GB2444983A

GB2444983A - Plug with removable earth pin unit

Info

Publication number: GB2444983A
Application number: GB0625565A
Authority: GB
Inventors: Jon Ottar Birgisson; Petur Hannes Olafsson; Robert Scherle
Original assignee: STRAX UK Ltd
Current assignee: STRAX UK Ltd
Priority date: 2006-12-21
Filing date: 2006-12-21
Publication date: 2008-06-25
Anticipated expiration: 2026-12-21
Also published as: GB0625565D0; GB2444983B

Abstract

An electrical plug for a three pin socket, the plug having a base unit 12 with two conducting pins and an earth pin unit 10. The base unit has attachment means and the earth pin unit has complimentary attaching means. One of the attaching or complimentary attaching means has a projection with an overhanging flange and the other has a recess 36 with an overhanging flange such that the two overhanging flanges engage to hold the base unit and earth pin unit together. Preferably there is a locking mechanism formed from a projection on one unit that interlocks with a portion of a recess on the other unit thereby fastening the two units together. The base unit and earth pin unit may be brought into engagement by rotating the base unit relative to the earth pin unit.

Description

1 2444983 iectricaI Plug This invention relates to electrical plugs,

and particularly to plugs having a removable earth pin.

Conventional electrical plugs typically have a pair of conducting pins and may include a third pin, which may be used as an earth connection. An example of this is the British type G plug and socket. An earth connection is not always required such as where there is no externally accessible metal connection. In such situations the third pin is still required as they are generally used to open covers over the holes in the sockets for receiving the conducting pins.

In the type G plug, the third pin is often slightly longer than the conducting pins, and is arranged to operate a spring-loaded shutter within the corresponding connection point in the socket. This is a safety feature which prevents insertion of the conducting pins into the socket without simultaneous insertion of the third pin, to prevent a non-earthed connection being made. For this reason, all plugs to be used with this type of socket are provided with a third pin whether or not earthing is required. If the third pin does not act as an earth pin, it is known as a dummy pin.

The dimensions of a standard plug type G, for example BS1363, are constrained by the fixed displacement of the earth pin from the conducting pins, and by the surrounding case. However, it is often desired to have a plug of reduced proportions, for example if the plug is to be sent by post and posted through a letterbox.

Known approaches to providing a compact plug include a slidable third pin such as that disclosed in G Patent Application No. 2417 621. Here the third pin can slide between a first position and a second position in which the third pin is positioned such that the plug can be inserted into a socket. However, a potential problem with this type of plug with slidable earth pins is that it is difficult to ensure the pin is locked in the necessary position for insertion into a socket. Any error in displacement of the earth pin relative to the conducting pins will prevent the insertion of the plug into a socket.

Another known compact plug, such as that described in UK Patent Application No. 2 332 787, includes hinged pins. This allows the pins to be rotated between a position where they are folded into the body of the plug and where they allow insertion of the plug into a socket.

These solutions however, require space within the plug for the pins to be stored or to allow the earth pin to slide unobstructed. This tends to mean the plug body must be larger to accommodate the pins as well as all the other components, particularly if the plug is integrated into a charger unit or the like. Therefore it is desirable to further minimise the amount of space the plug takes up.

In accordance with a first aspect of the present invention there is provided a modular electrical unit for connecting to a three-pin plug socket, the unit comprising base unit including two conductors and attachment means and an earth pin unit including complimentary attachment means, wherein one of the attachment means and complimentary attachment means comprises a projection having an overhanging flange and the other of the attachment means and complimentary attachment means comprises a recess including an overhanging flange; the overhanging flanges being arranged to interengage such that the base unit and earth pin unit are held in engagement. By engaging the base unit and earth pin unit in such a way the attachment means can be confined to a relatively small area of the base unit thereby minimising the volume of the base unit.

Preferably the recess is provided on the upper surface of the base unit and even more preferably, the recess is provided on an elevated area of the base unit. These configurations further minimising the volume of the base unit required for the attachment means.

Optionally, the enlarged head and recess may be brought into engagement by rotating the base unit relative to the earth pin unit. Alternatively, the recess may be an open-ended groove and the overhanging flanges are brought into engagement by sliding the earth pin unit and base unit relative to each other in a plane parallel to the upper surface of the base unit.

Preferably, the electrical unit is provided with locking means arranged to hold the base unit and earth pin unit in the engaged configuration. This prevents the earth pin unit becoming detached from the base unit, for example by unwanted rotation or lateral movement of the earth pin unit relative to the base unit.

Preferably, the locking means comprises an upstanding portion and a depression arranged such that the upstanding portion only engages with the depression when the earth pin unit and base unit are in the required configuration.

