US1893940A - Regenerative piano - Google Patents

Description

Jan. 10, 1933.

.1. H. HAMMOND, JR 1,893,940

REGENERATIVE PIANO Original Filed July 24. 1926 4 Sheets-Sheet. l

wanm ymdfi Jan. 10, 1933. J. H. HAMMOND, JR

REGENERATIVE PIANO 1926 4 Sheets-Sheet 2 Original Filed July 24 WWII/WWW Jim. 10, 1933. J. H. HAMMOND, JR

REGENERATIVE PIANO Original Filed July 24. 1926 4 Sheets-Sheet 3 A M i i y 1 i l i i 1 M 0 1 y i W i y i l M Jan. 10, 1933. J. H. HAMMOND, JR

REGENERATI VE- PIANO Original Filed July 24, 1926 4 Sheets-Sheet 4 Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE BEGENERATIVE PIANO Application filed July 251, 1926, Seria1 No. 124,576. Renewed April 6, 1932.

This invention relates to musical instruments and more particularly to high power sound producers.

The invention has reference to a musical instrument of the type producing damped compressional waves and relates to means for increasing the energy impressed upon said waves.

A feature of the invention relates to the provision of a reverberatory element adapted to emit compressional Waves in combination with means for impressing upon the element energy having a predetermined frequency and a sound sourcetuned to the pre- 13 determined frequency for controlling the energy impressed upon the reverberatory element. I

A feature of the invention relates to the provision of an amplifying device having its :3 input connected so as to be controlled by a relatively low power source of sound, and its output directly connected to a reverberatory element positioned adjacent said sound source.

3 Other objects will appear from the following description taken in connection with the accompanying drawings, in which Figure 1 is a top plan view of one embodiment of the invention;

Figure 2 is a front elevation of the device of Fig. 1;

Figure 3 is a diagrammatic showing of a portion of the structure of Figures 1 and 2 in combination with an amplifying device;

Figure 4 shows a modified form of the reverberato-ry element of Fig. 3;

' Figure 5 shows another modification;

Figure 6 shows an electro static device for actuating the reverberatory element of the device;

Figure 7 shows an electro magnetic device actuated by the tune-d element.

Like reference characters refer to like parts in the several figures of the drawings.

parts will be identified by specific names for convenience of expression but they are intended to be as generic in their application to similar parts or equivalent construction as the art will permit.

In the following .description and claims,

Referring to the drawings and more particularly to Figures 1 and 2 thereof, there is shown a musical instrument of the form of a grand piano and includes a casing 10 having an upper apertured wall 11, and a lower apertured wall 12. l/Vithin the casing 10 there is provided a fixed metal frame 13 for supporting a plurality of tuned vibratory elements or strings such as 14 for producing sound.

A sounding board 15 is positioned adjacent said strings, and forms a reverberatory element energized by compressional waves emitted from the strings. For actuating the strings tuned to a note of the musical scale 0 l u I there 18 provided a percussion mechanism ineluding a hammer 16, each actuated through an operative connection of conventional form by .means of a key such as 17 included in a manual 18 ofthe piano.

The instrument is provided with usual pedals, such as a piannissimo pedal 20, a sostenuto pedal 21 and a fortissimo pedal 22 of conventional construction, but as these form no part of the present invention, it is thought that no further description thereof 70 is required. The instrument may also be provided with controllable closures for the apertures of the upper wall 11 of the casing 10 and for the lower wall 12. These closures may take the form of pivotally mounted modulat- S0 ing reflectors 23 for variably controlling and reflecting the sound waves emitted from the instrument. Each reflector may further be provided with a thin sheet of metal 24: on the inner face thereof, and may also include a layer of substantially sound insulating ma terial 25. The side walls of the casing may also be provided with a layer26 of sound insulating material for limiting the sound. The reflectors 23 of the upper group are provided with integral arms 27 respectively, the outer ends of which are pivotally connected to a rod'28. A link 29 (see Fig. 1) operatively interconnects the rod 28 to a radial arm 30 which is secured to a vertical rotatable shaft 31 as by being pinned thereto. The shaft 31 is journalled' in spaced bearing plates 32, 32, secured to the casing 10. Similarly the reflectors of the lower group are provided with integral arms 33, respectively, the outer ends of which are pivotally connected to a bar 34. A l1nk 35 operatively interconnects the bar 34 tag a second radial arm 36 secured to the shaft For operating the modulating reflectors to 42 is pivoted to a portion of the casing 10 as p at 43, and its other end is engaged by a rod fied, and their I to terminal posts 55 and 56.

