WO2005091443A1

WO2005091443A1 - Waterproof electrical connectors

Info

Publication number: WO2005091443A1
Application number: PCT/IB2005/000645
Authority: WO
Inventors: Tat-Kwong Cheung
Original assignee: Jim Fung Electrical Company Ltd; Davies, Paul, R.
Priority date: 2004-03-15
Filing date: 2005-03-15
Publication date: 2005-09-29

Abstract

An electrical connector pair comprising first and second detachable connectors, said first and said second detachable connectors respectively comprising plastic moulded first and second head portions, said first head portion of said first connector comprising a peripheral wall which defines a receptacle for receiving at least the front part of said second head portion of said second connector and said peripheral wall surrounds said head portion in a closely fitted manner, said front part of said second head portion and said receptacle including moulded guard ring means, the base of said receptacle and the front end of said front part of said second head portion of said second connector including corresponding collar and groove means, said collar and groove means being adapted so that, when said first and second detachable connectors are connected under normal use conditions, said collar and groove means being compressively engaged in a closely fitted manner forming a first water-tight barrier, said moulded guard ring means forming a second water-tight barrier.

Description

WATERPROOF ELECTRICAL CONNECTORS

FIELD OF THE INVENTION

This invention relates to electrical connecting means, devices and apparatus with fluid ingression protection and, more particularly, to waterproof electrical connectors.

BACKGROUND OF THE INVENTION

Electrical connectors with fluid ingression protection features are desirable in many applications. For example, they are essential for providing electrical power to applications such as under-water lighting and outdoor lighting such as Christmas lighting, garden lighting and party lighting. Electrical connectors with fluid ingression protection are generally referred to as waterproof electrical connectors, although fluid ingression properties are not limited to apply to water only. In many such applications, a good degree of water-tightness or liquid- ingression protection is essentially to ensure proper electrical operation and to alleviate the risk of fire hazards since water leakage may result in short-circuits and cause fire.

Conventional waterproof electrical connectors usually use rubber sealing rings or nitrile seals to form water-tight barriers to achieve water-tightness. For waterproof applications using rubber sealing rings, additional fasteners such as screws are usually needed to tighten corresponding parts in order to ensure a desirable level of water tightness. When using nitrile seals, it is known that some lubricants, hydraulic fluids and solvents can cause severe deterioration of their fluid blocking properties. Therefore, nitrile seals alone would not provide reliable long-term sealing. IEC 529 is an industry wide common standard for specifying the environmental protection level of enclosures around electrical and electronic equipment. Under IEC 529, an IP number comprising two digits is used to specify the environmental protection level of enclosures around electrical and electronic equipment such as electrical connectors. The prefix IP is an abbreviation of "ingress protection". An IP number comprises two digits, the first digit refers to the protection against solid objects and the second against liquid. The liquid ingression protection level is divided into eight classes in which the higher the number the better the liquid ingression protection. For example, 0 or X means no protection and level 6 means protection against a low pressure of water. Testing methods for compliance with the IEC 529 (or DINEDE 040-1) can be found in the websites of many professional testing laboratories and are incorporated herein for reference.

While waterproof electrical connection means are desirable in many applications, known waterproof electrical connection means usually requires the assembling of sealing parts which are somewhat complicated and hence skilled workers are required to assemble them. Hence, it is desirable if there can be provided waterproof electrical connection means which can be more easily used by the public.

OBJECT OF THE INVENTION Hence, it is an object of the present invention to provide waterproof electrical connecting means which are easy to assemble while providing a reasonable degree of ingress protection. At a minimum, it is an object of the present invention to protect the public with a useful choice of waterproof electrical connection means.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention has described an electrical connector pair comprising first and second detachable connectors, said first and said second detachable connectors respectively comprising plastic moulded first and second head portions, said first head portion of said first connector comprising a peripheral wall which defines a receptacle for receiving at least the front part of said second head portion of said second connector and said peripheral wall surrounds said head portion in a closely fitted manner, said front part of said second head portion and said receptacle including moulded guard ring means, the base of said receptacle and the front end of said front part of said second head portion of said second connector including corresponding collar and groove means, said collar and groove means being adapted so that, when said first and second detachable connectors are connected under normal use conditions, said collar and groove means being compressively engaged in a closely fitted manner forming a first water-tight barrier, said moulded guard ring means forming a second water-tight barrier.

