JPH1097239A - Bridge pressure regulator of piano - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bridge pressure regulating device capable of easily and efficiently regulating bridge pressures even after a soundboard and a frame are connected with each other. SOLUTION: This device is constituted to regulate the bridge pressures ΔHB of many strings S which are wound at their one-end parts to many tuning pins 3 disposed at the frame 5, are pressed at their intermediate parts to the surfaces of the bridges 1a fixed to the soundboard 2 connected to the frame 5 on the side opposite to the soundboard 2 and are extended in the state of winding their other ends to many pitch pins 4 disposed in juxtaposition with the frame 5 so as to exist near the bridges 1a. In such a case, the device is provided with bridge pressure regulating bars 7 as bridge pressure regulating means, by which the strings S may be supported at plural supporting heights varying from each other in the sections near the pitch pins 4. The bridge pressure ΔHB is regulated by selecting the one supporting height from the plural supporting heights.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piano piece pressure adjusting device for adjusting a piece pressure important for designing a string in an acoustic piano such as a grand piano.

[0002]

2. Description of the Related Art FIG. 10 shows an installation state of a string S in a treble portion of a conventional grand piano. As shown in the figure, the string S has one end wound around a tuning pin 52 provided on the frame 51 and the other end connected to the frame 5.
While being wound around the hitch pin 53 provided in 1,
An intermediate portion near the hitch pin 53 is in contact with an upper surface of a long piece 55 fixed to a sound board 54 connected to the frame 51, and is stretched with a predetermined tension by turning the tuning pin 52.

In order to be able to resist the pressing force of the string S, which will be described later, and to give the sound board 54 a tension, the sound board 54 is formed in advance with a "swelling" raised toward the long piece 55 side. ing. Also, a string pillow 56 is provided integrally with the frame 51 near the hitch pin 53,
The string S is placed on the string pillow 56 via the string pillow felt 57. Further, a capo / dastro bar 58 that projects integrally downward from the frame 51 is in contact with a portion of the string S on the tuning pin 52 side from above.

In this case, the long piece 55 is arranged such that the upper surface with which the string S abuts is higher than a substantially horizontal imaginary line P connecting the lower end of the capo-dastro bar 58 and the upper end of the string pillow 56. Have been. Due to the positional relationship between the string S and the long piece 55, the tension of the string S always acts on the long piece 55 as a pressing force from above, so that the vibration energy of the string S is transmitted through the long piece 55 to the soundboard. The sound is effectively transmitted to the speaker 54, and the volume and sound of the piano sound are improved. If the pressing force of the string S is too small, the transmission efficiency of the vibration energy of the string S is reduced and the sound quality of the piano sound is deteriorated. Since it is difficult to withstand the movement, so-called "piece drop" occurs or the string S is broken, it is extremely important to control the string to an appropriate size.

For this reason, conventionally, the level difference ΔHB between the upper surface of the long piece 55 and the imaginary line P before the stringing (broken line in FIG. 10) is defined as “piece pressure”, and this piece pressure ΔHB is set to a predetermined value before the stringing. By adjusting to the target value, the pressing force of the string S is optimized after the stringing by using the piece pressure ΔHB as a medium. After stringing, as shown by the solid line, the string S
The soundboard 54 sinks due to the pressing force, and the level difference becomes smaller. At this time, ΔHS is called “string pressure”.

Conventionally, the adjustment of the frame pressure is generally performed by a method called "frame pressure pressing". This piece pressure is
The frame 51 is temporarily placed on the sound board 54 with a pin board (not shown) interposed therebetween, and a horizontal piece pressure line is drawn on the side surface of the long piece 55 by using a predetermined jig. In this method, the upper surface of the long piece 55 is shaved. Or long piece 55
However, in the case of a single machining type in which the punching and pinning are completed before fixing to the soundboard 54, the height of the long piece 55 is adjusted to a predetermined size, and By manufacturing the frame and the frame 51 in a predetermined size in advance, a predetermined frame pressure is obtained when the frame and the frame 51 are assembled.

