WO2012007065A1

WO2012007065A1 - Junction box for electric cables

Info

Publication number: WO2012007065A1
Application number: PCT/EP2010/066081
Authority: WO
Inventors: Alexander Crolla; Pieter Lesage
Original assignee: Concrete Bvba
Priority date: 2010-07-12
Filing date: 2010-10-25
Publication date: 2012-01-19

Abstract

The invention is related to a junction box for enclosing electric cables or circuits, characterized in that the box comprises a housing comprising two or more parts (4, 5) configured to be assembled together to form an enclosure for one or more cables, strain relief portions (2) arranged to be fixed with respect to the enclosure and around the wire(s), and closing heads (1) configured to close off the enclosure. According to the invention, the closing heads are configured to close off the enclosure and relief the strain on the wires in one closing action.

Description

JUNCTION BOX FOR ELECTRIC CABLES

Field of the Invention

[0001] The present invention is related to junction boxes for closing off electric cables, in particular closing off the connection between cables (electric, data, fibre optic or other) or electric circuits.

State of the art

[0002] Typical features of junction boxes known in the art are :

- box with cable entrances and exits

- features to close the box (screws, screw cap, snaps,...)

- features to relief strain from the cables (with screws and bridge, screw clamp around cable,...)

- many different variations and forms (number of exits for cables, different principles to close, different IP (Ingress Protection) classifications, different materials , ... )

- mostly used to connect electric cables or to enclose a certain electric circuit.

[0003] In existing systems, closing the box and the strain relief of the cable are separate functions which are activated by different and separate actions. This complicates the handling and assembly of the junction box. Summary of the invention

[0004] The invention is related to a junction box and method of assembling such a junction box, as described in the appended claims. When a ^xconical' contact surface is mentioned, this is meant to describe a contact surface which is conical with respect to the common central axis of the housing, the strain relief portion and the closing head .

[0005] The invention is thus related to a junction box for enclosing electric cables or circuits, characterized in that the box comprises

• A housing comprising two or more parts configured to be assembled together to form an enclosure for one or more cables,

· Strain relief portions configured to be fixed with respect to the enclosure and around the cable (s),

• Closing means configured to close off the enclosure by a closing action,

wherein the closing means are closing heads, to be placed around the cable (s), each closing head being provided with a first inner contact surface arranged to be clamped by the closing action onto an outer contact surface of the enclosure, to thereby close off the enclosure, and provided with a second inner contact surface, arranged to be clamped by the same closing action onto an outer contact surface of a strain relief portion, to thereby establish the strain relief on the cable (s) .

[0006] In a junction box according to the invention, all of said inner and outer contact surfaces may be conical contact surfaces. In another embodiment, said first inner contact surface of each closing head comprises a conical portion and a cylindrical portion. [0007] According to an embodiment, each housing part comprises a contact portion, said contact portions being configured to be assembled together to form a conical outer contact surface extending outwards from the housing and wherein each closing head comprises an inner conical contact surface configured to push the contact portions of the housing parts together when the inner conical contact surface is clamped onto the outer conical contact surface.

[0008] According to another embodiment, wherein each housing part comprises a contact portion, said contact portions being configured to be assembled together to form an outer contact surface comprising a cylindrical part extending outward from the housing and a conical part extending outward from the cylindrical part, and wherein each closing head comprises an inner contact surface comprising a cylindrical part and a conical part, and wherein said inner contact surface is configured to push the contact portions of the housing parts together when the inner contact surface is clamped onto the outer contact surface.

[0009] In a junction box according to the invention, in at least one pair of inner and outer contact surfaces, one contact surface may be conical or comprise a plurality of conical surfaces, and the other contact surface may be defined by a ridge portion, configured so that the ridge portion is the first area to enter into contact with the conical surface when the inner and outer contact surfaces are assembled together.

[0010] In another embodiment, at least one of said contact surfaces is formed by a plurality of contact sub^¬ surfaces .

[0011] According to an embodiment, the outer contact surface of each strain relief portion is a deformable surface arranged to exert a gripping force on the cable when the second inner contact surface is clamped onto the deformable surface. Said deformable surface may for example be formed by lamellae or by a rubber conical surface .

[0012] According to an embodiment, the housing parts comprise retention areas formed by vertical wall portions, and wherein the strain relief portions comprise rectangular shaped portions configured to be inserted between the vertical wall portions.

