Abstract:
A hand-held compressible and expandable device is used to develop and measure the persons grasping strength and grasping dexterity. The device in preferably compressed and/or expanded by the user&#39;s digits. Preferably, the device is both compressible and flexible so that the user must provide a linearly or controlled force to compress the device successfully. In one embodiment, the device has a spring that is both compressible and flexible. One end of the spring has a finger pad and at the other end a thumb pad. The ability of the user to compress the spring between the finger and the thumb gauges the users grasping strength, while the ability of the user to compress the spring in a linear fashion provides a measure of the user&#39;s dexterity. The device also can be configured to automatically count the number of successful and/or unsuccessful compressions mechanically, optically or electrically. The compressibility, flexibility and difficulty of use of the device is modified using a variety of mechanisms besides modifying the stiffness, diameter, length or other properties of springs including rubbers, foam rubber elements and hinges. The device is particularly useful to provide a low cost diagnosis and therapy for patients and individuals that need to develop or regain grasping strength and dexterity.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to devices for developing and measuring grasping force and grasping dexterity. In particular, it relates to compressible and expandable devices that are compressed or expanded by a person&#39;s digits to develop and measure the person&#39;s grasping force and grasping dexterity. The device can be used in a regiment that allows for quantification, measurement and development of motor skills needed for grasping. 
     BACKGROUND 
     Adequate grasping force and grasping dexterity is required for individuals to perform tasks like eating, tying shoe laces and thousands of other everyday tasks. When an individual loses grasping strength or control, their independence and quality of life is severely compromised. Loss of grasping strength and dexterity can result from old age and various other health related causes such as injury or disease. The loss of grasping strength and dexterity may be temporary, as is often the case after a person experiences an injury or orthopaedic surgery and rehabilitation. The speed at which a person can regain proper operation of the hands and digit control after surgery or disease greatly depends on the amount and quality of physical therapy that the individual receives. Personal physical therapists can be very expensive and are not available to each and every patient that requires therapy to regain grasping strength and dexterity. 
     Thus, patients that cannot afford physical therapy or do not have such services available for one reason or another have to rely on self motivation in order to develop or regain proper operation of the hands after injury. Unfortunately, if the patient is bed ridden he or she will not have the opportunity to tie shoes, wash dishes and the like which can help them to regain dexterity and strength in the hands. 
     There are several other reasons why an individual may wish to improve his or her grasping strength or grasping dexterity. For example, musicians that use their hands to play instruments may wish to exercise their fingers in environments where practicing their instrument is not feasible or not possible. Rock climbers may wish to improve their grasping strength prior to a climb and surgeons may wish to improve their dexterity to improve their ability to perform delicate operations. 
     Physical therapy requires the measurement and development of different combinations of finger strength and dexterity. Unfortunately, the available methods to quantify hand and finger functions clinically only measure strength. Dexterity is only measured qualitatively by prior art methods. 
     Therefore, there is a need for a device that can be used to measure and to improve the grasping strength and grasping dexterity. Preferably, the device is hand-held and can be used in a regiment that measures individual&#39;s grasping strength and grasping dexterity. 
     OBJECTS AND ADVANTAGES 
     One object of the present invention is to provide a hand-held device that may be used in a therapy to exercise the digits of an individual in order to improve finger strength. The hand-held device allows individuals to remain substantially immobilized while exercising and developing their grasping strength. 
     It is a further object of the present invention to provide a device, which is flexible and measures grasping dexterity. The device not only allows the individual to develop grasping strength, but also his or her grasping dexterity. 
     It is yet another object of the current invention to provide a device for developing grasping strength and grasping dexterity, which is inexpensive, can reduce the cost of therapy, and allows individuals to develop grasping strength and grasping dexterity in a variety of environments. 
     It is also an object of the present invention to provide a device for developing grasping strength and grasping dexterity that yields a quantitative measurement of grasping strength and grasping dexterity. 
     SUMMARY OF THE INVENTION 
     These objects and advantages are obtained by providing a hand-held device with a compressible section. In one embodiment of the invention a user holds the device between the palm of his or her hand and applies a force with a finger to compress the device. Through repeated compressions of the device the user can measure and develop grasping strength. 
