Abstract:
The invention provides surgical or diagnostic tools and associated methods that offer user control for operating remotely within regions of the body. These tools include a proximally-located actuator for the operation of a distal end effector, as well as proximally-located actuators for articulational and rotational movements of the end effector. Control mechanisms and methods refine operator control of end effector actuation and of these articulational and rotational movements. An articulation lock allows the fixing and releasing of both neutral and articulated configurations of the tool and of consequent placement of the end effector. The tool may also include other features. A multi-state ratchet for end effector actuation provides enablement-disablement options with tactile feedback. A force limiter mechanism protects the end effector and manipulated objects from the harm of potentially excessive force applied by the operator. A rotation lock provides for enablement and disablement of rotatability of the end effector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/334,628 (filed Dec. 22, 2011), which is a divisional of U.S. patent application Ser. No. 11/787,543 (filed Apr. 16, 2007), now U.S. Pat. No. 8,100,824, which is a continuation in part of U.S. patent application Ser. No. 11/181,445 (filed Jul. 13, 2005), now U.S. Pat. No. 7,615,066 B2, which is a continuation of U.S. patent application Ser. No. 10/444,769 (filed May 23, 2003), now U.S. Pat. No. 7,090,637 B2, the disclosures of which are incorporated herein by reference. U.S. patent application Ser. No. 11/787,543 This application is also a continuation in part of U.S. patent application Ser. No. 11/121,668 (filed May 3, 2005), now U.S. Pat. No. 8,182,417, which claims priority to U.S. Provisional Patent Application No. 60/630,912 (filed Nov. 24, 2004), the disclosures of which are also incorporated by reference. U.S. patent application Ser. No. 11/787,543 is further related to the following concurrently filed U.S. patent applications: U.S. patent application Ser. No. 11/787,607 (filed Apr. 16, 2007; “Tool with rotation lock” of Hinman and Danitz), U.S. patent application Ser. No. 11/787,599 (filed Apr. 16, 2007, “Tool with end effector force limiter” of Hinman and Bertsch), U.S. patent application Ser. No. 11/787,605 filed Apr. 16, 2007, “Tool with multi-state ratcheted end effector” of Hinman), and U.S. patent application Ser. No. 11/787,608 (filed Apr. 16, 2007, “Articulating tool with improved tension member system” of Hegeman, Danitz, Bertsch, Alvord, and Hinman). 
    
    
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to articulating mechanisms and applications thereof, including the remote guidance and manipulation of surgical or diagnostic tools. 
     BACKGROUND OF THE INVENTION 
     Surgical procedures such as endoscopy and laparoscopy typically employ instruments that are steered within or towards a target organ or tissue from a position outside the body. Examples of endoscopic procedures include sigmoidoscopy, colonoscopy, esophagogastro-duodenoscopy and bronchoscopy. Traditionally, the insertion tube of an endoscope is advanced by pushing it forward, and retracted by pulling it back. The tip of the tube may be directed by twisting and general up/down and left/right movements. Oftentimes, this limited range of motion makes it difficult to negotiate acute angles (e.g., in the rectosigmoid colon), creating patient discomfort and increasing the risk of trauma to surrounding tissues. 
     Surgical procedures such as endoscopy and laparoscopy typically employ instruments that are steered within or towards a target organ or tissue from a position outside the body. Examples of endoscopic procedures include sigmoidoscopy, colonoscopy, esophagogastroduo-denoscopy, and bronchoscopy, as well as newer procedures in natural orifice transluminal endoscopic surgery (“NOTES”). Traditionally, the insertion tube of an endoscope is advanced by pushing it forward, and retracted by pulling it back. The tip of the tube may be directed by twisting and general up/down and left/right movements. Oftentimes, this limited range of motion makes it difficult to negotiate acute angles (e.g., in the rectosigmoid colon), creating patient discomfort and increasing the risk of trauma to surrounding tissues. 
     Laparoscopy involves the placement of trocar ports according to anatomical landmarks. The number of ports usually varies with the intended procedure and number of instruments required to obtain satisfactory tissue mobilization and exposure of the operative field. Although there are many benefits of laparoscopic surgery, e.g., less postoperative pain, early mobilization, and decreased adhesion formation, it is often difficult to achieve optimal retraction of organs and maneuverability of conventional instruments through laparoscopic ports. In some cases, these deficiencies may lead to increased operative time or imprecise placement of components such as staples and sutures. 
     Steerable catheters are also well known for both diagnostic and therapeutic applications. Similar to endoscopes, such catheters include tips that can be directed in generally limited ranges of motion to navigate a patient&#39;s vasculature. There have been many attempts to design endoscopes and catheters with improved steerability. For example, U.S. Pat. No. 3,557,780 to Sato; U.S. Pat. No. 5,271,381 to Ailinger et al.; U.S. Pat. No. 5,916,146 to Alotta et al; U.S. Pat. No. 6,270,453 to Sakai, and U.S. Pat. No. 7,147,650 to Lee describe endoscopic instruments with one or more flexible portions that may be bent by actuation of a single set of wires. The wires are actuated from the proximal end of the instrument by rotating pinions (Sato), manipulating knobs (Ailinger et al.), a steerable arm (Alotta et al.), by a pulley mechanism (Sato), or by manipulation of complementary portions (Lee). U.S. Pat. No. 5,916,147 to Boury et al. discloses a steerable catheter having four wires that run within the catheter wall. Each wire terminates at a different part of the catheter. The proximal ends of the wires extend loosely from the catheter so that the physician may pull them. The physician is able to shape and thereby steer the catheter by selectively placing the wires under tension. 
     Recently, surgical instruments, including minimally invasive surgical instruments, have been developed that are more ergonomic and which have a wider range of motion and more precise control of movement. These instruments may include mechanisms that articulate using a series of links coupled with one or more sets of tension bearing members, such as cables. As with conventional instruments used in minimally invasive surgery, rotation of the shaft and the end effector with respect to the handle is an important feature of cable and link type instruments to aid with dissecting, suturing, retracting, knot tying, etc. Ergonomic, flexible, and intuitive mechanisms that facilitate manual control and placement of the end effectors of such instruments are also important factors as medical procedures become more advanced, and as surgeons become more sophisticated in operating abilities. Further improvements in the features and design of surgical instruments are desirable. 
     SUMMARY OF THE INVENTION 
     It may at times be desirable to maintain the orientation or configuration of the distal end of steerable or articulating instruments that have use in medical fields or non-medical applications. This invention provides methods and devices for locking or otherwise maintaining the shape and orientation of steerable and articulating instruments. 
     Embodiments of the invention include a tool that includes a distal portion and a proximal portion, an articulation mechanism, and an articulation lock. In some embodiments of the tool, the tool is for medical applications, such as is a surgical or diagnostic tool. The articulation mechanism manipulates the angular orientation or configuration of the distal portion; it includes a pair of links, each pair including a proximal link and a distal link spaced apart from each other. The mechanism is adapted such that movement of the proximal link causes corresponding relative movement of the distal link. The relative movement of the distal link that corresponds to the proximal link movement may either mirror the movement of the proximal link or be reciprocal to it. 
     The articulation lock has an engaged state and a disengaged state, wherein in the engaged state the articulation lock impedes movement of the proximal link and corresponding relative movement of the distal link. In some embodiments the impeding of movement is a partial impeding of movement; in other embodiments the impeding is a substantial blocking or preventing of movement. In some embodiments impeding the movement of the proximal link causes the impeding of the corresponding relative movement of the distal link. 
