BRAKING ARRANGEMENT

The present invention relates to a braking arrangement for a rolling-up device, preferably for a roller shade, more particularly for the type of roller shade for which a spring is being tensioned when the roller shade is unrolled and for which the spring- tension rolls up the roller shade.

TECHNICAL BACKGROUND Most people that have used a conventional spring-tensioned roller shade have noticed that the roller shade goes up very rapidly when it is rolled up. This is unsatisfying and sometimes even dangerous from a user perspective. Hence, it would be advantageous if such roller shades could be rolled up with an essentially constant velocity. At the same time, it is advantageous for the roller shade design not to be all too complicated. It is advantageous if the number of components included can be kept down and that such components can be manufactured at a low cost. It is also desirable for the mounting of a roller shade to take place in a time that is as short as possible, with a labour that is as low as possible, whereby the cost for the manufacturing of roller blinds can be kept down.

Yet a disadvantage with many conventional spring-tensioned roller shades is that they quite often lose the spring-tension and the spring must then be manually re-tensioned. The roller shade gets tensioned when it is unrolled, but the spring must have a certain bias in order for the canvas thereafter to be rolled up again. For most people, manual tensioning of the spring is seen as time consuming and frustrating. Moreover, it is hard to achieve a correct tensioning of the spring and most often the tensioning will be too hard or too loose. If the spring tensioning is too loose, the roller shade does not manage to roll up completely and the spring must be re-tensioned in order for the roller shade not to hang halfway down. Even if it is desired to have the roller shade hanging halfway down in a particular position, it is very hard to adjust the spring tensioning to that precise position. If the spring tensioning is too hard, there is a risk: 1) that the centrifugal stop, that is used in most conventional spring-tensioned roller shades, is released, whereby you end up in square one again and have to re-tension the spring, 2) that the roller shade flies up at a dangerous speed when it is released, thereby risking over-rotation. Here, over-rotation means that the roller shade continues to rotate a couple of turns although the canvas of the roller shade has been rolled up completely. In case of too hard a bias, the spring is also exposed to severe stress that in time may affect

the physical properties of the spring and impair its strength. Hence, it would be an advantage if the normal roller shade user would not have to trouble his mind with such matters.

Another drawback of many conventional spring-tensioned roller shades is that the spring has a tendency to rattle against the roller shade tube when the roller shade is unrolled or rolled up.

Another property that in some cases can be desirable is if the roller shade can be rolled up easily to a given height, for example to form a curtain valance.

US 6,135,189 and US 6,003,584 describe a roller shade arrangement that makes use of a variable pitch twisted metal bar and a spring fastener with an inner screw-thread that translates laterally along the twisted bar when the roller shade is unrolled or rolled up. A tension spring (or a compression spring) is attached to the spring fastener and the spring will be extended (or compressed) when the roller shade is pulled down, where after the spring force can be used to roll up the roller shade. The spring force is balanced by the spring fastener translating along a variable pitch screw.

BRIEF ACCOUNT OF THE INVENTION

It is an object of the present invention to eliminate or at least minimize the above mentioned problems, which is achieved by a roller shade comprising a tube upon which a roller shade canvas is attachable, the roller shade being arranged to be attached in two external means of attachment, the roller shade further comprising a spring controlled drive mechanism that is tensioned when the roller shade canvas is unrolled, in order to be able to roll up the roller shade canvas again, the roller shade further comprising an inner bar inside the tube, which inner bar is arranged to be able to connect to at least one of the external means of attachment, and the tube furthermore being arranged to be rotatable about the inner bar, and furthermore a braking nut that is laterally translatable inside the tube and that encloses the inner bar and is arranged to rotate together with the tube, said braking nut being arranged to translate laterally along the inner bar as the tube rotates, the direction of the lateral translation depending on the rotary direction of the tube, whereby a braking action is formed from the work that is required to laterally translate the braking nut. Hence, this aspect of the invention solves the problem of braking a spring-tensioned roller shade.

According to additional aspects of the present invention:

The tube has a longitudinal groove and the braking nut has an outer guide groove adapted to said guide, whereby the braking nut is arranged to rotate together with the tube.

The braking nut has at least one contact surface against the inner walls of the tube, whereby friction arises at said at least one contact surface when the braking nut translates laterally, whereby a braking action is formed between the braking nut and the inner walls of the tube.

