Double-acting hydraulic piston-and-cylinder device

• US 4,854,428 A
• Filed: 09/22/1988
• Issued: 08/08/1989
• Est. Priority Date: 09/22/1987
• Status: Expired due to Term

• Current Assignee: OTTO BOCK Orthopadische Industrie Besitz und Verwaltungs KG
• Original Assignee: OTTO BOCK Orthopadische Industrie Besitz und Verwaltungs KG
• Inventors: Horvath, Eduard
• Primary Examiner(s): Oberleitner, Robert J.
• Application Number:
  US07/247,896
• Time in Patent Office: 320 Days
• Field of Search: 188/298, 188/314, 188/315, 188/322.12, 188/322.16, 623/18, 623/39, 623/43, 623/44, 623/45, 92/41, 277/212 FB, 267/64.19, 267/64.23, 267/64.27
• US Class Current: 188/298
• CPC Class Codes: A61F 2/68 Operating or control means
• CPC Class Codes: A61F 2/74 fluid , i.e. hydraulic or pneumatic

Abstract

A double-acting hydraulic piston-and-cylinder unit adapted to constitute a damper for movements in a human joint prosthesis has a boot sealingly connected to the cylinder and the piston rod to receive the hydraulic fluid under pressure as the hydraulic fluid is displaced from one or the other of two cylinder chambers upon displacement of the piston rod. The boot has a conically widening region or segment sealingly secured to the rod and adjoining the cylindrical segment of the boot surrounding the cylinder in a transition segment formed as an outwardly convex bulge and designed to ensure that initial inward movement of the piston rod will give rise to a plate membrane deformation of the elastic boot while only further displacement will result in a rolling action of the membrane. This ensures a generally cylindrical uniform configuration of the boot in all positions of the rod as is essential for effective use in a prosthesis.

Claims

1. A double-acting piston-and-cylinder hydraulic unit which comprises:

means for forming a cylinder;

a piston axially shiftable in said cylinder and defining therein respective hydraulic-fluid-containing chambers on opposite sides of said piston;

a piston rod connected to said piston and extending axially out of said cylinder;

an elastically deformable boot surrounding said cylinder and said rod while forming therewith a hydraulic-fluid-pressurized variable-volume compartment, said boot having a generally cylindrical segment sealingly connected to said cylinder, an outwardly widening segment diverging from and sealingly connected to said rod, and a transition segment connecting said widening segment to said generally cylindrical segment,

said transition segment having, in an extended position of said piston rod, an outwardly convex shape and having a greater diameter than that of said generally cylindrical segment,

a ratio between the radius (R) of said transition segment at said greater diameter than said generally cylindrical segment and an axial distance (L) between a plane of said transition segment at its greatest diameter and a location closest to said cylinder at which said boot is sealingly connected to said rod being given by the relation;

space="preserve" listing-type="equation">3;

1 ≧

R/L ≧

1;

2; and

means for fluid communication between each of said chambers and said variable-volume compartment.

2. The double-acting piston-and-cylinder hydraulic unit defined in claim 1 wherein said ratio R/L is substantially 2:

1.

3. The double-acting piston-and-cylinder hydraulic unit defined in claim 1 wherein said transition segment forms an outward annular bulge of said boot in said extended position of said rod.

4. The double-acting piston-and-cylinder hydraulic unit defined in claim 1 wherein said boot is formed at a junction between said transition segment and said outwardly widening segment with a region of greater flexibility than the remainder of said boot.

5. The double-acting piston-and-cylinder hydraulic unit defined in claim 1 wherein said boot is formed proximal to its sealing connection to said cylinder with an outward annular bulge having a diameter greater than that of said generally cylindrical segment in said extended position of said rod.