Abstract:
A volume control pedal has an opposed emitter and receiver which are set up to establish an emission path therebetween. A shade is provided to intersect the emission path. Pedal operation induces relative displacement between the shade and emission that as a result varies the emission reception such that the receiver&#39;s output provides a control variable for volume control. The shade has a varying regions of light and dark as rendered by an image of a varying dot density pattern. This allows among other things producing the image by a computer-implemented process, as well as printing it on transparent stock such as optionally on a negative film by a film developing process.

Description:
CROSS-REFERENCE TO PROVISIONAL APPLICATION(S) 
   This application claims the benefit of U.S. Provisional Application No. 60/202,287, filed May 5, 2000. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a volume control pedal for musicians and more particularly relates to the pedal&#39;s circuitry as well as aspects of the mechanical construction in view of such circuitry. 
   2. Prior Art 
   Pedals for volume control are popular with performing musicians, whether vocalists or instrumentalists performing on, by way of non-limiting example, guitars, steel guitars, fiddles and so on. Volume control pedals are popular despite if a sound control engineer is involved. Musicians simply desire independent control of boosting or fading their performance at times when the feeling is there and in order to achieve certain effects. 
   Prior art volume control pedals have characteristically relied on potentiometers such as pulley-spun dial-type potentiometers for voltage control. It is an object of the invention to provide a distinctive alternative to potentiometers, dial- or plunger-type or otherwise, in a volume control pedal. 
   Eliminating potentiometers in favor of a better alternative is advantageous because the price of audio-quality potentiometers has increased dramatically over the years concurrently as quality has apparently gone down. Audio product manufacturers find that keeping an on-hand stock in sufficient quantities of a diverse assortment of different potentiometers of premium quality is an expensive investment. Every year the problem is exacerbated by rising costs, discontinued product lines, and the gradual cheapening of quality. In audio work, even slight changes in quality produce discernible problems in the final audio output. 
   Potentiometers are categorized according to many characteristics including what is sometimes known as taper. For instance there are potentiometers offered not only with linear or “audio” taper but also various logarithmic tapers. However the inventor hereof finds that the logarithmic-taper potentiometers he has experimented were undesirably inconsistent. Volume control pedals commonly use 500,00 ohm potentiometers made of hot molded carbon. The least imperfection causes problems that can be heard in the final audio output. Just as problematical, an audio equipment manufacturer can only obtain whichever taper profiles that potentiometer OEM&#39;s offer off-the-shelf unless the manufacturer is so large it can afford to order custom potentiometers. Regardless, the selection of potentiometers is fairly limited to a finite number of different products. 
   Since the 1960&#39;s the prior art has seen a series of “light beam” pedals, or pedals which used “light beam” circuits to control signal voltage. In the professional music world these light beam pedals had a sour reputation. There were at least three well-known problems with them:—they lost high-end frequency, they would often not go all the way OFF, and they didn&#39;t rock very comfortably underfoot. 
   The inventor hereof examined at least three varieties of these 1960&#39;s light beam pedals and discovered the following. The electronics inside all used a photo-resistor arrangement. These kinds of photo-resistors are sometimes called Cds cells. The light beam source in all instances was an incandescent light. The control over light intensity that shined on the photo-resistor was accomplished in one of three ways which in common shared the principle of the stroke of a shutter. The simplest way involved the simple eclipse of the light source by an opaque shutter. Full retraction of the shutter corresponded to full transmissivity of the light as full extension corresponded to full blockage, with varying degrees of transmissivity corresponding to intermediate positions accordingly. A second way used graduated material thickness in which a dark plastic wedge-shaped shutter&#39;s material thickness attenuated the light beam. That is, the thinner portions of the wedge corresponded to more transmissivity of the light beam as the thicker portions corresponded to more blockage. The third way had an opaque shutter that was formed with an elongated V-shaped slit. The width at the top of the V-shaped slit corresponded to maximum transmissivity of light as the vertex at the bottom of the V-shaped slit reached the point of full blockage. 
