Patent Publication Number: US-9905204-B2

Title: Pivotal supporting structure for fallboard of keyboard musical instrument

Description:
BACKGROUND 
     The present invention relates to a pivotal supporting structure for pivotally supporting a fallboard of a keyboard musical instrument in such a manner that the fallboard is openable and closable relative to the body of the musical instrument. 
     There have heretofore been known keyboard musical instruments where a fallboard (keyboard fallboard) is pivotally supported relative to the body of the musical instrument with a damper function secured for braking opening/closing movement of the fallboard. In a keyboard musical instrument disclosed in Japanese Patent No. 3849313, the fallboard pivotally mounted on a back lid of the keyboard is pivotally supported on a damper device (damper mechanism section) that is provided on the body of the musical instrument (or instrument body) and that has viscous resistance. In order to absorb misalignment between the pivot axis of the damper device and the pivot axis of the fallboard, a connection member and an absorbing member are interposed between the damper device and the fallboard. 
     In the pivotal supporting structure disclosed in the above-identified patent literature, however, the fallboard is pivotable relative to the keyboard back lid, and absolutely, the pivot center is a mechanism, such as a hinge, connecting the fallboard and the keyboard back lid for pivotal movement relative to each other. Further, the pivotal supporting structure disclosed in the above-identified patent literature is constructed so that axial misalignment between the pivot axis of the damper device and the fallboard is absorbed by axial misalignment adjusting members comprising the connection member and the absorbing member. 
     For that purpose, not only a pivotal supporting mechanism, such as the hinge, but also the misalignment adjusting members are essential. Further, because the pivot center of the fallboard does not necessarily coincide with the pivot center of the damper device, there is a likelihood that the damper function will not be exerted uniformly during the entire opening and closing strokes. 
     If one wants to mount the fallboard on the instrument body in such a manner that the fallboard pivots accurately about the pivot center of the damper device, then a construction corresponding to such a form of mounting has to be considered, which would make it difficult to realize easy mounting of the fallboard. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing prior art problems, it is an object of the present invention to provide an improved pivotal supporting structure for a fallboard of a keyboard musical instrument which, without requiring a hinge and a misalignment adjusting member, allows the fallboard to be easily mounted on the instrument body in such a manner that the fallboard can pivot about the pivot center of the damper mechanism section. 
     In order to accomplish the above-mentioned object, the present invention provides an improved pivotal supporting structure for a fallboard ( 10 ) of a keyboard musical instrument, the fallboard ( 10 ) being disposed between left and right side boards ( 11 ,  12 ) of the keyboard musical instrument, the pivotal supporting structure comprising: a first pivot section (J 1 ,  20 ) that pivotally supports a left end portion ( 10   a ) of the fallboard on the left side board ( 11 ); a second pivot section (J 2 ,  30 ) that pivotally supports a right end portion ( 10   b ) of the fallboard on the right side board ( 12 ). At least one of the first pivot section and the second pivot section includes: a damper mechanism (DM) provided on one of the side board and the end portion of the fallboard and having a driven member ( 29 ) constructed to receive pivotal movement; and a driving member ( 23 ,  123 ) corresponding to the damper mechanism (DM) and engageable with the driven member, the driving member ( 23 ,  123 ) being assembled so as to operate in interlocked relation to the other of the side board and the end portion of the fallboard, the damper mechanism being constructed to generate a load against pivotal force which the driven member ( 29 ) receives from the driving member ( 23 ,  123 ). Further, at least one of the first pivot section and the second pivot section includes: a pivoting member ( 38 ) pivotally supported on one of the side board and the end portion of the fallboard; and a retainer ( 30 ,  33 ,  36 ) corresponding to the pivoting member and fixed to other of the side board and the end portion of the fallboard, the retainer being constructed to position and retain the pivoting member at a predetermined position. Note that numerals and characters indicated in parentheses in this summary section represent, just for reference purposes, reference numerals and characters used in the accompanying drawings to depict various constituent elements of later-described embodiments of the present invention. 
