Balanced arm lamps
Encyclopedia
A balanced-arm lamp is a lamp with an adjustable folding arm which is constructed so that the force due to gravity is always counteracted by springs, regardless of the position of the arms of the lamp. Many lamp brands (such as the Anglepoise
, originator of the concept, and Luxo
L-1 as well as other devices, such as drawing board
s, use this principle.
For the physics
and theory behind balanced-arm lamps, see Classical mechanics
, linkage
and torque
. There are different methods to balance the lamp-cap of a balanced-arm lamp. Some lamps have two coil spring
s working in parallel on both sides of the pivoting arm. (A set of springs functions in the same way as a single spring.) Others are balanced with counterweights (a method frequently used in drawing-boards). Friction
between parts of the lamp arm can also be used to maintain balance. There are a number of mechanical solutions (coupling, hydraulics and pneumatic arms) which have occasionally been used for balanced-arm lamps.
. Springs can be located on the mechanical equivalent of the forearm or the upper arm, or both, as well as nearer the base. Some lamps use tension springs, and others use compression springs. The image at the left shows (left to right) a compression spring at rest, then under load, followed by a tension spring at rest, and then under load.
Springs have a limited lifting capacity and extension length.
Some springs can resonate, producing low-level unwanted noise.
Lamps balanced with one counterweight
A Advantages of one swinging counter balance is that the lamp can have a longer arm length.
Disadvantages is that the stand is less stable, the lamp need a heavy foot to stand stable.
animated film Luxo Jr.
.
International patent category : B23B31/171
- 1921 harmonica arm -
- 1991 -
Anglepoise lamp
The Anglepoise lamp is a balanced-arm lamp designed in 1932 by British designer George Carwardine.-History and development:Carwardine was a car designer and was, at the time he invented the Anglepoise lamp, a freelance design consultant specialising in vehicle suspension systems...
, originator of the concept, and Luxo
Luxo
Luxo ASA is a Norwegian manufacturer of lamps. Based in Oslo, it has sales throughout Europe and North America, with production plants in Norway, Sweden and California, United States. The company was founded in 1934 and is listed on the Oslo Stock Exchange....
L-1 as well as other devices, such as drawing board
Drawing board
A drawing board is, in its antique form, a kind of multipurpose desk which can be used for any kind of drawing, writing or impromptu sketching on a large sheet of paper or for reading a large format book or other oversized document or for drafting precise technical illustrations...
s, use this principle.
Configuration
A balance-arm lamp has a base, two connected arms fitted with springs, and a lamp-head. The lamp can be moved into any position, and the springs will maintain the position until moved again. The same mechanism can be employed in other devices with similar requirements, such as copy holders for typists and some computer display holders. This article uses the terminology lamp cap, forearm, upper arm and base for the four basic parts of these lamps.For the physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
and theory behind balanced-arm lamps, see Classical mechanics
Classical mechanics
In physics, classical mechanics is one of the two major sub-fields of mechanics, which is concerned with the set of physical laws describing the motion of bodies under the action of a system of forces...
, linkage
Linkage (mechanical)
A mechanical linkage is an assembly of bodies connected together to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for...
and torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
. There are different methods to balance the lamp-cap of a balanced-arm lamp. Some lamps have two coil spring
Coil spring
A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces...
s working in parallel on both sides of the pivoting arm. (A set of springs functions in the same way as a single spring.) Others are balanced with counterweights (a method frequently used in drawing-boards). Friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
between parts of the lamp arm can also be used to maintain balance. There are a number of mechanical solutions (coupling, hydraulics and pneumatic arms) which have occasionally been used for balanced-arm lamps.
Lamps balanced with springs
There are many variations of construction with springsSpring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
. Springs can be located on the mechanical equivalent of the forearm or the upper arm, or both, as well as nearer the base. Some lamps use tension springs, and others use compression springs. The image at the left shows (left to right) a compression spring at rest, then under load, followed by a tension spring at rest, and then under load.
