Keyboard device for electronic keyboard instrument and keyframe front for keyboard instrument

A keyboard device for an electronic keyboard instrument, capable of suppressing bouncing of a hammer returning to its original position. A key extends in a front-rear direction swingably about a balance rail pin. The hammer is formed vertically pivotally movable between initial and pivotally-moved positions about a hammer fulcrum provided near a rear end of the key and is placed on the key via a key contact portion in contact with a rear end of upper surface of the key from above, for pivotal motion by swinging of the key. A hammer cushion is provided on upper surface of the key at a predetermined location forward of the key contact portion to suppress bouncing of the hammer by contact with a cushion contact portion of the hammer returning from the pivotally-moved position to the initial position by releasing the key depression.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to Japanese Patent Application Numbers 161106/2018, filed on Aug. 30, 2018; 161107/2018 filed on Aug. 30, 2018; and 161108/2018 filed on Aug. 30, 2018, the entire contents of all of which are incorporated herein by reference

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a keyboard device for an electronic keyboard instrument having swingable keys each extending in a front-rear direction, and more particularly to a keyboard device for an electronic keyboard instrument, which has hammers each of which performs vertical pivotal motion above a rear end of an associated key in accordance with the motion of the key, and to a structure of a portion of the hammer, which is brought into contact with the key when the hammer is pivotally moved upward by being pushed up by the rear end of the associated key, in the keyboard device, as well as to a keyframe front for a keyboard instrument, which is applied to a keyboard instrument, such as an electronic piano, so as to hold a front rail pin for engagement with a front end of an associated key, in an erected state.

Description of the Related Art

Conventionally, as a keyboard device of the above-mentioned type, there has been known, for example, one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2013-125236 already filed by the present applicant. This keyboard device includes swingable keys each extending in the front-rear direction and hammers each vertically pivotally movably provided above a rear end of an associated one of the keys. Each of the keys is swingably supported on a balance rail pin erected at a location at about a longitudinal center of the key. On the other hand, each of the hammers is comprised of a hammer body made of a synthetic resin and formed in an arm-like shape extending in the front-rear direction, a pair of weight plates made of metal and attached to respective front ends of the left and right side surfaces of the hammer body, and a capstan screw screwed into a rear portion of the lower surface of the hammer body. The hammer body has a rear end formed with an arcuate shaft hole, and the shaft hole is engaged with a hammer fulcrum shaft of a hammer support, whereby the hammer is pivotally movably supported. Further, the capstan screw screwed in the hammer body has a lower end formed with a head having a lower surface formed into a spherical shape. The head of the capstan screw is in contact with a rear end of the upper surface of the key via cloth made of felt.

Further, conventionally, as a keyframe front for a keyboard instrument of the above-described type, there has been known, for example, one disclosed in Japanese Patent No. 5797074 filed by the present applicant. This keyframe front is formed by interconnecting a plurality of keyframe front molded articles each made of a synthetic resin such that the keyframe front extends in the left-right direction. Each of the keyframe front molded articles is comprised of a laterally elongated body part on which a plurality of front rail pins are erected at predetermined spaced intervals in the left-right direction and left and right connecting portions protruding from the respective left and right ends of the body part so as to connect the keyframe front molded article itself to left and right adjacent keyframe front molded articles, respectively. These left and right connecting portions have shapes substantially identical to each other in plan view, and while the left connecting portion has an upper half portion thereof cut out, the right connecting portion has a lower half portion thereof cut out. Further, the front end and the rear end of each of the left and right connecting portions have two screw holes, respectively, vertically extending therethrough, and a plurality of grooves extending parallel to each other in the left-right direction formed on the upper surface of the left connecting portion having its upper half cut out.

In the case of connecting adjacent two keyframe front molded articles to each other, first, the right connecting portion of one of the keyframe front molded articles and the left connecting portion of the other are vertically superposed one upon the other, and the front end and the rear end of the respective keyframe front molded articles are screwed to each other. Then, an adhesive is injected into a gap formed between the right end surface of the body part of the left one of the keyframe front molded articles screwed to each other and the left end surface of the left connecting portion of the right one of the keyframe front molded articles. The injected adhesive flows into each of the grooves formed on the left connecting portion of the right keyframe front molded article. As a consequence, the two keyframe front molded articles are connected to each other in a state in which the right connecting portion of the left one and the left connecting portion of the right one are joined by shiplap.

Further, the keyframe front formed by interconnecting the plurality of keyframe front molded articles as above is disposed along a front rail, which extends in the left-right direction, of a metal keyboard chassis and is screwed to the front rail at a plurality of portions.

In the keyboard device constructed as disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2013-125236, in a key-released state, the key is held in a posture slightly inclined downward and rearward, whereas the hammer is held in a substantially horizontal posture. The capstan screw is held with its axis inclined with respect to the vertical line. Specifically, the capstan screw is in a posture in which as a portion thereof is lower, the portion is positioned more rearward, i.e. the capstan screw is inclined downward and rearward. In this case, the front half of the lower surface of the head of the capstan screw is in contact with the rear end of the upper surface of the key. When the front end of the key is pushed down in this key-released state, the key swings about the balance rail pin, whereby the rear end of the key is raised. In accordance with this motion of the key, the hammer is pushed up via the capstan screw, thereby being pivotally moved upward about a hammer fulcrum shaft. Note that when the key is fully depressed, i.e. when the front end of the key is pushed down to its lowest position, the front end of the upper surface of the hammer is brought into abutment with a hammer stopper, whereby further pivotal motion of the hammer is blocked. Then, when the finger is released from the key being depressed, the hammer pivotally moved upward pivotally moves downward by its own weight and returns to its original position where the hammer was before the key depression. In this case, the rear end of the key is pushed down via the capstan screw in accordance with the downward pivotal motion of the hammer, and the key returns to its original position where it was before the key depression.

In the above-described keyboard device, when a hammer that pivotally moves downward in accordance with release of a depressed key is on the point of returning to its original position, the hammer can slightly bounce vertically due to a force generated by the pivotal motion of the hammer itself. The hammer is always held in contact with the key in a state placed on the rear end of the upper surface of the key via the capstan screw as described hereinabove, so that when the hammer bounces as above, the key swings in accordance with the bouncing of the hammer. More specifically, assuming that the key swings in accordance with the bouncing of the hammer on the point of returning to its original position, this prevents the depressed key from quickly returning to its original position where it was before the key depression, which sometimes causes trouble in musical performance.

Further, in a case where a hammer is pivotally moved upward in accordance with key depression of an associated key as described above, the posture of the capstan screw held in contact with the rear end of the upper surface of the key changes. Specifically, the head of the lower end of the capstan screw moves forward relative to the upper end of the same, whereby the capstan screw is brought into a posture inclined downward and forward. In this case, the rear half of the lower surface of the head of the capstan screw is in contact with the rear end of the upper surface of the key. More specifically, in the case where the hammer pivotally moves upward in accordance with depression of the key, the point of contact between the rear end of the upper surface of the key and the head of the capstan screw, i.e. the point of action of the key on the hammer not only moves upward, but also shifts from the front half of the lower surface of the head of the capstan screw to the rear half of the same. As a consequence, as the key is depressed, a distance between the hammer fulcrum shaft that pivotally supports the hammer and the above-mentioned point of action is progressively reduced. In this case, load applied from the hammer to the key progressively increases. Particularly in a case where soft key striking in which a key is slowly depressed is performed during musical performance, an increase in load immediately before termination of the key depression can cause the player to feel the key heavy.

