The positive-displacement pump (10) includes a pump body (12) delimiting a rubber pressurizing chamber (14), and a feeder (16) for feeding the chamber (14) with rubber. The feeder (16) includes a worm (42) able to rotate about a main axis (X) with respect to the pump body (12) and an absorption body (50) that absorbs pressure in the pressurizing chamber (14) and is axially secured to the worm (42). The absorption body (50) is distinct from the worm (42), and has a surface (54) delimiting the pressurizing chamber (14) and arranged axially in line with the worm (42).