US2843853A

US2843853A - Control mechanism for artificial ankle

Info

Publication number: US2843853A
Application number: US624303A
Authority: US
Inventors: Hans A Mauch
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-11-26
Filing date: 1956-11-26
Publication date: 1958-07-22
Anticipated expiration: 1975-07-22
Also published as: GB852362A; DE1069827B

Description

July 22, 1958 H. A. MAUCH coNTRoL MEcHANIsM FoR ARTIFICIAL ANKLE:

Filed Nov. 26, 1956 United States Patent O CONTRDL MECHANISM FOR ARTIFICIAL ANIGJE Hans A. Manch, Dayton, Ohio Application November 26, 1956, Serial No. 624,303

20 Claims. (Cl. 3-35) This invention relates to artificial legs, and more particularly to a control mechanism providing an improved ankle joint which connects the foot and the shank to substantially duplicate the foot control pattern as produced by the muscles of the natural leg.

In the natural leg, the foot is particularly controlled by plantar-fiexor muscles in the calf of the leg and by dorsi-exor muscles in the fore part of the shank. These two muscle groups hold the foot at substantially right angles to the shank during no-load conditions as, for instance during the swing phase of a stride. Under load, that is, during the stance phase, the plantar-flexor muscles control or limit the permissible upward motion of the sole of the foot from its normal rectangular no-load position substantially in such a way that they stop dorsi-flexion of the foot when the longitudinal axis of the shank is vertical in space or inclined forward from the vertical. This happens whether the foot rests on horizontal or uneven or inclined ground.

Designers and developers in the artificial limb art have encountered many problems in attempts to produce satisfactory artificial replacements for the natural limbs. The muscle control in natural limbs is complex and unique and has generally defied mechanical reproduction. This has been illustrated in previous attempts to provide a satisfactory artificial ankle joint for artificial legs. To date, the conventional ankle joint has been provided by a simple bolt connecting the shank and the foot of the artificial leg. Bumpers are generally inserted between the foot and the shank, both behind and ahead yof this bolt joint, to maintain them substantially at right angles hind the joint is soft while the bumper provided ahead` of the joint is stiff. to respectively cushion and limit plantar-flexion of the foot to 20 down from its normal right angular disposition to the shank and provide maximum dorsi-flexion limited to a substantially right angular disposition between the foot and the shank. In using this prior artificial ankle structure, if the amputee should step forward with his artificial foot and the heel should drop into a hole causing the foot to hit ground at an abnormal angle, the physical limitations of the bumper structure result in ball pressure being developed too early in the stride at a point when the shank is still inclined rearwardly from a vertical in space. This calls for a great effort on the part of the muscles of the good leg since the amputee is forced to push himself over the artificial leg at an awkward angle of attack. On the other hand, if the ball of the artificial foot should seat in the hole in a stride, the artificial shank would tend to buckle forward without warning since the ball pressure develops too late causing instability. This `can create both great strain on the muscles of the amputee and, in

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all probability, an uncontrollable fall with possible consequent injury.

Similarly, walking up or down a hill using an artificial leg incorporating the prior art ankle joint structure presents difliculties due to its control limitations. In walking up-hill, for example, the bumper-type dorsiflexion control element prevents the shank from moving beyond a right angular disposition to the foot. This puts a great effort on the muscles of the amputees good leg since he has to pole-vault over the artificial leg at an awkward angle of attack. On going downhill, buckling of the artificial leg is probable due to the fact that the ball pressure develops too late in the stride. Therefore, the ankle joint of the prior art is highly inadequate as compared to the muscle control in the ankle of a natural leg which on application of load specifically provides that dorsi-flexion is stopped and the shank reaches stability at a vertical in space, independently of the angular disposition of the foot relative to the shank or in space. Thus, the artificial leg employing the prior art ankle joint is generally satisfactory only under the simplest of conditions, such as walking on level ground. Manual adjustment of the dorsi-fiexion stop, for instance by changing of the height of the bumpers, may be provided but this will be awkward to do while walking and will be mainly used by the amputee for more permanent changes such as adjusting the leg for shoes of different heel height or in a case where he has to walk up or down an. incline of considerable length and having a fairly constant angle of inclination.

