A gate latch is a locking mechanism that is used to secure gates on fences or stakes on truck beds using a metal bar and lever that is raised to open the latch and lowered to close it. Although they do not have...
This article is a thorough examination of rotary latches and their use.
You will learn:
A rotary latch is a locking mechanism that secures openings such as doors, enclosures, cabinets, and panels so that they are locked and unable to accidentally open. They are referred to as slam latches since they lock in place by being pushed against the striker. The basic design of a rotary latch includes a housing, jaw, lever, and spring with the housing used to hold the components of the latch and to mount it. Rotary latches are part of a broader group of latches referred to as slam latches due the need to slam a door or lid to engage the latch.
Although there are several forms of rotary latches, the basic types are double, single, and one and two stage rotary latches with a single rotary latch having a single rotating element while double rotary latches have two rotating elements. A two-stage rotary latch secures in place in two stages or actions. An actuator is attached to a rotary latch by a rod or cable and is used to disengage the latch and release it such that a door or panel can be opened.
Rotary latch systems are easy to install and have been used for decades to secure car doors, storage trunks, and the doors of bulky heavy equipment. The exceptional holding power of rotary latches is unaffected by vibrations, stress, or harsh conditions. The popularity of rotary latch systems is due to how easy they are to operate. While other latch systems require multiple steps to disengage them, rotary latch systems can be disengaged by the touch of a button that releases the latch and opens an enclosure.
The basic function of a rotary latch is relatively simple since they are designed to secure and hold an opening closed. The selection of the right size and strength of a rotary latch can be critical to the operation of a mechanical system and intended application. To determine the correct rotary latch for an application, it is necessary to have an understanding of the various types regarding their function, strength, and viability.
The general groupings of rotary latches are single, double, and one and two stage latches. From these general categories, rotary latches divide into more specific types in regard to materials, actuators, workloads, and other parameters to assist in the selection of the right rotary latch for an application.
Every rotary latch provides a variety of latch options that determine its performance and viability. The initial consideration for selecting a rotary latch is decided by the type of opening and whether it is rigid or flexible. More complicated and intricate systems can have several triggering options that require adjustment and adaptations to fit the latch into the total system.
A single stage rotary latch has a single rotor that can be installed for right- or left-hand closing. It has one rotor that engages with the striker. Single stage rotary latches are the simplest form of rotary latch and are designed for light to medium applications. Regardless of its simple design, single stage rotary latches come with a variety of trip levers and mounting axles. They are carefully matched with a door of the proper weight for optimum performance.
One of the main reasons for the use of single stage rotary latches is their compact design, which gives them flexibility. In most cases, single stage rotary latches have multiple actuation points that allow for stacked actuator levers that makes the latches the most configurable of all forms of rotary latches.
Two stage rotary latches are designed for heavy workloads and are commonly used in car doors. They come with built-in bumpers that trap the striker between rubber bumpers and the rotor, which eliminates noise and vibrations during the latch’s operation. Two stage rotary latches are similar to single stage latches in their appearance but differ in how they attach to the striker.
The use of two stage rotary latches is due their ability to provide increased security with their secondary latching position. This aspect of their operation prevents false latching and their ability to tolerate misalignments. As with single stage rotary latches, two stage rotary latches can have multiple actuator points, which provides designers with several options.
The design of two stage rotary latches has one rotor that attaches to the striker. Like single stage rotary latches, single rotor rotary latches are used for light to medium loads regardless if they are one or two stage latches. The single rotor gives them a compact design capable of fitting into any space even if they have multiple actuators. They are limited by the thickness and weight of the door to which they can be attached.
Double rotor rotary latches further increase the strength of rotary latches and can tolerate a higher level of misalignment. Additionally, they are designed for extremely high workloads with two single rotors that gives them a wider catch opening, which is the reason for their increased tolerance of misalignments. Double rotor rotary latches are designed for medium to heavy duty use and linkage that allows for direct handle actuation. As with all forms of rotary latches, double rotor rotary latches allow for left- or right-hand mounting and push or remote release.
