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WO2025133897A1 - Mechanical joint for an articulated arm of a surgical robot - Google Patents

Mechanical joint for an articulated arm of a surgical robot Download PDF

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Publication number
WO2025133897A1
WO2025133897A1 PCT/IB2024/062748 IB2024062748W WO2025133897A1 WO 2025133897 A1 WO2025133897 A1 WO 2025133897A1 IB 2024062748 W IB2024062748 W IB 2024062748W WO 2025133897 A1 WO2025133897 A1 WO 2025133897A1
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WO
WIPO (PCT)
Prior art keywords
joint element
plane
joint
disc
profiles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/IB2024/062748
Other languages
French (fr)
Inventor
Antonello FORGIONE
Renzo ZALTIERI
Giuseppe Emanuele CAMPO
Martina DE LANDRO
Pietro CANNOVA
Andrea Stefano CIULLO
Michele MAIMERI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
VALUEBIOTECH Srl
Original Assignee
VALUEBIOTECH Srl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by VALUEBIOTECH Srl filed Critical VALUEBIOTECH Srl
Publication of WO2025133897A1 publication Critical patent/WO2025133897A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/70—Manipulators specially adapted for use in surgery
    • A61B34/71—Manipulators operated by drive cable mechanisms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/30—Surgical robots
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods
    • A61B17/00234—Surgical instruments, devices or methods for minimally invasive surgery
    • A61B2017/00292—Surgical instruments, devices or methods for minimally invasive surgery mounted on or guided by flexible, e.g. catheter-like, means
    • A61B2017/003—Steerable
    • A61B2017/00305—Constructional details of the flexible means
    • A61B2017/00314—Separate linked members
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/30—Surgical robots
    • A61B2034/305—Details of wrist mechanisms at distal ends of robotic arms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/30—Surgical robots
    • A61B2034/305—Details of wrist mechanisms at distal ends of robotic arms
    • A61B2034/306—Wrists with multiple vertebrae

Definitions

  • the present invention relates to a mechanical joint for an articulated arm of a surgical robot, configured to connect two rigid segments of the articulated arm so as to allow controlled rotational movements between said rigid segments about one axis of rotation or about two axes of rotation separate from each other, in particular two perpendicular axes of rotation.
  • Robotic surgery is a surgical technique that involves the use of robots to move and control surgical instruments, as well as vision devices (for example cameras), within the patient's body during a surgical intervention.
  • Surgical robots are used especially in the field of minimally invasive surgery, as they allow to control with high precision and dexterity miniaturized surgical instruments that have been introduced into the patient's body (in particular the abdominal cavity) through small incisions.
  • articulated arms of the robot which during surgery are controlled from the outside by the surgeon or an assistant surgeon, for example by means of joysticks or other control members or apparatuses.
  • Such articulated arms comprise a plurality of rigid segments connected to each other by means of mechanical joints, which are configured to allow relative rotation of two adjacent rigid segments about at least one axis of rotation, typically a single axis of rotation or a pair of perpendicular axes of rotation.
  • control cables are provided that extend through the various rigid segments and the joints of the arm.
  • two control cables are provided that extend on opposite sides of that axis of rotation, so that the alternate application of tension to one cable or the other causes the rotational movement of one rigid segment with respect to the other about that axis of rotation in one direction or the opposite direction.
  • each of the two joint elements includes a pair of rolling profiles that are made as toothed profiles and mesh each with a corresponding rolling profile of the other joint element. Furthermore, in order to avoid relative movements between the toothed profiles in the direction perpendicular to the plane of rotation of the two joint elements, each joint element also includes a pair of curved profiles arranged internally with respect to the toothed profiles and each acting as a lateral retaining element for one of the toothed profiles of the other joint element.
  • an additional pair of profiles acting as lateral retaining elements is provided on each of the two joint elements, the structure of each joint element becomes more complex, as well as more expensive to manufacture, in particular in the case of very small joint elements.
  • a further object of the present invention is to provide a mechanical joint for an articulated arm of a surgical robot that has a simpler structure and is less expensive to manufacture than the prior art mentioned above.
  • An articulated arm for a surgical robot as defined in claim 8 also forms part of the present invention.
  • the present invention is based on the idea of making a joint having a first joint element, a second joint element and a pair of control cables, wherein:
  • the first joint element comprises a disc-shaped body and a pair of rolling profiles which protrude from said disc-shaped body towards the second joint element and are symmetrical with respect to a first plane of symmetry formed by a central diametral plane of said disc-shaped body, wherein said rolling profiles are configured in such a way that their projection onto said first plane of symmetry extends along an arc of circumference;
  • the second joint element comprises a disc-shaped body and a pair of rolling profiles which protrude from said disc-shaped body towards the first joint element and are symmetrical with respect to a second plane of symmetry formed by a central diametral plane of said disc-shaped body, wherein said second plane of symmetry coincides with said first plane of symmetry, and wherein each rolling profile of the second joint element is in contact with a respective rolling profile of the first joint element;
  • control cables extend through a pair of first holes in the disc-shaped body of the first joint element and through a pair of second holes in the disc-shaped body of the second joint element so as to cause, as a result of the application of a tensile force alternately on either of the control cables, the rotation of the second joint element with respect to the first joint element in a plane of rotation coinciding with the first and second planes of symmetry, by rolling of each rolling profile of the second joint element on the corresponding rolling profile of the first joint element;
  • said first holes extend out of the disc-shaped body of the first joint element, on the side facing the second joint element, at a plane perpendicular to the first plane of symmetry and passing through the center of the two rolling profiles of the first joint element, that is, through the center of the arc of circumference along which the projection of the two rolling profiles of the first joint element extends onto the first plane of symmetry
  • said second holes extend out of the disc-shaped body of the second joint element, on the side facing the first joint element, at a plane perpendicular to the second plane of symmetry and passing through the center of the two rolling profiles of the second joint element, that is, through the center of the arc of circumference along which the projection of the two rolling profiles of the second joint element extends on the second plane of symmetry.
  • each of the two joint elements are toothed profiles, more specifically helical tooth profiles. This allows both to avoid slippage between each pair of rolling profiles in contact with each other, thus ensuring that the relative movement between each pair of rolling profiles is a pure rolling movement, without slippage, and to avoid relative movements between the rolling profiles in the direction perpendicular to the plane of rotation of the two joint elements, without the need to add special lateral retaining elements.
  • the first holes are located at a distance from a straight line passing through the center of the two rolling profiles of the first joint element and perpendicular to the first plane of symmetry that is greater than the radius of those profiles.
  • the second holes are located at a distance from a straight line passing through the center of the two rolling profiles of the second joint element and perpendicular to the second plane of symmetry that is greater than the radius of those profiles.
  • FIG. 1 is a perspective view of a one-degree-of-freedom mechanical joint for an articulated arm of a surgical robot according to an embodiment of the present invention, in an operating position where the first joint element and the second joint element are aligned with each other;
  • Figure 2 is a side view of the joint of Figure 1 ;
  • Figure 3 is a perspective view similar to that of Figure 1 , but with the joint in a different operating position in which the first joint element and the second joint element are rotated by a certain angle to each other;
  • - Figure 4 is a side view similar to that of Figure 1 , but with the joint in the position of Figure 3;
  • - Figure 5 is a perspective view of a two-degree-of-freedom mechanical joint for an articulated arm of a surgical robot according to an embodiment of the present invention, in an operating position where the first joint element, the second joint element and the third joint element are aligned with each other;
  • FIG. 6 is a perspective view similar to that of Figure 5, but with the joint in a different operating position in which the first joint element and the second joint element are aligned with each other, while the third joint element is rotated by a certain angle relative to the second joint element;
  • FIG. 7 is a side view of the joint of Figure 5, with the joint in a different operating position in which the second joint element is rotated by the maximum possible angle of rotation in one direction relative to the first joint element, while the second joint element and the third joint element are aligned with each other;
  • FIGS. 8 and 9 are a perspective view and a plan view of the first joint element of Figure 5, respectively;
  • FIGS. 10 and 11 are a side view and a plan view from above, respectively, of the second joint element of Figure 5;
  • Figures 12 and 13 are a side view and a plan view from below, respectively, of the third joint element of Figure 5;
  • FIG. 14 is an exploded perspective view of an articulated arm of a surgical robot comprising a set of mechanical joints according to the present invention.