- netic material attached to the 44 connected to the rear end of a rocking pedal 45 mounted adjacent the pedals 20, 21, 22. A retractile spring 46 serves to maintain the pedal 45, the reflectors 23, and the associated parts, in the position shown in Figs. 1 and 2, with the reflectors open and the pedal up. f

The portion of the instrument so far described may be operated to produce damped compressional waves. For example, when a key 17 is depressed, the hammer 16 strikes the respective tuned vibratory element. The waves thus set up, set the sounding board 15 into vibration. The sounding board is relatively large, and. in contact with a considerable amount of atmospheric medium, and thus eilectively emits the energy of the waves into the surrounding medium. The waves actually emitted from the interior. of the casing may be limited in amplitude, and effectively controlled to produce desirable effects, by the use ofthe fourth pedal 45 for that purpose.

The damping of the waves may be modiamplitude :considerably increased by important features of the invention which will now be described- This mech anism includes-means for impressing high power energy upon the reverbatory element. The embodiment shown in Fig. 3 comprises a relatively small light sheet 50 of paramagsounding board 15 near the center thereof, and on a face opposite that which is proximate the thus to one terminal of thefilament 82. The

strings, and acted upon by an electromagnet 51, having a coil or winding 52. The arrangement is such that oscillatory energy applied to the magnet winding 52 acts upon the sheet 50 as an armature, and impresses the energy upon the reverbatory element 15. The ends of the winding 52 pf the magnet 51 are connected respectively by conductors 53, 54

For controlling the operation of the high power energy means, thereis provided a metal plate 60 (see Figs. 1 and-3) afiixed to the wall 11 and in spaced relation with the tuned strings 14. The plate 60 is placed close to the strings, thereby even when the strings are actuated with considerable force. mounted-ion insulating blocks'such as 61 (see the amplifier is of the grid resistance 98 and to the stat 102, als but not so close as to be contacted The plate 60 is terminal of which is connected by a conductor F 3) so as to be electrically insulated from other part's'of the instrument. The plate 60 is connected by an'electrical conductor 62 to one pole of a direct current source 63 of electric potential, the other pole of which is connected through a condenser 64 to one end of a Winding of a potentiometer 65, the other end of which is connected by conductor 66 to the string supporting frame 19 of the piano, and by a conductor 67 to a terminal post 68, conductor 69 to ground at 70. The winding of the potentiometer is engaged by a slider 71, which is-mounted on, but insulated from, a collar 7 2. The collar 72 is adjustably fixed upon the shaft 44. The slider is connected by a flexible conductor 73, and conductor 74 to a terminal post 75.

For amplifying the energy produced by striking the strings 14, there is provided an amplifier 80, shown within the dash-dot line 81 of the lower portion of Fig. 3. As shown coupled type. .Each stage includes a three electrode amplifying vacuum tube, preferably of the type having a high mutual conductance, and it is thought that a description of one will sufiice for all. Each tube comprises a heated filament 82 for emitting electrons, a grid 83 for controlling the passage of electrons, and a plate 84 on which the electrons impinge.