In an electronic piano having a keyframe front of the type disclosed in Japanese Patent No. 5797074, the keyframe front can thermally expand or contract e.g. due to changes in the temperature of an environment where the electronic piano is installed, which causes expansion or contraction of the keyframe front in the longitudinal direction. In general, the linear expansion coefficient of a synthetic resin forming the keyframe front molded article is larger than that of a metal forming the front rail, and therefore the keyframe front expands or contracts more than the front rail. In this case, a tensile force and a compressive force in the longitudinal direction acts on two keyframe front molded articles connected to each other at the connecting portions of the respective ends of these, and when these forces repeatedly act, bonding between the connecting portions of the respective keyframe front molded articles connected to each other can be lost.

When the bonding between the connecting portions of the respective keyframe front molded articles connected to each other is lost as mentioned above, the amplitude of expansion or contraction in the longitudinal direction of each of the keyframe front molded articles becomes even larger. Particularly when each of the keyframe front molded articles contracts, spacing between the adjacent front rail pins respectively erected on the two keyframe front molded articles becomes larger than spacing between the other front rail pins. As a consequence, a gap between each adjacent two of the keys engaged with the front rail pins is made larger, which causes variation in gaps between the keys on the keyboard of the electronic piano.

Further, when bonding the two keyframe front molded articles to each other, the adhesive is injected into the gap between the body part of the left keyframe front molded article and the left connecting portion of the right keyframe front molded article, as described above, so as to cause the adhesive to flow into each of the grooves on the left connecting portion. However, it is difficult to cause the adhesive to flow into each of the grooves, and when an inflow of the adhesive is insufficient, the bonding between the connecting portions of the respective two keyframe front molded articles cannot be sufficiently maintained over a long term. Therefore, the conventional keyframe front described above leaves room for improvement.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a keyboard device for an electronic keyboard instrument, which is capable of suppressing the bouncing of a hammer on the point of returning, after key depression of an associated key, to its original position where it was before the key depression, consequently causing the key to quickly return to its original position, thereby enabling a player to enjoy excellent playability of the electronic keyboard instrument.

It is a second object of the present invention to provide a keyboard device for an electronic keyboard instrument, which is capable of suppressing an increase in load acting on a key from a hammer, during key depression, to thereby enable the player to enjoy excellent playability of the electronic musical instrument without causing the player to feel the key heavy even when the key is softly depressed for musical performance.

It is a third object of the present invention to provide a keyframe front for a keyboard instrument, which makes it possible to maintain solid connection between keyframe front molded articles over a long term to thereby prevent occurrence of variation in gaps between keys on a keyboard.

To attain the above first object, in a first aspect of the present invention, there is provided a keyboard device for an electronic keyboard instrument, comprising a key extending in a front-rear direction and configured to be swingable about a key fulcrum located at about a center of the key in a longitudinal direction thereof, a hammer extending in the front-rear direction and configured to be pivotally movable in a vertical direction between an initial position and a pivotally-moved position about a hammer fulcrum provided at about a rear end of the key, the hammer being placed on the key via a first contact portion brought into contact with a rear end of an upper surface of the key from above, for being pivotally moved in accordance with swinging of the key, and a hammer bounce-suppressing member provided on one of the upper surface of the key and a lower surface of the hammer at a predetermined position forward of the first contact portion and configured to suppress bouncing of the hammer by being brought into contact with the other of the upper surface of the key and the lower surface of the hammer when the hammer returns from the pivotally-moved position to the initial position in accordance with release of the key depressed.

With the construction of the first aspect of the present invention, the key extending in the front-rear direction is configured to be swingable about the key fulcrum located at about the center of the key in the longitudinal direction, and the hammer extending in the front-rear direction is configured to be pivotally movable in the vertical direction about the hammer fulcrum provided at about the rear end of the key between the initial position which is a position before key depression and the pivotally-moved position which is a position after key depression. Further, the hammer is placed on the key via the first contact portion brought into contact with the rear end of the upper surface of the key from above, for being pivotally moved in accordance with swinging of the key. Further, the hammer bounce-suppressing member is provided on one of the upper surface of the key and the lower surface of the hammer at a predetermined location forward of the first contact portion.

When the front end of a key is pushed down in a key-released state, the key swings about the key fulcrum, so that the rear end of the key moves upward. In accordance with this motion of the key, the hammer in its initial position is pushed up via the first contact portion to pivotally move upward about the hammer fulcrum to a pivotally-moved position above the initial position. Then, when the finger is released from the key being depressed, the hammer pivotally moves downward about the hammer fulcrum and returns to its initial position. In this case, one of the upper surface of the key and the lower surface of the hammer comes into abutment with the hammer bounce-suppressing member provided on the other of the upper surface of the key and the lower surface of the hammer, whereby the bouncing of the hammer is suppressed. The bouncing of the hammer on the point of returning to the initial position after key depression can be thus suppressed, which enables the key to return in a shorter time to its original position where it was before key depression. As a consequence, it becomes possible for the player to play quickly and enjoy excellent playability of the electronic musical instrument.

Preferably, the hammer includes a second contact portion provided immediately forward of the first contact portion, and the hammer bounce-suppressing member is provided on the rear end of the upper surface of the key, and the second contact portion is in abutment with the hammer bounce-suppressing member from above when the hammer is in the initial position.

With the construction of this preferred embodiment, the hammer is provided with the second contact portion, and the hammer bounce-suppressing member is provided on the rear end of the upper surface of the key. Therefore, after release of the key being depressed, the second contact portion of the hammer is brought into abutment with the hammer bounce-suppressing member from above before the hammer returns to the initial position. This makes it possible to stably and effectively suppress the bouncing of the hammer on the point of returning to its initial position. Further, since the second contact portion of the hammer, which is brought into abutment with the hammer bounce-suppressing member, is provided immediately forward of the first contact portion which is in contact with the key, it is possible not only to bring the second contact portion into abutment with the hammer bounce-suppressing member in a relatively shorter time before the hammer returns to its initial position than in a case where the second contact portion is provided on the front end of the lower surface of the hammer, but also to reduce impact on the hammer bounce-suppressing member. Consequently, it is possible to obtain an effect of suppressing the bouncing of the hammer within a relatively wide range of pivotal motion when the hammer returns to its original position as well as to use the hammer bounce-suppressing member over a long term.

Preferably, the hammer bounce-suppressing member is made of urethane foam having a predetermined resilience.

With the construction of this preferred embodiment of the present invention, since the hammer bounce-suppressing member is made of urethane foam having a relatively low resilience, it is possible to effectively suppress the bouncing of the hammer on the point of returning to the initial position. Further, as the urethane foam, it is possible to adopt soft urethane foam which is not only low in resilience, but also lightweight and excellent in impact absorption and cushioning properties.

To attain the above second object, in a second aspect of the present invention, there is provided a keyboard device for an electronic keyboard instrument, including a key extending in a front-rear direction and configured to be swingable about a key fulcrum located at about a center of the key in a longitudinal direction thereof, and a hammer extending in the front-rear direction and having a rear end thereof supported such that the hammer is pivotally movable in a vertical direction about a hammer fulcrum provided at about a rear end of the key, the hammer being placed on a rear end of an upper surface of the key, for being pivotally moved in accordance with swinging of the key, wherein the hammer comprises a hammer body extending in the front-rear direction and having a rear end thereof pivotally movable about the hammer fulcrum, and a key contact portion provided such that the key contact portion protrudes downward from a rear end of a lower surface of the hammer body and configured to be brought into contact with the rear end of the upper surface of the key from above, wherein the key contact portion is configured such that during pivotal motion of the hammer, a distance between a contact portion thereof in contact with the upper surface of the key and the hammer fulcrum is approximately constant.

