US2647426A - Electrically operated musical instrument - Google Patents

Description

g- 1953 w. F. BATTLE ET AL ,4

ELECTRICALLY OPERATED MUSICAL INSTRUMENT Filed March :51, 1948 v r 2 Sheets-Sheet 1 INVENTURS W/LL/HM E BHTTLE (f 30 M/CHfiEL-fl B TTLE 3 BY WM.

g- 1953 w. F. BATTLE EI'AL 2,647,425

v ELECTRICALLY OPERATED MUSICAL INSTRUMENT Filed March 5 1, 1948 2 Sheets-Sheet 2 JNVENTURS W/LL/f/M E BHTTLE JTZUFH 5 5 Patented Aug. 4, 1953 INSTRUMENT ELEGTRICALLY OPERATED MUSICAL William F. Battle and Michael A. Battle, Lisbon, Ohio Application March 31, 1948, Serial No. 18,196

14 Claims. 1

This invention relates to electrically operated musical instruments in the nature of pianos or organs.

An object of the present invention is to provide an electrically operated musical instrument of the character described, which may be constructed of a minimum of parts, and in which the parts are generally of such a simple and relatively inexpensive nature as to make possible within the toy class, the production of an instrument capable of producing substantially any desired range of musical tones, and by which tunes may be played in the manner of a piano, organ,

or other keyboard instrument.

Another object of the invention is to provide a musical instrument of the character described utilizing audio frequency oscillations to produce different musical notes, and wherein harmonious combinations of notes may be produced by trill- ..ing.

stantially as viewed on the line 33 of Figure 1.

Figure 4 is a further enlarged fragmentary cross-section, taken substantially on the line 44 of Figure 3.

Referring particularly to Figures 1, 3 and 4, the musical instrument illustrated therein is a toy device in simulation of a piano or organ, the same including a box-like casing supported on spaced legs 2 I, 2! which are formed on downward extensions of the end panels 22 of the casing. A keyboard 23 includes a series of elongated elements or keys K1 to K16, which are suitably pivoted at 2 5, to a bottom panel of casing 20, to

extend forwardly with the upper portions thereof exposed for operation by finger action, on the order of a piano or organ. Rearward extensions 26 of the keys are yieldingly engaged by a corresponding series of separate fiat springs 21, of electro-conductive material, extending downwardly and forwardly from a cross-bar 28 arranged within the casing between the opposite end panels 22.

Each spring contact 21, in. addition to nor-v mally holding its respective key in horizontal position (see Figure 4), serves as a movable electrical contact, adapted to be urged yieldingly upwardly by finger pressure on the forward portion of the key, releasably to engage the contact 21 with a separate contact point 29 of a corresponding series thereof spaced along the underside of cross-bar 28. The contact points 21 are connected in series by an elongated electro-conductive element 30, secured along the underside of said cross-bar, the element 30 being connected to one side A of a D. C. power supply and oscillating circuit S, the same including a combined rectifier and beamed power output tube 3| and a sound-reproducing speaker 32, as will be described later (see Figure 2). As best shown in Figures 2 and 3, each spring contact 21 may have connected thereto a separate resistor (or resistors) of predetermined resistance, the resistors from left to right of the keyboard being electrically connected in one series thereof which in turn connects with the other side B of said sound-producing circuit. The resistors of this series are designated R1 to R16 from left to right of the keyboard. Any number of keys and a corresponding number of resistors may be provided, however. Thus, pressure on key K1, at the extreme left of the keyboard will close a key circuit C, on one side from A, through all of the entire series of resistors '34 to R15, for producing the lowest note on the instrument, through loud-speaker 32 in the circuit S. Pressure on key K2, alone, closes circuit C with resistor R1 omitted therefrom, to produce the next highest note on the musical scale and, similarly pressure on each successive key from K3 to K16 will produce notes of progressively increasing pitch by progressive elimination of additional resistors R2, to R15.

