US2379782A - Phonograph pickup - Google Patents

Description

July 3, 1945. L. J. BOBB 2,379,782

PHONOGRAPH PICK-UP Filed Sept. 11; 1943 s Sheets- Sheet 1.

:3 h L w] a y PHONOGRAPH PICK-UP Filed Sept. 11, 1943 3 Sheets-Sheet 2 L. J. 8055 v 2,379,782

Patented July 3, 1945 UNITED STATES PATENT OFFICE PHONOGRAPH moxur Lloyd J. Bobb, Philadelphia, Pa., assignor to Philco Radio and Television Corporation, Philadelphia, Pa., a corporation of Delaware Application September 11, 1943, Serial No. 502,003

15 Claims. (01. 179-100.)

This invention relates to electrical phonograph pick-ups.

One of the primary objects is to achieve high fidelity reproduction over a wide frequency band in a pick-up which can be manufactured inexpensively.

Another object is to minimize record wear.

A third object is to provide a pick-up of simple construction which can be used for playing both lateral-cut and hill and dale recordings.

Still another object is to provide a pick-up wherein the parts subject to wear and tear can easily be replaced at little cost without the necessity of returning the device to the factory.

A further object, is to provide a pick-up for use with lateral-cut recordings wherein the stylus is so cushioned that dropping the pick-up onto the record will not be likely to damage either the stylus or the record.

An additional object is to provide supplemental lateral stiffness which does not materially affect the response of. thepick-upbut which braces the stylusagainst excessive lateral displacement. at

the end of each record play when the stylus is engaged by the spiral eccentric groove.

One of the special problems with which this invention deals is that of excessive wear of lateralsistance to small amplitude vertical oscillatory motion, with the result that stylus contact pressure generated by pinch-effect is greatly restricted.

At the same time the aforesaid resilient mounting functions as a pivotal support for the vibratory unit permitting the same to oscillate laterally with only such resistance as is needed to provide essential damping. that it provides cushioning which is effective to prevent injury to the stylus and record which might otherwise result from dropping the pick-up onto the record instead of carefully setting it thereon.

The vibratory unit is so constructed as to provide high rigidity coupled with low mass wherecut records resulting from what is known as pinch-effect. This phenomenon arises from changes in width of the record groove due to lateral excursions of the recording stylus and manifests itself during the playing of a lateral-cut record in the form ofi vertically directed oscillatory force imparted to the styluswhich vertically directed oscillatory force causes corresponding increments of contact pressure between the stylus and record groove. The added contact pressure thus generated increases friction and.

thereby accelerates record deterioration.

The increments of contact pressure due to pinch-effect can come into being only tothe extent that complementary reactionary force is developed. In other words, it is only in proportion to the opposing reaction set up by the stylus that pinch-effect can cause contact pressure to be generated. If the stylus were toyield without offering any reaction (a condition impossible of fulfillment) there would be no consequential con--- fore all movements of the stylus, both lateral and vertical, imparted thereto by the record, are transmitted faithfully to the moving coil which is thereby enabled to generate voltage corresponding accurately to the recording.

Another feature of this invention has to do with the playing of lateral-cut and hill and dale recordings alternatively, with the same pick-up. The aforementioned vibratory unit is so con: structed that it will respond with equal facility to either type'of recording; but to be effective it is necessary that the magnetic field be altered whenever a change is made from lateral-cut to hill and dale recordingsand vice versa. 1'. have devised a field structure wherein the magnetic polarities can be altered very quickly and! easily to adapt the pick-up for the playing of either type of recording alternately.

Still another feature of special advantage is a unique self-contained vibratory unit which can easily be withdrawn and replaced and which is characterized by extremely low inertia and high rigidityfactors which are vital to high fidelity and long record life.

An additional feature which has proved of considerable value consists in the provision of electrical leads for the moving coil which are encased between flat strips of parchment paper or the like to provide stiffness, and so anchored that the This feature also is of value in saidleads and paper casing function to restrain the vibratory unit against excessive. rotation at the end of each record play when the stylus is engaged by the spiral eccentric groove-but without introducing stiffness adversely affecting the response of the pick-up.

