Abstract:
A support system for a user of a computer keyboard or for a person performing other manual tasks of extended duration includes a pair of supports which are positioned proximate to respective ends of the keyboard. A rod is supported between the pair of supports to provide a horizontal guide rail. A pair of trolleys support a pair of independently moveable cradles. Each cradle supports a portion of a user&#39;s lower arm, wrist and hand. When the user places his or her lower arms, wrists and hands in the cradles, the hands and lower arms are supported above the keyboard or other work surface so that the user is assisted in supporting the weight of his or her arms and hands. The cradles can be moved horizontally from left to right and vice versa as well as arcuately as the user&#39;s hands are moved closer to and farther from the user&#39;s body. Thus, the user is able to move his or her hands freely over the computer keyboard or other work surface even if the user does not have sufficient muscle tone to adequately support his or her arms for extended duration.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/042,516, filed on Mar. 16, 1998 (U.S. Pat. No. 5,876,362 issued on Mar. 2, 1999). 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is in the field of devices which support the lower arm, wrists and hands during the performance of repetitive tasks such as typing, data entry, parts assembly, or the like. 
     2. Description of the Related Art 
     Many personal and job-related tasks involve the use of computer keyboards, calculators and other data entry devices which require a person to have his or her arms and hands extended in front of the person&#39;s body for long durations. In addition, other tasks, such as assembly work, sewing, needlework, knitting, painting, or the like, require the arms and hands to be likewise extended. As a result of repeated periods of arm and hand extension, many persons have developed injuries such as carpal tunnel syndrome. In addition, because of aging, accidents, or certain diseases, some persons no longer have the ability to perform relatively simple tasks which require arm and hand extension. A number of devices have been developed to reduce the effects of such extension. For example, wrist pads are available to place in front of a keyboard to elevate the wrists and thereby change the angle of the hands with respect to the keyboard. Such wrist pads do not however assist the user when the user has to move his or her hands from side-to-side on the keyboard. In particular, if a person has weak muscles or the like, the person may be unable to move freely about the keyboard. Thus, additional assistance for using keyboards and for performing other tasks requiring arm and hand extension is desirable. 
     SUMMARY OF THE INVENTION 
     The present invention provides a free floating support system which is designed to support the arms and hands during prolonged tasks which require the arms and hands to be extended over a keyboard or other work surface. The system allows freedom of movement over the entire keyboard or work surface while providing full support for the arms and hands. The system is ideal for computer keyboards, typewriters, calculators, and horizontally disposed musical instruments (e.g., pianos and electronic keyboards). In addition, the system provides support while performing tedious assembly work, as well as while doing needlework, sewing, painting, and the like. 
     One aspect of the present invention is a system for supporting a hand of a user when performing manual tasks above a work surface. The system comprises a horizontally disposed guide rail supported a predetermined distance above the work surface. At least one trolley is positioned on the guide rail. The trolley provides horizontal movement along the guide rail and provides arcuate movement about the guide rail. A cradle is suspended from the trolley. The cradle is sized to support a user&#39;s hand, wrist and a portion of the lower arm above the surface. The cradle permits horizontal movement of the user&#39;s hand parallel to the guide rail and permits arcuate movement of the user&#39;s hand around the guide rail. Preferably, the guide rail is a round rod. Also preferably, the trolley comprises a linear bearing. Alternatively, the trolley comprises a flanged wheel. 
     Another aspect of the present invention is a system for supporting the hands of a user above a work surface such that the user can freely move the hands with respect to the work surface. The system comprises a first end support and a second end support to position a horizontally disposed guide rail above the work surface. A first trolley and a second trolley are positioned on the guide rail for horizontal movement thereon. A first cradle is suspended from the first trolley beneath the guide rail. The first cradle is positioned to support the user&#39;s left hand and left wrist and a portion of the user&#39;s lower left arm above the work surface. The first cradle moves horizontally with horizontal movement of the first trolley. The first cradle moves arcuately with respect to the guide rail. A second cradle is suspended from the second trolley beneath the guide rail. The second cradle is positioned to support the user&#39;s right hand and right wrist and a portion of the user&#39;s lower right arm above the work surface. The second cradle moves horizontally with horizontal movement of the second trolley. The second cradle moves arcuately with respect to the guide rail. Preferably, the rail is round, and the trolleys roll along the length of the rail and slide around the periphery of the rail. In particularly preferred embodiments, the trolleys are linear bearings. Alternatively, the trolleys comprises flanged wheels. Also preferably, the position of the cradle above the work surface is adjustable. 
