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: 
FIELD OF THE INVENTION 
     The field of this invention is jars for downhole use in operations such as drilling and fishing and more particularly to fluid operated jars that function bi-directionally. 
     BACKGROUND OF THE INVENTION 
     Jars are downhole devices that are used to impart a blow in an uphole or downhole direction to a stuck object. They have also been designed to impart rotary motion so that a drill bit can be turned as well as hammered during a drilling operation. There are the purely mechanical types that deliver a fixed jarring force triggered by pulling up on the string. There are hydraulic versions that generally have two telescoping members with fluid reservoirs annularly disposed in between. A small orifice through which the oil has to pass resists the initial pulling of the string. This passage is in a movable piston that isolates the two annular cavities as the pulling force is applied. Eventually, the movable piston with the orifice in it clears a narrow passage allowing oil to rush around it and allowing the telescoping members to contact each other to deliver a hammer blow to an anvil. 
     Yet other designs of jars have used the concept of valves in pistons, which when closed allow pressure buildup to move telescoping members with respect to each other and against the force of a spring. As more relative movement under these conditions occurs, the spring force eventually overcomes the hydraulic force holding the valve in the piston closed and the movement of the telescoping members is violently reversed. This results in a hammer blow delivered to an anvil as the tool reassumed the initial position for a repetition of the same cycle. A good example of this style of bi-directional jar is U.S. Pat. No. 5,803,182. While this design can hammer bi-directionally, it did not have the capability of also delivering rotary motion to a drill bit. Another example of a bi-directional hydraulic jar is U.S. Pat. No. 4,462,471. 
     Prior attempts to provide bit turning capability to jars involved the provision of a pin extending in a spiral slot to convert axial movement in the jar to a rotational output at the bit secures at its lower end. An example of this design is U.S. Pat. No. 4,958,691. It features the use of a plurality of tilting cams to insure rotation in a single direction for drilling. This tool did not have bi-directional capability and the mechanical reliability of the arrangement of the pin in the spiral slot was less than ideal. 
     The present invention addresses the limitations of the prior designs and seeks to accomplish a variety of objectives in a single tool, some of which will be enumerated. The jar of the present invention delivers bi-directional jarring capability in conjunction with the ability to impart rotational motion for drilling. The clutching system addresses the reliability issue in a drilling environment. Cushioning members reduce wear on valve seats from cyclical loading. Modularity allows for rapid conversion from bi-directional operation to unidirectional operation. Use of a singular spring system for jarring in opposite direction and other features allow reduction of overall length of the jar, in comparison to existing bi-directional jars. The number of parts is also reduced to aid the objective of reliability and overall length reduction. These and other objectives will be more apparent to a person skilled in this art from a review of the detailed description of the preferred embodiment described below. 
     Also relevant for background in the field of downhole jars are U.S. Pat. Nos. 4,076,086; 4,361,195; 4,865,125; 5,086,853; 5,174,393; 5,217,070; 4,462,471; 6,062,324; 6,035,954; 6,164,393; and 6,206,101. 
     SUMMARY OF THE INVENTION 
     A bi-directional jar with bit turning capability is disclosed. To jar down, weight is set down on the tool and pressure is built up on a piston to move the body up while compressing a spring. When spring force opens the valve in the piston, the housing comes down striking an anvil as the flow rushes through the piston before the valve recloses for another cycle. The valve member features a hydraulic brake to slow its movement after the valve is forced open. Clutching action comes from an angled spline acting through a spirally cut cylinder, which reduces in diameter to engage the bit to turn. A single spring acts on a pair of pistons for bi-directional jarring. Modularity allows rapid conversion to uni-directional operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a - 1   c  are a sectional elevation of the jar in the run in mode or in the ready for up impact mode; 
     FIGS. 2 a - 2   c  are the view of the jar in the ready for down impact mode; 
     FIGS. 3 a - 3   c  are the position subsequent to FIGS. 2 a - 2   c  after pressure buildup but before delivery of the downward jarring blow; 
     FIGS. 4 a - 4   c  are subsequent to the position of FIGS. 3 a - 3   c  with the valve open in the piston but prior to the delivery of the jarring impact; 
     FIGS. 5 a - 5   c  are the up impact position shown in FIGS. 1 a - 1   c  but after pressure buildup but before delivery of the upward jarring blow; 
