GB2077334A - A roller blind - Google Patents

Abstract

There is disclosed a roller blind with a spring loaded end fitting in which opposite ends of a coil spring 30 are carried by a part 13, fixed in one end of a hollow blind roller 10, and a part 34 which is mounted for axial sliding movement on a tube 18 fixed in a part 11 fixed with respect to a mounting bracket 22. The part 34 has internal longitudinal grooves 36 in which, in the normal longitudinal position of part 34, are received ribs 18a on the tube 18, the ribs 18a being confined to a short section of the tube. As the blind is tensioned and the spring 30 thus wound up, the number of turns in the coil spring 20 increases so that it extends longitudinally, and, before over-tensioning has proceeded sufficiently to damage the spring, the part 34 is pushed longitudinally beyond the ribs 18a allowing the part 34 to rotate on the tube 18 and thus relieve the tension in the spring. The part 34 thus forms, with the ribs 18a, a positive engagement clutch which is disengaged, when the spring is overwound but before the spring has become sufficiently overwound to suffer permanent damage. <IMAGE>

Description

SPECIFICATION A roller blind This invention relates to roller blinds, i.e. to blinds comprising a flexible strip of sheet material, one end of which is secured to a batten or the like and the other end of which is secured to a roller supported in mountings at the top of a window or like, the blind being rolled around the roller when the blind is not in use. In particular, the invention relates to roller blinds of a spring-loaded type in which a spring within the roller is progressively tensioned as the blind roller rotates, with respect to the mountings, during drawing of the blind off the roller, the tension spring providing the means by which the roller is subsequently caused to rotate in the opposite direction to wind the blind back on the roller.

In known roller blinds of the spring-loaded type, it is an inevitable result of the spring being made to meet the necessary criteria for operation that, if the spring is completely unstressed when the blind is fully wound onto the roller, the weight of the batten and the attached blind material is sufficient to cause the blind to unwind to a substantial extent from the roller so that the spring will not raise the blind fully. For this reason, a roller blind of the spring-loaded type must have its spring pretensioned so that the spring is still partly tensioned when the blind is fully wound onto the roller. With known roller blinds of the springloaded type, such pre-tensioning must be effected during installation in the respective window frames or the like.

Roller blinds of the spring-loaded type commonly have a free-wheel or one-way clutch mechanism incorporated in the roller and acting between the members between which the biasing spring also acts, such mechanism being arranged to allow free rotation of the roller against the bias of the spring in the direction corresponding to unrolling the blind but to permit only a very limited return movement of the roller under the action of the spring before arresting such movement if, after drawing the blind to the desired extent, the blind is then allowed to move back only slowly under the action of the spring, the one-way clutch mechanism being however arranged to be rendered ineffective if the roller is allowed to rotate rapidly under the action of the spring, so that the blind, once drawn, can be raised by first pulling it down slightly then allowing it to be rolled up quickly by the spring biased roller. Roller blinds of the spring-loaded type having such a one-way clutch mechanism are normally pretensioned by fitting the blind roller into the mountings, with the blind rolled on the roller and with the spring initially untensioned, drawing the blind to a predetermined extent from the roller to tension the spring, allowing the one-way clutch mechanism to hold the members between which the spring acts in the relative positions thus attained, removing the blind roller from its mountings, rewinding the blind manually without releasing the clutch mechanism and thus without reducing the tensioning of the spring, and refitting the roller in its mountings.Pretensioning of such blinds requires a measure of skill on the part of the persons installing the blinds, in order to ensure that the pretensioning applied is sufficient but not excessive.

It has been found that some people experience difficulty in acquiring the degree of skill required to effect raising of a roller blind of the spring-loaded type fitted with a one-way clutch mechanism of the kind already referred to and that such people, under the mistaken impression that their difficulty in effecting raising of the blind is due to the pretensioning being insufficient, increase the pretensioning by repeating the procedure by which the necessary pre-tensioning is effected initially with known blinds of this type, that is to say by removing the blind roller from its mountings, rewinging the blind manually without reducing the tensioning on the spring and re-fitting the roller in its mountings.If the same procedure is carried out each time that there is a failure to cause the blind to return to a raised position, a situation soon arrises where the spring is tensioned to its limit and is then damaged.

