Patent Publication Number: US-2021177534-A1

Title: Reusable surgical instrument with single-use tip and integrated tip cover

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/911,233, filed Feb. 9, 2016, which is the U.S. national phase of International Application No. PCT/US2014/051098, filed Aug. 14, 2014, which designated the U.S., and which claims priority to and the benefit of U.S. Patent Application No. 61/866,127, (filed Aug. 15, 2013, disclosing “REUSABLE SURGICAL INSTRUMENT WITH SINGLE-USE TIP AND INTEGRATED TIP COVER,” by William J. Park), each of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates generally to surgical instruments, and more particularly to surgical instruments including reusable and disposable components. 
     Description of Related Art 
     Robotically controlled surgical instruments are often used in minimally invasive medical procedures. (As used herein, the terms “robot” or “robotically” and the like include teleoperation or telerobotic aspects.) The surgical instruments are wholly reusable or wholly disposable. 
     Such surgical instruments typically include an end effector. Examples of end effectors include a tool such as forceps, a cutting tool, or a cauterizing tool. An end effector assembly including the end effector typically is mounted on a wrist mechanism at the distal end of a main tube of the instrument. 
     During a medical procedure, the end effector assembly and the distal end of the main tube can be inserted directly or through a cannula into a small incision or a natural orifice of a patient to position the end effector at a surgical site within the patient. The wrist mechanism is used to position, orient, and move the end effector when performing the desired procedure at the surgical site. Tendons, e.g., cables or similar structures, extending through the main tube of the instrument typically connect the wrist mechanism to a transmission or backend mechanism that typically is motor driven in response to a doctor&#39;s instructions provided via a master control system. The reusable surgical instruments employed during minimally invasive medical procedures are generally complex mechanical devices having many separate components (e.g., cables and mechanical members). 
     SUMMARY 
     In one aspect, an apparatus includes a disposable surgical instrument tip assembly, sometimes referred to as a disposable tip assembly. The disposable tip assembly includes a locking tip cover, an end effector assembly, and an actuator rod assembly. The actuator rod assembly is coupled to the end effector assembly. 
     In one aspect, the combination of the end effector assembly and the actuator rod assembly is installed on a tip interface at a distal end of a reusable instrument portion. After the combination is installed, the locking tip cover is installed on the end effector assembly and locked to the tip interface. In another aspect, the locking tip cover is installed on the combination of the end effector assembly and the actuator rod assembly to form a single assembly. This single assembly is then installed on the tip interface at the distal end of the reusable instrument portion. Thus, in the first example, the locking tip cover is not preinstalled and in the second example, the locking tip cover is preinstalled. 
     The locking tip cover includes an external cover and a locking device. The external cover has a proximal end portion and a distal end. The locking device is mounted inside the proximal end portion of the external cover. The locking device has an inner wall that defines a central lumen. 
     The end effector assembly includes an end-effector body assembly and an end effector. The end effector is coupled to the end-effector body assembly. The end-effector body assembly is enclosed within the external cover, when the external cover is installed. When the external cover is first placed over the end-effector assembly, the end-effector body assembly is mounted in the central lumen of the locking device so that the locking device has two degrees of freedom relative to the end-effector body assembly. 
     The actuator rod assembly is connected to the end effector assembly. The actuator rod assembly includes a first quick connect/disconnect element at a proximal end of the actuator rod assembly. 
     In one aspect, the end effector is a blade set. In this aspect, the end-effector body assembly is a clevis. The blade set is monopolar-curved scissors, in one embodiment. 
     In another aspect, the apparatus includes a reusable surgical instrument. The reusable surgical instrument includes a distal end portion comprising a tip interface. 
     The tip interface includes an instrument tip and a grip actuator element. The instrument tip includes a distal end, a lock interface element, and a central lumen. The grip actuator element is positioned in the central lumen of the instrument tip. The grip actuator element includes a second quick connect/disconnect element. The second quick connect/disconnect element is configured to mate with the first quick connect/disconnect element. In one aspect, the first quick connect/disconnect element comprises a ball, and the second quick connect/disconnect element comprises a socket configured to receive the ball. 
     The reusable surgical instrument also includes a tendon having a first end coupled to the second quick connect/disconnect element. The reusable surgical instrument further includes a push-pull drive assembly coupled to a second end of the tendon. In a first state, the push-pull drive assembly applies a first force to the tendon to move the second quick connect/disconnect element to a first location. The first location is distal to the distal end of the instrument tip. In a second state, push-pull drive assembly applies a second force to the tendon to move the second quick connect/disconnect element from the first location to a second location. In the second location, the second quick connect/disconnect element is positioned within the central lumen of the instrument tip. 
     In one aspect, the tip interface further includes a seal mounted on a proximal end the instrument tip. In another aspect, the tip interface includes a seal mounted on an outer circumferential surface of the grip actuator element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a surgical system that includes a surgical instrument with a reusable instrument portion and a disposable instrument tip assembly. 
         FIG. 2  is an illustration of a first aspect of a reusable instrument portion and a disposable instrument tip assembly. 
         FIG. 3  is an illustration of a second aspect of a reusable instrument portion and a disposable instrument tip assembly. 
         FIG. 4A  is an illustration of the initial step in attaching a disposable instrument tip assembly to a reusable instrument portion. 
         FIG. 4B  is a cutaway view of the apparatus of  FIG. 4A . 
         FIG. 5A  is an illustration of a second stage in attaching a disposable instrument tip assembly to a reusable instrument portion. 
         FIG. 5B  is a cutaway view of the apparatus of  FIG. 5A . 
         FIG. 6A  is an illustration of a third stage in attaching a disposable instrument tip assembly to a reusable instrument portion. 
         FIG. 6B  is a cutaway view of the apparatus of  FIG. 6A . 
         FIG. 7A  is an illustration of a fourth stage in attaching a disposable instrument tip assembly to a reusable instrument portion. 
         FIG. 7B  is a cutaway view of the apparatus of  FIG. 7A . 
         FIG. 7C  is an illustration of the apparatus in  FIG. 7A  with the external cover removed. 
         FIG. 7D  is an end view of the locking device of  FIG. 4A  from the proximal direction. 
         FIG. 8  is a cutaway view of the apparatus of  FIG. 2 . 
         FIG. 9A  is an illustration the configuration of a disposable instrument tip assembly and a reusable instrument portion during use. 
         FIG. 9B  is a cutaway view of the apparatus of  FIG. 9A . 
         FIGS. 10A to 10D  are cutaway illustrations of stages in attaching a disposable instrument tip assembly to a reusable instrument portion. 
         FIG. 11  is an illustration of a push-pull drive assembly. 
     
    
    
     In the drawings, for single digit figure numbers, the first digit in the reference numeral of an element is the number of the figure in which that element first appears. For double-digit figure numbers, the first two digits in the reference numeral of an element is the number of the figure in which that element first appears. 
     DETAILED DESCRIPTION 
     In accordance with an aspect of the invention, a surgical system  100  ( FIG. 1 ) includes a plurality of surgical instruments  101 ,  102 ,  103 . Surgical instrument  103  includes a reusable instrument portion  104  and a disposable surgical instrument tip assembly  105 , sometimes referred to as disposable tip assembly  105 . Disposable tip assembly  105  includes an end effector assembly that in turn includes an end effector such as a clamp, a grasper, scissors, a clip applier, or a needle holder. 
