FR2699752A1 - Cable gland for connection box of semi-trailer - Google Patents

Abstract

The cable gland is fitted in a hole in the wall (110) of a junction box (100). The gland has coaxial parts (200,300,400) each having an axial passage for the cable. The parts attach to each other, and exert a radial contraction on the central part (400) so that its inner wall is compressed onto the cable sheath.One of the parts (200) is shaped to fit round a boss (114) formed at the edge of the hole in the wall of the box, forming a seal and providing mechanical locking (208). The third part (300) screws (214) onto the first part, compressing the inner part (400).

Description

 The present invention relates generally to junction boxes, in particular for trailers or road tractors.

 It is conventional to equip a trailer or a road tractor with one or more junction boxes comprising a housing, a plurality of metal connection bars fixed in suitable arrangements inside the housing and a plurality of holes for the passage of incoming and outgoing electrical cables.

 Such a junction box allows the driver to carry out himself, in a relatively simple manner, the various electrical connections necessary for the supply of various auxiliary electrical or decorative components located on the trailer or on the tractor itself. , including clearance lights, string lights, etc.

 Since such a junction box is exposed to the weather, it is obviously necessary to ensure a seal at the level of the wire passage orifices.

The conventional technique for obtaining this seal consists in providing cable gland seals or the like on each incoming or outgoing cable at the associated orifice, each cable gland conventionally ensuring this seal.

 Such a solution is however disadvantageous in that the orifices intended to cooperate with the cable glands are conventionally relatively small, which prohibits engaging in the housing through an orifice a cable previously equipped with a connector for connection to the bars. therefore, arrive in the housing a plurality of wires devoid of connectors, which induces significant risks of wiring errors. In addition, it is impossible under these conditions to automate the connection of cables to the modules.

 In another known junction box, the orifices for the passage of the cables consist of notches formed in an edge region of a part of the housing, these notches being closed when a cover of said housing is put in place. In this case, the sealing is carried out using grooved seals made of elastomeric material engaged around the cables and in the notches before the housing is closed. This approach makes it possible to equip the various cables with terminal connectors, so as to overcome the drawbacks mentioned above. However, the quality of the seal obtained is poor.

 The present invention aims to overcome the drawbacks of the prior art, and to provide a junction box of the type indicated in the introduction, in which a satisfactory seal can be obtained in a simple and economical manner, while allowing passage through the orifices of cables pre-fitted with connectors.

 To this end, it provides a device for leaktight cable crossing through a wall of a housing, in particular in an electrical branch box of a road tractor, characterized in that it comprises in combination at least two generally coaxial elements each comprising a passage crossing for the cable, said elements being able to be fixed to each other by exerting on one of them an essentially radial stress in order to ensure the coming into sealed contact of an internal wall of at least one of said passages with said cable, in that one of the elements comprises a base provided with first locking arrangements and a bearing surface for a compressible seal, and in that said wall of the housing comprises a opening suitable for receiving the cable and the base and around which is defined another bearing surface for said compressible seal, and present in the region of said opening of the second locking arrangements capable of cooperating with the first locking arrangements for assembling said element provided with the base on the housing by compressing said seal between the bearing surfaces.

 Other aspects, objects and advantages of the present invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of example and made with reference to the appended drawing, in which the single figure is an exploded and cutaway perspective view of a device according to the present invention.

 Referring to the drawing, there is shown a wall portion 110 of a housing 100, in which an opening 112 of generally circular shape is made. A cylindrical collar 114 extends the opening 112 on the outside of the housing. In the inner wall of the collar, at the plane of the wall 110 of the housing, a re-entrant collar 113 is formed in which four notches 115 are regularly spaced angularly apart.

 The device according to the present invention comprises a first element 200, a first part of which, facing the housing 100, defines three generally cylindrical and coaxial skirts 202, 204 and 206. The outer skirt 206 has an inside diameter slightly greater than that of the collar . It also has a hexagonal outer section, for its rotation using an appropriate key.

 The intermediate skirt 204 has an outside diameter slightly less than the inside diameter of the collar, and has at its outer periphery four pins 208 capable of engaging, in an appropriate angular position of the first element relative to the housing, in the respective notches 115 of the re-entrant collar 113.

