- A small portable lamp usually powered by batteries.
- A brief brilliant flood of light from a photographic lamp.
- A bright light, as of a signal lamp, that flashes at regular intervals.
flashlight
Dictionary:
flash·light (flăsh'līt')  |
n.
| How Products are Made: How is a flashlight made? |
Background
A flashlight is a portable, battery-operated device used for illumination. A typical unit consists of one or more dry cell batteries arranged in a line inside a battery compartment that forms the handle of the light. The flow of electricity from the batteries to the bulb at the front end of the light is controlled through a switch mechanism placed between the batteries and the lamp.
History
Practical, portable light sources have been sought throughout history. Torches and candles were early sources of light but these were largely replaced with lanterns as people learned to burn various animal and mineral oils. However, it was not until the nineteenth century that electricity was harnessed to create light. The modern battery powered flashlight was created in 1898 by Joshua Lionel Cowen, the original owner of the American Eveready Battery Company. Cowen originally developed an idea for a decorative lighting fixture for potted plants. His fixture was composed of a metal tube with a lightbulb and a dry cell battery. Cowen passed his idea to one of his Eveready salespersons, Conrad Hubert, who turned the metal tube, lightbulb, and battery into the world's first flashlight and started selling the batteries and the flashlight. In the last hundred years, advances in technology have resulted in flashlights with hundreds of different styles and features. For example, flashlights are now made with rechargeable batteries that can be used multiple times. Other lights are designed for special operations, such as working underwater or in high-temperature conditions.
Design
The most common flashlight design is the simple household light that consists of a tube-like handle that contains the batteries. This handle is affixed to a threaded head assembly that houses the bulb mechanism. These units operate on standard batteries and provide a typical light output. Special designs are required for industrial or professional use. These lights are made from heavier gauge materials, and are more durable. They are also intended to produce a brighter beam of light. Flashlights with brighter beams are used by the police, firefighters, and the military. Camping lanterns are larger units, usually powered by heavy duty batteries. These frequently use fluorescent tubes as their light source because of their greater energy efficiency, however, this type of bulb does not cast as strong or directed a beam of light. Furthermore, the increased size and weight of this type of lantern limits its portability. Novelty flashlights are designed for use by children. These tend to be made of lightweight plastic and are notable for their visual design. The body of the light may be adorned with decorative plastic overlays that increase the child-appeal of the unit. Their designs are often based on favorite characters from popular cartoons or children's books. Finally, there are a variety of specialty lights designed for particular uses. For example, snake lights, flexible tubes that can be bent or twisted to provide light in hard to reach places. Others are designed to be small enough to fit on a key chain to illuminate keyholes.
Factors to consider when designing flashlights include light output, durability, and the ability to operate in special environments. Battery life is also an important factor, and some lights are designed to be plugged into an electrical outlet to be recharged or to maintain a charge until it is needed. Other lights use special bulbs, like the new generation flashlights built with light-emitting diodes. These are not as bright as conventional incandescent bulbs, but their power consumption is so low that they can last hundreds of hours on a set of conventional batteries, as compared to a few dozen hours for incandescent bulbs.
The Manufacturing Process
Plastic housing
- The plastic components used in flashlight construction are typically injection molded using polystyrene and other durable polymers. In this process, plastic pellets are mixed with plasticizing agents and colorants. This mixture is liquefied by heating and then injected into appropriately shaped molds via an injection plunger. The mold is then subjected to high pressure to assure that the molds are completely filled, and to hold the molds together against force of injected liquid plastics. The end closures are also molded, where usually both internal and external threads are molded. Pressures as high as 2,500 tons may be used for high-speed or multiple-cavity production molders.
- After the injection process, the molten plastic is cooled by forcing water through channels in the mold. The plastic hardens as it cools and the pressure is released. At this point, the two halves of the mold are separated and the plastic part can be removed for finishing. The plastic polymers used in this process are thermoplastic, meaning they can be repeatedly melted so the scrap pieces can be reworked to make additional parts. Therefore, there is very little wasted plastic in this process. Subsequent operations may be required to polish, cut, and finish the plastic parts.
