Improvements in Screw-drivers.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Screw-drivers.
I, DANIEL ROBERTSON HART of 4317 John Avenue, in the City and County of
Saint Louis, State of Missouri, United States of America (formerly of 112 East
Twenty Seventh Street, City and State of New York, United States of America) tram
car builder, do hereby declare the nature of my invention for IMPROVEMENTS IN
SCREW DRIVERS," and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
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The object of my invention is to provide a screw driver adapted to enter and fit very
closely the slots.of screw heads, and having its point so formed that its tendency to
slip sidewise during the insertion of a screw is effectually prevented, and having the
two side extremities of its point strengthened in such manner that danger of fracture
thereof is avoided.
My invention is more particularly adapted for round headed screws, but it may be
used with other forms of screw head.
In the accompanying drawing, Fig. 1 represents a front view of a hand screw
driver constructed according to my invention; Fig. 2 is a longitudinal section of a
portion of the same; Fig. 3 is a front view of a screw driver bit adapted to be used
in a bit stock; Fig. 4 is a side view of an ordinary wood screw, a portion being
broken away to show the slot; and Fig. 5 is a side view of a portion of a screw driver
of modified construction and showing a wood screw partially in section in conjunction
therewith.
a, designates an ordinary wood screw having a head portion, b, provided with a slot, c,
to receive the screw driver, the bottom of which slot has the ordinary concave form.
d, is a screw driver provided with a handle, e, having its point, f, made in convex
form so as to correspond with and fit upon the concave or arc-shaped bottom of the
slot, c. The sides of that portion, d', of the screw driver which engages with the slot
are sunk in the sides of the blade, and provided with concave shoulders, d³, in the
rear thereof, and the portion, d', may be made parallel or to taper slightly in thickness
from the point, f, having less thickness at the part, g, than at the point, f. The con-
cave shoulders, d², extend rearwardly from the edges of the blade near its point towards
the centre of the portion, d', and correspond approximately with the form of round
headed screws, and also have a rounded or cove-like junction, d³, with the said portion, d¹.
These concave shoulders may extend entirely to the point at the side extremities
thereof, if desired, but I preferably terminate them at a sufficient distance therefrom
to allow of the insertion of the point in the slots of ordinary flat head screws, and
which I have illustrated in Fig. 5, and which also shows a screw driver having a
straight point, to which my improvement is equally applicable.
It will be seen from the foregoing construction that the full thickness of the blade
extends to within a short distance of its point, and that the side extremities of the sunk
portion and where the most strain occurs tending to fracture the point, are thereby
strengthened without interfering with its insertion in the slot. It will also be seen
that by reason of the concave shoulders at the rear of the sunk portion no slipping of
the screw driver from the slot sidewise can occur when it is in use.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is,-
1. A screw driver having a sunk portion at its point adapted in thickness to enter
and fit the slots of screw heads, the rear of said sunk portion having concave shoulders
to correspond approximately with the form of round headed screws, substantially as
described.

page_text: 2. A screw driver having a sunk portion at its point adapted in thickness to enter
and fit the slots of screw heads, the rear of said sunk portion having concave shoulders
and a rounded or cove-like junction with the said sunk portion, substantially as
described.
3. A screw driver having a sunk portion at its point, convex in front and adapted
in thickness to enter the slots of screw heads, the rear of said sunk portion having
concave shoulders, substantially as described.
4. A screw driver having a sunk portion at its point, convex at its front end, and
having concave shoulders at its rear, and the said sunk portion tapering in thickness,
substantially as described.
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.