Improvements in Telescopic Fronts and Objectives for Optical Lanterns.
Year: 1887

page_text: Improvements in Telescopic Fronts and Objectives for Optical
Lanterns.
ALFRED WRENCH, 39 Grays Inn Road, London W.C., Optician, 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:-
My invention consists of an improved combination telescopic front for optical
lanterns and is constructed so that the tube which carries the lenses called the objec-
tives may be moved to any desired position to suit lenses of various focus--by means
of rackwork adjustments. I first make a wide ring provided with a bridge hearing,
and pinion-the ends of the pinion having suitable millheads to turn it by, this com-
bination is called a jacket (No. 1) and into this jacket I slide a tube provided with a
suitable rack which gears into the before named pinion, at one end of this tube I fix
a jacket (No. 2) and I make a second tube (No. 3) with a rack and a jacket fitted to
it to slide into No. 2 tube. Into this tube and jacket (No. 3) I slide a third tube with
a rack only fixed to it (No. 4) and into this tube I fit a barrel (containing the lenses
which may be of any suitable combination) having at its front end a pivotted plate or
shutter of the usual description. The jacket No. 1 has a suitable screw thread at one
end to scrow it into the front of the lantern and the length of the jacket is preferably
one inch. The tube and jacket No. 2 is preferably 4 times the length of No. I and the
tube No. 3 is increased in length and amount equal to the length of its jacket. The tube
No. 4 is also the amount of a jacket longer than No. 3. It will be seen that when placed
together i.e. the various tubes slid inside each other, the total length is only that of the
tube No. 4 but when extended (or racked out) the total length is about three times
that of tube No. 4. Referring to the drawings,
Fig. 1 is a plan of the jacket No. 1. Fig. 2 plan of tube and jacket No. 2. Fig. 3
plan of tube and jacket No. 3. Fig. 4 plan of tube No. 4. Fig. 5 an elevation of
the barrel. Fig. 6 front elevation of the complete telescopic front Figs 7 and 8 are
plans of the complete front open and closed. Figs. 9 & 10 are elevations of same.
A. A. A. are the millheads and pinions, BBB are the racks, CCC the jackets,
DDD the tubes. E is the barrel with its shutter F. GGG are the bridge pieces
to hold the pinions A. A A.

page_text: Although I employ 3 rackwork tubes to form my improved combination front it is
obvious that 2 or any larger number might be employed without departing from the
nature of my invention. I am also aware that a telescopic front with one rackwork
objective, and that a barrel to slide into a single rackwork objective is not new, but
my invention of two or more rackwork tubes in combination forming a telescopic front
is new.
Having now particularly described and ascertained the nature of my said Invention,
and in what manner the same is to be performed I declare that what I claim is,
1st. In a telescopic front for optical lanterns the combination of a jacket and two
or more tubes, each with a rack and pinion adjustment forming a telescopic lantern
front substantially as described.
2nd. The combination of two or more tubes with rackwork adjustments and an extra
tube with a rack arranged for the barrel E to fit into it.
3rd. The general combination forming my improved telescopic front for optical
lanterns substantially as described.
ROBERT A. LEE,
76, High Holborn, London, W.C.,
Agent for Applicant.