The D. C. power and oscillating circuit S, pre- I, viously referred to, may be connected to a volt source of A. C. electricity, as by means of a switch or other contact means 35, through lines a 1: and f--y from a filament a-f in the tube. Current flowing in the filament af will heat cathodes e and g and thereby activate the electrons thereof. A cathode circuit S1 in the circuit S, provides D. C. current which will vary in voltage correspondingly to the desired frequency of an A. C. or feedback circuit S2.

Cathode e, through line eL, connects theinner ends of inductively connected coils L1 and L2 of a transformer 31, and a cathode g connects with the anode b and grid 01 in a plate circuit P, through lines g--k-b and g -k-d, respective- 1y. The outer end of coil L2 connects the power line aa: through line Lz-h, and the outer end of coil L1, through line L1b, connects the two series of resistors of the key circuit C. A resistor [3, between cathode g and anode b, and condensers I4 and [5 on each side of the same from line gk to line L2h, provide a filter network to transform pulsating direct current from the cathodes into pure direct current in the D. C. circuit S2. A coil L3 has current induced thereto from coil L2, for energizing the coil Li of speaker 32, which in turn is adapted to produce sound in a manner to be described. Normally when none of the keys K1 to K16 is depressed, the closed D. C. power and oscillating circuit S is in an inactive condition in which no sound is produced in the system. A condenser [5, between the line from coil L2 to condenser [E and line L-e, provides a low impedance path for the audio frequency current in the B side of the circuit.

Stated otherwise, the condenser l6, in parallel with half of the transformer 3?, cancels some of the inductive reactance and gives a purer sine wave, or a pleasant musical sound.

If it is desired to operate the unit on batteries, the rectifier circuit may be eleminated, in which case the D. C. source from the battery would be applied at h. and 1/, and a low voltage battery would be connected between points It and j to heat the filament.

The use or operation of the unit to produce different tones of the musical scale in the speaker 32 will be best understood by further reference to the diagram of Figure 2, and by describing one complete cycle of frequency oscillation in the unit. With the above referred-to B-lcurrent applied at anode b and 3- current applied at cathode e, through transformer coil L2, steadily rising current will thereby flow in D. C. circuit S1 from anode I), through the tube, the direct current supply, the coil L2, and back to the cathode e, the rising voltage in coil is will cause an expanding magnetic field in the core of the transformer, with resulting expanding lines of force passing through coil L1 to induce therein a correspondingly rising current of A. C. nature, which flows in the A. C. circuit S2 through condenser ll, through the grid 0 to cathode e, and back to coil L1. The last-described circuit is termed in A. C. path for feedback to reach the grid 0.

By depressing any one of the keys K1 to K16 corresponding resistors R1 to R16 in key circuit C are applied in circuit S, as previously described. For example, by depressing key K16 the single resistor R16 is applied to circuit S, to complete a D. C. path from point B, through coil L1 to cathode e, to grid 0, back point A, and thereby to apply zero voltage to the grid 0, which will then be at the same potential as the cathode e. With zero bias thus placed on grid c the current at anode b will begin to rise in the manner previously mentioned, to cause rising current in coil L2, thereby inducing rising current in coil L1, which is 180 degrees out of phase with the anode current. Because the grid current is also 180 degrees out of phase with the anode current, the induced voltage of coil L1 is in phase with grid c and can be fed back to grid 0 to increase the feedback current at anode b.

