US2351530A - Method of sealing-in and molding lamp bulbs - Google Patents

Description

June 13, 1944. M. E, McGowAN METHOD OF SEALING-IN ANDy MOLDING LAMP BULB'S Original Filed Dec. 21, 1935 f 35 ai ya .q1 sa mvENToR M E. MC'YWH/V BY W MNM. ATTORNEY 1 Patented June 13, 1944 MET'HOD 0F SEALNGJN AND MOLDING LAMP BULBS Michael E. McGowan, Bloomfield, N. J., assig'nor to Westinghouse Electric t Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Original application December 2l., 1935, Serial No. 55,519, now Patent No. 2,212,842, dated August 27, 1940. Divided and this application July 13, 1940, Serial No. 345,310 f 1'1 calms.

This application is a division of my copending application, Ser. No. 55,519, :died December 2l, 1935, now patent No. 2,212,842, dated August 127, 1940, and owned by the assignee of the present application.

This invention relates to the manufacture oi' incandescent electric lamps and similar devices. and more particularly to a method for sealing together two glass parts of said devices and for shaping the seals, also for shaping the bulb neck to form an annular abutment to seat the edge of a lamp base, and the product of said method. I

The manufacture of devices of the above character, such as incandescent electric lamps, in cludes the operation of uniting what is termed a stem or mount, including a glass flare tube, to the neck portion of a bulb. In addition to the sealing operation it is desirable to shape the united parts while still plastic so that when completing the lamp another part termed the base may more readily be applied and held in tired relation to the bulb.

Machines for performing a sealing-in opera-= tion have long been used in the lamp making industry and it has been the practice to rst prepare the assembled parts by slowly heating to a conditioning temperature. This preliminary heating was considered necessary before subjecting the parts to the hot sealing fires. The preheating step retarded the speed of manufacture, particularly in connection with machines which operated continuously to give the maximum speed in production.

Developments in the lamp industry, especially those relating to high-speed production, include machines which will function to perforn'il the required operations without the necessity of stopping for time-consuming operations. In machines as heretofore employed the conveyor which carried the lamp parts was indexed to pro= vide a given number of stationary periods and obviously the rate of production was determined and dependent on the time required to perform the longest operation.

In my Patent No. 2,132,538, dated October il, 1938, and owned by the assignee oi' the present application, a machine is shown for performing the operation of sealing the bulb after exhaust. Obviously such a machine, which operates continuously at relatively high speed, would lose a great deal of its value if the preceding operation of sealing-in failed to perform with the necessary rapidity.

As above mentioned, it was believed that bulbs required preheating before being passed to the sealing hres; whereas, in accordance with the present invention, no preheating is employed but the lamp parts, while cold or at room temperew ture, are inserted into the'high temperature seai-a ing fires. This is possible by reason of the present method of circulating air `or other gas into the bulb during the sealing operation'. The air which passes the bulb surface directly in contact with the res is slightly warmed and thebulbl immediately absorbs some heat from the air. es the temperature of the bulb is raised, the circulating `air'ciissipates or carries away suiiicient heat to prevent the formation of internal stresses in the glass which might result in cracks as would ordinarily be expected Whena'cold glassbody is subjected toal quick temperature change.

The present invention also includes the operation of forming or shaping the bulb neck to receive a base. The formationof the bulb neck is important and has been accomplished heretotore by molding members, such as shown in Patent No. 2,006,231, issued June 25, 19,35. This patent shows a bulb neck formed to receive a base but, as will be noted, the contour of the bulb neck in cross section is made with rounded surfaces. This iollows the practice of avoiding sharp lcorners although it is of great advantage to provide a straight or fiat shoulder to hold a base, particularly when usedv with what is termed a mechanical base, where the base is held mechanically instead of by cement.

The present invention provides molding means which is formed so as to furnish .the bulb neck with s. sharp or substantially right angle shoulder or annulus. to provide a at face or contact surface which cooperates with other mechanical means to hold a base against relative movement when attached to a bulb, neck. Although a sharp-cornered shoulder is contrary to previous teachings and practice, bulbs shaped in accordance with the present method were subjected to the usual tests, including the storage of lamps over a period of months, for the determination of developed cracks. It was found that the present method gave a satisfactory and commercial lamp free frominternal stress and an extremelylow percentage of cracked or leaky lamps.

