Patent Description:
Previously, robotic surgical arms of robotic surgical systems were supported over a patient by mounting the robotic surgical arms to a patient's table or by mounting them to a patient side cart that was wheeled over the floor to the patient.

A patient side cart takes up floor space and typically requires cables routed along the floor between a master console and the patient side cart. The cords are easy to trip upon. Moreover, the patient side cart and the robotic surgical system require a set-up procedure. Sometimes instead to being at a patient's side, the patient side cart is positioned at the head or feet of the patient. After the surgery is completed, the patient side cart is moved out of the way. A patient side cart is heavy and difficult to move.

Additionally, while off the floor, mounting the robotic surgical arms to a patient's table typically limits the range of motion and the types of surgeries that may be performed. Robotic surgical arms may be mounted to either or both sides of the patient's table. However when mounted to the table, the robotic surgical arms are often limited in range of motion to avoid bumping one another.

It is desirable to mount the robotic surgical arms over a patient without cluttering the operating room floor while maintaining a significant range of motion in robotic surgical arms.

<CIT> discloses medical, surgical, and/or robotic devices and systems including offset remote center parallelogram manipulator linkage assemblies which constrains a position of a surgical instrument during minimally invasive robotic surgery.

The present invention is defined in the independent claims, with optional features being defined in the dependent claims.

The following drawings should be read with reference to the detailed description. Like numbers in different drawings refer to like elements. The drawings, which are not necessarily to scale, illustratively depict embodiments of the present invention and are not intended to limit the scope of the invention.

In the following detailed description of the embodiments of the invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one skilled in the art that the embodiments of the invention may be practiced without these specific details. In other instances well known procedures, components, and elements have not been described in detail so as not to unnecessarily obscure aspects of the embodiments of the invention.

In one embodiment of the invention, there is provided an apparatus comprising:.

There is also disclosed a set-up arm provided to support a robotic arm. The set-up arm includes a first set-up joint to couple to a support structure, a second set-up joint to couple to a robotic arm to provide support thereto; an idle link pivotally coupled between the first set-up joint and the second set-up joint, a counter balancing link coupled between the first set-up joint and the second set-up joint, a third pulley coupled to the counter balancing link between the counter balancing link and the first set-up joint, and at least one cable under tension wrapped over the first, second, and third pulleys, and coupled to the set up arm. The center points of the first pulley, the second pulley, and the third pulley form a triangle. The first set-up joint has a bracket with the first pulley rotatably coupled thereto. The counter balancing link generates a counter-balancing force to balance out a force of the weight or load at the second set-up joint. The counter balancing link includes a hollow housing having a cylindrical cavity with a first diagonally cut end forming an oval opening to increase stiffness. The counter balancing link further includes the second pulley rotatably coupled to the housing, the post coupled to the housing, and a first compression spring in the cylindrical cavity of the housing with its first end coupled to the housing. The first compression spring is under compression to balance out the force of weight at the second set-up joint. The at least one cable under tension is coupled to a second end of the first compression spring near its end.

Also disclosed is a counter-balanced arm including a first link, a second link pivotally coupled to the first link at a first pivot point, a third pulley rotatably coupled between the second link and the first link at the first pivot point, and a cable coupled to the second link, routed over the third pulley, the first pulley, and the second pulley. The first link can couple to a support mechanism at a first end. The first link has the first pulley rotatably coupled thereto. The second link has the second pulley rotatably coupled thereto. The second link further has a first compression spring having a first end coupled thereto. The cable is further coupled to a second end of the first compression spring to form a tension in the cable to counter balance a weight applied at an end of the second link.

Also disclosed is an apparatus including a linkage and a spring-cable-pulley balancing mechanism coupled to the linkage around a pivotal joint. The linkage couples to a support structure at a first end and support a weight at a second end. The spring-cable-pulley balancing mechanism counter balances the weight at the second end of the linkage. As the linkage is deformed to vertically adjust the height of the weight with a different moment arm length, the spring-cable-pulley balancing mechanism varies a cable path length to modify the compression of a spring and a tension in a cable to adjust the amount of counter balance force applied to the linkage.

Referring now to <FIG>, a robotic surgical system <NUM> is illustrated including a perspective view of an exemplary modular manipulator support assembly <NUM>, a platform linkage <NUM>, and a surgeon's console <NUM>. The platform linkage <NUM> may couple to a ceiling <NUM> or overhead support structure by means of a pair of brackets <NUM>. The modular manipulator support assembly <NUM> is slidingly coupled to the platform linkage <NUM>.

An operator O (generally a surgeon) performs a minimally invasive surgical procedure on a patient lying on an operating table T under the modular manipulator support assembly <NUM> and the platform linkage <NUM>. The operator O manipulates one or more input devices or masters <NUM> at the surgeon's console <NUM>. In response to the surgeon's inputs, a computer processor <NUM> of console <NUM> directs movement of endoscopic surgical instruments or tools <NUM>, effecting servo-mechanical movement of the instruments via the modular manipulator support assembly <NUM>. The image of the internal surgical site is shown to surgeon or operator O by a stereoscopic display viewer <NUM> in the surgeon's console <NUM>, and is simultaneously shown to assistant A by an assistant's display <NUM>. Assistant A assists in pre-positioning the manipulators <NUM>, <NUM> relative to patient P using set-up linkage arms <NUM>, <NUM>, <NUM>, <NUM>; in swapping tools <NUM> of the one or more of surgical manipulators for alternative surgical tools or instruments; and in operating related non-robotic medical instruments and equipment, and the like.

The modular manipulator support assembly <NUM> aligns and supports robotic manipulators, such as patient side manipulators <NUM> or endoscope camera manipulator <NUM>, with a set of desired surgical incision sites in a patient's body. The modular manipulator support assembly <NUM> generally includes an orienting platform <NUM> and a plurality of configurable set-up joint arms <NUM>, <NUM>, <NUM>, <NUM> coupleable to the orienting platform <NUM>. Each arm <NUM>, <NUM>, <NUM>, <NUM> is movably supporting an associated manipulator <NUM>, <NUM> which in turn movably supports an associated instrument. It will be appreciated that the depictions are for illustrative purposes only and do not necessarily reflect the actual shape, size, or dimensions of the modular manipulator support assembly <NUM>. This applies to all depictions described hereinafter.

In general terms, the arms or linkages <NUM>, <NUM>, <NUM>, <NUM> comprise a positioning linkage or set-up arm portion of system <NUM>, typically remaining in a fixed configuration while tissue is manipulated, and the manipulators <NUM>, <NUM> comprise a driven portion which is actively articulated under the direction of surgeon's console <NUM>. The manipulators <NUM>,<NUM> are primarily used for master/slave tissue manipulation, while the set-up arms <NUM>, <NUM>, <NUM>, <NUM> are used for positioning and/or configuring the manipulators <NUM>, <NUM> before use, when repositioning the patient, operating table, incision points, and the like.

For convenience in terminology, manipulators <NUM> actuating tissue with surgical tools <NUM> is sometimes referred to as a PSM (patient side manipulator), and a manipulator such as <NUM> controlling an image capture or data acquisition device, such as endoscope <NUM>, is sometimes referred to as an ECM (endoscope-camera manipulator), it being noted that such telesurgical robotic manipulators may optionally actuate, maneuver and control a wide variety of instruments, tools and devices useful in surgery.

The orienting platform <NUM> generally supports a plurality of set-up joint arms SJA1 <NUM>, SJA2 <NUM>, and SJX <NUM> for movably supporting the associated patient side manipulators <NUM>. Typically, each arm accommodates translation of the patient side manipulator in three dimensions (x, y, z) and rotation of the patient side manipulator about one vertical axis (azimuth). Generally, the set up joint arms <NUM>, <NUM>, and <NUM> support robotic surgical arms or patient side manipulators (PSM). Either or both of the right and left surgeon controls <NUM> may flexibly drive the robotic surgical arms or patient side manipulators coupled to the set-up joint arms <NUM>, <NUM>, and <NUM>. The surgeon O may select and switch between which arm he is controlling with the master controls <NUM> such as by using a foot pedal.

The orienting platform <NUM> further supports one set-up joint center arm <NUM> (SJC) for movably supporting the endoscope camera manipulator <NUM>. It will be appreciated that the set-up arms <NUM>, <NUM>, <NUM>, <NUM> may interchangeably support and position instrument <NUM> or camera <NUM> manipulators. Utilization of the orienting platform <NUM> to support the individually positionable set-up arms <NUM>, <NUM>, <NUM>, <NUM> and associated manipulators <NUM>, <NUM> advantageously results in a simplified single support unit having a relatively scaled down, compact size. For example, the single orienting platform <NUM> may obviate any need to individually arrange and mount each set-up arm <NUM>, <NUM>, <NUM>, <NUM> to a mounting base, which is often confusing and cumbersome. This in turn allows for a faster and easier set-up.

