The present invention relates to a roof window, particularly for installation in an inclined roof surface, comprising a primary frame, at least one secondary frame, such as a sash and/or an intermediate frame, and a lifting device including a lifting arm inserted between the primary frame and the at least one secondary frame, a sledge system and a coupling mechanism, the lifting arm having a first end rotatably connected with said sledge system slidably connected with the primary frame in a sledge guidance and a second end rotatably connected with the at least one secondary frame, the lifting device furthermore including a spring assembly configured to be coupled to the sledge system and to the first end of the lifting arm by means of said coupling mechanism, such that the spring assembly is able to assume an uncoupled condition and a coupled condition relative to the sledge system the coupling mechanism comprising a first coupling member associated with the spring assembly and adapted to cooperate with a second coupling member associated with the sledge system, and the first coupling member including a hook element and the second coupling member includes receiving means formed in the sledge system and configured to cooperate with said hook element in the coupled condition, in that the hook element is configured to assume at least a non-engagement position and an engagement position. The invention furthermore relates to a method for installing such a roof window, and a method for dismantling a secondary frame of the roof window.

Windows for installation in an inclined roof surface include the pivoting type hinged at or near the centre, the top-hinged type, and finally the roof windows that are top-hinged during normal operation but which pivot for cleaning. Examples of top-hung windows that pivot for cleaning are for instance disclosed in Applicant's WO-A-89/10460, EP 0 733 146 B1, EP 1 873 323 B1 and EP 2 762 665 A2. To make it possible to pivot the window sash approximately 180° to a convenient cleaning position, the sash structure is connected with an intermediate frame with frame arms, which in the closed position of the window are positioned between the upper parts of the frame and sash side members, and which during normal use of the window as a top-hung window follow the sash side members.

In roof windows in which the operation takes place either entirely or partially about a hinge axis at the top, it is known to balance at least part of the weight of the movable components by means of a lifting device inserted between a pair of associated side members of the stationary frame and the sash element, respectively, and having one end pivotally connected with one of the side members while its other end is hinged to a sliding shoe displaceable along the other side member, said shoe being urged by a tension spring in a direction so as to exert an outwardly directed pressure through the lever on the sash element. The purpose of this arrangement is to facilitate opening the window, and the dimensions may be chosen so that the spring can retain the top-hinged frame in equilibrium in a desired opening position.

Coupling and uncoupling of the spring assembly of such a window is known from e.g. EP 0 081 333 B1, wherein one end of the sash lifting-lever presents at least two pivot points having different distances from the pivot point at the other end of the lever, and being located to successively becoming operative during the opening of the window and successively increasing the effective length of the lever. Another disclosure is found in WO 89/010460 A1, wherein a slide shoe and a pre-stressed spring provided with coupling means adapted to be brought into engagement with each other during the installation of the window is described. Said coupling means include a tie rod connected on one end to said spring and to a coupling element on its other end. The coupling element engages a receiving recess in the sliding shoe by means of a traverse pin. This window however requires the installer to lift the entire weight of the sash with one hand while the other hand is placed in a potentially dangerous position between sash and frame during installation and dismantlement. In addition, window sashes are progressively gaining in weight as modern sashes include additional elements offering a greater range of functionalities, and better insulation properties require greater amount of materials being included in the construction of frames, panes and sashes.

Considering this, it is presently a challenge to provide a spring assembly and sledge system coupling mechanism that can bear current load requirements while offering an intuitive and easily manageable roof window simplifies installation and dismantlement.

It is therefore the object of the invention to provide a roof window, in which the secondary frame is easily installed and dismantled.

