WO2004097269A2 - Multi-position work tables - Google Patents

Abstract

A compact height adjustable work station utilizes a unique combination of support arms and linkages to achieve greater strength and a greater range of tabletop (20) height in the industry. The method for adjusting the work surface height is user operated and pressure assisted whereby the user requires a minimal effort to physically lift or lower the work surface to the desired tabletop height. The pressure assist can be variably located to counterbalance different tabletop weights. For automatic counterbalancing, an elongated extensible gas spring piston-cylinder (55) is adapted to be locked in any of its continuous range of infinite adjusted positions. Manual unclamping frees the counterbalancing gas spring (55) for readily changed, manual tabletop height level adjustment. A mid-range level or a high tabletop level may be achieved, adjusted by unclamping and minimum manual force.

Description

MULT -POSITION WORK TABLES

Field of the Invention

This invention relates generally to tables in the furniture field and, more specifically, to ergonomically designed office and industrial work stations.

The invention provides height adjustable multiple- position worktable levels producing ergonomic benefits to workers of various size while they are performing various work tasks. Research has shown that adapting a work station to the reach and viewing needs of a worker increases productivity and reduces the occurrence of injury.

The preferred embodiments of the invention are extremely economical to manufacture and readily operated by the user to achieve prompt and efficient movement of the tabletop between an infinite number of different level positions.

Mechanical and hydraulic jacks have been suggested, but they often compel the user to provide exhausting hand-cranking or careful monitoring of electrical pump controls. Moreover, such jacks introduce undesirable weight and considerable extra cost, making such jack- actuation undesirable for many users.

It is, therefore, the principal object of this invention to provide a height adjustable work surface that will move down to accommodate the smallest seated individual and then rise up to accommodate the tallest standing worker.

It is also an object of this invention to create a new height adjustable work station that will utilize a unique combination of cooperating support arms and linkages to provide greater strength and achieve a greater range of adjustment from a smaller form factor than could normally be accomplished. It is another object of this invention that the work station is user controlled and manually operated and that the work surface adjusts quickly up and down without the use of expensive electric motors or cumbersome manual cranks.

It is a further object of this invention that the motion of the support arms and linkages is pressure assisted by a pressurized gas piston cylinder to counterbalance the weight of the tabletop.

It is a still further object of this invention that the pressure assist can be variably located to counterbalance different tabletop weights.

It is another feature of this invention that the work station provides maximum legroom for seated positions and minimum use of office space in the standing position.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The Drawings

For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings (s) in which:

FIGURES 1A, IB, 1C and ID are successive schematic side elevation views of the first embodiment of the invention, with the tabletops shown elevated to successively greater height levels;

FIGURE IE is an enlarged schematic side elevation view of the first embodiment, clearly showing the component parts of the mechanism;

FIGURE IF is an exploded elevation view of the component parts of the first embodiment;

FIGURES 2A, 2B, 2C and 2D are comparable successive schematic side elevation views of the second embodiment of the invention, with the tabletops shown elevated to successively greater height levels; FIGURE 2E is an enlarged schematic side elevation view of the second embodiment, clearly showing its component parts;

FIGURE 2F is an exploded elevation view of the component parts of the second embodiment,

FIGURES 3A, 3B, 3C, 3D, 3E and 3F are successive schematic side elevation diagrams illustrating the cooperative interaction of the human user with the first embodiment of the invention, shown in its successive raised and lowered tabletop height levels;

FIGURES 4A, 4B, 4C, 4D, 4E and 4F are successive schematic side elevation diagrams illustrating the cooperative interaction of the human user with the second embodiment of the invention showing its successive raised and lowered tabletop height levels;

FIGURES 4G, 4H, 41 and 4J are schematic side elevation diagrams of a modified version of the second embodiment . FIGURES 4G and 41 show the lowest and the highest tabletop levels of this version, and FIGURES 4H and 4J are corresponding respective lowest and highest level diagrams showing the linkage of this modified second embodiment with the tabletop removed for clarity.

FIGURE 5 is an enlarged schematic side elevation diagram of the mechanism of the second embodiment, showing the virtual centers of rotation of the tabletops rear rim and its upper support link, both positioned rearwardly in space behind the mechanism by a substantial distance.

FIGURES 6, 7 and 8 are successive schematic side elevation diagrams of the mechanism of the second embodiment, showing its component parts in its lowest, middle and highest tabletop levels.

FIGURES 6A, 7A and 8A are corresponding successive schematic side elevation diagrams of the second embodiment, showing the successive changes in the shapes of the two parallelograms delimited by its pivot points during its transitions between height levels,

FIGURE 8 is a corresponding collection of schematic side elevation views of the same device shown in the same four different positions illustrated in FIGURES 3 and 4 as well as two additional positions 5 and 6. These diagrams of FIGURE 8 illustrate the user's manipulation of the simple controls of the worktable to move it from its lower level in position 1 toward a mid level position shown in FIGURES 2 and 3, and thence toward an upper position shown in positions 4 and 5 and finally to return it to the lower position of FIGURES 1 and 6 ;

FIGURES 9A and 9B are two different views of the pressurized gas cylinder valve control cable assembly incorporated in the preferred embodiments of the present invention, FIGURE 9A being a side view of the cable assembly and FIGURE 9B being a front view of the same component;

FIGURE 9C is a perspective side view of a pressurized gas spring piston-cylinder assembly;

FIGURE 9D is a schematic cross-sectional diagram of a pressurized gas spring piston-cylinder assembly, a Stabilus BLOC-O-LIFT^® "gas spring";

FIGURES 10A, 10B, IOC and 10D are four comparison charts, showing operation characteristics of the device;

FIGURES 11, 12, 13 and 14 illustrate a third preferred embodiment of the invention;

FIGURE 11 is a perspective corner elevation view of this different form of the worktable in its lower position, supporting a desk top computer on its upper worktable surface;

FIGURE 12 is a corresponding view showing the same table at a higher worktable height above the height shown in FIGURE 11; FIGURE 13 is an enlarged side perspective view of the same device in its upper position corresponding to that in FIGURE 12;

FIGURE 14 is a perspective bottom plan view of the third embodiment of the invention in which the pivoted linkage legs and the gas spring piston-cylinder are more clearly illustrated.

