Tools – Wrench – screwdriver – or driver therefor – Rigid jaws
Reexamination Certificate
2000-03-09
2001-07-31
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Rigid jaws
C081S186000
Reexamination Certificate
active
06267028
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hand tools, particularly wrenches and most particularly open end type wrenches.
BACKGROUND OF THE INVENTION
An open end wrench is a wrench that has an open ended wrench head used to turn and control the rotation of bolts, nuts and various fasteners. Examples of open end wrenches include, but are not limited to, double open end, combination, flare nut, flex head etc. An open end wrench can access fasteners under certain limited-access conditions where a closed end or box wrench cannot, however, an open end wrench is much weaker by design than a box wrench. The weakness is associated with the inevitable jaw spread produced by the cam effect of fastener to wrench, under torque. This inherent weakness reduces torque capacity and promotes fastener deformation and wrench wear.
Subsequently, there have been numerous attempts to increase the strength and torque capacity of open end wrenches. The use of sharp teeth or serrations has been relatively effective on all but extremely hard fasteners, however, this technology sacrificed the fastener to gain additional torque by leaving bite or shred marks on the fastener. The use of inclined and arcuate driving surfaces has been effective at reducing the bite marks and fastener deformation, however, this technology has been generally less effective at increasing wrench strength and torque capacity. In addition, most prior attempts to improve the torque capacity of open end wrenches have consequently produced an increase in the total free play arc between wrench and fastener which applicant believes to be objectionable to most users.
SUMMARY OF THE INVENTION
The present invention involves a unidirectional, high torque, open end wrench head which when turned in a predetermined direction can provide a substantial increase in torque capacity while reducing fastener deformation and wrench wear.
The present invention more specifically involves a one piece, open end wrench head for a fastener having at least two substantially parallel outer engaging surfaces creating an across-width dimension. The open end wrench head has an orifice which includes four principle internal engaging surfaces which are arranged about an imaginary central axis with the first and second internal engaging surfaces positioned on a first jaw and the third and fourth internal engaging surfaces positioned on a second opposing jaw. The first internal engaging surface is substantially flat and substantially parallel to the imaginary central axis and positioned closer to the open end of the wrench head than the second internal engaging surface. The second internal engaging surface diverges outward from the first internal engaging surface. The third internal engaging surface asymmetrically opposes the second internal engaging surface and is substantially flat and substantially parallel to the imaginary central axis and positioned farther away from the open end of the wrench head than the fourth internal engaging surface. The fourth internal engaging surface asymmetrically opposes the first internal engaging surface and diverges outward from the third internal engaging surface. The second and fourth internal engaging surfaces are spaced apart by a dimension slightly less than the across-width dimension of the fastener which provides a pinching effect to the fastener under torque. In some preferred embodiments the second and fourth internal engaging surfaces are substantially flat, while in other preferred embodiments the second and fourth internal engaging surfaces are substantially arcuate.
The present invention has been developed recognizing the inevitable jaw spread of a standard open end wrench under torque and the subsequent need to increase wrench strength and torque while reducing fastener deformation and wrench wear. The present invention wrench, therefore, relies upon a predetermined amount of jaw spread to develop a “pinch locking” effect and substantial surface-to-surface engagement with a fastener during the torque process. In addition, the present invention has been developed recognizing the need to achieve such increases in performance without increasing the total free play arc between wrench and fastener or precluding wrench head offset (“flip-flop”) capability.
Accordingly, it is an important objective of the present invention described above to significantly increase the strength and torque capacity of an open end wrench head without sacrificing the fastener by leaving bite marks, shred marks or otherwise deforming the fastener.
It is another objective of the present invention to achieve the improved performance without significantly increasing the total free play arc between wrench and fastener and while maintaining the ability to flip the wrench over or “flip-flop” the wrench in limited access situations.
It is another objective of the present invention that it be commercially viable, simple in design, and cost efficient to manufacture.
REFERENCES:
patent: D. 357618 (1995-04-01), Macor
patent: D. 412819 (1999-08-01), Macor
patent: 4776244 (1988-10-01), Olson et al.
patent: 5131312 (1992-07-01), Macor
patent: 5582083 (1996-12-01), Baker
patent: 5953968 (1999-09-01), Macor
Meislin D. S.
Proprietary Technologies, Inc.
LandOfFree
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