US2123706A - Method of manufacture of reflector bulbs - Google Patents

Description

July 12; 193 8. 0. H. BIGGS METHOD OF MANUFACTURE OF REFLECTOR BULBS Original Filed July 20, 1932 erretpei.

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BY% m ATTORN Y lNVEN UNITED STATES PATENT OFFICE METHOD OF MANUFACTURE OF REFLECTOR BULBS Orrick Howard Biggs, Beverly, Mass., assignor to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Original application July 20, 1932, Serial No, 623,504. Divided and this application September 28, 1933, Serial No. 691,322

8 Claims. (Cl. 9l-70) This invention relates to evacuated or gas-filled These and other objects and advantages of the vessels, and with particularity to a method of present invention will be apparent from the folprovlding such vessels with light-reflecting interlowing descriptions of specific embodiments of nal coatings. my new method, and of the article of manufac- In certain of the arts, for example in the inture obtained therewith, with reference to the candescent lamp art, it is desirable to provide the drawing in which: I lamp with an integral reflector, and for this pur- Fig. 1 is a side elevational view, partly in secpose it has been proposed to cover the outside surtion, of an incandescent lamp made according to face of the lamp with a coating of silver, or even my invention; to provide the lamp with a tight-fitting cap. Fig-2 is a side elevational view of a lamp bulb, These latter expedients, however, have certain with the neck of the bulb in section, showing how disadvantages which will become apparent from the shield used according to my invention is inthe following descriptions. I have found that a troduced into the bulb; reflecting layer of a specially chosen material Fig. 3 shows a device for treating a bulb accovering the inside surface of the lamp bulb is cording to my invention, with the upper portion in many respects superior to the prior art reflecof the bulb sectioned, in order to reveal the shield tors. It is one of the objects of the present inand ribbon filament in operative position;

vention to provide a vessel, for example the glass Fig. 4 is a detail view of the ribbon filament;

bulb of an incandescent lamp, with a firmly ad- Fig. 5 is a plan view of a device for finishing a herent and smooth internal coating having a high coated bulb, with a bulb in position; and

specular reflection characteristic, which coating Fig, 6 is a plan view of an alternative device is substantially free from contamination during for finishing b lb the life of the lamp. Referring to Fig. 1, numeral denotes the glass Another Object s to provide a method of bulb, 2 the filament, and 3 the base of an incano y (mating a Vessel With a light-reflecting descent lamp of any desirable shape, design, color,

material c fin d to a Dre-determined localized or other characteristics. The inside of the glass area on the inner s rface of h vesselbulb l is covered with a firmly adherent thin and. Another Object f the invention relates 130.3 smooth coating 4 of light reflecting material, as method of providing the interior wall of a vessel for example silver or aluminum, Lamps of this Such as a bul W a Smooth light reflecting type are especially suitable for use in lamp fix- 30 c a of aluminum. tures providing indirect illumination, and, accord- Another object is to provide a method of makjngly Fi 1 ho the reflecting layer as approxing bulbs with inside coatings of the ki imately covering the semi-spherical portion oppoferred to, in a satisfactory and inexpensive mant the t of a Spherical lamp It is, ner, to provide methods and means for evaporatever, understood that any portion of any con- 35 8 e as for example aluminum, Within a figuration, of the inside of a lamp of any desired vessel in order to coat its inside or a well defined shape or of any vesse1 generally, may b coated part thereof, with a firmly adherent and light reaccording t my invention fleeting ay r of t metal, d t p v d at- It is apparent that lamps of this type have the ing conditions for this process which Permit its important advantage that the reflecting layer 40 Practice in the most satisfactory manneris perfectly protected against any mechanical in- In certain typ s of lamps for example, those jury, or against vapors etc., to which exterior having a relatively long and restricted neck porcoatings are exposed Further, t rough t On a a Spherical bulb Portion, Ordinary face of exterior coverings heretofore employed,

coating methods are inapplicable to restrict the becomes easily covered t t, t, t which 45 coating W a Section only of the bulb, Particularly being difficult to remove without injuring the reif the coating is to be deposited by an evaporation fle tor t n poils t appearance f the PIOC SS- Accordingly a principal feature f the lamp, but also renders the installation less effiinvention relates to the novel method of coating cient due to the presence of an energy absorbing such lamps with a localized light reflecting coatblack body near the path of the refiectedlight. 50 ing of a vaporized metal such as aluminum. Still another important advantage of the inside Still another object is to provide a stencil or coating is the fact that it remains exceptionally shield which may be conveniently inserted into, 0001 during operation of the lamp, even l r and removed from, a vessel having a comparathan an uncoated lamp of similar rating. This tively narrow neck. is due to the circumstance that the radiant energy 55 passes through the glass walls once in the case of an ordinary bulb and twice in the case of an external reflector, whereas my new lamp reflects the rays without permitting them to penetrate the glass at the reflector, so that it remains cool to the extent for example, that a lighted and exposed, inside coated 300 watt lamp may be handled with unprotected hands.

