Abstract:
A keyboard support tray arrangement includes both a main support tray for supporting a computer keyboard and an auxiliary support pad for supporting a user&#39;s palm or wrist. The auxiliary pad is removably and height adjustably positionable adjacent the front of the main keyboard tray to provide increased convenience and flexibility of use. The auxiliary support pad is completely separable from the main keyboard tray. A multi-height connecting and actuating structure enables the auxiliary pad to be positioned relative to the main keyboard tray at one of a plurality of heights by manual actuation of a single lever which is swingable through only a small angular extent.

Description:
FIELD OF THE INVENTION 
     This invention relates to a keyboard support tray arrangement for a computer and, more particularly, to an improved keyboard support tray arrangement employing an adjustable wrist/palm support pad. 
     BACKGROUND OF THE INVENTION 
     Articulated keyboard support mechanisms are typically mounted on and associated with work surfaces and desktops to support a computer keyboard. Such mechanisms are additionally often provided with an associated support pad for a user&#39;s wrist or palm. These support pads are conventionally fixed height foam or gel pads that lie along the front edge of the keyboard support on the upper surface thereof. While keyboarding, a user may rest his wrists or palms on the support pad to improve ergonomics. Different users require different heights in order to adequately support their hands. Moreover, recent developments in ergonomics suggest that a user should occasionally alter the position of their hands in an effort to reduce repetitive stresses. A fixed height support pad does not provide the desirable height adjustment relative to the keyboard. Moreover, keyboards may have different heights. Thus, one height of a support adjacent one keyboard may be inadequate adjacent a different keyboard. In fact, it may be desirable to remove the support from the keyboard support mechanism. 
     Numerous keyboard support mechanisms have been developed for supporting a keyboard adjacent a worksurface. Some keyboard support mechanisms include a wrist or palm support fixed to the tray supporting the keyboard. In known arrangements, the height of the wrist support is adjustable to account for the differences in keyboard construction and users. For example, in some keyboard support mechanisms, the wrist support cooperates with two separate rotatable threaded members, which are rotatably secured to the keyboard support tray and individually manually rotated for adjusting the height of respective ends of the wrist support. Users of these types of mechanism experience difficulties in maintaining the support pad in a level orientation due to the difficulty in synchronizing movement of the two threaded members. Moreover, the threads typically require a plurality of time-consuming revolutions to adjust the height of the wrist support. In other more structurally complex mechanisms, the wrist support cooperates with a single lateral slide, which is slidably secured to the keyboard support tray and laterally slides to adjust the height of the wrist support. Examples of prior keyboard support mechanisms are found in: U.S. Pat. Nos. 4,545,554; 5,219,136; 5,375,800; 5,421,543; 5,443,237; 5,507,458; and 5,836,560. 
     It is an object of the invention to provide an improved keyboard support arrangement that accommodates both a keyboard support tray and a wrist/palm support pad while greatly improving upon both the structure and the convenience and flexibility of use in comparison to known structures. 
     More specifically, it is an object of the invention to provide a height adjustable wrist/palm support pad arrangement which is supported by a pair of rotatable camming hubs which are linked for synchronous rotational displacement and one of which has a manually-engagable actuator part to enable simple height adjustment by an operator. 
     More specifically, the present invention relates to a keyboard support arrangement which includes both a main keyboard support tray and a height adjustable wrist/palm support pad removably secured to the main keyboard support tray so as to provide increased convenience and flexibility of use with respect to the support pad. In the improved support pad arrangement, the support pad is easily selectively separable from or mountable on the keyboard support tray. A connecting assembly is provided on the pad for removably securing the support pad to the tray. 
     In accordance with a preferred embodiment of the invention, the keyboard support arrangement includes a keyboard support tray and a wrist/palm support pad adapted to support a user&#39;s wrist or palm thereon. A connecting and height adjusting structure detachably fixes the support pad on the tray upper surface and positions the support pad at one of a plurality of different heights. In one position of the connecting and height adjusting structure, the support pad is removable from the tray. In a second position, the support pad is secured to the tray at a first height. In a third position, the support pad is secured to the tray at a second height. 
     Further in accordance with the preferred embodiment of the invention, the connecting and height adjusting structure has two interconnected hubs each including radial flanges which are rotatably received in channels in the tray to rotatably fix the hubs to the tray. Once the support pad is attached to the tray, the connecting and height adjusting structure adjusts the height of the support pad relative to the tray by rotation of the hub causing opposed cam elements to react with and effect height adjustment of the support pad. 
