Abstract:
A coupling, for example, for an orthotic brace has a cam member with a first planar bearing face journalled for rotation on a planar bearing surface of a first coupling portion, and a second planar bearing face inclined to the first face and journalled to rotate relative to a planar bearing surface of a second coupling portion. A clamping device urges the faces and surfaces together to exert a frictional reaction retaining the cam member in a selected rotational position and retains the coupling portions rigidly opposed towards the cam member.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a coupling and more particularly although not exclusively to a coupling for use in an orthotic brace, for example, a hip, is shoulder, wrist or ankle brace. 
     BACKGROUND OF THE INVENTION 
     Known couplings of which the applicants are aware have not been as strong and rigid or as durable as may be considered desirable. For example, known ball and socket couplings that rely on set screws engaging the surface of the ball to locate the portions of the coupling are prone to slippage under bending stress, while the set screws deform and pit the surface of the ball and ultimately render it unserviceable. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention provides a coupling comprising first and second portions each comprising a planar bearing surface, a cam member having a first planar bearing face bearing rotationally on the planar bearing surface of the first portion and journalled thereto through a first journal bearing resisting lateral slippage, a second planar bearing face disposed in a plane inclined to the plane of the first bearing face and bearing rotationally toward the planar bearing surfaces of the second portion and journalled thereto through a second journal bearing resisting lateral slippage, and a clamping device urging said bearing surface toward said bearing faces of the cam member and generating a frictional reaction retaining each bearing surface in a selected rotational position with respect to the cam member. 
     Since the compressive forces are transmitted through opposing planar faces, great compressive stress can be applied and hence high frictional forces generated without permanently deforming the coupling elements. This provides a coupling of greatly improved strength characteristics. Further, the wedge-like cam member together with the slippage resistant journal bearings provide in effect a monolithic body in the clamped condition of the coupling, so as to provide a coupling with excellent rigidity and resistance to bending. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings 
     FIG. 1 shows an example of a brace incorporating a coupling in accordance with the invention. 
     FIG. 2 is an isometric view of the coupling in disassembled or exploded condition. 
     FIGS. 3 to  8  show isometric or side views of elements of the coupling. 
     FIG. 9 is a partially schematic side view partially in section of the coupling in assembled condition. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the accompanying drawings, FIG. 1 shows an example of a brace in accordance with the invention, and, more specifically, a hip abductor brace  10 , comprising a first generally channel shaped rigid brace portion  11  adapted to be applied to the rear of the hips of the patient and to be secured to the patient by straps  12 . Typically the straps  12  may be provided with hook and loop type fasteners (trademark VELCRO) for fastening them together. The brace  10  further comprises two rigid generally channel shaped second brace portions  13  adapted to be applied to the thighs of the patient and similarly provided with straps  14  for securing the brace portions  13  to the thighs. 
     The portions  11  and  13  may also be provided with resilient cushioning pads  16  that are interposed between the patient&#39;s body and the brace portions  11  or  13  and the straps  12  and  14  in order to increase the wearing comfort of the device for the patient. 
     Each second portion  13  is connected to the main portion  11  through an adjustable coupling  17  shown in more detail in FIG.  2 . 
     The coupling comprises first and second support arms  18  and  19  that are connected to the portions  11  and  13 , respectively. Preferably, as shown, the arms  18  and  19  are of channel section for increased strength and rigidity. Desirably, the arms  18  and  19  are connected to the portions  11  and  13  in such manner that they are longitudinally adjustable with respect thereto, in order to allow adjustment of the longitudinal spacing between the first and second portions  11  and  13 . In the example illustrated, each arm  18  and  19  is formed with a series of holes  21 . Each portion  11  and  13  may be formed with two or more similar holes that can be aligned with two or more holes selected from the holes  21  and connected thereto by conventional releasable fasteners. 
     The end of each arm  18  and  19  remote from the portion  11  or  13  is connected to, for example by welding, or is formed integrally with, a collar  22  shown in more detail in FIG.  3 . In the example seen in FIG. 3, the collar  22  comprises a rectangular base portion  23  that fits snugly with the channel of the arm  18  or  19  and is welded thereto, and an upper portion, preferably with a smoothly curved upper side  24 . A circular aperture  26  is formed through the collar  22 . 
     The opposing inner face  28  and outer face  27  of the collar  22  are planar, and, in the preferred form, are parallel to one another. 
     A generally cylindrical bushing  29  as seen in FIGS. 4 and 5 is received within each aperture  26 . The bushing  29  comprises a circular outer portion  31  that may be formed on one side with a flat  32  to accommodate the base of the channel in the arms  18  or  19 . The outer portion  31  has an annular inner face  33  that preferably extends at right angles to the axis of the bushing  29 . 
