A shower door assembly with linkage control comprising a stationary frame, a movable frame and an adjustment assembly disposed between the stationary frame and the movable frame. The adjustment assembly comprises at least two adjustment devices and locking devices for locking each of the adjustment devices. Each of the locking devices comprises a locking element and a guiding device along which the locking element can slide. An actuating arm is provided to release and lock adjustment devices all at once. Therefore, it is unnecessary to adjust each of the adjustment devices separately, facilitating the operation of adjustment.

CROSS-REFERENCE TO RELATED APPLICATION 
     The present invention claims priority from Chinese invention application No. 201410002366.2 filed on Jan. 3, 2014 in the name of Ideal Sanitary Ware Co., Ltd, the entire disclosure of which is herein incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a shower door, and in particular, to an adjustment assembly useful for the shower door, which achieves linkage control. 
     BACKGROUND OF THE INVENTION 
     Doors used for shower enclosure are often mounted against wall surfaces and the doors thus mounted are kept as vertical as possible. However, the wall surfaces of buildings are often not exactly vertical, for example, titled toward outside/inside by an angle. Therefore, if mounted completely along the wall surface, the doors may not be smoothly opened or closed. In this regard, it is necessary to adjust the distances between the top/bottom end of a door and a wall surface so as to keep the door in a vertical position. 
     To achieve this adjustment, a door assembly usually comprises a stationary frame to be attached to a wall surface, and a movable frame connected with a door panel, such as a glass door panel. The stationary frame is firstly attached to the wall surface and then the movable frame is moved toward the stationary frame, during which the distances between the top and bottom ends of the movable frame, and the stationary frame are such adjusted that the movable frame is in a vertical position, and thus so is the door panel. The stationary and movable frames are finally connected to each other by drilling thereon and by using fasteners. 
     However, in one aspect, the drilling operation requires at least two people to cooperate and is very time-consuming. In another aspect, the drilling may inadvertently cause damages to the surfaces of the frames (generally made of aluminum materials), which is undesirable to consumers. 
     In an aim to solve these problems, it was proposed solutions that do not involve drilling, by incorporating adjustment assemblies in the door assembly. However, when the relative distance between the stationary and movable frames needs to be changed, it is necessary to operate each of the adjustment assemblies separately. Further, the adjustment of the relative distance is normally achieved by the change of the engagements between teeth, so the minimum adjustment depends on the space between two adjacent teeth. If more precise adjustment is needed, the conventional solutions will not suffice. Moreover, these solutions require forming teeth on different components, causing increased complexity and cost for manufacture. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a shower door assembly that does not need drilling when assembling and can achieve linkage control of all of adjustment devices. 
     In one embodiment, a shower door assembly with linkage control is provided, the shower door assembly comprises a stationary frame, a movable frame and an adjustment assembly disposed between the stationary frame and the movable frame, the adjustment assembly comprising at least two adjustment devices and locking devices for locking each of the adjustment devices, wherein each of the locking devices comprises 
     a locking element having an upper locking portion and a lower locking portion, the upper and lower locking portions each comprising a first through hole and a second through hole in communication with the first through hole, the first through hole having a dimension greater than or equal to a dimension of an end surface of corresponding adjustment device, the second through hole having a dimension smaller than the dimension of the end surface of the corresponding adjustment device, the upper locking portion further comprising a upper securing portion and an actuating arm, the actuating arm passing through the upper securing portion, the lower locking portion further comprising a lower securing portion and a fixing element, the fixing element passing through the lower securing portion; and 
     a guiding device having an upper guiding element and a lower guiding element, 
     the upper guiding element comprising a first guiding slot along which the locking element is able to slide, a supportive platform for supporting the actuating arm, a first cavity for receiving one of the at least two adjustment devices, and a carrying platform for carrying the upper securing portion of the locking element, 
     the lower guiding element comprising a second guiding slot along which the locking element is able to slide, a second cavity for receiving other of the at least two adjustment devices, an elastic element for providing elastic force when pressed against the lower securing portion, and a third cavity located lower with respect to the second cavity and having the elastic element received therein, the fixing element passing through the lower securing portion and the elastic element and fixing to an upper wall of the third cavity. 
