Improvements in Photographic Shutters of the Roller Blind Type.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Photographic Shutters of the Roller Blind Type.
I, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, in the
County of Cheshire, Manufacturer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to photographic shutters of the roller blind type, and.
has for its object to provide a simple, convenient, and reliable form of shutter,
with timing device whereby an exposure of any desired length of time may be
given. The shutter is self-capping during setting; can be constructed to place
in any position on or in the lens mount, or close to the focal plane; and can be
adjusted to give more exposure to one part of the plate than another.
In carrying out this invention I make use of two separate blinds, each of
which is mounted to wind on a pair of rollers-one being a pawl-held winding
roller and the other a spring driven roller-all as is well known and commonly
understood.
The driving springs of these blinds are by preference arranged with a fixed
amount of tension on them, so that the said blinds are always driven at the same
speed, but I may provide means for increasing or diminishing this tension, as
required, in order to modify the rate of travel of the blinds. An indicator is
provided to show the degree of tension.
When setting the shutter for an exposure the blinds are both wound up at the
same time, either together, or in such a way that one of them precedes the other,
so as to keep the shutter opening covered during the time of setting, and thus
protect the sensitive surface from receiving light upon it.
When making the exposure the two blinds are released one after the other,
and the period of time elapsing between the release of one and the release of the
other is predetermined by the operator, and controlled and regulated by means
hereinafter described.
The advantages of a shutter constructed upon the above lines are obvious.
In roller blind shutters as commonly used a perforated blind is provided with
means for varying the rate of travel of the blind, and consequently the time that
the perforation therein takes to cross the lens, and thus control the exposure.
Therefore the shutter opens and closes slowly as compared with the length of
time that it remains open.
It is, however, a well-known and accepted fact, that, theoretically, a shutter
should open and close in an exceedingly small space of time, as compared with
the duration of the exposure; this result has, however, been difficult of obtain-
ment, and practically impossible, from the construction of shutters as hitherto
made, and on account of various mechanical difficulties.
By this invention I provide a simple means of effecting the desired result and
for controlling it. For example, the two blinds may have the tension of their
driving springs so arranged that their total travel is effected in the 100th of

page_text: adjustable, in relation to each other for altering the period of time between the
lifts.
It will be understood from the foregoing description that the shutter will give
exposures of a predetermined duration, but by combining suitable detents and
lifters with the pneumatic timing and release arrangements the shutter may be
caused to stop open as long as required, being opened by one pressure of the
trigger or ball, and not closing until a second pressure is applied.
If found necessary to minimise any shock or jerk produced upon release or
closing of the blinds, I may use buffers or retarding devices in any suitable way.
A shutter such as described is suitable for use either before or behind the
lens, or in the lens tube near the diaphragm, or as a focal plane shutter in front
of the sensitive plate.
In using the shutter in any of the first named three positions it is desirable
to only let the blinds follow each other at such a distance apart that the opening
in the shutter is never less than the diameter of the lens, by preference it is
better to have the opening one and a half times or twice the size. If the open-
ing is made less than the diameter of lens, the co-efficiency of the shutter is
considerably reduced although the exposure is shortened.
But in using it as a focal plane shutter, before the sensitive plate, the aperture
may be any size required, and as a matter of fact is preferred very narrow as
compared with the width of the plate. The width of opening may be varied by
varying the period of time between release of the blinds.
Although I have described the invention as applied to blinds that are wound
off one roller on to another and rewound in the reverse direction as ordinarily
used, I may instead use two endless blinds which revolve always in one direction,
or in the reverse direction for setting. These two blinds may be placed one
before the other, or inside each other, being carried over suitable rollers for the
purpose.
By making the tension or driving power greater on one blind than the other,
or by applying a brake or retarding device to one, the shutter can be made to
give more exposure to one part of the plate than another, for example, more to
the foreground and less to the sky.
Instead of pneumatic means for governing the separate release of the blinds
a spring driven dise or a train of wheels with a fly may be used.
D
1 1
L
T
1000
I, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham; in the
County of Chester, Manufacturer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
This invention relates to photographic shutters of the roller-blind type and
is designed to provide a simple convenient and reliable form of shutter whereby
an exposure may be given of any predetermined duration of time from a
minimum to a maximum required also to provide a shutter self capping during
setting or one in which the lens or plate will always be covered or protected
during setting and which may be placed in any position in or on the lens mount
or close to the focal plane and be so adjusted as to give more exposure to one
part of the plate than another.

