BlindsThe blinds are a simple arrangement of two half-blinds linked by tapes. The tapes are wound on a separate spindle at the top of the camera, that spindle and the spindle carrying the top blind are usually geared together, pulling out the speed-setting knob disengages the tape spindle so that it can be rotated separately.
Mirror MechanismThe mirror has a very unusual action that was the subject of Kershaw's 1904 patent. The mirror box is a self-contained unit that is not fixed to the camera, in fact it will slide out if a plate at the bottom of the camera is removed. The edge of the mirror is pin-jointed to an arm at the mirror's centre. The arm is pivoted and constrains the pin to move in a curved slot. The arm is connected via a link to the mirror setting lever (on the outside of the camera) pulling the setting lever down pulls the arm down which causes the pin to move around its curved slot.1
The top rear edge of the mirror is attached to an inner frame pivoted at the bottom of the mirror box, as the pin moves in its slot its top edge moves backwards pivoting the inner frame, as the pin moves further in the curved slot the top of the mirror is brought back. Pulling the setting lever down also extends a large spring which, when released, pulls up the mirror. On the other side of the camera the mirror is guided in a slot in the same way, connected to the arm is a dashpot to smooth the mirror action.
As the shutter was not self-capping the mirror box had to be made light-tight when the mirror was lowered. A baffle hinges upwards to connect to the lower edge of the mirror, it is raised by a linkage that connects the two arms of the mirror pin.
This design was intended to allow shorter focus lenses to be used. As the mirror pivots and moves back as it rises the edge nearest the lens moves nearly vertically until near the end of its travel when it moves forward to cover the focusing screen. The question has to be asked, did it work? Well, to some extent, at its introduction lens apertures were smaller, f6.8 or possibly f4.5 being the norm for a reflex, these had a significantly smaller diameter than later and faster lenses, so with early lenses there was less obstruction and the mirror movement was a benefit.
Shutter MechanismThe mechanism is a very simple affair. It is built onto a metal plate that an be removed from the camera leaving the blind spindles still in place. A large wheel is turned to wind the shutter, this moves a second gear wheel which rotates both the spindle to which the tapes are wound and the upper blind spindle. A large pawl acting on the second wheel prevents it running backwards. Pushing the release lever frees the pawl and the shutter unwinds. When set to T, a lever is moved that is struck by the release lever causing the end of the lever to move into the mechanism where it meets a tooth on the underside of the main wheel. This corresponds to the blinds being fully open, they are held in this position until the release lever is again pressed. On later shutters (from 1928) there are settings for both B and T and a more complicated means of holding the blinds.
The Videx used a simple shutter where the blinds are linked by tapes. The tapes are wound on their own roller placed just below the upper-blind roller. The winding knob winds the upper blind and the tape roller which is geared to it. Unusually, to change the speed the winding knob is pulled out and turned, this turns the upper blind which pulls more tape on to its roller or frees tape, the tape roller is under tension and winds up any free tape. The speeds are shown on a dial, on the opposite side of the camera, which is moved when the upper-blind roller is rotated, the dial also carries a stop that prevents further winding. The shutter can only be wound when the mirror is lowered, the speeds can only be changed when the shutter is wound. When the camera release is pressed the mirror is pulled up and a hook lifts the pawl engaging the lower-blind ratchet allowing the blinds to run down.
The Minex, of 1909, has two independent blinds mounted on separate sets of rollers. The aperture is formed by delaying the movement of the second blind.2
There are four versions of the shutter as fitted to the Minex camera (it was also sold separately for attachment to other cameras):
- First version, this corresponds to the patent description and illustrations in very early advertisements. It was very quickly replaced by the second version, certainly within a year. It has a separate I&B, T switch.
- Second version, the I&B, T switch is removed on this version, the settings are made directly on the speed dial, thus one control knob sets the full range of speeds including B and T, tensions the shutter and lowers the mirror. The speeds are selected by lifting and turning the knob so that a pin engages different holes. The control knob has a solid top, external studs are at 6 and 5 o'clock.
- Third version, this appeared before 1914. The control knob is retained by a slotted nut rather than being screwed to the shaft, external studs at 5 and 3 o'clock.
- Fourth version, the I&B, T selector returns but with a different mechanism to the first version. The control knob is retained by a slotted nut, no external studs. This change took place in 1926.
The illustrations and description below are for the box form cameras, the Folding model is generally similar but differs in detail. In each illustration the shutter is not tensioned.
Details of Second type
To tension the shutter the control knob (above and attached to the wheel I) is turned clockwise, this rotates the pinions PU and PL (via the intermediate gear P) which wind up the shutter blinds onto the upper rollers. P is prevented from running back by the ratchet A. The rotation of I causes J to rotate anti-clockwise, the pin MP acts on the lever M which turns down and re-sets the mirror. The mirror is locked in place by a spring catch.
The camera is fired by a release knob (or pneumatic connection) on the other side of the camera to the shutter mechanism. When the release is depressed the mirror is unlocked and free to rise. It is the movement of the mirror that fires the shutter. The mirror is attached to the lever N, as it rises N is displaced along with the links that pull on lever B, this raises the ratchet A allowing the lower blind to unwind (pulled by the spring in the roller at the bottom of the shutter) and for PL to rotate. The rotation of PL is transmitted via the upper part of P to the upper wheel of I (IU) which in turn rotates. At this stage the lower blind is uncovering the focal plane.
Extending down through IU is a pin. The position of the pin is determined when setting a shutter speed on the control knob, when the knob is lifted, turned and dropped back the pin on its underside engages a hole. The angular distance of the hole/pin from the neutral point determines the slit width of the blinds. As the wheel IU rotates the cam on the speed dial meets the pin TP and pushes it away, this causes lever T to move downwards. The end of T is in contact with pins EP, as T moves it in turn moves EP and the lever E. The other end of E is holding the upper blind in place by a stud on the lower wheel of P. Moving E frees the upper blind. However the lower wheel IL is still being locked by the lever G so the upper blind cannot move. As the wheel IU continues its rotation the pin meets a stud on the lower wheel IL and causes IL to rotate (the pin is locked in place by a flat spring on the face of IL). At this point the cam on the speed dial meets the pin GP, pushes it aside, and unlocks the wheel IL, thus the upper blind is free to follow the lower blind across the focal plane.
As they move the two wheels IU and IL and locked together so the slit width is fixed (mechanically) throughout its travel. But as the lower blind reaches the end of its journey the upper blind still has some distance to travel, as the wheel IU rotates it separates from IL (it runs a short distance up the threaded spindle to which it is screwed) this frees IL and the upper blind can finish its movement.
When the release is depressed, as well as freeing the mirror the movement is transmitted via a rod that runs the width of the camera and via several levers to the levers T and G, as the shutter is released lever T is raised and G is moved to lock the wheel IL in preparation for meeting the cam of the speed dial (instantaneous speeds) or lock the blind movement in the case of 'T' and 'B' settings.
When tensioning the shutter the control knob is turned, this rotates the upper wheel IU which winds the lower blind, fixed to this wheel is a pin, after a short distance of travel (to close the blinds) the upper pin meets the pin fixed to the lower wheel which causes the wheel IL to rotate and wind the upper blind.
