Elastic member for electronic drum, method for manufacturing an elastic member for electronic drum, and electronic drum

Abstract

To provide an elastic component for electronic drums that is highly uniform and precisely molded, a method for manufacturing an elastic component for electronic drums, and an electronic drum. [Solution] An elastic member for an electronic drum, provided between the drumhead and a sensor that detects vibrations of the drumhead, for transmitting vibrations of the drumhead to the sensor, having a single layer of polyurethane foam extending from one end on the drumhead side to the other end on the sensor side, wherein the shape of the cells of the polyurethane foam is substantially spherical.

Description

Technical Field

[0001] The present disclosure relates to an elastic member for an electronic drum, a method for manufacturing the elastic member for an electronic drum, and an electronic drum.

Background Art

[0002] An electronic percussion instrument or an electronic drum is known, in which a sensor detects a strike by hitting a striking surface, and a sound source module generates a sound based on the detected strike. For example, an electronic percussion instrument is known that includes a vibration sensor and a pressure sensor to enable more faithful reproduction of musical sounds for a player's striking operation (Patent Document 1). Also, an electronic drum is known that tensions a striking head and includes a striking surface sensor in contact with the striking head, thereby reducing the rigidity required for a cylindrical member and achieving cost reduction of materials and weight reduction (Patent Document 2). Also, an electronic percussion instrument is known that has a translucent striking surface and a striking mode display means, obtaining a good striking feel and visually displaying the striking mode of the struck surface (Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In many electronic drums, in order to prevent destruction of a sensor that detects vibration of a striking surface due to a strike, the strike on the striking surface is transmitted to the sensor via a vibration transmission member. While elastic materials are used as vibration transmission components, variations in the physical properties and shape of these elastic materials can lead to false detection of strikes, changes in feel depending on the area of ​​the striking surface even with the same device, and sometimes make it difficult to play electronic drums comfortably.

[0005] One embodiment of this disclosure aims to provide an elastic member for an electronic drum that is highly uniform and precisely molded, a method for manufacturing an elastic member for an electronic drum, and an electronic drum. [Means for solving the problem]

[0006] This disclosure includes the following aspects:

[0007] <1> An elastic member for an electronic drum, provided between the drumhead and a sensor that detects vibrations of the drumhead, for transmitting vibrations of the drumhead to the sensor, comprising a single layer of polyurethane foam extending from one end on the drumhead side to the other end on the sensor side, wherein the shape of the cells formed inside the polyurethane foam is spherical. <2> The cross-sectional shape of the cells in the polyurethane foam is circular. <1> Elastic component for electronic drums as described above. <3> It is a single-piece molded product. <1> or <2> Elastic component for electronic drums as described above. <4> Polyurethane foam has a skin layer on its outer surface. <1> ~ <3> An elastic component for electronic drums as described in any one of the following. <5> The density of the polyurethane foam is within the range of -14% to +16% relative to the density at the other end. <1> ~ <4> An elastic component for electronic drums as described in any one of the following. <6> A method for manufacturing an elastic member for an electronic drum, which is provided between the drumhead of the electronic drum and a sensor that detects vibrations of the drumhead, and which transmits vibrations of the drumhead to the sensor, comprising the steps of: producing a foaming material by mechanically foaming a polyurethane reaction composition; and producing an elastic member having a single layer of polyurethane foam extending from one end on the drumhead side to the other end on the sensor side by heat molding the foaming material. <7> The process of manufacturing polyurethane foam includes pouring foaming material into a mold. <6> A method for manufacturing an elastic member for an electronic drum, as described above. <8> <1> ~ <5> An electronic drum comprising an elastic member for electronic drums as described in any one of the above, and a sensor. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, it is possible to provide an elastic member for an electronic drum that is highly uniform and precisely molded, a method for manufacturing an elastic member for an electronic drum, and an electronic drum. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a front view of an elastic member for an electronic drum. [Figure 2] Figure 2 is a side view of an elastic member for an electronic drum. [Figure 3] Figure 3 is an explanatory diagram illustrating a method for manufacturing an elastic member for an electronic drum. [Figure 4] Figure 4 is a cross-sectional view of an electronic drum cut along a line perpendicular to the center of the drumhead. [Figure 5] Figure 5 is an explanatory diagram illustrating the parts used when measuring the density of each section of an elastic component for an electronic drum. [Modes for carrying out the invention]

[0010] The following describes in detail specific embodiments of an elastic member for an electronic drum and an electronic drum according to one embodiment of this disclosure. However, the elastic member for an electronic drum and the electronic drum according to one embodiment of this disclosure are not limited in any way to the following embodiments and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

[0011] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, "mass %" and "weight %" are synonymous. In the present disclosure, the amount of each component means the total amount of a plurality of substances when there are a plurality of substances corresponding to each component, unless otherwise specified. In the present disclosure, the diameter of the cells of the polyurethane foam is a value obtained by visually observing the cells using a microscope (VH-5000, manufactured by Keyence Corporation), measuring the longest diameter of the cells, performing this measurement on 20 randomly selected cells, and averaging these measured values. In the present disclosure, the hardness of the polyurethane foam by the rebound test is measured using a desktop precision universal testing machine (AGS-X, manufactured by Shimadzu Corporation) in the compression mode, measuring the maximum reaction force at 25% height compression at a compression speed of 100 mm / min, performing this measurement on 20 randomly selected cells, and averaging these measured values. In the present disclosure, the density of the polyurethane foam is the apparent density, and the apparent density is a value measured by the water displacement method.

