US1370462A - Apparatus for converting vibrations - Google Patents

Description

G. LOCKE.

APPARATUS FORCONVERTING VIBRA'TIONS.

APPLICATION FILED JULY 6, Hill.

Patented Mar. 1, 1921.

Fig. 1.

INVENTOR Guvou Loan stead of metal. i

GUYON LOCKE, OF BQSTON, MASSACHUSETTS.

APPARATUS FOR CQNVERTING VIBRATIONS.

Specification of Letters Patent.

Patented Mar. 1, 1921.

Application filed July 6, 1917. Serial No. 178,917.

1 all whom 1'2? may concern: Be it known that I, GUY N LOCKE, a citizen oi the United States, residing at Boston. in the county of Suifolk and State of Massachusetts, have invented new and useful Improvements in Apparatus for Converting Vibrations, of which the following is a specification.

This invention relates to improvements in converting apparatus for vibrations 0t sound. More particularly it is here 1llustrated as applied to a device capable of reproducing sounds from a phonographlc record, but the invention is also applicable for use in making the record, and may have applica 'on to other sorts of apparatus dealing with sound transmission. Une ob ect of this invention is to improve the quality or tone transmission or reproduction as compared with devices heretofore known of this class, working toward the ideal of reproduo ing the original sound without impa'ring its tone quality and relativevolumes through detects inherent in the apparatus. To this end the invention wholly or largely eliminates the use of metal from the parts of the apparatus through which the transmission of the vibrations is eiiected, and uses or- Lanic material, as c tgut and sheepskin, in- V arts oi the apparatus which are not in the direct course of the transmission of the vibrations, are convenientlv made of metal and are rendered insensitive to vibration by making these parts thick and heavy. The invention is concerned with these general principles and with deof construction and arrangement for i them successfully operative. Qther I to provide the improvements in cuts that are characteristic of the illustrated, among which are certain an \lllfitli, adjustments of tension, and dein the reproducer. To these ends are provided a relatively thick metal base for the sound box with an orifice for the passage of air vibrations to or from the horn or other sound concentrating or magnifying device; and the \il ntory wall or diaphragm of said sound box is composed of stiffened organlc tissue, such sheepskin, actuated, in the reproducer, by variations in the thrust thereon a still post oi organic tissue, as catgut. This post is held always in compression net the diaphragm by the needle bar, which, in turnfis held always pressing on the postby a piece of catgut, which is under tension. Said needle bar which may also be of organic structure, as bone, but for which metal has been found reasonably satisfactory, is mounted pivotally on a thick and heavy non-vibrating block that is supported on the heavy base of the sound box by a metallic spring, of permanent character, which tends to swing the block toward the sound box and thus through an intervening lever, puts tension on the catgut tie. This tic stretched between the said block and the needle bar and serving to hold the bar always against the diaphragm post acts as a tensile spring, with the result that the pressure of the needle bar on the diaphragm is practically uniform and unvarying except as varied by the needle in following the record. This tie of organic material ab sorbs longitudinally the movement of the needle bar without transmitting enough vibration to be communicated to the block in any appreciable degree. Liability of the catgut to variation of length with changes of humidity and other conditions of atmosphere is continuously and automatically compensated by the said slow moving permanent metallic spring which connects the said block with the heavy wall of the sound box. The invention may be embodied in various forms within the scope of the appended claims. lt is intended that these claims, by suitable expression, shall cover whatever features of patentable novelty existin the invention disclosed. An illustrative embodiment of the invention is shown in the accompanying drawings, wherein Figure 1 is an edge elevation in medial section through the device, which is assumed to stand with its needle pointing downward;

Fig. 2 is a face elevation of the same;

l 3 is a plan of the same, showing the edge remote from the needle; and

Fig. 4; is an enlarged view of a detail, corresponding to Fig. 2.

