Abstract The assembly includes at least one core of permanent magnet metal, a respective magnetizing winding embracing each core and a casing having walls at least partially enclosing each winding. An energizing circuit connected to each winding includes switch means selectively operable to energize the windings in a forward direction, to augment the permanent magnet flux of the cores, or in a reverse direction, to neutralize the permanent magnet flux of the cores. A timer in the energizer circuit is operable, following the lapse of a predetermind short interval after energization of the windings in the forward direction, to pick up a load by magnetic attraction, to deenergize the windings so that the load is held magnetically by the permanent magnet flux of the cores. The energizing circuit further provides a small holding current to the windings in the forward direction. Each core has a pole piece of magnetizable metal on its outer end and, in one embodiment of the invention, the pole pieces are pivotally secured to the associated cores so as to be swingable to embrace a load having a circular cross section such as, for example, an iron pipe.
An electromagnetic hoisting mechanism comprising, in combination, at least one core of permanent magnet material; a respective magnetizing winding embracing each core; a casing having wall means at least partially enclosing each winding; a current supply circuit connected to each winding and arranged for connection to a source of electric current; switch means in said supply circuit selectively operable to energize said windings in a forward direction to augment the permanent magnet flux of the associated cores or in a reverse direction to neutralize the permanent magnet flux of the associated cores; and timer means in said supply circuit activated, responsive to energization of said windings in said forward direction, to pick up a load by magnetic attraction, to deenergize said windings after a predetermined short time interval so that the load is then held magnetically solely by the permanent magnet flux of said cores.
Claim 2
Dependent Claim
145 words
An electromagnetic hoisting mechanism comprising, in combination, at least one core of permanent magnet material; a respective magnetizing winding embracing each core; a casing having wall means at least partially enclosing each winding; a current supply circuit connected to each winding and arranged for connection to a source of electric current; switch means in said supply circuit selectively operable to energize said windings in a forward direction to augment the permanent magnet flux of the associated cores or in a reverse direction to neutralize the permanent magnet flux of the associated cores; and timer means in said supply circuit activated, responsive to energization of said windings in said forward direction, to pick up a load by magnetic attraction, to deenergize said windings after a predetermined short time interval so that the load is then held magnetically solely by the permanent magnet flux of said cores.
Claim 3
Dependent Claim
70 words
An electromagnetic hoising mechanism, as claimed in claim 1, in which said supply circuit includes means operable, responsive to horizontal travel of said hoisting mechanism after such deenergization of said windings, to supply a reduced energizing current to said windings in said forward direction to augment the permanent magnet flux of the associated cores to prevent accidental dislodgment of a load, carried by said hoisting mechanism, by strikinG an obstruction.
Claim 4
Dependent Claim
165 words
An electromagnetic hoisting mechanism, as claimed in claim 1, in which there are two cores forming the respective legs of a permanent magnet having the shape of a relatively elongated channel and having a yoke forming the base of the channel; and a respective relatively elongated pole piece of permanent magnet material pivotally secured to the outer end of each leg for swinging about an axis extending parallel to the length of the associated leg; each pole piece having a groove extending centrally of its outer face and having a transversely convex elongated inner face concentric with said axis and closely adjacent and concentric with a transversely concave groove extending longitudinally of the outer end of the associated channel leg; whereby said hoisting mechanism is magnetically cooperable with a load having a curved external surface by orienting said pole pieces parallel to the axis of curvature of the load surface with the pole pieces engaging circumferentially spaced areas of the external surface of the load.