A pawl rotary latch is similar to a two stage rotary latch but has a rotating cam that turns to the latch and unlatch positions. The cam mechanism is arranged to catch the striker. At the first engagement, the pawl turns a quarter turn to grasp the striker. As the striker moves toward the latch body, the pawl turns another quarter turn to pull the striker into the latch body. A pawl latch allows movement in one direction and prevents return motion. They are used in combination with a ratchet wheel.
The different types of pawl latches include fixed grip latches and adjustable grip latches. Fixed grip latches are designed to fit any door frame and rotate to compress the latch against the door frame. Adjustable grip pawl latches engage the door frame or keeper as the handle rotates. They have a long shaft or bolt that separates the handle from the cam. The grip length can be adjusted to fit the dimensions of the door frame.
The wide use of rotary latches is due to their long useful life and their strength, durability, and exceptional performance in all conditions. They are used as a locking mechanism for cabinets, panels, doors, enclosures, and cages. The parts of a rotary latch include one or more actuators, a housing, rotor or rotors, lever, and spring with a rotary latch system being composed of the actuator, connector, and the rotary latch.
The latch of a rotary latch system is the heart of the system with the strength of a rotary latch system determined by the size and strength of the latch. There is an extensive selection of latches with ones capable of fitting the needs of any application. The choice of a one or two stage latch is dependent on how secure the rotary latch system has to be with two stage latches being more secure and capable of preventing accidental opening of secured doors.
A key part of a rotary latch is the rotor with most rotary latches having one rotor to engage the striker. Although single rotor latches are the more common form of rotary latch, double rotor latches are more forgiving in regard to misalignments and have far greater strength than single rotor latches. They are an essential part of the selection process when configuring a rotary latch system.
The actuator for a rotary latch system can come in a wide variety of forms, configurations, and mechanisms and are the only visible part of a rotary latch system. Actuators serve as the interface between the user and the latching mechanism. In addition to being the release mechanism for the rotary latch, the proper actuator can enhance the strength and security of the system.
The choice of an actuator begins by determining if it will be on the inside or outside of the application. Interior actuators are finger pull or push button and are used because they can be placed flush to the surface of the opening. Included as part of the large number choices for actuators are the types of materials used to produce them with materials varying between plastics and zinc or aluminum.
As with interior actuators, the choice of exterior actuators is very broad and includes a wide array of sizes, shapes, and designs. Exterior actuators can be flush mounted, surface mounted, push handles, or push buttons. In addition, keys or key codes are also possible. Cables are used for mechanical input to activate the actuator and allow for speedy and convenient entry. Although cables are a common form used for transferring mechanical energy, rods are also used as an alternative.
Cables for actuators are normally coated to improve their appearance and protect them. The materials used to produce cables are resilient and made of material that is resistant to the effects of weather conditions. A cable can be put through thousands of cycles, which necessitates that they be resistant to stretching or deformation. Liners designed for actuator cables allow the cable to flex and move without enduring wear during their many cycles.
In conditions where high security is required, an electromechanical actuator can be used that makes it possible to remotely release the rotary latch and monitor who is actuating the locking system.
As with the many forms of actuators there are just as many end fittings for cable connections and can be connected to the latch in several different styles. The range of cable end fittings offered by manufacturers include barrels, L, Z, eyelet, ball, and bare cale. The choice of end fitting is determined by how well it fits the needs of the application. Barrel fittings are general purpose fittings that can connect to any actuator, while L fittings are designed for the needs of rotary latches exclusively. They are installed with a retaining clip to prevent metal to metal contact.
The striker for a rotary latch is the part of the system that attaches to the rotary latch and is connected to the door or opening. They are in the form of a short rod or shaft or have a U shape like a U-shaped bracket. Strikers are made of highly durable material in order to withstand the multiple cycles of opening and closing of a door. As an opening closes, the striker makes contact with the rotor or rotors of the latch that encircle the striker as the opening closes. It is held firmly by the rotors and the locking mechanism.
