Patent ID: 7543857

Claim:
A self-locking coupling for joining conduit ends together, said self-locking coupling comprising: a first fitting having a concave surface facing radially outwardly from one end thereof; another end of said first fitting being adapted for attachment to one of the conduit ends; a second fitting having a receptacle at one end adapted to coaxially receive said first fitting, another end of said second fitting being adapted for attachment to another one of the conduit ends; a roller cam mounted on said second fitting, said roller cam comprising a cam body having a center, said cam body being rotatable about an axis offset from said cam body center, said cam body being movable into and out of said receptacle upon rotation about said offset axis; said roller cam further comprising an annular roller surrounding said cam body, said roller being rotatable relatively to said cam body, said roller having an outwardly facing roller surface engageable with said concave surface at a contact point when said first fitting is received within said receptacle, said cam body being rotatable about said offset axis into said receptacle to bring said roller surface into engagement with said concave surface at said contact point, a line of action passing through both said contact point and said cam body center upon engagement of said roller surface with said concave surface, said cam body center being positioned relatively to said offset axis such that said line of action initially passes to one side of said offset axis so as to create a first torque resisting rotation of said cam body about said offset axis into engagement with said concave surface, said line of action moving upon further rotation of said cam body and passing to another side of said offset axis so as to create a second torque opposite to said first torque and causing rotation of said cam body about said offset axis into engagement with said concave surface, said second torque holding said roller surface in engagement with said concave surface thereby locking said first fitting into engagement with said second fitting.