Electronically controlled prosthetic knee

Abstract

The present invention relates to a variable-torque magnetorheologically actuated prosthetic knee which utilizes a plurality of interspersed and alternating rotors and stators to shear magnetorheological fluid in gaps formed therebetween. Advantageously, by operating in the “shear mode” there is substantially no or negligible fluid pressure buildup or change. Moreover, the multiple MR fluid gaps or flux interfaces desirably allow for the production of a large torque at low speed—eliminating the need for a transmission—and also for a wide dynamic torque range. One embodiment of the invention allows the rotors and/or stators to close the gaps therebetween to create a frictional torque component, thereby forming a “hybrid” braking system which provides a total torque or damping which is a combination of viscous torque and frictional torque.

Description

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional application No. 60/177,108, filed Jan. 20, 2000, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to prosthetic joints in general and, in particular, to controllable braking systems for prosthetic knee joints.

2. Description of the Related Art

Three types of variable-torque brakes have been employed in prosthetic knees in the past: (i) dry friction brakes where one material surface rubs against another surface with variable force; (ii) viscous torque brakes using hydraulic fluid squeezed through a variable sized orifice or flow restriction plate; and (iii) magnetorheological (MR) brakes or dampers where MR fluid (containing small iron particles suspended in the fluid) is squeezed through a fixed orifice or flow restriction plate, with viscosity of the fluid being varied in response to an applied magnetic field. Each of these technologies, as conventionally practiced in the field of prosthetics, can pose certain disadvantages.

Though dry friction brakes can generally provide a substantial torque range for their size, undesirably, they are often difficult to control. After extended use, the frictional pads tend to wear, thereby changing the frictional characteristics of the brake and the torque response for a given commanded torque. Disadvantageously, this can cause unreliable damping performance, and hence adversely affect the gait of the amputee and also cause discomfort to the amputee. Consequently, dry friction brakes may need frequent servicing and/or replacement which undesirably adds to the cost.

Under high loading conditions, viscous torque brakes are susceptible to leakage of hydraulic fluid and possibly other damage due to excessive pressure build-up. Disadvantageously, this can result in an irreversible state, since once the brake unit is overloaded it cannot return to normal. Therefore, such a viscous torque brake for a prosthetic joint is prone to catastrophic failure, and hence can be unreliable and detrimental to the safety of an amputee.

The term “valve mode” refers to the control of the flow of a MR fluid through an orifice by the application of a variable magnetic field perpendicular to the direction of the flow in place of the mechanical valve used in conventional viscous torque brakes. Disadvantageously, a MR brake operated in the “valve mode” also develops internal fluid pressure buildup, and hence is still susceptible to traditional pressure-induced failure, thereby putting the amputee at risk.

SUMMARY OF THE INVENTION

Accordingly it is one important advantage of the present invention to overcome some or all of the above limitations by providing a variable-torque magnetorheologically actuated prosthetic knee which utilizes a plurality of interspersed and alternating rotors and stators to shear magnetorheological fluid in gaps formed therebetween. Advantageously, by operating in the “shear mode” there is substantially no or negligible fluid pressure buildup or change. Moreover, the multiple MR fluid gaps or flux interfaces desirably allow for the production of a large torque at low speed—eliminating the need for a transmission—and also for a wide dynamic torque range. One embodiment of the invention allows the rotors and/or stators to close the gaps therebetween to create a frictional torque component, thereby forming a “hybrid” braking system which provides a total torque or damping which is a combination of viscous torque and frictional torque.

In accordance with one preferred embodiment, a magnetorheologically actuated rotary prosthetic knee is provided for precisely and rapidly controlling lower limb movement. The prosthetic knee generally comprises a substantially central core and a pair of side plates, a plurality of interspersed and alternating magnetically soft rotors and magnetically soft stators, an electromagnet positioned between the core and the rotors and stators, and a pair of bearings. The core and the side plates are formed from a magnetically soft material to create a magnetic return path. The rotors and stators are arranged so as to form a plurality of gaps therebetween. The gaps contain a magnetorheological fluid which is sheared during knee rotation. The electromagnet is responsive to an electrical signal to generate a variable magnetic field to cause a controlled change in the viscosity of the magnetorheological fluid. The bearings are in rotary communication with the rotors and a shin portion of the lower limb to transfer rotary resistive torques from the prosthetic knee to the shin portion.

