Latch

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Window latch Fonsterhake.jpg
Window latch
Door latch Latch lock.jpg
Door latch
Opening a latch Offnen eines Riegels.gif
Opening a latch

A latch or catch (called sneck in Northern England and Scotland) is a type of mechanical fastener that joins two (or more) objects or surfaces while allowing for their regular separation. A latch typically engages another piece of hardware on the other mounting surface. Depending upon the type and design of the latch, this engaged bit of hardware may be known as a keeper or strike.

Contents

A latch is not the same as the locking mechanism of a door or window, although often they are found together in the same product.

Latches range in complexity from flexible one-piece flat springs of metal or plastic, such as are used to keep blow molded plastic power tool cases closed, to multi-point cammed latches used to keep large doors closed.

Common types

Deadbolt latch

A single-throw bolt. The bolt can be engaged in its strike plate only after the door is closed. The locking mechanism typically prevents the bolt from being retracted by force.

Spring latches

Knob has crescent-shaped bar which pulls back latchbolt when turned. Version on upper right has a lock; version on upper left does not. Kwikset uses this shape. Other companies have square or D-shaped bars. Spring latch.jpg
Knob has crescent-shaped bar which pulls back latchbolt when turned. Version on upper right has a lock; version on upper left does not. Kwikset uses this shape. Other companies have square or D-shaped bars.

Slam latch

A slam latch uses a spring and is activated by the shutting or slamming of a door. Like all latches, a slam latch is a mechanism to hold a door closed. The slam latch derives its name from its ability to slam doors and drawers shut without damaging the latch. A slam latch is rugged and ideal for industrial, agricultural and construction applications.

Cam lock

The base portion of a cam lock Cam lock-base.png
The base portion of a cam lock
Offset cam Cam lock-offset cam.png
Offset cam

A cam lock is a type of latch consisting of a base and a cam. The base is where the key or tool is used to rotate the cam, which is what does the latching. Cams can be straight or offset; offset cams are reversible. Commonly found on garage cabinets, file cabinets, tool chests, and other locations where privacy and security is needed. [4]

Norfolk latch

A Norfolk latch is a type of latch incorporating a simple thumb-actuated lever and commonly used to hold wooden gates and doors closed. In a Norfolk latch, the handle is fitted to a backplate independently of the thumb piece. [5] Introduced around 1800–1820, Norfolk latches, originating in the English county of the same name, differ from the older Suffolk latch, which lacked a back plate to which the thumbpiece is attached.

Suffolk latch

A Suffolk latch is a type of latch incorporating a simple thumb-actuated lever and commonly used to hold wooden gates and doors closed.

The Suffolk latch originated in the English county of Suffolk in the 16th century and stayed in common use until the 19th century. They have recently come back into favour, particularly on garden gates and sheds. They were common from the 17th century to around 1825, and their lack of a back plate made them different from the later, and neighbouring Norfolk latch (introduced 1800–1820). Both the Suffolk latch and Norfolk latch are thought to have been named by architectural draughtsman William Twopenny (1797-1873). [6] Many of these plates found their way into America and other parts of the world.

Crossbar

A crossbar on a door Asso, chiavistello porta Magnocavallo.JPG
A crossbar on a door

A crossbar, sometimes called a bolt, is a primitive fastener consisting simply of a post barring a door.

Crossbars were historically common, simple fasteners consisting simply of a plank or beam mounted to one side of a door by a set of cleats. The board could be slid past the frame to block the door. Alternatively, the bar can be a separate piece that is placed into open cleats or hooks, extending across the frame on both sides. The effect of this device is essentially the opposite of the crash bar in that its operation is to permit the door to be opened inward rather than outward. On a set of double doors, the same principle works, but needn't extend past the frame. The bar simply extends into another set of cleats on the other door such as to interfere with the door opening.

Cabin hook

A cabin hook latch Red latch.JPG
A cabin hook latch

A cabin hook is a hooked bar that engages into a staple. [7] [8] The bar is usually attached permanently to a ring or staple that is fixed with screws or nails to woodwork or a wall at the same level as the eye screw. The eye screw is usually screwed into the adjacent wall or onto the door itself. Used to hold a cupboard, door or gate open or shut. [9]

A cabin hook is used in many situations to hold a door open, like on ships to prevent doors from swinging and banging against other woodwork as the ship moves due to wave action. This usage spread also to other domains, where a door was required to be held open or a self-closing device is used to close the door.

