Scanning circuit board structure installed on front rail of piano keyboard rack

Abstract

The invention relates to the field of musical instruments, in particular to a scanning circuit board structure installed on a front piece of a piano keyboard frame, which comprises a scanning circuit board mainly composed of the front piece of the keyboard frame, a black key large woolen ring, a white key large woolen ring, a gasket, black keys, white keys, reflecting woolen blocks and an infrared photoelectric sensor, and the back of the scanning circuit board is connected with a flexible film flat cable. A long and narrow matrix scanning circuit board with an infrared photoelectric sensor pasted and welded on the surface transversely penetrates between a black key large woolen ring and a white key large woolen ring of a front gear of a piano keyboard frame, the infrared photoelectric sensor is pasted and welded on one side, close to the black key large woolen ring, of the front face of the scanning circuit board, rear protruding parts are arranged on one side, close to the black key large woolen ring, of the scanning circuit board at intervals, and screw holes are formed in the rear protruding parts. One side, close to the rear convex part, of the scanning circuit board is fixed on the keyboard frame front baffle through self-tapping screws penetrating through screw holes of the rear convex part, screw holes are formed in the other side, close to the front side edge of the white key large woolen ring, of the scanning circuit board at intervals, and the self-tapping screws penetrate through the screw holes to be fastened on the keyboard frame front baffle.

Description

Technical Field

[0001] The present invention relates to the field of musical instruments, and in particular to a scanning circuit board structure installed on the front edge of a piano keyboard frame. Background Art

[0002] Reflective infrared photoelectric keyboard scanning technology has been applied to some pianos. Patent ZL202320769826.9 "A photoelectric device for a piano" discloses a reflective infrared photoelectric switch matrix scanning circuit with a simple structure, few components and a small circuit board size. The circuit can be used in combination with the piano's action silent baffle, and the scanning circuit board is embedded in the profile guide of the silent baffle to detect the piano hammer's action, thereby obtaining information on the strength of the key playing. In addition, the circuit board can also be installed between the front and middle gears of the keyboard frame to directly monitor the action and strength of the keys. Both installation methods have their advantages and disadvantages: the first method works stably and has fine craftsmanship, but it requires the installation and maintenance of the piano's core action, which is a complex process and has high requirements; the second method is easy to install and does not affect the piano's core action, but the sensing distance between the photoelectric sensor and the bottom surface of the key is easily affected by the deformation of the keyboard frame and the bottom plate wood due to environmental climate change, which may cause the photoelectric sensor to fail to correctly receive infrared light reflections, affecting the stability of the scanning circuit. In order to solve the problem that wood is easily affected by the environment, some piano manufacturers have even developed metal casting keyboard frame bottom plates, but this material is not conducive to the stable fixation of the scanning circuit board, and it is not as convenient as screwing it into the wooden bottom plate. Therefore, it is urgent to design a scanning circuit board structure that is not affected by the climate and can maintain a stable sensing distance so that it can be installed in the front part of the piano keyboard frame. Summary of the invention

[0003] The purpose of the present invention is to solve the shortcomings of the prior art and provide a scanning circuit board structure installed on the front rail of a piano keyboard frame, which is used to make the combined structure of the piano and the circuit board compact, and the circuit board has high reliability and high response sensitivity for collecting key playing information, is not easily affected by wood deformation, and is easy to install.

[0004] In order to achieve the above-mentioned purpose, the present invention patent designs a scanning circuit board structure installed on the front rail of a piano keyboard frame, including a scanning circuit board mainly composed of a keyboard frame front rail, a black key felt circle, a white key felt circle, a gasket, black keys, white keys, a reflective felt block and an infrared photoelectric sensor, and the back of the scanning circuit board is connected to a flexible film cable, and a narrow matrix scanning circuit board with infrared photoelectric sensors soldered on the surface is across the black key felt circle and the white key felt circle of the front rail of the piano keyboard frame, the infrared photoelectric sensor is soldered on the front side of the scanning circuit board close to the black key felt circle, and the scanning circuit board is spaced apart on the side close to the black key felt circle, and a rear convex portion is provided on the rear convex portion, and a screw hole is provided on the rear convex portion, and the side close to the rear convex portion of the scanning circuit board is fixed to the front rail of the keyboard frame by self-tapping screws passing through the screw holes of the rear convex portion, and the other side of the scanning circuit board is spaced apart on the front side of the white key felt circle, and the self-tapping screws pass through the screw holes to fasten to the front rail of the keyboard frame.

