GB2151678A

GB2151678A - Roller blind

Info

Publication number: GB2151678A
Application number: GB08333861A
Authority: GB
Inventors: Raymond Peter Allen Brock
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-12-20
Filing date: 1983-12-20
Publication date: 1985-07-24
Also published as: GB8333861D0; GB2151678B

Abstract

A roller blind mechanism comprising a main coil spring 14 a first connection connecting one end of the main- spring 14 and the blind roller 10, a second connection connecting the other end of the main-spring and a stationary mounting 30, one connection incorporating a clutch mechanism 20, 34, 38 which normally maintains the connection and being arranged, when the main-spring has been wound to a predetermined condition by rotation of the blind roller, to be automatically released to an extent which permits continued rotation of the blind roller by further withdrawal of the blind, without further winding of the main-spring, whilst maintaining the tension of the main-spring substantially at its predetermined condition. <IMAGE>

Description

SPECIFICATION Roller blind mechanism This invention relates to roller blind main-spring de-coupling units and to roller blind mechanisms incorporating such units. Roller blinds commonly incorporate a return coil spring, referred to herein as the "main-spring", such roller blinds having the blind material itself secured to a roller which is supported between a pair of brackets (or end mountings) by which the blind as a whole can be located for example at the top of the window. When the blind is drawn down, the main-spring, located within the roller is wound up in such awaythatthe blind can be automatically retracted when it is no longer required. In many instances the main-spring is still slightly pre-stressed even when the blind is fully retracted in order to ensure adequate retraction over the last few inches of movement.

Problems are experienced with such blind mechanisms in that there is a tendency for the user either to apply too much pre-tensioning so that when the roller is fully drawn down the main-spring tends to get over-stressed, or that the blind, if properly pre-stressed for a particular window, may tend to be drawn down too far, again over-stressing the main-spring.

A proposal which allegedly overcomes some of these problems is shown in British Patent Specifications 2077334 and 2013762. This proposal utilises a clutch which is disengageable when the main-spring is tensioned beyond a pre-determined amount, such disengagement of the clutch allowing the spring to unwind with respect to the remainder of the mechanism, the intention being that, when the spring has relaxed, the clutch will re-engage either automatically or by slight manual adjustment of the mechanism.

This arrangement, therefore, whilst aiming to alleviate the problem of over-stressing of the mainspring, works on the basis that, after stressing has occurred to a predetermined extent, the main-spring is unwound to a considerable extent when the clutch is disengaged. Since the over-stressing of the main spring will almost certainly occur when the roller blind is fully open or drawn down, this will mean that the main-spring will have lost all or substantially all its return torque and to retract the blind, as a result of which it is necessary manually to roll up the blind or in some other way return the blind to its initial position.

The present invention has as its principal object the provision of a mechanism which will prevent over-stressing of the main coil spring of the blind in a simple and reliable way without substantial unwinding of the main-spring so maintaining the function of the main-spring without any further attention being required by the operator.

According to one aspect of the present invention a roller blind main-spring de-coupling unit which is arranged to be incorporated in a roller blind mechanism comprises a main-spring and a number of parts which include a blind roller and a stationary part, the unit being arranged, when so incorporated, normally to apply a torque between the main-spring and one of said parts whilst a blind is withdrawn from the roller to cause rotation of the roller and winding-up of the main-spring, over-stressing of the main-spring being prevented by the de-coupling unit relaxing its application of torque between said main-spring and said one part when the mainspring achieves a predetermined wound-up condition, yet maintaining said predetermined wound-up condition.

A particularly convenient arrangement includes an over-load coil spring which reacts with a cylindrical member which is fixed to one of said parts, the over-load coil spring having one end which is keyed directly or indirectly to the mainspring so that winding-up of the main-spring normally tends to cause the over-load coil spring to bind onto the cylindrical member to apply said torque, the achieving of said predetermined woundup condition of the main-spring causing the mainspring to be connected to the other end of the overload coil spring so as to release its binding on the cylindrical member and to release said application of torque.

