Patent ID: 8585339
Filing Date: 2013-11-19
Classification: A61C

Abstract:
1. A screw system comprising: a rotary tool; a male screw; a head part; and a hole formed at the head part, wherein, an inner peripheral face of the hole having an engaging recessed part so as to be engageable with an engaging projected part on an outer peripheral face of a tapered engaging part which is a top end part of the rotary tool, and a stepped part, and in a cross section containing a center axis of a screw member, which includes said male screw, head part and hole, the inner peripheral face of the hole is parallel to the center axis of the screw member, or the inner peripheral face of the hole becomes closer to the center axis of the screw member from the head part of the screw member toward the male screw and also is parallel to the center axis of the screw member, or the inner peripheral face of the hole becomes closer to the center axis of the screw member from the stepped part of the screw member toward the male screw, and only a head part side end edge of the hole and an end edge of the stepped part simultaneously engage with the engaging projected part of the rotary tool to wedge the engaging projected part, and at the head part side end edge of the hole an angle between the inner peripheral face of the hole and the head part of the screw member is 90±5 degrees and at the end edge of the stepped part an angle between the inner peripheral face of the hole and the stepped part is 90±5 degrees.