US1760092A - Electric phonograph reproducer - Google Patents

Description

May 27, 1930. A. A. THOMAS ELECTRIC PHONOGRAPH REPRODUCER Original Filed Dec. 11, 1926 INVENTOR Patented May 2 7, 1930,

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ntncrmo rnonoena'rfi nnrnonuonn Application the December 11; 1926, Serial No.'154,0 5 8. sewed Mal-E8, 1929.

a The present 1nvent1on relates sound-transmitting instruments,

: to electric and its object is to provide an electric phonograph reproducer of novel construction and improved 5 operation.

The reproducer of my invention is particularly adapted to play the new type of record,

in which the spi dred lines per inch. 13 My new comprising electric reproduceris characterized by utmost simplicity of construction,

merely a. resistance element and a whether lateral-cut or vertical-cut,

ral track runs to several hun ings,

conducting element, together with a vibratory stylus arm for varying the contact -len h or area between the two elements.

One ofthese elements is fixed, and the other consists of a resilient strip or flat spring con- 1 nected at one end to the fixed element. The

, two elements are properly connected in a tery circuit. The inherent tension of the rethat normally it lies in fixed element for a predesilient strip is such contact with the termined length. I A stylus arm bat-- is at its inner end in engagement with the free end of the 5 resilient strip.

the playing of When this. arm 1s vibrated a record, the resilient strip 1s -vibrated correspondingly and varies the contact length or area between the two elements.

In this way, the resistance of the circuit is the stylus arm,

varied in accordance with the vibrations of so that electric impulsesare set up in the reproducer circuit, and these impulses are utilized to operate loudspeaking mechanism.

It is immaterial whether the fixed element or the vibratory sprlng element is the resistance member. Usually, though, it is more practical to make the spring element of good conducting material and the fixed 4 element of carbon or other material of high electrical resistivity.

In a the resilient strip,

preferred form of my invention, the fixed element has a curved face with which fixed at one end, normally lies in contact for a predetermined length or area. The free from the contact is so connected to end of the strip curves away face of the fixed element and the stylus arm that vibra-' tions of the .latter exert a substantially tangential v This operation causes the push and pull on the spring strip.

vibratory. movements of the stylus arm to produce amplified variations in contact area or length between the-two elements,'so that the smallest vibrations of the stylus are sufiicient to generate electric impulses in the reproducer circuit.

The'practical advantages and utility of my new reproducer will become clear from a detailed description of the'accompanying drawcations of my invention. In these drawings, Fig. 1 shows in vertical cross-sectmn an in which I have shown several exemplifielectric phonograph reproducer constructed in accordance with my invention;

Fig. 2 is a front view of the device shown in I i Fig. lfwith the front cover removed; Fig. 3 is a diagrammatic, representation of a modified construction;

Fig. 4 shows in cross-section a reproducer. adapted for playing vertical-cut records of the Edison type, the stylus arm being shown in playing position;

Fig. 5 is a view similar to Fig. 4, showing made much more compact than the structures 1 represented in the drawings.

Referring to Figs. 1 and 2, there is a suitable casing indicated as a whole by 10, in which the reproducer' parts are mounted. This casing, which ly made of light metal, .such'as aluminum, and is provided with a hub ll for attachment to a supporting arm. It will be understood- 13 may piece, From the bottom ,of casing 10 pro is small and flat, is usualwithout illustration that thesupporting arm I, 7

I ject spaced lugs 16 adapted to receive a pair of Not bearings 17 or a needle arm 18. I 'mlghtsay here when I refer to the member 18 as a needle arm, I include any practical form of stylus arm, irrespective of whether the stylus is in the form of a needle or other record-playing memben, v

.In casing 10 is mounted a resistance member 19, which may simply be a bar of carbon, or made of any other suitable resistance material. The resistance bar 19 is supported in fixed positionby-insulating lugs 20 secured to the back-plate 13 by screws 21 or otherwise. a Any other practical means may be employed for rigidly supporting the resistance member 19 in proper position within the we ing. To the lower end of resistance bar19 1s secured a spring strip 22 of good conductlng material. A screw 23, or similar means, holds the spring conductor 22 firmly-attached to resistance member 19. As seen in Fig. 2,

the members 19 and '22 are secured together in alignment. The fastening device 23 is of such a nature that it prevents turning of the spring- 22.. A conductor 24 is connected to one end-of resistance member 19, and a conductor 25 is connected to the other end of the resistance member and also to the attached end of spring conductor 22.

