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CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to European patent application No. 05075058.7, filed 11 Jan. 2005, 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 holder for a vane of a vertical venetian blind assembly used, for instance, for covering an architectural opening, such as a window or door. 
     2. Description of the Related Art 
     Vertical venetian blinds have generally been provided with horizontally-extending head rails, holding a plurality of carrier or travellers that can be moved in spaced apart relationship along the longitudinal length of each head rail. Each carrier has typically supported a vertically-extending louver, slat or vane by a vane holder in such a manner that the user of the vertical blind can move the vane along the length of the head rail (e.g. by pulling on a first operating cord or pull cord) and also can rotate or tilt the vane about its vertical axis (e.g. by pulling on a second operating cord or tilt cord). For this purpose, each carrier has typically included a main body with a vertically oriented drive hub or worm wheel, which is drivingly connected to a worm gear. The bottom of each drive hub has supported a depending vane holder, adapted to hold securely the top of a vane. A horizontally-extending tilt rod or drive shaft has been provided in the head rail, extending through the carriers and engaging their worm gears, whereby rotation of the tilt rod about its longitudinal axis has caused the drive hubs of the carriers to rotate about their vertical axes so as to make the vane holders and the attached vanes tilt together. 
     A problem in mounting a vertical venetian blind in a slanted or sloped architectural opening is that, for each slope angle, different vane holders are required. Specifically, a suitable length has to be chosen for each related slope under which the blind is mounted, since the length of the vane holder influences the space the vane of the blind has for rotating and thus tilting. The steeper the slope, the longer the vane holder has to be. When the vane holder is too short, the upper marginal portion of the vane hits the head rail when rotated. When the vane holder is too long, it negatively influences the look of the blind, because light will leak into the room even when the blind is closed. Generally, a blind manufacturer will offer a limited number of different length vane holders. For slopes that are not covered in the assortment of vane holders, a compromise can be made by using a vane holder of a length that comes closest to the ideal one. So in practice, vane holders of a specific length will be used for a range of slope angles. This is not ideal and will lower the quality of the product. The same problem occurs with blinds that are to be mounted in arched or curved architectural openings. 
     U.S. Pat. No. 6,000,456 solves a different problem, based on a difficulty that can be encountered when mounting a vertical blind assembly adjacent an architectural opening. In particular, where the vanes of the vertical blind assembly are of a particular length, it is necessary that the head rail is positioned and mounted accurately relative to the architectural opening. If the head rail is mounted too high or too low, it becomes necessary to remount it, possibly causing undesirable damage to the architectural opening surrounding. As a solution to this problem, U.S. Pat. No. 6,000,456 proposes a vane holder having an adjustable length. The vane holder has a vane clasp and a clasp holder, the vane clasp having a first end, to which the vane of the blind is attached, and a second end which can be attached to the clasp holder. The holder, in turn, can be attached to a carrier of a vertical blind. The second end of the clasp has ratchet grooves, each of which can co-operate with a single locking tooth in the holder, such that a resilient ratchet-type mechanism is created. The clasp can be moved resiliently between engaging consecutively one of the securing points or ratchet grooves to the locking tooth in the holder so as to vary the height of the vane. 
     The length adjustable vane holders of U.S. Pat. No. 6,000,456 could theoretically solve the problem of for sloped vertical blinds. Unfortunately, this is not the case since such holders were originally designed only for correcting small inconvenient differences in length. Also a drawback of the adjustable ratchet of such holders is that it is difficult to control their adjustment. In order to overcome the connection between the operably engaged ratchet parts of these holders, one generally has to pull on them, but it is not uncommon that too much force is used and thereby the desired length of the holders is exceeded. This is because the correct amount of force is difficult to control. 
     SUMMARY OF THE INVENTION 
     In order to provide an adjustable length holder that can support a vane from a carrier of a vertical blind assembly and that can be more easily and reliably adjusted, the holder of this invention comprises:
         a length adjustable mounting extending from a top end connectable to the carrier to a bottom end connectable to a hook member for suspending the vane,   the length adjustable mounting comprising a first part and a second part which are operably interconnected to allow displacement of the two parts upwardly or downwardly relative to each other, by which the vertical length of the vane holder between the top end and the bottom end can be adjusted, the first and second parts being rotatably interconnected such that the rotation of one of the first or second parts relative to the other of the first or second parts results in the adjustment of the vertical length of the vane holder.       

