Patent Publication Number: US-6662886-B2

Title: Mudsaver valve with dual snap action

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application, pursuant to 35 U.S.C. 111(b), claims the benefit of the earlier filing date of provisional application Serial No. 60/194,204 filed Apr. 3, 2001, and entitled “Mudsaver Valve with Dual Snap Action”. The present application is related to patent applications, Ser. No. 09/824,374, entitled “Dual Snap Action for Valves” filed on Apr. 1, 2001. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention relates in general to a mudsaver valve and particularly to a mudsaver having a rotating ball valve with snap-action for both opening and closing the valve. 
     BACKGROUND OF THE INVENTION 
     Mudsaver valves, mounted on the bottom of the drilling rig kelly or top drive, serve to automatically retain drilling mud within the kelly or top drive and its supply hoses and tubing whenever the kelly or top drive is disconnected from the drillstring. The kelly or top drive is routinely disconnected to add or remove pipe from the drillstring. 
     Retention of drilling mud is desirable in order to avoid the loss of expensive mud, as well as the creation of slick and hazardous working conditions and the resultant loss of time due to rig floor cleanup. The mudsaver functions as a type of relief valve. Whenever the mudsaver is closed, it must support the hydrostatic head of the noncirculating fluid trapped above the mudsaver when the drillstring is separated from the mudsaver. However, when the mudsaver is reconnected in the drillstring, the valve must readily open when the mudpumps are started. 
     Several previous designs of mudsaver have been created and used, as is discussed below. However, most such designs have had significant drawbacks and are not widely used in the oilfield. Two very significant drawbacks to all of the designs reviewed below is their susceptibility to wear from abrasive fluids and their complex assembly. Partially open valves, particularly ball valves, experience significantly worsened fluid-induced wear rates. This is especially true when used with drilling mud, which is highly loaded with abrasive particles. 
     In fact, current mudsaver designs are so unsatisfactory that typical operations will retain the mud within the kelly or top drive by manual closure of a valve at the lower end of the kelly, called the kellycock. This situation is highly undesirable because the lower kellycock is a critical drilling safety component intended for occasional or emergency use. In addition, an actuator and its controls must be provided and maintained for the operator to close and open the lower kellycock. Thus, the provision of a suitable autonomous mudsaver would preserve the lower kellycock for its intended safety purposes. 
     The mudsaver described in U.S. Pat. No. 3,965,980 is one attempt to solve the problems set forth above. The valve described is basically a poppet relief valve. The poppet is spring-biased closed and is opened when drilling mud pressure acting on one side of the piston on the upper end of the sealed spring chamber exceeds the combined resistance of the biasing spring and the counter pressure within the sealed spring chamber. The poppet valve has a check valve mounted concentrically within its head to permit communication of mud pressure from below through the closed poppet for measurement above the mudsaver. Flaws in the design of the valve are its length, multiple-part outer body, difficult assembly and disassembly, and that its sealing plug and seat are subject to high erosion and attendant leakage due to mud circulation impinging both components. Drilco Inc. (a division of Smith International, Inc.) of Houston, Tex. markets the patented valve and SMF International of France markets a similar valve. 
     U.S. Pat. No. 3,743,015 describes another approach. This mudsaver has a rotatable, translatable ball sealing plug with a through hole. The valve is actuated by differential pressure across an annular piston. On the upper side of the piston, pump pressure acts, while on the other side, a biasing chamber provides a reference pressure (typically atmospheric). The ball is further urged toward its closed position by biasing springs. A means of locking the ball open by means of an externally operated wrench permits wireline operations through the valve. Drawbacks of the valve are the potential leakage paths through the side of its body, high operating forces on the valve with rapid increases in pump pressure or water-hammer, and an involved assembly and disassembly of the large number of parts positioned in crossbores. 
     A further approach is found in U.S. Pat. No. 4,262,693 which discloses a mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. This valve appears to be substantially similar to the mudsaver marketed by Arrowhead Continental, San Bernardino, Calif. An actuation piston is exposed to pump pressure on one side and a second bias pressure in a sealed spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston. The actuation piston is coupled to a rotator sleeve by means of one or more piston-mounted camming pins acting in one or more helical grooves in the rotator. Accordingly, axial movement of the piston imparts rotary motion to the rotator, which in turn rotates the ball by means of bevel gears. This mudsaver has relatively high frictional loads and multiple interacting parts. 
     Yet another approach is seen in the mudsaver valves offered by American International Tool Company, Inc. and A-Z International Tool Company. Their mudsavers retain the mud above the valve by comating annular flat sealing faces transverse to the mudsaver axis dividing an upper annular fluid path from a lower central fluid path. The flat faces are spring-biased together to remain in a closed position under non-flowing mud when the drillstring is separated. The lower flat sealing face constitutes a piston head which is exposed to the pressure above the sealing face on its upper side and the pressure downstream of the annular orifice between the sealing faces on the other side. Pump pressure is sufficient to overcome the spring bias and then the pressure drop across the annular orifice will maintain the valve open. This mudsaver has a coaxial poppet check valve to permit communication of pressure below the valve past the primary valve seal. The primary disadvantage of this valve is the tendency of the sealing faces to wear under direct flow impingement. 
     U.S. Pat. No. 5,509,442 discloses another mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. An actuation piston is exposed to pump pressure on one side and atmospheric bias pressure in a spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston, which in turn can cause valve shifting if permitted by an interlock system controlled by the presence of the abutting end of the drillstring below the valve. The tool is relatively long and has a jointed body which makes assembly and disassembly difficult. 
     U.S. Pat. No. 4,248,264 discloses a flapper valve-based mudsaver. The flapper is normally biased closed both by gravity and by a torsion spring. The flapper is mounted on an upwardly spring-biased piston ring concentric with the flow passage. Atmospheric pressure is retained within the spring chamber below the piston. When pump pressure forces the annular piston carrying the flapper valve and its seat downwardly, the flapper encounters a fixed annular tube concentric within the valve seat and passing through the annular piston. This unseats the flapper, permitting flow. Pressure from below will either unseat the flapper or, if it is already open, not permit the piston to travel to a position where the flapper will seat. If there is no pressure overcoming the spring bias, the piston moves up against the pressure of the retained mud and closes. This valve gradually opens and closes and is susceptible to wear. Furthermore, pressure surges produce high loadings on the flapper hinges. 