The striker must fit firmly into the rotor and rotary latch such that the opening does not shift or have any potential for being jostled open. Regardless of the simplicity of the striker, it is one of the most critical aspects of a rotary latch system since it secures an opening to prevent ingress. Strikers are normally made of steel, stainless steel, or other hardened metals to ensure their strength and resilience.
The strength, longevity, and durability of a rotary latch depends on the types of materials used to produce them. The factors that determine the choice of metals is in regard to how the rotary latch will be used with critical and high security latches requiring the use of hardened metals while rotary latches that have to endure less stress can be made of softer and less durable metals.
The metals used to produce rotary latches are carbon steel, alloy steel, stainless steel, aluminum alloys, and copper alloys, which are chosen for their formability, machinability, and strength. Once a latch has been formed, it may be subjected to secondary processes such as polishing or the addition of a coating to enhance its appearance. The types of coatings are chosen in accordance with the anticipated cycles the latch may have to endure.
The choice of aluminum for the manufacture of rotary latches is due to aluminum’s many positive properties that protect the metal from impact, moisture, and the effects of corrosion. The alloys chosen to produce latches are from the 6000 series of aluminum, which are strong alloys capable of withstanding constant use. Although the softer alloys may have a more pleasing appearance, they do not have sufficient strength to keep a latch secure. Aluminum is an ideal metal because it is easy to cast, forge, shape, and mold into some of the intricate shapes of rotary latches.
Brass has been used for many years as a material for the production and manufacture of latches. Due to the rise of other metals that are more durable, brass has been used less frequently in recent years. As a copper and zinc alloy, brass is castable, moldable, and strong. Its appearance may deteriorate over years and need regular cleanings. Regardless of its drawbacks, it can be found in certain parts of the world as a decorative and strong metal for the manufacture of rotary latches.
Bronze latches are used for multiple environments due to bronze’s high content of copper and tin. It is one of the more expensive metals used for the manufacture of latches and has an excellent appearance. The copper content of bronze makes it moldable and castable to produce harder and more durable latches capable of enduring multiple cycles.
Carbon steel is the toughest, strongest, and most durable of the metals used to produce rotary latches. Although it is difficult to work with, it is one of the least expensive of the metals used for latch manufacturing and is commonly forged or cast to achieve the proper shape. Carbon steel rotary latches are used for more stressful conditions that require multiple cycles of opening and closing. Due to its susceptibility to rusting and corrosion, carbon steel rotary latches are normally produced with a coating, metal plating, or painted.
Stainless steel is one of the more popular metals used for the manufacture of rotary latches due to its cost and protective coating that gives it exceptional appearance and longevity. As with carbon steel, stainless steel can be formed by casting and forging but can also be molded and stamped from sheets. It is more workable than carbon steel but has comparable strength. The appearance of stainless steel makes it ideal for residential and industrial use. Users choose stainless steel rotary latches over other materials due to the longevity of stainless steel compared to aluminum and carbon steel.
The various manufacturing methods used to produce latches place stress on the metal. In order to enhance the appearance of rotary latches, they are subjected to various finishing methods that remove marks, scratches, or other deformities from the surface of a latch. The methods used to improve the appearance and surface of rotary latches are painting, polishing, powder coating, and plating.
Aside from improving the appearance of a latch, the different processes provide a protective layer to prevent rust, corrosion, wear, and damage from impacts.
The most common methods used to fabricate latches are die casting, stamping, and forging, which are methods that form and shape metals into the parts for latches. In most cases, once the plates, discs, and sheets have been formed into the various components of a latch, they are assembled using various methods including spot welding or screwing the pieces together. Regardless of the resilience of the material used to produce a rotary latch, its assembly is critical since any loose or poorly connected component can lead to the failure of a latch.
Stamping involves the use of several different processes. Many of the components used for the assembly of latches are produced by stamping, which involves blanking, punching, embossing, and die stamping of sheets of metal. The shaping of latch parts by stamping includes the deformation of the metal material by force such that it takes on the required shape. The popularity of stamping is due to how quickly the process can be completed and the volume of parts that can be completed in a single run.
