Keyboard instrument

A electronic portable keyboard instrument includes a plurality of keys arranged in a first direction; a plurality of hammers respectively corresponding to the plurality of keys, each of the plurality of hammers including a force application point that is formed on one end side and that is pressed down when the corresponding key is pressed, a weight that is formed on another end side and imparts action weight to a pressed key, and a fulcrum formed between the force application point and the weight so that the hammer rocks in vertical directions about the fulcrum when the corresponding key is pressed; and a casing including at least one reinforcing member that is formed in a gap between the plurality of hammers so as to not be contacted by the weights of the hammers when the hammers rock about the respective fulcrums with a lateral positional shift in the first direction.

TECHNICAL FIELD

The present invention relates to a keyboard instrument including a keyboard device such as an electronic piano, and more specifically, to an electronic portable keyboard instrument, such as electronic portable piano.

BACKGROUND ART

Conventionally, in the field of electronic keyboard instruments such as electronic pianos, various methods of reinforcement have been utilized to improve the strength of the casing of the main instrument unit. For example, Japanese Patent Application Laid-Open Publication No. 2014-211618 discloses a casing structure in which a plurality of hanging portions having the dual function of reinforcing the casing and supporting sound adjusters (sound absorbers) for improving the acoustic properties of an electronic keyboard instrument are arranged along the sidewalls of the casing, and each hanging portion is connected to a sidewall of the casing via a connecting rib.

SUMMARY OF THE INVENTION

The casing structure disclosed in Embodiment 1 of the abovementioned application is effective in terms of improving strength around the periphery of the sidewalls of the casing but exhibits problems such as the following. In other words, by virtue of including a keyboard unit in which a plurality of keys are arranged in a line, the electronic keyboard instrument must have a casing which is elongated in the arrangement direction of the keys. In an electronic keyboard instrument having a casing of this type, designing the wall thickness of casing members to be thin in order to achieve reduced size and weight results in decreased strength in the lengthwise direction of the casing and makes the casing more prone to deformations such as bending and twisting, thereby making the main instrument unit more prone to damage and potentially having a negative impact on the operability or acoustic properties of the musical instrument. Therefore, there is demand for casing structures which solve these types of problems more effectively.

The present invention aims to effectively improve casing strength and to make it possible to reduce size and weight.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in one aspect, the present disclosure provides an electronic portable keyboard instrument, comprising: a plurality of keys arranged in a first direction; a plurality of hammers arranged in the first direction, respectively corresponding to the plurality of keys, each of the plurality of hammers including a force application point that is formed on one end side and that is pressed down when the corresponding key is pressed, a weight that is formed on another end side and imparts action weight to a pressed key, and a fulcrum formed between the force application point and the weight so that the hammer rocks in vertical directions about the fulcrum when the corresponding key is pressed; and a casing including a plurality of reinforcing members arranged in the first direction, each of the reinforcing members being formed in a gap between the plurality of hammers so as not to be contacted by the weights of the hammers adjacent to the reinforcing member when the hammers adjacent to the reinforcing member rock about the respective fulcrums with a lateral positional shift in the first direction, so that even if the keyboard instrument is placed vertically with one lateral end thereof being at a bottom and another lateral end thereof being at a top, the weights of the hammers leaning downward due to gravity do not contact any of the reinforcing members.

DETAILED DESCRIPTION OF EMBODIMENTS

Next, embodiments of the present invention will be described in detail with reference to figures.

FIGS. 1A-1Bare an external view illustrating an embodiment of a keyboard instrument according to the present invention. Moreover,FIG. 2is an assembly diagram schematically illustrating a configuration example of the keyboard instrument according to the present embodiment. Although here an electronic piano will be described as an example of the keyboard instrument, any other electronic musical instrument that has a casing extending in a direction designated as the lengthwise direction and that emits musical sounds in accordance with keypress operations from a user (performer) may be used.

As illustrated inFIGS. 1A and 1B, for example, the keyboard instrument according to the present invention includes a main instrument unit100of an electronic piano and a stand200on which and to which the main instrument unit100is rested and affixed. Here, as illustrated inFIG. 1B, for example, the main instrument unit100has formed on the bottom surface side thereof positioning recesses (described in more detail later) which mate with positioning protrusions202formed on the stand200side so that the main instrument unit100rests on the upper surface of the stand200at a prescribed position. The main instrument unit100thusly positioned on the upper surface of the stand200is fastened to the upper surface of the stand200via fasteners such as screws or bolts (not illustrated in the figure).

