CA1045599A - Vehicle lamp construction - Google Patents

Abstract

VEHICLE LAMP CONSTRUCTION

Abstract A lamp assembly wherein the lens portion is secured to the lamp housing by means of an elastomeric tape. The bonding tape replaces the gasket, gasket cement and retaining screws conventionally employed in current lamp assemblies.

Description

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Back~,round of _ hc Inv Qt_on Lamp asscmblies must be madc available in many varying shapes to accommodate modcrn design as found, for examp~.e, in the automotive industry. In addition, such l.amp designs are changed almost annually wi.th the result that it is generally not practical to produce ~such lamp~s in a fully sealed manner such as employed with vehicle headli~ ts. ~:~
Accordingly, lamp assemblies are conventionally manufactured ~ -by attaching the l.ens to the housin~ by first inserting a gasket therebetween, which in turn generally necessitates applying ~asket cement to the housing to-retain the gasket ~.
and aid in sealing, and then using screws or other fastencrs to mechanically hold the lens and housing ln assembled re-lationship.
It w-lll he appreciated that the convent:ional method of interconnecting lamp lens and housings requires, in a single assembly facility, many different sizes of screws and ~.sk`ets which, because of their relatively small size, are easily mishandled, dropped during assembl.y, improperly sorted as to size and damaged or stripped in the assembly proccss it-self. Al.l these factors give use to increased cos~ and lower:ing oF production volume.
The present invention contemplates overcoming the above problems by providing a unique lamp structure wherein ~ ~he lamp lens and housing are not:joined by ~echanical features.
. Summary of the Invention .
This invention relates ~o a lamp assembly wherein ~ .
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the lamp lens is secured to the lamp housing by means of a permanently pliable and flexible elastomeric material such as a butyl bssed tape. This bonding tape replaces the gasket, gasket adhesive and retaining ~cre~q commonly emplo~ed on presently available lamp ~nit~s.
The lamp assembly of this invcntion provides the ~ ~ '''"

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advantages of cos t savings through elimination of gaskets, gasket adhesives, screws, and the need for designing bosses into the housing to accept the screw fasteners. In addition, the lamp assembly herein described has been found to have a superior seal with respect to dirt and moisture and to permit greater latitude in lamp design since costly bezels can frequently be e]iminated.
A most important advantage of the lamp unit of this invention resides in the easier serviceability of bro~en lens.
Thus, the old elastomeric tape can simply be peeled from the housing, new tape applied, and a new lens placed in contact with the tape.
Thus, the present invention is concerned with an improvement in a lamp unit comprising a housing having a cavity for location therein of a lamp bulb and a lens for coverlng the open end of the cavity and in cooperation with the housing enclosing the lamp bulb, wherein the lens is sec-lred to the h~ln~ins bv elastomeric material and without mechanical fasteners to provide a generally dirt and moisture-free cavity, the elastomeric material being a tacky substantially non-curing permanently pliable elastomer, the elastomeric material being interposed between the lens and the housing in adhering contact therewith to hold the lens and housing in a : .
sealed and assem~led reLationship.

Description of the Dra~in~s Other obiects, advantages and features of the present invention will be made more apparent as this description pro-ceeds, reference being had to the accompanying drawings where-in:
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Figure 1 is a fragmentary perspective view of a ta~l light assembly in exploded position located in an auto-mobile r~ear quar~ter panel as embodied in the present invention;
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Figure 2 illustrates the tail lamp components generally shown in Figure 1 in an assembled relationship;
Figure 3 is a section taken generally along section