Actually there are two pins on the speed dial the one referred to above is the pin that controls the timing. There is also a small registration pin under the cam that engages the holes that can be seen around the outside of the speed dial. The larger pin drops into holes on the shutter wheel IU but for fast speeds the holes are close together and join to form a slot, the small registration pin matches a hole for each speed and so locks the larger pin at a certain position in the slot.
An early example of the version 2 shutter has two setting pins, MP. Presumably this was a fail safe device. On later examples the second pin has been cut away leaving a steel piece set in the brass wheel. (A large batch of wheels must have been made before the change).
Details of Third type
In this version the Lever T is located at the side of the wheel I instead of below. The main difference is in the shutter wheel I. The locking spring on the lower wheel is replaced by a short stud, the speed dial pin is able to ride upwards when meeting the stud and lock in place when it drops back. To free itself when completing its travel the upper wheel moves up the ramp IR (see illustration of fourth type). The wheel IU is held in place by a coiled spring in the control knob which pushes IU into contact with IL.
The lower blind is released in a similar way to the earlier version.
Once the speed dial pin has locked with the lower wheel the pin GP is moved out of the way by the speed dial cam allowing the upper blind to move. When set to 'B' the speed dial is raised very slightly, as a result the speed dial cam moves the pin TP when it passes rather than passing through the slot in TP. This takes place at the start of the exposure so that the upper blind is not held at P, it is though, still held by G which is released when pressure is removed from the shutter release.
Details of Fourth type
The shutter operates similarly to the third type but with simplifications and a few rearrangements. The most noticeable change is that a lever R (which has an external setting stud) now selects the I&B, T setting this brings the lever C into play which acts on the blinds gear wheel P. Movement of the upper blind is triggered when the speed dial pin locks with the lower wheel and meets the cam on the end of lever D and pushes the lever aside, previously the lever D was locking the wheel IL and preventing the upper blind from moving.
A very simple focal-plane shutter mechanism was used on Ensign cameras before the first world war. It was produced in many different forms and was also used on Ensign roller-blind shutters from about 1910.
BlindsThe lower blind is linked by friction to tapes joined to the top blind, the tapes wind onto a roller at the bottom of the camera next to the roller for the lower blind. The slit width is adjusted by continuing to wind the shutter once the lower blind has reached the top, which pulls through the extra length of tape required. At the end of the exposure the tape roller can pull the excess tape through the friction grip to close the aperture making the shutter self-capping.
The blinds are wound by turning a large winding wheel anti-clockwise, the wheel is locked by a pawl which prevents the mechanism running backwards when winding and once it is set. To release the shutter the pawl is moved clear of the wheel.
Setting the shutterExposure settings are made on a dial situated above the winding wheel and fixed to the same shaft, the dial contains a pin on its underside, a ring, drilled with holes representing different shutter speeds, surrounds the dial and can be depressed and moved to engage the pin in different position, the ring is engraved with the shutter speeds. On the underside of the ring is a plate carrying a lug. On setting the dial/ring to a particular speed the position of the lug has changed relative to the winding wheel. When the shutter is wound the winding wheel is eventually stopped when the lug comes into contact with a pin fixed to the camera. In this way the speed setting on the ring/dial affects the rotation of the winding wheel and so the amount of tape that is wound.
During exposure the winding wheel rotates clockwise and the blind unwinds pulled down by the tension roller. On instantaneous settings the movement of the winding wheel during exposure is not impeded.
B and TWhen set to B, pin A on the winding wheel has moved as far as it can and has rotated lever C across the winding wheel, the tail end of lever C has also been displaced. Plate B has moved downwards. On release, the winding wheel rotates clockwise and releases the blinds, movement is stopped when pin B meets the face of lever C. Lever C would rotate out of the path of pin B but the tail end of lever C is prevented from moving by the curved end of the release lever which has moved upwards. The intermediate lever has come into contact with the springy end of plate B and is trapped by a hook on the underside of the plate, this leaves the release pawl in the open position. On freeing the release knob the release lever moves down allowing lever C to rotate out of the path of pin B and the winding wheel to continues its travel. At the end of the exposure pin A lifts plate B upwards and is then held.
The T setting is similar to B except that the winding wheel does not travel so far when being set, as a result plate B is not displaced. When the shutter is fired the intermediate lever is not held by plate B and, as pressure is removed from the release knob, can move back allowing the release pawl to engage and hold the winding wheel.
The shutter comes in many versions with differences in detail, the version described above is from an Ensign Reflex. One drawback is that the shutter speed has to be set before winding.
Several patents are mentioned in connection with the shutter. The main ones are BP 27461/1910 by G.F. Prout, H. Holmes and Houghtons Ltd. which covers tensioning and releasing the shutter and BP 15548/1908 by F.P. Whitehead and W.F. Giles, which has a very similar mechanism and was also used on the T-P Unit shutter. BP 16353/1906 by T.T. Hora is sometimes included. Patent BP 27461/1910 itself mentions BP 12105/1909 by H.G. Chessher (Tella Camera Co.), this patent includes mounting the tape roller inside the blind roller which was used in the Roller-blind form of the Ensign shutter.3
Unit - Whitehead and Giles
An unusual self-capping arrangement was developed by F.P. Whitehead and W.F. Giles, it was sold by Thornton-Pickard as the Unit and was also used on other cameras.4
Early examples of the shutter which was sold by T-P from about 1910 had a tension selector cog on the left-hand side (when in use) and slit-width selector set on a dial on the right-hand side. The combination of tension and slit was looked up on an attached table which gave the speed. From 1912 the tension setting was no longer used and the speed was set directly on the dial. The Unit was replaced by the Ruby shutter on T-P cameras from 1913.
As with the later Ruby shutter the Unit is in a chassis that can be slotted into the camera body allowing all of the precision work to be contained within the shutter itself.
BlindsThe shutter consists of two blinds wound on separate sets of rollers. When untensioned blind 1, which is fixed to a lower roller by tapes, has its leading edge at the bottom of the camera. Blind 2 (which is nearer the focal plane) is the capping blind, its leading edge is at the top of the camera and covers the image area. Blind 2 is fixed to an upper roller by tapes and is pulled onto its upper roller by a spring in that roller.
Tensioning the shutterWhen the shutter is tensioned, by rotating the setting wheel K anti-clockwise, blind 1 is pulled to the top of the camera, this winds up the spring in its lower roller, C. The degree to which it is wound onto the upper roller (which gives the slit-width) is determined by the speed set on the setting ring. The pinion wheel, E, at this point does not engage C.
ReleasingWhen the release arm H is pressed the pinion wheel E is moved to engage both of the lower rollers C and D. The pawl M is then moved clear of the setting wheel K allowing K to rotate and the blinds to un-wind. Blind 2 drops to the bottom of the camera followed by blind 1 (the blinds move together but there is a gap produced by the tapes of blind 1), both movements being due to the spring in roller C which is strong enough to overcome the pull of the spring in the upper roller of blind 2.
