US2976441A

US2976441A - Electric lamp

Info

Publication number: US2976441A
Application number: US605773A
Authority: US
Inventors: Stahl Walter
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1956-08-23
Filing date: 1956-08-23
Publication date: 1961-03-21
Anticipated expiration: 1978-03-21

Description

March 21, w STAHL ELECTRIC LAMP Filed Aug. 23, 1956 INVENTOR. W/ILTE)? 57'fl/IL.

EA/EX United States Patent ELECTRIC LAMP Walter Stahl, East Orange, N.J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 23, 1956, Ser. No. 605,773

4 Claims. (Cl. 313-33) types, as for example high-wattage incandescent lamps of the gas-filled variety, it has become standard practice in the industry .to shield the basal end portion of such lamps from the light source and space immediately adjacent thereto. The foregoing requirement is necessitated by the fact that in the absence of such protection the transfer of heat from the filament to the sealed-in neck portion of the lamp envelope and base member attached thereto is sutliciently pronounced that excessively high base temperatures result during normal operation of the lamp thereby deteriorating the hasing cement and otherwise deleteriously affecting the life and trouble-free operation of the lamp and fixture or other associated equipment.

' Experience has demonstrated that the most effective and economic means of reducing the base temperature of a lamp is to interiorly mount a shield or deflector of suitable material between the base and filament in a plane transverse to the lamp axis to provide a. heat baffle and partition the basal end portion of the lamp envelope from the hot light source and gases of the lamp proper.

It has been the common practice prior to the present invention to fasten such shields directly to the lead-in conductors or stem portion of the filament mountby threading a suitably apertured heat deflecting element over the conductors or by providing a uniformly-slotted metallic disc having bent tongues adapted to slidably and frictionally engage oppositely disposed grooves formed in the stem press. While the latter arrangement obviated the necessity of insulating the shield from the lead-in conductors when shield material of an electrically conductive nature was utilized and greatly simplified the fabrication of the filament mount, it has been found that the disc frequently slipped off the stem press during nor mal handling of the finished mounts under factory conditions unless the parts were accurately formed and precisely mated in tight force-fitting engagement. Consequently, the utmost care in transferring the. assembled mounts and a 100% inspection for missing discs prior to loading the mounts on the sealing machine were required to prevent the manufacture of defective lampsprecautionary measures which were not only troublesome but time-consuming and impractical in view of the speed of the lamp assembly operation. In addition, and more significantly, the indentation of the stem press in forming the oppositely disposed grooves in accordance with this type construction materially reduced the thickness of the press portion, which area is generally "susceptible to thermal and .mechanical strains 'due to the very nature of the press forming operation and the breathing effect of the lead-in conductors which are embedded therein, thereby greatly reducing the inherent of the stem tube 14 and communicates an "915 I J i formed thereat, as shown in Fig. 2. The inner end dfthe i Patented Mar. 21, 19

mechanical strength of the stem in this normally critical area and adversely affecting the ability of the finished lamp to withstand high impact type shocks.

It is accordingly the general object of the present invention to overcome the foregoing and other difficulties and deficiencies associated with the prior art practices by the provision of a heat shielding assembly for an elec-' tric lamp which can be simply and economically incorporated therein without deleteriously afiecting the overall quality of the lamp.

A more specific object of the invention is to provide an electric lamp with an integral heat shielding structure which does not require a multiplicity of parts or precisely formed members and which can be efliciently and permently assembled during the high-speed fabrication of the lamp.

It is another object of the invention to provide a heat shield for an electric lamp which will not become detached from the stem or displaced from its assembled position thereon during handling and transfer of the filament mount prior to the sealing-in operation.

The aforesaid objects, and others which will become obvious to those skilled in the art as the description proceeds, are achieved by heat-forming a section of the stem in the usual manner to provide a substantially flat press and fabricating a heat shield of suitable material which is slit over a substantial portion of its length and shaped to include a flanged 'recess which nestingly receives the press, when the shieldis sprung over and seated on said press in a plane transverse to the stem axis. This provides an interlocking heat shielding structure which is not only economical and convenient to fabricate and assemble but exceedingly rugged.

