Capping machine head with cap aligning chuck

Abstract

There is disclosed a capping machine head for affixing screw caps on containers, which in one embodiment has a cylindrical magnet ring in the body of the head surrounding a cap chuck driving element in a low friction bearing in the head, each having an array of permanent magnets, preferably about fifty or more in number, distributed around their periphery. For certain angular relative positions of the ring and the chuck driving element, the north poles of one are face-to-face with the south poles of the other; displacement from such position causes torque on the order of tell to twenty inch pounds to be imparted to the chuck driving element. The chuck driving element rotates with the magnet ring until the resistance of a cap being threaded on the container exceeds a predetermined torque limit, after which the magnet ring rotates relative to the essentially stationary chuck driving element. The ring magnets may be in an axially misaligned position to reduce and control maximum torque value. Preferably the flux pattern of the magnets is elongated in an axial direction, by providing two rows of cylindrical magnets, or magnets which are elongated in that direction. The spring for urging the chuck downward is fully contained within the head. The chuck portion of the head has a plastic cap receiver with a relatively shallow toothed section spaced outwardly from an annular intrusion limiting shoulder; the receiver cylinder in the vicinity of the toothed section has little or no taper.