JPS6321018Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a piano frame, and more specifically, a string locking pin that is molded integrally with the frame, or a piano that is molded by inserting a string locking pin into the frame. Regarding frames.

As shown in Figure 1, the frame 1 of a conventional piano
is usually formed from a casting such as cast iron, and a protruding bearing 1a is provided on the upper flat plate part integrally with the frame 1, a hole is drilled on this bearing 1a, and a bearing pin 2 is press-fitted into the bearing 1a. Alternatively, a hole was similarly drilled in the lower flat plate portion, and the hit pin 3 was press-fitted into the hole. This process of drilling holes and press-fitting pins requires a large number of parts and labor, as each string requires a large number of pins, up to 230.

Recently, advances in casting technology have led to the proposal of a vacuum casting method, which has made it possible to create molds even with minute shapes that would cause the mold to collapse using conventional casting methods, and the resulting castings have become of high quality. Hereinafter, a description will be given with reference to FIGS. 2A to 2F, which are schematic explanatory diagrams showing one embodiment of the process of inserting the bearing pin 2 into the bearing 1a of the frame 1 using a vacuum casting method.

In the vacuum casting method, as shown in FIG. 2A, a mother mold 5 is placed on a base 4, and a film 6 is heated and softened to cover the mother mold 5. Air is taken in through the intake holes 8a, 8b, . Note that A in the figure indicates an air flow. Thereafter, as shown in FIG. 2B, a frame 9 is placed on the film 6 so as to surround the matrix 5, molding sand 10 is put in, the frame 9 is covered with a film 6', and then the air is passed through the intake pipe 7b. When the suction pressure is reduced, the molding sand 10 surrounded by the films 6, 6' and the frame 9 is solidified, and when the frame 9 is lifted upward, the matrix 5 is separated and the casting shown in FIG. 2C is performed. A lower mold X can be obtained. Bearing pins 2 for casting are embedded in each predetermined position of this lower mold X. After that, the upper mold Y for casting shown in FIG. 2D is formed by the same means as the lower mold X for casting, and then the lower mold X and the upper mold Y are made to match, and the upper mold shown in FIG. 2 E is formed. Molten cast iron 12 is cast through sprues 11a, 11b provided in Y. After cooling, the vacuum depressurization of the lower mold X and upper mold Y for casting is released, and as shown in FIG. You can get the frame.

By the way, in the bearing pin 2 portion of the insert-cast piano frame 1 obtained as described above, the bearing pin 2 is aligned along the direction in which the bearing pins 2 are arranged (direction D) as shown in FIGS. 3A and 3B. An uneven raised part (burr) 13 of the casting occurs at the hem of the cast member 2. As shown in FIG. 3C, in the step of covering the mother mold 5 with the film 6, the expansion and contraction ratio of the film 6 is different between the direction in which the protrusions 5a that are to become the bearing pins 2 are lined up (direction D) and the direction perpendicular thereto. This is due to the fact that a gap 14 is generated, albeit slightly, at the bottom of the protrusion 5a. This phenomenon is the same when the hitch pin 3 is inserted and when the bearing pin 2 and the hitch pin 3 are formed integrally with the frame 1. This uneven raised portion 13 has a negative effect on the tuning when the piano strings are strung.
This will damage the quality of the piano.

This invention was made in view of the above-mentioned drawbacks, and when forming the frame of a piano by integrally insert-casting the string locking pins 2 and 3 or the string rest for string locking, A string locking part that locks each string is formed to have a sawtooth shape, and a bearing pin 2 and a hitch pin 3 are planted near the top of this slope, and the strings are stretched in contact with these pins. The present invention provides a piano frame characterized in that it is configured to be locked.

Hereinafter, the piano frame according to this invention will be explained in detail with reference to the drawings. Note that a bearing pin 2 provided on a bearing 1 as a string locking pin will be taken as an example.

FIG. 4A is a schematic perspective view of main parts for explaining a piano frame 1 according to an embodiment of the invention;
FIG. 4B is a cutaway view taken along line E--E in FIG. 4A. In the figure, bearing 1a on frame 1
has a serrated shape, and a string locking pin (bearing pin) 2 is formed as an insert at the apex thereof, or is formed integrally with the frame 1 (or bearing 1a). As shown in FIG. 4B, the string 15 is stretched on the side of the slope 1b with a gentle slope so as to come into contact with the bearing pin 2. Note that 1c in the figure indicates a steep slope. By doing this, the elongation of the film on the string-locking side is smaller than on the side where the string is not locked, so the gap 14 of the film on the string-locking side can be reduced, and therefore, the gap 14 can be reduced. The resulting raised portion 13 on the frame can also be made smaller on the string locking side.

FIG. 5 is a schematic cutaway view of essential parts for explaining a piano frame according to another embodiment of the invention. In the figure, the bearing 1a on the frame 1 has a serrated shape, the bearing pin 3 is installed at a point slightly away from the apex, and the string 15 has the bearing pin 2 on the side of the slope 1b with a gentle slope.
It is stretched in contact with the

Since the piano frame according to this invention is constructed as described above, the side of the string locking pin (bearing pin/hitch pin) that the strings come into contact with (pressure contact) has a film that is stretched during the work of making the mold for casting. It is difficult for wrinkles to form due to the molding process, so uneven raised parts are not generated, and the casting process can be carried out well, and the casting of the frame can also be of uniform quality. In addition, the part that connects to the string locking pin is beautifully finished, so the strings can be tensioned reliably and smoothly.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view for explaining a conventional piano frame, Fig. 2 A to F are process schematic explanatory drawings for explaining an example of vacuum casting used in this invention, and Fig. 3 A is a schematic perspective view for explaining a conventional piano frame. A plan view for explaining the drawbacks of the bearing pin and bearing part of the conventional piano frame, Figure 3B is C in Figure 3A.
-C line cut view, FIG. 3C is a cross-sectional view of the process of covering the matrix with a film, and FIG. 4A is a schematic perspective view for explaining a piano frame according to an embodiment of this invention.
FIG. 4B is a cross-sectional view taken along the line E-E in FIG. 4A, and FIG. 5 is a cross-sectional view taken along the line E-E in FIG. 4A for explaining a piano frame according to another embodiment of this invention. . In the figure, 1... Frame, 1a... Bearing, 2... Bearing pin, 3... Hitachi pin, 4... Base, 5... Mother mold, 6... Film,
7...Intake pipe, 8...Intake hole, 9...Frame, 1
0... Foundry sand, 11... Sprue, 12... Molten cast iron, 13... Raised portion (burr), 14... Gap between matrix 5 and film 6, 15... String.

Claims (1)

[Scope of utility model registration request] In a piano frame in which string locking pins are inserted into the frame or string locking pins are integrally molded with the frame, the string locking pins are arranged in a string locking portion on the frame that locks each string. The string locking part has a serrated slope in the direction of , and a string locking pin is arranged near the top of the slope of the string locking part, so that the string locking part is locked in contact with the string locking pin. Features a piano frame.