     In some embodiments the tool further includes an end effector disposed at the distal portion. In some embodiments the end effector includes a surgical or diagnostic mechanism. In some embodiments the tool includes an end effector actuator disposed at the proximal portion. In some embodiments the tool includes a handle at a proximal end of the tool, and the handle includes the end effector actuator. 
     Some embodiments have an articulation lock that includes a link friction increasing element, such that when the lock is engaged, increased friction impedes movement of the links. Increasing friction can partially impede link movement such that the link movement is malleable. Increasing friction can also fully impede link movement such that link movement is substantially blocked or prevented. Thus at the baseline level of friction that manifests on the link surfaces, the links can be considered freely moveable. With increasing levels of friction, link movement is such that the articulation mechanism as a whole is malleable, and with further increase in friction, the articulation mechanism seizes such that there is substantially no movement. With the articulation mechanism in an articulated configuration, application of friction can prevent movement of links from that articulated configuration. 
     Some embodiments of the articulation mechanism include tension load bearing members connecting the links of link pairs; some of these embodiments include an articulation lock that includes a tension member adjusting mechanism to increase tension on the members. Some embodiments of tension load bearing members include cables, and such members may frequently be referred to simply as cables. Increasing tension on the cables increases friction on link surfaces that impedes link movement. As summarized above, increasing friction with a cable tension adjusting mechanism can impede movement of links such that they can move malleably or links may be substantially unable to move. 
     In some embodiments, the articulation lock includes a rigid element, which when the lock is engaged, is disposed such that it extends at least from a point proximal to the proximal link to a point at least distal to the proximal link. In other embodiments, the articulation lock includes a malleable element, which when the lock is engaged, is disposed such that it extends at least from a point proximal to the proximal link to a point at least distal to the proximal link. The articulation lock embodiments that include a malleable locking element are able lock the links in an articulated configuration. 
     In addition to an articulation mechanism and an articulation lock, some embodiments further include an end effector disposed at the distal portion; the end effector may comprise a surgical or diagnostic mechanism. The tool may further include a handle at the proximal end of the tool, and the handle may comprise an end effector actuator. 
     In embodiments of the tool, the relative movement of the distal link that corresponds to the movement of the proximal link in some embodiments may be reciprocal to the movement of the proximal link; in other embodiments the movement of the distal link may mirror the movement of the proximal link. 
     In some embodiments the articulation mechanism includes multiple pairs of corresponding links, a proximal link on the proximal portion of the tool and a distal link on the distal portion of the tool, such that movement of the proximal link causes corresponding relative movement of the distal link. Thus in typical embodiments, the proximal link of a pair that is most proximal on a tool operably corresponds to the distal link that is most distal on the tool. Similarly, the most distal proximal link corresponds to the most proximal distal link. Accordingly, intermediate proximal links accordingly correspond to intermediate distal links. 
     In addition to an articulation mechanism and an articulation lock, some embodiments further include an end effector disposed at the distal portion; an end effector actuator disposed at the proximal portion; a shaft disposed between the end effector and the end effector actuator; such that movement of the distal link causes angular movement of the end effector with respect to the shaft. In some of these embodiments, the articulation mechanism includes multiple pairs of links, each pair including a proximal link on the proximal portion of the tool and a distal link on the distal portion of the tool, such that movement of the proximal link causes corresponding relative movement of the distal link and angular movement of the end effector with respect to the shaft. 
     In some of the tool embodiments with an end effector, an end effector actuator, a shaft, and multiple pairs of links, the articulation mechanism includes tension load bearing members connecting the links and the articulation lock includes a tension load bearing member tension adjusting mechanism configured to increase tension on the members. In some embodiments the tension load bearing members comprise cables, accordingly, such tension load bearing members may be referred to as cables; accordingly, the tension load bearing member adjusting mechanism may be commonly referred to as a cable tension adjusting mechanism In some embodiments, the cable tension adjusting mechanism is disposed between the proximal and the distal links; in other embodiments the cable tension adjusting mechanism is disposed proximal to the most proximal link. In some of these embodiments, the cable tension adjusting mechanism includes a threaded member; in other embodiments, the cable tension adjusting mechanism includes a cam locking lever configured to increase the length of the shaft, thereby increasing tension on the cables. The cable tension adjusting mechanism, whether tensioned by a threaded member or a cam lever or any other mechanism, acts to vary the distance between the proximal and distal links. By such varying of distance, friction that resists movement between links can vary. These just-summarized embodiments of an articulation lock can lock links in an articulated configuration as well as in an unarticulated configuration. 
     In some of the tool embodiments with an end effector, an end effector actuator, a shaft, and multiple pairs of links, the articulation lock includes a locking rod disposed in a channel formed in one or more links. In some embodiments, the locking rod is rigid; in some it is malleable. When the locking rod is malleable, the articulation lock can lock links in an articulated configuration. 
     In some of these embodiments with an end effector, an end effector actuator, a shaft, and multiple pairs of links, the articulation lock includes a locking sleeve fitted over the multiple proximal links. In some embodiments, the locking sleeve is rigid; in some it is malleable. When the locking sleeve is malleable, the articulation lock can lock links in an articulated configuration. 
     In some of these just summarized tool embodiments with an end effector, an end effector actuator, a shaft, and multiple pairs of links, the articulation lock includes a rigid element which, when engaged, is disposed at least from a point proximal to the most proximal proximal link to at least to a point distal to the most distal proximal link. In some of these embodiments, the rigid element is disposed adjacent to the proximal links when in the engaged state. In some of these embodiments, the rigid element includes a sleeve that at least partially surrounds the proximal links when in the engaged state. In some of these embodiments, the sleeve is slidably mounted on the tool. In some of these embodiments with a slidable sleeve, the sleeve is disposed distal to the proximal links when in the disengaged state. 
     Embodiments of the invention include methods for using a tool, the tool comprising a distal portion and a proximal portion, an articulation mechanism and an articulation lock, the method including changing the position of the lock. In some embodiments, the tool is a medical tool configured for surgical or diagnostic methods. The articulation mechanism is for manipulating angular orientation of the distal portion, the articulation mechanism comprising at least one pair of links, the pair comprising a proximal link on the proximal portion and a distal link on the distal portion, the mechanism adapted such that movement of the proximal link causes corresponding relative movement of the distal link and the distal portion of the tool. The articulation lock has a disengaged state wherein the links move freely, and an engaged state wherein the lock impedes movement of the proximal link and corresponding relative movement of the distal link. 
     The tool may further include an end effector disposed at the distal portion of the tool, such that movement of the distal portion of the tool moves the end effector. The tool may further include an end effector actuator disposed at the proximal portion of the tool, such that moving the end effector actuator causes moving of the proximal link. In some embodiments, the tool may include a handle at the proximal end of the tool, and the handle may comprise the end effector actuator. In addition to an end effector disposed at the distal portion and an end effector actuator disposed at the proximal portion, the tool may further include a shaft disposed between the end effector and the end effector actuator; wherein movement of the distal link causes angular movement of the end effector with respect to the shaft. 
