CA1255736A - Bonded beam lamp - Google Patents
Bonded beam lampInfo
- Publication number
- CA1255736A CA1255736A CA000486633A CA486633A CA1255736A CA 1255736 A CA1255736 A CA 1255736A CA 000486633 A CA000486633 A CA 000486633A CA 486633 A CA486633 A CA 486633A CA 1255736 A CA1255736 A CA 1255736A
- Authority
- CA
- Canada
- Prior art keywords
- reflector
- lens
- adhesive means
- celsius
- lamp
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K1/00—Details
- H01K1/36—Seals between parts of vessel, e.g. between stem and envelope
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K3/00—Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof
- H01K3/12—Joining of mount or stem to vessel; Joining parts of the vessel, e.g. by butt sealing
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Non-Portable Lighting Devices Or Systems Thereof (AREA)
Abstract
BONDED BEAM LAMP
ABSTRACT
An electric lamp having an envelope, formed from a lens and a reflector that are sealed together by adhesive means, a light source and a base. The adhesive means has a curing temperature that is equal to or higher than the operating temperature of the lamp and a higher index of thermal expansion than the lens and reflector material. The adhesive means includes an epoxy, that is either heat or ultraviolet curable, which is disposed on the sealing surfaces of the glass lens and reflector. Sealing in this fashion obviates the need for flame sealing the glass lens and reflector together and results in a lamp that is substantially free from thermally induced strains in either the lens or the reflector.
ABSTRACT
An electric lamp having an envelope, formed from a lens and a reflector that are sealed together by adhesive means, a light source and a base. The adhesive means has a curing temperature that is equal to or higher than the operating temperature of the lamp and a higher index of thermal expansion than the lens and reflector material. The adhesive means includes an epoxy, that is either heat or ultraviolet curable, which is disposed on the sealing surfaces of the glass lens and reflector. Sealing in this fashion obviates the need for flame sealing the glass lens and reflector together and results in a lamp that is substantially free from thermally induced strains in either the lens or the reflector.
Description
~;~5 7~
84-1-0~5 -1-BONDED BEAM L~MP
CROSS REFERENCE TO COPENDING APPLICATION
In Serial No. 461,058-0, entitled ~Par Spot Lamp" and filed ~ugust 15, 1984 (William Thiry et al), ~here is described a spot lamp having a curved lens member. the inner surface of which has a series of radially disposed flutes formed therein defining a fluted portion which surrounds a centrally disposed stippled portion. The aforementioned application was assigned to the same assignee as the instant invention~
TECHN r CAL FIELD
The present invention relates in general to incandescent light sources and particularly bonded beam lamps, having two-piece envelopes, comprising a reflector and lens assembled by adhesive means. The reflector has an internal reflective coating for reflecting and directing light, originating from a ligh~ source located within the envelope, towards a coopexating lens through which the light is transmitted.
BACKGROUND
It is well known in the art to utilize PAR (parabolic aluminized reflector) or ER (eliptical reflector) lamps for general spot or flood lighting applications~ In particular, PAR and ER lamps have become exceptionally popular for short to medium distance outdoor uses as well as indoor for ~, 7~3~
di~play, ~ecoration, accent, in~pection and downlighti~g applications. Such lamp6 are manufactured and ~old by the as~ign~e of the in~tant :nvention. Typically, these lamps are of hardglass and include a medium 6kirt (screw-type3 or side prong base at the rear t~ereof for connecting the lamp to the dasired power ~ource.
The produc~ion of 6uch a66embled 6ub6tantially circular qlas6 reflector6 and lense6, however, can pre~ent numerous problem6. For example, stres~e6 created in the glas6 len6e~
and reflector~ during a6sembly by fu6ion sealing [i.a., flame 6ealing) can cau~e cracking t~ereof. The proces6 of flame ~ealing is not only expensive but it require~ the u6e of difficult-to-operate equipment. The thermally induced 6tres6 points can be the origin point o~ reflector or lens cracking and ~ubsequent non-containment upon fracture of a ligh~
source capsule located within the lamp. The~e proble~s are particularly evident in out6ide applications where the PAR or ER lamp may be 6ubjected to extreme tharmal gradient~.
Experience gained in ~e te~ting involved with automobile headlight design ha~ demonstrated ~hat the probability of such tharmally induced stre6se~ can be 6ignificantly reduced by using an adhesive, rather t~an flame sealing, to seal the gla~ reflector and lens together.
In the de6ign of automobile headlights, the quality of the lens-reflector ~eal depends largely on properly combining the i~dex of thermal expan6ion of the len~ and reflector material with the inde~ of thermal e~pansion of the adhesive to be used. The typical indice6 of thermal expan~ion for hardglas6 used in headlight~, 6uch as borofiilicate, and a 6uitable adhesive for bonding lamp gla~sware, such as an epoxy polymer which has been flexibilized, can diffe~ by a factor of about 10. The glas~-adhe~ive ~eal, when expo~ed to a decrea~ing ambien~ temperature, can have glas6 portions .~.2S577~
thereo~ eontrac~ing at a muc~ different rate ~an ~he adhesive portions thereof. Suc~ variations in coneraction cause ~tre6~e6 that will ultimately lead to weakeni~q of ~he lens to reflector 6eal or cracking of the gla68 . Li~ewi6e, in ot~er lamps where a lens and reflector must be ~oined to ~orm ~ ~ealed envelope, the proper combination of indice~ of thermal expansion o~ the lamp envelope material and adhesive for the lens-reflector seal i~ important in order to obeain a 6trong long-lasti~g 6eal.