[0012] The background leading to this embodiment will be described. The elastic member for an electronic drum mounted on the electronic drum is installed between the striking surface and the sensor, for the purpose of appropriately transmitting the vibration generated by striking the striking surface to the sensor, and also for the purpose of preventing false detection, such as after the second consecutive strike, by attenuating the vibration of the striking surface due to the impact, one or more are installed.

[0013] As materials for the elastic members for electronic drums, urethane foams, silicone resins, polypropylene resins, sponges thereof, rubber, etc. are used. As shapes, frustum of a cone shapes, pyramid shapes, frustum of a pyramid shapes, etc. are used. Specifically, bonded molded articles formed by bonding materials such as sliced sponges in 2 to 8 layers respectively, those obtained by polishing the bonded molded articles, those printed by a 3D printer while providing voids, etc. are used.

[0014] However, in these elastic members for electronic drums, variations may be seen in functions such as the degree of vibration attenuation. Due to variations in the degree of attenuation, vibrations from hitting the drumhead may not be properly transmitted to the sensor. For example, even for the same strike, depending on the area of the drumhead struck, the magnitude of the vibration transmitted to the sensor may change, or problems such as misdetection of the strike vibrations after the second and subsequent strikes may occur because the vibrations are not properly attenuated. Also, problems such as differences in the impact feeling such as the bounce after hitting may occur. As a result, comfortable playing of the electronic drums may become difficult.

[0015] In order to control the variations in vibration of the elastic member for an electronic drum, the present inventor focused on suppressing variations in both the physical properties and shape of the elastic member for an electronic drum and conducted intensive studies. As a result, it was found that an elastic member for an electronic drum having a polyurethane foam that is single-layer from one end on the drumhead side to the other end on the sensor side and in which the shape of the cells inside the layer is substantially spherical enhances the uniformity of the vibrations that attenuate after hitting the drumhead. Also, it was found that by a manufacturing method of an elastic member for an electronic drum including a step of manufacturing a foaming raw material by mechanically foaming a polyurethane reaction composition and a step of manufacturing a single-layer polyurethane foam from one end on the drumhead side to the other end on the sensor side by heat-molding the foaming raw material, an elastic member for an electronic drum with high uniformity and precisely molded is manufactured.

[0016] Although the mechanism by which the above effects are achieved is not clear, the above materials have been used for elastic components in electronic drums because they require appropriate elasticity, strength, etc. However, it has been difficult to precisely control the physical properties and shape of these materials. In contrast, it is presumed that the polyurethane foam used in the elastic component for electronic drums combines two characteristics: being a single layer extending from one end on the striking surface side to the other end on the sensor side, and having substantially spherical cells within the foam. This combination results in highly uniform vibration damping after striking the striking surface, making it a precisely molded elastic component for electronic drums. Furthermore, it is presumed that the method, which includes a process for producing foaming raw materials by mechanical foaming and a process for producing a single-layer polyurethane foam by heat molding, results in a highly uniform and precisely molded method for producing elastic components for electronic drums.

[0017] <Elastic material for electronic drums> An elastic member for an electronic drum (hereinafter also referred to as the elastic member), which is one embodiment of the present disclosure, is provided between the striking surface of an electronic drum and a sensor that detects vibrations of the striking surface, and is used to transmit vibrations of the striking surface to the sensor. It has a single layer of polyurethane foam extending from one end on the striking surface side to the other end on the sensor side, and the shape of the cells formed inside the polyurethane foam is spherical. The elastic member for an electronic drum is also called a sensor cone.

[0018] As shown in Figures 1 and 2, the elastic member 10 has a frustoconical shape, with a small circular surface 11 on the top and a large circular surface 12 on the bottom. The top surface 11 is one end on the striking surface side, and the bottom surface 12 is the other end on the sensor side, to which the sensor is attached. The top surface 11 and the bottom surface 12 are substantially parallel. Note that "substantially parallel" includes having an inclination angle as long as it does not impair the function of the elastic member 10. The shape of the elastic member 10 can be varied depending on the electronic drum or the like used. The elastic member 10 may also have a shape that includes holes for attaching peripheral devices such as sensors on the bottom surface 12, grooves for passing sensor wiring, etc. For example, the elastic member 10 has a top surface diameter of 5 mm, a bottom surface diameter of 40 mm, and a height of 35 mm in the Z direction.

