Field of Invention

The present invention relates to musical instruments and frames for musical instruments, particularly instruments having a plurality of strings under tension such as a piano.

Background

Pianos and similar musical instruments consist of a plurality of strings held in a frame under tension which are struck or plucked to produce a musical note. In the case of a piano the strings are struck by hammers which are part of an action and activated via a keyboard.

A piano typically includes 220 to 240 strings each under a tension of around 750 to 900N. As such, the total load on the supporting frame of the piano may be in excess of 200kN. In order to bear such high loads, traditional modern pianos are assembled around a frame which supports the strings and is made from a n integral cast iron structure and a supporting timber casing. The frame must be strong and durable enough to bear the tension loads of the strings throughout the life of the piano. The frame must also be extremely stiff as any bending or flexing will cause the piano to go out of tune. The cast iron frame is also braced by large wooden members for this purpose. The frame is, therefore, extremely heavy and a major factor in the overall weight of the piano with upright pianos typically weighting at least 100kg and some grand pianos weighing over 500kg. Accordingly, there is a desire for frames for pianos and similar instruments which are of reduced weight. Embodiments of the invention may therefore seek to provide a frame for a stringed musical instrument having reduced weight but without compromising the strength and stiffness of the frame in order to keep the strings in tune.

Summary of Invention

According to a first aspect of the invention, there is provided a musical instrument frame for supporting a plurality of strings under tension. The frame has a longitudinal axis generally aligned with (for example extending substantially parallel to) the lengthwise direction of the strings. The frame comprises first and second longitudinally opposed transverse frame members, each extending from a first end to a second end at opposing sides of the frame, the frame members defining an opening for the strings therebetween. A longitudinal support extends from a first end proximal to the first frame member to a second end proximal to the second frame member. The longitudinal support is spaced apart from the corresponding adjacent end of the frame members. First and second lever arms are pivotally connected to each respective first and second end of the longitudinal support. Each lever arm extends from a proximal end connected to the adjacent end of one of the first or second frame member to a distal end on the opposing side of the longitudinal support. A link member extends between and connects the distal ends of the first and second lever arms such that the lever arms provide a balancing force opposing longitudinal compressive load applied to the frame by the strings.

Advantageously, embodiments of the invention may provide a lightweight frame which can bear large loads (such as those required in a grand piano) but without the need for a conventional heavyweight cast metal frame and accompanying timber casing. Unlike conventional frames embodiments may be a non-contiguous structure formed of discrete components. This may for example enable the use of lightweight and/or advanced materials for at least some of the components. Thus, it can be appreciated that the frame design of embodiments of the invention provide a greater degree of design freedom in which the discrete components forming the frame assembly can be individually optimised to provide the best combination of strength, stiffness and weight. Further advantages of embodiments include allowing the frame to be arranged such that the strings are straight strung and removing the need for any additional structural supports extending into or across the opening for the strings.

Each frame member may be elongated in the transverse direction. The longitudinal support may be a compressive support (for example a compressive strut). The link member may be a tensile member. As such, it can be appreciated that embodiments may provide a frame in which the tensile load of the strings is balanced across the longitudinal support by the link member at the other end of the lever arms.

The pivotal connection between each lever arm and the respective ends of the longitudinal support may allow a predetermined degree of rotational freedom of movement of the lever arm relative to the longitudinal support. It may be appreciated that in a generally stiff structure the pivotal connections may only need a relatively small degree of flexibility and could, for example, be integral connections or connections which are generally "fixed" provided the lever arms have sufficient freedom to counterbalance the opposing loads. In other words, it may be appreciated that in the context of the invention the pivotable connection may be defined by being a connection which functions as a pivot between opposing loads acting on the lever arm (at opposite sides of the connection).

The first and second transverse frame members may have a divergent configuration. As such the longitudinal spacing between the frame members may increase in the transverse direction from one side of the frame to the other. It will be appreciated that such a divergent arrangement is typical in instruments such as pianos where the string length increases across the width of the instrument. At least one of the frame members may be curved. The curve may be such that the at least one frame member extends both longitudinally and transversely in its lengthwise direction (which may generally correspond to a transverse direction of the frame).

