The present invention relates to a ceiling panel comprising a top surface, a bottom surface and a surrounding edge extending between the top surface and the bottom surface, wherein at least one cutout extending from the top surface is adapted for engagement with a hanger adapted to be suspended in an overhead structure, wherein the at least one cutout is provided in the form of a first groove and a second groove, wherein the first groove forms an angle with the top surface of at least approximately 10 degrees, and wherein the second groove forms an angle with the first groove of at least approximately 10 degrees.

WO 2007/012077 discusses a prior art ceiling panel in which a channel of inverted-T configuration is formed in the top face from one edge of the panel to another. A hanger in the form of a profile also having inverted-T configuration is inserted into the channel from the end of the channel and displaced in its longitudinal direction until it is positioned at a distance from the edges of the panel. The hanger is suspended from an overhead structure by means of wire. However, a channel of inverted-T configuration is rather complicated to provide in a ceiling panel.

Typically, a channel of inverted-T configuration could be machined by chip removal, such as milling. However, in this way, quite a lot of material has to be removed, in order to provide space for the chip removing tool itself. Thereby the integrity of the panel is compromised resulting in reduced strength of the panel. Furthermore, in order to simplify the machining operation, it would be preferred to machine the channel from one edge of the panel to another, so that the tool may be introduced from the edge of the panel. This may also be required in order to introduce a tool large enough to provide the channel of inverted-T configuration with sufficient undercut in order to bear on the hanger. However, if the channel extends through the edges of the panel, the integrity of the panel is further compromised resulting in further reduced strength of the panel.

Another prior art suspended ceiling system is disclosed in US Patent No. 4,033083, which relates to fastening of mobile home ceiling boards. The ceiling board is in its top face provided with a first and second groove which are mutually angled and each form an angle with the top face. The ceiling board is suspended from an overhead structure by means of a fastening means having flanges engaging the grooves. The grooves extend through the edge of the board, and the flanges are introduced into the groove at the edge of the board and slid along in the groove.

The object of the present invention is to provide a ceiling panel adapted to be suspended in a ceiling, the ceiling panel having improved integrity and strength and being simple to manufacture.

In view of this object is provided a ceiling panel as outlined in the introduction, wherein the first groove and the second groove are positioned at a dis- tance from the edge of the ceiling panel.

Thereby, the integrity and consequently the strength of the ceiling panel may be improved, as the edges of the panel are intact. Further, as very little material need to be removed from the ceiling panel, a much stronger panel may be obtained compared to the prior art. Also a better integrity between the hanger and the panel may be obtained, as the flanges of the hanger may fit closely into the grooves obtained by cutting, because the flanges need not be slidable along grooves as in the prior art. In a structurally advantageous embodiment, the second groove forms an angle with the first groove of between 20 and 140 degrees, preferably between 50 and 120 degrees, and more preferred between 80 and 100 degrees.

In an embodiment, the first groove and the second groove are arranged symmetrically about a plane at right angles to the top surface. In this way, both manufacture of the ceiling panel and mounting of the hanger in the panel may be simplified.

In an embodiment, the first groove is deeper than the second groove, or vice versa. Thereby, the integrity and consequently the strength of the ceiling panel may be further improved, as for some embodiments one groove can be less deep, so that less material is removed, and consequently the weakness introduced by the groove is minimized.

In an embodiment, the first groove and the second groove are positioned so that they form parallel, longitudinal openings in the top surface. Thereby manufacture of the ceiling panel may be simplified. Furthermore, the configuration of the hanger may be simplified in that it may be composed by two lon- gitudinal profiles that are connected after insertion into the respective grooves.

In an embodiment, the distance between the first and the second groove increases in the direction away from the top surface of the ceiling panel, the distance between a first longitudinal opening of the first groove and a second longitudinal opening of the second groove is at least 90 per cent, and preferably approximately 100 per cent, of the extent of the first groove or of the second groove in a direction parallel to the top surface and at right angles to the longitudinal opening of the groove. Thereby, a compact hanger may be utilized, and flanges of the hanger adapted to be inserted into the grooves of the panel may project about halfway into the grooves in the mounted position of the hanger, whereby mounting of the second flange of the hanger is possible during a temporary displacement of the first flange all the way into its groove.

