Patent Publication Number: US-2021166897-A1

Title: Key structure

Description:
This application claims the benefit of People&#39;s Republic of China application Serial No. 201911191763.8, filed Nov. 28, 2019, the subject matter of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The disclosure relates in general to a key structure, and more particularly to a key structure providing mechanical press feeling. 
     Description of the Related Art 
     Input device is normally used as a communication interface between the user and the electronic device. The input device, such as a plurality of key structures. By pressing different keys, the user can enable the electronic device to generate corresponding actions. Of the different types of key structure, the mechanical key structure possessing the advantages of better hand touch, longer lifespan and shorter triggering course has won a great popularity over the years. 
     Typical mechanical key structure at least includes a keycap, a switch and a bottom plate. The keycap is disposed on the bottom plate and can movably reciprocate up and down through the switch. In detail, the keycap, limited by the switch, can movably reciprocate between the top end position and the bottom end along the vertical axis direction. When the keycap is pressed, the keycap can move to the bottom end position from the top end position and cause the switch to generate a triggering signal. Generally, the switch and the keycap are connected and tightly engaged with each other by inserting the plug disposed at the top of the switch into the slot disposed at the bottom surface of the keycap. 
     However, if the squeezing force generated between the plug and the slot is too large, the sidewall of the slot may be easily ruptured. On the contrary, if the squeezing force is too small, the plug may easily escape from the slot. And the balance between these two is difficult to grasp, which further enlarges the process variation and adversely affect the yield rate and the quality of the mechanical key structure. 
     Therefore, it has become a prominent task for the industry to provide an advanced key structure which has improved yield rate and the quality and is able to resolve the current technical problems. 
     SUMMARY 
     According to one embodiment of the present disclosure, a key structure is provided, wherein the key structure is provided includes a bottom plate, a first actuator and a keycap. The first actuator is disposed on the bottom plate and engaged with the keycap to make the key cap movably reciprocating along an actuating direction perpendicular to the bottom plate. Wherein, one of the first actuator and the keycap has a first slot; and the other one of the first actuator and the keycap has a first plug. The first plug is inserted in the first slot in parallel to the actuating direction. One of the first slot and the first plug includes at least one first protruding portion, which protrudes perpendicularly to the actuating direction and is conformally engaged with the other one of the first slot and the first plug. 
     According to aforementioned embodiments of the present disclosure, a key structure is provided. The key structure comprises a keycap and an actuator. The actuator is engaged with the keycap by a plug and a slot and enables the keycap to movably reciprocate along an actuating direction. At least one protruding portion protruding outward and perpendicular to the actuating direction is provided on the sidewall of one of the plug and the slot, and the hardness of the protruding portion is greater than the hardness of the sidewall of the other one of the plug and the slot. When the plug is inserted into the slot, the protruding portion squeezes the corresponding sidewall encountering the protruding portion and forms a recess on the corresponding sidewall to conformally engage with the protruding portion. Such that sufficient interference fit can be provided to make the actuator and the keycap tightly engaged. 
     By this approach, it is not necessary to additionally increase the difference in width dimension between the plug and the slot in order to form a tighter interference fit there between, and the lateral squeezing force applied by the plug to the sidewall of the slot can be greatly reduced. Thereby, the bursting risk of the keycap/switch due to excessive lateral squeezing force can be effectively reduced, on the premise of achieving a proper interference fit, when the slot and the plug are engaged. The processing yield of assembling the keycap and the switch as well as the quality of the key structure can be thus improved. 
     The present disclosure will be described in detail with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects of the disclosure will become better understood with regard to the following detailed description of the preferred but non-limiting embodiment (s). The following description is made with reference to the accompanying drawings. 
