US3221202A

US3221202A - Electric incandescent lamps

Info

Publication number: US3221202A
Application number: US176199A
Authority: US
Inventors: Mclintic William James
Original assignee: Thorn Electrical Industries Ltd
Current assignee: EMI Group Ltd
Priority date: 1962-02-28
Filing date: 1962-02-28
Publication date: 1965-11-30
Anticipated expiration: 1982-11-30

Description

Nov. 30, 1965 w. J. M LINTIC 3,221,202

ELECTRIC INCANDESCENT LAMPS Filed Feb. 28. 1962 WiLLlAM JAMES ML|NTIC INVENTOR.

ATTORNEY United States Patent 3,221,202 ELECTRIC INCANDESCENT LAMPS William James McLintic, London, England, assignor to Thorn Electrical Industries Limited, London, England, a British company Filed Feb. 28, 1962, Ser. No. 176,199 7 Claims. (Cl. 313-271) intervals where the wire is opened out or stretched out to be more or less straight. The continuously wound filament is in some respects more convenient and more economical, both in coiling and in the subsequent shaping or forming.

In the construction of a projection lamp with a continuously wound filament a grid of closely-spaced parallel filament sections is formed by bending the filament into a zig-zag arrangement, for example with alternate sec tions lying behind and between the adjacent sections to present a substantially unbroken illuminated area, this form being known as the biplane construction. At each bend in the filament one turn of the coil forms a loop by means of which the grid is supported.

In use the filament is heated to a temperature near its melting point and tends to unwind or twist to relieve strains set up during its winding. Particularly at the ends of the filament, which are normally rigidly fixed, this tends to cause distortion or squirming of the filament sections and in view of the close spacing of the sections this squirming produces a risk of short-circuiting of the end sections of the filament and of the setting up of arcs.

It is an object of the present invention to provide a filament mounting which will substantially reduce squirmmg.

In accordance with the invention there is provided an electric incandescent lamp having a grid of closelyspaced filament sections formed from a single continuously-wound coil filament, in which the end sections of the grid are straight, the ends of the filament are in line with the straight end sections, and the ends are plugged with a threaded plug, whereby twisting of the filament coil on heating is accommodated by a screwing movement over the plug.

The threaded plug may be formed by a core wire overwound with finer wire to give the effect of a thread.

One embodiment of the invention will now be described by Way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a general view of a projection lamp in accordance with the invention, and

FIG. 2 is a detail of the filament and its mounting.

The lamp is of conventional form, having a generally cylindrical glass envelope 10 mounted on a screw base 11. Within the envelope 10 a glass press 12

supports pillars

13 and 14 of stout wire which serve as supports for the filament assembly and also as leads for conveying current to the filament. An upper insulating bar 15 is attached to the

pillars

13 and 14 by brackets 16 and a lower insulating bar 17 is attached to the

pillars

13 and 14 by brackets 18. The upper insulating bar 15 supports a plurality of upper hooked supports 19 which are spaced apart and insulated from one another. The lower insulating bar 17 similarly supports a plurality of lower hooked supports 20.

ice

The tungsten filament 21 consists of a single continuously-wound length bent into a zig-zag formation between the hooked supports 19 and 20 (FIG. 2) with one turn of the coil forming a loop, such as 22, at each bend for attachment to the hooked support. The filament sections 23 extending between a lower and an upper hooked support are closely spaced, with alternate sections lying behind and between the adjacent sections, in the known biplanar formation, so as to present a substantially unbroken light source area.

The

end filament sections

24 and 25 of the grid are straight and are parallel to and equal in length to the adjacent filament sections 23. The ends 26 and 27 of the filament 21 are in line with the

straight end sections

24 and 25, respectively, of the grid and are mounted on threaded

plugs

28 and 29, respectively.

The threaded plug 28 is formed by a core wire 30 of refractory material such as tungsten or molybdenum overwound with finer Wire 31 to give the effect of a thread. It fills the Whole length of the end 26 of the filament up to the beginning of the end filament section 24. The end 26 of the filament 21 has been cut away in thedrawing to show the engagement of the turns of the filament with the turns of the thread formed by the fine wire 31.

The threaded plug 29 for the end 27 of the filament 21 is of similar construction.