     In the preferred embodiment of the invention the device is configured to be held between a finger and a thumb of the same hand. The user compresses the device in a compression direction with the finger and the thumb. In the most preferred embodiment of the invention, the device is also capable of bending or flexing in an off axis direction such that the user must compress the device in a predetermined fashion to achieve successful compression. The ease with which the device is designed to bend in an off axis direction determines the required grasping dexterity that the user must have to successfully compress the device. 
     To vary the skill level that is required in order to successfully compress the device, a variety of mechanisms are used. For example, different spring stiffnesses and dimensions can be used to increase or decrease the strength and dexterity required to successfully compress the device. Alternatively, flexible elements, hinges and the like can be integrated into the device to make the device more flexible and more difficult to compress. The variety of ways that the device can be modified for different user skill levels and different user goals will become clear in the ensuing examples. 
     The device can also be configured to operate in an expansion mode such that the user must apply an expansion force to the device in order to develop grasping strength and grasping dexterity. It is also possible that the device requires force to both expand and compress the device. In a particular embodiment of the current invention several springs are attached together by their ends. At the other ends of the springs there are loops for inserting fingers or thumbs. The user inserts his or her fingers and/or thumb into the loops and repeatedly expands the device in various directions to develop and measure grasping strength and grasping dexterity. 
     All of the embodiments described can be equipped with an automated counter that measures the number of successful or unsuccessful expansions and/or contractions of the device. A series of devices, which require a range of skill levels to operate, can be used in a designed grasping rehabilitation or grasping improvement program for patients, musicians and athletes alike. 
    
    
     BRIEF DESCRIPTION OF FIGURES 
     FIG. 1 shows a perspective view of a device made in accordance with the present invention, which is held in the palm of a hand. 
     FIG. 2 is a graph showing the spectrum of grasping abilities that can be measures by various springs. 
     FIG. 3 is a graph showing two rehabilitation paths that can be followed to develop and a patient&#39;s grasping strength and grasping dexterity. Path A shows the developments of the strength and dexterity simultaneously. Path B shows the development of the strength first, then dexterity. 
     FIGS. 4A-4D show perspective views of a spring device made in accordance with the present invention and its operation. 
     FIGS. 5A-5C show sectional side views of various finger pad configuration attached to the ends of springs. 
     FIGS. 6A-6B show cross-sectional views of a device made in accordance with the current invention with compressible metal spring strips. 
     FIGS. 7A-7B show cross-sectional views of a device made in accordance with the current invention with compressible metal spring strips and hinges. 
     FIGS. 8A-8C show plan side views of a device made in accordance with the present invention, having a compressible spring and a flexible material. 
     FIG. 9 shows a plan side view of an alternative embodiment of the current invention with two compressible springs and a flexible element between the springs. 
     FIG. 10 shows a cross-sectional view of a device for measuring grasping strength and grasping dexterity that has a compressible spring and finger pads attached to the spring through hinged pads. 
     FIG. 11 shows a cross-sectional view of an alternative embodiment of the current invention with two compressible springs, and a flexible element between the springs with a hinging center contained therein. 
     FIG. 12 shows a plan side view of a device with two compressible sections and three pivoting ball joint hinges. 
     FIG. 13 shows a device for measuring grasping strength and grasping dexterity that utilizes a spring, pivoting ball joint hinges, a compressible section and a flexible material. 
     FIG. 14 shows a device for developing grasping strength and grasping dexterity by exercising three digits of a hand. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective view  10  of a hand-held device  3  made in accordance with the current invention. The device  3 , has a finger pad  1  for positioning a finger tip  6  and a palm pad  2 , positioned at the opposing end for resting the device in the palm of a hand as shown. The compressible section of the device operates like a piston. A piston portion  7  resists compression because of a compressible element in the form of a spring  4  contained in a spring housing  8 . The user places the finger tip  6  on the pad  1  and repeatedly depresses the piston  7  in a linear compression direction  9  such that the piston  7  recedes into the housing  8 . The repeated operation of the device  3  as described is used to build up finger strength. A successful compression requires that the piston  7  be depressed to a predetermined depth. The device  3  can have any number of spring strengths tailored to a particular user&#39;s ability. 