The present invention further relates to a ceiling panel hanger comprising two flanges for engagement with a cutout in a top surface of a ceiling panel, the flanges being rigidly connectable and adapted for suspension in a ceiling structure wherein, in the connected and suspended state, carrying a ceiling panel, the first flange forms an angle with the horizontal of at least approxi- mately 10 degrees, and the second flange forms an angle with the first flange of at least approximately 10 degrees. The ceiling panel hanger is characterized in that the flanges are releasably connected or adapted to be connected after engagement with a ceiling panel. Thereby, the flanges may be inserted through longitudinal openings in the top surface of the ceiling panel, one after the other and subsequently connected, so that it is avoided to introduce the flanges through the edges of the panel. This may be easier, especially if the grooves in the ceiling panel are rather narrow in order to provide a good grip of the flanges, as in this case, longitudinal displacement of the flanges in the grooves would result in rather large friction. In this way, the first groove and the second groove in the ceiling panel may be positioned at a distance from the edge of the ceiling panel. Thereby, the integrity and consequently the strength of the ceiling panel may be further improved, as the edges of the panel are intact. By avoiding the necessity of sliding the flanges in the grooves of the panels, it is further pos- sible to install panels at locations with little space to the sides. The hanger is further very simple and cost effective, both in terms of production cost and installation time.

In a structurally advantageous embodiment, the second flange forms an an- gle with the first flange of between 20 and 140 degrees, preferably between

50 and 120 degrees, and more preferred between 80 and 100 degrees, and in that, preferably, in the suspended state, the first flange and the second flange are arranged symmetrically about a plane at right angles to the horizontal.

The choice of angle between the flanges is a compromise between the grip in the panel, ease of fitting the flanges in the grooves, and weakness of the panel introduced by the grooves. By having the first and secon flange arranged symmetrically about a plane at right angles to the horizontal a particularly simple embodiment is achieved, as it is hence possible to provide the first and second flange as identical flanges. This will further reduce production cost and further simplify installation. In a structurally particularly advantageous embodiment in terms of ease of installation and cost of production, the ceiling panel hanger comprises two substantially V-formed profiles forming a first part that constitutes one of the flanges of the ceiling panel hanger and a second part that constitutes a connecting flange contacting the connecting flange of the other profile, in that the connecting flanges are connected by means of fasteners, such as screws and nuts, in that at least one of the flanges is adapted to be suspended from an overhead structure, for instance in that it is provided with holes for the connection of suspension wires, and in that each profile is preferably formed from a sheet material, such as steel, which is bent at an angle, thereby forming the first part and the second part.

The present invention further relates to a suspended ceiling system compris- ing a ceiling panel and at least one ceiling panel hanger, the ceiling panel having a top surface and a bottom surface and a surrounding edge extending between the top surface and the bottom surface, the at least one ceiling panel hanger comprising two flanges being engaged in a cutout being formed in the top surface of the ceiling panel, the flanges being rigidly connected and adapted for suspension in a ceiling structure, wherein the first flange of the ceiling panel hanger forms an angle with the top surface of the ceiling panel of at least approximately 10 degrees, and the second flange of the ceiling panel hanger forms an angle with the first flange of at least approximately 10 degrees, and wherein the cutout in the top surface of the ceiling panel is provided in the form of a first groove in which the first flange of the ceiling panel hanger is engaged and a second groove in which the second flange of the ceiling panel hanger is engaged. The suspended ceiling system is characterized in that the flanges of the ceiling panel hanger are releasably connected or adapted to be connected after engagement with a ceiling panel.

Thereby, the flanges may be inserted through longitudinal openings in the top surface of the ceiling panel, one after the other, so that it is avoided to introduce the flanges through the edges of the panel, and the above-mentioned advantages may be obtained. Thereby a versatile suspended ceiling system is provided which allows mounting suspended ceiling panels in places with limited space to the sides.

