Improvements in Pantographs.
Year: 1893

page_text: Date of Application, 18th Jan., 1893
Complete Specification Left, 18th Oct., 1893-Accepted, 23rd Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in Pantographs.
I, WILLIAM BARNARD PINHEY of 6 Albion Road, Lewisham in the County of
Kent, Surveyor, do hereby declare the nature of this invention to be as follows:-
This invention for improvements in pantographs has for its object to provide
a pantograph of simple construction, not liable to get out of repair and which shall
be easily and readily adjusted to change the relative proportions of the original
drawing and copies obtained, and consists essentially in connecting together the
tracing, drawing, and fulcrum points by means of cords or threads and pulleys,
toothed gearing or other equivalent connections, in such manner that the original
drawing and the copy produced may bear any desired proportion to one another.
In one form of pantograph constructed according to this invention, two laths
or bars are so connected together that one may slide freely on, and parallel with
the other, the lower and shorter lath or bar having guides attached at suitable
points through which the upper and longer lath slides and by which the two laths
are held parallel to one another. To one end of the upper and longer lath is
attached the drawing pencil or pen while to the adjacent end of the lower and shorter
lath is attached the tracing point. The fulcrum point is secured to a strap or
casing which embraces both laths which slide freely through it. Attached to the
said fulcrum casing are two sets of pulleys connected to two corresponding sets
attached to either end of the lower sliding lath and connected with cords, the free
or hauling end of each cord being carried from the latter and secured to that end
of the upper lath which is most remote from it, so that the hauling cords in passing
to their respective points of attachment cross one another.
It will thus be seen that the apparatus comprises two sets of tackle of equal
purchase with sets of pullies attached to the ends of the lower sliding lath, and to
the fulcrum casing respectively; and as the hauling ends of the cords are secured
to opposite ends of the upper sliding lath, they are taut in all positions of the
fulcrum casing. The amount of purchase given to the pullies determines the
relative motions of the sliding rods, tracing, and drawing points and consequently
the ratio of the original drawing to the copy produced. By arranging the pulley
sheaves in conical order the plies of cord may be quickly changed to give any
required ratio.
In a modified arrangement of apparatus I dispense with the pullies and substitute
there for two pinions mounted on an arbor running in the fulcrum casing, one pinion
gearing with a rack on the drawing lath while the other gears with a similar rack
on the tracing lath, the relative differential motions of the laths and fulcrum point
depending on the relative diameters of the said pinions, which are capable of being
removed and others of varying diameters substituted.
In another toothed gearing arrangement, toothed racks on the sliding laths gear
with pinions mounted on arbors working in and projecting through the fulcrum
strap or casing. On one projecting arbor is mounted a changeable spur wheel
whose diameter depends upon the ratio of the original drawing and copy, while on
the other projecting arbor is mounted a pinion gearing with an idle stud pinion
mounted on a radial stud arm whose axis of rotation coincides with the said pinion
arbor, so that the stud pinion may be readily put into gear with spur change wheels
of different diameters and the radial stud arm clamped in position.
In another modification I dispense entirely with the employment of laths. In
his arrangement I mount two drums, whose relative diameters represent the
atio of the original drawing to the copy to be made, on an arbor running
na suitable fixing attached to one end of the table or drawing board. On

page_text: The whole apparatus rotates about a centre pin ae in the weight af and it will
e readily understood that the movement of either pencil or tracing points
mparts through the pulleys a a, ab a corresponding movement to the other point
he ratio depending upon the proportions of the said pulleys.
The sliding rods v, w, are here shown at right angles to one another but they
Moreover the
may be arranged at any other angle or parallel to one another.
connecting cord and pulleys might be replaced by racks and toothed wheels.
In using this invention as shown in Figs. 1 and 2 change pulleys having the
requisite proportions are first selected and mounted in position; the slides are then
set in such positions along the lath that their distances from the pivot have the
To
same proportion as the said pulleys. While in these positions the connecting
cords are secured to the said sliders and the apparatus is then ready for use.
facilitate the setting of the instrument for any desired ratio of original and copy
the lath or rod may be graduated according to any convenient scale of equal parts
with the pivot for zero. The two sliders can then be set in positions whose
distances from the pivot have the required ratio and the connecting cords then
secured.
In the arrangement shown in Figs. 3 and 4 the two points require to be set in a
The two laths may also be
similar manner,
the pivot point being taken as zero.
graduated to read to any convenient fiducial mark on the carrying frame.
The above description applies also to the case where the cord pulleys are replaced
by pinions, except that the racks and pinions are set instead of the cords and
pulleys.
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 that what I
claim is :-
1. A pantograph comprising two point and pencil carriers sliding on a rod
rotating about a fixed stud the relative motion of the said points being controlled
by means of cords connecting them to pulleys having the required proportions to
one another substantially as described.
2. The arrangement and construction of pantographs substantially as described
with reference to Figs. 1 and 2 of the drawings.
3. A pantograph comprising two sliding rods connected together by cords passing
round pulleys the relative motions of the said rods being determined by the
proportions of the said pulley substantially as described.
4. The arrangement and construction of pantographs substantially as described
with reference to Figs. 3 and 4 of the drawings.
Dated this 18th day of October 1893.
WHEATLEY & MACKENZ
40, Chancery Lane, London, W.C., Agents.