Mechanical stretching device of convertible sofa

A mechanical stretching device of a convertible sofa, comprising:

• left components and right components that are symmetrically disposed and fixedly connected to each other, wherein:
• the left components and the right components each respectively comprise a foot plate, a first foot lever, a second foot lever, a third foot lever, a fourth foot lever, a fifth foot lever, a side plate, a rotating shaft transmission member, a first connecting rod, a second connecting rod, a third connecting rod, a fourth connecting rod, a fifth connecting rod, a sixth connecting rod, a back member, a calf plate, a first support member, a second support member, a linkage member, a protective member, a seahorse member, and a bottom foot that are linked to each other;
• one side of a first end of the back member is rotatably connected to a first end of the side plate by an eighth rotating shaft;
• the other side of the first end of the back member is rotatably connected to a first end of the first connecting rod by a twenty-ninth rotating shaft;
• the other end of the first connecting rod is rotatably connected to one side of a first end of the linkage member by a twenty-fourth rotating shaft;
• one side of a second end of the side plate is rotatably connected to the fourth foot lever by a fifth rotating shaft;
• a bottom portion, close to the second end, of the side plate is rotatably connected to a first end of the fifth foot lever by a sixth rotating shaft;
• one side, close to a middle portion, of the side plate is rotatably connected to one side of a first end of the third connecting rod by a twenty-seventh rotating shaft;
• the middle portion of the side plate is rotatably connected to a first end of the seahorse member by a twenty-sixth rotating shaft;
• one side, close to the first end, of the side plate is rotatably connected to the other side of the first end of the linkage member by a twenty-eighth rotating shaft;
• two ends of the protective member are fixed on a top portion of the side plate through screws;
• one side of a second end of the linkage member is rotatably connected to a conveying end of the second support member by a nineteenth rotating shaft;
• the other side of the second end of the linkage member is rotatably connected to a first end of the second connecting rod by a twenty-fifth rotating shaft;
• a bent end of the seahorse member is rotatably connected to a first end of the fourth connecting rod by a twentieth rotating shaft;
• a straight end of the seahorse member is rotatably connected to a first end of the fifth connecting rod by a seventeenth rotating shaft;
• the first end of the third connecting rod is rotatably connected to a free end of the first support member by a thirtieth rotating shaft;
• a turning end of the third connecting rod is rotatably connected to the first end of the second connecting rod and the side plate by the twenty-seventh rotating shaft;
• the other end of the fourth connecting rod is rotatably connected to a middle portion of the first support member by a twenty-second rotating shaft;
• a fixed end of the first support member and a fixed end of the second support member are rotatably connected to the bottom foot by a fifteenth rotating shaft and a twenty-third rotating shaft respectively;
• a position, close to the first end, on the fourth foot lever is rotatably connected to a middle portion of the third foot lever by a twelfth rotating shaft;
• the first end of the fourth foot lever is rotatably connected to a first end of the first foot lever by an eleventh rotating shaft;
• the first end of the fifth foot lever is rotatably connected to a second end of the third foot lever by a fourth rotating shaft;
• a middle portion of the fifth foot lever is rotatably connected to a first end of the sixth connecting rod by a thirteenth rotating shaft;
• a position, close to a second end, on the fifth foot lever is rotatably connected to the first end of the fifth connecting rod by a fourteenth rotating shaft;
• a first end of the third foot lever is rotatably connected to a first end of the calf plate by a third rotating shaft;
• a turning portion of the calf plate is rotatably connected to a middle portion of the first foot lever by a tenth rotating shaft;
• a second end of the first foot lever is rotatably connected to a first end of the foot plate by a second rotating shaft;
• a second end of the calf plate is rotatably connected to a first end of the second foot lever by a ninth rotating shaft;
• a second end of the second foot lever is rotatably connected to a position, close to a first end, on the foot plate by a first rotating shaft;
• the first end of the sixth connecting rod is rotatably connected to a first end of the rotating shaft transmission member by a sixteenth rotating shaft;
• a second end of the rotating shaft transmission member is conveyably connected to the side plate by a seventh rotating shaft;
• a first limiting bushing is mounted on a position, between the first end and the turning end, of the third connecting rod;
• a second limiting bushing is mounted on the second end of the rotating shaft transmission member, and is fit-mounted with the seventh rotating shaft;
• a third limiting bushing and a fourth limiting bushing are respectively mounted on one side of the second end of the linkage member;
• a fifth limiting bushing is mounted on a position, close to a second end, on the fourth foot lever;
• a sixth limiting bushing is mounted on a position, close to a second end, on the foot plate;
• a first limiting surface, a second limiting surface, and a limiting bridge are disposed on the side plate;
• a third limiting surface is disposed on the second support member;
• a fourth limiting surface is disposed on the third connecting rod;
• a fifth limiting surface is disposed on the second foot lever;
• a sixth limiting surface is disposed on the fifth foot lever;
• a seventh limiting surface is disposed on the third foot lever;
• an eighth limiting surface is disposed on the sixth connecting rod;
• the first limiting bushing is disposed to fit positions of the first limiting surface and the sixth limiting surface;
• the second limiting bushing is disposed to fit a position of the eighth limiting surface;
• the third limiting bushing is fit-disposed with the second limiting surface;
• the fourth limiting bushing is fit-disposed with the third limiting surface;
• the fifth limiting bushing is fit-disposed with the seventh limiting surface;
• the sixth limiting bushing is fit-disposed with the fifth limiting surface;
• the limiting bridge is fit-disposed with the fourth limiting surface;
• and
• two locking springs are symmetrically mounted between the side plate and the sixth connecting rod of the left components and between the side plate and the sixth connecting rod of the right components respectively.