US2331122A - Stabilized phonograph arm - Google Patents

Description

Oct. 5, 1943. A. M. JONES K STABILIZED PHONOGRAPH ARM 2 Sheets-sheet 1' Filed Dec. ll, 14940 Oct. 5, l943. A. M. JONES 2,331,122

STABILIZED PHoNoGRAPH ARM `Filed De'c. 11, '1940 2 Sheets-Sheet 2 afwaaiented Oct. 5, 1943 UNITED STATES PATENT oFFIcE Application December 11, 1940, Serial No. 369,643

2 Claims.

This invention relates to a phonographic, re-

producing and recording apparatus, and the like,

masses and counterrotating masses, the pressure at the stylus being obtained by means of tension between the parts of the phonograph arm rather than the force of gravity; thus, movement of the phonograph will not tend to cause the arm to move and change its pressure or direction of pressure at the stylus, eliminating the condition known as jumping stylus.

A further object of this invention is the production of a pick-up arm which is simple in construction, may be manufactured commercially economically, and which may be designed to use the same essential parts as pick-ups of presentday manufacture.

A still further object of this invention is the production of a pick-up arm which is so foolproof and so similar in operation to the ones used in ordinary sound work, that re-education in its use will be unnecessary.

Other objects and advantages of the present invention will appear throughout the following specification and claims.

In the drawings: Figure 1 is a side elevational view of one form of my improved phonograph arm, certain parts being shown in section;

Figure l-A is an optional form of Figure 1;

Figure 2 is a vertical sectional view taken on line 2,-2 of Figure 1;

Figure 3 is a horizontal sectional view taken online 3 3- of Figure 1; l

Figure 4 is an enlarged vertical sectional view of the supporting post, a part of the arm and other associated parts;

Figure 5 is a perspective view of the tension means: engaging plate;

Figure 6 is a perspective view of the journal platefor the phonograph arm;

Figure 7 is a perspective view of the lower locking plate for the tension means `oi the phonograph arm;

Figure 8 is a perspective view of the lower end of the tension screw;

Figure 9 is a side elevational view of a modified form of phonograph arm, certain parts being shown in section;

Figure 9-A is an optional form of Figure 9;

Figure 9-B is a front end view of Figure 9, with an yadded optional means for holding the arm igid vertically with respect to abutting record;

Figure 10 is a top plan view of the phonograph arm and record associated therewith;

Figure 1l is a longitudinal fragmentary sectional view showing a further modified form of tension means for the phonograph arm;

Figure 12 is a longitudinal fragmentary sectional view of a still further modied form of tension means for the phonograph arm;

Figure 13 is a vertical sectional view showing a form of the means for resisting lateral swing of the phonograph arm;

Figures 14 and 15 are vertical sectional views similar to Figure 13, showing further modiiled forms;

l Figure 16 is a top plan view of a modified shock-resisting means for carrying a pick-up head; l

Figure 17 is a perspective view of a means for holding the outer end of a phonograph arm and Figure 18 is a vertical sectional view showingV a modifled form of the means for resisting lateral swing of the phonograph arm.

By referring to the drawings, it will be seen that 20 designates a pick-up arm which may be formed of light metal or molded plastics, the

pick-up arm 20 being preferably hollow along its under face and constituting a substantially U- shaped structure in cross section. A crystal or pick-up head 2| is carried by the outer end of the pick-up arm 20, as shown in Figure 3. A counter-balance 22 is carried bythe rear or opposite end of the Dick-up arm 20 with respect to the crystal or pick-up head 2|, so that both the lateral and vertical pivots oi' the arm are at its center of gravity. 'I'he arm should be reasonably lshort and light in weight.

