US3507973A

US3507973A - Touch sensitive capacitor timing percussion keying circuit

Info

Publication number: US3507973A
Application number: US725614A
Authority: US
Inventors: Lee De Pree
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-05-01
Filing date: 1968-05-01
Publication date: 1970-04-21
Anticipated expiration: 1987-04-21

Description

Apr-i121, 1970 L.DE PREE 3,507,973 TOUCH SENSITIVE CAPACITOR TIMING PERCUSSION'KEYING CIRCUIT Filed May 1, 1968 F/ G1 KEY SWITCHES X F/GZA' o PERCUSS/VE CIRCUIT 3,507,973 TOUCH SENSITIVE CAPACITOR TIMING PERCUSSION KEYING CIRCUIT Lee De Pree, 17 E. 8th St, Holland, Mich. 49423 Filed May 1, 1968, Ser. No. 725,614 Int. Cl. Gh 1/00, 1/02 US. Cl. 84-1.24 2 Claims ABSTRACT OF THE DISCLOSURE In an electronic pianoforte or similar percussive musical instrument, a key operated switch in conjunction with a capacitor, for supplying a controlled amplitude voltage pulse; the amplitude of the pulse dependent on the extent the capacitor is discharged by the timed operation of the switch, prior to the delivery of the pulse.

This invention relates to a key or button operated electrical switch for an electronic musical instrument wherein percussive tones are desired, and wherein the amplitude of the tone must be controlled by the speed with which the key'is depressed, as in a pianoforte.

One method of producing a percussive tone electronically is to pass electric oscillations of constant frequency and amplitude in the audio frequency range, to an electronic percussive keying circuit; said circut, when activated from a source of diminishing DC. voltage, transmitting the oscillations in gradually decreasing intensity until transmission stops; the strength of the transmitted signal being proportional to the DC voltage applied to the circuit.

A touch sensitive, capacitor timing, key operated switch for an electronic pianoforte, when used in conjunction with a percussive circuit as above, must perform the following functions:

(1) Charge a capacitor from a suitable D.C. supply.

(2) Partially discharge capacitor by timed switching;

controlled by key velocity.

(3) Transmit remainder of charge to percussive circuitry.

(4) Terminate D.C. current flow when key is released.

Heretofore, to perform the above functions, a switch needed either a plurality of moveable elements, or resorted to the use of sliding contacts. My invention embodies a simpler switch with one moveable element which will perform the above functions. The advantage of the invention will become more apparent upon reference to the following specification, in connection with the accompanying drawings in which:

FIGURE 1 is a block diagram showing the relationship of the switch to other elements in a typical electronic percussive circuit.

FIGURE 2A is a diagram of the key operated switch and actuator.

FIGURE 2B illustrates the operation of the switch by the moving and flexing of the moveable element.

In FIGURE 1, I show the flow of tones from source to audio output through the percussive circuits when said circuits are activated by operation of the key switches. FIGURE 2A is a diagram of a key switch and associated capacitor and resistor and a representation of a key 1 and the attached actuator 2. The drawing shows the switch position with the key at rest.

The key switch comprises a straight, moveable, elastic conductive element 3 and fixed

conductive elements

4, 5, and 6. Element 3 may be .02 inch diameter Phosphor United States Patent 0 "Ice bronze spring wire. The free end of element 3 is in contact with fixed element 4, which is connected to a suitable D.C. source, in this instance about plus 35 volts. Element 4 may be a Phosphor bronze wire buss supplying all the switches. The fixed end of 3, which is connected to ground through resistor 7 and capacitor 8, is so located that the free end of 3 contacts elements 6 before it contacts element 5 when the switch is operated.

When the piano key is depressed, contact between 3 and 4 is broken, and element 3 makes contact with element 6, a voltage decay buss, which may be a Phosphor bronze wire, through which a portion of the charge in capacitor 8 is dissipated. Said buss, however, is connected to a low voltage D.C. supply, the voltage being barely suflicient to fire the keying circuit; said voltage assures that although the piano key may be depressed very slowly, sufficient voltage remains in capacitor 8 to fire the keying circuit and produce an audible tone.

FIG. 2B shows the effect of flexing element 3 by further movement of actuator 2. As element 3 bears against 6, it flexes until contact is made with element 5, which is connected to the keying circuitry of the individual note being produced. Further flexing breaks contact at 6.

The duration of dwell of element 3 on 6 is determined by the speed with which the piano key is depressed. This in turn determines the amount of charge and resulting voltage remaining in capacitor 8, which in turn determines the initial amplitude of the tone or signal passed through the keying circuit when it is fired through element 5.

The gradual discharge of capacitor 8, through element 5 and the percussive circuit, results in a gradually diminishing audio tone. The tone is terminated when the capacitor has discharged or when the key is released.

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

1. An electrical switch, comprising a movable, elastic conductive element, one end of said element being fiexd, the moveable end contacting in sequence a plurality of fixed conductive elements, the fixed elements being so arranged that the duration of dwell of the movable element on some of the fixed elements is controlled by the rate of flexing of the moveable element when bearing against other of the fixed elements.

2. The combination as defined in claim 1 wherein one of the fixed elements supplies DC. voltage to electrically charge a capacitor through the moveable element, and wherein another fixed element, carrying a lower DC. voltage, serves to discharge the capacitor, the extent of discharge being dependent on the duration of dwell of the moveable element on the latter fixed element, and the extent of discharge limited by the electrical potential on the latter fixed element.

References Cited UNITED STATES PATENTS 2,482,548 9/1949 Kerkhof 84-126 3,018,353 1/1962 Mitchell ZOO-166.1 3,259,728 7/ 1966 De Rougemont et a1.

3,306,969 2/1967 Barber 84-124 3,333,043 7/1967 Slaats et al 841.26 3,197,709 7/1965 Antonio et al. 307208 X HERMAN KARL SAALBACH, Primary Examiner M. NUSSBAUM, Assistant Examiner US. Cl. X.R. 84-1.27

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3507973 Dated April 21 970 Lee De Pree Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

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