while allowing them to slide relative to each other the leaves 82 may have any other suitable configuration in accordance with other embodiments of the present disclosure in assembly each leaf 82 is pinned to the drive gear 56 by a respective pin 86 or may be secured to the drive gear 56 in any other suitable manner the fin 88 projects axially downstream in the illustrated embodiment a bushing or extension 68 engages an o ring associated with housing section 14 the bushing 68 fixedly locks into the housing to prevent rotation fins 88 engage a protruding ring having thin slots to engage the fins another ring may provide a sealing surface in the illustrated embodiment when assembled each pin is substantially equidistant radially to a center axis of the through hole 78 and orifice 76 the slots of the protruding ring are also substantially equidistant radially and substantially equally spaced circumferentially in the depicted embodiment each fin 88 is also substantially linear in the illustrated embodiment the assembled components of leaves 82 the protruding ring and drive gear 56 are thereafter further installed with an o ring into a recess of the housing bushing 68 may be fixedly attached to the housing section 14 by means of a key and slot boss and detent snap fit.