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Balanced-arm lamp 1
Balanced- arm lampA balanced-arm lamp is a lamp with an
adjustable folding arm which is constructed so that the force due
to gravityis always counteracted, regardless of the position of the
arms of the lamp. Many lamp brands (such as the Anglepoiseand Luxo
L-1 as well as other devices, such as drawing boards, use this
principle.
Configuration
These lamp arms invite comparison with a human arm: the lampcap
is the hand, and there are three joints (equivalent to the
wrist,elbow and shoulder) which connect it to the body, in this
casereprsented by the base. Just as with the human arm, the
advantagesof the three joints are that the arm can reach virtually
any point inspace within a hemisphere with a radius equal to the
arm's length.The same mechanism can be employed in other devices
withsimilar requirements, such as copy holders for typists and
somecomputer display holders. This article uses the terminology
lampcap, forearm, upper arm and base for the four basic parts of
theselamps.
For the physics and theory behind balanced-arm lamps,
seeClassical mechanics, linkage and torque. There are different
methods to balance the lamp-cap of a balanced-armlamp. Some lamps
have two coil springs working in parallel on both sides of the
pivoting arm. (A set of springsfunctions in the same way as a
single spring.) Others are balanced with counterweights (a method
frequently used indrawing-boards). Friction between parts of the
lamp arm can also be used to maintain balance. There are a number
ofmechanical solutions (coupling, hydraulics and pneumatic arms)
which have occasionally been used forbalanced-arm lamps.
Lamps balanced with springs
Compression and tensionsprings at rest and under
load
There are many variations of construction with springs. Springs
can be located on themechanical equivalent of the forearm or the
upper arm, or both, as well as nearer thebase. Some lamps use
tension springs, and others use compression springs. The image
atthe left shows (left to right) a compression spring at rest, then
under load, followed by atension spring at rest, and then under
load. Springs have a limited lifting capacity andextension length.
Some springs can resonate, producing low-level unwanted noise.
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Balanced-arm lamp 2
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 along 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 andforearm.
Two arms, one spring, one toothed wheel
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Balanced-arm lamp 3
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 lampsystem. The lamp cap rotates the same direction as the
upper arm and forearm.
Two Tension springsTwo parallelograms and two tension spring
sets
One tension spring controls the forearm, which is a
parallelogram having two bars. A strongerspring set controls the
upper arm, which has three parallel bars (see photo, right). (There
is aless stable construction with two parallel bars in the upper
arm which is less expensive tomanufacture.) Due to the parallel
linkage of the lamp, the lamp cap keeps pointing in the
samevertical 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
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Balanced-arm lamp 4
A lamp like the Anglepoise lamp has one parallelogram and two
extension springs. One spring controls the shortest arm of a
parallelogram. Parallelto 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 secondextension 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
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Balanced-arm lamp 5
A lamp like the Tolomeo desk lamp has no parallelograms in
either arm. In this modern lamp the tension springs are hidden in
the arms. The lampcap rotates the same direction as the upper arm
and forearm.
Compression springsCompression springs in the arms
The short arms (green) stay parallel.One spring puts pull force
on the bluearm. (If the blue arm is tilted back thesecond spring on
this arm gets pushforce.) The blue arm controls the twoparallel
arms (red) that make up theupper arm. The other spring puts
pullforce on the other blue arm. This armcontrols the forearm
(magenta). Thetwo springs can be the same size; onespring has to
lift more weight but ismore vertical. The other spring liftsless
weight but is more horizontal.
Compression springs near the foot
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Balanced-arm lamp 6
One compression spring controls a very short arm (grey). The
Roller chain cable connects this arm parallel to the forearm
(yellow). The longerspring 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 smallerbecause 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
Spiral spring controls a pantograph arm
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Balanced-arm lamp 7
Patent: GB1290891A from 1970
Torsion springs controls the pivoting arm
Lamps balanced by pressure and friction
Pressure and friction lamps
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Balanced-arm lamp 8
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 in the gap, and
the resulting friction holds the arm in balance.
Lamps balanced with one counterweightA Advantages of one
swinging counter balance is that the lamp can have a longer arm
length. Disadvantages is thatthe stand is less stable, the lamp
need a heavy foot to stand stable.
A single counterweight
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Balanced-arm lamp 9
This construction uses a chain to keep the arm with the
counterweight and the forearm parallel. The lamp-cap and
counterweight move in oppositedirections (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
construction formed by bars which are all hinged on each other. One
long bar extendspast the parallelogram construction and has a
counterweight. One short bar also extends past the parallelogram
construction and holds the lamp cap.The base haves a arc formed
stand so the counterweight does not hit the stand in vertical
position.
