Guide systems for laminated spring assemblies

A patient side-system includes a column with a rail and a counterbalance subsystem. The patient side-system may further include a braking subsystem. The counterbalance subsystem includes a spring assembly coupled at one end to the column with a spring member, and a housing movably coupled to the rail. The housing includes a drum to receive the spring member and a plurality of roller elements to guide a movement of the spring member winding or unwinding on the drum. If present, the braking subsystem includes a first pulley rotatably coupled to the column, a second pulley with a locking mechanism spaced apart from the first pulley and rotatably coupled to the column, and at least one brake cable wrapped around the first pulley and the second pulley with ends coupled to the housing. The locking mechanism can set a position of the housing along the column.

FIELD

The embodiments of the invention generally relate to robotic surgical systems. More particularly, the embodiments of the invention relate to a guide system for one or more laminated constant force spring (CFS) assemblies.

BACKGROUND

Previously, counterbalancing has been used for placement of robotic surgical arms in a static position prior to surgery. However, conventional counterbalancing mechanisms suffer from a number of disadvantages.

For instance, previously, robotic surgical arms have been positioned using conventional counterbalancing mechanisms. One conventional counterbalancing mechanism involves a constant force spring (CFS) assembly that controls the winding and unwinding of a spring member having at most three (3) laminations, namely three layers of material placed substantially in parallel and substantially in close physical proximity to each other, which wind and unwind from a common cylindrical drum.

This maximum number of laminations is partly due to the fact that, as the spring assembly is moved along a straight line of transport, the sections of the individual laminations (or layers) begin to separate from each other. Moreover, as the number of laminations increase, the separation becomes more pronounced, requiring more and more space for the spring assembly to operate. This poses a substantial problem where space for a counterbalance system is limited. Such limits are imposed by size requirements for the robotic surgical system.

In addition, the conventional counterbalancing mechanisms have failed to provide a high degree of safety, reliability and mechanical redundancy, since such mechanisms do not sufficiently spread the tension force in the event of a failure by one of the laminations within the spring assembly. In other words, the presence of two or three laminations within the spring assembly does not provide an acceptable level of safety because the failure of one lamination would result in a substantial reduction of the counterbalance force (e.g., 33-50% of the counterbalanced weight). In addition, carrying higher loads in a spring lamination adversely reduces the useful life of the spring assembly so that it will not likely survive for the entire expected life of the robotic surgical system.

BRIEF SUMMARY

The embodiments of the invention are summarized by the claims that follow below.

DETAILED DESCRIPTION

The embodiments of the invention are related to a guide system for one or more laminated constant force spring assemblies. According to one embodiment of the invention, the guide system is based on rolling elements that can be bearing or bushing supported, to reduce friction present as the spring members move past the roller elements. As alternative embodiments of the invention, the guide system may be based on a static guide surface or a moving guide surface.

In the following description, certain terminology is used to describe features of the invention. For example, the term “lamination” is generally defined as a strip of material placed substantially in parallel and in close physical proximity with other strips of material to collectively form a spring member. The laminations in a spring member typically wind around a common drum. These strips of material are biased to gravitate toward a “wound” state. Examples of types of material forming the lamination may include, but are not limited or restricted to a strip of metal or metal alloy (e.g., stainless steel). According to one embodiment of the invention, the strips of material (or laminations) forming a spring member are affixed together only at one end, but remain in close proximity to each other due to this affixation and the tension applied to the laminations. According to another embodiment of the invention, the strips of material (or laminations) forming the spring member are affixed together at both ends. In either case, one end of the spring member is wound around a drum as part of a constant force spring (CFS) assembly.

A “spring assembly” is generally defined as one or more constant force spring (CFS) assemblies, each of which includes a spring member.

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 methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments of the invention.