The orienting platform <NUM> may further include a display <NUM>. The display <NUM> may be used for set-up purposes, instrument changes, and/or for personnel viewing of a procedure. The display <NUM> is preferably adjustably mounted to the orienting platform <NUM> with a parallelogram linkage <NUM> so that personnel can view the monitor in a desired direction.

The platform linkage <NUM> movably supports the orienting platform <NUM> at a fifth hub <NUM>. That is, the fifth hub <NUM> is coupleable to the platform linkage <NUM>. The fifth hub <NUM> may be aligned with the pivot point of the set-up joint center arm <NUM>, which is preferably coincident with its incision site for the endoscope. The fifth hub <NUM> provides for rotation of the orienting platform <NUM> about a vertical axis as denoted by arrow SJC1 in <FIG>. Rotation of the orienting platform <NUM> about the pivot point of the endoscope manipulator <NUM> which is aligned with the surgical incision advantageously allows for increased maneuverability of the orienting platform <NUM> and associated set-up arms <NUM>, <NUM>, <NUM>, <NUM> in the direction in which a surgical procedure is to take place. This is of particular benefit during complex surgeries, as manipulator <NUM>, <NUM> positioning may be varied mid-operation by simply rotating the orienting platform <NUM> about the fifth hub <NUM>. Typically, the instruments will be retracted prior to rotation for safety purposes. For small rotations of the orienting platform <NUM> or tilting of the operating table, the low friction and balanced arms <NUM>, <NUM>, <NUM> may float while attached to the cannula during movement, pushed by force from the incisions.

Rotation of the orienting platform <NUM> about hub <NUM> (SJC1), rotation of the set-up joint arms <NUM>, <NUM> about hubs (SJA11), and rotation of the set-up joint auxiliary arm <NUM> about a hub are preferably power operated, but may alternatively be manual or computer controlled. Motors driving belt and pulley mechanisms for orienting platform rotation (SJC1) are within the orienting platform <NUM>. A brake system may also be included to allow the orienting platform <NUM> to be locked into place. Motors driving belt and pulley mechanisms for right, left, and auxiliary set-up arm rotation (SJA11, SJX1) <NUM>, <NUM>, <NUM> respectively may also be contained within the orienting platform <NUM>.

The platform linkage <NUM> generally comprises a linear rail <NUM>, a slideable carriage <NUM> coupleable to the rail <NUM>, and at least one arm <NUM> rotationally coupleable to the carriage <NUM> on a proximal end <NUM> and to the orienting platform <NUM> via hub <NUM> on a distal end <NUM>. The platform linkage <NUM> advantageously enhances maneuverability of the modular manipulator support <NUM> by accommodating translation of the orienting platform <NUM> in three dimensions (x, y, z). Movement of the orienting platform in a generally horizontal direction is denoted by arrow OP1. Movement of the orienting platform in a generally vertical direction is denoted by arrow OP2. Movement of the orienting platform in and out of the page is articulated by rotational movement of joint <NUM>, as denoted by arrow OP3. The platform linkage <NUM> further accommodates rotation of the orienting platform <NUM> about one vertical axis, as denoted by arrow SJC1. The arm <NUM> preferably comprises a four bar parallelogram linkage <NUM> extending between a pair of adjacent joints <NUM>, <NUM>. It will be appreciated that although the fifth hub <NUM> accommodates rotation of the orienting platform <NUM> (SJC1), the system may also be designed wherein the fifth hub <NUM> is rotationally coupleable to the platform linkage <NUM> so that the platform linkage accommodates pivotal motion of the orienting platform.

The orienting platform's <NUM> enhanced range of motion due to the platform linkage <NUM> permits access to incision sites over a wide range of the patient's body. This of particular benefit when performing complicated and lengthy procedures, where the manipulators <NUM>, <NUM> may be quickly repositioned mid-operation to alternative surgical sites. Typically, the instruments will be retracted prior to translation or rotation of the orienting platform <NUM> for safety purposes. The platform linkage <NUM> is preferably power operated, but may alternatively be manual or computer controlled. Motors may be located within the platform linkage <NUM> or orienting platform <NUM> to drive pulley and belt mechanisms. A brake system may also be included to allow the platform linkage <NUM> to be locked into place.

The platform linkage <NUM> may be mounted to a mounting base (not shown) via bolts and brackets <NUM> or other conventional fastener devices. The mounting base preferably comprises a ceiling-height support structure that may be coupled to the ceiling <NUM> so as to permit the manipulator support assembly <NUM>, <NUM> to extend generally downward from the base. A ceiling-height mounted manipulator support assembly <NUM>,<NUM> advantageously improves space utilization in an operating room, particularly clearing up space adjacent the operating table for personnel and/or other surgical equipment as well as minimizing robotic equipment and cabling on the floor. Further, a ceiling-height mounted manipulator support assembly minimizes the potential for collisions or space conflicts with other adjacent manipulators during a procedure and provides for convenient storage when the robotic surgery system is not in use.

The term "ceiling-height support structure" includes support structures disposed on, adjacent, or within an operating room ceiling and includes support structures disposed substantially below an actual ceiling height, especially in the case of a higher-than-typical operating room ceiling. The mounting base permits the manipulator support assembly <NUM>, <NUM> to be stored by pulling it against the wall. The mounting base may include existing architectural elements, such as original or reinforced structural elements, joists, or beams. Further, the mounting base may be formed from sufficiently rigid and stiff materials to inhibit vibration. Alternatively, passive means such as viscous or elastomer dampers or active means such as servo-mechanisms may be used to counteract vibration or interfloor movement of the hospital building in vertical and/or horizontal directions.

Each set-up joint arm <NUM>, <NUM>, <NUM>, <NUM> has simplified kinematics due to the improved range of motion provided by the manipulators <NUM>, <NUM>. Typically, the arms accommodate translation of the fixable links and joints in a generally vertical direction such as denoted by arrow SJC3 for arm <NUM> in <FIG> and arrow SJA13 for arm <NUM> in <FIG>,<FIG>. The arms also accommodate rotation of the fixable links and joints about two or three vertical axes.

Referring now to <FIG>, an exemplary set-up joint arm <NUM> and patient side manipulator <NUM> are illustrated. Set-up joint arm <NUM> is exemplary of each of the other set-up joint arms <NUM>, <NUM>, <NUM>. Patient side manipulator <NUM> is exemplary of the endoscopic camera manipulator <NUM>. Top views of the set-up joint arm <NUM> supporting the patient side robotic manipulator <NUM> are shown by <FIG>. The set-up joint arm <NUM> has four degrees of freedom (SJA11, SJA12, SJA13, SJA14), wherein the SJA11 joint is motorized and the other joints are manually positioned. <FIG> illustrate rotational motion of the set-up joint arm <NUM> as denoted by arrow SJA12. <FIG> illustrate both translational and rotational motion of the set-up joint arm <NUM> as denoted by arrows SJA13, and SJA14. The translational and rotational axes for the left set-up joint arm <NUM> (SJA2) is substantially similar to that of the right set-up joint arm <NUM> (SJA1).

As seen in <FIG>, arrows SJA11, SJA12, and SJA14 illustrate the rotational joints <NUM>, <NUM>, <NUM> respectively of the set-up joint arm <NUM>. The translational and rotational axes for the left set-up joint arm <NUM> (SJA2) are substantially similar to that of the right set-up join arm <NUM> (SJA1).

The set up joint arms <NUM>, <NUM>, <NUM>, <NUM> may be power operated, computer controlled, manually pre-configured, or a combination thereof. Preferably, joint SJA11 of the set-up joint arm <NUM> is motorized while the other joints are manually positioned. Motors may be located within the plurality of fixable links or orienting platform to drive pulley and belt mechanisms.

The fixable joints of the set-up arms <NUM>, <NUM>, <NUM>, <NUM> typically include a brake system to allow the joints to be locked into place after the arms are appropriately deployed. In <FIG>, the brake system releasably inhibits articulation of the fixable links <NUM>, <NUM>, and joints <NUM>, <NUM>, previously configured in at least substantially fixed configuration. The brake system is preferably biased toward the fixed configuration and includes a brake release actuator for releasing the fixable links <NUM>, <NUM> and joints <NUM>, <NUM> to a repositionable configuration in which the fixable links and joints can be articulated. The system may further include a joint sensor system coupling a plurality of the fixable links <NUM>, <NUM> and joints <NUM>, <NUM> to a servomechanism. The sensor system generates joint configuration signals. The servomechanism includes a computer and the joint sensor system transmits the joint configuration signals to the computer. The computer calculates a coordinate system transformation between a reference coordinate system affixed relative to a mounting base and the instruments using the joint configuration signals.

