Hydraulic control unit for prosthetic leg

• US 5,405,409 A
• Filed: 01/21/1994
• Issued: 04/11/1995
• Est. Priority Date: 12/21/1992
• Status: Expired due to Term

• Current Assignee: Ossur hf
• Original Assignee: Donald E. Knoth
• Inventors: Knoth, Donald E.
• Primary Examiner(s): Willse, David H.
• Application Number:
  US08/185,586
• Time in Patent Office: 445 Days
• Field of Search: 623/44, 623/39, 623/43, 623/26, 188/311, 188/322.19, 188/314, 267/124, 267/129, 92/85 R, 92/85 B, 92/84, 92/110
• US Class Current: 623/44
• CPC Class Codes: A61F 2/64 Knee joints
• CPC Class Codes: A61F 2/68 Operating or control means
• CPC Class Codes: A61F 2/74 fluid , i.e. hydraulic or pneumatic
• CPC Class Codes: A61F 2002/30405 made by screwing complementary threads machined on the parts themselves
• CPC Class Codes: A61F 2002/5003 having damping means, e.g. shock absorbers for implantable joints A61F2002/30563
• CPC Class Codes: A61F 2002/501 having an inflatable pocket filled with fluid, i.e. liquid or gas
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements

Abstract

A prosthetic leg has a pivotal knee joint and a hydraulic fluid control unit connected to provide variable forces which dampen flexion and extension of the knee and also bias the leg to its extended position. The unit includes an aluminum housing lined with an axially adjustable sleeve and control bushing defining a cylindrical operating chamber which receives a piston mounted on a tubular piston rod. The housing and operating chamber receive hydraulic fluid or oil which flows during movement of the piston through fluid control ports, channels and adjustable gaps defined by the sleeve and bushing for damping the movement of the rod. The piston rod encloses a gas filled flexible bladder which forms an oil accumulator during inward movement of the piston rod into a displacement chamber and also produces variable forces for moving the piston rod outwardly to its extended position. An annular seal engages an inner portion of the piston rod and prevents the higher hydraulic pressure in the displacement chamber from transferring to the operating chamber and the annular seal between the housing and the outer portion of the piston rod.

Claims

1. A hydraulic control unit in combination with a prosthetic leg assembly including an upper leg member for receiving the thigh portion of an amputee'"'"'s leg and a lower leg member pivotally connected to the upper leg member, said unit extending between said upper and lower leg members for producing movement of the prosthetic leg assembly simulating that of the natural leg over a wide range of walking speeds, said unit comprising an elongated tubular housing having an axis, said housing including a first end portion including means defining a displacement chamber for receiving hydraulic fluid and a second end portion defining a bore, a flow control member disposed within said bore and defining an operating chamber for receiving hydraulic fluid, a piston rod having an inner portion extending into said displacement chamber and an outer portion projecting from said housing, a piston on said inner portion of said piston rod within said operating chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control member and said operating chamber in response to axial movement of said piston and said piston rod within said operating chamber to effect damping of said piston rod, an accumulator for accumulating said fluid displaced within said displacement chamber when said piston rod moves into said housing and for maintaining a continuous static pressure on said piston rod for urging said piston rod outwardly from said housing, a first annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, a second annular sealing member supported by said housing inwardly of said first sealing member and between said operating chamber and said displacement chamber, and said second sealing member having a resilient annular surface positively engaging said piston rod and configured to prevent the continuous hydraulic static pressure within said displacement chamber from transferring past said second sealing member to said operating chamber and to said first sealing member to avoid leakage of hydraulic fluid from said housing past said first sealing member for significantly extending the service life of said unit.

2. A control unit as defined in claim 1 where in said second sealing member comprises an annular channel-like body defining a cavity receiving said hydraulic fluid within said displacement chamber, and spring means within said cavity and cooperating with said hydraulic fluid to urge said body against said piston rod.

3. A control unit as defined in claim 1 wherein said first sealing member comprises an annular channel-like body defining a cavity receiving said hydraulic fluid within said operating chamber, and spring means within said cavity and cooperating with said hydraulic fluid to urge said body against said piston rod.

4. A control unit as defined in claim 1 and including a first removable plug member for filling said operating chamber with said hydraulic fluid, and a separate second removable plug member for filling said displacement chamber with said hydraulic fluid.

5. A control unit as defined in claim 1 and including an annular spring member surrounding said piston rod for holding said first sealing member against said hydraulic fluid within said operating chamber to accommodate adjustment of said flow control member and displacement of said hydraulic fluid within said operating chamber.

6. A control unit as defined in claim 1 wherein said piston comprises an annular body of rigid plastics material mounted on said piston rod, and a ring member for releasably retaining said body on said piston rod.

7. A control unit as defined in claim 1 wherein said piston rod is tubular and encloses a gas filled flexible bladder positioned to receive the pressure of said hydraulic fluid within said displacement chamber, and a fitting secured to said outer portion of said piston rod for retaining said bladder.

8. A control unit as defined in claim 7 and including mating tapered tubular members receiving therebetween an open end portion of said bladder, and said tubular members are enclosed within said outer portion of said piston rod.

