Magnetic latching crossbar switches: A new development in magnetic properties of tool steel

A magnetic latching function in crossbar switch hold magnets is obtained by means of a specially designed magnet core made of high-carbon tool steel. The fabricated core detail is given a hardening heat-treating cycle, regulated to produce a particular degree of physical hardness that was found to impart the optimum combination of magnetic properties needed to obtain pulse operation and magnetic latching of the electromagnet under a wide range of contact spring loads. The nominal latching force developed with this new electromagnet design is 4 lbs, with a cylindrical core of only 0.11 square inch cross-sectional area. The electrical operating power need be only 2.5 watts applied for 0.100 second or about 18.0 watts for 0.015 second, and the reverse release pulse strength is about 50 per cent of the operate value. The coexisting values of coercive force, residual induction and magnetic permeabilities obtained in this design are new and useful to the art of designing electromagnetic switching devices with a magnetic latching function.