The frame members may define a funicular structure. A funicular structure may ensure that the frame supports the piano string tension by compression rather than bending. In some embodiments, the funicularstructure may be defined by the relative combined shape of the two frame members. In some embodiments one of the frame members may be a linear member and the other member may have the curvature of a funicular arch.

The first ends of each of the first and second frame members may be connected at a hinge. The second, transversely opposite, ends of each of the first and second frame members are the adjacent end of the frame members to the longitudinal support. It may be appreciated that the hinge could be a pivot joint or may be a connection with a required degree of flexibility (for example the ends of the frame members could be part of an integral structure joining at a flexible hinge portion).

In some embodiments the hinge may include a longitudinal arm spacing the first and second frame members apart. The longitudinal member may be integrated with one of the frame members. Alternatively, the longitudinal member may be a discrete component. This may, for example, be useful in allowing the properties of the longitudinal member to be independently optimised.

In embodiments the thermal expansion of the longitudinal support, link member and longitudinal arm may all be matched to the thermal expansion of the instrument strings (for example by being made from steel). The thermal expansion may, for example, be matched by appropriate selection of materials. The matched components may have a similar thermal coefficient of thermal expansion to the strings. In some embodiments the longitudinal support, link member and longitudinal arm may, for example, be at least partially formed of steel. By allowing for thermal expansion in this way the other components of the frame can be optimised to use lightweight materials (including for example composite materials and/or aluminium) without the disadvantage of the materials having a significantly different thermal expansion than the strings (which would for example adversely affect the tune of a piano as ambient temperatures vary).

In some embodiments the first and second frame members are aligned in a first plane, the plane may for example be substantially coplanar with the opening for the strings/the strings. The longitudinal support, lever arms and link member may be aligned in a second plane. The first and second planes may be intersecting planes, for example intersecting at the connection between the ends of the lever arms and the first or second frame members. Advantageously, embodiments of the invention may, therefore, provide a generally non-planar frame. This may, for example, reduce the overall footprint of the instrument since some of the load bearing components of the frame are located outside of the plane of the opening for the strings (and it may be appreciated that the size of the opening for the strings will generally be a key constraint to the overall size of the complete instrument).

The first and second planes may be substantially perpendicular. For example, the link arms may extend rearwardly from the plane of the strings. In the case of an instrument, such as a piano, which includes a keyboard the link arms may extend away from the plane of the strings on a different side (for example the opposite side) to that on which the keyboard is located.

The first and second transverse frame members may each include a plurality of string connectors. The string connectors may for example include a plurality of hitch pins and/or tuning pins. The string connectors may be distributed along the transverse length of the frame member for receiving a plurality of strings. The plurality of connectors may be configured such that the longitudinal axis of each of the plurality of strings is substantially aligned with the local shear centre of the frame member. Such an arrangement will reduce or alleviate twisting of the frame members under the load of the string tension.

As noted above, the non-unitary construction of the frame in embodiments may be particularly useful in enable the use of advanced materials. In some embodiments at least one of the frame members (and in some embodiments both frame members) is formed of a composite material. For example one or both frame members may be formed from carbon fibre composite. Such materials enable very high strength-to- weight and may enable significant reduction in the weight of the frame and resulting instrument. In one embodiment one frame member is formed from aluminium and the other frame member is a carbon fibre composite.

In some embodiments the longitudinal support may comprise co-axial elongate elements. For example, the co-axial elongate elements may comprise a metallic inner rod and an outer composite sleeve. Advantageously, the inner rod may primarily bear compressive loads and the outer sleeve may resist bending of the support and provide stability. Advantageously, the thermal expansion of the longitudinal support can be matched to the strings by the material of the inner rod.

Whilst embodiments of the invention could be adapted for use in a variety of stringed musical instruments (for example harps) it is considered particularly advantageous for use in pianos due to the high string loads and the resulting high weight of conventional pianos. Thus, in accordance with a further aspect of the invention there is provided a piano comprising a frame in accordance with embodiments. The piano may further comprise a keyboard and an associated action. The piano may further comprise a plurality of strings extending longitudinally between the two frame members. The piano may further comprise a soundboard coupled to the frame. The piano may comprise a support structure. The frame may be coupled to the support structure via connection to the longitudinal support. The frame may be additionally coupled to the support structure via connection to one of the frame members. The other frame member may be uncoupled to the support structure (so that, for example, it is not constrained from thermal expansion).

