Abstract:
A transportable offloading weight apparatus for supporting a portion of a patient&#39;s weight undergoing gait training is provided. The offloading weight apparatus employs a resilient suspension system to reduce the amount of weight borne by a patient. The offloading weight apparatus includes a frame having a connection linkage, a rope routed in the frame through a pulley system, a resilient cord that is attached to the frame at one end and connected to the connection linkage through one end of the rope, a harness support assembly secured to another end of the rope and a tension adjustor for applying tension to the resilient cord.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     None 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a device for offloading a portion of a patient&#39;s weight during gait training. 
     2. Discussion of the Related Art 
     Partial weight bearing gait training is a method of training and rehabilitating a patient that has completely lost or has suffered a reduced ability to ambulate. During training the weight of the patient is partially supported by an unweighing device. Specifically, the patient is able to undergo physical training such as learning or relearning to walk with the aid of a treadmill without having to support his entire body weight which would otherwise impose a significant obstacle during gait training. As gait training therapy progresses, the amount of body weight that is supported or off weighed may be gradually reduced. 
     Unweighing body support systems or weight offloading systems are commonly used during locomotion on a treadmill in the treatment of patients with neurological deficits and other clinical conditions such as lower extremity fractures, osteoarthritis, and lower extremity amputations. A patient suffering the effects of neurological trauma or disease that curtails the patient&#39;s ability to ambulate bearing his full body weight can gain gait motion with the aid of an unweighing system, assisted or unassisted, in order to retain muscle tone and gain strength. In addition, patients, especially athletes, can resume training earlier that would have been possible without the aid of weight offloading devices. 
     Weight offloading systems use a variety of methods to support a portion of a patient&#39;s body weight. Many systems in use today, employ a harness that is worn by the patient and is connected to overhead cables and/or ropes that apply an upward physical force to reduce a portion of the patient&#39;s body weight. In some systems, the supporting cables or ropes are affixed to a framework wherein the frame or a portion of the frame is upwardly adjusted until the force develops in the rope. In other systems, ropes run over a series of pulleys and weights are added to the ropes to develop a tension force in the rope which off loads the weight of the patient. Many of these systems measure the force applied to the patient through the rope or cable, which magnitude of the force is then displayed. 
     There are several different commercially available weight offloading gait training devices. In some systems, the frame is adjusted upwards to tension a rope that is attached to a harness worn by the patient. In these systems, however, there is no up or down movement without the load varying widely or disappearing. Some systems of this type add springs of various lengths to the rope in order to allow for a small amount of movement, but the load still varies widely, i.e., the movement of the patient will cause a substantial variation in the magnitude of the lifting force applied to the patient. In addition, these units have limited ranges. In other systems the rope is manually pulled. Although such manual systems allow a larger adjustment range, the movement of the patient still presents a loading problem. While other units use weights to adjust the tension in the rope, it is difficult to apply the load, and mobility of the unit is impracticable due to the swinging of the weights and difficulty to push them. Pneumatic units apply a more constant force and have greater ranges, but because such units require an air compressor they are not mobile. In addition to the various drawbacks associated with the particular systems, such systems are generally heavy and expensive. 
     Other drawbacks of known weight offloading gait training systems include the lack of a place for the therapist to sit while administering gait therapy, lack of accurately reading the unweighing load, frame sizes that do not accommodate a sufficient number of patient sizes. In addition, some available systems are restrictive to the extent a patient cannot easily change directions, and/or are not suitable to aid with assisting a patient out of a wheelchair. 
     What is needed is an apparatus to offload a portion of a patient&#39;s weight during gait training that allows the patient to move up and down during the natural motion of walking and running and still apply a reasonable constant force. 
     What is also needed is an apparatus to offload a portion of a patient&#39;s weight during gait training and catches the patient if there is too much movement or if the patient is unable to support even their reduced weight. 
     What is also needed is an apparatus to offload a portion of a patient&#39;s weight during gait training wherein the force should be relatively easy to apply. 
     What is further needed is an apparatus to offload a portion of a patient&#39;s weight during gait training that is mobile, lightweight and easy for the patient to push so the patient can ambulate over a floor surface. 
