JP2002297122A - Opening/closing controller for fallboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an opening/closing controller for fallboard which is capable of surely and slowly closing a fallboard, capable of making the fallboard lighter in weight, and capable of stably holding the fallboard without requiring vexatious adjustment. SOLUTION: This opening/closing controller has an oil damper 2 which has a casing 3 attached to the fallboard 1 and packed with oil and a revolving shaft 4 non-rotatably engaged with a piano body 15 and brakes the fallboard 1 when the fallboard 1 turns to a close position side, a ball stopper 8 which has a ball 23 disposed at either of the revolving shaft 4 and the casing 3 freely retractably with respect to the other peripheral surface and a spring 24 to energize the ball 23 toward the other and rugged parts 25 and 26 which are formed on the other peripheral surface, are engaged with the ball 23 of the ball stopper 8 and obstructs turning of the fallboard 1 to the close position side by being detained one another with the ball 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a keyboard cover opening / closing control device for controlling the opening / closing of a rotary keyboard cover such as a grand piano using an oil damper.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a keyboard cover provided with a conventional opening / closing control device of this kind. This keyboard cover 51
It is for a grand piano, and has a lid main body 51a and a lid retrofit 51b attached to a rear portion of an upper surface thereof, and an oil damper 52 is attached to a side surface thereof. The oil damper 52 includes a casing 53 filled with oil, and a rotating shaft 54 rotatably fitted to the casing 53. With the relative rotation of the casing 53 and the rotating shaft 54, the oil damper 52 moves in one direction. A large resistance torque is generated during rotation, and a very small resistance torque is generated during rotation in the other direction.

The casing 53 is embedded in the keyboard cover 51, and the rotating shaft 54 is non-rotatably engaged with the arm of a grand piano (not shown). It rotates with respect to the rotation shaft 54. The oil damper 52 is mounted such that a large resistance torque is generated when the keyboard cover 51 rotates in the closing direction. With the above configuration, the keyboard cover 51 is
At the time of closing, the oil damper 52 is braked with a large resistance torque, so that it is closed slowly and securely even when the hand is released from the keyboard cover 51. At the time of opening, the resistance torque of the oil damper hardly acts. Can be opened.

In the open position of the keyboard cover 51,
As shown in FIG. 7, since the keyboard 51 is in the upright state, the hand is slightly touched or the vibration is applied to the keyboard cover 51, and the keyboard 51 immediately starts rotating in the closing direction. is there. For this reason, a weight 55 is attached to the keyboard cover 51. The weight 55 is made of a material having a large specific gravity, such as iron, for example.
It is arranged on the side opposite to the lid body 51a. This weight 55
By applying a moment in the opening direction to the keyboard cover 51 due to the weight of the keyboard cover 51, the keyboard cover 51 is stably held at the open position.

[0005]

As described above, in the conventional opening / closing control device, the moment in the opening direction due to the weight of the weight 55 is made larger than the moment in the closing direction due to the weight of the keyboard cover 51 by its own weight. The keyboard cover 51 is held at the open position. In addition, the weight 55 must be arranged at a position near the oil damper 52 of the keyboard lid 51, and the length of the arm of the moment due to this must be short. Therefore, weight 5
In order to secure a large moment by the key 5, the weight must be considerably increased, and
1 The weight of the whole also becomes heavy. If the moment due to the weight of the weight 55 is too large, the closing operation force becomes excessively large and the keyboard lid 51 becomes difficult to close. Therefore, it is necessary to adjust the moment to an appropriate size. On the other hand, in the above-described configuration, since a subtle deviation such as the mounting position of the weight 55 directly appears as a deviation in the magnitude of the moment, there is a disadvantage that the adjustment is subtle and difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to surely and slowly close a keyboard cover, reduce the weight of the keyboard cover, and without requiring complicated adjustment. It is an object of the present invention to provide a keyboard cover opening / closing control device capable of stably holding a keyboard cover at an open position.

[0007]

SUMMARY OF THE INVENTION To achieve this object, a first aspect of the present invention is a keyboard cover rotatably attached to a piano body between an open position for opening a keyboard and a closed position for closing. Opening / closing control device for controlling the opening / closing of a keyboard, which is attached to the keyboard cover, is rotatably fitted to a casing filled with oil, and is rotatably fitted to the casing, and is non-rotatably engaged with the piano body. An oil damper having a rotating shaft, the oil damper being configured to brake the keyboard cover by the action of oil accompanying the relative rotation between the casing and the rotating shaft when the keyboard cover is rotated to the closed position side; A stopper mechanism for preventing the rotation of the keyboard cover toward the closed position by locking the casing and the rotating shaft to each other when the keyboard cover is at the open position. And said that you are.

