US1900104A - Method and apparatus for coating the interior wall of hollow bodies - Google Patents

Description

March '7, 1933., A. M. HAGEMAN ET AL METHODAND APPARATUS FOR-COATING THE INTERIOR WALL 0F HOLLOW BODIES Filed Dec. 9, 1927 3 Sheets-Sheet l INVENTOR AJVI. HAGEMAN A. F. L/ND e0 ATTORNEY March 7, 1933. A, M. HAGEMAN ET AL METHOD AND APPARATUS FOR COATING THE INTERIOR WALL OF HOLLOW BODIES Filed Dec. 9, 1927 3 Sheets-Sheet 2 INVENTOR A.M.HHGEMAN A. M. HAGEMAN ET AL March 7, 1933.

METHOD AND APPARATUS FOR COATING THE INTERIOKWALL OF ROLL 0W BODIES a sheets-sheet :5

Filed Dec. 9, 1927 INVENTOR A. M HAGEMAN ,4. F. Lnvos-r M BY Q ATTORNEY Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE AARON H. HAGEHAN, OI BLOOMIIIILILD, AND ALBERT I. LINDSTROM, OF N UTLEY, NEW JERSEY, ASBIGNOBS 'I'O WBTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA METHOD AND APPARATUS FOR COATING THE INTERIOR WALL OF HOLLOW BODIES Application filed December 9, 1927. Serial No. 238,734.

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In the manufacture of incandescent electric lamps, it is important to be able to provide a bulb, which is made either of a light diffusin vitreous material or of a clear glass bul having a coating of a light diffusing character and at the same time, obtain a maximum light efliciency. It has been proposed to obtain light difiusing effects by the employment of a so-called opalescent or opal glass. The opa lescent effect being attained by addin cryolite to a batch of glass during manu acture. This was an exp'enslve procedure and furthermore, such glass acts to decompose liberating gases, probably silicon-fluoride which are detrimental to the filament and shorten the life of the lamp. Furthermore, the light absorption .by reason of opal glass is extremely high and inasmuch as it is-not possible to.

obtain a uniform thickness of a bulb, the resultant transmitted light varied in intensity.

The nearest approach to the opalescent ef feet in connection with coated lamps was attained by the application of a coatmg to the outer surface of the bulb such, for example, as that set forth in Patent 1,613,758 January 11, 1927. I

The outside coating of bulbs, however, although giving a satisfactory light diffusing medium, did not attain the desired opalescent effect which may be defined as a light difl'using medium enclosed in a glossy or highly polished surface as the exterior surface of a lamp bulb. It has been proposed to etch the inside surface of a lamp bulb with an acid such as a hydrofluoric acid or other etching solution. This method physically changes the inner surface of the bulb, breaking the same into numerous minute hills and valleys which reflectlight at all angles and cause a diffusion of-the emitted light. Theetched surface, however, did not answer the requirement of producing a desirable opalescent ef fect, since the intensity of .a lamp filament is too great to be diffused uniformly by the roughened surface of the bulb and although the transmitted light was diffused to an appre ciable degree, a concentrated spot of light alwaysremained visible. Furthermore, the etching of a bulb by means of acid required the exercise of extreme care, since the acid fumes were deleterious to the workers and extreme caution was necessary in performing the etching operation.

The present invention aims to provide a lamp bulb with a light diffusing coating so arranged that the coating in combination with the smooth exterior surface of the bulb gives the desired opalescent or pearly effect.

As set forth in our copending application Serial No. 737,609 filed September 13, 1924 for coated article and method of making the same, the desired opalescent effect is attained by app-lying a light diffusing material to the inside "surface of a lamp bulb and it is an object of the present invention to provide a method and apparatus whereby such materialmaybe applied in a convenient and expeditious manner.

Another object of the invention is to provide amethod of coating the inside surface of a hollow transparent body with a uniform light diffusing layer.