     In one aspect, disposable tip assembly  105  includes a locking tip cover that locks disposable tip assembly  105  to reusable instrument portion  104 . In.  FIG. 1 , disposable tip assembly  105  is mounted on and locked to a tip interface at a distal end of reusable instrument portion  104 . In  FIG. 1 , the distal direction is towards the end of a surgical instrument where disposable tip assembly  105  is mounted and the proximal direction is towards backend mechanism  120 . 
     To facilitate mounting disposable tip assembly  105  on the tip interface of reusable instrument portion  104 , disposable tip assembly  105  includes a first quick connect/disconnect element and the tip interface includes a second quick connect/disconnect element. The second quick connect/disconnect element is coupled to a tendon. The tendon is also coupled to an actuator assembly that provides forces that push and pull (push/pull) the tendon. 
     As explained more completely below, the tendon pushes second quick connect/disconnect element beyond the distal end of the tip interface. The first quick connect/disconnect element is coupled to, e.g., mated with the exposed second connect/disconnect element. Then, the tendon pulls the mated pair of elements into a channel, sometimes referred to as a central lumen, in the tip interface. 
     Next, the locking tip cover is moved proximally until a stop is reached and then the locking tip cover is locked to the tip interface, e.g., the tip cover is rotated with respect to the tip interface. In one aspect, the locking tip cover includes two parts, an external cover and a locking device. The locking device is positioned within a proximal portion of the external cover. 
     In one aspect, the combination of the end effector assembly and the actuator rod assembly is installed on the tip interface at a distal end of a reusable instrument portion. After the combination is installed, the locking tip cover is installed on the end effector assembly and locked to the tip interface. In another aspect, the locking tip cover is installed on the combination of end effector assembly and the actuator rod assembly to form a single assembly. This single assembly is then installed on the tip interface at the distal end of the reusable instrument portion. Thus, in the first example, the locking tip cover is not preinstalled and in the second example, the locking tip cover is preinstalled. 
     In another aspect, the locking tip cover is a single component. For example, the external cover is not used and so the locking tip cover is the locking device. As described below, the external cover provides electrical isolation in one aspect. If the electrical isolation is not needed, only the locking device could be used as the locking tip cover. In another example, the locking tip cover is a single integral component—a one-piece component—that provides both the external cover functionality and the locking device functionality. 
     An end effector assembly includes an end-effector body assembly and an end effector. The end effector is coupled to the end-effector body assembly. The end-effector body assembly is enclosed within the external cover. The end-effector body assembly is mounted in a central lumen of the locking device so that the locking device has two degrees of freedom relative to the end-effector body assembly. 
     The disposable tip assembly also includes an actuator rod assembly connected to the end effector assembly. The actuator rod assembly includes the first quick connect/disconnect element at a proximal end of the actuator rod assembly. 
     The mating of the first quick connect/disconnect element of disposable tip assembly  105  with the second quick connect/disconnect element of the tip interface establishes a mechanical connection between the end effector and an actuator drive assembly. The actuator drive assembly generates forces that push/pull the tendon connected to the second quick connect/disconnect element. Also, in aspects where a voltage is applied to the end effector, the mated quick connect/disconnect elements provide an electrical path between the end effector and a supply voltage. 
     The external cover of disposable tip assembly  105  combined with an internal seal seals any fluids that enter the assembly within the assembly. This prevents a fluid path from an electrically energized portion of disposable tip assembly  105  from reaching the patient along an unintended route and prevents the fluids from reaching other parts of the surgical instrument. Also, the external cover provides electrical isolation, for the portions of the assembly not intended to supply energy, when a voltage is applied to the end effector. 
     A wholly reusable surgical instrument with monopolar-curved scissors is one of the most highly utilized robotic surgical instrument types. A voltage is applied to the curved scissors. 
     Unfortunately, the cutting performance of reusable monopolar-curved scissors is not as good as single-use laparoscopic instruments, primarily because the current density through the sharp blade edge dulls the blade. As a result, the sharpness of the blade declines over the life of the reusable instrument. The maximum life of the reusable instrument can be driven by the ability to maintain a sharp blade. 
     In one aspect, a surgical instrument  103  includes a disposable tip assembly  105  that in turn includes a disposable blade set. In one aspect, disposable tip assembly  105  is used for a single procedure and then disposed, e.g., assembly  105  is a single use disposable tip assembly. 
     However, in some situations, the disposable blade set may perform satisfactorily for more than a single procedure. In such situations, disposable tip assembly  105  may be used for more than one procedure if after each procedure the tip assembly is properly cleaned and sterilized. When disposable tip assembly  105  is used for more than one procedure, a new tip cover is used in each procedure. In this multi-use application, disposable tip assembly  105  is used until performance of the blade set is unsatisfactory to the surgeon and then is removed from reusable surgical instrument portion  104  and discarded. 
     Disposable tip assembly  105  not only provides the user with sharp blades, but also extends the life of reusable instrument portion  104 . No longer must the reusable part of surgical instrument  103  be discarded when the blade set becomes dull. Thus, the use of disposable tip assembly  105  may reduce the cost per procedure for surgical instrument  103  because portion  104  can be used in more procedures than the equivalent wholly reusable surgical instrument. The incremental cost of disposable tip assembly  105  may be offset by the extended life of the reusable instrument portion  104 . 
     As described more completely below, disposable tip assembly  105  with a disposable blade set is quickly and easily installed on and uninstalled from reusable instrument portion  104  using the quick connect/disconnect elements. The quick connection and disconnection enables efficient user workflow independent of whether the locking tip cover is preinstalled. 
     Also as described more completely below, an integrated tip cover fastens disposable tip assembly  105  onto reusable instrument portion  104  and ensures that cautery energy is only applied by the intended portions of the blades. This also simplifies the user workflow and reduces cost by minimizing the number of components in disposable tip assembly  105 . This advantage is applicable independent of whether the locking tip cover is preinstalled. 
     In one aspect, system  100  is the da Vinci® Surgical System commercialized by Intuitive Surgical, Inc. Each surgical instrument in the plurality of surgical instruments  101 ,  102 , and  103  is mounted on a docking port on a manipulator arm  111 ,  112 , and  113 , respectively. The docking ports of system  100  generally include drive motors that provide mechanical power for operation of instruments  101 ,  102 ,  103 . These drive motors are sometimes referred to as an actuator drive assembly. Each docking port may additionally each include an electrical interface for communication with the instrument mounted on that docketing port. 
     System  100  is illustrative only and is not intended to be limiting to this specific implementation. For example, disposable tip assembly  105  can also be used on surgical instruments in a teleoperated surgical system with a single entry port, which has a system configuration different from that illustrated in  FIG. 1 . 
     Using surgical instrument  103  as an example, reusable instrument portion  104  includes a transmission or backend mechanism  120 , a main tube  130  extending from the backend mechanism  120 , and a wrist mechanism  140  at the distal end of main tube  130 . Disposable tip assembly  105  is coupled to wrist mechanism  140 . 