As illustrated inFIGS. 1A, 1B, and 2, for example, the main instrument unit100generally includes a keyboard unit120, an upper casing140, and a lower casing160. The keyboard unit120includes on a front side thereof (user side; the near side in the figures) a plurality of keys as musical performance controls, and the user performs keypress operations to specify pitches.

The upper casing140includes a frame having an opening142which exposes the keys of the keyboard unit120, and on the upper surface of the frame on the rear side (far side in the figures) of the opening142, a control panel144including switches for performing operations such as adjusting volume or selecting tone color as well as a display panel or the like for displaying information about the music currently being performed or various types of settings information or the like is arranged. Furthermore, a sound source circuit board146which generates musical sounds in accordance with the pitches specified by keypress operations from the user and speakers148or the like which emit the generated musical sounds are installed into the upper casing140. In the lower casing160, the inner surface side (upper surface side in the figures) is connected to the keyboard unit120and the upper casing140, and the outer surface side (lower surface side in the figures) has formed therein positioning recesses and screw holes for resting and affixing on and to the stand200.

As illustrated inFIGS. 1A, 1B, and 2, in the keyboard unit120, a plurality of white keys122and black keys124are regularly arranged in a prescribed order in the lengthwise direction (left-right direction in the figures) of the main instrument unit100. Here, a total of 88 white keys122and black keys124are arranged in the keyboard unit120. These white keys122and black keys124are attached to a common keyboard chassis126so as to be individually rotatable in the vertical direction. In the keyboard unit120, the keyboard portion on the front side (near side in the figures) that is exposed from the opening142in the upper casing140is the region in which the user performs keypress operations, and the rear side (far side in the figures) is housed within the upper casing140. Note that in the present specification, the term “key” refers generally to both white keys and black keys unless specifically noted otherwise.

FIGS. 3A-3Bschematically illustrates the lower casing used in the keyboard instrument according to the present embodiment.FIG. 3Ais a view illustrating the outer surface side of the lower casing, andFIG. 3Bis a view illustrating the inner surface side of the lower casing. Here, the outer surface side of the lower casing corresponds to the lower surface side of the main instrument unit100illustrated inFIGS. 1A, 1B, and 2, and the inner surface side of the lower casing corresponds to the interior side of the main instrument unit100and to the upper surface side of the lower casing160illustrated inFIG. 2.

As illustrated inFIGS. 3A-3B, in the present embodiment a plurality of casing reinforcing sections310to340of different types are formed in the lower casing160in order to improve the strength of the casing of the keyboard instrument. Each of the casing reinforcing sections310to340includes a plurality of ribs constituted by plate-shaped members running in the lengthwise direction of the main instrument unit100or the lower casing160and in the widthwise direction of the main instrument unit100or the lower casing160which is orthogonal to the lengthwise direction. Here, as illustrated inFIGS. 2, 3A, and 3B, the lengthwise direction of the main instrument unit100or the lower casing160corresponds to the arrangement direction of the keys of the keyboard unit120, and the widthwise direction of the main instrument unit100or the lower casing160corresponds to the lengthwise direction of the keys which is orthogonal to the arrangement direction of the keys and in which the upper surfaces of the keys of the keyboard unit120extend.

Next, the each of the casing reinforcing sections310to340will be described in detail.

FIG. 4is a perspective view illustrating the primary components of a first casing reinforcing section used in the keyboard instrument according to the present embodiment, andFIG. 5is a cross-sectional view illustrating the primary components of the main instrument unit to which the first casing reinforcing section according to the present embodiment has been applied. Note that the cross-section illustrated inFIG. 5omits the upper casing in order to simplify the illustration.

More specifically, as illustrated inFIG. 3A, in the first casing reinforcing section310, a continuous channel312is formed in a region (first region) extending in the lengthwise direction of the lower casing160. As illustrated inFIGS. 4 and 5, the channel312has a recess which is recessed going from the outer surface side of the lower casing160towards the interior direction of the main instrument unit100(the inner surface side of the lower casing160), and within the channel312, ribs314including a plurality of plate-shaped members extending in the lengthwise direction of the lower casing160and ribs316including a plurality of plate-shaped members extending in the widthwise direction of the lower casing160orthogonal to the lengthwise direction are arranged in a grid pattern. Here, as illustrated inFIGS. 4 and 5, the ribs314and316have a height that is substantially equal to the depth of the channel312and are formed integrally within the channel312.

