Abstract:
A prosthesis joint including a base, a coupling element for attachment to a body part or a prosthesis section, which is attached to the base, and an attachment device for attachment to a prosthesis device, which is coupled to the base and pivotable around at least one axis. A locking device is coupled to the coupling element and operates to selectively block and enable movement of the attachment device with respect to the base providing locked and unlocked positions, respectively. A retention element is carried by at least one of the base and coupling elements and is elastically pre-stressed against the attachment device to provide a retention force for the attachment device so as to resist undesired pivoting movement.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This patent application claims priority from German Patent Application No. 10 2006 020 777.7 entitled “PROTHESENGELENK” filed on May 3, 2006, the entire contents of which are hereby expressly incorporated by reference. 
     TECHNICAL FIELD 
     This invention relates to the field of prosthetic appliances, more particularly to the field of prosthetic joints. 
     BACKGROUND OF THE INVENTION 
     Prosthetic joints are known which allow two prosthetic parts to swivel relative to one another, and which may be locked with respect to one another. These are generally simple uniaxial joints that may be fixed relative to one another in their respective angular position, optionally in discrete angular increments, by a locking device that blocks the two prosthetic parts. Locking or blocking devices may also be provided for motorized prosthetic devices, in particular to realize energy savings when a prosthetic part must be held in a fixed position under load. 
     When the lock is released and the distal prosthetic part is in an unlocked state, the part may fall downward due to gravity. This downward drop is generally not controllable, especially for non-motorized prosthetic devices. Thus, for prosthetic hands the problem arises that after the locking device is unlocked, the artificial hand drops downward without damping. This may also occur for forearm prostheses having a prosthetic joint in the elbow region; the situation is analogous for foot or lower-leg prostheses. 
     SUMMARY OF THE INVENTION 
     In some embodiments, a prosthetic joint, such as for a hand prosthesis, has a base and a coupling element associated with the base for attaching a body part or to a prosthetic part. A holding device for a prosthetic device, in particular an artificial hand, is connected to the base so as to be pivotable about at least one axis, whereby a locking device blocks the holding device with respect to the base, provides that a retaining element is elastically pretensioned against the holding device and acts upon same with a retention force. This retention force prevents the holding device bearing the distal prosthetic part (for a hand prosthesis, the artificial hand) from swinging downward immediately after the locking device is unlocked. 
     In particular for hand prostheses, the hand performing the unlocking operation cannot be used to support the artificial hand, since at that time it is occupied with unlocking the locking device. For other applications as well, it may be helpful if the prosthetic part is not rendered powerless immediately after unlocking, but, rather, if the prosthetic part is either held by a retention force in the position in which the unlocking occurred, or only a slow drop against the force of gravity takes place. 
     In some embodiments, pretensioning of the retaining element may be set in such a way that the holding device, in particular together with the prosthetic device attached thereto, is held in the unlocked position against the force of gravity. In some embodiments, therefore, the retention force is set to be at least equal to the force of gravity, resulting at least in a force equilibrium that prevents motion about the swivel axis. In some embodiments, the retention force is set so that the prosthetic device is just barely held, thus enabling subsequent intentional displacement or swiveling without a great expenditure of force. To allow the retention force to be adjusted when add-on parts or prosthetic devices are exchanged, the pretensioning of the retaining element is adjustable, for example by varying a spring pretension. 
     In some embodiments, the holding device includes catch elements in which the retaining element engages, the catch elements being designed in such a way that the retaining element or retaining elements are able to slide in and out of the catch elements. The catch elements are used on the one hand for setting discrete angular values, and on the other hand for reducing the pretensioning force necessary to hold the prosthetic device together with the holding device in position. In some embodiments, the catch elements may be designed as recesses, indentations, or projections that are either axially or radially oriented. The orientation depends on the alignment of the retaining element. 
     In an embodiment, the retaining element is designed as an elastic band, in particular as a round cord, which on the one hand simplifies manufacture and on the other hand allows a sufficiently large retention force while at the same time permitting insertion into and withdrawal from the recesses or indentations. 