In accordance with another preferred embodiment, a controllable magnetorheological brake for an artificial knee is provided to dampen knee joint rotation. The magnetorheological knee generally comprises a plurality of alternatingly arranged and spaced magnetizable rotors and magnetizable stators, a magnetorheological fluid, and a magnet. The rotors and stators are concentrically configured about a longitudinal axis of rotation of the artificial knee. The magnetorheological fluid resides in a plurality of gaps formed between the rotors and the stators. The magnet is responsive to an applied voltage and adapted to generate a variable magnetic field which passes through the rotors, the stators and the magnetorheological fluid. The shearing of the magnetorheological fluid in the gaps between the rotors and the stators creates a variable torque output which precisely controls the rotation of the artificial knee.

In accordance with yet another preferred embodiment, an electronically controlled prosthetic knee is provided for generating a wide dynamic torque range. The prosthetic knee generally comprises a plurality of rotors, a plurality of stators, and a fluid adapted to undergo a rheology change in response to an applied magnetic field. The rotors comprise a ferrous material. The rotors are rotatable and laterally displaceable about a longitudinal axis of rotation of the prosthetic knee. The stators comprise a ferrous material and are alternatingly interspersed with the rotors to form gaps therebetween. The stators are laterally displaceable about the axis of rotation of the prosthetic knee. The fluid resides in the gaps formed between the rotors and the stators. Actuation of the magnetic field generates during knee rotation a controllable variable knee damping torque.

In accordance with a further preferred embodiment, a rotary prosthetic knee for an amputee is provided. The prosthetic knee generally comprises a rotatable inner spline, a plurality of rotors engaged with the inner spline, a plurality of stators alternatingly interspersed with the rotors, an outer spline engaged with the stators, and a magnetically controlled medium residing in a plurality of sealed gaps between the rotors and the stators. The magnetically controlled medium is adapted to undergo a controlled bulk property change in response to an applied magnetic field such that the rotation of the rotors which shear the magnetically controlled medium is precisely controlled and the rotation of the prosthetic knee is variably damped to provide a substantially natural gait for the amputee.

In accordance with one preferred embodiment, a variable torque magnetorheological brake for a prosthetic knee is provided. The brake generally comprises a substantially central core, a first side plate connected to a first end of the core, a second side plate connected to a second end of the core and a rotatable and laterally displaceable blade positioned between the first side plate and the second side plate. The brake further comprises magnetorheological fluid in a pair of microgaps formed between the blade and the plates, and a magnet to generate a magnetic field such that a magnetic circuit is created through the core, the first side plate, the second side plate, the blade and the magnetorheological fluid. The microgaps have a size which is optimally minimized such that when the magnetic field has a zero value there is substantially no frictional contact between the blade and the side plates, thereby allowing the prosthetic knee to swing freely and provide a wide dynamic range.

In accordance with another preferred embodiment, a controllable rotary damper for an artificial knee is provided. The damper generally comprises a plurality of interspersed inner rotors and outer rotors, a plurality of magnetorheological fluid films, a pair of side plates and an electromagnet. The inner rotors and outer rotors are concentrically arranged about a longitudinal axis of the artificial knee. The magnetorheological fluid films are resident in a plurality of gaps between the inner rotors and the outer rotors. The pair of side plates sandwiches the inner rotors and the outer rotors with at least one of the side plates being laterally movable along the longitudinal axis of the artificial knee. The electromagnet is adapted to create a magnetic field through the inner rotors, the outer rotors, the magnetorheological fluid and the side plates. The relative rotation between the inner rotors and the outer rotors and the lateral movement of at least one of the side plates generates a variable damping torque to control the rotation of the artificial knee.

In accordance with one preferred embodiment, a prosthetic knee is provided. The prosthetic knee generally comprises a plurality of rotors, a plurality of stators and a fluid adapted to undergo a rheology change in response to an applied magnetic field. The rotors are rotatable about a longitudinal axis of the prosthetic knee. The stators are midstance212212 412 may comprise Hiperco Alloy 50®, Permendur V™ or Vanadium Pemendur Permendur, as available from Principal Metals, Vacoflux 50 as available from Vacuumschmelze of Hanau, Germany.

The core 412 is preferably formed by machining followed by heat treatment in a dry hydrogen atmosphere to achieve optimal magnetic properties. The core 412 is annealed in a dry hydrogen atmosphere preferably for about five hours at a temperature of about 820° Celsius. The core 412 is then cooled in a dry hydrogen atmosphere at about 150° Celsius/hour until a temperature of about 200° Celsius is reached. Care is taken to avoid contamination during heat treatment and any grease, oil, fingerprints and the like are removed using acetone or other suitable cleaning solvents. During heat treatment, the core 412 is preferably separated from the core side plates 416 and 418 to avoid any possible welding between the components.

