US3443464A

US3443464A - Soundboard ribs

Info

Publication number: US3443464A
Application number: US602061A
Authority: US
Inventors: Shoji Akagi
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1965-12-17
Filing date: 1966-12-15
Publication date: 1969-05-13
Anticipated expiration: 1986-05-13
Also published as: DE1497793A1; GB1133360A; DE6608237U; US3444771A; NL6617696A; FR1505750A; DE1497790B1

Description

SHOJI AKAGII SOUNDBOARD RIBS .May '13, 1969 Filed Dec. 1s. 1966 Sheet FIG. 3v

M y 13, 1969 SHOJI'JAKAGI 4 souunaonmi mas Filed Dec. 15, 1966 Sheet of 2 United States Patent 3,443,464 SOUNDBOARD RIBS Shoji Akagi, Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi, Shizuoka-ken, Japan Filed Dec. 15, 1966, Ser. No. 602,061 Claims priority, application Japan, Dec. 25, 1965, 40/105,892 Int. Cl. GlOc 3/06 US. Cl. 84195 13 Claims ABSTRACT OF THE DISCLOSURE A piano soundboard structure in which spaced apart ribs bounded to one surface of a soundboard are caused to have different acoustical characteristics respectively suitable for the operational frequencies of the respective parts of the soundboard to which the ribs are bonded, with the acoustical characteristics being varied by the use of different kinds of woods in different configurations for the ribs.

This invention relates to pianos and like musical instruments and more particularly to the soundboard structures of pianos and the like. More specifically, the invention concerns a new piano soundboard structure whose sound transmission characteristics for tones of high frequency are remarkably improved by a novel selection of the composition and arrangement of the ribs of the soundboard structure.

As is known, the soundboard structure of a piano is fabricated by bonding a plurality of ribs in spaced-apart arrangement on the reverse or back surface of a soundboard and bonding one or more bridges for supporting the strings of the piano to the front surface of the soundboard. The soundboard is fabricated by joining a number of straight-grained boards with grains in their longitudinal direction in side-by-side arrangement, with adjacent longitudinal edges being ordinarily joined by bonding with an adhesive (usually glue).

The ribs are disposed perpendicularly or substantially perpendicularly to the grain of the soundboard. Each rib is made of one of the coniferous woods such as fir and spruce (Picea jezoensis, Picea sitchensis, etc.) because of their excellent vibration transmission characteristics and rigidity in the grain direction. However, while spruce (including fir) is extremely good for transmission of vibrations of a number of hundreds of cycles per second, they are not as good for transmission of vibrations of higher frequencies of a number of thousands of cycles per second.

Furthermore, since the vibration modes of high frequencies are extremely small, and since, in comparison therewith, the spacing of the ribs is excessively large, the transmission of high-frequency vibrations particularly in the direction perpendicular to the grain of the soundboard (i.e., in the direction of the ribs) is poor. As a result, pianos known heretofore have been deficient in sound volume (intensity) and tone color of tones at high frequencies (not in the sense only of high and low of the fundamental frequencies of the tones, but in the sense of high and low of the frequencies including higher harmonics of lower tones).

It is an object of the present invention to improve the transmission of vibrations of not only treble tones but ice also higher harmonics of lower tones and to improve tone color in a piano.

The foregoing object has been achieved by the present invention, according to which, briefly stated, there is provided a sound board structure in which the ribs are in direct contact with and bonded to one surface of the soundboard and possess dilferent acoustical characteristics, with each rib having characteristics suitable for the operational frequencies of that part of the sound board to which it is bonded.

One method for causing the ribs to have difierent acoustical characteristics is to use a hardwood for some of the ribs and a softer wood for the others. Another method is to vary the composition and construction of the ribs depending on whether they are to correspond operationally to treble tones, medium tones, or base tones.

For example, it is possible to provide a rib of the above stated desired characteristics by combining into a single rib a thin central member or layer made of maple flanked on opposite sides with thin spruce side members bonded thereto, with the three members forming a laminated or sandwich structure. While ribs of such special construction can be provided over the entire area of the soundboard structure, the volume of tones of high frequency can be considerably increased by providing these special ribs over only the regions of the soundboard structure of treble tones.