         FIG. 1A  is a three-dimensional (3D) assembly diagram illustrating a key structure according to one embodiment of the disclosure; 
         FIG. 1B  is a 3D explosion diagram illustrating of the key structure of  FIG. 1A ; 
         FIG. 1C  is a partial cross-sectional view of the key structure taken along the tangent line S 1  of  FIG. 1A ; 
         FIG. 2A  is a 3D assembly diagram illustrating a key structure according to another embodiment of the disclosure; 
         FIG. 2B  is a 3D explosion diagram illustrating the key structure of  FIG. 2A ; 
         FIG. 2C  is an enlarged view illustrating a partial structure of a first actuator as depicted in  FIG. 2A ; 
         FIG. 2D  is an enlarged view illustrating a partial structure of a second actuator as depicted in  FIG. 2A ; 
         FIG. 2E  is an enlarged view illustrating a partial structure of a third actuator as depicted in  FIG. 2A ; 
         FIG. 2F  is a partial cross-sectional view of a key structure taken along the tangent line S 2  of  FIG. 2A ; 
         FIG. 2G  is a partial cross-sectional view of the key structure taken along the tangent line S 3  of  FIG. 2A ; and 
         FIG. 2H  is a partial cross-sectional view of the key structure taken along the tangent line S 4  of  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments of the present disclosure provide a key structure to resolve the problems of either a slot being easily ruptured, due to a squiring force while a plug is inserted into the slot to engage the keycap and the switch with each other, or the problems of the plug easily escaping from the slot, due to insufficient friction, so as to improve the yield and the quality of the key structure. For the object, technical features and advantages of the present invention to be more easily understood by anyone ordinary skilled in the technology field, a number of exemplary embodiments are disclosed below with detailed descriptions and accompanying drawings. 
     It should be noted that these embodiments are illustrative and for explanatory purposes only, not for limiting the scope of protection of the invention. The invention can be implemented by using other features, elements, methods and parameters. The preferred embodiments are merely for illustrating the technical features of the disclosure, not for limiting the scope of protection. Anyone skilled in the technology field of the disclosure will be able to make suitable modifications or changes based on the specification disclosed below without breaching the spirit of the disclosure. Designations common to the accompanying drawings are used to indicate identical or similar elements. 
       FIG. 1A  is a 3D assembly diagram of a key structure  100  according to one embodiment of the disclosure;  FIG. 1B  is a 3D explosion diagram illustrating the key structure  100  of  FIG. 1A ; and  FIG. 10  is a partial cross-sectional view of the key structure  100  taken along the tangent line S 1  of  FIG. 1A . In some embodiments of the disclosure, the key structure  100  can be adapted to a keyboard of an electronic device, such as a laptop or a desktop computer, to trigger a specific signal. 
     Refer to  FIG. 1A , the key structure  100  includes a keycap  101 , an actuator  102 , a bottom plate  103  and a circuit board  104 . The keycap  101  can be used in a horizontal bar key (such as the space key) or a key with normal size (such as a letter key). In the present embodiment, the keycap  101  is a normal size key. 
     The actuator  102  is disposed on the bottom plate  103  and coupled with the keycap  101 . The bottom plate  103  includes a top surface  103   a  and a bottom surface  103   b  opposite to the top surface  103   a . Besides, the bottom plate  103  further includes a receiving hole  103   c , which passes through the top surface  103   a  and the bottom surface  103   b  and enables the actuator  102  to be disposed in the bottom plate  103 . 
     In some embodiments of the disclosure, the actuator  102 , which can be a mechanical switch, includes at least one elastic force element, such as (but not limited to) a spring (not shown), configured to provide an elastic force, which enables the keycap  101  to movably reciprocate along the Z-axis direction (also referred as an actuating direction) after the actuator  102  and the keycap  101  are coupled together. In detail, when the user presses the keycap  101 , the keycap  101  moves towards the bottom plate  103  along the Z-axis direction. Meanwhile, the elastic force element of the actuator  102  provides the keycap  101  with a restore elastic force away from the bottom plate  103  along the Z-axis; when the user no more presses the keycap  101 , the restore elastic force enables the keycap  101  to move to the original position before the keycap  101  is pressed from the bottom plate  103 . 
     In some other embodiments of the disclosure, the actuator  102 , which can be a plunger switch, which is inserted into a guide member (not shown) and adjacent to the two sides of the switch of the key structure  100 . When the keycap  101  is driven by the switch, the actuator  102  moveably reciprocate along the Z-axis direction to guide and limit the keycap  101  to movably reciprocate within a specific range along the Z-axis direction. 
     The actuator  102  may include pins (not shown). When the actuator  102  is disposed on the bottom plate  103 , the pins can be inserted on the circuit board  104  and fixed by tin solder to electrically connect to the circuit board  104 . When the keycap  101  is moved to the pressed position from the un-pressed position, the actuator  102  can generate a trigger signal transmitting to the circuit board  104 . 