Referring now to <FIG> and <FIG>, the manipulators <NUM>, <NUM> are mechanically constrained so that a manipulator base <NUM> is at a fixed angle relative to horizontal. The manipulator <NUM> supported by the set-up joint arm <NUM> is angularly offset relative to horizontal in a range from forty degrees to about sixty degrees, preferably from about forty-five degrees to about fifty degrees. The manipulator <NUM> supported by the set-up joint auxiliary arm <NUM> is angularly offset relative to horizontal in a range from zero degrees to about twenty degrees, preferably by about fifteen degrees. The manipulator <NUM> supported by the set-up joint center arm <NUM> is angularly offset relative to horizontal in a range from forty degrees to about ninety degrees, preferably from about sixty-five degrees to about seventy degrees.

Preferably, the manipulators <NUM>, <NUM> comprise offset remote center linkages for constraining spherical pivoting of the instrument about pivot points <NUM> in space, wherein actuation of the fixable links and joints of the set-up joint arms <NUM>, <NUM>, <NUM>, <NUM> moves the pivot points. As discussed above, the overall complexity of the robotic surgical system may be reduced due to the improved range of motion of the system. Specifically, the number of degrees of freedom in the set-up joints arms <NUM>, <NUM>, <NUM>, <NUM> may be reduced (e.g., less than six degrees of freedom). This allows for a simpler system platform requiring less preconfiguration of the set-up joint arms <NUM>, <NUM>, <NUM>, <NUM>. As such, operating room personnel may rapidly arrange and prepare the robotic system for surgery with little or no specialized training.

Exemplary manipulators <NUM>, <NUM> providing for reduced mechanical complexity of the set-up arms <NUM>, <NUM>, <NUM>, <NUM> are described in further detail in <CIT>.

In <FIG>, the offset remote center manipulator <NUM> generally includes the manipulator base <NUM>, a parallelogram linkage base <NUM>, a plurality of driven links and joints <NUM>, <NUM>, and an instrument holder <NUM>. The manipulator base <NUM> is rotationally coupled to the parallelogram linkage base <NUM> for rotation about a first axis, also known as the yaw axis. The parallelogram linkage base <NUM> is coupled to the instrument holder <NUM> by rigid links <NUM>, <NUM> coupled together by rotational pivot joints. The driven links and joints <NUM>, <NUM> define a parallelogram so as to constrain an elongate shaft of the instrument or cannula <NUM> relative to a center of rotation (also referred to as a pivot point) <NUM> when the instrument is mounted to the instrument holder <NUM> and the shaft is moved along an insertion axis. The first axis and a first side of the parallelogram adjacent the parallelogram linkage base <NUM> intersect the shaft at the center of rotation <NUM>, wherein the first side of parallelogram is angularly offset from the first axis.

The manipulator base <NUM> of the surgical manipulators <NUM>, <NUM> is mounted and supported at a constant elevation angle by set-up arms <NUM>, <NUM>, <NUM>, <NUM>. The manipulator base <NUM> in this embodiment is fixed to a manipulator base support <NUM> of the set-up arms <NUM>, <NUM>, <NUM>, <NUM> by screws or bolts. Although the exemplary set-up arms <NUM>, <NUM>, <NUM>, <NUM> have a manipulator base support <NUM> suited to the geometry of a remote center manipulator <NUM>, <NUM>, manipulator base support <NUM> may take on a variety of alternative support configurations to suit other telesurgical manipulators. For example, the manipulator base support may be configured to support further alternative remote center manipulators, natural center manipulators, computed center manipulators, software center manipulators, and manipulators employing a combination of these functional principles. Further, as noted above, the manipulator base support <NUM> of the set-up arms <NUM>, <NUM>, <NUM>, <NUM> may interchangeably support and position instrument <NUM> or camera <NUM> manipulators.

In operation, once the motorized joint position SJAl <NUM> is set, typically to preset values, the user has only to align each remote center of the patient side manipulator with each incision. This may be done by attaching each patient side manipulator to the associated cannula which is already positioned within the incision. This automatically sets the set-up joint positions, as there is no remaining redundancy. The low friction and balancing of these three joints allows the patient side manipulators to float so that each manipulator can be controlled by holding it advantageously at a single point. Setting a motorized joint to a different position will result in a different azimuth angle for the patient side manipulator after the cannula is attached. In other words, the function of the redundant, motorized joint is to allow the patient side manipulator manipulator to be farther from or closer to another patient side manipulator or endoscope manipulator. Alternatively, after the cannula is attached, the azimuth can be adjusted by operating the motor while the set-up joint brakes are released and the cannula is held at the incision.

Each of the set-up joint arms <NUM>, <NUM><NUM>, <NUM> defines releasably fixable links and joints that are pre-configurable. Each set-up joint arm <NUM>, <NUM>, <NUM>, <NUM> includes at least one balanced, fixable, jointed parallelogram linkage structure <NUM> extending between a pair of adjacent fixable rotational joints <NUM>, <NUM>. The set-up joint arms <NUM>, <NUM>, <NUM>, <NUM> may be balanced by a variety of mechanisms including weights, tension springs, gas springs, torsion springs, compression springs, air or hydraulic cylinders, torque motors, or combinations thereof. In a preferred embodiment of the invention, a compact counter balancing mechanism is provided to balance the weight of the set-up joint arms and a robotic surgical arm, such as the patient side manipulators <NUM> and endoscopic camera manipulator <NUM>. Changes in tools or instruments <NUM> at the end of patient side manipulators <NUM> typically has no effect on the counter balancing mechanism as the weight of the tool or instruments is usually insignificant.

As shown in <FIG>, the set-up joint arm <NUM> includes the balanced, fixable, jointed parallelogram linkage structure <NUM> extending between a pair of adj acent fixable rotational joints <NUM>, <NUM>. The jointed parallelogram linkage structure <NUM> accommodates motion in a generally vertical direction, and the adjacent rotational joints <NUM>, <NUM> accommodate pivotal motion about vertical axes SJA12, SJA14. One or more linear or curved sliding axes could be used in lieu of any or all of the rotary ones. Each of the parallelogram linkage structures in the set-up joint arms may have a generally similar structure to the parallelogram linkage structure <NUM>, in this example comprising a parallel link <NUM> (including an upper link or idle link <NUM> and a horizontal or counter balancing link <NUM>), a proximal bracket <NUM>, and a distal bracket <NUM>. The proximal bracket <NUM>, and the distal bracket <NUM> may also be referred to as proximal and distal ends respectively of the parallel link <NUM>.

The parallel link <NUM> is pivotally jointed to proximal and distal brackets <NUM>, <NUM> respectively in a vertically-oriented planar parallelogram configuration. This permits pivotal motion of the parallel link <NUM> in the vertical plane, while constraining the brackets <NUM>, <NUM> to remain substantially parallel to one another as the parallelogram linkage structure <NUM> deforms or changes shape. As discussed previously, the rotational set-up joints <NUM>, <NUM> and their respective brackets <NUM>,<NUM> accommodate pivotal motion about the vertical axes SJA12, SJA14, respectively. Thus, the parallel link <NUM> and the bracket <NUM> may pivot in a horizontal plane about the set-up joint <NUM> and its axis SJA12.

As illustrated by <FIG>, the parallel link <NUM> includes the upper link or idle link <NUM> and the horizontal link or counter balancing link <NUM> pivotally coupled between and to the brackets <NUM>,<NUM>. The idle link <NUM>, the counter balancing link <NUM>, and the brackets <NUM>,<NUM> form the parallelogram linkage structure <NUM>. The bracket <NUM>, rotational joint <NUM>, and the manipulator <NUM> can move vertically with respect to the bracket <NUM> and rotational joint <NUM> as illustrated by arrows SJA13 in <FIG> and <FIG>.

<FIG> illustrates a right side magnified perspective view of the parallelogram linkage structure <NUM> including the idle link <NUM>, the counter balancing link <NUM>, the proximal bracket <NUM>, and the distal bracket <NUM>. As shown in <FIG>, the idle link <NUM> is pivotally coupled to the proximal bracket <NUM> at a pivotal joint <NUM> and to the distal bracket <NUM> at a pivotal joint <NUM>. The counter balancing link <NUM> is pivotally coupled to the proximal bracket <NUM> at a pivotal joint <NUM> and to the distal bracket <NUM> at a pivotal joint <NUM>. The pivotal joints <NUM>,<NUM>,<NUM>,<NUM> are located at the corners of the parallelogram linkage structure <NUM>.

