GB2470196A

GB2470196A - Ribbed sheet

Info

Publication number: GB2470196A
Application number: GB0908141A
Authority: GB
Inventors: David Goodwin
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-05-13
Filing date: 2009-05-13
Publication date: 2010-11-17
Also published as: GB0908141D0

Abstract

A method of manufacturing a sheet 1, preferably self-rolling sheet that if unrestrained will tend to roll itself back up, the method comprising the steps of: a) forming a sheet of plastic with an array of parallel ribs 1b, each linked to an adjacent rib by a thinner web portion 1a of the sheet; b) folding the sheet at the webs, in one direction relative to a roll, such that the material in the web area is deformed plastically, preferably inducing a curl into the sheet such that it will roll up. The sheet may be used in a roller blind. Also claimed is a roller blind with an elastomeric tensile rod which biases the roller to its rolled state. The webs may also be folded such that the web or hinge becomes flexible with a series of living hinges that allow the sheet to be rolled and unrolled and be relatively stiff in its flattened state.

Description

Roller Blind/ Screen

Field of the Invention

The present invention concerns improvements in and relating to roller blinds! screens and the like. Inter alia the present invention provides a new method of manufacturing a resiliently self-rolling sheet that when rolled up into a compact cylinder! roll form can be unrolled into a flat sheet form and if unrestrained will tend to roll itself back up. The method can also be varied for use to manufacture a sheet that is not necessarily self-rolling but can maintain its extended flattened state and yet may roll up easily to a compact form. The sheets can be used for roller blinds or a wide range of other applications

Background to the Invention

The conventional roller blind is normally manufactured from a sheet of textile fabric which is wrapped around a roller or opposing spindles. In the most basic blinds the rollers simply have pull cords or a chain loop that the user pulls to manually rotate the roller to roll or unroll the blind. If not also spring-loaded these fabric blinds are generally limited to vertical situations whereby the weight of the material keeps the blind flat.

In the better roller blinds the roller is spring-loaded to roll up the material around the roller. A spring mechanism also provides tension to keep the blind flat when used in orientations which might cause the fabric to sag, e.g. horizontal applications such as a conservatory roof or sky-light or hatch on a boat. Where a spring mechanism is provided, since the spring biases the roller to rotate to close the blind, a means of locking the blind in the desired position is normally provided. This is generally a ratchet housed in or on the roller or a friction, magnetic or mechanical means between the leading edge of the blind and the frame or other opposing part.

A more recent development is the introduction of blinds of resiliently self rolling sheets. Tensioned roller blinds formed from resiliently self rolling sheets can be more compact than roller blinds with spring-loaded rolling mechanisms and cheaper to manufacture. However, a common method for making these is to use an expensive shape-memory material such as MYLAR tm that is heated, coiled and cooled in the coiled state to pre-io tension it to that state. Examples of this are illustrated in US patents: US 3426115, US3195616, US 3687328, US3311160, US 5332021 and US 6435254. In other manufacturing methods a laminated sheet structure is made with layers of differing extent of stretch, as in US patents: US4809760 and US 4433711, US 4848437, US 5176774 and US 5443923.

It is an object of the present invention to provide an alternative to the existing methods of forming resiliently self rolling sheets for roller blinds and which may enable roller blinds to be made cheaply and to be optimally compact suitable for use in space-restricted locations.

One specific object application is for use as a blind system for boat hatches and port lights and in particular a system that provides both a blind and insect screen in one unit. The current arrangements for this consist of two opposing spring-loaded roller blinds attached together at their leading edges by magnets or other means and whereby the re-wind forces are balanced and the blinds rolled/unrolled so that the respective amount of shade and insect blind can be adjusted. The two cannot, however, be used simultaneously in an overlaid state and the arrangement cannot readily be departed from with the existing technology due to the limited pace available.

Sum mary of the Invention According to a first aspect of the present invention there is provided a method of manufacturing a resiliently self-rolling sheet that when rolled up into a compact cylinder! roll form can be unrolled into a flat sheet form and if unrestrained will tend to roll itself back up, the method comprising the steps of: a) forming a sheet of plastic with an array of substantially mutually parallel ribs each rib linked to an adjacent rib by a thinner web portion of the sheet; b) folding the sheet at the webs, in one direction relative to a roll, (ie clockwise or anti-clockwise), such that the material in the web area is deformed plastically and the angle of at least one rib, with respect to the previous rib is changed from being in-line to an inclined angle when the sheet is in stasis, thereby inducing a curl into the sheet such that it will roll is up. Preferably substantially each and every rib is inclined with respect to the previous rib.

