In environments where people and machines interact, ensuring safety is not just a regulatory requirement—it’s a practical necessity. The safety edge is one of the most effective tools used in automated systems to enhance safety. From industrial doors to robotic arms, safety edges help prevent injuries, reduce downtime, and improve system reliability.
This article explores safety edges, how they work, the different types available, and where they are commonly used so you can make informed decisions about integrating them into your operations.
What Is a Safety Edge?
A safety edge, a pressure-sensitive or sensing edge, is a protective device designed to detect contact or compression along its surface. When the edge is pressed or touched—typically due to a person or object being in its path—it sends an immediate signal to stop or reverse the motion of the associated machine.
Most commonly, safety edges are used on the leading edges of moving parts, such as automated doors, gates, machine guards, and industrial conveyors, where they act as a buffer between moving components and potential obstacles or humans.
Benefits of Using Safety Edges
- Prevents Injuries: Acts as a physical barrier and response trigger to protect humans.
- Reduces Equipment Damage: Stops machinery before a collision causes mechanical failure.
- Increases Productivity: Minimizes downtime by providing quick safety responses.
- Ensures Regulatory Compliance: Helps businesses meet OSHA, ISO 13849, and other safety standards.
- Flexible Installation: Can be retrofitted to existing systems or customized for new designs.
How Do Safety Edges Work?
Safety edges operate on a pressure-sensitive principle: they detect contact along their length and immediately trigger a response—usually stopping or reversing a machine—to prevent injury or damage. Here’s how the system works step by step:
1. Construction of the Safety Edge
A safety edge is typically made of a flexible rubber or polymer profile housing a sensor mechanism. The internal sensing component can vary depending on the type of safety edge, such as:
- Ribbon switch (resistive)
- Air pressure tube (pneumatic)
- Optical beam (infrared or LED-based)
- Mechanical switch
2. Mounting on Moving Parts
The edge is installed along the leading edge of a moving part, like a gate, lift platform, or machine guard. It forms the first point of contact between the machine and its surroundings.
3. Contact and Compression
When an object—such as a person, tool, or obstruction—comes into contact with the edge, it compresses the outer housing. This compression either:
- Closes a contact circuit (in resistive/mechanical types),
- Changes the air pressure inside a tube (in pneumatic types), or
- Interrupts a light beam (in optical types).
4. Triggering the Signal
This physical change activates the sensor inside, which instantly sends a signal to the machine’s safety controller or logic unit. The controller is programmed to respond immediately when the edge is triggered.
5. Machine Response
Upon receiving the signal, the system performs a predefined safety action, such as:
- Stopping all movement,
- Reversing the motion,
- Locking or unlocking components,
- Triggering alarms or indicator lights.
This rapid response helps prevent injury, equipment damage, or system errors.
6. Fail-Safe Design
Many safety edges include diagnostic circuits or are used with safety relays that detect disconnections, damage, or faults. If a malfunction is detected, the system defaults to a safe state, usually stopping all motion, to ensure continued protection.
In essence, safety edges work by turning a physical interaction—like a bump or compression—into an electrical signal that tells the machine to stop. They act as bright bumpers, combining mechanical flexibility with electronic responsiveness to provide an essential layer of safety in automated environments.
Types of Safety Edges
Safety edges come in various types, each designed to meet different environmental conditions, sensitivity requirements, and machine configurations. Choosing the right type is essential to ensure optimal safety, reliability, and compliance. Below are the most common types of safety edges and how they function:
1. Resistive (Ribbon Switch) Safety Edges
This type contains a conductive ribbon switch inside a flexible rubber housing. When compressed, the conductive elements touch, closing the circuit and sending a signal.
Key Features:
- Widely used in industrial automation
- Reliable for general-purpose safety
- Can be cut to custom lengths
Best For: Automatic doors, machine guarding, and edge protection in controlled environments.
2. Pneumatic (Air-Filled) Safety Edges
These edges contain a hollow rubber profile filled with air. When compressed, air is forced through a tube to a pressure switch, activating the safety signal.
Key Features:
- No electrical components on the edge itself
- Ideal for wet, dusty, or explosive environments
- Longer life in harsh conditions
Best For: Heavy-duty gates, transport vehicles, and environments with explosive gases or water exposure.
3. Optical (Infrared Beam) Safety Edges
An invisible light beam runs through the length of the edge. If the edge is bent or compressed, the beam is interrupted, and the system responds immediately.
Key Features:
- Very high sensitivity
- Fast response time
- More expensive and requires precise alignment
Best For: High-speed applications, delicate machinery, and precision robotics.
4. Mechanical Contact Safety Edges
These use a physical internal switch activated by compression or movement of the edge. When triggered, it mechanically closes a circuit to send a stop signal.
Key Features:
- Simple and low-cost
- Less durable in rugged conditions
- Limited sensitivity and flexibility
Best For: Basic access doors or systems with lower risk levels.
5. Capacitive Safety Edges (Less Common)
Capacitive sensors detect changes in electrical fields caused by a nearby object. They don’t require direct contact but can sense proximity.
Key Features:
- Non-contact sensing
- Useful for sensitive electronics or hygienic applications
- May be affected by environmental interference
Best For: Cleanrooms, medical devices, and electronics manufacturing.
Comparison Table (At a Glance)
| Type | Contact Method | Environment | Response Time | Application Examples |
|---|---|---|---|---|
| Resistive | Direct contact | Indoor/standard use | Fast | Machine guards, doors |
| Pneumatic | Air pressure | Harsh/wet/dusty | Moderate | Loading docks, outdoor gates |
| Optical | Infrared light | Clean/precise | Very fast | Robotics, automatic barriers |
| Mechanical Contact | Switch contact | Low-demand | Moderate | Light-use doors, home automation |
| Capacitive | Field detection | Sensitive/hygienic | Variable | Medical, electronics, food processing |
Each type of safety edge has specific strengths and ideal use cases. Factors like environment, required sensitivity, mounting surface, and budget should guide your decision.