A. Robotic Surgical System

Referring now toFIG. 1, a block diagram of a robotic surgery system100is illustrated to perform minimally invasive robotic surgical procedures using one or more robotic arms158. These robotic arms often support a surgical tool. For instance, a robotic surgical arm (e.g., the center robotic surgical arm158C) is used to support a stereo or three-dimensional surgical image capture device101C such as a stereo endoscope (which may be any of a variety of structures such as a stereo laparoscope, arthroscope, hysteroscope, or the like), or, optionally, some other stereo imaging modality (such as ultrasound, fluoroscopy, magnetic resonance imaging, or the like). Robotic surgery may be used to perform a wide variety of surgical procedures, including but not limited to open surgery, neurosurgical procedures (e.g., stereotaxy), endoscopic procedures (e.g., laparoscopy, arthroscopy, thoracoscopy), and the like.

A user or operator O (generally a surgeon) performs a minimally invasive surgical procedure on patient P remotely by manipulating control input devices160at a master control console150while observing the procedure through a stereo display device164. A computer151of the console150directs movement of robotically controlled endoscopic surgical instruments101A-101C via control lines159, effecting movement of the instruments using a robotic patient-side system152, also referred to as a patient-side cart.

The robotic patient-side system152includes one or more robotic arms158. Typically, the robotic patient-side system152includes at least three robotic surgical arms158A-158C (generally referred to as robotic surgical arms158) supported by corresponding positioning set-up arms156. The central robotic surgical arm158C may support an endoscopic camera101C. The robotic surgical arms158A and158B to the left and right of center, may support tissue manipulation tools101A and101B, respectively.

Generally, as shown in this embodiment of the invention, the robotic patient-side system152includes a positioning portion and a driven portion. The positioning portion of the robotic patient-side system152remains in a fixed configuration during surgery while manipulating tissue. The driven portion of the robotic patient-side system152is actively articulated under the direction of the operator O generating control signals at the surgeon's console150during surgery. The “driven portion” of the robotic patient-side system152may include, but is not limited or restricted to robotic surgical arms158A-158C.

As an exemplary embodiment, the “positioning portion” of the robotic patient-side system152that is in a fixed configuration during surgery may include, but is not limited or restricted to “set-up arms”156. Each set-up arm156may include a plurality of links and a plurality of joints. Each set-up arm may mount via a first set-up-joint157to a housing310that may be moveably attached to a cart column200, as is further described below with reference toFIG. 2.

An assistant A may assist in pre-positioning of the robotic patient-side system152over the table T relative to patient P as well as swapping tools or instruments101for alternative tool structures, and the like, while viewing the internal surgical site via an assistant's display154.

Referring now toFIG. 2, a perspective view of the robotic patient-side system152is illustrated. The robotic patient-side system152comprises a cart column200supported by a base202. One or more robotic surgical arms158are respectively attached to one or more set-up arms156that are a part of the positioning portion of robotic patient-side system152. Situated approximately at a central location on base202, the cart column200includes a protective cover210that protects components of a counterbalance subsystem and a braking subsystem (described below) from contaminants.

Excluding a monitor arm154, each robotic surgical arm158is used to control robotic surgical tools101A-101C. Moreover, each robotic surgical arm158is coupled to a set-up arm156that is in turn coupled to a carriage housing310in one embodiment of the invention, as described below with reference toFIG. 3. The one or more robotic surgical arms158are each supported by their respective set-up arm156, as is illustrated inFIG. 2.

The robotic patient-side system152generally has dimensions suitable for transporting between operating rooms. It typically can fit through standard operating room doors and onto standard hospital elevators. The robotic patient-side system152may have a weight and a wheel (or other transportation) system that allows the cart to be positioned adjacent an operating table by a single attendant. The robotic patient-side system152may be sufficiently stable during transport to avoid tipping, and to easily withstand overturning moments that may be imposed at the ends of the robotic arms during use.

Referring toFIG. 3, a perspective view of the cart column200of the robotic patient-side system152that is used to control the positioning of one or more set-up arms is shown. Cart column200is illustrated in rectangular form with each rectangular side200A-200D featuring a counterbalance subsystem300vertically adjusted along a rail370and a braking subsystem380.

According to this embodiment of the invention, counterbalance subsystem300comprises a carriage housing310that includes a first housing portion312and a second housing portion314(collectively housing portions312and314form the carriage housing310). The second housing portion314is adapted to cover and protect one or more linear bearing assemblies that enable mobility along the rail370and corresponding roller elements as shown inFIG. 5.

