US1803273A - Phonograph pick-up - Google Patents

Description

April 28, 1931. c. B. sAwYl-:R

I PHONOGRAPH PICK-UP Filed July 25, 1929 INVENTOR Charles Saver BY LIM/4 7 7776 Cd ATTORNEYS Patented lApr. 28, 1931 UNITED' s'ra'ras,l PATENT OFFICE CHARLES B. SAWYER, F CLEVELAND HEIGHTS, OHIO, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE CLEVELAND TRUST COMPANY, 0F CLEVELAND, HI, A. OORPQRA- PHONOGRAPH THICK-'UP application med :any 25, 1929. serial No. 380,779.

This invention relates to new and useful mechanism for receiving vibrations from phonograph records and the like, and particularly the utilization of the piezoelectric V ei'ect of crystals, especially of the Rochelle salt type, for converting such vibrations into electrical energy.

The Rochelle salt crystal lends itself articularly to the conversion of sound vi rations into electrical energy, since the electromotive force is pro ortional to the pressure upon the crystal. very accurate response or reproduction is obtained by arranging the crystal so that the action of the grooves in the l5 phonograph record'upon the needle applies a pressure upon the crystal which is proportional to the displacement of the grooves in the record.

One of the objects of the present invention is to provide such a mechanism as may be utilized for reproducing the sounds recorded on v a phonograph record with exceptional fidelity.

Another object is to provide a mechanism in which the vibrations received from the phonogra h record are converted into variations of electric potential which may be a plied to a thermionic amplifier or direct y to a telephone receiver in order to enerate 0 sound waves reproducing the origina sounds recorded on the phonograph record.

Another object of this invention is to provide a mechanism of great mechanical ruggedness and endurance which will not be i harmfully aected by mechanical shocks and stresses and which will not Wear out or change in quality with long use.

Another object of this invention is to produce a phonographic reproducing device 4" which will inherently eliminate a portion uof the scratching or rustling noises which are sometimes reproduced from the record by mechanisms that have previously been produced. v

A further object of this invention is to provide a device having a very large response when played upona phonograph record so that a comparatively small amount-of amplification will be needed to give a large response in the loud speaker or reproducer.

A still further object of the present invention is to provide a very economical and eiicient utilization of the piezoelectric crystalline material.

Thesebeing among the objects of the present invention, the same consist of certain features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawin and then claimed, having the above and oter objects 1n view.

In the drawin which illustrates a suitable embodiment of t is invention, Figure 1 shows the ap lication of the sound reproducing mechanism to a phonograph;

Fig. 2 is an enlarged plan view of the conical base section of the mechanism looking toward the needle-holding portion thereof;

Fi 3 is a side elevation of the crystalholding portion of the sound-reproducing mechanism; i

Fig. 4 is an enlarged perspective view of a cr stal;

ig. 5 is a cross-sectional view of the sound re reducing mechanism;

ig. 6 is a diagrammatic view showing the electrical hook-up for the sound reproducing mechanism showln the same connected with an amplifying devlce.

Referring to the accompanying drawings in which like numerals refer to like parts throughout the several views, ythe sound reproducing mechanism 1 is shown in Fig. 1 as being attached to and supported -by the goose-neck 2 of a phonograph tone arm 3. A needle 4, carried by the mechanism 1, engages with the grooves of the phonograph record.

. The sound-reproducing element 1, as shown in Fig. 5, comprises a base 6, a crystal holder 7 a nose-piece 8, and an electrlcal circuit which will be later described. The crystal holder 7 is of metal and embodies a relatively thin triangular-shaped web or vane 9 having a flanged cylindrical portion 1() at one end, which carries the needle 4, and a large conical portion 11 at the other end thereof, which is seated in a correspondingly shaped recess 12 formed in the base 6. A screw 13, carried by the base 6, is threaded into the conical end portion 11 of the lcrystal holder 7 to hold the cr stal holder in position in the base. Triangu arly 'sha ed crystalline elements 14 and 15 of -Roc elle salt, or other suitable crystalline m/aterial, are cemented to the opposite sidesfgfathe vane 9 with the ends thereof abutting against the conical end portion 11 and the flange 16 of the cylindrical end portion 10. These crystalline elements 14 and 15 are also mounted under compression to compensate for temperature chan es. Tinfoil electrodes 17 and 18 are suita l attached to the outer faces of the crystalline elements 14 and 15 respectively and are connected together by a connector wire 19 to form a single electrode. The base 6, being of metal, forms the other electrode.