One parallelogram with an extended counterweight
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Balanced-arm lamp 10
This lamp is similar to the one above, but as the counterweight
has a low position, the lamp needs no heavy foot for stability: the
centre of gravity islow. 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
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Balanced-arm lamp 11
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 morehorizontal the weight 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 counterweightsA lamp type like the Tizio works
like this. A balancing arm (theforearm) has on one side of an axis
a small counterweight and onthe other side a lamp cap. These parts
are lifted by a second biggerbalancing arm (the upper arm) that has
on the other side of asecond axis a heavier counterweight. The lamp
designed byEdouard-Wilfrid Buquet in 1929 works in this way. The
lamp is inthe collection of the Museum of Modern Art. The two axes
have adifferent angle, and this has some advantages. Lamp-cap
xfore-Arm = Arm x Small weight (Lamp-cap + Small weight) xupper-arm
= Arm x Big weight.
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Balanced-arm lamp 12
Lamps using other systems
Here are some less common ways ofbalancing 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
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Balanced-arm lamp 13
The 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 together the upper arm and the
forearm. It is called a gravity-locked or cam-locked elbow See here
[1].
Hydraulic arm
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Balanced-arm lamp 14
The Biggest pivoting arm lamp in the world is in Rotterdam. It
has one hydraulic cylinder to control the forearm, and one
hydraulic cylinder tocontrol the upper arm.
Pneumatic arm
Arm lamp with a pneumatic cylinder. The gravity compress the air
in the pneumatic cylinder.
In popular cultureTwo spring balanced desk lamps of this type
feature as the main characters in the Pixar animated film Luxo
Jr..
See also Engineering science and mechanics Industrial design
Light fixture Torsion spring Mechanical advantage Mechanical
engineering technology Moment (physics)
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Balanced-arm lamp 15
External links Dutch students from the University Delft
Netherlands [2] experimenting to balance a lamp. In Dutch but with
a lot
of images.
Patents historyClassifications IPC :F21V21/26International
patent category : B23B31/171 GB191104491 [3] An Improved Device for
Supporting or Suspending Electric Lamps and the like (1911) U.S.
Patent 1370231 [4] - 1921 harmonica arm - [5] 1923 parallelogram
& counter weight [6] 1926 friction [7] 1929 2 counter weight
[8] 1934 spring and counter weight FR757890 1934 CARWARDINE GEORGE
FR784932 1935 CARWARDINE GEORGE [9] 1937 friction [10] 1938 2
parallelogram 2 springs [11] 1939 2 pressure springs [12] 19..
a-symmetric arm-lamp [13] 1947 friction and a spring [14] 1949 [15]
1949 spring in the arm [16] 1954 friction arm1. U.S. Patent
3003737A11961 [17] -- 1961 [18] 1971 U.S. Patent 5333103A1 [19] -
1991 - EP0518569 1992 EP1274545 2003 mechanical coupling
devices
References[1] http:/ / www. tribtech. com/ app. 20. htm[2]
http:/ / www. ocp. tudelft. nl/ project2006/ wb14/ referenties.
html[3] http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/
GB191104491[4] http:/ / www. google. com/ patents?q=1370231[5]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB206435[6]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB254972[7]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB285045[8]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB481198[9]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB470502[10]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB489547[11]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB504791[12]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB536342[13]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB589994[14]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB618344[15]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB629364[16]
http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/ GB713378[17]
http:/ / www. google. com/ patents?q=3003737A11961
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Balanced-arm lamp 16
[18] http:/ / www. delphion. com/ cgi-bin/ viewpat. cmd/
GB1249774A[19] http:/ / www. google. com/ patents?q=5333103A1
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Article Sources and Contributors 17
Article Sources and ContributorsBalanced- arm lamp Source:
http://en.wikipedia.org/w/index.php?oldid=360396272 Contributors:
Addshore, BrucePodger, CSWarren, Chasnor15, J Milburn, Jlhughes,
Lumos3, Mars2035,Novangelis, Old Moonraker, Optigan13, Plrk, SDC,
ShelfSkewed, Sintaku, Stef breukel, Three-quarter-ten, Van helsing,
Walkersam, World arm lamp, Zippanova, 24 anonymous edits
Image Sources, Licenses and ContributorsImage:Compare human
arm.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Compare_human_arm.PNG
License: Public Domain Contributors: Stef breukelImage:Pressure and
expansion springs.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Pressure_and_expansion_springs.PNG
License: Public Domain Contributors: Stef breukelImage:extension
spring balanced arm support a flexible arm.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Extension_spring_balanced_arm_support_a_flexible_arm.PNGLicense:
