EP3227882B1 - Frame for a grand piano or a piano and method for improving such a frame - Google Patents

Description

The invention relates to a frame for a grand piano or upright piano and a method for improving such a frame. Such frames are also referred to in the prior art as a sprue, plate, cast plate, piano plate, piano string plate, "frame" or "iron plate".

In the context of this disclosure, the term “grand piano” is intended to encompass all keyboard instruments in which, when a key is pressed, a special mechanism hits hammers against strings which are stretched over a frame.

Out DE 570 099 A a one-piece frame for a grand piano made of light metal is known, the string bridge of which is formed in one piece with the frame and has resonance pianos in order to increase the sound vibrations.

Out U.S. 3,564,963 A a damping device for a frame known as a piano side plate is known, which is arranged as a connecting plate between adjacent longitudinal struts.

In DE 12 85 280 A and DD 20 970 A5 describes designs for a concert grand piano rest as well as a piano or grand piano rest. The design of the frame is not discussed in these documents.

Out U.S. 504,733 A the arrangement of disks made of hard wood, known as "acoustic disks", in the area of the soundboard is known. The discs should be arranged at a junction between ribs and a central web.

Out U.S. 1,732,748 A a piano is known on which, starting from the body of the piano, reflection elements are arranged which are intended to reflect back vibrations of the soundboard.

Out U.S. 4,602,548 A a method for pianos is known, the resonance body of which comprises a central bridge and a bass bridge, whereby the aim is to influence the amplitude and duration of two adjacent tones by attaching a weight to one of the bridges. The design of the frame is not discussed in this document.

Out DE 1 772 340 A a frame for a grand piano, called a piano string plate, is known, the sound of which is to be improved in that the loss factor of the cast iron used is within a predetermined range of values.

Out DE 27 10 505 B2 is a known as a piano plate frame for a grand piano with a front plate and back plate, on the surface (s) of which fine, bumpy patterns are formed. These fine patterns are intended to improve the response of the frame in a wide frequency range.

Out GB 1,103,687 A and FR 2 929 436 A1 Further frames for wings are known which comprise a front panel, a rear panel and longitudinal struts connecting the two panels.

The invention is based on the object of providing a frame for a grand piano or piano which is improved in terms of vibrations. Furthermore, a method for improving a frame for a grand piano or upright piano is to be provided.

The object is achieved according to the invention with the features of the independent claims. Further advantageous embodiments are described in the dependent claims.

A frame according to the invention for a grand piano or piano comprises a front panel, a rear panel and a plurality of longitudinal struts connecting the front panel and the rear panel. Here, at least one longitudinal strut with a minimum length of 500 mm, viewed in the direction of its longitudinal extent, is between the front panel and the rear panel in a discrete area of the longitudinal strut by partially increasing the cross-sectional area, by partially using a material with a higher density and / or by fixing a separate element In a discrete area of the longitudinal strut, at least one local mass maximum is formed, which extends over a length of the longitudinal strut of a maximum of 150 mm. It was determined through tests that a grand piano or piano can be significantly improved in terms of vibrations with a frame as described above insofar as vibrations generated when playing the grand piano or piano, in particular in the frame, are significantly reduced with the measures.

A maximum longitudinal extension of a maximum mass on a longitudinal strut of 150 mm means that when the mass element is formed using additional material (in one piece or in the form of subsequently supplemented additional masses), a local maximum mass that is clearly recognizable on the longitudinal strut is created, which extends over a length section of a maximum 150 mm and / or a material with a higher density is preferably continuously introduced into the longitudinal strut over a length section of 150 mm. In the case of additional masses, the area of the longitudinal strut to which the additional mass is attached is understood as the area of extent. This will be discussed in detail in connection with the description of the figures. A local mass maximum is understood, in particular in connection with this embodiment, to be a region of the longitudinal strut which, relative to two neighboring regions surrounding this region, has a higher mass per millimeter of length of the longitudinal strut. In a preferred embodiment, the at least one local mass maximum extends over a length range of at most 100 mm, in a particularly preferred embodiment the at least one local mass maximum extends over a length range of a maximum of 50 mm. If several local mass maxima are formed, the aforementioned value ranges preferably apply to all local mass maxima.

