Key switch device, keyboard with the key switch device, and electronic apparatus with the keyboard

What is claimed is:

1. A key switch device including:

a key top provided at its underside with a first engagement portion and a second engagement portion;

a third engagement portion in correspondence with the first engagement portion, and a fourth engagement portion in correspondence with the second engagement portion, both of which are arranged below the key top;

a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion;

a first gear portion provided near the first shaft in the first link member;

a second gear portion provided near the second shaft in the second link member; and

a switching section for performing a switching operation in accordance with the vertical movement of the key top;

the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first and second gear portions;

wherein the first gear portion is provided with a first upper tooth portion and a first lower tooth portion which are arranged in adjacent relation in a direction of width of the first link member and in upper-and-lower relation in a direction of thickness of the first link member,

the second gear portion is provided with a second upper tooth portion and a second lower tooth portion which are arranged in adjacent relation in a direction of width of the second link member and in upper-and-lower relation in a direction of thickness of the second link member, and

the first upper tooth portion and the second lower tooth portion, and, the first lower tooth portion and the second upper tooth portion, are allowed to move, while maintaining mutually overlapping contact relation, in association with the vertical movement of the key top.

2. The key switch device according to claim 1, wherein the first link member is provided with a pair of arms, and the first gear portion is provided in a tip end of each of the arms, and

the second link member is provided with a pair of arms, and the second gear portion is provided in a tip end of each of the arms.

3. The key switch device according to claim 1, wherein each of the first and second upper tooth portions is formed with a first curved surface which is curved upwards, and

each of the first and second lower tooth portions is formed with a second curved surface which is curved downwards.

4. The key switch device according to claim 3 wherein the first and second curved surfaces are in close contact with each other during the vertical movement of the key top.

5. A keyboard provided with at least one key switch device according to claim 1.

6. The key switch device according to claim 1, wherein an engagement relationship between the third engagement portion and the third shaft of the first link member and that between the fourth engagement portion and the fourth shaft of the second link member are established easier to release than an engagement relationship between the first engagement portion of the key top and the first shaft of the first link member and that between the second engagement portion of the key top and the second shaft of the second link member.

7. The key switch device according to claim 6 further including:

a first shaft support portion elastically deformable, provided at a lower portion of the first link member; and

a second shaft support portion elastically deformable, provided at a lower portion of the second link member;

the third shaft being provided in the first shaft support portion and the fourth shaft being provided in the second shaft support portion.

8. The key switch device according to claim 7, wherein the switching member includes a circuit board provided with a movable switch electrode and a fixed switch electrode,

the third and fourth engagement portions are constructed from an engagement member formed with a pair of longitudinal groove-shaped engagement portions and fixed on the circuit board, and

the third and fourth shafts are engaged in the corresponding longitudinal groove-shaped engagement portions of the engagement member.

9. The key switch device according to claim 8, wherein the engagement portions of the engagement member each include a portion formed in a round shape in section, with which the third and fourth shafts are brought into contact.

10. The key switch device according to claim 8, wherein the engagement member is produced by molding a linear material having a substantially circular shape in section into a predetermined shape and then cutting it into chips each having a unit length of the key switch device.

11. The key switch device according to claim 8, wherein the circuit board is constructed of an upper sheet provided with the movable switch electrode disposed on an underside, a lower sheet provided with the fixed switch electrode disposed facing the movable switch electrode, and a spacer body disposed between the upper and lower sheets to hold the movable switch electrode and the fixed switch electrode at a distance from each other, and

the spacer body is constructed to provide a space between the upper and lower sheets in an area having a shape corresponding to a lower end of the key top and a width larger than a width of the lower end of the key top.

12. The key switch device according to claim 11, wherein the spacer body is constructed of a dot spacer provided on the upper or lower sheet, the dot spacer being formed to form the area.

