JPH0226236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of finishing the head of a jack in a piano action, making it possible to eliminate the conventional method of coating the head with graphite.

The jack is an extremely important movement in piano action. In other words, the jack is rotatably attached to the jack, and moves up as the jack moves up when the key is pressed, and in the case of an upright piano, pushes up and rotates the butt, and a hammershank is attached to this butt. The strings are struck with a hammer attached to the tip of the string. In the case of a grand piano, the jack pushes up a hammer roller attached to a hammer shank, and the hammer attached to the tip of the hammer shank strikes the strings.

In this way, the jack operates at an important position in the action, and has a great influence on key presses. The jack must reliably push up and rotate the butt, and it must also quickly get under the butt (or hammer roller) as soon as the key is released, in preparation for the next key press. Therefore, as shown in FIG. 4, the conventional jack 4 (for example, the case of a grand piano) has the front upper edge 1a of the head section chamfered to approximately 0.5R.
In addition, graphite (graphite, etc.) 2 is applied over the front upper part 1c, the top surface 1b, and the front upper edge 1a, so that the head thereof is suitably smooth and its friction coefficient does not change over a long period of time. ing.
However, the other side that comes into contact with the head of jack 4 has skin (butt skin for upright pianos, roller skin for grand pianos).
Because the graphite is pasted, the graphite peels off after long-term use, and the wood itself appears on the surface, increasing the coefficient of friction, causing noise and significantly reducing the feel of the keys when pressed.

FIG. 1 is a perspective view of a material board 1 used to manufacture the main body of a grand piano jack. As shown in Figure 2, graphite 2 is applied over the front upper part 1c, the top surface 1b, and the front upper edge 1a covered with paper, and then cut vertically at required intervals as shown by the chain line P. 3 Obtain the jack body 3 as shown in the figure, form a groove 3a in its lower part, and form a fourth groove in this groove 3.
As shown in the figure, a separately processed heel 4a is inserted and attached to the jack body 3 to complete the jack 4.

As mentioned above, this invention does not apply graphite to the head of the jack, but instead coats the head of the jack (or the part corresponding to the head of the jack at the stage of the blank plate) with a metal body that rotates at high speed. This part is compressed and hardened into the desired shape to create a smooth surface that exhibits the same performance as a jack that has just been coated with conventional graphite, and this initial performance lasts longer than before. An embodiment thereof will be described below with reference to the drawings.

In FIG. 5, 5 is a metal body that rotates at high speed around a shaft 5b, and has a constricted portion 5a in the center. The shape of this constricted portion 5a is the shape of the head of the jack 4 to be completed, and the material plate 1 is pressed against the constricted portion 5a with a pressing force F, as shown in FIG. Of course, this material plate 1 is cut lengthwise to form the jack body 3 shown in FIG.
It may also be compressed by pressing on a.

FIG. 6 is a perspective view of the material plate 1 whose head is compressed by the device shown in FIG. Jack becomes 4. In this way, the front upper part 1c
The surface of the head that has been compressed and deformed by the metal body 5 that rotates at high speed across the top surface 1b and the front upper edge 1a has its wood fibers destroyed, compressed and hardened, and is compressed and deformed by the metal body 5 that rotates at high speed. As a result, the exterior surface became very smooth, and there was no need to apply graphite 2 at all.

As described above, according to the present invention, the head of the jack or the head of the raw material plate that will become the jack is pressed against a metal body rotating at high speed to compress and deform the head. As the parts are compressed and hardened, they become smooth, eliminating the need for the conventional coating of graphite, and furthermore, the effect is that the performance is maintained for a longer period of time than that of conventional graphite coatings.

[Brief explanation of drawings]

Figure 1 is a perspective view of the material plate used to make the jack.
Figure 2 is a perspective view of the head of the material plate shown in Figure 1 with graphite applied to it, Figure 3 is a perspective view of the jack body, Figure 4 is a perspective view of an example of a completed jack, and Figure 5. 6 is an explanatory side view of the pressing compression deformation process according to the present invention, and FIG. 6 is a perspective view of a blank plate obtained by the process shown in FIG. 5. 1a...Front upper edge, 1b...Top surface, 1
c... Upper front surface, 4... Jack, 5... Rotating metal body, 5a... Neck part.

Claims (1)

[Claims] 1 Press the front upper part 1c, the top surface 1b, and the front upper edge 1a in the head of the jack 4 against the constriction part 5a of the metal body 5 rotating at high speed, and press the front upper part 1c and the top part in the head of the jack 4. 1b and the front upper edge 1a are compressed and hardened into a desired shape to form a smooth surface.