This article will take an in depth look at friction hinges and their applications.
In this article we will discuss topics such as:
A friction hinge provides resistance to the pivoting motion of a hinge. These hinges can control or hold motion when pivoting objects open and close. They are also known as free motion, positioning, torque, and free stop hinges, and they are capable of creating a specific tolerance between mechanical components.
Torque is the operating principle behind friction hinges; torque is achieved by applying a certain amount of force. Additional friction is produced through the use of lubricants or springs. Friction hinges are placed on both sides of a door or window. When force is applied to open or close the door or window, the hinges will not fully open or close. Instead, they can maintain a stable, unmoving position.
Friction hinges’ design allows them to maintain the desired position for an extended period. In addition, they can be customized in several ways to meet specific needs; for example, friction hinges can be classified as one-way or two-way. One-way friction hinges exhibit resistance on only one side, while two-way hinges can have damping on either side. The customizability of friction hinges even makes it possible for them to have both one-way and two-way resistance in one hinge. Customized designs also provide variables in viscosity, temperature tolerance, and resistance.
Friction hinges are safe and convenient for use with machinery and equipment. They can include several features, such as lift assistance to minimize the force necessary to operate them.
The friction or torque strength of friction hinges can vary based on type, format, and internal mechanisms. All friction hinges work in an expected range with a plus or minus symbol (±) on every torque hinge. It is important to know the strength of torque or friction that a hinge can normally produce to help it work efficiently.
The best and most effective friction hinges have torque strength below or close to the lower limit. If the torque or friction is above the lower limit, the hinges won’t provide a free stop and will not stop on their own. If the strength is above the lower limit, at some point, the moveable components will become rigid and difficult to move.
All hinges are made of metal to ensure their durability and stability. When selecting a hinge, a critical part of the selection process is choosing the correct metal to fit the needs of the application where the hinge will be installed.
Metals vary according to their hardness, corrosion resistance, rust resistance, strength, and appearance. While these factors also apply to friction hinges, an additional factor for friction hinges is their durability and strength. This is because when a friction hinge is open, it has to be able to support the weight of a window or door that can weigh 1 to 10 pounds (0.45 to 4.5 kg).
The following factors are major considerations when selecting a friction hinge:
The metal used to produce a friction hinge determines where it can be applied, so this material needs to be ascertained early on. Many different metals are used in the production of friction hinges, with cold rolled steel, stainless steel, aluminum, bronze, and brass being the most common.
Cold rolled steel is an iron alloy that is formed at room temperature without exposure to heat. The process for cold rolling steel allows the metal to retain its strong physical characteristics, which makes friction hinges strong, durable, and long-lasting.
The term “stainless steel” refers to 200 alloyed metals made of iron, at least 2% of carbon, and chromium. The element that differentiates stainless steel from other metals is its chromium content, which forms a layer of oxidation when exposed to the air.
The ratios of chromium and carbon change according to the grade of stainless steel. The different alloy percentages change the properties of stainless steel, increasing its resistance to corrosion, temperature changes, and weldability and formability. Two common stainless steels used to make friction hinges are Grade 316 and Grade 18-8.
Aside from its natural resistance to corrosion, aluminum has several properties that make it an ideal material for manufacturing friction hinges. One of its main characteristics is its outstanding strength-to-weight ratio, which is far superior to other types of metal. Its light weight makes it easy to install and remove.
Regardless of its light weight, aluminum has the same durability and strength as heavier metals. Aluminum hinges can withstand the required weight of connected doors and windows without cracking or experiencing strain damage.
Brass is an alloy of zinc and copper. Modern brass is a combination of 67% copper and 33% zinc, with a 2% lead content to improve its machinability. Much like aluminum, stainless steel, and copper, brass is resistant to the effects of corrosion from saltwater, making it an ideal solution for friction hinges for boats.
Bronze hinges are strong, with excellent ductility and corrosion resistance. They are capable of withstanding the effects of friction from other metals without degrading. Bronze hinges have a pleasing aesthetic appearance, which is why they are more expensive than other friction hinges.
Steel is an alloy of iron, carbon, and trace elements. It is well known for its strength, durability, and longevity. Since steel is readily available, steel hinges are less expensive than other metal friction hinges. As a result, it is found in a wide assortment of applications and environments.