   The problems of the prior art light beam pedals were discovered to be arguably attributable to the following. As for loss of high end frequency, evidently the prior art light beam control circuits presented a music instrument having a magnetic pickup with a low-impedance output when the magnetic pickup needed to see a high impedance output in order to preserve the high end frequencies. The failure to go to full OFF appeared to be due to leakage of ambient light onto the photo-resistors. And the unnatural feel of the light beam foot pedals seemed to be caused by the absence of inherent drag as in dial-type potentiometers. Although there is no felt drag or friction between a shutter and light beam, the drag that the prior art light beam pedals introduced by way of springs still felt unnatural underfoot. In the absence of drag, the treadle was free to sink to full ON or OFF if the musician lifted his foot. However the drag that was introduced were simple spring arrangements which biased the treadle to a given “HOME” position nevertheless. The spring arrangements of the prior art failed to adequately balance the treadle in the position chosen for the moment by the musician (if he pulled his foot off). Moreover the springs could require a constant fight underfoot and did not shift and glide through or hold positions like pulley-spun dial-type potentiometer pedals. 
   These and other problems have plagued the prior art light beam pedals out of disfavor and virtual disuse, not all of which problems were likely discovered by the studies of the inventor hereof. What is needed is a solution which eliminates potentiometers in a volume control pedal without re-incorporating the problems associated with prior art light beam pedals. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a volume control pedal with a way of achieving volume control that is distinctive over the prior art way characterized by potentiometers as typically a pulley-spun dial-type potentiometer. 
   It is an alternate object of the invention to that the foregoing volume control pedal overcome the disadvantages associated with the prior art pedals as discussed above in the Background section. 
   It is another object of the invention to provide a control shade for a light-beam volume control circuit that is producible by a computer-implemented imaging process and which can then be printed or developed on a transparent sheet. 
   It is an additional object of the invention to provide a mechanical arrangement for holding the control shade in position at times when the user takes his foot off the pedal. 
   It is a further object of the invention to introduce a pre-amp between an audio instrument&#39;s magnetic pickup and the inventive light-beam control circuit in order to present the magnetic pickup with a high impedance output and thereby better preserve the high end frequencies in the audio signal. 
   These and other aspects and objects are provided according to the invention in a volume control pedal having a proportionate control system which operates on the variance of relative transmissivity sensed by a radiation collector. In an example embodiment of the invention, the radiation source optionally comprises an infrared light-emitting diode which preferably is powered to give a constant output. The emission sensor or collector optionally comprises an infrared/photo-transistor although alternatively a photo-diode works as well, and a photo-resistor presents another option still. The way in which the relative transmissivity received-by-the-sensor or -collector is adjusted preferably comprises the following:—eg., the relative displacement of a shade having varying regions of light and dark. For example, the shade may be provided with regions having at one extreme a region which is nearly fully transparent as opposed to another region which is nearly fully opaque, and including having a gradually changing grey scale extending between and smoothly merging the opposed regions. 
   Additional aspects and objects of the invention will be apparent in connection with the discussion further below of preferred embodiments and examples. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There are shown in the drawings certain exemplary embodiments of the invention as presently preferred. It should be understood that the invention is not limited to the embodiments disclosed as examples, and is capable of variation within the scope of the appended claims. In the drawings, 
       FIG. 1  is a diagrammatic view of a control signal system for feeding to an amplifier circuit in a volume control pedal in accordance with the invention; 
       FIG. 2  is a section view taken along line II—II in  FIG. 3  of the inventive volume control pedal&#39;s lower half or base portion; 
       FIG. 3  is a top plan view thereof; 
       FIG. 4  is a section view taken along line IV—IV in  FIG. 5  of the inventive volume control pedal&#39;s upper half or rocking treadle portion; 
       FIG. 5  is a bottom plan sectional view thereof taken in the direction of arrows V—V in  FIG. 4 ; 
       FIG. 6  is a schematic circuit diagram of an amplifier circuit for the volume control pedal in accordance with the invention; 
       FIG. 7   a  is a schematic circuit diagram of a power supply circuit for the volume control pedal in accordance with the invention; 
       FIG. 7   b  is a schematic circuit diagram of an alternative power supply circuit for the volume control pedal in accordance with the invention; and, 
       FIG. 8  is a schematic circuit diagram of dual potentiometer circuit(s) for the volume control pedal in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a control signal system  40  in accordance with the invention for a volume control pedal  20  in accordance with the invention. The clam-shell housing  21 , 22  of the volume control pedal  20  is shown in separate halves  21  and  22  by  FIGS. 2 and 4 . In  FIG. 2 , it shows the base half  21  that sets on the floor.  FIG. 4  shows the upper or rocking treadle portion  22 . The rocking treadle  22  and base  21  connect by a pivot pin (not shown) that extends through the respective pin apertures along the rocking axis  24  of the treadle  22 . 
