Forming tool for lamp bases

Abstract

A method of manufacturing a flash-free lamp base (10), wherein the lamp base (10) comprises a shell (14), an eyelet (16) and a glass, electrically insulating part (18) therebetween and joining the shell (14) and the eyelet (16), the shell and the eyelet being electrically conductive, the shell (14) having a tubular portion (14a) with an open end (14b) and a partially closed end (14c) defining a volume (14d) therebetween, the partially closed end (14c) including a tapered area (14e) terminating in a reentrant section (14f) that extends into the volume (14d) and defines an inner annulus (14g). The method of making the base comprises the steps of positioning the shell (14) and the eyelet (16) at a workstation (19) in spaced, axial alignment with one another defining a gap therebetween; actuating a first forming tool (20) through the tubular portion (14a) and into engagement with the tapered area (14e) and the inner annulus (14g); dispensing a quantity of molten glass (32) into the gap; and actuating a second forming tool (22) within the first forming tool (20) to form the molten glass (32) into an electrically insulating part (18) between the shell (14) and the eyelet (16). The base so formed is free from extraneous glass flashing and thereby provides a base less likely to contaminate the lamp manufacturing process.

Description

TECHNICAL FIELD

This invention relates generally to lamp bases and particularly to lamp bases that are free from glass flashing and to a method for making such lamp bases.

BACKGROUND ART

Lamp bases provide the support for internal lamp components and the electrical connection to those internal components. The usual lamp base associated with the common incandescent lamp, as well as other types of lamp, comprises two electrically conductive portions (a shell and an eyelet) joined by an electrically insulating portion of glass. The shell portion contains means for mating with a socket and, generally, this means comprises a series of threads.

For many years these lamp bases have been manufactured by an automated process whereby the shell and eyelet were positioned at a work station in a spaced apart manned and molten glass was inserted into the space between the shell and the eyelet. A forming tool was inserted into the shell to form the glass, leaving an aperture for a connecting wire to subsequently be inserted to make electrical connection to the eyelet. The shell was formed with an internal annulus about which the glass was adhered.

While this process has been used with great success, a problem has existed with excess glass being deposited within the shell and about the internal annulus. This excess glass is known as flashing and, during subsequent shipping of the bases to customers, the flashing, in the form of glass chips, can break off and cause later contamination in the lamp-making process.

DISCLOSURE OF INVENTION

It is, therefore, an object of the invention to obviate the disadvantages of the prior art.

It is another object of the invention to enhance lamp bases.

These objects are accomplished, in one aspect of the invention, by a base comprising: a first electrically conductive part, a second electrically conductive part and a glass, electrically insulating part therebetween and joining the first part and the second part, the improvement wherein: the first conductive part has a tubular portion with an open end and a partially closed end defining a volume therebetween, the partially closed end including a tapered area terminating in a reentrant section that extends into the volume and defines an inner annulus, the inner annulus being free from glass flashing whereby no glass particles inhabit the volume.

The base are manufactured by a method of manufacturing a flash-free lamp base wherein the lamp base comprises a first part, a second part, and a glass, electrically insulating part therebetween and joining the first part and the second part, the first part and the second part being electrically conductive, the first part having a tubular portion with an open end and a partially closed end defining a volume ltherebetween, the partially closed end including a tapered area terminating in a reentrant section that extends into the volume and defines an inner annulus, the steps comprising: positioning the first part and the second part at a workstation in spaced, axial alignment with one another defining a gap therebetween; actuating a first forming tool through the tubular portion and into engagement with the tapered area and the inner annulus; dispensing a quantity of molten glass into the gap and actuating a second forming tool within the first forming tool to form the molten glass into an electrically insulating part between the first part and the second part.

The employment of the dual forming tools insures that no excess glass is deposited internally of the shell, thereby obviating the condition caused by the breaking away of the unwanted and undesirable flashing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational, sectional view of a lamp that can utilize the invention;

FIG. 2 is an enlarged, sectional view of a prior art lamp base;

FIG. 3 is a similar view of a lamp base according to an aspect of the invention;

FIG. 4 is an elevational, sectional view of an apparatus for performing the invention;

FIG. 5 is an enlarged view of a portion of the apparatus; and

FIG. 6 is a flow chart of the method of performing the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.

