Keyboard musical instrument having fall-board assembled with case by means of Oldham's coupling

Abstract: An upright piano includes a fall-board (12) hinged to a upper sill (10f) and connected through a pair of flexible coupling (13) to side arms (10b), and each of the flexible couplings has a rotary damper (13b) embedded in the side arm and an Oldham's coupling (13a/ 13c/ 13q) connected between the fall-board and the rotary damper so that the Oldham's couplings take up misalignment between the rotational axis (AX1) of the fall-board and the rotational axes (AX2) of the rotary dampers.

Description: FIELD OF THE INVENTION This invention relates to a keyboard musical instrument such as a piano and, more particularly, to a keyboard musical instrument having a fall-board assembled with a case by means of a pair of couplings. DESCRIPTION OF THE RELATED ART A keyboard is an indispensable component of the keyboard musical instrument, and is accommodated in a stationary case. A fall-board is assembled with the stationary case, and protects the keyboard against undesirable damages. The fall-board is turnable between a closed position and an open position, and a suitable coupling is provided between the stationary case and the fall-board. The fall-board in the open position exposes the keyboard to a player, and allows the player to finger on the keyboard. On the other hand, when the fall-board is changed to the closed position, the keyboard is covered with the fall-board, and undesirable impact does not damage the keyboard. Various couplings have been proposed. A typical example is disclosed in Japanese Utility Model Publication of Examined Publication No. 5-48238, and figure 1 illustrates the prior art rotary damper disclosed therein. Although a pair of prior art rotary dampers 1 is provided between a fall-board 2 and a pair of side arms 3, only one prior art rotary damper 1 is shown in figure 1 together with part of the fall-board 2 and the associated side arm 3. The prior art rotary damper is broken down into an oil damper 1a and a connector 1b. The oil damper 1a includes a cylinder 1c filled with oil and a rotary member 1d inserted into the cylinder 1c. The cylinder 1c is embedded into the side arm 3, and is fixed to the side arm 3 by means of a plate 1e. Thus, the cylinder 1c is stationary with respect to the side arm 3. The rotary member 1d is rotatable with respect to the cylinder 1c, and the oil offers viscous resistance against the rotating motion of the rotary member 1d. A cubic projection 1f is formed on the top surface of the rotary member 1d. On the other hand, the connector 1b is attached to a side surface of the fall-board 2, and slit 1g is formed between projections 1h. When the fall-board 2 is assembled with the side arms 3, an erector aligns the slit 1g with the cubic projection 1f on both sides of the fall-board 2, and inserts the cubic projections 1f into the associated slits 1g, respectively. The fall-board 2 is supplied through the rotary dampers 1 by the side arms 3, and the rotary dampers 1 allow the fall-board to turn between the closed position and the open position. The viscous resistance against the motion from the closed position to the open position is weak, and the player easily rotates the fall-board to the open position. While the fall-board is moving from the open position to the closed position, the rotary dampers 1 gradually increase the viscous resistance, and assist the player so as to prevent the fall-board from collision against the key slip. The prior art rotary damper is appropriate for the fall-board of a grand piano, because the manufacturer easily aligns the axes of rotation of the prior art rotary dampers with the axis of rotation of the fall-board. However, it is difficult to use the prior art rotary damper in an upright piano. In detail, the fall-board of an upright piano is usually hinged to the upper sill, and, accordingly, the hinge is as long as the fall-board. If the prior art rotary dampers are inserted between the side surfaces of the fall-board and the side arms for the damping effect against the motion from the open position to the closed position, it is necessary to precisely align the rotational axis of the hinge with the rotational axes of the rotary dampers. If the axis is offset from the axes, the fall-board exerts bending moment on the rotary member 1d during the rotating motion between the closed position and the open position, and the prior art rotary damper is broken. Otherwise, the piano case is broken. If the fall-board of the upright piano is supported by means of the pair of prior art rotary dampers without the hinge, the serious bending moment is never exerted on the rotary members 1d. However, the fall-board of an upright piano is not so rigid as the fall-board of a grand piano. If the fall-board is not hinged, the fall-board is downwardly deformed due to aged deterioration, and the external appearance is degraded. This means that the hinge is indispensable for the upright piano. Thus, the prior art rotary damper is difficult to use. Another problem inherent in the prior art rotary damper is that the margin of misalignment is negligible. The rotary member 1d and the connector 1b are coupled through