Fastener driver

Claim 2

A fastener driver comprising a body having a fitting recess, said fitting recess having its inner periphery provided with a plurality of ribs and a plurality of engagement grooves defined between the respective adjacent ribs, said fitting recess forming a first circle at its cross section; each of said ribs forming at its cross section a partial circle bowed inside of the first circle; the center of the partial circle being situated on a corresponding radial line extending from the center of the first circle and within a range of said radial line defined between said latter center and a first intersection where two tangential lines intersect, said tangential lines being tangent to the first circle at second intersections respectively where the first circle intersects the partial circle, said partial circle of each said rib having a constant radius over the length of each said rib, and each rib extending in alignment with the generatrix of said inner periphery of said fitting recess.

Claim 3

A fastener driver according to claim 1 wherein said center of the partial circle is situated between the first intersection and a chord connecting the second intersections.

Claim 4

A fastener driver according to claim 2 wherein the ribs of the fitting recess are equidistantly spaced circumferentially of the fitting recess, and the diameter of the rib partial circle is defined by the equation:

Claim 5

A fastener driver according to claim 3 wherein the number of said ribs is four to eight.

Claim 6

A fastener driver according to claim 1 wherein said body is provided with a handle grip for rotating the body about the central axis of the fitting recess.

Claim 7

A fastener driver according to claim 5 wherein said handle grip radially extends from the body in a manner integral therewith.

Claim 8

A fastener driver according to claim 5 wherein said body is formed with a handle engaging hole; and said handle grip is detachably engageable with said engaging hole.

Claim 9

A fastener driver comprising a body having a fitting recess, said fitting recess having its inner periphery provided with a plurality of ribs and a plurality of engagement grooves defined between the respective adjacent ribs, wherein, when said driver is fitted to a fastener element having a similar cross section to that of the fitting recess, said ribs and engagement grooves of the fitting recess are engaged with corresponding grooves and lobes of the fastener element respectively, said fitting recess forming a first circle at its cross section; each of said ribs forming at its cross section a partial circle bowed inside of the first circle; the center of the partial circle being situated on a corresponding radial line extending from the center of the first circle and within a range of said radial line defined between said latter center and a first intersection where two tangential lines intersect, said tangential lines being tangent to the first circle at second intersections where the first circle intersects the partial circle, said partial circle of each said rib having a constant radius over the length of each said rib, and each rib extending in alignment with the generatrix of said inner periphery of said fitting recess; and the ribs and the engagement grooves of the fitting recess being respectively inclined to the central axis of the fitting recess at angles defined by the equations: 1* < or = Alpha Beta < 10* Alpha Beta < Nu theta where Alpha represents the inclined angle of the rib of the fastener driver, Beta the inclined angle of the engagement groove of the fastener driver, Nu the inclined angle of said corresponding groove of the fastener element, and theta the inclined angle of the lobe of the fastener element.

Claim 10

A fastener driver comprising a body having a fitting recess, said fitting recess having its inner periphery provided with a plurality of ribs and a plurality of engagement grooves defined between the respective adjacent ribs, wherein, when said driver is fitted to a fastener element having a similar cross section to that of the fitting recess, said ribs and engagement grooves of the fitting recess are engaged with corresponding grooves and lobes of the fastener element respectively, said fitting recess forming a first circle at its cross section; each of said ribs forming at its cross section a partial circle bowed inside of the first circle; the center of the partial circle being situated on a corresponding radial line extending from the center of the first circle and within a range of said radial line defined between said latter center and a first intersection where two tangential lines intersect, said tangential lines being tangent to the first circle at second intersections where the first circle intersects the partial circle, said partial circle of each said rib having a constant radius over the length of each said rib, and each rib extending in alignment with the generatrix of said inner periphery of said fitting recess; and the ribs and the engagement grooves of the fitting recess being respectively inclined to the central axis of the fitting recess at angles defined by the equations: 1* < or = Alpha Beta < 10* Alpha Beta < Nu theta where Alpha represents the inclined angle of the rib of the fastener driver, Beta the inclined angle of the engagement groove of the fastener driver, Nu the inclined angle of said corresponding groove of the fastener element, and theta the inclined angle of the lobe of the fastener element.

Claim 11

A fastener driver according to claim 8 wherein said center of the partial circle is situated between the first intersection and a chord connecting the second intersections.

Claim 12

A fastener element according to claim 9 wherein the ribs of the fitting recess are equidistantly spaced circumferentially of the fitting recess, and the diameter of the rib partial circle is defined by the equation:

Claim 13

A fastener element according to claim 10 wherein the number of said ribs is four to eight.

Claim 14

A fastener element according to claim 8 wherein said body is provided with a handle grip for rotating the body about the central axis of the fitting recess.

Claim 15

A fastener driver according to claim 12 wherein said handle grip radially extends from the body in a manner integral therewith.

Claim 16

A fastener driver according to claim 12 wherein said body is formed with a handle engaging hole; and said handle grip is detachably engageable with said hole.