Graco Dispensit 802-20 [4/14] Description of operation

DESCRIPTION OF OPERATION

1. The normal “ready” state of the system is as follows:

• The syringe or remote reservoir contains the dispensable material.

• The system has been purged, filling the dispense tube and needle with material.

• The bottom pinch-off piston is not pressurized but is held back by the spring closing the dispense tube

and holding back the dispensable material. (See “Fill” on drawing below.)

• The top pinch-off and dispense pistons are back (not pressurized).

2. The dispense cycle begins when the controller is activated.

3. The top pinch-off piston first moves forward to stop material supply and the bottom pinch-off piston moves

forward to release the dispense tube. (See “Dispense Delay” on sequential function drawing.)

4. The dispense piston then moves forward until stopped by the micrometer stroke adjust. This squeezes a

precise amount of material out of the dispense tube. (See “Dispense” on sequential function drawing.)

5. When the dispense cycle is complete, the spring pushes the bottom pinch-off piston back, sealing the

dispense tube to prevent material drip. Immediately after, the dispense piston and top pinch-off piston

withdraw allowing the material from the pressurized reservoir to refill the dispense tube. The system is again

in the normal “ready” state.

OPERATION ILLUSTRATION

Forward

Note: The above illustration is intended to explain the operation of the 802-20 dispense valve.

Top and middle pistons in the illustration are incorporated in the top piston of the 802-20

dispense valve.