     The method of changing the position of the lock may be applied to a lock in a disengaged state, and wherein the changing the position comprises engaging the lock. Engaging the lock may be applied to a tool wherein the articulation mechanism comprises tension load bearing members (cables for example), connecting the links and the articulation lock comprises a tension load bearing member (cable) tension adjusting mechanism configured to increase cable tension when engaging the lock. Engaging a lock with a cable tension adjusting mechanism may be applied to an articulation mechanism when it is in either an unarticulated configuration (which can be understood as a neutral or straight configuration), or it can be applied to an articulation mechanism when it is in an articulated configuration, in which case the articulated configuration is maintained as the mechanism is locked. Engaging a lock with a cable tension adjusting mechanism may include increasing tension on cables such that movement of the articulation mechanism is partially impeded; and by having its movement partially impeded, the articulation mechanism becomes malleable. Engaging a lock with a cable tension adjusting mechanism may also include increasing tension on the cables such that movement of the articulation mechanism is substantially blocked. Exemplary embodiments of a lock including a cable tension adjusting mechanism include a threaded element for increasing tension on the cables, and a cam lever mechanism for adjusting the length of the shaft, lengthening the shaft having the effect of increasing tension on the cables. 
     The changing of position such that the lock becomes engaged may be applied to a tool with a lock that includes a rigid element, and wherein engaging the lock comprises placing the rigid element where it extends from a point proximal to the proximal link to a point distal to the proximal link, and wherein engaging the lock substantially blocks movement of the distal portion. In some embodiments, the rigid element is a rod, in some embodiments the rigid element is a sleeve. 
     Engaging the lock may be applied to a tool with a lock that includes a malleable element, and wherein engaging the lock comprises placing the lock in a position where it extends from a point proximal to the proximal link to a point distal to the proximal link. Engaging a lock with a malleable element may be applied to an articulation mechanism when it is in either a neutral or unarticulated configuration, or it can be applied to an articulation mechanism when it is in an articulated configuration, in which case the articulated configuration is maintained. Exemplary embodiments of a malleable element include a rod and a sleeve. 
     The method of changing the position of the lock may be applied to a lock in an engaged state, and wherein the changing the position comprises disengaging the lock. Disengaging the lock may be applied to a tool wherein the lock comprises a cable tension adjusting mechanism configured to decrease cable tension when disengaging the lock. The cable tension adjusting mechanism may include a threaded member for decreasing tension in the cables. The cable tension adjusting mechanism may include a cam lever for adjusting the length of the shaft. 
     Disengaging the lock may be applied to a tool wherein the lock comprises a rigid element, and wherein the rigid element is removed from a position where it extends from a point proximal to the proximal link to a point distal to the proximal link. 
     Disengaging the lock may be applied to a tool wherein the lock comprises a malleable element, and wherein the malleable element is removed from a position where it extends from a point proximal to the proximal link to a point distal to the proximal link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings which are briefly described below. 
         FIG. 1  is a front perspective view of an articulatable surgical tool. 
         FIG. 2  is perspective view of a surgical tool in an articulated position. 
         FIG. 3  is an exposed side view of a surgical tool with an end effector actuator and an end effector both in an open position. 
         FIG. 4  is an exposed side view of a surgical tool with an end effector actuator and an end effector both in a closed position. 
         FIG. 5  is a side view of the proximal portion of a tool, showing the handle and proximal end of the shaft, with an articulation locking sleeve in a distal and unlocked position. 
         FIG. 6  is a side view of the proximal portion of a tool, showing the handle and proximal end of the shaft, with an articulation locking sleeve in a proximal and locked position. 
         FIG. 7  is a side view of another embodiment of surgical tool, with a different embodiment of an articulation locking sleeve in distal and unlocked position, and with an end effector actuator and an end effector both in a closed position. 
         FIG. 8  is a side view of the embodiment shown in  FIG. 7 , but with the articulation locking sleeve in a proximal and locked position. 
         FIG. 9  is a member of a series that extends through  FIG. 24 , showing details of a locking sleeve support mechanism, over which the sleeve slides.  FIGS. 9-13  show the sleeve support mechanism in the unlocked position.  FIG. 9  is a cross-sectional focus on details of a pair of shoulders formed in the sleeve, a corresponding pair of shoulder stops, a pair of detents on the sleeve that correspond to a pair of detents on the sleeve support. 
         FIG. 10  is a full cross sectional side view of the sleeve and sleeve support mechanism, with a circled portion representing the location of detail shown in  FIG. 9 . 
         FIG. 11  is a surface side view of the sleeve and sleeve support mechanism corresponding to the cross-sectional view of  FIG. 10 . 
         FIG. 12  is a proximal-looking perspective view of the sleeve encircled around the sleeve support, the sleeve in an unlocked position. 
         FIG. 13  is a distal-looking perspective view of the sleeve encircled around the sleeve support, the sleeve in an unlocked position. 
         FIG. 14  is a member of a series that extends through  FIG. 19  showing the sleeve and sleeve support mechanism in the locked position.  FIG. 14  is a proximal-looking perspective view of sleeve encircled around the sleeve support, the sleeve m a locked position. 
         FIG. 15  is a distal-looking perspective view of sleeve encircled around the sleeve support, the sleeve in a locked position. 
         FIG. 16  is a cross-sectional side view of the sleeve and sleeve support, analogous to the view of  FIG. 10 , but with the sleeve in a locked position. The encircled area indicates the location of detail shown in  FIG. 17 . 
         FIG. 17  is a cross-sectional focus on details of a pair of shoulders formed in the sleeve, a corresponding pair of shoulder stops, a pair of detents on the sleeve that correspond to a pair of detents on the sleeve support, the detail analogous to the view shown in  FIG. 9 , except that the sleeve is in a locked position. 
         FIG. 18  is a surface side view of the sleeve and sleeve support corresponding to the cross-sectional view of  FIG. 16 , the sleeve in a locked position. 
         FIG. 19  is a proximal-looking front end view of the sleeve and sleeve support showing push tabs and pull tabs on the sleeve, and anti-rotation ribs on the sleeve support. 
         FIG. 20  is a distal-looking perspective view of the sleeve without the sleeve support. 
         FIG. 21  is a proximal-looking perspective view of the sleeve without the sleeve support. 
         FIG. 22  is a side view of the sleeve without the support mechanism, proximal end up. 
         FIG. 23  is a perspective view of the isolated sleeve support mechanism. 
         FIG. 24  is a side view of the isolated sleeve support mechanism. 
         FIG. 25A  and  FIG. 25B  provide views of an articulation lock comprising a rod:  FIG. 25A  shows a rod, which as depicted could either be a rigid rod or a malleable rod, oriented for insertion into the proximal portion of a multi-link articulating mechanism.  FIG. 25B  shows a malleable rod in place within the mechanism, holding the mechanism in an articulated configuration. 
         FIG. 26A  and  FIG. 26B  provide detail views of the links depicted in  FIGS. 25A and 25B ;  FIG. 26A  proximal-looking perspective view;  FIG. 26B  is a distal looking perspective view. 
         FIG. 27  is a member of a series extending through  FIG. 34  showing another embodiment of the tool.  FIG. 27  is a perspective view showing an embodiment that is configured with a cylindrical sleeve comprising an internal threaded portion (not shown in this surface view), and with ball and socket type links. This articulation lock embodiment is of a type that adjusts the tension bearing members that connect articulating links, thereby increasing friction between links Encircled section of  FIG. 27  is shown in greater detail in  FIG. 28 . 
         FIG. 28  is an enlarged detail of  FIG. 27 , focusing on the cylindrical sleeve, and showing proximal links and a shaft extension portion. 
         FIG. 29  is a perspective view of the tool shown in  FIG. 27 , the tool in an articulated position. 
         FIG. 30  is a cross sectional view of the cylindrical articulation lock depicted in  FIGS. 27-34  showing the detail of the internal threaded portion with right hand and left hand threads that vary the tension on cables threaded through the links. 
