Orthopedic damping device

An orthopedic damping device with a movably mounted piston and at least one chamber which has a wall and in which a compressible medium is compressed by moving the piston in a first direction and decompressed by moving the piston in an opposite second direction. The chamber is connected to a discharge channel. A closure element is paired with the discharge channel. The closure element is movably mounted on a support. The support is coupled to the piston or is designed as a piston. The closure element is coupled to a contact region which can be moved relative to the support.

TECHNICAL FIELD

The invention relates to an orthopedic damping device with a movably mounted piston and at least one chamber which has a wall and in which a compressible medium is compressed by moving the piston in a first direction and decompressed by moving the piston in an opposite, second direction.

BACKGROUND

The orthopedic damping device can be used in particular in orthotic joints or prosthetic knee joints, but can also be used in principle in order to improve the behavior of pneumatic dampers.

With use of orthopedic damping devices that use a compressible medium, the medium is compressed in a compression chamber by reducing the chamber volume by means of a piston. The piston can be formed both as a linearly displaceable piston and as a rotary piston. If the force exerted onto the piston is reduced, for example in the event of a movement reversal, the compressed medium, for example air, is decompressed and exerts a restoring force. In the case of prosthetic or orthotic joints, this may lead to a catapult effect of a joint component, for example in the case of a lower leg component, which is disadvantageous in particular at high movement speeds.

SUMMARY

The object of the present invention is to provide an orthopedic damping device with which an improved adaptability of the expansion behavior and in particular of the extension behavior can be achieved.

This object is achieved in accordance with the invention by an orthopedic damping device having the features of the main claim. Advantageous embodiments and developments of the invention are disclosed in the dependent claims, the description, and the drawings.

In the orthopedic damping device according to the invention with a movably mounted piston and at least one chamber which has a wall and in which a compressible medium is compressed by moving the piston in one direction and decompressed by moving the piston in an opposite, second direction, the chamber is connected to an outlet channel, the outlet channel is assigned a closure element, the closure element is movably mounted on a support, the support is coupled to the piston or is formed as a piston, and the closure element is coupled to a contact region which can be moved relative to the support. As a result of this embodiment it is possible to provide a position-independent and direction-controlled venting of the chamber and to release the outlet channel at the moment when there is no longer any compression of the medium and the medium should be decompressed. Due to the position-independent and direction-controlled venting at the moment of reversal, for example from a flexion to an extension, it is possible on the one hand to utilize the damping and cushioning effect by the compression of the medium in the chamber and on the other hand to prevent a restoring movement from being forced by the pressure on the piston or to prevent the restoring tendency from being reduced. In preferred embodiments the support serves as an actuation element for the closure element. If reference is made hereinafter to a damping device, this is an orthopedic damping device, in particular for orthotic joints or prosthetic joints, in particular for knee joints. The support can be formed as a piston, piston rod, cylinder wall, chamber wall in a blocking element, or as a blocking element.

In accordance with a development the contact region to which the closure element is coupled is the wall of the chamber or the wall of a blocking element, which wall is arranged in the chamber or in a region coupled in terms of force or movement.

The piston may be formed as a rotary piston or cylindrical piston having a linear, reciprocal movement path.

The outlet channel may lead into the surrounding atmosphere or into a second chamber. In the embodiment with two chambers it is possible for the outlet channel to lead into the oppositely acting chambers, these being the flexion chamber and the extension chamber in the case of a joint device.

A sound damper may be arranged in or on the outlet channel in order to reduce the noise of the escaping medium. This is advantageous in particular in the case of orthotics or prosthetics in order to minimize the ejection noise for the user of the damping device and the surrounding environment.

The closure element can be mounted frictionally and slidingly on the contact region, such that the switchover of the closure element from the closed state to the open state can be performed by a frictional force.

The outlet channel can be guided through the piston itself, whereby a solution of simple design is provided.

The closure element can be resiliently pre-loaded against the contact region, whereby it is possible for a uniform contact force to be present in the contact region. The closure element is therefore self-adjusting, wherein a tensioning element can be provided, via which the frictional force of the closure element can be adjusted.

The closure element can be formed as a piston ring and can be mounted in a piston ring groove, such that the compression of the compressible medium, in particular air, is ensured in one direction, and in the other movement direction, due to the provision of a sufficient play and an outlet channel, the compressed air can escape through the outlet channel in the event of a reverse movement of the piston.

The closure element may also be mounted on a piston rod and in a blocking element surrounding the piston rod. The blocking element may be arranged within the cylinder, in which the piston is guided. The blocking element may delimit the respective chambers and may be arranged fixedly in the housing or the cylinder. The blocking element may also take on the function of the support. In the closing state, the closure element may bear against a seal surrounding the outlet channel, wherein the seal may be formed as an O-ring, which is arranged around the outlet channel and protrudes slightly beyond said channel, such that an airtight closure of the outlet channel is provided by the abutment of the closure element against the seal.

A second chamber can be arranged on the side of the piston opposite the first chamber, in which second chamber the compressible medium is compressed. In the event of an embodiment of this type, a double-acting piston is provided, which can be used to damp both the extension and flexion movement or the movement in a first and in a second direction. Depending on the orientation of the outlet channel and the closure element, the restoring force can be adjusted in each case by the expanding medium. It is also possible for both chambers to be coupled to an outlet channel and a closure element for direction-controlled venting of the respective chamber.

The blocking element can be mounted in a stationary manner in a housing forming the chambers, and it is possible by way of example for the blocking element to separate the first chamber from a double-acting damping cylinder, such that at least three chambers are formed on the whole, of which two are arranged on the other side of the blocking element.

The closure element can be coupled to the piston via a switching element, such that there is no need for a direct assignment of the closure element to the piston or the contact region.

The closure element and/or the outlet channel can be adjustably mounted or formed so as to be able to adjust the degree of maximum venting. Due to the adjustable embodiment, the closure element may also be completely deactivated if there is no desire for rapid venting.

In accordance with a development of the invention the chamber tapers conically in the direction of an end position of the piston. As a result of the tapering, the distance between the closure element and the cylinder wall or the chamber is reduced in the region of the end position, such that there is improved contact between the closure element and the chamber wall when the contact region is part of the chamber wall. Here, a comparatively small conicity is sufficient to obtain an improvement of the response behavior of the closure element. The embodiment of a conically tapering chamber can be provided by rolling, whereby a smoothing and strain hardening of the surface of the chamber are achieved in addition. The conicity can be provided over the entire length of the chamber or also only over a certain part. The cone angle may be between 0.2° and 1°, preferably 0.5°. Alternatively to a conical tapering of a chamber or a cylinder bore in the end region of the piston movement, it is also possible and is provided, in an embodiment of the support as piston rod, for this piston rod to have a widening, i.e. diameter increase, in the region of the end position. If the closure element or the switching element bears against the piston rod externally, the pressure and thus the frictional force increase in the region of the widening, which leads to a secure switching arrangement. The widening may also change in a constant manner over the entire path of relative displacement between support and switching or closure element or only in portions, such that an enlargement is provided only in certain portions.

The support can be arranged in a stationary manner inside the chamber and may thus cause a chamber division. The piston rod may pass through the support or a chamber delimitation.

The second chamber, which is fluidically connected to the first chamber, is advantageously formed as an open chamber and has a lower internal pressure compared with the first chamber when the first chamber is compressed. A counter pressure going beyond the ambient pressure is not established in the second chamber. It is thus possible that an undesirable spring effect, for example at the end of a flexion movement, will occur across the damping device on account of the enclosed air volumes. Rather, in the event of a minor return movement, i.e. extension, the outlet opening of the outlet channel is opened by the closure element, such that the overpressure prevailing in the first chamber is relieved and a spring-back effect is avoided. Ambient pressure preferably prevails in the second chamber.

DETAILED DESCRIPTION

FIG. 1shows a schematic sectional illustration of a damping device having a housing100, in which two pistons10are arranged so as to be longitudinally movable. The pistons10are interconnected by a piston rod80and, together with the housing and a support50, form two first chambers20, in which the medium disposed therein, for example air, is compressed in the event of a downwardly directed movement. Between the lower piston10and the lower edge of the support50, there is formed a second chamber22, which is likewise filled with the compressible medium, wherein in the event of a movement in the opposite direction, i.e. in the event of a movement of the lower piston10in the direction of the support50, the medium is compressed. The damping device can be used for example in prosthetics and orthotics, for example in prosthetic knee joints or orthotic knee joints, wherein, in accordance with the preferred situation of installation, on account of the high forces occurring, the two first chambers20counteract a flexion in the case of a knee joint, whereas the second chamber22counteracts an extension. Accordingly, the first chambers20can be referred to as flexion chambers and the second chamber22can be referred to as an extension chamber.

The piston rod80is guided through the support50, and seals90bear against the piston rod80, such that a substantial gastight termination is provided and no medium can flow from the upper flexion chamber20into the extension chamber22through the support50. Seals (not illustrated) are arranged on the piston10that likewise prevent the compressed medium from flowing past along the outer wall. An unwanted passage of gas from the flexion chamber20into the extension chamber or into the surrounding environment is therefore impossible. Provided an upper-side termination is provided, a second extension chamber22can be formed above the upper piston10.

The lower piston10and the piston rod80are provided with a connection channel85, such that the lower flexion chamber20and the upper flexion chamber20are fluidically connected to one another. An actuator chamber55is formed inside the support50and can be embodied as an annular space, in which a switching element75is arranged. The switching element75is mounted frictionally on the piston rod80via a sliding and friction element78, which can be formed as an O-ring, for example. The actuator chamber55is dimensioned such that the switching element75can be moved over a certain switching path. The switching path is indicated by the double-headed arrow.

A closure element40in the form of a switching valve is arranged inside the support50and is connected to the actuator chamber55via an outlet channel30. When the closure element40is open, air can pass from the flexion chamber20into the actuator chamber55and from there can escape into the surrounding environment through a sound damper35via a further outlet channel30. The damping device according toFIG. 1compresses the compressible medium in the event of a downward movement of the piston10due to the reduction of the chamber volumes of the flexion chambers20, wherein, on account of the connection channel85, a pressure compensation is implemented between both flexion chambers20. On account of the orientation of the closure element40in the form of a check valve, no air can escape from the upper flexion chamber20through the outlet channel30. On account of the friction between the switching element75and the piston rod80, for example on account of the O-ring seal78, the switching element75is slid against the lower delimitation of the actuator chamber55, wherein a possible coupling of the switching element75to the closure element40is disengaged. On account of the high compression within the flexion chambers20, in the event of a movement reversal of the joint, i.e. in the event of an extension, the involved joint components tend to spring forward or tend to extend very quickly and provide movement support, which may lead to an unwanted course of movement. In the event of a movement reversal of the piston10and therefore also of the piston rod80, the switching element75is also moved in the direction of the extension movement, which is indicated by the double-headed arrow. In the event of an upward movement of the switching element75, the check valve or closure element40is opened via an actuation element, for example a pin, such that the compressible medium inside the flexion chambers20escapes from the outlet channels30into the surrounding environment through the sound damper35. The closure element40is held open as long as the switching element75is in the switching position, for example at the upper end of the actuator chamber55. In the event of a renewed movement reversal, i.e. an additional flexion, the switching element75is disengaged from the closure element40, and the chamber volumes within the flexion chambers20are closed again, such that an effective flexion damping can be achieved on account of the pneumatic compression.

The switching element75is thus coupled to the closure element40via a contact region60, which corresponds substantially to the length of the stroke of the piston rod80.

The switching element75, in the exemplary embodiment shown inFIG. 1, presses against a tappet37, which inFIG. 1projects into the actuator chamber55from above. The tappet37is movably mounted and, as the switching element75is raised, is displaced into the support50and in this way opens the closure element40.

A variant of the invention is illustrated inFIG. 2, in which a detailed view of the damping device is shown. The piston10is mounted inside the housing100so as to be movable back and forth along a cylinder wall15. A piston ring groove14is formed on the piston periphery, in which groove a piston ring is arranged as closure element40. The piston ring groove14has an oversize relative to the width of the piston ring, such that the piston ring40as closure element has a slight play in the direction of movement of the piston10. The possibility of relative movement is indicated by the double-headed arrow. A small amount of play is provided between the outer periphery of the piston10and the wall15of the cylinder and has been illustrated in an exaggerated manner inFIG. 2. The piston ring40widens radially outwardly and bears movably against the wall15. The wall15at the same time forms the contact region between the closure element40and the piston10, which is in turn formed as a support for the closure element40. An outlet channel30is formed inside the piston10and is oriented substantially perpendicularly to the wall14of the cylinder. A seal34, for example in the form of an O-ring, is arranged around the opening of the outlet channel30in the region of the groove wall oriented perpendicularly to the wall15. In the event of an upward movement of the piston10, the piston ring40will be pressed within the piston ring groove14in the direction of the side wall opposite the seal34on account of the friction, such that a gap between the chamber20and the outlet channel30is opened. A compressible medium can pass through between the wall15, the piston outer diameter10and the gap between the piston ring40and the groove14, into the outlet channel30and from there can escape into the surrounding environment, for example via a piston rod. In the event of a movement reversal, when a flexion movement is introduced, the piston10is moved downwardly, and on account of the friction of the piston ring40this component acting as closure element is pressed against the seal34, such that the outlet channel30is closed. During the flexion movement, the flexion chamber20remains closed, such that the medium is compressed. On account of the construction, it is possible to achieve a load-independent, direction-controlled venting of the flexion chamber20or flexion chambers20.

A piston10with the piston ring40at the outer periphery is illustrated inFIG. 3. The piston ring is inserted in the piston ring groove14, and a further ring seal17is arranged above the piston ring in order to seal off the flexion chamber with respect to unwanted venting. Two sound dampers35for outlet channels are provided in the region of the piston rod receptacle.

The piston10is shown inFIG. 4in a partially transparent illustration. The upper ring seal17has been removed, and the piston ring40is inserted as closure element in the groove. It can be seen that the outlet channels30are formed within the piston10via transverse bores, which are guided radially inwardly. The outlet channels30are closed by stoppers32. The seal34on the upper side wall of the piston ring groove can be seen inside the groove14. The air from the flexion chamber passes via the outlet channels30through the sound dampers35into the surrounding atmosphere. A tensioning element45for the closure element40is arranged opposite the seal34, with which tensioning element it is possible to achieve and maintain a radial pre-load, such that a constant pressing force is ensured over a long period of time.

FIG. 5shows the piston10in a partially transparent illustration without ring seal17and without closure element40. The piston ring groove14can also be seen, as can the recess, arranged thereabove, for the ring seal17. A bore can be seen inside the piston ring groove14in the lower side wall, which bore is provided for manufacturing reasons in order to achieve the right-angled channel guidance of the outlet channels30and the connection to an opening in one of the side walls of the piston ring groove14. The outlet channels30are shown dark in the illustration.

InFIG. 6the piston10is shown in a sectional illustration, on the basis of which the closure element40and the seal34around the bore opening in a side wall of the piston ring groove14can be seen. The stopper32closes the outlet channel30radially outwardly, and the transverse bore formed within the outlet channel30leads to the sound damper35and discharges the compressed air into the surrounding environment in the event of a direction reversal of the piston10. The tensioning element45in the region of the outer wall of the piston10for radial widening of the closure element40is likewise shown. The tensioning element45may be assigned an adjustment element46, with which it is possible to adjust the tensioning element45. Alternatively or additionally, the adjustment element46may also be used as a positioning aid, by means of which the tensioning element45is secured with respect to a rotation about the cylinder longitudinal axis. Here, the adjustment element46can be formed as a separate component, which is arranged in the indentation or the slot provided for this purpose and engages with a recess or indentation on the tensioning element45and thus prevents a rotation. Alternatively, the adjustment element46can also be fixedly connected to the tensioning element45and can engage with the indentation, bore or recess in order to prevent the rotation of the tensioning element45.

The piston according toFIGS. 3 to 6is illustrated inFIG. 7as an upper termination of a damping device having a housing100. The piston10is moved by way of example via a thrust rod, which is connected to an upper joint component, along the longitudinal extension of the piston rod80in the cylinder of the housing100. If the piston10is moved together with the piston rod80downwardly, i.e. in the direction of the support50, the air inside the flexion chamber20will be compressed. On account of the friction of the closure element40at the outer wall of the cylinder, the closure element is moved in the direction of the seal34, the outlet channels30are closed, and no air can escape from the sound damper35into the surrounding environment. The ring seal17offers an additional sealing of the flexion chamber20. If a reverse movement is introduced, i.e. an extension, the piston10moves upwardly, the closure element40is pressed in the direction of the lower piston ring groove wall, and the channel30is opened. Air can flow from the flexion chamber20through the bores within the piston, past the seal34, into the surrounding environment. The extension chamber likewise has an outlet channel130and a sound damper135, via which air can be discharged from the extension chamber22into the surrounding environment during the extension movement, and it is also possible for air from the surrounding environment or from the extension chamber22to pass in a controlled manner into the flexion chamber20via an overflow valve150, for example when the flexion chamber20has been completely vented in the case of an interruption of the extension movement and in addition an extension takes place in order to prevent a negative pressure from forming within the flexion chamber20. A separate outlet channel140is for this purpose arranged between the flexion chamber20and extension chamber22, in which separate outlet channel an additional sound damper145(not visible inFIG. 7) can be positioned. The overflow valve150is advantageously likewise formed as a check valve. Air is also guided from the flexion chamber20into the extension chamber22when the flexion chambers20are to be vented and where appropriate the extension chambers22are to be aerated.

FIG. 8, in a detailed view, shows the position of the closure element40during the flexion movement. It can be clearly seen that the closure element40bears in the form of the piston ring against the seal34and terminates the outlet channel30in a sealing manner.

FIG. 9shows the position of the closure element40during an extension movement, it being possible to see a gap between the closure element40and the upper piston ring groove wall, whereby the permeability from the flexion chamber to the outlet channel30is ensured.

FIG. 10, in a sectional illustration, shows the tensioning element45with the adjustment element46, which causes the piston ring40or the closure element to be pressed against the cylinder wall. The frictional force between the closure element40and the contact region, i.e. the cylinder wall of the damping device, can be controlled via the tensioning element45and the adjustment element46. The greater the pre-load and radial widening of the closure element is, the greater the friction is and the more exactly and precisely the closure element responds to a direction reversal. In addition to the friction adjustment, a compensation of wear is also achieved via the tensioning element45.

As already discussed, the adjustment element46can also be provided in a non-adjustable embodiment. In this case it serves merely as a positioning element, by means of which a rotation of the tensioning element45about the longitudinal axis of the piston80is prevented.

FIG. 11shows a sectional illustration of the complete damping device, in which two flexion chambers20and an extension chamber22are arranged. The two flexion chambers20are fluidically coupled to one another via the piston rod80and the connection channel85. The structure of the piston10, which closes the upper flexion chamber20, is shown in detail inFIGS. 12 and 13and corresponds substantially to the structure according toFIGS. 3 to 10. In the event of a downward movement of the piston10in the direction of the lower chamber delimitation, the air in both flexion chambers20is compressed, and at the same time the outlet channel30is closed by the closure element40. In the event of the reverse movement, the closure element40remains stuck against the cylinder wall on account of the friction, until the lower side wall of the piston ring groove14slides the closure element40upwardly. Due to the movement within the piston ring groove14, the outlet channel30is opened and compressed air can escape past the closure element, through the outlet channel30and the sound damper35, into the surrounding environment. An uncontrolled escape is prevented by the upper ring seal17.

The structure of the piston10is shown inFIG. 12in an enlarged sectional illustration. The piston10is located in the extension position, i.e. the closure element40does not bear against the ring seal34, such that air from the flexion chamber20can flow past the piston ring40, for example in the region of the bore36for the outlet channel30, in the upper piston ring groove side wall into the outlet channel30. The air passes from the outlet channel30into the surrounding environment via the sound damper35.

FIG. 13shows the detailed illustration according toFIG. 12in the flexion position, in which the closure element40bears sealingly against the ring seal34, the outlet channel30is closed with respect to the flexion chamber20, and the damping device can compress the air in the flexion chamber as desired.

FIG. 14shows a perspective enlarged illustration of the piston10with the ring seal17with the closure element40and the widening tensioning element45.

In the previous exemplary embodiments the upper flexion chamber20was always vented. Of course, it is also conceivable to vent the lower flexion chamber20additionally or alternatively. In this case the outlet channel30is guided as a second bore through the piston rod80, such that a venting into the atmosphere is made possible in this way. Of course, an extension chamber can also be vented in a similar manner.

In particular, the closure element40can also be positioned better and more reliably by means of the tensioning element45. In accordance with a specific embodiment a tensioning element45with oval cross section is to be inserted into an oval recess provided for this purpose in the region of the piston ring slot.

In this way, not only a rotation, but also a torsion of the piston ring is prevented.

InFIG. 15a variant ofFIG. 11is illustrated, on the basis of which it is shown in an exemplary manner that the chamber20or the cylinder, in which the piston10is moved in a longitudinally displaceable manner, has a conical widening upwardly in the illustrated exemplary embodiment, such that, in the event of a flexion movement of a prosthetic knee joint, the gap always provided between the piston10and the chamber wall becomes increasingly smaller. In the illustrated exemplary embodiment the cone angle α is approximately 1°, however the conicity may deviate from this in principle. The cone angle α is dimensioned such that both at the upper and the lower reversal point of the piston movement, a displaceability within the chamber20is provided and a sufficient sealing via the ring seal is ensured. The closure element40slides along the inner side of the chamber20and is pressed against the chamber wall by the radially acting tensioning element45. With increasing flexion and a movement of the piston10downwardly, the pressure of the closure element40on the inner wall increases on account of the reducing gap between the piston10and the chamber inner wall, which leads to an increased friction, and therefore an improved switching capacity of the closure element in the end region of the stroke is provided. As soon as a movement reversal takes place, the closure element40sticks better to the chamber wall on account of the higher pressing force, such that the outlet channel30opens reliably. Besides the illustrated steady conical tapering in the flexion direction, i.e. in the direction of the lower reversal point, it is also possible to generate different pressing force levels by means of a stepped conical embodiment. It is thus possible, in the upper region, i.e. in the region of the maximum extension, to provide a cylindrical or practically cylindrical embodiment of the chamber20, whereas an increasing tapering or an enlargement of the cone angle α is provided approximately from the middle of the stroke movement, on the one hand in order to ensure an easy movability in the event of a small flexion, and on the other hand to ensure an improved switching reliability in the event of a high flexion or maximum flexion. In a variant according toFIG. 1the piston rod80is provided with different diameters, wherein the piston rod80has a cross section becoming larger upwardly, preferably a conical enlargement, such that the switching element75, with an increasing flexion of the joint and a movement of the piston10downwardly, bears against the piston rod80externally with an increasing stress. The conical widening of the piston rod80can be formed only in some regions, preferably in the region of the end position of the piston10, and the widening also does not have to be formed with a constant gradient, and instead the conicity can change over the movement range.

InFIG. 15it can be seen that the piston rod80passes through the blocking element separating the two chambers20from one another. The lower chamber20is fluidically connected to the upper chamber20via a longitudinal bore and a transverse bore in the piston rod80, such that a venting of the upper chamber20into the second chamber22or the free surrounding environment simultaneously also causes a venting of the lower chamber20. The spring-back effect at the end of the flexion phase is prevented due to the venting with pressure relief.

Due to the opening in the outlet channel it is possible in the event of a movement reversal to transfer the overpressure in the first chamber20into the surrounding environment or into a second chamber22, such that the air compressed during the flexion is discharged into the surrounding atmosphere, such that a complete pressure compensation takes place.