     What is further needed is an apparatus to offload a patient&#39;s weight during gait training that enables the patient to reverse his direction easily while pushing the unit without having to turn around a bulky system within a confined space. 
     Yet another need is an apparatus to offload a patient&#39;s weight during gait training allowing the rope a large adjustment range to accommodate different sized patients and having the force on the rope assist the patient rising out of a wheel chair or off a treatment table. 
     Other features and advantages of the present invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an apparatus for offloading a patient&#39;s weight during gait training that comprises any one or a combination of any group of the following items: (i) a frame that is constructed of lightweight materials; (ii) casters that support the frame and aid in the moving of the unit from place to place by rolling; (iii) handles configured to allow a patient to easily push the offloading device; (iv) a single rope arranged to allow a patient to turn completely around during gait training and reverse direction without having to turn the unit around (v) at least one resilient cord arranged so that a patient&#39;s upward and downward movements do not cause large load variances; (vi) a crank handle arranged to permit offloading weight to be adjusted up to about 180 lbs. (vii) a body harness that assists a patient to stand upright and out of a wheel chair; (viii) a second crank handle to adjust the height of the harness; ix) hard stops that limits the dynamic motion of the patient to a maximum of four inches in order to prevent the patient from falling; and (x) a seat attachable to the frame that allows the therapist to sit during gait training. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overall view of the weight offloading apparatus showing some internal parts. 
     FIG. 2 is a view of the inner mechanism of the weight offloading apparatus. 
     FIG. 3 is an overall view of the weight offloading apparatus with a seat. 
     FIG. 4 is a view of the inner mechanism of the weight offloading apparatus with motorized drives. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, the weight offloading apparatus or the unweighing apparatus is a gantry type unit that will straddle a patient. The lower legs  1  have large diameter roll locking casters  2 , 3 . One is steerable ( 2 ), one is fixed ( 3 ). The upper frame  4  is preferably made of lightweight high strength aluminum with removable covers. The upper frame  4  can be affixed to lower legs  1  at a choice of heights, preferably three. 
     There are two large pushing handles  5  mounted on the lower legs  1  which the patient may use to push the unit along the floor. The pushing handles  5  are preferably of an elongated broken-U shape so that they can be used with the patient facing in either direction. A therapist can also push or pull on the handles to assist the patient. The height of the pushing handles  5  are adjustable by pulling a spring loaded pull pin  6  in each of the handles, adjusting the height of the handles  5  and releasing the pins so that they engage in one of a series of holes in the handles. The pushing handles  5  can also be removed and/or may be configured in other ways well known in the art to allow the handles to be secured on the frame at any of a plurality of locations. 
     A rope  7  emerges from the center of the top side of the upper frame  4  and is attached to a padded crossbar  8 . At the ends of the padded crossbar  8  are cables  9  with a pair of quick release shackles  10  at the termination of the cables  9 . The pair of quick release shackles  10  are used to attach a patient harness (not shown) to the unweighing system. The patient harness can be quickly released in an emergency by pulling firmly on release tags  11  on each of the quick release shackles  10 . The quick release shackles  10  open to release the harness. 
     Mounted on the upper frame  4  is a battery operated load display  12 . The load display  12  reads the unweighing load on the rope  7 . The upper frame  4  also has a stop indicator window  13  and an approximate unweighing load window  14 . These windows are used to view indicators within the frame. An unweighing load crank handle  15  is used to adjust the magnitude of the unweighing load. A height adjusting rotating crank handle  16  is used to adjust the vertical height of the padded crossbar  8 . 
     In FIG. 2 the routing of the rope  7  and the function of the mechanism can be seen. Upon entering into the upper frame  4  the rope  7  runs over a first pulley  17  then onto a second pulley  18 . The first pulley  17  is mounted to a lever arm  19 . The lever arm  19  is rotatably mounted at one end to a plurality of bearings  20  that are constrained by a pivot shaft  21  fixed to the upper frame  4  (FIG.  1 ). A bar  22  is fixed to a second end of the lever arm  19 . It can be appreciated that when the load is applied to the rope  7  the lever arm  19  will rotate on the bearings  20 . The bar  22  presses upon a frame member  23  preventing the lever arm  19  from rotating. It can be appreciated that the bar  22  presses upon the frame member  23  with a force proportional to the force on the rope  7 . The proportion is determined by the ratio of the effective lever arm length on either side of the pivot shaft  21 . A strain gage is mounted to the bar  22  such that the force applied to the frame  23  by the bar  22  is measured. This measured load is proportional to the load on the rope  7  such that the rope load can be displayed on the load display  12  (FIG. 1) using standard strain gage electronic technology. 