Specifically a release bush may be arranged to be located within but normally spaced from the mainspring but which is arranged to be contacted by the interior of the main-spring when it reaches said predetermined condition, said release bush being connected to the other end of the over-load coil spring. A coupling part may be included to which the main-spring and the over-load coil spring are always connected, one said coupling part may have a substantially conical exterior surface arranged to be received within one end of the main-spring. Such an arrangement enables the use of the unit for different sizes of main-spring. The conical exterior surface may be slightly ribbed to facilitate a driving connection between the main-spring and the coupling part.

In one particularembodimentthe main-spring has its other end connected to the roller thereby to be rotated with the roller such that, on continued rotation of the roller after the relaxing of the application of said torque the coupling part is also rotated, the cylindrical member being secured to a stationary part.

In another embodiment the cylindrical member is connected to the roller to be rotated with it, and the other end of the main-spring is normally held stationary such that, on continued rotation of the roller, after the relaxing of the application of said torque, the coupling part remains stationary.

According to another aspect of the present invention a roller blind mechanism which is arranged to be connected to a blind roller carrying a flexible blind, incorporates a main coil spring which is arranged to be wound up when the blind is withdrawn off the blind roller, a first connection for inter-connecting a first pair of parts comprising one end of the main-spring and the blind roller, a second connection for inter-connecting a second pair of parts comprising the other end of the main-spring and a stationary mounting, at least one of the first and second connections incorporating a locking mechanism which normally maintains the said inter-connection between the parts of the respective pair, the locking mechanism being arranged, when the main-spring has been wound to a predetermined condition by rotation of the blind roller on withdrawal of the blind, to be automatically released to an extent which permits continued rotation of the blind roller by further withdrawal of the blind, without further winding of the main spring, whilst maintaining the tension of the main spring substantially at its predetermined condition.

The locking mechanism may conveniently include an over-load coil spring mounted closely to surround a further member which is connected to one of said parts of the respective pair, and the arrangement is such that, until said predetermined condition is reached, the over-load coil spring is caused to bind on the further member, but, after said predetermined condition is reached, the over load spring is caused to be released from the further member.

The invention may be carried into practice in various ways but two specific embodiments, will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-section of part of a roller blind which incorporates mechanism in accordance with the first embodiment of the present invention; Figure 2 is a longitudinal cross-section of an overload release bush incorporated in the mechanism of Figure 1; Figure 2(a) is an end elevation of the bush of Figure 2, viewed in the direction of arrow 1 a; Figure 3 is a longitudinal cross-section of a cone incorporated in the mechanism of Figure 1; Figure 4 is a longitudinal cross-section of a release sleeve; Figure 4(a) is a side elevation of the release sleeve of Figure 4;; Figure 4(b) is a detailed perspective view of a pair of flexible lugs which form part of the release sleeve shown in Figure 4(a); Figure 5(a) is a side elevation of an overload coil spring; Figure 5(b) is an end elevation of the spring of Figure 5(a) viewed in the direction of the arrow A; Figure 5(c) is a perspective view of the overload coil spring of Figures 5(a) and 5(b); Figure 6 is a longitudinal cross-section of a main shaft end member; Figure 6(a) is an end elevation of the main shaft end member, viewed in the direction of the arrow 5a; Figure 7 is a cross-section of the end member of Figure 6 taken on the line A-A; Figure 8(a) is an end elevation of a centralising member; Figure 8(b) is a side elevation of the centralising member of Figure 8(a);; Figure 8(c) is a side elevation of the centralising member of Figure 8(a) in an alternative position; Figure 8(d) is the reciprocal side elevation to Figure 8(a); Figure 9 is a perspective view of the various parts of Figures 2to 8 in an assembled condition; Figure 10 is a longitudinal cross-section of part of a roller blind which incorporates mechanism in accordance with the second embodiment of the invention; Figure 10(a) is a perspective view of the end assembly shown in Figure 10. and Figure 1 1 Is an end elevation of the mechanism of Figure 10 looking in the direction of arrow B.