This is achieved with a roof window of the kind mentioned in the introduction, which is furthermore characterised in that the coupling mechanism furthermore comprises a coupling plate arranged to assume at least a first position corresponding to the coupled condition and a second position corresponding to the uncoupled condition, the coupling plate allowing the hook element to assume said non-engagement position, that the hook element of the first coupling member has at least one hook portion facing the sledge system, that the hook element has a U-shaped configuration including a base plate portion and two flange portions, one hook portion being provided at one of or each of the flange portions, that the spring assembly comprises a tension rod including a rod portion extending substantially along the length of the spring assembly, and a head portion facing the hook element, the tension rod being provided with at least one inclined portion at the transition between the head portion and the rod portion, that the hook element is provided with an aperture in the base plate portion to allow passage of the tension rod such that the head portion of the tension rod is retained within the U-shape at the front side of the base plate portion and the rod portion at the back side, that the coupling plate of the coupling mechanism has a base portion located at the back side of the base plate portion of the hook element and is provided with an oblong aperture to allow passage of the rod portion of the tension rod, and wherein the coupling plate is slidable in the plane of the base portion substantially perpendicularly to the rod portion such that when in the first or bottom position, the hook portion is capable of assuming its engagement position, and in the second or top position, the hook portion is kept in its non-engagement position, that an angle element is provided near the head portion of the tension rod, having an aperture to allow passage of the rod portion of the tension rod, and that an end piece is provided, having an aperture to allow passage of the rod portion of the tension rod, the end piece furthermore having an upstanding wall, on which a protrusion is formed to surround the aperture of the end piece, and wherein two protruding flanges are provided at either side of the upstanding wall to define a track.

It is thereby possible to couple and uncouple the spring assembly from the sledge system by manually positioning the coupling plate in the selected position and opening and closing the sash to either release or engage the first coupling member. The coupling plate stays in the selected position until it is re-activated, this allowing for the installation or dismantling of the sash and/or intermediate frame in the stationary frame, as the first coupling member is free of its coupling with the sledge system and thus without interference of the bias of the spring assembly.

The hook element of the first coupling member has at least one hook portion facing the sledge system. This is advantageous from in particular an installation point of view.

In another presently preferred embodiment, the hook element of the first coupling member is arranged to slidably contact the sledge system in one direction and to engage said second coupling member in another direction. In addition to being simple in installation and dismantling, this also provides for a logical operation.

In a second aspect of the invention, a method for installing a roof window is provided.

In a third aspect of the invention, a method for dismantling a secondary frame of the roof window is provided.

Further preferred embodiments of the invention are set out in the dependent claims.

In the following description embodiments of the invention will be described with reference to the schematic drawings, in which

• Fig. 1 is a perspective view of a roof window, seen from the interior side and in an open position;
• Fig. 2 is a perspective view of details of a roof window with a lifting device, in a first embodiment of the invention and corresponding to the open position of the roof window of Fig. 1;
• Fig. 3 is an isometric view of the details of the roof window of Fig. 2, in a closed position of the window;
• Fig. 4 is a partially exploded view of the details of Fig. 3;
• Fig. 5 is an isometric view of the spring assembly shown in Fig. 3;
• Fig. 6 is a partial isometric view, on a larger scale, of the spring assembly shown in Fig. 5;
• Fig. 7 is a partial exploded isometric view of some elements of Fig. 6;
• Figs 8a to 8e are isometric views of the elements of Fig. 7;
• Fig. 9a is a partial isometric view, on a larger scale, of details shown in Fig. 3;
• Fig. 9b is an exploded, partial perspective view of details of the lifting device in another embodiment of the invention;
• Figs 10 and 11 are partial isometric views of details of the lifting device of the roof window in a second embodiment of the invention;
• Figs 12a to 12h are schematic partial side views of an embodiment of the roof window of the invention, during coupling and uncoupling of the lifting device;
• Figs 13a-13b, 14a-14b and 15a-15b are perspective views of details of the roof window in the second embodiment;
• Fig. 16 shows a schematic perspective view of details of a roof window in a further embodiment of the invention;
• Fig. 17 shows a schematic side view of details of a roof window in a still further embodiment of the invention;
• Figs 18a-18e are views corresponding to Figs 8a-8e, respectively, of details of the roof window in a third embodiment,
• Figs 19a-19b are views corresponding to Figs 13a-13b, respectively, of details of the roof window in the third embodiment;
• Fig. 20a is a view corresponding to Fig. 14a of details of the roof window in the third embodiment;
• Fig. 20b is a partial perspective view of details of the roof window in the third embodiment; and
• Figs 21 to 24 show partial or full, exploded, or sectional views of details of a roof window in yet another embodiment of the invention.

Referring initially to Fig. 1, the general configuration of a roof window which is top-hinged during normal operation and which pivots for cleaning is shown. Such a window is shown and described in further detail in Applicant's above-mentioned European patent No. 0 733 146 B1. In Fig. 1, a lifting device 10 is indicated which, referring now also to Fig. 2 to 9a, forms part of a first embodiment of the roof window according to the present invention.

