Patent Publication Number: US-6670532-B2

Title: Legs formed from laminated woody board and keyboard musical instrument using the same

Description:
FIELD OF THE INVENTION 
     This invention relates to a keyboard musical instrument and, more particularly, to a leg for supporting a musical instrument and a keyboard musical instrument having a case supported by legs on a floor. 
     DESCRIPTION OF THE RELATED ART 
     An acoustic piano is a typical example of the keyboard musical instrument. The acoustic piano is broken down into a keyboard, piano case and tone generating mechanism. Key actions, hammers, dampers and strings form parts of the tone generating mechanism. The tone generating mechanism is accommodated in the piano case, and is actuated with the keys for generating tones. The keys are laid on the well-known black-and-white pattern, and are essential parts of the keyboard. The keyboard is mounted on the key bed which forms a part of the piano case, and is exposed to a pianist for fingering. 
     FIG. 1 shows a typical example of the grand piano. Reference numerals  100 ,  120  and  140  designate the piano case, the keyboard and the tone generating mechanism, respectively. The piano case  100  has a case body  101  and three legs  102 . A key bed  101   a  and a frame (not shown) define the bottom of the piano case  100 , and a side board  101   b  extends along the periphery of the key bed  101   a  and the frame. Thus, the key bed  101   a , the frame and the side board  101   b  define an inner space of the case body  101 , and permits the manufacturer to install the tone generating mechanism  140  in the case body  101 . A top board  108  is hinged to the side board  101   b , and is opened and closed. 
     Three legs  102  are arranged at the vertexes of a triangle under the case body  101 . Two legs  102  are arranged in substantially parallel, and are directly bolted to the key bed  101   a . The remaining leg  102  is provided at the back of the two legs  102 , and is fixed to the frame. 
     The leg  102  is not a monolithic body. Various woody parts are assembled into the leg  102  as shown in FIG. 2. A leg column  103 , a leg block  104  and a caster  105  are the essential parts of the leg  102 . The leg column  103  and the leg block  104  are formed of wood. The leg column  103  is an inverted prismoid. A tenon  103 A is formed on the relatively wide top surface, and the caster  105  is attached to the relatively narrow bottom surface of the leg column  103 . The tenon  103 A is a short cylindrical projection, and two slits  103 B are formed in the tenon  103 A. The slits  103 B extend across the upper surfaces of the tenon  103 A in parallel to each other, and are exposed to the side surface of the tenon  103 A. The leg block  104  has an anvil-like configuration. The leg block  104  is gently increased in thickness from both ends toward the mid portion, and a cylindrical hole  104 A is formed in the mid portion. The cylindrical hole  104 A is open to both of the upper and lower surfaces of the mid portion, and is equal in diameter to the tenon  103 A. A pair of through-holes  104 B is formed in the leg block  104 . The through-holes  104 B are provided on both sides of the cylindrical hole  104 A. Though not shown in the drawings, threaded holes are formed in the key bed  101 A, and are spaced equally to the through-holes  104 B. 
     The leg column  103  and the leg block  104  are assembled into the leg  102  as follows. First, the worker aligns the tenon  103 A with the cylindrical hole  104 A, and inserts the tenon  103 A into the cylindrical hole  104 A. The lower surface of the leg block  104  is brought into contact with the upper surface of the leg column  103 , and the upper surface of the tenon  103 A becomes coplanar with the upper surface of the leg block  104 . The worker pushes the edge of a wedge  107  into one of the slits  103 B, and another wedge  107  into the other slit  103 B. The worker strikes the wedges  107  with a hammer, by way of example. Then, the wedges  107  are implanted into the tenon  103 A, and expands the slits  103 B. The upper portion of the tenon  103  is pressed against the inner surface of the leg block  104 , and the leg block  104  is fixed to the leg column  103 . 
     The leg  102  thus assembled is fixed to the key bed  101   a  as follows. The worker aligns the through-holes  104 B with the threaded holes formed in the key bed  101   a . The worker inserts a bolt  106  into one of the through-holes  104 B, and screws the bolt  106  into the threaded hole. Similarly, the worker inserts another bolt  106  into the other of the through-holes  104 B, and screws the bolt  106  into the other threaded hole. Thus, the leg block  104  is bolted to the key bed  101   a , and the leg  102  downwardly projects from the case body  101 . 
