পাতা:অনাথবন্ধু.pdf/৭২৯

Number 10 THE It was then proposed to drain the pot between draws, and to accomplish this a furnace was built with four pots mounted on a turntable and so arranged that each pot would be tilted at a certain point. In this way there would always be one pot used for drawing cylinders while the others would be heating and draining. An improvement on this the double reversible pot mounted on trunnions, invented by L. A. apparatus was Thornburg, in using which one side was always being drained while a cylinder was being drawn from the glass in the other. This apparatus is still used by the American Window (lass Company and it is doubtful if any other forin of receptacle for the molten glass can equal it for high output and economical operation. It was thought in the early days of machine operations that some change in the chemical composition of the glass, or in the character of the materials from which it was made, would be necessary in order to adapt it to the new working conditions. Considerable experimenting was done with various mixtures and various kinds of materials, but in the end it was found that the chemical composition that gave the best glass under hand bperations was also the best for machine operations. The original Lublers' machine made a cylinder about the size of a hand blown cylinder. It soon became obvious that production could be very materially increased by ladling a larger quantity of glass into the pot and drawing a longer cylinder which could be cut up, after lowering, into lengths suitable for flattening. in the control of drawing speed and air supply, This introduced complications but eventually the point was reached where five lattening lengths about 14 inches in diameter by 60 inches long could be produced at one draw. The next step-and almost important one in increasing production-was to increase the diameter of the cylinder. It was not possible 27 WINDOW GLASS MACHINE. SOS umugrnur \upa rur 5 srnum" "our"uz-mar to flatten a single strength cylinder that was much larger than the standard size of 14 inches in diameter by 60 inches long. It was suggested, however, that there would not be any difficulty in flattening, if the dimensions would be reversed, and flattening lengths produced which would be 19 inclhes diameter by 42 inches long, employing, of course, pots of larger diameter and containing a larger quantity of glass. This method was tried out and proved so successful that it was imme liately adopted in all factories operating machines. The size of the cylinders has since then been considerably increased, so that today, using a 36-inch pot, single strength cylinders are made up to 2l inches diameter by kti () inches long, and double strength up to 24, inches in diameter by 320 inches long. As the length of the cylinders was increased, another complication entered. It was found that even with the graduating valve opening and increasing with automatic precision the amount of air entering the cylinder, the pressure at the point of draw was not constant, but was applied in a series of surges which produced corrugations However, in the cylinder termed “pulsations.' Lubbers devised a means for overcoming the trouble sufficiently to meet the requirements of practical operations. That was to introduce an excess of blowing air and then allow a portion of it to escape through a vent hole. With the discovery of this principle, Lubbers completed the devising of a system of air control that stands today unchanged except in perfecting and applying improved mechanical details required by the huge cylinders now drawn. This outline gives an inadequate idea of the immense amount of study and research expended on the various prollems involved, and the numerous alterations in the mechanical details that were found necessary while the machine was being developed and conditions of machine operation determined. It was a tedious and difficult task, but one by one the difficulties