Patent Publication Number: US-7216687-B2

Title: Cord tensioner

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to European patent application No. 03078359.1, filed 24 Oct. 2003, which is hereby incorporated by reference as if fully disclosed herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a cord tensioner for a cord-guided covering, such as a roller blind, pleated blind or venetian blind or a combination of such blinds, for an architectural opening, such a vertical or a slanted window (e.g., a roof window). 
     2. Description of the Relevant Art 
     Cord tensioners have been conventionally used to keep guide cords of window coverings taut. Tensioned guide cords have been particularly important in coverings for slanted roof windows to prevent the fabrics and slats of the window coverings from sagging downwardly away from the windows. Cord tensioners have served to keep movable head rails, intermediate rails or bottom rails from sliding, under their own weight, down the guide cords. In this regard, the cord tensioners have maintained sufficient tension in the guide cords, so that there is enough friction between the guide cords and the movable rails to prevent the rails from sliding down the guide cords. 
     Cord tensioners for window coverings have traditionally been made from common tension springs as described in U.S. Pat. No. 4,733,711 and U.S. Pat. No. 4,557,309. However, such tension springs can be easily over stretched, particularly when movable rails of their window coverings are moved up or down abruptly. This is because the tension springs will bear any sudden force exerted on the guide cords before the movable rails slide along the guide cords. Any over stretching of the tension springs will reduce the tension in the guide cords and may make it necessary to retension the guide cords by either stretching the tension springs further or replacing them. 
     Tension springs have been protected against being over stretched by providing a cord between the two ends of each spring, so that the cord has a length less than the maximum allowable stretch of the spring along its axis. A problem with this solution is that the cord must always be too long for the spring in normal use, and the excess length of the cord can easily become snagged between the coils of the spring. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, a cord tensioner is provided for tensioning a guide cord of a cord-guided covering which has an upper rail, a lower rail and a blind material extending between the upper and lower rails and in which the upper rail, the lower rail or both are movable along the guide cord; the cord tensioner being positioned at, preferably in, the upper or lower rail; and the cord tensioner being a helically wound, extension spring that includes an axially stretchable, first spring body and an extension limiter to prevent the first spring body from being stretched further axially than a predetermined length; and wherein the extension limiter is integrally formed with the first spring body. 
     Advantageously, the extension limiter of the cord tensioner is rigid to prevent it from being snagged between coils of the first spring body. It is also advantageous, for ease and economy of manufacture of the cord tensioner, that the extension limiter is an uncoiled length of a spring wire material, from which the first spring body is also made. It is further advantageous that the extension limiter extends parallel to the axis of, preferably axially through, the first spring body and has a length greater than the unstretched axial length of the first spring body and thus extends beyond the axial length of the first spring body, to guide stretching of the first spring body axially. 
     It is also advantageous that the extension limiter includes a stem and a blocking member which prevents the spring body from being over stretched. It is further advantageous that the cord tensioner includes a second spring body that is axially spaced away from the first spring body and is also integral with the extension limiter and that each spring body acts as a blocking member for the opposite spring body. It is still further advantageous that the cord tensioner includes a second spring body that is axially spaced away from the first spring body and is also integral with the extension limiter and that the extension limiter also includes a blocking member between the two spring bodies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further aspects of the invention will be apparent from the detailed description below of particular embodiments and the drawings thereof, in which: 
         FIG. 1  is a schematic, partially perspective view of a cord-guided pleated blind with a fixed head rail and a movable bottom rail and two looped guide cords; shown in perspective view is a single cord tensioner of a first embodiment of this invention, mounted in the head rail; 
         FIG. 2  is a schematic view of the cord tensioner of  FIG. 1 ; 
         FIG. 3  is a schematic perspective view of a cord-guided pleated blind with two movable rails and two guide cords; shown in cross-section are two cord tensioners of  FIGS. 1 and 2 , mounted in the lower rail; and 
         FIGS. 4A–4B  are schematic views of second and third embodiments of the cord tensioner of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  show a first embodiment of a cord tensioner  1  of the invention in an otherwise conventional, cord-guided, pleated blind  2 , shown in  FIG. 1 . The blind  2  has a fixed, longitudinally-extending hollow upper rail or bar  3 , a movable, longitudinally-extending hollow lower rail or bar  5 , and a pleated blind material  7  extending between the rails  3 ,  5 . The blind  2  also has left and right, vertically-extending, elongated side guides  9 ,  11  which are perpendicular to, and in front of, the rails  3 ,  5  and are parallel to, and in front of, left and right, vertically-extending, marginal edges of the blind material  7 . The side guides  9 ,  11  are mounted in a window frame  13  which can be for a slanted roof window. The blind  2  also has left and right, vertically-extending, guide cords  15 ,  17  which are tensioned with the single cord tensioner  1  in the upper rail  3  and which can therefore hold the lower rail  3  in different vertical positions in the blind. 
