Patent Description:
A typical gait cycle consists of a stance phase, during which the knee must support the weight of the body, and a swing phase, during which the knee allows the foot to swing forward in advance of the next stance phase. In the design of a knee prosthesis or orthosis, it is desirable for the knee joint to provide sufficient torque in the stance phase to support body weight. In swing phase, it is desirable for the knee to swing almost freely, and at much higher speeds than required during the stance phase. The knee should also provide torque in the swing phase, to support suitable knee motion, such appropriate knee flexion for clearance between the foot and ground, full knee extension at the end of swing, and damping to avoid high impact torques at full extension. Further, in the stance phase, it is desirable for the knee to support weight against knee flexion, but to freely allow knee extension, to allow straightening of the knee without the possibility of knee buckling. Further, in the knee extension portion of the swing phase, it is desirable to allow knee extension, while resisting knee flexion, so that the knee will support the user at heel strike immediately upon heel strike or foot strike. The knee must switch between these respective behaviors essentially instantaneously (e.g., within tens of milliseconds).

Recently, powered knee prostheses have emerged. These prostheses typically employ an electric motor that drives the knee joint through a high-gear transmission ratio (e.g., <NUM>: <NUM>). With a high-gear transmission ratio, the knee can provide the high torque required for stance phase, but is generally unable to provide low output impedance required for the swing phase of gait. Also, the unidirectional behavior must be achieved via sensing (of torque) and closed-loop control, which is less reliable and functional than mechanical means. It is possible to provide low impedance also with feedback control, but this also requires other sensing (of output torque), and is less reliable and functional than mechanical means. As such, implementing these behaviors via feedback control severely compromises performance, particularly relative to systems that provide these behaviors by design. The net effect is that these systems are unable to effectively provide the behavioral characteristics of unidirectionality, low-impedance, and high-speed, and thus are compromised in all three of the above-stated behaviors.

United States patent application <CIT> disclosed a powered prosthetic thigh that can have a proximal portion configured to couple to a prosthetic hip socket and that can have a distal portion attached to the proximal portion. The distal portion can have a distal connector configured to couple to a prosthetic knee. The powered prosthetic thigh can also have a computer controlled actuator configured to rotate the prosthetic thigh relative to the prosthetic hip socket.

<CIT> discloses a variable gain impedance controller for use in a control system for controlling a motorized prosthetic or orthotic apparatus provided with a joint. The controller comprises a sensor input for receiving a signal indicative of an interaction between the apparatus and the ground, a torque sensor input for receiving a signal indicative of the torque at the joint and a variable gain scheduler in communication with the sensor input so as to receive data therefrom thereby providing a variable torque gain. The variable gain impedance controller adjusts its control on the apparatus based on the variable torque gain and the indicated torque so as to a) increase the joint resistance to motion when the signal received from the sensor input indicates an interaction between the apparatus and the ground and b) decrease the joint resistance to motion when the signal received from the sensor input indicates an absence of interaction between the apparatus and the ground.

Some other approaches for knee prostheses with variable transmission ratios have been proposed, but these change ratios slowly, and therefore are unable to make substantial changes in gear ratio within a small fraction of a stride. These systems also do not provide unidirectional characteristics. In the absence of fast changes and unidirectional behaviors in the transmission ratio, these systems are unable to provide the above discussed behaviors within a stride and, therefore, cannot provide the desirable characteristics listed above.

It would be desirable to have a new prosthesis or orthosis that provides a more seamless, smoother, reliable and quicker transition between appropriate dedicated behaviors.

The term embodiment and like terms are intended to refer broadly to all of the subject matter of this disclosure and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the claims below. Embodiments of the present disclosure covered herein are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the disclosure and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter. This summary is also not intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this disclosure, any or all drawings and each claim.

According to the invention, a knee prosthesis or orthosis includes at least one moveable joint and a torque modulating unit. The torque modulating unit is configured to impose a controllable torque on the at least one moveable joint. The torque modulating unit includes at least one of a motor or brake. The at least one of the motor or brake coupled to the at least one moveable joint via an electronically-controlled transmission. The electronically-controlled transmission is a two-speed transmission.

The disclosure, and its advantages and drawings, will be better understood from the following description of exemplary embodiments together with reference to the accompanying drawings. These drawings depict only exemplary embodiments, and are therefore not to be considered as limitations on the scope of the various embodiments or claims.

