Permanent magnet for extracting foreign bodies from the eyes - is of cobalt and rare earth alloy to provide power as great as electromagnet and shaped for easy handling

摘要

A permanent magnet is adapted for extracting foreign bodies from the eyes. The magnetic material is an alloy of cobalt with a rear earth (samarium) containing 58-76% of cobalt by weight. The magnet is cylindrical, with a tapering pole piece (or perhaps several, interchangeable). The length of the cylinder is 0.3-1.5 times its diameter (D); the dia. of the base of the pole piece is less than D (pref. 0.15-0.75D). For foreign bodies at the front of the eye there is a pointed pole piece of length 0.25-0.5d, for those at the back, a spherical cap pole piece extending less than 0.25D from the face of the magnet.