Abstract:
The present invention provides a method and an apparatus for use in a wellbore tool. The apparatus includes a body and a sliding member, wherein the sliding member and a mechanical portion moves between a first position and a second position. A valve assembly causes the sliding member and mechanical portion to shift to its second position at a predetermined flow rate of fluid through the body. The invention also provides an apparatus for a downhole tool that includes a mandrel and a sliding member disposed on the mandrel. The sliding member including a plurality of fingers and a plurality of heads, wherein the plurality of fingers are slideably recessed within a plurality of longitudinal grooves. The invention further provides a collet assembly that includes a body and at least two extendable members, whereby as the members extend outward, the members are rotated.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to an apparatus and methods for drilling, completion and rework of wells. More particularly, the invention relates to an apparatus and methods for activating and releasing downhole tools. More particularly still, the invention provides a hydraulically activated downhole tool.  
           [0003]    2. Description of the Related Art  
           [0004]    In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. The casing typically extends down the wellbore from the surface of the well to a designated depth. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore.  
           [0005]    It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well to a depth, whereby the upper portion of the second liner is overlapping the lower portion of the first string of casing. This process is typically repeated with additional casing strings until the well has been drilled to total depth. To properly place the additional casing strings within the wellbore, the end of the existing casing must be determined. A downhole tool, such as a tubing end locator, is typically employed to accurately locate the end of the existing casing.  
           [0006]    Typically, a conventional tubing end locator is run downhole on a tubing string. The end of the tubing is indicated when the tubing end locator runs out the end of the tubing and is then brought back uphole, thus shearing the finger and indicating the depth of the tubing. Therefore, conventional tubing end locators employing calipers, fingers or other protrusions are capable of only reading the end of the tubing once, and thus yield a low level of accuracy as to the depth of the tubing. Consequently, when a conventional tubing end locator is run downhole and brought back uphole at the tubing end, the calliper or finger is sheared completely off thus indicating the end of the tubing and destroying the calliper or finger and requiring the tubing end locator to be brought back uphole to be re-worked or re-tooled.  
           [0007]    A conventional tubing end locator may also be used to locate a preformed inner diameter profile, a collar or a nipple in an existing downhole casing. Conventional tubing end locators implement calipers or fingers which extend vertically upward and outwardly from the tubing end locator such that each calliper or finger is spring loaded and exerts an external pressure against the internal diameter and circumference of the tubing. Each calliper or finger deflects at each inner diameter profile juncture, thus indicating the location of the preformed profile, collar or nipple is located.  
           [0008]    Another form of a conventional tubing locator employs the use of bow springs to locate a preformed inner diameter profile, a collar or a nipple in an existing downhole casing. The locator tool includes high compressive springs and a set of bow springs extending radially from a mandrel on the tool. The bow springs extend vertically, longitudinally and radially outward from the mandrel thus contacting the internal circumference and surface of the casing or tubing, and establishing a constant internal resistance detected uphole at the surface. When the bow springs contact a preformed inner diameter profile, a collar, a nipple or tubing end, the bow springs will move either upwardly towards the surface at each collar indication, or downwardly towards the end of the tubing at each tubing end indication.  
           [0009]    Several problems may occur using a conventional tubing locator during a locator operation. One problem occurs when an excessive overpull is applied at the surface of the well during the location of the preformed inner diameter profile, collar, nipple or tubing end. In this case, the conventional tubing locator does not provide a failsafe mechanism that allows the locator tool to release and reset after applying the excessive overpull. Another problem occurs during the indication phase of the locator operation. After the conventional tubing locator has located the profile or tubing end, an overpull indication must be detectable at the surface of the well. However, the conventional tubing locator tool is unable to withstand an overpull that is easily detectable at the surface, therefore unable to accurately to determine the location of the profile.  
           [0010]    Other downhole tools are used throughout the well completion process. One such downhole tool is a conventional under-reamer. Generally, the conventional under-reamer is used to enlarge the diameter of wellbore by cutting away a portion of the inner diameter of the existing wellbore. A conventional under-reamer is typically run down hole on a tubing string to a predetermined location with the under-reamer blades in a closed position. Subsequently, fluid is pumped into the conventional under-reamer and the blades extend outward into contact with the surrounding wellbore. Thereafter, the blades are rotated through hydraulic means and the front blades enlarge the diameter of the existing wellbore as the conventional under-reamer is urged further into the wellbore.  