  • a mechanical joint for an articulated arm of a surgical robot is generally indicated 10.
  • the joint 10 is intended to be interposed between two parts of the robotic arm (not shown in those figures), which may be two rigid parts, or one rigid part and another joint, or yet two additional joints, so as to allow a controlled relative movement between the two parts of the arm between which the joint is interposed, where such movement is essentially a rotation in one plane or a combination of rotations in two separate planes, in particular two perpendicular planes.
  • rotation or “rotational movement” will be used in connection with the relative movement of the various elements of the joint, and then the term “plane of rotation” will be used to identify the plane in which such relative movement occurs, even though such relative movement is not a pure rotational movement.
  • the movement of each joint part with respect to the adjacent joint part results from a rolling movement of a pair of rolling profiles of one joint part on a corresponding pair of rolling profiles of the other joint part and thus has not only a rotational component but also a translational component.
  • the translational component of such movement is generally negligible compared to the rotational component, it will be referred to, for convenience, as rotational movement.
  • the joint 10 is a one-degree-of- freedom joint, and therefore it is capable of allowing a controlled rotational movement between the two parts of the arm connected to each other by the joint in a single plane.
  • An example of a two-degree-of-freedom joint will be described later with reference to Figures 5 to 13.
  • the joint 10 basically comprises a first joint element 12, intended to be connected to a first part of the arm (which, for convenience, will be assumed to be a rigid segment), and a second joint element 14, intended to be connected to a second part of the arm (which, for convenience, will be assumed to be a rigid segment).
  • the first joint element 12 comprises a disc-shaped body 16 having in a central portion thereof one or more through holes (not visible in Figures 1 to 4) that serve, for example, for the passage of cables or pipes intended to be connected to an instrument or device (not shown in Figures 1 to 4, but nevertheless of a per-se- known type, for example a surgical instrument or a vision device) mounted at the distal end of the robotic arm.
  • the disc-shaped body 16 forms, on the side facing the first part of the arm, thus on the side opposite to the second joint element 14 (bottom side, according to the point of view of a person looking at Figures 1 to 4), a flat face 16a.
  • the first joint element 12 further includes a pair of rolling profiles 18, which protrude from the disc-shaped body 16 towards the second joint element 14 (upwards, according to the point of view of a person looking at Figures 1 to 4) and are symmetrical with respect to a first plane of symmetry formed by a central diametral plane of the disc-shaped body 16 (i.e., a plane passing through the first longitudinal axis x1 ).
  • the rolling profiles 18 are configured in such a way that their projection on the first plane of symmetry extends along an arc of circumference, the center of which is denoted C1 in Figures 2 and 4 and is the same for the two rolling profiles 18.
  • the second joint element 14 comprises first of all a disc-shaped body 20 having in a central portion thereof one or more through holes 22 having the function of allowing the passage of the aforementioned cables or pipes.
  • the disc-shaped body 20 forms, on the side facing the second part of the arm, thus on the side opposite to the first joint element 12 (upper side, according to the point of view of a person looking at Figures 1 to 4), a flat face 20a.
  • the rolling profiles 24 are configured in such a way that their projection on the second plane of symmetry extends along an arc of circumference, the center of which is denoted by C2 in Figures 2 and 4 and is the same for the two rolling profiles 24.
  • Each rolling profile 24 of the second joint element 14 is in contact with a respective rolling profile 18 of the first joint element 12.
  • the rolling profiles 24 of the second joint element 14 have the same radius as the rolling profiles 18 of the first joint element 12, or rather the arc of circumference along which the projections of the rolling profiles 18 of the first joint element 12 on the first plane of symmetry extend has the same radius as the arc of circumference along which the projections of the rolling profiles 24 of the second joint element 14 on the second plane of symmetry extend.
  • center of the rolling profile will be used in connection with the centers C1 and C2 defined above and the term “ radius of the rolling profile” will be used in connection with the radius of the arc of circumference defined above.
  • the rolling profiles 18 and 24 are semicircular profiles, or rather the projections of these profiles on the first plane of symmetry and on the second plane of symmetry, respectively, are semicircular in shape.
  • the rolling profiles 18 and 24 are toothed profiles, meshing with each other, which makes it possible to avoid slippage between each pair of rolling profiles, and hence to ensure that the relative movement of one profile on the other is a pure rolling movement.
  • the teeth of the rolling profiles 18 and 24 extend over an arc of circumference of less than 180°, but still greater than 90°.
  • the angular extension of the teeth can be appropriately chosen depending on the specific application.
  • the two joint elements 12 and 14 are in a position aligned with each other, i.e., in a position such that the first longitudinal axis x1 (i.e., the central axis of the disc-shaped body 16 of the first joint element 12) coincides with the second longitudinal axis x2 (i.e., the central axis of the disc-shaped body 20 of the second joint element 14).
  • first longitudinal axis x1 i.e., the central axis of the disc-shaped body 16 of the first joint element 12
  • the second longitudinal axis x2 i.e., the central axis of the disc-shaped body 20 of the second joint element 14
  • the rolling profiles 18 and 24 are made as helical tooth profiles.
  • the use of helical teeth, in particular helical teeth with opposing helixes, makes it possible to avoid relative movements between the rolling profiles 18 and 24 in the direction perpendicular to the plane of rotation of the two joint elements 12 and 14 (a plane that, according to the above explanation, coincides with the aforementioned first and second planes of symmetry), without the need to use to special lateral retaining elements.
  • the joint 10 further comprises a pair of control cables 26 and 28 that are connected to the disc-shaped body 20 of the second joint element 14 in such a way that the application of a tensile force each time on the control cable 26 or the control cable 28 generates on the second joint element 14 a torque tending to make that joint element rotate with respect to the first joint element 12 in the aforementioned plane of rotation.
  • the control cables 26 and 28 extend through respective first holes 30 in the discshaped body 16 of the first joint element 12. These first holes 30 are arranged with their axes lying on the first plane of symmetry. Additionally, as shown in Figures 2 and 4, the first holes 30 extend out of the disc-shaped body 16 of the first joint element 12, on the side facing the second joint element 14, at a plane TT1 passing through the center C1 of the two rolling profiles 18 and perpendicular to the first plane of symmetry.
  • control cables 26 and 28 are constrained to the disc-shaped body 20 of the second joint element 14, on the side opposite to the first joint element 12 (i.e., immediately downstream of the second holes 32), by means of respective end members 34, each of which acts as a stop on a respective portion of the flat surface of the disc-shaped body 20 around the respective second hole 32.
  • end member 34 attached to the end of that cable exerts a downward thrust (with reference to the point of view of a person looking at Figure 2) onto the disc-shaped body 20 of the second joint element 14 in the area surrounding the second hole 32, thereby generating on the second joint element 14 a torque tending to make that element rotate to the left relative to the first joint element 12.
  • Figures 5 to 13 in which parts and elements identical or corresponding to those of Figures 1 to 4 have been given the same reference numbers, relate to a joint 10 of the two-degree-of-freedom type, that is, a joint capable of allowing controlled rotational movement between the two parts of the arm connected to each other by the joint in two separate planes, namely in two planes perpendicular to each other.