A pick-up arm supporting standard 23 is carried by a suitable mounting board 24 and this standard 23 extends in a vertical position, as shown in Figures 1 and 4. A tension adjusting screw 25 'is carried by the pick-up arm 20 adjacent the counterf-balance 22 and this tension adjusting screw' 25 is provided with a thumb head 28 (attached by a tight tting pin z-a) which extends above the arm 2|) to facilitate the operation of the screw 25. This screw carries a square-shaped nut or cap 21 upon the threaded portion ofthe screw 25, which threaded portion preferably extends about one-half of the length of the screw 25. It should be noted that square nut 21 is adapted to rest against the front face of the counter-balance 22 to prevent the nut 21 from rotating as it is threaded by screw 25 to an adjusting position. A locking plate 28 is carried by the bottom of the counter-balance 22 and this locking plate is provided with a toothed portion 29 upon its under face which is engaged by a toothed portion 30 carried by the lower end of the screw 25 to hold the screw 25 in a set position. A compression coil spring'3l is carried by the screw 25 and rests against the nut 21 at its upper end. The lower end of the spring 3| rests upon the rearwardly extending portion 32 of the tension control plate 33, the lower end of the screw 25 passing through the elongated slot. 34 in the rearwardly extending portion 32 of the tension control plate 33. The tension'control plate 33 is fixed upon the upper end of the standard 23, the tension' control plate 33 having a forwardly extending end 35 terminating in an upwardly extending lip 36. This end has an aperture 31 formed therein.

A vertically extending hollow tube 38 extends through the central aperture 33 of the tension control plate 33, and this plate 33 supports a rubber washer 40. This rubber washer in turn supports a metal journal plate 4| the journal plate 4| having a projecting tongue 42 which fits within the aperture 31 of the tension control plate 33 to prevent its rotating. The hole of plate 4| is somewhat larger than tube 38. This journal plate 4I in turn supports a rubber washer 43 and a metal washer 44 is carried by the Washer 43. The ends of the tube 38 are outturned to provide a securing ferrule to hold the vibration damping assembly together, the vibration damping assembly comprising the plates- 33 and 4| and the washers 40, 43 and 44. The wires 45 leading to the pick-up head pass through this tube 38, as shown in Figure 4. 'I'he journal plate 4| is pro- Figure l-a is an optional design of Figure l in which the arm 2lia is balanced for vertical movement at 48-a forward of the pivot of its standard 23--a allowing lateral movement. This design has the advantage of permitting the standard to be used further to the rear of the arm with a smaller weight '.2-a on the'. arm. The latter weight 22-a is smaller because it isfurther to the rear of pivot 26-a. The arm must be balanced about its standard 'Z3-a by means of an added weight 85 attached opposite the arm 20-a to its standard 23-a. This arm will have less inertia in a vertical plane, but more when rotating laterally.

By referring to Figure 9 it will be seen that a modied form of the invention is illustrated wherein a pick-up arm 2lib is shown having a counter-balance weight 22-b at its rear end. A tension control plate 33-a is supported upon the standard 23-b in a manner similar to that previously described with respect to Figure 1. A journal plate 4|-a is carried by a vibration damping assembly 43--a similar to that illus-` trated in Figure 1. In the structure shown in Figure 9, however, a tension spring is carried by a suspended pin 6| which pin is supported by the arm 2li-b, the lower end of the pin sliding through a round hole in the rearwardly extending portion 32-a of the tension. control plate 33-a.

This plate 33--a is provided with a forwardly extending tongue62 which carries a vertically extending adjusting screw 83, the screw'83 contacting a cushioned washer 64 which abuts the under face of the arm 2li-b, in all providing a stop for the pick-up arm 2lib adjustable to the turntable height and holding the arm 20--b rigid with respect to standard 23--b during operation.

vided with laterally extending journal portions 48 which are journaled in the sides of the pickup arm 20, as shown in Figure 3.

The standard 23 is supported upon the upper threaded end of a hollow sleeve 41 and the lower end of this-sleeve carries a tap or n ut 4 8-a. The sleeve 41 passes through the mounting board 24 and extends through a thimble 48 which also passes through the board 24. as shown in Figure 4. Shock absorbing washers formed of rubber or other material 49 and 50 are carried by the thimble 48 and engage the mounting board 24. A ball-bearing race 5| may be carried by the stand.- ard 23. as shown. A compression spring 52 is carried by the lower end of the hollow sleeve 41 and abuts against a washer 53. the washer 53 engaging a nut 54, which nut 54 is threaded on the lower end of the hollow sleeve 41. 'I'he pickup wire passes down through the standard 23 and the hollow sleeve 41.