It is, therefore, an object of the present invention to provide a simple and effective method for performing a high-speed sealing-in operation.

Another object of the invention is to provide a method which may be practiced using a continuously operating sealing-in machine.

A further object of the invention is to provide a method wherein a plurality of lamp parts, including a bulb, are directly positioned in a high temperature zone for a sealing-in operation without preheating.

A still further object of the invention is to provide a method for fusing a plurality of glass lamp parts together, and shaping the fused portion during the movement of the parts on a conveyor.

Another object of the invention is to provide a method of applying high temperature names to unheated lamp parts, and in performing ay sealing-in operation in the absence of detrimental strains or cracks.

A further object of the invention is to provide a lamp bulb having the neck portion thereof formed with a shoulder of substantially right `angular form in transverse cross section, free from detrimental stresses or cracks.

Other objects and advantages of the invention will be more clearly understood from the following description, together with the accompanying drawing in which:

Figs. 1 to 5, inclusive, show a bulb and stem in the various stages during the sealing-in and molding operations.

A machine constructed for practicing a method in accordance with the present invention comprises a conveyor rotated continuously at a given speed by means of a. motor as disclosed in my Patent No. 2,212,842, previously referred to. The conveyor carries heads or bulb holders 2B through a circular path and during a portiony of their movement with the conveyorthe heads are rotated relative to the conveyor.

The heads 2| are of similar construction and a. description of one will answer for all. Each head is provided with a rotatable manifold which in commotion with a bearing holds a hollow supporting shaft. Below the manifold, and constituting a part thereof, is a manifold extension secured to the supporting shaft by a lset screw.

Extending upwardly from the manifold are positioned a plurality of burners Il and l5l to -project flames I5' and II' as shown in lugs. 1 to 4, inclusive. These burners are mounted on stand pipes 'which communicate with es in thev manifold. The passages communicate with a channel in the manifold extension which-is stationary and is connected with ra gas or other combustible fluid supply pipe.

As the conveyor rotates, gas flows to the burners, as described in said parent Patent No. 2,212,842, and air is supplied to the head for other purposes to be presently explained. l

In the present embodiment of the invention the burners l5 and 5I rotate about the work part to be heated although it is to be understood that if desired a construction may be employed in which the work part maybe rotated and the burners held stationary. Y

'I'he work parts to be fused and united include abulb 15 and a stem or mount 1l. The bulb is so formed as to have a neck portion I1 and the mount includes a glass flare tube Il having a flared portion or flange 1l. One end of the flare tube is provided with a compressed portion or press 8| in which lead wires I2 and I3 are sealed. Extending from the press is an arbor Il `having support wires I0 to hold a filament IlV and extending downwardly from the press is an exhaust tube Il communicating with the bulb by` an orifice It'.

When sealing a lamp mount to a bulk the mount is held in vertical alignment with the longitudinal axis of the buib by means of the A exhaust tubewhich is inserted in a tubular receiver I9. This receiver is positioned in the upper end of a hollow shaft 9|. The receiver is arranged to extend above the shaft 9i and has a tapered mouth Ato receive the exhaust tube which is inserted into the receiver and the flange of the flare tube seats on the upper end 89' of the receiver.

The shaft il and the sleeve 91 are secured in fixed relation by a set screw 98 and constitute a stem support member movable as a unit longitudinally of the supporting shaft. The shaft Bi extends below the sleeve Il and is provided with an extended roller disposed in a cam track of a cam mountedvon a stationary bracket adjacent to the path of travel of the conveyor. The cam track is so formed that the roller is raised and lowered to reciprocate the stem support member for reasons tobe described later. The cam has an extension provided with a cam track to receive a rollerv at one end of an arm. The other end of the arm is fastened to a shaft of a valve for controlling vthe flow of air in passage 06.

In accordance with the present invention it is important, during the sealing operation, to provide a `circulation of air in the bulb before and during the application of heat to the bulb neck. During the sealing operation when the bulb neck has united with the flare tube and the glass is still plastic, the bulb wall is forced outwardly by air delivered through a passage |09 between shaft 9| and sleeve 91. This passage has its outlet at the top of the stem support but below the upper end B8 of the receiver 8l. Air is supplied to passage Il! and circulates within and around the bulb which is held in a support I I2.