In this way, by forming the channel312which extends in the lengthwise direction of the lower casing160and forming the ribs314and316arranged in a grid pattern within that channel312, even if the wall thickness of these components is designed to be thin in order to reduce the size and weight of the main instrument unit100, deformation (bending) in the direction orthogonal to the lengthwise direction of the lower casing160and the main instrument unit100that includes the lower casing160can be inhibited, and the strength of the casing can be improved. Moreover, by increasing the width of the channel312in the widthwise direction of the lower casing160and also forming the ribs316to be longer in accordance with that width, deformation (twisting) in a rotational direction about the lengthwise direction of the lower casing160and the main instrument unit100can be inhibited, and the strength of the casing can be further improved.

Furthermore, as illustrated inFIG. 4, in the first casing reinforcing section310, positioning members for resting the main instrument unit100at a prescribed position on the upper surface of the stand200are formed within the channel312of the lower casing160. When positioning protrusions202are formed on the stand side as illustrated inFIGS. 1A-1B, for example, positioning recesses318which mate with the positioning protrusions202on the upper surface of the stand200are formed within the channel312formed on the outer surface side of the lower casing160. The positioning recesses318are formed at a plurality of locations near both ends of the channel312that extends in the lengthwise direction of the lower casing160. Here, the positioning recesses318are formed by configuring the arrangement, shape, height, and the like of the ribs314and316in the channel312so as to correspond to the shape, height, and the like of the positioning protrusions202on the stand side. As illustrated inFIG. 4, when the positioning protrusions202on the stand200side have a cylindrical shape, for example, the positioning recesses318are formed by removing the ribs314and316in the portions that will mate with the cylindrical positioning protrusions202and forming arc-shaped supporting ribs (supporting portions)319so as to fit onto the cylindrical outer peripheral surfaces of the positioning protrusions202.

In this way, when rested on and affixed to the stand200, the main instrument unit100can be easily and reliably positioned using the positioning recesses318formed in the channel312. Here, forming the ribs314and316in a grid pattern within the channel312improves the strength of the lower casing160, which makes it possible to inhibit changes or shifts in the positions of the positioning recesses318resulting from deformation of the lower casing160or the main instrument unit100and also makes it possible to easily and reliably rest and affix the main instrument unit100on and to the stand200at a prescribed position.

Moreover, as illustrated inFIG. 5, in the first casing reinforcing section310the channel312is formed recessing from the outer surface side of the lower casing160towards the interior direction of the main instrument unit100, and therefore a protruding portion (protrusion) corresponding to the shape of the channel312is formed within the main instrument unit100(on the inner surface side of the lower casing160). In the present embodiment, the shapes and dimensions of the protrusion (channel312) and a hammer holder426(supporting member) which rotatably supports hammers422arranged corresponding to the keys of the keyboard unit120are configured such that the lower end (in the figure) of the hammer holder426rests on the upper surface (in the figure) of the protrusion. Here, with the hammer holder426resting on the protrusion (channel312), these components are fastened together using fasteners such as screws in order to install the keyboard unit120including the hammer holder426into the lower casing160.

This makes it possible to use the protrusion corresponding to the channel312to support the hammer holder426from below when installing the keyboard unit120into the lower casing160. Here, the ribs314and316formed in a grid pattern within the channel312improve the strength of the lower casing160, which makes it possible to inhibit deformation of the lower casing160and the main instrument unit100resulting from the weight of the keyboard unit120and from impacts or pressing forces accompanying keypresses. Moreover, the protrusion (channel312) and the hammer holder426are fastened together, which makes it possible to suppress abnormal noises and vibrations accompanying the rotation of the hammers when keys are pressed. The keyboard mechanism of the keyboard unit120will be described in more detail later.

Although in the present embodiment the ribs314and316are described as being arranged within the channel312in a grid pattern having quadrilateral spaces, the present invention is not limited to this configuration. Any configuration in which the ribs of the first casing reinforcing section310increase the casing strength in both the lengthwise direction and the widthwise direction of the lower casing160is possible, and as other examples of reinforcing structures, configurations in which the ribs314and316are arranged within the channel312in a truss pattern having triangular spaces or in a honeycomb pattern having hexagonal spaces may be used.

