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: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of application Ser. No. 11/348,909, filed Feb. 7, 2006 U.S. Pat. No. 7,527,104, entitled “Selectively Activated Float Equipment,” which issued May 5, 2009, the entirety of which is incorporated herein by reference. 

   BACKGROUND 
   The present invention relates generally to fluid control valves for production well equipment. In particular, this invention relates to back pressure valves for reverse cementing applications. 
   Production wells typically have valves and valve seats also known as check valves and back pressure valves. These valves are utilized in different applications in various industries including but not limited to the oil and gas industry. Current back pressure valves supply a one direction flow and a negative flow from the other direction. This may be desirable when a controlled flow is important for such purposes as safety well control while placing a casing string and/or tubing in a potentially active well. 
   Typical valves may be mechanically manipulated to selectively change the direction of flow during operations and then selectively change the flow direction back to an original direction. Valves are usually manipulated between configurations by mechanical movement of the casing/tubing, or placing an inter string inside the casing/tubing string to apply weight on the valve so as to hold the valve in an open configuration. Other mechanisms for manipulating valves include disabling the valve with a pressure activated ball or plug allowing flow to enter the casing/tubing string. But these valves cannot be reactivated, if desired. Other valves are manipulated when the casing bottoms in the rat hole at the bottom of the well bore so that the valve is mechanically held open by the set down weight. 
   SUMMARY OF THE INVENTION 
   The present invention relates generally to fluid control valves for production well equipment. In particular, this invention relates to back pressure valves for reverse cementing applications. 
   More specifically, one embodiment of the present invention is directed to a valve for a well pipe, the valve having the following parts: a valve collar connectable to the well pipe; an index piston coaxially positioned within the valve collar for longitudinal translation within the valve collar between closed, flow-open, and locked-open configurations; a detent in the index piston, wherein the detent restricts fluid flow in a circulation direction through a flow path through the index piston; a spring that biases the index piston toward the closed and locked-open configurations; and a plug of the valve collar that mechanically communicates with the index piston to be in corresponding closed, flow-open, and locked-open configurations. 
   According to a further aspect of the invention, there is provided a valve for a well pipe, the valve being made up of different components including: a valve collar connectable to the well pipe, wherein the valve collar comprises an indexing lug; an index piston coaxially positioned within the valve collar for longitudinal translation within the valve collar between closed, flow-open, and locked-open configurations, wherein the index piston comprises an index pattern comprising closed, flow-open, and locked-open positions such that when the indexing lug is positioned at the closed, flow-open, and locked-open positions, the index piston is configured in the closed, flow-open, and locked-open configurations, respectively; a detent in the index piston, wherein the detent restricts fluid flow in a circulation direction through a flow path through the index piston; a spring that biases the index piston toward the closed and locked-open configurations; and a plug of the valve collar that mechanically communicates with the index piston to be in corresponding closed, flow-open, and locked-open configurations. 
   Another aspect of the invention provides a method of regulating fluid circulation through a well casing, the method having the following steps: attaching a valve to the casing; running the valve and casing into the well, wherein the valve is in a closed configuration to maintain relatively higher fluid pressure outside the casing compared to the fluid pressure in the inner diameter of the casing; circulating fluid down the inner diameter of the casing and through the valve to the outside of the casing, wherein the valve is manipulated by the fluid circulation to an open configuration; and ceasing the circulating fluid, wherein the valve is manipulated to a locked-open configuration. 
   The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the exemplary embodiments, which follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings. 
       FIG. 1A  is a cross-sectional side view of an embodiment of a valve of the present invention, wherein the valve is shown in a closed configuration. 
       FIG. 1B  is a schematic side view of an embodiment of an index pattern and indexing lug, wherein the indexing lug is located in a closed position. 
       FIG. 2A  is a cross-sectional side view of the valve of  FIG. 1A , wherein the valve is shown in a flow-open configuration. 
       FIG. 2B  is a schematic side view of the index pattern and indexing lug of  FIG. 1B , wherein the indexing lug is located in a flow-open position. 