'Ihere is a cap I Il which fits the upper'spherical` surface yof the bulb and serves to hold the bulb on its support during the sealing-in operation When 'the bulb is to be removed the cap III is lifted by air under pressure.

In accordance with the present invention the sealed portion of the bulb is shaped or molded to a definite form and for this purpose molding members lli and |22 are provided. When the neck portion or seal is shaped by the molding members the shaped portion is so formed that the stem is positioned in predetermined space relation to the wall of the bulb and the filament is disposed in a given position relative to the shaped seal. The molds are mounted on the outer ends of mold-arms. The opposite ends of the arms are secured adjacent to the upper ends of vertical shafts rotatable in bearings. 'Ihe shafts are provided with pinions secured thereto and. in mesh so that a rotation of one pinion with its shaft will cause an opposite movement of the other pinion, thus rocking the arms to bring the molds into molding relation.

The several sealing stepsor operations performed by the machine fully described and claimed in the parent patent, previously referred to, will be understood more clearly by reference to the drawing.

A stem or mount is fed to a head at one conyeyor position. and a bulb is fed to the head at the next position. The stem and bulb are thus positioned as shown in Fig. 1. This is an important feature of the present invention since it is of great advantage to provide mechanism for performing a sealing-in operation without moving a bulb from one fire setting to another.

Heretofore, as above mentioned, when a sealmount were first moved into, and retained for a time interval in a preheating zone which was employed to remove any strains or internal stress within the glass parts. The assembled parts were then moved to another heat zone for a fusing or sealing operation. Obviously this required a time period for preheating and a time period for fusing operation and essentially slowed up the machine.

In accordance with the present invention, the preheating operation is eliminated since the present method makes it possible to seal-in and mold or shape the bulb neck in one position. This is accomplished, as above mentioned, by circulating air in the bulb during the fusing operation. It has been found that by providing the passage |09 for the delivery of air to the bulb, this flow of air, which first passes the initially heated wall of the bulb, is heated and acts to carry away or dissipate heat and has an annealing effect so that the fires 55 and l0' may be of relatively high temperature and directed in full force against the neck of the bulb, as shown in Fig. 1. By virtue of having the maximum radius of the receiver 89 smaller than the distance of the passage |09 from the axis of the shaft 9| the longitudinal discharge of air along the initially heated wall or neck of the bulb is not interfered with. These fires soften the glass which contracts and fuses with the ange 18 closing the bottom of the bulb, as shown in Fig. 2.

The air issuing from the passage |09 is then directed against the inner fused wall of the bulb neck below the ange and causes the wall to bulge, as shown in Fig. 3, and thin down until the lower end or cullet |4| is separated from the bulb, as shown in Figi 4. The cullet when severed from the bulb drops onto a receiving platform or chute Mi. At ythis time the molds |2| and |22 are moved into close relation with the softened bulb neck. The fires 55 and 56' serve to keep the molds at an elevated temperature.

It will be noted that when the molds close about the bulb neck the lower end of the bulb is above the bottom thereof. At this time the shaft 9| is lowered bringing the upper end of the stem receiver or holder flush with the lower inner surface of the molds, and the upper end of the holder 80 serves as a portion of the bottom surface of the mold. Air is then supplied to the bulb through passage 90 and exerts sufficient force to press the softened glass against the bottom wall of the mold. The mold could be made so thatI the molten bulb neck would more completely fill the mold, but, owing to variations in the thickness of the flare tube, the molds are made so as to allow for this variation; Thus when the bulb neck has been blown into the mold, as shown in Fig. 5, the thickness of the wall may vary but the outside overall length will be controlled It has been found that good results may also be obtained by introducing air into the bulb for circulation through passage 90 to the orifice 88. The air thus delivered to the bulb flows around the wall and serves to transfer heat from the wail when the bulb is subjected to the not sealing fires and to prevent cracking. When the air is delivered through the exhaust tube, it is necessary to temporarily terminate this flow of air just prior to the union between the bulb and flare tube, and to provide a current of air through passage |09 to sever the lower portion or cullet |4|.