In this keyboard cover opening / closing control device, when the keyboard cover is turned to the closed position side, the keyboard cover is braked by the action of oil caused by the relative rotation of the casing of the oil damper and the rotating shaft, and deceleration is performed. To ensure that the lid closes slowly. Further, when the cover is in the open position, the casing and the rotating shaft are mutually locked by the stopper mechanism provided on the oil damper, so that the cover is prevented from turning to the closed position side, It is held in the open position. As described above, since the keyboard cover is held in the open position by the interlock between the casing and the rotating shaft, the conventional weight 55 provided for the same purpose becomes unnecessary,
By abolition, the keyboard lid can be reduced in weight. Further, since the oil damper has a function of holding the keyboard lid at the open position in addition to the braking function when the lid is closed, unlike the conventional case where the weight 55 is attached separately from the oil damper, the The adjustment of the holding force can be easily performed without being affected by the mounting position of the weight 55 or the like.

According to a second aspect of the present invention, in the keyboard cover opening / closing control device of the first aspect, the stopper mechanism is provided on one of the casing and the rotating shaft so as to be able to protrude and retract from the other peripheral surface, and A ball stopper having a spring for urging the ball toward the other side, and a closed side formed on the other peripheral surface and locked together by the ball when the keyboard cover is in the open position; And a concave / convex portion for preventing rotation of the keyboard cover.

According to this configuration, the ball stopper is provided on one of the casing and the rotating shaft of the oil damper,
The ball is urged toward the other by a spring and is provided so as to be freely retractable. When the cover is in the open position, the ball and the uneven portion provided on the other peripheral surface are interlocked with each other, so that the cover is prevented from turning to the closed position, and Is held. As described above, according to the present invention, the stopper mechanism can be simply and inexpensively configured by simply providing the ball stopper on one of the casing and the rotating shaft and forming the uneven portion on the other peripheral surface.

According to a third aspect of the present invention, in the keyboard cover opening / closing control device according to the second aspect, the concave and convex portions extend circumferentially along the other peripheral surface of the casing and the rotating shaft, and the keyboard cover is in the closed position. It is formed between a position corresponding to the closed position where the ball of the ball stopper is located at one time and a position corresponding to the open position where the ball is positioned when the keyboard cover is at the open position, and is equivalent to the position corresponding to the closed position from the position corresponding to the open position. It is characterized in that it has a peripheral groove that becomes gradually shallower toward the part, and a concave part that is formed at the part corresponding to the open position so as to be continuous with the peripheral groove and that is deeper than the adjacent part of the peripheral groove.

According to this configuration, the keyboard lid is opened and closed while the ball of the ball stopper engages with the peripheral groove formed on the other peripheral surface of the casing and the rotating shaft, and is guided by this. When the keyboard cover reaches the open position, the ball engages with the deep recess connected to the circumferential groove. As described above, when the keyboard cover is in the open position, the ball of the ball stopper is engaged with the deep recess, so even if the keyboard cover is slightly touched or vibration is applied in this open state, Since the boundary between the peripheral groove and the peripheral groove serves as the resistance of the ball, the keyboard lid can be prevented from rotating toward the closed position, and thus the keyboard lid can be reliably and stably held at the open position. In addition, since the circumferential groove is formed so as to gradually become shallower from the position corresponding to the closed position of the keyboard cover to the position corresponding to the open position, the ball engaged with the concave portion can be securely locked, and the ball can be locked. It can be guided smoothly by the circumferential groove. Furthermore, when closing the keyboard lid,
When the ball is pulled to the closed position with a little force, the ball moves over the boundary from the recess and moves to the circumferential groove side, and then the hand is released from the keyboard cover, and the keyboard cover is slowly closed by the oil damper Operation can be obtained without hindrance.

According to a fourth aspect of the present invention, in the opening / closing control device for a keyboard cover according to the second aspect, the concave / convex portion is engaged with the ball of the ball stopper when the keyboard cover reaches the open position. It is characterized in that it has a projection that prevents rotation of the keyboard cover toward the closed position by being stopped.