Many buildings are built with fire-resistant doors to separate different parts of buildings and to allow people to be protected from fire and smoke. When using a cabin hook in such a situation, one should keep in mind that a fire-resistant door is an expensive and heavy item, and it only works as a fire door if it is always closed. To open the often heavy fire door easily, magnetic door holders are used that are released when the buildings electrical fire alarm system is activated by a fire. As cabin hooks must be activated manually, they are impractical for fire doors.

Toggle latch

Also named draw latch or draw catch. It has a claw or a loop that catches the strike plate (named catch plate in this case) when reaching a certain position. [10] [11]

Pawl

A pawl is a latch that will allow movement in one direction, but prevents return motion. Commonly used in combination with a ratchet wheel.

Applications

Architecture

A latch of some type is typically fitted to a door or window. [12]

Weaponry

Many types of weaponry incorporate latches with designs unique to the weapon.

Firearms

Firearms require specialized latches used during loading and firing of the weapon.

A break-action firearm is one whose barrels are hinged and a latch is operated to release the two parts of the weapon to expose the breech and allow loading and unloading of ammunition. It is then closed and re-latched prior to firing. A separate operation may be required for the cocking and latching-open of a hammer to fire the new round. Break open actions are universal in double-barrelled shotguns, double-barrelled rifles and combination guns, and are also common in single shot rifles, pistols, and shotguns, and can also be found in flare guns, grenade launchers, air guns and some older revolver designs.

Several latch designs have been used for loading revolvers. In a top-break revolver, the frame is hinged at the bottom front of the cylinder. The frame is in two parts, held together by a latch on the top rear of the cylinder. For a swing out cylinder, the cylinder is mounted on a pivot that is coaxial with the chambers, and the cylinder swings out and down. Some designs, such as the Ruger Super Redhawk or the Taurus Raging Bull, use a latches at the front and rear of the cylinder to provide a secure bond between cylinder and frame.

To fire a revolver, generally the hammer is first manually cocked and latched into place. The trigger, when pulled, releases the hammer, which fires the round in the chamber.

Knives

Various types of knives with folding or retractable blades rely on latches for their function. A switchblade uses an internal spring to produce the blade which is held in place by a button-activated latch. Likewise a ballistic knife uses a strong latch to restrain a powerful spring from firing the blade as a projectile until triggered by opening the latch. A gravity knife relies on a latch to hold the folding blade in an open position once released. A balisong uses a single latch to hold the folding blade both open and closed, depending on the position of the handles; by rotating 180 degrees the same latch can be used in either configuration. Balisong latches have numerous variations, including magnetic variants and some which can be opened via a spring when the handles are squeezed together.

Utility knives also often use a latch to hold a folding knife both open and closed. This allows it to be locked in orientation to the handle when in use, but also safely stowed otherwise. To open a knife of this type may require significantly more force than the weapons variety as an added safety feature. [13]

Other

Crossbows incorporate a type of latch to hold the drawn bowstring prior to firing.

Automobiles

Automobiles incorporate numerous special-purpose latches as components of the doors, hood/bonnet, trunk/boot door, seat belts, etc.

On passenger cars, a hood may be held down by a concealed latch. On race cars or cars with aftermarket hoods (that do not use the factory latch system) the hood may be held down by hood pins.

The term Nader bolt is a nickname for the bolt on vehicles that allows a hinged door to remain safely latched and closed. It is named after consumer rights advocate and politician Ralph Nader, who in 1965 released the book Unsafe at Any Speed which claimed that American cars were fundamentally flawed with respect to operator safety.

Latches in seatbelts typically fasten the belt which constrains the occupant to the body of the car. Particularly in rear seats slightly different latches may be used for each seat in order to prevent adjacent seatbelts from being attached to the wrong point. Inertial seatbelt release is a potential circumstance where, in a collision, the seatbelt latch can unintentionally come loose leading to potential injury of the passenger. An additional risk of seatbelt latches is that in some cases the occupant may believe the latch is secure (e.g., by hearing a characteristic click) when in fact it is not.

A parking pawl is a device that latches the transmission on automatic vehicles when put in park.

Bakeware

Close-up of springform pan SpringformPanSpring.jpg
Close-up of springform pan

A spring latch (in this case an over-center-latch) is used to hold the walls of a springform pan in place.

