You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
The present invention relates to an apparatus for operating a blind, in particular, but not exclusively, a vertical window blind, and also to a method of operating such a blind using the apparatus. 
     BACKGROUND OF THE INVENTION 
     It is known to provide a vertical louver blind comprising a plurality of louver carrier trucks constrained to move longitudinally within a headrail. Typically, each truck includes a louver carrier which is rotatable about a vertical axis. In such known vertical louver blinds, translational movement of the carrier trucks is effected by a first drive means and a rotation of the vertical louvers carried by respective louver carriers is effected by a second separate drive means. Each of the two drive means includes a respective operating apparatus whereby a user can control the operation of the drive means. Thus, conventional vertical louver blinds have two separate controls for arranging the blind in the desired configuration, which at best detracts from the aesthetic appeal of the blind, and at worst can be confusing for a user as to which operating apparatus has which effect, thus leading to frustration on the part of the user. 
     Accordingly, it is desired to provide a vertical louver blind with a simplified operating means. 
     SUMMARY OF THE INVENTION 
     Thus, in accordance with a first aspect of the present invention, there is provided a vertical blind assembly including a plurality of louver carrier trucks slidably carried within a headrail, each truck including a louver carrier mounted for rotation about an axis; wherein the blind assembly further includes an operating means selectively engageable with a first drive means for urging the trucks to move lengthwise within the headrail and a second drive means for rotation of the louver carrier of each truck about its respective axis. 
     Embodiments of the present invention thus only require a single operating means for the control of both the translational movement of the trucks along the headrail and the rotational movement of the louver carriers about their respective axes. 
     The operating means preferably comprises an operating wand. 
     Preferably, the operation of the vertical blind is caused by rotation of the relevant drive means, which in turn is effected by rotation of the wand when engaged with that drive means. 
     In a preferred embodiment, the wand includes an engagement element and each of the first and second drive means includes a receiving portion arranged to be capable of receiving at least a portion of the engagement element, whereby the desired drive may be achieved by interengagement of the engagement element, or a portion thereof, with the first or second drive receiving portion. 
     The wand desirably includes an upper wand portion which carries the engagement element, the engagement element being disengaged from one of the drive means and engaged with the other of the drive means via axial movement of the upper wand portion. 
     The first drive means may include a chain wheel capable of driving a chain which is preferably connected either directly or indirectly to at least one of the trucks for causing longitudinal movement of the or each truck within the headrail. The term “chain” is intended to include a cord comprising a plurality of equally spaced balls or spheres attached to the cord, as is conventially used with this type of blind assembly. Each louver carrier truck may be connected to the truck or trucks adjacent to it, and the chain may be connected to one of the trucks (the “lead” truck) such that movement of the lead truck longitudinally within the headrail results in the remainder of the louver carrier trucks either being pulled along behind it or pushed by it in the desired direction. This type of arrangement results in the simple and effective control of the movement of the louver carrier trucks within the headrail. 
     The second drive means preferably includes a generally cylindrical sleeve carrying an external worm gear. A common drive rod preferably cooperates with the louver carrier of each truck and carries a gear wheel which is meshed with the external worm gear of the sleeve such that rotation of the sleeve causes rotation of the drive rod via the gear wheel. This in turn results in rotation of each of the louver carriers. 
     The operating wand preferably includes at least one hinge to enable a user more easily to rotate the wand. More preferably, the operating wand includes two hinges and is arrangeable in the form of a crank. 
     In accordance with a second aspect of the present invention there is provided a method of operating a vertical blind apparatus according to the first aspect of the invention, the method including engaging the operating means with the first or second drive means and energising the engaged drive means to cause the desired movement of the louvers. Thus, if it is desired to effect translational movement of the carrier trucks along the headrail, then the first drive means is engaged and energised. Alternatively, if it is desired to rotate the louvers about their respective axes, then the second drive means is engaged and energised. 
     An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawing which shows an exploded view of one end of a vertical louver blind headrail assembly. 
     For the avoidance of doubt, it should be noted that in the following description, references to “up”, “down” and to related terms, refer to the orientation that the relevant component(s) of the blind adopt when installed for normal use, as they are shown in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an embodiment of the first aspect of the invention, namely a vertical blind headrail assembly  2  including a headrail  4 , an end cap  6  and an operating wand  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The operating wand  8  includes a lower wand portion  10  hingeably coupled at one end  9  to a first end  11  of an intermediate wand portion  12 . The other end  13  of the intermediate wand portion  12  is likewise hingeably coupled to a first end  15  of an upper wand portion  14 . This arrangement of upper wand portion  14 , intermediate wand portion  12  and lower wand portion  10  allows the wand to be arranged in the form of a crank, as shown in the drawing, which permits easier rotation of the wand  8 . 
