Sunshield device

Claim 1

A sunshield device for a window opening in a facade plane, comprising: at least one slat formed of light-refractive material arranged in the window opening so as to be rotatable about a longitudinal axis; the at least one slat having a flat upper side and on its underneath side is provided with prisms arranged one beside another without gaps; the prisms extending parallel to the longitudinal axis and having the form of an isosceles triangle in a cross-sectional plane at right angles to the longitudinal axis; a hypotenuse of the triangle being formed by the flat upper side and a catheti forming an inner angle with which a retro-reflection condition is fulfilled; said at least one slat having on its upper side a signal generator with a shading means for two light sensors, a parameter of the light sensors having an electrical value which is dependent upon a size of an irradiated surface of the respective sensor and an intensity of the radiation; the shading means being provided with a top panel spaced from the upper side of the slat and which defines opposite longitudinal edges and opposite transverse edges so that given projection of light from above the top panel onto the upper side, a rectangular shading zone is defined on said upper side; the two light sensors being arranged adjacent to one another on the upper side in such manner that their center points are located on different parallels to the longitudinal axis; partial surfaces of the sensor surfaces of the two light sensors adjacent one another being located in the shading zone; and the slat being coupled to a servo-motor which is itself connected to an ouput of an amplifier controlled at its input end in dependence upon a difference between the electrical values of the parameters of the two light sensors.