[0013] The closing heads and the strain relief portions may be provided with threaded portions, configured to establish said closing action by screwing the closing heads onto the strain relief portions.

[0014] Each of the strain relief portions may be integral with one of the housing parts or with one of the closing heads.

[0015] The invention is also related to a method for closing a junction box according to the invention, comprising the steps of :

· Placing a number of closing heads and strain relief portions over a same number of cable ends,

• Making a connection between the cable ends,

• Placing the strain relief portions in one part of the housing,

· Closing the housing by assembling the housing parts, thereby clamping the strain relief portions between the housings parts,

• Mounting the closing heads onto the housing and strain relief portions and performing the closing action, thereby simultaneously closing off the housing and establishing the strain relief on the cables. Brief description of the drawings

[0016] Figures la to le show the steps for assembling a junction box according to a first embodiment of the invention.

[0017] Figure 2 shows a view of a cross section of a junction box according to the embodiment of figure 1.

[0018] Figure 3 shows a blow-up cross section view and side view of the junction box according to the embodiment of figure 1.

[0019] Figure 4 shows a blow-up cross-section view and side view of the junction box according to a second embodiment .

[0020] Figures 5a to 5d illustrate the closing action of a junction box according to the embodiment of figure 4.

[0021] Figures 6a to 6d show various alternatives of an inner and outer contact surface as applicable in the invention . Detailed description of preferred embodiments of the invention

[0022] The junction box of the invention is configured so that the functions of closing the box and relieving strain on the cables are activated in one action. A single closing movement, for example a screw movement per cable will tighten the strain relief around the cable and simultaneously, pressure is applied to close off the box.

[0023] Figures 1 to 3 illustrate a junction box according to a first embodiment of the invention, which is not limitative to the scope of the invention, said scope being defined only by the appended claims. The junction box comprises a housing in the shape of a rectangular box and formed of an upper part 1 and a lower part 2. At opposing sides of the assembled housing, contact protrusions 3 and 4 extend from the housing (best visible in figure 3) , said contact protrusions 3 and 4 having a conical outer surface 5 extending outward from the housing, which is tapered towards the central axis 100 and terminated by a vertical wall surface 6, the latter being provided with a central opening for allowing the passage of cable ends 50 and 51. The term Vertical' is used purely with reference to the position of the junction box as shown in the drawings, and is not limitative to the invention's protection scope. Each of the conical contact protrusions 3 and 4 is formed of an upper contact portion 9 which is integral with the upper housing part 1 and a lower contact portion 10 which is integral with the lower housing part 2. Semicircular openings 11 are formed in each of the contact portions 9 and 10, so as to form the central opening for allowing the passage of the cable ends.

[0024] Inside each half (9,10) of the conical contact protrusions 3 and 4 are retention areas 15 and 16. These retention areas are configured to receive strain relief portions 20,21 so that these strain relief portions may be fixed with respect to the housing. In the embodiment shown, the retention areas are formed by vertical wall portions 17,18 (see fig. 3) . Each of the strain relief portions 20,21 comprises a rectangular or square shaped portion 22 (or any other suitable shape except a circular shape) , which fits into the space between the vertical wall portions 17,18 so that the strain relief portions may be held between the upper and lower housing parts 1 and 2. The rectangular form of the portions 22 ensures that the strain relief portions 20,21 when mounted in the closed housing, are unable to rotate with respect to the housing.

[0025] As seen in figure 3, the strain relief portions 20 and 21 comprise a central opening 23 for allowing passage of the cable ends. Extending outward from the rectangular portion 22 (and in the direction away from the housing) , the strain relief portions have a round shape, and comprise a cylindrical threaded portion 24, and an end portion having a conical outer surface 25, and preferably formed of a series of lamellae which can be pushed inwards to thus exert a pressure on the cable. A range of cable diameters can be used in combination with this type of strain relief portion, wherein the diameter of the cable will determine how far the closing head may be screwed onto the strain relief portion before the correct strain relief force is applied. Alternatively to the lamellae, the outer surface 25 may consist of a continuous conical surface, for example a flexible surface (e.g. rubber) which when contacted by the inner surface 34 will deform and become pressed around the cable. Alternatives to a conical surface (for the strain relief as well as for the closing off of the housing) are also possible, as will be explained in more detail further in this description with respect to figures 6a to 6d.

