Window blinds

Abstract: A window blind fabric comprises a low melt component and a high melt component and is stabilized by a heat treatment, which comprises heating the fabric to melt only the low melt component. On cooling, the low melt component sets and stabilises the fabric. The fabric suitably comprises a yarn which in itself contains low melt staple fibres or filaments and high melt staple fibres or filaments.

Description: This invention relates to window blinds and to a method of making window blinds. The invention relates in particular to window blinds comprising yarn-based fabrics which are given a heat treatment to improve their shape stability, the heat treatment melting a first component but not a second component. Window blind fabrics require to be shape stable. This is difficult to achieve. It is particularly difficult to achieve with louvre blinds, in which the blind comprises a number of narrow vertical strips of fabric. If the fabric lacks stability the strips of fabric will twist or curve. Shape instability of window blind fabrics is aided by the high temperatures adjacent to windows. For this reason window blind fabrics, in particular louvre blind fabrics, are generally coated, to stiffen them, typically using polyvinyl chloride or polyvinyl acetate. The result is a fabric which feels like a synthetic polymer rather than a textile product. Furthermore, the coating process is expensive, the capital outlay on a production coating machine being very large. Moreover, the process is not always wholly successful; the blinds frequently have to be weighted at the bottom to additionally hinder twisting or curving. Conventional blind fabrics of the type described are not readily cleanable; they cannot be machine washed or dry cleaned. The synthetic coating, may degrade in the light conditions, causing yellowing. US-A-4309472 describes window blinds having flat textile slats. In an attempt to overcome problems associated with earlier methods of stiffening fabrics to be made into slats, by finishing or coating methods, it proposes making fabric slats from fabrics which are stiffened by application of heat for a short period, to induce plastification and shrinkage. DE-A-2018762 discloses stiffened fabrics made up of multi-constituent yarns and fibres. At least two different fibre components are employed having different melting points and heat treatment is effected, preferably at a temperature below the melting point of the high melting point component, but above that of the low melting point component In some cases fusion may occur. The resultant fabrics are said to be useful as stiffener materials in known applications in which stiffeners were previously applied, for example in waistbands for trousers, lingerie and foundation garments, or in the manufacture of shoes, blouses, collars or cuffs. According to a first aspect of the present invention there is provided a louvre window blind comprising a plurality of strips of woven fabric which comprises a yarn made up of a plurality of staple fibres or filaments, wherein said yarn provides a low melt component of the fabric, which low melt component melts at a temperature of at least about 110°C, the fabric further comprising a high melt component which is stable against melting or degradation at the temperature at which the low melt component melts but which undergoes heat setting at that temperature, wherein the temperature at which the high melt component melts or degrades is at least about 20°C above the temperature at which the low melt component melts, and wherein said yarn has about 20 to about 180 staple fibres or filaments per given cross-section and in that the low melt component comprises about 10 to 50 percent by weight of said yarn, the fabric having been subjected to a temperature above the melting point of the low melt component but below the melting or degradation point of the high melt component, so as to cause the low melt component to adhere to the high melt component, wherein the edges of the fabric strips are formed by heat cutting to cause melting and enhanced stability along the edges, and wherein the fabric strips are shape stable and stiff, relative to equivalent untreated fabrics, and resistant to humidity, but retain a textile feel rather than the feel of a synthetic polymer; and are water washable under normal domestic or commercial conditions, without shrinkage or stretching. The fabrics retain a textile feel rather than the feel of a synthetic polymer, which results from the present coating processes which are required with existing fabrics. Boil washing may generally be carried out without damage to the fabrics of the invention. The temperature at which the high melt component melts or otherwise degrades is preferably at least about 50 °C above the temperature at which the low melt component melts. Suitably, the temperature at which the low melt component melts is about 110°C to about 210 °C, preferably 130°C to about 180°C, most preferably about 150 °C to about 180 °C. In one embodiment the yarn for the fabric comprises a plurality of staple fibres or filaments in which the high melt component is present as a core and the low melt component is present as a sheath around the core. In another embodiment the tow melt and high melt components are arranged with one on one side of the fibres or filaments which make up the yarn and the other on the other side of the fibres or filaments which make up the yarn. In another embodiment the yarn for the fabric is made up of a plurality of staple fibres or filaments of the low melt component and a plurality of staple fibres or filaments of the high melt component, the arrangement within the yarn preferably being substantially random. Suitably, the low melt component comprises about 20 to about 50 percent by weight of the yarn. The low melt component could, for example, be polyvinyl