Patent ID: 7474176

Claim:
A screw arrangement forming a screw cavity for receiving a threaded axle, the screw arrangement comprising: a first screw part, comprising: a first wall portion forming a first portion of the screw cavity and having a first interior surface and a first exterior surface; a first set of stationary semi-spheres formed on the first interior surface and protruding into the first portion of the screw cavity; and a resilient tongue extending in a spaced-apart relationship along the first exterior surface and comprising a bulge extending toward the first exterior surface; a second screw part, comprising: a second wall portion forming a second portion of the screw cavity and having a second interior surface and a second exterior surface; and a second set of stationary semi-spheres formed on the second interior surface and protruding into the second portion of the screw cavity; wherein the second portion of the screw cavity is also for receiving the first wall portion and the second exterior surface forms a recess for receiving the bulge when the screw arrangement is assembled; and a resilient part disposed between and biased to separate the first screw part and the second screw part when the screw arrangement is assembled, the first screw part and the second screw part then being held in communication by the bulge and recess; wherein the stationary semi-spheres are disposed to follow the turn of the threads of the threaded axle when the threaded axle is received into the screw cavity and rotated.