How to specify components for a rotary latch system

James Stroud of Southco explains the need to ensure compatibility between the critical elements of a rotary latch system as commonly found on enclosures and equipment in many different industries, and presents some important points to consider when specifying a complete latching system.

They say that 'the whole is greater than the sum of its parts' but is that always true? In any mechanical system, the best components will only deliver optimum performance if they are designed to work together and are properly connected - and nowhere is this better exemplified than in rotary latching systems.

Rotary latching systems are well established across a variety of different industries as an effective and reliable means of remotely opening interior and exterior doors, compartments, hoods and boots - combining security with push-to-close convenience. Typically, a rotary latch system comprises three main elements:

  • the rotary latch itself
  • the actuator (the interface with the end user)
  • the cable that connects these two components

One of the most common everyday uses for a rotary system is to remotely open the bonnet of a vehicle. In this application a mechanical lever (the actuator) is activated from the driver's seat, and the lever is connected (via a routed cable) to the latch (the rotary) that secures the bonnet. By pulling the lever, the rotary latch is triggered, allowing the bonnet to open remotely.

What ultimately governs the effective and reliable operation, maintenance requirements and end user satisfaction of the whole system is the level of compatibility between these three elements. Any compromise made in that matter will ultimately result in poor performance of the latch system. Therefore, with a multitude of options available, whenever possible, the design engineer should choose all latch elements from a proven supplier.

Latching the system

When specifying a rotary system, choosing the appropriate rotary latch is crucial because it acts as the heart of the system. The primary deciding factor in any application should be based on the size or strength of the latch required. For example, a stronger latch may be required to open doors on a large piece of off-highway equipment, whereas a light-duty, compact latch would be better suited for opening hidden storage compartments on a luxury yacht.

Another important design consideration is choosing between single or two-stage latching. Two-stage latching, for instance, is recommended if greater insurance against the possibility of 'false' latching is required, and prevents the possibility of a door accidentally opening or not completely closing. The best example of this feature is a vehicle door; if not completely shut, it stays latched, but a secondary effort is still required to shut the door completely.

There are a variety of latch options available that offer differing performance attributes. The choice will always to some extent be determined by whether the latch will be used on a rigid or a flexible panel; beyond that, some systems offer multiple triggering options, allowing the rotary latch to be easily configurable without having to change the overall design of the application.

Another important feature to consider when choosing a rotary latch is whether a single or double rotor is required. A majority of rotary latches are single-rotor devices, with only one rotor engaging the striker. Double rotor latches, however, tolerate misalignment and offer even greater strength than their single rotor counterparts, allowing them to withstand higher working loads. In addition, rotary latches are available with an integrated bumper that eliminates noise and vibration caused by normal operation by trapping the striker between a rubber bumper and rotor.

Actuating the system

As the only visible part of the mechanism, actuators serve as a 'touch point' or interface between end users and the latching mechanism itself. While functionality is undeniably important, the overall 'feel' of the actuator can create a powerful impression on end users. Depending on the needs of the application, the actuator can also provide enhanced strength and security, as well as improved industrial design.

Selecting the appropriate actuator generally depends on whether the actuation will take place on the interior or exterior of the application. For interior applications, finger pull/paddle actuators or pushbutton actuators are most commonly used as they provide a flush surface. Economical actuators such as a simple T-handle may also be chosen, which offer an equal level of direct force. With regard to material choice, a broad variety of options including moulded plastic, die cast zinc and cast aluminium are available. Plastic will provide the economical choice, but zinc or aluminium may be preferred due to strength considerations and the perceived quality of a metal product.

For exterior actuation, additional specification considerations come into play such as the desired level of security, the need for a larger design to accommodate gloved hand actuation, and available corrosion-resistant materials. The choice of product remains broad though, ranging from flush, surface-mount and push handles to push buttons. The ability to include multiple key code options is almost universally available across the range of actuators.

For enhanced access security in applications that are highly prone to theft or vandalism, such as construction equipment left overnight on a job site, an electromechanical access latch, such as a key fob connected to an internal electronic actuator, may be specified. The main advantage provided by electromechanical latches is the ability to control and monitor user credentials remotely, by generating a digital record of access that can then be used to demonstrate compliance with industry-accredited associations, such as CESAR in the United Kingdom.

Connecting the system

Once the rotary latch and actuator have been chosen, their operational effectiveness will only ever be as successful as the cable selected to connect them. Issues can occur in situations where the engineer specifies individual actuators and latches and then pieces them together without considering whether they will actually work together. To ensure the success of the application, designing a rotary latching system with the assistance of a supplier offering all three elements is paramount.

