JPS5937516B2 - Manufacturing method of adjustment button in piano action mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an adjustment button in a piano action mechanism.

Figure 1 A shows a part of the action mechanism of an applied piano and a grand piano, respectively. In an applied piano, the caps button a is pressed to properly push up the Witsupen W and Jack J by keystroke operation. In addition, in grand pianos, a regulator teng button b is used to control the thrusting motion of the jack J, taking into account the quick recovery after the hammer h hits the string. It is firmly fitted into the threaded part of the upper end of wire C0 implanted at the tip, and in the latter case, it is firmly fitted into the threaded part of the lower end of wire 02 which is vertically installed on the lower surface of hammer shank rail r, both of which are connected to the action mechanism. When making adjustments, the height of the installation can be adjusted by rotating these appropriately.

By the way, these capsun button a and regulator length button b are generally made of plastic products, and as shown in Figure 2 A and Machi, wire C□ (or C2)
It has a circular central vertical hole 1 for fitting into the vertical hole 1, and an adjustment hole 2 with a circular cross section for inserting a rotation pin that crisscrosses the vertical hole 1 at the top.

Such adjustment button a (or b) is made by plastic injection molding as described above, but in that case, if you try to mold the vertical hole 1 and the adjustment hole 2 crisscrossing it at the same time, the mold As shown in Fig. 3, there is a vertical pin 1a for forming the vertical hole 1 and a horizontal pin 2a for forming the adjustment hole (for convenience, these pins can move forward and backward when opening and closing the upper and lower molds). (only one pair of left and right ones are shown) is required, and the tip of the horizontal pin 2a must be shaped into a special curved shape as shown in the figure so as to match the shape of the surface of the vertical pin 1a.

It is quite difficult to process such a curved shape accurately, and even if it were possible to process it so that it matches the surface shape of the vertical pin 1a as shown in Fig. 4A, the horizontal pin 3
Since both sides of the tip of a have thin edges, these edges are not only easily corroded by the gas generated from the material during injection molding, but also open into dotted lines due to the gas pressure, and there is a hole in the same figure. There is a risk that burrs will come out and eventually block the adjustment hole 2.

Also, as shown in Fig. 5A, the tip of the horizontal pin 2a is connected to the vertical pin 1a.
If the adjustment hole 2 does not match the surface of the adjustment hole 2, as shown in the opening in the same figure, the resin may enter the adjustment hole 2 and block the adjustment hole 2, which may prevent the adjustment rotation pin from being inserted and make adjustment impossible.

For this reason, in the past, the adjustment hole 2 has mostly been provided by secondary processing such as drilling, but it is also difficult to perform drilling on a thin cylindrical button body, resulting in extremely low work efficiency.

This invention was devised in view of the above-mentioned circumstances.
A piano that eliminates the need for secondary machining by drilling, and allows vertical holes for wire insertion and horizontal adjustment holes for insertion of rotation pins to be formed in a thin cylindrical body by injection molding without blocking the holes. This provides a method for manufacturing an adjustment button in an action mechanism, in which a cylindrical body is molded by injection molding of plastic, and at the time of molding, a circular cross-section is formed in the longitudinal center of the cylindrical body for inserting the threaded part of the wire. A vertical hole is formed by forming a lower hole and an upper hole with a rectangular cross section continuous with the lower hole, and an adjustment pin is provided at the top of the cylindrical body so as to cross the flat circumferential wall of the upper hole in a criss-cross manner for insertion of a rotation pin. It is characterized by having holes formed therein.

The embodiment will be described with reference to FIGS. 6 to 8. A is a cylindrical adjustment button used for a capsun button or a regulation button,
It is formed by injection molding of plastic, and at the time of injection molding, the vertical center of the cylindrical body has a lower hole 10a with a circular cross section for fitting the threaded part of the wire C□ or C2, and a lower hole 10a with a rectangular cross section continuous with this. An upper hole 10b is formed, and an adjustment hole 20 for inserting a rotation pin is formed in the part of the upper hole 10b with a square cross section, which crosses toward the flat peripheral wall. .

In this case, the vertical pin in the mold for forming the vertical hole 10 is
It is necessary to create a shape that matches the design, but the processing is not as difficult as the one shown on the left.

As described above, according to the present invention, the tip of the horizontal pin for forming the adjustment hole does not need to have a special curved shape as described above, and can be easily processed as long as it is flat. It has good compatibility with the mold and is difficult to deform due to gas pressure, so there is no bulging during molding, and simultaneous injection molding is possible, eliminating the need for secondary processing using a drill, significantly improving work efficiency. can be improved.

[Brief explanation of the drawing]

Figure 1A is a side view of a part of the action mechanism of an applied piano. The figure shows a side view of part of the action mechanism of a grand piano. FIG. 2A is a vertical sectional view of a conventional adjustment button. The opening in the figure is a cross-sectional view taken along the line A-A. FIG. 3 is a partial perspective view showing the related structure of vertical pins and horizontal pins in a mold when vertical holes and horizontal holes of a conventional adjustment button are simultaneously molded by injection molding. FIG. 4A is a partial plan view showing the deformed state of the tip of the horizontal pin. The side view which shows the internal state of the adjustment hole at the time of the same figure. FIG. 5A is a partial plan view showing a state of misalignment between the vertical pin and the horizontal pin. FIG. 01t is a side view showing the internal state of the adjustment hole at that time. FIG. 6 is a longitudinal sectional view of an embodiment of this invention. Figure 7 is its bottom view. FIG. 8 is a cross-sectional view taken along line B-B. In the figure, ayA
...Adjustment button, 1,10... Vertical hole, 1
0a---lower hole, 10b---upper hole, 2
゜20...-Adjustment hole, 1a...Vertical pin,
2a...Horizontal pin.

Claims (1)

[Claims] 1 A cylindrical body is molded by plastic injection molding, and at the time of molding, a lower hole with a circular cross section for inserting the threaded part of the wire and an upper hole with a rectangular cross section are formed in the longitudinal center of the cylindrical body. a vertical hole, and an adjustment hole for inserting a rotation pin is formed in the upper part of the cylindrical body so as to cross the flat circumferential wall of the upper hole in a crisscross manner. Method of manufacturing adjustment buttons in.