  • the joint 10 comprises, in addition to the first joint element 12 and the second joint element 14 described above, a third joint element 36 arranged in series with respect to the first two joint elements 12 and 14.
  • the second joint element 14 further comprises, in addition to the pair of rolling profiles 24, an additional pair of rolling profiles 38 protruding from the disc-shaped body 20 on the side opposite to the rolling profiles 24.
  • the rolling profiles 38 are symmetrical with respect to a third plane of symmetry formed by a central diametral plane of the disc-shaped body 20, in particular with respect to a plane oriented perpendicular (or, more generally, inclined by a certain angle) to the second plane of symmetry.
  • the rolling profiles 38 are configured in such a way that their projection on the third plane of symmetry extends along an arc of circumference, which preferably has the same radius as that of the rolling profiles 24. More specifically, according to the embodiment proposed herein, the rolling profiles 38 are identical to the rolling profiles 24.
  • the third joint element 36 corresponds substantially to the second joint element 14 of the embodiment of Figures 1 to 4.
  • the third joint element 36 comprises first of all a disc-shaped body 40 having in a central portion thereof one or more through holes 42 for the passage of the aforementioned cables or pipes.
  • the disc-shaped body 40 forms, on the side facing the second part of the arm, thus on the side opposite to the second joint element 14 (upper side, according to the point of view of a person looking at Figures 5 and 6), a flat face 40a.
  • a central axis of the discshaped body 40 hereinafter referred to as the third longitudinal axis, which extends perpendicular to the flat face 40a, is denoted by x3.
  • the third joint element 36 further comprises a pair of rolling profiles 44, which protrude from the disc-shaped body 40 towards the second joint element 14 (downwards, according to the point of view of a person looking at Figures 5 and 6) and are symmetrical with respect to a fourth plane of symmetry formed by a central diametral plane of the discshaped body 40 (i.e., a plane passing through the third longitudinal axis x3).
  • the rolling profiles 44 are configured in such a manner that their projection on the fourth plane of symmetry extends along an arc of circumference.
  • Each rolling profile 44 of the third joint element 36 is in contact with a respective rolling profile 38 of the second joint element 14.
  • the rolling profiles 44 of the third joint element 36 have the same radius as the rolling profiles 38 of the second joint element 14.
  • rolling profiles 38 and 44 of the second joint element 14 and of the third joint element 36 respectively, what has been stated above in connection with the rolling profiles 18 and 24 of the first joint element 12 and of the second joint element 14, respectively, in particular the fact that they are helical tooth profiles, so as to ensure a pure rolling movement of one rolling profile on the other, without slippage, while also avoiding relative movements between the rolling profiles 38 and 44 in the direction perpendicular to the plane of rotation of the two joint elements 14 and 36.
  • the joint 10 comprises, in addition to the pair of control cables 26 and 28 described above, which are used to control the rotation of the second joint element 14 with respect to the first joint element 12, an additional pair of control cables 46 and 48 that pass through the first joint element 12 and the second joint element 14 and are connected to the disc-shaped body 40 of the third joint element 36 in such a way that the application each time of a tensile force onto the control cable 46 or the control cable 48 generates on the third joint element 36 a torque tending to make that joint element rotate in a plane of rotation coinciding with the aforementioned fourth plane of symmetry.
  • control cables 46 and 48 extend, in the order from the first joint element 12 to the third joint element 36, through respective first holes 50 (shown in Figure 9) in the disc-shaped body 16 of the first joint element 12, through respective second holes 52 (shown in Figures 10 and 1 1 ) in the disc-shaped body 20 of the second joint element 14 and finally through respective third holes 54 (shown in Figures 12 and 13) in the disc-shaped body 40 of the third joint element 36.
  • each first hole 50 is aligned with the respective second hole 52 and the respective third hole 54, so that each of the control cables 46 and 48 extends along a straight direction (in the present case a vertical direction) parallel to the direction on which the central axes x1 , x2 and x3 lie.
  • the second holes 52 are arranged with their axes lying on the third plane of symmetry.
  • the second holes 52 extend out of the disc-shaped body 20 of the second joint element 14, on the side facing the third joint element 36, at a plane TT2' passing through the center C2' of the two rolling profiles 38 of the second joint element 14 and perpendicular to the third plane of symmetry.
  • the third holes 54 of the third joint element 36 are arranged with their axes lying on the fourth plane of symmetry.
  • the third holes 54 extend out of the disc-shaped body 40 of the third joint element 36, on the side facing the second joint element 14, at a plane TT3 passing through the centers C3 of the two rolling profiles 44 of the third joint element 36 and perpendicular to the fourth plane of symmetry.
  • control cables 26 and 28 this allows, on the one hand, to greatly simplify the control of the second degree of freedom of the joint (i.e., the movement of the third joint element 36 with respect to the second joint element 14) by means of the two control cables 46 and 48, thereby making the control system more robust and reliable, and, on the other hand, to minimize the reduction in the lever arm with which the two control cables 46 and 48 act as the angular position of the third joint element with respect to the second one changes.
  • the second holes 52 are located at a distance d2' ( Figure 10) from the straight line passing through the centers of the two rolling profiles 38 of the second joint element 14 that is greater than the radius of those profiles, in particular greater than the radius of the pitch circle of the teeth of each of those profiles.
  • the third holes 54 are preferably located at a distance d3 ( Figure 12) from the straight line passing through the centers of the two rolling profiles 44 of the third joint element 36 that is greater than the radius of those profiles, in particular greater than the radius of the pitch circle of the teeth of each of those profiles.
  • d2' Figure 10
  • the third holes 54 are preferably located at a distance d3 ( Figure 12) from the straight line passing through the centers of the two rolling profiles 44 of the third joint element 36 that is greater than the radius of those profiles, in particular greater than the radius of the pitch circle of the teeth of each of those profiles.
  • the joint of the present invention makes it possible to control the movement of one joint element relative to the other over a very wide angular range, up to ⁇ 90°.
  • said figure shows the condition in which the second joint element 14 is rotated 90° relative to the first joint element 12, while the third joint element 36 is aligned with the second joint element 14.
  • Figure 14 shows an example of an articulated arm for a surgical robot, generally indicated 100, comprising a set of rigid arm segments that are connected two by two by joints according to the present invention, so that the movement of a surgical instrument T (or, more generally, any device or instrument that is useful during a surgical intervention) mounted at the end of the arm 100 can be controlled with n degrees of freedom in space, where n is given by the sum of the degrees of freedom of the various joints upstream of the surgical instrument T.
  • the articulated arm 100 comprises four rigid arm segments (denoted S1 , S2, S3 and S4, respectively), connected by three joints (denoted 10a, 10b and 10c, respectively), which in the present case are all two-degree-of-freedom joints, such that the total number of controllable degrees of freedom of the surgical instrument T is equal to six.
  • joints denoted 10a, 10b and 10c, respectively
  • the present invention has been described herein with reference to some embodiments thereof, but it is clear that other embodiments may be envisaged which share with those described herein the same inventive core, as defined by the appended claims.
  • joints with one or two degrees of freedom have been illustrated in the above description, it is still possible to envisage joints with more than two degrees of freedom, since it is in fact possible to obtain one more degree of freedom each time by simply adding a further joint element arranged in series with respect to the previous ones.