13. An electronic apparatus including:

a keyboard for inputting various data such as characters, symbols, and others, the keyboard being provided with a key switch device including:

a key top provided at its underside with a first engagement portion and a second engagement portion;

a third engagement portion arranged below the key top in correspondence with the first engagement portion and, a fourth engagement portion arranged below the key top in correspondence with the second engagement portion;

a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion;

a first gear portion provided near the first shaft in the first link member;

a second gear portion provided near the second shaft in the second link member; and

a switching section for performing a switching operation in accordance with the vertical movement of the key top;

the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first and second gear portions;

wherein the first gear portion is provided with a first upper tooth portion and a first lower tooth portion which are arranged in adjacent relation in a direction of width of the first link member and in upper-and-lower relation in a direction of thickness of the first link member,

the second gear portion is provided with a second upper tooth portion and a second lower tooth portion which are arranged in adjacent relation in a direction of width of the second link member and in upper-and-lower relation in a direction of thickness of the second link member, and

the first upper tooth portion and the second lower tooth portion, and, the first lower tooth portion and the second upper tooth portion, are allowed to move, while maintaining mutually overlapping contact relation, in association with the vertical movement of the key top;

display means for displaying the characters, symbols, and others; and

control means for controlling the display means to display the characters, symbols, and others based on input data from the keyboard.

14. A key switch device including:

a key top provided at its underside with a first engagement portion and a second engagement portion;

a third engagement portion arranged below the key top in correspondence with the first engagement portion, and a fourth engagement portion arranged below the key top in correspondence with the second engagement portion;

a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion;

a first gear portion provided near the first shaft in the first link member;

a second gear portion provided near the second shaft in the second link member; and

a switching section for performing a switching operation in accordance with the vertical movement of the key top;

the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first and second gear portions;

wherein the first gear portion is formed into a first single tooth with a contact surface,

the second gear portion is formed into a second single tooth with a contact surface, and

the first single tooth and the second single tooth are allowed to move, while maintaining mutually overlapping contact relation so that the contact surface of the first single tooth and the contact surface of the second single tooth usually contact during the vertical movement of the key top.

15. The key switch device according to claim 14, wherein

one of the contact surfaces is curved upwards, while the other is curved downwards, and

both the curved contact surfaces are in close contact with each other during the vertical movement of the key top.

16. A keyboard provided with at least one key switch device according to claim 14.

17. A key switch device including:

a key top provided at its underside with a first engagement portion and a second engagement portion;

a third engagement portion arranged below the key top in correspondence with the first engagement portion, and a fourth engagement portion arranged below the key top in correspondence with the second engagement portion;

a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion;

a first and a second arms formed in the first link member, each of which is provided with the first shaft;

a third and a fourth arms formed in the second link member, each of which is provided with the second shaft;

the first link member being provided with a first gear portion formed near the first shaft of the first arm and a second gear portion formed near the first shaft of the second arm;

the second link member being provided with a second gear portion formed near the second shaft of the third arm and a first gear portion formed near the second shaft of the fourth arm;

a switching section for performing a switching operation in accordance with the vertical movement of the key top;

the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first gear portion of the first arm and the second gear portion of the third arm and through a mutual contact relationship between the second gear portion of the second arm and the first gear portion of the fourth arm;

wherein each of the first gear portions in the first arm of the first linkmember and the fourth arm of the second link member is provided with a first tooth portion;

each of the second gear portions in the second arm of the first link member and the third arm of the second link member is provided with a second tooth portion; and

the first tooth portion of the first arm and the second tooth portion of the third arm, and, the second tooth portion of the second arm and the first tooth portion of the fourth arm, are allowed to move, while maintaining mutually overlapping contact relation, in association with the vertical movement of the key top.

18. An electronic apparatus including:

a keyboard for inputting various data such as characters, symbols, and others, the keyboard being provided with a key switch device including:

a key top provided at its underside with a first engagement portion and a second engagement portion;

a third engagement portion arranged below the key top in correspondence with the first engagement portion, and a fourth engagement portion arranged below the key top in correspondence with the second engagement portion;

a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion;

a first gear portion provided near the first shaft in the first link member;

a second gear portion provided near the second shaft in the second link member and in contact with the first gear portion; and

a switching section for performing a switching operation in accordance with the vertical movement of the key top;

the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first and second gear portions,

wherein the first gear portion is formed into a first single tooth with a contact surface, and

the second gear portion is formed into a second single tooth with a contact surface, and

the first single tooth and the second single tooth are allowed to move, while maintaining mutually overlapping contact relation so that the contact surface of the first single tooth and the contact surface of the second single tooth usually contact during the vertical movement of the key top;

display means for displaying the characters, symbols, and others; and

control means for controlling the display means to display the characters, symbols, and others based on input data from the keyboard.

