Abstract:
A device for adjusting the height of and relief force acting on a weight is especially provided to be used for walking therapy of paraparetic or hemiparetic patients within a locomotion training means. Said weight of the patient is supported by a cable. A first cable length adjustment means provides an adjustment of the length of the cable to define the height of said suspended weight. A second cable length adjustment means provides an adjustment of the length of the cable to define the relief force acting on the suspended weight. This allows a quick and reliable determination and adjustment of the height for different patients and of the relief force within the training program of every patient.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a device and a process for adjusting the height of and the relief force acting on a weight, especially on the weight of a patient within a locomotion training means to be used for walking therapy of paraparetic or hemiparetic patients. In other words, the invention relates to an automatic unloading device that allows unloading an object attached to one end of a rope by a precise counter force. Especially, the invention relates to a device and a process, which can be used within a locomotion training of patients with walking impairments in any phase of rehabilitation.  
       BACKGROUND OF THE INVENTION  
       [0002]     As mentioned above said type of unloading system can be used for different applications but is preferably intended for the use in body weight supported treadmill training. This type of training is for example being used to train neurologically impaired patients to walk again during rehabilitation. For such incomplete paraplegic patients the possibility exists of improving walking ability up to normality by means of adequate locomotion training. The required therapy at present takes place on a treadmill, where walking is first made possible for the patient by defined weight relief and partially by additional assisting guidance of the legs by physiotherapists (Wickelgren, I. Teaching the spinal cord to walk. Science, 1998, 279, 319-321). already in use, which actively move the legs of recumbent patients. During body weight supported treadmill training, a patient is walking on a treadmill, while he is partially suspended from part of his body weight.  
         [0003]     EP 1 137 378 discloses an automatic machine, which is used in treadmill therapy (walking therapy) of paraparetic and hemiparetic patients and which automatically guides the legs on the treadmill. Said machine consists of a driven and controlled orthotic device, which guides the legs in a physiological pattern of movement, a treadmill and a relief mechanism. The knee and hip joints of the orthotic device are each provided with a drive. Said orthotic device is stabilized on a treadmill with stabilizing means in such a manner that the patient does not have to keep his/her equilibrium. The orthotic device can be adjusted in height and can be adapted to different patients.  
         [0004]     The unloading is achieved by a counterweight that is attached to the other end of a rope, which is connected to the patient by a harness. This is by definition a simple method and the results are often acceptable for regular treadmill training. However, there are some disadvantages in using this method for this kind of therapy. One disadvantage is occurring if the patient has to be suspended by a large amount of his body weight. If a large mass has to be attached on the other side of the rope the inertia of the mass is causing large forces during the up and down acceleration of the body. Also, it is not very easy to change the amount of unloading during the training with most of the conventional counterweight systems. Either the therapist has to lift weight to or from the system to change the suspension or the patient has to be lifted by a winch to be able to connect additional counterweights to the system. to change the suspension or the patient has to be lifted by a winch to be able to connect additional counterweights to the system.  
         [0005]     Prior art discloses devices to provide a reliable positioning of the device height, but are cumbersome to adapt to different patients. Another limitation of this approach is furthermore the limited liberty of changes to be made in the course of the application of the walking program for the patient.  
         [0006]     One object of the invention is therefore to describe a device allowing faster response times and more precise determination of the height of the patient&#39;s position and of the relief force.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention relates on the insight that the functions of the cable adjustment means have to be separated to be able to achieve an electronically controlled fast adjustment of the relief force.  
         [0008]     The set object is met in accordance with the invention by means of a device in accordance with the wording of claim  1 .  
         [0009]     The features according to claim  1  uses two different cable length adjustment means. One is provided to adjust the length of the cable to define the height of the suspended weight. The other is provided to adjust the length of the cable to define the relief force acting on the suspended weight.  
         [0010]     The invention enhances the control of height and relief force through the separation of the functions. The height of the weight depends on the patient, whether he is a tall or a small person. This is adjusted at the beginning of a training session. The corresponding device can act slowly, even manually. The relief force has to be controlled during the actual therapy. The second cable length adjustment means divides the necessary relief force in a first static part, providing an approximate force response, and a second dynamic part, providing the fast fluctuations of the relief force while the patient is walking.  
         [0011]     Further preferred embodiments of the apparatus according to the invention are characterized in the dependent claims.  
         [0012]     In order to adapt the principles of the invention to a larger range of instruments the different devices are motorized and connected to a computer means with memory, the memory comprising database entries for different patients (height of suspension and intended general relief force) and different walking therapies (fine tuned relief force programs). This allows a quick and reliable determination and adjustment of the height for different patients and of the relief force within the training program of every patient.  
