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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to vibratory jarring devices used for removing devices from a flowbore. 
     2. Description of the Related Art 
     Jarring devices are used to remove objects from a flowbore. Typically, jarring devices are run into a flowbore and secured to a stuck device or object. Thereafter, the jarring device is actuated to generate jarring impacts which are delivered to the stuck device or object to free it from the flowbore. Jarring devices are described in U.S. Pat. No. 6,474,421, issued to Stoesz. 
     SUMMARY OF THE INVENTION 
     The present invention provides a jarring device that can be run into a flowbore on a running string and used to remove a stuck tool. The jarring device can be affixed to the stuck tool and then actuated to create jarring impacts that are imparted to the stuck tool in order to remove it from the flowbore. 
     An exemplary jarring device is described which includes an outer housing which defines an axial flow path therethrough. An impact rotator is retained within the housing and is rotatable therewithin between a first rotational position and a second rotational position. In the described embodiment, a torsional spring biases the impact rotator toward the first rotational position. Also in the described embodiment, fluid flow through the housing rotates the impact rotator from the first to the second rotational position. 
     Rotation of the impact rotator with respect to the housing creates jarring impacts which are transmitted through the housing to the stuck tool. In the described embodiment, impact surfaces on the impact rotator will impact complimentary impact surfaces on the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a thorough understanding of the present invention, reference is made to the to following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein: 
         FIG. 1  is aside, cross-sectional view of an exemplary wellbore containing a vibrator device constructed in accordance with the present invention. 
         FIG. 2  is a side, cross-sectional view of an exemplary vibrator constructed in accordance with the present invention. 
         FIG. 3  is an external, isometric view of a portion of an exemplary impact rotator used within the vibrator shown in  FIG. 2 . 
         FIG. 4  is an isometric, cutaway view of a portion of the impact rotator shown in  FIG. 3 . 
         FIG. 5  is a side, cross-sectional view of the housing of the vibrator shown in  FIG. 1 . 
         FIG. 6  is an isometric, partially transparent view of the vibrator shown in  FIG. 1 . 
         FIG. 7  is an isometric, partially transparent view of the vibrator of  FIGS. 1 and 6 , now having been moved to a position wherein an impact is created. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  depicts an exemplary wellbore  10  that has been drilled through the earth  12 . The wellbore  10  is lined with casing  14  and defines a flowbore  16 . The flowbore  16  contains a stuck tool  18  that must be removed by vibratory jarring. Although this example depicts the flowbore  16  which contains the stuck tool  18  as being defined by the wellbore casing  14 , those of skill in the art will understand that the flowbore that contains a stuck tool might as well be defined within a concentric liner or within production tubing that is disposed within the casing  14 . 
     A rotational vibrator  20  constructed in accordance with the present invention is shown being run into the wellbore  10  on a running string  22 . The running string  22  may be conventional end-to-end tubing string sections or coiled tubing, of a type known in the art. The running string  22  defines a central flow passage  24  through which fluid can be flowed. The vibrator  20  is removably secured to the stuck tool  18  by a latch or fishing neck arrangement of a type well known in the art. A surface-based pump  26  is used to flow drilling fluid or other fluid through the central flow passage  24  to operate the vibrator  20  during operation. 
     Construction and operation of the exemplary rotational vibrator  20  are shown in detail in  FIGS. 2-7 . The vibrator  20  includes an outer housing  28  which defines first and second interior chambers  30 ,  32  which are separated by an inwardly projecting flange  34 . An axial flow path through the housing  28  is defined by the first and second chambers  30 ,  32 . 
     One or more impact blocks  36  extend from the flange  34  into the second chamber  32 . In the embodiment depicted in FIGS.  2  and  5 - 7 , there are two impact blocks  36 . However, there may be more or fewer than two impact blocks  36 . An exemplary structure for one of the two impact blocks  36  is best seen in the cutaway view of  FIG. 5 , which shows one of the two impact blocks  36 . It should be understood that the half of the housing  28  that is not shown in  FIG. 5  will have a second impact block  36  which essentially mirrors the one shown in  FIG. 5 . Each impact block  36  presents an inwardly-facing radial surface  38  that has a reduced diameter. The impact blocks  36  also present radially-facing first impact surfaces  40 . 