Public Domain Contributors: Stef breukelImage:Extension spring
rolls over 2 wheels.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Extension_spring_rolls_over_2_wheels.PNG
License: Public Domain Contributors:Stef breukelImage:2 arm 1
spring 1 Tooth wheel.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:2_arm_1_spring_1_Tooth_wheel.PNG
License: Public Domain Contributors: Stef breukelImage:upper-arm 3
bars parallel.jpg Source:
http://en.wikipedia.org/w/index.php?title=File:Upper-arm_3_bars_parallel.jpg
License: Public Domain Contributors: Stef breukelImage:Angle poise
type of lamp.png Source:
http://en.wikipedia.org/w/index.php?title=File:Angle_poise_type_of_lamp.png
License: Public Domain Contributors: Stef breukelImage:single Lamp
arm, parralellogram ,2extension springs.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Single_Lamp_arm,_parralellogram_,2extension_springs.PNGLicense:
Public Domain Contributors: Stef breukelImage:lamp 2x arm, cable,
extension springs.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Lamp_2x_arm,_cable,_extension_springs.PNG
License: Public DomainContributors: Stef breukelImage:2 compression
springs 1 parallelogram lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:2_compression_springs_1_parallelogram_lamp.PNG
License: Public DomainContributors: Stef breukelImage:spring
balanced bending arm lamp.JPG Source:
http://en.wikipedia.org/w/index.php?title=File:Spring_balanced_bending_arm_lamp.JPG
License: Public Domain Contributors: StefbreukelImage:One Pressure
spring one parallelogram.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:One_Pressure_spring_one_parallelogram.PNG
License: Public DomainContributors: Stef breukelImage:Spiral spring
controls a pantograph arm lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Spiral_spring_controls_a_pantograph_arm_lamp.PNG
License: unknownContributors: World arm lampImage:2 torsion springs
balanced arm lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:2_torsion_springs_balanced_arm_lamp.PNG
License: Public Domain Contributors:Stef breukelImage:friction
rubber arm lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Friction_rubber_arm_lamp.PNG
License: Public Domain Contributors: Stef breukelImage:squeezing
rubber arm lamp outer position.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Squeezing_rubber_arm_lamp_outer_position.PNG
License: Public DomainContributors: Stef breukelImage:1 weight
chain lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:1_weight_chain_lamp.PNG
License: Public Domain Contributors: Stef breukelImage:1
Parallelogram + 1 Counterweight.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:1_Parallelogram_+_1_Counterweight.PNG
License: Public Domain Contributors:Rich Farmbrough, Stef
breukelImage:Pantographic parallel arms balance a light-weight-lamp
and counter-weight.gif
Source:http://en.wikipedia.org/w/index.php?title=File:Pantographic_parallel_arms_balance_a_light-weight-lamp_and_counter-weight.gif
License: Public Domain Contributors: Stef breukelImage:Complex
counter weight arm lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Complex_counter_weight_arm_lamp.PNG
License: Public Domain Contributors: StefbreukelImage:Counter
balanced straight arm lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Counter_balanced_straight_arm_lamp.PNG
License: Public Domain Contributors:Stef breukelImage:Lamp 2
counter weight.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Lamp_2_counter_weight.PNG
License: Public Domain Contributors: Stef breukelImage:Lamp 2 arms
2 counter weights outer position.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Lamp_2_arms_2_counter_weights_outer_position.PNG
License: PublicDomain Contributors: User:OrphanBotImage:Big and
small counterweight arm-lamp.gif Source:
http://en.wikipedia.org/w/index.php?title=File:Big_and_small_counterweight_arm-lamp.gif
License: Public Domain Contributors:Stef breukel, World arm
lampImage:arm-lamps having a vertical axis.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Arm-lamps_having_a_vertical_axis.PNG
License: Public Domain Contributors: StefbreukelImage:flexeble bars
lamp.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Flexeble_bars_lamp.PNG
License: Public Domain Contributors: Stef breukelImage:Tighten bold
friction arm system.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Tighten_bold_friction_arm_system.PNG
License: Public Domain Contributors: StefbreukelImage:Mechanical
locking joint.PNG Source:
http://en.wikipedia.org/w/index.php?title=File:Mechanical_locking_joint.PNG
License: Public Domain Contributors: Stef
breukelImage:Hydraulic-cylinder arm lamp.jpg Source:
http://en.wikipedia.org/w/index.php?title=File:Hydraulic-cylinder_arm_lamp.jpg
License: Public Domain Contributors: Stef breukelImage:pneumatic
arm lamp.PNG Source:
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License: Public Domain Contributors: Stef breukel
LicenseCreative Commons Attribution-Share Alike 3.0
Unportedhttp:/ / creativecommons. org/ licenses/ by-sa/ 3. 0/
Balanced-arm lampConfigurationLamps balanced with springsOne
Tension springTwo Tension springsCompression springsOther types of
spring
Lamps balanced by pressure and frictionLamps balanced with one
counterweightLamps balanced with two counterweightsLamps using
other systemsIn popular cultureSee alsoExternal linksPatents
history
License