19. A key switch device including:

two upper engagement portions provided extending downward from an underside of a key top;

two lower engagement portions arranged below the key top in correspondence with the upper engagement portions respectively;

a guide member for supporting the key top to guide vertical movement thereof, the guide member including a first link member provided with a first engagement member engaged in one of the upper engagement portions and a third engagement member engaged in one of the lower engagement portions and a second link member provided with a second engagement member engaged in the other upper engagement portion and a fourth engagement member engaged in the other lower engagement portion;

a switching member for performing a switching operation in accordance with the vertical movement of the key top;

wherein the third engagement member of the first link member is slidably engaged in one of the lower engagement portions and the fourth engagement member of the second link member is slidably engaged in the other engagement portion, and

motion restraining means for restraining horizontal motion of the key top in course of depression is disposed between one of the lower engagement portions and first link member and between the other lower engagement portion and the second link member.

20. The key switch device according to claim 19, wherein the motion restraining means includes a slide groove formed by a wall portion to which the third or fourth engagement member is brought into contact during non-depression of the key top and a sloped portion sloping from the wall portion, the slide groove being disposed in at least one of the lower engagement portions.

21. The key switch device according to claim 20, wherein the third or fourth engagement member is formed into a shaft member having an elliptic shape in side view so that the shaft member is slid in the slide groove along an inclined surface of the sloped portion in association with the vertical movement of the key top while turning a longitudinal axis of the elliptic shape into a horizontal situation or a vertical situation.

22. The key switch device according to claim 20, wherein the sloped portion slopes outwardly.

23. The key switch device according to claim 22, wherein the third or fourth engagement member is formed into a shaft member having an elliptic shape in side view so that the shaft member is slid in the slide groove along an inclined surface of the sloped portion in association with the vertical movement of the key top while turning a longitudinal axis of the elliptic shape into a horizontal situation.

24. The key switch device according to claim 19, wherein the motion restraining means including:

a shaft member formed extending from a side face of the first or second link members; and

a wall member formed near at least one of the lower engagement portions, for guiding the shaft member in contact therewith when the third or fourth engagement member is slid in association with depression of the key top.

25. A keyboard provided with one or more key switch device according to claim 19.

26. An electronic apparatus including:

a keyboard for inputting various data such as characters, symbols, and others, the keyboard being provided with a key switch device including:

two upper engagement portions provided extending downward from an underside of a key top;

two lower engagement portions arranged below the key top in correspondence with the upper engagement portions respectively;

a guide member for supporting the key top to guide vertical movement thereof, the guide member including a first link member provided with a first engagement member engaged in one of the upper engagement portions and a third engagement member engaged in one of the lower engagement portions and a second link member provided with a second engagement member engaged in the other upper engagement portion and a fourth engagement member engaged in the other lower engagement portion;

a switching member for performing a switching operation in accordance with the vertical movement of the key top;

wherein the third engagement member of the first link member is slidably engaged in one of the lower engagement portions and the fourth engagement member of the second link member is slidably engaged in the other engagement portion, and

motion restraining means for restraining horizontal motion of the key top in course of depression is disposed between one of the lower engagement portions and first link member and between the other lower engagement portion and the second link member;

display means for displaying the characters, symbols, and others; and

control means for controlling the display means to display the characters, symbols, and others based on input data from the keyboard.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a key switch device in which vertical and horizontal motions of a key top are guided and supported with a pair of link members which are operated synchronously when the key top is depressed with favorable operability; a keyboard provided with the key switch device; and an electronic apparatus provided with the keyboard; and particularly to a key switch device provided with link members including gear parts with improved structures for allowing synchronous action of the link members; a keyboard provided with the key switch device; and an electronic apparatus provided with the keyboard.

The present invention also relates to a key switch device in which a horizontal motion of a key top in course of depression is restrained to provide stable key operability, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

Moreover, the present invention relates to a key switch device in which a guide member including a key top is removably mounted on a circuit board, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

2. Description of Related Art

Conventionally, various types of key switch devices have been proposed. In association with the recent trend toward a thin key switch device, enhancement of key operability, etc., there has been proposed a key switch device in which a pair of link members support a key top for guiding vertical movement of the key top, and the link members are operated in synchronization with each other upon depression of the key top, thus achieving a reduction in thickness (height) of a key switch device and an enhanced key top operability.

For example, Japanese patent unexamined publication No. 11-003628 discloses a key switch device in which a pair of bearing portions each having two bearing holes are provided on the underside of a key top and a guide claw is provided at each end of two recesses formed on the upper surface of a support part. In this device, two support shafts of one gear link member are rotatably supported in the bearing holes, and also each end of a support shaft is slidably supported between the recess and the guide claw. Two support shafts of the other gear link member are rotatably supported in the bearing holes, and also each end of a support shaft is slidably supported between the recess and the guide claw.

