GB2499358A

GB2499358A - A system for obstructing unauthorised access to a socket

Info

Publication number: GB2499358A
Application number: GB1116322.7A
Authority: GB
Inventors: Paul Jones
Original assignee: South Bank University Enterprises Ltd
Current assignee: South Bank University Enterprises Ltd
Priority date: 2011-09-21
Filing date: 2011-09-21
Publication date: 2013-08-21
Also published as: GB201116322D0

Abstract

A system for obstructing unauthorised access to a socket 101 comprises a socket blocker removal tool 126 and a socket blocker 100. A pin extending from the socket blocker body 102 is configured for insertion into, and retention within, an aperture defined by a body of the socket 101. The socket blocker 100 has a first formation that, upon engagement with a co-operating second formation of the removal tool 126, enables an authorised user to extract the socket blocker pin from the socket aperture and gain access to the socket 101. The first formation may have a removal surface located within the socket blocker body 102 and may have a receiving aperture 103 with first and second aperture portions of first and second cross-sectional shapes. A key portion 128 with a cross-sectional shape complementary to that of the first cross-sectional shape may protrude from a shaft of the removal tool 126. When the removal tool 126 is engaged with a cam surface of the removal surface and rotated relative to the socket blocker 100, the tool 126 may also engage with the socket 101 to urge the pin at least partially out of the socket aperture.

Description

1

A SYSTEM FOR OBSTRUCTING UNAUTHORISED ACCESS TO A SOCKET

Field

5 This invention relates to a system for obstructing unauthorised access to a socket, and relates particularly, but not exclusively, to a system for obstructing unauthorised access to an electrical socket.

Background

10 Electrical sockets are commonly located in areas of buildings that are used by members of the public. Such areas include airport waiting rooms and restaurant seating areas. As the public are able to access electrical sockets in these areas, there is a tendency for them to plug personal appliances such as mobile phones or laptop computers into these electrical sockets so as to charge up the batteries of their 15 appliances. This is a problem to the management of these buildings because electricity consumption and therefore utility bills are increased without authorisation.

The present invention has been devised with the foregoing problem in mind.

Summary

20 In accordance with a presently preferred embodiment of the present invention there is provided a system for obstructing unauthorised access to an electrical socket, the system comprising: a socket blocker removal tool; and a socket blocker, the socket blocker having a body, a pin extending from the body that is configured for insertion into and retention within an aperture defined by a body of an electrical socket, and a first 25 formation for engagement with a co-operating second formation of the socket blocker removal tool; the arrangement being such that an authorised user can engage the second formation of the removal tool with the first formation of the socket blocker and extract the pin of the socket blocker from the aperture of the socket to thereby enable access to be had to the socket.

30 As the socket blocker is configured to be fixably inserted into a socket and to be removable only by an authorised user who is in possession of a removal tool, a device embodying the teachings of the invention makes it more difficult for members of the public to access sockets without the authorisation of the building owner. An associated advantage of the system proposed is that it also functions as an effective safety device 35 by obstructing children from accessing sockets.

In a preferred embodiment the pin is retained within the aperture of the socket by an interference fit with the body of the socket.

Such an interference fit increases the friction between the socket blocker and a socket into which it is inserted. This provides the advantage of increasing the difficulty of 5 removing the socket blocker from engagement with the socket.

In another preferred embodiment the first formation is defined by the body of the socket blocker and comprises a removal surface located within the body of the socket blocker.

Because the first formation is defined by the body of the socket blocker the 10 socket blocker may be formed using a single injection moulding process thereby providing the advantage of reducing its cost of manufacture. Furthermore, because the removal surface is located within the body of the socket blocker, this provides the advantage of further increasing the difficulty of removing the socket blocker from engagement with a socket without the use of a complimentary removal tool. 15 In a further preferred embodiment the first formation further comprises a receiving aperture having first and second aperture portions of first and second different cross sectional shapes; the removal tool comprises a key portion protruding from a shaft, the key portion having a cross sectional shape complementary to that of the first cross sectional shape; and the removal surface is within the second aperture portion adjacent 20 the first aperture portion.

