WO1995026171A1

WO1995026171A1 - Swing phase control unit for an artificial knee joint

Info

Publication number: WO1995026171A1
Application number: PCT/EP1995/001101
Authority: WO
Inventors: Gerhard Fitzlaff
Original assignee: Biedermann Motech Gmbh
Priority date: 1994-03-28
Filing date: 1995-03-23
Publication date: 1995-10-05
Also published as: EP0702538A1; DE4410730C1; CN1125903A; JPH08511190A

Abstract

Proposed is a servo-hydraulic swing phase control unit for an artificial knee joint. One end of the control unit has a head element (2) while the other end has a foot element which closes off a cylinder with a reciprocating piston (13) in it. In order to ensure movement-dependent control of the joint, the first and second spaces into which the piston divides the cylinder chamber are connected by a throttle duct (18, 19, 20) whose cross-section can be adjusted by a slide bar (21) as a function of the pressure in the two spaces (15, 16).

Description

Swing phase control for an artificial knee joint

The invention relates to a swing phase control for an artificial knee joint with a cylinder which is closed at one end with a head part and at the other end with a foot part, and with a piston which can be moved back and forth in the axial direction and which has an outward bore through a hole in the head part guided piston rod for connection to a thigh part of a prosthesis and a first space on the head part side bounded by the piston and a second part on the foot part side.

Such a device is known from US Pat. No. 5,062,857.

The object of the invention is to provide a swing phase control of the type described at the outset which is suitable for extreme walking conditions and which enables a pleasant sequence of movements in all conditions.

This task is solved by the swing phase control according to claim 1, 2 or 3.

The throttle channel is preferably provided in the interior of the piston rod, which simplifies the construction.

According to a preferred embodiment, the cylinder comprises an outer cylinder wall and at a distance therefrom an inner cylinder wall to form an annular chamber. The annular chamber is connected to the second space via a recess. The piston slides inside the cylinder space delimited by the inner cylinder wall. An annular piston spring-biased in the direction of the recess slides in the annular chamber. This ensures that the volume of the immersing piston rod is equalized and that the control reacts to the different stresses when the knee is bent and extended so that a natural sequence of movements is achieved. - 2nd

Preferred embodiments of the invention are characterized in the subclaims.

Further features and advantages of the invention result from the description of the exemplary embodiments with reference to the figures. The figures show:

Fig. 1 is a cross-sectional view of a first embodiment

Fig. 2 is a cross-sectional view of a second embodiment

Fig. 3 is a view of an enlarged section of the second embodiment

First embodiment:

As shown in FIG. 1, the device comprises an outer cylinder jacket 1 which is delimited by a head part 2 at its head-side free end and by a foot part 3 at its foot-side end. The connection is made in the manner indicated in the figure in each case by screwing the head and foot sections into the provided internal thread. In addition, a corresponding seal 4, 5 is provided.

At a distance from the outer cylinder jacket, an inner cylinder wall 6 is provided on the inside, the ends of which are inserted tightly in the head part or foot part. The outer cylinder wall 1 and the inner cylinder wall 6 enclose an annular chamber 7. At the foot end, the inner cylinder wall 6 has 8 bores 8. An annular piston 9 is slidably disposed in the annular chamber. This is in the manner shown in the figure via a pressure spring 10 acting on the one hand on the head part 2 and on the other hand on the annular piston stanchions 8 towards spring-loaded basic position. A piston 13 carried by a piston rod 12 is provided in the interior of the cylinder enclosed by the inner cylinder wall 6. The piston 13 separates inner space in the cylinder into a first space 15 on the head part side and a second space 16 on the foot part side by means of suitable seals 14. The second space 16 is connected via the bores 8 to the space of the annular chamber 7 adjoining it. The piston rod 12 is guided to the outside via a coaxial bore in the head part 2 and has an eyelet at its free end for connection to a thigh part of a prosthesis. The piston rod 12 is slidably mounted in the coaxial bore. The first space 15 is sealed by seals 17.

As can best be seen from FIG. 1, the piston rod 12 has a coaxial bore 18 in the section of the piston and in the region adjoining it on both sides. Immediately adjacent to the piston, throttle bores 19, 20 are provided on both sides in the axial direction, which connect the first space 15 and the second space 16 to the bore 18 and together form a throttle channel. A slide 21 is provided in the interior of the bore 18. This has a piston rod 22 which has a first piston 23 sliding in the bore 18 near its one end and a second piston 24 sliding in the bore 18 near its other end. The distance between the two pistons is so large that the pistons each limit the throttle bore 19 and 20 and the space between them, that is, the throttle channel.

Compression springs 25, 26 are provided on the back of the first piston 23 and the second piston 24, each of which rests against the bottom of the bore and against the piston and biases the slide 21 into the neutral position described above.

The first piston 23 delimits the throttle channel on one side and on the other in the manner described above On the one hand, a first preload chamber 27. The second piston 24 delimits the throttle channel on one side and on the other side, a second preload chamber 28. The first chamber 15 is connected via a bore 29 which has a negligible or only a low flow resistance, while the second space 16 and the second prestressing space 28 are connected to one another via a corresponding bore 30 which has a negligible or only a low flow resistance.

The foot part 3 has, in a known manner, bores 31 extending perpendicular to the longitudinal axis for connection to a lower leg part.

The cylinder interior is filled on both sides of the piston 13 with hydraulic fluid.

FIG. 1 shows the position of the servohydraulic swing phase control, in which the knee joint is bent over a longer period of time and an equilibrium has been established. In the case of an extension now taking place, the piston rod 12 is pulled outward in the direction opposite the arrow 32 and the piston 13 is thus slowly moved into its end position as far as the stop against the head part 2. The pressure in the first space 15 initially increases, while the pressure in the second space 16 decreases. The pressure in the first preload chamber 27 now becomes greater than that in the second preload chamber 28, with the result that the slide 21 moves in the direction of the foot part and initially closes the throttle bore adjacent to the first piston 23. The result of this is that a considerable spring force builds up in the first space 15, which dampens the stretching movement.

During its return movement from the extended position into the angled position, the piston with the piston rod is then moved downwards again in the direction of arrow 32. Now, in the second room 16, on the one hand, a considerable pressure, and on the other hand the annular piston is pressed back against the spring 10. If the movement is slow, the pressures in rooms 15 and 16 slowly balance out via the throttle channel. However, if the movement is rapid or even jerky, the pressure difference and thus the pressure difference in the first prestressing space 27 and the second prestressing space 28 is so great that the slide moves upwards and at least closes the adjacent throttle bore 20, so that the throttle channel is further reduced and an increased damping resistance builds up.

The force of the medium compressed in the second space, supported by the force of the compressed spring 10 of the annular piston 9, then pushes the piston upward during the subsequent stretching movement.

In the manner described above, it is thus achieved that a differently large amount of damping takes effect when the knee joint moves at different speeds. In addition, the provision of the annular channel with the spring-loaded annular piston when bending causes an additional spring force to be effective.

Second embodiment:

As shown in FIG. 2, the swing phase control has an outer cylinder wall 101 which is delimited by a head part 102 at its head-side free end and by a foot part 103 at its foot-side end. The connection is made in the manner indicated in FIG. 2 by screwing the head 102 and foot 103 into the internal threads provided. In addition, a corresponding seal 104, 105 is provided in each case.

At a distance from the outer cylinder wall 101, an inner cylinder wall 106 is provided on the inside, the ends of which are in turn inserted tightly in the head part 102 or foot part 103. The outer cylinder wall 101 and the inner cylinder wall 106 enclose an annular chamber 107. Inside the of A piston 113 carried by a piston rod 112 is provided on the inner cylinder wall 106. The piston 113 with seals 114 separates the interior space in the cylinder into a head space side first space 115 and a foot space side second space 116.

A continuous cylinder section 165 is provided in the foot part 103 coaxially with the piston rod 112. The cylinder section 165 has a first hollow cylinder 134 with a first diameter, which is connected at one end to the second space 116. At the end, a ring 145 is arranged coaxially, which has an inner diameter that is smaller than the first diameter. The cylinder section 165 further has a second hollow cylinder 135 with the first diameter, which is connected at one end to the outside. The two hollow cylinders 134, 135 are connected via a bore 143. The bore 143 has a diameter that is smaller than the first diameter. The foot part 103 has a first channel 133, which connects the second hollow cylinder 135 to the annular chamber 107.

