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CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 14/591,673, filed Jan. 7, 2015 and entitled “Shading device for an architectural opening and method for adjusting an end stop position of the shading device”, which claims priority to Netherlands Patent Application No. 1040593, filed on Jan. 8, 2014, and entitled “Shading device for an architectural opening and method for adjusting an end stop position of the shading device”, which applications are hereby incorporated in their entirety by reference as though fully disclosed herein. 
     
    
     FIELD 
       [0002]    The invention relates to a shading device for an architectural opening comprising a shade, a drive unit for extending and retracting the shade between a first and second end position, a spindle, a first end stop, stationary connected to the spindle near a first end of the spindle; at least one travelling nut, movably arranged on the spindle and operatively connected to the drive unit so as to move towards, respectively away from the first end stop as the shade is extended, respectively retracted. 
       BACKGROUND 
       [0003]    A respective shading device, as disclosed in applicant&#39;s European Application EP 2 216 492 A1, is equipped with a mechanical end stop system. Such mechanical end stop systems are known as so-called spindle &amp; nut end stop systems. A spindle &amp; nut end stop system may comprise a threaded shaft as the spindle, a wandering or travelling nut threaded on the shaft and at least one or two end stop members fixed on the shaft. 
         [0004]    A drawback of the known mechanical end stop system is that the travelling nut has to be screwed on the spindle before installing the last end stop. This limits the amount of possible constructions of the spindle with the end stops. Particularly at least on end stop has to be releasable in regard to the spindle. 
         [0005]    A further drawback of the known mechanical end stop system is that each end stop is designed as a separate part which needs to be fixed to the shaft such that the end positions of the shade are set as desired. Furthermore, for mounting the end stop member to the shaft a fixing means, preferably screws, pins or rivet, is needed. The end stop member may consist of two separate halves which have to be connected at the shaft. Thus, known mechanical end stop systems consist of several parts leading to a complex construction. As a consequence the assembling and/or adjusting of the shading device may be complex and time consuming. 
       SUMMARY 
       [0006]    It is a principal object of the present invention to enhance a shading device as mentioned in the preceding introduction and/or a travelling nut for such a shading device such that the assembling and/or arranging of a travelling nut around and/or onto a spindle is simplified. 
         [0007]    Preferably it is a further object of the present invention that the assembling and/or adjusting of the shading device, particularly the end stop assembly, is simplified. 
         [0008]    It is a further object of the present invention to provide a simple method for arranging a travelling nut on and/or around a spindle. 
         [0009]    Preferably it is a further object of the present invention to provide a simple method for adjusting the lower end stop position and/or upper end stop position of a shade providing a shade device according to the invention with at least one travelling nut moveably arranged on the spindle between the first and second end stop, whereby the first end stop, the second end stop and the spindle form an end stop assembly. 
         [0010]    The object of the invention is accomplished by a shading device as mentioned in the preceding introduction and/or a travelling nut for such a shading device, wherein the travelling nut comprises at least two segments for arranging the travelling nut around the spindle. 
         [0011]    As an advantageous result the travelling nut can be arranged around and/or onto a spindle in a quick and/or easy way. A travelling nut formed of at least two segments can be arranged around the spindle independent of the end stops. As the ends of the spindle may be blocked by the first and second end stop it is not possible to screw a usual nut on the spindle. Thus, the travelling nut is preferably designed such that the nut can be opened and/or closed by means of the two segments of the travelling nut. Even if the end stops are already fixed to the spindle, the travelling nut is mountable to the spindle. Preferably the travelling nut is formed as a split nut. 
         [0012]    Preferably the shading device is a roller blind. Particularly the shade is a sheet of flexible material. The shade may be attached upon the outer surface of a winding core such as a shade tube or roller. The travelling nut may interact with a driven portion of the shading device, such as aforementioned winding core, and the spindle may be stationary such that when the shading device is driven the travelling nut rotates and is displaced in an axial direction along the spindle. The spindle is preferably a threaded rod. When the travelling nut reaches the first or second end stop the nut can no longer be displaced along the spindle. Since the driven portion of the shading device is coupled with the nut, rotation of the driven portion will be stopped too. 
         [0013]    According to a further embodiment of the present invention the travelling nut has two segments which are hinged with each other for arranging the travelling nut onto the spindle. For the opening of the travelling nut the ring-like shape of the nut can be resolved by moving the two segments of the nut away from each other. As a result the travelling nut has an aperture with a size appropriate to accommodate the spindle in a centre of the nut. The centre of the nut has a threaded inner side which mate with a threaded outer side of the spindle. Preferably the two segments are formed as a first half and a second half of the travelling nut connected with each other by a flexible hinge. The first half, the second half and the flexible hinge may be formed as one piece and/or as one integral part, particularly made of plastic. 
         [0014]    Preferably the travelling nut is formed in one piece comprising a flexible hinge and a connection arrangement for detachably joining the two segments of the travelling nut. Thus, the travelling nut may be arranged on the spindle and/or removed from the spindle by the detachable connection as desired. The two segments of the travelling nut may comprise engaging means for securing the segments to one another. Particularly the connection is designed as a snap connection. A snap connection does not need any further mounting elements for connecting or disconnecting the segments of the nut. 
         [0015]    The connection arrangement may have a first joint element and a second joint element, which have complementary formations for an engagement with each other. Preferably the first joint element having a snap-on catch is assigned to a first half of the travelling nut. The second joint element may have a recess complementary formed to the snap-on catch. The second joint element may be assigned to a second half of the travelling nut. 
         [0016]    A further embodiment of the present invention provides the travelling nut comprising at least one engaging element on the outer circumference of the travelling nut for engagement with a complementary element on the inner surface of the winding core. Preferably the engaging element of the travelling nut interacts at least during normal operation of the shading device with the complementary element such that when the winding core is rotated around its longitudinal axis the travelling nut rotates and is displaced in an axial direction along the stationary spindle. 
         [0017]    The travelling nut may comprise several engaging elements which are equidistantly distributed over the circumference of the travelling nut. Preferably the travelling nut has at least two, three or four engaging elements. With only one single engaging element the winding core may be rotated 360° around its longitudinal axis for arranging the end stop assembly with the travelling nut arranged on the spindle within the inner cavity of the winding core. Providing several engaging elements spaced over the circumference of the nut allows inserting of the end stop assembly with the travelling nut in the inner cavity of the winding core by rotating the winding core around its axis with only a fraction of 360°. Preferably the end stop assembly with the travelling nut can be inserted into the inner cavity in rotation steps and/or angle steps of 180°, 120° or 90° of the winding core around its longitudinal axis. As a result the adjusting of the lower and/or upper end position of the shade is simplified and more precise. 
         [0018]    Preferably when the travelling nut interacts with and/or abuts the first end stop to set the upper end position of the shade, the upper end position of the shade is adjustable by removing the end stop assembly with the at least one travelling nut from the winding core while maintaining the orientation of the end stop assembly, rotating the winding core so as to unwind or wind up the shade as desired while still maintaining the orientation of the end stop assembly, preferably the orientation of the travelling nut relative to the spindle, and re-inserting the end stop assembly with the at least one travelling nut into the inner cavity of the winding core. 
         [0019]    The engaging element of the travelling nut may be formed as a groove. Preferably the groove is aligned parallel to the longitudinal axis of the winding core. The complementary element on the inner surface of the winding core may be formed as a bar extending parallel to the longitudinal axis of the winding core. In an alternative embodiment the travelling nut may be formed as a bar and the complementary element on the inner surface of the winding core may be formed as a groove. The bar and the groove extend parallel to the longitudinal axis of the winding core. 
         [0020]    According to a further embodiment of the present invention a first travelling nut and a second travelling nut are moveably arranged on the spindle between the first and second end stop. By using a first and second travelling nut the adjustment possibilities for setting the lower and upper end position of the shade are increased. Preferably the first travelling nut sets an upper end position of the shade by interacting with the first end stop. The second travelling nut sets a lower end position of the shade by interacting with the second end stop. The distance between the first and the second travelling nut on the spindle defines the amount and/or the length of the shade which can be unwind from or wind up on the winding core. 
         [0021]    According to a further embodiment the spindle length between the first end stop and the second end stop is predetermined and unalterable. As an advantageous result the spindle and the first and second end stop may form an end stop assembly as one single unit. Thus, the necessity of providing the end stops as separate parts besides the spindle can be avoided. As the first and second end stops may be already inseparably connected with the spindle any further assembling and/or adjusting of the first and second end stops can be omitted. This allows a simplified assembling and/or adjusting of the shading device, particularly the end stop assembly. 
         [0022]    Preferably the first end stop and the second end stop are inseparably connected with the spindle. The first end stop, the second end stop and the spindle may be formed in one piece or made as one integral part. Such an end stop assembly can be produced with reasonable costs. The end stop assembly consisting of the first end stop, the second end stop and the spindle may be made of plastic. The result is a single part or component including the spindle and the first and second end stop which is compact and space-saving. Preferably the first end stop and the second end stop are formed as opposing ends of the spindle. The length of the spindle between the first and second end stop is fixed and unchangeable. The first and/or second end stop may have a greater diameter than the spindle. The circumference of the first and/or second end stop may protrude over the circumference of the spindle. Thus, the inner sides of the first and/or second end stop oriented towards the spindle may serve as contact surfaces for the travelling nut or may have an abutment shoulder for interacting with a complementary abutment projection of the travelling nut. 
         [0023]    The first end stop, the second end stop and the spindle may form an end stop assembly. The end stop assembly in regard to the first end stop, the second end stop and the spindle may be produced as one piece and/or one integral component. Preferably at least one travelling nut is part of or arranged on the end stop assembly. Particularly a first travelling nut and a second travelling nut are parts of or arranged on the end stop assembly. The end stop assembly may be arranged to a fixed rod or shaft. During normal operation of the shading device the rod or shaft is stationary. As the end stop assembly is non-rotatable mounted to the stationary rod or shaft, the end stop assembly itself is stationary. Preferably the winding core is rotatable mounted around the end stop assembly. By rotating the winding core in a first direction a flexible cord or shade material can be unwound from the winding core. Rotating the winding core in a second direction and directed opposite the first direction winds the cord or shade up around the winding core. 
         [0024]    The end stop assembly may be formed as module. This module can be a component of a modular system for combining with components of the modular system. Preferably the components of the modular system which are combinable with the end stop assembly are stationary. A component of the modular system may be a rod, a counterbalance unit and/or a drive means. The modular system may allow for arranging all drive means for driving the winding core located at one end of the shading device. Preferably the components of the modular system, particularly at the end with the drive means, are designed such that they are stationary during normal operation of the shading device. The components may have a stationary point and/or a stationary central axis. 
         [0025]    Preferably the first end stop and/or the second end stop each have an end stop connector for connecting the first end stop and/or the second end stop with a separate component. Because of the end stop connectors the end stop assembly is usable as a module which can be combined with other components of a modular system. The end stop connector may be formed as an opening. Preferably the first end stop, the second end stop and the spindle have a channel extending from an end stop opening of the first end stop to an end stop opening of the second end stop. Particularly the end stop openings and/or the channel have inner formations which mate with outer formations of a rod for non-rotatable fixing to the rod. Caused by the mating formations the end stop assembly is non-rotatable fixed relative to the rod. Furthermore, the end stop assembly may be also fixed by the mating formations in regard to prevent an axial movement. 
         [0026]    According to a further embodiment of the present invention an end piece is arranged at an end of the winding core for mounting the winding core to a holding element. The end piece may be at least partly inserted into the inner cavity of the winding core. Preferably the holding element is mountable to a building structure. A building structure may be a wall, a ceiling and/or a reveal. The building structure may surround or define the architectural opening. Preferably the architectural opening is a window. The holding element may comprise a bracket. 
         [0027]    Preferably the end piece and the holding element have correspondingly designed fixing elements for realizing a non-rotating connection of the end piece with the holding element. The end piece may be stationary attached to the stationary holding element. Preferably by realizing the connection of the end piece with the holding element the spindle is non-rotatable mounted to the holding element. As the end piece is non-rotatable mounted to the end stop assembly, the first and second end stop as well as the spindle of the end stop assembly are also stationary. The fixing elements may be designed as snap-on fittings allowing quick engagement and disengagement of the correspondingly designed fixing elements. A first fixing element may be formed as a protrusion and a second fixing element may be formed as a recess for accommodating a protrusion and realizing a form-fitting connection. A first fixing element may be assigned to the end piece and a second fixing element may be assigned to the holding element or vice versa. 
         [0028]    According to a further aspect of the invention a bearing is assigned to the end piece. The bearing allows rotational movement of the winding core around the non-rotating end piece and the non-rotating spindle. Preferably the bearing is mounted to the outer surface of the end piece which interacts with the inner surface of the winding core. The end piece may be mounted to the winding core exclusively via the bearing. 
         [0029]    Advantageously the end piece is connectable to the holding element in either one of several different orientations of the end piece relative to the holding element. By providing the possibility of several different orientations in which the end piece is connectable with the holding element an adjusting of the lower and/or upper end stop position of the shade is simplified and more precise. Preferably the end piece and the holding element have several correspondingly designed fixing elements or fixing means equidistantly and coaxially distributed around the longitudinal centre axis of the winding core defining several discrete and equally distanced holding positions of the end piece in interaction with the holding element. Thus, the winding core with the end piece and the end stop assembly may be rotated around the longitudinal centre axis of the winding core with discrete rotation steps and/or angle steps. 
         [0030]    Preferably the end piece and the holding element provide at least four, six, eight, ten or twelve correspondingly designed fixing elements or fixing means which are equidistantly and coaxially distributed around the longitudinal axis of the winding core for defining accordingly discrete and equally distanced holding positions. Thus, the different holding positions may be distanced from each other according a rotation of the end piece and/or winding core around the longitudinal axis of the winding core in angle increments of 90°, 60°, 45°, 36° or 30°. 
         [0031]    The first fixing element of the end piece may have a stick with grooves as fixing means on its outer surface aligned parallel the longitudinal axis of the stick. The second fixing element of the holding element may have a recess with bars as fixing means formed complementary to the grooves of the first fixing element. 
         [0032]    According to a further embodiment of the present invention the first end stop and/or the second end stop are arranged on a stationary rod of a counterbalance unit. Preferably the first end stop or the second end stop interacts with the counterbalance unit for providing a preload for the counterbalance unit, particularly in an upper end position of the shade. The first or second end stop may interact with a pre-tensioned spring element of the counterbalance unit to hold the preload or pre-tensioning. The counterbalance unit may be generally similar to a counterbalance unit described in the applicant&#39;s published international applications WO 2010/089118 or WO 2013/129915. 
         [0033]    Another aspect of the invention is related to a method for arranging a travelling nut according to present invention around and/or onto a spindle. According to this method the outer circumference of the travelling nut is opened in a first step by separating two segments of the travelling nut. This may be achieved by opening the ring-like shape of travelling nut by displacing the two segments. In a next step the travelling nut and/or the two segments are arranged around the spindle. In a further step the two segments are connected with each other for closing the ring-like shape and/or the outer circumference of the travelling nut. 
         [0034]    The invention is also related to a method for adjusting the lower end stop position and/or upper end stop position of a shade providing a shade device according to the present invention with at least one travelling nut moveably arranged on the spindle between the first and second end stop, whereby the first end stop, the second end stop and the spindle form an end stop assembly. The method comprises the step of arranging the winding core having an end piece to a holding element mounted to a building structure. The winding core may be rotatable connected to the end piece by a bearing. Furthermore, the end piece may be non-rotatable connected to the spindle and/or end stop assembly. By arranging the end piece to the stationary mounted holding element, the end piece and the spindle, particularly the end stop assembly, is stationary. 
         [0035]    The method further comprises the step of rotating the winding core to the lower end stop position of the shade at which the travelling nut interacts with the second end stop of the spindle. The travelling nut is connected with the inner surface of the hollow winding core such that rotating the winding core rotates the travelling nut around the spindle, which leads to a movement of the travelling nut along the longitudinal direction of the spindle axis. In a next step the end piece is disengaged from the holding element. Preferably the whole winding core is removed from any holding elements. According to a further step the winding core is rotated together with the end stop assembly around its longitudinally axis for rolling up or rolling off the shade from the winding core to set the desired shade length. In a following step the connection between the end piece and the holding element is re-established. This method allows a quick and easy way to adjust at least one end stop position of the shade. 
         [0036]    Preferably the travelling nut during rotating of the winding core together with the end stop assembly remains its position in relation to the spindle and the second end stop. To set the desired shade length and/or an end stop position of the shade, the winding core including the end stop assembly is rotated around the longitudinal axis of the winding core. For the adjusting step there is no movement of the winding core relative to the spindle, particularly the end stop assembly. Thus, the travelling nut does not move relative to the spindle and remains abutting the second end stop. 
         [0037]    According to a further embodiment of the method and before arranging the winding core with the end piece to the holding element, the end stop assembly is inserted into the inner cavity of the winding core with the shade in its upper end position. Preferably at least one travelling nut interacts with and or abuts the first end stop. 
         [0038]    Preferably a first travelling nut and a second travelling nut are moveably arranged on the spindle between the first and second end stop. The distance between the first and second travelling nut sets the total length of the shade which may be wind onto or unwind from the winding core. The first travelling nut may be assigned to the first end stop for setting the upper end position of the shade. The second travelling nut may be assigned to the second end stop for setting the lower end position of the shade. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will best be appreciated in conjunction with the accompanying figures, wherein like reference numerals denote like elements and parts, in which: 
           [0040]      FIG. 1  is a schematic perspective view with partial removed elements of a shading device according to the present invention, 
           [0041]      FIG. 2  presents a schematic perspective view of a section with partial removed elements of the shading device according to  FIG. 1 , 
           [0042]      FIG. 3  is a further schematic perspective view of a section with partial removed elements of the shading device according to the invention, 
           [0043]      FIG. 4  presents a schematic perspective view with partial removed elements of a shading device according to the present invention disengaged from holding elements, 
           [0044]      FIG. 5  is a further schematic perspective view of a section with partial removed elements of the shading device according to the invention with two travelling nuts, 
           [0045]      FIG. 6  is an exploded view of a shading device according to the present invention. 
           [0046]      FIG. 7  is an exploded view of a holding element with an end piece for a shading device according to the invention. 
           [0047]      FIG. 8  is a first perspective view of an assembled holding element and an end piece according to  FIG. 7 , 
           [0048]      FIG. 9  is a second perspective view of an assembled holding element and an end piece according to  FIG. 8 , 
           [0049]      FIG. 10  is a schematic perspective view of an end stop assembly for a shading device according to the present invention with a travelling nut in an opened position, 
           [0050]      FIG. 11  is a schematic cross section of the end stop assembly with the travelling nut in the opened position according to  FIG. 10 , 
           [0051]      FIG. 12  is a further schematic perspective view of an end stop assembly for a shading device according to the present invention with a travelling nut in a closed position, and 
           [0052]      FIG. 13  is a schematic cross section of the end stop assembly with the travelling nut in the closed position according to  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0053]    The present invention will now be described more fully hereinafter with reference to the accompanying figures in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0054]      FIG. 1  is a schematic perspective view with partial removed elements of a shading device  10  according to the present invention and shows the shading device  10  assembled for normal operation. According to this embodiment the shading device  10  is a roller blind. The shading device  10  comprises a winding core, more particularly a shade tube  11 . The shade tube  11  is designed as a roller. On an outer surface  12  of the shade tube  11  a shade  13  is attached. The shade  13  is made of a flexible material that can be rolled up and rolled down the shade tube  11 . A free end of the shade  13  has a bottom rail  14  for stabilizing the shade  13  and/or operating the shade  13  by hand. 