'I'he pick-up arm 20 and its component parts including the adjusting spring 3|, are perfectly balanced on the laterally extending journals 46. and on the vertical axis of the arm. 'I'he shaft 23 with its component parts. comprising the vibration damping assembly, is also perfectly balanced independently about its axis. In other words; all pivots are at the centers of gravity of the parts which are adapted to pivot about them.

Standard 23-b is mounted on board 24-b through a ball-bearing pivot as in Figure 1.

The outer end of pick-up arm 20--b carries a hanger 11 interposed between cushion washers 13 and 14 and metal Washer 18. 'I'he construction and operation of this vibration damping hanger is very similar in construction and operation to the vibration damping assembly described in Figure 4. This U-shaped hanger 11 pivotally supports a pick-up head 19 at its center of gravity. A iiat spring 80 is secured to the under face of arm 20 and is slidably mounted through a suitable guide 8| so that there will be an even upward tension on the guide 8| for any position oi' the pick-up head 19. The tension on the spring 8U is adjusted by increasing or decreasing its length by means of a slidably mounted guide 12 through which spring feeds. This guide is frictionally held in a slot on the top of the arm 20-b. In order that the inertia of the head 18 will not cause a change in pressure at the stylus when subj ected to movement in a straight line, the pick-up head is shown mounted in its center oi gravity. So that the needle will be free to move up and down with undulations of the record and slight movement of the pick-up arm with respect to the turntable due to vibration of these parts, the head is pivoted so that the needle moves in an arc substantially perpendicular to the face of the record; otherwise, a force directed at the needle would tend to push against the pivot, which does not yield. In other words, the pivot of the head should be as low to the record and as far back from the needle as practicable. Relatively small inertia of the head 13 as compared with the tension upon it also allows this unrestricted vertical movement. 'I'he tension means 88 should direct a force substantially perpendicular to a plane running through its point of contact and the.

axis of the head; otherwise, it likewise will pull against the pivot` rather than cause rotation about it. 'I'he tension means should consist of a reasonably long spring so that the tension will not be diierent for the varying positions of the pickup head. In order to accomplish all of the above an elongated head such as is shown should be` used. Crystal heads are universally constructed.

relying solely on the other one, abutting the standard. Of course, either or both vibration damping assemblies may be omitted. and both would hardly be necessary.

In this arm` likewise as in the one of Figure 1. all pivots are at the centers of gravity of the parts which are collectively adapted to move about them lduring operation. v

In association with the larm 28-b a stop pin 15 is properly located upon the mounting" board 24--b and a supporting yoke 16 is also properly located to receive the arm 'Z8-b. The pick-up arm 28--b may be in the shape shown in Figure 10, if desired.

Figure 9-a shows an optional design of the arm of Figure 9 in which the arm is hinged at 66 to 'allow part 28c| to be lifted oil the record, either for changing needles or for changing records. In order to remove the arm for purposes of changing records, the pick-up head as shown in Figure 9 permits enough vertical movement so that the arm may be laterally moved aside without necessitating verticalA removal-of the arm itself, so hinging of the arm is not absolutely necessary especially where permanent needles are used. Part 28--c-2 is the other half of the arm and is connected to standard 23--c by means of a wing nut 69 which locks it in any vertical position desired. Parts 28--c-I and 28\c-'2 are locked rigidly together by hook 61.- The entire unit is balanced about the axis of the standard 23c by means of weight 65-a attached to the standard at the rear of arm 28-c.

Figure 9-b is a front-end view of Figure 9 with an added optional means for holding the arm stationary -vertically with respect to an abutting record. Part 18 is a rigid and smoothly finished piece of metal abutting the record immediately to the rear of the stylus and secured to arm 2li-d. The stopscrew 63 of Figure 9 is of course adjusted so that the tension of spring 68 acts against stop 18 instead of stop 63. Crystal 19-a is of course yieldably mounted as in Figure 9. Stop 18 is Figures 1 and 9. In this instance as shown in Figure 11, the standard 23-d supports a vibration damping assembly 82 somewhat similar to 4that described with respect to Figures 1 and 9.

