Improvements in what are known as Instantaneous Photographic Shutters.
Year: 1889

page_text: Date of Application, 26th Feb., 1889
Complete Specification Left, 25th Nov., 1889-Accepted, 18th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in what are known as Instantaneous Photographic
Shutters.
I, JAMES HEBER TAYLOR of Little Trinity, Cambridge, M.A. Queen's College
Oxford, M.A. Trinity College, Cambridge, B. Sc. London, do hereby declare the
nature of this invention to be as follows :--
The first particular of improvement consists in giving a balanced action to the
pneumatic, or other, release so as by preventing any displacement of the centre of
gravity and by opposing the acting forces to prevent the shocks and tremours com-
monly induced by the unbalanced actions in general use.
The next particular of improvement consists in so arranging the mechanism which
operates the leaves that the times of uncovering and of recovering the lens shall be
both small fractions of the whole time of exposure, itself very brief, and adjustable so
that the whole time may be varied, the ratio of the times of opening & of closing to
the full time of exposure remaining approximately constant.
The modes of effecting this end, in principle identical may be varied according as it
is desired to use simultaneous movement of (i) rectilinearly sliding leaves, (ii) pivoted
leaves or independent movement of leaves with either kind of motion, for opening &
closing the shutter.
To effect the simultaneous movement of two leaves opening from and closing to
a given diameter of the lens mount, 1 employ a circular disc, rotated by a coiled
spring or other suitable means, which disc carries pins, one on each side, towards
opposite extremities of a diameter and at equal distances from the centre, which
work the leaves of the shutter by means of cams so designed that the pins,
starting from fixed positions gradually impress a considerable velocity on the leaves,
which owing to their overlap, do not begin to uncover the lens till the pins have
undergone an angular displacement a, then, during a succeeding angular displace-
ment ẞ, the pins rapidly drive the leaves off, & uncover the lens ; after which,
while the pins undergo another angular displacement y, their action on the leaves
is gradually reduced to zero and there reversed, then through another angular
displacement y it is gradually increased, the lens still remaining uncovered, after which
by the velocity thus impressed upon the leaves the lens is again covered during
a succeeding angular displacement 3 of the pins, & the lens continuing closed the
movement is finally reduced to rest during the succeeding angular displacement a.
In the angular distance 2 y I carefully avoid bringing the leaves to rest by making
part of the cam concentric with the centre of the then movement of the leaves,
because the effect of this free passage of the pins would be to shorten the duration of
full opening of the lens relatively to the whole time of exposure: i.e. it would act
directly contrary to the stated object of the invention & besides this the strains on the
leaves, pins &c. caused by driving them by sudden impact from rest would damage
the works.
Sometimes, and especially for larger sizes, instead of forming the cams of full size
in the leaves of the shutter, I form then on a smaller scale in pieces of sheet metal
constrained to slide to & fro in a straight line & by a system of levers or other suitable
means multiply their movement on the leaves of the shutter. In this case also I
avoid a protracted interval of rest of the leaves, which would be still more injurious.
than in the simpler construction.
The angular movement of leaves about a pivot or pivots is effected by acting on
them by a pin either directly or through links, the pin being constrained to move
along a line but controlled as to its movement by a cam slot, into which it takes, in a
circular disc, driven by a coiled spring, or by other suitable means; the cam being 80.

page_text: formed that the leaves, if they are intended to recover the lens by reversing their
motion, go through phases of angular motion similar to those described above in the
case of rectilinearly moved leaves or if the smoother movement of a somewhat larger
piece of apparatus be preferred, the leaves after passing the zero may develop a move-
ment in the same direction & sweep on continuously to close the opening of the
shutter.
Lastly in the case of shutters whose opening & closing leaves are independently
driven I secure the same end by arranging that detents suitably driven at adjustable
intervals release first the opening & then the closing leaves.
In each & every form of shutter I arrange the moving parts so that there is no
displacement of the centre of gravity & that the forces are as nearly as may be
balanced.
Dated this 25th day of February 1889. .
