A rotary displacement pump includes a stator (42) fixed in a housing (20), a rotor including a shaft portion (8), a radially protruding web (12), a scraper (110) having an engagement slot (112) engaging the protruding web (12). A guide (92) retains the scraper (110) in a circumferential direction and allows the scraper (110) to move reciprocatingly in a substantially axial direction. The scraper includes first, second and third grooves (120, 124 and 127). The grooves are designed so that they accommodate a portion of the guide (92) and allow the reciprocating movement of the scraper (110).