US3069957A - Vibrato device for a musical instrument - Google Patents

Description

Dec. 25, 1962 'r. B. GIBBS VIBRATO DEVICE FOR A MUSICAL INSTRUMENT Filed se t'. 26, 1958 3 Sheets-Sheet 1 Dec. 25, 1962 1'. B. GIBBS 3,069

VIBRATO DEVICE FOR A MUSICAL INSTRUMENT Filed Sept, 26, 195.8 3 Sheets-Sheet 2 GENERATORS AMPLIFIER T. B. GIBBS VIBRATO DEVICE FOR A MUSICAL INSTRUMENT Filed Sept. 26, 1958 Dec. 25, 1952 3 Sheets-Sheet 3 United States Patent Gfihce 3,hii9,957

Patented Dec. 25, 1952 VHERATQ DEVKQE EGR A MUSlCAL LNSTRUME NT Thomas E. Gibbs, false Delavan, Win, assignor to Gibbs Manufacturing 8; Research Eorporation, a corporation of Wisconsin Filed Sept. as, 1953, her. No. 763,643 3 Claims. (Cl. ti t-1.25)

This invention relates to an electronic musical instrument and more particularly to tremolo and vibrato systems for an electronic organ.

The terms tremolo and vibrato, while sometimes loosely considered synonymous, technically relate to two different, although related, musical effects. The tremolo, or tremulant, effect is one in which the amplitude of the musical tones is varied a slight amount above and below the mean value of the tone, at a low or subaudio rate. The vibrato effect is one in which the frequency of the musical tones is varied slightly above and below the mean frequency, also at a low or subaudio rate. Where an instrument includes provision for both tremolo and vibrato, the two should operate in synchronisrn with both the amplitude and frequency of the tones increasing and decreasing simultaneously.

it is a principal object of the present invention to provide an electronic musical instrument with novel tremolo and vibrato systems, and a novel arrangement for synchronizing the operation of the two systems.

One feature of the invention is the provision, in an electronic musical instrument, of means for generating and reproducing musical tones, means for varying the intensity of the tones to create tremolo effect, and means for varying the frequency of the tones to create a vibrato effect, the intensity and frequency varying means being synchronized, preferably so that the intensity and frequency of the tones increase and decrease simultaneously. Another feature is that the organ utilizes tone generators in which the light from a amp is scanned to produce the musical tones, and the intensity of the light and the speed of the scan are varied to produce the tremolo and the vibrato effects, respectively.

A further feature is the provision of an electronic musical instrument in which the amplitude of the musical tones is effected by the intensity of a lamp, together with a tremolo control for varying the potential applied to the lamps, thereby varying the amplitude of the musical tones. Still another feature is that the lamp is energized from a power source having a resistor selectively connectable therewith for varying the amplitude of the potential applied to the lamp. Yet a further feature is that the power source includes a filter having a capacitor selectively connecta-ble therein for varying the amplitude of the potential applied to the lamp.

And another feature is the provision, in a musical instrument utilizing a tone generator having a moving element, the speed of which determines the frequency of the generated tone, of a vibrato system including means for varying the speed at which the moving element is driven, above and below the normal speed thereof. Yet a further feature is that the drive motor for the moving element of the tone generator is resiliently mounted, and means are provided for oscillating the motor about its drive axis, as an actuating arm secured to the motor and en ageable with an eccentric cam driven by the motor. 7

Further features and advantages of the invention will readily be apparent from the following specification and from the drawings, in which:

FIGURE 1 is a diagrammatic sectional view illustrating the basic elements of a tone generator of the type with which the present invention may be used;

FIGURE 2 is an exploded fragmentary view of the mask and scanning disc of FIGURE 1;

FIGURE 3 is a block diagram of the basic elements of a musical instrument with which the invention may be used;

FIGURE 4 is a schematic circuit diagram of an embodiment of the tremolo system;

FIGURE 5 is an elevation view of the tone generator chassis of an electronic musical instrument embodying the invention;

FIGURE 6 is an enlarged fragmentary view of the tone generator drive;

FIGURE 7 is an enlarged fragmentary view of the drive motor mounting, portions of the mechanism being eliminated in the interest of clarity of illustration; and

FIGURE 8 is an enlarged fragmentary view of the tremolo and vibrato cam.

