2 moves in a normal speed therefore in normal operation of the elevator car 2 the disk roller 110 rotates in continuous contact with the guide rail 1 in addition a rotary shaft holding spring 113 is preferably mounted to the disk roller 110 one end of the rotary shaft holding spring 113 is coupled to the rotary shaft 110 a of the disk roller 110 while the other end is fixed to a spring seat not shown on a connecting plate 410 the rotary shaft holding spring 113 is configured to play a role for maintaining height of the rotary shaft 110 a of the disk roller 110 while on the other hand the shaft holding spring 113 may allow the rotary shaft 100 a of the disk roller 110 to move upward in the event of urgent stopping of the elevator car 2 another rotary shaft holding spring 121 similar to or same as the rotary shaft holding spring 113 is also mounted to the cam 120 one end of the rotary shaft holding spring 121 for the cam 120 is coupled to a rotary shaft 120 a of the cam 120 while the other end is fixed to a spring seat not shown on the connecting plate 410 the rotary shaft holding spring 121 for the cam 120 maintains vertical position of the rotary shaft 120 a of the cam 120 but may also allow the rotary shaft 120 a of the.