Referring firstly to the embodiment of Figures 1 to 9, Figure 1 shows a roller 10 in the form of a tube to which a blind, manufactured for example from plastics or textile sheet material, may be secured in a conventional way. Only the left-hand end of the roller 10 is shown. The left-hand end of the roller 10 in Figure 1 is secured to a rotary part 11. This part 11 incorporates a generally radial flange 11A to the left of which are a number of pockets 11 B to receive ball bearings 12 for a purpose to be described.

Extending axially from the inner end of the flange 11A is a main body portion 11F having splines 11C by means of which the roller 10 is engaged. The part 11 F terminates at its right-hand end, in a surface 11 D, and mounted on this surface is one end 14A of a closely coiled main counterbalance spring 14 which will be referred to later.

The whole of the part 11 F is generally hollow and received within it are parts of a ball controller body 16 which is held stationary with respect to a fixing bracket 18. All these parts are relatively conventional and need not be considered further, except to say that the arrangement is such that, when the blind is drawn off the roller 10, for example to cover a window, the roller 10 rotates and, by virtue of its engagement with the part 11 F, the end 14A of.the main spring surrounding the surface 11 D is rotated in such a direction that the spring 14, although already closely coiled, is further wound in a winding up direction.

The ball bearings 12 in the pockets 11B act as a form of clutch in a conventional manner to retain the mechanism in a number of positions when the blind is fully or partly down. The blind can be returned to its retracted or wound-up position by applying a slight pull or jerk to the blind in such a way that the ball bearings 12 are released, and maintained released, whilst the roller winds up relatively quickly to the retracted position.

The manner in which the right-hand end of the main spring 14 is mounted, and the manner in which an overload mechanism is provided, in accordance with the present invention, to prevent overstressing of the main spring 14, will now be described.

The far right-hand end of the main spring 14 surrounds all or part of a cone 20, which is formed as a plastics moulding, the external surface of the cone being conical as shown both in Figure 1 and Figure.3. When assembled, the spring 14 is a tight fit on the external surface of the cone 20 as a result of which, so long as the cone 20 remains stationary, the spring 14 will continue to be wound up as the roller 10 is rotated by unwinding of the blind. The spring 14 continues to be wound up during unwinding of the blind until the locking mechanism, to be described, comes into effect.

As will be seen from Figure 1 and Figure 3, the cone 20 has a stepped bore formed in two distinct sections, namely a left-hand reduced diameter section 22A. and a right-hand enlarged section 228.

these two sections merging via a radial step 220.

Referring to Figure 3, it will be seen that the bore section 22B of the cone 20 has a small notch 24 extending inwardly from the right-hand end face of the cone. In the sense that the parts shown in Figures 2 to 6 are generally shown in their aligned but unassembled condition, it should be noted that the position of the notch 24 indicated in Figure 3 is in fact 180 degrees out of position for clarity, in order that the notch can in fact be seen in the section shown in Figure 3.

Located in this notch 24 is a short, axially extending, end 26A of an overload coil spring 26, shown in detail in Figures 5(a), 5(b) and 5(c) and also shown in section in Figure 1. This overload coil spring has a number of closely coiled turns and surrounds a cylindrical surface of a spigot portion 28 of a main shaft end member 30, shown in Figures 1 and 6. To the right of the spigot portion 28, the main shaft end member 30 has a generally radial flange 30A and beyond that, a shaft extension 30C terminating in an end button 30D. A centralising member 62, shown in detail in Figures 8(a), 8(b) and 8(c), rotates freely on the shaft extension 30C so providing stabilisation for the internal mechanism within the blind roller 10.To the left of the spigot portion 28, the end member has a reduced diameter sleeve portion 30E terminating in a frusto-conical end 30F, an annular notch 30G being provided, just inboard of the end 30F.

