Optoelectronic device for a piano

Abstract

This invention relates to the field of musical instruments, specifically to a photoelectric device for a piano. The device comprises a sound-dampening baffle, a sound-dampening baffle cushion, a damping pad, a torsion spring, a main shaft support, a swivel arm hook, and a scanning circuit board mainly composed of several reflective infrared photoelectric sensors. The scanning circuit board is connected to a flexible thin-film cable. The sound-dampening baffle is divided into several segments, each with a slot on its surface. The scanning circuit board and the flexible thin-film cable are respectively embedded in the slots of the sound-dampening baffle. The back of each scanning circuit board faces the sound-dampening baffle, and the circuit detection unit on the front of the scanning circuit board faces the hammer shank of the piano action, respectively engaging with a reflective block on the hammer shank of the piano action. The circuit detection units on the scanning circuit board are electrically connected in a row-column arrangement. Compared with existing technologies, this invention has the advantages of novel design, reasonable structure, simple installation, strong practicality, and suitability for installation on most upright pianos.

Description

Technical Field

[0001] This invention relates to the field of musical instruments, specifically to an optoelectronic device for a piano. Background Technology

[0002] Due to their simple structure and easy installation, reflective infrared photoelectric sensors are currently used in high-value silent pianos as keyboard scanning circuits. These circuits often require various chips for MCU control, resulting in relatively high costs, complex circuitry, and large board sizes for keyboard matrix scanning circuits used in silent pianos. In typical silent pianos, the soundproofing baffle (which blocks the piano hammers from striking the strings) and the keyboard detection scanning circuit (which reads key movements) are both components of the soundproofing system, but they are separate subsystems installed separately rather than as an integrated unit. The keyboard scanning circuit, installed in the narrow space below the piano keys, can sometimes be affected by environmental factors such as deformation of the piano's center plate and keyboard frame, or wear and tear over the years, leading to changes in position or repairs. This can cause the photoelectric sensor and its scanning circuit board, with their limited sensing range, to be unable to switch and compare on / off states, or the photoelectric sensor to remain either within or outside the reflective sensing area, preventing the photoelectric sensor and its scanning circuit board from functioning properly.

[0003] Chinese utility model patent CN202796012U discloses a piano mute device, which includes a mechanical damping system and an electronic scanning system. The mechanical damping system is located between the piano action and the strings to prevent the hammers from striking the strings. The electronic scanning system is located below the keys to quickly and alternately detect the sensors corresponding to each key. Due to the limited space under the keys and the varied environmental conditions, the piano's center plate and keyboard frame may deform or be worn down over time, requiring repositioning or repair. This can cause the sensors in the electronic scanning system to malfunction and become inaccurate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a piano photoelectric device with simple circuit, few components, small circuit board, good reliability and consistency, sensitive response, relatively low cost, not easy to deform, and simple process. Moreover, the device integrates the silent baffle and scanning circuit.

[0005] To achieve the above objectives, a photoelectric device for a piano is designed, comprising a sound-dampening baffle, a sound-dampening baffle cushion, a damping pad, a torsion spring, a main shaft support, a pivot hook, and a scanning circuit board mainly composed of several reflective infrared photoelectric sensors. The scanning circuit board is connected to a flexible thin-film cable. The sound-dampening baffle is divided into several segments, each with a slot on its surface. The scanning circuit board and the flexible thin-film cable are respectively embedded in the slots of the sound-dampening baffle. The back of each scanning circuit board faces the sound-dampening baffle, and the circuit detection unit on the front of the scanning circuit board faces the hammer shank of the piano's action mechanism, respectively connected to the hammer shank of the piano's action mechanism. The reflective blocks on the upper part of the circuit board are electrically connected in rows and columns to form 88 infrared photoelectric matrix scanning circuits. By acquiring the hammer handle movement information, the main control board calculates the playing and force of the keyboard. The circuit detection unit includes a switching circuit composed of resistors, diodes, and two NPN transistors. The bases of the two transistors are connected in series with resistors or diodes and then connected to the emitter output terminal of the photosensitive receiver tube in the infrared photoelectric sensor. The resistance value and voltage drop of the resistor or diode connected in series with the bases of the two transistors are different, and the switching thresholds of the gate circuits of the two transistors are also different, forming a time difference between the gate opening and closing.

