Siemens Aktiengesellschaft

Urs Riedi

Kurt Hess

A light receiver device, which is particularly suited for a smoke detector, has a flat substrate, a light receiver mounted on a front side of the substrate, and a shielding device present on at least a back side of the substrate opposite the front side. The shielding device is configured to at least partially shield against electromagnetic interference radiation impinging on the light receiver through the substrate. False alarms are thereby reduced, while the sensitivity of the light receiver is simultaneously increased. The shielding device is formed with a metal strip inserted through the substrate from the front side to the back side, and bent over a recess on the back side provided therefor, so that the light receiver is protected against interference radiation even on the back side. There is also provided an assembly method for producing a light receiver device.

Light receiver device having a shielding device extending on a back side of a substrate

The smoke detector contains an optical measuring chamber, having a sensor arrangement () with at least one light source (') and one light receiver (), and a labyrinth system () with screens () arranged on the periphery of the measuring chamber. The light source (&#x2032;) and the light receiver () are each arranged in a housing (). The above-mentioned housings () have an elongated shape and a small window opening The at least one light source (&#x2032;) and light receiver (&#x2032;) are arranged in the rear part of their housings (), so that between the window openings of the housings () and the light-penetrated optical surfaces of the at least one light source (&#x2032;) and/or the lens of the light receiver () a relatively large gap is formed. This gap is preferably greater than the diameter of the above-mentioned optical surfaces, or of the above-mentioned lens. In the measuring chamber between the light exit and entry side of the housings () and the screens () opposite them, a compact, open scattering space is formed.

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Jona, Switzerland

Urs Riedi