Springs have a limited lifting capacity and extension length.
Some springs can resonate, producing low-level unwanted noise.
One tension spring
| Spring-balanced upper arm, flexible forearm |
|---|
| This lamp has a stiff flexible tube as its forearm, and a spring-balanced arm to support it near the middle. That way there is a flexible lamp with a long reach. |
| Tension spring over wheels |
|---|
| The wheel to control the forearm is smaller than the wheel that controls the upper arm. The lamp cap rotates the same direction as the upper arm and forearm. |
| Two arms, one spring, one toothed wheel |
|---|
| With this technique the tension spring has a double function: it controls both the forearm and the upper arm. This is not a common arm lamp system. The lamp cap rotates the same direction as the upper arm and forearm. |
Two tension springs
| Two parallelograms and two tension spring Spring (device) A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication... sets |
|---|
| One tension spring controls the forearm, which is a parallelogram Parallelogram In Euclidean geometry, a parallelogram is a convex quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure... having two bars. A stronger spring set controls the upper arm, which has three parallel bars (see photo, left). (There is a less stable construction with two parallel bars in the upper arm which is less expensive to manufacture.) Due to the parallel linkage Linkage (mechanical) A mechanical linkage is an assembly of bodies connected together to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for... of the lamp, the lamp cap keeps pointing in the same vertical direction when adjusting the height of the lamp. As with most balanced-arm lamps, the whole assembly can rotate in the horizontal plane, and is mounted on a stable foot. |
| One parallelogram and two extension spring sets |
|---|
| A lamp like the Anglepoise lamp Anglepoise lamp The Anglepoise lamp is a balanced-arm lamp designed in 1932 by British designer George Carwardine.-History and development:Carwardine was a car designer and was, at the time he invented the Anglepoise lamp, a freelance design consultant specialising in vehicle suspension systems... has one parallelogram Parallelogram In Euclidean geometry, a parallelogram is a convex quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure... and two extension springs. One spring controls the shortest arm of a parallelogram. Parallel to this shortest arm there is the forearm. To keep these arms parallel there are two other parallel arms (upper arm) that are controlled by a second extension spring. The lamp cap rotates the same direction as the upper arm and forearm. |
| Single forearm bar, one parallelogram , two tension spring sets |
|---|
| The forearm of this lamp consist of a single bar. When it is adjusted, the angle of the lamp cap changes along with the arm. |
| Tension springs within the arms |
|---|
| A lamp like the Tolomeo desk lamp Tolomeo desk lamp The Tolomeo incandescent desk lamp is an icon of Italian modern design. It was designed by Michele De Lucchi and Giancarlo Fassina in 1986 for the Artemide company. In its original configuration, it consists of a heavy base, two straight polished aluminum arm sections , and a matte aluminum... has no parallelogram Parallelogram In Euclidean geometry, a parallelogram is a convex quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure... s in either arm. In this modern lamp the tension springs are hidden in the arms. The lamp cap rotates the same direction as the upper arm and forearm. |
Compression springs
| Compression springs in the arms |
|---|
| The short arms (green) stay parallel. One spring puts pull force Force In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform... on the blue arm. (If the blue arm is tilted back the second spring on this arm gets push force.) The blue arm controls the two parallel arms (red) that make up the upper arm. The other spring puts pull force on the other blue arm. This arm controls the forearm (magenta). The two springs can be the same size; one spring has to lift more weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... but is more vertical. The other spring lifts less weight but is more horizontal. |
| Compression springs near the foot |
|---|
| One compression spring controls a very short arm (grey). The Roller chain Roller chain Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like... cable Cable A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry... connects this arm parallel to the forearm (yellow). The longer spring controls the (blue) arm. The body (red) can turn in the horizontal plane. The body is connected to a stable foot. The body can be smaller because the pressure springs can protrude below the body. |
| A compression spring with one parallelogram |
|---|
| In this method, just one compression spring controls a pantographic arm. |
Other types of spring
| Torsion springs control the pivoting arm |
|---|
Lamps balanced by pressure and friction
| Pressure and friction lamps |
|---|
| This construction is quite common in Italian lamps. Gravity causes the parallelogram to deform, making the gap between the long arms smaller. This increases pressure on the rubber Rubber Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined... in the gap, and the resulting friction Friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:... holds the arm in balance. |
Lamps balanced with one counterweightCounterweightA counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
A Advantages of one swinging counter balance is that the lamp can have a longer arm length.Disadvantages is that the stand is less stable, the lamp need a heavy foot to stand stable.
