Patent Publication Number: US-7709717-B2

Title: Structure for electronic keyboard instrument

Description:
BACKGROUND 
   The present invention relates generally to structures for electronic keyboard instruments. More particularly, the present invention relates to an improved structure for an electronic keyboard instrument which includes a lower case having a bottom plate for mounting thereon a keyboard unit on a portion thereof closer to a human player (i.e., on a player-side portion of the bottom plate) and an upper case having an upper plate to cover an upper portion of the lower case, and in which the upper case is overlapped on the lower case from above the lower case. Further, the present invention relates to an improved structure for an electronic keyboard instrument of a type where an operation section is provided on the upper surface of the upper plate. 
   In recent years, circuit boards to be incorporated in electronic keyboard instruments have been getting smaller and smaller, and it has become possible to house a circuit board in an upright position or posture within a housing. One example of such electronic keyboard instruments is disclosed in Japanese Patent Application Laid-open Publication No. 2004-171038. In the disclosed electronic keyboard instrument, an instrument housing comprises two major components: a housing body section; and a rear housing section. 
   The housing body section includes a bottom plate for mounting thereon a keyboard unit, and the bottom plate has openings in its upper and back sides. On the rear housing section, there are provided a roof plate portion (upper plate) that covers the upper opening of the housing body section and a back plate portion that covers the back opening of the housing body section. Further, a main circuit board is mounted, by screwing or the like, to the back plate portion of the rear housing section in an upright position. In assembling the housing of such a conventionally-known electronic keyboard instrument, the main circuit board is mounted to the back plate portion of the rear housing section, and then the rear housing section is mounted to the housing body section by being sled relative to the housing body section frontward, i.e. toward a position where a human player of the keyboard instrument is supposed to be at the time of playing (hereinafter also referred to as “player side”). 
   However, with the housing of the aforementioned conventionally-known electronic keyboard instrument, it is necessary to screw the main circuit board to the back plate portion of the rear housing section, and thus, separate screwing operation has to be performed. Consequently, there has been encountered the problem that the assembling work tends to be extremely cumbersome. 
   Further, an operation section, including operation buttons etc., is provided on the upper surface of the roof plate portion of the rear housing section. Wiring section, drawn out from the operation section, is wired beneath and along the lower surface of the roof plate portion and connected to the main circuit board. In some cases, the wiring is wired to pass across a neighborhood of the upper end surface of a heat radiating plate provided on the main circuit board beneath the roof plate. Consequently, heat is dissipated toward the wiring section, so that there would occur inconveniences, such as unwanted melting of the coating of the wiring due to the heat from the heat radiating plate. Further, Japanese Patent Application Laid-open Publication No. HEI-10-126015 discloses forming perforated lines in a printed circuit board and removing unnecessary circuit board portions along the perforated lines at the time of attachment or mounting of the circuit board. However, so far, the removed circuited board portions have been discarded as unnecessary. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, it is an object of the present invention to provide an improved structure for an electronic keyboard instrument which can be assembled easily in a simplified manner. 
   It is another object of the present invention to provide an improved structure for an electronic keyboard instrument which can reliably prevent a wiring section from being adversely influenced by heat from a heat radiating plate. 
   In order to accomplish the above-mentioned objects, the present invention provide an improved structure for an electronic keyboard instrument which comprises a lower case having a bottom plate for mounting thereon a keyboard unit and an upper case having an upper plate covering the lower case, the structure further comprising: a first holding section provided on the bottom plate of the lower case and having a lower slit formed therein, the lower slit having an upward opening; a second holding section provided on the upper plate of the upper case and having an upper slit formed therein, the upper slit having a downward opening; and a circuit board disposed upright between the upper case and the lower case. When the lower case is covered with the upper case, the circuit board is fixed in place by being inserted at upper and lower edge portions thereof in the upper slit and lower slit, respectively. 
   According to the present invention arranged in the aforementioned manner, the circuit board can be appropriately held in place by being sandwiched vertically by the upper and lower cases, and thus, no particular screwing operation is required for mounting the circuit board to the upper and lower cases. Besides, the circuit board can be mounted to the upper and lower cases during the same time as mounting of the upper case to the lower case. As a result, the assembling work of the structure can be done easily in a simplified manner. Further, the circuit board can function as a reinforcement means for vertically reinforcing the upper and lower cases, so that the upper and lower cases can be prevented from undesirably deforming due to external force. Furthermore, with the circuit board sandwichingly held at its upper and lower edge portions between the upper and lower cases, the circuit board can be reliably prevented from falling and thus can be securely fixed within the upper and lower cases. 
   In an embodiment, the first holding section is provided on a portion of the bottom plate of the lower case remoter from a human player of the keyboard instrument than the keyboard unit, the second holding section is provided on a portion of the upper plate remoter from the human player than the keyboard unit, and the upper case and the lower case are fastened together by means of fastening elements with the lower case covered with the upper case. 