FIGURES 15A, 16A and 17A are successive schematic bottom plan diagrams of the elevating linkage of the third embodiment, shown respectively in the lowest, a middle and the highest positions of the tabletop height levels;

FIGURES 15B, 16B and 17B are successive side elevation diagrams of the movable legs and tabletop of the third embodiment, shown respectively in the lowest, a middle and the highest positions of the tabletop height levels,

FIGURE 18A is an enlarged bottom plan diagram of the tabletop underside portion of the elevating linkage of the third embodiment, in its highest level position shown in FIGURES 17A and 17B, with a bell crank having two equal length arms, and

FIGURE 18B is an enlarged bottom plan diagram similar to FIGURE 18A, showing a bell crank having arms of different length.

Brief Summary of the Invention

The invention comprises a method and apparatus for adjusting the height of a tabletop work surface by selecting among an infinite number of level positions .

The method for adjusting the tabletop work surface height is manually user operated and pressure assisted, whereby the user provides minimal effort to physically lift or push down the work surface to the desired tabletop height .

The invention incorporates a method and apparatus to variably locate the pressure assist device to specifically counterbalance different tabletop weights. The apparatus is a unique combination of cooperating support arms and linkages that maintain the work surface in a horizontal position throughout its range of motion. The unique linkage provides better strength geometry than other linkage designs and pivots about virtual centers in imaginary space to create a smaller overall form factor that takes up less space in the workplace.

Best Modes for Carrying Out the Invention The First Preferred Embodiment

In the first preferred embodiment, shown in FIGURES 1A- 1E, and 3A-3F, a tabletop work surface adjusts up and down and locks in position by controlling the movement of a pressurized gas spring piston-cylinder. The tabletop 20 is supported in a horizontal position throughout its range of motion by a linkage 21, a series of articulating linkage arms pivotally mounted on a column 22 upstanding from the rear of the table base 24. A pressurized gas spring piston- cylinder 55 is mounted between the linkage 21 and the table base 24 (FIGURE IE) . Opening and closing a valve 48 on piston-cylinder 55 (FIGURE 9A) determines the movement of the gas piston and unlocks or locks the position of the linkage .

The tabletop 20 adjusts from a low (seated) work height, FIGURES 1A and 3A to a standing work height, FIGURES ID, IE and 3D, to accommodate different size individuals performing various work tasks. The tabletop is adjusted manually by the user to the desired position. The amount of manual effort required to move the tabletop up and down is reduced to a minimum by the gas piston-cylinder which is pressurized to counterbalance the total weight of the tabletop and the objects on the tabletop. First and Second Embodiments

Comparison of FIGURES IE and 2E shows that tabletop 20 is supported in both the first and the second preferred embodiments by a pivoted linkage 21, which itself is pivotally mounted on column 22, upstanding from base 24.

In each embodiment a gas spring piston-cylinder assembly 55 has its ends pivotally connected to column 22 and to linkage 21.

The pivotally connected components forming linkage 21 are very similar in both the first and the second preferred embodiments. This is confirmed by comparing the exploded views of FIGURE IF and FIGURE 2F, where the various comparable components are arrayed side by side in these two FIGURES. The pivoted interconnections of each of these linkage components with the next is clearly shown in the assembled views of FIGURES IE and 2E, and their articulated movement is shown in FIGURES 3A-3F.

Thus, for the first embodiment, a central member is the cantilever arm 29, shown to be U-shaped in FIGURE IF, having rear pivot point 31, joining it to column 22, and a front pivot point 32 joining arm 29 to the underside of tabletop 20 via a top plate 33.

A bell crank 34 is pivotally joined at a central point to the cantilever arm 29 near its front end by a pivot 36.

An upper link 37 has an upper end joined to a rear point of top plate 33 by a pivot 38, and a lower end pivotally joined to an upper rear end of bell crank 34 by a pivot 39.

A forward link 40 has a front end pivotally joined to the lower end of bell crank 34 by a pivot 41, and a rear end pivotally joined to column 22 by a pivot 42 at a point substantially below pivot 31.

Gas spring piston-cylinder 55 has its upper end pivotally joined by a pivot 54 to an upper bridge plate 56 having a rear end anchored to pivot 31 on column 22, and a forward end anchored to a central point on cantilever arm 29, making bridge plate 56 integral with arm 29. Piston-cylinder 55 also has its lower end pivotally joined by a pivot 53 to a bed plate 57 anchored to the lower end of column 22.

The pivoting articulation of all of these pivotally connected components of linkage 21 is illustrated in the six successive diagrams of FIGURES 3A through 3F.

Pivoted Components of Second Embodiment

As shown in FIGURES 2E and 2F, the same components are connected in much the same fashion in the second preferred embodiment as they are in the first preferred embodiment, and the pivoting articulation of these components of linkage 21 is shown in the six successive diagrams of FIGURES 4A through 4F, and in FIGURES 6, 7 and 8.

Accordingly, the foregoing description of the linkage components of the first preferred embodiment is equally applicable to those of the second, and the corresponding components and pivot points have been given the same reference numerals in the FIGURES.

Cantilever arm 29 is V-shaped and bell crank 34 is generally triangular, but these do not change their function or cooperation.

Operation of the Gas Spring Piston-Cylinder

When the gas spring piston-cylinder 55 is ideally pressurized for the total weight of the tabletop, opening the control valve 48 will allow the tabletop to " float" with minimum hand pressure up and down throughout its range of motion. Closing control valve 48 locks the pressurized gas piston in its then current extension position. The amount of gas pressure is selected to counterbalance the total table weight .

The preferred pressurized gas spring piston-cylinder assembly 55 employed in the preferred embodiments of the invention is the Stabilus rigid blocking BLOC-O-LIFT^® gas spring, sold by Stabilus Inc. of Gastoria, North Carolina 28052-1898. BLOC-O-LIFT^® gas springs raise loads with an accurately tuned extension force and application-specific dampening while ensuring user-friendly movement sequences. In addition, BLOC-O-LIFT^® gas springs can be blocked in any position, with springing or rigid blocking in the extension or compression direction depending on the design, according to the Stabilus catalog. A schematic cross-sectional diagram of this device is shown in FIGURE 9D .

This gas piston-cylinder assembly counterbalances the weight of the table near the midpoint of its range of levels, and the rigid blocking BLOC-O-LIFT^® gas spring can be blocked in any position in its range. Variable blocking is produced by the valve 48 integrated into the piston, which separates both pressure chambers gas-tight. When valve 48 is closed, blocking the gas exchange between the two pressure chambers, the BLOC-O-LIFT^® gas spring is blocked, and the table level is locked. The valve 48 closes automatically when the valve tappet is released externally.

