with reference to fig1 and 2 , the principal components of a preferred embodiment of the present invention may now be described . upper arm 10 is configured to be attached to the upper rigid portion of an orthosis ( not shown ) that is fitted to a patient &# 39 ; s upper leg . on the face of each side of upper arm 10 is an upper thrust bearing race 14 . circumscribing upper thrust bearing race 14 is upper lock bearing race 12 . both upper thrust bearing races 14 and upper lock bearing races 12 are annular depressions in the face of upper arm 10 . preferably , upper arm 10 is formed of steel or a similarly strong material , and upper thrust bearing races 14 and upper lock bearing races 12 are machined into the faces of upper arm 10 . resting in upper thrust bearing races 14 and upper lock bearing races 12 are thrust bearings 18 and lock bearings 16 , respectively . thrust bearings 18 provide for smooth rotation of upper arm 10 with respect to lower arms 24 and 25 . lock bearings 16 provide the locking mechanism of the joint , as will be described more fully below . thrust bearings 18 and lock bearings 16 are preferably formed of steel for strength and for the ability of the material to resist deformation . a bearing cage 20 is fitted at each side of upper arm 10 adjacent to upper lock bearing race 12 . because each bearing cage 20 features an opening sized to fit each of lock bearings 16 , each bearing cage 20 holds each lock bearing 16 in a set position with respect to bearing cage 20 . on either side of upper arm 10 and the associated bearing cage 20 is fitted one of lower arms 24 and 25 . in the preferred embodiment , lower arms 24 and 25 are designed as mirror images of each other , such that when assembled as shown in fig2 they fit together to form a smooth silhouette . similar to upper arm 10 , lower arms 24 and 25 are intended to be attached to the lower rigid portion of an orthosis ( not shown ) that is fitted to a patient &# 39 ; s lower leg . on the interior face of each of lower arms 24 and 25 is a lower thrust bearing race 28 . circumscribing each lower thrust bearing race 28 is a plurality of arcuate lower lock bearing races 26 . lower thrust bearing races 28 are annular depressions in the face of lower arms 24 and 25 , aligned with and symmetrical to upper thrust bearing races 14 . lower lock bearing races 26 , however , are formed in an series of short races together forming an interrupted annular depression , with each of lock bearing races 26 matching the location of a particular lock bearing 16 and associated opening on bearing cage 20 . it will be seen that during assembly lock bearings 16 , and correspondingly bearing cage 20 , must be properly aligned with the lower lock bearing races 26 for the upper arm 10 and lower arms 24 and 25 to properly be fit together . as with upper arm 10 , lower arms 24 and 25 are preferably formed of steel or a similarly strong material , and lower thrust bearing races 14 and upper lock bearing races 12 are machined into the faces of upper arm 10 . nut 30 and bolt 32 pass through the opening in upper arm 10 and lower arms 24 and 25 , fastening together to hold the various components together while allowing rotation between upper arm 10 and lower arms 24 and 25 around the shaft of nut 30 . in the preferred embodiment , nut 30 and bolt 32 fit together by means of a press fit , but threads or other means of attaching nut 30 to bolt 32 may be employed , so long as free rotation of upper arm 10 with respect to lower arms 24 and 25 when the joint is unlocked is maintained . in the preferred embodiment , rotation of upper arm 10 with respect to lower arms 24 and 25 should be limited even in the unlocked position such that the rotation does not exceed that which would be encountered with a human knee during normal walking movements . stops 34 extending from lower arms 24 and 25 are employed in the preferred embodiment for this purpose . stops 34 extend towards each other and block progress of upper arm 10 past the point where it contacts stops 34 . in the preferred embodiment , total extension of the joint is limited to no more than 130 degrees . referring now to fig3 a , 3b , 4 a , and 4 b , the operation of the preferred embodiment of the present invention may now be described . in fig3 a and 3b , the preferred embodiment is depicted in the locked condition . each lower lock bearing race 26 is ramped at its inner surface as depicted in fig3 b . by rotational movement of bearing cage 20 , each lock bearing 16 is forced into the shallower end of the corresponding lower lock bearing race 26 . when rotation of the joint is attempted in the flexion direction in this condition , the bearing is “ pinched ” into this shallow region , and due to friction the rotation of upper arm 10 with respect to lower arms 25 and 26 is prevented . fig4 a and 4b depict the preferred embodiment in the “ home ” or unlocked position . in this case , bearing cage 20 is rotated slightly in the opposite direction , allowing each lock bearing 16 to remain in the deeper portion of the corresponding lower lock bearing race 26 when flexion rotation is attempted . the joint is thus allowed to rotate freely in both the flexion and extension directions when in this state . the rotation of bearing cages 20 which allows the locking and unlocking of the invention may be performed by means of a flexible filament , activator rod , or other activation means as are known in the art . tab 22 may be used to provide the mechanical linkage between bearing cages 20 and the activation means employed in any particular embodiment . in the preferred embodiment , a monofilament line ( not shown ) is employed for this purpose due to its strength and flexibility . a sheath ( also not shown ) may optionally be employed around the monofilament line between bearing cage 20 and a switch or other activation means used to sense weight being placed upon the leg bearing the orthosis and thereby activate the locking mechanism . in alternative embodiments , the locking and unlocking of the invention may be controlled by means of an electric or electronic signal . an electronic controller may be used in connection with the invention for the purpose of sending an appropriate signal in response to a control stimulus , such as the activation of an electrical or electronic sensor . in certain of these alternative embodiments , a solenoid may be used to activate the locking or unlocking mechanism in response to an electrical signal from the controller . it may be noted that the preferred embodiment has been described with certain features associated with an upper arm and certain features associated with a two - piece lower arm of an orthosis . these features could easily be flipped to the opposite arms in an alternative embodiment of the device . likewise , the upper arm could be formed of two pieces while the lower arm is a single piece in an alternative embodiment . while the term “ arm ” is used throughout to describe the main components of the preferred embodiment that act as a housing for the bearing components and connect with the orthosis upper and lower leg fittings , it should be understood that the “ arm ” components are not restricted to an elongated shape , and may in alternative embodiments comprise any shape capable of fulfilling the functions described herein . it may further be noted that while the invention has been described for use in connection with an orthosis , the device could also be used with a prosthesis or other devices intended to aid a person in walking . in addition , the invention might in alternative embodiments be employed with respect to spacesuits , pressure suits , robots , or other applications where a knee joint is indicated and a more natural or human - like gait is desired . the present invention has been described with reference to certain preferred and alternative embodiments that are intended to be exemplary only and not limiting to the full scope of the present invention as set forth in the appended claims .
an orthosis knee joint using a lock bearing arrangement is disclosed . the joint uses lock bearings that move in individual , arcuate races . the lock bearings are manipulated by means of a bearing cage from a locked position to an unlocked position . the locking mechanism is provided by the ramped shape of the bottom of the individual bearing races ; movement of the bearing cage pinches the bearings at the shallower end of the ramp when the lock is activated and rotational force is exerted in the flexion direction . movement in the extension direction , however , is still allowed in the locked position .