   In an embodiment, a heat radiating plate is disposed on a side of the circuit board remote from the human player. Thus, the heat radiating plate is provided remote from the keyboard with the circuit board interposed between the heat radiating plate and the keyboard, which can reliably prevent heat from being trapped in the keyboard unit. If the heat radiating plate is provided between the circuit board and the keyboard unit, heat would be trapped in a resin-made frame of the keyboard unit, so that imbalanced heat distribution would occur in the frame of the keyboard unit. As a consequence, the frame of the keyboard unit twists and the keyboard unit loses its flatness, so that uniformity among touch responses of the individual keys would be adversely influenced and thus the performance capability of the keyboard would deteriorate. However, in the present invention, where the heat radiating plate is disposed on the side of the circuit board remote from the human player (i.e., on the remote-from-player side of the circuit board), it is possible to prevent heat from being trapped in the keyboard unit. Thus, the present invention can effectively prevent the uniformity among the touch response of the individual keys and performance capability of the keyboard from deteriorating due to transfer of heat from the circuit board. 
   In an embodiment, the structure includes a heat radiating plate having concave and convex portions, and the heat radiating plate is provided in opposed relation to the circuit board in such a manner that vertical through-spaces are formed between the circuit board and the concave and convex portions. Here, the heat radiating plate is fixed to the circuit board in opposed relation thereto so that through-spaces extending in the vertical direction are formed between the circuit board and the concave and convex portions of the heat radiating plate, and thus, the circuit board can be mechanically reinforced by the heat radiating plate. As a result, the circuit board can even further reinforce the upper and lower cases, so that the upper and lower cases can be even more reliably prevented from deforming due to external force. In addition, because the through-spaces form air passageways in the vertical direction, it can even further enhance the heat-radiating effect. 
   In an embodiment, the lower slit of the first holding section includes first and second lower slits provided in such a manner that the circuit board is first inserted into the first lower slit and then inserted into the second lower slit following the insertion into the first lower slit. Because the circuit board is inserted into the first and second lower slits with some time difference, the circuit board can be attached smoothly to the lower case. Further, the first and second lower slits can cooperate to appropriately align the circuit board in a thickness direction of the circuit board. 
   In an embodiment, the lower slit of the first holding section includes first and second lower slits, and an opening of the first lower slit is located closer to the upper case than an opening of the second lower slit. Because the circuit board is inserted into the first lower slit and then into the second lower slit, the circuit board can be attached smoothly to the lower case. Further, the first and second lower slits can cooperate to appropriately align the circuit board in the thickness direction of the circuit board. 
   In an embodiment, the first lower slit and the second lower slit are arranged in alignment substantially along a key-arranged direction. With the first and second lower slits arranged in alignment substantially along the key-arranged direction, the circuit board can be securely held within the cases. 
   In an embodiment, the structure includes a resilient or cushioning member provided on at least one of outer surfaces of the circuit board and inner surfaces of the slit. With the resilient or cushioning member, the circuit board can be securely fixed within the slit with no wobble. Consequently, it is possible to prevent mechanical noise from being produced in tones generated by the keyboard instrument and thereby prevent generation of buzzer-like sound noise. 
   In an embodiment, the first holding section includes: a lower projecting portion that projects from the bottom plate toward the upper case and has the lower slit formed therein; a positioning wall portion that projects from the bottom plate toward the upper case and positions the circuit board in a key-arranged direction; and a connecting portion that interconnects the lower projecting portion and the positioning wall portion. The provision of the positioning wall portion allows the circuit board to be appropriately positioned in the key-arranged direction. Besides, with the integral formation, via the connecting portion, of the lower projecting portion and positioning wall portion, the positioning wall portion and lower projecting portion can be effectively reinforced. 
   According to another aspect of the present invention, there is provided a structure for an electronic keyboard instrument which includes: a lower case having a bottom plate for mounting thereon a keyboard unit; and an upper case having an upper plate covering the lower case and an operation section mounted on an upper surface of the upper plate, the structure further comprising: a circuit board provided between the upper case and the lower case and having a heat-radiating plate attached thereto; a wiring drawn out from the operation section and wired to pass across a neighborhood of an upper end surface of the heat radiating plate at least under a lower surface of the upper plate; and a heat blocking plate mounted to the upper plate. Here, the heat blocking plate is provided between the heat radiating plate and the wiring, and the heat blocking plate blocks transfer of heat from the heat radiating plate to the wiring. The heat blocking plate can block transfer of heat from the heat radiating plate to the wiring, and thus, it is possible to prevent inconveniences from being produced in the wiring due to influences of the heat from the heat radiating plate. 
   In an embodiment, the operation section includes an operation-section circuit board provided beneath and along the lower surface of the upper plate, and the heat blocking plate is provided by being initially formed integrally with the operation-section circuit board with a perforated line therebetween and then cut from the operation-section circuit board along the perforated line. With this arrangement, it is possible to prevent the heat blocking plate from being lost if it is kept integral with the operation-section circuit board until the operation-section circuit board and heat blocking plate are attached to the upper and lower cases. 