In one preferred embodiment, and referring in particular to FIGS. 27 and 28, the core 412 is dimensioned and configured such that the length L₂₇₁ is about 2.517 cm (0.991 inches), the length L₂₇₂ is about 5.56 mm (0.220 inches), the length L₂₇₃ is about 0.51 mm (0.020 inches), the length L₂₇₄ is about 0.51 mm (0.020 inches), the diameter D₂₇₁ is about 1.424 cm (0.5605 inches), the diameter D₂₇₂ is about 1.415 cm (0.557 inches), the angle θ₂₇₁ is about 10° and the diameter D₂₈₁ is about 1.88 cm (0.740 inches). In other preferred embodiments, the core 412 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 29-33 show one preferred embodiment of a core side plate 416 of a magnetorheologically actuated prosthetic knee of the present invention. The core side plate 416 preferably comprises a substantially central cavity or through hole 456 adapted to matingly form an interference fit with the end of the core portion 452 (FIGS. 26-28) and three approximately equally spaced through holes 458 arranged in a generally circular fashion to receive bolts or the like to fasten the various components of the prosthetic knee. The core side plate 416 further comprises a generally circular groove or recess 356 adapted to engage or mechanically connect with a flange of the electromagnet 414 (FIGS. 37-39). Thus, the electromagnet or magnetic coil 414 rotates as the core side plate 416 rotates.

Preferably, tapers or tapered surfaces or portions 470, 471 are provided on respective outer and inner surfaces of the core side plate 416. This advantageously decreases weight, saves material and also provides clearance space to facilitate assembly. The rotatable core side plate 416 forms a dynamic seal with a rotatable outer spline utilizing an O-ring or the like provided within a groove or flange of the outer spline.

Preferably, the core side plate 416 comprises an iron-cobalt (FeCo) high magnetic saturation alloy. In one preferred embodiment, the core side plate 416 comprises Iron-Cobalt High Saturation Alloy (ASTM A-801 Type 1 Alloy), which specifies a composition with about 50% cobalt. For example, the core 212 side plate 416 may comprise Hiperco Alloy 50®, Permendur V™ or Vanadium Pemendur Permendur, as available from Principal Metals, Vacoflux 50 as available from Vacuumschmelze of Hanau, Germany.

The core side plate 416 is preferably formed by machining followed by heat treatment in a dry hydrogen atmosphere to achieve optimal magnetic properties. The core side plate 416 is annealed in a dry hydrogen atmosphere preferably for about five hours at a temperature of about 820° Celsius. The core side plate 416 is then cooled in a dry hydrogen atmosphere at about 150° Celsius/hour until a temperature of about 200° Celsius is reached. Care is taken to avoid contamination during heat treatment and any grease, oil, fingerprints and the like are removed using acetone or other suitable cleaning solvents. During heat treatment, the core side plate 416 is preferably separated from the core 412 to avoid any possible welding between the components.

In one preferred embodiment, and referring in particular to FIGS. 30-33, the core side plate 416 is dimensioned and configured such that the diameter D₃₀₁ is about 3.353 cm (1.320 inches), the diameter D₃₀₂ is about 2.461 cm (0.969 inches), the blind-circle diameter D₃₁₁ is about 2.845 cm (1.120 inches), the diameter D₃₁₂ is about 2.43 cm (0.958 inches), the diameter D₃₁₃ is about 2.29 cm (0.900 inches), the hole diameter D₃₁₄ is about 2.95 mm (0.116 inches), the angle θ₃₁₁ is typically 120°, the diameter D₃₂₁ is about 4.80 cm (1.890 inches), the diameter D₃₂₂ is about 3.30 cm (1.300 inches), the diameter D₃₂₃ is about 1.88 cm (0.740 inches), the width W₃₂₁ is about 5.59 mm (0.220 inches), the width W₃₂₂ is about 1.27 mm (0.050 inches), the width W₃₃₁ is about 2.54 mm (0.100 inches), the width W₃₃₂ is about 0.508 mm (0.020 inches), the width W₃₃₃ is about 1.52 mm (0.060 inches), the radius of curvature R₃₃₁ is about 6.35 mm (0.250 inches), the radius of curvature R₃₃₂ is about 0.254 mm (0.010 inches), the angle θ₃₃₁ is about 30° and the angle θ₃₃₂ is about 10°. In other preferred embodiments, the core side plate 416 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 34-36 show one preferred embodiment of a second core side plate 418 of a magnetorheologically actuated prosthetic knee of the present invention. The core side plate 418 is substantially the same as the first core side plate 416 except that it comprises a substantially central cavity or through hole 457 adapted to matingly form an interference fit with the end of the core portion 454 (FIGS. 26-28) and a pair of through holes 472 which permit passage of electrical wires or leads connected to an electromagnet or magnetic coil 414 (FIGS. 37-39) of the prosthetic knee of the present invention.

