4
SICK WSU 26/2 – WEU 26/2
8 008 692/9-12-99 Technical Description · WSU/WEU 26-2 © SICK AG · Safety Systems · Germany · All rights reserved
3 Description of Function
2 Device/System Construction
The WSU 26/2 / WEU 26/2 serves
as a protective cut-off device to
protect hazardous areas on power-
driven machinery. The machinery
may be:
‡
plastics machinery
‡
stackers
‡
settling machinery
in the stoneworking industry
‡
machining centers
The WSU/WEU 26/2 must not be used as a hand or finger guard.
The WSU/WEU comprises:
‡
WSU 26/2 sender unit and
‡
WEU 26/2 receiver unit
Each complete break in the light
beam between the light sender and
light receiver triggers a signal which
can be used to immediately stop
the dangerous movement of the
power-driven machinery
(abbreviated as ”PDM”).
3 Description of Function
The WSU and WEU are mounted
separately in die-cast housings. Each
has its own power supply (
Fig. 2
).
The WSU contains a clock
generator and the sender diode.
The diode emits infrared pulses at
the clock rate set by the generator,
which are evaluated by the receiver
unit WEU if the light path is
uninterrupted.
The WEU contains the output
relays A and B, which pick up if the
light path is uninterrupted.
If the light path or the connection
between terminals 10 and 11 on
the WSU is interrupted (testing),
both relays are released.
1
Connection
for power supply
2
Power supply
3
Clock generator
4
Sender diode
5
LED, WSU
6
LED, WEU
7
Photoelectric converter
8
Amplifier
9
Relay with positively-driven contacts
10 Outputs
11 Test contact
Fig. 2: Principle of function of the WSU/WEU 26/2, AC version