In an embodiment, the first groove and the second groove are positioned at a distance from the edge of the ceiling panel. Hereby less material need to be removed from the panel, as the first and second groove may be machined by simple cutting, for instance by means of a circular saw, whereby only material corresponding to the thickness of the saw blade need to be removed. A hanger having flanges fitting the first groove and the second groove, respectively, may lock mechanically when inserted into the grooves. As very little material need to be removed from the ceiling panel, a much stronger panel may be obtained. Also a better integrity between the hanger and the panel may be obtained, as the flanges of the hanger may fit closely into the grooves obtained by cutting.

The present invention further relates to a method of mounting a ceiling panel in a ceiling structure, whereby at least one ceiling panel hanger is engaged in a cutout in a top surface of the ceiling panel, and whereby the at least one ceiling panel hanger is suspended in the ceiling structure. The method is characterized by that a first flange of the ceiling panel hanger is inserted into a first groove through a first longitudinal opening in the top surface of the ceiling panel, and by that a second flange of the ceiling panel hanger is inserted into a second groove through a second longitudinal opening in the top sur- face of the ceiling panel, and in that, after insertion of the second flange, the first flange and the second flange are connected. Thereby, less material need to be removed from the ceiling panel in which the hanger is to be mounted, and the above-mentioned advantages may be obtained. The hanger may lock mechanically when inserted into the grooves. With this method it is fur- ther possible to install a suspended ceiling panel in tight spaces, i.e. where there is little space to the sides.

In an embodiment, when the first flange of the ceiling panel hanger is inserted into the first groove through a first longitudinal opening in the top sur- face of the ceiling panel, the first flange is displaced in a direction inclined to the top surface of the ceiling panel and thereby enabling insertion of the second flange of the ceiling panel hanger into the second groove through the second longitudinal opening in the top surface of the ceiling panel, and, after insertion of the second flange, the first flange of the ceiling panel hanger is retracted partly out of the first groove, thereby enabling connection of the first flange and the second flange. Thereby, a compact hanger may be utilized and at the same time it may be obtained that the flanges of the hanger point away from each other in the direction from the top surface and into the panel. This latter configuration may be advantageous in that the bottoms of the grooves are spaced longer from each other, thereby improving the integrity of the panel structure.

The present invention further relates to a method of manufacturing a ceiling panel for suspension in a ceiling structure by means of a ceiling panel hanger, whereby at least one cutout adapted for engagement with the hanger is formed in the top surface of the ceiling panel. The method is characterized by that a first cut is performed in the top surface of the ceiling panel by means of a circular saw, whereby a blade of the circular saw is inclined to the top surface of the ceiling panel as the blade is advanced in its radial direction along the top surface, and by that a second cut is performed in the top sur- face of the ceiling panel by means of the circular saw, whereby the blade of the circular saw is inclined relative to its orientation during the first cut as the blade is advanced in its radial direction along the top surface. Thereby, less material need to be removed, and the above-mentioned advantages may be obtained. Further, a much simpler and easy method of manufacturing is ob- tained than it is the case, for instance, by prior art channels of inverted-T configuration.

The invention will now be explained in more detail below by means of examples of embodiments with reference to the very schematic drawing, in which

Fig. 1 is a cross-section through a part of a ceiling panel according to the invention,

Fig. 2 is a cross-section through a part of the suspended ceiling system in Fig. 3,

Fig. 3 is a perspective view of a suspended ceiling system according to the invention,

Fig. 4 is a side view of a profile of a ceiling panel hanger according to the invention,

Fig. 5 is an end view of the ceiling panel hanger in Fig. 4,

Fig. 6a to 6d illustrate a method of mounting of a ceiling panel hanger in a ceiling panel, Fig. 7 shows a cross-section through a part of another embodiment of the suspended ceiling system according to the invention,

Fig. 8 is a top view of a part of another embodiment of the suspended ceiling system according to the invention,

Fig. 9 is a perspective view of another embodiment of a suspended ceiling system according to the invention,

Fig. 10 is a perspective view of a suspended ceiling system according to an embodiment, and

Fig. 11 is a close up view of detail A of Fig. 10.