In one preferred embodiment, and referring in particular to FIGS. 35 and 36, the core side plate 418 is dimensioned and configured such that the length L₃₅₁ is about 1.14 cm (0.448 inches), the length L₃₅₂ is about 1.05 cm (0.413 inches), the hole diameter D₃₅₅ is about 1.78 mm (0.070 inches) and the diameter D₃₆₃ is about 1.42 cm (0.560 inches). The other dimensions D₃₅₁, D₃₅₂, D₃₅₃, D₃₅₄, θ₃₅₁, D₃₆₁, D₃₆₂, W₃ W₃₆₁ and W₃₆₂ are substantially the same as the dimensions D₃₁₁, D₃₁₂, D₃₁₃, D₃₁₄, θ₃₁₁, D₃₂₁, D₃₂₂, W₃₂₁ and W₃₂₂, respectively, as shown on FIGS. 31 and 32 and stated above for the first core side plate 416. In other preferred embodiments, the core side plate 418 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 37-39 show one preferred embodiment of an electromagnet, magnetic coil or wire spool 414 of a magnetorheologically actuated prosthetic knee of the present invention. The magnetic coil 414 generally comprises a bobbin 340 having a pair of flanges 342, 344 at each end, winding 350 generally circumscribing the bobbin 340 and connected to electrical lead wires 352. A pair of slots or through holes 346, 348 in the bobbin flange 344 permit passage of the leads 352 which connect to a battery or other power source.

The magnetic coil 414 is preferably generally cylindrical in shape and has a generally cylindrical through passage 358 for receiving the core 412 (FIGS. 26-28) to mechanically connect the magnetic coil 414 to the core 412. The flanges 342 and 344 are received in grooves or recesses of respective side plates 416 and 418 (FIGS. 29-36) to mechanically connect the magnetic coil 414 to the side plates 416, 418. Thus, as the core side plates 416, 418 rotate so do the magnetic coil 414 and core 412.

Preferably, the bobbin 440 is fabricated from polyphenylene sulfide having a temperature rating of about 200° Celsius. The winding 350 preferably comprises three hundred and forty turns of 30 AWG copper wire having a resistance of about 8.03 ohms (Ω) and a power rating of about 13.7 watts at about 10.5 volts DC. The winding insulation comprises a suitable material having a temperature rating of about 155° Celsius. Preferably, the lead wires 352 comprise 24 AWG stranded wire about 8 inches long and covered with a teflon insulation with an about 0.25 inches section stripped and tinned.

In one preferred embodiment, and referring in particular to FIGS. 38 and 39, the electromagnet or magnetic coil 414 is dimensioned and configured such that the length L₃₈₁ is about 1.138 cm (0.448 inches), the length L₃₈₂ is about 1.05 cm (0.413 inches), the width W₃₈₁ is about 0.762 mm (0.030 inches), the radius of curvature R₃₈₁ is about 0.381 mm (0.015 inches), the diameter D₃₈₁ is about 0.762 mm (0.030 inches), the diameter D₃₉₁ is about 2.45 cm (0.965 inches), the diameter D₃₉₂ is about 1.89 cm (0.745 inches), the diameter D₃₉₃ is about 2.02 cm (0.795 inches), the length L₃₉₁ is about 1.95 cm (0.766 inches), the length L₃₉₂ is about 1.74 cm (0.686 inches), the length L₃₉₃ is about 1.02 mm (0.040 inches), the length L₃₉₄ is about 1.02 mm (0.040 inches) and the thickness T₃₉₁ is about 0.635 mm (0.025 inches). In other preferred embodiments, the magnetic coil 414 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 40-44 show one preferred embodiment of an inner spline 422 of a magnetorheologically actuated prosthetic knee of the present invention. The inner spline 422 comprises a plurality of longitudinal grooves or notches 484 for engaging or mating with corresponding teeth of rotors 420 (FIGS. 45-47) and a substantially central cavity 476 for receiving the magnetic coil 414 (FIGS. 37-39). Preferably, the inner spline 422 comprises nine substantially equally spaced grooves 484 having a substantially rectangular or square shape with rounded corners.

The inner spline cavity 476 preferably includes three longitudinal cavities or passages 478 which are substantially aligned with the bolt-receiving holes of the core side plates 416, 418 (FIGS. 31 and 35). The passages 478 receive bolts or the like to fasten or secure the inner spline 422 and the core side plates 416, 418. The inner spline cavity 476 further includes a plurality of longitudinal recesses 360 which serve to reduce the weight of the inner spline 422, and hence that of the prosthetic knee.

The inner spline 422 preferably comprises a flange 480 at each end to receive an O-ring, gasket or the like to form a static seal between the rotatable inner spline 422 and the rotatable core side plates 416, 418. An adjacent step, shoulder or flange 362 is also provided on each end to facilitate mounting of the O-rings or gaskets on the inner spline 422 during assembly of the prosthetic knee.

