Rotating and translating capping head with static drive assembly

A capping head (1, 1A) for applying pre-threaded caps to containers, including:

• a shaft (2) movable according to a rotary motion about its axis and a translational motion along said axis;
• a first electric motor (5) for driving the rotary motion of the shaft (2), the first electric motor (5) having a stator (50) and a rotor (51, 51a) coaxially arranged around the shaft (2) and mounted in a stationary housing (6) so as to be decoupled from the shaft (2) as far as the translational motion is concerned;
• a first bushing (12), which is mounted at one end of the stationary housing (6) so as to seal the internal cavity thereof at said end, is passed through by the shaft (2) and is arranged to transfer the rotary motion of the rotor (51, 51a) to the shaft (2) thanks to the cooperation between ribs (15) provided on an inner surface thereof and grooves (14) provided on an outer surface of the shaft (2);
• Wherein:
• the head (1;
• 1A) further includes a second bushing (11) that is mounted at a second end of the stationary housing (6), opposed to the first one, so as to seal the internal cavity thereof also at that second end, and is passed through by the shaft (2) that is mounted in the same bushing (11) in a freely rotatable manner;
• the first electric motor (5) forms, together with the stationary housing (6) and the first and second bushings (12, 11), a self-standing module for driving rotation of the shaft (2);
• and
• said module (5, 6, 11, 12) can be associated, for driving the translational motion, either with a member (41) carrying cam follower rollers (42) arranged to cooperate with a mechanical cam (104, 104a) along the whole of the path run by the head (1) during a capping operation, or with a second electric motor (200) arranged to impart the translational motion to the shaft (2).