TM 5-4940-228-14
CHAPTER 6
REPAIR OF SPRAY COMPONENTS
Section I.
PRESSURE CUP
6-1. General.
The pressure cup is used when a small quantity,
less than a quart (. 946 1), of paint is to be applied.
The cup replaces black fluid hose and pressure tank
in actual operation. When spray gun trigger is pull-
ed, air is allowed to enter handle through pressure
tube into hole in cover, forcing diaphragm open. Air
enters cup and builds up pressure which forces
paint up fluid post and to spray gun fluid con-
nection. Amount of fluid flow is controlled by fluid
control on spray gun. A safety valve is located on
the cover which is set to open at 45 psi.
6-2. Disassembly.
Refer to Figure 6-1 and proceed as follows:
a. Unscrew cup (1) from cover (11) and remove
cup gasket (2).
b. Pressure tube (3) can be removed as an assem-
bly by unscrewing fitting “L” (5) from cover (11).
To disassemble pressure tube (3), unscrew fitting
(6) from fitting “L” (5) and unscrew other fitting
(6) from adapter (4). Place tube (7) with two fit-
tings (6) attached into a container of hot water for 2
to 3 minutes, this will make tube (7) soft and flex-
ible. Remove both fittings (6) from tube (7).
c. Unscrew jam nut (8) from stem (15), washer
(9) and diaphragm (10) can now be removed.
d. Unscrew safety valve (12) from cover (11) and
unscrew fluid post (13) from stem (15).
e. Unscrew stem (15) from cover (11), com-
pression nut (14) will now be free and can be re-
moved.
6-3. Cleaning and Inspection.
Clean all parts thoroughly with paint thinner. Do
not soak pressure tube (3) or cup gasket (2) in thin-
ner, some thinners can deteriorate or swell these
materials. All holes in cover (11) must be clear, di-
aphragm (10) must be clean and flat.
WARNING
A safety valve clogged with dried
paint cannot operate properly. Re-
place safety valve if body becomes
clogged. Cup could rupture at high
pressure and cause serious injury.
Inspect parts for excessive wear, damage, tears,
breaks or dents. Replace unserviceable parts.
6-4. Reassembly.
Refer to Figure 6-1 and proceed as follows:
a. Slide compression nut (14) over stem (15) and
screw stem (15) into cover (11).
b. Screw fluid post (13) into stem (15) and screw
safety valve (12) into cover (11).
c. Slide diaphragm (10), washer (9) and com-
pression nut (8) over fluid post; tighten com-
pression nut (8).
d. Screw fitting “L” (5) into cover (11) and screw
one fitting (6) into fitting “L” (5). Screw other fit-
ting (6) into adapter (4). Place tube (7) in a con-
tainer of hot water for 2 to 3 minutes, this will make
tube (7) soft and flexible. Slide tube (7) over both
fittings (6) one end at a time.
e. Place cup gasket (2) inside of cover (11) and
screw cup (1) into cover (11). Assembly is now com-
plete.
6-5. Testing.
Test by attaching to a spray gun. Refer to para-
graph 2-3. You can use water or paint thinner in-
stead of paint. Turn fan control on spray gun all the
way in (clockwise). Fill cup 1/2 full. Actuate trigger
to pressurize cup and check for a steady stream of
fluid leaving the spray gun fluid nozzle. Release
trigger and look for any fluid or air leaks.
6-1
