DK201770888A1

DK201770888A1 - Lifting device including a sledge system for installation in a roof window and a roof window comprising such a lifting device

Info

Publication number: DK201770888A1
Application number: DKPA201770888A
Authority: DK
Inventors: Ryberg Jesper; Vinther Hede Lasse
Original assignee: Vkr Holding A/S
Priority date: 2017-11-24
Filing date: 2017-11-24
Publication date: 2019-06-06
Also published as: WO2019101280A1; CN111386377B; PL3714124T3; DK179893B1; EA202091014A1; DK179893B9; CN111386377A; EP3714124A1; DK201770888A9; EP3714124B1

Abstract

The lifting device (10) is intended for a roof window comprises a lifting arm (14), a spring assembly (20) with a first coupling member, and a sledge system (30) configured to be slidably connected to one part of the roof window and including a sledge (31) and a second coupling member configured to cooperate with the first coupling member. A first end (12) of the lifting arm (14) is rotatably connected with the sledge system (30) and a second end (13) is configured to be connected to another part of the roof window. The sledge system (30) furthermore comprises a runner (32) with at least two faces, arunner inner face and a runner outer face, that the sledge (31) has at least two faces, a sledge inner face and a sledge outer face, the runner (32) comprising at least one wall portion (321, 322), and being configured to accommodate said sledge (31) against said runner inner face, and that said runner (32) is provided with at least one recess (324) opposite a respective receiving recess (314) in said sledge (31), said recesses (314, 324) forming part of said second coupling member.

Description

Title of Invention

Lifting device including a sledge system for installation in a roof window.

Technical Field

The present invention relates to a lifting device for a roof window, in particular for installation in an inclined roof surface, comprising a lifting arm, a spring assembly with a first coupling member, and a sledge system configured to be slidably connected to one part of the roof window and including a sledge and a second coupling member configured to cooperate with first coupling member, in which a first end of the lifting arm is rotatably connected with the sledge system and a second end is configured to be connected to another part of the roof window. The invention furthermore relates to a roof window incorporating such a lifting device.

Background Art

In roof windows for installation in an inclined roof surface in which the operation takes place either entirely or partially about a top hinge axis, 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 biased by the spring assembly 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.

The biased sledge system, or slide shoe, of such lifting devices is mounted on and moves in parallel with or along either the side frame member or the side sash element. The slide shoe typically slides in a guidance mounted on the respective sash or frame member. The spring assembly biasing the slide

DK 2017 70888 A1 shoe is typically located in parallel with the respective sash or frame member. During opening and closing of the window the slide shoe slides in the guidance, urging a lifting arm connecting the slide shoe and the intermediate frame, or sash member, to and from the parallel position. The rotation of the lifting arm about an axis in the slide shoe requires means for rotatably connecting these two parts.

Lifting devices for roof windows making use of slide shoes are known and may be found for example in applicant’s EP0408655 B1, which relates to a window, particularly designed to be installed in an inclined roof, comprising a frame, a sash hinged to the main frame at the top thereof, and a sash lifting arm inserted between the frame and the sash and having one end pivotally connected with a lateral frame or sash member and its other end pivotally connected with a slide that is displaceable along a corresponding lateral member of the sash or the frame, respectively, and is associated with a prestressed spring. Another example is found in Applicant’s EP0733146 B1, which relates to a window, particularly for installation in an inclined roof surface, comprising a main frame and a frame hinged to the top thereof as well as a frame lifting arm inserted between the main frame and the frame, said arm having one end pivotally connected with a lateral member of the main frame or the frame and its other end pivotally connected with a slide shoe which in a longitudinally displaceable manner is connected with the corresponding lateral member of the frame or the main frame, respectively, and which is associated with a pre-stressed lifting spring, as a coupling member on the slide shoe is adapted to be brought into engagement with a coupling member connected with the lifting spring when installing the window at the installation site. It is common within the solutions disclosed in the above-mentioned documents that slide shoes described therein are arranged to directly contact the corresponding lateral member of the stationary frame or the secondary frame in a longitudinally displaceable manner. Because of the relatively large forces involved, slide shoes of the type described herein must be strong enough to sustain the moment transferred from the lifting arm and the spring assembly, and thus are typically made of a resistant material such as a metal or similar

DK 2017 70888 A1 alloy. Movement of the metallic slide shoe on the guidance or frame member generates friction, which may result in irregular sliding of the slide shoe and thus imprecise operation of the roof window lifting device. Furthermore, over time, the same friction produces wear on both the slide shoe and the corresponding guidance or frame member leading to a poor fit between said parts, only further exacerbating said outcome. Given the wide-spread damage caused i.e. to slide shoe, frame and/or guidance, possible solutions may be restricted to exchanging the entire lifting device or even the entire roof window frame.

