This article will take an in-depth look at magnetic door latches.
The article will bring more detail on topics such as:
This chapter will discuss what magnetic door latches are and how they work.
A magnetic door latch is a type of latch that consists of a striking pad and a magnet and is used to keep doors and gates closed. Magnetic door latches are also known as magnetic door stops, magnetic door catches, and door magnets. These door latches are typically found on cabinets and lightweight doors.
A magnetic door latch is made up of a catch body that is magnetized and a ferromagnetic strike plate. They are used to provide automatic and convenient furniture door latching. Other designs use two magnets, one on the door and one on the frame. These are used for low-traffic and light-duty doors.
The hollow body of the magnetic door latch is typically made of non-ferromagnetic metal or plastic. A bar magnet is housed within the non-magnetic body. Steel plates are attached to the bottom and top sides of the bar magnet to concentrate the magnetic flux. The steel plates come into contact with the striker plate. The magnetic door latch is attached to the door jamb or frame, and the strike plate is attached to the door edge. These latches can be surface-mounted or concealed. When the door is closed, they make physical contact between the magnet and the metal strike plate. This process is required to keep a strong magnetic attraction.
The majority of magnetic catches are made up of an armature plate and a magnet. The magnet is attached to one side of an object, while the armature plate is attached to the other. Once both components are installed, the magnetic force holds both sides together. The joined sides can then be separated by pulling them apart, breaking the magnetic force.
Electromagnetic locks are another type of magnetic latch. These locks are powered by electricity and are usually linked to an access-control system, where they receive signals from other hardware such as motion sensors, requests to exit switches, or credential readers. These are frequently used in conjunction with exit devices that have built-in signal switches that connect to the magnetic locks.
Magnetic latches are fail-safe, which means that if the power is turned off, the device will remain unlocked. This also implies that power must be constantly supplied for the magnetic lock to remain locked. Some magnetic latches accept either AC (alternating current) or DC (direct current) power. Many magnetic locks, once engaged, will secure the door with hundreds of pounds of holding force. Some locations may be better suited to a higher holding force than others. Magnetic locks can be used with fire-rated openings if they are linked to a fire alarm system and are programmed to disengage when the alarm is activated so that if power goes out, those within a building using these locks are still able to leave freely.
Magnetic locks with holding forces ranging from 500 to 1,000 lbs. are ideal for interior wood and aluminum doors requiring lower security. Higher security doors with holding forces ranging from 1,000 to 3,000 pounds are recommended for use on heavier gauge, hollow metal doors and frames.
Locks come in a variety of shapes and sizes, including round, square, and rectangular. The larger the size, the greater the holding force. They can operate on either AC or DC, depending on the application, and have varying efficiencies based on the amount of power consumed. Some locks have battery backup systems that allow them to remain locked for an extended period in the event of a power outage.
An electromagnetic lock works on the principle of using electromagnetism to lock a door when it is energized. To achieve optimal operation, the holding force should be collinear with the load, and the lock and armature plate should be face-to-face. The magnetic lock is based on some fundamental electromagnetism concepts. It consists essentially of an electromagnet attracting a conductor with a force strong enough to prevent the door from being opened. A closer look reveals that these devices make use of the fact that a current flowing through one or more loops of wire (known as a solenoid) generates a magnetic field.
This concept works in free space, but the effect of the field is greatly amplified if the solenoid is wrapped around a ferromagnetic core, such as soft iron. This is because the material's internal magnetic domains align with each other, greatly increasing the magnetic flux density.
This chapter will discuss the design of magnetic door latches, their installation, and materials used. It will also discuss various considerations when choosing magnetic door latches.
A magnetic door latch is made up of a metal plate, usually made of steel, and a mounted magnet. Though not required, most magnets for this type of door are encased in plastic and have flanges for holes on three sides to attach the magnetic material to the door or the door frame.
The magnets have enough magnetic force to keep the door closed, but they can easily be disengaged when an external force is applied. After removing the contents of a cupboard or cabinet, for example, the door can be swung shut and the magnet returns to its original position. This mechanism is simple to use and stays securely in place.
Latches can have various design features that make them more suitable for a specific application. They can be made with a variety of materials, finishes, thicknesses, and other characteristics. Some of the general characteristics and specifications of latches are summarized below.
Material: Latches are typically made of metal. Carbon steel, alloy steel, stainless steel, aluminum alloys, and copper alloys are examples of these materials. Because of their formability, machinability, and strength, metals are the first choice for producing latches. If desired, secondary processes such as finishing and coating can improve their external characteristics. Other materials, such as plastics and rubbers, are normally used as trims or wraps to absorb shock or reduce vibration.