While the invention is susceptible to various modifications and alternative forms, specific implementations have been shown by way of example in the drawings and will be described in further detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention may comprise modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

According to the invention, a knee prosthesis or orthosis includes at least one moveable joint and a torque modulating unit. The torque modulating unit being configured to impose a controllable torque on the at least one moveable joint. The torque modulating unit includes at least one of a motor or brake. The at least one of the motor or brake being coupled to the at least one moveable joint via an electronically-controlled transmission. The electronically-controlled transmission being a two-speed transmission.

The knee prosthesis or orthosis of the present invention is advantageous in that it yields a knee joint that specifically provides: (<NUM>) high-torque, low-speed unidirectional extension torque, with little to no flexion torque (which is appropriate for the stance phase of the gait cycle); (<NUM>) low-torque, high-speed, low-impedance, bidirectional knee behavior (which is appropriate for the swing flexion phase of walking); and (<NUM>) low-torque, high-speed, low-impedance, unidirectional knee behavior in knee extension, with a simultaneous high resistance to knee flexion (which is appropriate for the swing extension phase of walking). The gear transmission ratios between the states are different by more than an order of magnitude, and the transmission is configured to change between these states under load on the order of less than <NUM> milliseconds, and desirably less than <NUM> or <NUM> milliseconds.

One non-limiting example of a knee prosthesis or orthosis that may be used is depicted in <FIG>. The knee prosthesis or orthosis <NUM> includes at least one moveable joint <NUM> and a torque modulating unit <NUM>. The knee prosthesis or orthosis <NUM> of <FIG> further includes a device control unit <NUM> that includes at least one accelerometer <NUM>. The at least one accelerometer <NUM> may be located within an inertial measurement sensor (IMU) <NUM>. The IMU <NUM> includes the at least one accelerometer <NUM> and at least one gyroscope <NUM>. The IMU may be a multi-axis IMU in one embodiment. One non-limiting example of a multi-axis IMU includes a plurality of accelerometers and a plurality of gyroscopes. The knee prosthesis or orthosis <NUM> of <FIG> further includes a load cell <NUM> and a knee joint encoder <NUM>. The load cell <NUM> assists in measuring the load of the knee prosthesis or orthosis <NUM>. The knee joint encoder <NUM> assists in measuring knee joint angle.

The torque modulating unit <NUM> is configured to impose a controllable torque on the at least moveable joint <NUM>. The knee prosthesis or orthosis <NUM> of <FIG> also further includes joints <NUM>, <NUM> as shown in <FIG>. The torque modulating unit <NUM> includes at least one motor or brake as will be discussed below. The at least one motor or brake of the torque modulating unit <NUM> is coupled to the at least one moveable joint <NUM> via an electronically-controlled transmission (ECT).

To provide a high-torque, low-speed, high-impedance behavior characteristic and also to separately provide a low-torque, high-speed, low-impedance behavior characteristic representative of knee behavior in stance and swing, respectively, the ECT used in the present invention is a two-speed transmission. Unlike common multi-speed transmissions, however, the two speeds in the ECT are spaced at least about an order of magnitude apart. For purposes of comparison, a standard automotive transmission typically changes gear ratios by a factor of <NUM> between adjacent gears. The gear transmission ratios used in the ECT of the present invention, however, should be at least about an order of magnitude different in ratio, in order to satisfy the torque, speed, and impedance differences associated with the stance and swing phases of gait. For example, in an embodiment, the gear transmission ratios in low gear and high gear should be at least a factor of <NUM> or at least a factor of <NUM> apart. In another embodiment, the transmission gear ratios should be different by a factor of <NUM>. In a further embodiment, the transmission gear ratios should be different by a factor of <NUM>.

In the embodiment described here, the two-speed transmission is based on a planetary gear transmission. The planetary gear transmission includes at least two transmission stages - an input planetary stage and an output planetary stage. In one embodiment, the input planetary stage includes at least an input sun gear, an input carrier link, and the output planetary stage includes an output carrier link. In this embodiment, the stages share a common ring gear (i.e., all stages share the same ring gear). Common ring gear means that the ring gears associated with each stage are rigidly coupled together.

In a typically embodiment, a sun gear, a carrier link, and at least three or more planet gears are used in each planetary stage (e.g., an input planetary stage and an output planetary stage). In this embodiment, each of the stages includes a common ring gear.

