Patent Description:
A variety of end effectors are known, each adapted to perform a particular surgical function. <FIG> illustrates a surgical instrument <NUM> having an electrocautery end effector. The surgical instrument comprises a base <NUM> by means of which the surgical instrument connects to the robot arm. A shaft <NUM> extends between the base <NUM> and an articulation <NUM>. Articulation <NUM> terminates in the electrocautery end effector <NUM>. The articulation <NUM> permits the electrocautery end effector <NUM> to move relative to the shaft <NUM>. It is desirable for at least two degrees of freedom to be provided to the motion of the electrocautery end effector <NUM> by means of the articulation.

Electrocautery end effectors receive power from a power source in order to perform their cauterising function. Typically, a power cable is connected to the electrocautery end effector. The power cable is ideally fed to the electrocautery end effector through the interior of the instrument, at least for the portion of the instrument which penetrates the patient. Thus, the power cable is ideally fed from the interior of the shaft <NUM>, through the articulation <NUM> to the electrocautery end effector <NUM>. Driving elements which drive the joints of the articulation <NUM> are also fed through the interior of the shaft and into the articulation. It is desirable that the electrocautery power cable fully accommodates movement of the joints of the articulation. Thus, it should not restrict movement of the articulation as a result of becoming taught. However, it should also not interfere with movement of the articulation as a result of becoming slack and catching on other components internal to the articulation. The power cable is insulated, and hence it is desirable that it does not rub on any components in the articulation which could lead to degradation of the insulation.

<CIT> describes an electrocautery end effector in which the power cable is connected to the base of the electrocautery end effector via a circular chamber in which the power cable is wound. The radial width of the channel of the chamber in which the power cable is wound significantly exceeds the width of the power cable, thereby enabling the power cable to be wound into the chamber at different and varying radii. This enables the chamber to house different lengths of cable. Thus, as the electrocautery end effector is articulated in one rotational direction, the power lead is withdrawn from the chamber to accommodate the articulation. As the end effector is articulated in the other rotational direction the power lead is further wound up in the chamber to accommodate the articulation.

<CIT> thereby describes an electrocautery instrument which enables the power cable to accommodate movement of the joints of the articulation without interfering with that movement. However, <CIT> relates to an electrocautery instrument having an external diameter of the order of <NUM> or greater. It is desirable to reduce the external diameter of surgical instruments in order to minimise internal tissue damage, and hence increase the body's ability to heal internally following an operation, thereby reducing recovery time. The mechanism described in <CIT> for managing the power cable of the electrocautery instrument is not effective for an instrument having a smaller external diameter, for example of less than <NUM>. This is because accommodating the power cable through changes in its wound radii in a chamber put too much strain on the power cable.

Thus, there is a need for an effective mechanism for managing the supply of power to an electrocautery end effector, which is suitable for a robotic surgical instrument having a small external diameter.

<CIT> describes surgical tools for use in minimally invasive telesurgical applications including an end effector pivotally mounted on a cable-driven wrist member. <CIT> describes a vessel sealing instrument comprising a cable-driven stepped jaw. <CIT> describes a bipolar cauterizing instrument comprising opposing grips for engaging tissue rotatably mounted on a wrist joint. <CIT> describes a wire and pulley driven manipulator for use in laparoscopic surgery.

The invention is defined by the independent claim.

<FIG> illustrates a surgical robot having an arm <NUM> which extends from a base <NUM>. The arm comprises a number of rigid limbs <NUM>. The limbs are coupled by revolute joints <NUM>. The most proximal limb 302a is coupled to the base by joint 303a. It and the other limbs are coupled in series by further ones of the joints <NUM>. Suitably, a wrist <NUM> is made up of four individual revolute joints. The wrist <NUM> couples one limb (302b) to the most distal limb (302c) of the arm. The most distal limb 302c carries an attachment <NUM> for a surgical electrocautery instrument <NUM>. Each joint <NUM> of the arm has one or more motors <NUM> which can be operated to cause rotational motion at the respective joint, and one or more position and/or torque sensors <NUM> which provide information regarding the current configuration and/or load at that joint. Suitably, the motors are arranged proximally of the joints whose motion they drive, so as to improve weight distribution. For clarity, only some of the motors and sensors are shown in <FIG>. The arm may be generally as described in the applicant's co-pending patent application <CIT> (published as <CIT>).

The arm terminates in an arm interface <NUM> for interfacing with an instrument interface <NUM> of the electrocautery instrument <NUM>. Suitably, the instrument <NUM> takes the form described with respect to <FIG>. The instrument has a diameter less than <NUM>. Suitably, the instrument has diameter less than <NUM>. The instrument diameter may be between <NUM> and <NUM>. The instrument diameter may be the diameter of the shaft. The instrument diameter may be the diameter of the profile of the articulation. Suitably, the diameter of the profile of the articulation matches or is narrower than the diameter of the shaft. The arm interface <NUM> comprises a drive assembly for driving articulation of the electrocautery instrument. Movable interface elements of the drive assembly interface mechanically engage corresponding movable interface elements of the instrument interface in order to transfer drive from the robot arm to the instrument. One instrument is exchanged for another several times during a typical operation. Thus, the instrument is attachable and detachable from the robot arm during the operation.