When the parts are assembled to the condition of Figure la a generally D section connecting shaft 33 is received within a similar D section bore in the end member 30, the shaft extending into the spigot 28.

Extending coaxially between the shaft 33 and the main-spring 14 is a spacing sleeve 60F which aids centralisation of the components. The left-hand end of the shaft 33 is received in a suitable recess within the stationary ball controller body 16.

In this way, therefore, the shaft 33 is maintained stationary at all times, and by virtue of the D shaped interconnection between the shaft 33 and the end member 30, this member is accordingly always stationary, so providing a stationary surface to the spigot 28 upon which the overload coil spring 26 is received.

When the parts are assembled the overload coil spring 26 is slightly stretched over the spigot 28 in such a way that the spring 26 is quite tightly received on the spigot 28 and adheres frictionally to it. The other end 26B of the overload coil spring 26, like the end 26A, also projects axially as can be seen in Figures 5(a) and 5(c). This end 26B is received within a notch 34A extending inwardly from the right-hand end of a release sleeve 34, the detail of which can be seen in Figures 1 and 4. Thus from Figure lit can be seen that the release sleeve 34 has a main portion 34B which closely surrounds the reduced diameter sleeve portion 30E of the end member 30.The right-hand end 34C of the release sleeve 34 is slightly enlarged in its internal bore in order to extend around the step formed between the portion 30E and the spigot 28 of the end member 30.

Towards its left-hand end the release sleeve 34 is formed with two pairs of diametrically opposite flexible lugs 36 and 37, these lugs being generally rectangular but being connected at only one end to the remainder of the sleeve 34 to act as tongue-like projections protruding slightly proud of the remainder of the surface of the sleeve 34 (see Figure 4(b)).

Referring to Figure lit will be seen that the lugs or tongues 37 closely abut the left-hand end of the cone 20. In the assembled condition of Figure 1 the other pair of lugs or tongues 36 are forced inwardly by the internal surface of an overload release bush 38, (the detail of which also appears in Figure 2) to engage in the annular notch 30G adjacent the lefthand end of the main shaft end member. The bush 38 has an internal radial flange 38A provided with a central hole 38B which has a clearance fit with the external surface of the shaft 33.The flange 38A effectively divides the bore of the overload release bush into two sections, namely a shorter left-hand section 38C, and a longer right-hand section 38D, this latter section having a pair of longitudinal grooves 38E situated diametrically opposite one another and into which the lugs or tongues 36 extend when the parts are assembled. In the assembled condition the left-hand end of the release sleeve 34 abuts the right-hand side of the flange 38A. The engagement of the lugs or tongues 36 within the grooves 38E effectively provides a key between the bush 38 and the sleeve 34 such that any rotation of the bush 38 is transferred directly to the sleeve 34.

The external diameter of the bush 38 is such that when the blind roller is in its retracted position, the main counterbalance spring 14 does not contact the external surface of the bush 38, but extends in a generally cylindrical manner between the opposed ends of the rotary part 11 at the left-hand end of the assembly and the cone 20 at the right-hand end of the assembly.

Thus in the region of the bush 38 the spring will normally follow the contour indicated by the chaindotted line 40.

As has previously been indicated, as the blind is drawn down and the roller 10 is rotated, this tends to wind up the spring 14 since its right-hand end is tightly engaged on the cone 20 and this cone is held stationary by virtue of the fact that the right-hand end of the cone engages the overload coil spring via the notch 24 in the cone. The overload coil spring, as has been described, is already a tight-fit on the spigot 28 and the direction of coiling of the overload spring 26, and the direction of winding of the main spring 14 are such that the overload coil spring 26 tends to be stressed in a tightening direction at this time, so increasing the grip on the spigot 28, and thus ensuring the cone 20 is maintained stationary during normal operation of the blind. In this way therefore the main spring 14 can be wound up, as the blind is withdrawn, to produce the required return torque within the spring 14 to cause retraction of the blind at the appropriate time, During this normal operation the winding of the spring 14 is not sufficient for it to reach the position shown in Figure 1, i.e. where a portion of the main spring 14 has reduced in diameterto engage the external surface of the overload release bush 38.

