FEED MECHANISMS COMPRISING AN ENDLESS MEMBER CONFIGURED AS A DOUBLE HELIX

摘要

A feed mechanism comprising a rotor and an endless flexible belt carried by the rotor. The rotor comprises a pair of cylindrical guide members arranged coaxially one within the other, the guide members being mounted for rotation in unison about a common axis. Each of the guide members provides a helical groove defining a respective feed channel, the grooves being of the same pitch and opposite hand, and the belt is constrained by the guide members to extend helically along the feed channels in sliding engagement with the guide members. The belt protrudes from one of the feed channels to engage a restraining surface which restrains the belt against rotation so that, in response to rotation of the rotor, the belt is continuously advanced along one of the feed channels and returned along the other, thereby providing a continuously advancing non-rotary bearing surface which bears against the restraining surface.