Tension Spring

What is a Tension Spring :

A Tension Spring, also known as an Extension Spring is a closed coiled Spring (no gap between coils) designed to absorb and store energy by resisting pulling forces. Made from Spring steels, it features hooks or loops on both ends that allow it to be attached to different objects. When pulled, a Tension Spring stretches and when released it’s returns to its original shape, creating resistance and restoring energy.

● How it’s looks :

A Tension Spring appears as a coil of metal, with two hooks or loops at each end to attach to other components. When stretched, the coils extend apart, pulling against the force applied.

● Purpose :

The primary purpose of a Tension Spring is to store energy and exert a pulling force when it’s stretched. When force is applied, the Spring resists extension and pulls back, creating tension.

● Where it’s used :

Tension Springs are used in various applications where a pulling force is required. Common uses include :
# Garage doors : To support opening and closing.
# Trampolines : To create bounce.
# Automobile interiors : For seat recliners and latches.
# Household items : Such as pliers, toy sand exercise equipment.

● How it’s function :

The Tension Spring functions by storing mechanical energy when stretched. When the force stretching it is removed, it releases this energy to return to its original shape. This pulling force, created by the Spring’s resistance to extension, is essential for applications that require a return to a starting position.

● Difference between Compression Spring & Tension Spring :

# Tension Spring : Works by resisting an applied pull force. It contracts to return to its original shape when the pulling force is removed.
# Compression Spring : Works by resisting an applied push force. It compresses under pressure and expands to its original shape when the force is released.

● Why it’s also called an Extension Spring :

It’s called an Extension Spring because it extends or lengthens in response to the applied force. Unlike compression Springs that compress under load, Tension Springs operate by stretching.

Tension Spring Manufacturers in India :

We are leading Tension Spring Manufactures in India up to the following capacity :

Wire Dia. – Up to 30 mm.
Outer Dia. – Up to 300 mm.
Total Length – Up to 2000 mm.
Total Coils – As per Drawing / Data.
Load Bearing Capacity – Up to 20 Tons. per piece

● Painting and Coating used :

Synthetic Enamel Paint, Powder Coating, Phosphate, Zinc Coating etc.

● Raw-material Grades used :

Spring Steels as per Indian standard – BS:970 EN-42, BS:970 EN-45, BS:970 EN-47, 50Cr.V4, 50Cr.4V2, 51Cr.V4, 50Cr.MoV4, 50Si7, 55Si7, 60Si7, SUP-9, SUP-9A, SAE-5160, IS:4454 Part-1 Grade-2, IS:4454 Part-1 Grade-2D, Stainless Steel etc. and others similar foreign grades JIS, ASTM etc.

Tension Spring Hook :

Tension Springs are always found with both sides Hooks to attach between two components to operate with a pulling force. They are tightly wound (closed coil) and have hooks on both ends, which allows them to stretch and return to their original shape when tension is applied and released.

● How do the Hook look :

The Tension Spring hooks are shaped to connect securely to components. They vary in style and can be open loops (half round), closed loops (full round) or even shaped in custom designs to ensure strong attachment. The specific shape of the hooks depends on the application requirements but all aim to provide a reliable connection and attachment.
# Machine Hooks : Coiled directly from the Spring end.
# Extended Hooks : Created from the wire’s natural extension.
# Cross-Over Hooks : One end crosses over the Spring coils for a stronger hold.

● Why Hook is necessary :

# Attachment points : Hooks provide attachment points to fix the Spring between two parts, making them functional under tension.
# Load distribution : They ensure the load is evenly distributed, reducing the risk of deformation or failure.
# Ease of installation : Hooks make installation straightforward, allowing the Spring to be easily attached and removed.
# Functionality in motion control : They help maintain the position of various components and support movement and they are commonly used in applications like automotive and machinery.

Tension Spring manufacturing formula :

Tension Spring design formula based on the forces it will need to withstand and the characteristics of the material used. Here’s a basic guide on how to approach the calculations and what each factor means :

● Applicable extension strength (Load capacity) :

This is the force or load the Tension Spring needs to support when extended. Determine the maximum load the Spring will handle in it’s application. This load requirement will help decide the overall strength required, impacting wire diameter, material and coil tightness.
# Determination of Wire diameter : A thicker wire diameter increases the Tension Spring’s strength but reduces flexibility. Choose a wire diameter based on the required load strength. A higher load typically requires a thicker wire, whereas lighter loads can use thinner wires.
# Calculate total Length and number of Coils :
The total length, including the number of active coils (those that deform under load) and the end loops or hooks, impacts the Spring’s extension and load distribution. The active length determines how much the Spring will stretch under load, while end hooks contribute to the Spring’s functionality and attachment in applications.
# Determination of Outer diameter : The outer diameter influences the Tension Spring’s stiffness and load capacity. Larger diameters provide more flexibility but less load capacity. Use a smaller diameter for higher load capacity but remember it will also make the Spring stiffer.
# Determination of Total Length / Free Length : The total length of the Tension Spring when it’s not under tension is crucial, as it affects how much the Spring can stretch. Longer Springs stretch more, providing a greater range of motion but less immediate resistance. Decide the length based on how much stretch or travel is required for the Spring’s function.
# Determination of Raw material grade : Selecting the correct raw material is essential for durability and performance. Different materials have varying strengths, resistances to corrosion and flexibility. High-carbon steel, stainless steel and alloy steels are common choices, each suited to different environments and load requirements.
# Verify against operational condition :
Finally, ensure the design meets operational conditions, including maximum extension limits, fatigue life and safety margins. Simulation tools or empirical testing are often used to confirm the Spring’s performance under load.

Tension Spring manufacturing process :

● Raw material selection :

The process begins by selecting the right raw material based on the Spring’s required thickness and grade. Materials are chosen carefully to ensure durability, flexibility and longevity. This initial step is crucial, as the material quality will impact the Spring’s performance and ability to withstand tension.

● Hot coiling process :

Once the material is selected, it undergoes a hot coiling process. Here, the raw material is heated to high temperatures, making it malleable enough to be coiled into the desired shape while maintaining inner (ID) and outer diameters (OD) as specified. The heated material is then wound around a mandrel to form coils, allowing the Spring to achieve its fundamental structure.

● Hook preparation :

After coiling, hooks are created at both ends of the Spring. These hooks are essential for the Spring’s function, as they enable it to attach to other components in various applications. The hooks are formed carefully to ensure they are durable and can withstand the required tension during usage.

● Heat Treatment process :

Once the hooks are prepared, the Spring undergoes heat treatment. This step is vital for enhancing the Spring’s strength and flexibility. During heat treatment, the Spring is exposed to specific temperatures, allowing it to achieve the required hardness and resilience, which ensures long-lasting performance.

● Extension function test :

After heat treatment, each Spring is subjected to an extension function test. This test evaluates the Spring’s elasticity and ability to extend to the desired length without losing its form or function. Only Springs that pass this test proceed to the final stages.

● Final dimension & quality checking :

The Spring then undergoes a detailed inspection to verify its dimensions and overall quality. This ensures that each Spring meets the specified tolerances for length, coil diameter and hook shape, along with confirming that it performs correctly under the designated load.

● Painting / Coating :

Finally, the Spring is painted or coated to provide additional protection from corrosion, wear and environmental damage. This finishing step not only improves durability but also enhances the Spring’s aesthetic appeal, making it suitable for various applications.

Each of these steps contributes to the creation of a high-quality, reliable Tension Spring suitable for a range of industrial applications.