A front panel of a grand piano in the context of the invention is understood to mean an element which establishes a connection between the longitudinal struts on the side (front) of the frame that is aligned with the keys of a grand piano. A rear panel of a grand piano in the context of the invention is understood to mean an element which connects the longitudinal struts on the side (rear) remote from the keys. In the case of wings, the back plate usually extends along the curved sides (this is usually the right side) to the rear end. The frame serves - together with the notch or rim and wall surrounding the frame - to absorb the tensile and bending forces emanating from the strings of a grand piano. Frames for grand pianos or a piano are currently mainly manufactured as cast frames, using both common gray cast iron and special cast materials. The invention can be implemented both with a cast frame and with frames made differently, in particular frames made from several individual parts that are firmly connected to one another. The front panel, rear panel and longitudinal struts of the frame according to the invention can therefore be designed in one piece or manufactured in one or more individual parts and firmly connected to one another. In the case of several individual parts, the connection can be made in a form-fitting, force-fitting and / or material-locking manner. A separate element can also be fixed in a discrete area of the longitudinal strut in a form-fitting, non-positive and / or cohesive manner.

As an example of non-positive connections, reference is made to the tightening of additional masses by means of clamping devices similar to screw clamps or by means of other clamping devices.

As examples of form-fitting connections, the screwing of additional masses into openings provided for the additional masses is given Referred to the longitudinal strut or the attachment of additional masses by means of a rivet connection.

As an example of material connections, reference is made to the fixing of additional compounds by means of a soldered, welded or adhesive connection.

Frames according to the invention can also be made from composite materials, such as from material compositions comprising carbon and one or more metal materials, cast iron and steel or aluminum and lead.

A local maximum mass within the meaning of the invention can also be formed by removing material in an area or several adjacent areas of a frame that is adjacent to a maximum mass to be achieved. This can be done in particular by milling, grinding and / or with the aid of a cutting process.

A longitudinal strut of the frame according to the invention, on which the at least one local mass maximum is formed, has at least one connection area to a further element, at least one local mass maximum being formed on this longitudinal strut at a distance from this node. In the present case, the term connection area refers in particular to so-called nodes, ie connections to a cross strut running between two or more longitudinal struts or connection areas to an element surrounding the frame, for example a connection area of the longitudinal strut for so-called locking. In other words, according to the above-mentioned practical embodiment, at least one further local mass maximum is formed independently of connection areas (nodes etc.) formed on the frame, the main function of which is the connection to a separate, further element. In the present case, “at a distance” means that in the case of a frame according to the invention which has a plurality of connection areas to a further element, at least one further local mass maximum between two adjacent connection areas or between a connection area and the front panel or between a connection area and the rear panel is formed or arranged.

It is preferred if, in a frame according to the invention, the mass of a length of one millimeter of the longitudinal strut in the area of a local mass maximum compared to the mass of at least one area adjoining the local mass maximum in the longitudinal direction is by at least 5 percent, preferably by at least 7 percent and more preferably at least 10 percent, increased. This can also be referred to as a significant local mass maximum.

The mass of a length section of one millimeter of the longitudinal strut is preferably increased by at least 10 percent compared to the mass of areas adjoining in both directions in the longitudinal direction of the longitudinal strut.

In further preferred embodiments, the mass in the area of the local maximum is increased by at least 15 percent compared to an adjacent area (or preferably both adjacent areas), in a particularly preferred embodiment by at least 20 percent. It has been shown that with the formation of significant mass maxima as described above (minimum mass increase compared to adjacent sections in one or in both directions of the longitudinal extension of the longitudinal strut), a particularly significant vibration-related improvement can be achieved.

In a further practical embodiment of a frame according to the invention, which can be realized alternatively or in addition to the embodiments described above, several local mass maxima are formed on at least one longitudinal strut. In this regard, it has been shown that the formation of 2 to 15 local mass maxima a longitudinal strut with a length of approx. 1000 mm is particularly advantageous.

It has also proven to be advantageous to increase the mass of a longitudinal strut as the local maximum mass in a central, elongated area, the central area preferably extending over at least half the length of the longitudinal strut. It preferably begins at a distance from the front panel and extends in the longitudinal direction of the longitudinal strut up to a region at a distance from the rear panel. The middle area extends preferably over at least 25 percent, preferably at least 50 percent and particularly preferably at least 75 percent of the length of the longitudinal strut (measured from the front panel to the rear panel).