The needle arm 18 is at its inner end provided with a lateral projection or nose-piece 26adapted to engage thefree end of spring conductor 22.' A spring 27, secured at one end to the front plate 14;- of the casing, bears against the needle arm 18 to counterbalance the effect of contact spring 22 on the needlearm. In other words, the two springs 22 and 27 oppose eachother and normally hold the needle arm in a neutral or balanced position, as indicated in Fi 1. I

i The operation 0% the reproducer above described is as follows: Assuming the needle to be in record-playing position, when the inner end of the needle arm. moves to the left (as viewed in Fig. 1), the conducting spring 3 22 is forced toward the fixed resistance member 19, whereby the contact area or length between the members 19 and 22 is increased. Since the member 22 is of good conducting material, it decreasesv the resistance of the circuit proportionately to the increased contact surface between the members 19 and 22.

- In Fig. 1, the dotted line 22 represents dle arm moves in the opposite direction indicated b I I roughly the position of the spring contact 22 when the inner end of needle arm 18 has moved toward the left. Now, when the neeagainst the tension of spring 27, (that is,'to-

ward the right as viewed in F1 1), the

spring conductor 22 automatica y moves away from the resistance bar 19, as roughly dotted line 22. This means that the resistance of the circuit is increased by-an amount depending-upon the extent of movement of spring' contact 22. The inin accordance with the vibrations of the needle arm 18. To put this differently: the vibrations of the needle arm cause the contact spring 22 to short-circuit a variable portion of resistance 19, thereby setting up current impulses in the reproducer circuit; Fig. 1 plalnly shows that the vibrations of the stylus point 28'are transmitted-to the inner end 26 of the needle arm in amplified rela tion, so thatthe smallest movements of'the stylus are suflicient to produce vibration of the resilient conductor 22 for causing variations of resistance in the reproducer circuit.

These resistance changes, as already stated, produce corresponding current impulses in the battery circuit, and these impulses are amplified b suitable apparatus to operate a loudspea er. Inasmuch as amplifying transmission circuits for electric phonographs are well understood, I need not go into tedious details concernin the same, especially since my invention as'nothing to do with any particular type of amplifier. It is suflicient that'in Fig. 6 I have indicated a battery 29, a step-,uptransformer 30, an elec tromagnetic driving unit 31, and a cone diaphragm' 32. Amplifying tubes may be inserted, if necessary, depending uponthe type of loudspeaker tobe operated. The part 31 may therefore be considered as any suitable apparatus for amplifying the current impulses of the battery circuit to a suflicient degree for actuating the loudspeaking diaphragm 32.

In the diagrammatic representation of Fig. 3, the curved line 33 represents the contact surface of a fixed resistance member, which may be a curved bar of carbon or constructed of any'other resistance material suitable for this purpose. Current-leads 34 are connected to opposite ends of resistance member 33 for including the same in a battery circuit. A spring strip 35 of good conduct- ;ing material is co'nnectedat point 36 to resistance member 33. The' free end 37 of spring conductor 35 is connected to the inner end of needle arm 18. The normal position of spring conductor 35 and needle arm 18 is shown in full lines in Fig. 3. When the needle arm moves into the position .18, the

spring conductor'35 is forced into increased contact with the resistance element33, as rggghly indicated by dotted line 35", and the resistance of the circuit is correspondingly decreased. When'the needle arm vibrates intothe position indicated bydottedline 18F,

it pulls the-spring contact 35 away from the fixed. resistance member 33 into. a position line 35 indicated approximately by the curved dotted parts, the resistanceof the circuit is increased.

It will be noticed that in Fig. 3 the needle arm 18 exerts a tangential pushand. pull on the arcuate contact spring 35, and this action results in an amplified movement of the spring, with correspondingly To make this clear, let us suppose that, when the arm 18 and contact spring 35 are in normal position, the spring lies in contact with resistance member 33 from point'36 to point :0 This may-be said to determine the normal resistance of the battery circuit. We shall further assume that the dotted-line positions of theparts 18 and 35 in Fig. 3 represent the maximum circuit is now a minimum,

amount of movement to either side of normal position. When the needle arm vibrates to position 18*- and pushes the contact spring into position 35, the contact length between the members 33 and 35 has been increased to point y. The-resistance of the on the assumption above made. When the needle armswings to position 18, contact spring 35 engages the resistance member 33 only from point 36 to point z, and thecircuit resist-anceis now a maximum. If the positions 18 arid .18 of the needle arm are at equal distances from the central ornormal position, the increased contact length or area represented by the arc is substantially equal (theoretically, at least) to the decreased contact length represented by the arc w-z. Between the extreme points 3 and 2 an almost infinite number of resistance variations are possible to represent all movements of the styluspoint.