     The blind material  7  can be opened and closed by moving the lower rail  5  vertically along the side guides  9 ,  11 . The blind material  7  has four rows of openings: outer and inner, left rows of openings  21 ,  23 , through which the left guide cord  15  can pass through the blind material, and outer and inner, right rows of openings  25 ,  27 , through which the right guide cord  17  can pass through the blind material. The left and right outer rows  21 ,  25  are positioned closer to the respective left and right side guides  9 ,  11  than the left and right inner rows  23 ,  27 . 
     The cord tensioner  1  is mounted in the upper rail  3 . The left guide cord  15  is routed from the head rail  3 : downwardly through the blind material  7  through its outermost left row of openings  21  and then to the bottom rail  5 . The left guide cord  15  then passes: longitudinally through the bottom rail  5  to the right side guide  11 , downwardly and then around a right mounting block  29 , upwardly through the right side guide  11 , the lower bar  5  and then the inner left row of openings  23 , and then back into the upper rail. Similarly the right guide cord  17  is routed from the upper rail  3 : downwardly through the blind material  7  through its outermost right row of openings  25  and then to the lower rail  5 . The right guide cord  17  then passes: longitudinally through the lower rail  5  to the left side guide  9 , downwardly and the around a left mounting block  31 , upwardly through the left side guide  9 , the lower bar  5  and then the inner right row of openings  27  and then back into the upper rail. 
     The cord tensioner  1 , as shown in detail in  FIG. 2 , includes a spring body  33 . The spring body  33  is preferably a helically-wound extension spring having a plurality of adjacent spring coils  35  wound about its longitudinally-extending axis. The spring body has, at opposite longitudinal ends, a left or inner body end  37  and a right or outer body end  39 . 
     On the left body end  37  of the spring body  33  of the cord tensioner  1  is an extension limiter  41 . The extension limiter  41  is preferably formed integrally with the spring body  33  by an unwound or uncoiled length of the same spring material that forms the spring body. The extension limiter includes a stem  42  with a fixed end  42 A and a free end  42 B. The fixed end  42 A of the stem  42  is attached to the outer body end  39  of the spring body, and the stem extends from the fixed end  42 A parallel to the axis of, preferably axially through, the spring body  33  and its coils  35 , to and beyond the inner body end  37  of the spring body. The cord tensioner  1  is preferably mounted in the upper rail  3 , so that the axis of its spring body  33  and its extension limiter  41  extend longitudinally. 
     On the free end  42 B of the stem  42  is a blocking member  43  which is preferably an integrally formed loop or hook-shaped end on the free end  42 B. Alternatively, the blocking member  43  can be a separate member, releasably attached to the free end  42 B. The blocking member  43  is of a size and shape that prevents the spring body  33  from being stretched longitudinally beyond the blocking member. If the stem  42  is coaxial with the spring body  33 , the blocking member  43  should have at least one dimension, transverse to the axis of the spring body, that is larger that the cross-section of the spring coils  35 , transverse to the axis of the spring body. 
     As seen from  FIG. 1 , the guide cords  15 ,  17  are connected to the longitudinally opposite ends  37 ,  39  of the spring body  33  of the cord tensioner  1  in the upper rail, so that the spring body is suspended or floats between the two guide cords. The left guide cord  15  is slidably attached to the left body end  37 , and the right guide cord  17  is slidably attached to the outer body end  39 , preferably by lacing each guide cord about the last or the last couple of coils  35  of the spring body  33 , adjacent each opposite end  37 ,  39 . When one or both of the guide cords  15 ,  17  exert force longitudinally on the cord tensioner  1 , the spring body  33  is stretched longitudinally and axially along the longitudinally-extending extension limiter  41  towards the blocking member  43 . However, the blocking member prevents the spring body from being over-stretched, past the blocking member, in case the force of the guide cords is excessive. 