[0006] The present invention also has the following preferred technical solutions:

[0007] 1. The 88 hammer handles correspond to 88 detection circuit units mainly composed of infrared photoelectric sensors. Each unit is electrically connected to each other in a row and column relationship to form an 8*11 array matrix scanning circuit.

[0008] 2. The scanning circuit board is a PCB board with a width of less than 16 mm. The components of each detection circuit unit are soldered on the surface. The spacing of the infrared photoelectric sensors of each detection circuit unit corresponds to the spacing of the hammer handle of the action. The back of the scanning circuit board has parallel wiring in the shape of ribbon cables.

[0009] 3. The flexible film cable is located between the scanning circuit board and the silent baffle. One end of the flexible film cable is connected to the scanning circuit board, and the other end is inserted into the socket of the cable adapter board and then transferred to the main control board. The flexible film cable is narrower than the scanning circuit board.

[0010] 4. The slot on the surface of the silent baffle is dovetail-shaped, and the total thickness of the scanning circuit board and components and the height of the slot are both lower than the thickness of the silent baffle buffer pad.

[0011] 5. It also includes an adapter plate bracket, the main body of which is L-shaped. One side of the L-shape is connected to the cable adapter plate, and the other side of the L-shape is connected to the rotating arm hook. The adapter plate bracket has a through hole located above the clamp-shaped hook of the rotating arm hook for inserting the pin of the torsion spring covered with a plastic sheath.

[0012] 6. The cable adapter board is led from the flexible flat cable through the gap between the top cover and the piano back plate (marker) to the outside of the piano, and connected to the main control board box with external counterweight. The bottom of the main control board box is provided with multiple sets of baffles connected by parallel cylindrical shafts. The baffles can be rotated 90 degrees to be opened. The opened baffles are perpendicular to the bottom plate of the main control board box and parallel to the front panel of the main control board box. Alternatively, they can be embedded in the main control board box, parallel to the bottom plate of the main control board box and perpendicular to the front panel of the main control board box.

[0013] 7. The main shaft support is fixed to the firing mechanism frame by bolts. The shaft at the end of the mute baffle is inserted into the ring at the top of the main shaft support and extends out to connect to the arm hook. The arm hook is connected to one end of the wire rope, and the other end of the wire rope is connected to the mute control switch.

[0014] 8. One end of the rotating shaft of the silent baffle with a through hole at the end is fastened together with the rotating arm hook and the adapter plate bracket with screws, and the other end is inserted into the ring of the rotating shaft sub-bracket and then extends out to connect with the locking shaft ring.

[0015] 9. A double P-clamp pivot bracket is provided between different sections of the mute baffle. The side of the double P-clamp pivot bracket is shaped like two symmetrical irregular P-shapes coming together. The P-shapes come together to form an upper hollow circle that clamps the pivot of the mute baffle with a slightly smaller diameter. The top of the symmetrically joined P-shapes is connected by a thin plastic sheet. The bottom of the symmetrically joined P-shapes is provided with interlocking buckles. The lower part of the hollow circle of the double P-clamp pivot bracket is provided with screw slots for connecting the action frame. The double P-clamp pivot is fastened to the threaded hole of the bracket on which the damper striker is originally installed in the action frame by screws.

[0016] Compared with the prior art, the advantages of this invention are:

[0017] This invention features a novel design that relies on a simple reflective infrared light sensor detection circuit. By placing the scanning circuit board within the slot of the mute baffle, the infrared photoelectric matrix scanning circuit and the mute baffle are integrated into one unit. This design is structurally sound, low in cost, easy to install, highly practical, and suitable for installation on most upright pianos. Attached Figure Description

[0018] Figure 1 This is a side view of the device of the present invention installed on a piano action mechanism;

[0019] Figure 2 This is a circuit diagram of the infrared photoelectric matrix scanning circuit in the device of the present invention;

[0020] Figure 3 This is a schematic diagram of the front of the infrared photoelectric matrix scanning circuit board in the device of the present invention;