The construction of Fig. 3 is particularly adapted for use on the new style of longp'laying record. in which the needle track is several hundred lines to the'inch." The smallest vibrations of the stylus point are sufficient to produce vibratory movements of the resilient conductor 35 to vary the resistance of the circuit. As indicating the greatly amplified transmission ratio between the stylus point 28 and'spring conductor 35, it will be seen in Fig. 3 that when the stylus travels through the minute arc between points 28 and 28 the resistance variation-of the circuitis represented by the comparatively long arc na -y. Thus, theoretically speaking, the

eiiect produced by the construction of- Fig.

3 is represented by the ratio of arc w-y to.

are 2828 In actual practice, of course, one may expect deviations from these theoretical considerations, but the principle of I need hardly explain thatthe various, positions of the parts as indicated-by dotted lines in Fig.3 are not to beregarded as mathematically correct,-b'ut rather as approximate visual indications of In this last-named position of the i in vertical position amplifying the movements of needle arm 18 and spring conductor 35. The maximum vibrations of these parts are very much smaller than would appear from Fig. 3. Since the needle arm 18 is connected to spring conductor 35, the, latter also acts as a centeringv spring for the needle arm and no additional spring is required for that purpose, thereby increasing the simplicity-of this device.

The .modification of Figs. 4 and 5 shows an adaptation of the invention to records of the Edison type. As is dwell known, these'records are'played by a stylus usually in the moves in a vertical plane. there is a suitably shaped casing 38 supported by -an arm '39., which is mounted to swing horizontally and also in a vertical plane. From the bottom of casing 38 extend a pair of lugs 40, between which vertical-cut The inner or rear jecting into the casing through a slot 46. e A

resistance member 47 is mounted in fixed position withinthe casing 38, as by means of insulating studs 48. Circuit conductors 49.

are connected to the opposite ends of-resistance member 47. A spring blade 50 of good conducting material is connected at 51 to one end of resistance member'47. The other end of spring-contact 50 is connected at 52 to the inner end of extension 45. The inherent tension or resiliency of spring conductor 50 is such that normally it tends-to lie against the resistance strip 46, so that the stylus arm 41 is normally held in the position shown in Fig. 5. The contact of the stylus arm with the bottom of the casing at point 53 limits the upward movement of the rear portion of the stylus arm under the action of spring 50. \Vhen the stylus point 44 is' placed on a record, the weight ofthe reproducer automatically causes the stylus arm 41 to assume an approximately horizontal position against the normal tension of spring 50, which is now about halfway in contact with resistance element 47. This position of the parts is shown in Fig. 4. As the stylus arm 41 vibrates, the contact areaor length between members 47 and 50 iscorre'spondingly varied to produce current impulses in the battery circuit,

as already explained. The spring 50 not only causes resistance variations in accordance with the movements of the stylus, but it also actsto hold the stylus arm ina balanced or floating condition during the playing of a record. This produces an exceedingly sensitive instrument, which is instantly responsive to the minutest vibrations of the stylus point.

1n Figs. 4 and 5, as in Fig. 3:, the action of the stylus arm is to exert a substantially tangential push and pull on the connected con-I Fig. 3 applies to Figs. 4 and 5.

I would call special attention to the utter simplicity of my new electric reproducer. There is no magnet, no coil and no chamber filled with carbon granules. I have only a resistance element, a conducting element, and

tact spring, so that what has been said about a stylus arm. This simple construction makes it possible to manufacture the device at a correspondingly low cost. The absence of a magnet reduces the weig t or pressure at the stylus point, so that the most delicately grooved records can be played without danger of mechanical injury to the frail walls of the groove. Then, too, by doing away with a magnet and its vibratory armature, I eliminate all magnetic drag or bias. exerted on the stylus arm in electromagnetic reproducers of prior construction. In my new reproducer, the vibratory contact spring offers just the proper load or mechanical resistance to the stylus and is always free to respond accurately to the stylus vibrations.

An important feature of my invention lies in the'fact that identical movements of the stylus produce identical variations of resistance and thereby identical current'impulses, as will be understood from the description of .Fig. 3.- In other words, the same tones are always reproduced in the same wayassuming, of course, that the other parts of the complete reproducing mechanism are in proper working condition. In the case of the old microphone reproducers, the same vibrations of the needle arm cannot produce exactly the same changes of resistance, be-

cause the carbon granules are never twice in the same position. Furthermore, the movements of thev packed granules against and over each other, pell-mell, tend to produce an electrical disturbance resulting in what is known as microphone noises. These are said to be due to the rubbing or grinding action ofthevibratory granules against each other. Now, in my reproducerthis objection does not exist, because the vibratory controlling element engages the fixed element in a smooth rollingcontact wholly devoid of friction.