Various forms of steel include:
Titanium forms titanium oxide on its surface when it is exposed to oxygen. The oxide layer is resistant to chemicals, corrosion, and rust, with high strength-to-weight and strength-to-density ratios. Some grades of titanium have tensile strength comparable to steel with a fraction of the density.
The most common uses for titanium are in aerospace due to its exceptional strength and low density. There are multiple grades of titanium, each with different properties and applications.
Friction hinges, also known as torque or position control hinges, provide resistance to their pivoting motion using a mechanism built into the hinge that generates friction. They are designed to hold lids, doors, panels, displays, and windows in position for easy access.
The opening motion of a friction hinge is smooth and effortless, requiring very little force. Their firm positioning prevents springback, hard slamming, and unexpected shutting of an open door, window, or other object. As a result, friction hinges protect objects and people from harm and provide easy, convenient access to equipment.
When a friction hinge is opened, it generates rotational force that generates friction to provide the stopping mechanism. Three basic types of friction created by a friction hinge are curl, disk, and pipe.
Curl friction generates friction from the presence of a spring steel sheet wrapped around a shaft. Spring steel can return to its initial position without deformation. As with disc and pipe friction, the curl friction structure is located inside the hinge.
Disc friction is the friction that happens between alternating, disc-shaped rotating bodies and fixed stationary bodies. The stationary body resists the motion of the rotating body.
Pipe friction is a method of joining tight-fitting parts that depend on friction. It creates a lasting bond with perfect alignment. In a friction hinge, it is the shaft forced through the knuckles.
Torque is the force that creates the friction mechanism to hold a door, panel, or window open. The torque of a friction hinge has to match the weight of the object upon which the hinge will be placed.
When selecting a friction hinge, it is necessary to calculate the maximum torque a door or flap will generate and the maximum torque the hinge can support. The torque generated by a door, panel, or flap is equal to the distance from the rotation center to the door’s center of gravity multiplied by the weight of the door.
The various calculations for the torque of a door are based on the assumption that the door is flat, though this is not always the case since some doors are “L” shaped.
The number of times a hinge opens or closes depends on the expected life of the application. If the appropriate hinge is made of the right materials, the life expectancy of a friction hinge will last the lifetime of its application.
A properly chosen hinge has the necessary torque to consistently perform efficiently and smoothly for a long time.
The resistance shown by a hinge during its rotation is called dynamic torque, which must be in good condition to ensure good performance.
Static torque is the resistance generated when a friction hinge is rotated. It is the force that holds a door or flap in position and must be constantly monitored for its ability to hold the position of the door or flap.
Springback is the motion that flexes back when the force or friction is removed from the hinge.
Free play indicates the motion of a friction hinge before there is a sufficient amount of torque buildup. It provides the ability to move a door, flap, or panel to its required position. Free play is a negative aspect when insufficient torque builds up and a door closes due to the lack of friction. The manufacturers of friction hinges supply information regarding the free play in a hinge.
Aesthetic appeal of a friction hinge is necessary when it will be visible, such as on a display, a lid for a product, or a cabinet door in a kitchen. In many cases, friction hinges are not visible and do not require a pleasing appearance. On laptop computers, they are designed to blend in with the color of the computer casing and are very small.
The selection of a friction hinge for caustic or hostile environments depends on the material from which the hinge is made. Soft metals incapable of repelling acids or corrosive substances should not be chosen. Manufacturers provide stipulations regarding the material used to manufacture a hinge, with advisories as to where and in what environment a hinge may be used.
An endless number of hinges can be configured, designed, and engineered to fit any friction hinge application. As a result, friction hinges are widespread, from commercial products such as kitchen cabinets and laptop computers to industrial uses for electrical enclosures and machine covers. Hinge manufacturers work with clients to perfect and develop friction hinges to fit specific applications and requirements.
The above features should be considered when choosing a friction hinge. The flexibility and adaptability of friction hinges make them an ideal choice when control of an opening is necessary.
Friction hinges come in many sizes, shapes, and amounts of torque, each capable of performing different functions. The unique and unusual capabilities of friction hinges make them valuable as a door, flap, panel, or window solution.
The three common types of friction hinges are one-way, detent, and adjustable. The design and purpose of these friction hinges are to serve as a support and convenience for users. They provide protection and easy access.
With all friction hinges, torque is the key to holding an open device’s position. In the case of a one-way friction hinge, constant torque is only manifested in one direction without any torque in the reverse direction.