It is particularly preferred if, in addition to such an elongated area with increased mass, a further mass maximum or several further mass maxima are formed in this area.

In relation to a longitudinal strut with a length of approx. 1000 mm, the middle area can, for example, extend over a length of approx. 900 mm and begin at a distance of approx. 10-50 mm from the front panel. In a particularly preferred embodiment of the longitudinal strut of a frame according to the invention, 2 to 15 further mass maxima, preferably 5 to 12 mass maxima and more preferably nine mass maxima, are formed within the above-described central region. The mass of the middle section of the longitudinal strut is increased by at least 10 percent compared to the mass of the other areas and the mass of the mass maxima in the area of the middle areas is also increased by at least 10 percent compared to the middle section (without additional mass maxima). Preferred absolute positions for the mass maxima are mentioned in the description of the figures.

Preferably, several local mass maxima are formed on several, and particularly preferably on all, longitudinal struts, in particular in one the manner described above. It was found in tests that the formation of a plurality of local mass maxima allows frames according to the invention to be further improved in terms of vibration technology.

If in a frame according to the invention at least one longitudinal strut (and preferably all of the longitudinal struts) have a closed surface in the region of the at least one local mass maximum, the frame is particularly appealing not only in terms of vibration, but also optically. A closed surface means in particular that the surface should be free of openings such as through bores (not closed by other inserted elements), blind bores or other hollow spaces of other design.

In a further practical embodiment of a frame according to the invention for a grand piano or piano, the profile of the at least one longitudinal strut with a local maximum mass has a height that is greater than the width, at least over a predominant length range between the front panel and the rear panel. All longitudinal struts preferably have such a profile, in particular all those that have a local mass maximum. A "predominant length range" means here that the height over at least 50 percent of the length of the longitudinal strut (measured from the connection point of the longitudinal strut to the front panel to the connection point of the longitudinal strut to the rear panel) is greater than the width. In this context, the height should be the direction of extension parallel to the gravitational force of a frame built into the wing, the height being the difference between the "highest" and the "lowest" point (viewed in the direction of the gravitational force). The width means the extension of the longitudinal strut in the transverse direction, the transverse direction being oriented perpendicular to the force of gravity and perpendicular to the longitudinal direction of the longitudinal strut (center line).

In the case of a piano, the frame is rotated by 90 ° in relation to the grand piano. In this case, the height of the longitudinal strut should be regarded as the extent of the longitudinal strut in a direction perpendicular to the force of gravity, namely the extent of the longitudinal strut in the horizontal direction, which leads from the front with the keys of the piano to the rear of the piano. In this case, the length of the longitudinal strut means the extension in the direction of the gravitational pull and the width means the extension in the horizontal transverse direction.

A frame according to the invention for a grand piano or upright piano, which is designed as a cast frame, is particularly high quality and resilient as well as preferred in terms of vibration. The frame including the front panel, rear panel, longitudinal struts and any transverse struts - and particularly preferably including all local mass maxima, is preferably manufactured as a one-piece component.

The cross-sectional area of at least one longitudinal strut with a local maximum mass of a frame according to the invention is preferably T-shaped or conical over the predominant area of the longitudinal direction between the front panel and the rear panel. In the case of a T-shaped design, it is preferred if the top line of the "T" is oriented horizontally (i.e. perpendicular to the force of gravity) and the stem of the "T" extends upward from the top line against gravity. With this geometry, bending and tensile stresses in the strings can advantageously be absorbed. If the cross-sectional area is conical, it is preferred if the cross-section is tapered upwards (i.e. against the force of gravity), i.e. the cross-sectional area has a greater width in the lower area than in the upper area.

The invention is not restricted to the preferred cross-sectional surface configurations described above. It also extends to any other cross-sectional geometries of longitudinal struts formed on frames for grand pianos or pianos.

The protection of the invention also includes grand pianos or pianos in which frames as described above are used.

The thickness of the front panels and / or rear panels of frames according to the invention is, in particular in the case of frames manufactured as cast parts, preferably 2-20 mm, particularly preferably 4-14 mm and more preferably 8-10 mm.