The present invention provides a control mechanism inthe ankle joint of an artificial leg which produces forces in that joint which closely duplicate the forces provided by the muscles in the ankle joint of the natural leg. The improved control mechanism of the invention will stop dorsi-flexion of the ankle joint whenever the longitudinal axis of the shank is approximately vertical in space or in instances where it is disposed inclined forward from the vertical. This will occur independently of the relative angle between the shank and the foot of the artificial leg. The mechanism is so designed to limit the `dorsi-flexion only on application of load to the artificial ankle and upon load removal it will tend to make the foot assume a position vapproximately rectangular with the shank. The invention mechanism further provides for adequate control of plantar-flexion. The foot control pattern of a natural leg is thus mechanically reproduced.

An object of the invention is to provide an improved ankle joint for an artificial leg.

A further object of the invention is to provide an improved control mechanism for producing forces about a joint to positively define the limit of the angular dis position of the elements providing the joint.

A further object of the invention is to provide an improved control mechanism for the ankle joint of an artificial leg which will produce forces in that joint duplicating closely the forces produced by muscles in the ankle joint of the natural leg.

An additional object of the invention is to provide a control mechanism for the ankle joint and foot of an artificial leg which will stop dorsi-flexion of the ankle joint whenever the longitudinal axis of the shank is approximately vertical in space or inclined forwardly from the vertical, independently of the relative angle between the shank and the foot, on application of load thereto.

Another object of the invention is to provide a control mechanism for the ankle joint of an artificial leg which will limit dorsi-flexion of the ankle joint under load conditions at a point when the longitudinal axis of the shank is approximately vertical in space or inclined forwardly thereof and will cause the foot to assume a position approximately rectangular with the shank under no-load conditions.

Another object of the invention is to provide an improved joint mechanism for controlling relative movement of the elements comprising the joint.

A further object of the invention is yto provide Van improved mechanical joint for connection of the foot and shank of an artificial leg which will cause'the foot to be controlled in a manner as provided by the muscles in the natural leg.

Another object of the Iinvention is to provide an improved joint mechanism for connecting the foot and shank of an artificial leg which will hydraulically control the relative disposition of the foot and the shank under load co-nditions at all times in a manner as provided by the dorsi-fiexor and plantar-flexor muscles of the natural leg.

Another object of the invention is to provide a control mechanism for the ankle joint of an artificial leg possessing the advantageous structural features, the inherent meritorious characteristics, and the mode of operation herein described.

With these and other incidental objects in view which will more fully appear in the specication, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the drawings wherein is found one, but obviously not necessarily the only form of embodiment and application of the invention;

Fig. l shows a fragmentary vertical cross-sectional view illustrating a mechanical form of the invention as applied to the ankle joint of an artificial leg between the shank and the foot;

Fig. 2 is a cross-sectional view taken on line 2--2 of Fig. l;

Fig. 3 is a view of an artificial leg similar to that illustrated in Fig. 1 but incorporating a hydraulic version of the invention; and

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 3.

The invention can be best described with reference to the drawings wherein a mechanical embodiment is illustrated in Figs. l and 2. As shown, a foot 1 of an artificial leg is connected to a shank 2 to pivot relative thereto about a pivot axis .3. The shank 2 is aihollow wooden structure covered with rawhide and its lower end is provided by a plug or wooden block 4 which is outwardly contoured to simulate the configuration of a natural ankle. The block 4 is centrally apertured at 5.

The foot 1, formed on wood covered with raw hide, is provided with a substantially cylindrical recess 6 transversely of its rear or heel portion 7, in the upper surface thereof. The forming of the wood defining the recess 6 provides parallel side surfaces 8 connected by cylindrically curved front and rear surfaces 9 which cup about the depending extremity of the ankle block 4 at the lower end of the shank. The lower extremity of the block 4 has its forward and rearward surfaces curved towards each other to mate in nesting relation to the front and rear cylindrically curved surfaces 9 which define the upper portion of the recess 6. This enables a pivotal relation between the foot and the shank. The recess 6 is defined at `its central fore and aft portion by a base surface 1@ cylindrically curved about the axis3 at a radius less than that of the surfaces 9 which nest the lower end of the shank. The cylindrically curving extremities of the surface 1t) are diverted in a common horizontal plane to connect to the inner limits ofthe surfaces 9 and provide spaced shoulders 11 thereby facing upwardly of the foot 1.

