Latch

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Opening a captured draw bolt-style latch Offnen eines Riegels.gif
Opening a captured draw bolt-style 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 deadbolt latch is 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 latch bolt 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 latch bolt 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

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. [3]

Electronic cam lock

Electronic cam lock Electronic-cam-lock.jpg
Electronic cam lock

Electronic cam locks are an alternative to mechanical cam locks. The appearance of the electronic cam lock is similar to the mechanical cam lock, but it is different in the lock cylinder.

The keyhole of a mechanical cam lock is usually the same as an ordinary padlock. A physical key is used to unlock the lock. The physical key has a notch or slot corresponding to the obstacle in the cam lock, allowing it to rotate freely in the lock.

Different from mechanical cam locks, electronic cam locks use an electronic key to unlock. The key needs to be programmed which contains the user, unlocking date, and time period. The electronic cam lock has no mechanical keyhole, only three metal contacts are retained. [4] When unlocking, the three contacts on the head end of the electronic key are in contact with the three contacts on the electronic cam lock. At this time, the key will supply power to the electronic cam lock and read the ID number of the electronic cam lock for verification and match. If successful, the lock can be unlocked.

The emergence of electronic cam locks aims to improve the safety and functionality of traditional mechanical cam locks.

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.

Comparison of Suffolk and Norfolk latches. Latches Suffolk Norfolk.svg
Comparison of Suffolk and Norfolk latches.

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 in traditional homes and country cottages. 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). [5] Many of these plates found their way into America and other parts of the world.

Norfolk latch

Norfolk latch, circa 1939 Henrietta S. Hukill, Norfolk Latch, c. 1939, NGA 29097.jpg
Norfolk latch, circa 1939

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. [6] 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.

Crossbar

A wooden crossbar on a door Asso, chiavistello porta Magnocavallo.JPG
A wooden crossbar on a door
An aldrop latch, a form of draw bolt Amizmiz, Old Shop Door.jpg
An aldrop latch, a form of draw bolt

A crossbar, sometimes called a bolt or draw bolt, is a historically common and simple means of barring a door. In its most primitive form it employs a plank or beam held by or placed onto open cleats on a door, which is shifted to be held fast by a corresponding cleat on an adjacent jamb.

A crossbar for double doors employs the same principle, but, in most cases, must be manually set in place and removed due to its width being greater than both doors.

A crossbar for a single jamb may be "captured" on the door by U-shaped bails, or anchored by a bolt on its inboard end and pivoted up and down into open cleats, making it a form of latch.

A "draw bolt" style closure adds a handle for sliding its bolt - the source of the term "bolting a door". A variant with a slot in the handle for dropping it over a hasp to secure it with a lock is known as an aldrop. Most modern draw bolts are made of metal, and may be used to secure a door from the outside or the in.

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 closed during a fire. To hold an often heavy fire door open simply, electromagnetic door holders are used that release when a building's fire alarm system is activated. As cabin hooks must be released 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. It is 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 butterfly knife 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. Butterfly knife 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

<span class="mw-page-title-main">Warded lock</span> Type of keyed 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.

<span class="mw-page-title-main">Pin tumbler lock</span> Lock mechanism

The pin tumbler lock, also known as the Yale lock after the inventor of the modern version, is a lock mechanism that uses pins of varying lengths to prevent the lock from opening without the correct key.

<span class="mw-page-title-main">Combination lock</span> Lock using symbols rather than a key

A combination lock is a type of locking device in which a sequence of symbols, usually numbers, is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed symbols which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Types range from inexpensive three-digit luggage locks to high-security safes. Unlike ordinary padlocks, combination locks do not use keys.

<span class="mw-page-title-main">Lock and key</span> Mechanical or electronic fastening device

A lock is a mechanical or electronic fastening device that is released by a physical object, by supplying secret information, by a combination thereof, or it may only be able to be opened from one side, such as a door chain.

