US2806444A

US2806444A - Silica coating apparatus for incandescent lamp bulbs

Info

Publication number: US2806444A
Application number: US475656A
Authority: US
Inventors: Leo C Werner; Stanley A Lopenski; Nicholas J Rainone
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1954-12-16
Filing date: 1954-12-16
Publication date: 1957-09-17
Anticipated expiration: 1974-09-17

Description

SILICA COATING APPARATUS FOR INCANDESCENT LAMP BULBS Sept", 1957 L. c. WERNER EI'AL 2 Sheets-Sheet 1 Filed De. 16, 1954 2 Mex E m W 5 2 N20? W W4 J mm 0% v 57/ 3 w% Y B Sept 17, 1957 L Q WERNER ErAL SILICA QOAT ING APPARATUS FOR INCANDESCENT LAMP BULBS 2 Sheets-Sfieet 2 IN V EN TORfi' Filed Dec. 16, 1954 United States PatentO SILICA COATING APPARATUS FOR INCANDESCENT LAMP BULBS Leo C. Werner, Cedar Grove, Stanley A. Lopenski, Pompton Plains, and Nicholas J. Rainone, Clifton, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 16, 1954, Serial No. 475,656

5 Claims. (Cl. 118-51) The present invention relates to incandescent lamps and, more particularly, to improved silica coating apparatus for such lamps.

In the manufacture of high wattage incandescent lamps, for example, the 100 watt gas fill type, various types of light diffusing coatings for the lamp bulbs have been employed. In the past, frosting or etching of the incandescent lamp envelope has been most commonly used. More recently, a silica coating on the interior surface of the lamp bulb, deposited thereon preferably by electrostatic means, has been employed.

In the conventional apparatus for the electrostatic silica coating of an incandescent lamp bulb, the bulb is placed on a rotating chuck or head and is heated by a gas fire to render the glass envelope electrically conducting. In addition, the hot ionized gas on the outside of the bulb and the burner serve as a positive electrode. A silica powder nozzle and probe which are reciprocable up and down within the lamp bulb seated on the rotating chuck, serve as the negative electrode. The silica powder or smoke which is a mixture of high pressure air and finely suspended silica particles is blown from an aspirator at the bottom of a combination plowder pot and expansion chamber against a metal target in the expansion chamber portion of the combination pot and expansion chamber. The larger particles or agglomerates fall back into the silica powder below and the finely divided particles are blown into the rotating bulb through the nozzle. The negatively charged silica powder particles are repelled by the negatively charged probe and attracted to the positively charged lamp envelope where they are firmly attached to the bulb wall by the electrostatic field.

As the powder within the combination silica powder pot and expansion chamber is used, it is apparent that the silica powder volume will decrease and the expansion chamber volume within the combination pot will increase. This means, assuming a constant silica delivery air pressure, that the density or fineness of the silica smoke thus produced will vary, depending upon the amount of silica powder within the combination pot. Again the silica powder tends to accumulate on the side walls of the combination pot, producing a crater effect andfeeding powder to the discharge opening only from the crater-like center. 7

e A further defect of the conventional silica smoke gencrating apparatus is the inherent inability to clean out or clear the expansion chamber, between the coating cycles.

An additional defect of the conventional silica coating apparatus is the adherence of the silica smoke to the walls of the silica smoke delivery tubes, expansion chamber, aspir'ator, and silica powder pot.

A still further defect of the conventional silica coating apparatus is the inability of the present lamp envelope heating burners to uniformly heat the lamp bulb. The bulb is usually heated by a plurality of individual burners which are judicially juxtaposed about the bulb rotating on the chuck therebelow and are aimed at selected points on the lamp bulb surface.

The rubber or copper tubing which may connect the powder pot or reservoir and the expansion chamber or the aspirator at the bottom of the powder reservoir to the target within the expansion chamber, or the smoke tube which connects the expansion chamber to the head are all subject to the accumulation of silica smoke on the walls thereof. It is believed that the silica powder has a kinetic negative charge and the rubber or copper tubing is positive. Thus the silica powder is attracted to the walls of the copper or rubber tubing and clean-out is rendered more difficult.

