Patent Publication Number: US-7591275-B2

Title: Handle body for an adjustable multi-purpose crutch

Description:
RELATED APPLICATIONS 
   The invention relates to U.S. Provisional Patent Application No. 60/837,167 filed Aug. 11, 2006 and co-pending applications with Ser. Nos. 11/707,297 and 11/707,815. 
   BACKGROUND 
   Mankind has long used various shapes and sizes of sticks as supportive aids in their mobility. Over the past century or so, what is today commonly called a crutch has evolved into more specialized shapes. Those devices that are currently considered as traditional crutches aid mobility, but their design and use may also contribute to the development of significant medical problems. 
   As these walking aids have evolved, the primary focus appears to have followed the following design objective: reduce the cost of manufacturing to enhance mass production and marketing capabilities. The previous designs for walking aids have lacked ergonomic design objectives addressing medical problems related to the disabilities and have failed to reduce or eliminate these problems. 
   Three specific medical problems resulting from using the traditional crutch are: (1) injury from loss of traction, (2) carpal tunnel syndrome, and (3) neuropathy. While the first of these problems may be obvious to the general public, the other problems are not as obvious. Carpal tunnel syndrome is a painful or numb condition of the wrist and hand resulting when tissues that form a tunnel-like passage in the wrist swell and pinch a nerve within the passage. Repetitive movement, as in typing or knitting, often causes this condition. 
   The handle of a typical clutch is generally round like a dowel, which offers little, if any resistance to rotation of the hand and wrist. Because medical practitioners recommend using the handle to provide principal support for the body weight, rather than the shoulder supports, this using of the handle places abnormal pressure on the forearms, hands and wrists of the user. Without adequate and proper stability for these members, carpal tunnel syndrome may result from long-term use of the typical crutch. 
   Neuropathy is any disease to the nervous system. In the case of long-term crutch users, the term neuropathy describes damage to nerves in the shoulder or underarm area resulting from use of the traditional crutch. Carrying the body weight on the shoulder support, unfortunately, is quite common. A significant contributing cause of neuropathy is attributed to this abnormal pressure and to the shoulder absorbing repeated impact when the crutch makes contact with the supporting surface. 
   According to the U.S. Census Data, the total number of people in all age groups in the U.S. with disabilities is about 51 million.  U.S. Census Bureau, June - September  2002  Data from the Survey of Income and Program Participation . Of those 51 million people, about 9.1 million people use a walker, a crutch or a cane. Id. Thus, there is a large population that may benefit from improvements in the design of walking aids. The incidence of injury from loss of traction, carpal tunnel syndrome, and neuropathy within these groups indicates that the medical problems associated with use of traditional crutches have not been adequately addressed in the design of walking aids. 
   Once adjusted for a particular user, the traditional crutch is designed to have a single configuration. That configuration has a fixed length, which becomes a problem when navigating a changing environment, such as stairs, curbs, restaurants, and other obstacles. 
   It is to solving these and other problems that the present invention is directed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a side elevation view of an adjustable crutch constructed in accordance with a preferred embodiment of the present invention. 
       FIG. 2  shows a side elevation view of an adjustable crutch constructed in accordance with a preferred embodiment of the present invention. 
       FIG. 3  shows a side elevation view of an adjustable crutch constructed in accordance with a preferred embodiment of the present invention. 
       FIG. 4  shows a detailed view of the handle assembly shown in  FIG. 1 . 
       FIG. 5  shows a cross-sectional view of the cross section  5 - 5  shown in  FIG. 4 . 
       FIG. 6  shows a cross-sectional view of the cross section  6 - 6  shown in  FIG. 5 . 
       FIG. 7  shows a top view of a handle in accordance with a preferred embodiment of the present invention. 
       FIG. 8  shows an elevation view of the handle shown in  FIG. 7 . 
       FIG. 9  shows a cross sectional view of the cross section  9 - 9  shown in  FIG. 7 . 
       FIG. 10  shows a perspective view of a human hand holding the handle shown in  FIG. 8 . 
       FIG. 11  shows a top view of a lever on the handle assembly shown in  FIG. 9 . 
       FIG. 12  shows a cross-sectional view of the cross-section  12 - 12  of the lever shown in  FIG. 11 . 
       FIG. 13  shows a side elevation view of the spindle shown in  FIG. 9 . 
       FIG. 14  shows an end view of the spindle shown in  FIG. 13 . 
       FIG. 15  shows a cross-sectional view of the foot assembly shown in  FIG. 1 . 
       FIG. 16  shows a side elevation view of the foot assembly shown in  FIG. 1 . 
       FIG. 17  shows a perspective view of the foot shown in  FIG. 15 . 
       FIG. 18  shows an elevation view of the spacer shown in  FIG. 15 . 
       FIG. 19  shows an elevation view of alternative embodiment of the spacer shown in  FIG. 18 . 
       FIG. 20  shows a cross-sectional view of a foot assembly without a spring. 
       FIG. 21  shows an elevation view of the foot assembly shown in  FIG. 20 . 
       FIG. 22  shows a side elevation view of a cane with a foot assembly of the present invention. 
       FIG. 23  shows a side elevation view of a walking stick with a foot assembly of the present invention. 
       FIG. 24  shows a front view of a ladder with a foot assembly of the present invention. 
       FIG. 25  shows a side elevation view of a ladder with a foot assembly of the present invention. 
       FIG. 26  shows a side elevation view of a device with a foot assembly of the present invention. 
       FIG. 27  shows a cross-sectional view of a foot pad of the present invention. 
       FIG. 28  shows a bottom view of a foot pad of the present invention. 
       FIG. 29  shows a partial, cross-sectional view of the shoulder support assembly shown in  FIG. 1   
       FIG. 30  shows a partial, exploded view of the shoulder support assembly shown in  FIG. 1 . 
