Rockwell Automation 440L GuardShield Type 4 and Remote Teach User Manual - Manual (Page 7)

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GuardShield™ Safety Light Curtain User Manual
5
Original instructions
GuardShield Light Curtain
Principle of Operation
The GuardShield safety light curtain consists of a non-matched pair of
optic units, i.e., transmitter and receiver with the same protected height
and resolution. The transmitter and receiver operate on +24V DC.
The maximum distance between transmitter and receiver is referred to
as the protective field width or range. The protective field height is the
distance between the first and last beam in the device.
The transmitter emits sequential pulses of infrared light which are
received and processed by the GuardShield receiver. The
synchronization of the timing of the emission and reception of
infrared light pulses is accomplished optically by the first beam
adjacent to the GuardShield status LEDs. This beam is referred to as
the synchronization beam. Because the GuardShield transmitter and
receiver are optically synchronized, no electrical connection is required
between the transmitter and receiver.
The GuardShield receiver has two safety outputs, Output Signal
Switching Devices (OSSDs) and one nonsafety auxiliary output. When
the GuardShield transmitter and receiver are properly powered and
aligned, all OSSDs are current sourcing +24V DC with a switching
capacity of 500 mA. The two safety OSSDs are cross monitored and
short-circuit protected. Interruption of the sensing field causes the
receiver to switch the sourced current OFF (0V DC).
Restoring the GuardShield sensing field, (in Guard only configuration)
causes all outputs (OSSDs) to switch to the active high state (resume
current sourcing +24V DC with a switching capacity of 500 mA).
The GuardShield Light Curtain
The GuardShield safety light curtain consists of a transmitter and a
receiver.
Figure 1: Components of the GuardShield
The upper and lower limit of the protective field is shown by markings
on the housings.
The GuardShield with an Integrated Laser Alignment system has the
limits of the protected height indicated by the yellow border on the
laser label and target label.
The
width of the protective field is derived from the length of the
light path between sender and receiver and must not exceed the
maximum rated width of the protective field (7 m…14 mm (22.9
ft…0.55 in.), 18 m…30 mm (59.0 ft…1.18 in.)).
Cascading
The GuardShield, Type 4 POC is also available in cascading segments
which allow a number of GuardShield transmitters and receivers to be
interconnected. This product configurability allows the GuardShield to
protect multiple sides of a machine or simply adds flexibility when
positioning the GuardShield in various applications.
Standard GuardShield cascading segments are offered in protective
heights from 320 to 1760 mm in both 14 mm and 30 mm resolutions.
Cascading segments of 160 mm are not offered, however a 160 mm
GuardShield can be used as the last segment in a cascading system.
Cascading GuardShields with an integrated laser alignment system are
offered in protected heights from 320 mm to 1600 mm. It is possible
to mix standard GuardShield light curtains with integrated laser
alignment systems.
A maximum of three GuardShield light curtains can be interconnected
with a common pair of OSSDs. There are no limitations for the total
number of beams in a cascading system and the maximum number of
beams possible is in three 1760 mm, 14 mm resolution GuardShield
interconnected segments. The individual segments can have mixed
resolutions, i.e., 14 mm and 30 mm as long as the pairs have the same
protective heights and resolutions.
Cascading segments can be used as standalone light curtain pairs or
can have up to three segments interconnected. These cascading
segments all function as independent light curtains.
When cascading segments are used as standalone pairs or as the last
segment in a cascading system, it is necessary to use a termination plug
on the top connector of the GuardShield cascading receiver. It is also
Transmitter Receiver
Up to three GuardShield POC segments can be interconnected.