GB654839A - Apparatus for projecting motion pictures - Google Patents

Abstract

654,839. Kinematograph projectors. VITARAMA CORPORATION. July 28, 1947, No. 20288. Convention date, Feb. 1, 1944. [Class 97 (i)] Apparatus for projecting motion pictures on to a cylindrical screen comprises means for continuously feeding a kinematograph film through a cylindrical gate having an aperture longer than one frame of said film, a lens system, means for rotating the lens system about an axis which coincides with the geometrical axis of the gate, means for projecting a beam of light, which is narrow relatively to said film frame, through said aperture, frame and lens system and means for rotating said light beam about the geometrical axis of the gate at an angular velocity greater than the angular velocity of the film in the gate and at the same angular velocity as the lens system to cause each of the successive film frames to be scanned while traversing the full length of the aperture, said lens system serving to focus the image, scanned by the light beam, on to the cylindrical screen. In the projector shown, a film 21 passes round a guide roller 22 through a cylindrical gate defined by channelled members 29, 30 and plates 27, 27<SP>1</SP> and is engaged by a continuously-rotating sprocket 23. Each film frame is illuminated by one or other of two lamps 31, 31<SP>1</SP> mounted together with reflectors 33, 33<SP>1</SP> in a frame which rotates with a shaft 34 about the geometrical axis of the gate. Also carried by the shaft for rotation therewith is a lens holder 25 through which and the film passes a narrow light beam reflected from a conical mirror 28. Shaft 34 is driven through a gear 37 to rotate in the required time relation with the rotation of sprocket 23 so that Vb/Vf=A/A-F, where Vb and Vf are the angular velocities of the rotating beam and of the film respectively, A is the angle subtended by the arc of the gate aperture at the axis of rotation and F is the angular distance between successive film frame centres. A commutator 40 comprising a conducting segment 41 and brushes 42, 43 serves to illuminate the operative lamp 31 or 31<SP>1</SP>. The image of each film frame is projected on to a cylindrical screen, the geometrical axis of which preferably coincides with the axis of rotation.