U.S. patent number 3,754,286 [Application Number 05/219,670] was granted by the patent office on 1973-08-28 for artificial foot having ankle flexible mount.
Invention is credited to Michael W. Ryan.
United States Patent |
3,754,286 |
Ryan |
August 28, 1973 |
ARTIFICIAL FOOT HAVING ANKLE FLEXIBLE MOUNT
Abstract
An artificial foot including an improved ankle and foot mount is
attached to a conventional stump mounted artificial leg. A coil
spring extends downwardly from rigid attachment to the artificial
limb in the vicinity of the ankle at the upper end and attaches
rigidly to a plate in the plane of the sole of the foot at the
lower end. The sole plate, extending from the heel to the ball of
the foot, cantilevers from the coil spring to emulate natural foot
action during walking. A second sole plate support, capable of
accommodating both tension and compression as well as side to side
foot motion, extends from a mount on the sole plate at the ball of
the artificial foot upwardly at an angle to a mount on the ankle of
the artificial limb. This provides improved toe action of the
artificial limb. Provision is made for mounting either a spring or
a variable resistance shock absorber to act in combination with the
second spring to imulate natural foot motion.
Inventors: |
Ryan; Michael W. (Vallejo,
CA) |
Family
ID: |
22820238 |
Appl.
No.: |
05/219,670 |
Filed: |
January 21, 1972 |
Current U.S.
Class: |
623/49; 623/52;
623/56; 623/26; 623/55 |
Current CPC
Class: |
A61F
2/66 (20130101); A61F 2/6607 (20130101); A61F
2002/5075 (20130101) |
Current International
Class: |
A61F
2/60 (20060101); A61F 2/66 (20060101); A61F
2/50 (20060101); A61f 001/04 (); A61f 001/08 () |
Field of
Search: |
;3/30-35,1.2,2,6-8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
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525,347 |
|
Jun 1921 |
|
FR |
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523,329 |
|
Apr 1921 |
|
FR |
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Claims
What is claimed is:
1. An artificial foot adapted to simulate the flexing motion of a
normal foot, said artificial foot comprising:
a rigid horizontal ankle plate having an exposed upper attachment
surface, said ankle plate having a forward portion and a rearward
portion;
a rigid horizontal sole plate disposed below the ankle plate and
substantially parallel therewith, said sole plate having a
heel-defining portion substantially beneath the rearward portion of
the ankle plate and a ball-defining portion extending beyond the
forward portion of the ankle plate;
a substantially vertical coil spring disposed intermediate the
ankle plate and the sole plate, said coil spring having an upper
end rigidly attached to the lower surface of the ankle plate and a
lower end rigidly attached to the upper surface of the sole plate;
and
a bar extending from the forward portion of the ankle plate to the
ball-defining portion of the sole plate, said bar universally
pivotably connected to said ankle plate at one end of said bar and
to said sole plate at the other end of said bar to allow relative
rotation therebetween while maintaining a fixed radial distance
therebetween.
2. The invention of claim 1 and additionally comprising ball
sockets on the forward portion of the ankle plate and the
ball-defining portion of the sole plate, and wherein the bar has
balls mounted at either end thereof, said balls captured in said
ball sockets.
3. The invention of claim 2 and wherein the forward portion of the
ankle plate has a depending inclined planar surface substantially
normal to the longitudinal axis of the bar, and wherein the ball
socket on the forward portion of the ankle plate is mounted on said
depending planar surface, and wherein the ball-defining portion of
the sole plate has an upwardly projecting inclined planar surface
substantially normal to the longitudinal axis of the bar, and
wherein the ball socket on the ball-defining portion of the sole
plate is mounted on said upwardly projecting planar surface.
4. The invention of claim 1 and wherein the sole plate has cutout
portions therein to reduce the weight of said sole plate.
5. The invention of claim 1 and wherein said ankle plate has an
aperture therethrough, and additionally cmprising a threaded bolt
projecting upwardly through the aperture in said ankle plate to
facilitate attachment to an artificial leg.
