Abstract:
The invention relates to a tilt-stable rotating joint suitable for technical orthopedic components, including a forked external joint part with two limbs whose parallel inner walls pointing towards each other form a slit of a given width and are provided with flush continuous holes. A flat inner joint part protrudes into the slit and a continuous hole, and a shaft arrangement protruding through the continuous holes forms a rotating bearing surface with a cover surface. The tilt-stability is increased because the shaft arrangement is formed by sections protruding from the inner joint part, having an external diameter corresponding to the internal diameter of the continuous holes of the limbs. Stability is also increased by the fact that the shaft arrangement is rotationally fixed to the inner joint part and sliding bearings are formed between the walls of the continuous holes of the limbs and the sections of the shaft arrangement.

Description:
This patent application is the national stage of International Application No. PCT/DE2005/002025, which claims priority to German Application No. 10 2004 054 384.4 filed on Nov. 8, 2004; the entire contents of both applications are hereby expressly incorporated by reference. 
     TECHNICAL FIELD 
     The invention relates to a tilt-stable rotating joint for an orthopedic component. 
     BACKGROUND OF THE INVENTION 
     Tilt-stable rotating joints are needed in a wide variety of applications. The design of a tilt-stable rotating joint is particularly problematic if only a limited space is available for the rotating joint and if, consequently, the rotating joint has to be made especially flat in order not to appear too bulky. 
     Rotating joints of this kind are needed in particular in technical orthopedic components, that is to say in orthoses or prostheses. Since the rotating joints have to satisfy stringent safety requirements, they need to have a high level of stability against tilting and should have no appreciable play outside their rotation plane. 
     Tilt-stable rotating joints of this kind, as are used in particular for orthoses, comprise a flat inner joint piece into whose through-hole a ring made of a sliding metal is pressed. The shaft arrangement is designed in the form of a screwed union, such that the screw sleeve with its smooth cylindrical jacket surface corresponds to the diameter of the ring of sliding metal that is pressed in. Both parts of the screwed union are provided with radially protruding heads that are located, preferably recessed, on the outer face of the branches. To ensure that the screwed union is connected in a rotationally fixed manner to the branches of the fork-shaped outer joint piece, one of the heads and its associated recess in the branch can be made rotationally asymmetrical, with the result that this head is mounted secure against rotation in its recess, and the screwed union therefore only has to be tightened on the other side. 
     SUMMARY OF THE INVENTION 
     The rotary bearing surface of a conventional rotating joint of the type mentioned above is formed by the through-opening in the inner joint piece, such that the tilt stability has to be generated only via an annular bearing surface arising from the material thickness of the inner joint piece. The tilt stability of the rotating joint is obtained from precise manufacture with low production tolerances between the cylindrical jacket surface of the screwed union and the pressed-in ring made of a sliding metal. 
     The object of the present invention is to improve the tilt stability of the rotating joint of the type mentioned at the outset. 
     To achieve this object, a tilt-stable rotating joint of the type mentioned at the outset is characterized in that the shaft arrangement is formed by sections which protrude from the inner joint piece and have an external diameter corresponding to the internal diameter of the through-holes of the branches. In addition, the shaft arrangement is connected in a rotationally fixed manner to the inner joint piece, and slide bearings are formed between the walls of the through-holes of the branches and the sections of the shaft arrangement. 
     The rotary bearing surface of a conventional rotating joint of the type mentioned at the outset is formed by the through-opening in the inner joint piece, such that the tilt stability has to be generated only via an annular bearing surface arising from the material thickness of the inner joint piece. The rotating joint according to the invention comprises includes a rotationally fixed unit between the inner joint piece and the shaft arrangement, such that the joint is supported between the shaft arrangement and the walls of the though-holes of the branches. The support is thus achieved on both cylindrical jacket surfaces of the shaft arrangement in the area of the branches, such that the shaft arrangement is supported according to the invention on two slide bearings spaced apart from one another. This ensures a considerable enlargement of the slide-bearing surface and improved tilt stability. 