Light source
- Incandescent bulbs are the most common light source used in flashlights. These consist of a metal filament sealed in a glass bulb. When the filament is exposed to an electric current the resistance of the wire causes it to heat up and emit light in the visible wavelengths. The filament is welded to two wires that pass though holes in a cylindrical glass bead that forms the base of the bulb. This structure is placed in a fixture and a cylindrical glass envelope that is closed at one end is placed over the filament. The open end of the glass envelope rests against the glass bead.
4 The structure is placed inside a vacuum chamber and heat is applied to seal the glass envelope to the glass bead. The heat causes the glass to soften, and may cause the filament to be displaced to one side. Therefore, care must be taken to ensure the filament is properly aligned or the bulb will not project a beam of light in the right direction.
Other possible light sources include fluorescent bulbs, which are often used in camping lanterns. These bulbs emit light due to the excitation of gas molecules inside the bulb. LEDs, or light emitting diodes, are used in some specialty lights; these emit light when exposed to extremely low levels of electric current. The bulb is often fitted in front of a polished aluminum reflector that helps to focus the light during operation.
Switch and controls
- The electronic circuitry of a flashlight varies depending on its design. Simple lights rely on an off/on switch to make the connection between the wires connecting the battery terminals to the wires extending from the base of the bulb. This type of switch is most commonly a slide type that moves up or down to make the proper connection. The switch assembly is more complicated in the more sophisticated lights. One United States patent describes a flexible metal strip that is depressed to create a contact between the wires.
Assembly
6 Depending on the design and the manufacturers capability, units may be assembled on an automated conveyor line or by hand. Some models, particularly those using small watch batteries, have the battery inserted during assembly. Otherwise, the unit may be assembled without the batteries that are inserted later by the consumer. This operation involves screwing the lamp assembly onto the threads on the casing.
Packaging
- Assembled units may be placed in some form of outer packaging, such as a clear plastic blister pack or clam shell. The plastic shell may then be attached to a cardboard display card or packed in a box prior to shipping.
Quality Control
Completed flashlights undergo a series of quality control tests to ensure they function properly. First, the bulb must be checked to ensure it is properly aligned with the reflector; if it is misaligned performance may suffer. Second, the switch assembly is evaluated to determine if it makes proper contact with the electrical leads. Third, the seal on the battery compartment must be checked to determine if moisture will not inadvertently enter the battery compartment. This seal must allow venting of gasses that may be formed during battery operation.
The bulb itself must meet separate quality standards. Generally, Division 2-approved flashlights are temperature-rated as TI to T6, where Tl is a temperatures less than, or equal to, 842°F (450°C) and T6 is less than, or equal to, 185°F (85°C). Testing labs used by flashlight manufacturers include Factory Mutual Research Corporation, Underwriters Laboratories, and Demko.
Hazardous environment
Any flashlight that will be used in a hazardous environment or confined space must be properly tested to ascertain that it meets or exceeds all applicable safety standards for those locations. Hazardous Locations are defined by the National Electric Code and include the following classifications. Class I locations are areas where flammable gases may be present in sufficient quantities to produce explosive or flammable mixtures. Class II locations can be described as hazardous because of the presence of combustible dust. Class III locations contain easily ignitable fibers and filings. Hazardous atmospheres are further defined by "groups." These include atmospheres containing acetylene, hydrogen, or gases or vapors of equivalent hazard, such as ethylether vapors, ethylene, cyclo-propane, gasoline, hexane, naptha, benzene, butane, propane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas. Metal dust, including aluminum, magnesium, and their commercial alloys, may also create hazardous atmospheres. Environments containing carbon black, coal or coke dust, flour, starch, or grain dusts, are classified by the Code. Flashlights designed for use in these environments are individually tested before leaving the factory.
The Future
Manufacturers continue to improve upon the design of their flashlights. New models with improved power sources are becoming increasingly popular. For example, the power plant of a new self-powered flashlight is the revolutionary Freeplay Generator, which is a unique and patented mechanism that stores kinetic energy in a carbon steel spring as the user turns a winding handle. This energy is released as electrical energy when the light is turned on, thus powering the light without any other external power source.
Other improvements in flashlights include tougher polymers for improved durability and smarter computer technology that will allow automatic shut off mechanisms to conserve battery life. Finally, increasingly sophisticated molding techniques will allow the creation of novelty flashlights in a wider variety of shapes and colors.
