Tools – Wrench – screwdriver – or driver therefor – Having work engaging and force exerting portion inserted...
Reexamination Certificate
2002-01-12
2003-12-02
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Having work engaging and force exerting portion inserted...
C081S441000
Reexamination Certificate
active
06655241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to fastener driver tool bits and, more particularly, to fastener driver tool bits that include features that prevent or reduce the tendency of a tool bit end to “skip” or “slide out” from the slots in fastener heads.
2. Background of the Prior Art
Screwdrivers, tool bit fastener drivers, Phillips screwdrivers and the like, when inserting or extracting a fastener from a workpiece, will at times “slip” or “skip” from the slot in the head of a fastener while imparting rotary motion to the fastener. Generally, the bit end of the fastener driver skips from the fastener after the fastener has been completely inserted into the workpiece, or when attempting to remove a corroded or relatively “old” fastener from the workpiece. When the tool bit skips from the fastener, the end of the bit has a tendency to tear away or wear down a portion of the side walls forming the slot in the head of the fastener. Repeated skips can deform the slot side walls such that the tool bit is incapable of imparting rotary motion to the fastener.
Prior art driver bits have attempted to correct the skipping problem by including relatively small recesses in the side walls of the flutes or crossing members that form the tip or drive portion of the bit. The recesses form edges that grip or “bite” into the side walls of the slot to promote rotary motion transfer between the driver bit and fastener. The recesses are machined in each side wall of each crossing member such that a right angle is formed between the recesses and the longitudinal axis of the bit when taking a side elevation view of the bit. Further, recesses are machined radially across the flutes to form multiple concentric arc segments when taking a drive end elevation view of the bit as disclosed in U.S. Pat. No. 4,998,454.
The problem with prior art driver bits that include recesses that grip the side walls of the slot of the fastener, is that there are an excessive number of recesses which structurally weaken the bits causing the bits to routinely break or deform when rotary motion sufficient to rotate the fastener, is imparted upon the bit from a rotary driver. A need exist for a driver bit that is capable of gripping the side walls that form the slot in the head of a fastener, and that is sufficiently strong to impart, without deforming or breaking, required rotary motion upon the fastener.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a screwdriver type tool bit that will not slide out from the slots (anti-skip) in a fastener when a rotary force is imposed upon the tool bit while inserting or extracting the fastener from a workpiece.
A principal object of the present invention is to provide an improved fastener driver that “grips” a side wall forming a slot in the head of the fastener. A feature of the improved fastener driver is one or more recesses in predetermined side walls of crossing members of a “Phillips type” screwdriver. An advantage of the improved fastener driver is that engagement between the driver and the fastener is maintained while the fastener is inserted into or extracted from a workpiece. Another advantage of the improved fastener driver is that constant rotary motion is imparted from the driver to the fastener when the fastener is inserted into or extracted from a workpiece.
Another object of the present invention is to provide gripping capability to a fastener driver while maintaining the structural strength of the driver. A feature of the improved fastener driver is one or more recesses forming edges that engage or “bite” into walls forming a driver receiving slot in a fastener. Another feature of the improved fastener driver is one or more recesses disposed in one of two side walls of each crossing member, the fastener driver being comprised of four crossing members. An advantage of the improved fastener driver is that the bit end of the driver maintains engagement with the fastener while imparting rotary force thereupon without bending or breaking the bit end.
Yet another object of the present invention is to provide a fastener driver having one or more recesses in side walls of the crossing members, the recesses being inclined relative to the longitudinal axis of the driver. A feature of the improved fastener driver is longer gripping edges formed by the inclined recesses. An advantage of the improved fastener driver is that gripping capability is increased without decreasing structural integrity.
Still another object of the present invention is to provide an improved blade type or “standard” fastener driver. A feature of the improved standard screwdriver is one or more recesses machined in opposing side walls of the screwdriver. An advantage of the improved standard screwdriver is that the screwdriver is capable of gripping a corresponding fastener thereby maintaining engagement between the screwdriver and fastener while the fastener is inserted into or extracted from a workpiece.
Another object of the present invention is to improve the gripping capability of a standard screwdriver while maintaining structural strength. A feature of the standard screwdriver is one or more recesses extending across a portion of each side wall forming the bit end of the screwdriver. An advantage of the standard screwdriver is that substantially the same amount of bitting edge from the partially extending recesses (compared to a recess extending totally across each side wall) engage the side walls forming the corresponding slot of the fastener thereby providing gripping capability and maintaining the quantity of rotational force that may be imparted from the screwdriver to the fastener.
Another object of the present invention is to improve the gripping capability of a Phillips screwdriver when inserted into relatively shallow receiving recesses disposed in a fastener. A feature of the screwdriver is one or more recesses disposed relatively close to the bit end. Another feature of the screwdriver is a crowned bit end formed from arcuate crossing members. An advantage of the screwdriver is that the entire edge of the recesses engage corresponding side walls of the recesses in the fastener to maximize gripping capability. Another advantage of the screwdriver is that the arcuate crossing members allow the crown portion of the bit end to engage a center portion of the fastener while the crossing members accommodate a foreign material built-up in the corners of the fastener recesses thereby promoting complete engagement between the edges of the recesses in the bit end and the walls of the recesses in the fastener.
Briefly, the invention provides an anti-skip fastener tightening and/or extraction device comprising a tool bit end having a plurality of crossing members, each crossing member having at least one recess positioned in a side wall, said recesses forming edges that engage corresponding portions of a fastener to maintain engagement between said tool bit end and the fastener when forcibly rotating the fastener to drive the fastener into a workpiece, said recesses forming edges that engage corresponding portions of the fastener to maintain engagement between said tool bit end and the fastener when forcibly rotating the fastener to extract the fastener from a workpiece.
REFERENCES:
patent: 1738405 (1929-12-01), Thal
patent: 1741349 (1929-12-01), Sullivan
patent: 1899489 (1933-02-01), Wickbergh
patent: 2389129 (1945-11-01), Bishop
patent: 4084478 (1978-04-01), Simmons
patent: 6223634 (2001-05-01), Hughes et al.
Cherskov & Flaynik
Meislin D. S.
LandOfFree
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