Moreover, although the present embodiment describes a configuration in which, as the first casing reinforcing section310, the channel312having a recess which is recessed going from the outer surface side of the lower casing160towards the interior direction of the main instrument unit100is formed and the ribs314and316are arranged in a grid pattern within the channel312, the present invention is not limited to this configuration. As the first casing reinforcing section310, rather than forming the channel312, ribs arranged in a grid pattern in a region on the inner surface side of the lower casing160(interior side of the main instrument unit100) corresponding to the region in which the abovementioned channel312is formed may protrude out and may extend along the lengthwise direction of the lower casing160. Similar to the embodiment described above, this configuration also makes it possible to improve the strength of the lower casing160. Here, the lengthwise and widthwise ends of the ribs arranged in a grid pattern may be connected together via a frame-shaped rib arranged surrounding the outer periphery of the ribs. This allows the frame-shaped rib to serve the same function as the sidewalls of the channel312in the embodiment described above, thereby making it possible to further improve the strength of the casing.

FIG. 6is a plan view illustrating the primary components of a second casing reinforcing section used in the keyboard instrument according to the present embodiment, andFIGS. 7 and 8are cross-sectional views illustrating the primary components of the keyboard mechanism of the main instrument unit to which the second casing reinforcing section according to the present embodiment has been applied. Note that the cross-sections illustrated inFIGS. 7 and 8omit the upper casing in order to simplify the illustrations.FIGS. 9A-9Billustrates an example of interference between hammers and ribs of the second casing reinforcing section used in the keyboard instrument according to the present embodiment.FIG. 10is a plan view illustrating an example of arrangement gaps between the ribs of the second casing reinforcing section used in the keyboard instrument according to the present embodiment.

More specifically, as illustrated inFIGS. 3B and 6, in the second casing reinforcing section320, ribs (reinforcing members)322including one or more plate-shaped members extending in the widthwise direction of the lower casing160are arranged on the inner surface side of the lower casing160in regions corresponding to gaps between the hammers422arranged corresponding to the respective white keys122and black keys124arranged in the keyboard unit120. Moreover, in the second casing reinforcing section320, a rib324which connects together the plurality of ribs322extending in the widthwise direction is arranged extending in the lengthwise direction of the lower casing160orthogonal to the widthwise direction of the lower casing160. As illustrated inFIGS. 6 and 7, in the present embodiment, on one end side (lower end side inFIG. 6; left end side inFIG. 7) the ribs322extending in the widthwise direction of the lower casing160protrude out towards the inner surface side of the lower casing160in a manner corresponding to the shape of the channel312formed in the first casing reinforcing section310described above and are connected to a sidewall of the protrusion extending in the lengthwise direction. In other words, the one or more ribs322are formed in a region (second region) that is adjacent to the region (first region) in which the channel312of the lower casing160is formed, and the sidewall of the protrusion corresponding to the channel312functions as the rib324and connects together the plurality of ribs322in the lengthwise direction.

Here, in order to better describe the second casing reinforcing section320, the keyboard mechanism of the keyboard unit used in the present embodiment will be described. Although here the keyboard mechanism for the white keys122will be described, the black keys124have the same keyboard mechanism.

As illustrated inFIG. 7, the keyboard mechanism of the keyboard unit includes the common keyboard chassis126to which the white keys122and the black keys124are attached so as to be rotatable in the vertical direction, a hammer unit420for providing action weight to keypress operations on each of the white keys122and the black keys124attached to the keyboard chassis126, and switches410which switch ON in accordance with keypress operations on the white keys122and the black keys124.

On the front side edge (left edge in the figure) of the keyboard chassis126(the user side of the main instrument unit100), a front leg402is formed protruding upwards in the figure towards the white keys122. On an upper portion of the front leg402, key guides404for preventing lateral shifting in the arrangement direction of the keys (the direction orthogonal to the page in the figure) when the white keys122rotate are formed, and on the front side (left side in the figure) of the front leg402, stoppers406for constraining the uppermost positions and lowermost positions of the white keys122when rotating are formed. Moreover, on the rear side (right side in the figure) of the front leg402of the keyboard chassis126, a unit attaching portion408to which the hammer unit420is attached is formed protruding upwards in the figure.