Some preferred embodiments of this invention are illustrated in the accompanying drawings,

wherein:

Fig. 1 is a front elevational view of an electrical pick-up embodying the principal features of the invention;

Fig. 2 is a side elevational view of the same;

Fig. 3 is a top plan view of the same;

Fig. 4 is a bottom plan view of the device;

Fig. 5 is an enlarged fragmentary sectional view showing the vibratory unit more clearly;

Fig. 6 is a sectional view taken along the line 6-8, of Fig. 5;

Fig. 7 is a sectional view taken along line '|--l of Fig. 6;

Figs. 8 and 9 are views, corresponding gener-' ally to Figs. 5 and 6, of a modification having a different form of resilient mounting;

Fig. 10 is a. perspective view of the mounting element;

Figs. 11 and 12 are further views of still another modification with a different form of resilient mounting;

Fig. 13 is a perspective view of the mounting structure;

Fig. 14 is a sectional view of another embodiment taken along line lll4 of Fig. 16;

Figs. 15, 16 and 17 are end, top plan, and bottom plan views, respectively of the same;

Fig. 18 is an enlarged fragmentary sectional view showing the vibratory unit and its mountins;

Fig. 19 is a perspective view showing the mounting elements for said unit; and

Fig. 20 is an enlarged cross-sectional view of a fiat cable employed in'the device.

Referring first to Figs. 1 to 4, inclusive, reference numeral l identifies the free end of a tone arm which may be pivoted at its remote end (not shown) to swing in a horizontal plane and also in a vertical plane. To' said arm'is attached a pick-up 2 whereof the stylus 3 is intended to engage the groove of a recordingwhich recording may be either lateral-cut or of the hill and dale variety.

The pick-up comprises a magnetic field structure identified as a whole by numeral 4 and a vibratory unit identified as a whole by numeral 5.

Magnetic field structure 4 (see Fig. 1) includes a soft iron member 6, a pair of soft iron polepieces I and 8, a spacer block 9 of brass or other non-magnetic material, a permanently magnetized block I0 and a second permanently magnetized block ll. Blocks i0 and II preferably are made of a magnetic material such as Alnico but can be ordinary magnet steel. Block H) serves as a spacer between member 6 and pole-piece I and is clamped between those members by means of a pair of brass screws l2 and I3. Non-magnetic spacer block 9 is clamped between member 6 and pole-piece 8 by a pair of screws I4 and I5 which should be of non-mag netic material. v

Magnetized block II is rotatably mounted on the shank of a stripper bolt l6 which is threaded into block 9. The threaded end of said bolt is of smaller diameter than the shank, and the head of said bolt does not bind block II. The

and dale recordings.

latter adheres tightly to the contacting ends of member 8 and pole-piece 8 by reason of magnetic attraction, but it can be rotated about bolt l6 as a center without much efiortespecially if the contact surfaces are lubricated.

role-piece I has a fixed magnetic polarity whereas the polarity of pole-piece 8 is reversible and depends upon the position of block ll. Rotating said block degrees reverses the polarity of pole-piece 8. Thus, the two polepieces 'I and 8 may be of the same polarity or of opposite polarity. When the two pole-pieces are of opposite polarity magnetic flux will flow from one to the other via the center pole 6 which constitutes an integral part of member 5. When the two pole-pieces are of like polarity the fiux will follow separate parallel magnetic circuits having a common path through the center pole 6'.

For playing lateral-cut recordings the two pole-pieces 1 and 8 must be of opposite polarity. For playing hill and dale recordings the two pole-pieces must be of like polarity in which case the center pole acquires a definite polarity opposite to that of pole-pieces I and 8. A changeover of the pick-up from lateral-cut to hill and dale requires only a 180 degree rotation of block II. The vibratory unit is at all times conditioned to respond to either lateral-cut or hill and dale recordings. The oscillatory movements of the vibratory unit when playing lateral.- cut recordings is indicated by the arcuate doubleheaded arrows ll (Figs.,1 and 5). The oscillatory movements of said unit when playing hill and dale recordings is indicated bythe vertical double-headed arrow l8.

As previously stated, one of the features of this invention resides in the mounting of the vibratory unit in such manner that it offers very little resistance to small'amplitude upward movement in response to pinch-effect while at the same time not interfering with lateral oscillatory rotation of the unit which must take place concurrently with the up and down movements resulting from pinch-effect. This same characteristic renders the pick-up efficient also in the playing of hill and dale recordings.

How this is accomplished is illustrated in Figs.

5, 6 and '7. while alternative arrangements are shown in the subsequent figures 8 to 19 inclusive.

Referring now to Figs. 5, 6 and 7, vibratory unit 5 is seen to comprise a cup-like body member l9 made of thin sheet material such as parchment paper or aluminum. The upper part l9a of the body member is cylindrical and annular whereas the lower portion l'llb is conical. Mounted at the apex of the cone and firmly secured thereto is a stylus mounting 20 in which is embedded the stylus 3usually a sapphire. Wound upon and carried by the cylindrical annular portion l9a is a coil of fine wire 22. This 'is known as the moving coil. The vibratory unit thus described has little mass and is distinctly rigid so that the vibrations of stylus 3 are transmitted to the moving coil with, little loss throughout a wide frequency band. The response curve is remarkably fiat from the lowest audible frequencies up to about ten kilocycleswhich means fidelity of a high order. The rigidity of body member l9 holds true with respect to both lateral oscillations, such as are imparted to it in the playing of lateral-cut recordings, and vertical oscillations such as are imparted to it in the playing of hill This likewise holds true with respect to vertical oscillations imparted to face of the body member.

aware: p

and 28 there is substituted a single U-shaped soft the stylus by reason of pinch-eilfect in the playing of lateral-cut recordings. It will be apparent that vertical motion imparted to the vibratory unit by pinch-effect inthe course of playing lateral-cut records does not result in the generation of voltage or current.

As clearly depicted in Figs. and 6, the moving coil encircles the lower end-of center pole 6' and is disposed in two magnetic flux-traversing gaps 23 and 24 formed by pole-pieces 'l and 8 conjointly with center pole 6'.

The center pole functions not only as such (when playing "hill and dale recordings) but also as a magnetic core for the moving coil when playing lateral-cut recordings, and as a supporting element for vibratory unit 5, which is suspended thereon.

The means whereby the vibratory unit is attached to center pole 6' and centered thereon comprises a pair of highly resilient inserts 25 and 26, preferably formed of soft rubber or other material having commensurate resilience. These are somewhat elongated, as shown in Figs. 5 and 6, and rectangular in cross-section, as shown in Fig. 7. These inserts are secured in slots cut inopposite sides of center pole B and preferably 7 cemented in place.' Circumferentially the two inserts engage body member it along the internal surface of cylindrical portion l9a, and'the lower ends of the inserts are preferably beveled, as shown, to conform to the internal conical sur- The inserts engage the body member with enough pressure to ensure its retention against gravity, but preferably not so tightly but that the unit can be withdrawn quite easily when replacement becomes necessary. Thus the vibratory unit is free of permanent attachment and is held only by the frictional engagement thereof with the inserts.

The soft rubber inserts are positioned as shown in Fig. 7 at right angles to the pole-pieces, and they function as resilient self-damping pivots about which the vibratory unit rotates oscillatorily when actuated by a lateral-cut record. The approximate pivotal center is indicated in Fig. 5. Thus the vibratory unit oscillates about the vertical axis of the device extending upwardly from the stylus.