In particularly practical embodiments, the height of individual longitudinal struts of a frame according to the invention for a grand piano or piano is between 15 mm and 100 mm, preferably between 30 mm and 85 mm and particularly preferably between 40 mm and 65 mm.

In particularly practical embodiments, the width of individual longitudinal struts of a frame according to the invention for a grand piano or piano is between 2 mm and 100 mm, preferably between 4 mm and 80 mm and particularly preferably between 6 mm and 65 mm.

1. a) Wiederholtes Anspielen mehrerer Töne über die Tastatur des Flügels oder Pianos und gleichzeitiges Ermitteln mindestens eines Bereichs an einer oder mehreren Längsstreben eines Rahmens mit einem lokalen Schwingungsamplitudenmaximum,
2. b) Positionieren und Befestigen mindestens eines als Zusatzmasse dienenden separaten Elements nur in einem ermittelten Bereich einer Längsstrebe oder an einer zu dem ermittelten Bereich beabstandeten Position an dem Rahmen derart, dass die Schwinungsamplitude in dem gemäß Schritt a) ermittelten mindestens einen Bereich reduziert wird.

The invention also relates to a method for improving a frame of a grand piano or piano with at least the following method steps:

1. a) Repeated playing of several tones via the keyboard of the grand piano or piano and simultaneous determination of at least one area on one or more longitudinal struts of a frame with a local oscillation amplitude maximum,
2. b) Positioning and fastening at least one separate element serving as additional mass only in a determined area of a longitudinal strut or at a position spaced apart from the determined area on the frame such that the oscillation amplitude is reduced in the at least one area determined in accordance with step a).

In this context, a local oscillation amplitude maximum is understood to mean in particular areas on a longitudinal strut which vibrate more strongly when playing at least one note over the keyboard of the grand piano or piano, i.e. have a greater oscillation amplitude than the neighboring areas of the longitudinal strut (viewed in the longitudinal direction of the longitudinal strut) . In this context, the oscillation amplitude is understood to mean the absolute amount of the maximum deflection in the transverse direction to the longitudinal direction of the longitudinal strut. It is preferred in a first process step to first reduce the oscillation amplitude in the area of a longitudinal strut with the largest local oscillation amplitude maximum, i.e. in the area with the absolute oscillation amplitude maximum of this longitudinal strut. However, the method according to the invention can also be carried out only for selected local oscillation amplitude maxima.

In a method according to the invention, it is particularly preferred to find an arrangement for the separate element which reduces the oscillation amplitude in the region of the oscillation amplitude maximum by as large an amount as possible. In practice, areas with a local oscillation amplitude maximum can be created in a simple manner by scanning with the hand while playing keyboard tones.

Alternatively, it is possible to use devices by means of which areas of local oscillation amplitude maxima of longitudinal struts as well as the amplitude itself or a sensible alternative measure for the amplitude can be determined exactly. In this regard, reference is made in particular to the use of acceleration sensors and the use of so-called laser vibrometers with measurements at discrete reference points and / or with measurements on reference surfaces.

With the aid of acceleration sensors, which can be positioned at various points on a longitudinal strut, the acceleration can be measured as a measure of the amplitude as an alternative to the magnitude of the amplitude. It is assumed that the acceleration a longitudinal strut behaves proportionally or at least analogously to the oscillation amplitude, that is, from an acceleration measured in terms of magnitude, a high oscillation amplitude in terms of magnitude is deduced.

With the help of laser vibrometers, which are preferably positioned on holding devices and aligned with an edge of a longitudinal strut, absolute values for the deflections (amplitudes) of a longitudinal strut caused by sound vibrations can be measured.

It is particularly suitable for a quick and uncomplicated determination of particularly strongly vibrating areas (i.e. areas with large oscillation amplitudes) if chromatic scales of the grand piano or piano to be improved are played repeatedly, while a longitudinal strut to be improved in terms of vibration is in - for example 50-100 mm large - is touched with a finger at regular intervals. The area of the strongest oscillation can be felt directly with the finger on most grand pianos or pianos. A simple approach to reducing the oscillation amplitude in a determined area with a large oscillation amplitude is to position an additional element that functions as an additional mass in the determined area and to fix it (e.g. by clamping). In individual cases, however, it can also lead to a (possibly even greater) reduction in the oscillation amplitude if a separate element serving as an additional mass is attached to a position spaced apart from the determined area. If necessary, this can be determined through tests.

