US2077489A - Piano string system - Google Patents

Description

April 20, 1937. A. E. P. STLUND ET AL. 2,077,489

PIANO STRING SYSTEM Filed Juiyao, 1955 3 Sheets-Sheet l April 20, 1937 A. E. P. STLUND ET AL, 2,077,489

PIANO STRING SYSTEM Filed July 20, 1955 3 Sheets-Sheet 2 W Il f M f, QM.

April zo, 1937. A E, p STLUND ET' AL 2,077,489

PIANO STRING SYSTEM Filed July 2o, 1955 5 sheets-sheet 3 Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE PIANO STRING SYSTEM Application July 20, In Sweden 1 Claim.

The present invention relates to an improved hammer mechanism in pianos having a substantially rectangular string frame, particularly so called square pianos. In pianos of the latter kind the strings are usually so arranged that the striking points of the hammers must be located to a great extent in the rear part of the frame involving the inconvenience that the hammer mechanism or action must be arranged at a como paratively great depth under the strings and that, furthermore, a mechanism construction is obtained which is not suitable from a dynamical point of view. To overcome this inconvenience it has been proposed to so arrange the bass and treble strings that the striking points of the hammers can be located at the front part of the frame nearest to the clavier as is the case in grand pianos. This arrangement of the hammer mechanism renders the transmission of motion, or energy, from the keys to the hammers of the bass strings diiicult due to the fact that in such an arrangement the bass strings extend substantially diagonally relative to the frame and the striking line of the bass strings will form, therefore, a considerable angle with the striking line of the treble strings. According to the present invention, this difficulty has been overcome by the arrangement of auxiliary keys between the ordinary key rods and the hammers of the bass strings, as will be more clearly described with reference to the accompanying drawings.

Figure 1 is a horizontal section through the upper portion of a square piano according to the invention. Figure 2 is a Vertical section on the 35 line 2-2 in. Figure l. Figure 3 is a partial horizontal View of an arrangement of the hammer mechanism intended for the bass strings. Figure Il shows a perspective View of the latter arrangement.

The string frame consists of a heavy rectangular portion I and of a bottom positioned within said rectangular portion and provided with recesses, the bottom comprising a front portion 2 and a rear portion 3. The strings are assembled in two groups, viz. one group of bass strings 4 and one group of treble strings 5. All strings are secured to the frame in ordinary manner by means of tuningl pins 6 and hitch pins l. The tuning pins of the bass strings as well as of the treble strings are arranged in the front portion 2 of the bottom of the string frame. The pins 1 are arranged in the rear bottom portion 3 of the frame. Some of the treble strings bear in known manner against a tensioning bar 8, placed over 55 the strings, a so called capotasto, which tension- 1935, Serial No. 32,372 July 11, 1933 ing bar is made integral with the frame and extends rom one end thereof to a strengthening rib 9 running across the frame. The other treble` strings are in known manner drawn through notches in a tensioning bar IIJ, a so called agrarie, which is secured by means of screws to the front bottom portion 2. The bass strings 4 are secured in similar manner in a tensioning bar I I secured to the bottom portion 2 and extending right across the left front corner of the frame. Arranged at the rear ends of the strings are so called steps, namely a bass step I2 for the bass strings and a treble step I3 for the treble strings. The treble step I3 follows substantially the line in which the pins 'l are arranged and thus extends from the right side of the frame all the way to the left rear corner of the frame. The steps I2 and I3 are arranged on the sounding board I4 which is provided under the frame, and serve in known manner to transmit the Vibrations from the strings to the sounding board. By arranging the treble strings in the manner shown on the drawings a very even distribution of the pressure from the strings over the entire sounding board is obtained.

The described arrangement of the strings makes it possible to place the striking points of the actions or hammer mechanisms in the front portion of the frame near the clavier. The dot and dash line I5 indicates the position of the striking points for the treble strings, whereas the dot and dash line I6 indicates the position of the striking points of the bass strings. As will be seen the striking line of the treble strings extends substantially parallelly with the front side of the frame whereas. the striking line of the bass strings extends obliquely across the left corner of the frame adjacent the clavier. Thanks to the oblique position of the striking line of the bass strings a greater number of strings can be housed within the bass string group than would have been possible if the striking line I6 were positioned in the extension of or parallelly with the striking line I5 for the treble strings.

