US3808346A

US3808346A - Movable contact strip adapted for touch responsive tone control electronic musical instrument

Info

Publication number: US3808346A
Application number: US00269229A
Authority: US
Inventors: T Nagano
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1971-09-14
Filing date: 1972-07-05
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30
Also published as: JPS5543439Y2; JPS4839924U

Abstract

A movable contact strip especially adapted for a touch responsive tone control key switch mechanism wherein the tone control depends upon the duration of time during which the movable contact strip is shifted from one stationary contact or break contact to the other stationary contact or make contact. The strip has a portion made more rigid than the remaining portion thereof at least between the point where the strip is actuated by the actuator and the point where the strip makes a contact with the stationary contacts. The existence of said more rigid portion enables the strip to travel well in proportion to the movement of the key, particularly at high velocity, attaining an accurate tone control as desired.

Description

United States Patent 1191 Nagano Apr. 30, 1974 [54] MOVABLE CONTACT STRIP ADAPIED 3,705,254 12/1972 Amano 84/I.1 FOR TOUCH RESPONSIVE TONE 3,708,605 l/l973 Ohno 84/1,] 3,673,303 6/1972 Amano 84/l.0l q fig g f MUSICAL 2,959,693 11/1960 Meyer 84/1.01 x INS R 3,041,568 6/1962 BlSSOnelte (it a] ..84/Dig. 7 [75] Inventor: Takehiko Nagano, Hamamatsu, 2,497,661 2/1950 Dome 84/l.01 Japan 501,543 7/1893 Singer ..84/l.l l I 2,555,040 5/1951 Jordan ..s4/1.01 x 1 3] gne ppon Gakkl Sella Kabushikl 3,328,507 6/1967 Peterson ..s4/1.1 x

Kalsha, Hamamatsu-shi, shlzuoka'ken Japan Primary Examiner-Stephen J. Tomsky [22] Filed: July 5, 1972 Assistant Examiner-Stanley J. Witkowski pp No: 269,229 Attorney, Agent, or Fzrm--Flynn & Frishauf ABSTRACT [30] Forelgn Apphcatmn Pnomy Data A movable contact strip especially adapted for a touch Sept. 14, l97l Japan 46-84032 res o sive tone control key switch mechanism wherein the tone control depends upon the duration [52] US. Cl 84/L1, 84/ 1.27, 84/DIG. 7 of time during which the movable Contact strip is [51 Int. Cl. t. Gloh l/00 hift d from one stationary ontact or break contact [58] Fleld of Searc to the other stationary contact or make contact. The strip has a portion made more rigid than the remaining 200/170 R, 1 0 D G- 338/69 portion thereof at least between the point where the strip is actuated by the actuator and the point where Refel'flwes Cited the strip makes a contact with the stationary contacts. UNITED STATES PATENTS The existence of said more rigid portion enables the 1,051,675 1/1913 Breed s4/1.1 Strip "ave! in the movement 1,318,977 10/1919 Dal-Icy n 84] the key, particularly at high velocity, attaining an ac- 3,634,593 1/1972 Nagano 84/].01 at ton ntr l as desired. 3,651,730 3/l972 Adachl 84/].27 X 7 Claims 8 Drawing Figures MOVABLE CONTACT STRIP ADAPTED FOR TOUCH RESPONSIVE TONE CONTROL ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention relates to a key switch mechanism for deriving a tone signal from a tone generator of a keyboard type electronic musical instrument and more particularly to a movable contact strip for use in a key switch mechanism of an electronic musical instrument adapted for a touch responsive tone control.

A keyboard type electronic musical instrument generally includes key switches for deriving tone signals from tone generators upon key depression. However, these key switches are only used for the delivery of tone signals from the tone generators, and are not adapted to effect a touch responsive tone control of the level of tone signals produced by the tone generators exactly in accord with the velocity with which the keys are depressed.

With the ordinary electronic musical instrument, the

touch responsive tone control is simulated by expression control by means of an expression pedal which adjusts the volume of sounds produced by tone signals.

In recent years, there have appeared on the market some types of electronic musical instrument capable of touch responsive tone control. One of the touch responsive tone control systems used in these recent types of electronic musical instrument is provided with a key switch mechanism consisting of a pair of station ary contacts, that is, a break and a make contact, and a movable contact strip therebetween which, when actuated by the key, has its engagement changed from the break contact to the make contact, thereby carrying out the touch responsive tone control, utilizing the fact that the time required for the movable contact strip to have its engagement changed from the break contact to the make contact varies with the velocity with which the key is operated. However, the movable contact strip of the'key switch mechanism of electronic musical instruments just mentioned consists of a relatively soft thin leaf-like member. Such leaf-like member can make its operating velocity agree with that of a key while it moves slowly, but fails to have the velocity match the rapid movement of the key. Therefore, any of these recent electronic musical instruments fails to effect full touch responsive tone control exactly in conformity to the key operating velocity.

It is accordingly the object of this invention to provide a key switch mechanism capable of obtaining full touch responsive tone control exactly in accord with the key operating velocity.