[0005] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the scanning circuit board is mainly composed of 88 infrared photoelectric sensors, forming 88 detection circuit units, and the 88 circuit detection units are electrically connected in a row and column relationship to form an infrared photoelectric matrix scanning circuit, and the 88 circuit detection units correspond to detecting the bottom surfaces of 88 keys on the piano keyboard frame, and the infrared photoelectric sensor corresponding to each black key is located below the front end of the black key, and the infrared photoelectric sensor corresponding to each white key is evenly aligned with the white key flat pin in the center of the white key felt circle below the white key.

[0006] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the rear protrusion of the scanning circuit board and its screw holes are correspondingly arranged between the adjacent black keys #D / bE and #F / bG, or #A / bB and #C / bD of the keyboard, and are located below the adjacent white keys B and C, or the adjacent white keys E and F.

[0007] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the 88 infrared photoelectric sensors on the scanning circuit board respectively correspond to the white reflective felt blocks provided on the bottom surfaces of the upper black keys or white keys, and the reflective felt blocks corresponding to the black keys are located at the front end of the bottom surfaces of the black keys.

[0008] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the scanning circuit board is composed of two to four sections for realizing segmented scanning, and the back of each scanning circuit board is connected to the FFC / FPC flexible film cable, and is hidden in the gap space formed by the gasket between the scanning circuit board and the front guard of the keyboard frame, and is led out from the left and right ends of the front guard of the keyboard frame to connect to the scanning port of the sound source main control board.

[0009] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein FFC / FPC film cable sockets with opposite contact surfaces are respectively provided at both ends of the scanning circuit board, and the film cable is inserted into either the left or right end of the film cable socket to connect to the same scanning port of the sound source main control board.

[0010] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the spliced ​​ends of each scanning circuit board segment used for segmented scanning are provided with a semi-rear convex portion and a semicircular notch in the semi-rear convex portion on one side close to the large felt circle of the black key.

[0011] Preferably, the scanning circuit board structure provided by the present invention also includes other technical features, wherein the height from the top of the infrared photoelectric sensor soldered to the side of the scanning circuit board close to the black key felt circle to the front surface of the keyboard frame is more than 1 mm lower than the thickness of the black key felt circle.

[0012] Compared with the prior art, the present invention has the following better technical effects: The invention is reasonably designed and easy to install. It does not require a conventional circuit board fixing bracket, which effectively reduces costs. The connection film wiring of the scanning circuit board is hidden along the bottom of the circuit board, and the wiring is neat and orderly, while enhancing the reliability and stability of the reflective infrared photoelectric matrix scanning circuit board. This design is highly practical and suitable for various piano keyboards, which helps promote the transformation of traditional pianos to digitalization and intelligence. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described below in conjunction with the accompanying drawings.

[0014] Figure 1 It is a right side view of the structure of the present invention; Figure 2 A top perspective view of a scanning circuit board and a front rail of a piano keyboard frame in the first embodiment; Figure 3 This is a bottom view of a scanning circuit board in Embodiment 1; Figure 4 for Figure 3 A partial enlarged schematic diagram of the unconnected thin film cable; Figure 5 This is a front view of the scanning circuit board and the front rail of the piano keyboard frame of the second embodiment; Figure 6 for Figure 5 Embodiment 2 A partial enlarged schematic diagram of a scanning circuit board viewed from above; In the figure: 1. front stop of keyboard frame, 2. large felt ring of white keys, 3. flat pins of white keys, 4. self-tapping screws on the front side, 5. film cable, 6. scanning circuit board, 7. washers, 8. large felt ring of black keys, 9. flat pins of black keys, 10. white keys, 11. black keys, 12. reflective felt blocks, 13. infrared photoelectric sensors, 14. self-tapping screws on the rear convex part, 15. rear convex part, 16. middle scanning circuit board, 17. left scanning circuit board, 18. socket protrusion, 19. middle board socket protrusion, 20. left board socket protrusion, 21. middle board film cable, 22. left board film cable, 23. screw slot on the front side, 24. FFC / FPC upper socket, 25. FFC / FPC upper socket, 26. semicircular notch on the semi-rear convex part, 27. film cable connecting left and right boards, 28. left and right board connecting sockets. DETAILED DESCRIPTION

