air. It is in the control valves and mechanism for operating the moulds that improvements have been effected. In the earlier press machines the plunger was directly connected with the piston, result- ing in an equal pressure throughout the stroke. The later types in vhich the power is transmitted through toggles are much more efficient, since a slower motion and increased press. ire are obtained as the plunger nears the end of its stroke. This arrangement con- forms to what has been found to be the best practice in using the hand-lever press 1 . If too much glass be fed into the mould, less pres- sure is required to form the article than if there is a comparative shortage of glass when a heavy pull is required on the lever. The toggle machine, therefore, is adapted to compensate for variations in the quantity of glass fed into the mould.
In another type of press machine a series of moulds is arranged on a rotating plate, and by means of air pressure the mo ild containing the molten glass, when it reaches a point immediately beneath the plunger, is forced upwards to meet the fixed plunger. This type of machine is employed in making deep pressed ware such as tumblers and is usually adapted only to solid moulds. Press machines natu- rally vary very much in size according to the ware to be produced. Probably the largest of its kind is one operated i:i America for the production of glass burial caskets, which measure up to 6 ft. 3 in. in length. The machine weighs about 6 tons, and is capable of de- veloping a pressure of about 700 tons.
Press and Blow Machines. This type of machine is used in greater numbers and of more varied forms than any other class of glass machinery. It is essentially the bottle machine. It may be interesting to note that the first attempt to produce a machine for making bottles was the work of an English nan, although it is to American skill and enterprise that the successful development of this complex machine is due. A press and blow machine is designed to perfonn two distinct operations. In the first the neck of the bottle is formed by pressure in what is known as the pirison mould, and in the second the body is blown and finished in the blow mould. In general the machine consists of two circular plates, either disposed one above the other and capable of a step by step rotation abo.it a central pillar, or arranged side by side, the second being driven fro/n the first by an intermediate pinion or gearing also by a step by step motion. At regular intervals near the periphery of one plate (the upper one in the first case) are situated the parison moulds for form- ing the neck, and on the other plate similarly situated are the blow moulds for forming the body. All the necessary movements, includ- ing the rotation of the plate, the actuation of the plunger, the automatic opening and closing of the moulds, and the transfer of the blank from the parison mould to the blow mould are performed by air pressure. In certain types of machine the last-mentioned operation is not performed automatically, but by hand.
The sequence of operations in making a bottle on such a machine is as follows. A supply of molten glass is fed into the blank mould, either by one of the various types of automatic feed or by a gatherer using the usual form of punty rod. A blowing head then makes con- tact with the mould and blows the glass down on to the plunger, thus forming the neck of the bottle. The plunger is withdrawn, and the table advanced to the next position. A puff of air is blown into the orifice, to blow the glass to the full size of the blank mould. Again the table advances, and at the third position the mould opens and the glass blank is transferred to the blow mould situated on the second table. This mould closes round the glass, and the blowing head takes up the correct position to supply the necessary air pressure to blow the bottle to the required shape. The mould again advances and opens at the next position when the finished bottle is removed and transferred to the annealing lehr. Considerable difficulty was experienced in producing satisfactorily small narrow-necked bottles, but within the last few years the di (iculties have been overcome and satisfactory results have been obtained on fully autonatic and semi-automatic machines. Naturally the speed of production de- pends on the type of machine and the size of the ware being pro- duced, but the capacity of some of the later types of machine may be gathered trom the fact that eight or nine bottles of one quart capacity can be produced in one minute, and smaller even faster.
Blow Machines. The use of this type of machine is not nearly so common as that of the press and blow machine. They are princi- pally used in the production of electric lamp bulbs, la up chimneys, tumblers and similar light hollow ware. The main difference and special feature of these machines is that the moulds are coated internally with carbonized material, and the article is rotated in the mould during the period of blowing. It is therefore obvious that ware produced in such a mould must have a smooth regular surface, and any kind of figuring or ornamentation is out of the question. These machines may be semi-automatic, in which case a gatherer is necessary to feed the required quantity of glass to the machine, or they may be fully automatic, in which case the machine sucks up the molten glass from the tank. The former type of machine com- prises generally four vertical frames mounted on a cast-iron base frame. A horizontal shaft carrying four circular discs runs in suitable bearings situated at the head of the vertical frames. Mounted loosely on the shaft and close to the discs are four arms, which, by means of suitable cams and tripping devices, can be rotated between a horizontal and vertical position. Each arm is provided with a small air pump at its extremity. On a level with the arm when in the
horizontal position is a small disc, which serves the purpose of a marverer. This disc, mounted in a bearing attached to the back of the frame receives its motion from the vertical disc. A suitable mould disposed at the base of each vertical frame is mounted on a horizontal spindle capable of movement through 90. When in the horizontal position, the mould is submerged in a trough of water situated in the base casting. The moulds are hinged, and the opening and closing movements are effected by a rod at the back.
