Improvements in Photographic Lens Shutters.
Year: 1889

page_text: Date of Application, 11th Mar., 1889
Complete Specification Left, 11th Dec., 1889-Accepted, 18th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Photographic Lens Shutters.
We, THOMAS RUDOLPH DALLMEYER, of 25 Newman Street, Oxford Street, in
the County of Middlesex, Optician, and FRANOIS BEAUCHAMP, of Hope Cottage,
Whalebone Lane, Chadwell Heath, in the County of Essex, Engineer do hereby
declare the nature of this invention to be as follows:-
This invention relates to improvements in photographic lens shutters of the kind
described in the specification of a patent granted to us dated the 12th day of October
A.D. 1887, No. 13844.
In the invention described in the specification of the aforesaid patent the shutters
are opened more or less gradually, and as soon as opened they begin to close again
more or less gradually, so that the quantity of light reaching the photographic film
gradually increases as the shutters open and gradually decreases as the shutters
close, the closing commencing immediately after the maximum opening has been
obtained the result being that the plate receives the maximum quantity of light for
an instant only. The object of one part of our invention is to cause the shutters to
open as instantaneously as possible, to remain wide open for a definite length of time,
and then to close as instantaneously as possible, whereby the plate receives the
maximum quantity of light during a longer portion of the time occupied in the
opening and closing of the shutters than in the arrangements described in the aforesaid
specification.
In order to effect this object we move the shutters to and from each other by means
of two levers somewhat in the manner described in the aforesaid specification but
preferably so arranged that cach lever is operated independently of the other instead
of one lever being operated by the other as in that case. We operate the said levers
by means of a crank pin rotated by means of a coiled spring. This crank pin engages
in a curved slot in each of the shorter arms of the levers, the said slots being so
shaped that the crank pin acting upon them for a very small portion of its revolution
suffices to move the two levers far enough to open the shutters to their fullest extent,
when that is effected the crank pin passes along portions of the slots in the levers
which are concentric with the path of the crank pin for another and larger part of its
revolution whereby the levers are not acted on by the crank pin, and the shutters are
consequently held wide open while the crank pin is traversing these concentric parts
of the slots. The crank then reaches and acts upon parts of the slots which are
not concentric with its path and move the levers so as to close the shutters during
another very small portion of its revolution. The axis of the crank or crank plate
carrying the crank pin, which is actuated by a coiled spring as before explained,
carries a disc furnished with three stops. Two of these stops come in the line of a
catch or pawl on a releasing lever. When the axis is turned winding up the coiled
spring until the catch or pawl drops behind the first of these stops the shutters are
wide open and are held so by the said catch and first stop so that the necessary
focussing can be effected. When the axis is turned further so that the catch or pawl
drops behind the second of the stops the shutters are closed again and are held so by
the said catch and second stop until the catch is withdrawn from behind the said stop,
when the coiled spring acts, turning the crank pin and causing the practically instan-
taneous opening of the shutters, their retention wide open for a definite time, and
then their practically instantaneous closing as before explained. The third stop on
the aforesaid disc has a twofold function, firstly, when the shutters are in the closed
position it comes against a suitable stop so as to prevent rotation of the crank pin
beyond a certain point, whereby the said crank pin is prevented from pressing
unduly on the slots in the levers, and secondly, it forms a means in conjunction

page_text: with an adjustable stop on the releasing lever or with a stop on a separate lever
whereby the shutters can be held open any required length of time when a long
exposure is desired.
Another part of our invention consists of improved means of guiding the two
shutters in their horizontal movements to and from each other. Instead of
the shutters sliding in grooves made in the upper and lower parts of the lens
mount we arrange them to slide at their upper or lower ends on a guide rod or
spindle placed at the upper or lower part of the lens mount and we leave them
free at their other ends, the points of connection of the actuating levers with the
sliding shutters being preferably placed near the aforesaid guide rod or spindle. By
these means the possibility of the shutters jamming in their guides is avoided.
Dated this 11th day of March 1889.
T. R. DALLMEYER.
F. BEAUCHAMP.
Per W. H. Beck,
115, Cannon Street, London, E.C., Agent.
COMPLETE SPECIFICATION.
Improvements in Photographic Lens Shutters.
We, THOMAS RUDOLPH DALLMEYER, of 25 Newman Street, Oxford Street, in
the County of Middlesex, Optician, and FRANCIS BEAUCHAMP, of Hope Cottage,
Whalebone Lane, Chadwell Heath, in the County of Essex, Engineer, 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, reference
being had to the accompanying two shects of Drawings, and to the letters and figures
marked thereon, that is to say
:-
This invention relates to improvements in photographic lens shutters of the kind
described in the Specification of a Patent granted to us dated the 12th day of October
A. D. 1887 No. 13,844.
In the invention described in the Specification of the aforesaid Patent the shutters
are opened more or less gradually, and as soon as opened they begin to close again
more or less gradually so that the quantity of light reaching the photographic film
or plate gradually increases as the shutters open and gradually decreases as the
shutters close, the closing commencing immediately after the maximum opening bas
been obtained, the result being that the film or plate receives the maximum quantity
of light for an instant only. The object of one part of our present invention is is to
cause the shutters to open as instantaneously as possible, to remain wide open for a
definite length of time, and then to close as instantaneously as possible, whereby the
plate receives the maximum quantity of light during a longer portion of the whole time
occupied from the commencement of the opening to the completion of of the closing
of the shutters than in the arrangements described in the aforesaid specification.
And in order that our said invention may be fully understood, we will now proceed
sto describe the same by the aid of the accompanying Drawings, in which Figure 1
is a front-view of the lens,mount, showing the mechanism for actuating, holding, and
releasing the shutters, the latter being in the fully opened or focussing position,
Figure 2 is a section taken on line XX of Figure 3, 'Figure 3 is a front view of the
shutter mechanism with the front plate removed, the shutters being shown in the
closed, position, and Figure 4. is a similar view with the shutters in the fully opened
position.
In order to effect the above described object, we move the shutters A.A' to and from
each other by means of two levers B.B fulcrumed at B Bx respectively and coupled
together by a pin B fixed on the lever, B taking into. a. slot. B³ in the lever B so
ithat the two levers move together somewhat in the manner described in the aforesaid
Specification, being operated by means of a crank pin C:rotated by means of a coiled
spring:D one-end-of which is secured to the inner circumference of the fixed

