Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
1. Field of the Invention
The present invention relates to fastener
devices and more particularly to a screw driver and
screw head system.
2. Discussion of the Background of the Invention
Screws are one of the most widely used
fastener devices. Generally they are made with a
shank portion and a head portionO The shank portion
is threaded, for example, with a metal or wood screw
thread. In the common type of screw the head portion
is dome-shaped and has a slot with straight parallel
walls. The screw driver used with such screw heads
has a flat bottom edge and opposite slightly outwardl~
angled sides To rotate the screw requires that the
user exert pressure on the screw driver, both in a
rotative direction and toward the screw head, to retain
the blade in the slot. Frequently, when the screw is
difficult to turn, the blade has a tendency to be
forced out of the screw head slot by the rotative
pressure on the screw driver.
The field of screw head designs and special
~orms of screw drivers is crowded with hundreds, if
not thousands, of attempts to pr~vide a screw head -
screw driver system which is relatively low in cost
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and yet may provide a firm and secure turning force
on the screw. For example, the "Phillips" (trademar~)
screw head and screw driver system utilizes a cruciform
screw head impression to provide such an improved
contact. A number of proposed screw head designs, some
of which are discussed below, have suggested the use of
a screw head slot having one or more undercut walls and
a screw driver blade having an outwardly angled foot
portion. That arrangement provides a cam action when
rotative force is applied to the screw driver, which
tends to draw (cam) the screw driver blade downwardly
(inwardly) toward the screw head. Such cam action permits
the user to apply only rotative force, and not pressure,
along the screw axis to the screw driver and helps
retain the screw driver and screw head in contact during
the user's rotation cf the screw driver.
The prior art includes the patents discussed
below, as well as many others. However, there is still
a need for a relatively low cost screw driv~r - screw
head system which will permit the user to apply only
rotat~ve force and yet which will retain contact between
the screw driver and screw head.
In U.S. Patent 3,897,812 to Arnn for "Screw
Driver" the blade has two opposed cut-away portions 24
formed by side ribs 26. The foot portion 28 has "wedge
like bites 30" and "is generally isosc~les trapezoidal in
cross-section" and with "a flat base 32" (column 2,
lines 38-42).
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Another patent to Arnn, U.S. Patent 3,923,088 for <cBiting
Screw Driver, has the cross-sectional view of the foot portion
being curved (Fig. 3) or generally isosceles trapezoidal in
shape with a flat base (Figs. 6,10) and with a center blade
bulbous portion (Figs. 5-7) or cut-away portions, i.e., indenta-
tions (Figs. 8-11). The screw driver is for use with standard
screw heads whose 510ts have strai~ht vertical walls, as shown
in Figs. 12, 13 of the Arnn Patent 3,923,088, and see its
column 1, lines 23-26.
U.S. Patent 3,695,321 to Garehime for ffCavity Head Screw
and Driving Tool Therefor shows a screw head having a complex
geomtry which may be difficult to produce at a low cost. It
has a central cavity and two partial slots whose walls converge
(as seen in top view) and are undercut (as seen in side view).
In U.S. Patent 2,792,039 to Wing for Slotted Screw Head
and Driver Therefor Having Non-Burring Engagement, and in
U.S. Patent 2,677,985 to Vaughn for ~<Slotted Screw Head, a
screw driver having an arcuate bottom edge fits in an arcuate
slot having flat and parallel side walls which are then undercut
to form four rounded undercut portions. The screw head may
appear to be relatively complex and costly.
The U.S. Patents 3,120,251 and 3,026,920, both to York
for <~Screwdriver, like the Wing patent, show a screw driver
having an arcuate bottom edge which fits into a screw head slot
having an arcuate bottom and which may have under cut side walls.
In ~S. Patent 2,800,936 to West for Cruciform Screw
Driver there is shown a ~ype of cross recess having a center
cavity and opposed undercut and overcut side walls.
In U.S. Patent 2,68~,094 to Lissy for Nonslip Screw
Driver and Screwhead, a screw driver has a protruding bottom
flared projections 17 and 18 which fit into undercut spaces
15,16 of the walls of a screw head slot. The projections act
only when the screw driver is rotated in one direction (clock-
wise as in Fig. ~) and have no effect when the screw driver is
reversed in direction.
One-way>~ screws are employed when it is desired to
screw in the screw using an ordinary screw driver, but removal
using such a screw driver is not possible. For e~ample, such
screws may be used to fasten lock plates to doors. One type of
aone-way screw has a head without a slot, but divided into
four sectors about a common center. Two opposed sectors are
raised and have straight walls facing in the same rotative
direction and about 360 apart. The straight wall sectors are
separated by sectors in the form of ramps. The screw may be
inserted by the screw driver blade being turned clockwise and
pushing on the two straight walls. ~hen the screw driver is
rotated counterclockwise it rides upward on the ramps and does
not turn the screw.