   The base  21  carries a plastic mounting bracket  26  which in one example version of the invention is produced from transparent acetate. The flange  27  of the bracket  26  is fastened to a wall of the base  21 . The stem  28  of the bracket  26  provides a mounting surface for a polyester film or “shade”  42  which will be more particularly described below. The treadle  22  carries an inverted U-shaped mounting block  30  that has arms  32  which extend down to lower terminations formed with apertures  33  for mounting matching emitter and collector (or sensor) devices  34  and  36  as follows.  FIG. 1  shows the matching emitter  34  and collector  36  devices to comprise an infrared radiation-emitting diode  34  and an infrared/photo-transistor  36 , respectively. The infrared radiation-emitting diode  34  and infrared/photo-transistor  36  are potted opposite each other across the gap  39  of the opposite arms  32  of the inverted U-shaped mounting block  30 . The opposite positions of the emitter  34  and sensor  36  define a light axis  38  between each other. Preferably the sensor  36  is chosen from one of a photo-transistor or photo-diode, although a photo-resistor offers a further option. 
   The emitter device  34  is preferably chosen for providing a high intensity radiation source. In the preferred example the inventor has chosen a very high intensity light-emitting diode (LED) for the emitter  34 , and then has arranged the shade  42  and collector  36  such as photo-transistors or photo-diodes in accordance with this high intensity LED source. The use of a high intensity source  34  in contrast to the prior art incandescent-light sources provides multiple advantages. The use of a high intensity light source preserves the premium quality of the audio output better, which may be due in significant part to the incorporation of the high intensity device  34 . The high intensity device  34  also eliminates the problem of leakage of ambient light onto the collector or sensor  36 . Use of the high intensity device  34  obtains full OFF even when used in outdoor daylight settings. The photo-transistor (or photo-diode or the like) sensor  36  is arranged in connection with this high intensity source such that the low intensity of background ambient light appears not to operate or otherwise degrade the sensor&#39;s sensitivity to the high intensity source. Additionally the emitter and sensor devices  34  and  36  preferably operate in the infrared, which further seems to reduce the deleterious effects on the sensor  36 &#39;s sensitivity to ambient light leakage into the foot pedal  20 &#39;s housing. 
   When the base  21  and treadle  22  are assembled together (not shown), the shade  42  (fixed to the base  21 ) fits in the gap  39  between the arms  32  of the inverted U-shaped mounting block  30  (fixed to the treadle  22 ). In use, a musician rests his or her foot on the treadle  22  to rock it to any position between extremes of fully depressed (toe down, heel up) or fully retracted (toe up, heel down). Rocking the treadle  22  causes relative displacement between the light axis  38  and shade  42 .  FIG. 2  shows that the shade  42  remains stationary relative to the floor. Hence when the treadle  22  is rocked from one position to a successive position, the light axis  38  is in fact moved relative to the stationary shade  42 . The shade  42  and light axis  38  are arranged as shown on the base  21  and treadle  22  respectively for convenience of this description and do not limit the invention to this arrangement only because, the arrangement could be made any alternative way to achieve relative displacement of the shade  42  and light axis  38 . 
