US1438642A - Polyphone sound box and mounting therefor - Google Patents

Description

Ill/VE/l/TOR [I] III. l

Patented Dec 12 19220 I g 1W ATTORNEYS J. GRAHAM.

POLYPHONE SOUND BOX AND MOUNTING THEREFOR.

APPLICATION FILED IAN-9,1922.

J. GRAHAM POLYPHONE SOUND BOX AND MOUNTUQ'G THEREFOR. APPLICATION ULED JAN.9.1922.

Piaf mm Dec; 2 SHEETSSHEET 2.

MWM FM ATTORNEYS Patented DeelZ, W22.

an are near n use.

JOHN GRAHAM, OF STRATFORD, CONNECTICUT.

POLYPHONE SOUND BOX AND MOUENTING THEREFOR.

Application filed January 9, 1922. Serial No. 527,860.

T all'whom it may concern Be it knownthat 1, JOHN GRAHAM, citizen of the United States, residing at Stratford, Connecticut, have invented a new and useful Improvement in Polyphone Sound Boxes and Mountings Therefor, of which the following is a specification.

This invention relates particularly to talking-machines of the i type known as polyphones, wherein two or more styli ff-track simultaneously in the record-groove.

I EBroadly, stated, the invention comprises I firstlyjfla novelpolyphone sound-box; and,

secondly, 'suitable mechanism whereby the plurality of reproducing-styli are maintained in such 1re lativ'e"position that they can be lowered with certainty into simultaneously operative engagementwith the same 'groove, and whereby said styli will always be in tangential relationshipwith the side-wall of the engaged portion of the groove. Furthermore, said mechanism is likewise applicable to the ordinary talkingmachine with a single stylus,.for maintaining i lution of the record-groove. The invention such stylus in said tangential relationship.

More particularly, the invention comprises a sound-box having two separate and distinct diaphragms, each. with its own stylus, the two styli being in proximity for tandem engagement in the same convo further comprises, in its preferred form,

the swivelling of a sound-box (having either a single'stylusor two styli) for rotative adjustment upon vertical axis at the end of the tone-arm or other carrier; and, in combination with such swivelled sound-box, the provision of suitable mechanism actuated by the advance or swing of the tone-arm or carrier for automatically impartingto the swivelled sound-box the progressive rotary adjustments requisite for maintaining the stylus or styli in the desired tangential relationship aforesaid. Said polyphone sound-box can be used without the adjusting-mechanism aforesaid; and said adjusting-mechanism can be used with a singlestylus sound-box; butpreferably the two features are employed in combination. Finally, the invention comprises the various features of construction and arrangement.

hereinafter set forth and claimed.

The invention will be best understood by reference to the accompanying drawings,

W sh et for h a preferred. embodiment thereof in the form of a polyphone machine carrying tWo styli and designed for playing records of the disc form having a spirally-disposed record-groove of the laterally-undulating or zigzag type. But said drawings are presented merely for the sake .of illustration, since the invention is not limited to that specific type of machine and record, nor to the preferred structure there by set forth.

In saidillustrative drawings: 7

Fig. 1 is a plan'view showing in full lines the swinging arm presenting a polyphone sound-box in one position of operative engagement with the record-disc, another operative position of said arm and sound-box being indicated by broken lines;

Fig. 2 is. an edge view, partly broken' away, of the new polyphone sound-box itself; r

F i 3 is a diagram illustrating the relations ip of the parts with respect to the (in the center'of the usual stud on the turntable). 2 is a'swingiI1g-.arm for' carrying the sound-box, here shown as a hollow sound-conveying member, which may be of the usual or any preferred shape. The inner end of said arm isshown as a horizontally-oifset elbow which is'swivelled, on horizontal'a'xis, to a corresponding horizontal offset or elbow at one side of the-upper end of the vertical tubular member 3, which latter is rotatably mounted upon stationar upright tube 4, to swivel on vertical axis Said stationary tube 4 communicates with the usual horn (not shown). The two hollow members 2 and 3 thus constitute the usual swinging tone-arm, of whichmember 3 is the down-turned elbow. Theforegoing is old.

