US2506692A - Mounting unit for phonograph tone-arms - Google Patents

Description

y 1950 E. o. THOMPSON 2,506,692

MOUNTING UNIT FOR PHONOGRAPH TONE-ARMS Filed Oct. 11, 1947 K INVENTOR. lulllllllmmw L /W5? 0 190M 10 BY F/GZ 2. 63, Q 4 %,,,,M I f Adi/V7) Patented May 9, 1950 UNITED STATES PATENT QFFICE MOUNTING UNIT FOR PHONOGRAPH TONE-ARMS 4 Claims. 1

The present invention relates to phonograph apparatus and, particularly, to phonograph apparatus of the type having a pivotally mounted tone-arm adapted for playing engagement with a record supported on a turntable. Specifically, the invention has to do with improvements in the mounting of the tone-arm.

In phonograph apparatus of the type above mentioned, the tone-arm which carries the pickup, is customarily mounted to swing freely in a direction transverse to the record supporting surface of the turntable, so that the pick-up needle can be brought in and out of engagement with the playing surface of the record, and so that the tone-arm will be free to move with undulations of the record. The tone-arm is also mounted to swing in a direction paralleling said surface of the turntable, so that the tone-arm can be moved out of the playing field to allow changing of records, and so that the pick-up needle will be free to track the record groove. Because the tone-arm is free to pivot in the two above mentioned directions, sudden translatory or rotatory movements of the phonograph result in undue displacements of the tone-arm and cause the pick-up needle to jump oil or slide across the record. For these reasons, ordinary phonographs are adapted to play properly only when in a stable and substantially level position. They are not suited to play while in transportation, and are particularly incapable of adequately playing in driven vehicles, such as automobiles, which are subject to shocks, jars, and vibrations due to abrupt stopping and starting, traveling up and down hills and over bumps, and changing direction from a straight line path into a curve or turn.

It is, therefore, the primary object of this invention to provide a phonograph which is adapted to play in any position and which can play properly in transportation, particularly, in moving vehicles. To that end, the invention employs a tone-arm mounting which allows the tone-arm to be pivotally moved about two perpendicularly related axes but which effectively prevents accidental displacement of the tone-arm about said axes and, thus, insures positive retention of the pick-up needle in the record groove, even when the phonograph is subjected to severe jolts.

Another object of the invention is to provide a tone-arm mounting which makes the above mentioned advantages possible, and which has a simplified construction capable of being readily associated with other existing parts of the phonograph without necessitating material changes therein. This object of the invention is obtained by means of a unitary structure which is adapted to provide for normal swinging movements of the tone-arm but which functions to counteract any tendency of the tone-arm to move abnormally under influence of shocks, jolts, jars or unusual severe movements of the phonograph.

Still another and more specific object of the invention resides in the provision of a tone-arm mounting arrangement which makes it possible to balance the tone-arm both statically and dynamically so that the pick-up needle will not slide across nor leave the surface of the record during the playing thereof, even should the: phonograph be subjected to unusual shaking or swinging motions in any direction. For that purpose, the invention provides a tone-arm supporting unit in which counterbalancing and counterrotating means, having moments of inertia dynamically balancing those of the tone-arm assembly, are so coupled to said assembly that said moments of inertia oppose undesired movements of the tone-arm assembly.

These and other objects of the invention, and the manner in which they are obtained, will be fully understood from the following description. based on the accompanying drawing which illustrates a preferred embodiment of the invention, and in which:

Figure l is a side elevational view showing a tone-arm mounting constructed in accordance with the invention, certain parts being broken away for clarity of illustration;

Figure 2 is an enlarged elevational-sectional view looking in the general direction of arrows 2--2 of Figure 1; and

Figure 3 is an exploded view of certain parts of the arrangement as shown in Figure 1, and illustrates the mode of assembling the tone-arm mounting unit with the phonograph base plate and tone-arm.