     Another aspect of the present invention is a system which supports the hands of a user above a work surface. The system comprises a first support and a second support to position a horizontal guide rail above a work surface between the two supports. The guide rail has an outer periphery. A first trolley and a second trolley are positioned on the guide rail. The trolleys move along the guide rail and slide about the periphery of the guide rail. A first cradle is suspended from the first trolley and a second cradle is suspended from the second trolley. The first and second cradles move longitudinally below the guide rail and move arcuately about the guide rail. Each of the first and second cradles comprises a first portion to support a portion of the lower arm of a user and comprises a second portion extending from the first portion to support the wrist and hand of the user. Preferably, the first support and the second support are adjustable to vary the position of the horizontal rail above the work surface. Also preferably, the first support and the second support are adjustable to vary the horizontal position of the horizontal rail with respect to an edge of the work surface. 
     Another aspect of the present invention is a system for supporting a hand of a user when performing manual tasks above a computer keyboard. The system comprises a horizontally disposed guide rail supported above the computer keyboard. At least one trolley is positioned on the guide rail. The trolley provides horizontal movement along the guide rail and provides arcuate movement about the guide rail. A cradle is suspended from the trolley. The cradle is sized to support a portion of a user&#39;s hand, wrist and lower arm above the computer keyboard. The cradle has side portions to constrain a portion of the user&#39;s lower arm therebetween. The cradle has an extended forward portion to support the user&#39;s wrist and hand. The cradle permits horizontal movement of the user&#39;s hand parallel to the guide rail and permits arcuate movement of the user&#39;s hand around the guide rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described below in connection with the accompanying drawing figures in which: 
     FIG. 1 illustrates a perspective view of a first embodiment of the present invention when being used to support a person&#39;s arms and hands over a keyboard; 
     FIG. 2 illustrates a side elevational view of the first embodiment of the present invention showing one of the side supports and illustrating the suspension of the wrist cradle beneath the overhead rail; 
     FIG. 3 illustrates a plan view of the first embodiment of the present invention showing the overhead rail in more detail and showing the trolley wheels which provide free left-to-right and front-to-back swinging movement of the wrist cradles; 
     FIGS. 4A,  4 B and  4 C illustrate cross-sectional views of the overhead rail showing the placement of a trolley wheel on the rod so that the trolley wheel can roll on the rod for left-to-right movement (as viewed in FIG. 3) as well as pivot on the rod to provide front-to-back swinging movement; 
     FIG. 5 illustrates an alternative embodiment of the present invention with a desktop mounted support structure, with wrist cradles which provide additional support and with an alternative trolley system; 
     FIG. 6 illustrates the alternative embodiment of FIG. 5 with the support structure reversed to permit a user to place a keyboard closer to the edge of the desktop; 
     FIG. 7 illustrates the wrist cradle of FIGS. 5 and 6 in more detail; 
     FIG. 8 is a view taken along the lines  8 — 8  in FIG. 5 which shows the wrist and palm support provided by the wrist cradle; 
     FIG. 9 is an enlarged view with a partial cross section of the linear bearing of the trolley system of FIGS. 5 and 6 showing the inner bearing and the outer shell; 
     FIG. 10 is elevational view of the linear bearing of the trolley system of FIGS. 5 and 6 showing the placement of the supporting wires on the outer shell of the bearing; 
     FIG. 11 illustrates a further alternative embodiment of the trolley structure which uses a single flanged wheel to support each wrist cradle; 
     FIG. 12 illustrates the desktop clamp used in the embodiment of FIGS. 5 and 6; 
     FIG. 13 illustrates a cross-sectional view of the clamping knob of FIG. 12; 
     FIG. 14 illustrates a cross-sectional view of the fixed plate of FIG. 12; 
     FIG. 15 illustrates the desktop clamp positioned on the edge of a desktop; 
     FIG. 16 illustrates an alternative embodiment to the system illustrated in FIGS. 5 and 6 in which the vertical support rods are mounted directly into the desktop or work surface; and 
     FIG. 17 is an enlarged exploded view of a portion of the desktop of FIG. 16 showing the mounting of the vertical support rod directly into the desktop. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As illustrated in FIGS. 1-4, the wrist support system in accordance with the first embodiment of the present invention comprises two vertical end supports  2 ,  3  at each end of a horizontally disposed tracking rod or overhead rail  1 . In the illustrated embodiment, the tracking rod  1  comprises a standard plated steel rod, or the like, to provide a substantially non-bending span between the two end supports  2 ,  3 . For example, the rod  1  may advantageously be ⅜ inch in diameter. The rod  1  is preferably threaded at each end. The rod  1  is fastened at each end by two nuts  4 ,  5 , and  6 ,  7 , respectively, with one nut being on each side of the respective tops of the end supports  2 ,  3 . 
