Patent Publication Number: US-10309185-B2

Title: Releasable ratchet device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a releasable ratchet device. 
     BACKGROUND OF THE INVENTION 
     A ratchet device typically comprises a mandrel device with a grooved area and a locking device comprising locking grooves configured to be engaged with the grooved area of the mandrel device. Axial movement between the mandrel device and the locking device is allowed in a first direction when the locking device is engaged with the mandrel device while movement between the mandrel device and the locking device is prevented in a second direction opposite of the first direction. Hence, a ratchet device may be considered as a locking mechanism for preventing relative movement between two parts in one direction only. 
     Such ratchet devices are commonly used in tools and/or other type of equipment for use in oil and/or gas wells, such as packers, plugs, straddles etc., where the ratchet device typically is used to allow the tool to be brought from a first state to a second state (for example from a run state to a set state) while preventing the tool going from the second state and back to the first state. 
     SUMMARY OF THE INVENTION 
     One or more embodiments of the present invention provide a releasable ratchet device having two states, a first state where the ratchet device is working as a normal ratchet device, i.e. that movement between the mandrel device and the locking device is allowed in one direction only, and a second state where movement between the mandrel device and the locking device is allowed in both directions. In one or more embodiments, the releasable ratchet device can be brought from the first state, to the second state and also back to the first state again a repeated number of times. 
     One or more embodiments of the present invention relate to a releasable ratchet device, comprising: a mandrel device comprising a grooved area; a locking device comprising locking grooves configured to be engaged with the grooved area of the mandrel device; where the releasable ratchet device may be configured to be in a locked state, in which axial movement between the mandrel device and the locking device is allowed in a first direction when the locking device is engaged with the mandrel device and movement between the mandrel device and the locking device is prevented in a second direction opposite of the first direction when the locking device is engaged with the mandrel device; characterized in that the releasable ratchet device further comprises: a releasing device configured to bring the releasable ratchet device to a released state, in which axial movement between the mandrel device and the locking device is allowed in both the first direction and the second direction. Further details of embodiments of the invention are set forth in the description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a first embodiment of a releasable ratchet device in an initial state; 
         FIG. 2  illustrates a perspective view of the first embodiment in a locked state; 
         FIG. 3  illustrates a perspective view of the locking device and releasing device in the initial and locked state; 
         FIG. 4  illustrates a perspective view of the locking device and releasing device in the released state; 
         FIG. 5  illustrates a first cross sectional view of the locking device; 
         FIG. 6  illustrates a second cross sectional view of the locking device; 
         FIG. 7  illustrates an alternative embodiment of the locking device and releasing device in the locked state schematically; 
         FIG. 8  illustrates the embodiment in  FIG. 7  in the released state; 
         FIG. 9  illustrates yet an alternative embodiment of the locking device and releasing device in the locked state schematically; 
         FIG. 10  illustrates the embodiment in  FIG. 7  in the released state; 
         FIG. 11  corresponds to  FIG. 6 , where an outer housing is provided outside the locking device. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention will now be described with reference to the enclosed drawings. It is now referred to  FIG. 1 . Here, a releasable ratchet device  1  is shown. The releasable ratchet device  1  is here used in a well tool. Hence, the releasable ratchet device  1  has a substantially cylindrical form, with a longitudinal axis indicated by a dashed line I. The right side of  FIG. 1  is the lowermost side of the releasable ratchet device  1  and the left side of  FIG. 1  is the uppermost side of the releasable ratchet device  1 , i.e. the right side is faced towards the bottom of the well. The releasable ratchet device  1  comprises a mandrel device  10  and a locking device  20 . 
     The mandrel device  10  is substantially cylindrical, where an outside surface of, i.e. a radial outside of, the mandrel device  10  is comprising a grooved area  11  and a smooth area  12 . The grooved area  11  is provided circumferentially around the mandrel device  10 . The smooth area  12  is also provided circumferentially around the mandrel device  10 , but axially displaced in relation to, and adjacent to, the grooved area  11 . 
     In  FIG. 6 , cross section of the mandrel device  10  is indicated by a dashed line. Here, it is shown that the mandrel device  10  comprises a recess  14  in the longitudinal (i.e. axial) direction. 
     It is now referred to  FIG. 3 . The locking device  20  comprises a substantially cylindrical locking ring  20   a  with an axial through bore  20   b . The locking device  20  comprises locking grooves  21  provided on the inner surface of the through bore  20   b . Hence, the locking grooves  21  are provided radially inside of the locking device  20 . 
     The locking grooves  21  are configured to be engaged with the grooved area  11  of the mandrel device  10 . The grooves of the grooved area  11  and the locking grooves  21  have a direction perpendicular to the longitudinal direction I, i.e. to prevent relative axial movement between the locking device and the mandrel device  10  in one direction. 
     Hence, as is known for a person skilled in the art, a releasable ratchet device  1  may be configured to be in a locked state, in which axial movement between the mandrel device  10  and the locking device  20  is allowed in a first direction A when the locking device  20  is engaged with the mandrel device  10 . Moreover, movement between the mandrel device  10  and the locking device  20  is prevented in a second direction B opposite of the first direction A when the locking device  10  is engaged with the mandrel device  20 . As indicated in  FIGS. 1 and 2 , the directions A and B are coinciding with, or parallel with the longitudinal axis I. This may be achieved by providing the grooves of the grooved areas  11  and the locking grooves  21  with different angles, allowing movement in one direction and preventing movement in the opposite direction. This is considered known for a skilled person. 
     It is now referred to  FIGS. 4, 5 and 6 . A slit  23  is provided axially through the substantially cylindrical locking ring  20   a . Hence, a radial expansion of the locking ring  20   a  is allowed. 