With more particular reference to the drawing, Figure 1 shows a turntable 5 and a tone-arm 5. The turntable is conveniently mounted on a base plate 1, and is adapted to be rotated in the usual manner by means of a suitable motor (not shown). The turntable is further adapted to support a record, as is indicated at 8, and to rotate the record in relation to the tone-arm 6. The tone-arm carries a pick-up 9 which is provided with a needle Ill disposed for engagement with the customary spiral modulated groove of the record. As shown, tone-arm 6 is supported to swing about two perpendicularly related axes. Swinging movement of the tone-arm about one of said axes base plate.

3 allows for movement of said tone-arm in a direc tion transverse to the plane of the turntable, in order that the pick-up needle may be brought in or out of engagement with the record, and in order that the tone-arm may accommodate it self to undulations of the record. Swinging movementofthe-gtone-arm abeut the other 'ofgsaid axes allows for movement of said tone-arm in a direction generally parallel to the plane of the turntable, in order that said tone-arm may be;

moved out of and into the playing field and in order that the pick-up needle may follow the} record groove, unobstructedly.

In accordance with the inventioneandiaslillusl entirety, by the reference numeraL U, and, which.

is constructed and arranged to provide for movement of the tone-arm in the two above named'idirections. For that purpose, unit ll includes a generally cylindrical supporting member; 'or standard 1 2 .'which; as more clearly shown,- in ;Figure;2;.has ears l3gadapted to provide-diametrically opposed: bearings l4; These bearings. may be; of an-y. suitable construction, and are adapted to, receive. a rotatable shaft or pivot. l5. Ascan best be seen in said Figure 2; the: sides of: the tome-armv 6-. are; provided: with bifurcated trunnions;l-fiswhich.are-adapted-to engage pivot I Stand. tobe rigidly connected thereto, as by means-of suitable: locking elements- L1. Thus; the tonearm can; beswungatiright; angle: to-the longitudipal; axis: of; the mainsupporting member l-2-. 'Iihge member I2" is arranged; for rotation, about its; longitudinal; axis, on the, base plate- 'l. This is conveniently accomplishedby providing aballbearingconnection which; as=more clearly shown inEigureaZ is mounted on member Mandhas-a part II flradapted to be fixedly-secured t: the base plate. For; that purpose,- the member l2; to,-

gethen' with; its; ball-bearing; connection;. isreceivedjinan opening 19in the-base plate, andi-the part I8 of the ball-bearing connection has a;;1ip 20 disposed to; bear on, the one side of the base plates The part l8 further-has a threaded per.- tion' 2-! in engagement with anut- 22: adaptedzfor bearing engagement, with the, other side of the In this manner; thetone-arm isiree to rotate with member I2 about theflongitudinal axis ofthe latter. As.i1lustrated;in= Figure 1-; a r coil spring-23, which has oneorits endsattached to a connection: 24'. on the toneearm, and which has its other end attached to-a'brackett 25;secured,

asrbyvmeans oi-jfastening; element 28, on; a; rotatable} member; 12; serv s. -t ma ntain; he-.- pi k-up needle in proper tracking engagement-with; the recordigroovet As. hereinbefore stated the, tone-arm, accord ing toithe presentjinvention is adapted to-be-perfectly balanced-statically and; dynamically about both of its axes of rotation so as not; tobedeleteriously afiected by shocksorvibrations to which the-phonographmay besubjected. For that-purpose; andas particularly shown in E ure; 1,. the toneearm' s provided; w h: an d p r ion: whichprojectsbeyond theipivot; l5, and acoun terbalancing weight 28 is: attached to this ex tended; portion. 'l lhe -massot Weight 28.- and. of the extendedportionjl onone side of thepivotal axes-issuch thatitaccurately-balancesthe mass ofqthepick upandof the tone-armportion on the otherside; of said; axesi, Because; of this. con:

struction, it: will be understood that; in eife t; the

tonerarm assembly; iszpiuoted: for rotation: at; its Center. of gravity; so; that, the toner-arm... when; at

rest, is perfectly balanced. In order to allow for critical adjustment in balancing the tone-arm, the weight 28 is adjustably mounted on the tonearm portion 21. This is conveniently accomplished by providing said portion with a slot 29, and by providing the weight with a suitable releasable-locking element 36:. passing through said slot. Afterloosening element 3%, the: weight may be slidably adjusted until perfect balance is secured, and then the weight may be retained in adjustedpositiomby tightening said element.