A control housing 12 having the configuration of a cylindrical sector has a cylindrically curved base 13 which seats in recess 6 adjacent to the central cylindrical surface 10. The base 13 has forwardly and rearwardly projecting extensions 14 which lie in a common plane and respectively seat to the shoulders 11 in recess 6, fixed thereto by screws 23 engaged through the heel 7. The housing 12 is fixed'to foot 1 thereby to have its sector shaped side plates 15 project upwardly therefrom. The side plates 15 have upwardly projecting ear portions at their apex.

A bolt 18 having an expanded head and neck portion at one end extends through the apertures 17 of the side plates 15 to have the head abut the outer surface of one plate 15 to dispose the adjacent neck portion within its aperture 17. A nut 19 which threadedly engages the other end of the bolt 18 outwardly of the other side plate 15 is provided with a necked portion, similar to the neck portion of bolt 18, extending within the aperture 17 of said other plate. It is noted that the dimension of each aperture 17 is greater than that of the neck portions of the bolt 18 and the nut 19 for purposes to be described.

Two circular steel brake discs 20, separated by a spacer tube 21, mount about the bolt 18 between the housing side plates 15 to dispose the brake discs in end abutting relation to the respective neck portions of the bolt 18 and the nut 19. In this manner the entire unit assembly consisting of bolt 18, nut 19, brake discs 20, and spacer bushing 21 is pivotally connected to housing 12 by means of the bolt 18 and nut 19 being disposedin the apertures 17 in side walls 15. Therelative enlargement of apertures 217 permits relative vertical displacement of this unit assembly and housing 12 as will be described.

Rotatably mounted about'the spacer bushing 21 intermediate brake discs 20 is a second bushing 25. A steel lever 26 is pivotally connected at its upper end in a bifurcated bracket 24 which is adjustably connected to the rear inner wall of the shank 2 by a screw 27 therethrough having counter nuts 28 threadedly engaged thereabout to abut the inner surface of the shank wall. By turning the screw 27, which is accessible externally of the shank, the normal disposition ofthe upper end of the lever 26 can be adjusted for purposes to be described. The lever 26 depends from bracket 24 through the central aperture 5 in'block 4 in the lower end of the shank to receive bushing 25 snugly through an aperture therein adjacent to and spaced from its lower extremity. This disposes the lower end 29 of lever'26 in spaced relation to base 13 in control housing 12. The lower end 29 of the lever 26 is wedge-shaped to diminish in thickness from the front to the rear of the foot. Seated about bushing 25 to either side of lever 26 are roller type elements 30 and 31. Snap rings 32 in grooves about the bushing 25 seat in recesses in the outer faces of the roller elements 30 and 31 to hold the elements 26, 30 and 31tightly together on the bushing.

Screws 34 and 35 extend from within shank 2 through the block l4 at diametrically opposed positions relative the aperture 5. These screws 34 and 35 respectively thread-- edly engage in the upper surfaces of roller-like elements 3,0 and 31 to either side of the lever 26 to pull them into form fitting recesses in the under side of block 4 and thereby fix the entire assembly including bolt 18, nut 19, spacer bushing 21, brake discs 20, spacer bushing 25, roller elements 30, 31 and lever 26 to the shank 2. This effects al suspension of the housing 12 and the foot 1 by the neck portions of bolt 18 and nut 19 under no-load conditions as illustrated in Fig. 2 ofthe drawings.

Blind holes 37 and 38 are respectively provided in the under surface of block 4in the central plane of shank 2 immediately of the forward and rear surfaces thereof. Coil springs 39 and 40 respectively seat at one end in the blind holes 37 and 38 and at .the other end over the upwardly projecting ends of adjacent screws 23 which fix housing 12 in the recess 6 of 'foot 1. The

springs

39 and 40 are thus angularly disposed respectively forwardly and rearwardly of the pivot axis 3 to bias the foot to a normal no-load position approximately at right angles to the shank 2.