When blind 1 has reached the end of its travel the connection between the rollers is broken this allows blind 2 to be pulled up by the spring in its top roller. Blind 2 now covers the image area when the shutter is next tensioned.
B settingThe setting wheel K is rotated to its full extent when the pin N moves the lever P across the face of the setting wheel. The end of P is held by a pin P7 on a spring plate. On exposure the wheel K rotates (clockwise), the pin O comes into contact with the lever P and is held, this corresponds to the blinds being fully open, when the release lever is freed the capping blind, 2, is pulled back to its top roller as normal.
The setting ring found on late versions is the same as was used on the Ruby shutter.
The Ruby shutter replaced the earlier Unit shutter on Thornton-Pickard cameras. It was a self-capping model with two independent blinds, the slit was produced by varying the tape length. The mechanism is simple and rugged and consequently in many cases still works. In the description below the slightly odd numbering matches the patent drawings. The illustrations are of an early Ruby Reflex.5
Tensioning the shutterThe two setting wheels B, B1, are locked together during the first part of the setting movement, that is, until the lower blind is fully wound and the adjustment of the exposure slit is obtained by further winding the setting wheel B to draw more tape onto the upper roller. The wheel B operates pinion Z which winds blind a, B1 operates z1 which winds blind a1.
On winding the external knob C on the shaft c in an anti-clockwise direction, the rear wheel B, controlling the upper blind a, is rotated and carries with it the wheel B1, controlling the lower blind a1, by means of a pivoted catch D which engages a pin d extending from the wheel B through a concentric slot d1 in the wheel B1. The knob is wound until the catch D is disengaged from the pin d by a fixed projection L. At this point the wheel B1 and blind a1 are held wound by the release lever F engaging a notch between the two setting wheels. The knob C is again rotated to further wind the blind a, during this operation the pin d travels in the slot d1. The face of the wheel B is provided with a series of notches, e, which are engaged to hold the wheel B by a spring pawl E projecting through the wheel B1. The notches correspond to the exposure slits. On a ring between the shutter mechanism and the knob C are a second series of notches, X, corresponding to e, the notch (and so the required slit width and exposure) can be selected by turning the ring, the movement of the knob C is limited by the setting (the patent shows the notches X on the wheel B1).
ReleasingOn releasing the shutter lever F, both blinds run down together until the pin e2 rides upon the slope of a stop-plate G, thereby retracting the pawl E from the wheel B. The wheel B1 is stopped by the edge g on the plate G, the wheel B continues to run down to close the slit until the pin d again comes to the end of the slot d1, and is re-locked to the wheel B1 by the spring catch D.
B settingFor Bulb exposures, the winding of wheel B is continued until the pin d reaches the other end of the slot d1 where it engages in, and rocks the spring catch H, so that on actuating the lever k the lever F is also operated, releasing the shutter which runs down until the catch H is arrested, by the lever K at the open aperture. The exposure is completed by releasing the lever k which frees H, and the parts return to their initial position.
The Leica shutter is a very simple mechanism built with a minimum of parts. It consists of two blinds with the slit formed by a time delay. The leading blind is mounted on a spring roller with the tapes of the following blind mounted on an adjacent spring roller. The following blind is attached to a large take-up drum with the tapes of the leading blind attached to drums at either end. On pressing the release button the leading blind is released and unwinds through a distance equal to that of the slit, the following blind is then released and the blinds move together across the focal plane.6
The detail of the shutter changed over its long life, the illustrations are of a Leica I of 1928.
There are two gear trains deployed in the shutter. The first transmits the movement of the film-advance knob to the top of the sprocket drum. The second, at the bottom of the camera, transmits the rotation of the sprocket drum to the take-up drums of the blinds. The timing device sits on top of the take-up drums.
Setting the ShutterThe film is advanced, and the shutter wound, by turning a knob situated above spindle 200. This motion is transferred to the wheel 203 at the top of the sprocket drum 204 on spindle 30. Spindle 30 is loosely coupled to the lower gear train: as 30 rotates a pin, 102, drives pin 103 which is mounted on a disc above gear wheel 26. Thus motion is transferred to the lower gear train, finally gear wheel 25 rotates causing spindle 1 and the drums 2 and 3 on which the tapes for the leading blind are wound to rotate. The drum 7, on which the following blind is wound is loosely coupled to drum 2 and also rotates. Both blinds are wound onto their take-up drums and the springs in rollers 21 and 24 are tensioned. A coiled spring in the winding knob prevents backward movement of the mechanism (a pawl was used in early models). A pin on the underside of wheel 25 limits rotation and so stops the winding motion.
Shutter ReleaseOn pressing the release button, 32, spindle 30 moves downwards and displaces a leaf spring 29. The two pins 102 and 103 are also disengaged freeing the lower gear train and so the blinds are free to move. As the leaf spring 29 is lowered so rod 31 is pushed down, the top of 31 carries a catch 33 which is also lowered. At this point the leading blind is free and travelling across the focal-plane. The second blind is being held. Drum 7 carrying the following blind is connected by a short rod to the timing mechanism and arm 10 in the mechanism. Arm 10 is trying to rotate but is held by catch 33. As spindle 1 rotates (as a result of the leading blind moving) the arm 15 carrying pin 17 will move catch 33 and free arm 10 allowing it to rotate and the following blind to move across the focal-plane. Arm 15 is attached to the external speed dial and can be lifted and positioned by locating pin 16 in holes drilled in plate 12, the hole selected determines the exposure. The loose connection between the take-up drums 7 and 2 consists of a connecting rod working in an arcuate slot, this allows enough free movement of 7 to continue its travel at the end of the exposure to cap the blinds.
Film Re-windThe sprocket drum must be able to move freely and rotate backwards when the film is re-wound and therefore has to be decoupled from the top and bottom gear train. This is accomplished by moving a small lever on the top of the camera, below the lever is a cam which acts on a spindle, 101, and lowers it. At the top of 101 is a gear within the train connecting the film-advance knob to the sprocket drum, this is displaced and so decouples the sprocket drum from the upper gear train, the bottom of spindle 101 acts on a disc on spindle 30 sited above gear wheel 26, this is displaced separating the two pins 102 and 103 and so freeing the sprocket drum from the lower gear train.
This shutter was developed by Arthur Newman for use on Newman & Guardia Reflex cameras - the Self-Focusing Reflex of 1902 and the Square Reflector of 1904. It is built into a chassis as a self-contained unit, on the Square Reflector it attached to the very rear of the camera after the revolving back mechanism. On the Self-Focusing Reflex it fitted into the body of the camera but could be simply unclipped and removed for cleaning or adjustment.
This separation from the mirror movement and shutter/mirror release required some difficult connection arrangements. The shutter release was on the camera body, it had first to trip the mirror and then release the shutter. The mirror had also to be lowered before the shutter was wound as it was not self-capping. The result is an ingenious design occupying little space but also one that is unsuccessful; it would be more suited to a precision instrument than a camera that had to stand up to hard use. Another drawback, one disliked by many photographers, was the very small winding wheel requiring several turns to set the shutter.
