US2942888A - Phonograph and tone arm - Google Patents

Description

June 1960 T. R. DUNCAN 2,942,888

PHQNOGRAPH AND TONE ARM Filed April 13, 1953 2 Sheets-Sheet 1 4. FIG. 2.

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ATTOR N EYS PHONOGRAPH AND TONE ARM Filed April 13, 1953 2 Sheets-Sheet 2 INVENTOR THEODORE R. DUNCAN BY 75 WMvk/M g5 ATTORNEYS 83 United States l atent 2,942,888 PHON AND TONE ARM Theodore R. Duncan, North Hollywood, Calif, assignor This invention has to do generally with phonographs in which sound reproduction accomplished inechanically.

An object of the invention is to provide an extremely simple phonograph device which can be manufactured at very low cost.

Another object is to provide a phonograph construction which is unusually compact, is adapted to be made in small units and thus may be incorporated readily into toys and other small articles. r

A further object is to provide novel and elficien't means for receiving vibrations. from the reeord'magnifying them and transmitting them to a diaphragm. In this connection it is an object to provide a sound pickup means carrying a record-engaging needle-and having a diaphragm-engaging member or portion which is adapted to bear resiliently against the sound diaphragm, serving to tension the diaphragm.

More particularly it is an object to provide a sound pickup arm carrying a record-engaging needle wherein the arm is pivotally mountedat one end and has a diaphragm-engaging portion spaced from the mounting point with resilient means between the mounting point and the diaphragm-engaging portion. in this connection, it is an object to provide a construction wherein the resilient means just referred to may be an integral portion of or an inherent quality of the pickup and also a construction wherein a separate resilient member is employed. V

- It is an object also to provide a sound pickup am having a part which is torsionally resilient and which twists somewhat as a needle carried thereby is actuated by the record groove and having a cantilever-like dia phragm-engaging part for transmitting the twisting movement to the diaphragm in greatly magnified condition and preferably in a direction at right angles to the original vibratory movement of the needle.

Another object is to provide a novel construction wherein the sound pickup arm is used to stress or spring the diaphragm and the latter serves to maintain the tone arm in a stressed condition and also hold the needle against the phonograph record.

Still another object is to provide a construction which eliminates the necessity of a rigid connection between thetone arm and the diaphragm.

A further object is to provide a phonograph device embodying a box-like member having opposed major walls in which one Wall is used to support a phonograph record for rotation andthe opposite wall is used as a sound diaphragm.

Another object is to provide a phonograph device in which the sound diaphragm is directly over or opposite the record disk and parallel thereto. A further object in this connection to provide such a construction wherein the diaphragm and record are relatively close and a tone arm is used to transmit vibrations to about the center of the diaphragm.

ice

A further object is to provide a construction wherein the sound pickup arm engages the diaphragm in a inanner to permit the to slide over the surface of the diaphragm progressively as the needle moves radially inwardly of the record. 7 v

Yet another object is to provide a sound pickup means which minimizes needle hiss.

These and other objects will be apparent the drawings and the following description thereof.

Referring to the drawings; Fig. l is a plan view of the device embodying the invention; n

Fig. 2 is a view of the device of Fig. 1 on an enlarged scale withthe cover removed; h

Fig. 3 is a sectional view on line 33 of Fig. 1 on the same scale as Fig. 2;

Fig. 4 is a fragmentary sectional view on line 4--4 of Fig. 1 on the same scale as Fig. 2;

Fig. 5 is a diagrammatic view showing the action of the tone arm;

Fig. 6 a plan view showing a sound pickup a'rin means embodying another form of the invention;

Fig. 7 is an 'elevational view in the direction indicated byline 7-7 of Fig. 6;

Fig. 8 i s an elevational view in the direction of line 8-;8 of Fig. 7;

Fig. 9 is a fragmentary sectional plan view of a device embodying a sound pickup arm means for use with billand-dal'e records; V

Fig. l0 'is an ielevational view of the -arrnot Fig. 9 in the direction indicated by line 16-10 thereof; 7

Fig. 11 is an elevational view of the of Fig. 9 in the direction indicated by line 11-11 of Fig. 9;

Fig. :12 is a fragmentary sectional plan view of a device embodying another form of the invention;

fig. 13 is a fragmentar sectional view on line 1313 of Fig. 12.

v Morepanicnlarly describing the invention, referring first to Figs. l 5 whe'fein I illustrate one embodiment of my invention, '11 indicates a box or housing forming part of my phonograph device. This may, for convenience, comprise interfitting top and bottom members 12 and 13 of cardboard :or any of a variety of other common ma- 'terials, such as metal, wood or plastic, for example.