       FIG. 3A  is a cross-sectional side view of the valve of  FIGS. 1A and 2A , wherein the valve is shown in a locked-open configuration. 
       FIG. 3B  is a schematic side view of the index pattern and indexing lug of  FIGS. 1B and 2B , wherein the indexing lug is located in a locked-open position. 
       FIG. 4  is a cross-sectional side view of an embodiment of a valve of the present invention fixed in a casing by a cement attachment. 
       FIG. 5A  is a cross-sectional side view of an embodiment of a valve of the present invention, wherein the valve is shown in a closed configuration. 
       FIG. 5B  is a schematic side view of an embodiment of an index pattern and indexing lug, wherein the indexing lug is located in a closed position. 
       FIG. 6A  is a cross-sectional side view of the valve of  FIG. 5A , wherein the valve is shown in a flow-open configuration. 
       FIG. 6B  is a schematic side view of the index pattern and indexing lug of  FIG. 5B , wherein the indexing lug is located in a flow-open position. 
       FIG. 7A  is a cross-sectional side view of the valve of  FIGS. 5A and 6A , wherein the valve is shown in a locked-open configuration. 
       FIG. 7B  is a schematic side view of the index pattern and indexing lug of  FIGS. 5B and 6B , wherein the indexing lug is located in a locked-open position. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   The present invention relates generally to fluid control valves for production well equipment. In particular, this invention relates to back pressure valves for reverse cementing applications. The details of the present invention will now be described with reference to the accompanying drawings. This specification discloses various valve embodiments. 
   Referring to  FIGS. 1A ,  2 A, and  3 A, cross-sectional side views of a valve  1  are illustrated. The valve  1  has several major components including: a valve collar  10 , a detent in the form of a ball cage  20 , an index piston  30 , an index pattern  40 , a spring  50 , and a poppet plug  60 .  FIGS. 2A and 3A  also illustrate cross-sectional side views of the valve  1 . In  FIG. 1A , the valve  1  is shown in a closed position. In  FIG. 2A , the valve  1  is shown in a flow-open position. In  FIG. 3A , the valve  1  is shown in a locked-open position.  FIGS. 1B ,  2 B, and  3 B illustrate schematic side views of the index pattern  40 . In each of these figures, an indexing lug  11  is shown in a different position as described more fully below. 
   Referring to  FIGS. 1A ,  2 A, and  3 A, each of the major components of the valve  1  are described. The valve collar  10  is a cylindrical structure that houses the other major components. The valve collar  10  has three sections, including: the indexing section  12 , the mounting section  13 , and the seat section  14 . The mounting section  13  has female threads at its upper and lower ends, wherein male threads of the indexing section  12  are made up to the upper end of the mounting section  13  and male threads of the seat section  14  are made up to the lower end of the mounting section  13 . The indexing section  12  has a shoulder  15  wherein the inside diameter of the indexing section  12  is smaller below the shoulder as compared to above the shoulder  15 . The mounting section  13  has a stem mount  16  that extends from the inside diameter side wall of the mounting section  13 . The stem mount  16  is an arm having an annular eyelet at its distal end for receiving a stem  33  of the index piston  30 . The seat section  14  has a beveled valve seat  18  for receiving the poppet plug  60 . 
   The ball cage  20  is a somewhat umbrella-shaped structure mounted to the top of the index piston  30  that serves as a ball valve type of detent. The ball cage  20  has a support shaft  21  that extends along the longitudinal central axis of the ball cage  20 . The ball cage  20  also has a cylindrical strainer section  22  that has an outside diameter slightly smaller than the inside diameter of the indexing section  12  of the valve collar  10 . The strainer section  22  is mounted to the support shaft  21  via a top plate  23 . The strainer section  22  has a plurality of side holes  24  that allow fluid communication through the strainer section  22 . The top plate  23  also has a plurality of top holes  25  that also allow fluid communication through the ball cage  20 . The ball cage  20  is connected to the index piston  30  via the support shaft  21 , which extends into a recess in the top of the index piston  30 . The support shaft  21  is threaded, welded, or otherwise connected to the index piston  30 . The lower edge of the strainer section  22  sits on the top of the index piston  30  and may also be connected thereto. The ball cage  20  also comprises a plurality of balls  26 , which are freely allowed to move about within the ball cage  20 . The outside diameter of the balls  26  are larger than the inside diameter of the side holes  24  and top holes  25  so that the balls  26  are retained within the ball cage  20 . 