[0007]

However, in the conventional method of adjusting the frame pressure by pressing the frame, it is necessary to carefully cut the entire upper surface of the long piece 55 manually so as to match the frame pressure line. However, this shaving operation takes a very long time, which is one of the factors that increases the manufacturing cost. In addition, long piece 5
In the case where the frame 5 is a single-piece processing type, the frame press-out is not necessary, but the accuracy of the frame pressure directly depends on the exfoliation of the soundboard 54 and the dimensional accuracy of the frame 51, while the exfoliation of the soundboard 54 Since the dimensional accuracy of 51 is inherently limited due to its manufacturing method, there is a problem that the frame pressure cannot be accurately obtained as a result.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to easily and efficiently adjust the frame pressure even after the soundboard and the frame are connected to each other. It is intended to provide a device.

[0009]

In order to achieve this object, the present invention is directed to a method in which one end is wound around a number of tuning pins provided on a frame, and a piece fixed to a sound board connected to the frame is opposite to the sound board. In order to adjust the pressure of the strings of a number of strings that are stretched while the other end is wound around a number of hitch pins arranged in parallel with the frame at the vicinity of the piece while the intermediate part is in contact with the surface of A piece pressure adjusting device for a piano, wherein a string near a hitch pin can be supported at a plurality of different supporting heights, and by selecting one supporting height from the plurality of supporting heights. And a piece pressure adjusting means for adjusting the piece pressure.

[0010] According to this piano piece pressure adjusting device, the string can be supported at a plurality of supporting heights in the vicinity of the hitch pin by the piece pressure adjusting means. , That is, the piece pressure changes. Therefore, for example, one support height is selected from a plurality of support heights of the strings according to the height of the pieces after connecting the frame and the soundboard, and the string pressure is adjusted by supporting the strings. it can. In addition, since the supporting height of the string is changed at the part near the piece, the change in the supporting height of the string is almost the same as the change in the piece pressure. can do.

As described above, even after the frame and the soundboard are connected, the piece pressure can be adjusted without directly touching the pieces, so that the conventional troublesome work of pressing the pieces becomes unnecessary. Even when the piece is processed as a single piece, the piece pressure can be easily and efficiently adjusted while compensating for the edging of the soundboard and the dimensional accuracy and assembly accuracy of the frame.

In this case, the piece pressure adjusting means is constituted by a piece pressure adjusting bar having a substantially triangular cross section having three sides different in length from each other, and the piece pressure adjusting bar is provided between the piece and a number of hitch pins. A plurality of hitch pins are attached to the frame with one surface including any one of the three sides in contact with the surface of the frame and including a plurality of hitch pins, and a plurality of corners facing the one side are provided. It is preferred to support the strings of

According to this structure, the piece pressure adjusting bar has a triangular cross-sectional shape and the lengths of the three sides are different from each other. In this case, different heights are obtained. And
The piece pressure adjusting bar is attached to the frame along the gap between the piece and the number of hitch pins, and supports a number of chords at a corner facing the bottom surface, that is, a vertex. Therefore, by selecting the mounting direction of the piece pressure adjusting bar, that is, which surface is to be the bottom face, and changing the supporting height of the strings, it is possible to simultaneously and efficiently adjust the piece pressure for a large number of strings.

In this case, it is preferable that the piece pressure adjusting bar has a long groove extending continuously along the length direction thereof.

In an acoustic piano, usually, the pieces are formed in a curved shape, and the hitch pins are also arranged in a curved shape along the pieces. On the other hand, by providing the long groove as described above in the piece pressure adjusting bar, the rigidity of the piece pressure adjusting bar is reduced and it is easy to bend. Therefore, the piece pressure adjusting bar is provided between the curved piece and many hitch pins. It can be easily arranged while bending and deforming.

