Dome-shaped contact plate giving crispy feeling of click and sheet with contact plate

[0002] 1. Field of the Invention

[0003] The present invention relates to a contact plate for use as a movable contact of a push-button switch, and more particularly to a disc contact plate press-formed into a dome shape, a sheet with the contact plate, and the structure of a switch device using the sheet.

[0004] 2. Description of the Prior Art

[0005] Known structures of a contact plate for use as the movable contact of a push-button switch include the structures illustrated in FIG. 8 through FIG. 12. FIG. 8 through FIG. 10 are sectional views showing the relationship between a movable contact and a fixed contact, and FIGS. 11 and 12 illustrate the relationship between the manipulative force on and the shifted quantity of the movable contact.

[0006] FIG. 8 shows a state in which a disc movable contact 51 formed by cupping a thin metallic sheet into a dome shape is mounted over a central fixed contact 53 and a peripheral fixed contact 54, each similarly consisting of an electroconductive metallic sheet, arranged on the inner bottom face of a housing 52 consisting of synthetic resin or the like.

[0007] The movable contact 51 is formed of a skirt 51arising from the outer circumference of a disc at a prescribed angle toward the center of the disc and a dome 51b, which is continuous from the skirt 51aand can be repetitively inverted. The skirt 51aand dome 51bare connected to each other by a smooth bend 51c. An outer peripheral end 51dof the skirt 51ais in contact with the peripheral fixed contact 54 at all times, and the inside of the top of the dome 51bconstitutes a contact 51e, which comes into contact with the central fixed contact 53 when the dome 51bis repetitively inverted.

[0008] A gap is formed between the central fixed contact 53 and the peripheral fixed contact 54, with the central fixed contact 53 being formed a step below the peripheral fixed contact 54. As indicated by curve A in FIG. 11, when the dome 51bof the movable contact 51 is inverted the distance (shifted quantity) L1 between the contact 51eand the central fixed contact 53 can be greater by the level difference of the step, thus the shifted quantity after the inversion of the movable contact 51bcan be set greater than otherwise, resulting in a crispy feeling of click. In the diagram the vertical axis represents the manipulative force F, and the horizontal axis represents the shifted quantity L.

[0009] Incidentally, AO in the diagram denotes the tactile sensation (click feeling) curve of the movable contact 51 and LA denotes the point where the reaction force after the inversion of the movable contact 51 is at its minimum, i.e., the settable maximum of the shifted quantity.

[0010] FIG. 9 illustrates a state in which the movable contact 51 is mounted over a circuit board 55 on which a circuit pattern is formed of a copper foil or the like. In this case, since a central fixed contact 56 and a peripheral fixed contact 57 are formed of a copper foil or the like in a planar form over the circuit board 55, the distance (the shifted quantity) L2 between the contact 5Se and the central fixed contact 56 is less than L1 when the dome 51bof the movable contact 51 is inverted.

[0011] FIG. 10 shows a movable contact 58 formed in a state in which the rising angle θc of a skirt 58ais set more nearly upright than θb shown in FIG. 9 (θb<θc) so that when the dome 58bof the movable contact 58 is inverted the distance (the shifted quantity) L3 between a contact 58eand the central fixed contact 56 becomes equal to L1 (L3=L1). As indicated by curve C in FIG. 12, when the dome 58bof the movable contact 58 is inverted, the distance (the shifted quantity) L3 between the contact 58eand the central fixed contact 56 can be greater, the shifted quantity after the inversion of the movable contact 58 can be set greater than otherwise, resulting in a crispy feeling of click.

[0012] However, in the above-described structure of the movable contact 51 according to the prior art, when it is to be used in the planar circuit board 55 and when the dome 51bof the movable contact 51 is inverted, the distance (the shifted quantity) L2 between the contact 51eand the central fixed contact 56 is less than L1. The shifted quantity thus becomes smaller after the inversion of the movable contact 51 as indicated by B in FIG. 11, resulting in a problem of a dull feeling of click.

[0013] Further, if the rising angle θc of the skirt 58ais increased, the reaction force of the tactile sensation curve CO of the movable contact 58 will take on a negative value at point LC as shown in FIG. 12, resulting in a problem that the movable contact 58 remains inverted instead of automatically returning to the original state.