4
Improvements in what are known as Instantaneous Photographic
Shutters.
I JAMES HEBER TAYLOR, of Little Trinity, Cambridge, M.A. Oxford & Cambridge,
B. Sc. London, 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 :-
A. The first particular of improvement consists in giving a balanced action to the
pneumatic or other release, so as, by preventing any displacement of the centre of
gravity and by opposing the forces which act, to prevent the shocks and tremours
commonly induced by the unbalanced actions in general use.
I do this by making two pistons of equal weight and dimensions act simultaneously,
in opposite directions, to move the leaves of the shutter directly (Figure 8) or by the
intervention of levers; or to effect the release of the leaves (a) by allowing a detent
to fall into gaps in the parts of the piston rods which are always outside the cylinders;
or (3) by making the piston rods give a small rotation to a cylindrical pin, whose
section at its bearings is circular, but which is cut away at a convenient point so as to
make a release. Figure 10 illustrates this method, the pin being there cut away so
as to leave only one quadrant. Another very convenient way of shaping the pin for
a release is to cut it down to parallel planes equidistant from its axis.
In the figure named small pins, passing through the extremities of the piston rods,
take into slots on a diameter of a disc attached to the pin in a plane at right angles to
its axis.
B. The next particular of improvement consists in arranging the mechanism
which operates the leaves so that the times of uncovering & of recovering the lens
shall be both small fractions of the whole time of exposure, itself very brief, and
adjustable so that the whole time may be varied, the ratio of the times of opening
& of closing to the full time of exposure remaining approximately constant.
proceed to show how I effect this in the case of rectilinearly siiding leaves. In
Figure 1, O is the centre of a lens diaphragm. The smallest circle shows the
position of a stop of the lens: the next larger circle is the fixed diaphragm.
The mixtilinear figure between P & Q (shown again in Figure 3) is the opening
in the leaf of the shutter, whose first motion is in the direction of the arrow:
the leaf being constrained to move along A O.
B is a pin rigidly connected with an axis at A, and driven round by suitable means
in the direction shown by the arrow near F... The leaf of the shutter is carried by a
transverse rectilinearly slotted frame B K, into which slot the pin B takes. On
releasing the shutter, while the pin moves from B to D, (L BAD
=
a) the leaf
does not uncover the lens, but it moves so that the point P comes up to 0.
While the pin moves from D to F, (LDA F = ẞ) the lens is fully uncovered;
while the pin moves from F to I, (L FAI = 2y) the lens remains full open, the

page_text: =
motion of the leaf having been gradually brought to rest & reversed while the pin
B)
passed through the point H. While the pin passes from I to J, (LIA J:
the lens is closed: while the pin moves from, J to K, (L JAK a) the lens is
covered by the original overlap. In the figure the distance QH is, for perspicuity,
unnecessarily long. If the pin moved at a constant velocity, the figure would
represent a shutter which kept the lens full open about five sevenths of the whole
time of exposure: But if the pin is driven by a spiral spring of the ordinary
type, the movement of the pin is accelerated and the full area ratio is much less
than five sevenths.
In this case there is the disadvantage that the sudden stoppage of the rapidly moving
pin at the end of the exposure is very destructive to the mechanism. The straight
cam has the disadvantage of moving the leaf to and fro, while the lens is full open,
a distance equal to the difference between H A & F G. The great size of the
circle B H K is a further disadvantage.
To obviate the destructive shock at the end of the movement, instead of driving the
pin by a single spring, I drive it by two springs which act in opposite directions ;
these springs being so arranged that their tensions are equal and opposite when the
pin is at, or near, J. The use of two springs in this way will be made clear when I
come to the explanation of Figure 6. To make the whole time variable, the full-area
ratio remaining constant, the tensions of both springs may be varied simultaneously,
so as to make their tensions always equal and opposite when the pin is at the point J.