Furthermore, on the rear side (right side in the figure) of the unit attaching portion408of the keyboard chassis126, a sound emission board412having mounted thereon the switches410that switch ON in accordance with keypress operations on the white keys122is installed. On the sound emission board412, a plurality of the switches410are provided for both the white keys122and the black keys124that are arranged in a line, and these switches410are mounted individually corresponding to the white keys122and the black keys124above the sound emission board412. Moreover, a processing circuit which generates musical sound information on the basis of ON signals output from the switches410in accordance with keypress operations on the white keys122is also mounted on the sound emission board412.

Furthermore, a key attaching portion414is formed further on the rear side (right side in the figure) than the board installation portion of the keyboard chassis126, and the rear ends of the white keys122(right ends in the figure) are attached to the key attaching portion414via support shafts416which support the white keys122so as to be rotatable in the vertical direction. In addition, on the rear edge (right edge in the figure) of the keyboard chassis126, a rear leg418is formed extending down from the key attaching portion414. On this rear leg418, stoppers419for constraining the uppermost positions and lowermost positions of the hammers422of the hammer unit420when rotating in accordance with keypress operations on the white keys122are formed.

As illustrated inFIGS. 6 and 7, the hammer unit420includes the plurality of hammers422which are arranged corresponding to the respective white keys122and black keys124and individually rotate in accordance with keypress operation on the keys, thereby providing action weight, as well as the hammer holder426which is formed in common for the white keys122and the black keys124and supports the hammers422corresponding to the keys via support shafts424so as to be individually rotatable. As illustrated inFIG. 7, the hammer holder426is attached to the lower surface side of the unit attaching portion408of the keyboard chassis126described above.

As illustrated inFIG. 7, each hammer422includes a main hammer unit432made of a metal material, a key-engaging portion434(force application point) formed on one end side (left end side inFIG. 7) of the main hammer unit432, a weight436(weighted point) formed on the other end side (right end side inFIG. 7) of the main hammer unit432, and a support shaft424which is formed between the weight436and the key-engaging portion434of the main hammer unit432and rotatably supports the main hammer unit432. Here, as illustrated inFIGS. 6 and 7, the weights436of the hammers422are formed to have larger planar shapes as viewed from the lengthwise direction of the lower casing160(arrangement direction of the keys) and greater thicknesses in the lengthwise direction of the lower casing160(arrangement direction of the keys) than the main hammer units432between the weights436and the support shafts424, thereby setting weights for providing prescribed action weights to the keys. Note that although the hammers422have substantially the same shapes for white keys and for black keys, keypress positions of keypress operations as well as key shape and the like are different for the white keys122and the black keys124, and therefore the planar shapes, thicknesses, weights, dimensions from the support shaft424to the weight436and to the key-engaging portion434, and the like of the hammers422are designed to be slightly different.

As illustrated inFIG. 7, in the main instrument unit100including the keyboard unit120having the keyboard mechanism described above, when the user is not performing any keypress operations (initial state), the hammers422are biased by the weight of the weights436to rotate clockwise about the support shafts424, and the weights436are constrained to lowermost positions by virtue of contacting the lowermost stopper419formed in the keyboard chassis126. Moreover, the key-engaging portions434of the hammers422press the keys upward, thereby setting the keys to their initial positions (uppermost positions).

When the user then performs a keypress operation, as illustrated inFIG. 8, the white key122or black key124rotates counterclockwise about the support shaft416. As a result, the key-engaging portion434of the hammer422is pressed downward by the key, the hammer422rotates counterclockwise about the support shaft424and causes the weight436to rise, and the action weight based on the weight of the weight436is applied to the key. Then, as the keypress operation proceeds and the key-engaging portion434of the hammer422is pressed further downwards by the key, the weight436of the hammer422rises further and contacts the uppermost stopper419formed in the keyboard chassis126, thereby stopping the rotation of the hammer422and constraining the uppermost position thereof, and the lowermost position of the key is constrained (lowermost key state).

In this keypress operation, during the period before the weight436of the hammer422contacts the uppermost stopper419, the switch410mounted on the keyboard chassis126is depressed by the key and switches ON, thereby causing musical sound information corresponding to that key to be generated. On the basis of this musical sound information, a musical sound is generated by the sound source circuit installed into the upper casing140and is then emitted from the speakers148. Then, when the user completes the keypress operation, the hammer422rotates clockwise under the weight of the weight436, the weight436contacts the lowermost stopper419and is constrained to the lowermost position, and the key-engaging portion434presses the key upwards and sets the key to its initial position (uppermost position). In this way, in the hammers422, the weights436and the key-engaging portions434respectively move about the support shafts424in the vertical direction in a rocking manner.