The rubberfrom which the inserts are molded or cut is preferably quite soft and yieldable and generally homogeneous. Consequently the inserts offer very little impediment to vibratory rotation of the unit. Also, the resiliency of the inserts is such that small amplitude vertical movements of the vibratory unit. meet with exceedingly little opposition. This factor, in conjunction with the small mass of the vibratory unit, minimizes reaction to vertical vibration due to pinch-effect. At the same time the vertical resiliency of the inserts renders the pick-up well adapted to the playing of hill and dale recordings.

of tone arm I may, of course, be counterbalanced to ensure that the stylus pressure is, not greatly in excess of what is needed to keep the stylus in the record groove. I have found that stylus pressures of the order of 0.5 ounce are ordinarily sufficient. v

The structure of Figs. 8 to 10 is exactly the same as that of Figs. 5 to 7 except for the substitution of a modified form of soft rubber insert and such alterations as are needed to accommodate the modified insert. The vibratory unit is unchanged, but in place of the two inserts 2-5 The weight of the field structure, as well as that rubber insert 21. This involves the provision of a diametrical slot 28 extending across the bottom end of center pole 6?. Insert 21, functions in the same manner as previously described with respect to inserts and 26.

Another modification is illustrated in Figs. 11 to 13. Here the vibratory unit remains unchanged, but a third form of soft rubber insert is employed. This comprises a strip 29 of rectangular cross-section extending crosswise through a slot 30 milled in the bottom face of the center pole. Two slots BI and 32 preferably of slightly greater width than that of insert 29 (see Fig. 13) are milled in opposite sides of the center pole. These latter slots afford clearance so that the two ends of insert 29 overhang the. ends of slot 30 in the manner of cantilevers. This arrangement increases somewhat the vertical resiliency of the mounting and makes it possible, if desired, to use rubber which is somewhat less resilient than would otherwise be indicated.

Each of the aforementioned three forms of rubber inserts serve to provide resilient pivots which are highly yieldable with respect to both rotational oscillations and vertical oscillations of the vibratory unit. Thethree forms shown are substantially gquivalent and it will be apparent that there are numerous further modifications possible within the scope of the invention.

There is shown in Figs. 14 to 20, inclusive, a pick-up embodyin the present invention but designed for use with lateral-cut recordings exclusively. Here the vibratory unit 5 is substantially the same as previously described and the rubber inserts 33, 34 supporting the vibratory unit are substantially like those of the first-described embodiment. The center member 35 functions as a magnetic core for the vibratory unit and as: a supporting element; but it is not a pole-piece since it is anchored at its upper end in a block 36 of non-magnetic insulating material into which the shank 35a is pressed. The field magnet structure comprises a permanently magnetized block 3! secured by screws 38, 39 between two pole-pieces 40. M. As shown most clearly in Figs. 15 and 17 these pole-pieces partly encircle and arespaced from the center member 35 to form a pair of arcuate magnetic flux-traversing gaps 42, 43 in which is situated the moving coil.

A featfire of the device (applicable also to the previous y described embodiments) is the flat ribbon-like cable 44shown in cross section on a greatly enlarged scale in Fig. 20. This cable interconnects the two ends of the moving coil with soldering terminals 45, 46 and comprises a pair of spaced wires 41, 48 interposed between two .005" thick parchment paper laminae 49, 50 cemented together and forming a rather stiff ribbon approximatelyone-eighth inch wide. The upper end portion of the cable is attached at 5| (see Fig. 14) by means of a suitable adhesive, to the block 36. and the lower portion 52 of said cable extends horizontally to effect a junction with the moving coil. The pivotal center about which the vibratory unit oscillates rotationally is below the point of connection between cable 44 and the moving coil, and said cable has such stiffness that it impedes rotation of the vibratory unit when the amplitude ofrotation has gone beyond the maximum normally imparted by the record undulations. The cable does not become materially effective as a stiffening agent so as to influence the response of the pick-up; but when a considerably larger amplitude of rotational force is imparted to the vibratory unit the cable becomes effective as a mechanical resistance medium.

Thus, at the end of each record play when the stylus is engaged by the spiral eccentric groove the lateral force imparted thereto is considerably greater than the maximum rotational force brought to bear .upon the stylus by the record undulations during the playing of a recording. The supplemental stiffness provided by cable 44 becomes eifective to a measurable degree only when this greater force tending to rotate the vibratory unit excessively comes into being; that is to say, only at the end of each record play.