     In one embodiment, the upper and lower locking portions form in one piece. In another embodiment, the upper and lower locking portions detachably connected to each other by a linkage element. 
     In one embodiment, the locking element further comprises one or more intermediate locking portions, each of the intermediate locking portions comprising a first through hole and a second through hole in communication with the first through hole, the first through hole having a dimension greater than or equal to a dimension of an end surface of corresponding adjustment device, the second through hole having a dimension smaller than the dimension of the end surface of the corresponding adjustment device. Correspondingly, the guiding device further comprises one or more intermediate guiding elements, each preferably having same structures as the upper guiding element. 
     In one embodiment, each of the upper locking portion, the lower locking portion and the possible intermediate locking portion(s) further comprises a third through hole in communication with the first through hole and symmetrically disposed with respect to the second through hole about the first through hole. The third through hole has a dimension smaller than the dimension of the end surface of the corresponding adjustment device. The third through hole preferably has same dimension as that of the second through hole. 
     In one embodiment, each of the adjustment devices comprises an adjustment element and a carrier element bearing the adjustment element. The adjustment element has smooth side surfaces exposed for engaging with the locking device. 
     In one embodiment, the carrier element comprises connection wings for connecting to the movable frame, an upper loading frame connecting to the connection wings, a lower loading frame in parallel with the upper loading frame and in connection with the connection wings, and an opening which, together with the upper and lower loading frames, defines a space for receiving the adjustment element. 
     In one embodiment, the carrier element further comprises a front blocking plate connecting with the free ends of the upper and lower loading frames respectively, in order to prevent the adjustment element from moving outside the space. 
     In one embodiment, the adjustment element further comprises end surfaces, a top surface and a bottom surface, with one of the end surfaces in contact with the front blocking plate. At least one of the top and bottom surfaces is provided with a sliding groove. Correspondingly, a portion of at least one of the upper and lower frames forms a guiding rail for engaging within the sliding groove such that the adjustment element can be stably received within the space. 
     In one embodiment, the adjustment element is not provided with the sliding groove, but instead, the adjustment element has a height preferably greater, more preferably slightly greater, than a height of the opening, such that the adjustment element can be received in the space by virtue of its flexibility. 
     In one embodiment, the adjustment element has a length equal to or slightly smaller than that of the space. 
     By operation of the actuating arm, the adjustment devices can be locked or released all at once, without the need of operating the adjustment devices one by one. Therefore, a linkage control of the adjustment assembly is achieved. In addition, the locking devices are able to lock the adjustment element at any position along the side surfaces of the adjustment element, such that the relative distance of the stationary and movable frames can be adjusted continuously. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of an exemplary locking device, wherein some parts are omitted for clarity purpose. 
         FIG. 2  shows a schematic view of an exemplary upper guiding element. 
         FIG. 3  is a rear view of the upper guiding element as shown in  FIG. 2 . 
         FIG. 4  shows a schematic view of an exemplary lower guiding element. 
         FIG. 5  shows the lower guiding element of  FIG. 4  from another view. 
         FIG. 6  shows a schematic view of an exemplary stationary frame. 
         FIG. 7  shows another example of locking element. 
         FIG. 8  is an exploded view of an exemplary adjustment device. 
         FIG. 9  shows the adjustment device of  FIG. 8  in assembly state. 
         FIG. 10  schematically shows the assembly of an exemplary adjustment device and an exemplary movable frame. 
         FIG. 11  schematically shows the assembly of an exemplary adjustment device and a locking device, wherein the adjustment device is not locked. 
         FIG. 12  schematically shows the assembly of an exemplary adjustment device and a locking device, wherein the adjustment device is locked. 
         FIG. 13  schematically shows the assembly of another exemplary adjustment device and a locking device, wherein the adjustment device is not locked. 
         FIG. 14  schematically shows the assembly of another exemplary adjustment device and a locking device, wherein the adjustment device is locked. 
         FIG. 15  schematically shows the assembly of yet another exemplary adjustment device and a locking device, wherein the adjustment device is not locked. 
         FIG. 16  schematically shows the assembly of yet another exemplary adjustment device and a locking device, wherein the adjustment device is locked. 