     The upper wand portion  14  is connected at its other end to a wand operating element  18  via a universal joint element  16  which is common in wand-operated drive apparatus. 
     The operating element  18  includes an engagement pin  20  which is friction fitted within an aperture  19  through the operating element  18  such that both ends of the engagement pin  20  project beyond the outermost cylindrical surface of the operating element  18 . 
     The operating element  18  includes towards its upper end a shoulder  36  and extending axially from the shoulder  36  a cylindrical projection  38  having a diameter smaller than the diameter of the main body of the operating element  18 . 
     Upon assembly of the headrail apparatus, the operating element  18  is located within a through hole  17  in the base of the end cap  6  whereby a connecting portion  23  of the operating element  18  extends beyond the through hole  17  and is hingeably connected to one end of the universal joint element  16 . The main body of the operating element  18  is sized such that it is axially slidably within the through hole  17 . A cylindrical sleeve  22  having a bore  21  of diameter substantially equal to that of the diameter of the through hole  17  is then arranged such that the bore  21  surrounds a portion of the operating element  18  and is arranged substantially coaxially with the through hole  17 . The length of the bore  21  is less than the length of the main body of the operating element  18  and the operating element can slide axially within the bore  21 . The cylindrical sleeve  22  carries on its outer cylindrical surface an external worm gear  24 . It also includes a pair of channels  26  coaxially arranged on the upwardly facing surface of the sleeve  22  on opposite sides of the bore  21 . 
     The engagement pin  20  is then friction fitted within the through hole  19  with its opposite end portions extending therefrom. The channels  26  are arranged to be capable of receiving the projecting end portions of the engagement pin  20 . 
     A top plate  40  covers an upper portion of the end cap  6  and an aperture  42  through the top plate  40  receives an upper end portion of the projection  38  of the operating element  18  such that the projection  38  acts as a journal borne within the aperture  42 . 
     The top plate  40  also has rotatably coupled thereto a chain wheel  28 , which includes a cylindrical bore  30 . The cylindrical bore  30  is arranged to be substantially coaxial with the aperture  42  and the projection  38 , and is sized to receive therewithin a portion of the projection  38 . The chain wheel  28  also includes on its downwardly facing end surface a pair of channels (not shown) corresponding to channels  26  in the upwardly facing end surface of the cylindrical sleeve  22 . 
     The louver blind headrail assembly  2  further includes a metal drive rod  52  which extends the length of the headrail  4  passing through each of the louver carriers (not shown). The drive rod  52  carries at one end thereof a gear wheel  50  having on its outwardly facing cylindrical surface a plurality of teeth  51 . The gear wheel  50  is rotatably coupled to the end cap  6  such that the teeth  51  mesh with the external worm gear  24 , whereby rotation of the cylindrical sleeve  22  results in a corresponding rotation of the metal drive rod  52 . This in turn co-operates with a torque transfer apparatus within each louver carrier truck to rotate the louver carrier about a vertical axis, thus rotating a louver suspended from the louver carrier. 
     In use, to move the carrier trucks longitudinally within the headrail  4 , the upper wand portion  14  of the operating wand  8  is moved axially upwards until the engagement pin  20  engages with the downwardly facing channels (not shown) formed in the chain wheel  28 . The wand is then rotated and a cord carrying a plurality of equally spaced plastic balls (not shown) is driven to rotate by virtue of jaws  32  of the chain wheel  28  engaging with respective plastic balls on the chain. The chain is connected to the lead, louver truck (not shown) which is caused to move longitudinally within the headrail  4  in a direction which is dependent upon the sense (i.e. clockwise or anti-clockwise) in which the chain wheel is rotated by the operating wand  8 . The remaining trucks are either pulled or pushed by the lead truck, depending upon the direction in which the lead truck is moved. 
     Alternatively, if a user desires to rotate each louver about its vertical axis, then the upper wand portion  14  of the operating wand  8  is moved axially downwards until the projecting ends of the engagement pin  20  engage within the channels  26  of the sleeve  22  and the operating wand is then again rotated in the desired sense. The external worm gear  24  is meshed with the teeth  51  of the gear wheel  50  and rotation of the cylindrical sleeve  22  results in rotation of the drive rod  52  via the external worm gear  24  and the gear wheel  50 . The rotation of the drive rod  52  results in the rotation about a respective vertical axis of the louvers carried by the carrier trucks. Again, the direction or sense of the rotation is determined by the direction or sense in which the operating wand is rotated. 
     This preferred embodiment has been described by way of an example only and it will be apparent to those skilled in the arts that many alterations can be made that are still within the scope of the invention.

Summary:
An apparatus for operating a vertical louver blind having a plurality of louver carrier trucks slidably mounted within a headrail, wherein each of the carrier trucks includes a louver carrier which is mounted for rotation about a vertical axis, and an operating wand which is selectively engageable with first or second transmissions at any given time.