[0019] The elastic member has a single layer of polyurethane foam extending from one end to the other. That is, the elastic member has one layer of polyurethane foam extending from the top surface 11 at one end to the bottom surface 12 at the other end. The elastic member is, so to speak, a single-material product, an integral structure product, or a monolithic product. Furthermore, the elastic member is a single-material component without seams, joints, adhesive parts, etc., and the polyurethane foam is not composed of multiple parts. It is also preferable that the elastic member is an unprocessed product that does not undergo polishing or other molding processes after molding.

[0020] For example, conventional laminated products, which are made by bonding multiple layers together with adhesive, can be difficult to achieve with high precision and identical shape due to differences in adhesive thickness, and it can be difficult to make the structure and physical properties identical for multiple components. Since the elastic component has a single layer of polyurethane foam, it is a single-material part that does not require processing such as bonding. As a result, the structure and physical properties are uniform throughout the elastic component, resulting in high homogeneity and precise molding. Therefore, the physical properties of a single elastic component are highly uniform, and it is precisely processed in terms of dimensions, the degree of parallelism between the top and bottom surfaces, etc. Furthermore, multiple elastic components exhibit high uniformity in terms of physical properties and shape.

[0021] The elastic member has a spherical cell shape formed inside the polyurethane foam. The cell shape refers to the shape of one of the multiple voids contained inside the polyurethane foam. "Spherical" means substantially spherical, and "substantially spherical" includes a single cell being a distorted sphere, or two or more cells being continuous, as long as the function of the elastic member is not impaired. Furthermore, a substantially spherical cell shape may have an opening in part of the sphere, or the entire sphere may be closed. In the shape of polyurethane foam cells, the spherical sizes are substantially the same. "Substantially the same size" means that the spherical sizes of the cells are identical, as long as the function of the elastic member is not impaired, and that the cells include spherical sizes that are similar to each other to the extent that they appear identical (e.g., -10% to +10%).

[0022] In elastic members, the substantially spherical shape of the polyurethane foam cells results in a uniform structure and high physical properties. Furthermore, because the cell shape is less prone to orientation, biases in physical properties such as vibration transmission are less likely to occur, and twisting is also less likely to occur.

[0023] From the viewpoint of performing desirable functions as an elastic member, the spherical diameter of the polyurethane foam cells is preferably 0.08 mm to 0.28 mm, more preferably 0.10 mm to 0.26 mm, and even more preferably 0.12 mm to 0.24 mm. The spherical shape of the cells is preferably substantially uniform throughout the elastic member 10.

[0024] The hardness of the polyurethane foam obtained by rebound testing is determined by measuring the maximum rebound stress when an elastic member 10 with a height of 35 mm before compression is compressed to 26.25 mm, and using the value of the measured maximum rebound stress. From the viewpoint of performing desirable functions as an elastic member 10, it is preferable that the hardness be 11.6 N to 20.0 N, more preferably 12.4 N to 19.2 N, and even more preferably 13.3 to 18.3 N. The standard deviation of hardness obtained by rebound testing in multiple elastic members is preferably 2.000 or less, more preferably 1.000 or less, and even more preferably 0.500 or less.

[0025] The shapes of the multiple elastic members are preferably uniform. For example, the heights of the multiple elastic members are preferably uniform, and the standard deviation of the heights of the multiple elastic members is preferably 0.500 or less, and more preferably 0.100 or less. The height of the elastic members can be measured using a digital caliper (for example, manufactured by Mitutoyo Corporation).

[0026] As the elastic members are constructed as described above, they possess appropriate physical properties as elastic members, are highly uniform, and are precisely molded. Therefore, in electronic drums using elastic members, whether one elastic member is used or multiple elastic members are used, vibrations are appropriately transmitted to the sensor, the degree of damping of the impact remains constant, and a comfortable playing experience can be provided to the performer in the electronic drums.

[0027] The cross-sectional shape of the cells in the polyurethane foam is preferably circular. "Circular" means substantially circular, and "substantially circular" means that, in the cross-section of the polyurethane foam, a single cell may be a distorted circle, and two or more circular cells may be continuous, as long as the function of the elastic member is not impaired.

[0028] The cross-sectional shape of the cells in the polyurethane foam can be any direction. Since the cells of the elastic member are uniformly sized spheres, it is preferable that the cross-sectional shape of the cells be substantially circular, regardless of the direction of the cross-section. In other words, in the elastic member, it is preferable that the cross-sectional shape of the cells in the cross-sections obtained by cutting the elastic member in at least two different directions is circular in all cases. As described above, since the spherical shape of the cell is substantially uniform throughout the elastic member, the cross-sectional shape of the cell is circular, and it is preferable that the diameter of the circular cross-section is also substantially uniform throughout the elastic member. The diameter of the circular cross-section is the same as the diameter of the spherical shape described above. The standard deviation of the cell diameters in the multiple elastic members is preferably 0.100 or less, and more preferably 0.030 or less.

[0029] The elastic component is preferably a single-piece molded product. Since the elastic component is a single-piece molded product, it is preferable that it is an unprocessed product manufactured from a single material in a single molding process. This results in an elastic component that is highly reliable, uniform, and precisely molded.