     U.S. Pat. No. 4,889,837 discloses a poppet-type mudsaver in which the poppet is restrained against downward movement by an integral spider which abuts a stop shoulder. The poppet seat is a spring-loaded annular piston which translates away from the poppet when the pump pressure exceeds the atmospheric pressure acting on the piston area and the spring preload. The poppet is free to reciprocate upwardly if there is pressure from below the closed valve. This valve is not full opening, so it is subject to flow abrasion. 
     As pointed out above, a mudsaver is subject to tremendous wear from the abrasive particles in the mud. Currently, all of the mudsaver valves open and close in the traditional manner, where the valve is partially open during the opening and closing of the valve leading to rapid wear of the valve. 
     Several downhole safety valves have attempted to limit wear by incorporating a valve that opens or closes in one rapid movement (a “snap action” valve). For example, U.S. Pat. No. 3,749,119 discloses a valve reopening operator sleeve retained in either an upper position or a lower position by the engagement of annular latch grooves with an annular garter spring. Although closure of the main valve is not impacted by the sleeve, the reopening of the valve is. Shifting of an independent inner sleeve mounted within the valve reopening sleeve downwardly to a first position permits closing an activator valve at the upper end of the reopening sleeve. The closure of the activator valve permits the reopening sleeve to be pumped downwardly from its upper position to its lower position to force open the main valve. The reopening sleeve is disengaged from its lower position by independent upward movement of the main control sleeve. The main valve and the activator valve are both flapper valves and are both spring-biased closed. The garter spring does not cause snap action in this application, but rather serves as a releasable retainer on a secondary operator. 
     U.S. Pat. No. 3,070,119 (“Raulins”), U.S. Pat. No. 3,126,908 (“Dickens”), and U.S. Pat. No. 3,889,751 (“Peters”) all disclose valves using latches for snap action. Raulins has a latch based on spring-loaded balls which act directly on the sealing poppet of the valve to provide snap action closure only. The sealing poppet of the valve is loaded by pressure drop across an integral internal flow beam. This load is supported by an annular array of balls which are spring-biased inwardly to engage a shoulder on the sealing poppet. The biasing load on the balls is provided by a very large axial force from an axially-acting coil spring bearing on a conically tapered ball support ring. The snap action is only in one direction and is actuated by forces applied to the sealing member, rather than an independent actuation mechanism. 
     The Peters apparatus is similar to that of Raulins, but the latch arrangements differ. Peters permits the sealing plug to move a limited amount prior to closing and uses axially translating balls that shift from one groove to another to release. Raulins permits substantially no sealing plug movement prior to latch release and does not use axially translating balls. The Dickens apparatus relies on an actuator with either a collet latch or ball latch released by movement to a disengagement groove under flow forces. A lost motion mechanism is required to link the actuator to the valve in order to accommodate the movement without affecting valve position. A very high axial bias force on the latch mechanism is required. The valve closing and opening require high flows to occur, so that reliable snap action is not a certainty with this device. 
     U.S. Pat. No. 4,160,484 discloses a flapper-type valve in which the flapper is biased to be normally closed, but is held open by a tube latched by a collet mechanism which releases at a predetermined load. The valve functions independently of the tube when the tube is not in position to paralyze the valve. The collet serves only to retain the tube in position and the latch does not provide for snap action. 
     All of the described devices either have a sealing plug directly loaded and held against closure until a predetermined release load is obtained or they rely upon a lost motion mechanism to effect closure. Not one of these devices has a reliable bi-directional snap action. 
     Thus, a need exists for a mudsaver valve that is less susceptible to abrasive wear to provide long life and reliability. In addition, a need exists for a mudsaver valve that can be adjusted to accomodate variations in mud weight and is short in length and easily assembled and disassembled. 
     SUMMARY OF THE INVENTION 
     The invention contemplates a simple device for solving the problems and disadvantages of the prior approaches discussed above. The mudsaver valve of the present invention provides a mechanism for a quick, automatically operating, snap acting opening and closing mechanism which is resistant to wear. 
     One aspect of the invention provides a reliable set of means for causing the combination of a valve operator and a valving member to exhibit bi-directional snap-acting behavior in the opening and closing actions of the combination. 
     Another aspect of the invention provides a reliable means of causing bi-directional snap-acting behavior in which the effecting bistable mechanism acts directly on the valving member. 
     A further aspect of the invention provides a means for inducing bi-directional snap-acting behavior in a valve operator and valve member combination in which the valving member is a rotary ball valve. 
     An additional aspect of the invention provides an automatic, full-opening, ball-type mudsaver valve with snap-acting opening action, as well as snap-acting closing action. 
     Yet another aspect of the invention provides a mudsaver valve which readily communicates drillstring pressure below the valve to above the valve without operator intervention. 
     A further aspect of the invention provides a mudsaver valve for which the sealing ball plug is automatically unseated in the event of very rapid mud pump pressure buildup or waterhammer, so that operating friction is reduced. 
     In addition, this invention provides a mudsaver valve which can be readily adjusted for changing mud densities. 
     Yet another aspect of the invention provides a mudsaver valve which is simple to assemble and disassemble under field conditions. 
     A further aspect of the invention provides a mudsaver valve, adapted for connecting a kelly or a top drive and a string of drill pipe, having a tubular valve body with a through bore flow passage, the body configured to connect to a drill string at its lower outlet end and to connect a kelly or a top drive at its upper inlet end. The mudsaver valve has a nontranslating rotatable ball with a through hole, where the ball is rotatable between a first and a second end position about coaxial central pivot pins journaled by a ball cage, such that when the ball is in the first position the ball through hole is aligned with the bore flow passage and when the ball is in the second position the ball through hole is misaligned with the bore flow passage to prevent flow through the valve. The valve has a valve seat that seals against the lower side of the ball and a dirt excluder that seals against the upper side of the ball. The valve has a reciprocable camming means for rotating the ball between the first and second end positions, a detent means that interacts with the ball to retain the ball in either end position until sufficient force is applied to the ball to overcome the interaction of the detent means with the ball, and an actuating means 
     for displacing the camming means to rotate the ball, where the actuating means is responsive to valve inlet pressure on a first face and other forces on a second face that is obverse to said first face. Thus, when the actuating means applies sufficient force to the camming means to overcome the interaction of the detent means with the ball, the ball will rotate from one end position to the other end position. 