     An inner cylindrical stub portion  34  has a diameter smaller than portion  31  and fits snugly within the aperture  26  in the collar  22 . The bushing  29  has a circular opening through it defined by a generally inwardly tapering and more preferably conical outer bore  35  and an inner bore  36  that generally tapers outwardly and is preferably conical outwardly from the inner end of the stub portion  34 . 
     In the assembled condition, a wedge shaped cam member  37 , as shown in more detail in FIGS. 6 and 7, is journalled on the stub portion  34  and engages rotationally on the inner face  28  of the collar  22 . 
     As seen in the drawings, the cam member  37  is preferably cylindrical, and has a continuous outer planar bearing face  38  that preferably is inclined to the axis of the member  37 , and hence is generally elliptical, and a continuous inner planar bearing face  39  disposed in a plane inclined to the plane of the outer face  38 , and preferably at right angles to the axis of the member  37 , and hence is preferably annular. 
     The outer face  38  of the cam member  37  is formed with a cylindrical recess  41  with its axis at right angles to the face  38  of diameter such that it snugly receives the outside diameter of the stub  34  so that the cam  37  is journalled for rotation on the stub  34  and the engagement between the stub  34  and the recess  41  prevents transverse slippage of the cam member  37  relative to the bushing  29  and hence relative to the collar  22  and arm  18  or  19  with respect to which the bushing  29  is retained laterally against slippage by virtue of its snug engagement in the aperture  26 . 
     The depth of the recess  41  is sufficient that a clearance is retained between the continuous land at its base and the inner end of the stub  34 , so that the stub  34  does not space the member  37  from the collar inner face  28 . 
     In the example illustrated, two cam members  37  are employed having their inner bearing faces  39  journalled together through interposition of a cylindrical washer  42  of a diameter to fit snugly within a cylindrical recess  43  formed at right angles in each inner annular face  39 . The depth of the recess  43  is again sufficient that in the assembled condition there is a slight axial clearance between an end of the washer  42  and the annular inner end of the recess  43  so that the faces  39  can be placed in contact with one another and are not spaced apart by the washer  42 . 
     A cylindrical bore  44  passes through each cam member  37  between the recesses  41  and  43 . 
     In the assembled condition of the coupling, a releasable clamping device exerts compressive force between the outer sides of the bushings  29 . In the preferred form, as seen in the drawings, the clamping device comprises a tensile member, for example, a threaded stud  46  passed through the bushings  29 , collars  22 , cam members  37  and washer  42 . 
     In the example illustrated, one end of the threaded stud  46  is provided with an enlarged head  47  and a nut  48 , preferably a locknut, is threaded on the opposite end. Preferably a convexly contoured, and more preferably part spherical, for example, hemispherical, washer  49  that fits snugly on the shaft of the stud  46  is interposed between each bushing  29  and effective portion of the clamping device, in this case the head  47  or nut  48 , so that the washer  49  bears on the tapering side of the bore  35  and distributes the compressive stress applied by the clamping device evenly over the area of contact between the washer  49  and bushing  29 , so as to resist a tendency for the washer  49  and bushing  29  to become permanently deformed when compressive force is applied. This stress distribution is preserved at the various angles of inclination that the stud  46  or other clamping device may adopt relative the axes of the bushings  29  in use. In the example illustrated, as will be appreciated from consideration of FIG. 9, the washer  49  contacts the tapering bore  35  along a generally annular zone. 
     In use, with the clamping device in a released condition, by swiveling one cam member  37  about its journal bearing relative to an adjacent arm, for example, arm  18 , and, if necessary, swiveling the other cam member  37  about its journal bearings relative to the first-mentioned cam member  37  and relative to its adjacent arm  19 , the arms  18  and  19  can be adjusted through a range of angles and rotational positions relative to one another. As each cam member  37  rotates, the inner face  28  of the adjacent collar provides a continuous planar bearing face, generally annular, on which the cam bearing face  38  rotates. 
     As the relative angles and positions of the axes of the arms  18  and  19  are adjusted, the angle and position of each end of the clamping device such as stud  46  and hence of the washers  49 , varies relative to the collars  22  and bushings  29 , so that the washers  49  swivel within the bores  35  on which they bear, and, as mentioned above, bear at an annular zone of contact with the bushings  29 . 
     Once the arms  18  and  19  have been set at a desired relative angle and position, the clamping device is tightened, for example, the nut  48  is tightened up by rotation relative to the threaded stud  46 . The head  47  may have a socket  52  to receive a hex or like key to assist in locating the stud  46  to facilitate rotation relative to the nut. When the coupling is fully tightened, the collars  22  are compressively gripped between the outer portions  31  of the adjacent bushings  29  and the outer bearing faces of the cam members  37 . Since the compressive forces between the bushings  29  and collars  22 , between the collars  22  and the adjacent outer bearing faces  38  of the cam members  37  and between the inner opposing bearing faces  39  are borne by opposing planar faces, great compressive stress can be applied without risk of permanent deformation of the material from which the coupling elements are made. As a result, great frictional reaction between the interengaging elements can be derived, so that, once fully tightened up the coupling is highly resistant to dislocation or displacement. Further, as will be appreciated from consideration of, for example, FIG. 9, once the coupling is tightened up the wedge-like cam members  37  form, in effect, a monolithic block between the inner faces of the collars  22 , since the journalling stubs  34  and washer  42  prevent relative lateral shifting or slippage of the journalled elements, while the outer portion  31  of the bushings  29  tightly engage the outer faces of the collars  22 , and the stubs  34  prevent lateral shifting of the collars  22 , so that the joint, once secured, is of great strength and rigidity. 