Fig. 3 shows a perspective view of a suspended ceiling system 1 according to the invention. The suspended ceiling system 1 comprises a ceiling panel 2 that is suspended by means of two ceiling panel hangers 3. However, any suitable number of ceiling panel hangers 3 may be employed. The ceiling panel hangers 3 are suspended from a not shown overhead structure by means of wires 4. The suspended ceiling system 1 is preferably of the so- called island type, wherein separate ceiling panels are suspended at a distance from each other, thereby forming so-called islands hanging from an overhead ceiling structure. The islands may among other things improve the acoustic properties of a room and may have decorative properties.

The ceiling panel 2 in Fig. 3 comprises a top surface 5 and a bottom surface 6 and a surrounding edge 7 extending between the top surface 5 and the bottom surface 6. The ceiling panel 2 shown is rectangular, but it may have any suitable form, among others square, triangular, oval, round or forms composed by such forms. The ceiling panel 2 may have varying thickness. The ceiling panel 2 is preferably made of mineral wool, such as stone wool, and preferably of a density in the interval of 60-150 kg/m ³ , and preferably a thickness of at least 20 mm. The area weight may be, for instance, between about 2-5 kg/m ² , but any suitable material could be used according to the invention. The material is preferably substantially compact and substantially dimensionally stable.

Fig. 1 shows a cross-section through a part of the ceiling panel 2 in Fig. 3 adapted for engagement with a ceiling panel hanger 3. Two cutouts in the form of a first groove 8 and a second groove 9 are formed in the ceiling panel 2 so that they extend from the top surface 5 and are adapted for engagement with flanges 10, 11 of a ceiling panel hanger 3 as shown in Fig. 2. In the embodiment shown, the first groove 8 forms an angle a with the top surface of 45 degrees, and the second groove 9 forms an angle b with the first groove 8 of 90 degrees. In this case, the first groove 8 and the second groove 9 are arranged symmetrically about a plane at right angles to the top surface 5. However, the first groove 8 may form any suitable angle with the top surface of at least approximately 10 degrees, and the second groove 9 may form any suitable angle with the first groove 8 of at least approximately 10 degrees. The preferred angles a, b may depend on the flexibility and the dimensional stability of the material of the ceiling panel 2. For instance, if the dimensional stability of the material is very good, the angle a and/or the angle b may be rather small.

In the embodiment shown in Fig. 3, the first and second grooves 8, 9 are positioned at a distance from the edge 7 of the ceiling panel 2, so that they do not penetrate the edge. In this way, the integrity and stability of the ceiling panel is improved, and the grooves are not visible from below the panel which may be preferred for esthetical reasons. In the embodiment shown in Fig. 2, the ceiling panel hanger 3 comprises two substantially V-formed profiles 18, 19 forming a first part that constitutes one of the flanges 10, 11 of the ceiling panel hanger and a second part that constitutes a connecting flange 13. The two connecting flanges 13 of either pro- file, respectively, contact each other and are releasably connected by means of screws 14 and nuts 15. Any suitable number of screws 14 are inserted through holes 16 in the connecting flanges 13, see Figs. 4 and 5. Other suitable fasteners or locking means, for instance clips or even glue or soldering may be used. The ceiling panel hanger 3 is suspended by means of the sus- pension wires 4 inserted through holes 17. Each V-formed profile 18, 19 is preferably formed from a relatively thin sheet material, such as steel, which is bent at an angle, thereby forming the first part and the second part. However, it may also be injection moulded or extruded in plastic material. In this embodiment, the ceiling panel hanger 3 forms an inverted Y, whereby the flanges 10, 11 fits into the grooves 8, 9, respectively, of the ceiling panel shown in Fig. 1 as described above.

