LAMPHOLDER FOR AN ELECTRIC LAMP

Lampholder for an electric lamp.

The invention relates to a lampholder for an electric lamp which comprises: a housing which defines a lamp cavity having a lamp entrance; contact members for supplying electric energy to a lamp after its insertion into the lampholder; an electric cable entering an end portion of the housing opposite to the lamp entrance and electrically connected to the contact members; and a resilient sealing member for sealing the housing around the electric cable.

Such a lamp holder is known from German Utility Model J 548 (25-02-

50).

The known lampholder has screwthread at the outside of the housing with which a nut cooperates in order to exsert pressure to an O-ring which is used as the resilient sealing member to seal the housing around the cable. When the lampholder is assembled, the contact members have to be inserted into the housing via the lamp entrance, which causes the electric cable to be slid through the holder, too.

Apart from the lamp entrance, the lampholder is sealed in a gastight and watertight manner. Its assembling is, however, laborious and time consuming.

It is an object of the invention to provide a lampholder of the kind described in the opening paragraph, which is of a construction which is simple and can be simply realised.

According to the invention this object is achieved in that the housing has a channel for each contact member, open to the lamp cavity, in which channels the contact members are held and into which the contact members, being connected to the cable, are introduced from the end portion of the housing along a substantially rectilinear path, and the sealing member has a first tubular portion which envelopes a longitudinal portion of the cable in a clamping manner, and a second portion enveloping the end portion of the housing in a clamping manner.

The lampholder of the invention is of a simple construction and can be simply realised. As the contact members can be inserted from the rear, the cable need not to be threaded through the housing. The substantially rectilinear movement in mounting the contact members also contributes to an easy and fast assembling. The sealing member can easily be applied by sliding the member over the cable to the housing to be slid subsequently with its second portion over the end portion of the housing. The first and the second portion of the sealing member may be in line. In this embodiment the first portion envelopes a portion of the cable which is substantially outside the housing.

In a favourable embodiment, however, the second portion surrounds the first portion. In this embodiment the first portion envelopes a longitudinal portion of the cable which may be substantially inside the housing. This embodiment has the advantage that the constructional length of the lampholder is relatively short. Another advantage is an increased ease of assembling. The sealing member needs to be slid over the cable over a relatively short portion thereof, the second portion e.g. being turned inside out. To that end, the sealing member can be pulled over the cable, being seized at its second portion. The contact members are subsequently connected to the cable and the cable with the contact members is mounted in the housing. The first portion of the sealing member may then be in its final position. The second portion may subsequently be brought into its final position by simply swinging it over. Little or no friction has to be overcome then. Friction is, however, to be coped with in case the sealing member is slipped over the end portion of the housing. The resilient sealing member may be made of e.g. rubber, such as butylene rubber or silicone rubber. The resilient sealing member may be fixed to the housing by its own resilient force, or in addition by an adhesive, e.g. by silicone resin. In the case the second portion of the sealing member is swung over to occupy its final position, the concealed use of such an adhesive is very easy, because a sliding movement of the member over the surface of the housing which could displace the adhesive is substantially avoided, then.

It is favourable for the ease of assembling if the end portion of the housing has an outer surface which is tapering.

The lampholder may be secured to a device in which it is to be used by providing a seat for the lampholder in the device, e.g. a clamping seat.

The housing may, however, itself have means for fixing the holder to a wall or in an opening in a wall, e.g. a flange, e.g. a flange having holes for e.g. screws, or a twin-flange defining slots and enabling the mounting of the lampholder in an opening in a wall e.g. in a bayonet-type movement. Alternatively, the housing may have resiliently mounted barbed hooks for being slid through an opening in a wall and snapping behind that wall, while a portion of the housing abuts the wall. These fixing means may be integral with the housing. Alternatively, however, the housing may at an outer surface thereof be provided with means, e.g. with opposite sets of nocks, which allow to mount fixing means as desired, e.g. by snapping them between such sets of nocks.

It is convenient if the channels in the housing have resilient means allowing the contact members to pass when they are mounted, and snapping behind them after they have passed, so as to block their return.