<span class="mw-page-title-main">Deadbolt</span> Locking mechanism

A deadbolt or deadlock is a type of lock morticed into a wooden door where a bolt is thrown into the door frame, using a key from either side, to secure the door. It is distinct from a spring bolt lock because a deadbolt can only be opened by a key or handle. 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, as well as make the door more resistant to forced entry. A deadbolt is often used to complement a spring-bolt lock on an entry door to a building.

<span class="mw-page-title-main">Lever tumbler lock</span> Type of lock

A lever tumbler lock is a type of lock that uses a set of levers to prevent the bolt from moving in the lock. In the simplest form of these, lifting the tumbler above a certain height will allow the bolt to slide past.

<span class="mw-page-title-main">Mortise lock</span> Lock with mortise cut into doorjamb

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. The design is widely used in domestic properties of all vintages in Europe.

<span class="mw-page-title-main">Bored cylindrical lock</span>

A bored cylindrical lock is a lockset which is installed by boring two circular holes in the door. Door handles may also use the same installation.

<span class="mw-page-title-main">Crash bar</span> Door opening mechanism

A crash bar is a type of door opening mechanism which allows users to open a door by pushing a bar. While originally conceived as a way to prevent crowd crushing in an emergency, crash bars are now used as the primary door opening mechanism in many commercial buildings.

<span class="mw-page-title-main">Door furniture</span> Items that are attached to a door or a drawer to enhance its functionality or appearance

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.

<span class="mw-page-title-main">Door handle</span> Device to open or close door

A door handle or doorknob is a handle used to open or close a door. Door handles can be found on all types of doors including exterior doors of residential and commercial buildings, internal doors, cupboard doors and vehicle doors. There are many designs of door handle, depending on the appropriate use. A large number of handles, particularly for commercial and residential doors, incorporate latching or locking mechanisms or are manufactured to fit to standardised door locking or latching mechanisms.

<span class="mw-page-title-main">Breechblock</span> Part of the firearm action

A breechblock is the part of the firearm action that closes the breech of a breech loading weapon before or at the moment of firing. It seals the breech and contains the pressure generated by the ignited propellant. Retracting the breechblock allows the chamber to be loaded with a cartridge.

<span class="mw-page-title-main">Padlock</span> Portable locks with a shackle that may be passed through an opening

Padlocks are portable locks usually with a shackle that may be passed through an opening to prevent use, theft, vandalism or harm.

<span class="mw-page-title-main">Electronic lock</span> 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.

<span class="mw-page-title-main">Electric strike</span> Door locking hardware whose mechanism is electromechanical

An electric strike is an access control device used for door frames. It replaces the fixed strike faceplate often used with a latch. Like a fixed strike plate, it normally presents a ramped or beveled 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 pull/push the door to open it 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.

<span class="mw-page-title-main">Break action</span> Type of firearm action

Break action is a type of firearm action in which the barrel(s) 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-barreled shotguns, double-barreled rifles, combination guns, and are commonly found in single shot pistols, rifles, shotguns, including 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.

<span class="mw-page-title-main">Door security</span> Methods to prevent unwanted entry

The term door security or door security gate 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.

<span class="mw-page-title-main">Electromagnetic lock</span> Door locking device

An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate.

<span class="mw-page-title-main">Lockset</span>

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, latch bolt, 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.

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. Latch bolt definition at Answers.com Archived 2011-06-28 at the Wayback Machine
  3. "Cam latch". McMaster-Carr. Retrieved 2008-10-17.[ permanent dead link ]
  4. ,"Passive electronic lock and key",issued 2013-05-15
  5. Article on Suffolk Latches Archived 2015-01-20 at the Wayback Machine
  6. "Suffolk Latches". Hand Forged Traditional Ironmongery. 17 June 2007. Archived from the original on 19 February 2012.
  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: "Topeak® Cycling Accessories — Products - ALiEN™ DX". Archived from the original on 2008-12-22. Retrieved 2009-01-01. (viewed 1 January 2009)