With the construction of the second aspect of the present invention, the key extending in the front-rear direction is configured to be swingable about the key fulcrum located at about the center of the key in the longitudinal direction, and the hammer extending in the front-rear direction has its rear end supported such that the hammer can pivotally move in the vertical direction about the hammer fulcrum provided at about the rear end of the key. The hammer has the key contact portion protruding downward from the rear end of the lower surface of the hammer body extending in the front-rear direction and configured to be brought into contact with the rear end of the upper surface of the key from above. This key contact portion is configured such that during pivotal motion of the hammer, the distance between the contact portion thereof in contact with the upper surface of the key and the hammer fulcrum is approximately constant. Thus, differently from the conventional keyboard device in which the hammer is placed on the rear end of the upper surface of the key via the capstan screw, the keyboard device according to the second aspect makes it possible to suppress an increase in load applied to the key from the hammer when the hammer is pivotally moved in accordance with key depression. As a consequence, even when performing soft key depression in which the key is slowly depressed for musical performance, the player does not feel the key heavy, and therefore it is possible to enjoy excellent playability of the electronic musical instrument.

Preferably, the key contact portion has a bottom formed in an approximately arcuate shape in side view, and the bottom comprises a front bottom portion that forms a front half of the bottom and can be brought into contact with the key and a rear bottom portion that forms a rear half of the bottom and cannot be brought into contact with the key.

With the construction of this preferred embodiment, the bottom of the key contact portion, which is formed in an approximately arcuate shape in side view, has the front bottom portion forming the front half of the bottom, which can be brought into contact with the key, and the rear bottom portion forming the rear half of the bottom, which cannot be brought into contact with the key. Consequently, when the hammer moves upward in accordance with depression of the key, only the front bottom portion of the front half of the key contact portion of the hammer comes into contact with the rear end of the upper surface of the key only, so that differently from the conventional keyboard device in which the rear half of the head of the capstan screw comes into contact with the rear end of the upper surface of the key, the keyboard device of the present preferred embodiment makes it possible to suppress reduction of the distance between the contact portion of the key contact portion, which is in contact with the upper surface of the key, and the hammer fulcrum, with relative ease, whereby it is possible to easily achieve the action and effects described above.

More preferably, the keyboard device further comprises a hammer cushion provided immediately forward of the key contact portion on the rear end of the upper surface of the key and configured such that in a key-released state, a predetermined portion of the lower surface of the hammer is in abutment with the hammer cushion from above, and the front bottom portion is formed in an arcuate shape which has a predetermined curvature radius so as to maintain the hammer in the key-released state in substantially the same posture before and after the hammer cushion undergoes aging deformation.

With the construction of this preferred embodiment, the hammer cushion is provided on the rear end of the upper surface of the key at a location immediately forward of the key contact portion, and in the key-released state, the predetermined portion of the lower surface of the hammer is in abutment with the hammer cushion from above. This brings the hammer into abutment with the hammer cushion, on the point of returning to the initial position after release of the depressed key, whereby it is possible to suppress impact on the hammer on the point of returning to its original position and the bouncing of the hammer.

Further, the long-term use of the electronic piano sometimes causes the hammer cushion to be progressively crushed and undergo aging deformation due to being repeatedly pressed by the hammer from above, resulting in a lowered level of the upper surface of the hammer cushion. In this case, if the front bottom portion of the key contact portion is formed in an arcuate shape which has a relatively small curvature radius, in the key-released state, the hammer is brought into a posture inclined downward and forward compared with a correct posture before occurrence of the aging deformation, which can make e.g. musical tone-generating timing and sound volume in the electronic keyboard instrument different from correct timing and correct sound volume. To avoid this, the front bottom portion of the key contact portion is formed in an arcuate shape, which has a relatively large predetermined curvature radius, so as to maintain the hammer in the key-released state in substantially the same posture before and after occurrence of the aging deformation of the hammer cushion. This makes it possible to maintain the hammer in its correct posture in the key-released state over a long term even when the hammer cushion undergoes aging deformation, to thereby prevent occurrence of the above-described inconvenience.

Preferably, the key contact portion comprises a contact protrusion integrally formed with the hammer body and having a protruding shape protruding downward, and a protrusion cover having the front bottom portion and the rear bottom portion and removably mounted on the contact protrusion.

With the construction of this preferred embodiment, by mounting the protrusion cover having the front bottom portion and the rear bottom portion on the contact protrusion integrally formed with the hammer body, it is possible to form the key contact portion having the front bottom portion and the rear bottom portion with relative ease. Further, the protrusion cover is removable from the contact protrusion of the hammer body, so that e.g. in the case of changing the design of the front bottom portion and the rear bottom portion, it is possible to easily change the design by changing the protrusion cover alone, without changing the whole hammer.

To attain the above third object, in a thirst aspect of the present invention, there is provided a keyframe front for a keyboard instrument, which is formed to extend in a left-right direction, by interconnecting ends of a plurality of keyframe front molded articles each made of a synthetic resin and extending in the left-right direction, and on which plurality of front rail pins for engagement with front ends of a plurality of keys, respectively, are erected in a state arranged side by side in the left-right direction, wherein one keyframe front molded article of each adjacent two of the keyframe front molded articles has an end thereof provided with a connecting engagement protrusion protruding toward the other keyframe front molded article adjacent thereto and having a predetermined shape in plan view, and the other keyframe front molded article has an end thereof provided with a connecting engagement recess which is formed in a recessed shape fittable with the shape in plan view of the connecting engagement protrusion and engages the connecting engagement protrusion in a state immovable relative to the connecting engagement protrusion in the left-right direction.

With the construction of the third aspect of the present invention, by connecting the ends of a plurality of keyframe front molded articles each made of a synthetic resin and extending in the left-right direction to each other, a keyframe front is formed which extends in the left-right direction and on which a plurality of front rail pins are erected in a state arranged side by side in the left-right direction. Further, an end of one of each adjacent two of the keyframe front molded articles is formed with the connecting engagement protrusion having a predetermined shape in plan view, and an end of the other keyframe front molded article is formed with the connecting engagement recess which is engaged with the connecting engagement protrusion. This connecting engagement recess is formed in a recessed shape fittable with the shape in plan view of the connecting engagement protrusion and engages the connecting engagement protrusion in a state immovable relative to the connecting engagement protrusion in the left-right direction. By thus fitting the connecting engagement protrusion and the connecting engagement recess with each other into a state immovably engaged with each other, it is possible to connect the adjacent two keyframe front molded articles to each other by their own mechanical connection, so that even when the keyframe front molded articles expand or contract due to thermal expansion or contraction, solid connection between the ends of the respective two keyframe front molded articles can be maintained. As described above, according to the present invention, it is possible to maintain solid connection between each adjacent two of the keyframe front molded articles over a long term to thereby prevent occurrence of variation in gap between the keys on the keyboard.

Preferably, the connecting engagement protrusion includes a first protrusion having a predetermined width in a front-rear direction and extending over a predetermined length in the left-right direction, and a second protrusion provided on a tip end of the first protrusion and protruding over a predetermined length at least in one of a forward direction and a rearward direction.

With the construction of this preferred embodiment, the connecting engagement protrusion including the first protrusion and the second protrusion is formed in an L shape or a T shape in plan view, and engages the connecting engagement recess in a state fitted to each other, whereby it is possible to relatively easily and stably connect adjacent keyframe front molded articles to each other in a state immovable relative to each other in the left-right direction.

Preferably, the keyframe front comprises fixing means for fixing the connecting engagement protrusion and the connecting engagement recess to each other in a state held in intimate contact with each other in a vertical direction.