the small projection and the narrow slit 1g. This means that the rotational axis of the fall-board is surely aligned with the rotational axes of the prior art rotary dampers 1. This requirement results in a hard assembly work, because an erector is required to keep the heavy fall-board at the aligning position without obliquity and jogs. When the erector assembles the fall-board with the piano case, a suitable jig may be available for the assemblage. Moreover, even though the jig is available, the accurate alignment between the rotational axis of the fall-board and the rotational axes of the rotary dampers requires difficult work for the erectors. Thus, the assembling work under the small margin is hard for the erectors. Another prior art rotary damper disclosed in Japanese Patent Publication of Unexamined Application No. 63-55592 has a pair of gears. The gears are respectively connected to the rotary member and a projection of the connector, and are meshed with each other. A pair of gears allows the connector and, accordingly, the fall-board to turn around the rotary member, and takes up the offset between the rotational axis of the fall-board and the rotational axes of the rotary members. However, the pair of gears merely takes up extremely small offset. In other words, the margin for the assemblage is extremely small, and the assembling work is still hard for the erectors. Thus, the prior art rotary damper disclosed in the Japanese Patent Publication of Unexamined Application is not available for the upright piano due to the production cost and the difficulty in the assembling work. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a keyboard musical instrument, which has a fall-board connected to a case by means of economical flexible couplings. To accomplish the object, the present invention, as set out in claim 1, proposes to use an Oldham's coupling as the economical flexible couplings. In accordance with one aspect of the present invention, there is provided a keyboard musical instrument comprising a case having an opening, a keyboard supported by the case and exposed to the opening, a fall-board assembly changed between an open position for exposing the keyboard to a player and a closed position for covering the keyboard, a pair of rotary dampers attached to one of the fall-board assembly and the case and offering resistance against a rotating motion of the fall-board assembly from the open position to the closed position and a flexible coupling including a pair of Oldham's couplings connected between the other of the fall-board assembly and the case and the pair of rotary dampers. 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 prior art rotary damper in the disassembled state; Fig. 2 is a perspective view showing an upright piano according to the present invention; Fig. 3 is a perspective view showing a flexible coupling used in the upright piano in disassembled state; Fig. 4 is a side view showing essential part of the flexible coupling attached to a fall-board; Fig. 5 is a partially cut-away plane view showing the flexible coupling inserted between the fall-board and a side arm; and Figs. 6A to 6C are cross sectional views showing the relative relation between a cylinder and a rotary member forming a rotary damper incorporated in the flexible coupling. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to figures 2, 3 and 4 of the drawings, an upright piano embodying the present invention largely comprises a piano case structure 10, a keyboard 11 accommodated in the piano case structure 10, plural sets of strings (not shown) stretched inside the piano case, key action mechanisms (not shown) and hammer assemblies (not shown) installed inside the piano case structure 10 and functionally connected to the keyboard 11 for striking the sets of strings and a fall-board 12 turnably connected to the piano case structure 10. The fall-board 12 is moved between a closed position and an open position. The fall-board 12 in the closed position is substantially horizontal, and covers the keyboard 11. The fall-board 12 turns over 120 degrees to 130 degrees, and reaches the open position. The fall-board 12 in the open position exposes the keyboard 11 to a player as shown in figure 2. The keyboard 11, the key action mechanisms, the hammer assemblies and the strings are well known to person skilled in the art, and no further description is incorporated hereinbelow. In the following description, term "front" means a position closer to a player fingering on the keyboard 11. The piano case structure 10 includes two side boards 10a spaced from each other, two side arms 10b respectively projecting from the side boards 10a toward the front side, a key bed 10c laterally extending between the side arms 10b, a key slip 10d laterally extending on the key bed and two key blocks 10e. The keyboard 11 is mounted on the key bed 10c, and the key slip 10d is provided in front of the keyboard 11. The key blocks 10e are provided on the key bed 10c between the keyboard 11 and the side arms 10b. The piano case structure 10 further includes a key stop rail (not shown), an upper sill 10f (see figure 3), an upper front board 10g, a lower front board 10h and a top board 10j. The key