     According to the present invention, the pair of the damper mechanism (DM) and the driving member ( 23 ,  123 ) is provided on at least one of the left and right pivot sections (J 1 , J 2 ), the pivot center of the driven member ( 29 ) of the damper mechanism (DM) becomes a pivot axis of the fallboard on at least one end portion of the fallboard as the fallboard is pivotally opened or closed. The damper mechanism (DM) is provided on one of the side board and the end portion of the fallboard, and the driving member ( 23 ,  123 ) is assembled so as to operate in interlocked relation to the other of the side board and the end portion of the fallboard. Provision of such a damper mechanism (DM) can provide a stable pivoting touch as the fallboard is opened or closed. Further, the pair of the pivoting member ( 38 ) and the retainer ( 30 ,  33 ,  36 ) is provided on at least one of the left and right pivot sections (J 1 , J 2 ), and the pivot axis of the pivoting member ( 38 ) coincides with the pivot axis of the fallboard on at least one end portion of the fallboard as the fallboard is pivotally opened or closed. Because the pivoting member ( 38 ) is positioned and retained at the predetermined position via the retainer ( 30 ,  33 ,  36 ), the fallboard is assembled to the side board in such a manner that it is pivotable relative to the side board. Because the pivoting member extends in a direction perpendicular to the pivot axis, a direction of relative movement of the pivoting member when the pivoting member is to be assembled to or removed from the retainer is generally perpendicular to the pivot axis, the pair of the pivoting member ( 38 ) and the retainer ( 30 ,  33 ,  36 ) can be easily constructed so that, when operations are to be performed for assembling the fallboard to the side boards or removing the fallboard from the side boards, the fallboard only has to be moved in a direction generally perpendicular to the pivot axis, i.e. in an up-down or front-rear direction or the like, as viewed from the front of the keyboard, or in other words, in a direction other than a left-right (lateral) direction where the fallboard is sandwiched by the left and right side boards so that it cannot be easily moved. Such a construction can facilitate assembly to or removal from the body of the musical instrument. In this way, the fallboard can be readily mounted on the body of the musical instrument (instrument body) between the left and right side boards in such a manner that it is pivotable about the pivot center of the damper mechanism, without requiring a hinge and an axial misalignment adjusting member. 
     In an embodiment, the pair of the damper mechanism and the driving member may be provided on any one of the first and second pivot sections. However, the present invention is not so limited, and the pair of the damper mechanism and the driving member may be provided on each of the first and second pivot sections; namely, two pairs of the damper mechanisms and the driving members may be provided. 
     In an embodiment, the pair of the pivoting member and the retainer may be provided on any one of the first and second pivot sections. However, the present invention is not so limited, and, as another embodiment, the pair of the pivoting member and the retainer may be provided on each of the first and second pivot sections; namely, two pairs of the pivoting members and the retainers may be provided. 
     In an embodiment, the pair of the damper mechanism and the driving member and the pair of the pivoting member and the retainer may be provided on different ones of the first and second pivot sections; namely, one of the pairs may be provided on the first pivot section, and the other of the pairs may be provided on the second pivot section. In another embodiment, the pair of the damper mechanism and the driving member and the pair of the pivoting member and the retainer may both be provided on the same pivot section; namely, both of the pairs may be provided on the same first or second pivot section. 
     In an embodiment, if the pivoting member is not provided on the at least one of the first joint section and the second joint section which includes the pair of the damper mechanism and the driving member, the driving member may be fixed to the other of the side board and the end portion of the fallboard where the damper mechanism is not provided. If the pivoting member is provided on the at least one of the first joint section and the second joint section which includes the pair of the damper mechanism and the driving member, the driving member may be constructed to pivot together with said pivoting member. 
     In an embodiment, the pivoting member may include a pivoting arm, the retainer includes a gap space that removably receives therein the pivoting arm, a positioning member for positioning the pivoting arm received in the gap space, and a fixing member for fixing the pivoting arm received and positioned in the gap space. With such arrangements, the pivoting arm can be easily positioned at the predetermined position by merely being inserted into the gap space of the retainer. 
