Touch switch for electrical appliances and electrical appliance provided with such switch
A touch switch for an electrical appliance having a capacitive flat electrode, a light source, a transparent cover and a printed circuit board connected to the electrode is disclosed. The light source is mounted on a face of the printed circuit board opposite the transparent cover and the printed circuit board presents a cut-out for allowing light transmission from the light source towards the transparent cover.
1. A capacitive touch switch for an appliance comprising:
a non-conductive transparent cover;
a printed circuit board below the non-conductive transparent cover, said printed circuit board including a cut-out portion;
a touch electrode mounted on the printed circuit board adjacent the cut-out portion;
a light source mounted below the printed circuit board at a position offset from the cut-out portion; and
a light guide extending below the printed circuit board, wherein the light guide directs light emitted by the light source through the cut-out portion of the printed circuit board towards the non-conductive transparent cover.
2. The capacitive touch switch of claim 1 , wherein the touch electrode is in the form of an annular track surrounding a majority of the cut-out portion of the printed circuit board.
3. The capacitive touch switch of claim 1 , further comprising:
an auxiliary layer interposed between the non-conductive transparent cover and the printed circuit board, the auxiliary layer having a transparent zone including an opaque icon.
4. The capacitive touch switch of claim 3 , wherein the auxiliary layer is a light filtering polymeric film.
5. The capacitive touch switch of claim 1 , wherein the printed circuit board is fixed to the non-conductive transparent cover by a non-conductive adhesive.
6. The capacitive touch switch of claim 1 , wherein the light guide includes a protrusion extending into the cut-out portion of the printed circuit board, wherein the light guide directs light from the light source through the protrusion towards the non-conductive transparent cover.
7. The capacitive touch switch of claim 6 , wherein the light guide is formed of plastic.
8. The capacitive touch switch of claim 6 , wherein the light guide further includes a seat portion defining a channel into which the light source extends.
9. The capacitive touch switch of claim 6 , further comprising:
a metal spring mounted between the non-conductive transparent cover and the printed circuit board and in contact with the touch electrode.
10. The capacitive touch switch of claim 9 , wherein the metal spring extends around the periphery of the light guide protrusion.
11. The capacitive touch switch of claim 10 , wherein an enlarged end of the metal spring is sandwiched between the printed circuit board and the light guide.
12. The capacitive touch switch of claim 9 , wherein the light guide further includes a reflective portion adapted to reflect light from the light source through the protrusion.