Note: Descriptions are shown in the official language in which they were submitted.
21 3+999
Prosthetic Joint
The invention relates to a prosthetic joint, especially a
knee or hip joint, with an upper joint part, a lower
joint part, a joint axle connecting these two joint parts
together in pivotable fashion, and nonrotatably connected
with one joint part, and a damping of the joint swing.
Damping a knee joint hydraulically is known. A hydraulic
damping cylinder located outside the joint is provided
for this purpose, said cylinder being articulated at one
end on the lower joint part and acting with its piston
rod on a lever connected with the upper joint part.
Summary of the Invention
A goal of the invention is to improve known designs.
In accordance with one aspect of the present invention
there is provided a prosthetic joint having an upper
joint part, a lower joint part, a joint axle joining
these two joint parts pivotably with one another and
nonrotatably connected with one of said joint parts, and
a damper of the joint swing, wherein: a) the damper is
integrated into one of the two joint parts and acts
directly on the joint axle nonrotatably connected with
the other joint part; b) the damper has an enclosed
displacement chamber concentrically surrounding the joint
axle at least partially or over its circumference, said
chamber being divided by the joint axle, made in the form
of a rotary piston, into two sectional chambers;
c) sectional chambers of the displacement chamber are
connected together by two throttle-check valves connected
in parallel and acting in opposite directions; d) both
throttle-check valves are controllable from the exterior
separately from one another; and e) a force loading the
joint causes a predefined closure of one of said
throttle-check valves.
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The design according to the invention, in its application
as a knee joint, in addition to the known braking knee,
permits a swing phase control in which the swing
resistance can be adjusted separately for flexure and
extension.
The throttles can basically be controlled mechanically or
by an electrical positioning drive. It is advantageous
according to the invention for a throttle to be
controlled by an axially displaceable throttle rod whose
displacement can be effected for example by a manually
adjustable knurled screw or the like.
Particularly in a prosthetic joint designed as a knee
joint, it is advantageous for a force loading the joint
to cause a predefined closure of the bending throttle.
This can be accomplished in the design in the form of a
telescopic, force, or moment control.
Preferably, the rotary piston has a rectangular piston
plate abutting the two ends and the cylindrical inside
wall of the enclosed displacement chamber by a sealing
frame. The latter can preferably be held in place by a
retainer screwed to the piston plate. This results in a
displacement chamber enclosed on all sides with a single
defined leak provided in the area of the rotary piston
seal. It is advantageous in this regard for the rotary
piston seal sealing the displacement chamber from the
exterior to be located outside the rotary piston bearing.
Lubrication of the rotary piston bearing is provided by
the pressure prevailing the displacement chamber, in
other words by the hydraulic oil which should therefore
have superior lubricating properties.
Additional features of the invention will be explained in
greater detail in
1.
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conjunction with further advantages of the invention with
reference to an embodiment.
The drawing shows one embodiment of the invention as an
example.
Figure 1 shows a knee joint in a side view;
Figure 2 is the representation in Figure 1 in an end view;
Figure 3 is the representation in Figure 1 in a top view;
Figure 4 is a lengthwise section along line A-A in Figure 2;
Figure 5 is a lengthwise section along line C-C in Figure 2;
and
Figure 6 is a cross section along line B-B in Figure 1.
A knee joint is shown as an example of a prosthetic joint,
said knee joint consisting of an upper joint part 1 and a
lower joint part 2 located slightly eccentrically with
respect to the latter. The pivotable connection of the two
joint parts l, 2 is provided by a joint axle 3 nonrotatably
connected with upper joint part 1. Upper joint part 1 abuts
the cylindrical surface 4 of lower joint part 2 with its
partially cylindrical lower side. Because of the eccentric
arrangement of the two parts with respect to one another,
during a joint swing upper joint part 1 rolls with its lower
side on cylindrical surface 4, which therefore serves as a
joint buffer over its entire surface. A separate joint stop
is therefore unnecessary.
To damp the joint swing, in the embodiment shown hydraulic
damping is provided that is directly integrated into lower
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joint part 2, said damping acting directly on joint axle 3,
Hydraulic damping comprises an enclosed displacement chamber
surrounding joint axle 3 over its circumference partially
concentrically, said chamber being divided by joint axle 3
in the form of a rotary piston into two sectional chambers
5a, 5b. For this purpose, joint axle~3 is provided with a
rectangular piston plate 6 extending in the axial and radial
directions, said plate abutting in sealing fashion the two
end walls of displacement chamber 5 with its two radially
extending end edges and abutting the cylindrical inside wall
of displacement chamber 5 with its axially extending
lengthwise edge. Preferably this seal is provided by a
sealing frame 7, mounted on piston plate 6 by means of a
retainer screwed to piston plate 6 and not shown in the
drawing.
Displacement chamber 5 is sealed from the exterior by a
rotary piston seal 8 located outside rotary piston bearing
9. Lubrication is provided by the pressure prevailing in
the displacement chamber 5, with displacement chamber 5
preferablx being filled with a hydraulic oil with superior
lubricating properties.
Sectional chambers 5a, 5b are connected together by two
throttle-check valves 10 connected in parallel and acting in
opposite directions. These valves are located in two bores
11 provided side by side in lower joint part 2, said bores
running perpendicularly to joint axle 3 and being sealed
from the exterior by sealing plugs 12.
A throttle rod 13 is provided to control the throttle of
each throttle-check valve 10 in the embodiment shown, said
rod being displaceable lengthwise by an adjusting device not
shown in greater detail, for, example a manually operated
knurled screw, and projecting with its upper free end shown
r
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in Figure 5 to a greater or lesser depth into the flow cross
section of the flow connection between the two sectional
chambers 5a and 5b. The possibility of separate adjustment
of the two throttle rods 13 allows the swing resistance to
be adjusted separately for flexure and extension. It is
also advantageous in this regard for loading of the knee to
result in closure of the bending throttle. This is ensured
by a telescopic, force, or moment control not shown in the
drawing.