As illustrated inFIG. 6, in the second casing reinforcing section320of the lower casing into which the keyboard unit having the keyboard mechanism described above is installed, at least one rib (reinforcing member)322is arranged extending in the widthwise direction of the lower casing160in a region corresponding to gaps between the hammers422arranged corresponding to the respective white keys122and black keys124. Here, the ribs322are formed integrally using the same or a similar resin material as the lower casing160. The shape, height, and thickness dimensions of the ribs322formed in the gaps between the hammers422are set such that no interference (such as contacting, touching, or grinding) occurs on the paths of the hammers422illustrated inFIGS. 7 and 8when rotating (rocking in the vertical direction) or within the range of lateral shifting in the arrangement direction of the keys (rocking in the lengthwise direction) as illustrated inFIGS. 9A-9Bduring such rotation or when the main instrument unit100is stood up vertically (or when the lengthwise direction of the main instrument unit100is otherwise treated as running up and down). Thus, if the keyboard instrument is placed vertically with one lateral end thereof being at a bottom and the other lateral end thereof being at a top, the weights of the hammers leaning downward due to gravity do not contact any of the reinforcing members. As illustrated inFIGS. 7 and 9B, for example, the ribs322have a planar shape in which the height (the dimension of protruding towards the inner surface side of the lower casing160) decreases in a stepped manner or a continuous manner going from the front side (user side; the portion connected to the rib324on the left side in the figures) towards the rear side (right side in the figures), or have notched portions that are notched out.

In this way, as illustrated inFIG. 9A, even if the hammers422undergo significant lateral shifting in the arrangement direction of the keys (vertical direction in the figure), the heights of the ribs322are configured to be lower in the areas that the main hammer units432or weights436of the hammers422would otherwise contact, thereby making it possible to avoid interference between the hammers422and the ribs322and also making it possible to suppress abnormal noises and vibrations accompanying the rotation or lateral shifting of the hammers. Note that the ribs322can have any planar shape that prevents interference due to rotation or lateral shifting of the hammers422and may have a planar shape in which the height decreases continuously in a linear or curved manner, for example.

Moreover, as illustrated inFIGS. 6, 7, 9A, and 9B, in order to improve the strength of the casing, it is preferable that the number of ribs322arranged and the arrangement gaps between the ribs322be set such that the plurality of ribs322are uniformly or substantially uniformly distributed in the lengthwise direction of the lower casing160, and it is also preferable that the lengths extending in the widthwise direction be set to be as long as possible. Here, as described above, the keypress positions of keypress operations as well as key shape and the like are different for the white keys122and the black keys124of the keyboard instrument, and therefore the planar shapes, thicknesses, weights, and the like of the hammers422arranged corresponding to the respective white keys122and black keys124are configured to be different. As a result, the paths and lateral shifting ranges of the hammers422when rotating are different for the white keys122and the black keys124. Therefore, as illustrated inFIG. 10, in the present embodiment the plurality of ribs322are arranged regularly or substantially regularly in the lengthwise direction of the lower casing160, and the arrangement gaps between the ribs322are set to be as equal as possible.

This makes it possible to arrange the plurality of ribs322regularly or substantially regularly in the lengthwise direction of the lower casing160and to also extend the ribs322to be as long as possible in the widthwise direction without causing interference on the rotation paths or lateral shifting ranges of the hammers422when keys are pressed, which in turn makes it possible to suppress abnormal noises and vibrations accompanying rotation of the hammers when keys are pressed as well as to inhibit deformation (bending) in the direction orthogonal to the widthwise direction of the lower casing160and the main instrument unit100, and further makes it possible to improve the strength of the casing.

Moreover, as illustrated inFIGS. 7 and 9B, in the second casing reinforcing section320, the ends on the front side (left side in the figures) of the plurality of ribs322extending in the widthwise direction of the lower casing160, where the height (the dimension of protruding towards the inner surface side of the lower casing160) is greatest, are connected to the sidewall of the protrusion protruding towards the inner surface side of the lower casing160as a result of the channel312being formed in the first casing reinforcing section310as described above.