According to a preferred embodiment of the present invention, there is also provided electrical connectors which the features of the individual first and second connectors described herein. Preferably, said collar and groove means comprising a pair of collar and groove members which are adapted for enclosing the electrical connection parts which are accessible for making electrical connection when said first and second connectors are connected during normal use, said collar and groove members including tapered engagement means so that when said collar and groove members are connected under normal use conditions said collar and groove members being in compressive engagement to form said first water-tight barrier.

Preferably, said groove member being formed on the bottom of said receptacle and tapering away from said receptacle so that, when said connector pair is connected for normal use, said collar member being inserted like a plug against said tapered groove member to enhance water tightness.

Preferably, said moulded guard ring means comprising a guard ring member moulded on said front part of said second head portion of said second connector, said guard ring member surrounding said second head portion and protruding away therefrom.

Preferably, the planes formed by said guard ring member and said collar member being substantially parallel.

Preferably, said collar member being formed on a free end of said second head portion of said second connector and protruding away therefrom along the direction of connection of said electrical connector pair.

Preferably, said collar member being formed on a free end of said second head portion, said free end of said second portion being substantially in contiguous contact with the bottom of said receptacle of said first connector when connected for normal use, the directions of protrusion of said collar member and said guard ring member being non-parallel.

Preferably, said directions of protrusion of said collar member and said guard ring member being substantially orthogonal. Preferably, said collar member being formed on a free end of said head portion of said second connector and tapering away therefrom, the extent of protrusion of said collar member away from the base of said free end being less that the depth of depression of said groove member so that a gap exists between the free end of said collar member and the bottom of depression of said groove member.

Preferably, said connector pair, further comprising tightening means for drawing said first and second connectors together so that, when said first and second connectors are tightened together by said tightening means, said first and second connectors are maintained in connection with said collar and groove means slightly deformed.

Preferably, a moulded circumferential flange being formed near the rear part of said second head portion of said second connector, said moulded circumferential flange and said peripheral wall of said first connected being adapted so that, when said first and second connectors are connected and tightened by said tightening means, said moulded circumferential flange and the free end of said peripheral being in compressive contiguous contact and forming a third water-tight barrier. Preferably, said moulded circumferential flange and said free end of said peripheral wall being engaged with slight deformation for enhanced water- tightness.

Preferably, conductive parts accessible for making electrical connection are disposed at the front end of said front part of said second connector and an electrical lead extending from the rear end of said second head portion of said second connector, said tightening means including a moulded plastic tightening cap which embraces the rear end of said second connector, said tightening cap including a base member and a peripheral wall, said base member having an aperture so that said tightening cap can approach the rear end of said second connector along said electrical lead and is rotatable with respect to said electrical lead, said peripheral walls of said tightening cap and said first connector including cooperative twist-type tightening means whereby said first and said second connects can be tightened together by twist-tightening of said tightening cap and said first connector.

Preferably, said twist-type tightening means including a bayonet type tightening connection comprising a stud and socket arrangement.

Preferably, said socket includes a groove which extends along a helical curve and said stud extends for a length along a helical curve commensurate with the curve of said socket.

