Adjustable height keyboard support

1. A keyboard support comprising:

a bottom horizontal support plate having front, rear and side edges defining a quadrilateral shape,

an upper horizontal keyboard support plate having front, rear and side edges defining a quadrilateral shape,

a first pair of parallel legs having first corresponding ends secured on a first horizontal axis to the underside of said upper support plate near its rear edge and second corresponding ends adapted to rest on the top of said bottom plate wherein said first corresponding ends of said first parallel legs are rigidly interconnected by a transverse member pivotally connected to the underside of said upper support plate,

a releasable retention structure positioned on the underside near said front edge of said upper support plate and formed from a mat with horizontally spaced parallel rows of downwardly open notches, and

a U shaped leg structure including a second pair of parallel legs having first corresponding ends pivotally connected to the upper side of said bottom support plate near its rear edge on a second horizontal axis and second corresponding ends rigidly interconnected by a horizontal connector adapted to releasably fit in a selected one of said plurality rows of notches, said first and second pairs of legs being pivotally interconnected intermediate their ends on a third horizontal axis, said horizontal axes being parallel to one another.

2. The keyboard support structure of claim 1 wherein said horizontal connector is cylindrical.

3. The keyboard support of claim 1 wherein said U-shaped leg structure is tubular.

4. They keyboard support of claim 1 wherein said keyboard support is adjustable to a collapsed position in which said plates are parallel and vertically separated a distance approximately the thickness of one of said legs.

5. The keyboard support structure of claim 1 wherein said first parallel legs and said transverse member form a U-shaped member.

6. The keyboard support structure of claim 5 wherein said releasable retention structure includes a plurality of parallel ridges extending downwardly from the underside of said upper support plate and forming said notches.

7. The keyboard support structure of claim 6 wherein said transverse member is tubular and is pivotally connected on said first parallel axis.

8. The keyboard support structure of claim 5 wherein said keyboard support structure has a collapsed position of adjustment in which said U-shaped leg structure and said U-shaped member have a nested relationship.

9. The keyboard support structure of claim 1 wherein said upper support plate extends laterally beyond said lower support plate.

10. The keyboard support structure of claim 1 wherein said releasable retention structure is positioned at the mid-line between said side edges of said upper support plate.

11. A keyboard support comprising:

a thin flat upper horizontal keyboard support plate having a front edge, a rear edge and a pair of laterally opposite side edges,

a thin flat lower horizontal support plate having a front edge, a rear edge and a pair of laterally opposite side edges,

first and second U-shaped tubular leg structures each of which have a pair of equal length legs extending from opposite ends, respectively, of a cylindrical horizontal connector,

said cylindrical horizontal connector of said first U-shaped tubular leg structure being pivotally connected on a first horizontal axis to the underside of said upper support plate parallel to and near its rear edges,

the distal ends of said legs of said second U-shaped structure being pivotally connected to the top side of said lower support plate near its rear edge on a second horizontal axis,

said legs of one of said U-shaped structures being positioned laterally inward of and adjacent to the legs of the other U-shaped structure and pivotally connected thereto intermediate their ends on a horizontal axis, and

a releasable connector positioned on the underside and at the mid-line between said side edges of said upper plate and formed from a mat with a plurality of laterally extending parallel grooves spaced from one another in a front to rear direction relative to said upper plate for selective releasably engagement by the cylindrical horizontal connector of said second U-shaped tubular leg structure so as to establish the elevation of said upper plate relative to said lower plate.

12. The keyboard support structure of claim 11 wherein said releasable connector is positioned near said front edge of said upper plate.

13. A keyboard support comprising:

a bottom horizontal support plate having front, rear and side edges defining a quadrilateral shape,

an upper horizontal keyboard support plate having front, rear and side edges defining a quadrilateral shape,

a first pair of parallel legs having first corresponding ends secured on a first horizontal axis to the underside of said upper support plate near its rear edge and second corresponding ends adapted to rest on the top of said bottom plate,

a releasable retention structure on the underside of said upper support plate and positioned at the mid-line between said side edges of said upper support plate and formed from a mat with horizontally spaced parallel rows of downwardly open notches, and

a U shaped leg structure including a second pair of parallel legs having first corresponding ends pivotally connected to the upper side of said bottom support plate near its rear edge on a second horizontal axis and second corresponding ends rigidly interconnected by a horizontal connector adapted to releasably fit in a selected one of said plurality rows of notches, said first and second pairs of legs being pivotally interconnected intermediate their ends on a third horizontal axis, said horizontal axes being parallel to one another.

14. The keyboard support structure of claim 13 wherein said releasable retention structure is positioned near said front edge of said upper support plate.