Improved Oakman insulator design.

Insulator.

The cut shows a form of insulator designed as an improvement over the ordinary glass petticoat form. The illustration explains itself. The interior surface has upon it annular projections forming grooves. The upper sides of these grooves are inclined, but their under sides

are nearly or quite horizontal. By this construction not only is the surface distance from the pin to the conducting wire increased, but the interior of the "petticoat" is much better protected from moisture by means of the ridges. These ridges protect the grooves, and thus keep at least a part of the surface dry, a consideration of great importance in insulation.

This insulator has recently been patented by Samuel Oakman of Melrose, Mass.