Preferably, said twist-type tightening means including a screw-threaded tightening arrangement. Preferably, conductive parts accessible for making electrical connection are disposed at the front end of said front part of said second connector and an electrical lead extending from the rear end of said second head portion of said second connector, said tightening means including a moulded plastic tightening cap which embraces the rear end of said second connector, said tightening cap including a base member and a peripheral wall, said base member having an aperture so that said tightening cap can approach the rear end of said second connector along said electrical lead and is rotatable with respect to said electrical lead, said peripheral walls of said tightening cap and said first connector including cooperative twist-type tightening means whereby said first and said second connects can be tightened together by twist-tightening of said tightening cap and said first connector.

Preferably, said tightening cap including a moulded sealing ring, said moulded sealing ring being adapted for compressive contact with said moulded circumferential flange of said second connector during normal use and forming a fourth water-tight barrier.

Preferably, said moulded circumferential flange of said first connector being compressively sandwiched between said moulded sealing ring of said tightening cap and the free end of the peripheral wall of said first connector during normal use.

Preferably, the free end of said tightening cap being formed into a moulded sealing collar for compressive contact with the corresponding regions in said peripheral wall of said first connector to form a fifth water-tight barrier. Preferably, said electrical lead and said aperture of said tightening cap being adapted for tapered engagement so that when said tightening cap being tightened with said first connector, a water-tight junction being formed between said electrical lead and said aperture. Preferably, said electrical lead adjacent portion of said head portion of said first connector being tapered away from said first connector.

Preferably, said tightening cap and said receptacle of said first connector together form a water-tight compartment enclosing said second electrical connector. Preferably, said first and second connectors being an electrical plug and socket pair.

Preferably, said compressive engagement between said collar and groove members increases along the direction of connection of said electrical connector pair so that slight deformation of said collar and groove members occur when said first and second detachable connectors are connected for normal use.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of this invention will be explained in further detail below by way of examples and with reference to the accompanying drawings, in which: Fig. 1 shows the electrical connector pair of a first preferred embodiment of the present invention connected for normal use conditions, Fig. 2 shows an electrical connector pair of Fig. 1 when detached,

Fig. 3 is a cross-sectional view of the connected electrical connection pair of Fig. 1 with enlarged view showing the various components,

Fig. 3A shows an enlarged view of the circled portion x-x of the connected electrical pair of Fig. 3,

Figs. 4A and 4B respectively show enlarged views of the first and second connectors and accessories,

Fig. 5A is a perspective view of the first connector of the first preferred embodiment of Fig. 1 , Fig. 5B is a perspective view showing a sealing cap for use with a first connector,

Fig. 6 is a cross-sectional showing the head portion when the first connector of Fig. 5A is sealed with the cover of Fig. 5B,

Fig. 6A is a perspective view showing the protective cover of Fig. 6, Fig. 6B is a perspective view of the protective cover of Fig. 6A from another side,

Fig. 6C is a cross-sectional view of the protective cover of Fig. 6A taken across the line intersecting the extension slug,

Fig. 6D shows an enlargement of the circled portion of Fig. 6C, Fig. 6E shows a perspective view from below showing a slightly curved track forming part of the tightening means,

Fig. 6F shows the connecting ribs on the protective cover,

Fig. 7 shows a second preferred embodiment of the present invention comprising a socket mounted with a first connector on a wall plate,

Fig. 7B shows a longitudinal cross-section of the wall socket of Fig. 7A,

Fig. 7C is an enlarged view of the circled portion of Fig. 7B,

Fig. 7D shows a base of the wall plate of Fig. 7A,

Fig. 8 shows a second preferred embodiment of a second connector of the present invention in the form of an electric plug with a cable fastening collar,

Fig. 8A is a disassembled perspective view of the 8 of Fig. 8,

Fig. 8A1 is a perspective view showing the cable fastening cap of Figs. 8 and 8A,

Fig. 8B is a perspective view showing the plug of Fig. 8A with a cable insertion plug shown,

Fig. 8B1 is a perspective view showing the head portion of the plug of Fig. 8B,

Fig. 8C is a perspective view showing the plug of Fig. 8B with the tightening cap attached, Fig. 8D shows the head portion and the electrical connection parts detached,