[0021] Figure 4 for Figure 3 Schematic diagram of the reverse side of the infrared photoelectric matrix scanning circuit board;

[0022] Figure 5for Figure 3 A magnified view of a portion of the image;

[0023] Figure 6 for Figure 4 A magnified view of a portion of the image;

[0024] Figure 7 This is a side view of the silent baffle plate on which the infrared photoelectric matrix scanning circuit board is installed in the device of the present invention;

[0025] Figure 8 for Figure 7 A side view of the assembly with a rotating arm hook installed at one end of the silent baffle;

[0026] Figure 9 for Figure 8 A frontal view of the noise-reducing baffle assembly;

[0027] Figure 10 This is a side view of an infrared photoelectric matrix scanning circuit board installed below a piano keyboard.

[0028] In the diagram: 1. Silent baffle buffer pad; 2. Scanning circuit board; 3. Reflector block; 4. Keyboard key; 5. Keyboard bracket; 6. Silent wrench box; 7. Wrench; 8. String; 9. Action frame; 10. Hammer handle; 11. Damper head; 12. Damper snap pad; 13. Photoelectric sensor; 14. Silent baffle; 15. Torsion spring; 16. Main shaft support; 17. Rotary arm hook; 18. Steel wire rope; 19. Pedal; 20. Pedal sensor plate; 21. Slot; 22. Flexible film cable; 23. Plastic sheath; 24. Adapter plate support; 25. Locking ring; 26. Secondary shaft support; 27. Double P-clamp shaft support; 28. Cable adapter plate; 29. ​​Main control board box; 30. Baffle plate; 31. Flexible flat cable. Detailed Implementation

[0029] The invention will be further described below with reference to the accompanying drawings. The structure and principle of the invention are very clear to those skilled in the art. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0030] Figure 1This is a basic structural diagram of the present invention. The mute baffle 14 replaces the damper strike block in a typical piano action. Therefore, a damper strike pad 12 is provided on the plate opposite the mute baffle 14 and the damper head 11 to prevent the damper head 11 from striking the mute baffle 14 and producing noise when the keys are played. On the front of the plate opposite the mute baffle 14 and the hammer handle 10, there are mute baffle buffer pads 1 and scanning circuit boards 2 with infrared photoelectric sensors 13 soldered onto them. The circuit detection units on each scanning circuit board 2 cooperate with the reflective blocks 3 on the hammer handle 10 of the piano action. The circuit detection units on the scanning circuit board 2 are electrically connected in a row-column relationship to form an infrared photoelectric matrix scanning circuit. By acquiring the hammer handle 10's movement information, the main control board calculates the keystroke and force. The pivot at the end of the mute baffle 14 is inserted into a ring on the upper part of the pivot main bracket 16, which is fixed to the action frame 9 with screws. The diameter of the ring is slightly larger than the diameter of the pivot of the mute baffle 14, allowing the pivot to rotate smoothly within the ring. The end of the pivot of the mute baffle 14 extending out of the ring is connected to the arm hook 17, which has two claw hooks for hooking the end of the wire rope 18. The other end of the wire rope 18 is connected to the wrench 7 in the mute wrench box 6. In practice, the other end of the wire rope 18 can also be connected to the piano pedal 19, and the movement of the wire rope 18 is controlled by the pedal 19, rather than by the wrench 7.

[0031] In silent mode, when the wrench 7 is pulled forward, the steel wire rope 18 in the sleeve is tightened, and the rotating arm hook 17 is pulled downward. Since the rotating arm hook 17 is firmly connected to the rotating shaft of the silent baffle 14, the silent baffle 14 rotates and tilts forward. At this time, the key 4 on the piano keyboard frame 5 is played. The key 4 pushes the piano action linkage mechanism to act, causing the hammer handle 10 and the hammer head at the top to strike the piano string 8. Due to the obstruction of the forward tilt of the silent baffle 14, the hammer handle 10 and the silent baffle buffer pad 1 collide, preventing the hammer head from striking the string 8. The string 8 is silenced and does not vibrate or produce sound. When the hammer handle 10 strikes the silent baffle buffer pad 1, the infrared light emitted by the reflective photoelectric sensor 13 on the scanning circuit board 2 below the silent baffle buffer pad 1 is reflected by the corresponding reflective block 3 on the hammer handle 10 and then received by the photoelectric sensor 13. The scanning circuit board 2 thus obtains the signal and intensity information of the piano key playing, which is transmitted through the electrically connected flexible film cable 22 and transferred to the main control circuit through the cable adapter plate 28. After the microprocessor calculates, it controls the electronic sound source to emit the corresponding musical audio for playback by the speaker or headphones.

