Abstract:
A portable modular device for the purpose of sensing key movement of a piano or keyboard, processing key movement information, and communicating at least key-note ON/OFF and key-note velocity information. A portion of the modular device, the key sensor strip, inserts between the keys and fallboard and mounts atop a piano or keyboard.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the filing of U.S. Provisional Patent Application Ser. No. 60/441,057, entitled “Piano/Keyboard Gap Strip for Sensing Key Movement”, filed on Jan. 21, 2003, and the specification thereof is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention (Technical Field) 
   The present invention relates to a device for sensing piano or keyboard key movement using a variety of sensors that are inserted into the piano or keyboard from atop the keys. 
   2. Description of Related Art 
   Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes. 
   There have been many ways sought to detect key movement on pianos and keyboards. Electronic keyboards have the advantage of building in key detecting devices during its design and manufacturing. However, older electronic keyboards, organs, and pianos are not equipped with key detecting devices and circuitry. New pianos are coming equipped with sensor units, and older piano can be retrofitted with sensor units. 
   Even though there are many types of sensing technologies used in these retrofit systems, such as optical couplers, piezo-electric material, mechanical switches, and magnetic coupling, most retrofit units must be installed by disassembling pianos and installing the sensor strip internal to piano. Once inside the piano, there are other sensing techniques used by major piano manufacturers to sense key movement by placing sensors beneath the key to virtually anywhere along the key linkages points all the way up to the key-string striking mechanism. 
   U.S. Pat. No. 5,567,902, U.S. Pat. No. 5,231,283, and U.S. Pat. No. 5,763,806 use optical sensing techniques to sense key movement from underneath the piano keys. None of these however have addressed sensing the black and white keys from atop the keys. It would be desirable to have a portable key sensing apparatus for over the top of the keys. 
   U.S. Pat. No. 4,790,230 discloses a keyboard device that is mounted on top of a keyboard and uses optical sensing for detecting key movement. However, while the invention detects key movement, it uses the visible portions of the keys for key sensing. U.S. Pat. No. 4,790,230 also has a challenging effort to sense black key movement accurately due to the black color of the black keys. Further, U.S. Pat. No. 4,790,230 or any patent that uses optical techniques in a portable device for sensing key movement from atop the keys must attempt to correct or compensate key sensing information from ambient light, and in some cases protect the device from damage or erroneous key-note information due to high levels of ambient light. 
   When using optical sensing, it would be desirable to eliminate the ambient light problem in dealing with an optical sensing technique from atop the keyboard. It would also be desirable to not use the obvious visual portion of the keys to detect key movement because of this problem and to further reduce the size of the apparatus. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates to a system for use with a piano, organ, or musical keyboard. The system preferably comprises an insertable sensor disposed atop the keyboard to sense both white and black key movement and circuitry to process sensor signals and transmit at least key-note ON/OFF information and key-note velocity. The system preferably comprises an insertable sensor insertable between a top surface of keys and a bottom surface of a fallboard. The system also preferably comprises an insertable protector to protect sensors from ambient light interference. 
   The insertable sensor detects key depression. The system preferably comprises a sensing strip operatively connected to the sensor for sensing movement of a portion of the key hidden from view. This sensing strip operatively connects to one or more sensors per key to sense a proportional amount of hidden key movement. 
   The sensor preferably comprises an energy contact and a corresponding energy receiving contact that by itself or when combined with another sensor produces an electrical signal strength proportional to movement of the key. The energy contact preferably comprises an optical emitter and an optical receiver that converts reflected optical energy provided by a key surface to an electrical signal proportional to displacement of the key. 
   The sensing strip can be operatively connected to a flexible strip that moves in relation to an associated key and provides energy to the sensing strip that is proportional to an amount of movement of the key. The sensing strip and the flexible strip can comprise a magnetically coupled emitter and receiver that converts a magnetic field strength to a corresponding electrical signal proportional to a displacement of the key. 
   The sensing strip and flexible strip can comprise a capacitively coupled emitter and receiver that converts an electric field strength to a corresponding electrical signal proportional to a displacement of the key. 