[0014] An object of the present invention, therefore, is to solve the problems noted above and provide a movable contact structure which, even when used in a planar circuit board, can provide a crispy click feeling and will not fail to return to an original position after being inverted.

[0015] In order to solve the problems noted above, according to a first aspect of the invention, there is provided a contact plate consisting of a disc formed into a dome shape by cupping a center of a thin metallic sheet in one direction, provided with a skirt rising at a prescribed angle from an outer circumference of this disc toward a center of the disc, and a dome which is continuous from this skirt and can be repetitively inverted, the connecting part between the skirt and the dome being formed in multiple steps via a plurality of bent portions.

[0016] According to a second aspect of the invention, a projection in contact with a fixed contact is formed on an inner face of the dome.

[0017] According to a third aspect of the invention, an external face of the dome of the contact plate according to the first or second aspect of the invention is stuck to an adhesive back face layer of an insulating sheet, and the contact plate and an lower face of the insulating sheet are covered with a peelable protective sheet.

[0018] According to a fourth aspect of the invention, a spacer sheet having an accommodating hole for accommodating the contact plate is provided between the insulating sheet and the protective sheet.

[0019] According to a fifth aspect of the invention, the protective sheet of the sheet with the contact plate according to the third or fourth aspect of the invention is peeled, and the sheet with the contact plate after peeling is stuck to a circuit board, over which a plurality of fixed contacts are arranged, by the adhesive back face layer of the insulating sheet so that the contact plate is opposite the fixed contacts.

[0020] According to a sixth aspect of the invention, there is provided a switch device having the contact plate according to the first or second aspect of the invention and an accommodating section, whose inner bottom face is provided with a housing over which a fixed contact is arranged and a suppressing member liftably snapped into the accommodating section, wherein the contact plate is arranged opposite the fixed contact to be suppressible by the suppressing member.

[0021] FIG. 1 is a sectional view showing the relationship between a movable contact, which is a preferred embodiment of the present invention, and a fixed contact.

[0022] FIG. 2 is a partial sectional view illustrating the connection section between the skirt and the dome of the movable contact embodying the invention.

[0023] FIG. 3 illustrates the relationship between the manipulative force on and the shifted quantity of the movable contact embodying the invention.

[0024] FIG. 4 is a sectional view showing a sheet-shaped switch device using the movable contact embodying the invention.

[0025] FIG. 5 is a sectional view of the essential part illustrating the sheet-shaped switch device using the movable contact embodying the invention.

[0026] FIG. 6 is an exploded perspective view of a switch device based on an insulating resin-made housing using the movable contact embodying the invention.

[0027] FIG. 7 is a sectional view of the essential part illustrating the switch device based on the insulating resin-made housing using the movable contact embodying the invention.

[0028] FIG. 8 is a sectional view showing an example of the relationship between a movable contact and a fixed contact according to the prior art.

[0029] FIG. 9 is a sectional view showing another example of the relationship between a movable contact and a fixed contact according to the prior art.

[0030] FIG. 10 is a sectional view showing still another example of the relationship between a movable contact and a fixed contact according to the prior art.

[0031] FIG. 11 illustrates an example of the relationship between the manipulative force on and the shifted quantity of the movable contact according to the prior art.

[0032] FIG. 12 illustrates another example of the relationship between the manipulative force on and the shifted quantity of the movable contact according to the prior art.

[0033] A preferred embodiment of the present invention will be described below with reference to FIG. 1 through FIG. 3. FIG. 1 is a sectional view illustrating the relationship between a movable contact and a fixed contact; FIG. 2 is a partial sectional view illustrating the connection section between the skirt and the dome of the movable contact; and FIG. 3 illustrates the relationship between the manipulative force on and the shifted quantity of the movable contact.

[0034] Referring to FIG. 1, a movable contact 1 is a thin metallic plate formed in a disc shape. This movable contact 1 is composed of a skirt 1arising from the outer circumference of the disc at a prescribed angle toward the center of the disc and a dome 1b, which is continuous from this skirt 1aand can be repetitively inverted, and the skirt 1aand dome 1bare formed in multiple steps via a plurality of bent portions 1cand 1d(two portions in this embodiment).

