24 have released the previous loop 23 since the diagonal back stitch 30 has been laid down by the insertion of the needle 21 into the backing material 20 since all needles 21 penetrated the backing material 20 before the cam follower 15b descended along the incline 26c the lateral shifting of the increment of the backing material 20 which has been penetrated will take place during the travel of the cam follower 15b along the incline surface 26c this shifting of the backing material will correspond in distance to the height of the lobe 25d i e the difference in the radius of the peripheral surface 16 and the radius of the surface 26c the needles 21 continue their descent until the needles 21 reach bottom dead center b d c as depicted in fig9 at that time the loopers 24 are still not engaging the loops 23 however the loops 23 have been inserted through the backing material 20 to the full extent of the travel of the needles 21 when the needles 21 begin their ascent or retraction back toward top dead center it will be understood that since the cam followers 15a and 15b both ride along the periphery 16 throughout this travel the needles 21 travel along parallel linear vertical paths in registry with their loopers to top dead center as.