Types of Interlocking Device

Interlocking devices or interlocks refer to the mechanical, electrical or other type of device, the purpose of which is to prevent the operation of hazardous machine functions under specified conditions. The standard that provides detailed definitions regarding interlocking devices and guards is EN ISO 14119 and provide rules and regulations to abide by to reduce the defeat of interlocking system. Additionally, the standards EN ISO 14119 also defines the types of interlocking devices in detail and included those that were not previously mentioned in the EN 1088. For instance, non-contact devices, coded and un-coded devices, including magnetic, inductive, ultrasonic, capacitive, RFID and optic are those that were no previously defined in the scope of EN 1088. The examples of these with related use is provided in the Annex C and Annex D of EN ISO 14119.

If we take into an account the coded interlocking devices the standard EN ISO 14119 defined it as the actuator that is designed specifically to actuate a specific position switch. Different levels of coding are also specified such as low level coding (variations of 1 to 9 are present in coding), medium level coding (10 to 1000 variations) and high level coding (more than 1000 variations are available. The table below provides an overview of the types of interlocking devices.

Guard locking

The standard EN ISO 14119 also specify and expands the type of guard locking from power to lock or power to release and include bi-stable locks in which power is applied to lock and to release a solenoid guard switch. It further discuss the permissibility of electromagnetic locks (the use of electromagnetic force without the tongue) under such circumstances as to ensure the safety of the machine taking into account such considerations as the distance to the potential hazard, monitoring of the holding force, in the event of power loss the stopping of time and indicating any event of forced entry. The standard also differentiates between locking for personnel protection (against injury) and locking for process protection (against interruption).

Annex A of the standard EN ISO 14119 offers guidance o static action forces based on the direction of opening force, posture and type of operator grip that is single or bi manual. It is the responsibility of manufacturer to specify the interlock strength that resist static action force and the designer to identify the required holding force related to an interlock guard. The table below shows the examples of static action forces as implied by the EN ISO 14119.

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