Heretofore in the molding of a bulb neck it has been the practice to carefully avoid any sharp corners; that is, all the corners were made of arcuate or rounded illlet form since it was believed that sharp bends or angular shoulders would subsequently cause cracks by reason of the strains set up in the glass. In lamp making, however, it is of great advantage to provide a sharply defined shoulder, especially in cases where itis necessary to have a close lit between a base and a bulb neck.

Ignoring prior teaching, the present invention provides a mold so formed that a bulb neck is shaped with a right-angle shoulder or abutment |42 and, by reason of the present method of sealing and shaping, the bulbs are found to be free from detrimental strains. Tests including the manufacture and storage of bulbs so made, clearly show that bulbs produced in accordance with the present invention are free from cracks, and resist the rough handling attending shipment as well as the lamps made heretofore, if not to a greater extent.

As shown in the drawing, the molds employed are shaped with ledges |45 so formed that the resultant formation of the bulb includes an annuN lar shoulder having a surface substantially transverse to the longitudinal axis of the bulb and substantially right angular in shape. Furthermore, the bulb neck is so formed as to provide a cylindrical plug or extension |46 with a relatively sharp edge |53. and adjacent to the abutment is formed a ring IIT which may be so proportioned as to snugly fit the inner surface of the unthreaded portion of a base which is usually in the form of a metal shell. Thus, when a base is positioned to surround the bulb neck it is ttted to the surface of the ring |41 and pressed against the seat or abutment |45. 'I'he extension I desirably corresponds with the minimum diameter of the base threads and flares outwardly on a curved surface to unite with the ring |41.

The hereinbafore mentioned advantages attributed to the special form of bulb neck have been directed to its use in connection with a base to be secured by mechanical means such as shown i and described in my Patent No. 2,119,681, dated June 7, 1938, and owned by the present assignee.

The abutment and sharp-comer formation is of great importance, however, in connection with.

plain tubular form or of threaded form, is fricn tionally fitted to the bulb neck and it has been found that when a basing cement is employed the quantity of cement necessary is relatively small and that a fraction of the amount ordinarily used serves to hold the base. It has also been found by providing the abutment and annular seat and by proportioning the lower end |53 of the extension of such diameter as to contact with the inner surface of the threaded portion of the base, when a threaded base is used, that'the base is held against lateral movement and the only duty of the cement is to prevent endwise movement of the base.

The structural arrangement of the bulb neck and base is such that very little strain is imposed on the cement and the base is prevented from rocking. As stated, a very thin layer of cement serves to hold the base against removal. This results in an economy of cement which is an important factor in connection with articles, such as incandescent electric lamps, produced in great quantities.

The present invention not only provides a new and improved sealing method, but a new article of Between the cylindrical plugy manufacture is produced in the form of a bulb neck adapted for use to hold a cemented base more firmly and constructed so as to cooperate with means for holding a base mechanically.

Although a preferred embodiment of the invention is shown and described herein, it is to be understood that modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. The method of sealing a bulb with a neck portion to a are tube which comprises creating a high temperature heat zone, assembling a bulb and are tube with the neck portion of said bulb surrounding an end of said flare tube, positioning said assembled parts with said neck portion in said heat zone, and blowing air between said neck portion and tube, along the inner surface of said neck portion, until the latter and said flare tube end are united by fusion.

2. The method of sealing a bulb having an elongated neck to the larger end of a flare tube which comprises assembling the bulb and tube ywith said larger end within said neck intermediate said bulb and the end of said neck, heating a portion of said neck adjacent to said larger end to fuse the latter to said neck, circulating air between said neck and tube and on into said bulb during the fusing period, and after sealing continuing the flow of air into said neck below the line of fusion to sever the cullet.

3. The method of sealing a bulb having an elongated neck portion to one end of a are tube which comprises assembling the bulb and tube with one end of said tube within said neck intermediate said bulb and the end of said neck portion, heating a portion of said neck adjacent to the end of said tube, at full sealing intensity,

to fuse said tube to said neck, and blowing air into the bulb between said neck portion and the end of said tube and on into the main portion of said bulb during the fusing period.