     The foregoing has outlined rather broadly several aspects of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or redesigning the structures for carrying out the same purposes as the invention. It should be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are believed to be characteristic of the invention, both as to its construction and methods of operation, together with the objects and advantages thereof, will be better understood from the following description taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1A shows a longitudinal section of the first embodiment of the mudsaver valve in its closed position; 
     FIG. 1B is a blow-up of a longitudinal half sectional view of the upper end of the valve cartridge of FIG. 1A showing the retention means for holding the valve internals in the body; 
     FIG. 1C is a blow-up of a longitudinal half sectional view of the lower end of the valve cartridge of FIG. 1A showing the seat assembly in its normal position bearing against the ball; 
     FIG. 2 shows a side view of the valve cartridge in its closed position; 
     FIG. 3 is a transverse sectional view taken along section line  3 — 3  of FIG. 2; 
     FIG. 4A shows a longitudinal sectional view of the seat biasing piston; 
     FIG. 4B shows a longitudinal sectional view of the valve seat and the seat travel limiter; 
     FIG. 5 shows a side view of the valve cartridge in its open position; 
     FIG. 6 (broken apart for clarity into FIG.  6 A and FIG. 6B) is a longitudinal half section along section line  6 — 6  of FIG. 5; 
     FIG. 7 is an external view of the valve cartridge interior elements without some of the outer elements shown, corresponding to FIG. 5, showing the configuration of the flat face of the ball and the camming actuator; 
     FIG. 8 is a partially exploded view of the valve cartridge; 
     FIG. 9 shows a cross-sectional view of the valve cartridge taken along section line  9 — 9  of FIG. 2; 
     FIG. 10 shows a cross-sectional view of the valve cartridge taken along section line  10 — 10  of FIG. 2; 
     FIG. 11 is a transverse cross-section of the valve cartridge taken along section  11 — 11  of FIG. 5; 
     FIG. 12 is a transverse cross-section of the valve cartridge taken along section  12 — 12  of FIG. 5; 
     FIG. 13 (broken apart for clarity into FIG.  13 A and FIG. 13B) is a longitudinal section of the second embodiment of the mudsaver valve in its locked-open position; 
     FIG. 14 is an enlarged detail of the seat portion of the longitudinal section of FIG. 1, showing the seat sealing against the closed ball; 
     FIG. 15 corresponds to FIG. 12, but with elevated pressure from below the ball causing the seat to lift off the ball surface; 
     FIG. 16 corresponds to FIG. 12, but with the seat biasing piston retracted so that the seat does not seal against the ball, as occurs with a pressure surge from above the ball; 
     FIG. 17 is a diagram showing the interrelationship of the forces on the piston as a function of position during the opening of the valve; and 
     FIG. 18 is a diagram showing the interrelationship of the forces on the piston as a function of position during the closing of the valve. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a mudsaver valve with an adjustable bi-directional snap action for opening and closing the valve. The mudsaver valve of the present invention provides a mechanism for communicating drillstring pressure below the valve to above the valve without operator intervention and means for automatically unseating the sealing ball plug in the event of very rapid mud pump pressure buildup in order to reduce opening friction. The mudsaver valve of the present invention is simple to assemble and disassemble under field conditions due to its cartridge construction and has an improved reliability and life span. 
     Referring now to the drawings, it is pointed out that like reference characters designate like or similar parts throughout the drawings. The Figures, or drawings, are not intended to be to scale. For example, purely for the sake of greater clarity in the drawings, wall thickness and spacing are not dimensioned as they actually exist in the assembled embodiment. For clarity, up is used to refer to the pump inlet side of the valve and is shown on the right hand side of all side views and longitudinal sections. 
     FIG. 1A shows a longitudinal section of one embodiment of a mudsaver valve  10 . The parts of the mudsaver valve  10  are fabricated of a suitable material such as alloy steel or stainless steel. The body  12  of the valve  10  is configured to be attached to a oilfield drillstring immediately below the kelly or top drive of the drilling rig. 
     Body  12  is a generally cylindrical pressure-containing tube with male threads  13  and sealing face  14  on its lower end for engaging the upper end of the drillstring and female threads  15  and sealing face  16  on its upper end for engaging the lower end of the kelly or top drive of the rig. A lower concentric bore  17  conveys fluid flowing out of the valve, while a central bore  18  houses a preassembled valve cartridge  20  shown in FIG.  2 . 
     Internal recess groove section  19  located between central bore  18  and upper end female thread  15  provides a shoulder for engaging the upper end of cartridge  20 . The upper end of cartridge  20  is shown in more detail in FIG.  11 B. The upper end of cartridge  20  has a segmented locking ring  24 , a backup ring  25 , and an entrapping snap ring  26 . FIG. 3 shows a cross section of the upper end of the cartridge. The segments of locking ring  24  have an outer diameter larger than the central bore  18 , but sized to engage the groove  19 . The snap ring  26  snaps into the groove  27  provided on the upper end of the inner bore of locking rings  24 . The segmented locking rings  24  are installed and removed through the throat of female thread  15 . The outer diameter of backup ring  25  entraps the segments of locking ring  24  by abutting their inner bore faces to engage groove  19 . Thus, the backup ring  25  prevents the inward collapse of segmented locking rings  24 . Shoulder  22  or locking ring  25  engage groove  18  of body  12  to entrap the valve cartridge  20  within the body  12 . 
     The lower end of cartridge  20  abuts shoulder  33  at the lower end of the mudsaver valve  10 . FIG. 1C more clearly shows the details of the valve seating arrangement in the description immediately following. Seat holder  37  has a transverse lower face which rests against body shoulder  33 , a first cylindrical counterbore with groove  38  for a conically-dished snap-ring  39  positioned therein, an adjoining and somewhat smaller diameter second cylindrical counterbore with a conical abutment transition shoulder  40  positioned between the first and second counterbores. 