Ie is believed, therefore, that there i8 a need for a lamp that can be a~6embled by a me~hod that 6ub6tantially eliminate~ thermally induced 6train6 in either the len6 or the reflector, unlike the traditional flame ~ealing technigue. Such a lamp would be deemed an even fureher advancement if a hig~er wattage capsule ~ould be u6ed, without the cGncern that the additional heat generated would cause a ~train induced failure.
DISCLOSURE OF THE INVENTION
T~erefore, it is a primary object of this invention to enhance the art of incande~cen~ lamp6 and particularly bonded beam lamps, operating at hi~her wattages, that are ~ubjected to extreme thermal gradients.
It is another object of ~hi~ invention to provide a bonded beam lamp that may be used more succe~fully in 6evere outdoor application~ without the concern that an abrup~
temperature change will cause a lamp envelope failure.
It i~ ~till another object of this invention to provide a bonded beam lamp ~hich will ~ucc2s~fully contain glas6 fragmene~ resulting from the fracture of a light ~ource capsule located ~i~hin the lamp.
3L ;~ r 5t7;3~;
In accordance wit~ one a~pect of t~e insta~t invent~on, ~here i6 provided an electric lamp co~pri6ing an envelope having a reflector and a lens ~ade of su~antially the same material ~ith a prede~ermined index of ~hermal expan6ion, a lig~t ~ource diæpo~ed within the envelope and 6ub6~antially ~urrounded by the reflector, and adhe6ive ~ean~ di6po6ed between and sealing the lens and reflector together, the adhesi~e means having a curing ~emperature ~hat i6 equal to or higher than the operating temperature of the lamp and a higher index of thermal expansion than the len~ and reflector material.
In accordance wit~ another aspec~ of the present inve~tion, there i6 provided a method of making an electric lamp, the lamp having an envelope formed ~rom a len6 and a reflector, the len~ and reflector having ~ealing surface6 on the lens and reflector peripheries, the method comprising the steps of: alumini~ing ~he reflector, mounting a light source within the reflector, disposing adhesive mean6 on t~e sealing surface of the lens and joining ~he len6 6ealing 6urface with the reflector sealing ~urface, the adhesive mean6 having a curing temperature that i6 equal to or higher than the operating temperature of t~e lamp and a highar index of thermal expansion than ~he material Porming ~he lens and reflector, curing t~e adhe6ive means to a temperature in the range of about 148 Cel6iu6 to 190 Celsiu~ for a period of time in the range of about 5 to 40 minutes ~ime.
~a~ 06~
BRI~F D~SC~IPTION OP ~HE DRAWINGS
PI~. 1 is a s~dg ~levatio~al view, par~ly ~ sec~ion. of an electric lamp const~uc~ed ~ accorda~ce wi~h the principle~ o ~hi i~ven~io~; and FIG. 2 ~s a ~a~mentary, ~ro~-sectional YieW of the l~ns and reflec~or s~aling ~ur~aces ~ ac~ordance with ~he presen~
invention.
BEST ~ODE FOR CARRYING OUT TH~ INVENTION
For a better unders~andi~g o~ the present invention together with o~er and further objects, advantages and capabilities thereof, reference i~ ~ade to ~he ~ollowi~g d~sclosure and appended clai~s in eonnectio~ wi~h the above-deficribed drawings.
~it~ refareA~e ~ow to the dra~ing~, there is shown i~
FIG. 1 an elsctric lamp lO ~ade i~ accordance with the teachings of ~e pre~e~t inventio~. Electric lamp lO
include~ an envelope 11, for~ed from a lens 12 and a cooperating r~flec~or 14, a lig~t ~ource 16 and a base 18.
Both lens 12 and reflector 14 are jsined by ad~esive mean~ 15 to form a lens-reflector seal 19 ~or la~p lO. ~ens 12 and reflector 14 can be formed by pressing ~ardgla~s in a mold followed by an anneali~q pro~e~s. Lens 12 ~ypically ~a& a slightly con~Y outer face and a~ optical pre~cription provided, for example, by a ~erie~ of radially di~po~ed flutes formed on ~he inner ~urface thereof defini~g a fluted portion which ~urrounds a centrally di~po~ed ~tippled portion, as deficribed in ~he aforementioned applicatio~
having Cana~ian Serial No. 461,058-0. Additionally, reflector 14 ~5~
has a concave inner surface 13 that includes a light reflective coating typically comprised o~ aluminum or silver. Reflec~or 14 is preferably a parabolic re~lector but it can also be an eliptical reflector. Lens 12 and reflec~or 14 preferably have substantially circular peripheries and sealing surfaces located approximately about these peripheries, respectively.
As previously discussed, flame sealing, producad, for example, by a flame trained on the glass reflector and lens sealing surfaces, can crea~e unacceptable stress patterns in envelope 11. In particular, stresses tend to concentrate a~out the lens-reflector seal 19, resulting in cracks about that area. The stresses created by flame sealing can be substantially eliminated by interposing adhesive means 15 between the aforementioned peripheral sealing surfaces to seal lens 12 to reflector 14. Acceptable adhesives for the use indicated above are those having a curing temperature that is equal to or higher than the operating temperature of the lamp and a higher i.ndex of thermal expansion than the lens and reflector material. Such an adhesive, a heat curable epoxy, may be obtained from the Amicon Corp. of Lexington, Massachusetts.
