AN IMPROVED ILLUMI- NABLE DIAL-PLATE APPLICABLE TO NIGHT-CLOCKS, MARINE COMPASSES, AND OTHER SIMILAR OBJECTS
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Thomas James Smith at the Office
of the Commissioners of Patents on the 16th December 1878. (A communica-
tion from abroad by Charles Desprez, Watch and Clock Maker, at present
residing at 23, Boulevard de Strasbourg, Paris, France.)
THOMAS JAMES SMITH, of the Firm of Robertson, Brooman, and Company, of
166, Fleet Street, in the City of London, Patent Agents. "AN IMPROVED ILLUMI-
NABLE DIAL-PLATE APPLICABLE TO NIGHT-CLOCKS, MARINE COMPASSES, AND OTHER
SIMILAR OBJECTS." [A communication from abroad by Charles Desprez, Watch
and Clock Maker, at present residing at 23, Boulevard de Strasbourg, Paris,
France.]
This Invention relates to a transparent dial-plate illuminated by means of a light
concentrated in the interior of a clock case, compass box, or other apparatus
having an indicating needle or hand, and which is required to be illuminated at
night.
By this means the light does not show or appear outside the case, all that is seen
are the figures on the dial and the indicating needle or hand.
By way of example, and to enable the Invention to be easily understood, this
system will now be described as applied to a night-clock.
The clock is composed of a box closed on all sides, in which the light is placed.
This light may be furnished by a spirit-lamp, a night light, a candle, or other means.
The front part is formed of an opaque dial-plate, but the figures marked on its
circumference and the indicating needle or hand are transparent, whereby when the
clock is lighted up they are rendered visible.
There are no mechanical parts between the dial and the light, the box or case
only containing the lamp or candle, the command of the hour hand or needle being
effected by the intermediation of wheels concealed in one of the supports of the
clock, operated by barrel mechanism in the base.
According to this Invention the clock is composed of a conical box, preferably tin,
having a reflector at its rear, reflecting the light from the lamp onto the dial forming
the front side of the box.

page_text: The lamp or other source of light is removable in the box, but when it is in place
its light is entirely invisible outside.
In the case of a fixed clock or apparatus a gas-jet may be employed for lighting,
a chimney being provided for the escape of the smoke.
The box is supported by two feet fixed to a base; the latter supports a pivoted
bracket terminated by a flat piece or stand for the lamp to rest on when the latter
is introduced into the box.
The dial plate is composed of a glass disc on which the figures are formed by
applying an opaque coat of black paint to the interior of the dial, and leaving the
figures intact; thus the figures alone remain transparent. Any other kind of
opaque dial with transparent figures, or a transparent dial with opaque may be
employed.
The central part of the glass disc is not of itself opaque but it appears so in
consequence of the super-position of a second disc, which is opaque in its centre, a
transparent hand or indicating needle being reserved.
The circumference of this latter disc is transparent so as not to hide the figures
marked on the dial-plate or first disc.
The second disc constitutes the movable hand or indicating needle of the clock; it
may be in front or at the back of the dial plate.
It is provided with teeth on its periphery and operated or put in motion through
the intermediation of wheels by means of a barrel-wheel arranged in the base. The
intermediary wheels are concealed in one of the feet. Any other mechanism
however may be employed, for operating the hour hand.or needle. In the applica-
tion of this Invention to marine night-compass boxes the light is reflected under
the horizontal dials.
The shape, materials, and dimensions of the constituant parts of this system may
be varied to suit the different purposes to which it may be applied.