Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2001-04-13
2002-04-23
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C200S0050EA
Reexamination Certificate
active
06376789
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a switch mechanism for key-entry operation and, more particularly, to a key-entry switch (hereinafter referred to as a key switch) preferably used for a keyboard incorporated as an input device in electronic equipment. The present invention also relates to a keyboard provided with a plurality of key switches.
2. Description of the Related Art
In the technical field of portable electronic equipment such as notebook-size personal computers or wordprocessors, etc., various techniques have been proposed to facilitate a reduction in height or thickness of the housing of equipment including a keyboard and to improve the portability of the equipment. Particularly, when the height of a keyboard provided with a plurality of key switches is to be reduced, it has been generally required to maintain the stroke of each key switch at a predetermined length to ensure constant operational properties thereof and, simultaneously, to reduce the entire height of the key switch upon both the non-operated (or switched-off) and operated (or pushed-down and switched-on) conditions thereof.
A conventional key switch for use in a relatively thin keyboard with a reduced height generally includes a base, a key top disposed above the base, a pair of link members for supporting the key top above the base and directing the key top in the vertical or up-and-down direction, and a switching mechanism for selectively opening/closing contact points in an electric circuit in accordance with the vertical or up-and-down movement of the key top. The conventional pair of link members has been provided essentially with any one of three types of configurations.
First type pair of link members may be referred to as a gear-link type, wherein the link members are assembled together into a reverse V-shape as seen in a lateral direction and meshed at toothed end regions thereof with each other, each link member being slidably engaged at a first end region thereof with the base and pivotably engaged at the toothed or second end region with the key top (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 11-3628). Second type pair of link members may be referred to as a pantograph type, wherein the link members are assembled together into an X-shape as seen in a lateral direction and rotatably joined at intersections thereof with each other, each link member being slidably engaged at a first end region thereof with one of the base and the key top and pivotably engaged at a second end region with the other of the base or the key top (see, e.g., Japanese Unexamined Utility Model Publication (Kokai) No. 5-66832). Third type pair of link members may be referred to as a modified pantograph type, wherein the link members are assembled together into an X-shape as seen in a lateral direction and slidably connected at intersections thereof with each other, each link member being slidably engaged at a first end region thereof with the base and pivotably engaged at a second end region with the key top (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 9-27235).
In the conventional key switch having any one of the above types of link members, the link members are shifted in a mutually interlocked manner, and the key top is thereby allowed to be moved in a parallel displacement in a substantially vertical direction relative to the base, while keeping a predetermined posture of the key top. Once the key top reaches a lowermost position of a vertical or key-entry stroke thereof, the link members are laid in a generally horizontal position under the key top and received inside an opening defined in the base. This arrangement permits the entire height of the key switch to be reduced in both the non-operated and operated conditions while maintaining the key-entry stroke of the key top at a desired length.
In the conventional key switch having the gear-link type pair of link members as described, each link member includes a pair of arms extending generally parallel to each other and a pair of axles formed at the second end region of the link member, i.e., the distal end region of the respective arms, the axles extending outward along the rotation axis of the second end region for pivotable engagement with the key top. Each arm of the link member is further provided with one or more teeth projecting outward from the second end region in a direction generally orthogonal to the rotation axis, the teeth constituting an interlocking element for meshable engagement with the second end region of the counterpart link member.
On the other hand, the key top is provided with two pairs of pivot supports for pivotably supporting the axles of the respective arms of the respective link members. The pivot supports are formed on the inner surface of the key top as separate plate-like projections extending generally parallel to one another. Each pivot support includes a bearing hole for pivotably receiving the axle of each arm of each link member and a slit communicating with the bearing hole. The slit of the pivot support is shaped and dimensioned so as to define an opening smaller than the associated axle of the link member. The slits of four pivot supports extend generally parallel to one another and in a direction generally perpendicular to the inner surface of the key top.
In the assembling process of the abovedescribed key switch, first the link members are arranged so as to engage the first end regions thereof to the base and to mesh the corresponding teeth thereof with each other, and are laid in a generally horizontal position to be received inside the opening of the base. In this state, the link members are positioned at a location substantially identical to a location defined by the lowermost position of key-entry stroke of the key top. Then, the key top is put on the link members so as to bring the respective pivot supports into contact with the associated axles, and is pushed down on the link members. Thereby, the axles are inserted into the slits of the correlate pivot supports under pressure to elastically deform the pivot supports, and are finally press-fitted into the bearing holes in a snap-fit manner. This configuration generally facilitates both the assembling process of the key switch and the construction of a mold used for molding the key top.
In the above conventional structure of the key switch having the gear-link type pair of link members, the base and the link members are typically shaped and dimensioned so that a slight clearance may be defined between the second end region (especially, the distal end of each axle) of each link member and the inner peripheral surface at the opening of the base after the assembling process is completed, so as to ensure the relatively easy press-fitting operation in the assembling process for the respective pivot supports of the key top fitted with the associated axles of the link members. However, such a clearance tends to enable the link members located inside the base opening to be slightly displaced in a horizontal direction, which may result in an incorrect intermesh between the toothed end regions or interlocking elements of the link members located inside the base opening due to an inadvertent mutual horizontal displacement caused between the link members before the key top is fitted to the link members.
If the key top is press-fitted to the incorrectly intermeshed link members as described, problems may arise wherein the tooth or teeth of the toothed end regions of the link members are deformed or damaged, which may affect the key-entry operation or stroke properties of the key switch. Accordingly, it is typically required for the assembling process of the conventional key switch to correct the intermeshed state of the gear-link type pair of link members before the key top is fitted with the link members.
In a typical assembling process of a conventional keyboard including a plurality of key switches having the above-described structure, a large-sized base panel (referred to as
Hayashi Kazutoshi
Maruyama Jun-ichi
Ohkubo Hitoshi
Terada Takashi
Friedhofer Michael
Fujitsu Takamisawa Component Ltd.
Staas & Halsey , LLP
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