Patent Publication Number: US-6906272-B1

Title: Key switch device having high drawability

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a key switch device, more particularly to a key switch device for computers and other data processing devices. 
   2. Description of the Related Art As shown in  FIG. 1 , a typical key switch device includes a base support composed of a substrate  1 , a membrane circuit member  2  mounted on the substrate  1 , a resilient layer  3  superimposed upon the membrane circuit member  2 , and a plurality of key caps  5  (only one is shown for simplicity) each of which is mounted on the substrate  1  through a cap support  4 . 
   Each cap support  4  includes two intersecting first and second frames  6  and  7  which are interconnected pivotally to each other. The first frame  6  has a substantially U-shape and includes two lateral rods  601  and an intermediate member  602  connected to the lateral rods  601 . Each lateral rod  601  is provided with a retaining hole  603  at the middle thereof. The second frame  7  is a four-sided closed frame which includes two rods  701  interconnected by a mortised member  702  and a slide pin  703  interconnecting the rods  701  opposite to the mortised member  702 . Two retaining pins  704  project outwardly and respectively from the rods  701 . The keycap  5  includes a top wall  501 , a pair of pivot retainers  502  and a pair of latch retainers  503  all of which project from the bottom side of the top wall  501 , and two guide members  504 . The pivot retainers  502  engage respectively two ends of the slide pin  703  of the second frame  7 , whereas the latch retainers  503  engage respectively two pins  604  of the first frame  6 . The guide members  504  serve to guide the first and second frames  6  and  7  so that they can be aligned properly with the key cap  5  upon assembly. 
   The aforesaid prior art suffers from a problem in that, when the key switch device is subjected to a drawability test, the first frame  6  is prone to stretch outward and deform, thus lowering the drawability of the key switch device. In addition, due to the increasing demand for the miniaturization of key switch devices, the use of the guide members  504  which take up substantial space of the key cap  5  is disadvantageous. Furthermore, the need to form the guide members  504  on the top wall  501  of the key cap  5  requires an additional molding material and can result in indentations in the key cap  5  due to shrinkage upon cooling of the molded product. Moreover, after assembly, the drawability of the pivot retainers  502  cannot be enhanced by providing the guide members  504 . 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a key switch device with a strong structure for a cap support so that the connection between the cap support and a key cap can be strengthened and the drawability of the key switch can be enhanced. 
   Another object of the present invention is to provide a key cap having a guide member with a reduced size and simple structure to facilitate manufacturing of the key cap. 
   Accordingly, a key switch according to the present invention comprises a key cap and a cap support. The key cap includes a top wall, a pair of pivot retainers, and a pair of latch retainers, the pivot and latch retainers projecting downward from a bottom side of the top wall. Each of the pivot retainers has a distal end disposed away from the top wall, two opposite side faces extending between and being connected to the top wall and the distal end, a pivot hole extending through the side faces and opening at the distal end, and a guide rib projecting outward from one of the side faces and extending from the top wall toward the distal end. The guide rib is tapered from the top wall toward the distal end and defines an inclined guide surface. The cap support includes two intersecting first and second frames which are connected pivotally to each other, the first and second frames being connected to the key cap through the pivot retainers and the latch retainers, one of the first and second frames having two inclined surfaces, the inclined surfaces being respectively slidable along the guide surfaces so that the inclined surfaces are guided by the guide surfaces when the cap support is pressed against the key cap during assembly of the cap support and the key cap. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which: 
       FIG. 1  is an exploded view of the prior art; 
       FIG. 2  is a sectional view of the first preferred embodiment according to the present invention; 
       FIG. 3  is an exploded view of a cap support and a key cap of the first embodiment; 
       FIG. 4  is a plan view of a first frame of the cap support; 
       FIG. 5  is a plan view of a second frame of the cap support; 
       FIG. 6  is a plan view of the first and second frames which are connected together; 
       FIG. 7  is a bottom view of the key cap; 
       FIG. 8  is a sectional view taken along line  8 — 8  of  FIG. 7 ; 
       FIG. 9  is a fragmentary perspective view of the key cap; 
       FIG. 10  is a sectional view of the cap support and the key cap which have been assembled together; and 
       FIG. 11  is a sectional view taken along line  11 — 11  of FIG.  10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification. 
   Referring to  FIG. 2 , the first preferred embodiment of the key switch device according to the present invention includes a cap support  100  mounted on a base  200  and a key cap  300  supported by the cap support  100 . The base  200  has first retention members  210  and second retention members  220  which project upward from the base  200 . The cap support  100  includes two intersecting first and second frames  10  and  20  which are connected pivotally to each other and which are made of plastic by injection molding. 
   Referring to  FIGS. 3 and 4 , the first frame  10  is configured as a four-sided closed frame and includes a first top member  11 , a first bottom member  12  and two spaced apart first lateral members  13  interconnecting the first top and bottom members  11  and  12 . Latch pins  111  project outwardly and respectively from two ends of the first top member  11 , whereas retention pins  121  project outwardly and respectively from the first bottom member  12 . The retention pins  121  respectively engage the first retention members  210  of the base  200 . Each first lateral member  13  is formed with a through hole  14  in an intermediate part thereof. The through hole  14  is tapered from an inner side  131  to an outer side  132  of the corresponding first lateral member  13 . 
