US2328862A - Phonograph record scanning device - Google Patents

Description

Sept. 7, 1194s. L. THOMPSON 2,328,862

PHONOGRAPH RECORD SCANNING DEVICE Filed Dec. 24, 1941 INVENTOR- BY L/Ncouv THOMPSON A 2A TTOR/VE V groove is relatively small orinadequate.

Patented Sept. 7, 1943 ome - rnonocmrn nnoonn SCANNING rm Lincoln Thompson, Cheshire, Conn, assignor to The SoundScriber Corporation, New Haven,

. Conn, a corporation of Connecticut Application December 24, 1941, Serial No. 424,333

I a 7 Claims.

This invention relates to phonographs, and more particularly to means for controlling the scanning movement of a phonograph stylus and stylus carrying arm across a record tablet.

When adjacent grooves-of'a phonograph record tablet are placed so close together that the depth of the groove is made relatively small in order to achieve the desired compactness of groove spacing; as in the case of compact, long playing commercial dictating machine records, and in other cases where the grooves are relatively shallow, the force holding the stylus in the desired groove becomes-relatively small and may be insufficient to enable the'stylusto propel the sound head with the desired force across the record tablet. Under these conditions. the sound head stylus may jump out of the desired groove vposition, ora relatively small disturbing force Another object is provide a record tablet operated scanning device of eflicient form for convenient attachment to a part of a stylus cara span, preferably of .soft elastic rubber-like matemay be sufficient to throw the stylus laterally out of the groove .and thus interrupt the scanning and the desired reproduction. For example, in aphonograph having a vertically pivto various other causes which are not subject to easy control, may produce. a similar result.

These difflculties have been found to be of special I importance when reproducing from record grooves produced by an embossing rather than a. cutting stylus, and particularly when the tablet is made of a plastic material.

An object of the present invention is to counteract one or more of the above difliculties and to improve the seanningor tracking movement of a phonograph stylus and the stylus'carrying arm across a record tablet.

Another object is to provide a record tablet operated device of simple and compact-form for eillciently piloting the scanning movement of a phonograph stylus and arm across the tablet.

Another object is to improve the scanning operation of a reproducing stylus and arm when the force tending to hold the stylus in the desired rial, is supported in predetermined relation with a sound head stylus. ,Means, consisting preferably of one or more auxiliary styluses supported by the bridge, are adapted to, engage and be pro-1 pelled by a record tablet for piloting the scanning path of the sound head stylus. Means for supporting the ends of the bridge span, may be included in an elastically extensible or deformable loop which also includes the span and is adapted to encircle the unit carrying the main stylus and to make a gripping engagement with r the unit. Means are provided at the ends of the span for spacing the span from the main stylus carrying unit to allow of free vertical flexing of stylus being disposed in predetermined relation side of the vertical projection of the bridge span with the main stylus and being preferably outon the horizontal plane through said point when the main stylus is in operating position, thus permitting the pilot stylus to be placed close to the main stylus while the bridge span remains clear from interference with vibration of the main stylus.

These and other objects and features of the invention willbe' apparent from the followin detailed description of a preferred form illustrative of the invention, in connection with the accompanying drawing and the appended claims.

In the drawing: Fig. 1 is a side elevation showing one form of auxiliary scanning device combined with a phonograph reproducing unit.

Fig. 2 is a plan view showing diagrammatically the lateral frictional force exerted by a record tablet on a phonograph stylus.

Another object is to guide the reproducing stylus and arm when the groove is discontinuous Fig. 3 is an end elevation of the Fig. 1 arrangement. g

Fig. 4 is an elevation of the auxiliary scannin device of Fig'. 1 T

Fig. 5 is an elevation of a two stylus auxiliary scanning element which may be provided in Fig. 4 between the lines A-'-A and ZB-Bzin place of the single stylus element shown in Fig. 4;

1 Fig. is a fragmentary elevation showing the auxiliary styluses of Fig. in assembled relation with the main stylus.

Fig. 7 is a perspective view showing a different arrangement for mounting the ends of an auxiliary stylus supporting bridge from that in Figs. 3 and 4.

