Abstract: A retractable cutter comprises a plunger that can be pressed to an on-position for pushing a thrust device of the cutter to guide a blade via a cam piston cartridge through a blade guide and partially outside a bottom retainer to expose the tip of the blade from a housing of the retractable cutter. In this on-position, a spring mechanism of the retractable cutter is engaged between the bottom retainer and the cam piston cartridge to provide a spring force for preventing the blade from extending any further. When the plunger is pressed to an off-position, the thrust device is positioned in such a way to enable the spring mechanism to rebound to its original position for retracting the blade back into the housing.

Abstract: Commutators for electro-dynamic machines such as electric motors comprise a cylindrical shell of insulated commutators bars, each of which has an outer layer with tangs extending from the outer layer and an inner layer with anchoring tabs extending therefrom. The commutating bars are typically produced from two strips of copper or other conductive metal. The inner layer may be formed of a thinner but stronger material, even of a non-conductive material, but is normally preferable to use two strips of copper to facilitate fusion of the materials together. The first strip, which is typically somewhat thicker than the second, is formed by punching so that partially formed tangs extend laterally from the side of the strip. The second strip is formed in a similar process to provide anchoring tabs extending from the sides of the second strip. These commutators can be produced economically and efficiently and can be adapted to a wide variety of applications and requirements.