         FIG. 31  is a member of a series extending through  FIG. 34  showing details of components of the articulation lock.  FIG. 31  shows the shaft extension portion, on the proximal portion of the shaft, from a proximal-looking perspective, with threads on the proximal portion. 
         FIG. 32  shows the shaft extension portion, on the proximal portion of the shaft, from a distal-looking perspective, with threads on the proximal portion, and showing holes and lumens for cables to pass through. 
         FIG. 33  shows the threaded plug portion of the articulation lock, configured within the proximal portion of the articulation lock, from a distal-looking perspective, showing left hand threads, and proximal facing concave bearing surface. 
         FIG. 34  shows the threaded plug portion of the articulation lock from a proximal-looking perspective, showing the lumens to permit cable sets to pass through. 
         FIG. 35  is a side exposed view of the proximal portion of a tool with an articulation lock comprising a locking lever and wedge that is located proximal to the most proximal links. This articulation lock embodiment is of a type that adjusts tension on the tension bearing members that connect articulating links, thereby increasing friction between links. The lever shown in an unlocked position. 
         FIG. 36  shows the articulation lock mechanism depicted in  FIG. 35 , but in a locked position, to prevent articulation. 
         FIG. 37  is a side exposed view of the proximal portion of a tool with an articulation lock mechanism comprising a cylindrical locking sleeve with a translating locking disc connected to tension bearing members. The mechanism is located proximal to the most proximal links. This articulation lock embodiment is of a type that adjusts tension on tension bearing members that connect articulating links, thereby increasing friction between links. The mechanism is shown in an unlocked position. 
         FIG. 38  shows the articulation lock mechanism depicted in  FIG. 37 , but in a locked position, to prevent articulation. 
         FIG. 39  is a side exposed view of the proximal portion of a tool with an articulation lock comprising a locking mechanism comprising a disc with a lever, the mechanism located proximal to the proximal link. This particular embodiment has only one pair of links and one set of tension bearing members. This articulation lock embodiment is of a type that adjusts tension on tension bearing members that connect articulating links, thereby increasing friction between links. The mechanism is shown in an unlocked position. 
         FIG. 40  shows the articulation lock mechanism depicted in  FIG. 39 , but in a locked position, to prevent articulation. 
         FIG. 41  is a side view of an instrument with cam-based articulation locking mechanism that is located between proximal and distal links. The cam mechanism effectively increases the length of the shaft. This articulation lock embodiment is of a type that adjusts tension on the tension bearing members that connect articulating links, thereby increasing friction between links. The lever shown in an unlocked position, thereby allowing articulation. 
         FIGS. 42A and 42B  provide detail views of the cam lock of  FIG. 41 .  FIG. 42A  depicts a locked position, and  FIG. 42B  depicts an unlocked position. The detail view emphasizes the difference in relative location of the telescoping shaft components in the two positions. 
         FIGS. 43A and 43B  provide perspective views of an articulating mechanism configured as a liver retractor, with a cam-based articulation locking mechanism that is located between proximal and distal links.  FIG. 43A  shows the lock in the unlocked position;  FIG. 43B  shows the lock in the locked position. This embodiment has no dedicated end effector; the mechanism itself serves as the engaging portion of the tool. 
         FIG. 44  is a perspective view of an articulating sheath device with an articulation lock in the form of a cylindrical sleeve comprising an internal threaded portion (not shown in this surface view) located between proximal and distal links. This articulation lock embodiment is of a type that adjusts tension on the tension bearing members that connect articulating links, thereby increasing friction between links. 
         FIGS. 45A and 45B  show a set of pivoting links that have a single degree of freedom.  FIG. 45A  shows an articulated configuration and  FIG. 45B  shows a straight, unarticulated position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Articulating Instruments 
     Steerable articulating instruments are described in U.S. Pat. No. 7,090,637; US 2005/0107667; US 2005/0273084; US 2005/0273085; US 2006/0111209, and US 2006/0111210. The articulating mechanisms of the tools described in those publications use multiple pairs of segments or links controlled, e.g., by multiple sets of cables, as well as tools that have a single pair of links, connected by a single set of cables, such as those described in U.S. Pat. No. 5,916,146. Depending upon the specific design of the device, the links can be discrete segments (as described, e.g., in U.S. Pat. No. 7,090,637) or discrete portions of a flexible segment (as described, e.g., in US 2005/0173085). The instrument may also include steerable or controllable links, e.g., as described in US 2005/0273084, US 2006/0111209, and US 2006/0111210. Embodiments of the invention are not specific to any particular type of link, and may include any type of link known in the art. 
     When using such articulating instruments, a user may manipulate the proximal end of the instrument, thereby moving one or more proximal links of the articulation mechanism. This movement results in relative movement of the distal link(s) corresponding to the proximal link(s). It may at times be desirable to lock or otherwise maintain the straight or bent shape of the instrument. In certain embodiments of this invention, the shape of the instrument is maintained by preventing movement of at least one of the proximal links with respect to the rest of the instrument. 
       FIGS. 1-6  show an articulatable tool  100  with an end effector  102  at its distal end and an end effector actuator  104  within a handle  106  at its proximal end. Instrument  100  may be used, e.g., in a laparoscopic procedure requiring grasping or cutting within a patient. Exemplary embodiments of the tool  100  may also may useful in endoscopic procedures, particularly when, as in some embodiments, the tool has a flexible shaft. Still other embodiments may be used for percutaneous procedures, such as a catheter. Still other embodiments include devices that are directed toward natural orifice transluminal endoscopic surgery (“NOTES”). Embodiments of the invention may include a wide variety of tools, some with medical or diagnostic purposes, and others that are applied to other types of tasks where the articulational capabilities of the tool provide benefit. Proximal articulation links  108  and  110  extend distally from handle  106 , and distal articulation links  112  and  114  extend proximally from end effector  102 . Proximal link  108  is connected to and moves with handle  106 . Likewise, distal link  112  is connected to and moves with end effector  102 . An elongated shaft  116  is disposed between the proximal links and the distal links. 
     Proximal and distal links of paired links are operably connected by tension bearing members, such as cables. Embodiments may include tension bearing members other than cables, but for simplicity and because cables are a typical embodiment, tension bearing members may be commonly referred to as cables. A set of control cables  118  is attached to proximal link  108 , extends through proximal link  110 , shaft  116  and distal link  114  and is attached to distal link  112 . A second set of control cables  120  is attached to proximal link  110 , extends through shaft  116  and is attached to distal link  114 . In this embodiment, there are three control cables  118  in the first set and three control cables  120  in the second set. It should be appreciated, however, that other numbers of control cables may be used to connect corresponding proximal and distal links. In addition, mechanisms other than cables may be used to connect corresponding links 
     As shown in  FIG. 2 , movement of handle  106  and proximal link  108  with respect to proximal link  110  moves end effector  102  and distal link  112  in a relative and corresponding manner. Likewise, movement of proximal link  110  with respect to shaft  116  moves distal link  114  with respect to shaft  116  in a relative and corresponding manner, also as shown in  FIG. 2 . This relative articulation movement provides a way for a user to remotely manipulate the end effector through movement of the handle. 
     In the embodiment illustrated in  FIGS. 1-4 , the end effector  102  is a pair of jaws. Actuation force is transmitted from end effector actuator  104  through a transmission that includes a linearly movable compression bearing member or rod  125  and a rotatable rod actuator  122 , as shown in  FIGS. 3 and 4 . In some embodiments, the tension bearing member or rod is also capable of bearing a compressive load, such that an end effector can be pushed by a force transmitted by the end effector actuator. 
