EP0063120B1

EP0063120B1 - Improvements relating to electrical plugs

Info

Publication number: EP0063120B1
Application number: EP81901909A
Authority: EP
Inventors: Harman Victor Usher; David C/O Harman V. Usher Cunningham
Original assignee: Bradshaw Raymond; Lapidus Alfred David Henry; Lapidus Robyn Griffith; Lapidus Samuel Henry Alfred
Current assignee: Bradshaw Raymond; Lapidus Alfred David Henry; Lapidus Robyn Griffith; Lapidus Samuel Henry Alfred
Priority date: 1980-07-15
Filing date: 1981-07-14
Publication date: 1986-10-08
Also published as: WO1982000387A1; EP0063120A1

Abstract

An electrical plug, particularly for domestic use for coupling appliances to socket outlet of a mains distribution system, is adapted to be fitted onto an appliance flex or cable without necessitating use of a screwdriver or other tool by virtue of being formed in two parts, namely a body portion (1) formed with terminal pins (4) insertable into the openings of a socket outlet and an insert (2) enterable into a recess (3) in the body portion (1). The insert (2) comprises a cable clamping arrangement (8) and conductor-receiving channels (10) formed with a right-angled bend and each leading to a termination member (19) in which a plunger (20) is axially movable against spring bias, the plungers (20) projecting from the front face of the insert (2). In the body portion (1) of the plug, the recess (3) has in its end wall three bores (18) located and dimensioned to accept the plungers (20) when the insert (2) is entered into the recess (3), and each bore (18) communicates with a terminal pad (17) coupled electrically to a respective one of the terminal pins (4). As the insert (2) is fully entered into the recess (3) in the plug body portion (1), the plungers (20) butt against the terminal pads (17) and are driven back against their spring bias and capture the conductor ends in the termination members (19).