stop rail (not shown) covers the rear portion of the keyboard 11, and the upper sill 10f is continued. As will be described hereinbelow, the fall-board 12 is hinged to the upper sill 10f. The upper front board 10g extends between the side boards 10a over the upper sill 10f, and the lower front board 10h extends between the upper surfaces of side boards 10a under the key bed 10c. The top board 10j extends between the side boards 10a, and closes the upper opening. Although back posts, a sound board and other boards are further incorporated in the piano case, they are not shown in figure 1. The upright piano further comprises a pair of flexible couplings 13 (see figure 3) provided between the side arms 10b and the fall-board 12 and a hinge 14 connected between the upper sill 10f and the fall-board 12. The hinge 14 offers an axis AX1 of rotation to the fall-board 12, and, accordingly, the fall-board 12 turns around the rotational axis AX1. The flexible couplings 13 are a kind of the Oldham's coupling, and provide large margin to the alignment with the fall-board 12. The fall-board 12 and the upper sill 10f are partially cut off, and the side surfaces 12a of the fall-board 12 and the side surfaces 10fa of the upper sill 10f are partially retracted. The flexible couplings 13 are attached between the retracted side surfaces 12a/ 10fa and the side arms 10b. In this instance, the piano case structure 10 except for the upper sill 10f serves as a case, and the fall-board 12, the upper sill 10f and the hinge 14 as a whole constitute a fall-board assembly. The flexible coupling 13 is broken down into a socket member 13a, a rotary damper 13b and a floating cum member 13c. The floating cum member 13c is engaged with the socket member 13a and the rotary damper 13b, and takes up misalignment between the rotational axis AX1 and axes of rotation AX2 of the rotary dampers 13b. Thus, the Oldham's coupling 13 makes the assembling work easy. The socket member 13a has a boss portion 13d and a ring portion 13e. A pair of holes 13f is formed in the boss portion 13d, and the boss portion 13d is fixed to the retracted side surface 12a by means of screws 13ga and nuts 13gb. The ring portion 13e forms a circular recess 13h, and the circular recess 13h has a center axis AX3 aligned with the rotational axis AX1. The floating cum member 13c is slidably received in the circular recess 13h. A pair of projections 13j inwardly projects from the inner surface of the ring portion 13e into the circular recess 13h, and the projections 13j are spaced by 180 degrees. The ring portion 13e is partially cut away so as to form a channel 13k. A cylinder 13m and a rotational member 13n form the rotary damper 13b. The cylinder 13m is embedded into the side arm 10b, and is fixed thereto by means of screws 13p. The rotary member 13n has an axis AX2 of rotation, and the rotational axis AX2 is aligned with the rotational axis AX1. A plate-like projection 13q is formed on the end surface of the rotary member 13n, and has thickness less than the width of the channel 13k. For this reason, the plate-like projection 13q can pass the channel 13k. When the ring portion 13e is thin, the channel 13k may not be formed in the ring portion 13e. The floating cum member 13c has a disk configuration, and has a diameter less than the diameter of the circular recess 13h. A pair of recesses 13ra is formed in one side surface of the floating cum member 13c, and a groove 13rb (see figure 5) is formed in the other side surface of the floating cum member 13c. The direction between the recesses 13ra is perpendicular to the longitudinal direction of the groove 13rb, and the direction between the recesses 13ra and the longitudinal direction cross a rotational axis AX4 of the floating cum member 13c. The distance between the bottom surfaces of the recesses 13ra and the circumference of the floating cum member 13c is greater than the distance between the top surfaces of the projections 13j and the inner surface of the ring portion 13e, and the projections 13j allow the floating cum member 13c to radially slide in the recesses 13ra. The groove 13rb is not seen in figure 3, and the plate-like projection 13q is loosely inserted into the groove 13rb. For this reason, even if the rotational axis AX1 is misaligned with the rotational axis AX2, the floating cum member 13c takes up the misalignment during the rotation of the fall-board 12. The rotary damper 13b is illustrated in figures 6A to 6C in detail. The rotational member 13n has a generally sectorial groove 13s, and the generally sectorial groove 13s extends along the rotational axis AX2. The bottom surface 13t of the generally sectorial groove 13s is round A partition wall 13u inwardly projects from the inner surface of the cylinder 13m, and the rotational member 13n is inserted into the inner space of the cylinder 13m in such a manner that the partition wall 13u splits the generally sectorial groove 13s into two chambers 13v/ 13w. A hole 13xa is formed in the partition wall 13u, and a check valve 13y is attached to the partition wall 13x. The partition wall 13u is slightly spaced from the bottom surface 13t, and a throttle 13xb is formed between the partition wall 13u and the bottom