[0030] The polyurethane foam may have an outer surface 13 (see Figure 1 or Figure 2). That is, the polyurethane foam may have a skin layer which is the outer surface. The polyurethane foam may have a skin layer which is the outer surface and a core layer which is the inner part of the skin layer. It is preferable that the polyurethane foam has a skin layer. Since the polyurethane foam is used as an elastic member, it is preferable that it recovers easily after deformation and exhibits little twisting. It is preferable that the polyurethane foam has a skin layer because it recovers easily after deformation of the elastic member, exhibits little twisting, and has appropriate elasticity as an elastic member. Furthermore, it is preferable that the polyurethane foam is an unprocessed product and has a skin layer. This results in an elastic member 10 that is more reliable, highly uniform, and precisely molded.

[0031] From the viewpoint of restoring the polyurethane foam and suppressing twisting, the skin layer is preferably 1 μm to 80 μm from the surface, more preferably 3 μm to 70 μm, and even more preferably 5 μm to 60 μm.

[0032] The polyurethane foam preferably has a density at one end that is within the range of -14% to +16% relative to the density at the other end. A density difference within this range between the top surface (one end) and the bottom surface (the other end) results in a more homogeneous polyurethane foam, which is preferable as an elastic member. The density is more preferably -12% to +12%, and even more preferably -10% to +10%.

[0033] Furthermore, it is preferable that the density of the polyurethane foam be uniform, even at parts other than the density at one end. For example, it is preferable that the density difference between any part of the polyurethane foam and the density of other parts be within the range of -14% to +16%, more preferably -12% to +12%, and even more preferably -10% to +10%. For example, it is preferable that the polyurethane foam has a uniform density in three parts: one end, the intermediate part between the other end, and the foam itself. It is preferable that the density is within the above range, as this results in high homogeneity in one elastic member and high uniformity across multiple members.

[0034] Furthermore, if the polyurethane foam has a skin layer, the density mentioned above is the density in the core layer excluding the skin layer. Also, the density in the core layer of the polyurethane foam is the apparent density, measured by the water displacement method. In polyurethane foam, the skin layer is a surface layer and has a different structure from the core layer.

[0035] <Method for manufacturing elastic components for electronic drums> One embodiment of the present disclosure, a method for manufacturing an elastic member for an electronic drum (hereinafter also referred to as the method for manufacturing an elastic member), is a method for manufacturing an elastic member for an electronic drum that is provided between the striking surface of the electronic drum and a sensor that detects vibrations of the striking surface, and transmits vibrations of the striking surface to the sensor, and includes the following steps. In other words, the method for manufacturing an elastic member for an electronic drum comprises a step of manufacturing a foaming raw material by mechanically foaming a polyurethane reaction composition (hereinafter also referred to as the foaming raw material manufacturing step) and a step of manufacturing an elastic member having a single layer of polyurethane foam extending from one end on the striking surface side to the other end on the sensor side by heat molding the foaming raw material (hereinafter also referred to as the polyurethane foam manufacturing step).

[0036] (Foaming raw material manufacturing process) The foaming raw material manufacturing process is a process of producing foaming raw materials by mechanically foaming a polyurethane reaction composition. The foaming raw material includes the polyurethane reaction composition and a foaming gas.

[0037] The polyurethane reaction composition contains a polyol component, a foam stabilizer, a catalyst, and an isocyanate component. The polyol component consists of polyols. Examples of polyols include polyether-based polyols and vegetable oil-based polyols. Two or more types may be used in combination.

[0038] Polyether-based polyols have the advantage of making polyurethane foam less susceptible to hydrolysis compared to ester-based polyols. As polyether polyols, polyether polyols for polyurethanes can be used, such as polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose. The polyether polyol preferably has 2 to 4 functional groups and a molecular weight of 400 to 8000, more preferably 2000 to 4000. Two or more types of polyether polyols may be used in combination.

[0039] Polyester-based polyols include polycaprolactone-based polyols and polycarbonate-based polyols, which have relatively good hydrolysis resistance, and their molecular weight is preferably 500 to 2000. Polycarbonate-based polyols have particularly excellent hydrolysis resistance. Examples of polycarbonate-based polyols include those obtained by the de-alcoholization reaction of polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol with dialkyl carbonates, dialkylene carbonates, and diphenyl carbonates. Two or more types of polycarbonate-based polyols may be used in combination.

[0040] Vegetable oil-based polyols mix well with hydrophobic polyether polyols and are effective in exhibiting hydrophobicity, making them preferred polyols for polyurethane foam used as sealing materials. Examples of plant oil-based polyols include those derived from castor oil, sunflower oil, rapeseed oil, linseed oil, cottonseed oil, tung oil, coconut oil, poppy oil, corn oil, and nut oils. Castor oil-based polyols and nut oil-based polyols are particularly suitable.

