A door handle or door knob is a mechanism 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. Door handles can be and have been made out of a wide variety of materials. Just a few examples include brass, white porcelain, brown mineral, cut glass, wood, and Victorian bronze.
Types
The most common and basic type of doors handle is the Lever latch door handle on a backplate found in residential houses and commercial and public buildings. Doors fitted with this handle have a latch that keeps the door shut. The door handle has only a lever handle which operates this latch. Pushing the handle down rotates the spindle, operating the tubular latch mechanism inside the door, allowing it to be opened. This type of door handle is used on interior doors that do not require to be locked. The lever latch handle is easy to install and use, and is available in a variety of styles and finishes.
The Lever lock door handle on a backplate is another type of door handle which operates similarly to the lever latch door handle. This type of handle on a backplate consists of a lever with a keyhole cut just below it. This allows a key to be inserted into the door to control a mortice sash lock. Just the like the lever latch, the door can be opened and shut by pushing the handle, but it can also be locked with a key. This locking mechanism is used on doors which can be opened by turning the handle if not locked, but can also be locked, requiring a key to open them.
The Lever Bathroom is typically used on bathroom doors as they can be locked and unlocked easily from the inside by turning the snib, but in an emergency can be opened from the outside by fitting a coin or similar object into a slot and rotating it. This lock is fitted with a mortice sash with the attached to a 5mm spindle which passes through the door.
The Lever Privacy is functionally similar to the Lever Bathroom in that it is locked by turning a snib on the inside and can be unlocked from the outside in emergencies. Unlike the Lever Bathroom, there is no mortice sash; locking is achieved by jamming the lever in a closed position.
Pull door handles or simply Pull handles are U-shaped, and are used especially in the kitchen but also for drawers. Usually made of stainless steel.
Usage
The location of the door handle along the horizontal axis on the door may vary between a few inches or centimeters away from the edge of the door to the exact center of the door, depending on local culture, decorative style or owner preference. The distance from the edge of the door to the center of the handle is called the backset. The location of the door handle along the vertical axis on the door may vary between. Door knobs can be difficult for the young and elderly to operate. For this reason, door handles in most American commercial and industrial buildings and in many households are lever-operated, rather than a knob, as the lever does not require a tight grip. Levers are also beneficial on doors with narrow stile widths where the reduced backset leaves insufficient space to comfortably turn a door knob. Most household door handles use a simple mechanism with a screw-style axle that has at least one flat side, which is passed through the door jigger, leaving some length exposed on each side of the door to which the handles are attached. Some handles are attached on both sides by screwing or sliding them directly onto the spindle, and then securing one or more retaining screws through the knob perpendicular to the flat of the spindle. Handles that lose traction can frequently be repaired by replacing or adjusting the set screw, which prevents them from slipping on the spindle. Other types of handles, typically used in Europe, slide onto the spindle but are affixed only to the door itself without use of set screws. Types of household handles:
Entrance: These door handles are typically used on exterior doors, and include keyed cylinders.
Privacy: Typically used on bedrooms and bathrooms; while they are lockable, they do not have keyed cylinders.
Passage: Also known as hall or closet, these do not lock and are used in hall or closet doors.
Dummy: These types are used for ball catch doors or other applications where a mechanism is not needed, but a similar aesthetic effect is desired.
Cars
Car door handles may protrude from the vehicle's exterior surface or be streamlined into the vehicle's contour. In some automobiles, especially luxury vehicles, the door handles may feature a key-less entry pad utilizing either a numerical code or thumb scan.
Foldables
On a balcony whose door has an outside shutter, a special door handle is used on the outer side. The protruding part of such handle can be folded sideways, so that the shutter can be fully closed without being obstructed by the door handle.
Pocket doors
A pocket door handle is a recessed rectangular insert, typically with operating hardware called a door pull. Door handles can also be called "handle sets". In addition there are door handles that are flush-mount and require pressing rather than turning or gripping, and there are touch-free, electronic, and motion-sensor door handles.
Infection control
Of concern is the fact that door handles are instrumental in the spread of many infections. For example, infection transmission can occur when an individual touches a handle and subsequently touches their eyes, nose or mouth, allowing microbes to be ingested. However, some materials, e.g. brass, copper and silver, are slowly poisonous to many germs. The exact mechanism is not known, but is commonly thought to be via the oligodynamic effect, perhaps by some other electrostatic effect. Brass and copper, for example, disinfect themselves of many door handle bacteria within eight hours. Other materials such as glass, porcelain, stainless steel and aluminium do not have this effect. Self-disinfecting door handles are particularly important in hospitals, but useful in any building.