     As shown in  FIG. 5  a recess  25  is provided in an axial direction in the axial through bore  20   b  of the locking ring  20   a , on an inner surface of the axial through bore  20   b . As shown in  FIG. 5 , three screw holes  25   a  are provided from the outside of the locking ring  20   a  and into the recess  25 . As shown in  FIG. 6 , a fin  22  is fixed in the recess  25  by means of screws  25   b  in the screw holes  25 . The fin  22  is protruding radially into the axial through bore  20   b . When the locking device  20  is provided outside the mandrel device  10 , the fin  22  of the locking device  20  is provided in the axial recess  14  in the mandrel device  10 . The fin  22  and the recess  14  are forming a guiding device. The guiding device is providing that axial movement between the mandrel device  10  and the locking device  20  is allowed, while rotational movement between the mandrel device  10  and the locking device  20  is prevented due to the engagement of the fin  22  in the axial recess  14 . 
     As shown in  FIG. 6 , the center axis  120  of the axial through bore  20   b  of the locking ring  20   a  is provided eccentric with respect to the center axis I of the device  1 . Hence, a thickness T of the locking ring  20   a  is varying along its circumference. As shown in  FIG. 6 , the slit  23  is provided in the thinnest part of the locking ring  20   a , while the fin  22  is located in the thickest part of the locking ring  20   a . As shown, the fin  22  is provided opposite of the slit  23  in  FIG. 6 , i.e. the fin  22  is displaced 180° in relation to the slit  23  with respect to the longitudinal axis I. In the unlocked state, the center axis  120  may be closer to, or may coincide with, the center axis I. 
     It is now referred to  FIGS. 3 and 4 . Here it is shown that the ratchet device  1  further comprises a releasing device  30 . The releasing device  30  comprises a wedging element  31  provided in the axial slit  23  of the locking device  20 . The releasing device  30  also comprises a connection element  32 . The connection element  32  is connected to an actuator (not shown) of the well tool. The actuator is here considered to control the axial relative movement between the releasing device  30  and the locking device  20 . As shown in  FIG. 4 , relative axial movement between the wedging element  31  and the locking device  20  is configured to provide an increase in the width w of the slit  23 . In  FIG. 4 , the releasable ratchet device  1  is in a released state, where the width w of the slit  23  in the released state is larger than the width w in the locked state. An increase in the width w is also an increase in the diameter of the bore  20   b.    
     Consequently, releasing device  30  is configured to press the locking device  20  radially out from engagement with the mandrel device  10  in the released state, i.e. the releasing device  30  is configured to bring the releasable ratchet device  1  to the released state, in which axial movement between the mandrel device  10  and the locking device  20  is allowed in both the first direction A and the second direction B, since the locking grooves  21  in the released state is no longer engaged with the grooved area  11  of the mandrel device  10 . 
     It is now referred to  FIGS. 1 and 2  again. In  FIG. 1 , the locking device  20  is in an initial state, with an axial distance between the grooved area  11  of the mandrel device  10  and the locking ring  20   a . Here, there is no engagement between the locking grooves  21  of the locking ring  20   a  and the grooves of the grooved area  11 . Movement of the locking device  20  in both directions A and b is possible due to the smooth surface  12 . In  FIG. 2 , the locking device  20  is in the locked state described above, and only movement in direction A is possible. 
     As described above, by axial displacement of the releasing device, the ratchet device  1  is brought to its released state, in which movement is possible in both directions A and B. The locking device  20  together with the releasing device may now be moved back towards the smooth surface  12  and further to the initial state. It should be noted that the locking device  20  and releasing device  30  may be stationary, while the mandrel device  10  is moved to the right in  FIG. 2 . The state cycle may then be repeated, the releasable ratchet device  1  is configured to be brought from the released state and back to the locked state again. 
     In the released state, the fin  22  of the locking device  20  will still be located in the recess  14  of the mandrel device  10 . 
     In  FIGS. 3 and 4 , it is shown that the contact interface  60  between the slit  23  and the wedging element  31  is curved or sine-shaped. 
     In an alternative embodiment shown in  FIGS. 7 and 8 , the contact interface  60  between the wedging element  31  and the slit  23  is substantially wedge-shaped or dovetail-shaped. 
     In yet another embodiment shown in  FIGS. 9 and 10 , the contact interface  60  of the slit  23  is straight, while the corresponding contact surface of the wedge element  31  comprises a straight part  31   a  and a wedge-shaped part  31   b , where the straight part  31   a  is in contact with the slit  23  in the initial and locked states and the wedge-shaped part  31   b  is in contact with the slit in the released state. 
     It should be noted that the axial length of the grooved area  11  can be considerably longer than that shown in the drawings. 
     According to the invention it is possible to reset plugging devices and other well tools several times without the need to pull the well tool to the surface. 
     It is now referred to  FIG. 11 .  FIG. 11  corresponds to  FIG. 6 . In  FIG. 11 , an outer housing  50  is provided radially outside of the locking device  20 . The outer housing has an inner diameter being slightly larger than the outer diameter of the locking ring  20   a  when the locking ring is in its expanded or unlocked state. The outer housing will ensure that the centre axis  120  of the locking ring  20   a  is substantially coinciding with the centre axis I of the device  1  in the unlocked or expanded state. Hence, it is avoided that only some of the locking grooves  21  are engaged with the grooved area  11  in the unlocked or expanded state. If the locking grooves  21  are only partially engaged with the grooved area when radially expanded, movement in direction B will still be prevented, and the device can not be considered to be in its locked state. 
     The outer housing  50  may be used for all embodiments described above. It should be noted that the outer housing may comprise a recess (not shown) for the releasing device  30 .