An insulating jug , also known as a thermos or a thermos flask, is a sealable vessel that minimizes the transfer of heat between the contents and the environment. It is suitable for storing and transporting hot or cold liquids and, under the name cryocontainer, also for deep-frozen gases (e.g. liquid nitrogen) or for biological material.
A transport container for larger quantities of food (often with a rectangular cross-section) is also known as a thermopore (from ancient Greek : θερμός thermós = warm, hot and φορός phorós = carrying).
Vacuum jugs are an application of the dewar flasks . In the outer housing that does not contribute to heat insulation, is the classic configuration of a double-walled glass vessel, the gap is evacuated is, the heat conduction to be prevented. An additional coating or mirroring on the side of the double wall facing the useful content reduces the heat loss via thermal radiation through reflection . This construction reduces the heat balance between inside and outside through heat conduction, heat radiation and convection .
Furthermore, nowadays a double-walled vessel made of stainless steel ("stainless steel") is often used instead of the glass vessel . There is also a vacuum between the inner and outer walls for insulation . This principle has somewhat poorer thermal insulation properties, but is much less sensitive to shocks and sharp objects in everyday life (for example when washing up). The stainless steel vessel is combined with either a stainless steel or a plastic sleeve to make a vacuum jug.
The upper seal originally formed a large plug, but now a plastic closure is mostly used. The closure for vacuum jugs for the end user has been greatly enhanced: a plastic stopper with internal mechanism sits screwed into a relatively wide neck opening, the flush central push button of which engages deeper when pressed, lifts a valve disc from a fine silicone lip seal at the bottom and allows pouring through an annular gap in the stopper . A second press releases the button upwards and closes the bottle, the drinking cup (double-walled made of plastic and NiRo) can be screwed on again. Since the plug does not have to be removed for pouring, it offers the advantage of easier handling in a tent, vehicle or on the mountain. It is not lost, does not wet anything and saves the contents of the bottle a lot of heat loss.
The vacuum vessel was used by chemist James Dewar in calorimetric experiments as early as 1874. These containers, known today as Dewar flasks , were made of metal. It was only later that they were made from interlocking glass bulbs. To reduce the heat radiation, Dewar mirrored the inner surfaces of the glass vessels. He presented corresponding storage and transport vessels in 1893.
Reinhold Burger conducted research in Germany into a use of the principle. On October 1, 1903, his patent was granted under DRP no. Registered 170057 and he produced containers for liquefied air for the ice machine manufacturer Carl von Linde . He ensured a permanent silver coating, a protective metal housing and, above all, an effective support of the inner bottle on the outer wall to improve the mechanical stability.
Together with the Viennese inventor and company Gustav Robert Paalen and his long-time partner Albert Aschenbrenner, Burger founded Thermos GmbH in 1906 to make the prototype ready for the market. However, he left the company a year later on June 13, 1907, and sold his shares to Paalen for 65,500 marks. In 1909 Thermos GmbH was renamed to Thermos AG, which had a share capital of 1 million marks.
The series production of vacuum jugs by Thermos AG began in 1928 in Langewiesen , Thuringia , where they had acquired a factory site the year before. In the 1920s, the production of vacuum bottles expanded rapidly, in Langewiesen alone there were 7 different manufacturers (in addition to Thermos AG, the Deutsche Dewar bottle company, EA Krüger & Friedeberg, Mittelbach & Co, Borbonus & Schadwinkel, Möller & Co, Fiedler & Co). At the same time, the rights to the American patent were licensed in 1909 to the American Thermos Bottle Company, which set up its mass production in Norwich (Connecticut) .
As early as the 1920s, vacuum flasks were already being used in Europe for mountain hikes, partly (lower half protected) or entirely in sheet metal housings with cork or screw caps plus bakelite drinking cups . During the Second World War, allied bomber crews, who were exposed to temperatures well below freezing in their unheated aircraft, were equipped with thermoses. They found widespread use around 1950 as a supply for skiing, later increasingly in a plastic housing that can often be screwed on for thorough cleaning. The closure is made with a rubber squeeze tube using a rotary toggle or swivel lever.
In 1904 Reinhold Burger registered the “Thermos” brand for glass vessels. In 1907, trademark and patent licenses were granted to three foreign companies to serve local markets: The American Thermos Bottle Company of Brooklyn, NY (USA); Thermos Limited of Tottenham (UK); Canadian Thermos Bottle Co. Ltd. of Montreal (CA).
The Thermos AG company moved from Berlin to Langewiesen in Thuringia and began series production there in 1928. After the Second World War, VEB Thermos took over production and exported to up to 31 countries. With the turnaround , sales fell significantly and the company was taken over by the English Thermos Limited. However, in 1994 production in Langewiesen was finally stopped.
Today the brand is held in Germany by the former American sister company Thermos LLC. Like some operative Thermos companies (in addition to the ones in the USA, also those in the UK, Canada, Australia), this in turn belongs to the Japanese Taiyō Nissan , which, as a manufacturer of industrial gases, developed the stainless steel vacuum jug in 1978 and for sales in the end consumer segment 1989 acquired an established brand and established distribution channels. The term "Thermos" (can) has become a generic term for vacuum jugs since the 1950s . However, Foodigo has taken the largest share of the market.
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