Considering this, it is presently a challenge to provide a roof window lifting device with a sliding arrangement that can bear current load requirements while offering a durably smooth, precise and efficient use, while providing a solution for convenient sliding means replacement.

Summary of Invention

It is therefore the object of the invention to provide a roof window lifting device in which a slide shoe, or sledge system, is provided with a durable sliding connection means to a corresponding frame member or guidance, thus providing smooth sliding, and thereby achieving precise and efficient operation of the roof window lifting device.

This is achieved with a roof window lifting device of the kind mentioned in the introduction, which is furthermore characterised in that the sledge system furthermore comprises a runner with at least two faces, a runner inner face and a runner outer face, that the sledge has at least two faces, a sledge inner face and a sledge outer face, the runner comprising at least one wall portion, and being configured to accommodate said sledge against said runner inner face, and that said runner is provided with at least one recess opposite a respective receiving recess in said sledge, said recesses forming part of said coupling member. With the provision of the runner, which accommodates the sledge and thus lies between the sledge and the frame member or guidance, friction between the sledge and the frame member or the guidance is avoided. Thus, so is the wide-spread damage to the frame member or guidance. Furthermore,

DK 2017 70888 A1 wear resulting from friction arising between the runner and the frame member or guidance is easily remedied by replacing only the runner. Finally, the functionality of the lifting device is not impaired by the runner surrounding the sledge, as the matching recesses make it possible to couple the sledge system safely to the spring assembly without special precautions.

In a preferred embodiment, the lifting device further comprises a sledge guidance for guiding said runner movement. A guidance offers an even surface along which the sledge can slide. Thus, the provision of a guidance allows for a smoother and more precise overall operation of the sledge system. Furthermore, a guidance may provide one or more side parts that may have the function of guiding the sledge during lifting device operation. This guiding function ensures that the sledge follows a predictable and repeatable path in the lifting device, thus enabling a smooth simultaneous operation when two or more lifting devices are installed between a roof window stationary frame and a sash frame. The clearance present between the at least one end face of the axle and the guidance ensures a reduction of friction between these parts and thus reduced cumulative friction when operating the lifting device. Such reduced friction contributes to enabling a smoother and more precise overall operation of the lifting device.

By “precise operation of the lifting device” it is meant that opposing stationary frame and movable sash elements align in an essentially parallel fashion, resulting in a tight juxtaposition of said opposing members in the closed window position. It is also meant that operation of the lifting device requires a predictable amount of force, as the tension spring bias is transferred with diminished hindrance to the lifting arm.

In another embodiment, said sledge and/or said runner further comprise means for reducing movement between said runner inner face and said sledge outer face. This embodiment is particularly advantageous in that the retention between the sledge and the runner as two separate parts is increased. In a preferred embodiment the fixation means are removable fixation means. By the provision of such removable fixation means, two advantages are achieved. First, undesired movement between the two parts is reduced.

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This ensures an increased subjection of the sledge in the runner, resulting in a smoother lateral displacement of the sledge in the frame member or guidance and a smoother overall operation of the lifting device. Secondly, and since the fixation means are removable, the runner is easily detachable from the sledge, thus permitting a convenient method for removing and replacing the runner from the sledge, if the need arises.

In one embodiment, the means for reducing movement between said runner inner face and said sledge outer face comprises a resilient upstanding portion in said runner and a respective opening in said sledge opposite said resilient upstanding portion. This arrangement results in the resilient upstanding portion securing the sledge through the respective opening in the sledge, thereby providing a robust contact point on the runner against which the sledge may abut in the case of there being forces present that urge the two parts in opposite directions or in the same direction with unequal acceleration. Furthermore, such an arrangement allows for convenient disassembly, as the sledge may simply be lifted off the runner with no hindrance.

In another embodiment, said means for reducing movement between said runner inner face and said sledge outer face comprises at least one flange on at least one runner wall portion arranged to abut said sledge. This arrangement constitutes another equally advantageous solution to removably fixing the sledge to the runner.

