Horizontally supported planar surfaces – Vertically adjustable – With force-multiplying means
Reexamination Certificate
1999-04-30
2001-09-11
Cuomo, Peter M. (Department: 3636)
Horizontally supported planar surfaces
Vertically adjustable
With force-multiplying means
C108S020000, C108S147190
Reexamination Certificate
active
06286441
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a workstation having a work surface table and, more particularly, to a motorized height adjustable table assembly and control system therefor.
Conventional workstations exist which have a height adjustable work surface, i.e., table, to accommodate different users and for different uses. For example, adjustable height tables are commonly made available for supporting computers and their accessories. Some conventional height adjustable tables have employed a mechanical adjustment assembly which allows for the work surface to be manually raised and lowered in height. The mechanical height adjustment assembly generally includes a manually-operated hand crank connected to a shaft and gear assemblies at opposite ends of the table, which are often driven together by a cross-connected shaft. The mechanical drive assembly, particularly the hand crank, generally consumes a large amount of space, can be difficult to operate, and often interferes with the use of the workstation.
Conventional workstation tables have also employed an electric motor for power assistance to adjust the height of the work surface. In one approach, the motor is generally configured to drive a cross-connected linkage connecting opposite ends of the table, and thereby requires a complex mechanical assembly. Another motorized approach is disclosed in U.S. Pat. No. 5,259,326 which discloses an automatic height adjustable workstation with a pair of motors for raising and lowering each table. The aforementioned multiple motor approach monitors the rotational speed of each drive arrangement and controls the motors by varying the speed of each motor to maintain a substantially level work surface. This approach requires a pulse width modulator for adjusting the speed of the motor to slow down a faster running motor to substantially equal the speed of the slower running motor. The required motor speed control, as well as required limit switches, add to the cost and complexity of the system. In addition, the aforementioned approach uses an in-line drive arrangement which requires the addition of a brake mechanism to prevent back driving of the work surface due to heavy loads. Accordingly, it is desirable to provide a motorized height adjustable table that is less expensive and easy to use.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a motorized height adjustable table is provided having a support base, a top assembly including a substantially horizontally disposed work surface, and first and second powered drive assemblies for raising and lowering the work surface. The first drive assembly includes a first electric motor engaged with the top assembly at a first location for effecting vertical movement of the top assembly to adjust the height of the work surface. The second drive assembly includes a second electric motor engaged with a second drive member engaged with the top assembly at a second location with the top assembly for effecting vertical movement of the drive assembly to adjust the height of the work surface. A controller is coupled to the first and second drive assemblies for simultaneously controlling the first and second electric motors to maintain a substantially level work surface. The controller senses a relative height displacement between the first and second drive members and deenergizes one of the motors until the relative difference in height between the first and second drive members is substantially zero.
According to another aspect of the present invention, a motorized height adjustable table is provided having a support base, a top assembly including a substantially horizontally disposed work surface, and first and second power drive assemblies for raising and lowering the work surface. The first drive assembly includes a first electric motor engaged with the top assembly at one location for effecting vertical movement of the top assembly to adjust the height of the work surface, and the first drive assembly further includes a first drive screw and a first cantilever assembly horizontally offset from the first drive screw and operatively connected thereto so that the first drive screw raises and lowers the first cantilever assembly to correspondingly raise and lower the work surface. A second drive assembly includes a second electric motor engaged with the top assembly at another location for effecting vertical movement of the top assembly to adjust the height of the work surface, and the second drive assembly includes a second drive screw and a second cantilever assembly horizontally offset from the second drive screw and connected thereto so that the second drive screw raises and lowers the second cantilever assembly to correspondingly raise and lower the work surface. A controller simultaneously controls the first and second motors. Accordingly, the offset between the drive screws and the cantilever assemblies causes load on the work surface to create a torque to resist movement of the work surface, thereby eliminating the need for a brake.
According to yet a further aspect of the present invention, a motorized height adjustable table is provided having a support base, a top assembly including a substantially horizontally disposed work surface, a first powered drive assembly including a first electric motor and a first drive arm engaged with the top assembly at one location for effecting vertical movement of the top assembly to adjust the height of the work surface, and a second powered drive assembly including a second electric motor and second drive arm engaged with the top assembly at another location for effecting vertical movement of the top assembly to adjust the height of the work surface. A controller is provided for simultaneously controlling the first and second motors to move the first and second drive arms, and the controller senses displacement of the first and second drive arms and determines a rate of the displacement over a period of time and deenergizes the one of the first and second motors as a function of the rate of displacement. Accordingly, the controller is able to detect an overload or limit condition based on the rate of displacement, thereby eliminating the need for separate limit and overload switches.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
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Baker Richard H.
Burdi Roger D.
Ooms John W.
Cuomo Peter M.
Price Heneveld Cooper DeWitt & Litton
Steelcase Development Corporation
Tran Hanh V.
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