   The index piston  30  has a plurality of flow ports  31  that extend through the index piston  30  parallel to the longitudinal central axis of the piston  30 . The inside diameter of the flow ports  31  are smaller than the outside diameter of the balls  26  of the ball cage  20 . An annular seal  32  is positioned in a recessed near the top of the outside circumference of the index piston  30  to form a seal between the index piston  30  and the valve collar  10 . The annular seal  32  restricts fluid flow between the two structures even as the index piston  30  translates longitudinally within the valve collar  10 . The indexing piston  30  also has an indexing J-Slot  34  in its exterior wall. The indexing J-Slot  34  has an index pattern  40  described in more detail below. The stem  33  extends from the bottom of the index piston  30  so as to connect the poppet plug  60  to the index piston  30  through the stem mount  16 . The poppet plug  60  is threaded, welded, molded, or otherwise fastened or connected to the end of the stem  33 . 
   As shown in  FIGS. 1A ,  2 A, and  3 A, the spring  50  is positioned concentrically around the stem  33  of the index piston  30 . At its upper end, the spring engages the lower face of the index piston  30  and at its lower end, the spring  50  engages a spring shoulder  17  at the upper edge of the stem mount  16 . In  FIG. 1A , the spring  50  is illustrated in a relaxed or expanded position, while in  FIG. 2A , the spring  50  is completely compressed. In  FIG. 3A , the spring  50  is only partially compressed. 
   The poppet plug  60  is connected to a lower most end of the stem  33  for longitudinal movement into and out of engagement with the valve seat  18  of the seat section  14 . The poppet plug  60  has a conical seal surface  61  for engagement with the valve seat  18 . The seal surface  61  terminates in a seal lip  62  that deflects slightly when the poppet plug  60  is inserted into the valve seat  18 . The deflection of the seal lip  62  ensures the integrity of the seal when the valve is closed. 
   Referring to  FIGS. 1B ,  2 B, and  3 B, the index pattern  40  defines several lug positions that are used to configure the valve in closed, flow-open, and locked-open positions. Closed positions  41  are located in the lower-most portions of the index pattern  40 . When the indexing lug  11  is located in one of the closed positions  41 , the valve  1  is configured in a closed configuration. Flow-open positions  42  are found in the upper-most portions of the index pattern  40 . As shown in  FIG. 2B , when the indexing lug  11  is positioned in one of the flow-open positions  42 , the valve  1  is configured in a flow-open configuration. Locked-open positions  43  are found in a medium lower position of the index pattern  40 . When the indexing lug  11  is in a locked-open position  43 , the valve  1  is in a locked-open configuration.  FIG. 3B  illustrates the indexing lug  11  in a locked-open position  43  which corresponds to a valve  1  configuration that is locked-open as illustrated in  FIG. 3A .  FIG. 1B  illustrates the indexing lug  11  in a closed position  41 , which corresponds to a closed valve  1  configuration as illustrated in  FIG. 1A .  FIG. 2B  illustrates the indexing lug  11  in a flow-open position  42  which corresponds to a valve flow-open configuration as illustrated in  FIG. 2A . 
     FIG. 4  illustrates a valve  1  of the present invention assembled into a casing  2 . The annular space between the valve collar  10  of the valve  1  and the casing  2  may be filled with a concrete or cement attachment  3  to allow the valve  1  to be drilled out of the casing should removal of the valve  1  become necessary. In other embodiments of the invention, the valve  1  may be connected to the casing  2  by any means known to persons of skill. For example, the valve  2  may be stung into a casing collar, or threaded into an internal casing flange. 