With this configuration, when the keyboard lid reaches the open position, the ball of the ball stopper and the projection of the concave and convex portion are locked in a state in which they are over each other. As a result, the projection can reliably prevent the keyboard cover from turning to the closed position side when the hand slightly touches the keyboard cover at the open position. Therefore, as in the case of the second aspect, the keyboard cover can be reliably and stably held in the open position, and the keyboard cover can be smoothly closed by the oil damper without any trouble.

According to a fifth aspect of the present invention, in the keyboard cover opening / closing control device of the first aspect, the stopper mechanism is provided on one of the casing and the rotating shaft so as to be able to advance and retreat with respect to the other peripheral surface. A spring, formed on the other peripheral surface,
And a projection that locks the leaf spring over the leaf spring when the lid reaches the open position, thereby preventing rotation of the lid toward the closed position. And

In this configuration, when the keyboard cover reaches the open position, the leaf spring and the projection are locked in a state in which they go over each other. The keyboard cover is securely held at the open position by the mutual locking of the leaf spring and the projection and the spring force of the leaf spring, so that the above-described operation of claim 4 can be obtained similarly. Further, in the present invention, since a simpler leaf spring is employed in place of the ball stopper according to claim 4, it is possible to further simplify and reduce the cost.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention.
1 shows an opening / closing control device for a keyboard lid of a grand piano according to an embodiment. The keyboard cover 1 shown in FIG. 1 is composed of a Lauan plywood or the like, and has a horizontally long rectangular cover main body 1a and a cover retrofit 1b attached to a rear portion of an upper surface thereof. I have.

As shown in FIG. 2, the oil damper 2 includes a casing 3 and a rotating shaft 4 rotatably fitted to the casing 3. The casing 3 has a casing main body 5 having a circular cross-section, one end of which is open and the other end of which is closed, and a flange-shaped rectangular mounting portion 6 integrally provided at one end, and is formed on the side surface of the keyboard cover 1. The casing main body 5 is embedded in an embedding hole (not shown), and is attached to the keyboard cover 1 by screwing the attaching portion 6 (see FIG. 1). The casing body 5 includes an oil filling portion 5a filled with oil and a small diameter portion 5b on the other end side having a smaller diameter than the oil filling portion 5a.
In addition, a ball stopper 8 described later is provided.

On the other hand, the rotating shaft 4 has a shaft portion 9 inserted into the casing body 5 of the casing 3, a larger-diameter fitting portion 10 connected to one end side in the axial direction, and an end face of the fitting portion 10. The protruding thick plate-shaped engaging portion 11 is integrally provided.
The fitting portion 10 is fitted to the casing body 5 via an O-ring 12. A female screw (not shown) is formed at one end of the casing 3, and a ring-shaped bearing 13 is screwed into the female screw via a male screw 13a. Supported. With the above configuration, the rotating shaft 4 is rotatably and liquid-tightly attached to the casing 3.

As shown in FIG. 1, the engaging portion 11 of the rotating shaft 4
Is non-rotatably engaged with a U-shaped hanging bracket 16 attached to the inner surface of the arm 15 (piano body) of the grand piano. Therefore, when the keyboard cover 1 is opened and closed, the casing 3 integral with the keyboard cover 1 rotates together with the keyboard cover 1, whereas the rotating shaft 4 does not rotate due to the engagement between the engaging portion 11 and the hanging bracket 16. The casing 3 rotates with respect to the rotating shaft 4 in a direction corresponding to the opening and closing of the keyboard cover 1. In addition, the keyboard cover 1 is a keyboard (not shown) in an almost upright state.
Is opened and closed between an open position (position shown in FIG. 1) for opening the key and a closed position (not shown) for covering the keyboard in a substantially horizontal state,
This closed position is determined by the keyboard cover 1 being in contact with a mouthpiece (not shown) of the piano body.

The shaft portion 9 of the rotary shaft 4 is composed of a large diameter portion 9a inserted into the oil filling portion 5a of the casing body 5, and a small diameter portion 9b fitted to the small diameter portion 5b. The outer peripheral surface of the large-diameter portion 9a is provided at intervals of 180 degrees in the circumferential direction.
One projection 17 is formed, and each projection 17 is
It protrudes radially outward of the large-diameter portion 9a and extends over the entire axial direction. An oil passage 18 is formed at the center of the protrusion 17 in the axial direction.
A movable valve 19 is provided so as to straddle the oil passage 18.