~ lectric lamp 10 includes a tungsten-halogen capsule 16 having an envelope containing an inert gas fill and a halogen disposed within. Capsule 16 is disposed within and is substantially surrounded by reflector 14 as well as being substantially perpendicular to lens 12. Capsule 16 is attached to and supported by mount 20. Reflec~or 14 has two ferrule holes 22 ~hrough which the capsule-mount assembly will be inserted and secured into place by an eyelet-epoxy-washer combination. Each lead of mount 20 is secured in each ferrule 22 by an eyelet 24, epoxy 26 and ,~ s~
57~3~
washer 28. Lamp 10 al60 includes a diode 30 and a fuse wire 32 ~oupled in serie6 with cap6ule 1~ and base 18. Envelope 11 of lamp 10 al60 includes an exhau~t hole tube 34 and a small 6teel ball bearing 35 tha~ serve6 a~ a plug.
Envelope 11, a~ illu6trated in FIG. 1, is one example of a lamp envelope t~at i~ al~o capa~le of con~aining glass fragments re6ulting from a po6sible, but unlikely frac~ure of cap~ule 16. Test re6ults ~ave shown t~at out of 60 lamp envelope6 formed by the method described here, all of the lamp6 6uccessfully contained glas6 fragment~ re6ulting from intentionally induced capsule failures. Of the 50 lamp6 made by the flame sealing technique, 3 lamp~ failed eo contain after intentional inducement of capsule failure. Therefore, the above described 6ealing technique results in a lamp envelope that will reliably contain gla~s fragment~ from a po~sible, but unlikely fracture of cap6ule 16.
Referri~g now to FIG. 2, there is illustrated a fragmentary, cross-6ectional view of t~e len~-reflector seal 19 having a len6 ~ealing, channel-like surface A and a reflector sealing ~urface B that are located about t~e peripherie6 of lens 12 and reflector 14, respectively.
During a6sembly of electric lamp 10, ad~esive means 15 i8 placed between 6ealing 6urface6 A and B. Sealing 6urfaces A
and B are joined when lens 12 and reflector 14 are pre~ed toge~er. Lamp 10 i6 then 6ubjected to a heat curing temperature in the range of about 14B Celsius to 190 Cel~ui6 for about 5 to 40 minute~ in order to cure adhe6ive means 15.
Contact between ~ealing surface6 A and B can degrade quic~ly with time upon impropelly combining the different indice6 of thermal expan~io~ of glas~ and adhesive mean~
used. For example, the index of thermal expan6ion for boro~ilicate glas6, conventionally used in sealed beam auto~otive ~eadligh~, typically is about 40 ~ 10~7cm/cm/~C
(i.e., cm ~ centimeter C = Celsiu~). W~ereas ~he index of ther~al expansion of a typically flexibilized ~poxy, suitable for ~ealing headlight glas6ware, typically is about 40 X
10 6c~/cm/C. That i8, the indice6 of thermal expansion of glass and adhe~ive means in a sealed beam headligh~ can differ, by a actor of about 10. Therefore, temperature changes, in particular decrea~ing temperature6, produce different rates o~ contraction for t~e glas6 and interposed adhesive mean~ creating more stre66 between the sealing 6urfaces thereby adver~ely affecting t~e gla~ lens to glass reflector contact along the outermost ~ealing surface6 where ad~esive means has been pre6sed away.
T~e sealing and ~tre~s problem~ found in automotive headlights, due to t~e differing rates of contraction for the lens and reflector ma~erial and interposed adhesive means, also exist in PAR and ~R lamps. In addition, the sealing problem in PAR a~d ER lamp6 i~ compounded by their higher operating temperature ~140 Celsiu6 - 150 Celsiu~ a~
compared to headlights (about 120 Cel~iu~, which in turn causes the failure of most adhe~ives having low toleraQce6 to high temperature6. Adhesive means 15, of the present invention, serve6 to alleviate 60mewhat the stre~se6 between sealing surfaces A and B due eo it~ ability to withstand the high compressive ~tres~ without breakdown at high operating tem~erature6 of the lamp, and therefore provide an operative lamp or an environment that varie6 frequently in temperature.
The present invenSion 6ignificantly reduces thermally induced 6tresse~ by eliminating fla~e fiealing as a method of creating a lens to reflector ~eal. Adhe~ive means 15, used to join lens 12 and reflector 14 together, must have a curing ~5'7~6 _g_ temperature ~at is ~qual to or higher than the operating temperature of lamp 10 and it must have a higher index of thermal expansion than the material that form~ lens 12 and reflector 14. Since the normal operating temperature of a lamp 8UC~ as lamp 10 is u6ually abou~ 140 to 150 C~lsius, the ad~e6i~e means used here will provide for a 6trong seal at 6uch ~igh temperature6 due to it6 own high curing temperature.
The material used to form lens 12 and reflector 14 i6 usually hardglass, and the predetermined index of Shermal expansion for such a material is about 40 ~ 10 7cm/cm/~C.
Adhesive means 15 of the present invention include~ an epoxy having a curing temperature that i6 in ~he range of about 148 Cel~ius to 190 Cel6iufi with an index of thermal expansion in the range of about 75 - 300 X 10 7cm/cm/C.
The curing time of the epoxy îs about 5 to 40 minutes. The epoxy currently in use has an index of thermal expan6ion of about 150 X 107cm~cm/C, a curing ~emperature of about 160 Celsius and a curing time of about 5 minute6. In addition, adhesive means 15 may also include ultraviolet cured epoxies that have similar expansion and temperature charactari6tics as the acceptable heat cured epoxie6 de6cribed earlier.
