What is a rotary latch and its uses?
Rotary latches are beneficial and important for many applications. In this article we cover:
How to choose the right rotary latch?
What kind of applications utilise a two-stage latch?
When should you use a two-stage latch?
How do you select the right actuator?
Bare and coated cables: how to choose
The benefits of vinyl-covered cables
What is a rotary latch?
For mechanical systems to operate effectively, it’s all about the right component. But the right components can only perform well if they’re designed to work together once properly connected.
Of all the types of latches, rotary latches are a great example of what we’re talking about. The absolute heart of a mechanical system, it’s vital that the right size or strength is selected for its intended application. Ignore this step and you have a poorly-performing project on your hands.
Remotely opening exterior and interior doors, bonnet or compartments, rotary latches offer maximum security and convenience in push-to-close engineering. Allowing for ambidextrous installation, the stylish design is also available with a rotary action cam for easy opening.
While compact-sized, light-duty latches might be ideal for anything from self-service equipment, to kiosks, postal terminals or even a data centre server cabinet. Heavy-duty equipment, such as construction or farm vehicles would require something like a heavy-duty door latch.
Convenient and easy opening of a car’s bonnet
Consisting of three key elements, the rotary latch is made up of:
- The rotary latch itself.
- The actuator (the interface with user).
- The cable which connects the two, with the component’s most common use ensuring easy opening of a car’s bonnet
Working remotely, the latch is activated from the driver’s seat via a mechanical lever, aka the actuator – and this means optimum convenience for the end user.
- Connected via a routed cable to the latch in the bonnet, the component works when the driver pulls the lever.
- Triggering the rotary latch, the bonnet can be opened remotely and the level of compatibility of its three elements ensures the overall reliability and effectiveness of the latch itself.
- It’s important, therefore, to always choose a latch from a trusted supplier, since any compromises with the component and its parts may result in a much poorer performance.
How to choose the right rotary latch
Without the right rotary latch, the mechanical system in which it operates will likely fail. But how do you choose the right latch?
Size and strength should be of utmost importance when selecting your latch – some are designed for larger doors on equally large equipment, while others are suited for applications requiring smaller components, where compact design and a snug and secure fit are important.
Understanding its unique application is key to selecting the right components for your project.
Single and Two-stage latches explained
It’s also important to take into account if the application is best suited to a single or two-stage latch, with the latter recommended to prevent the false latching conditions. The benefit to the end user is increased safety and increased security. Minimising the possibility of a door accidentally opening or not completely closing, the two-stage latch can prove instrumental for specific projects.
Single and Two-stage latches explained
If your rotary latch is required for higher working loads, it’s a good idea to select a two-stage latch. Often coming with a built-in bumper to trap the striker between a rubber bumper and the rotor, this kind of latch can eradicate vibration and noise as a result of the application’s standard operation.
What kind of applications utilise a two-stage latch?
One of the most common is car doors. A concealed operation means even if a car door isn't closed completely, it will still latch and won't open. If the door isn't completely closed, it will lead to rattling and vibrating, but this is easily remedied by giving it an extra push to ensure the latch is completely engaged. This push to close convenience results in the door latching firmly and uses low closing force.
When should you use a two-stage latch?
If your rotary latch is required for higher working loads, it’s a good idea to select a two-stage latch. Often coming with a built-in bumper to trap the striker between a rubber bumper and the rotor, this kind of latch can eradicate vibration and noise as a result of the application’s standard operation.
Rigid or flexible panels
Offering differing performance attributes, there are a variety of latches available – and for a host of applications. How you choose your latch depends also on where it’ll be used. Will it be utilised on a flexible or rigid panel, for example?
It’s worth considering that some latch systems offer multiple triggering options, which means the latch can easily be configured and mounted. This cuts out some work for the engineer, ensuring the overall design of the application doesn’t need to be altered at a later stage.
Boosted strength and security
The only visible part of the mechanism of the rotary latch is the actuator. The functionality of the interface between the latching mechanism and its users is vital. Plus, this vital component of the latch offers boosted strength and security, alongside being ergonomically designed – meaning the look and feel of the project is further bolstered.