       FIG. 31  shows a schematic view of a part of the shoulder support assembly shown in  FIG. 1 . 
       FIG. 32  shows a schematic view of a part of the shoulder support assembly shown in  FIG. 1 . 
       FIG. 33  shows the detail  24  of a portion of a frame as shown in  FIG. 1 . 
       FIG. 34  shows a front elevation view of a column shown in  FIG. 33 . 
       FIG. 35  shows a detailed view of a portion of the frame shown in  FIG. 1   
       FIG. 36  shows an elevation view of the strut shown in  FIG. 35 . 
       FIG. 37  shows a perspective view of a handle of the present invention atop a cane. 
       FIG. 38  shows a perspective view of the handle shown in  FIG. 37 . 
   

   DESCRIPTION 
     FIGS. 1-3  show a side elevation view of an adjustable crutch  100  of the present invention. The crutch  100  has an upper portion  102  with a shoulder support  104  that fits beneath an underarm of a user. The crutch  100  has a lower portion  106  connected to the upper portion  102  by a frame  108 . The frame  108  has a handle  110  for the user to grasp for lifting and moving the crutch  100  during walking and primary support of their weight otherwise. 
   The upper portion  102  also includes two upper tubes  112  that telescope inside lower tubes  114 , which are part of the frame  108 . The two upper tubes  112  are substantially parallel to one another and the two lower tubes  114  are substantially parallel to one another. As will be better described in regard to  FIGS. 4-6 , the handle  110  fits atop the lower tubes  114 . The lower portion  106  also has a foot assembly  116  that engages the ground when the user is walking with the crutch  100 . 
   As best seen in  FIG. 6 , tube holes  118  are defined along a length of each of the two upper tubes  112  such that the tube holes  118  are substantially aligned with and facing one another. Tube openings  120  are defined in each of the lower tubes  114  such that the tube openings  120  are substantially aligned with and facing one another. A diameter D 1  of each upper tube  112  is slightly smaller than a diameter D 2  of each lower tube  114  so that the upper tubes  112  slide freely inside the lower tubes  114 . 
   As will be further discussed in regard to  FIG. 6 , the handle  110  includes two locking pins  148 , 152  that are normally biased in an extended position to fit into the tube holes  118  and the tube openings  120  when the upper tubes  112  slide inside the lower tubes  114 . The locking pins  148 , 152  are moved to a retracted position by operating a lever  122 . When the lever  122  is depressed, the locking pins  148 ,  152  retract and the upper tubes  112  are free to slide inside the lower tubes  114 . When the lever  122  is released, the locking pins  148 , 152  are biased to the extended position and engage an outer wall  124  of the upper tube  112  as the upper tubes slide inside the lower tube  114 . 
     FIGS. 4-6  show the handle  110  used with the crutch  100  of the present invention. The handle  110  is shaped to fit a wide variety of human hands. The handle  110  is generally cylindrical in shape, has an average diameter of 2.5 to 5 centimeters (1 to 2 inches) and is typically 10 to 20 centimeters (4 to 8 inches) in length. The handle is formed from a first half-body  130  and second half-body  132  that fit together to form a body  135  of the handle  110 . For the embodiment shown in  FIGS. 4-6 , the first half-body  130  is identical to the second half-body  132 . Both half-bodies  130  and  132  have an inner face  134  with channels  136  defined therein to receive the working parts of a lock/release mechanism  138  for moving the locking pins  148  and  152  between the extended and the retracted positions. A handle assembly includes the handle  110  and a lock/release mechanism  138 . 
     FIG. 6  shows the lock/release mechanism  138  of the present invention. Individual parts of the lock/release mechanism  138  are shown in  FIGS. 13-16 .  FIGS. 13-14  show an end view and a cross-sectional view of the lever  122 .  FIGS. 13 and 14  show a side elevation view and an end view of a spindle  142  with integrally-formed upper paddle  144  and lower paddle  146 . 
   Returning to  FIG. 6 , the lock/release mechanism  138  includes the lever  122  that is depressed and released by the user to operate the lock/release mechanism  138 . The lever  122  has a thumb portion  140  attached to a spindle  142  by a set screw. As best seen in  FIGS. 11-14 , the spindle  142  fits into a bore  141  formed in the lever  122 . The spindle  142  has a round portion  143  and the two diametrically opposed paddles, upper paddle  144  and lower paddle  146 . The upper paddle  144  and lower paddle  146  engage a first locking pin  148  and a slide  150 . The first locking pin  148 , the slide  150  and a second locking pin  152  are housed in the channel  136  defined in the second half-body  132 . During assembly of the handle  110  and lock/release mechanism  138 , the spindle  142  fits through spindle opening  154  defined in one of the two handle half bodies  130  and  132 , into the bore  141  and the lever  122  is secured to the spindle  142  by the set screw. The first locking pin  148  has a notch  156  defined therein to receive the lower paddle  146 . 
   The channel  136  has a first chamber  158  to receive the slide  150  and a second chamber  160  to receive the first and second locking pins  148  and  152 . The first chamber  158  is separated from the second chamber  160  by wall  162 . 
   The slide  150  is a generally L-shaped structure with a paddle-engaging portion  164  at a slide first end  166  and an angle piece  168  at a slide second end  170 . The paddle-engaging portion  164  has a slide notch  172  defined therein to receive the upper paddle  144 . The angle piece  168  fits into a second locking pin notch  174 . 
   A compression spring  176  extends between the first locking pin  148  and the second locking pin  152 . The compression spring  176  has a length L selected such that the locking pins  148  and  152  are biased in the extended position when the locking pins  148  and  152  are positioned in the second chamber  160 . The spring constant of the compression spring  176  is selected to permit easy operation of the lock/release mechanism  138  by a disabled person with very little hand strength. Thus, the range of acceptable spring constants may vary from 0.5 lbs/in to 5 lbs/in (0.0875 kN/m to 0.875 kN/m). 
