vault 4 and the cap 8 the threads were anchored by forming an epoxy resin plug of 30 cm long between the vault 4 and cap 8 after gelification of the resin a polyurethane elastomer cushion 10 cm long and of a shore hardness a equal to 85 was flowed between the vault 4 and the cap 8 where the threads emerged the coupling was finished by fitting and screwing the heel and the lid on the vault 4 and the cap 8 after curing of the polyurethane elastomer at ambient temperature the assembly was reheated so as to ensure the end of hardening of the epoxy resin another lidded coupling or sleeve was placed at the other end of the sleeve the tube was then placed on a dynamic flexion test bench and held at a pressure of 200 bars the test was stopped without breakage after 6 million cycles this value should be compared with the three million five hundred thousand cycles obtained under the same conditions before breaking flush with the coupling of an identical flexible tube equipped with a similar sleeve but without elastomer cushion and having a plugging length of 40 cm instead of 30 cm the breakage of the same type of tube equipped with the same coupling without elastomer cushion subjected to a static pressure test was obtained at 540 bars over the current length.