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  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biomedical Technology (AREA)
  • Robotics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Heart & Thoracic Surgery (AREA)
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  • Molecular Biology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Manipulator (AREA)

Abstract

A mechanical joint (10) for an articulated arm (100) of a surgical robot is described, comprising a first joint element (12), a second joint element (14) connected to the first joint element (12) so as to be rotatable relative thereto, and a pair of first control cables (26, 28) for controlling the movement of the second joint element (14) relative to the first joint element (14). The first joint element (12) comprises a disc-shaped body (16) and a pair of toothed profiles (18) with helical teeth that protrude from the disc-shaped body (16) towards the second joint element (14) and are symmetrical with respect to a first plane of symmetry coinciding with a central diametral plane of said disc-shaped body (16). The second joint element (14) comprises a disc-shaped body (20) and a pair of toothed profiles (24) with helical teeth that protrude from the disc-shaped body (20) towards the first joint element (12) and are symmetrical with respect to a second plane of symmetry coinciding with a central diametral plane of such a disc-shaped body (20), wherein the first plane of symmetry coincides with the second plane of symmetry and each toothed profile (24) of the second joint element (14) meshes with a respective toothed profile (18) of the first joint element (12).

Description

MECHANICAL JOINT FOR AN ARTICULATED ARM OF A SURGICAL ROBOT
Technical field of the invention
The present invention relates to a mechanical joint for an articulated arm of a surgical robot, configured to connect two rigid segments of the articulated arm so as to allow controlled rotational movements between said rigid segments about one axis of rotation or about two axes of rotation separate from each other, in particular two perpendicular axes of rotation.
State of the art
Robotic surgery is a surgical technique that involves the use of robots to move and control surgical instruments, as well as vision devices (for example cameras), within the patient's body during a surgical intervention. Surgical robots are used especially in the field of minimally invasive surgery, as they allow to control with high precision and dexterity miniaturized surgical instruments that have been introduced into the patient's body (in particular the abdominal cavity) through small incisions.
The surgical instruments and the vision devices are in this case mounted at the ends of articulated arms of the robot, which during surgery are controlled from the outside by the surgeon or an assistant surgeon, for example by means of joysticks or other control members or apparatuses. Such articulated arms comprise a plurality of rigid segments connected to each other by means of mechanical joints, which are configured to allow relative rotation of two adjacent rigid segments about at least one axis of rotation, typically a single axis of rotation or a pair of perpendicular axes of rotation. To control the movement of each rigid segment of the articulated arm relative to the adjacent rigid segment, control cables are provided that extend through the various rigid segments and the joints of the arm. Specifically, for each degree of freedom of the arm, that is, for each axis of rotation about which two adjacent rigid segments of the arm are able to rotate, two control cables are provided that extend on opposite sides of that axis of rotation, so that the alternate application of tension to one cable or the other causes the rotational movement of one rigid segment with respect to the other about that axis of rotation in one direction or the opposite direction.
A mechanical joint for an articulated arm of a surgical robot having the features defined in the preamble of the attached independent claim 1 is known from US 2023/248417. According to that known solution, each of the two joint elements includes a pair of rolling profiles that are made as toothed profiles and mesh each with a corresponding rolling profile of the other joint element. Furthermore, in order to avoid relative movements between the toothed profiles in the direction perpendicular to the plane of rotation of the two joint elements, each joint element also includes a pair of curved profiles arranged internally with respect to the toothed profiles and each acting as a lateral retaining element for one of the toothed profiles of the other joint element. Evidently, since an additional pair of profiles acting as lateral retaining elements is provided on each of the two joint elements, the structure of each joint element becomes more complex, as well as more expensive to manufacture, in particular in the case of very small joint elements.
Summary of the invention
It is an object of the present invention to provide a mechanical joint for an articulated arm of a surgical robot of an improved type over the prior art mentioned above, in particular a mechanical joint that enables simple yet precise control of the relative rotational movement between the pair of rigid arm segments connected by means of the joint.
A further object of the present invention is to provide a mechanical joint for an articulated arm of a surgical robot that has a simpler structure and is less expensive to manufacture than the prior art mentioned above.
These and other objects are achieved according to the invention by virtue of a joint as defined in the attached independent claim 1 .
Additional advantageous aspects of the joint according to the invention are defined in the dependent claims, the subject matter of which is to be intended as forming an integral part of the following description.
An articulated arm for a surgical robot as defined in claim 8 also forms part of the present invention.
In summary, the present invention is based on the idea of making a joint having a first joint element, a second joint element and a pair of control cables, wherein:
- the first joint element comprises a disc-shaped body and a pair of rolling profiles which protrude from said disc-shaped body towards the second joint element and are symmetrical with respect to a first plane of symmetry formed by a central diametral plane of said disc-shaped body, wherein said rolling profiles are configured in such a way that their projection onto said first plane of symmetry extends along an arc of circumference;
- the second joint element comprises a disc-shaped body and a pair of rolling profiles which protrude from said disc-shaped body towards the first joint element and are symmetrical with respect to a second plane of symmetry formed by a central diametral plane of said disc-shaped body, wherein said second plane of symmetry coincides with said first plane of symmetry, and wherein each rolling profile of the second joint element is in contact with a respective rolling profile of the first joint element;
- wherein the control cables extend through a pair of first holes in the disc-shaped body of the first joint element and through a pair of second holes in the disc-shaped body of the second joint element so as to cause, as a result of the application of a tensile force alternately on either of the control cables, the rotation of the second joint element with respect to the first joint element in a plane of rotation coinciding with the first and second planes of symmetry, by rolling of each rolling profile of the second joint element on the corresponding rolling profile of the first joint element; and
- wherein said first holes extend out of the disc-shaped body of the first joint element, on the side facing the second joint element, at a plane perpendicular to the first plane of symmetry and passing through the center of the two rolling profiles of the first joint element, that is, through the center of the arc of circumference along which the projection of the two rolling profiles of the first joint element extends onto the first plane of symmetry, and wherein said second holes extend out of the disc-shaped body of the second joint element, on the side facing the first joint element, at a plane perpendicular to the second plane of symmetry and passing through the center of the two rolling profiles of the second joint element, that is, through the center of the arc of circumference along which the projection of the two rolling profiles of the second joint element extends on the second plane of symmetry.
With such a configuration of the two joint elements, it is ensured that the sum of the lengths of the free sections of the two control cables, that is, the sections of the two control cables that extend outside the disc-shaped bodies of the two joint elements between the first holes and the second holes, always remains constant during the rotational movement of the second joint element with respect to the first one. This allows, on the one hand, to greatly simplify the control of the movement of the joint by means of the two control cables, and thus to make the control system more robust and reliable, and, on the other hand, to minimize the reduction in the lever arm with which the two control cables act as the angular position of the second joint element with respect to the first one changes.
In addition, the rolling profiles of each of the two joint elements are toothed profiles, more specifically helical tooth profiles. This allows both to avoid slippage between each pair of rolling profiles in contact with each other, thus ensuring that the relative movement between each pair of rolling profiles is a pure rolling movement, without slippage, and to avoid relative movements between the rolling profiles in the direction perpendicular to the plane of rotation of the two joint elements, without the need to add special lateral retaining elements.
According to a preferred aspect of the invention, the first holes are located at a distance from a straight line passing through the center of the two rolling profiles of the first joint element and perpendicular to the first plane of symmetry that is greater than the radius of those profiles. Likewise, the second holes are located at a distance from a straight line passing through the center of the two rolling profiles of the second joint element and perpendicular to the second plane of symmetry that is greater than the radius of those profiles. In this way, greater lever arms are obtained for the two control cables, and thus, for the same tensile force applied on the control cables, greater control torques are obtained, and, additionally, the risk of interference between the control cables and the rolling profiles is avoided.