   Concerning the operation of the lock/release mechanism  138 , it is first noted that the locking pins  148  and  152  are normally biased in the extended position by the compression spring  176 . When the user depresses the thumb portion  140  of the lever  122 , the spindle  142  rotates the paddles  144 ,  146  in a counterclockwise direction for the lock/release mechanism  138  shown in  FIG. 6 . When the spindle  142  rotates, the lower paddle engages the first locking pin  148  in the notch  156 . When the lower paddle  146  engages the first locking pin  148 , the first locking pin  148  is moved toward the second locking pin  152 . Simultaneously, the upper paddle  144  engages the slide  150  in the slide notch  172 , and the slide  150  in turn exerts a force on the second locking pin  152  in the direction of the first locking pin  148 , thus compressing the spring  176 . When the slide  150  hits an outer wall of the chamber  158 , the locking pins  148  and  152  are in the retracted position. 
   When the user releases the lever thumb portion  140 , the compressed spring  176  pushes the first locking pin  148  and the second locking pin  152  away from one another so that the slide  150  and the first locking pin  148  return to their original extended position. Thus, the slide  150  and the first locking pin  148  engage the lower and upper paddles  144 ,  146  to rotate the wheel portion  142  back to the original position of the wheel portion  142 , which in turn returns the lever  122  to its original position. 
     FIGS. 7-10  show another embodiment of the handle  110 . For this embodiment, the handle half-bodies  130  and  132  are not identical. Rather, the first half body  130  contains all the working parts of the lock/release mechanism  138 , while the second half-body  132  has a blank inner face  180  without channels defined therein. The lock/release mechanism  138  shown in  FIG. 9  operates substantially the same as the lock/release mechanism  138  shown in  FIG. 6  and described above with regard to  FIG. 6 . However, the arrangement of the lock/release mechanism  138  within the handle half-body  130  is reversed. Thus, the spindle  142  is shown as being on the left in  FIG. 6 , but as being on the right in  FIG. 9 . This change in orientation does not affect how the lock/release mechanism  138  operates. The upper tubes  112  and the lower tubes  114  are not shown in  FIG. 9  for the sake of simplicity, but the sliding of the upper tubes inside the lower tubes is identical to that shown and described for the embodiment shown in  FIG. 6 . 
   Another important aspect of the handle  110  is a handle external geometry. The handle external geometry is designed to prevent or minimize the occurrence of carpal tunnel syndrome in long-term crutch users.  FIGS. 7-10  illustrate some of the external features of the handle  110  designed to prevent carpal tunnel syndrome. It is first noted that a particular handle  110  is designed to be used by only the right hand or the left hand of a person. The embodiment shown in  FIGS. 7-10  is designed to fit and be used by only a person&#39;s left hand. 
   The handle  110  has a body  111  with a rear post  181 , a front post  183 , and a palm grip  182  where the person&#39;s palm contacts the handle  110  upon gripping. The front post  183  has a front post upper opening  183   a  and a front post lower opening  183   b  defined therein. The rear post  181  also has a rear post upper opening  181   a  and a rear post lower opening  181   b  defined therein. The handle  110  also has a web  184  where a web of a person&#39;s hand between the thumb and the first finger contacts the handle  110  upon gripping. The handle  110  has a thumb rest  186  where the user&#39;s thumb is positioned when gripping the handle  110 . The thumb rest  186  is a contoured ridge formed on a side of the handle  110  that is slightly wider than a person&#39;s thumb. The contoured ridge of the thumb rest  186  is configured to project outwardly and downwardly from the handle web  184 , to extend at an angle downwardly along a length of the user&#39;s thumb, and to become substantially horizontal near a tin of the user&#39;s thumb.  FIGS. 8-9  show an imaginary line  190  that is parallel to a centerline of either one of the lower tubes  114 . 
   An uppermost portion of the palm grip  182  is on top of the handle  110 . The handle  110  is contoured downward from an uppermost portion of the palm grip  182  to the thumb rest  186  along a gripping contour surface  188 . Referring to  FIG. 9 , a plane  194  normal to the plane of the paper and tangent to a portion of the gripping contour surface  188  with a maximum curvature forms a gripping angle  192  with the imaginary line  190 . The gripping angle  192  has a value that is between seventy and seventy-five degrees, and is optimally about seventy-three degrees. This range of values of the gripping angle  192  provides a comfortable and natural fit for the human hand and helps to position the hand without undue stresses acting on the muscles and tendons of the hand and wrist and to restrict rolling and twisting motions of hands and wrists that contribute to carpal tunnel syndrome. 
   A bottom gripping surface  196  of the handle  110  extends from the rear post  181  to the front post  183 . An imaginary plane  198  substantially tangent to the bottom gripping surface  196  intersects the imaginary line  190  at a lower surface angle  199 . The lower surface angle  199  has a measure between eighty and eighty-five degrees and has an optimal value of about eighty-three degrees. This range of values for the lower surface angle  199  also helps to naturally position the hand such that undue stresses are not placed on the muscles and tendons of the hand and wrist and positions the hand to restrict rolling and twisting motions of hands and wrists that contribute to carpal tunnel syndrome. 
   A weight-bearing surface area of the palm grip  182  near the rear post  181  is about twice as large as a weight-bearing surface area of the web  184  near the front post  183 , which encourages a user to bear his weight on the palm of the hand instead of the web of the hand. This also contributes to reducing the rolling and twisting motions that contribute to carpal tunnel syndrome. The thumb rest  186  also provides a surface to position the thumb that physiologically and a psychologically encourages the user to refrain from the twisting and rolling motions that contribute to carpal tunnel syndrome. 