In the structure shown in Figure 11, however, a tension plate 83 is carried by the -vibration damping assembly 82 and is provided with a forwardly extending flat spring 84 which contacts a transverse pin 8 5 carried by the arm 28--e. A journal plate 86 is carried by the vibration .damping assembly 82 and is provided with a rearwardly extending tongue 81 which extends through the uptumed apertured ear 88 of the tension plate 83.

The journal plate 86 is provided with laterally extending journals 89 which provide apivot for vertical movement of the pick-up arm 28-e.

In Figure 12 there is illustrated a further modiiled formvwherein the pick-up arm 28-f is pivotally supported upon a vibration damping assembly 82a through the medium of the journais 89-a. A" tension plate 98 is supported upon the standard 23-e and this tension plate carries a weighted portion 9| (adapted to balance the forwardly extending tongue 93 of the journal plate which carries the journals 89va. An adjustable tension bolt 94 is suspended from the arm 28f and extends through a `slot in the forwardly extending end 95 of the tension plate 90. A setscrew 96 is carriedby the end 95 and engages a cushion washer 91 providing an adjustable vertical stop for the arm 28--f. In this pick-up design as well as all the others all pivots are at ythe centers of gravity of the yparts adapted to move about them.

In Figure 13 there is shown a form of the invention wherein the standard 23-1 is rotatably mounted through a thimble 1| carried by the mounting board 24-d. A gear 98 is carried by the lower end of the standard 23--f and meshes with a pinion 99 supporting a'ywheel |88, this wheel being journaled upon a hanger |8| of suitable type. The flywheel is weighted and geared so that its moment of inertia about its axis is exactly equal and opposite to that of the -entire pick-up assembly about its vertical axis made to have as little frictional resistance as posresisted by the stop 18. In Figure 9 the force is exerted on stop 63 rather than on the stylus. The stop of Figure 9-b is desirable for use with automatic record changers where several records are on the turntable at a time, as it will automatically adjust itself toA varying turntable heights, whereas that of Figure 9 will not. When any of the foregoing devices are used with automatic record changers, any added engaging parts should be counterbalanced'about their axes.

In Figure 11 there is shown a modified type of the invention wherein the pick-up arm 28-e is supported in a manner somewhat similar to that illustrated and described with respect to exactly counteracting any tendency for the bal' anced pick-up arm to rotate in a lateral plane due to its inertia when subjected to rotation.

In Figure 14 there is shown a modified form of the invention wherein the mounting board 24--e carries a thimble 1 |-a through which extends a pick-up arm supporting standard 23-g. This standard 23- g carries a bevel gear |82 which is secured thereto, and the standard 23-g also supports a freely rotating flywheel |83 at its llower end. The flywheel |83 carries a gear portion |84 near its center and an idle pinion |85 meshes with the gear |82, and the gear portion |84, the' idle pinion |05 being supported upon the hanger bracket |86. Likewise this wheel |83 is Weighted so thatits inertia. exactly opposes that of the pick-up assembly about the axis of its standard 23-g.

In Figure 15 there is shown a further modiiled form of the invention illustrating a mounting board 24-f which supports a standard 23-h upon which is iixedly secured a iiywheel |81. A nger |98 extends laterally from the standard 23--h and engages a vertical rod |89 which is pivoted upon a hanger bracket I|8. The lower end of the rod |89 extends through slotted aperture Hl formed in the flywheel |81, and this mechanism also opposes the pick-ups moment of inertia about the axis of the standard 23-h.

In Figures 13, 14 and 15, a ywheel is shown as being the most practicable rotating mass to be'used. However, any shaped mass pivoted at its center of gravity would be satisfactory. As the counter-rotating masses of Figures 14 and 15 rotate about the same axis as the pick-up arm they are scientically perfect; however, for practical purposes the` construction shown in Figure 13 with an independent axis for the ywheel 'will be entirely satisfactory for all practical purposes. Lever means instead of gears may be used in- Figure 13. These fiywheels illustrated in Figures 13, 14 and 15, which are. geared or engaged so that their moments of inertia are exactly equal to and will oppose that o1 the pick-up arm rotating in a horizontal plane, have a dual purpose: (1) They eliminate any tendency for the pick-up arm to rotate in a horizonta1 plane with respect to its support when the support is subjected to rotating movement, while at the same time free lateral movement of the arm is permitted to follow the feed of a record; and (2) the inertia of a mass in equilibrium will also hinder any lateral vibration from any cause whatsoever, being set up in the laterally engaged pick-up arm.