Fig. 8E shows the electrical means and the mounting base detached,

Fig. 8F shows a cross-sectional view of the assembled plug of Fig. 8, and Fig. 8G is an enlarged view showing the circled portion of Fig. 8F.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figs. 1-5A, there is shown a first preferred embodiment of an electrical connector pair 1 of this invention. The electrical connector pair comprises a first electrical connector 100 and a second electrical connector 200 which are connected for normal use as shown in Fig. 1. The first and second electrical connectors are respectively an electric socket and an electric plug which are also commonly and respectively known as female and male connectors. As can be seen more clearly in Figs. 2, 3, 4A and 5A, the first electrical connector 100 is an electric socket comprising a head portion 110 moulded of durable plastics with a retreated portion surrounded by an axially extending circumferential wall 150. Electrical connection parts are accommodated within the moulded head portion for receiving contact pins of a counterpart electrical plug. The electrical connection parts are accessible from the front and free end 120 of the head portion and comprise resilient contact parts known to skilled persons. The rear end 130 of the head portion is connected to an electrical lead 140 such as an electrical wire or cable. A circumferential peripheral wall 150 extends axially from the free end of the moulded head portion and extends away from the head portion so as to form a receptacle 160 for receiving at least the front part of the head portion of the second connector 200.

In this example, the peripheral wall 150 and the outer periphery wall 220 of the protruding head portion of the second connector 200 are substantially circular as a convenient sample, although peripheral walls of other corresponding shapes can be used without loss of generality.

To form a first water-tight barrier, a pair of groove and appropriately shaped collar means is provided respectively on the corresponding regions on the first and the second connectors. In this example, the groove means comprises a circumferential groove 170 formed at the bottom of the receptacle 160 of the first connector and surrounding the electrical connection parts. The collar means comprises a correspondingly shaped collar member 250 protruding from the front end of the front portion of the second connector 200. The groove and collar pair is adapted so that a substantially water-tight compartment is formed and defined by the circumference of collar when the pair is duly engaged. The collar and groove is made of durable plastics with a small resilience so that the pair forms a first ingression protection (the "first water-right barrier") when compressively engaged.

Referring to Figs. 2, 3 and 4B, the second connector 200 is an electrical plug which is adapted to form a complementary electrical and mechanical connection with the electrical socket of the first connector. The second connector comprises a plastic moulded head portion 210 with a peripheral wall 220 surrounding the electrical connection parts which are protruding pins shaped and sized according to various national and international standards. The plurality of conductive pins are shaped and adapted for making electrical and mechanical connection with the corresponding electrical connection parts on the first connector and are protruding from the front free end 230 of the second connector. An electrical lead 240 extends from the rear part of the moulded head portion 210 for making electrical connection to other parts of an electrical circuit. To ensure water tightness between the electrical lead and the second connector 200, a plastic head 270 is moulded around the periphery of the electrical lead. The collar means in this example includes a moulded peripheral collar 250 which extends from the free end of the head portion of the second electrical connector. As can be seen from the figures, the moulded collar 250 extends away from the lead portions and is provided to enhance water ingress protection. Specifically, the collar is tapered at its free end so that it can co-operatively form a compressive engagement with the corresponding groove on the first connector when it is pushed to be fitted inside the groove. A circumferential guard ring 260 is moulded on the outside of the peripheral wall and at a location intermediate the free end and the lead-end of the plug to form a second ingress-protection means (the "second water-tight barrier"). In addition, a circumferential flange 270 is moulded near the rear end of the head portion of the second connector to form another ingress-protection means (the "third water-tight barrier") to be described below. In order to ensure secured connection between the first and the second connector and to maintain a constant level of ingression protection, a tightening means is provided.