[0032] When wrench 7 is pulled back, it is in the position of Figure 1When in the middle position, the piano exits the silent mode, the steel cable 18 is loosened, the torsion spring 15 on the pivot of the silent baffle 14 rebounds, causing the arm hook 17 to rotate upward, the silent baffle 14 plate rotates and tilts backward, the silent baffle buffer pad 1 no longer blocks the hammer handle 10, at this time the key 4 on the piano keyboard frame 5 is played, the action mechanism causes the hammer head at the top of the hammer handle 10 to strike the string 8 and vibrate to produce sound. At this time, the reflective photoelectric sensor 13 on the scanning circuit board 2 below the silent baffle buffer pad 1 is located in the slot 21 near the rotating shaft. Even with a small backward movement, it can still obtain the signal and intensity information of the piano key playing from the corresponding reflective block 3 on the hammer handle 10. This signal is transmitted via the electrically connected flexible film cable 22 through the cable adapter plate 28 to the main control circuit. After processing, the microprocessor controls the electronic sound source to emit corresponding musical audio for playback by speakers or headphones. If the electronic sound source emits musical audio of other instrument timbres, it is superimposed with the original piano sound, achieving a dual-timbre effect. If the reflective photoelectric sensor 13 on the scanning circuit board 2 is located in the slot 21 near the silent baffle buffer pad 1, when the silent baffle 14 tilts backward, the backward movement is greater than that near the rotating shaft. The ability of the photoelectric sensor 13 to acquire infrared light from the reflective block 3 will be weakened, while the reflection is normal when tilted forward.

[0033] Figure 1 The reflective block 3 on the hammer handle 10 can control the reflection distance by attaching felt of different thicknesses, and also relaxes the allowable error of the deviation between the hammer handle 10 and the photoelectric sensor 13. It expands the arc surface of the round handle into a plane with a larger and better reflective surface. The reflective block 3 can be a lightweight elastic plastic ring glued to the hammer handle 10. The geometric surface of the infrared photoelectric sensor 13 on the scanning circuit board 2 facing the silent baffle 14 is a light color suitable for infrared light reflection. At the same time, a soft light-colored felt of appropriate thickness can be glued to the geometric surface to prevent impact. In implementation, reflective blocks 3 are set on each of the 88 hammer handles 10 of each piano action, corresponding to the reflective photoelectric sensor 13 in the scanning circuit board 2.

[0034] exist Figure 1 The diagram also illustrates that the piano is equipped with a pedal sensor plate 20, whose purpose is to transmit the pedal 19's pedal input signal to the main control circuit microprocessor, thereby producing the corresponding musical sound effect. (For ease of explanation,...) Figure 1 The cable adapter board 28 is not shown in the diagram, as it would obstruct the display of the silent baffle buffer pad 1 and the scanning circuit board 2. In practice, a flexible flat cable 31 with a plug can be used to connect one end to the cable adapter board 28 and the other end to the main control board. Figure 1 The diagram illustrates the main control board box 29 located on the top of the piano, with the flexible flat cable 31 connected to it being introduced into the piano through the gap between the top cover and the back of the piano to connect to the cable adapter board 28. Figure 1In this design, the baffle 30 is installed to prevent the main control board box 29 from moving backward when the panel is operated. One side of the baffle 30 is located at the bottom of the main control board box 29, connected to a cylindrical shaft, allowing it to rotate 90 degrees and embed itself tightly into the main control board box 29, preventing it from falling out. Multiple sets of baffles 30 connected by parallel cylindrical shafts facilitate the selection of suitable protruding parts of the main control board box 29. The baffle 30 can be rotated 90 degrees to be perpendicular to the bottom plate of the main control board box 29 and parallel to its panel. A counterweight can be placed on the rear side inside the main control board box 29 to enhance stability.