The Acrystal holder is preferably enclosed by the nose-piece 8, which is secured to the base 6 by screws 20 and which has a flange 21 extendin into a counterbored portion 22 formed in t e base 6. The other end of the nose-piece 8 is tapered and engages a rubber or resilient ring 23, which is carried by tne cylindrical end portion 10 of the cr stal hold.- er. A screw 24 extending throng openings in the nose-piece 8 and ring 23 is threaded into the end portion 10 to securely hold the needle 4 in position.

The base 6 is also formed with a recess 25 at one end, which telescopically receives a resiliently mounted ring 26, that is employed to attach the base to the open end of the phonograph goose-neck 2.

The wire 19, which connects the pieces of tinfoil 17 and 18 to form a single electrode, is provided with a leadwire 27 that extends through the base 6 and is connected to one terminal of a high resistance potentiometer 28. The other terminal of the potentiometer 28 is connected by a lead wire 29 to the base 6 which forms an electrode. The movable arm 31 of the potentiometer 28 is connected to the control member of any suitable thermionic device 32. The thermionic device 32 is connected by a lead Wire 33 to the-stationary terminal of the potentiometer 28 and by a lead wire 34 to a suitable transformer 35, which is connected to a sound amplifying device 36, such as a loud speaker. A battery 37, connected by lead wires 38 and 39 to thc potentiometer 28 and transformer 35,completes the electrical circuit.

The operation of the device is as follows: The circular motion of the rotating phonograph table causes the grooves in the record 5 to subject the needle 4 to lateral vibrationsat right angles to the groove, as indicated oy the double-headed arrow shown in Fig. `1 adjacent to the needle 4. The needle 4 transmits these lateral vibrations to the crystal holder 7 of the mechanism, and the mechanism 1 and tone arm 3 as a whole tend to move back and forth in accordance with the lateral vibrations. This movement,

however, is resisted by the inertia of the arm 3 and mechanism 1 and, as a result of the force applied to the crystal holder 7 by the needle 4 the vane 9 of the cr stal holder is subjected to bending stress ,which causes an alternate compression and tension of the crystalline elements 14 and 15 at the opposite sides of the vane 8. The crystalline ele- * nents 14 and 15 are so oriented and carried by the crystal holder 7 that the compression of one element and tension of the other element tend to produce an electromotive force of the same polarity on the outer surface; that is to sa when pressure is exerted on the crystal older-.7, the crystalline element onv one side which is compressed develops a positive charge relative to the center and the crystalline element on the other side, which is in tension, also develops a positive charge relative to the center. Furthermore, when4 the lpressure tends to bend the crystal holder init e-oppositedirection, the charge on the crystalline elements, with respect to the center, is reversed and becomes negative. Thus, when the needle is subjected to a vibrating or alternating pressure, an electromotive force is developed between the outer electrodes 14 and 15 and the vane 9 which forms the other electrode, which force is transmitted -through'the leads 27 and 29 to the potentiometer 28, or in other words an electrostatic field is produced at right angles to the axes of the crystalline elements.

Any desired portion of this electromotive force may be applied from the otentiometer to the control element of the t ermionic device 32, according to the position of the arm 31 of the potentiometer. The electromotive force is transmitted by the action of the thermionic device 32 through the transformer 35 to the loudspeaker or amplifier 36, vWhere it is converted into sound waves.

The electromotive force reproduced is of sufficient strength, so that if small volume is required the output of the mechanism can be, applied directly toa sound reproducing device, such as a telephone receiver or sensitive loud speaker unit without the interposition of the thermionic device 32.

The resilient ring-23 surroundin the cylindricalend 10 of the crystal holder functions to prevent an excessivemovement of the crystal holder w ich would tend to overload the crystalline elements, and also functions to safeguard the mechanism against injury due to excessive mechanical shocks. The cylindrical nose-piece 8 forms an enclosure for, the crystal holder and the attached crystalline elements and protects them from external mechanical injury.

The mechanism illustrated is very sensitive to vibration applied to the needle 1n a direction at right angles to the thin vane 9 of the crystal holder If, however, presure is exerted 1n directions more or less in the plane of the vane 9, such' as the scratches irregularities oftentimes occuring in the bottom of the groove, there will be comparatively little pressure exerted upon the c stelline elements, owing to the fact that the t 'n vane 9 is very stifi` and non-flexible in the direction of its widedirection. Furthermore, both crystalline elements would be compressed or expanded at the same time by forces acting 10 in this direction and the electroniotive forces generated will therefore tend `to neutralize crystals and the nism for reproducing with exceptional fidelity the ssounds recorded on a phonograph record.

It is to be understood that the shapes of particular methods and operations setl fort are. for explanation and illustration only and that `formal changes can be made in the invention without departing from the spirit and substance of the broad invention, the scope o-fl which is commensurate with the appended claims.