     The total longitudinal length of the extension limiter  41  from the fixed end  42 A of its stem portion  42  to its blocking member  43  is less than the maximum stretched longitudinal length of the spring body  33 . Preferably, the length of the extension limiter is such that blocking member  43  prevents the spring body  33  from being stretched beyond a length where its mechanical, particularly elastic, properties would be damaged. This ensures a longer mechanical life of the cord tensioner  1  and the blind  2 . 
     The extension limiter  41  provides a guiding function in its preferred coaxial arrangement with the spring body  33  in the cord tensioner  1 . When the spring body  33  is stretched or extended longitudinally and axially by a pulling force of the guide cords  15 ,  17 , the spring body is guided smoothly along the extension limiter  41 , thereby providing a smooth operation of the blind  2 . 
       FIG. 3  shows a blind  102  which is similar to the blind  2  of  FIG. 1  and for which corresponding reference numerals (greater by  100 ) are used below for describing the same parts or corresponding parts. 
     The blind  102  has a movable, longitudinally-extending, hollow upper rail or  103 , a movable, longitudinally-extending, hollow lower rail  105 , and a pleated blind material  107 , extending between the rails. The blind  102  also has left and right, side guides  109 ,  111 , mounted in a window frame  113 . The blind  102  further has left and right, guide cords  115 ,  117  which are tensioned with left and right, cord tensioners  101 L,  101 R, mounted in the lower rail  105 . The cord tensioners  101 L,  101 R each correspond to the cord tensioner  1  of  FIG. 2  and can therefore hold the rails  103 ,  105  in different vertical positions in the blind  102 . The blind material  107  can be opened and closed by moving the upper and lower rails  103 ,  105  vertically along the side guides  109 ,  111 . 
     The cord tensioners  101 L,  101 R are preferably fixed by the outer body ends  139 R,  139 L of their spring bodies  133 R,  133 L in the lower rail  105  in a conventional manner, such as with a screw or the like. The spring bodies  133 R,  133 L are preferably helically-wound extension springs, each with a plurality of adjacent spring coils  135 L,  135 R. The extension limiter  141 L,  141 R of each cord tensioner  101 L,  101 R extends along, preferably axially through, its spring body  133 L,  133 R and its coils  135 L,  135 R. Each cord tensioner  101 L,  101 R is preferably mounted in the lower rail  105 , so that the axis of its spring body  133 L,  133 R and its extension limiter  141 L,  141 R extend longitudinally towards each other. Additionally, the spring bodies  133 R,  133 L can be fixed by their blocking members  143 L,  143 R to the lower rail. 
     The left guide cord  115  is routed through the blind  102  from the top of the left side guide  109  to the bottom of the right side guide  111 . A top end  145  of the left guide cord  115  is attached to the top of the left side guide  109  by a top left mounting block  131 T, and from there, the left guide cord extends downwardly along, and to the rear of, an upper part of the left side guide  111  and then extends to the right into the open left end of the upper rail  103 . Inside the upper rail  103 , the left guide cord  115  extends to the right, along a left part  147  of the length of the inside of the upper rail  103 , towards the right side guide  111  and then extends downwardly through a first left opening  149  in the bottom of the upper rail. From the opening  149 , the left guide cord  115  extends downwardly through or along the pleated blind material  107  and through a second left opening  151  in the top of the lower rail  105 . Inside the lower rail  105 , the left guide cord  115  is laced through the inner body end  137 L of the left spring body  133 L of the left cord tensioner  101 L, and then, the left guide cord  115  extends to the right and generally parallel to the extension limiter  141 L of the left cord tensioner  101 L, towards the right side guide  111 . From the open right end of the lower rail  105 , the left guide cord  115  extends downwardly along, and to the rear of, a lower part of the right side guide  111  to the bottom thereof, where the left guide cord is attached by its bottom end  153  to a bottom right mounting block  129 B. 