The provision of a first aperture portion and a key portion with complementary cross sectional shapes makes it difficult for a person to use a removal tool that is not complimentary with the first aperture portion of the socket blocker, to remove that socket blocker from a socket.

25 In a preferred embodiment the receiving aperture extends entirely through the body of the socket blocker.

In another preferred embodiment the removal surface comprises a cam surface; the socket blocker removal tool being configured to ride up the cam removal surface, when the tool is engaged with the removal surface and rotated relative to the socket 30 blocker, and into engagement with the socket, to urge the pin at least part way out of the aperture of the socket.

By virtue of this arrangement a person can rotate the tool to move the socket blocker past a point of high friction with the socket to a point where the tightness of the interference fit between the socket blocker and the socket is reduced. Once in this latter 35 position, the socket blocker can easily be pulled the remainder of the way out from

engagement with the socket (using the removal tool, or alternatively by using one's fingers).

In a further preferred embodiment the socket blocker removal tool further comprises a finger grip or handle graspable by a user for manipulating the removal tool.

5 In a preferred embodiment the body of the socket blocker has a peripheral edge that lies flush with the socket in use. Such an arrangement makes it more difficult for an unauthorised person to prise the socket blocker from the socket (using their nails or a screwdriver, for example).

In a particularly preferred arrangement, a peripheral region of the body of the 10 socket blocker has a curved outer surface (the outer surface being the surface opposite that which is in abutment with the face of the socket in use).

In a further preferred embodiment the pin has a cam surface configured to form an interference fit with the body of the socket.

Such an interference fit further increases the friction between the socket blocker 15 and a socket into which it is inserted. This provides the advantage of increasing the difficulty of removing the socket blocker from engagement with a socket without the use of a complimentary removal tool.

In a preferred embodiment the cam surface on the pin is made of a different material to the pin.

20 In another preferred embodiment the cam surface on the pin is made of a softer material to the pin, and is configured to deform against the body of the socket on insertion of the pin into the socket.

Such deformation increases the tightness of the interference fit which further increases the difficulty of removing the socket blocker from engagement with a socket 25 without the use of a complimentary removal tool.

In a further preferred embodiment the pin has two cam surfaces, one provided on each of two opposite faces of the pin.

In one implementation, the socket comprises a pin receiving spring-clamp and the pin comprises a clamp receiving formation. The clamp receiving formation may 30 comprise a cut-away portion of the pin in which a distal part of the clamp is received when the pin is received in the clamp. The pin may comprise a pin head that is wider than at least part of said clamp receiving formation, the arrangement being such that respective arms of the clamp move apart when the pin head is moved into the clamp, and subsequently move towards one another into the clamp receiving formation formed 35 in the pin.

4

In another implementation, the pin may comprise one or more clamp engaging formations. The one or more clamp engaging formations may be formed in said clamp receiving formation.

In a preferred embodiment the socket blocker has a plurality of pins, each for 5 engagement with a respective aperture in the socket. One or more of the pins may include one or more cam surfaces and/or one or more clamp receiving formations and/or one or more clamp engaging formations as herein described.

Another aspect of the present invention provides a socket blocker for use with the system described herein, the socket blocker having a body, a pin extending from the 10 body that is configured for insertion into and retention within an aperture defined by a body of an electrical socket, and a first formation for engagement with a co-operating second formation of a socket blocker removal tool.

Yet another aspect of the invention provides a socket blocker removal tool for use with the system described herein, the socket blocker removal tool comprising a 15 second formation for engagement with a first formation of a socket blocker.

