A semi-free rotating crankshaft actuator to pre-stress and fast release a spring loadable plunger for an oral healthcare appliance

A method of providing semi-free rotating crankshaft actuation for an oral healthcare appliance, comprising:

• providing a chamber having a principal axis, an interior surface with a spring compression stop at a proximal end thereof, and at least one outlet at a distal end thereof;
• operating a spring loadable plunger within the chamber along the principal axis between a tensioned position near the proximal end of the chamber and a released position near the distal end of the chamber, wherein the spring loadable plunger comprises (i) a plunger having a distal end thereof configured for traversing the interior surface of the chamber along the principal axis in a fluid tight relationship and (ii) a spring, positioned over a proximal end of the plunger and positioned between the compression stop and the distal end of the plunger, having at least two compression states including a first compression state greater than a second compression state, wherein responsive to the spring being unloaded from the first compression state to the second compression state, the spring actuates the plunger at a first velocity from the tensioned position to the released position, wherein the released position comprises (a) a desired end position within the chamber in response to a first actuator condition and (b) an undesired end position within the chamber, different from the desired end position, in response to a second actuator condition, different from the first actuator condition;
• and
• cycling, via a crank mechanism, the spring loadable plunger between the tensioned and released positions, wherein the crank mechanism comprises at least a drive pin rotatably driven about a drive axis, and a crank shaft semi-freely rotatable about the drive axis, wherein the crank shaft couples to the spring loadable plunger and is partially driven about the drive axis via (i) the drive pin in a first operational mode that comprises loading the spring into the first compression state in response to the crank shaft pulling the plunger from the desired end position to the tensioned position, and (ii) the spring loadable plunger in a second operational mode that comprises actuating the plunger from the tensioned position to the released position in response to the spring being unloaded from the first compression state to the second compression state.