[0041] Examples of castor oil-based polyols include castor oil, reaction products of castor oil and polyols, and esterification reaction products of castor oil fatty acids and polyols. Examples of polyols to be reacted with castor oil or castor oil fatty acids include divalent polyols such as ethylene glycol, diethylene glycol, and propylene glycol, or trivalent or higher polyols such as glycerin, trimethylolpropane, hexanetriol, and sorbitol. Castor oil-based polyols preferably have 2 to 3 functional groups and a molecular weight of 300 to 3000, more preferably 500 to 1000. Examples of nut-based polyols include peanut-based and cashew-based polyols. Nut-based polyols preferably have 2 to 3 functional groups and a molecular weight of 300 to 3000, more preferably 500 to 1000. Two or more types of plant oil-based polyols may be used in combination. Oil-based polyols that do not contain reactive groups are also effective.

[0042] As a foam stabilizer, those known for use with polyurethane foam can be used. Examples include silicone-based foam stabilizers, fluorine-based foam stabilizers, and known surfactants. The amount of foam stabilizer is determined as appropriate, but an example is 0.01 to 12 parts by mass per 100 parts by mass of polyol component.

[0043] As catalysts, amine-based catalysts and organometallic catalysts for polyurethane foam can be used alone or in combination. Examples of amine-based catalysts include monoamine compounds, diamine compounds, triamine compounds, polyamine compounds, cyclic amine compounds, alcoholamine compounds, and etheramine compounds, and one of these may be used, or two or more may be used in combination. Examples of organometallic catalysts include organotin compounds, organoiron compounds, organobismuth compounds, organolead compounds, and organozinc compounds, and one of these may be used, or two or more may be used. The amount of catalyst is determined as appropriate, but an example is 0.05 to 5 parts by mass per 100 parts by mass of polyol component.

[0044] Furthermore, any additives may be added to the polyurethane reaction composition. Examples of such additives include chain extenders, crosslinking agents, fillers, dyes, pigments, antioxidants, and flame retardants. Examples of chain extenders include polyethylene glycol (PEG) and dipropylene glycol (DPG). When a chain extender is included, the amount of the chain extender is preferably 0.5 to 20 parts by mass per 100 parts by mass of the polyol component. Examples of crosslinking agents include polyhydric alcohols such as glycerin, butanetetraol, and polypropylene glycol, as well as diethanolamine and polyamine. When a crosslinking agent is included, the amount of the crosslinking agent is preferably 0.5 to 10 parts by mass per 100 parts by mass of the polyol component. Examples of fillers include alumina trihydrate, silica, talc, calcium carbonate, and clay.

[0045] The isocyanate component may be any type of isocyanate, such as aromatic, alicyclic, or aliphatic. It may also be a difunctional isocyanate having two isocyanate groups in one molecule, or a trifunctional or more functional isocyanate having three or more isocyanate groups in one molecule. These may be used individually or in combination.

[0046] For example, difunctional isocyanates include 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate (TDI), m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylenediisocyanate, and 3 Examples include aromatic compounds such as ,3'-dimethoxy-4,4'-biphenylenediisocyanate, alicyclic compounds such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and methylcyclohexane diisocyanate, and aliphatic compounds such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, and lysine isocyanate.

[0047] Furthermore, polymethylene polyphenyl isocyanate (polymeric MDI) can be cited as an example of isocyanates with two or more functions. Examples of isocyanates with three or more functions include 1-methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzol-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, triphenylmethane-4,4',4"-triisocyanate, etc. This can be achieved. Furthermore, the isocyanates are not limited to one type each, but may be one or more types. For example, one type of aliphatic isocyanate and two types of aromatic isocyanates may be used in combination. The isocyanate index is preferably 90 to 110. The isocyanate index is the value obtained by multiplying the number of moles of isocyanate groups per mole of active hydrogen groups contained in the urethane raw material by 100, and is calculated as [(equivalent amount of isocyanate in the foaming raw material / equivalent amount of active hydrogen in the foaming raw material) × 100].

[0048] As the foaming gas, a gas that does not adversely affect the reaction between the polyol and the isocyanate, such as dry air or nitrogen, is preferred. The foaming gas is suitable for polyurethane foam with an apparent density of 100-800 kg / m³. 3 A quantity that results in 10 to 1.4 times foaming is preferred, and specifically, it is preferable that the mixing ratio in the polyurethane reaction composition be 31 to 91% by volume. The mixing ratio of the foaming gas refers to the volume percentage of the foaming gas relative to 100 parts by volume of the polyurethane reaction composition excluding the foaming gas.

[0049] The foaming raw material is manufactured using mechanical foaming, where a mixture of polyurethane reaction composition and compressed foaming gas is supplied to an oak mixer or a nozzle with a narrowed tip, and then discharged from the oak mixer or nozzle. Mechanical foaming is also called the mechanical flossing method.

[0050] (Polyurethane foam manufacturing process) The polyurethane foam manufacturing process involves heating and molding the foaming raw material to produce a single layer of polyurethane foam extending from one end on the striking surface side to the other end on the sensor side. By heating and molding the foaming raw material, an elastic member 10 (see Figure 1 or Figure 2) having polyurethane foam is obtained.