A better understandingof the invention may be ob: tained by referring to the accompanying drawing in which like numerals of reference indicate similar parts throughout the several views, wherein:

Fig. 1 is an elevational view of an incandescent lamp embodying the heat shielding structure of this invention;

Fig. 2 is a fragmentary sectional view on an enlarged scale through the neck portion of the lamp along the line 11-11 of Fig. 1, in the direction of the arrows; showing the manner in which theheat shield is mounted on the stem press; a

Fig. 3 is an enlarged perspective view of the heat shielding assembly incorporated in the lamp shown in Fig. 1 and illustrates the structural relationship' of the parts in accordancewith a preferred embodiment of the present invention;

Fig. 5 is a perspective view of the stem pressipora tion of the lamp and illustrates one phase in fabricating the heat shielding assembly of this invention; and:v i

Fig. 6 is a perspective view of another embodiment of the heat shield according to the invention.

vAlthough theprinciples of this invention are broadly applicable to other types of lamps and similar electrical devices, the invention is usually employed in high-watt;

age incandescent lamps for generallighting serviceand V K hence has been so illustrated and will be so described.

Referring now to the drawing in detail, in Fig. 1 there.

is shown a large incandescent lamp d0 of high wattage Y rating, as for example 750 w., which includes the heat shielding arrangement of this invention The lamp 10; I I

generally comprises a pear shaped envelope 11. having; 3 j

' a constricted cylindrical neck portion which has'beei sealed to an inwardly projecting coaxial stem/tube 14' having a centrally disposed exhaust tubulation .ther ei h g l The vinward. end of the tribulation is fused to th stem tube 14 is also heat-softened and comprmsed to form a press 18 having substantially flat parallel sides extending transversely of the stem axis in accordance with conventional stem making techniques.

A pair of lead-in conductors 22 are sealed through the stem press 18 and project into the envelope 11 .in spaced apart relation whereas the exterior end portions thereof are fastened tothe threaded shell portion 12 of a base member carried by the sealed neck portion of the envelope 11 and to an eyelet embedded in an insulating button 13 secured to the end of the shell 12 to form an end contact 15 and facilitate connection of the lamp with a source of electrical power. A glass arbor 24 may be fused to the pressed portion of the stem tube 14 in coaxial alignment therewith so as to extend into the bulbous portion of the envelope 11 between the conductors 22 and serve as a standard for supporting a source of radiant energy, such as a coiled filament 30 of tungsten or other suitable material, and strengthening the mount assembly. The end of the arbor 24 is desirably shaped while plastic to form a button 26 into which a plurality of support wires 28 of refractory material, such as molybdenum, are inserted thereby to support the filament 30 in a desired geometrical configuration within the lamp envelope 11, as is customary in the art. The inner ends of the conductors 22 are securely fastened to the supports affixed to the ends of the filament 30 thereby connecting the filament 30 with the base member. Prior to the attaching of the basemember to the neck portion of the envelope 11, the lamp 10 may be exhausted and filled with inert gas, such as a mixture or nitrogen and argon, through the protruding exhaust tubulation which is subsequently tipped-off to sel the envelope in accordance with standard lamp making practice.

A laterally extending heat shield 20 of suitable size and material, preferably aluminum, is mounted onthe stem press 18 interlocking engagement therewith according to the invention and disposed so as to be substan tially coextensive with the neck portion of the envelope 11 and reflect the radiant heat emanating from the filament 30 and confine the hot gases to the bulbous portion of the envelope 11 thereby insulating the basal end portion of the lamp 10 and effecting the desired reduction in the base temperature.

The essence of this invention resides in the configuration of the heat shield and in the manner in which it cooperates with the stem press to provide an integral temperature modifying means and these are hereinafter more fully described. a

As shown in Fig. 4, the heat deflecting element of this invention comprises a circular shield 20 provided with a slit 23 which extends radially inward from the periphery of the shield 20 over a substantial portion of the shield length an'd communicates with an enlarged recess 25 of generally rectangular configuration disposed along the line of cleavage and formed by appropriately severing and depressing the shield material thereat outwardly to provide a pair of longitudinal extensions or ribs 21 which project transversely of the shield body along the sides of the recess 25 in substantially parallel relation. The recess 25 is proportional to accommodate the stem press 18 in a snug fit so that the ribs 21 are firmly seated against the sides of the press 18 when the shield 20is in assembled position thereon. The width of the radial slit 23 is appreciably less than the thickness of the press 18 so that when the press 18 is inserted into the recess 25 and the shield 20 is disposed in a cornmon plane the members are locked together. The recess 25 is also desirably centered with respect to the periphery of the shield 20 so that the press 13 is received centrally of the shield and oriented so as to besyrnmetrically disposed about the diameter traversed by the slit 23.