3--3 of Figure 2 showing the relationship of lamp housing, lens and elastomeric strip; and Figure 4 is a view similar to Figure 3 showing appli~
cation of the lamp lens to the e].astomeric strip.
Vetailed Description of the Invention Referring to Figure 1 of the drawi.ng, there is shown fragmentarily a rear ~uarter area of an automotive vehicle which includes a deck lid 10, bumper 12 and quarter panel 14.
The quarter panel 14 is provided with an aperture in which a tail lamp assembly 16 can be secured by conventional techniques.
It will be understood that the present invention is not limited to vehicle tail lamps and that the tail lamp is merely representative of a typical lamp to ~7hich the present invention is applicable.
The tail lamp assembly 16 comprises a cup-shaped ~ .
housing 18 which is provided with a socket for receivin~ a lamp bulb 20. The housing 18 can be fabricated of either metal or a plastic material such as acrylo-nitrile-butadiene-styrene .
polymer and the lamp housing ls generally formed with a peripheral flange 22. A lens 24 which is generally of a plastic material such as an acrylic polymer although it can be of glass, covers;the housing opening ana may include a differen~
~ co:lored area such as back-up lamp lens 25.
', The lamp assembly of.~his invention is unique in that ;~
the lamp lens and housing are ~oined to form a moisture and : :
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~ dirt proof cavity solely by means of an elastomeric material : :
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3~ 26. As lndicated above, there need be no mechani.cal attachmcn~ ~:
of the lens to the hoùsing as by screws or clampinl~ rings, ` : .
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thereby providing the advantages noted obove.

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The elastomeric matcrial 26 used in th~ lamp asse~b]y of this invention is a substantially non-curlng permancntly pliablc material which is available on the market from Protective Treatments, Inc. of Dayton, 0hio and identified as 9-B-2*. In general this material comprises one or more elastomers, plastici~ers and fillers which may optionally include tackifiers and other agents for s~pecial purpose.
Examplcs of elastomers useful in compounding material suitable for this invention include butyl rubber, chlorinated butyl rubber, brominated butyl rubber (for example, as described in U. S. Patent 2,903,437 to Van Epp), butadiene-styrene rubbers, high molecular weight polyisobutylené rubber tfor example, Vistanex*polybutene B-80, B-100 and B-120), butadiene-nitrile rubbers, polychloroprenes, natural rubber, polyisoprene, ~thylene-propylene rubber (for example, EPR 404* En;ay Chemical Co.) and ethylene-propylene terpolymers ~for exa~ple, EPT
3509*, En~ay Chemical Co.), and including ethylene-propylene-dicyclopentadiene terpolymers sold by Dutch State ~ines.
Ethylene-propylene terpolymers and ethylene-propylene rubber are elastomers which are random polymers of ethylene and -propylene, so they can contain some block structures of ethylene or.propylene in their molecular structure. In the terpolymers there is ln addit:ion an unsaturated side chain which provides a site for vulcanization. The various elastro meric polymers may be used in selected mixtures. Suitable butyl rubbers are copolymers of an olefin or a diolefin, for example, copolymers of ~a~ isobutylene with (b) butadiene, isoprene, dimethyl butadiene, pentadiene or piperylene, in the ratio range of about 70 to 99.S parts of weight of ~a) and 30 to 0.5 part by weigh~ of (b), havlng a preferred molecular weight`range of about 50,000 to 65,000 tStaudinger).
Varlous grades of such butyl rubbers containing isobutylene ; are available under the disignations GR-I, GR-I-17, GR-I-l~, * Trade ~Sark ~4 ,~ cbr/~
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GR-I-15, GR-I-40, GR-I-60 and GR I-80o (Exa~pLes are Etl~y Butyl 365 and En~ay Butyl 218.) Suitable haloy,enated butyl rubbers above described, ~or example, as disclos~d in U.S.
Patent 2,94t~,578, preferably those containing appro~imately one halogen atom for each double bond. Preferred chlorinated butyl rubber contains about one chlorine atom for each double bond, and has a molecular ~eight between 300,000 and 500,000, such as Enjay Butyl HT~10-66 of Enjay Chemical Co.
In general the various butyl rubber and chlorinated butyl rubber compositions commercially a~ailable can produce elastomeric materials exhibiting high hysteresis which is a desirable property, and are preferred, and this property can be modified by selection of other ingredients in the tspe.
The term butyl rubber identifies copolymers of isobutylene with a diene such as butadiene, isoprene, dimet~ylbutadiene, pentadiene or piperylene in the weight ratio range of about 70 to 99.5 par~ts isobutylene to 30 to 0.5 part of the diene.
component.
It is to be observed that the processin~ oils and other plasticizers, and the large proportion of plasticizer and filler also increase hysteresis. The use of natural rubber, butyl rubber cross linked with divinylbenzene, or polyisobutylene in the molecular weight range of about ~0,000 to 120,000, polychloroprene ("neoprene") as well as other low hysteresis elastomers, is desirable. Some of these produce an increase in spring back values.
Plasticizing oils generally increase softness and increase elongation and cold flow. Processing oils serve as inexpensive plasticizers. There are hundreds of such oils, which are general~y naphthenic and~paraff~nic hydrocarbon compounas, commercially available under the trade na~es of the suppIiers. They are generally sold as p~le or~red engine _5_ .