With the construction of this preferred embodiment, the connecting engagement protrusion and the connecting engagement recess are not only engaged with each other, but also secured to each other in a state held in intimate contact with each other in the vertical direction by the fixing means, and therefore the adjacent keyframe front molded articles can be more solidly connected to each other.

More preferably, the fixing means includes an adhesive for bonding the connecting engagement protrusion and the connecting engagement recess to each other in the vertical direction.

With the construction of this preferred embodiment, by using an adhesive as fixing means, it is possible to secure the connecting engagement protrusion and the connecting engagement recess to each other in a state bonded in the vertical direction.

Further preferably, one of the connecting engagement protrusion and the connecting engagement recess has at least one adhesive injection hole formed therethrough in the vertical direction and has a plurality of grooves formed on a flat surface thereof in contact with the other of the connecting engagement protrusion and the connecting engagement recess such that the plurality of grooves are continuous with the adhesive injection hole and extend radially therefrom.

With the construction of this preferred embodiment, one of the connecting engagement protrusion and the connecting engagement recess has at least one adhesive injection hole formed therethrough in the vertical direction and a plurality of grooves formed thereon which are continuous with the adhesive injection hole and extend radially therefrom. When bonding the connecting engagement protrusion and the connecting engagement recess by an adhesive, the two are fitted with each other and superposed one upon the other, and the adhesive is injected into the adhesive injection hole from outside, whereby the adhesive flows into the grooves radially extending from the adhesive injection hole. This makes it possible to stably supply the adhesive in a relatively wide range between the connecting engagement protrusion and the connecting engagement recess superposed one upon the other in a well-balanced manner as a whole, which makes it possible to solidly bond the connecting engagement protrusion and the connecting engagement recess to each other.

Further preferably, the fixing means further includes a fixing screw for screwing the connecting engagement protrusion and the connecting engagement recess to each other in a state fixed in the vertical direction by swaging.

With the construction of this preferred embodiment, the connecting engagement protrusion and the connecting engagement recess bonded to each other by the adhesive are screwed to each other in a state fixed in the vertical direction by swaging, and therefore it is possible not only to more solidly bond the connecting engagement protrusion and the connecting engagement recess, but also to stably maintain the state over a long term.

Furthermore preferably, the connecting engagement protrusion has a screw protrusion formed in a shape protruding in the vertical direction and having a screw hole formed inside for having the fixing screw screwed therein, and the connecting engagement recess has an insertion hole formed therethrough in the vertical direction for having the screw protrusion inserted therein.

With the construction of this preferred embodiment, while the connecting engagement protrusion is formed with the screw protrusion, the connecting engagement recess is formed with the insertion hole, so that work for assembling the keyframe front molded articles can be carried out with relative ease by fitting the connecting engagement protrusion in the connecting engagement recess while inserting the screw protrusion into the insertion hole. Further, by inserting the screw protrusion into the insertion hole in addition to fitting between the connecting engagement protrusion and the connecting engagement recess, it is possible to more solidly connect the keyframe front molded articles in a state immovable relative to each other in the left-right direction.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference to the drawings showing preferred embodiments thereof.FIGS. 1A and 1Bpartially show a keyboard device for an electronic piano in a key-released state, to which are applied a keyboard device and a keyframe front for a keyboard instrument, according to the present invention. As shown inFIGS. 1A and 1B, the keyboard device, denoted by reference numeral1, includes a plurality of keys2(only two white keys2aand one black key2bare shown inFIG. 1A) arranged side by side in a left-right direction of the electronic piano, a keyboard chassis3supporting the keys2, a hammer support4connected to the rear end of the keyboard chassis3, a plurality of hammers5(only one white-key hammer5aand one black-key hammer5bare shown inFIG. 1A) provided for the respective keys2and each configured to be pivotally moved in accordance with key depression of an associated one of the keys2, a plurality of let-off members6(only one of which is shown inFIG. 1B) provided for the respective hammers5and each configured to add let-off feeling during key depression of an associated one of the keys2, and a key switch7for detecting key depression information on the keys2.

The keyboard chassis3is formed by assembling, in parallel crosses, three support rails9, i.e. a front rail9a, a middle rail9b, and a rear rail9ceach extending in the left-right direction and arranged with predetermined distances therebetween in the front-rear direction, and a plurality of reinforcement ribs10each extending in the front-rear direction. The keyboard chassis3is secured to a keybed, not shown. The support rails9and the ribs10are made of metal plates formed into respective predetermined shapes by stamping and bending using a press.

A keyframe front11and a keyframe center12are secured to the lower surface of the front rail9aand the upper surface of the middle rail9b, respectively. The keyframe front11and the keyframe center12are thick plate-like members made of a synthetic resin and extend in the left-right direction along the whole length of the front rail9aand that of the middle rail9b, respectively. On the keyframe center12, there are erected a plurality of balance rail pins13(key fulcrums: two white-key balance rail pins13aand one black-key balance rail pin13bare shown inFIG. 1A) at front and rear locations corresponding to the white keys2aand the black keys2b, respectively, in a state arranged in the left-right direction. On the other hand, on the keyframe front11, there are erected a plurality of front rail pins14in a state arranged in the left-right direction.

FIGS. 2A and 2Bpartially show the front rail9aand the keyframe front11, on which the front rail pins14are erected.FIG. 2Ashows a state in which the keyframe front11is mounted to the front rail9a, andFIG. 2Bshows a state in which the front rail9ais omitted fromFIG. 2A. As shown inFIG. 2A, the front rail9ahas a top board15formed with a plurality of pin openings15aeach having a larger diameter than the outer diameter of the front rail pin14at locations corresponding to the respective front rail pins14, and the front rail pins14project upward through the respective pin openings15a. Note that two screws16and16appearing inFIGS. 2A and 2Bare for securing the front portion of the rib10(seeFIG. 1B) of the keyboard chassis3to the lower surface of the top board15of the front rail9a.

The keyframe front11is formed by connecting a plurality of keyframe front molded articles21each extending in the left-right direction to each other in the left-right direction.FIGS. 3A and 3BandFIGS. 4A and 4Bshow two keyframe front molded articles21and21that form a portion of the keyframe front11. Each of the keyframe front molded articles21is made of a predetermined synthetic resin (e.g. an ABS resin or polystyrene) and is comprised of a body part22formed with a plurality of pin holes22aand22bfor fixing the respective front rail pins14, and a right connecting portion23and a left connecting portion24protruding from the respective left and right ends of the body part22, which are used to connect itself to respective adjacent keyframe front molded articles21and21.

The front end of the body part22is formed with seven pin holes22aat predetermined spaced intervals in the left-right direction. Each of the pin holes22ais configured such that a front rail pin14a(seeFIG. 1B, andFIGS. 2A and 2B) for the associated white key2acan be erected with the lower end thereof press-fitted in the pin hole22a. On the other hand, the rear end of the body part22is formed with five pin holes22bat predetermined spaced intervals in the left-right direction. Each of the pin holes22bis configured such that a front rail pin14b(seeFIG. 1B, andFIGS. 2A and 2B) for the associated black key2bcan be erected in the same manner as the front rail pin14afor the white key2a. Note that each of the keyframe front molded articles21shown inFIG. 3AtoFIG. 4Bcorresponds to a one-octave section of the keyboard device.

On the other hand, the right connecting portion23is formed such that a lower half portion thereof is substantially cut out, and the left connecting portion24is formed such that an upper half portion thereof is substantially cut out. Further, the right connecting portion23of one of the keyframe front molded articles21and the left connecting portion24of the other are configured such that they are engaged with each other in a state vertically fitted with each other and immovable relative to each other in the front-rear direction and the left-right direction.