At any point in its movement when the control valve 48 is closed, the gas spring piston-cylinder 55 is thus locked in position, converting the gas spring 55 into a rigid link between its end pivots 53 and 54. A simple unclamping lever

26, FIGURES IE, 2E and 8A, controls the closing of the valve

48 via a "camera-shutter style" cable 50 to lock the tabletop in position. FIGURES 3A-3F show how the depicted user, operating the unclamping means, the release control actuator (a push button or grippable paddle lever) 26, acting through the flexible cable 50, locks the table in various positions or unlocks the gas piston-cylinder 55 for movement to and from various positions. The components of a typical pressurized gas piston-cylinder 55 controlled by lever 26 are depicted in FIGURE 9D .

Variable (lift) Pressure Assistance From Fixed Pressure Counterbalancing Spring

The gas springs or air spring piston-cylinder assemblies of this invention are lockable at any one of an infinite number of piston extension positions. The somewhat similar gas-charged trunk lid lifters or hood lifters for automobiles move the lid or hood up slowly to its uppermost position counterbalancing its weight. The user's manual closing of the trunk lid or hood adds a few extra pounds of force to the actual weight, overcoming the counterbalancing and slowly lowering the lid or hood to its lowest closed position.

Such lifters cannot be locked in any intermediate position.

The piston-cylinder assemblies 55 of this invention are designed to move the tabletop 20 buoyantly to a floating position, in the mid region of its raising or lowering range, when the lever 26 is actuated to unlock assembly 55. While lever 26 is actuated the user can slowly raise or lower the tabletop 20 to any selected new position by applying slight upward lifting or downward force, making its level adjustment easy by minimizing the adjustment force required.

Actuator 26 may be located on the underside of the tabletop at a central position under its front rim, as in FIGURE 14, but it is preferable to require both of the user's hands, by positioning lever 26 under the side rims near the front rim of the tabletop 20 or 61, as indicated in FIGURES IE, 2E, 4A-4F, 15A, 16A, 17A, 18A and 18B.

Levers 26 are essential to tabletop movement because engaging the control lever 26 to release the locking valve 48 requires the user's hands to be in contact with the table, gripping the front portions of both side rims.

Thus, if the table were to rise or fall at a speed or direction where the user were to fear losing control, the user could simply release his grip on the control lever 26 or even remove his hands from the table, and the table would automatically lock and stop motion, a "fail safe" result. It can be appreciated that the amount of gas pressure and the tabletop weight are dependent upon each other. If a fixed gas cylinder chamber pressure were to be specified for a given tabletop weight and the total tabletop weight were to increase, the tabletop would not "float" buoyantly in the user' s hand as easily requiring greater manual effort to raise the tabletop, and conversely less effort to lower it.

Generally the tabletop weight and the gas pressure are matched to the known use of the tabletop, i.e. as a light assembly table or as a heavier computer work station. However when the tabletop weight is purposely changed for a different task, the gas spring (with a fixed pressure) can be re-positioned to exert more or less counterbalancing force to compensate for more or less tabletop weight .

For positioning the gas pressure cylinder, preferably a Stabilus BLOC-O-LIFT^® gas spring, careful consideration of force, weight and structural vectoring need be taken into consideration. When the table start position (lowest position) FIGURE 1A is below a hinge point 31 on a fixed column 22, the table weight to be counterbalanced is less than the actual table weight as the base-column structure supports a vectored component portion of the actual weight. For instance, if the table weighing 100 pounds were positioned at 45 degrees below the hinge point, fifty percent of the weight would be born by the base-column structure 22-24, presenting only half the weight to be counterbalanced by the gas pressure cylinder 55. However, as the tabletop rises to a level even with the hinge point 31 the table presents its full 100-pound weight to be counterbalanced by the gas pressure cylinder 55.

Conversely, the gas pressure cylinder counterbalancing force is not dependent on gravity - its force is directly related to its piston stroke position. Gas cylinder pressures generally will have a range of force ratios of 1.4 to 1.0 - i.e., fully compressed a gas cylinder will exert 40% greater force than when its piston is fully extended.

The weight of the table - constantly varying by the effect of gravity and structural vectoring - is opposed by a gas cylinder pressure that diminishes constantly in a linear progression. This presents problems when the designer wishes to use the linearly diminishing gas pressure to counterbalance table weights that rise and fall in relation to the effect of gravity acting on the articulated linkage 21.

Referring now to the schematic diagrams of FIGURES 1A and 10A, a table weight of 100 pounds is positioned 30 degrees below the hinge point 31 in the lowest adjusted position of the first preferred embodiment . The gas pressure cylinder is fully compressed. Referring to FIGURE 10A, it can be seen that in this lowest position the tabletop 20 has one third of its weight supported by the base-column structure and the weight presented to be counterbalanced by the gas pressure cylinder is 66.6 pounds. The fully compressed gas pressure cylinder has 100% of its force available to lift 67% of the table weight. Thirty degrees of travel up brings the table horizontally even with the hinge point 31 (FIGURES IB and 3A) and increases the table weight to one hundred pounds and the base-column structure contributes zero to bear weight . The gas pressure cylinder has extended 40% of its stroke and depleted its force to 60% of its potential. In viewing the chart, FIGURE 10A, while the weight has increased by 34% - the gas pressure cylinder force has decreased 40%.

If attempting to use the gas pressure cylinder 55 as a counterbalance to neutralize the effort to move the tabletop, a different relationship of gas pressure cylinder location and table position must be realized. The table is affected by its position in relation to gravity. The gas cylinder is not affected by gravity - vector forces only affect the gas cylinder where force is shared with structure. It is important to use the structure to mechanically disadvantage the gas cylinder when the table weight is presented at a lower value and allow the gas cylinder to be less disadvantaged when the table weight increases .

Referring now to FIGURE 10B, when the table-top is located down 30 degrees as in FIGURE 10A (and one third of its weight is reduced) the gas pressure cylinder is located down 45 degrees against the same base-column structure as bears the weight of the table. When the table has rotated to 30 degrees travel and is fully horizontal at full weight, the gas pressure cylinder is 15 degrees from its neutral position - i.e. one sixth of its force is still being shared with the structure. Comparing the curves of the actual force output in FIGURES 10A and 10B, it can be seen that repositioning the gas pressure cylinder as in FIGURE 10B has caused the force to be more equal to the table weight in the beginning of travel and to become greater in the latter portions of travel . Changing the mount points and pressure amount of the gas pressure cylinder compared to the known position and weight of the tabletop can effectively determine how the table will rise and descend as influenced by the gas pressure cylinder.

