Patient support systems with rotary actuators having cycloidal drives

A patient support apparatus comprising:

• a patient support surface;
• a first member and a movable member, said movable member movable relative to said first member;
• and
• an actuator coupled to said movable member to move said movable member relative to said first member to thereby move said patient support surface, said actuator comprising:
• a gear assembly having an input member, an output member connected to said movable member, and a gear arrangement operable between said input member and said output member;
• and
• a motor configured to apply torque to said input member to rotate said output member through said gear arrangement,
• said gear arrangement comprising a cycloidal drive arranged to drive said output member when said motor applies torque to said input member,
• wherein said gear assembly has a forward drive efficiency and a back drive efficiency, said forward drive efficiency being greater than said back drive efficiency, wherein said forward drive efficiency defines a proportion of forward drive output power to forward drive input power when said forward drive input power is applied to said input member by said motor and said forward drive output power is available at said output member in response to said forward drive input power, and said back drive efficiency defines a proportion of back drive output power to back drive input power wherein said back drive input power is applied to said output member and said back drive output power is available at said input member in response to said back drive input power;
• and
• wherein said gear assembly comprises a planetary ring gear, planet gears meshing with said planetary ring gear, and a carrier supporting said planet gears, wherein said input member comprises an eccentric drive member fixed to said carrier to rotate with said carrier.