     In one embodiment of the invention, annular edges of the through-holes between the inner walls of the branches and the surfaces of the inner joint piece are also designed as slide bearings. The edges of the inner walls are preferably designed as slide bearings and protrude as raised edges from the rest of the respective inner wall, such that a defined annular bearing surface between inner wall and inner joint piece is obtained at the edge of the through-opening. 
     The wall of the through-holes of the branches is preferably formed by in each case an inserted slide-bearing sleeve. As an alternative to this, it is possible also to provide the surface of the screwed union in the sections of greatest external diameter with a slide coating. 
     In one embodiment of the slide-bearing sleeves inserted into the through-holes, these are, in each case, provided with a circular flange that bears on the inner walls of the branches. The inserted sleeves thus form both the radial slide bearings in the walls of the through-holes and also the axial annular slide bearings on the inner walls of the branches 
     The material thickness of the slide-bearing sleeves is preferably less than about 0.039 inches (about 1 mm) and is preferably between about 0.016 and about 0.028 inches (about 0.4 and about 0.7 mm), preferably about 0.020 inches (about 0.5 mm). 
     The slide-bearing sleeves can be pressed into the through-holes of the branches. Other connection techniques, such as adhesive bonding or welding, are also possible. It is also possible to design the surfaces in question as slide bearings by means of a chemical or physical surface modification. 
     In one embodiment of the invention, the shaft arrangement is formed by a screwed union composed of a screw and a screw bushing. The sections protruding from the inner joint pieces can have a greater external diameter, such that the screwed union forms a radially open groove whose diameter at the groove base corresponds to the internal diameter of the through-hole of the inner joint piece. By firmly tightening the screwed union, the rotationally fixed connection between the screwed union and the inner joint piece is obtained 
     The groove of the screwed union is preferably formed by a shoulder in the diameter of both parts of the screwed union. However, it is also conceivable to design only one part of the screwed union with a shoulder and thus form the groove with a groove base in only one part of the screwed union. 
     The depth of the radially open groove can be kept very small and is, for example, about 0.39 inches (about 1 mm) or less. The shoulder thus formed is entirely sufficient for creating the connection of the screwed union to the inner joint piece to form an in practice one-piece joint component. 
     Alternatively to being designed as a screwed union, the shaft arrangement can also be designed with a rivet arrangement which, together with bushings, forms the sections for the rotary bearing surface. 
     Alternatively, it is possible to press a bolt into the through-hole of the inner joint piece, the ends of the bolt protruding from the inner joint piece representing the sections for the rotary bearing surface. 
     Of course, it is possible to achieve the rotationally fixed connection between the shaft arrangement and the inner joint piece in many different ways. All connection techniques are conceivable, such as interlacing, welding, wedging, interference fit, etc. Also, an asymmetrical design of the through-hole and of a bolt, protruding via the through-hole, of the shaft arrangement can also be used. In addition to the inner joint piece the bolt naturally also comprises the circular cylindrical sections whose jacket surface is used to form the slide-bearing surface with the branches of the outer joint piece. 
     It is of course possible to dispense with the above-mentioned use of slide-bearing sleeves if a suitable sliding material is used for the shaft arrangement and the cylindrical inner wall of the through-holes in the branches of the outer joint piece. This can be done through a suitable choice of material and/or through hardening and coating the corresponding surfaces. 
     The fork-shaped outer joint piece does not have to be in one part and instead can be composed of two parts, which can also be held together by the shaft arrangement. Such an arrangement is useful when two inner joint pieces are designed with a toothed contour and mesh with one another. The inner joint pieces are both held in an outer joint piece composed of two cover-like parts which are arranged on both sides of the inner joint piece and form the branches of the fork-shaped outer joint piece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For production engineering reasons, the rotary bearing surfaces of the shaft arrangement, which form the rotary bearing together with corresponding through-holes in the branches of the outer joint piece, are preferably cylindrical. With conical rotary bearing surfaces and through-holes, for example, still greater tilt stability could be achieved, albeit with greater complexity of production. 
