US 3902398 A
A sound volume control device suitable for the expression control of an electronic musical instrument in which digital information is formed by slitted and unslitted portions on a swinging plate adapted to be swung by a pedal. plural-bit electrical signals are derived according to the swinging angle of the swinging plate by photoelectrically detecting digital position information. In response to the predetermined voltage level of respective electrical bit signals, signal attenuation devices or voltage dividers are selectively coupled to a signal transmission path, thereby obtaining a signal attenuation amount according to the swinging angle of the swinging plate.
Description (OCR text may contain errors)
United States Patent [1 1 Nakada et al.
[4 1 Sept. 2, 1975 SOUND VOLUME CONTROL DEVICE  Inventors: Akira Nakada; Masanobu Chibana;
Tsuyoshi Futamase, all of l-lamamatsu, Japan  Assignee: Nippon Gakki Seizo Kabushiki Kaisha, Japan  Filed: Dec. 13, 1973  Appl. No.: 424,460
 Foreign Application Priority Data Dec. 15, 1972 Japan 47-125965 Dec. 15, 1972 Japan 47-125966  US. Cl. 84/127; 84/].09; 84/D1G. l9; 179/1 VL; 323/74; 323/80; 323/94 R; 333/81  Int. Cl. GlOH 1/02  Field of Search 84/].18, 1.24, 1.27, 1.09, 84/].1, DIG. l9; 179/1 VL; 323/63, 66, 74,
2,999,202 9/1961 Ule 323/74 3,045,522 7/1962 Markowitz..... 84/].27 3,078,753 2/1963 Gibbs et a1 84/l.27 3,086,122 4/1963 Jones 84/1316. 19 3,165,638 1/1965 Henn et al. 84/DlG. 19
3,325,581 6/1967 Young 84/114 3,333,183 7/1967 Larn'son... 323/80 X 3,405,223 10/1968 Pavia 84/l.18 3,513,247 5/1970 Anderson et a1. 84/].18 3,558,793 l/l97l Nakada et al 84/1.l8 3,796,945 3/1974 Feldman et al. 323/74 Primary Examiner-Joseph W. Hartary Assistant ExaminerStanley J. Witkowski Attorney, Agent, or FirmDavid A. Blumenthal [5 7 ABSTRACT A sound volume control device suitable for the expression control of an electronic musical instrument in which digital information is formed by slitted and unslitted portions on a swinging plate adapted to be swung by a pedal. plural-bit electrical signals are derived according to the swinging angle of the swinging plate by photoelectrically detecting digital position information In response to the predetermined voltage level of respective electrical bit signals, signal attenuation devices or voltage dividers are selectively coupled to a signal transmission path, thereby obtaining a signal attenuation amount according to the swinging angle of the swinging plate.
8 Claims, 6 Drawing Figures SHEET 1 0 3 FIG.
PATENTEB 2 L975 SHEET 3 FIG. 5
SOUND VOLUME CONTROL DEVICE BACKGROUND OF THE INVENTION This invention relates to a sound volume control apparatus for use, for example, in the expression control of electronic musical instruments.
As sound volume control methods for the expression control of conventional electronic musical instruments, the following methods are examples of common practice: one method involves driving, through an expression pedal, a variable resistor inserted in a musical tone signal transmission path; second a method involves driving a shutter plate through an expression pedal to change the amount of light incident onto a photoelectric element or photoresistor such as Cds etc. inserted in a musical tone signal transmission path. In the method using the variable resistor, however, the resistor deteriorates with time and there is a correspondingly greater possibility that noises are produced. In the method using the photoelectric element, there is a great probability that its characteristics vary with time. This imparts a direct influence to a control parameter, with the attendant undesirable result. In the method using the variable resistor or photoelectric element it is necessary to lead a musical tone signal far into this element and it is therefore liable to suffer noises, hums etc. With the above-mentioned sound volume control device, a sound volume control mechanism will be large-sized and complicated in design in an attempt to simultaneously control the sound volume of musical tone signals of multiple channels, such an upper and a lower keyboard channel.
SUMMARY OF THE INVENTION It is accordingly the object of this invention to provide a sound volume control device capable of attaining a stable, but effective multi-channel sound control without rendering a sound control parameter subject to variation with time.
