Description Present invention concerns a solar junction box.

Particularly, present invention concerns a housing for an electric connection between a solar panel and a cable system.

A junction box for a solar panel comprises an electric connection and a housing to protect the connection from environmental influences such as moisture, dust and

conductive objects. The junction box is mounted on the solar panel and electrically connected to solar cells of the panel. At the time of installing the solar panel, the junction box is opened and an electric connection is made between a cable system and electric contacts of the cables that lead to the solar cells. After this, the junction box is closed again and, unless servicing is required, may remain unopened for several years or even several decades.

It is a requirement that the housing protects the electric connection well for a long time. Another requirement is that mounting, unmounting and servicing should be easy. Especially in contemporary installations that comprise hundreds or even thousands of solar panels, price is also an issue.

The invention sets out to provide a solar junction box that fulfils at least some of the given requirements. The

invention therefore proposes a junction box according to the features of the enclosed independent claims. Dependent claims give advantageous embodiments.

According to the invention, a solar junction box comprises a chassis element, a bushing for sealing a cable running through a wall of the chassis element and a first cable guide with an aperture for running through the cable, wherein the first cable guide is attached to an outside of the chassis element .

By placing the first cable guide on the outside of the chassis element, a lateral strain in the cable can be kept from the bushing so that the bushing may provide a sealing between the cable and the chassis element regardless of the lateral strain. An inside of the junction box can thus be better protected against influences like moisture or dust and an electrical connection that is located on the inside of the junction box may be better adapted to stay intact over a long time.

It is furthermore preferred that the first cable guide and the chassis . element are formed in one piece. The chassis element can especially be manufacturable by a moulding process. In this case an effort for providing the first cable guide can be small. It is also preferred that the chassis element has a surface that is adapted to be adhered to the solar panel wherein the first cable guide is open towards that surface. The other surface may close the otherwise open structure of the first cable guide so that after installation the cable is guided all around. At the same time this makes it possible that the first cable guide is manufactured through a moulding process that requires no more than two moulds.

In another embodiment the first cable guide extends along a shape of the letter U. This way the first cable guide may be better adapted to be in contact with an outer surface of a round cable. A friction between the cable and the first cable guide may thus be increased so that the first cable guide may be better adapted to retain the cable.

In another embodiment the first cable guide comprises a material that is less flexible than that of the bushing. The first cable guide may thus provide a rigid structure for holding and guiding the cable while the bushing comprises a softer structure that is better adapted for sealing than for retaining. In combination the cable may be both well held and well sealed with respect to the chassis element.

It is furthermore preferred that the first cable guide is spaced apart from the wall of the junction box, such as to allow for an axial end of the bushing. In other words, the bushing may axially extend beyond the wall of the chassis element and may thus provide a better sealing. An axial end of the bushing may abut the first cable guide or there may remain a space between the axial end of the bushing and the first cable guide. The axial space is preferred to be small, like in the range of one to 5 mm, particularly in the range of 2-4 mm. This axial space permits a deformation of the bushing, be it due to an axial pull on the cable, a

deformation through elevated temperatures or other. The junction box may further comprise a second cable guide attached to the chassis element on an outside of the junction box for holding and/or guiding the cable running through the first cable guide. Together with the first cable guide, the second cable guide may provide a better strain relief for the cable. A predetermined axial force on the cable, for instance in the region of about 60-80 N, may be sustainable without the cable slipping through the bushing. This may also allow to pull the cable through the second cable guide during installation .

It is furthermore preferred that the second cable guide and the chassis element are formed in one piece. As mentioned above with respect to the first cable guide, the chassis element may be manufacturable through a moulding process and an effort for providing the second cable guide may be small. Manufacturing costs for providing the chassis element with the first and second cable guides may thus be held low. The price of the chassis element may thus help to spread the product through the market so that initial costs for the moulding process may be redeemed. The chassis element may have a surface that is adapted to be adhered to the solar panel, wherein the second cable guide is open towards that surface. As mentioned above with respect to the first cable guide, this may help to better clamp the cable and at the same time manufacture the second cable guide in a moulding process with no more than two moulds.