[0015] In order to make the purpose, principle and structure of the present invention clearer, the following is further described in conjunction with the accompanying drawings and specific embodiments. The technology of this structure is easy to understand for professionals. The following embodiments are exemplary, not restrictive, and are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Any replacement or change of the technical solution and concept of the present invention should be covered within the protection scope of the present invention.

[0016] Embodiment 1: See also Figure 1 The scanning circuit board 6 is located below the bottom surface of the front part of the white key 10 and the black key 11, adjacent to the white key felt circle 2 in front and adjacent to the black key felt circle 8 in the back. The infrared photoelectric sensor 13 soldered on the surface of the scanning circuit board 6 is close to the black key felt circle 8, and the surface is at least 1 mm lower than the black key felt circle 8 to prevent the bottom surface from pressing the black key felt circle 8 and hitting the infrared photoelectric sensor 13 when the key is played. The front end of the bottom of the black key 11 directly above is pasted with a reflective felt block 12, which not only enhances the reflection sensitivity of the infrared photoelectric sensor 13, but also serves as a protection against impact. In order to prevent the felt circle from being worn out after years of playing, the reflective felt block 12 is preferably pasted with white medium and low density felt to prevent the high density felt from pressing the infrared photoelectric sensor to resist the sinking of the key and affect the playing feel. Usually, there is about 8 to 10 mm of wood solid between the front end of the bottom of the black key and the flat pin groove to prevent cracking. The reflective felt block must be staggered from the large black key felt circle under the key so as not to affect the sinking depth of the key. The front end 4 to 5 mm can cover the small-size infrared photoelectric sensor underneath it. If necessary, the front end of the bottom of the black key can also be wrapped to make the reflective felt block extend forward and increase the reflection area.

[0017] See also Figure 1The scanning circuit board 6 is fixed to the front rail 1 of the keyboard frame by the front side self-tapping screws 4 and the rear convex part self-tapping screws 14 through the washers 7. The height of the surface of the infrared photoelectric sensor 13 can be controlled to be at least 1 mm lower than the black key felt circle 8 by selecting a suitable thickness of the washers 7. Usually, the thickness of the felt circle is more than 5 to 7 mm, and the infrared photoelectric sensor 13 uses a small-sized reflective detection device with a thickness of 1.5 mm. Therefore, the thickness of the washers 7 is mostly 2 to 3 mm, and the thickness of some extreme ones is 1 mm. Therefore, the washers 7 form a gap of about 1 to 3 mm between the scanning circuit board 6 and the front rail 1 of the keyboard frame. In the figure, the film cable 5 is arranged in the gap on the back of the scanning circuit board 6 and is connected to the scanning circuit board 6. During implementation, the FPC film cable can be directly welded on the copper foil of the circuit on the back of the scanning circuit board 6, or a socket can be welded on the back of the scanning circuit board 6. A small-sized FFC / FPC connector with a spacing of 0.5 mm is preferred, and its area is less than the size of a fingernail and the thickness is about 2 mm. If the gap between the scanning circuit board 6 and the front guard 1 of the keyboard frame is less than 2 mm, a 1-2 mm deep groove can be chiseled and milled at the position of the socket corresponding to the front guard 1 of the keyboard frame to accommodate the FFC / FPC connector. Since the groove is not only shallow but also small in area, it can be achieved with simple tools.

