Vibrating Plate For Sound Instrument

Abstract

A vibrating plate for a sound instrument, such as a diaphragm of a loudspeaker, a sounding board of a piano or guitar, which comprises a plate of light material, such as paper, plastics, foamed plastics, metal or the like, said plate having pipes or cells formed therein or fixed thereto, said pipes or cells being filled with fluid under high pressure, thereby increasing flexural rigidity of said vibrating plate without appreciable increasing its weight.

Description

BACKGROUND OF THE INVENTION

This invention relates to a vibrating plate for sound instrument, such as a diaphragm of loudspeaker, a sounding board of piano or guitar or the like.

It is generally required for the vibrating plate for sound instrument to have relatively light weight and relatively high flexural rigidity. Accordingly the vibrating plate has been usually made by a plate of light material which is provided with reinforcing portions such as ribs to increase its flexural rigidity. However the provision of such reinforcing portions necessarily increases apparent weight per area of the vibrating plate and therefore it is difficult to provide a vibrating plate with very light weight with high flexural rigidity.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ideal vibrating plate which has relatively light weight together with relatively high flexural rigidity.

In accordance with the present invention there is provided a vibrating plate for sound instrument which comprises a plate of light material such as paper, plastics, foamed plastics, metal or the like, having at least one void in the form of pipe or cell, said void being filled with fluid under high pressure to increase flexural rigidity of said vibrating plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate preferred embodiments of the present invention in which:

FIG. 1 is a rear view of a vibrating plate according to an embodiment of the invention;

FIG. 2 is a sectional view of the vibrating plate as shown in FIG. 1;

FIG. 3 is a front view, partly broken, of a vibrating plate according to another embodiment of the invention;

FIG. 4 is a sectional view of the vibrating plate as shown in FIG. 3;

FIGS. 5 and 6 are front views, partly broken, showing other embodiments; and

FIGS. 7, 8, 9, 10 and 11 are sectional views showing further embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be explained with reference to the drawings which illustrate several embodiments of the invention.

FIGS. 1 and 2 illustrate an embodiment in which a vibrating plate consists of a plate 1, a spiral fine pipe 2 fixed on the rear side of said plate 1 and a radial fine pipe 3 fixed to the rear side of said spiral pipe, said pipes 2 and 3 being filled with fluid under high pressure. The plate 1 is made of material which is usually used for the vibrating plate for sound instrument, for example, paper, plastics, foamed plastics, metal or the like, and the pipes 2 and 3 are made of such material that is impermeable to the fluid used and is rather flexible but becomes self-supporting (flexurally rigid) by the pressure of the fluid filling the pipes, for example thermoplastic resin, thermosetting resin, glass or the like. The fluid filling the pipes may be gas such as air, hydrogen, helium, freon or carbon dioxide gas, or it may be liquid such as water, alcohol or ketone.

The flexural rigidity of the vibrating plate as shown in FIGS. 1 and 2 is considerably increased by the pressure of the fluid filling the pipes 2 and 3, but the weight thereof is only a little increased by the fluid under pressure, so that the apparent weight per area of the vibrating plate is kept at low value and thus the vibrating plate having light weight together with high flexural rigidity is obtained. When gas is used as the fluid, it is necessary to compress relatively large quantity of gas into the pipes to high density to obtain high pressure, but when liquid is used it is difficult to use finer pipes filled with smaller quantity of liquid to obtain the desired increase of flexural rigidity because the liquid has higher bulk modulus than that of the gas.

FIGS. 3 and 4 illustrate another embodiment in which a vibrating plate consists of a plate 11, a plurality of parallel pipes 12 fixed on one surface of said plate and a plurality of parallel pipes 13 fixed on the other surface of said plate at right angle to the pipes 12. The plate 11 and the pipes 12 and 13 may be made of some material as used in the embodiment shown in FIGS. 1 and 2, and the pipes are filled with fluid under high pressure.

In the embodiments as shown in FIGS. 1-4, the pipes 2, 3, 12 and 13 may be used independently or jointly. These pipes may be arranged in a single layer and communicated together, or they may be arranged in two layers (as shown in the drawings) or in more than two layers. The pipes may be arranged between two plates so as to form a sandwich construction. It is not always necessary to make the pipe of uniform diameter throughout its length, for example, the spiral pipe 2 as shown in FIG. 1 may be of gradually varying diameter from the center to outer end thereof. If the vibrating plate has a plurality of independent pipes, the fluid pressure may be changed in the respective pipes.