It is preferred if the method is carried out at least for all low (and high-energy) notes of a grand piano or piano. These tones particularly stimulate the longest of the longitudinal struts of the grand piano or piano.

Accordingly, a method is preferred that at least for one of the three longest longitudinal struts of a grand piano or piano, preferably for the two longest longitudinal struts and particularly preferably for the three longest longitudinal struts of a grand piano or piano to be improved. All struts of a frame whose greatest extent is in the longitudinal direction are regarded as longitudinal struts, with the horizontal direction perpendicular to the keyboard plane being regarded as the longitudinal direction in the case of a grand piano and the vertical direction in the case of pianos. To do this, all notes are to be played that stimulate the relevant longitudinal struts to vibrate with a relevant vibration amplitude. These are usually those tones of the grand piano or piano assigned to the lower (left) half of the keyboard, especially those assigned to the lower third of the keyboard. The method is preferably carried out for all tones. In a simplified embodiment, it can only be carried out for part of the tones, in particular with half or a partial range of all tones.

Fig. 1

einen Flügel gemäß Stand der Technik in einer Ansicht von der Seite (obere Darstellung) und in einer Ansicht von oben mit ausgewählten, insbesondere für die Erfindung relevanten Einzelelementen (untere Darstellung),

Fig. 2

eine perspektivische Darstellung einer ersten Ausführungsform eines erfindungsgemäßen Rahmens für einen Flügel,

Fig. 3

eine vergrößerte Darstellung der in Figur 2 mit III gekennzeichneten Längsstrebe des erfindungsgemäßen Rahmens,

Fig. 4a-4c

Schnittdarstellungen durch die in Figur 3 mit den Linien A-A, B-B und C-C gekennzeichneten Bereiche der Längsstrebe,

Fig. 5

eine perspektivische Darstellung eines Abschnitts einer Längsstrebe eines erfindungsgemäßen Rahmens für einen Flügel, an welcher verschiedene konstruktive Möglichkeiten zur Erzielung von Massemaxima dargestellt sind,

Fig. 6

eine Seitenansicht eines Abschnitts einer Längsstrebe eines erfindungsgemäßen Rahmens für einen Flügel mit einem als separates Element ausgebildeten, an dieser Längsstrebe angeordneten Massemaximum und

Fig. 7

ein Diagramm (Länge-Massen-Diagramm) zur Darstellung der Masse m pro mm Länge einer Längsstrebe eines Ausführungsbeispiels eines erfindungsgemäßen Rahmens über die Länge I der Längsstrebe von der Vorderplatte (0 mm) bis zur Hinterplatte (ca. 1000 mm).

Further practical embodiments and advantages of the invention are described below in connection with the drawings. Show it:

Fig. 1

a wing according to the prior art in a view from the side (upper illustration) and in a view from above with selected individual elements relevant in particular to the invention (lower illustration),

Fig. 2

a perspective view of a first embodiment of a frame according to the invention for a wing,

Fig. 3

an enlarged view of the in Figure 2 with III marked longitudinal strut of the frame according to the invention,

Figures 4a-4c

Sectional views through the in Figure 3 Areas of the longitudinal strut marked with the lines AA, BB and CC,

Fig. 5

a perspective view of a section of a longitudinal strut of a frame according to the invention for a wing, on which various structural options for achieving maximum masses are shown,

Fig. 6

a side view of a section of a longitudinal strut of a frame according to the invention for a wing with a mass maximum formed as a separate element and arranged on this longitudinal strut;

Fig. 7

a diagram (length-mass diagram) to show the mass m per mm length of a longitudinal strut of an embodiment of a frame according to the invention over the length I of the longitudinal strut from the front panel (0 mm) to the rear panel (approx. 1000 mm).

Figure 1 shows a wing 10 in a side view (upper illustration) and in a view from above (lower illustration). The wing 10 consists essentially of a base body 12 with a hinged cover 14. The base body 12 stands on feet 16 which are mounted on rollers 18.