It is an object of the present invention to provide means whereby a roller blind may be provided in which the risk of damage in this fashion is eliminated.

According to the invention there is provided a roller blind comprising a blind roller mounted between two mounting brackets disposed at opposite ends of the roller, one end of said roller having an end fitting comprising a first member attached to one of said two mountings, a second member fitted to the roller body and rotatable with respect to the first member about the roller axis, a helical spring extending along said axis within the roller and having one end mounted so as to be normally non-rotatable with respect to the first member and the other end mounted so as to be normally non-rotatable with respect to the second member, whereby rotation of one member with respect to the other in one sense stresses The spring so that it exerts an opposing spring bias, and wherein a clutch is provided which is arranged to allow the first member to rotate relative to said bracket when the torque exerted by the roller via said first element exceeds a predetermined amount less than that required to damage the spring.

The invention also comprises within its scope a spring loading end fitting for the roller of a blind in accordance with the invention, the end fitting comprising a first member for attachment to a mounting, a second member for fitting to an end of a blind roller body and rotatable with respect to the first member about an axis which, when the second member is fitted to a blind roller body, corresponds to the longitudinal axis of the blind roller body, a helical spring extending along said axis, said spring having one end fixed with respect to the one of said members and being fixed at its other end to a first element co-operating with a second element fixed with respect to the other of said members, the last-mentioned elements together forming a clutch normally engaged so as to prevent relative rotation of said elements about the axis and disengageable by tensioning of the spring beyond a predetermined amount, the clutch being re-engageable after the rotation of said second member relative to the first member, and consequent reduction in the tensioning of the spring, brought about by disengagement of the last-mentioned clutch.

The arrangement may be such that some manual operation is required for re-engagement of the clutch, but it is preferred that re-engagement of the clutch formed by said first and second elements should occur automatically.

Preferably the clutch formed by said first and second elements is a positive engagement clutch disengageable by axial movement to a predetermined degree of said first element with respect to said second element, in consequence of tensioning of the spring by relative rotation of the first and second members, when said tensioning has exceeded a predetermined amount.

Preferably the helical spring is so wound that in its unstressed state each turn lies against the adjacent turns, the sense of tensioning of the spring being such as to add to the number of turns in the spring and thus increase the axial length thereof with increased tensioning, an increase in the axial length of the spring beyond a predetermined extent releasing said positive engagement clutch.

In variants, the clutch formed by said first and second elements may be other than a positive engagement clutch, for example a friction clutch and may be arranged to disengage when the torque exerted between said first member and said second member via the spring exceeds a predetermined value, rather than relying upon lengthening of the spring during tensioning.

In a further variant, the biasing spring may be fixed with respect to the said first member at one end and fixed with respect to said second member at the other end, and a clutch provided in -that one of the mounting brackets for the blind roller which locates the first member, the last-mentioned clutch being arranged to allow the first member to rotate relative to said bracket when the torque exerted by the roller via said first element exceeds a predetermined amount, less than that required to damage the spring.

In those variants where the clutch provided to prevent damage to the spring is simply arranged to disengage or slip when a predetermined torque between the first and second members is exceeded, it may be advantageous to provide an axially extending member (additional to that limiting reduction in tensioning of the spring where the last-mentioned feature is also present) which is engaged by the coi!s of the spring when the latter has been tensioned to a predetermined degree, so that thereafter a substantial increase in torque applied via the last-mentioned clutch is required to produce even the slightest further rotational movement of said second member relative to the first member so that the actual torque at which the clutch slips or disengages is not critical.

Thus, in embodiments of the invention, in which the diameter of the spring is progressively decreased as the spring is tensioned, the additional axially extending member may be a cylindrical tube extending within the spring, this tube being additional to the tube which receives the spring and prevents the spring being completely untensioned.

An embodiment of the invention is described below with reference to the accompanying drawings in which: Figure 1 is a fragmentary view in axial section of part of a blind roller embodying the invention, Figure 2 shows, in side elevation a detail of the roller of Figure 1, and Figure 3 shows, in cross-section, the detail shown in Figure 2, in section along the line Ill-Ill in Figure 2.