Since t~e epoxy used ~ere ha6 an index of expansion greater t~an the hard~la~s forming the lens and reflector, a stronger seal will result due to a compre~sive 6tress being formed around t~e lens-reflec~or 6eal when the lamp i6 placed in an environment with a temperature below ~at which it was cured. This would occur during most, if not all, operating condition~ with the lamp on or off. In addition, the need for a specialized 6hape or form for sealing 6urfaces A and B
of lens 12 and reflector 14 is obviated by the use of the sealing technique6 taught by the pre~ent invention. In one 5~7;~
D-84~1-065 embodi~ent of the present invention, ehe lens sealiny surface A has a channel or rece6sed por~ion and reflector 6eali~g 6urface B has a fla~ge, thereby creating a self-aligning relationship when the lens 12 and rsflector 14 are ~ealed together by adhesive means 15 (6ee FIG. 2).
To assemble lamp 10, reflector 14 i~ fir6t of all aluminized by placing a light reflective coating on the inner surface 13 of reflector 14, typically comprised of aluminum or silver. Reflector 14 i6 aluminized in such a way as to provide an aluminum-free area near the reflec~or base where ferrule holes 22 are lo~ated. Eyelets 24 are then placed in ferrules 22 and a small amount of thermally cured epoxy 26 is injected around eyele~s 24. Washer6 28 are then placed about eyelets c4 whereupon eyelets 24 are s~aked. Capsule 16, which i6 attached to mount 20, is then inserted into ferrules 22 and then supported by the eyelet-epoxy-washer combination. The capsule-mount a~embly is then soldered into place. Adhesive mean6 15, which i8 preferably a thermally cured epoxy, i6 then a~plied to len6 12 whic~ i~
then joined with reflector 14, such that a self-aligning relationship is c~eated. The lens-reflector as6e~bly is then placed in an oven and brought to and kept at the requi~ite curing temperature (about 160 Celsius~ until such time a6 the epoxy is cured (about 5 to 40 minutes). Lamp 10 i~ then ~ubjected to a brief nitrogen flu~h through exhau6t tube hole 34 located in reflec~or 14. Exhaust tube hole 34 is thereafter plugged by using small 6teel ball bearing 35 and an ultraviolet cured epoxy. The diode-fu~e assembly and base 18 are then ~oldered into place.
Thus, there has been 6hown and described an improved electric lamp and method of making such a lamp which 6ubstantially reduces or eliminate6 thermally induced strain ~55t~36 ~n ei~er the len6 or the re~lector once ~hey have been ~oined together, unlike the ~raditional flame ~ealing technigue. The advantages of a strain-free PAR or ~R lamp include the following: a hig~er wa~tage tungsten-halogen capsule may be u~ed wi~hout ~he concern that the additional heat generated will ~au6e a 6train induced failure: t~e lamp may be used ~ore succe6s~ully i~ severe outdoor applications without t~e concern that a ~hermal shock will cause a lamp envelope failure and envelope failures due to a fracture of .lO a tungsten~alogen cap~ule will be ~ub6tantially eli~inated in bonded beam lamps . The above de~cribed invention may be utilized wherever the flame 6ealing technique is used in a lamp to seal two corre~ponding and opposing members together to form a single member.
~hile there have been shown and de6cribed what are at present considered the preferred embodiments of the invention, it will be obvious to those ~killed in the art that variou~ change6 and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
84-1-0~5 -1-BONDED BEAM L~MP
CROSS REFERENCE TO COPENDING APPLICATION
In Serial No. 461,058-0, entitled ~Par Spot Lamp" and filed ~ugust 15, 1984 (William Thiry et al), ~here is described a spot lamp having a curved lens member. the inner surface of which has a series of radially disposed flutes formed therein defining a fluted portion which surrounds a centrally disposed stippled portion. The aforementioned application was assigned to the same assignee as the instant invention~
TECHN r CAL FIELD
The present invention relates in general to incandescent light sources and particularly bonded beam lamps, having two-piece envelopes, comprising a reflector and lens assembled by adhesive means. The reflector has an internal reflective coating for reflecting and directing light, originating from a ligh~ source located within the envelope, towards a coopexating lens through which the light is transmitted.
BACKGROUND
It is well known in the art to utilize PAR (parabolic aluminized reflector) or ER (eliptical reflector) lamps for general spot or flood lighting applications~ In particular, PAR and ER lamps have become exceptionally popular for short to medium distance outdoor uses as well as indoor for ~, 7~3~
di~play, ~ecoration, accent, in~pection and downlighti~g applications. Such lamp6 are manufactured and ~old by the as~ign~e of the in~tant :nvention. Typically, these lamps are of hardglass and include a medium 6kirt (screw-type3 or side prong base at the rear t~ereof for connecting the lamp to the dasired power ~ource.
The produc~ion of 6uch a66embled 6ub6tantially circular qlas6 reflector6 and lense6, however, can pre~ent numerous problem6. For example, stres~e6 created in the glas6 len6e~
and reflector~ during a6sembly by fu6ion sealing [i.a., flame 6ealing) can cau~e cracking t~ereof. The proces6 of flame ~ealing is not only expensive but it require~ the u6e of difficult-to-operate equipment. The thermally induced 6tres6 points can be the origin point o~ reflector or lens cracking and ~ubsequent non-containment upon fracture of a ligh~
source capsule located within the lamp. The~e proble~s are particularly evident in out6ide applications where the PAR or ER lamp may be 6ubjected to extreme tharmal gradient~.