FIG. 5 illustrates another embodiment in which a plate 21 includes a network of pipe 22 in itself, and said pipe is filled with fluid under pressure. The network of pipe 22 may be built in the plate 21, or it may be previously molded as a separate member, which is embedded in the plate 22.

FIG. 6 illustrates a further embodiment of the invention, in which a plate 31 has a plurality of separate cellular voids 32 therein, instead of the network of pipe as shown in FIG. 5. The voids 32 may be formed by foaming the material of the plate 31 at the time of molding thereof. Such cellular construction may be adopted in the other forms of the vibrating plate. For example, the spiral pipe as shown in FIG. 1 or the straight pipes as shown in FIG. 3 may be provided with a plurality of partitions therein to form the cellular construction. In the cellular construction in which a plurality of voids are independent from each other, if a particular part of the vibrating plate is subjected to stress, the increase of the fluid pressure owing to the stress is limited to said particular part and is not unified throughout the plate, so that any part of the plate holds sufficiently high flexural rigidity.

FIGS. 7-11 illustrate other embodiments of the present invention. FIG. 7 illustrates a vibrating plate comprising a pair of sheets 41 and 42 of plastic film, metal foil or the like which are partly bonded together to form voids 43 therebetween. The voids 43 may be arranged in the form of a plurality of unidirectionally extending pipes, or in the form of independent cells.

FIG. 8 shows a vibrating plate comprising a pair of sheets 51, 52 of plastic film, metal foil or the like and a corrugated sheet 53 of similar material which is arranged between the sheets and bonded thereto to form voids 54. The voids 54 may be either formed in the form of pipes or cells. The constructions as shown in FIGS. 7 and 8 may be formed by partly bonding the sheets together such as by ultrasonic fusion, high-frequency fusion, electric heat fusion or adhesion, and then inflating non-bonded portions by blowing fluid thereinto, or they may be formed by previously forming the sheets in predetermined shape and connecting them together.

FIG. 9 illustrates a vibrating plate made of a plate 61 of foamed plastic such as foamed polystyrene in which are embedded pipes 62, which are filled with fluid under high pressure. The pipes 62 may be constructed in any form, such as radial form, spiral form or series of parallel pipes, and it may be arranged in a single layer or a plurality of layers. For a diaphragm of a loudspeaker, the proper flexural rigidity can be obtained by arranging the pipe 62 in the radial form including radially extending trunks and many branches diverging from said trunks, that is, in the form of a feather of an insect.

FIG. 10 illustrates a vibrating plate formed by a plurality of pipes 71 which are connected together being adhered side by side and filled with fluid under high pressure. FIG. 11 illustrates a vibrating plate 81 having a large void 82 in the central part thereof, which is filled with fluid under high pressure. The inside surfaces of the void are connected by means of rods 83.

In the various embodiments of the present invention as shown in the drawings, the void in the form of pipe or cell may be charged with the fluid under high pressure at the time of forming the vibrating plate. Alternatively, the void may be connected to a pump to pressurize the void as desired. If the wall of the void permits slight leakage of the fluid, the void may be maintained at a predetermined pressure by utilizing phenomenon of equilibrium between gas and liquid. The plate may be reinforced by embedding prestressed glass or metal fibers therein.

It will be understood that in accordance with the present invention the flexural rigidity of the vibrating plate can be considerably increased without appreciably increasing the weight, and thus a vibrating plate having light weight with high flexural rigidity can be obtained.

Claims

We claim:

1. A vibrating plate for a sound instrument, comprising a plate having at least one void which is filled with fluid under high pressure to increase flexural rigidity of said plate.

2. A vibrating plate for a sound instrument, comprising a plate and at least one pipe fixed to said plate, said pipe being filled with fluid under pressure to increase flexural rigidity of said plate.

3. A vibrating plate for a sound instrument, comprising a plurality of plates partly bonded together to form at least one void therebetween, said void being filled with fluid under pressure to increase flexural rigidity of said vibrating plate.

4. A vibrating plate for a sound instrument, comprising a plate having at least one void in the form of pipe therein, said void being filled with fluid under pressure to increase flexural rigidity of said plate.

5. A vibrating plate for a sound instrument, comprising a plate having voids in the form of cells, said voids being filled with fluid under pressure to increase flexural rigidity of said plate.

6. A vibrating plate for a sound instrument, comprising a plurality of pipes which are connected together side by side to form a plate, said pipes being filled with fluid under pressure to increase flexural rigidity of said plate.