US2499110A - Magnetostrictive phonograph pickup unit - Google Patents

Description

Feb. 28, 1950 s. R. RICH 2,499,110

MAGNETOSTRICTIVE PHONOGRAPH PICKUP UNIT Filed May 15, 1946 INVEN TOR.

STANLEY R. RICH MTTQRNEY Patented Feb. 28, .1950

UNI TiE D ESTATES PATENT OFF-I CE DIAGNEIQSTBICTIVEQHDNQGRABH .PICKUP Sta.1i1ey Rich, Cambridge, 'Mass., assignonto Tcbelneutschmann, .Gantom, Mass.

.Thezpresentfinvention.relatesitotapickup.device :hiwvhich mechanical vibrations .maybeconverted rintossoundtenergy. Themresent'ainuentionis more 'iparticularly applicable :togphonographgpickupidevicesorito-plronograph'rec'ording'.in.wvhichtheroperating selem'errt employs xa-wire .having .maxgneto- .EStI'idti'On properties '..maintained :normally unrder torsional stresses.

The invention is an improvement over my wpending'appiication serial .No. 524362, .filed 0otob'er 125,11945,:-now 'II. S. :PatentiNo. 2 47 1542, :granted May :31, 119.49, and :my application .;No. 26525926 zfiled .:March 8, 21946, new Patent .No.

2484360, :granted October .18, 19 14).

The present "application relates to means and method of construction of the phonograph pickup described 'in the r-aiorementioned applications :ure 1.

Figure 3;shows a detail ofthesmagnetostrictive *Wire unstrained in torsion abet-ore assembled itiie unit, and

Figure A :=shows the wire as assembled in the unit in, its istrained position but without :magnet and case. i

The device indicated in'theiiigures isicontained in :a :case :I :of insulating material which :is T6- -;cesse'd tto receive the .rest of the pickup runit.

The case itself may be moulded of thermosetting resins, hard rubber or other material and while rectangular in shape, may be formed with inner projections 3, 4 and 5 to receive the semi-circular or horseshoe permanent magnet 6. This magnet 6 is preferably made of powdered material such as of the alloy of aluminum, nickel and copper which has high magnetic retentivity. Such magnetic powdered materials may be moulded in plastic to form a permanent magnet which has very high retentivity although somewhat higher reluctance than the magnet of the same solid alloy metal. The magnet 6 may be retained within the casing by means of the leaf spring 1 which may be positioned on the inside circular sector of the magnet and bear against one side 8 of the case or in any other suitable known manner.

other in -which slots themagnetostrictive wire 5H is placed. This-magnetostrictive wire, .whichmay .be made of nickel or other suitable materials sshowing proper -magnetostrictive properties, -.is originally -formed as indicated in Figure 3 .with loops l2 and I3 at either endbent-aroundin dif- =Iierent "angular --directions. ,In Figure 3 these -;.planes coincide iat v1.80%. The direction,'.however, :may be less, if -.desired.

.At the .center-o'i the wire -.ll .asmall tube .12 *is :crimp'edover .the wire. This .may be soldered, welded or :even pressed-on. The .tube 12 -is:shor.t and 'of -sufiicient :inner diameter to receive the :stylus :wire M which. may be zmadeof platinum or have a platinum iridium ,point 15 to 1.giveit extreme .hardness.

The wire 1.4 is bent at ianeangle to provide .a

mortion 1:6;paralle1 to the wire and anotherpor- 130 case :bottom :a .little greater than the length -;of

