Porthole
The term porthole is used in several areas. It is most commonly used to describe a window in shipbuilding. The reason for the circular shape is to prevent twisting ( elasticity ).
Use in shipbuilding
Mostly a circular window is meant in the nautical language . In shipping , portholes serve as watertight side windows in the side wall of ships and submarines . The often round or rounded shape facilitates sealing and increases the compressive strength against the effects of water from the outside. The function of the portholes is the same as that of windows in a building: They are used to let in daylight or to ventilate the individual rooms below deck . In addition, it enables the environment to be observed. Because of this, portholes on ships are only installed above the waterline .
The construction of a porthole is usually kept relatively simple: A circular pane of glass is surrounded by an equally circular metal ring and connected to the ship's side on a hinge . If the porthole is not normally used to let in light (for example in cargo holds ), it can also be made of metal only. In addition, partially Porthole deadlights of metal attached, for example, during a storm to protect against broken glass or blackout when warships are used to attract any attention or to draw enemy fire. A seal between the ship's side and the porthole serves as protection against ingress of water. The size depends on the use and is between a few centimeters and a little less than a meter. Accordingly, the weight fluctuates between a few and a few hundred kilograms. The weight results from the glass and the metal ring, which is usually made of bronze , copper , iron , steel or aluminum . Bronze and copper are most commonly used because they are resistant to salt water . When planning portholes, care is taken to ensure that they fulfill their purpose on the one hand and that they must not impair the strength of the ship's side and thus that of the ship on the other.
Portholes can be operated from inside the ship, usually a lever is attached to open or close by hand.
They have a different meaning when used in submarines. There they are used to observe the environment and are usually not open. In addition, the portholes on submarines are usually concave to increase their resistance to external water pressure . This causes them to be pressed against the frame of the porthole. On the inside, they are usually not spherically curved, on the one hand this reduces the field of vision to the outside, and on the other hand, it reduces glass tensions that can occur due to the curvature. Depending on the depth at which the submarine is to be deployed, the portholes are up to several centimeters thick.
Use in space
In the same form as in ships, such windows are also used in space travel, for example on the International Space Station . They serve to be able to see outside.
They are usually made of quartz glass , as the glass has to withstand a temperature difference of several hundred Kelvin without jumping under the load. The frame is made of titanium and then covered with enamel .
In the case of the Apollo capsules , a porthole was installed in the stern, which enabled entry and exit at the beginning and end of each flight.
Use in washing machines
In another use, the term is used in connection with front-loading washing machines in the household sector, where a porthole serves as a loading hatch. The glass only fulfills a useful function here, but is no longer absolutely necessary today, since washing is usually automated. It allows you to observe the washing process from the outside without having to interrupt it.
The porthole has the opposite meaning here as in shipping: It serves to seal the washing machine from the outside and to prevent water from leaking. The production method is similar to that in shipbuilding, here too the frame is made of metal and the porthole has a lever to open and close it.
Use in architecture
In architecture , porthole, or more often ox-eye , denotes round or oval windows, as they were common especially in the Baroque era .
Use in automotive engineering
In the automotive industry, portholes were used especially by American manufacturers from the 1930s to the 1970s. The common name for this is Opera window .
Other uses
When English darts darts designating Bull's Eye (in short: the Bull ), the center of the target.
In the past, a fried egg was also called bull's eye , porthole or ox eye .