<FIG> illustrates a left side magnified perspective view of the parallelogram linkage structure <NUM> of the set up joint arm <NUM>. In one embodiment of the invention, the set-up joint arm <NUM> couples to a ceiling height support structure through the joint <NUM>.

At joint <NUM> between the bracket <NUM> and the idle link <NUM>, the set up joint arm <NUM> includes a potentiometer <NUM> to measure the position of the parallelogram linkage structure <NUM>. At joint <NUM> between the bracket <NUM> and the counter balancing link <NUM>, the set up joint arm <NUM> includes a set-up joint brake <NUM>. When engaged, the set-up joint brake <NUM> at the joint <NUM> can hold the position of the parallelogram linkage structure <NUM>.

<FIG> illustrates a cutaway view of the parallelogram linkage structure <NUM> including the idle link <NUM>, the counter balancing link <NUM>, the proximal bracket <NUM>, and the distal bracket <NUM>. The counter balancing link <NUM> includes a substantial portion of the spring-cable-pulley balancing mechanism <NUM> that generally operates around the pivotal joint <NUM>.

The spring-cable-pulley balancing mechanism <NUM> includes one or more cables <NUM> coupled to the set-up arm that are wrapped over a plurality of pulleys <NUM>-<NUM> and tensioned by a compressible spring assembly <NUM>. The one or more cables <NUM> may couple to the set-up arm by coupling to the set-up joints or the counter balancing link <NUM>. In one embodiment of the invention, the one or more cables <NUM> may have segments that wrap over the plurality of pulleys <NUM>-<NUM> in one direction, wrap around a pin or post <NUM> to couple to the counter balancing link, and then route back and wrap over the pulleys <NUM>-<NUM> in a reverse direction. Wrapping the one or more cables around the pin or post <NUM> in this manner is a convenient way to have segments of a single cable act like a redundant pair of cables. Alternatively one end of each of the one or more cables may be clamped to the pin or post <NUM> or coupled to the set-up arm, the counter balancing link <NUM>, or one or the set-up joints by some other coupling mechanism. At least one end of each of the one or more cables <NUM> is clamped to an end of a compression spring <NUM> of the compressible spring assembly <NUM>.

In one example, the compression spring <NUM> is a coil spring. A compression spring is considered safer than a tension spring for a number of embodiments of the invention. If a tension spring breaks, the ends may fly apart and it would then be unable to provide any load to balance out any weight. On the other hand, if a compression coil spring breaks, the coil at the broken point will move slightly to rest on the next coil in the spring. This slight movement may only change the load by a small amount (e.g., <NUM>-<NUM>%), which may be computed by multiplying the space between coils by the spring rate.

In one example, there are four cables <NUM> under tension that wrap over post <NUM> making a U-turn so that eight cable segments are coupled to the end of the spring <NUM>. In one example, there is a total tension of approximately <NUM>,<NUM> (<NUM> pounds) all of the eight cable segments such that each substantially shares <NUM>,<NUM> (<NUM> pounds) of tension.

In one example, the plurality of pulleys <NUM>-<NUM> are of equal diameter. Each of the pulleys <NUM>-<NUM> and the post <NUM> may include one or more tracks in which the one or more cables <NUM> are wrapped and guided to substantially maintain their alignment. Pulley <NUM> is concentric with the pivotal joint <NUM> coupling to a shaft at the pivotal joint. With the one or more cables <NUM> wrapped over it, the pulley <NUM> does not rotate relative to the counter balancing link <NUM>. However, the counter balancing link <NUM> and the pulley <NUM> rotate together about the pivotal joint <NUM> with respect to the bracket <NUM>. Pulley <NUM> is rotationally coupled to an adjustable mount <NUM> that is coupled to the bracket <NUM>. The adjustable mount <NUM> may slide in the bracket <NUM> to adjust the position of pulley <NUM> and further adjust the tension in the cable <NUM> and spring <NUM> during set-up and maintenance. Changing the length of one of the sides of the triangle (sides a or b in the theory described below), adjusts the counter-balancing mechanism for variations in spring rate or the amount of weight being balanced. However, the adjustable mount <NUM> is rigidly fixed in placed during operational periods so that the position of the pulley <NUM> rotatably coupled to the adjustable mount <NUM> does not change. Pulley <NUM> is rotationally coupled to the housing of the link <NUM> and thus pivots with the link about the pivotal joint <NUM>. The center points or center point positions of the pulleys <NUM>-<NUM> are the corners or vertices of a triangle.

Referring now to <FIG>, magnified cutaway views of the counter balancing link <NUM> and the counter balancing mechanism <NUM> in differing positions are illustrated. The link <NUM> includes a hollow housing <NUM> with a cylindrical cavity <NUM> to receive the compressible spring assembly <NUM>. In one example, the cylindrical cavity <NUM> is a circular cylindrical cavity. Including the compressible spring assembly <NUM> in the link <NUM> makes for a more compact counter balancing mechanism. The housing <NUM> of the link <NUM> has a slanted or diagonally cut end <NUM> to allow for movement against the bracket <NUM> and the joint <NUM> while maintaining the strength of the link. The slanted end <NUM> also provides an oval opening into the cavity <NUM> through which the spring assembly <NUM> may be assembled. The housing <NUM> of the link <NUM> also has an opposite slanted or diagonally cut end <NUM> to allow for movement against the bracket <NUM> and the joint <NUM> while maintaining the strength of the link.

In some applications, such as medical or robotic surgical systems, it is desirable to make the parallelogram linkage structure stiff so that a substantially solid supporting structure may be provided. This is useful in preventing undesired vibrations that may be excited by movement, such as from movements in the robotic arm. Referring momentarily to <FIG>, the pivotal joints <NUM>,<NUM> at one end and the pivotal joints <NUM>,<NUM> at an opposite end are positioned so as to be widely spaced apart with respect to the housing of the links <NUM>,<NUM>. That is, the pivotal joints of the idle link are located near the top outside portion of the link and the pivotal joints of the counter balancing link are located near the bottom outside portion of the link. This lengthens the left and right sides of the parallelogram linkage structure respectively along the brackets <NUM>,<NUM>. The stiffness of the sides of the parallelogram linkage structure along the brackets is proportional to a square of the distance of separation between the pivotal joints <NUM>, <NUM> and the pivotal joints <NUM>,<NUM>. A bottom side of the housing <NUM> of the link <NUM> is made relatively strong to make it stiff and withstand the tension and compression in the link <NUM> between the pivotal joints <NUM>-<NUM>. The upper link <NUM> provides additional stiffness and strength to withstand the tension and compression in the parallel link <NUM> through the structure of its housing between the pivotal joints <NUM>-<NUM>.

Moreover, a tube may be torsionally stiffened if the ends are not allowed to deform but are maintained in shape, such as a circular shape. Referring back to <FIG>, a small opening <NUM> in the slanted or diagonally cut end <NUM> of the housing <NUM> allows the one or more cables <NUM> to be routed into the cylindrical cavity <NUM>. To maximize stiffness, the small opening <NUM> in the slanted or diagonally cut end <NUM> through which the cables are routed is made as small as possible. In the oval opening at the opposite end <NUM> of the link <NUM>, a plug <NUM> is inserted to maintain the cylindrical shape of the cavity <NUM>. The plug has a slit <NUM> (see <FIG>) on one side. The slit <NUM> is forced apart by a screw after installation to expand the plug against the wall or walls of the cavity <NUM>. The plug <NUM> reduces the size of the oval opening to a smaller opening at the end of the link <NUM> to increase its torsional stiffness. When the link <NUM> is finally assembled together, the ends of the cavity <NUM> are substantially closed with small openings in each to maximize stiffness.

In some applications, the linkage need not be so stiff or support heavy loads such that a serial linkage structure may be employed instead of a parallelogram linkage structure. In which case, a first link may have one end directly coupled to a ground or indirectly coupled to ground and an opposite end pivotally coupled to a second link, the counter balancing link.

The spring assembly <NUM> includes the spring <NUM> and a cable clamping mechanism <NUM>. The cable clamping mechanism may also be referred to as a spring piston. The spring <NUM> is mounted against a flange <NUM> of the housing <NUM> at one end and coupled to the one or more cables <NUM> at an opposite end by the cable clamping mechanism <NUM>. The cable clamping mechanism <NUM> may include a clamping sleeve <NUM> and one or more cable end tensioners <NUM>. These and other elements of the cable claming mechanism <NUM> are described further below with reference to <FIG>.