     In an embodiment, the pivoting member may include a shaft section pivotably supporting the pivoting arm, and the positioning member may have a recessed portion that engages with the shaft section of the pivoting arm received in the gap space. Because the pivoting member is positioned by the shaft section, which pivotably supports the pivoting arm, being engaged with the recessed portion, the pivoting member can be positioned with a high accuracy with the pivot axis as a positioning reference. Further, in an embodiment, the recessed portion may have a bottom end portion, and the pivoting member may be positioned by abutting engagement between the bottom end portion and the shaft section. Because it suffices to insert the pivoting member into the gap space of the retainer until the shaft section of the pivoting member abuts against the bottom end portion of the recessed portion, the positioning of the pivoting member can be significantly facilitated. 
     Further, in an embodiment, the fixing member may include a fastening screw, and the pivotal supporting structure may be constructed in such a manner that a portion fastened by the fastening screw is exposed when the fallboard is in an opened position. Such arrangements can facilitate fastening operation by the fastening screw. Furthermore, in an embodiment, the pivotal supporting structure may be constructed in such a manner that the portion fastened by the fastening screw is invisible from outside when the fallboard is in a closed position. With such an arrangement, the outer appearance of the pivotal supporting structure can be improved because the portion fastened by the fastening screw is invisible from outside when the fallboard is in the closed position. 
     The following will describe embodiments of the present invention, but it should be appreciated that the present invention is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principles. The scope of the present invention is therefore to be determined solely by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a keyboard musical instrument to which is applied a pivotal supporting structure for a fallboard according to an embodiment of the present invention, which particularly shows a fallboard-opened state of the keyboard musical instrument; 
         FIG. 2  is a fragmentary exploded perspective view showing a relationship between a left pivot section and a mounting section; 
         FIG. 3  is a fragmentary exploded perspective view showing a relationship between a right pivot section and a mounting section; 
         FIG. 4A  is a front view of the mounting section, and  FIG. 4B  is a right side view of the mounting section; 
         FIG. 5  is a fragmentary exploded perspective view showing a relationship between the left pivot section and the mounting section according to a modification of the present invention; 
         FIG. 6  is a fragmentary exploded perspective view showing a relationship between the right pivot section and the mounting section according to a modification of the present invention; and 
         FIG. 7  is a fragmentary exploded perspective view showing a relationship between the left pivot section and the mounting section according to the modification of the present invention 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of a keyboard musical instrument  100  to which is applied a pivotal supporting structure for a fallboard (keyboard fallboard) according to an embodiment of the present invention, which particularly shows a fallboard-opened state of the keyboard musical instrument. Although the keyboard musical instrument  100  is constructed as an electronic keyboard musical instrument, it may be an acoustic keyboard instrument. 
     The keyboard musical instrument  100  includes an instrument body  101  and a fallboard  10 , and a keyboard section KB is mounted on the instrument body  101 . Hereinafter, the terms “left”, “right”, etc. refer to directions as viewed from a human operator or player sitting behind the keyboard section KB. 
     The instrument body  101  includes a left side board  11  and a right side board  12 , and the keyboard section KB and the fallboard  10  are disposed between the left and right side boards  11  and  12 . The fallboard  10  includes a plate section  13  that covers the keyboard section KB when the fallboard  10  is in a closed position. The plate section  13  functions also as a music stand. A left pivot section J 1  is provided on the left side board  11 , while a right pivot section J 2  is provided on the right side board  12 . The fallboard  10  is openable and closable relative to the instrument body  101  about a pivot center that is an axis line extending in a horizontal left-right direction on a front side (i.e., side remote from the human player) of the keyboard section KB. As will be described in detail later, the above-mentioned pivot center (or pivot axis) of the fallboard  10  is set by a left end portion  10   a  of the fallboard  10  being pivotally supported by the left pivot section J 1  and a right end portion  10   b  of the fallboard  10  being pivotally supported by the right pivot section J 2 . The left and right pivot sections J 1  and J 2  axially align with each other and thereby define a pivot axis line of the fallboard  10 . 
     A mounting section  20  is fixed to the plate section  13  on the left end portion  10   a  of the fallboard  10 , while a mounting section  30  is fixed to the plate section  13  on the right end portion  10   b  of the fallboard  10 . The mounting section  20  and  30  engage with the left and right pivot sections J 1  and J 2 , respectively. Namely, a combination of the left pivot section J 1  and the mounting section  20  functions as a first pivot section for pivotally supporting the left end portion  10   a  on the left side board  11 , while a combination of the right pivot section J 2  and the mounting section  30  functions as a second pivot section for pivotally supporting the right end portion  10   b  on the right side board  12 . 