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 showing, principally, the reverse side of a general example of a soundboard structure of a grand piano;

FIG. 2 is an enlarged, fragmentary perspective view showing one part of the soundboard structure shown in FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line IIIIII in FIG. 2;

FIG. 4 is a perspective view showing, principally, the reverse side of a soundboard structure illustrating one example of embodiment of the invention;

FIG. 5 is an enlarged, fragmentary perspective view showing another example of embodiment of the invention;

FIG. 6 is a fragmentary sectional view taken along the line VI-VI in FIG. 5;

FIG. 7 is a planar view of the reverse side of one example of a soundboard structure according to the invention for a grand piano of semi-concert type; and

FIG. 8 is a planar view of the reverse side of an example of a soundboard structure according to the invention for an upright piano.

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 the soundboard structure of a piano of general type with respect to an example thereof as illustrated in FIGS. 1, 2, and 3 is first presented, principally for the purpose of comparison,

As illustrated in FIG. 1 and as mentioned briefly hereinbefore, the soundboard structure of a piano, in general, has as its principal component a single substantially flat soundboard 11 made up of several soundboard elements in side-by-side arrangement with adjacent longitudinal edges glued or adhesively bonded together, with each element being a piece of good-quality, straight-grained Wood with its grain in its longitudinal direction. The soundboard 11 is provided on its reverse or back side with a plurality of ribs 12 bonded thereto in spacedapart, substantially parallel arrangement with their longitudinal directions perpendicular or substantially perpendicular to the grain of the soundboard 11, i.e., to the longitudinal direction of the soundboard elements 10. The soundboard 11 is provided on its front side with a bridge device (as shown in FIGS. 7 and 8) bonded thereto in a direction substantially diagonal to the grain of the soundboard 11, with the bridge device 15 having the function of supporting the strings of the piano.

The number of ribs 12 used for each soundboard differs with the type of piano, it being the common practice to use l7 ribs in a full-concert grand piano, 15 ribs in a semi-concert grand piano, 13 ribs in a small grand piano, and 11 ribs in an upright piano. Heretofore, it has been the common practice to fabricate all of the ribs for any one soundboard from the same kind if wood, particularly spruce (including fir) being ordinarily selected because of its good rigidity and sound transmission characteristics in its grain (longitudinal) direction.

However, when all of the ribs are made from the same kind of Wood, the sound transmission characteristics of the soundboard structure, especially the tone volume and tone color at high frequencies, become deficient.

The present invention contemplates the elimination of this deficiency by fabricating each rib in a manner such that it will have characteristics suitable for operational frequencies of that part of the soundboard to which it is bonded, as described more fully hereinbelow with respect to preferred embodiments of the invention.

In one embodiment of the invention as shown in FIG. 4, ribs 13 made of spruce as heretofore and ribs 14 made of hardwood such as maple, beech, and birch are bonded to a soundboard 11. It will be seen that the ribs are in direct contact with the surface of the board 11 and the hardwood ribs 14 are interposed alternately between every two adjacently disposed spruce ribs 13. All of the ribs in the treble region are hardwood ribs 14.

In order to fabricate the ribs partially of hardwood, it is possible to fabricate a certain number of the ribs among the total number of ribs entirely of a hardwood as indicated in FIG. 4. Alternatively, it is also possible to construct composite ribs each having, as viewed in cross section, one part made of a hardwood and the remaining part made of a softwood as shown in FIGS. 5 and 6. That is, in the example illustrated in FIGS. 5 and 6, the central part of a layer 13a of the rib 13 is made of a hardwood such as maple, beech or birch and the flanking parts or layers 1311 are made of a softer wood such as spruce, whereby a laminated or so-called sandwich construction is produced.

It has been found that excellent results can be obtained by making the width in the horizontal direction as viewed in FIG. 6) of the central part made of a hardwood equal to from /s to /3 of the total width of the completed rib. Accordingly, if the widths of the two flanking parts 13b are equal, the desirable ratio of the widths (in sequence from one side to the other) is from 2:1:2 to 1:1:1.