The sheets can be used for a wide range of applications including: window blinds; doors! access covers; screens such as space dividers! partitions, pull-down advertising panels, projection screens etc. Indeed, the invention has a rriyriad of other uses such as, for example, as tree guards for the base of saplings whereby the roll is opened to allow it to enclose the trees and protect it against animals but the tube is able to expand as the tree grows. For doors and cupboards it can be used to cover a door frame!aperture that can then be rolled up or sideways to allow access.

Tubular and curved forms can be made from flat panels that can have an array of applications. For example, the tightly rolled material can be unrolled and then wrapped around an object. The inherent spring in the material will close' the roll until it fits tightly around the object, an example of this being the afore-mentioned tree guard.

A sheet can be fabricated to include one or more rigid panel lengths in addition to the self rolling panel length so that the rolling/hinging is limited to specific zones.

It is also possible to fold the sheet locally and fix it to create a rigid tube around which the rest of the sheet can be rolled. For example this could be used as a room divider, which can be rolled up for storage or unrolled for use with one vertical or two opposing vertical ends being formed into rigid tubes which provide added stiffness and the ability to be self-supporting.

In a second aspect of the invention, webs/hinges can alternatively be elastically deformed such that the web/hinge becomes totally flexible This creates an array of parallel living hinges which enable the sheet to be rolled and unrolled and to stay in either orientation or anywhere between is without application of external force. A number of such living hinges could, if desired, be used in combination with a number of resilient-rolling hinges of the first aspect in one sheet.

Various levels of stiffness can be induced into the hinges such that the sheet is either very flexible with little resistance to be rolled/unrolled or such that the sheet naturally wants to roll up into a tight scroll or cylinder or anywhere between the two extremes. The amount of stiffness can be determined by the relative thickness of the web relative to the adjacent ribs, the cross section of the rib, the physical properties of the original plastic material and the amount of strain imposed on the hinge during processing.

A key advantage is that the sheet is relatively stiff in flat form, but can be easily rolled up into a tight cylinder for storage. This can be achieved by applying an in-line force to the leading edge of the blind, i.e., pushing the leading end back toward the fixed end which causes the sheet to automatically roll up into a cylinder.

If the hinges are relatively stiff and are folded so that they try to recover to their curled form, as described above, the sheet will easily self-roll into a scroll. There will be a resistance when the sheet is being un-rolled. If the hinges are very flexible, the sheet will both roll and unroll with little resistance.

The roll can be housed within a simple guide or guides that help to form the sheet into a cylinder when being rolled. This could be a simple tube with a slot to allow the leading edge of the blind to be unrolled/rolled. The insides wall of the tube guides the fixed' end into a cylinder. Rollers or any other guide or guides could be used.

If the sheet is designed to self roll, it is preferable that the sheet will either be run in a track or guides to keep the unrolled sheet flat (the free end will attempt to roll up) or the free end may instead be fastened down.

Preferably the material is polypropylene or polyethylene, both being suited is to form a reliable living hinge or resilient hinge when the material is locally thinned and then folded.

The process of cutting, creasing or indenting the sheet forms and/or compresses the remaining plastic to a pre-determined thickness. Where the strain induced is greater than the yield of the plastic this will plastically distort the hinge (i.e. place it outside the elastic range and into the plastic range). When the hinge is folded, the random orientated molecules or fibres will be orientated across the hinge, which prolongs the life of the hinge and for optimum strength.

The sheet can be relatively thick and therefore stiff (in one plane and in both planes if the sides are retained to prevent buckling) which has a number of advantages over, for example, a fabric blind: 1. It is possible to apply a force to the leading edge so that the blind rolls up without the flat area buckling. This would be impossible with a fabric blind that would be far too flexible.