The new polyphone sound-box 5, carried by the outer en of said m 2, as. t o, 110

ig. 1: 1 is the usual record-disc,- and A rs 1ts aXIS-Of-I'GYOlUtIOH cavities 66, one in each of its opposite faces, each closed by its own diaphragm 7,

there being thus provided the usualchain her at the rear of each diaphragm. These I 10 producing-stylus or needle 9, as by the usual set-screw 10. The parts are so constructed and arranged that the two needles 9 and 9 are quite close together (see Fig. 4); and "preferably their operative tips lie in the same vertical plane, which is parallel with the two diaphragms and midway between them (seeFig. 2 Y Since the surface of the usual disc record is not always a true plane, but is liable to be slightly warped (as exaggerated in dotted lines in Fig. 6) it might occur that with the rigid stylus-lever construction shown in Fig. 4 both needles 9 would not always maintain contact with. the bottombf the 'i'ecord-groove. There may therefore be provided a horizontal hinge 24 just below the fulcrum of one of the stylus-levers, and a spring 25 to hold the needle 9 in operative engagement with the bottom of the record-.

groove. Thus the weight of the sound-box and tone-arm holds the needle carried by the rigid stylus-lever in operative position while the hinged construction gives the vertical 7 play necessary to keep the other needlepolnt in proper position.

i The above-described polyphone sound-box may bexsecured to the tone-arm rigidly if desired, in which case it will give ac'ertain degree of satisfaction, in that the two stylustips (which will always be presented in the same fixed'relative position) can. be'lowered for-simultaneous engagement with the record-groove, and in that the two styli will vibrate two diaphragms instead of only one, and will thereby produce a greater volume of sound, and (in. the judgment of some authorities) will confer the advantage of more richness or roundness and fullness of sound. But preferably, and according to the full embodimentof the present invention,- as hereinafter set forth, said polyphone sound-box is rotatably adjustable on vertical axis with respect to the tone-arm, and suitable mechanism is provided for automaticallymaintaining its two styli in tangential relationship with the successivelyengaged convolutions of the record-groove.

- Referring now to Fig. 3: The are C, drawn from as its center and passing through the aforesaid axis A, represents the path of the tWo stylus-tips (here considered as a unit), as the tone-arm and styli swing uponthe aforesaid axis B as their center ofrotation. If the line AB be r0 i Q5 leas n eq a distance 31), then the line iaeaeae of said diameter will constitute a right angle; and therefore any line drawn from D to any point as E, E,- E, etc., on the circle will make a right angle with the line from suchpoint to A. In other words, the point Dis the common focus of the tangent lines drawn from the successive points E,

E, E, etc, where said are C'intersect-s the SUCCGSSLVG convolutions of the record-groove (here regarded as approximately concentric circles, whose center is A, rather than as convolutions of a true spiral). It is manifest that any and every line drawn from said focal point D to any position E (E', E, etc.) will be perpendicular to the line drawn from the latter point to the point A; in other words; every line from said focal point D which intersects the are C is tangent to the record-groove where the latter passes through that'point of intersection. Hence it is obvious that if, in the 90 course of the swing of the tone-arm on axis B, the sound-box can be progressively tilted (on vertical axis) to occupy the successive vertical planes of tangency radiating from said focal point D,-then throughout the swing of the tone-arm, the sound-box with its two stylus-tips will always occupy the. proper tangential relationship to the particular portion of the record-groove then engaged. Further, the angle ABE (sub- 10b:

tended by thetone-arm) equals the sum of the two angles BED and BDE. But the two angles last indicated are equal to each other; hence-said tone-arm angle ABE just twice the angle ADE (subtended from point D). In other words, in its travel across the record-disc, the sound-box should be progressively tilted on its vertical axis,

at just one-half the angular rate at which the tone-arm is advancing, inorder to keep '1 10 vided on the down-turned outer-end of the tone-arm, and the sound-box is suitably secured in place as by two screw-threaded p rods 11 passed horizontally through the sound-box and engaging in'a circumferential groove around said down-turned tip. By this structure and arrangement, the sound-boa can be tilted on ver cal aa ft aaaeaa which axis is preferably inthe same vertical plane with the two stylus-tips.

