US3673613A

US3673613A - Variable friction knee unit with an improved swing phase control of artificial legs

Info

Publication number: US3673613A
Application number: US132465A
Authority: US
Inventors: Charles C Asbelle; Michael F Arrigo; Kenneth E Hunting; Gene R Helmuth
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1971-04-08
Filing date: 1971-04-08
Publication date: 1972-07-04
Anticipated expiration: 1989-07-04

Abstract

A variable friction knee unit that applies independent braking forces at different times to the swing phase of an artificial leg during walking which simulates the actions and efficiencies of the quadriceps and hamstring muscles of the thigh. Two braking modes are applied with an additional continuous braking mode. One operates at each end of swing phase. The second brake is applied a few degrees after the first brake and superimposed over the first brake. Both brakes are applied at each end of the swing phase of the walking cycle. In addition to being operative at the terminus of the swing, the two brakes are engaged at different times and are superimposed over the application of continuous friction so that the deceleration is a stepping function thereby simulating the function of the quadriceps and hamstring muscles of the thigh. The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Description

United StatesPatent Asbelle'et al.

[ July 4,1972

[54] VARIABLE FRICTION KNEE UNIT WITH AN IMPROVED SWING PHASE CONTROL OF ARTIFICIAL LEGS [72] Inventors: Charles C. Asbelle, Oakland; Michael F. Arrigo, Berkeley; Kenneth E. Hunting, Hayward; Gene R. Helmuth, Castro Valley, all of Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy Barghausen ....3/28 Oliver ....3/26

I l i i x l Primary Examiner-Richard A. Gaudet Assistant Examiner-Ronald I... Frinks Attorney-R. S. Sciascia and Charles D. B. Curry [57] ABSTRACT A variable friction knee unit that applies independent braking forces at different times to the swing phase of an artificial leg during walking which simulates the actions and efficiencies of the quadriceps and hamstring muscles of the thigh. Two braking modes are applied with an additional continuous braking mode. One operates at each end of swing phase. The second brake is applied a few degrees after the first brake and superimposed over the first brake. Both brakes are applied at each end of the swing phase of the walking cycle. In addition to being operative at the terminus of the swing, the two brakes are engaged at different times and are superimposed over'the application of continuous friction so that the deceleration is a stepping function thereby simulating the function of the quadriceps and hamstring muscles of the thigh.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

10 Claims, 8 Drawing Figures PATENTEDJUL 4|972 3,673,613

sum 1 or 4 2 47 i i i H I I E l 1 I l 55 I3 INVENTORS CHA P'A'TENTEDJuL 4:972 3,673,613

sum 20F 4 VIIIIIIIII r INVENTORS 3 CHARLES C. ASB LE Ml AEL F. ARR KE TH E. N G

GENE R. HE U H TORN Y BACKGROUND OF INVENTION 1 Field of the Invention The present invention relates generally to a variable friction knee unit for swing phase control in artificial legs and more particularly to a unit that applies two separate braking forces at different times to the swing phase of an artificial leg during walking, to simulate the natural action of the muscles of the thigh.

2. Description of the Prior Art The prior prosthetic limbs employed the use of elastic bands, leather straps, wooden springs, and continuous-friction devices. And still other limbs employed hydraulic cylinders or spring-loaded brake materials to simulate thigh muscle function. All of the aforementioned units were very unreliable and unstable in operation as well as sensitive to temperature changes, humidity, and overloads such as the amputee falling.

SUMMARY OF THE INVENTION Although there have been attempts at designing variable friction knee brakes, the results have not been favorably consistent. Anearly model of the variable friction-brake used the dual braking concept in a different manner with limited success. The main device consisted of split oilite bronze bearings contained in a rubber bushing at the knee block to receive the knee bolt. By tightening a nut to squeeze the rubber bushing to close the gap in bearings provided the effective drag needed on the swing of the leg. The device consisted of a left conventional brake and a right variable friction brake. The conventional adjustable brake augmented the slight braking action of the two knee bearings. The right brake was also adjustable and oscillated between two rubber stops to provide the variable friction function. Although superior to any prior system, it still did not simulate the actions and effeciencies of the quadriceps and hamstring muscles of the thigh. If a graph were made representing the function of these aforesaid muscles during the swing phase operation, the friction application or energy absorption during the curve extension phase would appear as a normal bell-shaped curve. The walking cycle of the leg consists of a flexion phase and extension phase. As pointed out above, the prior device operated in a two-step operation Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of the knee portion of the artificial leg of the present invention, parts being broken away to illustrate the interior construction;