2. The material can automatically roll itself up without the need for a roller.

3. The material can span large horizontal apertures without significant sagging and therefore no tension system is required to keep the material taut. No system is required to retain the leading edge to keep the blind open in the desired position -the blind is simply unrolled to the desired amount and will stay in this position without assistance. (If the material is sprung to self-roll, the sides or the leading edge will need to be restrained).

For a combined sunblind and insect screen this provides a major advantage. Existing combined sunblind and insect screen designs, as discussed, have opposing spring tensioned fabric roller blinds, the insect screen is often a mesh sheet and the blind is an imperforate blackout sheet. The leading edge of each sheet has a handle to enable it to be unrolled, against the spring tension and, to prevent it from returning, the is opposing handles can be connected together so that the spring force in each sheet is balanced by the opposing one. This enables the sunblind and insect screen to be opened or closed to the desired degree of opening but as one is moved the other, if connected, rolls in the opposite direction.

It is therefore not possible to have the insect screen fully open and for the sun blind to be in any position as each can only move in a direct and opposing relationship -the sun blind will be fully closed if the insect screen is fully open. It is not possible to have maximum ventilation with the insect screen fully open and the aperture screened by the sunblind.

Ventilation is of particular concern in boats and similar environments where fresh air at night aids comfort. However, with the new sheets of the present invention the sun blind can be mounted either in front or behind the insect screen as it does not need to cooperate with the insect screen as there is no powerful spring trying to re-roll it. Therefore the insect screen can be fully extended (the only required position) and the sunblind can be opened to the amount required.

Another application is for shading of greenhouse, conservatory and other non-vertical windows whereby the relative rigidity of the material has very substantial advantages over fabric roller blinds. It is not necessary to tension the blind to keep it taut, one or more thin wires could be tensioned under the window and the blind mounted so that the material lies on top of the wire. At the fixed end a motor could be incorporated into the enclosure in which the blind is mounted or onto the fixing bracket.

The motor could have a wheel with teeth that engage into holes die cut along the blind edge. When the motor rotates the toothed wheel, the blind io will be driven up or down, depending on the direction of rotation. Therefore a low cost fully automated blind is possible without the complexity normally associated with mechanised blinds. The inherent material stiffness means that it is possible to stop the blind in any position; there is no tension and no need for any fixings or controls at the free end. The motor could be is linked to a sensor that controls the blind position, relative to climatic conditions: sunlight, heat gain etc.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation view of a sheet! panel of a first preferred embodiment of the invention; Figure 2 is a close-up side elevation view of a variant of the sheet of figure 1 that has a triple layer laminated construction with a blackout material (black layer) as the central layer; Figure 3 is a perspective view from above of the sheet of Figure 1 or 2 partly unrolled to its extended flattened state and Figure 4 is a corresponding view of the sheet fully unrolled; Figure 5a is a frontal perspective view from one end that shows a self-rolling blind housed within an enclosure whereby the internal profile encourages the blind to roll up when the blind's leading edge is pushed towards the enclosure, and Figure 5b is a side elevation view thereof; Figure 6 is a perspective view of a blind with a die cut hole at the leading end which can be hooked over an attachment point to secure the blind to the aperture (window, door etc) frame.

Figure 7 is a perspective view of a blind with punched holes along the lateral edges which engage with a toothed wheel to be driven io Figures 8a and 8b are side elevation views that show how the fixed end of the sheet can be made into a tube by folding the webs, part-rolling and permanently fixing the material of the sheet to itself. Figure 8c is a perspective view of the same.

Figure 9 is a perspective view from one end of the blind, showing a wall bracket that fits into the formed tube and allows the blind to rotate to roll or unroll.

Figure 10 is a plan view of a sheet with each hinge formed of intermittent slitting across the width of the sheet to provide resistance to buckling when rolling the blind. The interval between slits can be adjusted to suit the application.

Figures ha, llb and llc are side elevation views that show, respectively, ha a blade sequentially cutting each slit for a hinge from the upper surface, hIb a roller cutting a plurality of slits for the hinges and hIc a pair of blades or rollers, one or a set on each face of the sheet to cut slits on each face substantially simultaneously.

Figures 12a, 12b and 12c are end elevation views that show how a sheet can be used as a shower door where the sheet either rolls up or rolls around a track in the shower tray.

