Patent GB-621840-A (GB)
Title: Improvements in or relating to photographic reflex cameras
IPC: G03B19/12
Filed: 1944-12-12
Abstract: 621,840. Photographic cameras &c. POLLOCK, G. B. Dec. 12, 1944, No. 24924. [Class 98 (i)] Light rays entering the objective of a photographic reflex camera are directed along an axis at an angle to the photographic axis and through an auxiliary lens or lenses on this inclined axis, the directing means and lenses being mounted on a common movable support movable to and from the viewing position. The camera comprises an objective 6 and a taking chamber 8 at the rear of which is the film 9 carried by spools 10, 11. The pivoted reflex viewing mechanism 13 comprises a reflector 14 and two lenses 15, 16, the first lens being positioned on the taking axis and the second on the viewing axis. The lenses are retained in the recesses 15a, 16a by a spring clip 18 with bifurcated ends 19. The reflector 14 is backed with spring sheet material 20<SP>1</SP> which forces the reflector into engagement with the holding recesses in the housing 17. A hinged back 21 is secured to the camera by means of a spring-pressed catch 25 comprising a spring bolt with a milled-out central portion which receives the head of the catch. The bolt is moved sideways to release the catch. The shutter system forms part of the reflex viewing mechanism, a fixed plate 35 on the latter being carried in slots formed on the camera body and having an aperture 37. The movable plate 38 has an aperture 39 and a shoulder 41 thereon which is engaged in its lowest position by a corresponding shoulder 40 on the reflex member 13. A further hooked projection 44 on the plate 38 coacts with a projection 43 on the member 13. When the member 13 moves upwardly, the aperture 39 is uncovered and exposure continues until the projections 43, 44 engage and the plate 38 is moved so that the opening 37 is covered by the lower part of the plate. Upon the return movement of the member 13 the projections 40, 41 engage, and the plate 38 is carried downwardly. Ledges 48 at each side of the chamber 8 abut the lower edges 49 of the bottom wall 50 of the member 13 when the latter is in viewing position and prevent infiltration of light. The pivoted axis of the reflex member 13 comprises a shaft 51 surrounded by a bush 62 and a bore in the housing 17. The shaft 51 is attached at one end to a pulley 52 which is driven by a spring-belt 71 looped over a pulley 72 of the film feed. The pulley 52 carries ratchet pawls which engage fixed teeth on the casing as well as a hub part 53 which carries a ratchet 65 coacting with a similar part 65<SP>1</SP> on the bushing 62. The other end of the shaft 51 is journalled in a cylindrical slide member 58 carrying a threaded push-button 59, the inner end of which bears against the shaft 51, so that when it is pressed the ratchet teeth 65, 65<SP>1</SP> are disengaged, allowing the tension spring 66 to move the assembly 13 to the inoperative position simultaneously operating the shutter. Release of the push-button re-engages the teeth 65, 651. Rotation of the film feed knob 75 returns the member 13 and cocks the shutter, the spring- belt 71 rotating the pulley 52 and bringing the pawls into appropriate engagement with the ratchet teeth. The film spool is mounted at one end on a leaf-spring member and a coiledspring clutch prevents winding of the pulley 72 in the wrong direction. A pressure-plate 88 and a viewing aperture 86 for the conventional markings on the back of the film are also provided. Bulb exposures are obtained by screwing the button 59 away from the member 58. which has a projecting arm 91 with a lug 93. If now the button is depressed to release the member 13 and the shutter, the cylindrical portion 58 is moved inwardly before the button engages the shaft 51, and the lug 93 is in position to engage the edge 50 of the housing 17, thereby holding the shutter in open position. Release of the button moves the lug 93 out of engagement with the edge 50 and the shutter movement is completed. An eye lens 96 is provided for magnifying the viewed. image and a limiting aperture formed of metal or preferably ground glass or celluloid is provided at 95, the brilliant image to be taken by the camera being surrounded in the latter case by a slightly diffused image of adjacent portions to assist composition, or detect objects moving into the field of exposure. A pivoted focusing screen may be mounted between auxiliary lenses where none of the latter'is on the photographic axis so that either a brilliant image or a focused image can be viewed. A modified shutter for use where the diaphragm for viewing is to be larger than that for taking is shown in Fig. 12, the moving plate 13 having a larger opening 116 and an auxiliary smaller opening 117 for the photographic exposure which is brought into position adjacent the aperture 115 in the fixed plate 110 when the shutter is actuated. The shutter spring 118 secured in a slot 129 moves the plate 113 upwardly to a position engaging projections 123 on the fixed plate. As the reflector assembly 111 also moves upwardly, an edge 127 thereon forces a spring member 125 against the plate 113, deforming it outwardly so that it clears the projections 123 and completes its movement, drawing the opaque portion 128 over the exposure aperture 116. In cocking the assembly, the bottom shoulder 122 rides over the spring member 125 and when in engagement with the bottom stop 119, the shutter member 113 is moved down into position for viewing purposes. In Fig. 16 (not shown), a single plate shutter actuated by a bow-spring is combined with a prism viewing system, the first prism reflector of which is carried on the shutter-actuating arm and is moved from behind the objective lens when the shutter lever actuates the shutter for an exposure. In a further modification (not shown), a combination of two lenses and a reflector are mounted in a hinged light guard, the viewing rays being reflected through 90 degrees, and again at 90 degrees by a mirror into the eye-lens system.