       The invention will be explained in more detail below on the basis of illustrative embodiments depicted in the drawing, in which: 
         FIG. 1  shows an exploded perspective view of the parts of a first embodiment of a rotating joint according to the invention, 
         FIG. 2  shows an exploded view according to  FIG. 1  with an assembled inner joint piece, 
         FIG. 3  shows a cross section through the assembled rotating joint, 
         FIG. 4  shows a side view of the assembled rotating joint, 
         FIG. 5  shows a front view of the assembled rotating joint, 
         FIG. 6  shows another side view of the assembled rotating joint, 
         FIG. 7  shows a perspective view of the assembled rotating joint, 
         FIG. 8  shows an exploded perspective view of parts of a second embodiment of a rotating joint according to the invention, 
         FIG. 9  shows a perspective view illustrating the unit formed by the inner joint piece and the shaft arrangement, 
         FIG. 10  shows a perspective view of the assembled rotating joint according to the second embodiment, 
         FIG. 11  shows an exploded perspective view of parts of a third embodiment of a rotating joint according to the invention, 
         FIG. 12  shows a perspective view illustrating the unit formed by the shaft arrangement and the inner joint piece, 
         FIG. 13  shows a perspective view of the assembled rotating joint according to the third embodiment, 
         FIG. 14  shows an exploded perspective view of the parts of a fourth embodiment of a rotating joint according to the invention, 
         FIG. 15  shows a perspective view illustrating the design of a rotationally fixed unit made up of shaft arrangement and inner joint piece, 
         FIG. 16  shows a perspective view of the assembled rotating joint according to the fourth embodiment, 
         FIG. 17  shows an exploded perspective view of the parts of a fifth embodiment of a rotating joint according to the invention that is made up of two meshing inner joint pieces and of a common outer joint piece, 
         FIG. 18  shows a perspective view of the assembled rotating joint according to the fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The first illustrative embodiment of a rotating joint according to the invention, shown in  FIGS. 1 to 7 , has an outer joint piece  1  and an inner joint piece  2 . The outer joint piece  1  is fork-shaped at one end and has two branches  3  with parallel inner walls  4  that face each other and form a slit  5  of a predetermined constant width. In the area of the slit  5 , the branches  3  are provided with circular through-holes  6  that are the same size on both branches  3  and are aligned with one another. A slide-bearing sleeve  7  can be inserted into the through-holes  6 , in each case from the slit direction, that is, from inside the slit  5  outward, and extends with a cylindrical bushing part  8  across the width of the branch  3 , that is to say across the entire length of the through-hole  6 . The slide-bearing sleeve  7  also has a circular flange  9  that thus bears on the inner wall  4  of the associated branch  3 . 
     The inner joint piece  2  is formed by a flat rail piece, which can have a shape suited for the particular application. In the illustrative embodiment shown, the inner joint piece  2  is designed as a lower ankle-joint piece with two arms  10 ,  11  bent off in opposite directions. The inner joint piece  2  can have any desired shape, for example, the shape of a rectangular holding rail. The inner joint piece  2  is made of a flat material whose material thickness at one end is such that the inner joint piece  2  can be fitted with this end into the slit  5  of the outer joint piece  1 . At this end, the inner joint piece  2  has a through-hole  12  which, in the illustrative embodiment shown, has a circular shape and has a radius that is about 0.039 inches (about 1 mm) smaller than the through-holes  6  of the branches  3  of the outer joint piece  1 . 
     The through-hole  12  is accessible via the through-holes  6  and is fixed relative to the outer joint piece  1  by a shaft arrangement  15 . This is a screwed union made up of a screw  13  and of a screw bushing  14 . 