The electrocautery instrument <NUM> comprises an electrocautery end effector for cauterising tissue at the surgical site. As described with respect to <FIG>, the electrocautery instrument comprises an articulation between the instrument shaft and the electrocautery end effector. The articulation comprises several joints which permit the electrocautery end effector to move relative to the shaft of the instrument. The joints in the articulation are actuated by driving elements, such as cables. These driving elements are secured at the other end of the instrument shaft to the interface elements of the instrument interface. Thus, the robot arm transfers drive to the electrocautery end effector as follows: movement of a drive assembly interface element moves an instrument interface element which moves a driving element which moves a joint of the articulation which moves the electrocautery end effector.

The electrocautery end effector is powered by an electrocautery element which passes through the interior of the instrument shaft and the interior of the articulation to its connection point with the electrocautery end effector.

Controllers for the motors, torque sensors and encoders are distributed with the robot arm. The controllers are connected via a communication bus to control unit <NUM>. A control unit <NUM> comprises a processor <NUM> and a memory <NUM>. Memory <NUM> stores in a non-transient way software that is executable by the processor to control the operation of the motors <NUM> to cause the arm <NUM> to operate in the manner described herein. In particular, the software can control the processor <NUM> to cause the motors (for example via distributed controllers) to drive in dependence on inputs from the sensors <NUM> and from a surgeon command interface <NUM>. The control unit <NUM> is coupled to the motors <NUM> for driving them in accordance with outputs generated by execution of the software. The control unit <NUM> is coupled to the sensors <NUM> for receiving sensed input from the sensors, and to the command interface <NUM> for receiving input from it. The respective couplings may, for example, each be electrical or optical cables, or may be provided by a wireless connection. The command interface <NUM> comprises one or more input devices whereby a user can request motion of the end effector in a desired way. The input devices could, for example, be manually operable mechanical input devices such as control handles or joysticks, or contactless input devices such as optical gesture sensors. The software stored in memory <NUM> is configured to respond to those inputs and cause the joints of the arm and instrument to move accordingly, in compliance with a pre-determined control strategy. The control strategy may include safety features which moderate the motion of the arm and instrument in response to command inputs.

The command interface <NUM> also comprises one or more inputs whereby the user can request activation and/or deactivation of the electrocautery instrument. The software stored in memory <NUM> may be configured to respond to these inputs by causing power to the electrocautery instrument to be activated and/or deactivated in compliance with a pre-determined control strategy. The control strategy may include safety features which only cause power to be applied to the electrocautery instrument if certain conditions are met. Alternatively, the input from the user requesting activation/deactivation of power to the electrocautery instrument may bypass the control unit <NUM> and directly cause power to be applied to/withdrawn from the electrocautery instrument. Alternatively, the input from the user requesting activation/deactivation of power to the electrocautery instrument may pass to a separate control unit from control unit <NUM>. That separate control unit comprises a processor and memory. The memory stores in a non-transient way software that is executable by the processor to apply and withdraw power to the electrocautery instrument in compliance with a pre-determined control strategy. The control strategy may include safety features which only cause power to be applied to the electrocautery instrument if certain conditions are met.

Thus, in summary, a surgeon at the command interface <NUM> can control the electrocautery instrument <NUM> to move and can also control power to the electrocautery instrument to be activated/deactivated in such a way as to perform a desired surgical procedure. The control unit <NUM> and/or the command interface <NUM> may be remote from the arm <NUM>.

<FIG> illustrates the distal end of an electrocautery instrument <NUM>. The electrocautery end effector <NUM> illustrated is a monopolar hook. It will be understood that this is for illustrative purposes only. The electrocautery end effector may take any suitable shape. The electrocautery end effector <NUM> is connected to the shaft <NUM> by articulation <NUM>. Articulation <NUM> comprises joints which permit the electrocautery end effector <NUM> to move relative to the shaft <NUM>. A first joint <NUM> permits the electrocautery end effector <NUM> to rotate about a first axis <NUM>. The first axis <NUM> is transverse to the longitudinal axis of the shaft <NUM>. A second joint <NUM> permits the electrocautery end effector <NUM> to rotate about a second axis <NUM>. The second axis <NUM> is transverse to the first axis <NUM>.

<FIG> depicts a straight configuration of the electrocautery instrument in which the electrocautery end effector is aligned with the shaft. In this orientation, the longitudinal axis of the shaft <NUM> is coincident with the longitudinal axis of the articulation and the longitudinal axis of the electrocautery end effector. Articulation of the first and second joints enables the electrocautery end effector to take a range of attitudes relative to the shaft.

The articulation <NUM> comprises a first body part <NUM> and a second body part <NUM>. The first body part connects the shaft <NUM> to the second body part <NUM>. The first body part <NUM> is fast with the shaft <NUM>. The first body part is connected to the second body part by the first joint <NUM>. The second body part <NUM> connects the first body part <NUM> to the electrocautery end effector <NUM>. The second body part <NUM> is connected to the first body part by the first joint <NUM>, and is connected to the electrocautery end effector <NUM> by the second joint <NUM>. Thus, the first joint <NUM> permits the second body part <NUM> to rotate relative to the shaft <NUM> about the first axis <NUM>; and the second joint <NUM> permits the electrocautery end effector <NUM> to rotate relative to the second body part <NUM> about the second axis <NUM>.

The joints of the articulation are driven by driving elements. The driving elements are elongate elements which extend from the joints in the articulation through the shaft to the instrument interface. Suitably, each driving element can be flexed laterally to its main extent at least in those regions where it engages the internal components of the articulation and instrument interface. In other words, each driving element can be flexed transverse to its longitudinal axis in the specified regions. This flexibility enables the driving elements to wrap around the internal structure of the instrument, such as the joints and pulleys. The driving elements may be wholly flexible transverse to their longitudinal axes. The driving elements are not flexible along their main extents. The driving elements resist compression and tension forces applied along their length. In other words, the driving elements resist compression and tension forces acting in the direction of their longitudinal axes. The driving elements have a high modulus. The driving elements remain taut in operation. They are not permitted to become slack. Thus, the driving elements are able to transfer drive from the instrument interface to the joints. The driving elements may be cables.

