A suction cup is a device that is generally made out of a plastic or rubber product and has the shape of half of a sphere. Suction cups are generally not used on their own, but are employed as attaching devices. Because of their malleable nature, they can adhere to smooth surfaces. The surfaces must be nonporous in addition to being smooth. Suction cups can adhere to such surfaces as glass and metal. They generally cannot adhere to brick or wood unless those substances have been sanded flat and coated.
As per their name, suction cups create adherence through suction. When they are applied to a surface and pressed, they expel some of their air underneath the cup. When the pressure is alleviated, air cannot reenter the cup as long as it is has been applied to a flat surface. A higher atmospheric pressure then exists underneath the cup, holding it in place.
If the suction cup is made out of good materials and is well-designed, it can remain in place for quite some time. Furthermore, it is possible for suction cups to hold a significant amount of weight if they are designed and applied properly. Suction cups are often used, in combination with a hook, to hang calendars, signs, even posters. Sometimes, they are used to adhere a rug or mat to a floor. For example, plastic mats have been designed for the floors of showers and bath tubs. Intended to keep bathers from slipping as they enter and exit the tub, as well as during bathing, many of these plastic mats have suction cups on the bottom so that they stay in place.
Historians believe that suction cups were first invented around the 3rd century BC. Because plastic was not an available material at that time, suction cups were made out of halved gourds. At that time, many people believed that ailments could be cured through the process of blood letting. Although this is know known to be an ineffective method, it survived for many centuries after this period. The gourds were applied to suck blood out from internal organs. It is believed that Hippocrates was treated with this method.
The suction cup that is used in industry today was patented in 1882. The design is based on a natural biological design. The octopus has numerous suction cup-like features along its arms. This was the inspiration for today’s patented suction cup.