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You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of U.S. patent application Ser. No. 13/411,151 titled “ARCHED WINDOW COVERING CAPABLE OF ADJUSTING SIZE”, the subject matter of which is fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a window covering, and more particularly to an arched window covering capable of adjusting the size thereof. 
     2. Description of the Related Art 
     Arched window coverings are designed for semi-circular windows. In early days, the arched window covering is simply a fan-shaped shade attached to the window by glue or double-sided adhesive tape. The shade usually is damaged when it is taken off from the window to wash or to replace. Nowadays, an improved arched window covering is provided, which includes a rail and a fan-shaped shade. The rail is mounted on the window, and the shade is detachably mounted on the rail without the damage problem when wash or replace. However, the sizes of the windows are variable, and the length of the rail must fit the window. The arched window covering with too short rail can&#39;t shade the entire window. Therefore, it has to prepare a rail longer than the usual window, and the rail is cut to fit the specific window when the worker installs the arched window covering on the window. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide an arched window covering, which is able to adjust a size thereof to fit different windows. 
     According to the objective of the present invention, a shade mount of an arched window covering includes a base having an inserting portion and two connecting portions at opposite sides of the inserting portion; at least a spacer, which has two stop portions at opposite ends, connecting to the inserting portions of the base; and two rails movably connecting to the connecting portions and touching the stop portions of the spacer. 
     In an embodiment, the base further has a support portion, on which the spacer is provided, the inserting portion has an opening, which is separated into two sub-openings by the support portion, the spacer has the opposite ends inserted into the sub-openings and extending out of the base, and the rails have ends engaging the connecting portions of the base and the other ends extending outwards. 
     In an embodiment, the base has two case pieces, each of which has a protrusion, the protrusions of the case pieces are connected to form the support portion, a plurality of the spacers, which are arched plates with different lengths, are detachably stacked on the support portion, and the rails touch the stop portions of the longest spacer. 
     In an embodiment, the longest spacer has at least a protrusion on a bottom side, the shortest spacer has at least a slot on a top side, and the rest spacers have at least a protrusion and at least a slot on opposite sides to engage the neighboring spacers. 
     In an embodiment, the base has a hollow case, the inserting portion includes at least an opening on a top of the case and a plurality of slots on a bottom of the case, opposite ends of the spacers are inserted into the opening and engage the slots, the ends of the spacers extend out of the base, and the rails have ends engaging the connecting portions of the base and the other ends extending outwards. 
     In an embodiment, the base has two case pieces, each of which has a protrusion, the protrusions of the case pieces are connected to form the support portion, a plurality of the spacers, which are arched plates with different lengths, are detachably stacked on the support portion and engage the corresponding slots of the base. 
     In an embodiment, each of the spacers has at least a slot to engage the corresponding slot of the inserting portion. 
     In an embodiment, the spacer is a bendable plate, and the plate is bended to engage the specified slot of the inserting portion. 
     In an embodiment, the plate has a plurality of slots to engage the slots of the inserting portion. 
     In an embodiment, the shade mount further includes two boards connected to opposite of the base, wherein the spacer is between the boards 
     In an embodiment, each board includes a first board formed on the base and a second board detachably connecting to the first board. 
     In an embodiment, the spacers are a plurality of arched plates with different lengths, and the inserting portion has two sets of slots to respectively engage opposite ends of the arched plates, and gaps are formed between the neighboring arched plates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  and  FIG. 2  are perspective views of a first preferred embodiment of the present invention, showing the shade mount and the shade; 
         FIG. 3  is a perspective view of the first preferred embodiment of the present invention, showing the base of the shade mount; 
         FIG. 4  is a perspective view of the first preferred embodiment of the present invention, showing the base and the arched plates of the shade mount; 
         FIG. 5  is a perspective view of the first preferred embodiment of the present invention, showing the base, the spacer, and the rail of the shade mount; 
         FIG. 6  is a front view of the first preferred embodiment of the present invention, showing the rails touching the arched plate; 
         FIG. 7  is similar to  FIG. 6 , showing the distance between the rails being shortened by using less arched plates; 
         FIG. 8  is a perspective view of the shade mount of a second preferred embodiment of the present invention; 
         FIG. 9  is a perspective view of the shade mount of a third preferred embodiment of the present invention; 
         FIG. 10  is a perspective view of the arched plate of a fourth preferred embodiment of the present invention; 
         FIG. 11  is a front view of the fourth preferred embodiment of the present invention; 
         FIG. 12  is a perspective view of a fifth preferred embodiment of the present invention; 
         FIG. 13  is a sectional view along the  13 - 13  line of  FIG. 12 ; 
         FIG. 14  is a perspective view of a sixth preferred embodiment of the present invention, showing a single spacer engaged with the base; 
         FIG. 15  is a perspective view of the arched plate of an alternative preferred embodiment of the present invention; and 
         FIG. 16  is a front view of the sixth preferred embodiment of the present invention, showing two endmost slots of the single spacer are, similar to  FIG. 11 , respectively engaged with one of the two innermost slots of the base. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  and  FIG. 2  show an arched window covering of the first preferred embodiment of the present invention, including a shade mount  100  and a fan-shaped shade  200 . The shade  200  may be a honeycomb shade or a pleated shade. The present embodiment shows a honeycomb shade. 
