US 3309646 A
Abstract available in
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Description (OCR text may contain errors)
March 14, 1967 1. s. GOODMAN MULTIPLE-FILAMENT ELECTRIC INCANDESCENT LAMP Filed Feb. 11, 1965 n 5 Rm Q O 6 TM H m 1: 1 m3 m m G S I 2 mm m F a 4 A, 3 M W E/ $6 E m w Jim United States Patent Q This invention relates generally to electrical incandescent lamps and has particular reference to an improved base contact for a so-called three-light lamp.
As is well known, electrical connection with the dual filaments of a three-light incandescent lamp is achieved by means of lead wires which are sealed through the lamp stem and connected to the lamp base. The lead wire that is common to both filaments is fastened, as by soldering, to the rim of the metal base shell whereas the two remaining lead wires are attached to an end contact and an intermediate ring contact, respectively, anchored to the end of the base insulator.
The aforementioned end contact and intermediate ring contact are generally stamped from sheet brass, or other suitable material, and are connected to the respective lead wires by a globule of solder. Usually, the intermediate contactor member of the socket into whi h the lamp is placed will engage and frictionally seat against the fiat surface of the ring contact and, thus, provide a positive electrical connection between these members.
it frequently happens, however, that the socket terminal engages instead the projecting globule of solder that connects the intermediate ring contact to its lead wire. Under these circumstances the intermediate contact of the socket, which usually consists of a metal post or tongue, partially embeds itself in the solder. While this provides a very good connection, it has been found that the solder has a tendency to creep due to relatively high operatin temperatures which prevail within the base and socket when the lamp is energized. This creeping or gradual displacement of the solder is Sunciently pronounced in some cases that the solder works free from the socket terminal completely. This, in turn, causes arcing and eventual loss of contact with this portion of the lamp base. The lamp is thus not energized at the intermediate-intensity switch position and the customer erroneously concludes that one of the lamp filaments has burned out prematurely and that the lamp is of poor quality.
Since the intermediate contact posts of three-ligtht sockets are not spring loaded but are held in a fixed position, a relatively small amount of creep by the solder is sufficient to cause an open circuit between the socket and intermediate contact of the lamp base. This problem does not arise in the case of the center post socket contact since it is spring loaded.
In addition, since the socket terminal is embedded in only one side of the solder globule, vibrations transmitted to the lamp over a period of time frequently causes the socket terminal to walkout of the solder and create an open circuit. The lamp user again erroneously assumes that the filament has failed prematurely and that the lamp is defective.
It is accordingly the general object of the present invention to provide a multiple-filament electric incandescent lamp that overcomes the aforementioned and other problems of the prior art.
Another and more specific object is the provision of an improved intermediate contact for a three-light incandescent lamp that will etfect and maintain positive electrical connection with the corresponding terminal of a socket in which the lamp is inserted.
The aforesaid objects and other advantages are achieved in accordance with the present invention by placing a layer of soft electrically-conductive material over the exposed surface of the intermediate ring contact of the base to provide a continuous layer of easily deformable material in which the socket terminal will become embedded when the lamp is placed into its socket. The layer of soft material thus constitutes a deformable planar intermediate contact on the base that automatically achieves a positive electrical connection with the corresponding socket terminal that is not affected by directional creep or vibration. Preferably, the layer of soft deformable material comprises a layer of fused solder that comletcly covers and is bonded to the exposed laterallyextendiug surfaces of the intermediate ring contact.
A better understanding of the invention will be obtained by referring to the accompanying drawing, wherein:
FIGURE 1 is an elevational view of a three-light lamp incorporating the present invention; I
FIG. 2 is an enlarged plan view of a preformed ring of solder wire used in fabricating the improved base contact according to one form of the invention;
FIG. 3 is an enlarged elevational view of the base end of the lamp shown in FIG. 1 illustrating the manner in which the layer of fused solder is applied to the intermediate contact ring;
FlG. 4 is a plan view of the base end of the lamp prior to the melting of the ring of solder wire; and
FIG. 5 is a view corresponding to FIG. 3 illustrating the form and relationship between the end and intermediate contacts of the finished lamp.
While the present invention can be used with advantage in various types of electrical devices that require base members having insulators which carry a plurality of contacts, it is particularly adapted for use in conjunction with three-light incandescent lamps and has accordingly been so illustrated and will be so described.
/Vith specific reference now to the drawing, in FIG. 1 there is shown a three-light electric incandescent lamp if? comprising an envelope 12 which contains a lamp mount 14. The mount consists of the usual glass stern that is sealed to the neck of the envelope and two pairs of lead wires 15 36 and 17-18 which are sealed through the stem press and support a pair of coiled tungsten wire filaments 2% and 22 within the envelope. The lead wires 17 and 13 attached to the proximate ends of the filaments are twisted together within a suitable base member 24- attached to the end of the envelope 1?. and are connected to the rim of the metal shell 2c of the base to provide a base contact common to both filaments. The other pair of lead wires 15-15 extend through the base shell and suitable apertures in the base insulator 28 to an annular metallic member or intermediate ring contact and to a centrally-disposed end contact 32., respectively, to which they are connected.