Brief description of the drawings
Further features and advantages of the present invention will result more clearly from the following description, given purely by way of non-limiting example with reference to the accompanying drawings, in which:
- Figure 1 is a perspective view of a one-degree-of-freedom mechanical joint for an articulated arm of a surgical robot according to an embodiment of the present invention, in an operating position where the first joint element and the second joint element are aligned with each other;
- Figure 2 is a side view of the joint of Figure 1 ;
- Figure 3 is a perspective view similar to that of Figure 1 , but with the joint in a different operating position in which the first joint element and the second joint element are rotated by a certain angle to each other;
- Figure 4 is a side view similar to that of Figure 1 , but with the joint in the position of Figure 3; - Figure 5 is a perspective view of a two-degree-of-freedom mechanical joint for an articulated arm of a surgical robot according to an embodiment of the present invention, in an operating position where the first joint element, the second joint element and the third joint element are aligned with each other;
- Figure 6 is a perspective view similar to that of Figure 5, but with the joint in a different operating position in which the first joint element and the second joint element are aligned with each other, while the third joint element is rotated by a certain angle relative to the second joint element;
- Figure 7 is a side view of the joint of Figure 5, with the joint in a different operating position in which the second joint element is rotated by the maximum possible angle of rotation in one direction relative to the first joint element, while the second joint element and the third joint element are aligned with each other;
- Figures 8 and 9 are a perspective view and a plan view of the first joint element of Figure 5, respectively;
- Figures 10 and 11 are a side view and a plan view from above, respectively, of the second joint element of Figure 5;
- Figures 12 and 13 are a side view and a plan view from below, respectively, of the third joint element of Figure 5; and
- Figure 14 is an exploded perspective view of an articulated arm of a surgical robot comprising a set of mechanical joints according to the present invention.
Detailed description
With reference first to Figures 1 to 4, a mechanical joint (hereafter, for convenience, simply referred to as a joint) for an articulated arm of a surgical robot is generally indicated 10. The joint 10 is intended to be interposed between two parts of the robotic arm (not shown in those figures), which may be two rigid parts, or one rigid part and another joint, or yet two additional joints, so as to allow a controlled relative movement between the two parts of the arm between which the joint is interposed, where such movement is essentially a rotation in one plane or a combination of rotations in two separate planes, in particular two perpendicular planes.
In the description and claims that follow, the terms "rotation" or "rotational movement" will be used in connection with the relative movement of the various elements of the joint, and then the term "plane of rotation" will be used to identify the plane in which such relative movement occurs, even though such relative movement is not a pure rotational movement. In fact, as will become clear from the following description, the movement of each joint part with respect to the adjacent joint part results from a rolling movement of a pair of rolling profiles of one joint part on a corresponding pair of rolling profiles of the other joint part and thus has not only a rotational component but also a translational component. However, since the translational component of such movement is generally negligible compared to the rotational component, it will be referred to, for convenience, as rotational movement.
According to the embodiment of Figures 1 to 4, the joint 10 is a one-degree-of- freedom joint, and therefore it is capable of allowing a controlled rotational movement between the two parts of the arm connected to each other by the joint in a single plane. An example of a two-degree-of-freedom joint will be described later with reference to Figures 5 to 13.
The joint 10 basically comprises a first joint element 12, intended to be connected to a first part of the arm (which, for convenience, will be assumed to be a rigid segment), and a second joint element 14, intended to be connected to a second part of the arm (which, for convenience, will be assumed to be a rigid segment).
First of all, the first joint element 12 comprises a disc-shaped body 16 having in a central portion thereof one or more through holes (not visible in Figures 1 to 4) that serve, for example, for the passage of cables or pipes intended to be connected to an instrument or device (not shown in Figures 1 to 4, but nevertheless of a per-se- known type, for example a surgical instrument or a vision device) mounted at the distal end of the robotic arm. In the proposed embodiment, the disc-shaped body 16 forms, on the side facing the first part of the arm, thus on the side opposite to the second joint element 14 (bottom side, according to the point of view of a person looking at Figures 1 to 4), a flat face 16a. A central axis of the disc-shaped body 16, hereinafter referred to as the first longitudinal axis, which extends perpendicular to the flat face 16a, is denoted by x1 . The first joint element 12 further includes a pair of rolling profiles 18, which protrude from the disc-shaped body 16 towards the second joint element 14 (upwards, according to the point of view of a person looking at Figures 1 to 4) and are symmetrical with respect to a first plane of symmetry formed by a central diametral plane of the disc-shaped body 16 (i.e., a plane passing through the first longitudinal axis x1 ). The rolling profiles 18 are configured in such a way that their projection on the first plane of symmetry extends along an arc of circumference, the center of which is denoted C1 in Figures 2 and 4 and is the same for the two rolling profiles 18. Likewise, the second joint element 14 comprises first of all a disc-shaped body 20 having in a central portion thereof one or more through holes 22 having the function of allowing the passage of the aforementioned cables or pipes. In the proposed embodiment, the disc-shaped body 20 forms, on the side facing the second part of the arm, thus on the side opposite to the first joint element 12 (upper side, according to the point of view of a person looking at Figures 1 to 4), a flat face 20a. A central axis of the disc-shaped body 20, hereinafter referred to as the second longitudinal axis, which extends perpendicular to the flat face 20a, is denoted by x2. The second joint element 14 further comprises a pair of rolling profiles 24, which protrude from the disc-shaped body 20 towards the first joint element 12 (downwards, according to the point of view of a person looking at Figures 1 to 4) and are symmetrical with respect to a second plane of symmetry formed by a central diametral plane of the disc-shaped body 20 (i.e., a plane passing through the second longitudinal axis x2) coinciding with the aforementioned first plane of symmetry. The rolling profiles 24 are configured in such a way that their projection on the second plane of symmetry extends along an arc of circumference, the center of which is denoted by C2 in Figures 2 and 4 and is the same for the two rolling profiles 24. Each rolling profile 24 of the second joint element 14 is in contact with a respective rolling profile 18 of the first joint element 12. Furthermore, the rolling profiles 24 of the second joint element 14 have the same radius as the rolling profiles 18 of the first joint element 12, or rather the arc of circumference along which the projections of the rolling profiles 18 of the first joint element 12 on the first plane of symmetry extend has the same radius as the arc of circumference along which the projections of the rolling profiles 24 of the second joint element 14 on the second plane of symmetry extend.
In the following, for convenience, the term " center of the rolling profile" will be used in connection with the centers C1 and C2 defined above and the term " radius of the rolling profile" will be used in connection with the radius of the arc of circumference defined above.
As shown in particular in Figures 2 and 4, according to an embodiment of the invention, the rolling profiles 18 and 24 are semicircular profiles, or rather the projections of these profiles on the first plane of symmetry and on the second plane of symmetry, respectively, are semicircular in shape. In addition, the rolling profiles 18 and 24 are toothed profiles, meshing with each other, which makes it possible to avoid slippage between each pair of rolling profiles, and hence to ensure that the relative movement of one profile on the other is a pure rolling movement. In the example of Figures 1 to 4, the teeth of the rolling profiles 18 and 24 extend over an arc of circumference of less than 180°, but still greater than 90°. However, the angular extension of the teeth can be appropriately chosen depending on the specific application.
In Figures 1 and 2, the two joint elements 12 and 14 are in a position aligned with each other, i.e., in a position such that the first longitudinal axis x1 (i.e., the central axis of the disc-shaped body 16 of the first joint element 12) coincides with the second longitudinal axis x2 (i.e., the central axis of the disc-shaped body 20 of the second joint element 14). If, starting from this condition, a torque is applied onto the second joint element 14 tending to make this joint element rotate in the second plane of symmetry, the rolling profile 24 of the second joint element 14 will roll on the first rolling profile 18 of the first joint element 12 in one direction or the other depending on the direction of the applied torque, and, accordingly, the second joint element 14 will take a position rotated by a certain angle in one direction or the other with respect to the first joint element 12. In Figure 4, the angle of rotation of the second joint element 14 with respect to the first joint element 12, corresponding to the angle between the longitudinal axes x1 and x2 of the two joint elements 12 and 14, is denoted by a.