Experience gained in ~e te~ting involved with automobile headlight design ha~ demonstrated ~hat the probability of such tharmally induced stre6se~ can be 6ignificantly reduced by using an adhesive, rather t~an flame sealing, to seal the gla~ reflector and lens together.
In the de6ign of automobile headlights, the quality of the lens-reflector ~eal depends largely on properly combining the i~dex of thermal expan6ion of the len~ and reflector material with the inde~ of thermal e~pansion of the adhesive to be used. The typical indice6 of thermal expan~ion for hardglas6 used in headlight~, 6uch as borofiilicate, and a 6uitable adhesive for bonding lamp gla~sware, such as an epoxy polymer which has been flexibilized, can diffe~ by a factor of about 10. The glas~-adhe~ive ~eal, when expo~ed to a decrea~ing ambien~ temperature, can have glas6 portions .~.2S577~
thereo~ eontrac~ing at a muc~ different rate ~an ~he adhesive portions thereof. Suc~ variations in coneraction cause ~tre6~e6 that will ultimately lead to weakeni~q of ~he lens to reflector 6eal or cracking of the gla68 . Li~ewi6e, in ot~er lamps where a lens and reflector must be ~oined to ~orm ~ ~ealed envelope, the proper combination of indice~ of thermal expansion o~ the lamp envelope material and adhesive for the lens-reflector seal i~ important in order to obeain a 6trong long-lasti~g 6eal.
Ie is believed, therefore, that there i8 a need for a lamp that can be a~6embled by a me~hod that 6ub6tantially eliminate~ thermally induced 6train6 in either the len6 or the reflector, unlike the traditional flame ~ealing technigue. Such a lamp would be deemed an even fureher advancement if a hig~er wattage capsule ~ould be u6ed, without the cGncern that the additional heat generated would cause a ~train induced failure.
DISCLOSURE OF THE INVENTION
T~erefore, it is a primary object of this invention to enhance the art of incande~cen~ lamp6 and particularly bonded beam lamps, operating at hi~her wattages, that are ~ubjected to extreme thermal gradients.
It is another object of ~hi~ invention to provide a bonded beam lamp that may be used more succe~fully in 6evere outdoor application~ without the concern that an abrup~
temperature change will cause a lamp envelope failure.
It i~ ~till another object of this invention to provide a bonded beam lamp ~hich will ~ucc2s~fully contain glas6 fragmene~ resulting from the fracture of a light ~ource capsule located ~i~hin the lamp.
3L ;~ r 5t7;3~;
In accordance wit~ one a~pect of t~e insta~t invent~on, ~here i6 provided an electric lamp co~pri6ing an envelope having a reflector and a lens ~ade of su~antially the same material ~ith a prede~ermined index of ~hermal expan6ion, a lig~t ~ource diæpo~ed within the envelope and 6ub6~antially ~urrounded by the reflector, and adhe6ive ~ean~ di6po6ed between and sealing the lens and reflector together, the adhesi~e means having a curing ~emperature ~hat i6 equal to or higher than the operating temperature of the lamp and a higher index of thermal expansion than the len~ and reflector material.
In accordance wit~ another aspec~ of the present inve~tion, there i6 provided a method of making an electric lamp, the lamp having an envelope formed ~rom a len6 and a reflector, the len~ and reflector having ~ealing surface6 on the lens and reflector peripheries, the method comprising the steps of: alumini~ing ~he reflector, mounting a light source within the reflector, disposing adhesive mean6 on t~e sealing surface of the lens and joining ~he len6 6ealing 6urface with the reflector sealing ~urface, the adhesive mean6 having a curing temperature that i6 equal to or higher than the operating temperature of t~e lamp and a highar index of thermal expansion than ~he material Porming ~he lens and reflector, curing t~e adhe6ive means to a temperature in the range of about 148 Cel6iu6 to 190 Celsiu~ for a period of time in the range of about 5 to 40 minutes ~ime.
~a~ 06~
BRI~F D~SC~IPTION OP ~HE DRAWINGS
PI~. 1 is a s~dg ~levatio~al view, par~ly ~ sec~ion. of an electric lamp const~uc~ed ~ accorda~ce wi~h the principle~ o ~hi i~ven~io~; and FIG. 2 ~s a ~a~mentary, ~ro~-sectional YieW of the l~ns and reflec~or s~aling ~ur~aces ~ ac~ordance with ~he presen~
invention.
BEST ~ODE FOR CARRYING OUT TH~ INVENTION
For a better unders~andi~g o~ the present invention together with o~er and further objects, advantages and capabilities thereof, reference i~ ~ade to ~he ~ollowi~g d~sclosure and appended clai~s in eonnectio~ wi~h the above-deficribed drawings.
~it~ refareA~e ~ow to the dra~ing~, there is shown i~
FIG. 1 an elsctric lamp lO ~ade i~ accordance with the teachings of ~e pre~e~t inventio~. Electric lamp lO
include~ an envelope 11, for~ed from a lens 12 and a cooperating r~flec~or 14, a lig~t ~ource 16 and a base 18.