See also

Related Research Articles

Knife Tool with a cutting edge or blade

A knife is a tool with a cutting edge or blade attached to a handle. Mankind's first tool, knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. Originally made of rock, bone, flint, and obsidian, over the centuries, in step with improvements in metallurgy or manufacture, knife blades have been made from bronze, copper, iron, steel, ceramics, and titanium. Most modern knives have either fixed or folding blades; blade patterns and styles vary by maker and country of origin.

Warded lock type of key lock

A warded lock is a type of lock that uses a set of obstructions, or wards, to prevent the lock from opening unless the correct key is inserted. The correct key has notches or slots corresponding to the obstructions in the lock, allowing it to rotate freely inside the lock.

Pin tumbler lock

The pin tumbler lock is a lock mechanism that uses pins of varying lengths to prevent the lock from opening without the correct key. Pin tumblers are most commonly employed in cylinder locks, but may also be found in tubular pin tumbler locks.

Dead bolt

A dead bolt, deadbolt or dead lock is a locking mechanism distinct from a spring bolt lock because a deadbolt cannot be moved to the open position except by rotating the key. The more common spring bolt lock uses a spring to hold the bolt in place, allowing retraction by applying force to the bolt itself. A deadbolt can therefore make a door more resistant to entry without the correct key.

Mortise lock

A mortise lock is a lock that requires a pocket—the mortise—to be cut into the edge of the door or piece of furniture into which the lock is to be fitted. In most parts of the world, mortise locks are found on older buildings constructed before the advent of bored cylindrical locks, but they have recently become more common in commercial and upmarket residential construction in the United States. They are widely used in domestic properties of all ages in Europe.

Door furniture any of the items that are attached to a door or a drawer

Door furniture or door hardware refers to any of the items that are attached to a door or a drawer to enhance its functionality or appearance.

Door handle attached device used to open or close a door

The traditional door knob has a bolt or spindle running through it that sits just above a cylinder, to which the spindle is connected. Turning the knob pulls the cylinder in the direction of the turn. The end of the cylinder is the "latch bolt", which protrudes into a space carved out of the door frame, and which prevents the door from being opened if the knob is not turned. A spring or similar mechanism causes the latch to return to its protruding state whenever the knob is not being turned. Escutcheon plates are the keyhole covers, usually circular, through which keys pass to enter the lock body. If the door handles have a square or rectangular plate on which the handle is mounted this is called the backplate. The backplate can be plain, pierced for keyholes, or pierced and fitted with turn knobs and releases. The plate on the front edge of the lock where the latch bolt protrudes is called the faceplate.

Breechblock part of the firearm action

A breechblock is the part of the firearm action that closes the breech of a weapon at the moment of firing.

Door closer Mechanical device that closes a door in a controlled manner

A door closer is defined as any mechanical device that closes a door in a controlled manner, preventing it from slamming, in general after someone opens it, or after it was automatically opened. The force used to open the door is stored in some type of spring and when released this energy is then utilised to return the door to a closed position. Door closers can be linked to a building’s fire alarm system. Where doors need to be held open for the majority of the time they are held back with an electromagnetic device. When the fire alarm is triggered it cuts power to the electromagnetic hold-open device allowing the doors to close. These hold-open devices can be separate from the door closer or part of its design.

United Airlines Flight 811 1989 aviation accident

United Airlines Flight 811 was a regularly scheduled airline flight from Los Angeles to Sydney, with intermediate stops at Honolulu and Auckland. On February 24, 1989, the Boeing 747–122 serving the flight experienced a cargo door failure in flight shortly after leaving Honolulu. The resulting explosive decompression blew out several rows of seats, resulting in the deaths of nine passengers. The aircraft returned to Honolulu, where it landed safely.

A lock bypass is a technique in lockpicking, of defeating a lock through unlatching the underlying locking mechanism without operating the lock at all. It is commonly used on devices such as combination locks, where there is no natural access for a tool to reach the locking mechanism. Because the mechanism itself is not being manipulated, this could technically not be considered lockpicking at all. However, it does fall under the repertoire of techniques used to open locks.

Jatimatic Finnish submachine gun

The Jatimatic is a Finnish 9 mm submachine gun developed in the late 1970s and early 1980s by Jali Timari. The submachine gun made its debut in 1983. The Jatimatic was manufactured in very limited numbers initially by Tampereen Asepaja Oy of Tampere and later—Oy Golden Gun Ltd. The firearm was designed primarily for police, security forces and armored vehicle crews. It was never adopted into service by the Finnish Defence Forces, although the later GG-95 PDW version was tested by the FDF in the 1990s; the conclusion of the tests was that the GG-95 was not suitable as a service weapon.

