Minimally invasive repair method for wood defect of guqin body

Abstract

The invention discloses a minimally invasive repair method for wood defects of a guqin body, which comprises the following steps: S1, forming a slotted hole at the wood defect part of the guqin body, enabling the middle part of the slotted hole to stretch across the wood defect part, and forming the outer edge of the slotted hole to a defect-free wood guqin body; s2, preparing a repaired wood block, wherein the material of the wood block is the same as the wood of the guitar body; s3, gluing and embedding are conducted, specifically, the wood blocks are embedded into the corresponding groove holes after being coated with adhesives, and gaps between the groove holes and the wood blocks are filled with the adhesives; and S4, after the adhesive is solidified, polishing the surface of the wooden guitar body, so that the exposed parts of the adhesive and the wood blocks are flush with the surface of the guitar body. The method can effectively solve the problems in the prior art that the vertical texture of the wooden wedge for repairing the Guqin shrinks and cracks, the adhesive is single and loses efficacy, the sound quality is damaged by a large wound surface, and the repaired structure is easy to fall off.

Description

Technical Field

[0001] This invention relates to the field of musical instrument repair technology, specifically a minimally invasive repair method for wooden defects in the body of a guqin (a traditional Chinese stringed instrument). Background Technology

[0002] In the restoration of antique guqin (a seven-stringed zither), the traditional wooden soundboard and backboard are often made from aged wood, such as reclaimed wood from demolished houses from the Ming and Qing dynasties, often over a century old. Because these old materials are rare and precious, they often have many defects, including knots and cracks. Therefore, the knots and holes in the soundboard and backboard need to be repaired before the instrument can be used. The current process for repairing knots and holes in guqin wood typically involves removing the entire knot, or sometimes drilling a hole larger than the knot to remove it completely. Then, square or round wooden wedges, perpendicularly spaced and equidistant, are inserted and glued. The holes are then enlarged to a circle, square, or rectangular shape. Similarly, matching wooden wedges are glued and inlaid.

[0003] In addition, when repairing cracks in the wood of a musical instrument, existing techniques typically involve applying glue to the crack, securing it with clips, and then re-gluing it. Alternatively, several silver-nail-shaped (bow-tie-shaped) wedge holes are drilled at regular intervals along the length of the crack, and then silver-nail-shaped wooden wedges are made and inserted into the wedge holes.

[0004] The shortcomings of modern techniques for repairing defects in the wooden body of the guqin (a traditional Chinese stringed instrument) are: 1. When repairing knots / holes, the wooden wedge structure is flawed. The contact surface between the wooden wedge and the wedge hole is perpendicular, and the wood grain of the wedge is also perpendicular to the soundboard and backboard of the guqin. Due to the anisotropy of wood, the shrinkage of the wooden wedge and the guqin body is inconsistent. This results in the wooden wedge becoming dented and cracking appearing on the surface of the guqin body some time after the repair.

[0005] Poor bonding strength is due to the unscientific structure of the wooden wedges. Their function is merely to seal the holes; they do not create a strong physical connection with the instrument body, relying solely on the adhesive force of the glue. As the glue ages and the wooden wedges expand and contract with the instrument body, they will crack and detach.

[0006] 2. When repairing wooden cracks, there is a risk of the wood delaminating again due to changes in internal stress and aging of the glue. The damage to the wood of musical instruments is very large, destroying the original local structure and density of the material, resulting in changes in sound quality. Furthermore, the manufacturing process is complex, requiring high skill and experience to achieve a perfect fit between the wooden holes and wedges. Due to the large surface area of ​​the ingot-shaped structure, the anisotropic properties of the wood itself can cause some contact surfaces to delaminate, leading to loosening and detachment of fasteners. The repair process is time-consuming and labor-intensive. Summary of the Invention

[0007] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of this invention is to propose a minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither). This method can effectively solve the problems in existing guqin repair techniques, such as vertical grain shrinkage and cracking of wooden wedges, single adhesive failure, damage to sound quality from large wound surfaces, and easy detachment of repaired structures.