   The process for operating the valve is described with reference to  FIGS. 1A ,  2 A, and  3 A. When the valve is run into the well, the valve  1  is in the closed configuration with the spring  50  holding the valve  1  closed. In the illustrated embodiment, the spring  50  is compressed between the bottom face of the index piston  30  and the spring shoulder  17 . The force of the spring  50  biases the poppet plug  60  toward the valve seat  18 . In particular, the valve  1  is biased to a closed configuration. With the valve  1  in the closed configuration, the indexing lug  11  is located in a closed position  41  as shown in  FIG. 1B . As the casing  2  and valve  1  are run into the well, increasing fluid pressure from below the valve  1  is checked against the poppet plug  60  and is not allowed to enter the inner diameter of the casing  2 . 
   When it is desired to open the valve  1 , fluid may be circulated down the inner diameter of the casing  2  to the valve  1 . Due to gravity, fluid moving in the circulation direction, or any other forces in play, the balls  26  within the ball cage  20  seat themselves in the tops of some of the flow ports  31  (see  FIGS. 1A and 2A ). The circulating fluid then flows through the remaining open flow port(s)  31 . However, for fluid to flow through the valve  1 , the fluid pressure inside the inner diameter of the casing  2  must increase to overcome the fluid pressure outside the valve  1  and to overcome the bias force applied by the spring  50 . When the fluid pressure becomes large enough, the poppet plug  60  unseats from the valve seat  18  to allow fluid to circulate through the valve. The valve  1  becomes partially open. 
   As fluid is circulated through the valve  1 , the remaining open flow port(s)  31  present a relatively restricted cross-sectional flow area, a pressure differential is created across the valve  1 . As the flow rate increases, the pressure differential increases. When the pressure differential becomes great enough to overcome the bias force of the spring  50 , the valve  1  is reconfigured to the flow-open configuration (see  FIG. 2A ). In this configuration, the valve  1  is completely open and the indexing lug  11  is driven to a flow-open position  42  in the index pattern  40 . 
   The relative movement of the indexing lug  11  and the index pattern  40 , as the valve  1  moves from the closed configuration to the flow-open configuration, is described with reference to  FIGS. 1B and 2B . As the poppet plug  60  moves out of the valve seat  18 , the index piston  30  translates downwardly relative to the valve collar  10  and the indexing lug  11 . This relative movement corresponds to the indexing lug  11  moving upward in the index pattern from a closed position  41  to a flow-open position  42  (see  FIGS. 1B and 2B ). As the indexing lug  11  approaches the flow-open position  42 , the indexing lug  11  contacts and slides along an upper ramp  44 . As the indexing lug  11  slides along the upper ramp  44 , the index piston, ball cage  20  and poppet plug  60  rotate and translate relative to the valve collar  10 . As long as fluid continues to circulate at a sufficient flow rate through the remaining open flow port(s)  31  from the inside diameter of the casing  2  to the exterior of the casing  2 , the indexing lug  11  is driven to the flow-open position  42 . Simultaneously, the spring  50  collapses and the indexing J-slot  34  moves across the indexing lug  11  so as to position the indexing lug  11  in the flow-open position  42  of the index pattern  40  (see  FIGS. 1B and 2B ). 
   Fluid flow in the circulation direction through the valve  1  may be continued as long as desired to circulate the well. When flow in the circulation direction is discontinued (pumping stops), the pressure equalizes across the flow ports  31  allowing the spring  50  to push the poppet plug  60  upwards. This upward movement of the poppet plug  60 , stem  33 , and index piston  30  will index the indexing J Slot  34  to either the closed position  41  or the locked-open position  43 . The index pattern  40  has alternating closed positions  41  and locked-open positions  43 . Thus, each time flow in the circulation direction is continued and discontinued, the valve  1  will alternate between a closed configuration and a locked-open configuration. Because the index pattern  40  repeats itself indefinitely in circular fashion, there is no limit to the number of times the valve  1  may opened and closed. 