Preferably, the inner spline 422 is manufactured by wire electro-discharge machining (EDM). The inner spline 422 is preferably fabricated from titanium or a titanium alloy to provide a non-ferrous yet strong, hard surface with low weight to engage the rotors 420 and transmit torque from them. More preferably, the inner spline is fabricated from 6A1-4V titanium alloy.

In one preferred embodiment, and referring in particular to FIGS. 41-44, the inner spline 422 is dimensioned and configured such that the blind-circle diameter D₄₁₁ is about 2.85 cm (1.120 inches), the diameter D₄₁₂ is about 2.46 cm (0.970 inches), the passage diameter D₄₁₃ is about 2.95 mm (0.116 inches), the angle θ₄₁₁ is typically about 120°, the angle θ₄₁₂ is typically about 40°, the length L₄₂₁ is about 2.24 cm (0.881 inches), the length L₄₂₂ is about 1.96 cm (0.771 inches), the curved length L₄₃₁ is about 1.02 cm (0.402 inches), the curved length L₄₃₂ is about 4.17 mm (0.164 inches), the curved length L₄₃₃ is about 1.88 mm (0.074 inches), the curved length L₄₃₄ is about 8.92 mm (0.351 inches), the major diameter D₄₃₁ is about 3.63 cm (1.430 inches), the diameter D₄₃₂ is about 3.43 cm (1.350 inches), the diameter D₄₃₃ is about 2.90 cm (1.140 inches), the profile tolerance width W₄₃₁ is about 0.0254 mm (0.001 inches), the radii of curvature R₄₃₁, R₄₃₂, R₄₃₃, R₄₃₄, R₄₃₅ are about 1.27 mm (0.050 inches), 1.27 mm (0.050 inches), 0.762 mm (0.030 inches), 0.381 mm (0.015 inches), 0.381 mm (0.015 inches), respectively, the angle θ₄₃₁ is about 20°, the length L₄₄₁ is about (0.055 inches), the length L₄₄₂ is about 0.381 mm (0.015 inches), the length L₄₄₃ is about 0.127 mm (0.005 inches), the length L₄₄₄ is about 0.127 mm (0.005 inches), the diameter D₄₄₁ is about 3.345 cm (1.317 inches), the diameter D₄₄₂ is about 3.226 cm (1.270 inches), the radius of curvature R₄₄₁ is about 0.20 mm (0.008 inches) and the radius of curvature R₄₄₂ is about 0.51 mm (0.020 inches). In other preferred embodiments, the inner spline 422 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 45-47 show one preferred embodiment of one of the rotors or inner blades 420 of a magnetorheologically actuated prosthetic knee of the present invention. The preferably annular or ring shaped thin rotor 420 is generally circular in shape and comprises a substantially central cavity or through hole 486 having a plurality of inwardly extending teeth 488 adapted to engage or mate with the inner spline grooves 484 (FIG. 41). Preferably, the rotor 420 comprises nine approximately equally spaced teeth 488 which are generally rectangular or square shaped with rounded corners.

The rotors 420 are preferably fabricated from a mechanically hard, magnetically soft material that has a high saturation flux density. More preferably, the rotors 420 are fabricated from blue temper steel. The rotors 420 are preferably formed by wire electro-discharge machining (EDM). Advantageously, this permits a high degree of manufacturing precision and avoids or mitigates any backlash, jarring or play between the rotors 420 and inner spline 422 which may otherwise cause discomfort to the patient.

In one preferred embodiment, and referring in particular to FIGS. 45-47, the rotors 420 are dimensioned and configured such that the major outer diameter D₄₅₁ is about 4.851 cm (1.910 inches), the thickness T₄₆₁ is about 0.203 mm (0.008 inches), the curved length L₄₇₁ is about 9.12 mm (0.359 inches), the curved length L₄₇₂ is about 1.73 mm (0.068 inches), the major inner diameter D₄₇₁ is about 3.642 cm (1.434 inches), the minor inner diameter D₄₇₂ is about 3.439 cm (1.354 inches), the profile tolerance width W₄₇₁ is about 0.0254 mm (0.001 inches), the radius of curvature R₄₇₁ is about 0.508 mm (0.020 inches), the radius of curvature R₄₇₂ is about 0.254 mm (0.010 inches) and the angle θ₄₇₁ is about 40°. In other preferred embodiments, the rotors 420 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