   In one embodiment, the first half-body  130  and the second half-body  132  of the handle  110  are assembled together by screws. The screws fit into screw holes defined in the first half-body  130  and the second half-body  132  of the handle  110 . Threads are defined in borders of the screw holes so that the screws tighten against the threads. 
   The handle half-bodies  130  and  132  may be made of any suitable material. Suitable materials include, but are not limited to, plastic, resins, wood, metal, ceramic or composite material. Furthermore, although the handle  110  is shown as being formed by two half-bodies, it is also contemplated that the handle  110  may have a unitary body molded around a lock/release mechanism  138 . 
   The individual parts of the lock/release mechanism  138  may be plastic, metal, composite material or any other suitable material. 
   The foot assembly  116  for the adjustable multipurpose crutch  100  is shown in detail in  FIGS. 15-19 .  FIG. 15  shows a cross-sectional view of one embodiment of the foot assembly  116  while  FIG. 16  shows a side elevation view of the same embodiment. Although the foot assembly  116  is shown as being attached to the bottom of the crutch  100 , it is understood that the foot assembly  116  could also be attached to the bottom of other walking aids, such as canes, walkers, other types of crutches and walking sticks. 
   In  FIGS. 15-16 , a strut  200  extends downward from the bottom of the crutch  100 . A cylinder  202  is attached to strut  200  by a through-bolt  204  and secured with jam nut  206 . The through-bolt  204  fits through a first opening  208  in the cylinder wall  210 , a pair of opposed, elongated strut slots  212 , through a second opening  214 , and the jam nut  206  is tightened to a predetermined torque around threads on the through-bolt  204 . Because the strut  200  has the elongated slots  212 , the strut  200  is not rigidly fastened to the cylinder  202 , but is free to travel the height of the elongated slots  212 . 
   The strut  200  rests atop a spring  216  positioned in a cylinder void  218 . The cylinder  202  is pivotally attached by a foot bolt  220  and foot nut  222  to a dome-shaped foot  224 . The foot nut  222  is another jam nut tightened to a predetermined torque, so that the dome-shaped foot  224  is not rigidly secured against the cylinder  200 . The dome-shaped foot  224  has an outside upper surface  226  and an inside upper surface  228 . A cylinder lower edge  230  rides on top of the foot  224  outside upper surface  226  as the cylinder  202  rotates about the foot  224  in an orbital or swivel-type motion. A resilient foot pad  232  is attached to a bottom of the foot  224  by an adhesive. 
   The dome-shaped foot  224  has a hemispherical portion  234  and a flat ring portion  236 . A dome hole  238  in the hemispherical portion  234  allows passage of the foot bolt  220 . A spacer  240  is positioned on the foot bolt  220  near the foot bolt head  242  so that the foot bolt  220  is secured within the dome-shaped foot  224 . The dome hole  238  is a hole in the hemispherical portion  234 . The spacer  240  is disc-shaped and has a lower surface  244  with a lower diameter and an upper surface  246  with an upper diameter. The lower diameter is slightly larger than the lower diameter and the spacer  240  has a tapered edge  248  from the lower surface  244  to the upper surface  246 . The upper diameter of the spacer  240  is selected so that the spacer  240  cannot be forced through the dome hole  238 . The lower diameter of the spacer  240  is selected so that the tapered edge  248  substantially engages the inside upper surface  228  along the tapered edge  248 . 
   Two washers  250  and  252  are located between the head of the foot bolt  224  and the spacer  240 . The first washer  250  is a flat washer. The second washer  252  is a Belleville washer. A Belleville washer is conical or slightly cupped so that the Belleville washer has a spring characteristic. This spring characteristic provides a slight amount of flexibility in the joint formed between the cylinder  202  and the foot  224 , which in turns causes the cylinder  202  to more freely rotate about the foot  224 . It is well-known in the art that Belleville washers may be stacked in the same direction to give a higher effective spring constant to a joint or in opposite directions to reduce the stiffness of a joint. Thus, if it is found the joint between the cylinder  202  and the foot  224  is too loose or too tight, one may add more Belleville washers stacked in the same or opposite directions. 
   After passing through the dome hole  238 , the foot bolt passes through a cylinder bottom opening  253  and engages the foot nut  222 . Tightening the foot nut  222  on the foot bolt  220  to its predetermined torque secures the joint formed between the cylinder  202  and the foot  224 . Although  FIG. 15  is generally a cross-sectional view, the spring  216 , the foot bolt  220 , the spacer  240 , the washers  250  and  252 , the through bolt  204  and  206  are represented as a side elevation view. 
   The materials selected for the foot assembly may be any suitable materials. One suitable material for the spacer  240  may be nylon or plastic, because the spacer  240  must be durable when subjected to thousands of cycles of loading, but flexible enough so that the joint formed between the cylinder  202  and the foot  224  has some flexibility. 
     FIG. 17  shows a perspective view of the dome-shaped foot  224 . The foot  224  has a hemispherical portion  234  and a flat ring portion  236 . A dome hole  238  is located at the top of the hemispherical portion  234 . 
     FIGS. 18-19  show two embodiments of spacers  240 . In the first embodiment shown in  FIG. 18 , the spacer  240  has a lower surface  244  and an upper surface  246 . The tapered edge  248  of the spacer  240  defines a wedge that substantially conforms to the inside upper surface  228  of the foot  224 . In  FIG. 19 , the spacer  240  also has a lower surface  244  and an upper surface  246 . However, the tapered edge  248  defines a portion of the surface of a sphere, so that the tapered edge  248  more closely conforms to the inside upper surface  228 , as compared with the embodiment of  FIG. 18 . 
