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Патент USA US2116775

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May 10, 1938.
Filed March 5, 1936
Rafa liq-J iiyé'b
George RBIacKbu?v.
Patented May 10, 1938 ,
George P. Blackburn, South Portland, Maine
Application March 8, 1936, Serial No. 66,963
3 Claims.
The invention hereinafter to be described re
(Cl. 145-50)
lates, in general terms, to mechanics’ tools, but
deals more speci?cally with a novel screw-driver
The ordinary ?at blade screw-driver is de?
cient in several particulars. The end is usually
slightly tapering on two sides and when pressure
is applied to a screw to rotate it there is a
tendency for the blade to slip out of the slot.
tional type of screw-driver blade bear only on
screw-driving operation.
In my present invention I have sought to ac-
complish several objects. First, to provide a
screw-driver blade having double the contacting
25 surface of the ordinary single’, ?at type. Second.
to equip each of the elements comprising the
blade with friction-acquiring means calculated‘
to largely reduce the tendency of the blade to
slip out of the screw slot when operating under
excessive tortional strain. Third,.to supply facil
ities for removal of any broken or injured parts
comprising the blade by a simple ‘chuck arrangement. And fourth, to so construct the device
that it may serve either in the capacity of an
ordinary screw-driver applicable for single,
straight slotted screws, or for use with screws
having cross-shape slotted heads.
Other advantages and objects will appear as
the description of the invention proceeds; and
40 for a clearer understanding of the import of my
invention reference should be had to the ac
companying drawing in which like reference
characters are employed to identify similar parts,
and in which,
Fig. l is a perspective view of my improved
screw-driver construction;
Fig. 2 is a fragmentary perspective view of the
same, drawn to a greatly enlarged scale;
Fig. 3 illustrates, in perspective view, the end
of the screw-driver with two of the bits re
tracted to form a ?at, straight blade for single
slot screws;
Fig. 4 is a central longitudinal section through
an L!
the parts, as indicated by lines 4-4, Fig. 2;
Fig. 5 is a side elevation, partly in section, of
the collet portion of the chuck member;
Figs. 5a and 5b are end views of the smaller
and larger ends, respectively, of the collet;
Fig. 6 shows the screw-driver in place in a
60 cross-slotted screw head;
Fig. 11 shows the bits in transverse section
through one of the holes aligning. with the
Fig. 13 is the same as Fig. 12 with the addi
tional feature of having the ends of the bits or
the blade is quite apt to' damage ‘the side walls
hard usage the ?at blade unless of ample dimen
sions is frequently twisted out of shape in the
the screw-driver blade;
blades made tapering to fit a V-shape slotted '
of the slot to such an extent that it is dl?‘lcult
and sometimes impossible to maintain a hold
Fig. 9 is a modified form of bit end:
Fig. 10 is a very simple method of constructing
Fig. 12 shows the ends of the bits slightly 10
the upper corners of the slotted portion of the
screw, and if the screw strongly resists rotation
On the other hand. if the screw withstands
housed in the handle;
handle-securing pin;
10 Furthermore, the tapering sides of the conven
.ing grip of the blade on the screw;
Fig. 7 is a section on line 1-1, Fig. 6;
Fig. 8 shows the ends of the bits which are
Referring to; the drawing, I is a handle having
two scarfs, each cut transversely of and‘ at right
angles to the other and extending through and
for a short distance along the handle from its
I inner end, forming a cruciform shape slot. The 20'
handle is equipped with a ferrule '2, the‘ outer
end of the latter having a wall or head with an
opening shaped like a cross to receive the‘four
bits or blades 3 which extend for a. distance into
the body of the handle.
Extending from the screw-driving end of each 25
bit, for a distance somewhat greater than the
usual depth of the slot in a screw, are closely
spaced, transversely disposed serrations 4, the
serrations being cut or otherwise formed on both
faces of each bit, somewhat resembling a ?ne 30
cut ?le.
The object of this construction is to provide a
greater or more positive grip on the wall of the
screw slot, the serrations having a tendency to
embed themselves into the sides of the slot, par 35
ticularly when the screw strongly resists turning
in the screw-driving operation.
In Fig. 9 the serration principle is carried out
with but a single projecting ledge which con
tacts the wall of the slot at the extreme bottom 40
thereof. the character 8 representing the screw,
L the slot, and la the single serration.
The inner, longitudinal edges Ia of the bits I
are V-shape so that when brought together they
miter and form a solid center for the cross-shape 45
structure, the apices 5 of the edges of the bit“
mutually meeting on the axis of the complete
blade structure.
To secure the four bits together in the form 50
of an integrated cross-shape structure I employ
a compressible collet member 6, slightly taper
ing on its outside and having an external screw
thread 6a cut over its entire length.
The collet is split for nearly its full length by 55
four scarfs 1, one on each quarter of its circum
ference. The smaller diameter end 6b of the
collet is perforated by a cross-shape opening 8
similar in contour to that of the cross-sectional
shape of the assembled bits I. It will be observed.
by reference to Fig. 5d, that the scarfs 'I are lo
cated abreast, respectively, of the ends of the
cross in the opening 8.
Operating over the collet 6 is a closing sleeve 9
screw-threaded to fit the external
thread on the coliet member. .
By rotating the sleeve 9 so that it moves longi
'tiidinally-on the collet toward the screw-driving ‘
end of the blade, the parts are loosened sufficient
10 ly to permit free movement of the bits through
the opening I in the collet. This makes it pos
sible to secure the collet, which together with the
sleeve provides a very simple chuck structure, in
various positions along the screw-driver blade.