     The right guide cord  117  is routed as a mirror image of the left guide cord  115  through the blind  102 . In this regard, a top end  155  of the right guide cord  117  is attached to the top of right side guide  111  by a top right mounting block  129 T, then the right guide cord extends downwardly along the right side guide and then to the left into the open right end of the upper rail  103 . Inside the upper rail  103 , the right guide cord  117  extends to the left, along a right part  157  of the upper rail, towards the left side guide  109 , until the right guide cord extends downwardly through a first right opening  159  in the bottom of the upper rail. Thereafter, the right guide cord  117  extends downwardly through or along the pleated blind material  107  and then into a second right opening  161  in the top of the lower rail  105 . Inside the lower rail  105 , the right guide cord  117  is laced through the inner body end  137 R of the spring body  133 R of the right cord tensioner  101 R, and then, the right guide cord  117  extends to the left and generally parallel to the extension limiter  141 R of the right cord tensioner  101 R, towards the left side guide  109 . From the open left end of the lower rail  105 , the right guide cord  117  extends downwardly along, and to the rear of, a lower part of the left side guide  109  to the bottom thereof, where the right guide cord is attached by its bottom end  163  to a bottom left mounting block  131 B. 
       FIG. 4A  shows a second embodiment  201  of the cord tensioner of the invention which is similar to the cord tensioner  1  of  FIGS. 1 and 2  and for which corresponding reference numerals (greater by  200 ) are used below for describing the same parts or corresponding parts. 
     As shown in  FIG. 4A , the cord tensioner  201  has left and right, coaxial, spring bodies  233 L,  233 R which are preferably helically-wound extension springs, each with a plurality of adjacent spring coils  235 L,  235 R. Each spring body  233 L,  233 R includes an inner body end  237 L,  237 R and an outer body end  239 L,  239 R. Between the outer body ends  239 L,  239 R of the two spring bodies  233 L,  233 R is an integrally formed extension limiter  241 . The extension limiter  241  has a stem  242  that is an unwound length of the same spring wire material forming the spring bodies  233 L,  233 R. The stem  242  extends parallel to the axis of, preferably axially through, the spring bodies and their coils  235 L,  235 R. The stem  242  of the extension limiter  241 , as shown in  FIG. 4A , has a fixed left end  242 L, attached to the outer body end  239 L of the left spring body  233 L. The stem  242  extends from the outer body end  239 L: through the coils  235 L of the left spring body  233 L, then past its inner body end  237 L, then past the inner body end  237 R of the right spring body  233 R, then through it&#39;s coils  235 R, and then to its outer body end  239 R, to which the right fixed end  242 R of the stem  242  is attached. The extension limiter  241  thereby separates the two spring bodies  233 L,  233 R by a distance that is shorter than the maximum axial extension of either spring body. 
     The cord tensioner  201  is preferably mounted in a longitudinally-extending rail of a blind, so that the axis of its spring bodies  233 L,  233 R and its extension limiter  241 L extend longitudinally. The cord tensioner  201  can, for example, be used in a blind  102  as shown in  FIG. 3 , where its outer body ends  239 L,  239 R would be mounted (e.g., with screws) on to, preferably in, the lower rail  105  of the blind  102 . Thus the left guide cord  115  of the blind  102  would pull the inner body end  237 L of the left spring body  233 L longitudinally towards the inner body end  237 R of the right spring body  233 R along the extension limiter  241 . The extension of the left spring body  233 L would be limited by the inner body end  237 R of the right spring body  233 R. Similarly, the left guide cord  117  would pull the inner body end  237 R of the right spring body  233 R longitudinally towards inner body end  237 L of the left spring body  233 L along the extension limiter  241 . Thus, the axial extension of each spring body  233 L,  233 R would be effectively limited by the opposite spring body  233 R,  233 L. 
     If the longitudinal distance between the spring bodies  233 L,  233 R of the cord tensioner  201  has to be longer than the maximum axial extension of the spring bodies along the extension limiter  241 , separate cord tensioners  1 ,  101  of 
       FIGS. 1–3  can be used instead of the cord tensioner  201 . Alternatively, one or more blocking members (not shown) could be positioned at desired distances along the extension limiter  241 , between the spring bodies  233 L,  233 R, as in the cord tensioner  301  of  FIG. 4B . 
       FIG. 4B  shows a third embodiment  301  of the cord tensioner of the invention which is similar to the cord tensioner  201  of  FIG. 4A  and for which corresponding reference numerals (greater by 100) are used below for describing the same parts or corresponding parts. 