The lower illustration shows a view of the grand piano 10 from above without the cover 14 and without strings. In this illustration, the keyboard 22 arranged on the front side 20 and the frame 24 extending in the longitudinal direction (x direction) of the grand piano 10, which begins behind the keyboard 22 and extends to the rear side 26, can be seen. The frame 24 consists essentially of a front panel 28, a rear panel 30 and longitudinal struts 32 connecting the front panel 28 and the rear panel 30. The strings (not shown) are usually stretched from the front panel to the rear panel 30. A plurality of openings 34 are formed in the rear plate 30.

As in the illustration below of Figure 1 As can be seen, cross-sectional widenings 38 are formed on a plurality of longitudinal struts 32 in the area between the front panel 28 and the rear panel 30. In the areas with widened cross-sections 38, additional material is provided on the respective longitudinal strut 32, which protrudes laterally with respect to the profile extending from the front panel 28 in the direction of the rear panel 30.

In the areas with a lateral cross-sectional widening 38, the respective longitudinal strut 32 has an L-shaped profile. In the areas with two cross-sectional widenings 38 arranged on opposite sides, the respective longitudinal strut 32 has a profile that is T-shaped in cross-section.

The in the lower illustration of the Figure 1 recognizable cross-sectional widenings 38 are known from the prior art. They usually have a length of more than 150 mm.

Figure 2 shows an embodiment of a frame 24 according to the invention, the basic structure of which corresponds to that in Figure 1 The frame 24 shown corresponds, that is to say in the case of this frame 24 too, a front panel 28 is connected to a rear panel 30 spaced apart from it via longitudinal struts 32.

The in Figure 2 The frame 24 shown additionally has a cross strut 40 which connects several longitudinal struts 32 to one another.

The in Figure 2 The frames 24 shown are formed on two longitudinal struts 32 cross-sectional reductions 42 in that the profile has recesses on the underside that extend in the vertical direction (z-direction) in a discrete longitudinal area of the respective longitudinal struts 32. Such cross-sectional reductions 42 are known from the prior art, in particular of grand pianos or pianos, in which the space conditions require such constructions to be further reduced Elements, such as a wooden beam of a base body, to be able to lead through the area of the recesses.

In the Figures 1 and 2 the x-direction of the coordinate system is related to the wing 10 or the entire frame 24. The x-direction runs perpendicular to the extension direction of the keyboard 22 and thus along the left side edge of the base body 12 ( Figure 1 ) or perpendicular to the front edge of the frame 24 ( Figure 2 ). The inventive design of the in Figure 2 The frame 24 shown is only explained in connection with the following Figures 3-7 evident.

In the below explained Figures 3-6 only one longitudinal strut 32 is shown in each case. In these figures, the x-direction of the coordinate system was aligned in the longitudinal direction of the longitudinal strut shown.

Figure 3 shows the in Figure 2 with III marked area of a longitudinal strut 32 in an enlarged view. In the Figures 4a-4c are representations of the cross-sections oriented in the yz-direction along the in Figure 3 shown with lines marked AA, BB and CC. As in Figure 3 can be seen from the front cut surface 44, the longitudinal strut 32 in the in Figure 2 area marked III has a cross-sectionally T-shaped profile, the top line of the T being aligned horizontally and the trunk of the T extending upwards from the top line against gravity (direction of gravity g).

In Figure 3 is related to the Figures 4a, 4b and 4c It can be seen that a total of three mass maxima 36 are formed in different ways on the longitudinal strut 32. The maximum mass 36 formed in the region of the section line AA extends over a length range I ₁ , the second maximum mass 36 formed in the region of the section line BB extends over the length I ₂ , and the third maximum mass 36 extends in the region marked with CC over the Length I ₃ .

As in the Figures 4a-4c As can be seen, all mass maxima 36 are formed in that the T-shaped cross-section has been provided with a cross-sectional broadening 38. In the in Figure 4c length section of the longitudinal strut 32 shown, the area (and thus also the mass of defined length sections with constant cross-section and the same length) compared to the area of the front cut surface 44 is increased by approximately 7 percent. The additional cross-sectional area is in Figure 4c marked with 46, the delimitation of the additional area from the basic cross-sectional area being indicated by a dashed line. In the in the Figures 4a-4c The sectional representations shown are marked with dashed lines, the areas 46 which enlarge the cross section 46 and thus increase the mass. The increase in mass in the in Figure 4b section shown 56 percent and the in Figure 4a Sectional view shown 18 percent.