A rod 160 is provided concentrically in the cylinder section 165. The rod 160 has a first section 161 with an external thread. The external thread fits an internal thread provided in the second hollow cylinder 135. The first section 161 of the rod 160 is adjoined by a second section 162, which has an outside diameter that is smaller than the inside diameter of the bore 143. The second section 162 is followed by a conical end section 163 (FIG. 3). A first annular piston 142 is provided within the first hollow cylinder 135. The outer diameter of the first annular piston 142 is selected such that the first annular piston 142 can slide in the first hollow cylinder 165 in the axial direction, and the inner diameter of the first annular piston 142 is larger than the minimum diameter of the conical end section 163. The ring 145 forms a stop for the first annular piston 142. The first annular piston 142 is on the one hand on the annular projection formed by the bore 143 jump and on the other hand to the first annular piston 142 engaging first compression spring 144 in the manner shown in FIG. 2 biased into a basic position directed towards the head part 102. The basic position is defined by the ring 145. Between the annular piston 142 and the conical end section 163 there is a first throttle duct 152. In the basic position, the first throttle duct has its maximum cross section.

The angle of the conical end section 163 is preferably between 1 ° - 5 °; The angle of the conical end section 163 is preferably chosen to be as small as possible and the length of the conical end section 163 is as long as possible. The angle 2 ° and the length 10 mm are even more preferred.

By rotating the rod 160, the rod 160 is moved in the axial cylinder direction. This sets the maximum cross section of the first throttle duct 152.

Furthermore, a second channel 136 is provided in the foot part 103, which connects the annular chamber 107 to the second space 116. A check valve 157 is arranged in the second channel. The check valve 157 has a ball connected to a spring. The ball is pressed against an opening by the spring and closes the opening. The check valve 157 opens to the second space 116.

The piston rod 112 is guided to the outside via a bushing 108, which is provided in a coaxial bore in the head part 102, and has an eyelet at its free end for connection to a thigh part of a prosthesis. The piston rod 112 is slidably supported in the bushing 108. The first space 115 is sealed by seals 117. A coaxial cylinder bore 118 is provided in the piston rod 112 and is conical in the section of the first piston 113. The conical section of the cylinder bore 118 opens towards the foot part 103.

Bores 148 arranged spirally in the direction of the head part 102 are provided in the piston rod 112 (FIG. 3). The first space 115 is thus connected to the second space 116 through the bores 148 and through the cylinder bore 118. A first stop cylinder 146 with an external thread is provided within the cylinder bore 118. The external thread fits an internal thread provided in the cylinder bore 118. The first stop cylinder 146 has a rubber ring 158 at its end facing the foot part 103. At its other end, a hexagonal recess for a hex key is provided. In the first stop cylinder

146 is provided with a coaxial bore 149 with an internal thread.

A second stop cylinder 147 is also provided. The second stop cylinder 147 has a first section with an external thread. The external thread matches the internal thread of the first stop cylinder. A second cylindrical section with a diameter adjoins the first section. A circular stop plate 150 adjoins an end assigned to the second section of the second stop cylinder 147. The plate plane of the stop plate 150 is arranged perpendicular to the axis of the cylinder and a diameter of the stop plate is larger than the diameter of the second section. A slot for a screwdriver is provided at another end of the second stop cylinder. The first section of the second stop cylinder

147 is screwed into the first stop cylinder. The protruding second section of the second stop cylinder points towards the foot part 103.

A slide 121 designed as a hollow cylinder is slidably provided on the protruding section of the second stop cylinder 147. The slider 121 has a first end and a second end. The second end has a conical shape that matches the conical section of the cylinder bore 118. A second throttle duct 151 is formed between the conical shape of the second end of the slide 121 and the conical section of the second cylinder bore 118 (see FIG. 3). Through the first stop cylinder 146 with the rubber ring 158 and the first end of the slide 121 an upper Position of the slider 121 set. In the upper position, the cross section of the second throttle duct 151 is minimal. A lower position of the slide 121 is defined by the second stop cylinder 147 with the stop plate 150 and the second end of the slide 121. In the lower position, the cross section of the second throttle duct 151 is at a maximum.

An opening 155 with a check valve 154 is arranged in the piston 113. The opening 155 connects the first space 115 to the second cylinder bore 118. The check valve 154 has a ball connected to a spring. The ball is pressed by the spring against the opening 155 and closes the opening. The check valve 154 opens to the first space 115.

