| 摘要 |
<p>A lighting assembly (6) is carried by a frame which can be lowered to the foot of a mast (2) by means of a cable arrangement (16, 20). Latching devices (40) are provided for retaining the frame (8) at the mast head (4), each comprising a pivotable latching arm (42) biassed into a vertical orientation, and latch members (50) including a detent (50c). As the frame (8) is raised, the latching arm (42) is forcibly pivoted to one side by engagement of its tip (43) with an inclined surface (50a), but then springs back into engagement with an abutment (54). On subsequent slight lowering of the frame (8), the tip (43) engages the detent (50c) to retain the frame (8) in position relative to the mast head (4), with the arm (42) still being biassed slightly to one side of the vertical. To lower the lighting assembly, the frame (8) is raised slightly to disengage the tip (43) from the detent (50c), whereupon the arm (42) springs back to the vertical. The frame (8) is then lowered to engage the tip (43) with a sloping surface (50d) which forcibly pivots the arm (42) to the other side of the vertical, enabling the arm (42) to be disengaged from the latch members (50).</p> |
