The origin of thermos cups

The thermos flask is developed from the thermos flask, the principle of heat preservation is the same as the thermos flask, but people make the bottle into a cup for convenience.  In 1892, Oxford University, a Scotsman named James.  Sir Duvall invented the vacuum flask.  He put one bottle into the other and took the air out of the gap between the two bottles.  Because vacuum does not transfer 1950's heat, the hot or cold water in the thermos cup remains unchanged for a long time.  By this time, warm cups were at their peak, and family picnics, beach outings, and backcountry camping were all carried with them