Abstract:
There is disclosed a tilt control mechanism for a keyboard support platform. The keyboard support platform is of the type that includes linkage for connecting the platform to a work surface. The linkage further includes linkage arms that pivotally connect the keyboard support platform to the work surface. The tilt control mechanism comprises a tilt adjustment actuator arm and a pawl and ratchet connection between the actuator arm and the support platform. The pawl and ratchet provide a series of separate detent positions which define distinct length actuator arm connections between a fulcrum point and the support platform to thereby control the tilt of the platform.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/107,371, filed Nov. 6, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates in general to a support platform for a computer keyboard or the like and, more particularly, to a tilt control or pitch control mechanism for a keyboard support platform. The tilt control mechanism of the present invention permits the selective adjustment of the pitch or tilt of the support platform to allow the user to set the work angle of the keyboard. 
     The keyboard support platform construction is of the type generally shown in McConnell, U.S. Pat. No. 5,037,054 and U.S. Pat. No. 5,145,136, or Smeenge et al., U.S. Pat. No. 4,616,798. The aforesaid McConnell and Smeenge patents are incorporated herein by reference. Typically, a keyboard support platform is attached by parallel and/or non-parallel pivotal linkage arms to a slidable plate. The slidable plate, in turn, is mounted in a slide on the underside of a desk or other work surface. The slide permits the keyboard support platform and linkage to move between a storage position or retracted position to an extended or use position. The conventional pivotal linkage arms further permit the keyboard support platform to be adjusted to a useful operational work height. 
     The conventional keyboard support platform assemblies, however, are limited in the degree of keyboard tilt. That is, known keyboard platform assemblies limit the operational work angle of the keyboard and, therefore, do not ergonomically comply with the requirements of all users. Because conventional keyboard support platform assemblies are so limited, keyboard users have suffered from various debilitating medical conditions. As an example, it has been shown that without the proper work angle setting of the keyboard, users who perform considerable data entry on the keyboard have suffered from Carpal Tunnel Syndrome which is a medical disorder of the hand that creates numbness and pain in the fingers. Consequently, there is a need for an improved keyboard support platform assembly which provides not only adjustable work height of the keyboard but also improved adjustment of the tilt or work angle of the keyboard to prevent such debilitating medical conditions. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and provides a solution to the aforementioned problems associated with the known keyboard support platform assemblies. Accordingly, it is an object of the present invention to provide an improved adjustable support mechanism for a keyboard support platform. It is a further object to provide an adjustable tilt control mechanism which permits the user to set the pitch or angle of the keyboard support platform. 
     Briefly, in summary, the present invention comprises a tilt control mechanism for a keyboard support platform. The keyboard support platform is of the type that includes a linkage for connecting the platform to a work surface. The linkage further includes linkage arms which pivotally connect the keyboard support platform to the work surface. The tilt control mechanism comprises a keyboard support platform bracket having a tilt pivot axis connection to the linkage arms, and a tilt adjustment actuator arm pivotally attached at a fulcrum point at one end to the pivot axis connection. Connected between the actuator arm and support platform is a pawl and ratchet. The pawl and ratchet connection define distinct length actuator arm connections between the fulcrum point and the support platform to thereby control the tilt or pitch of the platform. 
     The full range of objects, aspects and advantages of the invention are only appreciated by a full reading of this specification and a full understanding of the invention. Therefore, to complete this specification, a detailed description of the invention and the preferred embodiment follows, after a brief description of the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The preferred embodiment of the invention will be described in relation to the accompanying drawing. In the drawing, the following figures have the following general nature: 
     FIG. 1 is a plan view of the tilt control mechanism of the invention as incorporated with a keyboard support platform; 
     FIG. 2 is an end elevation view of a keyboard support platform; 
     FIG. 3 is an exploded plan view of the component parts of the tilt adjustment mechanism of the invention of FIG. 1; 
     FIG. 4 is a side elevation view of the platform of FIG. 2; 
     FIG. 5 is a plan view of a keyboard support platform with a partial cut-away view of an alternative embodiment of the tilt control mechanism of the invention; 
     FIG. 6 is a side elevation view of a keyboard support platform of FIG. 5; 
     FIG. 7 is an exploded plan view of the component parts of the tilt adjustment mechanism of the invention of FIG. 5; 
     FIG. 8 is a side elevation view of the tilt adjustment mechanism of FIG. 7; and 
     FIG. 9 is a plan view of the tilt adjustment mechanism of FIG.  7 . 