The illustrations are of a shutter fitted to a Self-Focusing Reflex, the description is based on the patent specification.7
BlindsThere are two blinds wound on separate sets of rollers, each has a fixed aperture, the exposure slit is formed by the displacement of one blind relative to the other. Blind 1 is the inner blind wound on the bottom spring roller 5 and attached to the upper roller 6, blind 2 is wound on the bottom spring roller 7 and attached to the upper roller 8. The blind displacement (slit width) is achieved by continuing to wind roller 8 after blind 1 has been fully wound.
Setting the BlindsThe rollers 6, 8 are geared together by wheels 12, 11 and 10, 9. The intermediate wheels 10, 11 are mounted on a shaft 13 and are pressed together by a spring, 16, forming a friction clutch. The further winding of roller 8 is permitted by the wheel 11 slipping on the wheel 10. The pin 23 and the wheel 10 are rigidly fixed on the shaft 13. The clutch-sleeves 19, 20 and 21 rotate on shaft 13 and enclose the spring 16. The clutch-parts have their ends shaped into a single tooth such that after an amount of angular movement of one sleeve the teeth meet and the clutch-sleeves turn in unison. After completing a revolution, pin 23 turns the clutch-sleeve 19. After two revolutions, the sleeve 20 is turned by the sleeve 19, and finally, after four revolutions the sleeve 21 comes in contact with the pin 29 on the loose wheel 11. The movement of the wheel 11 with regard to the wheel 10 is therefore limited to four revolutions. The displacement of the roller 8 with regard to the roller 6 is shown by the indicating-disc 32.
Release MechanismThe roller 6 carries a disc with a notch 47 and is geared to the disc 51 having a notch 52. The catch-levers 30, 36 have pairs of projections 53, 55 and 54, 56, which engage simultaneously with the notches 47, 52. The roller 6 and disc 51 are so geared together that the notches are only brought into position for engagement when the shutter has made its full movement, for instance after the roller 6 has made four and a half turns and the disc 51 one and half turns. To hold the roller 6 during the winding of the shutter, the lever 36a engages with the ratchet wheel 36b. The lever 36a is disengaged simultaneously with the catch-lever 36. The catch-levers 30, 36 are operated by the mechanism for moving the mirror. When the mirror is lowered, a bar from the mirror disengages the catch 30, and the shutter is free to be wound. On raising the mirror the bar is drawn back which releases the catch 36 and makes the exposure.
The engagement sequence is:
- After exposure. Lever 30 engages 47 and 52. Levers 36, 36a lifted clear.
- Mirror set. Lever 30 lifted clear. Lever 36a engages 36b. Lever 36 pushed against 51.
- Shutter wound. Lever 36 engages 47 and 52.
- Shutter released. Lever 36, 36a lifted clear. Lever 30 pushed against 51.
Square ReflectorOn the Square Reflector the shutter is separated from the mirror/release by the revolving back. A pivoted spring lever inside the shutter housing operates on the levers 30, 36, a bar, H, attached to the mirror setting lever, G, passes through the revolving back and pushes on the lever. When the mirror is raised the bar extends into the shutter housing, thus preventing the revolving back from turning. When the mirror is lowered the bar is withdrawn allowing the revolving back to move. The lever 36a can move to engage the ratchet wheel 36b and lever 30 is moved clear allowing the shutter to be wound. When the shutter is released the bar moves into the shutter housing freeing levers 36, 36a allowing the blinds to move.
The shutter is slightly different to the Self-Focusing Reflex, the spring 16 is on a separate spindle allowing the clutch sleeves to be reduced in size.
The release and mirror controls are straightforward. Rotating the lever G tensions a large coiled spring situated beneath it, a lever E is also rotated. E is loosely connected to the edge of the mirror, rotating E lowers the mirror. At the end of the movement E is locked in place by the edge A1 of the rocking plate A. Pressing the release button L which is behind the area A2 rocks the plate A, lowers A1 and frees the lever E. The mirror now rises.
The shutter release bar H has a connecting rod attached to it terminating near the mirror setting lever G, as the mirror is set pressure on the connecting rod is removed and H is pushed clear of the shutter area. When the mirror is raised, at the end of the exposure, a plate attached to the coiled spring pushes the connecting rod and H into the shutter housing.
The T setting is interesting, it works on the release controls rather than within the shutter. A small catch, M, near the release button, L, is moved down, the mirror is lowered and the shutter wound so that the image area is completely uncovered. When the release is pressed the mirror rises, exposing the image, but the bar does not move into the shutter which would close the blinds. A second operation of the release is needed to move the bar into the shutter housing and operate the shutter. Moving the plate M lowers the plate D on the inside of the camera. C sits on top of D and is also lowered slightly, The result is that the lever E is caught a fraction before its normal completion, first by the edge C2 and then by the edge C1, the coiled spring below the setting lever G does not unwind completely and so does not hit the connecting rod of H.
K is a connection from the alternative release on the other side of the camera. J is a connection to the alternative position of the revolving back. Note the curved track of the mirror, this guides the front edge of the hinged section of the mirror after it has hinged down.
N&G Two Shutter Reflex
This camera is based on the Square Reflector (see above) but has in addition to the focal-plane shutter a two-blade return shutter mounted between the lens. When the front shutter is used the operations are:
- Open the shutter once the mirror is lowered.
- On release, close the shutter then raise the mirror.
- Fire the shutter.
The setting/raising of the mirror and the linkages to the focal-plane shutter and revolving back are the same as in the Square Reflector and are described above. A switch on the side of the camera sets which shutter is to be used. When the front shutter is used the focal-plane has to be manually opened, as do the front blades when the rear shutter is used.
The major part of the front shutter controls is in the body of the camera, from there, a single transmission bar is used to operate the front shutter. The bar moves both clockwise and anti-clockwise to make the settings, it is also telescopic for bellows extension.
The first illustration shows the camera in the untensioned state, mirror raised, and set for front shutter use. The setting for front or focal-plane shutter is by a stud near the mirror setting handle, G, this moves a plate, 2, inside the camera. One arm of 2 engages one of two notches on the end of plate 1. Plate 1 lies next to 7 which is connected to and follows the mirror movement. Hooks at each end of 7 engage the shaped end of the sliding plate 8 and the bar 4. The other end of 4 connects to lever 9 which rotates the transmission bar 10. Moving 2 also pushes the end of bar 4 to the left or right so that, when the front shutter is used, it can meet the hooks on 7, 2 also moves the connecting rod 11 which disengages the connection to the focal-plane shutter.
When set for Front shutter useMoving 2 draws the connecting rod 11 and the attached lever H away from the focal plane and prevents the focal-plane shutter from firing. The upper notch of 1 is engaged by the arm of 2. The mirror is in the up position and plate 7 is at the top of the camera. Lowering the mirror brings 7 down in an arcuate course. The upper end of 7 moves 4 and 8 down. Attached to the end of 4 is the lever 9 which rotates away from the camera body, this rotates the bar 10 which hinges a pallet near the lens box back which opens the blades. The movement of 4 depresses the end of lever 12 and brings the other end of 12 immediately under the release stud 6.