Figure 13 is a perspective view of the sheet used as a tree guard to enwrap the base of a sapling. The springy tube is unfurled and placed around the tree and is able to expand as the tree grows.

Figure 14 is a sectional view through a roller with internal rubber spring to assist rolling of the blind at the end that is attached to a fixing bracket that mounts the roller to a wall or other surface so that the rubber tension rod is twisted when the roller is rotated.

Figure 15 is an exploded assembly view of the end of the roller of Figure 14.

io Figure 16 is a further sectional view through the Figure 15 fixed! ratchet adjustable end of the roller.

Figure 17 is an exploded assembly view of the free end of the roller.

Description of the Preferred Embodiments

Referring firstly to Figure 1, this shows a moulded plastics sheet I of a first is preferred embodiment of the invention that has been formed or treated to have an array of parallel slots, creases or cuts which define thin section zones! webs 1 a of the sheet that will function as hinge lines. Between the slots, creases or cuts the material of the sheet remains relatively thicker and the thicker areas can be regarded as an array of parallel ribs lb each separated from an adjacent rib lb by a web la.

The preferred method of making the sheet 1 is to crease or cut! incise a pre-extruded! pre-manufactured sheet of a plastics such as polypropylene.

The sheet suitably has a typical thickness of around 0.1 to 2.0mm.

However, this is only a guide and the sheet thickness will depend on a number of factors such as the overall size and particularly the length, available space, required rigidity and memory etc. The cutting or creasing or deformation operation leaves the thin web 1 a between each rib' 1 b that enables each rib 1 b to hinge relative to the adjacent rib 1 b and therefore roll and unroll. Once the crease or slit is made, the hinge is folded to impose the desired strain.

The webs 1 a can be formed in a number of ways. The material may be slit by cutting blade that cuts into the material to a pre-determined depth -leaving the required material to form the hinge and with the added option of forming the cross section of the web la into the desired shape, i.e. radiusing the corners to reduce stress and therefore potential failure. The blade can be mounted on a machine that feeds the original material past the cutting blade so that parallel slits/creases are made at the required spacing -linked to the cycle of the blade. A second operation, in the same cycle, can fold each crease/slit so manufacture can be fully automated.

The shape of the blade can be designed to slit the material or displace it to form the web la. One or more blades may be used simultaneously.

The blade structures may alternatively be replaced by structures that are pressed into the material or ultrasonic horns that soften and displace the material. A preferred such latter method is to use an ultrasonic blade that locally melts or displaces the material and forms the web la/ hinge section. It is possible to use two horns' so that each side of the material is deformed and the hinge section is aligned with the centre of the material.

This method has a particular extra advantage when using a plastic sheet that is of laminated form incorporating an extra layer of dense material to provide additional blackout properties.

Referring to Figure 2, the laminated form of the sheet suitably has a thin layer of dense/opaque material 2 at the core, i.e. a black layer, sandwiched between lighter, more decorative layers 3, 4 above and below. It is therefore possible to deform the outer layers 3, 4, leaving mainly the blackout material layer 2 at the hinge/ web la intact for effective sun blockage.

Referring to Figures lib and lic, the multiple hinges la could be formed at the same time, two examples are: a) the sheet is passed under a roller ii or through a pair of rollers; or b) one or both rollers 5 have a series of blades 5a spaced at the desired hinge pitch, which indent or cut the sheet to the required depth.

As in Figure lic, a panel 6 with a series of parallel blades 6a may be placed on top or below the sheet 1 and the panel 6 and sheet 1 passed through a roller/press so that the roller/press forces the blades 6a into the sheet 1. This method is commonly used to make cardboard boxes and the machine is called a rotary press.

Referring to Figure 10, it is also possible to form the webs la so that they are not continuous across the width of the sheet 1 but intermittent -a small amount of virgin material being left or the depth of the web la reduced locally ic at intervals across the width. This will stiffen the sheet 1 locally and will reduce any tendency of the sheet 1 to buckle when attempting to roll up the sheet 1 by pushing on the leading edge. The interval between is slits can be adjusted to suit the application.

Another method of manufacture is to form the hinges during manufacture of the original material. The material is typically made by extrusion and it is possible to design the extrusion die with details to form the webs la or to have a secondary operation, immediately after the extrusion die, which will form the webs la by rolling, or similar operation whilst the material is still warm.