Fine Tuning the Counterbalancing Force

Turning now to FIGURE 10C, tabletop 20 starts from its lowest position (FIGURE 1A) down 30 degrees from hinge point 31. The fully compressed gas spring 55 is pivotally joined to linkage 21 at 40 degrees below "neutral", producing gas spring force exceeding the component of tabletop weight to be counterbalanced over the entire range of tabletop level positions .

As shown in FIGURE 10D, fine tuning the compressed gas spring pivot mounting on the linkage 21 by reducing 40 degrees below neutral down to 35 degrees below "neutral" brings the excess gas spring counterbalancing force even closer to the component of tabletop weight to be counterbalanced over the range of tabletop positions.

As the linkage 21 articulates, moving through the positions of FIGURES 4A through 4C, the gas piston-cylinder 55 becomes longer as the piston extends from the cylinder. As seen in these FIGURES and in FIGURE 2E, moving end 54 pivoted to cantilever arm 29 at 54B, describes an arc about rear pivot point 31 on column 22.

When the axis of piston-cylinder 55, from pivot point 53 to pivot point 54, is at 90° to the radius of that arc, from pivot point 54 to rear pivot point 31, this corresponds to the "neutral" tabletop level, where the components of tabletop and cargo total weight to be counterbalanced is maximum.

If the fully compressed piston-cylinder's moving end pivoted at 54B defines a radius to pivot point 31 angularly rotated below the neutral radius by 35°, substantially as suggested by FIGURE 2A, the gas spring' s maximum counterbalancing force is disadvantaged until the neutral tabletop level is reached, producing the optimum match of weight to counterbalancing force shown in the diagram of FIGURE 10D.

Alternative pivot bores where gas spring terminal pivots can be mounted are shown as bores 53 and 53A, 54 and 54A in FIGURES IE, IF, 2E and 2F. Selection among these alternatives allows the user to achieve the fine tuning 2E desired.

A diagram of the neutral position of a gas piston- cylinder 52 appears in FIGURE 18A. There, moving end 48 of the piston-cylinder, guided by the outer arm of the bell crank 69, describes an arc 67 about the central pivot 79 of bell crank 69. A line drawn from the piston-cylinder's fixed end pivot 82 (on the underside 67 of tabletop 61) is tangent to arc 67 at a point 68, where radius 68-79 is perpendicular to line 68-82, which nearly coincides with the central axis of gas spring 52. Radius 68-79 thus represents the neutral position of the Bloc-O-Lift in FIGURE 18A, and the acute angle 37.5° between radius 79-48 and neutral radius 79-68 indicates an angle greater than the 90° neutral position. The angles 30° and 45° in FIGURE 10B, angles 30° and 40° in FIGURE 10C, and angles 30° and 35° in FIGURE 10D all represent radii whose angles are deducted from the 90° angle of the neutral radius, before the piston-cylinder has extended to the neutral position. If the moving end 48 of the piston rod is below neutral by 30° or 45°, this reduces the moment arm of the counterbalancing force, thus disadvantaging the gas spring.

Upright Gas Piston-Cylinder and Linkage Location Points

The gas piston-cylinder 55 fixed-end and moving-end mount pivot points s 53, 53A, 54, 54A and the corresponding linkage and table base-column mount or pivot points are carefully positioned in relationship to each other.

Referring now to FIGURE 2B, a height adjustable table representing the second preferred embodiment of the present invention and adjusted with the cantilever arm 29 in a horizontal position, with its two terminal pivot points 31 and 32 on the same horizontal plane. It can be seen in FIGURES 2B, 2E, 5, 7 and 8 that the moving-end 54 of the. upright gas piston-cylinder 55 is mounted to the cantilever linkage arm 29, and the fixed-end 53 of the gas piston- cylinder 55 is mounted to the table column 22. In FIGURE 2E the moving-end 54 of the gas piston 55 is mounted to the linkage arm at point 54B at a specific distance from the pivot point 31 to exert 100% effort to raise a tabletop weight. To reduce the lifting force of the gas piston- cylinder 55, as shown in FIGURES 2E and 2F, the moving-end 54 can be repositioned at a lesser distance from pivot point 31 at location 54A producing a decreased mechanical advantage . Altering the mechanical advantage can be best understood by force-ratios. In FIGURE 2B, if the distance between the pivot point 31 and the table pivot point 32 were 12" and the weight on the tabletop were 10 pounds, the cantilever support arm 29 would be holding 10 foot pounds when in a horizontal position. If the moving-end 54 of the gas piston-cylinder 55 were located at a distance of 6" - the lifting force requirement of the pressurized gas piston- cylinder from half the distance would be doubled (a 2 to 1 force-ratio) requiring 20 foot pounds of piston lifting pressure .

Referring now to FIGURE 2E, if the moving-end 54 of the gas piston 55 were further relocated, and the distance were now reduced to 3" from the pivot point 31, the lifting force of the pressurized gas piston-cylinder (attempting to lift the same 10 pounds from now one quarter the distance) would be a 4 to 1 force-ratio - requiring 40 foot pounds of pressure .

However, gas pressurized pistons have a fixed gas pressure so when the gas piston (pressurized to lift 20 pounds as in FIGURE IE) is repositioned, the same (fixed lifting pressure) piston can only lift 20 pounds - not the required 40 pounds. Since the piston pressure is fixed, the only way the piston could lift the tabletop would be if table weight were reduced from 10 pounds to 5 pounds.

Hence it can be appreciated that the gas piston- cylinder 55 (with a fixed lifting pressure) can be positioned and repositioned at an increased or decreased mechanical advantage to compensate for increasing and decreasing total tabletop weights.

Further to the method of relocation of the gas piston mount points, the lift characteristics of the gas piston can be fine-tuned by addressing what portion of the existing stroke is utilized. Referring again to FIGURE IE, to the extent that the gas piston fixed-end 54 is moved inwards towards the pivot point 31 and the fixed-end mount point 53 remains the same, the gas piston moves through a correspondingly shorter stroke distance to lift the linkage via the cantilever arm through the same range of motion.

Depending upon the distance from the moving-end 54 to where the fixed-end 53 is relocated to the table column 22, e.g. at mount point 53A (FIGURE IE), which is further, or point 53 (FIGURES IE and IF) , which is closer, the stroke portion utilized will be determined to be at the beginning of piston travel (when the piston exerts the greatest force) or at the mid or end of its piston travel (when the piston exerts correspondingly less force) . Hence it can be further appreciated that a gas piston of any given fixed pressure (when repositioned closer to the pivot point) has a shorter stroke requirement. By locating the fixed-end at differing length locations to use different portions of the stroke, it can effectively adjust the lifting power characteristics of the gas piston stroke to also relate to varying total tabletop weights .