Finishing and Coating: Finishing and coating are secondary processes used to improve the surface qualities of latches and other products. Plating, powder coating, and painting are common secondary processes used in the manufacture of latches. Plating forms a thin layer of metal such as zinc, silver, or chromium, while electrochemical deposition adheres the metal to the part's surface. Powder coating, meanwhile, utilizes a spray gun to provide a protective layer of coating material to an object. Whether painting or using one of the other aforementioned coating processes, the goal is to make the latch more corrosion-resistant and suitable for outdoor use.
Polishing and Buffing: These steps are taken to achieve a smooth surface and a bright finish by removing burrs and other microscopic flaws from latches. Polishing can be done mechanically or electrochemically (via electropolishing).
Powder Coating and Painting: Again, these processes provide a protective layer of polymer material to the part's surface. Similar to metal plating, these processes add corrosion resistance to the metal latch. Furthermore, these coatings can be colored to improve the appearance of the product.
Strength: The strength of a latch can be categorized as being light, medium, or heavy-duty and these categories are dictated by the thickness of the material (typically metal) used to create latch plates, barrels, and rotors. Different thicknesses can be witnessed on the cams and bolts. Latches are made in a way that allows them to compact shearing effects and bending stresses.
Mounting: When installing latches, various types of mountings are available. In architectural applications, latches can be flush-mounted, mortised, or surface-mounted. Both the latch and the door surfaces are on the same level with a flush-mounted latch. Mortise latches are hidden inside the door's hollow cavity or pocket; only the handle and keyhole protrude from a mortise latch. Finally, surface-mounted latches are installed by simply bolting the latch assembly to the surface and frame of the door. There are no bores or holes required with surface-mounted latches.
Handedness: Deadlatches, and some designs of bolt, rotary, and slam latches, are available in either left-handed or right-handed configurations. Most designs are interchangeable with minor changes. However, if this option is unavailable, handedness can be determined by inspecting the position of the hinges. The hinge position, either left or right, indicates the handedness of the door and latch to be used.
The magnetic lock is appropriate for both inward and outward swinging doors. Brackets (L bracket, LZ bracket, U bracket) are used to align the armature for both applications. Filler plates are also used on door frames to provide a large, flat mounting area when the electromagnet is larger than the available mounting space on the door frame due to the geometry of the frame. The magnetic lock should always be installed on the secure side of the door. The majority of installations are surface mounted. Magnetic locks, cables, and wires should be routed through the door frame or flush-mounted with wire molding for safety. The installation process is as follows.
In in-swinging applications, the electromagnet is typically installed at the door's header in the opening corner. When equipped with full-length housing, magnetic locks can also be installed vertically in the door opening. The armature is bolted through the door and oriented to mate with the face of the electromagnet in this configuration. To provide locking holding force, the armature plate and electromagnet must make contact.
The electromagnet is typically installed on the side of the door header in out-swinging applications. The armature is mounted on a Z-shaped bracket in this configuration, orienting it to mate with the electromagnet. Magnetic locks are almost always included as part of a comprehensive electronic security system. A system like this could be as simple as an attached keycard reader or as complex as a connection to a central computer that monitors the building's security. Fire safety is also an important consideration regardless of the locking system chosen.
Other electromagnetic lock variations and improvements have been developed. The most notable is the shear lock, in which the armature does not directly pull off the face, but instead shears the load, similar to a mechanical stop. In contrast to the original (and now omnipresent) direct-pull type of magnetic latch, which typically works in either an in-swing or out-swing configuration, the shear magnetic lock allows a door to swing in both directions. To provide the appropriate holding force for the shear magnetic lock, two pins lock the armature onto the magnet itself and ensure that the magnet locks into place.
Regardless of their exact configuration, all door latches are made using both the metalworking process known as stamping, and the spot-welding process. Flat sheet metal is stamped or pressed into shapes during the stamping process. These shapes are later organized, assembled, and spot welded into full latches to complete the job. Manufacturers typically construct door latches with durable and sturdy materials to ensure that they can withstand the potential stress loads and heavy use that they may encounter. Included below are a few examples of such materials:
Aluminum: Aluminum is an excellent, lightweight material for door latches. Aluminum latches are long-lasting and rust-resistant. Aluminum is also one of the least expensive latch materials, so these latches are very affordable to consumers. However, because of its lightweight, this metal is more brittle than other latch materials.
Brass: Many homeowners use brass to enhance the design elements in their homes because of its stunning appearance. However, this is one of the least-common door latch materials. Depending on where they live, customers may have difficulty locating brass latches. Additionally, brass door latches need to be polished regularly for best appearance and, occasionally, for proper functionality.