Both lens 12 and reflector 14 are jsined by ad~esive mean~ 15 to form a lens-reflector seal 19 ~or la~p lO. ~ens 12 and reflector 14 can be formed by pressing ~ardgla~s in a mold followed by an anneali~q pro~e~s. Lens 12 ~ypically ~a& a slightly con~Y outer face and a~ optical pre~cription provided, for example, by a ~erie~ of radially di~po~ed flutes formed on ~he inner ~urface thereof defini~g a fluted portion which ~urrounds a centrally di~po~ed ~tippled portion, as deficribed in ~he aforementioned applicatio~
having Cana~ian Serial No. 461,058-0. Additionally, reflector 14 ~5~
has a concave inner surface 13 that includes a light reflective coating typically comprised o~ aluminum or silver. Reflec~or 14 is preferably a parabolic re~lector but it can also be an eliptical reflector. Lens 12 and reflec~or 14 preferably have substantially circular peripheries and sealing surfaces located approximately about these peripheries, respectively.
As previously discussed, flame sealing, producad, for example, by a flame trained on the glass reflector and lens sealing surfaces, can crea~e unacceptable stress patterns in envelope 11. In particular, stresses tend to concentrate a~out the lens-reflector seal 19, resulting in cracks about that area. The stresses created by flame sealing can be substantially eliminated by interposing adhesive means 15 between the aforementioned peripheral sealing surfaces to seal lens 12 to reflector 14. Acceptable adhesives for the use indicated above are those having a curing temperature that is equal to or higher than the operating temperature of the lamp and a higher i.ndex of thermal expansion than the lens and reflector material. Such an adhesive, a heat curable epoxy, may be obtained from the Amicon Corp. of Lexington, Massachusetts.
~ lectric lamp 10 includes a tungsten-halogen capsule 16 having an envelope containing an inert gas fill and a halogen disposed within. Capsule 16 is disposed within and is substantially surrounded by reflector 14 as well as being substantially perpendicular to lens 12. Capsule 16 is attached to and supported by mount 20. Reflec~or 14 has two ferrule holes 22 ~hrough which the capsule-mount assembly will be inserted and secured into place by an eyelet-epoxy-washer combination. Each lead of mount 20 is secured in each ferrule 22 by an eyelet 24, epoxy 26 and ,~ s~
57~3~
washer 28. Lamp 10 al60 includes a diode 30 and a fuse wire 32 ~oupled in serie6 with cap6ule 1~ and base 18. Envelope 11 of lamp 10 al60 includes an exhau~t hole tube 34 and a small 6teel ball bearing 35 tha~ serve6 a~ a plug.
Envelope 11, a~ illu6trated in FIG. 1, is one example of a lamp envelope t~at i~ al~o capa~le of con~aining glass fragments re6ulting from a po6sible, but unlikely frac~ure of cap~ule 16. Test re6ults ~ave shown t~at out of 60 lamp envelope6 formed by the method described here, all of the lamp6 6uccessfully contained glas6 fragment~ re6ulting from intentionally induced capsule failures. Of the 50 lamp6 made by the flame sealing technique, 3 lamp~ failed eo contain after intentional inducement of capsule failure. Therefore, the above described 6ealing technique results in a lamp envelope that will reliably contain gla~s fragment~ from a po~sible, but unlikely fracture of cap6ule 16.
Referri~g now to FIG. 2, there is illustrated a fragmentary, cross-6ectional view of t~e len~-reflector seal 19 having a len6 ~ealing, channel-like surface A and a reflector sealing ~urface B that are located about t~e peripherie6 of lens 12 and reflector 14, respectively.
During a6sembly of electric lamp 10, ad~esive means 15 i8 placed between 6ealing 6urface6 A and B. Sealing 6urfaces A
and B are joined when lens 12 and reflector 14 are pre~ed toge~er. Lamp 10 i6 then 6ubjected to a heat curing temperature in the range of about 14B Celsius to 190 Cel~ui6 for about 5 to 40 minute~ in order to cure adhe6ive means 15.
Contact between ~ealing surface6 A and B can degrade quic~ly with time upon impropelly combining the different indice6 of thermal expan~io~ of glas~ and adhesive mean~
used. For example, the index of thermal expan6ion for boro~ilicate glas6, conventionally used in sealed beam auto~otive ~eadligh~, typically is about 40 ~ 10~7cm/cm/~C
(i.e., cm ~ centimeter C = Celsiu~). W~ereas ~he index of ther~al expansion of a typically flexibilized ~poxy, suitable for ~ealing headlight glas6ware, typically is about 40 X
10 6c~/cm/C. That i8, the indice6 of thermal expansion of glass and adhe~ive means in a sealed beam headligh~ can differ, by a actor of about 10. Therefore, temperature changes, in particular decrea~ing temperature6, produce different rates o~ contraction for t~e glas6 and interposed adhesive mean~ creating more stre66 between the sealing 6urfaces thereby adver~ely affecting t~e gla~ lens to glass reflector contact along the outermost ~ealing surface6 where ad~esive means has been pre6sed away.
T~e sealing and ~tre~s problem~ found in automotive headlights, due to t~e differing rates of contraction for the lens and reflector ma~erial and interposed adhesive means, also exist in PAR and ~R lamps. In addition, the sealing problem in PAR a~d ER lamp6 i~ compounded by their higher operating temperature ~140 Celsiu6 - 150 Celsiu~ a~
compared to headlights (about 120 Cel~iu~, which in turn causes the failure of most adhe~ives having low toleraQce6 to high temperature6. Adhesive means 15, of the present invention, serve6 to alleviate 60mewhat the stre~se6 between sealing surfaces A and B due eo it~ ability to withstand the high compressive ~tres~ without breakdown at high operating tem~erature6 of the lamp, and therefore provide an operative lamp or an environment that varie6 frequently in temperature.