     It is preferred that device  3  be configured to be compressed by placing the device between a finger and a thumb and applying the appropriate force along a linear compression direction. It is most preferred that the ends of the device where the finger and thumb are positioned are capable of being displaced in an off axis direction from the linear compression direction. In this way, the user is required to consciously compress the device along the linear compression direction with a certain degree of dexterity. For this purpose coiled springs are particularly useful. The device can be configured to accommodate any number of digits. 
     FIG. 2 is used to illustrate variations of compression strength and dexterity required to obtain a linear compression of springs having various physical properties. A compliant spring requires less force to be compressed, while a stiff spring requires more force to be compressed. A wide, short spring is more stable because it requires a less precise alignment of forces to compress, while a narrow, long spring is more precarious because it requires a more precise alignment of forces to compress, thus requiring a greater degree of dexterity to compress. Different types of springs can be used to measure different combinations of finger force and grasping dexterity. For example, a lower degree of finger force and grasping dexterity can be measured with a wide (25 mm diameter), short (12 mm length), compliant (0.1 N/mm stiffness) spring, while a higher degree of finger force and grasping dexterity can be measured with a narrow (8 mm diameter), long (50 mm length), stiff (2 N/mm stiffness) spring. 
     For rehabilitation of a patient who has lost some grasping ability, or for training of a person to improve his or her grasping ability, different versions of the device can be used in series. As shown in FIG. 3, a patient or trainee first uses a compliant, stable device and works his or her way up to a precarious, stiff device in Path A. Alternatively, in Path B, a patient or trainee can start with a complaint, stable device, work his or her way up to a stiff, stable device, and then work his or her way up to a stiff, precarious device. The path can be customized for each patient&#39;s needs or each trainee&#39;s goals. 
     In addition, the dexterity of the patient or trainee&#39;s grasping ability can be quantifiably measured by varying the materials used in construction of the finger pads placed at the ends of the spring. Finger pads with high surface friction, such as sand paper or carpet, can be used to test low dexterity. Finger pads with low surface friction, such as Teflon® or smooth plastic, can be used to test high dexterity. Finger pads with intermediate surface friction, such as wood or cloth, can be used to test intermediate dexterity. Obviously, the more slippery the material used, the more difficult it will be for the patient or trainee to grasp and align the finger pads and then squeeze them together with an opposing force. By varying the texture of the surface, the sensory information of the fingers can be varied and used to quantify and test the influence of finger sensation on grasping ability. 
     FIG. 4A is a plan side view of an embodiment which can be used to measure and develop grasping force between a thumb and a finger. This embodiment is exemplified by a device  20  which utilizes a spring  28  and the properties of the spring described above. The device  20  has a pad  21  attached to a first end of the spring  28  and a second pad  21 ′ attached to the opposing end of the spring  28 . The device  20  is designed for compression along a linear compression direction  23  by applying an appropriate force to the pads  21  and  21 ′. FIG. 4B shows the device  20  held and compressed between a finger  31  and a thumb  32 . The user compresses the device as shown to build up finger strength and finger dexterity. FIGS. 4C and 4D illustrate the improper compression of the device  20 , wherein the spring  28  is not compressed along the linear compression direction  23 , as required. FIG. 4C shows a plan side view  40 , wherein the finger  31  and the thumb  32  are bent inward and apply to the device  20  a force which is not oriented along the linear compression direction  23 . Such force is herein called a non-linear force or off axis force, where the axis is taken to be along the linear compression direction  23 . The off axis force causes the spring  28  to bend away from the axis and produce a bow  41  in towards the hand (not shown). FIG. 4D shows a plan side view  50  of the device  20  wherein the finger  31  and the thumb  32  are bent outward and apply a non-linear force or off axis force to the device  20  causing the spring  28  to bend away from the axis to produce a bow  51  outwards from the hand (not shown). By counting a number of proper compressions, as illustrated in FIG. 4B, the device is used to measure grasping strength and dexterity. 