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i5~ -oils, are free of additives, ~nd the prefcrred oils are tl-ose having a viscosity range at 100 F. of about 100-~i,OOO S~S
(Saybolt Universal Scconds). Examples of such oils by trade names are, Necton 60:, Famax 58*, and Coray 80* and Sun Oil - 2280~:. They may be used in the ratio o~ about one to t~o - and a half times the weight of elastomeric polymer.
Examples of other suitable plasticizers are certain polychlorinated polyphenyls knoun commercially as "A~oclor"
1254*, "Aroclor" 1268*, low molecular weight polyisobutylene ("Vistanex"-:: L~l-MS), medium viscosity propylene po]ymer -(Polypropene C-175* of Amoco Chemicals Corp.), and polybutenes (for example, Oronite 128* and Polybutene H 1900~). Fibrous fillers, such as asbestos .and platy talcs and hydrated silicas, -rcduce or retard cold flow, and are present in the ratio of ~bout 30 per cent to 150 per cent of elastomer po~ymer.
It is generally preferred to include tackifiers in the compositions. Examples of suitable tackifiers are chlorinated biphenyls illustrated by "Aroclor" 1254*, "Aroclor"
1268* (which "Aroclors" also function as plasticizers) and "Aroclor" 1260*, non-reactive polymethylol phenol resin (commercia~ly available under the names Amberol ST-137X*;
Catalin 8318~'; and SP-1047~- of Schenectady ~arnish Co.), rosins, hydrogenated rosins and esterified rosins (Pentalyn ~1, Stav-Belite ester 3) and e~hylcneglycol monobutyl ether pelargonate.
Adhesion to glass and metal can be lncreased by incorporating ~nown adhesion promoters, for example, gamma-amino propyltriethyloxy silane (Silane A-llOO~ of Union Carbide Corp.), rosins, rosin esters and the like. The silane com-pound may be supplied to the glass as a primer to promote adhesion.
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Any of the known curing agents may be employed with the particular agent being determined primarily by the * -Trade ~lark -6- ~ ~

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elastomer component. Paradini~rosobenzene or para-quinone dioxime with lead dioxide ls a prepared curative with butyl ,' rubbers. With chlorinated butyl rubber the Rreferrea curin~
agent is zinc oxide. Sui~able accelerators may be u~ed in each case, and the compositions may include other substsnces to facilitate compounding and treatment ~uch as acid receptars, Rcorch retardants, roll release agent~, and,cure retarde~s. . '.
In order ~o maintain the elastomeric material in a pliable conditlon 'throu~hout itR life, the'am~unt of curing agent .~
employed is les~ than that amount required to efPect a full '.',.. :

cure. The following represent~ the components af commerclall.y available materials used in a formulation ~uitable for use '.. .
as the elascomeric material of this invent-lon.
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Component, Trade Name , Supplier ,. . :.
1. Chlorinated ~utyl Butyl HT 10-66* ~ y c~ic~L c~
Rubber , .
2. Nonheat-rea'ctive Amberol ST~137X* Rohm & Haa-R Co.
' phenolforma}dehyde' ,.
resln ~ ' '''' .:
3. Hydrogenated Wood Staybelite Re~in* Hercules Powder '-.~
Rosin ~ster' . Co. . ''.::

