Patent GB-792788-A (GB)
Title: Improvements in and relating to light projectors
IPC: G03B21/20
Filed: 1956-04-05
Abstract: 792,788. Projector lamps. GIGUET, P. R. April 5, 1956 [April 16, 1955], No. 10506/56. Classes 75(2) and 75(4) [Also in Group XXXVI] In a light projector in which the relative positions of a lamp 4, a rear reflector 56, 57 disposed behind the lamp and an annular reflector 30 in front of the lamp can be varied, the front reflector 30 is hyperbolic, the central part 56 of the rear reflector is elliptical, the rear reflector and the lamp are so connected that movement of the centre of the lamp along the optical axis relative to the front reflector is twice the movement of the rear reflector relative to the front reflector and in one position, preferably a central position, the centre of the lamp coincides with one focus of each reflector. The front reflector is fixed to a cylindrical front section 3 of the projector. The lamp and the rear reflector 56, 57 are mounted on separate carriages 43, 44, Fig. 4, slidable on parallel rods 42 extending across a framework 37 secured in the hollow base of the central section 1 of the projector. The lamp carriage 43 is connected by a lever 45 to the free end of an arm 47 pivoted at its other end on a vertical spindle 48 and the rear reflector carriage 44 is connected by a lever 46 to the middle of the pivoted arm 47. A bevel gear 50 is secured to the arm 47 and engages a pinion 51 on a horizontal shaft 52 having external operating knobs 53 and an adjustable shoe brake 54. The cylindrical central section 1 has air holes 20 and is lined with a concentric inner wall 21 having air holes 22. A rectangular aperture in the top of the central section 1 is covered by a cover 13 having air outlets 14 directing the issuing air to the rear. The flat rear end wall 5 of the central section has an aperture 7 covered by a detachable cover 23 having air inlets 24. Two opposed spindles for fitting the projector to a cradle are disposed on the central section on a horizontal transverse axis. The cylindrical front section 3 has air inlets 31 and is hinged at 25 to the central section 1. An arm 28 is pivoted to the front section and has a groove receiving a stud 29 on the central section, the stud being held in a bent end of the groove to keep the front section in raised position. The front hyperbolic reflector 30 extends up to the lamp and has a front focus half way along the central section. A lattice 32 comprises concentric cylindrical screens attached by a radius arm to a ring 33 engaged behind stops 34 on the front section. The peripheral part 57 of the rear reflector is part spherical with centre coinciding with the near focus of the elliptical central part 56. The lamp is held by two asbestos lined members clamped by a spring and secured to a vertical rod 60 on the lamp carriage 43. The lamp terminals engage in two sockets 62, 63 maintained in an insulating block 64 secured to the carriage. Each socket comprises two internally grooved half sockets 65, 66, Fig. 5, disposed between clamp members 67, 68 fastened together by two screws one of which has a lugged head 77 for manual adjustment. One of the half sockets extends downwardly below the clamp members and terminates in a rod 70 having nuts 71 for connecting a conductor. The insulating block 64, Fig. 11 in which the two sockets are maintained comprises four superposed sheets 78, 80, secured by screws to the lamp carriage. The two outer sheet 78 have circular apertures into which the sockets fit and the two inner sheets 80 have rectangular apertures for the clamp members 67, 68 and semi-cylindrical recesses forming, when assembled, two cylindrical outlets for the clamping screws with the lugged heads 77.