The sheets 1 can be cut, scored, moulded or extruded on one or both sides to create the alternating webs la (thin) and ribs lb (thick); and then the sheets 1 can be folded at the webs la to an angle of 180 degrees or less and the folding process strains the material in the web Ia. The folding can be undertaken sequentially and can be performed hot' or cold in order to set the angle of the web la relative to the adjacent rib lb. As folding of the webs la is continued, the sheet 1 will form into a scroll with the free end being guided within the previously formed ribs lb and webs la, i.e. within the initial 360-degree roll.

As discussed, the setting angle of the web la and the amount of strain imposed will affect the stiffness and memory. It is possible to bend the web la 180 degrees so that its new angle at stasis may be 90 degrees (allowing for spring back). This will encourage the sheet 1 to self-roll into a tight scroll as each web la tries to recover to the setting angle from being inline when unrolled. The actual angle will be determined by the roll diameter and where the position of the web 1 a is in the sheet 1-the closer to the centre, the smaller the diameter of the roll and the tighter the angle.

It is also possible to print the sheet 1 on one or two faces to enhance the blackout properties or to include a pattern or other graphical treatment.

The correct inks must be used to ensure flexibility and resistance to cracking! delamination.

Not all applications will require blackout properties and some may require a transparent or translucent material.

Blind/Screen Fabrication As discussed, the sheet 1 can be processed to have significant spring so that it automatically rolls itself up or the hinges! webs la designed to have greater flexibility and less memory but easier to roll into a tighter roll -less friction between layers as one layer has to slide over the adjacent layer during the rolling and un-rolling.

Referring to Figures 5a and 5b, these show a self-rolling blind 10 comprising the sheet 1 housed within an enclosure 11 whereby the internal profile of the enclosure 11 encourages the blind to roll up when the leading edge of the sheet 1 is pushed towards the enclosure 11.

In essence this provides a very simple method of fabricating a sunblind/screen from the sheet 1. As can be seen, the enclosure 11 has an elongate slot ha to enable the sheet 1 to be unrolled and extended from the enclosure 11 and then retracted by pushing the material back through the slot ha. The enclosure 11 may, as illustrated, be a tube with a slot ha running down one side or formed by mounting two or more separate components together to form the desired internal shape to encourage the sheet 1 to self-roll.

If required, the fixed' I roller end of the sheet 1 may be formed into a rigid tubular core by folding and then fixing the end folds. This will help rolling and this integral tube can be used to stop the end from coming through the enclosure slot ha thus the blind cannot be pulled completely out of the enclosure. Figures 8a and 8b show the fixed end of the sheet 1 being made into a tube by folding and permanently fixing the sheet 1 to itself.

io The end can be permanently fixed in this configuration by welding, adhesive bonding! use of double-sided adhesive tape or any other suitable means. This configuration replaces the need for a separate roller. The terminal creases can be designed to optimise the resultant tube for the application. This approach can also be used to create rigid zones for other is structural applications, for example, to enable the sheet to be self-supporting if vertically orientated.

A wall bracket 12 may be fitted into the formed tube as shown in Figure 9 and allows the blind to rotate to roll or unroll.

The blind may also be provided with a die cut hole 13 at the leading end which can be hooked over an attachment point 14 to secure the blind to the door or window frame, as illustrated in Figure 6. This can be used, for example, to ensure that the blind remains parallel to the window in the case of a portlight in the cabin of a boat whereby the movement of the boat will cause the portlight to move to and fro whilst the blind will tend to remain vertical. The blind can be hooked at its base to one or more fixing points at the base of the portlight. At the leading edge, a handle can be incorporated for pulling or opening the blind. This may be a simple finger or hand hole that is die cut or the end section may be folded back on itself to form a raised portion and then permanently attached by a welding!bonding!mechanical faster!interlock feature or a separate handle could be fixedly attached.

The blind can be modified readily for motorised or remote operation.

Figure 7 shows the blind with punched holesl5 along the edge of the sheet I which engage with a toothed wheel 16 which can be used to drive the blind open and shut. It can be used vertically or horizontally, the wheel can be motor or manual driven and if horizontal or angled, i.e. a conservatory roof, one or more tensioned wires will support blind.

