Mechanical extension device and suspension mechanism thereof

A mechanical extension device, comprising:

• a seat unit comprising a mounting plate, wherein the mounting plate is configured with a mounting plane and has a first rivet point, a second rivet point, a third rivet point, and a fourth rivet point;
• a link structure configured to connect to the mounting plate through the first rivet point and the second rivet point on the mounting plate;
• and
• a leg unit configured to connect to the mounting plate through the third rivet point and the fourth rivet point on the mounting plate;
• wherein the first rivet point, the second rivet point, and the third rivet point are each below the mounting plane;
• and a distance between a center of the fourth rivet point and an extension line of the mounting plane of the mounting plate in a direction perpendicular to the extension line of the mounting plane is not greater than 10 mm;
• wherein the link structure comprises a first link, a second link, and a third link, wherein a first end of the first link hinges to the first rivet point of the mounting plate, and a second end of the first link hinges to the third link;
• a first end of the second link hinges to the second rivet point of the mounting plate, and a second end of the second link hinges to the third link;
• and the first link, the second link the third link and the mounting late constitute a first four-bar structure;
• the mechanical extension device further comprises a control structure, wherein the control structure comprises a first control link, a second control link, a third control link, and a fourth control link;
• wherein a first end of the second control link hinges to the first control link, and a second end of the second control link hinges to the third control link;
• a first end of the fourth control link hinges to the first control link, and a second end of the fourth control link hinges to the third control link;
• and the first control link the second control link the third control link and the fourth control link constitute a second four-bar structure;
• wherein the control structure further comprises a fifth control link, a sixth control link, and a seventh control link;
• wherein a first end of the fifth control link hinges to the fourth control link and a second end of the fifth control link hinges to the third link;
• a first end of the sixth control link hinges to the second control link, and a second end of the sixth control link hinges to the third link;
• and a first end of the seventh control link hinges to an end of the second control link, and a second end of the seventh control link hinges to the third link.