     A problem is encountered in the prior art keyboard musical instrument in that the piano case  100  is liable to be rickety. 
     SUMMARY OF THE INVENTION 
     It is therefore an important object of the present invention to provide a keyboard musical instrument the case of which is steady and durable. 
     The present inventor contemplated the problem encountered in the prior art keyboard musical instrument, and noticed that the wedges  107  failed to work. The present inventor reasoned that the connection between the tenon  103 A and the leg block  104  was repeatedly subjected to the bending moment. When the user wanted to relocate the prior art keyboard musical instrument, he or she pushed the case body  101 , and exerted force thereon. The force gave rise to rotation of the casters  105 , and the prior art keyboard musical instrument slid on the floor. However, the casters  105  were vertically spaced from the case body  101  on which the force was exerted. This resulted in that bending moment was exerted on the connection between the tenon  103 A and the leg block  104 . The slits  103 B were strangulated, and, accordingly, the wedges  107  were partially pushed out. As a result, the tenon  103 A was loosened, and the piano case  101  became rickety. 
     A solution had been proposed. Plural bolts were embedded into the upper portion of the leg column  103 , and through-holes were formed in the leg block  104 . The bolts were inserted into the through-holes, and projected over the leg block  104 . The worker turned nuts on the bolts, and held the bolts in their places with nuts. However, the solution was costly and risky. Time and labor were consumed in the implantation of the bolts into the leg column  103 . This resulted in the high production cost. Moreover, the leg column  103  was not thick enough to receive the plural bolts. When the worker compelled the leg column  103  to receive plural bolts, extremely thin peripheral portion took place between the implanted bolt and the outer surface of the leg column  103 , and was liable to be broken under the application of the bending moment. The present inventor concluded that a monolithic leg was preferable. However, a monolithic leg shaped from a piece of wood was extremely expense. 
     To accomplish the object, the present invention proposes to form laminated members into a core of a leg. 
     In accordance with one aspect of the present invention, there is provided a leg incorporated in a keyboard musical instrument, and the leg comprises plural plates laminated on one another and assembled into a core and a coupling means for fixing the core to a body of the keyboard musical instrument. 
     In accordance with another aspect of the present invention, there is provided a keyboard musical instrument comprising a case having an inner space, a keyboard mounted on the case and having keys assigned notes of a scale, a tone generating mechanism accommodated in the inner space and connected to the keyboard for generating tones with the notes and plural legs, and each of the legs includes plural plates laminated on one another and assembled into a core and a coupling means for fixing the core to the body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the keyboard musical instrument will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view showing the external appearance of the prior art grand piano; 
     FIG. 2 is a fragmentary perspective view showing the parts to be assembled into the leg; 
     FIG. 3 is a perspective view showing the external appearance of a keyboard musical instrument according to the present invention; 
     FIG. 4 is a perspective view showing the structure of a core forming a part of a leg incorporated in the keyboard musical instrument; 
     FIGS. 5A to  5 D are perspective views showing a process for fabricating the leg according to the present invention; 
     FIG. 6 is a fragmentary perspective view showing a glued laminated woody member forming a part of a core of a leg incorporated in another keyboard musical instrument according to the present invention; 
     FIG. 7 is a fragmentary perspective view showing a glued laminated woody member forming a part of a core of a leg incorporated in yet another keyboard musical instrument according to the present invention; and 
     FIG. 8 is a perspective view showing a step incorporated in another process for fabricating a leg according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Referring first to FIG. 3 of the drawings, a grand piano embodying the present invention largely comprises a piano case  10 , a keyboard  30  and a tone generating mechanism  40 . In the following description, word “front” indicates a position closer to a pianist fingering a piece of music on the keyboard  30  than another position modified with word “rear”. 
     The keyboard  30  includes plural black keys  31  and white keys  32 , and these black and white keys  31 / 32  are laid on the well-known pattern. While a pianist is playing a tune on the keyboard  30 , the pianist selectively depresses the black and white keys  31 / 32 , and the depressed keys  31 / 32  actuate the tone generating mechanism  40  for generating tones. 
