Vacuum scroll pump

A method of assembling a scroll vacuum pump, the scroll vacuum pump comprising:

• an orbiting scroll having an orbiting scroll wall extending axially from an orbiting scroll base towards a fixed scroll, the fixed scroll having a fixed scroll wall extending axially from a fixed scroll base towards the orbiting scroll;
• an axially extending drive shaft having an eccentric shaft portion so that rotation of the eccentric shaft portion imparts an orbiting motion to the orbiting scroll relative to the fixed scroll;
• and
• an axial thrust bearing arrangement comprising:
• an array of ball bearings for bearing against the orbiting scroll base in an axial direction, each ball bearing describing a circular path over the orbiting scroll base during orbiting motion;
• a retainer having at least one thrust surface for bearing against the array of ball bearings and a plurality of bores;
• an adjustment mechanism comprising a plurality of adjustment members for for adjusting an axial position of said at least one thrust surface and thereby an axial position of the orbiting scroll base;
• and
• a plurality of biasing members for biasing the plurality of adjustment members relative to the at least one thrust surface, each of said plurality of biasing members being for a respective adjustment member of the plurality of adjustment members for causing threads of the respective adjustment member to bear against threads of a respective bore of the plurality of bores in the retainer for resisting play between the threads and/or increasing friction therebetween;
• wherein in a first assembly step the adjustment mechanism is adjusted to cause the orbiting scroll and the fixed scroll to contact to provide a datum position of the scrolls, and in a second assembly step the adjustment mechanism is adjusted to cause the orbiting scroll and the fixed scroll to be moved apart by a selected spacing relative to the datum position.