Publication: Electrical Review and Western Electrician
Chicago, IL, United States
The Unity Insulator for Telephone and Telegraph Lines.
The Minerallac Electric Company, 112 West Adams Street, Chicago, has developed a novel form of combined insulator and pin that has recently been placed on the market under the name of Unity insulator. These insulators are turned out of a solid piece of tough wood to exactly the shape desired, including one petticoat. The insulators are thoroughly impregnated with Minerallac insulating compound which also has excellent wood-preserving properties. Insulators of this general type of construction have been in use on the high-tension lines of a large central-station company for about eight years, being subjected to line voltages of 4,000, 9,000 and 12,000 volts. During this prolonged try-out period they have shown no deterioration in insulating qualities nor any tendency to crack or split.
The chief advantages of this insulator are its unbreakability both in shipment, installation and service; economy of installation, since the insulator and pin are in one piece; high insulating qualities, the insulation resistance being found to decrease only a few per cent under the most severe storm conditions.
A great difficulty that telephone and telegraph companies have had has been from malicious destruction of glass insulators by hunters, small boys, and anyone carrying a gun in the country who seem to have taken keen delight in making the insulators objects of target practice. The new type Unity insulators have been found to withstand bullets, shot and missiles of any kind. The insulators are extremely tough and thereby make the element of breakage practically insignificant. The insulating compound does not ooze out appreciably even when the insulator is subjected to great heat, as for instance in the arid districts of the Southwest, where the hot sun might be thought to produce a bad effect on these insulators. The insulators are easily packed and shipped at low cost compared to the ordinary glass or porcelain insulator, and are in themselves no more expensive than the latter. A large number of telephone companies have ordered them in the short time they have been placed actively on the market.