| 摘要 |
570,921. Light projectors. SIEMENS ELECTRIC LAMPS & SUPPLIES, Ltd., and ALDINGTON. J. N. Jan. 6, 1942, No. 196. [Class 75 (iv)] In a light projection apparatus an electric discharge lamp L, preferably a compact source metal vapour lamp, is arranged with the axis of its electrodes inclined to the mirror axis OF and with the optical centre of its arc coinciding with or nearer to the mirror than its focal point 0 so that its upper and more massive electrode UE lies outside the solid angle EOG subtended by the mirror EFG. The lower electrode LE may be chamfered to reduce any obstruction it may offer to the light rays reaching the mirror. A suitable inclination for the lamp is less than 45‹, say 30‹, to the normal mirror axis. When the projection apparatus is rotated to the vertical beam position a portion of the upper electrode always intersects a vertical line drawn from the centre of the arc and thus disperses the convection stream rising from the arc sufficiently to prevent the formation of a flame impinging on the lamp wall. |
