US3619702A

US3619702A - Miniature light bulb

Info

Publication number: US3619702A
Application number: US810762A
Authority: US
Inventors: Paul Albrecht
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-04-06
Filing date: 1969-03-26
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A miniature light bulb has a hollow cylindrical base into which the envelope of the bulb is inserted and from which a flat plug extends downwardly. The connecting wires of the bulb filament extend through the base to the plug to which they are mechanically and conductively secured.

Description

limited States atet [72] Inventor Paul Albrecht Bamherg, Germany [21] Appl. No. 810,762 [22] Filed Mar. 26,1969 [45] Patented Nov. 9, 1971 73] Assignee W. Albrecht-KG. Bamberg Bamberg, Germany [32] Priority Apr. 6, 1968 [33] Germany [31 A 29602 [54] MINIATURE LIGHT BULB 10 Claims, 7 Drawing Figs.

[52[ U.S.Cl 313/318, 339/144 R, 339/145 R [51 Int. Cl 1101,]5/48, H0 1 j 5/50 [50] FieldofSearch 313/318; 339/144, 145, 144 R, 145 R [56] References Cited UNITED STATES PATENTS 894,193 7/1908 Dean 339/144 Primary Examiner-David Schonberg Assistant Examiner-Toby H. Kusmer Attorney-Hane & Baxley ABSTRACT: A miniature light bulb has a hollow cylindrical base into which the envelope of the bulb is inserted and from which a flat plug extends downwardly. The connecting wires of the bulb filament extend through the base to the plug to which they are mechanically and conductively secured.

MINIATURE LIGHT BULB The invention relates to a miniature light bulb such as a light bulb with incandescent filament and more particularly to a light bulb with a flat base insertable into a correspondingly shaped bulb socket.

BACKGROUND Miniature light bulbs of the general kind above referred to are widely used as signal and indicating lights and more generally for illumination purposes, where the available space is limited, for instance, in radio and television sets, automobiles, boats, toys, etc.

Light bulbs with a flat base as now known are made of glass and the connecting wires for the filament of the bulb protrude from the base against which they are flattened without being secured thereto. It has been found that light bulbs with such loose connecting wires often do not make satisfactory contact when fitted into the bulb socket. The connecting wires tend to become laterally displaced so that one or both of the wires do not engage the terminal points of the socket. It is also technically difficult or even practically impossible to mass produce a flat base made of glass with tolerances close enough to assure an adequate pressure fit in the socket. Moreover, a flat glass base being rather delicate can be easily mechanically damaged so that the bulb must be discarded.

It is a broad object of the invention to provide a novel and improved miniature light bulb of the general kind above referred to which assures good contact connections, is safely held in its socket and not easily mechanically damaged.

A more specific object of the invention is to provide a novel and improved miniature light bulb of the general kind above referred to which can be economically produced by typical mass production techniques.

SUMMARY OF THE INVENTION The afore pointed out objects, features and advantages and other objects, features and advantages which will be pointed out hereinafter are obtained by providing a hollow cylindrical base made of a suitable plastic material. The upper part of the base receives the envelope of the bulb and the lower part mounts a flat plug. The connecting wires for the filament of the bulb are extended through the base mechanically and conductively secured on the end wall of the plug. A base made of plastic material can be produced in one operation and by typical mass production techniques with close tolerances so that the bulb is safely held in its socket thus assuring high quality contact. Moreover, the plastic base protects the bulb envelope, which is usually made of glass, so that the same is protected against breakage.

To maintain the wire ends in position and separated from each other, the invention provides that the plug of the bulb is divided by a partition wall into two mutually parallel and substantially equal branches. This partition wall also serves as a further guide of the light bulb and in particular of its plug in the socket into which the bulb is to be inserted.

According to a further aspect of the invention, the connecting wires extend beyond the lower end of the plug so that the bulb can be connected to a circuit, for instance, by soldering or welding without requiring the use of a socket.

In order to make the miniature bulb also useful for connection to printed circuit boards, the invention provides that the flat plug of the bulb includes bores or lengthwise grooves for accommodating the connecting wires. A pole element is fitted into each groove or bore at the bottom end of the plug and connected to the wires. Such pole elements can then be inserted into the conventional contact eyelets of the printed circuit board and soldered in position together with other circuit components connected to the printed circuit board.

A particularly advantageous embodiment of the invention is to fit upon each of the two branches of the plug a contact sleeve of generally U-shaped cross section, the sleeves encompassing the branches on three sides and also the bottom ends thereof. It has been found that such contact sleeves assure a particularly high contact quality when the bulb is inserted into its socket. Moreover, the sleeves prevent displacement of the wires and protect the same against damage. -To facilitate insertion of the bulb into its socket the contact sleeves may be tapered toward the bottom ends thereof.