     In another embodiment, the retaining element may also be designed as a dimensionally stable contact part that lies against the holding device and is elastically supported in the direction of the holding device. This is useful when a long service life is desired and consequently only a small amount of abrasion is permitted. Although in a relative motion of an elastic band with respect to the holding device the elastic band wears out fairly quickly, this is prevented by insertion of an elastically supported contact part. In some embodiments, the contact part may be designed as a bearing pin, such as a steel pin, and may lie against the holding device or engage with or contact the recesses, indentations, or projections. In some embodiments, a spring-loaded steel ball may also be used. 
     The locking device may be designed as a so-called “push-push element” which locks the holding device in a positive-fit manner with respect to the base. Once the locking device is actuated, a positive-fit lock is provided in a specified, discrete position. When the locking device is re-actuated, the positive-fit lock is released and motion against the retention force is made possible by the retaining element. It is likewise provided that the locking device is unlocked by pressing, and is locked by letting go. In that case it is not necessary to re-actuate multiple times. 
     In some embodiments, especially for a wrist prosthesis, it may be useful for the locking device to be displaceably supported parallel to the swivel axis, thus allowing more or less unnoticeable actuation at the wrist. This actuation is possible essentially independently of the position of the artificial hand relative to the base, since the artificial hand does not limit accessibility in any way. 
     A prosthesis joint including a base, a coupling element for attachment to a body part or a prosthesis section, which is attached to the base, and an attachment device for attachment to a prosthesis device, which is coupled to the base and pivotable around at least one axis. A locking device is coupled to the coupling element and operates to selectively block and enable movement of the attachment device with respect to the base providing locked and unlocked positions, respectively. A retention element is carried by at least one of the base and coupling elements and is elastically pre-stressed against the attachment device to provide a retention force for the attachment device so as to resist undesired pivoting movement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of a prosthesis joint according to the present invention. 
         FIG. 2  shows a cutaway view parallel to the swivel axis. 
         FIG. 3  shows a cutaway view perpendicular to the swivel axis. 
         FIG. 4  shows an individual view of a locking mechanism. 
         FIG. 5  shows an exploded view of an alternative embodiment of the prosthetic joint of the present invention. 
         FIG. 6  shows a detail view of a portion of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  we see an exploded view of a prosthesis joint  1  with a base  2  and a swiveling attachment device  4  which swivels around a swivel axis  24 . The attachment device  4  consists of a gear segment piece  41  which has two parallel gear segments  411 . These are connected to each other with a bridge  8 . Plate  42  is attached to this bridge  8 , onto which a further prosthesis part or device can be mounted. For example, an artificial hand (not shown) can be attached to the setscrew or grub screw  45 . In the parallel gear segments  411 , positioning holes  9 ,  10  are formed in which bushings  43 ,  44 , such as synthetic bushings, are able to be inserted. 
     The attachment device  4  is inserted into the base  2  so that the bushings  43 ,  44  are aligned with the relevant holes  11  in the positioning blocks  25 ,  26 . In addition, bolts  21 ,  22  extend into the holes  11 . The bolts  21 ,  22  form the running surface for the bushings  43 ,  44 . 
     In the gear segments  411 , recesses  415  and indentations  416  are found (see  FIG. 3 ), whose function and mode of action will be explained as follows. 
     A locking mechanism or device  5  is located around positioning or bearing blocks  25 ,  26  and is equipped with locking guides  51  which have protrusions  56  which extend in the direction of the recesses  415  of the gear segments  411 . 
     In the unlocked position, the protrusions  56  in the locking guides  51  are not in contact with the gear segments  411  and extend into the interim space between the gear segments  411 , so that each of the gear segments  411  can make contact with the protrusions  56 , which insert into the recesses  415 , independent of the direction of force of the locking mechanism  5  or the locking guides  51 . The locking mechanism moves in a direction parallel with the swivel axis  24  of the attachment device  4  between the locked and unlocked positions (see  FIGS. 1 and 2 ). 
