Planetary gears and access control systems

An access control system for restricting access through a passageway, the access control system comprising:

• a shaft which is rotatable about a central axis,
• a barrier fixed to the shaft to rotate therewith, and
• a brake assembly for applying a braking force to the shaft,
• wherein the brake assembly comprises a planetary gear, the planetary gear comprising
• a sun gear, a plurality of planet gears, a carrier, and a ring gear, wherein:
• each planet gear has a longitudinal axis parallel to a central axis of the sun gear and comprises a first gear portion, a second gear portion, and an intermediate portion between the first and second gear portions along the longitudinal axis, each of said gear portions being centered on the longitudinal axis, and wherein each planet gear is a rigid body such that none of the gear portions is rotatable relative to any of the other gear portions;
• the first gear portion of each planet gear engages with the sun gear;
• the second gear portion of each planet gear engages with the ring gear and not with the sun gear;
• the carrier is arranged parallel to the sun gear and between the intermediate portions of each planet gear;
• the carrier comprises a plurality of slots along its outer edge;
• and
• the intermediate portion of each planet gear is a reduced diameter waist portion arranged to locate in one of said slots so as to attach the intermediate portion to the carrier and so as to allow rotation of the planet gear about its longitudinal axis, and
• wherein the sun gear is centered on the shaft and is rotatable about the central axis of the shaft and relative to the shaft, and wherein one of the carrier or the ring gear is fixed against rotation and wherein the other of the carrier or the ring gear is connected to the shaft to rotate therewith, and wherein the brake assembly further comprises an electromagnetic brake comprising an electromagnet and an armature, the armature being connected to or integral with the sun gear to rotate therewith, wherein at least one of the electromagnet or the armature is moveable upon energization of the electromagnet between an operative position in which the electromagnet and the armature are in contact, and an inoperative position in which the electromagnet is spaced from the armature.