     The outer diameter of seat holder  37  closely fits within the central bore  18  of valve body  12  and has a large bevel where it abuts the abutment shoulder  33 . The outer diameter of seat holder  37  is reduced on its upper end and has an annular ridge  43  positioned in the reduced diameter section. The lower transverse face of annular ridge  43  provides a shoulder for engaging other segments of the valve. A male O-ring groove containing O-ring  47  is positioned on the outer diameter of the first cylindrical couterbore. Other valve components found at the lower end of cartridge  20  are a seat biasing piston  50 , a seat travel limiter  65  and a seat  75  biased by spring  80 . These components are shown in more detail in FIGS. 4A and 4B. 
     FIGS. 1C,  4 A and  14  show the annular seat biasing piston  50  and its interaction with seat holder  37 . The piston  50  has a stepped cylindrical outer wall with a threaded small diameter cylindrical section, an enlarged diameter cylindrical section, and transverse transition shoulder  52  therebetween. Conical chamber  54  between transition shoulder  52  and the enlarged outer cylindrical section is adapted to abut against comating transition shoulder  40  of seat holder  37 . Seat biasing piston  50  has a male O-ring groove, containing O-ring  56 , on its enlarged outer diameter section to sealingly engage the counterbore of seat holder  37 . The smaller cylindrical section has a male thread  57  on its outer surface. 
     The lower transverse face of seat biasing piston  50  provides a reaction shoulder for biasing forces applied by conically-dished snap ring  39  as seen in FIG. 1C, which functions much like a Belleville spring. The snap ring  39  is mounted in snap-ring groove  38  of seat holder  37  and provides an upward biasing force on seat biasing piston  50 . Seat biasing piston  50  is reciprocable within first cylindrical counterbore of seat holder  37 . The inner bore of seat biasing piston  50  has female O-ring groove, containing O-ring  60 , located intermediately along its length to sealingly engage the seat  75 . Upper transverse end shoulder  55  of piston  50  connects the interior bore cylindrical face of seat biasing piston  50  to the seat travel limiter  65 . Upward travel of seat biasing piston  50  under the biasing force provided by biasing snap ring  39  is limited by conical shoulder  40  of seat holder  37 . Area A 1 , the effective differential piston area of seat biasing piston  50 , is that transverse cross-sectional area contained between the enlarged diameter cylindrical section and the inner bore. 
     Seat travel limiter  65 , shown in FIG. 4B, has a thin annular wall with a female thread  66  on its inner, lower end for engagement with the male threads  57  on the smaller outer cylindrical face of seat biasing piston  50 . At the upper end of travel limiter  65  is transverse lip  67  projecting inwardly. Multiple holes  68  are positioned at approximately midlength of travel limiter  65  to provide fluid communication between its inner and outer cylindrical faces. An annular gap  69 , as seen in FIG. 1C, is provided between the outer diameter of travel limiter  65  and the second counterbore of seat holder  37  to permit fluid pressure communication to holes  68 . 
     Seat  75  has annular stepped cylindrical construction with a straight bore, smaller outer diameter cylindrical face  76 , and an enlarged diameter cylindrical upper head. The bore provides a portion of the main flow passage through valve  10 . The bore and smaller outer diameter cylindrical face  76  define a thin-walled lower end, while the upper transverse face  77  and stepped conical relief of the upper head form an annular line-contact sealing ridge  78 . Lower transverse face  79  of the upper head provides a reaction face for application of spring bias to seat  75 . A seat annular differential piston area A 2  is defined between the diameter of smaller cylindrical surface  76  and the diameter of sealing ridge  78 . Seat bias coil compression spring  80  reacts against lower transverse face  79  of seat upper head  75  and transverse upper shoulder  55  of seat biasing piston  50 . The force exerted and spring rate of spring  80  are less than those of snap ring  39 . 
     Turning now to FIGS. 6 and 8, ball  85  has a generally spherical outer surface  86 , a cylindrical through flow passage  87 , and mirror-image opposed flat faces  88  equispaced from the axis of the through flow passage  87 . The valve assembly operates by moving flow passage  87  into or out of alignment with the central flow passage of valve  10 . In FIGS. 1 and 2 the flow passage  87  is out of alignment with the central flow passage and the valve is closed. In FIGS. 5 and 6 the flow passage  87  is in alignment with the central flow passage and the valve is open. 
     Central to each of the flat faces  88  are concentric coaxial projecting cylindrical pins  90 , with axes perpendicular to the flat faces  88  and the axis of the flow passage  87 . Ball  85  is configured to rotate in a trunnion mount about its pins  90 . Mirror-image camming grooves  94 , as shown in FIG. 7, are provided in faces  88 . Camming grooves  94  are both parallel to faces  88  and inclined at an angle of 45° to the axis of flow passage  87 . Multiple detents  96  are located 90° apart in a circular array around ball pin  90  on face  88  of ball  85 . Two detents are coplanar with the axis of the ball through hole  87  and the rotational axis of ball  85  defined by pins  90 ; the other two detents are in a plane perpendicular to that axis and through the rotation axis of ball  85 . 
     Mirror-image split ball cage halves  100  and  101  provide support for the rotatable ball  85  as shown in FIG.  8 . Because of general anti-symmetry between ball cage halves  100  and  101 , only upper half ball cage  100  will be described. The upper half ball cage  100  has a generally half-cylindrical outer surface  102  which closely fits inside central bore  18  of the valve body  12 . The interior surface of the lower end of cage half  100 , as seen in FIG. 6B, is an annular half-ring with lower transverse face  104  and interior annular groove  105  having transverse lower shoulder  106 . 
     Groove  105  mates with annular ridge  43  of seat holder  37  so that the seat holder  37  and upper ball cage  100  are keyed together when entrapped within central bore  18  of valve body  10 . FIG. 9 shows how the diametrically-cut ends  108  of the lower end of cage half  100  comates on a diametral plane with opposed similar ends on lower ball cage  101  in order to establish close control of the interrelationship of the mirror-image features of the two ball cage halves  100  and  101 . 
     Referring to FIGS. 6 and 8, the top end on the inner surface of upper ball cage half  100  has an annular half-ring with an upper traverse face  113  and an interior annular groove  114  in its largest inner diameter upper cylindrical face  115 . Diametrically-cut ends  112  of annular upper face  113  comate and abut similar ring ends of the lower half ball cage  101  as shown in FIG.  10 . Diametrically-cut ends  108  and  112  are coplanar. 
