US3513247A - Photoresistor swell control for a musical instrument - Google Patents

Description

May 19, 1970 w. J. ANDERSON ETA-L 3,513,247

'PH OTORESISTOR SWELL CONTROL FOR A MUSICAL INSTRUMENT Filed May 2, 1967 ALBERTO E. KNIERKAMP v US. Cl. 841.18

United States Patent 3,513,247 PHOTORESISTOR SWELL CONTROL FOR A MUSICAL INSTRUMENT Walter J. Anderson, Elgin, and Alberto E. Kniepkamp, Chicago, Ill., assignors to Chicago Musical Instrument Company, a corporation of Delaware Filed May 2, 1967, Ser. No. 635,493 Int. Cl. Gh 1/02 3 Claims ABSTRACT OF THE DISCLOSURE A swell control for an electrical musical instrument embodies a photoresistor coupling the tone signal output to the signal reproducing means of the instrument. An incandescent light bulb is energized by direct current of low voltage to emit light the luminous intensity of which is insuflicient per se to excite the photoresistor. The bulb is selectively movable in a housing and disposed to emit light the luminous intensity of which selectively energizes the photoresistor to control conduction of the signal output to the reproducing means and secure variation in the volume of sound thereat.

The herein disclosed preferred embodiment of the invention is characterized by interrelated coactive elements that can be included in a swell pedal assembly and readily incorporated in circuit with the tone signal output system and the electroacoustic signal reproducing means of an electrical musical instrument and operated by the player to control the decibel level of sound at the reproducing means. The principal feature of the invention is the use of light the luminous intensity per se of which is insuflicient to excite a photoresistor coupling between the signal output system and the electroacoustic reproducing means of the instrument, which said light is emitted by an incandescent bulb energized by direct current oflow voltage. To utilize the light to excite the photoresistor means the bulb is selectively movable in a linear direction between minimum and maximum extremes to cause variation in exciting brightness of light falling on the photoresistive means and proportional variation in the resistance and conductivity thereof and accompanying conduction of the signal output to the reproducing means and control of the decibel level of sound thereat.

An important feature of the invention is a photoelectric volume control system wherein one or any desired number of tone signal channels may be connected in circuit with respective reproducing systems and a common light signal source for conversion thereof from a minimum conductive electrical state to a selected variable conductive electrical state and conversely by photoelectric means in each of said channels all of which are common to a single light source and may be activated and deactivated by means such as the expression pedal of an organ or equivalent means for varying the relationship of the light source to the photoelectric means in the respective tone signal channels.

Other objects and advantages are:

The provision of an expression control which is highly dependable in operation, requires infrequent servicing; eliminates transient noises inherent in prior systems employing potentiometers, rheostats and similar devices for making and breaking circuit between a tone signal source and a reproducing system; is simple and may be economically manufactured, and is of a general construction enabling use thereof as a self-contained part of the expression pedal assembly of an organ and requires no change mechanically or otherwise in adapting it to the signal output circuit of an electric or electronic organ or other similar electrical musical instrument.

3,513,247 Patented May 19, 1970 The invention consists substantially in the construction, combination, location and relative arrangement of parts and the method employed in connection therewith, all as will be more fully hereinafter set forth, as shown by the accompanying drawing and finally pointed out in the appended claims.

FIG. 1 is a view partly in section and partly in elevation of one exemplified embodiment of the invention.

FIG. 2 is a view in longitudinal section of the light responsive assembly showing the light source in its projected position relative to the light responsive device.

FIG. 3 is a perspective view of the light responsive device, the light source and the mounting board therefor showing the light source in its projected position.

FIG. 4 is a schematic view of one exemplified embodiment of the invention.

FIG. 5 is a view similar to FIG. 4 showing another exemplified embodiment of the invention.

FIG. 6 is a view similar to FIG. 4 showing a still further exemplified embodiment of the invention.

FIG. 7 is a detail sectional view showing the light source coupling means and interrelated guide rail.

In FIG 4, A is any well-known electric or electronic organ, the tone signal output of which has a preamplifier B, which, in turn, is coupled to a power amplifier D and associated electroacoustic transducer F via a light responsive device comprising a photoresistor C which may be of the type manufactured by or for General Electric Company of the United States'of America and identified as No. 65-15-1885GEB430G. Coactive with the light responsive device and mounted for reciprocal motion relative thereto is a light source consisting of an incandescent bulb 34 which may be of the type identified as No. 1819, also manufactured by or for said General Electric Company. The bulb is connected to a battery S, the voltage being relatively low in that only a minimum of light is required to obtain maximum conduction of photoresistor C, i.e., lowest resistance thereof; about on the order of 500 ohms when light of maximum luminous intensity falls thereon, the resistance increasing to several megohms when no light of exciting intensity strikes the photoresistor.

The resistance R of photoresistor C has one end coupled to the output of preamplifier B by a circuit lead wire W, the opposite end of the resistance connecting to ground through a 10K resistor R1, and as shown, a circuit lead wire W1 couples amplifier D to the junction point P between resistance R and resistor R1.

When the light bulb 34 is moved a predetermined maximum distance away from the light responsive device as would be the case where the expression pedal of an organ is in a full Off condition, light from the bulb 34 is of insufficient luminous intensity to have any effect on resistance R, which is non-conductive and functions completely to prevent transmission of tone signal energy to amplifier D.

Like parts in the several figures of the accompanying drawing will bear like reference numerals and characters.