Figure 16 is a top plan view of a modie'd shock-resisting means for carrying a pick-up head. |29 is a bar which is vdisposed laterally across the approximate center of a record by means of pivot |28 and latch |21. Pulley wheels |23 are pivoted at either end of bar |29 and engage an endless string |26. Freely moving slides |24 and |25 on bar |29 are attached to string I 2G, eachI at an opposite side of bar |29 and equally distant from the pulleys |23. Slide |25 is a pick-up carrying slide and carries a yieldably mounted'pick-up head such as illustrated at the extremity of the arm of Figure 9. Slide |24 is a weight carrying slide which is weighted so that its mass is exactly equal to the mass of |25 and attached parts. This device is a modiiied means of having a pick-up engaged with an equal mass moving oppositely with it in the same plane. The same is done in Figures `1 and 9; however, here the inertia of `the device may be much smaller and vertical movement of the entire device is impossible during operation. Latch |21 permits removal of the arm off the record for changing records.

In Figure 17 there is shown-a further modified form of the invention wherein the pick-up arm ||1 is illustrated, and this arm is engaged by an overhanging frame |8 which is provided with a felt or other friction strip ||9 on its lower face for frictiohally engaging the upper face of the pick-up arm ||1, preventing vertical movement of the arm and frictionally resisting sudden lateral movement. The frame ||8 is pivoted, as at |20, to a suitable support, and stop pins |2|, preferably adjustable, are suitably located to limit the downward swing of the frame ||8. Coil springs |22 are anchored at one end and secured at the other end to the inner face of the frame ||8near the forward end thereof beyond the pivots |20, to hold the frame in contacting relation with the pick-up arm ||1. When the frame 8 is raised, however, to cause the spring connection |22 to be raised above the pivot |20 the springs |22 will hold the frame ln an inoperative position out of contact with the pick-up arm H1. The pick-up arm shown is preferably mounted on pivots at its center of gravity and pressure at the needle point is obtained between the overlying bar ||8 and the pick-up arm itself by pressure in the frictional substance.

Figure 18 is a vertical sectional view showing a modified form for frictionally resisting lateral rotation of a phonograph arm. 'I'hestandard 23-i has attached to it a metal washer |31. Standard 23-i fits through a thimble 1|-b, which thimble is secured to mounting board 24-g. Frictional substance such as felt |30 is interposed between washer |31 and thimble 1 |b. Washer |34 carried by standard 23-1 abuts thimble 1|b and washer |30 on 23- abuts nut |38. Compression spring |38 is interposed between these two washers, causing a tension in the trictional substance |30. Nut |38 is threaded for adjustment so that the tension in the frictional substance |30 may be changed as desired.

In the modified forms of this invention an attempt has been made to render the inertia of the device ineffective in causing a change of pressure at the stylus when the device is subjected toy change 0f position. Any mass has inertia and tends when at rest to remain so and when'in motion to continue in motion in the same straight line or direction, unless acted upon by some external force. There are four possible kinds of movement which a mass may be subiected to and will tend to resist. They are: (1) rotation in a horizontal plane, (2) rotationin a vertical plane, (3) movement in a straight line vertically, and (4) movement in a straight line horizontally. As an example to point out how these movements are encountered in an ordinary vehicle, it will be shown how .they come into play in an automobile and then how the modified forms are adapted to overcome them.

