Abstract: A weight-sensing member is made from material with good toughness and elastic deformability characteristics and has a top end, a bottom end and a broadened portion located between and integral with the first and second ends. The broadened portion has a pair of opposed peripheries between the top and bottom ends, a horizontally extending through-hole, and a pair of S-shaped slots formed symmetrically on both sides of the through-hole. Each of the slots begins with an open end at a respective one of the opposed peripheries adjacent to a corresponding one of the top and bottom ends and terminates with a closed end near the through-hole. Each S-shaped slot divides partially the weight-sensing member into two separated parts, namely a higher part near the top end and a lower part near the bottom end. The lower part has a higher portion with a protrusion that extends into an opening that is formed in the higher part.