US2211602A - Electric lamp and similar device - Google Patents

Description

Aug. 13, 1940. J. R. LAIT ET AL ELECTRIC LAMP AND S-IMILAR DEVICE Filed May 18, 1939 Inventors James F?. Lait, Marcello Pirani,

Their` Attorney Patented Aug.'1, 1940 UNITED STATES Our invention relates in general to "electrio lamps and similar devices, and more particularly to .insulating beads or anchor members for'supk porting, and insulating from each other, a plurality of metallic wires or rods, and to their manufacture. The term wire, as used hereinafter, denotes any elongated metal body.

Insulating beads are much used for supporting' the leads or intermediate support wires of fila- 1'0 ments in electric incandesoent lampsand the leads or supports of electrodes in thermionic valves. Glass and ceramic materials are frequently used for such heads. v I It is often desirable that the bead remain rigid 15' and retain its insulating properties at temperatures exceeding 400 C. and possibly approaching 1000 C. Accordingly; it is the object of our invention to provide beads possessing the above properties and which are capable of being made by mass-production methods.

Further objects and advantages of our invention will appear from the following description and the accompanying drawing of a` species thereof.

In the drawing, Figs, 1, 2 and 3 are similar sectional views through a bead or anchor member comprising our invention and showing the successive steps involved in the manufacture of the same; Fig. 4 is a perspective View, partly in section and on an enlarged scale, of a bead or anchor member comprising our invention and useful in incandescent lamps for anchoring the ends of filament support wires; and Fig. 5 is a sectional View of the bead or anchor member 35 shown in Fig. 4.

The manufacture of an insulating bead according to the invention for supporting a plurality of wires comprises, in general, the following steps: (1) Forming from a ceramic material having a relatively high fusion temperature and a thermal expansion approx'mating that of the wires to be secured thereto, a body member provided with holes into which the wires fit, (2) filling the said holes, not 'neoessarily completely, 45 with glass having also a thermal expansion approximating that of the wires and melting at the said high temperature, and (3) forcing the ends of the wires into the said holes while the glass therein is in a plastic state. When the product thus formed is cooled down, the glass acts as a cement holding the wires in the holes; but if the wires nearly fill the holes the rigidity of the whole will depend little on the rigidity of the sistance between the wires will be 'that of the ceramic material therebetvveen The holes formed in' 'step (1) may be advantageously formed with 'a reduced inner portion, the inner portion fitting the wires closely while the outer wider portion provides space for the cementing glass. "The term "fit, however, does not necessarily imply thatthe wire is to' be held in 'the holes withoutthe useof cementing glass. Further, in order that the cementing glass completely fill'the holes, it ispreferable to provide the inner or'reducedportions of the holes with side passages leading to the surface of the block, through which airmay escape when the glass is introduced 'into the holes. In step (2) the ceramic may be heated to a temperature above the meltng point of th'e glass 'Whereupon rods of glass of appropriate diameter may be introduced into the holes and withdrawn again when the necessary quantity of glass has melted ofi from their ends. steps (2) and (3) can therefore readily be performed on machines similar to the well-known machines for inserting pig-tails into the stern of an incandescent lamp. Other procedures, however, are possible. Thus in step (2), the glass may be inserted as pieces of rod into the holes in the ceramic body while the latter is at room temperature, and the ceramic body then heated so as to melt the glass.

The thermai expansions of the ceramic body,

the cementing glass, and the wires to be supported thereby are deemed to be approximately the same if the final structure is not liable to crack under the changes of temperature to which it is exposed.

Where the wires to be supported are of molybdenum, a suitable ceramic is one having the following composition: Al2O3-64 per cent, SiO2-25 per cent, BeO--7 per cent, Mg--2 per cent, ThOz-Z per cent. The expansion of this material is about x 10- per C. Likewise, a suitable cementing glass is one having the following composition: SiO2-54.7 per cent, (Al2O3+Fe2O3)-- 20.9 per cent, Cao- .7 per cent, B2O3- .7 per cent, Bac-3.0 per cent. The expansion coefficient of this .glass is about 4.6 x 10- per C.

Steatite may be used as the ceramic. In this case, the wires may then be of nickel-iron having a similar eXpansion.

Referring to the drawing, the insulating bead or anchor member shown in Figs. 1-3 comprises a ceramic body I of the aforesaid composition and provided with a plurality of holes Z each having a reduced inner portion 3 terminating within the ceramic body. The ceramic body l is further provided with a plurality of side passages or holes 6, adjacent the inner end of the holes 2 and leading to the surface of said ceramic body, there being a side passage 6 for each of the holes 2. Wires 4 of molybdenum extend into the holes 2, the said wires being of such size as to have a sliding fit within the reduced inner portion 3 of the holes. Securing each wire 4 within its respective hole 2 is a quantity of cementing glass 5 of the above referred to composition.

Fig. 1 illustrates the ceramic body formed by step (1), while Fig. 2 shows the said body after step (2), in which the body is heated to a temperature above the melting point of the cementing glass 5 and rods of the said glass inserted into the holes and allowed to melt down so as to completely fill the reduced inner portions 3 of the holes 2 and, if desired, a part of the side passages 6 as well. Fig. 3 illustrates the completed bead according to' our invention after step (3), in which the wires are inserted into the holes 2 while the cementing glass 5 is still in a plastic state and the entire structure then allowed to cool down to room temperature. In this iatter step, part of the excess glass is likely to emerge at the outer ends of the side passages 6 when the wires 4 are inserted into the holes 2. Figs. 4 and 5 illustrate the invention as it might be applied to an incandescent lamp wherein the ceramic bead I' is secured to a support or arbor wire 'I the opposite end of which is secured to the lamp stern (not shown) in well-known manner. A plurality of filament-supporting anchor wires 4' have their ends secured within the holes 2', 3' by fused glass 5' in the manner described above in connection with Figs. 1-3. The filament (not shown) is supported by hooks or loops in the ends of said wires 4' and is arranged thereon in the form of an arc or horseshoe, as is well known.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An anchor member comprising a body of ceramic material having a plurality of holes therein terminating within said body and side passages extending laterally from a point adjacent the inner ends of said holes to a surface of said body, a support wire extending into each of said holes, and a quantity of fused vitreous material securing each of said wires in its hole and extending into the passage leading from said hole.

2. An anchor member comprising a body of ceramic material having a plurality of holes therein terminating within said body, a support wire extending into each of said holes, the inner ends of said holes being of reduced diameter to fit said wires c1ose1y,- and a quantity of fused vitreous material securing each of said wires in its hole.

3. An anchor member comprsing a body of ceramic material having a plurality of holes therein terminating within said body, a support wire extending into each of said holes, the inner ends of said holes being of reduced diameter to fit said wires closely and having side passages communicating therewith and extending laterally therefrom to a surface of said body, and a quantity of fused vitreous material securing each of said wires ir its hole and extending into the passage leading from said hole.

JAMES R. LAIT. MARCELLO PIR/ANI.

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