Other features, advantages and aspects embodying the teachings of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

20 Various aspects of the teachings of the present invention, and arrangements embodying those teachings, will hereafter be described by way of illustrative example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic top perspective view of a socket blocker;

Fig. 2 is a schematic underside perspective view of the socket blocker shown in

25 Fig. 1;

Fig 3. is a schematic enlarged perspective view of part of the underside of the socket blocker shown in Fig. 2;

Fig. 4 is a schematic perspective view of the socket blocker shown in Figs. 1 and 2 when installed in an electrical socket;

30 Fig. 5 is a schematic perspective view of a socket blocker removal tool for removing the socket blocker shown in Fig. 4 from the socket;

Fig. 6 is a schematic enlarged perspective view of part of the socket blocker removal tool shown in Fig. 5;

Fig. 7 is a schematic perspective view of the socket blocker in Figs. 1 and 2 and 35 the socket blocker removal tool in Fig. 5, prior to engagement of the removal tool with the socket blocker;

Fig. 8 is a schematic perspective view of the socket blocker and socket blocker removal tool shown in Fig. 7 after they have been engaged with one another;

Fig. 9 is a schematic perspective view of the socket blocker and socket blocker removal tool shown in Fig. 8, after the socket blocker removal tool has been rotated 5 relative to the socket blocker;

Fig. 10 is a schematic underside perspective view of the socket blocker and socket blocker removal tool of Fig. 9;

Fig. 11 is a schematic side view of the socket blocker and socket blocker removal tool shown in Fig. 9; and 10 Fig. 12 is a schematic perspective view of the socket blocker and socket blocker removal tool of Fig. 9 after the socket blocker has been disengaged from the electrical socket; and

Fig. 13 is a schematic side views of a conventional pin and pin clamp;

Figs. 14 to 16 are schematic side views of another pin and clamp; and 15 Figs. 17 to 19 are schematic side views of yet another pin and clamp.

Detailed Description

An illustrative implementation of the teachings of the invention will now be described with particular reference to a three-pin electrical socket of the type that is 20 commonly found in the United Kingdom. However, it should be remembered, that this implementation is merely illustrative, and hence that the teachings of the present invention may equally be applied to other types of electrical plugs (for example to a two-pin plug of the type commonly found throughout the remainder of Europe) without departing from the scope of the invention as defined by the accompanying claims. 25 With the above proviso in mind, reference will now be made to Figs. 1 and 2 of the accompanying drawings, in which there is depicted a socket blocker 100 for a system embodying the teachings of the invention. The socket blocker 100 comprises a blocker body 102 from which first, second and third pins 104, 106, 108 extend. The pins 104, 106, 108 are triangularly displaced from one another and are configured to mate 30 with the openings of an electrical socket (in this particular case, a conventional UK-style three-pin socket). Furthermore, the blocker body 102 defines a receiving aperture 103 configured to receive a removal tool (shown in Fig. 5) for removing the socket blocker 100 from an electrical socket. Preferably the receiving aperture 103 extends entirely through a location in the blocker body 102 between (preferably, substantially equidistant 35 from) the locations from which the triangularly displaced pins 104, 106, 108 extend.

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More specifically, the blocker body 102 defines a planar surface 110 which abuts against an external face of an electrical socket when the socket blocker 100 is in use. The close abutment of the socket blocker 100 to a socket makes it difficult for an unauthorised user to insert a tool (such as a screw driver) between the socket blocker 5 100 and a socket, thereby making it difficult to prise the socket blocker 100 out of a socket. Furthermore, the blocker body 102 is configured to reduce in cross-sectional area in a direction away from the planar surface 110 so as to make it difficult for someone to use a gripping tool (such as a pair of pliers) to grip and remove the socket blocker 100 from a socket. In a preferred implementation, an external surface of a 10 peripheral region of the blocker body 102 is inwardly inclined. Although, in another envisaged implementation, a peripheral region of the blocker body 102 has a curved external surface.

The pins 104, 106, 108 that extend from the blocker body 102 are substantially rectangular in shape and each define two narrower edge portions (or faces) 112 and two 15 wider edge portions (or faces) 114. The pins 104, 106, 108 are shaped such that they have a cross sectional shape complementary to that of the openings in an electrical socket (in this particular case, a conventional UK-style three-pin socket). Furthermore, so that the socket blocker 100 may be received in a standard UK electrical socket the pins 104, 106, 108 are configured such that the narrower and wider faces 112, 114 of 20 the first pin 104 are orthogonal to those of the second and third pins 106, 108.