In the above key switch device, a pair of middle shafts constituting each of the two gear link members is formed with gear portions having one tooth or two teeth at the upper ends. The tooth or teeth of each gear portion of the middle shaft of the gear link member engage the tooth or teeth of each gear portion of the middle shaft of the other gear link member. When the key top is depressed from a non-depression position (original position) through elasticity of a protrusion of an actuator provided on a rubber sheet, the support shafts of the gear link members are rotated in the bearing holes, while each of the support shafts is slid outwardly between the recess and the guide claw. At this time, the teeth of the gear portions of the gear link members are engaged with each other, thereby allowing synchronous operation of the link members.

The structure of the gear portion of each gear link member adopted in the key switch device in the abovementioned publication is explained below with reference to FIG. 26. FIG. 26 is a schematic perspective enlarged view of the gear portions of the gear link members in the conventional key switch device. In FIG. 26, a first gear link member 100 has a pair of middle shafts 101 and 102 on which support shafts 103 and 104 are provided protruding outwardly. The support shafts 103 and 104 are rotatably supported in the bearing holes of bearing portions provided on the underside of the key top.

Like the first gear link member 100, a second gear link member 105 has a pair of middle shafts 106 and 107 on which support shafts 108 and 109 are provided protruding outwards. The support shafts 108 and 109 are rotatably supported in the bearing holes of the other bearing portions provided on the underside of the key top.

A gear portion 110 is formed in the tip end of a middle shaft 101 of the first gear link member 100. This gear portion 110 is provided with a single gear tooth 111. A gear portion 112 is formed in the tip end of a middle shaft 102. This gear portion 112 is provided with double gear teeth 113.

A gear portion 114 is formed in the tip end of a middle shaft 106 of the second gear link member 105. This gear portion 114 is provided with double gear teeth 115. The gear tooth 111 of the gear portion 110 of the middle shaft 101 of the first gear link member 100 is engaged between the double gear teeth 115 of the gear portion 114 of the middle shaft 106. A gear portion 116 is formed in the tip end of a middle shaft 107 of the second gear link member 105. This gear portion 116 is provided with a single gear tooth 117. This gear tooth 117 is engaged between the double gear teeth 113 of the gear portion 112 of the middle shaft 102 of the first gear link member 100.

As above, the gear tooth 111 of the middle shaft 110 is engaged with the gear teeth 115 of the middle shaft 106, while the gear teeth 113 of the middle shaft 102 are engaged with the gear tooth 117 of the middle shaft 107. Thus, as the key top is depressed, the first and second gear link members 100 and 105 are synchronously operated, allowing downward movement of the key top with its horizontal condition maintained.

Meanwhile, an electronic apparatus such as notebook-size computers, mobile computer devices and the like have come into wide use rapidly. In association with this, a reduction in thickness of a keyboard associated with such the electronic apparatus has been promoted year after year. Accordingly, a key switch device is increasingly required to be reduced in thickness.

In the conventional key switch device mentioned above, however, the gear teeth 113 of the middle shaft 102 of the first gear link member 100 and the gear teeth 115 of the middle shaft 106 of the second gear link member 105 are formed in a double teeth configuration of an upper and lower teeth aligned and spaced in the thickness direction of the middle shaft 102 or 106. To help a further reduction in thickness or height of a key switch device, the gear teeth 113 and 115 have to be further reduced in thickness and size.

This makes it difficult to assemble the gear tooth 111 of the first gear link member 100 and the gear teeth 115 of the second gear link member 105, and the gear teeth 113 of the first gear link member 100 and the gear tooth 117 of the second gear link member 105 in a proper engagement relationship. As a result, an assembling efficiency of the key switch device would be deteriorated.

As mentioned above, the gear teeth 113 and 115 must be reduced in thickness and size to achieve a thinner key switch device, resulting in a decrease in durability of the gear teeth 113 and 115. Thus, a key switch device with high durability for long-term use could not be achieved.

In the case where the gear teeth 113 and 115 are made of a resin, each of which has a double teeth configuration; upper and lower teeth provided in aligned and spaced relation in the thickness direction of the middle shaft 102 or 106, the gear link member 100 (105) having such the gear teeth 113 (115) could not be molded by only a simple die constructed of upper and lower parts which are opened in the shaft thickness direction. In this case, a slide die which is removably arranged in parallel to the teeth is further needed to form the double teeth configuration. This slide die necessarily occupies space. Accordingly, the number of gear link members to be made with use of one die would be reduced. This decreases production efficiency of the gear link members.

