Helical coil wire insert for fixing bolts in concrete - has screwed collar engaging outside of insert to increase strength of attachment

摘要

A helical coil wire insert (1) in the form of a close coiled compression spring is cast in position in a mass of concrete forming a wall or floor. The coils then form a screw thread for the bolt (2). When it is necessary to limit the depth of penetration of the bolt (2), a plate (3) is inserted between two adjacent coils. This plate also increases the bond between concrete and insert. To increase the strength of the bond between concrete and insert still further, a collar (4) with a suitable threaded central hole is screwed onto the insert (1) before placing it in the concrete mould.