     Intermediate diameter cylindrical bore  116  of ball cage half  100  defines the outer side of a half-cylindrical annular cavity  117 . The lower side of annular cavity  117  is defined by an annular ridge  120  facing inward. This annular ridge  120  has a lower transverse face  121  that provides a reaction shoulder for at least one spring  144 . Spring  144 , reacting against faces  141  of dirt excluder  140  and traverse face  121  of upper half ball cage  100  and the corresponding face of lower fall cage  101 , may be a set of Bellville washers or other known spring type. 
     Intermediate to the length of upper ball cage  100 , parallel to the diametral plane of ends  108  and  112 , and configured to fit closely to flat  88  of ball  85  is planar surface  124 . Surface  124  extends downwardly from transverse face  121  to the bottom end of cage half  100 , providing clearance and support for the ball  85  and clearance for the dirt excluder  140 . The portion of upper half ball cage  100  between outer cylindrical surface  102  and planar surface  124  also provides structural support for the valve elements engaged with grooves  105  and  114 . 
     A central through hole  126  is positioned perpendicular to planar surface  124  with its axis coaxial with the longitudinal axis of the valve  10  journal pins  90  of ball  85  so that the ball is rotatable about its axis perpendicular to the longitudinal axis of the valve  10 . 
     Returning to FIGS. 2 and 5, elongated slot  130  is symmetrical about the valve midplane through ball cage ends  108  and  112  and centered about a plane which is normal to the diametral plane of ends  108  and  112  and parallel to the longitudinal axis of the valve  10 , but displaced laterally from the rotational axis provided by central through hole  126 . The sides of slot  130  are perpendicular to the diametral plane of ends  108  and  112  and the projection of the slot on said diametral plane is rectangular. 
     Drilled and tapped holes  132  and  133  are located in the plane defined by the axis of central through hole  126  and the longitudinal axis of valve  10 . One or more commercially available threaded-body spring plungers or ball plungers  134 , such as those shown in the Carr Lane Manufacturing Co. 1998 Catalog Component Parts of Jigs and Fixtures as items CL-70-SPS-1 or CL-70-SBP-3, are mounted in tapped holes  132  and  133  such as to engage ball detents  96  when the ball  85  is rotated into a suitable position. As shown in FIG. 6A, two spring plungers  134  on the upper half ball cage  100  are used in this embodiment. Although not shown in FIG. 6A, lower half ball cage  101  is not provided with plungers, but may optionally be so provided. 
     Dirt excluder  140 , as shown in FIG. 6A, is reciprocably housed within the top end of the interior of the upper and lower half ball cages  100  and  101 . Dirt excluder  140  has a straight through bore which serves as a portion of the main flow passage through the valve  10 , an elongated thin-walled cylindrical upper body, and an upset head with transverse upper face  141  and spherical lower face  142  which mates with spherical face  86  of ball  85 . Spring  144  is positioned between upper transverse face  141  of dirt excluder  140  and lower transverse face  121  of upper half ball cage  100  and the corresponding face of lower half ball cage  101 . Spring  144  biases spherical lower face  142  of dirt excluder  140  against surface  86  of ball  85  to effect a seal at their interface. Different types of biasing spring may be used such as a helical spring or, as shown, a set of Belleville spring washers. 
     Camming arm unit consists of a tubular body  150  with external threads  151  at its top end and mirror-image projecting camming arms  152  extending downwardly parallel to a diametral plane through the longitudinal axis, but offset from said axis. This can best be seen in FIGS. 7,  11  and  12 . Camming arm unit is reciprocable within the half ball cages  100  and  101 . 
     The interior surface of the top end of the tubular body  150  of the camming arm unit serves as a portion of the primary fluid passageway through the valve  10 . The bottom portion of the tubular body bore  154  is enlarged in order to clear the upper end of dirt excluder  140  and provide a narrow annular flow passage between bore  154  and the exterior of dirt excluder  140 . 
     The exterior of the tubular body  150  of the camming arm unit has two different outer diameters below the threaded top end. The second, larger outer diameter section has outwardly extending projections to which the offset parallel camming arms  152  are mounted as shown in FIGS. 8 and 12. The planar first inner faces of the camming arms are equispaced from the plane of symmetry of the camming arms  152  and clear the flat face  88  of ball  85 . The external faces of the camming arms  152  obverse to the first inner faces are cylindrical. The planar second inner faces and their obverse outer sides are normal to the first inner faces adjacent the flats  88  of ball  85 . 
     Near the bottom end of the camming arms  152  are coaxial pin-mounting holes which are located in the offset plane of the camming arms. Stepped cylindrical camming pins  157  have their smaller diameter press-fitted into the pin-mounting holes. The larger ends of the camming pins  157  are positioned on the inner side of camming arms  152  and engage the mirror-image camming grooves  94  of ball  85 . The camming arms  152  can reciprocate in the slot  130  of upper half ball cage  100  and the mirror-image lower ball cage  101  whenever the camming arm unit, composed of the tubular body  150  and camming arms  152 , is reciprocated within the bore of the half ball cages. Because the pins  90  of ball  85  are journaled in central through hole  126  of upper half ball cage  100  and the corresponding hole in lower half ball cage  101 , off-center forces imparted from camming pins  157  to the camming grooves  94  of the ball  85  will tend to cause ball  85  to rotate about its journaled axis. Downward forces applied to the camming arm unit will tend to open the ball  85 , while upward forces will tend to close the ball. 
     Annular piston  162  is coaxially attached by interior female screw threads  163  to the male threads  151  of the top end of camming tubular body  150 . An internal shoulder of piston  162  abuts the top end of camming arm unit  150  to serve as a travel stop during thread make-up. A female O-ring groove is located below threads  163  and contains O-ring  165 . O-ring  165  seals between the interior bore of piston  162  and the unthreaded upper portion of camming arm unit  150 . The moving seal surface for the piston  162  is its outside cylindrical surface. The upper transverse face of piston  162  is exposed to the mud pressure from hydrostatic pressure or combined pump and hydrostatic pressure. A through hole  168  is drilled parallel to the flow axis for valve  10  through the body of piston  162 , emerging on lower transverse face  169  of piston  162 . Another larger tapped hole  170 , intersecting through hole  168 , is bored partially through the piston body on an axis parallel to that of hole  168 , but slightly offset from hole  168 . 
