Overview
GuardShield™Introduction
The Allen-Bradley Guardmaster GuardShield is offered as a Type 2 and a Type 4 POC safety light curtain as well as a Type 4 PAC safety light curtain. The Type 4 POC GuardShield is offered in both 14 mm and 30 mm resolutions while the Type 2 is offered in 30 mm resolution only. The GuardShield PAC is offered with multiple beam configurations with varying beam spacings. All GuardShield family safety light curtains meet the requirements of IEC/EN 61496.
POC safety light curtains are designed to detect the presence of an opaque object of a minimum resolution. These devices are usually positioned in front of the point of operation hazard, however, they may also be used for perimeter guarding applications.
PAC safety light curtains are typically used as opto-electronic fences or as whole body detection devices to detect personnel or large objects when they pass through the sensing field. These PAC safety light curtains are typically positioned around an area or in front of a process entry or exit area.
The Allen-Bradley Guardmaster GuardShield is a two-box safety light curtain, consisting of a nonmatched transmitter and receiver pair. Any GuardShield transmitter of the same family (POC, PAC) and same resolution will work with any receiver of the same family and resolution. The synchronization between transmitter and receiver is achieved optically. The first beam adjacent to the receiver LEDs is the synchronization channel. This synchronization beam cannot be blocked in a fixed or floating blanking application.
The GuardShield safety light curtain has two transistor type PNP safety outputs, referred to as OSSDs (Output signal switching devices). These outputs may be connected to a safety relay module or directly to the primary control element of a machine if the EDM connection within the GuardShield receiver is also connected and configured.
The standard GuardShield receiver also has an auxiliary nonsafety output which can be connected to a PLC for status of the OSSDs, to a stack light for signaling or to control an in-feed motor, etc.
The standard GuardShield requires separate transmitter and receiver cables. The transmitter cable utilizes a 4-pin micro quick-disconnect (M12) connector and is offered in lengths from 2 meters to 30 meters. The receiver cable has an 8-pin micro quick-disconnect (M12) connector and is also offered in lengths from 2 meters to 30 meters.
Typical System Configuration
Components required for a "Guard only" system:
| 1. | Optic heads (operate on 24V DC—ordered as a pair (transmitter/receiver) |
| 2. | Cable—two required per pair—specify transmitter cable and receiver cable |
| 3. | Mounting brackets—included |
| 4. | Safety Relay Module—optional (Note: A Category 3 system may be possible by connecting the GuardShield OSSDs directly to two safety contactors and connecting and configuring the EDM mode of operation in the GuardShield receiver.) |
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The Allen-Bradley Guardmaster GuardShield Type 4 is a two-box light curtain with DIP switch selectable operating modes.
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Receiver DIP Switch Functions or GuardShield Type 4 POC
The standard GuardShield safety light curtain has DIP-switches located in both the transmitter and receiver endcaps. The DIP-switches are accessible through a hinged door that is secured to the endcap with a security screw.
The transmitter DIP-switches provide for the configuration and activation of Beam Coding and Machine Test Signal.
The receiver DIP-switches provide for configuration of all of the GuardShield safety light curtain's modes of operation.
GuardShield Safe 4
The GuardShield Safe 4 is a Type 4 safety light curtain offered in POC and PAC versions with basic ON/OFF functionality. The Safe 4 POC is offered in both 14 mm and 30 mm resolutions in protective heights ranging from 120 mm up to 1920 mm in increments of 120 mm.
The GuardShield Safe 4 PAC (Perimeter Access) is offered with two 120 mm modules providing 500 mm spacing and with three 120 mm modules providing 400 mm spacing. Both the two- and three-beam Safe 4 PAC versions have an operating range from 5 meters up to 30 meters.
The GuardShield Safe 4 POC and Safe 4 PAC are economical Type 4 safety light curtains with ON/OFF functionality and an integrated laser alignment system. The integrated laser alignment system consists of a constantly powered Class 2 visible laser located on the top of the transmitter and on the bottom of the receiver. The constantly powered integrated laser alignment systems allows a low level of laser light to be emitted. Simply touching a finger to the laser beneath the finger symbol reflects the low level of laser light back to a photo sensor which causes the laser light intensity to increase for five minutes or until a finger covers the laser reflecting the laser back to the photo sensor which signals a reduction of the intensity of the emitted laser light. This system assures that both the top and bottom of the Safe 4 pair are quickly and easily aligned or realigned if a light curtain or corner mirror is inadvertently moved during operation.
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GuardShield Safe 2
The GuardShield Safe 2 is a Type 2, SIL 2, PLd, safety light curtain offered with a 30 mm resolution in protected heights ranging from 120 to 1920 mm in 120 mm increments. The GuardShield Safe 2 is an economical, two-box safety light curtain with ON/OFF functionality and an integrated laser alignment system. The integrated laser alignment system consists of a Class 2 visible laser located at the top of the transmitter and the bottom of the receiver. Each laser has a target located opposite the laser on the transmitter and receiver. This integrated laser alignment system facilitates alignment at installation and during the course of usage if the Safe 2 pair is knocked out of alignment.
GuardShield Safe 2
The GuardShield Safe 2 is a Type 2, SIL 2, PLd, safety light curtain offered with a 30 mm resolution in protected heights ranging from 120 to 1920 mm in 120 mm increments. The GuardShield Safe 2 is an economical, two-box safety light curtain with ON/OFF functionality and an integrated laser alignment system. The integrated laser alignment system consists of a Class 2 visible laser located at the top of the transmitter and the bottom of the receiver. Each laser has a target located opposite the laser on the transmitter and receiver. This integrated laser alignment system facilitates alignment at installation and during the course of usage if the Safe 2 pair is knocked out of alignment.