     Another object of the invention is to provide a single actuator for both releasing the support pad from the keyboard support tray and adjusting the height of the support pad relative to the tray. More specifically, the rotatable hubs are linked together, and one of the hubs has a manually-engagable actuator part to effect synchronous rotation of the linked hubs to adjust the height of the support pad or release the support pad from the keyboard support tray. 
     Other objects and purposes of the invention will be apparent upon reading the following specification and inspecting the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating the keyboard support arrangement and its attachment to and position adjacent a conventional work surface; 
     FIG. 2 is a top view illustrating the keyboard support arrangement including the main keyboard support tray and the height-adjustable wrist support pad according to the present invention; 
     FIG. 3 is an exploded elevational view of the wrist/palm support pad arrangement of the present invention; 
     FIG. 4 is plan view the keyboard support tray; 
     FIG. 5 is an enlarged, fragmentary, cross-sectional view taken generally along line  5 — 5  in FIG. 4; 
     FIG. 6 is an enlarged, fragmentary, cross-sectional view taken generally along line  6 — 6  in FIG. 4; 
     FIG. 7 is a bottom view of the wrist support pad; 
     FIG. 8 is a rear elevational view of the wrist support pad; 
     FIG. 9 is a cross-sectional view taken generally along line  9 — 9  of FIG. 7; 
     FIG. 10 is a cross-sectional view taken generally along line  10 — 10  of FIG. 7 (i.e. centrally through the cylindrical cam wall; 
     FIG. 11 is an enlarged, partial cross-sectional view of the lower flat of the cam surface taken from FIG. 10; 
     FIG. 12 is a plan view of the connecting and height adjusting structure associated with the wrist support pad; 
     FIG. 13 is an enlarged cross-sectional view taken generally along line  13 — 13  of FIG. 12; 
     FIG. 14 is an enlarged cross-sectional view taken generally along line  14 — 14  of FIG. 12; 
     FIG. 15 is a front elevational view of the keyboard support arrangement with the wrist support pad in a lowered position as shown in FIGS. 1 and 2; 
     FIG. 16 is an enlarged, fragmentary cross sectional view taken generally along line  16 — 16  of FIG.  2  and showing the connecting and height adjusting structure in a lowered position; 
     FIG. 17 is a view similar to FIG. 16 but showing the connecting and height adjusting structure in a released position; 
     FIG. 18 is a front elevational view of the keyboard support arrangement similar to FIG. 15 but showing the wrist support pad in its raised position; 
     FIG. 19 is an enlarged fragmentary cross sectional view taken generally along line  19 — 19  in FIG.  18  and showing the connection and height adjusting structure in its raised position; and 
     FIG. 20 is a perspective partial view of the connecting and height adjusting structure. 
     Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “leftwardly” and “rightwardly” will refer to directions in the drawings to which reference is made. The word “forwardly” will be used in conjunction with the portions of the keyboard arrangement positioned closest to the user, and similarly the word “rearwardly” will refer to portions of the keyboard arrangement positioned remote from the user. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the overall arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar meaning. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, and specifically FIG. 1, there is illustrated an articulated keyboard support arrangement  10  according to the present invention. The arrangement  10  is adapted to be mounted on a conventional work surface or tabletop  11 , the latter having generally horizontal and substantially planar upper and lower surfaces  12  and  13 , respectively, with the work surface  11  terminating at a free front edge  14 . 
     A linkage assembly  15  secures the support arrangement  10  to the tabletop  11 . Examples of such a linkage assembly  15  are described in copending patent application Ser. No. 09/174,000 and U.S. Pat. No. 5,927,662, which are assigned to the same assignee as the present application. The &#39;000 application and &#39;662 patent are herein incorporated by reference. In brief, the connecting assembly  15  includes an elongate support arm  16 , which at the rear end thereof couples to a carriage  17  that is positioned under the tabletop  11 . The carriage  17  is preferably confined for sliding movement in a front-to-back direction of the tabletop  11  on an elongate track (not shown) stationarily and horizontally mounted on the lower surface  13  of tabletop  11 . The forward end of the support arm  16  mounts thereon the keyboard support arrangement  10 . 
     The keyboard support arrangement  10  includes a main keyboard support tray  21  and a support pad  22  for respectively supporting a computer keyboard and a user&#39;s wrist or palm. A connecting and height adjusting assembly  23  is fixed to the support pad  22 . As best shown in FIG. 3, the connecting and height adjusting assembly  23  removably secures the support pad  22  to the tray  21  and adjusts the height of the support pad  22  relative to the tray  21 . 