     Considering each cam member  37  individually, the inner face  39  of the member  37 , in the clamped position of the coupling, bears toward the opposing collar  22 , while the other cam member  37 , and the washer  42 , form part of a journal bearing journalling the member  37  for rotation relative to the collar  22 . 
     An advantage of the coupling as described is that it is adapted to be formed of inert non-corrodible materials, so that the coupling can be readily disassembled, cleaned and sterilized, for example, by autoclaving. Merely by way of example, the arms  18 ,  19 , collars  22 , stud  46  and nut  48  may be stainless steel and the bushings  29 , cam members  37 , and washers  42  and  49  may be aluminum, for example, anodized aluminum. 
     The structural portions of the brace portions  11  and  13  may be molded from readily cleanable and sterilizable plastics, for example, polyethylene and polyethylene/polypropylene copolymers. 
     Each arm  18  and  19  may have its collar  22  connected on an end portion  18   a  or  19   a  that is inclined with respect to the general plane of the main portion of the arm  18  or  19 . This provides further freedom of adjustment of the angles of the arms  18  or  19  relative to one another, since, as will be appreciated, the arms  18  and  19  may be rotated relative to the coupling  17  so that they extend parallel to one another or at extreme angles relative to one another. Further, the angled portions  18   a  and  19   a  facilitate access to head  47  and nut  48  to facilitate loosening and tightening of the nut  48  relative to the stud  46 . 
     Further, preferably each collar  22  is inclined with respect to a plane normal to the general plane of the end portion  18   a  or  19   a  on which it is connected. As will be appreciated, this provides further freedom of angular adjustment. 
     In one preferred form, merely by way of example, the angle a between each arm portion  18   a  or  19   a  and the main arm  18  or  19 , and the angle P between the collar  22  and a plane  51  extending normal to the general plane of the arm portion  18   a  or  19   a  are each about 11.25°, and the angle γ between bearing faces  38  and  39  of each cam member is about 22½°. As will be appreciated, this allows the angle between arms  18  and  19  to be varied between 0 and 90°. These angles are merely by way of illustration and smaller or greater angles may be employed. However, if the angles between the faces  38  and  39  are excessively large, problems may tend to occur if the stud  46  tends to bind on the sides of the bore  44  during swiveling adjustment. Preferably, angles α and β are each between 0 and about 30° and more preferably about 5 to about 15° and angle γ is preferably about 5 to about 35°, more preferably about 10 to about 30°. 
     Preferably, the bearing faces  39  of the cam members  37  that are in contact are at right angles to axes of the members  37  to provide increased stability in the clamped condition and so that, in the case in which an internal stud  46  is employed, the bores  44  remain coaxial and in alignment at all rotational positions, to reduce problems of the stud  46  binding on the inner side of a bore  44 . 
     Various other modifications may be made. If desired, the coupling may have only one cam member  37  having a bearing face  39  journalled direct to a collar  22 . The coupling may have three or more cam members  37  journalled in series to one another and to the collar  22  at opposite ends of the series. 
     In the preferred form, for ease of manufacture, the cam members  37  are similar to one another. However, one cam member  37  may have the angle between its inner and outer faces different from that of the other cam member  37 . Instead of using a washer  42  to journal the cam members  37  together, one cam member  37  may be formed integrally with a projecting annular collar on an inner face  39  received snugly in an annular recess within the inner face  39  of the other cam member. 
     While a hip brace has been described in detail above, as will be appreciated the coupling  17  may be used in other devices. For example, it may be used in a shoulder brace between portions adapted to be applied to the shoulder and upper arm, respectively, or in braces adapted to be applied to the wrist or ankle, for example. 
     Instead of using a tensile member such as a threaded stud  46  and nut  48 , other releasable clamping or compression applying devices may be employed to exert a compressive force to the outer sides of the washers  49 . For example, a stud passing internally through the coupling and having conventional quick disconnect over center cam devices at each end may be employed. Alternatively, an external C clamp or the like bridging externally of the coupling between the outer sides of the washers  49  may be employed. 
     While the invention has been described with respect to certain preferred embodiments as will be appreciated by those skilled in the art, it is to be understood that the invention is capable of numerous changes, modifications and rearrangements and such changes, modifications and rearrangements are intended to be covered by the following claims.