Operating instructions

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 reciprocal
strokes (see
Ä “Illustration of the stroke movement” on page 15 ). The
slide rod transmits the stoke motion to the metering diaphragms.
P_SI_0077_SW
1
52
4
6
7
8
10
3
Fig. 5: Section through the drive unit Sigma 2
1 Electric motor
2 Worm gear
3 Eccentric cam
4 Slide rod
5 Return spring
6 Stroke adjustment dial
7 Axle
8 Uptake fork
0
s s
a)
180 360 0
b)
180 360
ω ω
P_PL_0009_SW
Fig. 6: Stroke movement at a) maximum stroke length and b) reduced
stroke length.
s Stroke velocity
⍵ Cam rotational angle
+ Discharge stroke
- Suction stroke
Illustration of the stroke movement
Functional description
15