In these cases, it is preferable that the piece pressure adjusting bar is formed of one of hard resin and hard rubber, and has a constant cross-sectional shape along its length.

In this configuration, since the strings can be relatively firmly supported by the hard resin or the hard rubber constituting the piece pressure adjusting bar, a good piano sound can be secured while suppressing sound attenuation. Further, by having a constant cross-sectional shape, the piece pressure adjusting bar can be easily formed by, for example, extrusion molding of a hard resin or hard rubber.

Further, in these cases, it is preferable that the frame has a positioning step for positioning the piece pressure adjusting bar formed so as to extend between the piece and the plurality of hitch pins.

In this configuration, the piece pressure adjusting bar is pressed against the positioning step and is bent and deformed along the positioning step, whereby the frame can be easily and accurately positioned at a predetermined position on the frame. Then, in this positioning state, for example, by bonding the bottom surface of the piece pressure adjusting bar to the frame, the piece pressure adjusting bar can be easily attached to the frame.

Alternatively, the piece pressure adjusting means comprises a piece pressure adjusting laminated sheet body in which a plurality of sheets having a predetermined thickness are laminated and adhered to each other so as to be peelable from each other. Attached to the frame, with one of the front and back surfaces in the stacking direction in contact with the hitch pins of the frame in contact with the surface of the frame where a number of hitch pins are juxtaposed,
It is preferable to support the strings on the other surface of the front and back surfaces.

According to this structure, by changing the number of sheets to be peeled off from the frame pressure adjusting laminated sheet body, the height of the frame pressure adjusting laminated sheet body, that is, the supporting height of the strings is changed. The piece pressure on the strings can be efficiently adjusted at the same time.

In this case, it is preferable that the plurality of sheets are formed of one of hard resin and hard rubber.

In this configuration, the strings can be relatively firmly supported by the hard resin or the hard rubber, so that a good piano sound can be secured while suppressing sound attenuation.

Further, in these cases, it is preferable that the frame has a positioning step portion formed between the bridge and the plurality of hitch pins for positioning the bridge pressure adjusting laminated sheet body.

In this configuration, the frame pressure adjusting laminated sheet body is pressed against the positioning step portion and bent and deformed along the positioning step portion, so that the frame can be easily and accurately positioned at a predetermined position of the frame. In the positioning state, for example, by attaching the bottom surface of the piece pressure adjusting laminated sheet body to the frame, it can be easily attached to the frame.

Alternatively, it is preferable that the piece pressure adjusting means is formed at a plurality of positions in the axial direction of the hitch pin, and is constituted by a plurality of circumferential grooves around which a string can be wound.

According to this configuration, one of the plurality of circumferential grooves is provided.
By selecting one of them and supporting the strings in the selected circumferential groove, the supporting height of the strings changes, so that the piece pressure of each string can be easily adjusted. Further, since the hitch pin also serves as the piece pressure adjusting means, a separate piece pressure adjusting means is not required, and the piece pressure can be adjusted for each string.

In this case, the hitch pin is configured to be mounted on the frame by press-fitting into the mounting hole formed in the frame, and a press-fit depth determining press-fitting depth to the mounting hole is provided at a predetermined position in the axial direction thereof. It is preferable to have a large diameter portion for use.

In this configuration, the press-fitting depth at the time of press-fitting into the mounting hole of the frame is accurately determined by the large diameter portion formed at the predetermined position of the hitch pin. As a result, the variation in the mounting height of the hitch pin itself is reduced, and the variation in the supporting height of the string wound around the circumferential groove of the hitch pin is also reduced, so that the adjustment of the piece pressure can be performed efficiently.

In this case, the hitch pin is made of metal,
It is preferable that the large diameter portion for determining the press-fitting depth is formed by caulking.