chloride, polypropylene, polyamide, polyacetate, polyacrylic or polyester including partially oriented yield (POY) polyester, whereby an eventual fabric may shrink and densify on heat treatment. The high melt component could, for example, be polyacrylic, or polyester. The yarn for the fabric may be prepared in any available spinning or bulking process. Thus; the yarn may be produced, for example, by semi-worsted ring spinning (plain and fancy); cotton ring spinning; woollen ring spinning; worsted ring spinning: open and/break spinning/rotor spinning; paraffil wrap-yarn systems; hollow spindle systems; dreft spinning systems; and the Repco system. A suitable fabric for use in a window blind in accordance with the invention, incorporating a yarn comprising a low melt component, may be made wholly from that yarn, or that yarn may be present as one of a number of yarns used in the fabric. For example, the warp or the weft only of a woven fabric may comprise such a yarn, and not all of the warp or weft need be constituted by such yarns. Preferably, however, substantially all of the yarn of the fabric comprises a low melt component. The fabric is cut to shape, using a heat cutting technique this will cause melting and enhanced stability along the edges. The fabric may comprise one or more low melt components, and one or more high melt components. The fabric may be produced by any yarn-based method, for example weaving, warp laying, warp knitting or weft knitting. Weaving is preferred. In accordance with a further aspect of the invention there is provided methods of making a window blind as defined above the method being as defined in Claim 7. A heat treatment is employed which causes heat setting of the high melt component. Such a heat treatment may be a step additional to the heat treatment which melts the low melt component, or one step may cause both effects. The heat treatment described above may be achieved by any of the available methods, for example by means of hot air, preferably stentoring, whereby fabric is passed over gas burners, or by means of hot liquids, for example water under high pressure, or by contacting the fabric with a hot object such as a hot roller (calendering), or by treatment with a hot vapour, for example, steam or an organic vapour. The invention is used in the context of louvre blinds, where the demands on the narrow, vertical fabric strips, in particular in terms of their stabliity, are extreme. Fabrics used for the window blinds of the invention can be porous or non-porous, the latter being achieved without the need for further treatment if a fine fabric structure is produced. Fabrics used for the window blinds preferably include a flame resistant yarn, which may be a yarn of inherent fire retardant properties, but will preferably be a yarn which has been treated for flame retardancy prior to weaving. Suitable flame retardant yarns are flame retardant polyacrylic yarns (modacrylic), for example yarns sold under the Trade Mark TEKLAN, and flame retardant polyester yarns, for example yarns sold under the Trade Mark TREVIRA CS. Alternatively or additionally, the fabrics may be treated to increase their flame resistance/fire retardance after weaving. The invention will now be further described, by way of example, with reference to the following Examples. EXAMPLE 1 A differential melt fabric for window blinds was produced from the following bland of polyester fibres: 20% TREVIRA (Trade Mark) type 252 bi-component (core-sheath) polyester in 3 decitex 50mm staple. The core of this material is of high melt polyester, and the sheath is of polyester which melts at about 150°C; 80% standard polyester in 6.7 decitex 100mm staple. This material has a melting point around 240°C. (a) FIBRE PREPARATION AND YARN SPINNING The fibres were blended together in loose fibre form on a blend bed which took it into an opening machine which started the first stage of the mixing or blending of the fibres. From the opening machine the first stage of the blended fibres was fed into a cyclone blender which further mixed the fibres by means of gravity, centrifugal force and air currents. The fibres at that stage were roughly mixed, but in no alignment to the axis of the web. By means of ducting and air currents, the roughly mixed fibres were fed into the hopper feed of the carding machine. This machine by means of pins mounted on different sized rollers, further blended the fibre types, while at the same time straightening them to some degree along the axis of the card sliver. The card sliver containing the fibre blend was then put through three stages of drawing which further blended the two fibre types and further aligned them along the axis of the slivers. This was achieved by putting six slivers into each drawing machine and reducing the sliver weight by a factor of six giving a final blending of 216 mixings (6 x 6 x 6). The final drawn sliver was fed into a ring spinrung machine which further drew out the silver during the spinning process. The drawn sliver was twisted into a yarn at this stage, and the resulting yarn was collected on a ring tube. The yarn was wound from the ring tube on to a cone through an electronic clearer which took out faults and imperfections in the yarn after the spinning. The yarn at this stage was a randomly blended mixture of the two components. (b) WEAVING The differential melt yarn thus produced was woven across an air textured, standard polyester warp (high melt - 240°C), on a rapier weaving machine. The grey cloth on table details of the fabric are: 54 ends per inch of 420 decitex air-textured polyester warp; 28 picks per inch of 125 decitex differential mount fibre yarn as described above. Fabric width was 72.5 inches. (c) FINISHING The fabric was fed into a pin stentor machine for heat treatment. The machine had seven bays and the temperature of each bay was 150° C. The fabric speed was 10 metres per minute and the fabric was treated at 150°C for five minutes. The appearance of the fabric had not changed and the handle of the fabric was still textile in character. The fabric had, however, become much firmer. The full width fabric was slit into strips for vertical louvre blinds using heated cutters and was found to be fully stable when tested under a wide range of conditions, being very resistant to curving, cupping and twisting, even in high humidity and at high temperature. The full width fabric was trimmed at the edges and tested for roller blind use and it too was found to be fully competent in meeting the requirements of that use. In a further test the same material and the heat treatment was carried out at 180°C. The resulting fabric was also excellent, textile in handle but a stiffer fabric than that treated at 150°C FURTHER EXAMPLES By similar methods the following heat-stabilised fabrics were produced. The heat teatments were carried out at 180 °C, unless otherwise stated. Standard polyester/polyvinyl chloride (low melt component) 75/25 percent wt - weft only. Standard polyester/polyvinyl chloride - 66/34 percent wt - weft only. Standard polyester/polypropylene (low melt component)- 75/25 percent wt - weft only. Standard polyester/polypropylene- 60/40 percent wt - weft only. Standard polyester/low melt polyester- 66/34 percent wt - weft only. Polyester TREVIRA 252 (low melt component)-/polyester TREVlRA CS (flame retardant, high melt component) 72/28 percent wt - warp and weft. This fabric was finished as described above, on a five bay stentor, at 190°C. The finished fabric was slit using a machine with heated slitters, to seal the edges. Samples of the slit fabric were tested by washing In a household washing machine, for ten cycles on a "fast coloureds" setting. No effect on the fabric stability, feel or appearance was measured or discernable. Further samples of this fabric were sent for testing for flame retardancy at a testing laboratory. They were tested to British Standard Part 2 Type C and were passed. Further samples were tested for flame retardancy using French Standard Afnor tests, and the pass classification was to the highest standard, that of M1. All of the above examples resulted in the production of stable fabrics of textile rather than synthetic polymer character. The fabrics are water washable, in normal domestic equipment, at high temperatures.

Claims: A louvre window blind comprising a plurality of strips of woven fabric which comprises a yarn made up of a plurality of staple fibres or filaments, wherein said yarn provides a low melt component of the fabric, which low melt component melts at a temperature of at least about 110°C, the fabric further comprising a high melt component which is stable against melting or degradation at the temperature at which the low melt component melts but which undergoes heat setting at that temperature, wherein the temperature at which the high melt component melts or degrades is at least about 20°C above the temperature at which the low melt component melts, and wherein said yarn has about 20 to about 180 staple fibres or filaments per given cross-section and in that the low melt component comprises about 10 to 50 percent by weight of said yarn, the fabric having been subjected to a temperature above the melting point of the low melt component but below the melting or degradation point of the high melt component, so as to cause the low melt component to adhere to the high melt component, wherein the edges of the fabric strips are formed by heat cutting to cause melting and enhanced stability along the edges, and wherein the fabric strips are shape stable and stiff, relative to equivalent untreated fabrics, and resistant to humidity, but retain a textile feel rather than the feel of a synthetic polymer; and are water washable under normal domestic or commercial conditions, without shrinkage or stretching. A louvre window blind as claimed in Claim 1, wherein the low melt component of the fabric comprises polyvinyl chloride, polypropylene, polyamide, polyacetate, polyacrylic or polyester, and the high melt component of the fabric comprises polyacrylic or polyester. A louvre window blind as claimed in claim 1 or 2, wherein the low melt component of the fabric melts at a temperature in the range about 130°C to 190°C. A louvre window blind as claimed in any preceding claim, wherein substantially all of the warp and/or weft yarn of the fabric thereof comprises the low melt component in association with the high melt component. A louvre window blind as claimed in any preceding claim wherein the yarn of the fabric includes a flame resistant component. A louvre window blind as claimed in any preceding claim, wherein the fabric thereof is not coated with any composition to increase its stiffness or stability. A method of making a louvre window blind, as claimed in any preceding claim, the method comprising: weaving a fabric sheet which comprises the yarn; subjecting the fabric sheet to a temperature above the melting point of the low melt component and above the heat setting point of the high melt component but below the melting or degradation point of the high melt component, to cause the low melt component to adhere to the high melt component and to cause heat setting of the high melt component; subjecting the fabric sheet to a temperature below the melting point of the low melt component, to cause the low melt component to set; forming the fabric sheet into a plurality of said fabric strips by heat cutting to cause melting and enhanced stability along the edges thereof; and incorporating the fabric strips into window blind hardware to make said louvre window blind.

Inventors: POOLE PHILIP JOHN, POOLE, PHILIP JOHN
Applicants: POOLE PHILIP JOHN, POOLE, PHILIP JOHN
Application year: 1989
Main classification: E06B9
IPC codes: E06B9, D02G3