GB2214005A

GB2214005A - Light bulb holder

Info

Publication number: GB2214005A
Application number: GB8729774A
Authority: GB
Inventors: Chi Wing Fok
Original assignee: On Tat Bakelite Electric Works Ltd
Current assignee: On Tat Bakelite Electric Works Ltd
Priority date: 1987-12-21
Filing date: 1987-12-21
Publication date: 1989-08-23
Also published as: GB8729774D0

Abstract

This invention relates to a light bulb holder. The holder (1) has a body with two elongate channels (8) formed therein to receive electrodes for connecting an electrical supply to the light bulb mounted in the holder. Each electrode comprises a terminal member (9) fixed in the holder and a pin member (11) having a top hat cross section. A T-shaped link element is located in the respective channel between the terminal member and the pin member. A spring (12) which cannot be inserted into the pin member (11) is passed over the vertical section of the element (13). Thus, when a light bulb is mounted in the holder, the pin member (11) is pushed towards the terminal member (9) compressing the spring (12). The action of the compressed spring (12) urges the pin member (11) into positive contact with a terminal of the mounted light bulb. At the same time the link element (13) provides an electrical link between the terminal member (9) and the pin member (11). <IMAGE>

Description

LIGHT BULB HOLDER This invention relates to a light bulb hoder.

In a known light bulb holder, the body thereof is adapted to receive a light bulb, typically by means of a bayonet fixing or a screw fixing. Appropriate electrodes are mounted in the body both to connect to electrical contacts on the received bulb and to provide terminals for affixing wiring connected to an electrical supply. In the known holder, the electrodes are received in channels and comprise a terminal element for connecting to the wiring and a pin member for connecting to the contacts on the light bulb. Interposed therebetween is a spring means located both to urge the pin member into contact with the light bulb contacts and at the same time to establish electrical connection between the pin member and the terminal member.

One of the problems associated with such light bulb holders is that the channel receiving the pin member and spring means must be quite accurately engineered to avoid the spring being bent off axis in use. At the same time, it has been found that the spring can lose its elasticity when the maximum rated current is employed for the light bulb indeed, permanent deformation can occur. As a result, the electrical contact between the pin member and the light bulb contact cannot be guaranteed. Finally, the material required for suitable spring action of the spring means is not compatible with the requirements to have low resistance contact between the pin member and the terminal member.

It is an object of the present invention to provide an improved light bulb holder.

According to the invention there is provided a light bulb holder comprising a cylindrical body having one end adapted for mounting a bulb, and one or more electrodes for connecting an electrical supply to the mounted bulb, the or each electrode being located in a respective channel formed in the cylindrical body and comprising a terminal member fixed in the holder for connection to said supply, a pin member mounted to slidably extend a predetermined distance from the channel to make electrical contact in use with a contact of the mounted bulb, and spring means located between the terminal member and pin member to urge the pin member to its extended position to provide a positive engagement with the contact of the mounted lamp, characterised in that a generally rigid electrically conductive link element is provided between the terminal member and pin member to establish electrical contact therebetween, which link element allows the sliding of said pin member.

By employing a generally rigid electrically conductive link element in addition to the spring means, good contact between the pin member and the terminal member can be achieved without detrimental effects to the spring means.

In a preferred embodiment of the invention said spring means comprises a tension spring and the pin member has a top hat cross section and the spring has a diameter sufficient to prevent insertion into the pin member whereas said link element has a size permitting sliding insertion into and contact with the pin member.

An example cf the present invention wiii now be described with reference to the accompanying drawings, in which: Figure 1 illustrates an end view of a light bulb holder embodying the present invention, Figure 2 illustrates a section along the length of the holder through the line X-X shown in Figure 1, and Figure 3 illustrates the electrical connection between the terminal member and pin member of Figures 1 and 2 before and after mounting of a bulb.

Referring to Figures 1 and 2, a light bulb holder (1) comprises an elongate cylindrical body (2) formed of an insulating material such as bakelite. The body has a generally cylindrical shape with one end of the cylinder having L-shaped grooves (3) formed therein for a bayonet fixing for a light bulb. In known manner, the outer surface of the body (2) includes a threaded section (4) seperated from a further threaded section (5) by means of a lip (6). The threaded section (5) is formed to receive a cover to enclose and insulate the end of the body j; remote from the grooves (3). The section (4) is formed for receiving a threaded ring (not shown) for mounting a lamp shade in known manner.