Some means should be provided for securing the membars 12 and 13 together after the parts of the device have been assembled. The members 12 and 13 may be glued together or a detachable fastening means maybe employed in place thereof.

The boii 11 acts as a support for the various moving parts of the device and also as a sound-reproducing diaphragm. The bottom wall 15 of the box is apertured at 17 to receive the pin '18 on a crank 19 having a handle 20. A record disk R fits on the pin 18 and is retained by a resilient washer 22. A fiat washer 23 may be employed between the record disk and wall 15. The connection between the record disk and crank should be suificiently tight to prevent slippage between crank and record.

Within the box I mount a sound pickup or tone arm member, generally indicated by 25. This includes a main arm 26 terminating in a stepped end portion 27 which is fastened by rivet 28 to the bottom wall 15. The connection should permit easypivotal movement of the arm. However, the stepped end portion 27 should be fairly wide to act as a bearing surface to resist twisting movement of the tone arm, the reason for which will later appear. At the free end of the main arm there is provided a needle-mounting tab 30. A needle 31 is fixedly mounted in this tab and the portion of the arm below it.

The sound pickup arm is provided with a cantilever- 1 ,sponse.

like lever arm or diaphragm-engaging portion 36 which projects laterally of the main arm and terminates in an end portion 34 having a convex bearing area 35 which engages the under surface of the topwall 36 of the box.

described as being torsionally, resiliently stressed. Since the sound pickup arm is forced downwardly by the wall 36, the latter, in turn, is bowed upwardly and tensioned to serve as a sound diaphragm.

For the purpose of returning the needle to the first groove of the record I provide a reset tab 38 which projects upwardly through a slot 39 in the upper wall 36.

The particular sound pickup arm shown is designed for use with records in which the sound-produced variations in the regularity of the record groove are lateral or in the plane of the record. In the operation of the device, the crank 19 is turned to rotate the record disk. As'the needle traverses the record groove and vibrates back and forth as shown in exaggered form by broken lines in Fig. 5, the main arm of the sound pickup arm twists slightly about its longitudinal axis causing the lever arm 33 to pivotabout the axisof the main section andrend portion 34 to move up and down, thereby driving thediaphragm. The signal, or vibrations are therefore picked up, turned at right angles, and magnified. Also, since the sotmd'pickup arm is stressed or twisted slightly due to the contact end 34 thereof being depressed by the diaphragm wall 36 this provides a firm but resilient contact between the needle and the record groove and also between the contact bearing area 35 and the diaphragm surface. When pressed in the record groove inthis manner the needle maintains an intimate relation with the record signals; As the record rotates, the action appears to be as follows: .when the groove pennitsrthe needle to move to the left (Fig; 5) the pressure of contact is mo- 'mentarily relieved and this is transmitted up the lever arm to. the contact bearing area and the diaphragm moves toward the record surface. When the needle moves to the right the pressure against the needle point 7 'is momentarily increased and the diaphragm is moved away from the record.

The pickup arm may be made of a variety of materials, such as metal, plastic, wood or the like, so long as the, material has sufiicient flexibility and springiness or resiliency to permit of the main section of the arm responding to the needle vibrations by a slight twisting movement and also to permit of the pickup arm being originally stressed when the device is assembled. Howdisk by the pressure of the arm Thus when the pressure is suddenly reduced by downward motion of the cantilever arm the diaphragm follows instantly in re- This springy contact makes it unnecessary to provide a firm fastening between the arm and the diaphragm as in conventional constructions. 'At the same time this permits the contact bearing area 35 to slide across the under side of the diaphragm as the sound pickup arm'as a whole progresses inwardly of the record.