     Advantageously, the first part comprises one of a threaded spindle element or a spindle nut and the second part comprises the other of a threaded spindle element or a spindle nut and wherein the spindle thread and the nut thread are rotatably interconnected. It is especially advantageous that the threaded spindle comprises an elongated body with an outer surface having a screw thread and wherein the spindle nut comprises a nut body with an inner surface having a screw thread. 
     Also advantageously, the bottom end of the vane holder is rotatable relative to the top end of the vane holder. It is especially advantageous that: the first part comprises a threaded spindle element forming the top end of the holder and the second part comprises a spindle nut forming the bottom end of the vane holder and wherein the threaded spindle element and spindle nut are rotatably interconnected and rotation of the spindle nut causes the nut and the bottom end of the vane holder to move vertically; or the first part comprises a spindle nut which forms the top end of the vane holder and wherein the second part comprises a threaded spindle element which forms the bottom end of the vane holder and wherein the threaded spindle element and the spindle nut are rotatably interconnected and rotation of the spindle nut causes the threaded spindle element and the bottom end of the vane holder to move in a vertical direction towards or away from the top end of the vane holder. 
     Advantageously, a locking arrangement is provided between the top end and the bottom end of the vane holder which, in a locked position, prevents inadvertent rotation of the bottom end relative to the top end. It is especially advantageous that the locking arrangement comprises a vertically extending groove in the thread of the spindle element and a locking pin that is on the inner surface of the spindle nut and that can cooperate with the groove such that at one point in every 360 degree rotation of the bottom end relative to the top end, the locking pin lodges in the groove to lock the spindle element and spindle nut. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further aspects of the invention will be apparent from the following description and the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a vertical blind assembly including a vane holder of this invention; 
         FIG. 2  is an exploded perspective view of a first embodiment of the vane holder of the invention; 
         FIG. 3  is an exploded perspective view of a second embodiment of the vane holder of the invention; 
         FIG. 4  is a plan view of a fourth embodiment of the vane holder of the invention, attached to a carrier; 
         FIG. 5  is an exploded perspective view of the third embodiment of the vane holder of the invention; 
         FIG. 6  is a plan view of a fourth embodiment of the vane holder of the invention; and 
         FIG. 7  is an exploded perspective view of the fourth embodiment of the vane holder of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a vertical blind assembly  1  which includes a plurality of vertical vanes or louvers  3  suspended from a generally longitudinally-extending head rail  5  that is mounted at an upward slope or angle (from left to right in  FIG. 1 ). The vanes  3  may be conventional metal, plastic or fabric slats, each having an upper marginal portion  7  securely suspended vertically from a holder  15 . Each holder is attached to a conventional carrier or traveller (not shown) that extends downwardly for, is carried by, and can be moved longitudinally along, the head rail  5 . 
     As shown in  FIG. 1 , the head rail  5  may also be provided with a conventional pull cord  9  for moving a plurality of the carriers along the head rail and a conventional bead chain  11  which serves as a tilt cord for rotating a grooved tilt rod (not shown) of the head rail  5  so as to tilt the vanes  3 . 
       FIG. 2  shows the vane holder  15  with a carrier  13 , which can be carried by the head rail  5 . The vane holder  15  has a top end  15 A that is connectable to the carrier, a bottom end  15 B which carries a hook member  17 , and a length adjustable mounting  19  which provides the possibility of changing the vertical length of the vane holder between the top end  15 A and the bottom end  15 B. The length adjustable mounting  19  includes a top or first part  21  forming the top end  15 A of the holder  15  for attachment to the carrier  13  and a bottom or second part  23  forming the bottom end  15 B of the holder  15  for carrying a hook member  17 . The first part  21  has a threaded spindle element  25 , and the second part  23  has a threaded spindle nut  51  carrying the hook member  17 , so that the two parts can be displaced vertically relative to one another. 
     As shown in  FIG. 2 , the first part  21  of the length adjustable mounting  19 , which includes the threaded spindle element  25 , includes an elongated body  27  with a top base  29  a bottom base  31  and a threaded outer surface  33 . The threaded outer surface  33  has a circumferential screw-thread  35  of multiple windings  37 . Extending from the top base  29  vertically down to the bottom base  31  of the outer surface  33  is a groove  39 . The groove cuts through the windings  37  of the thread  35  and is part of a locking arrangement  75  which is explained further below. Extending upward from the top base  29  is a connector  41  for attachment to the carrier  13 ; for sloped blinds, the attachment of the vane holder  15  to the carrier  13  is preferably by a conventional intermediate gimbals mounting (not shown). 