     In the preferred embodiment, the end supports have respective first portions  2 A,  3 A which are positioned at an angle with respect to vertical, and the bottoms of the end supports are directed away from the user (see FIG.  1 ). The end supports have respective second portions  2 B,  3 B, which provide stable horizontal platforms for the for the first portions  2 A,  3 A when the system is positioned on a desk or the like. As illustrated in FIG. 2, the tracking rod  1  is positioned substantially over the centers of the second portions  2 B,  3 B so that the system is very stable and does not rock during use. Preferably, the second portions  2 B,  3 B include cushioned pads (not shown) or the like to inhibit sliding of the second portions  2 B,  3 B on a desktop or other working surface. 
     The end supports  2 ,  3  are spaced apart by a distance slightly less than the length of the tracking rod  1  (i.e., by the length of the tracking rod  1  less the lengths of the two threaded ends extending through and beyond the end supports  2 ,  3 ). The length of the tracking rod  1  is selected so that the end supports  2 ,  3  are positioned outside the working area. For example, when the system is used with a conventional computer keyboard having a width of approximately 18 inches, the tracking rod  1  advantageously has a length of 24-30 inches to accommodate the full width of the keyboard as well as a mouse pad, if desired. For packaging purposes, the tracking rod  1  can be provided in two sections (not shown) with one section having an outside threaded portion (not shown) and the other section having a tapped threaded portion. 
     The tracking rod  1  supports four grooved wheels  8 ,  9 ,  10 ,  11  which roll on the top side of the tracking rod  1  and thus roll along a straight line substantially parallel to a desktop or other surface on which the system is positioned. The center of each of the grooved wheels  8 ,  9 ,  10 ,  11  includes a sleeve bearing  12 ,  13 ,  14 ,  15 . Each sleeve bearing  12 ,  13 ,  14 ,  15  has a hole through its respective center. A respective wire loop  16 ,  17 ,  18 ,  19  passes through the hole in each of the four sleeve bearings  12 ,  13 ,  14 ,  15 . Each of the four wire loops  16 ,  17 ,  18 ,  19  straddles and extends below the tracking rod  1 , preferably without touching the tracking rod  1 , or at least not applying significant pressure on the tracking rod  1  so as to avoid significant frictional contact. 
     Below the tracking rod, each of the four loops  16 ,  17 ,  18 ,  19  has a respective turnbuckle  20 ,  21 ,  22 ,  23  attached to it such that each turnbuckle is disposed in a generally vertical position below the tracking rod  1  when the system is not in use. A respective chain  24 ,  25 ,  26 ,  27  is attached to the lower end of each of the four turnbuckles  20 ,  21 ,  22 ,  23 . The four chains  24 ,  25 ,  26 ,  27  are paired, and each pair of chains  24 ,  25  and  26 ,  27  is attached to a respective wrist cradle  28 ,  29 . In particular, the chains  24 ,  25  support the left wrist cradle  28 , and the chains  26 ,  27  support the right wrist cradle  29 . Together, the chains  24 ,  25 ,  26 ,  27  and the turnbuckles  20 ,  21 ,  22 ,  23  permit the wrist cradles  28 ,  29  to be positioned at any distance below the tracking rod  1  to accommodate different working environments and different personal preferences. For example, links can be removed from or added to the chains for gross adjustment, and the turnbuckle rotated for fine adjustment. It should be understood of course that other suspension devices, such as, for example, string, line or wire, can be used to support the wrist cradles  28 ,  29 . 