Suitably, each joint is driven by a pair of driving elements. The first joint <NUM> is driven by a first pair of driving elements A1,A2. The second joint <NUM> is driven by a second pair of driving elements B1,B2. Suitably, each joint is driven by its own pair of driving elements. In other words, each joint is driven by a dedicated pair of driving elements. Suitably, the joints are independently driven. A pair of driving elements may be constructed as a single piece. This single piece may be secured to the joint at one point, thereby ensuring that when the pair of driving elements is driven, the drive is transferred to motion of the joint about its axis. Alternatively, a pair of driving elements may be constructed as two pieces. In this case, each separate piece is secured to the joint.

The electrocautery end effector <NUM> is powered by an electrocautery element E1. The electrocautery element E1 is connected to the electrocautery end effector <NUM>. Suitably, the electrocautery element E1 terminates at the electrocautery end effector <NUM>. The electrocautery element E1 may be overmoulded with insulation material where it terminates at the electrocautery end effector. The electrocautery element E1 extends from the electrocautery end effector <NUM> through the articulation, through the shaft to the instrument interface. Suitably, the electrocautery element can be flexed laterally to its main extent at least in those regions where it engages the internal components of the articulation and instrument interface. In other words, the electrocautery element can be flexed transverse to its longitudinal axis in the specified regions. This flexibility enables the electrocautery element to wrap around the internal structure of the instrument, such as the joints and pulleys. The electrocautery element may be wholly flexible transverse to its longitudinal axis. The electrocautery element may not be flexible along its main extent. The electrocautery element resists compression and tension forces applied along its length. In other words, the electrocautery element resists compression and tension forces acting in the direction of its longitudinal axis. The electrocautery element has a high modulus. The electrocautery element remains taut in operation. It is not permitted to become slack. The electrocautery element may be a cable.

The electrocautery instrument of <FIG> further comprises a pulley arrangement around which the electrocautery element and the second pair of driving elements are constrained to move. The pulley arrangement may comprise a first set of pulleys <NUM>, a second set of pulleys <NUM>, and a third set of pulleys <NUM>.

The first set of pulleys <NUM> is rotatable about the first axis <NUM>. Thus, the first set of pulleys <NUM> rotate about the same axis as the first joint <NUM>. The first set of pulleys <NUM> comprises a first pulley <NUM> and a second pulley <NUM>. Both the first pulley <NUM> and the second pulley <NUM> rotate about the first axis <NUM>. The first pulley <NUM> and the second pulley <NUM> of the first set of pulleys are located on opposing sides of the first joint <NUM> in a direction transverse to the longitudinal direction of the shaft <NUM>. The first pulley <NUM> and the second pulley <NUM> are located on opposing sides of the first pair of driving elements A1,A2.

The second set of pulleys <NUM> is located between the first axis <NUM> and the shaft <NUM>. The second set of pulleys <NUM> are rotatable about axes which are parallel to the first axis <NUM>. The second set of pulleys <NUM> may comprise a first pulley <NUM> and a second pulley <NUM>. The first pulley <NUM> is rotatable about a third axis <NUM> which is parallel to the first axis <NUM>. The third axis <NUM> is offset from the first axis <NUM> both in the longitudinal direction of the shaft and also transverse to the longitudinal direction of the shaft. The second pulley <NUM> is rotatable about a fourth axis <NUM> which is parallel to the first axis <NUM>. The fourth axis <NUM> is offset from the first axis <NUM> both in the longitudinal direction of the shaft and also transverse to the longitudinal direction of the shaft. The third and fourth axes are parallel but offset from each other. The third axis <NUM> and fourth axis <NUM> are in the same plane perpendicular to the longitudinal direction of the shaft. By offsetting the first pulley <NUM> and the second pulley <NUM>, the driving element wrapped around each pulley is able to extend down the shaft after having wrapped around the pulley. The first pulley <NUM> and second pulley <NUM> of the second set of pulleys <NUM> are located on opposing sides of the first joint <NUM> in a direction transverse to the longitudinal direction of the shaft <NUM>. The first pulley <NUM> and second pulley <NUM> are located on opposing sides of the first pair of driving elements A1,A2.

The third set of pulleys <NUM> comprise a pair of redirecting pulleys <NUM>, <NUM>. The third set of pulleys is located in the articulation <NUM> between the first axis <NUM> and the second axis <NUM>. The redirecting pulleys are each located towards the outside edge of the articulation, on opposing sides of the articulation. Each redirecting pulley is located between the longitudinal axis of the articulation and the external profile of the articulation, on opposing sides of the articulation.

The second pair of driving elements B1,B2 is constrained to move around opposing sides of the first pulley <NUM> and the second pulley <NUM> of the first set of pulleys <NUM>. The second pair of driving elements B1,B2 is constrained to move around opposing sides of the first pulley <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>. The second pair of driving elements is constrained to move around opposing sides of the first pulley <NUM> of the first set of pulleys <NUM> and the first pulley <NUM> of the second set of pulleys <NUM>. The second pair of driving elements is constrained to move around opposing sides of the second pulley <NUM> of the first set of pulleys <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>.