4. Asbestos fiber 7M06 Grade* John~ Manvllle

5. Hydrated ~ilica Hi-Sil* . PPG Chemicals ..
~, 6. Platy talc ' Mistron Vapor* Sierra Talc &
. , Chemical 7. Processlng Oil ~un Oil 2280-3* Sun Oil Co. '' 8. Carbon black P-33 Carbon black* .R.T. Vanderbilt Co .
' 9. Tall Oil Fatty Acid Acintol FA2 Tall* Arizona ChemicaI. `
~0 Oil Fatty Acid Co.
10. ~eat-RPactive Phenol~ B R L ~741* Union Carbide ~ormaldehyde ~esin - Corp.
I 11. Dl-ortho- Permalux* , Dupont '.
., tolylguanidine salt of dicatechol borate The final composition ~ill pre~erably contaln at ,` .

least 75 parts of oil plasticizer per 100 parts of elasto~er * -Trade Mark ~. .

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i5~g and 75 parts of particulate filler pe~ 100 parts of el~stomer.
The elastomeric material of this invention can be employed in a t~pe form or as a pre-for~ed gasket whe~ein the material is packa~ea or supported on reLease paper which - can easily be stripped at the time of application. A~terna-tively, the material can be ~pplied in a bead from a gun type applicator. Figure 1 illustrates elastomeric material 26 in the form of a pre-formed gasket which is lai.d upon flange 22 of the lamp housing. The lens 24 is then pressed lD against the elastomeric ~aterial. In practice, the lamp assembly of this invention employing no mechanical fastening of the lens to the houslng is being employed as a parking lamp of a production buil~ automobile, and it has been found that excellent sealed units are obtained at room tem~erature when the l.ens is prcssed flgainst the elastomeric material.
with a pressure of about ten pounds per linear inch of bond :
length for a period of about five to ten seconds. The pressure should be sufficient to compress the elastomeric : : :
material in the area of the lens an amount of.about one-half the thickness of the material. Specific time and pressures will of course be dependent on the tape composition employed.
The composition of the elastomeric material used in the lamp unit of this invention should be cho~en so that it remains flexible and soft throughout its anticipated service life and should be of a thickness to insure sealing contact with both the irre~ular flange surface 22 of the housing and with the lens 24'D A thickness of about 0cl to 0.5 inch with a width of 0.25 to about 0.5 inch has been ~, ~ found sufficient to allow absorption or attenuation of tension ~.
forces by deormation without damage to the bond bet~1een . .
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elas:to~er and lens, or elastomer and housinK. If desired, a rib 28 may be provided about the periphery of the :Lens ..
as seen in Flgures 3 and 4 to e~ngnge and embed in the elas~o~
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~- meric matcrial. This ha~ thc advantage of providing a superior seal as opposed to planar surface contact.
It will be understood that this invention is not restricted to any particular type of lamp and that ~arious S changes and modifications maY be made without departing from the scope thereof.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a lamp unit comprising a housing having a cavity for location therein of a lamp bulb and a lens for covering the open end of said cavity and in cooperation with said housing enclosing said lamp bulb, the improvement which comprises securing said lens to said housing by elastomeric material and without mechanical fasteners to provide a generally dirt and moisture-free cavity, said elastomeric material being a tacky substantially non-curing permanently pliable elastomer, said elastomeric material being interposed between said lens and said housing and in adhering contact therewith to hold said lens and housing in a sealed and assembled relationship.

2. A lamp unit according, to Claim 1 wherein said lamp housing is provided with a peripheral flange having a face generally parallel to the plane of the open end of said cavity and wherein said strip of elastomeric material interposed between said lens and said housing is in adhering contact with said flange.

3. A lamp unit according to Claim 1 wherein said strip of elastomeric material is a highly viscous smooth, perma-nently tacky, putty-like mass at the time it is interposed between said lamp lens and housing.

4. A lamp unit according to Claim 1 where said strip of elastomeric material is selected from the group consisting of butyl rubber, divinylbenzene cross-linked butyl rubber, and mixtures thereof.

5. A lamp unit according to Claim 2 wherein said elastomeric material is in the form of a gasket and sup-ported by said housing peripheral flange.