Abstract:
A vibrating footplate provides operates at two or more distinct vibration modes to provide improved stimulation to bone and muscle of a human body having multiple modes of resonance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application 60/867,719 filed Nov. 29, 2006 hereby incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to mechanical devices for applying beneficial stress to the body for prevention of osteoporosis or stimulation of muscle and tissue. 
         [0004]    Bones in the human body are subject to constant remodeling in response to stresses that promote bone formation. Such stresses may occur during natural physical activity or exercise. 
         [0005]    One possible treatment for osteoporosis or bone loss may be machines which apply stress to a patient, for example, by means of the patient standing on a vibrating platform that simulates the stresses that would occur through natural activities. Such machines may be useful for those who are unable otherwise to obtain sufficient physical activity or as a method of supplementing physical activity in a more concentrated manner. 
         [0006]    An early device, described in U.S. Pat. No. 5,046,484 issued to C. Andrew L. Basset provides a platform that is periodically raised by means of the action of a cam and then dropped abruptly to simulate the natural footfall of an individual. In this case, the stress is caused by rapid deceleration of the platform at the bottom of its travel. The impact rate may be determined by measuring a natural rate of heel strikes when a patient is walking and is determined by the regular rotational speed of the motor. 
         [0007]    U.S. Pat. No. 6,659,918 issued to Hans Schiessl uses a crank arm to impart a simple harmonic motion to a similar platform at a frequency dictated by the rotational speed of a motor. 
         [0008]    U.S. Pat. No. 5,273,028 issued to Kenneth J. McLeod describe an alternative drive mechanism in which the platform is mounted on springs and driven at a resonant frequency by an electromagnetic actuator or rotating eccentric mass. Such systems provide a single excitation frequency to the platform whose ultimate movement is determined by the resonance of the system including the spring constant of the springs and the mass of the patient. 
       SUMMARY OF THE INVENTION 
       [0009]    The present inventor has recognized that the body is a complex system of resonant structures having linear and nonlinear elements. For example, lower lumbar vertebrae and hip joints are parts of different resonant structures and thus have different resonant responses. For this reason, inducing desirable levels of stress or muscle activity in different structures may require excitation simultaneously at two or more frequencies at different controlled amplitudes. Current systems which provide a single frequency of excitation, or in the case of an impact system, a single band of frequencies whose amplitudes are essentially uncontrollable, may provide less than optimal excitation of body structures. 
         [0010]    Specifically then, the present invention provides an apparatus for mechanical stimulation of the body, including a footplate for receiving feet of a standing person and a actuator attached to the footplate to impart a pattern of vertical motion to the footplate consisting of periodic accelerations at predetermined different times with predetermined different amplitudes. 
         [0011]    It is therefore one is an object of the invention to apply substantial energy at multiple different frequencies of vibration to a person as determined by the actuator. 
         [0012]    The accelerations may be in a frequency range from 10-100 hertz. 
         [0013]    Thus, it is an object of the invention to provide a system that may provide frequencies thought to be desirable for the stimulation of bone strength. 
         [0014]    The apparatus may include an adjustment means for changing the time between the periodic accelerations and thus a frequency range of the accelerations. 
         [0015]    It is thus an object of the invention to provide a system that allows adjustment of the stimulation frequency. 
         [0016]    The actuator may produce a predetermined displacement of the footplate independent of the weight of a body. 
         [0017]    It is thus an object of the invention to provide a system that may work with a variety of different patients without adjustment of springs or weights. 
         [0018]    The periodic accelerations may be selected to accommodate different resonant modes of different structures of the body. 
         [0019]    It is thus an object of the invention to provide a system that recognizes that the body is composed of loosely coupled different resonant structures. 
         [0020]    The actuator may include at least one cam having a non-circular profile. 
         [0021]    It is thus an object of the invention to provide a flexible, yet simple method of providing an arbitrary multi-frequency excitation pattern to the footplate. 
         [0022]    The invention may include cam followers attached to the footplate and resting against multiple synchronously rotated and phased cams. 
         [0023]    It is thus an object of the invention to provide a system that minimizes the mass and structure on the moving footplate. 
         [0024]    The cam followers may be compliant to control the acceleration of the footplate. 
         [0025]    It is thus an object of the invention to reduce high frequency components to the patient, such as may provide for less therapeutic benefit. 
         [0026]    The invention may provide a speed-controllable motor for adjustment of the time between the periodic accelerations. 
         [0027]    Thus, it is an object of the invention to provide an absolute frequency control independent of the particular patient. 
         [0028]    These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a simplified perspective view of the present invention showing a patient standing on a moveable footplate, the patient steadied by optional guide rails; 
           [0030]      FIG. 2  is a block diagram of the principal components of the present invention including a controller for controlling a motor drive that is connected to a motor rotating a set of cams driving the footplate of  FIG. 1 ; 
           [0031]      FIG. 3  is a side elevational view of the platform of  FIG. 1 , showing positioning of the cams on either side of the drive motor and their interaction with resilient cam followers attached to the footplate; 
           [0032]      FIG. 4  is a pair of aligned graphs showing motion of the footplate and frequency components of the motion of the footplate, the latter illustrating two frequency modes each with controllable amplitude defined by lobes on the cam; 
           [0033]      FIG. 5  is an exaggerated profile of the cams of the present invention showing multiple lobes of different height to provide for controlled amplitudes of different stimulation frequencies; and 
           [0034]      FIG. 6  is a figure similar to that of  FIG. 1  showing a patient on a seated version of the apparatus having a movable footplate and seat pan. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    Referring now to  FIG. 1 , a first embodiment of a bone stimulation system  10  of the present invention includes a floor unit  12  having an upper footplate  14  which may receive the feet of a standing person  16 . Rearwardly extending handlebars  18  attached to a post extending upward from the floor unit  12  may be grasped by the person  16  during use of the bone stimulation system  10 . A control panel  17  providing for an on an off switch and timer unit may be attached to the handlebars  18   
         [0036]    Referring to  FIG. 2 , the footplate  14  may have on its lower surface cam followers  20  resting against the upper surfaces of different multiple lobe cams  22  (only one shown for clarity) so that the footplate  14  moves along a vertical axis as the cams  22  rotates to follow the displacement dictated by the profiles of the cams  22 . The cams  22  may have multiple lobes  60 ,  62  of different heights so as to impart periodic accelerations  24  and  24 ′ respectively at different times having different amplitudes. Cams  22  may be rotated by a speed controllable motor  26  driven by a motor controller  28  so that the speed of rotation of the cams  22  may be controlled. A computer  30  may be connected to the motor controller  28  to control a particular stimulation regime with respect to on time and off time and frequencies of rotation of the cam  22  per instructions received from the control panel  17 . 