     The second part  23  of the length adjustable mounting  19 , which includes the spindle nut  51 , is suitable for carrying the hook member  17 . The spindle nut  51  has an elongated body  53  with a top base  55 , a bottom base  57  and a threaded inner surface  59  (not visible). The threaded inner surface  59  has a circumferential screw-thread  61  (not shown) of multiple windings  63  (not shown). 
     As also shown in the  FIG. 2 , the spindle nut  51  is vertically at least as long as, and preferably longer than, the threaded outer surface  33  of the spindle element  25 . The vertical lengths of the nut  51  and the spindle element  25  determine the maximum possible vertical length of the vane holder  15  which is reached when the top base  55  of the nut  51  is at the bottom base  31  of the spindle element  25 . Means for preventing the disengagement of the parts  21 ,  23  at this point can be provided, such as by closing the last thread winding on the bottom base  31  of the spindle thread  35  or the last thread winding on the top base  55  of the nut thread  61  or both. 
     In accordance with the invention, the spindle element  25  and the nut  51  are operably interconnected in that the nut  51  is rotatably placed about spindle element  25  and the nut thread  61  co-operates with the spindle thread  35 . In use rotation of the nut relative to the spindle results in a vertical displacement of the bottom end  15 B and the hook member  17  it carries either towards or away from the top end  15 A of the vane holder, depending on the type i.e. left or right handed screw-threads that are chosen. At the same time rotation of the nut  51  will also rotate the hook member  17  and change its orientation relative to the threaded spindle  21 , relative to the top of the vane holder  15 A and when the vane holder  15  is installed in a blind also relative to the carrier  13 . Thus in practice when the desired length of the vane holder is determined and even when the vane holder is assembled into a vertical venetian blind, only rotations of integers of 360 degrees can than be used to adjust the vertical position of the hook member. Rotations of less then 360 degrees would be unacceptable since they would change the angle of the hook member relative to the top end of the vane holder, while a change of the angle of the hook member should only be a direct result of the normal tilting action and only relative to the carrier to which the vane holder is attached. The length resulting from the adjustment per 360 degree turn, depends on the pitch of the thread of the spindle and nut. The length of the vane holder  15  and the vertical position of the hook member  17  relative to the top end  15 A of the vane holder  15  can thus be adjusted. 
       FIG. 3  shows a second embodiment  115  of the adjustable length holder of the invention which is similar to the holder  15  of  FIGS. 1-2  and for which corresponding reference numerals (greater by 100) are used below for describing the same parts or corresponding parts. 
     The vane holder  115  has a top end  115 A that is connectable to the carrier, a bottom end  115 B which carries a hook member  117 , and a length adjustable mounting  119  which provides the possibility of changing the length of the vane holder between the top  115 A and the bottom  115 B. The length adjustable mounting  119  of the second embodiment also comprises two-parts including a first part  121  having a top  115 A for attachment to the carrier and a second part  123  having the bottom  115 B for carrying a hook member  117 . The first and second parts  1211 ,  123  can be displaced vertically relative to each other. 
     As shown in  FIG. 3 , the first part  121  has a spindle nut  151  which includes an elongated nut body  153  with the top nut base  155 , the bottom nut base  157  and a the nut thread  161  on the inner surface  159  (not shown). The nut thread  161  comprises multiple windings  163  (not shown). Extending upward from the top nut base  155  is a connector  141  for attachment to the carrier  113  (not shown); for sloped blinds preferably attachment to the carrier  113  is preferably realized by an intermediate gimbals mounting (not shown). 
     The second part  123  includes a threaded spindle element  125  and carries a hook member  117 . The threaded spindle element  125  comprises an elongated body  127  with a top base  129  a bottom base  131  and a threaded outer surface  133 . The threaded outer surface  133  comprises a circumferential screw-thread  135  of multiple windings  137 . Extending from the top base  129  vertically down to the bottom base  131  of the outer surface is a groove  139 . The groove cuts through the windings  137  of the thread  135 , and is part of a locking arrangement  175  between the spindle and the nut of the adjustable mounting  119  which is explained further below. The spindle thread  135  is of course chosen to co-operate with the nut thread  161 . 
     As also shown in the  FIG. 3 , the spindle nut  151  is vertically, at least as long as, and preferably longer than, a threaded outer surface  133  of the spindle element  125 . The length of the nut  151  and the spindle element  125  determine the maximum possible length of the vane holder  115  which is reached when the bottom or free base  167  of the nut  151  is at the base  129  of the spindle element  125 . Means for preventing the disengagement at this point can be added such as closing the last thread winding on the top base  131  of the spindle thread  135  or the last thread winding on the free base  167  of the nut thread  161  or both. 
     In use, the first part  121  which includes the nut  151 , and the second part  123  which includes the spindle element  125  are operably interconnected in that the spindle element  125  is rotatably placed within the nut  151 . Rotation of the spindle element  125  relative to the nut  151  results in a vertical displacement of the bottom  115 B and the hook member  117  it carries either towards or away from the top  115 A of the vane holder. At the same time rotation of the spindle element  125  will also rotate the hook member  117  and change its orientation relative to the threaded nut  151 , the top of the vane holder  115 A and the carrier  113 . Thus, as in the first embodiment, in practice when realizing the desired length for the vane holder  115  and or adjusting it even when the vane holder  115  is assembled into a vertical venetian blind, integers of 360 degree rotations can than be used to adjust the vertical position of the hook member. 
     In the vane holders  15  and  115  of  FIGS. 1-3 , a locking arrangement  75 ,  175  is provided to ensure that during normal tilting action each vane holder  15 , 115  rotates as a single unit, and thus prevents the threaded parts  25 ,  51 ,  125 ,  151  of the adjustable mountings  19 ,  119  from inadvertently rotating relative to each other during the normal tilting action, which could result in an undesired vertical displacement of the hook member  17 ,  117  as well as an undesired radial lagging behind the desired tilt. The locking arrangement is provided between the threaded spindle element  25 , 125  and the nut  51 , 151  to prevent this undesired displacement and ensures rotation of the vane holder  15 , 115  during normal tilting as single body. The locking arrangement  75 , 175  comprises the vertically extending groove  39 , 139  in the thread  35 , 135  of the threaded spindle element  25 , 125 , and a lock pin  65 , 165  (not shown) on the inner surface  59 , 159  of the threaded nut  51 , 151  at a free base  67 ,  167  of the nut body  53 ,  153 . The free base  67 , 167  is the top nut base  55  in the first embodiment and the bottom nut base  157  in the second embodiment. The lock pin  65 , 165  (not visible) provides a locking action in the groove  39 , 139  such that during normal tilting the vane holder  15 , 115  acts as a single body. 
     For initially choosing and adjusting to the desired length of the vane holder  15 , 115  or for adjusting the length later, relative easy un-locking of the lock pin  65 , 165  from the groove  39 , 139  is realized by the lock pin being positioned on a relative flexible leg  69 , 169  of the nut body  53 , 153 . The leg portion  69 , 169  is realized between two parallel, adjacent slits  71 , 73 ;  171 , 173  in the nut body  53 , 153 . When the hook member  17 , 117  is rotated relative to top  15 A,  15 A of the vane holder  15 , 115 , the flexible leg portions  69 , 169  of the nut  51 , 151  flexes outward and the latch pin  65 , 165  disengages from the groove  39 , 139  of the spindle element  25 , 125 . 
       FIGS. 4 and 5  show a preferred, third embodiment  215  of the adjustable length holder of the invention which is similar to the holder  15  of  FIGS. 1-2  and for which corresponding reference numerals (greater by 200) are used below for describing the same parts or corresponding parts. 
     The vane holder  215  can be vertically adjusted between the top and bottom ends  215 A,  215 B without affecting the radial orientation of the bottom end  215 B and hook member  217  relative to the top end  215 A. Thus, this arrangement allows length adjustment by rotational movement of the second part  223  of the length adjustable  219  mounting relative to the first part  221  by less than 360 degree turns. This means that a more precise length adjustment can be realized. 
       FIG. 4  shows a carrier  213  with the vane holder  215 . The connection of the vane holder  215  to the carrier  213  can be of any desired arrangement for suspending the vane holder.  FIG. 4  shows a preferred gimbals mounting  216  for connecting the vane holder to the carrier in a sloped blind. 
     The vane holder  215  has a top end  215 A that is connectable to the carrier  213 , a bottom end  215 B which is suitable for connection to a hook member  217 , and a length adjustable mounting  219  which provides the possibility of changing the vertical length of the vane holder between the top  215 A and the bottom  215 B. The length adjustable mounting  219  includes a top or first part  221  comprising the top  215 A for attachment to the carrier  213  and a bottom or second part  223  comprising the bottom  215 B for connection to the hook member  217 , and these parts can be displaced relative to each other. 