' It may be pointed out as a reason why the end of the .cantilever arm moves up and down instead of sidewise that the friction of sidewise motion at ordinary sound frequencies would prevent it, that is, the amount of energy generated by the sound grooves is not sufiicient to overcome the weight of the arm and the friction with the diaphragm, however, the contact bearing area may easily move gradually across the diaphragm at a slower rate as the tone arm advances inwardly of the record.

In the form of the invention'described above the resiliency of the sound pickup arm is inherent in the and itself. Referring now to Figs. 6 and 7, I show a form of the invention wherein the sound pickup arm is made of more than one piece and a resilient member employed. In these figures, numeral generally indicates a sound pickup arm means which includes a main arm 46 having a stepped end portion 47 which is attached thereto in any suitable manner. The part 47 is apertured at 48 to receive a rivet or other mounting means. Pivotally mounted at the other end of the main arm 46 I provide a laterally extending cantilever-like lever arm or diae phragm-engaging member 50, a pin 51 serving to con: nect the arms. 'Member. is provided with a pair of tabs 52 in which a needle 53 is rigidly mounted. The member also has an end portion 54 which includes a convex bearing area 55 for engagement with a diaphragm wall D shown fragmentarily in broken lines in Fig. 8.

As viewed in Fig. 8, the member 50 is urged counter: clockwise by torsion spring 57, one end ofwhich is an chored in'a hole 58 in member 46 and the other end or which is disposed beneath member, 50. With this construction when the member 45 is pivotally mounted in a box or otherhousing in a manner similar to the mounti ing of member .25 previously described, member 50 is held down or toward the record disk R by diaphragm D engaging the outer end of member 50 thereby serving to place the spring 57 in torsional compression and also serving to hold the needle 53 in engagement with the record disk. If necessary, the record disk maybe biased upwardly toward the needle by yieldable means such as shown in Fig. 13 subsequently to be described. 7

.In the operation of the phonograph device embodying the sound pickup arm 45, the lever arm 50 oscillates about pin 51 as the needle is driven laterally by the signal in the record groove with the result that the vibrations or movements are transmitted to the sound diaphragm in magnified condition.

The sound pickup arm means so far described are particularly designed for use with record disks wherein the signal or variations in the groove of the record extend laterally or in the plane of the record. While such means will to some extent operate for records of the hill-anddale type wherein the signal or :variations in the groove of the record are at right angles to the plane of the record, I prefer to provide an alternate type of tone arm for playing these so-called hill-and-dale records.

One form of such means is shown in Figs. 9-11, being indicated generally; by' numeral 61. This pickup arm means includes a main arm 62. with a stepped mounting end portion 620 apertured at 62b to receive a rivet or mounting pin. The :pickup arm includes a transverse lever arm 63 which is conveniently formed of the same material and is integral with the main arm. iThe lever arm extends on opposite sides of the longitudinal axis of the main arm and includesa diaphragm-engaging portion 64 and a needle-mounting portion 65. The former terminates in an end tab' 66 having a raised bearing area 67 for engaging the diaphragm, The portion has a pair of spaced tabs 69 in which a needle 70 is mounted.

With the construction described, as the record rotates the vertical variations in the. recordjgroove actuate the needle 70 causing it to oscillate substantially vertically with the result that the lever 63 as a whole pivots about the longitudinal axis of'the section 62; the latter twisting to permit this, thereby driving the diaphragm. .Inplace of making the lever 63 intcgralwith section 62 I may pivotally mount the lever and use aspringmeans to bias it upwardly, as in the form shown in Figs. 6-8. In this connection, I have shown the pickup arm means as it would appear installed. In such position it is resiliently twisted or stressed in the same manner as the pickup arm means 25 of Figs. 1-4.

In Figs. 12 and 13 I show another form of sound pickup means for a hill-and-dale type record disk R, the latter being shown mounted in a housing 75 and biased upwardly by a compression spring 76.

