Pulsafeeder Pulsa Series Pulsamatic Controls - Manual (Page 4)

1. Introduction
1.1 General Description
The PULSAmatic actuator converts reciprocating motion of the pump into rotary motion to turn
the pump’s stroke adjustment screw. By selectively engaging either of the two oppositely oriented,
one-way clutches, one of two corresponding nuts hat ordinarily rotate freely on a “diamond”
actuator shaft is blocked form rotation when the shaft moves longitudinally in one direction. Thus
locked, the nut compels the shaft to rotate, thereby turning the adjustment screw to which it is
connected.
The actuator assembly consists of the following major components: the actuator shaft (a major
portion of which is in the form of a diamond screw), tow brake housings, two one-way clutches,
and two helix nuts. Mounted side-by-side, the two brake housings are concentric to the axis of the
actuator shaft. The helix nuts are located between the inner walls of the brake housings and the
surface of the shaft. One nut engages the right-hand thread of the shaft and other engages the left-
hand thread. Each nut rotates within a one-way clutch.
In operation, the actuator shaft reciprocates along its axis. When the brakes are de-energized, each
nut, along with its respective clutch, is free to rotate in alternation clockwise and counterclockwise
directions as it is driven by grooves in the shaft. Under this condition, the shaft and adjustment
screw do not rotate.
Upon energizing one of the brakes, the corresponding one-way clutch is utilized allowing the nut
to rotate only in one direction, while the shaft is moving longitudinally during the e discharge
stroke of the pump (linear motion of the shaft is now in the opposite direction), the clutch prevents
the nut from rotating, causing the shaft to rotate. This rotation is transmitted by a mechanism
inside the gearbox housing to the pump adjustment screw so that the piston stroke length is
changed. By energizing the other brake, the adjustment screw is rotated in the opposite direction.
To increase or decrease pump output, it is only necessary to selectively energize either brake.
Rotary motion of the actuator shaft also rotates a sleeve which in turn drives a gear train through a
spur gear pressed on one end of the sleeve. The gear train transfers outputs for a positional
feedback potentiometer and limit switches. A bevel gear mounted on the opposite side of the drive
sleeve is meshed with a hand wheel bevel gear and mechanical stroke position indicator.
A printed circuit board contains standard and optional control circuits. The incoming command
signal is compared with the internal feedback signal. If the two are equal or nearly so, no action
occurs. If the command signal is greater, one brake is energized, resulting in a corresponding
change in pump output (stroke length) and feedback signal. If the feedback signal is greater than
the command signal, the other brake is energized, changing the pump output and feedback signal
in the reverse direction. When the feedback signal matches the command signal, stroke length is
properly positioned and adjustment is halted.
The override switch, operable from outside the actuator assembly, disconnects the brakes from the
circuit board to permit manual adjustment using the hand wheel. The “out” position is for manual
operation and the “in” position is for automatic operation.