Description

This invention concerns improvements relating to electrical plugs for coupling domestic electrical appliances to socket outlets of the mains electrical supply.
In the United Kingdom, the standard domestic electrical plug commonly comprises a rigid plastics material plug body formed in two parts, namely a base and a cover arranged to be secured together by means of one or more screws which are accessible only when the plug is not plugged in to a socket outlet. The plug base has three terminal pins moulded into the plastics material of the base, namely an "earth" pin and "neutral" and "live" pins, with the pins projecting from the underside of the base to be received in corresponding openings of a socket outlet. The "earth" pin is commonly longer than the "neutral" and "live" pins for camming open the shutters commonly associated with the corresponding "live" and "neutral" openings of a socket outlet, a camming lever being provided in the "earth" opening of the socket outlet. In modern plugs, the terminal pins are of rectangular cross-section, but in previous and older plugs a circular cross-section was standard. The terminal pins moulded into the plug base are accessible from the other side of the base, that is from the inside of the plug, for connection thereto of the respective "earth", "neutral" and "live" conductors of an electrical flex or cable, and commonly are each provided with a screw-type terminal fixment for securing the conductor to the terminal. A fuse- holder is commonly provided between the "live" terminal pin and its screw-type fixment, and a cable clamp arrangement is commonly provided for securing the flex or cable to the plug base.
The standard British plug abovedescribed differs from the plug used throughout the rest of Europe. The European plug, as opposed to the British plug, commonly comprises a generally cylindrical housing formed at one end with an axial cable entry and open at the other end for receiving a plug body. The plug body has a wall portion which defines the plug end face when the plug body is assembled with the housing and two spaced-apart, circular cross-section "live" and "neutral" terminal pins are moulded into and project through the wall portion to be received in corresponding openings of a complementarily- shaped socket outlet. A pair of "earth" terminals constituted by terminal springs extend from the wall portion backwards with respect to the direction of extent of the two terminal pins to be received in outwardly open grooves formed in the plug housing to be accessible for contacting corresponding "earth" terminal springs provided in the socket outlet. Screw type fixments are provided in the plug body associated with the "live" and "neutral" terminals and with the "earth" terminal for securing the respective cable conductors thereto, and a cable clamp is provided in the plug body.
The assembly of a British or European plug onto an appliance flex or cable is a fairly simple and straightforward matter for the person possessed of average electrical skills or for the do-it- yourself enthusiast or handyman. However, it is nonetheless a fact that for many people the fixing of a plug onto a flex or cable is a task beyond their skills and beyond the scope of their manual dexterity. The number of screw fixments to be coped with is considered to be primarily responsible for the difficulty experienced by many people in fixing a plug to a flex or cable, and it is accordingly a primary object of the present invention to provide an electrical mains plug having no (or at least a reduced number of) terminal screw fitments and which can easily be assembled to a flex or cable without the aid of a screwdriver or any other tools.
There have been a number of prior proposals for domestic electrical plugs which limit the requirement for use of a screwdriver for assembling the plug to a flex or cable, but at the time when the present invention was made there was to our knowledge no such plug available to be purchased by the public. In CH-A-266487 for example a two-pin plug is described in which cutting blades are connected to the terminal pins and are arranged to make electrical contact with the insulated conductors of a flex when a relative movement is effected between either a bottom part of the plug which mounts the terminal pins or the terminal pins themselves and a top part of the plug, so that a screwdriver need not be used in assembling the plug for use, and in CH-A--383 458 an arrangement is described wherein a single screw-threaded member serves to drive the insulated flex conductors onto insulation piercing members connected to the terminals, so that only limited use of ^*a screwdriver is necessary. Neither of these prior early proposals would be capable of complying with the present day stringent safety regulations and technical standards which determine the suitability of electrical plugs and neither would be capable of safely carrying electrical leads of the magnitudes associated with domestic power supply circuits.
Another prior proposal is described in FR-A-1 533 366 and consists of a two-part plug in which a plug body portion has a recess formed therein into which an insert portion is adapted to be fitted. The plug body portion is generally in the form of a hollow cylinder which is closed at one end and open at the other, the hollow interior of the cylinder thus constituting the recess into which the insert portion, itself a generally cylindrical. body, is to be fitted. The plug pins are secured in the closed end of the plug body portion and have parts which extend into the hollow interior of the body portion along the side walls thereof. The insert portion has an axial bore for receiving a cable which is to be fitted to the plug end, at the end of the insert portion which is innermost in the assembled condition of the plug, has a number of individual conductor-receiving channels which lead from the axial bore to a corresponding number of axis-parallel grooves formed in the outer surface of the insert portion at positions which, when the insert is received in the body portion, align with the plug pin parts extending into the recess. In use of the thus-described arrangement, the conductor end portions of a flex or cable are stripped of their insulation and are threaded into the insert so as each to locate in a respective one of the grooves formed in the outer surface of the insert portion. The insert is then introduced into the plug body portion in the proper relative orientation for the conductor end portions to make electrical contact with respective ones of the plug pin parts extending into the recess. Leaf springs are provided in the grooves in the outer surface of the insert portion for ensuring contact between the stripped conductor end portions and the plug pins, and a cable clamping member is provided which comes into effect when the insert portion is inserted into the plug body portion.
Whilst the plug proposed in FR-A-1 533 366 is of an advantageous design as compared to the proposals of CH-A-266487 and CH-A-383458 abovementioned, principally in regard to its improved current carrying capabilities, nonetheless it has serious defects. In particular, the assembly of a cable to the insert portion is uncertain, and it cannot be known for sure that the bared conductor ends will not be displaced from their desired positions as the insert is positioned for insertion into the plug body portion. Furthermore, problems could arise if the stripped conductor end portions were made too long or too short, and the effectiveness of the cable clamping arrangement is uncertain.