       FIG. 2  is a fragmentary exploded perspective view showing a relationship between the left pivot section J 1  and the mounting section  20 . 
     The left (first) pivot section J 1  includes a pair of a damper mechanism DM and an engaging hole  23 . For example, the damper mechanism DM may be of a conventionally-known construction using a friction generating member having fluid viscosity resistance and slide resistance. The damper mechanism DM has a projection  29  that functions as a pivot shaft rotatable about a first pivot axis C 1 , and the projection  29  is, for example, in the form of an elongated ridge or a rectangular parallelepiped. The projection  29  is exposed in the inner surface  11   a  of the left side board  11  and functions as a driven member. Once the projection  29  receives pivotal driving force acting about the first pivot axis C 1 , the pivot section J 1  generates a load against the pivotal driving force. The damper mechanism DM only needs to have a damper function for braking pivoting movement and may be constructed in any desired manner. Note that the pivot axis C 1  of the driven drive member (projection  29 ) in the damper mechanism DM forms a pivot axis in the pivot section J 1 . 
     The mounting section  20 , which is fixed to the plate section  13  of the fallboard  10  by means of screws or the like, comprises a metal part  21  and a cover  22  covering the metal part  21 . The metal part  21  and the cover  22  may be formed integrally, and the metal part  21  has the engaging hole  23  formed therein. 
     As viewed in the axial direction of the first pivot axis C 1 , the projection  29  has a generally rectangular shape, rather than a circular shape, and has a flat driven surface  29   a . The engaging hole  23  is shaped in such a manner that it can be fitted over the projection  29  to engage with the projection  29  in a pivoting direction to thereby drive the projection  29  in the pivoting direction. When the engaging hole  23  is fitted over the projection  29 , pivoting force (pivotal driving force) of the mounting section  20  responsive to opening/closing movement of the fallboard  10  is transmitted to the projection  29  via the engagement between the engaging hole  23  and the projection  29 . The engaging hole  23  is provided in the mounting section  20  in correspondence with the damper mechanism DM and functions as a driving member engageable with the driven member (projection  29 ). The driving member (engaging hole  23 ) is assembled so as to operate in interlocked relation to one of the side board  11  and  10  end portion  10   a  of the fallboard  10  where the damper mechanism DM is not provided. In the illustrated example of  FIG. 2 , interlocked relation of the driving member (engaging hole  23 ) with the fallboard  10  is realized by the driving member (engaging hole  23 ) being provided on the mounting section  20  fixed to the end portion  10   a  of the fallboard  10 . 
     As the fallboard  10  duly assembled is pivotally moved in an opening or closing direction, the mounting section  20  including the engaging hole  23  pivots together or integrally with the fallboard  10  as a part of the fallboard  10 , so that the engaging hole  23  pivotally drives the projection  29 . Then, the damper mechanism DM generates a load to brake the fallboard  10 . Thus, by the engagement between the engaging hole  23  and the projection  29 , not only pivotal driving force is applied to the damper mechanism DM during the opening/closing movement of the fallboard  10 , but also the left end portion  10   a  is pivotally supported on the left side board  11  with the first pivot axis C 1  as the center of axis. 
       FIG. 3  is a fragmentary exploded perspective view showing a relationship between the right pivot section J 2  and the mounting section  30 . 
     The right (second) pivot section J 2  includes a pivoting member  38  pivotally supported on the right side board  12 , and a retainer (including a mounting section  30 , a recessed portion  33 , a male screw  36 , etc.) fixed to the right end portion  10   b  of the fallboard  10 . A shaft section  39  rotatable about a second pivot axis C 2  projects leftward from the inner surface  12   a  of the right side board  12 , and the pivoting member  38  is fixed to the shaft section  39  so as to rotate together or integrally with the shaft section  39 . The first pivot axis C 1  and the second pivot axis C 2  are axially aligned with each other, and these first and second pivot axes C 1  and C 2  form a pivot center (axis line) of the fallboard  10  duly assembled. 