Retention of a bulb in its socket may be further improved by providing in the side walls of each contact sleeve a cutout which is engageable with a spring in the socket. The edges in the contact elements defining the cutouts may be readily made with sharp comers so that the springs are safely retained in the cutouts. In contradistinction thereto it is technically very difficult to form sharp comer edges at recesses in a glass base. The comers in such base are usually rounded and hence are not capable of locating springs as well as sharp comers.

The invention further provides that the connecting wires are secured on the bottom side of the contact sleeves, for instance, by soldering or welding. This has the advantage that the soldering or welding points do not come in frictional sliding engagement with the inner walls of the socket when a bulb is inserted into the socket. Accordingly, the terminal points of the bulb are not likely to be damaged and are also not likely to accumulate dirt.

If the bulb is to be used for illumination purposes, its envelope is preferably so arranged that it partly protrudes from the top of the hollow cylindrical base. I

If it is desired to maintain the overall dimensions of the lamp as small as possible, the invention provides that the envelope is inserted within the base so that it does not protrude therefrom. Accordingly, light will emanate from the bulb in the form of a beam and in the direction of the lengthwise axis of the bulb.

Signal or indicating lamps are often required to produce a colored light such as a red or green light to indicate specific circuit conditions. This can be easily accomplished by covering the top end of the base with a colored translucent cover. This cover is preferably detachably mounted so that differently tinted covers can be readily used.

Other objects, features and advantages will be pointed out hereinafter and set forth in the appended claims constituting part of the application.

In the accompanying drawing several preferred embodiments of the invention are shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is an elevational side view of a miniature light bulb according to the invention,

FIG. 2 is an elevational view of the bulb taken in the direction of arrow ll of FIG. 1,

FIG. 3 is a section taken on line IIIIII of FIG. 2,

FIG. 4 is an elevational view similar to FIG. 1 of a modification of the light bulb,

FIG. 5 is an elevational view similar to FIG. I of another modification of the light bulb,

FIG. 6 is an elevational view similar to FIG. 1 of still another modification of the light bulb; and

FIG. 7 is a section similar to the section of FIG. 3 but showing a modification of the bulb base.

Referring now to the figures more in detail, the light bulb comprises a sealed and evacuated envelope 1 in which a filament 17 such as an incandescent filament is mounted in a conventional fashion. The envelope is fitted in an upper portion 2 of a hollow cylindrical base 3 made of a suitable plastic material such as polyvinylchloride. According to FIGS. I to S the envelope protrudes from the base and according to FIG. 6 the envelope 1 is fully concealed within its base.

Base 3 has at its lower end a flat or pinched plug 4 the end 5 of which is preferably tapered to facilitate the insertion of the bulb into a socket (not shown). A partition wall 6 divides the base into two preferably substantially equal branches 8. The partition wall is preferably also tapered at its end 7 and protrudes sidewise and endwise from the plug. Each branch 8 includes lengthwise bores 9 as is shown in FIG. 3 or grooves 16 in one of its sidewalls as shown in FIG. 7.

Claims

1. A miniature light bulb with pinched plug insertable into a bulb socket, said bulb comprising: a closed envelope including a filament; a base made of synthetic plastic material and having a hollow cylindrical upper portion and a lower portion, said upper portion encompassing said envelope portion and said lower portion constituting a plug having a substantially rectangular cross section; a pair of lead-in wires connected at one end to the filament, the other ends of the wires protruding from the envelope, and terminal strips having a channeled cross section, the web of each of said strips abutting against opposite sides of the plug and the branches of the strips straddling the sides of the plug adjacent to said opposite sides, said lead-in wires being mechanically and conductively secured to said terminal strips.

2. The bulb according to claim 1 wherein said webs of the terminal strips rest against the short sides of the plug and are extended and bent off to overlie parts of the end wall of the plug also.

3. The bulb according to claim 1 whErein said lead-in wires extend along the length of the plug and are secured to inside surfaces of the terminal strips.

4. The bulb according to claim 1 wherein a lengthwise rib protrudes from each of said adjacent sides of the bulb and is interposed between the facing edges of the branches of the terminal strips.

5. The bulb according to claim 1 wherein part of said envelope protrudes above the cylindrical portion of said base.

6. The bulb according to claim 1 wherein said envelope is fully concealed within the cylindrical portion of said base.

7. The bulb according to claim 6 wherein a translucent cover closes the upper end of said cylindrical portion of the base.

8. The bulb according to claim 1 wherein said plug includes lengthwise openings, and wherein pole elements are secured to the end wall of the plug, said lead-in wires extending through said openings and being connected to said pole elements.

9. The bulb according to claim 1 wherein said plug has lengthwise grooves in two of its sidewalls, and wherein pole elements are secured to the end wall of the plug, said lead-in wires being disposed within said grooves and connected to said pole elements.

10. The bulb according to claim 1 wherein said plug and the terminal strips thereon are tapered toward the lower end thereof.