Another object of the invention is toproduce a lam'p'bulb comprising a uniform light diffusing layer on the inside surface of a translucent body which layer in combination with the glossy exterior surface of the body, will constitute a light diffusing medium, giving the desired opalescent effect.

The smooth outersurface of a lamp bulb or other container provided with a light diflam may have the required depth of color as w en using various colored pigments.

- The invention is, of course, applicable for the coatin of various forms of hollow translucent bo ies, but is herein shown and described in connection with the coating of the inner wall of a transparent vitreous incandescent electric lamp bulb. 1

The above mentioned type of hollow body, namely a lamp bulb, comprises a sphere-like portion terminating in a relatively narrow opening or neck. The application of a coating material to the inner surface of this form of hollow body is extremely diflicult, particularly since, it is essential to apply the coating in such manner as to have the same of uniform density throughout. In an electric lamp bulb wherein a high temperatured filamentis disposed in close relation to the that any variation or defect in the character of the coating will be exa gerated and readily noticeable, giving the ulb an unfinished or defective appearance.

In accordance with the present method, therefore, it has been found that by first heating a bulb to a given temperature then applying a finely divided material to the inner surface of the bulb, preferably while the bulb is rotating, a layer of light diffusing material may be uniformly deposited. It has further been found that the coating is best applied when discharged in the form of a. spray such as a coniferous discharge from a spray gun nozzle. The discharge is produced within the bulb and directed to a wall thereof, while a relative movement between the bulb and the spray nozzle is effected until the entire surface of the bulb receives a light diffusing 4'0 layer.

The manipulation of the spray gun is important by reason of the close working relation necessary, inasmuch as the spray nozzle is confined to the space within the bulb. The '45 spray nozzle is introduced into the bulb at an angle to the longitudinal axis of the bulb, after which a discharge of sprayed material is produced. The nozzle is then moved lengthwise of the bulb to direct sprayed ma- 5 terial against the surface of the bulb from a point adjacent to the neck thereof to a point at the top of the bulb or the inter-section between the longitudinal axis of the bulb and the wall thereof. A rotation or relative movement of the bulb and spray nozzle during the spraying operation, preferably a rotation of the bulb, results in the deposit of a layer of sprayed material, but as the nozzle moves toward the end of the bulb, the

contour of the bulb is such that the distance between the spray nozzle and the bulb decreases, thus a rotation of the bulb causes the surface of the bulb at the narrow portion (or dead center of rotation) near the end to rotate at a less speed than the wider portion.

light diffusing wall, it will be appreciated Normally, therefore, the end of the bulb would receive an excessive amount of sprayed material. To avoid this, the s ray is kept from impinging directly upon t e end of the bulb and the spray gun is so manipulated that the body portion of the spray coats the inner surface -of the bulb up to a point adjacent to the end of the bulb and the roving particles of spray which surround the main body of the discharge are sufficient to cover the upper portion of the bulb with a layer of the same degree of intensity as is deposited upon the other portions of the bulb in the, direct path of movement of the spray discharge.

After the bulb has been sprayed, it is moved into a baking oven to dehydrate the coating. This baking operation depends, of course, upon the character of coating employed.

The present method of coating by the apparatus employedresults in a uniform deposit of coating upon the inner wall of a bulb and gives an article having a uniform light diffusing medium which, in combination with the lustrous outer surface of the bulb provides the desired opalescent effect.

The invention willbe more fully understood by reference. to the accompanying drawings in which: I

Fig. 1 is a more or less diagrammatic plan view of an apparatus for practicing the present method;

Fig. 2 is a side elevational view of the apparatus shown in Fig. l but with the spray mechanism removed for the sake of clarity;

Fig. 3 is an enlarged plan view of a portion of the machine shown in Fig. l and more clearly illustrates the spray gun mechanlsm;

Fig. 4 shows a bulb in position to be sprayed and with the spray gun about to enter the bulb;

Fig. 5 is av view similar to Fig. 3 which shows the spray gun within the bulb with a discharge of spray projected to the surface of the bulb.

