Transit vehicle door system

A door system for covering and uncovering an aperture disposed in a sidewall portion of a transit vehicle, said door system comprising:

• (a) at least one door panel;
• (b) an actuator providing both a rotary motion about an axis of said actuator for moving said at least one door panel between an open position uncovering such aperture and a closed unlocked position covering such aperture and a linear motion along said axis for moving said at least one door panel between said closed unlocked position and a closed locked position, said actuator including:
• (i) a cylinder disposed coaxial with said axis of said actuator, said cylinder having a first end and a second end and an inner surface enclosing an internal chamber of said cylinder,
• (ii) a piston positioned coaxially with said axis of said actuator and disposed in said internal chamber of said cylinder, said piston having a first end and a second end and a guide track formed in an outer surface thereof,
• (iii) at least one seal disposed on said piston for both sealing between said piston and said cylinder and providing a pressure boundary between a first chamber disposed adjacent said first end of said piston within said first end of said cylinder and a second chamber disposed adjacent said second end of said piston within said second end of said cylinder,
• (iv) a shaft having a first external portion disposed adjacent said first end of said cylinder and a second external portion disposed adjacent said second end of said cylinder is positioned coaxially with said axis of said actuator and passes through both said cylinder and a bore formed in said piston, said shaft having a shaft rotary motion connection disposed thereon for engaging a piston rotary motion connection disposed within said bore of said piston, said shaft rotary motion connection and said piston rotary motion connection cooperating to provide a rotary connection between said shaft and said piston so that rotation of said piston causes rotation of said shaft, said rotary motion connection of said shaft and said rotary motion connection of said piston permitting axial motion of said piston relative to said shaft,
• (v) at least one roller attached to said inner surface of said cylinder and engaging said guide track, said guide track having a first portion curving obliquely around said piston and a second portion running parallel to said axis of said piston so that when said roller is in said first portion of said guide track motion of said piston parallel to said axis of said cylinder causes rotation of said piston and when said roller is in said second portion of said guide track motion of said piston parallel to said axis of said cylinder rotation of said piston is inhibited,
• (vi) a stop disposed on said shaft for engaging said piston so that when said piston is moved into contact with said stop further axial motion of said piston causes axial motion of said shaft, said stop being positioned so that when said roller is in said first portion of said guide track said piston is not in contact with said stop so that rotary but not axial motion is communicated to said shaft and so that when said roller is in said second portion of said guide track said piston is in contact with said stop and causes axial motion of said shaft whereby axial motion of said piston provides a first rotary motion of said shaft and a second axial motion of said shaft,
• (vii) at least one fluid connection disposed in fluid communication with said first chamber of said actuator for controlling a fluid pressure in said first chamber to control a first pressure force exerted on said piston and thereby control said axial motion of said piston, and
• (viii) at least one fluid connection disposed in fluid communication with said second chamber of said actuator for controlling a fluid pressure in said second chamber to control a second pressure force exerted on said piston and thereby control said axial motion of said piston;
• (c) a first arm attached to said first external portion of said shaft and connected to said at least one door panel for both supporting and positioning said at least one door panel;
• (d) a second arm attached to said second external portion of said shaft and connected to said at least one door panel for both supporting and positioning said at least one door panel;
• and
• (e) a lock having a vehicle lock portion attached to such transit vehicle adjacent such aperture and a door panel lock portion attached to said at least one door panel, said door panel lock portion engaging said vehicle lock portion during said second axial motion of said shaft.