Under no-load conditions, the lower extremities of brake discs 20 are slightly spaced from the cylindrically curved surface of base 13 in a vertical sense and slightly spaced from the side walls 15 of housing 12 in a lateral sense. Steel balls 36 roll freely on the curved surface 13 in housing 12, respectively intermediate the inner sides of the discs and the wedge-shaped extremity 29 of lever 26 which depends centrally therebetween. The lower peripheries of roller-like elements 30 and 31 serve as guides for the free rolling steel balls 36. Thus parallel channels are provided for the free rolling balls. Limit pins 42 and 43 project from the respective g-uide elements 30 and 31 in symmetrically angularly disposed fashion fore and aft of the ankle joint in each channel. These pins 42 and 43 respectively limit the forward and rear movement of the balls 36 as they seek a lowermost position on surface 13 as determined by gravity.

lt is noted that the clearance provided between the brake discs 20 and the base surface 13 in housing 12 is less than the clearance provided by apertures 17 for vertical displacement of the bolt 18 therein. The reasons for this will become obvious. Also, recesses 49 are cut in the under surface of the shank extremity 4 to accomodate the upper portions of brake discs 20.

As previously indicated, Figs. l and 2 of the drawings show the mechanical version of the invention applied to provide the ankle joint of an artificial leg under a noload condition as during the swing-phase of a stride. The clearances between the brake discs and the base surface 13 of control housing 12 are maintained under the inuence of

springs

39 and 40 during no-load conditions. The springs also inuence and effect the approximately rectangular position of the foot in the shank 2 under no-load.

If, in making a stride the amputee swings the artificial leg forward and puts the foot to the ground, the weight of the amputee as transmitted through block 4 of shank 2 will cause downward displacement of the bolt 18 in housing 12. Since clearance between the brake discs 20 and the housing base surface 13 is less than provided for bolt 18 by apertures 17, the peripheries of discs 20 will seat to the cylindrically curved surface 13. Thus, on load, brake discs 20 carry the amputees weight. As the artificial leg is initially placed forward and down, the shank 2 is inclined backward from the vertical. The steel balls 36 and 37 always roll under the influence of gravity to seek a position perpendicularly below the pivot axis 3 irrespective of the angle between the shank and the foot or the position of the foot in space at that time. As the amputee continues his stride, the fore part of his foot moves to the ground and the shank'2 and lever 26 pivot forward to a vertical in space. At this time, the steel balls will also lie in this vertical. Thus, the Wedge extremity 29 of lever 26 is pivoted between the balls 36 to squeeze them laterally against the adjacent inside walls of brake discs 20. The brake discs cannot rotate since they are blocked by the friction between their peripheries and the curved bottom 13 of housing 12 due to the transmitted weight of the amputee. Accordingly, the lever will Wedge the balls 36 and 37 laterally to elastically spread the discs 20 into frictional engagement with side walls 15 of the housing 12. The mechanism as inuenced by the weight of the amputee thus becomes self-locking when the shank reaches a vertical in space. The angle established between the foot and shank as the shank reaches the vertical in space is maintained during further forward motion of the shank under load. This means that as the amputee moves forward, the heel of the foot rises off the ground and `the Weight of the amputee is then stably supported on the ball of the artificial foot in the same manner as provided in the natural leg.

At the beginning of the swing-phase, the amputee takes his weight off the foot and his foot oi the ground which relieves the pressure transmitted to the brake discs 20 by the steel balls. Being relieved of this pressure, the discs 20 will tend to seek their normal parallel position and shape. in the process they exert pressure inwardly against the steel balls 36 to bias them to the wedged extremity 29 of lever 26 and cause them to roll to the thinnest part of the wedge. This results in a slight plantar-flexion of the foot 1. This motion in conjunction with the removal of the amputee weight frees the foot 1 from its frictional engagement by the discs 20 and the foot is then biased to its approximately rectangular position relative the shank 2 under the influence of the biasing springs 39 and 40. This is the condition of the artificial leg on completion of its walking cycle.

' By adjusting the screw 27 to change the position of the upper end of lever 26 in shank 2, the approximately vertical position of shank 2 in space at which the balls 36 wil be wedged by lever 26 can be accurately and finely adjusted to meet the requirements of the specific amputee. To dampen the rolling motion of the gravity controlled steel balls, an elastic cover may be provided about the housing 12 to permit the housing to be filled with a suitable l'luid.

lt may accordingly be readily seen how much increase in flexibility and control is provided by the improved control mechanism in its inclusion in the ankle joint of an artificial leg.` ln contrast to the limits and restrictions imposed by the ankle structure in prior art artificial legs, the present invention enables a continuously stabilizing yforce condition in the leg in the manner provided by the muscles in the ankle joint of the natural leg.