The rolling profiles 18 and 24 are made as helical tooth profiles. The use of helical teeth, in particular helical teeth with opposing helixes, makes it possible to avoid relative movements between the rolling profiles 18 and 24 in the direction perpendicular to the plane of rotation of the two joint elements 12 and 14 (a plane that, according to the above explanation, coincides with the aforementioned first and second planes of symmetry), without the need to use to special lateral retaining elements.
Referring again to Figure 1 , the joint 10 further comprises a pair of control cables 26 and 28 that are connected to the disc-shaped body 20 of the second joint element 14 in such a way that the application of a tensile force each time on the control cable 26 or the control cable 28 generates on the second joint element 14 a torque tending to make that joint element rotate with respect to the first joint element 12 in the aforementioned plane of rotation.
The control cables 26 and 28 extend through respective first holes 30 in the discshaped body 16 of the first joint element 12. These first holes 30 are arranged with their axes lying on the first plane of symmetry. Additionally, as shown in Figures 2 and 4, the first holes 30 extend out of the disc-shaped body 16 of the first joint element 12, on the side facing the second joint element 14, at a plane TT1 passing through the center C1 of the two rolling profiles 18 and perpendicular to the first plane of symmetry.
Likewise, the control cables 26 and 28 extend through respective second holes 32 in the disc-shaped body 20 of the second joint element 14. These second holes 32 are arranged with their axes lying on the second plane of symmetry. Additionally, as shown in Figures 2 and 4, the second holes 32 extend out of the disc-shaped body 18 of the second joint element 14, on the side facing the first joint element 12, at a plane TT2 passing through the center C2 of the two rolling profiles 24 and perpendicular to the second plane of symmetry.
The control cables 26 and 28 are constrained to the disc-shaped body 20 of the second joint element 14, on the side opposite to the first joint element 12 (i.e., immediately downstream of the second holes 32), by means of respective end members 34, each of which acts as a stop on a respective portion of the flat surface of the disc-shaped body 20 around the respective second hole 32. In this manner, when a tensile force is applied onto the control cable 26, the end member 34 attached to the end of that cable exerts a downward thrust (with reference to the point of view of a person looking at Figure 2) onto the disc-shaped body 20 of the second joint element 14 in the area surrounding the second hole 32, thereby generating on the second joint element 14 a torque tending to make that element rotate to the left relative to the first joint element 12. On the other hand, when a tensile force is applied onto the control cable 28, the end member 34 attached to the end of that cable exerts a downward thrust (with reference to the point of view of a person looking at Figures 2 and 4) onto the disc-shaped body 20 of the second joint element 14 in the area surrounding the second hole 32, thereby generating on the second joint element 14 a torque tending to make that element rotate to the right relative to the first joint element 12, as shown in Figure 4. However, other solutions (per se known and therefore not illustrated in detail in the present description) can be envisaged for constraining the ends of the control cables 26 and 28 to the disc-shaped body 20 of the second joint element 14.
Due to the arrangement of the first holes 30 and second holes 32 in the discshaped body 16 of the first joint element 12 and in the disc-shaped body 20 of the second joint element 14, respectively, it is ensured that the sum of the lengths of the free sections of the two control cables 26 and 28 (indicated by 11 and I2, respectively, in Figures 2 and 4), i.e., of the sections of the two control cables 26 and 28 that extend outside the disc-shaped bodies 16 and 20 of the two joint elements 12 and 14 between the first holes 30 and the second holes 32, always remains constant during the movement of the second joint element 14 with respect to the first joint element 12. This allows, on the one hand, to greatly simplify the control of the movement of the joint (i.e., the movement of the second joint element 14 with respect to the first joint element 12) by means of the two control cables 26 and 28, and thus make the control system more robust and reliable, and on the other hand, to minimize the reduction in the lever arm with which the two control cables 26 and 28 act as the angular position of the second joint element with respect to the first one changes.
With reference to Figures 2 and 4, the first holes 30 are preferably located at a distance d1 from the straight line passing through the center C1 of the two rolling profiles 18 of the first joint element 12 that is greater than the radius of such profiles, in particular greater than the radius rp of the pitch circle of the teeth of each of such profiles. Likewise, the second holes 32 are preferably located at a distance d2 from the straight line passing through the center C2 of the two rolling profiles 24 of the second joint element 14 that is greater than the radius of such profiles, in particular greater than the radius rp of the pitch circle of the teeth of each of such profiles. This makes it possible to increase the arm of the force with which the control cables 26 and 28 act on the second joint element 14 to cause its rotation relative to the first joint element 12. In addition, this makes it possible to avoid the risk of the control cables 26 and 28 being "pinched" between the rolling profiles 18 and 24 when the second joint element 14 is close to the maximum angle of rotation relative to the first joint element 12. Such a positioning of the first holes 30 and the second holes 32 applies not only to the case where the rolling profiles 18 and 24 are helical tooth profiles, but also to the case of straight tooth profiles.
Figures 5 to 13, in which parts and elements identical or corresponding to those of Figures 1 to 4 have been given the same reference numbers, relate to a joint 10 of the two-degree-of-freedom type, that is, a joint capable of allowing controlled rotational movement between the two parts of the arm connected to each other by the joint in two separate planes, namely in two planes perpendicular to each other. Referring first to Figures 5 to 7, the joint 10 comprises, in addition to the first joint element 12 and the second joint element 14 described above, a third joint element 36 arranged in series with respect to the first two joint elements 12 and 14.
With regard to the first joint element 12 and the second joint element 14, what has been described above with reference to the one-degree-of-freedom embodiment of Figures 1 to 4 still applies. In this case, however, the second joint element 14 further comprises, in addition to the pair of rolling profiles 24, an additional pair of rolling profiles 38 protruding from the disc-shaped body 20 on the side opposite to the rolling profiles 24. The rolling profiles 38 are symmetrical with respect to a third plane of symmetry formed by a central diametral plane of the disc-shaped body 20, in particular with respect to a plane oriented perpendicular (or, more generally, inclined by a certain angle) to the second plane of symmetry. The rolling profiles 38 are configured in such a way that their projection on the third plane of symmetry extends along an arc of circumference, which preferably has the same radius as that of the rolling profiles 24. More specifically, according to the embodiment proposed herein, the rolling profiles 38 are identical to the rolling profiles 24.
As far as the third joint element 36 is concerned, it corresponds substantially to the second joint element 14 of the embodiment of Figures 1 to 4. In particular, the third joint element 36 comprises first of all a disc-shaped body 40 having in a central portion thereof one or more through holes 42 for the passage of the aforementioned cables or pipes. In the proposed embodiment, the disc-shaped body 40 forms, on the side facing the second part of the arm, thus on the side opposite to the second joint element 14 (upper side, according to the point of view of a person looking at Figures 5 and 6), a flat face 40a. A central axis of the discshaped body 40, hereinafter referred to as the third longitudinal axis, which extends perpendicular to the flat face 40a, is denoted by x3. The third joint element 36 further comprises a pair of rolling profiles 44, which protrude from the disc-shaped body 40 towards the second joint element 14 (downwards, according to the point of view of a person looking at Figures 5 and 6) and are symmetrical with respect to a fourth plane of symmetry formed by a central diametral plane of the discshaped body 40 (i.e., a plane passing through the third longitudinal axis x3). The rolling profiles 44 are configured in such a manner that their projection on the fourth plane of symmetry extends along an arc of circumference. Each rolling profile 44 of the third joint element 36 is in contact with a respective rolling profile 38 of the second joint element 14. In addition, the rolling profiles 44 of the third joint element 36 have the same radius as the rolling profiles 38 of the second joint element 14.
