DE1772340A1 - Cast iron metal piano string plate - Google Patents

Description

π, -Ing. Wilhelm Reicliel _cjni .

Frankiuri / Main-1 ⁵⁴⁹⁴ / ^K

Park street 13

NIPPON (LAKKI SEIZO KABUSHIKI KAISHA, Shizuoka-Ken, Japan

Cast iron metal piano string

The invention relates to a piano string plate made of cast iron metal.

The strings of the piano are stretched between tuning pins and fastening pins on the string plate. Since the tension of all strings taken together corresponds to a tensile force of up to 20 tons, the string plate must have sufficient strength to withstand this total force.

So that the string plates do not become too heavy and with strings in the length and arrangement required for acoustic reasons can be strung, they inevitably have a complicated shape with ribs and depressions and flat 'parts, as indicated in Figs. 1 and 2 of the accompanying drawings, which will be briefly described. Accordingly the iaitenplatten are currently cast from metal.

For this reason, at present, the stringboards for pianos are generally made of simple cast iron, i.e., gray cast iron manufactured as simple cast iron in a molten state flows easily and is well suited for watering. liin happy cast iron however, it is not suitable in all respects Satisfactory, ea has many problems with it themselves.

The main problem is akur-i y 3oher kind- , Vie har-iit-i * -> vxUhv- "t, the side plate serves h; m ': t ^ a.Jhiivib.:; Lr» H .1 ^ riui ■ .,.> / · Ν? ·: · Ίοα tung for <Hf! Tense K L-tvi <:;r; »aiten, dio '<ü> 2r ¹ L; ^ /; tfr3: ·.'·> · ■■. Ι ι a-

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should give off floor tones. But one knows that one is in direct contact with the strings in this way String plate affects the sound of the piano.

For example, it is known that the string plate must have the ability to suppress vibration, not with the strings is allowed to vibrate in resonance that the vibration properties are deteriorated when the thickness of the ribs, depressions and flat parts of the disk are too large, and that if the disk has a very large mass, its sound quality is much better. It should be pointed out, however, that in the current state of the art there are still many embossings with regard to the influence of the plate on the sound of the piano in which it is built must be clarified.

The second, albeit relatively secondary, problem is that it is proportionate great weight of the plate. As mentioned earlier, string plates are usually made of simple cast iron, However, because this material has insufficient strength has, the various parts of the plate must be made relatively thick. As a result, the plate about one third of the total weight of the piano for a conventional piano.

In view of this ■ weight problem, it would be natural possible to use a material with a lower density. However, this cannot be carried out easily without to degrade the sound of the piano.

For example, it was proposed that the plate from a Cast aluminum alloy to reduce weight. If you use such a record in a piano, however, the sound of the piano is deteriorated, so that

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these plates are not used frequently. Also are when replacing the plate material in view of the fact that the plate is part of the piano, the following points must be taken into account:

A piano string plate is provided with support ribs, which serve as a base for the piano strings and gradually wear off due to the frictional effect of the strings. The frictional effect is caused by the hammers striking the strings. As a result, the material has a Klaviersaiten- g plate be very abrasion resistant. In addition, the support ribs must have good sliding properties so that they do not hinder the movement of the strings under high tension when tuning.

The invention is therefore based on the object of creating piano string plates which significantly improve the sound of the piano and whose weight can be reduced without increasing the acoustic properties or mechanical strength worsen or decrease. The string support ribs of the plate should have high friction resistance and good sliding properties in terms of the frictional effect of the strings.

In order to achieve this object, it is considered essential that the properties of the plate material and the influence of the Plate material on the acoustic properties of the piano, in which the plate is installed, with a view to determining a defined basis for an optimal design and manufacture of piano string plates.

According to the invention this object is achieved in that the piano strings plate is made of a Gußeisenmetall whose inner damping factor or loss factor Q "between 1.5 x ΊΟ" ⁵ and 0.2 x 10 ~ ^5.