On release, initial pressure moves the transmission the bar 10 to close the blades. Stud 6 depresses lever 12 which raises 4 (a spring on top of 4 was pushing it down) this frees 4 from the end of 7 and allows 10 to rotate towards the camera body which closes the front blades. Plate 4 moves upwards, as a result of the rotation of 9, with its far end now in front of 7. Lever 9 is now resting on the raised, bevelled, section of 8. Further depression of the release knob frees 7 (by the ordinary Square Reflector mechanism) which now travels towards the top of the camera. Near the end of its travel it meets the end of 8 and slides 8 upwards, this allows lever 9 to drop further and rotate the bar 10, the pallet hinges forward and operates the blades of the front shutter.
When set for Focal-plane usePlate 2 moves rod 11 so that the attached lever H connects to the focal-plane shutter and moves lever 4 slightly to the right so that it is not in contact with plate 7.
Front ShutterThe front shutter is a two-blade return type with pneumatic regulation similar to the model fitted to the Postcard Sibyl. It fits into a 'lens box' and is completely removable allowing other lenses to be fitted to the camera, the shutter will also function when removed from the camera. The illustration shows the shutter removed from the lens box.
The shutter is controlled by a pallet which is moved by the transmission bar, the pallet hinges backwards to open the blades and forward to close the blades and then make the exposure. The pallet fits into a fork, 26, at the edge of the shutter. As 26 moves backwards the lever 27 engages a hole in a spring attached to the blades, 27 moves towards the top of the camera thereby opening the blades. This is the focusing position. The shutter is now tensioned by moving the arm 23 upwards until it is locked by the spring plate 30. When the body release is pressed the pallet hinges forward, this lifts 27 clear of the hole in the spring plate and the blades close. Continuing pressure on the body release brings the pallet further forward resulting in the arm 29 depressing 30, this frees the rod to which 23 is attached. 23 is pulled down by a spring attached to the top of the rod and fixed to the bottom of the shutter, its progress is retarded by the pneumatic delay cylinder. As 23 descends it meets the stud 21 and rotates it anti-clockwise which opens the shutter blades for the exposure. Further descent brings it into contact with the stud 24 (21 and 24 sit on the same lever) which is rotated clockwise to close the blades.
When the focal-plane shutter is used the blades are manually opened by moving the lever 22.
At the top of the shutter is a sliding plate 20, this has settings for 'Mirror', B or T and I. Normally the mirror setting is used, selecting the other settings allows the shutter to operate independently of the camera. A plate (not shown in the illustration) fits along the top of the shutter and carries a release button and cable release socket, these operate on plate 28 which moves 30 to release the blades.
N&G Folding Reflex
The shutter developed for the N&G Folding Reflex was also used, in a modified form, on the Dallmeyer Speed and Baby Speed Reflex cameras.
In its original form, as fitted to the Folding Reflex, the shutter mechanism is split into two halves situated each side of the camera. On the left, when in use, is the shutter/mirror release and controls for B, T and I, on the right is the timing and shutter setting wheels.
The description that follows is largely taken from the patent specification.8
Shutter BlindsThe shutter comprises two blinds one, 43, with an aperture 47 is wound on a spring roller 46 and the central part 45 of an upper roller. The other blind is wound on a spring roller 48 with tapes 44 wound on rollers 49 and 50 adjacent to, and on the same spindle as, the upper roller. When the blind 44 has been fully unwound from the spindle 48 the aperture 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 close the slit. This is allowed by the clutch arrangement in the upper roller where the part 45 can rotate while the rollers 49, 50 remain stationary.
Mirror SettingThe mirror is mounted on the axis 21 which contains a coiled spring tending to raise the mirror. The mirror is lowered by hand and held in place by moving arm 30, the arm has a series of projections (31, 32, 33) on the underside, the projection 31 is held by catch 34 on arm 35 when 30 is lowered. Lowering the arm 30 also moves pawl 80 to engage the gear wheel 66. Without lowering the mirror the shutter cannot be wound.
The arm 35 is connected with a release and timing lever 36 which has a catch 94 that engages one of the projections 31, 32, 33 depending on the shutter setting of B, T, I. The mirror pivot 21 also operates linkages whereby, when the mirror rises for an exposure, the link 29 engages the pawl 80, which holds the shutter in the set position, freeing the gear wheel 66.
B T I SettingThe setting of B, T, I is made by moving the pin 42 and the sliding plate 140. The edge of the plate has shoulders - 98, 99, 100 - which limit the angular movement of the arm 36.
For instantaneous exposures pin 42 is moved to the I setting (lowest) which brings shoulder 100 opposite the projection 41 on the lever 36. When the release lever, 37, is pressed the arm 30 and mirror are released, arm 30 rises, the shoulder 100 limits the movement of lever 36 and keeps the catch 94 free of the projections 31, 32, 33. The arm 29 then releases the shutter pawl 80.
For Time exposures pin 42 is moved to T (middle position) which brings shoulder 99 opposite the projection 41 so that on operating the release 37 the catch 94 on the lever 36 engages the projection 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 is to release the shutter pawl 80 but to be held in the path of a projection 96 on the gear wheel 66, arresting the shutter in the open position until the release 37 is again actuated to release the mirror from the catch 33.
For Bulb exposures 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.
Speed SettingThe speed of the shutter is controlled by a setting knob which positions a notched disc 73, freely mounted on the axis of wheel 64 and held by a spring catch 76. The disc 73 has a pin 74 extending into a slot 72 of a plate 69 which is also freely mounted on the same shaft as 64 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 (sited above pinion 66) and the pinion 66, the blinds of the shutter are wound by rotation of the winding pinion 201 via gear wheel 64, 201 is directly connected to the spindle carrying 45, 49 and 50. After one revolution of the wheel 64, the pin 71 engages the pin 70 on the plate 69. 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. The purpose of the floating plate 69 is that when set to T or B the wheel 71 needs to rotate more than 360 degrees, the slot 72 allows this extra movement. When the shutter unwinds the projection 96 on wheel 66 moves a plate 200 upwards which frees the notched wheel 73.
When used on the Dallmeyer cameras the B, T, I settings were moved to the same area as the shutter setting wheels.
Original, Ordinary 2 ½" x 3 ½"Spring powered sector with pneumatic regulation. When introduced in 1906 these were very simple but well-made shutters. The sector moves across the lens at uniform speed in alternate directions and can be tensioned in either position. The shutter is particularly quiet in operation.
The main spring fits over a spindle on the setting sector, its two ends are both at the bottom of the spindle and project forming arms that lie each side of a shaped projection. The shutter is tensioned when an external lever moves one of the arms through a short arc. As the arm is moved the setting sector is held by the release lever. Pressing the release lever frees the sector allowing it to rotate and relax the spring, as the sector rotates links force the blade across the lens opening.
The speeds are set by moving an external lever which moves the speed setting rod which adjusts the flow of air to and from the pneumatic cylinder. A 'B' setting is possible by a short depress of the release when the shutter is set to a slow speed. The setting sector is caught by the release lever at its middle notch.
The release of these shutters is on the side of the shutter. On very early examples the shutter blade is unpainted, after a very short time the blade was painted black and was marked with a + and O sign, these indicate which way the setting lever is to move to set the shutter.
