US3444771A - Piano soundboard assembly with auxiliary board - Google Patents

Description

y 0, 1969 HANZO TAGUCH. 3,444,771

PIANO SOUNDBOARD ASSEMBLY WITH AUXILIARY BOARD Filed Dec. 8, 1966 Sheet of :s

PRIOR ART. 2

FIG. 3(0) y 0,1969 HANZO TAGUCH. v 3,444,771

PIANO SOUNDBOARD ASSEMBLY WITH AUXILIARY BOARD Filed Dec. 8. 1966 Sheet 2 of 5 May 20, 1969 HANZO TAGUCHI PIANO SOUNDBOARD ASSEMBLY WITH AUXILIARY BOARD Sheet 3 Filed Dec.

FIG. 6

FIG. 8

United States Patent 3,444,771 PIANO SOUNDBOARD ASSEMBLY WITH AUXILIARY BOARD Hanzo Taguchi, Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kabushiki Kaisha, Shizuokaken, Japan Filed Dec. 8, 1966, Ser. No. 600,192 Claims priority, application Japan, Dec. 17, 1965, 40/77,934 Int. Cl. Gc 3/06 US. Cl. 84-194 10 Claims ABSTRACT OF THE DISCLOSURE A piano soundboard assembly having an auxiliary board interposed between and bonded to a soundboard on the side thereof provided with ribs at least at the treble tone portion of the soundboard, with the grain of the auxiliary board being at an angle to the grain of the soundboard, and the auxiliary board being preferably of maple and having a thickness of from 2 to 3 mm. when interposed between the ribs and the soundboard and of from 3 to 6 mm. when the ribs are omitted at the portion of the soundboard to which it is bonded.

This invention relates to pianos and like musical instruments and more particularly to the structure of the soundboard assembly of pianos and the like. More specifically, the invention concerns a new soundboard assembly having improved sound emission characteristics for treble tones and improved sound emission characteristics for treble tones and improved sound emission characterstics of higher harmonics (high-frequency components) of lower tones.

In general, a piano soundboard assembly comprises a single fiat soundboard made up of several pieces of relatively narrow soundboard elements in side-by-side relationship with their adjacent longitudinal edges bonded adhesively together, a plurality of ribs bonded adhesively to the back or under surface of the soundboard in apart and substantially parallel relationship in directions substantially perpendicular to the grain of the soundboard, that is, substantially perpendicular to the soundboard elements, and one or more bridges bonded adhesively to the front or upper surface of the soundboard for supporting the strings of the piano.

The soundboard is made of straight-grained boards of a coniferous wood such as fir or spruce (Picea jezoensis, Picea sitchensis), and the grains of these boards are selected to lie in the same direction as that of the edge joints. Among the various woods, fir and spruce are particularly suitable for use in a soundboard because of their superior rigidity and vibration characteristics in their grain direction, but the rigidity and vibration characteristics of these woods in the direction perpendicular or substantially perpendicular to their grain direction are poor.

Therefore, in order to compensate for this defect, a plurality of ribs are bonded onto the back surface of the soundboard in directions perpendicular to the grain of the soundboard. The ribs are spaced apart at certain intervals, with the ordinary practice being to use 17 ribs in a full-concert type grand piano, 13 ribs in a semiconcert type grand piano, and 11 ribs in an upright piano.

Since the vibration modes are large in the case of bass tones, the rib spacing does not impose a problem, and the differences in vibrations of the parts with and without ribs can be neglected, and it is possible to consider the entire soundboard structure as a uniform structure. In contrast, the vibration modes are small in the case of treble tone, and the spacing between the ribs presents a problem whereby the rigidity and vibration characteristics differ depending on whether or not a rib is present (that is, the soundboardhas difiiculty in vibrating at the parts thereof which have ribs), and it is thereby impossible to consider the entire soundboard as a uniform structure.

In the pianos known heretofore, there has been the drawback of the treble tones being lower in volume (intensity) than the lower tones and, moreover, having poor tone color.

It is an object of the present invention to provide a soundboard assembly for pianos in which the sound emission characteristics particularly for treble tones are improved.

Another object of the invention is to provide a soundboard assembly which can be considered to be of uniform nature without being affected by the arrangement of ribs.

Still another object of the invention is to provide a soundboard whose vibration is facilitated by reducing the propagation loss of the sound energy due to ribs.

A further object of the invention is to provide an improved soundboard assembly whose rigidity and vibration characteristics are not affected by differences in the wood grain direction of the soundboard per se.