In Figure 5 Another section of the longitudinal strut 32 with various other embodiments for forming local mass maxima 36 is shown. These are discussed below in the order of the arrangement in the direction of the arrow x beginning with the front cut surface 44.

The first mass maximum 36 is a cross-sectional broadening 38 similar to that in FIG Figure 4b shown.

The second maximum mass 36 is designed as a through opening 48 formed in the trunk of the T-shaped profile. Such a through opening 48 can be used to form a local mass maximum 36 in order to insert a material with a higher density into this through opening 48. As an alternative or in addition, a cylindrical element can be used which has a larger volume than material was removed from the longitudinal strut 32 by forming the through opening 48.

Through openings such as through opening 48 can also be used analogously as a local minimum mass if no element is used or an element is used whose mass is less than the mass of the material missing in the area of the through opening.

The third local mass maximum 36 was formed by a cross-sectional broadening 38 in the area of the top line of the T-shaped profile.

The fourth local mass maximum 36 was realized by a further cross-sectional widening 38, which has an irregular shape that is reminiscent of a revolver. Based on the shape, it should be visualized that mass maxima in the sense of the invention do not have to be formed by cuboid or otherwise regular shapes, but can be shaped as desired. In this respect, the person skilled in the art is free to determine suitable shapes, sizes and arrangements of mass maxima within the framework of the teaching according to the patent, in particular by an iterative procedure in accordance with the method steps according to the invention.

The fifth local mass maximum 36 is a cross-sectional increase 50 which was achieved by extending the trunk of the T-shaped profile upwards (in the z direction).

Figure 6 shows a longitudinal strut 32 of a frame according to the invention, not shown, together with a maximum mass 36, which is connected to the longitudinal strut 32 over a length I _L (here: 75 mm), but extends above the connection area over a greater length I _M (here: 200 mm). The effective and thus effective for the length of the maximum mass defined in claim 1 is in the in Figure 6 The embodiment shown, the length I _L and thus the length over which the additional recognizable mass element is connected to the basic geometry of the longitudinal strut.

Figure 7 shows the course of the mass per mm of length of a longitudinal strut, not shown, of a longitudinal strut according to the invention. A total of three local mass maxima are formed on the longitudinal strut.

The first mass maximum 36 and the second mass maximum 36 - viewed from the front plate - are designed as "mass jumps", ie the mass is increased by a percentage of at least 5 percent from a discrete point on the longitudinal strut (here: increase at the first mass maximum by about 25 percent and increase at the second mass maximum by about 46 percent compared to the immediately adjacent areas).

The third mass maximum lies in a range between a continuous increase in mass starting from a length I ₁ up to a length I ₂ and a continuous decrease in mass starting from a length I ₃ up to a length I ₄ . In this case, the area marked with x is regarded as the maximum mass 36, in which the mass per mm of length of the longitudinal strut is at least 5 percent higher than in the area in front of the length I ₁ or behind the length I ₄ . The area marked with x in this case corresponds to the length which is decisive for the maximum mass 36. The subsequent areas in which the mass per mm of length of the longitudinal strut deviates by a "jump" of 5 percent (not recognizable in the profile of the longitudinal strut and the "course" of the mass per mm of length of the longitudinal strut) is by the length x ₁ or at a distance of the length x ₂ from the maximum mass 36. Nevertheless, the third mass maximum 36 is a mass maximum according to the invention. In this respect, it is not necessary for a "jump" required for a maximum mass to be evident directly on the longitudinal strut itself or on the basis of a sudden increase in mass per mm of length of a longitudinal strut in a length-mass diagram.

The features of the invention disclosed in the present description, in the drawings and in the claims can be used both individually and in any combination for the implementation of the invention in its various embodiments may be essential. The invention is not restricted to the embodiments described. It can be varied within the scope of the claims and taking into account the knowledge of the competent specialist.