It can be lastly appreciated that instead of a number of different gas piston mount points on the table base and linkage arms, a sliding mount mechanism (or other means to variably locate the two mount points) can be utilized.

Forwardlv Projecting Air Spring Piston-Cylinder

In FIGURES 4G, 4H, 41 and 4J, a modified second embodiment of the invention is shown, with the substantially upright air spring piston-cylinder 55 replaced by a forwardly projecting air spring piston-cylinder assembly 51.

Piston-cylinder 51 is also preferably a Stabilus Block- O-Lift locking gas spring, having end points 53 and 54 for mounting it to the other linkage components (FIGURES 9C, 9D, 4G-4J) .

In FIGURES 4G and 4H, at the lowest level position of the tabletop 20, forwardly projecting air spring 51 is tilted downward, among the compactly associated components of linkage 21.

In FIGURES 41 and 4J, at the highest level position of tabletop 20, the extended gas spring 51 has pivoted upward to tilt upwardly, with its end points 53 and 54 respectively pivotally connected to the column 22 and to the cantilever arm 29, still positioned among the compactly associated components of linkage 21.

It can be understood from FIGURES 4G to 4J that the location and operation of the gas pressure piston-cylinders are unrelated to their orientation in relation to gravity, but they are still relatively affected by structural vectoring. A forwardly projecting near-horizontally positioned gas spring 51 is mounted in the second preferred embodiment, to produce the same range of motion and neutral buoyancy lift force as compared to the upright and near vertical gas springs 55.

In addition, when FIGURES 4G-4J are compared to FIGURES 6-8, for example, the absence of the upright gas spring 55 and its replacement by the forwardly extending gas spring 51 among the other components of linkage 21 creates a more streamlined and efficient column 22, with all of the linkage 21 including gas spring 51 forming a single articulating assembly directly under the tabletop.

Gas spring piston-cylinder assemblies 51 and 55 perform similar functions with efficiency, and both provide the same opportunities for fine tuning their counterbalancing force, as illustrated in FIGURES IOC and 10D.

Tabletop Parallelogram Support

A traditional "four-bar parallel arm system" creating a tabletop support link parallelogram defined by pivot points 32-38-39-36 is shown in FIGURES 6B, 7B and 8B. This four- bar parallelogram holds the tabletop 20 in a horizontal position, as the linkage 21 moves through its range of positions, locked by gas spring 55 whenever the unclamping lever 26 is not actuated.

A second four-bar parallelogram 31-36-41-42 guides the motion of linkage 21. Both of these four-bar parallelograms are shown in FIGURES 6A, 7A, 8A, where they are all shown to be unskewed or unflattened over the operating range of linkage 21, and their acute angles remain greater than 45 degrees throughout this range, assuring effective counterbalancing force transmission over the continuous range of tabletop height levels.

In fact, this system may be viewed as a "six-bar system" , in which the six bars are the rigid cantilever arm 29, defining line 31-32; rigid bell crank 34 defining line 37-36-41; forward link 40; upper link 37; an imaginary line 31-VCP (an imaginary virtual center pivot point in space) positioned substantially rearward behind the mechanism; and another-imaginary line VCP-38, both imaginary lines and point VCP being shown in FIGURE IE and 2E.

Imaginary line 31-VCP is parallel to line 32-38 joining the two pivot points supporting the tabletop 20. Imaginary line VCP-38 is parallel to line 31-32, joining the two terminal pivot points of cantilever arm 29.

Two additional virtual center pivot points are shown in FIGURE 5: VCP_L, the virtual pivot point for the rotation of the uppermost linkage pivot point 38; and VCP_T, the virtual pivot point for the rear rim of tabletop 20.

The presence of these imaginary virtual center pivot points VCP, VCP_L, and VCP_T, all substantially rearwardly behind column 22, base 24 and tabletop 20, produces an extremely compact mechanism with an unusually small form factor. This allows the mechanism to be backed up to the wall of a room, with no tangible components protruding behind it . Multiple Linkages

It will be readily understood that wherever one single column 22 and linkage 21 assembly is employed, it may be quite sufficient to counterbalance a small tabletop. Most wider tabletops will be more stable at all selected levels if they are supported by two column 22- linkage 21 assemblies. Indeed, three or more parallel linkage-column assemblies may be useful for supporting extra-wide tabletops. However, all such multiple column-linkage assemblies should be governed by a single unclamping lever 26, actuated by a single human user. If two levers 26 are employed on opposite front corners of the tabletop, they should preferably be ganged together, particularly when one central BLOC-0-LIFT° ("BOL") is installed. This produces "light" counterbalancing of lighter cargo loads. If two columns 22 are installed, each may have its own gas spring piston-cylinder 55, providing "heavy duty" counterbalancing of heavier loads. If each air spring 55 has its own lever 26, actuating either lever will unlock only one air spring, and the table will not be free to move until both levers 26 are actuated.

A third option provides "super heavy duty" counterbalancing of much heavier loads, and employs three gas spring units, which should all be unlocked ideally by a ganged pair of levers 26.

Gas Spring Piston-Cylinders Without Clamping

In other applications it may be desirable to use a gas pressure spring without clamping means having the same force characteristics as the Stabilus BLOCK-0-LIFT. Uncontrolled extension gas pressure springs also made by Stabilus are referred to as NON BLOCKING LIFT-O-MAT gas springs for lifting, lowering, moving, and adjusting table structures. On these occasions, the first or second preferred embodiment is utilized without the user unclamping the gas spring for raising or lowering and whereby the gas spring could be mounted for automatic full rise or mid position buoyancy. A raised linkage system with tabletop could rise like an elevator to reach a shelf where a box container could be placed on the tabletop, which would automatically lower to mid or full down position as a result of the weight of the box container. A worker loader located below could remove the box container from the tabletop, and with the weight removed the tabletop would return to its buoyant position or to a fully raised position to be re-loaded with another box container.

Without a user controlled locking device, the concern has been expressed that the tabletop under the force of the gas spring could "snap" up to the raised position, but the dynamic damping characteristics inherent to Stabilus gas springs can be employed to slow the linear motion of the tabletop so as to not create a motion speed danger.

The Third Preferred Embodiment

The third preferred embodiment of the invention relates to the office furniture field and more specifically to ergonomically designed computer desks and work stations, including adjustable height computer training tables for school classrooms.