[0008] To address the above problems, this invention provides a minimally invasive method for repairing wooden defects in the body of a guqin (a traditional Chinese stringed instrument), comprising the following steps: S1. A slot is made at the wooden defect of the instrument body, the middle of which spans across the wooden defect, and the outer edge of the slot extends to the undefected wooden instrument body. S2. Prepare a repair block, the material of which is the same as the wood of the instrument body; S3. Glue application and inlay: After applying adhesive to the wooden block, embed it into the corresponding slot and fill the gap between the slot and the wooden block with adhesive. S4. After the adhesive has hardened, sand the surface of the wooden instrument body so that the exposed parts of the adhesive and wood blocks are flush with the surface of the instrument body.

[0009] Preferably, the minimally invasive repair method for defects in the wood of a guqin (a seven-stringed zither) includes a crack repair method, the steps of which are as follows: A1. Several sets of slots are made at the cracked area. Each set of slots includes two straight grooves at an angle of ±45° to the crack with an allowable error of ±5°. The two straight grooves are arranged alternately in a figure-eight shape. The width of a single straight groove is 1.3±0.1mm and the depth is ≥3mm. A2. Prepare the repair wood block, which is a wood chip corresponding to the shape of the straight groove. The width of the wood chip is 0.1mm greater than the width of the groove, the length matches the straight groove, and the material is the same as the wood of the instrument body. A3. Glue application and inlay: After applying adhesive to the wood chips, they are embedded into the corresponding straight grooves. At this time, the wood chips are arranged alternately in a figure-eight shape and cross the crack at an angle of ±45° with an allowable error of ±5°. The adhesive force of the adhesive and the deformation resistance of the wood chip body together overcome the tension that causes the crack in the wood of the instrument to continue to expand. After A4 curing, sand the wood chips and solid adhesive surfaces until they are flush with the surface of the instrument body.

[0010] Preferably, the distance between the two straight grooves in each group of slots is 1 / 10 to 1 / 8 of the crack length.

[0011] Preferably, the minimally invasive repair method for wooden defects in the body of a guqin includes a method for repairing knots / holes, the steps of which are as follows: B1. Remove defects: Extend the four-pointed star boundary by 0.5-1mm along the outer edge of the knot / hole, and remove the defects within the boundary; B2. Create a slot. This slot is a stepped slot. The cross-sectional shape of each step of the slot is a four-pointed star structure. When creating the four-pointed star slot, it is necessary to expand the edge of the four-pointed star hole by 5-6mm and dig down 5-8mm along the curvature of the instrument body to form a stepped groove, based on step B1. B3. Make double-layered four-pointed star wooden wedges. Select the same wood as the body of the instrument and make double-layered four-pointed star wooden wedges. The upper layer of large wooden wedges matches the outer contour of the stepped groove, and the lower layer of small wooden wedges matches the holes after the defects are removed. B4. Glue application and inlay: After applying glue to the double-layered four-pointed star wooden wedges, insert them into the grooves to ensure that the grain of the wooden wedges is consistent with the grain of the instrument body; B5. Post-curing treatment: After the adhesive has cured, sand and smooth the surface of the wooden wedge until it is flush with the surface of the instrument body.

[0012] Preferably, the cross-section of the four-pointed star wooden wedge is a four-sided silver ingot buckle structure.

[0013] Preferably, the arc error of the stepped slot is ≤0.5°.

[0014] The advantages of this invention compared to the prior art are: In this invention, a minimally invasive method for repairing wooden defects in the body of a guqin (a traditional Chinese stringed instrument) is provided: 1. The core advantages of the four-pointed star wooden wedge repair technique: Anisotropic compensation: The four-sided silver ingot buckle structure makes the wood wedge grain completely parallel to the body of the instrument on the X / Y axes, reducing the shrinkage deviation to ≤0.3%; Double mechanical locking: The stepped double-layer wooden wedges form an inverted conical fit along the Z-axis, increasing the tensile strength by 3.8 times (test standard: ASTM D1037). Performance improvement data:

[0015] 2. Core advantages of minimally invasive crack repair technology: Wound volume ratio: Single-point repair only requires a groove of 1.3mm×30mm (volume≈58mm³), reducing material loss by 89% compared to the butterfly buckle process; Sound quality fidelity: Vibration modal analysis shows frequency deviation ≤0.5% (testing equipment: Kistler 3D scanning laser vibration meter); Prestressed locking: The wood chips arranged in a figure-eight pattern form a stress field with an angle of ±45° on both sides of the crack, which improves the shear strength; Failure prevention: The 0.1mm interference fit causes the wood chips to generate radial expansion force, which counteracts the wood shrinkage stress.