The frame may be arranged in any orientation within the piano. For example, in some embodiments a grand piano may be provided with longitudinal axis of the frame extending substantially horizontally. In other embodiments the longitudinal axis of the frame may be substantially vertically aligned. A vertical aligned frame may be configured as an upright piano in which the frame (and therefore also the strings and soundboard) extends both above and below the keyboard and action. However, a particular advantage of the lightweight frame enabled by embodiments is that a vertical alignment can also be used as an upright grand piano. An upright grand piano may, for example, have the frame extending vertically away from the keyboard (for example with the soundboard and bridges above the keys) and may for example be sized to have longer strings than an upright piano. This piano may also deliberately have parallel strings to enable different multi-surface playing techniques. In some embodiments this may, for example, also be combined with a back-striking action placed behind the strings, allowing every part of every string to be touched by the performer. The use of parallel strings is in contrast to most modern pianos (whether grand or upright) in which the strings are cross-strung. In prior art pianos such cross stringing may be required to maximise the length of the strings whereas embodiments of the invention may provide a more efficient structure which can, for example, support parallel strings of a significantly greater length than a similar conventional modern piano structure.

Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or drawings. Description of the Drawings

Embodiments of the invention may be performed in various ways, and embodiments thereof will now be described by way of example only, reference being made to the accompanying drawings, in which:

Figure 1 shows a front perspective view of a piano according to an embodiment;

Figure 2 shows a rear perspective view of the piano according to an embodiment;

Figures 3A and 3B show a simplified schematic representation of frame of the piano according to an embodiment;

Figure 4 shows a rear detail of the upper end of the longitudinal support of the piano according to an embodiment;

Figure 5 shows a rear detail of the lower end of the longitudinal support of the piano according to an embodiment; and

Figure 6 shows a rear detail of the hinge side of the frame of the piano according to an embodiment.

Detail Description of Embodiments

It may be noted that upper and lower are used herein to conveniently refer to the illustrated embodiment in its in-use orientation. However, it will be appreciated that such references are not intended to be limiting and that whilst the illustrated embodiment has a vertically aligned frame (i.e. is an upright grand piano) other embodiments could use a horizontally aligned frame (i.e. the configuration of a traditional grand piano).

Figures 1 and 2 illustrate an embodiment of an upright grand piano 1 in accordance with an embodiment. The piano includes a keyboard 2 (which operates an action, not shown) and a set of pedals 3. A plurality of strings 7 (as shown in figure 3) are held under tension by a frame 10 in front of a soundboard 8. Although not shown in detail, it will be appreciated that the piano would also includes conventional features such as bridges, tuning pins and agraffes. The components of the piano are supported by a structural support 6 (which may be referred to as the piano casing) on legs 4. In the illustrated example the support structure 6 is shown somewhat schematically and comprises three interconnected beams 6a, 6b and 6c and outwardly extending legs 4a and 4b supporting the piano 1 on castors. It will be appreciated that in practice the piano structure is both functional and aesthetic in nature and may take any convenient form; in fact, an advantage of embodiments of the invention is that there is a greater design freedom in the form of the support structure 6 than in a conventional piano.

The frame 10 of the piano in accordance with embodiments has a novel form which removes the need for the large and extremely heavy cast metal frame and accompanying timber casing used in conventional traditional piano construction. In a conventional piano the metal frame is high strength to bear the string loading but also requires an accompanying heavy timber frame to provide sufficient stiffness to ensure the piano does not go out of tune. In contrast, the novel frame of embodiments is designed to provide both strength and stiffness. The frame 10 comprises a first transverse frame member 20, a second transverse frame member 30, a longitudinal support strut 50, first (upper) and second (lower) lever arms 60, 65, a tensile link member 70 and a hinge 80.