[0018] Since the length of an 88-key piano keyboard is usually greater than 1.2 meters, processing a whole printed circuit board of more than 1.2 meters is not only difficult but also costly. Usually, there are 30 port lines in the 88-key scanning matrix, plus the power supply and ground wires. The scanning circuit board that only relies on one socket to connect more than 30 ports will be very wide and will be difficult to accommodate between the gaps between the white key felt circle and the black key felt circle. Therefore, the scanning circuit board is generally composed of two to four sections, which are scanned in sections. After the segmentation, the scanning matrix circuit bus is decomposed into each section, and the segmented scanning circuit board is also narrower. Each section can be moved flexibly, making it easier to match different types of keyboards, so that the photoelectric sensor on the scanning circuit board is more evenly aligned with the flat pin in the center of each key felt circle. See Figure 2 In this embodiment, the 88-key matrix scanning circuit is preferably divided into three sections, namely: Figure 1The scanning circuit board 6 shown in the figure, the middle scanning circuit board 16 with similar structure and function to the scanning circuit board 6, and the left scanning circuit board 17 with similar structure and function to the scanning circuit board 6. Based on the technical solution disclosed in the Chinese invention patent "A photoelectric device for a piano" (application number 202320769826.9), the 30 port lines of the 88-key infrared matrix scanning circuit port can distribute the number of port lines of the three-segment scanning circuit board according to the following technical solution: 8+8 lines, 8+8 lines, 8+6 lines, that is, the three-segment scanning board has a maximum of 16 scanning lines. In the first embodiment of the present invention, it is preferred that there are 3 power supply lines and 3 ground lines, totaling 22 core cables, then the 0.5 pitch FFC / FPC film cable is 11.5 mm wide, which can be covered by the scanning circuit board and laid in the 2 mm gap space formed by the gasket between the bottom of the scanning circuit board and the front guard 1 of the keyboard frame.

[0019] See also Figure 2 First, install the scanning circuit board 6 connected to the film cable 5 on the back, and lay the film cable 5 to the left. Next, install the middle scanning circuit board 16 connected to the middle plate film cable 21 on the back, cover the film cable 5 underneath it, and lay the middle plate film cable 21 to the left. Finally, install the left scanning circuit board 17 connected to the left plate film cable 22 on the back, cover the film cable 5 and the middle plate film cable 21 underneath it, and lead them out from the left end of the keyboard frame front guard 1 together with the left plate film cable 22 to the scanning port of the sound source main control board.

[0020] This method only exposes a small amount of film wiring at the end of the front guard 1 of the keyboard frame, and the wiring is neat. To make the scanning circuit board easy to repair, replace, pack and carry, and to meet different installation requirements. In this embodiment, FFC / FPC connection sockets with opposite socket directions are set on the back of the three-segment scanning circuit board near the left and right ends. A socket can be selected nearby according to the required outlet direction. Since the edge of the 22-core 0.5 mm pitch FFC / FPC socket exceeds the outer common tangent line near the two adjacent black key felt circles 8, a protrusion can be set in the gap between the two adjacent black key felt circles 8 of the socket or other suitable gaps to place the socket. See Figure 2 In this embodiment, the left scanning circuit board 17 is provided with left board socket protrusions 20 near the left and right ends, the middle scanning circuit board 16 is provided with middle board socket protrusions 19 near the left and right ends, and the scanning circuit board 6 is provided with socket protrusions 18 near the left and right ends.

[0021] See also Figure 3 , Figure 4, the infrared light matrix scanning circuit disclosed in the Chinese invention patent "A photoelectric device for a piano" (application number 202320769826.9) is used as the technical feature of this embodiment. The copper foil on the back of the scanning circuit board 6 is a parallel wiring structure. The width of the two FFC / FPC sockets near the left and right ends exceeds the wiring part and invades the socket protrusion 18. The FFC / FPC socket pins are connected to the copper foil-shaped wiring. See Figure 3 This embodiment also shows that there are differences between the two FFC / FPC sockets on the left and right ends. One is the FFC / FPC upper socket 24, and the other is the FFC / FPC upper socket 25. The two sockets are oriented toward the left and right ends of the scanning circuit board 6 respectively. This is to ensure that after the film cable is inserted, whether it is led out from the left or right end of the keyboard frame front guard 1, it can be connected to the same sound source main control board scanning port, and the opposite socket contact surfaces achieve an equivalent effect.

[0022] See also Figure 2 It also discloses that a rear convex portion 15 and a screw hole thereof are provided on one side of the scanning circuit board to which the infrared photoelectric sensor 13 is soldered, and are located between the adjacent black keys 11 #D / bE and #F / bG, or the black key 11 #A / bB and #C / bD of the keyboard, that is, below the adjacent white keys 10B and C, or the white keys 10E and F. The above-mentioned musical clefs can be used to express the specific positions of the black keys 11 and the white keys 10 on the 88-key piano, which should be known to those skilled in the art.

