GB2367698A

GB2367698A - Electrical socket with untouchable contacts

Info

Publication number: GB2367698A
Application number: GB0123225A
Authority: GB
Inventors: Duncan John Salton
Original assignee: BLAKLEY ELECTRICS Ltd
Current assignee: BLAKLEY ELECTRICS Ltd
Priority date: 2000-09-27
Filing date: 2001-09-27
Publication date: 2002-04-10
Anticipated expiration: 2021-09-27
Also published as: GB2367698B; GB0023601D0; GB0123225D0

Abstract

A lampholder 1 has a socket 7 containing an insulating post 10. The post reduces the cross-sectional area of the opening, so that it is more difficult for a person to touch the contacts 9 with a finger. A bulb (15, Fig 3) suitable for use with the socket has a recess (17, Fig 3) for the post. An adapter (11, Fig 2) may also be used to connect a component to the socket, and this too has a recess (14 , Fig 2) for the post.

Description

ELECTRICAL APPARATUS The present invention relates to electrical apparatus and particularly, but not exclusively, to a bayonet cap (BC) lampholder and to a lamp and adaptor for use therewith.

Conventional BC lampholders comprise a socket into which the cap of a lamp or an adaptor may be inserted and retained to make electrical contact between two conductive regions on the end of the cap or adaptor and respective spring loaded electrically conductive contacts disposed in the socket. A problem with such lampholders is that when no lamp or adaptor is fitted the electrically conductive contacts are exposed and can be touched by a person's finger inserted into the socket. Thus, such lampholders present an electrical shock hazard when the contacts are live and the lamphoider empty.

It is known to address this problem in lampholders for domestic use by providing a switch arrangement which disconnects the electrical contacts in the socket of the lampholder from their power supply when the lampholder is empty. However, the switch arrangement employed tends to be fairly delicate making it unsuitable for rough handling or exposure to dust and dirt as may be, for example, encountered on a construction site.

It is an object of the present invention to address the abovementioned problems.

According to an aspect of the present invention there is provided

electrical apparatus defining a socket having an opening leading to one or more electrical contacts housed in the socket and being adapted to receive an electrical component which, when received in the socket, will contact the one or more electrical contacts wherein the socket includes a formation extending in the opening and reducing the cross-sectional area of the opening.

Provision of the formation limits the size of objects that may be inserted into the socket to contact the one or more electrical contacts.

With appropriately sized apparatus, therefore, the formation reduces the likelihood of a person being able to touch the one or more electrical contacts, particularly with a digit. Indeed, it is preferable that this is the case.

The formation is preferably formed from an electrically insulating material. The socket may include a base and the formation may extend from the base into the opening. The one or more electrical contacts may also extend from the base. In one embodiment the apparatus is a lampholder and is preferably a BC lampholder. In this latter preferred embodiment the socket includes two or more electrical contacts extending from the base of the socket and the formation also extends from the base of the socket from a point between the electrical contacts. The formation extends beyond the electrical contacts at least as far as the contacts extend from the base. The formation preferably sufficiently reduces the cross

section of the opening to prevent solid objects of a diameter of 12mm or greater inserted into the socket from being able to touch the electrical contacts. The apparatus may provide a BC-22 lampholder. That is a lampholder sized to receive the bayonet cap of a lamp or an adaptor of nominal diameter 22mm. As such the apparatus comprises a socket with an opening of substantially circular cross-section of diameter greater than 22mm, typically 23mm. The formation is generally cylindrical in form with a diameter of about 6mm and is disposed substantially centrally and coaxially within the opening. The formation thus reduces the size of objects which can be inserted into lampholder to touch the contacts from 22mm to 8mm diameter, this being the size of the annular space surrounding the formation.

The socket may include a second formation which is preferably adapted to cooperate with a component intended to be received into the socket. This enables the type of components that may be received into the socket to be further limited to those being able to accommodate/cooperate with both the first and second formations. Thus voltage discrimination may be provided for, for example a lampholder may be arranged only to receive luminaries rated at 220V or higher, to prevent damage or injury resulting from insertion of luminaries of lower rating. In one embodiment, where the apparatus is a BC lampholder provision, for example slots or recesses, for receiving three lugs on a lamp is made. Such lamps may then be received

into the socket, but not sockets which only provide for receipt of two lugs or which provide for three lugs spaced differently.

