FRITSCH LABORETTE 24 with V-shaped channel - Manual (Page 20)

5 Working with the LABORETTE 24
The control system of the LABORETTE 24 is based on the frequency con-
trol of the vibration system. An electromagnet pulls a spring-mounted
brace and releases it again. The material is conveyed on the channel in
the preferred direction due to the spring and inertia forces. It performs
throwing movements on the channel in the process.
In the event of adhesive materials, the samples may jam in
the channel or compactions may occur. The conveyance of
very light material may be impaired. This is due to the oper‐
ating principle.
Vibration nodes and loops are formed, since the channel
resonates over its entire length with the vibration system.
As a result, inhomogeneous materials may be de‐mixed on
the channel. This is also due to the operating principle.
The control system is pre-set to the mechanical natural frequency (reso-
nance frequency) of the system. The control frequency corresponds to
the natural frequency of the vibration system if intensity=100% is dis-
played. The vibration intensity and hence the feed rate are controlled
directly by pressing the +/- keys to adjust the control frequency.
At resonance frequency (intensity=100% displayed), the
system is very soft and active (damping‐dependent
conveying speed). The control frequency in higher frequency
ranges is moved away from the resonance frequency by
pressing the MINUS key ‐ the LABORETTE 24 is operated in
the upper critical working range. The result is harmonious
conveyor vibrations at a constant conveying speed.
In the upper critical working range, the phase position between the exci-
tation and resonator tends towards 180°. This working range compen-
sates damping changes and at the same time maintains the harmonious
vibratory motion of the mechanical vibrator, which is why this setting,
for example, is suitable for difficult plastic samples. The conveying speed
is stable for lightweight to medium-weight samples.
Working principle
Working with the LABORETTE 24
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