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Details of the self-locking mechanism (Approach 2). 1—upper cylindrical wafer; 2 & 10—fixing bolts; 3—lower cylindrical wafer; 4—unidirectional wheel; 5—shaft; 6 & 14—washers; 7—interior sliding block; 8—walker leg; 9—feed screw; 10—semi-screw; 11—single helical compression spring; 12—stopper; 13—exterior sliding block; 15—rubber feet
