SOUNDBOARD APPARATUS AND METHOD OF FORMING

Abstract

The present invention concerns soundboard apparatus for a musical instrument, the apparatus comprising a soundboard substrate formed of composite fibrous resin bonded material having a thickness of between 0.75 mm and 3 mm; and an outer layer formed of ultra-violet light blocking material having a thickness of between 0.5 and 0.9 mm. Further, the present invention relates to a method of forming a soundboard apparatus, the method comprising the steps of: bonding multiple layers of woven or straight stranded fibrous material in a resinous matrix to form a soundboard substrate, wherein the soundboard substrate is formed such that it is oversized with respect to final soundboard substrate dimensions; and finishing the soundboard substrate to form the final substrate, the finishing process being constrained to ensure that the final substrate dimensions are not compromised.

Claims

1-23. (canceled)

24. A soundboard apparatus for a musical instrument, comprising a soundboard substrate formed of composite fibrous resin bonded material having a thickness of between 0.75 mm and 3 mm; and an outer layer formed of ultra-violet light blocking material having a thickness of between 0.05 and 0.9 mm.

25. A soundboard apparatus according to claim 24, wherein the outer layer is formed of one or more of wood material, metal foil, paint, or metal deposition.

26. A soundboard apparatus according to claim 24, wherein the outer layer is provided to one or both of an upper and an underside surface of the soundboard substrate.

27. A soundboard apparatus according to claim 24, further comprising an integrated bridge of composite fibrous material.

28. A soundboard apparatus according to claim 24, wherein woven layers of fiber in the substrate comprise a weave of a double strand weft and a single strand warp.

29. A soundboard apparatus according to claim 28, wherein in the majority of layers, the double strand weft of the three strand woven layer or layers of the substrate is aligned along the major length dimension of the substrate, and the single woven warp strand is aligned at right angles to the weft along the minor width dimension of the substrate.

30. A soundboard apparatus according to claim 24, wherein the substrate is formed of a mathematically odd number of layers of woven or unwoven strand fiber material, in each layer the fiber orientation being substantially orthogonal to its contiguous layer or layers.

31. A soundboard apparatus according to claim 30, wherein the substrate is formed of three, five or seven layers of unwoven straight strand fiber material.

32. A soundboard apparatus according to claim 31, wherein the two outer layers of the substrate are woven fiber material and the inner layers or layer of the substrate are unidirectional unwoven fiber material.

33. A soundboard apparatus according to claim 32, wherein the majority of the unidirectional unwoven fibers in the inner layers or layer of the substrate are orientated along the major length dimension of the soundboard.

34. A soundboard apparatus according to claim 28, wherein the unwoven fibers of the inner layer or layers of the substrate have a greater fiber diameter than the woven fibers in the outer layers.

35. A soundboard apparatus according to claim 24, wherein the substrate of a five layer sound board is formed with two outer layers of woven fiber composite material, having a three strand weave, and three inner layers of unwoven unidirectional fiber, two of which are aligned along the major dimension of the substrate, the fibers of the central layer being aligned along the minor dimension.

36. A soundboard apparatus according to claim 24, wherein the substrate of a three layer sound board is formed with two outer layers of woven fiber composite material and one inner layer of unwoven unidirectional fiber, the latter layer being aligned along the major dimension of the instrument substrate.

37. A method of forming a soundboard apparatus as claimed in any preceding claim, the method comprising the steps of bonding multiple layers of woven or straight stranded fibrous material in a resinous matrix to form a soundboard substrate, wherein the soundboard substrate is formed such that it is oversized in thickness with respect to final soundboard substrate dimensions; and dressing the soundboard substrate to form the final substrate, the dressing process being constrained to ensure that in the final substrate the fibers in the inner layers are not cut by the dressing process.

38. A method according to claim 37, wherein the dressing involves sanding and/or machining the soundboard substrate.

39. A method according to claim 37, wherein the soundboard substrate is finished to achieve a flatness and thickness tolerance of not more than 0.2 mm.

40. A soundboard apparatus for a musical instrument, the apparatus comprising:— a soundboard substrate formed of composite fibrous resin bonded material having a thickness of between 0.75 mm and 3 mm, wherein the substrate is formed of at least three layers of woven or unwoven strand fiber material, wherein the majority of fibers in the inner layers or layers of the substrate are orientated along the major length dimension of the soundboard, wherein the material of a central layer of the substrate has a greater fiber diameter than the other layers.

