Every operator knows that in case of an emergency or a hazardous situation on machinery and plants they must push the eye-catching red emergency stop button.
There are various ways to distribute your emergency stop; a standard pushbutton, pull cord, foot switch, etc. The foot switch is usually used if other machine functions are also operated by foot.
Emergency stop foot switches are a safety device used in industrial settings. They are operated by the workers foot, which makes them quick and simple to use.
These switches are designed to prevent injury to personnel, by breaking a circuit to stop the machinery they are using from functioning when people could be in danger and the machine needs to be switched off as quickly as possible.
Emergency stop foot switches may differ by the number of pedals they have, as well as the material that the pedal and its housing are made from.
Not all emergency stops foot switches have a housing, but often do as a protective cover stops them from being pressed accidentally. The protective cover should be larger dimensions, thus enabling a smooth operation of the switch, even with safety shoes.
The benefit of having an emergency stop foot switch rather than a hand operated button is an emergency stop switch located on the machine might not be appropriate, as very often users won’t be close to a machine during operation. The emergency stop foot switch will be in an easy location to access.
The Siemens single-pedal safety foot switch (3SE2924-3AA20) are used on machines and plants when operation by hand is not possible.
The switches have an interlocking function. The safety foot switches are protected by a guard hood against accidental operation and have fixing holes for them to be screwed to the floor.
The switches have two contact blocks, each with one NO contact and one NC contact. The NO contacts and NC contacts of the two contact blocks are connected for easy connection of a single-phase motor.
The normal workflow is initiated by pressing down the pedal as far as the pressure point so that the two NO contacts close, and the motor starts to run.
If in the event of danger, the pedal is pressed beyond the resistance of the pressure point, the positively driven NC contacts will open, and the motor is stopped.
At the same time the independent latching takes effect and holds the NC contacts in open position. This prevents the machine parts from continuing to run out of control or from being restarted.
After the hazard is eliminated, the machine can only be restarted after manually releasing the switch using a pushbutton on the top of the enclosure.
The contacts are then released again and return to their initial position (the NO contacts are open, and the NC contacts are closed).