Double-string rolling device

A double-string rolling device mounted on a roller blind;

• the roller blind including a shaft and a curtain mounted on the shaft;
• the double-string rolling device mounted on an end of the shaft to unfold or fold the curtain;
• the double-string rolling device comprising:
• a driving assembly comprising:
• a first engagement unit;
• a second engagement unit mounted on an end of the first engagement unit;
• a first ratchet unit sleeved on another end of the first engagement unit;
• the first ratchet unit configured to rotate in a first rotating direction;
• and
• a second ratchet unit sleeved on the second engagement unit;
• the second ratchet unit configured to rotate in a second rotating direction;
• the first rotating direction being opposite to the second rotating direction;
• and
• a controlling assembly connected to the driving assembly and comprising:
• a shell connected to the shaft of the roller blind and thus the shaft being secured;
• a first disc mounted in the shell and engaged with the first engagement unit;
• a first string wrapped around the first disc;
• a second disc mounted in the shell and engaged with the second engagement unit;
• a second string wrapped around the second disc;
• and
• a first elastic unit mounted between the first disc and the second disc.