The blind roller shown comprises a roller body formed by a length of generally cylindrical metal tubing 10 upon which a blind (not shown) is rolled and within which is accommodated the major part of an end fitting the nature of which is described below.

The end fitting comprises a first member, including an end part 11 adapted to be received in a mounting bracket, and a second member, rotatable with respect to the first member about the roller axis and including an end plug 12, of synthetic plastics, which is a push fit in the end of the length of tubing 10. The end plug 12 includes a collar part 13, reduced diameter portion of which makes frictional engagement with the interior of the tube 10 at the end thereof, and a spigot 15 extending into the tube 10 in an axial direction from the collar part 13. Rotation of the end plug 12 relative to the tube 10 is prevented by engagement of a longitudinal internal projection (not shown) on the tube 10 between two projections 14 extending radially outwardly from the part of spigot 1 5 nearer the collar part 13.An axial bore 16 extends through the end plug 12 and receives, as a free rotating fit, a small diameter metal tube q 8 which projects from the spigot 1 5 into the tube 10. The tube 18 has its outer end carried non-rotatably by the end part 1 the tube 18 being formed with longitudinal slots extending from said outer end so that the portions of the tube between the slots have the form of longitudinal projections of crescent shape in cross-section, these projections extending through slots of corresponding cross-sectional shape extending through end part 11, a central portion 20 of the end part 1 1 being received in the outer end of the tube and being connected with the remainder of the end part 11 by radial webs extending through said slots in the outer end of the tube 18. The tube 18 is prevented from separating from the end part 1 1 by a star fastener 23 of known kind fitted over the free end of the tube 18 which projects outwardly from the end part 1 1.

The central portion 20 of the end part 11 has a central axial projection which engages in a locating hole formed in a bracket 22, which bracket is, for example, secured by screws (not shown) to the frame of the window at which the blind is fitted. The bracket 22 is also provided with projections 24 (only one of which is shown) which engage in recesses 26 formed in the adjacent end face of the end part 11.

At its opposite end (not shown) the roller is rotatably mounted in a further bracket and an axial bias is maintained whereby the projections 24 are kept fully engaged with the respective recesses 26. The axial bias may be provided, for example, by a spring biased end fitting at said other end of the roller or by utilising a spring biased bracket or brackets. The roller can be removed from its brackets by displacing the roller, and with it the end part 11 away from the bracket 22 against said axial bias, dropping the end of the roller shown in Figure 1 from the bracket 22, then removing the opposite end of the roller from its bracket.

The end part 11 has an axially projecting spigot 28 rotatable within a corresponding counter-bore 38 extending from the outer end face of the end plug 12.

Between the end part 11 and the end plug 12 is a one-way clutch formed by rollers (not shown) each received in a respective slot extending outwardly from the bore 38 and engageable in shallow grooves formed at intervals on the exterior of the spigot 28, said one way clutch being so devised that rotation of the roller 1 0 with respect to the end part 11, in the sense to wind the blind onto the roller, may be prevented by wedging of the clutch rollers between their slots and said shallow groove on the spigot 28, but rotation of the roller 10 in the opposite direction is permitted since in the latter case the clutch rollers are pushed outwardly along their slots, away from the spigot 28.However, if the roller 10 is allowed to rotate rapidly enough relative to the end part 11 the one-way clutch is rendered ineffective to prevent rotation of the roller 10 in the sense to wind the blind on the roller while such rapid rotation is maintained.

The end plug 12 is retained axially, relative to tube 18, between the end part 11 and a washer 29 fitted over the tube 18 and bearing against a crimped portion 31 of the tube 18 which cannot pass through the washer 29. The construction of the one way clutch between end part 11 and end plug 12 is such that this clutch can arrest the end plug 12 in only a limited number of angular positions, e.g. three positions relative to the end part 11. As a result, once the blind is installed, there are a limited number of different levels in the window opening or the tike at which the batten at the lower edge of the blind can be maintained by the one-way clutch, and there will be a substantial difference in height between successive said levels.If a wide window is fitted with two blinds side by side, or if, for example, a plurality of similar windows arranged side by side in one wall of a building are each fitted with a respective blind, it might therefore occur, for example as a result of the blinds being of different lengths from point of attachment to the respective rollers to point of attachment to the respective battens, that it would not be possible to arrange that the bottoms of all of the blinds were held at the same intermediate level nearly enough to avoid an aesthetically displeasing irregular appearance to the eye, if the position of the end part 11 of each blind roller, with respect to its associated bracket 22 were fixed and invariable.