page_text: barrel E, and the other end to the spindle F. This crank pin C engages in a
curved slot G in the shorter arm of the levers B and in a similar curved-slot G¹
in the shorter arm of the lever B', the said slots being shaped as shown so that
the crank pin C, acting upon the upper part of the slot G₁ for a very short time at the
commencement of its partial revolution from right to left in Figure 3, suffices to move
the two levers B B₁ far enough to open the shutters A A' to their fullest extent as
shown in Figure 4; when that is effected, the crank pin C passes along portions of
the slots GG, which are at that time either concentric with the path of the crank pin for
another and larger part of its partial revolution, or are otherwise so shaped that the
levers are not, during that time, acted on by the crank pin C, and the shutters B B¹
are consequently held wide open as shown in Figure 4, while the crank pin is
traversing these parts of the slots. The crank pin then approaches the end of the
slot G and acts upon the lower part of that slot, moving the levers so as to close the
shutters into the position shown in Figure 3 during another very short time at
the end of its partial revolution from right to left. The axis F of the crank or
crank plate H, carrying the crank pin C, which is actuated by a coiled spring D as
before explained, carries a disc I furnished with three stops J, K, L. Two of these
stops, namely, J and K, come in the line of a catch or pawl M on a releasing lever N.
When the axis F has been turned by the milled head O in the direction of the arrow,
winding up the coiled spring D until the catch or pawl M takes in behind the first
of these stops, namely J, the shutters A A' are wide open, and are held so by the
said catch M and first stop J so that the necessary focussing can be effected.
When the axis F is turned further in the same direction so that the catch or pawl M
takes in behind the second of the stops, namely K, the shutters A A¹ are closed
again, and are held so by the said catch M and second stop K until the catch M
is withdrawn from behind the said stop by the releasing lever N (which is centred
at N*) when the coiled spring D acts, turning the axis F and crank pin C, causing
the practically instantaneous opening of the shutters, their retention wide open for
a definite time while the crank pin passes along the concentric parts of the slots,
and then their practically instantaneous closing as before explained. The third stop L,
on the aforesaid disc I, has a two fold function; firstly, when the shutters have
been closed by the spring D, the said stop L comes against a stop P which prevents
rotation of the crank pin C beyond a certain point, whereby the said crank pin is
prevented from pressing unduly on the slot G in the lever A and, secondly, it
forms a means in conjunction with an adjustable stop on the releasing lever N,
see Figure 2A, or with a stop Q' on a separate lever or link Q2, shown in dotted
lines in Figure 1, which can be thrown back out of the way when not required
as shown in full lines in the same Figure, whereby the shutters can be held open
any required length of time by means of the releasing lever N when a long exposure
is desired.
Another part of our invention consists of improved means of guiding the two
shutters in their horizontal movements to and from each other. Instead of the
shutters A A sliding in grooves made in the upper and lower parts of the lens
mount, we arrange them to slide at their upper or lower ends on a guide rod or
spindle R placed either at the upper or lower part of the lens mount, and we leave
them free at their other ends, the points of connection B4 B of the actuating
levers B B, with the sliding shutters A A', being preferably placed near the afore-
said guide rod or spindle R. By these means the possibility of the shutters jamming
in their guides is avoided.
In the drawings, S represents the frame or case in which the shutters and their
actuating levers are mounted, and T the front or cover plate of same.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what
we claim is
First In photographic lens shutters of the kind herein before referred to, the means
for causing the said shutters to open quickly, to remain wide open for a definite length

page_text: of time, and then to close quickly, as herein before described, and illustrated in the
Drawings hereto annexed, and for the purpose specified.
Second-The use, in connection with levers actuating photographic shutters of the kind
herein before referred to, of curved slots in each of such levers, the said slots being so
placed that one and the same actuating crank pin takes into both slots, and so formed that
the crank pin acts upon the sides of such slots to effect the quick opening and closing
of the shutters during small portions of its partial revolution, and is free to traverse
concentric or other suitably shaped portions of such slots during a larger portion of
such partial revolution without effecting any movement of the shutters, as herein-
before described, and illustrated in the drawings hereto annexed, and for the purpose
specified.
Third Mounting and guiding the upper or lower ends of the sliding shutters on a
guide rod or spindle R and leaving the opposite ends free as herein before described,
and illustrated in Figures 2, 3 and 4 of the drawings hereto annexed.
Dated this 11th day of December 1889.
T. R. DALLMEYER.
F. BEAUCHAMP.
Per W. H. Beck,
115, Cannon Street, London, E.C, Agent.