Theory Of Operation - Nordson A7A Customer Product Manual

6
A7A Single and Dual Automatic Airless Spray Guns

Theory of Operation

Part 1072640A
See Figure 2. This figure shows a cutaway view of a dual-chamber A7A
gun. The dual-chamber gun is two single-chamber guns mounted on a
manifold, sharing a single nozzle. Only one chamber is triggered at a time.
To trigger the gun, air pressure is applied to the bottom of the piston
assembly (2), which lifts the needle (4) off the seat (5). Coating flows
through the seat to the nozzle (8). When the air pressure is removed, the
spring in the packing cartridge (3) returns to the needle to the seat and
stops the flow of the coating material to the nozzle.
The packing cartridge seals prevent coating material from contaminating the
air piston. If the seals fail, coating material will flow out of the weep holes
above the fluid fittings.
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4
5
Figure 2 Gun Operation
1. Air fitting
2. Piston assembly
3. Packing cartridge
4. Needle
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8
5. Seat
6. Fluid fittings (inlet and outlet)
7. Nozzle nut
8. Nozzle
E 2019 Nordson Corporation
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