Extensive computer use has recently produced wide recognition of the importance of good ergonomic practices that increase productivity and reduce the occurrence of injury. At the heart of these practices is the adaptation of the work station to the size of the individual to promote proper work posture .

Most desks are basically stationary and do not move to accommodate the various sizes and shapes of individuals. Carpal tunnel syndrome, posture problems and other maladies are all caused by poor positioning of computer components in relation to the human user, who may be sitting for long periods of time and doing repetitive tasks. The emphasis today is to fit the desk surface to the computer user. Today' s computer users come in all ages and sizes and desks need to adjust to each individual user. To date, industry has responded with adjustable height keyboard platforms and monitor stands. There are also work stations that are adjusted incrementally (during assembly) to fit one desk to one user - they are not dynamically adjustable. There are now also adjustable height desks that rise and fall with crank handles or electric motors. These solutions are cumbersome and expensive.

Adjustable seats that keep the user's feet flat on the floor, keyboards at elbow height to reduce carpal tunnel repetitive stress, monitors high enough and far enough away to reduce neck and eye strain, etc are prevalent today. However, this is achieved by adding components such as adjustable keyboard trays to existing writing style desks of fixed height which are most often too high for today' s computer use. Smaller females and taller males work in compromised postures causing fatigue. Even when the computer components are properly positioned all the other work tools such as the mouse; telephone, adding machines, etc. are still out of proper reach.

The opportunity is to create a height adjustable desk surface that moves both the keyboard and monitor and everything else on the desk together in a quick and easy motion. This would address the sitting needs of any one individual user - but further, it is important to address the multiple shift work segments where computer work stations are shared by a number of different size individuals. Hence the work station should adapt to any one individual and to the range of sizes of all the other individuals in the workplace as it moves up or down to accommodate different sitting positions. Height adjustment is important beyond the office - recent concern has been directed at the growing number of school children being trained to use computers in the classroom. These students are seen sitting on high chairs trying to reach the desktop with legs dangling and neck straining to see the monitor. On average five students share a computer in U.S. classrooms - with the computer desk level fixed and each student struggling to adapt themselves to see and use the keyboards and monitors .

With this third preferred embodiment, illustrated in FIGURES 11, 12, 13, 14, and 15A through 18B, a unique desk is achieved that adjusts to the sitting height and reach of all size people. In this design the entire desktop surface raises and lowers in a dynamic fashion. To allow ease of adjustment a counterbalancing force compensates for the weight of the desk top and the computer and other components so the desktop seemingly floats up and down when the height adjustment is unlocked by actuating an unclamping means, and then maintains that position when the unclamping means lever is released.

Therefore it is the primary object of this embodiment of the present invention to create a height adjustable work surface that will conform to the proper posture requirements of children and adults.

It is a further object of the present embodiment to have the work surface level adjustable with relative ease so that its height can be quickly changed in a simple fashion.

It is a further object that the work station is manually controlled and moves quickly up and down without the use of electric motors or manual cranks .

The height adjustable work station of this embodiment of the invention utilizes a unique scissors shaped support leg assembly 60 on each side that pivots about an axle point 62 to raise and lower the desk height while maintaining the tabletop 61 in a horizontal position. The crossed legs 63 and 73 comprising one side of the scissors legs assembly 60 have rollers or wheels attached at one end and fixed brackets at the other. The upper front end of one leg 63 is pivotally bracketed at 64 to the underside of the front edge 65 of the tabletop. The other rear end of leg 63 has a wheel 66 in contact with the floor. The other leg 73 of the same side has a roller 74 in contact with the underside 67 of the rear portion of the tabletop. On its other front end is a pivotable bracket 76 in contact with the floor. The two legs 63 and 73 are attached at center by a pivot 62 to comprise a crossed leg shaped like an "X", under each side rim 77 of the table top 61. As the two legs pivot about the axle point 62, a scissoring action is created which changes their relative angle and hence the height of each "X" shaped leg assembly 63-73 supporting one side of tabletop 61.

As the angle of the two legs in relation to each other changes, it can be seen in FIGURES 15B, 16B and 17B that there is a corresponding relative distance change between the ends of the two support legs in both the horizontal and vertical directions. The two leg ends with rollers attached

66 and 74 produce the level change in tabletop 61 as they roll along the floor and the underside of the desktop. The upper fixed brackets 64 pivotally mounted to the underside

67 of the tabletop 61 and the lower brackets 76 resting on the floor remain fixed in position along their horizontal planes. When the relative change of angle occurs, the tabletop rises and descends while remaining in a horizontal position.

To control the angle between the legs, a rolling distance limiting device is connected to the rollers on the underside 67 of the tabletop. This device is an unclamping lever 26 on the underside of table 61, preferably under its edge rim 77 near its front rim 65. Lever 26 operatively connected by a shutter-type cable 50A to a valve 48 at the outermost piston end of the gas spring piston-cylinder 52. The outermost end of the extensible piston is also pivotally connected by horizontally pivoting linkage to the rollers 74, as shown in the upper right portion of FIGURES 15A, 16A, 17A, 18A and 18B.

As in the other embodiments, the linearly variable adjustment component is a gas filled piston-cylinder 55, which produces a counterbalancing force to compensate for table weight. By closing the gas valve 48 (FIGURE 9A) the piston-cylinder 52 can be locked in any position along its piston stoke.

Referring now to the drawings and especially FIGURES 11, 12, 15B, 16B and 17B, there are two scissoring leg assemblies 60 of the same dimensions shown as left and right leg support systems with four floor contacts to stabilize the desk.

When legs 63 and 73 are arranged in a scissors shape, they may be connected by an axle 62 which is fastened through the two aligned center points 62. As the legs go through the scissors action shown in FIGURES 11 to 12, and 15B, 16B and 17B, it can be seen that the fixed points and rolling points change distance relative to each other, and allow the tabletop to change height relative to the floor, while maintaining the tabletop in a fixed and rigid horizontal position. Referring now to FIGURE 14 the table or desk assembly is viewed from underneath in a perspective bottom plan view. It can be seen in FIGURE 15B that as the legs go through this scissors action, the horizontal distances increase as the legs spread and the desk lowers. The horizontal distances decrease as the legs come together in FIGURE 17B to raise the tabletop.