Although the internal coating may consist of any material which adheres firmly to the glass walls and provides a specular reflecting surface, my preferred method of coating bulbs consists substantially in evaporating a substance and condensing the vapors upon the inside walls of the vessel. Silver or any white metal that is capable of high specular reflection is suitable, but aluminum is preferable because it does not discolor to any objectionable degree during certain manufacturing operations, as heating and baking, whereas silver, for example, tarnishes quite easily, probably due to the copper contents of commercial silver, which is the only silver practical for purposes of this kind. I have also found that the color, and therefore the light reflecting characteristics of aluminum, are preferable to those of other metals.

My new process of internally coating bulbs, or vessels generally, of the above described nature, is preferably carried out with the aid of a device shown in Figs. 2, 3, 4. This device is supported by a casting l0 having a body II and two extensions I2 and I4, which may be suitably mounted upon a working table by means of an insulated clamp or similar conventional means not herein shown. The body ll of casting ID has terminal l5 of an electric lead i6 screwed thereto, and the upper extension I2 is provided with a conical rubber washer IS. A shield structure 20 comprises a sleeve 2| having an extension 22 at its lower end and a substantially conical collapsible shield 23 fastened to its upper end. The shield consists of leaves 24 which may be made of any suitable material, as for example thin sheet metal. The leaves overlap to make the shield tight, and at its apex the shield cone is so fastened to sleeve 2| that the leaves can be contracted, as shown in Fig. 2, permitting the bulb to be slipped over it. The shield being completely inserted, its leaves spread apart so that the approximately circular upper edge of the shield rests against the inside of the bulb wall.

. The lower extension 22 of shield sleeve 2| fits into extension I2 of casting I0, forming a joint as shown in Fig. 3.

The lower extension l4 of casting I0 is connected to port 3| of an exhaust pump manifold by means of a tube or hose 32. Conduit 34 with cock 3'! leads to an exhaust pump, and open conduit 35 with cock 36 connects the manifold with the atmosphere.

A ribbon filament 40, preferably made of tungsten, with a bowl shaped recess 4|, is screwed to leads 42 and 43. Lead 42 is fastened to casting ill at 44 and therefore in electrical connection with conductor l6. Lead 43 has an insulating covering 45, for example of glass, and extends downwardly through casting Ill and tube 32 into extension 39 of the pump fixture, and is fastened to seal 46, which is tightly 'joined to 30 by means of a rubber tube 41. Terminal 48 of conductor 49 is screwed to seal 46 and therefore in electrical connection with the'second lead of the ribbon filament.

With the aid of this device my new method is carried out in the following manner. A lamp bulb or other vessel is first carefully cleaned and dried in order to remove any dust or dirt which might mechanically impair the coating, and also in order to eliminate any harmful substances, as alkalies, which are especially harmful to aluminum films. The metal to be evaporated, as for instance aluminum, is placed on the filament in the form of pellets or small shavings, and the bulb is then slipped over the shield structure, as above described, and pressed against the rubber washer where a vacuum tight joint is established during the following evacuation process. Fig. 3 shows the bulb in this position. The pumps are then started and the bulb exhausted below the glow point, that is, to a vacuum of approximately 10 to 30 microns. During the exhaust period the bulb is heated, for example by means of an open flame, in order to drive out any occluded gases. During this step of the process the temperature of the bulb is approximately 300 degrees Centigrade. When the bulb has cooled slightly, the metal is quickly evaporated by heating the tungsten filament. The filament is heated by applying a sufficiently strong EMF across the leads l6 and 49. I have found that the reflecting film on the inside of the bulb is of superior quality if the evaporating process takes place fairly quickly, for example in approximately five seconds. The hot filament radiates considerable energy, and if maintained at a high temperature for a longer time, other parts of the enclosure might be also heated and release contaminating gases. The metal vapors condense quickly upon the surface of the bulb where it is not protected by the shield, but air should not be admitted until the filament has cooled down, in order to prevent oxidation.