[0023] The rear convex self-tapping screw 14 is passed through the central screw hole and the washer 7 to fix one side of each scanning circuit board section soldered with the infrared photoelectric sensor on the front rail 1 of the keyboard frame. In order to facilitate the fixation of the spliced ​​ends of each scanning circuit board section, in this embodiment, the spliced ​​ends of each scanning circuit board section are respectively provided with a semi-rear convex portion and a semicircular notch for splicing and fixed with a rear convex self-tapping screw 14.

[0024] In order to satisfy the space for setting the semi-rear convex part, the spliced ​​ends of each section of the scanning circuit board must also be located between the black key circles 8 of the adjacent black keys 11 #D / bE and #F / bG, or the black keys 11 #A / bB and #C / bD on the keyboard. At the same time, in order to comply with the characteristics of the matrix scanning circuit having 8 scanning lines in a group of rows and columns, the spliced ​​ends of the left scanning circuit board 17 and the middle scanning circuit board 16 are located between the black key circles 8 of the small-character group black keys 11 #D / bE and #F / bG, or between the 32nd key and the 33rd key from the left, that is, the left scanning circuit board 17 scans 32 keys; the spliced ​​ends of the middle scanning circuit board 16 and the scanning circuit board 6 are located between the black key circles 8 of the second group of small-character black keys 11 #D / bE and #F / bG, or between the 56th key and the 57th key from the left, that is, the middle scanning circuit board 16 scans 24 keys; the remaining 32 keys are scanned by the scanning circuit board 6, which is the preferred design.

[0025] Embodiment 2: See also Figure 5 , Figure 6 The present invention also provides another embodiment, which decomposes an 88-key piano keyboard into two left and right scanning sections, each with 44 keys. In this embodiment, the semi-circular notch 26 of the semi-convex portion is respectively set on the spliced ​​ends of the two scanning circuit boards and fixed with a self-tapping screw 14 of the convex portion, that is, the spliced ​​end is located between the black key circle 8 of the black key #D / bE and #F / bG of the small letter group. Due to the row and column characteristics of a group of 8 scanning lines of the matrix scanning circuit, the 4 keys closest to the spliced ​​ends of the left scanning circuit board 17 and the scanning circuit board 6 are scanned in the same group of rows and columns, so a left and right board connecting thin film cable 27 is provided between the two boards, which not only contains scanning lines but also includes power and ground lines, and the thin film cable 22 and the thin film cable 5 are respectively used for the left scanning circuit board 17 and the scanning circuit board 6 to connect to the scanning port of the sound source main control board.

[0026] In this embodiment, each thin film cable is not led out from the left or right end of the keyboard frame front guard 1, but is led out from under the two black key felt circles 8 adjacent to the keyboard frame front guard 1, and is located between two adjacent black key flat pins 9. Since the thickness of the thin film cable is about 0.1 mm, it is almost negligible and does not affect the organization and use of the keyboard. Figure 6 The left and right board connection sockets 28 of the schematic scanning circuit board 6 and the thin film cable connection socket of another sound source main control board are all 1 mm pitch FFC / FPC bent pin sockets, the socket thickness is about 3.5 mm, and the two sockets are arranged on the front side. Since the position of the white key felt circle 2 of the front gear 1 of the keyboard frame is usually higher than the black key felt circle 8 by about 1 mm, during installation, the washer 7 under the screw groove 23 on the front side needs to be increased accordingly. Of course, the groove can also be chiseled and milled without increasing the washer 7.

[0027] 1mm pitch FFC / FPC socket is more convenient for plugging and unplugging than 0.5mm pitch FFC / FPC socket, so this embodiment is suitable for the thin film cable lead-out connection in the middle of the keyboard frame front instead of the two ends, and the installation, splicing and connection of the left and right scanning circuit boards are also faster than the left, middle and right three sections. However, for the double-sided printed circuit board, the number of scanning lines in each section is greater than the number of scanning lines in the three-section decomposition due to the two-section decomposition. Therefore, this embodiment is more suitable for the keyboard frame front 1 with a slightly larger spacing between the white key felt circle 2 and the black key felt circle 8, but the multi-layer board is not restricted.