   The system can comprise a piezo-electric strip that converts mechanical energy to a negative or positive electrical signal proportional to a pressure by which the key is depressed or released. 
   The system sensing strip and flexible strip can comprise two or more electrical contact point pairs electrically biased that close when the key is at rest and open sequentially as the key is depressed. The sensing strip and flexible strip can comprise two or more optical coupler switches electrically biased that are switched on when the key is at rest and open sequentially as the key is depressed. 
   The present invention provides protection against unwanted ambient light and does not use the visual portion atop the keys. The present invention uses the combination of internal sensing and portable installation atop the keys to sense key movement. The present invention takes advantage of the inconspicuous narrow slot formed between the fallboard and the key when any key is depressed. The present invention provides a sensor strip that is installed between the keys and fallboard. Interconnecting circuitry contained in the present invention attaches the inserted sensor strip to a local circuit board or unit that processes, analyzes, and converts the key movement into a format suitable for further transmission to a computer or musical device sharing the same protocol and physical interface such as MIDI. 
   The rectangular design of the external vertical circuit board provides an ideal mounting means that eliminates the need for end-mounting hardware and provides stability during use. If the gap between the black keys and the fallboard is too wide, an additional rectangular strip can be sandwiched with the external vertical circuit board and its cover to keep the present invention firmly in place. Virtually any sensing device type can be used to detect key movement from atop the keys and inserted under the fallboard. 
   Accordingly, it is a primary object of the present invention to provide a portable, lightweight, and unobtrusive apparatus for sensing piano/keyboard key movement that is mounted atop the keyboard and senses key movement from the portion of the white and black parts that is hidden from view. 
   It is another object of the present invention to disclose various ways to sense key movement. 
   It is another object of the present invention to provide a simple attachment means utilizing the mechanical design of the device to easily insert under the fallboard and mount atop the keyboard to eliminate ambient light from affecting the sensor strip. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the present invention and are not to be construed as limiting the present invention. In the drawings: 
       FIG. 1  is a perspective cutaway view of a representative portion of a piano/keyboard and how the present invention would appear from atop of the keyboard (the perspective view illustrates an external vertical printed circuit board operatively connected to a sensing strip that inserts into the keyboard between the keys and underneath the fallboard); 
       FIG. 2A  illustrates a representative portion of the present invention fitted with at least one pair of optical transmissive couplers for each key; 
       FIG. 2B  illustrates how the present invention would appear after installation into the piano keyboard; 
       FIG. 2C  illustrates the principle for sensing key movement using optical-transmissive coupling off the keys; 
       FIG. 3A  illustrates a representative portion of the present invention fitted with at least one pair of optical transmissive couplers and a flexible reflective strip for each key; 
       FIG. 3B  illustrates how the present invention would appear after installation into the keyboard after installation into the piano keyboard; 
       FIG. 3C  illustrates the principle for sensing key movement using optical-transmissive coupling off the flexible reflective strip; 
       FIG. 4A  illustrates a representative portion of the present invention fitted with at least one pair of discrete sensing devices that are positioned on the sensing strip and on the flexible strip member; 
       FIG. 4B  illustrates how the present invention would appear after installation into the keyboard after installation into the piano keyboard; and 
       FIG. 4C  illustrates the principle for sensing key movement using the various sensing devices located on both the sensing strip and the flexible strip. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , the present invention is inserted into the keyboard from atop the keys with sensing strip  21  inserted between the keys and the bottom side of fallboard  11 . Sensing strip  21  comprises of a thin circuit board. Sensing strip  21  electrically connects to external circuit board  13  at a right angle. Circuit board  13  sits externally while sensing strip  21  is inserted and hidden from view. Once in place, the sensing devices rest over the top of their respective internal key surfaces. Technology has advanced to ultra-miniature sensing devices to keep the profile of sensing strip  21  board and parts extremely low. 