=thewire portion wl ii to-permit the "stylus .to be ;put fthroughithe case. .Themoil 1:8 :is wound over ethe wvire "before being inserted in the case. This is accomplished by laying the {coil I18 :around the itube i2 and then :twisting the tma'gnetostrictive 'zwire "forming :the winiiing 701' ncoil: lt' simultaneous iy 'onbothisides ofth'etube 4.2. It will 'be-"seen that: inthis .way currentifiowing throughtthe iiailves of'tm coil 'lrs will be-Sin opposite directions. After a single layer of coil has been wound on the magnetostrictive wire, the magnetostrictive wire is dipped in latex or latex is painted or applied on the magnetostrictive wire where the coil is being formed, as shown at 30, Figure 4. If desired, the wire may be coated with latex where the coil is to be formed before the coil is formed on the magnetostrictive wire. This serves both for damping and to secure the coil to the wire. When the coil has been wound on the magnetostrictive wire, the whole assembly is put in the case. For this purpose the case is provided with a small hole or opening l9 or slot as mentioned above through which the wire M will project. The loops l2 and I3 are twisted to engage the slots I0 56 and 9 respectively thereby giving the desired torsional stress to the magnetostrictive wire. The stylus wire may be formed with two bends l6, I1 terminating in the stylus point IS.

A guard 2| may be moulded as a part of the case around the position occupied by the stylus portions l6 and IT. This guard 2| may be wedgeshape with .the highestwall portion 22 just short of the extension of the stylus point I5, In this way the pressure on the stylus will only permit it to be retracted below the surface of the highest point of the wedge of the guard.

When the magnet, coil and wire have been put in place, a cover 23 may be applied in which suitable terminal connections may be placedto connect to the ends of the coil [8.

When the stylus has been worn through ordibly of the magnetostrictive wire coil and stylus is removed and a new one replaced. It will'be found that the cost of replacement is extremely reasonable and quickly accomplished. The operation of the unit is the same as described in the co-pending applications, the torsional oscillation of the wire serving to increase and decrease the magnetic properties of the wire in such a way to vary the flux threading the coil to produce additive efi'ects in both halves of the coil I8. This in part is responsible for the efiiciency in operation of the present invention.

Having now described my invention, I claim:

1. A pickup device comprising a magnet having poles at opposite ends, said poles having slots across their faces near their ends, a magnetostrictive wire having return bends at each end adapted when twisted torsionally with respect to its length to engage said slots, means coating said magnetostrictive wire providing a, flexible, yielding coating therefor, a stylus attached substantially at the mid-point of said magnetostrictive wire and a coil surrounding said wire positioned over said coating, said wire at each side of said stylus Wound in opposite sense.

2. A pickup device comprising a magnet having poles at opposite ends, said poles having slots across their faces near their ends, a magnetostric- 'across their faces near their ends, a magnetostrictive wire having return bends at each end adapted when twisted'torsionally with respect to its length .nary playing, the case is opened and the assem to position the ends to engage said slots and be held firmly therein, a short tube attached substantially at the mid-point of said magnetostrictive wire, a stylus wire having one end engaging the open end of said tube and held thereby, said stylus wire being bent with tWo angular bends having a longer bend substantiallyparallel to the magnetostri'ctive wire and a coil surrounding said magnetostrictive Wire at each'side of said stylus wound in opposite sense.

4. A pick-up device for a phonograph and the like; comprising an insulating casing, a fiat,

arched magnet having poles at opposite ends of the arch, positioned in said casing, said ends having slots recessed in the side faces thereof aligned longitudinally of the magnet, a, magnetostrictive wire havingsubstantially the same diameter as the width of the slot with return bends at each end thereof parallel to ,the Wire but normally not aligned with each other, said Wire adapted when twistedtorsionally with respect to its longitudinal' axis to align said return bends to engage said slots whereby the Wire is held in torsion, a stylus attached substantially at. the mid-point of said magnetostrictive wire, a coil surrounding said wire at each side of said'stylus wound in oppo- "site sense, said stylus projecting externally of said wound in opposite sense.

' STANLEY R. RICH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 351,905 Eickemeyer Nov. 2, 1886 499,549 Hunter 1 June 13, 1893 1,778,048 Thomas Oct.14, 1930 1,957,512 Weinberger May 8, 1934 1,959,005 Parshall May 15, 1934 2,168,721 Tinnerman Aug. 8, 1939 2,326,460 Hasbrouck Aug. 10, 1943 2,348,352 "Mallina' May 9, 1944 2,376,456 Sinnett May 22, 1945 2,399,585 Thompson Apr. 30, 1946

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