[0026] The junction box of the invention further comprises for each of the strain relief portions, a closing means. In the embodiment shown, these are cylindrical closing heads 30 and 31, configured to be screwed onto the strain relief portions 20/21 so as to close off the enclosure and simultaneously relieve the strain on the cables .

[0027] With reference to figure 3, each closing head has a hollow interior, comprising three portions along the central axis 100 of the closing head :

- a central threaded portion 32 corresponding to the thread 24 of the strain relief portion, - at the end that is closest to the housing, a portion defined by a vertical wall surface 33 and a conical inner surface 34,

- at the end that is farthest from the housing, a conical inner surface 35, the end of which defines a central hole 36 for passage of a cable end.

[0028] The conical inner surfaces 34 and 35 are configured with respect to the conical outer surfaces 5 and 25 respectively so that when the closing head is screwed onto the mounted strain relief portion, both conical inner surfaces exert a pressure on the respective outer conical surfaces, so that the housing parts 1 and 2 are pushed together, to thereby close off the housing. At the same time, the conical outer surface 25 is pressed around the cables so as to establish the strain relief on the cables. In the final closed state, the distance between the vertical walls 6 and 33 may be zero as shown in figure 2. However in most cases a non-zero distance will be present between these walls, which will depend on the cable diameter. As a consequence, the closing force exerted by the inner conical surface 34 on the outer conical surface 6 may also depend on the cable diameter. However, the design of the various components is such that said closing force is always above a minimum required value. In the second embodiment, described further, however, a manner is shown to obtain a constant closing force for a variety of cable diameters.

[0029] The assembly of the junction box shown in figures la to le takes place by the following steps :

- Step 1 (fig. la) : the closing heads 30/31 and strain relief portions 20/21 are placed over the cable ends 50/51,

- Step 2 (fig. lb) : the connection between the cables is made, according to a known connection method (not shown) ,

- Step 3 (fig. lc) : the strain relief portions 20/21 are placed in the lower part 2 of the housing, by inserting the rectangular portions 22 between the vertical wall portions 17/18 of the retention areas

15/16.

- Step 4 (fig. Id) : the housing is closed by placing the upper housing part 1 on the lower housing part 2, thereby holding the strain relief portions 20/21 between the housings parts 1 and 2,

- Step 5 (fig. le) : the closing heads 30/21 are screwed (subsequently or simultaneously) on the strain relief portions 20/21 (screw-thread of closing head on screw- thread of the strain relief portion) . This screw movement of the closing heads 30/31 on the strain relief portions 20/21 creates a pressure between both housing parts 1 and 2 to ensure closure, because the conical inner surface 34 of each closing head applies pressure on each of the conical outer surfaces 5 of the housing. At the same time, with this screw movement each strain relief portion is tightened around the cable because the conical inner surface 35 of the closing head applies pressure on the conical outer surface 25 of the strain relief portion.

- Together with impingement of the strain relief portions 20/21 between the housing parts 1 and 2, this ensures that the strain on the cable is relieved (now the cable can not be pulled out of the box) .

[0030] A second embodiment of the junction box of the invention is shown in figures 4 and 5. The strain relief portions 20 and 21 are the same as in the first embodiment. In this embodiment however, the outer surface of the contact protrusions 3 and 4 of the housing comprises a cylindrical part 40 extending outward from the housing, followed by a conical part 41 tapered towards the central axis 100, and terminated by a vertical wall 42 (provided with a hole for passage of the cables) . Likewise, the inner surface of the closing heads 30/31 comprises a corresponding cylindrical part 43, a conical part 44 and a vertical wall 45.

[0031] The assembly of the closing heads in the second embodiment is shown in detail in figures 5a to 5d. First, the housing parts 1 and 2 are pushed together by the pressure exerted by the inner conical surface 44 on the outer conical surface 41 (figures 5a and 5b) . When the housing parts are mounted around the strain relief portions, the closing heads are further screwed onto the housing while the inner cylindrical surface 43 is in contact with the outer cylindrical surface 40. The components are designed so that at this moment, the required pressure is exerted by the closing head on the contact surfaces 40 of the housing, in order to close off the enclosure. While this force remains constant, the closing heads may then be further screwed onto the strain relief portions, until the vertical walls 45/42 touch or until the correct gripping force is exerted by the conical surface 25 of the strain relief portion on the cable. This embodiment has the advantage that the force on the cable can be regulated within a given range, while the pressure on the housing parts remains constant. In this way, the correct gripping force can be applied on cables of different diameters, while a constant closing force is applied on the housing.