   As illustrated in  FIG. 3B , when the key is in the KEY UP position, reflective flexible member  24  is at its closest proximity to the sensing strip  21 . Each reflective flexible member  24 , emitter  22  and receiver  23  and the amount of reflected energy is at its maximum. 
   As shown in  FIGS. 2–4 , each sensing device provides for energy emitting device ( 22  or  42 ) and energy receiving device ( 23  or  43 ). The amount of emitted or received energy-gain is adjusted during the initialization and calibration setup of the overall system. The amount of received energy is at its maximum when the key is at rest and the amount of detected energy is at its minimum when the key is depressed. The detected received energy levels generated by the key movement detected is acquired and compared to predetermined key ON/OFF thresholds. Key movement velocity is determined based the acquisition system measurements and calculations. Sensing devices described herein are optical, magnetic, capacitive, piezo-electric, and mechanical contacts. At least one sensing device pair per key is inserted between the key and fallboard and any combination of sensing device types can be utilized for any or all keys. 
   In all cases, sensing receiver  23  or  43  senses emitter energy  22  or  42 . With the exception of the optical transmissive coupler embodiment shown in  FIG. 2 , an opposing flexible strip member is used as shown in  FIG. 3  and  FIG. 4 . In  FIG. 3A , flexible reflective strip member  24  is used. In  FIG. 4A , flexible circuit strip member  44  is used. 
   The exploded view of  FIG. 2A  shows the present invention fitted with at least one optical-transmissive coupler  22 ,  23  per key. As shown in  FIG. 2B  in the KEY UP position, the light received by the receiver  23  is at its maximum. As shown in  FIG. 2C , as the key is played and moves to the KEY DOWN position, the key underneath the sensing strip sensing device moves down and away from emitter  22  and receiver  23 . Less light from emitter  22  is reflected off the key and back to receiver  23 , and receiver  23  signal decreases. 
   The exploded view of  FIG. 3A  shows the present invention fitted with at least one optical-transmissive coupler  22 ,  23  per key and reflective flexible member  24 . Reflective flexible member  24  is used in the case where the natural reflectivity of the key is not suitable for direct light reflection. Reflective flexible member  24  can also be made up of a piezo-electric element. This arrangement would serve two purposes: flexible reflective piezo member  24  reflects light from emitter  22  back to optical receiver  23 , and flexible reflective piezo member  24  would generate an electrical signal proportional to the velocity by which the key was depressed or released. 
   As illustrated in  FIG. 3C , as the key is depressed to the KEY DOWN position, reflective flexible member  24  moves downward underneath sensing strip  21 . Reflective flexible member  24  moves away from emitter  22  and receiver  23 . Less light from emitter  22  is reflected back to receiver  23 , and receiver  23  signal decreases. If reflective flexible member  24  is piezo-electric material, its movement downward generates an electrical signal proportional to the velocity by which the key was depressed or released. 
   The exploded view of  FIG. 4  shows the present invention with sensing strip  21  accommodating receiver  43  and flexible strip member  24  accommodating the emitter  42 . The position of emitter  42  and receiver  43  are interchangeable. As illustrated in  FIG. 4B , when the key is in the KEY UP position, emitter  42  and receiver  43  are at their closest proximity to each other and the amount of received energy is at its maximum. As illustrated in  FIG. 4C , as the key is depressed to the KEY DOWN position, flexible member  24  moves downward accordingly and moves away from sensing strip  21 . Emitter  22  moves away from receiver  23  accordingly. Less energy is received by receiver  43 , and receiver  43  signal decreases. 
   Sensing strip  21  and flexible strip member  44  of  FIG. 4  can also comprise a series of electrical conductive pads. Flexible strip member  44  is biased with step voltages at the conductive pads. When the key is up and at rest, the conductive pads on the flexible strip member make contact with all contact pads located on the sensing strip. The received voltage is at its maximum in this position. As the key is depressed, fewer conductive pads are in contact between sensing strip  21  and flexible strip member  44 , and the received voltage begins to step down in strength. When the key is down, no or few pads are in contact, and the received voltage is at its minimum. 
   Although the present invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.