[0035] Figure 2 This is a circuit diagram of an infrared photoelectric matrix scanning system with 88 piano keys. Due to space limitations, some circuits and labels have been omitted; this is only a schematic diagram. The detection circuit unit, mainly composed of an infrared photoelectric sensor, includes resistors, diodes, and a switching circuit consisting of two NPN transistors. The bases of the two transistors are connected in series with a resistor or diode to the emitter output terminal of the photosensitive receiver in the infrared photoelectric sensor. Because the resistance and voltage drop of the resistor or diode connected in series with the bases of the two transistors are different, the switching thresholds of the two transistor gate circuits are also different, resulting in a time difference between gate switching. In the diagram, N01 to N88 are reflective photoelectric sensors, internally consisting of an infrared emitting diode and a phototransistor; RL1 to RL22 are the series resistors for the infrared emitting diodes within photoelectric sensors N01 to N88, respectively. The DC power supply E, filtered by an LC filter and connected in series with an RL resistor, supplies power to the four series-connected photoelectric sensor emitting diodes; R01 to R88 are the emitter resistors for the phototransistors within photoelectric sensors N01 to N88, which, together with the phototransistors, form an emitter follower circuit to amplify the current and improve the load capacity; T010 to T880 are for detecting each piano key 4 and the hammer handle, respectively. The starting timing switch transistor for the operation of reflector block 3 is an NPN type; R010 to R880 are the base limiting current resistors of switching transistors T010 to T880 respectively; T011 to T881 are the ending timing switch transistors for detecting the operation of each key 4 and hammer handle 10 reflector block 3, also NPN type; D01 to D88 are the base series diodes of switching transistors T011 to T881 respectively; D010 to D880 are the isolation diodes of switching transistors T010 to T880 respectively; D011 to D881 are the isolation diodes of switching transistors T011 to T881 respectively.

[0036] Figure 2The basic circuit detection unit consists of a photoelectric sensor and its emitter resistor, a start timing switch transistor and its base current-limiting resistor and isolation diode, and a stop timing switch transistor and its base series diode and isolation diode. The entire infrared photoelectric scanning circuit consists of 88 detection circuit units. Taking the photoelectric sensor N01 corresponding to the first key 4 and hammer handle 10 as an example, the working principle of the detection circuit unit is as follows: The DC power supply E, which can be +5V in practice, is current-limited and voltage-reduced by the series resistor RL1, so that the emitter diode in the photoelectric sensor N01 is in a stable infrared light emission working state. When the first key is played, the reflector block 3 on the corresponding hammer handle 10 will gradually approach the photoelectric sensor N01 and reflect the infrared light emitted by its internal emitter diode back to the surface of the photoelectric sensor N01. The phototransistor receives the light, generates a photocurrent, and amplifies it for output. The voltage of the emitter resistor R01 will gradually increase accordingly. When the threshold is reached, the switching transistor T010 is turned on. The scanning signal sent from port T by the main control board is then transmitted through the isolation diode. D010 outputs from the emitter of switching transistor T010 to the start timing port MK, initiating timing on the main control board. Due to the base of switching transistor T011 connected in series with diode D01, the voltage across the emitter resistor R01 gradually increases to approximately 0.7 volts above the conduction threshold of T010, turning on switching transistor T011. The scan signal sent from port T by the main control board then passes through isolation diode D011 and the emitter of switching transistor T011 to the stop timing port BR, stopping timing on the main control board. Based on Newton's second law, which states that acceleration is proportional to force, the main control board calculates the acceleration of reflector 3 based on the timing results, thereby determining the playing force and mapping the corresponding strong / weak key positions of the musical note according to the system hardware's preset force curve. In practice, the base of switching transistors T011 to T881 connected in series with diodes D01 to D88 can also be replaced with a series resistor.