FIG. 2 is a transverse sectional view of the knee;

FIG. 3 is an exploded sectional view showing certain details of construction of the unique dual offset brake system;

FIG. 3A is an exploded sectional view of one bearing structure of the dual bearing constant friction system;

FIG. 4A is a graphical representation of the normal walking cycle;

FIG. 4B is a graphical representation of the old two step device;

FIG. 4C is a graphical representation of the multiple step function device; and

FIG. 5 is a side view of the knee to show certain details of construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to facilitate understanding of the unique system, which is considered the subject of the present invention, a description of the relevant parts of the artificial limb (in conjunction with the present invention) follows. Referring to FIG.

thereby generating a very flat curve. However, it has been I found by experimentation that by using two friction brakes at both ends of the angular swing phase, arranged to operate only during the last stages, and by engaging one brake a few degrees ahead of the other brake in a multiple step function action we very closely approximate the swing phase function of the quadriceps and hamstring muscles during the extension phase as represented by the bell curve. It should be noted that during the flexion phase a multiple step function action would not be required because much less energy is required to decelerate the leg during the flexion phase.

STATEMENTS OF THE OBJECTS OF THE INVENTION tificial leg which will allow maximum clearance above the knee-bolt, permitting use with extremely long-above-knee amputation stumps as well as possible adaptation to most single knee structures.

I wherein the artificial limb 11 comprises shin portion 13 pivotally suspended from thigh portion 15 and having a foot (not shown) secured to the lower end of the limb ll. Thigh portion 15 is hollow and also adapted for fitted attachment to the stump of an amputee in the standard manner. Shin portion 13 is of hollow construction and of standard light-weight material. This construction is well known in the prosthetic limb art. The shin portion 13 and thigh portion 15 may be covered with any well known cosmetic material.

Referring to FIGS. 1 and 2, the pivotal suspension of the shin portion 13 of the limb 11 is provided by hinge straps l7 and 19 suspended from thigh portion 15 and secured to the shin portion 13. The hollow knee tubular bolt 23 extends through a transverse bore 21 in the thigh portion 15. Hinge straps l7 and 19 are rotatably attached at either end of tubular bolt 23. The pivotal hinge straps l7 and 19 located on shaft 23 are attached and secured to the inner wall of shin portion I3 in a standard manner of attachment well known in the art. The bolt 23 is secured to thigh portion 15 by strap screw 25. The variable friction braking device of the present invention comprises a first friction control brake device 27 and a second friction control brake device 37, a knee stop bumper arm 47 and continuous friction bearings 49 and 49' located on either side of the first brake device 27 and second break device 37, pivotally mounted on the knee bolt 23. The knee stop bumper arm 47 is located between first brake device 27 and second brake device 37, all being pivotally mounted on knee bolt 23.

FIG. 3 is an exploded sectional view showing certain details of construction of the unique dual oflset brake system of the present invention. Continuous friction is applied to knee bolt 23 by bearings 49 and 49' which are functionally and structurally the same. Therefore, the following discussion of bearing 49 is equally applicable to bearing 49. An exploded view of bearing 49 is illustrated in FIG. 3A as comprising a split bronze oilite bearing 49a encased in a neoprene cylinder 49!: which in turn is encased in aluminum casing 49c.

Bearings

49 and 49 are machined to fit on the shaft of tubular knee bolt 23. Outer casing 49c is hexagonally shaped and is cemented in transverse bore 21 of thigh portion 15. With tubular knee bolt 23 in position, an outer gland nut 49d screws into bearing casing 490 to compress neoprene cylinder 49b which in turn causes bearing 49a to clamp about bolt 23, thereby applying continuous friction in the same manner as bearing 49'. The dual continuous clamping or friction action of bearings 49 and 49' is used to apply the conventional brake friction which is applied to all rotations of knee bolt 23 within transverse bore 21" of thigh portion 15. This arrangement allows adjustment for wear of the bearings. The bearing device described is standard and well known in the art.

Referring to FIGS. 1, 2, and 3 wherein between first and second brake means 27. and 37 is knee stop bumper arm 47 made of aluminum, or other similar material, projecting down from thigh portion and into the plastic shin 13. The knee stop bumper arm 47 is pivotally suspended from the knee bolt 23 and has a single adjusting screw 51a located near the knee bolt 23. It should be noted that the knee stop arm 47 is fitted with two

oblong rubber bumpers

53 and 55.