Bronze: Bronze latches are more expensive than those made of other materials. A bronze latch, on the other hand, can complement a wide range of interior styles. Bronze is also resistant to chipping and rust, making it a long-lasting material. This type of door latch material can be kept in good condition by applying wax once a year to protect the latch and prevent patina.
Chrome: Consumers will come across many chrome latches while browsing different latches. This material is frequently used for latches because of its gleaming appearance. Chrome, on the other hand, is less durable as a latch material than stainless steel. Chrome latches are also more prone to chips and scratches over time when compared to many other latch material options.
Iron: Iron latches are distinguished by a black powder coating that protects the metal from the elements. This color is also appropriate for a variety of design styles. Regardless of this coating, iron latches are known to rust. Iron latches, on the other hand, will last a long time in areas where rust is not a problem. To keep the iron looking its best, it must be serviced regularly. It is recommended to use a ball of steel wool to remove rust spots before applying a protectant spray to the material's surface. The coating can also be provided with spray paint.
Stainless Steel: Stainless steel has a similar appearance to aluminum. Stainless steel, on the other hand, is known for its high durability and resistance to pressure. While powder-coated stainless-steel latches are available, the natural silver color of uncoated stainless steel provides a great modern look. Stainless steel is also already corrosion resistant on its own, making it an excellent material choice for those who are constantly plagued by rust. To keep the stainless-steel gate latch material in good condition, wash it with mild dish soap and warm water, then wipe it dry.
Plastics: Manufacturers can also use high-strength thermoplastics to construct plastic latches for those door latches with lighter requirements. Plastic latches perform just as well as metal latches in lighter-duty applications, with the added benefits of high impact resistance and flexibility.
When selecting magnetic catches, one of the first factors to consider is the material. All magnetic catches contain a magnet that is usually encased in a material. Some of them use plastic to accomplish this. Magnetic catches made of plastic are inexpensive, versatile, and long-lasting. Aluminum is also available as a lightweight, rust-resistant metal that is popular for magnetic catches.
When selecting magnetic catches, you should also consider the shape. Magnetic catches are most commonly made in rectangular shapes. Having said that, magnetic catches are also available in a variety of other shapes. Some of them are cylindrical. They are known as barrel magnetic catches and can hold multiple magnets. Don't forget to get the right size magnetic catches. They must fit the objects on which they are to be installed, regardless of material or shape.
When selecting magnetic door catches, consider the height, depth, and width. These measurements can be compared to the objects to which they will be paired to ensure that the magnetic catches will fit. When choosing magnetic latches, there are several additional factors to consider. Some examples are:
Traditional Door Latches vs. Electric Door Latches
The locking method of traditional door latches and electric door latches both have advantages and disadvantages. Traditional metal keys, key cards, or handheld remote controls can all be misplaced or broken, whereas numerical key codes can be forgotten (or learned and memorized by the wrong person). When necessary, key codes can be changed quickly and easily by the user, whereas changing physical locks and keys is much more involved, requiring specialized hardware and expertise. However, power outages present a problem for purely electronic door locks because they remain locked or unlocked until the power is restored or the battery is replaced; this is not an issue for traditional door latches.
Most electronic door locks have a combination of physical-locking control and electronic-locking control on the same door. For example, you may have a physical key for setup and emergency backup, but you may normally use the remote or keypad to lock and unlock the door. This adds an extra layer of convenience for the user, while also providing additional security and functionality. Electronic door locks for traditional swing doors are widely available, and electronic sliding door locks are becoming more common as well.
Traditional key locks employ some variation of the "pin and tumbler" method in which the lock cylinder is held in place by a row of small metal pins, each with an upper and lower half. The uneven "serrated" edge ensures that each pin moves a certain distance when a key is inserted and turned. Only when each pin is moved just enough to create a straight separation between the upper and lower halves of all pins can the cylinder be turned.
Electronic door locks also use "actuators," which connect the bolt or cylinder to a small motor that is completely hidden within the door or frame. An electrical impulse controls the motor, which can be triggered in a variety of ways, including an electronic card reader, a keypad, or a wireless remote control sensor. Whatever the trigger mechanism may be, the electronic door lock is programmed to activate the motor-driven actuator only after receiving the correct electronic input.
The types of magnetic door latches differ significantly depending on their complexity and application purpose. When analyzing their specific requirements to the variety of available designs, engineers, technicians, and all users should carefully evaluate each type of door latch. Luckily, there are several latch types available to meet the needs of various designs and applications.
Surface-mounted magnetic door latches are the most common magnetic locks. They can be installed on a frame's header for single and double door openings, or the strike jamb on single door openings. Surface-mounted magnetic door latches are best mounted on the push side of the opening, but they can also be mounted on the pull side.