Specifically, the right connecting portion23includes a base portion25continuous with the right end of the body part22and having approximately the same width in the front-rear direction as that of the body part22, and a connecting engagement protrusion26protruding rightward from the base portion25and having a lateral T shape in plan view. More specifically, the connecting engagement protrusion26is comprised of a reduced-width portion26a(first protrusion) having a width smaller than that of the base portion25in the front-rear direction and protruding rightward from the base portion25over a predetermined length, and an increased-width portion26b(second protrusion) continuous with the reduced-width portion26aand protruding rightward from the same over a predetermined length, with a width larger than that of the reduced-width portion26aand smaller than that of the base portion25in the front-rear direction.

The base portion25of the right connecting portion23has a front end and a rear end formed with slots25aand25b, respectively, each extending therethrough in the vertical direction and slightly elongated in the left-right direction. Further, as shown inFIG. 3B, at a predetermined location on the lower surface of the connecting engagement protrusion26, there is formed a cylindrical screw protrusion26cprotruding downward over a predetermined length and having a female screw formed on an inner peripheral surface thereof.

On the other hand, the left connecting portion24has a connecting engagement recess27continuous with the left end of the body part22and formed such that it has approximately the same shape in plan view as the shape formed by the above-described base portion25and the connecting engagement protrusion26of the right connecting portion23and is lower in height than the base portion25and the connecting engagement protrusion26by one step which corresponds to the thickness of the base portion25and the connecting engagement protrusion26. More specifically, the connecting engagement recess27includes a reduced-width portion27aand an increased-width portion27bwhich correspond, respectively, to the reduced-width portion26aand the increased-width portion26bof the connecting engagement protrusion26and has respective inner dimensions approximately equal to the outer dimensions of the reduced-width portion26aand the increased-width portion26b. Further, in a central portion of the connecting engagement recess27, there is formed an insertion hole27cextending therethrough in the vertical direction, for having the screw protrusion26cinserted therein when the keyframe molded articles21and21are connected to each other. Furthermore, the left front end and left rear end of the connecting engagement recess27are formed with slots28aand28b, respectively, each extending therethrough in the vertical direction and slightly elongated in the left-right direction.

In addition, the left connecting portion24is formed with a plurality of adhesive injection holes29(four holes in the present embodiment) for use when an adhesive is injected from the lower surface side of the left connecting portion24toward the upper surface side of the same. Specifically, the adhesive injection holes29each extending through the connecting engagement recess27in the vertical direction are formed around the insertion hole27cof the connecting engagement recess27. Further, on the upper surface of the connecting engagement recess27, there are formed a plurality of (eight, in the present embodiment) grooves29acontinuous with each of the adhesive injection holes29and radially extending therefrom.

The keyframe front molded articles21each constructed as above form the keyframe front11extending in the left-right direction by being connected to each other as follows: First, in two keyframe front molded articles21and21to be connected to each other, the connecting engagement protrusion26and the screw protrusion26cof one of the keyframe front molded articles21are fitted, respectively, in the connecting engagement recess27and the insertion hole27cof the other keyframe front molded article21from above. Then, a swaging screw31(fixing screw) is screwed into the screw protrusion26cfitted in the insertion hole27c(seeFIG. 3B). Thereafter, a predetermined adhesive is injected into each of the four adhesive injection holes29. As a consequence, the adhesive injected into each of the adhesive injection holes29flows into the radial grooves29acontinuous with the adhesive injection hole29, whereby the connecting engagement protrusion26of the one keyframe front molded article21and the connecting engagement recess27of the other keyframe front molded article21are bonded to each other.

The keyframe front11formed by interconnecting the plurality of keyframe front molded articles21as described above is secured to the front rail9aby inserting mounting screws32aand32b, from below, through the front slots25aand28aand the rear slots25band28bof the left and right connecting portions23and24of the respective two keyframe front molded articles21and21connected to each other and screwing the mounting screws32aand32binto respective screw holes formed in the top board15of the front rail9a.

FIG. 5Ashows a white key2aand a black key2b. As shown inFIG. 5A, the keys2have wooden key bodies41each extending in the front-rear direction and having a rectangular shape in transverse cross section and key covers42made of a synthetic resin and bonded to the upper surface and the front surface of the respective front half portions of the key bodies41. At a location at about the center of each key body41in the longitudinal direction of the same, there is formed a balance rail pin hole43, and the key2is swingably supported by the balance rail pin13erected on the keyframe center12via the balance rail pin hole43.

Each of the balance rail pin holes43of the key2has a substantially circular hole formed at and near the lower surface of the key body41and a whole upper portion thereof continuous with the circular hole formed in a slot-like shape which is elongated in the longitudinal direction of the key body41. Further, on each of the left and right inner surfaces of the balance rail pin hole43, there is provided a felt43aso as to hold the key2in smooth sliding contact with the balance rail pin13during its swinging motion.

A cushion44is bonded to the upper surface of the key body41at a location rearward of the balance rail pin hole43. The cushion44is provided so as to prevent the front end of the hammer5from being brought into direct abutment against the key2e.g. during musical performance or maintenance.

Further, the key body41has a front rail pin hole45opening downward (seeFIG. 1B) which is formed at a predetermined location in the front portion thereof, and the front rail pin hole45is brought into engagement with the front rail pin14erected on the keyframe front11, whereby the key2is prevented from laterally swaying during its swinging motion.

Furthermore, as shown inFIGS. 5A and 5B, on the rear end of the key body41of each of the white key2aand the black key2b, there are mounted a hammer contact height-regulating portion46for regulating the contact height of the hammer5in the key-released state and a hammer cushion47(hammer bounce-suppressing member) with which the hammer5is in contact in the key-released state and is brought into abutment on the point of returning to its original position (initial position) after having been pivotally moved in accordance with key depression.

The hammer contact height-regulating portion46is formed as a molded article made of a hard synthetic resin (e.g. an ABS resin) and having a predetermined shape. Specifically, the hammer contact height-regulating portion46is formed in a C shape in side view by an upper piece51extending in the front-rear direction over a predetermined length, a rear piece52continuous with the rear portion of the upper piece51and extending downward, and a lower piece53continuous with the lower end of the rear piece52and extending forward over a predetermined length. Further, on the left side of the hammer contact height-regulating portion46, there is provided a side wall54continuous with the upper piece51and the rear piece52.

As shown in5B, the upper piece51is comprised of an upper piece-fixing portion51athat forms the front half of the upper piece51and secures the upper piece51itself to the rear end of the upper surface of the key body41, and a hammer-receiving portion51bthat forms the rear half of the upper piece51and has an upper surface formed flat for receiving a key contact portion76, described hereinafter, of the hammer5in a state supporting the same from below. The upper piece-fixing portion51ais formed to be smaller in thickness than the hammer-receiving portion51b, and a C-shaped bracket, not shown, is hammered down from above, whereby the upper piece51is secured to the rear end of the upper surface of the key body41.

Further, the hammer cushion47formed in a block shape is fixed by bonding to the upper piece-fixing portion51aof the upper piece51. The hammer cushion47is made of soft urethane foam having a low resilience. This soft urethane foam is low in rebound resilience, and is also lightweight and excellent in impact absorption and cushioning properties. The hammer cushion47is provided for suppressing the bouncing of the hammer5on the point of returning, after key release, to its original position where it was before key depression, by contact between a cushion contact portion84, referred to hereinafter, of the hammer5and the hammer cushion47itself.

