Abstract:
Disclosed herein is an atmospheric chamber. The atmospheric chamber includes, a first opposing wall of the chamber and a second opposing wall of the chamber, end members sealingly joining the first and second opposing walls of the chamber to create a fluid tight volumetric space, and at least one support substantially bridging between the first opposing wall and the second opposing wall positioned between respective end members.

Description:
BACKGROUND OF THE INVENTION 
     Downhole tools such as actuators, for example, often use downhole hydrostatic pressures to create forces necessary to actuate the actuator. The actuator has a chamber that stores atmospheric pressure. The chamber includes an adjustable volume cavity that when exposed to downhole hydrostatic pressure is compressible to a smaller volume. Actuation is prevented from initiating until the chamber is positioned in a desired downhole location at which point the actuation is triggered. During compression, the actuator causes relative motion between portions thereof that is utilized in the actuation. 
     Downhole hydrostatic pressures, however, can be so great that the walls that define the pressure cavity of the chamber can fail due to crushing or bursting depending upon the direction in which the hydrostatic pressure is applied. As such, the art may be receptive of pressure chambers with improved resistance to over pressure failures. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed herein is a downhole pressure chamber. The pressure chamber includes, a first tubular having teeth extending from a surface thereof, a second tubular positioned coaxially with the first tubular having teeth extending from a surface thereof, the longitudinal teeth of the second tubular is axially slidably engaged with the surface of the first tubular, and the teeth of the first tubular is axially sidably engaged with the surface of the second tubular. The pressure chamber further includes, a first seal fixedly sealed to the first tubular and slidably sealed to the surface of the second tubular, and a second seal fixedly sealed to the second tubular and slidably sealed to the surface of the first tubular thereby defining a pressure cavity by the first seal, the second seal and an annular space between the two surfaces. 
     Further disclosed herein is a downhole pressure chamber. The downhole pressure chamber includes, a first tubular having a first end and a second end, a second tubular positioned coaxially with the first tubular having a third end and a fourth end, at least one first seal fixedly sealed to the first tubular at the first end and slidably sealed to an inner perimetrical surface of the second tubular, at least one second seal fixedly sealed to the second tubular at the third end and slidably sealed to an outer perimetrical surface of the first tubular thereby defining a pressure cavity by the at least one first seal, the at least one second seal and an annular space between the inner perimetrical surface and the outer perimetrical surface, and at least one support member positioned within the annular space is slidably engaged with at least one of the inner perimetrical surface and the outer perimetrical surface, the at least one support member is radially supportive of the first tubular and the second tubular. 
     Further disclosed herein is a method of making a downhole pressure chamber. The method includes, positioning a first tubular having a first end and a second end coaxially with a second tubular having a third end and a fourth end, slidably sealing the first end of the first tubular to an inner surface of the second tubular, slidably sealing the third end of the second tubular to an outer surface of the first tubular thereby defining a pressure cavity in an space between the inner surface, the outer surface and the two seals. The method further includes structurally supporting the first tubular with the second tubular while structurally supporting the second tubular with the first tubular with at least one support member slidably engaged with at least one of the first tubular and the second tubular in the annular space. 