6. The invention of claim 1 wherein said coil spring extending
between said ankle plate and sole plate has a diameter
substantially the same as the width of said ankle plate.
7. The invention of claim 1 and wherein said ankle plate, sole
plate, coil spring and support are encased within a rubber molding;
and said rubber molding is conformed in its exterior profile to the
shape of a foot.
Description
This invention relates to artificial limbs and more particularly to
an improved mount for an artificial foot to an artificial leg which
provides motion approaching that of the lost limb.
Heretofore artificial limbs have hinged the foot to the limb along
a hinge axis taken through the ankle. Two major deficiencies
result. First such limbs have been incapable of flexing
side-to-side about an axis taken parallel to the plane of the sole
from the toe to the heel. If for example the wearer of an
artificial limb steps on either a sloped surface, a small
irregularity such as a pebble, or turns rapidly, slipping commonly
results. For this reason many wearers of artificial limbs have
restricted mobility.
Secondly, such limbs transmit through the hinge the shock of the
heel coming down on the ground. Such shock can cause irritation to
the wearer, typically at the mount of his leg stump to the
artificial leg, seriously inhibiting the use of the artificial
limb.
It is an object of this invention, therefore, to provide an
artificial limb which permits flexure of the foot in the vicinity
of the ankle along an axis parallel to the sole taken from the toes
to the heel of the foot. Accordingly, at least one coil spring is
attached to the ankle of an artificial limb at its upper end,
attached to the sole of an artificial foot at its lower end and
allowed to flex in columnar flexure therebetween.
An advantage of this mounting of the artificial foot to the ankle
is that improved walking on uneven or sloped surfaces results.
Yet another advantage of this mounting is that damping of the shock
of the heel striking the ground during brisk walking results.
Yet another object of this invention is to provide improved toe
resistance combined with the foregoing artifical limb features.
According to this aspect of the invention, a support capable of
permitting side to side motion is mounted from the sole of an
artificial foot in the vicinity of the ball of the artificial foot
to the ankle.
An advantage of this toe to ankle support is that in one form of
the invention it can be a spring. This spring acts under tension
when the heel of the artificial foot strikes the ground during
walking and acts under compression when the weight of the wearer is
on the toe of the artificial limb during walking.
An advantage of this second ankle to ball of foot mounted spring is
that when it acts in compression improved toe action of the foot
relative to the ankle results.
An additional advantage of this second spring is that when it acts
in tension, improved heel action of the artificial limb
results.
Yet another advantage of this second ankle to ball of the foot
mounted coil spring is that it does not interfere with the
side-to-side flexure of the limb along about an axis taken from toe
to heel of an artificial limb.
Yet another object of this invention is to disclose a shock
absorber mount included in combination with the second spring
extending from the ankle to the ball of an artificial foot. This
shock absorber, is provided with a variable resistance with respect
to its stroke, first provides restrictive and slow damping
responsive to walking and thereafter with the passage of time
provides an accelerated release.
An advantage of this shock absorber is that a natural foot action
is more closely emulated by the variable resistance release of the
shock absorber.
Other objects, features and advantages of this invention will be
more apparent after referring to the following specification and
attached drawings in which:
FIG. 1 is a side elevation section of the spring mount of this
invention with the rubber form shown cut away;
FIG. 2 is a view from the bottom of the artificial limb looking
towards the top illustrating the mounting of the artificial
limb;
FIG. 3 illustrates the mount of the artificial limb in the vicinity
of the ankle;
FIG. 4a is a rear elevation section of the wearer of the artificial
limb walking away from the viewer and simultaneously stepping on a
rock to illustrate pivotal movement of the sole of the limb about
an axis taken from toe to heel of the shoe of the wearer;
FIG. 4b is a side elevation section of the view shown in FIG.
