An Instrument for Drawing Perspectives of Geometrical Forms.
Year: 1890

page_text: Date of Application, 31st Oct., 1890
Complete Specification Left, 31st July, 1891-Accepted, 5th Sept.. 1891
PROVISIONAL SPECIFICATION.
[Communicated from abroad by PIETRO FIORINI, of Turin, in the Kingdom of
Italy, Engineer.]
An Instrument for Drawing Perspectives of Geometrical Forms.
I, OLIVER IMRAY of No. 28 Southampton Buildings, Chancery Lane in the
County of London, Fellow of the Institute of Patent Agents, do hereby declare
the nature of this invention to be as follows:
According to this invention, a geometrical plan and elevation or section of some
geometrical figure being drawn near the upper left hand and lower right hand
corners of a sheet stretched on a board, and two tracing points carried by a system
of jointed and sliding bars being moved along the outlines of these figures, a thin
tracing point, pencil or pen draws near the lower left hand corner a perspective
view of the figure. In order to guide the connected bars there is a horizontal rule
fixed along the middle of the board with a groove in which two of the bars slide,
there is also a central vertical rule of the same kind extending over the lower half
of the board and there is another vertical grooved rule near the left hand side. A
mumber of moveable bars, some of them jointed together, some jointed to pieces
sliding in the grooves of the fixed bars and fitted to slide longitudinally through
these pieces serve to carry the tracers on the drawing pen or pencil.
Dated this 31st day of October 1890.
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
An Instrument for Drawing Perspectives of Geometrical Forms.
1, OLIVER IMRAY of No. 28 Southampton Buildings, Chancery Lane in the
County of London, Fellow of the Institute of Patent Agents, 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:-
According to this invention a geometrical plan and elevation or section of some
geometrical figure being drawn near the upper left hand and lower right hand
corners of a sheet stretched on a board and two tracing points covered by a system
of jointed and sliding bars being moved along the outlines of these figures
respectively, a third tracing point, pencil or pin draw near the lower left hand
corner a perspective view of the figure.
Fig. I of the accompanying drawings is a diagram illustrating the principles
according to which the instrument operates,
Fig. I shews the instrument as it would be in action.
Referring to Fig. 1. Assuming L T to be the earth line of two plans, P P¹ the
line of the plan of central projection, 0° and O₁ the projections of the point of
sight A A and B B the projections of any two points of the plan, O°A°, O° 13°,
OA, O B projections of the rays from the points 0° 0', consequently a a', bb'
are perpectives (central projections) of the points A° A', B° B. Drawing w w¹
parallel to L T at a distance from it equal to the distance of 0° from PP, and
from a point in it such as we which is also in P P letting fall perpendiculars
on the rays OA' O'B' respectively, these perpendiculars cutting L T at a and B
then a ßab. Consequently the intersections of the perpendiculars a A, 6B and
a A ẞ B drawn to P P and L T represent the central projections or perspectives

page_text: 1
of the points A° A and B° B. If the point A° A' is moved vertically so that its
vertical projection A becomes A', situated on the horizontal plane LT parallel
to IT, the vertical projection of its perspective will be moved the distance a¹ a
so as to be on the ray O A... If then, the point 04, be taken on the line O' 0° at
a distance from O' equal to A' A, and if from a perpendicular be let fall
on O, A cutting LT in a', then will a a, be equal to a' a', and the central
projection of the point A° A', will be at A, where meet the perpendiculars. A
and a A
Referring now to Fig. 11. On the board are fixed at right angles to one another
two guide bars L T and QQ. A rule A° R has at A° a tracing point which is
moved along the lines of the right hand projection and slides through a swivel O
moving a guide groove n o. AT piece Ach slides along L T and through
a swivel at A. Other T pieces figk da em slide along L T and QQ
respectively, carrying a tracer, pen or pencil at their crossing A. Also on de is a
swivel a through which A R can slide. Two bars ey are rigidly fixed at
right angles to each other. The bar u can slide through a swivel at w, and
through another swivel a carried on an extension of the T piece/g. The swivel w
is situated in the perpendicular line P P at a distance from T equal to the
distance of O from P P The bar ay slides through the swivel A on bc and
through a swivel O' on a bars which can slide lengthwise and has fixed at s its
upper end a rule M N at right angles to it, which rule can be moved to coincidence
with the horizontal lines of the plan in the left hand corner.
In order to facilitate the movements of the parts for the rectilineal slides may be
substituted systems of radial bars such as are shown at Fig. III where the ends A'D
of the two bars jointed together at E are made to move in the guides L T and Q Q¹
while the end A carries the tracer, and where A' E = A' E DE. To prevent
the parts of the instrument from coming in each other's way the bar any is made in
two parts fixed above and y y' fixed below uc. The other rules such as A° R
may also be inade in parts, the one part sliding within the other in each case; also
friction may be lessened by employing small rollers at the sliding parts.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare what I
claim is
―:
An instrument for drawing perspectives consisting of a tracing point a drawing
point and a rule connected by guided bars substantially as described with reference
to the accompanying drawings.
Dated thi. 2104 1
1001
ABEL & IMRAY,
Agents for the Applicant.