As a result, the sidewall of the protrusion is utilized as the rib324and the plurality of ribs322are connected together in the lengthwise direction of the lower casing160, which makes it possible to improve the strength of the ribs322extending in the widthwise direction of the lower casing160, makes it possible to inhibit deformation (bending) in the direction orthogonal to the lengthwise direction of the lower casing160and the main instrument unit100as well as deformation (twisting) in a rotational direction about that lengthwise direction, and makes it possible to further improve the strength of the casing. Furthermore, in this case a portion of the structure of the first casing reinforcing section310(the sidewall of the protrusion) is also used in the structure of the second casing reinforcing section320(the rib324), which makes it possible to reduce the space required for component layout within the main instrument unit100.

FIGS. 11A-11Bare a perspective view schematically illustrating a third casing reinforcing section used in the keyboard instrument according to the present embodiment.FIG. 11Ais an overall perspective view illustrating the lower casing to which the third casing reinforcing section has been applied, andFIG. 11Bis a perspective view illustrating the primary components on the outer surface side of the lower casing.FIG. 12is a cross-sectional view schematically illustrating the main instrument unit to which the third casing reinforcing section according to the present embodiment has been applied. Note that the cross-section illustrated inFIG. 12omits the upper casing in order to simplify the illustration.

More specifically, as illustrated inFIGS. 3B, 11A, 11B, and 12, the third casing reinforcing section330includes, in a region (third region) which extends in the lengthwise direction of the lower casing160and is a region on the front side (lower side inFIG. 3B; near side inFIGS. 11A-11B) in the widthwise direction corresponding to the keypress positions of the white keys122arranged in the keyboard unit120, a recess which is recessed going from the outer surface side of the lower casing160towards the interior direction of the main instrument unit100(the inner surface side of the lower casing160). More particularly, on the inner surface side of the lower casing160, ribs332including a pair of plate-shaped members arranged near to and facing one another and running in the lengthwise direction of the lower casing160as well as ribs334including plate-shaped members which extend in the widthwise direction of the lower casing160orthogonal to the lengthwise direction and connect together the pair of ribs332are arranged, for example. Here, as illustrated inFIG. 12, the ribs332and334are formed protruding upwards in the figure from the inner surface side of the lower casing160towards the white keys122of the keyboard unit120, but the shapes and heights of the ribs332and334are set such that a gap is formed between the keyboard chassis126of the keyboard unit120and the upper ends of the ribs332and334as well as the hanging portions of the ribs334adjacent to those upper ends.

In this way, by forming, in the region on the front side of the lower casing160, the pair of ribs332extending in the lengthwise direction as well as the ribs334which connect the ribs332together in the widthwise direction and extend to the outer sides of those ribs332, deformation (bending) in the direction orthogonal to the lengthwise direction of the lower casing160and the main instrument unit100can be inhibited, and the strength of the casing can be improved. Moreover, by forming the ribs332and334so as to protrude separated from the keyboard unit120in a region of the lower casing160directly beneath the keypress positions of the keys, even when the user performs a keypress operation, none of the associated impact or pressing force is directly transmitted to the lower casing160, which makes it possible to inhibit deformation (bending) of the lower casing160and the main instrument unit100and also makes it possible to suppress abnormal noises and vibrations when keys are pressed.

Note thatFIG. 3Billustrates an example in which the third casing reinforcing section330including the ribs332and334is arranged divided in two in the lengthwise direction of the lower casing160. Here, the ribs332and334are arranged divided in this manner to avoid a battery box which is the driving power supply of the main instrument unit100and is arranged substantially near the center of the lower casing160in the lengthwise direction, but the present invention is not limited to this configuration. By modifying the layout design of the lower casing160, a single continuous third casing reinforcing section330may be arranged, or the third casing reinforcing section330may be arranged divided into two or more sections.

Moreover, it is preferable that the ribs332and334be arranged near attachment bosses or attachment holes for fastening the upper casing140and the keyboard unit120to be assembled onto the lower casing160with fasteners such as screws. In this case, by forming the ribs332and334integrally with or connected to the attachment bosses and then fastening the upper casing140and the keyboard unit120, or by fastening the upper casing140and the keyboard unit120via attachment holes, the strength of the casing can be improved even when the ribs332and334are made of thin plate-shaped members, and the space required for component layout within the main instrument unit100can be reduced.