The tightening means comprises a tightening cap 300 with an internal hollow space which is sufficient to house the rear part of the head portion of the second connector. The tightening cap comprises a peripheral wall 310 which is adapted to be tightened with the first connector during normal use. The tightening cap also includes an aperture at its base so that the tightening cap can slide axially along the electrical lead and to move between an engaging position and non-engaging position in relation to the rear part of the head portion of the second connector. A twist-type tightening means is provided on the tightening cap and the corresponding regions on the first connector. In order to allow rotational or twist-type tightening so that there can be gradually increasing tightening between the first and the second connectors. A twist-type tightening mechanism such as a bayonet stud and slot pair or a screw-threaded tightening mechanism is formed on the tightening cap and the corresponding regions on the first connector. This can be seen from Figs. 4A and 4B in which the bayonet type fastening means is used as an example. In this preferred embodiment, the bayonet part comprises an extended stud with a curvature corresponding to the track or slot formed on the inside of the tightening cap. This allows a push-in and twist type tightening and securing. To obtain smooth and progressive compressive engagement between the groove and collar means to form the first water-tight barrier, the free end of the collar member is rounded so that it can be inserted into the corresponding groove member on the first connector like the insertion of a sealing plug into a hole. The groove can also taper away from the engaging surface 160 for further ingression proof. Turning now to the normal use or normal operating conditions of the electrical connector pair, the first and second connector are first press fitted together and the tightening cap is rotated or twisted in order to secure the two parts together. As can be seen from Figs. 3 and 3A, when the second connector 200 is inserted into the receptacle 160 of the first connector 100 with the collar 250 inserted into the corresponding groove 170, a first water-tight barrier is formed. The outer peripheral wall 220 of the second connector is dimensioned so that when the first and the second connectors are connected, the peripheral wall 220 is received by the receptacle 160 of the first connector in a closely-fitted manner. The moulded guard ring member 260 is formed on the periphery of the head portion of the second connector in such a manner that when the connectors are duly connected, a contiguous compressive engagement occurs between the inside of the peripheral wall 150 of the first connector and the guard ring 260 of the second connector to form a second water-tight barrier. The head portions of the first and second connectors, including the peripheral walls, are preferably made of hard and durable plastics which can be slightly resiliently deformed so as to form an enhanced ingression protection barrier between the head portions of the first and second connectors. Because of the close fitting relationship between the head portions, the moulded guard ring also serves to alleviate the risk of displacement between the head portions even when the tighting means is inadvertently removed.

The tightening means is provided to further enhance secured connection between the first and the second connectors. The tightening means includes a tightening cap 300 which is rotatable relative to the electrical lead and with its free end protruding from the rear part of the head portion. The peripheral wall 310 of the tightening cap which extends from the base of the tightening cap extends away from the electrical lead and towards the front free and of the head portion of the second connector. The peripheral wall 310 of the tightening cap is adapted and dimensioned so that when the first and the second connectors are connected under normal use connections and the tightening cap is tightened with the first connector, the peripheral wall of the tightening cap will be in closely fitted engagement with the front part of the peripheral wall 150 of the head portion of the first connector.

To provide additional ingression protection, a circumferential flange 270 is moulded near and surrounding the rear end of the head portion of the second connector. The circumferential flange 270 is adapted and dimensioned so that when the first and the second connectors are tightened together by the tightening means, the free end of the peripheral wall 150 of the first connector will be in compressive and contiguous contact with the circumferential flange 270, whereby the third water-tight barrier is formed. The head portions of the first and the second connectors are made, for example, of PVC or other durable hard plastics which can be slightly and resiliently deformed. It will be appreciated that a slight resilient deformation at the compressive contacts can enhance ingression protection. In addition, the tightening cap also includes a moulded sealing ring corresponding to the extent of the circumferential flange so that when the tightening cap is fully tightened with the first connector, a fourth water-tight barrier will be formed between the tightening cap and the circumferential flange for yet further enhancement of ingression protection. The compartment defined by the tightening cap and the receptacle, which is formed by the peripheral wall of the first connector, is formed as a water-tight compartment by providing a water-tight junction between the tightening cap and the electrical lead. This can, for example, be achieved by having the part of the electrical lead adjacent the rear part of the second connector tapers away from the rear portion so that a water-tight junction will be formed when the tightening cap is tightened with the first connector. The tightening cap is also moulded from hard plastics which are slightly and resiliently deformable and similar to the hard plastics of the first and the second head portions, hence a compressive water-tight barrier can be formed at the junction without loss of generality.