To avoid this disadvantage, and to ensure that the positions at which the lower end of the blind can be stopped by operation of the one-way clutch can be readily adjusted to relatively close limits, the end part 11 is formed with a large number of recesses 26 arranged at regular angular intervals about the axis of the roller and equally spaced from said axis, so that the end part 11 can be fitted in any of a correspondingly large number of angular positions with respect to the associated bracket 22, whereby fine adjustment of the level of the bottom edge of the blind in any arrested position may be obtained.Clearly once a series of blinds has been thus adjusted to ensure that in one position their lower edges are substantially level, it will be possible thereafter, without removing any of the blind rollers from their brackets, to achieve the same result at any of the other possible levels of the lower edges of the blinds.

Accommodated within the tube 10 is a helical wire spring 30 which is so wound that even in the unstressed state adjacent turns thereof lie in contact with each other. The overall form of the spring 30 is that of a cylinder necked down at either end to a reduced diameter, one end of the spring being resiliently engaged over a generally cylindrical portion 32 of the spigot 1 5, said portion 32 being of reduced diameter with respect to the remainder of the spigot 1 5, and providing the axially innermost, free end of the spigot 1 5. The final turn or final turns at that end of the spring 30 lie within a circumferential recess on the exterior of portion 32 adjacent the shoulder 34 formed at the junction of portion 32 with the remainder of the spigot 1 5.The opposite end of the spring 30 is engaged over a reduced diameter portion of a clutch element 34 which is generally cylindrical externally and has an axial bore of a diameter such as to receive the tube 18 as a free fit. However, in the position of the parts of the assembly when the spring 30 is stressed to a minimum, the element 34 corresponds in axial position with a portion of the tube 18 which is crimped, as shown diagrammatically in Figures 2 and 3, so as to have in cross-section the form indicated in Figure 3, comprising a cylindrical central portion of reduced diameter with respect to the remainder of tube 1 8 with longitudinally extending lateral ribs 18a projecting diametrally from said cylindrical central portion.

The bore through the element 34 has diametrally opposed longitudinally extending grooves 36 which receive the ribs 18a as a free sliding fit. The extreme end of the tube 18 remote from the end plug 12 passes through a central aperture in a spacer member 40 which fits closely within the tube 10 and is retained on the tube 18 by a star fastener 42. Located between the spacer 40 and the shoulder 34 of the end plug 12, and received freely within the tube 10, is a further cylindrical tube 44 which accommodates the entire spring 30.

The tube 44 has an internal diameter less than the external diameter of the major portion of the spring 30 in the unstressed state of the latter. The spring 30 must therefore be pre-tensioned, during assembly of the end fitting, by rotating the end plug 12 relative to the end part 11 (in such a sense as to wind up and add more coils to the spring 30 whilst at the same time reducing its diameter) until the spring 30 is small enough in diameter to allow the tube 44 to be slid over the spring, the spacer 40 and star fastener 42 being thereafter fitted. Upon release of the end plug 1 2 relative to the end part 11, after such pretensioning, to allow relative rotation under the action of the spring 30, such relative rotation will cease when the coils of the spring 30 are engaged with the internal surface of the tube 44, i.e. while the spring is still tensioned.As a result, a roller blind having the roller construction described can be fitted without any need for pre-tensioning when the blind is installed in a window opening or the like, although it will be clear that, if desired, additional pre-tensioning may be applied when the blind is so installed,in the usualy manner, i.e.

by drawing the blind off by the roller against the action of the spring 30 followed by removal of the roller from its brackets, winding of the blind manually on the roller and re-fitting the roller to its brackets.

