Fig. 742 is a diagram of a regenerative gas-furnace. Underneath the heating-chamber K, are placed four regenerative-chambers L, which are filled with fire-bricks, built up with spacea between them. The regenerative-cham bers work in paira, the two under the left-hand end of the furnace communicating with that end of the heating-chamber, while the other two communi cate with the opposite end. The gas enters the heating-chamber through the passage M, and the air enters through the pas sage N, whereby they are kept separate up to the moment of entering the heating-chamber, but are then able immediately to mingle intimately, producing at once an intense and uniform flame. From the air-flue, the entering air is directed by the reversing-valve P into the air regenerator, and there becomes heated ready for entering the furnace ; at the same time, the gas entering from the gas-flue is directed by the reversing-valve R into the gas-regenerator, where it also becomes• heated to the same temperature as the air. The products of combustion, on leaving the opposite end of the furnace, pass down through the second pair of regenerators (as shown by the arrows), and, after being there deprived of their heat, are directed by the reversing-valves P R into the chimney - flue. When the second pair of regene rators have become heated by the passage of the heated pro ducts of combustion, and the first pair cooled by the entering of gas and air, the valves P R are reversed by hand-levers, causing the currents to pass through the regenerators in the contrary direction, whereby the hot pair of regenerators are now made use of for heating the gas and air entering the furnaces, while the cool pair abstract the heat from the products of com bustion escaping from the fur nace. The supply of gas and air to the furnace is regulated by the atop-valves S Si, whereby the nature of the flame in the furnace may be varied at plea sure, whilst a chimney-damper T is used to regulate the amount of pressure in the furnace in relation to the atmosphere, so as to allow the opening of the doors or working-holes of the furnace.
Fig. 743 shows the application of the regenerative gas system to a flint-glass furnace. The advantages of the regenerative gas-furnaces are :—(1) saving of fuel, both in quantity and quality ; (2) great cleanliness in the manufactory ; (3) complete command of the heat.
simplest and oldest arrangement for annealing is a tunnel, about 30 ft. in length, either provided with a lateral fire at one end, or heated (as at the Murano works) by the waste heat from the melting-furnace, and having a tramway, with movable trucks for the goods, running down the centre. The trucks are mounted on small solid iron wheels, protected from the fire by the projection of the body or pan of the truck, and are moved by an endless chain and a windlass; the pans are provided with hooks, so that they can be fastened together, to form a continuous train. Figs. 744 and 745 are different views of such an arrangement. Fig. 746 is a section, showing a tram way, beneath the main tramway, on which the pans or trucks, after they have been emptied at the end of the tunnel farthest from the fire and the glass-house, are returned to the glass - house by means of an endless chain. The pans are piled one upon another, and the lowest is hooked into the endless chain, by which they are drawn from one end of the tunnel to the other.
Another arrangement for accomplishing the same purpose, of which Fig. 747 is a bird's eye view, is a flat, hori zontally - revolving iron wheel, worked upon the same principle as a turn-table. The diameter of the wheel is about 25-30 ft. The goods are placed upon the wheel at A, and are carried by the wheel away from the fires B to C, where they are removed and sorted. This is a very perfect arrangement, and works continuously. Its dis advantage is the large amount of space in the centre of the wheel, which is praotically useless.
Yet another arrangement for annealing glass has been devised by Dr. O. W. Siemens. According to this invention, glass to be annealed is placed on a travelling furnace-bed mounted on wheels, and heated in a permanent furnace. When this truck is filled, it is wheeled out of the furnace, and over it is immediately placed a cover, the edges of which are so immersed in sand as to prevent all access of air. The truck is then wheeled away and allowed to cool, whilst another is put in its place in the furnace. Fig. 748 shows a section on the line 1 1 of Fig. 749, which is a section on line 2 2 of Fig. 748. The kiln or stove is com posed of a fixed brickwork heating-chamber A, and a movable bed or truck B, in which are placed the articles to be annealed. The truck is constructed of sheet metal, the sides being provided with internal ribs B', to prevent the glass articles from coming into direct contact With them, while the bottom has a layer or lining B' of sand or other suitable non-conducting material ; it is mounted on wheels 0, which travel upon rails, as shown, so that it can be readily run into and out of the kiln. The truck is open at the top and inner end, so that, when in position in the kiln, the flames or hot gases issuing from the ports Al on either side can play freely into and over the whole surface of the floor, before escaping through the openings A' to the chimney D.
When the truck is in position in the kiln, a close joint is formed between the two, by means of sand-troughs E on the sides of the truck, into which clip flanges F, fixed to the brickwork of the kiln. When in this position, the interior of the truck is heated to the required temperature, and the articles to be annealed are introduced into it through the openings G, which are then closed by covers. When a truck has been filled, and the articles have been subjected to the heat of the stove for a sufficient length of time, the former is withdrawn, and its open end and top are im mediately closed by the hood or cover II, sus pended close in front of the kiln, the flanges of which hood dip into the sand-troughs E E', so as to form a close joint ; the truck, thus forming a closed chamber, is then run to any convenient locality, where it and its con tents are allowed to cool. The hood is then removed ; and, after the glass has been taken out, the truck is again ready for use. The combus tible gas for heating the kilns pabses from the main channel I, leading from a gas-generator, up through the flues J, to the openings A', where it meets the air entering through passages K. Slides L and L' are provided for regulating the supply of gas and air to the kiln, or cutting it off when a truck is moved. The space beneath the truck B being quite open to the atmosphere, the under-framing and wheels are kept sufficiently cool to preveut injury.