Electrical switch

FIELD OF THE INVENTION

This invention generally relates to the art of electrical switches and, particularly, to laminated electrical switches of the push-button type.

BACKGROUND OF THE INVENTION

Push-button electrical switches have been designed in a wide variety of configurations for a wide variety of applications. Such switches range from substantial three-dimensional structures having box-like housings to very thin or laminated switches, sometimes called “membrane” switches. Thin laminated switches often are used in conjunction with printed circuit boards. This invention is directed to improvements in such laminated switches.

SUMMARY OF THE INVENTION

An object, therefore, of the invention is to provide a new and improved electrical switch of the character described.

In the exemplary embodiment of the invention, the electrical switch includes an insulative substrate having a lower stamped metal circuit sheet supported thereon. The lower sheet includes a plurality of switch contacts and a plurality of leads for connecting the switch contacts to appropriate conductors. An upper stamped metal sheet is disposed over the insulative substrate and includes a plurality of embossed metal domes in registry with respective ones of the switch contacts. Depression of a selected one of the embossed metal domes engages the dome with a respective one of the switch contacts to close a circuit therethrough.

As disclosed herein, the lower stamped metal circuit sheet is insert molded in the insulative substrate and includes a common contact in engagement with the upper stamped metal sheet. The common contact is in the form of a peripheral contact outside the plurality of switch contacts. The upper stamped metal sheet includes a peripheral frame outside the plurality of embossed metal domes. The peripheral frame is in engagement with the peripheral contact. The plurality of embossed metal domes are electrically coupled to the peripheral frame.

A feature of the invention includes the insulative substrate having a plurality of integral pegs extending through apertures in the peripheral contact of the lower stamped metal circuit sheet and through apertures in the peripheral frame of the upper stamped metal sheet. The pegs are deformed, as by staking, to hold the upper stamped metal sheet and the insulative substrate together, with the peripheral contact in engagement with the peripheral frame.

In an alternative embodiment of the invention, an insulated circuit sheet is disposed between the upper stamped metal sheet and the insulative substrate. The insulated circuit sheet includes conductive pads in registry between the embossed metal domes and the switch contacts. The insulated circuit sheet is configured to hermetically seal the insulative substrate and lower stamped metal circuit sheet.

Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:

FIG. 1

is a top perspective view of a first embodiment of the electrical switch according to the invention;

FIG. 2

is a top plan view of the switch, with the upper stamped metal sheet removed;

FIG. 3

is a top plan view of the upper stamped metal sheet, alone;

FIG. 4

is a top plan view of the lower stamped metal circuit sheet;

FIG. 5

is a perspective view of the upper stamped metal sheet about to be assembled to the insulative substrate;

FIG. 6

is a top plan view of an insulated circuit sheet employed in a second embodiment of the invention;

FIG. 7

is an exploded perspective view of an electrical switch according to the second embodiment; and

FIG. 8

is a view similar to that of

FIG. 1

, but of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in greater detail,

FIG. 1

shows an electrical switch, generally designated

10

, according to a first embodiment of the invention. The switch includes three major components, namely: an insulative substrate, generally designated

12

and best seen in

FIGS. 2 and 5

; a lower stamped metal circuit sheet, generally designated

14

, supported on insulative substrate

12

and best seen in

FIG. 4

; and an upper stamped metal sheet, generally designated

16

and best seen in

FIGS. 1

,

3

and

5

.

Turning first to the lower stamped metal circuit sheet

14

of

FIG. 4

, the circuit sheet includes a generally rectangular, common peripheral contact

18

having cutouts

20

so that the common peripheral contact substantially surrounds and is spaced from a plurality of switch contacts

22

. The peripheral contact

18

may have other suitable shapes. The switch contacts are generally circular or disk-shaped and include leads

24

projecting beyond common peripheral contact

18

which includes it own lead

26

. Leads

24

and

26

of all of the contacts connect the contacts to appropriate conductors such as the circuit traces on a printed circuit board. Finally, common peripheral contact

18

includes at least one aperture

28

for purposes described hereinafter. A pair of apertures

28

are shown in the peripheral contact

18

of FIG.

4

.

FIGS. 2 and 5

show insulative substrate

12

to be generally rectangular and slightly larger than the peripheral bounds of common peripheral contact

18

of lower stamped metal circuit sheet

14

. However, the insulative substrate does not have to be rectangular in shape or larger than the peripheral bounds of the common peripheral contact

18

and may even be smaller. In fabrication, substrate

12

is of a dielectric material such as plastic or the like and is overmolded about the lower circuit sheet

14

except for leads

24

and

26

which project beyond one edge

30

of the substrate and except for switch contacts

22

which are exposed through circular openings

32

in the substrate. In addition, portions

18

a

of common peripheral contact

18

of lower circuit sheet

14

are exposed through rectangular openings

34

in the substrate. A plurality of pegs

36

are molded integrally with the substrate and project forwardly thereof as seen best in FIG.

