US2975556A

US2975556A - Heat-protective coating

Info

Publication number: US2975556A
Application number: US685865A
Authority: US
Inventors: Norman F Baird
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-09-24
Filing date: 1957-09-24
Publication date: 1961-03-21
Anticipated expiration: 1978-03-21
Also published as: NL231132A; GB847561A; NL103898C; DE1093480B

Description

March 2l, 1961 N. F. BAIRD 2,975,556

HEAT-PROTECTIVE COATING Filed Sept. -24, 1957 O '7"O @"2" C) AMPM/9W FT Eff/BD.

normally fabricated of brass. creased costs of brass have made it economically desir-4 able to substitute aluminum in place oft-the brass. This substitution of aluminum has the disadvantage that the aluminum base shell has `a tendency to melt somewhat United States Patent HEAT-PROTECTIVE COATING Norman F. Baird, Bloomfield, NJ., assignor to Wastinghouse E lectric Corporation, East Pittsburgh, Pa., a corporatlon of Pennsylvania Y y Filed sept. 24, 1957, ser. No. 685,865

6 claims. (cl. 49-7s) This invention relates to heat-protective coatings and,; more particularly, to heat-protective coatings forl processing aluminum base shells for lamps.

Incandescent lamp bases are prepared .by rst stamp- I ing a base shell into a predetermined configuration-which 1s normally generally cylindrical and threaded, termi-l nating in an inwardly-projected lip at the lower extremities of the base shell. trical contact for the lamp. An eyelet which is fabri-j cated of an electrically-conductive material such as brassis positioned in a centrally-disposed location" adjacent the lower extremities of the base shell proper, and this eyelet is electrically insulated from the base shell `by an insulating button such as glass. This eyelet forms aa second electrical contact for the incandescent lamp;

In the normal procedures of fabricating the lamp base,` the eyelet and base shell are placed into a mold and'- molten glass is inserted or poured into the lower inter1or surfaces of the base shell and aboutthe eyelet. This electrically insulates the eyelet from the base shell and serves to secure the eyelet in a centrally-disposedI position adjacent the lower extremities of the base'shell. In the practices of the prior art, the base shells were In `recent years, the in- 2,975,556 Patented Mar. 2 1, 1961 phat'e and sodium polyacrylate a water-vehicle;

1 the constituents of the coating are maintained within'perl de scent'lamp incorporating an aluminum base;

This base shell forms one elec-g Fig, 2 isa sectional elevation of an unprocessed alumif num base Shell; v :Fig- 3 isa perspective View of an electrically-conducting eyelet `before incorporation into the lamp base;

Fig-4 isa diagrammaticplanview of an apparatus for processing lamp bases, generally illustrating the opera# tions at various stations; l.lf-iig. 5 is a fragmentary, sectional view taken at station 3 in Figi 4 showing the -application of the heat-protec tive coating; j Y

Eig. 6 `is a fragmentary, sectional-view taken at staiV tion 4 in Fig. 4 showing the glassing operation; Fig 7 is a fragmentary, sectional view takenatstation 6 in Fig. 4 showing the plunger-die operation for form`T ingthe lpoured glass into the desired-conguration.

Althoughthe principles of the invention are generallyi applicable to any type of lamp which desirably incor porates an aluminum base, the invention has particular, reference with regard to -bases for incandescent-type lamps" and hence it has been so illustrated .and will be sol With specilic reference to the form ofthe invention illustrated in the drawing, in iFig. lis shown an incan; descent lamp 10 which generally comprises an envelopej 12, base 14, lead conductors 16 hermetically'seale'd through a stem press 18 and `sup-porting an incandes. cible lament 20 between their inwardly-extending extremities. One of the lead conductors is electrically connected to the Ialuminum base shell 22, which forms;

t one contact electrode for the lamp. The other leadl con-L.

during the so-called glassing operation when the moltenj glass is poured into the base shell. The melted aluminum sometimes forms a low-resistance pathebetween the eyelet and the base shell, thereby shorting out the lamp, and the melted aluminum is also objectionable from the standpoint of appearance. While the primary purpose of an incandescent lamp is to convert electrical energy into light, the esthetic appearance of-the lamp in the unburned condition is also a factor in promoting its initial sale to the user so that the maintenance of the base shell in as pleasing an appearance as possible is of great importance.