Figs. 6a to 6d illustrate the process of mounting the ceiling panel hanger 3 in the ceiling panel 2, in the embodiment shown in Figs. 1 and 2. Firstly, the first flange 10 of the first V-formed profile 18 is inserted fully into the first groove 8 of the ceiling panel 2, see Fig. 6a. Thereby, space above the top surface 5 is provided for insertion of the second flange 11 of the second V-formed profile 19 into the second groove 9 of the ceiling panel, see Fig. 6b. The second flange 11 is, however, only inserted approximately halfway into the second groove 9, see Fig. 6c. Thereby, space is provided for partly, that is approximately halfway, retraction of the first flange 10 from the first groove 8, whereby the connection flanges 13 of the V-formed profiles 18, 19 contact each other and may be connected to each other as described above, see Fig. 6d. It is noted that, in this case, the second groove 9 does not need to be as deep as the first groove 8, however, assembly and even manufacture may be facilitated when the grooves 8, 9 are of equal depth. It is further noted that, in the embodiment shown in Figs. 1 to 3, the first groove 8 and the second groove 9 are positioned so that they form parallel, longitudinal openings 20, 21 in the top surface 5 and that the distance be- tween the grooves increases in the direction away from the top surface of the ceiling panel. In order to allow the mounting process illustrated in Figs. 6a to 6d, the flanges 10, 11 are not inserted fully into the grooves 8, 9 in the final position, as it may be seen in Fig. 6d. However, advantageously, the grooves are not deeper than necessary, as this could influence the integrity of the ceiling panel. Therefore, it may be preferred that the distance X between the first longitudinal opening 20 of the first groove 8 and the second longitudinal opening 21 of the second groove 9 corresponds substantially to the extent Y of the first groove or of the second groove in a direction parallel to the top surface 5 and at right angles to the longitudinal opening of the groove, see Fig. 2. However, in order to take up tolerances, the grooves may be a little deeper, so that, for instance, X is approximately 90 per cent of Y.

Alternatively, in another embodiment, not shown, the distance X may be equal zero or close to zero. In this embodiment, the flanges 10, 11 have the form of combs, whereby the teeth of the combs may cross each other. Thereby, the connection flanges 13 of the V-formed profiles 18, 19 contact each other oppositely relative to the embodiment shown in Figs. 1 to 3. In this way, referring to Fig. 2, the connection flange 13 of the left-hand V-formed profile 18 would be placed to the right of the connection flange 13 of the right- hand V-formed profile 19. The comb-formed flanges 10, 11 could then reach until the bottom of the grooves 8, 9, as no retraction of a flange would be necessary at the mounting procedure.

The ceiling panel 2 may be manufactured by forming the grooves 8, 9 in the form of cutouts by forming a first cut in the top surface of the ceiling panel by means of a circular saw, whereby a blade of the circular saw is inclined to the top surface of the ceiling panel as the blade is advanced in its radial direction along the top surface. A second cut is then performed in the top surface of the ceiling panel by means of the circular saw, whereby the blade of the circular saw is inclined relative to its orientation during the first cut as the blade is advanced in its radial direction along the top surface. Preferably, the thickness of the grooves corresponds approximately to the thickness of the blade of the circular saw. The grooves may also be produced in other suitable ways, for instance by milling.

The thickness of the grooves may be slightly smaller than the thickness of the flanges 10, 11 to be introduced into the grooves, thereby ensuring a good grip. However, of course, the grooves may also be thicker than the flanges, as the flanges will still be mechanically locked in the grooves. The depth of the grooves may be a compromise between on the one hand a good grip be- tween the flange and the groove and on the other hand a good integrity of the panel. In other words, if the grooves are too deep, the integrity may be compromised. However, this could be counteracted by gluing the flanges into the grooves. In any way, a good compromise could be that the grooves extend until a depth D of 50 to 85, preferably 60 to 75, and more preferred about approximately 70 per cent of the thickness T of the panel, see Fig. 1 , whereby D is measured at right angles to the top surface 5 of the panel 2. In the embodiment shown in Figs. 1 to 3, an advantageous relation between the length of the flanges 10, 11 and the length of the ceiling panel 2 could be between 50 and 90, and preferably between 60 and 70. It is noted that the maximum length of the grooves 8, 9 may have to be longer than the flanges 10, 11 if the grooves are manufactured by means of a circular saw.