As shown, first housing portion312is adapted to house N laminated constant force spring (CFS) assemblies with N greater than or equal to one, such as the CFS assemblies320A-320B, that comprise the spring assembly350. Carriage housing310is moved in a substantially vertical direction supported by the winding and unwinding of one or more spring members of the spring assembly350, such as CFS assemblies320A-320B. In other words, the winding and unwinding operations by the CFS assemblies320A-320B exert a relatively constant upward force, counterbalancing the weight of set-up and robotic arms (such as set-up arm156illustrated inFIG. 2, which adjusts the pre-surgery positioning of the corresponding robotic arm158). As the number of links and joints in each set-up arm may vary, the weight between set-up arms may differ. Thus, a differing number of laminations may be used in each of the one or more spring members for each set up arm as their weights may differ.

The first housing portion312comprises a top surface315that includes a recessed area (also referred to as a pocket)316with a slot317. More specifically, an end of the set-up arm (not shown) is mounted on the top surface315and secured to the carriage housing by fasteners such as bolts. The slot (also referred to as a clearance hole)317may be used to feed electrical cabling through the set-up arm to control the robotic surgical arm. As an optional embodiment, it is contemplated that the set-up arm may be secured to the first housing portion312by any other attachment mechanism and, in fact, may be secured to other surfaces of the carriage housing310besides its top surface315.

Referring still toFIG. 3, the vertical position of the carriage housing310along cart column200is set by the braking subsystem380, which features two brake cables385that rotate around a first pulley390and a locking pulley392. One end of each of the two brake cables385is coupled to a bottom side of the carriage housing310via a spring loaded tensioner394, as is illustrated inFIG. 3. An opposite end of each of the two brake cables385is coupled to a top side of the carriage housing310via turnbuckles396, as is also illustrated inFIG. 3. This allows the cable tension in each of the brake cables385to be separately adjusted and maintained during operation.

The locking pulley392allows the cables385to be rotated, but has a locking mechanism that halts further rotation of the cables385until unlocked. By halting rotation by the locking pulley392, the carriage housing310is retained at the desired height by the cables385. For instance, when the carriage housing310is lowered vertically down the rail370, the cables385and pulleys390,392, are rotated in a clockwise direction. Likewise, when the carriage housing310is vertically translated upward toward a top cap portion220of the cart column200, the cables385and pulleys390,392, undergo a counter-clockwise rotation.

Referring toFIGS. 3 and 4, an exemplary embodiment of one or more spring members360,365for the spring assembly350is shown. The one or more spring members360,365are fed through an opening between the first housing312and the second housing314of the carriage housing310. In this exemplary embodiment of the invention, the spring assembly350includes the first CFS assembly320A with the first spring member360and the second CFS assembly320B with the second spring member365.

Herein, each of the spring members360and365include a plurality of laminations, such as four or more layers of material (laminations) with a first end355of the spring assembly350being attached to the top cap portion220of cart column200by bolting, laser welding, or any other method of attachment. As an example, the first spring member360includes at least seven laminations and perhaps up to nine laminations. The second spring member365includes at least seven laminations or perhaps ranges between seven to nine laminations. The number of laminations selected is based in part on the weight of the arms that are to be supported by the carriage housing310. In one embodiment of the invention, each layer of lamination is a strip of stainless steel approximately three (3) inches wide, sixty-seven to seventy-five (67-75) inches long, and twenty-thousandths of an inch (0.020) thick.

Of course, it is contemplated that spring assembly350may comprise a plurality of CFS assemblies with multiple spring members having multiple laminations or a single CFS assembly with a single spring member having at least four laminations or most likely more than or equal to seven laminations.

Referring now toFIG. 5, a cut-away view of a portion of the carriage housing310and the spring assembly350ofFIG. 3are illustrated. A stop barrier500is positioned below the top cap portion220of the cart column200into order preclude movement of the carriage housing310above a predetermined height. This prevents the carriage housing310from lifting off the guide rail370. As shown, the stop barrier500is a reinforced member that would come into contact with a top surface of the second housing314if the carriage housing310is lifted above a predetermined maximum height.

