What is a Pull Cord Switch? It's working and importance.

Belt conveyor systems are very popular to transport bulk material from one place to another safely and reliably. They are mainly used for transportation, feeding, and discharging of bulk solid material.

The capacity of a belt conveyor depends on the speed, shape, and width of the belt, methods of feeding, and solid properties. Belt conveyors are the most common form of material handling system used in the manufacturing and mining industries, thermal plants, and construction projects.

Well, today’s blog is not about the belt conveyor system but it is about the safety switch especially the pull cord switch installed in it.

So let’s not waste more time and let’s start it.

Table of Contents

What is a Pull Cord Switch?

There are several safety switches used in the belt conveyor to operate in emergency conditions. Pull Cord Switch is one of them, which operator or user can operate to stop the belt conveyor when an accident occurs.

Since the pull cord switch is a safety switch used to stop the belt conveyor, they are installed or mounted on the side of the conveyor with the pulling rope. If the length of the conveyors is too long then multiple pull cord switches are installed in a way that the pulling rope can be pulled on the conveyor at any point.

Construction

As you can see the several parts of the pull cord switches in the below images:

Name Plate ⇒ Nameplate contains details like type, contacts, rating, serial number, etc.

Cable Entry ⇒ Electrical cable can enter from the cable entry gland which is sealed with a rubber enclosure.

Operating Spindle ⇒ Operating spindle is equipped with steel rings to fix the rope. The worker can operate the switch by pulling the rope.

Mounting Mechanism ⇒ User can mount the switch using mounting bolts on the side of the conveyor.

Electrical Terminals ⇒ Maintenance personnel can use the normally open or normally close contacts depends on the logic used by the designer.

Operation

The pull cord switch is mounted on each side of the belt conveyor, preferably at about distance of 20 – 25 meters. When someone pulled the rope manually, the switch gets operated and remains in operating condition unless and until someone manually reset it to the normal position.

All the pull cord switches are connected in series or parallel as per the requirement with the two core cable to the control station. So when any of the pull cord switches is operated, it will stop the belt conveyor until the particular switch is manually reset.

Connection

Users can connect all the pull cord switches in parallel as well as series depends on the application and design and program the PLC. The below you can find the connection in parallel as well as series.

Pull cord switches connected in parallel ⇒