List of reference symbols

10

wing

12th

Base body

14th

lid

16

foot

18th

role

20th

front

22nd

keyboard

24

framework

26th

back

28

Front panel

30th

Backplate

32

Longitudinal strut

34

opening

36

Mass maximum

38

Cross-sectional broadening

40

Cross brace

42

Reduction of the cross-section

44

front cut surface

46

cross-section

48

Through opening

50

Increase in cross-section

Claims (15)

1. A frame for a grand piano (10) or an upright piano comprising a front panel (28), a rear panel (30) as well as a plurality of longitudinal struts (32) connecting the front panel (28) and the rear panel (30), characterised in that at least one local mass maximum (36) is formed on at least one longitudinal strut (32) having a minimum length of 500 mm, as viewed in the direction of longitudinal extent thereof, between the front panel (28) and the rear panel (30) in a discrete region of the longitudinal strut (32) by partially increasing the cross-sectional area, by partially using a material having a higher density and/or by fixing a separate element in a discrete region of the longitudinal strut (32), said local mass maximum extending over a length of the longitudinal strut of at most 150 mm, wherein the at least one longitudinal strut (32) on which the at least one local mass maximum (36) is formed has a connecting region to another element of the frame and at least one additional local mass maximum (36) is formed on this longitudinal strut (32) spaced apart from this connecting region.
2. The frame for a grand piano (10) or an upright piano according to the preceding claim, characterised in that in at least one local mass maximum (36) the mass of a longitudinal section of one millimetre of the longitudinal strut (32) in the region of a local mass maximum (36) is increased by at least 5 percent with respect to the mass of at least one region proximate to the local mass maximum (36).
3. The frame for a grand piano (10) or an upright piano according to the preceding claim, characterised in that a plurality of local mass maxima (36) is formed on at least one longitudinal strut (32).
4. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that from 2 to 15 local mass maxima (36) are formed on at least one longitudinal strut and/or the front panel (28), the rear panel (30) and the longitudinal struts (32) are formed integrally.
5. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that the mass of a longitudinal strut (32) as a local mass maximum (36) is increased over a central elongated region that extends over at least 25 percent of the length of the longitudinal strut (32).
6. The frame for a grand piano (10) or an upright piano according to the preceding claim, characterised in that at least one additional mass maximum (36) is formed in a region of a longitudinal strut (32) having an increased mass.
7. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that a plurality of local mass maxima (36) is formed on a plurality of longitudinal struts.
8. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that at least one longitudinal strut (32) has a closed surface in the region of the at least one local mass maximum (36).
9. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that the height of the section of at least one longitudinal strut (32) with a local mass maximum (36) exceeds the width at least over a predominant longitudinal region between the front panel (28) and the rear panel (30).
10. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that the frame (24) is designed as a cast frame.
11. The frame for a grand piano (10) or an upright piano according to one or several of the preceding claims, characterised in that the cross-sectional area of at least one longitudinal strut (32) with a local mass maximum (36) in the predominant region of the longitudinal extension of the longitudinal strut (32) between the front panel (28) and the rear panel (30) is designed predominantly as a T shape or as a cone.
12. A method for improving a frame (24) of a grand piano (10) or an upright piano, characterised by the following method steps:

    a) repeated playing of multiple tones via the keyboard (22) of the grand piano (10) or upright piano and at the same time determining at least one region of one or more longitudinal struts (32) of a frame (24) with a local vibration amplitude maximum,

    b) positioning and fastening at least one separate element serving as an additional mass only in a determined range of a longitudinal strut (32) or in a position spaced apart from the region thus determined on the frame (24) such that the vibration amplitude in the at least one region of the longitudinal strut (32) determined according to step a) is reduced.
13. The method according to the preceding claim, characterised in that the region of one or more longitudinal struts (32) with a local vibration amplitude maximum is determined by touching the longitudinal strut (32) with a finger.
14. The method according to claim 12 or 13, characterised in that the region of one or more longitudinal struts (32) with a local vibration amplitude maximum is determined with at least one acceleration sensor and/or at least one laser vibrometer.
15. The method according to one or several of claims 12-14, characterised in that the method is carried out for at least one of the three longest longitudinal struts (32) of a grand piano (10) or an upright piano and/or for all the tones of the grand piano (10) or the upright piano.

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