     The shade  200  is detachably mounted on the shade mount  100 . As shown in FIGs. from  FIG. 3  to  FIG. 6 , the shade mount  100  includes a base  10 , a plurality of arched plates  20 , so called spacers, and two rails  30 . 
     The base  10  includes two case pieces  11  for abutted connection to form a hollow case with a vertical opening  12 , so called inserting portion, at middle and two connecting portions  13 ,  14  at opposite sides. Each case piece  11  has two protrusions  11   a ,  11   b  for engagement. The engaged protrusions  11   a ,  11   b  form a semi-circular support portion S in the opening  12 . As shown in  FIG. 3 , the support portion S connects the case pieces  11  and separate the opening  12  into two sub-openings  12 A,  12 B. 
     The arched plates  20  have different lengths, and the shortest arched plate  20  may be fully attached to the support portion S, and the rest arched plates  20  are stacked on it in an order from the shortest one to the longest one. 
     Each arched plate  20  (except the shortest one) is provided with protrusions  20   a  and slots  20   b  on opposite sides to engage the neighboring arched plate  20 , and the arched plates  20  may easily disengage with each other as well. The shortest arched plate  20  only has the slots  20   b  on a top side. Therefore, the stack of the arched plates  20  has smooth bottom. The number of the arched plates  20  may change by removing the arched plate(s)  20  from the top of the stack. 
     Each arched plate  20  has two stop portions  20   c ,  20   d  at opposite ends. The opposite ends of the arched plates  20  are inserted into the sub-openings  12 A,  12 B and extend out of the base  10 .  FIG. 6  shows eight arched plates  20  are stacked on the support portion S, and  FIG. 7  shows six arched plates  20  are stacked on the support portion S. It is easy to tell that the overall diameter of the stack of eight arched plates  20  is wider than the stack of six arched plates  20 . In other words, the maximum distance between the stop portions  20   c ,  20   d  (the distance between two proximal ends  30   a  of rails  30 ) in  FIG. 7  is shorter than that in  FIG. 6 . 
     Each arched plate  20  is provided with a plurality of shade slots  20   e  as shown in  FIG. 4 . The shade slots  20   e  are used to engage the shade  200 . 
     Each rail  30  is an elongated member with a U-shaped cross-section. Proximal ends  30   a  of the rails  30  movably engage the connecting portions  13 ,  14  of the base  10  and touch the stop portions  20   c ,  20   d  of the arched plates  20 , and distal ends  30   b  of the rails  30  extend in opposite directions. Consequently, a distance between the distal ends  30   b  of the rails  30  in  FIG. 6  is longer than that in  FIG. 7 . It is easy to understand that we can change a length of the shade mount  100 , the distance between the distal ends  30   b  of the rails  30 , by adding or removing the arched plate(s)  20  rather than cutting the rail, and that will in turn increase or decrease the area of the shade  200  mounted on the shade mount  100  to fit the windows with different sizes. 
     As shown in  FIG. 3  and  FIG. 4 , each case piece  11  is provided with a semi-circular board  40  at an outer side so that the arched plates  20  can hide behind the boards  40 . The board  40  can include a first board  42  and a second board  41 . The first board  42  can be inherently formed on the case piece  11 , and the second board  41  detachably engages the first board  42  to form the semi-circular board  40 . 
     As shown in  FIG. 8 , a shade mount  100 A of the second preferred embodiment of the present invention includes a base  50 , a plurality of arched plates  53 , so called spacers, and two rails  54 . The base  50  consists of two case pieces to form a hollow case with an arched support portion at a center, and the rails  54  are two elongated members with U-shaped cross-sections. 
     The base  50  has two inserting portions at opposite sides. Each inserting portion includes an opening  51  at a top of the base  50  and a plurality of parallel slots  52  on a bottom thereof. The arched plates  53  have different lengths to be stacked on the support portion in sequence. At each end of the arched plate  53  a stop portion  53   b  is formed. The stop portion  53   b  is a narrow piece to fit the openings  51 . Two slots  53   a  are formed on opposite sides of the stop portion  53   b . The stop portions  53   b  of each arched plate  53  are inserted into the openings  51  with the slots  53   a  engaging the corresponding slots  52  of the base  50 . The same as the first preferred embodiment, the rails  54  connect to the connecting portions of the base  50  and touch the stop portions  53   b  of the arched plate  53 . We can adjust the length of the shade mount  100 A by adding or remove the arched plate(s)  53  to change the size of the shade.  FIG. 9  shows a shade mount of the third preferred embodiment of the present invention, which is basically the same as the second preferred embodiment, except that a base  50 ′ has corresponding slots  51 ′ and  52  at a top and a bottom to engage each arched plates of different lengths. 
