Automatic door
An automatic door is a portal equipped with a power-operated mechanism and controls that open and close upon receiving a signal from sensors detecting motion, presence, or other inputs, enabling hands-free access for enhanced convenience and accessibility.[1][2] The concept originated in the 1st century AD when Greek-Egyptian mathematician Heron of Alexandria devised pneumatic temple doors that opened via steam pressure generated from sacrificial fires, creating an illusion of divine intervention.[3][4] Modern electric automatic doors emerged in 1954, patented by Americans Lew Hewitt and Dee Horton, employing electric motors and initial photoelectric sensors for commercial applications like supermarkets.[5] Contemporary systems utilize diverse sensor technologies, including active infrared for precise detection, microwave radar for broader coverage, and dual-technology combinations to minimize false activations while ensuring safety through presence monitoring to prevent entrapment.[6][7] They adhere to standards such as those from the Americans with Disabilities Act (ADA), mandating minimum clear widths of 32 inches and compliance with Builders Hardware Manufacturers Association (BHMA) performance criteria for reliable operation in public spaces, thereby promoting universal access without requiring manual effort that could exceed safe opening forces.[8][9] Notable advancements include integration with building automation for energy efficiency and hygiene benefits, particularly post-pandemic, though occasional malfunctions highlight the need for regular maintenance to mitigate risks like unintended closures.[10][11]Types and Classification
Common Types
Automatic sliding doors consist of one or more panels that move horizontally along a track, typically activated by sensors detecting approaching pedestrians. These doors are favored in high-traffic commercial and public entrances due to their space efficiency and ability to handle bidirectional flow without obstruction.[12][13] Automatic swinging doors mimic traditional hinged doors but incorporate operators to push or pull panels open, often configured as single-leaf, double-leaf, or paired setups for one-way or two-way traffic. They suit applications requiring a conventional aesthetic, such as offices or healthcare facilities, and comply with accessibility standards like those from the International Building Code when equipped with hold-open features.[14][15] Folding or bi-fold automatic doors feature panels that accordion inward or outward upon activation, providing a compact solution for narrow openings where full swing or slide is impractical. Commonly used in retail or institutional settings with space constraints, these doors allow for wider clear openings relative to their frame size.[12][16] Revolving automatic doors rotate continuously around a central axis, typically in two-wing, three-wing, or four-wing configurations, minimizing air infiltration and enabling high-volume pedestrian throughput in climate-controlled environments like hotels and airports. They are engineered for security and energy conservation, with speeds regulated to prevent entrapment.[17][13] Less common variants include telescoping doors, which combine multiple sliding panels for extended opening widths, and curved sliding doors adapted for non-linear entrances, though these represent niche applications in specialized architecture.[14][18]Operational Categories
Automatic doors are operationally categorized primarily by their energy levels and actuation profiles, which determine speed, force, cycle frequency, and activation methods to suit varying traffic demands and accessibility needs. These categories—full-power (high-energy), low-energy, and power-assist operators—align with industry standards such as ANSI/BHMA A156.10 for power-operated swinging doors and A156.38 for low-energy operators, ensuring safety and performance consistency.[19] Full-power operators deliver rapid, forceful opening (typically 1-2 seconds to 90 degrees) for high-volume environments like airports or hospitals, using continuous sensor monitoring to handle thousands of cycles daily without manual intervention.[20] Low-energy operators, by contrast, operate at reduced speeds (around 3-6 inches per second) and forces (under 15 lbf), making them suitable for moderate-traffic settings such as offices or schools, often triggered by push buttons or proximity sensors rather than constant motion detection to conserve energy and minimize wear.[21] Power-assist operators bridge manual and automatic functions, providing motorized support only after an initial push (sensing 5-15 lbf of force), which enhances accessibility for individuals with mobility limitations while reducing the need for full automation in low-traffic areas.[20] These categories differ in control mechanisms and safety features. Full-power systems typically employ electro-mechanical or electro-hydraulic actuators with infrared or microwave sensors for activation, incorporating dual safety sensors (e.g., presence detection to prevent closing on obstacles) to comply with entrapment protection requirements under UL 325 standards, which mandate reversing forces below 40 lbf for pedestrian safety.[22] Low-energy models prioritize user-initiated activation via wave sensors or keypads, with slower closing speeds (under 3 inches per second) to allow manual override, though they still require safety edges or photo-eyes in high-risk installations.[19] Power-assist variants, often retrofitted to existing doors, use torque sensors to detect push force and assist throughout the cycle, but lack proactive sensor opening, limiting their use to scenarios where full automation is unnecessary or cost-prohibitive.[21]| Category | Typical Opening Speed | Activation Method | Cycle Capacity | Primary Applications |
|---|---|---|---|---|
| Full-Power | 1-2 seconds to full open | Motion/proximity sensors | High (thousands/day) | High-traffic commercial entrances |
| Low-Energy | 3-6 inches/second | Push button or wave sensor | Moderate | Accessibility-focused moderate traffic[19] |
| Power-Assist | Assists after manual push | Force/torque sensing | Low to moderate | Retrofit for existing manual doors[20] |