In FlGURES 1-3, certain basic elements of a preferred tone generator and musical instrument are shown, as an illustration of the type f instrument with which the novel tremolo and vibrato systems of the present invention may be used. While certain features of the present invention are particularly adapted for use with the illustrated tone generator and instrument, the invention is also susceptible of use with other types of tone gen erators and musical instruments, as will readily be apparent to those skilled in the art.

The basic elements of the preferred tone generator are illustrated in FEGURES l and 2. A mask 15 has formed thereon a series of light transmitting areas 16 which represent a particular tonal quality, the remainder of the mask being opaque. A scanning member 17, the major portion of the surface of which is also opaque, is provided with scanning slots 1% which are moved past the tone representing area 16-, by rotation of the scanning member. A lamp l9 emits light which passes through lens 26, uniformly illuminatin the tone representing areas in of the As scanning member 17 moves past mask 35, the light from areas in is scanned by slots if} and the resulting light variations impinge on a photosensitive device or photocell 21, which in turn converts the light variations to electrical signal variations appearat terminals 22. The tone generator is provided with a plurality of light transmitting mask areas, each with its own light source, for producing notes of differing tonal qualities, and by proper arrangement of tone representing areas and scanning slots, covering several frequencies.

in FIGURE 3, the basic elements of an electronic organ are shown. A plurality of tone generators 23 are connected through stop selectors 2 with keys 25. A preferred organ arrangement has twelve tone generators, one for each note in an octave. When a key 25 is pressed, certain lamps in the proper tone generator are energized, depending on the stops which have been selected. The resulting light variations are converted to electrical signals by the photocell in the tone generator, the electrical signals amplified and broadcast in audible form by speaker 12 The power source for the tone generator lamps 19, of which there may be several hundred, is illustrated in FiGURE 4. The power source is energized from a suitable source of power, as volts A.C., connected through leads 3d and 31 to the primary winding 32a of a low voltage power transformer 32. Secondary winding 32b of the transformer is center tapped and connected with a full wave rectifier circuit including selenium rectifiers 33 and 34. A filter circuit includes series inductor 35 and shunt capacitor as connected with the center tap and returned to a reference potential or ground 37. The tone generator lamps 19 are connected in parallel (through the key switch-stop selector mechanism, not shown in FIGURE 4) and across capacitor 36.

Even very slight variations in the potential applied to the tone enerator lamps cause a change in the intensity of the light thus in the amplitude of the generated signal. Accordingly, the filter of the power supply is such that the alternating component of the voltage in the output of the rectifiers is substantially completely eliminated. The simple single stage of inductance-capacitance filtering shown herein is intended merely to represent an adequate filter, and the actual filter used may include several similar sections.

The sensitivity of the tone generators to variations in the potential applied to lamps 19 is utilized in the system illustrated by the circuit of FIGURE 4 to provide a tremolo effect. In order to achieve a tremolo having both an increase and a decrease of the amplitude of the generated tones, above and below the nominal or normal value thereof when the tremolo system is not in operation, it is necessary that the output voltage of the power supply be increased above and decreased below its normal value. As will appear in detail below, this is accomplished by making two changes in the power supply circuit. First, a capacitor is shunted across the input of the filter to raise the output potential; and second, a resistor is connected in series with an input lead to the power supply to decrease the output potential. These two elements are alternately switched into the circuit, causing the potential applied to lamps 19 to vary above and below its value when the tremolo circuit is inoperative.

