Motorised screen assembly

Abstract

A toothed rack 12 is suitable for use with a screen assembly and includes two or more sections coupled together in end-to-end relationship by cooperating coupling formations 24, 26. At least one section of the toothed rack includes regions of reduced thickness 22 to allow said at least one section to be adjusted in length by snapping off portions thereof. Also provided is a screen assembly including a tensioned screen (2, fig 1) moveable between a pair of spaced guide tracks, and a control bar (10, fig 1) mounted on a free end of the screen between said guide tracks. Each of said pair of spaced guide tracks includes a toothed rack, a respective pinion being mounted at each end of said control bar in operative engagement with the toothed rack of the respective guide track. The pinions are rotatable by means of a drive assembly located within the control bar to raise and lower the screen.

Description

FIELD OF THE INVENTION This invention relates to a motorised screen assembly. BACKGROUND OF THE INVENTION It is known to provide blinds or screens fitted to a window or door opening, typically fixed to the upper face of the window opening or between the sides of the window opening adjacent the upper face thereof, for selectively obscuring the opening. In the case of a roller blind, such typically have a roller mounted at an upper side of the window or door opening around which a suitable screen is wound. The screen may be lowered and raised by rotating the roller. The lower end of the screen may be provided with a bar such that the screen hangs from the roller under gravity. It is known to provide an electric motor for rotating the roller and / or moving the guide bar to raise and lower the screen, such motor and associated gearbox being mounted adjacent the roller, typically within a housing of a head assembly of the blind. A problem with such known systems is that they do not operate satisfactorily when not mounted absolutely vertically due to the need for the screen to hang freely to allow smooth movement of the bar at the lower end thereof. Windows that are not arranged vertically, for example roof lights, are typically provided with screen assemblies fitted to the inside of the frame thereof for selectively obscuring the window. Such screen assemblies typically have a spring tensioned roller mounted at an upper side of the frame, around which a suitable screen is wound. A free end of the screen is attached to a movable beam or handle which is movably engaged, at its longitudinal ends, in side guide tracks arranged on opposite lateral sides of the screen. Typically the ends of the handle are provided with locking devices adapted to engage the guide tracks to lock the screen in any desired position against the restoring force of the tensioned roller. The locking devices typically comprise locking members, often in the form of eccentric cams or blocks, mounted to the ends of the handle to be rotatable between a locking position, wherein they engage the guide tracks to prevent movement of the screen, and an unlocked position, wherein the screen is free to move, the locking devices being rotatable to their locking positions under the tension applied by the tensioned roller on the screen and being rotated to their unlocked position by a force applied to the handle against the tension applied by the tensioned roller. Thus the locking devices can freely move along the guide track while the handle is being pulled against the tension of the roller and are automatically returned to their locking positions by the tension applied to the screen by the roller once the handle is released. A problem with these known screen assemblies is that they require manual operation. Attempts have been made to motorise screen assemblies by mounting a drive motor in the beam or handle at the free end of the screen and using a rack and pinion drive system, with racks on the sides of the guide tracks and pinions rotatably mounted on the ends of the beam or handle in engagement with the racks. A problem with such prior art screen assemblies is that the only fit a specific size of window or roof light due to the fixed length of the racks. SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a screen assembly for a window comprising a tensioned screen moveable between a pair of spaced guide tracks, a control bar being mounted on a free end of the screen between said guide tracks, wherein each of said pair of spaced guide tracks includes a toothed rack extending along a side wall of the respective guide track, parallel to the direction of movement of the control bar, a respective pinion being mounted at each end of said control bar in operative engagement with the toothed rack of the respective guide track, said pinions being rotatable by means of a drive assembly to move the control bar up and down the guide tracks, thereby raising and lowering the screen, wherein each toothed rack is formed from multiple sections coupled together in end to end relationship by cooperating coupling formations and wherein at least one section of each toothed rack includes regions of reduced thickness to allow said at least one section to be adjusted in length by snapping off portions of said at least one section at one or more of said regions of reduced thickness. Each guide track