Meanwhile, in the key switch device, when the key top is moved horizontally in a non-depression position or a depressed position, key operability becomes unstable and deteriorated. For preventing this, in most instances, restraints are put on the horizontal motion of the key top held in the non-depression or depressed position.

Furthermore, the horizontal motion of the key top in course of depression causes more serious problems in the key operability. In view of this point, restraints are also provided on the horizontal motion of the key top being in depression.

For instance, Japanese patent unexamined publication No. 6-44860 discloses a key switch device constructed as follows. An engagement bar of one of a pair of link members is slidably engaged in an engagement groove of an engagement portion provided on the underside of a key top. An engagement pin is slidably engaged in an engagement groove in an engagement portion of a holder member. An engagement pin of the other link member is slidably engaged in an engagement groove of an engagement portion provided on the underside of the key top. An engagement bar is slidably engaged in an engagement groove of an engagement portion of the holder member.

In this key switch device, upper and lower ends of each of the link members are slidably engaged in the corresponding engagement portions of the key top and the holder member. This key top may be moved horizontally in course of depression. Thus, a shaft provided on the outside of one of the link members is guided vertically in a shaft guide groove of a guide wall upright provided in the holder member in order to restrain the horizontal motion of the key top in depression.

Japanese patent unexamined publication No. 5-342945 discloses a key switch device constructed such that an upper end of one of a pair of link members is rotatably supported on the underside of a key top and a lower end of the same is slidably engaged in a holder member, and an upper end of the other link member is rotatably engaged on the underside of the key top and a lower end of the same is slidably engaged in the holder member. In this key switch device, as with the above device, the lower ends of the link members are slidably engaged in the holder member, which may cause the horizontal motion of the key top in depression. To restrain the motion of the key top in depression, a positioning pin of a positioning member provided in the holder member is guided to slide in a positioning groove of a positioning member provided extending downward from the underside of the key top.

The above key switch devices disclosed in the publications No. 6-44860 and No. 5-342945 can prevent the horizontal motion of the key top even in course of depression based on a cooperative action of the shaft of the link member and the shaft guide groove of the guide wall or a cooperative action of the positioning groove of the positioning member and the positioning pin.

In the key switch device disclosed in the publication No. 6-44860, however, the guide wall with the shaft guide groove needs to be formed in the holder member. This guide wall also needs a height corresponding to about half of the height of the key switch device. This presents a large obstacle to an attempt to reduce the height of the key switch device. Also, the structure of the holder member may become complicated, which causes an increase in cost for its manufacture.

In the key switch device disclosed in the publication No. 5-342945, it is also necessary to form the positioning member with the positioning groove and to form the positioning member with the positioning pin in the holder member. The positioning members have to be formed with a height about half of that of the key switch device. Therefore, as in the case of the above key switch device, there occurs a large obstacle to materialization of a thinner key switch device. The structure of the holder member may also become complicated, causing an increased cost for its manufacture.

Furthermore, there has been proposed a key switch device constructed such that vertical movement of a key top is guided with a guide member constructed of a pair of link members, in which a switching portion of a circuit board disposed on a base plate is operated in response to depression of the key top. This circuit board is provided with a movable switch electrode and a fixed switch electrode, which are normally held in a separate state. When the key top is depressed, operating a switch pressing portion provided in the link member, the facing movable electrode and fixed electrode perform a switching operation.

On the circuit board, engagement members for supporting a pair of link members are provided for each key top. The engagement members is integrally formed with the circuit board by punching or stamping a predetermined portion of an aluminum plate forming the circuit board into a longitudinal groove with use of a press or the like. In a normal state, the link members are held with the respective lower ends being in a closed state due to a spring or the like that urges the key top upwards. When the key top is depressed, the link members are compressed vertically while sliding their engagement projections provided on the lower ends outwardly into an open state. To allow this, the engagement member is formed in a longitudinal grooved shape.

