US2347055A - Electric lamp - Google Patents

Description

April 18, 1944. v w M JOHNSQN 2,347,055

ELECTRIC LAMP Filed Jan. 6,. 1943 PEI;

Inventor: WiLber" M. Johnson,

b8 WM His A'FEOYne Patented Apr. 18, 1 944 l v 2,347,05s

ELECTRIC LAMP.

Wilber M. Johnson, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application January 6, 1943, Serial No. 471,467

3 Claims.

My invention relates to electric lamps of the type comprising an enclosure for a light source, which enclosure is filled with gas, such as air.

A type of lamp in conjunction with which my invention is useful is known as a "Sealed Beam lamp and is now in extensive use in automobile headlights. One type of such lamp comprises a small electric incandescent lamp mounted within an enclosure having a reflector portion of paraboloidal or other suitable shape and a lens or cover portion secured at its periphery to the reflector portion to form an enclosure. The base of the incandescent lamp extends through the reflector portion and the enclosure is filled with air. Such lamps tend to breathe; that is, the air flows in and out of it, if the enclosure is not air=tight, since the enclosed. air expands and contracts as the temperature of the lamp rises' and falls. The air from the outside atmosphere entering the lamp enclosure under such conditions may be and usually is mixed with undesired and even harmful substances, such as water vapor which condenses on the inner surface of the enclosure and changes the pattern of the projected beam, or sulphur or other gaseous vapors which impair the surface of the reflector. In order to prevent such breathing action, it has heretofore been the practice to make the joint between the cover and the reflector and that between the reflector and the base of the lamp gas tight and oi substantial mechanical strength to withstand the increased pressure of the air in the enclosure when the temperature is raised by operation of the lamp, by the heating action of the sun or by heat from other sources.

The principal object of my invention is to provide a lamp of the above type which may breathe without being contaminated by material from the outside atmosphere. Another object of my invention is to reduce the manufacturing cost of such lamps. Further objects and advantages of my invention will appear from the following description thereof.

It is well known that gas tight seals of large mechanicalstrength are more difiicult and expensive to make than such seals of small mechanical strength. Further, in the fabrication of gas tight seals there is a certain amount of wastage or spoilage due to a portion of the seal being too weak mechanically to withstand the variations in gas pressure encountered under service conditions. According to my invention the hermetic seals of such lamps may be of small mechanical strength and in certain instances gas pervious, mechanical joints may be substituted for gas tight joints without harmful material from the outside atmosphere entering the lamp enclosure to the end that the cost of manufacture of such lamps is substantially reduced. Whereas prior efiorts have been in the direction of increasing the mechanical strength of the lamp enclosure to withstand increasing gas pressure and thus resisting the tendency of the lamp enclosure to breathe I proceed in the opposite direction to solve the common problem in a less expensive ,manner by permitting the lamp enclosure to breathe and thus avoid pressure changes with changes in temperature.- Instead of keeping the volume of the enclosure constant, which causes the pressure to change directly with the temperature, I provide means whereby the volume of the enclosure may change as the gas expands and contracts with changing temperature. The gas in the enclosure is then at atmospheric pressure under temperature conditions encountered in service which eliminates mechanical stress from this source on the seals. In accordance with my invention, the joints may be made, of lesser mechanical strength and thus with less expense by providing an easily collapsible and expansible pocket or chamber communi cating with the interior of the reflector lamp. In one embodiment of my invention the joint between the reflector and the lamp base may be pervious to air, thus eliminating one of the expensive hermetic joints or seals used heretofore.

In the drawing accompanying and forming part of this specification species of my invention are shown in conjunction with a Sealed Beam lamp of, a type well known in commerce. Fig. 1 of the drawing is a sid elevational, partly sectional View of the lamp, an electrical supply terminal therefor and an easily collapsible and expansible sleeve communicatin with the interior of the lamp; Fig. 2 is a fragmentary, partly sectional view of a similar lamp having an easily collapsible and expansible bag communicating with the interior thereof through a pipe or conduit, and Fig. 3 is a similar view of a bag similar to that shown in Fig. 2 communicating with the interior of the lamp through an orifice. Like numbers denote like parts in all theiigures.