   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 
     For better understanding of the objects and other features of the present invention, its preferred embodiments will be described hereinbelow in greater detail with reference to the accompanying drawings, in which: 
       FIG. 1A  is a lower perspective view of an upper case constituting a structure for an electronic keyboard instrument in accordance with an embodiment of the present invention, which particularly shows an inner or reverse side of the upper case, and  FIG. 1B  is an upper perspective view of a lower case constituting the structure together with the upper case; 
       FIG. 2  is a fragmentary enlarged perspective view of the lower case shown in  FIG. 1 ; 
       FIG. 3  is a fragmentary enlarged perspective view of the lower case shown in  FIG. 1 ; and 
       FIG. 4  is a sectional view of the electronic keyboard instrument, including the upper and lower cases, taken along the IV-IV line of  FIG. 2 . 
   

   DETAILED DESCRIPTION 
     FIG. 1A  is a lower perspective view of an upper case  20  constituting a structure for an electronic keyboard instrument in accordance with an embodiment of the present invention, which particularly shows an inner or reverse side of the upper case  20 .  FIG. 1B  is an upper perspective view of a lower case  10  constituting the structure together with the upper case  20 .  FIG. 2  is a fragmentary enlarged perspective view of the lower case  10  shown in  FIG. 1 .  FIG. 3  is a fragmentary enlarged perspective view of the lower case  10  with an analog circuit board  51  for sound system circuitry removed therefrom.  FIG. 4  is a sectional view of the electronic keyboard instrument, including the upper and lower cases  20  and  10 , taken along the IV-IV line of  FIG. 2 . In the figures, arrow “Y 1 ” indicates a “player side” in a front-back direction of the electronic keyboard instrument, arrow “Y 2 ,” indicates a side remote from the human player (i.e., remote-from-player side) in the front-back direction of the electronic keyboard instrument, arrow “Y 3 ” indicates a left side as viewed from the human player in a key-arranged direction, arrow “Y 4 ” indicates a right side as viewed from the human player in the key-arranged direction, and arrow “ 5 ” indicates a vertical direction of the electronic keyboard instrument. In the following description, the key-arranged direction is sometimes represented by reference numeral “Y 3 , Y 4 ”. 
   As shown in  FIGS. 1A and 1B , the structure according to the embodiment of the invention comprises: the lower case  10  having a bottom plate  11  for mounting thereon a keyboard unit  30  (see  FIG. 4 ) on a player-side portion thereof, and the upper case  20  having a roof or upper plate  21  for covering an upper portion of the lower case  10  and an operation section  22  provided on the upper surface of the upper plate  21 . As shown in  FIG. 4 , the inventive structure for an electronic keyboard instrument is formed by a structure in which the upper case  20  is overlapped from above on upper-end peripheral regions of the lower case  10 . 
   As shown in  FIGS. 1A and 1B , the above-mentioned analog circuit board  51  and a digital circuit board  52  having musical signal formation circuitry, including a tone generator, provided thereon, are housed within the upper case  20  and lower case  10 . These analog circuit board  51  and digital circuit board  52  are disposed in an upright posture parallel to the above-mentioned vertical direction Y 5 . The analog circuit board  51  and digital circuit board  52  are positioned in such a manner that their upper and lower edge portions E 1  extend in a direction of arrows “Y 6 ” parallel to the above-mentioned key-arranged direction Y 3 , Y 4 . 
   First, a construction of the lower case  10  will be detailed below. As shown in  FIG. 1B , the lower case  10  has a back upwardly-extending wall section  12 , front upwardly-extending wall section  13  and left and right upwardly-extending wall sections  14 . The back upwardly-extending wall section  12  extends upward from the edge of a remote-from-player-side (or “Y2-side”) portion of the bottom plate  11 . The front upwardly-extending wall section  13  extends upward from the edge of a player-side (or “Y1-side”) portion of the bottom plate  11 . Further, the left and right upwardly-extending wall sections  14  extend from the opposite (left and right) longitudinal ends, in the key-arranged direction Y 3 , Y 4 , of the bottom plate  11 . 
   The bottom platen of the lower case  10  has two pairs of first (or lower) circuit-board holding sections  151 R,  151 L and  152 R,  152 L, and lower bosses  16 . The one pair of the first circuit-board holding sections  151 R and  151 L are provided for sandwichingly holding the lower edge portion E 1  of the analog circuit board  51  and extend in the key-arranged direction Y 3 , Y 4  in spaced-apart relation to each other. The other pair of the first circuit-board holding sections  152 R and  152 L, on the other hand, are provided for sandwichingly holding the lower edge portion E 1  of the digital circuit board  52  and extend in the key-arranged direction Y 3 , Y 4  in spaced-apart relation to each other. 
   As illustratively shown in  FIG. 3 , the first circuit-board holding section  151 R comprises two first lower projecting portions  15 A, two second lower projecting portions  15 B, positioning wall portion  15 C and connecting wall portions (or connecting portions)  15 D, all of which are formed integrally. The other first circuit-board holding sections  151 L,  152 R and  152 L are constructed in a similar manner to the first circuit-board holding sections  151 R and thus will not be described in detail here to avoid unnecessary duplication. 