In FIGURE 14 and FIGURES 15A, 16A and 17A, an axle 72 is supplied connecting through the upper ends of legs 73 and mounting the rollers 74. In order to control the rolling distance, the axle 72 is connected to the unclamping lever 26 positioned near an outer front rim 65 of tabletop 61. The roller axle 72 is pivotally connected to a horizontally pivoting bell crank lever 69, whose innermost end is pivotally connected to the linkage bar 81 at pivot 80. The bell crank lever 69 is shaped like an L and is pivotally fixed at its central point to the underside of the tabletop 61 at pivot point 79. The outer end of the lever 69 is attached to the moving mount point of a gas valve 48, shown in FIGURES 9A, 15A, 16A, and 17A, positioned at the extensible outer piston end of a counterbalance force- generating pressurized gas piston-cylinder 52. The other end of the gas cylinder 55, preferably the Stabilus BLOC-O- LIFT ^®, is pivotally fixed at 82 to the underside 67 of the tabletop 61.

Referring again to FIGURE 14 and the scissors action of FIGURES 15A through 17B -- it can be seen that as the tabletop is lowered and the distance of the axle 72 from the fixed bracket 64 increases, the reversing action of the bell crank lever 69 causes the gas cylinder 52 to compress along its stroke. This compression provides the force to return the tabletop 61 upwards as the compressed gas seeks to resolve its increased stored pressure.

Upright, Forward Projecting or Horizontal Gas Springs

It will be noted that the lockable counterbalancing gas springs 51, 52 or 55 incorporated in each of the three embodiments of this invention provide the force required to counterbalance the weight of the tabletop and its cargo, in the same way causing the tabletop to float toward its buoyant mid-range level whenever the gas spring is unlocked by the user. At such times, each of the tabletops can be raised or lowered by very slight force applied to it by the user.

When the lever 26 is released by the user, the gas spring is locked, blocking the counterbalancing action and maintaining the tabletop at the last level selected by the user.

Thus the orientation of the gas spring piston- cylinders' central axis in each embodiment does not change or affect its counterbalancing action. Upright gas springs 55 (FIGURES 1-4F, 5-8A) , forward projecting gas springs 51 (FIGURES 4G-4J) and horizontally-oriented gas spring 52 (FIGURES 11-15A, 16A, 17A, 18A and 18B) are not dependent on gravity but only upon their pressurized condition to deliver their linearly varying counterbalancing force over the entire range of their full stroke length.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction with departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense .

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

What is Claimed is

1. A compact pivoted and counterbalanced table support mechanism providing the user with readily changeable and automatically clamped tabletop heights while maintaining the tabletop level, and counterbalancing the weight of the table and its cargo at a mid range level, while minimizing force applied by the user, when height levels are undamped, to raise or lower the tabletop through a continuous range of different height levels, comprising: a base, an elongated column upstanding from the rear of the base, a linkage pivoted near the top of the column and protruding forward and upward forming a tabletop-engaging portion, a tabletop overlying the linkage and having an upper surface, a lower surface, a front rim a rear rim, and two side rims joining the front rim to the rear rim, pivot means joining the tabletop to the tabletop-engaging portion of the linkage, an elongated extensible gas spring piston- cylinder having pivots joining each of its ends respectively to the column and the pivoted linkage, and which is normally clamped in any of its extended positions, and at least one manually actuatable unclamping lever mounted on one of the upper or lower tabletop surfaces, along a side rim near the front rim and connected, by a "camera shutter" style cable, to the gas spring piston-cylinder to unclamp it, whereby manual actuation of the unclamping means and application of manual table lifting or lowering force may be simultaneously performed by the individual user.

2. The counterbalanced table support mechanism defined in Claim 1, wherein the gas spring piston-cylinder is provided with two cylinder chambers separated by the piston having a lockable valve which when locked serves to isolate the two chambers, thereby blocking movement of the piston in the cylinder and preventing raising and lowering of the tabletop, and said valve when unlocked serving to connect the two chambers, thereby permitting raising and lowering of the tabletop, said valve being normally closed, and readily opened by manual actuation by the user of the unclamping lever on the tabletop.

3. The counterbalanced table support mechanism defined in Claim 2, wherein the pivot joining the extensible gas spring piston-cylinder to the pivoted linkage is positioned on said linkage at a point where the force provided by the compressed gas in the piston-cylinder substantially matches the component to be counterbalanced of the weight of the tabletop and its cargo at a mid-range position in said continuous range, while it exceeds said component at lower tabletop levels below said mid-range position and is less than said component at higher tabletop levels above said mid-range position, whereby the tabletop floats to a mid- range level, drifts down to the mid-range level from higher levels, and drifts up to the mid-range level from lower levels.

4. An economical and efficient method for manually adjusting the level of the tabletop in the mechanism defined in claim 2, comprising the steps performed by the individual user of :

Determining a changed new tabletop level desired, Manually gripping the unclamping means, thereby opening the valve between the two chambers of the gas spring cylinder, permitting the piston separating the two chambers to move to a different position, simultaneously applying lightweight vertical force manually to move the tabletop to the desired new level, and then releasing the unclamping means, whereby the released unclamping means closes the valve in the gas spring, clamping the tabletop at the desired new level selected by the user.

5. The mechanism defined in Claim 1 wherein said linkage comprises: a cantilever arm, having a rear pivot connecting the arm to the top of the upstanding column, a front pivot connecting the;- arm to the underside of ^' the tabletop, and an anchor point pivotally joining the arm to the uppermost end of the gas spring piston-cylinder, a forward link having a front end and a rear end, an upper link having an upper end and a lower end, and a bell crank having a central pivot joining it to the cantilever arm, a lower pivot joining it to a front end of the forward link, whose rear end is pivoted to said column, and a rear pivot joining it to the lower end of the upper link, whose upper end is pivotally joined to the underside of the tabletop.

6. The mechanism defined in claim 5, wherein the cantilever arm is formed as a V-shaped cantilever arm.

7. The mechanism defined in claim 5, wherein the cantilever arm is formed as a U-shaped cantilever arm.

8. The mechanism defined in claim 5, wherein the anchor point joining the gas spring's uppermost end is positioned on the cantilever arm at a point between its rear pivot and the central pivot joining the bell crank to the cantilever arm.

9. The mechanism defined in claim 5 wherein the two end pivots of the upper link form a first parallelogram with the bell crank's central pivot and the front pivot of the cantilever arm.

10. The mechanism defined in claim 5 wherein the two end pivots of the forward link form a second parallelogram with the rear pivot of the cantilever arm and the central pivot of the bell crank.

11. The mechanism defined in claim 9, wherein the ends of the upper side of the first parallelogram, delimited by the upper end pivot of the upper link and the cantilever arm's front pivot are respectively adjustable to skew the first parallelogram, whereby the tabletop may be shifted out of a horizontal orientation if desired by the user.