 At the bottom of the annular space defined between the intermediate 204 and external 206 skirts is defined a housing for an O-ring seal 500, preferably made of elastomeric material, a peripheral bead 205 being formed outwards from the intermediate skirt 204 for a suitable setting of the joint.

 Said lugs have a rear surface 208a (oriented away from the housing) which is essentially radial, occupying a predetermined axial position.

 The internal skirt 202 defines a through passage 210 for the electric cable (not shown), and has approximately the same axial extent as the intermediate skirt 204.

 On the side opposite their free ends, the three skirts are connected to each other by a body part 212.

 The first element 200 comprises a second part 214 of generally cylindrical shape, extending coaxially with the three skirts. This part 214 internally defines a housing 216 aligned with the cable passage 210. The part 214 is externally threaded at 218.

 The device of the invention also comprises a second part 300 in the form of a threaded plug, which has a cylindrical part 302 of hexagonal external section, for its rotation drive by a key, and which has an internal thread 304. At its opposite end at the housing 100, this part 302 joins a part in the general shape of a disc 306, an inner face of which defines a bearing surface for the purposes explained below. The interior housing defined by element 300 is indicated at 308.

 This part 306 has a circular opening 310 for the cable.

 The device finally comprises a third generally cylindrical part 400, which has a through passage 402 for the cable, the internal wall of said passage having, as shown here, a plurality of circular ribs of generally trapezoidal section, the end faces of said ribs being intended to come and apply against the cable as we will see later. In a variant not shown, the internal wall of said passage has a smooth surface.

The wall thickness of the element 400 varies along its length to define, in a direction away from the housing 100
a first region 404 of smaller diameter, capable of freely engaging in the housing defined by the second part XXX of the element 200,
- A region 406 of intermediate diameter, which has on its outer surface a plurality of bosses 407, the section of said bosses gradually increasing away from the housing 100 to increase the outer section of the element 400; thus the diameter of an imaginary circle tangent to the external surfaces of the bosses increases progressively from right to left in the figure, between a minimum value which is less than the internal diameter of the threaded part 214 of the first element and a maximum value which is greater than this internal diameter;
- Finally, a region 408 of larger diameter, this diameter however being sufficiently small to allow this region to be engaged in the housing 308 of the second element; the annular end face 410 of said region 308 constitutes a bearing surface intended to cooperate with the inner bearing surface defined by the bottom of the element 300.

 We will now describe the installation of the device of the present invention on the housing 100.

Initially, the second, then third then first element are engaged on the cable, the latter then being devoid of any connector at its free end.

 It will be noted that at least one such connector, provided that its overall dimensions allow it to pass through the collar 114 and the opening 112 of the housing 100, can then without inconvenience be fixed to the end of the cable.

 The first element 200 of the device being positioned on the cable so that a sufficient length of said cable extends from it, on the housing side, the third element 400 can then be placed in the housings 216, 308 of the first and second elements. The second element 300 is then screwed onto the threaded part 218 of the first element, so that its bearing surface comes to cooperate with the bearing surface 410 of the third element. As the screwing continues, the third element is therefore pushed towards the first element, and its intermediate region 406 provided with bosses 407 cooperates with the interior wall of the housing 216 of the first element 200 in the region of its entry, which tends to crush radially inward said intermediate region.

The material of the third element 400 is chosen so that this radial crushing causes, to a sufficient extent, an at least local reduction in the internal section of the cable passage 402, the end face of at least one rib then being pressed against the cable to ensure a seal.

 once a suitable tightening has been achieved, a whole unit is obtained which can be put in place on the housing as follows: the O-ring 500 is first put in place at the bottom of the space defined between the skirts 204 and 206. The assembly is positioned in line with the collar 114 of the housing and moved axially so that said collar engages between the intermediate skirt 204 and the outer skirt 206. At the end of the race, the pins 208 s 'simultaneously engage in the notches 115 of the re-entrant collar 113. There is then exerted on all three elements an axial pressure, the free end face of the collar 114 compressing the seal 500 and the radial faces 208a of the lugs 208 being caused to slightly exceed the plane of the inner face of the re-entrant flange 113. A rotation can then be imparted to the assembly to bring the lugs behind said flange 113 and lock the assembly, the join t 500 remaining compressed and ensuring a good quality seal between all three elements and the housing.

