US2593442A - Electric organ - Google Patents

Description

April 22, 1952 w.` HAKKARINEN ELECTRIC ORGAN 5 Sheets-Sheet l Filed pee. 17, 194? |80. Ha ,20a ZIO. 22o.

le n 2o 2| 22 FIG. 1..

lll /l April 22, 1952 W, HAKKARINEN 2,593,442 Y ELECTRIC ORGAN Filed Deo. 17, 1947 3 Sheets-Sheet 2 -TGZ. 15

April 2,2,k 1952 w. HAKKARINEN ELECTRIC ORGAN m s JWE m @0. NN N ON Q o. f s) H hw m. ml, SM @uw L@ Filed Dec. 17, l'?

Patented Apr. 22, 1952 UNITED STATES. PATENT crFlcE 2,593,442 ELECTRIC oRGAN William Hakkarinen, Washington, D. C. applicati@ December 17, 1947', serial No. 792,164

(ci. s4"-1.26

10 Claims. 1

My invention relates particularly to electronic I systems and more particularly to a circuit arrangement for electric organs.

One of the objects of my invention is to provide a circuit arrangement for an electric organ of great simplicity which may be inexpensively manufactured.

- Another object of my invention is to provide an electric circuit arrangement in which the control keyboard may be operated at a safe potential above earth and may be uninsulated and not constitute a hazard to the operator with respect to possible electric shock during operation of the organ.

Another object of my invention is to provide an improved circuit arrangement for generating a wide range of audible frequencies over the musical scale employing a minimum of electric equipment.

A further object of my invention is to provide a circuit arrangement for generating musical notes including an electric circuit in which the dynamic plate-cathode resistance is a function of the cathode-plate current for producing different oscillation frequencies.

A still further object of my invention is to provide an electron tube circuit arrangement for electric organs in which power' losses may be introduced into the pate circuit in proportion to changes in dynamic resistance for developing, across a load impedance in the electron tube circuit, conditions which cause the generation of oscillations at different frequencies.

A. still further object of my invention is to provide an arrangement of keyboard operated electric organ oscillation circuits controllable over a musical frequency range which may be readily associated with the radio and audio frequency portion of a conventional radio broadcast receiver for utilizing the sound reproducing system of a radio receiver as a reproducer of musical notes under control of the electric organ covered by my invention.

A still further object of my invention is to provide an improved construction of keyboard for electric organ circuits comprising a metallic stamping having intricately related fingerccntrolled resiliently displaceable key members.

Other and further objects of my invention reside in the improved circuit arrangement for electric organs and keyboard control therefor as set forth more fully in the specification hereafter following, by reference to the drawings,

in which:

. Figure 1 schematically illustrates the keyboard Vcontrolled oscillator system of my invention for ofconnection thereof to an audio frequency amplifying and sound reproducing system or to a head set for reproduction of the musical notes;

Fig. 3 is a transverse sectional View taken substantially on line 3 3 of Fig. 2 and illustrating on an enlarged scale the construction of the keyboard employed with the organ circuit of my invention; and y Fig. 4 schematically illustrates an adaptation of the electric organ circuit of Fig. l in which the output signal isA impressed between the grid and cathode of an electron tube which is generating radio frequency oscillations. Thus the radio frequency signal is modulated by the signal from the organ and acts as a carrier for the organ signal so that the organ can be played over a nearby radio receiver with no connection between the two required.

My invention is directed to an electric organ circuit which is very simple to manufacture and which may be produced on a mass production scale at low cost.

The circuit arrangement of my invention eliminates the complicated arrangemement of relaxation oscillators and the utilization of various resistor-condenser and inductance-condenser circuit components and the complications of tone frequency generators of the electrostatic and electromagnetic type receiver required in generating tones in electric organs. My invention erated are controlled by operating a transformer vfeed-back vacuum tube oscillator at a very low plate voltage and 'small plate current, under which conditions the frequency at which oscillations can be sustained varies with the amount of plate current flowing through the electron -tube.

With fixed capacitor, inductor and resistor values in the oscillator circuit one need only to change the cathode-plate current to cause a change in frequency. It is only necessary,

then, to aect the electron tube with means `which vary the cathode-plate current, or, what is effectively the "equivalent,- 'the dynamic plate re- 3 sistance of the electron tube to control the generated frequency.