     The rope is routed along second pulley  18 , then downwards along a third pulley  24 , then upwards around fourth pulley  25  and across the top side  50  of the upper frame  4  around a fifth pulley  26  which is affixed to the intersection of the top side and a second side of the upper frame  50  then along the second side of the upper frame  4  to the upper guide plate  27  where the rope is terminated and attached. Third pulley  24  is mounted to a first tube  28  with threaded bushings  29  at each end. A first threaded shaft  30  runs through the bushings  29  and runs through bearings at top and bottom ends. At the bottom end of the first threaded shaft a first miter gear  31  is fixed. A second miter gear  32  is meshed with the first miter gear  31  and fixed to a second shaft  33 . The second shaft  33  is rotatably mounted in bearings with the height adjusting rotating crank handle  16 . It can be seen that when rotating the height adjusting rotating crank handle  16  the threaded shaft  30  is caused to rotate. The tube  28  with threaded bushings  29  is loosely constrained such that it does not rotate with the threaded shaft  29 . The rotation of the threaded shaft  29  causes the tube  28  with attached third pulley  24  to move vertically. The height adjusting rotating crank handle  16  thereby causes the third pulley  24  with the rope  7  running therearound to move vertically. Considering the second end of the rope  7  that terminates on guide plate  27  to be fixed, it can be seen that the vertical motion of the third pulley  24  causes a vertical motion of the padded crossbar  8  as the rope  7  runs around the pulleys. It should be appreciated that for a given vertical movement of the third pulley  24  the padded crossbar  8  moves twice as far. In the scope of this invention, the tube  28  carrying fifth pulley  24  can move a maximum of about 28 inches on the threaded shaft  30 . Thus the padded crossbar  8  has a maximum vertical movement of about 56 inches to accommodate a vast range of patient sizes. 
     Height adjusting rotating crank handle  16  has a rotatable knob  34  which the user grasps to turn the height adjusting rotating crank handle  16 . The spring loaded rotatable knob  34  has two positions. As shown it has a small radius to rotate through as the handle is turned for the first position. This position is used for fast height adjustments of the padded crossbar  8  under a light load such as when no patient is attached. When a heavy load is present as when assisting a patient out of a wheelchair, the rotatable knob  34  can be moved farther out to position  35 . This is accomplished by pulling the spring loaded rotatable knob  34  out of an inner detent, sliding it out along a slot in height adjusting rotating crank handle  16  and dropping it back into an outer detent at position  35 . This outer position gives the user much more mechanical advantage to move the padded crossbar  8  with heavy loads. 
     As stated above the rope  7  terminates and is attached to the upper guide plate  27 . The upper guide plate  27  is free to slide vertically within the upper frame  4 . Its maximum upper and lower travel is limited by a plurality of fixed stops  36  that are affixed to the upper frame not shown. In this preferred embodiment of the invention the total movement of the guide plate is limited to about 4 inches. This is the general range a patient can move up and down without the load varying excessively. A heavy duty resilient or elastic cord  37  runs through the upper guide plate  27  with both ends of the elastic cord  37  exiting out the bottom surface of the upper guide plate. Both ends of the elastic cord  37  run down passing freely through a mounting bracket  38  and are terminated and attached to lower guide plate  39 . It can be seen that as the padded crossbar  8  moves, the rope  27  ultimately makes the upper guide plate move. When the padded crossbar  8  moves down, the upper guide  27  plate moves up. An indicator  42  is attached to the upper guide plate  27  and is visible to the user through the stop window  13  shown in FIG.  1 . It can be seen that if a patient attached to the padded crossbar  8  were to fall downward, the upper guide plate  27  would move upward only as far as the upper of the fixed stops  36  allow. Thus the patient is “caught” and can not fall more than a few inches. 