The capacitor, indicated at 38, is connected in series with a current limiting resistor 3E and through switch 49 to ground. Switch is operated at a low or subaudio rate, as four cycles per second by a cam 41 which preferably forms a part of the tone generator drive system, as will appear. Resistor 42 is coupled through transformer 43 with input lead 3% of the power supply. A shunt circuit shorting resistor 42 is intermittently completed by switch 44, which is mechanically ganged with switch 40 so that they operate in synchronism. When switches 4i} and 44 are closed, capacitor 33 is connected in the circuit increasing the output voltage of the power supply, and resistor 42 is shunted. When both switches are open, capacitor 38 is removed from the circuit and resistor 42 is effectively connected in the power supply input circuit reducing the output potential. By properly correlating the size of capacitor 38 and resistor 42, the increase and decrease in the amplitude of the musical tones may be made substantially equal so that a uniform variation above and below the normal amplitude is produced.

The operation of the tremolo circuit is controlled by a switch 45 shown in the tremolo On position. In this position, it completes the circuit for capacitor 355, to ground 37. In the Off position of the switch, the movable arm 45 completes a shunt circuit shorting resistor 42.

In a specific embodiment of the tremolo circuit, capacitor 38 has a value of 2000 microfarads and current limiting resistor 3? a value of 0.120 ohm. Resistor 4-6, 18 ohms, is connected across the contacts of switch 40, so that the switch will not have to carry all of the current through capacitor 38. However, this resistance is so high as compared with the reactance of the capacitor 38 and the other shunt elements in the power supply, that it has no appreciable effect on the operation of the circuit when switch 49 is opened. A capacitor 47, 4 f. (microfarad) shunts switch 4t Resistor 42 has a value of 166 ohms, and transformer a one-to-one turn ratio.

FIGURE 5 illustrates a drive arrangement for a preferred form of musical instrument incorporating the tone generators of FIGURES l and 2. Twelve tone generators 50, one for each note of the octave, are mounted on a tone generator panel 51 with drive pulleys a, for the rotatable mask members 17, extending rearwardly therefrom. The pulleys 559a are connected by an endless drive element 52 which also passes around adjustable idler wheel 53 to permit the necessary tension to be established. A drive motor 54 is mounted below the generator panel 51 and connected by drive belt 55 with a pulley 56 mounted on the shaft of one of the tone generators.

in FiGURE 7, it will be seen that the mount for motor 54 includes a bracket 58 secured to a support member 59. A clarnp which has two portions 6% and 61 and an adjusting screw 62 is carried from the lower end of bracket 58, supporting a metal ring 63 within which is a motor mounting element 64- of resilient material, as rubber. The motor mounting element has a plurality of inwardly extending deformable fingers 64a which engage surfaces 65 formed on the end bell 66 of drive motor 5- This arrangement shown for one end of the motor is repeated at the other end.

The drive shaft of the motor 54 carires a pulley 68 which is connected through drive belt with pulley 56 on the shaft 69 of one of the tone generator drive pulleys 51m. The other tone generators are driven from motor 54 through belts 55 and 52. The resilient mounting of rnotor 54 permits it to be rocked about its drive axis to vary the speed of drive belts 55 and 52. Secured to a pair of studs 70 and 71 which extend outwardly from the shell of motor 54 is an arm 72 having an actuating portion or cam follower 73. The arm portion 73 carries a bearing surface 74 engageable with an eccentric cam carried by shaft 69. Drive surface 7:-

held in contact with the cam by spring 76 connected between the upper end of arm portion 73 and fixed member 77. As cam turns, arm portion 73 moves back. and forth parting an oscillatory motion of several degrees extent to rnotor 54. This oscillatory motion is transmitted to the drive belt 55, modifying or modulating the constant speed of drive belt 52 and of the rotating scanning discs of each of the tone generators. The speed of drive belt 55 is increased above and decreased below its normal speed, transmitting a similar increase and decrease to the scanning discs of the tone generators. This results in a frequency modulation of the generated tone representing signals at a low or subaudio rate. Cam 75 has slotted mounting openings 75a therein, permitting adjustment of the amplitude of the frequency shift in the generated tones, above and below the normal frequency of the tones.

