Abstract:
A movable member position-sensing device includes a sensor and a biasing member in operable communication with both the sensor and a movable member configured to communicate a parameter to the sensor indicative of a position of the movable member.

Description:
BACKGROUND 
       [0001]    It is often desirable to determine relative positions of movable parts of a system, such as valving components in the downhole completion industry, for example. Although various devices and methods exist to enable an operator to determine relative positions of components, most have drawbacks of one sort or another that limit the scope of their use. Operators are, therefore, receptive to new devices and methods that provide alternate approaches to determining relative positions of components. 
       BRIEF DESCRIPTION 
       [0002]    Disclosed herein is a movable member position-sensing device. The device includes a sensor and a biasing member in operable communication with both the sensor and a movable member configured to communicate a parameter to the sensor indicative of a position of the movable member. 
         [0003]    Further disclosed herein is a method of determining the position of a movable member. The method includes biasing the movable member relative to a sensor, mapping output of the sensor to the position of the movable member, and determining the position of the movable member in situ based on the output of the sensor from the mapping. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0005]      FIG. 1  depicts a schematic view of a position-sensing device disclosed herein; 
           [0006]      FIG. 2  depicts a partial cross sectional view of an alternate position-sensing device disclosed herein; and 
           [0007]      FIG. 3  depicts a partial cross sectional view of another alternate position-sensing device disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0009]    Referring to  FIG. 1 , a position-sensing device disclosed herein is illustrated generally at  10 . The position-sensing device  10  illustrated in this embodiment includes, a movable member  14 , shown as a sliding sleeve of a downhole valve, a sensor  18 , shown as a force transducer, and a biasing member  22 , shown as a spring. The movable member  14  is movable relative to the sensor  18  in one of two directions  24 A and  24 B as depicted by arrows  28 . Movement of the movable member  14  in the first direction  24 A, towards the sensor  18 , causes an increase in a biasing force communicated to the sensor  18  by the biasing member  22 . Conversely, movement of the movable member  14  in the second direction  24 B, away from the sensor  18 , causes a decrease in a biasing force communicated to the sensor  18  by the biasing member  22 . Note that in alternate embodiments these forces versus movement relationships could be reversed. Mapping an output of the sensor  18  that correlates to all potential positions of the movable member  14  allows an operator to subsequently determine a position of the movable member  14  based on an output of the sensor  18 . 
         [0010]    In the embodiment of  FIG. 1 , the position-sensing device  10  is used in a downhole completion within a borehole  30 . The movable member  14  is a sliding sleeve that is slidable relative to a tubular  32  within which it is housed. A port  36  through a wall  40  of the tubular  32  can be partially occluded, completely occluded, or not occluded at all by the movable member  14  depending upon the positional location of the movable member  14  relative to the port  36 . Since the sensor  18  is fixed in relation to the tubular  32 , and outputs of the sensor  18  were mapped for all positions of the movable member  14  prior to the tubular  32  being run into the borehole  30 , any position of the movable member  14  can be determined in situ by determining the mapped position that correlates to a specifically sensed output value. In this embodiment the position of the movable member  14  can also be correlated to a percent of the valve that is open. 
         [0011]    Additionally, in this embodiment a temperature sensor  44  is incorporated into the position-sensing device  10  and is configured to monitor temperatures of the sensor  18 . Although shown as a separate component it should be noted that the temperature sensor  44  can be incorporated into the same circuitry employed by the sensor  18  to minimize any differential in temperature between where the pressure is sensed and where the temperature is sensed. Since outputs of the sensor  18  may vary depending upon actual temperatures of the sensor  18 , temperature compensation of the sensor output is possible with the temperature knowledge provided by the temperature sensor  44 . Similar temperature compensating can be employed to loads communicated by the biasing member  22  to the sensor  18  that are altered due to changes in temperature. 
         [0012]    Referring to  FIG. 2 , an alternate embodiment of a position-sensing device is illustrated generally at  110 . In the interest of brevity, similar items employed in both the position-sensing device  110  and the device  10  are not shown in this embodiment or described again hereunder. A sensor  118  of the device  110  is a pressure sensor. The pressure sensor  118  senses pressure of a fluid  120  housed within a chamber  121  defined primarily by a bellows  122  that serves as the biasing member in this embodiment. The chamber  121  is fluid tight and is bound by the bellows  122 , a wall  123 , and the pressure sensor  118 . A volume of the chamber  121  changes as position of the movable member  114  changes. For example, as the movable member moves in a first direction  124 A the volume of the chamber  121  decreases thereby increasing pressure of the fluid that is sensed by the pressure sensor  118 . Conversely, as the movable member moves in a second direction  124 B the volume of the chamber  121  increases thereby decreasing pressure of the fluid that is sensed by the pressure sensor  118 . It may be desirable to have the fluid  120  be compressible to permit larger repositions of the movable member  114  with smaller changes in pressure sensed. 
         [0013]    The bellows  122  allows the chamber  121  to change in volume while remaining hermetically sealed. Additionally, by making the bellows  122 , the wall  123 , and a housing  126  of the pressure sensor  118  out of metal and joining them together by brazing, soldering or welding, the chamber  122  can be made to remain hermetically sealed while being exposed to extreme environmental conditions, such as conditions commonly encountered in a downhole completion application. 
         [0014]    Referring to  FIG. 3 , another alternate embodiment of a position-sensing device is illustrated generally at  210 . As with reference to  FIG. 2  similar items employed in this embodiment as previous embodiments may not be shown or described again hereunder. The pressure sensor  118  is employed herein coupled with an alternate biasing member  222 . The biasing member  222 , as with the biasing member  122  includes a chamber  221  with the fluid  120  contained therein. The chamber  122  is defined by a tubular  234  slidably sealed to movable member  214  by a seal  238 , illustrated herein as an o-ring, and a wall  242  of the movable member  214 . A volume of the chamber  222  changes in response to movements of the movable member  214  towards and away from the pressure sensor  118 . The change in volume causes a change in pressure, sensible by the pressure sensor  118 . Since the change in pressure is proportional to the position of the movable member  214 , an output from the pressure sensor  118  corresponds to a unique and proportional position of the movable member  214 . 
         [0015]    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. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.