5

. Finally, countersunk circular areas

38

surround circular openings

32

in the substrate. Therefore, switch contacts

22

are preferably spaced below a top surface

40

of the substrate.

Upper stamped metal sheet

16

is disposed over insulative substrate

12

and includes a generally rectangular peripheral frame

42

of substantially the same dimensions as the substrate so that the frame can be assembled onto top surface

40

of the substrate. When the upper stamped metal sheet is assembled onto the substrate, peripheral frame

42

engages exposed portions

18

a

(

FIG. 5

) of common peripheral contact

18

(

FIG. 4

) of lower circuit sheet

14

.

Upper stamped metal sheet

16

also includes a plurality (three in the embodiment shown) of embossed metal domes

44

which are in registry with the three switch contacts

22

of lower circuit sheet

14

when the upper metal sheet is assembled to substrate

12

. In other words, the switch contacts are exposed through openings

32

in the substrate which, in turn, are in registry with embossed metal domes

44

. The embossed metal domes are electrically coupled or commoned to peripheral frame

42

by integral web portions

46

of the upper stamped metal sheet. Finally, the upper stamped metal sheet includes a plurality of apertures

48

for receiving integral pegs

36

of insulative substrate

12

. The pegs and apertures not only align the upper stamped metal sheet with the substrate and the switch contacts, but the pegs are deformed or staked as shown at

48

a

in

FIG. 1

to hold the upper stamped metal sheet against front face

40

of the substrate and to hold peripheral frame

42

of the metal sheet in engagement with portions

18

a

of common peripheral contact

18

through rectangular openings

34

in the substrate.

When it is desirable to engage a selected one of the embossed metal domes

44

with the respective switch contact

22

which is in registry with that selected metal dome, the dome is depressed in the direction of arrow “A” (FIG.

1

). The embossed dome enters countersunk area

38

in insulative substrate

12

and into engagement with the respective switch contact

22

. With peripheral frame

42

of upper stamped metal sheet

16

already in constant engagement with common peripheral contact

18

of lower stamped metal circuit sheet

14

, a circuit is closed through the switch contact in registry with the selected embossed metal dome and the common peripheral contact of the lower sheet.

Alternatively, if the switch contacts

22

are flush with the top surface of the molded substrate

12

, a spacer sheet (not shown) with apertures in registry with the switch contacts

22

may be laminated on the substrate

12

. In such an alternative to the first embodiment, the upper stamped metal sheet would be assembled onto the top surface of the spacer sheet and the embossed metal domes

14

would engage the respective switch contact

22

through the respective aperture in the spacer sheet.

FIGS. 6-8

show a second embodiment of the invention and like numerals have been applied in

FIGS. 7 and 8

corresponding to like components described above in relation to the first embodiment of

FIGS. 1-5

. Basically, the second embodiment of

FIGS. 6-8

is identical to the first embodiment except for the addition of an insulated circuit sheet, generally designated

50

and seen best in

FIGS. 6 and 7

. The insulated circuit sheet is disposed between upper stamped metal sheet

16

and insulative substrate

12

which has lower conductive circuitry

14

overmolded therewithin.

More particularly, insulated circuit sheet

50

is formed by a dielectric film

52

having circuitry, generally designated

54

, printed or laminated thereon, at least on the back or rear side thereof. Circuitry

54

includes a common contact

56

which is maintained in constant engagement with portions

18

a

of common peripheral contact

18

of lower stamped metal circuit sheet

14

through rectangular openings

34

in insulative substrate

12

. Circuitry

54

includes conductive pads

58

in registry with switch contacts

22

of lower conductive circuit sheet

14

. Contact pads

58

do not engage switch contacts

22

as the film-like circuit sheet

50

is disposed flush onto top face

40

of substrate

12

, and switch contacts

22

are recessed within countersunk areas

38

of the substrate.

In the second embodiment of

FIGS. 6-8

, when a selected one of embossed domes

44

of sheet

16

is depressed in the direction of arrow “B” (

FIG. 8

) the dome engages the aligned conductive pad

58

of circuit sheet

50

and drives the pad into engagement with the aligned switch contact

22

. With the conductive pad being commoned to peripheral contact

18

of lower stamped metal circuit sheet

14

through common contact

56

of circuit sheet

54

, a circuit is closed through the selected switch contact and the common contact of lower circuit sheet

14

. In the second embodiment, upper sheet

16

could be of plastic material.

It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.