[0037] A piano keyboard consists of 88 keys, and the entire infrared photoelectric scanning circuit is composed of 88 detection circuit units. In practice, it can be decomposed into a matrix scanning circuit with several horizontal rows and vertical columns forming a row-column relationship. Figure 2This diagram illustrates the entire infrared photoelectric matrix scanning circuit, composed of 11 rows and 8 columns of basic circuit detection units. The emitters of the start-timing transistors in each row are interconnected via the same MK port start-timing signal output line, and the emitters of the stop-timing transistors in each row are interconnected via the same BR port stop-timing signal output line. The start-timing signal output lines at the MK port and the stop-timing signal output lines at the BR port are shared by the 8 detection circuit units in the same row. Meanwhile, the anodes of the isolation diodes in each column are interconnected via the same T port signal input line. Therefore, an 88-key piano keyboard can be constructed using the same column of... The 11 detection circuit units share the same 8 T-port signal input lines. When the main control board is working, it sends scan signals to the 8 T-port signal input lines in sequence. When a key is played, the movement of the related hammer handle causes the photoelectric sensor in the corresponding detection circuit unit to detect the reflected photocurrent, which causes the emitters of the start timing transistor and the stop timing transistor to conduct in sequence. Thus, the main control board reads the scan signals from the MK port and BR port in sequence, calculates the playing force of the key, obtains the relevant key position according to the row and column relationship mapping table, and emits musical sounds of corresponding strength.

[0038] Because the components constituting the detection circuit unit have low power consumption, their surface mount size is also small. The entire infrared photoelectric matrix scanning circuit, composed of 88 detection circuit units, does not require a large integrated chip. Therefore, in implementation, the circuit can be laid out on a scanning circuit board 2 with a width of less than 16 mm. The surface layer is the component soldering layer, and the back layer is the wiring layer. Common ground and power supplies are also wider and laid out on the back side. Figure 3 , Figure 4 and Figure 5 , Figure 6 As shown. A photoelectric sensor 13 with a patch thickness of less than 2 mm is selected, and other resistors, capacitors, diodes, and transistors are even thinner. Therefore, the total thickness of the PCB board and components can be less than 4 mm, lower than the typically thicker 5 mm or more of the silent baffle buffer pad 1. Furthermore, by grouping according to the different number of keys and string arrangement of a piano, the entire infrared photoelectric matrix scanning circuit can be divided into multiple PCB board segments, typically three groups (high, medium, and low), with each group having a maximum of 40 keys. Correspondingly, the entire infrared photoelectric matrix scanning circuit can be composed of three scanning circuit boards 2. In implementation, a flexible thin-film cable 22, slightly narrower than the scanning circuit board 2, can be directly soldered to the copper foil ribbon cable at the back end of the scanning circuit board 2, and reinforced with resin to prevent the soldered flexible thin-film cable 22 from peeling off.

[0039] Figure 7 and Figure 8The diagram illustrates the profile cross-section of the soundproof baffle 14. The upper strip and the lower pivot are integrated. The front strip of the soundproof baffle 14 has a dovetail-shaped slot 21 with a height of less than 4 mm. The slot 21 is embedded with a scanning circuit board 2, which contains a photoelectric sensor 13. A slightly narrow flexible film cable 22 is laid between the scanning circuit board 2 and the soundproof baffle 14. The flexible film cable 22 sandwiched in the middle is generally 1 to 3 layers. A soundproof baffle buffer pad 1 is provided above the slot 21 on the front strip of the soundproof baffle 14. It is usually glued to the soundproof baffle 14 by rubber strips or felt strips. A sound-damping pad 12 is glued to the back of the soundproof baffle 14.

[0040] Figure 8 and Figure 9 The diagram illustrates the complete assembly of the soundproof barrier 14. The swivel hook 17 is installed at the right end of the soundproof barrier 14, meaning the steel cable 18 that tilts the soundproof barrier 14 forward and backward is located on the right side of the piano. In practice, depending on the internal space of the piano or customer requirements, the steel cable can also be placed on the left side of the piano; simply press... Figure 8 and Figure 9 The silent baffle assembly can be manufactured by mirroring the schematic diagram.