     Other end effectors (surgical, diagnostic, etc.) and end effector actuators may be used with the articulating tool of this invention. In some embodiments, the distal links, themselves, can comprise an end effector, such as, for example, a retractor. In some embodiments, the movable tension bearing member or rod may comprise any flexible tension bearing material; in some embodiments Nitinol offers particular advantages as it is sufficiently flexible to accommodate articulation, and yet resilient enough to carry a compressive load that allows the rod to open an end effector, such as a set of jaws. 
     Locking Articulation by Locking Proximal Links 
     In order to maintain a particular position of the end effector with respect to the shaft, the articulating tool of this invention has an articulation lock. In the embodiment shown in  FIGS. 1-6 , the articulation lock includes a movable sleeve  130 . In some embodiments the sleeve is rigid, as is the depicted example, but in other embodiments the sleeve may be malleable. Malleability may be imparted by variations in design, such as with folds in the sleeve, or by increasing of dimensions, or by use of malleable materials, or by use of combinations of materials that individually contribute flexibility or stiffness, or by any combination of these approaches. In the unlocked position shown in  FIGS. 1-5 , sleeve  130  is distal to proximal links  108  and  110 . In the locked position shown in  FIG. 6 , however, sleeve  130  has been moved proximally to a position adjacent to and covering links  108  and  110  as well as the proximal end of shaft  116 , thereby blocking relative movement between links  108  and  110  and between link  110  and shaft  116 . In this locked position, relative movement between distal links  112  and  114  and between link  114  and shaft  116  is prevented as well. 
     As shown in  FIG. 6 , a sleeve support mechanism  132  extends proximally from shaft  116  to provide sliding support for sleeve  130 . A distal stop  134  provides a limit of distal movement of sleeve  130 ; a similar stop (not shown) is provided on or within handle  106  to limit proximal movement of sleeve  130 . Detents, ridges or other mechanisms may be provided to maintain the sleeve in its proximal or distal positions and to provide tactile feedback to the user regarding the position of the sleeve. 
       FIGS. 7-24  show another embodiment of the invention. Articulatable tool  700  has an end effector  702  at its distal end and an end effector actuator  704  within a handle  706  at its proximal end. Tool  700  may be used, e.g., in a laparoscopic procedure requiring grasping or cutting within a patient. Proximal articulation links  708  and  710  extend distally from handle  706 , and distal articulation links  712  and  714  extend proximally from end effector  702 . Proximal link  708  is connected to and moves with handle  706 . Likewise, distal link  712  is connected to and moves with end effector  702 . An elongated shaft  716  is disposed between the proximal links and the distal links. The linkage between pairs of proximal and distal links may be with cables as in the embodiment of  FIG. 1  or by any other suitable tension bearing members. Likewise, operation of end effector  702  may be as in the  FIG. 1  embodiment. Alternative embodiments of the tool could have as few as a single pair of links, and a single cable set, or multiple pairs of links, and multiple cable sets. In any combination, the articulation lock now described would be appropriate and applicable 
     As in the embodiment of  FIGS. 1-6 , movement of handle  706  and proximal link  708  with respect to proximal link  710  moves end effector  702  and distal link  712  in a relative and corresponding manner. Likewise, movement of proximal link  710  with respect to shaft  716  moves distal link  714  with respect to shaft link  716  in a relative and corresponding manner. Such movements of the distal link, in alternative embodiments, can either reciprocate or mirror the movement of the proximal link, depending on whether the cables are strung directly (for reciprocal movement), or whether they are rotated 180° (for mirrored movement). This relative articulation movement provides a way for a user to remotely manipulate the end effector through movement of the handle. 
     In order to maintain a particular position of the end effector with respect to the shaft, the articulating tool of this embodiment has an articulation lock. In some embodiments of the inventive locking mechanism, as described further below in the “friction locking embodiments” section, the locking mechanism provides a state that lies between free articulation and substantially blocked articulation such that movement can be characterized as being “impeded”. Embodiments of mechanisms or methods described herein thus may also be characterized as mechanisms or methods that relate to permissibility of articulation such that articulation may occur freely, may occur not at all, or may occur in an impeded condition. 
     In the embodiment shown in  FIGS. 7-24 , the articulation lock includes a movable rigid sleeve  730 . In the unlocked position shown in  FIG. 7 , sleeve  730  is distal to proximal links  708  and  710 . In the locked position shown in  FIG. 8 , however, sleeve  730  has been moved proximally to a position adjacent to and covering links  708  and  710  as well as the proximal end of shaft  716 , thereby blocking relative movement between links  708  and  710  and between link  710  and shaft  716 . In this locked position, relative movement between distal links  712  and  714  and between link  714  and shaft  716 , and relative movement of the end effector, are all prevented as well. 
       FIGS. 9-24  show details of a sleeve support mechanism  732  attached to and extending proximally from shaft  716  and its interaction with sleeve  730 . In  FIGS. 9-13 , sleeve  730  is in the unlocked position. In this position, a pair of shoulders  734  that are formed in sleeve  730  abut a corresponding pair of shoulder stops  736  formed on support mechanism  732 . In addition, a pair of detents  738  formed on sleeve  730  is just distal to a corresponding pair of detents  740  formed on sleeve support mechanism  732 , as shown best in the detail view of  FIG. 9 . A central bore  742  provides space for the cables and the rod  125 , as seen for example in  FIG. 4 . The links are proximal to the sleeve support mechanism. The proximal face of the sleeve support part really has ball and socket features in it (not shown). Caroming surfaces  735  on shoulder stops  736  and circumferential space  737  are provided for tool assembly purposes. As sleeve  730  is drawn proximally over sleeve support mechanism  732  during assembly, engagement of a proximal sleeve surface with caroming surfaces  735  to push shoulder stops radially inward into space  737  to permit sleeve  730  to be drawn over the support mechanism. 
     Sleeve has pull tabs  744  to provide a grip for a user to move the sleeve proximally. Push tabs  746  provide a similar function for moving the sleeve distally. In the locked position shown in  FIG. 7 , pull tabs  744  nest with grooves  745  formed in a rotation knob  747  that may, in some embodiments, be used to rotate end effector  702  with respect to handle  706  and to lock the rotational position of the end effector. Further details of such a rotation knob and lock may be found in concurrently filed US patent application “Tool rotation lock” of Hinman and Danitz, This nesting feature is optional with respect to the articulation lock of this invention. 
     When pulled proximally, clearance channels  748  on the inner surface of sleeve  730  permit the sleeve to slide proximally with respect to detents  740 . In addition, anti-rotation channels  750  in sleeve  730  cooperate with anti-rotation ribs  752  in support mechanism  732  to prevent sleeve  730  from rotating as it moves proximally and distally. 
       FIGS. 14-19  show details of the sleeve and sleeve support mechanism of this embodiment in the locked position. As sleeve  730  is drawn proximally to provide the articulation lock, a pair of tabs  754  on sleeve  730  pass through recesses  756  in support mechanism  732  to engage stop shoulders  758 . In addition, as tabs  754  draw toward shoulders  758 , detents  738  on sleeve  730  pass over detents  762  on support mechanism  732  to hold sleeve  730  in the locked position and to provide further tactile feedback about the state of the articulation lock.  FIGS. 20-22  show further views of sleeve  730 , and  FIGS. 23-24  show further views of sleeve support mechanism  732 . 