Thus during normal operation of the blind the parts 38 and 34 are unaffected by the main spring 14.

If, however, the main spring 14 is wound beyond the normal extent such that the reduced portion of the main spring is formed and engages the external surface of the bush 38 to an extent that it grips the bush and tries to rotate it, such tendency to rotate will also be applied to the release sleeve 34.

By virtue of the fact that the left-hand end 26B of the overload coil spring 26 is engaged in the notch 34A of the release sleeve 34, any slight tendency for the bush 38 and the release sleeve 34 to rotate during further winding up ofthe main counterbalance spring 14, will cause the overload coil spring to be very slightly deformed to an extent which is sufficient for its locking grip on the spigot 28 to become a braking grip. This allows the overload coil spring to rotate whilst still braking with respect to the spigot 28 and thus ensure rotation of the cone 20.The effect of this arrangement therefore is that at the critical time when the main spring 14 tends to getoverwound it will trigger the release of the locking mechanism provided by the overload coil spring 26, and any further rotation of the roller tube 10 will merely rotate the already-wound main spring 14 in a bodily manner, whilst keeping it in its wound condition between the tapered surface 11 D and the external surface of the cone 20. In other words the parts 38 and 34 act as a form of trigger mechanism which releases the overload coil spring from its locked condition to a braking condition to an extent which is sufficient for the brake to allow continued rotation of all these parts during further rotation of the blind roller, but without causing further stressing or unwinding of the main counterbalance spring 14.

If at this time, therefore, it is desired to allow the blind to retract to its stored position, this can be achieved in the normal way, the required torque still remaining in the main spring 14 for this purpose.

All the parts 38,34, 20 and 30 can conveniently be formed as plastics mouldings which are readily assembled one within the other to the configuration shown in Figure 1. In practice, whilst it might be possible for the parts 38 and 34 to be formed as a single moulding since these are keyed to rotate together, for the arrangement specifically shown, they are separate mouldings for assembly purposes. This also provides the advantage that the bush 38 can, where required, be of a different size in order to provide a different external diameter for a different size of main spring 14. The same could apply to the cone 20 although it is believed that the conical surface provided by this cone will in itself provide a certain amount of flexibility in order for it to be able to adopt different diameter springs.The external surface of the cone is preferably formed with a series of circumferential ribs to ensure a good grip of the spring 14.

Another embodiment of the invention is shown in cross-section in Figure 10. A roller 50 to which a blind is to be attached, is affixed, in its central portion and at one end, to rotary castellated sleeves 52A and 52B, the cross section of which is shown in Figure 11. Thus each sleeve has five inner wall portions 52E from which extend five pairs of radial walls 52F, these pairs being interconnected by outer wall portions 52G which closely fit the interior of the roller 50. The inner surfaces of the wall portions 52E are provided with axial extending V-notches 52H.

The left hand sleeve 52A receives the splined hub 54F of an end member 54. The member 54 has a radial wall 54A terminating in an axial annular wall 54B which is loosely received in a recess 60A of an end mount 60.

The mount 60 has a radial end wall 60B and a short flange extending outwardly from the end of the wall 60C which forms the recess 60A.

Extending axially from the centre of the end wall 60B is a long sleeve 60D which lies within the hub 54F of the member 54. The right-hand end of the long sleeve SOD is of reduced diameter and has the end of the main spring 14 located on it. The hub 54F has an inturned flange 54G which is located in an axial groove formed on the surface of the long sleeve SOD, the right hand end of the groove being defined by an annular rib 60H. In this way the end member 54 can float slightly with respect to the mount 60 to accomodate slight misalignment of the path when assembled on an end bracket 18.

The assembly on the bracket is achieved by location of an integral extension 60J provided on the outside surface of the end wall 60B.