The pulleys <NUM>-<NUM> are in substantial alignment together in a plane such that their center points or center point positions are corners of a triangle. The relative positions of pulleys <NUM> and <NUM> to each other do not change when the link <NUM> and the linkage structure moves, such as illustrated by <FIG>. The relative positions of pulleys <NUM>,<NUM> and the post <NUM> to each other do not change when the link <NUM> moves. Thus, two sides of the triangle formed by the pivot points of the pulleys <NUM>-<NUM> do not change in length. However, the positions of the pulley <NUM> and the post <NUM> do change with respect to pulley <NUM>. The side of the triangle between pulleys <NUM> and <NUM> changes length as the link <NUM> and linkage structure are moved. That is the triangle formed by the pivot points of the pulleys <NUM>-<NUM> is adjustable in response to movement of the counter balancing link <NUM>. In a horizontal position of the counter balance link and the parallelogram linkage structure, such as illustrated in <FIG>, the adjustable triangle formed by the pivot points of the pulleys <NUM>-<NUM> may form a right triangle with at least one corner angle between the sides substantially being a ninety degree angle.

Consider for example, a linear distance X1 between pulleys <NUM> and <NUM> when the link <NUM> is angled upward as illustrated in <FIG>. The linear distance between the pulleys <NUM>-<NUM> increases to distance X2 when the link <NUM> is horizontal, as illustrated in <FIG>. A wrap angle of the cable <NUM> around individual pulleys <NUM>-<NUM> may change as well. However, the sum total wrap angle around the pulleys may remain constant as ends of the cable don't change angle relative to each other. The wrap angle is the angle around the pulley to which the cable makes contact. The wrap angle may also be viewed as the arctuate distance that a segment of the cable contacts the pulley. For example, the wrap angle of the cable <NUM> making contact to the pulley <NUM> is a first angle (<NUM> when the link <NUM> is angled upward as illustrated in <FIG>. In <FIG>, the wrap angle of the cable <NUM> making contact to the pulley <NUM> decreases to a second angle (<NUM> when the link <NUM> is horizontal as illustrated in <FIG>. Thus, as the post <NUM> moves with respect to the pulley <NUM> from its position in <FIG> to that of its position in <FIG>, some of the cable <NUM> may be paid out over the pulley <NUM> to compensate slightly for the increase in the distance between pulleys <NUM> and <NUM>. Moreover, the wrap angle of the cable <NUM> around pulley <NUM> increases from its initial position in <FIG> to that of <FIG>, and the wrap around pulley <NUM> increases also, so that the total wrap angle around all of the pulleys <NUM>-<NUM> is conserved. As the total wrap angle around all of the pulleys remains the same, a cable path length PL changes by the same amount as the difference between the linear distances X2 and X1. That is, the change in cable path length, delta(PL), can be determined by the following equation: <MAT>.

A change in the cable path length around the pulleys results in a change in tension in the spring <NUM> and the one or more cables <NUM>. For a given weight at the joint <NUM>, a greater moment at axis <NUM> is applied to the link <NUM> when the link is in the horizontal position as illustrated in <FIG> than when the link <NUM> is in the upward angled position as illustrated in <FIG>. This is due to different moment arm lengths in the different positions of the counter balancing link and the different deformations of the parallelogram linkage structure. Assuming the total cable length remains constant (e.g., there is no stretch or slippage in the clamps), as the distance X2 between the pulleys <NUM>-<NUM> becomes greater than X1, the cable <NUM> is pulled on and out from the link <NUM> to additionally compress the spring <NUM> and compensate for the greater moment being applied at the axis <NUM>. If the link <NUM> is moved further downward (not shown) past the horizontal position that is illustrated in <FIG>, an additional length of cable is pulled out from the link <NUM> to further compress the spring <NUM> and further increase the tension therein. As the link goes below horizontal, the triangle formed by the pulleys becomes obtuse and there is a loss in mechanical advantage for the spring. The loss in mechanical advantage is compensated for by the increased compression. As the link <NUM> moves back to its upward angled position, such as illustrated in <FIG>, the cable <NUM> is released back into the link <NUM> so that the spring <NUM> is decompressed and the tension is reduced in the spring <NUM> and cable <NUM> to compensate for a lower level of moment being applied at the axis <NUM>. In this manner after the initial tensions are set, the link <NUM> can properly counter balance a weight at differing positions with respect to the bracket <NUM> and the joint <NUM>.

<FIG> and <FIG> illustrate one embodiment of a counter balance link <NUM> and idle link <NUM> in a set-up arm. However, the counter balance link <NUM> and idle link <NUM> in the set-up arm may be further compacted trading off the amount of motion. For example, the counter balance link <NUM> may move positive and negative forty degrees from the horizontal position illustrated in <FIG>. If less motion is acceptable, the counter balance link may be further compacted.

Referring now to <FIG>, an embodiment of a more compact counter balance link <NUM>' in a set-up arm is illustrated. An idle link <NUM>' is coupled in parallel to the counter balancing link <NUM>'. The counter balance link <NUM>' may move positive and negative thirty degrees from a horizontal position, such as that illustrated by link <NUM> in <FIG>
Referring now to <FIG> and <FIG>, the link <NUM>' is somewhat similar to link <NUM> including similar elements with slight differences. For example, the link <NUM>' includes pulleys <NUM>'-<NUM>' and post <NUM>' similar to pulleys <NUM>-<NUM> and post <NUM> in link <NUM>. However the positions of the pulleys <NUM>',<NUM>' and post <NUM>' differ somewhat from the position of pulleys <NUM>,<NUM> and post <NUM>. The one or more cables <NUM>' in the link <NUM>' are shorter than cables <NUM> in link <NUM> given the lesser degree of motion. The hollow housing <NUM>' of the link <NUM>' is shorter than the hollow housing <NUM> of the link <NUM>. An opening <NUM>' into the cylindrical cavity <NUM>' of the housing <NUM>' differs somewhat from the opening <NUM> into the cylindrical cavity <NUM> of the housing <NUM>. The spring <NUM>' in the link <NUM>' is shorter than the spring <NUM> in the link <NUM>. But for these differences, the elements of link <NUM>' function similar to the elements of link <NUM>.

Referring now to <FIG>, a perspective view of the compact counter balance link <NUM> separate from the parallelogram linkage structure <NUM> is illustrated. At the slanted or diagonally cut end <NUM> of the housing <NUM>, the plug <NUM> closes the cavity <NUM> in the housing <NUM>. One or more cable end tensioners <NUM> extend out from the plug <NUM>. Near the opposite end of the housing is a shaft <NUM> extending through the housing with ends coupled to thereto.

Referring now to <FIG>, a perspective view of the compact counter balance link <NUM> is illustrated with the hollow housing <NUM> removed to better show the internal elements. Within the housing <NUM>, the pulley <NUM> is rotatably coupled to the shaft <NUM>. Within the housing <NUM> at the pivotal joint <NUM>, the pulley <NUM> is mounted on a shaft <NUM> between spaced apart pair of bearings <NUM> mounted on the shaft. The shaft <NUM> extends through the base of the housing <NUM> at one end. At the opposite end of the base at the pivotal joint <NUM>, another shaft <NUM> extends through the base of the housing <NUM> and has another pair of spaced apart bearings <NUM> mounted thereto.

The plug <NUM> has a cylindrical shape to match the cavity and has a flat end at one end and a slanted oval-like shaped end at an opposite end to match the slanted or diagonally cut end <NUM> of the housing <NUM>. The clamping sleeve <NUM> of the cable clamping mechanism <NUM> may be coaxial with the spring <NUM> in a center opening thereof so that it is substantially surrounded by the spring <NUM>.

Referring now to <FIG>, a magnified cutaway view of a portion of the compact counter balance link <NUM> is illustrated.

The cable clamping mechanism <NUM>, also referred to as a spring piston, includes the clamping sleeve <NUM> (also referred to as a counterbalance tube); a mating ring <NUM> (also referred to as a spring flange); a thrust bearing <NUM>, a preload adjustment nut <NUM>, and an anti-rotation plate <NUM> coupled together as shown.