     As shown in  FIG. 4 , the top part  221  of the length adjustable mounting  219  has a threaded spindle element  225  and the bottom part  223  comprises a threaded spindle nut  251  carrying the hook member  217 . The spindle element  225  and the nut  251  are operably interconnected in that the nut  251  is rotatably placed about spindle element  225 . The top part  221 , which has the threaded spindle element  225 , includes an elongated body  227  with a top base  229 , a bottom base  231  and a threaded outer surface  233 . The body  227  further has a plurality of outwardly extending wings  277 . The wings extend radially outwards from the vertical axis of the body  227  and are part of a locking arrangement  275 . Each of the radial or locking wings  277  ends in an outer surface  277 A. The outer surfaces  277 A of the wings  277  together shape the circumferential, discontinuous outer surface  233  of the spindle element  225  and comprise the spindle thread  235 . The spindle thread  235  has multiple windings  237 . 
     The bottom part  223  has the spindle nut  251  and a nut holder  391 , and the nut  251  is rotatably mounted on a nut holder  291 , which in turn carries the hook member  217 . The spindle nut  251  comprises an elongated body  253  with a top base  255  a bottom base  257  and a threaded inner surface  259 . The threaded inner surface  259  comprises a circumferential screw-thread  261  of multiple windings  263 . 
     The nut holder  291  comprises a bottom base  287  and at least one locking arm  285 . The bottom base  287  coincides with the bottom end  215 B of the vane holder. The bottom base  287  comprises a circumferential channel portion  283  and the at least one locking arms  285  extends vertically upwardly from the bottom base  287 . When there are more than one locking arms, they are parallel and spaced apart on the bottom base  287 . The channel portion  283  is a circumferential waist like portion. The nut holder bottom base  287  extends outwardly in circumferential direction beyond the channel portion  283  both above and below it. The at least one locking arm  285  thus extends upwardly from above the channel portion  283 . The locking arms  285  each have an outer surface  285 A which together form a circumferential, discontinuous outer surface  297  of the nut holder  291  which is smooth and not threaded. The threaded nut  251  is mounted about the locking arms  285  of the nut holder  291 , and is rotatable about the circumferential, discontinuous outer surface  297  of the nut holder  291 . The at least one locking arm  285  of the nut holder  291  is part of a locking arrangement  275  which prevents rotation of bottom end  215 B of the vane holder and of the hook member  217  it carriers relative to the top end  215 A of the vane holder. The locking arrangement  275  is described further below. 
     The nut  251  of the third embodiment further comprises at the bottom nut base  257  of the cylindrical nut body  255 , at least one radially inwardly projecting flange portion or foot  279  for attachment to and rotatable co-operation with the circumferential channel portion  283  on bottom base  287  of the nut holder  291 . The bottom nut base  257  of the cylindrical nut body  255  can additionally be provided with a number of slits, dividing the body into a plurality of lower legs  281 , each including one of the inwardly projecting feet  279 , that can flex slightly in and out for assembly to the circumferential channel portion  283  on the nut holder bottom base  291 . Since as described above the hook member  271  is carried by the nut holder bottom base  287 , which coincides with the bottom end  215 B of the vane holder, the nut  251  when assembled to the nut holder  291  carries the hook member  217  while being rotatable relative to the hook member  217 . As in the previous embodiments the nut thread  261  is of course chosen to co-operate with the spindle thread  235 . 
     The locking arrangement  275  comprises the at least one locking arm  285  on the nut holder  291  in slidable co-operation with the at least one locking wing  277  of the threaded spindle  223 . Adjacent radial wings  277  of the spindle body  227  are at angles to each other, such that between each pair of adjacent radial wings one locking arm  285  can be slidingly accommodated. The locking arm  285  of the locking arrangement  275  does not project radially beyond the outer radial wing surfaces  277 A or outer spindle surface  233  of the spindle element  225  and does not hinder rotation of nut  251  relative to the spindle element  225 . This arrangement of the co-operating locking arms with the wings prevents the rotation of the bottom end  215 B relative to the top end  215 A of the vane holder  215  and ensures that the vane holder  215  once assembled into a vertical venetian blind acts as a single element during operation of the blind. 
     In the third embodiment of the vane holder  215  there are four locking wings  277  on the spindle body  227  and four locking arms  285  on the nut holder  291 . The arms are spaced apart along in a general circular manner. The locking arms  285  are preferably of the same length as the nut  251  to ensure operation of the locking arrangement in any length of the vane holder  215 . If the locking arms where shorter than the nut  251  they could at a certain length of the vane holder be disengaged from the locking wings  277  of the spindle element  225  rendering the locking arrangement inoperable. 
     As shown in the  FIGS. 4 and 5 , the spindle nut  251  is at least as long as or longer than the threaded outer surface  233  of the spindle element  225 . The length of the nut  251  and the spindle element  225  determine the maximum possible length of the vane holder  215  which is reached when the top or free base  255 , 267  of the nut  251  is at the bottom base  231  of the spindle element  225 . Means for preventing the disengagement at this point can be added, preferred it to close the last thread winding  263  (not visible) at the free base  267  of the nut  251 . 
     When assembled, the adjustable mounting  219  comprises as top part  221  the threaded spindle element  225  and as bottom part  223  the nut  251  and the nut holder  291 . The hook member  217  is carried by the nut holder  391  as part of the bottom part  223  of the adjustable mounting  219 . The spindle nut  251  is rotatably mounted relative to the hook member  217  by the inwardly projecting flange  279  to the channel portion  283  on the nut holder  291  and relative to the threaded spindle element  225  by the connection between the nut thread and the spindle thread. The locking arrangement  275  between the hook member  217  and the spindle element  225 , including at least one locking arm  285  of the nut holder  391  in sliding co-operation and between two adjacent locking wings  277  of the spindle element  225 , ensures that the vane holder  215  rotates as a single element when it is mounted in a vertical blind assembly and during normal tilting of the vanes of the vertical blind assembly. The spindle nut  251  is rotatably placed about the outer surface of the spindle element  225 , and at the same time about the locking arms  285 . 
     In use, when the length of the vane holder  215  is chosen and set or needs to be adjusted, the nut  251  is rotated in clockwise or counter clockwise direction. This clockwise or counter clockwise rotation of the nut  251  translates into an upward or downward movement of the nut  251  relative to the spindle  223  depending on the sort of thread that is used. The upward or downward movement of the nut  251  directly causes an identical vertical movement of the hook member  217  because of the connection of nut  251  by the inwardly projecting flange  279  to the channel portion  283  on the nut holder  291 . Thus by rotation of the nut  251  the length of vane holder  215  between the top  215 A and the bottom  215 B reduces or increases, and the vertical position of the hook member  217  relative the top  215 A of the vane holder  215  is changed. The radial orientation of hook member  217  relative to the top  215 A of the vane holder remains unchanged due to rotational connection between the nut  251  and the hook member  217  and the due to locking arrangement  275  which prevents rotation of the hook member  217  relative to the spindle element  225 . 
       FIGS. 6 and 7  show a preferred, fourth embodiment  315  of the adjustable length holder of the invention which is similar to the holder  15  of  FIGS. 1-2  and for which corresponding reference numerals (greater by 300) are used below for describing the same parts or corresponding parts. The vertical length of the vane holder  315  can be adjusted between the top and bottom  315 A,  315 B without effecting the radial orientation of the hook member  317 . 
     The vane holder  315  has a top end  315 A that is connectable to a carrier (not shown), a bottom end  315 B which is suitable for connection to a hook member  317 , and a length adjustable mounting  319  which provides the possibility of changing the vertical length of the vane holder between the top  315 A and the bottom  315 B. The length adjustable mounting  319  includes a top or first part  321  comprising the top end  315 A of the vane holder  315  for attachment to a carrier and a bottom or second part  323  comprising the bottom end  315 B of the vane holder  315  for connection to the hook member  317 , and the two-parts can be displaced relative to each other. 
     The top part  321  has a spindle nut  351 , and the bottom part  323  has a threaded spindle element  325  carrying the hook member  317 . The spindle element  325  and the nut  351  are operably interconnected in that the nut  351  is rotatably placed about spindle element  325 . The top part  321  also has a nut holder  391  on which the nut  351  is rotatably mounted. The nut holder  391  includes a top base  393 , one or more parallel and spaced apart vertically locking arms  385  extending vertically downwardly from the top base  393  and ending in a bottom base  395 . The nut holder  391  and the locking arms  385  are part of a locking arrangement  375  which prevents rotation of the bottom end  315 B of the vane holder and of the hook member  317  relative to the top end  315 A of the vane holder. The locking arms  385  each have an outer surface  385 A which together form a circumferential, discontinuous outer surface  397  of the nut holder  391  which is smooth and not threaded. The threaded nut  351  is mounted about the locking arms  385  of the nut holder  391 , and is rotatable about the circumferential, discontinuous outer surface  397  of the nut holder  391 . The bottom base  395  of each locking arms  385  has outwardly flared edges preventing the nut  351  from detaching from the nut holder. Extending upwardly from the top base  393  of nut holder  391  is a connector  341  for connection of the vane holder  315  to a carrier. 
     The nut  351  includes a cylindrical nut body  353  which is shorter in length then the spindle element  325  and having an outer surface  354  and an inner surface  359 . The inner nut surface  359  comprises a screw thread  361  of multiple windings  365 . The nut body  353  can be cylindrical with a smooth or knurled outer nut surface  352  or it can be hexagonal. 
     The bottom part  323  of the length adjustable mounting  319  has the threaded spindle element  325  and is suited for carrying the hook member  317 . The threaded spindle  323  includes an elongated body  327  with a bottom base  331  which carries the hook member  317 . The spindle body  327  is in the shape of two parallel vertically locking wings  377  extending upwardly from bottom spindle base  331 . Each spindle locking wing  377  having with a top base  329  and a threaded outer surface  377 A. The threaded outer surfaces  377 A of both wings  377  together form a circumferential but discontinuous outer surface  333  of the spindle, with a circumferential but discontinuous spindle thread  335  of multiple windings  337 . 
     The locking arrangement  375  has at least one locking wing  377  on the hook member  317  that is in slidable co-operation with at least one locking arm  385  of the nut holder  391 . Adjacent locking wings  377  of the spindle element  325  are at angles to each other, such that between the adjacent locking wings  377  one locking arm  385  can be slidingly accommodated. The locking wings  377  of the locking arrangement  375  project radially beyond the outer radial arm surfaces  385 A of the nut holder  391  and its outer threaded surface  333  provides a suitable connection with the inner threaded surface  359  of the nut  351 . The at least one locking wing  377  is fixedly connected to the hook member  317 . It extends from a top hook base  387  of the hook member  317 . In the fourth embodiment of the vane holder  315  there are two locking arms  385  on the nut holder  391  and two locking wings  377  on the hook member  217 . 
     The cross-sectional shapes of both the locking wings  377  and the locking arms  385  and their relative positions on the top hook base  387  and the top nut holder base  393  are chosen to allow a slidable interaction between the nut holder  391  and the spindle element  325 . As can be best seen in  FIG. 7 , the locking wings  377  of the spindle element  325  and the locking arms  385  of the nut holder  391  have a general pie-point shaped cross-section. The wings and arms having a outer curved wall  377 A,  385 A and left and right inner walls  377 B, 377 C, 385 B, 385 C projecting radially inwards. The locking wings  377  are placed relative to each other at certain angles, such that between the two wings  377  between opposite inner walls  377 B,  377 C one of the locking arms  385  can be accommodated. This arrangement of the co-operating locking arms with the wings prevents the rotation of the bottom end  315 B relative to the top end  315 A of the vane holder  315  and also ensures that the vane holder  315  once assembled into a vertical venetian blind acts as a single element during operation of the blind. 
     The locking arms  385  of the nut holder  391  do not project radially beyond the outer circumferential threaded surface  333  of the locking wings  377  of the spindle  323 . Ensuring that the inner threaded surface  359  of the nut  351  comprising the nut thread  361  can co-operate with the outer radial threaded surfaces  333  of the spindle  323 . As is partly visible in  FIG. 7 , the inner nut thread  361  comprises a plurality of windings  363 . 
     When assembled, the adjustable mounting  319  comprises as top part  321  the threaded nut  351  and the nut holder  391  and as bottom part  323  the threaded spindle element  325 . The hook member  317  is carried by the bottom part  323 , the threaded spindle element  325  of the adjustable mounting  319 . The spindle nut  351  is rotatably mounted relative to both the nut holder  391  and to the threaded spindle element  325 . The locking arrangement  375  between the hook member  317  and the nut holder  391 , including the locking arms  385  of the spindle  325  in sliding co-operation with the locking wings  377  of the nut holder  391 , prevents rotation of the bottom end  315 B and of the hook member  317  relative to the tope end  315 A of the vane holder. The spindle nut  351  is rotatably placed about the outer surface of the spindle element  325 , and at the same time about the locking wings  377  of the nut holder  391 . 
     As shown in the  FIGS. 6 and 7 , the spindle nut  351  has a short ring like nut body  353 , and the nut holder  391  is at least as long as or longer than threaded outer surface  233  of the spindle element  325 . In stead of the nut  351 , in this embodiment the length of the nut holder  391  and the length of the spindle element  325  determine the maximum possible length of the vane holder  315 . The maximum length is reached when the top base  329  of the spindle element  325  is moved to the bottom base  357  of the nut  351 . In this respect the position of the nut  351  nearest the bottom portion  395  on the nut holder  391  is also determinative for the maximum length of the vane holder  315 . Means for preventing the disengagement of the spindle element  325  from the nut  351  can be to close the last thread winding  363  (not visible) at the bottom base  357  of the nut  351  or the last thread winding  337  at the top base  329  of the spindle element  325 . 
     In use, when the length of the vane holder  315  is chosen and initially set or when it needs to be adjusted, the nut  351  is rotated in clockwise or counter clockwise direction. This clockwise or counter clockwise rotation of the nut  351  translates into an upward or downward movement of the spindle element  325  and associated hook member  317  depending on whether a right or left handed the thread is used. Thus by rotation of the nut  351  the length of vane holder  315  between the top  315 A and the bottom  315 B reduces or increases, and the vertical position of the hook member  317  relative the top  315 A of the vane holder  315  is also changed. The locking arrangement  375  ensures that radial orientation of hook member  317  relative to the top  315 A of the vane holder remains unchanged during adjustment of the length of the vane holder as well as during operation of the blind when it is assembled to a blind. 
     Additionally, to prevent inadvertent vertical sliding displacement of the nut  351  along the nut holder  391 , protrusions  399  are placed on the outer surface of the locking wings  377  of the nut holder  391 . The protrusions  399  and the bottom flanges  395  of the nut holder  391  confine the nut  351  to its vertical position on the nut holder. Alternatively, the nut  351  can comprise an inner screw thread comprising a single winding instead of a plurality of windings. 
     All the vane holders  15 ,  115 ,  215 ,  315  include an additional locking arrangement for ensuring that the vane holder will act as a single body during normal tilting operation of the vanes in a blind. The locking arrangement either preventing inadvertent rotation during tilting, or preventing all rotation between the top end and the bottom end of the vane holder. However, other solutions to ensure that the vane holder will act as a single element during tilting are also possible. Such solutions include the choice of a nut thread and a spindle thread that allow relative rotation only by exerting a relative large rotational force on one or both of the parts, e.g. by ensuring a relative high friction between the threads. The force needed for rotation should be significantly larger than the force that would be caused by the normal tilting action. The length of a vane holder of such an embodiment could preferably only be set before assembly into a blind, i.e. during assembly of the various elements of the vane holder. Later length adjustment would be possible but less easily realized and could require dismounting the vane holder from the blind. 
     Alternatively during assembly of the various elements of the vane holder, the desired length could be set and fixated. The fixation can e.g. be realized by adhesive. The advantage of an easily set length is still there, less parts are still needed because any desired length can be produced by the top and bottom parts of the vane holder elements that are in stock. But once the length is set for a blind that will be mounted under a specific slope, it cannot be adjusted later. 
     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 “vertical”, “horizontal”, “upward”, “downward”, “upper”, “lower”, “inward”, “outward”, “longitudinal” and “lateral”, have been used only as relative terms to describe the relationships of the various elements of the spindle-type adjustable length vane holder of the invention. For example, when the vane holder is being assembled or when it is sold as a separate part of a vertical venetian blind, it can be in a generally horizontal position, and the holder in such a position would be within the scope of this invention. Also, the hook member  17 , 117 ,  217 ,  317  can either be integrally formed with the bottom end  15 B,  115 B,  215 B,  315 B of the vane holder  15 ,  115 ,  215 ,  315  or it can be connected thereto by any suitable means. The type of hook member is also not critical, so long as it is suited for carrying a vane.

Summary:
A vertically adjustable holder for interconnecting a carrier in a control system for a vertical vane covering for an architectural opening and a suspended vane includes two component parts which are rotatably adjustable relative to each other to increase or decrease the length of the holder and thus the spacing between the carrier and the suspended vane.