     The keycap  101  includes a column  101 A disposed on the bottom surface  101   d  of the keycap  101  and extending downward from the bottom surface  101   d  in the Z-axis direction. The column  101 A has a slot  111 . The top  102   a  of the actuator  102  may include a plug  121  extending upward from the top  102   a  of the actuator  102 . The shape of the plug  121  corresponds to the slot  111 , so that the plug  121  can be inserted and penetrated in the slot  111 . The sidewall  121   s  of the plug  121  includes at least one protruding portion  122 , which protrudes outward from the sidewall  121   s  perpendicular to the Z-axis direction. For example, the protruding portion  122  may be formed by a circular protrusion or a strip-shaped rib protruding from the sidewall  121   s  of the plug  121 ; and the hardness of the protruding portion  122  is substantially greater than the hardness of the inner wall  111   s  of the slot  111 . 
     For example, in the present embodiment, the plug  121  is a rectangular cylindrical body; the shape of the slot  111  corresponds to the plug  121 , and may be a rectangular groove. The protruding portion  122  includes a plurality of ribs (for example, ribs  122 A,  122 B, and  122 C) protruding from the sidewall  121   s  of the plug  121 . Moreover, each of the ribs  122 A,  122 B, and  122 C has a long axis L 1  forming an angle  81  with the Z axis direction that is not 180° (for example, 90°). 
     The width D 1  of the plug  121  is smaller than (or equal to) the width D 3  of the slot  111 ; the total width D 2  of the ribs  122 A,  122 B, and  122 C plus the width D 1  of the plug  121  are greater than the width D 3  of the slot  111 . When the plug  121  is inserted into the slot  111 , due to the difference in hardness, the ribs  122 A,  122 B, and  122 C protruding from the sidewall  121   s  of the plug  121  may squeeze the inner wall  111   s  of the slot  111 . Such that, a plurality of strip-shaped recesses  123  may be thus formed on the inner wall  111   s  of the slot  111  conformally engaged with the corresponding convex ribs  122 A,  122 B, and  122 C respectively. 
     By the friction between the protruding portion  122  and the inner wall  111   s  of the slot  111 , a proper interference fit can be provided, so that the actuator  102  and the keycap  101  can be tightly engaged with each other. It is no more necessary to insert a plug with a larger width dimension into a slot with a smaller width dimension for getting a tighter interference fit between the plug and the slot as in the prior art. Therefore, the risk of column  101 A bursting due to the lateral squeezing force applied by the plug  121  can be effectively reduced, under the condition of achieving the same interference fit (in comparison with that of the prior art). 
     In some embodiments of the present disclosure, the ribs  122 A,  122 B, and  122 C that have the farther distance away from the top  102   a  of the actuator  102  have higher protruding height. That is, the rib  122 A that has the farthest distance away from the top  102   a  of the actuating member  102  has the highest protruding height, and the rib  122 C that has the closest distance away from the top  102   a  has the smallest protruding height. When the plug  121  is inserted into the slot  111 , the squeezing force applied by the rib  122 C on the top of the column  101 A (that is, the top of the slot  111  with poor expansion elasticity) can be reduced. The risk of the column  101 A bursting can thus be further reduced. 
     However, the structure of the key structure  100  is not limited to this regard. For example, the cross-sectional shape of the plug  121  and the corresponding slot  111  (taken along the direction perpendicular to the Z-axis direction) is not limited to a rectangular shape. In some embodiments of the present disclosure, the cross-sectional shape of the plug  121  and the corresponding slot  111  (taken along the direction perpendicular to the Z-axis direction) may be circular, elliptical, arc, regular or irregular polygon. Alternatively, in some other embodiments of the present disclosure, the plug  121  can be disposed on the bottom surface  101   d  of the keycap  101 ; and the column with a slot may be correspondingly disposed on the top  102   a  of the actuator (not shown). In yet other embodiments, the protruding portions can be arranged on the inner wall of the slot. When the plug is inserted into the slot, the difference in hardness causes each protruding portion to squeeze the sidewall of the plug. And a plurality of strip-shaped recesses (not shown) may be formed on the sidewall of the plug. 
