Improvements in Reflectors for Bicycle Lamps and other sources of Light.
Year: 1898

page_text: Date of Application, 11th Mar., 1898-Accepted, 1st Oct.,
1898
COMPLETE SPECIFICATION.
Improvements in Reflectors for Bicycle Lamps and other sources of
Light.
I, EDUARD GRUMME, of 14, Hoch Strasse, Nuremberg, in the Empire of
Germany, Metal Goods Manufacturer, do hereby declare the nature of this inven-
tion, and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
In order to reflect in certain directions the rays proceeding from a source of
light, concave mirrors of suitable form arranged behind the said source of light
are usually employed. If, for instance, as in the ordinary projectors, the rays of
light are to be reflected approximately parallel to the optical axis, the reflecting
surface must be formed as a paraboloid, whilst if the reflected rays are to diverge,
an hyperboloidic concave mirror must be used. The manufacture of such concave
mirrors offers as is well known many difficulties not yet overcome more par-
ticularly as regards the hyperboloidic glass surface.
This invention has for its object to obtain the same action, that is to say the
reflection of the rays of light in suitable directions by means of a reflector which
can be easily made by the usual appliances employed in the manufacture of
optical glasses.
It has been found that a periscopic lens arranged behind the source of light
and coated on its rear side, that is to say the one turned away from the light,
with a reflecting substance, fulfils this object. Such a reflector acts as a lens
on the side turned towards the light, that is to say the rays of light falling on
the inner (concave) surface, are generally, in accordance with the known law,
broken and fall on the coated (convex) surface which acts as a mirror which
reflects the rays thus diverted, the rays which strike the lens at right angles
passing of course through it unbroken. By a suitable selection of the radii of
the concave and convex sides of the lens as well as of the relative position of the
reflector to the source of light, it is possible, as may easily be seen, to reflect
the rays of light, reaching the reflector from the source of light, at a suitable
angle, that is to say at an acute angle to the optical axis or parallel to the same.
In the accompanying drawings, Figures 1-3 are diagrammatic representa-
tions of three examples of the application of the invention.
In Figure 1 the proportion of the radii is about 20 to 10, and the reflected
rays S consequently diverge. In Figure 2 the proportion is about 20 to 13
whereby parallel reflected rays are produced, whilst in Figure 3 with a propor-
tion of radii of about 20 to 15 a case is shown where the reflected rays converge.
It is thus possible by means of a periscopic reflector to distribute the rays of
light from a flame if desired over a large surface lying in front or to direct them
in a parallel direction to a far distant point and converging to concentrate them
on a point close at hand, and there results from this an applicability extending
over the widest limits of the reflector for the cases arising in practice."
Figures 4 and 5 of the drawings show as an example the application of this
improved reflector to cycle lamps in which it is a question of illuminating as

page_text: intensely as possible the surface of the ground immediately in front of the wheel.
This object is of course naturally and most completely attained with diverging
rays, and consequently a periscopic reflector A having a concave inner and convex
outer surface is arranged behind the burner of the lamp or rather the illuminating
flame B in such a way that the latter is situated approximately in the geometrical
centre of the concave surface A', the rays are therefore reflected divergently in
the manner shown in Figure 1.
Of course this improved reflector may be employed in combination with any
suitable source of light and kind of lamp.
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:-
1. A reflector for producing rays of light diverging from, converging to, or
parallel with the optical axis, consisting of a periscopic lens the face of which
is turned from the light, is provided with a reflecting coating so that the front
surface of the lens that is to say the one facing the source of light generally
breaks the rays falling thereon, whilst the rear or coated surface reflects the
deflected rays after the manner of a concave mirror, substantially as herein-
before described.
2. A lamp for illuminating a large surface lying in front of it, characterised
by a periscopic reflector (A) such as hereinbefore described being arranged behind
the illuminating flame in such a way that the geometrical centre of the inner
(concave) surface of the lens approximately coincides with the centre of the flame
whereby divergent rays are projected from the reflector, substantially as herein-
before described.
Dated this 10th day of March 1800
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.