FIGS. 13A-13Care a perspective view schematically illustrating a fourth casing reinforcing section used in the keyboard instrument according to the present embodiment.FIG. 13Ais an overall perspective view illustrating the lower casing to which the fourth casing reinforcing section has been applied, andFIGS. 13B and 13Care perspective views illustrating the primary components of the fourth casing reinforcing section.FIG. 14is a cross-sectional view schematically illustrating the main instrument unit to which the fourth casing reinforcing section according to the present embodiment has been applied. Note that the cross-section illustrated inFIG. 14omits the upper casing in order to simplify the illustration.FIGS. 15A-15Bschematically illustrates an example of cable layout within the main instrument unit to which the fourth casing reinforcing section according to the present embodiment has been applied.FIG. 15Ais a view illustrating an example of speaker cable layout in the main instrument unit to which the fourth casing reinforcing section has been applied, andFIG. 15Bis a view illustrating an example of speaker cable layout for comparison.

More specifically, as illustrated inFIGS. 3B, 13A, 13B, 13C, and 14, in the fourth casing reinforcing section340, ribs (reinforcing members)342including a pair of plate-shaped members arranged near to and facing one another are arranged on the inner surface side of the lower casing160in a region (fourth region) which extends in the lengthwise direction of the lower casing160on the rear side of the keyboard unit120and is a region on the rear side (upper side inFIG. 3B; far side inFIGS. 13A-13C;FIG. 14) in the widthwise direction of the main instrument unit100. Moreover, in the fourth casing reinforcing section340, between the pair of ribs342, ribs344including plate-shaped members that connect together the pair of ribs342are arranged extending in the widthwise direction of the lower casing160orthogonal to the lengthwise direction. Here, as illustrated inFIGS. 13A-13C, the ribs344have substantially the same height as the ribs342. Furthermore, as illustrated inFIGS. 13A, 13B, 13C, and 14, in the upper ends of the ribs344, slits346including U-shaped or V-shaped grooves are formed for housing and holding in place between the pair of ribs342speaker cables150which connect between the sound source circuit board (circuit board)146and the speakers (sound emitters)148that are installed into the upper casing140and arranged on the rear side of the keyboard unit120. In addition, as illustrated inFIG. 15A, the height with which the ribs342and344protrude from the lower casing160is set such that the speaker cables150running between the sound source circuit board146and the speakers148as well as wires or electronic components of the sound source circuit board146do not overlap when viewed in a plan view or are not overly close to one another.

In this way, by forming the pair of ribs342extending in the lengthwise direction as well as the ribs344which connect the ribs342together in the widthwise direction in the region on the rear side of the lower casing, deformation (bending) in the direction orthogonal to the lengthwise direction of the lower casing160and the main instrument unit100can be inhibited, and the strength of the casing can be improved. Moreover, by using the slits346formed in the ribs344that connect together the pair of ribs342to hold in place and house between the pair of ribs342the speaker cables150running between the sound source circuit board146and the speakers148housed within the main instrument unit100, the speaker cables150and the sound source circuit board146can be prevented from overlapping in a plan view or being close to one another.

Here, if as illustrated inFIG. 15Bthe speaker cables150overlap with the sound source circuit board146in a plan view or are arranged overly close thereto, noise from the sound source circuit board146is introduced and makes the sound quality of the musical sounds emitted from the speakers148more prone to degradation. In contrast, in the present embodiment the height of the ribs342and344are set so as to prevent (to the greatest extent possible) the speaker cables150and the sound source circuit board146from overlapping in a plan view or being close to one another, therefore making it possible to reduce introduction of noise into the musical sounds emitted from the speakers148and to thereby improve sound quality. Moreover, in this case introduction of noise can be reduced without changing the arrangement of a connector147for the speaker cables150that is formed in the sound source circuit board146, thereby making it possible to use an existing circuit board as-is.

Furthermore, as illustrated inFIGS. 13A-13C, the ribs342are arranged near attachment bosses350for fastening the upper casing140and the keyboard unit120to be assembled onto the lower casing160with fasteners such as screws, and the ribs342are formed integrally with the attachment bosses350or connected to the attachment bosses350. In this way, the strength of the casing can be improved even when the ribs342and344are made of thin plate-shaped members, and the space required for component layout within the main instrument unit100can be reduced.

Although in the embodiment above a plurality of casing reinforcing sections of different types according to the present invention were described, the electronic keyboard instrument according to the present invention may include all of these casing reinforcing sections, may include any one of these reinforcing sections alone, or may include any combination of these casing reinforcing sections.

Although several embodiments of the present invention were described above, the present invention is not limited to these embodiments and includes the invention as set forth in the claims as well as configurations of equivalent scope.