       FIG. 2A  is a 3D assembly diagram illustrating a key structure  200  according to another embodiment of the disclosure;  FIG. 2B  is a 3D explosion diagram illustrating the key structure  200  of  FIG. 2A ;  FIG. 2C  is an enlarged view illustrating a partial structure of a first actuator  202  as depicted in  FIG. 2A ;  FIG. 2D  is an enlarged view illustrating a partial structure of a second actuator  205  as depicted in  FIG. 2A ;  FIG. 2E  is an enlarged view illustrating a partial structure of a third actuator  206  as depicted in  FIG. 2A ;  FIG. 2F  is a partial cross-sectional view of the key structure  200  taken along the tangent line S 2  of  FIG. 2A ;  FIG. 2G  is a partial cross-sectional view of the key structure  200  taken along the tangent line S 3  of  FIG. 2A ; and  FIG. 2H  is a partial cross-sectional view of the key structure  200  taken along the tangent line S 4  of  FIG. 2A . 
     The structure of the key structure  200  is substantially similar to that of the key structure  100 . The main difference is that the key structure  200  further includes a second actuator  205  and a third actuator  206 ; and each of the plugs  221 ,  225  and  226  respectively disposed on the first actuator  202 , the second actuator  205  and the second actuator  206  has a cross-cylinder structure. 
     In the present embodiment, the key structure  200  includes a keycap  201 , the first actuator  202 , the second actuator  205 , the third actuator  206 , a bottom plate  203  and a circuit board  204 . Wherein, the keycap  201  can be used in a horizontal bar key (such as the space key) including three columns  201 A,  201 B and  201 C arranged on the bottom surface  201   d  of the keycap  201  and extending downward from the bottom surface  201   d  along the Z-axis direction. The columns  201 A,  201 B, and  201 C respectively have slots  211 A,  211 B, and  211 C. 
     The first actuator  202 , the second actuator  205  and the third actuator  206  are respectively arranged on the bottom plate  203 . The bottom plate  203  includes an upper surface  203   a  and a lower surface  203   b  opposite to the upper surface  203   a . In addition, the bottom plate  203  also includes three adjacent holes  203   c ,  203   d  and  203   e  penetrating through the upper surface  203   a  and the lower surface  203   b  to allow the first actuator  202 , the second actuator  205  and the third actuator  206  respectively accommodating therein. 
     The first actuator  202 , the second actuator  205  and the third actuator  206  are engaged with the keycap  201 . In some embodiments of the present disclosure, the first actuator  202  may be a mechanical switch, including at least one elastic element, such as a spring (not shown), to provide elastic force. After the first actuator  202  is engaged with the keycap  201 , the keycap  201  can movably reciprocate along the Z-axis direction. The second actuator  205  and the third actuator  206  may be plunger switches respectively disposed adjacent to the two sides of the first actuator  202 . When the keycap  201  is pressed by the user to drive the first actuator  202  to reciprocate along the Z-axis direction, it can guide and limit the keycap  201  to reciprocate along the Z-axis direction within a specific range. 
     In addition, the first actuator  202  may include two pins (not shown). When the first actuator  202  is disposed on the bottom plate  203 , it can be inserted into the circuit board  204  and fixed by tin solder to electrically connect to the circuit board  204 . When the keycap  201  is pressed to move from a non-pressed position to a pressed position, the first actuator  202  can generate a trigger signal and transmit it to the circuit board  204  to turn on the circuit. 
     In detail, the top  202   a  of the first actuator  202  includes a plug  221  extending upward from the top  202   a  of the first actuator  202 . The shape of the plug  221  corresponds to the slot  211 A, so that the plug  221  can be inserted and accommodating in the slot  211 A. In the present embodiment, the plug  221  may be a cross-cylinder structure; it includes a first fin  221 A and a second fin  221 B that intersect each other, and extends upward in parallel to the Z-axis direction from the top  202   a  of the first actuator  202 . The shape of the slot  211 A corresponds to the plug  221 , and may be a cross-shaped groove; it includes a first groove  211 A 1  and a second groove  211 A 2  that intersect each other, corresponding to the first fin  221 A and the second fin  221 B, respectively. The width H 1  of the first fin  221 A is greater than the width H 2  of the first groove  211 A 1 ; the width H 3  of the second fin  221 B is less than or equal to the width H 4  of the second groove  211 A 2 . 