     Considering now FIGS. 1-4, the keyboard support tray  21  includes a generally horizontally enlarged and substantially planar upper surface  24  for supporting a conventional computer keyboard  25  thereon (shown in dotted lines in FIGS.  1  and  2 ). Grip surfaces  26  adjacent opposite sides of the tray upper surface  24  frictionally assist in holding the keyboard  25  on the tray. Ribs (not shown) may be positioned on the bottom surface of the tray to increase its strength and rigidity. The tray  21  may additionally include, substantially midway along each of right and left side edges  28  and  29  thereof, a recess  31  and a connecting member  32  located within recess  31 . The recesses  31  and connecting members  32  allow an auxiliary pad (not shown) to be connected to either the right or left side of the tray as described in greater detail in the &#39;000 application. 
     Referring now to FIGS. 4-6, the keyboard support tray  21  also includes a longitudinally and vertically curved front edge  33  and a notch  34  recessed in each of the front corners thereof. Two upwardly open recesses  35  are positioned in the tray upper surface  24  adjacent the front edge thereof and respectively positioned to the left and right of a central outward curvature of the front tray edge  33 . Both recesses  35  are generally cylindrical with the axes thereof extending generally perpendicular to the upper surface  24  and having a short axial length or depth relative to the diameter. More specifically, the recesses  35  are defined by an axially short cylindrical sidewall  36  extending downwardly from the tray upper surface  24  and a bottom wall  37  at the lower end of the sidewall  36  substantially closing the bottom of the recess  35 . Arcuate flanges  38 ,  39  extend radially inwardly from the top of the sidewall  26  and have an upper surface generally coplanar with the upper tray surface  24 . The first flange  38  is longer than the second flange  39 . The flanges  38 ,  39  are circumferentially spaced from each other to create arcuate entry openings  41 ,  42  therebetween and are vertically spaced from the bottom wall  37  to create radially inwardly open slots  44 . The left entry opening  41  (FIG. 4) is longer than the right entry opening  42 . Directly beneath the flanges  38 ,  39 , arcuate through channels  46 ,  47  are formed in the bottom wall  37  and have a length substantially equal to the length of corresponding flange. 
     Considering now the support pad  22  (FIGS.  7 - 9 ), it has a generally inverted cup-like shape defined by a generally planar top wall  51  and an unending skirt  52  depending downwardly from the periphery of the top wall  51 . In a preferred embodiment of the present invention, support pad  22  has a rigid plastic frame surrounded by a vinyl, user-contacting cushioning layer  55  fixed thereon. However, other constructions including an integrally molded plastic construction are within the scope of the present invention. 
     The top wall and skirt  51 ,  52  enclose a downwardly open cavity  53  and respectively have smooth outer top and side surfaces  56 ,  57  that may come into contact with a person using the support pad  22 . The cavity  53  may house ribs (not shown) for reinforcing the top wall and skirt  51 ,  52 . An elongate notch  58  is formed in the rear portion  59  of the skirt  52  and extends about two-thirds the length of the skirt rear portion  59 . Resilient nubs  61  are integral with and extend downwardly adjacent the front corners of the skirt  52 . The front portion  63  of the skirt  52  ideally has a curved shape similar to the front edge  33  of the keyboard tray  21 , but includes a forward semi-oval protrusion  64  that slopes up to the top wall  51  at a reduced rate relative to the remainder of the skirt front portion  63 . In the illustrated embodiment, the protrusion  64  is positioned to the left of the central outward protrusion of skirt front portion  63 . A central window  66  extends vertically through the protrusion  64 . 
     A mating structure  67  is provided on a bottom surface  69  of the top wall  51  in the cavity  53  for joining the connecting and height adjusting structure  23  to the palm or wrist support pad  22 . The mating structure  67  includes identical left and right axles  68  cantilevered to the bottom surface  69  of the top wall  51  and extending into the cavity  53  adjacent respective left and right ends thereof. The axles  68  are spaced from each other at a distance less then the length of the notch  58  and have a height slightly greater the height of the skirt  52  so that the axles  68  extend just outside the cavity  53 . Radially outwardly extending ribs  71  are formed along the length of the axles  66  to improve the strength and rigidity thereof. A fastener-receiving hole  72  is recessed in the free end and centered on the longitudinal axis of each axle  68 . 