   The relative movement of the indexing lug  11  and the index pattern  40 , as the valve  1  moves from the flow-open configuration to the locked-open configuration, is described with reference to  FIGS. 2B and 3B . When fluid flow in the circulation direction is discontinued, the valve  1  is no longed held in the flow-open configuration. The spring  50  pushes the index piston  30  upwardly relative to the valve collar  10  and the indexing lug  11 . This relative movement corresponds to the indexing lug  11  moving downward in the index pattern  40  from a flow-open position  42  to a locked-open position  43  (see  FIGS. 2B and 3B ). As the indexing lug  11  approaches the locked-open position  43 , the indexing lug  11  contacts and slides along a lower ramp  45 . As the indexing lug  11  slides along the lower ramp  45 , the index piston  30 , ball cage  20  and poppet plug  60  rotate and translate relative to the valve collar  10 . The spring  50  expands to drive the indexing lug  11  to the locked-open position  43 . Simultaneously, the spring  50  expands and the indexing J-slot  34  moves across the indexing lug  11  so as to position the indexing lug  11  in the locked-open position  43  of the index pattern  40  (see  FIGS. 2B and 3B ). 
   If the valve  1  had previously been in the locked-open configuration immediately before fluid flow in the circulation direction is started and stopped, the valve will then cycle to a closed configuration. The relative movement of the indexing lug  11  and the index pattern  40 , as the valve  1  moves from the flow-open configuration to the closed configuration, is described with reference to  FIGS. 2B and 1B . When fluid flow in the circulation direction is discontinued, the valve  1  is no longed held in the flow-open configuration. The spring  50  pushes the index piston  30  upwardly relative to the valve collar  10  and the indexing lug  11 . This relative movement corresponds to the indexing lug  11  moving downward in the index pattern  40  from a flow-open position  42  to a closed position  41  (see  FIGS. 2B and 1B ). As the indexing lug  11  approaches the closed position  41 , the indexing lug  11  contacts and slides along a lower ramp  45 . As the indexing lug  11  slides along the lower ramp  45 , the index piston  30 , ball cage  20  and poppet plug  60  rotate and translate relative to the valve collar  10 . The spring  50  expands to drive the indexing lug  11  to the closed position  41 . Simultaneously, the spring  50  expands and the indexing J-slot  34  moves across the indexing lug  11  so as to position the indexing lug  11  in the closed position  41  of the index pattern  40  (see  FIGS. 2B and 1B ). 
   In certain embodiments of the invention, the valve  1  may be cycled between closed, flow-open and locked-open configurations an unlimited number of times as the index pattern  40  around the index piston  30  is a repeating pattern without end. In other embodiments of the invention, the index pattern  40  may have more than one locked-open position  43 , such that the different locked-open positions  43  have different heights in the index pattern  40 . Locked-open positions  43  of different heights hold the valve  1  open in different degrees so as to make it possible to provide restricted flow through the valve  1  in the reverse-circulation direction. 
   According to one embodiment of the invention, a casing string  2  is deployed with complete well control while making up the casing string  2  and positioning it into the desired location of the well bore. Once the casing  2  is positioned at its desired location and the top end of the casing is secured with safety valves (cementing head or swage) the back pressure valve  1  may be disabled (without casing/tubing movement) allowing flow from the well bore to enter the string and exit from the top of the string which in return will allow placement of desired fluids into the well bore and around the casing string  2 . When the fluid is at the desired location within the well bore the movement of fluid can be stopped by reactivating the back pressure valve  1 . 
   Certain embodiments of the invention include cementing float equipment back pressure valves for reverse cementing applications. These valves involve the use of an indexing mechanism to activate and deactivate the back pressure valve allowing fluid movement from desired directions. The activation process may be manipulated as often as desired during operations of running casing in the hole or the actual cementing operations. 
