Abstract: A passive cycle skipping valve comprising a pawl and a wheel comprising a first plurality of pins, wherein a distal end of the pawl is configured to engage any of the first plurality of pins where when the second pin is separated from the first pin by at least a threshold pin separation distance, the valve opens and when the second pin is not separated from the first pin by at least the threshold pin separation distance, the valve does not open.

Abstract: Apparatus for placing covers (5, 8) on a cassette (1) and taking covers (5, 8) off a cassette (1) comprises an upper cover removal structure (100U), a lower cover removal structure (100L), and means for holding the cassette in place (170-176). The upper cover removal structure (100U) includes a central body portion (102), a pair of arms (104, 106) rotatably mounted at the end of the central body portion, and fingers (112, 114) located at the end of the arms (104, 106). The fingers (112, 114) can be moved up and down in a direction parallel to the main axis of the arms. The upper cover removal structure (100U) includes means for moving the upper cover removal structure (100U) toward or away from the cassette (1). The lower cover removal structure (100L) includes a central body portion and a pair of arms 156, 158 having fingers (190, 192) at the ends thereof. The arms can move inwardly or outwardly to grasp the bottom cover (8).