This invention structure provides, as do muscles in the natural leg, that whenever the shank moves to a vertical in space under load conditions a locked relation of the shank and foot is automatically effected. This means that the amputee employing the invention may walk uphill or downhill with ease. In walking uphill, the fact that the artificial shank is able to reach a vertical in space enables proper movement thereof without undue strain. Similarly, in going downhill7 the leg will lock dorsiflexion prior to a right angular disposition between the shank and foot to provide proper stabilization. The same advantages obtain in the instance of stepping into a `sudden depression withan artificial leg as improved by the invention. The inherent Walking di'iculties present when employing the ankle joint control mechanism of the prior art in such applications is eliminated.

Figs. 3 and 4 of the drawings illustrate a hydraulic embodiment of the invention wherein a foot'l of an artificial leg is connected to pivot relative a shank 2 about a pivot axis 3. The parts are shown as related under a no-load condition, as during a swing-phase of the leg. The shank 2' is hollow and its lower end is provided by a wooden block 4 outwardly contoured to simulate the configuration of a natural ankle. The block 4 is centrally apertured at 5.

The foot is provided with a stepped cylindrical recess 6' transversely of its heel portion 7, in the upper surface thereof. Parallel sides 8 defining the recess 7 to either side of the foot are connected by cylindrically curved front and rear surfaces 9 cupped about the depending extremity of the angle block 4 which nests within the foot so as to enable relative pivoting thereof. The stepping of the cylindrical recess 6' provides spa-ced shoulders 11, immediately adjacent the inner extremities of the surfaces 9', separated by a central recess providing a cylindrically curved surface 10. A housing 12 in the form of a cylindrical sector has its cylindrically curved base 13 seating to surface 10 between shoulders 11. The housing has front and rear walls disposed in a radial sense which respectively have projections 14 in a common plane seating to the shoulders 11. Screws 23 7 engage through the bottom of the heel 7 and projections 14 to fix the housing 12 to the foot 1 thereby. The side plates 15 of housing 12 are provided with aligned apertures 17 adjacent their upper limits.

A lever 26 is pivotally and adjustably connected within the shank 2 in the same manner as the lever 26 in the first embodiment of the invention so that the details thereof need not be repeated. However, the lever 26 is moditied as it depends through the aperture in the block 4 to expand and provide an arcuately recessed surface at its extremity which is located immediately adjacent the lower end of the shank. A vane type hydraulic piston 6i) is fixed in the recessed surface to form a depending extension of the lever 26. The piston 60 has an aperture 61 transversely of the foot which accommodates a pin 62. The pin 62 projects at either end through apertures 17 in housing 12. The apertures 17 are of greater dimension than the external dimension of the pin 62 for purposes to be described.

Balancing springs 39 and 40 are mounted between the under surface of the shank 2 and the foot 1 as in the first described embodiment of the invention to normally dispose the foot ysubstantially at right angles to the shank under no-load conditions. This is illustrated in Fig. 3 of the drawings.

A pin 63 is mounted to project through a portion of lever 26 in shank 2. A coil spring 64 about the lever 26 seats at one end to the inner surface of the block 4 about aperture 5 and at the other end to a cap plate 65 about the lever 26 to bias it in `abutment to the projections of pin 63. This effects a normal upward bias of the lever 26 to the shank 2. Since the lever is fixed to the piston 6l), this bias of the lever 26 pulls the upper curved surface of the piston 60 into form-fitting recesses in the under surface of the block 4.

The piston 60 which has a cylindrical contour at its upper end depends in housing 12 to a point slightly spaced from the surface 13 thereof. The adjacent front `and rear walls of the housing 12 are cylindrically curved at their upper extremities to accommodate the contour of the upper end of the piston 60. The normal no-load suspension of the housing 12', as illustrated, provides a clearance 65 between the upper ends of the front and rear walls of the housing and the surface of the piston 60 which is equal to the clearance between the lower end of the piston and the base surface 13 of the housing and equal to the clearance of pin 62 within apertures 17.