   The first and second lower projecting portions  15 A and  15 B are each formed on the remote-from-player-side portion of the bottom plate  11 , i.e. on a portion of the bottom plate  11  between the keyboard unit  30  and the back upwardly-extending wall section  12 . The first and second lower projecting portions  15 A and  15 B have first and second lower slits SL 11  and SL 12 , respectively, each of which is open upwardly (i.e., toward the upper case  20 ) and extends through the corresponding projecting portion  15 A or  15 B in the key-arranged direction Y 3 , Y 4 . The first and second lower slits SL 11  and SL 12  each have a slit width substantially equal to the thickness of each of the analog circuit board  51  and digital circuit board  52 . Further, the first lower projecting portion  15 A has a greater height, from the upper surface of the bottom plate  11 , than the second lower projecting portion  15 B. Thus, the upward opening of the first lower slit SL 11  is located closer to the upper case  20  than the upward opening of the second lower slit SL 12 . 
   In each of the first circuit-board holding sections  151 R and  152 R, located to the right (i.e., right side Y 4 ) of the human player, the positioning wall portion  15 C, first lower projecting portions  15 A and second lower projecting portions  15 B are disposed in a series or in alignment, in the mentioned order, along the key-arranged direction Y 3 , Y 4  (i.e., in the extending direction of the upper and lower edge portions E 1  of the corresponding circuit board). Similarly, in each of the first circuit-board holding sections  151 L and  152 L, located to the left (i.e., left side Y 3 ) of the human player, the positioning wall portion  15 C, first lower projecting portions  15 A and second lower projecting portions  15 B are disposed in a series or in alignment, in the mentioned order, along the key-arranged direction Y 3 , Y 4 . 
   Further, the first lower slit SL 11  formed in the first lower projecting portion  15 A and the two second lower slits SL 12  formed in the two second lower projecting portions  15 B are arranged in alignment substantially along the key-arranged direction Y 3 , Y 4 . The connecting wall portions  15 D are formed to interconnect between the positioning wall portion  15 C, first lower projecting portion  15 A and second lower projecting portions  15 B. Further, one of the two second lower projecting portions  15 B, which is located closer to the first lower projecting portions  15 A than the other second lower projecting portion  15 B, constitutes a reinforcing rib portion that extends in the front-back direction beyond the connecting wall portion  15 D and thereby reinforces the bottom plate  11 . 
   Furthermore, the positioning wall portion  15 C is provided to sandwichingly hold the analog circuit board  51  or digital circuit board  52  in the key-arranged direction Y 3 , Y 4 , i.e. in the extending direction Y 6 . The positioning wall portion  15 C contacts a side edge portion E 2 , in the key-arranged direction Y 3 , Y 4 , of the analog circuit board  51  or digital circuit board  52 , to thereby position the analog or digital circuit board  51  or  52  in the key-arranged direction Y 3 , Y 4 . 
   Each of the pairs of the first and second lower projecting portions  15 A and  15 B has a pair of tapered portions T opposed to each other in the front-back direction. Each of the tapered portions T is formed above the corresponding lower slit SL 11  or SL 12 ; the two tapered portions T in each of the pairs have respective upper surfaces that slant inwardly and downwardly to gradually approach each other in a top-to-bottom direction. Distance between the two tapered portions T in each of the pairs is set greater than the thickness of the corresponding analog circuit board  51  or digital circuit board  52 . 
   Each of the lower bosses  16  is provided on the bottom plate  11  to project upwardly toward the upper case  20 . Each of the lower bosses  16  has a threaded hole h 1  formed therethrough in the vertical direction Y 5 . In the illustrated example, six such lower bosses  16  are provided in a row in the key-arranged directions Y 3 , Y 4 . 
   Next, a construction of the upper case  20  will be detailed in detail. As shown in  FIG. 1A , the upper case  20  has a back downwardly-extending wall section  23 , front downwardly-extending wall section  24  and left and right downwardly-extending wall sections  25 . The upper plate  21  has a keyboard opening  21 A for exposing the keyboard unit  30 , and a speaker opening  21 B for exposing a speaker (not shown). The back downwardly-extending wall section  23  extends downward from the edge of a remote-from-player-side (Y2-side) portion of the upper plate  21 . The front downwardly-extending wall section  24  extends downward from the edge of a player-side (Y1-side) portion of the upper plate  21 . Further, the left and right downwardly-extending wall sections  25  extend upwardly from the edge of left and right longitudinal end portions, in the key-arranged direction Y 3 , Y 4 , of the upper plate  21 . 
   The upper case  20  has two pairs of second (or upper) circuit-board holding sections  261  and  262 , and upper bosses  26 . The second circuit-board holding sections  261  for sandwichingly holding the upper edge portion E 1  of the analog circuit board  51  are disposed in spaced-apart alignment along the key-arranged direction Y 3 , Y 4 . The second circuit-board holding sections  262  for sandwichingly holding the upper edge portion E 1  of the digital circuit board  52  are disposed in spaced-apart alignment along the key-arranged direction Y 3 , Y 4 . 
   As illustratively shown in  FIGS. 1A and 1B  and  4 , each of the second circuit-board holding sections  261  has an upper projecting portion  26 A that has an upper slit  26 B formed therein. Each of the second circuit-board holding sections  262  is similar in construction to the second circuit-board holding sections  261  and will not be described to avoid unnecessary duplication. The upper projecting portion  26 A is formed on a portion of the upper plate  21  located remote from the human player, i.e. on a remote-from-player-side portion of the upper plate  21  between the keyboard unit  30  and the back downwardly-extending wall section  23 , and projects downwardly toward the lower case  10 . The upper slit  26 B is open downwardly (i.e., toward the lower case  10 ) and extends through the corresponding projecting portion in the key-arranged direction Y 3 , Y 4 . The upper slit  26 B has a slit width substantially equal to the thickness of the corresponding circuit board  51  or  52 . 
