What is Pull Cord Switch : Working & Its Applications

In industrial areas, a conveyor system is fast & efficient machinery used for transporting different heavy materials, and loads within an area. This system is mainly used to reduce manpower, time, labor costs, boost production, and workplace risks. The controlling of a conveyor system can be done by using different safety switches like electronic switches, conveyor safety switches, pull cord switches, electronic conveyor switches, etc. So this article discusses one of the types of safety switches used in conveyor systems like the pull cord switch.

What is Pull Cord Switch?

A pull cord switch definition is an emergency switch that is used to stop the belt conveyor directly once an accident occurs. This switch is also known as a “rope operated emergency switch”. If the conveyor’s length is very long then several pull cord switches are required. So these switches are mounted on both sides of belt conveyors preferably every 15 to 20 meters. These types of switches are mainly designed for providing safety for men & machines to keep away from accidents and also to stop the machines in emergency cases.

Working Principle of Pull Cord Switch

The pull cord switch is very reliable and easy to use, one can’t go wrong with it. It consists of a lever called armature and an electromagnet. The armature has two metal strips on it which are connected to the poles of the electromagnet. When you pull the pull cord, it moves the armature towards one pole of the electromagnet and when you let go, it springs back to its original position by its own force. This mechanism makes sure that both poles of the electromagnet are not connected at any given time. Let us see how Pull Cord Switch works in a conveyor belt.

Pull Cord Switch in Conveyor Belt:

Pull cord switches are commonly used in conveyor belts as a safety device to stop the belt in case of an emergency or accident. The pull cord switch is attached at one end to the conveyor belt and at the other end to a movable barrier. In case of an emergency, if the person gets trapped between the conveyor belt and moving barrier, he can pull out the cord which will stop both the conveyor belt and the barrier automatically. This will help him get out of danger safely.

The mechanism of a pull cord switch consists of two parts:

1. A cord pulled by hand – This part is attached on one end to the conveyor belt and on other end to a movable barrier which stops automatically when pulled by hand. The length of this cord should be enough so that it can be pulled when required without any problem.

2. A spring – This spring acts as a counterweight for the first part (cord). When you pull out your hand from this spring, it releases the tension from your hand holding onto it and causes it to go back into its original position immediately after releasing your hand completely from it

Pull Cord Switch Specifications

The specifications of the pull cord switch vary based on manufacturers. So the common specifications of these switches include the following.

• The type of switch is waterproof.
• The power or Voltage is 230V AC.
• The current Rating is 6 A.
• The material used is Cast Aluminium.
• The frequency is 50Hz.
• Contact combination is 2NO + 2NC
• The grade of protection is IP 65.
• Operation is right, left, and both ways.
• The length of the rope is up to 110 Meters.

Construction

The pull cord switch is designed with different parts which are discussed below.

Name Plate

The nameplate of this switch includes the details of a serial number, contacts, type, rating, etc.

Cable Entry

The entry of the electrical cable is covered with a rubber enclosure.

Operating Spindle

This spindle includes steel rings which are useful to fix the rope. So this rope is used by the operator to control the switch by pulling it.

Mounting Mechanism

This switch can be mounted by the user with mounting bolts on the face of the conveyor.

Electrical Terminals

The electrical terminals of this switch include normally open (NO) or normally close (NC) contacts which work based on the logic utilized by the designer.

The pull cord switch operation is, it is mounted on every face of the conveyor belt at a distance of 20 to 25 meters. Whenever a person pulls the rope physically, then this switch gets operated and it comes to the normal position until someone resets it manually.

Types of Pull Cord Switch

We know that a pull cord switch is one type of safety switch which is used in the conveyor system. There are different types of pull cord safety switches used in conveyor systems which include the following.

Belt – Sway Switch

This switch is also known as a belt misalignment switch. This switch is normally arranged on both sides of the conveyor belt at near the edge. This switch is enclosed within a dust & weatherproof enclosure including IP65 grade protection. The main function of this switch is to run the conveyor system very smoothly and also guard it against damages.

