Compatibility in rotary latch sub-components

Typically, rotary latching systems comprise a rotary latch, actuator and connecting cable. What ultimately governs operational performance, maintenance requirements and user satisfaction is the compatibility between them. Any compromise will ultimately deliver poor performance. Therefore, whenever possible, the design engineer should choose all elements from a proven supplier.

The primary factor in latch selection should be the required size or strength. A stronger latch may be required to open doors on large off-highway equipment, whereas a light-duty, compact latch would be better suited for opening hidden storage compartments on a luxury yacht.

Another important consideration is choosing between single or two-stage latching. Two-stage latching is recommended if greater insurance against ‘false’ latching is required, and prevents the possibility of a door accidentally opening or not completely closing.

The choice of latch will to some extent be determined by whether it will be used on a rigid or a flexible panel; beyond that, some systems offer multiple triggering options, allowing easy latch configurability without changing overall application design.

Another important consideration is whether a single or double rotor is required. Most rotary latches are single-rotor, with only one rotor engaging the striker. Double-rotor latches, however, tolerate misalignment and offer even greater strength. Additionally, solutions are available with an integrated rubber bumper eliminating noise and vibration by trapping the striker between bumper and rotor.

Actuators

Actuators serve as a ‘touch point’ or interface between end users and the mechanism. While functionality is undeniably important, so is overall ‘feel’. Depending on application needs, they can also provide enhanced strength and security, and improved industrial design.

Actuator selection generally depends on whether actuation will occur on the application’s interior or exterior. For interior applications, finger pull/paddle actuators or push-button actuators provide a flush surface. Economical solutions such as a simple T-handle actuator may also be chosen, which offer an equal level of direct force. Various material options including plastic, zinc die cast and aluminium cast are available. Plastic will provide the economical choice, but zinc or aluminium may be preferred for strength considerations and perceived quality.

For exterior actuation, additional specification considerations come into play such as the desired security level, the need for a larger design to accommodate gloved hand actuation, and available corrosion-resistant materials. Product choice 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.

For enhanced access security in applications prone to theft or vandalism, an electromechanical access solution, like a key fob connected to an internal electronic actuator, may be specified. This can control and monitor user credentials remotely, generating a digital access record demonstrating compliance with industry-accredited associations.

Connecting the system

The latch and actuator’s operational effectiveness will only be as successful as the connecting cable. Issues can occur where the individual actuators and latches are specified and pieced together without considering compatibility. To ensure success, designing a system with assistance from a supplier offering all three elements is paramount.

The cable transfers the operator’s mechanical input to the latch enabling it to open quickly and safely. Engineers can generally choose between bare and coated cables – generally used in ‘line of sight’ applications – and jacketed cables which allow cable routing through the application (around corners), greater protection and ease of assembly. The main cable should ideally be stainless steel, combining corrosion resistance with strength and minimal stretch even after thousands of cycles. An acetal liner will ensure smooth cable running. A polypropylene ‘jacket’ protects the cable and enables it to turn through a bulkhead or via a curve.

Many manufacturers offer various cable end fittings. Those offering a complete rotary system will help determine which end fitting type is required for both actuator and latch to help guarantee correct cable selection, ensuring long-term compatibility, smooth, ergonomic operation and minimal maintenance.

To ensure maximum functionality and reliability, selecting a complete system of actuator, latch and cable from a recognised supplier, will ensure the entire system, as well as the individual components, has undergone extensive testing to meet and exceed industry standards.