Halogen Filament Lamp Having Stabile Filament Supporting Means

Abstract

A halogen filament lamp comprising an envelope having a pinch seal at one end and two series-arranged filaments within the envelope coupled by a brace having at least end portions formed as mandrils which are screwed into the ends of the filaments remote from the pinch seal. The brace is fastened to a supporting wire projecting from the pinch seal.

Parent Case Text

This is a continuation, division, of application Ser. No. 12,780, filed Feb. 19, 1970 now abandoned.

Description

The invention relates to an electric filament lamp, in particular a halogen filament lamp, which comprises a tubular lamp vessel having on at least one end a pinch seal with current conductors incorporated therein, two series-arranged filaments being stretched in the longitudinal direction of the lamp vessel, said filaments being connected electrically at their one end to the above-mentioned current conductors in the pinch seal and being coupled at their ends most remote from said pinch seal, said coupling being supported, at a place situated between said ends, by a supporting wire secured in the lamp vessel. Such an electric filament lamp is known.

In the known filament lamp the series-arranged filaments are formed by a single filament having two coiled parts with an intermediate stretched part. The intermediate part is freely supported by a supporting wire sealed in the pinch seal for securing the conductors for the filament.

The drawback of the known electric filament lamp constructed as a halogen filament lamp for copying purposes is that the intermediate stretched part is secured to the supporting wire in such manner that said part, after mounting to the supporting wire, has a large freedom of movement in a direction at right angles to the longitudinal direction of the tubular lamp vessel. Although the filament can consequently be connected in a very rigid manner to the conductors in the pinch seal, the coiled coil parts nevertheless do not assume a significantly prescribed position in the lamp vessel.

It is the object of the invention to provide a lamp construction in which said drawback is mitigated.

For that purpose, the electric filament lamp according to the invention, in which the series-arranged filaments are stretched in a particularly stable manner in the lamp vessel in the longitudinal direction of the lamp vessel, is characterized in that the coupling of the said ends is formed by a brace at least the end portions of which are formed as a mandril and are screwed in the relative ends of the coil of the filaments remote from the pinch seal, said brace being supported in or immediately near the centre of its length. So in this lamp a connection brace is used which is connected to the two coiled filaments as a separate coupling member. This coupling member is constructed at least at its ends, but preferably entirely, as a mandril which is screwed with either of its ends over some distance in an associated filament. As a mandril which is known per se is to be considered a conventional mandril which is provided with wire wound helically thereon, in which the material may be chosen to be tungsten or molybdenum.

By using such a mandril the manufacture of which presents few difficulties, the possibility is presented of starting from two straight filament coils and a coupling member which is likewise of a simple shape and which may have, for example, a U or V-shape. By screwing said filaments and the coupling member together which takes place prior to providing the pinch seal, the ends of the filaments remote from the pinch seal are oriented stabler in the lamp vessel than in the known lamp construction.

In order to obtain an even stabler stretching of the filaments it is of advantage to weld the brace in question to the supporting wire which is preferably incorporated in said pinch seal to which the filaments are connected. When the brace is connected in such manner, even a rotation of the brace relative to the pinch in a plane at right angles to the lamp axis is substantially entirely avoided. When a mechanical shock is exerted on the lamp, a movement of the two axially stretched filaments is considerably eliminated. This prolongs the lifetime of the lamp.

According to an embodiment of the filament lamp according to the invention, said brace comprises in or near the centre of its length a loop and the hook-shaped bent end of the supporting wire extends in said loop and keeps the brace at some distance from the pinch seal; said loop is preferably formed by at least three turns which comprise a common winding axis, said wires being secured to the supporting wire with the exception of the most remote turns, preferably by a spot welding operation. The common axis of the turns of said loop is then preferably directed axially in the lamp vessel and one of the limbs of the hook-shaped bent end of the supporting wire extends according to said axis. Both by supporting the brace by the hook-shaped part of the supporting wire and securing the loop to the said supporting wire, the additional advantage is obtained that, should the connection in a finished lamp be interrupted by some cause or other, the brace cannot immediately detach from the supporting wire. The lamp as such will remain useful in that case also.

In a further embodiment of the lamp according to the invention the supporting wire extends at least over a distance corresponding to the length of the filament axially in the lamp at a distance beyond the space present between the filaments. It has been found that with such an arrangement this part of the filament reaches a less high temperature, and furthermore influences the light radiation of the filaments more favourably than when said part of the filament would be arranged just between the two axially extending filaments.

