An Improved Pantograph.
Year: 1893

page_text: Date of Application, 27th Sept., 1893
Complete Specification Left, 27th June, 1894-Accepted, 11th Aug., 1894
PROVISIONAL SPECIFICATION.
An Improved Pantograph.
I, EDWARD ERNEST HILEY of Wookey Hole, Wells, Somerset, Gentleman,
do hereby declare the nature of this invention to be as follows:-
My invention relates to an improved pantograph and has for its object to
produce an instrument which is exempt from the defects inherent to the ordinary
jointed lever system of pantograph.
My improved pantograph is of simple construction and composed of few parts
the operation of which is such that the instrument is free from the shake and
Moreover it may
flexibility incidental to numerous joints and slender lever arms.
be readily adjusted to vary, to a practically unlimited extent, the relative propor-
tion of the reproduction to the original drawing.
The instrument is composed of two rack rods fitted to slide longitudinally upon
a main bar, the rack rods being geared together by a wheel and pinion so that the
longitudinal sliding movements of the rack bars are in the same ratio as that of the
wheel and pinion. This ratio may be varied to any required extent by changing
the wheel and pinion for another having a different ratio, provision being made to
enable the one rack bar to gear with wheels of different diameters by making the
guide in which it works adjustable transversely upon the main bar. The one rack
carries the pointer by which the lines of the original drawing, etc., are followed and
the other carries the pencil by which they are reproduced, the pencil and pointer
being interchangeable according as the reproduction is to be on an enlarged or
reduced scale.
The main bar works about a fixed centre near one end and the radial distance
from said centre of the pencil carrier varies proportionally to that of the pointer, so
that the distance moved over by the pencil carrier in the circular direction by the
swinging of the main bar upon its centre will also be proportional to that moved
over by the pointer, the same holding good for motion in any intermediate direction
produced by the conjoint sliding motion of the rack bars and the angular motion of
the whole instrument about its centre of motion.
Doted skin 27th day of Sontember 1802
An Improved Pantograph.
I, EDWARD ERNEST HILEY, of Wookey Hole, Wells, Somerset, Gentleman,
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 :-
My invention relates to an improved pantograph which is exempt from the
defects inherent to the ordinary lever system of pantograph, the construction and
operation being such that the instrument is free from the shake and flexibility
incidental to numerous joints and slender lever arms. The instrument is of simple
construction, is extremely accurate, and may be readily adjusted to vary, to a

page_text: practically unlimited extent, the relative proportion of the reproduction to the
original drawing.
The instrument is essentially composed of two longitudinally sliding rack rods
geared together by a wheel and pinion so that the sliding movements of the rack
bars are proportional and in the same ratio as the diameters of the wheel and
pinion, this ratio being variable, as required, by changing the wheel and pinion.
The rack bars are fitted to slide upon a main bar, and the one rack carries the
pointer by which the salient points, or it may be the lines, of the original drawing,
etc., are followed, and the other carries the pencil by which they are reproduced,
the pencil and pointer being interchangeable according as the reproduction is to be
on an enlarged or reduced scale. The main bar is pivoted on a fixed centre from
which the radial distance of the pencil carrier varies proportionally to that of the
pointer so that the distance moved over by the pencil carrier in the circular
direction by the angular motion of the main bar about its .centre will also be
proportional to that moved over by the pointer, the same holding good for motion
in any intermediate direction produced by the conjoint sliding motion of the.rack
bars and the angular motion of the whole instrument about its centre of motion.
The invention is illustrated in the accompanying drawings, formning part of this
Specification, wherein
Figure 1 is a plan view of the instrument.
Figure 2 is a plan view of the instrument, drawn to a larger.scale and curtailed
in length by intermediate portions being broken out.
Figures 3, 4, and .5, are cross-sectional elevations, on lines 3-3, 4-4, 5-5,
respectively.
The same letters of reference indicate the same parts in all the figures.
The main bar of the instrument is of any convenient length for use, say
between 3 and 4 feet, and is composed of two parts A, B, the upper one B resting
on the lower one A and the two being connected together by a pair of parallel
motion links C, C, so as to admit of the adjustment of the upper upon the lower
member in the transverse direction when the gearing is varied as hereafter described,
the member B being fixed after adjustment by a clamping screw D. E, F, are two
rack bars fitted to slide in longitudinal grooves a, b, in the two members A, B,
respectively wherein they are retained by clips a, b. These racks respectively
gear, the rack E with a wheel G and the rack F with a pinion H, the said wheel
and pinion turning together as one on a pin I fixed in the bottom of a box
projecting from the underside of the upper member B. The chamber in which
the gear wheel and pinion are contained is covered by a removable disc J (shown
in dotted lines) which serves to keep the said wheel and pinion in position to gear
with their respective racks. The member A is recessed to make room for the box
which projects downwards so that the wheel G may lie in the same plane as, and
gear with, the rack E, as shown. To the ends of the racks E, F, farthest from
the wheel and pinion are fixed carriers K, L in which the pointer and pencil
holders are interchangeably mounted. The carrier K is attached to the rack E
and bears upon the top of the bar A to resist the thrust of the pencil (assuming
it to be mounted in that carrier) whilst the carrier L is provided at its tail end
with a pivoted latch that engages, but works freely beneath, a flanged rib
affixed to the rear edge of the bar B, in order to prevent the carrier being tilted
by the overhanging weight of the pointer or other cause. Each of these carriers
is preferably in the form of a slide rest with dovetailed gibs between which fits the
dovetailed slide m of the pointer M, or the slide n of the pencil holder N, as the
case may be. The pointer M projects forwards and downwards immediately in
front of the bevelled edge of the main bar A and comes down sufficiently near to
the paper bearing the original design to enable the salient points or outlines to be
accurately followed. Its slide or holder m is adjustable in its slide rest according
to the variable transverse adjustment of the part B on the part A to suit the size
of gear wheel employed and a binding screw m' is provided to clamp the slide in
its carrier. The other carrier K is similarly constructed except that it is in the

