Abstract:
A pushbutton switch for use in a keyboard incorporated in an electronic typewriter, work processor, or the like gives a tactile feel to the finger of the operator corresponding to a clicking operation and, at the same time, produces a clicking sound. The switch comprises a casing, a switching device in the casing, a stem, and a leaf spring. This spring has an upright portion and a bent portion. The leaf spring is so mounted in the casing that when the stem is depressed, the bent portion is reciprocated. This causes the upright portion to collide with the inner surface of one side wall of the casing, thus producing a clicking sound.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pushbutton switch for use in a keyboard incorporated in an electronic typewriter, word processor, terminal equipment, or the like and, more particularly, to a pushbutton switch which, when operated, makes a clicking sound and allows the human operator to sense the operation through her tactile sensation. 
     BACKGROUND OF THE INVENTION 
     It is desired from the viewpoint of human engineering that a tactile feedback be provided in connection with pushbutton switches for use in a keyboard. Specifically, when a switch is depressed, it is actuated and, at the same time, the operator should be allowed to sense the actuation through her tactile sensation. This will permit her to recognize that the switch has been actuated, which means that she is no longer required to keep depressing the switch. Accordingly, the keyboard is easy for the operator to operate, and gives less feeling of fatigue. Pushbutton switches of this kind are disclosed in U.S. Pat. Nos. 3,829,632, 3,993,884, and 4,153,829, where a snap-action leaf spring is used to give the operator a tactile feel when a switch is depressed. Since it is desired to make the tactile feedback more certain, there is a need for a keyboard which can not only give the operator a tactile feel but also produce a clicking sound when a switch is operated. However, the prior art devices described above are simply able to give a tactile feel, and it has been difficult for them to make a clicking sound. 
     SUMMARY OF THE INVENTION 
     It is the main object of the present invention to provide a pushbutton switch which is excellent from the viewpoint of human engineering in that it can not only give a tactile feel but also produce a clicking sound within the switch casing when the switch is actuated. 
     The above and additional objects are achieved by a pushbutton switch comprising: a casing; a pushbutton stem; a leaf spring having an upright portion that bears on the inner surface of a side wall of the casing, a bent portion extending from the upright portion at an angle, a spring portion extending downwardly from the bent portion toward the stem to produce a clicking operation, and protruding portions formed at the front end of the spring portion; and wherein when the stem presses the protruding portions, the bent portion is reciprocated to cause the upright portion of the leaf spring to strike against the inner surface of the side wall of the casing, whereby giving the operator a tactile feel and, at the same time, producing a clicking sound. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation in cross section of a pushbutton switch according to the present invention, for showing the condition in which the switch is not depressed; 
     FIG. 2 is a side elevation in cross section of the switch shown in FIG. 1, for showing the condition in which the switch is being depressed; 
     FIG. 3 is a side elevation in cross section of the switch shown in FIG. 1, for showing the condition in which the switch has been fully depressed; 
     FIG. 4 is a perspective view of the leaf spring shown in FIG. 1; 
     FIG. 5 is a perspective view of the upper casing shown in FIG. 1 as viewed from the lower side of the casing; 
     FIG. 6 is a view similar to FIG. 1, but showing another example of a pushbutton switch according to the invention; 
     FIG. 7 is a view similar to FIG. 2, but showing the switch of FIG. 6; 
     FIG. 8 is a view similar to FIG. 3, but showing the switch of FIG. 6; and 
     FIG. 9 is a view similar to FIG. 4, but showing the leaf spring shown in FIG. 6. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1-5, there is shown a pushbutton switch embodying the concept of the present invention. This switch includes an upper casing 1 made from a synthetic resin such as PBT (polybutylene terephthalate), a stem 2 made from a synthetic resin such as nylon, a lower casing 3 made from a material similar to the material of the upper casing, a membrane switching device 5, a contact spring 6 made of stainless steel or similar material, and a leaf spring 7 made of stainless steel or similar material. 
     The condition in which the stem is not depressed is shown in FIG. 1, where the stem 2 has been inserted between step portions 1a and 1b (see FIG. 5) formed on the upper casing 1. The lower casing 3 and the stem 2 are provided with projections 3a and 2a, respectively. A coiled spring 4 is mounted between the projections 3a and 2a such that the stem 2 can reciprocate. The lower casing 3 is mounted to the upper casing 1 using a snap (not shown) after various components are received in the upper casing 1 as described below. 
     The switching device 5 is disposed between the step portion 1a of the upper casing 1 and the inner surface 1c of a side wall of the casing. The spring 6 is mounted to the device 5 to actuate it when the spring is pressed by the stem 2. The leaf spring 7 is disposed on the opposite side of the stem 2 from the device 5, and comprises an upright portion 7a and a spring portion 7c for producing a clicking operation, as shown in FIG. 4. Portions of the upright portions 7a are bordered by shoulder portions 7f, above which a bent portion 7b is provided. The spring portion 7c extends obliquely downwardly from the bent portion 7b. 
     The lower portion of the spring portion 7c is bifurcated, and each lower end of these two separated portions is provided with a protrusion 7d. The upright portion 7a of the spring 7 is disposed between the step portion 1d of the upper casing 1 and the inner surface 1e of the side wall. The spring portion 7c is disposed on the side of the stem 2 such that the spring portion 7c is depressed when the stem 2 is depressed. 