This form of the invention comprises a sound pickup arm means 80, with an extended end portion 81 apertured at 82 for the purpose of pivotally mounting the same by means of a rivet 83. The means 80 includes a main arm 85, the outer end of which carries a diaphragm-engaging or lever arm 86. The latter is connected to member 85 by a leaf spring 87 and includes a pair of spaced tabs 88 in which a needle 90 is fixedly mounted. Member 86 extends a substantial distance laterally of arm 85 and terminates in an end portion 91 which engages the diaphragm D. The spring 85 and part 86 may normally extend upwardly as shown in broken lines (Fig. 13) so that when the parts are assembled the diaphragm serves to hold the parts in the position shown in full lines in the drawing. In turn, the diaphragm is tensioned by the tendency of the spring to return to normal position. To avoid any critical dimensions or careful assembly problems, the spring 76 under the record insures contact between needle and record.

In this form of the invention the vertical oscillations of the needle are transmitted to the diaphragm through the member 86, the latter and spring 87 tending to pivot as a whole about the main arm 86.

Although I have illustrated and described a preferred form of my invention, I contemplate that various changes and modifications can be made without departing from the invention, the scope of which is indicated by the following claims.

I claim:

1. In a toy phonograph, a housing including a base, a resilient diaphragmatic cover, and a side wall supporting said cover in spaced opposed relationship to said base; a sound record disc having a sound groove; means rotatably carrying said disc in said housing including a spindle carried by said base; a sound pickup disposed in said housing including a pair of angularly disposed arm portions intersecting and integral with each other at their inner end portions, one of said arm portions constituting a main arm rigidly carrying a stylus needle at its inner end, and the other of said arm portions constituting a lever arm which has an outer end portion frictionally slideably engaging said cover; and pivot means swingably securing the outer end of said main arm to a substantially fixed portion of said housing at a point radially spaced from the periphery of said disc; means whereby said lever arm is biased toward said cover sufiiciently to maintain said cover in resiliently stressed condition, to urge the outer end of said stylus needle in engagement with said sound groove and to maintain the inner end portion of said main arm torsionally stressed, whereby lateral movement of said outer end portion of said stylus needle in response to its engagement with said sound groove will torsionally oscillate said main arm at its point of intersection with said lever arm and thereby cause said cover engaging outer end portion of said lever arm to vibrate in a plane perpendicular to said cover.

2. The combination of claim 1 wherein the outer end portion of said main arm terminates in a relatively wide portion through which said pivot means extends whereby to provide a relatively wide bearing surface engaging said base.

3. The combination of claim 1 wherein said arms are disposed right angularly to each other.

4. The combination of claim 1 which additionally includes resilient means interposed between said disc and said base.

5. The combination of claim 1 wherein said main arm is of rectangular cross-section and has its major width parallel with said disc, wherein said lever arm is of rectangular cross-section and has its major Width normal to the plane of the major width of said main arm, and wherein the cover engaging portion of said lever arm is resilient.

6. In a toy phonograph, a housing including a base, a resilient diaphragmatic cover, and a side wall supporting said cover in spaced opposed relationship to said base; -a sound record, having a sound groove, mounted in said housing for movement relative to said base; a sound pickup disposed in said housing including a pair of angularly disposed arm portions intersecting and integral with each other at their inner end portions, one of said arm portions constituting a main arm rigidly carrying a stylus needle at its inner end, and the other of said arm portions constituting a lever arm which has an outer end portion frictionally engaging said cover; and means securing the outer end of said main arm to a substantially fixed portion of said housing at a point radially spaced from the periphery of said disc; means whereby said lever arm is biased toward said cover sufliciently to maintain said cover in resiliently stressed condition, to urge the outer end of said stylus needle in engagement with said sound groove and to maintain the inner end portion of said main arm torsionally stressed, whereby lateral movement of said outer end portion of said stylus needle in response to its engagement with said sound groove will torsionally oscillate said main arm at its point of intersection with said lever arm and thereby cause said cover engaging outer end portion of said lever arm to vibrate in a plane perpendicular to said cover.

References Cited in the file of this patent UNITED STATES PATENTS 639,452 Smallwood Dec. 19, 1899,

724,435 Cheney Apr. 7, 1903 1,430,185 Rankin Sept. 26, 1922 1,918,777 Panish July 18, 1933 1,984,637 Foley et a1 Dec. 18, 1934 2,523,340 Bonsall Sept. 26, 1950 2,580,071 Bunyard Dec. 25, 1951 2,622,883 Kurzen Dec. 23, 1952

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