US Patent 8382067 Stem seal

Any stem seal using either a triangle-sectional bushing or ring as stem cylinder seals or a ball wedge/spherical socket mating arrangement as stem shoulder seals can individually withstand the same pressure as the burst pressure of bodies without failure. The sectional triangle of the triangle-sectional bushing or ring is truncated to provide a wearing and compressing allowance for the bushing or ring, and so will be again a full triangle or an untruncated triangle when the bushing or ring is fully worn. The ball wedge/spherical socket mating is a mating which uses ball wedges as a stop shoulder of stems and the spherical socket as a stop socket at stem exits.