A ROLLER BLIND, PARTICULARLY FOR USE AS BLACKOUT SHADE

Abstract: For a roller blind, particularly for use as a blackout shade, and with a spring-biassed roller bar and a blind (23) rolled on the roller bar and having along its lateral edges guide members (5, 6) guided in tracks in guide rails disposed at both sides of the window opening, and a bottom bar, a brake device is provided for retaining the bottom bar (7) in an arbitrary position against the effect of said bias-force by means of a cord arrangement with a cord (9, 10) which at the bottom of one guide rail (5, 6) is passed through said guide rail, the bottom bar (7) and the other guide rail (6, 5) to a fixture means (17, 17') at the top thereof. As friction means (14, 15, 14', 15') acting on the cord two pins (14, 15, 14', 15') are mounted in the bottom bar (7) over which the cord (9, 10) is passed in S-shape. To ensure parallel guidance of the bottom bar (7) in relation to the roller bar the cord arrangement may include two cords (9, 10) mounted in mirror-inversion.

Description: A ROLLER BLIND, PARTICULARLY FOR USE AS BLACKOUT SHADE. The invention relates to a roller blind, particularly for use as a blackout shade, comprising a spring-biassed roller bar designed to be mounted at the top of a window opening and a blind rolled on the roller bar and having along its lateral edges guide members guided in tracks provided in guide rails dis¬ posed at both sides of the window opening, a bottom bar for the blind being likewise provided, at both ends, with guide means engaging guideways in said guide rails, and being further controlled by means of a cord arrangement with a cord which from a fixture means at the bottom of one guide rail is passed through the part of said guide rail positioned beneath the bottom bar, the bottom bar itself, and the part of the other guide rail positioned above the bottom bar, to a fixture means at the top of the other guide rail. In roller blinds to be mounted in connection with skylights in inclined roofs use is made of a spring-biassed roller bar ensuring that the blind is kept tight in all positions between the completely raised position and the maximum drawn bottom position. In order to enable the bottom bar to be arrested in its bottom position and in a number of intermediate positions it is known to mount side rails along the longitudinal sides of the window frame, the side rails being provided with downwards facing recesses for engagement with pins or the like at the ends of the bottom bar. This makes it possible to retain the bottom bar in a limited number of intermediate positions. Such comparatively simple side rails are, however, not usable in connection with blinds for blackout shades of the above mentioned type, in which the side guide rails must be designed so as to ensure light-proofness at the edges of the window. At the top and at the bottom of the window opening light-proofness is obtained by providing the roller bar, which is most frequently enclosed in a cassette, as well as the bot¬ tom bar with appropriate sealing strips. n US-A-785 806 a roller blind of the above men¬ tioned type is disclosed in which the movement of the bottom bar is controlled by a double cord arrangement ensuring parallel guidance of the bottom bar in rela¬ tion to the roller bar, thereby preventing the bottom bar from getting jammed due to careless operation. In comparison with the prior art it is the object of the invention to provide a design of a roller blind, particularly for blackout shading, which makes it possible to retain the bottom bar against the spring bias force exerted on the roller bar in arbritrary positions between the top position and the bottom posi¬ tion. With a view to this, a roller blind of the above mentioned type is characterized in that a brake device for retaining the bottom bar in an arbitrary position against the effect of said spring bias includes a fric¬ tion member mounted in the bottom bar and acting on the cord, a device for tightening the cord being provided in association with one of said fixture means. With such a comparatively simple frictional brake device it has turned out to be possible to obtain a braking force which in any position of the bottom roller is sufficient to equalize the spring bias force. As it appears from the following the frictional brake device may be made to cooperate with the cord tighten¬ ing member and the spring bias of the roller bar in such a manner that the brake force does not reduce the operational comfort. In a preferred embodiment of the invention the means for parallel guidance include a supplementary cord arrangement passed through the guide rails and the bottom part, in reverse mounting in relation to said cord. The invention will now be explained in detail with reference to the schematical drawings, in which Fig. 1 shows a skylight equipped with a roller blind as a