Guidance offered in rotary latch selection

22nd August 2019
Posted By : Anna Flockett
Guidance offered in rotary latch selection

Ubiquitous in the car, truck and specialist vehicle industry, rotary latches make easy work of securing and remotely opening vehicle panels. They’re more typically used in applications involving bonnet, boot lid or storage compartments, e.g. on coaches, emergency vehicles or caravans etc. In these everyday situations we rely on comfortable, reliable manual operation to provide security and accessibility.

Essentra Components point out that at the design stage it is important to consider the three elements individually, as well as in combination.

While compact-sized, light-duty latches might be ideal for anything from self-service equipment, to kiosks, postal terminals or even vending machines. A stronger latch, meanwhile, may be required to open doors on a larger piece of off-highway equipment. This could include construction or farm vehicles, for example.

Providing convenient and easy remote opening the rotary latch is made up of:

  1. The rotary latch itself.
  2. The actuator (the interface with user).
  3. The cable which connects the two, with the component’s most common use ensuring easy opening of a car bonnet.

For example, single stage latches provide a secure way of closing a panel or door - this is the most common type of rotary latch where only one rotor will engage the striker. A double rotor, on the other hand, offers greater strength, making it ideal for higher loadings and to prevent false latching conditions, thus providing increased safety and increased security. Minimising the possibility of a door accidentally opening or not completely closing, the two-stage latch can prove crucial for specific projects.

One of the most common uses of a two-stage latch is for vehicle doors where even if the door isn’t closed completely, it will still latch and won’t open. Often coming with a built-in rubber bumper to trap the striker between bumper and the rotor, this kind of latch can eradicate vibration and noise as a result of the application’s standard operation. On top of this if the door isn’t completely closed, which will lead to it rattling and vibrating, this can easily be remedied by giving an extra push to ensure the latch is completely engaged.

Selecting the right actuator depends on if it will be used outside or inside the application, with interior applications utilising finger pull/paddle operation. 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, with multiple key code options available for almost all types. Manufactured from a range of materials, actuators can be made up of plastic, aluminium die cast, zinc or stainless steel. There may also be a need for a larger design to account for gloved hands in industrial environments.

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 mechanism connected to an internal electronic actuator, which will allow for greater security. The benefits of electromechanical devices include the fact that they can often 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.

The role of the cable is to transfer the mechanical input from an operator via the actuator to the rotary latch. Bare and coated cables are the common options with the later more commonly used in ‘line of sight’ applications. This type of cable is generally coated in vinyl which is more aesthetically-pleasing than their bare counterparts. On top of that, they protect the cable ensuring longevity and thus improved safety in situations such as on RV storage compartments where the actuator would be designed into the centre of the panel.

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 mitigate any noise between the latch and actuator also allowing for smoother operation and a simplified installation.

Where corrosion resistance is an issue then a stainless-steel cable should be selected for its corrosion-resistance, greater strength, minimal stretch characteristics and ability to move and flex - inside an acetal liner integrated into the jacketed cable. This ensures the cable runs smoothly where it turns around curves or through bulkheads. Cable end fittings available usually include an eyelet, ball fitting or bare cable so that engineers can always find the right attachment for the job.

Clearly the options are many and varied so consulting with the specialist team at a mainstream supplier such as Essentra Components is always a good idea to optimise the price/performance mix of an application.


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