     Surgical instrument  103  is also illustrative and is not intended to be limiting. For example, a parallel motion mechanism could be included between the distal end of main tube  130  and wrist mechanism  140 . 
     Drive cables or tendons and electrical conductors that are connected to wrist mechanism  140  extend through main tube  130  and connect to backend mechanism  120 . Backend mechanism  120  typically provides a mechanical coupling of the drive tendons to drive motors in system  100 . System  100  can thus control movement and tension in the tendons as needed to move or position wrist mechanism  140  and to operate an end effector in disposable tip assembly  105 . 
     In the example of  FIG. 1 , a camera system  150  is similarly mounted on a manipulator arm of system  100 . The views from camera system  150 , which maybe stereoscopic or three-dimensional, are viewed at a master control console (not shown). A processing system of system  100  provides a user interface enabling a doctor or other medical personnel to see and manipulate camera system  150  and instruments  101 ,  102 , and  103 . 
     For example, an arm  113  can be used to insert the end of surgical instrument  103  through a cannula in a small incision in a patient undergoing a medical procedure. Alternatively, in a single port system, surgical instrument  103  is inserted through a channel in an entry guide mounted in a cannula. Backend mechanism  120  is used to operate wrist mechanism  140  and the end effector at the surgical site inside the patient. The diameter or diameters of main tube  130 , wrist mechanism  140 , and disposable tip assembly  105  are generally selected according to the size of the cannula with which instrument  103  is used, and in an exemplary embodiment, wrist mechanism  140  and main tube  130  are about 4 mm, 5 mm, or 8 mm in diameter to match the sizes of some existing cannula systems. 
       FIG. 2  illustrates in more detail one aspect of a distal end of a reusable surgical instrument  203  that includes a reusable instrument portion  204  and a disposable tip assembly  205  affixed to portion  204 . Reusable instrument portion  204  includes a main tube  230  having a distal end coupled to a wrist  240 . The distal end of wrist  240  is coupled to a tip interface  245 . Arrow  290  shows the proximal direction and the distal direction with respect to reusable surgical instrument  203 . 
     Disposable tip assembly  205  is mounted on and connected to tip interface  245 , e.g., affixed to reusable instrument portion  204  in this aspect. Disposable tip assembly  205  includes a disposable blade assembly  206 . Use of a blade assembly with blades as the end effector is illustrative only and is not intended to be limiting to this specific end effector. In view of this disclosure, one knowledgeable in the field can implement an end effector assembly of the person&#39;s choice in the disposable tip assembly described herein. 
     Only a part of tip interface  245  is visible in  FIG. 2 . The remainder of tip interface  245  is contained within disposable tip assembly  205 . 
     In one aspect, disposable tip assembly  205  is a single use assembly. However, as described above for disposable tip assembly  105  in other aspects, disposable tip assembly  205  may be used in a limited number of surgical procedures, i.e., until the performance of the element is unsatisfactory, and then discarded. In the multiple use aspect of disposable tip assembly  205 , a new tip cover is used in each surgical procedure and the other parts of disposable tip assembly  205  are properly cleaned and sterilized. Independent of whether disposable tip assembly  205  is used in a single surgical procedure or in a few surgical procedures, the lifetime of disposable tip assembly  205  is less than the lifetime of the wrist and shaft, for example, of the surgical instrument and so is disposable relative to the surgical instrument. 
     Tip interface  245  and disposable tip assembly  205  are designed to minimize the longitudinal length distal to the last joint in wrist  240 . In addition, as explained more completely below, tip interface  245  and disposable tip assembly  205  are designed to permit easy connection and disconnection of tip interface  245  to disposable tip assembly  205 . In addition, the combination of tip interface  245  and disposable tip assembly  205  provides electrical isolation for any voltage that is applied to a blade in disposable blade assembly  206 . This combination of tip interface  245  and disposable tip assembly  205  also seals any electrically energized fluid created by such a voltage within the combination so that the electrically “hot” fluid does not contact the patient in an unintended manner and does not flow proximally into reusable instrument portion  204 . 
     Disposable tip assembly  205  makes at least a mechanical connection to surgical instrument  203  via tip interface  245 . In some aspects, an electrical connection is also made. A first mechanical connection is made between a mechanical actuator rod assembly in disposable tip assembly  205  and a grip actuator element in tip interface  245 . When the mechanical connection is made, in one aspect, an electrical connection also is established between a blade in blade assembly  206  and an electrical connector in the backend mechanism of surgical instrument  203  so that a voltage can be applied to the blade, e.g., about 3000 volts. Finally, a lockable mechanical connection locks disposable tip assembly  205  to tip interface  245  so that disposable tip assembly  205  is affixed to tip interface  245 . 
     In one aspect, the lockable mechanical connection is a partial rotation connection, e.g., disposable tip assembly is mounted on tip interface  245  and then rotated a quarter of a turn to lock disposable tip assembly  205  to tip interface  245 . An example of such a partial rotation connection is a bayonet connection. In another aspect, the lockable mechanical connection is implemented using threads on disposable tip assembly  205  and tip interface  245 . The mechanical connection is referred to as lockable, because when disposable tip assembly  205  is affixed to tip interface  245 , blade assembly  206  is locked in place and is ready for use. 
     In  FIG. 2 , at the proximal end of tip interface  245  are two ribs  245 R 1 ,  245 R 2  that extend radially outward from the outer surface of tip interface  245 . Ribs  245 R 1 ,  245 R 2  are optional. When a sheath is used over wrist mechanism  240 , the distal end of the sheath forms a seal with ribs  245 R 1 ,  245 R 2 . Also, in one aspect, pins are inserted through two openings  2450 P in the proximal end of tip interface  245  in attaching wrist mechanism  240  to tip interface  245 . 
       FIG. 3  illustrates another aspect of a disposable tip assembly  305  that is configured to be mounted on and connected to a tip interface  345 . Tip interface  345  is connectable to a wrist or other element of a reusable surgical instrument such as that shown in  FIGS. 1 and 2 . Arrow  390  shows the proximal direction and the distal direction with respect to disposable tip assembly  305 . 
     Disposable tip assembly  305  includes a disposable blade assembly  306 , a locking tip cover  310 , and an actuator rod assembly  308  (see  FIGS. 10A to 10D ). As explained more completely below, disposable blade assembly  306  includes a pair of blades, a clevis  307 , and a pin  307 P. 
     Also, as explained more completely below, in one aspect locking tip cover  310  includes two parts, an external cover  311  and a locking device  312 . In  FIG. 3 , external cover  311  has been made transparent to permit viewing the parts contained within external cover  311 . This for ease of illustration only and is not intended to imply that external cover  311  is or must be transparent. 
     In this aspect, locking device  312  has a cylindrical outer surface and threads  312 T formed in inner proximal surface. In one aspect, locking device  312  is a nut that is free to rotate on clevis  307 . Locking device  312  is made from a non-electrically conductive rigid material. 
     External cover  311  is made from a non-conductive flexible material, like silicone or a flexible, medical grade thermoplastic elastomer. An example of a thermoplastic elastomer is Pellethane® polyurethane thermoplastic elastomer provided by The Upjohn Company. (Pellethane® is a U.S. registered trademark of The Upjohn Company of Kalamazoo, Mich.). 