. In order to overcome the foregoing and other diicultiesof and objections to the prior art, it is the general object of this invention to provide a heat-protective coating for processing aluminum base shells in order to prevent any melting of the aluminum base shell.

-It is a further object to provide a method for glassing an aluminum base shell for a lamp wherein any tendency of` the aluminum to melt during the glassing operation is substantially inhibited.

It is another object to provide a method for glass` ing an aluminum base shell for a lamp wherein thinner baseshells may be used.`

The aforesaid objects of the invention, and other 'objects which will become apparent as the description proceeds, are achieved by providing a heat-protective coat# ing for processing aluminum base shells, which coating principally comprises an adrnixture of sodium borophosshell 22 and this coating may be applied as asprayb ductor is electrically connected to the centrally-disposedl and electrically-conducting eyelet 24, which eyelet isf electrically insulated from aluminum base shell by Vax insulating button 26 which may be fabricated of glass; Suchy -a lamp construction is generally well known.

In Fig. 2 is shown an aluminum base shell 22, beforei the glassing operation and such a base shell normally" has a generally-hollow-cylindrical and threaded coniguration. lThe lower portion of the base. shell formsv 'anl inwardly-projecting lip 28 which serves to hold'the glass insulating button 26.

In Fig. 3 is shown the electrically-conductingeyelety 24 which may be punched from brass, Ifor example, and? which eyelet has a centrally-disposed aperture 30 form ing a retaining lip which cooperates with thel pouredglass insulating button 26 to retain the eyeletin posifl tion. "f j In Fig. 4 is shown a diagrammatic plan view of a base-. fabricating machine 32, modiied slightly to provide f olf4 the application of the heat-protective coating as described herein. Such machines arel normally designedl to .be indexed through a plurality of positions orwork station; and at the station designated 1, the yeyelet Z4 is fedi' into the-receiving mold by conventional techniques. the station designated 2,l thebase shell 22 isfed f, the receiving mold by conventional practices. Atythfe; station designated 3 the heat-protective ,eoatinggis-apw plied to at least the :lower interior 'portionsoffithebse the' Baseshell z2.l 'This' moltenrglass `serves to separate the eyelet z4gfr'o`m A'the base shell 22. Thereafter, excessive fglass -is blown from the upper surfaces of the molds and from between thee-'molds at the glass-cutter stations designated '5 4and this also serves to partially cool the pouredf'glia's's. At the station designated 6, a glass plunger for swt-he interior surfaces of the poured glass into a generally conical configuration `so that when the center lamp" l'ea'dwire is later inserted into 'the base, it will be directed toward the aperture 30 in the centrally- 'dispose'd e'y'let 24. At the station designated 7,? an auxiliary glass plunger `serves 'further to cool the poured glass in order to secure Jthe eyelet 24 in the cooled glass button 26 and to secure the `cooled glass button 26 lin the base shell 22. vAt the station designated 8, a pin plunger removes any residue of glass from the aperture 30 -of the centrally-disposed eyelet Z4 and thereafter at shel 22h51 means ofa conventional atornizerv 36. If

desired, the'heaft-pro'tective coating could be applied to the, base shell 22 before the base shell was placed on the coatingV machine, but it is far more convenient automagically to apply this coa-fing after the shell 22 has' The heat-protective coating principally comprises 'from 31o-30% by weight sodium'borophosphate, from 10% to 15% by weightV sodium polyacrylate'and from n55% to 87% by Weight/Water. l The molten glass which Vis poured into the base shell during the glassing operation may have Ala temperature of from 1`l8`5 C. to l200 C., for example and, as noted hereinbefore, the aluminum uuderthese conditions has a marked tendencyto melt, at` least in discrete portions.V The heat-protective coating, as Yhereinbefores'peciiied, forms a barrier or heatprotective layer` between 'the molten vglass andthe aluminuxn base shell', substantially inhibiting any tendency for the' aluminumfba'se shell to melt.