'1" he insulator 28 may be fabricated from glass or a suitable plastic and is attached to and projects beyond the free end of the base shell 25 in the usual manner. The intermediate annular contact 3%) consists of a centrallydisposed ring of sheet metal, such as brass, that is anchored to the end face of the insulator.
In accordance with the teachings of this invention the exposed surface of the ring contact 3% that extends transverse to the lamp axis, and thus constitutes the socketengaging portion of such member, is covered with a substantially uniform layer 34 of fused solder or other soft electricallyconductive material. The end contact 32 comprises the usual globule of solder that connects the lead wire it; to a centrally located eyelet (not shown) embedded in the insulator 23.
The term soft as used in this description and in the appended claims means yieldable or deformable under pressure of the magnitude exerted by the intermediate =3 contactor or post terminal of a conventional three-light socket on the corresponding contact element of a lamp base that is screwed or otherwise placed into operative relationship with the socket.
The metallic ring contact 30 can be coated with a uni form layer of fused solder in a very convenient and expensive manner by forming a split ring 34 of solder wire, as shown in FIG. 2, and placing the ring on top of the intermediate contactor member 3-0 while the lamp i is held base end up, as illustrated in FIGS. 3 and 4. The lamp at this stage of manufacture is completely fabricated except for the completion of the basing operation. The lead wire thus has already been threaded through the holes in the insulator 23 and in the intermediate ring contact 30 and trimmed so as to lie flush with the exposed surface of the latter.
The lamp 10, as indicated by the arrow in FIG. 3, is then rotated about its longitudinal axis while in a vertical position and a concentrated flame 36 is trained on the ring 34' of solder wire until it melts and flows over the exposed laterally extending surface of the annular contact member 30. The action of the flux in the solder Wire securely bonds the solder to the contact member. Since the melted solder wets the metal ring 353 and not the insulator 28, it automatically spreads into a layer 3 4 of uniform and predetermined thickness, as shown in FIG. 5. The trimmed end of the lead wire 15 is thus electrically joined to the metal ring 30 by the layer 34 of fused solder.
The thickness of the layer of fused solder 34 is controlled simply by making the solder ring 34' from a preselected length of wire having the proper diameter. The volume of solder used, and hence the thickness of the layer, can easily be determined and controlled.
The thickness of the fused solder layer 34 is maintained within prescribed limits so that it is spaced a predetermined distance x axially from the tip of the end contact 32, as shown in FIG. 5. This spacing is important since it insures that the end contact 32 will engage and be firmly seated against the corresponding socket terminal when the lamp is inserted into the socket.
Satisfactory results have been obtained in the case of a 50/ 100/ 150 watt three-light lamp having a medium screw type base by using solder wire approximately 0.075 inch in diameter and consisting of tin and 80% lead. A split ring /2 inch in diameter fabricated from such solder wire formed a continuous and uniform layer of fused solder approximately 0.040 inch thick. on the intermediate ring contact of the lamp base, and the surface of the fused solder layer was spaced approximately 0.085 inch from the tip of the end contact.
It will be appreciated from the foregoing that the objects of the invention have been achieved insofar as a very reliable and inexpensive intermediate contact for a multiple-filament incandescent lamp has been provided which contact automatically effects and maintains positive electrical engagement with the corresponding terminal of a conventional three-light socket when the lamp is placed into such socket.
While one embodiment has been illustrated and del scribed, it will be appreciated that various modifications in the construction and method of forming the improved lamp contact can be made without departing from the spirit and scope of the invention.
I claim as my invention:
1. In a multiple-filament electric incandescent lamp having an envelope and a base comprising a metal shell that is attached to the envelope and carries an insulator that projects beyond the free end of said shell and has an end contact, the improvement comprising,
an annular metallic member that is fastened to said insulator and is axially spaced from said end contact,
a layer of electrically conductive material on the exposed surface of said metallic member which extends transverse to the lamp axis and thus comprises the contacting portion of said member, said layer of electrically conductive material being softer than said metallic member and of such thickness and configuration that it provides a second deformable planar contact for said lamp that extends completely around said annular member and is also axially spaced from said end contact, and
a lead wire extending through said base and envelope and connecting one of the filaments with said annular metallic member.
2. The improvement set forth in claim 1 wherein; said layer of electrically conductive material is of predetermined and substantially uniform thickness, and said lead wire is fastened to the annular metallic member by said layer of electrically conductive material.
3. In a three-light electric incandescent lamp having an envelope and a base which comprises a metal shell that is attached to the envelope and is closed by an insulator that projects beyond the free end of said shell and carries a centrally-disposed end contact and an intermediate metallic ring contact that are axially spaced from one another, the improvement comprising an ad herent layer of fused solder on and completely covering the exposed surface of said metallic ring contact which extends transverse to the lamp axis and thus constitutes the socket-engaging surface of said ring contact, the thickness of said layer of solder being less than the spacing between said end contact and ring contact whereby said layer of solder defines a deformable planar contact that is axially spaced from said end contact.
4. The improvement set forth in claim 3 wherein said layer of fused solder is of substantially uniform thickness and defines a planar contact that is spaced a predetermined distance axially from said end contact.
References Qited by the Examiner UNITED STATES PATENTS 2,064,364 12/1936 Thomas 339-446 2,999,220 9/1961 Werner 339146 EDWARD C. ALLEN, Primary Examiner. \V. D. MILLER, Examiner.