| 摘要 |
Three-position jack supplied by a pneumatic or hydraulic circuit, particularly for a gearbox, comprising an axle 7 provided with a piston 8, which moves in a casing 9 closed by a lid 3, characterised in that the said jack comprises two additional pistons 1 and 2, which slide between the piston 8 and the casing 9, the additional piston 1 having a greater cross-section than that of the additional piston 2, the piston 8 comprising a flange 15 for limiting the travel of the additional piston 2 and being associated with a plate 13 provided with a flange 14 for limiting the travel of the additional piston 1; the said jack having an orifice 10 for the supply of the chamber 21 lying between the two additional pistons 1 and 2 in the first position, an orifice 11 for the supply of the chamber 22 lying between the lid 3 and the additional jack 1 in the second position, an orifice 12 for the supply of the chamber 23 lying between the bottom 24 of the casing 9 and the additional jack 2 in the third position. <IMAGE>
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