Fig. 8 is a side elevation of the Fig.7 type of auxiliary scanning device in relation to a reproducing stylus.

Fig. 9 is a side elevation of the bridge span of Fig.7.

In Fig. 1, the reproducing arm unit I includes the reproducing sound head 2 and the horizontal reproducing or tone arm 3, connected together by the leaf spring hinge 4 which flexes vertically to permit the head 2 to swing up or down about a horizontal axis while the arm 3 remains fixed vertically; the arm 3 being swingable about a vertical axis of rotation passing through the stationary anti-friction. bearings 5, 5, which support the end of the arm remote from the reproducing head 2 which in turn supports the removable reproducing stylus 6 by the usually provided vibratory means, not shown except forthe set screw 6 for clamping the stylus in its socket.

- Pivots 5, 5 are held in a frame fast to the chassis 8 of the phonograph. The sound head 2 may be raised or lowered by the handle 9 fast to the head. The stylus 6 engages and scans the record disk tablet l0, supported on the turntable I I, the groove under the stylus being fed from left to right in Fig. 1, in a direction away from the vertical axis 5, 5.

On account of the friction of the stylus 6 on the record tablet 50, there is in general a component of frictional force urging the stylus laterally out of the spirally directed record groove 3|, Fig. 2. This component of force varies with the angular position of the arm 3 and becomes zero at only one position of the arm, which may be called a neutral position, as indicated by the line 5. I2, Fig. 2, and is that position of the arm in which the vertical plane including the point of the stylus 6 and the vertical pivot axis 5, 5, is tangent to the groove under the stylus.

When the arm 3 is on either side of said plane, the lateral frictional component increases with the angle made with the plane, and is a maximum at the extreme outer position. 5, l3 and the extreme inner position 5, It. The direction of the lateral component is toward the neutral 5,

l2 when the direction of travel of the groove under the stylus, is away from the vertical axis 5, 5, as indicated by the full line arrows in Fig. 2, at I3 and It, respectively. When the direction of groove travel is reversed, the direction of the lateral force is reversed as indicated by the dotted arrows at I3 and M, respectively.

These and other disturbing forces, including those due to accidental jarring of the phonograph, or due to gravity when the turntable or record diskis not in a hue horizontal position, are likely to increase any tendency for the stylus to dislocate from its desired groove position.

The scanning aid device I5-is provided to' counteract the described undesirable tendencies and difficulties of the scanning operation, and

toimprove the scanning movement of the wave transmitting or reproducing stylus of thephono-- graph. Device I5 is remote from the vertical pivot axis 5, 5, and is disposed in predetermined relation with the main stylus 6. The elastically flexible bridge span l6 supports the rigid auxiliary stylus H, which preferably has a sapphire or other long life type of point. The ends of the span is are preferably supported by including the span in a closed, elastically deformable. or

supported by imbedding its upper or unpointed I end directly in the material of span Hi. Span I6 is preferably placed under slight tension when attached to unit I, to insure of a positive normal position of the span and to provide the desired flexibility. One or more of the inside dimensions of the loop i5, before assembly with unit I, are made smaller than the corresponding dimensions of the portion of unit I to'be encircled, in order,

that the elastically deformable loop l5 may be stressed sufficiently when conforming with the shape of unit I, to provide suitable grippingforce to hold the loop and stylus ll in their desired predetermined relation with stylus 6, and to provide the desired tension in span 16. The described form of loop 15 may be conveniently assembled with or removed from unit I by simply stretching the loop sufficiently to allow it to pass over the end of unit I and stylus 6. The plane of the loop when in assembled position is sub-- stantially vertical, the longitudinal axis of the span being substantially horizontal and transverse to the main scanning direction of the styluses 5, H.