Although I have described the fixed elements 19, 33 and 47 as resistance members, and have referred to the vibratory elements 22, 35 and 50 as good conductors, it is obvious that the first-mentioned members may be made of good conducting material and the vibratory members may be constructed of resistance material. In practice it is more convenient to mount the resistance member in fixed position, but the alternative arrangement comes within thescope of my invention. The resistance members, as already stated,

There are, several high-resistance alj'loys' adapted for use in this invention. The resilient conductors may be of brass, spring steel, or other resilient metal of low electrical resistance. The sizeand shape of the two cooperating elements will naturally vary in different cases, and the most suitable dimensions of the parts can be determined only by actual tests and trials in any given design of instru ment. These things are within the skill of the mechanic.

The particular constructions shown in the drawings are to be regarded merely as illustrative embodiments of my invention and not in the nature of limitations or restrictions, unless so expressed in the claims which follow. Although I have shown and described my invention as a phonograph reproducer, it isevident that it ma be constructed as a telephone transmitter y substituting an acoustic diaphragm for the needle arm and make other obvious changes in the design. This will be understood without further explanation.

I purposely do not herein claim broadly the idea of an electric sound transmitter or reproducer in which a pair of elements having different electric conductivities are mounted to have variable contact with each other, and having avibratory member connected to one of said elements to short-circuit a variable length or area of the element having the lower conductivity. That fundamental concept is covered in my copending application, Serial Number 154,059, filed December 11,1926.

I claim as my invention:

' 1. An electric phonograph reproducer comprising a casing adapted to be supportedin operative relation to a record, a resistance element and a conducting element carried by said casing and adapted to be connected in circuit, means for rigidlysupporting one of said elements, the other element consisting of a resilient strip fixed at one end only so as to. be in permanent contact with the fixed element at that end, the inherent tension of said strip-being such that normally it lies in' contactwith said fixed element for a predetermined length and then bends away from said fixed element, and a vibratory stylus arm mounted on said casing and adapted to actuate"the movable portion of said resilient strip to vary the contact area between said elements, whereby the resistance of saidcircuit is varied in accordance with the vibrations of said arm.

2. An electric phonograph reproducer-comprising'a casing adapted to be supported in operative relation to a record, a resistance element mounted in fixed position in said casing and adapted to be connected in circuit, a resilient conducting. strip supported only at inherent tension of said strip being such that normally it lies in contactwith said element for a predetermined length and then bends away from said element, and a vibratory st lus arm mounted on said casing and adapte to actuate the movable portion of said strip to vary the contact area between said element and said strip, whereby the resistance of said circuit is varied in accordance with the vibrations of said arm.

3. An electric phonograph reproducer comprising aresistance element and a conducting element adapted to be connected in circuit, means for rigidly supporting one of said elements, the other element consisting of a curved resilient strip fixed at one end only so as to be permanently connected with the fixed element at that end, the inherent tension of said strip being such that normally it lies in contact with said fixed element for a predetermined length and then gradually curves awa' from said fixed element, and stylus mem er connected to the free end of said strip so as to exert a substantially tangential pushand pull on said strip, whereby the vibratory movements of said strip at its free end produce amplified variations in contact area between said two elements.

4. An electric phonograph reproducer comprising a resistance element having a curved contact face, means for supporting said element in fixed position, a curved resilient strip of good conducting material supported at one end in permanent contact with said element, the inherent tension of said strip being such that normally it lies in contact with the curved face of said element for a predetermined length and then gradually curves away from said facefmeans for connecting said resistance element in circuit, and a stylus member connected to the free end of said strip so as to exert a substantially tangential push and pull on said strip, whereby the vibratory movements of said strip at its free end produce amplified variations in contact area between said element and said strip.

5. An electric phonograph reproducer comprising a casing, a resistance element fixed in said casing and adapted to be con nected in circuit, a resilient conducting-strip supported only at one end so as to bein permanent contact with said element at that end, the inherent tension of said strip being such that normally it lies in contact with said element fora predetermined length and stylus arm pivoted then bends away from said element, and a to said casing'and at its inner end engaging the free portion of said strip, wherebythe resistance of said circu t is varied in accordance with the vibrations of said arm, which is so pivoted that its inner end vibrates in'amplified relation to the vibrations of the stylus.