Referring to FIG. 5 wherein the upper bumper 53 contacts knee block 57 and the lower bumper 55 will sequentially contact each of the inner rear surface of hypersensitive stop 59 of shin.l3 and forward portion 13a of shin 13. Upon flexing the knee past 90, knee stop arm 47 will contact forward portion 13a and upper bumper stop 53 will push against knee block 57' to allow for at least about 120 of knee flexion. Upon extending the knee 1] the knee stop arm 47 resumes its original position. Adjustment of the adjusting screw 51, shown in FIG. 2, on the knee stop arm 47, should be just enough to prevent the. knee stop 47 from moving forward during the walking cycle and to prevent it from making noise.

Referring to FIG. 3, knee stop arm 47 is provided with a transverse circular opening 470 with slot 47b extending tangentially outward therefrom. A bronze sleeve 61 may be positioned within the opening to act as a bearing. The function of the knee stop 57 is to determine the limit of the pivotal movement of the. shin l3 portion of the leg in the extension direction. The

bumpers

53 and 55 may be made of short sections of neoprene cord stock of 60 durometer which are installed so that as compression takes place it will minimize the tendency, as in prior models, of wiping" the bumper off its cemented surface.

Brakes

27 and 37 of the present invention are radically different in both function and materials from previous braking systems. That is, two brake bands are now employed for the variable deceleration function while two bearings apply continuous friction.

Referring to FIGS. .1, 2, and 3 wherein placement of

stops

31 and 41 are arranged for onebrake to be applied a few degrees before the other whereas rear bumper stops 29 and 39 are in line and apply friction forces on the flexion stage of the walking phase. As a result, the total braking effect comes about in two stages in. the extension phase rather than the more abrupt single stage. The significance of this result can be seen by reference to FIGS. 4A, 4B, 4C.

In FIG. 4A the area of the curve above the abscissa 1: represents the extension phase of the walking cycle whereas the area of the curve below the abscissa it represents the flexion phase of the walking cycle. It should be noted that curves shown in FIGS. 4B and 4C show only the extension phase of the walking cycle since both the old and new devices function in a similar mannerduring the flexion phase. Referring to FIG. 4A wherein the area between the horizontal lines a represents the application of continuous braking friction, the area crosshatched under the curve represents the total energy absorbed during the extension flexion phase of the normal walking cycle of a non-amputee. Step function line b is superimposed over the extension phase curve in FIG. 4A to show the simulated equivalent variable friction multiple braking system. Referring to FIG. 48 wherein cross-hatched area c represents the application of continuous friction that is the summation of the first brake friction and bearing friction. The area d under the curve represents the total energy absorbed during the extension phase. Step function 2 represents the application of a second brake or brake 2. Referring to FIG. 4C wherein the crosshatcl'led area f represents the application of the continuous bearing friction,.area 3 represents the .total energy absorbed during the extension phase. Step function It represents the sequential application of brake l and brake 2. FIG. 4A shows that more energy is required on the extension phase to decelerate the extension swing of the leg than on the flexion phase. Therefore, we can see that multiple step by step application of friction forces during the extension phase rather than continuous braking, plus a superimposed variable friction brake application to the continuous braking, will more closely approximate the nonnal walking curve as shown in FIG. 4A. Referring to FIG. 413 wherein the first brake acts in conjunction with the bearings and the second brake device is applied as a single step function thereby creating a relatively flat extension phase cycle; FIG. 4B shows that there is a great deal of variance from the ideal extension phase walking and swing phase cycle shown in FIG. 4A. Referring to FIG. 4C wherein the improved device with its step bystep friction application more nearly simulates the normal walking cycle shown in FIG. 4A; it has been found by experimentation that using continuous friction of the bearings, plus a step by step application of variable friction, approximates more closely the normal walking cycle and thereby simulates the action of the hamstrings and quadriceps muscles of the thigh. In final analysis, by comparing the normal swing phase cycle (shown in FIG. 4A) with the mechanical simulation systems (shown in FIGS. 48 and 4C) it can be readily observed that FIG. 4C more nearly simulates the normal extension phase cycle curve of the non-amputee, as shown in FIG. 4A.