[0028] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical solutions and novel concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A scanning circuit board structure installed on the front rail of a piano keyboard frame, comprising a scanning circuit board (6) mainly composed of a keyboard frame front rail (1), a black key felt ring (8), a white key felt ring (2), a gasket (7), black keys (11), white keys (10), a reflective felt block (12) and an infrared photoelectric sensor (13), and the back of the scanning circuit board (6) is connected to a flexible film cable (5), characterized in that: A narrow matrix scanning circuit board (6) with an infrared photoelectric sensor (13) mounted on the surface thereof is disposed transversely between the black key felt circle (8) and the white key felt circle (2) of the piano keyboard frame front rail (1). The infrared photoelectric sensor (13) is mounted on the front side of the scanning circuit board (6) close to the black key felt circle (8). A rear convex portion (15) is provided at intervals on the side of the scanning circuit board (6) close to the black key felt circle (8). The rear convex portion (15) is provided with a screw hole. The side of the scanning circuit board (6) close to the rear convex portion (15) is fixed to the keyboard frame front rail (1) by a rear convex portion self-tapping screw (14) passing through the screw hole of the rear convex portion (15). The other side of the scanning circuit board (6) close to the white key felt circle (2) is provided with screw holes at intervals on the front side edge. The front side self-tapping screw (4) passes through the screw hole and is fastened to the keyboard frame front rail (1).

2. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 1, characterized in that: The scanning circuit board (6) is mainly composed of 88 infrared photoelectric sensors (13), which constitute 88 detection circuit units. The 88 circuit detection units are electrically connected in a row-column relationship to form an infrared photoelectric matrix scanning circuit. The 88 circuit detection units correspond to detecting the bottom surfaces of 88 keys on the piano keyboard frame, and the infrared photoelectric sensor (13) corresponding to each black key (11) is located below the front end of the black key (11), and the infrared photoelectric sensor (13) corresponding to each white key (10) is evenly aligned with the white key flat pin (3) at the center of the white key circle (2) below the white key (10).

3. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 1, characterized in that: The rear convex portion (15) of the scanning circuit board (6) and its screw hole are correspondingly arranged between the black key circles (8) of the adjacent black keys (11) #D / bE and #F / bG, or #A / bB and #C / bD of the keyboard, and are located below the adjacent white keys (10) B key and C key, or the adjacent white keys (10) E key and F key.

4. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 2, characterized in that: The scanning circuit board (6) has 88 infrared photoelectric sensors (13), each corresponding to a white reflective felt block (12) provided on the bottom surface of the upper black key (11) or the white key (10), and the reflective felt block (12) corresponding to the black key (11) is located at the front end of the bottom surface of the black key (11).

5. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 1, characterized in that: The scanning circuit board (6) is composed of two to four sections and is used to realize segmented scanning. The back of each scanning circuit board (6) is connected to an FFC / FPC flexible film cable (5), which is hidden and laid in a gap space formed by a gasket (7) between the scanning circuit board (6) and the front of the keyboard frame (1), and is led out from the left and right ends of the front of the keyboard frame (1) to connect to the scanning port of the sound source main control board.

6. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 5, characterized in that: FFC / FPC film cable sockets with opposite contact surfaces are respectively provided at both ends of the scanning circuit board (6); the film cable (5) is inserted into any socket at the left or right end of the FFC / FPC film cable socket to connect to the same scanning port of the sound source main control board.

7. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 5, characterized in that: A semi-rear convex portion and a semicircular notch (26) of the semi-rear convex portion are provided on one side of the spliced ​​end of each scanning circuit board (6) for segmented scanning close to the black key felt ring (8).

8. A scanning circuit board structure installed on the front rail of a piano keyboard frame as claimed in claim 1, characterized in that: The height from the top of the infrared photoelectric sensor (13) soldered to the scanning circuit board (6) near the side of the black key felt circle (8) to the surface of the keyboard frame front guard (1) is more than 1 mm lower than the thickness of the black key felt circle (8).

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