Although a number of embodiments of the invention have been illustrated and described for purpose of disclosure, it will be seen that the invention is not limited thereto but is capable of other embodiments and modifications.

I claim:'

1. In a phonograph pick-up having a vertical axis, a magnetic field structure including a pair .of opposed spaced poles at either side of said axis,

a supporting element interposed between said poles and spaced therefrom to form two narrow magnetic flux-traversing gaps disposed at either side of said axis,a vibratory unit comprising a body member, a moving coil and a stylus, said body member being formed of thin sheet material and including a coil-carrying portion encircling said supporting element and disposed in both said gaps, said coil being wound on and carried by said coil-carrying portion and disposed in said gaps, said stylus being displaced from said coil lengthwise of said vertical axis, said body member including a second portion rigidly connecting said stylus with said coil-carrying portion and operative to transmit vibratory movements of said stylus to said coil-carrying portion and thence to said coil, and resilient means interposed between said supporting element and the interior of said body member and functioning to attach said vibratory unit to said supporting element, said resilient means engaging said body member at opposite points interiorly'of said coilcarrying portion and serving as resilient pivots to permit said vibratory unit to oscillate rotationally in response to lateral oscillatory movements of said stylus, said resilient means being further characterized in that it yields readily to small amplitude oscillatory movements of said unit in the direction of said vertical axis.

2. In a phonograph pick-up having a vertical axis, a magnetic field structure including a pair of opposed, spaced poles at either side of said axis, a supporting element of magnetic material interposed between said poles and spaced therefrom to form two narrow magnetic flux-traversing gaps disposed at either side of said axis, a vibratory unit comprising a bodymember, a moving coil and a stylus, said body member being formed of thin sheet material and including a cylindrical annular portion encircling said supporting element and disposed in both said gaps, said coil being wound on and carried by said cylindrical annular portion and disposed in said wound on and carried by said annular portion gaps, said stylus being disposed concentrically with said coil and displaced from said coil lengthwise of said vertical axis, said body member including a conical portion rigidly connecting said stylus with said cylindrical portion and operative to transmit vibratory movements of said stylus to said cylindrical portion and thence to said coil, and resilient means interposed between said supporting element-and the interior of said body member and functionin to attach said vibratory unit to said supporting element, said resilient means engaging said body member at opposite points interiorly of said cylindrical portion and serving as resilient pivots to permit said vibratory unit to oscillate rotationally in response to lateral oscillatory movements of said stylus, said resilient means being further characterized in that it yields readily to small amplitude oscillatory movements of said unit in the direction of said vertical axis.

3. In a phonograph pick-up having a vertical axis, a. magnetic field structure including a pair of opposed spaced poles at either side of said axis, a supporting element interposed between said poles and spaced therefrom to form two narrow magnetic flux-traversing gaps disposed at either side of said axis, a self-containned vibratory unit comprising a body member, a moving coil and a stylus, said body member being formed of thin sheet material and including a coil-carrying portion encircling said supporting element and disposed in both said gaps, said coil being wound on and carried by said coil-carrying portion and disposed in said gaps, said stylus being disposed concentrically with said coil and displaced from said coil lengthwise of said vertical axis, said body member including a second portion rigidly connecting said stylus with said coil-carrying portion and operative to transmit vibratory movements of said stylus to said coil-carrying portion and thence to said coil, and resilient means interposed between said supporting element and the interior of said body member and functioning to attach said vibratory unit to said supporting element, said supporting element being slotted to receive said resilient means, said resilient means engaging said body member at opposite points interiorly of said coil-carryin portion and serving as resilient pivots to permit said vibratory unit to oscillate rotationally in response to lateral oscillatory movements of said stylus, said resilient means being further characterized in that it yields readily to small amplitude oscillatory movements of said unit in the direction of said vertical axis.

