ABB JSHD4 Manuale di istruzioni originale - Pagina 6

Sfoglia online o scarica il pdf Manuale di istruzioni originale per Unità di controllo ABB JSHD4. ABB JSHD4 20. Three-position enabling device

Function description

Three-position principle

A three-position enabling switch provides signals that:

when activated, allows a machine or other equipment to be initiated by a separate start control, and

when de-activated, initiate a stop function and prevent an initiation of machine/equipment operation.

A three-position switch can also be used as a hold-to-run device. Used as such a device, the machine may already

be running and by putting the device in position 2 (ON) and removing it from a holder with position sensor, another

guarding system (light curtain, door interlock switch etc) is muted and the restricted area can be entered without

stopping the machine. Certain limitations in time, speed etc may be needed to ensure an acceptable safety level.

Two three-position switches are used and operated simultaneously, to provide a dual channel safety system.

The three positions are designated as follows:

Position 1: OFF state of the contact (actuator is not pressed)

Position 2: ON state of the contact (actuator is pressed to the normal enabling position)

Position 3: OFF state of the contact (actuator is fully depressed).

When released, the actuator always returns to position 1, regardless of whether it was in position 2 or 3. During this

return movement, the contact(s) remain open.

In addition to the three-position safety function, JSHD4 can be equipped other features such as push buttons for

selectable functions (start, stop, gripping tool, etc), an emergency stop or an anti-tampering sensor.

Anti-tampering device

Many versions of JSHD4 can be equipped with a sensor that prevents tampering (for instance by keeping the

three-position switches in ON-position using a rubber band or similar). The sensor detects a human hand and also

the small movements/vibrations that are normal when holding the handle. If both these requirements are fulfilled

(detected), a contact is closed. When properly connected, the contact can be used to open the safety circuit, and

thus prohibit tampering.

2TLC172052M0201, rev. A

2011-10-06

The symbol for three-position switches illustrates the three positions (OFF, ON

and OFF) with O and I, the pushing force from left to right, and the possible

switching travels (IEC 60947-5-8:2006).

An important characteristic for a three-position switch is that when returning

from position 3, the ON state is not reached – the contacts remain open.