     A Schrader valve  171  of the type commonly used as a fill valve for air-conditioning systems or tires is screwed into the internal threads provided in the bore of hole  170 . Schrader valve  171  seals against the walls of hole  170 , thus controlling admission of fluid or gas to and from the region below piston  162 . An upper hole  172  is provided that is larger, yet shallower, than hole  170 . Upper hole  172  is parallel to and intersects hole  170 . Hole  172  is provided with female threads which comate with the male threads of seal screw  173  which is installed in hole  172  in order to selectably fully isolate Schrader valve  171 . 
     Upper transverse face  174  of piston  162  is thus connected to lower transverse face  169  by the flow path constituted by intersecting holes  168 ,  170 , and  172 . Flow is controlled through this flow path by Schrader valve  171 , while selectively removable seal screw  173  prevents flow access to Schrader valve  171  when installed. Piston bias coil compression spring  176 , located adjacent the upper cylindrical outer surface of camming tubular body  150 , bears against lower transverse face  169  of piston  162  in order to urge the piston upwardly. 
     Reference chamber  180  is located exterior to and coaxial with camming tubular body  150  and piston  162 . On the lower end, reference chamber  180  has two reduced diameter external cylindrical sections which have annular transverse ridge  183  positioned therebetween. Annular ridge  183  is configured to engage annular internal groove  114  of upper half ball cage  100  and the corresponding groove of mirror-image lower half ball cage  101 . 
     Larger external cylindrical surface  184  closely fits to the central bore  18  of the body  12  of valve  10 . Cylindrical surface  184  has a male O-ring groove located near its upper end, with O-ring  186  mounted therein. Transverse upper shoulder  187  abuts shoulder  22  of the segmented locking rings  24  so that the internals of valve  10  are retained within valve body  12 . 
     The interior of reference chamber  180  has an upper end first cylindrical section with a female O-ring groove having an O-ring  193 , an enlarged bore intermediate cylindrical section, and a reduced diameter cylindrical section with a female O-ring groove and O-ring  194  positioned therein at the lower end. O-ring  194  seals against the the external cylindrical surface at the upper end of camming tubular body  150 . The annular space in between reference chamber  180 , piston  162 , and camming tubular body  150  between O-rings  193  and  194  constitutes a pressure-containing chamber  195  to which the piston  162  is exposed on its lower transverse face  169 . This chamber can be selectively precharged through Schrader valve  171  mounted in piston  162  whenever seal screw  173  is removed. Piston bias spring  176  is located within chamber  195  and bears against the lower interior transverse face of reference chamber  180 . Chamber  195  is pressure-isolated by O-rings  193 ,  194 , and  165  and seal screw  173 . 
     The internal components of the valve that fit into the valve body  12  are handled as a cartridge assembly with the exception of segmented locking rings  24 , backup ring  25 , and snap ring  26 . This is because annular grooves  105  and  114  of upper half ball cage  100  and the corresponding grooves of lower half ball cage  101  engage annular ridges  43  of seat holder  137  and  183  of reference chamber  180  to effectively hold the valve internals together axially. Whenever the internals are inserted into intermediate bore  18  of valve body  12 , then the cartridge is completely restrained on its outer diameter. Segmented locking rings  24  can then be inserted into groove  19  of body  12 , backup ring  25  inserted interior to the segmented locking rings, and then snap ring  26  inserted into the snap ring groove on the upper interior cylindrical face of the segmented rings. In this manner, the valve internals are additionally fully constrained to stay between lower internal transverse shoulder  33  of body  12  and the locking rings  24 . 
     FIGS. 13A and 13B show a second embodiment  210  of the valve which is suitable for locking the valve open to permit wireline operations through the valve to free pipe that has been stuck below the rig floor. This embodiment is substantially similar to the first embodiment of the valve discussed above and uses many of the same internal components. 
     One difference between the first and second embodiment is that the intermediate bore  218  of body  212  is elongated between interior transverse abutment shoulder  223  and internal recess groove  219  which engages the segmented locking rings  24  The additional length is used to accommodate latch sleeve  230  which is positioned between the upper transverse shoulder of the reference chamber  280  and the lower transverse face  22  of segmented locking rings  24 . Latch sleeve  230  has a constant outer diameter which closely fits bore  218  of body  212 . The interior of latch sleeve  230  has a lead-in chamfer and at least one interior groove  231 . The internal groove  231  is used to locate and engage a latchable/retrievable wireline-run lock-open sleeve tool such as the device shown in U.S. Pat. No. 4,220,176 or other commercially available devices. 
     A lock-open sleeve device  235  latched into position is shown as an integral entity without details of its selectably operable latching and retrieval mechanisms. Such devices are known in the downhole tooling art. Piston  262  is the same as that used for the first embodiment shown in FIG. 6B, but the series of holes  168 ,  170  and  172  containing the Schrader valve  171  and seal screw  173  are removed. 
     Valve body  212  has radial port  227  into which Schrader valve  171  is pressed or threadedly mounted in a manner similar to that of the first embodiment of the valve. The outer end of radial port  227  is threaded to accommodate seal screw  173 , which seals the outer end of Schrader valve  171  from external pressure. The extreme outer end of radial port  227  is countersunk in order to protect the head of seal screw  173 . For the embodiment of FIGS. 13A and 13B, reference chamber  280  contents are accessed through radial port  282 , which is axially positioned close to the location of radial port  227  in valve body  212 . 
     Two male O-ring grooves, containing O-rings  297 , are located straddling a recess at the exterior end of radial port  282  in reference chamber  280 . O-rings  297  seal the annular gap between bore  218  and reference chamber  280  to ensure that the fluid path formed by radial port  227  of body  212  and radial port  282  of reference chamber  280  is isolated from the interior flow passages of valve  210 . This permits pressure-containing chamber  195  to be selectively precharged through Schrader valve  171  whenever seal screw  173  is removed. 
     O-rings  186  and  47  prevent fluid passage around the outside of the valve internals. O-rings  56  and  62  prevent fluid passage around the seat biasing piston  50  and the seat  75 . Seat  75  is generally engaged against ball  85  except for the special conditions discussed in the description of the seat operation given below. 
