Abstract:
A keyboard switch comprises a key switch, a key top mounted on the key switch, stress transmission means for transmitting a depression force of the key top to a plurality of areas of the key top, and a common member for supporting the stress transmission means and engaging the key switch.

Description:
This application is a continuation of application Ser. No. 607,621 filed May 7, 1984. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard switch of an electronic equipment, and more particularly to a keyboard switch having a rectangular actuation key of a high rectangle ratio. 
     2. Description of the Prior Art 
     Various structures have been used in the prior art keyboards of electronic equipments. They are classified into two major categories, one in which a plurality of key switches are arranged and the other in which a plurality of switch patterns are arranged on a printed circuit board and the switch patterns are selectively shorted by depressing keys arranged on the switch patterns. In those structures, the keys are normally biased by springs oppositely to the depression direction, and when the key is to be actuated, it is depressed against the biasing force. 
     A space key or a shift key of a full keyboard for a typewriter or a computer uses a rectangular key having a rectangle ratio of larger than 1.5. If an end area of such a key is depressed, a rotating moment is created by the biasing force and thus, the key is subject to both the depression force and a force which tends to incline a key shaft provided at center of the key. As a result, if the key switch is arranged at the center of the rectangular key under the key, the keyboard will not be smoothly operated or may be broken during long term use. To avoid the above problem, a torsion bar structure shown in FIGS. 1 and 2 has been used in the prior art rectangular key. FIG. 2 shows a sectional view taken along a line A--A of FIG. 1. 
     In FIGS. 1 and 2, numeral 10 denotes a known key switch which is fixed to a mounting hole 51 of a keyboard chassis 50 by a flange 14 and a pawl 15. Precise positioning is done by a positioning projection 12 provided at a bottom of the flange 14, which positioning projection is fitted to a positioning hole of the keyboard chassis 50. A terminal 11 is provided at a bottom of the key switch 10 and is soldered to a printed circuit board 60. 
     A rectangular key 20 is fitted to a stem 13 formed at the top of the key switch 10. Only the key 20 projects from an equipment case, not shown. Torsion bar receptacles 21 are formed at a bottom of the key 20. Ends of a U-shaped torsion bar 30 engage with the torsion bar receptacles. The torsion bar 30 is slidably mounted on a bearing 40 mounted on the keyboard chassis 50. In the structure shown, the key switch 10 contains a biasing mechanism and the torsion bar 30 merely mechanically engages the ends of the key 20. 
     In this arrangement, when one end of the key 20 is depressed, the depression force is transmitted to the other end through the torsion bar 30. Therefore, smooth operation is assured and the key 20 is not inclined or tilted and forces tending to dislodge or break the key switch 10 and the stem 13 are not created. 
     However, the above arrangement needs the keyboard chassis 50 for mounting the key switch and the torsion bar and hence it is complex in construction, takes a long time to assemble. As a result, the cost of the equipment increases and compactness and lightness of the equipment are compromised. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a keyboard switch of a simple and inexpensive structure which assures a positive operation of a rectangular key. 
     It is another object of the present invention to provide a keyboard switch having a common member for a support of stress transmitting means for transmitting a depression force of a key top mounted on a key switch to a plurality of areas of the key top, and engagement of the key switch. 
     It is another object of the present invention to provide an electronic part having a bent terminal and a positioning projection for positioning the part on a printed circuit board. 
     It still is another object of the present invention to provide a key switch having a common support member to a support of stress transmitting means for transmitting a depression force of a key top mounted on a key switch to a plurality of areas of the key top and a support of the key switch, and a bent terminal and a positioning projection for fixing the key switch. 
