Fluid dispensing apparatus and method

A fluid dispenser comprising:

• a body;
• a chamber coupled to or formed as part of the body and configured to contain a quantity of the fluid;
• a piston coupled to the body and rotatable within the chamber to different positions, the piston movable relative to the chamber in a first direction along an axis to draw fluid into the chamber, and the piston movable relative to the chamber in a second direction opposite the first direction to discharge fluid from the chamber, the piston having different stroke lengths selectable via the different rotational positions of the piston and associated with different metered quantities of fluid to be drawn into the chamber;
• and
• a mechanism disposed between the piston and the body and configured to control movement of the piston relative to the chamber, the mechanism having an anti-reversal state inhibiting reversal of the piston during movement of the piston in the first direction or the second direction along the selected stroke length, the mechanism further having a neutral state permitting reversal of the piston.

A method of dispensing a metered quantity of fluid from a fluid dispenser, the fluid dispenser including a body, a chamber, and a piston, the method comprising:

• rotating the piston within the chamber to select a first rotational position of the piston from a plurality of rotational positions associated with different stroke lengths of the piston associated with different metered quantities of fluid to be drawn into the chamber, the piston movable in a first direction and a second direction along an axis in at least two of the plurality of rotational positions, and the first rotational position associated with a first stroke length to dispense a first metered quantity of fluid;
• inhibiting reversal of the piston via an anti-reversal feature positioned between the piston and the body during movement of the piston along the first stroke length;
• and
• permitting reversal of the piston for movement of the piston in the second direction via the anti-reversal feature on movement of the piston the entirety of the first stroke length.