page_text: lated by a small air hole through which air enters or is expelled from the
interior of the cylinder. The hole n may be either in the inner or outer cylinder
or both.
The pneumatic cylinder N is fitted on its exterior with a fixed stop n' to
engage the pawl or trigger to release the pulley K and blind B and with an
adjustable stop ² to engage the pawl or trigger to release the pulley G and
blind A. It is also provided with a projection to engage the pawl N by which
it is held when set in the position shown in Fig. 7. The adjustable stop n² is
in the form of a nut engaging a screw thread on the exterior of the cylinder.
The cylinder N is released from the catch N and permitted to descend with
the rack clear of the pinions H and L by rotating it about its axis part of a
revolution.
The pneumatic cylinder N is rotated the desired amount by a forked or bifur-
cated plate R on which traverses a pin or projection on the cylinder. The
fork R is pivoted in suitable bearings and is rotated by a pneumatic ball R¹
fitting under an arm and when the ball is released is returned by a spring 2
Figs. 5 to 8. A spring catch T engages the side of the fork to prevent a back-
ward movement before the cylinder N has completed its downward travel. The
pint on the cylinder engages the spring catch T and releases the fork R per-
mitting it and the cylinder to return to its first position as shown in Figs. 5,
6 and 8.
The time between the release of the blind B which is first released and the
blind A determines the duration of exposure and this is regulated by the position
of the movable stop 2 or the distance it is placed from the fixed stop n¹.
Instead of or in addition to regulating the release of the blind A and the
duration of exposure by a movable stop the speed of travel of the cylinder N
may be regulated by a valve N2 by which the aperture n may be more or less
closed as shown in Fig. 9.
Instead of a cylinder having a hole or valve I may use one that is practically
air tight, passing the piston through a stuffing box or equivalent. As the piston
works in the cylinder its rate of movement is dependent upon the rate at which
air may pass from one side to the other, for which purpose the piston may be a
tightly fitting one, having a notch or hole in it, or it may instead be a loosely
fitting one.
A spring presses upon the piston and so forces it against the air cushion.
The duration of exposure may be further increased by means of an adjustable
and movable latch W actuated by a second pneumatic ball R² connected to the
same pneumatic tube as the ball R'. The latch W is pivoted at w and is raised
and lowered by the pneumatic ball R². When the pneumatic balls R¹ R² are
inflated the ball R2 forces up the latch against the pawl or trigger h and prevents
the release of the pulley G the depression of the ball R2 moves the latch W
clear of the trigger h and permits the movement of the cylinder and stop n²
to release the pulley G. The pivot w of the latch W is fitted in a slot so that
the latch may be drawn clear of the trigger h.
In the modification shown in Figs. 12 13 and 14 the pneumatic cylinder N
is connected to a disc M which carries a rack or teeth m¹ on its periphery to
operate the winding of the pinion L' and H of the blind rollers. The plunger
The raising of
of the piston is pivoted to allow of an oscillating movement.
the cylinder N2 carries the disc M' round in the direction of the arrow the rack m
When wound the blinds
successively engaging the pinions and rotating them.
are held by the pawls m2 m³ engaging the cams and h¹. The descent of the
cylinder N and further rotary movement of the disc M is prevented by the
lever M2 engaging the teeth on the disc M¹. The lever M² is raised by the pneu-
matic ball R³ and the cylinder commences its downward stroke rotating the
disc the fixed stop m² releasing the one blind and the adjustable stop m³ the
other blind. The duration of exposure may be further increased by a snug or
projection m' on the side of the lever M³ engaging a pin m³ on the cylinder Na

page_text: the blinds are successively wound upon the rollers C and E maintained in a
rolled position for any desired period of time and subsequently successively
released substantially as and for the purpose described.
4. A photographic shutter having the several parts constructed and arranged
in combination substantially as described with reference to either of the figs. of
the drawings.
Dated this 90nd dow of Wahmour 1800
WM. P. THOMPSON & Co.,
6, Bank Street, Manchester, Patent Agents.