The electric organ of my invention has been developed particularly for use as an attachment to conventional radio broadcast receivers for readily converting the conventional broadcast receiver into an electricorgan.

The output of the electric organ circuit of my invention is applied to the radio frequency input or to the audio frequency amplifier and sound reproducing system of the conventional radio broadcast receiver, for reproducing, through the loud speaker of the radio broadcast receiver, the range of musical notes controlled by the'electric organ keyboard. It is realized that the electric organ of my invention may be produced as a complete instrument, vin itself. embodying an audio frequency amplifier and sound reproducing system. However, from the description hereinafter following it will be understood that the electric organ assembly may be a compact unit readily adaptable as an yauxiliary device to conventional radio broadcast receivers already available in the home forfobtaining much added enjoyment from a conventional radio receiver.

Referring to the drawings in detail, reference character I designates-1a' combined rectifier and oscillator tube which, 'for the purposes of explaining my invention,.may be designated as the 117N'1 type. The tube includes heater 2 cathode 3 for the oscillator, control grid 4 for the oscillator, screen grid 5 and plate 6. The rectier portion of the tube includes the rectier cathode i and the rectifier or diode plate 8. The tube circuit is connected to an alternating current system forming a supply line without the interposition of a power transformer to isolate the power line from the direct current voltages required- The power line. connection for the circuit is reuresentedat. 9 extending through control switch I0 to the heater 2. The direct current voltage required in the tone generating circuits isl secured by rectifying the alternating current from the power supply circuit 9 in the diode portion of the tube I. y power line from thel direct current voltages required is accomplished by the circuit arrangement including resistors II and l2 and I4. connected between the rectifier cathode 1 and one side of the power supply 9 at 9d. Because of the small power and voltage requirements 0f the toneeenerator these resistanees may be sumciently large to limit the alternating current which can ow between the. oscillator ground and either side of the power line 9 to a Value which is non-dangerous to an operator touching the metallic keyboard which is used. in. the system of my invention.l

A non-insulated keyboard is employed with the oscillator system or my invention SQ it makes no difference whether the operator contacts the keyboard,Y er not This results from the circuit arrangement by which the oscillator ground is The isolation of the pleted through the oscillator ground and through resistor I2 to tap 26. rihe inductive winding 23 is magnetically coupled with inductive winding 24 through magnetic core 25. Magnetic winding 24 connects between plate electrode 8 and the tap 26 between resistors II and i2 in the resistive circuit leading to the power supply line 9 in the path included in the rectifier portion of tube I. Thus, a regenerative coupling is provided between the control grid circuit of tube I and the plate circuit of tube I for the generation of oscillations therein. A by-pass condenser 21 connects between the ends of inductive windings 23 .and 24 immediately adjacent the control grid #l c ondensers disposed in a shunt path with the connected to either side of the line supply voltage 9 through resistors Il and I4 respectively. The

frequency generated is varied by limiting the cathode to plate current, that is, the current ow from cathode 3 to plate 5 by the self-biasing action of the amount of resistance from resistor I5 which is included in thev circuit between cathode 3, adjustable resistor I8 including adjustable tap I1, and connections through any one of the keys represented at I8, I9, 20, 2I and 22 connected through adjustable taps 18o, 19u, r 20a, 21a and 22a. on resistor I5, the circuit being comresistors as shown, that is, condenser` 2B is connected in shunt with the series arranged resistors II, I2 and I4 and condenser 29 is connected in shunt with resistor i2. Condenser 28 floats above either side of line potential so that resistors II and Ill can effectively isolate tap 26 or oscillator ground from the line shown at 9. The output of the oscillator system is coupled through condenser 3B with the resistive circuit constituted by resistance 3| across which the output terminals 32 connect through the resistance 3B.