As regards the roller end of the blind, this need not be an integrally formed roller. The fixed end of the blind may be attached to a separate roller -rod or tube -around which the material can roll. The ends of the roller may be mounted so that they can rotate but retain the end of the blind. With this arrangement it is possible to incorporate a spring within the roller so that it is tensioned when the blind material is pulled out. The spring will help the roller retract the blind material when being closed.

Referring to Figures 14 to 17, the illustrated preferred roller 17 is a tubular roller with an elastomer! rubber! elastic material, here referred to as an elastomeric torsion/tension rod 18, housed within the tube. The torsion/tension rod 18 is held at a free end of the roller 17 in a collet 19 locked to the roller 17 to twist with it as the roller 17 turns. At the other end of the roller 17, the end illustrated in Figure 15, the rubber tension rod 18 is attached via a further collet 21, a ratchet washer 22 and ratchet 23 to the mounting bracket 20 that mounts the roller to a wall. When the roller 17 is rotated, the torsion/tension rod 18 will be wound up and will store energy. It will also shorten in length. This shortening is used to hold the roller 17 and bracket assembly 20 together.

The mating ratchet arrangement comprising the ratchet washer 22 and ratchet 23 is incorporated into the design of the collet 21 and mounting bracket 20 at the fixed end of the torsion rod 18 so that the tension in it can be adjusted by simply rotating the collet in the bracket. The spring 18 will pull the ratchet 23 into engagement, thus preventing the spring 18 from unwinding. It is a simple matter to adjust the pre-tensioning of the spring! rubber tension rod 18 by rotating the collet 21 relative to the is bracket 20 with a tool or simply pulling the collet 21 out of ratchet-engagement and rotating it by hand and then re-positioning it. As the sheet I does not require a high spring force to keep it taut or for rewinding, the force is relatively light and therefore the use of a rubber tension rod 18 is acceptable from a stress point of view. However, a conventional spring arrangement can also be used.

It is not necessary to house the blind in an enclosure. The material can be formed with it's own integral fixing tube or attached to a separate roller.

With the former, a pair of brackets could be used to retain the integral tube to a fixing point. These may simply be a pair of opposing spigots, one end fits into the tube and allows the tube to rotate and the other attached to the mounting surface. With the latter, the roller may be mounted in a pair of brackets that allow the roller to rotate.

The sheet can be used for doors for a wide range of different purposes. In is examples the sheet could be used as a door to a cupboard or even for a shower cubicle. Figures 12a, 12b and 12c show how a sheet I can be used as a shower door where the sheet either rolls up or rolls around track in a shower tray.Being plastic, the material is inherently water and rot proof. The material could be used in a vertical orientation with the hinges running vertically. The door could be designed to roll up into a cylinder or to run around a track as per a tambour door. The advantage over a traditional door is compactness and it is suitable for installations where space is very tight.

For other uses of the technology to make any chosen structure/container/three dimensional form, it is easy to introduce creases, slots and holes into the unrolled material by die cutting or machining.

These features, particularly creases, could be at an angle to the hinges so that a flat sheet could be folded. The fold will then stiffen the material preventing it from rolling up. The structure/component can then be transported and stored in a compact roll or rolls and then unrolled and folded into shape on site etc