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-A-

In preferred embodiments, the string plates are each made of cast steel, nodular cast iron (also as spheroidal graphite cast iron) called), malleable cast iron or Meehanite cast iron. However, the invention is not limited to the use of just these Cast iron metals limited.

The invention will now be based on exemplary embodiments and Drawings described in more detail.

FIGS. 1 and 2 show the front and top views, respectively, of the string plate of a pianino and a grand piano.

Fig. 3 is a block diagram of an apparatus for measuring the loss factor of a string plate.

4 is a graphic representation of the dependence of the loss factor on the deformation for various cast iron metals and

Fig. 5 is a graph of the attenuation of a piano sound (440 Hertz) with an inventive and pianos fitted with conventional platters as a function of time.

However, since a piano strings plate which together with the piano strings an oscillatory structure, maintains the plate to swing, if one or more strings are struck · measurements related to the sound of the piano have now shown that the attenuation of the sound vibrations of the piano total by suitable Reduction in the absorption of vibrational energy by the plate can be desirably reduced.

That is, while so far the way in which the plate material does not define the acoustic properties of the piano in which the plate is installed is determined how

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already mentioned, according to the invention, the loss factor 'Q ~ of the plate material was first investigated to clarify this point. In this case has turned out to ⁵ that the akusti · »see properties ein.es piano greatly depending on

change this loss factor Q and that it is possible to produce pianos with the desired acoustic properties if one chooses the loss factor so that it is between. .1.5 · 1 (T ³ and 0.2 · 1 (T ⁵ is. ■ .. '

The internal friction losses of a metal represent a physi- | A kaiic phenomenon within the metal and generally depend on the type of oscillation into which the metallic material is set. Furthermore, the loss factor Q ~, which is a measure of these internal frictional losses, depends on various quantities, e.g. on the amplitude of an applied vibration and on the time (ie if, for example, a part of the material has been deformed _{f it} assumes a state internal frictional loss or damping occurs slightly, and then it returns to its original state over time).

As a result, measuring the loss factor encounters considerable:

* ι borrowed difficulties. However, since the acoustic influence of the j loss factor has a significant influence on the piano i, in which the ^ aitenplatte is installed, plates were examined from ■ Grußeiaenmetallen _f and it has been found that it is possible that loss factor raifc considerable accuracy gu measure «S.

En has also established that a device such as that shown in Fig. 3 can be omitted. the loss factor is suitable. The device contains an excitation coil 3, @% ne Msßspulö 4? hai β, & ηβη s & sich um elelrtx-omagnabiecha coil »imwöelt and äia jswells in front of the% idon oinar I'robe I ■ _ mgmvüia®b aind, which aa / ö? äirfc« n 2 is suspended, sov / le .Vy? - ·; -

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stronger 6 and 7, whose output 'resp. Input connected to coils 3 and 4, a switch 5, between the amplifier 6 and the coil 3 »an attenuator 8, between the input of the amplifier 6 and the output of the amplifier 7, an amplitude comparator 9> its input via a switch 12 with the connection of amplifier 7 and attenuator 8 is connected, the switch 12 being mechanically coupled to the switch 5, as indicated by the dashed line Line 13 is shown, a gate circuit 10 to which the output signals of the amplitude comparator 9 are fed and which is also connected to the connection of attenuator 8 and amplifier 7, and one to gate circuit 10 connected frequency counter 11.

The following is an example of how the loss factor a sample 1 is measured with the aid of the device.

First, a sample 1 with dimensions of 1 χ 10 χ mm cut out of a previously prepared string plate from the central part of the cross-section in the direction of Thickness of the plate. The dimensions given are chosen because the oscillation frequency of this sample is then im The range is from 800 to 1000 Hertz and in the oscillation range of the middle part of the piano oscillation frequencies from 27 »5 to Corresponds to 4186 Hertz.

