GB2089563A

GB2089563A - Electric Incandescent Lamp

Info

Publication number: GB2089563A
Application number: GB8137475A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1980-12-16
Filing date: 1981-12-11
Publication date: 1982-06-23
Also published as: BE891472A; JPS57124846A; CA1169471A; NL8006801A; FR2496339B1; GB2089563B; FR2496339A1; DE3148822A1

Abstract

An electric incandescent lamp has a lamp envelope 1 the pinch 2 of which extends into a recess 10 of an insulating body 7 and is secured to body 7 by means of cement 11. The insulating body 7 forms part of a lamp cap 6. On the surface 15 of the pinch a projection 12 is present which determines the depth to which the pinch 2 extends in the recess 10 of the insulating member 7. <IMAGE>

Description

SPECIFICATION Electric Incandescent Lamp The invention relates to an electric incandescent lamp having a glass lamp envelope which comprises a pinch, in which lamp envelope a filament is accommodated, connected to current supply conductors which emanate in a vacuum-tight manner through the pinch and which are connected to the contacts of a lamp cap which consists for the greater part of an electrically-insulating body, the pinch of the lamp envelope extending in a recess in the insulating body and being secured therein by means of a cement. Such a lamp in which the insulating member is a ceramic body is known from Netherlands Patent Application 6717374 and may be used as a projection lamp, a studio lamp, or a theatre lamp.

In all cases in which a lamp is used in an optical system, the filament should be aligned with respect to the lamp cap so that, when the lamp is placed in a lamp holder of an optical system, the filament occupies a previously determined position in said system.

Lamps for the above-mentioned application often consume a high power and emit light of a high colour temperature. The resulting high pinch temperature necessitate the use of a lamp cap having an insulating member of ceramic or of a synthetic resin which can withstand high temperatures, up to approximately 4000 C, and necessitate the use of a cement for the connection of the lamp cap to the lamp envelope.

The curing of cement requires a comparatively long time. In that time, the lamp envelope and the lamp cap should remain fixed and aligned so as to prevent any displacement of the filament relative to the lamp cap. This involves a prolonged occupation of the alignment apparatus and increases the cost of the lamp.

It is the object of the invention to provide a lamp construction which enables the cement which connects the lamp cap to the lamp envelope to be cured outside an alignment apparatus.

According to the invention this object is achieved in a lamp of the kind mentioned in the opening paragraph in that at least one projection which determines the depth to which the pinch extends into the recess in the insulating member of the lamp cap is present on the surface of the pinch.

In manufacturing lamps, the filament can be positioned in the lamp envelope with great accuracy at a given distance from a reference on the pinch. By constructing the reference on the pinch as one or more projections on the surface of the pinch and proportioning said projections so that when lamp cap and lamp envelope are united the projection(s) cannot penetrate into the recess or cannot penetrate into the recess in the insulating member of the lamp cap further than a previously determined amount, the distance from the filament to the lamp cap is fixed in the lamp according to the invention. This distance, the socalled light centre length, is the most important parameter of the position of the filament.

The construction of the lamp according to the invention makes it possible to cure the cement which secures the lamp envelope and the lamp cap together without an alignment apparatus being kept occupied during the curing period. In lamps in which the centre of gravity of the lamp envelope is situated near the lamp cap and a stable support of the lamp envelope by the projections on the pinch surface is ensured, it is even not necessary to use mechanical auxiliary means, such as a lamp or a jig, to fix the lamp envelope relative to the lamp cap during curing.

In an embodiment of the lamp according to the invention, a projection is present on the pinch surface on each of the two oppositely-located wider side faces of the pinch. In a modified embodiment, two or more projections are present on each of these two side faces. In this modified embodiment the lamp envelope during the manufacture of the lamp has a particularly stable position with respect to the lamp cap.

The projections on the pinch surface may bear against the insulating member itself laterally of the recess therein. Another possibility is that the recess in the insulating body is covered for the greater part by means of a glass, ceramic, synthetic resin or metal disc which has an aperture through which the pinch of the lamp envelope can only be passed up to the projection(s). In this embodiment commerciallyavailable lamp caps may be used which are destined to be united with a lamp envelope in a conventional manner so as to form a finished lamp.