4a;
FIG. 5 is a side elevation section of the artificial limb shown in
FIG. 1 with a variable resistant shock absorber mounted to the
artificial limb;
FIG. 6 is a side elevation section of the variable resistant shock
absorber illustrating how varying resistance is achieved with
respect to the stroke of the shock absorber; and,
FIG. 7 is a side elevation section of the artificial limb shown in
FIG. 1 with a sled bar mounted between the ankle and toe.
Referring to FIGS. 1-3 and with specific reference to FIG. 1 an
artificial limb is shown broken off in the vicinity of the ankle A.
The improved foot and ankle mount is shown mounted to the
artificial limb in the vicinity of its ankle A.
In its simplest form the invention includes an ankle plate 14, a
mounted coil spring 16, and a sole plate 18. Coil spring 16 is
welded to ankle plate 14 at its upper end, to sole plate 18 at its
lower end, and thus forms a cantilevered type support for the
protruding toe relative to the ankle A. Sole plate 18 extends from
the ball of the foot at 20 to the heel of the foot 22. As shown
here plate 18 curves upwardly in an arcuate fashion in the vicinity
of the heel 22 so as to conform to the rounded part of the
heel.
As in most conventional artificial foot constructions a surrounding
rubber 25 is poured and cured in a mold which restricts it to the
shape of a foot so that sole plate 18, spring 16, and ankle plate
14 are all encased within the artificial limb. Typically, rubber 25
is conformed to the shape of the foot of the wearer.
Referring to FIG. 2, the bottom of sole plate 18 may be viewed.
Typically, this plate is apertured at a large aperture 30 so as to
provide exposure through the sole of the foot and the center of the
coil spring to the bottom side of ankle plate 14. This permits a
wrench or the like to tighten a nut 33 on a bolt 35 to effect rigid
attachment of the ankle plate 14 to the ankle A of an artificial
limb. Additionally, sole plate 18, typically made of a relatively
heavy steel, is provided with one or more cut-outs 37 to lighten
its weight.
Spring 16 is selected along certain defined parameters. Typically,
the spring is selected to a diameter which is slightly smaller than
the width of the foot in the vicinity of ankle A. Secondly, the
compressive force of the spring is selected so that the full weight
of the wearer being placed on the foot will result in approximately
one-fourth of an inch compression of the spring. In the case of a
185 pound man, when full weight is placed on spring 16 compression
of one-fourth of an inch will result. Finally, the spring is
selected to provide a columnar resistance so that side-to-side
bending of plate 18 about an axis 40 taken from the ball of the
foot at 20 to the heel of the foot at 22 is resisted but
nevertheless permitted. (see FIGS. 4a and 4b.)
It can be thus seen that sole plate 18 is in effect cantilevered to
ankle 14 by the spring action of spring 16.
In addition to spring 16, sole plate 18 at its ball portion 20 is
mounted by a second coil spring 45 to ankle plate 14. Typically
sole plate 20 is provided with a first spring mount 46 and ankle
plate 14 provided with a second spring mount 47. Typically, mounts
46 and 47 are rigidly connected to the sole plate 18 and ankle
plate 14 respectively by welding. Spring 45 is mounted between the
mounts so as to be capable of acting both in tension and in
compression. For resistance of bending moments, paired half-rounded
shafts 49 and 50 and extending from mounts 46 and 47 respectively
are confronted at their respective flat surfaces within spring 45
so as to provide some columnar rigidity to spring 45. It should be
noted that tilting of sole plate 18 about axis 40 (see FIG. 2)
extending from toe to heel of the artificial foot in the plane of
the sole is permitted by second spring 45.
Having set forth the mechanics of this artificial limb, attention
can now be directed to its dynamics with respect to FIGS. 4a and
4b. Referring to these figures, a wearer of the limb is shown
stepping on a pebble, an unacceptable obstacle for most prior art
artificial limbs. As can be seen, plate 18 is shown tilting about
an axis 40 parallel to the plane of the sole plate just as a
natural foot would conform to the presence of pebble 18. The
artificial foot conforms to the presence of the pebble.