The roof window comprises a primary frame in the form of a stationary frame 1 configured for installation in an inclined roof surface. At least one secondary frame is connected to the stationary frame 1, in the embodiment shown a first secondary frame in the form of a sash 2 carrying a pane 4, and a second secondary frame in the form of an intermediate frame 3. The intermediate frame 3 is fastened to the stationary frame at a top mounting fitting 5, and the sash 2 is hinged at the top of the roof window, via the intermediate frame 3 to the stationary frame 1, to render the roof window top-hung during normal operation. The sash 2 is also pivotally connected to the intermediate frame 3 in order to be able to rotate the sash 2 to provide access to the outside of the pane 4, for instance for cleaning purposes. To that end, the intermediate frame 3 is provided with a frame hinge part 6 of pivot hinge fitting. Although not shown in detail, it is clear to the skilled person that the sash 2 is provided with the counterpart sash hinge part of the pivot hinge fitting.

A lifting device 10 is composed of a spring arrangement 20 and a sledge system 30 which cooperate to assist in the opening of the window, that is, bringing the secondary frame or frames to an angled position relative to the primary frame. Here, from a closed position, the user operates the operating device of the window in the form of a handle 7 at the bottom member of the sash 2. The bias of the spring arrangement 20 of the lifting device 10 acts on a lifting arm 14 inserted between the stationary frame 1 and the intermediate frame 3. In turn, the lifting arm 14 exerts a moment on the intermediate frame 3 and hence to the sash relative to an axis through a top hinge pin 11. In combination with the force exerted by the user on the handle 7, transferred to a lifting moment, the moment resulting from the weight of the sash 2 with pane 4 is overcome. Closing the window from the open position entails the opposite movements of the sash 2 and relevant parts of the lifting device 10. A similar lifting device may be provided at each side of the roof window. Finally, the roof window is provided with a ventilation device 8 acting to allow passage of air also in the closed position of the window.

In further detail, the lifting arm 14 has a first end 12 rotatably connected with a sledge system 30, which in turn is slidably connected with the primary frame 1 in a sledge guidance 16, and a second end 13 rotatably connected with the at least one secondary frame 3, the lifting device 10 furthermore including a spring assembly 20 configured to be coupled to the sledge system 30. As the sledge system 30 is connected to the lifting arm 14, the spring assembly 20 is in turn configured to be connected to the first end 12 of the lifting arm 14 by means of a coupling mechanism to be described in further detail below, such that the spring assembly 20 is able to assume an uncoupled condition and a coupled condition relative to the sledge system 30.

Figs 5 and 6 show the general components of the spring assembly 20 of a roof window. Further details and advantages of the particular spring assembly 20 are the subject of Applicant's co-pending patent application filed on the same day as the present application, and is shown for information purposes only in Figs 21 to 24. The present invention is however applicable to any kind of spring assembly. Thus, the general components of the spring assembly are: a tension rod 22 accommodating a buffer spring system 28 and a main spring system 29. The buffer spring system 28 acts as an auxiliary system to the main spring system 29. In order to adapt one and the same spring assembly to varying roof inclinations, an adjustment means is provided in the form of a movable adjustment plate 26 which is placed in one of several recesses 27a in a spring casing 27 accommodating the buffer spring system 28.

As shown, the buffer spring system 28 comprises an outer spring 281 and an inner spring 282 of substantially identical pre-defined lengths. The pre-defined length of the springs 281, 282 is typically chosen according to the dimensions of other parts of the lifting device. In the mounted condition, the inner spring 282 is accommodated inside the outer spring 281 so as the axes of the respective springs extend substantially co-axially.

In the embodiment shown, the outer spring 281 and the inner spring 282 of the buffer spring system 28 have mutually different spring constants, and the outer spring 281 and the inner spring 282 of the buffer spring system 28 have mutually opposite thread directions.

The spring assembly 20 here further comprises at least one spring plug 283, 284 configured to be in contact with the respective end of the inner spring 282 of the buffer spring system 28 in the mounted condition. That is, here the two spring plugs 283 and 284 form the respective ends of the buffer spring system 283 and 284. At the manufacture stage, it is advantageous that the spring plugs 283, 284 is provided with friction-increasing means at the surface configured to be in contact with the respective end of the inner spring 282 of the buffer spring system 28. In this way, the two springs are kept together in a safe manner.

