Abstract:
Knee braces generally have been rigid in both the knee bending direction and in the knee straightening direction unless a manually operated release is incorporated in them to allow the knee to bend. Desirably a braced knee joint should effectively duplicate the compound, complex, actions of a normal knee. The key to knee braces is the knee joint housing. The housing herein carries a number of cam action pawls, with teeth adapted to engage the internal teeth of a ratchet ring mounted in the housing. Cam action return springs and the shape of the cam action pawl teeth allow rotation of the ratchet ring in a leg straightening direction while still supporting a load. The leg can then be extended during walking while at the same time being prevented by the cam action pawls from buckling in the knee bending direction.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
   The invention described in this patent was made by an employee of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties. 

   CROSS-REFERENCES TO RELATED APPLICATIONS 
   There are no applications related to this application. 
   FIELD OF THE INVENTION 
   This invention relates to orthopedic leg braces, especially those which brace the upper and lower portions of a user&#39;s leg and which incorporate a knee joint assembly between the upper and lower braces. 
   BACKGROUND OF THE INVENTION 
   There is a long-standing need for leg braces for knees impaired by temporary or permanent loss of neuromuscular control or by loss of control of a knee joint through a knee injury. For stability or bracing, such knee braces must have stays or brace members secured firmly to the leg both below and above the knee with a knee joint housing between the brace members. 
   It is generally realized, as is discussed in the Lewis et al. U.S. Pat. No. 4,361,142, that it is particularly difficult to provide orthopedic knee appliances which provide stability while still duplicating or accommodating the complex flexion and extension actions which a knee undergoes. At the same time the braced knee joint must effectively duplicate the compound, complex, actions of a normal knee. Otherwise the knee brace may well be injurious to the user. 
   A study of the prior art shows that duplication of normal knee actions has not been fully accomplished. Thus knee braces generally have been rigid in both the knee bending direction and in the knee straightening direction unless a manually operated release is incorporated in them. As one example a double-locking ratchet knee joint, pivotally connected between the upper and lower leg, is described in U.S. Pat. No. 4,520,804. Relative pivotal movement between the knee joint and upper and lower leg sections is achieved manually by a pair of actuatable locking levers. Rotary movement of the ratchet wheel is effected only by manual rotation of a locking pawl control lever. Presently, then, it is not possible to straighten the leg as in normal walking, especially for traveling up steps. 
   An object of this invention is to provide a knee brace allowing a leg bent at the knee to be straightened while at the same time being prevented from buckling in the knee bending direction. 
   Another object of the invention is the provision of a knee brace which is releasable so that it can free wheel in both directions when it is not in use, that is, under a no load condition. 
   Still another object is to provide a knee brace which will lock in any position because its locking mechanism functions in small increments. 
   Existing knee brace locking devices have been either cone clutches, roller type clutches or single pawl ratchet devices. Variations in friction due to clutch surface conditions, as well as the distance pawls must normally travel before engaging or locking, can lead to a knee joint which gives way. My issued patent, U.S. Pat. No. 5,490,831 overcame many of these disadvantages, but as noted in the prior art, there is still room for improvement. This invention embraces a major step in that direction. 
   SUMMARY OF THE INVENTION 
   Orthopedic knee brace assemblies usually include upper and lower side braces to support a user&#39;s leg with a knee joint housing between them accommodating means for pivotal movement. The key to knee braces, then, is the knee joint housing. The knee joint housing herein is in the form of inner and outer housing members. The upper side brace is integral with the outer housing member, and the lower side brace is integral with the inner housing member. A ratchet ring having internal teeth is mounted in the outer housing member so that it rotates when the upper side brace swivels. A number of cam action pawls, with teeth adapted to engage the internal ratchet ring teeth, are mounted in the inner housing member. The cam action pawls are provided with return springs to hold the pawl teeth in engagement with the ratchet ring teeth. The inner and outer housing members are coupled together to form a knee joint hinge. Ratchets are created in the housing when the cam action pawls in the inner housing member engage the teeth inside the ratchet ring in the outer housing member. A control mechanism moves the cam action pawls into and out of a locking engagement with the ratchet ring teeth. Cam action return springs and the shape of the cam action pawl teeth allow rotation of the ratchet ring in a leg straightening direction while still supporting a load. The leg can then be extended during walking while at the same time being prevented by the cam action pawls from buckling in the knee bending direction. An actuating rod acts on the control mechanism to bring the cam action pawls into and out of a locking engagement with the ratchet ring teeth so that the cam action pawls are engaged during the load-bearing phase of walking. Otherwise the teeth are disengaged. 
