Extension unit, adjustment structure, and seat frame

An extension unit of a seat frame, comprising:

• a base plate;
• a lifting unit connected to the base plate;
• a foot adjustment unit connected to the lifting unit;
• and
• a backrest adjustment unit connected to the lifting unit;
• wherein the lifting unit comprises a first lifting connecting rod, a second lifting connecting rod, a third lifting connecting rod, a fourth lifting connecting rod, and a seat surface mounting portion;
• the first lifting connecting rod, the second lifting connecting rod, the third lifting connecting rod, and the fourth lifting connecting rod are different from each other, a first end of the first lifting connecting rod is hinged to the base plate, a second end of the first lifting connecting rod is hinged to a first end of the third lifting connecting rod, a second end of the third lifting connecting rod is hinged to a first end of the seat surface mounting portion, a second end of the seat surface mounting portion is hinged to a first end of the fourth lifting connecting rod, a second end of the fourth lifting connecting rod is hinged to a first end of the second lifting connecting rod, and a second end of the second lifting connecting rod is connected to the base plate;
• the first lifting connecting rod and the second lifting connecting rod are hinged at a first rotating fulcrum, and the first rotating fulcrum is located in a middle region of at least one of the first lifting connecting rod or the second lifting connecting rod.

An adjustment structure of a seat frame, comprising:

• an elevation unit, comprising a support, a first elevation rod, a second elevation rod that is different from the first elevation rod, and a connecting piece, wherein a first end of the first elevation rod is hinged to the support, and a second end of the first elevation rod is hinged to the connecting piece;
• a first end of the second elevation rod is hinged to the support, and a second end of the second elevation rod is hinged to the connecting piece;
• and
• an extension unit, comprising a base plate, a lifting unit, a foot adjustment unit, and a backrest adjustment unit, wherein the base plate is fixed to the connecting piece;
• wherein the lifting unit comprises a first lifting connecting rod, a second lifting connecting rod, a third lifting connecting rod, a fourth lifting connecting rod, and a seat surface mounting portion;
• the first lifting connecting rod, the second lifting connecting rod, the third lifting connecting rod, and the fourth lifting connecting rod are different from each other, a first end of the first lifting connecting rod is hinged to the base plate, a second end of the first lifting connecting rod is hinged to a first end of the third lifting connecting rod, a second end of the third lifting connecting rod is hinged to a first end of the seat surface mounting portion, a second end of the seat surface mounting portion is hinged to a first end of the fourth lifting connecting rod, a second end of the fourth lifting connecting rod is hinged to a first end of the second lifting connecting rod, and a second end of the second lifting connecting rod is connected to the base plate;
• the first lifting connecting rod and the second lifting connecting rod are hinged at a first rotating fulcrum, and the first rotating fulcrum is located in a middle region of at least one of the first lifting connecting rod or the second lifting connecting rod.