   The valve may be activated as follows. First, when the valve  1  is in the normal operation mode (closed position), flow from the outside is checked (see  FIG. 1A ). The well may be circulated from the inside of casing to outside without deactivation of back pressure valve  1 . Increased flow rate creates pressure drop across flow ports  31 , thus indexing the valve into the open position (see  FIG. 2A ). Releasing the flow pressure allows the lug to hold the valve  1  open (see  FIG. 3A ). Flow from either direction can be achieved at this time (circulation or reverse-circulation) (see  FIG. 3A ). The valve may be closed again by increased flow rate from the inner diameter to outside of casing/tubing  2 . ( FIG. 2A ) This allows the valve  1  to return to normal operation (no flow allowed from outside to inside). ( FIG. 1A ) This process can be repeated as often as desired. 
   The valve  1  allows complete well control while running the casing/tubing  2  in the hole with the ability to circulate the well without manually activating the indexing mechanism. When desired the valve can be locked-open to perform reverse circulation. If or when desired the valve can be activated again to shut off (check) the flow from annuals gaining complete well control again with the ability to release any pressure trapped on the side of the casing/tubing string. The valve can be activated and deactivated as often as desired. 
   Referring to  FIGS. 5A ,  6 A, and  7 A, cross-sectional side views of an alternative valve  1  are illustrated. The valve  1  has several major components including: a valve collar  10 , a detent flapper  27 , an index piston  30 , an index pattern  40 , a spring  50 , and a flapper plug  63 . In  FIG. 5A , the valve  1  is shown in a closed position. In  FIG. 6A , the valve  1  is shown in a flow-open position. In  FIG. 7A , the valve  1  is shown in a locked-open position.  FIGS. 5B ,  6 B, and  7 B illustrate schematic side views of the index pattern  40 . In each of these figures, an indexing lug  11  is shown in a different position as described more fully below. 
   Referring to  FIGS. 5A ,  6 A, and  7 A, each of the major components of the valve  1  are described. Similar to the previously described embodiment, the valve collar  10  is a cylindrical structure comprising an indexing section  12 , a mounting section  13 , and a seat section  14 . As before, the indexing section  12  has a shoulder  15 . The mounting section  13  has a stem mount  16  that extends from the inside diameter side wall of the mounting section  13 . The stem mount  16  is an arm having an annular eyelet at its distal end for receiving a stem  33  of the index piston  30 . The seat section  14  has a beveled valve seat  18  for receiving the flapper plug  63 . 
   As shown in  FIGS. 5A ,  6 A and  7 A, the index piston  30  has a plurality of flow ports  31  that extend through the index piston  30  parallel to the longitudinal central axis of the index piston  30 . At least one detent flapper  27  is positioned at the opening of at least one of the flow ports  31 . An annular seal  32  is positioned in a recessed near the top of the outside circumference of the index piston  30  to form a seal between the index piston  30  and the valve collar  10 . The annular seal  32  restricts fluid flow between the two structures even as the index piston  30  translates longitudinally within the valve collar  10 . 
   In this embodiment of the valve  1 , the indexing section  12  of the valve collar also has an indexing J-Slot  34  in its interior wall. The indexing J-Slot  34  has an index pattern  40 . The stem  33  extends from the bottom of the index piston  30  through the stem mount  16 . As shown in  FIGS. 5A ,  6 A, and  7 A, the spring  50  is positioned concentrically around the stem  33  of the index piston  30 . At its upper end, the spring engages the lower face of the index piston  30  and at its lower end, the spring  50  engages a spring shoulder  17  at the upper edge of the stem mount  16 . In  FIG. 5A , the spring  50  is illustrated in a relaxed or expanded position, while in  FIG. 6A , the spring  50  is completely compressed. In  FIG. 7A , the spring  50  is only partially compressed. The flapper plug  63  is connected to a lower most end of the seat section  14  of the valve collar  10  for pivotal movement into and out of engagement with the valve seat  18  of the seat section  14 . The flapper valve seats in the valve seat  18  and is biased to a closed position by a spring as is known in the art. The flapper plug  63  has a conical seal surface  61  for engagement with the valve seat  18 . The flapper plug  63  is opened by the stem  33  when the stem extends through to the seat section  14  to push the flapper plug  63  from its biased position in the valve seat  18 . When the index piston  30  and stem  33  are driven downwardly relative to the flapper valve, the stem extends through the valve seat  18  to push and hold the flapper valve open. In further embodiments of the invention, the poppet plug  60  or flapper plug  63  are replaced with any valve mechanism known to persons of skill. 