Fig. 7 shows another embodiment of the suspended ceiling system 1 according to the invention. In this embodiment, the distance between the grooves 8, 9 decreases in the direction away from the top surface 5 of the ceiling panel 2. It is noted that in this case, the flanges 10, 11 may be fully inserted into the grooves 8, 9, respectively, as no retraction of the first flange 10 is necessary after insertion of the second flange 11. Preferably, as seen in the figure, the ceiling panel hanger does not cover much of the surface of the ceiling panel, as this could reduce the insulating effect of the ceiling panel. Therefore, the parts of the ceiling panel hanger extending above the ceiling panel form an angle with the top surface of the ceiling panel.

Fig. 8 shows yet another embodiment of the suspended ceiling system 1 according to the invention. In this embodiment, one ceiling panel hanger 3 is provided at either corner of the ceiling panel 2. Only one comer of the ceiling panel is shown in the figure. The ceiling panel hanger 3 is composed by a first part 22 and a second part 23 that in the mounted position shown are connected by means of flanges 24 that are suspended by means of wire. A first flange 25 of the first part 22 is partly inserted into a first groove 27 of the ceiling panel 2, and a second flange 26 of the second part 23 is partly inserted into a second groove 28 of the ceiling panel 2. The first groove 27 and the second groove 28 form longitudinal openings 29, 30, respectively, that are at right angles to each other. Any other suitable angle is also possible. In the embodiment shown, the first groove 27 and the second groove 28 each form an angle of 45 degrees with the top surface 5 of the ceiling panel. However, many different configurations are possible. For instance, the first groove 27 may form an angle of 45 degrees with the top surface 5 and the second groove 28 may form an angle of 90 degrees with the top surface 5. The process of mounting the ceiling panel hanger 3 in the ceiling panel 2 in this em- bodiment is similar to the process illustrated in Figs. 6a to 6d.

Fig. 9 shows yet another embodiment of the suspended ceiling system 1 according to the invention. In this embodiment, similarly to the embodiment in Fig. 8, one ceiling panel hanger 3 is provided at either corner of the ceiling panel 2. However, in this embodiment, the ceiling panel hangers have a cross-section similar to that of the embodiment shown in Fig. 7, but the length of the hangers is substantially shorter, as it may be seen in Fig. 9.

Other variations and combinations of suspended ceiling panels and hangers are also possible, such as providing larger islands by combining adjacent ceiling panels as shown in Fig. 10. The suspended ceiling system 1 in Fig. 10 corresponds to the ceiling system in Fig. 3, and similar parts are denoted by the same references. The suspended ceiling system 1 in Fig. 10 is made up of two ceiling panels 2 as indicated by the division line 32. The illustrated sys- tern comprises a common set of ceiling panel hangers 3 crossing the division line 32. Hence in this embodiment the longitudinal openings 20, 21 will

Fig. 11 illustrates a close-up of the edge at the division line 32 of the two adjacent ceiling panels 2. If considered convenient or beneficial the adjacent edge portions of the ceiling panels 2 may be glued as indicated by glue 31. A method of mounting ceiling panels could hence include the introductory step of applying glue 31 to the edges intended to abut of two adjacent ceiling panels 2. Next step could be aligning the ceiling panels and bringing the edges together for the glue 31 to join the panels to form a unitary, glued ceiling panel. Preferably mounting of the the ceiling panel hangers 3 could take place before the glue has cured in order to keep the ceiling panels 2 aligned, and preferably the glue should be allowed to cure fully before suspending the ceiling panel hangers 3 with the ceiling panels from the overhead structure.

It is also anticipated to provide even larger islands by combining further ceiling panels as will be evident to the skilled person.