   Referring to  FIG. 5  in combination with  FIG. 3 , the second frame  20  is also configured as a four-sided closed frame and includes a second top member  21 , a second bottom member  22 , and a pair of spaced apart second lateral members  23  interconnecting the second top and bottom members  21  and  22 . A pair of pivot pins  211  project outwardly and respectively from two ends of the second top member  21 , whereas a pair of retention pieces  221  are formed in the second bottom member  22 . The retention pieces  221  engage respectively the second retention members  220  of the base  200 . Each second lateral member  23  is formed with a retaining pin  24  which projects outwardly from an intermediate part of the corresponding second lateral member  23 . The retaining pin  24  has an outermost head  242 , an inner neck part  241  and a shoulder  243  formed between the outermost head  242  and the inner neck part  241 . In this embodiment, the outermost head  242  is formed as a hemi-spherical shape whose diameter is larger than that of the inner neck part  241  and that of the corresponding through hole  14 . 
   Referring to  FIG. 6  in combination with  FIGS. 2 and 3 , the first frame  10  is connected to the second frame  20  by inserting the retaining pins  24  into the respective retaining holes  14  until the outermost heads  242  project outwardly from the respective retaining holes  14  and the shoulders  243  engage the respective outer sides  132  of the first lateral members  13 . When the first and second top members  11  and  21  are moved respectively toward the second and first bottom members  22  and  12 , the cap support  100  is placed in a collapsed state. Due to the larger diameter of each outermost head  242  and due to the engagement of each shoulder  243  with the outer side  132  of the corresponding first lateral member  13 , each retaining pin  24  can be prevented from being released from the corresponding through hole  14 , thereby strengthening the connection between the first and second frames  10  and  20 . 
   Referring to  FIGS. 7 ,  8  and  9  in combination with  FIG. 3 , the key cap  300  includes a top wall  31 , a pair of pivot retainers  32  for connection with the pivot pins  211 , and a pair of latch retainers  33  for connection with the latch pins  111 . The pivot retainers  32  and the latch retainers  33  are formed on and project downward from a bottom side  311  of the top wall  31 . Each pivot retainer  32  has a distal end  325  disposed away from the top wall  31 , and two side faces, i.e. inner and outer side faces  327 ,  328 , which extend between and connect with the top wall  31  and the distal end  325 . The inner side faces  327  of the pivot retainers  32  face toward each other, and the outer side faces  328  thereof are respectively opposite to the inner side faces  327 . Each pivot retainer  32  further has a pivot hole  322  that passes through the inner and outer side faces  327  and  328 , and two guide ribs  323  which project outwardly from the outer side face  328  and which extends from the top wall  31  to the distal end  325 . Each guide rib  323  is tapered from the top wall  31  to the distal end  325  and defines an inclined guide surface  326 . 
   Referring to  FIGS. 10 and 11  in combination with FIG.  3 , the first bottom member  12  of the first frame  10  has two spaced apart inclined surfaces  123  and an indentation  122  between the inclined surfaces  123 . When the cap support  200  is in the collapsed state, the second top member  21  and the pivot pins  211  are received in the indentation  122 . Each inclined surface  123  faces the corresponding pivot pin  211 . The key cap  300  is assembled with the cap support  100  when the cap support  100  is in the collapsed state. 
   In assembly, the pivot pins  211  of the second top member  21  are pressed into the respective pivot holes  322  of the pivot retainers  32 , and the latch pins  111  of the first top member  11  are pushed into the respective latch retainers  33 . The pivot pins  211  are respectively inserted into the pivot holes  322  through the open distal ends  325  of the pivot retainers  32  along an insertion direction (A) (see FIG.  10 ). As the pivot pins  211  are pressed into the respective pivot holes  322 , the inclined surfaces  123  of the second top member  12  are slid along and guided by the guide surfaces  326  of the guide ribs  323  so that the cap support  100  is properly aligned with the key cap  300  to be quickly and correctly assembled with the key cap  300 . Note that each of the guide surfaces  326  and the inclined surfaces  123  is inclined with respect to a line (B) parallel to the insertion direction (A) and that the inclining angles of the guide surfaces  326  and the inclined surfaces  123  with respect to the line (B) are substantially the same. 
   Due to the presence of the guide surfaces  326  of the guide ribs  323  and the inclined surfaces  123  of the first lateral members  13 , the cap support  100  can be automatically guided toward and aligned with the key cap  300 , thereby facilitating assembly of the cap support  100  and the key cap  300 . Since the guide ribs  323  are relatively small, the entire area, volume and weight of the key cap  300  are reduced, thus fulfilling the requirements for the miniaturization of the key cap  300 . 
   In addition, since the guide ribs  323  are relatively small compared to the guide members  504  of the prior art, the problems resulting from shrinkage upon cooling can be alleviated, thereby facilitating the manufacture of the key cap  300  and decreasing the quantity of defective products during the manufacture of the key cap  300 . 
   Furthermore, because of the provision of the guide ribs  323  on the pivot retainers  32 , the connecting area between each pivot retainer  32  and the top wall  31  is increased, thus reinforcing the connection between each pivot retainer  32  and the top wall  31  to enhance the drawability of the key cap  300 . 
   While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.