| A single counterweight |
|---|
| This construction uses a chain to keep the arm with the counterweight Counterweight A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides... and the forearm parallel. The lamp-cap and counterweight move in opposite directions (both away from the base or both towards it). The balance that is required is shown by the following formula: d1 = Lamp-cap to base; m1 = weight of lamp-cap d2 = counterweight to base; m2 = weight of counterweight m1 × d1 = m2 × d2 |
| One parallelogram with one counterweight |
|---|
| This lamp has a heavy base, with a parallelogram pantograph Pantograph A pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen... construction formed by bars which are all hinged on each other. One long bar extends past the parallelogram construction and has a counterweight Counterweight A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides... . One short bar also extends past the parallelogram construction and holds the lamp cap. The base haves an arc formed stand so the counterweight does not hit the stand in vertical position. |
| One parallelogram with an extended counterweight |
|---|
| This lamp is similar to the one above, but as the counterweight has a low position, the lamp needs no heavy foot for stability Mechanical equilibrium A standard definition of static equilibrium is:This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next.... : the centre of gravity is low. The counterbalance does not swing but slides an rotate safer around the stand. |
| Three parallelograms with one counterweight |
|---|
| This lamp stand has a complex construction with matching narrow openings. This lamp is out of production . |
Lamps balanced with two counterweights
| A single arm with two counterweights |
|---|
| With this lamp the movement is very limited (the arm moves up and down only) but the technique is nice to look at. As the forearm becomes more horizontal the weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... ceases to be balanced on both side of the base. The weight of the base is needed to avoid over-balancing. |
| Two arms with two counterweights |
|---|
| A lamp type like the Tizio Tizio Tizio is a desk lamp created by Richard Sapper for Artemide in 1972. It has been selected for the Compasso d'Oro industrial design award in 1979. An item of it is part of the collections of the Metropolitan Museum of Art and of the Museum of Modern Art.... works like this. A balancing arm (the forearm) has on one side of an axis a small counterweight Counterweight A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides... and on the other side a lamp cap. These parts are lifted by a second bigger balancing arm (the upper arm) that has on the other side of a second axis a heavier counterweight. The lamp designed by Edouard-Wilfrid Buquet in 1929 works in this way. The lamp is in the collection of the Museum of Modern Art Museum of Modern Art The Museum of Modern Art is an art museum in Midtown Manhattan in New York City, on 53rd Street, between Fifth and Sixth Avenues. It has been important in developing and collecting modernist art, and is often identified as the most influential museum of modern art in the world... . The two axes have a different angle, and this has some advantages. Lamp-cap x fore-Arm = Arm x Small weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... (Lamp-cap + Small weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... ) x upper-arm = Arm x Big weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... . |
Lamps using other systems
Here are some less common ways of balancing arms.| Lamps having a vertical axis |
|---|
| This kind of lamp has a forearm balanced by weight or springs. Its disadvantage is that the upper arm cannot point up or forwards. |
| Friction |
|---|
| friction Friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:... between the twisted arm controls the movement between the arms. /> This arm system also works with friction. |
| Mechanical coupling devices |
|---|
| This lamp works by coupling Couple (mechanics) In mechanics, a couple is a system of forces with a resultant moment but no resultant force. Another term for a couple is a pure moment. Its effect is to create rotation without translation, or more generally without any acceleration of the centre of mass.The resultant moment of a couple is called... together the upper arm and the forearm. It is called a gravity-locked or cam-locked elbow See here. |
| Hydraulic arm |
|---|
| The Biggest pivoting arm lamp in the world is in Rotterdam Rotterdam Rotterdam is the second-largest city in the Netherlands and one of the largest ports in the world. Starting as a dam on the Rotte river, Rotterdam has grown into a major international commercial centre... . It has one hydraulic cylinder to control the forearm, and one hydraulic cylinder to control the upper arm. |
| Pneumatic arm |
|---|
| Arm lamp with a pneumatic cylinder. The gravity compress the air in the pneumatic cylinder. |
In popular culture
Two spring balanced desk lamps of this type feature as the main characters in the PixarPixar
Pixar Animation Studios, pronounced , is an American computer animation film studio based in Emeryville, California. The studio has earned 26 Academy Awards, seven Golden Globes, and three Grammy Awards, among many other awards and acknowledgments. Its films have made over $6.3 billion worldwide...