     The non-conductive flexible material is either overmolded or bonded into place, and the non-conductive flexible material acts as an insulation barrier covering portions of an active electrode not intended for patient contact. This material is flexible to allow for opening and closing of the blades. The proximal end of external cover  311  also has a feature that acts as a fluid seal, preventing electrically hot fluids from contacting the patient in an unintended location. 
     The mechanical actuation of disposable blade assembly  306  is provided through a ball and socket interface, which is an example of a quick connect/disconnect interface. A ball  309  on the proximal end of actuator rod  308 R fits into a socket  347  that is located at the distal end of a grip actuator element  346 . Ball  309  and socket  347  are examples of a first quick connect/disconnect element and a second quick connect/disconnect element, respectively. The use of ball  309  and socket  347  is illustrative only and is not intended to be limiting. In view of this disclosure, one knowledgeable in the field can implement a quick connect/disconnect interface with two elements that provide the connect/disconnect functionality described herein while preserving the other features associated with quick connect/disconnect interface, e.g., a cylinder with filleted edges. 
     One aspect of the connect/disconnect interface is that the interface has a rotational degree of freedom, e.g., ball  309  can rotated in socket  347 . As main tube  230  is rolled, the tendon connected to the connect/disconnect interface is fixed at the proximal end. The rotational degree of freedom of the connect/disconnect interface allows reduction of the torsional stiffness of the tendon compared to a tendon connected to an interface that did not have a rotational degree of freedom. 
     Grip actuator element  346  is positioned in and slides longitudinally in a lumen of instrument tip  348  and is coupled to a tendon  352 . A wrist-disposable tip adapter  350  is affixed to the proximal end of instrument tip  348 . A seal (not visible in  FIG. 3 ) is positioned between the proximal end of instrument tip  348  and wrist-disposable tip adapter  350 . The seal isolates the wrist and main tube from electrically “hot” fluid that might otherwise pass through disposable tip assembly  305  into a central lumen of instrument tip  348 . Tendon  352  passes through a guide (not shown) that is mounted in a central lumen at the proximal end of wrist-disposable tip adapter  350 . In one aspect, the guide is implemented as a flexible bushing. Tendon  352  passes through a wrist and so is flexible. 
     The distal end of instrument tip  348  includes an orientation alignment feature, in this example, a flat surface  349 A. A corresponding orientation alignment feature is provided in the proximal end of clevis  307 . The two orientation alignment features mate such that when instrument tip  348  is affixed to disposable tip assembly  305 , disposable tip assembly  305  is properly oriented on the reusable surgical instrument portion. 
     The use of a single flat surface is illustrative only and is not intended to be limiting. In another aspect two opposed flat surfaces are used as the orientation alignment features. The particular alignment features used depends on the characteristics of the end effector of the disposable tip. For monopolar-curved shears, a single flat surface is used, because the end effector is asymmetric and needs to be installed in a unique orientation. If the end effector could be installed in one of two orientations, two opposed flat surfaces could be used as the orientation alignment features. In view of this disclosure, those knowledgeable in the field can use any orientation alignment features that provide the functionality described herein with respect to the orientation alignment features. 
     Instrument tip  348  also has a lock interface element, e.g., threads  348 T on the outer surface that mate with threads  312 T. The threads are used to lock disposable tip assembly  305  to tip interface  345 . 
       FIGS. 4A, 5A, 6A, 7A, and 9A  illustrate connecting disposable tip assembly  205  to reusable instrument portion  204 .  FIGS. 4B, 5B, 6B, 7B, 8, and 9B  are cross-sectional drawings of the elements in  FIGS. 4A, 5A, 6A, 7A, 2, and 9A , respectively. 
     In  FIG. 4A , disposable tip assembly  205  is positioned for connection to reusable instrument portion  204 .  FIG. 4B  is the corresponding cross-sectional view. Grip actuator element  446  has been pushed out of a lumen  457  in instrument tip  448  so that socket  447  is positioned distally of the distal end of instrument tip  448 . In  FIGS. 4A and 4B , the distal direction is towards the tips of blades  406 B 1  and  406 B 2  in disposable blade assembly  206  and the proximal direction is towards the backend mechanism of surgical instrument  203  as show by arrow  490 . In one aspect, grip actuator element  446  is moved about 0.18 inches (4.5 mm) from a normal closed position of grip actuator element  446  (see  FIGS. 2 and 8 ) to receive ball  409  of disposable tip assembly  205 . 
     A shown in  FIG. 4B , disposable blade assembly  206  includes two blades  406 B 1  and  406 B 2  that are connected to clevis  407  by a first pin  407 P. A second pin  408 P of actuator rod assembly  408  is positioned in a slot in the proximal ends of blades  406 B 1  and  406 B 2 . Pin  408 P is moved in the slot to actuate the blades. In one aspect, second pin  408 P passes through and floats in a distal end of a solid cylindrical rod  408 R in actuator rod assembly  408 . 
     In one aspect, blades  406 B 1  and  406 B 2  are monopolar-curved blades that are made of 17-4 PH stainless steel conditioned to H 900 , which is referred to herein as 17-4 stainless steel. In one aspect, blades  406 B 1  and  406 B 2  are formed using electrical discharge machining (EDM). In another aspect, blades  406 B 1  and  406 B 2  are stamped out of 301 stainless steel. 
     Blades  406 B 1  and  406 B 2  are thin, e.g., have thicknesses of about 0.020 inches (0.5 mm). The cutting surface of blades  406 B 1  and  406 B 2  has a length of about 0.35 inches (8.9 mm) exposed cutting surface when open in one aspect. In this aspect, the length of the blade from the distal end to clevis pin  407 P is about 0.50 inches (12.7 mm). Blades  406 B 1  and  406 B 2  are slightly curved and are flexed to provide bias. In one aspect, the radius of the blade curve is about 0.35 inches (8.9 mm). 
     The blades would normally interfere with one another but to assemble the blades, the blades have to deflect. The force required to deflect the blades is what produces the bias force between the blades, in one aspect. This force is a function of the blade geometry (curve), the blade thickness, and the gap between the arms of clevis  407  and the blade stack that is established during the swaging process. This bias eliminates the need for a bias spring that is typically found in surgical scissors. However, in some aspects, the biasing could be provided by biasing springs such as Belleville washers. 
     Clevis  407  can be made of one an electrically non-conducting material and an electrically conducting material. An electrically non-conducing material suitable for clevis  407 , for example, is made of glass-filled polyphthalamide (PPA). The glass-filled material has adequate strength, biocompatibility, sterilization compatibility, and PPA has very good arc tracking resistance, which is an advantage in high voltage monopolar cautery. A suitable PPA is available from Solvay Plastics under Amodel® PPA A-1133 HS. (Amodel® is a U.S. registered trademark of Solvay Advanced Polymers, L.L.C. of Alpharetta, Ga.) An electrically non-conducting clevis  407  lengthens any possible unintended arc path from blades  406 B 1  and  406 B 2  and/or actuator rod assembly  408  to the patient and/or the body of the instrument when a voltage is applied to blades  406 B 1  and  406 B 2 . 