~ Ob~ectives and Features of the Invention
It is an objective of the present invention to provide a
screw head and screw driver system in which the user's entire
force may be applied to rotate the screw and the co-action of
the screw driver and screw head will act to maintain them in
contact.
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It=is an objective of the present invention to provide
such a screw and screw driver system in which the user's rotative
force on the screw driver is resolved by the cam action between
the screw head and the screw driver into force toward the screw
head, both for insertion and removal of the screw, and which
will permit the screw to be turned when there is limited vertical
access to the screw head.
It is an objective of the present invention to provide
such a screw and screw driver system in which the screw head
may be economically produced using high-speed conventional metal
working machinery and the screw driver may also be relatively
low in cost.
It is an objective of the present invention to provide
such a screw and screw driver system in which, after the screw
driver blade is positioned in the screw head, it may be locked
in position by a slight clockwise rotation o~ the screw driver
and, after the screw is fastened, may be unlocked by a slight
counterclockwise rotation; and for removal of the screw
counterclockwise rotation of the screw driver locks it in
position on the screw head, and after the screw is removed
slight counterclockwise rotation releases it from the screw
head.
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It=is an objective of the present invention to provide
such a screw and screw driver system in which the screw head may
be utilized on wood screws, sheet metal screws and machine screws
as well as on other types of screws.
It is a feature of the present invention to provide a
screw and screw driver system in which the screw comprises a
shank portion having an exterior thread, a head portion, and an
imaginary central axis. The head portion has a plateau portion
connected to the shank and two opposed raised protruding portions
(sectors) equidistant from the axis and in, but not filling,
opposite quadrants of said plateau portion, the closest distance
between them being D. Each of the protruding portions has two
flat side walls perpendicular to each other, with each side wall
being parallel to a side wall of the opposite protruding portion.
The distance between the parallel side walls along an imaginary
line perpendicular thereto and meeting an imaginary extension of
one side wall is E + E'. Each of the side walls is cut back so
that they are angled inwardly toward the axis. The other two
opposite ~uadrants of the plateau portion are flat and lie in a
single plane.
Th~ screw driver fits against the screw head portion
and comprises a handle portion, a shank portion and a blade
portion. The blade portion has a flat bottom edge with a
width W, two flat opposed cam sides starting at the bottom edge
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and ang~ed inwardly therefrom, and two flat opposed side walls
angled outwardly from the top of the cam sides. The blade
width W is less than the gap D and greater than the side wall
distance E + E'.
Brief Description of the Drawings
Other objectives and features of the present invention
will be apparent from the following detailed description of the
inventor's best mode of practicing the invention. The detailed
description should be taken in conjunction with the accompanying
drawings.
:In the drawings:
Figure 1 is a side plan view of the screw utilized
in the present invention;
Figure 2 is a top plan vi.ew of the screw of Figure l;
Figure 3 is a cross-sectional view of the screw taken
along line A-A of Fig. 1 looking in the direction of the arrows;
Figure 4 is a side plan view of a portion of the shank
portlon and its blade of the screw driver utilized in the
present inventi~n;
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Figure 5 is a front plan view of the portion of the screw
driver in Figure 4; and
Figure 6 is a cross sectional view taken along line B-B
of Figure 5 looking in the direction of the arrow.
Detailed Descrip_i n of the Invention
The present invention involves a screw having a conven-
tional shank portion and a special constructed head portion of
a screw driver having a special construction which is utilized
in connection with that screw.
~ s shown in Fig. 1, the screw 10 comprises generally a
shank portion 11 and a head portion 12, both of which are formed
along a common central axis 13. The shank portion 11 is of con-
ventional construction and has, in the embodiment shown in Fig.
1, a wood screw thread 14 at its lower end, terminating in a
point 15. Alternatively, and not shown, the shank portion 11
may have other types of threads such as a machine thread for
fitting into a machine part or nut or a sheet metal screw thread.