The sequence of operations in making an electric bulb is as follows : A gatherer having withdrawn from the pot or tank a mass of glass on his blowpipe secures the latter in contact with a rubber washer, forming part of the air pump at the end of the machine arm when the arm is in a horizontal position. The mass of glass on the end of the blowpipe, which is slowly rotating, comes into contact with the marverer, which is also rotating in the same direction. After a short period a cam comes into operation, causing a slight puff of air to be given to the glass through the blowing iron. The arm now assumes a vertical position with the glass at the bottom, and at the same time the mould takes up a vertical position, and the operator by pulling a lever causes the moull to close over the glass. Whilst the glass still attached to the end of the blowpipe is kept rotating in the mould, a puff of air is admitted through the blowpipe and expands the glass into the desired bulb. The operator then opens the mould, withdraws the blowing iron from the machine, and places it in an adjacent stand, when another operator severs the bulb from the iron with shears; the iron is cleaned off and is again ready for use.
A brief description of the other type of machine, which is fully automatic, is as follows: The machine rotates by a step by step mov2 rient about a vertical axis at the rate of about two revolutions per minute, and is provided with six double arms actuated by cams disposed on a vertical drum. The first operation is the projection of the cantilever head into the furnace, when glass sufficient for two bulbs is sucked up by vacuum into the blank moulds; the cantilever head then withdraws and the glass blanks are released and deposited in cups. The cantilever heads are capable of being rotated about a horizontal axis, and the cups are in their top position when receiving the glass. At this point a rod is forced up into the glass to form a hale for the blowing operation. The machine is rotated to the next position and the head moves into the horizontal plane when the gliss blank receives the first puff of air; at the next rotation of the machine the head assumes a vertical position with the partly formed b.ilb hanging downwards. At this stage either a reciprocating or a swinging motion is imparted to the head in imitation of a hand- worker's movements. The mould is then raised, and closes over the partly formed bulb, and a final puff of air is given. The next rotary movement of the machine opens and lowers away the mould, and the finished bulb is removed by hand. From the time that the glass is fed into the cups of the head until the bulb is blown the glass is kept rotating. Before the mould is again brought into operation it passes through a mixture of soap and water.
Sheet or Window Glass Machinery. The earlier attempts to manufacture window glass by machinery better illustrate the tendency to imitate the methods which had proved by long practice to be best suited to production by hand. The objective of all the earlier machines was the production of as perfect a cylinder of glass as possible. Patents and improvements related rather to modification of detail than variation of first principles. The general method em- ployed in this type of machine is to bring a ring or circular bait of metal into contact with the molten glass, to raise the bait by mechanical means, and at the same time supply air under a low but increasing pressure into the cylinder of glass so formed.
The following will give in brief the outline of a machine which is being successfully worked at the present time: A pot or receptacle about 3! ft. in diameter, and of a denth sufficient to hold the quantity of glass required in making a cylinder is charged by means of a ladle with molten glass taken from a tank furnace. A structure alongside the pot is so arranged as to permit of a bait being raised vertically by means of a motor to the full height of the cylinder to be drawn. The bait, which consists of a short hollow cylinder about I ft. in diameter, furnished with an internal lip at its lower end, is lowered into the molten glass contained in the pot, which has been left standing for a short time until the glass has attained the correct drawing temperature. As the bait is lowered the glass flows over the lip and solidifies, thus forming a starting point for the cylinder. An operator standing on a platform well above the pot level starts the motor, which raises the bait, and at the same time air under pres- sure is admitted through the top of the bait. The cylinder of g'ass quickly increases in diameter, and the pressure of air is arranged to give the desired dimension. In order to ensure a uniform thickness of wall, both the speed of drawing and the pressure and volume of air are increased to counteract the increased viscosity of the glass due to falling temperature. When the full cylinder, 40 ft. long and weighing about 1,000 lb., has been drawn, it is cracked off from the pot; the lower portion is swung out and the cylinder lowered into a horizontal position ; the top portion or cap is cracked off and the remainder is divided into convenient lengths for handling ; these are usually about 5 ft. long. The remaining processes of slitting and flattening are similar to those followed in hand-made cylinders.
In a later, and not yet so widely used, type of machine the sheet is drawn directly from the tank and requires no subsequent flatten-