     Cylinder pins  52 ,  53  are inserted into the locking guides  51 , which are supported on compression springs  54 ,  55 . The compression springs  54 ,  55  are positioned in a space between the base  2  and a coupling mechanism or element  3 . In the coupling mechanism  3  there are holes or guides  12 ,  13  for a retention element  6 , presently two elastic cords or rods, which are generally oriented parallel to the swivel axis  24 . The retention element  6  can also be formed from a closed elastic band. In the installed condition the retention element  6  grips the indentations  416  on the side of the gear segment  411  facing away from plate  42  and is elastically supported. The base  2  and the coupling element  3  are connected with two screws  31 ,  32 . 
       FIG. 2  shows a side view of prosthesis joint  1  in a mounted and locked position. The base  2  is connected to the coupling element  3  with screws  31 ,  32 . The gear segment  41  is screwed or glued to plate  42 . In  FIG. 2 , the position of the bolts  21 ,  22  in the bushings  43 ,  44  can be seen within the gear segments  411 . The bolts  21 ,  22  are screwed into the base  2  at the bearing blocks  25 ,  26 . Between the bolts  21 ,  22  there is free space in which protrusion  56  of the locking guides  51  extends. In  FIG. 2 , the locked position is shown, in which the protrusion  56  is inserted into a recess  415 . Thus, plate  42  is not free to swivel around the swivel axis  24 . However, when unlocked, the plate  42  is free to swivel up to ±60° from in the starting position shown. 
       FIG. 3  shows a cutaway perpendicular to the swivel axis  24  and shows the interface of the retention element  6  with the indentations  416 . The retention element  6  can be made of a pair of elastic staves, rods or of cord. The retention element  6  is pretensioned in the direction of the gear segments  41 , in the present model in a radial direction, so that retention force is exerted on the attachment device  4 . This retention force is increased by the indentations  416  which are found on the underside of gear segment  411 , so that the retention element  6  can be mounted with relatively little pretensioning. Due to the evenly spaced indentations  416  or stop indentations, various stop positions can be set, preferably in even angle intervals. The stop indentations  416  can have the same intervals as the locking recesses  415  and can be positioned in relation to each other, so that in each position of the attachment device  4  in the unlocked mode, locking can occur through axial movement of the locking mechanism  5  (not illustrated in this view). In one aspect, the locking mechanism  5 , of the present invention, includes an element that engages the attachment device  4  with a positive fit. 
     Free spaces  52 ′,  53 ′ can be identified in  FIG. 3 , in which the cylinder pins  52 ,  53  are movable. The cylinder pins  52 ,  53  are acted upon via compression springs  54 ,  55  with a retention force, so that the locking mechanism  5  is always spring loaded in one direction. In the starting position, the locking mechanism  5  is in the locked position and is held there. In the locked position, there is a fixing of the attachment device  4  by the interface or engagement of the protrusions  56  into the locking recesses  415 . If pressure is introduced against the spring force, the protrusions  56  are moved out of the locking recesses  415  and enable a swing or pivoting of the attachment device  4 , or the artificial hand attached to it, around the swivel axis  24 . If the locking mechanism  5  is released, it springs back due to the retention force of the compression springs  54 ,  55  and brings the protrusions  56  back into interface or engagement with the locking recesses  415 . 
     An alternative can be a so called push-push-element, which is returned to the starting position after being twice activated. 
       FIG. 4  shows a locking mechanism  5  with the locking guides  51  and the protrusions  56  in individual views. The cylinder pins  52 ,  53  (not shown in this view) can be inserted into the holes  57 ,  58 . 
     An alternative to the design illustrated, with a direct coupling of an elastic retention element  6  with the gear segments  41  and/or the attachment device  4 , can be a contact part of a hard or abrasion resistant material between an elastic element and the gear segments  41  and/or the indentations  416 . Through this, the sliding of the retention element  6  or contact parts is made easier on one hand, and on the other hand, the life of the prosthesis is increased. 
     It is also possible to have an axial retention force, instead of a radial effective retention force. For example, there can be stop recesses or protrusions in recesses in the side surface of the gear segments  41 , which interface with the retention elements. For example, a spring loaded bearing could interface into a calotte-shaped recess. 