It also applies to the rolling profiles 38 and 44 of the second joint element 14 and of the third joint element 36, respectively, what has been stated above in connection with the rolling profiles 18 and 24 of the first joint element 12 and of the second joint element 14, respectively, in particular the fact that they are helical tooth profiles, so as to ensure a pure rolling movement of one rolling profile on the other, without slippage, while also avoiding relative movements between the rolling profiles 38 and 44 in the direction perpendicular to the plane of rotation of the two joint elements 14 and 36.
Referring to Figure 5, in this case the joint 10 comprises, in addition to the pair of control cables 26 and 28 described above, which are used to control the rotation of the second joint element 14 with respect to the first joint element 12, an additional pair of control cables 46 and 48 that pass through the first joint element 12 and the second joint element 14 and are connected to the disc-shaped body 40 of the third joint element 36 in such a way that the application each time of a tensile force onto the control cable 46 or the control cable 48 generates on the third joint element 36 a torque tending to make that joint element rotate in a plane of rotation coinciding with the aforementioned fourth plane of symmetry.
With regard to the control cables 26 and 28, what has been explained above with reference to the embodiment of Figures 1 to 4 still applies.
With regard to the control cables 46 and 48, on the other hand, they extend, in the order from the first joint element 12 to the third joint element 36, through respective first holes 50 (shown in Figure 9) in the disc-shaped body 16 of the first joint element 12, through respective second holes 52 (shown in Figures 10 and 1 1 ) in the disc-shaped body 20 of the second joint element 14 and finally through respective third holes 54 (shown in Figures 12 and 13) in the disc-shaped body 40 of the third joint element 36.
In the condition of Figure 5, in which the three joint elements 12, 14 and 36 are aligned with each other, that is, the central axes x1 , x2 and x3 of the respective disc-shaped bodies lie in the same direction (in the present case the same vertical direction, with respect to the point of view of a person looking at Figure 5), each first hole 50 is aligned with the respective second hole 52 and the respective third hole 54, so that each of the control cables 46 and 48 extends along a straight direction (in the present case a vertical direction) parallel to the direction on which the central axes x1 , x2 and x3 lie.
More specifically, the second holes 52 are arranged with their axes lying on the third plane of symmetry. In particular, as shown in Figure 11 , the second holes 52 extend out of the disc-shaped body 20 of the second joint element 14, on the side facing the third joint element 36, at a plane TT2' passing through the center C2' of the two rolling profiles 38 of the second joint element 14 and perpendicular to the third plane of symmetry.
Likewise, the third holes 54 of the third joint element 36 are arranged with their axes lying on the fourth plane of symmetry. In particular, as shown in Figure 12, the third holes 54 extend out of the disc-shaped body 40 of the third joint element 36, on the side facing the second joint element 14, at a plane TT3 passing through the centers C3 of the two rolling profiles 44 of the third joint element 36 and perpendicular to the fourth plane of symmetry.
The control cables 46 and 48 are constrained to the disc-shaped body 40 of the third joint element 36, on the side opposite to the second joint element 14 (i.e., immediately downstream of the third holes 54), by means of respective end members 56 (shown in Figure 5), each of which acts as a stop on a respective portion of the flat surface of the disc-shaped body 40 around the respective third hole 54. In this manner, when a tensile force is applied onto the control cable 46, the end member 56 attached to the end of said cable exerts a downward thrust (with reference to the point of view of a person looking at Figure 5) on the discshaped body 40 of the third joint element 36 in the area surrounding the respective third hole 54, thereby generating on the third joint element 36 a torque tending to make said element rotate with respect to the second joint element 14 towards the side of the control cable 46. Likewise, when a tensile force is applied onto the control cable 48, the end member 56 attached to the end of said cable exerts a downward thrust on the disc-shaped body 40 of the third joint element 36 in the area surrounding the respective third hole 54, thereby generating on the third joint element 36 a torque tending to make that element rotate with respect to the second joint element 14 towards the side of the control cable 48. However, other solutions (per se known and therefore not illustrated in detail in the present description) are possible for constraining the ends of the control cables 46 and 48 to the discshaped body 40 of the third joint element 36.
Also in this case, as with the embodiment of Figures 1 to 4, the above-described arrangement of the holes in the disc-shaped bodies of the various joint elements ensures that the sum of the lengths of the free sections of each pair of control cables remains constant. In the present case, this applies not only to the control cables 26 and 28, but also to the control cables 46 and 48. Regarding the latter, thanks to the arrangement of the second holes 52 and the third holes 54 in the disc-shaped body 20 of the second joint element 14 and in the disc-shaped body 40 of the third joint element 36, respectively, it is in fact ensured that the sum of the lengths of the free sections of the two control cables 46 and 48, i.e., of the sections of the two control cables 46 and 48 that extend outside the disc-shaped bodies 20 and 40 of the two joint elements 14 and 36 between the second holes 52 and the third holes 54, always remains constant during the movement of the third joint element 36 with respect to the second joint element 14. As described above for the control cables 26 and 28, this allows, on the one hand, to greatly simplify the control of the second degree of freedom of the joint (i.e., the movement of the third joint element 36 with respect to the second joint element 14) by means of the two control cables 46 and 48, thereby making the control system more robust and reliable, and, on the other hand, to minimize the reduction in the lever arm with which the two control cables 46 and 48 act as the angular position of the third joint element with respect to the second one changes.
Preferably, the second holes 52 are located at a distance d2' (Figure 10) from the straight line passing through the centers of the two rolling profiles 38 of the second joint element 14 that is greater than the radius of those profiles, in particular greater than the radius of the pitch circle of the teeth of each of those profiles. Likewise, the third holes 54 are preferably located at a distance d3 (Figure 12) from the straight line passing through the centers of the two rolling profiles 44 of the third joint element 36 that is greater than the radius of those profiles, in particular greater than the radius of the pitch circle of the teeth of each of those profiles. Such a positioning of the second holes 52 and the third holes 54 applies not only to the case where the rolling profiles 38 and 44 are helical tooth profiles, but also to the case of straight tooth profiles.
As shown in Figure 7, the joint of the present invention makes it possible to control the movement of one joint element relative to the other over a very wide angular range, up to ±90°. Indeed, said figure shows the condition in which the second joint element 14 is rotated 90° relative to the first joint element 12, while the third joint element 36 is aligned with the second joint element 14.
Finally, Figure 14 shows an example of an articulated arm for a surgical robot, generally indicated 100, comprising a set of rigid arm segments that are connected two by two by joints according to the present invention, so that the movement of a surgical instrument T (or, more generally, any device or instrument that is useful during a surgical intervention) mounted at the end of the arm 100 can be controlled with n degrees of freedom in space, where n is given by the sum of the degrees of freedom of the various joints upstream of the surgical instrument T. In the example of Figure 14, the articulated arm 100 comprises four rigid arm segments (denoted S1 , S2, S3 and S4, respectively), connected by three joints (denoted 10a, 10b and 10c, respectively), which in the present case are all two-degree-of-freedom joints, such that the total number of controllable degrees of freedom of the surgical instrument T is equal to six. A variety of other configurations of the robotic arm are of course conceivable, depending on the specific application. The present invention has been described herein with reference to some embodiments thereof, but it is clear that other embodiments may be envisaged which share with those described herein the same inventive core, as defined by the appended claims. In particular, although joints with one or two degrees of freedom have been illustrated in the above description, it is still possible to envisage joints with more than two degrees of freedom, since it is in fact possible to obtain one more degree of freedom each time by simply adding a further joint element arranged in series with respect to the previous ones.