           [0011]    The conventional under reamer may also be used in a back-reaming operation. In the same manner as the under-reaming operation, the fluid is pumped into the under-reamer and the blades extend outward into contact with the surrounding wellbore. Thereafter, the blades are rotated through hydraulic means and the back blades enlarge the diameter of the existing wellbore as the under-reamer is urged toward the surface of the wellbore.  
           [0012]    Several problems may occur using a conventional under-reamer during an under-reaming or back-reaming operation. One problem occurs when an unmovable obstruction is encountered during the under-reaming or back-reaming operation. In this situation, the front or the back blades on the conventional under-reamer may be damaged as the under-reamer is urged furthered toward the unmovable obstruction. Another problem is particularly associated with the back-reaming operation. During the back-reaming operation, the blades must remain open and the under-reamer must be able to withstand a strong pulling force to effectively remove a portion of the existing wellbore diameter. However, the conventional under-reamer typically is unable to remain open during a back-reaming operation to effectively enlarge the wellbore diameter.  
           [0013]    A need therefore exists for apparatus with a hydraulic valving system that provides a failsafe mechanism that allows the apparatus to withstand a sufficient overpull while permitting the apparatus to release and reset after applying an excessive overpull. There is yet a further need for an apparatus with a hydraulic valving system that will provide a failsafe mechanism that allows the apparatus to close when an unmovable obstruction is encountered. There is a final need for an apparatus with a hydraulic valving system that ensures the apparatus will remain open during a back-reaming operation.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention provides a method and an apparatus for use in a wellbore tool. The apparatus includes a body having a center bore and at least one side port permitting fluid communication between the bore and an annular area between the tool and the wellbore. The apparatus further includes a sliding member, wherein the sliding member moves between a first position and a second position and a valve assembly that causes the sliding member to shift to its second position at a predetermined flow rate of fluid through the body. The apparatus also includes a mechanical portion movable with the sliding member between the first and second positions.  
           [0015]    In another embodiment, the invention provides for an apparatus for a downhole tool that includes a mandrel, a plurality of ramped sections radially disposed around the mandrel and a plurality of longitudinal grooves radially disposed between the plurality of ramped sections. The invention further includes a sliding member disposed on the mandrel, the sliding member movable between a first and second position the sliding member including a plurality of fingers and a plurality of heads, wherein the plurality of fingers are slideably recessed within the plurality of longitudinal grooves.  
           [0016]    In another embodiment, the invention provides a collet assembly for use in a wellbore, the collet assembly includes a body and at least two extendable members movable independent of the body, the members are extendable outwards. The collet assembly further includes a sliding member attached to each member, the sliding member remotely movable between a first and second position. The collet assembly also includes a ramp formed on the body whereby, the members are urged along the surface to extend outwards and as the members are extended outwards, the members are rotated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.  
         [0018]    It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0019]    [0019]FIG. 1 illustrates a cross-sectional view of one embodiment of an apparatus in accordance with the present invention.  
         [0020]    [0020]FIG. 1A is a side view of the collet fingers and the collet head.  
         [0021]    [0021]FIG. 1B is a section view of FIG. 1A illustrating the collet fingers disposed in the grooves.  
         [0022]    [0022]FIG. 2 is an enlarged cross-sectional view of apparatus illustrating the flow of fluid though the apparatus prior to the actuation of the collet.  
         [0023]    [0023]FIG. 3 is a cross-sectional view of the apparatus after the collet head has expanded outward into contact with a tubular.  
         [0024]    [0024]FIG. 3A is a side view of the collet fingers and the collet head illustrating the collet head expanded outward.  
         [0025]    [0025]FIG. 4 is an enlarged cross-sectional view of the apparatus illustrating the activation of a relief valve.  
         [0026]    [0026]FIG. 5 is a cross sectional view of an alternative embodiment of the collet for use with the apparatus.  
         [0027]    [0027]FIG. 5A is a bottom view of the embodiment shown on FIG. 5.  
         [0028]    [0028]FIG. 6 is a cross sectional view illustrating the radial expansion of the collet.  
         [0029]    [0029]FIG. 6A is a bottom view of the embodiment shown on FIG. 6.  
         [0030]    [0030]FIG. 7 is a cross sectional view of another embodiment of the apparatus in accordance with the present invention.  
         [0031]    [0031]FIG. 8 illustrates a cross sectional view of the apparatus after the blades have expanded outward.  