     However, in some aspects, clevis  407  can be made from an electrically conducting material. An electrically conducting clevis  407 , for example, is made of stainless steel. In one aspect, 17-4 stainless steel is used. However, any stainless steel that can be used in metal injection modeling could be used. 
     In one aspect, actuator rod assembly  408  is made of 17-4 stainless steel and includes a solid cylindrical rod  408 R with ball  409  at the proximal end of cylindrical rod  408 R. In one aspect, the overall length of actuator rod assembly  408  is 0.28 inches (7.1 mm). The diameter of cylindrical rod  408 R is 0.090 inches (2.28 mm) and the length is 0.28 inches (7.1 mm). In one aspect, ball  409  has a diameter of 0.70 inches (17.8 mm). Also, in one aspect, the backside of ball  409 —the proximal side—has a small flat region to aid in manufacturing of the part. There is a transition region  408 T between neck region  408 N and ball  409 . Transition region  408 T reduces the diameter to the diameter of cylindrical rod  408 R. 
     Locking tip cover  410  provides an electrically insulating seal component between the electrically hot active components of disposable tip assembly  205  and unintended contact with the patient. The electrically insulating seal component includes a rigid, non-conductive component, i.e., locking device  412 , which locates disposable tip assembly  205  within instrument tip  448  and an overmolded seal, e.g., external cover  411 . This seal also provide an isolation barrier component for fluids that enter disposable tip assembly  205 . 
     In one aspect, locking device  412  is molded using an amorphous thermoplastic polyetherimide (PEI) material. An example of an amorphous thermoplastic PEI material is ULTEM® amorphous thermoplastic PEI material manufactured by Saudi Basic Industries Corporation (SABIC). (ULTEM® is a U.S. registered trademark of SABIC Innovative Plastics, Inc. besloten vennootschap (b.v.) NETHERLANDS Plasticslaan 1 Bergen op Zoom NETHERLANDS 4612PX.) In another aspect, locking device  412  is molded using a glass-filled polyphthalamide (PPA) such as that described above. 
     In one aspect, external cover  411  is made of a silicone rubber with high tear strength, e.g., a tear-resistant silicone elastomer. The silicone rubber is biocompatible and withstands at least 4 kV. Additionally, the high temperature resistance of silicone is advantageous with respect to the any heat that might be generated as energy is applied to the blades. An example of such a silicone rubber is sold by Dow Corning Corporation as Silastic® Biomedical Grade ETR Elastomer Q7-4750. (Silastic® is a U.S. registered trademark of Dow Corning Corporation of Midland, Mich.) Other suitable materials include flexible, medical grade elastomers including polyurethane thermoplastic elastomers such as Pellethane® polyurethane thermoplastic elastomer provided by The Upjohn Company. Any materials and any dimensions provided herein are illustrative only and are not intended to be limiting to those specific dimensions and materials. 
     Disposable tip assembly  205  has a longitudinal axis  491 . Locking device  412  is free to rotate around longitudinal axis  491  and so free to rotate around clevis  407 . Locking device  412  has a circumferential interior surface  412 A that is flat in the cross-sectional view of  FIG. 4B  and extends distally from a proximal end of locking device  412  to a shoulder  412 B formed perpendicular to interior surface  412 A in this aspect. 
     A length of interior surface  412 A substantially parallel to longitudinal axis  491  is selected based on at least two criteria. First, the length of interior surface  412 A is such that when locking tip cover  410  is moved distally so that a proximal stop is encountered ball  409  extends beyond external cover  411  as shown in  FIGS. 4A and 4B . In one aspect, male bayonet elements (see elements  712  in  FIG. 7D ) extending from circumferential interior surface  412 A interfere with a surface on clevis  407  such that locking tip cover  410  is captive. Second, when disposable tip assembly  205  is moved proximally so that assembly  205  is mounted on and affixed to reusable surgical instrument portion  204 , as described below, the length is such that shoulder  407 B at the distal edge of surface  407 A abuts shoulder  412 B (see  FIG. 8 ). 
     It should be understood that the features of surface  412 A and shoulder  412 B shown in  FIG. 4B  are illustrative only and are not intended to be limiting. In general, inner surface  412 A and shoulder  412 B of locking device  412  are selected to work with outer surface  407 A and shoulder  407 B of clevis  407  to provide the functionally just described. In general, shoulders on both locking device  412  and clevis  407  are designed to lock clevis  407  in places as the two components are drawn together and locking device  412  is actuated. 
     Locking device  412  includes two protrusions  712  ( FIG. 7D ) extending radially inward from interior surface  421 A that are used to lock to disposable tip assembly  205  to instrument tip  448  through the use of a bayonet fixture or a one quarter turn type feature as described more completely below. The use of a one quarter turn locking mechanism allows the length of surface  412 A to be minimized relative to a threaded connection and so helps to minimize the non-articulated length of disposable tip assembly  205  distal to the last joint. In addition, the use of the one-quarter locking mechanism reduces the outer diameter of locking device  412  and so helps to reduce the outer maximum outer diameter of disposable tip of assembly  205 . 
     Tip interface  245  includes an instrument tip  448 . Instrument tip  448  has a central lumen  457  in which is positioned a grip actuator element  446 . A distal end of instrument tip  448  includes an orientation alignment feature  449 , in this example, includes flat surface  449 A. A corresponding orientation alignment feature (not visible in  FIG. 4A ) is provided at the proximal end of clevis  407 . The two orientation alignment features mate such that when instrument tip  448  is affixed to disposable tip assembly  205 , disposable tip assembly  205  is properly oriented on reusable surgical instrument portion  204 . 
     Proximal to flat surface  449 A on instrument tip  448 , in this aspect, is a lock interface element, e.g., a female bayonet receptacle  448 B. In one aspect, instrument tip  448  is made of an electrically non-conducting rigid material such the glass-filled polyphthalamide described above. If electrical arc tracking is not of concern, an alternative material is an organic polymer thermoplastic such as polyether ether ketone (PEEK). Also, if electrical isolation is not needed, instrument tip  448  could be made from a medical grade stainless steel. 
     In one aspect, the maximum diameter of orientation alignment feature  449  is 0.160 inches (4.06 mm) and the flat surface has a length in the longitudinal direction of 0.065 inches (1.65 mm) and a length in a direction perpendicular to the longitudinal direction of 0.068 inches (1.72 mm). An outer diameter of instrument tip  448  in the region of receptacle  448 B is 0.215 inches (5.45 mm). Lumen  457  has an inner diameter of 0.10 inches (2.54 mm). As noted previously, the citation of particular materials and sizes is illustrative only and is not intended to be limiting to these particular materials and sizes. 
     Grip actuator element  446  includes a grip drive element  458 , sometimes referred to as element  458 , which is mounted in a lumen of a grip actuator insulator  453 . Grip actuator insulator  453  slides longitudinally in central lumen  457  of instrument tip  448 . The outer surface of grip actuator insulator  453  has a dumbbell shape, e.g., a central portion of the outer surface is depressed relative to the proximal and distal end portions of the outer surface. 
     A seal  454  extends around the central portion of the outer surface of grip actuator insulator  453 . Seal  454  forms a seal between the inner wall of instrument tip  448  and grip actuator insulator  453 . Thus, seal  454  isolates the wrist and main tube from electrically hot fluid that passes through disposable tip assembly  205 . Seal  454  moves parallel to a longitudinal axis  492  of instrument tip  448  and so helps to reduce the non-articulated length distal to the last joint. In one aspect, seal  454  is made from the tear-resistant silicone elastomer that was described above. In this aspect, grip actuator insulator  453  is made from the glass-filled polyphthalamide described above. 
     In this aspect, grip drive element  458  is made of 17-4 stainless steel, which was described above. Grip drive element  458  has a central lumen extending from a proximal end of element  458 . A distal portion of element  458  is a socket  447 . Socket  447  is sized and configured to mate with ball  409 . 
     A hypotube  455 , e.g., an aglet, is crimped to a distal end of tendon  452 . The hypotube and tendon combination is inserted in the central lumen of grip drive element  458  and is then laser welded to grip drive element  458 . Alternatively, hypotube  455  could be crimped into place. Grip actuator insulator  453  is bonded to grip drive element  458 . In another aspect, grip actuator insulator  453  is overmolded on grip drive element  458  after hypotube  455  is fixed to grip drive element  458 . 
     In one aspect tendon  452  is a braided tungsten cable contained in an electrically insulating sheath (jacket). In one aspect, the sheath is a tube of a fluoropolymer such as ethylene tetrafluorethylene (ETFE). In addition to the insulating properties, the sheath increases the push/pull stiffness of tendon  452  and so helps to reduce buckling of tendon  452 . 
     A wrist-disposable tip adapter  450  is affixed to the proximal end of instrument tip  448 . Tendon  452  with sheath  456  passes through a guide  451  that is mounted in a central lumen of wrist-disposable tip adapter  450 . In one aspect, guide  451  is implemented as a flexible bushing. Guide  451  is molded using a fluoropolymer such as polytetrafluorethylene (PTFE) or fluorinated ethylene propylene (FEP). 
     In  FIGS. 4A and 4B , a knob ( FIG. 11 ) or a lever has been moved that in turn moves tendon  452  in the distal direction so that socket  447  is pushed beyond the distal end of instrument tip  448 . As indicated above, locking tip cover  410  has also been moved in the distal direction until clevis  407  contacts a stop, e.g., a proximal side surface of external cover  411 . This exposes ball  409 . A user can see the two quick connect/disconnect components, ball  409  and socket  447  that must be mated to start the attachment of disposable tip assembly  205  to reusable instrument portion  204 . 
     In  FIGS. 5A and 5B , ball  409  has been placed in socket  447 . In this example, ball  409  is positioned in socket  447  at an angle to longitudinal axis  492  of instrument tip  448 . In  FIGS. 6A  and  6 B with ball  409  in socket  447 , disposable tip assembly  205  is moved so that longitudinal axis  491  of tip  205  is aligned with longitudinal axis  492  of instrument tip  448 . 
     When tendon  452  in  FIG. 6A  is pulled in the proximal direction, disposable tip assembly  205  is pulled in the proximal direction. As disposable tip assembly  205  moves in the proximal direction, orientation alignment feature  449  is aligned with the corresponding feature in disposable tip assembly  205 . The alignment of orientation alignment feature  449  with the corresponding feature in disposable tip assembly  205  ensures that the two components are properly oriented. 
     Hence, as illustrated in  FIGS. 7A and 7B , when grip actuator insulator  453  reaches the limit of travel towards the proximal end of central lumen  457 , ball  409  and socket  447 , a proximal portion of rod  408 R, and grip actuator element  446  are positioned inside central lumen  457 . The orientation alignment features have assured that the proximal end of clevis  407  has mated with the distal end of instrument tip  448 . 
       FIG. 7C  is a prospective view of the configuration in  FIGS. 7A and 7B  with locking tip cover  410  removed.  FIG. 7C  shows that after the mating, bayonet guide feature  407 C of clevis  407  aligned with a first portion of bayonet female receptacle  448 B on instrument tip  448 . One protrusion  712  ( FIG. 7D ) of locking device  412  is slid through the channel formed by bayonet guide feature  407 C of clevis  407  and the first portion of bayonet female receptacle  448 B until shoulder  407 B of clevis  407  abuts shoulder  412 B of locking device  412 . Locking device  412  is then rotated clockwise, in this aspect, into a second portion of bayonet female receptacle  448 B. The rotation locks locking tip cover  410  to tip interface  245  at the distal end of reusable instrument portion  204 . 
     As indicated above,  FIG. 2  is an illustration of locking tip cover  410  mounted on and locked to reusable instrument portion  204 .  FIG. 8  is a cross-sectional illustration of  FIG. 2 .  FIG. 8  shows a mechanical connection between blades  406 B 1 ,  406 B 2 , actuator rod assembly  408 , grip actuator element  446 , and tendon  452 . This mechanical connection permits mechanical actuation of blades  406 B 1 ,  406 B 2 , as described more completely below, by push-pull action of tendon  452 . 
     When, for example, disposable blade assembly  206  is a disposable monopolar curved scissor assembly, an electrical connection exists between disposable tip assembly  205  and reusable instrument portion  204 . This electrical connection is made through the ball and socket connection used for the mechanical connection and actuation. To maintain isolation between blades  406 B 1 ,  406 B 2  and the instrument joints, instrument tip  448  is made from an electrically non-conductive material. Additionally, while not required, making clevis  407  from an electrically non-conductive material lengthens any potential arc paths between the exposed portion of blades  406 B 1 ,  406 B 2  and the instrument joints. Thus, the locked combination of disposable tip assembly  205  and disposable tip interface  245  provides both an electrical connection and electrical isolation between components. 
     The locked combination of disposable tip assembly  205  and disposable tip interface  245  also provides an insulating seal  454  that creates an isolation barrier for fluids between the electrically hot active electrode and the patient. In one aspect, external cover  411  provides an overmolded seal  410 S at the proximal end of disposable tip interface  245 . Seal  410 S is formed between a lip of cover  411  and an outer circumferential surface of instrument tip  448 . 
     In  FIG. 8 , tendon guide  451  is shown in greater detail.  FIG. 8  shows that guide  451  extends from the lumen in wrist-disposable tip adapter  450  proximally through wrist  240  and main tube  230 . In one aspect, tendon guide  451  extends proximally to the proximal end of main tube  230 . 
     In  FIGS. 9A and 9B , tendon  452  is pushed distally by an actuator drive assembly (not shown). The motion of tendon  452  pushes grip actuator element  446  distally in central lumen  457  of instrument tip  448 . The motion of grip actuator element  446  pushes actuator rod assembly  408  distally. Pin  408 P slides in the slots of blades  406 B 1 ,  406 B 2 , which in turn causes blades  406 B 1 ,  406 B 2  to pivot about pin  407 P and open as shown in  FIGS. 9A and 9B . When tendon  452  is pulled proximally, blades  406 B 1 ,  406 B 2  close. 
       FIGS. 10A to 10D  are cross sectional drawings of tip interface  345  and disposable tip assembly  305 .  FIGS. 10A to 10D  illustrate the connection of tip interface  345  to disposable tip assembly  305 . Although, it is not shown in these drawings, tip interface  345  is located at the distal end of a reusable surgical instrument portion similar to reusable surgical instrument portion  204 . 
