IMPROVEMENTS IN HOLOPHOTAL PROJECTORS OR APPARATUS FOR PROJECTING CONCENTRATED LIGHT
Year: 1885

page_text: Projecting Concentrated Light.
I ROOKES EVELYN BELL CROMPTON of Mansion House Buildings Queen Victoria
Street in the City of London Engineer do hereby declare the nature of the said
invention for IMPROVEMENTS IN HOLOPHOTAL PROJECTORS OR APPARATUS FOR
PROJECTING CONCENTRATED LIGHT to be as follows:-
Hitherto considerable difficulty has been found in supporting or suspending the
larger costly mirrors or composite lenses used for concentrating the rays of an
electric or other lamp and projecting them into a more or less parallel beam, it has
been found necessary to secure these mirrors or rings on elastic supports so they
may not suffer injury from vibration or external shocks, more particularly from
those caused by the discharge of heavy guns.
Blocks or rings of india rubber which have been used heretofore, do not possess
sufficient elasticity for the purpose and moreover present the disadvantage that
vulcanized rubber has a tendency to decompose under the heat of the lamp, and
injuriously effect the silvering of the mirror I therefore suspend the mirror on a
large number of metallic springs, I secure these springs to a moveable ring, and
I form them in such manner that their elasticity enables them to yield to shocks,
whether applied more particularly in a direction parallel to that of the optical axis
of the mirror or ends or in any direction in a plane at right angles to that axis-
In order to compensate for the weight of the mirror, I arrange the springs closer
together at the lower part of its circumference, than at the upper part―The form
of the springs may either be that of a series of Z shaped pieces of steel phosphor
bronze or other suitable material, one end of which is formed to clasp the edge
of the mirror, and the other end is screwed down to the moveable ring above
mentioned, or I sometimes make a moveable ring in 2 or other suitable number of
parts and use short spiral springs bedded in suitable recesses in these two or other
number of parts, to resist all shocks parallel to the optical axis of the mirror, and
I arrange other and separate springs to resist tangential shocks.
In place of spiral springs other equivalent forms of metallic springs may be
employed as found most convenient to the particular construction.

page_text: Projecting Concentrated Light.
I ROOKES EVELYN BELL CROMPTON of Mansion House Buildings Queen Victoria
Street in the City of London 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:-
...
My invention relates to means of supporting the larger costly mirrors or
composite lenses used for concentrating the rays of electric or other lamps, and
projecting them into a more or less parallel beam.
Hitherto these have been supported on india rubber blocks or rings; but these
rings are not elastic enough to secure perfect safety, and the vulcanised rubber has
a tendency to decompose under the heat of the lamp, which also causes tarnishing
of metallic mirrors.
.+
* I therefore suspend the mirror on a large number of metallic springs fixed to a
moveable ring or otherwise suitably, supported, and I form these springs in such a
manner that they yield to shocks in any direction. In order to compensate for
the weight of the mirror I arrange the springs closer together at the lower part
of its 'circumference than at the upper part. The springs may be Z shaped pieces
of phosphor bronze, steel, or other suitable material, one end being formed to clasp
the mirror while the other is fixed to the moveable ring or equivalent support above
mentioned,
I sometimes make the moveable ring in two or more parts, and use short spiral
springs bedded in suitable recesses in these parts. These springs take any shocks
along the axis of the mirror, and I arrange other springs to take side shocks.
Instead of spiral springs, any suitable form may be used for the springs.
In the accompanying drawings a in Figs. 1 and 2 is the mirror, it is supported
by the metallic springs c, c which are fixed at one end to the moveable ring b, b,
while the other end d, d'clasps the edge of the mirror.
Figs. 7 and 8 shew'enlarged views of one spring.
Figs. 3 and 4 shew springs arranged to take end shocks.
spiral springs and 6 part of the moveable ring.
a is the mirror ff two
In Figs. 5. and 6 an arrangement of spiral springs for taking up side and front
shocks is shewn. a is the mirror and g is one of a series of part rings co-operating
with a ring i under the holding pressure of a screw i¹ to form a screw clamp for
holding the mirror a in its position. The clamp is, held by the spring h fastened
to the moveable ring b. The front portions of the clasps g of course only obscure
a portion of the mirror here and there.
When the moveable ring is taken off the lamp the mirror may come away with
it. This allows the mirrors to be easily and safely changed, and protects them
from shocks due to firing guns or other jars. My method is of course, equally
applicable to the support of lenses of lamps of various descriptions.
1

page_text: 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. In an electric lamp or holophote supporting the lenses or mirrors on metallic
springs, substantially as set forth.
2. In an electric holophote or search light supporting the mirrors by means of
elastic metallic supports.
3. In an electric holophote or search light, connecting the mirror or lens or lenses
by means of elastic metallic springs to a moveable ring.
4. Mounting lenses or mirrors for electric lamps substantially as set forth.
Dated this 7th day of July 1886.
W BROOKES & SON,
Agents for the said Rookes Evelyn Bell Crompton.