The present invenSion 6ignificantly reduces thermally induced 6tresse~ by eliminating fla~e fiealing as a method of creating a lens to reflector ~eal. Adhe~ive means 15, used to join lens 12 and reflector 14 together, must have a curing ~5'7~6 _g_ temperature ~at is ~qual to or higher than the operating temperature of lamp 10 and it must have a higher index of thermal expansion than the material that form~ lens 12 and reflector 14. Since the normal operating temperature of a lamp 8UC~ as lamp 10 is u6ually abou~ 140 to 150 C~lsius, the ad~e6i~e means used here will provide for a 6trong seal at 6uch ~igh temperature6 due to it6 own high curing temperature.
The material used to form lens 12 and reflector 14 i6 usually hardglass, and the predetermined index of Shermal expansion for such a material is about 40 ~ 10 7cm/cm/~C.
Adhesive means 15 of the present invention include~ an epoxy having a curing temperature that i6 in ~he range of about 148 Cel~ius to 190 Cel6iufi with an index of thermal expansion in the range of about 75 - 300 X 10 7cm/cm/C.
The curing time of the epoxy îs about 5 to 40 minutes. The epoxy currently in use has an index of thermal expan6ion of about 150 X 107cm~cm/C, a curing ~emperature of about 160 Celsius and a curing time of about 5 minute6. In addition, adhesive means 15 may also include ultraviolet cured epoxies that have similar expansion and temperature charactari6tics as the acceptable heat cured epoxie6 de6cribed earlier.
Since t~e epoxy used ~ere ha6 an index of expansion greater t~an the hard~la~s forming the lens and reflector, a stronger seal will result due to a compre~sive 6tress being formed around t~e lens-reflec~or 6eal when the lamp i6 placed in an environment with a temperature below ~at which it was cured. This would occur during most, if not all, operating condition~ with the lamp on or off. In addition, the need for a specialized 6hape or form for sealing 6urfaces A and B
of lens 12 and reflector 14 is obviated by the use of the sealing technique6 taught by the pre~ent invention. In one 5~7;~
D-84~1-065 embodi~ent of the present invention, ehe lens sealiny surface A has a channel or rece6sed por~ion and reflector 6eali~g 6urface B has a fla~ge, thereby creating a self-aligning relationship when the lens 12 and rsflector 14 are ~ealed together by adhesive means 15 (6ee FIG. 2).
To assemble lamp 10, reflector 14 i~ fir6t of all aluminized by placing a light reflective coating on the inner surface 13 of reflector 14, typically comprised of aluminum or silver. Reflector 14 i6 aluminized in such a way as to provide an aluminum-free area near the reflec~or base where ferrule holes 22 are lo~ated. Eyelets 24 are then placed in ferrules 22 and a small amount of thermally cured epoxy 26 is injected around eyele~s 24. Washer6 28 are then placed about eyelets c4 whereupon eyelets 24 are s~aked. Capsule 16, which i6 attached to mount 20, is then inserted into ferrules 22 and then supported by the eyelet-epoxy-washer combination. The capsule-mount a~embly is then soldered into place. Adhesive mean6 15, which i8 preferably a thermally cured epoxy, i6 then a~plied to len6 12 whic~ i~
then joined with reflector 14, such that a self-aligning relationship is c~eated. The lens-reflector as6e~bly is then placed in an oven and brought to and kept at the requi~ite curing temperature (about 160 Celsius~ until such time a6 the epoxy is cured (about 5 to 40 minutes). Lamp 10 i~ then ~ubjected to a brief nitrogen flu~h through exhau6t tube hole 34 located in reflec~or 14. Exhaust tube hole 34 is thereafter plugged by using small 6teel ball bearing 35 and an ultraviolet cured epoxy. The diode-fu~e assembly and base 18 are then ~oldered into place.
Thus, there has been 6hown and described an improved electric lamp and method of making such a lamp which 6ubstantially reduces or eliminate6 thermally induced strain ~55t~36 ~n ei~er the len6 or the re~lector once ~hey have been ~oined together, unlike the ~raditional flame ~ealing technigue. The advantages of a strain-free PAR or ~R lamp include the following: a hig~er wa~tage tungsten-halogen capsule may be u~ed wi~hout ~he concern that the additional heat generated will ~au6e a 6train induced failure: t~e lamp may be used ~ore succe6s~ully i~ severe outdoor applications without t~e concern that a ~hermal shock will cause a lamp envelope failure and envelope failures due to a fracture of .lO a tungsten~alogen cap~ule will be ~ub6tantially eli~inated in bonded beam lamps . The above de~cribed invention may be utilized wherever the flame 6ealing technique is used in a lamp to seal two corre~ponding and opposing members together to form a single member.
~hile there have been shown and de6cribed what are at present considered the preferred embodiments of the invention, it will be obvious to those ~killed in the art that variou~ change6 and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (14)
1. An electrical lamp comprising:
an envelope having a reflector and lens made of substantially the same material with a predetermined index of thermal expansion, said lens and reflector having sealing surfaces located about the lens and reflector peripheries;
a light source disposed within said envelope and substantially surrounded by said reflector; and adhesive means disposed between and sealing said lens and reflector together, the temperature of said adhesive means and said sealing surfaces of said lens and reflector being approximately 140°C or greater during steady state operation of said lamp, said adhesive means having a curing temperature that is equal to or higher than said operating temperature of said lamp and a higher index of thermal expansion than said lens and reflector material such that said envelope in the vicinity of said reflector lens seal is in a substantial degree of compression at temperature below said curing temperature of said adhesive.
an envelope having a reflector and lens made of substantially the same material with a predetermined index of thermal expansion, said lens and reflector having sealing surfaces located about the lens and reflector peripheries;
a light source disposed within said envelope and substantially surrounded by said reflector; and adhesive means disposed between and sealing said lens and reflector together, the temperature of said adhesive means and said sealing surfaces of said lens and reflector being approximately 140°C or greater during steady state operation of said lamp, said adhesive means having a curing temperature that is equal to or higher than said operating temperature of said lamp and a higher index of thermal expansion than said lens and reflector material such that said envelope in the vicinity of said reflector lens seal is in a substantial degree of compression at temperature below said curing temperature of said adhesive.