4. The method of sealing a bulb having an elongated neck portion to one end of a ilare tube which comprises assembling the bulb and tube with one end of said tube within said neck intermediate said bulb and the end of said neck portion, heating a portion of said neck adjacent to the end of said tube to fuse said tube to said neck, causing a flow of air between said neck portion and the end of said tube, and along the inner surface of the former, during the fusing period, and after sealing continuing the flow of air to sever the neck portion below the place of union to remove the cullet.

5. The method oi' uniting a mount having a flare tube to a bulb with main and neck portions comprising supporting said parts with the neck of the bulb surrounding the larger end of said nare tube, heating the neck to cause it to contract and seal to said larger end, and causing a iluid to pass into the bulb between said flare tube and neck, over the heated surface of said neck and circulate within the main portion of said bulb before and during the sealing operation.

6. 'I'he method of uniting a bulb with main and neck portions to a mount of an incandescent electric lamp having a flare tube, comprising supporting said parts with the neck portion oi said bulb surrounding the ilare tube oi' said mount and extending beyond said tube, heating said neck portion to seal it to said flare tube, circulating a fluid during the sealing operation by rst, directing said fluid between said tube and neck l admitting gas to the and then, after sealing, against'v the bulb neck below the seal portion, to sever the lower part o1' said neck portion, moving molding members about said seal while still plastic, and forcing a fluid under pressure into said bulb to shape said neck portion in said molding members.

7. 'I'he method of sealing bulbs having main and neck portions to nare tubes. comprising supporting a bulb with its neck portion surrounding one end of such a tube and extending there beyond, heating said neck portion around said tube, at full sealing intensity while the latter is cold, blowing gas between said neck portion and tube and on into the main portion of said bulb while heating until sealing takes place, terminating the flow of gas into the main portion of said bulb just prior to the union of the bulb and nare tube, and after sealing admitting gas to the neck below said union to remove the cullet therefrom.

8. The method of sealing bulbs having main and neck portions to iiare tubes, comprising supporting a bulb with its neck pox-tion surrounding one end of such a tube, heating the neck portion while blowing sin longitudinally between the tube and inner surface of the neck portion, and on into said bulb, sealing said neck portion to one end of said tube, continuing blowing of said air to sever the cullet below the seal portion. moving molds to clamp over the seal portion ot said neck, while soft, and introducing nuid under pressure to said bulb to cause the seal portion to expand and lill said molds.

9. The method of sealing bulbs having main and neck portions to flare tubes, comprising supporting a bulb with its neck portion surrounding one end of such a tube and extending therebeyond, heating said neck portion around said tube to seal it to one end thereof, blowing gas between said neck portion and tube and on into the main portion of said bulb while heating until sealing takes place, terminating the now of gas into said main portion .lust prior to the union of the neck portion and flare tube, after sealing neck portion below the union to remove the cullet therefrom. moving molds to clamp over the seal portion of said neck, said molds being formed with shoulders and inner surfaces, so as to form a shoulder on said neck portion and cause the part of said neck portion adjacent said eal to terminate in a cylindrical portion joined to said tube by an annular portion extending transverse to the longitudinal axis of the bulb, and whereby said cylindrical portion is joined to said shoulder by a ring portion, having a diameter intermediate that of the shoulder and cylindrical portion, and connected to the latter by a curved flaring portion, and admitting fluid pressure to said bulb to cause the seal portion to expand and nil said molds to accurately produce the shoulder, cylindrical, annular. ring, and curved rlaring portions.

10. The method of uniting a bulb with main and neck portions to s. mount of an incandescent electric lamp having a nare tube, comprising supporting said parts with the neck portion of said bulb surrounding the ilare tube of said mount and extending beyond said tube, heating said neck portion around said tube at full sealing intensity while the latter is cold to seal said neck portion to said tube, circulating a iluid during the sealing operation by first, directing it between portion, and on into the main portion of the bulb,

said tube and neck portion and on into the main portion of the bulb, and then after sealing. against the neck portion below the union, to sever the cullet therefrom, moving molding members about said union while still plastic, and forcing a uid under pressure into said bulb to shape the neck portion in said molding members.

1l. The method oi' sealing bulbs having main and neck portions to nare tubes, comprising supporting s bulb with its neck portion surrounding one end or such a tube and extending therebeyond, heating said neck portion to seal it to said tube, blowing gas between said neck portion and tube and on into the main portion ot said m

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