According to the present invention therefore there is provided an electrical plug for use for connecting the power supply lead of a domestic electrical appliance to a socket outlet of a mains electrical distribution system by means of a sheathed cable comprising a plurality of individually insulated conductors within an insulating sheath, the said plug comprising a body portion having a plurality of terminal pins to be inserted into the corresponding openings of a socket outlet, an insert portion to which a cable as abovementioned may be assembled as a preliminary step in the connection of the plug to the cable and which is enterable into a recess in said body portion of the plug for completing the connection of the plug to the cable, and a cable clamping arrangement for gripping the sheath of a cable as aforesaid, the insert portion and the recess being arranged such that the insert portion is enterable into the said recess in only a predetermined orientation of the insert portion relative to the plug body portion and is movable within the recess for completing the connection of the plug to the cable only by linear movement of the insert portion relative to the plug body portion without relative rotation therebetween, and the insert portion including a plurality of separate conductor-receiving channels each for receiving a respective one of the conductors of the cable to which the plug is to be connected and each arranged for receiving a conductor end portion therein at a location to be accessed for making electrical contact between the respective conductor and a respective one of said pins when the insert portion is entered into said recess, and a plurality of separate cooperating contact-establishing means provided in said insert portion and in said recess for establishing electrical contact between each of said pins and a conductor end portion received at a respective one of said locations when said insert portion is entered into said recess, as known from FR-A-1 533 366 abovementioned, which is characterised in accordance with the invention in that said cable clamping arrangement is provided at one end of said insert portion which is outermost when the insert portion is fully entered into said recess and is arranged to clamp the cable to the insert portion, and the cooperating contact-establishing means are each provided at the opposite end of said insert portion from the cable clamping arrangement in the direction of insertion of the insert portion into the recess and at a cooperating surface of said recess, and said conductor-receiving channels each include a first channel portion and a second channel portion, said first channel portion being formed in a surface of said insert portion and extending from the vicinity of said cable clamping arrangement generally in the direction of insertion of said insert portion into the recess to a location whereat it communicates with said second channel portion, and said second channel portion comprising an aperture extending into said insert portion transversely to said first channel portion and transversely to the direction of insertion of the insert portion into the recess, said aperture serving to receive therein and precisely locate the end portion of a respective conductor of the cable, and each of said cooperating contact-establishing means being operative within a respective one of a plurality of further apertures formed in said insert portion and extending in the direction of insertion of the insert portion into the recess and intersecting respective ones of the first-mentioned apertures.
The invention thus resides in the concept of providing a plug insert portion which can be readily assembled to the end of an appliance flex or cable by positively engaging the flex or cable with the clamping means, which is preferably of a type which does not involve screw fitments, and fitting the conductor ends of the flex or cable into the respective conductor-receiving channels which retain and positively locate the conductor ends. The plug insert portion then is inserted into its accommodating recess in the plug body portion and the arrangement of the plug body portion and the insert portion is such that when the two are brought together reliable electrical continuity is established with certainty between the conductors of the flex or cable and the terminal pins of the plug.
The arrangement could be such that the plug body portion was provided with pins or other electrical contact establishing means projecting into said recess, and the insert portion was arranged to engage with the recess such that the pins entered into electrical contact with the conductor end portions engaged with the insert portion.
Alternatively, the insert portion might have contact-making terminal pins projecting therefrom, which pins are adapted to mate with corresponding socket portions formed in an inner end wall of the recess and to enter the said socket portions and contact the plug terminal pins when the insert portion is entered into the recess. The contact-making terminal pins might be spring loaded so that as the insert portion is forced home manually into the recess in the plug body portion, so the contact-making terminal pins are forced back against their spring bias by virtue of their engagement with the plug terminal pins and, by virtue of being thus forced back, are forced into firmer contact with their respective conductors.
In either of the arrangements abovementioned, insulation displacement techniques could be utilised to advantage thereby obviating the need to bare the conductor ends of insulation and making assembly of the plug according to the invention to a flex or cable and even more simple.
The insert portion might desirably be arranged to lock into the recess in the plug body. For example, the plug body portion might incorporate a locking catch weakly spring biassed into an inoperative condition out of position to interact with the insert portion and arranged such that the action of plugging the plug into a socket outlet mechanically urged the locking catch against its bias into an operative condition.
The plug according to the invention will preferably incorporate fuse protection of the "live" terminal, for example by means of a pop-up type of fuse mounting accessible on the face of the plug base only when the plug is disengaged from a socket outlet.
A polarising arrangement, such as a key formed on the insert to be engageable with a keyway in the plug body recess, is desirably provided to ensure that the insert portion can be inserted into the recess only in a specified orientation.
The invention, together with features and advantages thereof, will best be appreciated from consideration of the following detailed description of exemplary embodiments made with reference to the accompanying drawings wherein:-
Figures 1A and 1 B are respectively top plan and part sectional side elevation views of a first embodiment of the invention with the insert portion shown detached from its accommodating recess in the plug body portion, the cross-sectional view of Figure 1 B being taken on the line B-B of Figure 1A and internal components within the plug body portion being shown schematically in Figure 1A; and
