spring 92 a plurality of adjustment holes 952 with same internal diameter located around the perimeter of the tension adjustment stand 95 where a insertion pin 96 can be inserted into any adjustment hole 951 to push turn the tension adjustment stand 95 and to set the twist of the torque spring 92 refer to fig8 and 9 there is a little different from the second preferred embodiments the difference between the second and third preferred embodiments are two ends of the axle rod 101 placed with a pair of tension adjustment stands 105 the tension adjustment stands 105 are similar to the tension adjustment stand 95 in fig7 the different is on the same surface of a insertion hole 1051 of the tension adjustment stand 105 have a protective ring 1053 the other different are a pair of insertion portion 1021 each axially outward from the ends of a torque spring 102 the insertion hole 1051 receive a metal tubing 952 for insertion portion 1021 of the torque spring 102 winds into the metal tubing 952 to avoid overly concentrating the torque so the tension adjustment stands 105 and 105 u2032 of this embodiment where the appropriate height of protective rings 1053 are receive the ends of the torque spring 102 the protective rings 1053 are wrapped around the periphery of the torque spring 102 to cover the ends of the torque spring 102 and to position the torque spring 102 so the insertion portion 1021 of the torque spring 102 is wrapped in the protective rings 1053 and 1053 u2032 for holding purpose so the torque spring 72 will preserves the direction of an axle rod 101 and when the torque spring 102 is twisted it won 39 t shake nor will.