The movable valve 19 includes a peripheral wall 19a and first and second vertical walls 19b, 1b extending from both ends in the circumferential direction.
9c having a U-shaped cross section. The peripheral wall 19a
It is curved in the circumferential direction at the same curvature as the inner peripheral surface of the casing body 5 and is in sliding contact with it. In addition, both hanging walls 19b, 19c
The interval between them is larger than the width of the projection 17 and engages the projection 17 with play in the rotational direction. Also, the first vertical wall 19
b, a second oil passage 2 having a larger area than the first oil passage 20 in the second vertical wall 19c.
1 are formed respectively.

As described above, the ball stopper 8 according to the present invention comprises the small diameter portion 5 of the casing body 5 of the casing 3.
b. As shown in FIG. 3, the ball stopper 8 is provided so as to penetrate the small-diameter portion 5b, and has a cylindrical holder 22 having one end opened inside the small-diameter portion 5b. Can rotate freely to the shaft 4
And a coil spring 24 (spring) housed in the holder 22 and biasing the ball 23 toward the small-diameter portion 9b of the rotary shaft 4. .

On the other hand, on the peripheral surface of the small diameter portion 9b of the rotating shaft 4,
A circumferential groove 25 and a concave portion 26 with which the ball 23 of the ball stopper 8 is engaged are formed. The circumferential groove 25 has a small diameter portion 9b.
Are formed along the circumferential direction on the peripheral surface of the. In particular,
The circumferential groove 25 holds the ball 2 when the keyboard lid 1 is in the closed position.
3 extends between a position corresponding to the closed position and the vicinity of the position corresponding to the open position where the ball 23 is located when the keyboard cover 1 is at the open position, and gradually moves from the position corresponding to the closed position to the position corresponding to the open position. It is formed to be shallow.
The concave portion 26 is provided at a position corresponding to the open position of the small-diameter portion 9b.
5 and is deeper than an adjacent portion of the circumferential groove 25.

Next, the operation of the keyboard cover opening / closing control device having the above configuration will be described with reference to FIGS. FIG.
(A) shows a state where the keyboard cover 1 is in the closed position,
That is, the ball stopper 8 is located at an end (a position corresponding to a closed position) of the circumferential groove 25 on the side opposite to the concave portion 26, and the ball 23
Are engaged with the circumferential groove 25. From this closed position, the keyboard cover 1
Is rotated toward the open position, the casing 3 and the ball stopper 8 move in a predetermined direction (for example, an arrow A in FIGS. 2 and 3) with respect to the rotating shaft 4 while the ball 23 is guided by the circumferential groove 25. Direction). As a result, the second vertical wall 19c of the movable valve 19 comes into contact with the protrusion 17 by the pressure of the oil, and the second oil passage 21 having a larger area communicates with the oil passage 18 of the protrusion 17, whereby the oil is reduced. The damper 2 generates a very small resistance torque.
Therefore, the keyboard cover 1 can be easily opened with a small opening operation force.

When the keyboard cover 1 reaches the open position, FIG.
As shown in (b), the ball 23 of the ball stopper 8
Engages with the recess 26 beyond the circumferential groove 25. As described above, when the keyboard cover 1 is in the open position, the ball 23 is engaged with the deep concave portion 26. Therefore, even if the keyboard cover 1 is slightly touched or vibrated in this open state. Since the boundary portion with the circumferential groove 25 becomes the resistance of the ball 23, the keyboard cover 1 can be prevented from rotating toward the closed position, and thus the keyboard cover 1 is reliably and stably held at the open position. be able to. Further, since the circumferential groove 25 is formed so as to gradually become shallower from the position corresponding to the closed position of the keyboard cover 1 to the position corresponding to the open position, the ball 23 engaged with the concave portion 26 can be securely locked. With the ball 23
Can be smoothly guided by the circumferential groove 25.

Next, when the keyboard cover 1 is closed, when the keyboard cover 1 is pulled toward the closed position with a slightly strong force, the ball 23
After moving over the boundary from the recess 26 to the circumferential groove 25 side, when the user releases the keyboard cover 1 after that, the keyboard cover 1 turns to the closed position side by its own weight. With this rotation, the casing 3 rotates in the opposite direction (for example, the direction of arrow B in FIGS. 2 and 3) with respect to the rotation shaft 4, so that the first vertical wall 19 b of the movable valve 19 When the first oil passage 20 having a smaller area communicates with the oil passage 18, a large resistance torque is generated. As described above, when closing the keyboard lid 1, the keyboard lid 1 is braked and decelerated by the large resistance torque of the oil damper 2, so that the keyboard lid 1 can be surely closed slowly.

