unit housing in a vertical plane away from the arm.

An elongated neutral pole piece 2| of solid, laminated or powdered iron construction, is perpendicularly secured to the contact plate 2| centrally intermediate its height to dispose the pole longitudinally within the housing.

This pole piece terminates at equally spaced distances from the opposed ends of the housing, and is provided with a longitudinal knife-edge 22 projecting slightly beyond the open face of the housing,

A single coil 23 is wound on the neutral pole and lies entirely within the housing. This coil is tied to the circuit wires I0 brought to, the unit.

- housing through the pick-up arm B.

A pair of elongated permanent bar magnets 24 are, placed in the unit housing one adjacent each longitudinal side wall of the housing paralleling the neutral pole piece and each being separated;

tions with their fields opposed, north to south,-

as shown in Fig. 4, this providing a, short magnetic circuit with excellent keeping qualities, while a heavy construction of the central neutral pole 2| will provide a better magnetic saturation of the entire circuit.

Extension pieces 25 are secured to the outer ends of the permanent magnets, exposed at the open face of the housing, which for a spaced distance project transverse the open face overlying a portion of the coil 23 and providing a greater and more positive attraction area to the armature which is to be described.

In audio frequency pick-up units of the same general type as that heretofore described a rigid single piece armature has been used in conjunction with a pair of pole pieces in such a manner as to vibrate therebetween, with needle impulses conveyed thereto, to induce varying E. M. F. in a coil to be converted by a speaker unit to the notes or tones being reproduced from a record. However the resonance reproduction of such a unit is limited by the inability of the rigid armature to accommodate the greatly varied vibrations, When the needle of such a unit encounters a high note, in recording or reproducing, the armature moves at a high rate of speed thereby inducing an extremely high E. M. F. in the coil and causing an over emphasis of the note. Inversely the same is true with a reduced armature action with the lower notes which causes a greatly reduced E. M. F. in the coil and a loss of the low notes. Consequently, the net result of such a unit is a distorted, unbalanced quality of the reproduction, or recording, as a whole.

The armature system that I propose and introduce turns the undesirable characteristics of such a magnetic unit to advantage in providing a unit of substantially unlimited resonance which is free from distortion and which produces high tonal quality.

The structure of this improved unit incorporates an armature or movable element 26 which is composed of a single flexible unit, or two separate units 25a and 26b connected by a flexible linkage with the needle 21 being rigidly connected to thatunit of the two, or portion of the flexible unit, designed to have a higher fundamental period of vibration.

, The Figs. 6 through 8 illustrate the possible constructions of this armature with Fig. 6 disclosing the separate units 26a and 26b, the unit 7 26a being of a lighter construction than unit 261).

When the armature, unit disclosed in Fig. 6 is used in the unit, as shown in Fig. 5, the smaller unit, 25a, is longitudinally balanced on one end portion of the knife-edge 22 of the neutral pole disposing the needle, which is removably carried in a housing D formed integrally with the unit, beyond the unit housing. The second portion, 26b, of the armature is similarly balanced on the remaining portion of the knife-edge with a reduced portion thereof overlying the first portion 26a, being spaced thereabove by a plain rubber spacer 28. The two units are then secured to the neutral. .pole, in their balanced positions, by a pair of studs 29, one of which passes through enlarged holes, which permit the units to seesaw, in the overlapping sections and the spacer '28 into the neutral pole, and the second stud which passes through the enlarged unit into the pole. Each of the studs are provided with sponge rubber or like washers between the armature and their head portions thus providing a damping action but allowing accurate counteraction of the magnetic pull without sacrificing sensitivity of the unit.

The modifications of the armature shown in Figs. '7 and 8 include respectively, a single piece made into a pair of flexible units 30 and 3| by a pair of parallel, overlapping transverse slots 32; and a single unit 33 tapered in thickness throughout its length.

Keeping in mind those armature forms illustrated the operation of the unit is as follows.

As the needle travels its course that section of the armature carrying the needle, and having a greater fundamental vibration period, will follow impulses imparted thereto at all frequencies and, when the needle contacts a high note this first section, having a higher fundamental period of vibration, will follow the exact tone frequency. However, inability of the flexible connection between the sections to follow the great vibration speed of this first section will cause the heavier section, or portion, to remain idle, or substantially so, thus preventing an increase in the coil induced E. M. F. sufficient to cause an overemphasis and distortion of the high note and thereby reproducing the note with superior tonal quality. Inversely with contact of a lower note by the needle the reduced vibration of the first section or portion will produce sufiicient inertia in the flexible coupling to cause vibration of the heavier section, or portion, thus re-enforcing the E. M. F. to produce a true note on the lower scale which otherwise would be lost.

Thus it may be seen that an improved and novel audio frequency magnetic pick-up unit has been provided with the heretofore set forth objects and advantages.

Having thus described and explained the structure and function of this invention what I desire to claim in Letters Patent is:

I claim:

1. An armature for audio frequency magnetic pick-ups comprising a segmented unit the segments of the unit being of different weights, securing the unit to a neutral pole support, and one of said studs connecting the segments of the armature units whereby said segments of the armature have fundamental periods of vibration.

2. An armature for audio frequency magnetic pick-ups, comprising a segmented unit, the segments of the unit being of different weights, the segments being aranged in overlapped spaced relation with respect to each other, and means for securing the segments to a pole piece, whereby the periods of vibration of said armature segments are fundamentally different.

3. An armature or. movable element for frequency magnetic pick-ups, for positioning on a neutral pole piece, comprising a unit embodying a heavy. segment and a substantially light segment, the heavy segment having a cut-away portion in the lower surface thereof extending inwardly from one end thereof, a bolt extending through the heavy segment adjacent to the opposite end thereof, securing the heavy segment to the neutral pole piece, said substantially light segment being disposed within the cutout portion in spaced relation with the surface of the heavy segment, and a bolt passing through the segments connecting the segments with the neutral pole piece, providing a flexible armature with segments having periods of vibration fundamentally diiferent.

"GEORGE L. MILLER.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Hutter Jan. 6, 1931 McClatchie Dec. 8, 1931 Burt Sept. 6, 1932 Niumber f; 1 1,975,907

Sollie Jan. 23, 1934 10 6 Name Date Strauss Oct. 9, 1934 Miller Apr. 14, 1936 Bender Aug. 24, 1937 Edwards June 20, 1939 Thompson Nov. 19, 1940 Bruderlin Oct. 30, 1945 Reason Apr. 16, 1946 Baker June 24, 1947

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