In another embodiment at least part of one said runner wall portion is thinner than said other wall portion, and a first journal section is thinner than a second journal section. By this thinner runner wall portion and journal section, the lifting arm may be arranged in close alignment with the secondary frame or sash, thus reducing skewness of the lifting arm when this is contacting both the axle associated with the main frame, and the secondary frame. Lack of skewness results in smoother and more precise operation of the lifting device when opening and closing the roof window.

In another embodiment, the sledge comprises at least one narrowing caused by at least one segment of wall portion being non-parallel with respect to the other wall portion. By said narrowing, a clearance is generated between

DK 2017 70888 A1 the sledge wall part and the frame member or guidance. Such a clearance may be advantageous when inserting the axle into the sledge wall parts.

In one presently preferred embodiment, in which the lifting device furthermore includes an axle connected to the first end of the lifting arm, the runner further comprises a bowl portion arranged to receive the axle, and the sledge comprises a corresponding opening opposite the bowl portion. Proper control and guidance of the movement of the lifting arm during operation is thus ensured. The axle may for instance be adapted to further contact at least one cut-out in the runner wall portions. The cut out facilitates direct insertion of the axle in the sledge system during assembly. Furthermore, the cut out edge may extend circumferentially along the edge of the axle end face, further providing support and stabilization means to the axle. By stabilization it is meant that the cut-out edge will contribute to maintaining the axle in place by reducing the possibility for the axle being displaced laterally within the sledge 31 wall parts

In a second aspect of the invention, a roof window incorporating such a lifting device is provided.

Other presently preferred embodiments and advantages will be apparent from the appended description and drawings.

Brief Description of Drawings

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

DK 2017 70888 A1 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. 9 is a partial isometric view, on a larger scale, of details shown in Fig. 3;

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 13 to 18 are partial or full perspective views of details of the roof window in the second embodiment;

Fig. 19 shows a schematic perspective view of details of a roof window in a third embodiment of the invention;

Fig. 20 shows a schematic side view of details of a roof window in a fourth embodiment of the invention; and

Figs 21 to 24 show partial or full, exploded, or sectional views of details of a roof window in a fifth embodiment of the invention.

Description of Embodiments

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, the contents of which are hereby incorporated by reference. In Fig. 1, a lifting device 10 is indicated, which, referring now also to Fig. 2 to 9, 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

DK 2017 70888 A1 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 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 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 having a first end 12 rotatably connected with a sledge system 30 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 and in turn the first end 12 of the lifting arm 14 by means of a coupling mechanism, such that the spring assembly 20 is able to assume an uncoupled condition and a

DK 2017 70888 A1 coupled condition relative to the sledge system 30. The coupling mechanism is the subject of Applicant’s co-pending patent application filed on the same day as the present invention.

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 buffer spring system 28 acting as an auxiliary system to a 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.

Further details of the sledge system 30 are shown in a second and presently preferred embodiment in Figs 10 to 11 and 13 to 16. Elements having the same or analogous function as in the first embodiment carry the same reference numerals.

In the preferred embodiments shown, a 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.

In the presently preferred embodiments described herein, the receiving means of the second coupling member include at least one receiving recess 314 in a 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 as the fourth embodiment shown in Fig. 20.

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Further details of the axle 40 shown in Figs 17 to 19 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 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 of the present invention comprises a runner 32, 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.

The runner 32 of the sledge system 30 comprises a runner 32 with at least two faces, a runner inner face and a runner outer face, and a sledge 31, with at least two faces, a sledge inner face and a sledge outer face, the runner 32 comprising at least one wall portion 321, 322, and being configured to accommodate said sledge 31 against its said runner inner face, and wherein said runner 32 is provided with at least one recess 324 opposite a respective receiving recess 314 in said sledge 31.

In the embodiment shown, the runner 32 is guided in the sledge guidance 16. Alternatively, the runner 32 could be guided directly in the primary frame 1.

Furthermore, the sledge 31 and/or said runner 32 further comprise means for reducing movement between said runner inner face and said sledge outer face. In the embodiment shown, the means for reducing movement between the runner inner face and the sledge outer face comprises a resilient upstanding portion 327 in the runner 32 and a respective opening 317 in said sledge 31 opposite said resilient upstanding portion 327.

Further means for reducing movement between the runner inner face and the sledge outer face comprises, in the embodiment shown, at least one flange on the at least one runner wall portion 321, 322 arranged to abut the sledge 31.