Hence, it has been found advantageous according to the invention to provide a separate expansion chamber suitably mounted on a cover of, and separable from, the silica powder pot. The separate chamber will provide a constant expansion chamber volume and more uniform generation of the silica smoke will result. In addition, we have provided an inverted conically shaped powder spreader beneath a continuously rotated powder paddle to prevent the crater-like accumulation of powder along the sides of the silica powder pot and to insure a constant volume of silica powder beneath the powder spreader and in contact with the powder pot discharge opening. Thus regardless of the amount of silica powder above the powder spreader a constant silica powder volume beneath the powder spreader and powder paddle insures a more uniform density of the silica smoke.

Again it has been found advantageous according to the invention to provide a solenoid operated bottom plate or plug for the expansion chamber mounted on the cover of the silica powder pot so that air may be blown back by means of a powder tube cleaner through the silica smoke tube expansion chamber and the reciprocable bottom plug in its open position to clean out any. agglomerates or heavy particles accumulated within the expansion chamber after the last coating cycle. In ad'- dition, we have provided a porous bag affixed to the cover of the powder pot to act as a pressure relief valve or pressure dilfuser during the blow-back operation.

Further, it has been found advantageous according to the invention to provide plastic tubing and a plastic coating for the expansion chamber "and powder pot. This tubing and coating may suitably be a polytetrafluoroethylene or the like. The plastic tubing and the plastic coated expansion chamber and powder pot provide a smooth inner wall which prevents the silica powder from adhering thereto. In addition, the plastic has either a neutral or a negative charge which will either have no attraction for, or repell, the negatively charged silica powder.

In addition, it has been found advantageous according to the invention to provide a burner contoured to the outline of a vertical section of the rotating bulb. The burner may be provided with a plurality of burner tips or holes staggered in a zig-zag fashion to provide a fairly wide soft flame in contact with the entire surface of the lamp ibulb which is to be coated, thus insuring uniform coating thereof. 7

In its general aspect, the present invention has as its objective an improved electrostatic silica coating apparatus for incandescent lamp bulbs.

A specific object of the present invention is an expansion chamber separable from a silica powder reservoir to provide a constant expansion chamber volume and more uniform silica smoke.

An additional object is, an inverted cone-like powder spreader mounted beneath a continuously rotatable powder paddle within the powder reservoir to prevent craterlike accumulation of powder along the side walls of the reservoir and to providea constant volume of silica =3 powder beneath the powder spreader and in contact with a discharge opening in the powder reservoir.

A still further object is an expansion chamber provided With a mechanically operated bottom plate for intermittently connecting said chamber to said powder reservoir and a powder tube cleaner for cleaning out accumulated agglomerates or heavy particles from the smoke expansion chamber.

A still further object of the invention is a powder reservoir provided with a porous bag mounted on the cover thereof to act as a pressure relief valve during the powder tube. cleaning operation.

A still further object of the invention is plastic tubing and a plastic coating for the expansion chamber and powder reservoir to reduce the accumulation of sillca smoke on the walls thereof.

Another object is a lamp bulb burner contoured to the outline of a vertical section of said bulb to uniformly heat the entire surface ofthe lamp which is to be coated.

Other objects of the invention will become apparent to those skilled in the art to which it appertains as the description thereof proceeds both by direct recitation and implication from the context.

Referring to the drawings in which like numerals of reference indicate similar parts throughout the several views:

Fig. l is a side elevational view partially in section of the improved electrostatic silica coating apparatus of the invention.

Fig. 2 is a plan elevational view of the silica powder reservoir and expansion chamber and showing the chamber in section along the line IL-II of Fig. l in the direction of the arrows.

Fig. 3 is. an enlarged vertical sectional view of the details of a lamp head and a powder tube cleaner of the invention.

Fig. 4 is a horizontal sectional view of the powder tube cleaner operating mechanism along the line IV-IV of Fig. 3 in the direction of the arrows.

Fig. 5 is an enlarged vertical sectional view of a coating nozzle.

Referring now to the drawings in detail and particulady to Fig. l, the reference numeral designates an improved electrostatic coating apparatus of the invention. This apparatus 10 has a silica powder reservoir 11 suitably mounted on a base plate of a frame 12 of an automatic silica coating machine upstanding from the floor. The frame 12 may comprise a stationary table 14 of generally elliptical shape mounted on a plurality of integrated supporting members (not shown) and a base plate. The table 14. carries a plurality of rotatable indexable heads 15.

The generally hollow hemispherical powder reservoir 11 may be provided with a plate-like cover 16 (Figs. 1 and 2). An expansion chamber 18 is mounted by means of a suitable flange about a powder return opening 20 in the cover 16. A bearing 21 (Figs. 1 and 2) may be Secured to the cover 16 for supporting a powder paddle shaft 22 journalled therein. The shaft 22 extends through the cover 16 and carries a silica powder paddle 24 on the lower end thereof. The shaft 22 is driven by suitable means, such as the motor 26 (Figs. 1 and 2). Adjacent the bearing 21, a hollow hub 26 is secured by its flange to the cover 16, as by bolts. The hub 26 carries afiixed thereto a porous bag 28 which functions as a pressure release valve during an expansion chamber clean-out operation hereinafter to be described.

An inverted cone-like powder spreader 30 (Fig. 1) is mounted on the bottom portions of the powder reservoir 11, close to, but with suflicient clearance from, the silica powder paddle 24. Silica powder 32 is disposed about the powder paddle 24 within the powder reservoir 11, over the powder spreader 30 and adjacent to a discharge opening 36 provided in the bottom portion of the powder reservoir 11. A retaining plate 38 supports a pipe 40 extending from the discharge opening 36 to an aspirator 42.

' may be threadable therein. A

A line 44 (Fig. l) connects one side of the aspirator 42 to a high pressure supply (not shown). A line 46 extends from the other side of the aspirator 42 through a mounting block 48 on the side wall of the expansion chamber 18 and into said chamber 18. The lines or tubes 44 and 46 may, according to the invention, be plastic, suitably polytetrafluoroethylene.

Expansion chamber A silica powder target 50 (Figs. 1 and 2) is adjustably mounted adjacent to the delivery end of the tube 46 by means of a rod 52 extending through the block 48 and adjustably held therein, as by means of a screw. It will be understood that by adjusting the distance between the pipe 46 and the target 50 and the angle of incidence between the silica powder 32 and the target 50, the silica smoke turbulence within the expansion chamber 18 (and hence the silica smoke density) may be controlled.

The expansion chamber 18 (Figs. 1 and 2) has a tapered bottom plate or plug 54 which seats in the powder return opening 20 in the cover 16. This plug 54 is carried on the lower end of an operating rod 56 of a solenoid operated air cylinder 58 mounted on a cover 59 of the expansion chamber 18. It will be understood that during the bulb coating portion of the cycle, the plug 54 separates the expansion chamber 18 from the powder reservoir 11. During the expansion chamber clean-out portion of the operating cycle, the plug 54 is opened, thus permitting the heavy accumulated agglomerates to deposit back (through opening 20) into the silica reservoir 11.

A smoke tube 60 (Figs. 1 and 2) extends through the cover 59 and is connected by means of a flexible plastic tube 62, suitably polytetrafluoroethylene, to a silica smoke injector nozzle assembly 70.

Smoke injector nozzle assembly The smoke injector nozzle assembly 70 (Figs. 1 and 3) is afiixed to one of the upwardly extending side walls of a generally U-shaped bridge 72. This bridge 72 (Fig. 1) has a pair of downwardly depending guide hubs 74, only one of which is shown in Fig. 1, and which are reciprocable on vertical rods or guides 76. The bridge 72 is reciprocated through conventional connecting linkage (not shown) by a coating stroke cam (also not shown).

As shown in Fig. 3 an outer insulated coating sleeve having its upper insulated portion 82 of reduced diameter and of insulating material, such as a suitable plastic, has a reinforcing metallic lower portion 84 to provide rigidity thereto. An exhaust line 86, afifixed to an aperture in the lower portion of the lower sleeve 84, extends to an exhaust means, such as a pump (not shown). A lower cap 87 is secured, as by means of screws, to the bottom portion of the lower sleeve 84. It will be understood that the lower end of the upper insulated portion 82, of the outer sleeve 80, is joined to the upper end of the lower metallic sleeve 84 of the outer sleeve 80, to form the outer sleeve 80.

The lower cap 87 (Fig. 3) supports and is secured to, by means of a screw 90 to an axial coating tube 92 which extends substantially the length of the outer sleeve 80. As shown in Figures 1 or 3 the lower portion of the coating tube 92 is connected to the flexible tube 62 of the smoke tube 60. The coating tube 92 may be providedbelow its junction with the line 62 with a trap 94 (Fig. 1)

for collecting any heavy agglomerates not disposable through the exhaust line 86.

The upper end of the coating tube 92 (Figs. 1 and 3) carries afianged coating nozzle (Figs. 3 and 5) which plurality of annularly arranged coating outlets 102, for Example 8, having an inside diameter of about .040 may extend from the interior of the coating tube 92 through the nozzle 100. A probe 104 (Figs. 3- and 5) projects axially from the upper surface of the nozzle 100 to serve as a negative side of a high frequency, high voltage circuit (not shown).

lamp bulb 112.

Head

Each of the heads 15 (Figs. 1 and 3) has a hollow body or sleeve 130 (Fig. 3) flanged at its upper end and provided with a pulley 132 on its lower end. This sleeve 130 has its flanged upper portion resting on and is rotatable in a bushing 134 carried by an annular retaining ring 136. These retaining rings 136 (shown in Fig. 3) liave flanged mounting portions on each end. The mounting portion on the left, when viewed in Fig. 3, may be suitably lower than the flanged portion on the right, so as to permit the pinning together of the overlapping flanged portions of adjacent retaining rings 136. These rings 136 are secured together to form a chain indexable from station to station on the periphery of the table 14 of the machine by a conventional indexing means (not shown).

Each of the rings 136 (Figs. 1 and 3) carries an outer guide rail roller (not shown) and an inner indexing roller (not shown) transverse to the joined ends. The indexing roller engages, and is indexed by, an indexing spider (not shown) located over the curved portions of the elliptical flanged table 14. The guide roller rides on a rail (not shown) to insure proper alignment of a head 15 at the work stations.

A hollow lava insulating bulb chuck 138 (Fig. 3) has a flanged lower portion 140 secured, as by lava pins, to the flanged upper portion of the hollow body 130 of the head 15. As shown in Fig. 3 the upper portion of the chuck 138 is suitably contoured to receive the neck portion of an incandescent lamp bulb 112.

Air blast powder tube cleaner An air blast powder tube cleaner 148 of the invention (Figs. 1, 3 and 4) is mounted adjacent a head 15 for use during the indexing of said head 15 from station to station to clean out the nozzles 100 (Fig. 5) and the adjacent parts of the silica smoke injector nozzle assemblies 70. Each of the cleaners 148 has an arm 150 (Fig. 4) mounted above the table 14 on a shaft 152. This shaft 152 is carried by a support plate 152 affixed to the table 14, and is spring biased by means of a return torsion spring 153 (Fig. 3). A free end 154 of the arm 150 (Fig. 4) is generally annular in shape and is provided with an air blast tube 156 (Fig. 3) extending radially inwardly from the periphery of the free end 154 to an air blast cleaner hole 158, extending vertically from the tube 156 to the bottom surface of the end 154. The air blast cleaner line 156 is connected to a suitable source of high pressure air (not shown) which may be actuated by a solenoid controlled valve (not shown) at the desired time.

It will be understood that the arm 150 is pivotable on the shaft 152 adjacent a pulley 132 of a head 15 and carries a cam 159 (Fig. 4) in engagement with the pulley 132. The pulley 132 at a coating station maintains the arm 150 (through its cam 159) in its out position shown in the solid lines of Fig. 4. When a head 15 indexes, the indexing pulley 132 of a head 15 disengages itself from the non-indexing cam 159 thus permitting the spring biased arm 150 to swing over into axial alignment with a coating nozzle 100 which is now in its retracted lowermost position as shown in dotted line of Fig. 3. Simultaneously with the arrival of the air cleaner delivery hole 158 above the nozzle 100 a short blast of high pressure air is released therethrough to the nozzle 100, the coating tube 92, the upper portion 82 of the outer sleeve 80 of the smoke injector nozzle assembly 70 to the line 62, the smoke tube 60, the expansion chamber 18 and the now open plug 54 thereof and into the silica powder reservoir 11, thus removing the powder agglomerates from the above-mentioned parts and returning them to the powder reservoir 11.

Itwill be understood that the solenoid operated air cylinder 58 (Fig. 1) on the expansion chamber 18 has opened the plug 54in the bottom of the expansion chamber 18 prior to the indexing of a head 15 from the coating station of the machine 110.

Burner A burner (Figs. 1 and 3) contoured to the outline of a vertical section of the bulb 112 is secured by means of a bracket 182 to table 14 of the frame 12 of the coating machine. This burner 180 may be providedwith holes arranged in arrowhead zig-zag fashion in three rows to provide a wide enveloping soft flame for uniformly heating the bulb 112 to the desired electrical conductivity.

Thus, it will be seen from the foregoing description that we have provided, according to the invention, an improved electrostatic coating apparatus 10. The apparatus 10 of the machine has a separate expansion chamber 18 suitably mounted on, and separable from, a cover 16 of a silica powder reservoir 11. The separate expansion chamber 18 provides a constant expansion chamber volume and more uniform silica smoke.

In addition, we have provided an inverted cone-like powder spreader 30 beneath a continuously rotated powder paddle 34 to prevent the crater-like accumulation of powder 32 along the side walls of the silica powder reservoir 11. The powder spreader 30 insures a constant volume of silica powder 32 beneath the powder spreader 30 and in contact with the powder discharge opening 36 in the botom of the silica powder reservoir 11 to provide a constant volume of silica thereat.

Further, we have provided a bottom plug 54, for the expansion chamber 18, which is reciprocable by a solenoid operated air cylinder 58 mounted on the cover 59 of the expansion chamber 18, to seal the expansion chamber 18 from the powder reservoir 11. The plug 54 may be moved to its open position by the cylinder 58 to permit the removal of heavy particles of silica powder 32 from the smoke injector nozzle assembly 70, smoke tube 60 and expansion chamber 18 after the completion of the coating cycle by means of the air blast powder tube cleaner 148. The porous bag 28 mounted on the cover 16 of the powder reservoir 11 acts as a pressure relief valve during the air blast cleaning operation.

We have provided the inner surfaces of the powder reservoir 11, opening 36, pipe 40, aspirator 42, line 46, expansion chamber 18, plug 54, smoke tube 60, connecting line 62 and air tube 92 with a coating of a plastic, such as polytetrafluoroethylene. In fact, the

tubes

40, and 46, smoke tube 60 and tube 62 may be polytetrafluoroethylene and will have no attraction for, and hence will repel, the negatively charged silica powder 32. A suitable polytetrafluoroethylene is manufactured by E. I. du Pont de Nemours & Co. Inc. of Wilmington, Delaware under the trade name of Teflon. Further, we have provided a burner 180 contoured to the outline of a vertical section of the rotating bulb 112 on the head 15. The burner 180 may be provided with a plurality of burner tips or suitable holes staggered in zig-zag fashion to provide a wide soft flame for contacting the entire surface of the rotating bulb 112 which is to be coated.

Although a preferred embodiment of the invention has been disclosed, it will be understood that modifications may be made within the spirit and scope of the invention.

We claim:

1. An improved silica coating apparatus for incandescent lamp bulbs comprising a frame, a silica powder reservoir on said frame, an expansion chamber mounted on said reservoir, means on said expansion chamber for separating said expansion chamber from said reservoir, an aspirator near said reservoir for delivering silica smoke to said expansion chamber, a hollow rotatable head for securing a lamp bulb to be coated thereon, andmeans for connecting said expansion chamber to said head.

2. An improved silica coating apparatus for incandescent lamp bulbs comprising a frame, a silica powder reservoir on said frame, an expansion chamber mounted on said reservoir, means on said expansion chamber for separating said expansion chamber from said reservoir, an aspirator near said reservoir for delivering silica smoke to said expansion chamber, a hollow rotatable head for securing a lamp bulb to be coated thereon, a smoke injector nozzle assembly on said frame beneath said head and reciprocable within said head, and means for connecting said expansion chamber to said smoke injector assembly.

3. An improvedsilica coating apparatus for incandescent lamp bulbs comprising a frame, a silica powder reservoir on said frame, an expansion'chamber mounted on said reservoir, means on said expansion chamber for separating said expansion chamber from said reservoir, an aspirator near said reservoir for delivering silica smoke to said expansion chamber, a hollow rotatable head for securing a lamp bulb to be coated thereon, a smoke injector nozzle assembly on said frame beneath said head and reciprocable within said'head, means for connecting said expansion chamber to said smoke injector assembly, and an air blast powder tube cleaner on said frame adjacent said head for cleaning out said smoke injector assembly and said expansion chamber.

4. An improved silica coating apparatus for incandescent lamp bulbs comprising a frame, a silica powder reservoir on said frame, an expansion chamber mounted on said reservoir, means on said expansion chamber for separating said expansion chamber from said reservoir, an aspirator near said reservoir for delivering silica smoke to said expansion chamber, a hollow rotatable head for securing a lamp bulb to be coated thereon, a smoke injector nozzle assembly on said frame beneath said head and reciprocable Within said head, means for positively charging a bulb and negatively charging an associated smoke injector nozzle assembly, means for connecting said expansion chamber to said smoke injector assembly, an air blastipowder tube cleaner on said frame adjacent said head for cleaning out said smoke injector assembly and said expansion chamber, and means on said frame positioned adjacent said bulb in the plane of the longitudinal axis of rotation for uniformly heating said bulb for improved electrical conductivity.

5. An improved silica coating apparatus for incandescent lamp bulbs comprising a frame, a silica powder reservoir on said frame, an expansion chamber mounted on said reservoir, means on said expansion chamber for separating said expansion chamber from said reservoir, an aspirator near said reservoir for delivering silica smoke to said expansion chamber, a hollow rotatable head for securing a lamp bulb to be coated thereon, a smoke injector nozzle assembly on said frame beneath said head and reciprocable within said head, means for positively charging a bulb and negatively charging an associated smoke injector nozzle assembly, polytetrafluoroethylene means for connecting said expansion chamber to said smoke injector assembly, an air blast powder tube cleaner on said frame adjacent said head for cleaning out said smoke injector assembly and said expansion chamber, and means on said frame positioned adjacent said bulb in the plane of the longitudinal axis of rotation for uniformly heating said bulb for improved electrical conductivity.

References Cited in the file of this patent UNITED STATES PATENTS l,900,104 Hageman et al Mar. 7, 1933 2,046,360 Bohlke July 7, 1936 2,336,946 Marden et al. Dec. 14, 1943 2,426,016 Gustin et al Aug. 19, 1947 2,438,561 Kearsley Mar. 30, 1948 2,593,920 Reynolds Apr. 22, 1952 2,679,822 Kuebler June I, 1954 2,706,963 Hug Apr. 26, 1955

Claims

1. AN IMPROVED SILICA COATING APPARATUS FOR INCANDESCENT LAMP BULBS COMPRISING A FRAME, A SILICA POWDER RESERVOIR ON SAID FRAME, AN EXPANSION CHAMBER MOUNTED ON SAID RESERVOIR, MEANS ON SAID EXPANSION CHAMBER FOR SEPARATING SAID EXPANSION CHAMBER FORM SAID RESERVOIR, AN ASPIRATOR NEAR SAID RESERVOIR FOR DELIVERING SILICA SMOKE