surface 13t. The generally sectorial groove 13s and, accordingly, the two chambers 13v/ 13w are filled with incompressible fluid 13z such as damping oil, and the cylinder 13m and the rotational member 13n seals the damping oil 13z in the chambers 13v/ 13w. The throttle 13xb allows the damping oil 13x to bidirectionally flow between the two chambers 13v and 13w. However, the check valve 13y blocks the hole 13xa from the damping oil 13z flowing from the chamber 13w to the chamber 13v, and the damping oil 13z only flows through the hole 13xa from the chamber 13v to the chamber 13w. For this reason, when the damping oil 13z flows from the chamber 13w to the chamber 13v, the damping oil 13z flows only through the throttle 13xb, and is subjected to large viscous resistance. On the other hand, while the cylinder 13m and the rotational member 13n are relatively rotated as indicated by arrows in figure 6A, the check valve 13y opens the hole 13xa as shown in figure 6B, and the damping oil 13z flows through the hole 13xa. The hole 13xa merely offers negligible viscous resistance against the damping oil, and the cylinder 13m and the rotational member 13n are smoothly changed to the relative position shown in figure 6C. The chamber 13v is maximized in volume in the relative position shown in figure 6A, and is minimized in the relative position shown in figure 6C. On the other hand, the chamber 13w is maximized in volume in the relative position shown in figure 6C, and is minimized in the relative position shown in figure 6A. The minimum volume is approximately zero. Thus, the rotary damper 13b varies the viscous resistance depending upon the direction of the rotation. In this instance, the rotary damper 13b offers the large resistance during the rotation of the fall-board 12 from the open position to the closed position and the negligible resistance from the closed position to the open position. The fall-board 12 is assembled with the piano case structure 10 as follows. First, the hinge 14 is connected to the front surface of the upper sill 10f and the rear surface of the fall-board 12. The fall-board 12 thus hinged with the upper sill 10f form in combination a fall-board assembly. Subsequently, the rotary dampers 13b and the socket members 13a are attached to the side arms 10b and the retracted side surfaces 12a/ 10fa, respectively. Cylindrical recesses 10ba have been already formed in the side arms 10b (see figure 5), and the rotary dampers 13b are snugly received in the cylindrical recesses 10ba, respectively. The rotary dampers 13b are screwed to the side arms 10b, respectively. On the other hand, the retracted side surfaces 10fa/ 12a define side recesses 12b, and the socket members 13a are inserted into the side recesses 12b, respectively. The screws 13ga and the nuts 13gb fix the socket members 13a to the fall-board 12. The nuts 13gb have been already positioned at appropriate positions where the axis AX3 is aligned with the axis AX1, and the nuts 13gb serve as an alignment mark. Even if the fall-board assembly is disassembled from the piano case structure 10 at user's home, erectors easily align the fall-board assembly with the piano case structure 10 by using the screws 13ga and the nuts 13gb. Subsequently, the floating cum members 13c are respectively inserted into the circular recesses 13h, and the projections 13j are engaged with the recesses 13ra. The erector turns the rotational members 13n so as to make the plate-like projections 13q become vertical. The erector holds the fall-board 12 vertical, and moves the fall-board assembly downwardly so as to insert the plate-like projections 13q through the channels 13k into the grooves 10rb, respectively. After the assemblage, a pianist is assumed to play a tune on the upright piano. The player lifts the front portion of the fall-board 12 so that the fall-board 12 turns from the closed position toward the open position. While the fall-board 12 is rotated, the damping oil 13z is forced to flow from the chamber 13v to the other chamber 13w. The damping oil 13z presses the check valve 13y, and the check valve 13y is spaced from the partition wall 13u. For this reason, the rotational members 13n are moved with small viscous resistance, and the player easily moves the fall-board 12 to the open position. The player fingers on the keyboard 11, and plays the tune on the upright piano. After playing the upright piano, the player pulls down the front portion of the fall-board 12, and the fall-board 12 turns from the open position to the closed position. While the fall-board 12 is turning from the open position to the closed position, the damping oil 13z is forced to flow from the chamber 13w to the other chamber 13v. The check valve 13y is pressed against the partition wall 13u, and closes the hole 13xa. For this reason, the damping oil 13z flows the narrow throttle 13xb, and offers the large viscous resistance to the rotational members 13n and, accordingly, the fall-board 12. The viscous resistance is so large that the fall-board 12 gently reaches the closed position without impact against the key slip 10d. As will be appreciated from the foregoing description, the flexible couplings 13 offer large margin between the rotational