Kegalfdingthe constituents of the heat-protective coating, sodiuml borop hospha'tehasv a high Water of hydrationand also has the property of encasing steam at'highV temperatures. Theencasedsteam serves they dualV function'of providing an excellent insulating layer and also im'p'airing the v'adhe`renc'e of the sodium borophosphate for ,the'base' shell, which isf/highly vdesirable `as will be explained hereinafter. A solution of sodium bo'rophosphate in Water, however, has a relatively low viscosity and will not `adhere `to the aluminum base shell in sufficient amounts ,to provide the proper degree of protection during the glassing operation- Sodium poly'acirylate vhas ya high, viscosity, is yreadily soluble inwalter, as is'sodium borophosphate, and sodium polya't:ryl'atev has ahigh heatof vaporizationl This material, however, tendsjto leave a 'carbonacleou's residue after beingheated, whichresidue isrn'ot readily removed hva water wash; rlffhis residue impairs the appearance of the vcompleted base 'and alsotends to form low-electrical-resistanee pat-hs;

When f'amixtuie fof sodium' borophosphate and sodium polyacrylate 1in 'water solution is utilized as a heat-protective coating, the benets of both of these constituents are realized. Thus the` admixtu-re'has Vsuflicent viscosity (for Vexample 32 c.p.s.) to provide an adequate amount of the heat-protective coating on the base and the steam which is encased by the sodium borophosphate renders the admixture very poorly adherent to the aluminum base shell at high temperatures. Thus any coating residue is readily -removed by a water Wash. In addition, the in- I dividual constituents of lthe admixture both -have a very ance of the heat-protective coating. A

If less than the indicated proportionscomprising the admixture are used, the beneicial effects ofY the heatprotective coating are minimized. If theproportions of the sodium borophosphate land the polyacrylate are greater than the maximum permissible amounts indicated hereinbefore, the viscosity of the resulting coating tends to be excessive and an excessive amount of thecoatng material isdepsited. In addition, there is sometendency for residues where a Vrelatively -l'ar'ge amount tof 'coating material has to be reinoved by ag'wa'ter wash andthe adherence of the coating material for the aluminum vbase shell is somewhat increased, which also inhibits the re-l moval of the vcoating' material by ali/'atei- Wash, v The preferred formulation for ythe heat-protetive vcoating is about 5% byweight sodium borophosphate,-about 10% by weight sodium polyarylate and about y% by weight water. l Y g x I t is also possible to incorporate s mall anouiitsof otherY additives into the heat-protective 4coating Yand Yif desired, 5% by Weight of ammonium polyacrylte may be 'sbs'tituted'inplace of an equivalent -ainontofl i vehicle in th'egfor'e'goin'g preferred specific embodiment. This somewhat increases the capacity for-heat absorption of the coat-ing', but such other smallv additives are notl necessary fo'r good results. Other materialsmay be substituted in place 'ofthe ammonium polyarylate vadditive, *such Vas an equivalent weight of potassium silicate, for-example. v i j I In Fig. 6 is shown they glassing operation at the station designated"4 in Fig'. 4'. In this operation, a pree determined amount of molten glass is poured or inserted into'the coated base, such glassipou'ring techniques being Well known.y As a specific eiiample, in the case 'of `a medium-'screw type base,"about 3.6 grains ofl glass may be lused'.` The glass may vary,'but 'as a vspeciiic example, it may have' thecoinpos'it'ion of 9.5% by weight cullet glass', '2.52% byV weight MnOZ, 1.26% by weight KNO3, 0.87% by weightlNHg) 2SC., and `0.35% by weight Cr203. The cullet glass, as'V "usedV herein, has the composition 76.8%- by weight Si02, 17.4% lb'y Weight NaZO, 0,6% by weight K2`O, `0;4% byweight CaO' and 316% by weight Mg'O. It should be understoodV th'at this glass is only given vby way of specic example and other glasses and glassing lcomposi'tions' may be substituted. V