[0035] A circuit board 2 consists of an insulating planar laminate, and over its surface are formed a central fixed contact 2a, and a peripheral fixed contact 2bof an electroconductive circuit pattern made of a copper foil or the like.

[0036] The movable contact 1 is mounted to be opposite the central fixed contact 2aand the peripheral fixed contact 2b, and the outer peripheral end 1eof the skirt 1ais in contact with the peripheral fixed contact 2ball the time, and the inner face of the top of the dome 1bconstitutes the contact 1f, which goes out of contact with the central fixed contact 2awhen the dome is repetitively inverted.

[0037] In one embodiment, the rising angle θd of the skirt 1aof the movable contact 1 is formed to be more nearly upright than θb according to the prior art shown in FIG. 9 (θb<θd), and this θd is formed to be equal to θc according to the prior art shown in FIG. 10 (θc=θd).

[0038] Thus, the configuration is such that when the dome 1bof the movable contact 1 is inverted the distance (shifted quantity) L4 between the contact 1fand the central fixed contact 2abecomes equal to L1 (L4=L1) and, as the distance (the shifted quantity) L4 between the contact 1fand the central fixed contact 2awhen the dome 1bof the movable contact 1 is inverted is greater, the shifted quantity after the inversion of the movable contact 1 can be set greater than otherwise as indicated by D in FIG. 3, resulting in a crispy feeling of click. In the diagram the vertical axis represents the manipulative force F, and the horizontal axis, the shifted quantity L.

[0039] Further, while the rising angle θd of the skirt 1aof the movable contact 1 is formed more nearly upright, the connecting part of the dome 1bto be connected to this skirt 1ais connected via the two bent portions 1cand 1d, and it is possible to generally reduce the angle formed by the bent portion 1dof the bent portions with the dome 1b. Accordingly, the tactile sensation curve DO formed when the dome 1bis inverted can be brought close to the tactile sensation curve AO according to the prior art shown in FIGS. 11 and 12, with the result that the point LD, where the reaction force of the tactile sensation curve DO reaches its minimum, never becomes negative and the movable contact 1 can automatically return to its original position without fail.

[0040] FIG. 4 and FIG. 5 illustrate the structure of a sheet-shaped switch device using the movable contact 1.

[0041] In the drawings, a circuit board 3 is formed of a laminate of phenol resin or the like, and pluralities of central fixed contacts 4aand peripheral fixed contacts 4b, consisting of electroconductive copper foils or the like, are arranged over the surface of this circuit board 3.

[0042] An insulating sheet 5 is formed of an insulating film, and its lower face is fully covered with an adhesive layer, to which the dome 1bof the movable contact 1 is stuck to integrate the movable contact 1 with the insulating sheet 5.

[0043] A spacer 6 is also formed of an insulating film, and its lower face is also covered with an adhesive layer. At its center are provided a plurality of accommodating holes 6afor accommodating the movable contact 1.

[0044] The spacer 6 is stuck to the lower face of the insulating sheet 5, and the back face of the movable contact 1 stuck to the insulating sheet 5 is covered with a protective sheet 20. This protective sheet 20 consists of a film whose face opposite the adhesive layer on the lower face of the spacer 6 is peelably coated, and these elements are stacked to form a sheet with the contact plate.

[0045] A sheet-shaped switch device is formed by peeling the protective sheet 20 from this sheet with the contact plate and sticking the insulating sheet 5 and the spacer 6 to the circuit board 3 so that the movable contact 1 is placed opposite the central fixed contact 4aand the peripheral fixed contact 4b.

[0046] Then the movable contact 1 is in such a state that the dome 1bis separate from but opposite the central fixed contact 4aand the outer peripheral end 1eof the skirt 1ais in contact with the peripheral fixed contact 4ball the time.

[0047] In this case, in the movable contact 1 are formed a plurality of projections 1g(three in this embodiment) scattered in the contact 1f, which is the inner face of the top of the dome 1b. By providing the contact 1fwith the projections 1gin this way, the contact of the contact 1fcan be stabilized even if dust or the like invades the contact 1f, resulting in improved dustproofness. Incidentally, while even a single projection 1gwould be effective, in other embodiments a plurality of projections would be even more effective.