     Further disclosed herein is an atmospheric chamber. The atmospheric chamber includes, a first opposing wall of the chamber and a second opposing wall of the chamber, end members sealingly joining the first and second opposing walls of the chamber to create a fluid tight volumetric space, and at least one support substantially bridging between the first opposing wall and the second opposing wall positioned between respective end members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a partially sectioned perspective view of the downhole pressure chamber disclosed herein; 
         FIG. 2  depicts a side view of the downhole pressure chamber of  FIG. 1 ; 
         FIG. 3  depicts a cross sectional view of the downhole pressure chamber of  FIG. 2  taken at arrows  3 - 3 ; 
         FIG. 4  depicts a partial cross sectional view of an alternate embodiment of the downhole pressure chamber disclosed herein shown in an expanded pressure cavity configuration; and 
         FIG. 5  depicts a partial cross sectional view of the downhole pressure chamber of  FIG. 4  shown in a compressed pressure cavity configuration. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A detailed description of several embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring to  FIGS. 1 and 2 , the downhole pressure chamber  10  disclosed herein is illustrated. The downhole pressure chamber  10  includes a first tubular, disclosed herein as mandrel  14 , a second tubular, disclosed herein as housing  18 , a first seal  22  and a second seal  26 . The mandrel  14  and the housing  18  are made of a rigid material such as metal, for example. The mandrel  14  has a first end  30 , a second end  34 , an outer perimetrical surface  38 , with a plurality of longitudinal teeth  42  extending therefrom, and a pair of perimetrical grooves  46  receptive of the first seal  22 , disclosed herein as a pair of o-rings (not shown in  FIG. 1 ). The housing  18  has a third end  50 , a fourth end  54 , an inner perimetrical surface  58 , with a plurality of longitudinal teeth  62  extending therefrom, and a pair of perimetrical grooves  66  receptive of the second seal  26 , disclosed herein as a pair of O-rings (not shown in  FIG. 1 ). The first seal  22  slidably seals to the inner perimetrical surface  58  while the second seal  26  slidably seals to the outer perimetrical surface  38 , thereby defining a pressure chamber  70  by the inner perimetrical surface  58 , the outer perimetrical surface  38 , the first seal  22  and the second seal  26 . A volume of the pressure cavity  70  changes as the mandrel  14  and housing  18  move axially toward or away from one another. The volume of the pressure cavity  70  is greatest when the first end  30  is as far from the third end  50  as is possible from the sliding engagement of the mandrel  14  with the housing  18 . Similarly, the volume of the pressure cavity  70  is smallest when the first end  30  is as near to the third end  50  as is possible from the sliding engagement of the mandrel  14  with the housing  18 . As such, the downhole pressure chamber  10  can be used as an actuator by causing the mandrel  14  and the housing  18  to move axially relative to one another in response to pressure differentials between the pressure cavity  70  and a downhole environment external to the pressure cavity  70 . For example, if the pressure chamber  10  is positioned downhole with atmospheric pressure within the pressure cavity  70  and downhole hydrostatic pressure is exposed externally to the pressure cavity  70  pressure forces will act to compress the volume of the pressure cavity  70  thereby causing the mandrel  14  to move axially relative to the housing  18 . Actuation of the relative motion of the mandrel  14  and the housing  18  is prevented until a triggering event or after release of a release member that may occur based upon a selected pressure differential or simply a particular downhole pressure level. 
     In an alternate embodiment, not shown, the longitudinal teeth  42  and  62  may be configured in a spiral pattern along the mandrel  14  and the housing  18  respectively. As such, during compression of the pressure cavity  70  the mandrel  14 , in addition to moving axially relative to the housing  18  would also move rotationally. Such rotational motion could be utilized to rotationally actuate a tool, for example. 
     Hydrostatic pressures downhole can reach pressures in the range of about 3,000 to about 20,000 pounds per square-inch (psi). At such extreme pressures the housing  18  and the mandrel  14  are susceptible to crushing or bursting. Embodiments disclosed herein provide support to the housing  18  and mandrel  14  to minimize the possibility of such failures. The housing  18  and the mandrel  14  mutually support one another as will be described below. 