Referring to the drawings, which repre sent the invention arranged in a phonograph reproducer, the needle bar is marked the post connecting it with the diaphragm is markec 11; the diaphragm itself 12; and the back wall, with which the diaphragm cooperates to form a sound box, is marked 13, having an opening 14 for passage of air and for the transmission of vibrations therein to the tube (not shown) on the end of which the reproducer is adapted to be screwed by the threads 15 in the ordinary manner. The back wall 13 is preferably made heavy by using material so thick that it does not respond to any ordinary vibrations, or at least responds with such a high period that it does not produce appreciable effect thereon. The front wall of the sound box is the diaphragm 12 which preferably is made of sheepskin or other organic tissue and may conveniently be of the same sort of material as is used for drum heads. The diaphragm is stiffened and its characteristics are damped by a layer of cork 16 extending over the greater part of its body surface, the cork'being secured to the diaphragm by glue or other suitable means. The cork extends from a place near the center, where it is relatively thick to a place near the periphery where it has become tapered down to a thin edge. The sheepskin continues for a short radial distance, beyond the outer edge of the cork is clamped between two gaskets 17, which, being of rubber, serve to prevent the transmission through them of sound vibrations. The under gasket fits between the diaphragm and the back wall of the sound box and is of the right thickness to maintain the diaphragm at a proper distance from said wall. A ring 18 of sulficiently heavy material adapted'to fit into a flange 19 may be used to press against the upper gasket and thereby secure the diaphragm in position. For protection of these parts, a covering ring 20 may be fastened on the outer face of the diaphragm holding ring 18, this ring 20 having if desired, open space in the vicinity of the needle bar soas to allow room for convenient manipulation. The back wall of the sound box 18 may be concaved toward the throat or opening 14-, graduating the distance from the diaphragm and providing a greater volulne of air near its center. At the middle of the diaphragm, on the outer side, is the transmitting post 1.1 which preferably is made of catgut, and may be described in kind and diameter by saying that I have found a section of the C string of a cello suitable. This post is prepared by tying a silk cord 21 tightly about each end, cutting off the ends close to the cord, making a central hole through the diaphragm, setting the postso that its lower end projects a slight distance through the hole and then'searing this projecting end over the under edge of the hole so that it is held there securely, after which the post may be further secured by an application of wax 22 to a considerable depth on the outer side of the diaphragm. This wax holds the post perpendicularly, and more or less fills the central hole in the cork. A little wax may be applied on the under side of the diaphragm around the end of the post, a representation of this beingomitted in the drawing in the interest of clearness. Vibrations are transmitted der inward pressure transmitted to it from the needle bar through this post as a strut. The degree of pressure is so designed that the tension on the diaphragm produces the proper amount of damping, which together with the fixed load of cork produces the best characteristics. While the cork is not stiff enough to prevent absolutely any bending of the underlying portion of the diaphragm it may be believed that it restrains the diaphragm to an even behavior over a wide range of impressed frequencies, which of course enables it to neutralize or offset the resonance of the other components of the acoustical mechanism. The nature of the organic tissue is such that with long usage the sheet might lose its stiffness and become too flabby at the central portion. By definitely attaching all parts of the diaphragm together by a normally stiff, although slightly flexible sheet, such as cork, and by grading the thickness of this packing from the center toward the edges, or by otherwise compensating for the irregular behavior of the diaphragm a support is added, in which the cellular structure of the cork adds certain features resembling a truss construction, capable nevertheless, owing to the inherent springiness of the cork of yielding enough to permit of the diaphragm receiving and spreading over a large area the vibrations impressed upon it by the post 11. The largeness of the area, for which I have found a circle having a diameter of three inches suitable, coupled with the flexibility of the diaphragm where a peripheral zone an eighth of an inch wide is left uncovered by the cork at the edge allows a considerable amplitude of vibration. The slight concavity of the rear wall of the sound box favors the reception of these vibrations by the air therein, and their transmission in concentrated form as sound waves through the delivery tube 14:.

The vibrations of the diaphragm reproduce 'movements of the needle bar 10, the tail of which swings'toward or away from the head ofithe post 11, thereby pushing the diaphragm farther inward, or allowing it to swing back more nearly into a plane than is the shape or position it occupies when in its normal position of rest, at which time it is without abrasive or destructive action. The

