Publication: Electrical Review - London
THE INSULATOR IN THE MAKING.
A Description of the Methods Employed by Messrs. Taylor, Tannicliff & Co., Hanley.
ALTHOUGH our readers are probably well aware of the progress and extent of things electrical in the Potteries district, yet few of them realise that at least one important section of the local industry is the manufacture of porcelain insulators and fittings for the electrical trades.
Of the several firms engaged in the business, one of the beet known is that of Taylor. Tunnicliff & Co., Hanley, whose factory we are able to describe through the courtesy of Mr. Thomas Taylor, the chairman of the concern.
Originally commenced in 1867, the business was carried on for 10 years, at Havelock Works, Hanley, then the present extensive premises at Eastwood, Hanley, were taken over, and these have since been developed to meet the growing business, which a few years back was turned over to a limited liability company, with Mr. Taylor as chairman.
As compared with ordinary potting, the business of insulator-making is highly technical, necessitating the use of specially prepared clay, special machinery, and most accurate workmanship ; in fact, a large staff of skilled mechanics is kept constantly employed in constructing and renewing machinery.
Owing to the care necessarily exercised in the preparation of the materials employed, the firm calcines and grinds this for itself.
Fig. 1 shows one side of the mill where, after calcination and preliminary crushing, the Cornish stone (boulder flints), glazes, &c., are water-ground in large circular pans, the latter being lined with chert pavers, over which heavy stones or runners are driven, after the charge of material is placed in the pans. The material is thus reduced to the consistency of a cream, fine enough to pass through silk lawns of 90 to 120 strands to the inch, through which it is forced by special machinery. It then passes to large store arks under the grinding pans ready for mixing with the various components that go to make up the "body," or clay, for the various articles required.
Many advantages arise from the firm grinding its own material, as this enables the manufacturer to import from Cornwall and elsewhere, the raw material direct from the mines that produce the quality he specially requires for the particular class of goods he makes, and to dispense with local millers, who grind and sell to the general or domestic trade.
From the store arks the components to form the "body" are pumped through conduits to the mixing room, where the blending proper takes place. This is a most important department where the knowledge and experience of the practical potter are utilised to produce, by the judicious blend¬ing of the necessary components, the body be requires for his special trade, and in some cases the com¬ponents number six or seven varieties. In this way a class of goods are produced, superior to foreign makes, which consist of probably only two components after blending. The whole of the components forming the body are again passed through a series of fine silk lawns to the final mixing ark. The old process wan then to pass the body still in its liquid state on to heated kilns, where the water was evaporated, leaving the body in a plastic state, but this is superseded by a more modern method, whereby the slip, a milky fluid, is pumped into a specially made filter press, consisting of a number of doable trays about 90 in number. These double trays, measuring about 6 ft. x 2 ft., are lined with a double layer of specially woven cotton sheeting, and are connected with the pumps by iron piping leading to nozzle taps in the centre of each filter tray, the whole being firmly bolted together by tie rods. The pumps force the water through the cloths in-the filter trays, in a clear transparent stream, leaving the clay between the trays, which are then opened and separated, and the lining of clay rolled up for removal (see fig. 2) to the pug mill for further preparation and storage for the general supply of the factory.
The first, and one of the moat important operations in the manufacture of an insulator, takes us back to one of the oldest, if not the oldest, handicrafts in the world, viz., the "potter's wheel," and although steam and electric power have of recent years been utilised for driving the potter's wheel, the manipulation of the potter himself, or thrower, as he is called, who site over it as shown in fig. 4, is exactly the same as 5,000 years ago. A clay ball is weighed by the attendant to suit the size of article to be made, which the potter puts on the revolving wheel in front of bins, and then with both hands dexterously encloses it us it revolves, and so spins it, as it were, into a central position, when it is easily shaped into either an insulator or a solid pillar, from which a number of small articles may be afterwards formed on the lathe. Or the potter may " break the ball," viz., make it hollow by pressing his thumb into the centre of it as it revolves, and so convert the solid ball of clay into a variety of hollow shapes such as vases, jugs, mugs, basins, &c.; a good workman, in the space of, say, 10 minutes, being able to form as many articles of many different shapes and sizes.
The English manufacturers maintain that insulators made by this process are, without doubt, superior to the cheaper foreign made ones, which are not "thrown" on the potter's wheel, and which are imported here, and even exported again to our Colonies, and in some cases certified as English made. The thrower, in making an insulator, uses no "tools," but simply spins or forms the article entirely with his lauds.
When the clay is in a very soft state, the insulators are carried away by the attendant to a stove or hot room to dry part of the moisture out of them, and then pass to the "turner" (fig. 7) in such consistency that they can be fixed on the lathe, and turned like soft wood into the finished shape and size. The screw hole for the iron bolt is tapped in the interior, and the insulator then passes on to another stove or hot room, after which each one is examined by women attendants, or fettlers, for any faults in manipulation or drying (fig. 6). Hundreds of varieties of electric porcelain articles from various de¬partmental undergo the same scrutiny, and receive the finishing touches necessary, before passing to the final hot room or stove, where all moisture is eliminated prior to their subjection to the severe temperature of the oven fire, which is somewhat over 1,000° C.
In the rooms adjoining the ovens the articles are placed in coarse clay boxes (saggars), and carried into the oven proper (fig. 8). The interiors of the ovens are circular in shape, and the first layer of saggars is placed on the floor at the extreme circumference, thus forming the "first ring"; other saggers are placed on the top of these, and other rings formed within the first ring until the oven is filled by a series of rings built up one upon the