         FIG. 17  shows another exemplary upper guiding element of the present invention. 
         FIG. 18  shows another exemplary lower guiding element of the present invention. 
         FIG. 19  shows another exemplary stationary frame of the present invention. 
       Elements that are irrelevant to the spirit of the invention are omitted from the drawings for the purpose of clear illustration of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will be described in more detail by the following examples in reference to the accompanied drawings. 
       FIG. 1  shows a locking device according to one example of the invention. The locking device comprises a locking element  30  and guiding devices  31 ,  32 , which are cooperated to lock an adjustment element  10 . 
     In the example, the locking element  30  comprises a upper locking portion  35  and a lower locking portion  36 , with each of the locking portions comprises a first through hole  351 ,  361  and a second through hole  352 ,  362  in communication with the first through hole. The first through hole  351 ,  352  has a dimension greater than or equal to that of an end surface  102  of the adjustment element  10 . The second through hole  352 ,  362  has a dimension less than that of the end surface  102 . Therefore, the adjustment element  10 , which is disposed on a carrier element  20 , can pass through the first through hole  351 ,  352 , but not the second through hole  352 ,  362 . 
     The locking element  30  further comprises an upper securing portion  354  at the upper locking portion  35 , a lower securing portion  364  at the lower locking portion  36 , an actuating arm  40  ( FIG. 11 ) passing through the upper securing portion  354 , and a fixing element  329  ( FIG. 5 ) passing through the lower securing portion  364 . 
     In the example, the upper and lower locking portions  35 ,  36  are detachably connected by a linkage element  33 . The detachable connection can be achieved by a number of methods known in the art. In the present example, linkage holes  356 ,  366  are respectively provided to the upper and lower locking portions  35 ,  36 , and are connected to hooks  331  provided at both ends of the linkage element  33 , such that the upper and lower locking portions  35 ,  36  are connected. 
     In other examples, the upper and lower locking portions  35 ,  36  are form in a single piece, as shown in  FIG. 7 . In this situation, no linkage element  33  is necessary. 
     With reference again to  FIG. 1 , the guiding device comprises an upper guiding element  31  and a lower guiding element  32 . As shown in more detail in  FIGS. 2 and 3 , the upper guiding element  31  comprises a first guiding slot  314  along which the locking element  30  is able to slide; a supportive platform  313  for supporting the actuating arm  40 ; a first cavity  312  for receiving one of the adjustment elements  10 ; and a carrying platform  319  for carrying the upper securing portion  354  of the locking element  30 . 
     In the example, the first guiding slot  314  is interrupted between the supportive platform  313  and the carrying platform  319 . In another example, the first guiding slot  314  is continuous as long as the guiding elements provide a passage for the actuating arm to pass through and to abut against the supportive platform  313 . 
     In the example, see  FIGS. 4 and 5 , the lower guiding element  32  comprises a second guiding slot  324 . The locking element  30  is able to slide along the first guiding slot  314  and enters into the second guiding slot  324  and slides therein. The lower guiding element  32  further comprises a second cavity  322  for receiving other of the adjustment element  10 , an elastic element  321  for providing elastic force when in contact with the lower securing portion  364 , and a third cavity  323  located below the second cavity  322  and having the elastic element  321  received therein. The fixing element  329  passes through the lower securing portion  364  and also the elastic element  321  and is fixed to an upper wall  325  of the third cavity  322 . In the example, the elastic element  321  is a spring. 
     The upper and lower guiding elements  31 ,  32  are connected to the stationary frame by suitable methods. In the example, see  FIGS. 2 to 5 , the upper and lower guiding elements  31 ,  32  each has linkage elements  316 ,  318  and  326 ,  328  respectively. A plurality of threaded holes are provided at bottom side of the stationary frame  60 , wherein a threaded hole  62  is position in corresponding to the linkage elements such as  316 ,  318 , such that the guiding elements  31 ,  32  are connected to a space  63  of the stationary frame  60  by fasteners. 
