An Improvement in Mathematical Drawing Instruments.
Year: 1897

page_text: Date of Application, 9th Feb., 1897
Complete Specification Left, 15th Oct., 1897-Accepted, 8th Jan., 1898
PROVISIONAL SPECIFICATION.
An Improvement in Mathematical Drawing Instruments.
I, CHARLES HENRY JAMES CLAYTON, of No. 5 Keston Road, East Dulwich, in the
County of London, Draughtsman, do hereby declare the nature of this invention
to be as follows:-
I attach to a suitable handle in the case of a drawing pen or pencil or to a
suitable radius leg in the case of compasses a bracket carrying a wheel having
suitably formed teeth designed to engage with a projection formed upon or
attached to a moveable pen or pencil and I provide within or upon the handle or
radius leg as the case may be a spring or weight designed to operate upon the
moveable pen or pencil in order that by the alternate raising and lowering of the
pen or pencil by means of the toothed wheel and the spring or weight dotted
lines may be drawn.
An improvemen In
I, CHARLES HENRY JAMES CLAYTON, of 5 Keston Road, East Dulwich, in the
County of London, Draughtsman, 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:—
The instruments hereinafter described are designed for the drawing of dotted
lines on plans and the like, and comprise a dotting pen, a dotting pencil and
dotting compass legs or points for pen and pencil.
Referring to the accompanying drawings Fig. 1 is an enlarged side view of the
dotting pen and Fig. 2 an enlarged part sectional view of the same with the
bracket removed to shew more clearly the arrangement of the moving parts.
In these figures a a is a tubular handle to the lower end of which is affixed by
a set screw or other suitable means a metal bracket a a¹ through which passes a
pivot dd part of which is plain so as to run free in its bearing in the bracket and
the end of which is screwed with a left-hand thread. Upon this pivot is screwed
a motion wheel or disc b b of metal or other suitable substance (preferably having
a milled edge) and one of a series of cams or wheels ce the outer circumference of
which is out into suitably shaped teeth and spaces to correspond to the spaces dots
and dashes in the dotted lines to be drawn.

page_text: Affixed upon the outer blade of a drawing pen g g by means of a set screw hh
or other convenient means is an adjustable link f f the lower portion of which
projects outwards so as to form a guide and bearing against the inner face of
the bracket a a¹. The under side of the link is shaped to a blunt edge in order
that it may engage easily with the teeth and spaces of the cams or wheels as the
latter revolve when the link is so adjusted as to engage directly with these, or with
the upper surface of the pawl ee hereinafter described when the latter is interposed
to give a higher lift to the pen or pencil. Fig. 3 is a vertical section of the link
shewn in Figs. 1 and 2 which is of a length suitable for use with the pawl e, e.
Other suitable lengths may however be used when the link is used without the
pawl.
Passing through the blades of the pen is a bolt jj having a square head to form
a vertical guide for the parallel inner sides of the adjustable link and square under
the head so as to prevent twisting when the mill-headed nut k (Fig. 1) is operated
for the regulation of the gauge of the pen.
In Figs. 1, 2 and 4 e e e is the pawl above referred to which is loosely pivoted
by means of a set screw to a lug on the rear edge of the bracket a¹ a¹ and which
has a portion of its lower surface shaped to a blunt edge so as to engage easily
with the teeth and spaces of the cams or wheels as the latter revolve. The upper
surface is curved preferably to an arc struck from the centre of the pivot 7 d.
Fig. 4 is a plan view
the pawl.
In Fig. 20, 0, 0, is a spindle which is screwed or otherwise suitably affixed to
the drawing peng and which is made of such a diameter as to loosely fit for the
whole or part of its length the internal circumference of the tubular handle a
within which it is free to move vertically. At the upper end of the spindle and
between it and the cap g which is screwed into the upper end of the handle is
placed a spiral spring por, alternatively, a loose weight or, alternatively, the
spindle itself may be of sufficient weight to render other loading unnecessary, so
that by these means or either of them the point of the pen may be returned to the
surface drawn upon after the alternate lifting motion by means of the operations
herein before described.
In Fig. 11, is a shaped thin metal plate attached to the leading edge of the
bracket a¹ a¹ to serve as a finger guard against the pen when in use.
The plate
is at its lower part bent inwards so as to form a guide-blade and guard m against
the edge of the T square or straight edge n in drawing and is of such a length
that when the whole instrument is held vertical the guide blade m and the motion
wheel b are both in contact with the surface drawn upon.
Alternatively a small vertically placed wheel may be pivoted to the guide
blade so as to lessen friction with the surface drawn upon.
The dotting pencil is provided with the same form of mechanism as the dotting
pen above described; but in place of a drawing pen a screw-motion or slide-motion
pencil holder of ordinary form for the reception of loose leads is fitted to the
spindle; the link above described being in this case attached to the pencil-holder,
or the link may be dispensed with, and a horizontal pin passing from the pencil-
holder through a vertical slot in the bracket be substituted so as to form at once
a means of lifting the pencil by the cam or the pawl and a guide to prevent any
twisting motion of the pencil during use.
The dotting compass legs for pen or pencil are substantially and respectively
indentical as to mechanism with the dotting pen and dotting pencil above described
but of suitable size for the purpose; the tubes being provided near the upper end
with a joint of any suitable form, having a shank for fitting the same to an ordinary
pair of compasses with detachable legs: the guide-blade and guard-plate may
however in these cases be dispensed with.
An alternative form of compass leg is shewn in Figs. 5 and 6 and is formed by
the dotting pen or pencil above described to which is fitted a clip-shank b, b, b,
consisting of a pair of jaws or clamps shaped to fit the handle, to which it is
clamped by means of set screws passing through the lugs, one pair of which are

page_text: attached by means of one of the set screws to the lug end of a slip-shank cc for
fitting the same to an ordinary pair of compasses with detachable legs.
Having now particularly described and ascertained the nature of my said In-
vention and in what manner the same is to be performed I declare that what I
claim is:
1. The dotting pen substantially as and for the purpose described.
2. The dotting pencil substantially as and for the purpose described.
3. The dotting compass legs substantially as and for the purpose described.