THE MAC FADDEN-PEIL INCANDESCENT LAMP.
THE accompanying engravings illustrate the method of construction of an incandescent lamp recently patented by Carl K. Mac Fadden and John Peil of Chicago, which, according to the inventors, is not only clear of all existing patent claims, but also covers several new features tending to reduce the cost of manufacture of incandescent lamps.
The main feature consists in utilizing the insulating properties of a thin coat of enamel on the inleading wires which are let into the glass receiver through a metal seal around the wires. To insure a perfect seal, the inleading wires are wound in a spiral form before they are given their coat of enamel and the seal is thus made two or three inches in length in a metal plug of small size.
Fig. 1 shows the principle as applied to a lamp using a bulb having a heavy moulded base. One terminal of the filament is the metal plug or seal, thus doing away with one of the inleading wires and simplifying the construction to some extent. After the seal is made by pouring melted alloy around the wire as it stands in place in the space to be filled by the metal seal, a small quantity of cement is poured over the top of the metal stopper, which cement soon hardens and makes a perfect seal.
In Fig. 2 the same seal is used, but it is in this case made in an inleading flange in a metal cap, which, when closed at one end by a mica disc, leaves a space to be filled by a tapering plug which contains the seal for the inleading wires. The cap is so made as to have a spiral corrugation on its outer surface and can thus be used in Edison sockets as commonly made.
The alloy seal used in all cases has the property of expanding slightly as it solidifies and as it is poured in around the wire in a melted state, grips the wire tightly as it cools. In the second case shown, the seal unites to the surface of the metal cap in a thorough manner. The metal cap is enameled on its inner surface and in this manner the cement really unites the glass surface of the cap to the glass neck of the lamp bulb. The cement used softens at about 400 deg. Fahr., and in this case will allow any unequal expansion of the metal cap and glass bulb to take place without injury to the seal. The cap may be readily removed by placing the base of the lamp over a glass jet, when the heat will soften the cement, and the cap and bulb may be separated.
The caps and enameled wires are cheap to manufacture, and the sealing up of the lamps can be done in a rapid and yet perfect manner. It will be readily seen that the use of platinum is entirely done away with, and that the lamp is thoroughly waterproof, having no plaster of paris or other absorbent insulating material in its construction. The cost of manufacture in quantities has been variously estimated from 2 to 6 cents less than that necessary to make all-glass lamps of the usual type.