     FIGS. 20-21  show another embodiment of a foot assembly  116  for which there is no spring as there is for the embodiment shown in  FIGS. 15-16 . In  FIGS. 20-21 , the strut  200  extends downward from the bottom of the crutch  100 . A cylinder  402  is attached to strut  200  by a through-bolt  404  and secured with a jam nut  406 . The through-bolt  404  fits through a first opening  408  in the cylinder wall  410 , a pair of opposed, strut holes  412 , through a second opening  414 , and the jam nut  406  is tightened to a predetermined torque around threads on the through-bolt  404 . For this embodiment, unlike the embodiment shown in  FIGS. 15-16 , the strut  200  is rigidly fastened to the cylinder  402 . 
   The strut  200  rests atop a void bottom  423  positioned in a cylinder void  418 . The cylinder  402  is pivotally attached by a foot bolt  420  and foot nut  422  to a dome-shaped foot  424 . The foot nut  422  is another jam nut tightened to a predetermined torque, so that the dome-shaped foot  424  is not rigidly secured against the cylinder  200 . The dome-shaped foot  424  has an outside upper surface  426  and an inside upper surface  428 . A cylinder lower edge  430  rides on top of the foot  424  outside upper surface  426  as the cylinder  402  rotates about the foot  424  in an orbital or swivel-type motion. A resilient foot pad  432  is attached to a bottom of the foot  424  by an adhesive. 
   The dome-shaped foot  424  has a hemispherical portion  434  and a flat ring portion  436 . A dome hole  438  in the hemispherical portion  434  allows passage of the foot bolt  420 . A spacer  440  is positioned on the foot bolt  420  near the foot bolt head  442  so that the foot bolt  420  is secured within the dome-shaped foot  424 . The dome hole  438  is a hole in the hemispherical portion  434 . The spacer  440  is disc-shaped and has a lower surface  444  with a lower diameter and an upper surface  446  with an upper diameter. The lower diameter is slightly larger than the upper diameter and the spacer  440  has a tapered edge  448  from the lower surface  444  to the upper surface  446 . The upper diameter of the spacer  440  is selected so that the spacer  440  cannot be forced through the dome hole  438 . The lower diameter of the spacer  440  is selected so that the tapered edge  448  substantially engages the inside upper surface  428  of the hemispherical portion  434 . 
   Two washers  450  and  452  are located between the foot bolt head  442  and the spacer  440 . The first washer  450  is a flat washer. The second washer  452  is a Belleville washer. 
   After passing through the dome hole  438 , the foot bolt passes through a cylinder bottom opening  453  and engages the foot nut  422 . Tightening the foot nut  422  on the foot bolt  420  to its predetermined torque secures the joint formed between the cylinder  402  and the foot  424 . Although  FIG. 20  is generally a cross-sectional view, the foot bolt  420 , the spacer  440 , the washers  450  and  452 , the through bolt  404  and the nut  406  are represented as a side elevation view. 
     FIG. 22  shows a cane  500  with a foot assembly  116  of the present invention attached to a strut  200  at a bottom of the cane  500 . 
     FIG. 23  shows a walking stick  502  with a foot assembly  116  of the present invention attached to a strut  200  at a bottom of the walking stick  502 . 
     FIGS. 24-25  show a front elevation view and a side elevation view of a ladder  504  with a foot assembly  116  of the present invention attached to a strut  200  at a bottom of the ladder  504 . 
     FIG. 26  shows a device  506  with a foot assembly  116  of the present invention attached to a strut  200  at a bottom of the device  506 . The device may be a chair or table with the strut  200  being a leg of the chair or table. The device may also be motor mounts, shock absorbers, or any other device that is supported by a foot assembly. 
     FIGS. 27-28  show an alternative embodiment of a foot pad  260 . The foot pad  260  is generally a resilient, pliant material, that attaches to the dome-shaped foot  234  by deforming the foot pad  260  and slipping the foot pad  260  onto the foot  234 . The foot pad  260  is held in place by a retaining flange  262  and a ring-shaped inner lip  264  at the top of the foot pad  260 . A bowl-shaped depression  266  is defined in the top of the foot pad  260 . The foot pad  260  has a central cavity  268  and a circumferential groove  270  defined on a bottom surface  272  of the foot-pad  260 . A radial channel  274  provides a fluid pathway between the circumferential groove  270  and an ambient environment. The circumferential groove  270  surrounds a circular contact face  276  that engages the walking surface. The circumferential groove  270  and the radial channels  274  define four segmented faces  278  that also engage the walking surface. As best seen in  FIG. 27 , the bottom surface  272  is slightly convex. 
   The bottom surface  272 , along with the circumferential groove  270 , the radial channels  274 , and the center cavity  268  defined therein, determine the traction between the foot pad  260  and the walking surface. The shape of the bottom surface  272  provides a significant area of contact with the walking surface, regardless of whether the user of the walking aid is standing still or walking on the walking surface. The material forming the foot pad  260  should be rubber or other flexible material that conforms readily to the contours of the walking surface, provides a high degree of friction, and is resistant to wear. 
   The design of the foot pad  260  described above allows liquids on the walking surface to be expelled outward through the radial channels  270  as a weight of the user is applied to the walking aid. Loose debris, such as sand and dirt, which might otherwise reduce traction, may be expelled by air pressure as the user exerts weight on the walking aid and thereby flattens the convex bottom surface  272 . The slightly convex shape of the bottom surface  272 , combined with the central cavity  268 , the circumferential groove  270 , and the radial channels  274 , is designed to: (a) compress and expel air and water that may reduce frictional contact with the walking surface, and (b) under the weight of the user, create a partial vacuum with smooth and slick walking surfaces in order to combine adhesion with friction to optimize and sustain traction. 