In the annular chamber 107 i. , a second annular piston 109 slidably arranged. This is prestressed in the manner shown in FIG. 2 into a basic position directed towards the foot part 103 via a pressure spring 110 acting on the one hand on the head part 102 and on the other hand on the second annular piston 109. The additional volume of the immersed piston rod 112 is received in the annular chamber 107.

The foot part 103 has, in a known manner, bores (not shown here) extending perpendicular to the longitudinal axis for connection to a lower leg part of the prosthesis.

The head part 102 and the socket 108 have a closable third channel 166, which extends at one end into the first space 115 and which extends outwards at its other end.

The operation of the swing phase control is described below:

The inside of the cylinder is filled with a hydraulic fluid. For this purpose, the rod 160 is unscrewed from the foot part and is 166 at the other end of the third channel a vacuum pump connected. Then the hydraulic fluid is filled through the cylinder portion 165. The rod 160 is then screwed into the foot part 103 and the third channel 166 is closed.

FIG. 2 shows the position of the swing phase control, in which the knee joint is bent over a longer period of time and an equilibrium has been established. In the now following stretching, the piston rod 112 is pulled outward in the opposite direction to the arrow 132 and the piston 113 is thus moved into its end position as far as the stop on the bushing 108. The pressure in the first space 115 increases first, while the pressure in the second space 116 decreases. This has the consequence that the slide 121 moves in the direction of the foot part 103 until it is in the lower position. When stretched, the hydraulic fluid flows from the first space 115 through the bores 148 and through the first throttle channel 151 into the second space 116. As a result of the movement, the bores 148 are covered in sequence by the bushing 108, as a result of which the flow resistance between the first room 115 and the second room 116 increased. This gently brakes the stretching movement until the leg is fully extended. Due to the check valve 157, no pressure difference can build up between the second space 116 and the annular chamber 107 and the cylinder section 165 during the stretching movement.

During its return movement from the extended position into the angled position, the piston 113 with the piston rod 112 is then moved downward again in the direction of the arrow 132. Since all bores 148 are covered by the bushing 108 at the beginning of the return movement, the check valve 154 initially opens and enables the return movement to begin. Now a considerable overpressure is formed in the second space 116 on the one hand and on the other hand the first ring piston 142 is pressed back against the first spring 144 and the second ring piston 109 against the second spring 110. Furthermore, the slide 121 becomes the upper one against the direction of movement Position moves, whereby the minimum cross section of the second throttle channel 151 is established. If the movement is slow, the pressures in rooms 115 and 116 equalize via throttle channels 151, 152. However, if the movement is rapid or jerky, the pressure difference between the second space 116 and the cylinder section 165 and the annular chamber 107 is so great that the first annular piston 142 is moved against the first spring 144 in the direction of the foot part 103, so that the Cross section of the first throttle duct 152 is minimal or, with the appropriate setting by the rod 160, the first throttle duct 152 is completely closed. This suddenly creates an increased damping resistance.

The force of the medium compressed in the second space 116, supported by the force of the compressed springs 110, 144 of the annular pistons 109, 142, then pushes the first piston 113 upward during the subsequent stretching movement.

By turning the rod 160, the rod 160 is moved in the axial cylinder direction and thus the maximum cross section of the first throttle channel 152 changes. This makes it possible to determine the immersion speed of the first piston 113, from which the damping changes noticeably. The maximum and minimum cross section of the second throttle duct 151 is set by rotating the stop cylinders 146 and 147.

In the embodiment described above it is achieved that differently large damping takes effect with flexion movements of the knee joint of different speeds. Furthermore, the slider 121 provided with its upper and lower position ensures that the forces which act differently in the flexion and extension of the knee joint are compensated for, and thus a uniform movement sequence is guaranteed. In addition, the spirally arranged bores 148 ensure that the knee joint is gently braked when the extension is fully extended. The adjustable cross-sections of the throttle individual channels of the swing phase control to the respective wearer of the artificial knee joint is possible.

Claims

PATENT CLAIMS

1. Swing phase control for an artificial knee joint with a cylinder closed at one end with a head part (2) and at its other end with a foot part (3) and with a piston (13) which can be moved back and forth in the axial direction a piston rod (12) guided outwards through a bore in the head part (2) for connection to a thigh part of a prosthesis and a first space (15) on the head part side bounded by the piston (13) and a second space on the foot part side ( 16), a throttle duct (18, 19, 20) connecting the first and the second space (15, 16) and a slide (21) for adjusting the cross section of the throttle duct as a function of that in the two spaces (15, 16) prevailing pressure.