     FIGS. 14-16 show the configuration of the valve seating arrangement for each of the three operating modes of the closed valve. The same valve seating arrangement is used in all embodiments of this invention. For FIG. 14, the configuration of the valve shown is that assumed when the valve is disconnected from the drillstring and the mud column above the valve is being retained. The seat  75  is shown in sealing engagement with ball  85  in this case. 
     In FIG. 15, the configuration of the valve is for the case when there is a substantial net pressure retained in the connected drillstring below the closed ball. For this case, the seat  75  is forced away from the closed ball so that pressure communication is established between spaces below and above the ball. This condition permits measurement of the retained pressure below the closed valve by the rig standpipe pressure gauges. 
     FIG. 16 shows the valve for the case when a pump-induced pressure surge from above occurs while the closed mudsaver is connected into the drillstring. In this case, the seat biasing piston  50  is moved away from the ball  85  sufficiently to engage the main seat  75  with the seat travel limiter  65  and unseat seat  75  from ball  85 . 
     Operation of the Embodiments of the Invention: 
     A major advantage of the mudsaver valve of the present invention is the incorporation of a bi-directional snap action valve. In order to obtain bi-stable snap action for a valve or its actuator, it is necessary to meet the following four conditions for both the opening and closing travel directions: 1) an end travel stop must be provided at each limit of motion; 2) a biasing force which reverses direction and opposes shifting of the valve to another position as the actuator or sealing member moves from one travel stop to the other; 3) the biasing force must be applied to hold the actuator or valve sealing member against or near the end travel stops whenever the actuating forces are less than the biasing forces; and 4) a critical level of actuating force must be applied in the direction of travel such that the resisting forces and biasing forces are exceeded throughout the length of travel for either direction. 
     These four criteria for bi-directional snap action can be provided by a variety of bistable mechanisms such as garter springs, canted springs, and magnetic mechanisms. Several different means for achieving an adjustable dual snap action are disclosed in copending patent application Ser. No. 09/824,374 entitled “Dual Snap Action for Valves” filed on Apr. 1, 2001, which is incorporated herein by reference. 
     The general opening and closing operation of the valve  10  is as follows. The ball  85  of the valve  10  is caused to rotate from a closed position for which mud is retained above the ball to an open position for which flow is possible through the ball as a consequence of pressures applied to pressure-responsive actuating piston  162 . Biasing forces are applied to piston  162  in order to maintain ball  85  closed when the hydrostatic mud column above ball  85  is exerting pressure on the piston  162 . In operation, it is necessary to have an excess of biasing force over hydrostatic pressure-induced force for a variety of conditions, such as surge pressures from movement of the valve for pipe handling or variations in mud weight. Normally, spring  176  provides sufficient bias to handle mud weights necessary for most conditions. The strength of the spring is based upon the maximum height of the mud column to be retained and the desired mud density at which opening is desired. However, additional valve closing bias can be applied by introducing air or nitrogen pressure into chamber  195 , so that it will exert additional valve closing forces on piston  162 . 
     It is undesirable for a ball valve to be either partially open or partially closed when it is susceptible to flow-induced wear. In addition, a mudsaver valve should be insensitive to lesser variations in either hydrostatic or pump pressure. FIG. 17 shows the relationship of forces acting on the piston  162  as a function of distance of travel for valve opening. These forces are friction, the bias spring force, the gas pressure force, the detent resistance, and the mud pressure force. Both friction and the spring force are predetermined; the gas pressure is adjustable and is set according to the mud density to be retained. The mud pressure force is determined solely by drilling needs and is generally high while drilling. The detenting force is also selectively controllable during fabrication. In addition, the cartridge construction of the valve makes it a simple and rapid process to remove the cartridge, replace the existing detenting members for applying force such as the spring pins  134 , with other spring pins of a different biasing force and replace the valve cartridge in the body. 
     Interaction of spring pins  134  with detents  96  on face  88  of ball  85  provides forces which resist movement of the fully-open or fully-closed ball  85  by the forces applied to piston  162  and thence to the ball  85  by camming arms  152  and camming pins  157 . The configuration of detents  96  is selected to coact with the spring forces and spring pin nose geometry of spring pins  134  in order to provide specific forces resisting ball movement. Once resisting forces are overcome by pressure applied to upper surface  174  of piston  163 , the unbalanced pressure force is sufficient to cause movement fully to the new assembly position. For example, when the bias of spring  176 , precharge pressure in chamber  195 , and the resistance of spring pins  134  in the detents  96  of closed ball  85  in FIG. 1 are overcome by pump pressure, the overcoming pressure will force the ball to an open position as shown in FIG.  6 . 
     The excess pressure required to initiate movement of the ball is strictly due to the snap-through action obtained from the resistance of spring pins  134 . The spring pin resistance drops to a negligible value after the pin escapes from detent  96 . Excess pressure is necessary to overcome the increase of forces from compression of spring  176  and the gas pressure in chamber  195  that occurs with the opening travel of piston  162 , as well as to overcome possible variations in friction involved in moving the ball. 
     Excess force on the piston is also required to move the valve from the open position of FIG. 6 to the closed position of FIG. 1, as may be seen from the curves of FIG.  18 . For valve closing, the closing effort provided by the combination of the spring bias and the gas pressure force have to overcome friction, the mud pressure forces, and the detent forces. The detent forces should be such that, when the mud pressure drops sufficiently, the gas pressure force and the spring bias will be adequate to overcome friction and thereby ensure full closure. By varying the spring rate of spring pins  134  and the slope and depth of the detents  96  which influence valve opening and closing, the resistive forces of the snap-action mechanism can be made direction dependent. 
     When the biasing forces on piston  162  and the detent-induced forces on the ball are exceeded during opening, the force on piston  162  is sufficient to move the piston and the attached camming arm  152  downwardly toward the ball  85 . As camming arm  152  moves, its attached camming pins  157  interact with camming grooves  94  of ball  85  to cause ball rotation. The reverse action occurs for reclosure of the valve. 
