Retractable work station

A retractable work station suitable for use with a computer keyboard has a parallel swing-link suspension for selectively moving a working platform surface from a fully retracted position, to an advanced working position, while maintaining unchanged the inclination of the platform surface. The apparatus is equipped with a brake for immobilizing the linkage in any desired intermediate position. The platform is adjustably secured to a moveable frame portion of the apparatus so that the inclination of the work platform can be selectively adjusted. One embodiment incorporates tension springs to urge the platform towards either one or the other of its bi-stable positions i.e. fully retracted or fully extended. An inverted embodiment of the apparatus maintains itself in a selected one of its two bi-stable positions without the need for springs. The shape of the respective links of the suspension assures the maintenance of an adequate free space over the platform when retracted, for storage of a keyboard apparatus thereon.

This invention is directed to a suspension system for attachment to a desk 
or other support structure, and, more particularly, to a suspension system 
for a retractable work station for use with, for example, a typewriter or 
computer keyboard. 
The utilization of a computer system within an office environment can be 
greatly enhanced if the accessed elements, particularly the keyboard, are 
made readily accessible upon demand, and can yet be stored in a retracted 
condition to free work space for other activities, and/or withdraw the 
keyboard to a less exposed locale when it is not in use. 
One known arrangement relies upon a generally linear fixed track having a 
carriage slideably mounted thereon so as to provide a desired range of 
advancement or retraction, and a pivoted arm extending from the carriage 
to provide components of elevation and inclination position variation, for 
a working platform secured to the arm. 
The present invention provides a retractable work station having a 
pivotably retractable work platform mounted by a link suspension system so 
as to provide horizontal and vertical displacement simultaneously, while 
maintaining a constant attitude of a working platform of the work station. 
The subject system further provides a bi-stable spring loaded system 
wherein the suspension link mechanism pivots the working platform from a 
first, retracted position wherein the platform is held in a first 
restrained position, to a second, fully advanced position wherein the 
suspension link mechanism is again secured in restrained relation. 
The invention further provides brake means for releasably securing the 
working platform in any position, including positions intermediate the 
aforementioned advanced and retracted positions. 
The invention further provides a suspension link mechanism having one or 
more pairs of links each link being cranked intermediate the ends thereof, 
having the cranked portions in back-to-back relation so as to maintain a 
predetermined clearance space above the working platform, for storage of a 
keyboard thereon then in a retracted position. 
The invention further provides adjustable attachment means connecting the 
working platform to a moveable frame portion, which frame portion 
interconnects the individual lever members of the supporting link system. 
The adjustable attachment means permits pivotal adjustment of the 
inclination of the working surface of the working platform. 
A further emobidment provides a bi-stable system wherein the self weight of 
the working platform and its load is relied upon to secure it in the 
working and in the retracted biasing position, without springs, gas 
cylinders or other similar biasing devices. 
Thus there is provided a manually repositionable work station apparatus 
having at least two degrees of freedom of movement, comprising a mounting 
frame; at least one pair of links having two links of substantially equal 
effective length pivotably secured in spaced apart relation to the 
mounting frame and to a moveable frame portion of the apparatus having a 
working platform secured thereto, to provide a predetermined range of 
displacement of the work station from a fully extended working position to 
a fully stowed position while maintaining the attitude thereof 
substantially constant. 
There is further provided an adjustable brake means for selectively 
securing at least one link in non-moving relation relative to one or other 
of the frame members so as to substantially immobilize the moveable frame 
position relative to the mounting frame.