The two-speed transmission includes at least a ring clutch and a carrier clutch in one embodiment. The ring clutch and the carrier clutch are solenoid-actuated clutches in one embodiment. Both of the ring and the carrier clutches are configured independently to be either in an engaged state or a disengaged state. In the disengaged state, the ring clutch in one embodiment allows the common ring gear to rotate relative to ground. The term "ground" as used herein includes grounding to a frame, grounding to housing, or the like. In the engaged state, the ring clutch in one embodiment prevents or inhibits the common gear from rotating relative to ground. In the disengaged state, the carrier clutch in one embodiment allows the input carrier link to rotate relative to ground. In the engaged state, the carrier clutch in one embodiment prevents or inhibits the input carrier link from rotating relative to ground.

Referring to <FIG>, a schematic <NUM> of a high-gear transmission ratio (stance) for a two-stage planetary gear transmission according to the invention is shown. <FIG> depicts a schematic <NUM> of a low-gear transmission ratio (swing) for a two-stage planetary gear transmission according to the invention.

The schematic <NUM> of <FIG> includes a first stage (input) and a second stage (output) of a planetary gear transmission of a high-gear transmission ratio (stance). The schematic <NUM> of <FIG> includes a first stage (input) and a second stage (output) of a planetary gear transmission for a low-gear transmission ratio (swing). Thus, schematics <NUM>, <NUM> of <FIG> both depict exactly two stages.

Both of the schematics <NUM>, <NUM> of the planetary gear transmission includes a common ring gear <NUM>, an input planet gear <NUM>, an output planet gear <NUM>, an input sun gear <NUM>, and an output sun gear <NUM>. The input planet gear <NUM> is connected to the output sun gear <NUM> via an input carrier link <NUM>. The output planet gear <NUM> is connected to an output carrier link <NUM>. The input is the input sun gear <NUM> and the output is the last carrier link (carrier link <NUM> in schematics <NUM>, <NUM>).

In this embodiment, the input carrier link <NUM> can be grounded via a carrier clutch. In this embodiment, the carrier clutch is an electromagnetic clutch. In this embodiment, the common ring gear <NUM> is separately grounded by a ring clutch. The ring clutch in this embodiment is a unidirectional electromagnetic clutch. The carrier and ring clutches can be engaged or disengaged in various combinations to provide: (<NUM>) a high-gear transmission ratio appropriate for stance phase; (<NUM>) a low-gear transmission ratio appropriate for swing phase; and (<NUM>) a combination thereof that enables a low-gear transmission ratio against extension and high-impedance against flexion.

In the high gear (i.e., high-gear transmission ratio) of <FIG>, the input common ring gear <NUM> is locked to ground, while all of the other components remain free. In the low gear (i.e., low gear transmission ratio) of <FIG>, the common ring gear <NUM> is allowed to spin freely, while the input carrier link <NUM> and the output sun gear <NUM> are grounded. With this change of configuration between schematics <NUM>, <NUM>, differences in the gear transmission ratio of a factor of at least <NUM> to <NUM> are easily achievable.

In addition to a two-stage planetary gear transmission such as discussed above with respect to <FIG>, a planetary gear transmission can have additional stages in other embodiments. For example, referring to <FIG>, schematics of a three-stage planetary gear transmission are shown. More specifically, schematic <NUM> of <FIG> includes a first stage (input), a second stage, and a third stage (output) of a planetary gear transmission of a high-gear transmission ratio (stance). <FIG> depicts a schematic <NUM> that includes a first stage (input), a second stage and a third stage (output) of a planetary gear transmission of a low-gear transmission ratio (swing).

Both of the schematics <NUM>, <NUM> of the planetary gear transmission includes an input common ring gear <NUM>, the input planet gear <NUM>, a second stage planet gear <NUM>, the output planet gear <NUM>, the input sun gear <NUM>, a second stage sun gear <NUM>, and the output sun gear <NUM>. The input planet gear <NUM> is connected to the second stage sun gear <NUM> via an input carrier link <NUM>. The second stage planet gear <NUM> is connected to the output sun gear <NUM> via an input carrier link <NUM>. The output planet gear <NUM> is connected to an output carrier link <NUM>.