     FIGS. 6 a - 6   c  are the view of FIGS. 5 a - 5   c  shown after the built up pressure is released and before delivery of the upward jarring blow; and 
     FIG. 7 is a perspective view of the clutch showing the spline drive; 
     FIG. 8 is a perspective of the helix housing showing the internal teeth in hidden lines. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 a - 1   c , the apparatus A has a top sub  10  to which a tubing string (not shown) of coiled or rigid tubing can be attached. Upper shaft  12  is secured to top sub  10  at thread  14 . A plurality of elongated slots  16  are aligned with the longitudinal axis of upper shaft  12  to allow flow in passage  18  to pass around valve member  20  when valve member  20  is off of upper seat  22 , as will be explained below. Impact cap  24  is secured to upper shaft  12  at thread  26 . An opening  28  is in the lower end of impact cap  24 . Upper seat  22  surrounds opening  28  inside of impact cap  24 . A shock-absorbing ring  30  is sandwiched between upper seat  22  and impact cap  24 . Ring  30  also surrounds the opening  28  in its position below upper seat  22 . Valve member  20  is slidably mounted in passage  18  and during the run in position can fall toward its ultimate position against upper seat  22 . It may stop short of upper seat  22 , but, for up jarring with tension applied to top sub  10 , fluid pressure in passage  18  will ultimately seat valve member  20  on upper seat  22 . During down jarring, slots  16  will permit flow to bypass valve member  20  through open opening  28  on impact cap  24 . 
     Mounted around upper shaft  12  is upper sub  32 . Upper sub  32  is connected to main barrel  34  at thread  36 . Main barrel  34  has an impact shoulder  38  (FIG. 1 b ) and a thread  40  to attach the helix housing  42  at its lower end. Helix housing  42  has an internal helix  44 , see FIG. 8, whose purpose will be explained below. 
     Within main barrel  34  is dart body  46 . Dart body  46  has a central passage  48  that terminates in one or more lateral outlets  50 . Surrounding dart body  46  are springs  52  and  54 . Spring perch  56  is supported off a shoulder on main barrel  34  and acts as the lower support for spring  52 . An upper flange  58  on dart body  46  rests on spring  52  during run in. Dart bushing  60  rests on another internal shoulder in main barrel  34  and supports the lower end of spring  54 . Mounted above spring  54  is trip bushing  61 . Trip bushing  61  is designed to move up into contact with spring perch  56  when upward movement of the main barrel  34  urges dart bushing  60  upwardly, as will be explained below. A carbide insert  62  acts as a lower valve member when disposed against seat  64 , as will be explained below. A series of openings  66  allow springs  52  and  54  to compress without fluid resistance of a pressure buildup in annular space  68 . A tappet  70  is secured at the top of passage  48 . Tappet  70  has an extending pin  72  around which flow can enter passage  48  through passage  74  in tappet  70 . During run in, valve member  20  rests on pin  72 . For up jarring, valve member  20  is seated against upper seat  22 . Ultimately, pin  72  will force valve member  20  off upper seat  22  to deliver an up jarring force, as will be explained below. 
     Also mounted in main barrel  34  is piston  76 , which supports impact ring  78 . Annular seat  80  surrounds passage  82  through piston  76 . Shock absorbing ring  84  supports annular seat  80  against shock from contact by carbide insert  62 , as will be explained below. Shaft  86  is connected to piston  76  at thread  88 . Shaft  86  continues passage  82  to the lower end  90  where a drill bit can be connected for drilling or where the apparatus A can be attached directly or indirectly to a stuck object downhole for up and/or down jarring blows. 
     A coil clutch  92  is disposed between helix housing  42  and shaft  86 . FIG. 7 illustrates a perspective view of coil clutch  92 . It has a central passage  94  so it can be mounted over shaft  86 . It has a helical spline  96  that meshes with helix  44  on helix housing  42 . FIG. 8 shows in dashed lines the internal helix or spline  44  that meshes with the helical spline  96  on coil clutch  92 . Referring again to FIG. 7, the coil clutch has a cylindrical body  98  that is spirally cut in one or more spirals  100 . When helix housing  42  moves up the meshing of helical spline  96  with spline  44  causes rotation of coil clutch  92  in a direction that tends to expand the diameter of the spiral  100 . What this does is prevent engagement of shaft  86  by spiral  100 . When the helix housing  42  comes back down, it turns the coil clutch  92  in the opposite direction causing the spiral  100  to constrict around shaft  86 . The downward motion of helix housing  42 , which is prevented from rotation on its axis by keying upper sub  32  to upper shaft  12  (keying feature not shown), through the engagement of splines  96  and  44 , imparts a rotation to the coil clutch  92 , now securely grabbing the shaft  86 . As a result, the shaft  86  rotates and eventually receives a downward jarring blow when impact shoulder  38  strikes impact ring  78 , as will be explained below. 
