IMPROVEMENTS IN PHOTOGRAPHIC APPARATUS
Year: 1885

page_text: I BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent do hereby
declare the nature of the said Invention for IMPROVEMENTS IN PHOTOGRAPHIC
APPARATUS a communication to me from abroad by Ferdinand Denis of Villefranche-
sur-Saône in the Department of the Rhône in the Republic of France, Clock
Maker to be as follows:-
This Invention has for its object to obtain in photographic apparatus instantaneous
focussing and automatic fixing.
In these apparatuses, the front of the dark chamber carrying the lens is fixed to
the horizontal board serving as support, the back carrying the glass or screen is
fixed to a slide running upon the same horizontal board, this slide is ordinarily
manipulated by a pinion running on a fixed rack.
After having found the focus, the slide is fixed with a binding screw.
With this system the focussing is very uncertain on account of the play necessary
between the rack and the pinion, the fixing of the slide is not always effected at
the exact focus which is sometimes attained only after long and difficult trials.
To remedy this defect the rack is, according to the present invention, replaced
by a screw with triangular threads mounted between points in such manner as to
be capable of turning upon its axis without having the least play in a longitudinal
direction.
The slide carries a half nut which is caused to bear upon the screw by the
pressure of a spring and which can be removed from it by a pressure exerted by
the hand upon a button.
The slide is further transformed into a carriage by the addition upon its sliding
sides of three pulleys with angular profile rolling horizontally in grooves of similar
form worked in the horizontal board.
Two of these rollers placed on the same side of the slide have their axles fixed,
the third which is opposite to them is pushed by a spring. This arrangement
neutralizes the effects of all wear or expansion and preserves to the carriage a very
easy motion without any play either lateral or vertical.

page_text: For obtaining the focus, the half nut is pushed back by pressing upon its button,
and at the same time the carriage is moved by hand to the desired point where it
is simply left; the half nut then again applies itself to the screw, and the carriage
remains fixed at the desired point with a variation which cannot exceed the half
of the screw thread which is also very fine. If desired the carriage can be caused
to return to this exact position by causing the screw to turn a small distance in the
proper direction.
COMPLETE SPECIFICATION.
Improvements in Photographic Apparatus.
I BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent, do hereby
declare the nature of this invention, a communication to me from abroad by
Ferdinand Denis of Villefranche-sur-Saône in the Department of the Rhône in the
Republic of France Clockmaker, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :—
This Invention has for its object to obtain in photographic apparatus instantaneous
focussing and automatic fixing.
In these apparatuses, the front of the dark chamber carrying the lens is fixed to
the horizontal board serving as support, the back carrying the glass or screen is
fixed to a slide running upon the same horizontal board, this slide is ordinarily
manipulated by a pinion running on a fixed rack.
After having found the focus, the slide is fixed with a binding screw.
With this system the focussing is very uncertain on account of the play necessary
between the rack and the pinion, the fixing of the slide is not always effected at
the exact focus which is sometimes attained only after long and difficult trials.
To remedy this defect the rack is, according to the present invention, replaced
by a screw with triangular threads mounted between points in such manner as to
be capable of turning upon its axis without having the least play in a longitudinal
direction.
The slide carries a half nut which is caused to bear upon the screw by the
pressure of a spring and which can be removed from it by a pressure exerted by
the hand upon a button.
The slide is further transformed into a carriage by the addition upon its sliding
sides of three pulleys with angular profile rolling horizontally in grooves of similar
form worked in the horizontal board.

page_text: Two of these rollers placed on the same side of the slide have their axles fixed,
the third which is opposite to them is pushed by a spring; this arrangement
neutralizes the effects of all wear or expansion and preserves to the carriage a very
easy motion without any play either lateral or vertical.
For obtaining the focus, the half nut is pushed back by pressing upon its button,
and at the same time the carriage is moved by hand to the desired point where it
is simply left; the half nut is then again applied to the screw, and the carriage
remains fixed at the desired point with a variation which cannot exceed the half
of the screw thread which is also very fine. If desired the carriage can be caused
to return to this exact position by causing the screw to turn a small distance in
the proper direction.
And in order that the said invention may be more clearly understood and readily
carried into effect, I will proceed aided by the accompanying drawings more fully
to describe the same
Figure 1 is a longitudinal section through the axis; Figure 2 is an underside
view; Figures 3 and 4 are cross sections drawn respectively on the lines 1. 2. 3 and
4 and 5 of the plan.
The same letters of reference indicate like parts in all the figures.
The carriage slide A rolls upon the sides B B¹ of the framing by means of three
Vor bevelled edged rollers running in channels of similar form made in the
sides B, B¹.
Two of these rollers C, C¹ have their axes fixed upon the carriage, whilst the
third, D, which is opposite to them is mounted in a carrier E, oscillating around
the pivot F; a spring G acting upon an arm H fixed solidly with this carrier tends
to press the roller against the side B' of the framing in such manner as to prevent
all shaking either laterally or vertically of the carriage and to neutralize the effects
of all kinds of wear and of expansion whilst at the same time preserving entire
freedom of movement.
The axes of these rollers are further mounted upon pivots as shown at Figures 3
and 4.
A triangular threaded screw I traverses the framing and the carriage slide; it is
fixed to the framing by the supports L, L, in one of which is placed a screw J, the
point of which penetrates into a circular groove of the screw in order to prevent
all play in the direction of the length.
The screw freely traverses the carriage without touching it, and is only fixed
thereto by two half nuts O, O¹, carried by spring arms N, N¹, which tend to apply
them with sufficient force upon the screw so that the carriage is fixed in an invari-
able manner the triangular threads of the screw never being capable of having any
play in the half nuts, the perfect contact of which is ensured by the springs.
In order to displace the carriage it is only necessary to separate the half nuts
from the screw, this result is obtained by pressing upon the button M which by
means of the cranked piece P bears upon the lever R which acts directly upon the
square S, fixed to one of the spring arms N₁ which carries the half nut O¹, this
latter will therefore be separated from the screw and will carry its neighbour with
it by means of a small pin V which is fixed to it.
The button M, works in the interior of an envelope or container X which is
siezed between the thumb and the finger by the middle whilst the index finger
presses upon the button, the operator will therefore after having liberated the
carriage from the screw be able very readily to conduct it by hand to the precise
point it should occupy, then to fix it invariably by liberating the button M, which
effects the immediate application of the half nuts upon the screws.
When a further slight adjustment is required, this may be obtained by slightly
turning the screw in the proper direction by means of the button I¹.
It will be understood that the screw can be replaced by a fixed shaft of any
suitable form carrying upon its entire length regular grooves or recesses with

page_text: which would engage brasses with grooves or recesses of similar form which would
replace the half nuts.
The dimensions and the arrangements of detail of these apparatus will necessarily
vary with those of the dark chambers to which they will be applied, but they may
be modified for each particular case without changing the principle thereof.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. In the focussing mechanism of photographic apparatus mounting the carriage
slide with rollers having a V or bevelled edged profile of any suitable angle
substantially as herein shown and described and for the purpose stated.
2. In the focussing mechanism of photographic apparatus the arrangement of
one or several of these rollers placed opposite to the others working upon moveable
axes, pressed by springs and serving as above described to obviate the effects of all
kinds of wear and of expansion and to neutralize all lateral or vertical play in the
motion of the carriage substantially as herein shown and described.
3. Automatic, instantaneous and absolute fixing of the carriage by the screw or
grooved shaft as soon as the button which is the organ of connection and discon-
nection is released substantially as herein shown and described.