Hydraulic control unit for prosthetic leg

• US 5,443,521 A
• Filed: 12/30/1993
• Issued: 08/22/1995
• Est. Priority Date: 12/21/1992
• Status: Expired due to Term

• Current Assignee: Ossur hf
• Original Assignee: Mauch Laboratories, Inc.
• Inventors: Phillips, William L., Knoth, Donald E.
• Primary Examiner(s): Willse, David H.
• Application Number:
  US08/175,645
• Time in Patent Office: 600 Days
• Field of Search: 623/39, 623/44, 267/64.27, 267/117, 188/311, 188/322.19, 188/314, 403/152, 403/161, 403/163, 403/221, 403/224, 403/226
• US Class Current: 623/44
• CPC Class Codes: A61F 2/60 Artificial legs or feet or parts thereof
• 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
• CPC Class Codes: Y10T 403/32967 Attached to or integral with one member
• CPC Class Codes: Y10T 403/454 Connecting pin traverses radially interposed elastomer

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 preferably sealed gas pressurized 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 continuous higher hydraulic static 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 for use with a prosthetic leg assembly 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, flow control means disposed within said bore and defining an operating chamber for receiving hydraulic fluid, a piston rod having an inner portion extending into said housing and an outer portion projecting from said housing, a piston on said inner portion of said piston rod within said operating chamber, means defining a fluid accumulating chamber connected to receive fluid from said displacement chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control means 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 flexible bladder within said accumulating chamber for accumulating said fluid displaced from said displacement chamber to said accumulating 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, an annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, said bladder including opposing films of flexible plastics material, said films having adjacent peripheral portions heat sealed together to form a pressure chamber between said films, a pressurized gas within said pressure chamber, a second annular sealing member supported by said housing inwardly of the first said sealing member and engaging said piston rod between said operating chamber and said displacement chamber, and said second sealing member having means for preventing 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 hydraulic control unit for use with a prosthetic leg assembly 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, flow control means disposed within said bore and defining an operating chamber for receiving hydraulic fluid, a piston rod having an inner portion extending into said housing and an outer portion projecting from said housing, a piston on said inner portion of said piston rod within said operating chamber, means defining a fluid accumulating chamber connected to receive fluid from said displacement chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control means 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 flexible bladder within said accumulating chamber for accumulating said fluid displaced from said displacement chamber to said accumulating 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, an annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, said bladder including opposing flexible films of uniform thickness and having adjacent continuous peripheral portions sealed together to form an enclosed pressure chamber between said films and a sealed flange extending completely around the periphery of said bladder, each of said films having multiple layers of different thermoplastics materials including a substantially gas impermeable layer, and said sealed pressure chamber enclosing a gas having a pressure substantially above atmospheric pressure.

3. A control unit as defined in claim 2 wherein said housing includes a lower end portion defining a laterally extending bore, a pair of opposing tubular bushings projecting into said bore, each of said bushings including a head portion projecting outwardly from said bore, a support pin extending through said bushings and having a cylindrical center portion within said bore and external grooves within said head portions of said bushings, said bushings comprising a semi-rigid plastics material and having corresponding internal ribs projecting into said grooves within said pin for retaining said pin, and each of said bushings having a circumferentially extending external groove within said bore and surrounding a circumferentially extending internal rib engaging said cylindrical center portion of said pin for effectively dampening relative movement between said housing and said support pin.

4. A control unit as defined in claim 2 wherein said flow control means comprise a tubular sleeve within said bore and 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.

5. A hydraulic control unit for use with a prosthetic leg assembly 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, flow control means disposed within said bore and defining an operating chamber for receiving hydraulic fluid, a piston rod having an inner portion extending into said housing and an outer portion projecting from said housing, a piston on said inner portion of said piston rod within said operating chamber, means defining a fluid accumulating chamber connected to receive fluid from said displacement chamber, a supply of hydraulic fluid within each of said operating and displacement chambers, said fluid flowing within said flow control means 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, means within said accumulating chamber for accumulating said fluid displaced within said displacement chamber to said accumulating 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, an annular sealing member supported by said housing and engaging said piston rod for confining said fluid within said operating chamber, said housing including a lower end portion defining a laterally extending bore, a pair of opposing tubular bushings projecting into said bore, each of said bushings including a head portion projecting outwardly from said bore, a support pin extending through said bushings and having a cylindrical center portion within said bore and external grooves within said head portions of said bushings, said bushings comprising a semi-rigid plastics material and having corresponding internal ribs projecting into said grooves within said pin for retaining said pin, and each of said bushings having a circumferentially extending external groove within said bore and surrounding a circumferentially extending internal rib engaging said cylindrical center portion of said pin for effectively dampening relative movement between said housing and said support pin.

6. A control unit as defined in claim 5 wherein said head portion of each said bushing is larger than said bore and forms a spacer for positioning said lower end portion of said housing on said pin.