     The operation of the novel pushbutton switch constructed as described above is next described by referring to FIGS. 2 and 3; FIG. 2 shows the condition in which the stem 2 is being depressed, and FIG. 3 shows the condition in which the step 2 has been fully depressed. 
     When the stem 2 is depressed, it pushes inclined surfaces 7e on the protruding portion 7d, shifting sidewardly (to the right in the drawings) the upright portion 7a of the spring 7 toward the stem 2 from the top of the spring 7, i.e., from the vicinity of the bent portion 7b. The upright portion 7a therefore moves away from the inner surface 1d of the side wall of the casing 1. Then, the spring 7 bears on protruding portions 1f of the upper casing 1 near the bent portion 7b. 
     At the same time, the spring 6 is depressed, but not sufficiently to actuate the switching device 5. Further depression of the stem 2 causes the stem 2 to ride on the protruding portions 7d of the spring 7, as shown in FIG. 3, to give the operator a tactile feel, due to the abrupt transition between the sliding parts. At this time, the stem 2 acts to push the protruding portions 7d laterally, urging the leaf spring 7 toward the inner surface 1e of the side wall. Then, the upright portion 7a of the spring 7 moves back (to the left of the drawings) and strikes on the inner surface 1e of the side wall, producing a colliding sound, or a clicking sound. Concurrently, the spring 6 presses against the switching device 5, actuating it. That is, just when the switch is actuated, a tactile feel is given to the operator, and a clicking sound is produced. 
     When the stem 2 is then released, the coiled spring 4 moves the stem 2 upward, so that the stem 2 disengages from the protruding portions 7d. At the same time, the switching device 5 is restored to the off condition. Namely, the device is restored to the condition shown in FIG. 1. 
     The distance between each step portion 1d of the casing 1 and the inner surface 1e of the side wall is made larger than the thickness of the leaf spring 7, but the distance can be made equal to the thickness, because the portion of the spring 7 located above the shoulder portions 7f is not constrained by the step portions 1d, although movement of the portion of the spring 7 lying below the shoulder portions 7f is restricted by the step portions 1d of the casing 1, as shown in FIG. 4. In any event, the requirement is only that the upper portion of the spring 7 can reciprocate. 
     Referring next to FIGS. 6-9, there is shown another pushbutton switch according to the invention. FIG. 6 shows the condition in which the switch is not depressed. FIG. 7 shows the condition in which it is being depressed. FIG. 8 shows the condition in which it has been fully depressed. The leaf spring of the switch is shown in FIG. 9. This switch is similar to the switch shown in FIG. 1 except for the leaf spring and, therefore, the components other than the spring will not be described below. 
     The leaf spring 7 is comprised of an upright portion 7a, a bent portion 7b, and a spring portion 7c for producing a clicking operation. The upright portion 7a has spring portions 7g on its both sides and a protrusion 7h that comes into abutting engagement with the inner surface 1e of the side wall of the upper casing 1. The spring portion 7g engages with a grooved side wall A (indicated in perspective in FIG. 5 and shown in section in FIGS. 6 and 7) of the upper casing 1. The lower portion of the spring portion 7c is bifurcated, and each lower end of these two separated portions is provided with a protrusion 7d. 
     In the operation of the pushbutton switch constructed as described in connection with FIGS. 6-9, when the stem 2 is depressed, it pushes inclined surfaces 73 of the protrusions 7d to cause the upper portion of the leaf spring 7, i.e., the portion near the bent portion 7b, to be thrown toward the stem 2. Thus, the protrusion 7h of the spring 7 moves away from the inner surface 1e of the upper casing 1, bringing the portion close to the bent portion 7b into abutting engagement with the projection 1f of the casing 1. At the same time, the contact spring 6 is depressed, but not sufficiently to actuate the switching device 5. Further depression of the stem 2 causes it to ride on the protrusions 7d, giving the operator a tactile feel corresponding to the clicking operation. At this time, the stem 2 pushes the protrusion 7d laterally. This permits the spring 7 to return to the side of the inner surface 1e of the side wall, and then the projection 7h of the spring 7 collides with the inner surface 1e to produce a colliding sound, or a clicking sound. At the same time, the switching device 5 is depressed by the spring 6, thereby actuating the device. That is, just when the switch is actuated, a tactile feel is given to the operator, and a clicking sound is produced. 
     Under this condition, if the stem 2 is then released, the coiled spring 4 pushes the stem 2 upward. The stem 2 therefore moves away from the protrusions 7d. At the same time, the switching device 5 is driven into the off condition. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made therein without departing from the spirit and scope of the invention. For example, the switching device 5 is depressed by the depression spring 6 in the described examples, but the device may be replaced with an other switching device such as a reed switch. Further, the invention is not limited to a switch using a depression spring. Also, the protrusion 7h formed on the leaf spring 7 as shown in FIG. 6 may be replaced by a protrusion formed on the inner surface 1e of the side wall of the upper casing 1. 
     As can be understood from the description thus far made, the novel switch has the bent portion of the leaf spring which is reciprocated to produce a colliding sound when the spring portion of the leaf spring is pressed by the stem. Hence, the switch gives the finger of the operator a tactile feel corresponding to the clicking operation and, at the same time, it can produce a distinct clicking sound. Consequently, the operator can certainly recognize that the switch has been actuated, by means of both the tactile sense and the clicking sound. Thus, a pushbutton switch is provided which is easy to operate, gives less feeling of fatigue, and is excellent from the viewpoint of human engineering.