The third set of pulleys <NUM> are positioned so as to redirect the second pair of driving elements B1,B2 from the first set of pulleys <NUM> to the second joint <NUM>. The second pair of driving elements B1,B2 is constrained to move around redirecting pulley <NUM> (not visible in <FIG>). Redirecting pulley <NUM> rotates about a first redirecting pulley axis <NUM>. The first redirecting pulley axis <NUM> is at an angle φ to the first axis <NUM>. The redirecting pulley <NUM> causes the driving element B1 to wrap more fully around the second joint <NUM> than would happen if the redirecting pulley <NUM> was not there, thereby increasing the length of engagement between the driving element B1 and the second joint <NUM>.

The electrocautery element E1 is constrained to move around opposing sides of the first pulley <NUM> of the first set of pulleys <NUM> and the first pulley <NUM> of the second set of pulleys <NUM>. The electrocautery element E1 is constrained to move around redirecting pulley <NUM>.

Redirecting pulley <NUM> rotates about a second redirecting pulley axis <NUM>. The second redirecting pulley axis <NUM> is at an angle ϑ to the first axis <NUM>.

The electrocautery element E1 has a symmetrically opposing path around the pulley arrangement to the driving element B1. In the straight configuration of the electrocautery instrument in which the electrocautery end effector is aligned with the shaft, the path of the driving element B1 around the pulley arrangement is rotationally symmetrical about the longitudinal axis of the shaft <NUM> to the path of the electrocautery element about the pulley arrangement. The path length of the electrocautery element E1 between the shaft and the second joint is the same as the path length of the driving element B1 between the shaft and the second joint. Thus, as the electrocautery end effector is articulated by the articulation <NUM>, the electrocautery element E1 remains taut whilst accommodating full rotation of the first and second joints.

The electrocautery element E1 is connected to the electrocautery end effector <NUM> at a connection point <NUM>. Between the pulley arrangement and the connection point <NUM>, the electrocautery element E1 is constrained to wrap around the second axis <NUM>. This is more easily seen on <FIG>. The electrocautery element E1 wraps around the second axis at least one full revolution in a straight configuration of the electrocautery instrument in which the electrocautery end effector is aligned with the shaft. The electrocautery element E1 may wrap around the second axis one and a half revolutions in the straight configuration of the electrocautery instrument. Suitably, the electrocautery element E1 is seated in a groove about the second axis <NUM> (not shown). As the electrocautery end effector <NUM> is articulated about the second joint <NUM> in a first rotational direction, the electrocautery element E1 winds about the second axis <NUM>. The electrocautery element E1 thereby accommodates the rotation without becoming slack. As the electrocautery end effector <NUM> is articulated about the second joint <NUM> in a second rotational direction which opposes the first rotational direction, the electrocautery element E1 unwinds about the second axis <NUM>. The electrocautery element E1 thereby accommodates the rotation without becoming so taut as to restrict the rotation of the electrocautery end effector in the second rotational direction.

<FIG> illustrates an exemplary arrangement of the driving elements and electrocautery element in the shaft of the electrocautery instrument. The outer casing of the shaft is not shown for ease of illustration.

As can be seen in <FIG>, the electrocautery element E1 is attached to one of the driving elements in the shaft. The electrocautery element E1 is attached to one of the second pair of driving elements in the shaft. In the example illustrated, the electrocautery element E1 is attached to the second one B2 of the second pair of driving elements. This is the other driving element of the second pair of driving elements to the driving element which the electrocautery element E1 has a symmetrically opposing path through the articulation. The electrocautery element E1 is attached to the driving element such that the electrocautery element E1 moves with the driving element as the driving element is actuated. In this way, the electrocautery element E1 is actuated to wind/unwind about the second axis <NUM> so as to accommodate rotation of the electrocautery end effector <NUM> about the second axis. Since the electrocautery element E1 is constrained to move over the first axis <NUM> in the same manner as the second pair of driving elements, the electrocautery element E1 also accommodates articulation of the first joint <NUM> about the first axis <NUM>. The electrocautery element E1 may be bonded to the driving element B2. For example, by heat shrink <NUM> (<FIG>).

The driving elements may be composed of different portions. For example, the portion of the driving element which engages components of the instrument interface (such as pulleys and interface elements) may be flexible. Similarly, the portion of the driving element which engages components of the distal end of the surgical instrument (such as the pulleys and joints in the articulation) may be flexible. Between these two flexible portions, the driving element may comprise a spoke. In the example of <FIG>, each driving element A1, A2, B1, B2 comprises a spoke portion A1s, A2s, B1s, B2s within the shaft. The spokes are stiffer and stronger than the flexible portions. Suitably, the spokes are rigid. The spokes may be hollow. Typically, the spokes have a larger diameter than the flexible portions. Thus, the flexible portions may be cables, and the spokes hollow tubes. The flexible portions may terminate where they meet the spokes. Alternatively, the spokes may encapsulate the material of the flexible portions. For example, the spokes may be rigid sheaths which cover flexible cables.

Suitably, the electrocautery element E1 is connected to the spoke portion of the driving element B2.