In order that span l6 may be free to yield by flexing vertically and deflecting torsionally, a

spacer I8 is provided ateach end of the bridge span, the spacers l8 being integral with the loop l5 and projecting from the loop into the opening thereof, thus spacing the span from the bottom of unit i.

Span l6 and stylus I1 are preferably positioned I slightly in advance of stylus 6 in the main scanning direction of the styluses over disk If], this direction being opposite to that of the travel of the disk under the stylus. The middle portion of span I6 is positioned close to, but out of contact with stylus 6 and its vibratory supporting means, in order to bring the support for stylus I! close to stylus 6 without interfering with the vibration and normal movement of stylus 6 in its support, this relation being indicated in Fig. 1.

' It will be seen that the line between the point of reproducing stylus 6 and the point where the stylus projects from its support, is inclined to the disk ill at an acute angle pointing in the direction of disk travel under the stylus, in accordanee with usual practice in the art, while the corresponding line between the point where stylus I! projects from the loop span l6 and the point of stylus II, also is inclined to the disk and makes a'n acute angle therewith pointing in the direction of disk travel under stylus H. In its simplest and preferred form, stylus l I is approximately straight and is positioned with its axis in a vertical planeincluding the pivot axis 5, 5, when subjected to no outside force. I

Pilot stylus l1 scansthe disk I0 with less wear to the stylus and the record and less load on the disk than is produced by stylus 6, since stylus l1 acts as a smaller mass and is free to vibrate in its elastic support "3 without being called on to reproduce the record waves for transmission. The wear and the load produced by stylus I! may be still further reduced by making the angle of inclination of the stylus to the disk, smaller than in the case of stylus 6. The angle of inclination blank space between recordings than would be possible with the single pilot stylus ll of Fig. 4. vIt will be understood however that the spacing of reproducing stylus 6 should be large enough to permit of suitable reproduction of the higher frequency components in the record waves, whereas the angle of pilot stylus l1 may be smaller, since it is not limited by any such reproducing requirement.

The point of stylus I! is preferably located outsidev of the vertical plane defined by the longitudinal axis of the span 16 when the reproducing head 2 is in reproducing-position, this plane being the plane of the loop when the span forms a part of the loop, as in Figs. 1 to 4. One advantage of this relation is that the points of ,the styluses ,6 and I1 may be positioned close together without the span I 6 being too close to stylus 6. An effective arrangement for this purpose is obtained when the point of stylus I1 is outside of the vertical projection of span It on the horizontal plane through'the point of stylus I1, and stylus 6 is in its reproducing position as shown in Fig. 1. It will be seen that stylus I1 projects outwardly from loop [5 in a direction diverging from the plane of the loop; Bridge span l6 and stylus II are preferably located-a predetermined distance in advance of reproducing stylus 6 in the main scanning direction of the styluses to avoid encroachment on stylus 6, but it will be understood that stylus I! may be located behind stylus Q in some cases, for example where there is more room for the bridge supporting means in that location.

Stylus I! is also preferably spaced to one side of stylus 6 a predetermined distance radially'of Idisk Ill, such as a distance equal to one or a few groove spacings. In one case where adjacent grooves were spaced about five thousandths (,005) of an inch apart, the predetermined distance between styluses I1 and 6 laterally of the grooves pose stylus I! may again be on either side of stylus 6, depending on whether the disk is scanned in a radially inwardor outward direction.

By placing stylus l I in advance of stylus 6 radially of disk l0, with the described spacing between the styluses, it is possible in the case of a disk having a series of discontinuous record grooves, representing separately dictated or interrupted recordings spaced relatively close togather, for thestylus IT to ride into and engage a startingportion of one of the grooves before stylus 6 reaches the end of the previousgroove. Stylus Il may thus serve to pilot or guide stylus shaped form of bridge span l6 of soft elastic rubber, or like material, with the ends of the span supported in a d-iiferent manner from that of Figs. 1 to 4. At each end of span It, a groove 30 is provided, extending across the end of the span, the span being supported by a pair of tongues or flanges l9, one of which fits into each of the pair of grooves 30, 30, and presses into the same with suflicient force to hold the ends of the bridge span positively in a fixed position. The tongues l9 form the inwardly directed ends, re-