A detailed description of the amplifier 80 will now be given. The

terminal post is connected by a conductor 90 to one terminal of a shunting or grid leak resistance 91 and to tube 92 of the first 83 of vacuum stage. The other terminal of the resistance .91 is grounded, The plate 84 of the first stage tube 92 is connected to one terminal of i a plateresistance 93 the other terminal of which is connected by a conductor 94 positive pole of a high voltage source of electromotive force, such as a battery 95 for applying a positiveeleetric potential to the plate 84 with respect to the filament 82. The negative pole of the battery 95 is connected to a common filament return conductor 96 and plate 84 is also connected through a condenser 97 to one terminal of a shunting or grid leak grid of vacuum tube 99 of the second stage. The other terminal of the resistance 98 is connected to-the nega tive pole of a low voltage source 98' of electric potential, the other pole of which is second stage tubes 92, 99 are connected across the four stage, resistance to the afilament heating battery 100, there being rheostat 101 a d for the tube 99 a series rheo djustable, for controlling the filament heating currents. The plate 84 of the second sta e tube is connected to one terminal of a p ate resistance 103, the other provided foil-file tube 92 an adjustable series 104 to the positive pole of the battery 95, whereby a high positive potential is applied to the plate of the tube 99 with respect to its filament. The plate of. the tube 99 is also connected through a condenser 105 to one terminal of a shunting or grid leak resistance 106 and to the grid of vacuum tube 107 of the third stage. The other terminal of the resistance 106 is connected by a conductor 108 to the negative pole of a biasing battery 109, a by pass condenser 110 being provided in shunt with the battery, The positive pole of the battery 109 is connected to one pole of a filament heating battery 111, which is also shunted by a by pass condenser 112. The plate of the tube 107 is connected to one terminal of a plate resistance 113, the other terminal of which is connected by a conductor 114 to the positive pole of a source of direct current such as a battery 115, the other pole of which is connected to a common filament I return conductor 116 and thus to one terminal of the filament of the tube 107. The com ductor 116 is grounded to the ground 70. The battery 115 is shunted by a by pass condenser 117. The plate of the tube 107 is also connected through a condenser 118 to one terminal of a shunting or grid leak resistance 119 and to the grid of vacuum tube 120 of the fourth stage. The other terminal of the resistance 119 is connected to the negative pole of the biasing battery 109. The filaments 82 of the third and fourth stage tubes 107 and 120, are connected across the battery 111, there being provided for the tube 107 an adjustable series rheostat 121, and for the tube 120 a similar rheostat 122 for controlling the respective filament heating currents. A by pass condenser 123 is connected from the tube 120 is connected by a conductor 124 to the terminal post'55, the circuit extending thence, conductor 53, winding 52, conductor 54, terminal post 56, and over a conductor 125 to the positive pole of the battery 115, whereby-a high positive potential is applied to the plate of the tube 107. The plate 60 and the amplifying means 80 thus operatively interconnect the sound source 14 and the emitting sounding board 15.

In the modified embodiment shown in Fig. 4 a separate sounding board 200 is mounted in the casing 10. For applying amplified energy thereto an oscillating device is provided, including a tube 201, preferably of copper, which is attached to the sounding board 200. Around thetube 201 there is mounted an annular magnet 202 formed of soft iron, having a winding 203 recessed therein. A source of direct current 204 is connected across the terminals of the winding 203, for energizing the winding, and thus producing a magnetic field of constant polarity about the cylinder 201. Within the tube 201 there is provided a sec- 0nd annular magnet 205, the terminals of the conductor 108 to ground. The plate of i board, thus improving the effect. The mag net windings 52 are connected in multiple, and to the terminal posts 55, 56, which are connected to the amplifier 80 in the same manner as is shown with respect to the terminal posts 55, 56 of Fig. 3.

The modified form shown in Fig. 6 shows electrostatic means for impressing amplified energy upon the sounding board. In this embodiment a conducting plate 210 is ailixed to a face of the sounding board 15. Adjacent to, and slightly spaced from the plate 210 is a fixed plate 211 mounted upon spaced brackets 212, 212, and adjustable as by thumb nuts 21.3. The fixed plate 211 is connected by a conductor 214 to one terminal of a resistance or impedance 215 and to the terminal post 56. The sounding board plate 210 is connected through a condenser 216 to the other terminal of the resistance 215 and thus to the terminal post 55. The terminal posts 55 and 56 are connected to the amplifier 8 0 in the same manner as is shown with respect to the terminal posts 55, 56 of Fig. 3.

The modified form shown in Fig. 7, may housed instead of the capacitative form of pickup shown in Fig. 3. In this embodiment, there is shown a bracket 220 extending across the interior of the casing 10 instead of, and in the same manner as, the plate 60 of Fig. 3. The bracket 220 is itself, however, inactive, serving only as a support. Mounted thereon is a plurality of angles 221 each supporting a magnetized core 222, having both ends 223 turned into proximity with the tuned string 14. lVound on the core 222 is a coil 224 of insulated wire. It is understood that one such core and coil is provided for each 'note of the musical scale of the instrument, and positioned adjacent the tuned elements corresponding to the notes, respectively. The coils are connected in multiple, and to conductors 225 and 226. The conductor 226 extends to one terminal of the potentiometer winding 65, the other terminal of which is connected to the conductor 225 and also to the terminal post 68. The slider 71 is connected by conductors 73. 74 to the terminal post 75. The terminal posts 68 and 7 5 are connected to the input of the amplifier 80 as in the manner shown in Fig. 3.