Should it occur that, as a result of excessive pre-tensioning of the spring 30 at the point of installation of the blind, the end plug 12 is rotated to too great an extent with respect to the end part 11, the spring 30 is not broken or damaged as would be the case with conventional springloaded roller blinds but instead, as successive turns are added to the spring 30, since these turns are in abutting engagement with each other, the spring 30 is lengthened so that the element 34 is pushed progressively to the right in Figure 1 until eventually the grooves 36 are freed from the ribs 1 8a allow the spring 30 to unwind by rotation of the element 34 with respect to the tube 1 8.It has been found that in practice the spring 30, once the element 34 has been freed in this fashion from the ribs 18a, will relax to the state in which the coils in the intermediate portion of the spring are in engagement with the tube 44. Normally when the spring 30 has relaxed to this state the element 34 engages automatically over the crimped part of the tube 18 but even should this be prevented by reason oi the grooves 36 being out of alignment with ribs 18a, a very limited rotation of roller 10 with respect to member 20 will suffice to engage the element 34 over the ribs 36. Thus instead of the spring being broken the assembly is simply returned to the condition at which pre-tensioning in situ was commenced so that no damage has been done.

It will be appreciated that the provision of the tube 44 around the spring 30 as a means of maintaining a predetermined amount of pretensioning of the spring and the provision of the clutch arrangement constituted by element 34 and the crimped portion of the tube 18 are features which may be employed separately, i.e. a roller blind construction might have the clutch arrangement formed by the element 34 and crimped portion of the tube 18 but not the tube 44 around the spring or conversely might have the tube 44 around the spring but not the clutch arrangement formed by element 34 and the crimped portion of the tube 18.

The blind roller described herein with reference to the drawings is also described in, and is the subject of claims in, our co-pending Application No. 7902224 (201 3762 A).

Claims (4)

1. A roller blind comprising a blind roller mounted between two mounting brackets disposed at opposite ends of the roller, one end of said roller having an end fitting comprising a first member attached to one of said two mountings, a second member fitted to the roller body and rotatable with respect to the first member about the roller axis, a helical spring extending along said axis within the roller and having one end mounted so as to be normally non-rotatable with respect to the first member and the other end mounted so as to be normally non-rotatable with respect to the second member, whereby rotation of one member with respect to the other in one sense stresses the spring so that it exerts an opposing spring bias, and wherein a clutch is provided which is arranged to allow the first member to rotate relative to said bracket when the torque exerted by the roller via said first element exceeds a predetermined amount less than that required to damage the spring.

2. A roller blind according to claim 1 wherein said clutch is provided in said one of said mounting brackets which is attached to said end fitting, the c'lutch being arranged to allow first member to rotate relative to said bracket when the torque exerted by the roller via said first element exceeds a predetermined amount less than that required to damage the spring.

3. A roller blind according to claim 1 wherein said spring has one end fixed with respect to one of said members and is fixed at its other end to a first element co-operating with a second element fixed with respect to the other of said members, the last-mentioned elements together forming a clutch normally engaged so as to prevent relative rotation of said elements about the axis and disengageable by tensioning of the spring beyond a predetermined amount, the clutch being re-engageable after the rotation of said second member relative to the first member, and consequent reduction in the tensioning of the spring, brought about by disengagement of the last-mentioned clutch.

4. A spring-loaded end fitting for a roller blind roller, the fitting comprising a first member for attachment to a mounting, a second member for fitting to an end of the blind roller body and rotatable with respect to the first member about an axis which, when the second member is fitted to a blind roller body, corresponds to the longitudinal axis of the blind roller body, a helical spring extending along said axis, said spring having one end fixed with respect to one of said members and being fixed at its other end to a first element co-operating with a second element fixed with respect to the other of said members, the last-mentioned elements together forming a clutch normally engaged so as to prevent relative rotation of said elements about the axis and disengageable by tensioning of the spring beyond a predetermined amount, the clutch, being reengageable after the rotation of said second member relative to the first member, and consequent reduction in the tensioning of the spring, brought about by disengagement of the clutch.

