US3479915A - Action mechanisms for grand pianos - Google Patents

Description

Nov. 25, 1969 YOSHIYUKI MATSUMOTO 3,479,915

ACTION MECHANISMS FOR GRAND PIANOS Filed March 27, 1967 2 Sheets-$heet 1 INVENTOR.

N v- 1969 YOSHIYUKI MATSUMOTO 3,47 ,91

ACTION MECHANISMS FOR GRAND PIANOS Filed March 27, 1967 2 Sheets-Sheet 2 IN VEN TOR.

United States Patent O 3,479,915 ACTION MECHANISMS FOR GRAND PIANO Yoshiyuki Matsumoto, Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kahushiki Kaisha, Hamamatsushi, Japan, a corporation of Japan Filed Mar. 27, 1967, Ser. No. 626,204 Claims priority, application Japan, June 18, 1966', 41/ 57,921 Int. Cl. Gc 3/18 US. Cl. 84-239 1 Claim ABSTRACT OF THE DISCLOSURE A grand piano action mechanism having an arm operatively related with a key, a repetition lever rotatably mounted on the arm, a jack rotatably mounted on one end of the arm to push up a hammer, a repetition spring disposed beneath the repetition lever to push it upwardly, a spring seat movably mounted between the repetition lever and one end of the repetition spring so as to control the magnitude of the repulsive force of the spring.

BACKGROUND OF THE INVENTION This invention relates to action mechanisms for grand pianos for transmitting motions of keys to hammers.

In a conventional action mechanism for grand pianos adapted to transmit the motion of a key to a hammer to move it to strike a string, the upward movement of the key is transmitted to a jack to push it upwardly'and the jack is moved to strike a hammer through a hammer roller which is positioned to contact the upper end at the jack. Such mechanism is so constructed that once the action mechanism has operated to strike the strings, the tip or upper end of the jack is disengaged from the hammer roller so that even when the key is held in the pressed down condition the hammer can be restored to its original position. When the key moves slightly back to the original position in order to be pressed down again, the hammer will be pushed up by a repetition lever under the action of a repetition spring so as to permit the tip of the jack to return back to the position beneath the hammer roller through the action thereof which is mounted on the lower surface of the hammer. Usually the repetition spring is disposed beneath the repetition lever with one of its ends arranged to slide on the bottom surface of a groove formed on the under surface of the repetition lever. The repulsive force of this spring is adjusted to form the satisfactory function of the action mechanism by bending a portion of the spring.

This adjustment of the repulsive force of the repetition spring which is performed during the manufacturing steps of the pianos has a great influence upon the playing condition thereof. When this repetition power is insufficient the repetition lever will not be imparted with sutficient power required to push up the hammer roller with the result that it is impossible to bring back the jack to the original position during a short period in which the key is again pressed down before it is restored to the normal position. Conversely, if the repulsive force of the spring is too large, although preparation for the next striking action of the string can be completed rapidly because the jack can rapidly come back to the position beneath the hammer roller after striking the string, as the hammer is strongly pushed up by the repetition lever under the bias of the spring, there is a fear that the hammer may strike the string with excessive force. Even if the hammer does not actually strike the string the shock caused by the reaction of repulsion gives uncomfortable touch feeling to the finger of the player through the key. Thus, it is necessary to adjust the spring within a narrow range which assures that the action mechanism can faithfully follow the movements of the key which are repeated at short intervals and that no reaction of the hammer is transmitted to the key.

However it is not easy to cause plastic deformation of a spring made of a resilient material such as a piano wire or a Phosphor bronze wire in small gaps (usually about 8 mm.) between adjacent action mechanism. Although it is possible to use springs having constant configuration and repulsive force, practically it is impossible to make equal the weight of the key and the frictional resistance of each slidable portion for all action mechanisms associated with 88 keys. Thus, in order to cause all action mechanisms to have identical operating characteristics, each spring must be carefully and finely adjusted as stated above by highly skilled engineers, which of course requires much labor and time.

SUMMARY OF THE INVENTION This invention provides a grand piano action mechanism including a spring which is effected by moving one end thereof and is arranged to push up a repetition lever, said one end being seated upon a spring seat which is mounted on a threaded bolt which is located beneath the repetition lever and extending therethrough and the position of the spring seat is moved by turning the threaded bolt to adjust the repulsive force of the spring. By this means the repulsive force of the spring can be readily and accurately adjusted to the most proper value corresponding to the inherent conditions of the associated action mechanism, namely the frictional resistance of various tilting parts or the weight of the hammer.

An object of this invention is to provide a novel action mechanism for grand pianos, wherein the operating characteristics thereof can be readily and accurately adjusted.

Another object of this invention is to provide an improved action mechanism for grand pianos wherein the variation in the operating characteristics can be restrained which may occur after many times of striking strings or may be caused by the variation of weather conditions, by utilizing a material having large frictional strength and small variation in the coefficient of friction due to moisture in the atmosphere as the material for constructing said spring seat which receives one end of the spring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of one example of an action mechanism for grand pianos embodying the principle of this invention;

FIG. 2 is a side view, partly in section, of the essential portion of the action mechanism shown in FIG. 1; and

FIG. 3 is a side view, partly in section, of the essential portion of a modified action mechanism of this invention.

Referring now to the accompanying drawings, more particularly to FIGS. 1 and 2, an action mechanism provided between a key 1 and a hammer 2 comprises an arm 4 with one end rotatably supported by a support 3, a repetition lever 6 which is pivotally supported at its center on an upright pedestal 5 mounted on said arm 4, and a jack 8 which is pivotally connected to the end of the arm 4 opposite to the support 3 thereof and adapted to push up a hammer roller 7 to strike hammer 2. The upper or free end of the jack 8 extends through a bore 9 provided at one end of the repetition lever 6 so that once the mechanism is operated to strike the string the jack 8 can rotate in the clockwise direction in the bore 9 until its tip is moved to a position not to engage the lower surface of the hammer roller 7. The repetition lever 6 and the jack 8 are respectively provided with stops 10 and 11 which define the stationary positions thereof.

Below the lower surface of the repetition lever 6 is provided a spring seat 13 which is rotatably secured to a threaded bolt 12 which is threaded through the lever 6. As best shown in FIG. 2, one end of a repetition spring is inserted in a groove 14 provided in the spring seat 13 to bias said lever. For turning the bolt, a groove is provided on the upper end thereof which is located at a level above the upper surface of the lever 6, and at the lower end of the bolt is secured a disc shaped locking member 17 which is housed in a cavity 16 in the spring seat 13 so as to rotatably support the spring seat 13. By turning the threaded bolt, the distance between the spring seat 13 and the lower surface of the lever is increased or decreased. In response to this movement of the spring seat the angle of bend a of the repetition spring is decreased or increased whereby to adjust the force which acts to push up the repetition lever.

When the spring seat 13 is set at a suitable position by means of the threaded bolt and when the key 1 is operated to strike the string under this condition, the movement of the key is transmitted to the arm 4 to cause it to rotate in the counterclockwise direction, as viewed in the drawing, around the pivot on the support 3. As the arm 4 is rotated in this direction, the jack 8 mounted on one end thereof will be pushed upwardly together with the hammer roller 7 to rotate the hammer 2 for effecting striking action of the string.

As the hammer moves downwardly after striking the string, the hammer roller 7 will engage the action mechanism. However, at this time, since the jack 8 has moved in the bore 9 of the repetition lever 6 to a position at which it will not be engaged by the hammer roller, the hammer will slightly depress the repetition lever 6 by the hammer roller 7 carried thereby, and thereafter the rotation of the hammer will be prevented since the left hand end thereof engages an upright back check 18 moutned on the end portion of the key 1.

When the key 1 is slightly brought back to the original position during repeating string striking operations, the repetition lever 6 will push up the hammer roller 7 by the action of the repetition spring 15, thus permitting the jack 8 to reset so that its upper end engages the hammer roller 7, so as to bring the action mechanism to prepare for transmitting the next upward movement of the key 1 necessary for striking the string with the hammer 2.

The operating condition of the action mechanism is infiuenced by the magnitude of the repulsive force of the repetition spring and in the improved action mechanism of this invention the magnitude of the repulsive force of the spring can be adjusted by turning the threaded bolt 12 to vary the position of the spring seat 13. Where the repulsive force of the spring 15 is too small to sufficiently push up the hammer roller by the repetition lever 6 to a position wherein the upper end of the jack 8 can be promptly restored to the position beneath the hammer roller, the threaded bolt 12 is turned in such a direction that the distance between the upper surfaces of the spring seat 13 and the repetition lever 6 increases. This decreases the angle a of bent spring 15, thus providing a sufficient repulsive force to push up the repetition lever '6 instead of conventional plastic deformation of the spring. Conversely, where the repulsive force of the spring 15 is too large, the hammer 2 having completed its string striking action will drop to depress the repetition lever 6 and then in such a case, the threaded bolt 12 can be turned in the opposite direction to decrease the repulsive force of the spring. In any case, turning of the threaded bolt results in a minute but positive change in the distance between the spring seat 13 and the repetition lever 6. In other words, the repulsive force can be very accurately adjusted within a desired narrow range.