   The upper bosses  26  are provided on the reverse or underside of the upper plate  21  to project downwardly toward the lower case  10 . The upper bosses  26  are formed at predetermined positions such that they are aligned with and placed on the corresponding lower bosses  16  of the lower case  10  as the upper case  20  and lower case  10  are assembled together in overlapped relation to each other. 
   The following paragraphs describe the analog circuit board  51  and digital circuit board  52  to be housed in the upper case  20  and lower case  10  of the structure. The analog circuit board  51  and digital circuit board  52  are each in the shape of a rectangular plate as viewed from the front. Heat radiating plate  55  is attached to the analog circuit board  51 , as shown in  FIGS. 2 and 4 . 
   As shown in  FIG. 2 , the heat radiating plate  55  is in the form of a metal plate, which has concave and convex portions alternating in the key-arranged direction Y 3 , Y 4 . The concave and convex portions are formed by bending the metal plate. The heat radiating plate  55  is positioned on a remote-from-player side (Y2-side) of the analog circuit board  51 . The heat radiating plate  55  is fixed in opposed relation to the analog circuit board  51  in such a manner that through-holes (through-passage spaces)  60  extending in the vertical direction Y 5  are formed between the analog circuit board  51  and the concave and convex portions of the plate  55 . Thus, the heat radiating plate  55  is positioned in such a manner that its surface B faces in the direction Y 2  opposite from the human player. 
   Further, a plurality of heat radiating holes  17  for radiating heat, produced from the analog circuit board  51 , to outside of the upper case  20  and lower case  10  are formed in portions of the bottom plate  11  and back upwardly-extending wall section  12  located near the analog circuit board  51 . Namely, the heat radiating holes  17  are provided in the portion of the back upwardly-extending wall section  12  opposed to the surface B of the heat radiating plate  55 . 
   Tapes (resilient or cushioning members)  70 , each made of a resilient material, are affixed to portions of the analog circuit board  51  and digital circuit board  52  to be sandwiched by the first circuit-board holding sections  151 R,  151 L,  152 R,  152 L and second circuit-board holding sections  261 ,  262 . 
   The following lines describe an operation-section circuit board  53  housed in the upper and lower cases  20  and  10  constructed in the aforementioned manner. The operation section  22  includes the operation-section circuit board  53 , which is screwed to the lower surface of the upper plate  21  in parallel relation to the latter. Wiring section L drawn out from the operation section  22  is wired beneath and along the lower surface of the upper plate  21  and connected to the analog circuit board  51  and digital circuit board  52 , as shown in  FIG. 1A . Namely, the wiring section L has a portion wired to pass across a neighborhood of the upper end surface of the heat radiating plate  55 . The portion of the wiring section L, wired to pass across the neighborhood of the upper end surface of the heat radiating plate  55 , would be adversely influenced by heat produced from the analog circuit board  51  and flowing within the through-holes  60  in a bottom-to-top direction of the through-holes  60 , so that inconveniences would be produced in the wiring section L. 
   Thus, in the instant embodiment of the invention, a heat blocking plate  54  is provided adjacent to the portion of the wiring section L disposed in the neighborhood of the upper end surface of the heat radiating plate  55  so that the wiring section L can be prevented from being influenced by the heat. The heat blocking plate  54  is mounted to the upper plate  21  by screwing with the wiring section L interposed between the heat blocking plate  54  and the upper plate  21 . For this purpose, there may be used a circuit board blank integrally having a circuit board portion for the heat blocking plate  54  and a circuit board portion for the operation-section circuit board  53  with a perforated line therebetween, in which case the heat blocking plate  54  is cut or separated from the operation-section circuit board  53  along the perforated line. In other words, the heat blocking plate  54  is provided by being initially formed integrally with the operation-section circuit board  53  with a perforated line therebetween and then cut from the operation-section circuit board  53  along the perforated line. 
   As shown in  FIG. 4 , the keyboard unit  30 , housed in the upper and lower cases  20  and  10  constructed in the aforementioned manner, includes a plurality of black keys  31  and white keys  32  arranged in the key-arranged direction Y 3 , Y 4 , and a switch circuit board  33 . The switch circuit board  33  includes a plurality of switches each of which is turned on in response to depression of a corresponding one of the black and white keys  31  and  32 . 
   The following lines describe a sequence of operations for assembling the structure for an electronic keyboard instrument constructed in the aforementioned manner. First, the wiring section L, drawn out from the operation section, is wired beneath and along the lower surface of the upper plate  21  in advance. Then, the circuit board blank, integrally having the circuit board portions for the heat blocking plate  54  and operation-section circuit board  53 , is fixed by screwing to the lower surface of the upper plate  21  with the wiring section L interposed between the heat blocking plate  54  and the upper plate  21 . After that, the circuit board blank is cut along the perforated line to be separated into the heat blocking plate  54  and operation-section circuit board  53 . 
