Repeating nail-feeding structure for pneumatic nailing machine

A repeating nail-feeding structure for a pneumatic nailing machine, installed in said pneumatic nailing machine, said pneumatic nailing machine having a magazine loaded with a strip nail, a nail-discharging head connected to said magazine and receiving said strip nail to be ejected, an air inlet connected to an air pressure source, a pushing part turning on said air pressure source for supplying a working air stream, and an air outlet discharging said working air stream, said repeating nail-feeding structure comprising:

• an air stream guiding tube, said air stream guiding tube being provided with a first end and a second end, said first end being coupled with said air outlet to receive said working air stream discharged through said air outlet;
• an automatic return cylinder, said automatic return cylinder being fixed to said pneumatic nailing machine, and provided with a cylinder pipe, a piston stein and a return spring, said cylinder pipe being provided with an air stream inlet coupled with said second end and an air escape outlet discharging said working air stream, said piston stein being passingly provided within said cylinder pipe and shifted to a retracted position through said working air stream coining from said air outlet, as well as returned to an extended position through the pressing of said return spring;
• and
• a shifting element, said shifting element being fixed to said piston stein and provided with a shifting lever, said shifting lever advancing said strip nail along with motion of said piston stein.