     The pivoting member  38  includes an arm  38   a  extending radially so that the arm  38   a  pivots in a plane perpendicular to the axis line of the second pivot axis C 2 , and a fastening hole  37  formed as a female thread is formed in one of free end portions of the pivoting member  38 . Note that the shaft section  39  need not necessarily be rotatable and may be fixed to the right side board  12 , in which case it suffices that the pivoting member  38  be pivotable relative to the shaft section  39  about the second pivot axis C 2 ; in short, it is only necessary that the pivoting member  38  (arm  38   a ) be constructed to be pivotable about the second pivot axis C 2 . Note that the pivoting member  38  may be of any desired shape. 
       FIG. 4A  is a front view of the mounting section  30 , and  FIG. 4B  is a right side view of the mounting section  30 . 
     As shown in  FIGS. 3, 4A and 4B , the mounting section  30  is fixed to the plate section  13  of the fallboard  10  by screws or the like. The mounting section  30  comprises a metal part  31  and a cover  32  covering the metal part  31 . In the metal part  31  are formed the recessed portion  33  of a generally inverted U shape to permit entry therein of the shaft section  39 , and a fastening hole  34  corresponding to the fastening hole  37  of the pivoting member  38 . The fastening hole  34  need not be threaded. An opening  32   a  is formed in a lower end portion of the cover  32  that positionally corresponds to an entrance to the recessed portion  33 . A gap space communicating with the opening  32   a  is formed between the end portion  10   b  of the fallboard  10  and the metal part  31 , and the arm  38   a  of the pivoting member  38  is insertable in the gap space. 
     The recessed portion  33  extends in a longitudinal direction of the metal part  31  and has a bottom end portion  33   a  of a semicircular concave shape. Namely, with the pivoting member  38  duly assembled to the mounting section  30 , the recessed portion  33  extends in a direction perpendicular to the axis line of the second pivot axis C and ends in the bottom end portion  33   a . With the pivoting member  38  duly assembled to the mounting section  30 , the bottom end portion  33   a  abuts against the shaft section  39  and thereby functions as a means for positioning the pivoting member  38  at a predetermined position. With the pivoting member  38  duly assembled to the mounting section  30  and positioned at the predetermined position in the aforementioned manner, the fastening hole (female thread)  37  of the pivoting member  38  (arm  38   a ) faces the fastening hole  34  of the metal part  31 , and thus, the male screw  36  can be screwed into the fastening hole (female thread)  37  by being inserted into the fastening hole  34  and tightened to be tightened. In this manner, the pivoting member  38  is fixed to the mounting section  30 . The mounting section  30 , including the above-mentioned metal part  31 , cover  32 , recessed portion  33 , pivoting-member-inserting gap space, etc., and the fixing screw  36  function as a retainer for retaining the pivoting member  38  at the predetermined position. 
     Next, a description will be given about an example operational sequence for mounting the fallboard  10  on the keyboard musical instrument  100 . 
     The fallboard  10  having the mounting sections  20  and  30  fixed to the plate section  13  is fabricated in advance. First, the engaging hole  23  ( FIG. 2 ) of the left mounting section  20  of the fallboard  10  is fitted over and fittingly engaged with the projection  29  of the damper mechanism DM provided on the left side board  11 . Then, with the engaging hole  23  and the projection  29  kept fittingly engaged with each other, a portion of the fallboard  10 , mainly the right end portion  10   b , is moved downward so that the pivoting member  38  ( FIG. 3 ) provided on the right side board  12  is inserted, from below, into the gap space of the right mounting section  30  of the fallboard  10 . Because the downward movement of the fallboard  10  at that time is in an up-down or front-rear direction substantially perpendicular to the pivot axis of the fallboard  10 , the fallboard  10  can be moved easily so that the pivoting member  38  can be inserted into the gap space, and thus, the mounting operations can be extremely facilitated. 
     As noted above, the gap space in which the pivoting member  38  is insertable is formed inside the cover  32  between the end portion  10   b  of the fallboard  10  and the metal part  31 , and the opening  32   a  is formed in a portion of the cover  32  that positionally corresponds to the entrance to the recessed portion  33 . As the free end portion of the pivoting member  38 , where the fastening hole  37  is located, is inserted through the opening  32   a , the recessed portion  33  is brought into engagement with the shaft section  39  and then guided by the shaft section  39  until then the bottom end portion  33   a  is brought into abutment against the shaft section  39 . 