         [0055]    The shade tube  11  is hollow and has an inner surface  15  defining an inner cavity  16 . Within the inner cavity an end stop assembly  17  is arranged. The end stop assembly  17  comprises a spindle  18 , a first end stop  19  and a second end stop  20 . In this embodiment the first and second end stop  19 ,  20  are formed integrally with the spindle  18 . 
         [0056]    The end stop assembly  17  is mounted to an end piece  21 . Here the first end stop  19  is arranged adjacent to the end piece  21 . The shade tube has a first tube end  22  and a second tube end  23 . The end piece  21  is inserted in the inner cavity  16  of the shade tube  11  at the first tube end  22 . The end piece  21  and the end stop assembly  17  are non-rotatable mounted to each other. A bearing  24  is arranged at the end piece  21  connecting the end piece  21  with the inner surface  15  of the shade tube  11 . Thus, the shade tube  11  is rotatable relative to the end piece  21  and the end stop assembly  17 . 
         [0057]    A travelling nut  25  is moveably arranged on the spindle  18  between the first and second end stop  19 ,  20 . With an engaging element on the outer surface the travelling nut  25  interacts with a complementary element  26  on the inner surface  15  of the shade tube  11 . In this embodiment the complementary element  26  is designed as a bar extending parallel to the longitudinal axis of the shade tube  11 . 
         [0058]    The first and second tube ends  22 ,  23  are respectively coupled to first and second holding elements  27 ,  28 . Each of the holding elements  27 ,  28  comprises a bracket  29  for mounting to a building structure. Furthermore, holding element  27  assigned to the end piece  21  of the first tube end  22  has a mounting disc  30 . In this embodiment the mounting disc  30  comprises a drive means for driving the shade tube  11 . The mounting disc  30  has a stationary recess which is non-rotatable fixed to the bracket  29  while the drive means of the mounting disc  30  is rotatable relative to the recess. The end piece  21  has a stick which is also non-rotatable connected to the mounting disc  30 , namely to the recess of the mounting disc  30 . Thus, the end stop assembly  17  is mounted via the end piece  21  to the holding element  27 . 
         [0059]    The second tube end  23  has a stationary axle stub  31  extending out of the inner cavity  16  of the shade tube  11 . The axle stub  31  and the end piece  21  forms a rotation axis of the shade tube  11  around the longitudinal centre axis of the shade tube  11 . The axle stub  31  is non-rotatable coupled to the bracket  28  by an appropriate complementary mating formation  32 . The axle stub  31  is coupled by a further bearing  33  to the inner surface  15  of the shade tube  11 . The further bearing  33  is inserted in the inner cavity  16  of the shade tube  11  at the second tube end  23 . The bearing  33  allows rotation of the shade tube  11  relative to the stationary axle stub  31 . 
         [0060]      FIG. 2  presents a schematic perspective view of a section with partial removed elements of the shading device  10  according to  FIG. 1 . The spindle  18  is a threaded shaft. In this embodiment the spindle  18  is hollow to accommodate an end of a stationary rod (not shown). This rod may be an extension of axle stub  31  according to  FIG. 1  or a rod of a counterbalancing unit. The external thread of spindle  18  mates with the internal thread of travelling nut  25 . 
         [0061]    The first and second end stops  19 ,  20  are forming end parts of the spindle  18 . Furthermore, the first and second end stops  19 ,  20  have a greater diameter than the spindle  18 . Inner sides  34  of the first and second end stops  19 ,  20  have an abutment shoulder for contacting and stopping the travelling nut  25  which has a complementary abutment shoulder. 
         [0062]    The first and second end stops  19 ,  29  each have a mounting part  35  for mounting the end stop assembly  17  to a rod (not shown). In this embodiment the mounting part  35  is designed as a bore for receiving a fixing means like a screw, pin, bolt, etc. The mounting part  35  and/or fixing means may interact with a rod (not shown) which is inserted in the hollow end stop assembly  17  through one of the end stop openings  36 . Accordingly, each end stop opening  36  can serve as connector for connecting the end stop assembly  17  to a stationary component of the shading device  10 . 
         [0063]    According to  FIG. 2  the travelling nut  25  is arranged in a mid region of the spindle between the first and second end stop  19 ,  20 . Thus, the shade tube  11  may be driven to roll up or unroll the shade  13 . 
         [0064]      FIG. 3  is a further schematic perspective view of a section with partial removed elements of the shading device  10  according to the invention. The travelling nut  25  interacts with the second end stop  20 . More particularly, an abutment shoulder of the travelling nut  25  abuts a complementary abutment shoulder at the inner side  34  of the second end stop  20 . Thus, the travelling nut  25  cannot be moved any further away from the first end stop  19 . This position of the travelling nut  25  corresponds to the lower end stop position of the shade  13 . In the lower end stop position of the shade  13 , the shade  13  cannot be unrolled any further of the shade tube  11 . Only a rotation of the shade tube  11  in an opposite direction to roll up the shade  13  is possible. Such a rotation of the shade tube  11  will move the travelling nut  25  along the spindle  18  towards the first end stop  19 . 
         [0065]      FIG. 4  presents a schematic perspective view with partial removed elements of a shading device  10  according to the present invention disengaged from holding elements  27 ,  28 . As in  FIG. 3  the travelling nut  25  is contacting the second end stop  20  and the shade  13  is in its lower end stop position. The arrangement according to  FIG. 4  shows the shading device  10  in a setting position for setting or adjusting the lower end stop position of the shade  13 . The disengagement from the holding elements  27 ,  28  allows to roll up or unroll the shade while rotating the shade tube  11  together with the end stop assembly  17  without any relative movement of the spindle  18  or the travelling nut  25  in regard to the shade tube  11 . As a result the lower end stop position of the shade  13  is adjustable. 
         [0066]    The holding element  27  has a fixing element  37 . In this embodiment the mounting disc  30  comprises the fixing element  37  which is stationary coupled to the bracket  29 . The fixing element  37  of the mounting disc  30  has as a recess for receiving and interacting with a correspondingly designed fixing element (not shown) of the end piece  21  for realizing a stationary connection of the end piece  21  with the holding element  27 . 
         [0067]    The fixing element  37  of the holding element  27  and the respective complementary fixing element of the end piece  21  have equidistantly and coaxially distributed fixing means (not shown) to allow several different orientations of the stationary end piece  21  relative to the stationary holding element  27 . When disengaged from the holding element  27  the end piece  21  is rotatable to several discrete and equally distanced holding positions around a centre axis of the mounting disc  30  in which the end piece  21  is connectable to the holding element  27 . 
         [0068]    Furthermore, the mounting disc  30  includes a drive unit in the form of a drive wheel  59 . The drive wheel  59  is rotatable mounted relative to the fixing element  37  of the mounting disc  30 . For normal operation the drive wheel  59  is fixed to the shade tube  11  according to  FIGS. 1 to 3 . A cord or chain (not shown) may be arranged to the drive wheel  59 . By driving the drive wheel  59  via a cord or chain the shade tube  11  can be driven around the centre axis of the shade tube  11  and the stationary end stop assembly  17 . 
         [0069]      FIG. 5  is a further schematic perspective view of a section with partial removed elements of the shading device  10  according to the invention with two travelling nuts  25 ,  38 . First travelling nut  38  is assigned to the first end stop  19  for setting the upper end stop position of the shade  13 . The second travelling nut  25  is assigned to the second end stop  20  for setting the lower end stop position of the shade  13 . Both travelling nuts  25  and  38  are identically designed. The distance between the first and second travelling nut  25 ,  38  defines the length of the shade  13  which can be rolled on or up rolled from the shade tube  11 . The smaller the distance between the first and second travelling nut  25 ,  38 , the greater the windable length of the shade  13  is. 
         [0070]    The second travelling nut  25  abuts according to  FIG. 5  the second end stop  20  like in  FIG. 3 . Thus, the travelling nut  25  cannot be moved any further away from the first end stop  19 . This position of the second travelling nut  25  corresponds to the lower end stop position of the shade  13 . For reaching the upper end stop position of the shade  13 , the shade tube  11  has to be rotated such that both travelling nuts  25 ,  38  are moving towards the first end stop  19 . The upper end stop position of the shade  13  is reached when the first travelling nut  38  abuts the first end stop  19 . 
         [0071]    Additionally  FIG. 5  shows a rod  39 , which has not been shown in  FIGS. 1 to 4  for clarity reasons, but which is also part of the embodiment of the present invention according to  FIGS. 1 to 4  as well. The rod  39  is inserted through end stop openings  36  into the hollow end stop assembly  17  and through the hollow spindle  18 . The end stop assembly  17  may be additionally fixed to the rod  30  by the mounting parts  35 . The rod  39  is stationary coupled to the holding elements  27 ,  28 . The rod  39  forms a stationary central axis of the shading device  10  around which the shade tube  11  is rotatable in normal operation of the shading device  10 . In this embodiment the rod  39  is part of a counterbalance unit. 
         [0072]      FIG. 6  is an exploded view of a shading device  10  according to the present invention. In this embodiment the end stop assembly  17  has two travelling nuts  25 ,  38 . In an alternative embodiment the end stop assembly  17  may have only a single travelling nut  25 . 
         [0073]    The shading device  10  comprises a counterbalance unit  40 . The counterbalance unit  40  serves for balancing the shade  13  in every desired position of the shade  13 . 
         [0074]    The end piece  21  may be replaced by an alternative end piece  41 . The end pieces  21 ,  41  comprise a break device for slowing down or braking the rotation of the shade tube  11 . According to a further alternative end piece  21  may be replaced by an adapter, particularly in the form of end piece  41 , but without a break device. End pieces  21  and  41  both have a stationary fixing element and a bearing  24 . 
         [0075]    Mounting unit  42  or  43  may be used as an alternative to mounting disc  30 . The mounting units  42 ,  43  are designed to be mounted on the inner face of the brackets  29  like the mounting disc  30 . In this embodiment the mounting units  42 ,  43  are drive units configured to drive the shade tube  11 . For this purpose the mounting unit  43  has a cord  44 . Pulling the cord  44  activates a drive means coupled with the shade tube  11 . The mounting unit  42  needs an additional chain (not shown) to drive a drive means to rotate the shade tube  11 . The drive means of the mounting units  42 ,  43  are rotatable to a stationary fixing element  37  of the mounting units  42 ,  43  which may be similar to the fixing element  37  of the mounting disc  30 . 
         [0076]      FIG. 7  is an exploded view of the holding element  27  with the end piece  21  for a shading device  10  according to the invention. In detail the mounting disc  30  of the holding element  27  is shown in an exploded view. The mounting disc  30  comprises the drive wheel  59 , a bearing ring  60 , the fixing element  37  and a mounting cover  61 . 
         [0077]    A ball chain  62  is provided for arrangement around the drive wheel  59 . The fixing element  37  has a mounting plate  63 . The mounting plate  63  has a tube like projection  64 . The projection  64  provides a recess  65 . The inner side of the recess  65  has several fixing means  66 . For clarity not all fixing means  66  have a reference numeral. In this embodiment the fixing means  66  of the fixing element  37  are formed as bars extending longitudinal to the projection  64 . 
         [0078]    For assembling the mounting disc  30  to the bracket  29  the mounting cover  61  is arranged at the outer side of bracket  29 . Then the fixing element  37  is coupled with its mounting plate  63  to the inner side of the bracket  29  and coupled with the mounting cover  61 . Thus, the fixing element  37  is stationary mounted to the bracket  29 . The drive wheel  59 , ball chain  62  and bearing ring  60  form a drive unit which is attachable to the bracket  29  and the fixing element  37 . The drive wheel  59  is rotatable to the bearing ring  60  and the fixing element  37 . 
         [0079]      FIG. 8  is a first perspective view of an assembled holding element  27  and the end piece  21  according to  FIG. 7 . By pulling at one side of ball chain  62  the ball chain  62  and the drive wheel  59  which is coupled with the ball chain  62  rotates around the fixing element  37 . The drive wheel  59  has several coupling members  67  for coupling the drive wheel  59  to the inner side of the bearing  24  of end piece  21 . 
         [0080]      FIG. 9  is a second perspective view of the assembled holding element  27  and the end piece  21  according to  FIG. 8 . The end piece  21  has a fixing element  68 . The fixing element  68  of end piece  21  is stationary. In this embodiment the fixing element  68  is formed as a stick. The fixing element  68  is surrounded by the bearing  24  which is rotatable around the fixing element  68 . At the outer circumference of the fixing element  68  are several fixing means  69 . For clarity not all fixing means  69  have a reference numeral. According to this embodiment the fixing means  69  are designed as grooves. 
         [0081]    The fixing means  69  of the end piece  21  are complementary formed to the fixing means  66  of the fixing element  37  of the holding element  27 . Fixing means  66  and  69  are equidistantly distributed around the centre axis of the fixing element  37  and  68  respectively. Fixing element  68  of end piece  21  can be inserted into the recess  65  of the fixing element  37  to establish a stationary coupling between end piece  21  and the holding element  27 . Because of the several fixing means  66  and  69  several different holding positions of the end piece  21 , namely the fixing element  68 , relative to the holding element  21 , namely the fixing element  37 , are realizable. Dependent of the amount of fixing means  66 ,  69  the fixing element  68  is connectable with the fixing element  37  in predetermined angle increments around the centre axis of the end piece  21 . This allows a precise adjustment of the lower and/or upper end stop position of the shade  13 . 
         [0082]    The inner side of the bearing  24  has several coupling members  70  which are complementary to the coupling members  67  of the drive wheel  59 . By establishing the connection between both fixing elements  37  and  68  the coupling members  67 ,  70  are also coupled with each other. 
         [0083]      FIG. 10  is a schematic perspective view of an end stop assembly  17  for a shading device  10  according to the present invention with a travelling nut  25  in an opened position. Travelling nuts  25  and  38  may (but need not) be identical. The following description of travelling nut  25  applies also to travelling nut  38 . 
         [0084]    The travelling nut  25  is has articulated segments. More particularly, it comprises two segments  45 ,  46  which are hingedly connected by a flexible hinge  47 . In this embodiment, the segments  45 ,  46  are designed as a first half  45  and a second half  46  respectively of the travelling nut  25 . The flexible hinge  47  allows to flip open the travelling nut  25  for arranging the travelling nut  25  around the spindle  18 . The flexible hinge  47  is according to this embodiment substantially made as a flexible plastic strip which is flexibly connected with the two halves  45 ,  46 . 
         [0085]    For engaging the travelling nut  25  around the spindle  18  the travelling nut  25  is in its open position and half  45  is arranged to the spindle  18  such that the external thread  48  of the spindle  18  mates with the internal thread  49  of the half  45 . 
         [0086]    The first half  45  of the travelling nut  25  has a first joint element  50  and the second half  46  of the travelling nut  25  has a second joint element  51 . The joint elements  50 ,  51  are formed complementary to each other for realizing an engagement with each other. By engaging both joint elements  50 ,  51  with each other the two halves  45 ,  46  are connected to realize a closed position of the travelling nut  25 . 
         [0087]      FIG. 11  is a schematic cross section of the end stop assembly  17  with the travelling nut  25  in the opened position according to  FIG. 10 . According to this embodiment the first joint element  50  is designed as a snap-on catch and the second joint element  51  is designed as a recess complementary formed to the snap-on catch. 
         [0088]    As the flexible hinge  47  is made as a flexible strip the two halves  45 ,  46  are displaced from each other in the opened position of the travelling nut  25 . The flexible hinge  47  has several formations  52 ,  53  which mate with complementary formed formations  54 ,  55  on the halves  45 ,  46  in a closed position of the travelling nut  25 . 
         [0089]    The end stop openings  36  and the hollow spindle  18  have several grooves  56  at the inner side of a tube section of the end stop assembly  17 . These grooves  56  mate with complementary formed bars of a rod  39  for avoiding any rotation of the end stop assembly  17  relative to the rod  39 . 
         [0090]      FIG. 12  is a further schematic perspective view of the end stop assembly  17  for the shading device  10  according to the present invention with the travelling nut  25  in a closed position. In comparison to  FIG. 11  the travelling nut half  46  has been swung with the flexible hinge  47  around the spindle  18  for coupling the nut halves  45 ,  46  with each other. In the closed position of the travelling nut  25  the two halves  45 ,  46  form a ring shaped travelling nut  25 . The travelling nut  25  is moveably guided on the spindle  18 . 
         [0091]      FIG. 13  is a schematic cross section of the end stop assembly  17  with the travelling nut  25  in the closed position according to  FIG. 2 . The snap-on catch  50  is snapped on the correspondingly formed recess  51 . Thus, the halves  45 ,  46  of the travelling nut  25  are detachable joined with each other. 
         [0092]    The flexible hinge  47  is aligned to the travelling nut  25 , whereby the formations  52  and  53  engage the formations  54  and  55  respectively. An outer surface  57  of the travelling nut  25  contacts the inner surface  15  of the inner cavity  16  when the end stop assembly  17  with the closed travelling nut  25  is inserted into the shade tube  11 . In this case the connection between the two halves  45 ,  46  cannot be unintentionally opened. The contact of the outer surface  57  of the travelling nut  25  with the inner surface  15  of the inner cavity  16  prevents a unintended opening of the travelling nut  25 . 
         [0093]    The outer surface  57  of the travelling nut  25  has engaging elements  58 . In this embodiment the travelling nut  25  has two engaging elements  58  which are formed as grooves. The engaging elements  58  are assigned to the first half  45  and the second half  46  respectively. When the end stop assembly  17  with the travelling nut  25  is inserted into the inner cavity  16  of the shade tube  11 , the engaging elements  58  engage a complementary element in the inner surface  15  of the shade tube. In this embodiment this complementary element is formed as a bar  25  as shown in  FIGS. 1 to 5 . 
         [0094]    Although preferred embodiments of the present invention and modifications thereof have been described in detail herein, it is to be understood that this invention is not limited to these precise embodiments and variations and may be effected by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. 
         [0095]    The use of expressions like: “particularly”, “preferably” or “especially preferred” etc. is not intended to limit the invention. Features which are not specifically or explicitly described or claimed may be additionally included in the structure or method according to the present invention without deviating from its scope.

Summary:
The invention relates to a shading device for an architectural opening comprising a shade, a drive unit for extending and retracting the shade between a first and second end position, a spindle, a first end stop, stationary connected to the spindle near a first end of the spindle and at least one travelling nut, movably arranged on the spindle and operatively connected to the drive unit so as to move towards, respectively away from the first end stop as the shade is extended, respectively retracted. The travelling nut is articulated in circumferential direction into segments, with at least two segments being detachably connectable to each other at one of their ends.