     It is yet another object of the present invention to provide a key switch in which a support for stress transmitting means for transmitting a depression force of a key top mounted on a key switch to a plurality of areas of the key top is integral with the key switch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are respectively a longitudinal sectional view and a cross-sectional view, taken from line A--A in FIG. 1, of a prior art keyboard switch, 
     FIGS. 3 and 4 are respectively a longitudinal sectional view and cross-sectional view, taken from line B--B in FIG. 3, of a keyboard switch of the present invention, 
     FIGS. 5A and 5B are respectively a top view and a longitudinal sectional view, taken from line C--C in FIG. 5A, of a bracket used in the keyboard of the present invention, and 
     FIGS. 6A and 6B are a side elevational view and a bottom view, respectively, of the key switch of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description of the preferred embodiments of the present invention, the like elements to those of the prior art structure shown in FIGS. 1 and 2 are designated by the like numerals and the explanation thereof is omitted. 
     FIGS. 3 and 4 show a keyboard switch of the present invention. FIG. 4 shows a sectional view taken along a line B--B of FIG. 3. In the present invention, the torsion bar 30 is borne by a bracket 40&#39; formed to cover a key switch 10&#39;. 
     The keyboard chassis of the prior art structure is omitted and the key switch 10&#39; is fixed to a printed circuit board 60&#39; by soldering a terminal 11&#39; thereto. Positioning relative to the printed circuit board 60&#39; is done by fitting a positioning projection 15&#39; formed at the bottom of the key switch 10&#39; to a positioning hole formed in the printed circuit board 60&#39;. As shown, the terminal 11&#39; is bent so that the key switch 10&#39; can be tentatively fixed to the printed circuit board 60&#39;. A positioning projection 12&#39;, sometimes referred to hereinafter as a &#34;fitting&#34; member, at the bottom of a flange 14&#39; of the key switch 10&#39; is fitted to a positioning hole formed in the bracket 40&#39; so that the key switch 10&#39; is positioned to the bracket 40&#39; and the torsion bar 30. 
     Structures of the bracket 40&#39; and the key switch 10&#39; are shown in detail in FIGS. 5A and 5B and FIGS. 6A and 6B. 
     FIG. 5A shows a top view of the bracket 40&#39; and FIG. 5B shows a sectional view taken along a line C--C of FIG. 5A. Numeral 41&#39; denotes a positioning hole to which the positioning projection, or fitting member 12&#39; is fitted, and numeral 42&#39; denotes a bearing to which the torsion bar 30 is fitted. 
     FIG. 6A shows a side elevational view of the key switch 10&#39; and FIG. 6B shows a bottom view. Two positioning projections 15&#39; are formed at the bottom of the key switch 10&#39;. Terminals 11&#39; are bent. In the structures shown in FIGS. 5A and 5B and FIGS. 6A and 6B, by designing a height A of the bracket 40&#39; relative to a length B between a lower surface of the flange 14&#39; of the key switch 10&#39; and the bottom of the key switch 10&#39; with an appropriate margin (for example, approximately 0.1 mm), the key switch 10&#39;, the bracket 40&#39; and the torsion bar 30 can be mounted with proper positional relationship by the positioning members. 
     In assembling the keyboard switch, the bracket 40&#39; is fitted to the key switch 10&#39;, then the positioning projection 15&#39; and the terminal 11&#39; are fitted to the mounting hole and the positioning hole formed on the printed circuit board 60&#39; and the terminal 11&#39; is soldered. Subsequently, the torsion bar 30 is mounted on the bearing 42&#39; of the bracket 40&#39;, the torsion bar receptacle 21 of the key 20 is engaged with the end of the torsion bar 30, and the key 20 is fitted to the stem 13&#39;. 
     As described hereinabove, according to the present invention, the keyboard chassis 50 which was necessary in the prior art structure can be omitted and the structure is simplified. Accordingly, the number of members to be positioned is reduced, the assembly work is simplified and the equipment can be reduced in size and weight. Since the torsion bar of the present invention is not positioned relative to the key 20 through the keyboard chassis, the assembly accuracy can be improved, the possibility of failure is reduced and positive operation is assured.