In order that the invention may be readily carried into effect, one embodiment thereof will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which:

FIGS. 1 and 2 are two longitudinal cross-sectional views of the lamp according to the invention, in which

FIG. 1 is a cross-sectional view taken on the line I--I of FIG. 2, and

FIG. 2 is a cross-sectional view taken on the line II--II of FIG. 1.

The lamp shown is a halogen filament lamp destined for copying purposes. It comprises a tubular lamp vessel 1 which is sealed at one end by a flat pinch seal 3. At its other end said lamp vessel is closed by a sealed exhaust tube 5. The lamp is filled with a gas filling which is commonly used for halogen filament lamps and which will not be described in detail.

Two conductors 7 and 9 are incorporated in the pinch seal 3 and are secured to foils 11 and 13 to which current wires 15 and 17 entering the lamp vessel are secured. These connections are incorporated in the seal 3 in a gas-tight manner.

The pinch seal 3 furthermore comprises a supporting wire 19 which is enclosed with its free end in the space resulting from sealing the exhaust tube 5. A quartz glass beam 21 is secured to the supporting member. This beam is provided by fusing two halves 23, 25 to one assembly with the interposition of two mandrils 27 and 29 and the supporting wire 19. The mandrils 27 and 29 are formed from the metal wires 15 and 17 which are would helically with another wire.

The mandrils 27 and 29 are screwed in the ends of the coiled coil filaments 31 and 35. Another mandril 37 constructed in a similar manner to the mandril 27 or 29, is formed as a U-shaped brace in which a loop 39 constituted by three turns is provided. The ends of this brace are screwed in the filaments 31 and 35. The supporting wire 19 furthermore has a bent variation as is shown in FIG. 2. The part 41 of this supporting wire extends laterally of the members 31 and 35 axially in the lamp. An angular bent part adjoins this part 41 and has a horizontal limb 43 and a vertical limb 45 which is threaded through the loop 39.

So in this lamp construction the support of the two series-arranged coiled coil filaments is effected by a common brace which is held in place by the limb 45 of the supporting wire 19. Furthermore the loop 39 is welded to the said limb 45 at its three turns 47, 49, 51. It should be ensured that the most remote turns 47 and 51 of the loop 39 are not welded to the limb 45. Actually it has been found that this furthers the resilience of the overall loop connection when an external shock is exerted on the lamp.

Assembling the lamp is carried out as follows: first the filaments 31 and 35 are screwed on the two ends of the mandril 37. If desirable, though not strictly necessary, the connections may be spot-welded. The mandrils 27 and 29 are then screwed in the filaments 31 and 35. The resulting assembly and a supporting wire 19 are then united in a jig (not shown) by a quartz block obtained in the above described manner. Finally, in another jig (lkewise not shown) the assemblies 11,7 and 13,9 are secured. The brace 37 is then moved axially and the filaments 31 and 35 are stretched so that the loop 39 can be moved over the free end of the limb 45. The loop 39 is then secured to the supporting wire 19 by spot welding.

A quartz tube which is open at both ends is then placed over said assembly, which tube is deformed to a conventional pinch seal 3 after local heating to softening and by means of pinching memebers.

The quartz tube which is still open at one end is then rinsed via its previously provided exhaust tube 53 (shown in broken lines in FIG. 1) filled with a suitable gas filling, and sealed.

In the filament lamp described, the choice of the materials of the conductors 7,9, foils 11, 13, mandrils 27 and 29, filaments 31, 35 and brace 37 constructed as a mandril and the supporting wire 37 has not been further mentioned. This choice does not differ from that which is conventional in halogen filament lamps.

Claims

What is claimed is:

1. An electric filament lamp comprising: an evacuated tubular envelope having a pinch seal on at least one end; a halogen atmosphere within said evelope; current conductors embedded within one pinch end; two series-arranged filaments stretched parallel to each other in the longitudinal direction within said envelope, said filaments being electrically connected to said current conductor at ends proximate to said pinch seal; a brace within said envelope and electrically connected to said filament ends remote from said pinch seal, at least the end portions of said brace being formed as mandrils which are screwed into respective ends of said filaments, the brace and filament ends making mechanical contact in a direction substantially parallel to the longitudinal direction of said envelope, said brace including a central loop portion having at least three

in the longitudinal direction of said envelope turns having a common winding axis; and a supporting wire within said envelope and embedded in said pinch seal, said supporting wire having a substantially hook-shaped bent end extending into said loop portion to maintain the brace at a distance from the pinch seal, said turns of the loop portion except those most remote from one another being secured to said supporting wire.

2. An electric filament lamp as claimed in claim 1 wherein said supporting wire extends axially in the lamp at least over a distance corresponding to the length of said filament at a distance beyond the space present between said filaments.