4. A spring-loading end fitting for a roller blind roller, the fitting comprising a first member for attachment to a mounting, a second member for fitting to an end of a blind roller body and rotatable with respect to the first member about an axis which, when the second member is fitted to a blind roller body, corresponds to the longitudinal axis of the blind roller body, a helical spring extending along said axis, said spring having one end fixed with respect to one of said members and being fixed at its other end to a first element cooperating with a second element fixed with respect to the other of said members, the lastmentioned elements together forming a clutch normally engaged so as to prevent relative rotation of said elements about the axis and disengageable by tensioning of the spring beyond a predetermined amount, the clutch being reengageable after the rotation of said second member relative to the first member, and consequent reduction in the tensioning of the spring, brought about by disengagement of the last-mentioned clutch.

5. An end fitting according to claim 4 so arranged that after such rotation of said second member relative to the first member to reduce the tensioning of the spring, re-engagement of the clutch formed by said first and second elements occurs automatically.

6. An end fitting according to claim 4 or claim 5 wherein the clutch formed by said first and second elements is a positive engagement clutch disengageable by axial movement to a predetermined degree of said first element with respect to said second element, in consequence of tensioning of the spring by relative rotation of the first and second members, when said tensioning has exceeded a predetermined amount.

7. An end fitting according to any of claims 4 to 6 wherein the helical spring is so wound that in its unstressed state each turn lies against the adjacent turns, the sense of tensioning of the spring being such as to add to the number of turns in the spring and thus increase the axial length thereof with increased tensionsing, an increase in the axial length of the spring beyond a predetermined extent releasing said positive engagement clutch.

8. An end fitting according to claim 4 or claim 5 wherein the clutch formed by said first and second elements is arranged to disengage when the torque exerted between said first member and said second member via the spring exceeds a predetermined value.

9. An end fitting according to claim 8 including an axially extending component which is engaged by the coi!s of the spring when the latter has been tensioned to a predetermined degree, so that thereafter a substantial increase in torque applied via the last-mentioned clutch is required to produce even the slightest further rotational movement of said second member relative to the first member so that the actual torque at which the clutch slips or disengages is not critical.

10. An end fitting according to claim 9, in which said axially extending component is a cylindrical tube extending within the spring.

11. An end fitting according to any of claims 4 to 10 wherein an axially extending member is so disposed in relation to the spring, and so dimensioned, that relative rotation about said axis to the ends of the spring with respect to each other in a sense such as to reduce the tensioning in the spring and the torsional stressing of the spring is arrested by engagement of the coils of the spring with the surface of said axially extending member, as a result of radial movement of said coils with respect to the axis, before the fully unstressed state of the spring is reached,

12. A roller blind having an end fitting according to any of claims 4 to 11.

New claims or amendments to claims filed on

2.7.81.

Superseded claims 1-4.

New or amended claims:

1. A roller blind comprising a blind roller mounted between two mounting brackets disposed at opposite ends of the roller, one end of said roller having an end fitting comprising a first member attached to one of said two mounting brackets, a second member fitted to the roller body and rotatable with respect to the first member about the roller axis, a helical spring extending along said axis within the roller and having one end mounted so as to be normally nonrotatable with respect to the first member and the other end mounted so as to be normally nonrotatable with respect to the second member, whereby rotation of one member with respect to the other in one sense stresses the spring so that it exerts an opposing spring bias, and wherein a clutch is provided which is arranged to allow relative rotation of said ends of the spring in the sense corresponding to unwinding of the spring, without corresponding relative rotation between the roller and said bracket, when the stressing of the spring exceeds a predetermined amount less than that required to damage the spring.

2. A roller blind according to claim 1 wherein said clutch is provided in said one of said mounting brackets to which said first member is attached, the clutch being arranged to allow said first member to rotate relative to said bracket when said torque exerted by the roller via said first element exceeds a predetermined amount.

3. A roller blind according to claim 1 wherein said spring has one end fixed with respect to one of said members and is fixed at its other end to a first element co-operating with a second element fixed with respect to the other of said members, the last-mentioned elements together forming said clutch and said clutch being normally engaged so as to prevent relative rotation of said elements about the axis and said clutch being disengageable by tensioning of the spring beyond a predetermined amount, the clutch being reengageable after the rotation of said second member relative to the first member, and consequent reduction in the tensioning of the spring, brought about by disengagement of the clutch.