     In  FIG. 10A , disposable tip assembly  305  ( FIG. 3 ) is positioned for connection to tip interface  345 . Grip actuator element  346  ( FIG. 10A ) has been slid in a central lumen  357  of instrument tip  348  so that socket  347  is positioned distally of the distal end of instrument tip  348 . In  FIGS. 10A to 10D , the distal direction is towards the tips of blades  306 B 1  and  306 B 2  in disposable blade assembly  306  and the proximal direction is towards wrist-disposable tip adapter  350  as show by arrow  1090 . In one aspect, grip actuator element  346  is moved about 0.18 inches (4.57 mm) from a normal closed position of grip actuator element  346  (see  FIG. 10D ) to receive ball  309  of disposable tip assembly  305 . 
     As shown in  FIG. 10A , disposable blade assembly includes two blades  306 B 1  and  306 B 2  that are connected to clevis  307  by a first pin  307 P. A second pin  308 P is positioned in a slot in the proximal ends of blades  306 B 1  and  306 B 2  so that pin  308 P moves in the slot to actuate the blades. Second pin  308 P passes through and floats in a distal end a solid cylindrical rod  308 R in actuator rod assembly  308 . 
     In one aspect, blades  306 B 1  and  306 B 2  are monopolar curved blades equivalent to blades  406 B 1  and  406 B 2 . Clevis  307  can be made of an electrically non-conducting material or an electrically conducting material. An electrically non-conducing material suitable for clevis  307  is the glass-filled polyphthalamide described above. An electrically non-conducting clevis  307  lengthens any possible unintended arc path from blades  306 B 1  and  306 B 2  and/or actuator rod assembly  308  to the patient when a voltage is applied to blades  306 B 1  and  306 B 2 . An electrically conducting clevis  307  can be made of 17-4 stainless steel. However, any stainless steel that can be used in metal injection modeling could be used. 
     Actuator rod assembly  308  is made of 17-4 stainless steel and includes a solid cylindrical rod  308 R with ball  309  at the proximal end of cylindrical rod  308 R. In one aspect, the overall length of actuator rod assembly  308  is 0.34 inches (8.6 mm). The diameter of cylindrical rod  308 R is 0.090 inches (2.28 mm) and the length is 0.34 inches (8.6 mm). In one aspect, ball  309  has a diameter of 0.070 inches (1.78 mm). There is a transition region  308 T between neck region  308 N and ball  309 . Transition region  308 T reduces the diameter of ball  309  to the diameter of cylindrical rod  308 R. 
     Locking tip cover  310  provides both an electrically insulating seal component and an isolation barrier. The insulating seal component is a rigid, non-conductive component, i.e., locking device  312 , which locks disposable tip assembly  305  to instrument tip  348  and an overmolded seal, e.g., external cover  311 . 
     In one aspect, locking device  312  is molded using a glass-filled polyphthalamide (PPA) such as that described above. Other suitable material include PEI)(ULTEM®, as described above. In one aspect, external cover  311  is made of a silicone rubber with high tear strength, e.g., a tear-resistant silicone elastomer. The silicone rubber is biocompatible and withstands at least 4 kV. An example of such a silicone rubber is sold by Dow Corning Corporation as Silastic® Biomedical Grade ETR Elastomer Q7-4750. Other suitable materials include flexible, medical grade elastomers including polyurethane thermoplastic elastomers such as that Pellethane polyurethane thermoplastic elastomer provided by The Upjohn Company. Any materials and any dimensions provided herein are illustrative only and are not intended to be limiting to those specific dimensions and materials. 
     Disposable tip assembly  305  has a longitudinal axis  391 . Locking device  312  is free to rotate around longitudinal axis  391  and so free to rotate around clevis  307 . Locking device  312  has a circumferential interior surface  312 A that is flat in the cross-sectional view of  FIG. 10A  and extends distally from a proximal shoulder  312 C of locking device  312  to a distal shoulder  312 B. In this aspect, both shoulders  312 B and  312 C are formed perpendicular to interior surface  312 A. The two shoulders and the flat surface define a groove in the interior surface of locking device  312 . 
     A length of interior surface  312 A substantially parallel to longitudinal axis  391  is selected based on at least two criteria. First, the length in the proximal direction is chosen so that when locking tip cover  310  is moved distally and the protrusion  307 B on the outer surface of clevis  307  abuts shoulder  312 C, ball  309  extends beyond the proximal end of external cover  311  as shown in  FIGS. 10A and 10B . Second, when external cover is moved proximally so that assembly  305  is mounted on and affixed to reusable surgical instrument portion  304 , as described below, the length is such that protrusion  307 B abuts shoulder  312 B (see  FIG. 10D ). 
     It should be understood that the features of surface  312 A and shoulders  312 B and  312 C shown in  FIG. 10A  are illustrative only and are not intended to be limiting. In general, inner surface  312 A and shoulders  312 B and  312 C of locking device  312  are selected to work with clevis  307  to provide the functionally just described. In general, shoulders on both locking device  312  and clevis  307  position clevis  307  in the proper location as the two components are drawn together and locking device  312  is actuated. 
     Tip interface  345  includes an instrument tip  348 . Locking device  312  includes a thread  312 T that is used to attach disposable tip assembly  305  to threads  348 T on the outer surface of instrument tip  348 . Instrument tip  348  has a central lumen  357  in which is positioned a grip actuator element  346 . A distal end of instrument tip  348  includes an orientation alignment feature  349 , in this example, includes flat surface  349 A (not visible in  FIG. 10A ). A corresponding orientation alignment feature is provided at the proximal end of clevis  307 . The two orientation alignment features mate such that when instrument tip  348  is affixed to disposable tip assembly  305 , disposable tip assembly  305  is properly oriented on the reusable surgical instrument portion. 
     Grip actuator element  346  slides longitudinally in lumen  357  of instrument tip  348 . In this aspect, grip actuator element  346  is made of 17-4 stainless steel. A distal portion of element  346  is a socket  347 . Socket  347  is sized and configured to mate with ball  309 . 
     A hypotube  355 , e.g., an aglet, is crimped to a distal end of tendon  352 . The hypotube and tendon combination is inserted in a central lumen of grip actuator element  346  and is then laser welded to grip actuator element  346 . Alternatively, hypotube  355  could be crimped in place in grip actuator element  346 . 
     In one aspect tendon  352  is a braided tungsten cable contained in an electrically insulating sheath (jacket). In one aspect, the sheath is a tube of a fluorpolymer such as ETFE. In addition to the insulating properties, the sheath increases the push/pull stiffness of tendon  352  and so helps to reduce buckling of tendon  352 . 
     A wrist-disposable tip adapter  350  is affixed to the proximal end of instrument tip  348 . A rigid non-conductive seal  354  is mounted between the proximal end of tip  348  and wrist-disposable tip adapter  350  to seal central lumen  357 . Tendon  352  with sheath  356  passes through seal  354  and a guide  351  that is mounted in a central lumen of wrist-disposable tip adapter  350 . In one aspect, guide  351  is implemented as a flexible bushing. Guide  351  is molded using a fluorpolymer such as PTFE or FEP. 
