Abstract
The invention relates to a prosthetic foot with a foot part 2 and a lower leg part 4 that is connected to the foot part 2 such that it can be pivoted about a pivot axis 6 and that can be locked in various pivot angles relative to the foot part 2,the connection between the lower leg part 4 and the foot part 2 having a clearance in the pivot direction when the foot part 2 is locked on the lower leg part 4, the prosthetic foot having at least one friction element 14 arranged between the foot part 2 and the lower leg part 4 and applying a frictional torque that counteracts a pivoting of the foot part 2 relative to the lower leg part 4 when the foot part 2 is locked relative to the lower leg part 4.
Claims
1. A prosthetic foot, comprising: a foot part; a lower leg part; a connection between the lower leg part and that the foot part, wherein the lower leg part is connected to the foot part such that it can be pivoted about a pivot axis, and wherein the lower leg part is lockable in various pivot angles relative to the foot part, wherein the connection between the lower leg part and the foot part has a clearance in a the pivot direction when the foot part is locked on the lower leg part; and at least one friction element arranged between the foot part and the lower leg part which applies a frictional torque that counteracts a pivoting of the foot part relative to the lower leg part when the foot part is locked relative to the lower leg part.
2. The prosthetic foot according to claim 1, wherein the at least one friction element is configured to generate the frictional torque independently of whether the foot part is locked relative to the lower leg part, so that the lower leg part also has to be pivoted relative to the foot part against the frictional torque.
3. The prosthetic foot according to claim 1, wherein the lower leg part is lockable relative to the foot part by a form-fitting connection.
4. The prosthetic foot according to claim 3, wherein the lower leg part and the foot part each comprise form-fitting elements designed to correspond to each other, and wherein the at least one friction element is arranged on at least one of the form-fitting elements.
5. The prosthetic foot according to claim 3, wherein the lower leg part and the foot part each comprise form-fitting elements that are designed to correspond to a separate form-fitting component, wherein the at least one friction element is arranged on the form-fitting component and/or on at least one of the form-fitting elements.
6. The prosthetic foot according to claim 5, wherein the form-fitting component is mountable mounted on the lower leg part or the foot part.
7. The prosthetic foot according to claim 1 wherein the at least one friction element is arranged on the pivot axis.
8. The prosthetic foot according to claim 1 wherein the pivot axis is a virtual pivot axis.
9. The prosthetic foot according to claim 1 wherein the at least one friction element comprises a coating of a bearing surface of the foot part and/or a bearing surface of the lower leg part and/or a bearing surface of a third component.
10. The prosthetic foot according to claim 1 wherein the at least one friction element has no impact on a clearance in an the axial direction between the lower leg part and the foot part.
11. The prosthetic foot according to claim 1 wherein the at least one friction element comprises a damping element.
12. The prosthetic foot according to claim 1 wherein the at least one friction element is arranged about the pivot axis.
13. The prosthetic foot according to claim 9 wherein the third component is selected from the group of a shaft and a form fitting component.
14. The prosthetic foot according to claim 11 wherein the damping element is a hydraulic damping element.
Description
[0026] In the following, a number of embodiment examples of the invention will be explained in more detail with the aid of the accompanying drawings. They show
[0027] FIGS. 1 to 4 - schematic sectional views through parts of prosthetic feet according to some embodiment examples of the present invention,
[0028] FIGS. 5 and 6 - schematic views of the ankle moments during a step cycle,
[0029] FIGS. 7 and 8 - schematic sectional views through parts of prosthetic feet according to further embodiment examples of the present invention,
[0030] FIG. 9 - the schematic view of a prosthetic foot according to an embodiment example of the present invention,
[0031] FIG. 10 - the schematic view of a further prosthetic foot,
[0032] FIG. 11 - the schematic view of two components of a prosthetic foot and
[0033] FIGS. 12 and 13 - schematic views of part of a prosthetic foot.
[0034] FIG. 1 shows a sectional view through a part of a prosthetic foot, wherein a foot part 2, of which only a fastening element is shown, is connected to a lower leg part 4 such that it can be pivoted about a pivot axis 6. Only a part of the lower leg part 4 with an adapter 8 is shown, to which a further prosthetic part can be fastened. In FIG. 1, the lower leg part 4 is connected with a shaft 10 in a torque-proof manner, the pivot axis 6 extending within said shaft and said shaft being rotatably mounted in two specially provided mounts 12 in the foot part 2. In FIG. 1, a friction element 14 is located between the lower leg part 4 and the right side of the foot part 2, said friction element being arranged about the shaft 10 in the embodiment example shown. A screw 16 is arranged in a specially provided thread bore in the shaft 10, said screw having a screw head 18. A disc spring 20 is located between the screw head 18 and the outside of the foot part 2, wherein said spring can be compressed and thus energetically charged by screwing the screw 16 into the shaft 6. The disc spring 20 supports itself on the outside of the foot part 2, so that the lower leg part 4 fixed on the shaft 10 is pulled by the screw 16 and the disc spring 20 towards the right leg of the element of the foot part 2 shown, thereby compressing the friction element 14. In this way, the frictional torque applied by the torque element 14 can be adjusted.