[0016] 3. Overall benefits and improved process efficiency: The time required for repairing knotted wood has been reduced from 8 hours / point to 2.5 hours (a reduction of 69%), and the pass rate for crack repair has increased from 48% to 96%. In terms of the protection of cultural relics value, the wood replacement rate in the repaired area is <5% (compared to >30% for traditional techniques), meeting the requirements of the "Principle of Reversible Restoration" (Standard: GB / T30237-2013). Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is an illustration of the effect of repairing wood crack defects in this invention; Figure 2 This is an illustration of the repair effect of wood knots / holes in this invention; Figure 3 This is a three-dimensional structural diagram of the double-layered four-pointed star wooden wedge in this invention; As shown in the figure: 1-body; 2-crack; 3-straight groove; 4-wooden piece; 5-stepped groove; 6-four-pointed star wooden wedge; 7-adhesive. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] Combination Figures 1-3 The present invention provides a minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither), comprising the following steps: S1. A slot is made at the wooden defect of the instrument body 1, the middle of the slot spans across the wooden defect, and the outer edge of the slot extends to the wooden instrument body without defects. S2. Prepare a repair block, the material of which is the same as the wood of the instrument body; S3. Apply adhesive and fit: After applying adhesive 7 to the wooden block, embed it into the corresponding slot and fill the gap between the slot and the wooden block with adhesive. S4. After the adhesive has hardened, sand the surface of the wooden instrument body so that the exposed parts of the adhesive and wood blocks are flush with the surface of the instrument body.

[0023] Preferably, the minimally invasive repair method for defects in the wood of a guqin (a seven-stringed zither) includes a crack 2 repair method, the steps of which are as follows: A1. Several sets of slots are made at the cracked area. Each set of slots includes two straight grooves 3 with an angle of ±45° to the crack and an allowable error of ±5°. The two straight grooves are arranged alternately in a figure-eight shape. The width of a single straight groove is 1.3±0.1mm and the depth is ≥3mm. A2. Prepare the repair wood block, which is a wood chip 4 corresponding to the shape of the straight groove. The width of the wood chip is 0.1mm greater than the width of the groove, the length matches the straight groove, and the material is the same as the wood of the instrument body. A3. Glue application and inlay: After applying adhesive to the wood chips, they are embedded into the corresponding straight grooves. At this time, the wood chips are arranged alternately in a figure-eight shape and cross the crack at an angle of ±45° with an allowable error of ±5°. The adhesive force of the adhesive and the deformation resistance of the wood chip body together overcome the tension that causes the crack in the wood of the instrument to continue to expand. After A4 curing, sand the wood chips and solid adhesive surfaces until they are flush with the surface of the instrument body.

[0024] Preferably, the distance between the two straight grooves in each group of slots is 1 / 10 to 1 / 8 of the crack length.

[0025] Preferably, the minimally invasive repair method for wooden defects in the body of a guqin includes a method for repairing knots / holes, the steps of which are as follows: B1. Remove defects: Extend the four-pointed star boundary by 0.5-1mm along the outer edge of the knot / hole, and remove the defects within the boundary; B2. Create a slot, which is a stepped slot 5. The cross-sectional shape of each step of the slot is a four-pointed star structure. When creating the four-pointed star slot, it is necessary to expand the edge of the four-pointed star hole by 5-6mm and dig down 5-8mm along the curvature of the instrument body to form a stepped groove based on step B1. B3. Make double-layered four-pointed star wooden wedges 6. Select the same wood as the body of the instrument and make double-layered four-pointed star wooden wedges. The upper layer of large wooden wedges matches the outer contour of the stepped groove, and the lower layer of small wooden wedges matches the holes after the defects are removed. B4. Glue application and inlay: After applying glue to the double-layered four-pointed star wooden wedges, insert them into the grooves to ensure that the grain of the wooden wedges is consistent with the grain of the instrument body; B5. Post-curing treatment: After the adhesive has cured, sand and smooth the surface of the wooden wedge until it is flush with the surface of the instrument body.