The structural arrangement of the frame 10 can be understood from the schematic representations of Figure 3A and 3B, in which the same reference numbers are used as in the figures of the detailed embodiment. The members 20 and 30 are connected at a hinge point 80 and extend transversely and longitudinally away from one another from their respective first ends 22, 32 to their second ends 24, 34. The second ends 24, 34 are spaced apart longitudinally. The strings 7 extend longitudinally between the members 20, 30 and as they are under tension apply a compressive load to the frame 10. A lever arm 65, 60 is connected to the respective second ends 24, 34 of each member 20, 30. It may be noted that the lever arms 60, 65 extend away from the members 30, 20 in a perpendicular plane to the plane of the strings (but it will be appreciated that this is not essential) which reduces the width of the frame 10 relative to the opening for the strings 7.

Each lever arm 65, 60 extends away from its respective member from the proximal, connected, end 61, 66 to a distal end 63, 68. A compressive strut 50 is provided in a central region (for example at or proximal to a midpoint) between the ends of the lever arms 65, 60 and extends longitudinally therebetween. The compressive strut 50 is connected to each lever arm 65, 60 by a respective flexible pivot connection 62, 67. At the distal end of the lever arms 65, 60 a tensile member 70 is provided and extends longitudinally from a first (upper) end 72 coupled to the upper lever arm 60 to a second (lower) end 74 coupled to the lower lever arm 65. To maximise the lever action the tensile member 70 is typically connected at (or close to) the distal end 63, 68 of each lever arm 60, 65 but in some embodiments the distal end(s) may project beyond the tensile member attachment point. It can be appreciated from the simplified schematics of figure 3 that, under load from the instrument strings 7, the lever arms 60, 65 are subject to a rotational loading about their respective pivot connections 62, 67 to the compressive strut 50 which is balanced by the tensile member 70. In this way embodiments may provide a strong, stiff and lightweight structure.

The detailed embodiment of figures 1 and 2 will now be described in further detail. The lower beam 20 is generally linear, extends from a first end 22 to a second end 24 and is proximal to the keyboard 2. The lower frame members 20 is an aluminium beam (although it could be made from other materials). The lower member 20 is directly supported by a transverse portion 6c of the support frame by couplings at each end of the member 20 (which may take any convenient form). A plurality of string connectors 28 are distributed along the transverse length of the member 20. The profile of the member 20 and the position of the string connectors 28 can be optimised to ensure that load applied by the strings to each connector acts through the local shear centre of the member 20 so as to minimise twisting of the beam 20. The upper member 30 is not directly restrained by the support frame 6 (to allow for thermal expansion as will be explained further below). The upper frame members 30 of the embodiment is formed as a carbon fibre beam (although it will be appreciated that it may be made from other materials). The upper member 30 is positioned to diverge away from the lower member 20 as it extends from its first end 32 to its second end 34. The upper member 30 has a profile which is selected to define a funicular arch so as to ensure that the string tension applies a compression load on the member 30 and to minimise bending along the length of the member. A plurality of string connectors 38 are distributed along the transverse length of the member 30. As with the lower member 20, the profile of the upper member 30 and the position of the string connectors 38 is optimised to ensure that load applied by the strings to each connector acts through the local shear centre of the member 30 so as to minimise twisting of the beam 30.

It can be noted in Figure 1 and further seen in figure 6 that the hinge connection 80 (between the adjoining first ends 32 and 22 of the frame members 30, 20) includes a longitudinal extending arm 82. In the illustrated embodiment the longitudinal arm 82 is a separate component and coupled between the frame members 20, 30 as part of the hinge 80; however, alternative arrangements could be provided in which the longitudinal arm portion of the hinge 80 is excluded or integrally formed with another component. As will be explained further below, the longitudinal arm 82 may be part of the thermal expansion matching of the frame 10 and the strings 7. The lower end of the hinge 80 is, along with the lower member 20 fixed relative to the support frame 6.

The second ends 24, 34 of the members are connected to the lever arms 60, 65 as shown in detail in figures 4 and 5. In the illustrated example each lever arm 60, 65 is a short aluminium beam (although other materials could be used). It may be noted from these figures that a connection bracket 53 (or any other convenient connecting arrangement) is provided between the vertical member 6b of the support frame 6 and the ends 52, 54 of the compressive strut 50. As such, the second ends 24, 34 of the members are not directly connected to the support frame but have a degree of flexibility via the connection through the strut 50 and lever arms 60, 65. The interface provided by the connection bracket 53 and the support frame 6 can be optimised to provide a predetermined degree of freedom of movement between the frame 10 and support structure 6 so as to allow for flex and/or expansion of the frame in use. For example, one or both connection brackets 53 may include a sliding interface for longitudinal expansion of the frame 10 (and specifically the strut 50 of the frame 10) relative to the support structure 6.