According to the present invention, and referring also the schematic views of Figs 12a-12e showing the stages of coupling and de-coupling, the coupling mechanism comprises a first coupling member 21 associated with the spring assembly 20 as is shown most clearly in Fig. 6.

The first coupling member 21 is adapted to cooperate with a second coupling member associated with the sledge system 30. In the first, second and third embodiment shown in Figs. 10-11 and 13a-15b, and Figs 18a-20b, the second coupling member comprises a sledge 31 forming part of the sledge system 30, and the sledge 31 includes receiving means configured to cooperate with the first coupling member 21 in the coupled condition.

In all of the embodiments shown, the first coupling member includes a hook element 21 to cooperate with the second coupling member including its receiving means formed in the sledge system 30. The hook element 21 is configured to assume at least a non-engagement position and an engagement position, and the coupling mechanism furthermore comprises a coupling plate 25 arranged to assume at least a first position corresponding to the coupled condition and a second position corresponding to the uncoupled condition, the coupling plate 25 allowing the hook element 21 to assume said non-engagement position. Operation of the presently preferred embodiments will be described in further detail in connection with Figs 12a to 12h.

In the embodiment shown, the hook element 21 of the first coupling member has at least one hook portion 214 facing the sledge system 30. This provides for a particularly easy and safe coupling procedure.

Even though the coupling mechanism could function well with only a single hook and receiving means pair, it is preferred that the hook element 21 as shown in for instance Fig. 8d has a U-shaped configuration including a base plate portion 212 and two flange portions 213, one hook portion 214 being provided at each of the flange portions 213.

Turning now in particular to the exploded view of Fig. 7 and the detailed individual views of Figs 8a to 8e, the tension rod 22 of the spring assembly 20 comprises includes a rod portion 221 extending substantially along the length of the spring assembly 20, and a head portion 222 facing the hook element 21, the tension rod 22 being provided with at least one inclined portion 223, 224 at the transition between the head portion 222 and the rod portion 221.

In the first embodiment, the hook element 21 of the first coupling member is provided with an aperture 211 in the base plate portion 212 to allow passage of the tension rod 22 such that the head portion 222 of the tension rod 22 is retained within the U-shape at the front side of the base plate portion 212 and the rod portion 221 at the back side.

The coupling plate 25 of the coupling mechanism has a base portion 252 which in the assembled position is located at the back side of the base plate portion 212 of the hook element 21, i.e. opposite the sledge system 30, and is provided with an oblong aperture 251 to allow passage of the rod portion 221 of the tension rod 22, and wherein the coupling plate 25 is slidable in the plane of the base portion 252 substantially perpendicularly to the rod portion 221 such that when in a bottom position, the hook portion 21 is capable of assuming its engagement position, and in a top position, the hook portion 21 is kept in its non-engagement position.

Furthermore, the coupling plate 25 is here provided with a bottom flange 253 formed on the base portion 252 to abut on the at least one inclined portion 223 in the non-engagement position via the base plate portion 212. This brings about the actual retention of the hook element 21 in its non-engagement position in the embodiment shown.

The coupling plate 25 is provided with a cut-out 254 at the top of the base portion 252 to form at least one, preferably two, upstanding lugs 255. This eases the application of tools and the re-entry into the coupling position. Furthermore, the cut-out 254 allows for accommodation of reinforcement or stiffening elements for the sash.

In principle the configuration of the connection between the first coupling member and the spring assembly 20 may be carried out in any suitable manner as long as it fulfils the requirements due to the relatively large forces involved. A robust structure as in the present embodiment includes an angle element 23 provided near the head portion 222 of the tension rod 22, having an aperture 231 to allow passage of the rod portion 221 of the tension rod 22.

Here, an end piece 24 is furthermore provided, having an aperture 241 to allow passage of the rod portion 221 of the tension rod 22, the end piece 24 furthermore having an upstanding wall 242, on which a protrusion 243 is formed to surround the aperture 241 of the end piece 24, and wherein two protruding flanges 244 are provided at either side of the upstanding wall 242 to define a track 245.