According to the present invention, briefly stated, there is provided, in a piano soundboard assembly having a soundboard, a bridge device secured to one surface of the soundboard for supporting the strings of the piano, a plurality of ribs secured in spaced-apart disposition on the opposite surface of the soundboard, and an auxiliary board interposed between and bonded to the ribs and the soundboard with an angular disposition such that the grain of the auxiliary board is at an angle with respect to the grain of the soundboard. By this construction and arrangement of the soundboard assembly according to the invention, the afo-restated objects thereof can be achieved.

According to the invention, the auxiliary board may be provided to cover the entire one surface of the soundboard, but in most cases, the desired results can be attained by providing the auxiliary board in only the treble region of the soundboard.

The nature, principle, utility, and details of the invention will be more clearly apparent from the following detailed description when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals.

In the drawings:

FIG. 1 is a perspective view of a known soundboard assembly;

FIG. 2 is a sectional view taken along the line 11-11 in FIG. 1 in the direction indicated by the arrows;

FIG. 3(a) is a perspective view showing one example of a soundboard assembly embodying the invention;

FIG. 3(b) is a plan view showing an example of a grand piano soundboard assembly provided at its treble region with an auxiliary board according to the invention;

FIG. S-(c) is a plan view showing an example of an upright piano soundboard assembly provided at its treble region with an auxiliary board according to the invention;

FIG. 4 is a sectional view taken along the line IVIV shown in FIG. 3(a) in the direction indicated by the arrows;

FIG. 5 is a sectional view taken along the same plane as FIG. 4 and showing a modification of the construction and arrangement shown in FIG. 4;

FIG. 6 is a perspective view showing another example of embodiment of the invention;

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 6 in the direction indicated by the arrow; and

FIG. 8 is a sectional view taken along the same plane as FIG. 7 and showing a modification of the construction and arrangement shown in FIG. 7.

As conducive to and as a basis for a full understanding of the nature and utility of the present invention, the following brief consideration of a soundboard assembly of conventional construction is presented, principally for the purpose of comparison.

Referring to FIGS. 1 and 2 showing one example of such known construction, the soundboard assembly is made up of a flat soundboard 1 consisting of a pluraltiy of substantially parallel soundboard elements bonded along their adjacent longitudinal edges to form joint lines 5, a plurality of spaced apart ribs 2 bonded to the back or undersurface of the soundboard 1 in directions substantially perpendicular to the grain of the soundboard 1, and bridges 3 secured to the front or upper surface of the soundboard 1 in substantially diagonal directions for supporting the piano strings (not shown).

In the example shown in FIGS. 1 and 2, two bridge structures are used, but depending on the type and size of the piano, two bridge structures or one bridge structure (as shown in FIG. 3(b)) may be used.

For achieving the aforestated objects of the invention, the rigidity of the soundboard assembly in the direction of the ribs 2 is uniformly increased according to the invention by interposing a thin auxiliary board 4 between the soundboard 1 and the ribs 2 at the treble region H of the soundboard assembly as shown in FIGS. 3-(a) and 4 and integrally bonding together the parts thus assembled. The auxiilary board 4 has a grain direction which is substantially perpendicular to the grain direction of the soundboard 1.

In a piano having 88 keys, the treble region lies in the vicinity of keys 64C to 71G and above. In full-concert and semi-concert grand pianos, from 3 to 4 ribs from the treble end of the soundboard cover the treble region as shown in FIG. 3(b), and in upright pianos two ribs cover the treble region as shown in FIG. 3(0).

It has been found that by this construction and arrangement according to the invention, in view of the resulting rigidity of the entire soundboard assembly, the ribs 2 lying where the auxiliary board is provided can be reduced in height by an amount approximately equal to the thickness of the auxiliary board to reduced propagation loss due to the ribs 2, and, moreover, the vibrations of the soundboard can also be facilitated. In some cases, it is not necessary to use ribs at the treble tone portion of the soundboard covered by the auxiliary board, and, therefore, the ribs which would conventionally be placed over this portion may be omitted.

For the auxiliary board 4, a material which has excellent frequency characteristics for vibration propagation at high frequencies (as, for example, maple or birch) is suitable when worked to a thickness of a few millimeters. For example, it has been found that when the soundboard 1 has a thickness of from 7 to 10 mm., a thickness of the auxiilary board 4 of from 2 to 3 mm.

(which is approximately /3 of the thickness of soundboard) is suitable. It has been ascertained further that, in the case where ribs are not used at the treble tone portion of the soundboard as mentioned above, an auxiliary board for covering this portion which is made of maple and has a thickness of from 3 to 6 mm. is suitable. Furthermore, since the peripheral edge of the soundboard 1 is bonded to the main structure of the piano, the auxiliary board 4 may be made gradually thinner toward the soundboard periphery to be bonded to the piano main structure, as shown in FIG. with the aim of facilitating the vibrations of the soundboard.

