Locking device of extendable and retractable container semi-trailers

A locking device of extendable and retractable container semi-trailers comprising:

• at least two link bars;
• at least two lock pin assemblies;
• a crossmember;
• a falling tube;
• and a pull assembly;
• two ends of said pull assembly being connected with at least one said link bar and one said lock pin assembly respectively;
• said pull assembly comprising an automatic locking and releasing device fixed rotatably between a bottom plate and a top plate of said crossmember;
• said pull assembly being rotated round said automatic locking and releasing device to a locking place, and said automatic locking and releasing device locking said pull assembly;
• and said falling tube acting on said automatic locking and releasing device, and said pull assembly being release;
• said pull assembly further including a body, and said automatic locking and releasing device being arranged at one end of said body;
• said automatic locking and releasing device including an outer pipe connected with said body, a plurality of openings being opened on said body around the outer pipe, an inner pipe being inserted into said outer pipe, a plurality of lock rods being connected with said inner pipe and being respectively inserted into said openings, a bottom bracket being fixed to said bottom plate of said crossmember, a top bracket being fixed with said top plate of said crossmember, a resilient member being sleeved out of said inner pipe;
• wherein elasticity of said resilient member makes the inner pipe move upwardly, then said inner pipe passes through said top bracket and said bottom bracket and is fixed between said top bracket and said bottom bracket;
• said pull assembly being jointed to said crossmember, and a top end of the inner pipe passes through said top bracket and said top plate of said crossmember and is exposed above the crossmember;
• and said pull assembly being rotated to said locking place, and said lock rods will pass through said bottom bracket and insert into said openings to lock said pull assembly tightly;
• and responsive to said falling tube bumping said top end of said inner pipe exposed above said crossmember, said inner pipe moves downwardly and said lock rods draw back from said openings to release said pull assembly.