US1062275A - Sounding-board. - Google Patents

Description

F. PRANKEL. SOUNDING BOARD.

APPLICATION FILED SEPT. so, 1911.

Patented May 20, 191.3

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ll/jin'egis'esl. I v I ven/Zora UNTTED STATES PATENT OFFICE.

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' spense-anos of Lettere raient. Application filed SeptemberSU, 1911. Seal No'. 652,124.

Patented May 2o, 191e.

To' all whom t may concern.'

Be it known that I, FRIDOLF FRANKEL, a subject of the King of Sweden, residing at Stockholm, in the Kingdom of Sweden, have 5 invented new and useful -Improvements in Sounding-Boards, of which the following is a specification, reference being had to the drawing accompanying hereof.

and forming a part This invention relates td the manufacturing of sounding-boards for pianos and other g ciently well secured to the frame and suitably stretched therein. It is'to be observed that, in order to obtain a good resonance, it is indispensable that the sounding-board'has a certain high tension. l

In attachingV sounding-boards te their frames several mistakes have been committed. The frames were usually formed by "two extended metal rings between which the sutliciently heated sheet-metal plate was placed. The plate was thereupon while hot clamped in position by screws. extending through holes in the rings and the plate. It

has, however, been found that, when the tension is very high, the screws cannot sufficiently clamp the plate but allow it to slip.

, Moreover, the rings, as usually constructed, 40 were too weak to withstand the tension, and, therefore, were distorted or caused'to yield.'

The fastening of the plate in a heated condition, in order to obtain a sufticienttension by the contraction of the plate in cooling, is

connected with diiiiculties, for as soon as the heat-ed plate is brought into contact with the cold metal rings, the edge of the plate is cooled and contracts. y The inner part of the plate is, therefore, caused to belly and the tension arising as the plate cools is not sufficient to fully stretch the plate. The tension obtained is too small and so irregularly distributed that a good resonance will not be obtained.

The object of the invention is to remove the said drawbacks and make it possible to Y obtain perfectly goodsoundingboards of sheet-metal. g

Onev part of the invention consists in this that the' plate is slitted' or cut .at the 4edge so that 'a'series of tongues are'formed which.

are fastened vto the frame suitably by bein able way, such as by'bending. vthetongues l around a downwardly projectingiange, by'

' screws, or by a band placed while hot around the tongues atthe outer side ofthefframe'.

exposing the sounding-board secured to' the g Another part of the invention consists in:

bent over `the outer edge of the'jsame an thereupon secured to the frame any 'sut' frame' to normal pressure, at or inear the bearing surface of the frameilsoas to force the sheet metal plate' out ofte plane ofthe bearing surface. This method of stretching i the sounding-board4 may be` used'eitherin 'combination with the method ofi/fastening l'it hereinbefore described of the said method.

or independently V The invention furtherconsists in the construction and combination Aof parts hereinafter set forth.

The new method may be carried into effect in several ways, someof which will be described with referen'ce to the drawing.

'r igure 1 is a vertical fragmentary section through the end arts of ay frame having a plate attached to it in the manner setgforth.

Fig. 2 is a plan-view, on a reduced scale'from that of Fig. l, of they s litted plate.t Fig. 3.

is a plan-view of the rame. l Figs. 4: to 9 show modifications.

Referring to the drawing-,the 4frame l is suitably provided with'a stay or stays. (Fig.

3) for strengthening it.i ,Theplate used for the sounding-board -isslitted at the edge, as

shown at l (Fig. 2), so that a series o f.

tongues 5 are formed by'means of. which the plate may be attached to the frame` According to Fig. l, the tongues' ,ofthe plate" are` bentover the edge of the frame '1 and beneath a rim 6 at, the outer side thereof and further about a downwardly projecting flange 7 of the frame. f

.In the modified form shown in Fig. 4 the tongues 5, as before, are bent over the edge and catch under the rim 6 of the frame, but instead of being then bent around the lower part of the frame they are secured thereto by screws 8. The modification shown in Fig. 5 differs from the former in this that the ends vof the ton es 5 are jammed against an edge or ange 9. y 'In all thev frames shown the outer edge of the frame around which the 'st-rips or tongues 5 are bent-is at. a higher level than 'the inner edge l1. The sheet-metal strips or tongues may be still further stretched by means of screws l2 against the said inner edge 1l', as

indicated by dashed and dotted linesl in Fig# l. Between the edges 10- and 114 is suitably a recess or depression allowing the tongues to be forced below the edge 11l by which the tension is still moreincreased. By tighten.- ing the screws l2, after the plate 3 has been fastened to the frame, the plate will be stretched vto a certain extent before the tongues will bear on the edge 1l, and when the screws are further tightened, the tongues are bent down into the recess or cavity between the edges l0 and ll so that the sheetmetal plate is strongly stretched and the desired resonance is obtained. rlhedesired highvtension of the plate may also be obtained by otherwise causingthe plate to ex- 'tend over a longer .way than the plane through the outer edge of the frame. vThis may be performed for inst-ance by screws 13 (Fig. 6) screwed into the frame from its rear side so as to lift the plate above the level of the outer edge. To the same end a nut 14 (Fig. 7) l operated by a screw may be placed between the plate and the frame.

According to the embodimentsof the invention shown 1n Figs. 8 and 9, the tongues 5 are bent around the frame, whereupon a heated metal strip l5 is placedaroundthef tongues so as to clamp the same when it cools. The outer side of the frame may extend obliquely (Fig. 8) or at right angles to the plane of the frame.

The stretching devicesv hereinbefore described permit, if desired, to stretch the sounding-board harder at the part-s of the same next to the treble parts of the piano, which is effected by simply tightening the screws harder at the said parts. have found that an extremely excellent instrument is obtained, if the sounding-board' is stretched harder at the treble than at the bass or the intermediate parts. If the tongues formed at the edge of the soundingboard are sufficientlyY stiff, either by themselves or by suitable reinforcement, the fastening of the sounding-board may be effected by -simply bending the tongues over *the outer edge of the frame, without'any other fastening means being employed,

l. ln musical instruments, the combination of a sounding board, a frame, a sheetmetal plate resting on and secured to the frame, and screws forcing the sheet metal plate out of the plane of the bearing surface of the frame, substantially as and for the purpose set forth.

2. in musical instruments, the combinationof a sounding-board', a frame, a sheetmetal plate having a slitted edge extending beyond the outer edge of the frame and secured thereto, and screws forcing the sheetmetal plate out of the plane of said edges, substantially as and for the purpose setforth.

3. ln musical instruments, the Combination of a sounding-board, a frame having an outer edge and an inner edge extending' at a lower level than the outer one, a sheetmetal plate having a slitted edge extending frame between the outer edge and the inner one and forcing the sheet-metal plate' against the inner edge of the frame.

4. .ln musical. instruments the combination of a sounding-board, a frame having an outer edge and an inner edge extending at a lower level than the outer one and separated from the latter by a recess 1n the frame, a sheet-metal plate having a slitted edge extending beyond the outer edge of the frame and secured thereto, and screws placed in the frame between the outer edge and the inner one and forcing the sheetmetal plate againstthe inner edge of the frame.

FRIDOLF FRANKEL.

lVitnesses Ano. SnnNSuN, KARL lluNcsKoo.

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