The keyboard construction employed for the control of the electric organ circuit is illustrated in Figs. 2 and 3. The oscillator system is assembled, as represented at 34 in Fig. 2, on a base support 35 which also provides mounting means for the sub-base 36 which carries the resistor, represented at I5, corresponding to the resistor I5 in Fig. 1. The resistor l5 is generally of the wire-wound type extending vertically to enable adjustable tap connections to be made with the resistance winding by the several taps which I have represented at Ia, ida, 2cd, 2m, and 22a extending from terminal points ESD, I9b, 2Gb, 2lb and 22b, etc., leading to the keys designated in Fig. 1 as I8, I9, 20, 2| and 22 respectively. A symmetrically arranged set of taps is provided adjacent the opposite side of base 36 leading to other keys of the keyboard system. rhe key- .board system is representedas comprising a pair of flat resilient metallic plates designated by reference characters 31 and 3.3. The metallic plates 31 and 38 are spacially related to each other by means of the supporting sub-base 39 and the supporting members 48 and 4I carried thereby. Supporting member 48 provides a support for the resilient plate S8. Resilient plate 33 is divided into a multiplicity of transversely extending tongues which form keys and which may be individually depressed to establish electrical connection with contact members supported beneath the ends of the keys, as represented, for example, in Fig. 3. Similarly, resilient plate 31 is supported on supporting member lli and the individual keys thereof may be depressed to establsh connection with the contacts positioned beneath the plate as represented at 43. The contacts 43 are arranged at spaced intervals along the strip of insulation material 6,5 mounted on supporting member 66 as shown. Each of the plates 31 and 38 are slotted, as represented at 31a and 38a to provide, in effect, a combined structure in which the laterally extending flexible resilient strips constitute keys of the organ and may be depressed to establishconnection with the contacts located below the ends of the strips. Re.- siliency or flexibility is imparted to the several keys by reason ofthe punched out or slotted construction represented at 37a and 38a which may be further augmented by the recessed construction represented for example at 31o and 31e. In order to simulate a piano or organ keyboard I may omit certain of the keys in the positions 31d, 31e, etc. Also, I further simulate a conventional keyboard by painting the keys 31 black and keys 33 white. Thus, different values of resistance on the tap resistors I5 may be introduced into the cathode plate circuit. The output of the oscillator system at 32 may be connected through lead 45, represented in Fig. 2, to a plug connector 44, which may be inserted into the audio frequency input of the conventional radio brcadcast receiver so that the amplifier and sound reproducing system of the conventional radio broadcast receiver operates to reproduce the musical notes secured by changes in the cathode resistor l5. In the arrangement shown I have successfully covered the range of musical notes Ge through Fe but I desire that it be understood that various ranges may be readily covered. Where it is desired to reproduce merely the musical notes developed by the oscillator system, without amplication through the broadcast receiver, the output circuit 32 is connected to the head telephone receivers 45, as represented in Fig. 2. The power line cord is di' and the male connector 46.

The cathode plate current ow is interrupted by the keyboard action to prevent any time delay from the closing of a keyboard switch and the generation of a frequency such as would occur if the keyboard switch only acted in the grid to cathode circuit.

The ampliner circuit is made to feed back to its own input circuit a voltage of the proper phase and amplitude for generating oscillations. The necessary conditions are that the voltage fed back from the output circuit is about 180 degrees out of phase with voltage developed across the load impedance in the plate circuit and that the feed-back voltages have sufficient magnitude to develop the output power necessary to-produce the input voltage. In this circuit the phase difference required is mostly developed by the feed-back transformer when properly connected. The frequency at which the oscillations occur in this low power oscillator circuit, in which resonant circuits are not used, is the frequency at which the feed-back voltage is of exactly the proper phase and amplitude to permit the electron tube to supply the requisite input voltage. Therefore, when the plate current is limited to certain various values, the power' output developed across the load impedance is varied and as the frequency at which oscillations can occur is a function of the power developed across the load impedance which, in turn, is governed by the cathode to plate current within the tube, the frequency is controlled by the amount of plate current flowing.

Viewed from another angle, the dynamic platecathode resistance is in function of the cathode- Thus, the power lossesplate current flowing. introduced into the plate circuit vary with the changes in the dynamic resistance, and, as a result of these losses, the power developed across the load impedance varies, which is a condition to permit the oscillator to supply different frequencies. The adjustable multi-tapped resistor I5 is used either as a voltage divider or the equivalent of a bank of variable resistors. With this arrangement the organ can be tuned to exactly the desired frequencies even though the elec- 'iv trical characteristics of the vacuum tube l and the transformer 23-25-24 may vary widely.