   Referring more closely to  FIG. 2 , by way of a non-limiting example, the shade  42  varies gradually from a fully transparent upper border  43  to a fully opaque lower border  44 . Given this non-limiting example as shown by the drawing(s), when the treadle  22  is fully depressed (toe down, heel up), the light axis  38  aligns in or near the fully opaque region  44  at the lower margin. Conversely, when the treadle  22  is fully retracted (toe up, heel down), the light axis  38  aligns in or near the fully transparent region  43  at the upper margin. 
   Briefly stated for now, control signal  46 &#39;s adjustment and consequent control over volume or loudness is achieved by the relative displacement between the light axis  38  and shade  42 . The amplifier circuitry  50  which will be more particularly disclosed in connection with  FIG. 6  incorporates a voltage-controlled-amplifier chip  52 . By inputting to the voltage-controlled-amplifier chip  52  an adjustable control signal  46 , this allows adjustment to the amplifier chip  52 &#39;s output strength. Causing changes in such a control signal  46  is achieved by the control signal system  40  shown by FIG.  1 . 
   Referring to  FIG. 1 , the infrared emitter  34  is aimed at the photo-transistor  36  such that the given transmission beam  38  is established. The infrared emitter  34  provides an emission output at a constant value. The constant value of the emission output is a function of the power supply feed  70 / 70 ′ as shown by  FIGS. 7   a  and/or  7   b  and described more particularly below. The photo-transistor  36  receives a portion of the emission output as shown and indicated as the light axis or alternatively the transmission beam  38 . The relative strength of the received signal  38 ′ is reckoned as 100% transmissivity when there is no external attenuation or “shading” of the emission ‘received’  38 ′ from the emitter. The shade  42  allows scaled changes in the transmissivity of the ‘received’ emission  38 ′ from values corresponding to about 100% transmissivity for fully transparent regions  43  of the shade  42 , to about 0% (zero percent) transmissivity for fully opaque regions  44  of the shade  42 . More simply, the more emission  38 ′ passed through the shade  42 , the more of its power or intensity that reaches the photo-transistor  36 . The less emission  38 ′ passed through the shade  42 , the less of its power or intensity that reaches the photo-transistor  36 . 
   The photo-transistor  36  conducts in proportion to the emission (or radiation predominantly in an IR band) power  38 ′ it receives. Hence, the more emission  38 ′ passed through the shade  42 , the more the photo-transistor  36  conducts. Conversely, the less emission  38 ′ passed through the shade  42 , the less the photo-transistor  36  conducts. The output of the photo-transistor  36  is the control signal  46  for the voltage-controlled-amplifier chip  52  of FIG.  6 . As a result, causing changes in the output  46  of the photo-transistor  36  ultimately allows volume adjustment of the voltage-controlled-amplifier chip  52 &#39;s output audio signal  62 . 
   The shade  42  is produced with varying light and dark regions of grey tones on a polyester camera film. In fact, the grey scale is achieved by varying the dot density of a dot matrix printed on the film. As shown by  FIG. 1 , the dot density on the shade increases from virtually nil at the lower transparent border  43  to virtually opaque at the upper opaque border  44 . 
   It is an inventive aspect that the gradation of the dot density can be arranged in accordance with a definite mathematical formula. This in turn determines a performance feature of the volume control pedal  20  as measured by in what way the volume is controlled relative to movement of the treadle  22 . The gradations can be smooth or not (eg., discontinuous). At least smooth gradations can be established as linear or non-linear, wherein one of the more popular non-linear gradations has a logarithmic profile or the like. In fact, the gradations can be given any infinite variety of an arrangement as desired. Again, any arrangement in the gradations of the grey scale can be associated with the relative displacement between the shade  42  and light axis  38 . 
   The preferred method of establishing a grey scale on the shade  42  is achieved by computer imaging. Among other things, this allows arranging the gradations in the grey scale in accordance with a prescribed mathematical formula. The computer imaging systems employed by the inventor hereof in producing the proof-of-concept prototypes were those used to grey-tone pictures for printing newspapers photos. For newspapers, printed black-and-white photos are typically resolved from a computer-image rendered in a dot matrix. Such a dot matrix being so imaged by a computer can be printed or “developed” on camera film. 
