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The ABC’s of Torque Hinges

An Easy Guide to understand friction hinge technologies and how to find the right one.

What is a Torque Hinge?

A torque hinge, also known as a friction or position control hinge, is a hinge designed to provide resistance to the pivoting motion of the hinge itself. This is achieved by a mechanism within the hinge that generates friction to provide resistance which prevents a component from moving unwantedly. This makes them great when you want to hold lids, doors, panels or display devices in a desired position for safety and convenience. 

A common example are the hinges used on most laptops. The display stays shut until the user opens it, and remains in the position the user leaves it in. 

Torque hinges are also designed to provide smooth and seamless operation throughout the opening range so a user does not have to jerk or pull on a flap to get it open. They also prevent spring back making it hard to slam something shut therefore, reducing the risk of equipment damage or worse, injuries to the user.

     

 

 

 

 

 

 

 

Torque Hinges are also called Friction Hinges

 

Three Advantages of Using Torque Hinges

Efficiency
Stops at any angle without a stopper.

 

 

 

Clean Design
Lid supports are not needed, allowing maximum space inside the application.

 

 

Safety
Prevents unwanted movement hence provides additional safety for users.

 

 

How Does It Hold In Any Position?

What holds torque hinges in place? 

The structure of the torque hinge shaft uses friction. When the door or flap is opened or closed, the motion (the rotational force of the object) generates friction, activating the free- stop mechanism. 

There are 3 basic types of mechanisms that can be used to create the friction in the hinge; a curl type, disk type, and pipe type. A more complex type (not referenced ) is an Omega clip type. 

How Friction Is Generated?


Disc structure
Shifting discs sandwiching a fixed disc are moved. 

 

 

Curl structure
A shaft inside a rolled spring sheet is rotated. 

 

 

 

Pipe structure
A shaft press-fitted into a plastic pipe is rotated. 

 

Friction inside the torque hinge holds the lid in any position. 

Applications

 

 

 

 

 

 

 

 

Suitable for lids or access panels on machinery, display monitors, lighting, cabinets etc.
Torque hinges are available in a variety of torque strengths, specifications, mounting positions and features making them functional for all types of applications. To specify the right one, you must consider the function that the hinge needs to deliver, the weight and dimensions of the object that the hinge will facilitate and how you want to mount the hinge. You must identify any environmental factors like heat or moisture that could effect the hinges’ performance. And of course, the aesthetic design is important to ensure the right look of your application. 

 

Selecting the Right Torque Hinges 

Torque Strength 

A key step in selecting the correct torque hinge for your project is finding a hinge that has the strength to support the object it will facilitate. Torque is the force that will be put on the friction mechanism and the hinge’s specification needs to match the actual torque that the object will put on the hinge. 

Torque hinges should list in their spec sheet, the max torque which the object mounted must be less than in order to function properly. Be sure to check the torque capacity based on the total number of hinges to be used. 

 

Hinge By Types

Butt Hinges
Common design for swinging doors.

 

 

 

 

Torque Hinges
Various mounting positions for upward opening lids.

 

 

 

 

Concealed Type
Various mounting positions for upward opening lids.

 

 

 

 

Swivel, Dual Axis Hinges
Various mounting positions for upward opening lids.

 

 

 

 

Beyond Just Friction

Specialized features provide added convenience and value. 

One Way Torque Hinge
Friction is applied in only one direction allowing doors or lids to be opened easier while still maintaining the position control or “free-stop” as friction is applied in the closing direction. 

 

 

 

Bi-Directional Torque Hinge
Torque is only generated in the downward direction. The torque direction reverses when the hinge opens at over 90º. This allows the flap to hold in position at angles of 180º. 

 

 

 

Adjustable Torque Hinge
The amount of friction exerted by the hinge can be adjusted to the desired strength simply with a hex key or similar tool. 

 

 

 

Detent Torque Hinge
A mechanical detent is designed at the closing point to eliminate spring back ensuring that the lid remains completely closed.

 

How To Calculate Torque

Torque is the force required to rotate something along an axis. It can be calculated by measuring the distance of the door or lid from the hinge side to the opposing edge and multiplying that by the weight of the door or lid. Then take the resulting value and divide it by 2. 

 

 

 

 

 

Determine Which Torque Hinge Will Work For You

 

 

 

 

 

 

 

 

Simplified for flat-shaped lids or doors.

 

Understanding Torque Units (Metric) 

The unit for the torque moment with hardware in metric is ‘kgf·cm’ or , ‘N·m’(SI unit).

1kgf = 9.80665 N 

9.80665 is the Standard acceleration of gravity. 

Difference of N·m and kgf·cm 

 

 

 

 

 

 

 

Selection of Torque Hinge

Two tips to select the torque hinge.
1) Determine the maximum torque that the door or flap will generate
2) Know what the maximum torque the hinge(s) can support 

Maximum Torque Generated by the Door or Flap 

Keep in mind, the max torque for the door or flap must be lower than the maximum torque that the hinges can manage 

 

 

 

 

 

You have to consider torque tolerance. 

If torque tolerance is 20%, the minimum door moment has to be:
1. lower than ‘torque -20% ’.
2. higher than ‘torque +20%’. 

Formula for Torque Generated By The Door 

The torque generated by the door can be calculated from (center of gravity) and (weight) of the door. 

 

 

 

 

 

 

 

 

Example:
When installing two torque hinges as below picture, which one is the most suitable?  (Torque tolerance: 20%) 

● Torque hinge A (0.4 N·m / pc.) 

● Torque hinge B (1.0 N·m / pc.) 

● Torque hinge C (4.5 N·m / pc.)  

 

 

 

 

 

Solution:
The most suitable torque hinge is: 
Torque hinge B (1.0 N·m / pc.) 

 

 

Torque Formula

The torque generated by the door can be calculated as below: 

0.2m x 0.8 kgf x 9.80665 ÷ 1.57 N·m÷N 

The torque generated per hinge is: 

1.57 N·m ÷ 2 ÷ 0.79 N·m 

Torque has to be stronger than 0.79 N·m per hinge. 

Considering the torque tolerance 20 %, it has to be stronger than 0.95 N·m. 

The answer is: Torque hinge B (1.0 N·m / pc.) 

Keep in mind that the formula above assumes that the lid is “flat.” In many cases, lids are “L” shaped or have other attributes which need to be taken into consideration in order find the actual point of the center of gravity. To simplify your effort, we have created a tool that will do the calculations and suggest hinges in our line up that will fit your specific application. 

Online Tool to Simply Your Selection Process 

The Sasuga-kun tool was designed to help calculate the torque generated by your door, flap or monitor and suggest suitable Motion Design Tec® products that could work with your application. All you need to do is input values such as weight and dimensions, select a few options and conveniently find the right hardware. 

Visit Sasuga-kun by clicking the link below and select the Industrial Experience 

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