In order to render the vibrato inoperative, the bearing surface 74 of arm portion 73 is moved out of contact with cam 75 by energizing an electromagnet 78 which attracts an armature 79 carried at the end of arm portion 72. Movement of armature 79 upwardly moves bearing surface 74 to the left, against the action of spring 76. Deenergization of electromagnet 78 releases the arm, allowing spring 76 to move bearing surface 74 to the right into engagement with cam 75.

As pointed out above, where an organ is provided with both tremolo and vibrato systems, it is desirable that the operation of the two systems be synchronized, so that both the amplitude or intensity of the generated tones and the frequency thereof increase and decrease simultaneously. Accordingly, switches 40 and 44 in the tremolo circuit (FIGURE 4) are arranged for actuation by cam 75, as shown in FIGURE 8. Cam follower St} bears against the surface of cam 75 and actuates the switch operating member 81.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In an electrical musical instrument, a plurality of tone signal generators of the type which have rotatable members the speed of rotation of which determines the pitch of the tones generated, an electric motor having a frame and a shaft which rotates at a constant speed with respect to the frame, drive transmission means connecting said motor shaft to said rotatable members for driving each of said rotatable members individually at a speed which is a constant function of the speed of said motor shaft, means mounting said motor frame for rocking movement about the axis of said shaft, oscillatory means connected to be driven by said motor shaft and adapted when activated to rock said motor frame in substantially a simple harmonic manner about the shaft axis at a vibrato frequency, and means operable at will for deactivating said oscillatory means and for holding said motor frame in substantially a fixed position. i

2. In an electrical musical instrument, a plurality of tone signal generators of the type which have rotatable members the speed of rotation of Which determines the pitch of the tones generated, an electric motor having a frame and a shaft which rotates at a constant speed with respect to the frame, drive transmission means connecting said motor shaft to said rotatable members for driving each of said rotatable members individually at a speed which is a constant function of the speed of said motor shaft, means mounting said motor frame for rocking movement about the axis of said shaft, oscillatory cam means connected to be rotated by said motor shaft, a cam follower secured to said motor frame and adapted to bear against said cam to rock said motor frame about the shaft axis at a vibrato frequency in response to rotation of said cam, and means operable at will for swinging said cam follower away from said cam and for holding said motor frame in substantially a fixed position.

3. In an electrical musical instrument, a plurality of tone signal generators of the type which have rotatable members the speed of rotation of which determines the pitch of the tones generated, an electric motor having a frame and a shaft which rotates at a constant speed with respect to the frame, drive transmission means connecting said motor shaft to said rotatable members for driving each of said rotatable members individually at a speed which is a constant function of the speed of said motor shaft, means mounting said motor frame for rocking movement about the axis of said shaft, oscillatory cam means connected to be rotated by said motor shaft, a cam follower secured to said motor frame and adapted to bear against said cam to rock said motor frame about the shaft axis at a vibrato frequency in response to rotation of said cam, electromagnetic and armature means adapted for swinging said cam follower away from said cam and for holding said motor frame in substantially a fixed position in response to energization of said electromagnetic means, and circuit means operable at will for energizing or deenergizing said electromagnetic means.

References Cited in the file of this patent UNITED STATES PATENTS 1,991,727 Brimberg Feb. 19, 1935 2,033,232 Eremeeff Mar. 10, 1936 2,130,251 Richards Sept. 13, 1938 2,460,868 Appel Feb. 8, 1949 2,509,923 Hanert May 30, 1950 2,542,065 Van Wye Feb. 20, 1951 2,565,033 Leonard Aug. 21, 1951 2,681,584 Williams June 22, 1954 2,746,334 Williams May 22, 1956 2,818,761 Williams Jan. 7, 1958 FOREIGN PATENTS 523,362 Great Britain July 12, 1940 656,792

Great Britain Sept. 5, 1951

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