Patent GB-804739-A (GB)
Title: Improvements in or relating to electric projection lamps, particularly for vehicles
IPC: F21V17/00
Filed: 1956-06-01
Abstract: 804,739 Electric lamps. GENERAL MOTORS CORPORATION. June 1, 1956 [June 15, 1955], No. 16974/56. Classes 39(2), 75(2) and 75(3) '[Also in Groups XX and XXIII] An electric lamp, more particularly for use as a vehicle lamp, and comprising a light source associated with a reflector and lens, is provided with reference elements. lying in a plane having a predetermined angular relation to the direction of light transmitted by the lamp, whereby the light beam is directed in the requisite direction when the lamp is mounted on a vehicle. In the example the lamp is of the all glass sealed beam type comprising a reflector portion 11, Fig. 12, with a reflective inner surface 12 and an annular front flange 13 with a plurality of spaced seating projections 14 which define plane 37 behind the flange 13. A lens or cover glass 26 has an annular flange 27 which is fusion sealed to the annular flange 13 of the reflector 11, and the interior surface of the lens may be formed with flutes and prisms 28 in known manner. In order that the lamp may be mounted to effect geometrical aiming of the beam with optical precision the portion of the face of the lens adjacent to the periphery is provided with integral reference elements in the form of three equally spaced projections or bosses 30-32, with front surfaces 30a-32a respectively which are subsequently subjected to grinding to define an aiming plane while the lamp is mounted in an adjustable manner in an aiming head 40, Fig. 5, where its position is adjusted so that the axis of projection of an intense illumination portion of the light rays from a filament 21 is in a desired relation with co-ordinate lines, Fig. 6 (not shown). on an aiming screen 55. The aiming head 40, Fig. 5, comprises a supporting member 42 with a circular opening to receive an annular socket member 43 formed with a spherical seating surface 44 to engage a spherical surface 47 of a member 46 carrying a coaxial seating-ring 48 upon which the seating-projections 14 at the rear of the periphery of the lamp reflector 11 are placed. The lamp is secured temporarily in position by retaining-levers 51 which are pivotally-mounted on the member 46 and have resilient projections 52 which engage the flange 27 of the lamp. The light beam from the lamp is Projected through an optical system, e.g. a condensing lens 54, and after adjusting the member 46 upon the seating 44 of the socket 43 to obtain the desired direction of the beam relative to the screen 55, the said member 46 is fixed in position relative to the support 42, e.g. by a locking-screw (not shown). The aiming plane is next established by altering the faces of the reference elements 30-32 by grinding or machining them while lamp is thus held in the support 42 (see Group XXIII). In the example the lamp is provided with a main filament 21 at approximately the focal point of the reflector, and a minor filament 22 below the main filament, with leading- in wires 20a-20c connected to metal ferrules mounted oh bosses 17a, 17b and 17c (not shown) on the rear of the reflector portion 11.