     The plug  221  further includes at least one protruding portion  222  protruding outward from the sidewall  221   s  of the second fin  221 B perpendicular to the Z-axis direction. For example, the protruding portion  222  may be formed by a circular convex point or a strip-shaped rib protruding on the sidewall  221   s  of the second fin  221 B; and the hardness of the protruding portion  222  is substantially greater than the hardness of the inner wall  211 As of the second groove  211 A 2 . In the present embodiment, the protruding portion  222  includes a plurality of ribs (for example, ribs  222 A,  222 B, and  222 C) protruding from the sidewall  221   s  of the second fin  221 B. Moreover, each of the ribs  222 A,  222 B, and  222 C has a long axis L 2  forming an angle  82  with the Z axis direction that is not 180° (for example, 90°). 
     When the plug  221  is inserted into the slot  211 A, the first fin  221 A and the first groove  211 A 1  can form a tightly interference fit by the squeezing force due to the width difference between these two; and the sidewalls of the second fins  221 B and the second groove  211 A 2  are just in contact to, but not tightly squeezing with each other. Each of the ribs  222 A,  222 B, and  222 C protruding from the sidewall  221   s  of the second fin  221 B may squeeze the inner wall  211 As of the second groove  211 A 2  due to the higher hardness, and a plurality of strip-shaped recesses  223  may be formed on the inner wall  211 As of the second groove  211 A 2  and conformally engaged with the corresponding convex ribs  222 A,  222 B, and  222 C. 
     The second actuator  205  and the third actuator  206  include guide parts  205 A and  206 A and movable parts  205 B and  206 B, respectively. The guide parts  205 A and  206 A are fixed on the bottom plate  203  through the holes  203   d  and  203   e  of the bottom plate  203 , respectively. The movable parts  205 B and  206 B respectively pass through the guide holes D of the guide parts  205 A and  206 A, and are stopped and restricted within a certain range by the guide parts  205 A and  206 A, and movably reciprocate along the Z-axis direction. The key structure  200  may further include a balance bar  207 . With the arrangement of the balance bar  207 , the movable parts  205 B and  206 B can synchronously reciprocate in the guide parts  205 A and  206 A, which can prevent the keycap  201  from being skewed. 
     The top  205 B 1  of the movable part  205 B may include a plug  225  corresponding to the slot  211 B of the keycap  201  and engaged with each other. In the present embodiment, the plug  225  may be a cross-cylinder structure; it includes a third fin  225 A and a fourth fin  225 B that intersect each other, and extends upward parallel to the Z-axis direction from the top  205 B 1  of the movable part  205 B. The shape of the slot  211 B corresponds to that of the plug  225  and may be a cross-shaped groove; it includes a third groove  211 B 1  and a fourth groove  211 B 2  intersecting each other, corresponding to the third fin  225 A and the fourth fin  225 B, respectively. The third fin  225 A has a width greater than that of the third groove  211 B 1 ; the fourth fin  225 B has a width less than or equal to the width of the fourth groove  211 B 2 . 
     The plug  225  further includes at least one protruding portion  252 , which protrudes outward from the sidewall  225   s  of the fourth fin  225 B perpendicular to the Z-axis direction. For example, the protruding portion  252  may be formed by a round convex point or a strip-shaped rib protruding from the sidewall  225   s  of the fourth fin  225 B; and the hardness of the protruding portion  252  is substantially greater than that of the inner wall  211 Bs of the fourth groove  211 B 2 . In the present embodiment, the protruding portion  252  may be a plurality of ribs (for example, ribs  252 A,  252 B, and  252 C) protruding from the sidewall  225   s  of the fourth fin  225 B. Moreover, each of the ribs  252 A,  252 B, and  252 C has a long axis L 5  forming angle  85  with the Z axis direction that is not 180° (for example, 90°). 
     When the plug  225  is inserted into the slot  211 B, the third fin  225 A and the third groove  211 B 1  can form a tightly interference fit by the squeezing force due to the width difference between these two; and the sidewalls of the four fins  225 B and the fourth groove  211 B 2  are just in contact to, but not tightly squeezing with each other. Each of the protruding ribs  252 A,  252 B, and  252 C protruding from the sidewall  225   s  of the fourth fin  225 B may squeeze the inner wall  211 Bs of the fourth groove  211 B 2  due to the higher hardness; and a plurality of strip-shaped recesses  253  can be formed on the inner wall  211 Bs of the fourth groove  211 B 2  and conformally engagement with the corresponding ribs  252 A,  252 B, and  252 C, respectively. 