Figures 2A and 2B show a second embodiment of the invention in views similar to those of Figures 1A and 1B respectively.
Referring first to Figures 1A and 1 B, the electric plug shown therein is of the three-pin type employed in the United Kingdom. As shown, the plug comprises a body portion 1 and an insert 2 enterable into a recess 3 in the body portion 1. The body portion 1 and insert 2 are each moulded from high impact, rigid synthetic plastics material and, as is schematically represented in the Figures, brass terminal pins 4 are moulded into the plastics material. A fuse holder 5 also is incorporated into the moulding, the fuse being accessible through a pop-up cover (not shown) provided in the base of the plug so as to be accessible only when the plug is not plugged in to a socket outlet.
Schematically represented conductors 6, constituted by brass strappings integral with or otherwise firmly affixed to the terminal pins 4, couple the terminal pins 4 to insulation displacement type terminal pins 7 which project into the recess 3 from its end wall.
Referring to the construction of the insert 2, it will be seen to comprise a cable clamping arrangement 8 located in a cable input port 9, and three conductor-receiving channels which are each formed with a right-angled bend defining first channel portions 10a and second channel portions 10b. A bore 11 provides access to the vertically-oriented limb 10b of each channel so that when the insert 2 is entered into the recess 3 in the body portion 1 of the plug, the insulation displacement pins 7 will enter the bores 11 and will penetrate into the second channel portions 10b.
A key 12 is formed on the underside of the insert 2 for cooperation with a keyway 13 formed in the base of the recess 3 to ensure that the insert 2 can be entered into the recess 3 in the correct orientation only. A locking member 14 is provided in the body portion 1 of the plug with spring biassing, for example by means of an elastomeric collar 15, towards the base of the plug so that when the plug is inserted into a socket outlet the contact of the locking member 14 with the surface of the socket outlet urges the member 14 against its bias towards the recess 3 and into engagement with a locking formation 16 formed in the underside of the insert 2.
In use of the plug of Figures 1A and 1B and in order to attach the plug to an end of an electrical flex or cable, it is necessary only to cut back a short section (about 2 cms) of the outer cable sheath so as to expose the insulated conductors and it is not necessary to cut back the conductor insulation. The respective "earth", "neutral" and "live" conductors are inserted to their fullest extent into the respective channels 10a, 10b, the cable is engaged with the cable clamping arrangement 8 by inserting the cable between the two resilient limbs of the cable clamp, and the insert 2 with cable thus attached is entered into the recess 3 in the plug body 1 to its fullest extent and until the insert becomes flush with the surface of the plug body 1 and does not project therefrom. The arrangement of the locking member 14 and the nature of its cooperation with the formation 16 in the insert 2 are such that if the insert is not fully received in the recess 3, then the locking member 14 cannot engage with the formation 16 and thus cannot be depressed which prevents the plug from being engaged sufficiently with a socket outlet to make live electrical contact therewith; only if the insert 2 is fully entered into the recess 3 can the locking member 14 be depressed and the plug engaged with a socket outlet.
Referring now to Figures 2A and 2B, where the same reference numerals are used for like parts as were used in Figures 1A and 1B, a second embodiment is shown which differs from the first embodiment above-described principally in regard to the manner in which electrical continuity is established between the conductors of a flex or cable fitted to the insert 2 and the plug terminal pins 4.
Considering first the body portion 1 of the plug, it will be seen that the terminal pins 4 are coupled with the plastics material of the plug to brass terminal pads 17 which may be integral with the terminal pins 4 or can be strapped thereto by electrically conductive straps 6. The terminal pads 17 are wholly encapsulated within the plastics material of the plug body, but can be accessed for the purpose of making electrical contact thereto through bores 18 which, as shown, extend part way into the terminal pads 17.
The insert 2 has moulded into it three brass termination members 19 each formed with a bore which serves as part of the vertical limb 10b of a respective one of the conductor-receiving channels 10 as shown. Retained within each of the members 19 is a spring-loaded axially-displaceable plunger 20, the spring being schematically shown. The plungers 20 project through apertures 11 in the front of insert 2 and are sized to fit within the bores 18 in the body portion 1.
In use of the plug of Figures 2A and 2B, the conductors of an electrical flex or cable are bared at the flex or cable end and a short length (less than 1 cm) of the conductor insulation is removed so that each conductor has a bared end. With the flex or cable lodged in the cable clamp 8, the individual conductors are laid into the channels 10 with their bared conductor ends inserted to their fullest extent into the bores in the members 19. The insert is then entered into the recess 3 in the plug body 1 which brings the plungers 20 into registry with the bores 18. As the insertion proceeds, the plungers 20 enter the bores 18 and their leading ends butt against the terminal pads 17 and thereafter, the final stage of insertion of the insert 2 causes the plungers 20 to be driven back against their spring bias and into firm mechanical engagement with the bared conductor ends. Insertion is complete when the locking member 14 clicks into the detent 16 in the base of the insert 2, and in this condition the insert 2 is retained securely in the plug body 1 and the bared conductor ends are retained in secure mechanical and electrical contact with the members 19.
From the foregoing, it will be appreciated that the invention provides an electrical plug, for use with a mains socket outlet, which can be assembled to the end of an appliance flex or cable very easily and without the need for any tools other than whatever may be required to release the conductors of an end part of the flex or cable from its outer sheath and, in the case of the second embodiment, to bare the conductor ends of their insulation. It will of course be appreciated that the second embodiment could readily be adapted for insulation displacement techniques which would obviate the need to bare the conductor ends. Tests have demonstrated that with a plug as above described connected to a flex or cable and the plug engaged with a socket outlet, tension applied on the flex or cable will cause the plug to disengage from the socket and will not pull the insert out of the plug body; the plug is thus safe in use.
While the invention has been described with particular reference to a British type three-pin plug, it will readily be appreciated by those possessed of appropriate skills that the invention is equally applicable to the continental European type of plug and indeed, so far as the Applicants are aware, to any and all types of domestic plug currently in use.