     The tone generating mechanism  40  includes key actions, hammers, dampers and strings. The key actions are linked with the black and white keys  31 / 32 , and are selectively actuated by the depressed keys  31 / 32 . The key actions are engaged with the hammers, and the hammers are driven for rotation through an escape by the associated key actions linked with the depressed keys  31 / 32 . The dampers are held in contact with the associated strings in so far as the associated keys  31 / 32  are staying at the rest positions. When the pianist depresses a black or white key  31 / 32 , the associated key action causes the damper to be spaced from the string before the escape. Thus, the damper allows the string to vibrate before the rotation of the hammer. The hammer travels in the trajectory toward the string, and strikes the associated string. The string vibrates so as to generate the tone. The hammer rebounds on the string, and returns toward the key action. When the pianist releases the depressed key, the black/ white key  31 / 32  returns toward the rest position, permits the hammer and the key action to return to the rest positions. 
     The piano case  10  is broken down into legs  1 , case body  20  and a top board  25 . The case body  20  is supported by three legs  1 , and has an upper opening. The top board  25  is hinged to the case body  20 , and is opened and closed by the pianist. 
     A key bed  21  and frame (not shown) define the bottom of the case body  20 , and a side board  23  extends along the periphery of the bottom. Thus, the key bed  21 , the frame and the side board  23  defines an inner space of the case body  20 . The tone generating mechanism  40  is accommodated in the inner space. The keyboard  30  is mounted on a front portion of the key bed  21 , and the tone generating mechanism  40  occupies the inner space over the rear portion of the key bed  21 . 
     The legs  1  downwardly project from the case body  20 , and occupy the vertexes of a triangle. Namely, two legs  1  are fixed to the key bed  21 , and the other leg  1  is fixed to the frame. The three legs  1  are similar in structure to one another, and description is made on one of the legs  1  with reference to FIG.  4 . 
     The leg  1  is broken down into a core  1 A, a caster  3  and a pair of decorative panels  5  (see FIG.  5 D). The core  1 A consists of a pair of glued laminated woody members  2 . Each of the glued laminated woody members  2  is formed from a plurality of thin wood plates P 1 , P 2 , . . . and Pn or plywood. Plural sheets of veneer may be used as the plurality of thin wood plates P 1 , P 2 , . . . and Pn. The plural thin wood plates P 1 , P 2 , . . . and Pn are concentrically curved, and are laminated on one another. The thin wood plates P 1 , P 2 , . . . and Pn are glued with adhesive compound. The glued laminated woody members  2  have an inverted L-letter shape, and have respective long portions  2 A and respective short portions  2 B. The glued laminated woody members  2  are directed in such a manner that the long portions  2 A are faced in the opposite directions, and are fixed to each other. Thus, the glued laminated woody members  2  are symmetrically arranged with respect to the contact surface between the long portions  2 A, and are assembled into the core  1 A. The decorative panels  5  have a contour corresponding to the front and back surfaces of the core  1 A. One of the decorative panels  5  is adhered to the front surface of the core  1 A, and the other decorative panel  5  is adhered to the back surface. Thus, the decorative panels  5  put the boundaries between the plural thin wood plates P 1 , P 2 , . . . and Pn out of sight. 
     Through-holes  2 C are formed in the short portions  2 B, and permit bolts to pass therethrough. The bolts are corresponding to the bolts  106 , and serve as a coupling means. The short portions  2 B are held in contact with the lower surface of the key bed  21  or the frame, and the core  1 A is fixed to the key bed  21  or the frame by means of the bolts together with the decorative panels  5 . The caster  3  is fixed to the lower surface of the core  1 A. 
     As will be understood, the monolithic legs  1  are used in the grand piano according to the present invention. The monolithic leg  1  is equivalent to the leg column  103  and the leg block  104 . However, any coupling means such as the tenon  103 A, the through-hole  104 A and the wedges  107  are not required. For this reason, even though the bending moment is exerted on the legs  1  during the relocation of the grand piano, the bolts well withstand the bending moment without looseness. Thus, the grand piano according to the present invention is steady and durable. 
     The monolithic leg  1  is fabricated through a process according to the present invention. FIGS. 5A to  5 D show the process sequence. First, straight thin wood plates SP 1 , . . . and SPn are prepared as shown in FIG.  5 A. The straight thin wood plates SP 1 , . . . and SPn may be shaped by using a wood working machine or a blanking. The straight thin wood plate SP 1 / . . . /SPn is partially constant in width, and the remaining portion  2 A is tapered toward the other end. The constant width portions  2 B are corresponding to the short portions  2 B of the glued laminated woody members  2 , and the tapered portions  2 A are corresponding to the long portions  2 A of the glued laminated woody members  2 . 