Because the tone-arm is perfectly balanced in the manner above described, translatory movementsro-ithe phonograph in directions transverse to either therotatable member i2 or to the rotatable pivot l5', will not deleteriously affect the inertia. of, the tone-arm. Accordingly, the tonearm, if moving under influence of the radial leadforce-developed by the spiral groove of the record, will tend to continue its normal movement, although thephonograph mfiyrbe subjected toseverejolting in directionstransverse to the pivotalaXes-of the tone-arm;

However, the-inertia ofthe balanced tone-arm would be deleteriously affected by unusual-rotatory movements; ofthe phonograph in; directions corresponding to the axeszof the tone-arm, Such rotatory movements ;tend to develop torquef orces which, in turn, tend-s tor produce; abnormal rotae tional displacements of; the; tone-arm, with the result that. the pickupneedletends toslidei-over or-to leave thesurface of thegrecord 111501516 3130 overcome these conditions; the finvehticiliprovides the unit I i with count rba an ineza fl* Q 1 T0r ta inem a s w ich ndto: u terectr hg fiects of such rotatory; movementspf the phonograph.

For the purposez of. counteracting the effectg of; those rotatory movements which; tend tocause abnormal, displacement oh the: tone-arm about the axis,ofrotationat pivot 15, a mass, indicated generallyatfil (Figures 1.. and; 2;) and, mounted torotateat itscenter of: gravity on a support 3.2; is so connected-withv said pivot as: to 'rotate in a; directionopposite to the-- direction in which said: Divot, tends to rotate. under influence, of such rotatory movements of. thephonograph. In the embodiment illustrated,inethe drawinga the rotate able mass and its support are housed an enlarged portion 33; of the tone-arm supporting member l2; The-mass,- asshowmconsistsof; a pair of balan edv flywheels; 3d and tea, a shaft- 35 interconnectin the: fiywheels-at their centers; and a gea 36 fix dz oh shaft; Th support: 32 ineludessuitable;bearingsfi]. (Eigurejz) which-are p d: o n ag the shaft? tease. as. to. suppor sa d t-.i i hz ts gea and? flywheelsin perfectly balanced condition. 'The gear .36 engagesms ear ent .8 n cvid ddnz ne end of; anarm 3.9,;the other, indi t-W i h:is' i eidir secured; .asrindicated at t-dinfligure Z'gtothepivoti 1530f the toner-arm, in, such amann r. that saidarm-.tilrcxtendsfrom said pivot and; to. he ylindrical: supportin member. 2 Thefiywheelesha it a um-gear assein hl whi h. constitut s; therotatable mass: 31 is uch: hat: its: m ment; .13 nertia; about: shaft: 35; a t y dv ami al y ala cesz he moment f; in;- r -iax f the o ema emblr-ab utn vctz tfiand in lud nszthe. arm. 3 9 and: e arqsesmentcfiii .1 T Thus; t mass 12p sesha endency; of? the tone armrto, rotate aboutlthe axis; of pivot [5, when c vibrations tend to: mpartrctatorvmovements, to the phonograph; in directions corresponding to axis of; rotationalfpivot. l5;

lor: he; p pose o counteractin the; eiiect. hos rotatory Increments; Whichi end; to

cause abnormal displacement of the tone-arm about the axis of rotational supporting body i2, another mass, indicated generally at l I is mounted to rotate at its center of gravity and is so connected with said body as to rotate in a direction opposite to the direction in which said body tends to rotate under influence of such rotatory movements of the phonograph. In the arrangement shown, the rotatable mass M consists of a balanced flywheel 42 and a pinion 43 rigidly connected with said flywheel. The flywheel-andpinion assembly is rotatably suspended on a stud 44 suitably attached to the lip 20 of part 18 of the ball-bearing connection, which part is fixedly secured to base plate I. The pinion 43 engages a gear-toothed element iii provided on the circumferential surface of enlarged portion 35 of the tone-arm supporting member 12. The fiyWheel-and-pinion assembly constituting the rotatable mass M is such that its moment of inertia, about stud 44 exactly dynamically balances the moment of inertia of the complete tonearm assembly, about the vertical axis of member I2, including the mass 3|, connecting arm 39 and segment 38. Thus the mass 4| opposes the tendency of the tone-arm to rotate with supporting member l2 about the longitudinal axis of the latter, when shocks or vibrations tend to impart rotatory movements to the phonograph in directions corresponding to said axis of the rotational member l2.

