Magnetic safety clutch for rotary lawnmower

Claim 1

A magnetic safety clutch apparatus for use with a rotary lawnmower having a main frame, a prime mover mounted on said frame, a prime mover drive shaft extending downwardly of said main frame, a rotary lawnmower blade adaped to be rotated by said drive shaft on a vertical axis, and a lawnmower operating handle mounted to a said main frame, said apparatus including: A. a source of electromotive force on said frame; B. a magnetic flux-producing coil fixedly mounted to said main frame in concentric, surrounding relation to said drive shaft; C. a housing of electromagnetic material encompassing said coil; D. a first magnetic clutch plate fixed to said drive shaft to rotate therewith and situated in close relationship to said coil housing to provide a low reluctance path between said first clutch plate and said housing; E. a second magnetic clutch plate mounted to rotate with said blade and freely rotatably mounted with respect to said drive shaft and movable axially of said drive shaft between an engaged, drive transmitting, position and an unengaged position with respect to said first clutch plate; F. means to limit axial movement of said second clutch plate to retain it within the effective magnetic field of said coil when energized; G. a lever action hand switch mounted to said operating handle to be readily accessible to an operator of said lawnmower, said hand switch being biased to be normally situated in an inoperative condition and being manually movable to and maintainable in an operative condition; and H. circuit means including said hand switch, said circuit means being operative to electrically connect said magnetic coil to said source of electromotive force when said hand switch is in its operative condition and to disconnect said coil from said source when said hand switch is in its inoperative condition.