, In Fig'. 7 is shown the glass-forming'operation at the station designated"6 in Fig. 4. In this operation the glass-forming plunger 38 provides the interior surface of thepouredglass with an inverted, generally-conical configuration inforider that thecenter lead wire may beinserted, 'into the eyelet by automatic equipment.V The plunger station follows the glass pouring station ata sufficient time `interval that the glass has 'partiallyyco'oled so that it isin aaplasticistat'e rather than la molten state. Thereafter,-at the staion designated ".7 in Fig. V4,J a` conventional auxiliaryglass plunger whichV is internally cooled with water, for `example, isV inserted into the base in order tosubstantiallycool the poured glass. An additional plunger, 'not shown, punches any residual Vglass which may'remain'within the centrally-disposed aperture 30 within the eyelet 24 inorder that the center'lead wire may be inserted therethrough during'theplamp fabricadirt and other impurities as well as the residual heatprotective coating which remains.

In the cleaning process, any commercial cleaner may be used and the bases are placed into the cleaningy solutions and agitated. This removes substantially all traces of dirt and other impurities as well as residual heat-protective coating. By way of specic examples of suitable cleaning solutions, the bases may be agitated in a dilute solution of nitric and sulphuric acid at a concentration of 40 to 45 Baume. Alternatively, the bases may be cleaned with a 5% solution of ammonical soap or with a 3% to 5% lauryl-sulphate-type detergent, such as is commercially available under various trademarks. Other commercially-available cleaning solutions may be substituted for the specific examples given hereinbefore.

It may be desirable in some cases to dispense with the eyelet and to secure the lead wire to the exterior surface of the glass insulating button 26 by means of an epoxy-resin cement, for example. In such an embodiment, the procedures used in fabricating the base would be identical with those as outlined hereinbefore, except that the eyelet would not be placed into the mold.

The foregoing steps need not be carried out on the automatic equipment as outlined hereinbefore, but may be carried out by hand, if desired, although from the production standpoint, it is economically desirable to fabricate the bases on an automatic basis.

A further advantage of the heat-protective coating disclosed herein is that the aluminum base shells may be made thinner, if desired, thus eliminating the cost of using added aluminum in the base shells. tion, in the practices of the prior art it has been necessary to provide the aluminum base shell with a certain minimum thickness, for example .0125 inch for a mediumscrew-type base, in order that the aluminum base shell has suiiicient thermal capacity to absorb suflicient heat from the molten glass to prevent excessive melting of the aluminum. Even with this thickness of the aluminum base shell, considerable melting of the aluminum has been encountered. Where the heat-protective coating is interposed between the molten glass and the aluminum base shell, the thermal capacity required for the aluminum base shell is decreased and a medium-screW-type base shell having a thickness of only .0105 inch is generally satisfactory and will display substantially no melted portions.

It will be recognized that the objects of the invention have been achieved by providing a heat-protective coating for processing aluminum base shells as well as a method for processing aluminum base shells wherein any melting of the aluminum due to the molten glass is substantially eliminated. In addition, the aluminum base shells may be made thinner, if desired.

While in accordance with the patent statutes, one bestknown embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

l. A heat-protective'coating for processing aluminum base shells for lamps, said coating principally comprising from 3% to 30% by weight sodium borophosphate, from to 15% by weight sodium polyacrylate, and from 55% to 87% by weight Water.

2. A heat-protective coating for processing aluminum base shells for lamps, said coating principally comprising about 5% by weight sodium borophosphate, about 10% by Weight sodium polyacrylate, and about 85% by weight Water.

3. The method of glassing an aluminum base shell for a lamp, comprising applying to at least the lower interior surfaces of the aluminum base shell a heat-protective `coating principally comprising from 3% to 30% by weight sodium borophosphate, from 10% to 15% by In explanaweight sodium polyacrylate and from 55% to 87% by Weight water, inserting a predetermined amount of molten glass into a mold containing said coated base shell to till a selected portion of said coated base shell, cooling said base and said glass to secure said glass in said base, and thereafter cleaning said base with a cleaning solution to remove residual heat-protective coating.