4. In a phonograph pick-up having a vertical axis, a magnetic field structure including a first pole member constituting a supporting element, and at least one additional pole member forming a magnetic flux-traversing gap with said first pole member, a vibratory unit comprising a cuplike body member, a moving coil and a stylus, said body member including an annular upper portion traversing said gap and encircling said first-mentioned pole member, said coil being and disposed in said gap, said stylus being situated on said vertical axis and displaced from said coil lengthwise of said axis, said stylus being rigidly attached to and carried by said body member, and resilient insert means within said body member and interconnecting said vibratory unit with said first pole member, said insert means constituting resilient pivots for said vibratory unit and characterized by resiliency permitting said vibratory unit to oscillate vertically with little restraint relatively to said pole members, and also to oscillate rotationally with little restraint.

5. In a phonograph pick-up having a vertical axis, a supporting element, resilient means carried by said supporting element, a stylus, said re silient means being constructed and arranged to function as a pivotal support for said stylus and apropos permitting said stylus to oscillate ireely both lat erally of said axis and parallel thereto, means defining a magnetic flux-traversinggap encircling said supporting element, amoving coil disportion terminating at its base extremity in an annular tube-like portion on which said coil is wound, said cone portion beingconnected at its apex to said stylus, said body member beingoperative to transmit at least the rotational oscillations of said stylus to said coil, said resilient means being located interiorly of said annular tube-like portion and serving as a, pivotal support for said body member and coil.

6. In a phonograph pick-up having a vertical axis, a supporting element, a pair of resilient elongate inserts situated at diametrically opposite sides of-said element and projecting therefrom laterally of said axis, said inserts being seated in slots formed in said element and extending tory unit comprising a cup-like body member, a moving coil and a stylus, said body member having a tube-like annular upper portion and a cup-like conical lower portion to the apex of which said stylus is rigidly connected, said coil being Wound on and carried by said upper portion, said inserts frictionally engaging the interior periphery of said upper portion at diametrically opposite points and thus forming elongate pivotal supports for said body member, said inserts also engaging the conical interior surface of said lower portion to afford abutment means for said body member with respect to upward movements thereof.

7. In a phonograph pick-up having a vertical axis, a supporting element, said element being slotted diametrically across its lower end and also slotted lengthwise at two opposite sides upwardly from the slot formed in its lower end, a U-shaped resilient insert seated in the slots formed in said element and secured therein, said insert having diametrically opposite leg portions projectingradially from said element and also extending lengthwise of said element and parallel to said axis, said leg portions constituting a pair of pivotal supports, a vibratory unit suspended on said pivotal supports and comprising a cup-like body member of thin sheet material the upper portion of which is frictionally engaged internally by said pivotal supports, said vibratory unit including a moving coil wound on and carried by the upper portion of said body member, and a stylus secured to the lower extremity of said body member, said resilient insert being yieldable to both vertical and rotational oscillatory movements of 'said unit.

8. In a phonograph pick-up, a supporting element having a slot extending diametrically across itslower end, an elongate resilient insert seated in said slot and extending diametrically of said element, the ends of said insert projecting radially from said element in opposite directions, and a vibratory unit comprising a cup-like body member made of thin sheet material, the upper portion of said body member being annular and tube-like and encircling the ends of said insert and in frictional engagement therewith, the lower portion of said body member being conical and depending from said upper portion, a stylus rigidly attached to the lower terminus of said conilengthwise thereof parallel to said axis, a vibrasaid upper portion, said insert serving as a pivotal support for said vibratory-unit and as a x upward moveyieldable abutment with respect to ments of said unit.

- 9. An electric phonograph pick-up operative with both lateral-cut and "hill and dale" recordings, alternatively, and comprising a magnetic field structure in combination with a vibratory unit, said field structure including two distinct magnetic circuits having a common portion defined by a center pole, each of said circuits including an individual pole spaced from said center pole to form an individual gap, each of said circuits including an energizing permanent magnet individual thereto and determinant of the polarity of its said individual pole, at least one of said magnets being bodily reversible for reversing the polarity of its associated individual pole, said vibratory unit comprising av moving coil disposed in said gaps and a stylus for actuating said coil, said vibratory unit being pivoted to rotate oscillatorily in response to actuation of said stylus by lateral-cut recordings, said vibratory unit being resiliently mounted to permit straight-line oscillation thereof transversely of said gaps in response to actuation of said stylus by hill and dale recordings.