[0026] Preferably, the cross-section of the four-pointed star wooden wedge is a four-sided silver ingot buckle structure.

[0027] Preferably, the arc error of the stepped slot is ≤0.5°.

[0028] To more clearly illustrate the specific embodiments of the present invention, an example is provided below: This invention discloses a minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither). The principle behind repairing knots / holes in the guqin wood is as follows: Based on the anisotropic characteristics of wood, a four-pointed star (four-sided silver ingot-shaped) structure is designed. This solves the problem of the firmness and stability of the connection between the wood and the body in the horizontal and vertical directions (x-axis and y-axis). In the vertical direction (z-axis), a double-layered structure with different sizes of four-pointed stars is used. The wooden wedges overlap with the four-pointed star wedge holes in the body, significantly improving the bonding strength and controlling the risk of cracking. Wooden wedges of the same type, similar age, and consistent grain are selected for repair. The construction process for repairing the wooden wedges and holes in the guqin body using four-pointed star wooden wedges is as follows: ① First, draw a slightly larger four-pointed star pattern around the knot or hole. Remove the joints and holes within the pattern. ② Enlarge the edge of the four-pointed star hole by 5-6 mm, and then, depending on the location of the hole on the body, dig a step (groove) of varying depth from 5 mm to 8 mm. The groove of the four-pointed star should be the same as the curvature of the body. ③ Select wood of the same size, age, and grain as the instrument body to make corresponding wooden wedges. ④ Apply glue and embed the wedges into the wedge holes, ensuring a tight fit. After the glue has cured, smooth out any protruding parts of the wood to complete the process. Four-pointed star wooden wedges are used to repair knots in the guqin wood. The advantages of the knot / hole repair technique are: 1. The physical structure of the four-pointed star wedge solves the problem of weak connection and cracking between the wedge and the instrument body in the original process, both horizontally and vertically (x-axis and y-axis directions). 2. The physical structure of the four-pointed star wedge can simultaneously repair existing cracks on both sides of knots or holes in the instrument body. 3. The double-layered structure of the four-pointed star solves the problems of concavity and weak adhesion between the wedge and the instrument body in the vertical (z-axis) directions.

[0029] This invention discloses a minimally invasive repair method for wooden defects in the body of a guqin (a traditional Chinese stringed instrument). The principle behind this method is to cleverly design a new physical structure that utilizes the anisotropic properties of wood to fix the crack. A figure-eight mortise and tenon joint fixing process is employed, in which straight wooden strips (pieces) are alternately embedded in the straight grooves created at the crack, with glue applied. Because the two pieces of wood are not parallel, they form an angle, which is used to fix the crack.

[0030] Advantages of minimally invasive repair techniques: 1. Minimal damage to the instrument's soundboard. Only a few thin, 2-3 cm long linear wounds appear on the soundboard, reducing the damaged area by over 90%. 2. Improved connection strength between fasteners and the instrument. This repair technique changes the shape of the fasteners used in the original process. Only simple straight wooden strips are needed, alternating between forward and reverse V-shapes, inserted into the straight grooves created at the crack. This cleverly utilizes the physical structure to reinforce the cracked area, and the linear structure solves the problem of secondary cracking between the wood and the repair material caused by the anisotropy of the wood. 3. Minimized impact on local material density. The impact on tone and timbre is negligible. 4. Simple and efficient process. The construction process is simplified, the processing difficulty is reduced, and work efficiency is improved. The quality of the repair is enhanced. Minimally Invasive Repair Techniques for Wooden Instruments: 1. Use a special tool to create a 1.3 mm wide groove at the crack (the length and shape depend on the size and shape of the crack), forming an angle of approximately 45 degrees with the crack. 1. Cut several V-shaped grooves (3mm or more deep, depending on the location of the crack) according to the length of the crack. 2. Apply glue to the wood strips (0.1mm wider than the groove width) and insert them into the grooves. 3. After the adhesive has cured, sand the wood strips (strips) that are higher than the surface of the instrument smooth. Finishing and painting complete the process.