Ribs of the above described construction may be provided, for example, at only the treble region of the soundboard 11 or may be partly provided over the entire soundboard. In this case the lower-frequency sounds are transmitted by the softwood, and the higher-frequency sounds are transmitted by the hardwood. Therefore, according to the present invention it is possible to increase the tone volume over a wider frequency range than was heretofore possible.

In a specific example of embodiment of the invention as illustrated in FIG. 7, of the ribs 12 on the reverse side of a soundboard structure of a grand piano, three (2 to 5 4 are suitable) ribs in the treble region of the soundboard are made of hardwood such as maple, beech, and birch or are laminated composite ribs of softer wood and hardwood as illustrated in FIG. 6. The remaining ribs, i.e., the ribs at the medium and bass regions are made of a softer wood such as spruce.

Another specfic embodiment of the invention as applied to an upright piano is illustrated in FIG. 8 showing the back of the soundboard structure. Two of the ribs 12a and 12b in the treble region are laminated composite ribs as illustrated in FIG. 6.

The soundboard structures illustrated in FIGS. 7 and 8 are provided with bridge devices 15. In the example shown in FIG. 7, the bridge device is in the form of a continuous curved member (rertangular in cross section), while, in the example shown in FIG. 8, it is divided into two parts. In either case, the main portion of the bridge device is in a substantially parallel direction relative to the grain direction of the soundboard.

When the ribs in a soundboard structure are made partially of hardwood, and the remaining parts of the ribs are made of spruce as described above, the vibrations of medium and low frequencies are transmitted well by the spruce, while the vibrations of high frequencies are transmitted well by the hardwood. Therefore, by the use of the piano soundboard according to the invention, it is possible to obtain high tone volume and, moreover, excellent tone color even at high frequencies.

While the invention has been described above with respect to examples of application thereof to grand pianos, it will be obvious that the invention can be applied with equal facility and effectiveness also to upright pianos.

What I claim is:

1. A piano soundboard structure comprising a soundboard having opposite surfaces, a plurality of ribs in direct contact with one surface of the soundboard and being bonded to such surface, and a bridge device bonded to the opposite surface of the soundboard, certain of said ribs being of hardwood, and the remainder of said ribs of softer wood.

2. The piano soundboard structure as claimed in claim 1, in which said hardwood is selected from among maple, beech and birch.

3. The piano soundboard structure as claimed in claim 1, in which said certain ribs are of laminated bonded construction consisting of elongated layers of hardwood and elongated'layers of softer wood.

4. The piano soundboard structure as claimed in claim 3, in which said certain ribs consist of a central layer of hardwood sandwiched between outer side layers of softer wood.

5. The piano soundboard structure as claimed in claim 4, in which said certain ribs consist of a central layer of maple sandwiched between outer side layers of spruce.

6. The piano soundboard structure as claimed in claim 4, in which the thickness of the central layer of hardwood is from /5 to /3 of the total width of the rib.

7. The piano soundboard structure as claimed in claim 1, in which said certain ribs of hardwood are provided at the treble region of the soundboard.

8. The piano soundboard structure as claimed in claim 7, in which said hardwood is selected from maple, beech and birch.

9. The piano soundboard structure as claimed in claim 7, in which said certain ribs provided at the treble region are from 2 to 5 inclusive of ribs at the highest treble region.

10. The piano soundboard structure as claimed in claim 7 in which said certain ribs are of laminated bonded construction consisting of an elongated central layer of hardwood and elongated outer side layers of softer wood.

11. The piano soundboard structure as claimed in claim 10 in which said certain ribs of laminated bonded construction consists of a central layer of maple sandwiched between outer side layers of spruce.

5 12. The piano soundboard structure as claimed in claim 10 in which said certain ribs of laminated bonded construction are two ribs provided at the treble region of the soundboard. 13. The piano soundboard structure as claimed in claim 1 in which said ribs of hardwood and said ribs of softer 5 wood are disposed in alternate relationship in the mediumtone region and bass region of the soundboard.

6 References Cited UNITED STATES PATENTS 2/1873 Steinway 84-195 5/1927 Mehlin 84-192 RICHARD B. WILKINSON, Primary Examiner.

L. R. FRANKLIN, Assistant Examiner.