[0041] Figure 8 The rotating arm hook 17 is a strip-shaped metal piece with a U-shaped cross-section. One end has a round hole for inserting the end of the shaft of the silent baffle 14; the other end has two claw hooks for hooking the end of the wire rope 18. Above the rotating arm hook 17 is an L-shaped adapter plate bracket 24. Four threaded holes on one side of the L-shape are used to fix the square cable adapter plate 28; two holes on the other side of the L-shape are used to connect the rotating arm hook 17. One of the holes is used to fasten the shaft of the silent baffle 14 with a through hole at the end, the rotating arm hook 17, and the adapter plate bracket 24 together with screws. The adapter plate bracket 24 also has a through hole above the clamp-shaped hook of the rotating arm hook 17 for inserting the pin of the torsion spring 15 with a plastic sheath 23. The plastic sheath 23 is used to prevent the torsion spring 15 from vibrating and causing noise. The other pin of the torsion spring 15 is embedded in the limiting groove of the main shaft bracket 16.

[0042] Figure 9 The middle silencer 14 is grouped according to the hammers of the action's tone range. Typically, a piano action has three hammer groups: treble, alto, and bass. Each group is connected by a steel support, the action frame 9, which serves as both a connection between the action and the main piano component (the sound source marker) and a fixation point for the damper's rebound. Therefore, the silencer 14, replacing the damper's rebound point, is connected to the four steel supports between the hammer groups by a main pivot support 16, one or more double-P-clamp pivot supports 27, and a secondary pivot support 26. To avoid obstruction of the forward- and backward-leaning silencer 14 by the vertical steel supports of the action, the thin plate at the obstructing part of the silencer 14 is sawn off, leaving only the circular pivot portion. Therefore, the diagram illustrates... Figure 9 The silent baffle 14 is divided into three parts: left, middle, and right. Correspondingly, the scanning circuit board 2 inserted into the slot 21 is also divided into three pieces. Each board is electrically connected to the main control board via three flexible thin-film cables 22 and then to the cable adapter board 28. The middle circuit board covers the left thin-film cable within the slot 21, while the right circuit board overlaps and covers the middle and left thin-film cables within the slot 21. Thin film sheets can be used to line the left and middle circuit boards to fill the slot 21. Adhesive is applied to the scanning circuit board 2 and the slot 21 to prevent unnecessary displacement of the scanning circuit board 2 within the slot 21 due to vibration. Thin buffer pads are attached to both sides of the exposed flexible thin-film cables 22 not covered by the circuit boards within the slot 21 to prevent noise during vibration.

[0043] During implementation, to facilitate the installation and adjustment of the mute baffle 14, a double P-clamp pivot bracket 27 is provided between different sections of the mute baffle 14. The upper part of the side shape of the double P-clamp pivot bracket 27 is hollow, and the lower part is vertical. The double P-clamp pivot bracket 27 can be made of high-strength engineering plastic. The side shape is two roughly symmetrical irregular P-shapes that come together to form an upper hollow circle that can clamp the pivot of the slightly smaller diameter mute baffle 14. To prevent it from falling off, the top of the symmetrically joined P-shapes is connected by a thin plastic sheet, and the bottom of the symmetrically joined P-shapes is provided with interlocking buckles. The lower part of the hollow circle of the double P-clamp pivot bracket 27 is provided with screw slots for connecting the action mechanism bracket. Thus, the double P-clamp pivot bracket 27 can easily clamp the pivot of the mute baffle 14 and connect it to the action mechanism bracket with screws. The original mounting bracket for the damper strike block is securely fastened with threaded holes. To ensure the reliable and stable operation of the mute baffle 14, the main shaft bracket 16 and the secondary shaft bracket 26 at both ends of the mute baffle 14 have closed rings at their heads to prevent the shaft from coming out of the bracket when the mute baffle 14 tilts forward or backward under force. Since the main shaft bracket 16 and the secondary shaft bracket 26 are installed at the ends of the action without the damper head 11 obstructing them, the mute baffle 14 is easy to install and remove. The locking ring 25 is designed to prevent the mute baffle 14 from horizontally shifting along with the scanning circuit board 2, so that the misaligned scanning circuit board 2 will not fail to correctly detect the action information of the hammer shank 10, and also to prevent the shaft at the end of the mute baffle 14 from being pulled out of the ring at the head of the secondary shaft bracket 26.