spectively, of a pair of brackets 20, 20, project- 'ing downwardly from the rigid supporting plate 2|, which is attached to the lower side of unit i by any suitable means, such as screws 22 passing through holes 23 in plate 2| and threaded into unit I. It will be seen that brackets 20, 20 serve as spacers to hold the upper surface of span IG spaced below the bottom side of unit I, so that the span may be free to yield by flexing vertically or deflecting torsionally, as in the case of span l6, Figs. 1 to 4.

It will be understood that two pilot stylusesll, II, as described in connection with Figs. 5, 6,

or the substitute form of single pilot stylus-11,

" described in connection with Fig. 4, may be utilized in the span 16 of Fig. '7. Fig. 8 shows a side view of the Fig. '1 type of span support as it appears when utilizing either the single pilot stylus I! of Fig. 4, or the double form of Fig. 5,

the stylus II being directly in front of stylus l1 when viewed as in Fig. 8.

, The bridge l6 form of support for stylus I], as described in connection with the drawing, has been found to offer several advantages over various other forms of ,support, one advantage 7 being that the bridge provides an efllcient bal- 6 over the blank ungrooved space between two successive recordings, so that stylus 6 may be led into the desired groove without requiring manual resetting of the sound head position.

' The section of bridge span l6 between vertical lines A-A and 3-3 in Fig. 5, may be substi- -.tuted for the similar section between lines A-A and 3-3 in Fig. 4, to provide two or more stylus 6 radially of disk III while crossing a larger styluses I1, ll, inplace'of the single stylus l1 anced support for the pilot stylus and provides a balanced control of the position of the pilot 'stylus by acting directly between the unit I and each side of the pilot stylus, thereby tending to minimize the introduction of unwanted components of force tending to move the sound head unit in undesired directions as a result of distortioh of the pilot'stylus support when yielding grooves are packedvery closely together for the sake of compactness and consequently are by to up and down movements in'the level of the record surface, or as a result of eccentrlcities in the record groovecausing irregular directions of groove travel under the stylus, or as a result of other disturbing forces. For example, by employing a bridge to support the pilot stylus in a balanced manner fromeach side of the stylus, it will be seen that the stylus avoids the undesirable t ndency to move in an are around merely one en cl of the stylus support, as would be the tendency if the stylus were yieldingly supported wholly from one side alone. When the record of shallow embossed grooves in a plastic record disk, as well as in other cases, the bridge form of pilot stylus support has been foundsto be be particularly advantageous.

The bridge type of pilot stylus-support lends itself to compact construction, and as combined is not affected by in the preferred or loop form, is particularly adapted for convenient attachment to a sound head unit without requiring the use of any tools or complicated operations, and without requiring any machine operation on or alterationin the original constructionv of the unit to which it is applied. The loop form is therefore particularly convenient for attachment to phonographs which are to be conditioned for reproducing recployed in the span I6 and the loop i5, may be of any suitable variety other than plastic, provided the bridge form is maintained with its elastic and balanced characteristics similar to those of the elastic bridge 16. stylus I! may in general be'advantageously applied, not only to a reproducing arm unit, but to any type of stylus propelled sound head carriage where the stylus propelling force needs to be supplemented or is discontinuous, or where an auxil-, iary' stylus is to be combined for any purpose with 1 the main transmitting stylus. Although stylus I! has been described as being preferably a rigid stylus supported from anelastic material, it will be understood that for some situations where a flexible auxiliary stylus or a plurality of them,

such asbristles in brush-like form, are to be employed, either of the described forms of bridge 1 6, shown in Figs. 1 to 4, or 7, .8, may be employed to provide a compact, convenient and eflicient form of support. The auxiliary stylus 11, while preferably located in advance of and to one side of stylus 6, may be placed to track in the same turn of the groove as stylus 6, either in advance of or behind stylus 6 in the scanning direction, in cases where the advantages of the preferred position of stylus H is not important.