6. An electric phonograph reproducer comprising a casing, a resistance element I and cenducting element a ap ed to be connected in circuit, means for rigidly sup porting one ofsaid elements in said casing, the other element consisting of a curved resilient strip fixed at one end only so as tobe permanently connected with the fixed impulses in said circuit.

7. An electric phonograph reproducer comprising a casing, a resistance element rigidly mounted in said casing and adapted to beconnectedixi circuit to control loudspeaker mechanism, said element having a curved contact face, a curved resilient strip of good conducting material connected at one end to said element and free at its. other vibrations of said needle arm produce amplified resistance variations between said two elements and thereby generate current that end, the inherent tension of end, the inherent tension of said strip being such that normally it lies in contact with the .curved face of said element for a predetermined length and then gradually curves away from said face, and a stylus arm'pivoted to said casing and connected at its inner end to the .free end of said strip so as to exert a substantially tangential push and pull on said strip, whereby the vibrations of said arm produce amplified resistance variations between said element and said strip and thereby generate current impulses 111 said circuit.

8. In an electric phonograph reproducer adapted to play vertical-cut records, a casing provided with a vibratory resilient strip fixed at one end, a substantially horizontal stylus arm pivotedv tosaid casing so as to vibrate in a vertical plane and conne'cted'to the free end of said strip, and means whereby the vibratory movements of said strip produce current impulses in a reproducer circuit, said resilient strip sustaining thev stylus arm 1n floating condition during record-playing operation and also holding said arm in predetermined idle position on the casing.

9. An electric phonograph reproducer for playing vertical-cut records, comprising a casing adapted to'be supported on a movable arm,'a resistance element ri 'dly mounted in said-casing, said element contact face, a curved resilient strip of good conducting material connected at one end to said element and free at its other end, said strip being so mounted as to vibrate in a vertical plane, the'inherent tension of said strip being such that normally it lies in contact w th the c rv d f e f a d em nt f r aving a curved a' predetermined length, a substantially hori- 'zontal stylus arm pivoted to said casing so as to vibrate in a vertical plane, means for connecting the rear end ofsaid stylus arm to the free end of said resilient strip, whereby said arm exerts a substantially tangential push and pull on said strip to vibrate the same and thereby vary its contact length with said resistance element, and means 'for so connectingsaid element and contact strip in a repro ducer circuit that the vibratory movements of said strip produce current impulses in said circuit, said resilient strip sustaining the sty lus arm in floating condition during recordplayin operation and also holding said arm in predetermined idle position on the casing.

10. An electric phonograph reproducer comprising a casing adapted to be supported in operative relation to a record, a high-resistance member mounted in said casing and adapted to be connected in circuit, a low-resistance member arranged in said casing in contact with said first-named member, means for supporting one of said members in flied position,.and a stylus arm carried by said cas mg for operating the other member to cause said low-resistance member to short-circuit a I variable portion of said high-resistance member in accordance with the vibrations of said 11; An electric phonograph .repioducer 14. An electric phonograph reproducer comprising a pair of elements having diiferent electric conductivities, means for rigidly supporting one of said elements, means'for movably supporting the other element so as to have variable contact wih 3 the rigid ele-" ment, said movable element being inherently elastic and self-restoring, and a vibratory stylus member-for operating said movable element to short-circuit a variable length or area of theelementhaving the lower conductivity,- said movable elastic element being comprising the combination of a curved 5 spring strip of conducting material support ed atone end, a resistance member rigidly mounted tov have variable contact with said curved strip, and a stylus for vibrating said strip to short-circuit a variable length or area of said member, the inherent resiliency of said spring strip automatically holding said stylusin predetermined normal position.

12. An electric phonograph reproducer comprising a movable spring conductor of relatively low resistance mounted for vibratory movement, a stationary resistance member. arranged to have variable contact with said spring conductor, and a stylus for vibrating said conductor to short-circuit a variable length or area" of said resistance member, the inherent resiliency of said spring 2 conductor automatically holding said stylus in predetermined normal position.

.13. An electric phonograph reproducer comprising a pair of elements having difierent electricconductivities, means forrigidly supporting one of said elements, means for movably supporting the other element so as to have variable contactwith the fixed element,

" said movable element being inherently elastic and self-restoring, and a stylus connection for vlbrating said movable element to short-circ'uit ggyariable length or area of the element haviiig the lower conductivity, said movable elastic elenient bein adapted to automatically restore said sty us connection to normal position. I v

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