![Suction-lifter-one-cup](https://upload.wikimedia.org/wikipedia/commons/f/f9/Suction-lifter-one-cup.jpg)
A suction cup, also known as a sucker, is a device or object that uses the negative
fluid pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
of air or water to adhere to
nonporous
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
surfaces, creating a
partial vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
.
Suction cups are peripheral traits of some animals such as
octopus
An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...
es and
squid
True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...
s, and have been reproduced artificially for numerous purposes.
Theory
The working face of the suction cup is made of elastic, flexible material and has a curved surface. When the center of the suction cup is pressed against a flat, non-porous surface, the volume of the space between the suction cup and the flat surface is reduced, which causes the air or water between the cup and the surface to be expelled past the rim of the circular cup. The cavity which develops between the cup and the flat surface has little to no air or water in it because most of the fluid has already been forced out of the inside of the cup, causing a lack of pressure. The pressure difference between the atmosphere on the outside of the cup and the low-pressure cavity on the inside of the cup keeps the cup adhered to the surface.
![Suction cup 2](https://upload.wikimedia.org/wikipedia/commons/f/f5/Suction_cup_2.jpg)
When the user ceases to apply physical pressure to the outside of the cup, the elastic substance of which the cup is made tends to resume its original, curved shape. The length of time for which the suction effect can be maintained depends mainly on how long it takes for air or water to leak back into the cavity between the cup and the surface, equalizing the pressure with the surrounding atmosphere. This depends on the porosity and flatness of the surface and the properties of the cup's rim. A small amount of mineral oil or vegetable oil is often employed to help maintain the seal.
Calculations
The force required to detach an ideal suction cup by pulling it directly away from the surface is given by the formula:
:
where:
:''F'' is the
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
,
:''A'' is the area of the surface covered by the cup,
:''P'' is the pressure outside the cup (typically
atmospheric pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...
)
This is derived from the definition of pressure, which is:
:
For example, a suction cup of radius 2.0 cm has an area of
(0.020 m)
2 = 0.0013 square meters. Using the force formula (''F'' = ''AP''), the result is
''F'' = (0.0013 m
2)(100,000 Pa) = about 130
newtons
The newton (symbol: N) is the unit of force in the International System of Units (SI). It is defined as 1 kg⋅m/s, the force which gives a mass of 1 kilogram an acceleration of 1 metre per second per second. It is named after Isaac Newton in r ...
.
The above formula relies on several assumptions:
# The outer diameter of the cup does not change when the cup is pulled.
# No air leaks into the gap between the cup and the surface.
# The pulling force is applied perpendicular to the surface so that the cup does not slide sideways or peel off.
Artificial use
![GoPro camera mounted on car](https://upload.wikimedia.org/wikipedia/commons/a/a5/GoPro_camera_mounted_on_car.jpg)
Artificial suction cups are believed to have first been used in the third century,
B.C., and were made out of
gourd
Gourds include the fruits of some flowering plant species in the family Cucurbitaceae, particularly ''Cucurbita'' and ''Lagenaria''. The term refers to a number of species and subspecies, many with hard shells, and some without. One of the earli ...
s. They were used to suction "bad blood" from internal organs to the surface.
Hippocrates
Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history of ...
is believed to have invented this procedure.
The first modern suction cup patents were issued by the United States Patent and Trademark Office during the 1860s. TC Roche was awarded U.S. Patent No. 52,748 in 1866 for a "Photographic Developer Dipping Stick"; the patent discloses a primitive suction cup means for handling photographic plates during developing procedures. In 1868, Orwell Needham patented a more refined suction cup design, U.S. Patent No. 82,629, calling his invention an "Atmospheric Knob" purposed for general use as a handle and drawer opening means.
Suction cups have a number of commercial and industrial applications:
* To attach an object to a flat, nonporous surface, such as a refrigerator door or a tile on a wall. This is also used for
mooring ships.
* To move an object, such as a pane of glass or a
raised floor
A raised floor (also raised flooring, access floor(ing), or raised-access computer floor) provides an elevated structural floor above a solid substrate (often a concrete slab) to create a hidden void for the passage of mechanical and electrica ...
tile, by attaching the suction cup to a flat, nonporous part of the object and then sliding or lifting the object.
* In some toys, such as
Nerf
Nerf is a toy brand formed by Parker Brothers and currently owned by Hasbro. Most of the toys are a variety of foam-based weaponry, with other Nerf products including balls for sports such as American football, basketball, and baseball. The ...
darts.
* As toilet
plunger
A plunger, force cup, plumber's friend or plumber's helper is a tool used to clear blockages in drains and pipes. It consists of a rubber suction cup attached to a stick (''shaft'') usually made of wood or plastic. A different bellows-like desi ...
s.
* To climb up almost or completely vertically up or down a flat, nonporous surface, such as the sides of some buildings. This is part of
buildering
Buildering (also known as edificeering, urban climbing, structuring, skywalking, boulding, or stegophily) describes the act of climbing on the outside of buildings and other artificial structures. The word "buildering", sometimes misspelled bil ...
, which is also known as urban climbering.
* To hold an object still while it is worked on, such as holding a piece of glass while performing edge grinding.
On May 25, 1981,
Dan Goodwin
Daniel Goodwin (born November 7, 1955 in Kennebunkport, Maine) is an American climber best known for performing gymnastic-like flag maneuvers and one arm flyoffs while free soloing difficult rock climbs on national TV and for scaling towering sk ...
, a.k.a. SpiderDan, scaled
Sears Tower
The Willis Tower (originally the Sears Tower) is a 108-story, skyscraper in the Loop community area of Chicago in Illinois, United States. Designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM), ...
, the former world's tallest building, with a pair of suction cups. He went on to scale the Renaissance Center in Dallas, the
Bonaventure Hotel
The Westin Bonaventure Hotel and Suites is a , 33-story hotel in Los Angeles, California, constructed between 1974 and 1976. It was designed by architect John C. Portman Jr.. The top floor has a revolving restaurant and bar. It was originally ow ...
in Los Angeles, the
World Trade Center
World Trade Centers are sites recognized by the World Trade Centers Association.
World Trade Center may refer to:
Buildings
* List of World Trade Centers
* World Trade Center (2001–present), a building complex that includes five skyscrapers, a ...
in New York City, Parque Central Tower in Caracas, the Nippon TV station in Tokyo, and the Millennium Tower in San Francisco.
Spider-man aka SpiderDan Goodwin the Skyscraperman scales the Millennium Tower in San Francisco - YouTube
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See also
* Horror vacui (physics)
In physics, horror vacui, or plenism (), commonly stated as "nature abhors a vacuum", is a postulate attributed to Aristotle, who articulated a belief, later criticized by the atomism of Epicurus and Lucretius, that nature contains no vacuums bec ...
* Magdeburg hemispheres
The Magdeburg hemispheres are a pair of large copper hemispheres, with mating rims. They were used to demonstrate the power of atmospheric pressure. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum a ...
*Self-sealing suction cup The self-sealing suction cup is a suction cup that exerts a suction force only when it is in physical contact with an object. Unlike most other suction cups, it does not exert any suction force when it is not in contact with an object. Its grasping ...
References
{{Authority control
Tools
Vacuum
Joining
la:Cucurbita (animalium)