     Referring to  FIGS. 1 ,  2 , and  3  the longitudinal teeth  42  of the mandrel  14  extend from the outer perimetrical surface  38  a dimension to substantially bridge an annular space  74  that exists between the inner perimetrical surface  58  and the outer perimetrical surface  38 . Thus, the longitudinal teeth  42  are in slidable engagement with the inner perimetrical surface  58 . Similarly, the longitudinal teeth  62  of the housing  18  extend from the inner perimetrical surface  58  a dimension to substantially bridge the annular space  74  that exists between the inner perimetrical surface  58  and the outer perimetrical surface  38 . Thus, the longitudinal teeth  62  are in slidable engagement with the outer perimetrical surface  38 . As such, both sets of longitudinal teeth  42 ,  62  support both the mandrel  14  and the housing  18 . Specifically, radially inward movement of the inner perimetrical surface  58  that precedes crushing of the housing  18  by the hydrostatic pressure is counteracted by support of the housing  18  by the mandrel  14  through the teeth  42 ,  62 . Similarly, radially outward movement of the outer perimetrical surface  38  that precedes bursting of the mandrel  14  by the hydrostatic pressure is counteracted by support of the mandrel  14  by the housing  18  through the teeth  42 ,  62 . To assure that an axial portion of the mandrel  14  and housing  18  are not unsupported by the teeth  42 ,  62  the teeth  42  extend from the first end  30  to beyond midway between the first end  30  and the second end  34 , and the teeth  62  extend from the third end  50  to beyond midway between the third end  50  and the fourth end  54 . By extending beyond midway between the ends  30 ,  34 ,  50 ,  54  the teeth  42 ,  62  are assured to overlap axially thereby assuring axial support to the mandrel  14  and the housing  18 . Alternate embodiments may, however, have teeth that do not axially overlap as long as the axial gap between the teeth does not exceed specific dimensions as will be described with reference to  FIGS. 4 and 5 . In order to overlap axially the teeth  42 ,  62  must be arranged so as not perimetrically interfere with one another. This is accomplished by orienting the teeth  42  to aligned with gaps  76  between the teeth  62 , and similarly, to align the teeth  62  with the gaps  76  between the teeth  42 . 
     Perimetrical spacing of the teeth  42 ,  62  is also important to assure that the teeth  42 ,  62  are not too far apart to adequately support the mandrel  14  and housing  18 . Structural calculations are known in the industry to assure that the housing  18  does not crush under the differential pressure across its tubular structure. Similar structural calculations are known in the industry to assure that the mandrel  14  does not burst under the differential pressure across its tubular structure. These structural calculations among other things include material properties, structural geometry and pressure differentials. With such calculations a safety factor can be determined. Low safety factors such as those less than one, for example, are susceptible to failure if additional support is not provided. In such cases, embodiments disclosed through the teeth  42 ,  62  or through support rings (to be described with reference to  FIGS. 4 and 5  below) can be utilized to provide the additional support needed. For embodiments using the teeth  42 ,  62  a maximum gap  78  between adjacent teeth  42 ,  62  should be maintained. One method of calculating the maximum gap  78  is: [((safety factor−1) divided by 0.167)+3] times 5% of the circumference of the tooth outer diameter (OD). This equates to a range of 15% of the circumference of the tooth OD for safety factors of 1 to 0.03% of the circumference of the tooth OD for safety factors of 0.5. Through other calculations the maximum axial unsupported gap is found to be 2 to 4 times the radial thickness of the wall of the housing  18 , depending upon the safety factor. 