In carrying the invention into practice, use is made of a pedal expression assembly shown in detail in FIG. 1 as comprising a rigid horizontally disposed base plate 10 having at its rear end a vertical bracket 11 on which a foot pedal 12 is mounted for vertical tilting motion about a bushing 12 through which passes a supporting shaft 12b. The pedal consists of a longitudinal rigid metallic plate 14 faced at its upper surface with resilient material 15. Integral with bracket 11 is a stop extension 11a disposed and arranged to limit pivotal motion of the pedal from a full Off to a full On condition, said extension having a resilient stop bumper 17 adapted to freely engage the rear end of plate 14. Loosely encircling the bushing 12 is a steel coil spring 18 having a long extremity 19 attached 3 at to plate 14 and a short extremity 21 attached at 22 to said bracket 11, the function of the spring being to cause the convolutions thereof to resiliently grip the bushing-clutchlike and automatically retain the pedal in any selected position of tilted adjustment when pressure of the foot of the player is removed therefrom, and also to insure smooth operation of the pedal.

Forwardly of bracket 11 and attached to plate 10 is a vertical metallic stop member 23 having at its upper end a resilient stop bumper 24 for limiting tilting motion of the pedal in a clockwise directon between said bumper 24 and aforementioned bumper 17.

In FIGS. 1, 2 and 3, a vertical rectangular panel board 25 of hard electrical insulating material is situated forwardly of stop member 23 and disposed transversely of plate 10 and supported by brackets 26, 26 having bifurcated branches 26a attached to said plate by screw fastening means 27 enabling adjustment of the board longitudinally of said plate. Fixed to the board is a hollow tubular light housing 28 open at both ends and formed of hard smooth surfaced plastic material having electrical insulating properties. The front of the housing is flanged as at 28a, and as shown in FIG. 2 the housing extends horizontally through board 25 with the flanged end thereof firmly secured against one side of the board by a fastening element at the opposite side of the board.

Telescopically received in said housing 28 are two interrelated hollow tubular members 29 and 30 of the same material as said housing. These members are nested partly within each other and firmly welded together to provided a substantiall integral rigid body adapted for free reciprocal motion in said housing. Member 29 forms a receptacle for a lamp socket 31 having a bayonet slot 32 to receive the retaining stud 32a of the aforementioned incandescent light bulb 34. The base of the lamp socket is contracted and passes through a U-shaped coupling member 35 and is upset against wall 36 thereof enabling attachment of circuit lead wires W2 and W3 to the light bulb 34.

In FIG. 1 a motion imparting means consisting of a rigid steel rod M is pivoted at 37a to plate 14 of the expression pedal 12 and disposed forwardly of shaft 12b. The rod extends downwardly and forwardly, the lower end terminating in a trunnion M2 received in apertures M3 in the coupling 35 and having one end freely engaged with a rail M4 fixedly mounted on base plate 10 of the expression pedal assembly. As shown, the rail is disposed parallel to the axial center of housing 28. A coil retractile spring M1 has one end attached to base plate 10 so that the spring has a toggle motion in response to push and pull actuation of said rod M enabling compensating to changes in tilting motion of said pedal and whereby the free end of the trunnion is resiliently maintained in operative riding engagement with said rail that uniform. reciprocal motion is imparted to light bulb in a plane coaxial with said housing 28.

Referring to FIG. 5, two photoresistors C are spaced apart from each other, each adapted to be connected in a signal transmission and reproducing system substantially in the manner shown and described in the description of FIG. 4. Coactive with both photoresistors for simultaneous activation and deactivation thereof is a light source consisitng of bulb 34 which is operable in the manner described in the description of FIG. 4.

Referring to FIG. 6, four photoresistors C are shown spaced apart from each other and arranged to form a circular group. Each photoresistor is adapted to be connected to a signal channel individual thereto and having an amplifier and associated electroacoustic transducer as set forth in the description of FIG. 4, the respective channels being common to a light source 34 which we can assume is mounted for reciprocal motion respectively into and out of the field of activating sensitivity of said photoresistors enabling converting the resistances thereof from a non-conductive electrical state into a variable conductive state in response to selected reciprocal motion of said light source. The resistance of the photoresistors are of the same impedance value, the reason being that ordinarily, in each channel of a stereophonic organ the expression should be the same, i.e., about on the order of 25 decibels.

Functionally, all of the several embodiments of the invention are the same, the difference being merely in the number of tone signal channels and interrelated light responsive devices in circuitry including one or more reproducing systems, in each embodiment only a single light source being required for controllng activation of the light responsive devices.

While we have shown and described several embodiments of the invention respectively diifering from each other only by the number of tone signal channels and associated light responsive device, this is by way of illustration as the number can be increased according to the type of musical instrument and the number of reproducing systems used as would be the case in some stereophonic systems.

What we claim as our invention is:

1. A swell control for a musical instrument having a tone signal output system and a signal reproducing system, said control comprising, a photoresistor coupling the tone signal output system to the reproducing system, an incandescent light bulb of low voltage selectively movable in a housing enabling light of desired luminous intensity to activate the photoresistor and thereby control conduction of the signal output to said reproducing system, and a panel board at one side of which the photoresistor is mounted and at the other thereof the housing is mounted and opens onto the light exciting field of the photoresistor.

2. A swell control according to claim 1 wherein the housing, the panel board and the light bulb are all thereof elements of a swell pedal assembly having motion imparting means responsive to operation of the pedal of said assembly for moving the light bulb between two linearly spaced apart positions in said housing.

3. A swell control according to claim 2 wherein there is included in said assembly means for maintaining the pedal in any desired position of tilted adjustment.

References Cited UNITED STATES PATENTS 1,956,350 4/1934 Hammond 84--1.27 X 2,822,429 2/1958 Watson 179100.3 3,318,991 5/1967 Cookerly et al 84-1.27 X 3,374,316 5/1968 Slaats et a1 841.27 X

WARREN E. RAY, Primary Examiner U.S. Cl. X.R. 841.27; 250-234

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