Referring to Fig. 1 of the drawinathe lamp lfi comprises a reflector" member II of, paraboloidal shape having a flange l2 rolled over onto the outer surface of the peripheral portion of a lens I3. A gasket I4 of flexible, air impervious material, such as rubber, is interposed between the reflector H and the lens l3 and is compressed therebetween to form an air-tight or hermetic seal between the reflector II and the lens I3. In some types of commercial lainps the reflector II, the lens I3 and the gasket III are held together by a clamping ring. A small incandescent-lamp I5 is mounted in the space defined by the reflector II and the lens I3 and is supported therein by its metal base I6 which extends through an opening in the apex of the reflector II and which is soldered to the reflector II. The incandescent lamp I5 may be of the type disclosed and claimed in the Severin Patent No. 2,227,324, issued December 31, 1940, and assigned to the assignee of this application and which comprises, in addition to the base I5, a glass bulb I! having a neck portion extending into the base I 6 and secured thereto by basing cement. The lamp I5 has a pair of filaments supported in the bulb I"! by current in-leads which pass through the stem of the bulb I1 and connect with spaced contacts I8 on the base I6 of the lamp I5. The filaments, the stem and the in-leads of the lamp I5 have been omitted from the drawing for purposes of simplicity of illustration. A connector member l9 fastened to the end of a current or power supply cable 20 engages with the terminals I8 of the lamp I5 in the usual manner.

The lamp I described above is well known in commerce and the above described structure constitutes no part of my invention.

As pointed out above, 'prior efforts have been in the direction of making the lamp I0 air-tight to prevent the ingress of contaminating, deleterious material into the lamp enclosure. Thus, the space between the base I and the reflector II has been filled with solder to make the joint therebetween air-tight or hermetic at pressures above and below atmospheric pressure and a special composition impervious to air has been used to seal the space between the base I6 and the bulb I! for the same purpose, all as disclosed in copending application Serial No. 385,672, filed March 28, 1941, and assigned to the assignee of this application. Such precautions and special procedures add to the cost of manufacture of the lamps and are eliminated by my invention which comprises, in the embodiment thereof illustrated in Fig. 1, an easily collapsible and expansible sleeve 2| of material impervious to air, such as soft rubber, oiled silk, or the like, surrounding the member I9 and the portion of the lamp base I6 outside the reflector I I. The sleeve 2| is provided with two rings 22 of flexible material, such as soft rubber. The rings 22 are of such diameter that they are stretched and under tension when mounted on the cable 20 and on the flange 23 on the reflector II. The flange 23 is integral with the reflector II and provides an annular groove 2|, one of the rings 22 is stretched sufliciently to pass the member I9 into the sleeve 2|. The opposite ring 22 is then stretched to permit the engagement of the member IS with the contacts I8 and thereafter the ring 22 is placed in the groove formed by the flange 23. The rings 22 grip the cable 20 and the surface of the groove with sufficient force to prevent seepage of air from the ambient into the sleeve 2| under the conditions described below.

It is advantageous in the practice of my invention to provide a low resistance path for the flow of air between the interior of the lamp I0 and the interior of the sleeve 2|. The building up of pressure in the lamp I0 and concomitant stress on the gasket I 4 is thus avoided. Accordingly, instead of filling the annular space between refor one of the rings 22. In mounting the sleeve flector I I and the base It of the lamp I5 with solder as has been the practice heretofore, in an effort to seal this space, only sufliclent solder is used to support the lamp I5 in the reflector II without sealing the said space. I prefer to solder the base I5 to the reflector II at three spaced places around the base I6 so as to leave spaces between said base I6 and said reflector II for the free flow of air between the lamp I0 and the sleeve 2|. Thus, when the lamp I0 is at the temperature of the ambient and the sleeve 2| is collapsed, air flows freely from the lamp I0 into the sleeve 2| as the temperature of the lamp I0 increases and the air therein expands when the lamp I5 is energized. The sleeve 2| expands as the air from the lamp I0 enters it. When the lamp I5 is deenergized and the reflector lamp I0 cools, the air therein contracts. The uncontaminated air from the sleeve 2| then flows back into the lamp III through the mechanical joint between the reflector II and the base I8 and the sleeve 2| collapses. The above cycle is repeated each time the temperature of the lamp I0 rises above and then falls to the temperature of its surroundings.

It is apparent from the foregoing that the difference in the air pressure inside and outside the lamp I0 is inappreciable at all times, that the expensive air-tight seal between the lamp base I6 and the reflector II as well as that between the lamp bulb I1 and the base I6 have been eliminated and that the mechanical stress on the seal between the reflector I and the cover I3 has been minimized while the ingress of contamination from the ambient into the lamp I0 is prevented by my structure, Further, the sleeve 2| is easily detachable from the lamp I0 and attached to a new lam-p when lamp replacement is necessary.