In one preferred embodiment, the ratio between the rotor major outer diameter (D₄₅₁) and the rotor major inner diameter (D₄₇₁) is about 1.3. In another preferred embodiment, the ratio between the rotor major outer diameter (D₄₅₁) and the rotor major inner diameter (D₄₇₁) ranges between about 1.2 to about 5. In yet another preferred embodiment, the ratio between the rotor major outer diameter (D₄₅₁) and the rotor major inner diameter (D₄₇₁) ranges between about 1.1 to about 10. In other preferred embodiments, this ratio may be varied with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIGS. 48-50 show one preferred embodiment of one of the stators or outer blades 430 of a magnetorheologically actuated prosthetic knee of the present invention. The preferably annular or ring shaped thin stator 430 is generally circular in shape and comprises a substantially central cavity or through hole 490 adapted to non-contactingly receive the inner spline 422 and a plurality of outwardly extending teeth 492 on the stator outer periphery which are adapted to engage or mate with grooves or notches on the interior of a rotatable outer spline of the prosthetic knee. Preferably, the stator 430 comprises nine approximately equally spaced teeth 492 which are generally rectangular or square shaped with rounded corners.

The stators 430 are preferably fabricated from a hard ferrous material that has a high saturation flux density. More preferably, the stators 430 are fabricated from blue temper steel. The stators 430 are preferably formed by wire electro-discharge machining (EDM). Advantageously, this permits a high degree of manufacturing precision and avoids or mitigates any backlash, jarring or play between the stators 430 and outer spline which may otherwise cause discomfort to the patient.

In one preferred embodiment, and referring in particular to FIGS. 48-50, the stators 430 are dimensioned and configured such that the major inner diameter D₄₈₁ is about 3.658 cm (1.440 inches), the thickness T₄₉₁ is about 0.203 mm (0.008 inches), the curved length L₅₀₁ is about 1.18 cm (0.464 inches), the curved length L₅₀₂ is about 3.66 mm (0.144 inches), the major outer diameter D₅₀₁ is about 5.07 cm (1.996 inches), the minor outer diameter D₅₀₂ is about 4.867 cm (1.916 inches), the profile tolerance width W₅₀₁ is about 0.0254 mm (0.001 inches), the radius of curvature R₅₀₁ is about 0.508 mm (0.020 inches), the radius of curvature R₅₀₂ is about 0.254 mm (0.010 inches) and the angle θ₅₀₁ is about 20°. In other preferred embodiments, the stators 430 may be dimensioned and/or configured in alternate manners with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

In one preferred embodiment, the ratio between the stator minor outer diameter (D₅₀₂) and the stator major inner diameter (D₄₈₁) is about 1.3. In another preferred embodiment, the ratio between the stator minor outer diameter (D₅₀₂) and the stator major inner diameter (D₄₈₁) ranges between about 1.2 to about 5. In yet another preferred embodiment, the ratio between the stator minor outer diameter (D₅₀₂) and the stator major inner diameter (D₄₈₁) ranges between about 1.1 to about 10. In other preferred embodiments, this ratio may be varied with efficacy, as required or desired, giving due consideration to the goals of providing a suitably compact, light weight and/or durable artificial knee, and/or of achieving one or more of the benefits and advantages as taught or suggested herein.

FIG. 51 shows a magnetorheologically actuated prosthetic knee 510 having features and advantages in accordance with another preferred embodiment of the present invention. In this embodiment, the magnetic return path passes through the exterior of the prosthetic knee 510. Such a configuration can allow for a more compact and/or light weight system design. Other suitable magnetic return paths can be selected or configured, as needed or desired, giving due consideration to the goals of achieving one or more of the benefits and advantages as taught or suggested herein.

Referring to FIG. 51, a magnetic field 540 is generated by the actuation of an electromagnet or magnetic coil 514 preferably positioned between a plurality of interspersed alternating rotors (inner blades) 520 and stators (outer blades) 530 and an outer magnetically soft housing or casing 512 of the prosthetic knee 510. The active portion of the magnetic field 540 passes (travelling substantially in the lateral direction 542) through the rotors 520, stators 530 and the magnetorheological fluid in the gaps therebetween. The return path of the magnetic field 540 passes radially outwards through a magnetically soft side plate 516, laterally through the knee exterior 512 and radially inwards through a second magnetically soft side plate 518.

While the components and techniques of the present invention have been described with a certain degree of particularity, it is manifest that many changes may be made in the specific designs, constructions and methodology hereinabove described without departing from the spirit and scope of this disclosure. It should be understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be defined only by a fair reading of the appended claims, including the full range of equivalency to which each element thereof is entitled.

Claims

1. A prosthetic knee, comprising:

a plurality of rotors being rotatable about a longitudinal axis of said prosthetic knee;

a plurality of stators alternatingly interspersed with said rotors to form gaps therebetween;

a fluid adapted to undergo a rheology change in response to an applied magnetic field and residing in said gaps formed between said rotors and said stators;

whereby, controlled variation of said magnetic field varies the fluid rheology and shearing of said fluid caused by relative rotation between said rotors and stators during knee rotation generates a controllable variable knee torque.