     Subsequently, adhesive compound is spread over the contact surfaces of the straight thin wood plates SP 1 , . . . and SPn, and the straight thin wood plates SP 1 , . . . and SPn are placed in a bending press machine. Force F is exerted on the straight thin wood plates SP 1 , . . . and SPn, and are formed into the glued laminated woody member  2  as shown in FIG.  5 B. The constant width portions  2 B are formed into the short portion  2 B corresponding to the leg block  104 , and the tapered portions  2 A are formed into the long portion  2 A corresponding to the leg column  103 . 
     Subsequently, adhesive compound is spread over the back surfaces of the glued laminated woody members  2 , and the glued laminated woody members  2  are assembled in such a manner that the long portions  2 A are brought into back-to-back contact with each other as shown in FIG.  5 C. The glued laminated woody members  2  are clamped under application of force P. The adhesive compound fixes the glued laminated woody members  2  to each other, and the core  1 A is obtained. 
     The caster  3  is fixed to the bottom surface of the core  1 A, and the decorative panels  5  are adhered to the front and back surfaces of the core  1 A as shown in FIG.  5 D. Thus, the core  1 A, the caster  3  and the decorative panels  5  are assembled into the monolithic leg  1 . 
     As will be appreciated, the monolithic leg  1  is obtained through the wood machining, bending press and adhesion. These steps are less expensive rather than the shaping from a piece of wood. Thus, the monolithic leg  1  is lower in production cost than a monolithic leg  1  shaped from a piece of wood. 
     Second Embodiment 
     Turning to FIG. 6 of the drawings, a reinforcing sheet  4  is inserted between the thin wood plate P 2  and P 2 +1. The thin wood plate P 2 +1 is not shown in FIG. 6, and the reinforcing sheet  4  is hatched for easily discriminating it. Although only one reinforcing sheet  4  is shown, more than one reinforcing sheet  4  may be inserted into the set of thin wood plates P 1 , P 2 , . . . and Pn. The reinforcing sheet  4  is shaped as similar to the thin wood plates P 1 , P 2 , . . . and Pn. Any kind of material is available for the reinforcing plate  4  in so far as the reinforcing sheet  4  of the selected material enhances the mechanical strength of the monolithic leg implementing the second embodiment. The reinforcing sheet  4  is flexible or rigid. However, it is preferable to shape a sheet of selected material into the contour same as the thin wood plates P 1 , P 2 , . . . and Pn. A sheet of metallic fiber fabric, a sheet of synthetic resin fiber fabric, a sheet of carbon fiber fabric and a sheet of carbon fiber reinforced synthetic resin is, by way of example, appropriate for the sheet to be shaped into the reinforcing sheet  4 . 
     The reinforcing sheet or sheets  4  and the thin wood plates P 1 , P 2 , . . . and Pn are formed into the glued laminated woody member  2 , and a pair of glued laminated woody members  2  are assembled into the core  1 A. The caster  3  is fixed to the lower surface of the core  1 A, and the decorative panels  5  are adhered to the front and back surfaces of the core  1 A as similar to the leg  1  of the first embodiment. 
     The monolithic legs implementing the second embodiment are bolted to the case body  20  of the grand piano. Since the monolithic legs are enhanced in mechanical strength, the grand piano is further steady and durable. 
     Third Embodiment 
     Turning to FIG. 7, a pair of glued laminated woody members  2 D and a reinforcing block  6  are assembled into a core  1 D. Straight thin wood plates are twice bent, and are adhered to one another. A reinforcing sheet or sheets may be inserted into the set of thin wood plates. Adhesive compound is spread over the back surface of the glued laminated timbres  2 D, and the glued laminated woody members  2 D are brought into back-to-back contact with one another. When the adhesive compound is cured, the glued laminated woody members  2 D are assembled like a Y-letter, and the short portions  2 B are spaced from each other. Thus, a trigonal prism-like space takes place between the short portions  2 B. The reinforcing block  6  has the contour corresponding to the trigonal prism-like space. When the reinforcing block  6  is inserted into the trigonal prism-like space, the sloping surfaces of the reinforcing block  6  are held in face-to-face contact with the oblique surfaces between the long portions  2 A and the short portions  2 B. The reinforcing block  6  is adhered to the oblique surfaces of the core  1 D. 