41. A soundboard apparatus according to claim 40, wherein the substrate has five layers, and wherein the majority of fibers of a central layer of the substrate are aligned across the minor width dimension of the soundboard, with the majority of fibers in the two inner layers adjacent the central layer being orientated along the major length dimension of the soundboard.

42. A soundboard apparatus according to claim 40, wherein the substrate has three layers, and wherein the majority of fibers of a central layer of the substrate are aligned along the major length dimension of the soundboard.

43. A piano or similar percussion instrument incorporating a soundboard apparatus according to claim 24.

Description

[0029] Examples of the present invention will now be described by way of example and with reference to the drawings, of which;—

[0030] FIG. 1 shows a perspective view of a piano incorporating soundboard apparatus of the present invention; and

[0031] FIG. 2 shows plan view of the piano of FIG. 1.

[0032] The piano illustrated has two bridges. Other typical concepts of piano design may incorporate one, two or three bridges. As shown in FIGS. 1 and 2, a piano 1 has a soundboard 2 on which are provided two bridges, a long bridge 3 for transferring vibrational energy from the strings tuned to the treble and tenor notes to the soundboard and a bass bridge 4 for transferring vibrational energy from the strings tuned to the bass notes to the soundboard. On the upper surface of each bridge is provided a plurality of string bridge interfaces (agraffes) 5 is provided. The agraffes hold the strings firmly in contact with the upper surface of the bridges.

[0033] A desirable feature of all piano soundboards is that sound energy be distributed uniformly throughout the board at the same time. The velocity of sound in wood is greatest along the length of the wood grain. It is thus general practice to align the grain of spruce boards along the major dimension of the soundboard. Sound energy propagating across the board being substantially slower can be assisted by aligning the belly bars in the minor dimension direction. It is however probable that early instrument designers adopted this configuration with the objective of developing an integrated sheet of wood comprising planks held together by the ribs.

[0034] In this connection, the applicant has found that when manufacturing composite sheet materials for a soundboard containing fibrous materials, it is convenient to build up the sheet material with two outer layers of woven fibre and an odd number of inner layers of un woven unidirectional fibre. Fibre direction in each layer being orthoganol to the contiguous layer. The selection of different weaves, fibre gauge, number of layers of each weave and fibre orientation thus enable the designer to optimise the rate of distribution of vibration energy uniformly throughout the board with or without use of reinforcing belly bars which in traditional wood boards serve that purpose.

[0035] As stated above, the velocity and transmission of sound energy in a fibre composite sound board is highest along the length of straight fibres. The sound quality and harmonic content from such a soundboard as described above is similar to that of a conventional thickness spruce board but it is typically more powerful. Using the string bridge interface system disclosed in the applicant's earlier patent disclosure No. WO 2010 086690 A2, the downbearing load on the soundboard is alleviated and therefore relatively unstressed except by vibration, The soundboard will not therefore progressively collapse under string load to the point at which adequate contact is lost between string and bridge cap which would result in poor sound and loss of efficiency of transfer of vibration energy into the soundboard from the string. For this reason the lifespan and durability of the instrument housing the described soundboard is greatly lengthened.

[0036] Composite sheet materials are typically manufactured by laying up several layers of resin impregnated fibre weave on a flat former plate and then curing this in a heated vacuum furnace. Whereas the under surface developed against the plate can be made reasonably flat and smooth, the upper surface (called the rough side) is not usually so smooth or accurate. Uncontrolled variation in thickness of the material of such a soundboard may lead to uncontrolled variability in sound quality across the registers of the piano. After forming and curing the board it is thus desirable to sand or machine both surfaces flat and to control the precise thickness of the board. However, post-forming work of any nature on composite fibre sheet materials may result in cutting of the fibres at the surface. Exposing the cut ends to atmospheric oxidation can severely weaken the material and result in deterioration of its strength with time. Under stress, the cut fibres at the surface may progressively detach from the resin matrix under shear forces. Oxidation can then more easily penetrate into and weaken the structure of the sheet.