Claims

1. An electrical plug for use for connecting the power supply lead of a domestic electrical appliance to a socket outlet of a main electrical distribution system by means of a sheathed cable comprising a pluraljty of individually insulated conductors within an insulating sheath, the said plug comprising a body portion (1) having a plurality of terminal pins (4) to be inserted into the corresponding openings of a socket outlet, an insert portion (2) to which a cable as abovementioned may be assembled as a preliminary step in the connection of the plug to the cable and which is enterable into a recess (3) in said body portion (1) of the plug for completing the connection of the plug to the cable, and a cable clamping arrangement (8) for gripping the sheath of a cable as aforesaid, the insert portion (2) and the recess (3) being arranged such that the insert portion (2) is enterable into the said recess (3) in only a predetermined orientation of the insert portion (2) relative to the plug body portion (1) and is movable within the recess (3) for completing the connection of the plug to the cable only by linear movement of the insert portion (2) relative to the plug body portion (1) without relative rotation therebetween, and the insert portion (2) including a plurality of separate conductor-receiving channels (10) each for receiving a respective one of the conductors of the cable to which the plug is to be connected and each arranged for receiving a conductor end portion therein at a location to be accessed for making electrical contact between the respective conductor and a respective one of said pins (4) when the insert portion (2) is entered into said recess (3), and a plurality of separate cooperating contact-establishing means (7; 18, 20) provided in said insert portion (2) and in said recess (3) for establishing electrical contact between each of said pins (4) and a conductor end portion received at a respective one of said locations when said insert portion (2) is entered into said recess (3), characterised in that said cable clamping arrangement (8) is provided at one end of said insert portion (2) which is outermost when the insert portion (2) is fully entered into said recess (3) and is arranged to clamp the cable to the insert portion (2), and the cooperating contact-establishing means (7; 18, 20) are each provided at the opposite end of said insert portion (2) from the cable clamping arrangement (8) in the direction of insertion of the insert portion (2) into the recess (3) and at a cooperating surface of said recess (3), and said conductor-receiving channels (10) each include a first channel portion (10a) and a second channel portion (10b), said first channel portion (10a) being formed in a surface of said insert portion (2) and extending from the vicinity of said cable clamping arrangement (8) generally in the direction of insertion of said insert portion (2) into the recess (3) to a location whereat it communicates with said second channel portion (10b), and said second channel portion (10b) comprising an aperture extending into said insert portion (2) transversely to said first channel portion (10a) and transversely to the direction of insertion of the insert portion (2) into the recess (3), said aperture serving to receive therein and precisely locate the end portion of a respective conductor of the cable, and each of said cooperating contact-establishing means (7; 18,20) being operative within a respective one of a plurality of further apertures (11) formed in said insert portion (2) and extending in the direction of insertion of the insert portion (2) into the recess (3) and intersecting respective ones of the first-mentioned apertures.