15 The peripheral surface of the sleeve is knurled
so that it can be wrung on to the collet with
greater facility, but in case hand-gripping of the
sleeve does not procure su?lcient pressure to bind
the bits, there is provided a hole 9a in the sleeve
20 for use with a spanner wrench.
The bits are made of hardened steel, and while
constructed to withstand ordinary wear and tear
they are, like all other tools of this class suscepti
ble of breakage should they be subjected to exces
25 sive torsional strain in the screw-driving opera
tion. With the construction as herein outlined
it is an easy matter to replace a broken or injured
bit with a new one.
In the operation of replacing a broken bit the
30 collet sleeve 9 is ?rst loosened, then the pin In,
which passes through the ferrule 2, handle I,
and notches in the inner edges of all four of the
bits, is withdrawn. The injured bit or bits may
now be removed and one or more new ones insert
3a. ed in their place.
It will be observed by reference to Fig. 8 that
there are two holes I I through the bits, longitudi
nally spaced, relatively, and that these holes are
drilled diagonally, or at such an angle as will per
mit the pin ll to contact all four bits, as is more
clearly illustrated in Fig. 11. Thatportion of the
bit assembly in which are the two holes II is
housed within the handle of the screw-driver.
The present invention contemplates, primarily,
a screw-driver applicable for use with cross slot
ted screws. As constructed, however, I am able
to convert this type of driver into one adapted for
operating with screws having a single, straight
slot; and in Fig. 3 I have illustrated the parts so
arranged that they will accomplish this object.
All that is required to make the change is to
reposition two oppositely disposed bits in the
four-bit assembly.
The same preliminary operation as is per
formed in the replacement of a broken bit is gone
55 through with, namely, the sleeve 9 is loosened
and the pin l0 withdrawn. Then two oppositely
disposed bits 3 are forced further into the handle
until half portions of the two original holes ll
align, as clearly illustrated in Fig. 3
This leaves the driving end of the blade with
two aligning bits, adapted to serve in driving
screws having a single, straight slot in their
The ability to re-arrangethe bits so that the
65 screw-driving end embodies either a straight or
_ a cross-way blade gives the screw-driver a more
or less universal character, in that screws of at
least two varying types of slotted heads may be
used in connection with it.
A simple, cheaply constructed form of cross
wise blade is shown in Fig.‘ 10, in which the bits
are made integral and of the same width and of
the same thickness throughout their lengths. '
with the serrations 4 cut or otherwise formed on
the faces of each branch of the cross.
The serrations perform a very important func
tion in screw-driving. operations as a hold on the
screw by the driver can be obta'inedwhere. fre
quently a smooth blade will not be effective.
What I claim is:
1. A screw-driver comprising a handle, a fer
rule secured on said handle and having in its
outer end an opening made in the form of a
cross, four ?at, straight bits adapted to be as
sembled in the shape of a cross, and in this form
insertable in said handle through the cross-shape
opening in said ferrule, the inner edges of said 15
bits being bevelled two ways, providing a miter
joint construction when said bits are brought to
gether on the axis line of said handle, coincident
with the intersecting point of the central lines
cutting the cross openings in said ferrule, means 20
to secure said bits in said handle, and a chuck
mechanism, including a collet and sleeve, mount
ed on said bits adjacent the screw-driving ends
thereof. '
2. A screw-driver comprising a handle having 25
a transversely disposed hole adjacent one end
thereof, two scarfs, each one cut transversely of
and, through the other, extending from the ex
treme inner end of said handle toward the outer
end, a ferrule on the inner end of said handle 30
having therein a transversely disposed hole align
ing with the hole in said handle, said ferrule fur
ther having an aperture in its outer end of cross
shape contour, four ?at, straight bits having V
shape inner edges arranged in the form of a cross 35
and meeting at the axis line of said handle, the
cross-sectional contour of said bits when thus
arranged conforming to the contour of the aper
ture in said ferrule and the lines de?ning the. two
scarfs in said handle. means to secure said bits in‘ 40
said handle in either one of two different ar
rangementaone with the extreme outer ends of
all bits ?ush, and the other with two of said bits
positioned in advance of the other two, and a
plurality of serrations on both faces of said bits
extending from the screw-driving ends thereof
toward the said handle.
3. A screw-driver comprising a handle having
a cross-slotted end portion and a ferrule-secur
ing hole therethrough, a ferrule mounted on said 50
cross-slotted end portion of the handle and hav
ing a transverse hole registering with the fer
rule-securing hole in the handle, the outer end
of said ferrule having a cross-shape ‘ opening
aligning. longitudinally, with the slotted end of 55
said handle, four bits, each having a V-shape in
ner edge, adapted when assembled with their
V-shape edges mutually engaging. to form a cross
insertable in said handle and v?tting the cross
shape opening in said ferrule, said bits when as—
sembled with their outer ends ?ush having two
longitudinally spaced holes passing diagonally
through notches in the inner edges of all of said
bits, a split collet, having a tapering screw thread
on its periphery and an opening in one end con
forming to the contour of the assembled bits,
mounted on and adjacent the screw-driving end
of said bits, and a closer sleeve having an inter
nal thread ?tting the external thread on said col
let, and operable thereover, for the purpose of
bringing said bits into strong mutual engagement.
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