<FIG> illustrates the distal end of a second exemplary electrocautery instrument <NUM>. The electrocautery end effector <NUM> illustrated is a bipolar device having two electrocautery end effector elements <NUM> and <NUM>. The electrocautery end effector elements depicted are opposing jaws. It will be understood that this is for illustrative purposes only. The electrocautery end effector elements may take any suitable shape. As another example, the electrocautery end effector elements may be scissors. The electrocautery end effector <NUM> is connected to the shaft <NUM> by articulation <NUM>. Articulation <NUM> comprises joints which permit the electrocautery end effector <NUM> to move relative to the shaft <NUM>. A first joint <NUM> permits the electrocautery end effector <NUM> to rotate about a first axis <NUM>. The first axis <NUM> is transverse to the longitudinal axis of the shaft <NUM>. A second joint <NUM> permits the first electrocautery end effector element <NUM> to rotate about a second axis <NUM>. The second axis <NUM> is transverse to the first axis <NUM>. A third joint <NUM> permits the second electrocautery end effector element <NUM> to rotate about the second axis <NUM>. Suitably, rotation of the first electrocautery end effector element <NUM> about the second axis <NUM> is independent of rotation of the second electrocautery end effector element <NUM> about the second axis <NUM>.

<FIG> depicts a straight configuration of the electrocautery instrument in which the electrocautery end effector is aligned with the shaft. In this orientation, the longitudinal axis of the shaft <NUM> is coincident with the longitudinal axis of the articulation and the longitudinal axis of the electrocautery end effector. Articulation of the first, second and third joints enables the electrocautery end effector to take a range of attitudes relative to the shaft.

The articulation <NUM> comprises a first body part <NUM> and a second body part <NUM>. The first body part connects the shaft <NUM> to the second body part <NUM>. The first body part <NUM> is fast with the shaft <NUM>. The first body part is connected to the second body part by the first joint <NUM>. The second body part <NUM> connects the first body part <NUM> to the electrocautery end effector <NUM>. The second body part <NUM> is connected to the first body part by the first joint <NUM>, and is connected to the electrocautery end effector <NUM> by the second and third joints <NUM> and <NUM>. Thus, the first joint <NUM> permits the second body part <NUM> to rotate relative to the shaft <NUM> about the first axis <NUM>; and the second and third joints <NUM> and <NUM> permit the electrocautery end effector <NUM> to rotate relative to the second body part <NUM> about the second axis <NUM>.

The joints of the articulation are driven by driving elements. The properties of the driving elements are as described with respect to the electrocautery instrument of <FIG>. Suitably, each joint is driven by a pair of driving elements. The first joint <NUM> is driven by a first pair of driving elements A1,A2. The second joint <NUM> is driven by a second pair of driving elements B1,B2. The third joint <NUM> is driven by a third pair of driving elements C1,C2. Suitably, each joint is driven by its own pair of driving elements. In other words, each joint is driven by a dedicated pair of driving elements. Suitably, the joints are independently driven. A pair of driving elements may be constructed as a single piece. This single piece may be secured to the joint at one point, thereby ensuring that when the pair of driving elements is driven, the drive is transferred to motion of the joint about its axis. Alternatively, a pair of driving elements may be constructed as two pieces. In this case, each separate piece is secured to the joint.

The electrocautery end effector <NUM> is powered by a pair of electrocautery elements E1,E2. The electrocautery elements connect to separate parts of the electrocautery end effector <NUM> which are insulated from each other. In the example of <FIG>, the first electrocautery element E1 is connected to the first electrocautery end effector element <NUM>, and the second electrocautery element E2 is connected to the second electrocautery end effector element <NUM>. Suitably, the first electrocautery element E1 terminates at the first electrocautery end effector element <NUM>, and the second electrocautery element E2 terminates at the second electrocautery end effector element <NUM>. The first electrocautery element E1 may be overmoulded with insulation material where it terminates at the first electrocautery end effector element. The second electrocautery element E2 may be overmoulded with insulation material where it terminates at the second electrocautery end effector element. When the two electrocautery end effector elements are closed onto tissue, current can be applied via the electrocautery elements to cut or coagulate the tissue captured between the end effector elements.

The electrocautery elements E1,E2 extend from the electrocautery end effector <NUM> through the articulation, through the shaft to the instrument interface. Suitably, each electrocautery element can be flexed laterally to its main extent at least in those regions where it engages the internal components of the articulation and instrument interface. In other words, the electrocautery element can be flexed transverse to its longitudinal axis in the specified regions. This flexibility enables the electrocautery element to wrap around the internal structure of the instrument, such as the joints and pulleys. The electrocautery element may be wholly flexible transverse to its longitudinal axis. The electrocautery element may not be flexible along its main extent. The electrocautery element resists compression and tension forces applied along its length. In other words, the electrocautery element resists compression and tension forces acting in the direction of its longitudinal axis. The electrocautery element has a high modulus. The electrocautery element remains taut in operation. It is not permitted to become slack. The electrocautery element may be a cable.

The electrocautery instrument of <FIG> further comprises a pulley arrangement around which the electrocautery elements E1, E2 and the pairs of driving elements are constrained to move.

The pulley arrangement comprises a first set of pulleys <NUM> rotatable about the first axis <NUM>. Thus, the first set of pulleys <NUM> rotate about the same axis as the first joint <NUM>. The first set of pulleys <NUM> comprises a first pulley <NUM> and a second pulley <NUM>. The first and second pulleys are centrally located in the articulation, on either side of the longitudinal axis <NUM>. The first pulley <NUM> is adjacent the second pulley <NUM>. The first pulley may abut the second pulley. The first and second pulleys are fast with each other. The first and second pulleys are constrained to rotate together about the first axis <NUM>.

A first one of the first pair of driving elements A1 is constrained to move around the first pulley <NUM>, and terminates at that first pulley <NUM>. A second one of the first pair of driving elements A2 is constrained to move around an opposing side of the second pulley <NUM>, and terminates at that second pulley <NUM>. Thus, the individual driving elements A1 and A2 are not connected to each other around the first joint <NUM>. Driving element A1 may terminate in a crimp, that crimp being captured in a feature on the first pulley <NUM>. Similarly, driving element A2 may terminate in a crimp, that crimp being captured in a feature on the second pulley <NUM>. Tension applied to driving element A1 causes the first joint to rotate in one rotational direction about the first axis <NUM>, and tension applied to driving element A2 causes the second joint to rotate in the opposing rotational direction about the first axis <NUM>. Since the driving elements A1 and A2 are constrained to move around different pulleys, they are offset from one another, lying on either side of a plane with separates the first and second pulleys <NUM>, <NUM>. The first and second driving elements A1 and A2 have symmetrically opposing paths around the first set of pulleys <NUM>.

The first electrocautery element E1 is constrained to move around the first pulley <NUM> as it passes from the shaft <NUM> to the electrocautery end effector <NUM>. E1 moves around the opposing side of the first pulley <NUM> to that which the first driving element A1 is secured to. The second electrocautery element E2 is constrained to move around the second pulley <NUM> as it passes from the shaft <NUM> to the electrocautery end effector <NUM>. E2 moves around the opposing side of the second pulley <NUM> to that which the second driving element A2 is secured to. Thus, E1 is constrained to move around an opposing side of the first pulley <NUM> to the side of the second pulley <NUM> which E2 is constrained to move around. Thus, E1 and E2 have symmetrically opposing paths around the first set of pulleys <NUM>.

Separating the first pair of driving elements A1 and A2 to drive the first joint <NUM> about different pulleys <NUM>, <NUM>, enables space to run the electrocautery elements E1, E2 over the first joint about separate paths which are identical in length but symmetrically opposed. This enables the electrocautery elements E1, E2 to equally accommodate motion of the electrocautery end effector <NUM> about the first axis <NUM>.

The first set of pulleys <NUM> further comprises a third pulley <NUM> and a fourth pulley <NUM>, both of which are rotatable about the first axis <NUM>. The third pulley <NUM> is located on one side of the first and second pulleys <NUM>, <NUM>, and the fourth pulley <NUM> is on the other side of the first and second pulleys <NUM>, <NUM>. The third pulley <NUM> and the fourth pulley <NUM> are located on opposing sides of the first pair of driving elements A1,A2. The second pair of driving elements B1,B2 is constrained to move around opposing sides of the third pulley <NUM> and the fourth pulley <NUM> of the first set of pulleys <NUM>. The third pair of driving elements C1,C2 is constrained to move around opposing sides of the third pulley <NUM> and the fourth pulley <NUM> of the first set of pulleys <NUM>.

The second and third pairs of driving elements are each constrained to extend over the first joint <NUM> in order to reach the second and third joints respectively. Thus, the first one of the second pair of driving elements B1 passes over one side of the third pulley <NUM> of the first set of pulleys on the first joint axis <NUM>, and the second one of the second pair of driving elements B2 passes over an opposing side of the fourth pulley <NUM> of the first set of pulleys on the first joint axis <NUM>, so that whatever rotation there is of the second body part <NUM> about the first joint <NUM>, the length of the second pair of driving elements B1,B2 is maintained the same. Similarly, the second one of the third pair of driving elements C2 passes over one side of the third pulley <NUM> of the first set of pulleys on the first joint axis <NUM>, and the first one of the third pair of driving elements C1 passes over an opposing side of the fourth pulley <NUM> of the first set of pulleys on the first joint axis <NUM>, so that whatever rotation there is of the second body part <NUM> about the first joint <NUM>, the length of the third pair of driving elements C1,C2 is maintained the same. If the arrangement of the instrument interface is symmetric for both the second pair of driving elements B1,B2 and the third pair of driving elements C1,C2, then the length of the second pair of driving elements is the same as the length of the third pair of driving elements for all rotation angles of the second body part <NUM> about the first joint <NUM>.

The pulley arrangement may further comprise a second set of pulleys <NUM> located between the first axis <NUM> and the shaft <NUM>. The second set of pulleys <NUM> are rotatable about axes which are parallel to the first axis <NUM>. The second set of pulleys <NUM> may comprise a first pulley <NUM> and a second pulley <NUM>. The first pulley <NUM> is rotatable about a third axis <NUM> which is parallel to the first axis <NUM>. The third axis <NUM> is offset from the first axis <NUM> both in the longitudinal direction of the shaft and also transverse to the longitudinal direction of the shaft. The second pulley <NUM> is rotatable about a fourth axis <NUM> which is parallel to the first axis <NUM>. The fourth axis <NUM> is offset from the first axis <NUM> both in the longitudinal direction of the shaft and also transverse to the longitudinal direction of the shaft. The third and fourth axes are parallel but offset from each other. The third axis <NUM> and fourth axis <NUM> are in the same plane perpendicular to the longitudinal direction of the shaft. By offsetting the first pulley <NUM> and the second pulley <NUM>, the driving element wrapped around each pulley is able to extend down the shaft after having wrapped around the pulley. The first pulley <NUM> and second pulley <NUM> of the second set of pulleys <NUM> are located on opposing sides of the first joint <NUM> in a longitudinal direction of the shaft <NUM>. The first pulley <NUM> and second pulley <NUM> are located on opposing sides of the first pair of driving elements A1,A2.

The second pair of driving elements B1,B2 is constrained to move around opposing sides of the first pulley <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>. The second pair of driving elements is constrained to move around opposing sides of the third pulley <NUM> of the first set of pulleys <NUM> and the first pulley <NUM> of the second set of pulleys <NUM>. The second pair of driving elements is constrained to move around opposing sides of the fourth pulley <NUM> of the first set of pulleys <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>.

The third pair of driving elements C1,C2 is constrained to move around opposing sides of the first pulley <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>. The third pair of driving elements is constrained to move around opposing sides of the third pulley <NUM> of the first set of pulleys <NUM> and the first pulley <NUM> of the second set of pulleys <NUM>. The third pair of driving elements is constrained to move around opposing sides of the fourth pulley <NUM> of the first set of pulleys <NUM> and the second pulley <NUM> of the second set of pulleys <NUM>.

The second pair of driving elements B1,B2 has a symmetrically opposing path around the first and second sets of pulleys <NUM>, <NUM> than the third pair of driving elements C1,C2. In the straight configuration of the instrument in which the end effector is aligned with the shaft, the path of the second pair of driving elements B1,B2 about the pulley arrangement is rotationally symmetrical about the longitudinal axis of the shaft <NUM> to the path of the third pair of driving elements C1,C2 about the pulley arrangement.

The pulley arrangement may further comprise a third set of pulleys <NUM> located in the articulation between the first axis <NUM> and the second axis <NUM>. The third set of pulleys <NUM> comprise a pair of redirecting pulleys <NUM>,<NUM>. The redirecting pulleys are each located towards the outside edge of the articulation, on opposing sides of the articulation. Each redirecting pulley is located between the longitudinal axis of the articulation and the external profile of the articulation, on opposing sides of the articulation.

The third set of pulleys <NUM> are positioned so as to redirect the second pair of driving elements B1,B2 from the first set of pulleys <NUM> to the second joint <NUM> and to redirect the third pair of driving elements C1,C2 from the first set of pulleys <NUM> to the third joint <NUM>. The second pair of driving elements B1,B2 is constrained to move around redirecting pulley <NUM> (not visible in <FIG>). Redirecting pulley <NUM> rotates about a first redirecting pulley axis <NUM>. The first redirecting pulley axis <NUM> is at an angle ϑ to the first axis <NUM>. The third pair of driving elements C1,C2 is constrained to move around redirecting pulley <NUM>. Redirecting pulley <NUM> rotates about a second redirecting pulley axis <NUM>. The second redirecting pulley axis <NUM> is at an angle φ to the first axis <NUM>. The redirecting pulley <NUM> causes the second pair of driving elements B1,B2 to wrap more fully around the second joint <NUM> than would happen if the redirecting pulley <NUM> was not there, thereby increasing the length of engagement between the second pair of driving elements B1,B2 and the second joint <NUM>. Similarly, the redirecting pulley <NUM> causes the third pair of driving elements C1,C2 to wrap more fully around the third joint <NUM> than would happen if the redirecting pulley <NUM> was not there, thereby increasing the length of engagement between the third pair of driving elements C1,C2 and the third joint <NUM>.

The electrocautery elements E1, E2 are routed from the first set of pulleys <NUM> to the electrocautery end effector <NUM> through the second body part <NUM>. An exemplary routing is shown in <FIG>. From the pick up point on the second pulley <NUM> of the first set of pulleys <NUM>, the second electrocautery element E2 enters a first end <NUM> of a through hole <NUM> in the second body part <NUM>, passes through the through-hole <NUM> and emerges from a second end <NUM> of the through-hole <NUM>. The second end <NUM> of the through-hole <NUM> is located between the redirecting pulley <NUM> and the second joint <NUM>. The second electrocautery element E2 then passes in a channel in the electrocautery end effector to a through-hole <NUM> to its connection point with the electrocautery end effector element <NUM>. The first electrocautery element E1 has a symmetrically opposing path to the second electrocautery element E2 from the pick up point of the first pulley <NUM> of the first set of pulleys <NUM> to the electrocautery end effector element <NUM>.

The electrocautery elements E1, E2 are secured to their respective electrocautery end effector elements <NUM>, <NUM> at connection points. For example, each electrocautery element may be crimped to its respective electrocautery end effector element by deforming the electrocautery end effector element mechanically. The electrocautery element and its electrocautery end effector element may then be overmoulded with insulation material.

Suitably, during assembly, each electrocautery element is attached to its electrocautery end effector element whilst the electrocautery instrument is in a configuration in which that electrocautery element has the highest tension. In this configuration, the second body part <NUM> is in a maximum rotational position about the first joint <NUM> relative to the shaft <NUM>, and the electrocautery end effector element is in a maximum rotational position about the second/third joint relative to the second body part <NUM>. On returning the electrocautery instrument to the straight configuration, the tension on the electrocautery element is reduced. The length of each electrocautery element through the articulation <NUM> is similar to the length of one of the second pair of driving elements. This enables the electrocautery element to accommodate movement of the electrocautery instrument about the first, second and third joints without the electrocautery element becoming overly slack or taut.

Alternatively, each electrocautery element E1, E2 of the bipolar electrocautery instrument may wrap around the second axis <NUM> as described with respect to <FIG> and <FIG>.

<FIG> illustrate a bipolar electrocautery instrument having two electrocautery end effector elements <NUM>, <NUM> with the electrocautery elements E1, E2 connected to separate ones of the end effector elements. Alternatively, the electrocautery elements E1, E2 may be connected to the same end effector element. This may be because the bipolar electrocautery instrument only has a single end effector element. Alternatively, the bipolar electrocautery instrument may have two or more end effector elements, but only one is powered by the electrocautery elements. In either case, the two regions of the end effector element that the electrocautery elements are connected to are electrically isolated from each other. When both regions are contacting tissue, current is applied through the electrocautery elements causing the captured tissue to be cauterised.