The embodiment of my invention illustrated in Fig. 2 of the drawing comprises an easily collapsible and expansible bag 24 which is impervious to air and which has a neck portion 25 which grips the enlarged end portion 26 of a tubular extension 2'! on the reflector The bag 24 may consist of soft rubber, oiled silk, or similar material, and the neck portion 25 thereof ,may consist of soft rubber or other material capable of gripping the end portion 25 of the extension 21. This embodiment of my invention is particularly useful in conjunction with lamps made in the conventional manner, that is, with the space between the base Hi and the reflector sealed with solder as shown at 28. While a special sealing composition may be used to make the space between the base I6 and the bulb I'I air-tight in accor dance with the application referred to above, I prefer to omit such composition and thus save its cost when using this embodiment of my invention. This may be done Without risk of contamination from the ambient entering the lamp II) because the usual basing cement offers appreciable resistance to the flow of air between the base I6 and the bulb I'I whereas the resistance to the flow of air through extension 21 between the lamp l0 and the bag 24 is inappreciable. Thus, as the air in lamp I0 expands with increasing temperature, it flows from lamp I0 into the bag 24. The same uncontaminated air flows back into lamp II] when the air contracts when the lamp temperature falls. In this embodiment as in the embodiment illustrated in Fig. 1, the building up of pressure in the lamp It] with its accompanying stress on the seals is avoided without permitting contamination to enter lamp I0 pressures.

The embodiment of the invention illustrated in Fig. 3 is the same as that illustrated in Fig. 2 except that the bag 24 is provided with a ring 29 which is similar to rings 22 illustrated in Fig. l

and which clamps :about an annular groove formed by a circular, outwardly flaring flange 30 on the reflector H and about the opening 3| in said reflector H. This is a more compact arrangement than that shown in Fig. 2 and may be preferred where mounting space for lamp III is small.

In the species of my invention illustrated in Figs. 2 and 3 of the drawing, the easily collapsible and expansible member is mounted only on the replaceable lamp in per se and not on the permanent parts ofthe installation or vehicle. When the lamps are to be placed in stock for a time before being used, these embodiments may be preferred since the bag 24 may be placed thereon to serve the same purposes as it I0 is in use.

In order to eliminate moisture or water vapor in the lamp In it may be flushedwith dry air and a getter, such as calcium chloride, may be disposed in the sleeve 2 I, the bag 2, the conduit 21, or on the member l9. Under certain service conditions it may be desirable to use both the sleeve 2| and the bag 24 on a single lamp for attaining the objects and advantages of my invention.

While I have illustrated and described my invention in conjunction with headlamps of a commercial type for vehicles, I contemplate that it may be used with other types of lamps and with lamps used for other purposes. Further, electrical conductors in the form of metal wires or rods may be used for passing energy into the lamp instead of a lamp base.

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

l. A lighting unit comprising an enclosure including a reflector, and an electric lamp in said enclosure, said enclosure containing a gaseous atmosphere and being normally air-tight but sub- :Iect to leakage through a portion thereof upon does when the lamp expansion and contraction oi the internal atmosphere when the lamp is turned on and off, and an air-tight easily collapsible and expansible baglike member connected with the interior of said enclosure, said bag-like member having suflicient volume to accommodate the internal atmosphere which is expanded when the lamp is lighted and to prevent a rise in pressure suflicient to cause the internal atmosphere to leak out of the enclosure to the exterior atmosphere, the internal atmosphere in said member being returned to the enclosure when the unit cools.

2. A lighting unit comprising an' enclosure including a concave reflector and a cover glass sealed together at their peripheries, and an electric lamp mounted in an opening in said reflector, said enclosure containing a gaseous atmosphere and being normally air-tight but subject to leakage through said opening upon expansion and contraction of the internal atmosphere when the lamp is turned on and oif, a detachable current supply connector at the exterior of said enclosure engaging terminals on said lamp, and an airtight easily collapsible and expansible bag-like member engaging the reflector around the said opening therein and enclosing the said connector, said bag-like member having sufficient volume to accommodate the internal atmosphere which is expanded when the lamp is lighted and returning the atmosphere pocketed therein to the enclosure when the unit cools.

3. A lighting unit comprising anenclosure including a concave reflector and a cover glass sealed together at their peripheries, and an electric lamp in said enclosure comprising a bulb and a base, said lamp base being mounted in an opening in said reflector and hermetically sealed to the margin of said opening, said enclosure containing a gaseous atmosphere and being normally air-tight but subject to leakage through the interior oi the said lamp base, and an air-tight easily collapsible and expansible bag-like member connected with the enclosure through an opening in said reflector, said bag-like member having suilicient volume to accommodate the internal atmosphere which is expanded when the lamp is lighted and to prevent a rise in pressure suflicient to cause the internal atmosphere to leak through the lamp base to the exterior atmosphere, the internal atmosphere in said member being returned to the enclosure when the unit cools.

WILBER M. JOHNSON.

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