Spool valve actuator

A method for activating and locking a spool valve, comprising:

• applying a working force to spool valve;
• translating the working force, through a spool valve shaft attached to the spool valve, to a spool valve actuator in a cylindrical actuator case connected to a proximal end of the spool valve and oriented coaxially with a spool axis, and comprising an indexing mechanism and main spring;
• moving the spool valve shaft in a distal direction along the spool axis, such axial movement causing:
• moving of a ratchet member slidably attached to the spool valve shaft in the distal direction along the spool axis, away from a stop fixed to a proximal end of the cylindrical actuator case, wherein the ratchet member is keyed to the stop to prevent relative rotation between the ratchet member and the stop;
• engaging, via the moving of the ratchet member, a distal edge of the ratchet member comprising a plurality of distally facing teeth with a proximal portion of a positioner, the proximal portion comprising a plurality of extending positioning members configured to engage the distally facing teeth of the ratchet member;
• moving, as a result of the engagement of the ratchet member and positioner, the positioner in the distal direction along the spool axis and away from the stop;
• rotating, as a result of the engagement of the ratchet member and positioner, the positioner relative to the stop;
• moving, as a result of removal of the working force, the positioner in a proximal direction along the spool axis toward the stop;
• engaging, via the moving of the positioner in the proximal direction, the positioning members of the proximal portion with one of a first set of slots of a first length in the stop at regular circumferential distances and a second set of slots of a second length in the stop at regular circumferential distances offset from the first set of slots.