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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION  
       [0001]     The present invention relates to circulation tools of a type used downhole in a well for transferring fluid through ports from a bore within the tool to an annulus surrounding the tool and for subsequently closing the ports to pass fluid through the tool. The circulation tools of the present invention are sometimes referred to as surge tools or surge reduction tools.  
       BACKGROUND OF THE INVENTION  
       [0002]     Downhole circulation tools have been used for decades to selectively flow fluid from the interior of a tubing string or work string to the annulus surrounding the tool. Some tools have the ability to selectively close off circulation ports to subsequently pass fluid down the tubing string or work string. Many of these tools, however, make it difficult or unreliable to pass a cementing plug through the work string after the circulation ports are closed without damaging the plug. Other tools require that the work string be placed on bottom or engage some type of restriction in the well to cycle the tool. Various types of circulation tools have thus been devised for circulating fluid within a tubular string to an annulus, and for subsequently moving a sleeve to close the annulus so that fluid can be passed through the tool.  
         [0003]     Prior art circulation tools for selectively closing off flow through a side port in the tool and for subsequently passing cement and cement plugs through the tool include tools with a deformable or expandable seat to allow the ball to pass through the seat and thus through the tool once the sleeve has shifted to close off flow ports in the tool. This type of tool significantly restricts the size of the cement plug which may be reliably passed through the tool, and the deformable seats may damage the plug wiper seals or rubber wafers while passing through the deformable seat. As a consequence, cementing operations are adversely affected since an unknown quantity of cement may pass by the wiper plug after the wiper plug has passed through the tool. Other types of tools employ a flangible disc within the bore of the tool. Pressure builds up on top of the disc to shift a sleeve to close off the circulation ports. A subsequent increase in pressure breaks the flangible disc. Fragments from the disc can be very damaging, however, to a cementing plug which is subsequently passed through the tool. Disc fragments may cut or tear at the wiper plug, thereby damaging the wiper plug.  
         [0004]     Another type of tool utilizes a J-type mechanism for moving the sleeve between the open and closed positions. This type of tool or a tubular extending downward from the tool conventionally sits on the bottom of the well so that weight can be applied to manipulate the J-type mechanism.  
         [0005]     Other types of surge tools do not provide substantially a full bore opening through the tool, and the restriction in the ID of the tool is thus a significant detriment to the use of the tool.  
         [0006]     U.S. Pat. No. 6,275,929 discloses a circulation tool with axially moveable sleeves. Similar tools are disclosed in U.S. Pat. Nos. 6,571,875 and 5,176,208. U.S. Pat. No. 5,402,850 discloses a tool for reverse circulation of fluid in the wellbore. A circulation tool with wash ports is disclosed in U.S. Pat. No. 4,987,841. Another type of circulation tool is disclosed in U.S. Pat. No. 4,657,092. A downhole tool with a combination ball valve and sliding sleeve is disclosed in U.S. Pat. No. 5,335,731.  
         [0007]     The disadvantages of the prior art are overcome by the present invention. An improved downhole circulation tool which may be reliably used with cementing operations is subsequently disclosed.  
       SUMMARY OF THE INVENTION  
       [0008]     In one embodiment, a circulation tool for use downhole in a well is suspended in a well from a tubular string. The tool includes a tubular housing including one or more bypass ports for circulation between a bore within the housing and an annulus surrounding the housing. A sleeve is axially movable within the housing and supports axially spaced seals. A rotatable ball has a small diameter flow port therein and a seat surrounding the small diameter flow port for seating engagement with a ball or other plug. The ball is rotatable to an open position such that a large diameter through port in the ball has an axis generally aligned with the axis of the tubular housing.  
         [0009]     In one embodiment, the large diameter port has a diameter of at least 90 percent of an innermost diameter of the axially movable sleeve. Cam members interconnected with the ball are movable within slots in the sleeve to rotate the ball to the open position.  
         [0010]     These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1A  is a half sectional view of an upper portion of the circulating tool positioned such that the circulation ports are open for communication with the annulus.  
         [0012]      FIG. 1B  is a half sectional view of the upper portion of the tool positioned such that the circulation ports are in the closed position.  
         [0013]      FIG. 1C  is a half sectional view of a lower portion of the circulation tool with the circulation ports in the open position.  
         [0014]      FIG. 1D  is a half sectional view of a lower portion of the circulation tool with the circulation ports in the closed position.  
         [0015]      FIG. 2  is a side view of the ball rotating mechanism generally shown in  FIGS. 1C and 1D .  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]      FIGS. 1A and 1C  together illustrate a suitable embodiment of the circulation tool  10  according to the present invention. The upper portion of the tool includes a top connector  18  threadably connected at  20  to an outer sleeve shaped housing  12  which contains one or more circumferentially spaced circulation ports  16  therein. A seal  22  is provided between the top connector  18  and the housing  12 , and an inner sleeve  46  having a tapered upper end  48  extends downward for positioning adjacent the ball  52  at seat  53 . Upper piece  24  is fixed between sleeve  32  having enlarged head  26  and a lower surface on the threaded connector  18 . Shear member  28  axially interconnects the upper piece  24  with sleeve  30 , which has port  33  therein. The sleeve  46  is biased downward by coil spring  42  (see  FIG. 1C ), which acts on pusher  59  which acts on a roller which is part of cam assembly  82 . The cam assembly  82  is attached to ball  52  via a screw. The spring force applied to the sleeve  46 , pusher  59 , and cam assembly  82  holds ball  52  against sleeve  56 , which is pinned with shear members  64  to sleeve  44 . Sleeve  32  is prevented from downward movement by the shoulder  27  on housing  12  adjacent head  26 . The ring  38  at the lower end of sleeve  32  is contained by snap ring shoulder  40  on housing  12 , and by sleeve  32 . The ring  38  also engages a lower shoulder on the sleeve  44  to prevent upward movement of the sleeve  44 . Port  33  in the sleeve  30 , port  47  in the sleeve  46 , port  45  in the sleeve  44 , and port  49  in the sleeve  46  (see  FIG. 1A ) allow fluid communication between the interior of the tool and the chamber which houses the spring  42 , and prevent pressure lock during actuation of the tool.  