Referring now to <FIG> and <FIG>, the plug <NUM>, is inserted into the cavity <NUM> to plug up the opening in one end of the housing <NUM>. The fastener <NUM> is inserted into the threaded hole <NUM> to maintain the alignment of the plug <NUM> in an appropriate position along the cavity wall. A spreading screw <NUM> is inserted into a threaded opening <NUM> in the split side of the plug <NUM>. A set screw <NUM> may be inserted into a threaded opening <NUM> to provide a backstop for the spreading screw <NUM>. Alternatively, the threaded opening <NUM> may be filled solid forming part of the split flange. As the end of the spreading screw <NUM> aligns and mates with the end of the set screw <NUM>, the split <NUM> and the plug <NUM> begin to expand. With further tightening of the screw <NUM>, the split <NUM> expands further forcing the sides of plug tightly against the wall of the cavity <NUM> to torsionally stiffen the compact counter balance link <NUM>. If the plug <NUM> is to be removed, the set screw <NUM> may be removed and the spreading screw <NUM> may be replaced with a special screw that has threads removed near its head, so that it can turn freely on the threads on that side of the split. If the sides of the plug <NUM> are stuck in expansion against the wall of the cavity, the special screw may be further threaded into the opening <NUM> pulling the split side of the plug together and the sides of the plug away from the wall of the cavity. In this manner, the plug should be more readily removed from the cavity <NUM> for disassembly and maintenance of the counter balance link.

The plug <NUM> has a center opening <NUM> to allow the one or more cable end tensioners <NUM> to pass through to the clamping block <NUM>. The one or more cable end tensioners <NUM> are used to remove slack and pre-tension the one or more cables <NUM> with substantially equal tension during assembly. The one or more cable end tensioners <NUM> are better illustrated in <FIG>.

Referring momentarily to <FIG>, each of the one or more cable end tensioners <NUM> includes a pre-tensioning spring <NUM> and a cable terminator <NUM>. The cable terminator <NUM> may be a ball, a sphere, a tube, a cylinder, or other block shape. The cable terminator <NUM> has a cylindrical opening <NUM> to slide over the end of the cable <NUM>. The cable terminator <NUM> may be crimped to an end to the cable <NUM> to retain the spring <NUM> on the cable. The pre-tensioning spring <NUM> is trapped between the clamping block <NUM> of the clamping sleeve <NUM> on one side and the cable terminator <NUM> on the opposite side. The pre-tensioning springs <NUM> pull out on the one or more cables <NUM> to pretension the cables prior to clamping the clamping block <NUM> thereto.

Referring now back to <FIG> and to <FIG> and <FIG>, the clamping mechanism <NUM> includes the threaded counter balance sleeve <NUM>,the clamping block <NUM>, the mating ring <NUM>, the thrust bearing <NUM>, the ribbonizer <NUM>, the threaded nut <NUM>, and the alignment plate <NUM>. The one or more cables <NUM> are routed through the spring <NUM>, the ring <NUM>, the bearing <NUM>, the threaded sleeve <NUM>, the ribbonizer <NUM>, and the nut <NUM> into and through openings <NUM> of the clamping block <NUM> and an opening <NUM> in the alignment plate <NUM>.

The ribbonizer <NUM> is formed of two ribbonizer halves 1015A-1015B. Each half 1015A-1015B has a planar portion 1202A-1202B, respectively, that are spaced apart to planarize and substantially align the one or more cables <NUM> for routing over the pulley <NUM>. When the halves are coupled together, the planar portions 1202A-1202B in each leave an opening <NUM> into the ribbonizer <NUM>. The two ribbonizer halves 1015A-1015B include a slot 1212A-1212B respectively to receive the clamping block <NUM>. During assembly, the two ribbonizer halves 1015A-1015B are inserted into and fit tightly within the threaded sleeve <NUM>. The ribbonizer halves further include a ridge segment 1224A-1224B to mate with a circular edge of the threaded sleeve <NUM>, acting as a stop so that the ribbonizer does not move further down into the threaded sleeve. The clamping block <NUM> doesn't move relative to threaded sleeve <NUM> or the ribbonizer <NUM>.

The clamping block <NUM> may be formed of five clamping plates 1214A-1214B, 1215A-1215C stacked over each other together to clamp to the one or more cables <NUM>. The five clamping plates 1214A-1214B, 1215A-1215C capture the one or more cables <NUM> in grooves 1204A-1204B between each. Each of the interior clamping plates 1215A-1215C may include a pair of grooves 1204A on one side and a pair of grooves 1204B on the opposite side and a pair of holes <NUM> to allow the clamping screws 1028A-1208B to slide through. The outer clamping plate 1214A may include the pair of grooves 1204B in a bottom side while the outer clamping plate 1214B includes the pair of grooves 1204A in a top side. The grooves 1204A-1204B are a little shallower than half the diameter of a cable <NUM>. In one embodiment of the invention, the diameter of each of the one or more cables <NUM> is <NUM> (<NUM> inches) The clamping plates are stacked next to each other, with a cable segment or cable <NUM> in each groove, nestled partway into the groove in a plate on one side, and in the groove of another plate on the other side. The parallel pair of grooves 1204A-1204B in the clamping plates respectively align up together with the parallel pair of grooves 1204B-1204A of another clamping plate forming the openings <NUM> in the clamping block <NUM> to clamp around the cable or cable segments.

The outer clamping plate 1214A further includes a threaded opening <NUM> to receive the threads of the clamping screw 1208A and a through opening <NUM> to allow the clamping screw 1208B to pass through it into the other clamping plates. The outer clamping plate 1214B further includes a threaded opening <NUM> to receive the threads of the clamping screw 1208B and a through opening <NUM> to allow the clamping screw 1208A to pass through it into the other clamping plates. Thus, the outer clamping plates 1214A-1214B may be substantially similar to reduce cost. In this manner, the clamping screws 1208A-1208B squeeze all clamping plates together from opposite sides to conserver space and assemble the clamping block <NUM> together. The screw clamping force is not divided up between the joints of the clamping plates, but rather is applied to all. Thus, the clamping screws 1208A-1208B may be small screws and can still clamp with a substantial clamping force around the cables.

In one example, with five clamping plates and four joints between them each having a pair of grooves between them, eight cables or eight cable segments of four cables may be received. With additional clamping plates more cables or cable segments may be received. Alternatively, additional grooves may be provided in each to increase the number of cables or cable segments clamped by the clamping block <NUM>. Alternatively, fewer grooves may be provided in each to increase the clamping force. In one embodiment of the invention, the clamping plates may only have one groove instead of a pair of grooves per side to provide twice the clamping force. To clamp around eight cables or eight cable segments of four cables, nine clamping plates are provided, two outer clamping plates 1214A-1214B and seven interior clamping plates.

As previously mentioned, the two ribbonizer halves 1015A-1015B include a slot 1212A-1212B respectively so that the ribbonizer <NUM> may receive the clamping block <NUM>. The threaded sleeve <NUM> also includes a pair of slots <NUM> on opposite sides to receive a portion of the clamping block <NUM> and hold it in place. The clamping block <NUM> is in turn fitted into the opening <NUM> in the anti-rotation plate <NUM> to keep the clamping block <NUM>, the threaded sleeve <NUM>, and the ribbonizer <NUM> from rotating in the cavity <NUM> of the housing <NUM>.

An end of the ribbonizer <NUM> is bolted to the anti-rotation plate <NUM>. At least one pair of fasteners <NUM> are inserted through at least one pair of diagonally spaced apart holes <NUM> in the anti-rotation plate <NUM>. The pair of fasteners <NUM> are threaded into at least one pair of threaded holes <NUM> to couple the ribbonizer to the anti-rotation plate.

The threaded sleeve <NUM> has an external thread <NUM> to threadingly engage an inner thread <NUM> of the nut <NUM>. The tension adjustment in the one or more cables <NUM> is provided by rotating the nut <NUM> onto the threaded sleeve <NUM> to compress the compressible spring <NUM>. The internal threads <NUM> of the nut <NUM> match the outer threads <NUM> of the threaded sleeve <NUM>.

Each end of the one or more cables <NUM> has a cable terminator <NUM> crimped near its end and a spring <NUM>. The spring <NUM> is trapped between the cable terminator <NUM> and the end of the clamping block <NUM>. If there were no springs <NUM>, it would be difficult to make the tensions the same in the one or more cables <NUM>, because the cables are not manufactured exactly the same length, and they may stretch varying amounts during initial assembly. During assembly, the clamping plates of the clamping block <NUM> are initially left loose. The compression on the compression spring <NUM> and the tension in the one or more cables is partially adjusted for the expected weight. The spring assembly <NUM> including the clamping mechanism <NUM> is run back and forth in the housing <NUM> by pivoting the link <NUM> to take out the initial stretch. At this point, all the tension on each cable is being applied to the springs <NUM>. Due to the variations previously mentioned above, some of the springs <NUM> may be compressed more than others. The difference in tension between the one or more cables <NUM> or their segments is the difference in length times the spring rate of the springs <NUM>. For example, if the difference in length between a pair of segments or cables is <NUM>,<NUM> (<NUM>,<NUM> inches) and the spring rate is <NUM>,1N/mm (<NUM> pounds/inch), the difference in tension is <NUM>,<NUM> (<NUM> pounds). The difference in tension in other cables or cable segments may be within a range of ten pounds, such as <NUM>,<NUM> to <NUM>,<NUM> (<NUM> lb or <NUM> lb) for example.

