Tools – Wrench – screwdriver – or driver therefor – Having work engaging and force exerting portion inserted...
Reexamination Certificate
2000-09-22
2002-06-04
Hail, III, Joseph J. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Having work engaging and force exerting portion inserted...
C081S436000
Reexamination Certificate
active
06397710
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to screwdrivers for driving Phillips-type socket screws. These type of screwdrivers are also known as Cross head, star, Pozidriv and Reed & Prince. In particular this invention relates to a screwdriver with an improved blade configuration.
Referring to
FIG. 1
, a prior art Phillips or cross-point, No.2 screwdriver
11
has a drive axis
13
and a bit
15
at its distal end. Bit
15
has four orthogonal blades
17
that are each tapered at approximately 26 degrees or less relative to drive axis
13
. The tip
19
of bit
15
is further tapered from the blades
17
to form a conical point. Screwdriver
11
is sized for driving socket screws such as the No.2 screw
21
shown, although screwdriver
11
could also drive No.1 or No.3 screws as well. Screw
21
has an axis
23
and a countersunk head
25
with a slotted socket
27
. When viewed from above, slotted socket
27
appears as a cross or addition symbol that is well suited to be driven by the orthogonal blades
17
of screwdriver
11
. Socket
27
has an axial depth of approximately 0.125 inches into head
25
, although screwdriver
11
penetrates only about 0.100 inches therein.
The tapered inner surfaces of socket
27
are inclined at an angle that is approximately 26 degrees or more relative to axis
23
. The difference in tapers between blades
17
and socket
27
allow screwdriver
11
to be easily inserted and removed from screw
21
during operation. However, the taper difference also forces screwdriver
11
to contact screw
21
exclusively along its socket threshold region, indicated by brackets
29
. Since contact points
29
are unsupported above the top surface of screw
21
, socket
27
will tend to wear over time and may even become stripped out and unusable. Also note that the deep penetration of screwdriver
11
into screw
21
and the similarities of their tapers prevent the axis
13
of screwdriver
11
from being tilted more than about one degree off axis
23
of screw
21
(i.e. two degrees total in any plane). Sometimes it is not possible to be within one degree due to obstructions, making it difficult to properly drive screw
21
.
Phillips head type screwdrivers are also known to “cam-out” of the screw socket while in use. The term “cam-out” is known in the art and refers to the tendency of the screw blades when under increasing torque to move out of the screw slot. This may occur in a violent manner, injuring the hands of the user and damaging the screw socket, thereby making it difficult for repeat applications of a screwdriver.
SUMMARY OF THE INVENTION
A Phillips-shaped screwdriver has a cylindrical metal shaft having an axis coaxial with an insertion direction for driving a screw having a socket. The bit section is formed on a distal end of the shaft and has a diameter equal to the shaft, tapering to a conical portion. The bit section has a first circumferential groove formed in the exterior. Blades are formed on the bit section and consequently each blade has a groove extending across its width that is in a common plane with each other blades groove. A distal end of the first groove is substantially axial where it intersects the bit section. When the screwdriver engages the screw socket, the conical portion inserts to a depth which allows the circumferential groove to substantially align with a top portion of the socket, and a surface area on the bit section engages an interior surface area of the socket for transmitting torque receiving surfaces. The circumferential groove provides a clearance between the bit section and socket top. This design provides a wobble of four degrees total. A variety of shapes may be selected for the circumferential groove. Typically, convex, concave, flat, straight, and v-shaped grooves have been chosen, but any combination of the above may be selected to obtain desired characteristics relating to “cam-out” and a force required to pull it from the screw socket while under torque load. The number of grooves provided on each blade of the bit will vary with the number of different size screws that can be driven by that bit. In another embodiment, the bit section is formed on a distal end of the shaft and has a diameter equal to the shaft tapering to a frustoconical portion. In this design the amount of wobble may be up to six degrees total.
REFERENCES:
patent: 1782981 (1930-11-01), Anderson
patent: 3409058 (1968-11-01), La Pointe
patent: 3831648 (1974-08-01), Hill et al.
patent: 3985170 (1976-10-01), Iskra
patent: 4105056 (1978-08-01), Arnn
patent: 4111078 (1978-09-01), Seamon
patent: 4434688 (1984-03-01), Bowles
patent: 4998454 (1991-03-01), Chaconas et al.
patent: 5224402 (1993-07-01), Pettersson
patent: 5269209 (1993-12-01), Baker
patent: 6216569 (2001-04-01), Hu
patent: WO 90/01399 (1990-02-01), None
Phillips Head Screwdriver, A Man's Life, Cosmic Toolkit at http://www.manslife.com/hardmach.
Untitled Document at http://www.sears.com.
Thomas Register of American Manufacturers at http://www5.thomasregister.com.
Bracewell & Patterson L.L.P.
Danganan Joni B.
David Baker Inc.
Hail III Joseph J.
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