US Patent 7758085 Tube couplings

A tube coupling for receiving and holding an end of a tube includes a coupling body having a hollow stem adapted to engage in a tube to be secured to the coupling body. A cap is mounted on the coupling body and encircles the stem with a gap between the cap and stem to receive the tube engaged over the stem. A tube locking device is located in the cap for locking the tube against withdrawal from the stem and a locking ring is located on the stem within the cap. The ring has both inwardly and outwardly projecting teeth for engaging respectively the inner and outer surfaces of the cap and stem to lock the cap on the stem.