The lower end of piston 60 has a rectangular recess 66 to the rear thereof providing a forward depending wall 69 and two side walls 70 guiding a steel ball 67 which rolls freely on the curved base surface 13 of the housing. The forward depending wall portion 69 defining the recess 66 has an aperture 68 in the arcuate path of the ball 67 so that the ball may close the aperture 68 when fully seated to the forward wall 69.

A cover 71 of elastic material, preferably of synthetic rubber, is cemented or bonded to the upper part of the lever 26' in aperture 5 and to the outside of the housing 12 to completely seal the control mechanism and the housing, which is lled with hydraulic fluid.

The hydraulic embodiment of the invention is shown in Figs. 3 and 4 of the drawings in a condition where no load is applied to the ankle joint as during the swingphase of a stride. ln this situation, the springs 39 and 40' cause the foot 1 to assume a position approximately rectangular with the shank and tend to maintain the foot in this position at all times. This is possible because the hydraulic iiuid in the housing 12 can move freely through the clearances between the piston 6l) and the housing and will not obstruct the normal motions of the piston. If, in making a stride, the amputee swings the articial leg forward and places the foo-t on the ground, there is immediate load transferred to the foot. A verticalldisplacement occurs between the pin 62 and the housing 12, as enabled by the apertures 17', resulting in a closing of the clearances between the piston 60 and the housing 12 at the upper and lower ends of the piston 60. ln the stride during the initial application of load to the foot, the shank 2' and connected lever 26 are inclined back from a vertical in space. The steel ball 6'7 on the cylindrically curved base surface 13 of the housing rolls to a position perpendicularly below the pivot axis 3 no matter what the angle may be between the shank and the foot or no matter what the position of the foot in space happens to be at that time. This rolling motion of the steel ball is dampened by the hydraulic fluid in the housing. lf now, in continuing the stride, the amputee moves the shank of the leg forward with the foot still on the ground, the shank and the lever 26 approach a vertical in space. This motion will not be obstructed by the hydraulic system provided since as the piston pivots with the lever the hydraulic fluid can ow from the rear to the front side of the piston through the aperture 68. When the shank and the lever,26 are disposed approximately vertical in space, the ball 67 located in the recess 66 in the depending extremity-of the vane will close the aperture68. Since, on initial application of load to the foot, all the clearances between the vane and the housing surfaces were closed and sealed, the fluid flow in the hydraulic system is now completely blocked. The hydraulic system locks and on further forward rnotion of the shank the angle established between the foot and the shank when the shank reachedthe vertical in space is maintained. This means that the foot 1 will move forward in a rolling fashion with the heel 7 rising off the ground until the weight of the amputee is supported only on the ball of the yartificial foot. On lifting the leg to initiate a swing-phase, the amputee takes his weight off the artificial leg and all clearances between the piston vane and the housing 12 are re-established, permitting hydraulic fluid flow about the vane. The foot 1 is freed from the locking position and will return. to its normal rectangular position relative the shank under the influence of the springs-39 and 40. Thus, a walking cycle of the artificial leg is provided. The Iadjustment of the position of the lever 26 within the shank is effected as previously described with respect to the mechanical embodiment presented herein.

To summarize, the invention provides a control mechanism for the angle joint of an artificial leg to produce forces in that joint which closely duplicate the forces provided by the'muscles in the ankle joint of a natural leg. The improved mechanism is such that it will stop dorsi-flexion of the ankle joint whenever the longitudinal axis of the shank is approximately vertical in space or inclined forward from the vertical, independently of the relative angle between the shank and foot at the time. The invention as applied to an artificial leg further provides that the foot under no-load conditions will tend to assume, in an elastic manner, a position approximately rectangular with the shank.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specie as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprises an illustrative form of several modes of putting the invention into effect and the invention is therefore claimed in any of its forms or modications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

l. In an artificial leg, a shank, ya foot pivoted thereto at the lower end, means connecting the foot and the shank for providing that the limit of dorsi-flexion is determined by the shank assuming a vertical in space under load conditions, and means for normally maintaining said foot at right angles to said shank under no-load conditions.