As shown, at least part of one the runner wall portion 321,322 is thinner than the other wall portion 321, 322, and a first journal section 321a, 322a is thinner than a second journal section 321a, 322a.

The sledge 31 further comprises at least one narrowing 313 caused by

DK 2017 70888 A1 at least one segment of the wall portion 311, 312 being non-parallel with respect to the other wall portion 311,312. In this way, a clearance is generated between the sledge wall part and the frame member or guidance.

In the embodiment shown, the runner 32 further comprises a bowl portion 323 arranged to receive the axle 40, and the sledge 31 comprises a corresponding opening 317 opposite the bowl portion 323. The bowl portion 323 and the opening 317 are arranged so that the distance between the bowl portion 323 and the sledge first wall portion 311 is greater than the distance between the bowl portion 323 and the sledge second wall portion 312.

The runner 32 further comprises at least one cut-out 325, 326 in at least one wall portion 321,322 arranged to receive the axle 40.

The runner 32 here further comprises an edge portion 328 as a cut-out on at least one end.

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 the sides of the guidance.

Turning now to the more detailed representation in Fig.17, the axle 40 is arranged so that a clearance is present between at least one end face of the axle 40 and the guidance 16. In the drawing shown, the clearance is achieved by the axle being shorter than the width of the runner 32, thus generating a clearance between the axle 40 and parts that may come into contact with the runner 32. In the image shown, the space generated is shared equally between the two axle end faces, thus generating clearance on both end of the axle 40.

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In any case, what is intended is that the axle 40 does not come into direct contact with the stationary frame 1 or with the guidance 16, if present.

The runner 32 houses the sledge 31 which accommodates the axle 40 through the sledge wall portion holes. Together, the runner and the sledge form the sledge system, which is connected to the spring assembly via a coupling mechanism as shown in Fig.12d. The bias of the spring assembly 20 of the lifting device 10 acts on a lifting arm 14 inserted between the stationary frame 1 and the intermediate frame 3 through the transfer of moment between the spring or springs in the spring assembly, and the sledge 31, via the coupling mechanism, which urges the sledge system to slide, and transfer the moment to the lifting arm via the axle, as shown in Fig.12c. The axle of the invention is arranged to sustain and effectively transfer these relatively large forces. To this end, the axle is arranged to contact, if appropriate, a bowl portion in the sledge 31 or the runner 32, as shown in Fig.17. The bowl portion is arranged to receive the axle and thereby partially transfer the strain exerted by the lifting arm to the sledge system, thus supporting the axle. In the drawing shown, the bowl portion is arranged so as to provide sufficient space between the bowl portion and the sledge for the lifting arm end 12 to be accommodated in that space. In any case, it is known to the person skilled in the art that the axle of the invention is arranged to contact the bowl portion in a manner that is effective for supporting the axle.

Also in Fig.17, the axle 40 is arranged so as to contact at least one cut-out 325, 326 in the wall portions 321,322 of the runner 32. The cut out edge may be arranged to extend circumferentially along the edge of the axle end face, thereby providing further support to the axle and contributing to maintaining the axle in place by reducing the possibility for the axle being displaced laterally within the wall portions of the sledge 31.

Above the invention has been described with reference to the sash and frame of a roof window, but it will be understood that it also applies to other frame structures, such as for example door frames.

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List of reference numerals primary frame (stationary frame) first secondary frame (sash) second secondary frame (intemediate frame) pane top mounting fitting frame hinge part of pivot hinge fitting

Handle ventilation device lifting device hinge pin first end of lifting arm second end of lifting arm lifting arm top bearing fitting sledge guidance spring assembly first coupling member / hook element

0 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

218 bottom edge portion

219 inclined edge portion tension rod

221 rod portion

222 head portion

223 first inclined portion

224 second inclined portion

225 adjustment ring angle element

231 aperture

232 upstanding leg

233 bottom leg

234 protruding flange

235 gap end piece

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241 aperture

242 upstanding wall

243 protrusion

244 protruding flange

245 track coupling plate

251 oblong aperture

252 base portion

253 bottom flange

254 cut-out

255 upstanding lug adjustment plate spring casing

27a recess for adjustment plate buffer spring system

281 outer spring

282 inner spring

283 spring plug

284 spring plug main spring system

291 spring

292 spacer tube sledge system 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 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

