SCROLL PUMP APPARATUS AND METHOD

A scroll pump 101 with drive shaft 115, fixed scroll 105, orbiting scroll 103, has at least one actuator 129-n for adjusting the axial position of the orbiting scroll or the fixed scroll (fig.7). Each of the scrolls has a wrap, or involute scroll wall 107, 111 which extends axially towards the base 109,113 of the opposing scroll, the actuator can open a gap or spacing between the scroll and the opposing wall reducing the throughput of the pump without altering the motor 116 driving speed. Spacing can be sensed by a [capacitive] sensor 127-n on either scroll to actively target a specific spacing. Target spacings of 5, 10, 15, 20 microns are given, chosen by operating temperature and pressure. A baseline zero spacing may be found by driving the pump and sensing the slowing of rotation. Scroll walls may be PTFE coated. Also disclosed is positioning an actuator on the shaft distal to the orbiting scroll (fig.1), and having several angularly spaced actuators which operate to alter the 2D/3D orientation between the bases of the scrolls, for example to ensure the base plates are substantially parallel. Application: vacuum pump.