. 2. In an artificial leg, a shank, a foot pivoted thereto at the lower end, gravity controlled means connecting the foot and the shank in operative relation on application of load to the artificial leg to establish the limit of dorsi-flexion of said foot at the point at which the shank is at a vertical in space, irrespective of the angular disposition of the foot at that time.

3. In an artificial leg, a shank, a foot pivoted thereto at the lower end, gravity controlled means connecting the foot and the shank in operative relation under load to establish the limit of dorsi-fiexion to the point at which the shank is disposed at a vertical in space irrespective of the angular disposition of the foot, and means intermediate the foot and the shank operative on removal of load from said leg to establish the foot at approximately right angles to the shank.

4. In an artificial leg, a shank, a foot, means suspending the foot in pivotal relation to said shank including a housing having a cylindrically curved base, a gravity controlled ball element freely rolling on said base seeking its lowest point at -all times, and means in said housing operatively connected to said shank and operative on dorsi-exion of said foot to be locked by said ball element to said housing on said shank reaching a vertical in space under load.

5. In an artificial leg, a foot, a shank having means pivotally suspending said foot for relative vertical movement, brake means associated with said shank and sald foot, said shank and said foot being responsive to load for relative vertical movement to operatively assoc1ate said brake means in said foot, said brake means being responsive to movement of said shank under load to a vertical position in space to lock said foot to said shank at the angle therebetween at that instant, irrespective of the angle of the foot in space.

6. In an artificial leg, a shank, a foot connected thereto for movement about a pivot axis therebetween, means for normally maintaining a rectangular disposition of said shank to said foot, gravity controlled means continuously seeking a vertical with said pivot axis and means connected to said shank responsive to weight application to said leg to operatively connect with said gravity controlled means in said foot to lock said foot to an angle to said shank as effected on said shank being established at a vertical in space or beyond under load conditions.

7. In an artificial leg, a foot, a shank, pivot means connected to said shank suspending said foot in pivotal relation thereto, brake means mounted on said pivot means and depending in said foot, and means in said foot operative to engage said brake means on application of load to said shank to limit dorsi-fiexion of said foot on said shank reaching a vertical in space.

8. In combination, a first member, a second member, means connecting said members for pivoting of one of said members relative the other, means for normally maintaining said members substantially at right angles under no-load conditions, gravity operated control means mounted to one of said members and means operatively mounted to said connecting means and operative with said control means on application of load to said members to limit the pivoting of said members at a point where one of said members reaches a vertical in space, irrespective of the angular disposition of the other of said members thereto.

9. In an artificial leg, a foot, a shank, a recess in said foot nesting the lower end of said shank for pivoting of said foot relative thereto, a housing means seated in said recess and fixed to said foot, means suspending said housing in pivotal relation to said shank including a pivot means extending through enlarged apertures in said housing for suspension of said housing under no-load conditions, a lever pivotally mounted about said pivot means having its upper end connected to the shank and its lower end depending in said housing, said housing having a concave base, brake means on said pivot means depending in said housing spaced laterally of said lever and vertically of said base, spherical means rolling freely on said concave base intermediate said lever and said brake means whereby on application of load to said foot through said shank, said brake means will engage said base and on said shank reaching a vertical in space during dorsifiexion of said foot, said lever will wedge said spherical means and said brake means to said housing to prevent further dorsi-exion.

l0. In combination, a shank, a foot, means providing a joint therebetween, brake means operatively connected with said joint means and gravity controlled means mounted to said foot for operating with said brake means to limit dorsi-exion of the foot at the instant. the connected shank reaches a vertical in space or forwardly thereof.

1l. In an artificial leg, a foot, a shank nesting in said foot to provide for relative pivotal movement thereof, means for suspending said foot from said shank, means normally maintaining a rectangular disposition of said foot to said shank under no-load conditions, said suspension means including a housing in said foot containing hydraulic fluid, a vane-type piston pivotally connected to said suspension means and said shank depending in said housing to normally permit movement of Huid thereby, gravity controlled means in said housing operatively associated with said piston, and an aperture in said piston to normally permit relative pivoting of said foot and said shank, whereby, on application of load to said shank said piston will seat to said housing and said gravity operated means will seal the aperture in said piston to prevent relative displacement of fluid and to lock said shank to said foot at the angle established therebetween on said shank reaching a vertical in space.