2. The electric lamp according to Claim 1 wherein said reflector is and aluminized parabolic reflector.
3. The electric lamp according to Claim 1 wherein said reflector is an eliptical reflector.
4. The electric lamp according to Claim 1 wherein said adhesive means includes an epoxy having a curing temperature in the range of about 148° Celsius to 190° Celsius and an index of thermal expansion in the range of about 75 - 300 X 10-7cm/cm/°Celsius.
5. The electric lamp according to Claim 4 wherein said epoxy has a curing time in the range of about 5 to 40 minutes.
6. The electric lamp according to Claim 4 wherein said epoxy has a curing temperature of about 160° Celsius, a curing time of about 5 minutes and an index of thermal expansion of about 150 X 10-7cm/cm/°Celsius.
7. The electric lamp according to Claim 5 wherein said lens and reflector material is hard glass and said predetermined index of thermal expansion is about 40 X 10-7cm/cm/°Celsius.
8. The electric lamp according to Claim 1 wherein said lens sealing surface has a recessed portion and said reflector sealing surface has a flange to create a self-aligning relationship when said lens and reflector are sealed together by said adhesive means.
9. The electric lamp according to Claim 1 wherein said light source includes a tungsten-halogen capsule mounted within said reflector, said reflector having ferrules through which said capsule is mounted using a combination of an eyelet, a washer and epoxy.
10. A method of making an electric lamp, said lamp having an envelope formed from a lens and a reflector, said lens and reflector having sealing surfaces on the lens and reflector peripheries with adhesive means therebetween, the temperature of said adhesive means and said sealing surfaces of said lens and reflector being approximately 140°C or greater during steady state operation of said lamp, said lens and reflector being made of substantially the same material with a predetermined index of thermal expansion, said method comprising the steps of:
aluminizing said reflector;
mounting a light source within said reflector;
disposing said adhesive means on said sealing surface of said lens and joining said lens sealing surface with said reflector sealing surface, said adhesive means having a curing temperature that is equal to or higher than said operating temperature of said lamp and a higher index of thermal expansion than the material forming said lens and reflector; and curing said adhesive means to a temperature in the range of about 148° Celsius and 190° Celsius for a period of time in the range of about 5 to 40 minutes such that said envelope in the vicinity of said reflector/lens seal is in a substantial degree of compression at temperatures below said curing temperature of said adhesive.
aluminizing said reflector;
mounting a light source within said reflector;
disposing said adhesive means on said sealing surface of said lens and joining said lens sealing surface with said reflector sealing surface, said adhesive means having a curing temperature that is equal to or higher than said operating temperature of said lamp and a higher index of thermal expansion than the material forming said lens and reflector; and curing said adhesive means to a temperature in the range of about 148° Celsius and 190° Celsius for a period of time in the range of about 5 to 40 minutes such that said envelope in the vicinity of said reflector/lens seal is in a substantial degree of compression at temperatures below said curing temperature of said adhesive.
11. The method according to Claim 10 wherein said reflector is a parabolic reflector.
12. The method according to Claim 10 wherein said reflector is an eliptical reflector.
13. The method according to Claim 10 wherein said adhesive means includes an epoxy having an index of thermal expansion in the range of about 75 - 300 X 107/cm/cm°
Celsius.
Celsius.
14. The method according to Claim 13 wherein said epoxy has a curing temperature of about 160° Celsius, a curing time of about 5 minutes and an index of thermal expansion of about 150 X 10-7 cm/cm° Celsius.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US64731684A | 1984-09-04 | 1984-09-04 | |
| US06/647,316 | 1984-09-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1255736A true CA1255736A (en) | 1989-06-13 |
Family
ID=24596480
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000486633A Expired CA1255736A (en) | 1984-09-04 | 1985-07-10 | Bonded beam lamp |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0173992B1 (en) |
| JP (1) | JPS6166358A (en) |
| CA (1) | CA1255736A (en) |
| DE (1) | DE3582101D1 (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2419432A (en) * | 1944-12-01 | 1947-04-22 | Electric projector lamp | |
| US4302697A (en) * | 1979-11-19 | 1981-11-24 | Wagner Electric Corporation | Pressure relief hole seal for a sealed-beam headlamp |
-
1985
- 1985-07-10 CA CA000486633A patent/CA1255736A/en not_active Expired
- 1985-09-02 EP EP85111047A patent/EP0173992B1/en not_active Expired - Lifetime
- 1985-09-02 DE DE8585111047T patent/DE3582101D1/en not_active Expired - Fee Related
- 1985-09-03 JP JP19328885A patent/JPS6166358A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0173992A2 (en) | 1986-03-12 |
| JPS6166358A (en) | 1986-04-05 |
| DE3582101D1 (en) | 1991-04-18 |
| EP0173992B1 (en) | 1991-03-13 |
| EP0173992A3 (en) | 1988-10-26 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |