The read head is fastened to the fixed part of the safety guard and is connected to the evaluation unit via a two-core screened cable. The actuator fastened to the safety guard is moved towards the read head by closing the door. When the switch-on distance is reached, power is supplied to the actuator via the read head and the read head transfers the actuator's data to the evaluation unit.

Transponder-coded read heads

Actuator and read head have a wide operating distance and a broad hysteresis. Misalignment of the door will therefore not result in the system switching off unintentionally. If the actuator is positioned exactly at the limit of the switch-on distance, vibration at the safety guard will not cause the machine to stop unintentionally.

Design and functionality

A CES read head and a solenoid are integrated into the CEM read head. The CEM read head is connected to the CES evaluation unit with a round M8 plug connector. The CEM actuator of identical design also has a metal plate in addition to the transponder; this plate acts as an armature for the solenoid coil.

When the safety door is closed, the CEM actuator enters the operating distance of the CEM read head. The transponder signals are transferred, and then the evaluation unit closes the safety contacts and sets the OUT output 'high'. By applying voltage to the solenoid for the CEM read head, strong magnetic forces can be generated between the coil (in the read head) and the armature (in the actuator).

Depending on the design, locking forces of approx. 500 N or 1000 N respectively are applied between the CEM actuator and the CEM read head. Practical experience has shown that these magnetic forces effectively prevent any opening, even if the user applies considerable effort.

Use of the read head even in extremely harsh environments

The read heads CEM have an extremely robust design. The high degree of protection IP 67 and the metal housing allow the read head to be used in extremely harsh environments. The armature plate for the CEM actuator has spring mountings and can be tilted up to an angle of ± 4°. Therefore, when a maladjusted safety door is closed, the CEM actuator adjusts itself independently to the surface of the CEM read head. It is not necessary to readjust the safety door when using the read heads CEM. When mounting the read head CEM, it is only necessary to ensure that the CEM actuator is guided in front of the CEM read head when the door is closed, so that the strong adhesive forces can be generated.

Because the read head has only a small number of moving parts which can wear, the mechanical life of the CEM read heads is virtually unlimited.

Different versions

EUCHNER provides two CEM housing designs. The two versions differ in their dimensions, according to the size of the solenoid. The safety switch CEM with a locking force of 1000 N is used with large, heavy safety doors. This read head has an additional M8 plug connector for the connection of an external LED display. When voltage is applied to the coil, it is indicated to the user that the safety door is in the locking position. A display close to the door handle is of advantage particularly for large, solid doors.

The smaller version of the read head CEM has a locking force of approx. 500 N. It is suitable for securing smaller safety doors and safety flaps.

An LED indicator in the M8 male socket on the read head indicates to the user when voltage is applied to the solenoid.

With or without remanence

In particular during metal machining, the residual magnetism (remanence) in the guard locking solenoid can cause problems. In the open state, metal chips may be drawn to the contact area. The next time the guard is closed, there will be a gap between the actuator and read head that will limit the locking force. To avoid this effect there are read heads without remanence. These are de-magnetized when the safety guard is opened such that metal chips adhering to the surface fall off.

Adjustable adhesive force

This version has an adhesive force also with the guard locking switched off. In this way it is intended, e.g., to prevent the safety door opening due to vibration or similar. The adhesive force can be adjusted using a programming adapter to 30 N, 50 N or 80 N.

Your advantages

• Safety switch with transponder coding
• Every actuator is unique
• Maximum protection against tampering
• Integrated solenoid for process protection
• Unintentional opening of the safety door is prevented
• Safety switch and solenoid form a compact unit
• High solenoid locking forces (500 N or 1000 N)
• Protection of the machining process
• Simple operating principle
• No wearing parts
• Robust housing for harsh environments
• Connection via M8 plug connector
• Low wiring effort
• Easy to replace if servicing is required
• Approved by employers' liability insurance association and UL (Canada and USA)

Important: The device is only allowed to be used as guard locking if there is no hazard due to overtravelling machine movements. The guard locking is only used for process protection.