Where to Learn More
Books
Ahmstead, B.H. Manufacturing Processes. New York: John Wiley & Sons, 1977.
Other
"Inventors." http:/finventors.about.com (January 2001).
[Article by: Randy Schueller]
| Word Tutor: flashlight |
IN BRIEF: n. - A small portable battery-powered electric lamp.
I like to have a flashlight near in case the electricity goes out.
| Wikipedia: Flashlight |
For other uses, see Flashlight (disambiguation).
A flashlight (called a torch outside North America) is a portable electric spotlight that emits light from a small incandescent lightbulb or from one or more light-emitting diodes (LEDs). Typical flashlight designs usually consist of the light source located in a housing containing a parabolic reflector or specially shaped lens to shape the flashlight beam, a transparent window to protect the light source from damage and debris, a power source (typically electric batteries), and an electric power switch.
While most flashlights are intended to be hand-held, there are also helmet-mounted flashlights designed for miners and campers and battery-powered lights for bicycles. Some flashlights are powered by hand-cranked dynamos or electromagnetic induction or are recharged by solar power.
The name flashlight is used mainly in the United States and Canada. In other English-speaking countries, the more common term is torch or electric torch.
Contents |
History
In 1896, the first dry cell battery was invented. Unlike previous batteries, it used a paste electrolyte instead of a liquid. This was the first battery suitable for portable electrical devices, as it did not spill or break easily and worked in any orientation.
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Misell's Patent 617,592
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1899 flashlight
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On 10 January 1899, American Electrical Novelty and Manufacturing Company obtained U.S. Patent No. 617,592 (filed 12 March 1898) from David Misell, an inventor.[1] This "electric device" designed by Misell was powered by "D" batteries laid front to back in a paper tube with the light bulb and a rough brass reflector at the end.[2][3] The company donated some of these devices to the New York City police, who responded favorably to them.[4]
These early flashlights ran on zinc–carbon batteries which were incapable of providing a steady source of electric current and needed to be 'rested' periodically to continue functioning.[5] Because these early flashlights also used energy-inefficient carbon-filament bulbs, this occurred at short intervals. Consequently, they could be used only in brief flashes, hence the popular name flashlight.[3]
Incandescent
Incandescent flashlights use incandescent bulbs containing a electrical filament of tungsten wire, which gives off light energy as well as heat. The bulbs are evacuated with an inert gas (usually argon, sometimes with traces of halogen: in higher quality models, xenon is used). A popular example of an incandescent flashlight is the Maglite by Mag Instrument which are capable of producing 40 to 50 lumens [1].
LED
Recently, flashlights which use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available.
LEDs have existed for decades, mainly as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, California United States, introduced the Luxeon LED, a high-power white-light emitter. For the first time this made possible LED flashlights with power and running time better than some incandescent lights. The first Luxeon LED flashlight was the Arc LS in 2001.
LEDs can be significantly more efficient than incandescent lamps at lower power levels and so use less battery energy than ordinary lightbulbs. Such flashlights have longer battery lifetimes, in some cases hundreds of hours, although the LED efficiency advantage diminishes at higher power levels. LEDs also survive sharp blows that often break conventional lightbulbs.
LED flashlights are often electronically regulated to maintain constant light output as the batteries are depleted. By contrast, the output of a non-regulated flashlight changes proportionally to the voltage of the battery, resulting in a significant decline in output as battery capacity - and thus voltage - drops as the flashlight is used. LEDs also have the advantage of maintaining a specific color temperature regardless of input voltage or current, while the color temperature of an incandescent bulb declines with the power available.
While lower-power LED flashlights generate little heat, more powerful LED lights do generate significant amounts of heat – although not as radiant energy, as the semiconductor junction inherently dissipates heat. For this reason higher-powered LED flashlights usually have aluminum bodies and can become quite warm during use. The aluminum bodies act as a heatsink for the high-power LED. Very few high-output LED flashlights use a plastic body, since plastics do not conduct heat as well as metals.
HID
Another less common type of flashlight uses a High Intensity Discharge (HID) lamp as the light source. HID lamps work by discharging an electric current between two electrodes in a capsule filled with a mixture of metal halide salts and argon, producing an extremely bright light.
