A lifting device for a roof window

The present invention relates to a lifting device for a top hung roof window, said device comprising a lifting arm having a first end connectable to a sash or frame element of said window, and a second end pivotally connected to a slide block adapted for slidable engagement with an opposite frame or sash element, the slide block being in turn connected to a primary biasing means arranged to urge the slide block in a first direction. It is increasingly popular to include attics for living. Often it is possible to considerably increase living floor space at a reasonable price compared to building an extension to a house, which may be impossible anyway if it is in a densely built area. Further, with the right windows, a former attic may be transformed into a comfortable and light dwelling, and often with a nice view to the landscape, the skyline and/or the sky, which will considerably raise the value of the house or flat.

A roof window construction is disclosed in EP 0 733 146 Bl (to the applicant). This construction is popular, as the sash of the roof window is balanced by a lifting device as outlined in the introduction, whereby the window is easy to operate and the sash may be parked in an arbitrary open position for ventilation. A further example of a lifting device enhancing the operational comfort is disclosed in US 5,615,522.

In some countries, however, the regulations dictate an emergency exit or rescue opening to accept that a former attic is used for living. Although the roof window construction disclosed in EP 0 733 146 Bl can provide a large opening in a window of a predetermined size, which opening will allow most people to escape or be rescued there through in case of emergency, the construction does not comply with the most strict regulations regarding rescue openings. In order to meet the regulations, measures must be taken, either by providing a dedicated rescue opening made to purpose, or by utilizing a roof window having a larger size than said predetermined size, which will at least increase the cost of converting the former attic into a dwelling, or not even be possible due to the installation conditions.

It is hence an object of the present invention to provide a lifting device, which can provide a sufficiently large opening to provide for a roof window of a predetermined size to be utilized as a rescue opening.

To achieve this object, the lifting device as outlined in the intro- duction is characterized in that the lifting arm is extendable and comprises a secondary biasing means urging to extend the lifting arm.

Hereby, the lifting arm may extend to push the sash to a larger angular position in regard to the frame of a window of a predetermined size, and thereby provide a considerably larger escape opening to allow exit through the window than what would have been possible to obtain with a window of the predetermined size incorporating a lifting device of a traditional kind.

The primary biasing means may be a gas spring, but according to an embodiment the primary biasing means is a helical spring. Helical springs are low tech, robust and do not change characteristics over time, so the basic functionality of the window will not be deteriorated over time. Furthermore, helical springs are relatively cheap.

It is conceivable to use a helical spring as the secondary biasing means, but it is preferred that the secondary biasing means is a gas spring. Such gas springs are standard, mass-produced components, which can be purchased at a reasonable price, and hence will not add significantly to the total cost of the lifting device.

To increase the versatility of the lifting device, the device may further comprise an auxiliary biasing means arranged in conjunction with the primary biasing means to provide enhanced lifting force.

To further increase the versatility of the lifting device, the auxiliary biasing means may be provided with adjustment means to allow the lifting force to be adjusted. Hereby it is rendered possible to adjust the lifting force of the lifting device to the specific needs dependent on inclination of the roof, weight of the sash, any accessories mounted on the sash etc.

In an alternative or supplementary embodiment, the auxiliary biasing means is provided with adjustment means adapted to influence an active angular interval of the auxiliary biasing means. Hereby the

auxiliary biasing means may be rendered operative or non-operative in a given angular interval of opening of the window, which functionality may further increase the versatility of the lifting device.

According to an embodiment, the secondary biasing means is adapted for releasable locking in an un-extended position. Hereby it is possible to operate the window as an ordinary roof window under normal conditions, and release the secondary biasing means only in exceptional occasions for exit through the window. This may be advantageous as operation of the window under normal conditions is facilitated, especially for relatively short people, as the opening range of the window is restricted during normal use of the window, and hence the handle of the sash is easier to reach.

In a further aspect of the invention a roof window is provided, said roof window comprising a frame and a movable, top hung sash and a lifting device as described above being arranged at an upper corner of the window.

Providing only a single lifting device may be sufficient for relatively small windows having a relatively light sash construction, or when the window is mounted in a roof having a steep inclination. However according to an embodiment the roof window may comprise a lifting device at both upper corners of the window, which will provide increased lifting capability and decrease the load on the sash due to the symmetric application of the lifting force of the lifting device on the sash.

In the following the invention will be described in more detail by way of example and with reference to the accompanying drawings, in which

Fig. 1 is a photograph of a roof window fitted with a lifting device according to the invention,

Fig. 2 is a photograph of a detail of the roof window of Fig. 1, Fig. 3 is a perspective view of the lifting device according to the invention,

Fig. 4 is a side view of the lifting device in an open position, Fig. 5 is a side view of the lifting device in a position of extended opening, and

Fig. 6 is a perspective view of the lifting device mounted with springs.

