Patent GB-190628174-A (GB)
Title: Improvements in and connected with Photographic Shutters
Inventor: GILES WALTER FREDERICK
Filed: 1906-12-11
Granted: 1907-11-07
Abstract: 28,174. Giles, W. F. Dec. 11. Shutters.-In a selfcapping roller-blind focalplane shutter of the kind in which two separate blinds are used, the blinds are wound on rollers which are geared together in such a manner that, when a catch is released, both blinds travel in the same direction over the surface to be exposed, the aperture necessary for exposure of the plate being the space between the top of one blind and the bottom of the other. The width of this aperture can be varied at will, and can also be made to vary during the exposure of the plate. In the Provisional Specification, it is stated that the same principle may be applied to lens shutters. When the width of the aperture corresponds to the full opening in the shutter box, the apparatus automatically sets itself for time exposures; but, when the aperture between the blinds is less than the full opening, the exposure is, always instantaneous. As shown in Fig. 1, the blind F' is wound up, and the blind F is in the process of being wound up. The blind F is wound up by pressing and turning the knob N. The inward pressure on the knob N frees the pinion N' from its engagement with a projection on the plate U<3>, Fig. 2, thus leaving the roller C free to rotate, and also frees the clutch M which normally engages with the chain-drum I, thus leaving the chaindrum I free to rotate on the spindle of tho roller C. The rolling-up of the blind F causes the driving-spring K to be wound up. The spring K<1> in the roller B is weaker than the driving-spring K, and is always kept in a state of strain. The blinds F, F! having been wound on the rollers C. B, and the aperture adjusted to the required width, the plate may be exposed by disengaging the catch from the teeth of the pinion N<1>; the blind F is then drawn down under the influence of the coiled spring K. At the same time the clutch M being in engagement with the drum I and the rollers C, E being geared together through the chain J, the blind F' is also drawn down against the force of the spring K<1>, and the exposure of the plate is made. The spring K<1> is then coiled and is ready to roll up the blind F' again, whenever the knob N is pressed. If the rollers D, E are of different sizes, an aperture varying during exposure is obtained. To expose the focussing-screen for focussing purposes, the blinds are wound up ; then by pressing and rotating the knob T<12>, the blind F' is wound down again. The inward pressure releases the clutch T from the drum I<1> and frees the roller E. After focussing, the button T9 is pressed to free the clutch T<4> and the collar T<2>, thereby releasing the roller E from its spring and allowing the spring K<1> to draw up the blind F<1>. The release of the shutter is effected by pressing the pin W, attached to the sliding bar S. A pin Q<5> connects the sliding bar S with the sliding plate U so that they move downwards together ; a pin U<2> in the plate U- engaging in a slot in the plate or pawl U<3> forces the pawl outwards, thus setting the pinion N' free and releasing the shutter. When a time exposure is required, the blind F, together with a sufficient quantity of tape G to give an aperture equal in width to the .width of the plate, is wound on to the roller C. On the disk Q<3>, which rotates with the spur-wheel Q<1> gearing with the pinion N', is a cam projection Q<3> so placed that when the aperture corresponds in width to the width of the plate, the pin Q<5> is raised through the agency of the lever Q<4>, and no longer engages with the bar S. When the bar S is pushed downwards by means of the pin W, the plate U does not move until a pin Q<7> on the bar S reaches the end of a slot U<1> in the plate U. The shutter is then released, but, at the moment when the whole plate is exposed, a stop on. the spur-wheel Q<1> comes in contact with a stop R<3> on the bar 8, thus arresting the shutter. The pressure on the pin W being released, the bar S and the plate U are restored to their normal positions by means of springs. The projection on the plate U<3> once more engages with the pinion N', holding the shutter in position, and the pin Q<5> again engages in its hole in the bar S. When the exposure is completed, a second pressure on the pin W releases the shutter F and finishes the exposure ; or the shutter F' may be drawn up by pressing the knob T<9>. Other methcds of gearing are described, and also an automatic means of rolling up the blind F<1> after an exposure has been made, for the purpose of having a double thickness of cloth between the plate and the light. Specification No. 22,134, A.D. 1904, is referred to.