Retractable pipe assembly of air blow gun

A retractable pipe assembly of an air blow gun, comprising:

• an extension pipe comprising a front connecting end and a rear connecting end, the front connecting end and the rear connecting end respectively having threads thereon, the front connecting end having an inner inclined surface at an end edge thereof, the extension pipe having a stepped through hole which has a large diameter part, a small diameter part and a stepped stop between the large diameter part and the small diameter part;
• a lock unit comprising a lock member, an elastic collet and a deformable seal member, the lock member having a first end and an opposing second end, the first end of the lock member having an inner threaded hole, the second end of the lock member having a through hole which has a diameter smaller than that of the inner threaded hole, the through hole communicating with the inner threaded hole, the elastic collet and the seal member being accommodated in the lock member, the deformable seal member located on the inner inclined surface, the inner threaded hole of the lock member being threadedly connected to the threads of the front connecting end of the extension pipe, one end of the elastic collet having a cone surface, the cone surface having a plurality of slots which are disposed around the cone surface;
• and
• a blow pipe inserted in the stepped through hole of the extension pipe, the blow pipe comprising a stop ring screwed to an end of the blow pipe, the stop ring being accommodated in the extension pipe and stopped by the stepped stop.