         [0032]    [0032]FIG. 9 is an enlarged cross-sectional view of apparatus illustrating the activation of the relief valve. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]    [0033]FIG. 1 illustrates a cross-sectional view of one embodiment of the invention used with a locator tool  100 . Typically, the locator tool is run into the wellbore on tubing string to a predetermined point. Thereafter, the locator tool is activated causing fingers to expand radially outward and then locator tool is slowly pulled upward in the wellbore to find a preformed profile within an existing tubular. When a weight gage shows an increase in overpull, the locator tool will be located in the profile.  
         [0034]    As shown in FIG. 1, the tool  100  includes a top sub  105 . The top sub  105  includes an internal threaded section  130  to accept a tubing string (not shown). The top sub  105  further includes a shoulder  110  at a lower end to be used as a stop during operation of the tool  100 . The top sub  105  is connected to an upper portion of a mandrel  115  or body via another threaded connection. As illustrated, the mandrel  115  runs the entire length of tool  100 . The mandrel  115  includes a bore  295  to act as a fluid conduit through the tool  100 .  
         [0035]    A spring housing  120  is disposed at the upper end of the mandrel  115 . The spring housing  120  includes a spring housing shoulder  125  to abut shoulder  110  during operation of the apparatus  100 . The spring housing  120  encloses a relief valve  330 . In this embodiment, the relief valve  330  includes a first biasing member  145 , an upper piston  135 , and a ball  140 . However, other forms of relief valves may be employed, so long as they are capable of selectively controlling fluid flow. The main function of the relief valve  330  is to provide a means of releasing fluid from a chamber  325  when fluid pressure within the chamber  325  reaches a predetermined level. As shown, the first biasing member  145  is disposed between the spring housing  120  and the mandrel  115  and biases the movement of the upper piston  135 . Upon a fluid force the ball  140  acts against the upper piston  135 , thereby urging the upper piston  135  axially in the spring housing  120 . The spring housing  120  further includes a spring housing passageway  305  to allow fluid to exit apparatus  100 .  
         [0036]    [0036]FIG. 1 further illustrates a housing  155  or sliding member disposed around mandrel  115 . The housing  155  is movable between a first and a second position. The housing  155  includes a housing passageway  255  that acts a conduit for fluid to activate the relief valve  330 . An upper seal  150  is disposed between the mandrel  115  and the housing  155  and creates a fluid tight seal between the mandrel  115  and the housing  155 , thereby preventing fluid from traveling out the mandrel  115 . Additionally, a chamber shoulder  165  is formed in the housing  155  to be later used to urge the housing  155  axially upward.  
         [0037]    An upper dog  170  is disposed around mandrel  115  below the chamber  325 . The upper dog  170  secures a lower piston housing  180  to the mandrel  115 . The lower piston housing  180  is disposed beneath a portion of housing  155  and encloses a one-way check valve  160 . In the preferred embodiment, the check valve  160  is a unidirectional pressure energized seal. However, other forms of the check valves may be employed, so long as they are capable of selectively controlling fluid flow. The primary function of the one way check valve  160  is to permit fluid flow from a port  185  into an inner passageway  260  while preventing fluid exiting the inner passageway  260  to the port  185 .  
         [0038]    As shown on FIG. 1, the port  185  in the mandrel  115  permits fluid from the mandrel passageway  295  to pass through the check valve  160  and subsequently in to the inner passageway  260  that is formed between the lower piston housing  180  in the mandrel  115 . The inner passageway  260  connects the check valve  160  to the chamber  325  and then to an outer passageway  175 . The outer passageway  175  is formed between the lower piston housing  180  and the housing  155 . The lower piston housing  180  further includes an aperture  205  that connects to the outer passageway  175  to an inner portion of the lower piston housing  180 .  
         [0039]    The inner portion of the lower piston housing  180  contains a low flow valve  210 . The primary function of the low flow valve  210  is to permit fluid to exit the apparatus  100  at a low pressure differential in the mandrel passageway  295  while preventing fluid from exiting the apparatus  100  at a high pressure differential. In the preferred embodiment, the low flow valve  210  includes a lower piston  195 , a second biasing member  240  and a plurality of seals. However, other forms of low flow valves may be employed, so long as they are capable of selectively controlling fluid flow at predetermined pressures.  