Most of the metals used to produce rotary latches are able to be stamped and include stainless steel, steel alloys, aluminum, brass, and copper alloys. In addition to stamping being highly productive, it produces very tight tolerances, which is a necessity for the assembly of latches since they have to be produced very accurately to fit into small spaces.
The forging process is similar to stamping in that a metal disc, sheet, or plate is formed using force and hammering. The three methods of forging are open die, closed die, and upset and include hot forging and cold working. In all cases, several pounds of pressure are applied multiple times to form and shape the parts of a rotary latch. Forging improves the strength of parts by changing their grain structure. Latch parts that are produced by forging normally require some form of secondary finishing due to the waste or flash that is connected to parts after being shaped.
As with stamping, forging produces exceptional tolerances that are within an acceptable range. The process is used to manufacture nearly every component of a rotary latch including the striker. Forging can require multiple passes of a piece through a forge in order to achieve the proper shape. Aside from the need to trim completed parts as part of secondary processing, additional adjustments can include the adding of holes, bending, and cutting of shapes into the workpiece.
Stamping and forging are forms of cold working processes that pound, hammer, and force metal sheets and billets into a mold or specific shape. They are based on applying pressure to a workpiece in order to achieve a necessary shape. During stamping or forging, the workpiece is a solid form even though it may be heated to make shaping it easier. With casting, the metal is melted and poured into a mold or die.
Casting takes many forms and involves the use of permanent or temporary molds. Metal ingots, billets, or slabs are melted in a furnace and moved by a crucible to the mold where they are poured into the mold through a sprue or riser. Permanent molds come in two halves that are tightly fitted together while nonpermanent molds can take several forms such as sand, wax, or other materials.
Unlike stamping and forging, the mold for casting has to be designed to account for shrinkage that occurs during the cooling process. This is a critical part of the process since it influences the tolerance of the final part. The popularity of the casting process is its ability to produce latch parts with the most minute details and intricacies with shapes that perfectly match the design of the latch.
Regardless of which process is used to produce the components of a rotary latch, every part has to be put through secondary processing, which can include the addition of holes, smoothing of surfaces, bending, shaping, and configuring components to be able to efficiently fit together. Although the tolerances of parts may be exceptional, each part of a rotary latch has to fit precisely to ensure the strength and durability of the latch. Secondary processes are used to shape and form each piece such that they fit together. In many cases, welding and screws are used to connect and secure components.
For many years, rotary latches have been used in a wide range of applications from securing cupboards to ensuring car doors are tightly sealed. Their strength and dependability have made them an essential part of engineer designs. Rotary latches have been chosen for many applications due to their superior performance compared to cam latches and push to close latches.
Unlike other latches that require several actions to disengage them, rotary latches can be disengaged by the push of a button or the pulling of a switch. This particular aspect of their operation makes it possible to quickly enter an enclosure. In addition, the engagement of the locking mechanism of a rotary latch includes a simple push or slamming of a door or lid to tightly and securely close a door or opening.
One of the main reasons for the popularity of rotary latches is how securely they engage to prevent accidental entry. They can be designed without any visible means of entry, which prevents them from being susceptible to break ins or theft. The security of rotary latches is why they are preferred by auto manufacturers for the securing of compartments. Specialty rotary latches can be opened by an interior button or switch.
The long life of rotary latches decreases their cost and makes them an ideal locking mechanism. The simple structure of rotary latches makes it possible to install them in a wide array of applications. Their maintenance free design precludes any need to replace them during their useful life. Since materials used to manufacture rotary latches are exceptionally strong and durable, they are not susceptible to damage from wear and tear or external factors such as impacts, abrasions, or being pummeled. The sturdiness of rotary latches makes them ideal for indoor or outdoor use.
There is a rotary latch to fit any conditions or environment due to the wide selection of available rotary latches. Over the many years of their use, rotary latches have been configured, adapted, and engineered to fit any set of circumstances with custom made rotary latches being continually added as new and unique conditions arise. Rotary latch manufacturers work closely with their customers to ensure that customers get the exact latch to match their application and needs. The key to the use of rotary latches is their compact design, which makes it possible to fit them into any environment regardless of how stressful or harsh.
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