But it is simpler to use springs sufficiently strong to give the most rapid exposure
If the cam
desired, & to vary the time by the application of a suitable friction brake.
in the leaf, instead of being a straight line, between the points where the perpendiculars
from and I upon CA meet B K, took the form of the circular arc FHI; the pin
when it reached F would not drive the leaf any further, when the shutter was full
open, but would fly round in the slot, the leaves remaining at rest, until at I it struck
with force on the leaf-slot and drove the leaf by impact to close the lens. This
arrangement would be contrary to the stated object of the invention, since the pin
would traverse the arc FI quicker and thereby reduce the full area ratio: and it
would introduce an impact very destructive of the life of the shutter. Figure 2 shows
a form of cam which reduces the amplitude of the movement of the loaf while the pin
moves from F to I. When the overlap has recovered the lens, it is well to allow a
little further movement of the pin beyond K, without effect on the leaf, by continuing
the cam in the form of an arc of the circle D H I.. Sometimes, especially for larger
lenses, instead of forming the cams full size in the leaves of the shutter, or attachments
of them, I form the movement on a small scale in pieces of metal constrained to slide
to & fro in a straight line, and by a system of levers, or other suitable means, multiply
their movement on the leaves of the shutter. In this case an interval of rest of the
leaves would be still more injurious than in the simpler construction. The leaf would
now be represented by Figure 3. The leaves ought to be made of exactly the same
weight, so that their equal and opposite movements may not displace the centre-of
gravity of the shutter. The second leaf whose initial movement is downward is driven
by a pin B, at the other extremity of the diameter BO B'.
I, next proceed to describe how I effect the angular movement of leaves about a
pivot or pivots, taking first the case of leaves which recover the lens by reversing
their movement.
A is the centre of the lens
O, Figure 4, is the common pivot of two leaves.
diaphragm, the dotted circle represents the full. opening. The figure gives only the
The
leaf whose initial motion to uncover the lens is in the direction of the arrow.
position of the other leaf is obtained by reversing the figure about the line A. A².
The lines A O A', BO B', &c. are drawn to show the construction of the cam track.
Each leaf is made as light as possible and balanced about O so that no movement. of
the leaves affects the centre of gravity of the apparatus. A pin is constrained to move
between Fand A' in the straight line AOA', and this pin takes into slots in the
leaves, represented in direction, for the leaf shown, by the curved line F D C BA¹.
When the pin has brought the point G on to the line-A O, the overlap of-the-leaves

page_text: is just uncovered: When the pin has brought H on to the line A O the lens is full
open, and it remains full open, till, after reversal of the motion of the leaves, the
pin K has brought the point C on to the line A 0: When B¹ comes on to the
line A O the lens is just closed; then, the motion continuing, the leaves overlap as at
first, the last portion of the cam being in the straight line A O A', so that there may
be a little space in which the movement of the pin may be stopped, the leaves remaining
locked at their overlap. In Figure 4 the curve has not been brought to touch the
line DO D¹ as it might have been.
Figure 5 represents the corresponding leaf of a shutter in which the leaves do not
reverse their movement but sweep on to close the lens. The leaf as before is balanced
about O. The position of the other leaf is obtained by turning the figure over
about A O A¹. In each case I drive the pin, by preference, by two springs, acting in
opposite directions in the straight line A O, and so arranged that their tensions just
balance when the shutter is just shut; i.e. when B' is on the line O A.
I will now explain the action of the two equal and opposite springs, and the advan-
tages which their employment offers. Suppose P, P' (Figure 6) to be two pegs two
feet apart, let two equal springs have one extremity of each attached at P & P¹
respectively, & the other extremity of each attached under tension at Q1 to an object
which is free to slide along the line P P¹. It is plain that Q will rest midway
between P & P¹. Now if the slider be moved so that Q1 comes 3 inches nearer to Pi,
it is plain that the tension of the spring towards P is increased, and that towards P¹
diminished. If now the slider were let go it would move with accelerating velocity
towards the neutral point midway between P¹ & P, and passing this would still go on
for some distance before the increasing tension towards P¹ caused it to stop. The
subsequent vibration does not concern us. The movement, supposing that the
elasticity were perfect would take place under the action of a force varying as its
distance from the neutral point. By application of the Integral Calculus we can
divide the distance from the commencement of movement to the neutral point into
parts a, b, c so that the time of describing the part b may be any fraction of the time of
describing the part c. I believe the following figures are approximately correct. If
the distance be divided into 20 equal parts, then the time of describing the fifth is th
of the time of describing the remaining 15. If however the movement of the slider is
not free, i.e. if it has to do work, the ratio will be altered; & the more, the heavier
the work is.