   To date the inventor has produced shades  42  measuring 1-¾ inches high (4.5 cm) in strips of between about 1 to 1-½ inches wide or so (eg., 2.5 to 3.8 cm) out of sheet film stock measuring full page size (ie., double ledger or 17 inches by 21 inches (43 cm by 53 cm)). An example of pseudo-code for generating such a computer-imaged sheet of film would recite as follows:
         Gradient angle→90°.   Horizontal bars→1-¾ inches.   Bar height→1-⅝ inches.   Bar width→1-{fraction (45/64)} inches.   Dot pattern→diamond, 1600 dpi, 90% highlight.
 
Any suitable film type will suffice including for example the polyester-base negative films of Anitec or alternatively Safelight&#39;s Encapsulite R20 (Red) and like 0.004 inch (0.10 mm) polyester-base equivalents. Individual shades  42  are cut to size and to date, simply hot glued to the acetate mounting bracket  26  (see, eg., FIGS.  2  and  3 ).
       

   Given the foregoing, the transmission axis  38  between the emitter  34  and photo-transistor  36  is established vis-a-vis the emitter&#39;s and collector&#39;s  34  and  36  opposed mountings in the arms  32  of the inverted U-block  30  hanging from the treadle  22 . The base  21  and treadle  22  are pivoted such that rocking the treadle  22  traces the transmission axis  38  up or down on the shade  42 . Moving the transmission axis  38  down to a region of greater grey shading  44  or up to regions of lesser shading  43  correspondingly results in greater or lesser proportions of the transmissivity  38 ′ being blocked by the shade  42 . Greater or lesser blocking of the transmissivity  38 ′ to the photo-transistor  36  results in lesser or greater proportions of the control signal  46  being fed into to the voltage-controlled-amplifier chip  52 , which in turn causes the audio output volume  62  to be turned down or up respectively. Whereas the immediately preceding description comprises one example description of a scheme of control  40 , persons having routine skill in the art might alternatively utilize inverted circuit devices in which one or more of the above-described relationships would constitute inverse relationships, and in which case other devices would be correspondingly inverted (or not) to achieve the desired overall result. 
     FIG. 6  shows aspects of the example amplifier circuitry  50  in accordance with the invention. The infeed audio signal  56  is obtained from a suitable jack and is supplied to a pre-amp circuit  54 . The pre-amp circuit  54  provides the infeed audio signal  56  with a high impedance in order to preserve the premium quality of the high end frequency range of the audio infeed signal  56 . The infeed audio signal  56  can be either of music level or line level. A music level signal typically measures in the millivolts whereas a line level signal typically measures about a volt. The pre-amp circuit  54  provides filters for the infeed audio signal  56  before supplying it to an eight-pin operational amplifier  58  that performs the pre-amp functions. A suitable audio pre-amp chip  58  might be Burr Brown&#39;s OPA  604 . From the pre-amp chip  58 , the infeed signal  56  is fed into the sixteen-pin “voltage-controlled-amplifier” chip  52  (eg., in the drawings, “VCA Amp”). A suitable voltage-controlled-amplifier chip  52  might be an Analog Devices SSM2018T. The strength of the amp chip  52 &#39;s output audio signal  62  is controlled by the control signal system  40  shown by and described above in connection with FIG.  1 . 
     FIG. 7   a  shows a power supply circuit  70  for the volume control pedal  20  in accordance with the invention. The power infeed preferably comes by and through an adapter that plugs into a public utility 120 VAC supply and discharges a feed of low voltage DC. It is this low voltage DC that is brought into the pedal. The power feed comes into the power supply circuit and first encounters a bridge rectifier, a voltage regulator, filter capacitors, and then ultimately to a DC-to-DC converter. The output of the DC-to-DC converter is a dual polarity DC supply having a positive, a negative and a common. The dual polarity output is then processed through filter capacitors and current-limiting resistors, after which it is available for powering the other circuit devices of the invention.  FIG. 7   b  shows an alternative power supply circuit  70 ′ for the volume control pedal  20  in accordance with the invention. Conditioning the DC power supply to output at consistent values is significant for the emitter or light source  34 . It is an aspect of the invention that the emitter  34  shines with constant emission power so that variations sensed in the received signal strength  38 ′ are properly taken as control variations induced by the relative displacement of the shade  40 , and not external noise or excursions in the 120 VAC feed. 