   Then, the heat radiating plate  55  is fixed to the analog circuit board  51  in overlapped relation to one side or surface of the analog board  51  so that the through-holes  60  extending in the vertical direction Y 5  are formed between the analog circuit board  51  and the concave and convex portions of the heat radiating plate  55 . The tapes (resilient or cushioning members)  70  are affixed to the portions of the analog circuit board  51  and digital circuit board  52  to be sandwiched by the first circuit-board holding sections  151 R,  151 L,  152 R,  152 L and second circuit-board holding sections  261 ,  262 . Then, the respective upper edge portions E 1  of the analog circuit board  51  and digital circuit board  52  are inserted into the upper slits  26 B, formed in the upper projecting portions  26 A, in such a manner that they are sandwiched or held by the upper projecting portions  26 A of the second (or upper) circuit-board holding sections  261  and  262 ; at that time, the upper edge portion E 1  of the analog circuit board  51  is held by the upper projecting portions  26 A in such an orientation where the heat radiating plate  55 , mounted to the analog circuit board  51 , is located remote from the human player. 
   After that, the upper case  20  is overlapped from above on upper-end peripheral regions of the lower case  10  in such a manner that the respective lower edge portions E 1  of the analog circuit board  51  and digital circuit board  52  are sequentially inserted in the first lower slits SL 11  and second lower slits SL 12  and the analog circuit board  51  and digital circuit board  52  are inserted between the corresponding opposed positioning wall portions  15 C. More specifically, the analog circuit board  51  and digital circuit board  52  are first inserted in the first lower slits SL 11  and thereby sandwichingly held (i.e., provisionally secured) by the first lower projecting portions  15 A. At that time, the analog circuit board  51  and digital circuit board  52  can be readily introduced into the first lower slits SL 11  by being guided along the tapered portions T formed in the first lower projecting portions  15 A. 
   After that, the analog circuit board  51  and digital circuit board  52  are inserted into the second lower slits SL 12  and thereby sandwichingly held by the second lower projecting portions  15 B. At that time, the analog circuit board  51  and digital circuit board  52  can be readily introduced into the second lower slits SL 12  by being guided along the tapered portions T formed in the second lower projecting portions  15 B. 
   Then, the upper case  20  and lower case  10  are secured or fastened together by screws (fastening elements) inserted from below the lower case  10 , through the screw holes h 1  of the lower bosses  16 , into screw holes h 2  of the upper bosses  26 . In this manner, the assembly of the structure for an electronic keyboard instrument is completed. 
   According to the above-described inventive structure for an electronic keyboard instrument, the upper case  20  and lower case  10  are fixed together by screwing with the upper case  20  overlapped on the upper-end peripheral regions of the lower case  10  in such a manner that the respective edge portions E 1  of the analog circuit board  51  and digital circuit board  52  are inserted in the first and second lower slits SL 11  and SL 12  and the upper slits  26 B and thereby sandwichingly held by the first and second projecting portions  15 A and  15 B and upper projecting portions  26 A. The analog circuit board  51  and digital circuit board  52  can be sandwichingly held, in the vertical direction Y 5 , between the upper case  20  and the lower case  10  in the aforementioned manner, and thus, no separate screwing operation is required for attaching the analog circuit board  51  and digital circuit board  52  to the upper and lower cases  20  and  10 . Further, because the analog circuit board  51  and digital circuit board  52  can be mounted to the upper and lower cases  20  and  10  as the upper case  20  is mounted to the lower case  10 , the necessary assembling work can be performed easily in a simplified manner. Further, the analog circuit board  51  and digital circuit board  52  can function to mechanically reinforce the upper and lower cases  20  and  10  in the vertical direction Y 5 , so that the upper and lower cases  20  and  10  can be reliably prevented from deforming due to external force. Furthermore, because the upper and lower edge portions E 1  of the analog circuit board  51  and digital circuit board  52  are sandwichingly held by the first and second projecting portions  15 A and  15 B and upper projecting portions  26 A, the two circuit boards  51  and  52  can be reliably prevented from filling in the front-back direction and thus can be securely fixed within the upper and lower cases  20  and  10 . 
   Furthermore, with the above-described inventive structure for an electronic keyboard instrument, where the heat radiating plate  55  is provided on the remote-from-player side (Y2-side) of the analog circuit board  51  and the surface B of the heat radiating plate  55  faces away from the player side (i.e., in the direction of arrow Y 2 ), it is possible to prevent heat from being trapped in the keyboard unit  30 . If the heat radiating plate  55  is disposed between the analog circuit board  51  and the keyboard unit  30 , for example, heat would be trapped in the keyboard unit  30 , so that imbalanced heat distribution would occur in a frame (that is formed of, for example, resin) of the keyboard unit  30 . As a consequence, the frame of the keyboard unit  30  twists and the keyboard unit  30  loses flatness, so that uniformity among touch responses of the individual keys would be lowered and the performance capability of the keyboard would deteriorate. However, because the instant embodiment of the structure can prevent heat from being trapped in the keyboard unit  30 , it can effectively prevent the uniformity among the touch response of the individual keys and performance capability of the keyboard from deteriorating due to heat from the analog circuit board  51 . 