The most severe changes of position which an automobile is subjected to are non-rotational, such as stopping and starting, sudden movement up and down hills or bumps, and movement from the straight path when turning a, curve, especial- 1y at high speeds (centrifugal force). Next in importance is rotational movement in a vertical plane. This is encountered when the car noses up or down hills or bumps, with one end of the car going up or down with respect to the other, and is apt to be sudden. Least in importance or severity is rotation in a horizontal plane. This would only be encountered severely when a car breaks into a skid, one end of the car moving sidewise more than another. It would be encountered also in turning curves, but would not be sudden. When it is considered the time that it takes to make a complete U-turn and the steady amount of force that it takes to completely rotate an object such as the device used in this invention during that same period of time, it will be seen that rotational movement encountered on curves is not a great factor under ordinary driving conditions in producing a force on the needle of a pick-up arm.

The device illustrated in Figure 1 has its lateral and vertical pivots at its center of gravity. In other words, the masses of the arm are equal on all sides of the pivots; thus, it is impossible for straight movement in any direction to tend to make this arm rotate about either of its axes. As this arm is affected by rotational movement it was advised in the specications to keep its moment of inertia about its axes low, using lightweight parts in a reasonably short arm. It helps to put as many parts as possible, such as the spring tension assembly, to the rear of the axes Aso that they will aid in counterbalancing rather than having to be counterbalanced.

The pick-up illustrated in Figure 9 also 'has all of its parts balanced about its axes so that direct movement of the phonograph is ineffective in causing the arm or parts to rotate. To overcome the inertia of the arm and movement in a vertical plane, the great mass oi the arm is held rigid, allowing vertical movement only in the pick-up head or sound box which has such a small m`assl that its inertia when pivoted at its center of gravity is practically negligible. This prevents the pick-up head digging in or Jumping out of the groove when vertical rotation of the vehicle is encountered as explained above on jolts or in starting up or down'hills. The pick-up head, due to its construction described in the speciilcations with reference to Figure 9, is free to move up and down without a change in pressure at the stylus to follow the undulations of an uneven record or to accommodate small variation of the space between the pick-up arm and the tum-table due to vibration of these parts when subjected to shock and movement.

There is only one type of movement left which must be overcome, and that is rotation in a horizontal plane.

a horizontal plane and engaged with the pick-up so that its moment of ,inertia about its axis is equal and opposite to that of the pick-up. When this unit is attached to a phonograph and the phonograph is twisted or rotated in a horizontal plane, the pick-up arm will not be free to remain still with the phonograph revolving beneath it; and the entire unit will rotate together. When the counter-rotating means of Figures 13, 14 and 15- is used in connection with Figure 9, each of the four movements to which a phonograph may be subjected is overcome.

A stabilized arm such as has been described in this invention may be used not only with sound transmission equipment but any other equipment where necessary that it be free to move in a manner similar to a phonograph reproducing or recording head and yet be held in a state or equilibrium with respectto its support when movement oi' the support is encountered.

This is accomplished by using a mass rotating counter to that of the pick-up in trains and other vehicles or places where sudden movements, shocks and vibrationsare encountered, such as would render ordinary pick-ups useless. In an automobile, permanent installation may be made by installing the pick-up, connected `to play through the radio, inthe glove compartment, using a spring-driven or 6volt electric motor for turning records. Portable phonographs orradio-phonograph combinations are frequently taken along in automobiles and other vehicles during trips, and when equipped with.the stabilized pick-up arm may still be used while the vehicle is in motion. In passenger vehicles when radio programs are undesirable or cannot be received, considerable pleasure will be afforded through the use of phonographs.

Passenger transportation companies, advertis'ers, scientists, the Army Signal'Corps, and others, could use to advantage the pick-up arm described in this invention.

Havngdescribed the invention, what I claim as new is:

1. A device of the class described comprising a' supporting standard, a pick-up arm carried by the supporting standard, a weight pivoted at its center of gravity and geared to said standard to rotate in an opposite direction to the pick-up arm and mounted to rotate in a plane parallel with the swing of the pick-up arm.

2. A device lof the class described comprising a pick-up arm mounted to rotate about a pivot at its center of gravity, a weight pivoted-at its cen.- ter of gravity to rotate in a plane parallel to the movement of the pick-up arm, and connecting means for rotating the weight counter to the rotation of the pick-up arm.

ALLEN MONROE JONES.

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