Perimeter Access Control (PAC)
Allen-Bradley Guardmaster PAC safety light curtains consist of two families, the GuardShield PAC family and the Safe 4 PAC family. The GuardShield PAC family is offered with multiple beams with various beam spacings for short range applications (16 meters or less). The Safe 4 PAC family is offered with multiple beams (2 or 3) with various beam spacings for long range (5…30 meters).
PAC safety light curtains are opto-electronic through-beam devices typically used to detect personnel around hazardous equipment or machinery. PAC safety light curtains are usually used as an opto-electronic fence and when used with corner mirrors, can provide two- or three-sided detection around the perimeter of hazardous machinery.
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PAC safety light curtains are generally of resolutions that provide detection of limbs and bodies of personnel, i.e., 50 mm, 70 mm, 90 mm and up. It is also common for PAC safety light curtains to be offered with a limited number of infrared beams spaced at consistent distances from one another, such as 3 beams with 400 mm spacing between beams, or 2 beams with 500 mm beam spacing.
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Muting
PAC safety light curtains are also used in conveyorized processes and very often are used in conjunction with a muting module. Muting is the temporary automatic suspension of the protective function of the safety light curtain.
Muting modules can be integrated into the light curtain's receiver or external to the light curtains. Rockwell currently offers external muting modules.
This muting function allows material to move through the safety light curtain’s sensing field without stopping the machine, however, if a person attempts to pass through the safety light curtain, they will be detected and the machine will stop. The differentiation between material and personnel is determined by the use of muting sensors. These muting sensors create a particular switching sequence together with the safety light curtain as the material passes through the process.
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Conveyorized muting
Muting sensors are typically used in pairs and depending upon the sensor configuration and muting module, allow either uni-directional or bi-directional travel of material through the safety light curtain.
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Four-sensor muting for this particular muting module in Figure 2 allows a single direction of travel. A particular sequence is also required in this configuration; muting sensor 1 must be interrupted first followed by muting sensor 2 and then the safety light curtain, then muting sensor 3 and finally muting sensor 4. It is necessary with this particular muting module to have the light curtain’s sensing field interrupted within 3 seconds of muting sensor two being interrupted. Also, the material must block muting sensor 3 and muting sensor 4 before clearing muting sensors 1 and 2 or the muting function is overridden and the safety light curtain would become active causing a nuisance shutdown of the machine if the material is within the light curtain sensing field.
An interruption of the safety light curtain sensing field would cause the machine or the hazardous motion to be turned off. The muting cycle is completed when the material clears muting sensor 4.
The muting sensors must be spaced appropriately from the safety light curtain and each other in order to ensure that the sensors cannot be interrupted by personnel, causing the activation of the muting function.
A requirement of muting in machine applications is for indication that the muting function is activated. This is typically accomplished by the use of a muting lamp. The various muting modules offered by Rockwell Automation have an output for the connection of a muting lamp.
GuardShield Perimeter Access Control (PAC)
The Allen-Bradley Guardmaster GuardShield PAC safety light curtain system is a two-box design. This means the safety light curtain does not need a separate controller to operate in a guard-only mode with manual reset. Therefore, the safety outputs of the light curtain (OSSDs) can be connected directly to any safety relay that will accept PNP inputs.
The following are some common configurations of light curtain systems. The numbers on the drawing indicate the ordering steps to follow to ensure that a complete system is specified.
Components required for a multiple-beam PAC system, see Figure 3:
- Optic heads (operate on 24V DC)—ordered as a pair (transmitter/receiver) mounting brackets included
- Cables—separate 4-pin transmitter and 8-pin receiver
- Safety relay if EDM is not used
- Corner mirrors (for multiple side protection)
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Components Required for PAC with Muting, see Figure 4:
| 1. | Optic heads (operate on 24V DC) with muting module—ordered as a pair (transmitter/receiver) |
| 2. | It is also possible to use other Allen-Bradley Guardmaster muting modules such as the MSR42 or the MSR22LM muting module |
| 3. | Power supply |
| 4. | Cables for light curtains |
| 5. | Muting indication |
| 6. | Sensors for muting |
| 7. | Sensor accessories |
| 8. | Sensor cordsets |
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Perimeter Access Control Overview
Typical System Configurations
The Allen-Bradley Guardmaster Safe 4 PAC safety light curtain system is a two box design. This means the safety light curtain does not need a separate controller to operate in a guard-only mode. Therefore, the safety outputs of the light curtain (OSSDs) can be connected directly to any safety relay that will accept PNP inputs.
The following are some common configurations of light curtain systems. The numbers on the drawing indicate the ordering steps to follow to ensure that a complete system is specified.
Components required for a multiple-beam Safe 4 PAC, see Figure 5:
| 1. | Optic heads (operate on 24V DC)—ordered as a pair (transmitter/receiver) |
| 2. | Cables—5-pin cables for transmitter and receiver |
| 3. | Safety relay |
| 4. | Power supply—120V AC to 24V DC |
| 5. | Mounting brackets—minimum of 4 per optic head pair |
| 6. | Corner mirror columns (for multiple side protection) |
| 7. | Mounting stand if required |
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