Describing Geometrical Figures.
Year: 1888

page_text: Describing Geometrical Figures.
We JAMES FREDERICK BENNETT of Wrights Hill, Sheffiold, in the County of York
Manufacturer, WILLIAM GLOVER MANN, of Oxford Street, Sheffield aforesaid, Clerk,
and LOUIS SPENCER of Cemetery Road, Sheffield aforesaid, Bank Cashier do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
Our present invention relates to improvements upon the mathematical compass
or instrument described in the Specification of Letters Patent No. 9876 of the 8th
day of July 1884, granted to the above named James Frederick Bennett and
another, and by means of which Volutes, Ellipses and other geometric figures could
be drawn; the chief features of which were a non-rotating leg, upon which a tem-
plate of any desired shape could be fixed, and against which a steel guide leg
(connected with the pen leg) is constantly pressed by means of a suitable spring;
thus when the instrument is used, the guide leg follows round the configuration of
the periphery, or perimeter, of the template, and causes the pen, to describe a
facsimile of the said template. There are however certain objections to the use. of
a spring especially where there are sudden, or considerable, variations in the forin
of the template, and the object of our present invention is to overcome these objec-
tions, and to generally improve the instrument.
And in order that our Specification may be clear, and our invention well defined,
we annex a sheet of drawings showing our improvements as applied to a mathematical
compass; similar letters of reference indicate similar parts in any of the figures.
Fig. 1, represents a complete instrument made according to our invention.
Fig. 2, is a plan of the template, showing the groove or path.
Fig. 3, the joint of the instrument with the washers (Fig. 4) removed.
Fig. 5, top part of the leg B:
Fig. 6, top view of joint when complete.
The instrument consists of a non-rotating leg A attached to a foot A2 by means of a
ball joint, the ball being attached to the end of the leg, and the foot forming the
socket to receive and retain the ball. The foot is provided with two points A³ which
prevent any movement, and the otherwise universal movement of the ball joint, is
stopped in its rotary action by means of a fixed cross pin passing across the socket
and entering an open groove formed in the bottom half of the ball. The top of the
[ Di C17

page_text: leg A, is made cylindrical and is fitted into the head piece A'. The shank of the leg
being made of such a shape as will prevent the template Fig. 2 (& marked D) from
turning round, that shown being triangular. The template may be fixed at any
desired position upon the shank of the leg by a set screw passing through the boss D
or the boss may be made elastic by crosscuts, and be held in position by frictional
contact. This leg works very freely in the joint shown in Fig. 6.
The leg marked B, is of ordinary construction, and is usually made with a pen
or pencil; this leg and the guide bar C, are held together at the joint with much
firmness, so that any movement imparted by the template to the guide bar, is trans-
mitted to the leg. Upon the bar C, we place a slide block E, which can be adjusted
longitudinally, and fixed at any desired point; it is fitted with guide-pin F, which
may be rigid, or may have a short vertical movement controlled by a spring G; the
function of the guide-pin F, is to engage with the sunk path H, upon the face of the
template D, or with its equivalent, such as a raised path, or fillet.
It will therefore be seen that when the template D, is moved to the desired position
upon the leg A, and the guide pin F, is adjusted so as to engage with the template,
if the head of the compass is rotated, the guide-pin will follow the sunk path on the
template, and will cause the pen attached to the leg B, to describe a corresponding
figure on the paper of any desired size, and by moving the template up or down
variations of the said figure may be obtained.
The guide-bar C, may be connected to the leg B, by means of a quadrant if desired,
so as to retain the two members at any required distance apart.
The top joint is made as follows, the part A, shown in Fig. 3, has a double
joint piece, the two sides of which are marked I, I, in Fig. 6, the leg B, has a
single plate J, as also has the bar C, marked K in Fig. 6. The plates of C and B
are put together and placed between the plates of A, and the centre pin or screw is
put through the centre hole shown in Fig. 5; these two plates are then pressed tightly
together by means of the circular nuts M, which fit the holes of the part A. The
two washers L, L, (see figs. 4 & 6) are also screwed upon the projecting ends of
the centre pin, and bear against the nuts M, thus the joint plates of the leg B, and
bar C, can be held together with any desired amount of pressure by means of the
nuts M, while the leg A, is free to turn easily upon the periphery of the nuts. In
some cases the parts B, and C, may be rivetted together sufficiently tight for the.
purpose, and a hole for the centre pin made through the centre of rivet.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1-A mathematical instrument or "
"
compass for describing geometrical figures,
having a non-rotating foot and leg, constructed substantially as hereinbefore described,
and shown, for the purpose specified..
2-In mathematical instruments or « compasses," such as hereinbefore described,
the combination with a non-rotating leg; of a template, having formed on its face
a sunk path (or groove) or an equivalent raised path (or fillet) of any desired con-
figuration, to engage with the point or end of a guiding pin, connected with and con-
trolling the movement of the pen or pencil, for the purpose specified and substantially
as described.
3-In mathematical instruments having three chief members or legs, the construction
of the joint, for the purpose specified, and substantially as described and shown.
ROBT. F. DRURY,
Agent for the Applicants.