preferably includes a channel within which the respective toothed rack is received. Each section of each toothed rack may comprise a base portion adapted to be received within the channel of a respective guide track and a toothed portion extending from the base portion. The base portion is preferably wider than the toothed portion, the respective channel into which each toothed rack is received having opposing lips adapted to retain the base portion of the respective toothed rack therein. The regions of reduced thickness are preferably formed in the base portion of said at least one section of each toothed rack and may extend transversely across the base portion and extend substantially the full depth of the base portion of said at least one section of each toothed rack. The coupling formations may be formed in the base portion of each section of each toothed rack. The coupling formations may comprise a male coupling integrally formed on an end of at least one first section of each toothed rack and a female coupling formed in an end of at least one second section of each toothed rack, said female coupling being adapted to receive said male coupling to couple said first and second sections together in end to end relationship. Each male coupling may comprise an enlarged head portion adapted to be received in a cooperating enlarged portion of the female coupling to prevent separation of said first and second sections in a direction parallel to the direction of movement of the control bar. In one embodiment, each male coupling and corresponding female coupling may be T-shaped in profile. At least one section of each of said toothed racks may include a lead in portion having teeth of gradually reducing height in a direction towards an outermost end of said toothed rack, to facilitate engagement of the respective pinion with the toothed rack. The lead in portion preferably defines an upper end of the respective toothed rack. An end of said at least one section adjacent said lead in portion may include a stop or projection adapted to engage an abutment or cooperating portion of an upper end of said channel within which the toothed rack is mounted to ensure both racks are accurately located and correctly aligned in the guide tracks. The pinions may be mounted at either end of a drive shaft extending through the control bar. An electric motor may be provided within said control bar, said motor being operatively coupled to said drive shaft for rotating said pinions. In a further aspect of the present invention there is provided a toothed rack for use with a screen assembly, said toothed rack comprising two or more sections coupled together in end to end relationship by cooperating coupling formations and wherein at least one section of the toothed rack includes regions of reduced thickness to allow said at least one section to be adjusted in length by snapping off portions of said at least one section at one or more of said regions of reduced thickness. Each section of the toothed rack preferably comprises a base portion and a toothed portion extending from the base portion. The base portion may be wider that the toothed portion and wherein said regions of reduced thickness are formed in the base portion of said at least one section of the toothed rack. The regions of reduced thickness preferably extend transversely across the base portion and extend for substantially the full depth of the base portion of said at least one section of the toothed rack. The coupling formations may comprise a male coupling integrally formed in an end of at least one first section of the toothed rack and a female coupling formed in an end of at least one second section of each toothed rack, said female coupling being adapted to receive said male coupling to couple said first and second sections together in end to end relationship. Preferably each male coupling comprises an enlarged head portion adapted to be received in a cooperating enlarged portion of the female coupling. In one embodiment each male coupling and corresponding female coupling may be T-shaped in profile. At least one section of the toothed rack may include a lead in portion having teeth of gradually reducing height in a direction towards an outermost end of said toothed rack, to facilitate engagement of a pinion with the toothed rack. Said at least one section adjacent said lead in portion may include a stop or projection at a distal end thereof adapted to, in use, engage an abutment or cooperating portion of an upper end of said channel within which the toothed rack is mounted to ensure both racks are accurately located and correctly aligned in the guide tracks. BRIEF DESCRIPTION OF THE DRAWINGS A motorised screen assembly in accordance with an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a motorised screen assembly in accordance with an embodiment of the present invention; Figure 2 is a detailed perspective view of a portion of the screen assembly of Figure 1; Figures 3 and 4 illustrate the installation of a toothed rack into a channel in a guide track of the screen assembly of Figure 1; Figure 5 is a plan view from the rear of a portion of a toothed rack of the screen assembly of Figure 1; Figure 6 is a detailed view of cooperating coupling formations of the toothed rack of Figure 5; Figure 7 is an exploded view of the coupling