axis AX1 of the fall-board assembly and the rotational axes of the rotational members 13n, and make the assembling work easy. Even if the rotational axis AX1 is offset from the rotational axes of the rotary dampers, neither rotary dampers 13b nor the fall-board assembly are broken. The Oldham's couplings 13a/ 13c/ 13q are economical rather than the pair of gears in total, because the assembling cost is drastically reduced. Thus, the flexible couplings 13 do not seriously increase the production cost of the upright piano. Finally, the flexible couplings 13 take up the misalignment through the relative motion between the projections 13j/ 13q and the recesses/ groove 13ra/ 13rb, and erectors easily assemble the fall-board 12 with the piano case structure 10. Especially, the nuts 13gb are embedded into the retracted side surfaces of the fall-board 12 at the positions where the axis AX1 is aligned with the axes AX3. For this reason, the erectors can attach the socket members 13a to the fall-board 12 without serious misalignment. Even if misalignment takes place, the Oldham's couplings 13a/ 13c/ 13q absorbs the misalignment. The Oldham's couplings are assembled only through the insertion of projections into the recesses/ groove, and the erectors easily assemble the fall-board 12 with the piano case structure 10 at user's home. The separation of the fall-board 12 from the piano case structure 10 is also easy. Although a particular embodiment of the present invention has 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 scope of the present invention. For example, the projections 13j may be replaced with a single bar. In this instance, the floating cum member 13c has a single groove instead of the pair of recesses 13ra. The recesses/ groove 13ra/ 13rb may be formed in the socket member 13a and the rotational member 13n. In this instance, the projections are formed in the floating cum member 13c. If a fall-board is light, the chambers 13v/ 13w may be filled with the air instead of the damping oil. A suitable stopper or a cover plate may be attached to the socket member 13a after the insertion of the floating cum member 13c into the circular recess 13h so as to prevent the floating cum member 13c from coming out. The flexible couplings 13 may be used for an automatic player piano, a mute piano or an electronic keyboard musical instrument. The rotary dampers 13b and the Oldham's couplings may be attached to the fall-board and the piano case, respectively.

Claims: A keyboard musical instrument comprising a case (10) having an opening, a keyboard (11) supported by said case (10) and exposed to said opening, a fall-board assembly (12) changed between an open position for exposing said keyboard (11) to a player and a closed position for covering said keyboard (11), a pair of rotary dampers (13b) attached to one of said fall-board assembly and said case and offering resistance against a rotating motion of said fall-board assembly from said open position to said closed position, and a coupling (13) connected between said pair of rotary dampers and the other of said case (10) and said fall-board (12), characterized in that said coupling includes a pair of Oldham's couplings (13a/ 13c/ 13q) for absorbing a misalignment between said fall-board assembly (12) and said case. The keyboard musical instrument as set forth in claim 1, in which said pair of Oldham's couplings has a first axis (AX4) of rotation aligned with a second axis (AX1) of rotation of said fall-board (12). The keyboard musical instrument as set forth in claim 1, in which each of said Oldham's couplings has a first member (13a) attached to said other of said fall-board assembly (12) and said case (10) and formed with one of a slider (13j) and a guide space (13ra) for allowing said slider to move therealong, a second member (13q) connected to the associated rotary damper (13b) and formed with one of said slider (13q) and said guide space (13rb) arranged in perpendicular to said one of said slider (13j) and said guide space (13ra) of said first member (13a), and a floating member (13c) provided between said first member (13a) and said second member (13q) and formed with the other of said slider (13j) and said guide space (13ra) associated with said first member (13a) and the other of said slider (13q) and said guide space (13rb) associated with said second member (13q). The keyboard musical instrument as set forth in claim 3, in which said first member (13a) is attached to said fall-board assembly (12), and said second member (13q) is connected to a rotational member (13n) of said associated rotary damper (13b). The keyboard musical instrument as set forth in claim 4, in which said first member (13a) has a boss portion (13d) attached to said fall-board (12) and an engaging portion (13e) formed with said one of said slider (13j) and said space (13ra) and projecting from said boss portion (13d) so as to align a first axis (AX1) of rotation of said fall-board assembly (12) with a second axis (AX4) of rotation of said floating member (13c).

Inventors: INOUE SATOSHI, INOUE, SATOSHI, Inoue, Satoshi c/o Yamaha Corporation
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1998
Main classification: G10C3
IPC codes: G10C3