     The wrist cradles  28 ,  29  may be of any suitable material which provides a reasonable range of flexibility to accommodate different sizes of wrists without being too flexible such that the wrist cradles wrap around the wrists and bind the wrists. For example, in a prototypical embodiment, an arcuate portion of a large diameter automotive rubber hose was found to provide adequate flexibility and support. It is anticipated that many plastic materials will be suitable for the wrist cradles. 
     The grooved wheels  8 ,  9 ,  10 ,  11  greatly reduce friction and allow omnidirectional motion of the wrist cradles  28 ,  29 . When the wrist cradles  28 ,  29  are moved from left to right and from right to left horizontally (as viewed by the user in FIG. 1 or in FIG.  3 ), the wheels  8 ,  9 ,  10 ,  11  roll along the top of the tracking rod  1  along a generally horizontal line. Absent movement by the user, the wrist cradles  28 ,  29  hang directly below the tracking rod  1  as illustrated by the position of the loop  16 ,  17 ,  18 ,  19  in FIG.  4 A. When the wrist cradles  28 ,  29  are moved toward the user and away from the user (FIG.  1 ), the wheels  8 ,  9 ,  10 ,  11  pivot around the circumference of the tracking rod  1  as indicated in FIGS. 4B and 4C (i.e., the wheels  8 ,  9 ,  10 ,  11  move arcuately about the tracking rod  1 ). By using flanged wheels  8 ,  9 ,  10 ,  11 , as illustrated in FIGS. 4A-4C, the frictional contact with the tracking rod  1  is very low so that the wheels  8 ,  9 ,  10 ,  11  freely pivot on the tracking rod  1 . The wheels readily roll and pivot simultaneously so that the cradles can move left or right at the same time as the cradles move forward or backward. Thus, for example, a user can readily move his or her hand from a key at the left end of the lowest row of the keyboard to a key at the right end of the highest row of the keyboard in one easy movement. In the illustrated embodiment, the wheels  8  and  9  are not coupled and may move independently with respect to each other. Similarly, the wheels  10  and  11  are not coupled and may move independently with respect to each other. In alternative embodiments, the wheels  8  and  9  may be coupled together and the wheels  10  and  11  may be coupled together so that a substantially constant spacing is maintained between the wheels in each pair of wheels. 
     When using a conventional keyboard having a sloped key layout, it is anticipated that the cradles  28 ,  29  will be positioned over the keyboard such that the fingers of a user&#39;s hand will be generally proximate to the lower row of keys on the keyboard. Then, as the user moves the cradles way from the user&#39;s body, the cradles will swing upward so that the user&#39;s fingers move up the slope of the keyboard. The four turnbuckles  20 ,  21 ,  22 ,  23  are readily adjusted to change the arc length of the swing of the wrist cradles to compensate for differing keyboard slopes. 
     FIGS. 5-15 illustrate further alternative embodiments of the present invention. In particular, FIGS. 5 and 6 illustrate a wrist support system  100  which can be mounted to the edge  104  of a desktop  102 . 
     The embodiment of FIGS. 5 and 6 includes a first cradle  110  for the right wrist and a second cradle  112  for the left wrist. The first cradle  110  is suspended from a first hanger  120  by a first support wire  122  and a second support wire  124 . The second cradle  112  is supported from a second hanger  130  by a third support wire  132  and a fourth support wire  134 . The first and second support wires  122 ,  124  pass through respective holes on opposite sides of the first cradle  110 . The third and fourth support wires  132 ,  134  pass through respective holes on opposite sides of the second cradle  112 . In the preferred embodiment, the first, second, third and fourth support wires  122 ,  124 ,  132 ,  134  comprise 0.039 inch (1 millimeter) piano wire, or the like, positioned in a respective sleeve  140 ,  142 ,  144 ,  146 . The sleeves advantageously comprise silicon plastic tubing, or the like. As shown in more detail in FIG. 7, the end of each support wire is bent into a generally U-shape to support the cradle, and the free end is passed back into the respective sleeve to preclude the free end from snagging a user&#39;s skin or clothing and also to assist in maintaining the U-shape of the support wire. 