Additionally, it will be noted that since there is no hinge in the
vicinity of the ankle when the weight of the wearer is placed on
the artificial foot in the vicinity of sole plate 18 at heel 22 two
effects will occur. First, spring 16 will serve to absorb the
shock. Secondly, sole plate 18 will pivot about its point of
attachment to spring 16 placing spring 45 under tension. Further
improved damping of the foot motion will result.
Additionally, when the weight on the artificial limb is shifted, as
by walking, so that a portion of the weight is placed at sole plate
18 in the vicinity of the ball of the foot at 20 both spring 16 and
spring 45 will come under compression. Improved toe action
results.
Referring to FIGS. 5 and 6, an additional embodiment of this
invention is illustrated. As shown a shock absorber and spring
combination 60 is mounted between mounts 46' on sole plate 18 at
the ball of the foot 20 and mount 47' on the leading portion of
ankle plate 14. A coil spring 62 capable of acting in both tension
and compression is concentrically wound about an inner shock
absorber 64. Shock absorber 64 is shown in section at FIG. 6 and
includes a conventional cylinder 65 closed at one end, a piston 66
mounted for sliding movement interior of the cylinder 65 and a rod
67 which attaches to mount 47' at ankle plate 14. A second mount 68
at the closed end of the cylinder attached to mount 46' effecting
attachment of the unit to sole plate 18 in the vicinity of the ball
of the foot at 20.
Cylinder 65 has a goove 70 of variable dimension described in its
sidewalls. From the neutral position of the piston shown at 66
goove 70 is provided with a narrow portion 71 which restricts fluid
flow from one side of piston 66 to the other side of piston 66. At
the lower portion 72 of the groove 70 the groove expands in
dimension and accelerated stroke of piston 66 with decreased
resistance is provided.
It can thus be seen on movement of mount 47' towards mount 46', as
when the weight of the wearer is on the ball of the foot a
controlled movement will result. First, there will be a general
resistance of the shock absorber 64 to rapid pivotal movement of
the ball of the foot 20 towards the ankle plate 14. Thereafter, and
with the increasing passage of time cylinder 66 will pass
downwardly and towards the wider portion 72 of the channel 70.
Fluid will escape from one side of the piston to the other side
with greater rapidity. Accelerated movement with decreased
resistance will result.
Since the return of the foot to a neutral position in rapid fashion
is usually desired, a one way valve 80 can be provided in pistons
66 permitting rapid return of the fluid from the upper portion of
cylinder 65 to the lower portion of cylinder 65.
It can be seen at once that the shock absorber 64 of variable
resistance when incorporated with the spring action of spring 62
provides improved foot motion. Initially and under conditions of
brisk walking resistance emulating that of the natural foot muscles
in the vicinity of the ball of the foot will be provided. However,
where the wearer stands for relatively long periods of time with
the weight on the ball of the foot, sole plate 18 will conform
gradualy to the plane of the ground on which the wearer of the limb
is walking. This will produce a natural and stabilizing foot
action.
Referring to FIG. 7, the simplest form of the ankle to sole plate
support is illustrated. A bar 80 is shown having to balls 82 and 83
mounted at either end. These balls are captured in and held
securely to ball joint mounts 46" and 47" at the sole plate and
ankle respectively. Since the ball joint mounts encompass more than
one-half a sphere, the balls are held securely against both tension
and compression. As is apparent bar 80 while maintaining the
distance between the ankle and sole plate at 20 constant will
permit the desired side-to-side motion of the sole plate relative
to the ankle.
It will of course be realized that numerous modifications can be
made to my invention without departing from the spirit and scope
thereof. Specifically, varying springs or combinations of
vertically aligned springs could be used in substitution for spring
16. Moreover, a fluid shock absorber alone, a spring alone, or both
combined can be used between the mounts at the sole plate in the
vicinity of the ball of the foot at the lower end and the ankle
plate at the upper end. Likewise, other modifications can be made
to my invention without departing from the spirit and scope
thereof.
* * * * *