In associating the tone-arm mounting unit I! with the phonograph, the tone-arm supporting member [2 of said unit is introduced, as represented in Figure 13, through opening IQ of base plate 7, and is guided in said opening until lip 26 of ball-bearing connection part It comes in contact with the confronting side of said base plate. The nut 22 is then engaged with threaded portion 2! of said part I8, and is tightened until the unit becomes securely clamped on the base plate. Bracket 25 is then secured to member I2 by means of fastening element 26. The tonearm 6 may then be rigidly connected with said member by engaging bifurcated trunnions 16 with pivot i5 and by tightening the fixing elements I! on said pivot which, in order to insure positive connection, may be provided with suitable depressions disposed to receive the end of said elements 11, as shown in Figure 2. When mounted, the tone-arm is accurately balanced on its support by adjusting weight 28, if this is found necessary. Spring 23 (Figure 1) which is adapted to supply the required needle pressure on the record, is then connected to the tone-arm 6 and bracket 25.

From the foregoing description, it will be appreciated that the present invention provides a simple yet dependable arrangement whereby the tone-arm of a phonograph is capable of free normal movement during the playing of a record, but is effectively checked against undesired movements, in all directions. Moreover, from the preceding description it will be appreciated that the invention makes it possible to provide a mounting unit for a phonograph tone-arm, which unit functions to insure proper playing of a record regardless of the position of the phonograph or of any swinging or shaking motion to which the phonograph may be subjected. Particularly, the provision of a tone-arm mounting unit as herein described, has the advantage that it can be readily used to replace the usual tone-arm support provided on phonographs, especially because such a unit can be mounted without the exercise of exceptional skill.

I claim:

1. A unit for mounting a phonograph tone-arm to rotate about two perpendicularly related axes, said unit comprising a tone-arm supporting member, means arranged on the supporting member to mount the same for rotation about one of said axes, a flywheel structure supported by said means to rotate in aplane transverse to said one axis and connected with said member for rotation counter to the rotation of the latter, a tone-arm engaging element mounted on said member for rotation therewith about said one axis and for rotation relative to said member about the other of said axes, and a second flywheel structure supported by said member to rotate in a plane transverse to said other axis and connected with said element for rotation counter to the rotation of the latter.

2. A unit as set forth in claim 1, in which the supporting member is hollow, the first-mentioned flywheel structure is supported exteriorly of said member by the stated means, and the second-mentioned flywheel structure is supported interiorly of and by said member.

3. A tone-arm mounting unit comprising a generally cylindrical member, support means arranged on said member to mount the same for rotation about its longitudinal axis, a flywheel structure supported by said means to rotate about an axis substantially paralleling the mentioned rotational axis of said member, a connection between said member and flywheel structure to rotate the latter counter to the rotation of said member, a rotatable shaft provided on said member and extending in a plane transverse to the rotational axis of said member and adapted for connection with a tone-arm, said shaft being arranged for rotation with said member and for rotational movement with respect thereto about an axis extending substantially at right angles to the rotational axis of said member, a second flywheel structure housed and supported within said member to rotate about an axis substantially paralleling said shaft, and a connection between said shaft and second flywheel structure to rotate the latter counter to the rotation of said shaft.

4. A tone-arm mounting unit as set forth in claim 3, in which the first-mentioned connection includes a pinion attached to the first-mentioned flywheel, and a toothed wheel afiixed to the generally cylindrical member and in mesh with said pinion; and the second-mentioned connection includes a gear as part of the second flywheel structure, and an arm secured to the rotatable shaft and having a toothed rack in mesh with said gear.

ELMER O. THOMPSON.

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

UNITED STATES PATENTS Number Name Date 2,033,729 Montfort Mar. 10, 1936 2,263,979 Bruno Nov. 25, 1941 2,331,122 Jones Oct. 5, 1943

Images