     Due to the prosthesis joint of the current invention, an uncontrolled falling of a prosthesis device after unlocking is hindered without affecting adjustability. It can be arranged so that the stop elements are removed from engagement, so that a spontaneous change in position is possible without additional adjustment force. It is also basically possible to set the pre-tension and therefore the retention force to the personal wishes of the wearer and to be able to adjust it for changing situations. 
     The prosthesis joint can either be attached to a body part or to another prosthesis section, such as onto a lower arm prosthesis. 
     In addition to the use as a prosthetic wrist, other joint elements can be effected, such as knee or elbow joints. It may also be used in motor driven prostheses in order to reduce energy consumption. The retention force in the unlocked position can be selected to be so slight that the drive must only provide a slightly higher output. This additional expenditure is compensated for by removing the need of using the motor to hold prosthesis devices. The control of the drive can occur via myoelectrical signals. 
     In another embodiment, like components have the same reference number as those in the first embodiment.  FIG. 5  shows a variant of prosthesis  1  in an exploded view which shows the retention element  6  as steel pins. These pins  6  are pre-tensioned over an elastic strap  61  or an elastic element against a bushing  410 , which loads this retention element  6  with retention force. The bushing  410  is connected with the gear segment part  41  with screws  412  and transfers the radial retention force from the bushing  410  to the attachment device  4 . The two part configuration of the retention element  6 , in the form of steel pins, and an elastic element  61 , provides increased retention and minimization of wear and tear. 
     The elastic strap  61  and/or another elastic element is positioned in the recess  612 , of which only one is shown, in base  2 . Accordingly, an additional recess is located in the upper section  2 ′ of base  2 . In this aspect, the present invention may be seen to include a retention element  6  as a dimensionally stable contact part which abuts the attachment device  4  and is elastically positioned in a direction towards and away from the attachment device  4 . 
     The bushing  410  is also made of steel, just as the retention element  6 , in order to produce an abrasion minimizing materials pairing. Alternatives could also be indentations  416  formulated directly on the gear segment part  41 . 
       FIG. 6  shows the prosthesis joint  1 , pursuant to  FIG. 5 , in a detail view without upper section  2 ′ of base  2 . One can see that the gear segment part  41  is made of a single piece and, in addition, forms the attachment device  4  for a coupling element for the prosthetic hand (not shown). A locking and unlocking mechanism  5  enables a quick and easy locking and unlocking of an adaptor for a artificial hand in the attachment device  4  mechanism gear segment  41 . The locking of the attachment device  4  against a swivel or pivoting movement occurs via the locking device  5  made up of bars  516 . Bars  516  can be pivoted out of the preset interface or engagement position via pins  510  with a retention force provided by springs  512 . The bars  516  are positioned in the base  2  and are spring loaded. The pins  510  abut a spherical actuation surface for the locking device  5 . The locking device  5  is primarily designed as a pressure button and is held in the starting position, in which the bars  516  interface with the locking recesses  415 , via a compression spring  59 . If the button  50  is pressed, the pins  510  will be pressed against the bars  516  by the spring force and will move them out of contact. When the button  50  is released, there is a reverse movement. 
     For the quickest locking and unlocking of the artificial hand with the attachment device  4 , as with a quick-connect feature, an additional pressure button  7  is added, which reaches over an axis  70  through the bushing  410  and is coupled with a force transfer element  71 . This force transfer element  71  is coupled with a key element  73  via pins  72 , which is movable and positioned in the attachment device  4  with spring force of a spring  74  acting against element  75  which is secured to piece  41 . If the button  7  is actuated, the key element  73  is moved by the force of spring  74  in the direction of the screwed in thrust bearing and does not release the artificial hand. To lock the artificial hand, button  7  is held in, whereby the attachment device  4  is prepared for the insertion of the adaptor of an artificial hand. After pressing and releasing the button  7 , the adapter is automatically locked due to the retention force of spring  74 . This also provides that the adapter be inserted into the attachment device  4 , which moves the key element  73  on its own and finally locks it into the attachment device  4 . 
     In one aspect, the present invention provides pre-stressing of the retention element by an amount sufficient to hold the attachment device in the unlocked position against the force of gravity.