As described with respect to the electrocautery instrument of <FIG>, the electrocautery elements may be attached to the driving elements in the shaft. Specifically, the second electrocautery element E2 may be attached to one of the second pair of driving elements in the shaft. For example, E2 may be attached to B1 in the shaft. The first electrocautery element E1 may be attached to one of the third pair of driving elements in the shaft. For example, E1 may be attached to C1 in the shaft. Each electrocautery element is attached to the driving element in the shaft such that the electrocautery element moves with the driving element as the driving element is actuated. The electrocautery elements may be bonded to their respective driving element, for example by heat shrinking. The driving elements may be composed of flexible portions and spoke portions as described with respect to <FIG>. The electrocautery elements may be connected to the spoke portion of the driving elements.

At the proximal end of the electrocautery instrument, the shaft is attached to the base where the instrument interfaces the robot arm. <FIG> illustrates an exemplary proximal end <NUM> of the electrocautery instrument described in <FIG>. The driving elements are routed to instrument interface elements. For example, driving elements B1,B2 are routed to instrument interface element <NUM>. Instrument interface element <NUM> interfaces a drive assembly interface element of the robot arm, which drives the instrument interface element <NUM>, and hence the driving elements B1, B2 linearly parallel to the longitudinal axis of the shaft of the instrument.

As described above, the electrocautery element E1 is attached to a driving element in the shaft of the instrument. The electrocautery element E1 and the driving element bifurcate in the shaft proximal to where the shaft is attached to the base of the instrument. The electrocautery element E1 is routed through the instrument base to where it is electrically connected to a connector <NUM>. The connector <NUM> connects the electrocautery element E1 to a power source. Any suitable connector may be used. For example, <FIG> illustrates a banana plug as the connector to the power source. The electrocautery element may wrap around the connector several times, as shown in <FIG>. This wrapping provides strain relief.

The electrocautery element E1 is routed from the connector <NUM> to the shaft <NUM> by any suitable route. The electrocautery element E1 is constrained by its connection to the driving element in the shaft, and hence its path through the base of the instrument does not need to be constrained. Thus, the electrocautery element E1 may be unconstrained in the instrument base between its connection to the driving element in the shaft and its connection to the connector <NUM>. Alternatively, the electrocautery element E1 may be lightly constrained between its connection to the driving element in the shaft and its connection to the connector <NUM> so as to prevent it chafing on any internal components of the base or interfering with the operation of any internal components of the base. For example, the electrocautery element E1 may pass through through-hole <NUM>. This prevents it interfering with driving element B1. The electrocautery element E1 may be tightly constrained between its connection to the driving element in the shaft and its connection to the connector <NUM>, in a similar manner to the constraints of the driving elements A1,A2, and B1,B2. For example, the electrocautery element E1 may be constrained to move around a similar set of pulleys (or a subset of the pulleys) as that around which the driving elements A1,A2 and the driving elements B1,B2 are constrained to move. In this case, the electrocautery element E1 remains taut in the instrument base, thereby preventing interference with the driving elements A1,A2,B1,B2. The interior housing of the base may be shaped so as to reduce the likelihood of chafing the electrocautery element E1. For example, <FIG> illustrates an example in which the interior casing of the base comprises radii <NUM>, <NUM> which the electrocautery element E1 bears against as it is routed from the shaft to the connector. A tension pulley <NUM> is mounted on a resilient lug <NUM> in such a location as to tension the electrocautery element E1 against the radii <NUM>, <NUM>.

A corresponding proximal end to that illustrated in <FIG> and <FIG> may be implemented for the bipolar electrocautery instrument described with respect to <FIG>. In this case there are two electrocautery elements E1 and E2. E1 and E2 are each routed from their connections to the driving elements in the shaft to their individual connections with the connector using any of the mechanisms described with respect to <FIG> and <FIG>. As in the remainder of the electrocautery instrument, the electrocautery elements E1 and E2 are insulated from each other in the base.

Claim 1:
A robotic surgical instrument comprising:
a shaft (<NUM>);
an electrocautery end effector (<NUM>) powered by an electrocautery element (E1), wherein the electrocautery element is a cable; and
an articulation (<NUM>) connecting the electrocautery end effector to the shaft, the articulation comprising:
a first body part (<NUM>) and a second body part (<NUM>);
a first joint (<NUM>) driveable by a first pair of driving elements (A1, A2), the first joint permitting the electrocautery end effector to rotate about a first axis (<NUM>) transverse to a longitudinal axis of the shaft and permitting the second body part to rotate relative to the shaft about the first axis,
a second distal joint (<NUM>) driveable by a second pair of driving elements (B1, B2), the second joint permitting the electrocautery end effector to rotate about a second axis (<NUM>) transverse to the first axis and permitting the electrocautery end effector to rotate relative to the second body part about the second axis; and
a pulley arrangement around which the second pair of driving elements and the electrocautery element are constrained to move;
wherein the electrocautery element is constrained to move around the first axis and constrained to wrap at least one full revolution around the second axis; and
characterised in that in the straight configuration of the instrument in which the electrocautery end effector is aligned with the shaft, the path of the electrocautery element around the pulley arrangement is rotationally symmetrical about the longitudinal axis of the shaft to the path of the first one of the second pair of driving elements around the pulley arrangement, and wherein the electrocautery element is attached to a second one of the second pair of driving elements in the shaft