As shown in Figure 1 OA this extension 60J defines a block having four square corner portions 60K defining a pair of intersecting transverse grooves 60L. The block is so formed as to provide a slight undercut 60M along each edge into which extend a pair of parallel ribs 18D of a channel portion 18E of the brackets 18.

The innerwall ofthechannel portion 18E is provided with a catch 18F which, when the parts are assembled hooks over two of the square corner portions 60K and lies in one of the transverse grooves 60L to secure the blind in position.

By virtue of the arrangement described the bracket 18 can be secured by means of mounting flanges to a side, vertical or downwardly facing wall and the blind assembly addressed to and located into the bracket channel 18E in any of these positions. This results in the blind being located very close to the surface to which the bracket is secured which is particularly advantageous when the blind is located on brackets secured to downwardly facing surfaces of a window reveal since the blind does not then have a large gap between it and the reveal.

The eft hand end 14A of the mainspring engages the right hand end of the long sleeve 60D so that the left hand end of the mainspring 14 is maintained stationary at all times.

A central shaft 33 is rotatably mounted within the hollow central bore 60E of the sleeve SOD by means of a bush bearing cap 58. The shaft 33 extends to the right co-axially within the mainspring 14, and a spacing sleeve 60F also extends co-axially between the shaft 33 and the mainspring 14. The right hand end of the spacing sleeve 60F abuts the flange 38A of the overload release bush 38.

The right hand end of the shaft 33 extends beyond the spacing sleeve 60F enabling the end member 30 to be affixed to it, the D-shaped section of the shaft keying the end member 30 to the shaft. The mechanism between the overload release bush 38 and the end member 30 is assembled in exactly the same manner as described in the first embodiment.

Hence the right hand end of the mainspring 14 surrounds all or part of the cone 20 forming a tight fit such that, when the cone 20 rotates, the right hand end of the mainspring rotates.

To the right of the end member 30 is the centralising member 62, which is the same component used in the first embodiment but used in an orientation which enables it to transmit rotation.

It thus forms a drive star which is mounted on a shaft extension 30C and held axially by an end button 30D. Lugs 62A extend from the left hand face of the drive star 62 to locate drivably in slots 30H in the right hand face of the radial flange 30A. As shown in Figure 11, drive arms 62B located drivably in grooves 52C of the central rotary spider 52B, so that, when, the blind is drawn, rotation of the roller 50 drives the mounting sleeves, the left hand end one 52A of which drives the rotary clutch member 54, and the centre one 528 of which drives the drive star 62. The drive star 62, in turn, rotates the end member 30 by means of the lugs 62A.

If the mainspring is not wound to its limit, then, as outlined in the first embodiment, the overload spring 26 grips the spigot 28 and transmits drive from the end member 30, via the end projection 26A of the spring to the cone 20 and so to wind the mainspring 14.

In a similar manner to that disclosed in the first embodiment, when the mainspring reaches a certain loading level, a portion becomes sufficiently reduced in diameter to engage the external surface of the overload release bush 38 which, via the release sleeve 34, tends to rotate the left hand end of the overload spring and causes the grip of the overload spring 26 on the spigot 28 to relax. When this condition is reached, further unwinding of the blind, and hence rotation of the end member 30 does not wind the mainspring since the overload spring now slips on the spigot 28 thus not transmitting drive to the cone 20.

Summarising, the second embodiment utilises the same mainspring "saver" mechanism as the first embodiment acting in reverse, so that when the mainspring reaches its fully wound condition it remains stationary in the second embodiment whereas it bodily rotates in the first embodiment.

This second embodiment allows the central end of the mainspring to be driven, thus enabling two mainsprings to be driven from the same roller 52B if required. This is a desirable feature for blinds which are particularly heavy.