As shown, the angle element 23 is provided with an upstanding leg 232 and a bottom leg 233, the aperture 231 of the angle element 23 being provided in the upstanding leg 232, and wherein two protruding flanges 234 are provided substantially in parallel to the bottom leg 233 and each defining a gap 235 relative to the upstanding leg 232.

In the assembled state, the end piece 24 is positioned with the back side of its upstanding wall 242 abutting the front side of the upstanding leg 232 of the angle element 23, between the bottom leg 233 and the protruding flanges 234, and wherein the base portion 252 of the coupling plate 25 is received slidably in the track 245 of the end piece and the respective gaps 235 of the angle element 23.

In order to obtain a smooth movement during the coupling procedure, each flange portion 213 of the U-shaped the hook element 21 here includes an apex 210 at the front end, a rounded transition 215 between the apex 210 and the hook portion 214, a bottom edge portion 218 between the hook portion 214 and the base plate portion 212, an opposite top portion 217, and at least one inclined edge portion 216, 219 between the top portion 217 and the apex 210.

In the third embodiment, the components of the coupling mechanism shown in Figs. 18a-18e have a substantially corresponding configuration as in Figs. 8a-8e. The following differences are present in the embodiment shown; they may be present individually or in combination: The hook element 21 is provided with two grooves 217a in the top portion 217 to provide for possible further guidance. The protruding flanges 244 of the end piece 24 are provided with a respective rib portion 244a and two bent flange portions 246 on the side facing the spring arrangement 20. The angle element 23 is provided with enlarged aperture sections 231a adjoining the aperture 231 in order to accommodate the bent flange portions 246. In this way, easy assembly and safe retention in use is achieved. Finally, the coupling plate 25 is provided with friction-increasing portions 256, for instance in the form of riffling or other surface treatment to increase the friction to enhance the retention of the coupling plate 25 in the desired position. Corresponding friction-increasing portions may be provided on the opposite side of the base portion 252. The friction-increasing portions may also be provided as separate elements for instance a film or the like applied to the base portion 252. The components of the coupling mechanism need to be dimensioned suitably relative to each other in order to avoid excess frictional forces but at the same time allow for proper operation.

Further details of the sledge system 30 are shown in the second and third embodiments in Figs 10 to 11 and 13a to 15b, and Figs. 18a-20b. Elements having the same or analogous function as in the first embodiment carry the same reference numerals. Only differences relative to the first embodiment will be described in detail.

Referring now in particular to Figs 10-11, 13a-13b and 15a, the sledge 31 of the sledge system 30 comprises a bottom portion 310, a first wall portion 311 and a second wall portion 312, one receiving recess 314 being preferably provided at each of the transitions between the first wall portion 311 and the bottom portion 310 and between the second wall portion 312 and the bottom wall portion 310, and wherein a hole 315 is provided in the first wall portion 311 and a hole 316 is provided in the second wall portion 312 for receiving an axle 40 connected to the first end 12 of the lifting arm 14. Finally, the sledge 31 is provided with a second opening 318 and an incision 319 to make room for other parts of the lifting device 10.

In the third embodiment of the roof window shown in Figs. 19a-19b, the sledge 31 has been made longer relative to the sledge of the first and second embodiments. This provides the sledge 31 with a larger strength. As a consequence, the incision 319 is made longer.

In the presently preferred embodiments shown and described herein, the receiving means of the second coupling member include at least one receiving recess 314 in the sledge 31 of the sledge system 30. The second coupling member could also take other shapes. One conceivable, alternative solution would be to utilise the axle 40 as receiving means. This alternative solution is shown in Fig. 17.

Further details of the axle 40 shown in Figs 15a-15b, 16 and 20b are given for information purposes only and are the subject of Applicant's co-pending patent application filed on the same day as the present application.

In general, the components of the lifting device are subjected to high loads, in particular in large roof windows and in low roof pitches. In such fields of application, the required lifting capacity of the lifting device may amount to close to 500 Nm. Loads of these magnitudes not only pose severe demands on the components but also require high performance of the spring assembly.

