US2206650A - Tone amplifier for pianos - Google Patents

Description

2, 1940- R. w. E. SPERRY 2, 06,650

TONE AMPLIFIER FOR PIANOS Filed Nov. 19, 1938 2 Sheets-Sheet 1 I 5 5 z I [Z I "j 15. [4 I f INVENTOR. 1691/ 1445. $7524):

A- 1 ORNEYi 2, 1940- R. w. E. SPERRY 2,206,650

TONE AMPLIFIER FOR PIANOS Filed Nov.- 19, 1938 2 Sheets-Sheet 2 INVENTOR. 2674 PH 14 E. .SPf/FE).

Patented July 2, .1940

PATENT OFFICE v 2,208,650 TONE AMPLIFIER FOR PIANOS Ralph w. E. Sperry, De Kalb, 111., assignor to The Rudolph Wurlitzer Company, Cincinnati,

Ohio, a corporation Application November 19, 1938, Serial No. 241,297

7 Claims.

.This invention relates to a structure for amplifying the tone of a piano, and particularly for carrying the string vibrations toward the middle portion of the sounding board, being particularly 5 applicable to the smaller piano structures necessitating the bridge being located too near to the fixed edge of the sounding board.

It has been found that in the smaller piands, and particularly such as are commonly known as the baby grand or the butterfly grand,

there is not sufficient room within the casing to permit locating the string bridge sufiiciently distant from the fixed edge of the sounding board to give the desired deep mellow tone. Thus, wherein the longer strings, such as the higher treble and bass strings, extend substantially the full width of the piano casing, this problem particularly arises and results in a deadening oi the sound because of insufficient freedom of vibration oi the sounding board wherethe bridge operates too closely to the casing.

To improve these conditions, and as particularly applied to the longer strings, it has been found that the deeper more mellow tone may string vibration not only directly through the bridge to the sounding board, but in addition through the bridge to a lever extending toward the middle portion of the sounding board so as to transmit vibrations thereto. This arrangement may take several forms of structure.

vThat herein more specifically disclosed pertains primarily to the higher treble strings, a differenttype of lever arrangement being required for the bass strings. However, the same invention as herein disclosed applies equally to both. More specifically, a lever in the form of a metal or wooden strip is provided having one end firmly anchored to the frame and extending 40 therefrom toward the, middle portion of the sounding board where its inner end bears thereon. Said strip extends across the bridge in contact therewith so that vibrations set up by the strings through the bridge will be transmitted throimh the arm to the sounding board.

In another form, the lever arm has its inwardly extending free end merely in fixed or adjustable contact with the middle portion of' the sounding board. It is sumcient for the purpose of this invention that provision be made to transmit the vibrations set up in the bridge by the strings inwardly of the sounding board.v

The full-nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a sectional view through the bridge and sounding board of a piano with one form r of lever construction mounted thereon. Fig. 2 is a plan view illustrating one type of bridge and the pomtion of the lever with respect thereto be obtained by providing means to transmit the and the treble strings. Fig. 3 is the same'as Fig. 1, showing a modified form of lever construction. Fig, 4 is the same as Figs. 1 and 3, showing a further modified form. Fig. 5 is the same as Fig. 1 showing still another modification. 'Fig. 6 is the same as Hg. 2 illustrating the invention as applied to the usual bridge construction.

In the drawings there is shown a portion of a piano having a casing i8 and metal plate i l to which is secured a pin block i 2 having the string pins l3 thereon. Anchored to the pins i3 are the usual treble strings M which extend over and bear upon the bridge E5. The bridge is mounted in the usual manner upon the sounding board It supported by the ribs H, the peripheral edge of the sounding board being secured to the framework i8 in the usual manner. Adjacent the end of the bridge i 5 near the higher treble strings, the bridge is notched on its underside to provide an opening indicated at l9 through which a vibration transmitting lever arm 20 extends.

The lever arm 20 is arrangedto extend crosswise of the bridge from the frame I8 toward the middle portion of the sounding board. One '25 end'of the lever arm is rigidly secured and anchored .between the frame structure and the plate II or pin block. As shown in Fig. 1, the other end of the arm is rigidly secured by a suitable screw 2| at or near the middle portion thereof, but preferably spaced therefrom by a block 22. An adjusting screw 23, extending through the bridge l5 and having its and bearing upon the lever arm 20, may be employed to adjust thetension of the lever arm with respect to the bridge and sounding board. b

There may be one or more such lever arms employed at spaced intervals along the bridge, either in respect to the treble strings or the bass strings, or both. As shown herein, it is sufficient, so far'as the treble strings are concerned, that a single lever arm be located adjacent that end of the bridge on which the higher treble strings bear.

