Keith L. Walker

Denman Island, British Columbia

Drafting Desk with Electric Lift Top

Figure 1: top down

Abstract

This is a general-purpose writing and work desk with a top that can be positioned at any angle from flat (0°) to 60° for drafting. The lift mechanism is electrically operated, controlled by a switch on the front of the desk.

Figure 2: top raised

Figures 3 & 4: lift mechanism

Figure 3 shows the lift mechanism, including the power supply and motor assembly at the bottom.		Figure 4 shows a closeup of the lift mechanism in a partially raised position.

The desk top is raised by a 24 volt DC motor which drives a rotating threaded shaft. A hinged bracket rides up or down the threaded rod as it rotates. Two struts connect the moving bracket to the desktop, raising or lowering it.

Schematic

A single switch controls the circuit. There are 3 positions: UP, OFF and DOWN. In the OFF position, primary power to the transformer is interrupted. In the UP or DOWN position, DC power of the appropriate polarity is applied to the motor. Limit switches at the top and bottom of the lift mechanism not only interrupt power to the motor, but also short-circuit the motor to provide dynamic braking.

FIgure 5: schematic

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