In addition to the aspects covered by the present application, precautions have also been taken to mitigate adverse effects of the load in the top hinge pin 11 and the top bearing fitting 15. In order for the top hinge pin 11 to be safely lodged in the top bearing fitting 15 at all times, the top hinge pin 11 has been formed with a head and is furthermore secured against rotation. In order to transfer the load on the top hinge pin 11 exerted by the sash via the intermediate frame safely to the top bearing fitting 15, the top bearing fitting 15 is provided with protrusions (not shown in detail).

In order to control the frictional forces more precisely at the movement of the sledge system 30 in the sledge guidance 16, the sledge system 30 comprises a runner 32 in the embodiments described and shown in particular in Figs. 10-11, 14a-14b, and 20a-20b, configured to accommodate the sledge 31 and being provided with at least one recess 324 opposite the respective receiving recess 314 of the sledge 31 of the second coupling member. Further details of the runner 32 are shown for information purposes only; such details are the subject of Applicant's co-pending patent application filed on the same day as the present application. It is noted that the present invention is applicable also to sledge systems in which there is no runner, or a runner of a different configuration. In the embodiment shown, the runner 32 is formed of a plastic material such as POM which may also be provided with a coating of for instance Teflon^® or other treatment having the function to act as a lubricant to reduce the friction.

The narrowing 313 on the runner 32 is made for reasons of space availability. By forming the runner slenderer in one side, it is possible to make 322a thicker, and tolerances are accommodated in the side where 322 is - in that way the axle 40 is guided such that the end 402 does not protrude to wear on the side of the guidance.

An edge portion 328 is provided as a cut-out in order to allow space for other parts of the assembly. A flange portion 329 scrapes the guidance to force for instance smudge gathered in the sledge guidance 16 to the sides of the guidance.

In principle, the coupling mechanism may be designed in any suitable manner and operated accordingly, as long as the fundamentals as outlined initially are fulfilled. As will be understood from the following description of the operational steps performed during coupling and uncoupling of the spring assembly 20 from the sledge system 30 in the embodiments shown and described in the above with reference to the sequence of Figs 12a to 12h, the hook element 21 of the first coupling member is in the presently preferred embodiments arranged to slidably contact the sledge system 30 in one direction and to engage said second coupling member, in the embodiments shown the sledge 31, in another direction, namely by being forced in the opposite direction to ensure engagement with the first and second coupling members by the components of the lifting device itself. Not all elements are indicated by reference numerals in Figs 12a to 12h for ease of readability and it is referred to the above description of the remaining Figures for detailed explanations.

Turning first to Fig. 12a, the roof window is shown in its closed condition, that is the secondary frame or frames are lying substantially in parallel with the primary frame. Here, the intermediate frame 3 represents the secondary frames, and the position of the sledge guidance 16 and the spring assembly 20 indicate the corresponding position of the stationary frame 1 although not shown, i.e. here substantially horizontal for reasons of clarity, even though the stationary frame 1 will most often be installed in an inclined roof surface prior to coupling the spring assembly 20 to the sledge system 30. The coupling mechanism is not yet active, and the sledge system 30 is consequently located at a distance from the spring assembly 20. From the break-out enlarged view of Fig. 12a is apparent the position of the coupling plate 25 in its first position, i.e. bottom position, and corresponds to the engagement position of the hook element 21 in which coupling is possible.

When opening the window by rotating the intermediate frame 3 about the top hinge pin 11, the lifting arm 14 rotates as well, and the sledge system 30 moves in the direction of the spring assembly 20 and its associated first coupling member in the form of hook element 21. When approaching the position shown in Fig. 12b, the hook element 21 slides up on the sledge 31 and is able to rotate slightly on the tension rod 22, as the base plate portion 212 of the hook element 21 is able to move relative to the inclined portion 223 on the back side of the head portion 222. The coupling plate 25 is still in its first, or bottom position. During the continued movement in the opening direction of the intermediate frame 3 and the ensuing translational movement of the sledge system 30, the hook portions 214 of the hook element 21 will reach a position just above the receiving recesses 314. As the spring assembly 20 is biased and exerts a pull in the tension rod 22, to the left in Fig. 12b, the hook element 21 will be subjected to a clockwise moment which in turn forces the hook portions 214 to enter the receiving recesses 314 of the sledge 31.

Once the coupling has taken place, the hook element 21 withdraws further to the left due to the bias of the spring assembly, the hook portions 214 are drawn into stable engagement with the receiving recesses 314 in the sledge 31 as shown in Fig. 12c.