In a particularly preferred implementation the narrower faces 112 of the first pin 104 and the wider faces 114 of the second and third pins 106, 108 have a cam surface 116, herein after referred to as a ramp portion, extending outwardly therefrom. The ramp portions 116 are configured to form an interference fit with the body of an electrical 25 socket when the socket blocker 100 is in use. This arrangement increases the tightness with which a socket blocker 100 is held within an electrical socket thereby making the socket blocker 100 even more difficult to remove from a socket without a removal tool.

The ramp portions 116 may be made of the same material as the pins from which they extend and may be integral to the pins themselves if the socket blocker 100 is 30 formed by a single injection moulding process. Alternatively, the ramp portions 116 may be made of a different material to the pins from which they extend and may be fixed to the pins (for example by means of an adhesive) or formed with the pin (for example by a dual injection moulding process). In particular the ramp portions 116 may be made of a softer material to the pins from which they extend, for example, the pins 104, 106, 108 35 may be made of plastic and the ramp portions 116 may be made of rubber. When the ramp portions 116 are made from such a softer material than the pins, the ramp portions

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are able to deform against the body of a socket when the socket blocker 100 is inserted thereinto. This deformation allows a tighter interference fit to be formed between the socket blocker 100 and a socket which makes it even more difficult for a person to remove the socket blocker 100 from a socket without using a removal tool.

5 With further reference to Fig. 3 (in which there is shown a perspective view of the underside of the blocker body 102), the receiving aperture 103 in the blocker body 102 has first and second aperture portions 118, 120 of first and second cross sectional shapes respectively. Although, it is not important that the first and second aperture portions 118, 120 have different cross-sectional shapes, however, it is important that the 10 second aperture portion 120 is wider than the first aperture portion 118.

In the particular embodiment shown in Fig. 3, the cross-sectional shape of the first aperture portion 118 is triangular (although it could be any shape, for example a square). Furthermore, the cross-sectional shape of the second aperture portion 120 is substantially defined by three removal surfaces 124 which are cam surfaces and are 15 each located adjacent respective edge portions of the triangular shaped first aperture portion 118. This arrangement provides that when the socket blocker 100 is in use, only a removal tool which has a cross-sectional shape complimentary to that of the first aperture portion 118 is able to be inserted into the receiving aperture 103. In particular, such a complimentary removal tool is able to be inserted into the receiving aperture 103, 20 through the first aperture portion 118, and into the second aperture portion 120.

After insertion into the receiving aperture 103, the portion of the removal tool which extends into the second aperture portion 120 is able to interact with the removal surfaces 124. The removal tool does this by moving into engagement with the removal surfaces 124 when the removal tool is rotated relative to the blocker body 102. In 25 particular, the removal tool is made to bare on the removal surfaces 124 when it is rotated relative to the blocker body 102 which causes reaction forces to be exerted by the removal surfaces 124 on the removal tool. These reaction forces thereby cause the removal tool to ride up the removal surfaces 124 as the removal tool is rotated relative to the blocker body 102. In use a removal tool may be so moved up the removal surfaces 30 124 into engagement with an electrical socket thereby urging the socket blocker 100 out of the electrical socket.

As previously mentioned, when a socket blocker 100 is inserted into an electrical socket 101, as shown in Fig. 4, it is extremely difficult for a person to remove it from the socket without a complimentary removal tool. With reference to Fig. 5, such a removal 35 tool 126 comprises a key portion 128 protruding from a shaft 130 and a finger grip (or handle) 134 gripable by a user for manipulating the removal tool 126. In particular, the

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key portion 128 has a cross-sectional shape complementary to that of the first aperture portion 118 of a receiving aperture 103 such that it is able to be received therein.

In the particular embodiment shown in Fig. 6, the key portion 128 is triangular (like the first aperture portion 118 in Fig. 3) and has indentations 132 for receiving the 5 corresponding tab portions 122 which protrude internally from the socket body 102. However, different socket blockers 100 may have different arrangements (and numbers) of tab portions 122. Therefore, complimentary removal tools 126 having corresponding different arrangements (and numbers) of indentations 132 are required to remove such differently configured socket blockers from electrical sockets. This prevents an 10 unauthorised person in possession of a non-complimentary (differently shaped) removal tool, from using their removal tool to remove another person's socket blocker 100 from a socket without authorisation. In other envisaged embodiments of the invention one or more tab portions 122 may protrude from the key portion 128 and one or more indentations 132 may extend into the socket body 102.