[0032] Any junction box according to the invention is different from existing systems by the following features :

- closing the box and tightening the strain relief portions in one movement/action - fewer parts

- no tools required (a lot of existing product require pliers or screwdriver)

- simpler parts for production

[0033] Specific advantages/improvements of the invention with respect to the prior art are :

- with one screw movement two different clampings are realized; one concentric around the cable and a second clamping linear between the two housing parts 1 and 2. - pressure direction of the clamping between the housing parts (1 and 2) is different than the axis of the screw movement.

[0034] The inner and outer contact surface cited in appended claim 1, and embodied by surfaces 34 and 5 in the embodiment of figure 3, are not limited to cases wherein both the inner and outer surface comprises a conical surface with a substantially corresponding conical shape of the respectively interacting surfaces. This shape may in fact differ, as long as the inner surfaces are capable of exerting the required pressure on the outer surfaces. Some examples of such embodiments are shown in figures 6a to 6d. Figure 6a illustrates the case applied in the embodiment of figure 3 : two corresponding conical surfaces 52/53. Figure 6b shows the case wherein the inner surface 61 of the right-hand part 58 (e.g. the inner surface of a closing head) is conical and the outer surface (e.g. the contact surface of a strain relief portion) of the left- hand part 59 is formed by the circular ridge portion 60 defined by the cylindrical surface 62 and the vertical wall 63. The ridge 61 is the first area to enter into contact with the inner conical surface 61, when the two parts are assembled together. Instead of a perfectly cylindrical portion and a vertical wall, these surfaces may deviate therefrom (for example slightly conical surface instead of cylindrical) . The left-hand part 59 may be formed of or comprise a flexible portion with a substantially rectangular cross-section such as a sealing ring. In that case, the inner conical surface 61 will exert a pressure on the sealing ring, thereby deforming the ring and pressing it around the cable, to obtain the strain relief. As seen in figure 6c, an outer conical surface 70 may also be present on the left-hand part 59, whereas the inner contact surface on the right-hand part 58 is formed by the circular ridge portion 71 separating the inner cylindrical surface 72 and the vertical wall portion 73. Once again, the ridge portion 71 is the first area to enter into contact with the outer conical surface 70 when the two parts are assembled together. Still alternatively, the conical surface may consist of conical sub-surfaces, said sub-surfaces for example being formed at the end of a number of ribs 80 placed around the circumference of the right-hand part (see figure 6d) . It is understood by the skilled person that various variants of these systems or other combinations between these systems are possible, for example ridge portions (like 60 and 71) in combination with conical ribs 80 or vice versa. A possible variant is a component wherein the circular ridge portion (60 or 71) is formed of a series of sub-portions arranged around the circumference of the ridge.

[0035] Any of the above described combinations can be applied for establishing the strain relief as well as the closing of the housing. Some of the strain relief principles described above are known per se from existing systems wherein strain relief and closing are obtained by separate actions. Any further aspects or details from such known systems may be applied in a junction box according to the invention. [0036] Further possible variants that are included in the scope of the invention are the following :

- the number of cable exits in the junction box may be one, two (as shown in the drawings) or more,

- the form and dimensions of the cables (round, square, flat,...) may differ,

- the form and dimensions of the junction box and its parts may differ,

- the internal function of the box is not limited to the embodiment described

- various modes of placement or mounting of the box

IP classification of the closed box (clamping of the 2 housing parts can be done with the aid of rubbers or other systems resulting in a higher or lower classification)

- number of housing parts of the box (the embodiments shown are with 2 housing parts, but it also works with a higher number) .

- The housing parts 1 and 2 could also for example be attached to each other with a hinge

- The closing head 30/31 can also have a version without opening for a cable, to close off a cable exit without a cable,

- The strain relief portion 20/21 can also be a part of one of the housing parts 1 or 2 or it can be a part of a closing head 30/31,

- The strain relief can be executed according to other known principles different from the ones described above,

- The closing heads can also be attachable to the box with another movement than a screw movement (snap on, bayonet,...). In such an embodiment, the inner contact surfaces 34/35 (as in embodiment 1) or 43/44/35 (as in embodiment 2) of the closing heads remain the same as in the described embodiment, but the threaded part 32 is replaced by an adequate connection part (e.g. snap or bayonet) . Likewise, the threaded part 24 of the strain relief portions is replaced by a corresponding connection part while the contact surfaces remain the same.