In this configuration, the large-diameter portion for determining the press-fitting depth can be instantaneously and efficiently formed by swaging.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows a back mechanism of a grand piano to which the present invention is applied. As shown in the figure, this back mechanism is composed of a soundboard 2 to which pieces (long pieces 1a and short pieces 1b) are fixed and a sound board 2 connected to the soundboard 2 by screws or the like from above, and a large number of tuning pins 3 and hitch pins. 4 and a number of strings S stretched between the tuning pin 3 and the hitch pin 4.

The long piece 1a and the short piece 1b have a predetermined curved shape and are adhered to the upper surface of the soundboard 2. As shown in FIG. 3, in order to be able to resist a pressing force of a string S described later and to give tension to the soundboard 2, “swelling” raised on the upper surface side is previously provided on the soundboard 2. Is formed. The tuning pin 3 and the hitch pin 4 are mounted on the upper surface of the frame 5 through mounting holes (not shown) formed after casting on the frame 5. The pieces 1a are arranged in a curved shape near the opposite side of the tuning pin 3 along the long pieces 1a (see FIG. 2).

FIG. 3 shows how the strings S are installed in the treble section. The string S has one end wrapped around the tuning pin 3 and the other end wrapped around the corresponding hitch pin 4, and the middle part is in contact with the upper surface of the long piece 1 a. Finally, it is stringed with a predetermined tension. Further, a capo / dastro bar 6 abuts from above on the string S at an intermediate position between the tuning pin 3 and the long piece 1a, so as to give the string S a lower kink. This Capo Dastro Bar 6 is shown in FIG.
Are provided integrally on the back surface of the bone portion 6a of the frame 5 shown in FIG.
It protrudes downward.

Further, a frame pressure adjusting bar 7 is attached to the frame 5 as frame pressure adjusting means so as to extend between the long piece 1a and a number of hitch pins 4. The string S is supported. After connecting the soundboard 2 and the frame 5, this piece pressure adjusting bar 7
Prior to stringing of the string S indicated by a two-dot chain line in FIG.
B, and after stringing, a string pressure ΔHS corresponding to a predetermined piece pressure ΔHB is obtained as shown by a solid line.

The piece pressure adjusting bar 7 is made of, for example, extruded hard resin or hard rubber, and has a substantially triangular cross-sectional shape as shown in FIG. A long groove 8 is formed continuously on each of the first to third surfaces 7a, 7b, 7c along the length direction thereof. Further, the first to third surfaces 7a, 7
The lengths L1, L2, L3 of the b, 7c, that is, the lengths of the sides of the triangle constituting the cross-sectional shape are as shown in FIG.
They are all different, and are designed to satisfy the relationship of L1>L2> L3. As a result, the height of the piece pressure adjusting bar 7 is
As shown in FIG. 1, when the first surface 7a is the bottom surface, the first height H1 is a minimum (for example, 5 mm), and when the second surface 7b is the bottom surface, the second height H2 is an intermediate size. (For example, 7 mm), and becomes the maximum third height H3 (for example, 10 mm) when the third surface 7c is the bottom surface.

As shown in FIG. 2, the piece pressure adjusting bar 7 having the above-described structure is formed as a continuous piece over the entire high-pitched portion of the grand piano. On the other hand, a positioning step 9 is formed integrally with the frame 5 so as to extend between the long piece 1a and the many hitch pins 4, and the piece pressure adjusting bar 7 is attached to the positioning step 9. It is installed along.

Next, a method of adjusting the frame pressure by the frame pressure adjusting bar 7 will be described in detail with reference to FIG. The adjustment of the piece pressure is performed before the string S is stringed (before the stringing is performed by the tuning pin 3) after the soundboard 2 and the frame 5 are connected, and FIG. Is shown. FIG. 7A shows a case where the relative height of the long piece 1a with respect to the frame 5 after the connection of the soundboard 2 and the frame 5 is low (hereinafter, referred to as “relative height of the long piece 1a”). In this case, the piece pressure adjusting bar 7 is moved to its first surface 7a.
Is attached to the frame 5 with the bottom as a bottom. This allows
Since the supporting height of the string S becomes the minimum H1, the imaginary line P1 connecting the supporting position and the lower end of the capo-dastro bar 6 also becomes lower, so that the imaginary line P1 and the long piece 1a
, That is, the frame pressure, can be adjusted to a predetermined value ΔHB.