     The screw  13  is composed of a cylindrical screw head  16  that is provided integrally with a threaded pin  17 . The external diameter of the cylindrical screw head  16 , is substantially similar to the internal diameter of the cylindrical bushing part  8  of the slide-bearing sleeve  7 , such that the slide-bearing sleeve  7  forms a rotary bearing surface with the screw head  16 . The screw head  16  also has a small shoulder  18 , which is formed by a reduction in diameter and as a result of which the screw head  16  has a section  19  whose external diameter corresponds to the internal diameter of the through-hole  12  of the inner joint piece  2 . 
     Similarly, the screw bushing  14  includes a through-opening  20 , with an inner thread for receiving the threaded pin  17 , and an outer cylindrical jacket surface  50  whose external diameter is substantially similar to the internal diameter of the slide-bearing sleeve  7 . The width of the cylindrical jacket surface  50  is substantially similar to the width of the cylindrical bushing part  8  of the slide-bearing sleeve  7 . Adjoining it, the cylindrical jacket surface  50  is provided with a shoulder  21 , which is formed by a cylindrical section  22  with a slightly reduced diameter. The external diameter of the cylindrical section  22  is substantially similar to the internal diameter of the through-hole  12 . 
       FIG. 2  illustrates that the screwed union shaft arrangement  15  forms a functionally uniform part with the inner joint piece  2 . However, this can only be put together upon assembly of the rotating joint and cannot be preassembled in the manner shown in  FIG. 2 . 
     At its end remote from the through-holes  6 , the outer joint piece  1  is provided with a rectangular recess  23  forming a chamber that is open toward the wide side and toward the end face and into which the end-piece of a rectangular flat rail can be inserted. The recess is delimited by a rear wall  24 , in which there are two through-holes  25  for screwed fastening of the flat rail inserted into the recess  23 . 
       FIG. 3  shows a vertical section through the rotating joint assembled from the parts shown in  FIG. 1 . It will be seen that the inner joint piece  2  is held in a groove  26  of the screwed union  15 . This groove  26  is formed by the shoulders  18 ,  21  and by the adjoining sections  19 ,  22  of the screw head  16  and of the screw bushing  14 . 
     At their axial end faces, the screw head  16  and the screw bushing  14  each have two diametrically opposite blind holes  27  that allow the screw  13  and the screw bushing  14  to be rotated by means of a suitable tool. 
     The inner joint piece  2  is mounted radially with an exact fit in the groove  26  of the screwed union  15  and bears axially on the flange  9  of the slide-bearing sleeve  7 . The screwed union  15  for its part, lies with the cylindrical outer faces of screw head  16  and screw bushing  14  on the cylindrical bushing parts  8  of the slide-bearing sleeve  7 . As a result, the actual rotary bearing is formed for the rotation movement of the inner joint piece  2  relative to the outer joint piece  1 . During the rotation movement, a relative movement of the inner joint piece  2  with respect to the screwed union  15  will not generally take place. The connection between inner joint piece  2  and screwed union  15  can be rotationally fixed by a form-fit engagement, which can be formed, for example, by a square hole in the inner joint piece  2  and a corresponding design of the shoulders  19 ,  21  of the screwed union  15 . In this case, the screwed union  15  has to be supplemented by an additional screw. 
     Whereas in conventional rotary bearings of this kind the rotary bearing is formed on the inner wall of the through-hole  12  of the inner joint piece  2  relative to a cylindrical screwed union and can therefore be supported against tilting movements only via the material thickness of the inner joint piece  2 , In the first embodiment of the rotating joint according to the invention shown here, the support for the rotation movement takes place on the two bushing parts  8  of the slide-bearing sleeve  7  and thus extends along the length of the screwed union  15  and the total thickness of the outer joint piece  1  with the two branches  3 , thus ensuring considerably increased stability against tilting 
       FIG. 4  shows a side view of the assembled rotating joint from the side on which the recess  23  and the screw bushing  14  are located. The free end of the threaded pin  17  can be seen in the screw bushing  14 . 