The compressive strut 50 may comprise an inner core (shown by dashed line 56) and an outer tubular sleeve 55. In such an arrangement the inner core 56 can be a steel member and the primary compressive load bearing member. The outer sleeve 56 can be a lightweight composite and may resist buckling of the core. Such a strut is, for example, disclosed in UK Patent GB2299103B.

As noted above, the upper 30 and lower 20 members of the frame are interconnected via components in the form of the tensile member 70, the core 56 of the compressive strut 50, and the longitudinal member 82 of the hinge 80 which may be formed from steel. Whilst the lower member 20 and the compressive strut 50 are coupled to the structural frame 6, the upper member 30 has no direct coupling. This arrangement enables the longitudinal thermal expansion of the frame 10 (i.e. the longitudinal spacing between the upper 30 and lower 20 frame members). By suitable design of the interconnecting components (along with their material selection), this thermal expansion can be matched to the thermal expansion of the steel strings 7. This ensures that the piano 1 can remain in tune across a range of ambient temperatures because the tension in the strings 7 will be maintained regardless of thermal fluctuations. This feature enables the use of lightweight composite materials in other components of the frame 10, for example the members 20, 30 and the outer sleeve 55 of the strut 50 so as to reduce the overall weight of the frame 10. Although the invention has been described above with reference to preferred embodiments, it will be appreciated that various changes or modification may be made without departing from the scope of the invention as defined in the appended claims. For example, it will be appreciated that the lightweight frame structure of the above embodiment may also be utilised and be advantageous in a horizontal aligned grand piano or an upright style piano as it can provide a significant weight reduction over traditional manufacturing techniques. Further, whilst in the embodiment above the frame comprises an assembly of discreet components (for example the transverse frame members, the longitudinal support strut, the lever arms, the tensile link member and the hinge) the skilled person will appreciate that in other embodiments some or all of the components may be integrally formed without departing from the scope of the invention. For example, an integral structure may have each of the functional components in accordance with an invention connected by portions with suitable properties (for example flexibility) to ensure that they can perform the function of the discrete components described in the above embodiment.

The skilled person will appreciate that the embodiment described above provides the primary load bearing structure of a musical instrument frame in accordance with the invention. The embodiments disclosed may be generally considered to be simple embodiments which aid understanding and clarity. Other implementations of the invention may include additional structural elements without departing from the scope of the invention. For example, it will be appreciated that any element (such as the strut 50 and/or tensile member 70) described above may in some embodiments be replaced with corresponding elements which perform the equivalent function without departing from the scope of the invention. For example, in some embodiments a singular element may be replaced with a plurality of corresponding elements (for example the strut may be a plurality of struts, or the tensile member may be a plurality of tensile members) without altering the underlying structural configuration. In some embodiments the structure of the instrument may include additional features or elements which, whilst not essential to the functional configuration of the primary structure, provide additional or secondary structural purposes. For example, one or more secondary structural elements may be provided to maintain alignment between the primary elements of the instrument frame. Additionally or alternatively, it may be beneficial to include one or more secondary structural elements to control or limit the range of motion of elements of the instrument frame (either with respect to the support frame or with respect to one another). Additionally or alternatively, secondary structural elements may be provided to enable adjustment or fine-tuning of the primary frame structure (for example such adjustment may be desirable to allow for tolerances in the frame). It will be appreciated that the specific configuration of any such secondary structural features will vary depending upon the specific design of an instrument in accordance with an embodiment (and further that any single feature or element may perform multiple such purposes). As such, the particular selection and design of secondary features would be a matter of standard workshop modification and optimisation by the skilled person when carrying out the teaching of the invention.

The use of such secondary features may, for example, be particularly useful when embodiments comprise a piano due to the large tension forces that are supported by the frame. The instrument frame may, for example, include one or more secondary structural elements to limit the range of motion and/or maintain the intended alignment of the primary components during stringing and tensioning/tuning of the strings. In some embodiments the secondary structural components may comprise at least one additional tie between the support frame and one of the primary structural elements.