Patent ID: 6904833

Claim:
A closed asymmetric spline wrench for turning a threaded fastener, the fastener having a fastener central axis and generally radially outwardly extending fastener splines from the fastener central axis and separated by recesses, each fastener spline having a tightening surface for tightening the fastener in response to the application of sufficient torque to the tightening surface, and a loosening surface for loosening the fastener in response to the application of sufficient torque to the loosening surface; said wrench having a wrench central axis, and comprising: a body having a plurality of wrench splines extending generally radially inwardly with respect to the wrench central axis and separated by alternating radial recesses, each of said wrench splines fitting in a respective recess of the fastener for engaging the fastener splines for applying torque to the fastener splines to turn the fastener; the central wrench axis being generally coaxial with the central fastener axis when said wrench splines are fitted in the fastener recesses; each wrench spline having a first surface on a first side of said wrench spline and a second surface on a side opposite from said first side of said wrench spline; said first surface having an inner end relatively close to said wrench central axis and an outer end, said first surface making a first interior angle with a radius intersecting said inner end, and said second surface having an inner end relatively close to said wrench central axis and an outer end, said second surface making a second interior angle with a radius intersecting said inner end of said second surface, said second interior angle being less than said first interior angle; said body having inner joining surfaces intersecting said first surface and said second surface of each of said wrench splines, said intersections being curved surfaces for engaging a fastener and effecting a lower amount of concentrated stress than intersections composed of linear corners.