       FIG. 10  shows a single flexible plate  60 , the spacer, having a plurality of slots  61  along its longitudinally opposite sides. The plate  60  is bent to engage the slots  61  to the specified slots  52  on the base  50  of the shade mount  100 A as shown in  FIG. 8 . As shown in  FIG. 11 , the plate  60  may be flexed to engage the slots  52  proximate to a center of the base  50 , or may be extended to engage the slots  52  distal to the center of the base  50 . The same as above, the rails connect to the base and touch the plate so that the length of the shade mount will decrease when the plate  60  engages the proximal slots  52 , and will increase when the plate  60  engages the distal slots  52 , and therefore, the size of the arched window covering changes, so as to fix different window sizes. 
       FIG. 12  shows a shade mount of the fifth preferred embodiment of the present invention, including a base  70 , a plurality of arched plates  72 , and two rails  74 . The base  70  has a support portion  76  and an inserting portion to engage the arched plates  72 . As shown in  FIG. 13 , the inserting portion includes two sets of slots  78  on a top of the base  70  and on opposite sides of the support portion  76  to respectively engage slots (not shown) of the arched plates  72  like above embodiments. Because of the restraint of the slots  78  the shortest arched plates  72  does not touch the support portion  76 , and there are small gaps between the neighboring arched plates  72 . The base  70  has no opening or slot on the bottom, and ends of the arched plates  72  are received in the base  70 . The base  70  further has two one-piece boards  80  to hide the arched plates  74 . The rail  74 , comparing with the rail  30  shown in  FIG. 2 , has an extra wall  82  under a pair of engaging portions  84  which engage the fan-shaped shade (not shown), and the wall  82  will touch the longest arched plates  72 . The function of the shade mount of the fifth preferred embodiment is the same as above. 
     As mentioned above, the spacer illustrated in  FIG. 10  is the single flexible plate  60 , which has a plurality of slots  61  along its longitudinally opposite sides. In  FIG. 14 , the plate  60  is further disclosed to be engaged with the base  50  illustrated in  FIG. 8 . More specifically, the base  50  includes a top board  50   a  and a bottom board  50   b , wherein the inserting portion of the base  50  includes the opening  51  provided on the top board  50   a , and the plurality of slots  52  provided on the bottom board  50   b . The plate  60  passes through the opening  51  with two ends thereof, and two of the slots  61  are engaged with two of the slots  52  of the bottom board  50   b . In this way, the plate  60  is bent and engaged with the base  60 . In other embodiments, the top board  50   a  can be omitted, as long as two of the slots  61  of the plate  60  can be respectively engaged with one of the slots  52  of the bottom board  50   b.    
     The plate  60  depicted in solid lines in  FIG. 11  engages the base  50  with two slots  61  located nearest to two ends of the plate  60  (i.e., the two endmost slots  61 ), wherein these two endmost slots  61  are respectively engaged into one of the two slots  52  of the base  50  which are also located nearest to lateral edges of the base  50  (i.e., the two endmost slots  52 ). In such case, the distance between two ends of the plate  60  is the longest, which consequently makes the space between the two rails  54  as the largest. On the other hand, the plate  60  depicted in dotted lines in  FIG. 11  engages the base  50  with two slots  61 , which are away from two ends of the plate  60 , wherein these two slots  61  are respectively engaged into one of the two slots  52  which are located nearest to a center of the base  50  (i.e., the innermost two slots  52 ). The distance between two ends of the plate  60  can be adjusted accordingly between the endmost slots  52  and innermost slots  52 , so that the space between the two rails  54  can be adjusted as a result. A portion  60 A of the plate  60  may extend out of the base  50 , and such portion  60 A can be cut off. The aforementioned methods are all compatible to be applied for effectively changing the radius of the arched window covering. 
     As shown in  FIG. 15 , in other embodiments, an inner or outside surface, or both inner and outside surface of the spacer can be further provided with a plurality of cutting slots  62 , which are arranged parallel to a short axis direction of the spacer. With such design, when the spacer is engaged with the slots  52  of the base  50  on different demands, the portion  60 A of the plate  60  which extends out of the base  50  can be directly snapped off without the need of using any tools. 
     However, it&#39;s not always necessary to cut off or snap off any portion of the plate  60 . As shown in  FIG. 16 , the two endmost slots  61  of the plate can be also engaged with the two innermost slots  52 . Though the plate  60  is bent further in this situation, the whole plate  60  is still covered behind the boards  40 . In other words, the intact plate  60  can be used as a single spacer to adjust the radius of the arched window covering as well. 
     The description above is only a few preferred embodiments of the present invention and the equivalence of the present invention is still in the scope of claim construction of the present invention.

Summary:
An arched window covering having shade mount with a base, at least a spacer, and two rails wherein a shade is mounted on the shade mount and the width of the spacer is adjustable and positioned on the base such that the rails movably engage the base and a length of the shade mount is changeable by changing the width of the spacer to thereby adapt to a differing size of a shade mounted on the shade mount by adjusting the spacer rather than cutting the rail to fit the windows with different sizes.