5
Functional description
5.1
Drive unit
The metering pump is an diaphragm pump, the stroke length of which can
be adjusted. An electric motor (1) drives the pump. A worm gear (2) steps
down its drive rotation A cam (3), in conjunction with the uptake fork (8)
converts this into an oscillation movement of the slide rod (4). A return
spring (5) presses the uptake fork together with the slide rod positively
against the cam thus producing the reciprocal stroke. The stroke length
can be adjusted using the stroke adjustment dial (6) and the axle (7). The
different stroke lengths are in effect caused by a limitation of the return
stroke, see figure. The slide rod transmits the stoke motion to the metering
diaphragms.
Fig. 6: Section through the drive unit Sigma 1
1 Electric motor
2 Worm gear (not visible)
3 Eccentric cam
4 Slide rod
5 Return spring
6 Stroke adjustment dial
7 Axle
8 Uptake fork
The stroke movement of the displacement body is continuously measured
and regulated so that the stroke is executed according to a previously set
dosing profile, see chapter
‘Set-up’
-
‘Metering’
.
The following dosing profiles are available:
n Normal
n Discharge opti.
n Suction opti.
Illustration of the stroke movement
Functional description
20
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