     The mating structure  67  further includes two sleeve-like cylindrical walls or cams  75  extending cantileveredly downwardly from the bottom surface  69  of the top wall  51 , each wall  75  encircling a respective axle  68 . The free end of each wall  75  is recessed to define an annular cam surface  73 . The cam surfaces  73  are identical and thus only one will be described in detail. The cam surface  73  faces axially away from the bottom surface  69  of the top wall  51  and is radially spaced from the encircled axle  68 . As shown linearly in FIG. 10 by taking a cross section along the center of cylindrical wall  75 , the cam surface  73  has a tooth-like cam pattern  74  that repeats itself three times to complete a circle. Accordingly, each pattern  74  of the cam surface extends about 120 degrees around the wall  72 . Each pattern  74  is the same, and therefore only one will be described in detail. 
     In the clockwise direction (or leftwardly in FIG.  10 ), the cam surface pattern  74  begins with a short inclining ramp  76  followed by a short upper flat  77 . The upper flat  77  precedes a long declining ramp  78 , which in turn is followed by a lower flat  79 . A generally vertical or axially extending wall or shoulder  81  transitions the flat  79  to the ramp  76 , and thereafter begins an identical subsequent cam surface pattern. Both flats  77 ,  79  extend in vertically-spaced planes that are generally perpendicular to the center axis of the wall  75 . The lower flat  79  is positioned within the cavity  53  and thus does not extend downwardly past the skirt front portion  63 . A depression  82  is formed in the lower flat  79  (FIG.  11 ). 
     Considering now the connecting and height adjusting assembly  23  (FIGS.  3  and  12 ), it has two connecting members or hubs  84 ,  86  for removably connecting the support pad to the keyboard supporting tray  21 . An elongate link  88  joins the hubs  84 ,  86 , and a biasing mechanism  89  is mounted to each hub  84 ,  86 . The two hubs  84 ,  86  are similar and thus one hub will be described in detail followed by the differences on each of the two hubs. 
     The hub  84  includes a central cylindrical hub part  91  and a longitudinally extending through opening  92 , which is partially closed at an upper end  93  by an integral radially inwardly extending annulus  94 . Thus, the opening at the hub upper end  93  has a smaller diameter than the opening at the lower end  96  of the hub part  91 . An integral disk  98  extends annularly around the outer surface of the hub part  91  and is spaced upwardly a short distance from its lower end  96 . An integral cylindrical rim  99  cantilevers downwardly from the outer peripheral edge of the disk  98  and ends at the same plane as the hub lower end  96 . Arcuate flanges  101 ,  102  extend radially outwardly and partially along the free edge  104  of the rim  99  and are substantially coplanar to the hub lower end  96  and rim free edge  104 . One flange  101  is longer than and positioned generally diametrically opposite the other flange  102 . Cam followers formed as pins  106  stand upwardly from the disk  98  generally parallel to the center axis of the hub  91 . The pins  106  are equal in number to the number of repeating patterns in the cam surface  73  and, consequently, in the illustrated embodiment there are three pins  106  on each hub  84 ,  86  spaced 120 degrees from each other. 
     The two hubs  84 ,  86  differ as follows. The disk  98  of control hub  84  (FIGS. 3 and 12) has an annular extension  108  extending outwardly through a greater radial extent than the disk  98  of hub  86 . In the illustrated embodiment, the extension  108  is integral and coplanar with the disk  98 . The extension  108  has through openings  109  aligned with each of the flanges  101 ,  102  and an arcuate projection  111  from which a control handle  112  extends radially outwardly. On the arcuate projection  111  there are a plurality of embossed indicators  113 ,  114 ,  115  that respectively indicate the in/out (insert/release) position of the hub, the low position, and the high position. The control handle  112  has upraised grips on both the lower and upper surfaces thereof to provide a gripping surface for a person grasping the control handle. The extension  108  also has, diametrically opposite the control handle  112 , two opposed, spaced apart upstanding resilient cantilevered prongs  119  each having an outwardly projecting latch  121  adjacent the free end thereof. 
     The right hub  86  (FIGS. 3,  12  and  14 ), unlike the left hub  84 , does not have an annular extension  108 , but instead has ears  117 ,  118  extending radially outwardly directly from the peripheral edge of disk  98  and fixed thereto are two opposed, spaced apart upstanding resilient prongs  119  which each have an outwardly projecting latch  121  adjacent the free end thereof. 