According to this invention there is provided a sound volume control apparatus comprising a movable plate bearing along its moving direction, in the form of a plurality of binary coded rows having the respective weights of l, 2, 4, 8 digital position information varying in content by the minimum binary units; a digital information readout means located at a predetermined position within the range of movement of the movable plate and adapted to produce plural-bit electrical signals corresponding to said plural binary coded rows by detecting a moving amount of the movable plate through readout of said digital information; and plural signal attenuation means provided in an audio signal transmission path and adapted to attenuate the amplitude level of audio signals an amount corresponding to the moving amount of the movable plate by being operatively coupled to said audio signal transmission path in response to the predetermined voltage level of the pluralbit electrical signals.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of the operating portion of a sound volume control device according to one embodiment of this invention;
FIG. 2A is a schematic view of a swinging shutter plate bearing digital position information used in the operating portion shown in FIG. 1;
FIG. 2B is a partial enlarged view of FIG. 2A;
FIG. 3 is a schematic view for detecting the digital position information of the swinging shutter plate;
FIG. 4 is a schematic circuit diagram of a sound volume control section according to one embodiment of this invention; and
FIG. 5 is a schematic circuit diagram of a sound volume control section according to another embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT There will be explained the case where a sound volume control device this invention is applied to the expression control of electronic musical instruments. In FIG. 1 a reference numeral 11 shows an expression pedal. The expression pedal 11 is swingably mounted to a base 12 with an axis 13 as a fulcrum. The pedal 11 is operated by a human foot 14 and the sound volume of a musical tone signal is controlled according to the swinging angle of the pedal. For this reason, a shutter plate 15 adapted to be swung into the interior of the base 12 is provided on the lower surface of the pedal 11. As shown in FIG. 2A, for example, 7 binary coded rows 16A, 16B are arranged on the shutter plate along the swinging direction of the shutter plate. Each of the binary coded rows consists of at least one slitted portion (painted black in the drawings) corresponding to either a binary l or O and at least one unslitted portion corresponding to a binary 0 or l respectively the unslitted portion being alternately arranged with respect to the slitted portion and having the same length as the slitted portion. The respective binary coded rows 16A, 16B, 16C 16G are given the weights of l 2, 4 32, respectively. Suppose that a length ofthe slitted portion or unslitted portion ofthe binary coded row 16A is unity. Then, the respective slitted and unslitted portions of the other respective binary coded rows 16B, 16C, 16D 166 have a length of substantially 2, 4, 8 32. A digital quantity, represented by the respective binary coded rows, is varied along the swinging direction of the shutter plate by amounts corresponding to the minimum digital amount of the least significant bit, e.g., binary coded row 16A. It is possible to arrange on the shutter plate a binary coded row 17 for instructing conversion of the digital representation which is used for the purpose as will later be described. As shown in FIG. 3 a light source 18 is provided within the base I2 to permit light to be passed through the respective slitted portions of the shutter plate 15. A shutter plate swinging angle detecting device 21 is provided in the light passage, having photoelectric elements 19A to 19G and 20, such as photoresistors, corresponding to the binary coded rows 16A to 16G and 17, respectively. A 7-bit electrical signal corresponding to the swinging angle of the shutter plate 15, ie the depressed angle of the pedal 1 l, is obtained by the photoelectric elements 19A to 19G.
FIG. 4 shows a circuit for treating digital signals from the photoelectric elements 19A to 19G of the detector 21. The output signals obtained through the photoelectric elements 19A to 19G are coupled through amplifiers A] to A7 to gates G1 to G7. That is, the gates G1 to G7 are selectively driven according to the swinging angle of the shutter plate 15. A reference numeral 30 shows a signal tramsission path in which buffer amplifiers B1 to B9, for example emitter followers, having a gain of unity are connected in cascade.
Resistors RM to R70 are connected to the output sides of the buffer amplifiers B1 to B7, respectively. To the output sides of the resistors Rla to R711, resistors Rlb to R7!) which, together with the resistors Rla to R7a, constitute voltage dividers, respectively, are coupled through gates G1 to G7. The gates G1 to G7 are enable by the output signals corresponding to a binary or 1 from the respective amplifiers Al to A7 to cause the voltage dividers to be selectively coupled to the signal transmission path 30, thereby controlling the sound volume of the signal according to the swinging angle of the shutter plate 15. The gates G1 to G7 may be relays or semiconductor switching elements such as transistors. The gate may be so constructed as to be enabled by a positive output voltage or by zero output voltage from the amplifier. Suppose that the attenuation ratios Rlb/Rla Rlb, R2b/R2a R2b, R3b/R3a R3 b R7b/R7a R717 of the abovementioned voltage dividers are O.5db, l.0db, 2.0db 32.0db, respectively. Then it will be evident that there will be obtained a sound volume control range or dynamic range of 63.5db. When the included angle of the circular shutter plate shown in FIG. 2A is 30,a sound volume is stepwise varied from odb down to 63.5db while the shutter plate is swung through an angle from 030. With the sound volume control device according to this invention it is only necessary to couple the output signals of the amplifiers A1 to A7 to the respective gates and it will be understood that the sound volume control of multi-channel signals can be easily effected.
With the embodiment shown in FIG. 4 the sound volume control of the signal is affected only by the binary coded rows 16A to 16G. In this case, however, a situation is liable to occur wherein the sound volume is not varied as desired according to the swinging angle of the pedal 11. The situation may arise at the location where the digital representation of the shutter plate 15 is varied, for example, from the 7-bit signal 0000001 to 00000l0". More specifically, when the shutter plate 15 faces the light source 18 at a location indicated by a line 28-28 in FIG. 28, a 7bit electrical signal 000001 1 temporarily appears. In order to avoid this situation it is necessary to retain the current digital amount 0000001", until a new digital amount 00000l0" is detected by the detector 21 through the swinging movement of the shutter plate 15.