In the operation of the instrument with the amplifier 80 in action, when the musician strikes a key 17 to actuate a hammer 16 to and-the vibrating string at a'frequency depending upon thefrequency of vibration of the string. This change incapacity changes the charge on the condenser 64, and thus changes the potential on the grid 83 of the waves, comprising a source ofsound, a revertube 92 with respect to ground. The changes in potential modify the space current'of the tube, and there appear in the plate circuit amplified unidirectional impulses having frequencies determined and controlled by the vibration of the string. These impulses are further amplified bythe second, third, and

- board 15 causing it fourth stages, and thus energy of. greatly increased power, but of like frequency, is producedby the amplifier. This energy is impressed by the magnet 51 upon the sounding to emit compressional waves of great intensity.

It will be noted that some of the energy emitted by the sounding board 15 is fed back to the string, and thus a regenerative effect of great value in controllingthe decrement of the waves is secured. By varying the positionof the slider 71by the foot, the musician can vary'the damping, and the amplitude of the sounds as desired. Furthermore. by varying the position of the modulating reflectors 23 the sound may be variably controlled.

The operation of the modified form of Fig. 4 is similar to that ust described, theenergy of the output of the amplifier 80 being applied to the magnet 205, to set up an alternating field of force. The direct current field set up by the magnet 202 thus causes the tube 201 to vibrate in accordance with the oscilla- 'tions of the current traversing the coil 202, and the vibrations are thus applied to the sounding board 200.

210, 211 are correspondingly varied.

cordingly changes in attractive force betwe en' "Fig. 6, when the The operation of the embodiment of Fig.

5 will, it is thought, be obvious, from the foregoing description, it being understood that, the energy is impressed upon the sounding board at a variety of points therein.

In the operation of the embodiment of potential across the terminal posts 55. 56is varied by the operation of the amplifier 80, the charges on the plaice these plates occur, causing relative movement of the plates. The plate 211 is fixed. and thus the plate 210 is moved, carrying with it the portion of the vibration of the sounding board.

- The operation of the embodiment shown in Figure 7 is similar to that described in connection Iwith Figure 3, except that the change in potential on the grid 83 of the tube 92', is caused by current induced in the pickup coil 224 by variations in its magnetic field of force.

The invention on which this application is 'tatably positioned brating said element, means of relatively low power including tuned vibratory devices arranged adjacent said reverberatory element, a source of high power energy,.controlled by said'vibratory devices for actuating the high power vibratory means, and movable modulating reflectors in a wall of said casing for controlling the emission .of. sound from the instrument.

3. A musical instrument comprising 2. casing, a sounding board within said casing, means of relatively high power for vibrating said board, means of relatively low power including tuned vibratory devices arranged adjacent said sounding board, a source of high power energy controlled by said vibratory devices for actuating the high power vibratory means, modulating reflectors roin a wall of the casing to limit the amplitude of sound emitted therefrom, and means controlled at the will of an operator for actuating said reflectors.

4. A musical instrument comprising a casing having apertures, in the casing, means of relatively'high power for vibrating said-board, means of relatively low power including tuned strings arranged adjacent said sounding board, a source of high power energy controlled by said strings for actuating the high power vibratory means, controllable closures in the apertures of said casing, and a pedal operatively connected to said closures.

5. A device for producing compressional waves, comprising a casing having apertures,

a source of sound within said casing, a reberatory element adjacent said source, a

source of'energy controlled by said source a sounding board withforvibrating said element at the frequency of the sound waves produced by said source, and means for mechanically limiting the sound emitted through the apertures of said casing.

7. A musical instrument comprising a casing'having apertures, a reverberatory element positioned .within the casing, means of high power for impressing energy upon said element, means of low power including tuned vibratory devices arranged adjacent said reverberatory element, a source of energy con trolled by said vibratory devices. for actuating the high power energy impressingmeans, and mechanical means for limiting the volume of sound emitted through said apertures.