The head portion 12 comprises a round disk-like portion 20
having a flat top 21 and flat bottom 22. As seen in top view,
it is divided into four equal sectors (quadrants). Two
protrud~ng sectors (bosses) 23 and 24, respectively, are integral
with the top portion 20 and protrude therefrom inthe direction
of the arrow 25. As shown in Figs 1 through 3, each of the
sectors 23,24 may be formed from a dome and consequently has an
arcuate outer face, respectively 26,27. Each of the protruding
sectors 23,24 has two side walls, respectively side walls
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28,29,-~n the case of portion 23, and side walls 30,31 in the
case of portion 24. The side wall 2~ is perpendicular ~90
angle) to the side wall 29 and the side wall 30 is perpendicular
(90~ angle) to the side wall 31. The side walls are canted,
i.e., undercut, in relation to the axis 13, so that they act as
camming members~ The side walls 28, 2g, 30 and 31 are flat.
An imaginary set o~ cross lines 32, 33 may be drawn so
that they cross at the axis 13, are perpendicular to one another,
and are in a single plane on the surface of the top member 20.
The walls 28, 29 and 30,31 are set back from these imaginary
lines 32,33. The points of the protruding sectors 23,24 are
chamfered (cut off) at 34,35, or they may be rounded, so that
the screw head does not have sharp points.
The minimum distance between the protruding sectors 23
and 24 is labeled D. The distance between the imaginary cross
line 33 and the top edge of the protruding sector 23 closest
to that line is labeled E. Similarly, the distance between the
imaginary cross line 33 and the top edge of the protruding
sector 24 (the edge closest to that line) is labeled E'. There
is a certain critical relationship between the distances D and
E' and E and the size and shape of the screw driver, which will
be explained subsequently.
The screw driver utilized in the present invention is
shown in Figs. 4 through 6. The screw driver includes a handle
portion 39, which may be of conventional construction, a shank
portion 40, which may be round and of conventional construction,
and a blade portion 41. The blade portion 41 comprises two flat
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opposite sides 42 and 43 which are angled inwardly in relation-
ship to the central imaginary axis 44 in the direction toward
the bottom end of the blade portion. The blade portion has a
flat bottom 45 and two opposite sides 46, 47 which are angled
inwardly towards the axis 44 starting at the bottom 45. The
blade is uniform in cross-section~ a cross-section thereof
being shown in Fi~. 6.
The width of the flat bottom 45 of the blade portion is W
(see Fig. 6). The width W is greater than the combined distances
E and E'. Consequently, one cannot connect the screw driver and
the screw head of Figs. 1-3 by bringing the blade so that the
length of its flat bottom 45 is aligned (parallel) with the
cross line 33. The top innermost edges of the side walls 29
and 30 are too close together to permit the entry of the bottom
45 of the blade portion 41 between those side walls by downward
pressure with the blade's length in alignment with the imaginary
line 33.
To insert the screw driver of Figs~ 4-6 into the screw
head of Figs. 1-3 the user must insert the bottom width W
20 ;between the inward ends of the protruding sectors 23 and 24.
The distance D between those inward ends i5 greater than the
width W of the bottom of the screw driver blade. Consequently,
the screw driver may be inserted so that its bottom 45 rests on
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the top 21. Such insertion is perpendicular to line D. In the
;;~ 25 ~next step the user will rotate the screw driver blade 45~ in
the clockwise direction so that the sides 46 and 47 of the blade
are in contact, respectively, with the side walls 23 and 31.
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The cut hack of the side walls 28 and 31 cooperate with the
slant of the sides 46,47 of the blade to provide a camming
action. Only rotational force need be applied to the screw
driver in order to maintain contact between the screw driver
blade and the screw head. Alternatively, after insertion of
the scxew driver blade between the protruding sectors, i.e.,
with the length of the bottom 45 perpendicular to the line D,
the blade may be turned 45 in the counterclockwise direction
to loosen the screw, i~e., to turn it counterclockwise. In
either case, the blade may be removed from the screw head by
placing the length of the bottom 45 perpendicular to the line
D. It may be removed as its width ~ is less than the distance
D. In the above-described system it is critical that D> F
and D > E + E' and E + E'> W.
Modifications may be made within the scope of the
present invention. For example, the handle and elongated shank
of the screw may be replaced by a shank and hPad (handle
portion) that will fit into a tool, such as a ratchet tool.
A ratchet tool equipped with the screw driver blade portion of
the present invention may be used to insert or remove the
above-descrihed screws when there is limited access in the
direction of the screw axis. The screw may be turned by a tool
lying in the same plane as the bottom face of the screw head.
Another modification i5 to place a guide indentation
in the screw head and a similar guide protrusion on the end of
the screw dri~er. For exam~le, the guide indentation in the
screw head would be at the center of the screw head and may be
a cone-shaped indentation. A cone-shaped protrusion (boss) would
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be added at the face 45 of the screw driver. The cone-shaped
protrusion would be used to locate the screw driver on the
screw-h~ad.