Furthermore, there has recently been proposed a key switch device using a membrane switch sheet having a three-layer configuration as a circuit board. This is constructed of an upper sheet having a lower face on which a predetermined circuit pattern including a movable switch electrode is provided, a lower sheet having an upper face on which a predetermined circuit pattern including a fixed switch electrode arranged facing the movable electrode is provided, and a spacer sheet disposed between the upper and lower sheets to separate the movable and fixed electrodes and provided with a switching hole in a position where the movable and fixed electrodes face each other. When this membrane switch sheet is used, an engagement member molded from metal such as aluminum, iron, and the like in a flat plate shape, is fixed on the sheet with adhesive. Examples thereof are shown in Japanese patent unexamined publications Nos. 9-190735 and 10-172380. In those devices, upper ends of a pair of link members are engaged in engagement portions formed on the underside of a key top to combine the link members.

In a manufacture process of a keyboard provided with a plurality of the key switch devices constructed as above, or in actual use by a user of an electronic apparatus such as a personal computer provided with the key switch devices, when troubles such as the mixing of foreign matters into the key switch device or malfunction therein occur, the following procedures have to be taken; pulling out the key top, checking the inside condition of the key switch device; repair or replacement thereof; and then reattaching the key top. In the case where the engagement members have been press-made in the circuit board, the pressed portions include right-angled corners of substantially 90 degrees in section, causing the engagement protrusion of the link member to snag on the edge in pulling the key top, thereby disabling the link member from being pulled out. Thus, only the key top is removed. The pair of link members combined through the respective upper ends engaged in the engagement portions of the key top are released from the engagement relation to the key top while only the lower ends are held in the engagement relation to the engagement members of the circuit board, thus allowing the link members to be held in random orientations. As a result, at reattachement of the key top, proper positioning and engaging between the link members and the key top become very difficult.

The above problem would occur not only in the case where the engagement member is integrally formed in the circuit board by a press but also in the case where the flat plate shaped engagement member is bonded to the membrane switch sheet as long as the engagement member has a corner of a sharp edge for engaging the engagement protrusion of the link member.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a key switch device with an enhanced assembling efficiency of link members to maintain high assembling efficiency of a whole key switch device while flexibly coping with the needs for a thinner key switch device, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

Another object of the present invention is providing a key switch device usable for long term without deterioration in durability of link members, and provided with the link members which can be molded by a simple die constructed of upper and lower parts without using a slide die, thereby to enhance production efficiency of the link member, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

Furthermore, another object of the present invention is to provide a thinner key switch device capable of restraining horizontal motion of a key top in course of depression with a simple structure, causing no increase in cost, thereby to achieve stable key operability, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

Another object of the present invention is to provide a key switch device capable of simply easily reattaching a key top after pulled out, and achieving the ease in assembly, a keyboard provided with the key switch device, and an electronic apparatus provided with the keyboard.

Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve the purpose of the invention, there is provided a key switch device including: a key top provided at its underside with a first engagement portion and a second engagement portion; a third engagement portion in correspondence with the first engagement portion, and a fourth engagement portion in correspondence with the second engagement portion, both of which are arranged below the key top; a guide member for supporting the key top to guide vertical movement of the key top, the guide member including a first link member provided with a first shaft movably engaged in the first engagement portion and a third shaft movably engaged in the third engagement portion and a second link member provided with a second shaft movably engaged in the second engagement portion and a fourth shaft movably engaged in the fourth engagement portion; a first gear portion provided near the first shaft in the first link member; a second gear portion provided near the second shaft in the second link member; and a switching section for performing a switching operation in accordance with the vertical movement of the key top; the first and second link members being arranged such that, in association with the vertical movement of the key top, the first and second link members are operated in synchronization with each other through a mutual contact relationship between the first and second gear portions; wherein the first gear portion is provided with a first upper tooth portion and a first lower tooth portion which are arranged in adjacent relation in a direction of width of the first link member and in upper-and-lower relation in a direction of thickness of the first link member, the second gear portion is provided with a second upper tooth portion and a second lower tooth portion which are arranged in adjacent relation in a direction of width of the second link member and in upper-and-lower relation in a direction of thickness of the second link member, and the first upper tooth portion and the second lower tooth portion, and, the first lower tooth portion and the second upper tooth portion, are allowed to move, while maintaining mutually overlapping contact relation, in association with the vertical movement of the key top.

According to another aspect of the present invention, there is provided a keyboard provided with at least one of the immediately preceding key switch device.

According to another aspect of the present invention, there is provided an electronic apparatus including: a keyboard for inputting various data such as characters, symbols, and others, the keyboard being provided with a key switch device including: a key top provided at its underside with a first engagement portion and a second engagement portion; a third engagement portion arranged below the key top in