     In alternative embodiments (not shown), the first, second, third and fourth support wires  122 ,  124 ,  132 ,  134  comprise flexible cables, such as, for example, seven-strand braided stainless steel wires from Sevenstrand Corporation, 899 West Cowles Street, Long Beach, Calif. The flexible cables are preferably looped through the holes in the cradles  110 ,  112  and are clamped at the first and second hangers  120 ,  130 . 
     In the illustrated embodiment, each of the first and second hangers  120 ,  130  is generally triangularly shaped with a base and an opposing apex. A U-shaped portion of each of the first and second support wires  122 ,  124  engages a respective hole at each end of the base of the first hanger  120 . A U-shaped portion of each of the third and fourth support wires  132 ,  134  passes through a respective hole at each end of the base of the second hanger  130 . Again, the free end of each support wire at the hangers  120 ,  130  is passed back into the respective sleeve for the reasons discussed above. 
     The apex of each of the hangers  120 ,  122  is suspended from a respective trolley  150 ,  152  which is mounted on a horizontally disposed guide rod  154 . As will be discussed in more detail below in connection with FIGS. 9 and 10, the trolleys  150 ,  152  comprise linear bearings mounted within a cylindrical plastic shell. A hanger wire  160  supports the first hanger  120  from the trolley  150 , and a hanger wire  162  supports the second hanger  130  from the trolley  152 . 
     The horizontal rod  154  advantageously comprises a stainless steel rod having a substantially circular cross section and having a diameter of approximately 0.375 inch (9.5 millimeters). The horizontal rod  154  has a length of approximately 30 inches (76.2 centimeters) between first and second ends. 
     The horizontal rod  154  is welded or otherwise connected to a first elbow  170  at the first end and to a second elbow  172  at the second end. The first elbow  170  has a tubular portion  174  which receives a first support rod  176 . The second elbow  172  has a tubular portion  178  which receives a second support rod  180 . Preferably, the first and second support rods  176 ,  180  comprise steel or aluminum and have solid circular cross sections with diameters of approximately 0.375 inch (9.5 millimeters). The tubular portions  174 ,  178  of the first and second elbows  170 ,  172  have inside diameters of approximately 0.375 inch (9.5 millimeters) with sufficient tolerance to removably receive the first and second rods  176 ,  180 . 
     The first support rod  176  has a generally vertical portion  182  proximate to the desk top  102  and a non-vertical portion  184  disposed at an angle with respect to the vertical portion  182 . The second support rod  180  has a generally vertical portion  186  proximate to the desk top  102  and a non-vertical portion  188  disposed at an angle with respect to the vertical portion  186 . For example, in the preferred embodiment, the non-vertical portions  184 ,  188  are disposed at an angle of approximately 20 degrees with respect to the vertical portions  182 ,  186 . 
     The first support rod  176  is positioned in a first clamp  190 , and the second support rod  180  is positioned in a second clamp  192 . The clamps  190 ,  192  are secured to the edge  104  of the desktop  102 . A lower portion of the first support rod  176  is threaded and is engaged with a first vertical adjustment knob  194 . A lower portion of the second support rod  180  is threaded and is engaged with a second vertical adjustment knob  196 . The first vertical adjustment knob  194  rests on the first clamp  190 , and the second vertical adjustment knob  196  rests on the second clamp  192 . As the first and second vertical adjustment knobs  194 ,  196  are turned clockwise or counterclockwise, the first vertical support rod  176  and the second vertical support rod  180  are caused to move up or down to thereby adjust the position of the horizontal rod  154  with respect to the desktop  102 . Preferably, the adjustment knobs  194 ,  196  are adjusted so that the rod  154  is level and is a desired distance above the desktop  102 . By adjusting the position of the rod  154 , it is not necessary to adjust the position of the cradles  110 ,  112  with respect to the rod  154  in the manner described in connection with the embodiments of FIGS. 1-4. The vertical adjustment knobs  194 ,  196  are advantageously constructed from PVC or other suitable material (e.g., metal). Preferably, the knobs  194 ,  196  are constructed in a octagonal shape and are sized to be sufficiently large that the knobs can be easily turned with a user&#39;s hand rather than requiring a wrench or other tool. 