     The cord tensioner  301  has left and right, coaxial, spring bodies  333 L,  333 R which are preferably helically-wound extension springs, each with a plurality of adjacent spring coils  335 L,  335 R. The spring bodies each include an inner body end  337 L,  337 R and an outer body end  339 L,  339 R, and between the outer body ends  339 L,  339 R is an integrally formed extension limiter  341 . The extension limiter  341  has a stem  342  that is an unwound length of the same spring wire material forming the spring bodies  333 L,  333 R. The stem  342  extends parallel to the axis of, preferably axially through, the spring bodies and their coils  335 L,  335 R. The stem  342  has a blocking member  343  that can be integrally formed with the stem by adding one or more extra coils on the stem between the spring bodies  333 L,  333 R. The transverse cross-section of the blocking member  343  must be larger than the transverse cross-section of the coils  335 L,  335 R of the spring bodies. The blocking member  343  should be larger in a direction transverse to the axis of the spring bodies than the cross-section of their coils  335 L,  335 R, transverse to the axis of the spring bodies. 
     The cord tensioners  1 ,  101 ,  202 ,  301  of the invention can be used in any conventional cord-guided blinds for many different types of windows without having to be redesigned. It may be necessary, for windows that are exceptionally steeply slanted and/or with bigger surfaces and/or for heavier blinds, to use a spring body  33 ,  133 L,  133 R,  233 L,  233 R,  333 L,  333 R that is bigger and stronger. It is of course well known that changes in diameter, number of windings, material used, etc. will result in different spring characteristics. 
     This invention is, of course, not limited to the above-described embodiments which may be modified without departing from the scope of the invention or sacrificing all of its advantages. In this regard, the terms in the foregoing description and the following claims, such as “axial”, “vertical”, “transverse”, “longitudinal”, “perpendicular”, “upwardly”, “downwardly”, “inner”, “outer”, “right”, “left”, “front”, “rear”, “top”, “bottom”, “upper” and “lower”, have been used only as relative terms to describe the relationships of the various elements of the cord tensioner for a cord-guided window covering of the invention as shown in the Figures. 
     For example, the blinds  2 ,  102  can be provided with one or more additional movable, longitudinally-extending rails and additional blind materials  7 ,  107 , between the additional rails, and the guide cords  15 ,  17 ,  115 ,  117  can pass longitudinally through the additional rails to guide vertical movement of the additional rails within the blinds. Thereby, for example, a roller blind could be combined with a pleated blind in the same window, using a mutual intermediate bar. The pleated blind of such a composite blind could be cord guided, while the roller blind could be guided by side guides. The side guides for such a blind would preferably have a channel portion, and the free rims of the roller blind that are guided in the channel portion of the side guides could have side guiding pips preventing the roller blind material from escaping from the channel portions of the side guides. The roller blind could be at the top portion of the window and the pleated blind at the bottom. The blind at the top portion could also be a roller blind type insect screen. 
     Also, the cord tensioners  1 ,  101 R,  101 L,  201 ,  301  need not be at the upper or lower rail of the blind  2 ,  102  but could be at any additional longitudinally-extending rail of the blind. 
     The blinds  2 ,  102  could also be venetian blinds with guide cords perpendicular to their horizontal slats for guiding the slats when the blind is opened or closed. 
     Also, the rails  3 ,  5 ,  103 ,  105  of the blinds  2 ,  102  and any additional rails are not necessarily hollow but can be longitudinally-extending profiles that are open to front and/or back, such as a U-shaped profile or an I-shaped profile. The guide cords  15 ,  17 ,  115 ,  117  would then be routed along the open back of the rail profiles, and the cord tensioner(s)  1 ,  101 R,  101 L,  201 ,  301  could be attached to the back of the profiles. In this regard, although it is preferred that the cord tensioners are attached to an interior surface of the rails  3 ,  5 ,  103 ,  105  of the blinds  2 ,  102 , the cord tensioners can be attached instead to an exterior surface of such rails or could even be closely adjacent to an exterior surface of such rails. 
     Furthermore, the cord-guided blind, in which the cord tensioners  1 ,  101 R,  101 L,  201 ,  301  are used, is not necessarily in a rectangular form. A blind for a triangular or a pentagonal shaped window could also be used, as long as the blind is a cord-guided blind.