It is furthermore preferred that the second cable guide extends along a shape of the letter L. This may give the second cable guide a certain flexibility so that the cable can be pulled through the second cable guide in an

installation process of the cable. After installation, the second cable guide may be flexible enough to press laterally on the cable hard enough to clamp the cable securely. Advantageous combinations of the first and second cable guides may have additional features. For instance, the first and second cable guides may have axes along which to pass the cable, the axes been shifted in parallel. This may require the cable to run along a bending of about 180° between the first and second cable guides. The first and second cable guides may help to maintain a minimal bending radius of the cable so that the cable is not damaged by creasing and the cable may remain installed at the junction box for a long period of time, for instance several years or even several decades. The alignment of the axes may also help distributing forces between the first and second cable guides. The cable may thus be securely held at the junction box and tightly sealed against the junction box by the bushing. In another embodiment the chassis element has a surface that is adapted to be adhered to the solar panel and the axes lie in a plane that encloses an acute angle with the surface. This may help clamp down the cable to the surface. An optional inner torsion of the cable may help to maintain the cable's rigidity, especially in the section between the first and second cable guides.

In another preferred embodiment, the junction box further comprises another chassis element and the bushing is held between the two chassis elements. This may also contribute to an ease of manufacturing the chassis element in one piece through a moulding process, for instance with the first and/or second cable guides. The other chassis element may also be manufacturable through a moulding process. It is especially preferred that both chassis elements can be produced in a moulding process with no more than two moulds for each of the elements. The chassis elements may be moulded, especially through a plastic injection moulding process, using only two moulds in total.

According to a preferred embodiment a bushing is held between the two chassis elements. Preferably a section of the bushing adjacent to the recess has a lateral lip that runs in a direction around the bushing.

According to a further preferred embodiment, there are several parallel lips that run around the bushing.

According another preferred embodiment, all of said several parallel lips preferably are in contact with a recess of said second chassis element.

According to a preferred embodiment, a first part of said parallel lips is in contact with a recess of said first chassis element and a second part of said parallel lips is in contact with a sealing gasket. The invention will now be described in more detail with reference to the enclosed figures, in which

Fig. 1 shows an exploded view of a junction box for a solar panel;

Fig. 2 shows the junction box of Fig. 1 in a closed

state ;

Fig. 3 shows a first cross section of the junction box of

Figs . 1 and 2 ;

Fig. 4 shows a second cross section of the junction box of Figs. 1-3;

Fig. 5 shows a third cross section of the junction box of

Figs. 1-4;

Fig. 6 shows the junction box of Figs. 1-5 when the

junction box is mounted on the back of a solar panel and

Fig. 7 shows the junction box of Fig. 6 from a different perspective . Figure 1 shows an exploded view of a solar junction box 100. Physical dimensions of the exemplary embodiment depicted in Figure 1 are approx. 85 x 112 mm. The junction box 100 comprises a first chassis element 102 and a second chassis element 104 which are adapted to be held together such that there is a confined space 106 that can be used for an electric connection. In order to run a cable 108 between the outside and the inside of the junction box 100, the junction box 100 further comprises a bushing 110 with an axial aperture 112 for the cable 108. The bushing 110 is preferred to have a first axial end section 114, a second axial end section 116 and an axial middle section 118 that lies between the first and second axial sections 114 and 116. It is preferred that the axial middle section 118 has as smaller diameter than the first and second axial sections 114, 116. The bushing 110 is expandable also in its axial length, such that the axial length of the middle section 118 increases during mounting of the bushing 110. In a mounted state, i.e. when the bushing 110 is mounted in the recess 120, the axial length of the middle section 118 has the same length as the axial length of the recess 120. Each chassis section 102, 104 comprises at least one recess 120, wherein corresponding recesses 120 face each other to constitute the aperture 112. The bushing 110 is adapted to lie in the aperture 120 such that the chassis elements 102, 104 lie on opposite sides of the bushing 110. A diameter of the aperture 112 is by preference about as large as an outer diameter of the middle section 118 of bushing 110. As can be seen in Figure 1, there may be two ore more than bushings 110 with associated apertures 112 in the chassis elements 102, 104 for running more cables 108 between the outside and the inside of the junction box 100.

It is preferred that there is a groove 122 formed between the chassis elements 102 and 104. In one embodiment, the groove 122 is formed in only one chassis element, for instance the first chassis element 102 as shown in _. Figure 1. The other chassis element 104 serves to close the groove 122 with the gasket 124 inside when the junction box 100 is closed. In another embodiment, the groove 122 is formed at least in part in both chassis elements 102 and 104. It is also preferred that there are three or even more grooves 122 in parallel formed in the chassis elements 102 and/or 104.