     Once the bottom end portion  33   a  abuts against the shaft section  39 , the mounting section  30  and the pivoting member  38  are placed in a positional relationship as shown in  FIGS. 4A and 4B . In this manner, the positioning function for positioning the pivoting member  38  and the mounting section  30  in the direction vertical to the axial direction of the second pivot axis C 2  can be performed by the engagement between the recessed portion  33  and the shaft section  39 . 
     Once the pivoting member  38  and the mounting section  30  are duly positioned in the aforementioned manner, the fastening hole  34  and the fastening hole  37  are linearly aligned with each other. In this condition, the screw  36  is screwed through the fastening hole  34  into the fastening hole  37 , so that the pivoting member  38  and the mounting section  30  are fixedly fastened together. This fastening operation is performed with the fallboard  10  kept in the opened position. Because the fastening hole  34  is exposed rightward when the fallboard  10  is the opened position, the fastening operation can be done with ease. When the fallboard  10  is in the closed position, on the other hand, the fastening hole  34  is invisible as viewed from the right by being hidden behind the right side board  12  and thus the portion fastened by the screw  36  is invisible, with the result that the outer appearance would not be impaired. 
     Even if the recessed portion  33  is formed to be longer in length such that the pivoting member  38  is fixed to the mounting section  30  by means of the screw  36  with no abutment between the bottom end portion  33   a  and the shaft section  39 , a certain degree of the positioning function can be performed. In such a case, the mounting section  30  is moved in a direction where the recessed portion  33  is movable while being guided by the shaft section  39 , and then the fastening hole  37  and the fastening hole  34  are positioned in linear alignment with each other by the eye of a human operator and then fastened together by the screw  36 . 
     In this way, the fallboard  10  can be mounted on the instrument body  101  by means of substantively one fastener member (screw  36 ) in such a manner that the fallboard  10  is pivotable about the first and second pivot axes C 1  and C 2 . Further, no hinge or the like is required to permit pivoting movement of the fallboard  10 . Furthermore, no dedicated mechanism for correcting axial misalignment is required to permit the fallboard  10  to pivot about the second pivot axis C 2 . 
     Because the engaging hole  23  of the mounting section  20  pivotally drives the projection  29  of the pivot section J 1  in response to an opening/closing operation of the fallboard  10 , the pivot section J 1  generates a load against the pivotal driving force such that appropriate brake force is applied to the opening/closing movement of the fallboard  10 . Note that, when the fallboard  10  is to be removed, fallboard removing operations may be performed by first removing the screw  36  and then merely reversing the aforementioned operational sequence executed for mounting the fallboard  10 . Thus, the fallboard removing operations can be facilitated for reasons similar to the reasons set forth above for the fallboard mounting operations. 
     According to the instant embodiment, as the pivoting member  38  is inserted into the mounting section  30  with the engaging hole  23  and the projection  29  kept engaged with each other, the pivoting member  38  and the mounting section  30  are positioned relative to each other in the front-rear and up-down directions. Then, by screwing the screw  36  through the fastening hole  34  into the fastening hole  37  in that condition, the pivoting member  38  and the mounting section  30  can be fixedly fastened together. In this way, the fallboard  10  can be readily mounted on the instrument body  101  so that it can pivot about the pivot axis (C 1 ) of the damper mechanism section (pivot section J 1 ), without requiring a hinge and an axial misalignment adjusting member. 
     Further, because the pivoting member  38  and the mounting section  30  are positioned through the engagement between the recessed portion  33  and the shaft section  39 , the positioning can be facilitated. Particularly, through the abutment between the bottom end portion  33  and the shaft section  39 , the pivoting member  38  and the mounting section  30  can be positioned relative to each other in the direction vertical to the second pivot axis  39 . Besides, the shaft center of the shaft section  39  is the second pivot axis C 2 . In this way, the pivoting member  38  and the mounting section  30  can be positioned on the basis of the second pivot axis C 2  (i.e., with the second pivot axis C 2  used as a positioning reference), and thus, they can be positioned with a high accuracy. 