page_text: form of a compound slide rest, being fitted to slide, to a minute extent, upon a:
dovetail base affixed to the rack in the longitudinal direction of the latter, under
the control of an adjusting screw the purpose of which is, that of a fine adjust-
ment in order to vary to a minute extent the distance between the pointer and;
pencil in setting them to the exact ratio.required.
The bevelled front edge of the lower member A is graduated in inches, or to
any scale, and opposite to the zero of this scale is a centre 'hole O formed in a
Jug fixed to the bar A. This hole fits upon a pin suitably fixed on the drawing
board which pin is the centre about which the whole instrument is moved in passing
the pointer from one point to another of the design to be reproduced when those
points are not on the same radius to the centre O. The pencil holder is adapted
to keep the pencil point raised off the paper by means of a spring when moving
the pointer from one point of the original to another, the pencil being mounted
in a split tubular bolder to enable it to slide up and down and being pressed to
mark a point on the paper corresponding to that at which the pointer is placed.
If it be required that the pencil should make continuous lines instead of merely
plotting off points the action of the spring would be reversed so as to continuously
press the pencil on to the paper.
For enlarging, the pencil holder is placed in the carrier K and the index in L,
these positions being reversed for reducing.
In order to adjust the instrument to a given ratio, (say 3 to 1), the wheel and
pinion of proper relative diameter having been selected and placed on the pivot I,
the index and pencil are brought opposite numbers on the scale which are in the
ratio of 3 to 1 making use of the fine adjustment in order to bring the pencil
accurately opposite to the number on the scale. Then by moving the one rack
longitudinally in its groove so as to cause the index to move a certain distance
towards or away from the centre 0 (as from one point of the original drawing to
another on the same radius) a proportional amount of motion will be imparted to
the pencil holder according to the ratio of the pinion and wheel; and in swinging
the bar A upon its centre O so as to move the index from one point of the original
to another on a different radius, the amplitude of the arc described by the pencil
will be in the same ratio to that described by the index as the ratio of the radial
motion of the one to the radial motion of the other, and similarly for any
combined radial and circular motion.
A number of combined wheels and pinions of different ratios would be provided
for use with the instrument, the pinions being preferably of constant diameter,
whilst the wheels vary in diameter in any ratio to the diameter of the pinion,
between, say, 8 to 1 and 1 to 1.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The herein described pantograph or instrument for use in enlarging and
reducing drawings and the like, constructed to operate substantially as specified.
2. In a pantograph, the combination of longitudinally sliding racks to which the
pencil and pointer are respectively attached, with a wheel and pinion gearing
respectively with the racks and turning together as one, and with a main har
pivoted upon a centre and upon which the racks are fitted to slide, substantially as
specified.
3. In a pantograph consisting of a main bar pivoted to swing about a centre,
longitudinally sliding racks carrying the pointer and pencil respectively and
geared together by a wheel and pinion, as described, constructing the main bar
of two parts forming the guides for the two racks and connecting them together
by parallel motion links so as to adapt the racks to gear with wheels of different
diameters whilst maintaining the parallelism of the racks, as specified.
4. In a pantograph constructed of racks geared to operate carriers on a pivoted
"

page_text: main bar, as described, mounting the pencil and pointer interchangeably in their
carriers, substantially as and for the purpose specified.
5. In a pantograph constructed of racks geared to operate carriers, as described,
the combination, with the one carrier of a compound slide for fine adjustment in
.setting the instrument exactly to a given ratio, as specified.
Dated this 27th day of June 1901
E. E. HILEY,
By A. M. & Wm. Clark,
53, Chancery Lane, Chartered Patent Agents.