TESK-ZL Mechanical Key Interlock Safety Switch IP67 Stainless Steel Machine Guard Lock

1. Product Overview

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The Schmersal TESK-ZL series is a robust electro-mechanical guard locking safety switch designed for critical access control to hazardous machinery where unplanned or unsafe door opening poses significant risks. Featuring a unique ​zero-position locking mechanism​ (the "ZL" designation), it employs a fail-safe cam mechanism integrated with a high-strength ​solenoid locking bolt, ensuring the guard remains securely locked during both normal operation and critical failures like power loss. Constructed with a durable ​zinc alloy die-cast housing​ achieving ​IP67/IP69K protection, it withstands high-pressure washdowns, dust, oils, and impacts common in demanding environments like food processing, automotive, and heavy industry. The switch operates in conjunction with a separately mounted ​high-security magnetic actuator (Type E)​​ on the movable guard. Its defining attribute is a spring-loaded positive locking mechanism that automatically engages when the door closes and remains latched until explicitly released via an electrical unlock signal, preventing accidental openings even during control system failures. M12 connectors simplify installation.

​2. Key Technical Parameters

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The TESK-ZL operates at ​24V DC (±10%)​, generating a substantial ​2,000 N locking force​ - significantly higher than standard solenoid locks - to physically prevent door actuation under unsafe conditions. It incorporates ​Force-Guided Relays (FGR)​​ as 1 NC (Safety, K1/K2) + 1 NO (Lock Monitoring, K3/K4) with ratings up to ​6A @ 250V AC / 10A @ 24V DC. Certified to ​Performance Level PL e (ISO 13849-1, Category 4)​​ and ​Safety Integrity Level SIL 3 (IEC 62061)​, it satisfies the highest safety requirements. The ​Type E magnet coding​ provides strong tamper resistance. Critical mechanical attributes include:

• ​Mechanical Locking:​​ Spring-actuated zero-position lock guarantees door remains secured during power failure.
• ​Power-to-Unlock:​​ Requires deliberate 24V signal to retract the bolt for access.
• ​Fail-Safe Behavior:​​ Loss of power does not release the lock; unlocking requires active command.
  Operating temperature range: ​​-25°C to +70°C. LED status indicators show power (yellow), guard closed/locked (green), and unlocked (red). Mechanical endurance exceeds ​1 million cycles. Conforms to ​EN ISO 14119 Type 4​ for guard locking.

​3. Primary Applications and Use Cases

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The TESK-ZL is essential for machinery where guarding integrity must be maintained absolutely, particularly in processes with ​long cycle times, ​high inertia components, or ​stored energy hazards. Key installations include ​large stamping/punching presses, plastic injection molding machines, industrial ovens/furnaces, heavy metal forming equipment, robotic welding/palletizing cells, and CNC machining centers. Its high holding force and zero-position locking are critical for preventing access during dangerous operations involving crushing, shearing, molten material, or high-speed rotation. Applications extend to ​high-bay warehouses (AS/RS)​, ​automotive paint shops, and ​foundries​ where vibrations or thermal expansion could compromise lower-force locks. It ensures compliance with Lockout/Tagout (LOTO) and hazardous energy control (ISO 14118) requirements by guaranteeing doors cannot be opened while danger exists, even during total power loss or control system faults. Ideal for safety doors requiring delayed or controlled access only after energy dissipation.

​4. Product Advantages and Functional Benefits​
This switch delivers critical operational and safety benefits:

• ​Absolute Locking Security (2,000 N):​​ Physically prevents guard movement against significant force, deterring deliberate circumvention.
• ​Zero-Position Locking Principle:​​ Maintains guard security indefinitely during power failures or control faults - a fundamental safety advantage.
• ​High Diagnostic Coverage (PL e, SIL 3):​​ FGRs enable circuit-level monitoring for faults, maximizing system availability.
• ​Tamper-Resistant Design (Type E Magnet):​​ Resists defeating by external magnets or mechanical manipulation.
• ​Harsh Environment Suitability (IP67/IP69K, Zinc Alloy):​​ Ensures reliability under extreme washdowns, chemicals, and impacts.
• ​Power-to-Unlock Safety:​​ Prevents access unless explicitly released by the safety PLC upon confirmed safe state.
• ​Reduced Downtime:​​ Robust construction minimizes failures; lock-monitoring contact signals pre-failure conditions.
• ​Simplified Compliance:​​ Inherently meets strictest standards (ISO 13849-1 Cat 4, EN ISO 14119 Type 4) for safety-rated guard locking.

​5. Core Functionality and Safety Sequence​
The TESK-ZL operates through a fail-safe mechanical-electrical sequence centered on the zero-position principle:

1. ​Automatic Locking:​​ Upon guard closure, the solenoid bolt automatically springs into the locked position via internal cam mechanics. No power is needed to achieve lock engagement.
2. ​Safe State Signalling:​​ The guard position (K1/K2 NC) and lock status (K3/K4 NO) contacts change state, signaling the safety PLC the guard is closed and locked.
3. ​Machine Operation:​​ The guard remains physically blocked by the bolt while machinery operates.
4. ​Conditional Unlocking:​​ To access the hazard zone, the safety PLC must:
   • ​Confirm safe machine state​ (e.g., movement stopped, energy dissipated).
   • ​Apply 24V DC power to the unlock solenoid​ deliberately.
   • Only then will the solenoid retract the bolt, allowing the guard to be opened.
5. ​Fail-Safe Guarantee:​​ Loss of control power, PLC failure, or wiring faults do not release the lock. The bolt remains extended by spring force (zero-position), maintaining safety until explicitly unlocked under safe conditions. Power is only required for unlocking, not locking. Resetting requires re-closing the guard to re-engage the automatic lock. This sequence is fundamental for preventing access under hazardous conditions.

Packaging & Shipping

Company Information
Xiamen ZhiCheng Automation Technology Co., Ltdit is a leading global supplier of control system components. We specialize in control systems and drives.

With many years of experience in the industrial sector, we consistently deliver the highest quality of spare parts.which make sure that all this jobs are

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