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A suction cup, also sometimes known as a sucker, is an object that uses negative fluid pressure of air or water to adhere to nonporous surfaces and in the process creates a partial vacuum.^[1] They exist both as artificially created devices, and as anatomical traits of some animals such as octopi and squid.

Vacuum

The concept that's most important, and what makes a suction cup's bond strong, is the creation of a vacuum. 

When a suction cup is pressed against a surface, it pushes out all of the air beneath it and creates a vacuum 

between the cup and the surface. This vacuum holds the suction cup tightly, and it will continue to do so until 

the pressure on the outside of the cup becomes lower than the pressure on the inside of the cup.

Removal

When a suction cup is removed, it creates a loud, popping sound. That is the sound of the air rushing in to 

fill the vacuum that the suction cup created. A suction cup that is flexible, such as those made of rubber or 

PVC, can be stretched and tugged while still maintaining its vacuum. Often the vacuum much be broken by 

peeling up one edge of the suction cup and allowing air to rush in and break the bond.

The working face of the suction cup 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 fluid between the cup and the surface to be expelled past the rim of the

circular cup. When the user ceases to apply physical pressure to the centre of the outside of the cup, the elastic substance of which the cup is made tends to resume its original, curved shape. Because most of the fluid has already been forced out of the inside of the cup, the cavity which tends to develop between the cup and the flat surface has little to no air or water in it, and therefore lacks pressure. The pressure difference between the atmosphere on the outside of the cup, and the low-pressure cavity on the inside of the cup, is what keeps the cup adhered to the surface.

Details:    suction cup for machines feet

Specifications