   The foot pad  260  is also designed to be resistant to hydroplaning. Just as a car may hydroplane while driving on wet pavement, a traditional crutch foot can hydroplane when a user walks on a wet surface using crutches. The bottom surface of the foot pad  260  has been designed to expel water through the circumferential groove  270  and the radial channel  274  and, thus, reduce the likelihood of hydroplaning of the foot pad  260  while walking over a wet walking surface. 
   The upper surface of the foot pad  260  is shaped to mate with the dome-shaped foot  234 . The mating of the irregularly shaped foot pad  260  and the foot improves stability of the foot pad  260  under normal operation. The shape of the retaining flange  262  and the inner lip  264 ; facilitates easy replacement of worn foot pads  260  and also helps to keep the foot pad securely on the dome-shaped foot  234 . 
     FIGS. 29-32  show various views of the pivoting shoulder support  104  for the adjustable multi-purpose crutch  100 .  FIG. 29  shows a cross-sectional view of an upper portion  300  of the shoulder support  104 . A shoulder spring  302  is attached to a channel section  304  by two rivets  306 . The shoulder spring  302  has two floating spring ends  308  that are not attached to the channel section  304 . The shoulder spring  302  is bent in a bow-tie shape and has two loops  310  with a narrow portion  312  at which the shoulder spring  302  is secured to the channel section  304 . 
   As seen in  FIG. 29 , two bolt holes  314  are formed at lower ends of the channel section  304  to receive pivot bolts  316  (shown in  FIG. 30 ). An indentation  318  is formed in a side of the channel section  304 . The purpose of the indentation  318  will be discussed in the description of  FIG. 30 . A shoulder pad  320  covers the shoulder support upper portion  300  for cushioning the shoulder support upper portion  300  for use under a person&#39;s arm. 
   The shoulder support upper portion  300  is designed so that the person&#39;s underarm rests on top of the shoulder pad  320  between the two loops  310 . Although users are typically advised to support the user&#39;s weight with the hands, many users find themselves resting their weight on the shoulder supports. When a long-term crutch user uses ordinary crutches, the supporting of one&#39;s weight by resting the underarms on the shoulder supports contributes to neuropathy in the shoulder area. 
   The shoulder support  104  has a concave downward upper surface  322  which is positioned beneath an underarm of a user and a concave upward lower surface  324 . The lower surface  324  is concave to accommodate a forearm of the user when the user positions the adjustable crutch  100  at a mid-arm position or a lower position. 
     FIG. 30  is a partial section view, and a partial exploded view of the shoulder support  104 . The shoulder pad  320  is not shown to add clarity to  FIG. 30 . The shoulder support  104  is pivotally attached to a first tube cap  326  and a second tube cap  328  that are each positioned atop one of the telescoping upper tubes  112 . As best seen in  FIG. 30 , the tube caps  326  and  328  are attached to the upper tubes  112  by tube set screws  330 . The tube set screws  330  are screwed into threaded tube cap set screw holes  332  and apply a force on the upper tubes  112  when tightened. Although tube set screws  330  are shown in  FIG. 30 , it is anticipated that rivets may also be used to attach the tube caps  328  to the tubes  112 . 
   The shoulder support channel section  304  pivots on pivot bolts  316  that pass through tube cap holes  334  and bolt holes  314 . Each pivot bolt  316  is generally cylindrical with a threaded portion  336  and an non-threaded portion  338 . A nut  340  is attached to the end of the pivot bolt  316 . 
   The second tube cap also has a stud bolt  342  which is positioned inside a stop spring  344 . The stop spring  344  fits inside a first bore  346  in the second tube cap  328  and abuts a shoulder  348  formed at a plane where the first bore  346  becomes narrowed to a second bore  350 . Once the stop spring  344  is positioned inside the first bore  346 , the stud bolt  342  may be inserted through the stop spring and through the first bore  346  and the second bore  350 . A knob  352  is positioned on a first end  351  of the stud bolt  342  and a stop  354  is positioned on a second end  358  of the stud bolt  342 . The stop  354  is sized and shaped to fit into indentation  318 . 
   The stud bolt  342  has a length selected so that, when the shoulder support  104  is assembled and the knob  352  is pulled by a user, the stop  354  is removed from the indentation  318 . When the knob  352  is released, and the indentation  318  is aligned with the stop  354 , the stop fits into the indentation  318 . A spring constant of the stop spring  344  should be selected so that a person with little hand strength is capable of pulling the knob  354 . A ridge  356  on each tube cap  326  and  328  prevents the pivoting channel section  304  from rotating more than 180 degrees. 
     FIGS. 31-32  show schematic views of the pivoting action of the channel section  304  with respect to the tub caps  328 . The channel section  304  pivots about the pivot bolt  316  which fits through the tube cap opening  334  (shown in  FIG. 30 ).  FIG. 31  shows the channel section  304  in an upright position. When the user wishes to move the channel section  304 , and in turn the shoulder support  104 , to another position, the user pulls the knob  352  to retract the stop  354  from the indentation  318  and then applies a force to the side of the channel section  304  causing the channel section  304  to pivot about the pivot bolt  316 . The channel section  304  can pivot only ninety degrees in either direction because the ridge  356  blocks rotating the channel section  304  past ninety degrees. 
   It is generally expected that most users will find the shoulder support  104  more comfortable in a vertical or upright position when the adjustable crutch  100  is used beneath the underarms. Generally, this will be the fully extended position, as appropriate for that user&#39;s height, as shown in  FIG. 1 . When the crutch is lowered to the mid-arm position shown in  FIG. 2 , the user will probably want to have the shoulder support  104  used at an angle. When the adjustable crutch is in the retracted position shown in  FIG. 3 , the user will probably prefer to have the shoulder support  104  used in a horizontal position, as shown in  FIG. 32 . In this position, the adjustable crutch may be used as a cane and the shoulder support lower surface  324  provides support to the forearm and wrist of the user for added leverage and control. 
