Recessed screw

• US 5,553,983 A
• Filed: 11/09/1993
• Issued: 09/10/1996
• Est. Priority Date: 11/17/1992
• Status: Expired due to Term

• Current Assignee: Yugenkaisha Shinjo Seisakusho
• Original Assignee: Yugenkaisha Shinjo Seisakusho
• Inventors: Shinjo, Katsumi
• Primary Examiner(s): Wilson, Neill R.
• Application Number:
  US08/149,624
• Time in Patent Office: 1,036 Days
• Field of Search: 411/402, 411/403, 411/404, 411/405, 411/919, 81/436, 81/460
• US Class Current: 411/404
• CPC Class Codes: B25B 15/005 with cross- or star-shaped cross-section
• CPC Class Codes: F16B 23/00 Specially shaped nuts or heads of bolts or screws for rotations by a tool detachable ornamental heads for screws A47G3/00; screwdrivers, wrenches B25B
• CPC Class Codes: Y10S 411/919 Screw having driving contacts

Abstract

A recessed screw has a recess formed in the head of screw, with the recess being defined as a superimposition of two equilaterally-triangular recesses each having vertices shaped arcuate and arranged coaxially with a phase shift of 60° around the screw axis. The recess thus has alternating six grooves and six driven vanes having side walls extending parallel with the axis, and an inner ridge of vane is a conically curved sticking wall inwardly slanted towards a bottom of the recess. A cross-sectional area of groove is larger than that of each vane. A driver bit has six driving vanes in conformity with the grooves and six valleys each interposed between the adjacent driving vanes and corresponding to the driven vanes in the recess, such that a biting action appears between the recess and bit, the driving vanes can be strengthened, and any conventional bit for Torx screws can be used with the recessed screw.

Claims

1. A recessed screw comprising a screw body having a head with a recess formed therein, the recess being defined as a coaxial superimposition of two equilaterally-triangular recesses which each have arcuate vertices and which are arranged with a phase shift of 60°

about a longitudinal axis of the recessed screw to thereby provide six engagable grooves and six driven vanes alternating with one another at regular angular intervals, inner ridges of each of said driven vanes being chamfered to form a conically curved sticking wall which is inwardly slanted towards a bottom of the recess, with sidewalls of each driven vane converging to form a point at the inner end of the sticking wall as the sticking wall intersects the bottom of the recess, the sidewalls of each driven vane extending in parallel with the longitudinal axis of said screw to provide flat planes continuing to a partially cylindrical surface of the corresponding arcuate vertex, the cross-sectional area of each engagable groove being larger than the cross-sectional area of each of the adjacent driven vanes over at least the inner half of the recess, each cross-sectional area being defined by a first circle inscribing innermost points of said six driven vanes and a second circle circumscribing the arcuate vertices of said six engagable grooves.

2. A recessed screw in accordance with claim 1, wherein the ratio of the diameter of the inscribed circle to the diameter of the circumscribed circle is in the range of from 0.70 to 0.75.

3. A recessed screw comprising a screw body having a head with a recess formed therein, said recess being defined as a coaxial superimposition of two equilaterally-triangular recesses which each have arcuate vertices and which are arranged with a phase shift of 60°

about a longitudinal axis of the recessed screw to thereby provide six engagable grooves and six driven vanes arranged at regular angular intervals, each engagable groove having an arcuate outer bottom and inner sidewalls, with adjacent sidewalls of each pair of adjacent engagement grooves defining one of said six driven vanes, the sidewalls of each driven vane extending in parallel with the longitudinal axis of the recessed screw, and inner ridges of each driven vane being chamfered to form a conically curved sticking wall which is inwardly slanted towards a bottom of the recess, wherein over at least the inner half of the recess the cross-sectional area of each engagable groove is larger than the cross-sectional area of the adjacent driven vane.

4. A recessed screw in accordance with claim 3, wherein the ratio of the diameter of a circle inscribing the innermost points of said six driven vanes to the diameter of a circle circumscribing the arcuate vertices of said six engagable grooves is in the range of from 0.70 to 0.75.