| 摘要 |
<p>Draw bolt having a housing (14, 50, 70) including a passageway (32) within which a bolt (24, 46, 72) is slidably mounted. A plurality of annuli (18, 54, 78), each of which has an internal slot (40, 58), are aligned in the passageway (32) and are restrained from axial movement. Each annuli (18, 54, 78) has a plurality of symbols on an external surface to indicate the position of the slot (40, 58). The alignment of the slot (40, 58) and symbols is adjustable by relative movement of a body (36, 56, 90) including the slot (40, 58) and an element (34, 60, 88) bearing the symbols. The bolt (24, 46, 72) includes at least one radially extending spigot (26, 86). Movement of the bolt (24, 46, 72) along the passageway (32) is possible only when the or each spigot (26, 86) is aligned with the slots (40, 58) of the annuli (18, 54, 78).</p> |