         [0037]    Referring now to  FIG. 3 , the footplate  14  may include a support plate  32  being substantially rigid and, supporting on its upper surface, a traction material  34  providing a no-slip surface for receiving the feet of the person  16 . The rigid plate  32  may have downwardly extending shafts  36  at each of its four corners received by the bores of upwardly extending sleeves  38  attached to a base plate  40 . The upwardly extending sleeves  38  engage slidingly with the downwardly extending shafts  36  to guide motion of the footplate  14  along the vertical axis of the accelerations  24  and  24 ′. The base plate  40  that may rest against the floor, for example, on shock absorbing feet  42 . 
         [0038]    A set of four cams  22  rotating about horizontal axes may be positioned near each of the four corners of the plate  32 , beneath the plate  32 . Shafts  44  of the cams are mounted for free rotation on bearings and pillow blocks (not shown). The shafts  44  have timing belt pulleys  48  interconnected by a timing belt  46  fitting about timing belt pulleys  48  on each of the shafts  44  so that the cams  22  turn in unison and in the same phase, meaning that the relative position of each cam  22  is the same at all times. 
         [0039]    A separate timing pulley  48  on one shaft  44 , not visible in  FIG. 3 , and timing belt  50  connects that shaft  44  to a corresponding timing pulley  54  on the motor  26 . The motor  26  may be connected to the variable speed motor controller  28  held within the floor unit  12  and a computer  30  (previously shown in  FIG. 2 ). 
         [0040]    At all times during operation, the height of the footplate  14  is determined by the abutment of the outer periphery of the cams  22  with cam followers  20  positioned at the lower surface of plate  32  and resting on each of the cams  22 . The cam followers may include a lower wear surface  56  reducing the friction between the cams  22  and the cam followers  20  when the cams  22  are rotating. Above the wear surface  56 , the cam followers  20  may be composed on an elastomeric foam  58  serving as a spring element between the plate  32  and the cams  22  providing some attenuation of the peak forces applied to the footplate  14  and high frequency vibration as may be desired. 
         [0041]    Referring now to  FIGS. 4 and 5 , each cam  22  may have three primary lobes  60 , in this case positioned at 120° spacing around the cam  22  and three secondary lobes  62  also spaced at 120° in between each of the primary lobes  60 . The primary lobes  60  and secondary lobes  62  and having a different radii with respect to a center  64  of the cam  22  controlling the relative excursions of the footplate  14  as each lobe  60  and  62  rides against the cam followers  20 . 
         [0042]    Referring to  FIG. 4 , a y-axis motion of the footplate  14  along the axis of accelerations  24  and  24 ′ as a function of time shows complex time domain excursion  66  that are not sinusoidal (that is not composed primarily of a single sinusoid or single frequency in steady-state or in a resonant decay) associated with the complex shape of the cam  22 . This complex time domain excursion  66  creates multiple distinct frequency modes  70  at different frequencies. The two most dominant frequency modes  70 ′, attributable to the lobes  60  and  62 , have substantial energy and energy&#39;s that match each other to within 20 percent. Notably the frequency of the higher frequency dominant mode  70 ′ may be less than twice the frequency of the lower frequency dominant mode  70 ′ providing closer frequency spacing then can be obtained in a standard harmonic typical with the prior art. Additional frequencies modes  70  may be obtained by the impact like interaction between the cam  22  and the cam follower  20 . Generally the absolute frequency of the modes  70 ′ can be adjusted up and down by changing by the rotational speed of the cams  22 . Proper design of the profile of the cams  22  allows the energy and frequency of each mode  70  to be tailored as desired and/or additional modes to be generated. 
         [0043]    Referring now to  FIG. 6 , in an alternative embodiment the person  16  may sit on a first seat unit  12 ′ having a seat pan  14 ′ constructed according to the floor unit  12  described above. The seat pan  14 ′ may be elevated sufficiently so that the person&#39;s feet may rest on the footplate  14  of the floor unit  12 . In this case, handlebars  18  may be positioned on the side of the seat pan  14 ′ to support the person  16  in a seated posture aided by of seat back  19 . Simultaneous vibration of floor unit  12  and seat unit  12 ′ may provide for a therapeutic action for individuals who cannot stand during treatment. Alternatively, vibration of the seat unit  12 ′ alone may be provided using the above described multifrequency mechanism, for example, in situations where the floor unit  12  is not warranted, for example for a patient being rehabilitated after hip surgery or who otherwise cannot accept force on their legs, or in situations where a floor unit  12  can not physically be accommodated, for example, in the cockpit of an aircraft. 
         [0044]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.