The retaining of the current digital amount and switching to a new digital amount are effected by the binary coded row 17 for instructing conversion of the digital amount. The positional relation between the slitted and unslitted portions of the binary coded row 17 and those of the least significant binary coded row 16A is shown in FIG. 28. It will be understood that in FIG. 2B switching to a new digital amount is performed when the slitted portion of the binary coded row 17 confronts the light source 18. The switching to a new digital amount may be effected when the unslitted portion of the binary coded row faces the light source 18. The retaining of the current digital representation and switching to a new digital representation may be effected by a circuit shown in FIG. 5. Amplifiers A1 to A7 have the same circuit arrangement and, in FIG. 5, only the circuit arrangement of the amplifier A1 is shown by way of example. From an amplifier A0 coupled to a photoelectric element 20 corresponding to the binary coded row 17 for instructing conversion of the digital representation and having the shown circuit arrangement, a positive output voltage corresponding to the slitted portion and a zero output voltage corresponding to the unslitted portion are derived. In the amplifier A1, a transistor O1 is, of such a transistor as to be turned ON and OFF by the electrical state of a photoelectric element 19A. The output of the transistor O1 is coupled through transistors Q3, Q2 and O5 to each collector of transistors Q7 and Q8 constituting a flipflop circuit. The trigger signals are impressed with an opposite polarity to the collectors of the transistors Q7 and Q8. The transistors Q3 and Q5 are enabled or disabled by transistors Q4 and Q6 to the bases of which are supplied the outputs of the amplifier A0. Only when the amplifier A0 produces a positive output voltage, the transistors Q4 and Q6 are enabled and, therefore, the flip-flop circuit can change its state in accordance with the output state of the transistor Q1. The output of the flip-flop circuit is coupled through transistor O9 to a gate G1. More specifically, only when the slitted portion of the binary coded row 17 confronts the light source 18, can the flip-flop change its state; and, before the slitted portion of the binary coded row 17 faces the light source, the flip-flop does not change its electrical state irrespective of any output state of the transistor Q1. Therefore, when the digital representation. is switched from 0000001 to 0000010, a temporary witching to 00000l l" is prevented.
With the above-mentioned embodiment, though there is shown only a pedal type sound volume control device, a rotation type or slide type may be used instead. Though the digital amount is detected by passing light through the slitted portion of the shutter plate, the digital amount may of course be read out utilizing the reflection of light.
What we claim is:
1. A sound volume control apparatus comprising:
a. a plate bearing n rows of binary indicia,
.b. a digital readout means for reading said 11 binary rows upon relative displacement of said plate and said readout means,
c. said readout means aligned with said n binary rows for producing in response thereto an n-bit signal representing one of 2" possible values, and
d. a plurality of n signal attenuators connected in an audio signal transmission path, said attenuators each being electrically connected and independently responsive to one bit of said n-bit signal whereby said audio signal is attenuated by an amount dependent upon the n-bit signal.
2. A sound volume control apparatus as recited in claim I wherein:
a. said audio signal transmission path comprises a plurality of cascade connected buffer amplifiers; and
b. said signal attenuators each comprise a combination ofa voltage divider and one of said buffer amplifiers, the output of said buffer amplifier being input to said voltage divider.
3. A sound volume control apparatus as recited in claim 2 wherein said voltage divider comprises:
a. a first resistance connected to the output of said b. a second resistance grounded at one end; and
c. gating means for connecting the ungrounded end of said second resistance to said first resistance in response to said plural-bit code. 4. A sound volume control apparatus as recited in claim 1 wherein said digital readout means comprises: a. illuminating means for producing light directed towards said plate; and b. a plurality of light detecting means corresponding respectively to said plurality of binary coded rows on the plate for detecting the relative displacement of the plate and readout means. 5. A sound volume control apparatus as recited in claim 4 wherein:
a. said binary coding is represented by slots in said plate; and b. said illuminating means and said light detecting means are disposed on opposite sides of said platev 6. A sound volume control apparatus as recited in claim 1 wherein:
a. said plate bears a further binary coded row thereon with elements whose boundaries do not correspond with the boundaries of elements on any other binary coded row thereby permitting alteration of said plural-bit electrical signal; and
b. said digital readout means comprises:
i. first means for retaining said plural-bit electrical signal,
ii. second means for reading said further binary coded row and generating a signal corresponding to said elements thereon, and
iii. third means for permitting said first retaining means to assume the plural-bit electrical signal output corresponding to a new relative displacement only in response to generation ofa signal by said second means 7. A sound volume control apparatus as recited in claim 1 wherein said plate is movable and said readout means is stationary.
8. A sound volume control apparatus according to claim 7 in which said movable plate is moved by a pedal.