Conical Springs

Conical Compression Springs for Long Travel and a Compact Solid Height

Conical compression springs, also known as cone springs, have a larger outside diameter at one end and a smaller outside diameter at the other. During compression, the smaller coils can telescope into the larger coils. This allows the spring to achieve a particularly compact solid height while providing a long spring travel.

The wide base of a conical spring also provides greater lateral stability than many cylindrical compression springs. Conical compression springs are therefore particularly suitable for applications with limited axial installation space.

Febrotec supplies a wide range of conical compression springs made from stainless spring steel. Use the product table to select a suitable spring by outside diameter, wire diameter, free length, spring force, spring rate and solid height.

How to Select the Right Conical Compression Spring

Proceed in the following order:

1. Determine the installation diameters: Define the maximum permissible large outside diameter Da1 and the required small outside diameter Da2.

2. Define the free length: Select a free length L0 that fits the available installation space.

3. Determine the working travel: Calculate the difference between the free length and the installed or compressed length.

4. Determine the required spring force: Compare the required force with the spring rate c and the force values shown in the product table.

5. Check the solid height: Ensure that the available installation space is greater than the specified solid height Lc.

6. Consider the operating environment: Check whether the material and temperature range are suitable for the application.

Within the approximately linear operating range, the spring force can be estimated using:

F ≈ c × s

where:

• F is the spring force in N,

• c is the spring rate in N/mm,

• s is the spring deflection in mm.

The spring deflection is calculated as:

s = L0 − L

where L is the compressed spring length.

Meaning of the Technical Data

The force value F1 applies when the spring is compressed to:

L = 0.5 × L0

This corresponds to a spring deflection of 50% of the free length.

Advantages of Conical Compression Springs

Conical compression springs offer several advantages:

• compact solid height due to telescoping coils,

• long spring travel in relation to the free length,

• improved lateral stability,

• reduced risk of buckling,

• compact installation dimensions,

• suitability for small mechanical and electrical assemblies.

The conical springs in the Febrotec standard range have a variable pitch. This produces an approximately linear spring characteristic over a larger part of the available spring travel. Conventional conical springs with a constant pitch often have a progressive spring characteristic.

Solid Height and Maximum Compression

When the spring is compressed, the smaller coils move inside the larger coils. This allows the coils to nest together and results in a much lower solid height than with a comparable cylindrical compression spring.

For the standard springs listed here, the solid height is generally approximately twice the wire diameter:

Lc ≈ 2 × d

The force at solid height Fc should not automatically be used as the normal operating force. For dynamic or frequently repeated movement, an adequate safety margin from the maximum compression should be maintained.

Material and Temperature Range

The standard conical compression springs are manufactured from stainless spring steel 1.4310, also known as X10CrNi18-8.

The material is suitable for many general industrial applications and for use in humid environments. It is not recommended for permanent contact with seawater or highly chloride-containing environments. Due to cold forming, the material may be slightly magnetic.

The stated material temperature range is:

−200°C to +250°C

The actual permissible operating temperature depends on the required spring force, service life, load cycles and environmental conditions.

Spring Ends and Winding Direction

The spring ends are closed and not ground. The springs are right-hand wound.

The supporting surfaces should be designed so that both spring ends are seated securely. The larger and smaller diameters must also have sufficient radial clearance throughout the entire spring travel.

Typical Applications

Conical compression springs are frequently used in applications such as:

• battery contacts,

• electrical contacts and push buttons,

• automotive components,

• medical devices,

• electronic assemblies,

• compact return mechanisms,

• fixtures and small mechanical assemblies.

Their compact compressed height makes them particularly useful where a conventional cylindrical compression spring would require too much axial space.

Custom Conical Compression Springs

In addition to the standard springs available from stock, Febrotec can supply custom conical compression springs according to your requirements.

Customisable characteristics include:

• large and small spring diameters,

• wire diameter,

• free length,

• spring rate,

• spring force,

• material,

• spring ends and winding direction.

Please provide the available installation dimensions, required spring travel, spring force and operating conditions with your enquiry.

Frequently Asked Questions About Conical Compression Springs

What is the difference between a conical spring and a cylindrical compression spring?

A conical spring has different diameters at its two ends. Its coils can telescope into one another during compression, resulting in a much lower solid height. A cylindrical compression spring normally has the same coil diameter over its entire length.

Do conical compression springs always have a progressive spring rate?

No. Many conventional conical springs with a constant pitch have a progressive spring characteristic. The springs in the Febrotec standard range use a variable pitch to provide an approximately linear spring rate over a larger part of the spring travel.

Can a conical spring be compressed to its solid height?

The spring can be compressed to the specified solid height, and the corresponding force Fc is shown in the product table. However, the solid height should generally not be used as the normal working position in frequently cycling applications.

Why are conical springs more stable?

The larger coil diameter forms a broad base, which improves lateral stability and reduces the tendency of the spring to buckle during compression.