Improvements in Knives for Paper Cutting Machines
Year: 1898

page_text: Date of Application, 8th Mar., 1898-Accepted, 7th May, 1898
COMPLETE SPECIFICATION.
Improvements in Knives for Paper Cutting Machines,
I, THOMAS FRANCIS MCCOY, of 250, 78th Street, in the City and State of New
York, United States of America, Engineer, 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 an improvement in knives for paper-cutting machines,
and has for its object to provide means for rendering such knives again service-
able after being worn. These knives have a limited vertical adjustment along
the knife-bars, and after the cutting edge has been worn substantially to the
length of this adjustment the knives were heretofore rendered useless. I propose
to provide the knife when worn with an additional back which permits its further
adjustment and thereby greatly increases the length of its life.
In the accompanying drawings, Figure 1 is a face view, partly in section, of my
improved knife; Figure 2 a cross section thereof, showing it attached to the knife-
bar; Figure 3 a cross-section on line 3-3, Figure 1; Figure a face view of a
modification of the knife; Figure 5 a cross-section on line 5-5, Figure 4;
Figure 6, a face view of a further modification of the knife; and Figure 7 a
cross-section on line 7-7, Figure 6.
The letter a represents the usual wrought-iron body or blade of a knife for paper-
cutting machines, being a long flat bar having a bevelled edge, to the back of
which the steel cutting edge b is welded. The blade a is provided at suitable
intervals with transverse perforations a adapted for the reception of fastening-
screws c, having nuts c¹, and by which the knife is attached to the knife-bar d.
This knife-bar is provided with an offset d' above the blade and with set-screws e
passing through the offset, by means of which the blade is rendered vertically
adjustable to a limited extent. The fastening-screws c pass through upright
slots of the knife bar, so that such screws may follow the adjustment of the blade.
To lower the blade, the nuts c¹ are loosened, the screws e turned down, and the
nuts c again tightened up. When the screws c have reached the lower extremities
of slots, further adjustment of the knife ceases, and knives worn to require
further lowering were rendered useless.
In order to permit the knives when so worn to be again rendered useful, I
attach to the upper or blunt edge a³ a back f, which is a long narrow strip of
metal of the same thickness as the thickness of the blade. The back f is pre-
ferably secured to the blade by means of the keys, plugs, or dovetail wedges g,
(illustrated in Figures 1 and 3). Here the blade a and back f are provided at
their contiguous edges with dovetail recesses opening into one another and
adapted for the reception of the keys or plugs. These keys are preferably cast
into the recesses, and when set will effectively connect the parts.. To procure a
better finish, it is desirable that the front and back of the keys be counter-sunk,
as illustrated in Figure 3.
I prefer to arrange between the keys 9 a number of dowel-pins h, that pass
longitudinally through back f and into the upper or blunt edge of the blade a.
As the knives in paper-cutting machines have a slanting downward motion, it is

page_text: of importance that the connection between back and knife be such as to effectively
This result is accomplished to a
resist the shearing strain thereby produced.
satisfactory extent by the combined use of the keys g and dowel-pins h, the keys
effecting a firm connection, while the dowel-pins serve to assist in taking up the
shearing strain.
The back should be provided with perforations f¹ in alinement with the per-
forations a¹, the distance between the perforations f¹ and upper edge of back f
being preferably equal to the distance between perforations a¹ and edge a².
After the back has been fitted to the knife the screws e are again turned up, so
that the back rests against the offset, Figure 2, and in this way the knife may
be used up to an additional length equal to the height of the back. Thus the life
of the knife is prolonged to a considerable extent, and the steel cutting edge b
may be used up to near its upper terminal.
In Figures 4 and 5 the connecting-keys are made in the form of centrally-con-
tracted elliptical plugs i in lieu of being made of the angular form shown in
Figures 1 to 3.
In Figures 6 and 7 the wedge-shaped keys are replaced by screws k, that pass
longitudinally through the back and engage tapped openings in the blade.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
First. A knife for paper-cutting machines, composed of a perforated blade, a
back perforated in alinement with the blade, and means for connecting the back
with the blunt edge of the blade, substantially as specified.
Second. A knife for paper-cutting machines, composed of a recessed blade, a
recessed back, and wedge-shaped plugs that engage the recesses and connect said
back to the blunt edge of the blade, substantially as specified.
Third. A knife for paper-cutting machines, composed of a recessed blade, a
recessed back, connecting-plugs engaging the same, and dowel-pins that pass
longitudinally through the back and into the blunt edge of the blade, substantially
as specified.
Dated this 8th day of March 1898: