CROSS-REFERENCE TO RELATED APPLICATION 
     This application corresponds to and claims priority to European Application No. 98204081.8, filed Dec. 3, 1998. This European application is hereby incorporated by reference as though fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     This invention relates to a combination of an end cap and a mounting support for a roller, especially a roller of an architectural covering and particularly a winding roller for a covering for an architectural opening, such as a window blind or shade. 
     b. Background Art 
     Combinations of end caps and mounting supports for rollers are known from British patent specification GB 434 043 and Dutch published patent application NL 84 00103. In each of the combinations of an end cap and a mounting support of these publications, the end cap can be engaged and disengaged from the mounting support. Either the end cap or the mounting support has an axially open slot or recess for accommodating an axially projecting pin or protuberance on the other and there are means adjacent to the axial recess to engage and hold the axial pin within the axial recess and to release the axial pin from such engagement. From these publications, it has also been clear that there could suitably be a kinematic inversion of their axial recesses and axial pins on their end caps and mounting supports that would simply lead to different positions for these elements. 
     However, access to the means for engaging and releasing the axial pin from the axial recess on such end caps and mounting supports has generally been only from one direction. As a result, access to the means for engaging and releasing the axial pin, which could well be resilient, to activate or deactivate it has been somewhat limited. In this regard, winding rollers for window shades and blinds have typically been mounted in confined spaces near the top of window frames. Also the axial recesses of winding rollers have often been placed in hard-to-reach vertical or horizontal positions, depending on whether the mounting supports have been affixed to a wall or to a ceiling adjacent to the window. This has frequently made it difficult to engage or disengage the axial pin from the axial opening when installing or removing a winding roller of a shade or blind from a window frame. 
     SUMMARY OF THE INVENTION 
     In order to overcome or ameliorate at least some of the disadvantages of known combinations of end caps and mounting supports, the combination of an end cap and mounting support of this invention comprises: an end cap disengagably engagable with a support bracket and one of the end cap and the support bracket being provided with: a laterally open slot for accommodating an axially extending protuberance on the other of the end cap and the support bracket; and closing means to prevent the protuberance from escaping from the laterally open slot; wherein the closing means comprises a rotatable locking collar surrounding the laterally open slot and having a circumferential entrance opening which can be aligned with the laterally open slot by rotation of the locking collar relative to the laterally open slot from a closed position to an open position, thereby selectively providing access to the laterally open slot through the circumferential entrance opening. 
     Advantageously, the end cap and mounting support combination also comprises means for retaining the locking collar in the closed position. Preferably, the retaining means comprise a resilient spring means for biasing the locking collar into its closed position. 
     Advantageously, the end cap and mounting support combination further comprises a manually engagable projection on diametrically opposite sides of the locking collar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further aspects of the invention will be apparent from the detailed description below of particular embodiments and the drawings thereof, in which: 
     FIG. 1 is a longitudinal or axial cross-section through a winding roller of a shade or blind; the roller is journalled between a pair of mounting brackets and has, on one of its longitudinal ends, a first embodiment of an idle end cap of this invention; 
     FIG. 2 is a perspective view showing the idle end cap of FIG. 1 in an open position; 
     FIG. 3 is a perspective view, similar to FIG. 2, showing the idle end cap of FIG. 1 in a closed position; 
     FIG. 4 is an exploded perspective view of a second embodiment of the idle end cap of this invention; 
     FIG. 5 is a schematic end view of a central pin and a leaf spring of the second embodiment of the idle end cap of FIG. 4; 
     FIG. 6 is a schematic axial elevation view of the central pin and leaf spring of the second embodiment of the idle end cap of FIG. 4; 
     FIG. 7 is an exploded perspective view of a third embodiment of the idle end cap of this invention; 
     FIG. 8 is an end view of the third embodiment of the idle end cap of FIG. 7; 
     FIG. 9 is a perspective view of the third embodiment of the idle end cap of FIG. 7; 
     FIG. 10 is an exploded perspective view of a fourth embodiment of the idle end cap of this invention; 
     FIG. 11 is an axial cross-section of a locking collar of the fourth embodiment of the idle end cap of FIG. 10, viewed in the direction of the arrows XI—XI of FIG. 10; 
     FIG. 12 is an exploded perspective view of a fifth embodiment of the idle end cap of this invention; 
     FIG. 13 is an end view of the fifth embodiment of the idle end cap of FIG. 12; 
     FIG. 14 is an axial cross-section of the fifth embodiment of the idle end cap of FIG. 12, viewed in the direction of the arrows A—A of FIG. 13; and 
     FIG. 15 is an axial cross-section of the fifth embodiment of the idle end cap of FIG. 12, viewed in the direction of the arrows B—B of FIG.  14 . 
     In these Figures, corresponding parts in different embodiments are referred to by corresponding names and by the same last two reference numerals. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows, in longitudinal or axial cross-section, a roller shade, generally  1 . The ends of the roller shade  1  are attached to a pair of conventional left and right, support brackets  3 ,  5  for mounting the roller shade on a wall, adjacent to a window (not shown). For convenience, the left and right brackets  3 ,  5  can be identical to limit the number of items that need to be stocked by those who sell or install the roller shade  1 . The roller shade  1  has an axially extending, elongate hollow tubular winding roller  7 , about which are a plurality of windings of a flexible shade  9 . The top end of the shade  9  is attached to the roller  7  in a conventional manner. 
     Within the left end portion of the roller  7 , as shown in FIG. 1, is a generally tubular, idle end cap  11  of this invention. As described below, the idle end cap  11  can be mounted on, and rotatably journalled relative to, the left bracket  3  in a conventional manner. A conventional driving end cap  13  for rotating the roller  7 , when winding or unwinding the flexible shade or blind  9 , is mounted on the right bracket  5  as shown in FIG.  1 . The driving end cap  13  has a grooved pulley  14  for engagement with a driving cord (not shown). 
     As seen from FIGS. 1-3, the idle end cap  11  includes: a generally tubular, axially extending, outer body  15 , to be inserted in the left end of the roller  7 ; a generally cylindrical, axially extending, central pin  17 , concentrically received within a generally tubular, axially extending, central bore  18  of the outer body  15 ; and a generally tubular, axially extending, rotatable locking collar  19  concentrically located between the central pin  17  and the outer body  15 . The left end of the central pin  17  is provided with a laterally or axially open, radially extending, central slot or recess  20 , by which it can engage a laterally elongate, relatively flat tab or protuberance  21  extending axially to the right on the left bracket  3  as shown in FIG.  1  and described below. The outer body  15 , which is non-rotatably received in the roller  7 , is free to rotate with the roller  7  around the central pin  17 , which is held stationary by the tab  21  on the left bracket  3 . 
     The locking collar  19 , as shown in FIGS. 2 and 3, is only capable of limited rotation about the central pin  17  of the idle end cap  11 . FIG. 2 shows a first rotational end position of the locking collar  19  after rotation in the clockwise direction of arrow  22 . In this first end position of FIG. 2, the central slot  20  is in communication with a circumferential entrance opening or radial opening  23  in an enlarged, axially extending, left end portion  24  of the locking collar  19 . As a result of its communication with the radial opening  23  in the locking collar  19 , the central slot  20  is open, so that the flat tab  21  of the left bracket  3  (not shown in FIG. 2) can be radially inserted in the central slot  20 . FIG. 3 shows a second rotational end position of the locking collar  19  after rotation in the counter-clockwise direction of arrow  25 . In the second end position of FIG. 3, the central slot  20  is no longer in communication with the radial opening  23  in the left end portion  24  of the locking collar  19  and is therefore closed, so as to securely hold the flat tab  21  of the left bracket  3  (not shown in FIG. 3) within the locking collar. 
     As also seen from FIGS. 2 and 3, a radially projecting sector  27  is provided on the outer surface of the axially extending, left end portion  28  of the central pin  17 . The projecting sector  27  limits rotational movement of the locking collar  19  relative to the central pin  17  to an arc within an annular recess  29  inside the axially extending, left end portion  24  of the locking collar  19 . However, both the central pin  17  and the locking collar  19  can otherwise rotate 360° relative to the outer body  15 . 
     To facilitate the rotation of the locking collar  19  about the central pin  17 , the left end portion  24  of the locking collar  19  is also provided with at least two, radially extending ridges or projections  31 ,  33  which facilitate the grasping and rotation of the locking collar by hand. Preferably, the ridges  31 ,  33  are circumferentially spaced around the outer surface of the left end portion  24  of the locking collar  19  so that at least one of them can be grasped in whatever position the idle end cap  11  is mounted on the left bracket  3 . In this regard, it is preferred that the ridges be on diametrically opposite sides of the locking collar  19 . 
     As further seen from FIG. 1, the central pin  17  has a bifurcated, preferably mushroom-shaped, structure  35  on the right end of its relatively thinner, axially extending, right end portion  37 . This right end portion  37  of the central pin  17  fits closely but rotatably within a right end portion  38  of the central bore  18  of the outer body  15 , and the bifurcated, right end structure  35  of the central pin is adapted to snap-fit behind an annular edge  39  at the left end of a generally cylindrical, central cavity  41  at the right end of the outer body  15  and its central bore  18 . Thereby, the bifurcated, right end structure  35  of the central pin  17  engages the annular edge  39  of the central cavity  41  of the outer body  15  to hold the central pin  17  securely within the outer body  15 . 
     As still further seen from FIG. 1, the left end portion  28  of the central pin  17 , which carries the central slot  20  at its left end, is thicker than the right end portion  37  of the central pin. As a result, the left end portion  28  of the central pin also fits closely but rotatably within the locking collar  19  but cannot move axially to the right into the thinner right end portion  38  of the central bore  18  of the outer body  15 . A right end portion  42  of the locking collar  19  also fits rotatably: i) about the left end portion  28  of the central pin  17  and ii) within the left end portion  43  of the central bore  18  of the outer body  15 , which is wider than the right end portion  38  of its central bore  18 . It is preferred that means (not shown in FIGS. 1-3) be provided in the idle end cap  11  of FIGS. 1-3 for restraining free rotation of the locking collar  19  about the central pin  17  when the radial opening  23  in the locking collar has been positioned to close the central slot  20  in the central pin. Such restraining means can include: means for increasing the sliding friction between the central pin  17  and the locking collar  19 ; means providing an index between the central pin and the locking collar; or a resilient biasing means for urging the locking collar in the counter-clockwise direction of arrow  25  in FIG.  3 . Several embodiments of the idle end cap of this invention, with different resilient biasing means acting between the central pin and the locking collar to restrain free rotation of the locking collar about the central pin, will be described below with reference to FIGS. 4-15. 
     As also seen from FIG. 3, a funnel-shaped recess  44  is formed between a portion of the locking collar  19  and the projecting sector  27  of the central pin  17  in the closed position of the locking collar  19 . The recess  44  forms an entrance for a conventional flat pin of a support bracket (such as is seen in FIG. 1) into the central slot  20  of the central pin  17  when the central slot  20  is closed by the locking collar  19 . By pressing the inclined side edges of the recess  44  against such a bracket pin, the locking collar  19  will be rotated clockwise to a sufficiently open position to allow the bracket pin to enter the central slot  20  via the radial opening  23  in the locking collar  19 , notwithstanding any means that have been provided in the idle end cap  11  for restraining such rotation when the central slot  20  is closed. 
     FIGS. 4-6 show a second embodiment  111  of the idle end cap of the invention, which is similar to the idle end cap  11  of FIGS. 1-3 and for which corresponding reference numerals (greater by 100) are used below for describing the corresponding parts. 
     The idle end cap  111 , shown in FIGS. 4-6, has: an outer body  115 , to be inserted in the left end of the roller  7  of FIG. 1; an axially extending, central pin  117 , concentrically received within the outer body  115 ; and a rotatable locking collar  119  between the central pin  117  and the outer body. 
     A resilient biasing means for urging the locking collar  119  in the counter-clockwise direction is provided by a leaf spring  145 . After the central pin  117  has been inserted into the locking collar  119 , the leaf spring  145  can be inserted in a transverse slot  147  in the right end of the left end portion  128  of the central pin  117  and in a corresponding pair of radially aligned, transverse slots  149  that are in the right end of the right end portion  142  of the locking collar  119  and are radially aligned with the transverse slot  147  in the central pin. Preferably, the transverse slots  147  and  149  are each open at the respective right end of the left end portion  128  of the central pin  117  and the right end portion  142  of the locking collar  119 . The resulting subassembly can then be inserted into the central cavity  118  of the outer body  115  and retained therein by the bifurcated right end structure  135  of the central pin  117 . 
     FIGS. 5 and 6 schematically show the position of the leaf spring  145  with respect to the central pin  117 . For clarity, the locking collar  119  and the outer body  115  have been deleted in FIGS. 5 and 6. In FIG. 5, which is an end on view of the central pin  117 , the leaf spring  145  is shown (in solid lines) aligned in the transverse slot  147  in the central pin  117  with the central slot  120  in the central pin and is also shown (in dotted lines) in tangentially deflected positions  145 A and  145 B. Aligning the transverse slot  147  with the central slot  120  in the central pin  117  is not necessary, but it is preferred because it is easier to form both when making the central pin  117  by injection molding. The deflected positions  145 A and/or  145 B of the leaf spring  145  result when the locking collar  119  and its pair of transverse slots  149  are rotated relative to the central pin  117 . 
     FIGS. 7-9 show a third embodiment  211  of the idle end cap of the invention, which is similar to the idle end cap  111  of FIGS. 4-6 and for which corresponding reference numerals (greater by 100) are used below for describing the corresponding parts. 
     The idle end cap  211 , shown in FIGS. 7-9, has: an outer body  215 , to be inserted in the left end of the roller  7  of FIG. 1; an axially extending, central pin  217 , concentrically received within the outer body  215 ; and a rotatable locking collar  219  between the central pin  217  and the outer body. A coil spring  245  serves as a resilient biasing means for urging the locking collar  219  in the counter-clockwise direction. The coil spring  245 , upon assembly of the central pin  217  and the locking collar  219 , is engaged between a first radial surface  247  on the projecting sector  227  of the central pin  217  and a facing second radial surface  249  (shown in dotted lines in FIG. 8) in the annular recess  229  within the locking collar  219 . Preferably, a cylindrical cavity is provided in one or both, particularly both, of the opposite radial surfaces  247 ,  249  to retain the coil spring  245  in position between them and to provide room for its compressed windings when the opposite radial surfaces  247 ,  249  abut one another in the open position of locking collar  219  and its radial opening  223 , relative to the central slot  220  in the central pin  217 . 
     FIG. 9 shows how either ridge  231 ,  233  on the left end portion  224  of the locking collar  219  can be urged to move in a clockwise direction  222  to rotate the locking collar and its radial opening  223  clockwise into an open position relative to the central slot  220  of the central pin  217 . Such clockwise movement of the ridges  231 ,  233  and the locking collar  219  is against the force of the coil spring  245 , urging the locking collar  219  to rotate in a counter-clockwise direction. Since the central pin  217  and locking collar  219 , as a sub-assembly, are freely rotatable in the central bore  218  of the outer body  215 , clockwise rotational movement of the ridges  231 ,  233  will only put the central slot  220  of the central pin in communication with the radial opening  223  in the locking collar when the flat tab  21  of the bracket  3 , shown in FIG. 1, is engaged in the central slot  220  so as to keep the central pin  217  stationary. This is, in fact, the only situation in which one would need to open the locking collar  219  by hand. 
     FIGS. 10 and 11 show a fourth embodiment  311  of the idle end cap of the invention, which is similar to the idle end cap  111  of FIGS. 4-6 and for which corresponding reference numerals (greater by 200) are used below for describing the corresponding parts. 
     The idle end cap  311 , shown in FIGS. 10-11, has: an outer body  315 , to be inserted in the left end of the roller  7  of FIG. 1; an axially extending, central pin  317 , concentrically received within the outer body; and a rotatable locking collar  319  between the central pin and the outer body. The central pin  317  has a cavity  351  that is in the outer circumference of its left end portion  328  and that extends to, and is open at, the right end of the left end portion  328  of the central pin. The locking collar  319  has an L-shaped torsion spring  345 . One leg  353  of the L-shaped torsion spring  345  is mounted in a recess  355  in the outer circumference of the right end portion  342  of the locking collar  319 . The other leg  357  of the torsion spring  345  extends radially inwardly of the right end portion  342  of the locking collar  319  where this other leg  357  engages the cavity  351  of the central pin  317 . In this regard, FIG. 11 shows, in detail, the mounting of the torsion spring  345  in the locking collar  319 . 
     FIGS. 12-15 show a fifth embodiment  411  of the idle end cap of the invention, which is similar to the idle end cap  311  of FIGS. 10 and 11 and for which corresponding reference numerals (greater by 100) are used below for describing the corresponding parts. 
     The idle end cap  411 , shown in FIGS. 12-15, has a central pin  417  with a cavity  451  that is in the outer circumference of its left end portion  428  and that extends to, and is open at, the right end of the left end portion  428  of the central pin. As best seen in FIG. 14, the locking collar  419  is provided with an integrally formed, L-shaped torsion spring  445 . One leg  453  of the L-shaped torsion spring  445  is mounted in a recess  455  in the outer circumference of the right end portion  442  of the locking collar  419 . The other leg  457  of the torsion spring  445  extends radially inwardly of the right end portion  442  of the locking collar  419  where this other leg  457  engages the cavity  451  of the central pin  417 . 
     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 “left”, “right”, “longitudinal”, “lateral”, “bottom”, “top”, “axial”, “radial”, “clockwise”, “counter-clockwise”, “inner”, “outer” and “end”, have been used only as relative terms to describe the relationships of the various elements of the combination of an end cap and a mounting support for a roller of the invention. For example, the idle end caps  11 ,  111 ,  211 ,  311 ,  411  and support brackets  3 , 5  could also be used in combination with the winding roller of a roller blind for a window, as well as with a winding roller for the lifting cords of a folding blind or other collapsible window coverings. Likewise, the outer body  15 ,  155 ,  215 ,  315 ,  415  could be modified to achieve additional objectives in the operation of the roller  7 . 
     While embodiments and applications of the present invention have been shown and described, it would be apparent to one skilled in the art that other modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the claims that follow.
An end cap and mounting support combination comprising an end cap ( 11, 111, 211, 311, 411) disengagably engagable with a support bracket ( 3) and one of the end cap and the support bracket being provided with: a laterally open slot ( 20, 120, 220, 320, 420) for accommodating an axially extending protuberance ( 21) on the other of the end cap and the support bracket; and closing means to prevent the protuberance from escaping from the laterally open slot; wherein the closing means comprises a rotatable locking collar ( 19, 119, 219, 319, 419) surrounding the laterally open slot and having a circumferential entrance opening ( 23, 123, 223, 323, 423) which can be aligned with the laterally open slot by rotation of the locking collar relative to the laterally open slot from a closed position to an open position, thereby selectively providing access to the laterally open slot through the circumferential entrance opening.