         [0013]     A benefit of the device according to the invention is therefore that any patient can readily mount the apparatus to use the treadmill therapy, which is very easy to adjust for his needs. No special preparation of the treadmill, and no dedicated elastic means are required. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a perspective view of a device according to one embodiment of the invention, and  
         [0015]      FIG. 2  shows a schematic diagram of the controller in combination with the device according to  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]      FIG. 1  shows a perspective view of a device for adjusting the height of and relief force acting on a weight according to one embodiment of the invention.  
         [0017]     The device comprises two main components: one static part  1  and another dynamic part  2 . The static component  1  comprises a winch  10  controlling a primary cable  11  to which the patient is attached. In the embodiment shown the primary cable  11  fixed at the turning sleeve of the winch  10  is running preferably parallel to the longitudinal main axis  20  of the dynamic part  2  of the device. Said longitudinal main axis  20  is directed vertically to the ground.  
         [0018]     Cable  11  is redirected by a fixed roller  12  towards the dynamic part  2  of the device, engages the moving roller  21  being part of said dynamic part  2  and leaves the dynamic part  2  as adjusted cable portion  13  of the cable  11 . The cable  11  is then leaving the device redirected by one or more fixed rollers  14 ; the corresponding prolongation of the cable  11  has received the reference numeral  30 .  
         [0019]     A patient who intends to use a known apparatus for a treadmill therapy, e.g. according to EP 1 137 378, is attached in said prolongation  30  of the cable  11  in a harness (not shown) oriented vertically. The winch  10  is statically suspending the patient so he cannot fall and therefore is also responsible for the safety of the patient per se.  
         [0020]     Although within the preferred shown embodiment of the invention winch  10  is used to statically adjust the length of cable  11  provided to said harness, it is also possible to fix cable  11  at the location of the winch  10  and to provide a drive unit connected to the fixation of a roller upstream of the dynamic part  2 , e.g. roller  12 , so that said roller  12  can be moved in direction of longitudinal axis  20 . In another embodiment not shown in the drawings it can be a roller (or a combination of rollers) downstream of the dynamic part  2 , e.g. roller  14 , being mounted with a drive unit so that said roller(s)  14  can be moved in direction of longitudinal axis  20  to adjust the length of the cable  11  provided to attach a patient. Within a third embodiment the static part  1  comprises a unit connected to the frame  32 . In said case the static part  1  does not act directly on the cable. Said unit is provided to move frame  32  in the direction of longitudinal axis  20 . With a fixed end of cable  11  said movement of frame  32  moves roller  21  and therefore lengthens or shortens the free cable  13 .  
         [0021]     All these alternative units for winch  10  can constitute the static part  1  of the device to provide a static adjustment of the length of the cable  11  provided in said prolongation  30  which corresponds to the intended height of the harness for use in a walking therapy.  
         [0022]     The dynamic part  2  comprises an elastic means. The elastic means of the embodiment is a spring means  22  provided as two helicoidal springs provided on either side of a central spindle  23 . Beside the use of helicoidal springs  22  it is also possible to use different types of elastic means, being able to exert a force in the approximate range of the intended weight to be attached to the prolongation  30  of the cable  11 .  
         [0023]     Springs  22  are attached between a bottom plate  24  and a top plate  25 . The bottom plate  24  is attached to a spindle drive  31  connected with spindle  23  engaging a thread within bottom plate  24 . Spindle drive  31  shows a handle but can also be motorized and connected to a control unit. Top plate  25  is connected to a pulley  21 , pulling the cable  11  down. Through use of the redirection of cable portion  13  the rollers  12 ,  14  and  21  have the function of a pulley block. It can be intended to use even more redirections to translate the adjustment of the cable length of the prolongation  30  into a much smaller movement of the pulley  21 .  
         [0024]     In parallel with the springs  22 , i.e. parallel to the axis  20 , there is a linear drive  26  attached to the pulley  21  via the top plate  25 . By this linear drive  26  the force of the springs  22  can be reduced or enhanced. Between the pulley  21  and the dynamic control component acting on the springs  22  and linear drive  26 , there is a force transducer  27  that measures exactly how much force is being applied to the rope  13  by the pulley  21 . The force transducer  27 , connected in series to elastic means  22 , is connected to a electronic control unit. The control unit is preferably forming a closed loop control unit.  
         [0025]     The linear drive  26  is controlled by said electronic control unit, e.g. provided as a computer system, through a closed loop controller in such a way, that the force acting on the force transducer  27  can be controlled precisely. The force acting on the force transducer  27  is mostly directly proportional to the force acting on cable  13  at the harness. Due to frictional effects the force can be considerably influenced, especially following the choice of the material of the rope  13  and/or the pulleys. These differences from direct proportionality can be controlled through a programmed controller and/or through introduction of a disturbance value.  