[0051] The method of heat molding is not limited to any conventional method used to cure mechanically foamed foaming material. For example, by placing the foaming material into a mold having the shape of an elastic member and heating it, an elastic member having a single layer of polyurethane foam extending from one end on the striking surface side to the other end on the sensor side can be formed. The heating method can be adjusted depending on the type of polyurethane reaction composition, and in some cases, curing may be performed without heating.

[0052] In the polyurethane foam manufacturing process, a skin layer, which is the surface layer of the polyurethane foam, may be formed. Unlike the core layer, the skin layer is an area with a low or no air bubble content and is formed over the entire outer surface of the polyurethane foam. The thickness of the skin layer can be adjusted by controlling the heat molding process, etc.

[0053] By curing the foaming raw materials through mechanical foaming, it is possible to control the incorporation of air bubbles in advance, compared to polyurethane foams produced by chemical foaming or other methods, and because there is less volume change of the raw materials during the reaction or curing process, the cells have high homogeneity and can be molded into precise shapes.

[0054] The polyurethane foam manufacturing process preferably includes pouring foaming material into a mold. The mold can be any mold used for reacting and curing a mechanically foamed polyurethane reaction composition. The shape of the mold can be any shape that allows for the integral molding of an elastic member and is used for reacting and curing the polyurethane reaction composition. Because the foaming material is reacted and hardened using a mold, elastic components can be integrally molded, resulting in a higher degree of cell homogeneity and precise shaping.

[0055] The series of steps in the manufacturing method of an elastic member will be explained using a flowchart. As shown in Figure 3, first, the raw materials are stirred by a stirrer 21 (step S100, foaming raw material manufacturing process). If the foaming agent is a gas, it is also stirred together with the other raw materials at this stage to prepare the foaming raw material 22, which is a polyurethane reaction composition containing bubbles.

[0056] Next, the foaming material 22 is poured into the mold 23 and cast (step S110). Then, the reaction proceeds and it hardens (step S120). Heating may be performed during hardening. After hardening is complete, the mold is removed to obtain the elastic member 10 (step S130).

[0057] <Electronic Drums> An electronic drum (hereinafter also referred to as an electronic drum) according to one embodiment of the present disclosure comprises a striking head, an elastic member for an electronic drum according to one embodiment of the present disclosure, and a sensor.

[0058] As shown in Figure 4, the electronic drum 30 comprises a striking head 31, an elastic member 10, a sensor 32, sensor wiring 33, and a housing 34. The striking head 31 constitutes the striking surface. The striking head 31 and the elastic member 10 (see Figure 1 or Figure 2) are positioned such that vibrations are transmitted by the elastic member 10 when the striking surface is struck by the stick 35. For example, the striking head 31 is positioned on the upper surface 11, which is one end of the elastic member 10 on the striking surface side. If, for example, the electronic drum 30 is installed with the striking surface in a substantially vertical direction, like a bass drum in a drum kit, then the one end of the elastic member 10 on the striking surface side will be positioned horizontally, depending on the arrangement of the striking surface.

[0059] The sensor 32 is positioned to detect vibrations transmitted to the elastic member 10. For example, the sensor 32 is positioned facing the bottom surface 12 of the elastic member 10. The sensor 32 may be positioned so as not to touch the bottom surface 12 of the elastic member 10, or it may be bonded to the bottom surface 12, or another means may be provided to support the striking surface or the elastic member 10 so as to make contact with the bottom surface 12 of the elastic member 10 while maintaining an appropriate distance.

[0060] The sensor 32 can be any sensor capable of detecting vibrations transmitted to the elastic member 10. A pressure sensor can be used, and acceleration sensors, touch sensors, etc., may also be used. For example, a piezoelectric element (i.e., a piezo element) can be used.

[0061] One or more elastic members 10 are arranged in the electronic drum. The position of the elastic members can be appropriately determined depending on the type of electronic drum, etc. For example, if the electronic drum has one elastic member 10, it is preferable to place it in the center of the striking surface, and if there are multiple elastic members 10, it is preferable to place them at equal intervals around the periphery of the striking surface. In the case of multiple elastic members, one elastic member 10 may be placed in the center of the striking surface in addition to the periphery.

[0062] The electronic drum 30 is equipped with a highly uniform and precisely molded elastic member 10, so that vibrations caused by striking the drumhead are appropriately transmitted to the sensor 32. Therefore, problems caused by variations in the physical properties or shape of the elastic member 10 are suppressed. Consequently, playing the electronic drum can be made more comfortable.

[0063] Although the example of the elastic member 10 being mounted on an electronic drum 30 has been described, the elastic member 10 can be used in any device that has the function of appropriately transmitting vibrations caused by striking to a sensor. For example, in the case of electronic musical instruments, it can be used in electronic percussion instruments such as electronic tambourines, electronic congas, and electronic cajons, as well as electronic taiko drums, electronic cymbals, electronic marimbas, electronic vibraphones, and synth pads. In addition to electronic musical instruments, it can be used in game controllers, training equipment, medical equipment for rehabilitation, sports analysis devices, toys, etc. [Examples]

[0064] Next, an elastic member for an electronic drum according to one embodiment of the present disclosure will be described in more detail by reference to examples. However, the elastic member for an electronic drum according to the present disclosure is not limited in any way by these examples.