15 How an authorised user removes a socket blocker 100 from an electrical socket

101 will now be described.

Firstly, as is shown in Fig. 7, an authorised user aligns the key portion 128 of the removal tool 126 with the first aperture portion 118 of the receiving aperture 103 in the blocker body 102. To help a user achieve this the removal tool 126 may be provided 20 with an indicator 127 which indicates how to correctly align the removal tool 126 with the receiving aperture 103. In the embodiment shown in Fig. 7, a user is required to hold the removal tool 126 such that the indicator 127 is on top before it is able to be inserted into the receiving aperture 103.

Next, the key portion 128 is inserted into the receiving aperture 103 such that it 25 extends through the first aperture portion 118 into the second aperture portion 120 (see Fig. 8). The removal tool 126 is then rotated in a clockwise direction relative to the socket blocker 100 (see Fig. 9).

With reference to Figs. 10 and 11, when the removal tool 126 is rotated clockwise relative to the socket blocker 100, the key portion 128 initially rides up the cam 30 removal surfaces 124 into engagement with the body of the electrical socket 101 as previously described. When the removal tool 126 is rotated further in a clockwise direction the reaction force of the socket 101 on the removal tool 126, is transferred via the key portion 128 to the socket blocker 100. This transfer of force urges the socket blocker 100 away from the socket 101 as the key portion 128 rides further up the cam 35 removal surfaces 124 on rotation of the removal tool 126.

9

With reference to Fig. 12, when the removal tool 126 has been sufficiently rotated relative to the socket blocker 100 the key portion 128 is no longer in alignment with the first aperture portion 118. In this instance, if a user pulls the removal tool in a direction away from the socket 101, the key portion 128 bears on the removal surfaces 124 of the 5 blocker body 102. This allows a user to pull the socket blocker 100 entirely out of the socket 101. Alternatively, a user may pull the socket blocker 100 part way out of the socket 101 such that the planar surface 110 of the blocker body 102 is no longer in engagement with the socket 101. This will allow a user to remove the socket blocker 100 the rest of the way out of the socket 101 by inserting their nails or a tool between the 10 socket blocker 100 and the socket 101 and pulling the socket blocker 100 away from the socket 101.

Referring now to Fig. 13, some previously proposed electrical sockets are provided with generally horseshoe-shaped spring clamps 136. These clamps are configured so that respective arms 137 of the clamps move away from one another in 15 respective directions A and B as as a pin P is pushed between them in direction C as an electrical plug is inserted into the socket. The arms of the clamp are driven apart by the pin P against a resilient bias that tends to draw the arms back together. As a result of this arrangement, the arms clamp down onto the pin, thereby improving the electrical connection between the plug and the socket. In some instances the socket comprises a 20 clamp for each pin, and in other instances only one or more of the pins is or are clamped

In one implementation of the teachings of this invention, one or more of the pins 104, 106, 108 of the socket blocker 100 may be configured to cooperate with such clamps are to make it even harder to remove the socket blocker 100 from a socket.

In this implementation, as shown in Fig. 14, at least one of the pins 104, 106, 108 25 of a socket blocker 100 is provided with one or more clamp receiving formations 138 in the vicinity of a distal end of the pin. The clamp receiving formation, in the particular example illustrated in Fig. 13, comprises a cut-out formed in each narrower face 112 of the pin 104, 106, 108 that provides a wider pin head 139 behind which the distal ends of the arms 137 of the clamp can locate (as shown in Figs. 15 and 16) when the pin 104, 30 106, 108 is pushed between them. Specifically, as the pin is pushed between the arms of the clamp, the arms move outwardly (i.e. away from one another) as shown in Fig. 15 to allow the pin head to pass between them. Once the pin head has passed between them, the resilient nature of the clamp causes the arms to move back towards one another, whereupon the distal ends of those arms are received in the clamp receiving 35 formation 138 in the pin.