Electronic lock locking device which operates by means of electric current

An electronic lock is a locking device which operates by means of electric current. Electric locks are sometimes stand-alone with an electronic control assembly mounted directly to the lock. Electric locks may be connected to an access control system, the advantages of which include: key control, where keys can be added and removed without re-keying the lock cylinder; fine access control, where time and place are factors; and transaction logging, where activity is recorded. Electronic locks can also be remotely monitored and controlled, both to lock and to unlock.

Electric strike door hardware

An electric strike is an access control device used for doors. It replaces the fixed strike faceplate often used with a latchbar. Like a fixed strike, it normally presents a ramped surface to the locking latch allowing the door to close and latch just like a fixed strike would. However, an electric strike's ramped surface can, upon command, pivot out of the way when the lock on the door is in the locked position and the door is opened, allowing a user to open the door without operating the mechanical lock or using a mechanical key. After the door is opened past the keeper, the keeper returns to its standard position and re-locks when power is removed or applied, depending upon the strike's configuration.

Break action firearm action using a hinge to expose the breech

Break action is a type of firearm action in which the barrel or barrels are hinged much like a door and rotate perpendicularly to the bore axis to expose the breech and allow loading and unloading of cartridges. A separate operation may be required for the cocking of a hammer to fire the new round. There are many types of break-action firearms; break actions are universal in double-barrelled shotguns, double rifles and combination guns, and are also common in single shot rifles, pistols, and shotguns, and can also be found in flare guns, grenade launchers, air guns and some older revolver designs. They are also known as hinge-action, break-open, break-barrel, break-top, or, on old revolvers, top-break actions.

The term door security may refer to any of a range of measures used to strengthen doors against door breaching, ram-raiding and lock picking, and prevent crimes such as burglary and home invasions. Door security is used in commercial and government buildings, as well as in residential settings.

Lockset

A lockset is the hardware and components that make up the locking or latching mechanism that can usually be found on a door or other hinged object but can also include sliding doors and dividers. The components of a lockset can include the door handles, latchbolt, dead bolt, face plate, strike plate, escutcheon, thumbturn, push button, turn button, and other trim. The lockset and associated hardware typically defines a door's function and how a user could access the two adjacent spaces defined by the opening associated with the lockset.

Recoil operation is an operating mechanism used to implement locked-breech, autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action.

This is a glossary of locksmithing terms.

References

  1. "Basic Technical Fundamentals of Builders Hardware Mortise, Bored and Auxiliary Locks". Sargent Manufacturing Company, an ASSA ABLOY Group company. Archived from the original on 2012-09-07. Retrieved 2014-09-26.
  2. Note 'Latchbolt' label on Lockset diagram Archived 2011-05-31 at the Wayback Machine
  3. Latchbolt definition at Answers.com Archived 2011-06-28 at the Wayback Machine
  4. "Cam latch". McMaster-Carr. Retrieved 2008-10-17.
  5. "Suffolk Latches". Hand Forged Traditional Ironmongery. 17 June 2007. Archived from the original on 19 February 2012.
  6. Article on Suffolk Latches Archived 2015-01-20 at the Wayback Machine
  7. Porter, Brian; Christopher Tooke (2007). Carpentry and Joinery 3. Butterworth-Heinemann. p. 200. ISBN   978-0-7506-6505-6.
  8. interiordezine.com Archived 2008-10-15 at the Wayback Machine
  9. Beazley, Elisabeth (1990). Beazley's Design and Detail of the Space Between Buildings. Taylor & Francis. p. 230. ISBN   978-0-419-13620-0.
  10. catch-plate Archived 2017-10-08 at the Wayback Machine , wordnik.com
  11. What is the proper term for a latch that uses a loop and lever to draw things together? Archived 2017-10-09 at the Wayback Machine , diy.stackexchange.com
  12. Blanc, Alan (2014-10-29). Internal Components. Routledge. ISBN   9781317893950.
  13. For example, this bicycle multi-tool contains a knife with a safety latch: "Archived copy". Archived from the original on 2008-12-22. Retrieved 2009-01-01.CS1 maint: archived copy as title (link) (viewed 1 January 2009)