The roof window 10 partially shown in the photo of Fig. 1 is adapted for mounting in an inclined roof and has a predetermined size. For instance, it may be chosen as one of several roof windows in a range of different sizes. The window 10 comprises a frame 11 and an openable, top hung sash 12 supporting a glass pane 13. The window 10 incorporates a lifting device 1 to more or less counterbalance the weight of the sash 12, whereby the window can be operated easily, and even be parked in an arbitrary position. In Fig. 1 the sash 12 is in a fully open position, in which the window can be used as a rescue opening to be used, i.a., as an exit. The lifting device 1 comprises a lifting arm 2 arranged to lift the sash 12 in respect to the frame 11. At a first end 3 the lifting arm 2 is connected to a sash element of the sash 12, and at a second end 4 to a slide block (not shown) sliding in a guideway 14 on the top side of a frame element of the frame 11, said frame element being opposite to the sash element. The slide block is in turn connected to a tie rod (not shown) connected to a primary biasing means 6, in this case a helical spring, which will urge the slide block downwards in the guideway 14, and thereby lift the sash 12 as illustrated. The lifting device 1 further comprises secondary biasing means 7, which becomes effective at an opening angle of 40-45° and continues to a max opening angle and a corresponding opening height depending on the dimensions of the window. In the embodiment shown, the max opening angle is approximately 67° corresponding to an opening height of about 120 cm by extension thereof. The embodiment shown further comprises auxiliary biasing means 8, which may be adjusted to provide initial lifting depending on inclination of the roof and the weight of any accessories on the sash. In the embodiment shown, the window 10 is equipped with a set of lifting devices, one at each side of the sash 12. This is partly because of the restricted space available for the secondary biasing means 7. In the shown embodiment, the necessary lifting capacity is approximately 1000 N, whereas the largest possible gas spring mountable at the sash

has a lifting capacity of 1100 N at the time of delivery. However gas springs tend to fade with time at a rate of approximately 2% per year, so it is advisable with a safety margin.

The primary biasing means 6 and the auxiliary biasing means 8 can be seen in the photograph of Fig. 2. The primary biasing means 6 is a helical tension spring, which is connected to the sliding block 5 via a tie rod 15. The auxiliary biasing means 8 is a helical compression spring, which becomes effective at abutment with the abutment 16, which is moveable for adjustment. The abutment 16 may be adjusted by positioning the abutment 16 in one of a series of notches 21, such as nine positions, in a secondary guideway 22. Hence the auxiliary biasing means 8 may be adjusted to the inclination of the roof and the weight of the sash etc. to cooperate with the primary biasing means 6 during initial opening of the window 10. The function is described in more detail in EP O 733 146 Bl.

Referring now to Fig. 6, the lifting device is seen mounted with a primary biasing means 6 in the form of a helical spring which is connected to the slide shoe 5 of the lifting device via the tie rod 15. An auxiliary biasing means 8, namely a helical spring, is arranged around the tie rod 15. In the illustrated position, the auxiliary biasing means 8 is not active, as it is free floating between the end of the primary biasing means 6 and the abutment 16.

The lifting device can be seen in isolation in Fig. 3, however without the primary biasing means. The position shown corresponds to a situation in which the sash is lifted to an open position, however prior to extension of the secondary biasing means 7. This corresponds to the maximum opening of the prior art window construction of EP 0 733 146 Bl. In the embodiment shown in Fig. 3, the lifting arm 2 comprises a secondary biasing means 7 in the form of a gas spring. A first end 3 of the lifting arm 3 is connected to a fitting or intermediate sash 17. The intermediate sash 17 is connected to a frame fitting 19 by a hinge 18. A sash may be connected to the intermediate frame 17 at a pivot hinge 20, to thereby achieve a window, which is operable as either a centre-hung window or a top-hung window.

In the perspective view of Fig. 3, the slide block 5 is in an extreme position in the guideway 14, urged by the primary biasing means (as mentioned not shown in this Figure), whereby the lifting arm 2 is raised, whereby the intermediate sash 17, in turn, is raised to a maximum, normal opening. The term "normal" refers to the normal use of the window, i.e. when the window is utilized for providing ventilation and a view to the outside. Fig. 4 is a corresponding side view illustrating the lifting device in the maximum, normal opening, in which the intermediate sash 17 is raised by the lifting arm 2, but the secondary biasing means 7 is not extended, i.e. it is in its un-extended position. In the embodiment shown, the maximum, normal opening is an opening of about 40-45°. This corresponds to the maximum opening which is possible to obtain in a roof window having a predetermined size.

In a subsequent step, the secondary biasing means 7 is ex- tended, raising the intermediate sash 17 further to an escape opening as illustrated in the side view of Fig. 5. In the embodiment shown, the escape opening is an opening of about 65-70°. The size of this opening is thus considerably larger than the maximum opening obtainable by the lifting arm 2 in its un-extended position only. For a roof window having a given predetermined size, the maximum opening is thus increased by the provision of the extendable lifting arm urged by the secondary biasing means. In order to secure maximum operational comfort during normal use of the window, the secondary biasing means may be locked in a releasable manner in the un-extended position (i.e. as shown in Fig. 4). Means for providing the releasable locking may be in any suitable form, and the release function may for instance be performed automatically by pushing the handle and thereby overriding a blocking mechanism, or by unlocking a locking mechanism.

The term "lifting device" is intended to cover any counterbalanc- ing, biasing or lifting device, as will be understood by the skilled person. In other words, the term "lifting device" is not restricted to a device urging the sash to an open position, but will also cover devices, which only partially carry the weight of the sash, i.e. a counterbalancing or lifting aid to facilitate opening of the window.

Other embodiments than the ones shown in the drawing and explained above are obviously feasible. Although the embodiment shown comprises a primary biasing means arranged in parallel to a frame side part, it will be evident to the skilled person that a kinematical reverse situation is also possible in which the primary biasing means is arranged in parallel with a sash side part. It is also possible to let the secondary biasing means constitute the lifting arm, thus making a separate lifting arm redundant.