[0048] In this embodiment, if the inner face of the movable contact 1 is provided with the projections 1g, a greater distance (the shifted quantity) can be secured between the projections 1gand the central fixed contact 4a, resulting in a crisp click feeling.

[0049] Incidentally, although the spacer 6 for accommodating the movable contact 1 is used in the foregoing embodiment, the configuration is not limited to this, but the spacer 6 can as well be dispensed with to have the insulating sheet 5 directly hold the movable contact 1.

[0050] FIG. 6 and FIG. 7 illustrate the structure of a switch device based on an insulating resin-made housing using the movable contact 1.

[0051] In the drawing, a housing 7 is formed of an insulator, such as synthetic resin, in a box shape with an opening in the top face. On the inner bottom face of an accommodating section 7aformed in the opening in this housing 7 are arranged a central fixed contact 8aand a peripheral fixed contact 8bconsisting of electroconductive metallic plates.

[0052] Over the central fixed contact 8aand the peripheral fixed contact 8bis formed the movable contact 1 opposite them. In this case, the dome 1bis separate from but opposite the central fixed contact 8aand the outer peripheral end 1eof the skirt 1ais in contact with the peripheral fixed contact 8ball the time.

[0053] A stem 9, similarly formed of an insulator such as synthetic resin, is provided with a suppressive manipulating part 9aprotruding from the opening in the housing 7, a flange 9band an operating projection 9cfor suppressing the dome 1bof the movable contact 1.

[0054] A cover 10, formed of a planar metallic plate or the like, covers the opening in the housing 7, and prevents the stem 9 from springing out by keeping the flange 9bof the stem 9 in contact with the inner face of the cover 10.

[0055] By inserting the movable contact 1 and the stem 9 into the opening in the housing 7, covering the opening in the housing 7 with the cover 10 and fixing it by caulking or otherwise, the switch device based on the insulating resin-made housing is formed. In this case, too, the movable contact 1 comprises a plurality of projections 1g(three in this embodiment) scattered in the contact 1f, which is the inner face of the top of the dome 1b, resulting in improved dustproofness.

[0056] As heretofore described, the contact plate according to the present invention consists of a disc formed into a dome shape by cupping the center of a thin metallic sheet in one direction, provided with a skirt rising from the outer circumference of this disc toward the center of the disc, and a dome which is continuous from this skirt and can be repetitively inverted, the connecting part between the skirt and the dome being formed in multiple steps via a plurality of bent portions. Accordingly it is possible to generally reduce the angle formed by one of these bent portions with the dome, with the result that the point where the reaction force of the tactile sensation curve reaches its zero never becomes negative and the failure of the movable contact to automatically return to its original position can be prevented. Moreover, the shifted quantity after the inversion of the movable contact can be set to a greater value, resulting in a crispy click feeling.

[0057] Also, since projections are formed on the inner face of the dome which come in contact with the fixed contact, the contacting of the contact can be stabilized even if dust or the like invades the contact, resulting in improved dustproofness.

[0058] Also, the external face of the dome of the contact plate is stuck to the adhesive back face layer of an insulating sheet, and the contact plate and the lower face of the insulating sheet are covered with a peelable protective sheet to provide a sheet with the contact plate, with the result that fitting to a planar circuit board is facilitated and the protective sheet can prevent dust from sticking to the contact part during the handling.

[0059] Also, since a spacer sheet having an accommodating hole for accommodating the contact plate is provided between the insulating sheet and the protective sheet, the contact plate can be securely fixed in a prescribed position of the insulating sheet.

[0060] Also, after peeling the protective sheet, the sheet with the contact plate may be stuck to the circuit board by the adhesive layer of the insulating sheet to facilitate formation of a sheet shaped switch device. Since the circuit board, having a plurality of fixed contacts, is thereby arranged so that the fixed contact is opposite the contact plate, the sheet-shaped switch device gives a crispy click feeling and automatically returns without failure to the original position after being inverted.

[0061] Also, since a switch device has the contact plate and an accommodating section, whose inner bottom face is provided with a housing over which a fixed contact is arranged and a suppressing member liftably snapped into the accommodating section, and the contact plate is arranged opposite the fixed contact to be suppressible by the suppressing member, a switch device based on an insulating resin-made housing which automatically without fail returns to the original position and gives a crispy click feeling can be easily obtained.