Referring now to the drawings with greater particularity, there is shown in FIG. 1 an incandescent lamp 12 having a base 10 that comprises a shell 14, an eyelet 16 and a glass, electrically insulating part 18 therebetween and joining the shell 14 and the eyelet 16. The shell 14, and the eyelet 16, are electrically conductive, and can be formed from any suitable material, for example, aluminum or brass or a combination thereof, as is known.

In FIG. 2 there is shown a prior art lamp base 100 comprised of a shell 140, an eyelet 160 and a glass insulator 180 joining and electrically isolating the shell and the eyelet. The shell 140 has a tubular portion 140a with an open end 140b and a partially closed end 140c defining a volume 140d therebetween. The partially closed end 140c includes a tapered area 140e terminating in a reentrant section 140f that extends into the volume 140d and defines an inner annulus 140g. As shown in the drawing, this prior art lamp base had glass flashing 140h that accumulated in the reentrant section 140f during the manufacture of the base. This flashing is subject to breaking off during shipment of the bases into particles of glass called “fingernails” and these fingernails can find their way into subsequent lamp making processes and cause substantial down time for the lamp manufacturers.

The lamp base 10 shown in FIG. 3 obviates the problem of fingernails. Herein, the lamp base 10 comprises a shell 14, an eyelet 16 and a glass, electrically insulating part 18 therebetween and joining the shell and eyelet into a cohesive assembly. As noted previously, the shell and eyelet are electrically conductive

The shell 14 has a tubular portion 14a with an open end 14b and a closed end 14c defining a volume 14d therebetween. The partially closed end 14c includes a tapered area 14e terminating in a reentrant section 14f that extends into the volume 14d and defines an inner annulus 14g. The inner annulus 14g is free from glass flashing whereby no glass particles or “fingernails” inhabit the volume 14d.

Fabrication of the flash-free lamp base occurs by positioning the shell and eyelet at a workstation in spaced, axial alignment as shown in FIG. 4. Specifically, the shell 14 and the eyelet 16 are aligned along a vertical axis 30. A first forming tool 20 is actuated along the axis 30 through the tubular portion 14a into contact with the tapered area 14e and the inner annulus 14g of the shell 14.

A given quantity of molten glass 32 is dispensed into the space or gap between the shell 14 and the eyelet 16 and then a second forming tool 22 is actuated along the axis 30 and through the first forming tool 20 to contact and form the molten glass 32 into the desired configuration.

Since the first forming tool 20 has an inside surface 20a (see FIG. 5) that fits tightly against the inner annulus 14g of the shell 14, the molten glass is completely prohibited from entering the reentrant portion 14f. According, there is no flashing to break loose during transportation of the base to a lamp manufacturer and, subsequent processing of the lamp bases onto a lamp envelope proceeds without the danger of fingernails interrupting the smooth flow of the lamp making equipment.

While the invention has been described with reference to threaded lamp bases, it is applicable to other bases such as those designated as bayonet type bases. It is also applicable to all sizes of lamp bases, from candelabra to mogul.

While there have been shown and described what are present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.

Claims

1. In a base for a lamp, said base comprising: a shell, an eyelet and a glass, electrically insulating part therebetween and joining said shell and said eyelet being electrically conductive, the improvement wherein: said shell has a tubular portion with an open end and a partially closed end defining a volume therebetween, said partially closed end including a tapered area terminating in a reentrant section that extends into said volume and defines an inner annulus, said inner annulus being free from glass flashing whereby no glass particles inhabit said volume.

2. In a method of manufacturing a flash-free lamp base, wherein said lamp base comprises a shell, an eyelet and a glass, electrically insulating part therebetween and joining said shell and said eyelet, said shell and said eyelet being electrically conductive, said shell having a tubular portion with an open end and a partially closed end defining a volume therebetween, said partially closed end including a tapered area terminating in a reentrant section that extends into said volume and defines an inner annulus, the steps comprising: positioning said shell and said eyelet at a workstation in spaced, axial alignment with one another defining a gap therebetween; actuating a first forming tool through said tubular portion and into engagement with said tapered area and said inner annulus; dispensing a quantity of molten glass into said gap; and actuating a second forming tool within said first forming tool to form said molten glass into an electrically insulating part between said shell and said eyelet.