- The braking nut is arranged to translate between two end positions, a first end position in which the roller shade is unrolled and a second end position, where the section between the two end positions constitutes a braking section, which gives the advantage that the spring-tensioned drive mechanism can be biased already in the manufacturing of the roller shade and also gives the advantage that it is easy to adapt the roller shade to achieve a curtain valance - by unrolling the roller shade to a desired length before inserting it in the means of attachment when the braking nut is in its second end position.

The inner bar has screw threads at least in the braking section and the braking nut has at least one inner thread adapted to the screw threads, whereby the braking nut will translate laterally as the tube rotates about the inner bar. At least one of the end positions is formed by the cessation of screw threads on the inner bar.

- The screw threads on the inner bar have a variable pitch, the pitch preferably increasing progressively from one end position to the other, giving the advantage that the braking nut will translate a longer distance per revolution of the tube when the pitch is higher, and vice versa, whereby a braking action against the inner walls of the tube can be controlled via the variable pitch.

- The braking nut has an inner resilient mechanism, where the resilient mechanism exerts a spring force against the inner bar.

Said at least one thread of the braking nut is resilient.

Said at least one thread of the braking nut is flexibly revolving in order to adapt to a variable angle of incidence of the thread groove, giving the advantage that the braking nut will adapt to a varying pitch, thereby not jamming as the pitch changes.

- The braking nu is split in two halves, giving the advantage that the braking nut can expand as it translates, thereby pressing itself out against the inner walls of the tube and acting as a drum brake.

- The two halves of the braking nut are loosely joined together, thus enabling for the braking nut to expand while simultaneously keeping the braking nut in place about the inner bar.

- The inner bar may, at least in the braking section, have a slightly conical shape, whereby an increased conicity in the braking section results in an increased braking action.

The drive mechanism comprises a torsion spring, which torsion spring is attached in one end thereof to the inner bar at one end of the tube and the second end of the torsion spring being attached to a movable spring fastener that is arranged to rotate together with the tube, giving the advantage that the torsion spring is tensioned as the tube rotates about the inner bar. The movable spring fastener is not laterally fixed other than by the torsion spring, giving the advantage that the load on the torsion spring is decreased and that rattling of the torsion spring decreases when the roller shade is unrolled or rolled up.

The braking nut is positioned at the first end position when the torsion spring is maximally tensioned and the torsion spring is biased by a predetermined number of revolutions when the braking nut is at the second end position.

According to additional aspects of the invention, an external means of attachment for the roller shade with a protection against over-rotation, which protection against over-rotation is composed of a lower protrusion on the external means of attachment, having an extension that is longitudinal in relation to a tube that is arranged in the outer means of attachment, the parallel extension being longitudinal in relation to the tube below the centre line of the tube, giving the advantage that the roller shade is prevented from over-rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an exploded view over a preferred embodiment of the present invention, where

Fig. 2 A shows a view over the halves of the braking nut, as seen from the side, where Fig. 2B shows the braking nut as seen from the side, where Fig. 2C shows a three-dimensional view over the halves of the braking nut, where Fig. 2D shows the braking nut enclosing the inner bar, half a half of the braking nut having been cut away in order to elucidate the arrangement of the resilient parts and the threaded part, where

Fig. 3 A shows a simplified cross-section of the roller shade, and an external means of attachment, the roller shade being in a rolled-up position, where

Fig. 3B shows a simplified cross-section of the roller shade, and an external means of attachment, the roller shade being in an unrolled position, Fig. 4 A shows a schematic cross-section of the screw-threads of the inner bar,

Fig. 4B shows a schematic view over the screw-threads of the inner bar.

DETAILED DESCRIPTION

Fig. 1 shows an exploded view over a preferred embodiment of a roller shade according to the present invention. The roller shade comprises an elongated tube 1 on the outside of which a roller shade canvas 24 (see Fig. 3a, 3b) can be attached. The tube has a first 14 and a second end (not shown) as well as an inner longitudinal guide 10 that extends from the first end 14 to the second end. Preferably, the guide 10 is of rectangular cross- section. An inner bar 2 is arranged inside the tube 1 and the tube 1 is arranged to be rotatable about the inner bar 2. The first end 5 of the inner bar mouths at the first end 14 of the tube and is adapted to connect to a first external means of attachment 16 (see Figs. 3a, 3b), preferably by the first end 5 of the inner bar having two rectangular protrusions adapted to corresponding rectangular apertures in the first external means of attachment 16.