As shown in FIG. 5B, when the relative height of the long piece 1a is slightly higher than that of FIG.
Is attached to the frame 5 and the support height of the string S is set to H2 of an intermediate size, and the imaginary line P2 at that time is taken from the imaginary line P1 in the case (a). Also, by setting the height to be high, it is possible to adjust to the predetermined frame pressure ΔHB.

Further, as shown in FIG.
When the relative height of the string S is even higher, the support height of the string S is set to the maximum H3 by attaching the piece pressure adjusting bar 7 to the frame 5 with the third surface 7c as the bottom surface, and the virtual line P3 at that time. Is further increased to obtain a predetermined piece pressure ΔH.
B can be obtained similarly.

After the adjustment of the piece pressure as described above, the piece pressure adjusting bar 7 has one corner thereof abutting on the positioning step 9 as shown in FIG. By doing so, it is finally accurately positioned with respect to the frame 5, and in this state, it is attached to the upper surface of the frame 5 by, for example, bonding. In this case, the rigidity of the piece pressure adjusting bar 7 is reduced by forming the long groove 8,
Since it is easy to bend, bending deformation can be easily performed.

As described above, according to the piece pressure adjusting bar 7 of this embodiment, the long piece 1 after the soundboard 2 and the frame 5 are connected.
By selecting the mounting direction of the piece pressure adjusting bar 7, that is, which of the first to third surfaces 7a to 7c is to be the bottom surface in accordance with the height a, and changing the support height of the strings S The piece pressures for a large number of strings S can be easily and simultaneously adjusted. In addition, since the supporting height of the string S is changed at a portion near the long piece 1a, the amount of change in the supporting height of the string S becomes almost the same as the amount of change in the piece pressure. , Can be adjusted effectively. further,
Since it is obtained as data that the variation in the relative height of the long piece 1a is usually within the range of 5 mm, the piece pressure can be sufficiently adjusted by the piece pressure adjusting bar 7 having the dimensions described above.

As a result, even after the soundboard 2 and the frame are connected, the long piece 1a is not directly manipulated.
Since the piece pressure can be adjusted, the conventional troublesome work of extruding the piece becomes unnecessary, and even when the long piece 1a is machined alone, the removal of the soundboard 2 and the dimensional accuracy and assembly accuracy of the frame 5 are compensated. However, the piece pressure can be easily and efficiently adjusted.

FIGS. 6 and 7 show a second embodiment of the present invention. In this embodiment, as the piece pressure adjusting means,
The difference is that a piece pressure adjusting laminated sheet body 11 is used instead of the piece pressure adjusting bar 7 of the first embodiment described above.
As shown in FIG. 7, this piece pressure adjusting laminated sheet body 11
It is formed in an elongated prism shape by laminating and bonding a predetermined number (for example, 10) of sheets 12 having a predetermined thickness (for example, 1 mm). Each sheet 12 is made of hard resin, hard rubber, or the like. Also, sheet 1
The gap between the sheets 2 and 12 is adhered by an adhesive having an adhesive strength smaller than the strength of the sheet 12 itself, and the sheets 12 can be peeled off one by one. The thickness can be adjusted at a pitch of the thickness of the sheet 12, for example, 1 mm pitch.

As shown in FIG. 6, the piece pressure adjusting laminated sheet body 11 has one side surface in contact with the positioning step 9 of the frame 5 like the piece pressure adjusting bar 7 of the first embodiment. Thus, the string S is supported on the upper surface while the bottom surface is adhered to the frame 5.