The window is now ready for normal operation, and during the subsequent closing of the intermediate frame 3, the movement of the lifting arm 14 pulls the sledge system 30 towards the top of the window, i.e. to the right as shown in Fig. 12d. The closing movement takes place during simultaneous further bias of the spring assembly 20 as is known per se.

Should the need for removal of the secondary frame or frames arise, the roof window is prepared for uncoupling by first rotating the intermediate frame 3 to an open position. Then, the coupling plate 25 is brought from its first or bottom position to its second or top position by an upwards movement, indicated by arrow A in Fig. 12f. In the embodiment shown, the window is not entirely open in the position of Fig. 12f, that is, the sledge system 30 is not in its left-most position but distanced from the spring assembly 20 by some millimetres. In practice, the sash is rotated to its fully open position and then moved slightly back in the closing direction such that the coupling plate 25 is free to be moved upwards. In this position the coupling plate is held in its upper most position by means of friction. The hook element 21 is still engaged with the sledge system 30 as the hook portions 214 are gripping the recesses 314 of the sledge 31 until the user grabs the sash and lifts it. During this movement, the hook element 21 is allowed to turn upwards in the counter-clockwise direction. This brings the hook element 21 to its non-engagement position in which coupling is not possible. This action is brought about in that the bottom flange 253 of the coupling plate 25 abuts on the back side of the base plate portion 212 of the hook element 21. The hook element 21 is thus affected by a counter-clockwise moment which keeps it in the non-engagement position. The secondary frame(s) may now be dismantled from the primary frame, here thus the intermediate frame 3 with sash 2 and pane 4 lifted off the connection with the stationary frame 1. The lifting of the coupling plate 25 may in principle take place in any suitable manner. However, in order to ensure that unwarranted release does not take place, use of a suitable tool is preferably prescribed.

Bringing the roof window back to a position prepared for coupling takes place by simply rotating the intermediate frame 3 in the closing direction. Towards the end of the closing movement, the lifting arm 14 pushes the coupling plate 25 downwards, in the direction of arrow B in Fig. 12h. Once the counter-clockwise moment previously acting on the hook element 21 is released, the hook element 21 is able to rotate in the clockwise direction to assume the position shown in Fig. 12a.

1

primary frame (stationary frame)

2

first secondary frame (sash)

3

second secondary frame (intemediate frame)

4

pane

5

top mounting fitting

6

frame hinge part of pivot hinge fitting

7

handle

8

ventilation device

10

lifting device

11

hinge pin

12

first end of lifting arm

13

second end of lifting arm

14

lifting arm

15

top bearing fitting

16

sledge guidance

20

spring assembly

21

first coupling member / hook element
210 apex
211 aperture
212 base plate portion
213 flange portion
214 hook portion
215 rounded transition edge portion
216 inclined edge portion
217 top portion
217a groove in top portion
218 bottom edge portion
219 inclined edge portion

22

tension rod
221 rod portion
222 head portion
223 first inclined portion
224 second inclined portion
225 adjustment ring

23

angle element
231 aperture
231a enlarged aperture sections
232 upstanding leg
233 bottom leg
234 protruding flange
235 gap

24

end piece
241 aperture
242 upstanding wall
243 protrusion
244 protruding flange
244a rib portion
245 track
246 bent flange portions

25

coupling plate
251 oblong aperture
252 base portion
253 bottom flange
254 cut-out
255 upstanding lug
256 friction-increasing portions

26

adjustment plate

27

spring casing
27a recess for adjustment plate

28

buffer spring system
281 outer spring
282 inner spring
283 spring plug
284 spring plug

29

main spring system
291 spring
292 spacer tube

30

sledge system

31

second coupling member / sledge
310 bottom portion
311 first wall portion
312 second wall portion
313 narrowing
314 receiving recess
315 hole
316 hole
317 first opening
318 second opening
319 incision

32

runner
320 bottom portion
321 first wall portion
321a first journal section

322

second wall portion
322a second journal section

323

bowl portion

324

recess

325

cut-out

326

cut-out

327

resilient upstanding portion

328

edge portion

329

flange portion

40

axle
401 rifled end
402 other end
403 markings
404 location mark

50

friction brake device
51 friction brake element
52 first cone
53 second cone
54 spring plug