his is a proposed method of connecting PVC piping which can expand or contract with temperature changes without causing leaks at solid "glue points" (non-pressurized transport).If this has already been thought of before . . . my congratulations to the original inventor.
The "O" ring rolls through 360 degrees so that it is in the sealing position in an unstressed state. The inserted pipe must be prepared with a special tool which bevels the edge and cuts the groove which corresponds to the groove in the manufatured female "coupler". When two pipes are inserted into the coupler, a predetermined amount of play is left to accomodate thermal expansion/contraction.
Notice that the "O" ring is compressed in the sealed state but not as much as when passing -to- the sealed state.
Here is a ready made variant. Just glue it on the ends of two pipes.