12. In combination, a first member, a second member pivotally related to said first member, means operatively connecting said rst and second members including hydraulically controlled means and gravity operated means, said hydraulic control means and gravity operated means being responsive to load on said members to lock said members in the relative position effected therebetween on one of said members reaching a vertical in space, irrespective of the angular disposition of said members at that time.

13. In combination, a foot member, a shank member, means pivotally suspending said foot relative said shank, a lever means pivotally connected to said shank and depending to said foot in connected relation to said suspension means, said lever pivoting with said shank on application of load thereto and means in said foot for wedging said lever and said shank in a locked position to said foot on said shank reaching a vertical in space under load conditions.

14. In an artificial leg, a shank, a foot, pivot means mounted to said shank, a recess in said foot nesting the lower end of said shank, means pivotally mounting said foot to said pivot means providing for displacement of said shank relative said foot, brake means connected to said shank and depending `in the recess in said foot in slightly spaced relation to said foot under no-load conditions, means maintaining said foot at approximately right angles to said shank under no-load conditions, gravity controlled means in said foot and operatively related to said brake means whereby on load being applied to said leg said brake means will be displaced to said foot and will lock said shank to said foot through the medium of said gravity controlled means on said shank being moved to a vertical in space or forwardly thereof under load.

15. Mechanism comprising, a rst member, a second member, means connected to said first member pivotally suspendingsaid second member under no-load conditions, brake means on said suspending means, gravity controlled means mounted to said second member and operatively related to said brake means, and means connected to said first member and operative with said gravity controlled means and brake means in response to movement of said first member to a vertical in space under load to lock to said members and maintain the angle between said members as provided at that time during continuing movement of said first member in the same direction.

16. In an artificial leg, a shank, a foot, means providing a joint therebetween having a uid-lilled housing and a piston operating in said housing connected therewith, said piston being displaced in said housing in response to relative pivoting of said shank and said foot about said joint, means defining bypasses for flow of tluid from one side to the other of said piston, said piston being operable on application of weight to said leg for effecting a closing of a portion of said bypass means and gravity control means for automatically closing the remainder of said bypass means whenever the shank goes to or through a vertical in space.

17. In an articial leg, a foot, a shank, means providing a joint therebetween having a hydraulic system operatively connected therewith including a hydraulic uidlled housing and a piston displaceable therein in response to relative movement of said foot and said shank, and means successively responsive to simultaneous application of weight on the legs and movement of the shank through a vertical in space to prevent displacement of fluid by said piston and to limit dorsi-exion of the foot at that instant.

18. In an articial leg, a foot, a shank, means providing a joint therebetween having a hydraulic system operatively connected therewith including a hydraulic iluid-illed housing and a piston displaceable therein in response to relative movement of said foot and said shank,

bypass dening means for permitting normal free displacement of said piston in said housing, a portion of said bypass defining means being partially closed in response to application of weight to the leg and gravity controlled means automatically responsive to movement of the shank through a vertical in space to close the remainder of said bypass means to tix the shank to the foot at the angle established therebetween at that instant.

19. In combination, a foot member, a shank member pivotally related to said foot member, a hydraulic system for controlling relative pivoting of said members, operatively connecting said members, including a fluid-lled housing and a piston and bypass means for normally establishing free movement of said piston in said housing and means under the influence of gravity for providing partial closing of said bypass means in response to application of weight to said leg and effecting complete closing thereof on movement of said shank through a vertical in space to lock the foot to the shank irrespective of the angle therebetween at that instant.

20. In an artificial leg, a shank, a foot, means providing a joint therebetween, a hydraulic system including a housing containing hydraulic fluid and a piston operatively connected with said joint so that said piston displaces hydraulic fluid whenever rotation occurs at said joint, and means defining two bypasses for the ow of said hydraulic uid from one side to the other of Isaid piston, said piston being operable to close one of the bypasses on application of weight to the leg, and a gravity controlled member operative to close the other bypass whenever the shank goes through the vertical in space to lock the foot to the shank at the angle provided therebetween at that time.

References Cited in the le of this patent UNITED STATES PATENTS