| 摘要 |
It comprises, between the assembly of columns 1 and upright of the gantry 3, the horizontal threaded spindle 6 provided with the main nut 11 and safety nut 12 conveniently spaced from one another, with the end of travel 28, as well as the end of travel 27 actuated by the lever 26 in the event of slackening of the chains 17 or 18 on account of obstacles on the descent, and also the microswitch 30 for the safety end of travel during ascent, which carries out three functions, one during the ascent of the carriages 20, 24 via the adjustable rod 32, another by means of the cable 33 upon collision with high vehicles or vehicles with upper projections, and a third one on account of breakage of the main nut 11, displacing the rod 35, 27 and 38, actuating the three means, the safety lever 31, of the microswitch 30, carrying the mechanical locking device 39 which acts in the event of breakage of the chains. <IMAGE>
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