Zero Speed Switch

A zero-speed switch is used within conveyor belts. This switch will stop the conveyor belt if the speed of this belt drops under the set speed. This system uses a controller and a sensor. The sensor in the conveyor system detects if the conveyor belt runs at a slow speed then it sends a command to the controller. Thus, based on the obtained signal, the necessary action will be taken through the controller. This switch is used in different industries for monitoring conveyor speed, monitoring industrial machinery speed, etc.

Heavy Duty Limit Switch

Heavy-duty limit switches are arranged within a strong weatherproof enclosure. The roller handle of this switch is available in different designs and sizes to suit particular requirements. These switches are most popular in conveyors, EOT cranes, elevators, steel mills, conveyors, transfer cars, and material handling equipment for detecting position sensing.

Material Flow Switch

The material flow switch is mainly designed to generate a signal if the flow at any point is disrupted. So this switch generates an alarm once the conveyor belt runs without materials. This switch includes a paddle, switch assembly & counterweight assembly. This switch is adjustable, so actuation is achievable at predetermined points.

Damaged Belt Detector

Damaged belt detectors are arranged on any side of the belt and this detector is used to detect the tears, and punctures on the conveyor belt and provides a way of the automatic shutdown to avoid the amount of injury to the conveyor belt. So these switches give protection to the conveyor belts. These detectors are almost maintenance-free due to their simple construction.

Pull Cord Switch Wiring Diagram

Generally, pull cord switches are connected on every side of the belt conveyor at a distance of about approximately 20 to 25 meters. Once someone manually pulled the rope, the switch gets activated & stays in operating state unless & until someone resets it to the ordinary position manually.

The pull cord switch wiring diagram is shown above. Here, pull cord switches are connected in parallel to a control system like PLC. In the above diagram, pull cord switches are connected to the control system in parallel by using two core cables. So once any of the pull cord switches are functioning, it will stop the working of the belt conveyor until the specific switch is reset manually. Similarly, the user can connect these switches in series also based on the application.  let us also see

How do you install a pull cord switch?

First, you need to find the correct place for your pull cord switch in your home. Then you can connect the wires according to their colors and snap them into place. If there’s no existing light fixture where you want the pull cord switch, then you can attach one directly above where it will be installed.

What is the difference between pull cord switches and push button switches?

Pull cord switches are usually used in applications where space is limited, or where the switch needs to be mounted in a difficult-to-reach location. They require a minimum of two wires (power and load). Pull cords can also be wired to other devices that operate on different voltage levels, like lights and appliances.

Push button switches are generally easier to install than pull cord switches. They are more compact and don’t require wires to connect them to other devices—they just have an input terminal and an output terminal that connects directly with the load (light, appliance, etc.).

Advantages

The advantages of a pull cord switch include the following.

• Easy to use.
• They do not need maintenance.
• Its performance is high.
• Its design is robust.
• This is an emergency switch or safety switch.
• This switch gives protection to machines by avoiding accidents and also stops the working of Machines in Emergency cases.
• The switch includes a reset button.
• It includes an optional LED indicator.
• It is available in single side or both side operations.

Disadvantages

The Disadvantages of a pull cord switch include the following.

• As compared to other switches, these switches are heavy.
• These are expensive.
• It requires maintenance.

Applications

The applications of pull cord switch include the following.

• This type of emergency switch is used as a security switch to stop the conveyor belt in an emergency case.
• These switches are conveyor safety devices that are used to connect with conveyor shut down systems in the event of emergency or maintenance.
• These are used in belt conveyor systems in different industries like cement, steel, coal, and power plants.
• These are also used in the packaging, food, and beverage industries.

What are the benefits of a pull cord switch?

A: Pull cord switches are a great way to avoid having to install a regular electrical switch. They’re also great for people who don’t want to use electricity in their homes, but still want to be able to control appliances.

Thus, this is all about an overview of a pull cord switch – working with applications. This is one type of safety switch used in the belt conveyor and it functions in emergency situations. This switch is operated by the user to control the belt conveyor once an accident takes place. Here is a question for you, what is a conveyor belt?