In the high gear (i.e., high-gear transmission ratio) of <FIG>, the input common ring gear <NUM> is locked to ground, while all of the other components remain free. In the low gear (i.e., low gear transmission ratio) of <FIG>, the common ring gear <NUM> is allowed to spin freely, while the input carrier link <NUM> and the second stage sun gear <NUM> are grounded. With this change of configuration between schematics <NUM>, <NUM>, differences in the gear transmission ratio of a factor of at least <NUM> to <NUM> are easily achievable.

This general transmission configuration is configured to function for a planetary gear transmission with any number of stages provided that the ring gear of each stage is a common ring gear.

There are two defined gear transmission ratios (high-gear ratio and low-gear ratios. In this embodiment there are two clutches (ring clutch and carrier clutch) on the transmission. In this embodiment, each of the ring and carrier clutches includes two states. The two states in the ring and carrier clutches are energized and de-energized. Because of the two gear transmission ratios and the two states, there are four possible states of transmission.

The sequence of clutch states that would be employed in a knee prosthesis or orthosis during walking are shown, for example, in <FIG>. In <FIG>, the axes represent an energized state of each ring clutch or carrier clutch. In the ON state, the ring and carrier clutches are energized, while in the OFF state, the ring and carrier clutches are de-energized. The ring and carrier clutches in this embodiment are electromagnetic. Referring to <FIG>, a chart <NUM> is depicted with four states - a first state <NUM>, a second state <NUM>, a third state <NUM>, and a fourth state <NUM>. Arrows A-D of the chart <NUM> show the direction of the flow of the states during a gait cycle.

In each state, the configuration of the ring and carrier clutches produces one of four behaviors in each the flexion and extension directions: a low-gear transmission ratio (low), a high-gear transmission ratio (high), over-determined locking (lock), and under-determined motion between input and output (slip or not engaged). Each state of the transmission is described in more detail below.

In the first state <NUM>, the ring clutch and the carrier clutch are both de-energized. The common ring gear in the first state <NUM> is grounded (only in one direction). The transmission is in its high gear against flexion. The high-gear transmission ratio is configured to support a weight of the prosthesis or orthosis of a user when standing on the knee prosthesis or orthosis. Because the ring clutch can only engage the transmission unidirectionally, the transmission slips against extension (i.e., does not resist extension movement). The unidirectional behavior of the transmission is configured to generate torque against knee flexion. The torque modulating unit is in the first state <NUM> when the prosthesis or orthosis user is standing on the prosthesis or orthosis (stance), providing support against flexion of the knee.

In the second state <NUM>, the ring clutch is energized and the carrier clutch is de-energized. The transmission assumes its underdetermined state. Energizing the ring clutch unlocks the ring gear. With the ring gear unlocked, the transmission has an extra rotational degree of freedom, decoupling the output from the input. The motor can no longer provide torque at the knee joint. The torque modulating unit is only in the second state <NUM> for a few milliseconds before entering the third state <NUM>. This is part of the transition from stance to swing, when the gear transmission ratio changes from high to low. The purpose of entering the second state <NUM> before entering the third state <NUM> is to avoid locking the transmission while it is moving, which has the potential to damage the transmission.

In the third state <NUM>, the ring clutch and the carrier clutch are both energized. The ring gear is unlocked and free to rotate, and the first stage or input carrier link is locked to the housing, preventing or inhibiting its rotation. In this configuration, the transmission is in its low gear. The low-gear transmission ratio enables the prosthesis or orthosis to allow a knee joint to swing freely when the knee prosthesis or orthosis is not supporting the weight of the user. Because the carrier clutch provides bi-directional locking in this embodiment, the motor can provide torques in both directions at the knee. The torque modulating unit remains in the third state <NUM> until the prosthesis or orthosis has completed swing flexion and enters swing extension.

In the fourth state <NUM>, the carrier clutch is energized and the ring clutch is de-energized. When the knee joint of the prosthesis or orthosis begins to extend while in swing phase, it is no longer necessary to energize the ring clutch. Because the ring clutch only provides unidirectional locking against flexion in this embodiment, and cannot resist extension, the ring clutch does not need to be energized during swing extension. The transmission is still in its low gear. If the prosthesis or orthosis is suddenly subject to a flexion load (e.g., if the prosthesis or orthosis user trips on something), then the prosthesis or orthosis automatically enters the high gear and is able to resist flexion. This mechanical fail-safe removes the lag-time from the controller that would otherwise have to switch the torque modulating unit into the high gear.