The contact members may be designed to contact pin-shaped contacts of an electric lamp, e.g. in that they are C-shaped in cross-section in order to receive such contacts with clamping action. Alternatively, however, bayonet-capped lamps or Edison- capped lamps may be mounted in the lampholder. To that end, contact means may be mounted in the lamp cavity which are secured to the contact members e.g. by means of a pin-shaped or tongue-shaped protrusion thereof, which is held with clamping force by the e.g. C-shaped contact members. Such contact means may be eccentric plates positioned on a bottom wall of the lamp cavity to contact a bayonet cap, or a central plate and a threaded ring to contact an Edison cap.

Apart from the lamp entrance, the lampholder of the invention is gastight and watertight. The lampholder may be used with a lamp of the kind described in the non- prepublished patent application EP 95 200 200.4 (PHN 15178). That lamp has a resilient cover member which clamps around and covers at least a portion of the lamp and which has a circumferential flexible collar. Inserted in the lampholder, the lamp seals the lamp entrance by means of said collar. Thereby, the contact members of the lampholder are screened from the ambient atmosphere, so as to avoid the risk of corrosion or short-circuiting of the contact members and the risk of explosion in case the ambient atmosphere is explosive.

The lampholder may be used to operate an electric lamp, e.g. an incandescent lamp or a discharge lamp, on e.g. mains voltage. Embodiments of the lampholder according to the invention are shown in the drawings, in which

Fig. 1 is a first embodiment, partly in side elevation, partly in sectional view; Fig. 2 is a second embodiment of the housing in sectional view;

Fig. 3 is a sectional view of the sealing member of Fig. 1 mounted on a cable.

In Fig. 1, the lampholder for an electric lamp has a housing 101. The housing defines a lamp cavity 103 having a lamp entrance 104. Contact members 105 are present for supplying electrical energy to the contacts 11 of a lamp cap 10 of a lamp having an envelope 31 mounted in the lampholder (see Fig. 4). The contact members can hold the contacts 11 of such a lamp with clamping force. An electric cable 106 enters an end portion 110 of the lampholder opposite to the lamp entrance 104 and is electrically connected to the contact members 105. A resilient sealing member 107 is present to seal the housing 101 around the electric cable 106. In the Fig., the housing 101 is made from polybutylene terephthalate, but alternatively polycarbonate or another, e.g. thermoplastic, resin may be used. The housing 101 has a channel 109 for each contact member 105, open to the lamp cavity 103, in which channels the contact members are held and into which the contact members connected to the cable 106 are introduced from the end portion 110 of the housing along a substantially rectilinear path.

On assembling the lampholder shown, the contact members 105, having connected thereto cable 106, are slid from the still open end portion 110 rectilinearly each into a respective channel 109 of the housing. The channels 109 have resilient means 114, in the Fig. tags which are integral with the housing, which allow the contact members 105 to pass and which snap behind them after they have passed, so as to block their return.

The housing 101 is provided with means 133 to fix the lampholder to a wall. In the Fig., these means are a twin flange 133 defining a slot 133' in which a boundary of an opening in a wall can be accommodated.

In the lampholder of Fig. 1, an electric lamp is shown having a lamp vessel 31 in which an incandescent body for use on mains voltage is mounted. The lamp has a cap 10 from which strip-shaped contacts 11 extend, which are in electrical contact with the contact members 105. The lamp has a cover 40, e.g. of silicone resin, which has circumferential, outwardly extending flexible collars 41, 41'. These collars seal the housing 101 at the lamp entrance 104.

In Fig. 2 the housing 101 is identical to the one of Fig. 1 except for the means 113 to mount the lampholder having this housing to a wall. These means consist of resiliently mounted barbed hooks, that approach one another when the lampholder is pushed through an opening in a wall, and spring back towards their original position when they have passed the wall. The portion 113' abuts the wall then.

In Fig. 3 the resilient sealing member 107 of Fig. 1 has been pulled over an end of cable 106, from which the insulating mantle has been removed. Contact members 105 (Fig. 1) can now be secured to the bare ends 106' of the conductors of the cable. The contact members 105 can then be slipped into a respective channel 109 of the housing 101 (Fig. 1). The lampholder is completed by swinging over the second portion 107b so as to envelope the end portion 110 in a clamping manner.