After the one or more cables are pre-tensioned, the clamp screws 1208A-1208B are tightened to clamp the one or more clamping plates of the clamping block around the one or more cables <NUM>. Then the compact counter balancing mechanism can be adjusted for proper balance by compression adjustment in the compression spring and adjusting the dimensions of the triangle formed by the center points of the pulleys. Prior to further adjustment, the total load in the spring <NUM> is about <NUM> (<NUM> lb), and if eight cable segments are used, about <NUM>/<NUM> or <NUM>,<NUM> (<NUM> lb) per cable segment. As long as each of the one or more cables <NUM> have the same characteristics, the difference in tension between the cable segments or cables remains. For example, some of the segments or cables will have a tension of <NUM>,<NUM> (60lb) while other will have a tension of <NUM>,<NUM> (63lb). The percentage variation in tension is relatively small, and each of the cable segments or cables share the load well. Another function of the springs <NUM> and cable terminators <NUM> of the cable end tensioners <NUM> is that if the clamp plates of the clamping block <NUM> were to slip, the cables <NUM> could only slide a little bit until the springs <NUM> went to their solid height. The cable terminators <NUM> of the cable end tensioners <NUM> are crimped sufficiently to the ends of the one or more cables so they will not give with the maximum load being applied to the spring <NUM>.

The preload balance adjustment nut <NUM> extends along a portion of the threaded sleeve <NUM> and includes an internal thread <NUM> to threadingly engage the external thread <NUM> of the threaded sleeve <NUM>. As the nut <NUM> is turned in one direction, it pulls out on the threaded sleeve <NUM> and compresses the spring <NUM> through the mating ring <NUM> and the thrust bearing <NUM>. The arrows <NUM>-<NUM> in <FIG> illustrate the direction of movement of the nut <NUM> along the sleeve <NUM> as the nut is turned to generate a larger tension in the spring <NUM> and the one or more cables <NUM>. The coaxial threaded sleeve <NUM> and its cable clamp <NUM> are moved outward away from the spring <NUM> to increase the tension in the spring <NUM> and the one or more cables <NUM>. The nut <NUM> is turned in an opposite direction so that the threaded sleeve <NUM> and its cable clamp <NUM> move into the spring <NUM> thereby releasing tension in the spring <NUM> and the one or more cables <NUM>. In a bottom side of the housing <NUM> are one or more openings <NUM> into the cavity <NUM> to gain access to and adjust the nut <NUM>.

Due to friction, the nut <NUM> can't be adjusted when the full force of the spring <NUM> is pushing on it. There are pin holes <NUM> in the each side of the housing <NUM> into which spring holding pins may be inserted. To pin the spring <NUM>, the counter balancing mechanism is pulled up or down until an appropriate pair of pin holes <NUM> on each side of the housing line up with the groove <NUM> in the mating ring <NUM> and put a restraining pin (not shown) in from each side to restrain the spring <NUM> from releasing. Lifting up on the counter balance link <NUM> relieves the tension force from the cables so that the adjustment nut <NUM> can be turned easily. After the adjustment nut <NUM> is rotated an appropriate amount, the restraining pins are removed from the groove <NUM> and the pin holes <NUM> so that the spring <NUM> releases back into a position along the cavity <NUM> to apply a tension in the one or more cables <NUM>.

The mating ring <NUM> mates the spring <NUM> to the clamping mechanism. The mating ring <NUM> includes an aligning lip <NUM> on one side. The aligning lip <NUM>, along with the body of the threaded sleeve <NUM>, hold the spring <NUM> in alignment at one end within the cavity <NUM> of the housing <NUM>. An opposite side of the mating ring <NUM> couples to the thrust bearing <NUM>.

On one side, the thrust bearing <NUM> allows the nut <NUM> to rotate so that its threads <NUM> can threadingly engage the threads <NUM> of the threaded sleeve <NUM>. The opposite side of the thrust bearing <NUM> presses down against a side of the mating ring <NUM> to compress the spring <NUM>.

Referring now to <FIG> and <FIG>, the anti-rotation plate <NUM> has one or more protrusions <NUM> (see <FIG>) that engage recesses (not shown) within the cavity <NUM> of the housing <NUM>. A rectangular opening <NUM> in the anti-rotation plate <NUM> receives the clamping block <NUM>. One or more bolts or fasteners <NUM> couple the anti-rotation plate <NUM> to the top of the threaded sleeve <NUM>. The one or more protrusions <NUM> of the anti-rotation plate <NUM> when engaged into the recesses of the cavity in the housing deter the threaded sleeve <NUM> and the clamping block <NUM> from rotating within the cavity <NUM> as the pre-tensioning nut is turned. This allows the pre-tensioning nut to adjust the tension and avoids the one or more cables <NUM> from twisting together. With the protrusions <NUM> in the recesses, the anti-rotation plate <NUM> moves along the wall of the cavity <NUM> with the threaded sleeve <NUM> as the nut <NUM> is turned and as the spring is compressed and released by the one or more cables <NUM>.

As shown in <FIG>, the plug <NUM> may include a split <NUM> along a top portion to split it into split portions and allow the end cap to slightly compress when inserted into the cavity <NUM> of the housing <NUM>. As is illustrated in <FIG>, the plug <NUM> includes a fastener <NUM> near its top portion having the split <NUM>. The fastener <NUM> forces the split portions of the plug <NUM> apart to expand the plug <NUM> against the walls of the cavity <NUM>. A fastener <NUM> is inserted through the housing <NUM> and threaded into a bottom portion of the plug <NUM>. The fastener <NUM> aligns the plug <NUM> within the cavity <NUM>. One end of the springs of the cable end tensioners <NUM> couples to the clamping block <NUM>. The opposite end of the springs couple to a cable terminator that is crimped onto each of the one or more cables.

To couple the cable clamping mechanism to the one or more cables near their ends during assembly of the parallel linkage structure <NUM> and the counter balancing link <NUM>, the compression spring <NUM> is pinned into a compressible state by inserting a pair of pins into one of the holes <NUM> on each side of the housing <NUM> so that the nut <NUM> may be turned. From the post <NUM>, the one or more cables <NUM> are routed over the pulleys <NUM>-<NUM> or <NUM>'-<NUM>' and into the cavity <NUM>,<NUM>' and through the spring <NUM>. The one or more cables are further slid through the clamping plates of the clamping block <NUM>. Each of the one or more cables <NUM> is independently pre-tensioned by the one or more cable end tensioners <NUM> to remove the slack in the cables and to substantially equalize an initial tension in each. In one example, the initial tension in each cable is set by the spring <NUM> in the cable end tensioner <NUM>. In one example, the initial tension in each cable is on the order of <NUM>,<NUM> (<NUM> pounds).

After pre-tensioning the one or more cables <NUM>, the clamping mechanism is engaged to clamp the one or more cables to the clamping block <NUM>. The clamping screws are turned to move the clamping plates to capture the one or more cables against the clamping block <NUM>.

Next, the one or more cables <NUM> are tensioned to counter balance an expected weight or load that is to be supported at the set-up arm. The load may be the weight of a robotic arm, medical equipment, further linkage or other devices that may couple to the parallelogram linkage structure. The pre-load adjustment nut <NUM> is turned to adjust the tension in the spring <NUM> and establish a tension in the cables. The tension in the spring <NUM> may be substantially equally shared by the one or more cables <NUM>. The position of block <NUM> to which the pulley <NUM> is coupled may also be adjusted as needed to compensate for spring variations or load variations.

With the counter-balancing link assembled and calibrated in the parallelogram linkage structure, the expected weight or load on the set up arm can be balanced out so that the linkage structure can be readily moved in a vertical direction against the force of gravity. As the linkage structure is moved, the moment or force at the joints of the counter-balancing link may vary. The counter-balancing link <NUM> balances out or compensates for the variance or change in moment or force at its joints. Generally, the variable force or moment generated by the counter-balancing link <NUM> to balance out or compensate for the moment or force at its joints may be referred to as a counter balancing force or counter balancing moment. The one or more cables <NUM> wrap or unwrap over the pulleys <NUM>-<NUM> in the counter balancing link <NUM> to compress or decompress the spring <NUM> and respectively increase or decrease the tension in the one or more cables <NUM> in generating the counter balancing force. An increase in tension in the one or more cables <NUM> balances out an increase in moment or force at the joints of the counter balancing link <NUM>. A decrease in tension in the one or more cables <NUM> balances out a decrease in moment or force at the joints of the counter balancing link <NUM>.