Referring to FIG. 3 wherein the first and second friction brake means comprises two

variable friction brakes

27 and 37 disposed upon bolt 23 on each side of knee stop arm 47 and between

adjustable bearings

49 and 49;

thevvariable friction brakes

27 and 37 apply their forces superimposed over the constant friction of the knee bearings 49 and 49'. Two brake bands '33 and 43 are made of automobile brake band material rather than the standard leather brake material. While the single original leather limb brake presented a friction surface of about 0.79 square inches, the new pair of brakes now encircling the surface of bolt 23 present a total friction surface of about 3.76 square inches, an increase of 475 percent.

Referring to FIGS. 2 and 5, when the shin 13 is extended from a flexed position, bolt 23 and the knee stop arm 47, which is secured in frictional engagement therewith, the lower bumper 55 of knee stop arm 47 will remain in position with its lower extremity abutting the posterior or hypersensitive stop 59 of the shin portion 13 of limb 11. As shin portion 13 is extended, the upper bumper 53, mounted on the farside of the knee stop arm 47, approaches stop 57 of the thigh 15. This prevents further pivotal movement of the shin portion 13 and provides a positive extension stop.

As shin 13 is flexed rearwardly, the arm 47 moves therewith until the upper bumper 53 thereof on its rear side engages stop portion 57' of the thigh 15. This limits the amount of flexion. However, since the arm 47 is secured to the shaft 23 for rotation therewith, as a consequence of the frictional pressure of the sleeve 61, further flexion of the shin 13 is possible. This allows an amputee with along leg stump to bend shin 13 of his leg past the right angle position with respect to the thigh.

Dual friction variable brake system: Referring to FIG. 2 wherein the

bearings

49 and 49 provide the continuous application of friction forces to the knee bolt 23; the second braking mode is superimposed over the first braking mode and both are applied to each end of the swing phase of the walking cycle while the bearings are applying continuous friction. Referring to FIG. 3 wherein the first variable frictionbrake 27 comprises a rear horizontal bumper 27a, a vertical front bumper 27b and adjusting screw 35; the rear bumper stop 29 engages with rear horizontal stop 27a and front bumper stop 31 engages with front vertical stop 27b. Second variable friction brake 37 comprises a rear horizontal bumper 37a, a front vertical bumper 37b, and adjusting screw 45. The rear bumper 37a engages with rear bumper stop 39 and front bumper 37b engages with front bumper stop 41.

Front bumperstops

31 and 41 are offset in the horizontal plane from each other by about one-eighth inch so that the first brake 27 will apply a friction force about 5 in are before the application of friction forces of the second brake 37 during the extension phase.

That is, bumper stop 31 is about one-eighth inch ahead of bumper stop 41 in the horizontal plane. Bumper stops 29 and 39 are not offset from each other so that during the flexion phase of the walking cycle both brakes are applied at the same time. The first brake 27 has a builtin lag so that the first brake 27 is not applied immediately upon rotation but is applied a few degrees of are after application of continuous bearing friction. This creates a step by step application of friction forces so that the swing phase deceleration will more closely approximate the normal swing phase cycle curve, thereby simulating the movement of the hamstring and quadriceps of the thigh.

What is claimed is:

l. A variable friction knee unit for an artificial limb including a thigh portion pivotally attached to a shin portion and a swing phase cycle control located in said thigh portion to control the flexion phase and extension phase of said swing phase said control comprising:

a. first variable friction means;

b. second variable friction means;

c. continuous friction means;

d. friction actuation means to intermittently actuate said first means and said second means;

e. means for pivotally mounting said first means, said second means, and said continuous means;

f. said first means and said second means being operatively connected to said mounting means .whereby said first means and said second meanS are independently actuated by said actuation means; and

g. stop means to limit the angular displacement of said shin during said flexion phase and said extension phase.

2. The device recited in claim 1 wherein said actuation means comprises:

a. first actuation means;

b. second actuation means;

c. third actuation means;

d. fourth actuation means;

c. said first actuation means and said third actuation means independently and sequentially controlling the application of friction by each of said first means and said second means during said extension phase;

f. said second actuation means and said fourth actuation means concurrently controlling the application of friction by said first means and said second means during said flexion phase.

3. The device recited in claim 2 wherein said first actuation means is structurally offset from said third actuation means whereby said second friction means is actuated subsequent to said first friction means wherein said second actuation means and said fourth activation means are in structural alignment whereby said second friction means and said first friction means are activated simultaneously to apply friction.

