Improvements in or connected with Field Glasses.
Year: 1896

page_text: Date of Application, 28th Apr., 1896-Accepted, 30th May, 1896
COME LEIE SIECIFICATION.
Improvements in or connected with Field Glasses.
A communication by EMILE TOUSSAINT, of 4 Mariannenplatz, Berlin, in the
Empire of Germany, Mechanic.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of 'The Agency for
Foreign Patent Solicitors 6 Lord Street, Liverpool, and 6, Bank Street,
Manchester both in the County of Lancaster, 118 New Street, Birmingham in the
County of Warwick, and 322 High Holborn in the County of Middlesex, Civil
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:-
This invention has for its object an arrangement for suddenly increasing the
degree of magnifying power without necessitating the glass being removed from
the eyes in such field glasses as are more particularly used for military observations,
as well as by tourists and sportsmen.
The arrangement consists in a convex glass being inserted ordinarily in front of
each of the two oculars of the field glass, so that the magnifying effect produced
by the oculars is diminished, and by a mechanism being arranged which by means
of one and the same grip of the hand moves aside the convex glasses placed in
front of the oculars, and simultaneously pushes forward the objectives to an
extent which equals the difference of the focal distance of the objective alone, and
the focal distance of the combination of the objective and the convex glass
inserted in front of its respective ocular.
In the accompanying drawings
Figure 1 shows an elevation of the field glass when shut up, one of the oculars
being shown in section with the convex glass inserted in front of it;
Figure 2 is a horizontal section on the line - of Fig. 1.
Figure 3 shows one half of the field glass with the adjusting device when the
convex glass is moved aside, and the objectives pushed forward; separate
important parts are shown in section;
Figure 4 a horizontal section of Figure 3;
Figure 5 is a section of the whole adjusting mechanism;
Figures 6, 7 and 8 are details.
a are the oculars, o the objectives, p are the convex glasses which are moved in
and out.
The screw of the set screw b connected with the framework or setting of the
eye glasses a, is mounted on a bexagonal sheath or holder c, Figs. 3, 5 and 6, the
inner hollow space of which has a circular section. In this hollow space a round
spindle d, Figs. 5 and 6, is mounted which is connected with the sheath c by
means of a pin e in such a way that it is displaced longitudinally together with the
latter, whilst short diametrical slots f (Figs. 2 & 4) in the sheath c allow a small
independent rotation of the spindle d. The latter is slotted from its lower end to
a length corresponding to the maximum displacement of the ocular a, and through
this slot g, (Figs. 5 and 6) a pin h projects, which pin lying transversely is
attached to a tube k revolubly mounted in the bridge. This tube carries a
knob l, Fig. 7.
If the tube k be turned by means of this knob it carries with it by means of
the pin the spindle and also the pin e attached to the latter. The two ends of