The role of the cable is to transfer the mechanical input from the operator via the actuator to the rotary latch to enable it to open as quickly and safely as possible. Engineers generally face a choice between bare and coated cables - generally used in 'line of sight' applications - and jacketed cables that offer the ability to route a cable through the application (around corners), greater protection and ease of assembly into the customer's application. The main cable should ideally be stainless steel, which combines corrosion resistance with strength and minimal stretch even after thousands of cycles. An acetal liner will ensure the cable runs smoothly, while a polypropylene 'jacket' will protect the cable from damage and enable it to turn through a bulkhead or via a curve.

Many manufacturers offer a range of cable end fittings - barrel, 'L', 'Z', eyelet, ball fitting and bare cable are among the most common. Suppliers that offer a complete rotary system will help to determine which type of end fitting is required for both the actuator and the latch to help guarantee the correct cable selection for the task, ensuring long-term compatibility, smooth and ergonomic operation and minimal maintenance.

Conclusion

The components chosen for remote latching systems play a decisive role in enhancing the overall quality of a latching system. To ensure maximum functionality and reliability, care must be taken in selecting an appropriate latch mechanism based on the specific requirements of the application. A tactilely pleasing actuator that also performs on a functional level creates a powerful perception of quality and improves user experience. Finally, a high-quality cable is vital to connecting the latch and actuator for a complete system. By selecting a complete system of actuator, latch and cable from a recognised supplier, engineers can be assured that the entire system - as well as the individual components - has undergone extensive testing to meet and even exceed industry standards.

For further information about rotary latching systems go to www.southco.com.

