Model CA
Cascading Safety Light Curtain
Product Overview
The Ultimate in Safety - Quality -
Value - Flexibility
Cascading safety light curtains provide the user the ability to
connect additional sets of light curtains by daisy chaining multiple emitters and receivers together. The
interconnecting cables are factory supplied and the user defines length. The cascading of safety light
curtains provides mulitple areas of guarding in any plane (X, Y, Z), while utilizing the control reliable
dual safety outputs from the Category 4 safety device for the safety outputs to the machine control. The
ability to guard multiple areas on irregular shaped machines by cascading safety light curtains reduces
wiring and provides a lower cost yet effective machine guarding solution.
The Model CA Cascading Safety Light Curtain is
an infrared safety light curtain that is designed to the IEC 61496 standard. When properly installed, it protects
the machine operator by passing an invisible infrared light beam across an area to be guarded and examining whether
or not the light beam(s) are blocked. If the light beam(s) are blocked, monitored solid state outputs will open,
issuing a “STOP” command to the machines normally closed (N.C.) “STOP” circuit. The CA System is composed of
transmitting units (EMITTERS), and receiving unit (RECEIVERS). The entire system is control reliable Category 4
(per IEC 61496). A single fault anywhere within the Model CA will not prevent at least one of the solid state
outputs from opening up, (allowing a “STOP” command) when either a beam is broken or an internal fault
occurs.
Theory of
operation.
The Model CA Cascading Safety Light Curtain protects an area by
projecting a curtain of infrared light. The infrared emitters and receivers face each other across the field to be
protected. Each LED pair is spaced along the length of the pylons at regular intervals from .5" (12mm), up to 8"
(203mm) depending on the application. The smaller spacing are for finger guarding, the larger spacing are for body
protection. The emitter/receiver pairs are scanned sequentially (one at a time) by a very short pulse of infrared
light starting from bottom (cable end), and working up to the end, until every beam pair has been scanned. Two 16
bit computers in the first emitter pylon and two 16 bit computers in the first receiver pylon control the
operation, as well as cross check each pylon.
The
System.
The Model CA Cascading Safety Light Curtain employs infrared
technology in a small sealed NEMA 4 (IP 67) aluminum housing with an infrared passing (daylight filtering) acrylic
lens. This system provides harmless invisible protection and an unobstructed view of the guarded area. There are
two parts to the Model CA: An Emitter pylon and a Receiver pylon. The Emitter pylon has no outputs. The Receiver
pylon contains two monitored solid state 24vdc outputs. Both pylon sets are synchronized to each other
electronically as they are connected together with the interconnect cables to the top and bottom of the next set of
pylons.
System
Safety.
The Model CA Cascading Safety Light Curtain incorporates redundant, and diverse
technology that provides a backup for every system that could cause an unsafe condition.
External Device Monitoring
(EDM).
A method in which the Model CA Category 4 cascading
safety light curtain logic monitors the state of various external control devices. The control devices are external
and not part of the Model CAlight curtain pylons. A lockout or stop signal will result if an unsafe state is
detected in an external device. The External Device Monitoring (EDM) is an optional function of the Model CA safety
light curtain for monitoring the status of external devices such as gate and door switches, safety switches or the
main control element of the drive (MPCE). Solid state outputs are turned on separately to be checked and to assure
neither output has been shorted, before fully turning on.
Design
Criteria.
Designed to meet IEC 61496-1 & 2, UL 1998, UL subject 491, OSHA, ANSI, CSA,
ANSI-RIA R15.06-1999
Microprocessor redundancy for both Emitter and Receiver pylons
Redundant, monitored, 24vdc solid state outputs (PNP)
Watchdogs on CPU’s and outputs prevent unintentional output during
lockups.
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