[0035] Here, the frictional torque applied by the friction element 14 counteracts a pivoting of the foot part 2 relative to the lower leg part 4. A clearance in the axial direction in relation to the pivot axis 6 between the foot part 2 and the lower leg part 4, which is represented by the gap 22, is not affected by the friction element 14 in the embodiment example shown. A locking element can lock the foot part 2 and the lower leg part 4 relative to each other along the drawn line 24; however, a clearance in the pivot direction about the pivot axis 6 remains.
[0036] FIG. 2 depicts a similar embodiment in which the lower leg part 4 is connected in a torque-proof manner to the shaft 10 in which the axis 6 extends. In contrast to the embodiment shown in FIG. 1, in FIG. 2 there are two friction elements 14 arranged between the two legs of the foot part 2. Instead of the screw 16 with the disc spring 20 arranged under the screw head 18, a wedge 26 is inserted into the shaft 10 on the right-hand side, said wedge expanding the shaft 10 at that point and thus enabling the force transmission required.
[0037] FIG. 3 shows a foot part 2 that is connected to the shaft 10 such that it is torque-proof. The lower leg part 4 is rotatably mounted on this shaft 10. A friction element 14 is located between the left leg of the foot part 2 and the lower leg part 4, while a disc spring 20 is located on the opposite side. Said spring is tensioned and compressed by the screw 16 passing through the shaft 10, thereby creating the necessary force.
[0038] FIG. 4 depicts a similar embodiment to FIG. 3 in which the foot part 2 is connected in a torque-proof manner to the shaft 10, on which the lower leg part 4 is mounted in a torque-proof manner. A friction element 14 is arranged on each side of the lower leg part 4, said friction elements being compressed by the force applied by the screw 16 and the disc spring 20.
[0039] FIG. 3 shows a schematic diagram that depicts the course of the ankle moment (y axis) over the step cycle (x axis). The cycle begins with the heel strike, from which point onwards a negative torque is exerted that acts on the ankle in the plantar flexion direction. Due to the clearance, the foot part and lower leg part strike against each other, which is depicted by the cloud 28. Over the course of the step, the torque initially increases in strength, which leads to it becoming more negative in FIG. 5. From the moment at which the foot is fully on the ground, a positive torque is exerted, which acts on the ankle in the dorsal flexion direction. At the transition, the torque changes sign and a zero crossing occurs, which is shown by the cloud 30. As the direction of the acting torque changes, another impact occurs between the foot part and the lower leg part, which is associated with a noise upon impact in prosthetic feet according to the prior art. In the present invention, this noise is reduced or even completely prevented by the frictional torque.
[0040] Only when the foot leaves the ground again (toe-off) does the torque return to zero and the third impact of the foot part and the lower leg part occurs, shown by the cloud 32.
[0041] FIG. 6 depicts a schematic enlargement during the respective stops. In the case of the stops depicted by the clouds 28, 32, the curve of the torque extends from left to right, i.e. from the positive torque to the negative torque. Here, the acting torque must be slightly negative before the movement between the foot part and the lower leg part enabled by the clearance occurs. The distance 34 corresponds to twice the frictional torque. If the movement occurs, the angle between the foot part and the lower leg part slides to the right by an amount, which is depicted by the distance 36. This distance corresponds to the clearance. In the case of the impact indicated by the cloud 30, the torque is reversed.
[0042] FIG. 7 shows a sectional view through a part of a prosthetic foot perpendicular to the pivot axis 6. The latter features a projection 38 which can be inserted into 2 specially provided recesses 40. A friction element 14 is arranged in such a way that it comes into contact with the shaft 10, thereby applying a frictional torque. A pressure exerted by the friction element 14 on the shaft 10 can be adjusted via a screw 42 that is connected to an actuation element 44. As such, the frictional torque can also be adjusted.
[0043] FIG. 8 depicts a similar view. The shaft 10 features the projection 38, which can be engaged in the recesses 40. A friction element 14 is shown on the side of the shaft 10 opposite the projection 38, said friction element exerting a frictional torque on the inside of the mount 12 in which the shaft 10 is mounted.