One-way friction hinges make it easy to open a lid, device, panel, door, or display, but they make it more difficult to close them. This particular function is helpful for use with large or heavy doors.
The benefit of detent friction hinges is their ability to hold an opening completely closed to prevent springback and hold connected objects in place. Once a door or opening is opened, it remains open and in place. Unlike traditional hinges that allow for free motion, detent friction hinges limit the motion of an opening and hold the door or opening in position, removing its ability to move or reposition.
Detent hinges are like all other hinges, with two leaves and a connecting knuckle. However, their differentiating factor is a spring embedded in their structure, which applies force to hold a door or opening in position. When properly installed, detent friction hinges remove any concerns regarding a door closing or opening freely.
Adjustable friction hinges make it possible to adjust the amount of torque by rotating a screw with a 180° rotation at the top of the hinge shaft. They are referred to as position control hinges since they allow the flexibility to define and change the movement, operation, and positioning of a panel or door. These changes are applied without additional cost, hardware, or installations. In addition, adjustable friction hinges can have concealed mountings for a clean presentation.
When products need a hinge that stays in position to meet the needs of an application, the first choice is a friction torque positioning hinge that can remain stable regardless of the amount of force. One of the names applied to friction torque positioning hinges is free stop hinges, which allow a lid or top to remain at a fixed angle.
Friction hinges can be designed with different amounts of torque to meet specific needs and requirements, with torque applied in any direction.
Friction stay hinges are variable torque hinges used for security and for providing safe opening and closing of windows. They are adjustable hinges placed in a slide to provide controlled movement of windows.
Top hung friction hinges have a handle at the bottom of the window, with the friction hinge placed at the top of the window. The window opens from the bottom. The friction hinge springs back to facilitate its opening. Windows with top hung friction hinges are pushed outwards from the bottom.
The sizes of top hung hinges can be adjusted according to the size of a window, with sizes ranging from 8 to 24 inches (20 to 61 cm). They are made of stainless steel with a thickness of 0.1-0.2 inches (2.6 to 3 mm). Top hung hinges are used for windows and can be installed with double glazed or aluminum windows.
Side hung friction hinges are designed so that a window can open like a door. The handle of the window is at the side of the opening, with the hinges at the bottom or top. The window opens from the side like a door or the top like a hatch.
One of the names for torque or friction hinges is a constant torque hinge, where the leaf and pin keep the hinge in a set position. There are an endless number of these complex, specially-designed hinges, each of which has a special function to meet the needs of specific applications.
Of the many assorted choices of friction hinges, the constant hinge is the most basic type. It can be opened to any position, which it holds until the appropriate force is applied. This is unlike other models with a preset angle to which they are opened and remain.
The SB-188 series has a torque range from half an inch per pound to 14 inches per pound. It is used on medical equipment, small LCDs, lids, covers, and safety guards.
The model series ZE-188 is made with balanced and unbalanced torque in right- and left-hand configurations. It comes with torques of 1 to 8 inches per pound in a slim profile and substantial mounting geometry.
A ZC-188 series friction hinge has a torque range from 3 inches to 8 inches per lb with a closed housing. As with ZE-188, it has a balanced and unbalanced torque. It is made of various materials depending on the manufacturer and has a 30,000 life cycle.
The SB-200 series has a torque of 3 inches per pound up to 20 inches per pound or more. It is used in headrests, medical devices, lids, covers, and LCDs. An SB-200 series hinge has high torque in a small package.
Series ZC-250 has a torque range of 5 inches up to 17 inches per pound. The shaft of the ZC-250 series is coined and bent. It has a life cycle of 30,000 with 360° shaft rotation and is capable of maintaining its position in any place of the rotation.
The ZE-375 series has a torque range of 10 inches per pound up to 120 inches per pound for specific models. Depending on the model, it can have one-way or centralized torque with a left- or right-hand opening. It is used for arm support, headrests, medical devices, lids, and covers.
SB-500 has different torque ranges depending on the model of hinge. Its torque range is from 20 to 70 inches per pound. It is used in medical devices, LCD displayers, headrests, and arm supports. SB-500 series hinges are another small hinge with a high torque range.
MA-685 series friction hinges have exceptional holding torque with adjustability. They have a 360° rotation hollow tube shaft capable of pivoting and staying put in any possible position without backlash. The torque range for the MA-685 is between 25 and 100 inches per pound with a balanced and symmetric torque.
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