   DESCRIPTION OF THE INVENTION 
   It is not known in the art that multiple pawls permit a ratchet wheel to be locked when rotated a distance much shorter than the distance it must rotate when one pawl is used in a knee brace. Two pawls are disclosed in U.S. Pat. No. 4,520,804, but they are employed to enable the user to quickly and easily alter the relative pivotal movement and positioning between upper and lower leg sections. One pawl limits clockwise rotation, and one pawl limits counterclockwise rotation. The double locking ratchet knee joint in U.S. Pat. No. 4,520,804 accomplishes this movement through the use of manually actuatable locking levers. Thus, heretofore knee braces would not lock until the pawl moved a distance of at least one full tooth, during which the user&#39;s leg was unsupported. As will be appreciated, herein the pawl can be made to move less than the distance between two teeth. For a better understanding of how this is accomplished a description of the invention in conjunction with the accompanying drawings will be helpful. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the use of a knee brace constructed in accordance with this invention. 
       FIG. 2  is a cross sectional sketch illustrating a two pawl knee brace mechanism of the invention. 
       FIG. 3  is an isometric sketch showing the spool and shaft portions of the two pawl actuating mechanism. 
       FIG. 4  is a cross sectional sketch illustrating a four pawl pivotal knee joint of the invention. 
       FIG. 5  is an isometric sketch showing the spool and shaft portions of the four pawl knee brace mechanism. 
       FIG. 6  is a cross sectional diagrammatic view of the four pawl pivotal knee joint hinge of  FIG. 4 . 
   

   THE INVENTION 
   Referring now to these drawings, a knee brace  2  constructed in accordance with this invention is illustrated in  FIG. 1 . The brace resembles conventional knee braces having right and left supporting brace members  4  and  6  along with a knee joint assembly  7 . The physiology of a knee brace requires that the brace on each side of the knee be different in orientation, but that each brace include identical knee joint assemblies. This being the case only the brace on one side of a leg, illustrated by reference character  6  herein, the left brace relative to the user, need be discussed in detail. In  FIG. 1  it can be seen that left brace  6  includes an upper side brace  8 , and a lower side brace  9  with housing  10  holding a mechanical pivotal knee joint assembly. To secure the knee brace to the leg  5 , bands or straps  12  and  14  of flexible material such as fabric or leather are used with fasteners such as VELCRO® or snaps. One band  12  is wrapped around the upper leg to hold upper side brace  8  against that portion of the leg, and if the lower side brace  9  is not held firmly against the lower leg portion by a shoe  13  or an actuating mechanism such as a heel plate or an ankle flexure, a lower band  14  is used. 
   It is to be understood that the upper side brace  8  and lower side brace  9  should move relative to each other in a manner simulating, as closely as possible, ordinary leg movements. It is this relative movement that is the essence of this invention. In  FIG. 1  it can be seen that since the upper leg must move from a bent leg position to a straight leg position, the upper side brace  8  must move relative to the lower side brace  9  as does a leg. To this end knee joint housing  10  is made up of two elements, an inner housing member and an outer housing member. Since the upper side brace must move as the leg is bent, upper side brace  8  is bolted or riveted, or otherwise rigidly connected, using holes  18  ( FIG. 2 ) to outer housing member  19 . Similarly lower side brace  9  is rigidly connected using holes  58  (also  FIG. 2 ) to inner housing member  20 , allowing the knee to flex when the user is not requiring support. These inner and outer housing members or elements, to be described in conjunction with the remaining figures, are coupled together to form a pivotal knee joint hinge in which the two housing members can rotate relative to each other. 
   Now that the invention has been described in general terms in conjunction with  FIG. 1 , it remains to describe it now more specifically in conjunction with  FIG. 2 . It has been emphasized that the key to such braces is the mechanical knee joint assembly within housing  10  illustrated in  FIG. 1 .  FIG. 2  is a cross sectional diagrammatic view of one type of mechanism contemplated by this invention, and housed as a mechanical knee joint in housing  10 . It can be seen that the upper side brace  8  is integral with the outer housing member  19 , being keyed thereto at  18 . Lower side brace  9  is joined to the inner housing member  20 . A ratchet ring  31  having internal teeth  29  is mounted in the outer housing member  19  so that ratchet ring  31  rotates when the upper side brace  8  swivels. It has been indicated hereinbefore that a number of cam action pawls, with teeth adapted to engage the internal ratchet ring teeth, are mounted in the housing. They are mounted for operation around a central shaft or sleeve  30  which is joined to the inner housing member  20 . Two such cam action pawls  22  and  24  are illustrated in  FIG. 2 . Cam action pawls  22  and  24  are spring pawls having teeth  33  which engage the teeth  29  in the ratchet ring. Cam action pawls  22  and  24  pivot about pins  25  and  26  in order to engage the teeth of the ratchet ring when the pawls are advanced by a spool  28  to be described subsequently. The pawls will then be held in place by the action of springs  32  which are seated in a sleeve or shaft  30 , the shaft being a hollow cylinder surrounding and supporting rotating drive spool  28 , as shown in  FIG. 3 , also to be described in greater detail. 