The low-gear transmission ratio is configured to have asymmetric behavior in which the two-speed transmission is configured to resist extension with a low resistance while resisting flexion with a high resistance.

In one embodiment, the two-speed transmission is configured to be in at least a first state, a second state or a third state. The two-speed transmission in the first state provides the high-gear transmission ratio when resisting flexion or providing extension, while providing little to no torque when resisting extension or providing flexion. The two-speed transmission in the second state provides the low-gear transmission ratio. The low-gear transmission ratio is bidirectional. The two-speed transmission in the third state provides the low-gear transmission ratio when resisting extension or providing flexion, while also providing a high resistance when resisting flexion or providing extension.

In another embodiment, the two-speed transmission is further configured for a fourth state. The two-speed transmission in the fourth state provides the high-gear transmission ratio. The high-gear transmission ratio is bidirectional.

In a further embodiment, the two-speed transmission is configured to be in at least a neutral state, in which the two-speed transmission is disengaged from at least one of the motor or brake.

Referring to <FIG>, a torque modulating unit <NUM> is shown according to the invention. The torque modulating unit <NUM> grounds the first stage carrier and the second stage sun-gear (which is rigidly connected to the first stage carrier). The torque modulating unit <NUM> includes an electric motor/brake <NUM>, a first stage sun gear or motor output <NUM>, a wave disk spring <NUM>, a plain bearing <NUM>, a planetary gear transmission <NUM> that includes a plurality of carriers links <NUM>, <NUM>, <NUM>, a transmission output <NUM>, a back-drivable lead screw <NUM>, a common ring gear <NUM>, a ring clutch capstan cable guide <NUM>, a ring clutch solenoid <NUM>, an O-ring <NUM>, and a carrier clutch <NUM> that includes a carrier clutch armature <NUM> and a carrier clutch solenoid <NUM>. The carrier clutch solenoid <NUM> and the plain bearing <NUM> form carrier clutch solenoid stator <NUM>. The plain bearing <NUM> in one embodiment comprises ferrous steel.

The motor or brake <NUM> is coupled to at least one moveable joint (e.g., the at least one moveable join <NUM> in <FIG>) via an electronically-controlled transmission. The motor or brake <NUM> is coupled to an input sun gear and at least one moveable joint being directly or indirectly coupled to the output carrier link. The electronically-controlled transmission is a two-speed transmission. The carrier link <NUM> is a first stage carrier link. The carrier link <NUM> is configured to translate along an input shaft. Upon energizing a solenoid affixed to ground, the magnetic field resulting from the solenoid pulls the carrier link <NUM> along the input shaft to make grounded contact. The carrier link <NUM> is a second stage carrier link, and the carrier link <NUM> is a third stage carrier link.

The torque modulating unit <NUM> is configured as an electromagnetic disk clutch. Thus, in this embodiment, the carrier clutch armature <NUM> is a ferromagnetic disk clutch armature. The carrier clutch armature <NUM> is collinearly fixed to the first stage carrier <NUM> of the planetary gear transmission <NUM>. It is contemplated that the carrier clutch armature may be formed from materials other than ferromagnetic material.

The carrier clutch stator <NUM> is collinearly fixed to the electric motor/brake <NUM>. The electric motor/brake <NUM> and the carrier clutch stator <NUM> are fixed to the housing. The planetary gear transmission <NUM> is supported by a pair of thin-section bearings so that it is able to freely rotate (when not constrained by the ring clutch or grounded). The wave disk spring <NUM> separates the carrier clutch armature <NUM> and the carrier clutch solenoid stator <NUM> when the torque modulating unit <NUM> is de-energized. The O-ring <NUM> is fixed to the carrier solenoid stator <NUM> and becomes compressed by the carrier clutch armature <NUM> when the carrier clutch <NUM> is energized. The plain bearing <NUM> encircles the carrier clutch armature <NUM> and the O-ring <NUM>. The O-ring <NUM> in one embodiment is a medium durometer square-cross section O-ring.

