| 摘要 |
Disclosed is a crane hoist system having a hoist drum (33), a drum drive motor (37) and control and power circuit limit switches (47, 49). The improvement involves a first trip bar (75) coupled to the power circuit limit switch (49) and a second trip bar (57) coupled to the control circuit limit switch (47). The bars (75, 57) are vertically aligned and both are pivot mounted at their corresponding ends (79, 87). The second trip bar (57) is mounted for movement independently of the first trip bar (75). If the control circuit limit switch (47) fails to function as the second bar (57) is moved a suitable distance upwardly, such bar (57) contacts and lifts the first bar (75) which, in turn, trips the power limit switch (49). In one embodiment, both bars (75, 57) are straight and elongate and in another, the second bar (57) is "U" shaped.
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