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328 edge portion

329 flange portion axle

401 rifled end

402 other end

403 markings

404 location mark friction brake device friction brake element first cone second cone spring plug

Claims

1. A lifting device (10) for a roof window, in particular for installation in an inclined roof surface, comprising a lifting arm (14), a spring assembly (20) with a first coupling member, and a sledge system (30) configured to be slidably connected to one part of the roof window and including a sledge (31) and a second coupling member configured to cooperate with the first coupling member, in which a first end (12) of the lifting arm (14) is rotatably connected with the sledge system (30) and a second end (13) is configured to be connected to another part of the roof window, c h a r a c t e r i s e d in that the sledge system (30) furthermore comprises a runner (32) with at least two faces, a runner inner face and a runner outer face, that the sledge (31) has at least two faces, a sledge inner face and a sledge outer face, the runner (32) comprising at least one wall portion (321, 322), and being configured to accommodate said sledge (31) against said runner inner face, and that said runner (32) is provided with at least one recess (324) opposite a respective receiving recess (314) in said sledge (31), said recesses (314, 324) forming part of said second coupling member.

2. A roof window lifting device according to claim 1, wherein the lifting device further comprises a sledge guidance (16) for guiding said runner (32) during movement.

3. A roof window lifting device according to any one of claims 1 or 2, wherein said sledge (31) and/or said runner (32) further comprise(s) means for reducing movement between said runner inner face and said sledge outer face.

4. A roof window lifting system according to claim 3, wherein said means for reducing movement between said runner inner face and said sledge

DK 2017 70888 A1 outer face comprises a resilient upstanding portion (327) in said runner (32) and a respective opening (317) in said sledge (31) opposite said resilient upstanding portion (327).

5. A roof window lifting device according to any one of claims 3 and 4, wherein said means for reducing movement between said runner inner face and said sledge outer face comprises at least one flange on said at least one runner wall portion (321, 322) arranged to abut said sledge (31).

6. A roof window lifting device according to any one of the previous claims, wherein at least part of one said runner wall portion (321,322) is thinner than said other wall portion (321, 322), and a first journal section (321a, 322a) is thinner than a second journal section (321a, 322a).

7. A roof window lifting device according to any one of the previous claims, wherein said sledge (31) further comprises at least one narrowing (313) caused by at least one segment of the wall portion (311,312) being non-parallel with respect to the other wall portion (311, 312).

8. A roof window lifting device according to any one of the previous claims, wherein said runner (32) further comprises a bowl portion (323) arranged to receive an axle (40) connected to the first end (12) of the lifting arm (14), and said sledge (31) comprises a corresponding opening (318) opposite said bowl portion (323).

9. A roof window lifting device according to claim 0, wherein said bowl portion (323) and said opening (318) are arranged so that the distance between the bowl portion (323) and said sledge first wall portion (311) is greater than the distance between the bowl portion (323) and said sledge second wall portion (312).

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10. A roof window lifting device according to any one claims 8 and 9, wherein said runner (32) further comprises at least one cut-out (325, 326) in at least one wall portion (321,322) arranged to receive the axle (40).

11. A roof window lifting device according to any one of claims 8 to 10, wherein said sledge (31) further comprises at least one hole (315, 316) in at least one wall portion (311, 312) arranged to receive the axle (40).

12. A roof window lifting device according to any one of the previous claims, wherein said runner (32) further comprises an edge portion (328) as a cut-out on at least one end.

13. A roof window lifting device according to any one of the previous claims, wherein said runner (32) further comprises a flange portion (329) on at least one end.

14. A roof window lifting device according to any one of the previous claims, wherein said runner (32) and/or said sledge (31) are formed of a plastic material such as POM.

15. A roof window lifting device according to any one of the previous claims, wherein said runner (32) and/or said sledge (31) are provided with a lubricant coating for reducing friction.

16. A roof window, particularly for installation in an inclined roof surface, comprising a primary frame (1), at least one secondary frame (2, 3), such as a sash (2) and/or an intermediate frame (3), and at least one lifting device (10) according to any one of claims 1 to 0, wherein said lifting arm (14) is inserted between the primary frame (1) and the at least one secondary frame (2, 3), the lifting arm (14) having a first end (12) rotatably connected with said

DK 2017 70888 A1 sledge system (30) slidably connected with the primary frame (1) in said sledge guidance (16) and a second end (13) rotatably connected with the at least one secondary frame (3).