pressure of the needle bar upon the post 1.1 results fundamentally from a spring 24 which as represented is a flat metallic torsional spring. The heavy back 13 of the sound boX supports a bridge consisting of uprights 25 and the spring 24:; and the latter carries a heavy block of metal 26 which is rather thick and which approximately covers and overlies the face of the diaphragm, outside of the needle On this block are two ears 27 supporting a pivot pin 28 on and extending transversely of the needle bar, forward of the diaphragm post 11. The needle bar is adapted at its extreme forward end 29 to hold a needle by any suitable means, and at its extreme rear end presses against the post 11, and has its fulcrum intervening at the pivot 28. Turning on the pivot is restrained in one direction by the contact of its tail with the post ii, and in the other direction by the pull. of a catgut tie 30. The block 26 is so set on the spring 2st, and the latter is so set on its supports 25, that the spring 2i tends constantly to throw the blocl' 26 toward the post ll. Hence the pivots 28 are thrust toward the diaphragm, and the tail of the needle bar 10, engaging the post 11, tends to be swung on these pivots toward the block 26, and is in fact swung so far as it is permitted by the catgut tie 30, which extends from the block to the needle bar forward of its pivots 28. The tie therefore opposes movement of the tail of the needle bar lever toward the block 26, and away from the post 11. The apparatus when set up comes to rest with the parts in such position that the turning impulse transmittec from spring 2-il through the catgut is resisted in equilibrium by the elastic res'itance of the diaphragm 12 to inward hurling. The catgut string 30 may be arranged in various ways, but as illustrated it is anchored to the needle bar by pass through simple conical hole 31 therein and being l rotted at 32 on the re mote side of the hole; and is secured to the block 26 by passing through a hole 33 therein, over bridge 3 thereon, and being secured by a screw around which it wound just under the head of the screw. A small depression in the surface oft-he block serves to receive it. Having been given a bi around the screw it can be easily drawn over the bridge and adjusted as to length turning the screw By reason of its strucand method of mounting the catgnt tie .es to prevent the transmission of vibra- The tie does not come in direct a. t with the block 26, but passes over i e 3% and thence through the hole Thus it serves as an insulating device 'entiug the transmission of all vibrations n one to the other except such as may be in its longitudinal direction; and those are eliminated or rendered harmless by the elastic cellular structure of the organic mateone bein the cat 'ut strin 30 and the other the catgu't post 11. For the catgut tie I lind a section of the A string of a violin suitable. The needle bar itself may preferably be of material which transmits vibrations of sound as perfectly as possible without altering their character. To this end I have found aluminum apparently satisfactory, although other materials can be used if the needle bar is of suitable solidity and proportions, such as bone, ivory or very hard wood.

W'hen in use the vibrations emanating from the movement of the record needle are transmitted "through the insulated needle bar to the post of organic tissue, with the result that the post is more sensitive than any other of which I am aware, and produces a more robust and natural tone, giving in consequence a liner reproduction. The lightness ol the moving parts, comprising the diaphragm with its cork, the cellular post and the aluminum needle bar, acting under constant tension of the catgut, permits the use of a larger diameter of diaphragm than can be .ffectively used with some other types, which would have too much inertia if made as large as this diaphragm can be made. Experiments which I have conducted indicate that the device reproduces all kinds of human voices in a noticeably superior manner, and that the characteristic tones of musical instruments are reproduced especially well, particularly the tones of stringed instruments. This leads to the belief that the use of catgut and cellular tissue,which are the characteristic sound producing elements of stringed instruments, renders the device partic arly suitable for reproduction of tones of such instruments, doubtless because the device is receptive to all kinds of overtones and combinations of overtones and transmits them more perfectly than devices made of other material. Moreover the superior results which I have attained with the described apparatus lead to the belief that the discovery of this apparatus and combination of materials has disclosed the means by which a. new and very high degree of proficiency can be attained in the recording and reproduction of sounds, the principle being that sounds which ordinarily would be heard by a human. hearer, being v'brations coming to his auditory nerve through the air and animal tissue and bone, shall be best recorded and reproduced by vibrations which pass only through air, organic or cellular tissue, and bone, or the close equivalents of these materials. If any vibrations are lost or added by this means they are the same ones that are lost or added to in the ordinary human hearing of sounds; and therefore the reproduced sound is heard with a quality that seems natural. As the human ear bones, and the described apparatus uses aluminum for itsneedle bar, it appears that bone or ivory on account of its close texture and hardness may be substitutet for the aluminum, due consideration being given to the relative size and weight of parts.

The reproducer illustrated is so heavy that in mounting the same I prefer to coun terbalance it, so that only a very small fraction of its weight rests upon the record which the needle is following. T his g es a lightness of touch and at the time serves the record from wear, so that the mechanical effect is crmcentrated in a rcgroduction or" the vibrations. I also prefer make the tube, through which the sound is conducted from the sound post to a horn other augmenting means, of rather li metal in order to minimize the effect oi us container upon the sound v'bra'tions that passing through the air within it. The form of apparatus illustrated is adapted for use with records having lateral vibrations. By suitable mounting and charming the angles of the needle it can be adapted to on records having hill and d vibra tion" The catgut of the tie is ale va lzitions in length due to changes in humidity and other characteristics of the atmosphere. Such changes of dimension are very small in absolute measurement, although they might make much difference in tonal effect it no compensation for them W provided. The apparatus is automatic in its correction of such. For exaiiple, upon any. contraction of the tie 30 the effect is merely that the block 26 is swung the merest' fraction of a degree on its permanent torsion spring 24:, not appreciably changing the net normal pressure on the post 11. Upon elongation the reverse occurs. In either case the parts come to rest with the catgut 30 having no appreciable diil'eren-ce of tension from that originally impressed upon it by the torsion spring 2%. The weight and shape of the block 26 is such that its inertia and different vibratory period prevent it from responding to the vibrations of the needle bar, as transmitted to it by difierence of tension of the tie 30 w iich result during the course of sound reproduction. Its compensating efiect is only for those slower changes which occur with change of general conditions. 7