   As seen in  FIGS. 33-35 , the frame  108  includes the handle  110 , the two lower tubes  114 , an upper cross plate  370 , a lower cross plate  372 , and a column  374  that extends from the upper cross plate  370  to a position just below the lower cross plate  372 . A torsion-resistant webbing  376  extends below the lower cross plate  372 . 
   The column  374  is welded to and extends from an underside of the upper cross plate  370 . A column lower end  379  passes through a column opening  380  defined in the lower cross plate  372 . Lower ends  382  of the lower tubes  114  are open so that the upper tubes  112  may extend beyond the lower tubes&#39; lower ends  382 . 
   As best seen in  FIG. 34 , the column  374  has adjustment holes  384  defined therein on opposing sides of the column  374 . The strut  200 , shown in  FIG. 36 , slides inside the column  374  and has strut openings  386  defined therein on opposing sides of the strut. The position of the strut  200  within the column  374  is fixed by a V-spring. The position of the strut  200  may also be fixed by a simple pin that protrudes through the column adjustment holes  384  and the strut openings  386 . 
     FIGS. 37-38  show an embodiment of a handle  600  similar in its outside geometry to the handle  110 , but the handle  600  rests atop a cane  602 . The handle  600  has a body  604  with a rear post  606 , a front post  608 , and a palm grip  610  where the person&#39;s palm contacts the handle  600  upon gripping. The handle  600  also has a web  614  where a web of a person&#39;s hand between the thumb and the first finger contacts the handle  600  upon gripping. The handle  600  has a thumb rest  612  where the user&#39;s thumb is positioned when gripping the handle  600 . The thumb rest  612  is a contoured ridge formed on a side of the handle  600 . The thumb rest  612  is slightly wider than a person&#39;s thumb. The contoured ridge of the thumb rest  612  is configured to project outwardly and downwardly from the handle web  614 , to extend at an angle downwardly along a length of the user&#39;s thumb, and to become substantially horizontal near a tip of the user&#39;s thumb. The handle  600  may be attached to the cane  602  by set screws. The handle  600 , like the handle  110 , is shaped to prevent undue stresses from being exerted upon the muscles and tendons of the hand and wrist of a user. 
   When compared to the handle  110 , the handle  600  has a larger upper gripping surface, which is formed by the palm grip  610  and the web  614 . The upper gripping surface also curves to more closely conform to the curvature of user&#39;s palm and fingers, making the grip around handle body  604  more comfortable. The handle  600  also has an extended thumb rest  612  that forms a greater portion of the overall width of the handle body  604 , when compared to the handle  110 . The increased area of the upper gripping surface, combined with the more closely conforming curves of the upper surface, enhances the user&#39;s ability of the user to grip the handle  600  and to control the handle  600 . 
   A palm grip base  616  between the rear post  606  and the palm grip  610  also has an increased area, when compared with the handle  110 . Because of this increased area, the user distributes the user&#39;s weight, which in turn results in less reactive pressure exerted by the handle  600  on the user&#39;s hand. An upward curve  618  of the palm grip base  616  also prevents the user&#39;s palm from spreading and, thus, improves the load distribution across the palm. When the handle  600  is used with the adjustable crutch  100 , the upward curve  618  also provides a more comfortable separation of the user&#39;s hand from the upper tube  112  that protrudes through the rear post  606 . For a traditional dowel-shaped crutch handle, the user&#39;s palm meets the crutch handle at a 90-degree angle, which can cause discomfort after the user applies his weight to the handle. The upward curve  618  reduces that discomfort. 
   A forward part  620  of the thumb rest  612  is also deepened on the inside of the user&#39;s thumb, when compared to the thumb rest  186  of handle  110 . This feature enhances the user&#39;s grip on the handle  600  significantly. This relative “deepness” is due in part to having a higher web  614  at a base of the user&#39;s thumb when the user grips the handle  600 . 
   The materials selected for the upper tubes and lower tubes may be steel, stainless steel, aluminum, titanium, carbon fiber composite material, or any alloys of these or other metallic materials. The materials selected for use must be rust and corrosion resistant in order to ensure the telescoping action of the upper tubes inside the lower tubes is not impeded. In one embodiment, the material used for the tubing is cold drawn aluminum, so that the tubes will be formed with high accuracy and with low tolerance for errors. The high accuracy of the cold drawing process is desirable because the upper tubes must reliably slide inside the lower tubes without jamming. 
   The material selected for the shoulder support may be wood, plastic, metal, polymer, rubber or any alloy or combination thereof. The material selected for all the components of the adjustable crutch should be inexpensive so that the cost of production of the adjustable crutch is kept low. Because the adjustable crutch  100  is to be used by disabled people, who may have atrophied muscles, all of the material should be light in weight. However, all of the material must have sufficient strength to perform the function intended. 
   The overall objective of this adjustable multi-purpose crutch is to improve and extend mobility for the handicapped by incorporating ergonomic and medical considerations in its design. The telescoping feature of the upper tubes  112  inside the lower tubes  114  permits simple adjustments allowing the user to adapt the adjustable crutch readily to changing environmental conditions. Less obvious are ergonomic features that address medical problems common to the traditional crutch with the express purpose of reducing or eliminating them. These problems are 1) loss of traction that may result in injury, 2) carpal tunnel syndrome, and 3) neuropathy. 
   Traction is improved with a foot assembly  116  featuring a spring-loaded swivel joint with a contoured foot pad. Up to an angle of about 25 degrees, the foot assembly  116  adapts readily to the supporting surface, providing immediate traction. Spring-loading the foot assembly  116  cushions and reduces the shock of impact with that surface. As the user moves forward into the next step, the unloading of this spring  216  provides an extra boost to the user. Once planted on the supporting surface, traction remains firm even when the user rotates. 