The second end of the tube (not shown) can be inserted in a second external means of attachment 17 (see Figs. 3a, 3b). The attachment of the second end of the tube is conventional and is not focused upon in connection with the invention, but the tube 1 is arranged to be rotatable in relation to the second outer means of attachment 17. When the roller shade is mounted between the external means of attachment, the tube can accordingly rotate in relation to the external means of attachment 16, 17 at the same time as the inner bar 2 maintains fixed.

A centrifugal stop mechanism 7, 8, 9 surrounds the inner bar 2 at the first end 14 of the tube. The centrifugal stop mechanism 7, 8, 9 is preferably of conventional type and comprises an inner stop element 7, two metal balls 8 and an outer stop element 9. The inner stop element 7 is arranged to rotate together with the inner bar 2, the outer stop element 9 is arranged to rotate together with the tube 1 and the metal balls 8 interact with the inner stop element 7 as well as with the outer stop element 9 in order to achieve a centrifugal stop function. A fixed spring fastener 11 surrounds the inner bar 2 in conjunction with the first end 5 of the inner bar and the centrifugal stop mechanism 7, 8, 9. The fixed spring fastener 11 is fixed at the inner bar 2. A torsion spring 12 is attached

at one of its ends to the fixed spring fastener 11 and thereby to the inner bar 2. The torsion spring 12 surrounds the inner bar 2 and the second end 12 of the torsion spring is attached to a movable spring fastener 13. The movable spring fastener 13 surrounds the inner bar 2 and is free to rotate about the same, and is also allowed to translate laterally (when the spring is tensioned it will be somewhat elongated laterally and vice versa). The movable spring fastener 13 is furthermore arranged to rotate together with the tube 1 of the roller shade, which is preferably achieved by an outer groove in the movable spring fastener 13 that interacts with the tube 1 guide 10. When the tube 1 rotates by the roller shade canvas (see Figs. 3a, 3b) being pulled down at the same time as the inner bar 2 is fixed to the first external means of attachment 16 (not shown), the torsion spring 12 will be tensioned since the movable spring fastener 13 rotates together with the tube 1 at the same time as the fixed spring fastener 11 is fixed to the non-rotating inner bar 2. Preferably, the torsion spring 12 is lubricated with a lubricating agent.

The inner bar 2 is furthermore provided with a braking section 3 along which a braking nut 4 acts. The braking section 2 is delimited by two end positions 19, 20, a first end position 19 and a second end position 20. The braking section 3 is provided with screw threads 6 and the braking nut 4 is provided with corresponding internal threads. The end positions 19, 20 of the braking section are preferably formed by cessation of the screw threads 6 on the inner bar 2. The braking nut 4 is provided with an external groove 4i (see Fig. 2B) adapted to the guide 10 of the tube 1, whereby the interaction between the guide 10 and the external groove 4i of the braking nut results in the braking nut 4 rotating together with the tube 1 as the tube 1 rotates. When the tube 1 rotates about the inner bar 2, the internal threads of the braking nut 4 interact with the screw threads 6 of the braking section, whereby the braking nut 4 translates between the end positions 19, 20 of the braking section. When the braking nut 4 reaches an end position 19, 20, the tube 1 is prevented from further rotation in the direction of rotation in question, and consequently the canvas of the roller shade cannot be further rolled up or unrolled depending on which of the two end positions 19, 20 the braking nut 4 is at. The work required to translate the braking nut 4 will give a brake action on the rotation of the tube. When the braking nut 4 translates along the braking section 3, the friction between the braking nut 4 and the inner bar 2 and between the braking nut 4 and the inner walls of the tube 1 will give a brake action on the rotation. As it normally is desired to have an even brake action, it is advantageous if the work required to translate the brake 4 varies depending on the degree to which the roller shade is rolled up, since the spring tension of the torsion spring 12 varies. When the torsion spring 12 is maximally tensioned (i.e. when the roller shade is unrolled), the spring force is the largest and