2. The prosthetic knee of claim 1, wherein said stators are rotatable about the longitudinal axis of said prosthetic knee.

3. The prosthetic knee of claim 1, wherein at least one of said rotors and said stators are laterally displaceable about the longitudinal axis of said prosthetic knee to create mechanical contact between adjacent rotors and stators to provide a frictional component to the torque.

4. The prosthetic knee of claim 1, wherein said rotors and said stators comprise a magnetically soft material.

5. The prosthetic knee of claim 1, wherein said rotors and said stators comprise generally annular disks.

6. The prosthetic knee of claim 5, wherein said rotors and said stators have a thickness of about 0.2 mm (0.008 inches).

7. The prosthetic knee of claim 1, wherein said plurality of rotors comprises hundred or less rotors and said plurality of stators comprises hundred or less stators.

8. The prosthetic knee of claim 7, wherein said plurality of rotors comprises forty rotors and said plurality of stators comprises forty one stators.

9. The prosthetic knee of claim 1, wherein said gaps between said rotors and said stators have a size in the range from about 10 microns (μm) to about 100 microns (μm).

10. The prosthetic knee of claim 9, wherein said gaps between said rotors and said stators have a size of about 40 microns (μm).

11. The prosthetic knee of claim 1, wherein said rotors and said stators comprise generally cylindrical tubes.

12. The prosthetic knee of claim 1, wherein said rotors and said stators comprise blue temper steel or silicon steel.

13. The prosthetic knee of claim 1, wherein said fluid comprises a magnetically controllable medium.

14. The prosthetic knee of claim 1, wherein said fluid comprises a magnetorheological fluid adapted to undergo a viscosity change in response to variation in said magnetic field.

15. The prosthetic knee of claim 1, further comprising a magnet to generate said magnetic field which passes through said rotors, said stators and said fluid.

16. The prosthetic knee of claim 1, further comprising a generally central core in mechanical communication with a pair of side plates to form a magnetic return path for said magnetic field.

17. The prosthetic knee of claim 16, wherein said core and said side plates comprise an iron-cobalt (FeCo) high magnetic saturation alloy.

18. The prosthetic knee of claim 16, wherein at least one of said side plates is laterally displaceable about the longitudinal axis of said prosthetic knee.

19. The prosthetic knee of claim 1, further comprising:

a substantially central core and a pair of side plates formed from a magnetically soft material to create a magnetic return path; and

an electromagnet positioned between said core and said rotors and said stators and being responsive to an electrical signal to generate said magnetic field to cause a controlled change in the rheology of said fluid.

20. The prosthetic knee of claim 1, further comprising a rotatable inner spline with said rotors engaged with said inner spline.

21. The prosthetic knee of claim 20, wherein said inner spline comprises a plurality of longitudinal grooves and each of said rotors comprises a plurality of teeth matingly engaged with said longitudinal grooves of said inner spline.

22. The prosthetic knee of claim 20, wherein said inner spline comprises a titanium alloy.

23. The prosthetic knee of claim 20, further comprising a pair of bearings in rotary communication with said inner spline.

24. The prosthetic knee of claim 23, further comprising a pair of rotatable side mounting forks with each in mechanical communication with one of said bearings to facilitate connection of said prosthetic knee to a prosthetic shin.

25. The prosthetic knee of claim 1, further comprising an outer spline with said stators engaged with said outer spline.

26. The prosthetic knee of claim 25, wherein said outer spline comprises a plurality of longitudinal grooves and each of said stators comprises a plurality of teeth matingly engaged with said longitudinal grooves of said outer spline.

27. The prosthetic knee of claim 25, wherein said outer spline comprises an anodized aluminum alloy.

28. The prosthetic knee of claim 25, wherein said outer spline comprises a pyramid stub to facilitate connection of said prosthetic knee to a residual limb socket.

29. The prosthetic knee of claim 1, further comprising a magnetic exterior portion and a pair of mechanically connected magnetic side plates to create a magnetic return path for said magnetic field.

30. The prosthetic knee of claim 1, further comprising a cushioned flexion stop system to control the maximum flexion of said prosthetic knee.

31. The prosthetic knee of claim 1, further comprising a cushioned extension stop system to control the maximum extension of said prosthetic knee.

32. The prosthetic knee of claim 1, further comprising an extension assist device for facilitating in extending said prosthetic knee.

33. The prosthetic knee of claim 1, further comprising a controller to control and monitor the actuations of said prosthetic knee.

