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Prosthetics Research Study

Alan L Aulie

Ernest M Burgess

An adjustable hydraulic damper involves a piston member operating within a hydraulic cylinder where the hydraulic cylinder wall is adjustably deformed to vary the annular space between a piston head and the inside cylinder wall through which hydraulic fluid must pass. The wall of the cylinder is adjustably deformed through an annular ramp formed circumferentially about the outside of the cylinder and having an angled bearing surface. A compression nut, having an angled inside circumferential surface, threadingly engages the outside of the cylinder, wherein rotation of the compression nut causes its angled inside surface to bear on the ramp of the cylinder wall, thereby producing a local, uniform, annular deformation of the inside surface of the cylinder wall. The amount of deformation, and thus the flow of fluid through the annular space, is adjustable by rotation of the compression nut. For bi-directional damping, with two opposing piston heads on the piston member, each piston head utilizes a separate compression nut. In such form, each piston head also includes an internal valve, formed of a plurality of longitudinal interior passageways valved by a flexible baffle, to permit free flow of fluid through the piston head not directly involved in the damping action. An accumulator, in the form of an annular foam ring, is positioned on the piston member in the low pressure region between the first piston head and the opposing second piston head to provide piston rod volume compensation.

Adjustable hydraulic damper

A prosthetic joint includes an anterior linking and support member and a posterior linking and support member, formed of a resilient material, which act as cantilever flat springs to provide an intrinsic extension bias while furnishing the rigid structure necessary to support the axial loads and extension moments induced by the amputee. A prosthetic knee joint includes a base formed of a resilient polyamide such as nylon 6/6, from which an anterior linking and support member, generally of an L-shape, and a posterior linking and support member, monolithically extend upwards. Formed to provide the inherent stability of four-bar linkage, these resilient linking and support members are pivotally attached to a yoke member to act as cantilever single-leaf flat springs which provide an intrinsic extension moment to the prosthetic knee joint which may vary according to the amount of flexion of the knee joint. The extension moment of the knee joint is translated into compression at the anterior linking and support member and tension at the posterior linking and support member, thereby allowing the use of a relatively low-strength resilient material in the knee joint construction. A common double-acting hydraulic damper is used to reduce the swing rate of the knee joint, permitting a desired gait and reducing terminal impact at full extension.

Hinge structure for prosthetic joint

A prosthetic alignment device having a shank member, an alignment body, and setscrews to adjust the angular orientation of the shank member and secure the shank member in place relative to the alignment body. The alignment body has a body cavity into which the shank member is inserted, a concave bearing surface for engaging a spherical radius of curvature of the end of the shank member, and an annular opening for inserting the end of the shank member. Angulation of the shank member inside the body cavity causes the annular opening to elastically deform and exert a hoop stress on the shank member increasing the securing force therebetween.

Prosthetic alignment device supplementally secured by a hoop stress

A prosthetic ankle having an elongated tubular shank, which provides bending. The shank is part of a monolithic ankle with the lower portion being a flexure joint. The flexure joint has a flexing post defined by an entrapment kerf. The entrapment kerf allows relatively free movement of flexure within defined limits in axial rotation, dorsi and plantar flexion, inversion and eversion. The kerf surfaces provide resistance to axial rotation during dorsiflexion.

Growing community of inventors

Indianola, WA, United States of America

Alan L Aulie