     Again referring to FIG. 4A, the device  20  is equipped with an automated counter  27 , such that when the device is compressed correctly and completely the counter  27  registers a compression. The counter  27  is attached to the pad  21 , which is attached to a first end of the spring  28 . When a contact  22  of the counter  27  contacts a contact point  29  on the pad  21 ′, a compression is registered. It will be obvious to one skilled in the art that there are any number of counter configurations that can be implemented. Again referring to FIG. 4A, the counter  27  can be mechanical, optical, or electrical. In the present case counter  27  is electrical and is attached to an external meter  26  by a connection  25  such that successful compressions can be displayed remotely. Further, the counter  27  can easily be configured to measure both successful and unsuccessful compression and varying degrees thereof. Further, it is understood that all following embodiments can be equipped with a counter such as that which is described above. 
     Not only can the finger and thumb pads be made of a variety of materials but they can also exhibit a variety of shapes and sizes. FIGS. 5A-C illustrate a few exemplary shapes for finger and thumb pads. In FIG. 5A a pad  52  is a flat surface attached to a compressible element  53 ; in FIG. 5B, a pad  54  is contoured to make compressing the device easier and the pad  54  is attached to a compressible element  55 ; and in FIG. 5C a pad  56  is convex and attached to the compressible element  57  providing less contact area with the finger than a flat or contoured pad making successful compressions of the device more difficult. It is also noted that the finger and thumb pads do not have to be directly attached to a compressible element and the compressible element does not need to be a coil spring. The compressible section of the device may be made from a variety of pliable, flexible or resilient materials including plastic, rubber and foam rubber. Alternatively, the compressible section of the device may be made from a combination of different compressible materials. 
     FIGS. 6A-B show cross-sectional views of an alternative embodiment of the current invention, wherein a device  60  whose compressible section consists of spring strips  63  and  63 ′. The spring strips  63  and  63 ′ are flexible as shown in FIG.  6 B and can be deformed by applying the appropriate force to pads  62  and  64 . In FIG. 6B the device  60  is shown in a compressed state. 
     FIGS. 7A-B illustrate cross-sectional views of yet another embodiment of the current invention. In this embodiment the device  61  has spring strips  65  and  67  that at joined by hinges  69  and  69 ′. By applying the appropriate pressure to pads  66  and  68 , the device  61  is compressed to a state, such as that which is shown in FIG.  7 B. 
     The compressible sections or elements that have been described above return to their original extended position in the absence of an applied force. It is, however, considered to be within the scope of the invention to have a device with a compressible and expandable section that is resistive to both. In this design it is required to have finger and thumb attachments that secure the respective digits of the operator to the device such as to allow the user to apply the appropriate force in both an expansion and a compression direction. For example, the compressible and expandable section can be a pneumatic or friction resistive telescoping element that provides resistance to both compression and expansion. 
     FIGS. 8A-C show an alternative embodiment of the current invention. In FIG. 8A, two stems  76  and  78  are attached to pads  72  and  74  and portions of the stems  76 ,  78  are lodged within a flexible element  73 . The flexible element  73  is preferably a soft material such as flexible rubber or foam rubber. The stems  76  and  78  are capable of being displaced in a linear compression direction  79  as shown in FIG.  8 B. The element  73  is flexible along an off axis direction as shown in FIG.  8 C. Preferably, there is a spring  75  within the flexible element  73 , to provide resistance to compression. However, the device may also operate on pneumatic or resistive principle previously mentioned so that resistance is provided in both the compression and expansion directions. Alternatively, the stems  76  and  78  are securely fastened to the flexible element  73  and spring  75  is absent. The flexible element is sufficiently soft to allow for linear compression of the device when pressure is applied to the pads  72  and  74  without spring  75 . 