Applications of Safety Edges
Safety edges are essential wherever machines, moving parts, or automated systems pose a risk of impact, crushing, or entrapment. These pressure-sensitive devices protect people, equipment, and materials in a wide range of industries. Below are the most common and critical applications of safety edges:
1. Automatic Doors and Gates
Purpose: Prevent injuries from door or gate closures.
How They Help: Installed on the leading edge, safety edges detect any obstruction during closing and trigger the door or gate to stop or reverse.
Common Use Cases:
- Sliding doors in commercial buildings
- Industrial roller shutters
- Swing gates and garage doors
2. Industrial Machinery
Purpose: Protect operators from moving or hazardous components.
How They Help: Safety edges are mounted on moving platforms, barriers, or machine arms to halt motion upon contact.
Common Use Cases:
- Packaging machines
- Lift tables and platforms
- Presses and robotic arms
3. Conveyor Systems
Purpose: Prevent injury and material damage.
How They Help: Placed at entry/exit points or hazardous zones, safety edges stop the conveyor when a person or object is detected in a dangerous position.
Common Use Cases:
- Baggage handling at airports
- Manufacturing lines
- Parcel sorting systems
4. Medical and Assistive Equipment
Purpose: Protect patients and caregivers.
How They Help: Safety edges stop motion if something gets caught or pressed on adjustable beds, lift chairs, or medical tables.
Common Use Cases:
- Hospital beds
- Patient transfer lifts
- Dental and exam chairs
5. Public Transportation Systems
Purpose: Ensure passenger safety.
How They Help: Mounted on bus, train, or tram doors, safety edges prevent doors from closing on passengers.
Common Use Cases:
- Metro rail systems
- Automated shuttle doors
- Airport people movers
6. Warehouse Automation and AGVs
Purpose: Prevent collisions and system damage.
How They Help: Automated Guided Vehicles (AGVs) and moving racks use safety edges as bumpers to stop movement when they contact obstacles.
Common Use Cases:
- Smart warehouses
- E-commerce fulfillment centers
- Robotics-based logistics systems
7. Theatre and Stage Equipment
Purpose: Prevent backstage accidents.
How They Help: Safety edges installed on moving stage platforms or retractable floors prevent injury to crew and performers during set changes.
Common Use Cases:
- Lifts and rotating stages
- Orchestra pits
- Trap doors
Wherever something moves, safety edges can help ensure it does so safely. Their real-time detection and fast response make them vital in automation, transportation, healthcare, and industrial settings.
Key Considerations When Choosing a Safety Edge
Selecting the right safety edge is essential for ensuring your safety system’s effectiveness and reliability. A poorly chosen edge may lead to false triggers, missed activations, or rapid wear, undermining the protection it’s meant to provide. Below are the critical factors to evaluate when choosing a safety edge for your application:
1. Application Environment
Consider the physical conditions in which the safety edge will operate:
- Wet or humid areas → Use pneumatic or sealed resistive types.
- Dusty or dirty environments → Choose designs with IP-rated protection.
- Hazardous or explosive zones → Opt for non-electrical edges like pneumatic ones.
2. Type of Motion and Risk Level
Evaluate how the machinery moves and what potential risks exist:
- Fast-moving equipment → Needs quick response time (optical or resistive).
- Crushing or trapping hazards → Require high-sensitivity edges with broad activation zones.
- Low-speed gates → May use simpler mechanical contact edges.
3. Required Sensitivity and Actuation Force
Some applications require the edge to activate under slight pressure, while others tolerate more force:
- Low actuation force (5–20 N) → Ideal for human contact safety.
- High actuation force (50+ N) → Better for industrial material handling.
4. Edge Profile and Mounting Requirements
Match the edge’s shape and size to the installation surface:
- Choose flat, angled, or round profiles based on the mounting area.
- Consider mounting accessories like aluminum carriers, end caps, or clips.
5. Electrical Interface and Safety Controller Compatibility
Ensure that the safety edge integrates seamlessly with your system:
- Confirm compatibility with existing safety relays or logic controllers.
- Choose between Normally Open (NO) or Normally Closed (NC) circuits based on fail-safe logic.
- For long-distance setups, use edges with integrated signal monitoring or diagnostics.
6. Certification and Standards Compliance
Safety edges should comply with relevant local and international standards:
- Consider certifications like ISO 13849, IEC 61508, or EN 1760-2.
- Ensure that the safety edge is part of a system that meets Performance Level (PL) or Safety Integrity Level (SIL) requirements.
7. Durability and Maintenance
Choose materials and designs that withstand wear and environmental exposure:
- UV-resistant and weatherproof materials for outdoor use
- Oil and chemical resistance for industrial environments
- Replaceable profiles for long-term cost-efficiency
8. Length and Customizability
Select a safety edge that is available in required lengths or can be cut to size:
- Some models offer custom cut-to-length options.
- Others may have modular connectors for fast replacement or expansion.
Choosing the right safety edge is not one-size-fits-all. Take a holistic approach—consider environmental factors, system integration, sensitivity, and compliance—to ensure you’re installing a safety solution that’s truly fit for purpose.
Conclusion
Safety edges might be small components, but they significantly impact protecting lives and equipment. Incorporating safety edges is a simple yet effective safety upgrade, whether automating a production line, installing an access gate, or retrofitting older machinery.
They’re fast-acting, versatile, and vital for compliance, making them a must-have in any safety-focused automation system.