Sealed beam
Encyclopedia
A sealed beam is a type of lamp
that includes a reflector
and filament as a single assembly, over which a front cover (lens
) of clear glass, is permanently attached. Previously, automotive headlamp
s used a separate small bulb and reflector covered with a ribbed lens to avoid glare from the filament. This cover would be clamped on with a grommet to seal it. The method's deficiencies prompted the invention of the sealed beam system.
s may be of the sealed beam type, meaning that the reflector, the lens array on the front and the bulb are all one unit that must be replaced together in case of burnout. They are clamped into a structure for aiming the beams to meet safety requirements. Every time the headlight is replaced, the aiming of the beams must be checked. Headlights using sealed beams were introduced in the United States in 1940 and became mandatory from the following year until the 1984 model year; cars prior and subsequent to that date could have a variety of shapes of headlamps. The limited range of standard sealed-beam lamps restricted styling options for automobiles, and current headlamp designs allow mandated light levels to be obtained with more compact lamps.
Sealed beams come in various voltage
s, most commonly 6, 12, 28, 120 and 230 V. Aircraft
landing lights, which are also used in open air concerts and for stage lighting
, are sealed beams that have a very narrow beam
spread.
Modern sealed beams have an additional envelope around the filament, whereas older types do not. The inner envelope contains a halogen
to improve the life of the filament and enable more light for the same power; for this to work, the halogen must be confined to the area around the filament by the second envelope, commonly made of fused quartz
to withstand the filament's heat. These "halogen sealed beams" appeared on U.S. cars in 1978 to enable halogen technology under Federal Motor Vehicle Safety Standard 108
, which at the time required sealed beam headlamps; they continued even after FMVSS 108 was amended to permit composite headlamps in 1983, and came to dominate the sealed beam lamp market.
, sealed beam lamps are often used. A common size, also used in rock
concert
s, as well as outdoor architectural
lighting, is the parabolic aluminumized reflector
64 (PAR64). PAR lamps are measured in non-SI
units of measurement equal to one eighth of an inch
, so a PAR64 light is a light that is 8 inches in diameter. The fixtures that such sealed beam lights go into are called "PAR cans", so a PAR64 fixture is an 8 inches (203.2 mm) can.
Other popular sizes are PAR56, PAR38, and PAR36.
Beam spreads are designated as FL (flood), SP (spot), NSP (narrow spot), and VNSP (very narrow spot), as stamped on the back of the lamp's reflector.
A PAR64 sealed beam typically comes in 250 W
, 500 W, or 1000 watt.
Sealed beam lamp arrays are also in use by modern lighthouse
s.
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
that includes a reflector
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
and filament as a single assembly, over which a front cover (lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
) of clear glass, is permanently attached. Previously, automotive headlamp
Headlamp
A headlamp is a lamp, usually attached to the front of a vehicle such as a car or a motorcycle, with the purpose of illuminating the road ahead during periods of low visibility, such as darkness or precipitation. Headlamp performance has steadily improved throughout the automobile age, spurred by...
s used a separate small bulb and reflector covered with a ribbed lens to avoid glare from the filament. This cover would be clamped on with a grommet to seal it. The method's deficiencies prompted the invention of the sealed beam system.
Automotive headlamps
Headlights for automobileAutomobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s may be of the sealed beam type, meaning that the reflector, the lens array on the front and the bulb are all one unit that must be replaced together in case of burnout. They are clamped into a structure for aiming the beams to meet safety requirements. Every time the headlight is replaced, the aiming of the beams must be checked. Headlights using sealed beams were introduced in the United States in 1940 and became mandatory from the following year until the 1984 model year; cars prior and subsequent to that date could have a variety of shapes of headlamps. The limited range of standard sealed-beam lamps restricted styling options for automobiles, and current headlamp designs allow mandated light levels to be obtained with more compact lamps.
Sealed beams come in various voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s, most commonly 6, 12, 28, 120 and 230 V. Aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
landing lights, which are also used in open air concerts and for stage lighting
Stage lighting
Modern stage lighting is a flexible tool in the production of theatre, dance, opera and other performance arts. Several different types of stage lighting instruments are used in the pursuit of the various principles or goals of lighting. Stage lighting has grown considerably in recent years...
, are sealed beams that have a very narrow beam
Light beam
A light beam or beam of light is a narrow projection of light energy radiating from a source into a beam. Sunlight is a natural example of a light beam when filtered through various mediums...
spread.
Modern sealed beams have an additional envelope around the filament, whereas older types do not. The inner envelope contains a halogen
Halogen lamp
A halogen lamp, also known as a tungsten halogen lamp, is an incandescent lamp with a tungsten filament contained within an inert gas and a small amount of a halogen such as iodine or bromine. The chemical halogen cycle redeposits evaporated tungsten back on to the filament, extending the life of...
to improve the life of the filament and enable more light for the same power; for this to work, the halogen must be confined to the area around the filament by the second envelope, commonly made of fused quartz
Fused quartz
Fused quartz and fused silica are types of glass containing primarily silica in amorphous form. They are manufactured using several different processes...
to withstand the filament's heat. These "halogen sealed beams" appeared on U.S. cars in 1978 to enable halogen technology under Federal Motor Vehicle Safety Standard 108
Federal Motor Vehicle Safety Standard 108
Federal Motor Vehicle Safety Standard 108 regulates all automotive lighting, signalling and reflective devices in the United States. Like all other Federal Motor Vehicle Safety Standards, FMVSS 108 is administered by the United States Department of Transportation's National Highway Traffic Safety...
, which at the time required sealed beam headlamps; they continued even after FMVSS 108 was amended to permit composite headlamps in 1983, and came to dominate the sealed beam lamp market.
Building and stage lighting
In stage lightingStage lighting
Modern stage lighting is a flexible tool in the production of theatre, dance, opera and other performance arts. Several different types of stage lighting instruments are used in the pursuit of the various principles or goals of lighting. Stage lighting has grown considerably in recent years...
, sealed beam lamps are often used. A common size, also used in rock
Rock and roll
Rock and roll is a genre of popular music that originated and evolved in the United States during the late 1940s and early 1950s, primarily from a combination of African American blues, country, jazz, and gospel music...
concert
Concert
A concert is a live performance before an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, a choir, or a musical band...
s, as well as outdoor architectural
Architecture
Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...
lighting, is the parabolic aluminumized reflector
Parabolic aluminized reflector light
A parabolic aluminized reflector lamp is a type of electric lamp that is widely used in commercial, residential, and transportation illumination. Usage includes locomotive headlamps, aircraft landing lights, and residential and commercial recessed lights...
64 (PAR64). PAR lamps are measured in non-SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
units of measurement equal to one eighth of an inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
, so a PAR64 light is a light that is 8 inches in diameter. The fixtures that such sealed beam lights go into are called "PAR cans", so a PAR64 fixture is an 8 inches (203.2 mm) can.
Other popular sizes are PAR56, PAR38, and PAR36.
Beam spreads are designated as FL (flood), SP (spot), NSP (narrow spot), and VNSP (very narrow spot), as stamped on the back of the lamp's reflector.
A PAR64 sealed beam typically comes in 250 W
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
, 500 W, or 1000 watt.
Sealed beam lamp arrays are also in use by modern lighthouse
Lighthouse
A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses or, in older times, from a fire, and used as an aid to navigation for maritime pilots at sea or on inland waterways....
s.