An Improved Instrument for Reproducing Drawings.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
An Improved Instrument for Reproducing Drawings.
I, ERNST GUSTAF SJUSTRAND, of Blasieholmstorg 14, Stockholm, Sweden,
Technological Student, do hereby declare the nature of this invention to be as
follows:-
The instruments heretofore used for the reproduction of drawings to any desired
scale, the so-called pantographs, consist essentially of four bars pivotally con-
nected with each other by means of pins so as to form a parallelogram which is
furthermore made movable about a fixed point. No matter how accurately the
said pins are made, there is always a certain amount of lost motion at these pins,
and the instrument therefore does not give sharp reproductions. Moreover, the
bars are in the way when a ruler or T-square is used and the instrument takes
up considerable space.
The instrument forming the subject of my invention is free from lost motion
at the joints, it can be used in geometrical drawing without forming any obstruc-
tion, and owing to its simple construction it can be made more accurate, durable
and inexpensive than the pantographs.
The instrument is shewn in plan in Figure 1, and partially in side elevation
in Figs. 2 and 3. B is a heavy pedestal suitable for placing on the drawing table
and in which is journalled a vertical shaft about which the whole instrument can
be rotated. On the shaft is fixed a sleeve A in which can be shifted longitudinally
a graduated tubular rod C preferably of square section, which rod can be locked
to the said sleeve A by means of the clamping-screws s and carries at its ends
pivots for two pulleys or wheels D, D', of equal size and connected with each
other by means of fine metal-wires b, b', causing them to accompany each other in
their rotation. One end of wire is clamped to the pulley by means of the
screw c, and its other end is adjustably attached to the pulley 1 by means of
the tubular nut d. By turning the nut d the wire can be shortened or
lengthened somewhat. The wire 1 is attached in an identical manner to the
pulley D by means of the screw e and to the pulley D by means of the nut
From pulleys D, D¹, issue in opposite directions the graduated tubular rods E, E
preferably of square section, said rods being movable in sleeves e, Fig. 2, attached
to the underside of the pulleys D, D' by means of screws f, and carrying, one of
them, a guide-point, F, and the other a pencil-point F¹.
The instrument is used as follows: The rod C is adjusted in such a manner that
it is divided at the centre of rotation in the ratio of the required scale. The rods E, Et
are so adjusted at the distances of their points from the centres of the pulleys are
to each other as the ratio of the scale. The drawing to be reproduced is placed
under the guide-point F, and a paper under the pencil-point F¹. The point F
is moved along the outlines of the drawing, and the pencil-point F1 now reproduces
the latter to the scale desired. To admit of raising the pencil-point during this
operation, the string is introduced. This string is fixed to the lever h, Fig. 3,
passes through an eye underneath the centre of pulley D¹ and another eye under

page_text: are so adjusted that the distances of their points from the centres of the pulleys are
to each other as the ratio of the scale. The drawing to be reproduced is placed
under the guide-point F, and a paper under the pencil-point F. The point F
is moved along the outlines of the drawing, and the pencil-point I now reproduces
the latter to the scale desired. To admit of raising the pencil-point during this
operation, the string is introduced. This string is fixed to the lever h, Fig. 3,
passes through an eye underneath the centre of pulley D¹ and another eye under
the centre of pulley D to the pin F where it is tied. By pulling on this string t
the lever his oscillated, Fig. 3, and the pencil-point consequently lifted. k, in
Fig. 3, is a support for the rod E. Evidently various unossential alterations
might be made in the construction of the instrument. For instance, in place of
making the rods E, E, so as to be shifted they may be fixed and the points F FI
made movable. Moreover, one of the rods E, E may be fixed and not graduated
while the other only is graduated, and many other variations may be introduced.
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 instrument for reproducing drawings, the combination of a pivotally
supported sleeve, a bar passing adjustably through said sleeve and rotatable there-
with, wheels at the end of said bar connected one to the other so as to move
synchronously and having each a cross rod projecting the one at the opposite side
of the apparatus to the other; said rods bearing respectively an inscribing and
a guiding point, substantially as described.
2. In an instrument for reproducing drawings, the means for securing syn-
chronous and exactly proportionate motion in the bar E' and its tracing point F¹
to the motion of the bar E and guiding point F, consisting essentially of the
wheels D D respectively pivoted to one end of the bar C and constrained to move
equally by means of the rods or wires bb¹ attached to the said wheels, substantially
as described and shewn.
3. In an instrument for reproducing drawings, the drawing point F1 pivoted at
the end of the rod E', supported by the prop k and capable of being raised or
lowered by the lever and cord or wire t, substantially as described and shown.
4. In an instrument for reproducing drawings, the combination of parts, sub-
stantially as and for the purposes described and shewn in the drawings accompany-
ing the Provisional Specification.
Dated the 21st day of February 1899.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.