Fig. 6 shows a spray gun in its advanced position within the bulb to spray the upper portion thereof; and,

Fig. 7 is a view showing the spray nozzle in position adjacent to a steam jet for cleaning the nozzle.

An apparatus for practicing the present method may comprise a conveyor 10 provided with an odd number of bulb holders 13. In the present illustration, 37 bulb holders are employed and the conveyor moves intermittently in stages so that every other bulb holder is applied to spraying mechanism. An oven 14 extends about the path of movement of the conveyor so as to receive the mov- The use of the'single oven to preheat the bulbs and bake the coated bulbs isv accom plished by having the conve or with an odd this bulb will not be removed from the conveyor but will pass through the oven for a ba ing operation. This is accomplished by having-means associated with the conveyor atA which operates to eject a bulb, by means to be in the form of a fan or cone is effected in the later described, from a holder so that the bulb will drop into a chute 17. The mechanism for actuating the holder to, release the bulb opother holder so that a sprayed lamp will only be ejected upon its second application to the said mechanism which causes its ejection from the holder.

With this arrangement, it will be evident that as the conveyor moves in the direction of the arrow X a coated lamp and an empty holder will be moved toward the oven 14. Before the empty holder enters the oven 14, however, the operator at B inserts a new bulb into the holder. Since the conveyor indexes for every two bulbs, the bulb which has already been sprayed will pass the spraying mechanism upon the second revolution of the sprayed bulb with the conveyor, this is due to the odd number of bulb holders in the conveyor. The spraying operation is performed by the spray gun 16, which operation will be hereinafter more fully described.

During the spraying, it is preferable to rotate the bulbs. For this purpose, each bulb holder may have a shaft 18 supported in bearings 19 on the conveyor 10. These shafts may be disposed radially with respect to the axis of rotation of the conveyor and the end of each shaft may be provided with a pinion 20 positioned to mesh with a gear wheel 21. This gear wheel may be mounted on a shaft 22 and driven by means of a'pulley 23 connectedwith a suitable source of power (not shown).

As the conveyor moves the bulb holders to the spraying position, the pinions 20 will en age with the gear wheel 21, causing a rotatlon of the bulb. As the conveyor moves each bulb holder away from the spraying position, the pinion 20 will be moved away from the gear wheel, thus terminating the rotation of the bulb holder, although it is evident that if desirable, a series of gear wheels 21 may be provided so that the bulbs may be rotated throughout their movement through the oven.

The foregoing description sets forth the general operation in transporting and positioning the bulbs for the spraying operation. As more clearly shown in Fig. 3, the spray mechanism 16 for spraying the bulb comprises a slide plate 24 upon which is mounted a cross-head 25 for carrying a spray nozzle erates, however, to remove a bulb from every 7 type attac ed toatubular portion throughwhich thefinely divided spray material is caused to flow. The spray materi'al may enter the tubular portion 27 through a flexible tube 28,v which tube, may be connected to a,

container 29- containing the spray'material'.

The container is usually elevated above the 26. The. s ray nozzle may be; of M21; suitable spray un so that the spray. material nor-- mallyows by gravity into thespray gun.

The discharge of the spray substantially.

usual manner by the discharge'of air which enters a conduit 30 and is directed across a tip 31 of the nozzle 26 by means of an angularly directed outlet orifice 32 as show-nin Figs. 5 and '6. This discharge of air passin across the nozzle tip 31 results in the usua ejector effect to atomize and project. finely divided material flowing through the tubular passage 27. Means are provided forterminating the flow of coating materialexcept when the nozzle 26 is within the bulb. Such means may comprise a cam 33 which engages a valve 34 to cut off the air flow when the spray gun is in its outer or removed position with respect to a bulb. The cam 33. is actuated upon a movement of the spray gun into the bulb by reason of a lever arm 35 extending from the'cam which engages with a pin 36 on a stationary arm 37. Means for moving the nozzle 26 of thespray gun into and out from a bulb 15 may comprise a lever arm 38 which may be rocked in the direction of the arrow Y by any suitable means (not shown). The said arm 38 is provided with a link 39 pivoted at 40 to the cross-head 25. An oscillation of the arm 38, therefore, Wlll cause a movement of the said head with a consequent movement of the spray nozzle 26.

In order to properly coat a bulb, it is desirable to move the nozzleinto the bulb at an angle to the longitudinal axis of the latter. This is accomplished in the present structure by providing the head 25 with a guide finger 41 movable between angularly disposed tracks 42 and 43. These tracks are arranged to lie beneath the bulb when the same is held in position for spraying. It will thus .be evident that as the cross-head is moved toward the bulb, the nozzle 26 will be guided therein. It will be understood that in order to permit a movement of the nozzle and its associated parts in an angular direcat the ends of levers l6 and 4:7. The levers are pivoted on a head 48 slidable'on a shaft 49 extending from a hub 50 which is secured to the conveyor 10. At one, end of the shaft 49 is a jaw 51 and a spring 52 disposed between the jaw and the head 48 serves to normally close the jaws 45 and 46 to grip a bulb.

When the conveyor is in position to eject a bulb, an extension 53 on the head 48 engages a suitably positioned cam-member 54 causing the head to move toward the bulb and release the same. The above described mechanism for holding and discharging abulb is used for preheating the bulb and for baking the same after the coating has been applied so that the baking temperature and the preheating temperature are the same, preferably about 350 C. It will be understood, however, that if desirable, two ovens may be employed and that the preheating temperature may be about 350 C. or above and the baking temperature may be about 350 C. or above.

Although any suitable coating composition may be employed, it has been found that the present method gives satisfactory results when a coating is provided containing sodium silicate, a filler such as Kaolin and a pigment with a suitable amount of water mixed in a ball mill until a homogeneous mixture is obtained. A mixture of this character is well known in the lamp coating art and is more fully set forth' in Patent 1,581,-

In practicing the present method,'bulbs or blanks are fed to the holders until the first bulb is intermittently moved to a position in operative relation to the spraying mechanism 16. At the spraying station, the nozzle 26 is moved into and out from the bulb to deposit a layer of spray material on the interior surface of the bulb, which operation is more clearly shown in Figs. 4 to 6. As will be noted, the nozzle 26 travels through a path at an angle to the longitudinal axis of the bulb. It is obvious, however, that the nozzle 26 may be moved through a'predetermined path and the bulb may be held at an angle, in which case, the spray nozzle 26 might, for example, be moved horizontally. The result of this operation would, however, be the same as moving the nozzle as above set forth.

The spraying of the interior surface of a hollow body such as a lamp bulb is a difficult and exacting operation. With the present apparatus the nozzle 26 is moved into the neck 55 untiladjacent to a point as indicated by the dotted line 56 at which time the spray gun is operated to vproject a fan or conical shaped discharge 57 of finely divided material. .Thus the spray is produced within the article. The spray gun nozzle is then moved along the path indicated by the dotted line 58 which path has been chosen so as to keep the concentrated portion 59 of the spray as far from the surface wall 60 receiving the spray as is possible. The distance of the nozzle withrelation to the said wall is limited by the dimensions of the bulb.

The importance of heating the bulb prior to spraying will be appreciated for the reason that the s ray must not run when it is applied to the ulb, but must be in such condition as to readily adhere to the surface and cover the same. When coating the outside surface of a bulb, the distance between the bulb and the spray nozzle may be relatively long, thus the particles may becomparatively dry before reaching the bulb. The combination of the sprayed material applied within and to a wallof a heated bulb is an important step in the present method.

As the gun moves into the bulb, thebulb is rotated at relatively high speed, thus causing an impingement or deposit of the spray material over the interior surface of the bulb.

Inasmuch as the bulb is rotated about its axis indicated by the dotted line 61, theupper end or tip 62 015 the bulb will be in the dead center of rotation and rotate at relatively low speed as compared with the adjacent wall of the bulb.

As the spra Y gun moves into the bulb, the' enlarged portlon of the bulb will receive a certain amount of spray material owin to the length of time to which the wall oi the bulb is subjected to the discharge of spray. It has been found that in order to obtain a uniform layer of sprayed material upon the inside surface of the bulb, the comparatively dense portion 63 which may be termed the main body thereof, should be moved so that this main body of spray does not reach the top portion 62 of the bulb. The spray gun is, therefore, moved until the main body of the spray is discharged adjacent to a point on the'dead center of rotation of the bulb so that the free or roving particles of spray which are projected from the main body will be deposited upon the upper wall of the bulb to produce a layer which, by reason of the relatively long time period the upper wall is exposed to the roving particles of spray will produce a layer of material upon the upper wall equal in density and thickness to the deposit upon the adjacent wall or the remainder of the interior surface of the bulb.

In producing a sprayed lamp bulb, the thickness of the coating may be determined by the character of the material used or by the number of reciprocable movements or 1 into and out from 5 coating 1s desired. the spray nozzle .may be coatin involves the coating and in operation necessitates bulb neck until the same becomes plastic. If

passes of the spra nozzle, within the bulb.

If a light coating is to be obtained, it may only be necessary toimove the spray nozzle the bulb, or if a heavier moved back and forth severaltimes within thebulb. v It will be noted that the present method of As illustrated in the drawings, the nozzle is shown as' movableimto andout from the bulb in suchmannerthat the. spray nozzle is held asfar from the surface to be sprayed as practical. In practicing the present method,

it .hasalso been found that good'results are obtained by moving the nozzle into the bulb through apath inaccordance with'the contour of the surface to be coated. By this manner of manipulating the nozzle, the outlet or discharge orifice of. the nozzle may be maintained a uniform distance from the bulb.

As hereinbefore mentioned, it has been found that the degree of the'density of the coating may be controlled by the number of movements or passes of the nozzle into and out from the bulb and that the rate of .speed of rotation of the bulb may be varied so that the surface to be coated will be exposed to the spray for a longer or shorter period.

It has further been found that when utilizing the preheating step it is possible to dispense with the final baking step. The bulb when preheated acts to dehydrate the applied by leaving out the final baking step the operation of coating is expedited and a greater quantity of bulbs may be coated in a given time period than has heretofore been possible;

By producing the spray after the nozzle 7 has entered the bulb, it is possible to avoid a deposit of sprayed material upon the neck of the bulb. This is an advantage since after the bulb has been sprayed it is necessary to perform what is termed a sealing-in operation. This operation consists in fusing the neck of the bulb to another lamp part termed a mount which latter part includes the filament and supporting structure. The sealingthe heating of. the

a deposit of another material such as a coating is applied to the bulb neck, the operation of heating is more difficult, since the coating absorbs heat and, therefore, makes it so difficult to properly melt the glass and fuse the bulb neck to the lamp mount.

When employing the present apparatus to discharge a coating material containing sosilicate, a nozzle is employed which disicharges the sprayed material at an angle to bodily manipulation of, 10 a disc arge. of spray within the body to be if a unf form layer is to be applied. It has been found, however, that the fine articles of the sprayed materialbecome lo ged; be--.

tween the air outlet orifice 32 of the spray nozzle and the tip 31 thereof and that these particles build up to such a degree as to offer an obstruction and change theyangle at which the spray is projected. It will be evident that if during operation, the angle of the spray is changed, the accuracy of operation is affected since a greater or lesser-amount of spray will-be deposited upon the upper surface of the bulb. The character of the sodium silicate coating composition is suchth'at the buildingsup of material upon the spray nozzle offers a considerable detriment to continuous and effective results. 1

The present invention, however,-"provides meansformaintaining the nozzle free from an accumulation of material which means consists in the use of a nozzle associated with a source of steam supply'to project a. jet of steam 65 against the nozzle tip. A steam nozzle may be positionedso as to direct discharged steam against the spray nozzle tip to clean the sameafter each movement of the pozzle from a bulb after a spraying opera- 1on.

By this method, the spray nozzle enters the bulb for each operation in such condition as to leave it free to operate for the discharge of the spray at the predetermined angle. It i has been found that, With the present com-' position of coating using sodium silicate, that the moisture of the steam combined with its heat and the velocity with which it is" pro ected from anozzle, serves to cut the 1 sodium silicate and keep the nozzle clean. It is, of course, obvious that any other fluid maybe employed as moist hot air or fluid of such characteras to serve to remove the particular composition used for the coating.

Inasmuch as the jet of fluid is projected against the nozzle. after each operation of,

the same-for acoating of a bulb, air projected at high velocity will serve to. remove any particles of composition should they'adhere too firmly to the nozzle. The use of steam, however, not only dislodges the particles and by reason of the moisture afiects a more complete removal of any material that may be come deposited upon the nozzle tip or between the tip and the air outlet orifice.

The present method and apparatus not only serves to coat the interior surface of bulbs in an efiective and eflicient manner to produce a layerof uniform density and thickness, but by'reason ofthe present meth- 0d, the lamp bulbs may be coated at the high rate of speed required in connection with other lamp making operations, whereby coated lampsmay be produced at a minimum cost.

is shown, it

Although apreferred embodiment ofapparatus for practicing the present method isto be understood that modifi-. cations may be made therein as well as variations in the method without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is: I

1. An a paratus for depositing a layer of a light di usin material upon the inner surface of a lamp laulb which comprises mechanismhaving a. spray discharge orifice 'for light difl'using material, means for movin said mechanism into and out from said bulb and means for preventing an accumulation of spray material adjacent to said orifice.

n apparatus for depositing a coating of light diffusing material upon the inner wall of a lamp bulb which comprises a spray nozzle having a conduit for spray material and an outlet orifice for directmg a spray of maadjacent to one side of terial at an angle to the longitudinal axis of said conduit, means for moving said nozzle into and out from said bulb and means for preventing accumulation of sprayed material adjacent to said outlet to maintain the I discharge material at the required angle. 3. An apparatus for spraying a light difside of said bulb, means for causing a spray discharge against the opposite side of said means for rotating said bulb about its lon ltudinal axis, means for heating the bulb so t at the coating materialwill pass through a heated environment and become partially dry before deposit upon said bulb and will completely dry upon striking the heatedbulb to ve a smooth uniform non-flowing layer.

l ii testimony whereof, we have hereunto subscribed our names this 8th day of December, 1927. J

AARON M.'HAGEMAN." ALBERT F. LINDSTROM.

fusing material on the interlor surface of a transparent hollow body of light transmitting material having a constricted neck por-- tion and an enlarged body portion, comprising a spray gun having an extensionfor conucting spray, material, a nozzle at the free end of said extension, means for moving said extension to cause said nozzle to travel into said body through a path intersecting the longitudinal axis of said body, means for causing a discharge of spray material at a predetermined point in the path of travel of said nozzle and means for rotating said body about said axis.

4. An apparatus for spraying a light diffusing material on the interior surface of a transparent hollow bo y of light transmitting material having a constricted mouth portion and an enlarged body portion, comprising a spray gun having an extension for conductin coatmgmaterlal, a nozzle at'the free end 01 said extension, means for moving said extension to cause said nozzle to travel through a path so as to dispose the nozzle said body, means for actuating said gun to cause a discharge of sprayed material against the opposite side of said body and means for rotating said body about its longitudinal axis during-the discharge of sprayed material, An apparatus for coating the interior surface of a lamp bulb having a constricted neck with a light difi'using material, comprising means for heating the bulb, a spray nozzle having a sprayoutlet orifice, means for moving said nozzle into said bulb througha path intersecting the longitudinal axis of deposit of ight diffusing

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