     FIG. 8  shows a pair of dial- or twist-type potentiometers  80  and  82  providing preferential settings adjustment. These potentiometers  80  and  82  can be simple, small devices which are accessed through apertures in the base  21  by a thin-bladed screw-driver or like blade (not shown). Twisting the screw-driver while the blade is inserted in a socket for it allows turning the dial of the given potentiometer  80  or  82 . One potentiometer  80  provides adjustment of the control signal  46  (ie., its voltage) as situated between the photo-transistor  36  and voltage-controlled-amplifier chip  52 . This potentiometer  80 &#39;s adjustment allows setting the ON/OFF transition point of the audio output signal  62  of the voltage-controlled-amplifier chip  52 . In other words, this allows the user to establish at what relative angle between the treadle  22  and base  21  constitutes the ON/OFF transition point (eg., the angle where the audio output signal  62  is perceptibly ON if treadle  22  moved out of the OFF range and thus into the ON range, or correspondingly the same angle where the audio output signal  62  is perceptibly OFF if treadle moved back from the ON range and hence back into the OFF range). 
   This potentiometer  80  allows the user to set up the volume control foot pedal  20  in a way the user finds comfortable. That is, a user may find that his or her foot rests most naturally on the treadle  22  at a given angle. This potentiometer  80 &#39;s adjustment allows the user to establish the ON/OFF transition angle of the treadle  22  to become either that given angle or some other angle measured from that given angle, all according to that user&#39;s own personal preference. 
   The other potentiometer  82  provides adjustment of the audio output signal  62  between the voltage-controlled-amplifier chip  52  and the line-out jack(s) (eg., there normally are plural or multiple line-out jacks). A user may choose to have the full output strength given by the pedal  20  to be quieter or louder under different circumstances. Hence prior to a given instance of use, a user can diminish the relative loudness of the extreme loudest output of the pedal  20 . The user does this by the second potentiometer  82 . 
   Other aspects of the pedal  20  are shown by  FIGS. 2 and 5 . Unlike the prior art pedals, especially the ones using pulley-spun dial-type potentiometers, the shade  42  does not physically rub anything and hence its operation is drag-free. In spite of that, it is desirable nonetheless to introduce drag or inertia into the rocking of the treadle  22  so that the treadle  22  more stably holds itself in position. It is desirable if a user is required to apply light foot pressure in order to break the inertia or frictional “sticking” of the treadle  22  at rest, such that when the treadle  22  is brought to stop a successive time, the treadle  22  once again tends to stick or “freeze” there in that successive position. To achieve the foregoing, the base  21  is configured to prop up a counter-acting rocking cam  90  that is biased by a spring  92 . The cam  90  is produced from a slick plastic such as an oil-impregnated nylon or PET and the like. The cam  90 &#39;s arcuate cam edge  94  contacts the treadle  22  on a machined-smooth slideway  96  recessed in the web of the treadle  22  as shown in FIG.  5 . 
   Various advantages of the invention include the following. The control signal system  40  in accordance with the invention (see, eg.,  FIG. 1 ) provides musicians with distinctively different effects than are gotten by conventional electric-conductor type potentiometers. Whereas the deciding merits of which sounds better is certainly subjective, the invention is distinctive, and its distinctiveness is winning admirers. The operating principle behind this distinctive performance is not truly known. It may be due in part to the smooth transitions in the grey scale gradations given by the computer-imaged shade  42 . 
   Also, since the shade  42  is easily produced by computer imaging, the shade  42  can be produced in a multitude of variations which are yet highly reproducible in order to allow economical realization of any infinite number of volume control schemes  43 - 44 . Moreover, any given shade  42  allows removal and replacement with any other shade in order to provide the user with different effects than what was gotten by the previous shade  42 . 
   The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art. The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.