The auxiliary board 4 is used for its function of improving the sound emission particularly to treble tones. However, the pianos, such as upright pianos and small grand piano, in which the volume of emitted sound is deficient over the entire sound range, the sound volume can be increased by using an auxiliary board 4 to extend over the entire area of the soundboard assembly as shown in FIGS. 6, 7 and 8. In this case, also, the thickness of the auxiliary board 4 may be uniform therethroughout as 4 shown in FIG. 7 or it may gradually taper toward the periphery as shown in FIG. 8.

By the above described construction and arrangement of the soundboard assembly according to the invention, in which the soundboard 1 and auxiliary board 4 are bonded together (usually with glue) .and combined with their respective grains at right angles, the rigidity and vibration characteristics of the soundboard assembly are not affected by differences in the grain direction of the soundboard per se. Accordingly, it is possible to produce a soundboard assembly which can be considered as being uniform and which is unaffected by the the positional arrangement of the ribs even in the treble region.

Therefore, the present invention affords, in a relatively simple manner, an improvement in the sound emission of pianos, particularly in the treble tone region, whereby it is possible to obtain balanced tones over the entire tone range of the piano.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What I claim is:

1. A piano soundboard assembly comprising, in co1nbination, a soundboard of Wood, bridge means defined by at least one bridge for supporting strings and secured to one surface of the soundboard, a plurality of ribs secured in spaced-apart arrangement on the other surface of the soundboard, an auxiliary board of wood better than that of the soundboard with respect to the frequency characteristics for vibration propagation at high frequencies, said auxiliary board being interposed between the soundboard and at least two of the ribs with a disposition such that the grain of the auxiliary board is at an angle to the grain of the soundboard and said auxiliary board having a thickness approximately one-third of the thickness of the soundboard.

2. The piano soundboard assembly as claimed in claim 1 in which said angle between the grains of the auxiliary board and the sound board is substantially a right angle.

3. The piano soundboard assembly as claimed in claim 1 1n which the auxiliary board is provided in the treble region of the soundboard.

4. The piano soundboard assembly as claimed in claim 1 in which the auxiliary board is provided in between the soundboard and the ribs including a first rib provided at the part of the soundboard corresponding to the higher notes and at least one of the second, third, and fourth ribs counted from said first rib toward the bass portion of the soundboard.

5. The piano soundboard assembly as claimed in claim 1 in which the auxiliary board is of maple and has a thickness of from 2 to 3 mm.

6. The piano soundboard structure as claimed in claim 1 in which the auxiliary board is bonded to the soundboard over one entire surface thereof.

7. A piano soundboard assembly comprising, in combination, a soundboard, bridge means defined by at least one bridge for supporting strings and secured to one surface of the soundboard, a plurality of ribs secured in spaced-apart arrangement on the other surface of the soundboard, an auxiliary board interposed between the soundboard and at least two of the ribs with a disposition such that the grain of the auxiliary board is at an angle to the grain of the soundboard, and the thickness of the auxiliary board being of maximum value in parts of the auxiliary board immediately opposite said bridge means and gradually decreasing therefrom toward the periphery of the soundboard.

8. A piano soundboard assembly comprising, in combination, a soundboard, bridge means defined by at least one bridge for supporting strings and secured to one surface of the soundboard, a plurality of ribs secured in spaced-apart arrangement on the other surface of the soundboard, an auxiliary board interposed between the soundboard and at least two of the ribs with a disposition such that the grain of the auxiliary board is at an angle to the grain of the soundboard, said auxiliary board being provided in the treble region of the soundboard, and the height of each rib measured perpendicularly to the surface of the soundboard in the part thereof bonded to the auxiliary board being less than that of the ribs in the parts of the soundboard not bonded to the auxiliary board by a quantity approximately equal to the thickness of the auxiliary board.

9. A piano soundboard assembly comprising, in com bination, a soundboard of wood, a bridge means defined by at least one bridge for supporting strings and secured to one surface of the soundboard, a plurality of ribs secured in spaced-apart arrangement on the other surface of the soundboard in which the treble tone region is excluded, and an auxiliary board of wood secured to the treble tone region on the under surface with a disposition of the grain of the wood of said auxiliary board being References Cited UNITED STATES PATENTS 1,747,307 2/1930 Leland et -al 84l92 2,469,522 5/ 1949 Sauerland 84l92 FOREIGN PATENTS 365,496 12/1922 Germany.

1,739 1/ 1909 Great Britain.

RICHARD B. WILKINSON, Primary Examiner.

20 J F. GONZALES, Assistant Examiner.

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