Ordinary quarter-plateSpring powered sector with pneumatic regulation.
Similar to the shutter fitted to the smaller Ordinary model but the shutter spring now sits over the pivot point of the blade, the setting sector is also centred on pivot point. As a result the delay cylinder is angled upwards. This symmetric arrangement does away with the links that connected the spring to the blade and would have given more even travel of the blade in its two directions of movement. The spring itself is contained in a small housing on the face plate of the shutter.
The shutter release is now at the lower left of the face plate. A spring pushes the release lever upwards. Two buffers have been introduced to cushion the blade movement.
SpecialThe shutter fitted to the Special model is very similar to that fitted to the quarter-plate Ordinary. The blade has lost its top connecting strip and now consists of two circular lobes.
Baby, New Special, New IdealThe improvement over the shutter fitted to the Special is the inclusion of a separate I, T, B selector. A sliding stud on the front is used to make the selection which moves a plate with shaped projections in line with the (internal) release lever. The release lever is lifted by the projections, to free the shutter, and additionally may be caught or slip over the projections depending on the setting. The release button on the face plate now moves a short lever which acts on the edge of the I, T, B lever which moves sideways.9
Excelsior, VitesseTwo-blade pivoted return. Compared to earlier Sibyls the main spring has been considerably strengthened allowing a higher top speed and a different blade action. The I, B, T selection is much more positive than in other Sibyls and is more reliable. The shutter, though, is much noisier than other models.10
The blades are opened and closed by moving a small stud sited below the lens, a link connects the stud to a cam. A small pin on the link engages in a slot in the cam, rotation of the cam moves the pin and hence moves the shutter blades. The slot is shaped such that as the cam rotates the pin moves at first quickly, to open the blades, then slowly during the exposure and then quickly to close the blades. Above the cam is a 'trigger plate' that is held by the release levers, above the trigger plate is the main spring that powers the shutter.
When tensioned the trigger plate is held by the first (top) of the release levers, on depression of that release lever the main spring is free to unwind. A sliding I, B, T selector plate works in conjunction with the release levers. The external release button sits above and depresses the selector plate and so operates the levers. Each lever is pushed up at the left by a spring, the selector plate holds the levers down or frees them, the right hand ends of the levers interfere with the movement of the trigger plate as it tries to rotate. The photograph shows the I setting, moving the selector plate up gives B and then T. When the lever is moved to the B position the middle lever is depressed the other end is raised, when the shutter is released by the top lever the trigger plate rotates but is then held by the middle lever until pressure is removed from the release knob. When set to T the bottom lever rises, it was held down by the separate T plate, on release the trigger plate can rotate until it meets the end of the middle (B) lever where it is held until pressure is removed from the release button, it is then held by the lowest (T) lever until the release knob is again pressed. When set to I, the B and T levers are inoperative.
The exposure is determined by a pneumatic delay cylinder, this is connected to a 'speed selector plate', The speed selector plate is moved up and down by the speed dial on the front of the camera. When the shutter blades are open the trigger plate comes into contact with a stud on the speed selector plate and its movement is retarded whilst the pneumatic delay runs its course.
Post CardTwo-blade pivoted return. The shutter is set by raising a rod until a second notch on the rod catches in a fork which is the end of the release linkage. When the release is pressed the fork is lowered allowing the setting rod to drop, in doing so the release arm first moves the 'open stud' which opens the blades, the arm then moves the 'close stub'.
The I, B, T lever on the front plate moves a plate which determines the amount of depression of the release and release linkage. When set to I the movement of the fork is enough to free the setting rod. When set to T the depression is small, enough to free the rod but the fork can rise to catch and hold the rod at another notch. When set to B the depression is large, the rod is freed but is then caught when the top of the fork falls into a notch on the front of the rod.
De Luxe, ImperialTwo-blade pivoted return. This is an unusual shutter with two main springs that are used alternately.
With the setting bar in its lower position the lower spring is in compression. The upper setting arm is now moved to its upper position by moving an arm on the face plate, this compresses the upper spring. The shutter can now be released by depressing the release, the lower spring extends and operates the shutter blade by moving the setting bar upwards. The two blades are connected by two pivoted links which are moved by the setting bar, at the start and end of an exposure the links are in a V position, as they are moved into line the blades are forced apart.
ShuttersThe Universal shutter is a sector type, spring powered with pneumatic regulation. The shutter is set by pulling up the rod R which compresses the spring M. As R is raised so the single blade B is pulled up until the 2nd of two catches, C, on the edge of the blade is held by the release lever A. The speed is set by moving the lever S, this changes the rate that air can escape from the cylinder P into the chamber E and hence the length of the exposure (subject of BP 20649/1892). When the door of the camera is closed a spring-loaded rod attached to the door lies beneath the release lever A and projects onto the index plate at F, this is the shutter release. Pressing on the rod at F lifts one arm of A, the other arm disengages the catch C of the shutter blade. The blade is now able to move across the lens pushed by the spring M and regulated by the pneumatic cylinder P. An alternative means of release is to fit a pneumatic release to the socket at the bottom of the rod N.
The blade has on its edge two catches or notches, C. The 2nd one is held by the lever A when the blade is fully raised ready for an exposure, the 1st catch is held by A when the opening in the shutter blade is over the lens, this provides a T setting. The usual way of making a time exposure is to set the speed to a ½, release the shutter and quickly remove the finger from F, the shutter blade will then be held at the 1st catch.
On some models the notches, C, are replaced by small projections located close to the where the blade pivots, these are still engaged by the lever A which is now lengthened. The shutter on the right shows this arrangement.
The shutter is not self-capping, when being set it is protected by a separate capping blade in the door of the camera. When the shutter release is pressed it first moves the capping blade clear and, if fitted, opens the spring door on the front of the camera, it then connects with the lever A. To focus using the focusing screen the shutter is raised until the held by the 1st catch. A small amount of pressure at F will open the spring door and move the capping blade aside, a catch on the index plate is then moved over the end of the shutter release to prevent the capping blade returning. The same arrangement is used with the pneumatic release and for time exposures i.e. the shutter is fully set, the release F is partially depressed and the capping locked in the open position.
The shutter (right) is from a High Speed, on this model the setting rod is separate to the piston rod. The setting rod is on the right and is pulled back after setting by its own spring. The shutter on the far right is from a 3 ¼" x 2 ⅜" Special B, it is fitted with a supplementary spring that runs from the Index plate to the piston rod. The spring can be unclipped from the piston rod and fixed to the Index plate when not in use. Only a single set of speeds is marked so its function is not clear.
