Piston pump with locking pistons

A pump assembly for dispensing a liquid from a container comprising:

• a piston chamber-forming body having a cylindrical fluid chamber disposed about an axis and open at an axially outer end,
• a piston-forming element comprising a piston member and an actuator member,
• the piston member extending from the actuator member coaxially inwardly through the outer end of the fluid chamber into the fluid chamber and engaging the fluid chamber to form a liquid pump,
• the piston-forming element including a central axially extending stem with a passageway therethrough for passage of the liquid discharged by the liquid pump axially outwardly to a discharge outlet on the actuator member axially outwardly of the piston chamber-forming body,
• wherein in coaxial reciprocal movement of the piston-forming element relative the piston chamber-forming body about the axis between a retracted axial position and an extended axial position the liquid pump dispenses liquid from the container out the discharge outlet,
• the piston chamber-forming body including a collar member for engagement with an opening of the container,
• the collar member having an inner guide tube coaxially about the axis open at both an axially inner end and an axial outer end, the guide tube having a cylindrical radially inwardly directed inner guide surface,
• a lug member extending radially inwardly from the inner guide surface,
• the lug member extending radially inwardly from the inner guide surface over a circumferential extent C, a radial extent R, and an axial extent A,
• the piston-forming element having an outer slide tube fixed to the actuator member at an axially outer end and extending axially inwardly to an open axial inner slide tube end,
• the slide tube coaxially about the piston member radially outwardly about the piston member,
• the slide tube having a radially outwardly directed outer tubular slide tube wall,
• a pair of axially extending circumferentially spaced cut slots each cut radially through the slide tube wall from a respective inner slot end open to the inner slide tube end to a respective blind outer slot end located spaced axially outwardly from the inner slide tube end,
• a first finger member defined in the slide tube wall between the cut slots with the first finger member extending from an axially inner distal end of the first finger member to an axially outer end of the first finger member where the first finger member merges into the slide tube wall between the outer slot ends,
• the first finger member deflectable by radially inwardly directed forces to move the distal end radially inwardly relative the slide tube wall,
• the slide tube having an axially extending first slide channel extending radially inwardly from the slide tube wall,
• the first slide channel and the lug member complementarily sized in circumferential extent and radial extent such that when the slide tube is rotated about the axis relative the guide tube to a first operative rotational position the lug member slides axially in the first side channel permitting relative coaxial sliding between the retracted position and the extended position for operation of the liquid pump to dispense the liquid,
• the slide tube having an axially extending first stop slot extending radially inwardly into the slide tube wall,
• the first stop slot and the lug member complementarily sized in circumferential extent and radial extent such that when the slide tube is rotated about the axis relative the guide tube to a first inoperative rotational position the lug member is received in the first stop slot and engagement between the slide tube and the guide tube limits relative coaxial sliding to prevent operation of the liquid pump to dispense the liquid,
• the first finger member located on the slide tube circumferentially between the first slide channel and the first stop slot,
• in relative rotation of the guide tube and the slide tube about the axis from the first inoperative rotational position to the first operative rotational position the first finger member blocks the circumferential movement of the lug member until with relative rotation about the axis a camming surface of the lug member and a cammed surface on the first finger member engage deflecting the first finger member radially inwardly out of the path of the lug member permitting the lug member to rotate circumferentially therepast from the first inoperative rotational position to the first operative rotational position.