     An impact rotator  42  is disposed within the housing  28 . The exemplary impact rotator  42  depicted includes a lower impact portion  44  and an upper spring retaining portion  46 . These two portions  44 ,  46 , in the embodiment shown in  FIG. 2 , are made up of two separate pieces that are assembled together. The exemplary impact rotator  42  resides within the housing  28  such that the spring retaining portion  46  resides within the first chamber  30 , and the lower impact portion  44  extends through the flange  34  and into the second chamber  32 . A rotational bearing  49  ( FIG. 2 ), of a type known in the art, is preferably disposed between the spring retaining portion  46  and the flange  34  to permit ease of rotation for the impact rotator  42  within the housing  28 . Preferably also, an annular fluid seal  47  (also  FIG. 2 ) is disposed between the impact portion  44  and the flange  34 . 
     The spring retaining portion  46  is generally cylindrical in shape and presents an outer annular spring retaining groove  51  about its outer circumference. A torsion spring  54  is located within the spring retaining groove  51 . Preferably, the torsion spring  54  is a coiled element. One end of the coiled element is affixed to the housing  28  while the other end is affixed to the spring retaining portion  46 . The torsion spring  54  therefore retains the impact rotator  42  is a first rotational position ( FIG. 6 ) with respect to the housing  28 . When the impact rotator  42  is rotated within the housing  28  to a second rotational position ( FIG. 7 ), the torsion spring  54  is stressed and will tend to bias the impact rotator  42  back toward the first position. A central axial opening  55  is formed within the spring retaining portion  46 . 
     The impact portion  44  of the impact rotator  42  is depicted in  FIGS. 3 and 4  apart from the other components of the vibrator  20 . The impact portion  44  includes a central body  48  that is generally cylindrically shaped. A blind bore  50  is formed within the central body  48 . Directional flow ports  52  are disposed through the central body  48  permitting fluid communication between the blind bore  50  and the exterior of the central body  48 . As best seen in  FIG. 4 , the ports  52  are preferably oriented so as to flow fluid within the blind bore  50  outwardly along a generally tangential path, which is represented by arrows  54 . Although two ports  52  are shown in the depicted embodiment, those of skill in the art will understand that there may be more or fewer than two such ports  52 . 
     Impact shoulders  56  extend radially outwardly from the central body  48  and are shaped and sized to reside within the second chamber  32  of the housing  28 . The impact shoulders  56  present radially-facing second impact surfaces  58 . 
     In operation, fluid is flowed by the pump  26  through the flow passage  24  of the running string  22 . The fluid enters the first chamber  30  of the housing  28 , as indicated by the arrow  60  in  FIG. 6 , and enters the blind bore  50 . In the first rotational position, depicted in  FIG. 6 , the flow ports  52  are located so that they are not blocked by the impact blocks  36 . As a result, fluid flowing in the direction of arrow  60  will exit the blind bore  50  through the directional flow ports  52  (arrow  54 ) and then exit into the second chamber  32  as depicted by arrow  62  in  FIG. 6 . As the fluid exits the flow ports  52 , a rotational moment is imparted to the impact rotator  42  by this flow, causing the impact rotator  42  to rotate in the direction of arrow  64  in  FIG. 4  from its first rotational position ( FIG. 6 ) to the second rotational position ( FIG. 7 ). In the second rotational position, the flow ports  52  are blocked by the reduced diameter interior radial surfaces  38  of the impact blocks  36 , thereby precluding fluid flow through the flow ports  52  and through the housing  28 . The second impact surfaces  58  of the impact shoulders  56  will impact against first impact surfaces  40  of the impact blocks  38  creating a jarring vibration which will be transmitted through the housing  28  of the vibrator  20  to the stuck tool  18 . The torsion spring  54  will then return the impact rotator  42  to the first rotational position. Thereafter, the cycle of operation is repeated as fluid flow through the flow ports  52  again moves the impact rotator  42  from the first rotational position to the second rotational position and creates a second jarring vibration. 
     The invention also provides a method for removing a stuck device, such as device  18 , from a flowbore  16 . The vibrator  20  is run into the flowbore  16  and is engaged with the stuck device  18 . Fluid is flowed through the flow passage  24  of the running string  22  and into the vibrator  20  and causes the vibrator  20  to create jarring impacts in a vibrating manner as described previously. The impacts are transmitted to the stuck device  18  until is removed from the flowbore  16 . 
     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein. The invention is limited only by the claims that follow and any equivalents thereof.

Summary:
A jarring device includes an outer housing which defines an axial flow path therethrough. An impact rotator is retained within the housing and is rotatable therewithin between a first rotational position and a second rotational position to create a jarring impact. A torsional spring biases the impact rotator toward the first rotational position. Fluid flow through the housing rotates the impact rotator from the first to the second rotational position.