As described above, according to the present embodiment, the keyboard cover 1 is held in the open position by locking the ball 23 of the ball stopper 8 with the concave portion 26, so that the keyboard cover 1 is provided for the same purpose. The conventional weight 55 is unnecessary,
Due to the abolition, the keyboard cover 1 can be reduced in weight.
Further, since the oil damper 2 has a function of holding the keyboard lid 1 in the open position in addition to the braking function when the keyboard lid 1 is closed, unlike the conventional case in which the weight 55 is attached separately from the oil damper, Adjust the holding force of the keyboard cover 1 with the weight 5
5 can be easily performed without being affected by the mounting position of the device 5 or the like.

FIGS. 4 and 5 show a second embodiment of the present invention. As shown in both figures, this embodiment differs from the first embodiment in that a projection 31 is provided as a stopper on the peripheral surface of the small diameter portion 9b of the rotating shaft 4 instead of the peripheral groove 25 and the concave portion 26 of the first embodiment. It is. The protrusion 31 is provided in the small diameter portion 9b
Are formed in the vicinity of the portion corresponding to the open position of the above. Keyboard cover 1
5A is in the closed position shown in FIG. 5A, the ball 23 of the ball stopper 8 is located at a position corresponding to the closed position, as in the first embodiment. When the keyboard cover 1 is rotated from this state to the open position, the casing 3 and the ball stopper 8 rotate in the direction of arrow A with the ball 23 in contact with the peripheral surface of the small diameter portion 9b. And the ball 23
When the cover 1 climbs over the protrusion 31 shortly before reaching the open position, and when the cover 1 is in the open position, as shown in FIG. 5B, the protrusion 31 is brought into contact with the protrusion 31 from the open position side. Locked by 31. Therefore, in the present embodiment, the rotation of the keyboard cover 1 to the closed position side can be reliably prevented by the projections 31. As a result, the keyboard cover 1 can be reliably and stably held at the open position. The effects of the embodiment can be obtained similarly.

FIG. 6 shows a third embodiment of the present invention. As shown in the drawing, the present embodiment is significantly different from the above-described first and second embodiments in that a leaf spring 41 is used instead of the ball stopper 8. The leaf spring 41 includes a central chevron-shaped protrusion 41a, and engagement portions 41b, 41b extending to both sides from the protrusion 41a.
On the other hand, a circumferential groove 42 extending in the circumferential direction is formed at a predetermined position on the circumferential surface of the small-diameter portion 9 b of the rotating shaft 4.
The engaging portions 41b, 41b of the leaf spring 41 are slidably and non-removably engaged with each other, and the protrusion 41a protrudes outward through the opening of the circumferential groove. At a predetermined position on the inner peripheral surface of the small-diameter portion 5b of the casing 3, a projection 43 protruding inward is formed.

FIG. 6 shows a state where the keyboard cover 1 is in the open position. That is, as the keyboard cover 1 rotates from the closed position (not shown) to the open position side, the casing 3 rotates counterclockwise in the drawing, and the projection 43 slightly before the keyboard cover 1 reaches the open position. Moves over the projection 41a while pushing down the leaf spring 41 against its spring force. And
When the keyboard cover 1 is in the open position, as shown in the figure, the projection 43 abuts on the projection 41a from the open position side and is locked. Therefore, in the present embodiment, the rotation of the keyboard cover 1 toward the closed position can be reliably prevented by the locking of the projection 43 by the leaf spring 41 and the spring force of the leaf spring 41. As a result, the effects of the above-described embodiment can be obtained similarly, such as the keyboard cover 1 can be reliably and stably held at the open position. Further, in the present embodiment, as compared with the first and second embodiments, a simpler leaf spring 41 is employed instead of the ball stopper 8, so that the configuration can be further simplified and reduced in cost. In the present embodiment, the leaf spring 41 is arranged on the rotating shaft 4 side and the projection 43 is arranged on the casing 3 side. However, it is needless to say that these arrangements may be reversed.