     Passages  102  prevent liquid lock in annular space  104  due to relative movement of the helix housing with respect to shaft  86 . Bushing  106  allows the shaft  86  to turn in helix housing  42  with reduced wear. Seals  108  seal between piston  76  and main barrel  34  to facilitate pressure buildup on piston  76  when carbide insert  62  has landed on it. Seals  110  seal between impact cap  24  and main barrel  34 . 
     The main parts now having been described, the operation of the tool will now be reviewed. To jar down and rotate shaft  86 , weight is set down on top sub  10  with the bit (not shown) attached at lower end  90 . As shown in FIGS. 2 a - 2   c , setting down weight allows pin  72  to displace valve member  20  from upper seat  22  and flow to bypass valve member  20  through slots  16  and out through opening  28 . Carbide insert  62  is advanced into close proximity of seat  80  or may even land on it. If contact is not made just from setting down, the onset of pressure into passage  18  will push carbide insert  62  into contact with seat  80 . Pressure builds on piston  76  which can&#39;t move down, so the pressure drives up main barrel  34 , as shown in FIGS. 3 a - 3   c . Pressure maintains the dart body  46  against piston  76  up to a point. Dart bushing  60  is moved up with main barrel  34  to compress spring  54  against a travel stop  55  supported from dart body  46 , only after stop  55  engages a shoulder  57  on dart body  46 . However, before that can happen, spring perch  56  compresses spring  52  against flange  58  on dart body  46 . Upward movement of helix housing  42  turns the coil clutch due to the meshing of splines  96  and  44 . When helix housing  42  moves up, spiral  100  does not grab shaft  86  so that the coil clutch simply turns with respect to shaft  86 . 
     At some point, depending on the set down weight on top sub  10  the force from springs  52  and  54  overcomes the fluid pressure on piston  76  and carbide insert  62  lifts up from seat  80 , as shown in FIGS. 4 a - 4   c . As a result of flow being re-established, main barrel  34  is propelled down and dart body  46  is propelled up. As dart body  46  is propelled up, its lateral outlets  50  are obstructed by dart bushing  60 . This obstruction acts as a fluid brake on the upward motion of dart body  46 , because the rate of fluid passing through dart body  46  is dramatically reduced. This fluid brake is more reliable than shock bumpers used in past designs and wear on the cycling parts is reduced. Meanwhile, the rapid downward motion of helix housing  42  spins the coil clutch  92  in a manner so as to constrict spiral  100  on shaft  86 . Since helix housing  42  is constrained against rotation around its longitudinal axis and at the same time it is engaged through the meshing of splines  44  and  96  and spiral  100  is gripping shaft  86 , a turning force is imparted to shaft  86 . At the end of the movement of the main barrel  34 , shoulder  38  delivers a downward jarring blow to impact ring  78 . The tool now resumes the position in FIGS. 2 a - 2   c  for another cycle. 
     FIGS. 1 a - 1   c  also show the position of the tool connected to a downhole stuck object (not shown) at lower end  90  and an upward pull applied through the tubing to top sub  10 . In this position, valve member  20  is on or near upper seat  22 . If valve member  20  is not on seat  22 , turning the pump on will drive it the rest of the way to contact. Pressure can now build on impact cap  24 , which moves in tandem with valve member  20 . As this is happening, the string (not shown) is being further tensioned as impact ring  13  moves away from shoulder  15 . Valve member  20  pushes down on pin  72 , which drives down dart body  46  to compress the springs  54  and  52  via stop  55  and flange  58 . Eventually springs  54  and  52  provide enough force to allow pin  72  to displace valve member  20  from seat  22 . Flow can resume through impact cap  24  and the tension held in the tubing string (not shown) connected to top sub  10  drives up top sub  10 , upper shaft  12 , and impact ring  13  mounted to it. Impact ring  13  hits shoulder  15  on upper sub  32  to deliver the upward jarring blow. From the position in FIGS. 6 a - 6   c  the tool returns to the position of FIGS. 1 a - 1   c . It should be noted that stretching out the tool for an up jar, as shown in FIGS. 1 a - 1   c , puts the upper end  43  of helix housing  42  in contact with shoulder  45  on piston  76  so that the up jarring blow passes from impact ring  13  to upper sub  32 , to main barrel  34 , to helix housing  42  that is now shouldered on shoulder  45  to communicate the up jarring blow to the piston  76 . 
     Coil clutch  92  can be omitted from the apparatus A if it is to be used purely as a jarring tool and not for drilling. Doing this will eliminate the turning force applied to shaft  86  but it will still get the downward jarring blows when impact shoulder  38  hits impact ring  78 . The apparatus A is a modular construction that allows it to be configured for jar up only, jar down only, jar up and down with no rotation, or jar down with rotation. Higher wearing components are simply removed from the assembly before use to get the desired effect. To eliminate up jarring, valve member  20  is removed. To eliminate down jarring carbide insert  62  or/and seat  80  are removed. To eliminate rotation, coil clutch  92  is removed. 
     Apart from the modular nature of the apparatus A, it delivers rotational force in a more reliable manner than the pin following a spiral slot technique used in U.S. Pat. No. 4,958,691. The meshing of inclined splines  44  and  96  is a far stronger connection that can stand up to the high cycle rates experienced by the apparatus A. The clutching action is also significantly more reliable than the array of cams used in that same prior art patent. The coil clutch  92  can have its spiral  100  made from a coil spring, a braided weave that exhibits action akin to the well known finger trap, or from a cylinder that is helically cut by a variety of techniques one of which could be laser cutting. It can have a single or multiple helixes. The cylinder could be cut in other patterns, which respond to rotation in opposed directions by an increase or decrease in diameter. Different materials can be used for coil clutch  92  and surface treatments can also be incorporated to improve grabbing action upon constriction or engagement. Other ratchet mechanisms to obtain the clutching action for single direction rotation are also contemplated within the scope of the invention. 
     In another feature of the invention, a single spring can be used instead of coil springs  52  and  54 . Other spring types such as Belleville washer stacks, compartments with compressible gases and fluid chambers with controlled leakage rates can be used as the source that provides the force to allow flow to resume, setting the stage for a jar in the up or down direction. To reduce tool length, a single spring system or equivalent system acts as the force to allow flow to resume, whether jarring in the up or the down directions. This is to be compared to other tools such as the jar tool shown in U.S. Pat. No. 5,803,182 that requires discrete springs for the jar up valve and the jar down valve, thereby adding complexity and length to the tool. 
     The apparatus A features shock absorbing rings  30  and  84  which can be made from a variety of metallic and non-metallic materials compatible with the anticipated temperature and fluid conditions found for the particular application. The rings can be solid or in segments and can have a variety of cross-sectional shapes. Their purpose is to absorb shocks on their respective seats  22  and  64  from the frequent cycling experienced in these types of jars. These rings are not the only form of shock absorbers in the apparatus A. The dart body  46  is accelerated upwardly during down jarring when the carbide insert  62  lifts off seat  64 . Rather than having such rapid acceleration stopped by repeatedly striking a fixed object, as depicted for example in U.S. Pat. No. 4,958,691, the apparatus of the present invention uses the rushing fluid through the dart body  46  as a hydraulic brake, as openings or lateral outlets  50  become temporarily obstructed by dart bushing  60  to rapidly decelerate the dart body  46  as it approaches impact cap  24 . There need not be a collision of these parts before a return of the dart body  46  to the neutral position. Wear on the parts from cyclic impacts is reduced, if not totally eliminated. It should be noted that other materials could be used for valve action instead of carbide, as mentioned for insert  62  without departing form the invention. The apparatus A can be used with or without known designs of accelerators, typically used with jars in shallow depths. 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.

Summary:
A bi-directional jar with bit turning capability jars down when weight is set down on the tool and pressure is built up on a piston to move the body up while compressing a spring. When spring force opens the valve in the piston, the housing comes down striking an anvil as the flow rushes through the piston before the valve recluses for another cycle. The valve member features a hydraulic brake to slow its movement after the valve is forced open. Clutching action comes from an angled spline acting through a spirally cut cylinder, which reduces in diameter to engage the bit to turn. A single spring acts on a pair of pistons for bi-directional jarring. Modularity allows rapid conversion to uni-directional operation.