Preferably, the unit having the depression is further provided with a ramp arranged to facilitate movement of the projection to the recess during engagement of the base unit and the earth pin unit. The presence of a ramp aids the movement of the projection to a raised area of the unit where the depression is situated.

In an alternative locking mechanism the upstanding portion and depression are each provided with at least one overhanging flange arranged to engage with each other when the earth pin unit is in the desired position. The presence of the overhanging flanges acts to further reduce the likelihood of relative movement of the earth pin unit and base unit. The overhanging flanges may comprise a projection at 90 degrees to the upstanding portion and the walls of the depression.

Optionally the projections may include a further extension at 90 degrees from the projection further restricting relative movement of the two units.

The earth pin unit and base unit may be removeably attachable. Alternatively, if desired the earth pin unit and base unit may be attached in such a manner that they cannot be disengaged.

Optionally, the conducting pins on the base unit are a first pair of conducting pins and the electrical unit further comprises a sleeve including a second pair of conducting pins; the sleeve being arranged to engage with the base unit such that the second pair of conducting pins are in contact with the first pair of conducting pins. This enables a user to alter the configuration of the conducting pins in order that they can be used with different types of plug sockets Preferably, the first and second pairs of conducting pins are different shapes. For example the first pair of conducting pins may be substantially rectangular in shape and the second pair of conducting pins may be substantially circular in shape allowing the electrical unit to be used in both standard UK and European plug sockets.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

Figures Ia to ic illustrates an earth pin unit of the present invention; Figure 2 illustrates a base unit of the present invention; Figure 3 illustrates a partial cross-section through the base unit; and Figure 4 illustrates an assembled electrical unit; Figure 5 illustrates a base unit of an alternative embodiment of the electrical unit; Figures Ba and 6b respectively illustrate an earth pin unit and base unit having an alternative locking mechanism.

Figures 1 and 2 illustrate a pin unit 10 and a base unit 12. The pin unit 10 and base unit 12 can be assembled into the electrical plug configuration illustrated in Figure 4.

Once assembled they can be inserted into a socket in the usual manner.

The pin unit 10 comprises a body 14 having a pin 16 projecting from it. The pin 16 may be a conducting earth pin or a dummy pin. The pin 16 may be integral with the body 14 or may, alternatively, be attached to the body 14 using any suitable means.

The pin unit 10 is provided with a member 18. The member 18 extends from the body 14 of the pin unit 10 and includes a stem 20 and a head 22. The head 22 has two projections extending, at least partially, in a perpendicular direction to the axis of the stem thereby defining overhanging flanges 23.

The base unit 12 has a body 24 and two conducting pins 26. The base unit 12 also contains elements arranged to allow the electrical plug to carry out its function. For example, the electrical unit may be used as a low voltage power supply for charging a mobile telephone. In this case the base unit 12 will contain components connected to the conducting pins 26 and an electrical cable or socket on the unit.

The body 24 is provided with a recess 28. The recess 28 is preferably provided with at least one overhanging flange 30 around the upper periphery as illustrated in Figure 3. The recess 28 is configured to allow the head 22 of the projection 18 on the pin unit 10 to be inserted into the recess 28 in one orientation.

The pin unit 10 can then be re-orientated, for example by rotating the pin unit 10 relative to the base unit 12 such that the at least one flange 23 on the pin unit 10 engages with the at least one flange 30 on the body 24. This results in the pin unit 10 being held in the configuration shown in Figure 4 when the projection 18 is inserted into the recess.

The recess is deep enough to enable the member 18 to be inserted into it and be held in place. The recess is situated on the upper surface of the base unit and may be provided in a raised area of the base unit. This means that the recess does not extend through the entire depth of the base unit. Therefore the elements within the plug do not require rearranging to accommodate the attachment of the earth pin, thereby reducing the total volume of the electrical unit.

The pin unit 10 and the base unit 12 may be provided with locking means arranged to hold the pin unit 10 in place once it has been engaged with the base unit 12. The locking means may, in one example, comprise an upstanding portion 32 provided on the pin unit 10 arranged such that it is received by a depression 34 provided in the base unit 12. The upstanding portion 32 and depression 34 are arranged to engage with each other, when the electrical plug is assembled. They act to prevent relative rotation or longitudinal motion of the pin and base units. This holds the pin unit 10 and base unit 12 in the assembled configuration, as shown in Figure 4.

The recess and depression in the base unit 12 are provided on an elevated area of the base unit and a ramp 36 is provided to facilitate the raising of the upstanding portion to the depression. A degree of resilience in the materials of the engagement between the pin unit and base unit allows the pin unit to be lifted as the upstanding portion moves up the ramp and across the surface of the base unit before dropping into the depression If desired the projection and upstanding portion may be provided upon the base unit and the recess and depression within the earth pin unit. Alternatively, a combination of may be provided upon each unit. The position of the recess and projection will depend upon the method of engaging the earth pin and base units, and may be varied accordingly.

The electrical unit may also be provided with a sleeve unit (not shown) provided with a pair of conducting pins. The conducting pins are a different shape to those on the base unit. For example, the shape of the conducting pins on the base unit may be rectangular, e.g. for use in LJF( electrical sockets, but the shape of the conducting pins on the sleeve may be cylindrical, e.g. for use in European electrical sockets.

The sleeve unit may be engaged with the, base unit such that each of the conducting pins on the base unit is brought into contact with the conducting pins on the sleeve. This means that the plug may be inserted into a socket that is complimentary to the shape of the conducting pins on the sleeve, allowing the electrical plug to be used in different territories.

Preferably, the pin unit is removably connected to the base unit in order that it can be attached when it is required, e.g. in UK, and removed when it is not required, e.g. in Europe.

In an alternative embodiment, shown in Figure 5 the pin unit is provided with a member 18 as described above. The base unit 12 is provided with a recess arranged as an undercut groove 36 on the upper surface of the base unit's body.

The recess is arranged to receive the member such that an overhanging flange forming part of the member interlocks with an overhanging flange forming part of the recess. In this manner the pin unit can be held in position relative to the base unit.

In a further embodiment, shown in Figures 6a and 6b the upstanding portion 38 of the locking means is provided with a projection extending, at least partially, in a perpendicular direction to the axis of the stem thereby defining an overhanging flange 40.

The depression 42 is a groove provided with an overhanging flange 44 around the upper periphery. The depression is also provided with an enlarged entrance 46 into which the upstanding portion 38 is inserted. The pin unit 10 and the base unit 12 are then rotated relative to each other in order that the overhanging flange 40 of the upstanding portion 38 and the flange 44 of the depression 42 engage with each other to hold the earth plug unit and base unit in the assembled configuration.

The projection, recess, upstanding member and depression may be provided with one or more flanges in any combination suitable for holding the pin unit and base unit in the desired configuration.

Claims

1. A modular electrical unit for connecting to a three-pin plug socket, the unit comprising: (a) a base unit including two conductors and attachment means; and (b) an earth pin unit including complimentary attachment means wherein one of the attachment means and complimentary attachment means comprises a projection having an overhanging flange and the other of the attachment means and complimentary attachment means comprises a recess including an overhanging flange: the overhanging flanges being arranged to interengage such that the base unit and earth pin unit are held in engagement.

2. A modular electrical unit as claimed in Claim 1 wherein the recess is provided on the upper surface of the base unit.

3. An electrical plug as claimed in Claim 1 wherein the enlarged head and recess are brought into engagement by rotating the base unit relative to the earth pin unit.

4. A modular electrical unit as claimed in Claim 1 wherein the recess is an open-ended groove and the overhanging flanges are brought into engagement by sliding the earth pin unit and base unit relative to each other in a plane parallel to the upper surface of the base unit.

5. A modular electrical unit as claimed in any of Claims 1 to 4 wherein the recess is provided on an elevated area of the base unit.

6. A modular electrical unit as claimed in any preceding claim wherein the electrical unit is provided with locking means arranged to hold the base unit and earth pin unit in the engaged configuration.

7. A modular electrical unit as claimed in Claim 6 wherein the locking means comprises an upstanding portion and a depression arranged such that the upstanding portion only engages with the depression when the earth pin unit and base unit are in the required configuration.

8. A modular electrical unit as claimed in Claim 7 wherein the unit having the depression is further provided with a ramp arranged to facilitate movement of the projection to the recess during engagement of the base unit and the earth pin unit.

9. A modular electrical unit as claimed in Claim 7 wherein the upstanding portion and depression are each provided with an overhanging flange arranged to engage with each other when the earth pin unit is in the desired position.

10. A modular electrical unit as claimed in any preceding claim wherein the earth pin unit and base unit are removeably attachable.

11. A modular electrical unit as claimed in any preceding claim wherein conducting pins on the base unit are a first pair of conducting pins and the electrical unit further comprises a sleeve including a second pair of conducting pins; the sleeve being arranged to engage with the base unit such that the second pair of conducting pins are in contact with the first pair of conducting pins.

12. A modular electrical unit as claimed in Claim 11 wherein the first and second pairs of conducting pins are different shapes.

13. A base unit for use in the modular electrical unit of any preceding claim.

14. An earth pin unit for use in the modular electrical unit claimed in any of Claims ito 12.

15. An electrical plug substantially as herein described with reference to and as shown in any combination of the accompanying drawings.

16. A pin unit substantially as herein described with reference to and as shown in any combination of the accompanying drawings.

16. A base unit substantially as herein described with reference to and as shown in any combination of the accompanying drawings.