Footrest mechanism, chair support structure and chair having same

A footrest mechanism, comprising a first support component, a first folding arm, a first rotating member and a first leg connecting rod;

• wherein the first leg connecting rod is connected to the chair component, and is pivotally connected to the first rotating member;
• the first folding arm is pivotally connected to the first rotating member and the first support component, respectively;
• and the first support component is pivotally connected to the first leg connecting rod;
• a first leg four-bar mechanism is defined by the first support component, the first folding arm, the first rotating member and the first leg connecting rod four-bar;
• the first leg connecting rod is capable of moving towards or away from the chair component, and rotating relative to the first rotating member, so as to drive the first leg four-bar mechanism to contract or expand;
• the first leg four-bar mechanism has a first state and a second state;
• when the first leg four-bar mechanism is in the first state, the first folding arm is close to the first rotating member, the first leg connecting rod is configured for driving the first support component to move close to the first rotating member, and the first leg four-bar mechanism is folded;
• and
• when the first leg four-bar mechanism is in the second state, the first folding arm is away from the first rotating member, and the first leg connecting rod is configured for driving the first support component to move away from the first rotating member, and the first leg four-bar mechanism is expanded.