Improvement in Hand Shears for Cutting Sheet Metal and other analogous Hard Materials.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvement in Hand Shears for Cutting Sheet Metal and other
analogous Hard Materials.
I, GEORGES THUILLIER, Manufacturer, of Nogent, Haute-Marne, France, do
hereby declare the nature of this invention to be as follows:-
It is known that ordinary hand shears do not permit of hard materials such as
sheet zinc, tin, etc., being properly cut to any desired curve; in fact, if with
those shears it is desired to cut a sheet of metal of concave curve, the part of this
sheet which is already cut will be brought to bear against the wide face of the
upper blade so that, in order to be able to continue to effect the cut, it is neces-
sary to incline the shears in such a way as to permit of this cut part passing
over the blade by bending or twisting itself more or less; but the shears will
then be in an absolutely unfavourable position for cutting, and can consequently
only produce defective work.
These hand shears are further always difficult to employ for cutting hard
materials, even when such cutting is to be effected in a straight line, because
the force to be exerted by the workman increases rapidly as the
point of cutting becomes further and further removed from the axis
of articulation of the blades. This is the case for two reasons;
the first being that even if the angle which the blades form during the
cut remain constant, the force to be exerted by the workman would already
increase, on account of the variation of the relation between the arms of the
lever, proportionately to the increase of the distance between the cutting point
and the axis of articulation of the blades; the second is that this cutting angle
diminishes progressively during the closing of the blades, so that the force to be
exerted further increases considerably from this fact; it is evidently the fact
that the less this angle, the more rapid the cut, and consequently the work to
be effected in a given time increases considerably..
My invention relates to a new form of hand shears, in which the two disadvan-
tages above indicated are obviated.
My improved shears, enable the cutting to be effected without twisting, even
when following very accentuated concave curves in sheets of any hard material,
from the fact that the upper blade is shaped in such a way that the metal cut
can glide and pass over it without having to bend itself; further they render
the cut in all cases easy, because owing to the conformation of the upper blade,
the force exerted for effecting the cut remains constant, the angle of the blades
at the cutting point increasing in proportion to the closing of the shears.
The upper blade instead of being high and flat like the other blade, is of very
little height and of lenticular section so as to present to the side of the lower
blade no longer a straight and vertical edge; but a convex inclined surface, over
which that part of the sheet already cut can easily pass and slide; this it does
without having to twist because that part of the upper blade which is behind
the cutting point descends beneath the level of the upper.edge of the under blade

page_text: by reason of the movement of the closing of the blades. This descent of the
upper blade beneath the cutting edge of the other blade becomes particularly
pronounced if this upper blade is curved or bent in the direction of its length. It is
also this curved forin in the longitudinal direction which enables me to increase
the angle which the blades form with the cutting point as this point becouies
further and further removed from the axis of articulation. In fact the angle
formed by the blades with the cutting point when the shears are nearly closed;
is greater than the angle which they form at the moment when they begin to out.
Data 1.41
L
1000
11.
Improvement in Hand Shears for Cutting Sheet Metal and other
analogous Hard Materials.
I, GEORGES THUILLIER, Manufacturer, of Nogent,.. Haute-Marne, France, 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:-
It is known that ordinary hand shears do not permit of hard materials such as
sheet zinc, tin, etc., being properly cut to any desired curve; in fact if with
these shears it is desired to cut a sheet of metal of concave curve, for example
as shown in Fig. 1 of the annexed drawing, the part z of this sheet which is
already cut will be brought to bear against the wile face y of the upper blade,
so that, in order to be able to continue to effect the cut, it is necessary to incline
the shears in such a way as to permit of this part passing over the blade by
bending or twisting itself more or less; but the shears will then be in an
absolutely unfavourable position for cutting, and can consequently only produce
defective work.
These hand shears are further always difficult to employ for cutting hard
materials, even when such cutting is to be effected in a straight line, because the
force to be exerted by the workman. increases rapidly as the point of cutting
becomes further and further removed from the axis of articulation of the blades.
This is the case for two reasons; the first being that even if the angle' which
the blades form during the cut remain constant, the force to be exerted by the
workman would already increase, on account of the variation of the relation
between the arms of the lever, proportionately to the increase of the distance
between the cutting point a and the axis of articulation 'v of the blades; the
second is that this cutting angle diminishes progressively during the closing of
the blades, so that the force to be exerted further increases considerably from
..this fact; it is evidently the fact that the less this angle, the more rapid the
cut, and consequently the work to be effected in a given time increases con-
siderably.
My invention relates to a new form of hand shears, in which the two disadvan-
tages above indicated are obviated.
My improved shears, shown in perspective in Fig. 2, enable the cutting to be
effected without twisting, even when following very accentuated concave curves
in sheets of any hard material, from the fact that the upper blade is shaped in
such a way that the metal cut can glide and pass over it without having to bend
itself; further they render the cut in all cases easy, because, owing to the
conformation of the upper blade, the force exerted for effecting the cut remains

page_text: constant, the angle of the blades at the cutting point increasing in proportion
to the closing of the shears.
Figs. 3 to 5 of the accompanying drawings show the kind of form by meons
of which I obtain these results.
Fig. 3 shows the new shears open,
Fig. 4 shows them nearly closed, and
Fig. 5 is a transverse section through the line 5-5 of Fig. 4.
It will be seen that the upper blade a instead of being high and flat like
the other blade b, is of very little height and of lenticular section so as to
present to the side of the lower blade not a straight and vertical edge, but a
convex inclined surface, over which that part of the sheet already cut can easily
pass and slide this it does without having to twist, because that part of the
upper blade which is behind the cutting point descends beneath the level of the
upper edge of the under blade by reason of the movement of the closing of the blades.
This descent of the upper blade beneath the cutting edge of the other blade
becomes particularly pronounced if this upper blade is curved or bent in the
direction of its length, as shown in the drawing. It is also this curved form in
the longitudinal direction which enables me to increase the angle which the
blades form with the cutting point as this point becomes further and further
removed from the axis of articulation e. I will in fact be seen in Figs. 3
and 4 that the angle formed by the blades with the cutting point when the
shears are nearly closed, is. greater than the angle e which they form at the
moment when they begin to cut.
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 hand shears for cutting sheet metal and other hard materials com-
prising, in combination, two blades arranged in the manner of shear blades, the
lower blade having a flat inner surface and a rectilinear cutting edge, whilst the
upper blade is of lenticular section applied against the flat of the other blade, at
an inclination which remains constant from one end to the other, essentially as
herein before described and with the object indicated.
2. The hand shears for cutting sheet metal and other hard materials, substan-
tially as hereinbefore described, and shown in the accompanying drawings.
Dated this 31st day of March 1900.
ALLISON BROS.,
Agents for the Applicant.