Rotary frame and grade

A rotary frame, comprising:

• a rotary ring, provided with a recessed portion and an opening communicated with each other, the opening is in U circumferential direction of the rotary ring;
• the rotary ring being configured to be symmetrical with respect to its own center line, and the center line passing through the rotary center of the rotary ring and the center of the opening;
• a first connecting piece, fixed at the periphery of the rotary ring, one end of the first connecting piece being attached to the periphery of the rotary ring and the other end of the first connecting piece being separated from the periphery of the rotary ring;
• a second connecting piece, the second connecting piece and the first connecting piece being arranged symmetrically with respect to the center line, the second connecting piece being also fixed at the periphery of the rotary ring, and one end of the second connecting piece being attached to the periphery of the rotary ring and the other end of the second connecting piece being separated from the periphery of the rotary ring;
• and
• a supporting base, fixed on an inner wall of the rotary ring and located in the recessed portion;
• wherein the rotary ring comprises:
• an arc-shaped section, configured to be arc-shaped;
• a first flat plate section, fixed at one end of the arc-shaped section;
• a second flat plate section, fixed at the other end of the arc-shaped section;
• a first protruded section, fixed on an end part of the first flat plate section away from the arc-shaped section, the end part of the first protruded section away from the first flat plate section being a first protruded end, and the first protruded end being protruded away from the rotary center of the rotary ring;
• and
• a second protruded section, fixed on an end part of the second flat plate section away from the arc-shaped section, the end part of the second protruded section away from the second flat plate section being a second protruded end, and the second protruded end being protruded away from the rotary center of the rotary ring,
• wherein the first protruded end is separated from the second protruded end to form the opening of the rotary ring;
• and the arc-shaped section, the first flat plate section, the second flat plate section, the first protruded section and the second protruded section jointly form the recessed portion in a surrounding way;
• wherein a first inserting groove is formed on an end part of the first protruded section away from the first flat plate section, a second inserting groove is formed on an end part of the second protruded section away from the second flat plate section, and the supporting base is inserted in the first inserting groove and the second inserting groove.