Folding cover for air filter unit

A folding cover, comprising two frame assemblies, wherein,

• the two frame assemblies are symmetrical about a central point;
• each of the two frame assemblies comprises two first frames and two second frames;
• the two first frames are disposed opposite to each other, and the two second frames are disposed opposite to each other;
• the two first frames are connected to the two second frames, respectively;
• each of the two first frames comprises a first end, a second end, a first top surface, and a first bottom surface;
• a semicircular plate is fixedly disposed on the first end of each first frame;
• each of the two second frames comprises a third end, a fourth end, a second top surface, and a second bottom surface;
• the second top surface of each second frame comprises a semicircular groove;
• the semicircular groove is disposed on the third end of the second frame;
• the semicircular plate is rotatably disposed within the semicircular groove;
• and the second end of the first frame is pivotally connected to the fourth end of the second frame.