         [0017]     Referring now to  FIG. 1C , the ball  52  includes a pair of cam assemblies  82 .  FIG. 1C  shows a small diameter port  55  having a seating surface  54  therein.  FIG. 1D  shows the ball rotated so that the large diameter bore  40  is in line with the bore  13  through the tool, with the bore  40  in the ball  52  having an interior diameter at least 90 percent as great as an innermost diameter of both the lower sleeve  56  and the upper sleeve  46 .  
         [0018]     Pusher  59  movably interconnects the lower end of sleeve  46  with sleeve  44 , which has a slot  88  therein, as shown in  FIG. 2 . Sleeve  56  is provided below the ball  52 , and is sealed thereto by O-ring  57 . Seal  58  seals between the sleeve  56  and the sleeve member  44 , which has a seal  62  for sealing engagement with the ID of the housing  12 . Shear member  64  interconnects the sleeve  56  with the sleeve  44 , and threads  61  interconnects the lower end of sleeve  44  with the sealing sleeve  68 . Sealing sleeve  68  carries a seal  70  at its upper end and a seal  74  at its lower end, with spacer  72  provided between these seals. Lower end component  76  is threaded at  75  to the lower end of sleeve  68  for maintaining the seals  70  and  74  in position on the sleeve  68 .  FIG. 1C  shows a port  16  open for circulation with the annulus, while  FIG. 1D  shows the port  16  sealed off by the seal  70  above the port  16  and seal  74  below the port  16 . Through port  63  in the sleeve  68  prevents pressure lock during operation of the assembly while moving between the open port to closed port positions.  
         [0019]     During operation of the circulation tool, fluid conventionally travels upward through the full diameter bore and passes outward through one or more of the circulation port  16  to the annulus surrounding the tool. Some fluid may also flow upward through the small diameter port  55  in the ball  52 . When it is desired to close off the ports  16 , e.g., for a cementing operation, multiple size or multiple diameter balls may be dropped to the seat of the surface  54  of the ball, thereby raising the pressure above the ball  52 . This creates a downward force which acts on the assembly, shearing the pins  28  and moving the sleeves  30 ,  44 , and  68  downward, thereby closing off the port  16 . Shoulder  31  on sleeve  30  passes under the lock ring  38 , thereby locking the tool in the circulation port closed position. After the sleeve  56  has closed off the ports  16 , shear pins  64  shear during the final movement, lowering the ball  52  as it rotates to the full bore open position. With the sleeve  68  in the fully closed position and the ball  52  rotated to the full open position, a full bore is provided through the circulation tool.  
         [0020]     The circulation tool of the present invention is particularly well suited for operations involving the run in of the liner in a well, and the subsequent cementing of the liner by pumping through the work string. When the liner is run in a well, a check valve at the bottom of the liner is conventionally opened so that well fluid enters and passes upward through the liner. The work string or drill pipe at the upper end of the liner thus begins to fill with fluid, and desirably most of that fluid passes through the circulation tool to the annulus rather than continuing up the drill string or work string. Once the liner is at bottom and positioned for cementing in place, a ball is dropped from the surface and lands on the ball  52 , closing off the port  55  through the ball and creating a downward force to move the sleeve  68  to the closed position. As previously explained, the ball rotates after the sleeve  68  moves to the closed position to provide a full bore flow path through the circulation tool, at which time the dropped ball may be released to either be caught by a conventional ball catcher or passed to the bottom of the string. Plugs or darts may then be passed through the drill string or work string to cement the liner in place, with the darts or plugs passing through the open bore  13  in the circulation tool, which is not restricted and has no sharp edges to damage the plug or wiper.  
         [0021]     For the embodiment depicted, the seals between the sleeve  68  and the housing  12  are provided on the sleeve. In other embodiments, the seals could be provided on the housing. In a preferred embodiment, a ball is provided with a hole therein, so that when the ball is closed some fluid can pass from below to above the ball. This construction allows fluid to drain from above to below the ball in the event the operator needs to pick up on the tubular string before setting the liner in place. Although various types of plugs may be used for seating with the flapper, a preferred plug is a ball. The seat on the ball is also configured for seating with balls of various sealing diameters, thereby increasing the versatility of the tool.  
         [0022]     Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.

Summary:
A circulation tool  10  for use downhole in a well includes a housing  12  having one or more bypass ports  16  for circulation between a bore in the housing and an annulus surrounding the housing. A sleeve  68  is axially movable within the housing, and axially spaced seals  70, 74  seal between the sleeve and the housing when the sleeve is in the closed position. A ball  52  is rotatably mounted to the sleeve, and includes a seat  54  about a central bore  55  in the ball for engagement with a plug. When the sleeve closes off the circulation ports  16 , the ball is rotated to the open position with a substantially full bore diameter.