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(11) | EP 1 083 254 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Pull cord for blinds and method of making same |
| (57) A method of manufacturing a control cord for use in a covering for architectural
openings includes the steps of providing spools of high tensile strength and low abrasion
characteristic yarns, tensioning the yarns and winding the yarns under tension on
bobbins, placing the bobbins in a braiding apparatus and making an eight-carrier braid
from the yarns on the bobbins, and passing the braided cord through a treatment apparatus
where a urethane coating is applied to the yarns and heat cured. |
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates generally to pull cords used in coverings for architectural openings and more particularly to a braided pull cord and the method of making the cord.
Description of the Relevant Art
[0002] Most coverings for architectural openings, such as windows, doors, archways and the like, have an operating mechanism that is controlled by a flexible element that can be a fiber based cord, a beaded chain or the like. The control cord or the like typically depends from one end of a headrail for the covering and extends into the headrail through a friction brake and subsequently through carrier elements and around a plurality of pulleys and the like that are associated with the operation of the covering. As a result, the control cord is frictionally engaged at a number of locations and, depending upon the frequency of operation of the covering and the abrasiveness of the elements with which the cord comes into contact, the control elements can easily deteriorate.
[0003] In the case of fiber based cords, the abrasion caused by the various elements in which it comes into contact, causes rapid deterioration of the cords. Cords that have deteriorated have to be replaced and many operating cords in coverings for architectural openings are replaced on an annual basis. When the covering has been warranted, the replacement cost is borne by the manufacturer and, accordingly, the quality and longevity of control cords is a significant economic factor in the covering industry.
[0004] A typical fiber based cord used in coverings for architectural openings is braided from polyester fibers, with the cords typically including sixteen carrier fibers. After braiding of the cord, it is heat treated and wound on storage rolls before being incorporated into a covering product. The braid is relatively tight.
[0005] In trying to resolve the problem of rapidly deteriorating operating cords, applicants initially looked to the hardware of the system to remove any abrasive surfaces across which the cord had to pass. By redesigning various plastic molded parts and the parting lines in the plastic molds for the parts, the wear cycle was improved. The redesigned components were later coated with low friction materials such as Teflon® or zinc to reduce abrasion, but only marginal improvement was noticed. Further, the coatings tended to wear off over time and with exposure to UV light. Applicants then decided that the focus for improving the wear cycle of operating cords needed to be on the cord itself and it is to this end that the present invention has been made.
SUMMARY OF THE INVENTION
[0006] The cord of the present invention is made from high tensile strength fibers with low abrasion characteristics, such as polyethylene fibers. The fibers are braided in an eight-carrier braid that is wound under very high tension and ultimately finished with a urethane coating that is heat cured. The resultant product has provided a wear cycle of many times that achieved with state-of-the-art cords thereby almost removing the problem of manufacturers in having to record coverings for architectural openings. In accordance with the method for making the eight-carrier braid, high tensile strength fibers with low abrasion, such as might be polyethylene fibers, are wound under high tension onto yarn bobbins and eight of the yarn bobbins are then utilized in a conventional braiding apparatus to braid the cord. The braided cord is held under tension and passed through a two-stage heat setting process wherein a urethane coating is applied to the braided cord and the coating is heat cured in the final stage. After the second stage of heating, the cord is wound onto spools for storage until they are strung into coverings for architectural openings.
[0007] Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of a preferred embodiment, taken in conjunction with the drawings and from the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Fig. 1 is a block diagram illustrating the steps in the process of making the cord in accordance with the present invention.
[0009] Fig. 2 is a fragmentary diagrammatic isometric view showing yarn from which the cord will be braided being passed from supply spools under tension to bobbins.
[0010] Fig. 3 is a fragmentary isometric illustrating the bobbins carrying the yarns under tension and being positioned in a braiding apparatus and with the braided cord being wrapped on a storage spool.
[0011] Fig. 4 is a diagrammatic view showing yarn from storage spools being passed through a two-stage process for coating the yarns with urethane and heat curing the urethane on the yarn before accumulating the yarns on storage spools.
[0012] Fig. 5 is a fragmentary elevation showing the braided cord in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] The method of making a braided control cord for use in coverings for architectural openings in accordance with the present invention is illustrated in a block diagram in Fig. 1. It will there be appreciated that fibers or yarns from which the cord is to be braided are first unwound from spools on which they are supplied and then wound under high tension onto bobbins. From the bobbins, eight yarns are braided into a cord also under high tension and the braided cord is subsequently wound on a transfer spool. The cords are unwound from the transfer spools under tension and fed into a treating apparatus where they are coated with urethane and immediately heat cured in a two-stage process so that the urethane coating is dried and fully cured on the braided cords. After the coating has been heat cured, the yarn is stored on storage spools from which it can be removed when incorporating the cord into an operating mechanism for a covering for architectural openings.
[0015] With reference to Fig. 2, a device 10 for unwinding yarn 12 from preformed spools 14 of yarn is shown in series with a conventional tensioning apparatus 16 for the yarns and a conventional apparatus 18 for wrapping the yarns on bobbins 20 under tension. To provide even greater tension in the yarn than is provided by the conventional tensioning apparatus 16, the yarns are passed through an additional but conventional washer tensioner 21 before they are received by the tensioning apparatus 16. The device 10 for unwinding the yarn from the spools 14 can be seen to include a plurality of spindles 22 on which the spools 12 of yarn are disposed and the yarn is threaded through low friction ceramic guides 24 associated with each spool so that they can be passed individually to the washer tensioner 21 before passing on to the tensioning apparatus 16. In the tensioning apparatus, they are tensioned in a conventional manner with washer tensioners 25 so that the yarns 12 when passed down to the bobbins 20 are fed to and wound on the bobbins under tension. Each of the devices and apparatuses 10, 16 and 18 are conventional items such as manufactured by Ratera of Spain.
[0016] The yarns 12 have a high tensile strength in the range of 28-35 grams/denier, and preferably 30 grams/denier, and have low coefficients of friction, low abrasion characteristics and are durable from a flex fatigue standpoint. Examples of yarns that would be suitable for this purpose are Kevlar manufactured by DuPont in the United States, Nomex manufactured by DuPont, Twaron manufactured byAkzo of The Netherlands, Dyneema manufactured by DSM of Holland or Spectra manufactured by the Allied Signal Division of Honeywell, Inc., Petersburg, Virginia. The yarn or fibers are preferably polyethylene. The tension under which the yarns 12 are wound on the bobbins 20 is preferably in the range of 115 to 140 grams and desirably 120 grams.
[0017] Looking next at Fig. 3, the bobbins 20 with the yarn 12 wound thereon under tension, are placed in a braiding apparatus 26 of a conventional type such as of the type manufactured by Ratera of Spain. In the preferred embodiment of the invention, eight yarns are braided into a cord 27 and after braiding, wound onto a transfer spool 28. The denier of the yarns is preferably in the range of 275 to 375, which is greater than the denier of yarns typically braided into control cords, as can be evidenced by reference to Figs. 5 and 6, with Fig. 5 being a cord braided in accordance with the present invention and Fig. 6 a prior art braided cord.
[0018] The transfer rolls of braided cord are then operatively connected to a treatment apparatus 30 (Fig. 4) for final treatment of the cord. Each transfer spool 28 of cord is rotatably mounted on a bracket 33 on the upstream end of the apparatus 30 so that the cord can be fed into and through the treatment apparatus under tension via a conventional tensioner 34. The tension in the cord is preferably in the range of 150-200g, with 150 grams being ideal. In the apparatus, 30 the braided cord 27 is first fed through a chamber 36 where the cord is padded with a urethane coating that is applied to the cord. The chamber 36 is fed from a urethane reservoir 37. By way of example, the coating might be either sprayed onto the cord or the cord might be drawn through a bath of the urethane in order to apply the desired coating to the cord. The latter is preferred. Immediately after the cord is coated with the urethane, it is passed through a heating chamber or oven 38 where the urethane is dried. The temperature in the heating chamber 38 is preferably in the range of 120-140°C even though temperatures outside that range would work as it would primarily affect the drying time. Subsequent thereto, the cord is passed through another heating chamber 39 where the urethane is cured. The temperature in the curing chamber 39 is preferably in the range of 100-120°C even though, again, temperatures outside that range would work as the temperature primarily affects the curing time. The total time for drying and curing should ideally be in the range of 60-120 seconds, with 90 seconds being desired. After the cord 27 has been padded with the urethane coating and cured, the final braided cord is wrapped onto a storage spool 40 that is rotatably mounted on brackets 42 at the downstream end of the apparatus 34. When a predetermined supply of the braided cord 27 is wound onto the storage spool 40, the spool is removed and retained for later use in the assembly of a covering for an architectural opening. The apparatus 30 for treating the cord with a urethane solution and curing the cord is conventional and may be of the type manufactured by Andersson Mek of Sweden. The urethane solution is a mixture of urethane and water in a concentration of 10% urethane by volume. The urethane is miscible in/with water and preferably itself comes from the chemical family of polyester, polyether polyurethane dispersions and can come from various sources but a urethane marketed under the designation Baypret DLV Dispersion Corporation by Bayer Corporation of Pittsburgh, Pennsylvania, has been found suitable for the cord of the present invention.
[0019] A cord formed in accordance with the present invention and as illustrated in Fig. 5, has been found to provide a wear cycle that is approximately ten times that of conventional cords that are presently in use.
[0020] Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example, and changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.
1. A method of making a control cord for use in coverings for architectural openings
comprising the steps of:
providing a spool of high tensile strength yarn with the yarn havinglow abrasion characteristics,
removing the yarn from the spool and passing it through a tensioning device,
wrapping the yarn under tension on bobbins,
placing the bobbins in a braiding apparatus from which an eight-carrier braid is made, and
passing the braided cord through a treatment apparatus where a coating of urethane is applied to the braided cord and the cord is dried and heat cured.
2. A cord for use in a covering for an architectural opening made from the steps of:
providing a spool of high tensile strength yarn with the yarn having low abrasion characteristics,
removing the yarn from the spool and passing it through a tensioning device,
wrapping the yarn under tension on bobbins,
placing the bobbins in a braiding apparatus from which an eight-carrier braid is made, and
passing the braided cord through a treatment apparatus where a coating of urethane is applied to the braided cord and the cord is dried and heat cured.
3. The method of claim 1 or the cord of claim 2 wherein the yarn has a tensile strength
in the range of 28-35 grams/denier.
4. The method or cord of claim 1, 2 or 3 wherein the yarn is wrapped on the bobbins under
a tension in the range of 115 to 140 grams.
5. The method or cord of any preceding claim wherein the yarn has a denier in the range
of 275-375.
6. The method or cord of any preceding claim wherein the tension in the braided cord
when the urethane coating is applied is in the range of 150-200 grams.
7. The method or cord of any preceding claim wherein the cord is heat dried in a temperature
range of 120-140°C.
8. The method or cord of any preceding claim wherein the cord is heat cured in a temperature
range of 100 to 120°C after being heat dried.
9. The method or cord of any preceding claim wherein said urethane coating is a mixture
of urethane and water in a concentration of 10% urethane by volume.