The result of this arrangement is that that group of strings bearing upon the portion of the bridge lying closest to the frame not only permits vibration directly through the bridge to the sounding board, but through the bridge to the lever arm 20 which in turn transmits the vibrations to the middle'portlon or the sounding board. Thus, the vibrations normally transmitted to the sounding board atthat portion along which the bridge bears is amplified by the further transmission of vibrations to the middle 0 portion of the board. In the modified form shown in Fig. 3, the lever arm I20 is provided with an adjustable screw -l2i which bears upon a metal plate I22 which initurn bears upon the sounding board. Thus, 60

In the modified form, as shown in Fig. 4, the

lever arm extends over instead of under the bridge. Thus, there is shown an arm 22!! having in its inner end an adjustable screw 22l extending therethrough and bearing upon a washer 222 which in turn bears upon the sounding board. In this structure, there is also an adjustable screw 223 extending into the top of the bridge and adjustably spacing the lever arm thereabove. For anchoring the opposite end of the lever arm to the frame, a block 224 is provided to which it is secured, the block in turn being secured to the pin block or plate.

In the modified form, as shown in Fig. 5, the lever arm 320 is glued securely-to the bridge under which it extends, as indicated at 323. The inner end of the leverarm is likewise glued to the block 32L which is in turn glued to the upper surface of the sounding board.

In the illustrative plan view shown in Fig. 2, the bridge H5 is terminated short of the higher treble strings, being supplemented by arr expansion bridge H6 which .extends across the sounding board in chord-like fashion so as not to be too closely located with respect to the piano frame. In this construction, the lever arm, herein shown as that of Fig. 1, extends under the chord-like extension H6 toward the middle portion of the sounding board.

In the illustrative plan view shown in Fig. 6, the bridge 215 extends to all the treble strings. In this construction, the lever arm, likewise shown as that of Fig. 1, extends under the bridge 2l5 near its end and toward the middle portion of the sounding board upon which it bears.

The invention claimed is:

' 1. In a piano structure the combination with a supporting frame, a sounding board secured thereto, and a string plate having a pin block thereon to which the respective strings are secured, of a bridge supported by the sounding board having a portion thereof approaching the frame over which the strings bear for transmitting vibration to the sounding board, and a lever arm extending substantially transversely to and in contact with said bridge, one end being secured to said frame and the other end extending inwardly toward the middle portion of the sounding board and bearing thereon for transmitting vibrations from the bridge to the sounding board.

2. In a piano structure the combination with a supporting frame, a sounding board secured thereto, and a string plate having a pin block thereon to which the respective strings are secured, of a bridge supported by the sounding board having a portion thereof approaching the frame over which the strings bear for transmitting vibration to the sounding board, a lever arm extending substantially transversely to and. in contact with said bridge, one end being secured to said frame and the other end extending inwardly toward the middle portion of thesounding board and bearing thereon for transmitting vibrations from the bridge to the sounding board, and adjustable means associated with said lever arm for varying the bearing pressure thereof on the bridge andsounding board.

3. In a piano structure the combination with a supporting frame, a sounding board secured thereto, and a string plate having a pin block thereon to which the respective strings are secured, of a bridge supported by the sounding board terminating short of the higher treble strings, and a chord-like bridge extension having one end secured to the first-mentioned bridge and extending transversely of the higher treble strings, said extension lying a substantial distance inwardly from the pin block and bearing the higher treble strings for transmitting their vibra tions to the sounding board at a greater distance inwardly from the pin block than the first-mentioned bridge.

4. In a piano structure the combination with a supporting frame, a sounding board' secured thereto, and a string plate having a pin block thereon to which the respective strings are secured, of a bridge supported by the sounding board terminating short of the higher treble strings, a chord-like bridge extension having one end secured to the first-mentioned bridge and extending transversely of the higher treble strings, said extension lying a substantial distance inwardly from the pin block and bearing the higher treble strings for transmitting their vibrations to the sounding board at a greater distance inwardly from the pin block than the first-mentioned bridge,and a lever arm havingone end secured to the frame and extending inwardly substantially transversely of said bridge extenthereto, and'a series of piano strings connected with said frame and extending over said board,

of a vibration transmitting lever arm having one end secured to said frame and extending inwardly therefrom toward the middle portion of the sounding board and bearing on said sounding board for transmitting the vibrations set up in said strings inwardly from the frame to the sounding board near the middle portion thereof.

6. In a piano structure, the combination with a supporting frame, a sounding board secured thereto, and a string plate having a pin block thereon to which the respective piano strings are secured, of a bridge supported by the sounding board adjacent said frame over which the strings bear for transmitting vibrations to said board, and auxiliary means bearing against said bridge and board extending inwardly from the bridge over the upper surface of the board toward the middle portion thereof for transmitting a portion of said vibrations directly from the bridge to the middle portion of the board.

'7. In a piano structure, the combination with a supporting frame, a sounding board secured thereto, and a string plate having a pin block thereon to which the respective strings are secured, of a bridge supported by the sounding board over which the strings bear for transmitting vibrations thereto', and a lever arm bearing against said bridge and extending substantially transversely thereof over the upper surface of the sounding board toward the middle portion thereof with the extended end of said arm-bearing upon said sounding board for transmitting vibrations thereto. 1

RALPH W. E. SPERRY.

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