As previously described, the second housing314of the carriage housing310is movably coupled to the rail370mounted on the cart column200. More specifically, first housing312houses a number of components, including but not limited to one or more CFS assemblies320, namely the first and second CFS assemblies320A and320B, and a first roller element540. The first CFS assembly320A includes a cylindrical drum510supported by a shaft520positioned laterally across first housing312. The cylindrical drum510is rotatably coupled to the first and second housing portions312,314of the carriage housing310by the shaft520. Similarly, the second CFS assembly320B is positioned below the first CFS assembly320A and features the same general construction.

One or more spring members360,365are fed through opening530between the first and second housings312and314. According to one embodiment of the invention, the first spring member360is aligned and in parallel with the second spring member365. The first spring member360includes multiple laminations, such as seven-to-nine laminations as an illustrative example, that are wound around the drum510of the first CFS assembly320A. Likewise, the second spring member365includes multiple laminations, such as seven-to-nine laminations for example, that are wound around a drum (not shown inFIG. 5, see drum615inFIG. 6for example) of the second CFS assembly320B.

The first roller element540comprises a guide shaft542placed laterally within carriage housing310and generally in parallel with the shaft520. Bearings544are placed at the ends of the guide shaft542and rotationally coupled to an inner surface of the first housing312so that the guide shaft542can be rotated as first spring member360passes. A roller546is placed over a substantial portion of the guide shaft542to apply pressure and prevent contact of lamination1(referring toFIG. 4) of the first spring member360with the second housing312.

Second housing314houses one or more linear bearing assemblies that are coupled to at least one inner wall of second housing314and are movably coupled to the rail370. For instance, according to one embodiment of the invention, a first linear bearing assembly550is vertically oriented within second housing314at a location adjacent to the first CFS assembly320A. A second linear bearing assembly660(not shown inFIG. 5, seeFIG. 6) is vertically oriented within second housing314at a location adjacent to the second CFS assembly320B.

A pair of roller elements570and580is positioned above and below first linear bearing assembly550, to assist in the guiding of spring members. As shown, the second roller element570applies pressure to prevent contact of lamination y of the second spring member365with the first housing312or the linear bearing assembly550. The first roller element540applies a force against the first spring member360, while concurrently, the second roller element570applies a force against the second spring member365.

The third roller element580is positioned below first linear bearing assembly550and below shaft520toward a bottom curvature of drum510. The third roller element580applies a force against the second spring member365upon its passing to or from the second CFS assembly320B.

Referring toFIG. 6, a more detailed cut-away view of an embodiment of the carriage housing310is shown.FIG. 7provides a further illustration of the guide system as well. Second housing314houses the second linear bearing assembly660that is coupled to at least one inner wall of second housing314and are movably coupled to the rail370. Second linear bearing assembly660is vertically positioned adjacent to second CFS assembly320B. Second linear bearing assembly660provides additional support for carriage housing310.

A fourth roller element690is positioned above the second linear bearing assembly660and above shaft625toward a top curvature of drum615. As illustrated inFIG. 6, the cylindrical drum615is rotatably coupled to the first and second housing portions312,314of the carriage housing310by the shaft625. The fourth roller element690features a roller692that applies a force against the second spring member365upon its passing to or from second CFS assembly320B. This assists in maintaining minimum separation distance of laminations forming second spring member365. Moreover, second CFS assembly320B includes a pair of flanges622placed on both sides of drum615to prevent laminations from sliding off drum615. Of course, although not shown, flanges may be used by the second CFS assembly320A as well.

Referring now toFIG. 8, a second embodiment of the guide system utilized by the robotic patient-side system152ofFIG. 2is shown. According to this embodiment of the invention, chassis housing810comprises a plurality of CFS assemblies320A and320B arranged side-by-side, where each CFS assembly320A and320B is adapted to receive a separate spring member800and805featuring one or more laminations. The chassis housing810may be translated vertically as represented by arrow A.

In lieu of roller elements as described above, a guide wall820is positioned along cart column200so as to exert a force along the straight section of spring members800and805. This force prevents the laminations of the spring members800and805from separating. As shown, there is no relative motion between the surface of the guide wall820and spring members800and805.