[0044] FIG. 9 shows a prosthetic foot with the foot part 2 and the lower leg part 4 on which an adapter 8 is located. The foot part 2 can be pivoted relative to the lower leg part 4 via the shaft 10. A form-fitting element 46, which is not shown in FIG. 9 and is connected to the lower leg part 4, for example in a torque-proof manner, can be displaced along a displacement direction, for example by actuating an actuation element, for example by pressing a button, said direction being perpendicular on the drawing plane in the embodiment shown in FIG. 9. In the engaged state, the form-fitting element engages in a correspondingly designed second form-fitting element that is fixed to the foot part in a torque-proof manner. Due to the clearance between the lower leg part 4 and the foot part 2 and the respective form-fitting elements, a small movement is still possible. The foot part 2 also features various springs 48, which ensure the required elasticity. The friction element 14 is not visible in the view shown. Preferably, the form-fitting element to be disengaged is spring-loaded in the direction of the engaged position.
[0045] FIG. 10 shows a further embodiment of a prosthetic foot with the foot part 2 and the lower leg part 4 on which an adapter 8 is located. A rail 50 is located on the foot part 2 that the lower leg part 4 can glide along. It has an elongated hole 52 with multiple grooves 54 that serve as different locking position for the lower leg part 4 on the rail 50. The form-fitting element 46, which in this case is designed as a pin, for example, can be fixed in each of these grooves 54, thereby locking the lower leg part 4 in the respective position. To this end, the pin 46 can be disengaged, for example, manually or mechatronically and thus disengaged from the grooves 54. The position of the lower leg part 4 can then be displaced and adjusted relative to the foot part 2. The pin 46 is then re-engaged and thus re-engaged with one of the grooves 54. In the embodiment example shown, the lower leg part 4 can consequently displaced along the line 56, which is designed in the shape of a circular arc and features a virtual point of rotation 58.
[0046] FIG. 11 schematically depicts how the problem to be solved by the present invention emerges. Schematically visible is a gearwheel 60 which is connected to the shaft 10 in a torque-proof manner in the embodiment example shown. The combination of gearwheel 60 and shaft 10 is arranged in a mount 12, which is designed as a hollow gearwheel. The mount is connected to the lower leg part 4 or the foot part 2 and the gearwheel 60 with the respective other part.
[0047] In the upper part of FIG. 11, the gearwheel 60 subjected to a counter-clockwise torque with the shaft 10, so that the respective counter-clockwise flanks of the individual teeth of the gearwheel 60 rest on the respective flanks of the inwardly projecting teeth of the mount 12. Upon the transition to the lower part of FIG. 11, the load direction changes and the torque acting on the shaft 10 changes sign. Under this torque, the gearwheel 60 is loaded clockwise with the shaft 10. Due to the clearance between the gearwheel 60 and the mount 12, a minimal movement of the two components relative to each other is possible until the situation depicted in the lower part of FIG. 11 is reached. In this situation, the counter-clockwise flanks of the teeth of the gearwheel 60 rest on the inwardly projecting teeth of the mount 12. As a minimal movement has taken place between the upper situation in FIG. 11 and the lower situation, a noise occurs at each point where a tooth of the gearwheel 60 strikes the mount 12, said noise being indicated by the arrows 62.
[0048] FIGS. 12 to 13 show two views of a joint of a prosthetic foot according to an embodiment example of the present invention. One can see part of the lower leg element 4 and of the foot part 2, which are arranged to pivot against each other about a pivot axis. They are arranged on a shaft 10, not depicted here, which is inserted into the mount 12 shown in FIG. 12. In FIG. 12, the gearwheel 60 is shown in the engaged state. It engages in a correspondingly designed form-fitting element 64 which, like in FIG. 11, is designed as a mount. It results in the situation depicted in FIG. 11.
[0049] FIG. 13, on the other hand, shows the gearwheel 60 in the disengaged position. It has been displaced along a displacement direction, which in FIG. 13 extends parallel to the mount 12 through which the shaft can be pushed, and thus disengaged from the correspondingly designed form-fitting element 64.
TABLE-US-00001 Reference list 2 foot part 4 lower leg part 6 pivot axis 8 adapter 10 shaft 12 mount 14 friction element 16 screw 18 screw head 20 disc spring 22 gap 24 line 26 wedge 28 cloud 30 cloud 32 cloud 34 distance 36 distance 38 projection 40 recess 42 screw 44 actuation element 46 form-fitting element 48 spring 50 rail 52 elongated hole 54 groove 56 line 58 virtual point of rotation 60 gearwheel 62 arrow 64 corresponding form-fitting element