     Further, if the fallboard  10  is placed in the opened position with the pivoting member  38  and the mounting section  30  kept duly positioned relative to each other in the aforementioned manner, the fastening hole  34  is visibly exposed rightward, and thus, the fastening operation can be performed with ease. If the fallboard  10  is placed in the closed position after assembly, on the other hand, the fastening hole  34  is invisible as viewed from the right by being hidden behind the right side board  12  and thus the fastened portion is invisible, with the result that the outer appearance can be improved. 
     Whereas the construction in which the projection  29  (driven section or member) is driven by the engaging hole  23  functioning as a driving member has been described above by way of example in relation to the mechanism of the section where the mounting section  20  drives the pivot section J 1  in response to the opening/closing movement of the keyboard  10 , the present invention is not so limited. For example, as shown in  FIG. 5 , the driven member provided in the pivot section J 1  may be constructed to be subjected to (receive) pivotal driving force acting about the first pivot axis C 1 , and the driving member provided in the mounting section  20  may be constructed in a manner corresponding to such a driven member. 
       FIG. 5  is a fragmentary exploded perspective view showing a relationship between the left pivot section J 1  and the mounting section  20  according to a modification (modified embodiment) of the present invention. The pivot section J 1  has two projections  129  as the driven members, and the mounting section  20  has two engaging holes  123  formed therein as the driving members. The engaging holes  123  are fitted over respective ones of the projections  129  so that the engaging holes  123  can apply pivotal driving force to the corresponding projections  129 . 
     Alternatively, two recessed portions may be formed in a surface DP in place of the two projections  129 , and two projections corresponding to the recessed portions may be provided, by welding or otherwise, on the metal part  21  in place of the engaging holes  123  so that the recessed portions and the projections can be fitted with each other. 
     Various other structural relationships between the driving member and the driven member are also possible. For example, three or more projections  129  and three or more engaging holes  123  may be combined. Further, the projection  29  shown in  FIG. 2  may be of any desired special shape having the driven surface  29   a  unless the shape is a circular columnar shape. For example, the projection  29  may be of a plus (+) shape, flower shape, polygonal shape, circle segment shape, half moon shape, or the like. 
     Furthermore, the construction with which to provide the mounting sections  20  and  30  on the fallboard  10  may be other than the one described above. For example, the engaging hole  23  of the mounting section  20  and the recessed portion  33  of the mounting section  30  may be formed in the body of the fallboard  10  itself. 
     Furthermore, the positional relationship between the damper mechanism DM and the mounting section  20  constituting the first pivot section J 1  may be reversed. Namely, the damper mechanism DM may be provided on the end portion  10   a  of the fallboard  10 , and a mounting mechanism corresponding to the mounting section  20  may be provided on the left side board  11 . In this manner, the damper mechanism DM provided on the fallboard  10  can be pivotally driven by the mounting mechanism provided on the left side board  11 . 
     Similarly, the positional relationship between the pivoting member  38  and the mounting section  30  (retainer) constituting the second pivot section J 2  may be reversed. Namely, a pivoting mechanism corresponding to the shaft section  39  and the pivoting member  38  may be provided on the end portion  10   b  of the fallboard  10 , and a mounting mechanism corresponding to the mounting section  30  (retainer) may be provided on the right side board  12 . In such a case, with the fallboard  10  duly assembled, the pivoting member  38  pivotally supported on the end portion  10   b  of the fallboard  10  is fixed to the right side board  12 , so that the fallboard  10  pivots relative to the pivoting member  38 . 
     Whereas the foregoing paragraphs have described various examples in which the pair of the damper mechanism DM and the mounting section  20  (driving member  23  or driving members  123 ) constituting the first pivot section J 1  is provided on the left side while the pair of the pivoting member  38  and the mounting section  30  (retainer) constituting the second pivot section J 2  is provided on the right side, the positional relationship between the two pairs may be reversed as necessary. 