During the fabrication of the mount assembly the inner end portion of the stem tube 14 is molded to form a press 18 previously referred to. The press 18 may be conveniently formed by compressing the glass walls of the stem tube 14 inwardly while plastic by means of a pair of cooperating press-jaws in the customary manner. The jaws are desirably positioned so that they contact the stem tube 14 slightly behind its inward extremity permitting the glass thereat to flow freely and form a protruding lip or shoulder 16 along the peripheral edge of the tube end, as shown in Figs. 2, 3 and 5. In contrast to the prior art practice utilizing a specially formed press section having slots or grooves therein disposed to receive bent portions of the shield, the configuration of the press 18 required in accordance with the principles of this invention is such that the end of the stern tube 14 is merely compressed to form a section with pressed side surfaces which are substantially flat and parallel throughout thehir length and breadth thus providing a press 13 of substantially uniform thickness terminated along one edge by a peripheral shoulder portion 16 and along the other by the flared portion of the stem tube 14 (see Fig. 2). This configuration can be very easily obtained with standard stem-making machines and press-forming methods thereby obviating the need for specially shaped press-jaws or precisely molded presses. The foregoing construction also serves to increase the strength of the mount structure insofar as the indentation of the press 18 and subsequent thinning out of the glass over the portions of the lead-in conductors 22 embedded therein is kept to a minimum.

In assembly the lamp 10 according to the invention, the shield 20 is tilted with respect to the stem axis and the press 18 forcibly inserted into the radial slit 23 springing the shield 20 in scissor-like fashion, as illustrated in Fig. 5, and providing an opening which enables the shield 20 to be slidably threaded over the press 18 until the latter is received by the recess 25 whereupon the shield 20 is permitted to spring back to its normally uniplanar configuration or, if not naturally resilient, is bent to be so disposed thus assuming the position illustrated in Fig. 3 and completing the assembly. With the shield 20 so positioned the ribs 21 are brought back into parallelism and bear tightly against the sides of the press 18, as shown in Fig. 2, thereby firmly seating the shield 20 on the press 18 and serving to stabilize and support the shield in a plane transverse to the stem axis. In addition, the shield 28 when in this as sembled position is prevented from slipping laterally off the press 18 by the inward edges of the slit 23 and is restricted longitudinally by the peripheral shoulder 16 and proximate flared portion of the stem tube 14, which cooperating structural relationships are best illustrated in Figs. 3 and 2 respectively.

The use of aluminum as the shield materialis preferred inasmuch as aluminum is relatively inexpensive, is sufficiently reflective and resilient, and can be easily formed into the desired shape by 'well known stamping techniques. The thickness of the shield material and the dimensions and shape of the shield, slit and recessed portions and conjoined extensions will vary depending upon the lamp rating and the configuration and size of the envelope neck and stem press. In the particular example illustrated the shield was fabricated by stamping a disc about 2 inches in diameter from sheet aluminum 10 mils thick and Working the material to form a radial slit approximately .07 inch wide and a recess approximately .175 inch wide and .75 inch long. Since the rib extensions are desirably formed from the material pressed outwardly in fabricating the recess, they will have a vertical span approximately one half the recess width and in the instant case projected approximately .085 inch from the main body of the shield.

In Fig. 6 there is shown another embodiment of the invention wherein a heat shield 20a is provided having a radial slit 23a and recess 25a, corresponding to those previously described in conjunction with the preferred form of the invention, but in which intermediate segments of the rib sections are bent upwardly to form a plurality of matching oppositely-disposed tabular extensions 21a, 32 which construction effectively doubles the span of the extensions and enhances their stabilizing effect on the shield 20a in its assembled position on the press 18.

As will be apparent to those skilled in the art, other shield configurations and material may be employed. The only limitations are that the shield have a slit therein which extends inwardly from the shield periphery and is so proportioned and formed that its peripheral breadth is less than the thickness of the stern press, and that such slit join with an enlarged recess and suitably disposed extensions which are adapted to receive the stem press and support the shield laterally of the stem when the shield is firmly seated in interlocking position thereon.