Referring to Fig. 4 in detail, reference number 49 designates a combined rectifier and amplifier tube similar to electron discharge tube I in Fig. l, except for the heater 5i] which is supplied with a different voltage. Another` electron discharge tube 5i with heater 52 in series connection with heater 5G, has a cathode 53, control grid 5d, screen grid :'55, and plate 55, and is used to generate a radio frequency signal in conjunction with inductor winding 51 which is regeneratively coupled to inductor 58. Condenser !59 resonates inductor 53 and the tuned circuit is coupled to the control grid 54 by condenser G. The audio frequency signal is coupled through condenser to resistor S2 which connects to cathode 53 and to resistor 6| joined to the grid 58. Resistor 63 connects tap 26 to inductor 5'! and plate oy-pass condenser 611 which joins to cathode The oscillator system connected with tube 5i is designed to produce radiation over a suilicient distance to couple with the circuits of the standard broadcast receiver arranged in the neld of the oscillator so that no physical connection between the organ unit and the broadcast receiver is required. Moreover, the constants of the circuit of the oscillator of tube 5I are designed so that modulation may be produced over the Ientire frequency spectrum determined by the Acuit connected with oscillator tube El.

rPhe system of my invention has been found to be very practical in operation and considerably adds to the enjoyment of the use of the conventional radio broadcast receiver when operated from time to time a-s an electric organ.

I realize that modications may be made in the circuit arrangement and the manner of applying the generated frequencies to the sound reproducing system, and I desire it to be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

l. A system for producing electrical oscillations comprising an electron tube including at least a cathode, a control grid, and an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production of oscillations, a resistance connected in common to said input and' output circuits, a multiplicity of progressively arranged taps on said resistance terminating in contacts, keys depressible to contacting relation with said contacts and connected in a path common to said input and output circuits for effecting step by step loading of both said input and output circuits and an additional resistance connected in said input circuit and selectively adjustable for variably loading said input circuit.

2. A system for producing electrical oscillations comprising an electron tube including a cath- 6de, a control grid, and an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production of oscillations, a resistance device, a plurality of progressively arranged taps on said resistance device, a multiplicity or" depressible keys having coacting contacts aligned therewith, a connection extending from said cathode to said keys, connections extending from said coacting contacts to said taps, and an additional resistance device connected in circuit with said input circuit and selectively adjustable for variably loading said input circuit.

3. A system for producing electrical oscillations comprising an electron tube including a cathode, a control grid, and an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production or" oscillations, a resistance device connected in a path common to said input and output circuits, a multiplicity of progressively arranged taps on said resistance device, contacts connected to each of said taps, selectively depressible keys coacting with each of said contacts for introducing into said circuits predetermined increments of power losses for correspondingly changing the frequency of oscillation of said circuits, and an additional resistance device connected in circuit with said input circuit and selectively adjustable for variably loading said input circuit.

4. A system for producing electrical oscillations comprising an electron tube including a cathode, a control grid, and an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production of oscillations, means for selectively producing increment by increment changes in the dynamic plate-cathode resistance of said circuits for producing corresponding changes inthe cathode-anode current now in said circuits, and separate means connected in circuit with said input circuit and selectively adjustable for variably loading said input circuit.

5. A system for producing electrical oscillations comprising an electron tube including a cathode, a control grid, and an anode, a separate cathode and anode, an input circuit interconnecting said rst mentioned cathode and said control grid, an output circuit interconnecting said rst mentioned cathode and anode, means regeneratively coupling said circuits for the production of oscillations, a source of alternating current, a heater for each of said cathodes energized from said source of alternating current, circuit connections for said second mentioned separate cathode and anode for rectifying said alternating current and applying the rectified current to said circuits, a resistive load having, a series oi progressively arranged taps thereon, contacts connected with said taps, keys selectively depressible into contacting relation with said contacts, a circuit eX- tending through said resistive lead and through said keys in a path common to said input and output circuits, and a separate resistive load connected in circuit with said input circuit and selectively adjustable for variably lcadingsaid input circuit.

