Improvements in Engraving Machines.
Year: 1896

page_text: Date of Application, 26th Mar., 1896-Accepted, 2nd May, 1896
Improvements in Engraving Machines.
I, FRIEDRICH WILHELM SABEL of Coblenz in the Empire of Germany
Surveyor 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 :-
In the Specification of Letters Patent No. 3549 of 1890 an engraving machine
is described for producing a reduction and reversed drawing upon a printing
plate in which the points a, and b, (Fig. 1) of the parallelogram L, O, N, M, which
are to be guided straight are attached to lenniscoidal guides, whose inaccuracies in
guiding straight are compensated for by a corrective curve.
This guide although it acts excellently, presents several inconveniences, because
it is complicated in construction and occupies much space. To obviate these
inconveniences is the object of my present invention.
If a circle is caused to roll without a sliding movement upon a straight line the
centre of the circle will move in a straight line, while each point of the
circumference of the circle describes a cycloid.
Having regard to this fact the inventor makes the points a, and b, to be guided
straight (Fig. 1), by the axes of two segments of circles or quadrants F, or circular
discs G which roll upon a straight ruler T or T.
In this case the inventor overcomes the difficulty of pressing F or G against- T
or T' and the rolling of these parts, without a sliding movement by making the
segments F or circular discs G of iron or steel and causing their periphery to bear
against a permanent or electromagnet which forms the straight ruler.
By the magnetic power the segment F or the circular disc G is pressed firmly
against the ruler T or T in such a manner that a rolling movement without sliding
is obtained, which is absolutely necessary by reason of the great mobility of the
entire machine.
In order to enable the segments For the circular disc G carrying the parallelo-
gram L, M, N, O, to move upon the table they must be supported, for which
purpose I make use of small carriages upon which the centre b, of the circular
disc G, or the points b, 61, 62, of the segment F are supported, in the following
peculiar manner.
The corner points b', 13, (Fig. 1.) of the segment F, describe cycloids, upon
whose path the small carriages, on which these points rest must travel in the
rolling movement of F, upon T.
The two cycloids may be replaced approximately by two arcs of circles, whose
most favorable centres, a, can best be determined empirically, in order to see the
extent of deviation of the circumference from the cycloid, which should not amount
to upwards of 5 millimetres on both sides.
These centres x, x¹, give the directions of the axles for two small four-wheeled
carriages W (Figs. 3 and 4) on which the point or b³, rests.
If the axles w, w, are directed to the point x, or ', (Fig. 2) the position of the
axles is such that the carriage will move in a circle whose centre is r, or ¹.
In order to equalise the small difference between the circle and the cycloid, the
point b', or 2, is not firmly connected with the frame of the carriage W, but rests
upon a segmental bracket w³, (Fig. 4) which can roll upon the frame plate of the
carriage.
Its apex forming the centre of the rolling circle (Figs. 5 and 6) possesses a point

page_text: bearing for the point of the axis 6' (or 62) Fig. 4, which latter can therefore be
moved to the right or left as far as the deviation of the circumference of the circle
from the cycloid may render necessary.
The centre b, of the segment F, rests in like manner upon a four-wheeled
carriage W, (Figs. 1 and 7,) but with parallel axles, a similar segmental bracket
with point bearings equalising any small inequalities in the motion of the
carriages.
If in lieu of the segment, use is made of a circular disc F, especially in small
machines their centre b, as shown in Figs. 8 and 9 is likewise supported upon the
segmental bracket w², resting on the carriage plate. w³, of a small four-wheeled
carriage with parallel axles.
In both instances the axle b, is connected by the rod L of the parallelo-
gram L, O, N, M.
It is expedient to employ in both cases a permanent magnet, in order to
dispense with the motive power (galvanic battery) for an electromagnet. This
magnet T or T' (Figs. 7 and 8) is secured upon a suitable support arranged on
the table.
Such a magnet serving as a ruler may be constructed by connecting two steel
plates t, t, (Figs. 10 and 11) by an intermediate piece t¹, of brass said plates being
embraced by single magnets t, composed of single steel strips which magnets will
then communicate their magnetic power to the plates t..
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 constructional form of the engraving machine protected by Letters
Patent, No. 3549-of-1890, characterized by the-feature that the-points a, and b, of
the parallelogram L, O, N, M, which are to be guided straight constitute axes of
the circular discs G, or of the segments F, of circles, whose peripheries bear
against a magnetic ruler and are adapted to roll upon the latter.
(2.) For supporting the central axis b, of the circular disc G or of the segment F,
of a circle, mentioned in the first claim, a rolling carriage W, upon whose frame
rolls a segment bracket 102, which at its centre carries the point-bearing for the
parallelogram L, O, N, M, connected to the axis b.
(3.) A modification of the carriage carrying a segment-bracket w³, for the
purpose of supporting the rolling points of the segment F, of a circle in such a
manner that the lines of the carriage axles, intersect each other at the centre of
the circle approximated to its cycloid.
Dated this 26th day of March 1896.
S. S. BROMHEAD,
97 Newgate Street, E.C., Patent Agent.