     Fluid pressure is always communicated from above the ball  85  through the gaps between dirt excluder  140 , the camming tubular body  150  and the split half ball cages  100  and  101 . This first gap communicates with the gap between ball  85  and valve body  12  and then the cavity between seat  75  and seat bias piston  50  through gap  69  between seat holder  37  and seat travel limiter  65  through multiple holes  68 . Thus differential area A 1  on seat bias piston  50  is exposed to the pressure above the valve on its upper transverse face and the pressure below the valve on its lower face. Similarly, differential area A 2  on the valve seat is exposed to the pressure above the valve on its lower face and the pressure below the valve on its upper face inside the annular sealing ridge  78 . In this manner, the seat bias piston  50  and the seat are made responsive to the relative pressure differences between the pressures above and below ball  85 . The behavior of the seat in various modes is described further below with reference to FIGS. 14-16. Under normal operating conditions, seat  75  remains in contact with ball  85  when the valve is closed, open, or shifting. 
     The opening and closing behavior of the valve  210  shown in FIGS. 13A and 13B is identical to that of the first embodiment shown in FIGS. 1 and 6. If a pressure precharge is to be applied to chamber  195  for valve  210 , it is done by removing seal screw  173  from body  212  and injecting a predetermined pressure using either air or nitrogen through Schrader valve  171 . Seal screw  173  is then replaced to isolate chamber  195  and Schrader valve  171  from external pressures. Latch sleeve  230  is operational only if it is necessary to use a wireline-run lock-open sleeve device  235  to latch the valve  210  open in the event pipe becomes stuck and is inaccessible below the rig floor. In such an event, the lock-open sleeve  235  may be run down the bore of the kelly on wireline while valve  210  is held open by mudpump circulating pressure until it engages in the latch grooves  231  of latch sleeve  230 . Lock open sleeve has a nose section which extends through the open ball  85  to constrain it to remain open even when the mud pumps are turned off. After the wireline running tool for lock-open sleeve  235  is retrieved, wireline or pump-down devices can be run through the bore of lock-open sleeve  235  and the open valve  210 . Lock-open sleeve  235  can be retrieved in the conventional manner so that the valve  210  can return to its normal functioning pattern. This type of lock-open device can also be applied with the valve of the first embodiment of this invention. 
     In FIG. 14, the ball  85  is closed and annular sealing ridge  78  of seat  75  is sealing against spherical surface  86  of ball  85 , so that mud above the valve is retained. This situation is the normal condition when the pumps of the rig are turned off and the mudsaver valve is disconnected from the drillstring. The pressure of the retained mud is transmitted to the lower transverse face  79  of seat  75 , so that seat  75  is biased against the ball by both the differential pressure acting on seat piston area A 2  and the force of seat bias spring  80 . In this case the seat  75  does not contact the seat travel limiter  65 . Seat biasing piston  50  is held against seat holder  37  by the biasing force of conical snap ring  39 , which exceeds the force of the retained mud pressure acting on differential seat biasing piston area A 1 . 
     In FIG. 15, the valve is shown in its configuration assumed whenever the mudsaver valve is still connected to the drillstring with the pumps off, the ball  85  closed, and higher pressure is present below than above the ball  85 . The pressure differential from below acting on area A 1  further assists to bias seat bias piston  50  against its stop in seat holder  37 . However, when the pressure differential acting on area A 2  of seat  75  exceeds the relatively low bias force of seat bias spring  80 , seat  75  will be forced away from contact with the spherical surface  86  of ball  85 . This separation of seat  75  from sealing engagement with ball  85  permits transmission of pressures (of more than a minimal level due to the bias from spring  80 ) from below the mudsaver valve to the region above the valve. This automatic transmission of pressure permits the standpipe pressure gauges of the rig to be used to measure the pressure below the valve. 
     In FIG. 16, the valve is shown in its configuration assumed whenever the valve is reconnected to the drillstring and a pressure surge from the rapid startup of the rig mudpumps encounters the closed valve. This situation does not occur for slow, smooth startups of the rig mudpumps. The bias force applied to the seat bias piston  50  by conical snap ring  39  is such that bias piston  50  remains against its stop in seat holder  37  for any normal hydrostatic mud pressures which may be encountered with the valve closed and separated from the drillstring. Whenever a rapid pump pressure surge encounters the closed ball  85 , forces build rapidly in the operating mechanism of the valve, but friction with the valve seat also builds at the same rate since the inertia of the valve prevents instant opening. High contact stresses with attendant wear can occur in a conventional mudsaver in such a situation. However, for the valve of this invention, the pressure differential from the surge acting on area A 1  will be sufficient to overcome the bias force of conical snap ring  39  to force seat bias piston  50  away from its stop in seat holder  37 . When sufficient movement away from the ball by seat bias piston  50  occurs, transverse lip  67  of seat travel limiter  65  abuts upper transverse face  77  of seat  75  and pulls seat  75  out of engagement with ball  85 . The effective differential area exposed to the surge pressure at that time is (A 1 −A 2 ). This unseating of ball  85  in surge conditions permits the ball to be opened with much lower forces, thus minimizing wear of the valve components. Once the ball is opened, the seat and seat bias piston revert to their normal positions shown in FIG.  14 . 
     Advantages of This Invention: 
     This invention provides a mudsaver valve that has an extended reliable service by avoiding fluid erosion of valve components caused by fluid wear on a partially open or closed valve. The valve avoids this fluid erosion by using a dual snap action. 
     A further advantage of the valve is that it is operated with less force and, hence, wear when the pumps are turned on rapidly so that a strong pressure pulse is produced. This advantage results from the unseating of the valve seat for strong pressure pulses from above. 
     Another advantage of this invention is that it may be readily adjusted to permit operation with high mud densities. 
     In addition, the valve may be locked open by an accessory tube when it becomes inaccessible downhole due to a stuck pipe, thereby permitting wireline operations through the valve so that the pipe may be freed. 
     Yet another advantage is that elevated pressure from below is readily transmitted past the valve seat, so that the standpipe pressure of the well can be determined through the valve when the pumps are stopped and still connected to the drillstring. 
     Still yet another significant advantage of the valve is its modular construction, which may easily be removed from and reinstalled into the valve body without the necessity for handling several loose pieces or dealing with large threaded connections. 
     It may be seen from the foregoing description that this valve provides a definite improvement in the operation of mudsaver valves, enabling improvements in service life and ease of operation. The disclosed valve will perform substantially better in abrasive service than conventional valves, due to the avoidance of flow concentration during initial valve opening and final valve closing. It is to be understood that this invention is not limited in its application to the details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purposes of description and should not be regarded as limiting.