blackout shade, provided according to an embodiment of the invention, Fig. 2 is a cross-section of a side guide rail, Fig. 3 is a schematical diagram of a brake device and a device for parallel guidance with two mirror-inverted cord arrangements, and Figs 4 and 5 illustrate a holder for friction members for the two cord arrangements, designed to be mounted in the bottom bar of the roller blind. In the roller blind for a blackout shade illus¬ trated in Fig. 1 a spring-biassed roller bar, not shown in detail, is enclosed in a cassette 1 mounted atop the window opening in such a manner that it fits light- proof to the window main frame. A blind 2 of light- proof material is rolled on the roller bar. Guide mem¬ bers, e.g. in the form of semispherical buttons 3 which, as illustrated in Fig. 2, are guided in tracks 4 provided in guide rails 5 and 6 disposed at either side of the window opening are in a manner known per se spaced apart along both of the lateral edges of the blind 2, at distances which may for instance vary from 3 to 10 cm. At the bottom the blind is fastened in a bottom bar 7 having guide means at the ends, likewise engaging guideways 8 in the guide rails 5 and 6. Since due to the spring bias acting on the roller bar the blind is constantly biassed in the raising direction in order to be kept tightened, an arresting mechanism is needed to retain the drawn blind 2 in the bottom position of the roller bar 7 as well as in intermediate positions. In order to obtain an stepless variable arrest¬ ing in arbitrary positions of the bottom bar 7, said arresting mechanism includes a brake device of which an embodiment is illustrated in Fig. 3. In this case the brake device comprises a mirror-inverted arrangement of two cords 9 and 10, of which the cord 9 shown in solid lines in the figure is passed from a fixture means 11 at the bottom of the left guide rail 5 up through a track 12 in this guide rail, shown in Fig. 2, and over a roller or pin 13 through the bottom bar 7 in which a friction member acting on the cord in the illustrated embodiment includes two pins 14 and 15 around which the cord is passed in S-shape and from there further on to the opposite end of the bottom bar 7, from where it is passed over a roller or pin 16 through the part of the guideway 12 positioned above the bottom bar 7 of the right slotted guide 6 to a fixture means 17 at the top of said slotted guide. The fixture means 11 and 17 may appropriate¬ ly be provided in retaining means, e.g. a plastic plug, that may be inserted at the bottom of the guide rail 5 and a clip-like plug that may be mounted at the top of the guide rail 6. With the view of tightening the cord 9, the upper end thereof is connected with a tension spring 18 mounted in the fixture means 17. As mentioned above, the cord 10 is mirror- inverted in relation to the cord 9, and the fixture and cord guiding means for this cord have the same reference numerals as the corresponding members for the cord 9, but further marked with an apostrophe. This double cord arrangement provides for obtaining both an effective braking capable of retain¬ ing the bottom bar 7 arrested in an arbitrary posi- tion between the top and the bottom, and an accurate parallel guidance of the bottom bar 7 in relation to the roller bar mounted in the cassette 1. The braking effect is caused by the S-shaped twisting of the cords 9 and 10, respectively, around the pins 14, 15 and 14', 15', respectively, the friction between the cords and said pins and the ten- sion exterted by the springs 18 and 18". As regards the equilibrium as to force of the system the following formula applies to both of the cords 9 and 10 S χ = S 2 . e^ • α wherein S! and S 2 are the cord tension before and after the cord is passing the pins 14, 15 and 14', 15', respectively, μ is the friction of each cord against the actual pin, and α is the total of the angle changes of the two entwinements of each cord, in this case 360°. The illustrated S-shaped cord path represents only an embodiment, because reversal of direction may be effected by means of a single pin around which the cord may be passed in an entwinement of 360°. This, however, involves the inconvenience that the cord when running off the pin will slide against itself, thereby being exposed to more wear than in the illustrated example with two entwinements of 180°. It is apparent that the braking force may be controlled by choosing a larger number of pins, other angle changes of the cord entwinement round the indivi¬ dual pins and stronger or weaker springs. By these means the braking force is easily dimensioned so that the bottom bar may be safely retained in arbitrary positions. Experiments have shown that the embodiment illustrated in Fig. 3 allows the cords to stand far more than 10,000 raisings and drawings of the blind with no substantial wear and deterioration of the braking effect. At the same time the cooperation of the fric¬ tional brake device with the springs 18, 18' and the spring bias in the roller bar, not shown, entail that the braking force does not hamper the operation of the blind. At a pull downwards at the bottom bar 7 the cord tension between the bottom bar 7 and the springs 18, 18' suddenly increases due to the brake device, whereas the cords between the brake roller 7 and the fixture means 11, 11' slacken, thereby causing the braking effect to decline so that the blind may easily be drawn. When the blind is raised the full braking force from the brake device must incidentally be over¬ come but the raising movement is supported by the spring bias of the roller bar. The cord inverting arrangement in the bottom bar may advantageously be provided in that the pins 14, 15 and 14', 15', respectively, are mounted in a common holder 19 design for being fixed in the bottom bar 7, as illustrated in Figs 4 and 5. In this holder the cord paths for the cords 9 and 10 are separated by a partition wall 20 and in contradiction to the schematical illustration in Fig. 3 the reversal of both cord paths is provided by means of two common pins 21 and 22 extending through the holder 19 on both sides of the partition wall 20. The invention is not restricted to the illus- trated design of the brake device with an arrangement of reversal for the cords, the braking force being achieved with other designs of the friction members acting on the cords. If the parallel guidance of the bottom bar 7 is ensured in another way, a double cord arrangement is neither necessary, even though this must be supposed to allow the simplest design. The applicability of the invention is not res- tricted to blinds for blackout shades but may include any form of roller blind with a constantly spring- biassed blind for which it is desired to have the possibility of arresting in arbitrary positions.

Claims: P A T E N T C L A I M S 1. A roller blind, particularly for use as blackout shade, comprising a spring-biassed roller bar designed to be mounted at the top of a window opening and a blind rolled on the roller bar and having along its lateral edges guide members (3) guided in tracks (4) provided in guide rails (5, 6) disposed at both sides of the window opening, a bottom bar (7) for the blind (2) being likewise provided, at both ends, with guide means engaging guideways (8) in said guide rails (5,6), and being further controlled by means of a cord arrangement with a cord (9, 10) which from a fixture means (11, 11') at the bottom of one guide rail (5, 6) is passed through the part of said guide rail posi- tioned beneath the bottom bar (7), the bottom bar (7) itself, and the part of the other guide rail (6, 5) positioned above the bottom bar (7), to a fixture means at the top of the other guide rail, characterized in that a brake device for retaining the bottom bar (7) in an arbitrary position against the effect of said spring bias includes a friction member (14, 15, 14', 15') mounted in the bottom bar (7) and acting on the cord, a device (18, 18') for tightening the cord (9, 10) being provided in association with one of said fixture means. 2. A roller blind as claimed in claim 1, characterized in that the friction member includes a reversing member for the cord, firmly mounted in the bottom bar (7) . 3. A roller blind as claimed in claim 2, characterized in that said reversing member comprises two pins (14, 15, 14', 15') disposed in the bottom bar and over which the cord (9, 10) is passed in S-shape. 4. A roller blind as claimed in claim 3,* characterized in that the two pins (14, 15, 14', 15') are provided in a common holder (19) to be mounted in the bottom bar (7) . 5. A roller blind as claimed in any of the pre¬ ceding claims, characterized in that said fixture means (11, 17, 11', 17') for the cord (9, 10) are provided in retaining means to be inserted in respective ends of the two guide rails (5, 6) . 6. A roller blind as claimed in claim 5, characterized in that the cord tightening member (17, 17') consists of a tension spring (18, 18') mounted in one of said fixture means (17, 17') and connected with the actual cord end. 7. A roller blind as claimed in any of the preceding claims, in which the cord arrangement for ensuring parallel guidance of the bottom bar (7) in relation to the roller bar includes two cords (9, 10) passed through the guide rails (5, 6) and the bottom bar (7) in reverse mounting, characterized in that said holder (19) as the friction member for both cords (9, 10) includes two common reversing pins (21, 22), and that the holder is pro- vided with a partition wall (20) for separating the two cord paths.

Inventors: KOLD OVE, MIKKELSEN TORBEN, KOLD, OVE, MIKKELSEN, TORBEN
Applicants: RASMUSSEN KANN IND AS, V. KANN RASMUSSEN INDUSTRI A/S
Application year: 1993
Main classification: E06B9
IPC codes: E06B9