     The non-vertical portions of the support rod  176 ,  180  permit the horizontal rod  154  to be positioned in two locations over the desktop  102  to allow a user to choose where the user&#39;s hands are supported. In FIG. 5, the support rods  176 ,  180  are oriented with the non-vertical portions  184 ,  188  directed over the desktop  102  before inserting the support rods  176 ,  180  into the respective elbows  170 ,  172 . In this orientation, the horizontal rod  154  is positioned over the desktop  102 , and the user&#39;s hands are positioned inward from the edge  104  of the desktop  102 . Thus, the user&#39;s hands are positioned over a keyboard  200  which is located on the desktop  102  away from the edge  104  of the desktop  102 . 
     In contrast to the orientation in FIG. 5, the non-vertical portions  184 ,  188  of the support rods  176 ,  180  are turned by 180° in FIG. 6 so that the non-vertical portions  184 ,  188  are directed away from the desktop  102 . Thus, in FIG. 6, the horizontal rod  154  is positioned away from the edge  104  of the desktop  102 , and the user&#39;s wrists and hands are supported over a keyboard  200  which is located at the edge  104  of the desktop  102 . Thus, the user has a choice of where to position the keyboard to accommodate individual preferences. 
     As discussed above in connection with the embodiments of FIGS. 1-4, the trolleys  150 ,  152  move laterally on the rod  154  to permit lateral movement (i.e., left and right movement) of a user&#39;s hands across the keyboard  200 . The trolleys  150 ,  152  also permit forward and backward movement of the user&#39;s hands with respect to the rows of the keyboard  200 . The use of linear bearings for the trolleys  150 ,  152  permit a smoother movement and also provide a more compact appearance for the trolleys  150 ,  152 . 
     The first cradle  110  is shown in more detail in FIGS. 7 and 8. The second cradle  112  is preferably interchangeable with the first cradle  110 , and the following description also applies to the second cradle  112 . As illustrated, the first cradle  110  comprises an outer shell  300  formed in a generally semicircular shape between a first side  302  and a second side  304 . The first side  302  and the second side  304  are spaced approximately 4 inches (10.1 centimeters) apart. A first hole  306  in the first side  302  and a second hole  308  in the second side  304  receive the support wires  122  and  124 , respectively. 
     As illustrated in FIG. 8, a portion of the user&#39;s lower arm and a portion of the user&#39;s wrist are supported by an arcuate bottom portion  310  between the two sides  302 ,  304 . The bottom portion  310  extends forward past the two sides  302 ,  304  to a generally flat extended portion  320  which supports the user&#39;s palm. The flat extended portion  320  may also support a portion of the user&#39;s wrist. In the illustrated embodiment, the extended portion  320  has a width of approximately 1.5 inches (3.8 centimeters). Preferably, the extended portion  302  has a raised portion  322  at the end thereof. The raised portion  322  conforms the end of the extended portion  320  with the concave contour of the user&#39;s palm to provide additional comfort to the user. The overall length of the cradle  110  in one embodiment is approximately 8.25 inches (21 centimeters). 
     In the preferred embodiment, the cradle  110  is stamped from aluminum having a thickness of approximately 0.060 inch (1.5 millimeter). The cradle  110  can also be constructed from other materials, such as for example, plastic. 
     In the preferred embodiment, the inner portion of the cradle  110  in contact with the user&#39;s lower arm, wrist and palm is lined with a cushioning material  330 . In the preferred embodiment, a 0.125-inch (3.2-millimeter) layer of neoprene material similar to the material used to line wet suits has been found to be particularly advantageous. The neoprene provides cushioning and the nylon cloth liner isolates the neoprene from the user&#39;s skin and clothing. The cushioning material  330  is fastened to the cradle  110  with glue or other suitable bonding material with the nylon cloth liner of the cushioning material  330  exposed. Other suitable lining material may also be used. 
     FIGS. 9 and 10 illustrated the first trolley  150  in more detail. The second trolley  152  is substantially similar to the first trolley  150 , and the following description also applies to the second trolley  152 . 
     As illustrated in FIG. 7, the first trolley  150  comprises an linear bearing  400 . The linear bearing  400  is preferably an IKO Model LBB 6 linear bearing available from IKO Nippon Thompson Co., Ltd., of Tokyo, Japan. The linear bearing  400  has an inner surface having an inside diameter slightly greater than 0.375 inch (9.5 millimeters) so that the linear bearing  400  fits on the rod  154 . The construction of the linear bearing  400  is well known. The linear bearing  400  has a plurality of internal bearing races. Each bearing race has a plurality of bearings which run longitudinally along the inner surface of the linear bearing so that the rod  154  is supported by a plurality of bearings. The linear bearing  400  moves freely longitudinally along the rod  154  and also moves freely arcuately about the rod  154 . 