   Referring to  FIGS. 5B ,  6 B, and  7 B, the index pattern  40  defines several lug positions that are used to configure the valve in closed, flow-open, and locked-open positions. Closed positions  41  are located in the upper-most portions of the index pattern  40 . When the indexing lug  11  is located in one of the closed positions  41 , the valve  1  is configured in a closed configuration. Flow-open positions  42  are found in the lower-most portions of the index pattern  40 . As shown in  FIG. 6B , when the indexing lug  11  is positioned in one of the flow-open positions  42 , the valve  1  is configured in a flow-open configuration. Locked-open positions  43  are found in a medium upper position of the index pattern  40 . When the indexing lug  11  is in a locked-open position  43 , the valve  1  is in a locked-open configuration.  FIG. 7B  illustrates the indexing lug  11  in a locked-open position  43  which corresponds to a valve  1  configuration that is locked-open as illustrated in  FIG. 7A .  FIG. 5B  illustrates the indexing lug  11  in a closed position  41 , which corresponds to a closed valve  1  configuration as illustrated in  FIG. 5A .  FIG. 6B  illustrates the indexing lug  11  in a flow-open position  42  which corresponds to a valve flow-open configuration as illustrated in  FIG. 6A . 
   In the embodiments of the invention illustrated in  FIGS. 5A ,  6 A, and  7 A, one or more flapper valves  27  are seated in the tops of the flow ports  31 . To allow restricted flow through the flow ports  31  in the circulation direction, at least one of the flow ports  31  is not equipped with a flapper valve. In still further embodiments of the invention, the ball cage  20  or flapper valves  27  are replaced with any valving system known to persons of skill, wherein the valving system provides restricted fluid flow through the flow ports in the circulation direction, and unrestricted fluid flow through the flow ports  31  in the reverse-circulation direction. 
   The valve described with reference to  FIGS. 5 ,  6  and  7  is operated in a similar manner as that described for  FIGS. 1 ,  2  and  3 . 
   As described herein the detent in the indexing piston takes on many forms. In  FIGS. 1A ,  2 A, and  3 A, the detent is a fewer number of balls  26  than flow ports  31 . In alternative embodiments of the invention, the ball cage  20  retains the same number of balls  26  as flow ports  31 , but each of the balls has grooves in their exterior surfaces so that when the balls  26  lodge or seat themselves in the openings of the flow ports  31 , a relatively smaller amount of fluid passes through the grooves in the balls  26  and into the flow ports  31 . In  FIGS. 5A ,  6 A, and  7 A, the detent is a fewer number of detent flappers  27  than flow ports  31  in the indexing piston  30 . In an alternative embodiment of the invention, the detent has the same number of detent flappers  27  as flow ports  31 , but the detent flapper(s)  27  only partially closes the flow port(s)  31  when the detent flapper(s)  27  moves to a closed position. For example, where the flow port(s)  31  has a circular cross-section, the detent flapper(s)  27  has a half-moon cross-section to only partially close the flow port(s)  31 . 
   Therefore, the present invention is well-adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the invention has been depicted, described, and is defined by reference to exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the invention are exemplary only, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.

Summary:
A valve for a well pipe, the valve having the following parts: a valve collar connectable to the well pipe; an index piston coaxially positioned within the valve collar for longitudinal translation within the valve collar between closed, flow-open, and locked-open configurations; a detent in the index piston, wherein the detent restricts fluid flow in a circulation direction through a flow path through the index piston; a spring that biases the index piston toward the closed and locked-open configurations; and a plug of the valve collar that mechanically communicates with the index piston to be in corresponding closed, flow-open, and locked-open configurations.