SUMMARY OF THE INVENTION A key switch mechanism for touch responsive tone control to which this invention is adapted comprises a pair of stationary contacts, namely, a break and a make contact, and a movable contact strip fixed at one end and provided at the other end with contact sections for abutting against the break and make contacts responsively and, when actuated by the key, so designed as to have its engagement changed from the break contact to the make contact.

The time required for the movable contact strip to have its engagement changed from the break contact to the make contact varies exactly in conformity to the velocity with which the key is depressed.

In order to provide the corresponding relationship of the time above-mentioned with the key velocity (the time varies inversely with the key velocity), according to the present invention the actuating portion of the movable contact strip is intermediate the ends of the strip, and, that portion of the movable contact strip which is defined between the actuating point at which the .movable contact strip is actuated by the key and the aforementioned contact sections is provided with means for rendering the portion more rigid than the remaining portion thereof.

According to an embodiment of this invention, the aforesaid specified portion of the movable contact strip has a rib formed along the lengthwise central line thereof.

According to another embodiment of the invention, the specified portion of the movable contact strip has elongate protrusions disposed along both lengthwise edges thereof.

According to still another embodiment, the specified portion of the movable contact strip is made thicker than the remaining portion thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a touch responsive tone control system for which the present invention is adapted;

FIG. 2 represents a relationship of the operating velocity of a key and that of a movable contact strip;

FIG. 3 is a schematic side view, partly in section, showing the relative positions of a key and a key switch for touch responsive tone control;

FIG. 4A is a top view of a movable contact strip according to an embodiment of the present invention;

FIG. 4B is a sectional view on line 4B-4B of FIG. 4A;

FIG. 5A is a top view of a movable contact strip according to another embodiment of the present invention;

FIG. 5B is a sectional view on line 58-58 of FIG. 5A; and

FIG. 6 is a longitudinal sectional view of a movable contact strip according to still another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 the reference numeral 1 represents a key actuated switch consisting of a movable contact strip 2, a stationary (break) contact 3 and another stationary (make) contact 4. The movable contact strip 2 normally abuts against the break contact 3 to constitute a path for charging a capacitor 5 from a DC source or battery 6. A resistor 7 is connected parallel with the capacitor 5 to constitute a discharge path thereof. The make contact 4 is connected to a diode 8 disposed in the forward direction with respect to the polarity of the battery 6 and to a capacitor 9 which stores the voltage of the capacitor 5 when the movable contact strip 2 is switched or shifted from the break contact 3 to the make contact 4. The voltage stored in the capacitor 9 is supplied to a keyer 10 which is already impressed with a tone signal from a tone generator 11. The keyer 10 may consist of, for example, a variable resistor comprising a field effect transistor.

The tone signal from the tone generator 1 1 is drawn off through the conduction path defined between the source and drain of the transistor and conducted to a utilization circuit including tone coloring filters and amplifiers. The voltage stored in the capacitor 9 is supplied to the gate of the aforesaid transistor to control conductivity across the source and drain thereof.

There will now be described by reference to FIG. 1 the operation of a touch responsive tone control system for which the present invention is adapted. The time required for the movable contact strip 2 to have its engagement changed from the break contact 3 to make contact 4 is expected to vary in accordance with the velocity with which the key is operated. Accordingly, the amount of voltage discharged from the capacitor 5 through the resistor 7 also varies in accordance with the key operating velocity. It will be apparent, therefore, that the level of the voltage stored in the capacitor 9 when the movable contact strip 2 abuts on the make contact 4 also varies in accordance with the key operating velocity. Since conductivity across the conduction path of the transistor is controlled by the voltage of the capacitor 9 accurately matching the key operating velocity, there can be drawn a tone signal from the keyer 10 at a level varying in accordance with the key operating velocity.

FIG. 2 shows the relationship of the key operating velocity and the velocity with which the movable contact strip changes its position. With the prior art movable contact strip, the operating velocity of the movable contact strip indicates, as illustrated in a solid line, some delay from the key operating velocity when it considerably increases, though the velocity of the movable contact strip presents a linear agreement with the key operating velocity while it falls within a certain range, thus failing to provide good touch responsive tone control as intended. The broken line of FIG. 2 shows the ideal operating velocity of a movable contact strip substantially matching or in proportion to the movement of a key, for which this invention is primarily intended.

FIG. 3 is a schematic sectional view showing the relative positions of the key and key switches. Below a keyboard frame 20 supporting a large number of keys 21 (only one indicated) are disposed key switches l associated with the respective keys 21. The movable contact strip 2 of the key switch 1 is fixed at one end to an insulation member 22 and normally abuts at the other end against the break contact 3. The make contact 4 is disposed below the break contact 3. To the underside of the substantially central part of the key 21 is attached an actuator 23, which extends through the frame 20 down to the movable contact strip 2. When the key 21 is depressed, the actuator 23 causes the movable contact strip 2 to have its engagement changed, as indicated in a broken line, from the break contact 3 to the make contact 4.

In this case, the operating velocity of the prior art movable leaf-like contact strip fails, as previously described, exactly to follow the movement of the key for the reason given below. The outermost or free end of part by the key, it presents flexure or sagging between the point at which it is depressed by the actuator and the free end. Since, however, the free end alone tends to be brought back to its original position due to its inertia, the movement of the free end fails exactly to accord with that of the key, especially at higher speed. This invention eliminates the above-mentioned drawback by imparting greater rigidity to that portion of a movable contact strip which is defined between its free end and the point at which it is depressed by the key actuator than the other portion of the contact strip.

FIGS. 4A and 4B jointly illustrate a movable contact strip according to an embodiment of this invention. This movable contact strip has a rib 27 formed along a lengthwise central line between its free end 26 and the point 25 at which it is depressed by the actuator 23 upon key depression so as to render the ribbed portion more rigid than the other portion of the contact strip. The reason why there is not formed any rib in that portion of the contact strip which is defined between the aforesaid point 25 and fixed end 28 is that the latter portion should be fully flexible. Both sides of the free end 26 are provided with contact pieces 29 which are made to abut against the break and make

contacts

3 and 4 respectively.

The movable contact strip may be prepared from nickel silver. When the movable contact strip was made of a sheet of nickel silver, the dimension of the strip was selected such that: the distance between the actuated point 25 and the center of the contact piece 29 was 15 mm; the distance between the actuated point 25 and the end of the strip 2 fixed to the insulation member 22 was 25 mm; the thickness and width of the strip were respectively 0.14 mm and 4.0 mm; and the rib 27 extended from the actuated point 25 toward the free end 26 was 1 mm wide, 0.5 mm high, and 10.5 mm long, whereby there were obtained good results.

According to this invention, the contact piece 29 at the free end 26 is prepared by depositing a layer gold, silver or alloys thereof to provide good electrical contact between the contact piece 29 and the break and make

contacts

3 and 4.

FIGS. 5A and 5B collectively show a movable contact strip according to another embodiment of this invention. This contact strip has elongate protrusions 30 extending perpendicularly to the plain of the strip, instead of a rib 27 of FIGS. 4A and 43, formed along both lengthwise edges of a corresponding portion to the ribbed portion of FIGS. 4A and 4B which similarly extend from the actuated point 25 toward the free end 26, thereby rendering the portion more rigid than the remaining portion of the contact strip.

FIG. 6 indicates a movable contact strip according to still another embodiment of this invention. Most of the portion of the contact strip which is defined between the actuated point 25 and the free end 26 is formed into a thicker section 31 than the remaining portion of the movable contact strip so as to be rendered more rigid. The thicker section 31 may be formed fully transversely across the movable contact strip in substantially the same length as the rib 27 of FIGS. 4A and 48.

What is claimed is:

1. An electronic musical instrument for deriving a tone signal from a tone generator upon key depression with the tone signal level being varied in accordance with the velocity of operation of a key by the operator, comprising:

a tone generator;

means for controlling the-tone signal level of the tone signal generated by the tone generator;

contact to said make contact when actuated by v the key at said actuating portion; and

stiffening means on said'movable contact strip between said actuating portion and said contact section for rendering a portion of said movable contact strip which is located at least between said contact sections and said actuating portion more rigid than the remaining portion thereof and for causing the velocity of movement of said contact sections to be a function of the velocity of movement of said actuating portion.

2. Apparatus according to claim 1 wherein said stiffening means comprises at least one rib formed on the surface of the movable contact strip along its lengthwise direction.

3. Apparatus according to claim 1 wherein said stiffening means comprises protrusions formed along both lengthwise edges of said movable contact strip.

4. Apparatus according to claim 1 wherein said stiffening means comprises a portion of said movable contact strip made thicker than the remaining portion thereof.

5. Apparatus according to claim 4 wherein said thicker portion extends substantially transversely across said movable contact strip.

' 6. Apparatus according to claim 1 wherein said controlling means is responsive to the time for said movable contact strip to be switched from said break contact to said make contact.

7. Apparatus according to claim 6 wherein the tone signal level is controlled to be a function of said time.

Claims

1. An electronic musical instrument for deriving a tone signal from a tone generator upon key depression with the tone signal level being varied in accordance with the velocity of operation of a key by the operator, comprising: a tone generator; means for controlling the tone signal level of the tone signal generated by the tone generator; a key switch mechanism coupled to said controlling means for causing the tone signal level to be a function of the velocity of operation of the key, the key switch mechanism including: a key; a pair of break and make contacts; a movable contact strip fixed at one end and provided at the other end with contact sections for abutting against said break and make contacts, said movable contact strip having an actuating portion intermediate the ends thereof coupled to the key and being switched from said break contact to said make contact when actuated by the key at said actuating portion; and stiffening means on said movable contact strip between said actuating portion and said contact section for rendering a portion of said movable contact strip which is located at least between said contact sections and said actuating portion more rigid than the remaining portion thereof and for causing the velocity of movement of said contact sections to be a function of the velocity of movement of said actuating portion.

6. Apparatus according to claim 1 wherein said controlling means is responsive to the time for said movable contact strip to be switched from said break contact to said make contact.