US Patent 11173936 Collapsible frame for a cart

A collapsible cart frame includes four vertical bars defining four corners of the cart frame, four scissor linkages extending between different pairs of the vertical bars to define four sides of the cart frame and four wheels mounted at the bottom ends of the vertical bars. The scissor linkages are configured to expand and collapse independently from one another. Each of the lower scissor ends are attached to a pair of vertical bars at a fixed height and each of the upper scissor ends are slidably attached to the pair vertical bars. Height defining elements selectively define heights of at least one of the upper scissor ends of each of the scissor linkages.