     The unweighing load is determined by how much the elastic cord  37  is stretched. The lower guide plate  39  has threaded bushings and is mounted to a third threaded shaft  40 . A fourth miter gear  61  is meshed with a third miter gear  41  and are affixed to a fourth shaft. The fourth shaft is rotatably mounted to an unweighing load rotating crank handle  15 . It can be seen that by rotating the unweighing load rotating crank handle  15  the lower guide plate  39  can be made to move vertically up or down to increase or decrease the tension in the elastic cord  37 . The tension in the elastic cord  37  can be varied from zero with the lower guide plate  39  in the uppermost position preferably up to 180 lbs. with the lower guide plate  39  in the lowermost position. A scale  43  configured to display the approximate tension in the resilient cord is attached to lower guide plate  39 . The scale  43  is equipped with an indicator label to display the tension that is visible to the user through the approximate unweighing load window  14  (FIG.  1 ). The scale  43  indicates the position of the lower guide plate  39  and thus the approximate unweighing load range. 
     The elastic cord  37  is sufficiently long so that a small movement of the upper guide plate  27  caused by the patient moving the padded crossbar  8  up and down while walking does not vary the tension in the cords excessively. Thus normal walking does not vary the unweighing load excessively. 
     Note that when the elastic cord  37  is tensioned, the upper guide plate  27  is pulled downward against the bottom of the fixed stop  36 . It will remain there until a load is placed on the padded crossbar  8 . 
     In use, the approximate unweighing load is set by rotating the unweighing load rotating crank handle  15  until the elastic cord  37  is tensioned to the desired range as indicated on the scale  43  viewed through the window  14 . At this point the upper guide plate  27  is pulled against the lower of the fixed stops  36 . Next the padded crossbar  8  height is adjusted by rotating the height adjusting rotating crank handle  16  until it is just over the patients head. Next the patient wearing a harness is attached to the padded crossbar  8 . The padded crossbar  8  is raised by rotating the height adjusting rotating crank handle  16  until tension starts to develop in the rope  7 . The user continues to crank the height adjusting rotating crank handle  16  but the padded crossbar  8  will eventually stop moving up. 
     Instead, the upper guide plate  27  will be pulled up off the lower fixed stop  36 . Now the tension in the elastic cord  37  is transferred to the rope  7  and thus to the patient. The load now may be measured through the strain gage on the bar  22  and displayed on the unweighing load display  12 . The height adjusting rotating crank handle  16  is turned until the upper guide plate  27  is centered between the fixed stops  36 . This is shown by the indicator  42  in the stop window  13 . At this point the unweighing load can be finely adjusted by again turning the unweighing load rotating crank handle  15 . 
     In addition, the frame may be equipped with a releasable seat (FIG. 3) mounted to the frame to allow a therapist to be seated while administering therapy. Alternatively, the seat may be collapsible mounted to the frame as well. 
     The functions of the crank handles  16 ,  15  may be supplemented by a motorized drive  51  (FIG. 4) that may operate either independently or as a replacement for the crank handles. The motorized drive  51  would be preferably battery powered. Otherwise, if powered from a wall socket, movement of the entire unit would be hampered since the power cord might get in the way or restrict such movement. Even if motorized, the unit should still have the crank handles to cover the possibility of power outage. 
     One motorized drive  51  (FIG. 4) may be provided to move the crossbar  8  relative to the frame in the same way that turning the height adjusting rotating crank  16  may be turned to effect the same relative height adjustment. Such a height adjusting rotating crank  16  and the motorized drive may be considered height adjustors. A further motorized drive  56  (FIG. 4) (preferably battery powered) may be provided to supplement the function of the unweighing load rotating crank handle  15 , or in its stead, by driving the lower guide plate  39  to increase or decrease the tension in the elastic cord  37  in the same manner that turning the unweighing load rotating crank handle  15  would accomplish such a change. Both the unweighing load rotating crank handle  15  and the further motorized drive may be considered tension adjustors.