While the invention has been described as being of particular utility in connection with a phonograph sound head of the reproducing type, it will be seen that the described attachment may also be applied toa sound head of the recording type for the purpose of aiding the tracking of the recording stylus on a pregrooved record blank of the type described in U. S. Patent No. 1,522,547

to B. F. Roehrig, or for guiding the recording stylus advancing over an ungro ved surface of a record blank while the auxiliary stylus follows the groove already produced by the recording stylus, it being necessary merely to provide a starting groove in the desired direction between the points where the recording and auxiliary styluses engage in contact with the record, the starting groove being of the'form shown for example in U. S. Patent No. 1,959,423 to H. C. Harrison. The described attachment may also'be used in various other combinations where a conveniently mount- Th bridge "5 and auxiliary.

ungrooved section, a reproducer head carrying an inclined reproducing stylus for scanning said I record, and an auxiliary non-reproducing pointed pilot stylus of rigid material resiliently carried by said head and ofiset from said reproducing stylus by a distance equal to a whole number of grooves said pilot stylus being also inclined to said record and extending in the same general direction as said reproducing stylus, whereby the blank ungrooved section between said pair of grooves will be bridged automatically without requiring manual setting of said reproducer head.

2. In a phonograph employing a record having a pair of recorded grooves separated by a smooth ungrooved section, a reproducer head carrying an inclined reproducing stylus for scanning said record, and an auxiliary non-reproducing pointed pilot stylus of rigid-material resiliently carried by said headand oifset from said reproducing stylus by a distance equal to a whole number of grooves, said pilot stylus extending in the same general direction as said reproducing stylus and inclined to said record with a smaller angle. 3. In a device for attachment to a phonograph stylus-carrying unit for aiding the scanning of said'stylus in the grooves of a phonograph record. a closed elastic rubber loop encircling said unit, certain of the inside dimensions of said loop being smaller than the corresponding dimensions of the encircled portion of said unit, said loop having a gripping engagement with said unit, and an auxiliary groove-engaging pointed, stylus supported by said loop for assisting in holding the said stylus in the grooves of a phonograph record,

a bridge of elastic resilient material having bearings on said unit at a pair of spaced points and carrying an, auxiliary non-reproducing pilot stylus in vertically and torsionally defiectable relation to said grooves, said pilot stylus being spaced a predetermined distance to one side of said main stylus laterally of the scanning direction thereof to bridgeover the blank ungrooved spaces between two successive recordings.

6. In a device for attachment to a phonograph stylus-carrying unitfor aiding the tracking of said stylus in the grooves of a phonograph record,- a bridge of elastic resilient material having bearings on said unit at a pair of spaced points and carrying a pair of auxiliary non-reproducing pilot styluses spaced laterallyin advance of and behind the main reproducing stylus respectively by distances equivalent to whole numbers of grooves.

7. In a. device for attachment to a phonograph reproducing stylus for aiding the tracking of said stylus in the grooves of a phonograph record, a bridge of elasticresilient material attached to said unit, an auxiliary pointed pilot stylus supported by said bridge and oflset from said reproducing stylus by a distance equal to a whole number of grooves, said pilot stylus being of smaller mass than said reproducing'stylus so as to reduce the wear and load upon said record.

LINCOLN THOMPSON.

, CERTIFICATE or CORRECTION. Patent No. 2,528,862. 7 September 7, 19145.

- LINCOLN Tnonrson.

It" is hereby certified that error eppe-ars in the printed specification ofthe above numbered patent requiring correction as follows: Page 14., sec- 0nd column, line 65, claim7, after the word 'sty lus' insert "l mit"; and that the said Letters Patent should. be read with this correction therein that the same may conform to the record of the case iii the Patent Office.

Signed and sealed this 26th day of October, A. 1). 19A 7 Henry Van Arsdale, .('Sea1) ActingCominiesioner of Patents.

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