The gasket 124 may be a self contained gasket, for instance made from rubber, silicone or a polymer. It is preferred that the gasket 124 comprises a polymeric foam and the gasket 124 may be manufactured from a liquid inside the groove 122. In the shown, preferred embodiment, the gasket 124 is not interrupted by the bushing 110; instead, the gasket 124 is preferred to run essentially in one plane and leave that plane only to circumvent the bushing 110. In the area of the circumvention, the gasket 124 may lie adjacent to bushing 110. For locking the chassis elements 102, 104 together when the junction box 100 is closed, it is preferred that one of the chassis elements, for instance the first chassis element 102 as shown in Figure 1, comprises a snap-in nose 126, while the other chassis element 104 comprises a corresponding recess 128 for receiving the snap-in nose 126. There may also be several snap-in noses 126 and corresponding recesses 128 for even distribution of closing forces of the junction box 100. The snap-in noses 126 and corresponding recesses 128 are preferred to be located on the outside of junction box 100. It is furthermore preferred that the snap-in noses 126 are configured to be unlockable with a simple tool such as a screwdriver or by hand without any tool at all.

According to one embodiment, each chassis element 102, 104 also carries an eye 130 for securing the two chassis elements 102, 104 together if desired. In one option, one of the chassis elements, for instance the second chassis element 104 as shown in Figure 1, comprises a first cable guide 132 with an aperture 133 for running through the cable 108. The first cable guide 132 is preferred to extend along a shape of the letter U, wherein the shape in the picture of Figure 1 is in an upside down position with respect to the letter U. The first cable guide 132 lies on an outside of the junction box 100 and is displaced by

preference such that an axial contact with the bushing 110 can be made. In another embodiment, there may be a small axial gap in the range of 1 to 5 millimetres, by preference between 2 and 4 millimetres. The first cable guide 132 will prevent the cable 108 from creasing when a lateral force pulls an outside section of cable 108 in a lateral direction. The first cable guide 132 is preferred to be in one piece with the chassis element 104 and the material of the first cable guide 132 is preferred to be more rigid than the material of the bushing 110. In another preferred environment, one of the chassis

elements, for instance the second chassis element 104 in Figure 1 furthermore comprises a second cable guide 134 for holding a section of the cable 108. As will be explained in more detail further down, the cable 108 is preferred to run from the inside of the junction box 100 through the bushing 110 and the first cable guide 132, make a turn of about 180° and then run through the second cable guide 134. The second cable guide 134 is preferred to extend along a shape of the letter L, wherein the shape in the picture of Figure 1 is turned upside down with respect to the letter L.

One of the chassis elements 102, 104, for instance the second chassis element 104 in Figure 1, may have an outer surface 136 for adhering to a solar panel. When the surface 136 is pressed against another surface, connections to open

structures of the first cable guide 132 and the second cable guide 134 may be closed so that the cable 108 is held on all sides.

In another preferred embodiment, the surface 136 is level and may comprise one or more apertures 138, so that the aperture 138 is laterally surrounded by sections of the adhering surface 136. When the surface 136 rests against a another surface, especially the back surface of a solar panel, the apertures are closed. It is preferred that the surface 136 is adhered to the other surface such that the aperture 138 is sealed. Glue or cement may be used for adhering the junction box 100 to the other surface.

Inside the junction box 100, there may be additional

structures for supporting an electric connection between wires of the cable 108. In one embodiment, the junction box 100 comprises a conductive rail 140 for making an electric connection. One of the chassis elements, for instance the second chassis element 104 in Figure 1, may carry a snap- in support 142 for the rail 140. It is preferred that the snap- in support 142 is configured such that the rail 140 may be inserted into the chassis element 104 without tools and held there by the snap- in support 142. It is especially preferred to provide several rails 140, for instance three rails 140 as shown in Figure 1.

The junction box 100 may also comprise an electric element 144 for connecting to two rails 140. The electric element 144 may especially comprise a Schottky diode. The chassis element 104 comprising the snap-in support 142 may also comprise a guide 148 for clamping an electric contact of the element 144 so that a position of the element 144 in the chassis element 104 is fixed. An electric connection between the element 144 and the rail 140 may be done through this mechanism alone or another way of connecting may be in place, such as soldering the electric contact of the element 144 to the rail 140.

It is preferred that significant features of the chassis elements 102, 104 are configured such that moulding the chassis elements 102, 104 can be carried out with a mould that comes in no more than two parts.