12. The mechanism defined in claim 5 wherein, during raising and lowering travel of the tabletop through its continuous range of different height levels, the rear rim of the tabletop, and the pivot point joining the underside of the tabletop to the upper end of the upper link, both move along circular arcuate paths having equal radii of curvature about respective virtual center points positioned behind all parts of the mechanism by substantial distances , whereby the mechanism itself occupies a minimum volume and achieves a compact minimum form factor.

13. The mechanism defined in claim 8 wherein the components of the linkage defining the first parallelogram are dimensioned to make the first parallelogram substantially rectangular for a mid-range level of the tabletop, whereby the acute angles at the apices of the first parallelogram are no smaller than 45° at the lowermost level and at the uppermost level of the tabletop, thus avoiding flattening of the first parallelogram and assuring effective force transmission by the linkage throughout the continuous range of tabletop height levels.

14. The counterbalanced table support mechanism defined in claim 1, wherein each manually actuatable unclamping lever is mounted under the side rim of the tabletop, near its front rim, where it is conveniently presented for gripping by the human user.

15. A compact pivoted and counterbalanced table support mechanism providing the user with readily changeable and automatically clamped tabletop heights while maintaining the tabletop level, and counterbalancing the weight of the table and its cargo at a mid range level, while minimizing force applied by the user, when height levels are undamped, to raise or lower the tabletop through a continuous range of different height levels, comprising: a linkage supported by an underlying floor, a tabletop overlying the linkage and having an upper surface, an underside surface, a front rim, a rear rim, and two side rims, a pair of downslanting legs each having an upper end pivotally anchored on a first transverse axis to the tabletop' s underside near its front edge, and each having a lower end pivotally supporting a wheel rotatable on a second transverse axis, a pair of upslanting legs each having a lower end pivotally anchored to a floor-supported bracket on a third transverse axis directly below said first transverse axis, and each having an upper end pivotally supporting a roller supporting said underside surface of said table rotatable on a fourth transverse axis directly above said second transverse axis , one downslanting leg of each pair being adjacent to an upslanting leg, the mid-points of both adjacent legs being pivotally joined on a fifth transverse axis, the rollers being positioned and connected for ganged rolling motion toward and away from the tabletop' s rear rim, a link having a rear end connected to said ganged rollers and having a front end, a bell crank having an inner end, an outer end, and a central pivot point pivotally connected to the underside of the tabletop, the inner end also being pivotally connected to the front end of said link, and the outer end having a pivot point thereon, an extensible gas spring piston-cylinder having pivots joining each of its ends respectively to a fixed point and to the outer end of said bell crank and which is normally clamped to block telescoping movement of the piston in the cylinder in any of its extended positions , and manually actuatable unclamping lever means mounted on one of the upper or lower tabletop surfaces, and connected, by a "camera shutter" style cable, to the gas spring piston-cylinder to unclamp it, whereby manual actuation of the unclamping lever means and application of manual table lifting or lowering force may be simultaneously performed by the individual user.

16. The compact table support mechanism defined in claim 15, wherein the gas spring piston-cylinder is provided with two cylinder chambers separated by the piston having a lockable valve which when locked serves to isolate the two chambers, thereby blocking movement of the piston in the cylinder and preventing raising and lowering of the tabletop, and said valve when unlocked serving to connect the two chambers, thereby permitting raising and lowering of the tabletop, said valve being normally closed, and readily opened by manual actuation by the user of the unclamping lever means on the tabletop .

17. The compact table support mechanism defined in claim 15, wherein the gas spring piston-cylinder is positioned substantially horizontally near the underside surface of the tabletop, and wherein said fixed point is a point on the underside surface of the tabletop.

18. The compact table support mechanism defined in claim 15, wherein said bell crank is dimensioned with unequal ends , the outer end being shorter than the inner end, whereby the central pivot point is closer to the outer end pivot point and farther away from the inner end pivot point .

19. The compact table support mechanism defined in claim 15, wherein the central pivot point and the inner and outer end pivot points of the bell crank and the fixed point are all adapted to be repositioned, whereby the mechanical advantage may be selectively altered to change the relationship of the linearly decreasing gas spring force, produced by telescoping extension of the piston, to the changing component of tabletop weight at different level positions as affected by gravity.

20. A compact pivoted and counterbalanced table support mechanism providing the user with readily changeable and automatically clamped tabletop heights while maintaining the tabletop level, and counterbalancing the weight of the table and its cargo at a mid range level, while minimizing force applied by the user, when height levels are undamped, to raise or lower the tabletop through a continuous range of different height levels, comprising: a linkage supported by an underlying floor having pivoted components and protruding upward forming a tabletop-engaging portion, a tabletop overlying the linkage and having an upper surface, a lower surface, a front rim, a rear rim, and two side rims joining the front rim to the rear rim, pivot means joining the tabletop to the tabletop-engaging portion of the linkage, an elongated extensible gas spring piston- cylinder having two ends, with pivots joining one of its ends respectively to a fixed point and the other end to the pivoted linkage, and which is normally clamped in any of its extended positions, and at least one manually actuatable unclamping lever mounted on one of the upper or lower tabletop surfaces, and connected, by a "camera shutter" style cable, to the gas spring piston-cylinder to unclamp it, whereby manual actuation of the unclamping lever and application of manual table lifting or lowering force may be simultaneously performed by the individual user.

21. A compact pivoted and counterbalanced table support-elevator mechanism providing the user with readily changeable tabletop heights while maintaining the tabletop level, and counterbalancing the weight of the table and its cargo at a topmost level, while minimizing level changing speed when height levels are changing, to raise or lower the tabletop through a continuous range of different height levels, comprising: a base, an elongated column upstanding from the rear of the base, a linkage pivoted near the top of the column and protruding forward and upward forming a tabletop-engaging portion, a tabletop overlying the linkage and having an upper surface, pivot means joining the tabletop to the tabletop-engaging portion of the linkage, an elongated extensible gas spring piston- cylinder having pivots joining each of its ends respectively to the column and the pivoted linkage, and which has no clamping or locking capability in any of its extended positions, whereby the tabletop without cargo automatically rises, responding to the counterbalancing force supplied by the gas spring piston-cylinder to a high loading level, for receiving a predetermined cargo whose extra weight exceeds the counterbalancing force, causing the tabletop to descend to an unloading level, and after unloading the tabletop automatically repeats the cycle.