Two springs used in this way must of course be much stronger than if either were
used alone but they offer this very great advantage, that the destructive shock at
the end of the motion can be very much reduced, or done away with.
:
In Figures 4 & 5 the curves represent cams designed to make the leaves move so
as to give as good a full-area ratio as possible, with the given magnitudes of O A
A B & B E.
It is plain from inspection of Figure 5, that if instead of the curvilinear cam, a
rectilinear one were drawn, from the same point on A. O produced, making an
obtuse with A O so as to cut all the lines, then the shutter would open & close but
without regard to the question of what point of the cain ought to come over A O
produced at any time in the movement. With double acting shutters with rectilinear
eams I use the appliance represented in Figure 6.
P, P' are attachments of the frame of the shutter.
is free to move along P P' in either direction.
fram of the shutter immediately above the lens tube.
vertical slider moves.
H
Through P & P¹ the slider P P¹
H', K K' are V guides on the
Between H H' & K K' a small
In the apparatus from which Fig. 6 is drawn the vertical moveinent of the small
slide is half an inch. A pin through the centre of this slider at right angles to
its plane of movement passes through the frame and through the slots in the leaves
below & through a cam R S in the slider P P₁ above. The cam R S is designed
to suit the theory of movement for the full-area ratio required. P & P carry
steel wires hooked back towards the ends of the bars. At Q & Q' are similar
hooks turned the opposite way. Equal springs link P¹ & Q', P & Q respectively,

page_text: their neutral point being just when the cam R S has raised the vertical_slider so
as just to close the shutter. The short horizontal part of the cam at R (where
the leaves are locked at overlap) brings the shock at the end of movement perfectly
under control. In this case the movement of the sliders alters the position of the
centre of gravity. This can be obviated by duplicating the system of sliders,
making them move in opposite directions & each work one leaf.
It may be desirable to add detents which shall prevent recoil of the leaves after they.
have closed the lens to the extent of the overlap, unless the precaution be taken to
leave a slight preponderance of force towards closing.
For a shutter whose opening and closing leaves, whether single or paired, are
independently driven, a convenient arrangement for adjusting the full-area ratio
is to employ a circular disc, rotatable by a spring about an axis at right angles
to its surface, the disc carrying one fixed projection of suitable figure, while a
second is carried on an arm which moves about the axis of the disc, and has its
centre of gravity at the centre, & can be clamped at any distance from the fixed
projection. The disc is driven by a spiral spring & when it is released one pro-
jection releases the opening leaf or leaves & the second the closing leaf or leaves.
Since the weight of the disc acts at its centre, its rotation does not alter the position
of the centre of gravity of the shutter, & the disc being allowed to rotate freely, under
the action of the spring, till it comes to rest, the shock which would be caused by
stopping it is avoided.
Figures 7, 8, 9. show modes in which I produce similar movements, of a photo-
graphic shutter, by perfectly balanced pneumatic mechanism. In each of these three
figures O is the centre of the lens diaphragm, & the dotted circle, centre O, the fixed
diaphragm.
In each of these figures
The direction in which it would
In figures 7, 8 the larger circles represent the lens mount.
only one of the two leaves of the shutter is shown.
move to uncover the lens being shown by the arrow.
In Figure 8 two thin leaves, in which openings of the form indicated are cut, are
freely moveable through slots cut through opposite sides of the lens mount close to the
fixed diaphragm. Each leaf is attached to the rod of a light piston accurately fitted
in a cylinder whose axis runs through the middle of the opposite slots in the lens tube.
