Foldable and expandable pet carrier bag

A foldable and expandable pet carrier bag, comprising a pet carrier bag body, wherein the pet carrier bag body is provided with a first pet door and a backside, the backside is provided with a foldable expanding part;

• when the expanding part is expanded, the expanding part forms a cuboid or a substantially cuboid structure;
• the expanding part comprises a top wall, a bottom wall, a left side wall, a right side wall and a front side wall;
• both the left side wall and the right side wall are made of a foldable material, the front side wall and the backside are symmetrically arranged;
• the front side wall comprises a first circumference and the top wall comprises a second circumference, the first circumference is provided with a first support ring, and the second circumference is provided with a second support ring;
• a connecting piece detachably fixed on the pet carrier bag body is provided in the bottom wall;
• when the pet carrier bag is folded, the front side wall and the top wall are rotated downward and overlapped on the bottom wall and the backside respectively;
• the left side wall and the right side wall are folded towards an inner portion of the expanding part respectively;
• the bottom wall and the front side wall that overlapped on a surface of the bottom wall are swung upward and overlap on the top wall of a surface of the backsides;
• wherein in a partially folded state, when folding the expanding part, the front side wall and the top wall are rotated downward to overlap on the bottom wall and the backside, respectively, and the left side wall and the right side wall each forms an approximately right-angled triangle structure, and
• in the partially folded state, a pet pad in the pet carrier bag body is pulled out to place and overlap with a top surface of the front side wall of the bottom wall, to form a small balcony;
• and wherein in a fully folded state, the approximately right-angled triangles are folded inside the expanding part, respectively, and the bottom wall and the front side wall, overlapped on the surface of the bottom wall, are swung upward to overlap on the top wall of the surface of the backside, and the connecting piece is fixedly connected to the pet carrier bag body.