How do you select the right actuator?
This depends on if it’ll be used outside or inside the application, with interior applications utilising finger pull/paddle versions. Push buttons are also an option for interior applications, thanks to the fact that they provide a flush surface, but sleek, economical T-handles can also be considered. The latter allows for an ergonomic grip when it comes to triggering the system into action.
Actuator materials
Manufactured from a range of materials, actuators can be made up of plastic, aluminium die cast, or zinc. For those looking to keep their project costs down, plastic is the most economical choice, but for increased performance, aluminium or zinc offer boosted strength.
Security and exterior actuation
What level of security are you looking for? Other specification considerations come into play for exterior actuation, including the level of security required. Corrosion-resistant materials, such as stainless steel, may also be a requirement, as is the need for a larger design, which can account for any gloved hands which may be working on the specific project.
Actuators range from surface-mount to flush, as well as push buttons and push handles, with multiple key code options available for almost all types.
If the application in question is vulnerable to vandalism or theft – if, for example, it’s being used in an enhanced security application – an electromechanical access device should be considered. This is simply a key fob connected to an internal electronic actuator, which will allow for greater security.
Benefits of electromechanical devices include the fact that they can remotely monitor and control a user’s credentials, as well as creating an accurate, digital record of access. This can then be utilised when demonstrating the component’s compliance with industry-accredited associations.
Bare and coated cables: how to choose
The role of the cable is to transfer the mechanical input from the operator via the actuator to the rotary latch. What this does is allow it to open safely and quickly. But which type of cable do you choose?
- Bare and coated are the options for engineers, with the later more commonly used in ‘line of sight’ applications.
- Utilised in projects where the cable needs to be located in an area which is separate from the actual rotary latch itself, this type of cable is generally coated in vinyl.
The benefits of vinyl-covered cables
These are generally more aesthetically-pleasing than their bare counterparts. On top of that, they protect the cable themselves, which ensures improved safety.
Coated cables and applications
In terms of their application, the use of coated cables may require the need for several, wide panels to be installed down the side of a vehicle – for example, on an RV – for storage purposes. For a project of this kind, the actuator would be designed into the centre of the panel. This offers greater ergonomic properties and ensures that the rotary latches are situated on the edge of the panel, thereby ensuring its closure against the frame.
On rotary latches which can be triggered directly, via push buttons or lever-style actuators, no connected cable or rod is needed. Instead, a rubber-cover trigger will alleviate any noise between the latch and actuator. This allows for smoother operation and a simplified solution for engineers.
Ideal for applications with a short distance between the actuator and rotary latch, the direct actuation design allows the actuator and rotary latch to be mounted on different sides of the application for optimum performance and ease.
Corrosion resistance
In terms of which cable should be used for this application, stainless steel should be selected for its corrosion-resistance and strength:
- Offers minimal stretch.
- Can move and flex inside the jacket – an acetal liner is integrated into the jacketed cable.
- Cable runs smoothly and turns around a curve or through a bulkhead for optimum performance.
- Maximum flexibility – rotary systems can be easily incorporated into existing designs which may already feature an actuator.
With a range of cable end fittings on offer, including eyelet, ball fitting and bare cable, manufacturers ensure engineers can always find the right tools for their application.
Barrel fittings
Easy to attach to any actuator or rotary latches, barrel fittings are also extremely compact.
L fittings:
- Eliminate metal-on-metal contact
- Are designed with rotary latches in mind
- Used with a retaining clip, they’re a great choice
Meanwhile, Z fittings can be used minus a retaining clip. The drawback for this type of fitting, though, is that they don’t offer the same level of resistance to vibration.
Eyelet fittings
Designed to accommodate round hardware like cylindrical mounting pins, eyelet fittings are ideal for applications where the cable is threaded through a hole and feature a set screw to tighten down on. In this instance, the bare cable is the best option for the engineer.
From single to two-stage latches, whatever the application, there’s a rotary latch for you.
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