To provide yet further ingression protection, the free end of the tightening cap is tapered so as to form a fifth water-tight barrier with a protruding circumferential moulded ring formed on the step junction between the peripheral wall 150 and the rear part of the head portion 110 of the first connector. While the above preferred embodiment has been explained with reference to the first and second connectors which are respectively electrical socket and plug, it will be appreciated that the first and second connectors can be respectively a plug and a socket without loss of generality. It will be appreciated that a water-tight electrical connection pair can be assembled easily by a user by first inserting the second connector into the first connector and then tighten the first and the second connectors by the tightening cap which can be performed easily by an ordinary user.

Referring to Fig. 6, there is shown a second preferred embodiment of an electrical connector 500 of the present invention. The connector 500 comprises an electrical connector 510 and a shielding member 520. The electrical connector 510 is identical to the first connector of the first preferred embodiment, although it will be appreciated that it can be a plug or a socket. The shielding member is adapted so that when assembled together, it forms an electrical connector with ingression protection on the electrical connector. The electrical connector is substantially identical with the first connector of the first preferred embodiment and includes a plastic moulded head with a peripheral wall defining a receptacle for receiving a counterpart electrical connector. The shielding member comprises a shielding cap with an inner peripheral wall 521 and an outer peripheral wall 523. The outer peripheral wall 523 is similar in dimension and structure to the peripheral wall of the tightening cap 310 and includes tightening means for making twist-type engagement with the peripheral wall of the second connector. The inner peripheral wall 521 of the shielding cap is similar in dimension and structure to the head portion of the second connector 200 of the first preferred embodiment. Specifically, it comprises a free front end 525 with a collar member 527 protruding therefrom. The collar member 527 is adapted and dimensioned for closely fitted engagement with the groove 170 on the receptacle of the electrical connector 510. It will be noted that apart from the electrical parts, the structure of the shielding member is substantially a combination of the housings of second electrical connector 200 and the tighting cap 300. Similar to the collar member 250 on the second connector 200 of the first preferred embodiment, the collar member 527 tapers away from the head portion of the second connector and has a rounded end for smooth and progressive engagement with the collar member. Referring to Figs. 6A - 6F, it will be noted that the shielding member resembles a double layer plug for ingression protection.

Referring to Figs. 7A - 7D, there is shown a third preferred embodiment 3 of the present invention comprising a wall plate 31 mounted with an electrical connector 32. The electrical connector is substantially similar to the first electrical connector 100 and can be a plug or a socket, although a socket is shown. As can be seen from the cross-sectional views of Figs. 7B and 7C, the head portion of the electrical connector 32 is similar to that of the first connector 100 of the first preferred embodiment and comprises a peripheral wall which defines a receptacle for receiving a counterpart electrical connector with a circumferential groove member formed at the base of the receptacle. The wall plate 3 of Fig. 7D shows an example of a suitable wall plate for mounting the first connector.

Referring to Figs. 8 - 8G, there is shown a fourth preferred embodiment 4 of the present invention using the second connector of the first preferred embodiment as a convenient example demonstrate electrical connector which can be assembled to an electrical lead with a reasonable degree of ingression protection without undue difficulty or complexity. Referring to the exemplary second connector shown in Fig. 8, an ingression-protectiop cable interface is provided at the rear end of the connector. The cable interface includes an insertion plug 510 and a tightening cap 520. The inserting plug is adapted for fitting insertion into the moulded collar member extending from the rear part of the head portion of the connector as more particularly shown in Figs. 8B and 8F. The rear collar member of the connector tapers away from its head portion so that after a cable has been inserted into the cable plug and inserted into the collar, a watertight junction will be formed when the cap is tightened towards the head portion of the connectors. The tightening means between the collar member and the cap member is similar to the twist-cap tightening means described above and can also be a screw-threaded tightening means.

