motion in the x y plane that is to say when a force is applied to drive member 112 wherein the applied force has both vertical and horizontal components assembly 110 is resistant to torsional motion with respect to both the direction of the horizontal component of the applied force and the substantially planar surface 14 of work platform 12 however assembly 110 in response to the applied force traverses a substantially coherent path with respect to the direction of the horizontal component of the applied force coupler 114 of assembly 110 is relatively vertically compliant to accommodate for variability in thickness such as caused by cross seams in limp material f moreover coupler 114 is substantially resistant to linear or rotational motion relative to drive member 112 in the x and y direction fig6 shows the spring coupling assembly 117 for an embodiment of a limp material segment coupling assembly 110 in accordance with the present invention in the illustrative embodiment spring coupling assembly 117 includes three bent sheet springs 120a 120b and 120c sheet springs 120a 120b and 120c are each comprised of a resilient sheet extending from a first end to a second end along spring axes 118a 118b and 118c respectively sheet springs 120a 120b and 120c are coupled at the inner end to drive member 112 and at the outer end to segment coupler 114 wherein the sheet springs are bent along axes perpendicular to spring axes 118a 118b and 118c respectively in the.