Gear Speed Change
RW 20.n and RW 20 DZM.n only
Should it be necessary to change the gear speed in the course of
setting up an experiment or process with glass apparatus, then
attention must be paid to the movement of the stirrer attachment by
the eccentric bearing bush and to the movement in the axial direction.
If this is unacceptable, the stirrer attachment must be loosened in the
chuck.
Turning (counter-clockwise) the bearing bush at the black knurled
surface over the chuck disengages the gears. The center axis of the
stirrer attachment shifts 2.2mm in the radial direction. The bearing
bush is then moved 5.5mm up or down in the axial direction
according to the range to be set. Turning back (clockwise) the bearing
bush re-engages the gears and swings the center axis of the stirrer
attachment back to its original position.
Motor Circuit Breaker
The ball race capacitor motor, protected to IP 42, is maintenance-
free. In its winding it carries a special overheating circuit breaker
(self-locking temperature limiter) which shuts down the motor
permanently if the permissible motor temperature is exceeded.
This special type of circuit breaker is used when the automatic
reactivation of the protected unit after overheating is undesirable or
impermissible. The principle of the temperature limiter is that of a
switch that heats up and isolates the motor from the power supply
when the maximum permissible temperature is reached.
12
When the self-locking temperature sensor is tripped, the yellow
glow lamp (B) on the front plate of the unit lights up to indicate the
motor overload and the stoppage of the motor. In this case the unit
(See Fig. 5)
can only be switched back on after it has been switched off for
approx. 4-5 minutes by pressing the rocker switch (A) on the front
plate or by disconnecting the mains plug.
After this short cooling period, the contacts in the current circuit are
closed again and the unit is operational once more.
Speed Display
The rotation speed is adjusted with the rotary knob (C) on the front
plate of all RW 20.n stirrer units.
RW 20.n
speed is set via the scaling of the rotary knob position. The plate
(Fig. 5) attached to the side of the unit lists the speeds attained at
the set scale values. (The values apply only when low loads are
acting on the stirrer shaft.)
RW 20 DZM.n
speed is displayed directly in revolutions per minute (rpm) on the
LCD display (D). The display can only show speeds up to max. 1999
rpm, which means that the off-drive shaft may be moving at a faster
speed than displayed when there are low loads acting on the stirrer
shaft.
RW 20 DZM.n P4
speed is displayed directly by the LCD display (D), as in the RW 20
DZM.n. As the toothed gear train is no longer adjustable and is set
to the lowest speed, the entire rpm range can be displayed.
In the RW 20.n unit, a defined rotational
In the RW 20 DZM.n unit, the rotational
In the RW 20 DZM.n P4 unit, the rotational
RW201095EU