       FIG. 5  shows a front view of the assembled rotating joint. It can be seen that the rotating joint can be formed with a very narrow structure which, when used as an orthotic joint for example, does not look bulky on supported limbs of a human body. 
       FIG. 6  shows a side view of that side of the assembled rotating joint on which the screw head  16  is located. 
       FIG. 7  illustrates the assembled rotating joint according to the first embodiment in a perspective view. 
       FIGS. 8 to 10  show a second embodiment of a rotating joint according to the invention. This differs from the first embodiment only in terms of another design of the shaft arrangement  15 . In this embodiment, it is formed by a rivet  28  and two bushings  29 ,  30 , which protrude with shoulders  31  of slightly reduced external diameter into the through-hole  12  of the inner joint piece  2 . As a result, they form sections with a greater external diameter which, together with the slide-bearing sleeves  7 , form the slide bearing between the outer joint piece  1  and the inner joint piece  2 . 
       FIG. 9  shows that the two bushings  29 ,  30  are held together by the rivet  28  and are pressed against the material of the inner joint piece  2 , such that a rotationally fixed connection exists between the bushings  29 ,  30  and the inner joint piece  2 . The view in  FIG. 9  is unrealistic and for illustrative purposes only, because the bushings can be secured on the inner joint piece  2  by means of the rivet  28  only when the inner joint piece  2  has been inserted with an exact fit into the outer joint piece  1 . Therefore, the view in  FIG. 9  serves only to explain how the bushings  29 ,  30  are secured on the inner joint piece  2  in the assembled state, as is shown in  FIG. 10   
     In the third embodiment of a rotating joint according to the invention, shown in  FIGS. 11 to 13 , the shaft arrangement  15  is formed by a bolt  32  which is dimensioned such that it is held in the through-opening  12  of the inner joint piece  2  by an interference fit. As is illustrated in  FIG. 12 , sections of the bolt  32  protrude from both sides of the inner joint piece  2  and, together with the slide-bearing sleeves  7  fitted into the through-holes  6  in the branches  3  of the outer joint piece  1 , form the slide bearing shown in the assembled state in  FIG. 13 . 
     The fourth embodiment of the invention, shown in  FIGS. 14 to 16 , corresponds to the first embodiment of  FIGS. 1 to 7 , but without the slide-bearing sleeves  7 . The screw head  16  and the threaded pin  17  and the inner wall of the through-holes  6  in the branches  3  of the outer joint piece  1  are designed as slide bearings, which is made possible by a choice of a suitable material or by a surface treatment of the slide-bearing surfaces 
     The fifth embodiment of a rotating joint according to the invention, shown in  FIGS. 17 and 18 , is composed of two inner joint pieces  2 ′, and of an outer joint piece  1 ′ that is composed of two individual parts forming the branches  3 ′. The outer joint piece  1 ′ is thus common to both inner joint pieces  2 ′. Accordingly, the branches  3 ′ of the outer joint piece  1 ′ have two through-holes  6  that are each aligned with a through-hole  12  of one of the inner joint pieces  2 ′. 
     Accordingly, the rotating joint is formed by two shaft arrangements  15  which, as in the described fourth embodiment, are composed of a screwed union formed by a screw  13  and screw bushing  14 . In this embodiment too, the use of slide-bearing sleeves  7  can be dispensed with by virtue of a suitable choice of material or a suitable design. 
     Between the shaft arrangements  15 , the two inner joint pieces  2 ′ abut one another via respective outer toothed formations  33  that mesh with one another. In this way, the rotation movements of the two inner joint pieces  2 ′ relative to the outer joint piece  1 ′ are synchronized, which is useful for the design of a knee joint, for example for an orthosis. The shape of the inner joint piece  2 ′ is adapted for this purpose. 
     Without any additional complexity, the rotating joint according to the invention permits increased tilt stability together with a narrow structure of the rotating joint.