When the clutch is de-energized, rotation and lateral translation of the carrier clutch armature <NUM> are constrained by the wave spring <NUM> and the plain bearing <NUM>, respectively. When the ring clutch solenoid <NUM> is de-energized (i.e., in the OFF state), the spring element keeps the carrier clutch solenoid stator <NUM> and the carrier clutch armature <NUM> separated, and the O-ring <NUM> is not engaging the carrier clutch armature <NUM>. When the ring clutch solenoid <NUM> is energized (i.e., in the ON state), the carrier clutch armature <NUM> is pulled to the carrier clutch solenoid stator <NUM> and is engaged by the O-ring <NUM>, creating a high-friction interface between the stator <NUM> and the armature <NUM>, locking the armature <NUM> to the stator <NUM>, and preventing or inhibiting rotation of the armature <NUM>. This prevents or inhibits rotation of the first stage carrier link and the second stage sun gear.

The ring and the carrier clutches desirably use friction-based locking that permits locking in any configuration. The ring and the carrier clutches desirably use solenoid-actuation permits state changes within several milliseconds, and therefore within a single stride of the gait cycle.

In one embodiment, the ring clutch is a unidirectional clutch. In the engaged state, the ring clutch allows unidirectional rotation of the common ring gear relative to ground. The unidirectional ring clutch is a capstan clutch in one embodiment.

In another embodiment, the ring clutch is selectively unidirectional or bidirectional. The ring clutch in this embodiment includes a first ring clutch and a second ring clutch. The engagement of the first and second ring clutches prevents or inhibits rotation of the common ring gear in both directions, and the selective disengagement of one of the first and second ring clutches allows unidirectional rotation of the common ring gear relative to ground in one of two directions. The selective disengagement of both the first and second ring clutches allows bidirectional rotation of the common ring gear relative to ground.

In a further embodiment, the ring clutch is a bidirectional clutch, such that in the engaged state, the ring clutch prevents or inhibits rotation of the common ring gear relative to ground in both directions.

Referring to <FIG>, a ring clutch <NUM> is shown according to the invention. The ring clutch grounds the common ring gear, and is engaged during the stance phase to provide unidirectional holding against knee flexion. To provide a high holding torque, the ring clutch <NUM> employs a capstan-type design. It is contemplated that the ring clutch may not include a capstan-type design in other embodiments.

The design of the ring clutch <NUM> is beneficial in that it: (<NUM>) enables high holding torque with a low activation force, due to the exponential self-amplification property of a capstan; and (<NUM>) provides a unidirectional holding torque, which accommodates the previously described asymmetrical resistance desirable in the stance phase and late swing phase (i.e., low-impedance resistance to extension and high-impedance resistance to flexion).

The ring clutch of <FIG> includes a sleeve <NUM>, a common ring gear <NUM>, a wire rope <NUM>, a spring element <NUM>, an adjustable anchor point <NUM>, a solenoid armature <NUM> and a solenoid stator <NUM>.

The sleeve <NUM> is typically an aluminum sleeve. It is contemplated that the sleeve may be made of other materials, including other metallic materials. The sleeve <NUM> is pressed onto the common ring gear <NUM>. The ring gear may be a ECT common ring gear. The wire rope <NUM> is wrapped a plurality of times around an exterior of the sleeve <NUM> as shown in <FIG>. The wire rope <NUM> is typically a steel wire rope. It is contemplated that the wire rope may be made of other materials, including other metallic materials. The wire rope <NUM> is stiff and is compliant with the sleeve <NUM> and together form a capstan with a high static friction coefficient.

The spring element <NUM> applies tension to one end of the wire rope <NUM>, while the other end of the spring element <NUM> is grounded to the housing by the adjustable anchor point <NUM>. The adjustable anchor point <NUM> is adjustable via a set screw thereon that permits adjustment of the preload tension on the spring element <NUM>. The distal ends of the spring element <NUM> and wire rope <NUM> are fixed to the solenoid armature <NUM>. The solenoid armature <NUM> is located or positioned within the solenoid stator <NUM>.

When the common ring gear <NUM> and the sleeve <NUM> are turned away from the end of the wire rope <NUM> that is secured to the adjustable anchor point <NUM>, the force applied by the spring element <NUM> is multiplied by the capstan effect, producing a much larger holding force in the wire rope <NUM> secured to the anchor points. The effect is a strong holding torque that resists the motion of the rotating torque, effectively grounding the common ring gear. When a rotating torque is applied in the opposite direction (towards the ends of the wire rope <NUM> that is secured to the anchor point), the spring element <NUM> does not apply enough force to create a strong holding torque, and the drum rotates in the direction of the applied torque. This makes the ring clutch <NUM> a unidirectional clutch (i.e., the engagement that it provides is directionally dependent). The effect this has is similar to an overrunning clutch, where the rotating shaft inside the clutch is free to spin in one direction, but is locked in the opposite direction.