         [0026]     The force transducer  27  can also be mounted to measure the force acting on the pulley  14 , on the pulley  12  or near the patient at the other side  30  of the cable  11 , being the connecting link to a harness supporting the patient (weight  40 ).  
         [0027]     A treadmill training of a neurologically impaired patient can be performed as follows: First the patient, attached to the other side  30  of the cable  11  with a harness, would be suspended over the walking surface by the winch  10  (static unloading system  1 ) until standing.  
         [0028]     The amount of unloading is defined by the control unit. A small motor attached to the spindle drive  31  that determines the tension of the springs  22  would then extend the springs  22  up to a length that more or less corresponds to the desired unloading of the patient. Like this the dynamic system is already unloading the patient nearly with the desired force.  
         [0029]     This closed loop control of body weight support allows for perfect accommodation of partial weight bearing exercise.  
         [0030]     The up and down movement of the patient causes the force to be not constant during the training if only the springs  22  were attached. Therefore the linear drive  26  can adjust the position of the pulley  21  online, as controlled by the close loop controller, so the force acting on the rope  11  will be constant, or corresponding to a desired force trajectory, during the whole training. Within other embodiments the dynamic drive adds a motor driven force to the spring force in a manner to compensate the influence of the position of the device on the spring force due to friction based effects due to the choice of the material of the rope and the pulleys.  
         [0031]     The device can only guarantee a precise, desired unloading, as long as the weight can be adjusted by the linear drive  26 . This is not possible anymore, if the patient moves up or down too much, meaning that the linear drive  26  is approaching the end of the range of motion. This is detected by the control unit, as the movement of the linear drive  26  is measured with a position sensor, e.g. a ultrasound transducer mounted beneath top plate  25 . The control unit can therefore readjust the position of the patient with the winch  10  in terms to bring the linear drives  26  back into the range of operation.  
         [0032]      FIG. 2  shows a schematic diagram of the electronic controller unit in combination with the device according to  FIG. 1 . The winch  10 , the actuator  26 , e.g. the linear drive, and the bias means  31 , e.g. the spindle drive, are shown receiving an controller signal I and outputting a signal proportional to a well-defined force F or position x. The boxes of  FIG. 2  showing a actual device according to  FIG. 1  have received the same reference numeral, although it is clear for someone skilled in the art that the boxes of  FIG. 2  further comprise the electronic controller components to deliver the control signals mentioned.  
         [0033]     Numeral  40  is used to define the weight of e.g. a human subject to use the treadmill for which the device for adjusting the height of and the relief force acting on said weight  40  is provided. A position sensor  34  (not shown in  FIG. 1 ) measures X real  and outputs X measured . The force sensor  27  measures F real  and outputs F measured . The (static) position of the cable x measured  is input to the winch controller  35 , acting via a control signal I winch  on the winch  10  to define the predetermined height, which can be input to the winch controller  35  via a key means or an electronic signal of said electronic control unit comprising the walking program for a patient.  
         [0034]     The key means or an electronic signal of said electronic control unit comprising the walking program for a patient generates the input F desired . A mixer  36  is provided to output the difference signal of F desired  and F measured . Said difference signal F diff  is input to a force controller  37  outputting the corresponding control signal I drive  which is fed to the actuator  26  to dynamically change the length of the cable  13  to control the force relief.  
         [0035]     F desired  is also the input to the spring load controller  38 , outputting a signal I springs  to bias means  31 , which in turn moves bottom plate  24  to adjust the static weight compensation by springs  22 . The length of the springs  22  is controlled with the bias means  31  to move the bottom plate  24  into a position that the tension of the springs  22  is such that patient is unloaded approximately by the desired force F desired.  The spring load controller  38  has therefore a far slower response than the force controller  37 .  
         [0036]     In another embodiment of the device according to  FIG. 1 a  position sensor  34  (not shown) is provided to directly measure the length of the springs  22 . This can be a position sensor mounted near top plate  25  measuring the distance of said sensor from bottom plate  24  or from the element holding pulley  12  or  14 . Said position sensor inputs a spring length signal to the controller as shown in  FIG. 2 , especially into block  38  showing the spring load controller. Additionally the signal issued from position sensor  34  is fed to the force controller  37  to generate a disturbance value. As mentioned above frictional effects can hamper the usual proportionality between spring length and load. The additional feeding of the actual position value to the force controller  37  and/or the spring load controller  38  enables the controller to adapt the force F drive . In this respect it is advantageous to feed F desired  directly to the force controller  37  in order to have a actual base for the generation of I drive  to generate a force F drive  adapted to the friction within the whole device.