Screw driver with four fan-shaped blades

Details Screw driver with four fan-shaped blades Screw driver with four fan-shaped blades

2000-08-14

2001-09-18

Hail, III, Joseph J. (Department: 3723)

Tools

Wrench, screwdriver, or driver therefor

Having work engaging and force exerting portion inserted...

C081S436000

Reexamination Certificate

active

06289775

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to a screw driver exclusively applied to drive a specialized screw having compound drive recesses as shown in
FIG. 20
of U.S. patent application Ser. No. 09/193,489, whereby a screw can be driven by various conventional drivers, i.e. slot, Phillips (cross), square-cross, square, and double-cross recesses, particularly to the screw driver with a drive bit provided with four fan-shaped blades symmetrically disposed with respect to each other, between every two neighboring fan-shaped blades and has an elongated rectangular hollow indented space, a square blunt bottom protrusion formed and situated at the center section of the free end of the drive bitjoining the four fan-shaped blades and the four hollow indented spaces.
2. Description of the Related Art
Conventional fastener drive recess types include slot recess (A) shown in
FIG. 1
, cross recess (B) shown in
FIG. 2
, cross-square combination recess (C) shown in
FIG. 3
, square recess (D) shown in
FIG. 4
, and double-cross recess (as available under the trademark POZI) (E) shown in FIG.
5
. Drive recess structures of aforementioned types generally cannot stand comparatively large torque due to their structural weaknesses and uneven pressure distribution. Typically, if a screw resists turning, then upon applying an increased torque to the driver bit, it slips upwardly out of the drive recess. The more frequent this slippage occurs, worse damage is imposed on both the drive recess and the drive bit. Loose engagement (the drive bit wobbles excessively within the drive recess) is one of the major aspects to consider when both the drive recess and the drive bit fail to withstand a large driving torque.
Five kinds of screw driver bits are shown respectively in
FIGS. 6
,
8
,
10
,
12
and
14
. In
FIG. 6
a slot drive bit is designed to drive recess A (as shown in FIG.
1
), and
FIG. 7
shows how the slot drive bit is engaged in the compound drive recess. On the sample principle, in
FIG. 8
a Phillips drive bit which corresponds to recess B (
FIG. 2
) engages within the compound drive recess as shown in FIG.
9
. In
FIG. 10
a cross-square drive bit which corresponds to recess C (
FIG. 3
) engages within the compound drive recess as shown in FIG.
11
. In
FIG. 12
a square drive bit which corresponds to recess D (
FIG. 4
) engages within the compound drive recess as shown in FIG.
13
. In
FIG. 14
a double-cross recess (as available under the trademark POZI) drive bit which corresponds to recess E (
FIG. 5
) engages within the compound drive recess as shown in FIG.
15
.
Although the screw driver bits, as shown in
FIGS. 6-13
, are capable of driving the aforementioned compound drive recess, they all fall short of being adequate to either maintain a best possible retention between the drive bit and the drive recess, or supply the maximum driving torque to the aforementioned compound drive recess. Hence, a specific screw drive bit with four fan-shaped blades for the aforementioned compound drive recess is devised to achieve their maximum performance.
Next, the screw drivers disclosed in U.S. Pat. Nos. 2,764,197 and 3,913,647 are specifically designed to fit in recess B (as shown in
FIG. 2
of U.S. Pat. No. 2,764,197) but not for the aforementioned compound drive recess; therefore, the maximum driving torques the above two screw drivers can supply will be less than this present invention when they are applied with the aforementioned compound drive recess.
SUMMARY OF THE INVENTION
The objective of the present invention is to offer a screw driver to fit in a particular compound drive recess which can be driven by several conventional drive bits (i.e. slot, cross, square-cross, square-cross, double-cross). With this invention, the aforementioned compound drive recess will be able to stand its maximum limit of driving torque supplied by the inventive driver. Further, the inventive driver is highly stable when retained within the drive recess to assure a smooth screw driving process.
The physical feature of this invention includes four fan-shaped blades symmetrically positioned with respect to each other, between every two adjacent ones of the fan-shaped blades include an elongated rectangular hollow indented space, and a square blunt protrusion is formed and situated in the common lower center section joining the four fan-shaped blades and the four hollow indented spaces.
The screw driver with a drive bit of the present invention has been found to be capable to lodge securely in the drive recess once the drive bit turns. Also, the four fan-shaped blades provide a complete and stable retention superior to conventional screw drive bits (i.e. shown
FIGS. 6
,
8
,
10
,
12
and
14
.)


REFERENCES:
patent: 4998454 (1991-03-01), Chaconas et al.
patent: 1562074 (1969-04-01), None

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