[0037] The applicant has therefore established that by forming a soundboard substrate with a sacrificial woven layer on each side, it is possible to sand the board to the precise flatness and thickness required while the inner and undisturbed multiple layers or layer of fibre retain the required strength, acoustic properties and stiffness.

[0038] Typically but not exclusively, an odd number of layers of woven or unwoven strand fibre material are used with the majority of fibres in all layers being orientated along the major length dimension of the board in each layer. The inner un woven unidirectional fibre layers may be typically but not exclusively of slightly greater fibre diameter.

[0039] The precise weave and orientation chosen is selected to distribute vibration energy as evenly in time as possible within the board. Preferably however, the sound board substrate outer layers have a three strand weave with a double strand (the weft) aligned along the major dimension (length) of the board and a single strand (the warp) aligned at right angles to the weft across the board in the second and fourth layer. The inner layers provide the strength and stiffness required while the two outer layers, are sacrificial material that can be dressed and thus reduced in thickness by sanding to achieve flatness and precision of thickness of the whole soundboard.

[0040] Recent development in carbon sheet forming, using a resin absorbing detachable cloth over the sheet while it is cured have enabled manufacture of soundboards of excellent thickness uniformity and flatness on both sides. Thin boards made by this method have been found to have sufficiently close tolerance on thickness that finish machining is not necessary.

[0041] Composite material and carbon fibre in particular is subject to degradation by ultra violet light. In manufacture of a soundboard we apply one or more layers of veneer wood or other UV light excluding material to the upper surface of the board which is the surface most likely to be exposed to ultra violet light. The applicant has determined that such veneer, if of the order of 0.7 mm thickness, has no undesirable influence on the acoustic properties of the board. Various paints metal foils and metal coating deposition and other surface treatments that reflect UV light can also be used for the same purpose.

[0042] Piano soundboards conventionally are fitted with one or more wooden bridges which transfer vibration energy from the strings to the soundboard. These bridges are normally made of beech and/or ebony and maple wood. The grain direction is typically predominantly vertical to optimise transfer of sound energy as efficiently as possible along the grain. Some manufacturers treat the wood to increase its hardness. Manufacture of a composite or carbon fibre bridge integral with the soundboard is facilitated if the soundboard itself is the same composite material. A carbon fibre bridge may be bonded to the upper surface of the soundboard. To ensure best acoustic energy transfer the thickness of the bond material must be minimal and less than 0.1 mm.

[0043] It follows that flatness of the sheet material and the under surface of the bridge in a bonded pair is critical in manufacture. Such bridge is advantageous for efficient transfer of vibration energy by virtue of the favourable low sound absorption characteristics of carbon or other fibre composites. A bridge made of these composites will be stiffer than a wooden bridge, and this could impart excess stiffness in the soundboard unless the bridge height of the composite material bridge is minimised. A typical wooden piano bridge is 30 to 35 mm height. A bridge of composite material would normally be 15 to 25 mm height.

[0044] The present invention can thus provide a piano or similar percussion instrument soundboard manufactured from composite fibrous resin bonded material of thickness from 0.75 mm to 3 mm built into the instrument with an agraffe (clip) system connection between the strings and the soundboard that does not impose significant downloading force on the soundboard.

[0045] Moreover, the piano or similar percussion instrument soundboard can comprise multiple layers of woven or straight stranded fibrous material bonded in a resinous matrix. The board can be manufactured on both sides to achieve flatness and thickness tolerance of not more than 0.2 mm. It will be appreciated that the contour thickness may vary in different zones of the board.

[0046] The flatness and thickness may be controlled by sanding or machining. The sanding or machining operation is preferably constrained in depth to ensure that the central or several inner layers of resin bonded fibres which are required to provide the necessary strength, acoustic properties, and thickness shall not be cut or damaged by the machining or sanding operation. The two or more outer layers thereby provide sacrificial material for adjustment of flatness and thickness. The sanding process is carried out using a precision belt sanding machine which removes the high spots leaving a flat smooth surface.

[0047] Further, the upper surface at least and optionally both surfaces of the soundboard may advantageously be covered by one or more veneered layers of wood material, paint or metal deposition to exclude ultra violet light which may otherwise degrade the composite material.

[0048] Additionally, an integrated or bonded bridge of similar material may be provided in which the fibres in the bridge section are principally aligned in the vertical plane.