Some advantages of this design are that they produce more light than an incandescent flashlight using the same amount of electricity, and the lamp will last longer and is more shock resistant than a regular incandescent bulb, as they lack the relatively fragile electrical filament found in incandescent bulbs.[citation needed] However; they are much more expensive (due to the need for a ballast and other circuitry to start and operate the lamp) and are usually rather bulky. An example of an HID flashlight is the Surefire Hellfire Weaponlight.
Other designs
A headlamp is a flashlight worn on the head.
Sometimes a light is mounted to a handgun or rifle.[6] See also Streamlight and SureFire.
Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled lanterns of the day, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles.
Although most flashlights are designed in a manner that allows the user to replace the batteries and the bulb as needed, fully-sealed disposable flashlights do exist, such as the Garrity Life Lite, and various inexpensive keyring lights. In a disposable flashlight, when the batteries are depleted or the bulb fails, the entire product is thrown away or recycled and a new one purchased to replace it.
Power sources
The most common power source for flashlights is the battery. Many types of batteries are suitable for use in flashlights, such as button cells, alkaline batteries, lithium batteries and rechargeable NiMH and lithium ion batteries. The choice of batteries will depend on the light source used, and will usually play a determining role in the form factor of the flashlight.
Some flashlights are solar powered, using the energy generated from a solar cell to charge an on-board battery for later use.
Mechanical power
Main article: Mechanically powered flashlight
Some flashlights have an electrical generator built into them. One type of dynamo-powered flashlight has a winding crank connected to a small alternator that feeds several diode bridges with their outputs connected in parallel feeding a field effect transistor that charges a capacitor that connects to one or more LEDs. Others generate electricity using electromagnetic induction. They use a strong permanent magnet that can freely slide up and down a tube, passing through a coil of wire as it does. Shaking the flashlight will charge a capacitor or a rechargeable battery that supplies a current to a light source, typically a light-emitting diode or, more rarely, an incandescent light bulb. Such flashlights can be useful during an emergency, when batteries may not be available.
See also
 |
Wikimedia Commons has media related to: Flashlight |
- Carbide lamp
- Dyno torch
- Headlamps worn affixed to the head
- Maglite
- Penlight
- SureFire
- Streamlight
- Arc Flashlight
- Philips Lumileds Lighting Company
References
- ^ Patent number: 617592 by David Misell
- ^ History of Batteries (and other things)
- ^ a b Flishlight Museum
- ^ Steve Hathcock. "Give Me a Light". Island Breeze. http://spislandbreeze.com/ideas_more.php?id=532_0_12_0_M. Retrieved 2007-02-05.
- ^ Brooke Schumm. "Nonrechargeable Batteries". The Electrochemistry Encyclopedia. http://electrochem.cwru.edu/ed/encycl/art-b02-batt-nonr.htm. Retrieved 2007-02-05.
- ^ Using Gun Lights
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Translations: Flashlight |
Nederlands (Dutch)
zaklantaarn, flitslicht, flitslamp, foto gemaakt bij flitslicht
Français (French)
n. - (Phot) ampoule de flash, (US) torche électrique, feu à éclats
Deutsch (German)
n. - Taschenlampe, Blitzlicht
Ελληνική (Greek)
n. - ηλεκτρικός φακός, προβολέας
Italiano (Italian)
torcia elettrica, flash
Português (Portuguese)
n. - lanterna (f)
Русский (Russian)
карманный фонарь
Español (Spanish)
n. - linterna de mano, linterna de petaca, bombilla de flash, flash, lámpara de flash
Svenska (Swedish)
n. - blinkfyr, fotoblixt, ficklampa
中文（简体）(Chinese (Simplified))
手电筒, 闪光灯
中文（繁體）(Chinese (Traditional))
n. - 手電筒, 閃光燈
日本語 (Japanese)
n. - 閃光, 回転灯, 懐中電灯
العربيه (Arabic)
(الاسم) ضوء يضيء ويطفىء بشكل متقطع
עברית (Hebrew)
n. - אור-איתות, פנס
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| How Products are Made. How Products are Made. Copyright © 2002 by The Gale Group, Inc. All rights reserved. Read more |
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