     In  FIGS. 10A and 10B , a knob ( FIG. 11 ) or a lever has been moved that in turn pushes tendon  352  in the distal direction so that socket  347  extends beyond the distal end of instrument tip  348 . As indicated above, locking tip cover  310  has also been moved in the distal direction to expose ball  309 . Thus, allows a user to see the two quick connect/disconnect components, ball  309  and socket  347  that must be mated to start the attachment of disposable tip assembly  305  to the reusable instrument portion. 
     In  FIG. 10B , ball  309  has been placed in socket  347 . In  FIG. 10C  with ball  309  in socket  347 , tendon  352  is pulled in the proximal direction, which in turn pulls disposable tip assembly  305  in the proximal direction. As disposable tip assembly  305  moves in the proximal direction, orientation alignment feature  349 A is aligned with the corresponding features in disposable tip assembly  305 . The alignment of orientation alignment feature  349 A with the corresponding features in disposable tip assembly  305  ensures that the two components are properly oriented. 
     Hence, as illustrated in  FIG. 10C , when grip actuator element  346  reaches the limit of travel towards the proximal end of central lumen  357 , ball  309  and socket  347 , grip actuator element  346 , and a proximal portion of cylindrical rod  308 R of actuator rod assembly  308  are positioned in central lumen  357 . The proximal end of clevis  307  has mated with the distal end of instrument tip  348 . 
     In  FIG. 10D , locking device  312  has been screwed onto instrument tip  348  so that disposable tip assembly  305  is mounted on and affixed to tip interface  345 . This locks disposable blade assembly  306  in place. 
     In this configuration, there is a mechanical connection between blades  306 B 1 ,  306 B 2 , actuator rod assembly  308 , grip actuator element  346 , and tendon  352 . This mechanical connection permits mechanical actuation of blades  306 B 1 ,  306 B 2 , in a manner similar to that described above for blades  406 B 1 ,  406 B 2 . 
     When, for example, disposable blade assembly  306  is a disposable monopolar curved scissor assembly, an electrical connection exists between disposable tip assembly  305  and the reusable instrument portion. This electrical connection is made through the ball and socket connection used for the mechanical connection and actuation. To maintain isolation between blades  306 B 1 ,  306 B 2  and the instrument joints, instrument tip  348  is made from an electrically non-conductive material. Additionally, while not required, making clevis  307  from an electrically non-conducting material lengthens any potential arc paths between the exposed portion of blades  306 B 1 ,  306 B 2  and the patient. Thus, the locked combination of disposable tip assembly  305  and disposable tip interface  345  provides both an electrical connection and isolation between components. 
     The locked combination of disposable tip assembly  305  and disposable tip interface  345  also provides an insulating seal  354  that creates an isolation barrier for fluids between the electrically hot active electrode and the patient. In one aspect, external cover  311  provides an overmolded seal  310 S at the proximal end of disposable tip assembly  305 . Seal  310 S is formed between a lip of cover  311  and an outer circumferential surface of instrument tip  348 . 
       FIG. 11  is an illustration of one aspect of a rotary grip drive assembly  1100 , which is an example of a push-pull drive assembly. Rotating knob  1171  in a first direction (clockwise) causes sheathed tendon  1152  to move in a first linear direction (down in  FIG. 11 ). Rotating knob  1171  in a second direction (counter clockwise) opposite the first direction causes sheathed tendon  1152  to move in a second linear direction (up in  FIG. 11 ) that is opposite in direction to the first linear direction. Movement of tendon  1152  in the first linear direction results in grip actuator element  346  ( FIG. 10A ) in one aspect, and grip actuator element  446  ( FIG. 4B ) in another aspect, being pushed in the distal direction. Conversely, movement of tendon  1152  in the second linear direction results in grip actuator element  346  in one aspect, and grip actuator element  446  in another aspect, being pulled in the proximal direction. 
     Typically, knob  1171  is used to position the grip actuator element for engaging and disengaging the actuator rod assembly in the disposable tip assembly. When the disposable tip assembly is mounted on and locked to the reusable instrument portion, an actuator drive assembly is used to control the movement of sheathed tendon  1152  in response to input from a user at a master control station. 
     In  FIG. 11 , a drive shaft  1170  has a first end configured to couple to the actuator drive assembly. The particular configuration used to couple to the actuator drive assembly depends on the system in which rotary grip drive assembly  1100  is included. Knob  1171  is mounted on a second end of drive shaft  1170 . Two capstans  1160  and  1163  are also mounted on drive shaft  1170 . 
     A first cable  1161  has a first end affixed to capstan  1163 . Cable  1161  passes around pulley  1174  and a second end of cable  1161  is attached to a first arm  1162  at a first end of lever  1175 . A second cable  1164  has a first end affixed to capstan  1160 . Cable  1164  passes over pulley  1174  and a second end of cable  1164  is attached to a second arm  1165  at the first end of lever  1175 . First arm  1162  is opposite and removed from second arm  1165  at the first end of lever  1175 . 
     Lever  1175  is mounted on a rod  1176  that functions as the fulcrum (pivot point) for lever  1175 . Sheathed tendon  1152  is affixed to a second end of lever  1175 . In this example, lever  1175  is a Class 1 lever because the fulcrum is between the effort (the forces supplied by cables  1161  and  1164 ) and the load (sheathed tendon  1152 ). Sheathed tendon  1152 , in this aspect, moves in a direction opposite to the direction of the force on the first end of lever  1175 . 
     While in this example, lever  1175  is implemented as a Class 1 lever, this is illustrative only and is not intended to be limiting. In other aspects, a Class 2 lever or a Class 3 lever could be used. For a Class 2 lever, the load is between the fulcrum and the effort, and for a Class 3 lever, the effort is between the fulcrum and the load. 
     As used herein, “first,” “second,” and “third” are adjectives used to distinguish between different components or elements. Thus, “first,” “second,” and “third” are not intended to imply any ordering of the components or elements. 
     The above description and the accompanying drawings that illustrate aspects and embodiments of the present inventions should not be taken as limiting—the claims define the protected inventions. Various mechanical, compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known circuits, structures, and techniques have not been shown or described in detail to avoid obscuring the invention. 
     Further, this description&#39;s terminology is not intended to limit the invention. For example, spatially relative terms—such as “beneath”, “below”, “lower”, “above”, “upper”, “proximal”, “distal”, and the like—may be used to describe one element&#39;s or feature&#39;s relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions (i.e., locations) and orientations (i.e., rotational placements) of the device in use or operation in addition to the position and orientation shown in the figures. For example, if the device in the figures were turned over, elements described as “below” or “beneath” other elements or features would then be “above” or “over” the other elements or features. Thus, the exemplary term “below” can encompass both positions and orientations of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes include various special device positions and orientations. 
     The singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. The terms “comprises”, “comprising”, “includes”, and the like specify the presence of stated features, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups. Components described as coupled may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. 
     All examples and illustrative references are non-limiting and should not be used to limit the claims to specific implementations and embodiments described herein and their equivalents. Any headings are solely for formatting and should not be used to limit the subject matter in any way, because text under one heading may cross reference or apply to text under one or more headings. Finally, in view of this disclosure, particular features described in relation to one aspect or embodiment may be applied to other disclosed aspects or embodiments of the invention, even though not specifically shown in the drawings or described in the text.