Rockwell Automation Allen-Bradley 140M, Руководство пользователя

Страница: 22 / 192

22 Rockwell Automation Publication 450L-UM001F-EN-P - March 2022
Chapter 3 Operation
The first laser beam, or the last beam near the end of the sticks, optically
synchronizes the timing of the emission and reception of infrared light pulses.
These beams are referred to as the synchronization beams. Because the
GuardShield systems are optically synchronized, no electrical connection is
required between the transmitter and receiver sticks.
The unique design of the GuardShield platform allows every 450L safety light
curtain transceiver to transmit and receive infrared light. In contrast to the
classical architecture of common pure transmitter and receiver light curtain
systems, GuardShield transceiver sticks exchange protective field information
via infrared light. Therefore infrared light is not only sent from a transceiver
working as a transmitter to a receiver. As indicated in
Figure 10 , a transceiver
stick configured as a receiver transmits some infrared light to the transmitter.
The dashed lines in
Figure 10 indicate the synchronization beams.
Figure 10 - Schematic Display of Beam Center Lines
The slightly slanted beams and the maximum operating angle of the IR light
require that a transmitter and a receiver stick are installed beyond a minimum
operating distance. A 450L safety light curtain system is safe against
manipulation because a transmitter stick cannot be installed directly in front
of a receiver stick.
A GuardShield transceiver, which acts as a receiver, has two OSSD safety
outputs and, depending on the plug-in that is used, one additional non-safety
auxiliary output. When the GuardShield transmitter and receiver are properly
powered, aligned, not obstructed, and the start/restart mode has been
correctly initiated, both the OSSDs and the auxiliary output are ON (output
voltage = +24V DC). The two safety OSSDs are cross fault monitored and short-
circuit protected.
Interruption of the sensing field causes the receiver OSSD to switch OFF
(sourced current 0 mA DC, source voltage 0V DC).
For automatic restart: No obstruction of the GuardShield sensing field causes
the two safety outputs (OSSD) to switch to the active high (On) state
(+24V DC).
With the appropriate resolution, the GuardShield safety light curtain system
provides finger or hand protection. The resolution corresponds to the
diameter of the provided test rod belonging to the safety light curtain. The test
rod is reliably detected when positioned in the protective field. The resolution
of a GuardShield stick is printed on the product label.
ATTENTION: The Auxiliary output is only a status output for diagnosis
purposes to connect, for example, an indicator lamp. Do not use this output
for safety purposes.