The closing heads can be designed to be operated manually or with tools.

Any suitable material may be used for the components described above. A preferred embodiment uses components made of plastic materials, for example polycarbonate .

Claims

1. A junction box for enclosing electric cables or circuits, characterized in that the box comprises

• A housing comprising two or more parts (1,2) configured to be assembled together to form an enclosure for one or more cables (50,51),

• Strain relief portions (20,21) configured to be fixed with respect to the enclosure and around the cable ( s ) ,

· Closing means (30,31) configured to close off the enclosure by a closing action,

wherein the closing means are closing heads (30,31), to be placed around the cable (s), each closing head being provided with a first inner contact surface (34; 43, 44) arranged to be clamped by the closing action onto an outer contact surface (5;41,42) of the enclosure, to thereby close off the enclosure, and provided with a second inner contact surface (35) , arranged to be clamped by the same closing action onto an outer contact surface (25) of a strain relief portion (20,21), to thereby establish the strain relief on the cable (s) .

2. Junction box according to claim 1, wherein all of said inner and outer contact surfaces are conical contact surfaces.

3. Junction box according to claim 1, wherein said first inner contact surface of each closing head comprises a conical portion (44) and a cylindrical portion (43) .

4. Junction box according to claim 2, wherein each housing part (1,2) comprises a contact portion (9,10), said contact portions (9,10) being configured to be assembled together to form a conical outer contact surface (5) extending outwards from the housing and wherein each closing head (30,31) comprises an inner conical contact surface (34) configured to push the contact portions (9,10) of the housing parts (1,2) together when the inner conical contact surface (34) is clamped onto the outer conical contact surface (5) .

5. Junction box according to claim 3, wherein each housing part (1,2) comprises a contact portion (9,10), said contact portions (9,10) being configured to be assembled together to form an outer contact surface comprising a cylindrical part (40) extending outward from the housing and a conical part (41) extending outward from the cylindrical part (40), and wherein each closing head (30,31) comprises an inner contact surface comprising a cylindrical part (43) and a conical part (44), and wherein said inner contact surface is configured to push the contact portions (9,10) of the housing parts (1,2) together when the inner contact surface (43,44) is clamped onto the outer contact surface (40,41).

6. Junction box according to claim 1, wherein in at least one pair of inner and outer contact surfaces, one contact surface is conical or comprises a plurality of conical surfaces, and the other contact surface is defined by a ridge portion (60,71), configured so that the ridge portion is the first area to enter into contact with the conical surface when the inner and outer contact surfaces are assembled together.

7. Junction box according to any one of the preceding claims, wherein at least one of said contact surfaces is formed by a plurality of contact sub-surfaces (80) .

8. Junction box according to any one of the preceding claims, wherein the outer contact surface (25) of each strain relief portion (20,21) is a conical outer surface (25) is a deformable surface arranged to exert a gripping force on the cable when the second inner contact surface (35) is clamped onto the deformable surface.

9. Junction box according to any one of the preceding claims, wherein the housing parts (1,2) comprise retention areas (15,16) formed by vertical wall portions (17,18), and wherein the strain relief portions (20,21) comprise rectangular shaped portions (22) configured to be inserted between the vertical wall portions (17,18).

10. Junction box according to any one of the preceding claims, wherein the closing heads (30,31) and the strain relief portions (20,21) are provided with threaded portions (32,24), configured to establish said closing action by screwing the closing heads onto the strain relief portions .

11. Junction box according to any one of the preceding claims, wherein each of the strain relief portions (20,21) are integral with one of the housing parts (1,2) or with one of the closing heads (30,31) .

12. Method for closing a junction box according to claim 1, comprising the steps of :

• Placing a number of closing heads (30,31) and strain relief portions (20,21) over a same number of cable ends (50,51) ,

• Making a connection between the cable ends,

· Placing the strain relief portions (20,21) in one part of the housing,

• Closing the housing by assembling the housing parts (1,2), thereby clamping the strain relief portions (20,21) between the housings parts,

· Mounting the closing heads (30,31) onto the housing and strain relief portions and performing the closing action, thereby simultaneously closing off the housing and establishing the strain relief on the cables.