Referring next to Figs. 1 and 5: Around the down-turned elbow 3' (which journals is supported and freely'journalled the horizontal disk 12presenting an arcuate toothed portion or segmental rack 13. Fast upon said elbow 3, and below said disk, is a sec- -ond horizontal arcuate toothed portion or segmental rack 14:. Journalled, by vertical pivot 15, upon a nearby standard, aretwo other segmental racks 16 and 17 rigidly secured together, one above the other, and

engaging respectively the first-named racks 13 and 14. The ratio of the four racks aforesaid is such that the angular movement or rotation of fixed rack 14,- due to the advance of the tone-arm, produces rotation of the disk 12 at just one-half that rate. For example, the two lower mutually-engaging racks 14: and 17 maybe of equal radius,

whilethe radius of upper rack 16 (fast to rack 17) is half the radius of its engaging rack 13 (on disk..12).- Two'links 18 and 19 pivotally connect the sound-box with said disk 12. The front end of link 18 is connected to I thefront of the sound-box by vertical pivot 20, while its rear end is connected to the front of said disk 12 by vertical pivot 21;

Y tive lengths of the two links are likewise as herein set tent. Parts cf the in erter. may

equal so that the two links and the soundbox and disk, with their four vertical pivots, constitute in 'efl'ect a collapsible parallelogram whose opposite-sides are always equal and parallel. I

By means offthe mechanism above described, it will be seen that the advance of the tone-arm, as it is fed across the recorddisc', causes the sound-box and its two styli to assume the progressively-tilted,

positions indicated by the dotted lines in ig. 3; and that the two styll will always be in proper tangential relationship to the particular convolution engaged by them.

As hereinabove set forth, said automatic progressive adjustment is especially desirable in connection with a polyphone soundbox, yet is equally applicable to a singlestylus sound-box; and the polyphone structure ma be employed without such automatic a justment, yet is preferably used in combination therewith.

The invention has thus been fully described in all its details, but only for the sake of clearness. The invention is not limited to the precise features and details be omitted, and others transposed, and other modifications of construction and arrangement resorted to, without in any case departv ing from the spirit of the invention.

upon upright tube 4), .and near its bottom,

a stylus-lever and a reproducing-stylus for each diaphragm, the combination (with the foregoing) of means for maintaining the tangential relation of said styli to the successive portions of the record-groove en-' gaged thereby, said means comprising a horizontal rack fast to said vertical portion,

a horizontal disc rotatable upon. said por- I tion and presenting a rack, two other horizontal racks secured fast together'and pivoted to engage respectively the first two racks, and links whose ends are pivoted to said sound-box and to said disc respectively to constitute an angle-variable parallelogram, whereby the horizo'ntalmovement of said swinging-member. produces angular swivelling of said sound-box at one half the rate of the angular swing of said member.

2. In a talking-machine,'the combination of a membersuch as a tone-arm, having a vertical-portion by which it is journalled to swing horizontally, a sound-box swivelled on a vertical axis upon the outer end of said member, a-rack fast to said vertical-portion, a disk rotatable upon said portion and presenting a rack, two other racks secured fast together and pivoted to engage respectively the first two racks, and

said disk respectively to constitute an angutwo links whose arms are pivoted to said sound-box andto larly adjustable parallelogram, 1 whereby the swing of said member'produces angular swivelling of said sound-box at half the angular rate of said member.

3. In a talking-machine, a horizontallyswinging member such'as a tone arm, a sound-box swivelled at the outer end of said member upon a vertical axis and having twoseparate and distinct diaphragms with a stylus-lever and a reproducing-stylus for each diaphragm, the axis of said swivel be-' ing in the same vertical plane with said styli, and means actuated by the swing elle'd at the outer end of said member uiion sound-passage leading from behind each vertical axis and carrying a stylus, and diaphragm to a common sound-conveyor, means actuated by the swing of said memand a stylus-lever co-aoting with each diaber for causing said sound-box to swivel at phragm and carrying its 'own reproducing- 5 half the angular rate of said member, stylus, one of said levers comprising a hori- 1 5 whereby said stylus is maintained ,in tanzontally-pivoted joint with yieldingmeans gential relation to the record-groove} such as a spring for maintaining its stylus throughout its travel across'the record-disc. in operative engagement with the record.-

5. sound-box presenting two separate 10 and distinct diaphragms and having .a JOHN GRAHAM.

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