     Though not shown in FIG. 7, a caster is fixed to the lower surface of the core  1 D. Decorative panels  5 A are adhered to the front surface and the black surface of the core  1 D. The monolithic legs implementing the third embodiment are fixed to the case body  20  of a keyboard musical instrument, and render the keyboard musical instrument steady and durable. 
     The reinforcing block  6  enhances the mechanical strength of the monolithic leg, and is, accordingly, desirable. The monolithic leg implementing the third embodiment has external appearance like the conventional leg  102 . 
     As will be appreciated from the foregoing description, the legs according to the present invention are hardly broken by virtue of the monolithic structure, and render the keyboard musical instrument steady and durable. 
     Moreover, the process for fabricating the monolithic leg according to the present invention is economical rather than a monolithic leg shaped from a single piece of wood. 
     Although particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. 
     The leg according to the present invention may be used for another kind of keyboard musical instrument such as, for example, an upright piano, a silent piano, an automatic player piano, an organ, a harpsichord, a celesta and an electric keyboard. 
     The silent piano is a kind of composite musical instrument. An acoustic piano is combined with an electronic tone generating system, and a hammer stopper is provided between the hammers and the strings. The hammer stopper is changed between a free position and a blocking position. While the hammer stopper is staying at the free position, the strings are struck with the hammers as usual. However, when the hammer stopper is changed to the blocking position, the hammer stopper enters the trajectories of the hammers. While a pianist is playing a tune on the keyboard, the depressed keys give rise to rotation of the hammers, and the hammers rebound on the hammer stopper before striking the strings. Thus, the pianist can practice the fingering without any piano tone. The electronic tone generating system includes key sensors, which monitor the black and white keys, respectively. The key sensors generate key position signals representative of the current key positions of the associated keys. The key position signals are supplied from the key sensors to a controller. The controller periodically checks the key position signals to see whether or not any one of the black and white keys changes the current key position. When the controller notices a depressed key, the controller specifies the depressed key, and calculates the key velocity. The controller produces music data codes such as, for example, MIDI (Musical Instrument Digital Interface) data words representative of the key motion, and supplies the music data codes to a tone generator. The tone generator generates an audio signal from the music data codes, and supplies the audio signal to a sound system. Thus, the pianist can confirm his fingering through the electronic tones. 
     The automatic player piano includes an automatic playing system in an acoustic piano. The automatic playing system has solenoid-operated key actuators and a controller. The solenoid-operated key actuators are, by way of example, provided on or in a key bed, and are respectively associated with the black and white keys. A set of music data codes representative of a performance are supplied to the controller, and the controller sequentially generates driving signals from the set of music data codes. The driving signals are selectively supplied to the solenoid-operated key actuators. Then, the solenoid-operated key actuators project the plungers, and the plungers move the associated black and white keys. As a result, the hammers strike the associated strings, and the original performance is reproduced by the automatic playing system. The hammer stopper may be installed in the automatic player piano. 
     The laminated board may be formed from a plurality of thin plates formed of synthetic resin or fiber-reinforced synthetic resin. Carbon-fiber reinforced synthetic resin sheets are also available for the laminated board. 
     The core  1 A and the caster  3  may be assembled into a leg without the decorative panels  5 . 
     Two sets of thin wood plates P 1 , P 2 , . . . and Pn may be formed into the core  1 A as shown in FIG.  8 . In detail, adhesive compound is spread over the contact surfaces of the thin wood plates P 1 , P 2 , . . . and Pn of the two sets as well as the back surfaces of the thin wood plates Pn. The two sets of thin wood plates P 1 , P 2 , . . . and Pn are laminated, and are clamped with force P. The two sets of thin wood plates P 1 , P 2 , . . . and Pn are formed into the core  1 A. Thus, the step shown in FIG. 8 is corresponding to the steps shown in FIGS. 5B and 5C. 
     The caster may be retractable into the core. If a keyboard musical instrument is light, the caster may be replaced with a non-slip block, or the core is directly placed on a floor. Thus, the caster is not an indispensable element of the monolithic leg according to the present invention. 
     The plural thin wood plates may be assembled into the core by means of a suitable clamp.