The sample 1 is hung horizontally from two very thin wires 2, each of which is attached at a point 15 "7 mm from the sample. The electromagnetic coils 3 and 4 are arranged in such a way that they Both ends of sample 1 confront j which is excited to forced vibrations j "The excitation energy supplied to the sample is then ab-r lt, at, and cite amplitudes during natural damping

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of the sample are measured in vacuum of at least ¹ O "mm Hg at room temperature

-1 ■ The loss factor Q is determined using the following equation:

(1)

where A _{1 is} the amplitude at the measuring point at the beginning of the measurement and Ap is the amplitude of the η-th oscillation afterwards.

- 1 ·

Since the loss factor Q depends on the amplitude, the measurements with different amplitude values must be carried out at the beginning of the Measurement are repeated in order to "determine this dependency, Accordingly, the dependence on the deformation (or compression) at maximum amplitude is examined. The maximum amplitude is measured with the aid of a microscope up to 0.01 mm, and smaller values of the amplitude are obtained from the Attenuation values calculated. The deformation then results. according to the following equation:

6max = 9.0 X \ (2)

1 .

in the £ max the maximum deformation on the sample surface,. (6 the oscillation amplitude,
h is the sample thickness and
1 is the sample length.

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The measured values obtained in this way for samples with various cast iron metals are in I ¹ Ig. 4, which shows the respective dependence of the loss factor on the deformation. Curve (A) shows the dependency of the loss factor when using simple cast iron, curve (B) the dependency when using Meehanite cast iron, curve (C) the dependency when using nodular cast iron (sample 1), curve (D ) the dependency when using malleable cast iron, curve (E) the dependency when using nodular cast iron (sample 2) and curve (F) the dependency when using cast steel.

As you can see, with the exception of simple cast iron (curve A), the loss factor becomes smaller in the event of a deformation

—4-5

than 10, especially less than 10, is largely constant. Therefore the value of the loss factor for a deformation of 10 is taken. While the upper limit of all these values is 1.5 * 10, the lower limit value should be around 0.2 * 10 ^J. The reason for this is that if the internal frictional losses are very small, the piano will sound too metallic.

As already mentioned, the string plate according to the invention is made from a cast iron metal with special properties. "Cast iron metal" is also, but not limited to, cast steel, meehanite cast iron, nodular cast iron and malleable cast iron will. The loss factor of a cast iron metal of this type depends heavily on parameters such as the composition of the metal, its structure and the graphite configuration depend on how it in Pig. 4 is shown. This also applies to ductile iron, which is a preferred string plate material according to the invention, and in this case the influence is graphitic onfiguriition particularly large.

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The reason why simple cast iron makes up a large part of the Absorbs vibration excitation energy, can be explained by that the graphite is crystallized in this cast iron in the form of flakes and. these graphite flakes one Cause the notch effect, through which the viscosity of the "zones" around the graphite is increased.

The loss factor increases with increasing spheroidization of the Graphite in cast iron metal and is heavily dependent on the rate of spheroidization of the graphite. The spheroidization of graphite in cast iron metal also depends on the tensile strength of the metal, which increases with increasing spheroidization. Because of this dependence of the string plate material on the internal friction losses of the metal must therefore the spheroid • idization rate of graphite in the cast iron metal so be selected so that this metal has a tensile strength of at least 37 kgf / mm. .

This tensile strength is measured in a conventional manner. For the investigations according to the invention, all test items were with a thickness of 5 mm and a width of 20 mm of any one Cut out part of the string plate and form a test piece with parallel sides 15 cm wide.

Since the loss factor of the plate according to the invention on this

Way is kept small, the attenuation of the sound becomes a The piano in which this plate is built in is extremely small. Therefore, the timbre becomes bright and, moreover, the tonal volume becomes more precise great. '

Since the piano is an almost to perfection sophisticated musical instrument, you have already different parts of the piano, which are known _t that depends on them, the sound of Laviere!; with verscMectenen far measurement QR

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It therefore seems unlikely that any further improvements to these parts would make another major contribution for the acoustic improvement of the piano.