9. A control unit as defined in claim 1 and including an annular bearing supported by said housing and surrounding said inner portion of said piston rod adjacent said second sealing member, and said bearing includes means forming a low friction surface engaging said piston rod.

10. A control unit as defined in claim 1 wherein said flow control member comprises a tubular sleeve slidably supported by said housing for axial adjustment, a control bushing disposed within said sleeve and defining said operating chamber, and said bushing and sleeve have means defining a series of flow control passages extending through said bushing from said operating chamber and axially between said bushing and said sleeve.

11. A hydraulic control unit in combination with a prosthetic leg assembly including an upper leg member for receiving the thigh portion of an amputee'"'"'s leg and a lower leg member pivotally connected to the upper leg member, said unit extending between the upper and lower leg members for producing movement of the prosthetic leg assembly simulating that of the natural leg over a wide range of walking speeds, said unit comprising an elongated tubular housing having an axis, means for pivotally connecting said housing to one of said leg members, said housing including a first end portion including means defining a displacement chamber for receiving hydraulic fluid and a second end portion having a substantially cylindrical inner surface defining a bore, a tubular flow control member engaging said inner surface of said housing and defining an operating chamber for receiving hydraulic fluid, a piston rod having an inner portion extending into said displacement chamber and an outer portion projecting from said housing, means for pivotally connecting said outer portion of said piston rod to the other leg member, a piston on said inner portion of said piston rod within said operating chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control member and said operating chamber in response to axial movement of said piston and said piston rod within said operating chamber to effect damping of said piston rod, an accumulator for accumulating said fluid displaced within said displacement chamber when said piston rod moves into said housing in response to pivoting of the leg members and for maintaining a continuous static pressure on said piston rod for urging said piston rod outwardly from said housing, a first annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, a second annular sealing member supported by said housing inwardly of said first sealing member and engaging said piston rod between said operating chamber and said displacement chamber, and said second sealing member having a resilient annular surface positively engaging said piston rod and configured to prevent the continuous hydraulic static pressure within said displacement chamber from transferring past said second sealing member to said operating chamber and to said first sealing member to avoid leakage of hydraulic fluid from said housing past said first sealing member for significantly extending the service life of said unit.

12. A control unit as defined in claim 11 wherein said accumulator comprises a gas filled flexible bladder positioned to receive the pressure of said hydraulic fluid within said displacement chamber.

13. A control unit as defined in claim 12 wherein said piston rod is tubular and encloses said bladder, and a fitting secured to said outer portion of said piston rod for retaining said bladder within said piston rod.

14. A control unit as defined in claim 11 wherein said second sealing member comprises an annular channel-like body defining a cavity receiving said hydraulic fluid within said displacement chamber, and a spring member within said cavity and cooperating with said hydraulic fluid to urge said body against said piston rod.

15. A control unit as defined in claim 11 and including an annular spring member surrounding said piston rod for holding said first sealing member against said hydraulic fluid within said operating chamber to accommodate adjustment of said flow control member and displacement of said hydraulic fluid within said operating chamber.

16. A control unit as defined in claim 11 and including an annular bearing supported by said housing and surrounding said inner portion of said piston rod adjacent said second sealing member, and said bearing includes means forming a low friction surface engaging said piston rod.

17. A control unit as defined in claim 11 wherein said flow control member comprise a tubular sleeve slidably supported by said housing for axial adjustment, a control bushing disposed within said sleeve and defining said operating chamber, and said bushing and sleeve have means defining a series of flow control passages extending through said bushing from said operating chamber and axially between said bushing and said sleeve.

18. A hydraulic control unit in combination with a prosthetic leg assembly including an upper leg member for receiving the thigh portion of an amputee'"'"'s leg and a lower leg member pivotally connected to the upper leg member, said unit extending between said upper and lower leg members for producing movement of the prosthetic leg assembly simulating that of the natural leg over a wide range of walking speeds, said unit comprising an elongated tubular housing having an axis, said housing including a first end portion defining a displacement chamber for receiving hydraulic fluid and a second end portion defining a bore, a flow control member disposed within said bore and defining an operating chamber for receiving hydraulic fluid, a tubular piston rod having an inner portion extending into said displacement chamber and an outer portion projecting from said housing, a piston on said inner portion of said piston rod within said operating chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control member and said operating chamber in response to axial movement of said piston and said piston rod within said operating chamber to effect damping of said piston rod, a gas filled flexible bladder within said piston rod for accumulating said fluid displaced within said displacement chamber when said piston rod moves into said housing and for maintaining a continuous static pressure on said piston rod for urging said piston rod outwardly from said housing, a first annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, a second annular sealing member supported by said housing inwardly of said first sealing member and between said operating chamber and said displacement chamber, and said second sealing member having a resilient annular surface positively engaging said piston rod and configured to prevent the continuous hydraulic static pressure within said displacement chamber from transferring past said second sealing member to said operating chamber and to said first sealing member to avoid leakage of hydraulic fluid from said housing past said first sealing member for significantly extending the service life of said unit.