     Typically, rigid elements lock an articulation mechanism in a single configuration, generally “straight”. Some embodiments of rigid elements may not be “straight” however; as some embodiments may assume a bent or curved configuration that is desirable for a particular application. Thus, as useful as it may be for many applications, rigid element locking, in contrast to malleable locking, is a locking that is typically limited to a single locked configuration. Malleable locking mechanisms, in contrast, provide an ability that rigid elements generally lack, which is to lock an articulating mechanism in any of the various articulated configurations that the mechanism can assume. 
     As will be described further below, other features come with articulating mechanisms that have a locking mechanism based on friction locking, in contrast to the rigid or malleable element locking. This friction-based type of locking allows various locked states that include a substantially blocked movement (like that of rigid element lock embodiments), as well as a partially-impeded movement (similar but not identical to that of malleable element lock embodiments). The motion impedance provided by the friction lock is adjustable or tunable in degree in accordance with the degree to which tension in the mechanism is adjusted. The friction lock embodiments and features are described further in a section below. 
       FIGS. 25 and 26  show a locking rod embodiment of an articulation lock.  FIG. 25A  shows a simple rod  201  aligned to be inserted into an articulating tool  200  with a set  202  of multiple links (15, in this case). Only the proximal portion of the tool is seen, it has no proximal handle, but has a shaft  205 .  FIG. 25A  could represent either a rigid rod or a malleable rod, depending on the nature of the material from which the rod is fabricated.  FIG. 25B  shows the rod as a malleable rod  201 , after insertion into tool  200 , and after the articulating mechanism has been manipulated so as to articulate it. In the present state, the mechanism is locked.  FIG. 25B  also provides a perspective view of the proximal face of the most proximal link  210 , where it can be seen that the rod has entered and occupies a channel  215  in the link, such channel being continuous throughout the links in the mechanism.  FIGS. 26A and 26B  show such a link, from a distal-looking and proximal-looking perspective, respectively. The rod channel  215  is in the form of an open groove; in other embodiments, the channel could be circumferentially closed. 
     It can be seen that the locking rod, whether rigid or malleable, operates by being disposed proximal to each proximal link whose movement it blocks to a point distal to each blocked proximal link. Inasmuch as the illustrated tool embodiment  200  includes 15 links, the rod is disposed proximal to the most proximal link, and extends to a point distal to the distal-most proximal locked link. In some embodiments, a proximal subset of the proximal links may be locked by a rod, leaving the more distal of the proximal links unlocked. The rod does not extend into the distal region of the articulating mechanism; it exerts its locking force only by way of locking the proximal links. The proximal links that are locked by a rod transfer the blockage of their movement to the distal links by way of the tension bearing members connecting them. 
     Friction Locking Embodiments: Locking by Adjusting Tension of Tension Bearing Members 
     Articulation lock embodiments in this section arc generally of a type that involves locking movement between articulating links with friction. Links, as described above, typically occur in proximal-distal pairs that are operably connected to each other by a set of tension bearing members, such as cables. The cables are configured in such a way that movement of the proximal link transfers to the corresponding or complementary distal link of the pair by way of the cables or other tension bearing members. Some embodiments of articulating mechanism to which friction-based locking may be applied include ball and socket links, but other types of links, such as single-degree-of-freedom pivoting links, are also included as embodiments ( FIGS. 45 and 46 ). 
     Friction-based locking mechanisms described herein include a mechanism that adjusts the tension of the tension bearing members. Tension can be increased either by decreasing the length of cables connecting the links while the distance between links remains unchanged, or by increasing the length of the distance between links, while not changing the length of the connecting cables. Each approach is exemplified by embodiments below. 
     In a neutral or unlocked position, the tension of cables is at a baseline level according to specifications appropriate for the mechanism and its application. With increasing tension, as applied by a tension adjusting mechanism, pressure between the links increases, which increases friction between the links, and the friction impedes movement across the interface between the links. Thus, by such locking mechanisms, an articulating mechanism can move from (1) an unlocked state, where links are freely movable, or movable at some baseline level of freedom, to a state (2) where movement between links is partially impeded and wherein the articulation mechanism as a whole is malleable, to a state (3) where movement between links is substantially blocked, and the articulation mechanism as a whole is “seized”. 
     The friction locking mechanisms have other features that distinguish them from rigid- or malleable-element-based mechanisms described above. One feature characteristic of friction locking, per described embodiments, involves a locking process that occurs with substantial uniformity throughout the proximal-to-distal length of the locked portion of the articulating mechanism. (This locking process as a whole differs from the rigid or malleable element-based approaches where the direct locking action of the mechanism occurs in the one or more proximal links, and wherein the tension bearing members transfer that locked state to the distal links, causing them to lock in this secondary manner.) The locked portion of an articulating mechanism need not include the entire length. An inner portion of the length (i.e., a set of link pairs including the more distal of the proximal links and the more proximal of the distal links) may be locked, leaving the outer portion of the length (i.e., a set of link pairs including the more proximal of the proximal links and the more distal of the distal links) free to articulate. For example (referring to  FIG. 4 ) tension could be increased in cable set  120  (which connects links  110  and  114 ) while leaving cable set  118  (which connects links  108  and  112 ) without additional tension beyond baseline. In this case, links  110  and  114  are locked, while  108  and  112  are free to articulate. 
       FIGS. 27-34  show an embodiment of this invention that utilizes a friction-based locking mechanism. As in the above-described embodiments, articulatable tool  800  has an end effector  802  at its distal end and an end effector actuator  804  within a handle  806  at its proximal end. Tool  800  may be used in any of a variety of types of procedures, including for example, laparoscopic procedures that require grasping, cutting, or sealing within a patient; it could further be used percutaneously as a catheter, and in an embodiment that includes a flexible shaft, it could be used in endoscopic procedures. 
     Tool  800  has ball and socket links consisting of proximal active links  808  and  810  separated by a bushing  809 . Proximal link  808  is connected to and moves with handle  806 . A second proximal bushing  811  is disposed between link  810  and an articulation lock (described in more detail below) on the proximal end of the shaft  816 . The bushings have convex surfaces interacting with corresponding concave surfaces on the links  808  and  810  and on the proximal end of the articulation lock. Likewise, distal active links  812  and  814  are separated by a bushing  813 , and a second distal bushing  815  is disposed between the distal end of shaft  816  and active link  814 . Distal link  812  is connected to and moves with end effector  802 . Like their counterparts, spacer links  813  and  815  have convex surface on their ends which interact with corresponding concave surfaces on active links  812  and  814  and on the distal end of shaft  816 . Sets of articulation cables  818  and  820  extend between the proximal and distal active links to control the articulation of the tool. Operation of end effector  802  may be as in the  FIG. 1  embodiment, where movement of end effector actuator  804  moves rod  825  to open and close the end effector jaws. Further details of the types links suitable for use with this invention, such as ball and socket joints, and pivoting single-degree-of freedom joints, or any type of joint where friction affects the movement of links relative to each other, may be found in US 2005/0273084 US 2006/0111209, and US 2006/0111210. 
     As in the other embodiments, movement of handle  806  and proximal link  808  with respect to proximal link  810  moves end effector  802  and distal link  812  in a relative and corresponding manner. Likewise, movement of proximal link  810  with respect to shaft  816  moves distal link  814  with respect to shaft  816  in a relative and corresponding manner. This relative articulation movement provides a way for a user to remotely manipulate the end effector through movement of the handle, as shown in  FIG. 29 . 
