GB2114822A - Resilient socket for an electric light source - Google Patents

Abstract

A fluorescent tube socket comprises an electrically insulating one piece socket housing (1) consisting of a head (5) containing metallic spring contacts and grooved to accommodate the terminals of the fluorescent tube, a foot (3) connectible in appropriate positions to a support body (11) in accordance with the required nominal length of a given fluorescent tube, and a resiliently deformable web (4) connecting the foot (3) and the head (5). The head (5) may be provided with a starter socket connected by snap-in fixing claws. The advantages of the socket are that the resilience of the web (4) can accommodate variations in length of fluorescent tubes as well as vibrations and other small displacements, and furthermore the mounting and removal of fluorescent tubes is easy. <IMAGE>

Description

SPECIFICATION Resilient socket for an electric light source The invention concerns a socket for an electric light source; and although the invention is not so restricted, it will hereafter be described with reference to a socket for a tubular discharge lamp commonly referred to as a fluorescent tube. Such a tube has electrically conductive metallic contacts in the form of leaf springs disposed in an electrically insulating socket housing made expediently from a plastics material, the contacts being electrically contactable by the current leadin terminals of the fluorescent tube, positively engaged by ribs formed on the socket housing and electrically connectible with coupling leads.

It is a characteristic of the construction of most known and used fluorescent tube sockets that in a socket housing of electrically insulating material there is provided a rimmed rotating part which can be rotated between leaf springs that are electrically contactable by the lead in terminals or pins of the fluorescent tube and which support leaf springs in their mutually opposite positions, the rotating part being formed with openings for accommodating the pins or terminals of the fluorescent tube. After placing the fluorescent tube in position and rotating it, by virtue of the position of the rotating part, the grooves guiding the pins are closed and thus the socket fixes the fluorescent tube and at the same time assures electrical current conduction. Such a construction is e.g. disclosed in Hungarian Patent Specification No. 1 63,758.

A drawback of known fluorescent tube sockets is that the positioning of the fluorescent tube in the appropriate grooves of the rotary parts and its subsequent angular displacement is very cumbersome, especially in the case of fittings mounted on the ceiling. In certain cases the 'scatter' or variations in the longitudinal dimensions of fluorescent tubes and the possible inaccuracy in the distance between the mounted sockets may prevent the mounting of the fluorescent tubes or may allow them to fall out after being placed in position. The contact members pressing from two sides of the pins of the fluorescent tube frequently provide uncertain or unreliable electrical contact, and thus both the mechanical fixing and the electrical contacting of the fluorescent tubes may be unsatisfactory.This is particularly critical in locations subjected to vibrations, e.g. in vehicle or street illumination and can lead to the destruction of the fluorescent tube before its design serve life.

An aim of the invention is to provide an improved fluorescent tube socket which is less sensitive to variations in the longitudinal dimensions of fluorescent tubes, which enables the positioning and fixing to be carried out by a single movement in an easy manner, which can 'follow' or accommodate vibrations and oscillations and which provides electrical contacts of greater reliability in all operational conditions.

The above aim is achieved with a fluorescent tube socket which has a socket housing comprising, according to the invention, the contacts, a head part formed suitably for accommodating the current supply pins or terminals of the fluorescent tube, a foot part which can be rigidly fixed to a support body in a position appropriate to the given length of the fluorescent tube, and a web connecting the head part and the foot part and formed as an undivided, integral one piece member with the said parts and which is resiliently deformable to change its shape. The fluorescent tube socket according to the invention may expediently be made by injection moulding and its material may be a thermoplastic synthetic resin, expediently for instance 'Makrolon', 'Rilsen', 'Moplen' (Trade Marks) or the like.The head part is provided with lead-in grooves which open into through-going bores accommodating the pins of the fluorescent tube and which taper in the direction of these bores to that on placing the fluorescent tube into position its pins may readily be guided into the said grooves as a consequence of the resilience of the web, and the pins may then penetrate into the bores in a manner which assures excellent mechanical fixing and good electric contact. To this end it has proved expedient to form the web connected to the foot part in a V-shape, or U-shape with the U lying on its 'side', wherein the web can resiliently change its shape and can be subjected to several thousand bending operations without any residual deformation or fatigue.The head part may connect to the foot part in such a way that, in the operational position with a fluorescent tube of nominal dimensions in position, the head portion is in a plane perpendicular to the foot portion and the internal plane of the head portion with the lead-in grooves makes an angle of less than 900 with the plane of the supporting body or the foot portion in the unloaded position without the fluorescent tube. In this way, the secure holding and electrical contacting of fluorescent tubes shorter than the nominal dimensions is also reliably assured.

The head portion may have a back plate connected to the accommodation apertures in the head portion by means of snap-in fixing claws. As is known, to operate fluorescent tubes it is necessary to use so-called starters and it has been previously recognised that the sockets containing the latter may expediently be combined with the sockets for the fluorescent tubes. The fluorescent tube socket according to the invention may also be provided with a starter socket connected to the above-mentioned accommodation apertures of the head part by snap-in fixing claws, wherein in the complete unit including the starter socket, the series-connection of the starter can be assured without additional wiring by replacing one of the leaf-spring contacts.The force provided by the resilient deformation of the contacts employed in the fluorescent tube sockets according to the invention clamps the electric contact leads against the internal wall of the socket housing and thus the mounting can be carried out without the use of tools.

The foot portion of the fluorescent tube socket according to the invention can be fixed to the supporting body by traditional threaded connections but expediently fixing claws may be formed on the foot portion which can be snapped into appropriate openings in the supporting body and after snapping-in they assure a positionally stable fixing of the socket housing.

To remove the fluorescent tube the head portion of the socket housing is simply bent outwardly, permitted by the resilience of the web, whereby the fluorescent tube pins are pulled out of the bores. For the purposes of protection against over-stressing the socket housing may be provided with a limiting plate placed in an appropriate groove of the foot portion and cooperating with a projection or abutment on the head or foot part.

An advantage of the fluorescent tube socket according to the invention is that it can 'follow' over several millimetres in the direction of the length of the fluorescent tube any movement that may be induced, by virtue of the fact that the socket is flexible and is clamped against the fluorescent tube from both sides.

The contact pins of the fluorescent tube may be sunk into apertures in the socket which are formed with a tolerance that is optimal for their role. This method of fixing can 'follow' the displacement no matter what the displacement of the fluorescent tube is in such a way that the electrical contact remains permanent.

Mounting a fluorescent tube in the socket is very simple in any position of the fitting, even with overhead fittings. The tube is placed in the sockets such that the current lead-in pins are passed into the grooves of the head part and then by a light but continuous pressure are pushed until abutting.

Removal of the fluorescent tube is also very simple. One socket housing is pushed away from the fluorescent tube and thus freed fluorescent tube ube is lifted out. Thus the cumbersome rotational movement is obviated.

The constructional material, which is a thermoplastic, enables the manufacture and mounting both to be readily automated. The fluorescent tube socket (including the starter socket) according to the invention has in total only three metallic contacts and may be produced extremely simply.

Preferred embodiments of the invention are described below, merely by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a side elevation, partly in section, of the fluorescent tube socket according to a first preferred embodiment of the invention; Figure 2 is a front elevation of the socket housing according to Figure 1 taken from the side of the fluorescent tube; Figure 3 is a diagrammatic bottom plan view of the socket housing according to Figures 1 and 2 and provided with an additional threaded fixing; Figure 4 is an elevation of the fluorescent tube socket with the back plate removed and showing the internal construction and the contacts and lead wires; Figures 5 and 6 are diagrammatic elevations illustrating the placing in and removal of a fluorescent tube;; Figure 7 is a diagrammatic side view of a socket housing provided with a starter socket and a starter; Figure 8 is a front elevation of the embodiment provided with a starter socket but without the starter; Figure 9 is a back rear elevation of the starter socket showing the contacts and fixing claws; Figures 10 and 11 are detailed elevation and cross-section of the back plate closing the fluorescent tube socket; Figure 1 2 is a perspective view on an enlarged scale of a limiting plate for protecting the socket against excessive bending; and Figure 1 3 is an elevation by way of example of the socket provided with the limiting plate.

The preferred embodiment according to the invention shown in the various views of Figures 1 to 4 illustrates a fluorescent tube socket provided with a housing 1 containing contacts 8; a head portion 5 which has guiding grooves 7 tapering towards through-going bores 1 2 for accommodating the current lead-in pins 27 of the fluorescent tube 27; internal ribbing in the head portion 5 for maintaining the contacts 8 in a stable and accurate position by means of fixing claws 2 which can be snapped into appropriate positions in relation to a supporting body 11 in dependence on the nominal length of a given fluorescent tube 27; a foot portion 3 which can be connected rigidly against displacement to the head portion 5, optionally by way of an additional threaded connection 25; and a resiliently deformable web portion 4 connecting the foot portion 3 and the head portion 5 and being made of one piece with said portions. The socket housing 1 is made from a thermoplastic synthetic material, e.g. Makrolon, by injection moulding. The shaping of the web portion 4 and the constructional material employed therefor enable the web portion 4 to be deformed in the direction of arrows 6 shown in Figures 1 and 6 several tens of thousands of times without any permanent change of shape or fatigue.

As may be seen in Figure 5, when no fluorescent tube is mounted in position, the internal plane of the head portion 5 facing the fluorescent tube 27 makes an angle with the plane of the foot portion 3 or of the supporting body 11 which is less than 900, whereby fluorescent tubes 27 shorter than the nominal length can still be reliably held and fixed with a certain amount of prestressing. The plane of the back of the head portion 5 makes a small angle with the vertical and at its top, in the unstressed position as viewed in Figure 5, the 'gap' to the vertical plane is about 2 mm.

Figure 5 illustrates the mounting of a fluorescent tube 27. In the course of this operation the fluorescent tube 27 is pushed in the direction of the arrow 26 until it abuts the guiding grooves 7.

The manner of removal of the fluorescent tube 27 is shown in Figure 6 wherein, according to the Figure, the right-hand socket housing 1, or its head part 5, is bent by about 10 mm to free the pins of the fluorescent tube 27 and then the fluorescent tube can be removed in the direction shown by the arrow 29 from the socket housing.

The open back of the head portion 5 of.the socket housing 1 according to the invention may also accommodate a starter socket 13. This can be achieved by replacing the contacts 8 with contacts 14 and 1 5 (Figure 9) so that the starter socket 13 can be snapped by fixing claws 24 into receiving apertures 1 9. in this way the starter 14 can without additional wiring be connected electrically in series with the fluorescent tube 27.

By virtue of the resilient deformation of the contacts 8 or 1 5 the connecting leads 9 are fixed against the internal walls of the socket housing 1 and of the starter socket 1 3. To release them, a tool can be introduced into the aperture 21 in the direction of arrow 28 (Figure 4) whereby the connecting wires 9 can be pulled out of the receiving grooves 20 by releasing the clamping force. In the embodiments without a starter socket the open back of the socket housing 1 can be closed by a back plate 17 by way of fixing claws 18 which are also to be snapped into reception apertures 1 9.

To remove a fluorescent tube 27 it is necessary to bend the head portion 5 of the socket housing 1, as has already been described above and shown in Figure 6. To prevent the web portion 4 from being overstressed it is expedient to use an impeding or limiting plate 22 that can be inserted in a groove 23 of the foot portion 3 and which cooperates with a projection 10 and an abutment 1 6 to prevent the socket housing 1 from being bent excessively.

The invention is not limited to the preferred embodiments described purely by way of example, but within the scope of the accompanying claims it can be realised in various other embodiments and variants as regards its construction and the materials used.

Claims (11)

1. A socket for an electric light source such as a tubular fluorescent lamp, comprising a socket housing of electrically insulating material, in which are disposed leaf-spring-like electrically conducting metallic contacts which can be brought into electrical connection with the lead-in terminals of the light source and which are positively held by appropriately formed retaining means of the socket housing and which can be electrically connected to an electrical power supply conductor, the socket housing consisting of a head portion which contains said contacts and which is suitable for accommodating the said lead-in terminals, a foot portion which can be rigidly fixed to a support body in appropriate positions corresponding to the nominal length of a given light source and a resiliently deformable web portion connecting the foot portion and the head portion, all of said portions constituting an integral one-piece unit.

2. A socket according to claim 1, wherein the constructional material of the socket housing is a thermoplastic synthetic material.

3. A socket according to claim 1 or 2 wherein the head portion is provided with guiding grooves opening into through-going bores for accommodating the said terminals and tapering in the direction towards the bores.

4. A socket according to any preceding claim wherein the web portion is V-shaped or is prone U-shaped.

5. A socket according to any preceding claim wherein the head portion is connected to the foot portion in such a manner that in the operative position of the foot part with a light source mounted in position, the angle between the plane of the foot part and the internal plane of the head portion is 900 while in the unloaded position, with no light source mounted, the foot part or its support body makes an angle of less than 900 with the head portion.

6. A socket according to any preceding claim wherein the head portion is provided with a back plate secured by means of snap-in fixing claws that can be snapped into receiving apertures in the head portion.

7. A socket according to any of claims 1 to 5 wherein a starter socket is connected without additional wiring to the head portion by way of fixing claws that can be snapped into receiving apertures of the head portion, the starter socket and the head portion partially sharing contact members.

8. A socket according to any preceding claim wherein the contact members electrically connect the power supply conductors by means of resilient deformation and fix them against the wall of the socket.

9. A socket according to any preceding claim wherein the foot portion is connected to the support body by a threaded connection.

10. A socket according to any of claims 1 to 8 wherein the foot portion is provided with snap-in fixing claws for rigidly connecting the socket housing to the support body.

11. A socket according to any preceding claim wherein a deformation-limiting plate is placed in a groove of the foot portion to prevent overbending, and on the head and on the foot portions there is a projection and an abutment, respectively, for cooperating with the limiting plate.

1 2. A socket according to any of claims 2 to 11 wherein it is made by injection moulding.

1 3. A socket substantially as herein described with reference to and as shown in a) Figures 1 to 6 of b) Figures 7 to 11 or a) orb) in combination with Figures 12 and 13 of the accompanying drawings.