     The top  206 B 1  of the movable part  206 B may include a plug  226  corresponding to the slot  211 C of the keycap  201  and engaged with each other. In the present embodiment, the plug  226  may be a cross-cylinder structure; it includes a fifth fin  226 A and a sixth fin  226 B that intersect each other, and extends upward from the top  206 B 1  of the movable part  206 B parallel to the Z-axis direction. The shape of the slot  211 C corresponds to that of the plug  226  and may be a cross-shaped groove; it includes a fifth groove  211 C 1  and a sixth groove  211 C 2  that intersect each other, corresponding to the fifth fin  226 A and the sixth fin  226 B, respectively. The fifth fin  226 A has a width greater than that of the fifth groove  211 C 1 ; the sixth fin  226 B has a width less than or equal to the width of the sixth groove  211 C 2 . 
     The plug  226  further includes at least one protruding portion  262 , which protrudes outward from the sidewall  226   s  of the sixth fin  226 B perpendicular to the Z-axis direction. For example, the protruding portion  262  may be formed by a circular convex point or a strip-shaped rib protruding from the sidewall  226   s  of the sixth fin  226 B; and the hardness of the protruding portion  262  is substantially greater than that of the inner wall  211 Cs of the sixth groove  211 C 2 . In the present embodiment, the protruding portion  262  may be a plurality of protruding ribs (such as, protruding ribs  262 A,  262 B, and  262 C) protruding from the sidewall  226   s  of the sixth fin  226 B. Moreover, each of the ribs  262 A,  262 B, and  226 C has a long axis L 6  forming an angle  86  with the Z axis direction that is not 180° (for example, 90°). 
     When the plug  226  is inserted into the slot  211 C, the fifth fin  226 A and the fifth groove  211 C 1  can form a tightly interference fit by the squeezing force due to the width difference between these two; and the sidewalls of the sixth fin  226 B and the sixth groove  211 C 2  are just in contact to, but not tightly squeezing with each other. Each of the protruding ribs  262 A,  262 B, and  262 C protruding from the sidewall  226   s  of the sixth fin  226 B may squeeze the inner wall  211 Cs of the sixth groove  211 C 2  due to the higher hardness, and a plurality of strip-shaped recesses  263  can be form on the inner wall  211 Cs of the sixth groove  211 C 2  and conformally engaged with the corresponding ribs  262 A,  262 B, and  262 C. 
     By conformally engaging the protruding portions  222 ,  252 , and  262  with the inner walls  211 As,  211 Bs, and  211 Cs of the slots  211 A,  211 B, and  211 C, respectively, proper interference fits can be provided, so that the first actuator  202 , the second actuator  205  and the third actuator  206  are tightly combined with the slots  211 A,  211 B, and  211 C, respectively. Therefore, the width dimensions of the first fin  221 A, the third fin  225 A, and the fifth fin  226 A can be appropriately reduced to ease the squeezing force generated between the plugs  221 ,  225 , and  226  and the corresponding slots  211 A,  211 B, and  211 C, so as to moderate the lateral stress applied to the columns  201 A,  201 B, and  201 C. Under the condition of achieving the same interference fit, in comparison with that of the prior art, the bursting risk of the columns  201 A,  201 B, and  201 C can be effectively reduced. 
     According to aforementioned embodiments of the present disclosure, a key structure is provided. The key structure comprises a keycap and an actuator. The actuator is engaged with the keycap by a plug and a slot and enables the keycap to movably reciprocate along an actuating direction. At least one protruding portion protruding outward and perpendicular to the actuating direction is provided on the sidewall of one of the plug and the slot, and the hardness of the protruding portion is greater than the hardness of the sidewall of the other one of the plug and the slot. When the plug is inserted into the slot, the protruding portion squeezes the corresponding sidewall encountering the protruding portion and forms a recess on the corresponding sidewall to conformally engage with the protruding portion. Such that sufficient interference fit can be provided to make the actuator and the keycap tightly engaged. 
     By this approach, it is not necessary to additionally increase the difference in width dimension between the plug and the slot in order to form a tighter interference fit there between, and the lateral squeezing force applied by the plug to the sidewall of the slot can be greatly reduced. Thereby, the bursting risk of the keycap/switch due to excessive lateral squeezing force can be effectively reduced, on the premise of achieving a proper interference fit, when the slot and the plug are engaged. The processing yield of assembling the keycap and the switch as well as the quality of the key structure can be thus improved. 
     While the disclosure has been described by way of example and in terms of the preferred embodiment (s), it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.