| 摘要 |
A descender is disclosed which includes a base plate (10), including first and second sheaves (16, 18) and an arm defining a third sheave (28). The descender also includes means, for biasing the arm to rotate about the pivot away from the base, and stop means for preventing the arm from pivoting further than a predetermined angle away from the base. Further provided are second adjustable stop means for restricting the distance the arm can travel towards the base when the biasing means is overcome and the arm pivoted towards the base. In use, with a rope passing below the first sheave, above and around the third sheave and above the second sheave, the resistance force applied to the rope is at maximum when the arm is pivoted so that the third projection is closest to the longitudinal axis. The descender is operable in two modes: a first mode in which the descender operates as a descender for controlling the rate of descent of a person sliding down the rope, in which mode the adjustable second stop means can be used to control the rate of descent; and a second mode wherein the descender is used with substantially no tension on the rope passing through the descender as a belay in which mode the biasing means keep the arm and base apart to allow rope to be fed through the descender relatively freely.
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