What I claim is: 1. In a piezo-electric device, in combination, a support formin an inner electrode,

va pair of portions of piezo-electric material having outer electrodes connected together, said portions being so secured to said support that each portion constrains the movement of the other and so-arranged that upon mechanical vibration of said support a relatively great pressure is applied to said portions, whereby electrostatic potentials of high .intensity and like signs are produced on the outer electrodes, and a potential of opposite sign is produced on the inner electrode. y y

2. In a phonograph pick-up, 1n combination, a support and a (portion of piezo-elec tric material so oriente that when said portion is expanded or contracted by said support in the direction of its longitudinal 'axis it produces an electrostatic field at substantiallyright angles to said axis, said portion bein flexibly constrained so that when .a bendging moment is supplied an electrostatic field is produced.

3. In a phonograph pick-u in combination, a support, a ortion o piezo-electric material so oriente that when said portion is expanded or contracted by said support in the direction of its longitudinal axis it .vice of a holder havin -field into sound waves.

y u 4. 'A piezo-electricfdevice including a portion of piezo-electric material so oriented with respect to the cr stalline axes that when alpres'sure is ap lie to said portion in the direction of its ongitudinal axis an electrostatic field is produced substantially at right angles to said axis, said portion being mounted under compression, whereby the natural period is raised and the effects of temperature changes are eliminated.

5. The combination in a' piezo-electric de spaced shoulders, a pair of portions of piezo-electric material mounted etween said shoulders, and a record engaging means carried by one end of said holder, the other end of said holder being of suflicient Wei ht as to be unaffected by vibration of sait? means Within the audible frequency range, said portions of piezoelectric material bei mounted under` compression, wherebyrvi ration of said record engaging means causes application of pressure to said portions in the direction of their longitudinal axes, and said portions being so arranged and oriented that an electrostatic field will be set up substantially at right angles to said .longitudinal axes.

6. In a phonograph pick-up, a relatively thin vane having shoulders at. the ends thereof, a pair of portions of piezo-electric material secured to said vane and mounted under compression between said shoulders, a record engaging means carried by one end of said vane, and a base rigidl supporting the other end of said vane, said use being of sufficient weight as to be unaffected by vibration of said means occurring within the audible frequency range, said portions of piezo-electric material being so oriented that when they are expanded or contracted in the direction of their longitudinal axes by the vibration of said vane they produce an electrostatic field at substantially right angles to said axes.

7. In a phonograph pick-up, a relatively thin vane having shoulders at the ends thereof, a pair of portions of piezoelectric inaterial secured to said vane and mounted under compression between said shoulders, a record engaging means carried by one end of said vane, a base rigidly supporting the other end of said vane, said base being of sufficient weight as to be unaffected by vibration of said means occurring within the audible fre- .r

quency range, said portions of piezo-electric material being so oriented that when they are expanded or contracted in the direction of their longitudinal axes by the vibration of said vane they produce an electrostatic field charges relative to being sufiiciently held as to be unaffected by vibrations of said means occurring within the audible frequency range, said portions of piezo-electric material being so oriented that when they are alternately expanded and contracted by the vibrations of said record engaging means they produce an electromotive force, and means for converting said electromotive force into sound Waves. Y 9. In a phonograph pick-up, a relatively thin iiexible vane having shoul ers at its ends,

a record enga ing means carried by one end of said vane, t e other end ofsaid vane being sufficiently held as not to be affected by Vvibrations of said means, and portions of iezoelectric material secured to opposite sides of said vane and mounted under com ression between said shoulders, said portions eing so oriented that when the vane is subjected to vibrations within the audible frequency range they alternately expand and contract, and alternately develop positive and negative the center thereof which produce an electromotive force, and means for' converting said electromotive force into sound waves.

v 10. In a phonograph pick-up device, a relatively thin flexible vane, a record engaging means carried by one end of said vane, the ther end of said vane being sutliciently held as not to be aiected by the vibration of said vane, and portions of piezo-electric material secured to opposite sides 45 of said vane and oriented to alternately-expand and contract when said vanel is vibrated in the audible requency range and alternatelyl develop positive andnegative charges' relative to the center thereof which produce an' electromotive force, and means for converting said electromotive force into sound waves.'

11. In -a phonograph 4pick-u device, n relatively thm vane having shou ders at the ends thereof,'a pair of portions of piezoelectric material secured to said vane and extending between said shoulders a record engaging means carried by one end of said vane, a base rigidly supporting the other end of said vane, said -base being of sufficient weight as to be unaiected by vibration of said means occurring within the audible frequency range, said portions of piezo-electric material being so oriented that when they are expanded or contracted in the direction of their longitudinal axes -by the vibration of said vane they produce an electrostatic eld at substan-y

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