In the shown example the bass strings are superposed on the treble strings and drawn through a recess El in the lower edge of the stifening rib 9. For the purpose oi further strengthening the frame, stiifening ribs I8 and i9 are provided.

The treble keys 26 are in ordinary manner ulcruined by means of pins 2l on a balance rail 22 disposed on the bottom 23 of the box 24 enclosing the string frame and the mechanisms or actions. The key rods actuate in known manner the hammers 25 by means of levers 26 which are pivoted on a supporting rail 21. Upon actuation of the keys the hammers 25 are pushed upwards thereby that the key by means of a shoulder 28 actuates the lever 26 which in turn actuates the hammer 25 at the cam 3| by means of the so-called jack or sticker 30 which is actuated by a spring 29. At the same time the damper 32 normally resting on the strings is actuated through the catching arm 33, secured to the inner end of the key and actuating a. link rod 34 by means of which the damper is pivotally secured to the sounding board.

The arrangement described cannot be used conveniently for the hammer mechanism of the bass strings due to the fact that the striking line I6 of the bass strings forms a considerable angle with the striking line I5 of the treble strings, the lateral space available for the hammer mechanism of the bass strings being then considerably reduced. In such an arrangement it is therefore diflicult to obtain an entirely satisfactory functioning of the different parts of the mechanism. This inconvenience is avoided according to the invention by arranging the hammer mechanism for the bass strings in the manner shown in Figures 3 and 4.

As is clear from Figure 3, the hammer mechanism for the bass strings is angularly displaced in relation to the latter in such a manner that the hammer shanks extend substantially perpendicularly to the striking line I6 of the strings,

the space between the hammers then becoming sufficient to lenable the individual hammers and appertaining mechanism to move freely in relation to each other. The hammers 25 which are all of equal length are pivoted in a supporting rail which consequently extends about parallelly with the striking line I5. The other parts of the hammer mechanism are arranged so as to be .lo movable in the same planes as the hammers or in planes parallel therewith respectively. 'I'he key rods 29, on the other hand, are arranged in ordinary manner approximately perpendicular to the front side of the string frame. They are fulcrumed in the balance rail 22 which forms a small angle with the front side of the frame so that a suitable leverage is obtained.

For the purpose of transmitting the movement from the keys to the hammers, each hammer is 50 provided with an auxiliary key 36 disposed under the appertaining hammer mechanism and adapted to swing in the plane of movement of the hammer or in a plane substantially parallel therewith respectively and which at its free end is pivotally connected with the extended end of the appertaining key rod 20. In the example shown in Figure 4, said connection consists of a pin 31 secured to the auxiliary key which pin with its thin end engages a hole in the outer end of the key rod, the pin bearing against the key by means of a felt-covered shoulder. At the opposite end the auxiliary key is pivotally supported in a transverse balance rail 39 by means of a pin projecting into a spacious hole in a depending flange 4I on the balance rail. By means o1' a pin 42 which is movable in a slit 43 in a horizontal portion 44 of the balance rail 39 the auxiliary key is guided so that it is held in a vertical position. The lever 26 is actuated by the auxiliary key by means of a shoulder 28 in similar manner as by the key rod 20 in Figure 2. Said lever carries in addition to the jack'or sticker 30 also a lifting arm 45 which serves in known manner to lift the hammer 25 so that the jack or sticker 30 can resume its operative position under the cam 3l after it has been brought to take up a position laterally of the cam 3| on account of the bell crank lever 46 striking against the stopping pin 41. The lifter is for this purpose actuated by a thread spring 29 which also serves as a restoring spring for the jack in that its other end is connected with the jack 30 at 48. The catching arm 33 is in this case arranged on the auxiliary key whereas the damper 32 is actuated by the auxiliary key by means of a pin 49 projecting from the link rod 34.

A piano having a horizontal string frame of substantially rectangular shape, the bass strings extending substantially diagonally nelaftive to such frame and the hammers pertaining to said bass strings angularly displaced relative to the key rods thereof, comprising auxiliary keys arranged above the key rods and pivotally connected with said key rods at the rear ends thereof, said auxiliary keys being arranged to swing in the planes of movement of said hammers, thereby transmitting energy from said keys to said hammers upon actuation of said keys.

ARTUR EINAR PETRUS STLUND. SVEN GUNNFORS.

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