2. Swing phase control for an artificial knee joint with a cylinder closed at one end with a head part (102) and at its other end with a foot part (103) and with a first piston (113) which can be moved back and forth in the cylinder in the axial direction a first piston rod (112) guided outwards through a bore in the head part (102) for connecting to a thigh part of a prosthesis and a first space (115) on the head part side delimited by the first piston and a second space (116) on the foot part side, with a the throttle channel connecting the first and second spaces (115, 116), the flow resistance of which is adjusted in the axial direction as a function of the position of the piston rod (113).

3. swing phase control for an artificial knee joint with one closed at one end with a head part (102) and at the other end with a foot part (103) Cylinder and a piston (113), which can be moved back and forth in the cylinder in the axial direction, with a piston rod (112) guided outwards through a bore in the head part (102) for connection to a thigh part of a prosthesis and one through the piston (113 ) limited first room at the top

(115) and a foot-side second space (116), the second space (116) having a first region (137) adjoining the piston (113) and one with a throttle channel (152) and a slide with the first region (137) connected second region (138), and the slide adjusts the cross section of the throttle channel (152) depending on the pressure prevailing in both regions.

4. swing phase control for an artificial knee joint according to claim 3, characterized in that the throttle channel (152) is provided in the foot part (103) and as a cylinder section (135) with a first hollow cylinder (134) with a first diameter, in the coaxial a rod (160) with a conically extending end section (153) is provided, is configured and that in the first hollow cylinder (134) a first annular piston (142), which forms the slide, is provided, the outer diameter of which is selected in this way is that the slide can slide in the axial direction in the first hollow cylinder and its inside diameter is larger than the minimum outside diameter of the conically extending end section (163) of the rod (160).

5. swing phase control for an artificial knee joint according to claim 3 or 4, characterized in that the cylinder has an outer cylinder wall (101) that at a distance from the outer cylinder wall (101) an inner cylinder wall (106) to form the second region ( 138) of the second room

(116) is provided, in which a second annular piston (109) is provided, which is pretensioned towards the foot part (103) by a spring (10), and that the piston (113) in the interior of the inner cylinder wall ( 106) of limited cylinder space.

6. swing phase control for an artificial knee joint according to claim 2, characterized in that the throttle channel in the interior of the piston rod (12) is provided.

7. swing phase control for an artificial knee joint according to claim 2, characterized in that as a throttle channel in the piston rod (112), a first bore (118), one end of which extends into the second space (116) and a plurality of bores (148) in the piston rod (112) in the axial cylinder direction are provided one after the other, connecting the first bore (118) with the first space (115) and that the bores (148) are arranged such that the piston rod position tion in the axial direction, in which the first space (115) has its minimum volume, at least one bore (148) is covered by the head part (102).

8. swing phase control for an artificial knee joint according to claim 1, characterized in that the throttle channel is provided in the interior of the piston rod (12) and is designed as a cylinder bore (18) and that the slide (21) comprises a first piston (23) which delimits the throttle duct (18) on one side and a first preload space (27) on its other side, and that the first piston (23) comprises a piston rod (22) and this at a distance from the first Piston (23) carries a second piston (24) which delimits the throttle channel on its side facing the first piston (23) and on its other side a second preload space (28).

9. swing phase control for an artificial knee joint according to one of claims 1, 6 to 8, characterized in that the cylinder comprises an outer cylinder wall (1) that at a distance from this an inner cylinder wall (6) to form an annular chamber (7th ) is provided with a recess (8) for connecting the ring chamber (7) to the first or the second space (15, 16) and the piston (13) in the interior of the inner cylinder wall (6) limited cylinder space slides, and that in the annular chamber (7) is provided with an annular piston (9) spring-biased towards the direction of the recess (8).

10. swing phase control for an artificial knee joint according to one of claims 2, 6, 7, characterized in that the throttle channel (151) as a second cylinder bore (118) in the piston rod (112) with a conical section and a second slide (121) as Hollow cylinder is provided with a tapered end which, with the tapered end, delimits the throttle channel (151) in the conical section of the second cylinder bore (118).