Surface-mounted magnetic locks can have housings that vary in size and come in a variety of finishes. These magnetic locks are generally recommended for indoor use, but they can be used on exterior openings as well, though they will require more maintenance if installed outside.
As suggested by the name, these magnetic locks are concealed in both the door and the frame with this type of latch. Because they are not surface mounted, these magnetic locks are commonly referred to as "shear locks." Instead of a direct pull, the pull force is in a "shear" direction. They can be installed inside the frame and door, as well as at the bottom of the door and on the floor.
Shear locks require a minimum distance between them, so take extra care when preparing the opening for these types of locks, especially if they are mounted on the floor. They connect to hardware similar to surface-mounted magnetic locks, and are linked to the same types of access control systems.
Power is required to unlock a fail-secure latch. If there is a power outage, the door will remain locked and no users, even those with valid credentials, will be able to enter. Fail-secure locks are required for areas that must be kept secure at all times, such as server rooms, IT suites, storage areas containing confidential information or high-value equipment, and research labs.
Although a fail-secure magnetic lock ensures security, it may be necessary to allow authorized users access. In that case, the lock should have a backup power source, such as a battery. In the event of a power outage, fail-secure locks prevent unauthorized access. They can, however, allow users to exit from the inside as a safety precaution.
Power is required for fail-safe locks to remain locked. If the power goes out, the door will open to any user, regardless of their entry authority. Fail-safe locks are essential in areas where safety is the most important requirement: for example, in areas where users must be able to open a door in any circumstance.
As a result, they are ideal for emergency exits or stairwell doors. If fail-safe locks are used in areas where a high level of security is required, backup power sources can still be installed to prevent unauthorized users from entering.
Magnetic touch latches use a magnet attached to the end of a spring-loaded plunger to keep the door closed. When a user presses the door, the spring-loaded plunger pops open, ejecting the door. The user then presses once more to compress the spring-loaded plunger and secure the magnet to the metal door or striker plate.
This chapter will discuss the various applications and benefits of magnetic door latches.
Magnetic door catches are primarily used for lightweight doors made of materials such as plywood, plastic, or certain metals that do not require or are unable to support a larger latching mechanism. They are a versatile option for commercial buildings because they can be used to secure entry points both inside and outside and can be installed on a variety of doors. They are frequently used on emergency exits, delayed-egress doors, and controlled-egress doors. The automotive industry and construction industry both utilize equipment with latches. The following bulleted items list many useful magnetic lock applications:
The primary benefits of using magnets and catch plates are their simplicity and dependability. Unlike mechanical door catches, these specially-designed, door-latching devices are long-lasting and never need to be replaced. They hold any lightweight door permanently in place once properly positioned, eliminating the need for a locking mechanism or moving parts.
Magnetic door catches are the ideal solution for keeping doors closed in a kitchen, laboratory, workshop, or storage room due to their one-of-a-kind design. They open and close with a simple pull and a swing of the magnetic toward the catch plate. Some advantages are as follows:
Remote operation: By adjusting the power source, magnetic locks can be turned on and off remotely.
Easy to install: Because there are no interconnecting parts, magnetic locks are generally easier to install than other locks.
Quick to operate: Magnetic locks (excluding fail-secure latches) unlock instantly when the power is turned off, allowing for faster release than other locks.
Sturdy: Magnetic locks may also be less susceptible to multiple blows than conventional locks. When a magnetic lock is forced open with a crowbar, the door or lock is less likely to be damaged. Additionally, an electromagnetic lock has no moving parts that can fail.
Magnetic door latches also come with their disadvantages; some of these disadvantages are mentioned below:
The magnetic door latch is based on the basic electromagnetic concept that the electronically charged particles in certain materials are attracted to bond to one another. A magnetic door latch is a type of latch that consists of a striking pad and a magnet and is used to keep doors and gates closed. Magnetic door latches are also known as magnetic door stops, magnetic door catches, and door magnets. Though not required, most magnets for this type of door are encased in plastic and have flanges for holes on three sides to attach the magnet to the door or the door frame. An electromagnetic lock works on the principle of using electromagnetism to lock a door when it is energized.
To achieve optimal operation, the holding force should be collinear with the load, and the lock and armature plate should be face-to-face. Magnetic door latches are used throughout a variety of industries and for different purposes. The automotive industry, for example, relies on these devices for use in door locks, seatbelts, and with shifting and braking applications. Magnetic door latches are commonly used to close various cupboards and drawers. You most likely pass right by magnetic door latches every time you walk by your washing machine or refrigerator. Both commercial and home security systems frequently rely on magnetic door latches. There are several magnetic latch types available to meet the needs of various designs and applications and these latches differ significantly depending on their complexity and purpose. When analyzing the requirements of their specific needs, one should carefully evaluate these different types of latches.
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