Abstract A spindle (242 414 542 642) for driving a bung of a cartridge is provided. The spindle includes a generally circular shaft having an outer surface (560). The generally circular shaft extends from a distal end to a proximal end of said circular shaft. A first helical groove (219 519 619) is provided along a first portion of the outer surface. The first helical groove having a first pitch. A second helical groove (221 521 621) provided along a second portion of the outer surface of the generally circular shaft. The second helical groove overlapping the first helical groove. The second helical groove having a second pitch. (Figure 28)
