Patent GB-158194-A (GB)
Title: Improvements in and relating to reflex photographic cameras
IPC: G03B19/12
Filed: 1919-09-26
Abstract: 158,194. Mason, P. G., and Newman & Guardia, Ltd. Sept. 26, 1919. Cameras, reflex; shutters, roller-blind. -In a reflex camera, the complete release of the shutter for instantaneous exposures, and the release and arrest of the shutter in its open condition for time and bulb exposures are determined by the position or positions taken up by the mirror after release and preparatory to an exposure, the release of the shutter being effected by detent mechanism actuated by the mirror. The mirror 17, Fig. 12, is normally under the influence of a spring coiled on the axis 21 tending to raise it and is held in the focussing position by an arm 30, Fig. 5, on the axis 21. The arm 30 has a series of projections 31, 32, 33, the projection 31 engaging a spring catch 34 on a detent arm 35 when the mirror is set for focusing by the handle 90. The arm 35 is operatively connected with a release and timing lever 36 which has a catch 94 to engage one or other of the stops 31, 32, 33 on the arm 30 according to the setting of the roller-blind shutter for a " B," " T," or " I " exposure. The mirror pivot 21 also operates links 26, 28, 27, 29, Fig. 12, whereby, when the mirror rises for an exposure, the link 29 engages the spring pawl 80 which holds the shutter in set position. The movement of the mirror controls the shutter for different exposures according to the setting of a pin 42, Fig. 5, attached to a plate 140 having shoulder straps 98, 99, 100 which limit the angular movement of the release lever 36. For an instantaneous exposure the pin 42 is moved to the " I " position and brings the shoulder 100 opposite a projection 41 on the lever 36. On operating :he release 37 the arm 30 and mirror are released, and the latter moves right up to an horizontal position against the stop 101, the shoulder 100 holding the lever 36 and catch 94 thereon clear of any of the projections 31, 32, 33. The arm 29, Fig. 12, then releases the shutter pawl 80. For time exposures the pin 42 is moved to the " T " position and brings the shoulder 99 opposite the projection 41 so that on operating the release 37 the catch 94 on the lever 36 engages the stop 32 on the arm 30 and on the return of the release 37 the catch 94 engages the projection 33. The corresponding movement of the arm 29, Fig. 12, is to release the shutter pawl 80, but to be held in the path of a projection 96 on the gear wheel 66 of the shutter, arresting it in open position until the release 37 is again actuated to release the mirror from the catch 33. For bulb exposures the pin 42 is set in the " B " position, bringing the stop 98 into position to arrest the projection 41. On operating the release 37, the catch 94 arrests the projection 31 on the arm 30, and the corresponding movement of the arm 29 is to release the shutter pawl 80 and engage the projection 96, holding the shutter open as long as the release 37 is held. To cushion the impact of the mirror lever 30 with the stops and its movement after an instantaneous exposure, the lever 36 has a yielding blade spring 95, Fig. 9, which snaps into position under the stops when they are engaged by the catch 94, and in the case of an instantaneous exposure a stop 145<1> engages the catch 94 when the arm 30 reaches the horizontal position. To allow the mirror to be re-set, a cam 144<1> on the arm 30 moves the spring 95 into an inoperative position when the release lever 36 returns to normal position. The shutter comprises two blinds, one 43, Fig. 17, with an aperture 47 and wound on a spring roller 46 and the central part 45 of an upper roller, and the other wound on a spring roller 48 and w.ith tapes 44 wound on rollers 49, 50 adjacent to and on the same spindle as the upper roller. The roller 45, Fig. 15, is keyed to the spindle 51 and the rollers 49, 50 are connected to the spindle 51 by internal clutches each consisting of a ratchet member 52 keyed to the spindle 51 by a pin and slot 144, 145, Fig. 16, and pressed into engagement with a freely mounted companion member 53 by a spring 59. The members 53 have shoulders 54 gripping the rollers 49, 50 under the action of spring washers 56 held in place by screws 58 and washers 57. The shutter is wound by a knob 68, Figs. 1 and 12, which rotates wheels 66, 64, the latter gearing with the pinion 61 on the spindle 51. The rotation of the spindle and the roller 45 carries with it the side rollers 49, 50 through the friction of the spring washers 56. When the blind 44 has been fully unwound from the spindle 48 the apertured blind 43 can be further wound on the roller 45 to an adjustable extent forming a slit of predetermined size. On running down for an exposure when the blind 44 is fully re-wound on the roller 48, the blind 43 continues to wind on the spring roller 46 to reclose the slit by the action of the clutch members 52 overrunning the members 53, the rollers 49, 50 remaining stationary. The setting of the shutter is controlled by a setting knob 77, Figs. 1 and 12, which positions a notched disc 73, Fig. 13, freely mounted on the shaft 65 of the wheel 64 and held by a spring catch 76. The disc 73 has a pin 74 extending into a slot 72, Fig. 14, of a plate 69 which is also freely mounted on the shaft 65 and itself carries a pin 70. This pin is normally adjacent to a pin 71 on the pinion wheel 64. On rotating the winding knob 68 and the pinion 66, the blinds of the shutter are wound, and after one revolution of the wheel 64 the pin 71 engnges the pin 70 on the plate 69 and the blinds are further wound to the extent allowed by the slot 72 and until rotation is stopped by the pin 74 on the setting-disc 73 integral with the knob 77.