Patent EA-001555-B1 (EA)
Title: Spiral drive system for threaded fasteners
Inventor: STACY W DODD
IPC: B21K1/46
Filed: 1998-10-28
Abstract: 1. A threaded fastener having a longitudinal axis (44) and a driver-engageable recess (18) at an end of the fastener, the recess having a central portion (20); a plurality of wings (22) radiating outwardly from the central portion, the wings each being defined by a pair of side walls (24, 26); characterized by at least one of the side walls being configured to define a segment of a spiral that has an initial point (54) spaced from the longitudinal axis of the fastener by an initial radius (Ri) and extends to an outer terminal point at a radius that is no more than about 3.5 times that of the initial radius. 2. A fastener as defined in claim 1 further characterized in that no portion of the spiral segment has a tangent to which a perpendicular line makes an angle to a radius from the longitudinal axis to the point of tangency that is less than 17 degree . 3. A threaded fastener as defined in claim 1 further characterized in that the spiral comprises a constant gap spiral. 4. A threaded fastener as defined in claim 3 further characterized in that the spiral is defined by the equation    where: θ = the rotation angle (in radians) of a ray crossing the curve at a distance R from the axis of rotation; Ri = the initial radius as measured from the axis of rotation to the initial point of the spiral; and R = the radius of the spiral at a rotation angle θ, also measured from the axis of rotation. 5. A threaded fastener as defined in claim 4 further characterized in that the spiral segment defined by the drive wall extends from the initial point to an outer terminal point that lies at a radius that is about three times that of the initial radius. 6. A threaded fastener as defined in claim 2 further characterized in that the spiral segment defined by drive wall extends from the initial point to an outer terminal point that lies at a radius that is about two times that of the initial radius. 7. A threaded fastener as defined in claim 1 further characterized in that the arc circumscribed by the spiral drive wall is no more than about 125 degree . 8. A threaded fastener as defined in claim 1 further characterized in that the arc circumscribed by the spiral drive wall is no more than about 90 degree . 9. A threaded fastener as defined in claim 1 further characterized in that the arc circumscribed by the spiral drive wall is no more than about 45 degree . 10. A threaded fastener as defined in claim 1 further characterized in that each of the wings has an installation wall (24) and a removal wall (26) and wherein the removal wall has said spiral configuration. 11. A threaded fastener as defined in claim 1 further characterized in that each of the wings has an installation wall (24)and a removal wall (26) and wherein the installation wall is configured to include said spiral. 12. A threaded fastener as defined in claim 1 further characterized in that each of the wings (24) has an installation wall (26) and a removal wall and wherein both of the installation and removal walls have said spiral configuration. 13. A threaded fastener as defined in any one of claims 10-12 further characterized in that one of the walls is configured to have a greater torque capacity than the other. 14. A threaded fastener as defined in claim 13 further characterized in that the side wall with greater torque capacity comprises the removal wall (26). 15. A threaded fastener as defined in any one of claims 10-12 wherein each of the installation and removal walls is configured to have substantially equal torque capacity. 16. A threaded fastener as defined in claim 1 wherein the walls of the wing are symmetrical about a radial plane extending from the longitudinal axis of the fastener through the wing. 17. A threaded fastener as defined in claim 1 wherein the walls of the wing are asymmetrically disposed about a radial plane extending from the longitudinal axis of the fastener through the wing. 18. A threaded fastener having a longitudinal axis and a driver-engageable recess (18) at an end of the fastener, the recess having an installation drive wall (24) and a removal drive wall (26); at least one of the drive walls being configured to define a segment of a spiral that has an initial point (54) spaced from the longitudinal axis of the fastener by an initial radius (Ri) and extends to an outer terminal point at a radius that is no more than about 3.5 times that of the initial radius. 19. A threaded fastener having a longitudinal axis and a head, an external surface extending about at least part of the periphery of the head characterized by the external surface including at least one side wall configured to define a segment of a spiral that has an initial point (54) spaced from the longitudinal axis (44) of the fastener by an initial radius (Ri) and extends to an outer terminal point at a radius that is no more than about 3.5 times that of the initial radius. 