The piston, instead of being discoid, is of the form of a cylindrical tube closed
at the end where the leaf is attached. N is the nozzle of a metal, tube for the
attachment of a flexible tube to bring the air blast. Above N the tube branches
to the two cylinders at S, S¹. In Figures 7, 8 the dotted lines at U show the
open end of the cylindrical piston. At R there is a hole or holes in the cylinder.
When the air blast falls on the piston at P, it drives it along freely, because of the
holes at R, first of all reducing the overlap of the leaves and then rapidly
uncovering the lens; and when the lens is just uncovered the end U of the cylindrical
piston, covers the holes R & checks the movement while the elongated opening in
the leaf passes over the fixed diaphragm: When the leaves are on the point
of beginning to close the lens the end of the slot T in the cylindrical piston comes
over a hole in the cylinder and, allowing the air to pass off freely from the inner
end of the piston enables the lens to be rapidly closed. The leaves are placed by
hand in the position for another exposure.
The arrangement in Figure 8 is long, & Figure 7 shows a mode of arranging the
same leaf and its cylinder in a more compact form. The cylinder and leaf in Figure 7
are in the proper position-with regard to one-another, but one end of the cylinder is
not drawn, & the connection between the leaf and the piston is represented as broken
to gain space. The second cylinder may be placed either on the opposite side of the
lens mount, or behind the one shown. In the first case the axes of the two cylinders
should be in the plane which passes through the slots in the lens tube in the second
case the axes should be equidistant from this plane before & behind it.
Figure 9 shows a modification of the design of Figure 7, in which instead of a
cylindrical piston open at one end, a cylindrical piston of double length open at both
ends and closed in the middle is used.

page_text: The advantages to be gained are, 1st that the leaf is now supported at both ends,
2nd that the action of the piston is now readily reversible. In the figure only those
openings in the piston & cylinder which determine the movement in the direction of
the arrow are shown. The others are situated at the same distances as these respec-
tively from the other ends of the piston & cylinder.
When, after an exposure, the piston has been driven to the other end of the
cylinder; a slide, drawn by hand, stops the opening S & opens one at S', & closes the
openings at R & U and opens others at R¹ & U'.
One and the same slide may be arranged to make by one movement the required
changes of openings for the cylinder which works each leaf. This arrangement,
being of the character of the slide valve of a steam engine requires no illustration.
In this wholly pneumatic system the variation of the total time of exposure may
most conveniently be produced by variation of the pressure of the air blast. The
tube which joins the nozzle N to the source of the blast must be flexible but not
extensible. A convenient way to get a variable blast is to use a piston attached
by a spring or springs to one end of a cylinder in which it moves just freely:
the other end of the flexible tube being attached to a nozzle borne by the same
end of the cylinder. At the opposite side of the piston a screw is attached which by
a nut draws up the piston to any required extent; a lever moved by hand releases the
nut when desired & leaves the piston free to move & force out the air to act upon the
pistons of the shutter.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. The application of balanced action to the pneumatic or other release of a photo-
graphic shutter substantially as described.
2. The arrangement of the mechanism which operates the leaves of a photographic
shutter so that the times of uncovering and of recovering the lens shall be both small
fractions of the whole time of exposure, itself very brief & adjustable, so that the whole
time may be varied, the ratio of the time of opening and of closing to the full time of
exposure remaining approximately constant; and this whether simultaneous sliding
leaves, or pivoted leaves (which may or may not reverse their movement) be employed:
no period of rest being allowed if the motion of the leaves is reversed in the middle of
the exposure.
3. Similar division of the whole time of exposure by the use of independently driven
opening and closing leaves, released at suitable intervals, substantially as described.
4. The employment of equal springs acting in opposite directions to move the leaves
of shutters substantially as described.
5. The employment of an air blast to drive pistons which meet with resistance varied
to produce the required division of the whole time of exposure, substantially as
described in Figures 7, 8, 9 and the accompanying verbal explanations, whether as in
those figures the pistons are directly connected with the leaves of the shutter, or the
pistons act on the leaves of the shutter by the intervention of levers or other mechanical
device.
Dated this 92nd Jan
1
1000