GB559131A - Improvements in or relating to the sealing of tins and like containers - Google Patents

Abstract

559,131. Closuring containers. FRASER & SON, Ltd., J., and ROBINS, W. H. Nov. 9, 1942, No. 15828. [Class 125 (ii)] [Also in Group XXII] Soldering.-A tin or like container filled with dry foodstuffs and having its lid sealed thereon except for a small opening, has the opening closed, such as by soldering in a chamber from which air pressure is reduced considerably below atmospheric and the chamber charged with an inert gas to a pressure substantially above atmospheric prior to closing the opening. The containers are placed in a chamber 10 with one or more gas-tight doors 11. The top of the chamber has a swelling 18 with windows 19, 20 and a universal joint 21 for an electrically heated soldering iron 22, packing such as a gland or one or more slip-washers being provided to maintain the joint in a fluidtight condition irrespective of whether the internal pressure is below or above atmospheric. A multi-way valve 24 connects the chamber 10 either to a vacuum pump 25 through a pipe 26 or to a cylinder 27 of inert gas such as carbon dioxide or nitrogen by a flexible pipe 28. The valve 24 may also be arranged to connect the chamber with the atmosphere or a normally pliable release valve may be used. A pressure gauge 36 is also provided. Water vapour given off during evacuation may be condensed by a condenser in the pipe 26. A rack 31 secured to the chamber may support a number of gas cylinders. The gas is fed at a pressure greater than atmospheric so that the chamber can be charged with gas to a pressure say one or two lbs. per sq. in. above atmospheric. When using carbon dioxide the gas may flow into the chamber from a low-pressure cylinder fed from a highpressure cylinder through a pressure reducing valve so as to avoid excessive frost. Nitrogen is used direct from a high-pressure supply, being controlled by a valve 32. Large chambers may be provided across the top and sides with a number of soldering-irons. The tins become bulged by the gas and may be tested for leaks by immersing in a liquid and leaky tins may also be detected in store due to loss of the bulged shape.