We, JOHN CRISP FULLER and GEORGE FULLER both of Newcastle Wharf Works, Old Ford Road, Bow, in the County of Middlesex, Electricians and Telegraph Engineers, and WILLIAM EDWARD LANGDON of The Lawn, Belper, in the County of Derby, Electrica1 Engineer, do hereby declare the nature of this invention and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement:--

Our invention refers to Improvements in Porcelain and other Insulators, such as are generally employed for the support of aerial line wires, or conductors, conveying currents of electricity for telegraph and other purposes commonly known as "line insulators" as distinguished from "terminal insulators" In such insulators it is desirable that the surface distance, between the point at which the conductor is attached to the insulator, and the point at which the ware of the insu1ator forms a junction with its support or bolt, should be as great as possib1e, because the greater the distance between the said points, the less is the loss of current by leakage and the more efficient the insulator, and it is the primary object of our invention to produce such an insulator as will satisfy the above requirements combined with a simple and practical construction.

Our invention will be readi1y understood by the following description having reference to the accompanying drawing whereon Figure 1 is a vertical section and figure 2 an elevation of an insulator constructed according to our invention, Figure 3 being an elevation of a similar insulator hereafter referred to. Similar letters of reference refer to like parts in the several figures.

According to our invention we form the insulator in such a manner as to provide three or more deeply out vertical grooves or channels, such as A A A, Fig. 1, thereby practically forming a triple shed, such as B B B. The proportionate depth of these channels may be as shown at Fig. 1 or they may be varied somewhat to suit requirements, we have however found the construction or proportions shown to be suitable generally, it being convenient that the lower portion of the inner shed should be Capable of easily cleansing, and be washed by rain, when in their position on the poles or other supports.

The surfaces of the insulators according to our invention may be plain upon their outer surfaces as shown at Figure 2 or serrated with concentric rings as shown at figure 3, such serrations being described in the Specification of Patent No. 4450 dated September 19th 1882 granted to ourselves. 

Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed we declare that what we claim as our Improvements in Porcelain and other Insulators is as follows:

1. The arrangement and construction of three or more deeply cut vertical grooves or channels the one extending below the other, whereby the surface distance between the conductor and the bolt is increased all substantially as and for the purposes described and illustrated with reference to the accompanying drawings.

2. The combination with an insulator having deeply cut grooves or channels, and as claimed by claim 1, of the serrated surface in the form of concentric rings all constructed and arranged substantially as and for the purposes hereinbefore described.

Dated this third day of April 1894.

                                                        BREWER & SON

                                       London and Leeds, Agents for Applicants.