[0031] Finally, for any aspects of this invention not fully described, mature products and technologies from the prior art are used.

[0032] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A minimally invasive method for repairing defects in the wood of a guqin (a seven-stringed zither), characterized in that, Includes the following steps: S1. A slot is made at the wooden defect of the instrument body, the middle of which spans across the wooden defect, and the outer edge of the slot extends to the undefected wooden instrument body. S2. Prepare a repair block, the material of which is the same as the wood of the instrument body; S3. Glue application and inlay: After applying adhesive to the wooden block, embed it into the corresponding slot and fill the gap between the slot and the wooden block with adhesive. S4. After the adhesive has hardened, sand the surface of the wooden instrument body so that the exposed parts of the adhesive and wood blocks are flush with the surface of the instrument body.

2. The minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither) according to claim 1, characterized in that: Including crack repair methods, the steps are as follows: A1. Several sets of slots are made at the cracked area. Each set of slots includes two straight grooves at an angle of ±45° to the crack with an allowable error of ±5°. The two straight grooves are arranged alternately in a figure-eight shape. The width of a single straight groove is 1.3±0.1mm and the depth is ≥3mm. A2. Prepare the repair wood block, which is a wood chip corresponding to the shape of the straight groove. The width of the wood chip is 0.1mm greater than the width of the groove, the length matches the straight groove, and the material is the same as the wood of the instrument body. A3. Glue application and inlay: After applying adhesive to the wood chips, they are embedded into the corresponding straight grooves. At this time, the wood chips are arranged alternately in a figure-eight shape and cross the crack at an angle of ±45° with an allowable error of ±5°. The adhesive force of the adhesive and the deformation resistance of the wood chip body together overcome the tension that causes the crack in the wood of the instrument to continue to expand. After A4 curing, sand the wood chips and solid adhesive surfaces until they are flush with the surface of the instrument body.

3. The minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither) according to claim 2, characterized in that: The distance between the two straight grooves in each group of slots is 1 / 10 to 1 / 8 of the crack length.

4. The minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither) according to claim 1, characterized in that: Including methods for repairing knots / holes, the steps are as follows: B1. Demolition of defects: Extend the four-corner boundary by 0.5-1mm along the outer edge of the knot / hole, and remove the defects within the boundary; B2. Create a slot. This slot is a stepped slot. The cross-sectional shape of each step of the slot is a four-pointed star structure. When creating the four-pointed star slot, it is necessary to expand the edge of the four-pointed star hole by 5-6mm and dig down 5-8mm along the curvature of the instrument body to form a stepped groove, based on step B1. B3. Make double-layered four-pointed star wooden wedges. Select the same wood as the body of the instrument and make double-layered four-pointed star wooden wedges. The upper layer of large wooden wedges matches the outer contour of the stepped groove, and the lower layer of small wooden wedges matches the holes after the defects are removed. B4. Glue application and inlay: After applying glue to the double-layered four-pointed star wooden wedges, insert them into the grooves to ensure that the grain of the wooden wedges is consistent with the grain of the instrument body; B5. Post-curing treatment: After the adhesive has cured, sand and smooth the surface of the wooden wedge until it is flush with the surface of the instrument body.

5. A minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither) according to claim 4, characterized in that: The cross-section of the four-pointed star wooden wedge is a four-sided silver ingot buckle structure.

6. A minimally invasive repair method for wooden defects in the body of a guqin (a seven-stringed zither) according to claim 4, characterized in that: The arc error of the stepped slot is ≤0.5°.

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