   Moreover, according to the above-described inventive structure for an electronic keyboard instrument, the heat radiating holes  17  are provided in a portion of the back upwardly-extending wall section  12  opposed to the heat radiating plate  55 , and such heat radiating holes  17  can even further enhance the heat-radiating effect. 
   Furthermore, according to the above-described inventive structure, the heat radiating plate  55  is fixed to the analog circuit board  51  in overlapped relation thereto so that the through-holes  60  extending in the vertical direction Y 5  are formed between the analog circuit board  51  and the concave and convex portions of the heat radiating plate  55 , and thus, the analog circuit board  51  can be reinforced by the heat radiating plate  55 . As a result, the analog circuit board  51  can even further reinforce the upper and lower cases  20  and  10 , so that the cases  20  and  10  can be even more effectively prevented from deforming due to external force. In addition, because the through-holes (through-passage spaces)  60  form air passageways in the vertical direction Y 5 , it can even further enhance the heat-radiating effect. 
   Furthermore, according to the above-described inventive structure, the openings of the first lower slits SL 11  are located closer to the upper case  20  than the openings of the second lower slits SL 12 , so that the analog circuit board  51  and digital circuit board  52  can be inserted first into the first lower slits SL 11  and then into the second lower slits SL 12 . With such first and second lower slits SL 11  and SL 12  permitting insertion therein of the analog and digital circuit boards  51  and  52  with a time difference, the analog and digital circuit boards  51  and  52  can be attached smoothly to the lower case  10 . Further, the first and second lower slits SL 11  and SL 12  can cooperate to properly align the analog and digital circuit boards  51  and  52  in the front-back-direction (i.e., thickness direction of the circuit boards  51  and  52 ). 
   Furthermore, according to the above-described inventive structure, the first and second lower slits SL 11  and SL 12  are arranged in alignment along the key-arranged direction Y 3 , Y 4 , and thus, the analog and digital circuit boards  51  and  52  can be attached to the lower case  10  even more smoothly. Moreover, the provision of two, or a plurality of, second lower projecting portions  15 B and second lower slits SL 12  allow the analog and digital circuit boards  51  and  52  to be attached to the lower case  10  even more smoothly. Furthermore, with the two second lower slits SL 12  arranged in the extending direction Y 6  (i.e., key-arranged direction Y 3 , Y 4 ), the analog and digital circuit boards  51  and  52  can be attached to the lower case  10  even more smoothly. 
   Furthermore, according to the above-described inventive structure, the tapes (resilient members or cushioning members)  70  are affixed to the portions of the analog circuit board  51  and digital circuit board  52 , and thus, the analog and digital circuit boards  51  and  52  can be securely fixed within the first and second lower slits SL 11  and SL 12  with no wobble. Consequently, it is possible to prevent mechanical noise from being produced in tones generated by the keyboard instrument and thereby prevent generation of buzzer-like sound noise. 
   Moreover, according to the above-described inventive structure, the provision of the positioning wall portions  15 C allow the first and second lower slits SL 11  and SL 12  to be properly positioned in the key-arranged direction Y 3 , Y 4 . Besides, with the integral formation, via the connecting wall portion  15 D, of the first and second lower projecting portions  15 A and  15 B, positioning wall portion  15 C, the positioning wall portion  15 C and first and second lower projecting portions  15 A and  15 B can be effectively reinforced. 
   Furthermore, the heat blocking plate  54 , mounted to the upper plate  21  with the wiring section L interposed between the heat blocking plate  54  and the upper plate  21 , is provided on a portion of the wiring section L which is wired to pass across a neighborhood of the upper end surface of the heat radiating plate  55 . Consequently, the heat blocking plate  54  can block transfer of heat from the heat radiating plate  55 , and thus, it is possible to prevent inconveniences from being produced in the wiring section L due to influences of the heat from the heat radiating plate  55 . 
   Moreover, because the heat blocking plate  54  is provided by being cut, along the perforated line, from the circuit board blank integrally having circuit board portions for the heat blocking plate  54  and operation-section circuit board  53 , it is possible to prevent the heat blocking plate  54  from being lost if it is kept integral with the operation-section circuit board  53  on the blank until the operation-section circuit board  53  and heat blocking plate  54  are attached to the upper and lower cases  20  and  10 . 
   Whereas the lower case  10  in the above-described embodiment has the back upwardly-extending wall section  12 , the present invention is not so limited. For example, the lower case  10  may have an opening formed in the remote-from-player-side portion thereof, and the upper case  20  may have a back plate to close the opening formed in the remote-from-player-side portion of the lower case  10 . Namely, as long as the lower case  10  has at least the bottom plate  11  while the upper case  21  has at least the upper plate  21  and the upper case  20  is mountable from above to the lower case in overlapped relation thereto, the shapes of the two cases  20  and  10  are not limited to those in the above-described embodiment. 
   Furthermore, according to the above-described inventive structure, the bottom plate  11  of the lower case  10  has the first and second lower projecting portions  15 A and  15 B with the first and second lower slits S 11  and S 12  formed therein, but the present invention is not so limited. For example, if the bottom plate  11  has a sufficient thickness, the first and second lower slits S 11  and S 12  may be formed directly in the bottom plate  11  without the first and second lower projecting portions  15 A and  15 B being provided. 