[0065] <Example 1> An elastic member was manufactured using the apparatus shown in Figure 3. A polyurethane reaction composition was prepared using the following raw materials, and nitrogen was used as the foaming gas. The nitrogen mixture ratio was set to 65% by volume based on the total volume of the polyurethane reaction composition. This was then stirred with a stirrer. Subsequently, it was cast using a mold, cured, and demolded to obtain an elastic member. Solution A (polyol component, mixed with the following ingredients): • Polyol 1: Polyether polyol, product name; PP-3000, manufactured by Sanyo Chemical Industries, Ltd., molecular weight 3000, number of functional groups 3, propylene oxide content 100%, 49.0 parts by mass • Polyol 2: Castor oil-based polyol, product name; HS 3G-500B, manufactured by Toyokuni Oil Co., Ltd., molecular weight 2500, number of functional groups 2.2, 10.0 parts by mass • Polyol 3: Castor oil-based polyol, product name; HS CM-025P, manufactured by Toyokuni Oil Co., Ltd., molecular weight 840, number of functional groups 3, 17.0 parts by mass • Polyol 4: Cashew nut-derived polyol, product name: NX-9203, manufactured by Cardolite, molecular weight 1350, number of functional groups 2, 20.0 parts by mass • Chain extender: Dipropylene glycol, 3.0 parts by mass • Metal catalyst: Organic acid salt catalyst, product name; EP73660A, manufactured by PANTECHNOLOGY, 4.0 parts by mass • Foam stabilizer: Silicone-based foam stabilizer, product name: SZ-1952, manufactured by Toray Dow Corning. Solution B (polyisocyanate component): • Isocyanate: Polymeric MDI (Crude MDI), Product name: M5S, manufactured by BASF Inoac Polyurethane, NCO%: 34%, 8.0 parts by mass

[0066] The resulting elastic members had a skin layer over their entire surface, with a top diameter 11 of 5 mm, a bottom diameter 12 of 40 mm, and a height of 35 mm in the Z direction (see Figure 1 or Figure 2). Multiple elastic members were fabricated, and 20 randomly selected members were measured and evaluated. Details of the fabricated elastic members are shown in Table 1. The 20 selected members are referred to as samples.

[0067] <Example 2> A molded product was obtained in the same manner as in Example 1. The skin layer on the side of the molded product was removed by polishing to obtain an elastic member. Multiple elastic members were prepared. Details of the obtained elastic members are shown in Table 1.

[0068] <Comparative Example 1 to Comparative Example 3> Products 1 to 3, which are used as elastic components for electronic drums, were designated as Comparative Examples 1 to 3, respectively. Product 1 was made by bonding five urethane sheets together with adhesive and then processing them into a truncated cone shape. Its size was the same as that of the elastic member in Example 1. Product 2 consisted of five urethane sheets bonded together with adhesive, with a stepped shape on the sides, and the size was the same as the elastic member in Example 1. Product 3 was formed by bonding five urethane sheets together with adhesive, then processing them into a truncated cone shape, and forming a skin layer over the entire outer surface. Its size was the same as that of the elastic member in Example 1. Multiple copies of each elastic component were fabricated. Details of the elastic components obtained as described above are shown in Table 1.

[0069] <Comparative Example 4> An elastic member was obtained in the same manner as in Example 1, except that a chemically foamed polyurethane reaction composition was used and chemical foaming was performed. Multiple elastic members were prepared. The raw materials for the polyurethane reaction composition are as follows.

[0070] Solution A (polyol component, mixed with the following ingredients): Polymer polyol (manufactured by Mitsui Toatsu Co., Ltd., product name "POP34 / 28") 100 parts by mass, foaming agent (C5F 12 ), 10 parts by mass Foam stabilizer (manufactured by Toray Silicon Corporation, product name "SF2910") 1.0 part by mass Catalyst (Stanus Octoate, manufactured by Chukyo Oils Co., Ltd.) 0.3 parts by mass Water 1.3 parts by mass Amine catalyst (manufactured by Nippon Emulsifier Co., Ltd., product name "LV33") 0.3 parts by mass Solution B (polyisocyanate component): Polyisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate MTL")

[0071] The above-described solution A and an amount of solution B that results in an isocyanate index of 110 were mixed with a stirrer 21 to prepare a urethane resin composition. This composition was then poured into a mold similar to that of Example 1, reacted, foamed, and cured, and after curing at 110°C for 4 hours to obtain a frustoconical molded product. The molded parts were used directly as elastic members. Multiple elastic members were created, and 20 randomly selected members were measured and evaluated. Details of the fabricated elastic members are shown in Table 1. The 20 selected members are referred to as samples.