Referring to FIG. 1, the subject work station apparatus 10 has a platform 
12 supported from beneath a support member 14 such as a portion of a table 
or desk, as shown in phantom. A bi-stable retraction/extension mechanism 
16 is secured by flanges 18, 20 to the undersurface of member 14, by means 
of screws (not shown). A fixed mounting frame 17, of which flanges 18, 20 
form a part, has parallel side plates 22 in spaced apart relation having 
spacers 19 and an inclined plate end portion 21 extending therebetween. A 
pair of link sets 23, 25 are located, one on each side of the mounting 
frame 17, each link set comprising a forward elbow link 24 and a rearward 
elbow link 26 pivotally secured at 27, 29 respectively. A moveable frame 
portion 28 of the apparatus 10 has the links 24, 26 pivotally secured 
thereto at 31 and 35, respectively. 
In FIG. 1 the platform portion 12 is in a fully forward working position, 
having illustrated thereon in phantom a typical keyboard of a computer, 
mounted upon rubber pad 13 of the electrically grounded type. The upper 
surface 75 of the rubber pad 13 constitutes a work surface 75 for the 
user. 
Referring to FIG. 2, the platform portion 12 is shown in a fully retracted 
stowed position by reverse pivoting of the elbow links 24, 26. Being of 
equal effective length, the links 24, 26 maintain the moveable frame 
portion 28 in a generally constant orientation for all positions. In the 
advanced position of FIG. 1 and the retracted position of FIG. 2, the 
elbow links 24, 26 are positioned in overlapping abutting relation, being 
held tightly pressed together by a pair of coil springs 79 (see FIG. 3) 
enclosed within protective rubber sleeves 37. The location of the cranked 
elbow links 24, 26 in back-to-back relation (see FIG. 6) ensures the 
preservation of a clear stowage space for a keyboard upon the platform 12 
when in the fully retracted, stowed condition. 
The springs 79 are carried by transverse bar 39 which extends through the 
side plates 22 of frame 17. The remote ends of springs 79 are pivoted to 
the link 26 by way of stub arms 41 extending transversely from the 
rearward links 26. 
Referring to FIGS. 1, 2 and 3 it will be seen that the geometry of the 
arrangement is such that the stub arms 41 traverse the axis defined by bar 
39 and pivot point 29, about which elbow link 26 rotates. Thus in the 
fully extended working position of work station apparatus 10, shown in 
FIG. 1, the springs 79 are positioned above pivot point 29, whereas in 
FIGS. 2 and 3 the axis of springs 79 is positioned below the pivot point 
29, having traversed the axis extending between bar 39 and pivot point 29. 
This overcentre relationship provides a bi-stable characteristic to the 
apparatus, the springs 79 tending to move the work platform 12 to one or 
other of its terminal positions, except in the unstable dead centre 
position. 
Referring to FIGS. 2 and 3, in regard to the adjustable brake means, the 
moveable frame portion 28 is of hollow section, having a pivot pin 43 
extending transversely therethrough. The ends of pivot pin 43 are 
immovably secured at 31 to the forward links 24. Any displacement of the 
linkage, to move platform 12, creates relative rotation between pivot pin 
43 and frame portion 28. 
A bifurcated brake block 45 straddles the pivot pin 43, having a threaded 
screw 47 and nut portion 49 in selectively compressing relation with the 
legs 51 of block 45. Thus tightening of the screw 47 compresses brake 
block 45 in gripping relation about pivot pin 43, to preclude relative 
rotation therebetween, so as to lock the platform 12 in its instantaneous 
position, despite the turning force exerted by the springs 79 acting upon 
the link mechanism, or the load normally carried by the platform 12. 
In the retracted position shown in FIGS. 2 and 3 it will be seen that a 
predetermined minimum working clearance sufficient for placement of a 
keyboard exists at all times above platform 12, so that the keyboard need 
not be removed in the fully retracted position. A thin foam pad 70 (see 
FIG. 3), is preferably provided on either one of the contacting surfaces 
71, 72 of the links 24, 26 to soften such contact and to form, together 
with the contacting surfaces 71, 72 abutment means to preclude movement of 
the platform 12 in a manner to reduce the working clearance to a value 
less than said minimum value. 
Referring to FIGS. 3 through 5, each of the two control locking devices 50 
comprise a threaded bolt portion 47, a head portion 49 having axially 
extending splines 53 at the outer end thereof. A driving cap 55 has 
internal splines 57 mating with the splines 53, and a torque arm 59, for 
manually tightening or slackening the bolt portion 47. A coil spring 58 
and cap screw 72 retain driving cap 55 in secured relation to the bolt 
head portion 49, the spring 58 permitting manual repositioning by axial 
displacement of the cap 55, to disengage splines 57 from the mating 
splines 53 of the bolt head 49. This permits independent angular 
rotational repositioning of the torque arm 59 for convenience of the user, 
without effecting any change to the torsion exerted by bolt portion 47. 
The above described adjustable torque arm arrangement is a proprietary 
handle arrangement known as the "ELESA" (trade mark) handle. 
A platform tilt control means 65 comprises a pivot pin 67 pivotally 
connecting a frame portion 73 of platform 12 to the moveable frame portion 
29. The adjustable control locking device 50 operates to tension the 
carriage bolt 69 and lock the members frictionally in secured relation. 
This affords a range of angular inclination of up to about 12 degrees to 
the working surface 75 of the platform 12. 
FIG. 6 shows the platform 12 locked in an intermediate position, the 
springs 35 being just off the aligned neutral position (which is 
unstable). 
While the bi-stable characteristic of the foregoing disclosed embodiments 
relies upon the springs 79, the inverted arrangement in FIG. 7 likewise 
remains in either of its extremes of location, under the influence of 
gravity, due to the interaction of the elbow links 24, 26. 
While the illustrated embodiment shows two pairs of elbow links, one pair 
on each side of the moveable frame portion 28, in order to ensure optimum 
working stability to the platform 12, it will be understood that a single 
pair of elbow links can provide the requisite positional displacement of 
the platform 12. 
While but two embodiments of the apparatus have been described and 
illustrated in the drawings, any modifications thereto may be made by a 
person skilled in the art while keeping within the spirit of the 
invention, and the following claims are intended to protect all forms of 
the invention lying within their ambit.