Improvements in Engraving Machines.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Engraving Machines.
I, FREDERICK WILLIAM SABEL, Geometer of Coblenz, Germany, 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 :-
This invention relates to improvements in engraving machines and has for its object
to render the reductions of maps or other drawings produced by a pantograph capable
of being forthwith engraved or printed upon a plate of stone metal or other suitable
material. The essential feature of the invention consists in using a pantograph as a
moving lever in order to draw the reduced drawing by means of a parallelogram. To
impart the greatest degree of accuracy to the instrument slotted guides are avoided
through link guides being used. Such guides search through the smallest source of
faults, provided the required subsequent positions of the pivoting points are
attended to which is obtained in a well known manner by the use of pins travelling
in points.
The apparatus is shewn in general view in Fig. 1 and is arranged in the proportion
of 1:4 that is to say that the drawing is reduced to of its size. E, C, B and D are
the arms of a pantograph in which A is the pivoting point, the contour following
pin and c the engraving point, style, or graver. With the point c which reproduces
the reduction correctly, are connected the four rods L, M, N, O whose ends c, a, b,
and t form a parallelogram having equal sides. When the two opposite points a and b
are moved in a straight line, the point b describes in a manner well known and
obviously apparent a figure which reproduces with the same dimensions the drawing
described by the point c.
When accordingly the lines of a drawing are travelled over, there is formed a more
or less reduced but correct fac simile of the same 2 according to how the instrument
is set while the style (diamond or steel graver) engraves such fac simile reversely as a
reflected picture ³, on a stone or other printing plate so that the impression taken
therefrom may reproduce the right or positive image of the reduction.
According to this invention the guidance of the points a and b along the straight
lines drawn by both is not carried out, as will be hereinafter more fully referred to by
means of slots such guides leading to serious mistakes as the applicant duly ascertained.
This caused him to use every endeavour in discovering a straight link guide for the
object in view. As however all similar straight link guides are only approximately
straight a regulating or correcting guide is used and this permits the straight motion
to be obtained. The inventor has selected as a suitable straight link guide the well
known lemniscoid link.
When the four links K K and H¹, H¹, articulated at p, p, 1, 1, to the table are
connected at their ends e de d to the two coupling rods J, the two points a and b
describe in a well known manner during the to and fro motion of the instrument
a line deviating but little from a straight line passing through a and b which line is
rendered accurately straight by means of the following arrangement. The two rods ;
are connected at both their extremities not with the two bars H¹ but with H3 which
are articulated at g upon the levers H. The latter oscillate at i upon the said
bars H¹ while their long arms carry at their ends the two rollers m which are guided
along the two curves H². The bars H¹ serve only to carry the two bars H3 which
slide by means of pins in slots formed in H' and thence transmit the motion of the
lever H upon the ends d of the bars J. The two curves H2 are empirically determined
by assuming that the two points a and b are guided along an accurately adjusted line
while two pins inserted in the axes of the rollers m drawing the curve will determine
the true curve through the shifting of the radii of the rollers. The condition required
is that the pivots p, 1 should be fixed and their relative position constant. The

page_text: •
construction of the instrument is illustrated in plan in Fig. 1, the pantograph which
in Fig. 1 is set at 1: 4, being set here at 1: 10, while the position 1: 3 is
shewn in dot and dash lines.
The point or pivot A is placed upon a cross bar A³ resting upon two pillars A', A².
The whole of the apparatus can slide upon an iron rail A firmly connected to the
table, and can be tightly fixed by screwing on the nuts provided therefor, so that the
· pivot A remains a fixture. The bar B is arranged to oscillate upon the bar B¹ and is
carried by the two rollers B¹. The slot C carried by the roller c¹ terminates at the
pivot A.
The strong slots E and D are connected with B and C, the former carry the point f.
The moveable rod F acts as safety means to prevent any lateral deviation. To equalize
the load of the arms D and F carried upon the said point the rod or arm G2 is arranged to
move upon the pillar G' and upon the same can likewise move to and fro the rollers G³
fixed in a frame suspended to a rod s of the arm D. For adjustment to the desired
reducing proportion the rods B, C, E, D, F are provided with corresponding holes.
The parallelogram is attached to the pin or point c which gives the reduction, the
former being properly secured in the various joints so that it cannot become dis-
connected during the various adjustments. The pivots p of the link carried by the
rollers K² rest upon blocks K¹ which are firmly fixed to the table top. The coupling
rods are articulated at K and carry on one side the corner points a and b of the
parallelogram and on the other the fastening points of the counter link. The rod H³
is fastened to the rod j, and carries a pin x sliding in a slot of the lever H¹ pivotted
upon or the slot may be formed in H³ and the pin be fixed to H. Upon the pivot i
arranged upon H', is fixed the double armed lever H* one extremity of which is held
at 9 upon H³ while the other is guided by the roller m upon the correction curve H².
A spiral spring H connected by the arm H' to H¹ presses m constantly upon the
curve H2 which with the fixed fulcrum rest upon a piece H7 connected with
the table.
In order to place the style or graver in a safe position it is fixed to a slotted bar R,
connected by the slot y to the pin y' fixed upon the slotted bar N' which is articulated
to M and O. The cross piece P serves to maintain N' constantly parallel to N.
In order to support the weight of the parallelogram and of its parts, a pillar U¹ is
provided and has a moveable arm U2 at the front end of which is attached the rod U³.
At one end of the latter rod the arm N is suspended to a wire s', while the other end
carries a box U4 weighted by means of slot, in such a manner that the style 6 may
bear upon the stone plate S with the pressure necessary for engraving.
This stones is placed on slides s¹ which can be moved by the handle S*.
b
Having now particularly described and ascertained the nature and particulars of
my said invention and in what manner the same is to be performed I declare that what
I claim is
1. An engraving machine by means of which a reduction can be engraved as a
reflected image upon a plate or stone, characterized by the combination of a panto-
graph (B, C, E, D) with a parallelogram (LO N M) in such a manner that the
transfer of the image is effected from the pantograph acting as a lever to the
parallelogram substantially as and for the purpose described.
2. In an engraving machine such as above claimed the arrangement whereby the
points a, b, of the parallelogram which should be guided in a straight line are attached
to lemniscoid links, one link (H¹) of which is not directly connected with the coupling
rodj but is jointed thereto by means of a lever (H* H³) influenced by a correction
curve (H2) in order to guide the points a and b in an accurately straight line sub-
stantially as and for the purpose set forth.
Dated this 5th day of March 1800