Measuring and testing – Meteorology – Precipitation
Patent
1994-12-30
1996-07-09
Noland, Thomas P.
Measuring and testing
Meteorology
Precipitation
29595, 29849, 340602, 49357, G01W 114, E05F 1520
Patent
active
055333915
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an electric rain sensor for mounting on the outside of the main frame or on another stationary member of an openable window, in particular a skylight, of the type where opening and closing may be carried out by means of an electrical maneuvering device, said rain sensor comprising a sensing element with two electrodes opposite one another in or on a substantially plane sensing surface of an insulating holder, the distance between the electrodes being less than the size of a raindrop, means for applying a voltage between the electrodes and an electrical circuit connected to the electrodes for detecting a change in an electrical quantity caused by the presence of raindrops, a heating element being mounted on the holder for drying of the sensing surface, and the holder being produced by molding of an electrically insulating thermoplastic.
Such rain sensors are known for instance from DE-A-2363978, DE-A-4023673, and DE-A-3939317 in addition to CA-A-1119669 and are often installed in connection with electrically operated windows in order to ensure the closing of an open skylight in the event of rain or snow. In known installations the sensing element is frequently positioned inside on the main frame, in order to avoid exposure to bad weather resulting in contamination and corrosion to such a degree that the sensor no longer functions as intended. Positioning the sensing element on the inside, however, often results in a particular drawback, namely that it frequently is placed in such a manner--for instance on a vertical section of the main frame--as to be sheltered from the wind when the wind is in certain directions thereby being struck by the rain either too late or not at all.
DE-C-3 246 412 discloses a humidity sensing element for industrial application, wherein the electrodes are imbedded in an added insulating layer.
With some types of rain sensors a relatively long period of time may pass before the sensing surface--after having been exposed to rain--dries and consequently the window can only be opened after a significant time delay with respect to the end of the rainfall.
It has been attempted to avoid these problems by the positioning of a rain sensor of the kind mentioned above on the outside and attaching an electrical heating element to the sensor, the heating element being either permanently activated or turned on immediately after the sensor has become wet.
SUMMARY OF THE INVENTION
It is the object of the invention to provide an electric rain sensor to be mounted on the outside that avoids the mentioned drawback such that the risk of malfunction is reduced to a significant degree achieving in addition an even higher degree of safety against a malfunction caused by corrosion of electrodes, and furthermore a particularly robust and inexpensive design.
According to the invention this is achieved in that the heating element, and supply lines therefor and for the electrodes, are manufactured as inserts of the holder by molding of an electrically conducting thermoplastic polymer into excavated recesses and/or grooves in the holder.
In order to avoid the risk of desintegration of the exposed electrode sections at the sensor surface a preferred embodiment of the rain sensor is--according to the invention--characterized in that the electrodes comprise protective electrode coatings made from a weather resistant electrically conductive material on the sensor surface.
The invention furthermore relates to a method of manufacturing a sensing element for an electric rain sensor. According to the invention a simple and inexpensive manufacture of the sensing element is achieved by a method in which the jointly molded inserts of the electrodes and the heating element, in addition to their respective supply lines, are produced by molding an electrically conducting thermoplastic polymer into appropriately shaped excavated recesses and/or grooves in the holder.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be explained further with ref
REFERENCES:
patent: 3961301 (1976-06-01), Fraioli
patent: 4264902 (1981-04-01), Miller
patent: 4578995 (1986-04-01), Meyer
patent: 4665351 (1987-05-01), Nyberg
patent: 4837986 (1989-06-01), Gagne
patent: 5115601 (1992-05-01), Yamaguchi et al.
Bartholin Niels
Brade Claus B.
Noland Thomas P.
V. Kann Rasmussen Industri A/S
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