   Moreover, according to the above-described inventive structure, the upper plate  21  of the upper case  10  has the upper projecting portions  26 A each with the upper slit  26 B formed therein, the present invention is not so limited. For example, if the upper plate  21  has a sufficient thickness, the upper slits  26 A may be formed directly in the upper plate  21  without the upper projecting portions  26 A being provided. 
   Furthermore, whereas the heat radiating plate  55  in the above-described embodiment is provided on the remote-from-player side of the analog circuit board  51  in such a manner that the surface B faces away from the player side (i.e., in the direction of arrow Y 2 ), the present invention is not so limited, and the shape and position of the heat radiating plate  55  are not limited to those in the above-described embodiment. 
   Furthermore, whereas each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L in the above-described embodiment has two second lower projecting portions  15 B and two second lower slits SL 12 , the present invention is not so limited. For example, each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L may have only one or more than two second lower projecting portions  15 B and second lower slits SL 12 . 
   Furthermore, whereas each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L in the above-described embodiment has the second lower projecting portions  15 B and second lower slits SL 12 , the present invention is not so limited. For example, each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L may have no such lower projecting portion  15 B and second lower slit SL 12 . 
   Moreover, whereas the positioning wall portion  15 C and first and second lower projecting portion  15 A and  15 B are interconnected via the connecting wall portion  15 D in the above-described embodiment, the present invention is not so limited. If the positioning wall portion  15 C and first and second lower projecting portion  15 A and  15 B each have a sufficient mechanical strength, for example, they need not necessarily be interconnected via the connecting wall portion  15 D. 
   Furthermore, whereas each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L in the above-described embodiment has the positioning wall portion  15 C, the present invention is not so limited. For example, each of the circuit-board holding sections  151 R,  151 L,  152 R and  152 L need not have the positioning wall portion  15 C. 
   Moreover, whereas the heat blocking plate  54  in the above-described embodiment is provided by being cut, along the perforated line, from the circuit board blank integrally having circuit board portions for the heat blocking plate  54  and operation-section circuit board  53 , the present invention is not so limited, and the heat blocking plate  54  and the operation-section circuit board  53  may be fabricated separately. 
   Furthermore, in the above-described embodiment, the tapes  70  are affixed, as the resilient or cushioning means, to the outer surfaces of the analog circuit board  51  and digital circuit board  52 . However, the present invention is not so limited; for example, such tapes  70  may be affixed to the inner surfaces of the first and second lower slits SL 11  and SL 12  and upper slits  26 B. 
   Moreover, the first circuit-board holding sections  151 R,  151 L,  152 R and  152 L and the second circuit-board holding sections  261  and  262  are not limited to those in the above-described embodiment. For example, the analog circuit board  51  and digital circuit board  52  may each be sandwichingly held in the thickness direction by at least one of the first and second lower projecting portions  15 A and  15 B and the upper projecting portions  26 A. In such a case, each of the first and second lower projecting portions  15 A and  15 B is tapered in such a manner that the slit formed therein has a width gradually decreasing in the downward direction, while each of the upper projecting portions  26 A is tapered in such a manner that the slit formed therein has a width gradually decreasing in the upward direction. By pressing the analog circuit board  51  and digital circuit board  52  into such first and second lower slits SL 11  and SL 12  and upper slits  26 B, it is possible to prevent buzzer-like sound noise during generation of tones, even without the above-mentioned tapes (resilient means)  70 . 
   Furthermore, in the above-described embodiment, the lower and upper edge portions E 1  of the analog and digital circuit boards  51  and  52  are held in contact with the bottom surfaces of the first and second lower slits SL 11  and SL 12  and upper slits  26 B, respectively. However, the present invention is not so limited. For example, the analog circuit board  51  and digital circuit board  52  may be sandwichingly held in the thickness direction by the first and second lower projecting portions  15 A and  15 B and upper projecting portions  26 A with their edges spaced from at least one of the bottom surfaces of the first and second lower slits SL 11  and SL 12  and the bottom surfaces of the upper slits  26 B. In such a case, a rubber adhesive agent may be poured into the gaps formed between the edges of the analog circuit board  51  and digital circuit board  52  and the bottom surfaces of the first and second lower slits SL 11  and SL 12  and/or the bottom surfaces of the upper slits  26 B; thus, the analog and digital circuit boards  51  and  52  can be securely fixed within the first and second lower slits SL 11  and SL 12  and the analog and digital circuit boards  51  and  52  can be securely fixed within the first and second lower slits SL 11  and SL 12  with no wobble, so that it is possible to prevent buzzer-like sound noise during generation of tones generated by the keyboard instrument. 
   Whereas the foregoing have described representative preferred embodiments of the present invention, various other modifications are also possible without departing from the basic concept of the present invention. 
   This application is based on, and claims priority to, JP PA 2007-000837 filed on 5 Jan. 2007 and JP PA 2007-000838 filed on 5 Jan. 2007. The disclosure of the priority applications, in its entirety, including the drawings, claims, and the specification thereof, is incorporated herein by reference.