4. The device recited in claim 3 wherein said first, second, third, and fourth actuation means are bumper stops wherein said first variable friction means and said second variable friction means are variable friction brakes, said brakes including brake linings.

'5. The device recited in claim 4 wherein said first brake and said second brake each comprises:

a. horizontal rear bumper;

b. vertical front bumper;

c. said vertical bumper of said first brake being in intermittent operative contact with said first bumper stop;

d. said horizontal bumper of said first brake being in intermittent operative contact with said second bumper stop; e. said vertical bumper of said second brake being in intermittent operative contact with said third bumper stop; and 1 f. said horizontal bumper of said second brake being in intermittent operative contact with said fourth bumper stop.

6. The device recited in claim 5 wherein said first bumper stop is aligned in the horizontal plane ahead of said third bumper stop so that said vertical bumper of said first brake contacts said first bumper stop a few degrees in are before said vertical bumper of said second brake'contacts said third bumper stop, whereby said second brake is activated subsequent said first brake thereby causing a two-stage variable friction braking action.

7. The device recited in claim 6 further includes a continuous friction braking means being superimposed over the variable application of friction of said first brake and said second brake.

8. The device recited in claim 7 wherein said continuous friction means is a bearing device, said bearing comprising a. first bearing;

b. second bearing;

0. said first bearing and said second bearing applying continuous bearing friction precedent to the friction braking action of said first brake and said second brake.

9. The device recited in claim 8 wherein said first brake and said second brake are positioned on either side of a flexion extension lirniting stop and interjacent said first bearing and second bearing, said first brake, said second brake, said limiting stop, said first bearing, said second bearing all pivotally mounted on a circular bolt, said bolt extending through the thigh portion of an artificial limb to form an axis joint to con trol the flexion and extermion of a shin portion of an artificial limb. I

10. The device recited in claim 9 wherein said first brake and said second brake include a brake lining made of automobile brake band material, said lining operatively circumambient said bolt.

I i t t

Claims

1. A variable friction knee unit for an artificial limb including a thigh portion pivotally attached to a shin portion and a swing phase cycle control located in said thigh portion to control the flexion phase and extension phase of said swing phase said control comprising: a. first variable friction means; b. second variable friction means; c. continuous friction means; d. friction actuation means to intermittently actuate said first means and said second means; e. means for pivotally mounting said first means, said second means, and said continuous means; f. said first means and said second means being operatively connected to said mounting means whereby said first means and said second mEanS are independently actuated by said actuation means; and g. stop means to limit the angular displacement of said shin during said flexion phase and said extension phase.

2. The device recited in claim 1 wherein said actuation means comprises: a. first actuation means; b. second actuation means; c. third actuation means; d. fourth actuation means; e. said first actuation means and said third actuation means independently and sequentially controlling the application of friction by each of said first means and said second means during said extension phase; f. said second actuation means and said fourth actuation means concurrently controlling the application of friction by said first means and said second means during said flexion phase.

5. The device recited in claim 4 wherein said first brake and said second brake each comprises: a. horizontal rear bumper; b. vertical front bumper; c. said vertical bumper of said first brake being in intermittent operative contact with said first bumper stop; d. said horizontal bumper of said first brake being in intermittent operative contact with said second bumper stop; e. said vertical bumper of said second brake being in intermittent operative contact with said third bumper stop; and f. said horizontal bumper of said second brake being in intermittent operative contact with said fourth bumper stop.

6. The device recited in claim 5 wherein said first bumper stop is aligned in the horizontal plane ahead of said third bumper stop so that said vertical bumper of said first brake contacts said first bumper stop a few degrees in arc before said vertical bumper of said second brake contacts said third bumper stop, whereby said second brake is activated subsequent said first brake thereby causing a two-stage variable friction braking action.

8. The device recited in claim 7 wherein said continuous friction means is a bearing device, said bearing comprising a. first bearing; b. second bearing; c. said first bearing and said second bearing applying continuous bearing friction precedent to the friction braking action of said first brake and said second brake.

9. The device recited in claim 8 wherein said first brake and said second brake are positioned on either side of a flexion extension limiting stop and interjacent said first bearing and second bearing, said first brake, said second brake, said limiting stop, said first bearing, said second bearing all pivotally mounted on a circular bolt, said bolt extending through the thigh portion of an artificial limb to form an axis joint to control the flexion and extension of a shin portion of an artificial limb.