2. An electrical plug as claimed in claim 1 wherein said cooperating contact-establishing means (7) are constituted by said body portion (1) having terminals (7) projecting into said recess (3) from an inner end wall thereof and said insert portion (2) being arranged such that when the insert portion (2) is fully entered into the recess (3) the said terminals (7) enter into electrical contact with the conductor end portions received in said second channel portions (10b).

3. An electrical plug as claimed in claim 2 wherein said terminals (7) projecting into the recess (3) in the body portion (1) comprise insulation dislacing terminal members arranged to displace the insulation of said insulated conductors and contact the respective conductors as the insert portion (2) is entered into said recess (3).

4. An electrical plug as claimed in claim 3 wherein said insulation displacing terminal members (7) comprise insulation piercing pins.

5. An electrical plug as claimed in claim 1 wherein said cooperating contact-establishing means (18, 20) are constituted by said insert portion (2) having contact-making terminal members (20) received in said further apertures (11) and projecting from a front face of said insert portion (2), and said terminal members (20) are adapted to be received in corresponding socket members (18) formed in an inner end wall of said recess (3) and, when received therein, to make electrical contact with the terminal pins (4) of the plug.

6. An electrical plug as claimed in claim 5 wherein said contact-making terminal members (20) projecting from a front face of the insert portion (2) each comprise a spring-biassed plunger (20) displaceable within a bore of a terminal member (19) mounted within the insert portion (2), the said bore communicating with a respective one of the conductor-receiving channel portions (10b) formed in the insert portion (2) such that when the insert portion (2) is entered into the recess (3) in the body portion (1) the plungers (20) are driven back against their spring bias and into electrical and mechanical contact with the conductor ends received in the respective channel portions (10b).

7. An electrical plug as claimed in any of the preceding claims wherein said insert portion (2) has a key portion (12) adapted to be received in a keyway (13) formed in a wall of the recess (3) in the body portion (1) whereby the insert portion (2) can be entered into the recess (3) only in a predetermined proper orientation.

8. An electrical plug as claimed in any of the preceding claims wherein the body portion (1) of the plug is provided with means (14) operative in use of the plug to lock the insert portion (2) into the recess (3) in the body portion (1).

9. An electrical plug as claimed in claim 8 wherein the body portion (1) of the plug includes a locking member (14) which is spring biassed towards an inoperative condition wherein a portion of the locking member protrudes from that surface of the plug wherefrom the terminal pins (4) project for engagement with the openings of a socket outlet, and the insert portion (2) has a formation (16) adapted for engagement with said locking member (14) when the insert portion (2) is fully entered into the recess (3) and when the said locking member (14) is driven against said spring bias into engagement with said formation (16) by engagement with the surface of a socket outlet wherein the plug is plugged.

10. An electrical plug as claimed in any of the preceding claims wherein the plurality of further apertures (11) in the insert portion (2) comprise bores formed in the solid material of said insert portion (2) for receiving and guiding parts (7; 20) of said contact-establishing means (7; 18, 20) positively into engagement with conductor end portions received in said second channel portions (10b).

11. An electrical plug as claimed in any of the preceding claims wherein said first and second conductor-receiving channel portions (10a,10b) of each said channel (10) are so inclined with respect to each other that when a conductor is laid into a channel (10) and bent to conform to the channel configuration, the inherent rigidity of the conductor will act to inhibit withdrawal of the conductor from the channel under tension applied to the cable of which the conductor forms part.

12. An electrical plug as claimed in any of the preceding claims wherein a fuse mounting (5) is provided in said plug body portion (1) and is accessible only via that surface of the plug wherefrom the terminal pins (4) project for engagement with the openings of a socket outlet.

13. An electrical plug as claimed in any of the preceding claims wherein the plug body portion (1) comprises a bottom surface wherefrom said plurality of terminal pins (4) project generally perpendicularly thereto, a top surface spaced apart from and substantially parallel to said bottom surface, and side surfaces extending between said top and bottom surfaces and generally perpendicularly thereto, and wherein said recess extends from an opening in a side surface of said plug and inwardly of the plug body portion in a direction generally transverse to the respective side surface.

14. An electrical plug as claimed in any of the preceding claims wherein said cable clamping arrangement (8) is of a type which does not involve screw fitments.