According to another aspect of the present invention there is provided an electrical component suitable for insertion into a socket to make contact with one or more electrical contacts disposed in the socket the component including a recess for accommodating a formation extending in the socket.

Such a component may be used with apparatus according to the first mentioned aspect of the invention.

The component may comprise an adaptor for making electrical contact between an electrical contact disposed in a socket and another electrical component, for example a cable. The component could also comprise a lamp, for example with a bayonet cap. The recess preferably corresponds in shape to the formation to be accommodated therein. The recess may comprise a cavity.

The invention provides electrical apparatus, including lampholders, which can provide IP2 protection against finger entry. IP2 is part of the International specification of levels of protection offered by certain electrical equipment. IP2 concerns protection against a standard test finger and solid objects greater than 12mm diameter.

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings of which:

Figure 1 is a partially cut away perspective view of a lampholder according to the invention ; Figure 2 is a part cross-sectional view of the lampholder of Figure 1 with an adaptor partially inserted therein; and Figure 3 is a part cross-sectional view of a lamp according to the invention.

Referring to Figure 1 there is shown a BC lampholder, generally 1.

The lampholder 1 is of a type that may be used to form so-called festoon lighting, that is several lights in parallel sharing a common source. As such the lampholder 1 includes two apertures 2,3 on opposite sides respectively of its base portion 4 through which a length of electrical cable 5 extends.

In common with conventional BC lampholders the illustrated lampholder 1 comprises a generally cylindrical upper portion 6 extending from its base portion 4. The upper portion 6 defines a socket 7 of substantially circular cross-section for receiving the bayonet cap of a lamp or a suitable adaptor. The inside surface of the socket 7 includes two or more L-shaped recesses 8 for receiving projections on a bayonet cap or adaptor and operative to retain a bayonet cap or adaptor in the socket when it is inserted therein and rotated relative thereto. Inside the socket 7 extending from the base of the socket are two spring loaded electrical contacts 9. These take the form of pins and are resiliently biassed towards the open end of the socket and may be depressed into the base portion 4

of the lampholder against the action of the resilient bias. When a bayonet cap or adaptor is inserted into the socket 7 this causes the contacts 9 to be partially depressed into the base 2 of the lampholder so that the contacts 9 are urged into contact with electrical contacts on the bayonet cap or adaptor to establish electrical contact therewith. All this is, of course, known.

Where the illustrated lampholder 1 differs from the prior art is through the provision of a formation 10, formed from an electrically insulating material, which extends from the base of the socket 7 between and beyond the two electrical contacts 9. The formation 10 is generally cylindrical in shape and extends beyond the electrical contacts 9 towards the open end of the socket 7 by at least the length of the contacts 9. The formation 10 may be circular in cross section or it may, as illustrated, include scallops in opposite sides respectively of its longitudinal axis allowing its diameter to be increased but still allowing for clearance between it and the contacts 9.

The formation reduces the cross sectional area of the part of the socket leading towards the electrical contacts 9.

The formation 10 serves to prevent, or at least considerably reduce the risk of, a person's digit, especially finger, inserted into the socket 7 contacting either of the electrical contacts 9, and thus reduces the risk of electrical shock. The presence of the formation 10 provides IP2 protection against finger entry. The formation 10 is relatively easy to manufacture

and does not adversely affect the electrical or mechanical integrity of the lampholder as compared to some known methods of providing protection against finger entry. Apart, of course, from those components which are required to be electrically conductive the lampholder 1 is made from moulded plastic components. The formation 10 is integrally formed with one of those components.

It will be apparent that a suitable formation to inhibit finger entry could be introduced into other forms of lampholder, for example the type described in GB 2248527A having three electrical contacts.

Referring to Figure 2, in which the same reference numerals are used as in Figure 1 to identify corresponding components, an adaptor 11 is shown partially inserted into the socket 7 of the lampholder 1. Adaptors are, of course, known per se and are used to electrically connect a cable 12 to a lampholder 1. Conventional adaptors are arranged to fit into a BC lampholder and include electrical contacts 13 on their front end which, on insertion of the adaptor into a lampholder, make electrical contact with the contacts 9 therein. Where the illustrated adaptor 11 differs over conventional adaptors is that it includes a recess 14 on its front end into which the formation 10 in the lampholder 1 is received when the adaptor 11 is inserted into the socket 7 thereof.

Of course, without the recess 14 the adaptor could not be inserted into the socket 7. This can convey some useful benefits as it is now

possible to limit which adaptors may be inserted into a given socket, for example so that certain equipment may only be connected to a compatible power supply.

The adaptor may be wired as described in GB 2248527A.

The cross section of the formation 10 and recess 14 could adopt a variety of different shapes, for example round, oval, scalloped, triangular and square to enable a number of different pairs of lampholders and adaptors to be produced not having any cross-compatibility.

Referring to Figure 3, a lamp 15 according to the invention comprises a bayonet cap 16 including two or more lugs 18, which, similar to the adaptor 11 of Figure 2, is of conventional form save for inclusion of a recess 17 for accommodating the formation 10 of a lampholder 1 into which it is received. The same considerations that apply to the accommodation of a formation by the adaptor of Figure 2 apply equally to the lamp of Figure 3. The lamp 15 itself could be of any desired type, for example filament, fluorescent or gas discharge. Gas discharge lamps can convey advantages when used in festoon lighting, for example for construction sites or outdoor decoration as they give a greater light output per watt compared to tungsten filament lamps which reduces the amount of current that need be carried. This can be a problem on construction sites where a lower than normal mains voltage is commonly used, typically 11 ou but which can be lower, for example 36V. Also, the higher initial cost of gas discharge

lamps makes the additional cost of producing a special lamp cap easier to justify.

In one embodiment a lamp or adaptor includes three lugs for receipt by three slots or recesses in a socket in which the lamp or adaptor is to be inserted.

Sockets made in accordance with the invention could be incorporated into festoon lighting along with conventional sockets not including a formation to enable conventional lamps and adaptors to be used in some sockets of the festoon.

The above embodiments are described by way of example only, many variations are possible without departing from the invention.

Claims

CLAIMS 1. Electrical apparatus defining a socket having an opening leading to one or more electrical contacts housed in the socket and being adapted to receive an electrical component which, when received in the socket, will contact the one or more electrical contacts wherein the socket includes a formation extending in the opening and reducing the cross-sectional area of the opening.
2. Apparatus as claimed in claim 1, wherein the formation is formed from an electrically insulating material.
3. Apparatus as claimed in either claim 1 or 2, wherein the socket includes a base and the formation extends from the base into the opening.
4. Apparatus as claimed in claim 3, wherein the one or more electrical contacts also extend from the base.
5. Apparatus as claimed in claim 4, wherein the socket includes two or more electrical contacts extending from the base of the socket and the formation also extends from the base of the socket from a point between the electrical contacts.
6. Apparatus as claimed in claim 5, wherein the formation extends beyond the electrical contacts at least as far as the contacts extend from the base.
7. Apparatus as claimed in any preceding claim, wherein the formation

reduces the cross-section of the opening to prevent solid objects of a diameter 12mm or greater inserted into the socket from being able to touch the electrical contacts.
8. Apparatus as claimed in claim 7, comprising a socket with an opening of substantially circular cross-section of diameter greater than 22mm and wherein the formation is generally cylindrical in form with a diameter of about 6mm and is disposed substantially centrally and coaxially within the opening.
9. Apparatus as claimed in claim 7, wherein the socket includes a second formation.
10. Apparatus as claimed in claim 9, wherein the second formation is adapted to cooperate with a component intended to be received into the socket.
11. A lampholder comprising apparatus as claimed in any preceding claim.
12. A BC lampholder comprising apparatus as claimed in any preceding claim.
13. A BC lampholder as claimed in claim 12 including three or more slots or recesses for receiving lugs on an electrical component for insertion into the holder.
14. An electrical component suitable for insertion into a socket to make contact with one or more electrical contacts disposed in the socket the component including a recess for accommodating a formation

extending in the socket.
15 A component as claimed in claim 14 comprising an adaptor for making electrical contact between an electrical contact disposed in a socket and another electrical component.
16. A lamp comprising a component as claimed in either claim 14 or 15.
17. Apparatus as claimed in any of claims 1 to 10 having a component as claimed in any of claims 14 to 16 received into the socket thereof.
18. A lampholder substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.
19. A lamp substantially as herein described with reference to Figure 3 of the accompanying drawings.