     In the accompanying drawing, like reference numerals are used throughout the various figures for identical structures. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the figures, the keyboard support platform, such as platform  10 , is typically attached to linkage arms  4  by means of a first pivot shaft  12  and a second pivot shaft  14 . The linkage arms are conventionally connected to a slide bracket assembly  6  which, in turn, is attached to the work surface. Typically, the bracket assembly  6  supports the weight of the keyboard platform and permits sliding movement of the keyboard platform from a retracted position to an extended position. The platform  10  may be pivoted about the shaft  12  in order to adjust the tilt or pitch of the platform. The shaft  14  fits through an arcuate slot  16  to accommodate the change in pitch of the platform  10 . 
     The subject matter of the present invention relates to a mechanism which permits adjustment of tilt about the shaft  12  by movement of the platform along the range defined by the arcuate slot  16 . Referring to FIGS. 1-4, in a preferred embodiment, the mechanism includes an actuator arm block  20  which is fitted over the shaft  14  and thus remains fixed in position relative to the axis defined by the shaft  14 . The actuator arm  22  connects the actuator arm block  20  to the platform  10 . As more fully discussed below, by adjusting the length of the connection defined by the actuator arm  22  between block  20  and the platform  10 , one is able to adjust the tilt of the platform  10  to any of a number of incremental positions. Thus, the actuator arm  22  and the mechanism for connecting and adjusting the length of the connection of that arm  22  to the platform  10 , herein described as a pawl and ratchet mechanism, relates specifically to the subject matter of the invention. 
     The actuator arm  22  is connected to the actuator arm block  20  by means of a pivot or pin  24 . Pivotally connected to the actuator arm  22  by a pin  28  is a pawl which is further defined as a roll pin arm  26  and a roll pin  30 . The roll pin arm  26  receives the roll pin  30  which fits within opening  31  defined in the roll pin arm  26 . As illustrated in FIG. 1, the roll pin  30  operatively engages with a ratchet which is defined as a number of spaced detents  32  further defined in a detent slot  34  in the platform  10 . A spring  35  connected between the roll pin arm  26  and the end of the actuator arm  22  biases the roll pin arm  26  toward the actuator arm  22 . The spring  35  also causes the roll pin  30  to be engaged with a detent  32  and remain engaged therewith. 
     Depending upon the detent  32 , which is engaged by the pin  30 , one is able to control the pitch or tilt of the platform  10  inasmuch as one thereby adjusts the length of the actuator arm  22  between pin  24  and the detent  32  engagement with the platform  10 . This length adjustment of the actuator arm  22  causes the tilt or pitch of the platform  10  to vary. As preferred, the detents  32  are spaced to provide 5° increments in tilt of the platform  10 . 
     As a secondary or failsafe alignment feature of the invention, the actuator arm  22  includes a pin or rivet  36  which projects from the actuator arm  22  into an inclined slot  38  in the platform  10 . The configuration of the slot  38  as well as the detent slot  34  provides accommodation for variance of the pitch or tilt of the platform as the arm  22  is pivoted clockwise or counterclockwise about the pin or rivet  24 . 
     A release arm  40  is pivotally attached to the actuator arm  22  by means of a pin  42 . The release arm  40  includes an inclined cam surface  44  and a release projection  46  which cooperates with a release tab  48  in the platform  10 , described in greater detail below. The distal end of the actuator arm  22 , the end opposite the pivot  24 , includes a crimp or projecting lip  50  which cooperates with the release arm  40 . 