     In order to maintain a particular position of the end effector with respect to the shaft, the articulating tool of this embodiment has an articulation lock. In this embodiment, the articulation lock is a mechanism that elongates the tool&#39;s shaft  816  with respect to the articulation cable sets, thereby applying tension to the ball and socket interfaces of the links. This interface tension provides sufficient friction to maintain the orientation of the links with respect to each other, thereby locking the articulating tool and preventing further articulation. It should be appreciated that the tool can be locked in a straight configuration (as shown in  FIG. 27 ) or in a bent configuration (as shown in  FIG. 29 ). 
       FIGS. 30-34  show details of the articulation lock of this embodiment. Right handed threads  832  are formed on the exterior of a shaft extension  817  on the proximal end of shaft  816 . Surrounding the proximal end of shaft extension  817  is a cylindrical sleeve  830  having an internal threaded portion  834  with right handed threads corresponding to threads  832  on shaft extension  817 . Also disposed within the bore of sleeve  830  is a threaded plug  836  with left handed threads corresponding to a second internal threaded portion  838  of sleeve  830  that also has left handed threads. The proximal end of plug  836  has a concave bearing surface  840  that interacts with the convex bearing surface of bushing  811 . 
     In its unlocked position, the articulation lock of this embodiment is rotated clockwise to a position in which the cable sets  818  and  820  are slack enough to permit the active and spacer links to move with respect to each other. To lock or prevent articulation, sleeve  830  is rotated counterclockwise, thereby moving plug  836  and shaft extension  817  away from each other. This elongation of the effective length of the tool applies tension to the cables and forces the convex and concave bearing surfaces of the bushings and links against each other. The friction caused by this tight engagement locks the tool in its articulated position. 
     Ball plunger  842  extends radially inward from sleeve  830  and acts as a detent by extending into a slot  84 , a slot that the ball plunger hits at different axial locations. The slot takes the place of a single hole for the ball of the ball plunger to fall into. In this way, the ball plunger and a single slot can form multiple stop detents at each 360 degree rotation of the sleeve  830 . Multiple ball plungers and slots can be used to increase the resolution of the detents. Counter torque pins  846  are disposed in corresponding holes in the plug and shaft extension, respectively. These pins keep the shaft extension  817  and the plug  836  at the same angular orientation and allow the two components to translate axially with respect to each other when the sleeve  830  is rotated. Further details of the articulation lock are shown in  FIGS. 31-34 .  FIG. 32  shows lumens  850  to permit cable sets  818  and  820  to pass through the shaft extension. Hole  852  ( FIG. 32 ) is the hole that counter torque pins  846  ride in (this hole and the one 180 degrees from it), and  FIG. 34  shows lumens  848  to permit cable sets  818  and  820  to pass through the plug  836  Holes  853  In ( FIG. 34 ) accept the counter torque pins. Call it holes  848  ( FIG. 33 ) are for articulation cables. 
       FIG. 35  is a side exposed view of the proximal portion of a tool  900  with an articulation lock comprising a locking lever  905  and locking wedge  910  fitted into a circular locking groove  920  with ramped surfaces. The groove  920  is formed from the proximal face of proximal link  108  and the distal face of a locking disc  915 . Cables of cable set  118  go through oversize holes in link  108  and are anchored in locking disc  915 . This articulation lock embodiment is of a type that adjusts tension on the cables that connect articulating links, thereby increasing friction between links. The lever  905  is shown in an unlocked position.  FIG. 36  shows the articulation lock mechanism depicted in  FIG. 35 , but in a locked position, to prevent articulation. 
     Locking wedge  910  is narrow at its point of attachment to the lever  905 , flaring outward from its base. Locking groove  920  is wide at its radial base, and narrows as it progresses radially outward. The sloping proximal and distal walls of the groove may be considered ramps; the angles of the ramps complement the angles of the proximal- and distal-facing surfaces of the wedge  910 . Locking disc  915  encircles a proximally-projecting spindle portion  109  of link  108 , and is slidable on that portion. Locking disc  915  is pulled or biased distally by the tension of cables  118 , its distal movement is stopped by a shoulder  925  on the proximal face of link  108 . The effect of the action of the locking lever is to pull the locking wedge  910  radially outward of groove  920 ; in so doing, the wedge  910  pushes the locking disc  915  proximally. As the disc  915  is pushed proximally, it pulls on the cables of cable set  118 , thereby increasing their tension. By this action, the articulation lock is locked. This locking action is variable, according to the degree to which the wedge is pulled out of its groove. 
     In  FIGS. 35 and 36 , the locking lever  905  is bent at the point of pivotable connection  906 . A slot  907  accommodates the linkage to the base of locking wedge  910 . The slot is sufficiently wide to accommodate movement of wedge distally and proximally, as it moves according to the relative proximal-distal position of the wedge. The locking lever  905  depicted here is a mere example of any number of mechanisms that could controllably and reversibly move the wedge  910 . The lever as depicted has no tine to fix the locking lever in any position, but many mechanisms are known to fix the position of the lock. A ratchet mechanism, for example, could provide a variable level of locking tension in the cables, such that the mechanism could be fixed in a malleable condition. In another variation, the angle of the locking wedge  910  could be shallow enough such that the locking mechanism, when locked, stays in place due to friction between the locking wedge  910  and the walls of the grove  920 . In other words, the angle between the mating components could be shallow enough that the tension in the cables could not back-drive the mechanism. In this case, the locking lever  905  would need to be pushed upward to unlock the mechanism. 
       FIG. 37  is a side exposed view of the proximal portion of a tool  1000  with an articulation lock mechanism comprising a cylindrical locking sleeve  1030  with a translating locking disc  1015  connected to tension bearing members. This articulation lock embodiment is of a type that adjusts tension on tension bearing members that connect articulating links, thereby increasing friction between links. Locking sleeve  1030  is rotatable around proximal link  1108 ; the sleeve has an internal threaded portion which mates with external threads of locking disc  1015 , moving the disc proximally and distally depending on the direction the locking sleeve is turned. Locking disc  1015  encircles a proximally-projecting spindle portion  1109  of link  108 , and is slidable on that portion. Locking disc  10515  is pulled or biased distally by the tension of cables  1036 , its distal movement is stopped by a shoulder  1125  on the proximal face of link  1108 . A slot  1032  in the sleeve mates with a flange  1034  in link  1108  to prevent translating movement either proximally or distally, as the sleeve is rotated. As the proximal-distal position of the sleeve is thus fixed, rotational translation force is imparted to the locking disc  1015 , which due to its connection to the cables  1036 , thereby adjusts the tension on the cables. Counter torque pins (not shown) similar to counter torque pins  818  in  FIG. 30  could be provided to prevent the locking disk  1015  from rotating when the locking sleeve  1030  is rotated. 
     The mechanism is shown in an unlocked position in  FIG. 37 , and in locked position in  FIG. 38 , where the locking disc  1015  can be seen to have moved to a more proximal position. By moving proximally with the cables attached, the cables have thus accumulated a higher level of tension. 
     The particular embodiment shown in  FIGS. 37 and 38  shows a set of three proximal links and a single set of cables. This number of links and number of cable sets is only an example of combinations of links and cable sets to which friction based articulation locking mechanisms, per embodiments described herein may be applied. Articulation locks of all types described herein may be applied to embodiments without limitation to the number of links and without regard to the number of cable sets, connecting the links, nor to the number of cables in the sets. Further, articulation locks that are friction-based, can be applied to any articulating mechanism that makes use of links whereby an increase in the tension of cables connecting the links causes an increase in friction as the surfaces of articulating links as they move relative to or across each other. 