10

As will be appreciated by persons skilled in the art, as the arms of the clamp are biased towards one another, this biasing force must be overcome to move the arms outwardly and withdraw the plug blocker from the socket. As a consequence of this, the socket blocker shown in Figs. 14 to 16 is more difficult to withdraw than a socket blocker 5 with pins of the type shown in Fig. 13 where the arms of the clamp merely slide along the pin when the blocker is withdrawn from a socket. As a consequence of this, the blocker depicted in Figs. 14 to 16 is even more difficult to extract from a socket without the extraction tool.

In a modification of the arrangement depicted in Figs. 14 to 16, the clamp 10 receiving formation 138 provided in the pin 104, 106, 108 may be provided - as shown in Figs. 17 to 19, with one or more clamp engaging formations 140. As will be appreciated, the purpose of the clamp engaging formations 140 is to engage with the distal end an arm of the clamp to provide a second obstruction to withdrawal of the pin from a socket.

15 In the particular implementation shown in Figs. 17 to 19, the pin 104, 106, 108 is provided with three clamp engaging formations 140 that each comprises a projection from the region of the pin that forms the clamp receiving formation 138. In a preferred implementation the projections may, as shown in Figs. 17 to 19, be generally triangular in cross-section, but in other implementations they may have other shapes (for example, 20 semicircular or hemispherical). Providing a plurality of spaced clamp engaging formations is advantageous because socket clamps 136 tend to come in various shapes and sizes, and providing a plurality of clamp engaging formations 140 along a part of the length of the pin 104, 106, 108 increases the likelihood of the distal end of an arm of a clamp 136 catching on at least one of the formations 140 when the pin is inserted into a 25 socket opening.

Providing more than one formation 140 along the length of a pin 104, 106, 108 also has the additional advantage of yet further increasing the difficulty of withdrawing a socket blocker 100 from a socket without the removal tool 126. Specifically, if a clamp 136 is required to move over more than one formation 140 upon insertion of a socket 30 blocker 100 into a socket, the clamp must be re-flexed a corresponding number of times in order to move the clamp back over each of the formations 140 when the socket blocker is pulled back out of the socket.

It will be appreciated that whilst various aspects and embodiments of the present invention have heretofore been described, the scope of the present invention is not 35 limited to the particular arrangements set out herein and instead extends to encompass

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all arrangements, and modifications and alterations thereto, which fall within the scope of the appended claims.

For example, the socket blocker 100 may have any number of pins. In one envisaged embodiment the socket blocker 100 has only one pin extending from the 5 blocker body 102. In this arrangement, the aperture into which the key of the removal tool is inserted need not necessarily extend all of the way through the body of the socket blocker. For example, the aperture in the body may open to an internal cavity, the cross-sectional area of which is greater than that of the aperture so that a key of a removal tool can be inserted into the cavity and rotated to a position where the key can bear upon an 10 internal surface of the blocker body - at which point, a user can pull the tool to extract the pin of the socket blocker from the socket. In such an embodiment it may be sufficient to block access to only one of the socket apertures (for example to the earth aperture of a standard UK three pin socket). Alternatively, the socket blocker could be configured so that the blocker body 102 covers at least one of the two remaining socket 15 openings in use so as to obstruct a person from inserting a two pin plug of the type commonly used in Europe into the remaining two apertures of the UK socket.

In another envisaged implementation, the pins 104, 106, 108 may have circular cross sections and may have one or more generally frustoconical ramp portions 116 provided thereon. More specifically, the pins 104, 106, 108 need not be substantially 20 rectangular and may in fact have a square or any other cross sectional shape depending on the shape of the socket openings into which the socket blocker 100 is to be inserted. Furthermore, the pins extending from the blocker body 102 do not need to have two ramp portions 116 in order to form an interference fit with an electrical socket and may in fact comprise any number of ramp portions 116 or have no ramp portions 116 at all. 25 More specifically, the pins may be configured so that they can form a tight interference fit with openings in an electrical socket without the need for ramp portions 116.