34. A prosthetic assembly, comprising:

the prosthetic knee as recited in claim 1;

a stump socket in mechanical communication with said prosthetic knee and adapted to receive the residual limb of an amputee;

a prosthetic shin portion in mechanical communication with said prosthetic knee; and

a prosthetic foot in mechanical communication with said prosthetic shin portion.

35. A prosthetic device, comprising:

at least one rotor being actuatable about an axis of the device;

at least one stator being spaced from said at least one rotor and forming a gap therebetween; and

a fluid adapted to undergo a rheology change in response to an applied magnetic field and residing in said gap;

wherein controlled variation of said magnetic field varies the fluid rheology, and shearing of said fluid caused by relative rotation between said at least one rotor and said at least one stator during device rotation generates a controllable variable torque; and

wherein said prosthetic device comprises a prosthetic joint.

36. The prosthetic device of claim 35, wherein said at least one rotor is generally cylindrical.

37. The prosthetic device of claim 35, wherein said at least one stator is generally cylindrical.

38. The prosthetic device of claim 35, wherein said at least one rotor and said at least one stator are generally cylindrical.

39. The prosthetic device of claim 35, further comprising an outer housing.

40. The prosthetic device of claim 39, wherein said outer housing includes a connector for facilitating connection to a stump socket or a residual limb of an amputee.

41. The prosthetic device of claim 40, wherein said connector is a pyramid connector.

42. The prosthetic device of claim 35, wherein the joint is a prosthetic knee.

43. The prosthetic device of claim 35, wherein said fluid comprises a magnetorheological fluid.

44. The prosthetic device of claim 35, further comprising at least one sensor for measuring an angle of rotation between said at least one rotor and said at least one stator.

45. The prosthetic device of claim 35, further comprising a microprocessor.

46. The prosthetic device of claim 35, in combination with a prosthetic foot mechanically coupled to the joint.

47. A prosthetic device system, comprising:

an outer generally cylindrical member comprising a substantially cylindrical cavity;

an inner generally cylindrical member provided within said substantially cylindrical cavity, wherein said inner and outer generally cylindrical members are rotatable about a device axis of rotation relative to one another;

a magnetorheological fluid residing in a cavity between said inner and outer generally cylindrical members; and

a connector at a top end of said outer generally cylindrical member for facilitating connection to a stump socket or a residual limb of an amputee;

wherein a damping torque to control device rotation is provided by shearing of said magnetorheological fluid; and

wherein said prosthetic device system comprises a prosthetic joint system.

48. The prosthetic device system of claim 47, wherein said connector is a pyramid connector.

49. The prosthetic device system of claim 47, wherein said inner generally cylindrical member is rotatable about a knee joint axis of rotation relative to said outer generally cylindrical member.

50. The prosthetic device system of claim 47, wherein said inner generally cylindrical member is mechanically connected to a prosthetic foot.

51. The prosthetic device system of claim 47, further comprising side walls for enclosing said magnetorheological fluid.

52. The prosthetic device system of claim 47, further comprising an electromagnet for applying a magnetic field to said magnetorheological fluid.

53. The prosthetic device system of claim 52, wherein said electromagnet is coupled to one of said generally cylindrical members.

54. The prosthetic device system of claim 52, further comprising a power source connected with said electromagnet.

55. The prosthetic device system of claim 47, further comprising a feedback control system to control and monitor actuations of the prosthetic joint system.

56. The prosthetic device system of claim 47, further comprising at least one sensor for measuring an angle of rotation between said inner and outer generally cylindrical members.

57. The prosthetic device system of claim 47, further comprising a microprocessor and one or more sensors to provide control and monitor actuations of the prosthetic joint system.

58. The prosthetic device system of claim 47, wherein said magnetorheological fluid is sheared between adjacent cylinders.

59. A device to be worn by a wearer at a joint location, comprising:

a first surface;

a second surface spaced from said first surface to form a gap therebetween;

a fluid adapted to undergo a rheology change in response to an applied magnetic field and residing in said gap;

at least one of said first surface and said second surface being movable relative to the other;

wherein, variation of said field varies the rheology of said fluid and shearing of said fluid caused by relative motion between said first and second surfaces generates a controllable variable damping of the device; and

wherein the device comprises a prosthetic device, and wherein said prosthetic device comprises a prosthetic joint.

60. The device of claim 59, wherein said prosthetic joint comprises a prosthetic knee.

61. The device of claim 59, wherein said fluid comprises a magnetorheological fluid.

62. The device of claim 59, wherein said fluid comprises a magnetically controllable medium.

63. The device of claim 59, wherein said first and second surfaces are generally cylindrical.

64. The device of claim 59, wherein said field varies the viscosity of said fluid.