     As further illustrated in FIG. 9, the linear bearing  400  is press-fit into an outer sleeve  410  having an inner surface  412  and an outer surface  414 . In the illustrated embodiment, the outer sleeve  410  comprises PVC or other suitable plastic material which has an inner diameter selected to closely match the outer diameter of the linear bearing  400 . For example, in the preferred embodiment, the linear bearing  400  has an outer diameter of approximately {fraction (5/32)} inch (15 millimeters) such that when the linear bearing  400  is press-fit into the outer sleeve  410  having an inner diameter of approximately {fraction (5/32)} inch, the linear bearing  400  fits snugly in the outer sleeve  410  without deforming the linear bearing  400 . If the inner diameter of the outer sleeve  410  is too small, the bearings within the linear bearing  400  may bind such that the linear bearing  400  no longer moves freely on the rod  154 . 
     As further illustrated in FIG. 9, a circumferential groove  420  is cut into the outer surface  414  of the PVC sleeve  410 . The groove  420  receives and holds the hanger wire  160 . Preferably, the hanger wire  160  is wound approximately 1¼ times around the outer surface  414  in the groove  120 . The two free ends of the hanger wire  160  are formed in first and second J-hooks  530 ,  532 . The two free ends are passed through the upper hole in the first hanger  120  (FIGS.  5  and  6 ), and the two hooks  530 ,  532  prevent the first hanger  120  from disengaging from the hanger wire  160 . 
     FIG. 11 illustrates an alternative embodiment of a trolley  500  which can be used in place of the trolley  150  or the trolley  152 . The trolley  500  of FIG. 11 uses a grooved wheel  502  which is similar to the grooved wheels  8 ,  9 ,  10 ,  11  of FIGS. 1-4. However, in FIG. 11, only a single wheel  502  is used to support each cradle  110  or  112 . An axle  504  passes through the center of the wheel  502  and is connected to a first side bar  506  and to a second side bar  508 . The first side bar  506  is fastened to the midpoint of a horizontal hanger  510 . The horizontal hanger  510  has first and second ends with a first hole  512  proximate to the first end and a second hole  514  proximate to the second end. When supporting the first cradle  110 , the first support wire  122  passes through the first hole  512 , and the free end of the support wire  122  is inserted into the end of the sleeve  140 , as discussed above. Similarly, the second support wire  124  passes through the second hole  514 , and the free end of the second support wire  124  is inserted into the end of the sleeve  142 . A second trolley (not shown) for the second cradle  112  has a similar structure. 
     The second side bar  508  is not fixed to the horizontal hanger  510 . Rather, the second side bar  508  is spaced apart from the horizontal hanger  510  by a distance that is slightly less than the diameter of the rod  154 . The second side bar  508  is sufficiently resilient to permit the trolley  500  to mounted on the rod  154 . Thereafter, the resiliency of the second side bar  508  prevents the trolley  500  from being inadvertently dislodged from the rod  154  until sufficient force is applied in the vertical direction in FIG. 11 to force the rod  154  between the second side bar  508  and the horizontal hanger  510 . 
     FIGS. 12-15 illustrate the first clamp  190  in more detail. The second clamp  192  is substantially similar to the first clamp  190 , and the following description also applies to the second clamp  192 . 
     As illustrated in FIG. 12, the first clamp  190  comprises an upper fixed head  600 , an externally threaded cylindrical shank or stem  602 , and an internally threaded knob  604 . Preferably, as shown in FIG. 14, the fixed head  600  is swaged or staked onto the stem  602  in a conventional manner. For example, the stem  602  preferably has a lip  610  formed on one end thereof. The fixed head  600  is positioned on the lip  610  with a portion of the stem  602  extending above the fixed head  600 . The extended portion is swaged or staked to fix the fixed head  600  to the stem  602 . 