     FIG. 9 shows a device  80  that has two springs  83  and  85  housed in spring housings  87  and  89 , respectively. The springs  83  and  85  are compressible by applying the appropriate pressure to the T-shaped pad sections  82  and  84 . In addition to the springs  83 ,  85  described above, the device has a resilient material  86  held between the springs  83 ,  85  by supports  88  and  81 . The resilient material  86  provides flexibility to the device  80  in the off axis directions whilst the two springs  83  and  85  provide for compressibility of the device in the linear compression direction. 
     FIG. 10 shows a cross-sectional view of a device  90  that has a spring  97  positioned between two spring supports  96  and  98 . The finger and thumb supports  92  and  94  are attached to the spring supports  96  and  98  through two swiveling ball joint hinges  93  and  95 . The ball joint hinges  93  and  95  require a higher degree gripping dexterity from the user to compress the device  90  along a linear compression direction. To aid the user in holding on to the device the finger and a thumb the pads  92  and  94  have roughened gripping surfaces  99  and  99 ′. The roughened gripping surfaces  99  and  99 ′ may be provided by attaching a cloth or abrasive material to the pads  92  and  94 , or by patterning the surface of the pads  92  and  94 . 
     FIG. 11 shows a cross-sectional view of a device  100  similar to the device shown in FIG.  9 . Like the device  80  shown in FIG. 9, device  100  has two springs  103  and  105  housed in spring housings  101  and  101 ′, respectively. The springs  103  and  105  are compressible by applying the appropriate pressure to the T-shaped sections  102  and  104 . A resilient material  107  is held between the two springs  103 ,  105  by supports  106  and  108 . The resilient material  107  provides flexibility to the device in the off axis direction. Additionally, the spring housings  101  and  101 ′ are attached together through a pivoting hinge  109  which provides additional flexibility to the device in the off axis direction while the two springs  103  and  105  provide for compressibility of the device in the linear compression direction. 
     FIG. 12 is a cross-sectional view of a device  110  that has two compressible chambers  111  and  113 . The compressible chambers  111  and  113  allow the device  110  to be compressed in a linear compression direction as indicated by arrows C. There are also three pivoting ball joint hinges  114 ,  112  and  116 . The pivoting ball joint hinge  112  allows the device to bend at the center portion of the device  110  in the off axis direction and the pivoting ball joint hinges  114  and  116  allow the pads  117  and  118  pivot. Any number of pivoting and hinging elements can be added to the device  110  to increase the level of difficulty and accuracy required to compress the device along a linear compression direction indicated by arrow C. Thus a series of such devices can be used in a rehabilitation program, wherein the user is given more and more difficult devices to compress as gripping strength and gripping dexterity is improved. 
     In yet another embodiment of the current invention, illustrated in FIG. 13, a device  120  for measuring gripping strength and dexterity utilizes all of the elements described above. The device  120  has compression chambers  126  and  125  that are compressible by applying the appropriate pressure to pads  122  and  124 . In addition to the compressible chambers  126  and  125 , the device has a coiled spring  127 , which also provides resistance to compression of the device along a linear compression direction indicated by arrow C. The pads  122  and  124  are attached to the top portions of the compressible chambers  126  and  125  through pivoting ball joint hinges  121  and  123  that allow the pads  122  and  124  to pivot. In the center portion of the device there is a third pivoting ball joint  129  surrounded by a flexible resilient material  128  that helps control the bending of the device  120  in an off axis direction. 
     The devices described above are designed to develop the gripping strength and gripping dexterity through a regimen that exercises one finger or one finger and a thumb. FIG. 14 illustrates an embodiment of the current invention that allows for the development of gripping strength and dexterity through the exercise of three digits. The device  130  has three springs  131 ,  133  and  135 , centrally attached together through an attachment section  137 . The finger pads  132 ,  134  and  136  are equipped with loop supports through which a user inserts three digits. The device is expanded or compressed to help develop gripping strength and gripping dexterity. 
     Several modifications to the embodiments described are considered to be within the scope of the current invention. For example, all the embodiments described can be equipped with a counter to measure the number of successful or unsuccessful compression and/or expansions of the device. Further, the device can be configured to any number of digits. Therefore, the scope of the current invention is to be determined by the claims and their legal equivalents.