     The connecting link  88  is an elongate bar which, in the preferred embodiment, has an L-shape cross section. The length of the link  88  is less than the length of the notch  58  in the skirt rear portion  59  and generally approximately equals the distance between axles  68 . The link  88  has attachment apertures  122  at each end thereof extending generally transverse to the longitudinal direction of the link. The apertures  122  have diameters generally equal to the nonbiased position of the cantilevers  119 . 
     During construction of the connecting and height adjustment assembly  23 , the cantilevers  119  are forced into respective apertures  122  and yield to allow the latches  121  to pass through the apertures  123 . Once past the apertures  122 , the latches  121  are forced outwardly by the resilience of the cantilevers  119  and extend over the upper surface of the link  88  to pivotally join the link  88  to the hubs  84 ,  86  whereby relative rotational movement can occur between the cantilevers  119  and the link. Consequently, the link  88  connects the two hubs  84 ,  86  so that when the control hub  84  rotates, then the other hub  86  also rotates an equal amount. 
     The joined hubs  84 ,  86  and link  88  are mounted in the support pad cavity  53  with the prongs  117 ,  118  and connecting link  88  adjacent the notch  58  in the skirt rear portion  59 . The upper end  93  of each hub part  91  slides over one of the axles  68 . The ribs  71  of the axle having a maximum diameter slightly less than the opening at the hub upper end  93  so that the axle extends into the through opening  92  of the respective hub. In one method of mounting the hubs  84 ,  86  and link  88  to the mating structure  67  of the pad  22 , the pins  106  are aligned with the upper flats  77  and the prongs  117 ,  118  and link  88  are partially received in the notch  58 . A biasing member  89 , here shown as a coil-type compression spring, is positioned in each of the voids between the hub wall  91  and axle  68 . The biasing member  89  is held under tension in the void between the annulus  94  and washers  123  spaced from the annulus, the washers being positioned adjacent the lower end  96  of the hub. A fastener  124 , shown as a screw in the illustrated embodiment, extends through the center opening of the washer  123  and is received in the fastener-receiving hole  72  to hold the washer at a fixed distance relative to the axle  68  and pad  22 . The fastener  124 , reverse functional description acting through the spring and washer, rotatably joins the hubs  84 ,  86  to the respective axles  68 . 
     The spring member  89  has opposite ends thereof engaged and fixed to the washer  123  and hub top wall  93  respectively, and thus the spring  89  continuously biases the support pad downwardly toward the respective hub which in turn is fixed to the keyboard support tray  21 . This causes the cylindrical cam  75  to be urged downwardly so that the annular cam surface  74  is maintained in contact with the free ends of the pins  106 . 
     The connecting and height adjusting assembly  23  has four distinct modes corresponding to the position of the pins  106  on the four distinct cam surfaces in each pattern  74 , namely the ramp  76 , upper flat  77 , ramp  78  and lower flat  79 . When the connecting and height adjusting assembly  23  is joined to the pad  22 , the pins  106  are aligned with the upper flats  77 , and this corresponds to the lowered position (FIGS. 15 and 16) of the support pad  22  as explained in greater detail below. 
     However, the assembly  23  also has an in/out (or attachment) position (FIG. 17) to permit the pad  22  and connecting and actuating assembly  23  to be attached to or detached from the tray  21 . When the pad  22  and the assembly  23  mounted thereon are detached from the tray  21 , the assembly  23  is normally maintained in its lowered position wherein the springs  89  urge the ends of pins  106  into engagement with cam flats  77 . To attach the pad  22  to the tray  21 , the paid is positioned over the tray so that the lower ends of hubs  84 ,  86  are positioned directly over the recess  35 . 