The hammer contact height-regulating portion46is mounted to the rear end of the key body41, in a state in which three surfaces thereof, i.e. the lower surface of the upper piece51, the front surface of the rear piece52, and the side wall54are held in intimate contact with the respective three surfaces of the key body41, i.e. the upper surface, the rear end surface, and the left side surface of the rear end of the key body41, and the lower piece53is held in contact with the rear end of the lower surface of the key body41.

In the key-released state of the key2having the hammer contact height-regulating portion46mounted thereon, the rear piece52of the hammer contact height-regulating portion46is placed on a cushion55fixed to the rear rail9c, as shown inFIG. 1B. Therefore, the hammer-receiving portions51bof the hammer contact height-regulating portions46of all the keys2are at the same level in the key-released state.

FIGS. 6A to 6CandFIGS. 7A and 7Bshow the hammer support4. As shown in these figures, the hammer support4is formed by connecting a plurality of molded articles each made of a synthetic resin and provided e.g. for a one-octave section to each other in the left-right direction. The hammer support4extends over the length of all the hammers5in the left-right direction and is screwed to the rear rail9cof the keyboard chassis3. The hammer support4is comprised of a hammer supporting portion61erected in the vicinity of the rear rail9cand a switch-mounting portion62extending forward and obliquely upward from the upper end of the hammer supporting portion61. In the upper end of the hammer supporting portion61, there are provided hammer fulcrum shafts63(hammer fulcrums) for pivotally supporting the respective hammers5.

Further, the hammer support4has a plurality of partition walls64for separating the hammers5adjacent to each other, with a predetermined spacing therebetween in the left-right direction, and each of the hammer fulcrum shafts63extends between each adjacent two of the partition walls64and64in the left-right direction. As shown inFIG. 6C, the hammer fulcrum shaft63has a cross-sectional shape formed in a so-called oval shape in which front and rear portions of a circle, the center of which corresponds to the axis of the hammer fulcrum shaft63, are cut out.

Specifically, the hammer fulcrum shaft63has an outer peripheral surface formed by a pair of upper and lower curved surfaces63aand63aand a pair of front and rear flat surfaces63band63beach extending between the curved surfaces63aand63a. In the hammer fulcrum shaft63formed as above, the upper and lower curved surfaces63aand63aare set as segments of a circle having a diameter of a length L1, and the distance between the front and rear flat surfaces63band63bis set to a length L2which is shorter than the length L1.

FIG. 8andFIG. 9Ashow the hammer5. As shown inFIG. 8andFIG. 9A, the hammer5is comprised of an arm-like hammer body71extending in the front-rear direction and two weight plates72and72mounted to the front ends of the respective left and right side surfaces of the hammer body71with rivets70. The hammer body71is made of a hard synthetic resin, and each of the weight plates72is made of a metal material, such as steel, having a relatively large specific gravity.

The hammer body71has a rear end formed with an engagement portion73for engagement with the hammer fulcrum shaft63of the hammer support4. The engagement portion73has an arcuate shaft hole74formed in a C shape in side view, and the opening of the shaft hole74has front and rear guide surfaces75and75formed to expand outward. The shaft hole74has a diameter which is slightly larger than the diameter (length L1) of the circle partially formed by the upper and lower curved surfaces63aand63a, and the opening has a width L3which is slightly larger than the length L2between the front and rear flat surfaces63band63bof the hammer fulcrum shaft63and smaller than the length L1. The hammer5can be mounted/removed to/from the hammer fulcrum shaft63of the hammer support4via the opening of the shaft hole74, and the shaft hole74is engaged with the hammer fulcrum shaft63, whereby the hammer5is pivotally supported by the hammer support4.

Further, as shown inFIG. 9A, at a predetermined location on the rear portion of the bottom surface of the hammer5, there is formed a key contact portion76(first contact portion) protruding downward for being brought into contact with the above-described hammer contact height-regulating portion46of the key2from above. The key contact portion76is comprised of a contact protrusion77integrally formed with the hammer body71of the hammer5and a protrusion cover78mounted to the hammer body71such that the protrusion cover78covers the contact protrusion77.

As shown inFIG. 9B, the contact protrusion77of the key contact portion76protrudes downward and has a lower surface formed in an arcuate shape. Further, a front upper portion of the contact protrusion77of the hammer body71is formed with a hook-receiving portion79that is engaged with a hook82, referred to hereinafter, of the protrusion cover78. The hook-receiving portion79is formed in a recessed shape open downward and has an upper end formed with an engaging recess79a.

On the other hand, the protrusion cover78is formed as a molded article made of a predetermined resilient material (e.g. elastomer) and having a predetermined shape. Specifically, as shown in FIGS.9B and9C, the protrusion cover78is comprised of an cover body81open upward for accommodating the contact protrusion77in a state in which the cover body81covers the contact protrusion77, and the hook82extending upward from a front end of the cover body81for engagement with the hook-receiving portion79of the hammer body71.

Further, as shown inFIGS. 9B and 9C, a front half portion (left half portion as viewed inFIG. 9B) of the bottom surface of the cover body81is formed with a front bottom portion81ain an arcuate shape having a relatively large curvature radius, and on the other hand, a rear half portion of the bottom surface thereof is formed with a rear bottom portion81bin an arcuate shape having a curvature radius smaller than that of the front bottom portion81a. The rear bottom portion81bis formed by cutting out a portion of the rear half portion of the bottom of the cover body81such that the rear bottom portion81bis positioned inward (upward, as viewed inFIG. 9C) of an imaginary line obtained by extending the arcuate outline of the front bottom portion81arearward, to thereby form a step from the front bottom portion81a.

Furthermore, an upper end of the hook82of the protrusion cover78is formed with a lug82a. This lug82ais engaged with the engaging recess79aof the hook-receiving portion79, whereby the protrusion cover78is securely mounted to the hammer body71in a state fitted on the contact protrusion77.

As shown inFIG. 8andFIG. 9A, the cushion contact portion84(second contact portion or predetermined portion) for abutment with the hammer cushion47secured to the rear end of the upper surface of the key2is provided on the bottom surface of the hammer body71. The cushion contact portion84is formed at a predetermined location forward of the key contact portion76(immediately forward of the same) and has a lower surface formed flat.

Further, at a location forward and upward of the engagement portion73of the rear end of the hammer body71, there is formed an actuator portion86for actuating the key switch7by pressing the same in response to key depression. Furthermore, an engagement protrusion87having a plate shape is protrudingly formed on the upper surface of the hammer body71at a location at about the center thereof in the front-rear direction, for engagement with the let-off member6during key depression.

As shown inFIGS. 1A and 1B, the key switch7is comprised of a switch board7aformed by a printed circuit board and switch bodies7beach formed by a rubber switch and provided on the lower surface of the switch board7afor an associated one of the keys2. The switch board7ahas a rear end thereof inserted into the switch-mounting portion62of the hammer support4and screwed to the same. In the key-released state, each of the switch bodies7bis opposed to the actuator portion86of the associated hammer5with a spacing therefrom.

Each of the let-off members6is formed as a molded article made of a resilient material having a predetermined shape, and is mounted to the switch-mounting portion62of the hammer support4as shown inFIG. 1B. The let-off member6extends downward and rearward from the switch-mounting portion62and has a head6aformed on a tip end thereof via a neck portion. In the key-released state, the head6ais opposed to the engagement protrusion87of the hammer5.

Further, as shown inFIGS. 1A and 1B, on the bottom surface of the front end of the switch-mounting portion62of the hammer support4, there is provided a hammer stopper88for restricting upward pivotal motion of the hammer5. The hammer stopper88is attached to the switch-mounting portion62such that it extends in the left-right direction.

Next, a description will be given of the operation of the keyboard device1constructed as above. When the key2is depressed in the key-released state shown inFIGS. 1A and 1B, the key2pivotally moves about the balance rail pin13in the counterclockwise direction as viewed inFIG. 1B, and in accordance with this motion of the key2, the hammer5is pushed up via the key contact portion76and pivotally moves upward (in the clockwise direction as viewed inFIG. 1B) about the hammer fulcrum shaft63.

The engagement protrusion87engages the head6aof the let-off member6during the pivotal motion of the hammer5and presses the let-off member6via the head6awhile compressing the same, whereby a reaction force acting on the hammer5from the let-off member6increases. When the hammer5further pivotally moves, the engagement protrusion87is disengaged from the head6a, whereby the reaction force from the let-off member6abruptly disappears. Such an increase and a disappearance of the reaction force from the let-off member6gives a let-off feeling analogous to one given by an acoustic piano.

Thereafter, a front portion of the hammer5comes into abutment with the hammer stopper88located above, whereby the upward pivotal motion of the hammer5is terminated (pivotally-moved position). During the upward pivotal motion of the hammer5, the actuator portion86of the hammer5presses the switch body7bof the key switch7to thereby turn on the key switch7, whereby key depression information of the key2is detected according to the amount of pivotal motion of the hammer5and output to a tone generation controller (not shown). Then, the tone generation controller controls tone generation of the electronic piano according to the detected key depression information.

Now, a description will be given, with reference toFIG. 10AtoFIG. 12, of a state of contact between the key2and the hammer5and a touch weight felt during key depression.FIG. 10Ashows a contact position of the hammer5on the key2in the key-released state, andFIG. 10Bshows a contact position of the hammer5on the key2in the key-depressed state. More specifically,FIGS. 10A and 10Bshow the contact position of the key contact portion76of the hammer5on the hammer-receiving portion51b(only the position on the upper surface of the hammer-receiving portion51bis shown inFIG. 10AtoFIG. 11B) of the hammer contact height-regulating portion46of the rear end of the key2. As shown inFIG. 10A, in the key-released state, the key contact portion76of the hammer5is in contact with the hammer-receiving portion51bof the key2at a predetermined position P1of the front bottom portion81aof the bottom surface of the protrusion cover78. In this case, the distance between the axis of the hammer fulcrum shaft63of the hammer support4and the predetermined position P1is R1. Further, in this case, the cushion contact portion84of the hammer5is placed on the hammer cushion47of the key2.

Further, as shown inFIG. 10B, in the key-depressed state, the key contact portion76of the hammer5is in contact with the hammer-receiving portion51bof the key2at a predetermined position of the front bottom portion81aof the bottom surface of the protrusion cover78, more specifically at a predetermined position P2of the rear end of the front bottom portion81aslightly rearward of the predetermined portion P1. In this case, a distance R2between the axis of the hammer fulcrum shaft63of the hammer support4and the predetermined position P2is approximately equal to the distance R1in the key-released state (R2R1). This means that during time from the start of depression of the key2to the termination of the key depression (i.e. state in which the key2has been fully depressed), the distance between a point of contact between the hammer-receiving portion51bof the key2and the key contact portion76of the hammer5, i.e. a point of action of the key2on the hammer5, and the axis of the hammer fulcrum shaft63is held approximately constant.

On the other hand,FIGS. 11A and 11Bcorrespond, respectively, toFIGS. 10A and 10B, and show a comparative example of the hammer5in which a protrusion cover90having a smooth bottom surface formed as a bottom portion90ahaving an arcuate shape is used in the key contact portion76in place of the protrusion cover78having its bottom formed with the step as shown inFIGS. 10A and 10B, and also, the hammer cushion47is omitted from the rear end of the upper surface of the key2. In the key-released state shown inFIG. 11A, the key contact portion76of the hammer5is in contact with the hammer-receiving portion51bof the key2at a predetermined position Q1of a front portion of the bottom portion90aof the protrusion cover90. In this case, a distance S1between the axis of the hammer fulcrum shaft63of the hammer support4and the predetermined position Q1is approximately equal to the distance R1indicated inFIG. 10A(S1≈R1).

Further, in the key-depressed state shown inFIG. 11B, the key contact portion76of the hammer5is in contact with the hammer-receiving portion51bof the key2at a predetermined position Q2of a rear portion of the bottom portion90aof the protrusion cover90. In this case, a distance S2between the axis of the hammer fulcrum shaft63and the predetermined position Q2is shorter than the distance S1(S2<S1). This means that in the comparative example in which the protrusion cover90is applied to the key contact portion76of the hammer5, during time from the start of depression of the key2to the termination of the key depression, the distance between the point of action of the key2on the hammer5and the axis of the hammer fulcrum shaft63is progressively reduced.

FIG. 12shows examples of a keystroke as a downward shift of the front end of the key2during key depression and changes in load felt as touch weight dependent on the keystroke during time from the start of key depression to the termination of key release, with respect to each of an example of the present embodiment (solid lines) and a comparative example (broken lines). As shown inFIG. 12, in a range from 0 mm to approximately 6 mm of the keystroke, there is no large difference between the example of the embodiment and the comparative example. Further, in a range from approximately 6 mm to approximately 8 mm of the keystroke, let-off feeling is generated by an increase and a disappearance of the reaction force from the let-off member6, and therefore it is possible to obtain similar let-off feeling in both of the example of the embodiment and the comparative example.

Further, within a range from approximately 8 mm to approximately 9 mm of the keystroke, an increase in the load in the comparative example is larger than in the example of the embodiment. This means that in the comparative example, immediately after impartment of let-off feeling, the player feels the key2heavy in depression thereof. In contrast, in the example of the embodiment, immediately after impartment of let-off feeling, the increase in the load is more gentle than in the comparative example, and therefore it is possible to give a touch feeling analogous to that of an acoustic piano without making the key2felt heavy in depression thereof. Note that in a range from approximately 9 mm to approximately 10 mm of the keystroke, the load sharply increases because the hammer5pivotally moved upward comes into abutment with the hammer stopper88, whereby further upward pivotal motion thereof is blocked.

When the key2is released after termination of the key depression, the hammer5having been pivotally moved upward pivotally moves downward by its own weight to press the rear end of the key2downward via the key contact portion76. This causes the key2to pivotally move in the opposite direction to the direction of its pivotal motion performed during the key depression and return to the key-released state shown inFIGS. 1A and 1B. Further, in this case, the cushion contact portion84of the hammer5comes into abutment with the hammer cushion47of the key2from above, whereby the bouncing of the hammer5is suppressed.

FIG. 13shows examples of changes in the keystroke of the key2during return of the same to its original position due to key release in the fully-depressed state, with respect to each of the example of the embodiment (solid lines) and the comparative example (broken lines) in which the hammer cushion47is omitted from the rear end of the upper surface of the key2. Note that a position indicated by a keystroke of 0 mm inFIG. 13corresponds to a position of the key2in the key-released state (hereinafter referred to as “the reference position”).

When release of the key2is started in the fully-depressed state thereof, the front end of the key2moves up and then the key2vertically vibrates about the reference position and then stops, in both of the example of the embodiment and the comparative example, as shown inFIG. 13. This vibration of the key2occurs in accordance with vertical bouncing of the hammer5caused by a force generated when the hammer5having been pivotally moved upward pivotally moves downward to return to its original position.

In the comparative example, the hammer cushion47is not provided on the rear end of the upper surface of the key2as described hereinbefore, so that when the hammer5is on the point of returning to its original position after having been pivotally moved upward, the vertical bouncing of the hammer5cannot be suppressed. For this reason, the key2in the comparative example vertically vibrates relatively largely about its reference position as indicated by the broken line inFIG. 13, and therefore it takes longer time before the vibration of the key2is stopped.