FIG. 6 shows an example of the adjustment of the frame pressure by the frame pressure adjusting laminated sheet body 11. That is, when the relative height of the long piece 1a is (a) low, for example, three sheets 12 are peeled off and the remaining sheet is made seven, and when the relative height of the long piece 1a is an intermediate height, two sheets 12 are peeled off. The remaining eight sheets are set. (C) When the sheet pressure is high, the sheet 12 is not peeled off at all, and all the sheets 12 are used to obtain a predetermined frame pressure ΔHB.
Can be obtained.

As described above, in the present embodiment, the height of the frame pressure-adjusting laminated sheet body 11 can be
In other words, the support height of the string S can be adjusted, so that the first
As in the embodiment, the piece pressures for a large number of strings S can be simultaneously and efficiently adjusted. In the present embodiment, particularly, the support height of the string S is set to the thickness of the sheet 12, for example, 1 m.
m can be changed in multiple steps with a pitch of m
This has the advantage that the piece pressure can be adjusted more finely.

FIGS. 8 and 9 show a third embodiment of the present invention. In this embodiment, a special hitch pin 14 having a larger diameter is used in place of the normal hitch pin 4 in the two embodiments described above. A groove 15 is formed.

The hitch pin 14 is made of the same steel as the normal hitch pin 4, has a diameter of about 3 mm, and is attached to an attachment hole 16 formed in the frame 5 by press fitting. In addition, three circumferential grooves 15 are formed at predetermined positions in the axial direction of the hitch pin 14 at intervals of about 2.5 mm, and each has a width and a depth so that the string S can be securely wound. doing. Therefore, in the present embodiment, one of the three circumferential grooves 15 is selected, and the string S is supported by the selected circumferential groove 15, thereby achieving the above-described 2nd.
As in the first and second embodiments, the piece pressure can be easily adjusted. Further, in this embodiment, in particular, since the hitch pin 14 also serves as the piece pressure adjusting means, there is an advantage that a separate piece pressure adjusting means becomes unnecessary and the piece pressure can be adjusted for each string S.

The hitch pin 14 is formed with a large diameter portion 17 for determining the press-fitting depth at a predetermined position below the circumferential groove 15 by caulking. The large-diameter portion 17 allows the press-fitting depth of the hitch pin 14 into the mounting hole 16 of the frame 5 to be accurately determined. As a result, the hitch pin 14
Since the variation in the mounting height of itself is reduced and the variation in the support height of the string S wound around the circumferential groove 15 is also reduced, the adjustment of the piece pressure can be performed more efficiently.

The present invention is not limited to the embodiments described above, but can be implemented in various modes.
For example, in the embodiment, one piece of the piece pressure adjusting bar or the piece piece of the piece pressure adjusting laminate is attached to the treble portion of the grand piano. However, these may be divided into two or more in the treble portion. Alternatively, it is of course possible to apply the piece pressure adjusting bar or the piece pressure adjusting laminated sheet body to another sound range, in which case, the piece pressure adjusting bar or the piece pressure adjusting laminated sheet body is divided and provided for each sound range. Alternatively, it may be provided as a continuous one for the entire sound range.

Further, the dimensions and the like of each piece pressure adjusting means shown in the embodiment are merely examples, and depending on the actual state of the piece pressure variation immediately after the connection between the soundboard and the frame, etc.
Can be changed. Further, the embodiment is an example in which the present invention is applied to a grand piano, but can be applied to an upright piano. In addition, it is possible to appropriately change the configuration of details within the scope of the present invention.

[0053]

As described above, the frame pressure adjusting device of the present invention has an effect that the frame pressure can be easily and efficiently adjusted even after the soundboard and the frame are connected. .

[Brief description of the drawings]

FIG. 1 is a view showing a method of adjusting a piece pressure according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a back mechanism of the grand piano to which the present invention is applied.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a partial perspective view of a piece pressure adjusting bar.

FIG. 5 is a side view of a piece pressure adjusting bar.

FIG. 6 is a diagram showing a method of adjusting a piece pressure according to a second embodiment of the present invention.