The shutter fitted to the De Luxe is similar in that it is a sector type, spring powered with pneumatic regulation, but its mechanism is very different. The shutter (shown here unset) is pivoted at M, it is rotated during exposure by the movement of O which is attached to a small lobe opposite the blade, during tensioning it is rotated in the opposite direction by moving a lug near to O. The shutter is set by pulling up a rod by a knob on the top of the camera, this rotates the blade to the set position and tensions the coiled spring M. The rod works behind the face-plate of the shutter and is attached to a short lever, when the rod is lifted the lever presses down on and moves a lug attached to the shutter blade near to O thereby raising the shutter blade. The speed is set by moving the lever S this moves the post T to the left or right. The top of the post works within a slot of the lever L. When the shutter is set the link N moves down forcing the end of the lever L that is attached to the piston rod of P up thereby setting the pneumatic delay. The piston of P always assumes the same position and air enters P at the same rate. Changing the speed setting alters the position of the fulcrum of the lever L i.e. where L and T meet. At high speeds the fulcrum is to the left, a short downward movement of the piston causes a large movement of the link N which rotates the blade past the lens. At a slow speed the pillar T is to the right, now a large movement of the piston rod is required to rotate the shutter blade. The arm D moves within an open cylinder probably providing a damping action and brake at the end of the exposure.
In other respects the shutter works in a similar way to the ordinary Universal. It is released by a release rod at F or by pressing U, both move the lever A which holds the blade by the catch C.
The diaphragm is adjusted by moving the lever I.
The Nydia was a strut camera produced by Newman & Guardia.
The 1900 model Nydia shutter was not self-capping, small changes to the tensioning arrangement made around 1902 made it self-capping.
The self-capping model consists of two blades each with a rectangular opening. The blades slide rectilinearly and are attached to an arm which moves in a small arc. Also attached to the arm is a piston fitting into a pneumatic delay cylinder. Around the centre of the arm is a coiled spring the two ends of which are extended to lie each side of a stud on the upper part of the arm.
To tension the shutter one end of the spring is moved by an external lever. When the shutter is released the coiled spring causes the arm to rotate and the blades to slide across. From this position the shutter can again be tensioned by moving the other end of the spring. Thus on alternate exposures each blade moves in the opposite direction, the delay (exposure) is caused by filling or emptying the cylinder of air.
On the earlier, 1900, model one end of the spring is fixed, the other moves with the arm as above. To tension the shutter the arm is moved to the left. The delay is caused by filling the cylinder with air. The blades are the same shape as the later model.
The Patent is a simple three-blade leaf shutter with pneumatic delay. It was introduced in 1912 or 1913 and based on the patent of A.S. Newman. It was originally called the Accurate, later the Perfect.11
The shutter is set by moving a lever on the front plate which tensions a coiled spring. When the spring is tensioned a plate, underneath the spring, catches on the end of the release lever. Operating the external release shifts this lever and allows the spring to unwind. A short depress of the release when the shutter is set to a slow speed results in a second projection on the plate catching the release lever, this gives a B setting. When the blades are fully open a stud is momentarily held in a spring mechanism at the top of the shutter. The blades are operated by a pivoting plate having slots for pins attached to the blades, the plate is moved by the main spring. A dial on the front of the shutter sets the speed by moving the speed setting rod of the delay cylinder.
This shutter was used on the rigid-bodied or jumelle type camera of 1899.12
The shutter consists of a set of metal plates with a variable separation between them moving across the focal plane. The plates are connected by a pleated-leather sleeve to the lens area which cuts off light except to the shutter plates. The light-tight sleeve is removable.
A large amount of design and production effort has been expended in making the shutter self-capping and tensioned by the changing box. The mechanism may seem overly complicated but in the context of the time it was an advanced design with little else for comparison.
The shutter provides, on this example, 120 settings, but some are duplicated. The slit width has 10 settings between 1 and 10 mm, the speed of travel has 12 settings obtained by varying the tension in a coiled spring.
The slit width is set by moving a lever on the bottom of the camera, this turns a screw (V) attached to one of the shutter plates, increasing or decreasing the slit width. The lever requires two turns to alter the slit by 1 mm, as the lever is turned it also moves a pointer around the edge of the speed dial.
The rate of travel is set by moving an arm on the speed dial, this varies the tension in the coiled spring. The spring is connected to a large wheel inside the camera. The edge of the wheel is grooved to hold a cord (F). The cord is attached at each end to the shutter plates and runs through a loop attached to the wheel. In the untensioned position the plates are at the bottom of the camera, the tension in the spring has rotated the wheel and pulled the cord some way round the wheel. In setting the shutter the plates are moved to the top of the camera which pulls on the cord causing the wheel to rotate back providing the shutter tension.
Setting the shutterTwo hooks (r) at each end of the shutter plates are engaged by the draw of the changing box, as the box is pushed in the end of the box meets the hooks and pushes the shutter plates to the top of the camera.
ReleaseThe shutter is released by pulling back on two triggers situated on the top of the changing box, this pushes pins onto the hooks depressing them and freeing them from the edge of the changing box. The shutter can then move across the focal plane.
Self-cappingIf it were not required to be self-capping the mechanism would be straight forward. The shutter plates comprise a top plate (d1) a lower plate (d6) and a closing plate (d3), the arrangement, much simplified, is shown in the accompanying diagram. When unset the plates are at the bottom of the camera, the slit adjustment screw (V) is in contact with its setting lever and can be adjusted. The screw V actually works on a plate behind d6 to which d6 is loosely attached. In setting the shutter the plates are slid to the top of the camera, the lower edge of d3 pushes on d6 to maintain contact with d1. At the start of the exposure the springs r are released allowing the plate d3 to drop, pins on d3 act on d6 and bring that plate down to the extent set by the screw V i.e. the slit width is formed. The shutter is at this point moving across the focal plane. At the end of the exposure d3 strikes the bottom of the camera, d6 also stops when in contact with the lower edge of d3, d1 stops when it strikes d6, thus the slit is closed. Two large springs (k) running from the front of the camera to the shutter plates push down on d1 ensuring contact with d6 except during exposure. Essentially the plates are able to slide relative to each other the slit only being formed during exposure.
The Talmer was a detective camera introduced in 1890, the shutter described here is a slightly later model. It is a good example of a two-blade guillotine type as fitted to British cameras of the period.
1893 ShutterThe shutter is a two-blade guillotine type with both blades operating in the same direction, it is spring powered with a separate friction device controlling the release of the second blade.
The image below shows the shutter in the unset position. When set the blades are moved to the right and the springs A and B, connected to the blades are tensioned. Spring C, attached to the Speed Control Carriage is also tensioned. Spring D is put in compression.
The shutter speed is set on the cam at the top of the camera, this sets the tension in spring F which tends to turn lever E anti-clockwise. The end of lever E rests on a cork-covered pin attached to the Speed Control Carriage. During the exposure the Speed Control Carriage is pulled to the left by spring C, its speed of travel (and hence the exposure time) is determined by the friction between the cork pin and the lever E. The greater the tension in spring F the greater the friction between lever and pin and the longer the exposure.
On release Spring A pulls blade 1 across the lens opening to start the exposure. Blade 2 is held by the end of lever E. The Speed Control Carriage is pulled to the left but is slowed by friction with lever E. When the Speed Control Carriage reaches the end of its travel lever E is free to rotate and so release blade 2 which is pulled to the left by spring B.
The shutter is set by a lever in the camera moving the blades to the right, the lever is acted on by a further lever moved by the changing mechanism.
Adams de Luxe
The de Luxe was a box-form detective camera made from 1898. The shutter is a single-blade sector type, spring powered with pneumatic regulation. A separate capping blade is within the camera. The shutter is completely removable and held in place by two spring catches. The mechanism is interesting as a closed pneumatic cylinder is used with the length of the piston stroke controlling the exposure.