     Referring to  FIGS. 4 and 5 , an embodiment of the downhole pressure chamber  110  disclosed herein is illustrated. The downhole pressure chamber  110  includes a first tubular, disclosed herein as mandrel  114 , a second tubular, disclosed herein as housing  118 , a first seal  122  and a second seal  126 . The mandrel  114  and the housing  118  are made of a rigid material such as metal, for example. The mandrel  114  has a first end  130 , a second end  134 , an outer perimetrical surface  138  and a pair of perimetrical grooves  146  receptive of the first seal  122 , disclosed herein as a pair of o-rings. The housing  118  has a third end  150 , a fourth end  154 , an inner perimetrical surface  158  and a pair of perimetrical grooves  166  receptive of the second seal  126 , disclosed herein as a pair of o-rings. The first seal  122  slidably seals to the inner perimetrical surface  158  while the second seal  126  slidably seals to the outer perimetrical surface  138 , thereby defining a pressure chamber  170  by the inner perimetrical surface  138 , the outer perimetrical surface  138 , the first seal  122  and the second seal  126 . A volume of the pressure cavity  170  changes as the mandrel  114  and housing  118  move axially toward or away from one another. The volume of the pressure cavity  170  is greatest when the first end  130  is as far from the third end  150  as is possible from the sliding engagement of the mandrel  114  with the housing  118 . Similarly, the volume of the pressure cavity  170  is smallest when the first end  130  is as near to the third end  150  as is possible from the sliding engagement of the mandrel  114  with the housing  118 . As such, the downhole pressure chamber  110  can be used as an actuator by causing the mandrel  114  and the housing  118  to move axially relative to one another in response to pressure differentials between the pressure cavity  170  and a downhole environment external to the pressure cavity  170 . For example, if the pressure chamber  110  is positioned downhole with atmospheric pressure within the pressure cavity  170  and downhole hydrostatic pressure is exposed externally to the pressure cavity  170  pressure forces will act to compress the volume of the pressure cavity  170  thereby causing the mandrel  114  to move axially relative to the housing  118 . 
     Wherein radial support for the mandrel  14  and housing  18  of the embodiment of  FIGS. 1-3  was through a plurality of teeth  42 ,  62 , the embodiments of  FIGS. 4 and 5  support the mandrel  114  and housing  118  through at least one support ring  174 . The support rings  172  are positioned in an annular space  174  defined by the perimetrical surfaces  138  and  158 . The support rings  172  are dimensioned to substantially bridge the annular space  174  and are in slidable engagement with the perimetrical surface  138  and  158 . As such the support rings  172  radially support both the mandrel  114  and the housing  118 . Specifically, radially inward movement of the inner perimetrical surface  158  that precedes crushing of the housing  118 , by the hydrostatic pressure, is counteracted by support of the housing  118  by the mandrel  114  through the support rings  172 . Similarly, radially outward movement of the outer perimetrical surface  138  that precedes bursting of the mandrel  114 , by the hydrostatic pressure, is counter acted by support of the mandrel  114  by the housing  118  through the support rings  172 . To assure that the mandrel  114  and housing  118  are adequately supported by the support rings  172  the support rings  172  are positioned along the annular space  174  with an axial gap  178  of no more than about 2 to about 4 times the radial thickness of the housing  118  as described above. 
     Since the support rings  172  are slidably engaged with both the mandrel  114  and the housing  118 , the support rings  172  are free to move axially within the annular space  174 . A plurality of biasing members  182 , disclosed herein as coil springs, are positioned on both sides of each of the support rings  172 . The plurality of biasing members  182  provide substantially equal forces to the support rings  172  such that each of the biasing members  182  maintain substantially equal length with one another. The equal lengths of the biasing members  182  centers the support rings  172  such that an equal distance is maintained on each axial side of the support rings  172 . Maintaining substantially equal lengths of the biasing members  182  allows a designer of the system to design in the axial gap  178  such that it does not exceed a desired maximum dimension. 
     Additionally, the support rings  172  have one or more recesses (not shown) in at least an inner radial surface or an outer radial surface thereof or other openings facilitative of pressure communication to the next adjacent pocket of fluid to prevent sealing of the support rings  172  to the perimetrical surfaces  138 ,  158  that could create undesirable pressure pockets between adjacent support rings  172 , for example. 
     In an alternate embodiment of the pressure chamber, not shown, support members could be fixedly attached to both a mandrel and a housing such that they bridge an annular space therebetween. Such support members may be raised surfaces that slidably engage with one another at a radial interface therebetween, for example. In so doing the support members provide radial support to both the mandrel and the housing. In such an embodiment, however, the relative movement of actuation of the mandrel with the housing would be limited to the dimension of the maximum axial gap as described in reference to  FIGS. 4 and 5 . This limitation will assure that neither the mandrel nor the housing have an excessive non-supported portion. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.