         [0040]    The lower piston  195  is movable between a first and a second position. As illustrated on FIG. 1, the lower piston  195  is biased upward by the second biasing member  240  in the first position, thereby allowing fluid flow from the aperture  205 . As depicted, the second biasing member  240  consists of wave springs. However, other forms of biasing members, such as coil springs, wave washers or combinations thereof may be employed.  
         [0041]    The low flow valve  210  includes a plurality of seals to prevent fluid leakage. In this respect, a first piston seal  215  is disposed on the inner portion of the lower piston  195  to create a fluid tight seal between the lower piston  195  and the mandrel  115 . Furthermore, a second and a third piston seal  190 ,  220  are disposed between the lower piston housing  180  and an outer portion of the lower piston  195 . The second and third piston seal  190 ,  220  are used to create a fluid tight seal around aperture  205  after the lower piston  195  moves axially downward to the second position. In addition, a lower seal  230  is disposed around the lower piston housing  180  to create a fluid tight seal between the lower piston housing  180  and the housing  155 .  
         [0042]    A dog housing  235  is disposed at the lower end of the piston housing  180 . The dog housing  235  is held at a predetermined location on the mandrel  115  by a lower dog  225 . The second biasing member  240  abuts against the dog housing  235 . In this respect, the dog housing  235  acts as a support member for the second biasing member  240 . In the same manner, the dog housing  235  acts as a support member for a third biasing member  245 .  
         [0043]    The third biasing member  245  is disposed around mandrel  115  and captured between the dog housing  235  and a collet  250  or mechanical portion. The third biasing member  245  is constructing and arranged to permit axial movement of the collet  250  upon at predetermined force. In the preferred embodiment, the third biasing member  245  is a coiled spring. However it is within the scope of the present invention to use other forms of a biasing member, so long as they are capable of providing the necessary force to bias the collet  250 .  
         [0044]    As depicted on FIG. 1, the collet  250  is in a first position. The collet  250  is an annular member disposed of around mandrel  115  and connected to the housing  155 . The collet  250  moves between the first position and a second position along an axial path on mandrel  115 . In the preferred embodiment, the collet  250  includes a plurality of equally spaced collet fingers  285 . Each of the fingers  285  includes a collet head  275 . As shown, the collet  250  in the first position permits the collet fingers  285  and the collet head  275  to rest against the lower portion of the mandrel  115 .  
         [0045]    As shown on FIG. 1, the lower portion of mandrel  115  includes a plurality of equally spaced ramp sections  290 . In the preferred embodiment, the numbers of ramp sections  290  correspond to number of collet fingers  285 . Each ramp section includes a tapered surface  310  and a substantially flat surface  315 . The ramp sections  290  are constructed to interface with the collet heads  275  during operation of the apparatus  100 . It should be noted that the outer portion of the collet  275  is a radial distance equal to or less than the radial distance of the outer portion of the ramp sections  290 , thereby allowing the apparatus  100  to obtain the location of a tubular  265  with a small inside diameter as shown on FIG. 1.  
         [0046]    [0046]FIG. 1A is a side view of the collet fingers  285  and the collet heads  275 . Visible specifically are heads  275  formed at an end of fingers  285  that are attached to the housing  155  at an upper end. The heads  275  are constructed and arranged to act on the tapered surfaces  310  of the mandrel  115  as the heads  275  are moved upwards relative to the tapered surfaces  310 . The mandrel  115  includes grooves  335  for housing the collet fingers  285 , the grooves  335  are formed longitudinally between the ramped sections  290 . In this manner, the fingers  285  are recessed in the mandrel  115 . FIG. 1B is a section view of FIG. 1A illustrating the fingers  285  disposed in the grooves  335 .  
         [0047]    [0047]FIG. 2 is an enlarged cross-sectional view of the apparatus  100  illustrating the flow of fluid though the apparatus  100  prior to actuation of the collet  250 . During operation, fluid from the surface of the wellbore is pumped through the mandrel passageway  295  typically to some other downhole tool (not shown) such as a nozzle or mud motor. A pressure differential causes the fluid to pass through port  185 , as illustrated by arrow  320 . From port  185 , the fluid flows through check valve  160  and into the inner passageway  260 . Fluid continues through the inner passageway  260  around the upper dog  170  and into the chamber  325  and then into the outer passageway  175 . Next, fluid in the outer passageway  175  flows inwardly through aperture  205 . From aperture  205 , fluid flows through the second biasing member  240 , around the lower dog  225 , and third biasing member  245  exiting the tool  100  through a collet passageway  340 . In this manner, a portion of the fluid within the mandrel bore  295  exits the tool  100  into the surrounding wellbore.  
         [0048]    [0048]FIG. 3 is a cross-sectional view of the apparatus  100  after the collet head  275  has expanded outward into contact with the tubular  265 . As the fluid flow is increases the differential pressure within the mandrel passageway  295  increases, thereby causing pressurized fluid to enter port  185 . The pressurized fluid entering the port  185  creates a force that acts against the upper portion of piston  195  in the low flow valve  210 . At a predetermined point, the force against the upper portion of piston  195  becomes greater then the biasing force on the lower portion of the piston  195  created by the second biasing member  240 . At that point, the lower piston  195  starts to move axially downward compressing the second biasing member  240 . The piston  195  continues to move axially downward until the third piston seal  220  passes aperture  205  as shown on FIG. 3. In this manner, the movement of the piston  195  to the second position closes off the fluid pathway through the aperture  205 .  
         [0049]    Thereafter, fluid entering the port  185  flows through the one-way check valve  160  into the inner passageway  260  and around the upper dog  170 . The fluid is prevented from flowing through the aperture  205  because the aperture  205  is closed. Therefore, fluid pressure builds within the chamber  325  and creates a force that acts against the chamber shoulder  165 . At a predetermined point, the force on the chamber shoulder  165  becomes greater than the biasing force created by the third biasing member  245 . At that point, the chamber  325  fills with fluid, thereby urging the housing  155  axially upward and compressing the third biasing member  245 . The housing  155  continues to move axially upward until the spring housing shoulder  120  contacts the sub shoulder  110 . At that point, the housing  155  reaches the second position.  
         [0050]    The movement of the housing  155  to the second position causes the collet  250  to move axially upward to the second position since the collet  250  is connected to the housing  155 . As the collet  250  starts to move axially upward, the collet head  275  slides along the tapered surface  310  toward the flat surface  315  of the ramped section  290 . The movement of the collet head  275  along the tapered surface  310  causes the collet head  275  to move radially outward into contact with a surrounding tubular  265 . As shown, the collet head  275  is in full contact with a groove  270  formed in the tubular  265 .  
         [0051]    The collet  250  and housing  155  may be shifted from the second position to the first position by reducing the flow of fluid through the mandrel passageway  295 . As the fluid flow is reduced, the differential pressure within mandrel passageway  295  is also reduced, thereby allowing the lower piston  195  to move axially upward exposing the aperture  205 . Thereafter, fluid from the chamber  325  and the mandrel passageway  295  may flow into the aperture  205  and through the second biasing member  240  exiting out the collet passageway  340  as discussed in a previous paragraph. In this manner, the fluid in the chamber  325  is removed allowing the third biasing member  245  to urge the collet  250  and the housing  155  from the second position to the first position, thereby disengaging the collet head  275  from the tubular  265 .  
         [0052]    [0052]FIG. 3A is a side view of the collet fingers  285  and the collet heads  275  illustrating the collet heads  275  expanded outward. As shown, the collet fingers  285  have moved axially upward within the grooves  335 . As further shown, the collet heads  275  have traveled up a portion of the tapered surface  310 , thereby causing the collet heads  275  to extend radially outward.  
         [0053]    [0053]FIG. 4 is an enlarged cross-sectional view of apparatus  100  illustrating the activation of the relief valve  330 . The main function of the relief valve  330  is to provide a means of releasing fluid from chamber  325  when the pressure within the chamber  325  reaches a predetermined amount. After the collet head  275  is fully engaged with the tubular  265  as shown in FIG. 3, the tubing string and apparatus  100  is pulled upward to verify location of the tubular  265 . A sensing device (not shown) connected to the tubing string indicates the upward force. If the force indicated on the sensing device is within a specific range then there is full engagement of the collet head  275  and the tubular  265 . However, the upward force may break the collet fingers  285  if the force is not maintained within a predetermined range. To prevent damage to the collet fingers  285 , the relief valve  330  senses the pressure build up in chamber  325  and releases fluid out of the chamber  325 , thereby causing the housing  155  and the collet  250  to move from the second position to the first position. The movement to the first position causes the collet head  275  to release the tubular  265 , thereby preventing damage to the collet fingers  285 . In this manner, the relief valve  330  acts as a backup to the hydraulic system, thereby preventing damage to the apparatus  100 .  
         [0054]    The increased pressure in the chamber  325  creates a force in the fluid located in housing passageway  255 . The fluid force acts against the ball  140 . At a predetermined point, the force on the ball  140  becomes greater than the biasing force created by the first biasing member  145 . At that point, the ball  140  urges the upper piston  135  axially upward, thereby compressing the first biasing member  145 . The upward movement of the ball  140  and the upper piston  135  exposes the spring housing passageway  305 . Therefore, fluid in the chamber  325  is permitted to travel up the housing passageway  255  and exit out the apparatus  100  through the spring housing passageway  305 . In this respect, the housing  155  and the collet  250  is permitted to return to the first position.  
         [0055]    [0055]FIG. 5 is a cross sectional view of an alternative embodiment of the collet  250  for use with the apparatus  100 . In this embodiment, rotational movement is used to engage the collet head  275  with the surrounding tubular (not shown). The collet  250  is moveable between the first and second position in the same manner as described in the previous paragraphs. FIG. 5 illustrates the collet  250  in the first position, wherein the collet head  275  is in contact with the mandrel  115 . The collet head  275  is constructed and arranged to act on the tapered surface  310  of the mandrel  115  as the head  275  is moved upward relative to the tapered surface  310 . The mandrel  115  includes grooves  335  formed longitudinally between the ramped sections  290  for housing the collet fingers  285 . In this manner, the fingers  285  are recessed in the mandrel  115 . FIG. 5A is a bottom view of the embodiment shown on FIG. 5.  
         [0056]    [0056]FIG. 6 is a cross sectional view illustrating the radial expansion of the collet  250 . As shown, the collet fingers  285  have moved axially upward in the grooves  335 . As further shown, the collet heads  275  have traveled up a portion of the tapered surface  310 , thereby causing the collet heads  275  to rotate outward. The rotation of the collet heads  275  causes a rotational force to act against the collet fingers  285 . The collet fingers  285  are constructed and arranged of a material that permits a predetermined rotational force to be applied to the collet fingers  285  when the collet  250  is in the second position while allowing the collet fingers  285  to return to the original shape when the collet  250  is in the first position. In this manner, the collet heads  275  are rotated outward allowing collet heads  275  to radially expand into contact with a profile (not shown). FIG. 6A is a bottom view of the embodiment shown on FIG. 6.  
         [0057]    [0057]FIG. 7 is a cross sectional view of another embodiment of the apparatus  400  in accordance with the present invention. As shown, apparatus  400  is downhole tool called an under-reamer. Typically, an under-reamer is run down hole with the blades in a closed position to a predetermined location. Subsequently, fluid is pumped into the under-reamer and the blades extend outward into contact with the surrounding wellbore. Thereafter, the blades are rotated through hydraulic means and the under reamer is urged downward enlarging the diameter of wellbore. The under reamer may also be used in a back reaming operation. During a back reaming operation, the under reamer is pulled toward the surface of the well while the blades enlarge the wellbore diameter.  
         [0058]    As shown on FIG. 7, the apparatus  400  includes many of the same components of the apparatus  100 . For example, a mandrel  115 ,  415 , a mandrel passageway  295 ,  595 , a check valve  160 ,  460 , a first biasing member  145 ,  445 , upper piston  135 ,  435 , a relief valve  330 ,  630 , a chamber  325 ,  625 , an outer passageway  175 ,  475 , an aperture  205 ,  505 , a shoulder  165 ,  465 , an inner passageway  260 ,  560 , a port  185 ,  485 , a low flow valve  210 ,  510 , a first piston seal  215 ,  515  a second piston seal  190 ,  490 , a third piston seal  220 ,  520 , a lower piston  195 ,  495 , a second biasing member  240 ,  540 , and a third biasing member  245 ,  545 . Each of the components listed function in the same manner as previously discussed for the apparatus  100 .  
         [0059]    Additional components used in the apparatus  400  include an exit aperture  440  to allow fluid to exit the relief valve  630  and a seal member  425  to seal the relief valve  630 . The apparatus  400  further includes a bottom port  455  to allow fluid to exit the apparatus  400 . Additionally, apparatus  400  includes a piston  450  that moves between a first position and a second position due to fluid pressure in the chamber  625 . The lower end of the piston  450  abuts against rods  470 . The rods  470  are used to open and close a blade mechanism  420  that controls a pair of blades  480 . As shown on FIG. 7, the blades  480  in a closed position.  
         [0060]    [0060]FIG. 8 illustrates a cross sectional view of the apparatus  400  after the blades  480  has expanded outward. During operation of apparatus  400 , fluid is pumped through the mandrel passageway  595  exiting out the bottom port  455 . As fluid flows through the bottom port  455 , a pressure differential created in the passageway  595 . The pressure differential causes fluid to enter the check valve  490  and exit through aperture  505 .  
         [0061]    As the fluid flow is increased the differential pressure increases within the mandrel passageway  595  causing fluid to enter the outer passageway  475 . As the fluid fills the outer passageway  475 , a force is created that acts against the upper portion of piston  495  in the low flow valve  510 . At a predetermined point, the force against the upper portion of piston  495  becomes greater then the biasing force on the lower portion of the piston  495  created by the second biasing member  540 . At that point, the lower piston  495  starts to move axially downward compressing the second biasing member  540 . The piston  495  continues to move axially downward until the third piston seal  520  passes aperture  485  as shown on FIG. 8. In this manner, the movement of the piston  495  to the second position closes off the fluid pathway through the aperture  485 .  
         [0062]    Thereafter, fluid entering the check valve  460  flows into the inner passageway  560  toward the chamber  625 . As fluid collects, a pressure builds within the chamber  625  that creates a force that acts against the chamber shoulder  465 . At a predetermined point, the force on the chamber shoulder  465  becomes greater than the biasing force created by the third biasing member  545 . At that point, the chamber  625  fills with fluid, thereby urging the piston  450  to start moving axially downward and compressing the third biasing member  545 . Furthermore, the piston  450  urges the rods  470  against the blade mechanism  420 , thereby opening the blades  480 . The piston  450  continues to move axially until the blades  480  are fully opened. At that point, the piston  450  reaches the second position, thereby allowing the apparatus  400  to conduct a under reaming operation or a back reaming operation.  
         [0063]    The piston  450  may be shifted from the second position to the first position by reducing the flow of fluid through the mandrel passageway  595 . As the fluid flow is reduced, the differential pressure within mandrel passageway  595  is also reduced, thereby allowing the lower piston  495  to move axially upward exposing the aperture  485 . Thereafter, fluid from the chamber  625  may flow down the inner passageway through the aperture  485  and into the aperture  505  exiting the apparatus  400 . In this manner, the fluid in the chamber  625  is removed allowing the third biasing member  545  to urge the piston  450  from the second position to the first position, thereby releasing the pressure on the rods  470  and allowing the blade mechanism  420  to close the blades  480 .  
         [0064]    [0064]FIG. 9 is an enlarged cross-sectional view of apparatus  400  illustrating the activation of the relief valve  630 . The main function of the relief valve  630  is to provide a means of releasing fluid from chamber  625  when the pressure within the chamber  625  reaches a predetermined amount. After the blades  480  are fully extended as shown in FIG. 8, the apparatus  400  is urged downhole to conduct an under-reaming operation or is urged toward the surface to conduct a back-reaming operation. During the operation, an obstruction may be encountered that may damage the blades  480  if they remain open. Therefore, to prevent damage to blades  480 , the relief valve  630  senses the pressure build up in chamber  625  and allows the fluid to exit the chamber  625 .  
         [0065]    The increased pressure in the chamber  625  creates a force that acts against the upper piston  435 . At a predetermined point, the force on the upper piston  435  becomes greater than the biasing force created by the first biasing member  445 . At that point, the upper piston  435  moves axially upward, thereby compressing the first biasing member  445 . The upward movement of the upper piston  435  causes the seal member  425  to move pass the exit aperture  440 , thereby allowing fluid to flow out of the apparatus  400 . As the fluid exits out of the chamber  625 , the piston  450  moves from the second position to the first position, thereby causing the blade mechanism  420  to close, therefore preventing damage to the blades  480 .  
         [0066]    The hydraulic components consisting of a check valve, low flow valve, and a relief valve as constructed and arranged in apparatus  100  and apparatus  400  may also be used in the following list of down hole tools: mechanical packers, a valve system for inflatable elements, logging tools/gauging tools, orienting device/kick subs, expandable bits, whipstock setting tools, hammers, inside tubing cutters, accelerators, indexing tools, centralizers, anchors, tool for shifting sleeves, packers, wireline tools, overshots, spears, tractors and others.  
         [0067]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.