滚柱齿轮

由于滚子齿轮式凸轮在旋转时互相配合，机械以有效运作。

guide, roller, cable

messenger roller office printing machine

farmyard manure spreader with horizontal roller

ball-and-roller bearing

embossing roller for modifying the structure of threads, yarns or the like

roller clutch

three-roller plate roll

dancer roller