The present invention can be implemented in various modes without being limited to the embodiments described above.
For example, in the first and second embodiments, the oil damper 2
A ball stopper 8 is provided on the casing 3 side of the rotary shaft 4.
Although the peripheral groove 25, the concave portion 26, and the projection 31 are formed as uneven portions on the side, they may be arranged reversely on the casing 3 side and the rotating shaft 4 side. Although the embodiment is an example in which the present invention is applied to a keyboard cover of a grand piano, a keyboard cover of another type of piano having a cover body and a cover retrofit, for example, a keyboard cover of a grand piano-type electronic piano Of course, it may be applied to Other, ball stopper 8
It is possible to appropriately change the configuration of the details, including the configuration and the shape of the concave and convex portions, within the scope of the present invention.

[0033]

As described above, the keyboard cover opening / closing control device of the present invention can securely close the keyboard cover slowly and slowly, can reduce the weight of the keyboard cover, and does not require any complicated adjustment. This has the effect that the lid can be stably held at the open position.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an opening / closing control device for a keyboard cover of a grand piano according to a first embodiment of the present invention before the keyboard cover is attached to a brace.

FIG. 2 is an exploded perspective view of an oil damper of the opening / closing control device of FIG.

FIG. 3 is a sectional view showing an operation of the opening / closing control device of FIG. 1;

FIG. 4 is a partial perspective view of an oil damper of an opening / closing control device according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing the operation of the opening / closing control device of FIG. 4;

FIG. 6 is a cross-sectional view illustrating an opening / closing control device according to a third embodiment of the present invention.

FIG. 7 is a side view showing an example of a keyboard cover of a conventional grand piano provided with an opening / closing control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Keyboard lid 2 Oil damper 3 Casing 4 Rotating shaft 8 Ball stopper 15 Arm (piano main body) 23 Ball 24 Coil spring (spring) 25 Circumferential groove (irregular part) 26 Concave part (irregular part) 31 Projection (irregular part) 41 Leaf spring 43 protrusion

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference)

Claims (5)

[Claims] 1. A keyboard cover opening / closing control device for controlling opening and closing of a keyboard cover attached to a piano body so as to be rotatable between an open position for opening a keyboard and a closed position for closing the keyboard, Attached to the keyboard lid, a casing filled with oil, and rotatably fitted to this casing,
A rotating shaft that non-rotatably engages the piano body,
An oil damper that brakes the keyboard lid by the action of the oil accompanying the relative rotation of the casing and the rotation shaft when the keyboard lid rotates toward the closed position; and A stopper mechanism for preventing the rotation of the keyboard cover toward the closed position by locking the casing and the rotating shaft to each other when the keyboard cover is at the open position. An opening / closing control device for a keyboard cover. 2. The stopper mechanism includes a ball provided on one of the casing and the rotating shaft so as to be able to protrude and retract from the other peripheral surface, and a spring for urging the ball toward the other. A ball stopper, formed on the other peripheral surface, and when the keyboard cover is in the open position, is locked to the ball to prevent rotation of the keyboard cover toward the closed position. The opening / closing control device for a keyboard cover according to claim 1, further comprising: 3. The closed position where the ball of the ball stopper is located when the keyboard cover is at the closed position, wherein the uneven portion extends circumferentially along the other peripheral surface of the casing and the rotating shaft. It is formed between the corresponding position and the vicinity of the open position corresponding position where the ball is located when the keyboard cover is in the open position, and gradually becomes shallower from the closed position corresponding position toward the open position corresponding position. 3. The peripheral groove according to claim 2, further comprising: a peripheral groove; and a concave portion formed at a position corresponding to the open position so as to be continuous with the peripheral groove and deeper than a portion adjacent to the peripheral groove. 4. Open / close control device for the keyboard lid. 4. When the keyboard cover reaches the open position, the uneven portion is locked in a state in which the ball stopper rides over the ball with respect to the ball, so that the keyboard moves toward the closed position. The opening / closing control device for a keyboard cover according to claim 2, further comprising a projection for preventing rotation of the lid. 5. The stopper mechanism includes: a leaf spring provided on one of the casing and the rotating shaft so as to be able to advance and retreat with respect to the other peripheral surface; and a stopper formed on the other peripheral surface. And a projection that locks the leaf spring over the leaf spring when reaching the open position, thereby preventing rotation of the keyboard cover toward the closed position. The opening / closing control device for a keyboard cover according to claim 1, characterized in that: