Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2001-09-07
2002-09-03
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
Reexamination Certificate
active
06444933
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application takes priority from Japanese Patent Application No. 2001-014245 filed Jan. 23, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a key switch for a keyboard used as an input device in a personal computer and so on, and more particularly to such a key switch which can promote miniaturization and thinner-shaping of the keyboard, realize a large key stroke, and secure a key input and key operating feeling by imparting a clicking sensation at the time of key operation. Particularly, this key switch has a simple overall construction and thus enables assembly processes thereof to be easily and simply performed.
2. Description of the Prior Art
While a key has been more and more thinly formed in accordance with a tendency of thinner-shaping of keyboards in recent years, a large key stroke and clear key operating feeling with respect to key operation are required so as to enhance operability of a key input and to secure certainty of the key input. Various key switches have been proposed to be used for this kind of keyboard.
For example, Japanese Patent Laid-open No. Hei 8-279316 proposed the following key switch.
In the proposed key switch, means for guiding the vertical movement of a key top is constituted by a first link member and a second link member joined with each other in a form of a character “X” to guide the vertical movement of the key top. The first link member is formed with a spring member having a switch operating part at its end, and a supporting plate is formed with an inclined projection part having an inclined surface. When the key top is pushed down, pressure load of the key top is increased as the spring member is slid along the inclined surface of the inclined projection part. If the spring member is slid beyond the inclined projection part and then falls onto a switch sheet surface, the pressure load of the key top is suddenly lowered to impart a clicking sensation to a user. Simultaneously, the switch operating part of the spring member comes into pressing-contact with a switching section to achieve a switching-on key action.
This key switch can realize miniaturization and thinner-shaping of the keyboard by using the guiding member of the link structure instead of using a rubber spring. The key switch also imparts the clicking sensation by forming the inclined projection part in the supporting plate and sliding the switch operating part of the spring member beyond the inclined projection part to change the pressure load of the key top.
Since this conventional guiding member of the link structure is constituted by the first and second link members and is manufactured by assembling these link members, however, there is a drawback in that a number of processes are required for the assembly of the link members, thus increasing a manufacturing cost of the key switch.
The manufacturing cost is further raised because mechanical working of the supporting plate, such as forming the inclined projection part in the supporting plate, is needed to obtain the clicking sensation.
Also, the key top descends and collides directly with the frame without means of shock absorption, with the result that there is another problem of causing a noise.
Moreover, a pivot coupling is used for joining a keyboard frame and the links with each other, and the projection (pivot axis) of the pivot coupling is directly contacted with the frame, thereby causing still another problem in that the projection made of soft material is apt to be worn away by friction with the frame made of aluminum, etc. and so the life span of the overall key switch is shortened.
Furthermore, since a FPC (Flexible Printed Circuit) lying on the frame is not fixed, but may be moved to deviate a contact of the FPC from a point to which the pressure of the key top is applied, there is still another problem in that the key top does not exactly press the contact of the FPC even when it is pushed down, which results in a failure of the key input operation.
On the other hand, a multiple key switch for use in special keys such as a “space” key, an “enter” key and the like is so long that the pressure from the key top is not transmitted uniformly to the links and the key top gets crooked during the operation, thereby making it difficult to obtain a reliable contact force. In order to solve this problem, a link bar, etc. is used to transmit the pressure uniformly, but this requires additional assembly processes and so increases manufacturing costs.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to overcome the above-mentioned problems, and it is an object of the present invention to provide a downsized, thin and inexpensive key switch by forming a guiding member having a simple link structure.
It is another object of the present invention to provide a key switch, which imparts a clicking sensation using a simple structure.
It is still another object of the present invention to provide a key switch, which generates less noise and realizes precise key switch actions.
It is further still another object of the present invention to provide a key switch, which transmits pressure uniformly when used as a multiple key switch.
To accomplish this object, there is provided a key switch in accordance with the present invention, the key switch comprising: a key top for receiving pressure from a user's finger; a link for lowering the key top when pressure is applied to the key top and pushing the key top upwardly when the pressure is released; and a flexible printed circuit (FPC) provided on an upper surface of a keyboard frame for recognizing the key action by a pressing-contact of the link therewith, wherein the link has a first and a second legs being pivot-coupled with each other, a return plate spring applying a returning force to the key top, and a contact plate spring coming into pressing-contact with the FPC, the first leg being also pivot-coupled with the frame and the second leg being also freely pivot-coupled with the frame through an slot-shaped hole, so that the second leg and the frame are slid relative to each other along the slot-shaped hole and stops the relative sliding movement at an end of the slot-shaped hole when the key top is pushed down against a resilient force of the return plate spring, and if the pressure load of the key top is further increased, the return plate spring takes a nearly rectilinear shape to abruptly reduce the pressure load, thereby imparting a clicking sensation.
Preferably, a contact projection is formed on a lower surface of the contact plate spring.
It is preferred that two return plate springs are formed while the contact plate spring being formed between the return plate springs, but the return plate spring is one in number and the contact plate spring is one in number.
Preferably, the first leg, the second leg, the return plate spring and the contact plate spring are integrally formed to constitute the link, the return plate spring may be separately formed of resilient metallic material such as steel, etc. and then is assembled to or insert-molded into the link, which is desirable in view of securing durability.
The first leg is simply and easily attached to and detached from the frame if resilience having a tendency to be outwardly bent.
The link can be simply manufactured at a low cost if it is formed by a mold.
It is also preferred that a pair of upright holes are formed in the frame, projections formed at both ends of the second leg are inserted into the upright holes, and the FPC is located between the projections and the frame. At least one of the upright holes is preferably located in an upper end portion of the frame and is opened upwardly.
Preferably, a projection is formed on a lower surface of the key top and the contact plate spring is formed in a nearly stair-like shape so that the pressure of the key top is absorbed by the contact plate spring after the return plate spring takes a nearly rectilinear shape.
The contact plate spring is preferably prov
Friedhofer Michael
Greenlee Winner and Sullivan P.C.
SMK Korea Co., Ltd.
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