As shown in FIG. 3, the contact between the spring seat and the spring can be improved by providing a concave spherical recess 22 on the underside of a spring seat 21 and by urging one end of a spring 23 having a small radius of curvature against the inner surface of the recess. This is because the spring 23 and the spring seat 21 engage each other with a very small area resembling a point contact, thus greatly decreasing the effect of friction between these two members and assuring free rotational movement of the repetition lever 6. Other parts of FIG. 3 which are identical to those shown in FIGS. 1 and 2 are designated by the same reference numerals so that it is believed to be unnecessary to describe them again.

In FIGS. 1, 2 and 3, the spring seat is made of a material which has sufficient mechanical strength not to cause extensive deformation or breakage due to the contact pressure with the spring and a strength against friction which is sufficient to assure that the spring seat will not be damaged by the friction with the spring. However, as the pressure and friction imparted to the spring seat from the spring are not so large, metals such as steel or aluminum or any one of many types of synthetic resins may be used for this purpose. From the standpoint of the weight of the spring seat and economy it is advisable to make the spring seat of a material which can be readily formed by means of injection moulding, for example, a synthetic resin such as polyamide resin or polyacetal resin. The threaded bolt can also be made of similar substances. When the spring seat is constructed to contact with a bent portion which is formed at one end of the spring as shown in FIG. 3, then the seat can he tilted or rotated without causing any damage to the spring so that the spring seat and the bolt may be formed integrally, that is, to construct them such that they can be interconnected without permitting any relative rotation therebetween.

The construction described above well protects the operating condition of the action mechanism due to friction which is created after many times of operations or from variations of humidity of the atmosphere. In conventional action mechanisms, as the repetition spring is directly in contact with the lower surface of a groove provided on the bottom surface of a repetition lever made of wood the bottom surface of the groove will be gradually worn out due to the friction caused by the operation of the action mechanism, thus degrading the desired operating conditions which are set initially to the desired conditions. Moreover, the wooden repetitions lever absorbs moisture or is dried due to the variation in the moisture contained in the atmosphere thus resulting in the variation in the frictional resistance between the lever and the spring. Again the piano cannot maintain its constant operating condition. However by utilizing above mentioned metal or synthetic resin as the material for constructing the spring seat such variations in friction and frictional resistance caused by moisture are prevented so that the predetermined constant operating condition can be maintained over a long period.

Increase in the manufacturing cost by the provision of the spring seat and the threaded bolt can be completely offset by the saving of labor and time necessary to adjust 'the spring. The interval of time required for effecting fine adjustment of the repetition spring in the action mechanism embodying this invention could be reduced to only about 20 minutes when compared with a period of 60 to 80 minutes which was required to adjust the operating condition of the action mechanism by causing a spring to undergo a plastic deformation as has heretobefore been the practice.

While the invention has been explained by describing particular embodiments thereof, it will be apparent that improvements and modifications may be made without departing from the scope of the invention.

What is claimed is:

1. An action mechanism for grand pianos comprising an arm and a key, the arm being operable by the key; a repetition lever and a jack pivotally mounted at-spaced locations on said arm, said jack extending through a bore in said lever; a hammer and a hammer roller, said jack being operable when the key is depressed to pivot the hammer by engaging the hammer roller to cause the hammer to strike a piano string, the jack, when the string is struck, being permitted to move from an operative position to a position in which the jack is disengaged from the hammer roller; a spring biasing said lever in a direction to permit said jack to return to its operative position; a threaded bolt screwed through said repetition lever, said bolt having a flat enlarged end; and a spring seat secured about the enlarged end of the threaded bolt in a loose but captive manner to allow the bolt end to rotate therein and References Cited UNITED STATES PATENTS 1,929,939 3/1935 Dasenbrook 84-239 2,157,028 5/1939 Sperry 84-174 2,172,253 9/1939 Morse et al 84-239 2,263,088 11/1941 Hofmann 84-239 2,411,005 11/ 1946 Schulze 84-239 RICHARD B. WILKINSON, Primary Examiner J. F. GONZALES, Assistant Examiner

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