When the apparatus is in use as on a record havinglateral vibrations or undulations,

the described combination affords a protective device of value which preserves the record from wearing out with notable effect. Because of the composite action of the two strings 30 and 3 it will be understood from Fig. 1 that, assuming the record to be traveling toward the eye, past the needle held at 29, the lateral vibrations of the needle will act as hereinbefore described, and the sys tem of springs will ease the pressure on the sides of the track in the record which results from the usual irregularity of those records. It is a matter of common knowledge that ordinarily the needle will sway the sound tran mitting arm, supporting its way back and forth as the record revolves on its axis. The wearing of the need against the side of the track is ameliorated by this combinaorganic origin, but a reasonable scope of equivalents is claimed, including synthetic substitutes having like properties even though not cellular in precisely the same us having a vibrating dia- :or transmitting and converting "ibrations, and liming a needle bar,

i cellular tissue having length eater than its 'aineter, and constituting aconncctitui transmitting vibrations betw' en the needle bar and the diaphragm.

ln apparatus having a vibrating diapbra for transmitting and converting sound vibrations, a pivotally mounted needle bar, substantially without internal vibrations, combined with elastic supporting 11G elements of cellular tissue arranged to act oppositely thereon with respect to movement of the bar about its pivot, one or" said elements being in the line 01" transmission of vibrations of the diaphragm.

In apparatus having a vibrating diaphragm for transmitting and converting sound vibrations, a pivotally mounted needle bar, substantially without internal vibrations, combined with elastic supporting elements of cellular tissue arranged to act oppositely thereon with respect to movement of the bar about its pivot, one of said elements being a strut under compression, through which the vibrations of the diaphragm pass.

l. In apparatus having a vibrating diaphragm for transmitting and converting sound vibrations, at pivotally mounted needle bar, substantially without internal vibrations, combined with catgut elements arranged to act oppositely thereon with respect to movement oi the bar about its pivot, one of said elements being in the line of transmission of vibrations of the diaphragm.

5. In apparatus having a vibrating diaphragm for transmitting and converting sound vibrations, the combination of a pivotally mounted needle bar; elastic supporting elements of cellular tissue, arranged to act oppositely on said bar, one of which elements is in the line of transmission of vibrations of the diaphragm; a substantially non-vibratory block supporting the other said element; and an elastic support for said block, whereby the normal tension of said needle bar supports is controlled.

6. In apparatus having a vibrating diaphragm for transmitting and converting sound vibrations, the combination with a needle-bar-lever transmitting said vib'ations of a catgut tie holding one arm of the lever; and a block to which said tie is anchored, the said tie being under tension and having free suspension from a rigid, non-vibratory edge on said block.

7. In apparatus for transmitting and converting sound vibrations, the combination of a rigid stylus-carrying needle bar; restraining means of elastic cellular tissue acting oppositely on said bar in affecting its vibrations; and a diaphragm of cellular tissue to which are communicated the vibrations or one of said restraining means of the needle bar.

8. In apparatus having a vibrating dia phragm and a needle bar for transmitting and converting sound vibrations, the combination of a frame holding the diaphragm, a block on which the needle is pivotally mounted, and a spring pressing the "frame and block together; the said spring being relatively heavy and essentially unresponsive to said vibrations; and there being another spring, relatively light and essentially responsive to the movement of the needle bar, anchored on said block, and tending to maintain the needle bar in position that makes the diaphragm taut.

9. In apparatus for transmitting and converting sound vibrations, the combination of transmitting elements comprising ten sion and compression members consisting wholly of cellular tissue, said apparatus including a diaphragm, a needle bar, and elastic supporting means acting through the needle bar to keep the diaphragm taut.

10. In apparatus for transmitting and converting sound vibrations, the combina' tion of a diaphragm of tissue subject to modification by atmospheric conditions, a needle bar and a strut transmitting vibrations between them, and means whereby the strut is maintained under compression and the diaphragm distorted from a plane by the strut in the direction away from the strut.

Signed by me at Boston, Massachusetts, this 22d day of June, 1917.

GUYON LOCKE.

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