hence it is desired to have a larger braking action when the roller shade is unrolled and progressively to decrease it simultaneously with its rolling up. In order to increase the friction between the braking nut 4 and the inner wall of the tube 1, the braking nut is divided in two halves 4a, 4b in order to enable for the braking nut 4 to expand on action of the braking nut 4. In the preferred embodiment, the braking nut halves 4a, 4b are partly interconnected, for practical reasons, in order for the braking nut 4 and its inner parts not to fall apart if the inner bar 2 with the braking nut 4 is pulled out from the tube 1. The interconnection will however still allow the braking nut 4 to expand and the interconnection area acts as a hinge by which the braking nut 4 can open up like a clam shell. The braking nut 4 is furthermore provided with resilient parts 4c and a threaded part 4d. The resilient parts 4c will press the threaded part 4d against the inner bar 2 with the screw threads 6, whereby also the halves 4a, 4b of the braking nut are pressed apart - against the inner wall of the tube 1. When the speed of rotation speed is high, the threaded part 4d moreover tries to climb on the walls of the screw threads 6 and since the braking nut 4 can expand the braking nut halves 4a, 4b will be increasingly pressed out against the inner wall of the tube 1 as the speed increases. This leads to increased friction against the inner wall of the tube 1 and consequently the braking action will increase (i.e. the braking nut 4 will act as a drum brake). In order further to control the braking action, the pitch of the screw threads 6 is varied within the braking section 3. Figs. 4A and 4B schematically illustrate how the pitch Sj, s _2;... ,s _n of the screw threads 6 on the inner bar 1 in Fig. 1 is varied. In the present description, the pitch S ₁ , S ₂ ,...,S _n is defined as the distance between the centres of two adjacent thread grooves. In the preferred embodiment of the invention, the pitch S ₁ at the first end position 19 is lower in order to progressively increase to a pitch S _n at the second end position 20, i.e. S ₁ < S _n . As seen in cross-section, the thread grooves are of U-shape and the thread walls are outwardly inclined, i.e. the upper width tl of the thread groove is larger than the lower width tl . The width tl , t2 of the thread groove is the same over the entire braking section 3. Regarding the angle of incidence α _1; α ₂ ,...,θn+i of the thread groove, this will change from the first end position 19 to the second end position 20, since the pitch S ₁ , S ₂ ,...,S _n changes. Accordingly, the angle of incidence O ₁ at the first end position will increase progressively to an angle of incidence α _n+1 at the second end position 20, i.e. (X ₁ < (X _n+ i. For a given number of tube revolutions, the braking nut 4 translates a shorter horizontal distance along the braking section 3 when the pitch is lower as compared to when it is higher. A great deal of the braking work arises from the force of the braking nut halves 4a, 4b against the inner wall of the tube 1 in combination with the distance on which the force acts (i.e. the distance that the braking nut translates along the inner walls of the tube 1), and thanks to the variable pitch this distance can be varied. The

spring force 12 is largest when the roller shade is in an unrolled position and is about to be rolled up, and the braking nut halves 4a, 4b will be maximally pressed out against the inner wall of the tube 1. In the preferred embodiment, the pitch increases progressively from the first end position 19 to the second end position 20. When the roller shade is in an unrolled position, the braking nut 4 is at the first end position 19 and translates as the roller shade is rolling up, to the second end position 20. In the preferred embodiment, the variable pitch is accordingly adapted to reduce the braking action when the roller shade is completely unrolled, in order thereafter to progressively increase the braking action as the roller shade is being rolled up; simultaneously, the spring force is the largest - and consequently also the drum brake action of the braking nut 4 due to the climbing of the threads - when the roller shade is unrolled, in order thereafter to progressively decrease. In other words, the variable pitch is used for exact adjustment of the braking action, such that a uniform rolling-up is achieved.

The braking nut 4 will now be described with reference to Figs. 2A, 2B, 2C and 2D. Fig. 2A shows the two braking nut halves 4a, 4b as seen with their insides up. Fig. 2B shows the braking nut halves 4a, 4b joined together and seen from the side, but without the inner bar 2 (see Fig. 1 or Fig. 2D). Fig. 2C shows a three-dimensional view of the braking nut halves 4a, 4b. Fig. 2D shows the braking nut 4 enclosing the inner bar 2, where half the braking nut half 4a has been cut away in order to elucidate the arrangement of the resilient parts 4c and the threaded part 4d. The braking nut 4 consists of two braking halves 4a, 4b. The braking nut halves 4a, 4b are preferably die cast from plastics. Each one of the braking nut halves 4a, 4b has a longitudinal and corresponding cavity 4f adapted to the screw threaded inner bar 2 such that the braking nut halves 4a, 4b are able to enclose the inner bar 2. In the first braking nut half 4a a diagonal room 4e is arranged to follow the curvature of the braking nut half 4a and in the second braking nut half 4b a transverse room 4k is arranged. First, the resilient parts 4c are positioned in the diagonal room 4e and thereafter the threaded part 4d, interacting with the screw threads 6 of the inner bar 2 in accordance with Fig. 2D, the resilient parts 4c pressing the threaded part 4d against the thread groove. The transverse room 4k acts as a collecting vessel for dirt and decreases the chance of dirt negatively affecting the interaction between the threaded part 4d and the screw threads 6. As seen from the inside of the braking nut 4 (see Fig. 2A), the diagonal room 4 is shaped as an hourglass. The hour-glass shape allows the threaded part 4d to adapt by the threaded part 4d being able to turn sidewise around its centre point, following the angle of incidence α _1; α ₂ ,...,α _n (see Fig. 4B) that changes over the braking section 3. Without this possibility for the thread of the braking nut to adapt to the angle of incidence α ₂ , ... ,α _n of the thread