   In this design, adjustments in length or height of the crutch  100  are simple and need no tools. The medical practitioner and the user can make adjustments in a few seconds to fit the body proportions of the user. Adjustable configurations are listed below: 
   1) the full-length crutch height; 
   2) a mid-level height with horizontal positioning of the shoulder support functioning similar to the forearm clutch or “Canadian cane,” giving forearm support; 
   3) telescoped to the height of a traditional cane with wrist support; and 
   4) fully telescoped. 
   Both of the latter two configurations can be achieved easily for storage in a car, restaurant, home, or overhead storage bin on an airliner or tour bus. In the mid-level configuration, when the crutch is pressed against the hip, the crutch provides considerable leverage that reduces hand strength needed to control body movement and the crutch itself. 
   Height adjustments of the telescoping of the crutch  100  are controlled by a locking mechanism  138  contained internally within the handle  110 . On each handle  110 , positioned strategically to minimize unintended release of the lock/release mechanism  138 , is a single lock/release mechanism  138  to provide easy leverage for those with weakened hand strength. This lock/release mechanism  138  includes two spring-loaded locking pins  148  and  152  that engage the two sets of concentric vertical tubes  112  and  114  within the handle  110 . 
   A primary contributing factor to carpal tunnel syndrome is repetitive rotation of the wrist and hands. Where the basic dowel-shape of the traditional crutch handle offers little restriction to this type motion, the handle of the present invention is designed to 1) align the hand and wrist in a natural position, vertically and horizontally, and 2) prevent such repetitive motion while in use. Several of the handle contours are critical in preventing or reducing abnormal pressures on certain nerves, tendons, and muscles. The term “natural position” means that the hand is in a position for which the muscles and tendons are in a state of reduced stress, when compared with the hand being in an “unnatural” position. 
   The importance of ergonomics in handle design for crutches is emphasized by an anomaly: medical practitioners caution the user to support their body weight by the handles, not the shoulder support, because of the risks of damage to nerves in the shoulder (neuropathy); yet, the majority of long-term users of crutches have weakened muscles in their forearms, wrists, and hands, and even those with normal strength levels are unaccustomed to such abnormal stress on those muscles. With the traditional crutch, following directions of their medical practitioner elevates fatigue levels quickly, and incurs the risk of carpal tunnel syndrome. If the patients do not follow those directions, and support their weight on the shoulder supports, they incur the risk of neuropathy. It is logical to incorporate every ergonomic design feature available into the contours of this handle that assists the user in obtaining maximum control and comfort, while minimizing muscular effort and medical risks. 
   Consistent with accepted procedures, standards, and goals in the medical community, the handles of this design are left- and right-oriented, and have greatly expanded upper weight-bearing surfaces that encourage supporting body weight on the handles rather than shoulder supports. With the hand positioned naturally on a handle, the handle&#39;s contours closely follow those of the hand. For example, a broadened, flattened upper weight-bearing surface begins at the base of the hand, and increases in width toward the front. It is comfortable, reduces fatigue, and restricts rolling and twisting motions of hands and wrists of the type that contribute to carpal tunnel syndrome problems. These complex ergonomic contours are not possible on a single, universal-purpose handle. 
   The angular positioning of the handle in relation to the vertical tubes is also critical in achieving the specific design objective of reducing or eliminating problems with carpal tunnel syndrome. In much the same way that the front wheels of a car are built with a “toe-in” alignment with the frame, human arms rotate at angles to the fore-and-aft centerline of the body. Accordingly, a similar “toe-in” effect is achieved in this design by raising the upper rear surface of the handle several degrees higher than the front (vertical alignment), and making the outside of the rear end of the handle wider than the front (horizontal alignment). 
   Since there is no central neural pathway in which nerves in the armpit area are concentrated, the problem of neuropathy is addressed by enlarging surface area and distributing the load on the shoulder support more evenly across the enlarged surface. The load-bearing surfaces of shoulder supports on traditional crutches generally represent a very shallow arc, and are narrow. For many users, this concentrates the load in the center of the shoulder support, and becomes a prime contributing factor in damage to nerves. Since these supports are typically static structures, the load remains centered as weight of the user is applied to it. 
   In the design of the present invention, at least four features are built into the shoulder support to address problems with neuropathy: 1) the load-bearing surface is enlarged to distribute the user&#39;s weight more evenly over a greater area, 2) the arc of the load-bearing surface is increased, 3) the load-bearing surface is spring-loaded to: a) readily flex and adapt under load to the contours of the user&#39;s shoulder, contributing to spreading the load more evenly, and b) complement the spring-loaded ball-joint foot in absorbing impact shocks to the user&#39;s shoulder area. In addition, the load-bearing surface is padded with a rubber cushion, and 4) the shoulder support may be turned horizontally to either side of vertical, to work in conjunction with either of the optional cane configurations. While it locks in the vertical position when used as a crutch, an index pin is provided at its base (on the front side for easy access by the user) to release the lock for conversion to cane-length configurations. Collectively, these features not only accommodate a broader spectrum of users (height-wise and weight-wise), but provide a substantially increased degree of comfort and mobility to all users. Muscles used with a crutch may differ somewhat from those used with a cane. With these optional configurations readily available, the user may rest some muscles by switching to another configuration, thereby reducing the onset of fatigue and extending endurance. According to field tests conducted by medical experts, these features succeed in providing greater comfort while simultaneously minimizing the risks of neuropathy. 
   While costs are an ever-present factor, design objectives for this walking aid are not primarily to lower costs to a minimum, but to improve mobility for those needing more comfortable and flexible mobility support, while reducing medical risks common to the traditional crutch, particularly for those faced with long-term use. 
   The above-described subject matter is to be considered illustrative, and not restrictive. The appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.