6, A system for producing electrical oscillations comprising an electron tube including a cathode, a control grid, and an anode, a separate `cathode and anode, an inputV circuit interconnecting said first mentioned cathode and said control grid, an output circuit interconnecting said rst mentioned cathode and anode, means regeneratively coupling said circuits for the production of oscillations, a source of alternating current, a heater for each of said cathodes energized from said source of alternating current and applying the rectified current to said circuits, an impedance load having a series of progressively arranged taps thereon, contacts connected with said taps, keys selectively depressible into contacting relation with said contacts, a circuit eX- tending through said impedance load and through said keys in a path common to said input and output circuits, and a separate impedance load connected in circuit with said input circuit and selectively adjustable for variably loading said input circuit.

7 A system for producing electrical oscillations comprising an electron tube including a cathode, a control grid, and an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production of oscillations, means for producing step by step changes in the dynamic anode-cathode eiective resistance for producing corresponding changes in cathode-anode current flow, a coacting electron tube circuit comprising anoscillator, a resistor element having a multiplicity of spaced progressively arranged taps thereon, a multiplicity of selectively controllable playing keys individual to said taps, said resistor element and said keys being connected in circuit between the control grid and cathode of said rst mentioned tube, and means controlled by changes in current flow in said first mentioned circuits for determining the frequency of operation of said oscillator over the range of frequencies resulting from changes in the dynamic anode-cathode resistance of said first mentioned circuits.

8. A system for producing musical tones, an electron tube including a cathode, a control grid, an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, means regeneratively coupling said circuits for the production of oscillations, a resistive device connected in common with both said input and output circuits, a multiplicity of progressively arranged to each of said taps, separate resistive means for Vvariably loading said input circuit, and selectively depressible keys coacting with each of said contacts for supplying said input and output circuits with predetermined increments or" direct current power, said increments of direct current power producing corresponding increments of alternating current power in the output circuit, and said increments of alternating current power in said output circuit controlling thefrequency of oscillation of said circuits.

9. A system for producing musical tones, an electron tube including a cathode, a control grid, an anode, an input circuit interconnecting said cathode and control grid, an output circuit interconnecting said anode and cathode, an audio frequency transformer system including a pair of electromagnetically coupled windings with one of said windings in said input circuit and the other of said windings in said output circuit for regeneratively coupling said circuits for the production of audio frequency oscillations, a resistance device common to said input and output circuits, a multiplicity of progressively arranged taps on said resistive device, contacts connected to each of` said taps, a separate adjustable resistance device individual to said input circuit, selectively depressible keys coacting with each of said contacts for supplying said input and output circuits with predetermined increments of direct current power, said increments of direct current power producing corresponding increments of alternating current power in the output circuit, said increments of alternating current power in said output circuit controlling the frequency of oscillation generated by said circuits.

10. An oscillator for developing non-linear voltage waves of complex form comprising a thermionic tube including at least a cathode, a control electrode and an anode, a circcuit path connected between said control electrode and said cathode, said path including an adjustable resistor, a multiplicity of keys, a multiplicity of contacts coacting with said keys, a resistor element in said circuit path having progressively arranged spaced taps thereon, connections between said taps and said contacts, the end of said resistor element which connects with said circuit path being connected to a point of predetermined potential, a transformer winding included in said circuit path and connected to said point of predetermined potential and to said control electrode of said thermionic tube, a capacitor directly connected between said control electrode 3u and said anode of said thermionic tube, a trans- 10 former winding coupled in feedback relation to said rst mentioned transformer winding and connected intermediate the said anode and a point of positive potential, output terminal means, a circuit including a pair of resistors, a condenser connected to said anode and to a common connection to said pair of resistors, the rst of said resistors being connected` between said last named condenser and said point of predetermined potential, and the second of said pair of resistors being connected in series with said output terminal means and said point of predetermined potential.

WILLIAM H AKKARINEN.

REFERENCES CTED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 497,144 Teal May 9, 1893 1,033,786 Cox July 30, 1912 1,180,720 Howe Apr. 25, 1916 1,539,402 Nichols May 25, 1925 1,771,905 Uher, Jr July 29, 1930 1,823,724 Carlson Sept. l5, 1931 2,211,540 George Aug. 13, 1940 2,301,871 Hanert Nov. l0, 1942 2,328,282 Kock Aug. 3l, 1943 2,396,439 Schlesinger Mar. 12, 1946

Images