The

plugs

28 and 29 are bent outwards towards the

pillars

13 and 14 at a point beyond the

ends

26 and 27 of the filament. They are then spotwelded to

pillars

13 and 14 respectively and serve for the supply of current to the filament 21.

When the filament is raised to its operating temperature it tends to twist to relieve residual strains resulting from its Winding. This twisting in the end sections of the grid is accommodated by a screwing movement of the end of the filament over the threaded plug and the end section of the filament is thus maintained straight, squirming being avoided. Expansion of the coil due to rise in temperature facilitates this movement. To a lesser extent relief is also accorded to the interior sections 23, which would otherwise be affected by movement of

sections

24 and 25 when these are rigidly fixed in the conventional manner.

In an alternative construction the end filament sections of the grid are inclined away from the adjacent sections but the plugged ends are still kept in line with the respective end sections.

I claim:

1. An electric incandescent lamp comprising a base, a light-transmitting envelope mounted on said base, support means disposed within said envelope, a single continuously-wound coil filament mounted on said support means to form a grid of closely-spaced filament sections, said grid having straight end sections, all of said filament sections including said straight end sections being of equal length, and the ends of said filament having substantially the same pitch Winding as the adjoining end sections of the filament in line with said straight end sections, and a threaded plug forming part of said support means and plugging said ends of the filament, whereby twisting of the filament coil on heating is accommodated by a screwing movement over the plug.

2. A lamp as claimed in claim 1 in which the threaded plug is composed of a core wire overwound with finer wire to form the thread.

3. A lamp as claimed in claim 1 in which the end sections of the grid are inclined away from the adjacent filament sections.

4. A lamp as claimed in claim 1 in which the grid is of zig-zag formation, each pair of adjacent filament sections being joined by a single turn of the filament forming a loop attaching the filament to said support means.

5. A lamp as claimed in claim 4 in which alternate filament sections lie behind and between the adjacent sections.

6. A lamp as claimed in claim 4 in which said support means include upper and lower sets of hooked supports for said loops. 1

7. An electric incandescentlamp comprising a base, a sealed light-transmitting envelope, conductive pillars mounted in said base and extehdirig within said envelope, upper and lower insulatingbai's' attached to and extending between said pillars, upper and lower sets of hooked supports carried respectively by said upper and lower insulating bars, a single continuously-wound filament ar,-

ranged to form a zig-zag grid of closely-spaced filament sections joined by single turns of the filament engaged over said hooked supports, said grid having straight end, j

sections, all of said filament sections including said straigh end sections being of equal length, and the ends of said,

filament having substantially the same pitch winding as the adjoining end sections of the filament in line with said straight end sections, and a threaded plug in electrically-conductive attachment with said pillars plugging said ends of the filament, whereby said filament can turn without squirming on said plug when heated during operation of the lamp.

References Cited by the Examiner UNITED STATES PATENTS 1,292,482 1/1919 Keyes 313-315 2,134,574 10/1938 Pinkle 313315 2,404,992 7/ 1946 Stone 313271 2,449,679 9/ 1948 Van Horn 313271 2,523,033 9/1950 Leighton 3 l3278 5 2,605,440 7/1952 Gero 4 313273 X 2,950,413 8/1960 Jayneet a1 313-113 X DAVID J. Primary Examiner.

JJIIAMES D. Examiner.

Claims

1. AN ELECTRIC INCANDESCENT LAMP COMPRISING A BASE, A LIGHT-TRANSMITTING ENVELOPE MOUNTED ON SAID BASE, SUPPORT MEANS DISPOSED WITHIN SAID ENVELOPE, A SINGLE CONTINUOUSLY-WOUND COIL FILAMENT MOUNTED ON SAID SUPPORT MEANS TO FORM A GRID OF CLOSELY-SPACED FILAMENT SECTIONS, SAID GRID HAVING STRAIGHT END SECTIONS, ALL OF SAID FILAMENT SECTIONS INCLUDING SAID STRAIGHT END SECTIONS BEING OF EQUAL LENGTH, AND THE ENDS OF SAID FILAMENT HAVING SUBSTANTIALLY THE SAME PITCH WINDING AS THE ADJOINING END SECTIONS OF THE FILAMENT IN LINE WITH SAID STRAIGHT END SECTIONS, AND A THREADED PLUG FORMING PART OF SAID SUPPORT MEANS AND