However, it has been found that the by the invention Material exchange achieved sound improvement is much greater than that achieved by any improvements could be achieved on any other parts of the piano. It has been shown, for example, that not even musically trained people correctly understand the acoustic difference between a piano in which the plate according to the invention is built in, and can determine a conventional piano.

Another great advantage of the invention is its low weight of the plate, which results from the following reason: A cast iron metal in which graphite is spheroidized has mechanical and physical properties approximating those of steel. That is, the tensile strength of this metal lies between 37 and 100 kp / mm, which is relatively large compared to the tensile strength of ordinary cast iron, whose tensile strength is between 15 and 35 kp / mm .. Denial the thickness of the various parts of the plate can be reduced, thus reducing the weight of the plate greatly reduced.

Another advantage of the panel material according to the invention is the high toughness compared to the simple ordinary cast iron, that of the plate according to the invention is greater Resistance to loads as a plate made of simple cast iron. There is also the friction resistance the plate material is better, the support ribs of the plate are much more durable. If, moreover, the graphite is spherical, the support ribs will not chip or flake as easily, and at the same time it will result in a good gelling between the support ribs and the strings an ihraii ^^ öi ^ hrurig'a st hurry,

009843/0081 bad original,

In order to more clearly point out the advantages of the invention, will in the following an example of a preferred embodiment is given, but only to illustrate the invention and not is given to limit the scope of the invention.

example

For comparison, grand piano string plates were made of simple cast iron and made of ductile iron.

In detail, base metal for simple cast iron was melted in a cupola furnace with a composition suitable for high load-bearing capacity. The molten metal, called melt, was scooped into a pan and poured into a sand mold that was previously made to make a string plate. On the other hand, ductile iron frames were made by adding about 0.2 <f <> calcium carbide to the melt in the cupola furnace for desulphurization, then scooping the melt into a 1-pan with a Mg-Si-Fe alloy (with 0, 3 ° h Mg) was inoculated to spheroidize the graphite, and the melt was poured into a sand mold.

The chemical composition and mechanical properties of the cast iron metal plates thus produced were measured, and the result is shown in Table 1.

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Tensile strength ρ
(kp / mm)
Hardness (HRB)
modulus of elasticity
(kp / mm)
Loss factor (x10 ~ ⁵ ) Conventional
liche
plate Plate after the
invention sample
H Chemical together
setting ($)
C. 3.57 sample 3.45 Si 1.99 3.35 2.25 Mn 0.61 2.90 0.43 P. 0.06 0.41 0.04 S. 0.11 0.05 0.01 21.4
88.8
12 600
3.9 0.01 37.8
90.8
15 600
1.0 46.3
91.1
6,300
0.6

Table 1

The records produced in this way were built into pianos and strung. Then, the sound vibrations emitted from these pianos were measured. Specifically, each of the plates was installed in a grand piano , and then a 200 g piece of lead was dropped from a height of 20 mm onto the key corresponding to a tone of 440 Hz. The sound thus produced was recorded on an audio tape and then played back repeatedly, and then the attenuation curves for various pre- sequence components were recorded using a high-speed amplitude recorder.

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As a result, it was found that the piano in which the plate according to the invention was installed, had a lower damping effect than the piano in which the conventional Plate was built in. In FIG. 5, curve J represents the course of attenuation of a tone of 440 Hz in a piano in which the disk according to the invention was installed, and the curve K den The course of attenuation of the same note on a piano in which the conventional record was installed. These curves show clearly that the damping time in the first case is greater than in the second case is.

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Claims (1)

Claims 1 · Piano string plate made of cast iron metal, thereby characterized in that the loss factor (Q ~) of the cast iron metal is between 1.5 x 10 "* ^ and 0.2 x 10" * ^. 2 plate according to claim 1, characterized in that that the cast iron metal is cast steel or nodular cast iron or malleable cast iron or Meehanite cast. 3 · Plate according to claim 1 or 2, characterized in that the cast iron metal has a tensile strength of at least 37 kp / mm. BATH ORIGINAL 009843/0082