| 摘要 |
<p>A steering assistance device for a castor comprises a cam portion (39) having a lobe (41) which is fixed to the bottom of the fixing bolt of the castor and which is surrounded by a closed portion (43) of a capture device (42). The lobe (41) is engaged in an arcuate recess (49) of the capture device (42) in the dead centre position of the castor. The capture device (42) is formed of a plastics material and its sides and ends are resilient slats. The arcuate recess (49) is in one end and the two sides (50 and 52) carry inwardly projecting arms (51 and 53). Steering assistance is provided by resistance to angular displacement of the capture device (42) around the cam portion (39) which is provided by the resilience of the capture device (42), first progressively increasing to a maximum whilst the lobe (41) is engaged in the recess, secondly maintaining that maximum as it passes out of the recess (49), across a projection (58, 59) into engagement with one of the arms (51 and 53), and thirdly gradually reducing until it is released from the arm (51 or 53). The remainder of the swivelling movement is without resistance as there is a clearance around the cam portion (39).</p> |