8. A musical instrument comprising acasing, a sounding board positioned within said casing, means of high power for impressing energy upon said board, means of low power including tuned vibratory devices arranged adjacent said sounding board, a source of energy controlled by said'vibratory devices for actuating the high power energy impress ing means, and means for variably controlling the volume of sound emitted from'the interior of the casing.

9. A musical instrument comprising a sounding board means of high power for impressing energy upon said'board, means of low power including tuned strings arranged adjacent said sounding board, a source of energy controlled by said strings for actuating the high power energy impressing means,

' and means controlled, at the will of an operator -for variably controlling the energy produced by said source.

10. A device for producing compressional waves, comprising a source of damped compressional waves, ,a reverberatory element adjacent said source for emitting compressional waves, sound amplifying means interposed between said source and said reverberatory element, and electrical means for controlling the effectiveness of said last named means. Y

11.' A device for producing compressional waves, comprising a source of sound, a reverberatory element adjacent said source, a

source of energy controlled by said source for impressing upon said element energy of the frequency of the sound waves produced by said source, and means controlled at the will of an operator for controlling the effectiveness of said energy impressing source.

12. In a piano having a plurality of strings and a sound board, means for picking up vibrations from one of said elements, amplifying said vibrations and applying the amplified vibrations to the other of said elements, whereby the damping of the vibrations of said strings may be decreased at will and mechanical regeneration maybe obtained.

13. In a system of piano amplification, an electro-acoustic closed circuit, said circuit being adapted to derive energy from one vi? bratory part of said piano, amplify said energy and return the amplified energy to another vibratory part of said piano which is acoustically coupled to said first part.

14. A system of'amplifying musical tones in which a loud speaker produces mechanical vibrations in a sound board which in turn modifies electrical currents which are amplified and returned to the loud speaker for actuating the same. I

15. A system of piano amplification in which mechanical vibratory energy is transformed into corresponding electrical vibratory energy, amplified and retransferred to the piano in the form of vibratory mechanical energy.

16. In a piano having strings and a sounding board acoustically coupled, means for increasing the effective coupling comprising electrical means for picking up energy fromv said strings, amplifying said energy and applying the amplified energy to said sounding board.

17. In a piano having strings and a sounding board, a loud speaker unit having a vibratable element, said element being directly secured to said sounding board, means for modifying electrical energy in accordance with the variations of said strings, means for amplifying said energy and means for operating said loud speaker unit in ac cordance with said amplified energy.

18. In a piano having a vibrating system, a pedal for normally controlling the volume of sound emitted therefrom and means for amplifying the energy of said system, said means being controlled by the position of said pedal. p v

19. In combination, a piano having parts adapted to vibrate at dilferent frequencies, a pick-up device for picking upsaid frequencies, a sound propagating element, amplifying means between said pick-up device and sound propagating element, and regenerative means to feedback energy from the output of said amplifying means to its input. a

20. In combination, a piano having parts adapted to vibrate at diiferent frequencies, a pick-up device for picking up said frequencies, a sound propagating element, amplifying means between said pick-up device and sound propagating element, and regenerative means to feed back energy from the output of said amplifying means to its input and means for variably controlling energy between said pick-up device and sound propagating element.

21. In a piano, a plurality of strings tuned to different frequencies, a sound propagating element,- a plurality of electro-mechanical pick-up devices, one for each string, for separately directly picking up the vibrations of the different strings and electrical amplifying devices between said pick-up devices and said sound propagating element.

22. In a piano having strings adapted to vibrate at different frequencies, a plurality of separate pick-up dev ces for said strings to pick up different frequencies directly therefrom, a sound propagating element and amplifying means between said pick-up devices and sound propagating element.

23. In a piano having parts adapted to vibrate at different frequencies, a plurality of separate pick-up devices for said parts to pick up different frequencies, a sound propagating element and amplifying means between V said pick-up devices and sound propagating element.

24. In a piano having parts adapted to vibrate at different frequencies, a sounding board, a pick-up device for picking up said frequencies, a plurality of separate receiving units applyin sound energy 'to said sounding board, ampli ying means between said pick- .up device and separate receiving units, and

regenerative means to feed back energy from the output of said amplifying means to its input. 7

Signed at New York in the county of New York and State of New York this 16th day of July A. D. 1926.

JOHN HAYS HAMMOND, JR.

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