After the set-up arm has been moved into proper position and the load or weight balanced out, the set-up joint brakes may be applied to deter movement in the set up arm, the parallelogram linkage structure, and the counter balancing link <NUM>.

Referring now to <FIG>, a single link <NUM> is illustrated pivotally coupled to a vertical wall <NUM> at a pivot point O. The link <NUM> rotating in a vertical (and horizontal) plane can be balanced by a linear spring <NUM> so that it is in equilibrium in any position despite the effect of gravity. The force of gravity (f=mg) is equal to the mass m times the acceleration of gravity g which is exerted at the midpoint of the link. The length of the link <NUM> is <NUM> so that its midpoint is a distance l along the link. The linear spring <NUM> has a spring constant K and couples to the link <NUM> at a point v and the wall <NUM> at a point w. The link <NUM> makes an angle theta with the wall W as illustrated in <FIG>.

Referring now to <FIG>, a schematic diagram of the rigid link <NUM> is illustrated pinned at point O and held by the linear spring <NUM> attached to the vertical wall <NUM> at the point w. A distance x separates points w and v. A distance b separates points w and o. A distance a separates points o and v. A distance t is along a line between point o and a point normal to the line between points w and v.

For the link to be in equilibrium with the force of gravity, the moment Mo about the point O should be substantially zero. From <FIG> we can determine the equation for the moment Mo about the point O as: <MAT> where x<NUM> is the unstretched length of the spring.

Rearranging the terms of the equation we have <MAT>.

With the link <NUM> at an angle theta (θ) with the wall that is not equal to zero, we can substitute in an equation for t derived from similar triangles (see <FIG>): <MAT>.

Rearranging the equation to solve for t we find: <MAT>.

Substituting in the equation for t which cancels the sine terms we find: <MAT>.

If the unstretched length of the spring, x<NUM>, is equal to zero, the equation further reduces to: <MAT>.

Rearranging the terms to solve for the spring constant, we have: <MAT>.

Thus, the equation for the spring constant K indicates that the stiffness K of the spring <NUM> can be constant and independent of the angle theta θ of the link. The stiffness K of the spring can be constant and independent of the angle theta θ if the unstretched length x<NUM> of the spring <NUM> is chosen to be substantially zero. The unstretched length x<NUM> of the spring <NUM> may be set to substantially zero if the tension spring <NUM> is placed outside the line connecting the points w and v.

Therefore, the link <NUM> may be balanced for all of its positions if (i) the stiffness K of the spring is properly chosen according to the equation K = mgl/ab; and (ii) the spring is placed outside of the line wv between its connection to the link and a fixed reference point.

Referring now to <FIG>, a spring, pulley, and cable counter balancing mechanism for the link <NUM> is illustrated. <FIG> illustrates a tension spring <NUM> placed outside the line connecting points w and v so that the unstretched length x<NUM> of the spring <NUM> is effectively set to substantially zero. A cable <NUM> is routed from the spring <NUM> over a pulley <NUM> at the point v and coupled to the wall <NUM> at the point w. For accurate balance, the diameter of the pulley <NUM> should be small relative to the sides a and b of the triangle. However where spring loads are high, a cable that is strong enough to hold a load safely needs a pulley of an appropriate size so as not to fail from bending fatigue during use. Thus, the single pulley <NUM> may not be practical for some applications. In which case, a three pulley system may be used as illustrated in <FIG>.

<FIG> illustrates a schematic diagram of the rigid link <NUM> with a similar triangle to that of <FIG> illustrates a schematic diagram of a three pulley system corresponding to the schematic diagram of <FIG>. As described previously, the distance x separates points w and v. The distance b separates points w and o. The distance a separates points o and v. The distance t is along a line between point o and a point normal to the line between points w and v.

In <FIG>, a schematic diagram of a spring-cable-pulley balancing mechanism is illustrated with three pulleys 1512A-1512C for balancing the weight and moment of the link <NUM>. A cable <NUM> is wrapped around a portion of each of the three pulleys 1512A-1512C. Each of the three pulleys 1512A-<NUM> may be of equal diameter, and the distances a and b in the system can be maintained constant. However as the angle theta θ changes, the total cable path length (a + b +x) of the cable <NUM> changes by the same amount as x does, because the total wrap angle of the cable <NUM> on the three pulleys is constant. The change in cable length pulls or pushes on the spring of the spring assembly <NUM> and adjusts the counter balance force applied to maintain a substantially zero moment and balance out the weight of the link.

The additional weight of additional links and an attached robotic surgical arm may also be balanced out by a counter balancing force with an appropriate choice of spring constant K and cabling that is capable of withstanding the additional forces applied.

While a parallelogram link structure <NUM> of the set-up joint arm <NUM> has been described in detail with reference to the patient side manipulator (PSM) <NUM>, a parallelogram linkage structure may be also used in the set-up joint center arm <NUM> supporting the endoscope camera robotic manipulator <NUM> or other set-up joint arms or structures of a robotic surgical system.

As illustrated in <FIG>, the set-up joint center arm <NUM> comprises a relatively short, near vertical rigid arm defined primarily by the parallelogram link structure <NUM>. The set-up joint center arm <NUM> has a shorter parallelogram link <NUM> than the other three arms <NUM>, <NUM>, <NUM>. The set-up joint center arm <NUM> has three degrees of freedom that are typically manually positioned. The set-up joint center arm <NUM> is free of any redundant joints as the azimuth angle is controlled by the rotation of the orienting platform <NUM>. The set-up joint center arm <NUM> may be vertically translated similar as denoted by arrow SJC3. The general rotational motion of the set-up joint center arm <NUM> is denoted by arrow SJC4 in <FIG>.

While embodiments of the invention have been described in detail with reference to a ceiling mounted robotic surgical system <NUM>, the embodiments of the invention may be equally applicable to robotic surgical systems that do not mount to the ceiling but instead are supported by flooring or mounted to a table. Additionally, the embodiments of the invention have been described in detail with reference to a parallelogram linkage structure. However, the embodiments of the invention may be equally applicable to other linkages, such as serial linkage arm structures that are to be counter balanced or other parallel linkage structures that are to be counter balanced. Moreover, the embodiments of the invention have been described with reference to a spring-cable-pulley counter-balancing mechanism. The cable and pulleys may instead be a belt or strap and pulleys, a chain and sprockets, a perforated metal tape and pulleys with bull nose pins, or a timing belt and timing gears. The pulleys, sprockets, pulleys with bull nose pins and timing gears may be collectively referred to as rotating transmission devices. The cable, belt, strap, chain, perforated metal tape, and timing belt may be collectively referred to as a tension mechanism.

Claim 1:
An apparatus (<NUM>, <NUM>) comprising:
a linkage (<NUM>), comprising a link (<NUM>, <NUM>, <NUM>) coupled between a proximal bracket (<NUM>) and a distal bracket (<NUM>), the proximal bracket (<NUM>) coupled to a support structure (<NUM>, <NUM>, <NUM>) at a first end, the linkage (<NUM>) being adapted to support a load applied to a second end of the linkage (<NUM>) opposite the first end;
a balancing mechanism (<NUM>) coupled to the linkage (<NUM>) around a pivotal joint (<NUM>), the balancing mechanism (<NUM>) including a compression spring (<NUM>), a cable (<NUM>), and three pulleys (<NUM>, <NUM>,<NUM>) with center points of the three pulleys (<NUM>, <NUM>, <NUM>) forming corners of an adjustable triangle having one side which changes in length when the link (<NUM>, <NUM>, <NUM>) and the linkage (<NUM>) moves, with a first (<NUM>) of the three pulleys coupled to a shaft at the pivotal joint (<NUM>), wherein the cable (<NUM>) wraps over the three pulleys (<NUM>, <NUM>, <NUM>) and has a first end coupled to the compression spring (<NUM>) to counter balance the load applied to the second end of the linkage;
wherein the link (<NUM>, <NUM>, <NUM>) houses the compression spring (<NUM>) and is coupled to the three pulleys (<NUM>, <NUM>, <NUM>) and a second end of the cable (<NUM>);
wherein as the linkage (<NUM>) vertically adjusts the position of the load with a varying moment arm length, the balancing mechanism (<NUM>) varies a cable path length to modify the compression of the compression spring (<NUM>) and the tension in the cable (<NUM>) to adjust a counter balance force applied to the linkage (<NUM>); and
wherein a linear distance between the other two (<NUM>, <NUM>) of the three pulleys that are not the first of the three pulleys varies to modify the cable path length in response to changes in positions of the linkage (<NUM>) to adjust the counter balance force.