Patent ID: 7878555

Claim:
A coupling device for circular pipes, comprising: a body including a first coupling section at one portion thereof, a second coupling section at another portion thereof, a flange protruding from an end of the second coupling section, a coupling hole formed in the second coupling section, a circular pipe coupling hole extending from the coupling hole and a connecting hole extending from the circular pipe coupling hole and through the first coupling section; a circular pipe locking means including a first locking ring, a first support ring, a second locking ring, a ring, a first ring packing and a nut, which are inserted sequentially into the coupling hole of the body; a fixing member for fixing the nut to the flange of the body; and an adjustment member having an entrance hole corresponding to an outside diameter of a circular pipe, which will be inserted into the adjustment member, and threads formed on an outer circumference of the adjustment member, the threads engaging into a screw hole of the nut, thereby applying an external force to the first ring packing, the fixing member having a hole formed in one portion thereof, corresponding to a screw hole of the nut, and being configured to bend at another portion thereof to press against the flange when the nut and the flange of the body are inserted into the fixing member, thereby fixing the nut to the flange.