POTTERY MACHINERY

The potter's wheel is the earliest machine of which we have any record ; and yet, strange to say, no appliances have received so little development or improvement as those used by the worker in clay. The distaff and spindle have long been superseded hy the spinning jenny ; but the potter's wheel still remains practitically the some rude contrivance that has been known from the earliest ages. 

Remarkable as is the manual dexterity of the potter, enabling him to turn out articles of the same pattern with almost incredible rapidity, the keen competition of the present day calls for a still greater production, with a simultaneous reduction of wages. The application of power to potting is not such an easy problem, considering the great and rapid variations required in the speed, and in some cases a reversing of the motion. 

When the "thrower" does not turn the wheel with his feet, the motive power is generally supplied by women or children, who soon learn when to turn fast or slow by watching the work as it proceeds. If not absolutely the first to apply power to potting machinery, Mr. Wm. Boulton, of Burslem, may claim credit for having been the first to bring about a practical solution of the question ; and the series of various machines which he has put up at the works of Messrs Wedgewood, Etruria; Messrs. Minton, Stoke-upon-Trent, and many other well-known firms, justifies his title of potters' engineer.

In arranging works Mr. Boulton dispenses, as far as possible, with line shafting, and drives the various machines by a continuous rope, preferably of cotton, always running, and brought by a friction pulley into contact with the machines as required.

Fig. 1 the improved potter's wheel

Fig. 1, page 475, shows the improved potter's wheel. The inverted driving cone A, continually revolving is, by means of the lever and links made to touch the somewhat rounded driven cone B, with a varying portion of its surface, so as to give a great range of speed to the head C, on which the clay is placed.

Fig. 2 is an elevation, and Fig 3 a plan, of a similar machine, arranged to form one of a series.

An improved "jolley," or machine for making a quantity of articles of the same pattern, such as cups and saucers, is shown in elevation at fig. 4, and in plan at Fig 5.

This, it will be observed, forms one of a series of machines driven by the same cotton rope, although change of speed is not necessary in this case.

The spindle D, with its mould E, is made to revolve by the rope being brought in contact with the pully F, by the friction pully G being pressed with the operator's foot.

A "bat," or flat piece of clay, is placed in the mould E, and then the counter-weighted "profile" of template H, is brought down, so as to shape the inside of the article.

Fig. 6 shows an elevation, and Fig 7 a plan, of the automatic multiple machine, for producing a large number of similar articles, plates for instance.

In this case the rope, always running, causes the grooved pully J, and spindle K, to revolve. The motion is communicated by the worm and worm-wheel, and the horizontal shaft L, on which is keyed the bevel wheel M, with teeth on only a third part of its circumference. 

This drives the bevel wheel N, and therefore causes the vertical shaft O, with its table P, and three spindles and heads Q, Q¹ and Q² to revolve intermittently. 

A second rope is constantly running in close proximity to the head when in the position of Q, and, as soon as each of the three pullys comes in contact with it in turn, it revolves rapidly on its own axis. Meanwhile the other two heads, Q¹ and Q² being out of contact with the rope, remain motionless, so that the finished article can be removed from one, and a fresh "bat" put on the other. The cam R keeps the "profile" S raised until the proper moment, when it falls by its own weight; and the cam T acts on the arm U for cutting off the raw edge of the article. 

All the operations are performed automatically, no skilled labout is required in connection with this machine. 

The better class of goods, after having been moulded and partially dried, are turned by hand in the lathe. First a thin cut is taken off while the work revolves towards the tool; and then the article is polished while revolving in the opposite direction. 

Up to present the lathe has always been driven by the operator or his assistant, the change of motion being given as required. Fig 8 shows an elevation, and Fig. 9 an end view of Mr. Boulton's arrangement of lathe for being driven by power.

The bevel wheel V is constantly running, and the turner can bring it against one or other of the bevel pinions of the countershaft, by means of the pedal and rod W, a cotton rope communicating motion between the cone and grooved pulleys. In this case variation of speed in not required.

Potter's clay is made by mixing together proper proportions of ground flint, Crnwall stone, ball and China clay. The flint and stone are ground wet, in what is termed a flint mill, in which large stones, attached to arms on a vertical shaft, are driven round over a stone paved floor. 

Mr. Boulton's improvement in this apparatus consists in an arrangement of plates which cause the material to get under the stones more effectually.

The ball and China clay are delivered at potteries in hard lumps, which were formerly reduced to a liquid state by means of hand labour. This is now done more rapidly and effectually by the patent "blunger'" which consists of an octagonal pan with a revolving vertical shaft, carrying a series of knives set on the bevel.

This arrangement gives the solid clay a tendency to rise, and well mixes it with the water, at the same time cutting it to pieces. The "slip," consisting of these clays and the ground flint and stone, properly mixed with water, is forced by a pump into a filter press, where us us deprived of its excess water, and reduced to a suitable consistency.    

In order to prevent the cloths of the press from being burst when a certain pressure is attained, Mr. Boulton has devised the two arrangements of pump shown at Figs. 10 and 11.

In the former the rod of the ram is provided with the spring X, which yields, so that the ram does not enter the barrel, when the pressure exceeds the resistance of the spring .

The latter, however, is the form more usually adopted, because the resistance can be adjusted. In this case the plunger is loaded with the weights Y, and when the pressure exceeds their resistance the plunger and rod rise, so that the eccentric strap is clear of the eccentric in its revolution.   

Mr. Boulton utilises the exhaust steam of the engine for heating the drying chambers, thus saving both time and fuel; and also he arranges the shelves to revolve around a central axis, so that they may be filled and emptied without a man having to go in the chamber.

For grinding gold and colour, too, for printing the patterns, the muller and table are made to revolve by power in different directions, grooves being provided to prevent a vacuum being formed between them. 

In the automatic power-driven potter's machinery the production can be doubled; skilled labour is entirely dispensed with, and unskilled labout deminished by one half.