| 摘要 |
A roller assembly ( 10 ) to engage a track ( 100 ) having opposing generally parallel and transversely spaced first and second track portions ( 111, 112 ), the roller assembly including: a frame ( 11 ) including a shaped hole ( 15 ) and a slot ( 17 ) spaced from said shaped hole ( 15 ); a first roller ( 12 b) mounted to the frame hole ( 15 ) for rotation about an axis which is to be generally transverse of the track; a second roller ( 12 a) mounted in the frame slot ( 17 ) for rotation about an axis which is to be generally transverse of the track; wherein the frame slot ( 17 ) extends in a direction having a component generally normal to said axes and said track portions ( 111, 112 ) when in use, and the second roller ( 12 a) is movably mounted in the frame slot ( 17 ) for movement in said direction; and said assembly further includes a biasing member ( 18 ) mounted on the frame ( 11 ) and operatively associated with said second roller ( 12 a) to urge said second roller ( 12 a) in said direction so that in use the rollers ( 12 a , 12 b) are urged into contact with said track portions ( 111, 112 )
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