     In the above-described embodiment, the pair of the damper mechanism DM and the mounting section  20  (driving member  23  or driving members  123 ) and the pair of the pivoting member  38  and the mounting section  30  (retainer) are provided on the different pivot sections J 1  and J 2 . Such an arrangement corresponds to the case where the driving member(s)  23  ( 123 ) is provided on the side of the pivotally supporting structure where the pivoting member  38  is not provided, in which case the driving member(s)  23  ( 123 ) (mounting section  20 ) is fixed to one of the side board  11  and the end portion  10   a  of the fallboard  10  where the damper mechanism DM is not provided (i.e., the end portion  10   a  in the illustrated example of  FIG. 2 ). However, the present invention is not so limited, and the pair of the damper mechanism DM and the mounting section  20  (driving member(s)  23  ( 123 )) and the pair of the pivoting member  38  and the mounting section  30  (retainer) may be provided on the same pivot section J 1  or J 2 . In such a case, the driving member(s)  23  ( 123 )) is constructed to pivot together or integrally with the pivoting member  38 . Such a modification is shown in  FIG. 6 . 
       FIG. 6  shows the modification where the pair of the damper mechanism DM and the mounting section  20  (driving member(s)  23  ( 123 )) and the pair of the pivoting member  38  and the mounting section  30  (retainer) are provided on the same pivot section J 1  or J 2 . Note that, in  FIG. 6 , the same reference numerals and characters as those shown in  FIG. 3  represent the same elements as shown in  FIG. 3 . The damper mechanism DM is incorporated into the right side board  12 , and the pivot axis of the damper mechanism DM coincides with the second pivot axis C 2 . The driven member(s)  29  ( 129 ) (not shown in  FIG. 6 ) may be the same as the driven member(s)  29  ( 129 ) shown in  FIG. 2 or 5 . A pivot shaft  40  of the pivoting member  38  has an engaging hole(s) similar to the engaging hole(s)  23  ( 123 ) formed therein, and the engaging hole(s)  23  ( 123 ) (not shown in  FIG. 6 ) formed in the pivot shaft  40  is fitted over the driven member(s)  29  ( 129 ) removably or semi-fixedly. In this manner, the engaging hole(s)  23  ( 123 ) corresponding to the damper mechanism DM is constructed to pivot together with the pivoting member  38  corresponding to the retainer ( 30 ,  33  and  36 ). Namely, the arm  38   a  of the pivoting member  38  pivots together with the pivot shaft of the damper mechanism DM. In such a case, the left pivot section J 1  may comprise a simple removable pivot shaft structure.  FIG. 7  shows an example of the left pivot section J 1  comprising such a simple removable pivot shaft structure, where the same reference numerals and characters as those shown in  FIG. 2  represent the same elements as in  FIG. 2 . In this case, the left pivot section J 1  includes a cylindrical projection  41  fixed to the left side board  11 , and a cylindrical hole  42  formed in the mounting section  20  provided on the left end portion  10   a  of the fallboard  10 . With the fallboard  10  duly set to the side boards  11  and  12 , the cylindrical hole  42  of the fallboard  10  is pivotably fitted over the cylindrical projection  41  of the left side board  11 , so that the fallboard  10  can pivotally move in the opening or closing direction. The pivot axis of the cylindrical projection  41  and cylindrical hole  42  coincides with the first pivot axis C 1 . 
     As still another embodiment, the pair of the damper mechanism DM and the driving member(s)  23  ( 123 ) may be provided on each of the first and second pivot sections J 1  and J 2 ; namely, two pairs of the damper mechanisms DM and the driving members  23  ( 123 ) may be provided on the first and second pivot sections J 1  and J 2 . As still another embodiment, the pair of the pivoting member  38  and the retainer may be provided on each of the first and second pivot sections J 1  and J 2 ; namely, two pairs of the pivoting members  38  and the retainers may be provided on the first and second pivot sections J 1  and J 2 . 
     Whereas the present invention has been described above in relation to the preferred embodiments, it is not limited to such particular embodiments, and various other variations and modifications that do not depart from the gist of the present invention are intended to be included in the scope of the present invention. 
     This application is based on, and claims priority to, JP PA 2014-097473 filed on 9 May 2014. The disclosure of the priority application, in its entirety, including the drawings, claims, and the specification thereof, are incorporated herein by reference.