The shutter is set by pulling the end of the setting rod, the setting rod slides in a small brass block that is fixed to the drive rod. The drive rod is underneath the setting rod and carries the main spring. Pulling the setting rod brings with it the block, the drive rod, the shutter blade and compresses the main spring. On releasing the setting rod it returns under the force of its own spring. When the drive rod is fully extended the setting pin at the back of the shutter is engaged by the release catch preventing the drive rod and shutter blade from returning. Fixed to the drive rod is a block that is also fixed to a rod that connects to the end of the delay cylinder piston, as the drive rod is pulled out the delay piston is pulled into the delay cylinder. The speed dial is turned to adjust the speed, this turns a multi-start screw to which the delay cylinder is attached, thus the cylinder is moved relative to its piston.
On releasing the shutter the release lever at the back of the shutter is rocked, a pin attached to the lever engages a disc on the body of the camera to open the capping blade. Further pressure on the release frees the setting pin from the release catch. The drive rod is now pushed by the main spring and the shutter blade moves across the lens. The movement is impeded to a greater or lesser extent by the position of the delay piston. The end of the drive rod works within a damping cylinder. A second notch on the release catch holds the shutter in the open position for focusing and time exposures.
Adams Yale (early model)
The early models of the Yale had a two-blade pivoted return shutter fitted behind the lens. The blades are pivoted about two points each side of the lens. The shutter is powered by a coiled spring which is also used to regulate the speed.
The main spring is shown towards the bottom of the image, one end moves along an endless screw which is turned by a knob on the outside of the camera, in this way the shutter speed is varied.
Royal (Smyth's Patent)
This is a well-made shutter and a good example of a single-blade guillotine with capping blade fitted to a stereo camera. It has the unusual feature of being tensioned by operating the changing mechanism, a wire cord runs from the changing mechanism to the shutter.13
The illustration (right) shows the shutter in the unset position. When the changing mechanism is operated the cord retracts into the body and pulls the capping plate B and with it the shutter plate A to the set position, when set the catch a1 on plate A is held by the face d2 of lever D. When the changing mechanism is returned the spring B pulls plate B back to the left. When set for instantaneous exposures the plate T is pushed to the right, on pressing the release the lever D is rocked freeing the catch a1, plate A can now move to the left pulled by spring A to make the exposure. When set for time exposures T is pulled to the left, on release plate A moves to the left but catch a1 is held by lever E as the aperture X uncovers the lens, it is held in this position until further pressure on the release moves lever D which knocks lever E and frees a1. The patent shows the control knob for T closer to the shutter release.
This describes the shutter that was fitted to the first Kodak box camera. It is a complicated piece of mechanism completely unlike the rest of the camera. The shutter is a spring powered cylinder type of fixed speed. The lens is contained within the cylinder, the mounting for the lens forms a shaft on which the parts of the shutter are mounted.
The parts of the shutter are: the winding mechanism described in the patent as a motor; the cylinder that revolves to expose the lens; the release mechanism that releases the cylinder and stops it after half a revolution.14
Winding MechanismThe motor consists of a ratchet wheel 5 rotating loosely on the shaft 4. The part 51 of the ratchet wheel connects to spring 7 within the end of the cylinder 3. The spring 7 is the main spring that drives the shutter. A ratchet and pawl mechanism inside 5 allows the wheel 5 to rotate on 4 in only one direction. The drum 9 and its attached pulley 12 serve to rotate the ratchet wheel 5 and thus wind the spring 7. The drum 9 carries a spring pawl 10 that engages the teeth on drum 5. A spring 11 inside the drum 9 serves to return drum 9 and so retract the pulley 12 when the pull on 12 is removed, one end of the spring 11 is fixed to 9 the other to the shaft 4.
Winding the shutter is not limited to a single movement, the pulley can by operated several times and to a greater or lesser extent to wind the spring 7. When fully wound more than one exposure can be made before re-winding, though the instruction book describes the shutter being wound before each exposure.
CylinderThe cylinder has two cut-outs opposite each that expose the lens.
Release MechanismMounted on the part 30 is a double-ended pivoted latch, 23, the lower end of the latch is pushed by spring, 24, towards the plate 20. On the face of plate 20 are two abutments, 22. Plate 20 is fixed to the cylinder 3, as plate 20 revolves its motion is halted when the upper part of the latch (depressed by the release pin 25) meets an abutment, 22. In this way the cylinder is limited to moving through half a revolution. When pressure on the release pin is removed the lower half of the latch is pushed towards plate 20 and holds it at the other abutment. To release the shutter and make an exposure the release pin 25 is pressed, this frees the lower end of the latch and allows the cylinder 3 to rotate. The flat spring 27 rests against the edge of plate 20, it acts as a break on the rotation of the cylinder 3 and in conjunction with the shoulders 21 prevents recoil of the cylinder.
The shutter can be used for time exposures, the cylinder is held in the open position when the lower part of the latch 23 meets one of the grooves 29. To allow this the shutter is wound down by successive releases with the lens covered, the cylinder can then be rotated by hand until it is held by the latch and groove 29.
Pneumatic Delay Cylinders were a common method of regulating exposure. The delay can be whilst the piston moves into or out of the cylinder or, less commonly, alternate so both the in and out stroke are used.
The simplest has a cylinder open at the piston end with a valve to control air flow at the other end. The valve was often a shaped piece of metal working in a small hole in the cylinder. A problem with this arrangement was that only a small movement of the valve covered the entire speed range making calibration and manufacture difficult. Being open also allowed dust to enter the mechanism. Newman's Patent shutter of 1886 is of this type.15
Another arrangement was to have a sealed cylinder and to have air flow take place between an attached chamber. As the piston descends air flows out from the bottom of the cylinder and in at the top of the cylinder. A valve connected to the speed indicator would work in one of the holes. The shutter fitted to the N&G Universal has this arrangement.16
Rather than have a valve regulate the air flow, the length of the piston stroke could be varied. The speed setting altered the position of the cylinder relative to the piston (or the other way round). The advantages of this method was that there was no valve and therefore the inlet/outlet hole was of fixed size, secondly, a large movement of the cylinder was required to cover the speed range, this arrangement gave more precision in calibrating the speed setting. Newman's, rejected, patent of 1890 shows an open cylinder with the initial position of the piston altered by the speed setting. Hill and Adams' patent of 1892 shows a fixed piston and a moveable cylinder.17
The moving cylinder could be sealed and combined with a side chamber or air flow could be through a gap in the piston head. This type of delay was used on the Adams de Luxe camera of 1898 and is mentioned in Hill and Adams' patent, BP 12029/1892.
References & Notes
 BP 22698/1904.
 BP 6238/1912.
 BP 235560/1924.
 BP 19363/1902.
 BP 158194/1919.
 BP 8722/1912.
 BP 271330/1926.
 BP 13820/1912.
 BP 21873/1899.
 BP 6950/1888. US Pat. 388850/1888.
 BP 7156/1886.
 BP 20649/1892.