groove, the braking nut 4 would jam. The resilient parts 4c may e.g. be formed from one or more leaf springs, the resiliency being adjustable by the number of leaf springs, the leaf spring material (the leaf spring may e.g. be made of plastics or metal), and the leaf spring thickness. The first braking nut half 4a is provided with four protruding pins 4g, 4h, one in each corner, and the second braking nut half 4b has corresponding holes 4j for the pins 4g, 4h. On one side of the cavity 4f, the pins are shorter, i.e. short pins 4g, than the two opposing pins on the other side of the cavity 4f, i.e. the longer pins 4h. By pressing together the top of the pins 4g, 4h while heating, the braking nut halves 4a, 4b can be joined together as they enclose the inner bar 2, such that they no longer can be taken out from the holes 4j in which they are inserted. The play will be smaller for the shorter pins 4g than for the longer pins 4h, and the side with the shorter pins will act as a hinge. Thereby, the braking nut is allowed to flex (i.e. the braking nut 4 may expand and act as a drum brake). The advantage of fixing the braking nut 4 with a smaller play on one side of the braking nut halves 4a, 4b, along the inner bar, is primarily to make sure that the braking nut 4 is kept in place about the inner bar 2 even when the braking nut 4 and the inner bar 2 are not installed inside the tube 1 , thus facilitating the procedure of assembling the roller shade and if somebody disassembles the roller shade the braking nut 4 is kept in place, at the same time as the braking nut 4 is flexible enough to expand. Once the braking nut 4 has been installed inside the tube, the inner walls of the tube 1 will prevent the braking nut from falling apart and once inside the tube it would hence be perfectly sufficient for the pins 4g, 4h to be inserted in the corresponding holes 4j without the need of pressing any of the pin 4h, 4g tops. In the preferred embodiment the screw threads 6 are lubricated in order to keep down the friction between the braking nut 4 and the screw threads 6.

Figs. 3 A and 3B show a schematic cross-section of the roller shade and the external means of attachment 16, 17. The inner part of the roller shade is not shown. In the preferred embodiment, the cross-sections of the first and the second external means of attachment 16, 17 are the same, but naturally the means of attachment can be of different cross-sections, e.g. such that only one means of attachment 16, 17 has a protection 16c, 17c against over-rotation. It is also conceivable that the roller shade is inserted in a cassette. On the whole, the overall function of the roller shade according to the present invention does not depend on the external means of attachment, but the external means of attachment nevertheless have the advantage that they will prevent the roller shade from over-rotation, and the protection against over-rotation will also work on a spring-tensioned roller shade of conventional type. Fig. 3B shows the roller shade when the roller shade canvas 24 is completely unrolled and Fig. 3 A shows the situation

when the roller shade is rolled up. The means of attachment 16, 17 has two surfaces 16a, 16b; 17a, 17b that are parallel to the roller shade and that have an angle of 90° them between. The two surfaces 16a, 16b; 17a, 17b meet in a transverse surface at which transverse surface the ends of the roller shade are arranged. All of these three surfaces are provided with screw holes, such that the means of attachment 16, 17 can be attached in walls (parallel with the roller shade or transversal - in corners e.g.) and in the ceiling. One of the surfaces 16b, 17b has a concave bulge, the protection against over- rotation 16c, 17c that is longitudinal in relation to the tube. The drawings show a cord 27 having a knob 28 at its lower end and being attached to the roller shade canvas 24 at its upper end. By grabbing the cord with the knob, a user of the roller shade can pull down the roller shade canvas 24. At its lower end, the roller shade canvas 24 is increased in thickness 25, which for example may be achieved by folding up the canvas at its lower end and sewing the fold to the canvas, thereby creating a longitudinal pocket into which a stick can be inserted. By such a construction, an increased thickness 25 will be formed in the lower end of the canvas 24, which will stabilise the canvas 24 horizontally and act as a weight for the canvas 24 thereby aiding in keeping the canvas 24 straight. Increased thicknesses in the lower part of the canvas 24 are common in conventional roller shades. The drawing also shows the tube 1 upon which the canvas 24 is attached. The guide 10 is seen in the drawing but the inner parts of the roller shade have been omitted in order to keep the drawing simple. When the canvas 24 of the roller shade is rolled up and the tube 1 stops (i.e. when the braking nut 4 reaches the second end position 20), the lower part of the roller shade canvas 24 may due to the centripetal force, if the tube 1 has a rotational speed that is all too high before the stop, tend to continue the rotation, thereby risking over-rotation. The lower part of the canvas 24 with the increased thickness 25 will then interact with the rounded protections 16c, 17c against over-rotation, of the external means of attachment 16, 17, resulting in that the canvas 24 is prevented from continued rotation, thereby preventing over-rotation. Each rounded protection 16c, 17c have a concave bulge that is longitudinal in relation to the tube 1 and that is arranged at a distance from the roller shade such that a small gap is formed (not large enough however for the lower part of the canvas 24 with the increased thickness 25 to pass) between the completely rolled up canvas 24 and the protection 16c, 17c against over-rotation, which gap prevents the canvas 24 from wedging in. The protection against over-rotation is furthermore preferably positioned below the centre line of the tube 1.