Referring toFIGS. 4 and 5, it can be noted that in this earlier embodiment, lamination1of the second spring member365performs this same function, acting as a guide wall exerting a force along the laminations of the first spring member360. Contact is between lamination1of the second spring member365and lamination x of the first spring member360.

Referring toFIG. 9, a third embodiment of a guide system utilized by the robotic patient-side system152ofFIG. 2is shown. According to this embodiment of the invention, a guide system comprises a guide surface900placed on a chassis housing910that is adapted to house one or more CFS assemblies (e.g., CFS assembly320A). The guide surface900is coupled to the chassis housing910by a pair of fasteners912, as is illustrated inFIG. 9.

CFS assembly320A is adapted to receive a spring member950that is fed through an opening920in the guide surface900. The opening920is sized with an appropriate width and length to deter separation of the laminations forming the spring member950.

The chassis housing910may be coupled to a column960in a fixed position near the top of the column. The spring member950extends downward from the chassis housing910along the length of the column960. The end of the spring member950not wound onto the drum may couple directly to a set-up arm (not shown inFIG. 9, see set-up arm156inFIGS. 1-2). The set up arm is moved vertically along the column960to adjust its height to support a robotic surgical arm in a proper position. The set-up arm may be moveably coupled to a guide rail970along the column960. The spring member950unwinds from the drum of the CFS assembly320A when its end is pulled downward with the set-up arm. The spring member950winds up onto the drum when its end is pushed upwards with the set-up arm.

While only one CFS assembly320A including one spring member950is shown inFIG. 9, it is to be understood that more than one CFS assembly and one spring member may be used in the third embodiment of the invention.

In short, the embodiments of the invention are directed to a system to guide and constrain the movement of a spring assembly including (constant force) spring members. As previously mentioned, one of the drawbacks of multiple laminations for each spring member is that, as the laminations are moved through large extensions, the individual laminations (in the straight section of spring) spread out from one another. As the number of laminations is increased, this effect becomes more pronounced, requiring more and more space for the springs to operate.

The invention includes several methods for guiding the straight section of these laminations as the spring assembly is extended, allowing a more compact overall volume for packaging and operation of the spring members of the spring assembly. Each of the guiding methods prevents the outer laminations from separating too far away from the inside lamination. The extra material buildup is then taken up in loops around the spring drum. Since the diameter of the spring members on the drum varies inversely with the amount of buildup, the net volume taken up by the spring material around the drum does not change drastically, even with relatively long extensions and large numbers of laminations. This allows for compact packaging and operation of assemblies with a large number of individual laminations over large extensions.

The method of guiding can take several different forms. Possible categories include a static guide surface, a moving guide surface, or roller guides. Static and moving surfaces refer to motion of the guide surface relative to the free end of the spring. A static guide surface is essentially a wall that exerts force along the straight section of the spring material, preventing the laminations from separating. There is no relative movement between the spring material and the surface, so there is minimal increase in friction (seeFIG. 8). A moving guide surface involves feeding the spring past a surface. Here, there is relative motion between the guide surface and spring (SeeFIG. 9). Finally, roller elements can be used instead of the moving guide surface (SeeFIGS. 3-7). In addition, these methods of guiding the laminations hold for cases where the spring drum is attached to either the fixed or moving component in the assembly.

Currently two forms of these guiding mechanisms have been implemented with large lamination constant force spring assemblies in a system. In this system implementation (seeFIGS. 5-7), two constant force spring (CFS) members, each consisting of 7 to 9 laminations, are mounted within the carriage housing. The carriage housing, which translates vertically along the cart column on a linear bearing, supports a set-up arm. The laminations of the first CFS assembly are guided by the inside (front) lamination of the second CFS assembly (the second CFS assembly acts as a static guide surface for the top assembly). The laminations of the second CFS assembly are guided by bearing supported roller shafts, to prevent the springs from spreading back towards the cart column and rubbing on the linear bearing trucks. In this system implementation, the free ends of both CFS assemblies are rigidly fixed to the top of the cart column.

While certain exemplary embodiments of the invention have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the embodiments of the invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art after reading this disclosure. Instead, the embodiments of the invention should be construed according to the claims that follow below.