Claims

1. A roller blind main-spring de-coupling unit which is arranged to be incorporated in a roller blind mechanism comprising a main-spring and a number of parts which include a rotatable blind roller and a stationary part, the decoupling unit being arranged, when so incorporated, normally to apply a torque between the main-spring and one of said blind roller and said stationary part whilst a blind is withdrawn from the roller to cause rotation of the roller and winding-up of the mainspring, overstressing of the main spring being prevented by the de-coupling unit relaxing its application of torque between said main-spring and said one of said blind roller and said stationary part when the main-spring achieves a predetermined wound-up condition.

2. A unit as claimed in claim 1 including an overload coil spring which reacts with a cylindrical member which is fixed to one of said blind roller and said stationary part, the over-load coil spring having one end which is keyed directly or indirectly to the main-spring so that winding-up of the main-spring normally tends to cause the over-load coil spring to bind on to the cylindrical member to apply said torque, the achieving of the predetermiend woundup condition of the main-spring causing the mainspring to be connected to the other end of the overload coil spring so as to relax its binding on the cylindrical member and to relax said application of torque.

3. A unit as claimed in claim 2 including a release bush arranged to be located within but normally spaced from the main-spring but which is arranged to be contacted by the interior of the main-spring when it reaches said predetermined condition, said release bush being directly or indirectly connected to the other end of the over-load coil spring.

4. A unit as claimed in claim 3 including a coupling part to which the main-spring and the over-load coil spring are always connected.

5. A unit as claimed in claim 4 in which said coupling part has a substantially conical exterior surface arranged to be received within one end of the main-spring.

6. A unit as claimed in claim Sin which the mainspring has its other end directly or indirectly connected to the roller thereby to be rotated with the roller such that on continued rotation of the roller after the relaxing of the application of said torque, the coupling part is also rotated, the cylindrical member being secured to a stationary part.

7. A unit as claimed in claim 5 in which the cylindrical member is directly or indirectly connected to the roller to be rotated with it, and the other end of the main-spring is normally held stationary such that on continued rotation of the roller, after the relaxing of the application of said torque, the coupling part remains stationary.

8. A roller blind mechanism which is arranged to be connected to a blind roller carrying a flexible blind, the mechanism incorporating a main coil spring which is arranged to be wound up when the blind is withdrawn off the blind roller, a first connection for inter-connecting a first pair of parts comprising one end of the main-spring and the blind roller, a second connection for interconnecting a second pair of parts comprising the other end of the main-spring and a stationary mounting, at least one of the first and second connections incorporating a locking mechanism which normally maintains the said inter-connection between the parts of the respective pair, the locking mechanism being arranged, when the main-spring has been wound to a predetermined condition by rotation of the blind roller on withdrawal of the blind, to be automatically released to an extent which permits continued rotation of the blind roller by further withdrawal of the blind, without further winding of the main-spring, whilst maintaining the tension of the main-spring substantially at its predetermined condition.

9. A mechanism as claimed in Claim 8 in which the locking mechanism includes an over-load coil spring mounted closely to surround a further member which is connected to one of said parts of the respective pair, and the arrangement being such that, until said predetermined condition is reached, the overload coil spring is caused to bind on the further member, but, after said predetermined condition is reached, the overload coil spring is caused to be released from the further member.

10. A roller blind moulded assembly comprising a mounting bracket for securement to a stationary member such as a window reveal, the bracket defining an integral channel which is open at one end to receive a moulded mounting member on one end of a blind mechanism, the mounting member being of such configuration that it can be inserted into the bracket member of different orientations and latching means being integrally provided on the mounting member and the bracket to secure the mounting member to the channel.

11. A roller blind assembly comprising a bracket arranged to be secured to a stationary member such as a window reveal, an end support removably locatable on the bracket and having an axially extending portion in to which a main return spring is arranged to be mounted, and a roller support member located on the axially extending portion and capable of limited axial movement with respect to the end support to accomodate slight variations in bracket position.

12. A roller blind mechanism substantially as specifically described herein with reference to Figures 1 to 9 or Figures 10 and 11 of the accompanying drawings.