animated film Luxo Jr.
Luxo Jr.
Luxo Jr. is the first film produced in 1986 by Pixar Animation Studios, following its establishment as an independent film studio. It is a computer-animated short film , demonstrating the kind of things the newly-established company was capable of producing...
.
See also
- Engineering science and mechanicsEngineering science and mechanicsEngineering Science and Mechanics is a multidisciplinary and interdisciplinary engineering program and/or academic department at the Pennsylvania State University, Virginia Polytechnic Institute and State University, Georgia Institute of Technology, or University of Alabama. B.S., M.S., M.Eng., or...
- Industrial designIndustrial designIndustrial design is the use of a combination of applied art and applied science to improve the aesthetics, ergonomics, and usability of a product, but it may also be used to improve the product's marketability and production...
- Light fixtureLight fixtureA light fixture, light fitting, or luminaire is an electrical device used to create artificial light and/or illumination, by use of an electric lamp...
- Torsion springTorsion springA torsion spring is a spring that works by torsion or twisting; that is, a flexible elastic object that stores mechanical energy when it is twisted. The amount of force it exerts is proportional to the amount it is twisted. There are two types...
- Mechanical advantageMechanical advantageMechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...
- Mechanical engineering technologyMechanical engineering technologyMechanical engineering technology is the application of physical principles and current technological developments to the creation of useful machinery and operation design. Technologies such as solid models may be used as the basis for finite element analysis and / or computational fluid dynamics ...
- Moment (physics)Moment (physics)In physics, the term moment can refer to many different concepts:*Moment of force is the tendency of a force to twist or rotate an object; see the article torque for details. This is an important, basic concept in engineering and physics. A moment is valued mathematically as the product of the...
External links
- Dutch students from the University Delft Netherlands experimenting to balance a lamp. In Dutch but with a lot of images.
Patents history
Classifications IPC :F21V21/26International patent category : B23B31/171
- GB191104491 An Improved Device for Supporting or Suspending Electric Lamps and the like (1911)
- 1921 harmonica arm -
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB206435 1923 parallelogram & counter weight
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB254972 1926 friction
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB285045 1929 2 counter weight
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB481198 1934 spring and counter weight
- FR757890 1934 CARWARDINE GEORGE
- FR784932 1935 CARWARDINE GEORGE
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB470502 1937 friction
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB489547 1938 2 parallelogram 2 springs
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB504791 1939 2 pressure springs
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB536342 19.. a-symmetric arm-lamp
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB589994 1947 friction and a spring
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB618344 1949
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB629364 1949 spring in the arm
- http://www.delphion.com/cgi-bin/viewpat.cmd/GB713378 1954 friction arm
- 1991 -
- EP0518569 1992
- EP1274545 2003 mechanical coupling devices