[0072] For each of the elastic members obtained in Example 1, Example 2, and Comparative Examples 1-4, 20 were randomly selected, and the apparent density (g / m³) was determined for each. 3 The apparent density was measured using the water displacement method. The average of 20 apparent densities is shown in Table 1.

[0073] <Rating> (Cell diameter accuracy) For each of the obtained elastic members, 20 were randomly selected, and the cross-sections were observed after cutting with a band knife to measure the cell diameter of each. The standard deviation was calculated from the measured cell diameters of the 20 elastic members and is listed in Table 1 as the cell diameter standard deviation. Cell diameter accuracy was determined from the standard deviation value. The criteria for judgment were as follows: A and B were considered acceptable. The measurement results and evaluation results are shown in Table 1.

[0074] (Judgment criteria) A: Standard deviation is 0.030 or less B: Standard deviation is greater than 0.030 and less than or equal to 0.100 C: Standard deviation greater than 0.100

[0075] (Hardness precision) For each of the obtained elastic members, 20 were randomly selected and their hardness was measured by a rebound test. The standard deviation was calculated from the measured cell diameters of the 20 elastic members and is listed in Table 1 as the hardness standard deviation. Hardness accuracy was determined from the standard deviation value. The evaluation criteria were as follows: A and B were considered acceptable. The measurement results and evaluation results are shown in Table 1.

[0076] (Judgment criteria) A: Standard deviation is 0.500 or less B: Standard deviation greater than 0.500 and less than or equal to 2.000 C: Standard deviation is greater than 2.000

[0077] (Height accuracy) For each of the obtained elastic members, 20 were randomly selected and their height (in the Z-axis direction in Figure 1 or Figure 2) was measured. The standard deviation was calculated from the measured heights of the 20 elastic members and is listed in Table 1 as the height standard deviation. Height accuracy was determined from the standard deviation value. The criteria for judgment were as follows: A and B were considered acceptable. The measurement results and evaluation results are shown in Table 1.

[0078] (Judgment criteria) A: Standard deviation is 0.100 or less B: Standard deviation greater than 0.100 and less than or equal to 0.500 C: Standard deviation greater than 0.500

[0079] [Table 1]

[0080] (density distribution) In each of the 20 elastic members obtained in Example 1, as shown in Figure 5, they were divided into three equal parts in the Z direction (see Figure 1 or Figure 2), and then cut into upper, middle, and lower sections using a cutter. The apparent density was measured for the upper, middle, and lower sections. The density difference, calculated using the following formula, is shown in Table 2. (Top-Bottom):Top density-Bottom density (Top / Bottom-1):(Top Density / Bottom Density)-1 (Bottom / Top-1):(Bottom Density / Top Density)-1

[0081] [Table 2]

[0082] As shown in Table 1, the elastic members according to the embodiments of this disclosure have been demonstrated to be precisely molded and uniform in terms of cell diameter, hardness, and height. As shown in Table 2, the elastic members according to the embodiments of this disclosure have been demonstrated to be homogeneous, with density differences within a specific range within a single elastic member. Based on the above, it has been demonstrated that the elastic member according to the embodiment of this disclosure is highly uniform and precisely molded. [Explanation of Symbols]

[0083] 10 Elastic members 11 Top side 12. Base 13 Exterior 21 Agitator 22 Foaming raw materials 23 molds 30 Electronic Drums 31. Drumhead 32 sensors 33 Wiring for sensors 34 cabinets 35 Sticks S100~S130 Step x, y, z directions

Claims

1. An elastic member for an electronic drum, provided between the drumhead and a sensor that detects vibrations of the drumhead, for transmitting vibrations of the drumhead to the sensor, The aforementioned striking surface has a single layer of polyurethane foam extending from one end to the other end on the sensor side, The shape of the cells formed inside the polyurethane foam is spherical. Elastic component for electronic drums.

2. The elastic member for an electronic drum according to claim 1, wherein the cross-sectional shape of the cell is circular.

3. The elastic member for an electronic drum according to claim 1, which is a single-piece molded product.

4. The elastic member for an electronic drum according to claim 1, wherein the polyurethane foam has a skin layer on its outer surface.

5. The elastic member for an electronic drum according to claim 1, wherein the polyurethane foam has a density at one end that is in the range of -14% to +16% with respect to the density at the other end.

6. A method for manufacturing an elastic member for an electronic drum, which is provided between the drumhead of the electronic drum and a sensor that detects vibrations of the drumhead, and which transmits vibrations of the drumhead to the sensor, A process for producing a foaming raw material by mechanically foaming a polyurethane reaction composition, A process of manufacturing an elastic member having a single layer of polyurethane foam extending from one end on the striking surface side to the other end on the sensor side by heating and molding the foaming raw material, A method for manufacturing an elastic member for an electronic drum, comprising the features described above.

7. The method for manufacturing an elastic member for an electronic drum according to claim 6, wherein the step of manufacturing the polyurethane foam includes pouring the foaming material into a mold.

8. An elastic member for an electronic drum according to any one of claims 1 to 5, The striking surface head, The aforementioned sensor and, An electronic drum set equipped with [features].

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