The interior of the body (2) is formed to have two axial pillars (7) with an internal axial channel (8) linking either end of the cylindrical body (2).

An electrode is mounted in each channel (8) and the components of the electrode are shown in Figure 3.

Firstly, each channel (8) is formed to receive a pin member (11) which has a cross section in the form of a top hat. The pin member (11) is inserted into the channel (8) from the end remote from grooves (3) and the end of the channel (8) is formed with a flange to interact with the margin of the top hat form of the pin (11) whereby the pin member does not pass right through the channel (8). A spring (12) is then inserted into the channel. The spring (12) is selected to urge the pin member (11) to extend as far as possible from the channel (8). Thus, the diameter of the spring is selected to be small enough to allow insertion into the channel but is large enough to prevent inser'~^n ito the interior of the pin member.

Such a construction corresponds with the prior art.

Thereafter a terminal member (9) is mounted at the end of the channel (8) remote from the groove (3). The terminal member (9) comprises a brass block having a groove axially aligned with the body (2) for receiving wiring. A hole (10) formed perpendicularly to the axis of the body (2) is formed in the terminal member (9) to receive a screw for holding wire into the terminal.

A corresponding hole is formed in the body (2) so that when the retaining screw is passed through the body (2) and screwed into the hole (10), the terminals (9) are retained in position. Thus when a light bulb is inserted into the end of the body (2), contacts on the bulb interact with the pin members (11) and depress those members against the urging force of the spring (12). Once the pins on the light bulb locate with the bayonet fixing grooves (3) the bulb is retained in position and the pin members (11) are urged into positive contact with the electrical contacts on the bulb.

With the present invention, a T-shaped conductive element (13) is inserted into the spring (12) as shown prior to the mounting of the terminal members (9) in the body (2). The element (13) is selected to allow insertion into the interior of the pin member. Thus, as is shown in Figure 3, the pin member (13) provides electrical contact between the terminal member (9) and the pin member (11). When a bulb is inserted into the body (2, and the pin member (11) is depressed, the lower end of the T-shaped element (13) passes into the interior of the pin member (11) and touches the side thereof thereby establishing a good electrical contact between the pin member and the terminal member which is touched by the upper end of the T-shaped element (13). In this way, the primary route for conduction of electricity between the terminal member (9) and the pin member (11) is by means of the T-shaped element 113) rather than the spring (12). Thus, the T-shaped element (13) is formed from a highly conductive material which is in all likelihood not suitable for forming a spring (12). At the same time, the shaft of the T-shaped element (13) mounts the spring (12) to prevent any sideways deformation thereof.

It will be apparent from the present invention that the element connecting the terminal member (9) and the pin member (11) can take many different forms to establish suitable contact therebetween.

Claims

1. A light bulb holder comprising a cylindrical body having one end adapted for mounting a bulb, and one or more electrodes for connecting an electrical supply to the mounted bulb, the or each electrode being located in a respective channel formed in the cylindrical body and comprising a terminal member fixed in the holder for connection to said supply, a pin member mounted to slidably extend a predetermined distance from the channel to make electrical contact in use with a contact of the mounted bulb, and resilient means located between the terminal member and pin member to urge the pin member to its extended position to provide a positive engagement with the contact of the mounted lamp, characterised in that a generally rigid electrically conductive link element is provided between the terminal member and pin member to establish electrical contact therebetween, which link element allows sliding of said pin member.

2. A holder as claimed in Claim 1 wherein said resilient means comprises a spring.

3. A holder as claimed in Claim 2 wherein the pin member has a top hat cross section and the spring has a diameter sufficient to prevent insertion into the pin member whereas said link element has a size permitting sliding insertion into and contact with the pin member.

4. A holder as claimed in Claim 3 wherein the link element comprises a T-shaped piece of electrically conductive material the horizontal section of the T-shaped element contacting the terminal member and the vertical section of the T-shaped link element passing down the centre of the spring before contacting the pin member.

5. A lamp holder substantially as herein described with reference to the accompanying drawings.