Cordless roller shade

A cordless roller shade comprising:

• a head unit (1);
• a shading face (2) mounted on the head unit;
• an elastic dynamic device (13) mounted on the head unit;
• and
• a bottom unit (3) mounted on the shading face;
• wherein:
• the head unit includes a transverse rod (11) and two side brackets (12) mounted on two opposite ends of the transverse rod;
• the shading face has an upper end provided with an upper connecting portion (21) wound around the transverse rod of the head unit and a lower end provided with a lower connecting portion (22);
• the elastic dynamic device is mounted on one of the two side brackets and includes:
• a housing (131) having an interior provided with a receiving space (1311);
• two shafts (1312) mounted in the receiving space of the housing;
• two wheels (132) rotatably mounted on the two shafts;
• a fitting member (1321) mounted on one of the two wheels and secured to the transverse rod;
• a spring (133) mounted between the two shafts and wound around the two wheels;
• and
• a cover (134) mounted on the housing and provided with a through hole (1341) allowing passage of the fitting member;
• the spring has a thickness ranged between 0.1 mm and 0.2 mm;
• the bottom unit is mounted on the lower connecting portion of the shading face and includes:
• a mounting tube (31) having an interior provided with a receiving chamber (310);
• two end caps (32) mounted on two ends of the mounting tube;
• and
• at least one balance member (33) mounted in the receiving chamber of the mounting tube;
• the at least one balance member has a determined weight ranged between 0.1 kg and 1.2 kg;
• the shading face and the bottom unit have a total weight ranged between 1 kg and 5 kg, to balance a torque of the spring of the elastic dynamic device, so that the shading face is moved by the bottom unit to a determined position and is located at the determined position;
• the cordless roller shade further comprises a retainer (4) secured to the transverse rod of the head unit and detachably mounted on the other one of the two side brackets;
• the retainer includes:
• a casing (41) having a first end provided with an opening (411) and a second end provided with a pivot hole (412);
• a stop knob (42) mounted in the casing and having an end extending through and protruding from the pivot hole of the casing;
• a lid (44) mounted in the opening of the casing;
• and
• an elastic member (43) mounted in the casing and biased between the stop knob and the lid to push the stop knob to protrude from the pivot hole of the casing.