FIG. 7 is a partial perspective view of the piece pressure adjusting laminated sheet body.

FIG. 8 is a diagram illustrating a method of adjusting a piece pressure according to a third embodiment of the present invention.

FIG. 9 is an elevation view of the hitch pin of FIG. 8;

FIG. 10 is a diagram showing the installation state of strings S in a conventional grand piano.

[Explanation of symbols]

 1a Long piece 2 Sound board 3 Tuning pin 4 Hitch pin 5 Frame 7 Piece pressure adjustment bar 8 Long groove 9 Positioning step 11 Piece pressure adjustment laminated sheet body 12 Sheet 14 Hitch pin 15 Peripheral groove 16 Mounting hole 17 Large diameter part S string ΔHB Piece pressure

Claims (11)

[Claims] An end is wound around a large number of tuning pins provided on a frame, and an intermediate portion of the piece fixed to a sound board connected to the frame is brought into contact with a surface opposite to the sound board. A piece pressure adjusting device for a piano for adjusting the piece pressure of a number of strings that are stretched in a state where the other ends are wound around a number of hitch pins arranged in parallel with the frame in the vicinity, A piece configured to be able to support the string at a plurality of different support heights at a position near the hitch pin, and selecting one support height from the plurality of support heights to adjust the piece pressure; A piece pressure adjusting device for a piano, comprising pressure adjusting means. 2. The piece pressure adjusting means is constituted by a piece pressure adjusting bar having a substantially triangular cross-sectional shape having three sides different in length from each other. The piece pressure adjusting bar includes the piece and the plurality of hitch pins. Is attached to the frame with one surface including any one of the three sides in contact with the surface of the frame where the plurality of hitch pins are juxtaposed, and is opposed to the one side. 2. The apparatus according to claim 1, wherein the plurality of strings are supported at corners. 3. A piece pressure adjusting device for a piano according to claim 2, wherein said piece pressure adjusting bar has a long groove extending continuously along a length direction thereof. 4. The piece pressure adjusting bar is formed of one of a hard resin and a hard rubber, and has a constant cross-sectional shape along a length direction thereof. A piece pressure adjusting device for a piano according to item 1. 5. The frame according to claim 1, wherein the frame has a positioning step formed along the piece and the plurality of hitch pins for positioning the piece pressure adjusting bar. 5. The piece pressure adjusting device for a piano according to any one of 2 to 4. 6. The piece pressure adjusting laminated sheet body, wherein the piece pressure adjusting means is constituted by a piece sheet pressure adjusting laminated sheet body in which a plurality of sheets of a predetermined thickness are laminated and adhered so as to be peelable from each other.
Attached to the frame in a state where one surface of the front and back surfaces in the laminating direction is in contact with a surface of the frame where the plurality of hitch pins are arranged and is located between the piece and the plurality of hitch pins, The apparatus according to claim 1, wherein the string is supported by the other surface of the back surface. 7. The apparatus according to claim 6, wherein the plurality of sheets are formed of one of hard resin and hard rubber. 8. The frame has a positioning step for positioning the piece pressure adjusting laminated sheet body formed along the piece and the plurality of hitch pins. The piano piece pressure adjusting device according to claim 6 or 7. 9. The apparatus according to claim 1, wherein the piece pressure adjusting means is formed at a plurality of positions in the axial direction of the hitch pin, and is formed of a plurality of circumferential grooves around which the string can be wound. The piano piece pressure adjusting device according to claim 1. 10. The hitch pin is configured to be mounted on the frame by press-fitting into a mounting hole formed in the frame, and at a predetermined position in the axial direction,
The piece pressure adjusting device for a piano according to claim 9, further comprising a large-diameter portion for determining a press-fit depth into the mounting hole. 11. The apparatus according to claim 10, wherein the hitch pin is made of metal, and the large diameter portion for determining the press-fitting depth is formed by caulking.