Claims

Claims 1. A method of manufacturing a rollable sheet that when rolled up into a compact cylinder! roll form can be unrolled into a flat sheet form, the method comprising the steps of: a) forming a sheet of plastics with an array of substantially mutually parallel ribs each rib linked to an adjacent rib by a thinner web portion of the sheet; b) folding the sheet at the webs such that the material in the web area is deformed creating an array of parallel hinges which enable the sheet to be rolled and unrolled.
2. A method as claimed in claim 1, wherein in step b) the webs are folded in one direction relative to a roll, (ie clockwise or anti-clockwise), such that the material in the web area is deformed plastically and the angle of at least one rib, with respect to the previous rib is changed from being in-line to an inclined angle when the sheet is in stasis, thereby inducing a curl into the sheet such that it will roll up.
3. A method as claimed in claim 1, wherein in step b) the webs are folded such that the material in the web area is deformed elastically such that the web/hinge becomes totally flexible creating an array of parallel living hinges which enable the sheet to be rolled and unrolled and which enable it to stay in either state or anywhere between without application of external force, the sheet being relatively stiff in its flattened state.
4. A method as claimed in claim 1, 2 or 3 wherein substantially each and every rib is folded to be inclined with respect to the previous rib.
5. A method as claimed in claim 1 or 2, wherein the sheet is fabricated to include one or more rigid panel lengths in addition to the self rolling panel length so that the rolling/hinging is limited to specific zones.
6 A method as claimed in any preceding claim, wherein the sheet is folded locally and fixed to create a rigid tube around which the rest of the sheet can be rolled.
7. A method as claimed in any preceding claim, wherein the relative thickness of the web relative to the adjacent ribs, the cross section of the rib, or the amount of strain imposed on the hinge during processing are selected to provide a desired level of rolling! unrolling stiffness of the sheet.
8. A sheet formed by a method as claimed in any preceding claim.io
9. A roller blind formed from a sheet as claimed in claim 8.
10. A roller blind as claimed in claim 9, wherein the blind is configured to be rolled up by applying an in-line force to the leading edge of the blind, i.e., pushing the leading end back toward the fixed end.
11. A roller blind as claimed in claim 9 or 10, wherein the sheet is is housed within a guide or guides that help to form the sheet into a cylinder when being rolled.
12. A roller blind as claimed in claim 9, 10 or 11 as dependent on claim 2, wherein the sheet runs in a track or guides to keep the unrolled sheet flat (the free end will attempt to roll up) or the free end is instead fastened down.
13. A sheet as claimed in claim 8 wherein the sheet is of polypropylene or polyethylene.
14. A method as claimed in any preceding claim, wherein the step of deforming the plastics sheet comprises cutting, creasing or indenting the sheet to form and!or compress the remaining plastic to a pre-determined thickness.A roller blind as claimed in any of claims 8 to 12 in combination with an insect screen wherein the sheet of the sunblind is mounted either in front or behind the insect screen whereby the insect screen can remain fully extended while the sunblind can be opened to any extent required.16. A roller blind as claimed in any of claims 8 to 12 for shading of greenhouse, conservatory and other non-vertical windows.17. A roller blind as claimed in claim 16, the blind having one or more thin wires tensioned under the window and the blind mounted so that the material lies on top of the wire.18. A roller blind as claimed in claim 16 or 17, wherein the blind is motorised.io 19. A roller blind comprising a sheet of plastic with an array of substantially mutually parallel ribs each rib linked to an adjacent rib by a thinner web portion of the sheet.20. A roller bind as claimed in any of claims 8 to 12 or 15 to 19, wherein the roller blind comprises an elastomeric tensile rod to bias the roller of the roller blind to its rolled up state.21. A roller blind as claimed in claim 20, wherein the roller of the roller blind is tubular and the tensile rod is housed within the roller.22. A roller blind wherein the roller blind comprises an elastomeric tensile rod to bias the roller of the roller blind to its rolled up state.23. A method of manufacturing a resiliently self-rolling sheet that when rolled up into a compact cylinder! roll form can be unrolled into a flat sheet form and if unrestrained will tend to roll itself back up, the method comprising the steps of: a) forming a sheet of plastic with an array of substantially mutually parallel ribs each rib linked to an adjacent rib by a thinner web portion of the sheet; b) folding the sheet at the webs, in one direction relative to a roll, (ie clockwise or anti-clockwise), such that the material in the web area is deformed plastically and the angle of at least one rib, with respect to the previous rib is changed from being in-line to an inclined angle when the sheet is in stasis, thereby inducing a curl into the sheet such that it will roll up.24. A method of manufacturing a rollable sheet that when rolled up into a compact cylinder! roll form can be unrolled into a flat sheet form, the method comprising the steps of: a) forming a sheet of plastic with an array of substantially mutually parallel ribs each rib linked to an adjacent rib by a thinner web portion of the sheet; b) folding the sheet at the webs such that the material in the web area is deformed elastically such that the web!hinge becomes totally flexible creating an array of parallel living hinges which enable the sheet to be is rolled and unrolled and which enable it to stay in either state or anywhere between without application of external force, the sheet being relatively stiff in its flattened state.