10. An electric phonograph pick-up operative with both lateral-cut and hill and dale recordings, alternatively, and comprising a magnetic field structure in combination with a vibratory unit, said, field structure including twodistinct magnetic circuits having a common portion deiined by a center pole, each of said circuits having an individual pole spacedfrom said center pole to form an individual gap, each of said circuits including an energizing magnet individual thereto and determinant of the polarity ofits cal portion, and a coil wound on and supported said individual pole, at least one of said means being pivotally mounted to facilitate rotation thereof for reversing the polarity of its associated individual pole, said vibratory unit comprising a moving coil disposed in said gaps and a stylus for actuating said coil, said vibratory unit being pivoted to rotate oscillatorily in response to actuation of said stylus by lateral-cut recordings, said vibratory unit being resiliently mounted to permit straight-line oscillation thereof transversely of said gaps in response to actuation of said stylus by hill and dale recordings.

1'1. In a phonograph pick-up, a moving coil, means pivotally supporting said coil for rotational oscillation in a magnetic field, a stylus for rotationally oscillating said coil in conformity with record groove undulations, said coil normally functioning to generate voltage corresponding to said record groove undulations, and a relatively still ribbon-like element anchored at one portion and connected with said coil at a point spaced from said anchored portion, said element being operative to stiffen said coil against rotation in excess of whatis needed in the performance of its aforementioned normal function, said element exercising little or no restraint upon said moving coil in opposition to the vibratory actuation thereof efiected by the record groove undulations.

12. In a phonograph pick-up, a moving coil, means pivotally supporting said coil for rotational oscillation'in a magnetic field, a, stylus for rotationally oscillating said coil in conformity with record groove undulations, said coil normally functioning to generate voltage corresponding to said record groove undulations, and a, fiat ribbon-like cable leading to said moving cable comprising a plurality of parallel coil, said conduc strips oi'iinsulating material-constituting, con-.

Jointly, casing 'ior-said conductors, said conductors ing connected each at one end to said coil, said cable being anchored at a point spaced from said coil, said casing extending from said anchorage point substantially to said coil and having enough intervening length to permit said coil to osc llate freely in the performance oi its normal function, said cable being effective to stiflen said coil against rotation in excess of what is needed in the performance of said normal function.

13. In a phonograph pick-up oi the moving coil p a supporting element. a coil-supporting member encircling said element in spaced relation thereto, a magnetic field structure arranged to provide a flux-traversing gap in which the coil is disposed, resilient means carried by said sup- I porting element and engaging said coil-supporting member at opposite points so as to provide resilient pivots for said member, whereby the latter may oscillate about said pivots to move said coil in the flux-traversing gap, and a stylus attached to said coil-supporting member tooscillate the same- 14. In a phonograph pick-up, a magnetic field structure including a pair of spaced poles, a supasvavaa porting element interposed betweensaid poles and spaced therefrom to form narrow fluxtraversing gaps, a vibratory unit comprising a body member, a moving coil and a stylus, said body member including a coil-car yin p rtion encircling said supporting element and disposed in said gaps, and resilient means carried by said supporting element and projecting therefrom at opposite points and frlctionally engaging the type, a supporting element; a cup-like member having a coil-supporting portion encircling said element in spaced relation thereto, a magnetic field structure arranged to provide a flux-traversing gap in. which the coil is disposed; resilient means carried by said supporting element and engaging said member interiorly of its coil-sup porting portion at opposite points so astntprovide resilient pivots for said member, whereby the latter may oscillate about said pivots to move said coil in the flux-traversing gap, and a stylus attached to said cup-shaped member in substantial alignment with the axis thereof.

' LLOYD J. BOBB.

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