On the other hand, in the example of the embodiment, on the point of returning to its original position after having been pivotally moved upward, the hammer5comes into abutment with the hammer cushion47from above, whereby the bouncing thereof is suppressed. As a consequence, as indicated by the solid line inFIG. 13, the vibration of the key2about the reference position is suppressed in the example of the embodiment differently from the comparative example, and therefore it takes shorter time before the bouncing of the key2is stopped.

As described heretofore in detail, according to the present embodiment, the hammer5having pivotally moved upward in accordance with depression of the key2pivotally moves downward in accordance with key release to come into abutment with the hammer cushion47on the rear end of the upper surface of the key2via the cushion contact portion84on the point of returning to its original position. This makes it possible to suppress the bouncing of the hammer5on the point of returning to its original position, and consequently the key2returns in a shorter time to its original position where it was before key depression, which makes it possible to play quickly, whereby it is possible to enjoy excellent playability of the electronic musical instrument.

Further, the hammer cushion47is provided on the rear end of the upper surface of the key2(i.e. on the upper piece-fixing portion51aof the hammer contact height-regulating portion46), and in addition, the cushion contact portion84of the hammer5for abutment with the hammer cushion47is provided at a location immediately forward of the key contact portion76that works as a point of action for pivotally moving the hammer5by the key2. This makes it possible not only to bring the hammer5into abutment with the hammer cushion47in a relatively shorter time e.g. when the hammer5returns to its original position, but also to reduce impact applied to the hammer cushion47compared with the case where the hammer5is configured such that the front end of the lower surface hereof is brought into abutment with the hammer cushion. Consequently, it is possible to obtain an effect of suppressing the bouncing of the hammer5within a relatively wide range of pivotal motion when the hammer5returns to its original position as well as to use the hammer cushion47over a long term.

Furthermore, when the hammer5pivotally moves, only the front bottom portion81aof the key contact portion76of the hammer5comes into contact with the rear end of the upper surface of the key2(i.e. the hammer-receiving portion51bof the hammer contact height-regulating portion46), so that the distance between the contact portion and the axis of the hammer fulcrum shaft63of the hammer support4is approximately constant. This makes it possible to suppress an increase in load applied to the key2from the hammer5when the hammer5is pivotally moved in accordance with key depression. As a consequence, even when the player performs soft key striking in which the key2is slowly depressed during musical performance, the player does not feel the key2heavy, and therefore it is possible to enjoy excellent playability of the electronic musical instrument.

The long-term use of the electronic piano sometimes causes the hammer cushion47to be progressively crushed by being repeatedly pressed by the hammer5, resulting in a lowered level of the upper surface of the hammer cushion47. However, since the front bottom portion81aof the key contact portion76of the hammer5is formed in an arcuate shape having a relatively large curvature radius, the level of contact between the hammer5and the key2changes little even when the level of the upper surface of the hammer cushion47is lowered, which makes it possible to maintain the hammer5in a correct posture in the key-released state over a long term.

As described above in detail, according to the present embodiment, in adjacent two of the plurality of keyframe front molded articles21to be connected to one another, the right connecting portion23of one keyframe front molded article21of the two is formed with the connecting engagement protrusion26having a lateral T shape in plan view, and the left connecting portion24of the other keyframe front molded article21is formed with the connecting engagement recess27for engagement with the connecting engagement protrusion26. This connecting engagement recess27is formed in a recessed shape that can be vertically fitted with the shape, in plan view, of the connecting engagement protrusion26, and is engaged with the connecting engagement protrusion26in a state immovable relative to the connecting engagement protrusion26in the left-right direction and the front-rear direction. By thus engaging the connecting engagement protrusion26and the connecting engagement recess27in a state fitted to each other, it is possible to connect the adjacent two keyframe front molded articles21and21to each other by their own mechanical connection, so that even when the keyframe front molded articles21expand or contract due to thermal expansion or contraction, solid connection between the two keyframe front molded articles21and21can be maintained. As described above, according to the present embodiment, it is possible to maintain solid connection between each adjacent two of the keyframe front molded articles21and21over a long term to thereby prevent occurrence of variation in gap between the keys2in the keyboard device1.

Further, the connecting engagement protrusion26and the connecting engagement recess27are not only engaged with each other, but also secured to each other in a state bonded in the vertical direction using the adhesive, which makes it possible to achieve further solid connection between the adjacent keyframe front molded articles21and21. In addition, since the adhesive is injected through the plurality of adhesive injection holes29and then flows into the grooves29acontinuous with each of the adhesive injection holes29and radially extending therefrom. This makes it possible to stably supply the adhesive to a relatively wide range between the connecting engagement protrusion26and the connecting engagement recess27superposed one upon the other, in a well-balanced manner as a whole, which makes it possible to solidly bond the connecting engagement protrusion26and the connecting engagement recess27to each other.

Furthermore, since the connecting engagement protrusion26and the connecting engagement recess27bonded to each other by the adhesive are screwed to each other with the swaging screw31in a state vertically secured to each other by swaging, it is possible to more solidly bond the connecting engagement protrusion26and the connecting engagement recess27to each other and stably maintain the resultant state over a long term.

What is more, while the connecting engagement protrusion26is formed with the screw protrusion26c, the connecting engagement recess27is formed with the insertion hole27c, so that work for assembling the keyframe front molded articles21and21can be carried out with relative ease by fitting the connecting engagement protrusion26and the connecting engagement recess27with each other while inserting the screw protrusion26cinto the insertion hole27c. Further, since the connecting engagement protrusion26and the connecting engagement recess27are not only fitted with each other, but also the screw protrusion26cis inserted into the insertion hole27c, it is possible to more solidly connect the keyframe front molded articles21and21in a state immovable relative to each other in the left-right direction and the front-rear direction.

Note that the present invention is not limited to the above-described embodiment, but it can be practiced in various forms. For example, although in the above-described embodiment, the hammer cushion47is provided on the rear end of the upper surface of the key2, this is not limitative, but it is possible to provide a member similar to the hammer cushion47in the cushion contact portion84of the hammer5in place of the hammer cushion47.

Further, although in the embodiment, in the key contact portion76of the hammer5, the bottom of the protrusion cover78is formed with the front bottom portion81athat can be brought into contact with the key2and the rear bottom portion81bthat cannot be brought into contact with the key2, this is not limitative, but such portions can be formed integrally on the hammer body71.

Furthermore, although the hammer cushion47is made of soft urethane foam by way of example, this is not limitative, but any other material can be adopted, insofar as it is capable of suppressing the bouncing of the hammer5on the point of returning, after key release, to its original position where it was before key depression.

What is more, although in the embodiment, the connecting engagement protrusion26of the keyframe front molded article21is formed in a lateral T shape in plan view, it is possible to configure the connecting engagement protrusion26such that the increased-width portion26bon the tip end of the reduced-width portion26aprotrudes only either forward or rearward, for example, to thereby form the connecting engagement protrusion26into an L shape in plan view. As far as the shape, in plan view, of the connecting engagement protrusion26is concerned, it is possible to adopt any of various shapes that allows adjacent keyframe front molded articles21and21to be interconnected in a state immovable relative to each other in the left-right direction.

The detailed structure of each of the keyboard device1, the key2, the hammer5, the key contact portion76, the keyframe front11, and the keyframe front molded article21is described only by way of example, and it can be modified, as desired, within the scope of the subject matter of the present invention.

It is further understood by those skilled in the art that the foregoing are preferred embodiments of the invention, and that various changes and modifications may be made without departing from the spirit and scope thereof.