     Preferably, a thin rubber pad  620  is positioned on the stem  602  in contact with the fixed head  600 . In the preferred embodiment, both the fixed head  600  and the pad  620  are circular. For example, the fixed head  600  is advantageously a stainless steel washer having a diameter of approximately 1.75 inches (44.4 millimeters). 
     The stem  602  is a hollow cylindrical tube having an inside diameter of approximately 0.375 inch (9.5 millimeters) to receive the first support rod  176 . The stem  602  has an outside diameter of approximately 0.625 inch (15.9 millimeters) and is threaded as shown. 
     As illustrated in cross section in FIG. 13, the knob  604  comprises a solid head portion  700  and a cylindrical body portion  702  constructed from PVC or other suitable metallic or plastic material. The body portion  702  has an outside diameter of approximately 1.75 inches (44.4 millimeters) and an inside diameter of approximately 1.125 inches (28.6 millimeters). The body portion  702  has a cylindrical wall with a thickness of approximately 0.31 inch (7.9 millimeters). 
     The head portion  700  has a generally octagonal shape so that the head portion  700  can be gripped by hand or with a wrench. In the preferred embodiment, the head portion  700  has a maximum diagonal dimension of approximately 1.875 inches (47.6 millimeters). The head portion  700  is threaded in the center with threads  704  having an outer diameter of approximately 0.625 inch (15.9 millimeters) to match the outer threads of the stem  602 . 
     As illustrated in FIG. 15, the knob  604  is threaded onto the stem  602  with the edge  104  of the desktop  102  positioned between the pad  620  and the body portion  702  of the knob  604 . As the knob  604  is tightened, the pad  620  engages the top of the desktop  102 , and the walls of the body portion  702  of the knob  604  engage the bottom of the desktop  102 . By using the hollow cylindrical body portion  702  rather than a solid body portion for the knob  604 , the force caused by tightening the knob  604  is applied over a smaller surface area of the bottom of the desktop  102 . Thus, the clamp  190  can be readily tightened by hand or with minimal use of a wrench. 
     FIG. 16 illustrates a further alternative embodiment of the present invention in which a desktop  800  or other workstation surface is modified to include a first hole  802  (FIG. 17) having a first receptacle  806  positioned therein and to include a second hole (not shown) having a second receptacle  808  positioned therein. Each receptacle  806 ,  808  is sized to receive the first rod  176  and the second rod  180 , respectively. As shown in more detail in FIG. 17, in particularly preferred embodiments, the first receptacle  806  in the first hole  802  comprises a stem  810  similar to the stem  602  described above. A fixed head  812  is swaged or staked onto the stem  810 , as discussed above. The fixed head  812  advantageously rests on a pad  814 . The second receptacle  808  has a similar structure and is not shown in detail. 
     In the embodiment of FIGS. 16 and 17, the forces of the threaded lower portions of the rods  176 ,  180  are applied against the insides of the stems  810  rather than being applied directly against the material comprising the desktop  800 , thus preserving the integrity of the first hole  802  and the second hole (not shown). As discussed above, the knobs  194 ,  196  on the support rods  176 ,  180  are rotated to adjust the height of the support rods  176 ,  180  and thus adjust the height of the horizontal rod  154 . 
     The present system provides a natural resting position for the user&#39;s wrists and hands. Thus, for example, when using a computer keyboard in conjunction with a mouse, the present system assists the user in returning from a mouse operation to a keyboard without having to look at the keyboard to determine correct hand placement. Thus, the user can continue to watch the screen when transitioning between the two operations. 
     It can be readily seen from the foregoing that when the free floating support system in accordance with the present invention is used with keyboards, typewriters, data entry devices, musical instruments, and the like, or is used to assist in the performance of tedious assembly work, the system will greatly reduce stresses and strains to the wrists and arms. The present invention is particularly advantageous for a person having weak muscles such that the person cannot readily support his or her hands above a keyboard or other work surface. The cradles provide the necessary support so that the person&#39;s remaining muscular capabilities can be applied to the manipulation of the keyboard or to any other task rather than to the effort of supporting the wrists and hands. 
     While described in connection with a computer keyboard, it should be understood that the present invention has applicability to other repetitive activities, such as for example, assembly work, wherein a user works in a particular area with his or her hands above a work surface. 
     While preferred embodiments of this invention have been disclosed herein, those skilled in the art will appreciate that changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.