Contraction unit has position sensing device to record distance between head pieces and incorporates two overlapping measuring elements extending inside sleeve from one head piece to other

摘要

The contraction unit has a contraction sleeve (12) extending between two spaced apart head pieces (13,14). The contraction unit has a position sensing device (25) to record the distance between the head pieces and incorporates two overlapping measuring elements (26,27) extending inside the sleeve from one head piece to the other. The measuring elements each have a measuring head (30,31) fitted on the associated head piece by means of support rod (28,29) which is rigid in the longitudinal direction.