Claims

1. Mechanical joint (10) for an articulated arm (100) of a surgical robot, comprising a first joint element (12), a second joint element (14) connected to the first joint element (12) so as to be rotatable relative to the latter, and a pair of first control cables (26, 28) for controlling the movement of the second joint element (14) relative to the first joint element (14), wherein the first joint element (12) comprises a disc-shaped body (16) and a pair of rolling profiles (18) that protrude from said disc-shaped body (16) towards the second joint element (14) and are symmetrical with respect to a first plane of symmetry coinciding with a central diametral plane of said disc-shaped body (16); wherein the second joint element (14) comprises a disc-shaped body (20) and a pair of rolling profiles (24) that protrude from said disc-shaped body (20) towards the first joint element (12) and are symmetrical with respect to a second plane of symmetry coinciding with a central diametral plane of said disc-shaped body (20), wherein said second plane of symmetry coincides with said first plane of symmetry and the rolling profiles (24) of the second joint element (14) are each in contact with a respective rolling profile (18) of the first joint element (12); wherein the first control cables (26, 28) extend through a pair of first holes (30) in the disc-shaped body (16) of the first joint element (12) and through a pair of second holes (32) in the disc-shaped body (20) of the second joint element (14) so as to cause, as a result of the application of a tensile force alternately on either the one or the other first control cable (26, 28), the rotation of the second joint element (14) relative to the first joint element (12) in a first plane of rotation coinciding with said first plane of symmetry and said second plane of symmetry, by rolling of each rolling profile (24) of the second joint element (14) on the corresponding rolling profile (18) of the first joint element (12); wherein said first holes (30) extend out of the disc-shaped body (16) of the first joint element (12), on the side facing the second joint element (14), at a plane (TT1 ) passing through the center (C1 ) of the rolling profiles (18) of the first joint element (12) and perpendicular to said first plane of symmetry, and wherein said second holes (32) extend out of the disc-shaped body (20) of the second joint element (14), on the side facing the first joint element (12), at a plane (TT2) passing through the center (C2) of the rolling profiles (24) of the second joint element (14) and perpendicular to said second plane of symmetry, and wherein the rolling profiles (18) of the first joint element (12) and the rolling profiles (24) of the second joint element (14) are toothed profiles, meshing with each other, characterized in that said rolling profiles (18, 24) are helical tooth profiles.
2. Joint according to claim 1 , wherein said first holes (30) are located at a distance (d1 ) from a straight line passing through the center (C1 ) of the rolling profiles (18) of the first joint element (12) and perpendicular to said first plane of symmetry that is greater than the radius (rp ) of the pitch circle of the teeth of said profiles, and wherein said second holes (32) are located at a distance (d2) from a straight line passing through the center (C2) of the rolling profiles (24) of the second joint element (14) and perpendicular to said second plane of symmetry that is greater than the radius (rp ) of the pitch circle of the teeth of said profiles.
3. Joint according to claim 1 or claim 2, wherein the teeth of the rolling profiles (18, 24) of the first joint element (12) and of the second joint element (14) extend over an arc of circumference greater than 90°, preferably greater than 100°.
4. Joint according to any one of the preceding claims, further comprising a third joint element (36) connected to the second joint element (14) so as to be rotatable relative to the latter, and a pair of second control cables (46, 48) for controlling the movement of the third joint element (36) relative to the second joint element (14), wherein the second joint element (14) comprises a pair of additional rolling profiles (38) that protrude from the disc-shaped body (20) of that element towards the third joint element (36) and are symmetrical with respect to a third plane of symmetry coinciding with a central diametral plane of said disc-shaped body (20); wherein the third joint element (36) comprises a disc-shaped body (40) and a pair of rolling profiles (44) that protrude from said disc-shaped body (40) towards the second joint element (14) and are symmetrical with respect to a fourth plane of symmetry coinciding with a central diametral plane of said disc-shaped body (40), wherein said fourth plane of symmetry coincides with said third plane of symmetry and the rolling profiles (44) of the third joint element (36) are each in contact with a respective additional rolling profile (38) of the second joint element (14); wherein the second control cables (46, 48) extend through a pair of additional first holes (50) in the disc-shaped body (16) of the first joint element (12), through a pair of additional second holes (52) in the disc-shaped body (20) of the second joint element (14), and through a pair of third holes (54) in the disc-shaped body (40) of the third joint element (36) so as to cause, as a result of the application of a tensile force alternately on either the one or the other second control cable (46, 48), the rotation of the third joint element (36) relative to the second joint element (14) in a second plane of rotation coinciding with said third plane of symmetry and said fourth plane of symmetry, by rolling of each rolling profile (44) of the third joint element (36) on the corresponding additional rolling profile (38) of the second joint element (14); wherein said additional second holes (52) extend out of the disc-shaped body (20) of the second joint element (14), on the side facing the third joint element (36), at a plane (TT2') passing through the center (C2') of said additional rolling profiles (38) of the second joint element (14) and perpendicular to said third plane of symmetry, and said third holes (54) extend out of the disc-shaped body (40) of the third joint element (36), on the side facing the second joint element (14), at a plane (TT3) passing through the center (C3) of the rolling profiles (44) of the third joint element (36) and perpendicular to said fourth plane of symmetry; and wherein said additional rolling profiles (38) of the second joint element (14) and the rolling profiles (44) of the third joint element (36) are helical tooth profiles, meshing with each other.
5. Joint according to claim 4, wherein said additional second holes (52) are located at a distance (d2') from a straight line passing through the center (C2') of said additional rolling profiles (38) of said second joint element (14) and perpendicular to said third plane of symmetry which is greater than the radius of the pitch circle of the teeth of said profiles, and wherein said third holes (54) are located at a distance (d3) from a straight line passing through the center (C3) of the rolling profiles (44) of the third joint element (36) and perpendicular to said fourth plane of symmetry that is greater than the radius of the pitch circle of the teeth of said profiles.
6. Joint according to claim 4 or claim 5, wherein the teeth of said additional rolling profiles (38) of the second joint element (14) and of the rolling profiles (44) of the third joint element (36) extend over an arc of circumference greater than 90°, preferably greater than 100°.
7. Joint according to any one of claims 4 to 6, wherein said second plane of rotation is perpendicular to said first plane of rotation.
8. Articulated arm (100) for a surgical robot, comprising at least two rigid arm segments (S1 , S2, S3, S4) connected to each other by means of a mechanical joint (10a, 10b, 10c) according to any one of the preceding claims.
PCT/IB2024/062748 2023-12-22 2024-12-17 Mechanical joint for an articulated arm of a surgical robot Pending WO2025133897A1 (en)

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IT202300027849 2023-12-22

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US20210290322A1 (en) * 2018-09-17 2021-09-23 Covidien Lp Highly articulated laparoscopic joint including electrical signal transmission therethrough
CN115844541A (en) * 2022-12-15 2023-03-28 凌视医疗科技(武汉)有限公司 Powerful continuum apparatus arm for intracavity diagnosis and treatment
US20230248417A1 (en) * 2020-06-17 2023-08-10 The Chinese University Of Hong Kong Articulating surgical device

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US20150202013A1 (en) * 2012-07-24 2015-07-23 Richard Wolf Gmbh Shaft for medical instruments, comprising movable sections
US20140257331A1 (en) * 2013-03-11 2014-09-11 Samsung Electronics Co., Ltd. Laparoscopic surgical devices having wire reducer
US20160051274A1 (en) * 2014-08-20 2016-02-25 Brigham Young University Rolling joint jaw mechanism
US20210290322A1 (en) * 2018-09-17 2021-09-23 Covidien Lp Highly articulated laparoscopic joint including electrical signal transmission therethrough
US20230248417A1 (en) * 2020-06-17 2023-08-10 The Chinese University Of Hong Kong Articulating surgical device
CN112790854A (en) * 2021-01-18 2021-05-14 崔威 Medical micro-power torsion screwdriver
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