     In another example, with reference to  FIGS. 17-19 , the upper guiding element  31  has an extension  310  where at least one locking recess  311  is provided. Between the extension  310  and the carrying platform  319  and also on the supportive platform  313  are formed with locking slots  315 , with the locking recess  311  adjacent the path of the locking slots  315 . Similarly, the lower guiding element  32  has an extension  320  where at least one locking recess  327  is provided. On the lower guiding element  32  is formed with a locking slot  380 , with the locking recess  327  adjacent the path of the locking slot  380 . The stationary frame  60  has a guiding groove  66  defined by two ridges  65  which are able to insert into the locking slots  315 ,  380 , such that the upper and lower guiding elements  31 ,  32  can slide along the stationary frame  60 . When the guiding elements  31 ,  32  is suitably positioned, the ridges  65  will be pressed by a tool (such as a screw driver) in alignment with the recesses  311 ,  327 , so that the ridges will be deformed and forced into the recesses. The guiding elements  31 ,  32  will then be prevented from sliding and connected to the stationary frame  60 . 
     The stationary frame  60  can be attached to a suitable surface, such as a wall surface, by suitable methods. In the example, threaded holes  61  are provided at the bottom side of the frame  60  such that the frame can be attached to the wall surface by fasteners. The person skilled in the art will know other ways to achieve the attachment. 
     With reference again to  FIGS. 1 and 7 , in the example, the locking element  30  further comprises one or more intermediate locking portions  34 , each comprises a first through hole  341  and a second through hole  342  in communication therewith. The first through hole  341  has a dimension greater than or equal to that of the end surface  102  of the adjustment element  10 . The second through hole  342  has a dimension less than that of the end surface  102 . 
     Correspondingly, the guiding device further comprises one or more intermediate guiding elements  37 , each preferably having same structures as the upper guiding element  31 . 
     For purpose of standardization, each of the upper locking portion  35 , lower locking portion  36  and possibly existed intermediate locking portions  34  further comprises a third through hole  353 ,  343  or  363  which is in communication with the first through hole  351 ,  341 ,  361  and symmetrically positioned with respect to the second through hole  352 ,  342 ,  362  about the first through hole  351 ,  341 , 361 . The third through hole  353 ,  343 ,  363  has a dimension less than that of the end surface  102  and preferably same as that of the second through hole  352 ,  342 ,  362 . 
     In the example, the upper guiding element  31  has a spacer  317  arranged between the supportive platform  313  and the carrying platform  319 , such that the upper guiding element  31  has a height matching with that of the locking element  30 . 
     With reference to  FIG. 8 , it is shown an exemplary adjustment device which comprises the adjustment element  10  and a carrier element  20  carrying the element  10 . The adjustment element  10  has a smooth side surface  104 , exposed when loaded on the carrier element  20 . 
     The adjustment element  10  has end surfaces  102 , a top surface  106  and a bottom surface (not shown). In the example, at least one of the top surface and the bottom surface is provided with a sliding groove  11 . In other examples, the sliding groove can also be absent. 
     The carrier element  20  comprises connection wings  12  for connecting to a movable frame  50  ( FIG. 10 ), an upper loading frame  14  connecting to the connection wings  12 , a lower loading frame  13  in parallel with the upper loading frame  14  and in connection with the connection wings  12 , and an opening  17  which, together with the upper and lower loading frames  14 ,  13 , defines a space  16  for receiving the adjustment element  10 . 
     In the example, a portion of at least one of the upper and lower frames  14 ,  13  forms a guiding rail for engaging within the sliding groove  11  such that the adjustment element  10  can be stably received within the space  16 . 
     In other examples, when the adjustment element  10  is not provided with the sliding groove  11 , the adjustment element  10  has a height slightly greater than that of the opening  17 , such that the adjustment element  10  can be received in the space  16  by virtue of its flexibility. 
     In the example, the adjustment element  10  has a length equal to that of the space  16 . In other examples, the adjustment element  10  has a length slightly smaller/greater than that of the space  16 . 
     In the example, the carrier element  20  further comprises a front blocking plate  15  connecting with the free ends of the upper and lower loading frames  14 ,  13 , respectively, in order to prevent the adjustment element  10  from moving outside the space  16 . When the adjustment element  10  is received in the space  16 , one of the end surfaces  102  is in contact with the front blocking plate  15 . In other examples, the front blocking plate  15  may be absent. 