[0044] Figure 2 The infrared photoelectric matrix scanning circuit can also be directly installed below the piano key 4 for detection, such as as a keyboard scanning detection circuit for an electronic keyboard. Its principle is the same as that for detecting the hammer handle, but the force curve set by the main control board will vary depending on the hardware and response time, which can be corrected by software. Figure 10This is a schematic diagram showing the scanning circuit board 2 installed below the keys 4 of a piano keyboard frame 5. In practice, a light-colored, soft felt of appropriate thickness can be selected as the reflector block 3 and glued to the bottom of the keys. However, this application method has potential drawbacks: environmental climate and stress can cause deformation of the wooden keys 4 and keyboard frame 5, and prolonged playing can lead to wear and thinning of the cushioning pads under the keys 4, potentially causing some infrared photoelectric sensors in the scanning circuit board 2 to malfunction. This invention discloses... Figure 1 The solution of mounting the scanning circuit board 2 onto the piano action mute baffle 14 eliminates the need for... Figure 2 The solution eliminates potential risks and allows the infrared photoelectric scanning circuit board 2 and the silent baffle 14 to be pre-installed as one unit, shortening the time required to install the scanning circuit board 2 and the silent baffle 14 separately. It also prevents the scanning circuit board 2 from being corroded by liquid flowing from the keyboard or from being blocked by paper pieces or other objects.

[0045] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the invention, based on the technical solutions and novel concepts of the invention, should be covered within the scope of protection of the invention.

Claims

1. A photoelectric device for a piano, comprising a scanning circuit board mainly composed of a sound-dampening baffle, a sound-dampening baffle cushion, a damping pad, a torsion spring, a main support for the pivot, a pivot arm hook, and several segments of reflective infrared photoelectric sensors, wherein the scanning circuit board is connected to a flexible thin-film cable, characterized in that... The silent baffle is divided into several sections, and each section has a slot on its surface. The scanning circuit board and flexible thin film cable are respectively embedded in the slots of the silent baffle. The back of each scanning circuit board faces the silent baffle, and the circuit detection unit on the front of the scanning circuit board faces the hammer handle of the piano action. They cooperate with the reflective blocks on the hammer handle of the piano action. The circuit detection units on the scanning circuit board are electrically connected in rows and columns to form 88 infrared photoelectric matrix scanning circuits. By acquiring the hammer handle movement information, the main control board calculates the keyboard playing and force. The circuit detection unit includes a switch circuit composed of a resistor, a diode, and two NPN transistors. The bases of the two transistors are connected in series with a resistor or a diode and then connected to the emitter output terminal of the photosensitive receiver in the infrared photoelectric sensor. The resistance value and voltage drop of the resistor or diode connected in series with the bases of the two transistors are different, and the switching thresholds of the gate circuits of the two transistors are also different, forming a time difference between the gate switching. The 88 hammer handles correspond to 88 detection circuit units mainly composed of infrared photoelectric sensors. Each unit is electrically connected to the others in a row-column relationship to form an 8*11 array matrix scanning circuit.

2. The photoelectric device for a piano as described in claim 1, characterized in that... The scanning circuit board is a PCB board with a width of less than 16 mm. The components of each detection circuit unit are soldered on the surface. The spacing between the infrared photoelectric sensors of each detection circuit unit corresponds to the spacing of the hammer shank of the action. The back of the scanning circuit board has parallel wiring in the shape of ribbon cables.

3. The photoelectric device for a piano as described in claim 1, characterized in that... The flexible film cable is located between the scanning circuit board and the silent baffle. One end of the flexible film cable is connected to the scanning circuit board, and the other end is inserted into the socket of the cable adapter board and then transferred to the main control board. The flexible film cable is narrower than the scanning circuit board.

4. The photoelectric device for a piano as described in claim 1, characterized in that... The slot on the surface of the silent baffle is dovetail-shaped, and the total thickness of the scanning circuit board and components, as well as the height of the slot, are all lower than the thickness of the silent baffle buffer pad.

Images