The lamp according to the invention has the advantage that the afore-mentioned disc or the boundary of the recess in the insulating member forms a supporting surface for the cement which joins the lamp envelope to the lamp cap. In conventional lamps the recess in the lamp cap, after the pinch of the lamp envelope has been placed therein, is filled with sand so as to form a supporting surface for the cement and to prevent that a lot of cement is used. In the lamp according to the invention the use of sand is superfluous, as will become apparent hereinafter.

The lamp according to the invention may have a lamp cap for use in an Edison or bayonet lamp holder, or in a lamp holder of a different shape, for example, with one or more sockets. Due to the high colour temperature, the high yield and to the luminous efficiency of halogen incandescent lamps which remains the same during the lifetime, the lamp according to the invention may comprise halogen in addition to inert gas, and may hence have a lamp envelope of a type of glass having a high silicon dioxide content, for example, of 95% by weight or more, for example, quartz glass.

Embodiments of the lamp according to the invention are shown in the drawing. In the drawing Figure 1 and Figure 2 are a front elevation and side elevation, respectively, of a first embodiment, Figure 1 being a partial sectional view of the lamp cap; Figure 2a is a plan view of a component of that embodiment; Figure 3 is a front elevation of a second embodiment; Figure 4 is a sectional view taken on the line IV--IV of Figure 3; and Figure 5 is a analogous sectional view of a third embodiment.

In Figures 1 and 2 the lamp envelope 1 has a pinch 2 and a filament 3 which is connected to current supply conductors 4 and 5 which emanate in a vacuum-tight manner through the pinch 2 and are connected there to the contacts 8 and 9 of a lamp cap 6 consisting for the greater part of a ceramic body 7 of steatite. The contact 8 is previously secured to the body 7 by means of cement 1 6. The ceramic body has a recess 10 in which the pinch 2 of the lamp envelope 1 extends. At its surface, on the wider side faces 15, the pinch 2 has two pairs of projections 12 which determine the depth to which the pinch 2 extends in the recess 10 of the ceramic body 7. In this embodiment a metal disc 13 is provided which bears on an edge 14. The projections 12 bear on the disc 13. The lamp envelope 1 is connected to the lamp cap 6 by means of cement 11.Upon assembling the lamp, the stability of the lamp envelope 1 in the lamp cap 6 is still increased in that the current conductor 4 extends through the bottom of the lamp cap 6 at the area where the contact 9 is to be produced. The disc 1 3 substantially covers the recess 10 so that a supporting surface is presented for the cement mass 11 which is soft when being provided, and sagging away of said mass into the recess 10 is prevented. The aperature 1 7 in the disc 13 (Figure 2a) only allows the pinch 2 to be passed therethrough only up to the projections 13.

The reference numerals in Figure 3 and Figure 4 are 20 higher than those for corresponding components of the lamp of Figure 1 and Figure 2.

In these Figures, the contacts of the lamp cap 26 are plug pins 28 and 29. The recess 30 in the ceramic body 27 is proportioned so that the pinch 22 fits therein with a small amount of play. The projections 32 on the surface of the pinch 22, however, bear on the edge 34. In this embodiment the projections 32 are ribs which each extend over the whole width of the relevant wider face 35 of the pinch 22 on which they are present. The lamp shown in 220V 1,000W theatre lamp having during operation a pinch temperature of 4000C and a colour temperature of 3,000K.

In Figure 5 the pinch 42 has a projection 52 on only one wider side face 55. The remaining reference numerals are 20 higher than those of corresponding parts in Figure 4.

Claims

1. An electric incandescent lamp having a glass lamp envelope which comprises a pinch, in which lamp envelope a filament is accommodated, connected to current supply conductors which emanate in a vacuum-tight manner through the pinch and which are connected to the contacts of a lamp cap which consists for the greater part of an electrically-insulating body, the pinch of whe lamp envelope extending in a recess in the insulating body and being secured therein by means of a cement, characterized in that at least one projection which determines the depth with which the pinch extends into the recess in the insulating member of the lamp cap is present on the surface of the pinch of the lamp envelope.

2. An electric incandescent lamp as claimed in Claim 1, characterized in that the recess in the insulating body is covered for the greater part with a disc having an aperture through which the pinch of the lamp envelope can only be passed up to the projection.

3. An electric incandescent lamp substantially as herein described with reference to Figures 1 and 2, to Figures 3 and 4, or to Figure 5, of the accompanying drawings.