Southco: A guide to different types of closures

January 16, 2024

Manufacturer of products in the field of locking technology

Managing access to enclosures of all types requires various design considerations in the product development process. Access to an enclosure can be granted or denied in many different ways.

Typically, two surfaces, such as a panel and a frame, are joined together with a latch or locking mechanism to shield the contents of the enclosure from the user.

The common purpose of all latches is to keep a flap or door closed. The main difference between the various types of latch lies in the form of operation and the type of fastening. Ease of access, security, the environment and other design requirements can affect which latch type should be used for a particular application. Knowing the different types of fasteners available will help any engineer successfully design their product. But first, let’s start with a basic definition of the term “closure”.

What is a closure?

We all deal with fasteners on a daily basis. From the magnetic handle on the door of a kitchen cupboard to the release mechanism of a car boot, fasteners are ubiquitous. Simply put, a fastener is a fastening device that connects two surfaces together while allowing or restricting access to the inside of the enclosure.

Types of fasteners

The complexity of fasteners depends heavily on their intended use. Engineers should carefully consider the following types of fasteners when evaluating the requirements of their specific designs. There is a wide range of different latches available to meet the diverse requirements of different applications.

Latch closures

Latch closures are a simple, cost-effective type of closure that engineers can utilise for their applications. This type of latch consists of a housing that is usually attached to a moving panel or door and has a latch that can be rotated to “grip” a stationary or fixed panel. Once the door is closed, the bolt rotates behind the fixed plate to secure the moving plate or door.

The latch is operated by a simple turning movement, either by hand or with a tool. To increase security, a locking mechanism can be integrated into the bolt head. Bolt catches are generally used to close and secure cabinet doors and a range of other enclosures. Many bolt catches are available in different materials, such as stainless steel and zinc.

Compression latches

A compression latch is almost identical to a deadbolt latch in the way it works, as it consists of a housing and a latch that is operated by a turning movement by hand or with a tool. In a compression latch, however, the latch generates a clamping force between the two surfaces.

The compression reduces vibration or rattling or can compress a seal to ensure an adequate seal to protect against environmental influences such as dust or moisture. This protects machines from potential damage caused by external influences, reduces maintenance costs and extends their service life. Compression latches can provide a wide range of contact pressure depending on the requirements of the application.

Snap lock/snap latch

A snap lock holds doors or flaps securely in position by simply pushing them shut. This type of latch is characterised by the fact that it is not damaged when a door or flap is slammed shut. Unlike some other latches, the handle does not need to be turned for the latch to engage.

The way a latch works is extremely simple. The latch fitted to a swing door or flap consists of a housing and a latch with a compression spring. When the flap or door is closed, the latch is either pressed against a counter surface or hooks onto a closing bracket. The latch then either springs back behind the mating surface or engages on the closing bracket to hold the flap or door securely in position.

A lock can be integrated into the snap lock to provide additional security. Snap latches engage when closing and in some cases require the operation of a lever, handle or trigger to open. However, some other types of latches require only an opposing force to overcome the friction that holds the latch in place.

Latches are ideal for devices where the reliability of the closure is paramount, such as industrial equipment, construction and transport. Latches are available in visible and concealed variants in a variety of materials, such as plastic, steel and stainless steel, zinc plate, zinc-nickel plate and powder coatings. They are available with various mounting options such as surface mounting, flush mounting and snap-on or adhesive mounting. Retaining areas can be lockable or non-lockable and are available in several designs: Pull up recessed handle, handle pull, push button, pull button, finger slide and push release handle. Commercial refrigerators and car doors are two practical examples where snap locks are frequently used.

Tension latches

Tension latches use tension to pull two surfaces securely together in one plane. This type of fastener usually consists of two components. The first component is attached to one plate and serves as the actuating mechanism. The locking mechanism is attached to the second plate and acts as a retainer. The tension is created when the lever is hooked into the bracket.

Tension fasteners reduce vibrations or rattling and can generate contact pressure. Due to their simplicity, latches are often fitted to the outside of the front covers of heating, ventilation and air conditioning systems. Engineers designing a simple application will find that a tension fastener is the most cost-effective solution.

Sliding shutter

A sliding closure consists of a sliding or rotating housing attached to one face, while the fixed closing bracket is attached to the other face. The two surfaces are joined together when the sliding or rotating component moves behind the fixed component. Sliding latches can be designed to both resist vibration and prevent rattling. They are usually operated manually. Depending on the end application and load requirements, there are different designs and materials for sliding latches.

When selecting the appropriate latch type for a particular application, the engineer must gather all relevant information that could affect the performance of the latch, including size, force, weight and environmental factors, such as whether the latch will be used indoors or outdoors.

Closures for interiors

In general, the requirements for indoor applications are not as stringent as for outdoor applications. Engineers do not have to worry about external environmental factors such as UV rays and rain, as indoor closures do not have to withstand the elements. Engineers can choose closures made from cost-effective materials such as plastic or zinc to keep overall costs down. The level of security required for indoor applications may also be lower than for outdoor applications. Non-locking closures may be sufficient for indoor applications depending on access control requirements.

Outdoor applications

Outdoor closures are subject to much more stringent requirements than indoor closures. Engineers must consider all environmental factors and weather events – from ice to high humidity. Design considerations must therefore also include aspects such as corrosion resistance and material wear.

In addition, there are specific regulations and standards for the ingress of water and dust for each industry that must be complied with. For example, closures used in electrical appliances and food processing must fulfil certain design, construction or sealing requirements, such as IP, NEMA or UL specifications. Installing closures that meet these standards improves the overall performance of appliances, as water and dust cannot affect the mechanical and electrical systems.

When a closure is installed outdoors, the safety risks increase depending on the location and contents of the enclosure. For example, a utility company wishing to protect a remote electrical enclosure should install a shutter that only allows authorised personnel to access the enclosure. Engineers must also consider the risk of vandalism and tampering. Outdoor locks are usually made from stronger materials such as stainless steel and have more complex locking mechanisms for added security.

Mechanical or magnetic locks

Another consideration engineers need to make is how the locking mechanism works. Some types of locks have a mechanical or magnetic locking mechanism for securing doors, cabinets or flaps. Some latches have electronic functions that do not require the user to directly operate the latch to secure it.

Visible or concealed locks

The decision whether to choose a concealed or visible latch depends on the requirements of the end user and the operating environment. Visible latches are used when the user needs to see the latch in order to operate it. In some cases, however, latches must be concealed for security reasons. They can then be concealed behind a door or flap. Concealed latches also allow for clean, continuous surfaces that enhance the appearance of a product or appliance – such as a refrigerator door or slot machine.

Customised closures

Engineers should consider working with an experienced supplier to ensure they select the correct closure type for their application. The chosen closure should function as intended to allow or deny users access to an enclosure. Choosing the right shutter type is not only important for the proper performance of the application, but also affects the user’s perception. For example, a car owner will appreciate the satisfying feeling of closing a glove box if a high quality locking solution has been chosen. This can also improve their perception of overall vehicle quality. Author: Jonathan Coulter, Commercial Product Manager, Southco Inc.

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