Figure 2 shows the junction box 100 of Figure 1 in a closed state. The snap- in noses 126 have engaged with boundaries of the recesses 128 and keep the chassis elements 102, 104 locked together. In one embodiment, engagements of the snap- in noses 126 with the borders of the corresponding recesses 128 requires compressing the gasket 124 with a predetermined force. To disengage the snap-in noses 126, they can be bent laterally, either with a tool like a screwdriver or manually. After that, the chassis elements 102, 104 may be separated from each other and the junction box 100 may be opened. Sectional lines I-I and II-II show in which directions the junction box 100 is cut for the illustrations of Figure 3 and 5, respectively. Figure 3 shows a first cross section of the junction box 100 of Figures 1 and 2, wherein the section follows the line I-I in Figure 2.

Where the middle section 118 of the bushing 110 lies adjacent to the recess 120 in the chassis elements 102, 104, at least one lip 305 extends in a radial direction from the bushing 110 and runs in a direction around a longitudinal axis of bushing 110. In the shown, preferred embodiment, three lips 305 are positioned in parallel.

Figure 4 shows a second cross section of the junction box 100 of Figures 1 to 3 , wherein the section follows the sectional line I-I in Figure 2. Figure 4 is a magnified detail of

Figure 3 in an area of bushing 110. Note that most of the first cable guide 132 is cut away but it can be seen that the axial distance between the first cable guide 132 and an axial end of the bushing 110 may be small, like in the range of 1 to 5 mm, more preferred in the range of 2 to 4 mm.

As best seen in figure 4, the lips 305 of the bushing 110 interact with both the upper, i.e. first chassis element 102 and the lower, i.e. second chassis element 104.

The interaction between the second chassis element 104, i.e. the lower chassis element 104 as shown in Figure 4 and the three lips 305 is such that all three lips 305 have

interference with the recess 120 of the second chassis element 104. A reliable sealing engagement is thus achieved between the bushing 110 and the second chassis element 104 since the lips 305 seal and push against the surface of the recess 120. The interaction between the three lips and the first chassis element 102, i.e. the upper chassis element 102 as shown in figure 4 is similar. However, the middle lip 305 engages with the sealing gasket 124 (see also figure 3), so that this sealing lip 305 has interference with the sealing gasket 124. Due to the pressure created between this middle lip 305 and the sealing gasket 124, a reliable sealing is achieved.

The other two lips 305, 305, i.e. inner and outer lips 305, 305, are in contact with the first chassis element 102 in order to achieve interference with the surface of the recess 120 of the upper chassis element 102. Thus, a reliable sealing is achieved by the lips pushing against the surface of the recess 120 of the first chassis element 102.

Figure 5 shows a third cross section of the junction box 100 of Figures 1 to 4 , the section following the sectional line II-II in Figure 2. From the first chassis element 102, only small sections of the snap-in noses 126 are visible. The indicated groove 122 in the second chassis element 104 for the gasket 124 is optional. Figure 6 shows the junction box 100 of Figures 1 to 5 when the junction box 100 is mounted on the backside of a solar panel 605. The even surface 136 of second chassis element 104 is fastened to the backside of solar panel 605 with an adhesive. The adhesive is preferred to be stable over

temperatures up to at least 80 °C or more as the solar panel 605 may get hot during operation.

The cable 108 runs from the inside of the junction box 100 through the bushing 110 and the first cable guide 132, then makes a turn of about 180 degrees and passes through the opening of the second cable guide 134. A longitudinal axis 610 of the cable 108 at the first cable guide 132 may be further away from the solar panel 605 than another

longitudinal axis 615 where the cable 108 runs through the second cable guide 134. In this embodiment, the longitudinal axes 610, 615 lie in a plane that encloses an acute angle a with the plane in which lies the back of the solar panel 605 and the surface 136.

The cable 108 is preferred to have a diameter that is aligned with openings of the first cable guide 132 and the second cable guide 134 such that threading the cable 108 through the openings is possible after the junction box 100 has been disposed on the surface of solar panel 605 but at the same time there is enough friction between the cable 108 and first cable guide 132 or second cable guide 134 that a longitudinal strain on the cable 108 of a predetermined force in the range of about 50 to 100, most specifically 60 to 80 N can be resisted . Figure 7 shows the junction box 100 of Figure 6 mounted on the solar panel 605 from a different perspective. In this embodiment, two cables 108 are provided and each cable 108 runs through a corresponding second cable guide 134. In this embodiment, the cable guides 132, 134 lie on opposite lateral sides of the junction box 100.