   On examining ratchet ring  31  and cam action pawls  22  and  24  it will be appreciated that means must be incorporated in the knee joint assembly to advance the cam action pawls so that one of them will lock the ratchet ring during use, and so that the pawl will be held in the locked position until weight is no longer supported by the brace. One such means is illustrated in  FIG. 3 . 
     FIG. 3  is an exploded isometric view of a shaft or sleeve  30  and a drive spool  28 . Referring to  FIG. 3  it can be seen that drive spool  28  is adapted to fit slidably within shaft  30 . The shaft is a hollow cylinder provided with lower and upper flanges  35  and  45  respectively with holes for pins  25  and  26 . The spool is a spindle having two lobes  21   a  and  21   b  which are adapted to advance cam action pawls  22  and  24 . The outer portion of shaft  30  is provided with openings  38  through which tangs of the cam action pawls  22  and  24  project in order to be advanced by the lobes of the drive spool  28 . Shaft  30  also provides seats  36  for pawl return springs  32 , and the base  27  of drive spool  28  carries a recess  34  adapted to hold an actuator or cranking pin  39  as will be described. 
   It remains to return to  FIG. 2  to describe the components of the actuating mechanism or pawl drive means  40  which operates the ratchet pivotal knee joint of this invention. This can best be accomplished by describing the operation of the leg brace. In order to prevent the user&#39;s knee from buckling or collapsing during walking, knee joint assembly  7  must lock when it is supporting a user&#39;s weight. To this end the knee joint assembly must be adapted to be locked by upward linear movement of an actuator rod  40  that is urged upwardly by the pressure of the walking surface upon the rod end, or by a heel plate or ankle flexure as in the prior art. Actuator rod  40  is also illustrated in  FIG. 1 . By this embodiment actuator rod  40  extends slightly below the shoe sole so that during use the weight of the walker forces it upwardly toward housing  10 . This travel advances cam action pawls  22  and  24  by converting linear rod movement to angular spool movement so that drive spool  28  can advance the pawls. Herein this conversion is accomplished by a cranking action. As seen in  FIG. 3  the base  27  of spool  28  is provided with a cavity  34  having a size and depth to receive a cranking pin  39  illustrated in  FIG. 2 . As can be understood from  FIG. 2  as cranking pin  39  advances, spool  28  rotates slightly, say, twenty degrees, so that a return spring  32  can press teeth  33  of one of the pawls into engagement with ratchet teeth  29 . 
   To permit actuator rod  40  to advance, due to the force of a user&#39;s weight, beyond the point of pawl engagement, cranking pin  39  is carried in a slide  37  which also carries spring  46 . Slide  37  permits the actuator rod  40  to move beyond the pawl-locked position. At the same time spring  46  is compressed to hold drive spool  28  in position. To return actuating rod  40  to its lowered (no load) position a slot  47  is also incorporated in the actuator mechanism. Pin  49  is secured in inner housing  20  and passes through slot  47  allowing upper movement of the actuator rod, but with spring  48  returning the actuator rod to its downward no-load position when the knee brace  2  is not supporting weight. 
   PREFERRED EMBODIMENT OF THE INVENTION 
   Referring now to  FIG. 4 , it is to be understood that the knee joint assembly shown in this figure is the same as that illustrated in  FIG. 2  except that the pivotal knee joint hinge in  FIG. 2  includes two cam action pawls mounted 180 degrees apart whereas the preferred knee joint assembly  7  of  FIG. 4  includes four cam action pawls  41  through  44  mounted 90 degrees apart with only the teeth  33  of cam action pawl  41  in engagement with teeth  29  of ratchet ring  31 . It is noted that upper brace  8 , lower brace  9 , actuator rod  40 , and slide  37  (not shown) and slot  47  are the same components operating in the same manner as the components described in conjunction with  FIG. 2 . Since actuator  40  is identical in operation to that described in connection with  FIG. 2 , it is considered unnecessary to cut away  FIG. 4 , as was done in  FIG. 2 , and to repeat the actuation description. 