4. The method of glassing an aluminum base shell for a lamp, comprising applying to at least the lower interior surfaces of the aluminum base shell a heat-protective coating principally comprising about 5% by Weight sodium borophosphate, about 10% by weight sodium polyacrylate and about by Weight water, inserting a predetermined amount of molten glass into a mold containing said coated base shell to fill a selected portion oi coated base shell, cooling said base and said glass to secure said glass in said base, and thereafter cleaning said base with a Water-vehicle cleaning solution to remove residual heat-protective coating.

5. The method of forming in an aluminum base shell for a lamp a glass insulating section having embedded therein a `centrallydisposed and electrically-conducting eyelet insulated from said base shell, comprising placing said eyelet and said base shell into a mold and applying to at least the lower interior surfaces of said base shell a heat-protective coating principally comprising from 3% to 30% by weight sodium borophosphate, from 10% to 15% by Weight sodium polyacrylate `and from 55% to 87% by weight water, inserting into said incid a predetermined amount of molten glass covering said eyelet and the lower interior surfaces of said base shell and separating said eyelet from said base shell, partially cooling said glass, forming the upper surfaces of said partially cooled glass into a predetermined configuration, further cooling said formed glass to secure said eyelet in said cooled glass and to secure said cooled glass in said base shell, and thereafter cleaning said base with water-vehicle cleaning solution to remove residual heatprotective coating.

6. The method of forming in an aluminum base shell for a lamp a glass insulating section having embedded therein a centrally-disposed and electrically-conducting eyelet insulated from said base shell, comprising placing `said eyelet and said base shell into a mold and applying to at least the lower interior surfaces of said base shell a heat-protective coating principally comprising about 5% by weight sodium borophosphate, about 10% by Weight sodium polyacrylate and about 85% by Weight water, inserting into said mold a predetermined amount of molten glass covering said eyelet and the lower interior surfaces of said base shell and separating said eyelet from said base shell, partially cooling said glass, forming the upper surfaces of said partially cooled glass into a predetermined configuration, further cooling said formed glass to secure said eyelet in said cooled glass and to secure said cooled glass in said base shell, and thereafter cleaning said base with a water-vehicle cleaning solution to remove residual heat-protective coating.

References Cited in the file of this patent UNITED STATES PATENTS 1,011,586 Criggal Dec. 12, 1911 1,976,679 Fikenstscher et al. Oct. 9, 1934 2,158,044- Haller May 9, 1939 2,387,865 Kleeck Oct. 30, 1945 2,413,146 Larson Dec. 24, 1946 2,439,395 Leatherman Apr. 13, 1948 2,480,790 Truhlar Aug. 30, 1949 2,538,589 Poje Ian. 16, 1951 FOREIGN PATENTS 797,345 France Feb. 8, 1936

Claims

1. A HEAT-PROTECTIVE COATING FOR PROCESSING ALUMINUM BASE SHELLS FOR LAMPS, SAID COATING PRINCIPALLY COMPRISING FROM 3% TO 30% BY WEIGHT SODIUM BOROPHOSPHATE, FROM 10% TO 15% BY WEIGHT SODIUM POLYACRYLATE, AND FROM 55% TO 87% BY WEIGHT WATER.

3. THE METHOD OF GLASSING AN ALUMINUM BASE SHELL FOR A LAMP, COMPRISING APPLYING TO AT LEAST THE LOWER INTERIOR SURFACES OF THE ALUMINUM BASE SHELL A HEAT-PROTECTIVE COATING PRINCIPAL COMPRISING FROM 3% TO 30% BY WEIGHT SODIUM BOROPHOSPHATE, FROM 10% TO 15% BY WEIGHT SODIUM POLYACRYLATE AND FROM 55% TO 87% BY WEIGHT WATER, INSERTING A PREDERTEMINED AMOUNT OF MOLTEN GLAS INTO A MOLD CONTAINING SAID COATED BASE SHELL TO FILL A SELECTED PORTION OF SAID COATED BASE SHELL, COOLING SAID BASE AND SAID GLASS TO SECURE SAID GLASS IN SAID BASE, AND THEREAFTER CLEANING SAID BASE WITH A CLEANING SOLUTION TO REMOVE RESIDUAL HEAT-PROTECTIVE COATING.