Two-stage dispensing unit

A dispensing unit of a dispenser configured to dispense material on a substrate, the dispensing unit comprising:

• a main housing having a main chamber;
• a reciprocating piston assembly disposed in the main chamber and axially movable within the main chamber;
• a nozzle coupled to the main housing, the nozzle having an orifice that is co-axial with the main chamber of the housing;
• and
• an assembly coupled to the dispensing unit and configured to drive the up-and down movement of the reciprocating piston assembly, the assembly including
• a housing coupled to the main housing, the housing having a chamber co-axial with the main chamber, and
• an actuator disposed in the adjuster chamber and axially movable within the chamber, the actuator being configured to engage the reciprocating piston assembly and to drive the downward movement of the reciprocating piston assembly,
• wherein the reciprocating piston assembly includes a first piston portion having a lower end configured to pressurize fluid within the orifice of the nozzle and a second piston portion that is separate from the first piston portion and having an upper end configured to engage the actuator, and
• wherein the first piston portion is configured to move a first distance and the second piston portion is configured to move a second distance, which is different than the first distance.

A method of operating a dispenser to dispense material on a substrate, the dispenser comprising a main housing having a main chamber, a reciprocating piston assembly disposed in the main chamber and axially movable within the main chamber, a nozzle coupled to the main housing, the nozzle having an orifice that is co-axial with the main chamber of the housing, and an assembly coupled to the dispensing unit and configured to drive the up-and down movement of the reciprocating piston assembly, the reciprocating piston assembly including a first piston portion and a second piston portion, the method comprising:

• moving the first piston portion of the reciprocating piston assembly a first distance;
• and
• moving the second piston portion of the reciprocating piston assembly a second distance,
• wherein the second distance being greater than the first distance.