     With reference to  FIG. 9 , it is shown the adjustment element  10  and the carrier element  20  when assembled. As shown, when the adjustment element  10  is loaded on the carrier element  20 , the two side surfaces  104  of the adjustment element  10  are exposed outside. The top surface  106  is in contact with the top loading frame  14 , and one of the end surfaces  102  abuts against the front blocking plate  15 , and the other end surface  102  is accommodated in the opening  17 . 
       FIG. 10  shows the assembly of the adjustment device with an exemplary movable frame  50 . The movable frame  50  is provided with a receiving groove  51  into which the wings  12  can be inserted so that the whole adjustment device can be attached to the movable frame  50  and slide along the groove  51 . 
       FIG. 11  shows the assembly of one adjustment device, the upper locking portion  35  and the upper guiding element  31 . As shown, the adjustment device passes through the first through hole  351  and into the first cavity  312  of the upper guiding element  31 . The upper locking portion  35  is inserted into the first guiding slot  314 . The actuating arm  40  (a threaded rod in this example) passes through the upper securing portion  354  and the through hole  316  of the carrying platform  319  and then abuts against the supportive platform  313 . In the state as shown, the adjustment device can pass through the first through hole  351  and the first cavity  312  freely, so the position and angle of the movable frame  50  can be adjusted freely in relative to the stationary frame  60 . 
       FIG. 12  shows that the adjustment device is forced into the second through hole  352  such that it is locked. Specifically, when the position of the movable frame  50  in relation to the stationary frame  60  is determined, by rotation of the actuating arm  40 , the upper locking portion  35  will move upward due to counterforce, because the actuating arm  40  has one terminal end abutting against the supportive platform  313  and thus cannot move downward. However, the first cavity  312  is not able to move upward, the adjustment device therefore will be forced into the second through hole  352 . 
     In the present invention, the adjustment element  10  is generally made from flexible materials, such as rubbers, PU or modified PU, while the locking device is generally made of rigid materials, for example engineered plastics such as polyformaldehyde or Nylon  66 , or Zinc alloy. Therefore, the adjustment element  10  can be forced into the second through hole  352  by application of forces. When forced into the second through hole  352 , the adjustment device will be unable to move in relative to the stationary frame  60 . Therefore, relative position between the movable frame  50  and the stationary frame  60  is fixed. 
       FIGS. 13 and 14  show the assembly of an adjustment device with an intermediate locking portion  34  and an intermediate guiding element  37 . The locking of the adjustment device by the locking portion  34  is similar to that as shown in  FIGS. 11 and 12 , except that the intermediate locking portion  34  does not need additional actuating arm  40 , but instead, is moved upward by virtue of the linkage element  33  or along with the upper locking portion  35  when formed into one piece therewith. 
       FIGS. 15 and 16  show the assembly of an adjustment device with the lower locking portion  36  and the lower guiding element  32 . In  FIG. 15 , the adjustment device can pass the first through hole  361  and the second cavity  322  freely, so that the position and angle of the movable frame  50  can be freely adjusted in relation to the stationary frame  60 . As shown, the elastic element  321  is in its relaxed or slightly compressed state. By similar principle as that shown in  FIGS. 11 and 12 , the adjustment device is locked by the lower locking portion  36 , except that the lower locking portion  36  does not need additional actuating arm  40 , but instead, is moved upward by virtue of the linkage element  33  or along with the upper locking portion  35  when formed into one piece therewith. In the locked state, the elastic element  321  is in its compressed state due to the upward movement of the lower locking portion  36 . 
     When the relative position between the movable frame  50  and the stationary frame  60  needs to be changed, by contrarotation of the actuating arm  40 , the whole locking device is pushed to move downward along the first and second guiding slots  314 ,  324  due to the elastic force of the elastic element  321 , such that the adjustment device is released from the second through hole  352 ,  342 ,  362  and returns back to the first through hole  351 ,  341 ,  361  where the adjustment device can freely move again. 
     It should be understood that various example embodiments have been described with reference to the accompanying drawings in which only some example embodiments are shown. The present invention, however, may be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein.