IMPROVEMENTS IN GLASSES OR LENSES FOR PAVEMENT AND OTHER LIGHTS
Year: 1881

page_text: LETTERS PATENT to Andrew McLaren, of Upper Thames Street, in the City of
London, Ironfounder, for an Invention of "IMPROVEMENTS IN GLASSES OR
LENSES FOR PAVEMENT AND OTHER LIGHTS."
PROVISIONAL SPECIFICATION left by the said Andrew McLaren at the
Office of the Commissioners of Patents on the 26th July 1881.
ANDREW MCLAREN, of Upper Thames Street, in the City of London, Iron
Founder. "IMPROVEMENTS IN GLASSES OR LENSES FOR PAVEMENT. AND OTHER
LIGHTS."
This Invention consists in forming a lenticular or double convex lens with a
plane surface for receiving light, and a plane concave combined for dispersing and
diffusing light.
:
The accompanying Drawing shows the Invention clearly. a is the plane for
receiving the light; b, the convex surface; and c, the curve on the lower edge of
the prism for reflecting it, the portions b and c reflecting and dispersing the rays of
light in a more equable manner than has been done with prisms as hitherto made.
The curve c on the lower edge is an important feature, as it conveys the rays of
light from it in a radial manner and so distributes them that a greater space is
illuminated from the convex face and under the prism than has been found
possible with reflectors hitherto made.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Andrew McLaren in the Great Seal Patent Office on the 26th January
1882.
ANDREW MCLAREN, of Upper Thames Street, in the City of London, Iron
Founder. "IMPROVEMENTS IN GLASSES OR LENSES FOR PAVEMENT AND OTHER
LIGHTS."
The object of this Invention is the formation of pavement and like lenses or
prisms by moulding (with or without pressure) fluid glass with rounded front
surface and rounded bottom edge, in order to obtain a better concentration of light
therein and a maximum of reflection therefrom; also a better and wider spread
diffusion of rays than by the flat sided and square bottom edged lenses now used.
The front surface of my lens is of convex shape, and tapers from the stock to the
bottom edge, which is also convex, the back of the lens or prism being plane, but
set at an angle from the shoulder, so that a reverse reflection of light is diffused
in the opposite direction to that from the front, in consequence of which the
portion of light which is concentrated in the lens of present construction and is
therein held, is by my Invention deflected at angles from one face different to the
angles of deflection from the opposite face of the lens, a further distribution of
light taking place radially from the lower edge, which is curved or of convex
shape.
The annexed Sheet of Drawings clearly represent my Invention at Figures 1
and 2, which show respectively a side and a frout elevation, Figure 3 showing a
series of my lens in a frame, such as is fitted in pavements for lighting up cellars
or underground rooms to enable gas light to be dispensed with in the day time.
A is the tread or stock; B, the shoulder; C, the front face with a projecting
lip D, giving great thickness at the upper portion where the arc of concentration
is formed, and to ensure a diffusion of the whole of the light so concentrated
through the lower thinner portion of varying degrees of intensity according to the
diminishing thickness to the lower edge E, where a further distribution of rays
radially downward escape.
I am aware that plane surfaced lens with a great thickness at the upper part
and a tapering to the lower with the angle on one or on both sides for the
concentration and diffusion of light in underground rooms have been used, I
therefore make no claim to such lens, but having described the nature of my
said Invention 1 do claim,--
The rounded front faced and rounded bottom edged lens, as shown in the
annexed Drawings, whereby is obtained a more precise concentration of light and
a greater diffusion varying in intensity with increased brilliancy, as described.
In witness whereof, I, the said Andrew McLaren, have hereunto set my hand
and seal, this Twenty sixth day of January, in the year of our Lord
One thousand eight hundred and eighty two.
ANDREW MCLAREN. (L.S.)