       FIG. 39  is an exposed side view of the proximal portion of a tool  1100  with an articulation lock comprising a locking mechanism comprising a locking disc  1115  and with a side-mounted locking lever  1105 , the mechanism located proximal to the proximal link This particular embodiment has only one pair of links and one set of tension bearing members. As with the previously described embodiment the cables  1103  of the cable set slip through proximal link  108  and terminate in the locking disk  1115 . Adjusting the relative proximal-distal position of the locking disc through the action of the lever  1105 , thus adjusts tension on the cables. A tine  1110  on the handle secures the lever in the locked position (compare  FIGS. 39 and 40 ). The tine  1110  is but one of many mechanisms that could secure such a lever, other embodiments include, for example, a rack of teeth such that the lever could be held at various positions, thereby creating various levels of tension in the cables, and thereby, in a mid-position, fixing the articulation mechanism in a malleable state. 
     The mechanism of  FIG. 39  is shown in an unlocked position.  FIG. 40  shows the articulation lock mechanism depicted in  FIG. 39 , but in a locked position, to prevent articulation. In terms of the nature of this embodiment in general terms, this articulation lock embodiment is of a type that adjusts tension on tension bearing members that connect articulating links, thereby adjusting the amount of friction between links. In some embodiments, a locking disc (like disc  115 ) can be integrated into a link  110  (see  FIGS. 1-4  for reference). In such a configuration inner links  110  and  114  can be locked, while outer links  108  and  112  remain free to articulate. 
       FIG. 41  is a side view of a tool  1100  with cam-based articulation locking mechanism that is located between proximal and distal links. This articulation lock embodiment is of a general type that adjusts tension on the tension bearing members that connect articulating links, thereby increasing friction between links. In this embodiment, the link tension is adjusted by varying the effective length of the shaft, and more specifically, shaft length is varied by a cam mechanism  1210 . The lever is shown in an unlocked position, thereby allowing articulation. 
       FIG. 42  is a detail view of the cam lock of  FIG. 41 . ( 42 A) a locked position, and ( 42 B) an unlocked position. The detailed views of  FIG. 42  emphasize the difference in relative location of the telescoping shaft components in the two positions.  FIG. 42  provides a detail of cam mechanism  1210 , which comprises three main components, a cam lever  1212 , an inner shaft component  1214 , and an outer telescoping shaft component  1215 . The cam lever  1212  comprises a cam surface  1213  that rotates across the surface of flange  1216 , a portion of the inner telescoping shaft component  1214 . As the cam lever  1212  moves from an unlocked position to a locked position, the camming action forces the outer telescoping shaft component  1215  forward with respect to the inner shaft component  1214 , thereby lengthening the shaft. While the length of the shaft increases, the distance between the termination points of the cables in the links at the proximal and distal ends of the articulating mechanism increases, thereby increasing tension on the cables. As described above, increased tension in the cables is distributed through the length of the cable, increasing the friction associated with movement across the abutting surfaces of links on the proximal and distal ends of the articulating mechanism. Such friction impedes link-link movement to a degree that varies between converting free movement to malleable movement, to a seizure that substantially prevents movement. 
       FIG. 43  is a perspective view of tool  1300  with an articulating mechanism configured as a liver retractor, with a cam-based articulation locking mechanism  1310  that is located between proximal and distal links:  43 A shows the locking mechanism in the unlocked position;  43 B shows the locking mechanism in the locked position. The locking mechanism and its operation are substantially the same as described in the preceding embodiment. This embodiment has no other specific end effector; the mechanism itself serves as the engaging portion of the tool. This embodiment provides an example of a tool wherein the articulating mechanism itself, to which the inventive articulation lock is applied, is the functional portion of the tool, not a dedicated end effector Embodiments of the articulation locks disclosed in this present application may thus be appropriately fitted into devices such as the one shown in  FIG. 43  as well as into many other similar devices such as those disclosed in detail in U.S. Pat. No. 7,090,637 which is hereby incorporated by this reference. 
       FIG. 44  is a perspective view of an articulating sheath device  1400  with an articulation lock in the form of a cylindrical rotating sleeve mechanism  1410  comprising an internal threaded portion (not shown in this surface view) located between proximal and distal links. This type of device can make use of any of the articulation lock embodiments described herein; the particular embodiment described herein is provided by way of example as to how such locks may be applied. This articulation lock embodiment is of a type that adjusts tension on the tension bearing members that connect articulating links, in this embodiment it increases tension by making the shaft  1412  longer, thereby increasing friction between links. In the embodiment depicted, the shaft  1412  is rigid, but in other embodiments it may be flexible. The proximal portion of the device  1400  comprises a handle  1415 , and emerging from the proximal portion of the handle is a set of proximal links  1420  that correspond to a distal set of articulating links  1421 , emerging from the shaft  1412 . The handle further comprises an entry port  1424  for a flexible endoscopic tool or flexible endoscope  1425 , which is shown in the figure adjacent to the entry port  1424  and also emerging from the distal portion of the articulating sheath. The articulating links  1420  and  1421  are shown in greater detail in  FIGS. 45 and 46 , and described further below. 
     Embodiments of the inventive friction-based articulation locks described herein may be applied to articulating mechanisms that utilize any type of link that has a surface-to-surface relative motion with a neighboring link. Ball and socket type links represent one example; other types of links appropriate for embodiments of the articulation lock mechanism described herein include U.S. published patent applications. US2005/0273084, US2006/0111616, US2006/0111209, and US2006/0111210, all of which are hereby incorporated by this reference. 
       FIG. 45  shows a set of pivoting-hinge type links  1500 . In ( 45 A) the top two links are in pivoted in an articulated configuration, each one tipped at a hinge point where it has a single degree of freedom, and in ( 45 B) all links are in a straight, unarticulated position.  FIG. 45  shows a series of cable holes  1505  arrayed around the circumference of the rim of the link, and a large central bore  1510  The radial central bore can accommodate other instruments, or components of an instrument that control an end effector, or for electrical wires, or for lasers or fiber optical instruments. These pivoting-hinge type links are similar to the flex-hinge type of links described in U.S. patent application Ser. No. 10/948,911, except for differences in specifics of the hinge (pivoting vs. flex). These pivoting hinge joints have one degree of freedom, and thereby differ from ball and socket joints, which have two degrees of freedom. 
     Important for the articulation locking is that each link is connected to its adjacent link by a connection whose movement can be impeded by an axial load applied by increasing tension in the cables on which the links are strung. The impeding of movement can be either of a modest type, in which the link movement becomes malleable, creating a mechanism as a whole that is malleable, or the movement can be substantially blocked or seized up when a sufficient axial load is applied. When movement of links is substantially prevented, the mechanism as a whole becomes locked in configuration, whether the mechanism is straight or articulated. 
     While the inventive surgical instruments and devices have been described in some detail by way of illustration, such illustration is for purposes of clarity of understanding only. It will be readily apparent to those of ordinary skill and in the art in light of the teachings herein that certain changes and modifications may be made thereto without departing from the spirit and scope of the appended claims. For example, while the articulation mechanism and articulation lock embodiments described in here have typically been in the context of tools with an articulating mechanism comprising at least two links, the mechanisms may be used in an instrument comprising only a single link, a multiplicity of links, and with any number of cables or cable sets operably connecting the links. Further, the articulating mechanisms may be used in the absence of many features commonly associated with some articulatable instruments, such as handles, shafts, rotatability features, and dedicated end effectors. Finally, while the context of the invention is considered to be surgical or medical diagnostic procedures, the articulation locking mechanisms or tool having such mechanisms may have utility in other non-medical contexts as well.