20. A fastener as defined in claim 19 further characterized in that no portion of the spiral segment has a tangent to which a perpendicular line makes an angle to a radius from the longitudinal axis to the point of tangency that is less than 17 degree . 21. A threaded fastener as defined in claim 19 further characterized in that the spiral comprises a constant gap spiral. 22. A threaded fastener as defined in claim 21 further characterized in that the spiral is defined by the equation   where: θ = the rotation angle (in radians) of a ray crossing the curve at a distance R from the axis of rotation; Ri = the initial radius as measured from the axis of rotation to the initial point of the spiral; and R = the radius of the spiral at a rotation angle θ, also measured from the axis of rotation. 23. A threaded fastener having a longitudinal axis and a head, the head being formed to include driver engageable surfaces disposed about the longitudinal axis, further characterized by at least one of the surfaces being configured to define a segment of a spiral that has an initial point (54) spaced from the longitudinal axis (44) of the fastener by an initial radius (Ri) and extends to an outer terminal point at a radius that is no more than about 3.5 times that of the initial radius. 24. A threaded fastener and driver therefor, in combination, characterized by a threaded fastener as defined in claim 23; a driving tool having driving surfaces engageable with the drivable surfaces of the fastener, further characterized by the driving surfaces of the driving tool substantially paralleling those of the fastener but being of a different transverse cross-sectional size to enable the driver to be engaged with the head of the fastener so that their respective driving and drivable surfaces may be separated by a clearance adapted to permit limited rotation of the driver with respect to the fastener, the spiral surfaces of the driver and fastener being configured to enable substantial and simultaneous face-to-face contact when the driver is rotated through the clearance angle and into engagement with the corresponding faces of the fastener. 25. A threaded fastener and driver therefor, in combination, characterized by a threaded fastener as defined in claim 1; a driver having a shank and a tip formed at the end of the shank, the tip having a plurality of wings having side walls further characterized in that the side walls substantially parallel those of the recess but are of reduced transverse cross-sectional size to enable the driver to be inserted into the recess with a remaining clearance between the two and to permit limited rotation of the driver within the recess, the spiral surfaces of the driver and recess being configured to enable substantial and simultaneous face-to-face contact when the driver is rotated through the clearance angle and into engagement with the driving faces of the recess. 26. A driver and fastener combination as defined in either one of claims 24 or 25 further characterized in that said spiral surfaces are defined by a constant gap spiral. 27. A driver and fastener combination as defined in either one of claims 24 or 25 further characterized in that the spiral is defined by the equation   where: θ = the rotation angle (in radians) of a ray crossing the curve at a distance R from the axis of rotation; Ri = the initial radius as measured from the axis of rotation to the initial point of the spiral; and  R = the radius of the spiral at a rotation angle θ, also measured from the axis of rotation. 28. A driver and fastener as defined in claim 27 further characterized in that the spiral surface extends from an initial point spaced from the longitudinal axis of the screw by an initial radius and extends to a terminal point at a radius that is not greater than about 3.5 times the initial radius. 29. A driver and fastener as defined in claim 27 further characterized in that the terminal point is at a radius that is not greater than three times the initial radius. 30. A driver and fastener as defined in claim 27 further characterized in that the terminal point is at a radius not greater than about two times the initial radius. 31. A driver for driving a recess headed fastener, the driver having a shank, a nib formed at the end of the shank, the nib having a central portion and a plurality of wings radiating outwardly from the central portion, each of the wings having an installation wall and a removal wall, characterized by the wings being configured so that at least one of the installation or removal walls defines a segment of a spiral that has an initial point spaced from the longitudinal axis of the fastener by an initial radius and extends to an outer terminal point at a radius that is no more than about 3.5 times that of the initial radius. 32. A driver as defined in claim 31 further characterized in that no portion of the spiral segment has a tangent to which a perpendicular line makes an angle to a radius from the longitudinal axis to the point of tangency that i