formations of the toothed rack of Figure 5; Figure 8 is a side view of a portion of a toothed rack of the screen assembly of Figure 1; Figure 9 is a detailed view of a portion of the toothed rack of Figure 8; Figure 10 is a side view of an uppermost section of a toothed rack of the screen assembly of Figure 1; and Figure 11 is a detailed view of an upper end of the toothed rack section of Figure 10. DETAILED DESCRIPTION OF THE DRAWINGS A shown in the drawings, with particular relevance to Figures 1 and 2, a motorised screen assembly in accordance with an embodiment of the present invention comprises a tensioned screen 2, wound on a roller with a cassette 4 and moveable between a pair of spaced guide tracks 6,8 a control bar 10 being mounted on a free end of the screen 2 between said guide tracks 6,8. Each of said pair of spaced guide tracks 6,8 includes a toothed rack 12 extending along a side wall of the respective guide track 6,8, parallel to the direction of movement of the control bar 10, a respective pinion (not shown) being mounted at each end of said control bar 10 in operative engagement with the toothed rack 12 of the respective guide track 6,8, said pinions being rotatable by means of a drive assembly, preferably including an electric motor, to move the control bar 10 up and down the guide tracks 6,8, thereby raising and lowering the screen 2. The drive assembly may be located within the control bar 10. Each guide track 6,8 includes a channel 14 within which the respective toothed rack 12 is slidingly received. Each toothed rack 12 comprises a base portion 16 adapted to be received within the channel 14 of a respective guide track 6,8 and a toothed portion 18 extending from the base portion 16. The base portion 16 of each toothed rack 12 is wider than the toothed portion 16 thereof, the respective channel 14 into which each toothed rack 12 is received having opposing lips adapted to retain the base portion 16 of the respective toothed rack 12 therein, as illustrated in Figures 3 and 4. An uppermost end of each toothed rack 12 includes a lip 20 adapted to engage an upper end of a respective channel 14 to correctly position and align the toothed racks 12 within the channels 14 of the guide tracks 6,8. To allow the toothed rack 12 of each guide track 6,8 to be adapted in length to suit the size of the window opening in which the screen assembly is to be located, each toothed rack 12 is formed from multiple sections coupled together in end to end relationship by cooperating coupling formations, at least one section, preferably a lowermost section, of each toothed rack includes regions of reduced thickness 22 at intervals along its length to allow said at least one section to be adjusted in length by snapping off portions of said at least one section at one or more of said regions of reduced thickness. As shown in Figures 5 to 9, in one embodiment, the regions of reduced thickness 22 are formed in the base portion 16 of said at least one section of each toothed rack 12 to provide lines of weakness at which the rack may be snapped. The regions of reduced thickness 22 preferably extend transversely across the base portion and extend substantially the full depth of the base portion 16 of the respective section of each toothed rack 12. The coupling formations are preferably formed in the base portion 16 of each section of each toothed rack 12. The coupling formations comprise a male 24 coupling integrally formed on an end of at least one first section of each toothed rack 12 and a female coupling 26 formed in an end of at least one second section of each toothed rack, said female coupling being adapted to receive said male coupling to couple said first and second sections together in end to end relationship. In the embodiment shown in the drawings, each male coupling 24 and corresponding female coupling 26 are T-shaped in profile. An uppermost section 12A of each toothed rack 12 is preferably provided with a male coupling 24 at its lower end which the or each of the remaining sections of each toothed rack 12 may comprise a female coupling 26 at an upper end and a male coupling 2 at a lower end. As shown in Figures 10 and 11, the uppermost section 12A of each toothed rack 12 includes a lead in portion 28 adjacent its upper end, said lead in portion 28 having teeth of gradually reducing height in a direction towards the uppermost end of each toothed rack, to facilitate engagement of a pinion with the toothed rack. Each toothed rack 12 may comprise an uppermost section 12A, having a lead in portion 28 and an upper lip 20 for engaging an upper end of the channel 14 of the respective guide track 6,8 in which the toothed rack is mounted, and one or more further sections coupled in end to end relationship with the uppermost section 12A by said coupling formations. Preferably the uppermost section 12A is devoid of regions of reduced thickness 22, which the or each of the further sections are 5 provided with said regions of reduced thickness in the base portion 16 thereof to allow end portions of a lowermost rack section to be snapped off to facilitate adjustment of the overall length of the respective toothed rack 12. The invention is not limited to the embodiments described herein but can be 10 amended or modified without departing from the scope of the present invention.

Claims

1. A screen assembly for a window comprising a tensioned screen moveable between a pair of spaced guide tracks, a control bar being mounted on a free end of the screen between said guide tracks, wherein each of said pair of spaced guide tracks includes a toothed rack extending along a side wall of the respective guide track, parallel to the direction of movement of the control bar, a respective pinion being mounted at each end of said control bar in operative engagement with the toothed rack of the respective guide track, said pinions being rotatable by means of a drive assembly to move the control bar up and down the guide tracks, thereby raising and lowering the screen, wherein each toothed rack is formed from multiple sections coupled together in end to end relationship by cooperating coupling formations and wherein at least one section of each toothed rack includes regions of reduced thickness to allow said at least one section to be adjusted in length by snapping off portions of said at least one section at one or more of said regions of reduced thickness.

2. An assembly as claimed in claim 1, wherein each guide track includes a channel within which the respective toothed rack is received.

3. An assembly as claimed in claim 2, wherein each section of each toothed rack comprises a base portion adapted to be received within the channel of a respective guide track and a toothed portion extending from the base portion.

4. An assembly as claimed in claim 3, wherein the base portion is wider than the toothed portion, the respective channel into which each toothed rack is received having opposing lips adapted to retain the base portion of the respective toothed rack therein.

5. An assembly as claimed in claim 3 or claim 4, wherein said regions of reduced thickness are formed in the base portion of said at least one section of each toothed rack.

6. An assembly as claimed in claim 5, wherein said regions of reduced thickness extend transversely across the base portion and extend substantially the full depth of the base portion of said at least one section of each toothed rack.

7. An assembly as claimed in any of claims 3 to 6, wherein said coupling formations are formed in the base portion of each section of each toothed rack.

8. An assembly as claimed in any preceding claim, wherein said coupling formations comprise a male coupling integrally formed on an end of at least one first section of each toothed rack and a female coupling formed in an end of at least one second section of each toothed rack, said female coupling being adapted to receive said male coupling to couple said first and second sections together in end to end relationship.

9. An assembly as claimed in claim 8, wherein each male coupling comprises an enlarged head portion adapted to be received in a cooperating enlarged portion of the female coupling to prevent separation of said first and second sections in a direction parallel to the direction of movement of the control bar.

10. An assembly as claimed in claim 9, wherein each male coupling and corresponding female coupling are T-shaped in profile.

11. An assembly as claimed in any preceding claim, wherein at least one section of each of said toothed racks includes a lead in portion having teeth of gradually reducing height in a direction towards an outermost end of said toothed rack, to facilitate engagement of the respective pinion with the toothed rack.

12. An assembly as claim in claim 11, wherein said lead in portion defines an upper end of the respective toothed rack.

13. An assembly as claimed in claim 11 or claim 12, wherein an end of said at least one section adjacent said lead in portion includes a stop or projection adapted to engage an abutment or cooperating portion of an upper end of said channel within which the toothed rack is mounted.

14. An assembly as claimed in any preceding claim, wherein said pinions are mounted at either end of a drive shaft extending through the control bar.

15. An assembly as claimed in claim 14, wherein an electric motor is provided within said control bar, said motor being operatively coupled to said drive shaft for rotating said pinions.

16. A toothed rack for use with a screen assembly, said toothed rack comprising two or more sections coupled together in end to end relationship by cooperating coupling formations and wherein at least one section of the toothed rack includes regions of reduced thickness to allow said at least one section to be adjusted in length by snapping off portions of said at least one section at one or more of said regions of reduced thickness.

17. A toothed rack as claimed in claim 16, wherein each section of the toothed rack comprises a base portion and a toothed portion extending from the base portion.

18. A toothed rack as claimed in claim 17, wherein the base portion is wider than the toothed portion and wherein said regions of reduced thickness are formed in the base portion of said at least one section of the toothed rack.

19. A toothed rack as claimed in claim 18, wherein said regions of reduced thickness extend transversely across the base portion and extend for substantially the full depth of the base portion of said at least one section of the toothed rack.

20. A toothed rack as claimed in any of claims 17 to 19, wherein said coupling formations comprise a male coupling integrally formed in an end of at least one first section of the toothed rack and a female coupling formed in an end of at least one second section of each toothed rack, said female coupling being adapted to receive said male coupling to couple said first and second sections together in end to end relationship.

21. A toothed rack as claimed in claim 20, wherein each male coupling comprises an enlarged head portion adapted to be received in a cooperating enlarged portion of the female coupling.5 22. A toothed rack as claimed in claim 21, wherein each male coupling and corresponding female coupling are T-shaped in profile.

23. A toothed rack as claimed in any preceding claim, wherein at least one section of the toothed rack includes a lead in portion having teeth of gradually reducing 10 height in a direction towards an outermost end of said toothed rack, to facilitateengagement of a pinion with the toothed rack.

24. A toothed rack as claimed in claim 23, wherein said at least one section adjacent said lead in portion includes a stop or projection at a distal end thereof.1513

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