With key K16 still depressed, as the current in coil L2 increases, the feedback voltage in coil L1 will be correspondingly increased, until anode b collects all the electrons the cathode e can produce, but because the cathode e can supply a steady amount of electrons the current in anode b will remain constant, except for the feedback voltage which must return to zero because of this steady anode current, and as no expanding field will be created in coil L2, magnetic lines of force will thread coil L1. With this sudden return of feedback voltage to zero, the voltage of grid c will also be at zero, and the anode current must also drop to the value it had at zero grid voltage. When the fully expanded magnetic field of coil L2 begins to collapse, the magnetic lines of force will again thread coil L1, but this time the feedback voltage will be in negative direction, which will make the grid have a minus value and result in a further decrease in the current of anode b, and correspondingly result in a further reduction of the magnetic field of coil L2, this reduction continuing until finally there is no current flowing in anode b or the coil L2. As there will now be no feedback the grid 0 will again have zero voltage. The above described cycle will be repeated continuously at given audio frequency, determined by the resistance of resistor R16, to produce a given musical tone through speaker 32, as long as key Km remains depressed. successively lower tones in the musical scale are accomplished by depressing successive keys K15. K14, K13, etc., by which resistances R15, R14, R13, etc., of predetermined value are added as previously described. In other words, changes in tone are accomplished by adding or subtracting resistors R1 to R16 in circuit C, to change the voltage in the grid 0 with respect to the cathode.

It will be seen that by steadily holding down more than one key of keyboard. at a time only the note corresponding to the depressed key highest in they scale will be produced. Difierent harmonious effects may be produced, however, as by steadily depressing one key with one finger to produce a steady note, and vibrating a second key to. trill another note which is in harmony with the first note. This, is possible because the inertia of the inductance allows some tone to continue even after the key has been released. It is similarly possible to trill a plurality of notes, depending upon the speed with which the fingers can be moved to vibrate the keys.

Thus has been provided an electrically operated musical instrument, which may be very economically manufactured, and yet which is capableof producing a wide variety of pleasing musical notes and harmonious combinations of notes.

By providing a fixed value of resistance between the points A and B, the condenser I! may be of a variable nature, adapted to be selectively changed to provide different tones through speaker 32. In other words, this variable condenser could be utilized in conjunction with operation of the keys K1 to K15 to produce different tones in the manner accomplished through the resistors R1 to Rm. It is also possible to substitute suitable condensers for the resistors R1 to R16, to provide different frequencies of audio oscillation.

Other modifications of the invention may be resorted to without departing from the spirit thereof or the scope of the appended claims.

What is claimed is:

I. For use with a musical instrument having a sound producing speaker and a plurality of operable keys; an oscillator circuit comprising an electronic tube envelope having therein anode, cathode and grid elements, a transformer having a primary with an intermediate tap and a secondary for connection to said speaker, a filter element connected at one end directly to the anode, said cathode being connected to said tap, a condenser connecting one end of said primary to said grid, a second anode and a second cathode comprising a rectifier in said envelope, said cathodes having heaters connected in series and across a source of power, one terminal of said source of power being connected to said rectifier anode, the rectifier cathode being connected to the other end of said filtering element, the other terminal of said primary being connected to the other terminal of said source whereby to produce continuous oscillations above audible frequency, a resistor for each of said keys, means connecting said resistors in series, contact pairs allotted one to each key and arranged each to connect a corresponding portion of said series in shunt to said condenser in response to operation of its key to reduce oscillation frequency to a selected audible value.

2. The oscillator circuit as defined in claim 1 including a condenser shunting that portion of the primary winding between the tap and the end connected directly to the source of power and sized to fix the frequency of continuous oscillation.

3. The oscillator circuit as defined in claim 1 in which an additional filter element is connected between one end of the first filter element and the terminal of said source which is connected to one end of said primary.

4. The oscillator circuit as defined in claim 1 in which a condenser is connected between each end of said filter element and the terminal of said source which is connected to one end of said primary.

WILLIAM: F. BATTLE. MICHAEL A. BATTLE.

References Gitcd in the file of this patent UNITED STATES PATENTS Number Name Date 1,543,990 De Forest June 30, 1925 2,059,683 Farnsworth Nov. 3, 1936 2,045,172 Yungblut June 23, 1936 2,301,869 Hammond Nov. 10, 1942 2,301,871 Hanert Nov. 10, 1942 2,360,697 Lyman Oct. 17, 1944 2,384,931 Kessler Sept. 18, 1945 2,470,148 Demuth May 17, 1949

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