Although the edge of the coating is comparatively well defined, especially if the shield is carefully made and inserted, it is often desirable to remove excess metal in order to straighten the zigzag line which may have been left by the irregular edge of the shield. This finishing step is preferably performed with the aid of a small high speed bufiing wheel inserted in the bulb by means of an arrangement shown in Fig. 5. In this figure, 5| is a working table with a motor support 52, fulcrumed at 50, and bulb supporting means mounted thereon. The bulb supporting means comprises a lamp holder 54 with a base 55 and resilient arms 56, and a bulb guide 51 with arms 58 having rollers 59 rotatably mounted upon the ends thereof. Base 55 is mounted on a driving gear journalled at 62 and rotated with suitable speed by any means adapted for this purpose, as for example a worm gear within housing 65 driven by motor 66. The motor II has a base ll sliding upon rails 12 and rotating with support 52 around fulcrum 50. The motor 10 has a shaft ill with a buffer wheel mounted thereon. As indicated in Fig. 5, the bulb can be easily and quickly fastened in the rotating holder, the shaft 8| can be inserted in the bulb, and the edge of the coating straightened by means of the buffer wheel, which may be conveniently positioned and directed, as will be apparentfrom Fig. 5 and the above description, without further detailed explanation.

This method of finishing a bulb is quite satisfactory in the case of comparatively thin metal coatings, whereas for thicker films I found that an alternative method is preferable, the arrangement for this method being schematically shown in Fig. 6. In this figure, 92 is a felt disc impregnatcd with an abrasive, of about the diameter of the largest section of the bulb, and mounted on a spindle 9| which can be rotated at high speed, preferably about 3500 R. P. M., by means of any suitable drive. Fig. 6 indicates for this purpose a gear box 90 with driving shaft 95. The spindle 9| is long enough to permit insertion of the soft felt disc, which, upon being rotated at high speed, flattens out into a rather hard and stiff structure. The periphery of the disc approximately coincides with the coating edge to be cleaned, and is therefore in constant contact therewith, so that the entire available abrasive surface is always active, which assures speedy and certain action.

It should be understood that the present disclosure is for the purpose of illustration only, and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

This application is a division of application Serial No. 623,504 filed July 20, 1932.

The following other applications based on said application Serial No. 623,504 have been filed; divisional application Serial No. 182,735, filed December 31, 1937; continuation-in-part Serial No. 114,562, filed December 7, 1936 and continuation -in-part Serial No. 172,397, filed November 2, 1937 and continuation-in-part application Serial No. 183,063, filed Jan. 3, 1938.

I claim:

1. The methodoi partly coating the inside of a vessel having a bowl portion at one end and a restricted neck at the other end, with a reflecting coating confined to the bowl portion which comprises inserting a shield through the neck portion, expanding the shield to cover all but the bowl portion to be coated, subsequently evaporating a metal within the vessel, condensing the metal vapors to form a coating, collapsing the.

shield and withdrawing the shield through the neck portion.

2. The method of providing only the bowl portion. of a lamp bulb with an interior reflecting coating, which comprises inserting a shield through the neck of the bulb, expanding the shield to cover the part of the bowl which is to be kept uncoated, evaporating a metal within said bulb, subsequently collapsing the shield and withdrawing it through the neck.

3. The method of providing a bowl portion of a constricted neck lamp bulb with a metal coating, which comprises inserting a shield through the neck of the bulb, expanding said shield to cover the portion of the bulb which is to be uncoated, evaporating metal while the shield is within said vessel, condensing the metal vapor upon the unprotected bowl portion and upon the shield, collapsing the shield, withdrawing it through the bulb neck, and removing excess metal along the contours of the coating mechanically.

4. The method as in claim 3, in which the excess metal along the contours of the coating is removed by ,bufiing.

5. The method of providing a lamp bulb having a bowl portion and a neck portion with a metal coating over a part of its surface, the diameter of the cut-off between the coated and uncoated portions being greater than the diameter of the neck of the bulb, which comprises inserting a. shield through the neck, expanding the shield to protect the area which is not to be coated, subsequently evaporating a metal within said vessel, condensing the metal on the unprotected portion and on the shield, collapsing said shield, and removing said shield.

6. The method of claim 3, in which the aluminum is evaporated within fiveseconds.

7. The method of providing a bowl portion of a constricted neck bulb with a metal coating, which 8. The method of coating a part of a bulbwith an interior specular reflecting coating which comprises the steps in the order given, of cleaning the bulb surface free of alkalis, evacuating the bulb to a pressure below the glow point, baking the bulb at a temperature of the order of 300 C., inserting an expansible shield within the bulb and then expanding the shield into contact with the bulb surface, evaporating aluminum from a place inside the bulb, condensing the aluminum .on the bulb surface except where it is shielded by said shield, and collapsing and removing the shield after the condensation of the aluminum on the bulb surface.

ORR-10K HOWARD BIGGB.

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