Southco Europe Ltd

Touch Point, Wainwright Road
Warndon
Worcester
WR4 9FA
UNITED KINGDOM

+44 (0)1905 346722

info@southco.com

www.southco.com

More from Southco Europe Ltd

New compact display arm offers greater freedoms

Posted 1 week ago

New rotary latch actuator from Southco

Posted 3 weeks ago

Southco launches new branding

Posted 2 years ago

Southco earns UL Recognition Certification FTTA2/FTTA8

Posted 2 years ago

Southco expands Europe manufacturing operations into Poland

Posted 2 years ago

New low-profile captive screws with custom colour option

Posted 2 years ago

Five ways to future-proof industrial products

Posted 3 years ago

Engineered latching for enhanced usability

Posted 3 years ago

Padlockable compression latch with ergonomic T-handle

Posted 3 years ago

Cable splitter provides flexibility of actuation points

Posted 3 years ago

Padlockable compression latch with ergonomic T-handle

Posted 3 years ago

Tips for specifying stainless steel hinges

Posted 3 years ago

New counterbalance system supports heavy doors and covers

Posted 3 years ago

Captive quarter-turn fastener for vibration-resistant access

Posted 3 years ago

New shutter cam latch designed to prevent accidental opening

Posted 3 years ago

Microprocessor-controlled R4-EM 9 series electronic rotary latch

Posted 4 years ago

Southco's 4C Wing Knob Captive Screw offers tool-free access

Posted 4 years ago

A balancing act: the benefits of using counterbalance technology

Posted 4 years ago

Southco's torque hinge technology for EvoBus headrests

Posted 4 years ago

Aluminium compression latch provides adjustable grip

Posted 4 years ago

Southco acquires Counterbalance Corporation

Posted 4 years ago

Compact rotary latch series features dual trigger actuation

Posted 4 years ago

Corrosion-resistant all-plastic cam latch meets NEMA 4 and IP65

Posted 5 years ago

Southco launches new product handbook for 2015

Posted 5 years ago

Detent hinge has improved corrosion resistance and cycle life

Posted 5 years ago

Southco introduces new spring-loaded concealed pull handle

Posted 5 years ago

New sealed lever latch from Southco meets door IP ratings

Posted 5 years ago

Electronic access control: physically securing medical equipment

Posted 5 years ago

Southco continues to develop DZUS quarter-turn fastener range

Posted 5 years ago

Southco expands entry door systems with non-locking actuators

Posted 6 years ago

Compact two-stage rotary latch prevents false latching

Posted 6 years ago

Tilt display mount with non-counterbalanced torque option

Posted 6 years ago

Advancing electronic access in off-highway equipment

Posted 6 years ago

Southco helps to secure self-service postal system

Posted 6 years ago

Rugged compact tilt and swivel mount for smaller displays

Posted 6 years ago

Aluminium compression latch complies with EU fire standard

Posted 6 years ago

Southco provides robust access for Liebherr Cranes

Posted 6 years ago

Sealed, corrosion-resistant electronic rotary latch for outdoors

Posted 7 years ago

Lockable flush handle installs quickly and improves security

Posted 7 years ago

Lightweight hinge delivers double the torque to hold heavy doors

Posted 7 years ago

Flexible arm for medical workstations

Posted 7 years ago

Atos chooses Southco's access systems for datacentre security

Posted 7 years ago

Stainless steel version of DZUS Panex quarter-turn fastener

Posted 7 years ago

Enhanced lever latches deliver better performance

Posted 7 years ago

Southco acquires Unikey Industrial Components

Posted 7 years ago

Southco launches new website with improved navigation

Posted 7 years ago

Southco ensures safe and secure deliveries at parcel lockers

Posted 7 years ago

Southco helps Gidophone secure mobile charging stations

Posted 7 years ago

Medical equipment ergonomics vital in healthcare sector

Posted 8 years ago

Electronic locking swinghandle accepts HID proximity cards

Posted 8 years ago

RF remote control for wireless actuation of electronic locks

Posted 8 years ago

USB controller allows independent control of multiple devices

Posted 8 years ago

Complete rotary latch system offers off-highway security

Posted 8 years ago

Southco offers standard and customised cam latches

Posted 9 years ago

New Membrane Keypad Access Controller suits industrial equipment

Posted 9 years ago

Southco recognised for environmental achievements

Posted 9 years ago

Fasteners and hinges aid compliance with Machinery Directive

Posted 9 years ago

Southco launches E5 push-to-close cam latches

Posted 9 years ago

Wireless remote locking benefits industrial equipment

Posted 10 years ago

Latch can be locked/unlocked using electronic devices

Posted 11 years ago

Lift-and-turn compression latch suits large, heavy panels

Posted 11 years ago

Free guide to positioning technology

Posted 12 years ago

New catalogue for quick-access and retained fasteners

Posted 12 years ago

Fasteners for fixed guards - for the new Machinery Directive

Posted 12 years ago

New inject/eject mechanisms for CompactPCI boards

Posted 12 years ago

Compact push-to-close latches in stainless steel

Posted 12 years ago

Guide to the New Machinery Directive

Posted 12 years ago

Guide to the New Machinery Directive

Posted 12 years ago

Easy way to add electronic security to enclosures

Posted 13 years ago

Swing handle latch offers greater versatility

Posted 13 years ago

More technical articles
2 days ago
Automatic bearing lubrication brings ore inspiring results in mining
By installing automatic lubricators for bearings on its conveyor drive motors and belt pulleys, an opencast mine in Hungary has seen a range of benefits, including the prevention of unplanned downtime, longer bearing life and reduced repair work
2 days ago
Kinoulton company conveys COVID-combating masks
Here's a great example of the germ of an idea resulting in the combating of COVID
2 days ago
FLIR Systems announces four new Exx-Series handheld thermal imaging cameras
New E96, E86, E76 and E54 models feature enhanced thermal resolution and provide on-camera routing capability for more efficient inspections
3 days ago
New C-Mount lenses bring focus for machine and system builders
IDS now offers more than 20 new C-mount lenses with resolutions of 5, 8 and 10 MP as well as different focal lengths and optical classes
3 days ago
Backup DC motor for two rolling mill applications
Menzel Elektromotoren has built a replica of an old DC motor for a large German steel strip manufacturer
3 days ago
Distributed safety systems webinar 30th October 0930
In this webinar Pilz UK Product Manager David Collier will examine the state-of-the-art technology available to meet the demands of decentralisation
3 days ago
New narrow FeedThrough connectors save panel space
New from Cliff Electronics is the SLIMS FeedThrough Connector range, designed and manufactured in the UK
4 days ago
New autoglide 5 system from igus doesn’t need a guide trough
A new energy chain system for intralogistics and crane systems has been designed by motion plastics experts igus
4 days ago
New DC/AC converter unveiled by Phoenix Contact
With the arrival of its new DC/AC inverter (part of the Phoenix Contact Quint Power family) the company says that machine builders now have a compact solution to generate alternating current in DC applications
4 days ago
New-generation bullet train runs on NSK bearings
High-performance bearings from NSK are now operational in the newly developed N700S Shinkansen (bullet train)