Year: 1889

page_text: Ο
through the former, and to rotate, the spin lle n is perforated as shewn in Fig. 3. The
perforation is large enough to permit the spindle n to swing on its axis and this
pendulous motion is caused by the lever whose travel in either direction is limited
by suitable means. The lever o can he acted upon by hand or by pneumatic pressure.
In the latter case the lever o carries a plate o' placed at the rear of the casing B
(see Figs. 2 and 4). Under this plate in a recess in casing B a small rubber ball is
placed which by a rubber pipe s is connected with a larger ball held by the operator.
When pressure being exerted upon the large ball some of the air it contains is forced
into the small ball under the plate o' and this ball is expanded the plate o' will be
raised and the spindle n turned by the lever o. A spiral spring p surrounding the
spindle maintains the latter in its position of rest or brings it into the same.
The spindle has on that side which is turned towards the lever a two notches n¹n²
the bottom surfaces whereof are inclined as shewn in Figs. 6 to 7". Corresponding
with these notches the pins 9 and are provided on the lever a the former being
fixed as to the length projecting beyond the lever the latter being adjustable by the
following arrangement. A sleeve t firmly connected with the lever a encloses the
pin as well as a helical screw surrounding the same. Above the sleeve t a
stud projects from the pin a slot being provided in the sleeve t for its
accommodation. So long as the stud 2 bears on the edge of the sleeve t as shewn in
the drawing, the pin projects but little above the lever a. When it is to project
further the pin is so turned that the stud can enter the slot and permits the
spring to push the pin » forward.
יז
The operation of the device is as follows.
The action of this shutter is as follows:-supposing the shutter plates A and A' to
be in their position of rest and lever a in the position shewn in dotted lines in Fig. 1
the rubber or wire spring not being connected with the lever a but to the two
studs and consequently inactive, and the entire device placed upon the mount of
the lens.
'
Now if the lens is to be focussed the shutter must be entirely opened. This is
effected by placing lever a in a horizontal position because it will thien have so moved
the plates A A that their two apertures and the aperture in casing B are coincident
the lens being uncovered. When lever a is in this position the slot e¹ in the brake
disc e is exactly before the slot of the spring barrel d. If the pin m is now so
turned that the lug m engages with the two slots de¹ the disc e is retained in its
position and this spindle together with lever a and the plates A A' is also fixed.
When the object is focussed pin m is raised and the spiral spring e carries the lever a
and plates A A¹ back to their normal position.
The position of notches n¹ and n² of the spindle n shown in Fig. 6 and 6* is that
which they assume when the spindle is in its position of rest whilst the position of
pins and shewn in dotted lines in these figures corresponds to the position of rest
of lever a.
1
"
If the shutter is to be used for instantaneous work, the pin r remains in its "short"
position as shewn in Fig. 6. The lever a is moved from the position shown in dotted
lines into that shown in full lines. The pins 7 and in this operation pass the
notches n¹ and n² of spindle n. Now whilst pin freely passes through the notch n²
the pin finds an obstacle in the inclined. bottom of the notch n'. The spindle »
being capable of rotation the said inclined surface yields to the pressure exerted upon
it by the pin so that the latter passes along it. As soon as pin 7 has passed the
edge of the notch ¹ the pressure exerted upon spindle n ceases and spring p carries
it back to its normal position. The positions now occupied by pins q and relatively
to the notches n¹ and n² are shown in full lines in Figs. 6 and 6". The lower edge of
notch n bears against the pin 9 as in Fig. 6ª. This fixes the shutter in that position
in which it is ready for work. If now lever o is raised and the spindle n turned until
the notch n takes the position shown in Fig. 7" the shutter plates are released and
the spiral spring carries them back to their position of rest. In this movement the
apertures will be brought into conjunction and the lens is uncovered for a moment.
If the motion of the plates A A¹ is to take place somewhat less rapidly so as to

page_text: permit a longer exposure the nut g' is turned towards the right and thus the brake
blocks fare slightly pressed against the brake disc e. This increases the resistance to
be overcome by the spiral spring c and consequently reduces the rapidity with which
it can operate the lever a and plates A A. It follows that, the slower the motion of
the plates A A' is to be, corresponding to longer exposure, the more firmly must the
brake blocks ff be pressed against the brake-disc e.
