Edition du 24/02/09
/ 12 U508217-e Revision : 2
8
SECTION 4. OPERATION
1. Depress the SET button into its latched position.
The inward movement of the SET button causes:
a. The input drive to de-clutch so that its internal
parts are disconnected from the flow meter.
b. A "gate" to open that had blocked the Preset
buttons from operating.
2. Depress the appropriate Preset buttons to display
the quantity of fluid to be delivered. One depression
of each button will rotate its corresponding wheel
1/10 revolution or one digit in an additive direction.
Presetting one wheel will not affect other wheels.
3. Open the valve to start fluid flow by moving the
linkage between the Preset and the valve. (A handle
is normally supplied by the valve or meter
manufacturer for this function. Units with Series
7856 Switch are equipped with a handle.) This
action rotates the knockoff plate on the bottom of the
Preset case and:
a. The SET button pops out which locks out the
Preset buttons and engages the clutch between the
input shaft and the wheels.
b. The knockoff plate on the bottom of the Preset
case has two tabs that project into the case. When
the valve load is applied and the knockoff plate
rotates, the tabs move internal latches into their
"loaded" positions.
c. The knockoff movement locks out the SET button.
d. Fluid starts to flow. The flow meter drives the
Preset wheels directly in a subtractive direction.
e. When the first stage knockoff number is reached,
a series of notches in the wheels becomes aligned
and the first stage rake drops into the notches.
Then, a cam pulls the rake forward to release one of
the previously loaded latches. The release of the
latch allows the knockoff plate to move back
approximately 15°, 45' for a partially closed valve .
f. When the wheels reach zero, a second rake drops
into the notches and another cam pulls this rake
forward. This action releases the final latch and
allows the plate to move another 7° for a fully clo sed
valve.