     In operation, as depicted in FIG. 1, the platform  10  is raised to its highest or most clockwise tilt in the range of tilt by pulling upwardly on the platform  10 . By pulling upwardly on the platform, the release arm  40  is caused to pivot clockwise about the pin  42  whereby the inclined surface or cam  44  will engage against the roll pin arm  26  causing the arm  26  to pivot clockwise about the pin  28  against the biasing force of spring  35 . The roll pin arm  26  pivoting about the pin  28  in a clockwise sense releases the roll pin  30  from detent  32 . By pulling on the platform to move it in a clockwise direction, the release arm  40  is caused to engage the release tab  48 , and more particularly, the projection  46  engages the tab  48  as the arm  22  is pivoted toward the last detent position. This causes the arm  40  to be engaged with the crimp  50  thereby holding the assembly in a fixed locked open position with the roll pin  30  released from the slot  34 . When in this position, the entire platform  10  may be lowered to its low end of the tilt range. When so lowered to this low end, the release arm  40  is released or disengaged by the crimp  50 . The pin  30  may then be biased into one of the detent slots or openings  32 . 
     To summarize, the, condition of the platform  10 , as depicted in FIG. 1, is that of being almost at the top of the range of tilt and thus the length of the actuator arm  22  between pin  24  and detent  32  is at its shortest length. In contrast, at the longest length of the distance between the pin  24  and the roll pin  30 , the platform  10  is at its lowest end of the tilt range with intermediate steps represented by detents  32  therebetween. In practice, the platform  10  is raised to its uppermost tilt range by releasing the engagement of the roll pin  30  and the detents  32  as previously described. It is then moved to its lowest tilt range where upon the release arm  40  is disengaged causing the detent roll pin  30  to engage with the first detent  32 . Thereafter, by manually raising the platform  10 , the platform tilt may be adjusted from one detent to the next as the pin  30  moves from left to right in FIG.  1 . 
     Referring to FIGS. 5-9, an alternative preferred embodiment of the invention in depicted. In this embodiment, an actuator arm block  60  is fitted over the shaft  14 . As above, the actuator arm block  60  is connected to the actuator arm  22  through the means of the pin  24 . The pin  24  permits rotation of the actuator arm  22  relative to the actuator arm block  60 . Pivotally connected to the actuator arm  22  by a rivet  64  is the pawl. In a preferred embodiment, the pawl defines an actuator hook  62 . The actuator hook  62  receives a rivet  66  which, as above, operatively engages with the ratchet. That is, the rivet  66  fits into any one of the number of spaced detents  32  defined in the detent slot  34  in the platform  10 . The actuator hook  62  further defines an opening  68  for receiving a lock spring  70 . The lock spring  70  connects the actuator hook  62  to an opening  71  in an actuator hook lock  72 . The actuator hook lock  72  is pivotally connected to the actuator arm by a rivet  74 . The actuator hook lock  72  defines a cam surface  73  that contacts and engages the actuator hook  62 . Pivotally connected to the end of the actuator arm  22  through the use of a rivet  74 A is a lock-out handle  76 . 
     In operation to change the pitch of the keyboard platform, the lock-out handle  76  is manually rotated about rivet  74 A until the handle  76  contacts the actuator hook lock  72 , as depicted in FIG.  9 . The actuator hook lock  72 , in turn, pivots about rivet  74  causing the cam surface  73  of the hook lock  72  to contact the actuator hook  62  forcing the actuator hook  62  to rotate about the rivet  64  and thus lifting the rivet  66  away from the detent  32 . Once lifted away from the detent  32 , the rivet  66  may be incrementally positioned within an adjacent detent  32 , thereby effectively changing the tilt or pitch of the platform. The lock spring  70  holds the actuator hook  62  in operative engagement with the cam surface of the hook lock  72 . 
     Again, a failsafe alignment feature is incorporated which includes the pin  36  that projects from the actuator arm  22  into the inclined slot  38  in the platform  10 . As above, the configuration of the slot  38  accommodates the variance of the pitch or tilt of the platform as the arm  22  is pivoted clockwise or counterclockwise about the pin  24 . 
     The preferred embodiments of the invention are now described as to enable a person of ordinary skill in the art to make and use the same. Variations of the preferred embodiment are possible without being outside the scope of the present invention. Therefore, to particularly point out and distinctly claim the subject matter regarded as the invention, the following claims conclude the specification.