     A user grips the handle  112  and then rotates it clockwise in FIG. 2 so that the control hub  84  rotates about its associated axle  68  and the link  88  causes the other hub  86  to rotate about its associated axle  68 . This causes the pins  106  to ride along the ramps  76  and also causes the flanges  101 ,  102  of the hub parts  91  on hubs  84 ,  86  to align with the entry openings  41 ,  42  of the respective tray recesses  35 . That is, the longer flange  101  aligns with the larger entry opening  41  and the smaller flange  102  aligns with the smaller entry opening  42 , with the front edge of the pad  22  aligned with the front edge  33  of the tray  21 . In the illustrated embodiment, the attachment position is reached when the pins  106  ride completely up the ramps  76  and abut against the vertical shoulders  81 . In this position, the indicator  113  is visible through the window  66  to inform the user that the connecting and height adjusting assembly is in the in/out position. While the flanges  101 ,  102  are being inserted downwardly into the entry openings  41 ,  42 , the user must continue to hold the handle  112  in the in/out position against the urging of the spring member  89  which continuously urges the pins  106  downwardly along the ramps  76  toward the flats  77 . More specifically, the spring member  89  in the in/out position is compressed between the washer  123  and the annulus  94 . Once the hub flanges  101 ,  102  are fully received in the entry openings  41 ,  42 , they are now rotatably aligned with the slots  44 . The user now releases the handle  112 , whereby the urging of the spring members  89  is sufficient to cause the pins  106  to ride down the corresponding ramps  76  back toward the flats  77  so as to rotate the hub flanges  101 ,  102  into the slots  44 , thereby securing the connecting hubs  84 ,  86  to the tray  21 . If the spring members  89  do not have sufficient force to cause the pins  106  to ride down the ramps  76 , then the user may manually rotate the handle  112  counterclockwise so that the pins are again resting on the flats  77 . In this lowered and connected position, the hub flanges  101 ,  102  are now at least partially received in the slots  44  defined by the tray flanges  38 ,  39  to define a bayonet-type lock that prevents the connecting and height adjusting assemblies  23  and pad  22  from being removed from the tray  21 . In addition, in this lowered position, the indictor  114  is visible through the window  66 . 
     If it is desired to remove the pad  22  from the tray  21 , then the above procedure is followed in reverse order to move the connecting and actuating assembly  23  from the lowered position to the in/out position. More specifically, the user rotates the lever  112  clockwise so that the hub flanges  101 ,  102  align with the entry openings  41 ,  42 , and the pad  22  and connecting and height adjusting assembly  23  are then lifted from the tray. 
     With the pad  22  secured to the tray  21  by the connecting and height adjusting assembly  23 , it may be desired to alter the height of the pad  22  from the lowered position to another position, for example a high position (FIGS.  18  and  19 ). The user again grips the handle  112 , however, this time the handle  112  is rotated counterclockwise (in FIG. 2) which causes the pins  106  to ride on the corresponding ramps  78  against the biasing force of the spring members  89  while the hub flanges  101 ,  102  rotate further into the slots  44 . As the lever handle  112  rotates the control hub  84 , the link  88  moves longitudinally to synchronously rotate the other hub  86 . The notch  58  in the rearwall of pad  22  provides clearance for the link  88  during movement between the lowered and raised positions of the pad. The pins  106  travel throughout the lengths of the ramps  78  onto the lower flat  79 . The pins  106  engage the detent-like depressions  82  on the flats  79  to assist in holding the pad  22  in the high position. In this position, the distance between the annulus  94  and washer  123  is at its least extent (FIG. 19) and thus the spring members  89  are subjected to their maximum compression. 
     To lower the pad  22  from the high position, the user again grips the lever  112  but rotates it clockwise. The biasing member  89  assists in moving the pins  106  down the ramps  78  to the flats  77  so as to return the pad  22  to the lowered position. 
     In the illustrated embodiment, there are three identical tooth-like patterns in the annular cam surface  73 . Accordingly, to move from the insert/release position of the connecting and height adjusting structure  23  to the high position thereof, requires the lever  112  to travel about 120 degrees. Accordingly, the forward protrusion  64  on the pad  22  has an outer periphery that also measures about 120 degrees. The through window  66  of the protrusion  64  is centrally aligned and through which indicators  113 ,  114 ,  115  are visible. The in/out indicator  113  is visible through the window  66  to allow a user to visually confirm the insert/release position of the connecting and height adjusting structure  23 . Likewise, indicators  114  and  115  are visible through the window  66  to allow a user to visually confirm the low and high positions of the connecting and height adjusting structure  23 . Thus, the high and insert/release indicators  115  and  113 , which are the most remote from each other, are spaced about 120 degrees from each other. 
     While the above description specifically addresses three identical repeating cam patterns in the cam surface  73 , it will be understood that other numbers of patterns are also within the scope of the present invention. However, a plurality of at least three such patterns is preferred to stabilize the hubs  84 ,  86  as they rotate on the cam surfaces  73 . 
     The arrangement of the present invention thus significantly adjusts the height of the support pad relative to the keyboard support by use of only a single manual lever swingable through only a small arc, which is less than one-half revolution. For example, the height of the support pad  22  is raised ⅜ inch by rotating control lever  112  less than 120°, preferably about 100°, from the low position to the high position. 
     Additionally it is within the scope of the present invention to flip flop the position of the cam follower  106  and the cam  74 , and position the cam followers on the support pad and the cam on the hubs. 
     Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.