The invention is not limited to the above mentioned embodiment example but can be varied within the scope defined by the claims. It is for example realised that even if the

largest part of the braking action arises by the friction between the braking nut 4 and the inner walls of the tube 1, in the preferred embodiment, the friction between the braking nut 4 and the inner bar 2 can of course also be used to a greater extent. This may for example be achieved by a non-expanding braking nut 4, where instead the diameter of the inner bar 2 is changed over the braking section 3, preferably by the inner bar 2 being given a conical shape. A varied diameter of the inner bar 2 may of course be used also when a split braking nut 4 is used, whereby the braking nut 4 will press the more against the inner wall of the tube 1 the larger the diameter of the inner bar 2.

The braking nut 4, the inner bar 2, the spring fasteners 11, 13, the inner and outer stop elements 7, 9, and the external means of attachment 16, 17 are preferably die cast from plastics, but may of course also be made from other materials. The leaf spring may e.g. consist of a metal material and the inner bar 2 could be turned, milled or cast from a metal material.

The two variable air gaps between the braking nut 4 and the movable spring fastener 13, and between the braking nut 4 and the second end of the tube 1, respectively, may also be used separately or together in order to give a braking action by sealing at their respective ends - when e.g. the braking nut 4 translates towards the second end of the tube the air must be pressed out as the volume between the braking nut 4 and the second end of the tube decreases and when that air flow is obstructed the braking action increases.

Furthermore, the invention is naturally not restricted to the use of a single braking nut 4, but it is also conceivable to have a plurality of braking nuts that translate in parallel along the inner bar 2.

It is also realised that the torsion spring 12, instead of being attached to a movable spring fastener 13 at the second end of the torsion spring 12, could be attached to the inner bar 2 and then with a rotatable spring fastener at the first end 5 of the inner bar. In this case it is preferable that the torsion spring 12 is somewhat pulled out in the direction of the tube, since it cannot flex sideways in the same manner as the movable spring fastener 13.

It is also realised that one or both end positions 19, 20 of the braking section 3 can be formed in other ways than by cessation of the screw threads 6. For example, a simple stopping device can be inserted.

It is also realised that the invention is not limited to roller shades but that it also could be used for other purposes in which the braking of a rotating tube is needed, such as for Venetian blinds and projector canvases.

It is of course realised that braking would be effected on the roller shade even if the pitch was constant instead of progressively increasing, and the person skilled in the art will realise that the pitch can be varied in order to adjust for the properties of the torsion spring. It is also realised that the threads on the inner bar could be either left-handed or right-handed threads and that this will not affect the principle of the invention.

It is furthermore realised that the inner bar 2 and the thread function of the braking nut 4 can be used together with the inner bar 2 in a construction similar to those of US 6,135,189 and US 6,003,584, thereby improving those constructions. That is, by changing the torsion spring 12 of the present invention for a tension/compression spring, and moving the movable spring fastener 13 to the threaded section 3 of the inner bar 2; the movable spring fastener 13 suitably then being provided with an inner thread such that it may pull out or compress the spring as the spring fastener translates along the threaded section 3. In this case the braking nut 4 could be removed or remain and then run in parallel with the spring fastener 13. Alternatively, the braking nut 4 and the movable spring fastener 13 could be combined by removing the spring fastener 13 and instead attaching the tension/compression spring to the braking nut 4.