Molded Piston Seal With Anti-Leak Deported Split Line

A metering pump (10) for a medical injector (12) comprising a reservoir (6) and a cannula (8), the metering pump (10) comprising:

• a housing (16);
• a sleeve (14) at least partially received within the housing (16);
• a piston (18) at least partially received within the sleeve (14);
• and
• a seal (20) positioned over a portion of the piston, the seal (20) having a first portion (22), a second portion (24) opposed from the first portion (22), and a center portion (26) between the first portion (22) and the second portion (24), the center portion (26) defining a sealing surface (26a), the seal defining a split line (26b) located between the sealing surface (26) and one of the first portion (22) and the second portion (24), the split line spanning a full circumference of the seal and being entirely offset to one side of the center portion.