When the solenoid is de-energized (i.e., in the OFF state), the spring element <NUM> keeps the wire rope <NUM> engaged with the sleeve <NUM>, and the common ring gear <NUM> can only be turned in one direction due to the capstan effect. When the solenoid is energized (i.e., in the ON state), the solenoid compresses the spring element <NUM>, which negates the tensile force on the wire rope <NUM>. The wire rope <NUM> is naturally stiff, and becomes straighter as force from the spring element <NUM> is removed. This causes the wire rope <NUM> to move away from the surface of the sleeve <NUM>. With the wire rope <NUM> is no longer in contact with the drum, the clutch is disengaged, and the common ring gear <NUM> is free to rotate in both directions.

When the ring clutch solenoid is de-energized, the ring clutch is engaged. When the ring clutch solenoid is energized, the ring clutch is dis-engaged. When the carrier clutch solenoid is energized, the carrier clutch is engaged. When the carrier clutch is de-energized, the carrier clutch is disengaged.

It is contemplated that other ring clutches may be used than the ring clutch shown in <FIG>. Another non-limiting example of a ring clutch according to a further embodiment in shown in <FIG>. The ring clutch <NUM> of <FIG> utilizes two solenoid-actuated unidirectional capstan clutches that are arranged in opposing orientations, such that using a second unidirectional locking clutch permits locking of the common ring gear in one of four configurations: (<NUM>) bidirectional locking, (<NUM>) locking to flexion only, (<NUM>) locking to extension only, and (<NUM>) bidirectional unlocking.

The ring clutch <NUM> of <FIG> includes a sleeve <NUM>, a common ring gear <NUM>, a wire rope <NUM>, a plurality of spring elements 520a, 520b, a plurality of solenoid armatures 528a, 528b, and a plurality of solenoid stators 532a, 532b.

The flexion ring clutch and solenoid provides a grounding force for the common ring gear when a resistive knee flexion torque is applied, but permits knee extension with little or no resistance. The extension ring clutch and solenoid provides a grounding force for the common ring gear when a resistive knee extension torque is applied, but permits knee flexion with little or no resistance. The ends of each capstan for both clutches are grounded.

Referring to <FIG>, a ring clutch <NUM> is depicted according to another embodiment. The ring clutch <NUM> utilizes a solenoid-actuated positive engagement clutch. The ring clutch <NUM> includes an upper portion <NUM> that is fixed to housing, and a lower portion <NUM> that is fixed to the common ring gear. The upper and lower portions <NUM>, <NUM> of the ring clutch <NUM> have a geometry such that when the portions <NUM>, <NUM> are pressed together by an actuating force (e.g., a solenoid), they interlock with one another. When the upper and lower portions <NUM>, <NUM> are interlocked, an interface is created that prevents or inhibits the portions <NUM>, <NUM> from rotating relative to one another (i.e., they form a dog clutch). The ring clutch <NUM> resists bidirectional rotation of the ring clutch. This embodiment can be combined with the ring clutch <NUM>, such that the positive-engagement clutch shown here, which locks the ring gear in both rotation directions, can be used in parallel with a solenoid-actuated unidirectional-locking clutch, such that their combined use permits selective unidirectional or bidirectional locking of the ring gear.

The foregoing description of the embodiments, including illustrated embodiments, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or limiting to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art.

Although the disclosed embodiments have been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur or be known to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.

Claim 1:
A knee prosthesis or orthosis (<NUM>), comprising:
at least one moveable joint (<NUM>); and
a torque modulating unit (<NUM>, <NUM>), the torque modulating unit (<NUM>, <NUM>) configured to impose a controllable torque on the at least one moveable joint (<NUM>), the torque modulating unit (<NUM>, <NUM>) including at least one of a motor or brake (<NUM>), the at least one of the motor or brake (<NUM>) coupled to the at least one moveable joint (<NUM>) via an electronically-controlled transmission, characterized in that the electronically-controlled transmission is a two-speed transmission.