It is also envisaged that the removal surfaces 124 of the socket blocker 100 need not necessarily be cam surfaces and may be convex or concave sloped surfaces.

The above notwithstanding, it should also be noted that whist the accompanying 30 claims set out particular combinations of features described herein, the scope of the present invention is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

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1. A system for obstructing unauthorised access to a socket, the system comprising:

5 a socket blocker removal tool; and a socket blocker, the socket blocker having a body, a pin extending from the body that is configured for insertion into and retention within an aperture defined by a body of a socket, and a first formation for engagement with a co-operating second formation of the socket blocker removal tool;

10 the arrangement being such that an authorised user can engage the second formation of the removal tool with the first formation of the socket blocker and extract the pin of the socket blocker from the aperture of the socket to thereby enable access to be had to the socket.

15 2. The system of claim 1, wherein the pin is retained within the aperture of the socket by an interference fit with the body of the socket.

3. The system of claim 1 or 2, wherein the first formation is defined by the body of the socket blocker and comprises a removal surface located within the body of the

20 socket blocker.

4. The system of claim 3, wherein:

the first formation further comprises a receiving aperture having first and second aperture portions of first and second cross sectional shapes;

25 the removal tool comprises a key portion protruding from a shaft, the key portion having a cross sectional shape complementary to that of the first cross sectional shape; and the removal surface is within the second aperture portion adjacent the first aperture portion.

30

5. The system of claim 4, wherein the receiving aperture extends entirely through the body of the socket blocker.

6. The system of any of claims 3 to 5, wherein the removal surface comprises a 35 cam surface which the removal tool is configured to ride up, when the removal tool is engaged with the removal surface and rotated relative to the socket blocker, into

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engagement with the socket to urge the pin at least partially out of the aperture of the socket.

7. The system of any preceding claim, wherein the socket blocker removal tool 5 further comprises a finger grip or handle graspable by a user for manipulating the removal tool.

8. The system of any preceding claim, wherein the body of the socket blocker has a peripheral edge that lies flush with the socket in use.

10

9. The system of claim 8, wherein a peripheral region of the body of the socket blocker has a curved outer surface.

10. The system of any preceding claim, wherein the pin has a cam surface 15 configured to form an interference fit with the body of the socket.

11. The system of claim 10, wherein the cam surface on the pin is made of a different material to the pin.

20 12. The system of claim 11, wherein the cam surface on the pin is made of a softer material to the pin, and is configured to deform against the body of the socket on insertion of the pin into the socket.

13. The system of any of claims 10 to 12, wherein the pin has two cam surfaces, one 25 provided on each of two opposite faces of the pin.

14. The system of any preceding claim, wherein the socket comprises a pin receiving spring-clamp and the pin comprises a clamp receiving formation.

30 15. The system of Claim 14, wherein the clamp receiving formation comprises a cutaway portion of the pin in which a distal part of the clamp is received when the pin is received in the clamp.

16. The system of Claim 15, wherein the pin comprises a pin head that is wider than 35 at least part of said clamp receiving formation, the arrangement being such that respective arms of the clamp move apart when the pin head is moved into the clamp,

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and subsequently move towards one another into the clamp receiving formation formed in the pin.

17. The system of any preceding claim, wherein said pin comprises one or more 5 clamp engaging formations.

18. The system of Claim 17, when dependent on Claim 16, wherein said one or more clamp engaging formations are formed in said clamp receiving formation.

10 19. The system of any preceding claim, wherein the socket blocker has a plurality of pins, each for engagement with a respective aperture in the socket.

20. A socket blocker for use with the system of any preceding claim, the socket blocker having a body, a pin extending from the body that is configured for insertion into

15 and retention within an aperture defined by a body of a socket, and a first formation for engagement with a co-operating second formation of a socket blocker removal tool.

21. A socket blocker removal tool for use with the system of any of claims 1 to 19, the socket blocker removal tool comprising a second formation for engagement with a

20 first formation of a socket blocker.

22. A system, socket blocker, or socket blocker removal tool substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

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30