Locknut

Claim 1

A locknut for cooperating with standard screw thread convolutions on an externally threaded member, said locknut comprising a metal nut body having a countersunk opening extending axially therethrough, a screw thread formed in a sidewall of said opening, said screw thread including a plurality of standard thread convolutions and an outermost thread convolution having axially offset flank sections which are circumferentially spaced apart and are adapted to interfere with the screw thread convolutions on the externally threaded member to provide a locking action between said nut body and the externally threaded member, each of said axially offset flank sections having a radially innermost portion which extends radially inwardly of the crests of said standard thread convolutions and having a continuously curving inner flank surface which has a first circumferential extent at the root of said outermost thread convolution and a second circumerential extent which is smaller than said first circumerential extent at the crest of said outermost thread convolution To provide for frictional engagement between the crest portion of a standard thread convolution on the externally threaded member and said axially offset flank section prior to frictional engagement between the root portion of the thread convolution in the externally threaded member and the axially off set flank section during relative movement between said locknut and the externally threaded member, a face surface circumscribing said countersunk opening adjacent to said outermost thread convolution, said face surface extending transversely to the axis of said nut body and having a generally circularly extending line of intersection with said countersunk opening at locations which are circumferentially spaced from said axially offset flank sections of said outermost thread convolution, and a plurality of arcuate indentations extending axially and radially inwardly from said face surface into said outermost thread convolution at said axially offset sections of said outermost thread convolution, each of said indentations being formed by a continuous concave surface which forms a portion of a cone having a longitudinal axis extending at an acute angle to the axis of said nut body and having a base disposed radially outwardly of the root of said outermost thread convolution and a peak disposed radially inwardly of the crest of said outermost thread convolution, said concave surface having a continuously and radially outwardly curving line of intersection with said face surface, said line of intersection between said concave surface and said face surface being disposed radially outwardly of said circularly extending line of intersection between said countersunk opening and said face surface.