   A particularly novel feature of this invention is that when teeth  33  and  29  are locked together so that the user&#39;s knee joint will not bend, knee joint assembly  7  permits the bent knee to be straightened. As can be visualized, springs  32 , along with the design of the pawl teeth, lock the knee joint assembly against movement in the knee bending direction (counterclockwise in  FIG. 4 ), but permit movement in the knee straightening direction. An examination of the slopes of teeth  33  and  29  confirm that ratchet ring  31  can be rotated in a clockwise direction, in this instance the knee straightening direction. 
     FIG. 5  is an exploded isometric view of a shaft  30  and drive spool  28  resembling that of  FIG. 3  with drive spool  28  again being adapted to fit slidably within shaft  30 . As in the embodiment in  FIG. 3  the shaft is a hollow cylinder provided with lower and upper flanges  35  and  45  respectively. In this instance the flanges have four holes for the cam pawl pins. As in the  FIG. 3  embodiment the spool is also a spindle, but one having a different configuration in order to accommodate four pawls. Thus drive spool  28  is provided with four lobes  21   c ,  21   d ,  21   e , and  21   f . The outer portion of shaft  30  in this embodiment is provided with four openings  38  through which the four tangs of the four cam action pawls  41 ,  42 ,  43  and  44  project in order to be advanced by lobes of the drive spool  28 . Shaft  30  also provides seats  36  for pawl return springs  32 , and the base  27  of drive spool  28  carries a recess  34  holding the actuator pin as described hereinbefore. 
   The more closely a knee joint assembly is to simulate the functioning of a human knee, the smaller the increments between joint locking positions should be. The main thrust of this invention is the discovery that increment size is a function of the number of cam action pawls in the knee joint assembly. The function can be determined when the number of internal ratchet ring teeth are brought into the equation. Considering the invention herein, there are 45 teeth on the ratchet ring. With the ratchet ring being a circle, dividing 45 into 360 degrees reveals that the teeth herein are 8 degrees apart. The 4 pawls in the embodiment illustrated in  FIG. 4  are mounted 90 degrees apart. With the teeth being 8 degrees apart, there are 90/8, or 11.25 teeth in each quadrant. Hence when one pawl is fully engaged, the next pawl is 0.25 tooth distance (a fourth of the distance between two teeth) from engagement. In other words, considering the 8 degree ratchet teeth separation, a 2 degree rotation will cause the next pawl in  FIG. 4  to lock the leg brace. Likewise, in the 2 pawl pivotal knee joint hinge illustrated in  FIG. 2 , with the pawls being 180 degrees apart, and the teeth being 8 degrees apart, there are 180/8 or 22.5 teeth in each quadrant. In this instance a spool rotation of one-half of the distance between two teeth will cause the next pawl to engage. 
   It can be seen that by the practice of this invention the knee joint assembly locks with the upper brace moving extremely small distances, for instance two or four degrees, thus securing the knee joint in virtually any position to prevent the knee from collapsing. In addition, when actuated, the knee brace will positively lock in one direction while allowing rotation in the other direction. When not actuated, the knee brace will allow rotation in both directions. Further, the actuation means herein does not require that the mechanism be a part of a shoe or stirrup. Hence given the teachings of this invention ramifications and variations will occur to those skilled in the art. For example a protective tip, such as the rubber tip shown in  FIG. 1 , can be secured to the tip of the actuation rod. As another example bearings can be incorporated in the knee joint assembly of the invention so that outer and inner housing members  19  and  20  will be able to move more readily with respect to each other. The use of such bearings is illustrated in  FIG. 6 . This figure is a cross sectional view of the knee joint assembly of the invention showing pawls  42  and  44 , along with their pins  25  and  26 . Also shown are shaft  30 , drive spool  28  and spool cranking pin  39 . Bearings  50  and  52  are shown in  FIG. 6  in their respective races  54  and  56 , positioned between outer and inner housing members  19  and  20 . As another variation it will occur to one skilled in the art that the pawls need not have three locking teeth, but one or more can be utilized depending upon the calculation which determines the number and material necessary to support the load. Likewise the number of pawls rendering smaller and smaller locking increments will be determined by the sizes of the components. Such modifications, then, are deemed to be within the scope of this invention.