It will be noted here that the position of the seal 500 between the intermediate and outer skirts 204 and 206, a seal whose compression is ensured by the annular free end face of the collar 114, makes it possible to obtain a particularly satisfactory seal.

 Preferably, the housing is equipped with a plurality of openings produced as described above, capable of cooperating with a plurality of assemblies associated respectively with a plurality of electrical cables for arrival and departure.

 For the rest, the housing 100 can be of conventional design and include in its internal walls arrangements, such as grooves or the like, for the force fixing of conductive bars to several tongues themselves equipped with means for hooking in the material. (typically a plastic) of the housing.

 The present invention thus provides simple and economical means for cable crossings, these means cooperating with openings of a relatively large diameter, which makes it possible to equip the cables with the necessary connectors before their introduction and connection in the housing. By equipping these connectors with appropriate polarizing means (color codes, judicious form complementarities with respect to conductive bars, etc.), the risks of connection errors are thus minimized, and the assembly procedure is more easily automated.

 Of course, the present invention is in no way limited to the embodiment described above and shown in the drawings, but a person skilled in the art will know how to make any variant or modification in accordance with his spirit.

Claims (7)

 1. Device for leaktight cable crossing through a wall (110) of a housing (100), in particular in an electrical junction box for a trailer or road tractor, characterized in that it comprises in combination at least two elements (200, 300, 400) generally coaxial each comprising a through passage (210, 310, 402) for the cable, said elements being able to be fixed to one another by exerting on one of them (400 ) an essentially radial stress in order to ensure the coming into tight contact of an internal wall of at least one of said passages (402) with said cable, in that one of the elements comprises a base (204) provided with first locking arrangements (208) and a bearing surface for a compressible seal, and in that said wall of the housing has an opening (112) capable of receiving the cable and the base and around which is defines another bearing surface for said joint compr essential and present in the region of said opening of the second locking arrangements (113, 115) capable of cooperating with the first locking arrangements for assembling said element provided with the base on the housing by compressing said joint between the bearing surfaces .  2. Device according to claim 1, characterized in that it comprises  a first element (200) traversed by the cable, comprising said base (204), and in a region opposite to said base, a first axial clamping arrangement (218) disposed around a first housing (216),  a second element (300) traversed by the cable, comprising a second axial clamping arrangement (304) capable of cooperating with the first axial clamping arrangement and defining a second housing (308), the latter being axially delimited by a first surface d 'support,  a third element (400) traversed by the cable and capable of being engaged in the first and second housings, said third element comprising a second bearing surface (410) capable of cooperating with the first during the implementation of the arrangements of axial clamping, and, surrounding a cable passage (402), an outer wall portion (406, 407) inclined and able to cooperate with a wall (214) of said first housing during clamping to receive an essentially radial re-entrant force, a internal wall of said passage at the level of said inclined wall part then being applied in leaktight manner against the cable.  3. Device according to claim 2, characterized in that said internal wall of the cable passage (402) of the third element (400) has generally circular ribs of essentially trapezoidal section.  4. Device according to claim 2 or 3, characterized in that said inclined outer wall portion comprises a plurality of bosses (407) elongated essentially axially, of variable section.  5. Device according to one of claims 2 to 4, characterized in that the clamping arrangements comprise a thread (218) and a complementary thread (304).  6. Device according to one of claims 1 to 5, characterized in that the base comprises at least two coaxial skirts (204, 206) defining between them an annular housing, the bottom of which is capable of receiving said seal (500), and in that the housing wall (110) has around said opening an outgoing collar (114) capable of engaging in said housing to compress the seal during the implementation of the locking arrangements (208, 113, 115 ).  7. Device according to claim 6, characterized in that the first locking arrangements comprise at least two lugs (208) formed on the outer surface of one of the skirts (204) and in that the second locking arrangements comprise notches (115) formed around the opening (112) of the wall (110) of the housing.