In the above description, it will be appreciated that the various ingression- protection means can be used jointly, severally or in any appropriate combination which would be apparent to persons skilled in the art without loss of generality. The numbering of the various water-tight barriers is merely for convenient reference and does not restrict or indicate their relative priority, importance or efficiency.

While the present invention has been explained by reference to the preferred embodiments described above, it will be appreciated that the embodiments are only illustrated as examples to assist understanding of the present invention and are not meant to be restrictive on its scope. In particular, the scope, ambit and spirit of this invention are meant to include the general principles of this invention as inferred or exemplified by the embodiments described above. More particularly, variations or modifications which are obvious or trivial to persons skilled in the art, as well as improvements made on the basis of the present invention, should be considered as falling within the scope and boundary of the present invention.

Furthermore, while some embodiments of the present invention has been explained by reference to plugs and sockets, it should be appreciated that the invention can apply, whether with or without modifications, to electrical connectors generally without loss of generality.

Claims

1. An electrical connector pair comprising first and second detachable connectors, said first and said second detachable connectors respectively comprising plastic moulded first and second head portions, said first head portion of said first connector comprising a peripheral wall which defines a receptacle for receiving at least the front part of said second head portion of said second connector and said peripheral wall surrounds said head portion in a closely fitted manner, said front part of said second head portion and said receptacle including moulded guard ring means, the base of said receptacle and the front end of said front part of said second head portion of said second connector including corresponding collar and groove means, said collar and groove means being adapted so that, when said first and second detachable connectors are connected under normal use conditions, said collar and groove means being compressively engaged in a closely fitted manner forming a first water-tight barrier, said moulded guard ring means forming a second water-tight barrier.

2. An electrical connector pair of claim 1, wherein said collar and groove means comprising a pair of collar and groove members which are adapted for enclosing the electrical connection parts which are accessible for making electrical connection when said first and second connectors are connected during normal use, said collar and groove members including tapered engagement means so that when said collar and groove members are connected under normal use conditions said collar and groove members being in compressive engagement to form said first water-tight barrier.

3. An electrical connector pair of claim 2, wherein said groove member being formed on the bottom of said receptacle and tapering away from said receptacle so that, when said connector pair is connected for normal use, said collar member being inserted like a plug against said tapered groove member to enhance water tightness.

4. An electrical connector pair of claim 2, wherein said moulded guard ring means comprising a guard ring member moulded on said front part of said second head portion of said second connector, said guard ring member surrounding said second head portion and protruding away therefrom.

5. An electrical connector pair of claim 4, wherein the planes formed by said guard ring member and said collar member being substantially parallel.

6. An electrical connector pair of claim 4, wherein said collar member being formed on a free end of said second head portion of said second connector and protruding away therefrom along the direction of connection of said electrical connector pair.

7. An electrical connector pair of claim 4, wherein said collar member being formed on a free end of said second head portion, said free end of said second portion being substantially in contiguous contact with the bottom of said receptacle of said first connector when connected for normal use, the directions of protrusion of said collar member and said guard ring member being non-parallel.

8. An electrical connector pair of claim 7, wherein said directions of protrusion of said collar member and said guard ring member being substantially orthogonal.

9. An electrical connector of claim 4, wherein said collar member being formed on a free end of said head portion of said second connector and tapering away therefrom, the extent of protrusion of said collar member away from the base of said free end being less that the depth of depression of said groove member so that a gap exists between the free end of said collar member and the bottom of depression of said groove member.