If on the other hand the movement of plates A A¹ is to he still more rapid so as
further to shorten the exposure, or if spring c is not to be, used, say because it is
broken, then the stud a' on lever a is connected by the rubber spring i, or the spiral
spring, see Figs. 1 and 1" with the stud in the casing B. If now the spring i
(or) works in conjunction with spring c the movement of the plates A A' is more
rapid and the exposure shorter, when however spring i (or 1) is used alone the rapidity
will be approximately the same as if spring c is used alone.
As the lever a in order to operate the shutter has only to describe an arc of 80° the
time and power to effect this motion are reduced to a minimum and they are
appreciably less than with other mechanical shutters.
If the apparatus is to be employed as a shutter for longer exposures the pin ŕ is so
turned that the part passes into the slot and allows spring to propel the pin r
so that it projects beyond lever a as shown in Fig. 7. If the lever a is then brought
into the position shown in Fig. 1 and the spindle is turned by lever o so as to
release the lever a, the bottom face of the notch n' assumes the position shown in
Fig. 7 and notch that. shown in Fig. 7. Notch allows piùy to pass freely
whilst the upper edge of notch n prevents the pin ", which now projects, moving
further and thus stops the entire mechanism. This stoppage takes place at the
moment when the apertures of the plates A A are in line with that of the casing B
thus uncovering the lens. The exposure continues as long as spindle n remains in the
position shown in Figs. 7 and 7*. Only when the power acting on lever o. is removed
does spindle n return into the. position of rest. Then the bottom of notch n² again
resumes the position shown in Fig. 6 permitting all the parts to return to their
position of rest.
In shutters with two plates, like the one shown in the drawings the apertures in
the plates are always circular as shown in Fig. 1 consequently the exposure cominences
at the centre of the image and terminates there so that the sharpest definition is
always in the centre of the field whilst it should be in the foreground of the picture
which is not always in the centro of the plate.
Now in order to enable the longest exposure to be given to the foreground of the
picture, in whatever part of the field it may be, the following improvement is applied
to the plates A A'. When the foreground of the picture extends along a strip of even
width across the centre of the field vertically or horizontally, then the apertures in
the plates are made equilateral as shown in Fig. 9. This Fig. shows the plates in
the position which they assume both at the commencement and at the end of the
exposure.
If the strongest exposure is to extend horizontally across the picture the shutters
are placed parallel to the height of the same. If the longest exposure is to be along
the height of the picture the shutters are placed horizontally. In a similar manner
the longest exposure may be directed to any desired portion of the picture by variation
of the position of the shutters hereinafter referred to.
If the longest exposure in order to correspond to the foreground is to be brought
near one edge of the picture the apertures are made triangular see Fig. 8. If it is
to extend in a strip to about half the height or width of the image and is to decrease
somewhat beyond that the shape shown in Fig. 10 consisting in a combination of a
semicircle and a rectangle is adopted for the apertures of the shutter plates.
In the Figures S, 9 and 10 the dotted lines show the length and arrangement of the
plates when provided with two apertures as is required for stereoscopic views. It
will be understood that in such cases the casing B will be similarly extended and
fitted with a second aperture whilst the remainder of the construction is not altered.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed as communicated to me
by my foreign Correspondent I declare that what I claim is :-
1
1. In shutters for photographic lenses the mechanism for covering and exposing
the lens by the movement of two shutter plates A A¹, consisting substantially in a
lever a with spindle band spring c with spring barrel d.
2. The mechanism for increasing or decreasing the rapidity of motion of the
shutter plates, consisting of the brake-disc e the brake blocks ff the screw g and
nut g¹.
3. For keeping the plates A A' in position to permit focussing the pin m with
lug m' and the slots de in the spring barrel d and brake disc e.
4. The mechanism for controlling the motion of the shutter plates, consisting of
the spindle with notches n¹ n² lever o and spring p, together with pin q on lover a
and pin with spring and projection or stud moving in the sleeve t having a
slot t².
5. The rubber spring i, or the helical spring / serving to further the action of
spring c, or to replace the latter, as set forth.
6. The shutter plates adapted for giving increased exposure to the foreground by
making their apertures in the shapes shown in Figs. 8 and 10 as may be required.
Dated the 28th day of September 1889.
NEWNHAM BROWNE.