It will be recognized from the foregoing that the objects of the invention have been achieved by providing a heat shielding assembly which is not only more economical and easier to manufacture and assemble than the prior art structures, but which provides a locking-in feature that eliminates specially shaped parts and strengthens the lamp.

Although the best known mode of carrying out the present invention has been shown and described in accordance with the patent statutes, it will be understood that various modifications may be made without departing from the spirit and scope of the appended claims.

I claim:

1. An electric lamp comprising an envelope containing a source of radiant energy and an inert gas fill, a stem sealed to said envelope and extending inwardly thereof, a press formed in said stem having at least one pressed surface which is substantially fiat throughout its length and breadth and extends transversely of the stemaxis, lead-in conductors sealed through said press and connected to said source, and a unitary heat deflecting member on said stem provided with a slit which extends inwardly from the periphery of said member for a substantial distance and communicates with an enlarged recess adapted to receive said press, a part of said member along an edge of said recess being displaced outwardly to form a longitudinal extension, the width of said slit being less than the thickness of said stem press, said heat deflecting member being disposed on said stem in a plane transverse to the stem axis with said enlarged recess receiving said stem press and the longitudinal extension seated against the pressed surface thereof, whereby said heat deflecting member is locked and stabilized in its assembled position on said stem.

2. An electric lamp comprising an envelope containing a source of radiant energy and an inert gas fill, a stem sealed to said envelope and extending inwardly thereof, a press formed in said stem having pressed surfaces which are substantially flat and parallel throughout their length and breadth and extend transversely of'the stem axis, lead-in conductors sealed through said press and connected to said source, and a unitary heat shield on said stem, an interior portion of said shield being displaced outwardly to provide a centrally-disposed recess of substantially the same contour as the cross-sectional configuration of said stem press and a pair of parallelspaced ribs which extend transversely of the shield body along the sides of said recess, said shield having a slit which extends inwardly from its periphery and is aligned being less than the thickness of said stem press and said recess being proportioned to accommodate said stem press in a snug fit, said heat shield being disposed on said stern in a plane transverse to the stern axis with said enlarged recess receiving said stem press and said ribs seated against the pressed surfaces thereof, whereby said heat shield is locked and stabilized in its assembled position on said stem. 7

3. An electric lamp comprising an envelope having a cylindrical neck portion, a source of radiant energy and an inert gas fill within said envelope, a stem sealed to the neck portion of said envelope and extending inwardly thereof, a press formed in said stem having pressed surfaces which are substantially fiat and parallel throughout their length and breadth and extend transversely of the stem axis, said press having a terminating peripheral shoulder which in conjunction with a flared part of said stem defines the said pressed surfaces, lead-in conductors sealed through said press and connected to said source, and a unitary circular heat shield of resilient sheet material and smaller. diameter than said neck portion on said stem, an interior portion of said shield being displaced outwardly to provide a centrally-disposed recess of substantially the same contour as the cross-sectional configuration of said stem press and a plurality of matching tabular extensions which transversely depend from opposite sides of the shield body along the sides of said recess, said recess being proportioned to accommodate said stern press in a snug fit and being accessible from the periphery of said shield through a slit which splits the shield along the diameter containing said recess, the width of said slit being less than the thickness of the stem press, said heat shield being disposed on said stem between the peripheral shoulder of said press and the flared part of said stem in a plane transverse to the stem axis with said enlarged recess receiving said stem press and said tabular extensions resiliently seated against the pressed surfaces thereof, whereby said heat shield is locked and stabilized in its assembled position on said i stem.

sembly with a press formed therein comprising, a unitary member of yieldable'sheet material havinga slit therein which is narrower in breadth than the thickness of said press and extends inwardly from the periphery of said member for a substantial distance, an inward partof said member along said slit being displaced outwardly from theplane ofsaid member to provide an enlarged transverse to the stem axis. 7

References Cited in the file of this patent V UNITED STATES PATENTS 2,326,419 2,624,019 Leighton Dec. 30, 1952. Y 2,664,513 Morgan Dec. 29, 1953, 2,777,082 May Jan. 8, 1957v 4. A heat shield for an electric lamp having a stem as-.

Van Horn Aug. 10, 1943 i v