10. An electrical connector pair of claim 4 preferably, said connector pair, further comprising tightening means for drawing said first and second connectors together so that, when said first and second connectors are tightened together by said tightening means, said first and second connectors are maintained in connection with said collar and groove means slightly deformed.

11. An electrical connector pair of claim 10, wherein a moulded circumferential flange being formed near the rear part of said second head portion of said second connector, said moulded circumferential flange and said peripheral wall of said first connected being adapted so that, when said first and second connectors are connected and tightened by said tightening means, said moulded circumferential flange and the free end of said peripheral being in compressive contiguous contact and forming a third water-tight barrier.

12. An electrical connector pair of claim 11, wherein said moulded circumferential flange and said free end of said peripheral wall being engaged with slight deformation for enhanced water-tightness.

13. An electrical connector pair of claim 10, wherein conductive parts accessible for making electrical connection are disposed at the front end of said front part of said second connector and an electrical lead extending from the rear end of said second head portion of said second connector, said tightening means including a moulded plastic tightening cap which embraces the rear end of said second connector, said tightening cap including a base member and a peripheral wall, said base member having an aperture so that said tightening cap can approach the rear end of said second connector along said electrical lead and is rotatable with respect to said electrical lead, said peripheral walls of said tightening cap and said first connector including cooperative twist-type tightening means whereby said first and said second connects can be tightened together by twist-tightening of said tightening cap and said first connector.

14. An electrical connector pair of claim 13, wherein said twist-type tightening means including a bayonet type tightening connection comprising a stud and socket arrangement.

15. An electrical connector pair of claim 14, wherein said socket includes a groove which extends along a helical curve and said stud extends for a length along a helical curve commensurate with the curve of said socket.

16. An electrical connector pair of claim 13, wherein said twist-type tightening means including a screw-threaded tightening arrangement.

17. An electrical connector pair of claim 10, wherein conductive parts accessible for making electrical connection are disposed at the front end of said front part of said second connector and an electrical lead extending from the rear end of said second head portion of said second connector, said tightening means including a moulded plastic tightening cap which embraces the rear end of said second connector, said tightening cap including a base member and a peripheral wall, said base member having an aperture so that said tightening cap can approach the rear end of said second connector along said electrical lead and is rotatable with respect to said electrical lead, said peripheral walls of said tightening cap and said first connector including cooperative twist-type tightening means whereby said first and said second connects can be tightened together by twist-tightening of said tightening cap and said first connector.

18. An electrical connector pair of claim 17, wherein said tightening cap including a moulded sealing ring, said moulded sealing ring being adapted for compressive contact with said moulded circumferential flange of said second connector during normal use and forming a fourth water-tight barrier.

19. An electrical connector pair of claim 18, wherein said moulded circumferential flange of said first connector being compressively sandwiched between said moulded sealing ring of said tightening cap and the free end of the peripheral wall of said first connector during normal use.

20. An electrical connector pair of claim 18, wherein the free end of said tightening cap being formed into a moulded sealing collar for compressive contact with the corresponding regions in said peripheral wall of said first connector to form a fifth water-tight barrier.

21. An electrical connector pair of claim 13, wherein said electrical lead and said aperture of said tightening cap being adapted for tapered engagement so that when said tightening cap being tightened with said first connector, a water-tight junction being formed between said electrical lead and said aperture.

22. An electrical connector pair of claim 21 , wherein the said electrical lead adjacent portion of said head portion of said first connector being tapered away from said first connector.

23. An electrical connector pair of claim 13, wherein said tightening cap and said receptacle of said first connector together form a water-tight compartment enclosing said second electrical connector.

24. An electrical connector pair of claim 13, wherein said first and second connectors being an electrical plug and socket pair.

25. An electrical connector pair of claim 2, wherein said compressive engagement between said collar and groove members increases along the direction of connection of said electrical connector pair so that slight deformation of said collar and groove members occur when said first and second detachable connectors are connected for normal use.