page_text: this pin engage in the socket m of a two armed lever n', n', Fig. 2, revoluble on
the upper rounded end of the hexagonal sheath or holder c mounted in the
bridge, and cause this lever n', n' to swing in one direction or the other according
to the direction of rotation of the handle.
This two armed lever n', n², oscillates within the bridge ¹, (Figs. 2 and 3)
which is suitably hollowed out, and projects with the flat widened ends of its two
arms into the tubes r carrying the oculars.
Two apertures are formed in each of the flat or plate-like ends of this lever.
In one of these apertures of each arm a convex glass p is inserted, whilst the
second aperture q is free. The outward movement of the lever n', n³, is limited
by the ends of the plate shaped extensions encountering the wall of the tube r¹,
and these plate-shaped extensions are so designed that when the lever is at one
limit of its position, the centres of the two convex glasses p coincide with the
centre lines of the objectives and the oculars, Fig. 1 and 2, whilst in the second
limit position of the lever these centre lines pass through the centre of the
apertures g before-mentioned, Figs. 2 and 4.
9
Each objective o is mounted in a tube which is screwed into the bridge,
Fig. 5, and is adjustable on a tube screwed to the bridge 3. The bridge
carries in the axis of the set screw for the ocular a a tube k which adjusts itself
on the tube k revolubly mounted in the bridge. The tube k¹ is closed below.
A spiral spring s is arranged in the tubes k & k¹, the upper counterstop of such
spring being formed of a ring t soldered or rivetted firmly in the tube k.
The springs has a constant tendency to push forward the tube k¹ and with it
the bridge of the tube and the objective o. This movement is limited by the
outwardly bent front edge y of the tube, Fig. 8, and by an inwardly projecting
projection y' on the tube r³.
The securing of the tube when the glass is shut up takes place by means of
the pin h one end of which projects from the tube k, which pin on the pushing in
of the tube first enters into a groove u, Fig. 3, provided in the bridge, and on
the turning of the small lever or knob and therewith also of the tube k
subsequently, is transferred into a horizontal branch of this groove u.
A flat spring is mounted on the bridge in the slot in which the knob / may
be moved to and fro, which spring prevents any turning back of the small lever
or knob when it is in the position shown in Fig. 3. The objectives o are then
pushed out. If they are to be again pushed in, a pin w attached to the bridge it,
Fig. 3, pushes the spring back in such a way that the knob I can be turned back
again as far as up to the pin w.
The mode of using the field glass hereinbefore described is as follows:-
Assuming that the objectives o are in a pushed in condition, and are secured in
this position by means of the pin engaging in the groove u, by moving into a
suitable position the knob 1, the convex glasses p are thrown into position. The
field glass is therefore in the condition shown in Fig. 1. In consequence of the
refraction again produced by the convex glasses p, the focal distance of
the objective which of itself extends up to the point 1 (Fig. 1) is limited or
shortened to the point 2, and thereby the field of vision increased but simul-
taneously also the absolute magnifying power diminished of itself.
The oculars a are adjusted to the eye by means of the set screw b. If then any
object in the field of vision is to be subjected to a more careful inspection, it is
brought as far as possible into the centre of the field of vision, and then, by
pressing the finger on the knob l, without removing the field glass from the eye,
the knob is turned into the position shown in Figure 3, when the lever n n
makes, in the manner herein before described, such a movement that the free
apertures take the position of the convex glasses p and simultaneously the
fasteningu is released, that is to say, the compressed spring s is released and
thus the objective o is thrown forward."
The extent of this forward throw (Figure 3) is equal to the distance apart of
the two focal distances 1 and 2, so that the field glass then acting with full

page_text: magnifying effect remains in focus with the eye and allows the object in question
to be immediately inspected more distinctly.
Having now particularly described and ascertained the nature of the 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. A field glass with adjustable magnifying power, characterised by a lesser
magnifying power (which affords a larger field of vision) being produced by
means of oculars (a) whose power is weakened or diminished by convex
glasses (p) placed in front of them and by a stronger magnifying power being
produced without removing the field glass from the eye, by turning a small lever
or knob (1), which simultaneously moves aside the said convex glasses (p) and
causes the objectives (o) to be pushed out to an extent (2) which equals the
difference of the focal distances of the objective alone and of its combination with
the convex glass (p) inserted in front of the ocular, substantially as described.
2. A field glass of the kind described, in which the objectives (o) are secured in
their projected position by means of a flat spring (v) which springs up behind the
small lever or knob (1) serving for moving aside the convex glasses (p) and for
releasing the spring (s) which pushes forward the objectives, whilst on the field
glass being shut up, said spring is pressed on one side by means of a pin (w) fixed
in the bridge () carrying the objective tube (3), whereby the knob (1) is again
released, substantially as described.
3. The construction and combination of parts taken as a whole, forming the
improved field glass, substantially as hereinbefore described and illustrated.
Dated this 27th day of April 1896.
WM. P. THOMPSON & Co.,
Agents.