Actuation Mechanism for Braille Displays

Northern Illinois University
posted on 06/24/2010

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Refreshable Braille display is a tool commonly used by the visually impaired. The device is capable of refreshing or changing a pattern of Braille dots as the user reads each line from the display. NIU has patented a new economical and simpler refreshable Braille display design which employs bias compression springs, sliding blocks, pins, and a shape memory alloy (SMA) wire to create the Braille. In this invention the movement of each Braille dot requires only one moving part, the sliding block. The sliding block is actuated by the interaction between the bias compression spring and the wire. When a current is sent through the wire, the wire will flex or shorten three to five percent of its total length. With the wire activated, the sliding block retracts and gravity forces the pin to fall. When the current energy is cut the wire recovers to its original length with the assistance of the bias spring. The recovery of the wire in combination with the expansion of the spring forces the sliding block back to its original position. This movement of the sliding block back to its original position forces the pin upwards.

For persons with visual impairments

The present invention uses a shape memory alloy to actuate individual pin movements which is significantly less expensive than current Braille displays employing piezoelectric reeds for the same purpose. This new design benefits from automated manufacturing thereby greatly reducing costs associated with hand assembly. The use of a sliding block separates the forces applied by the user of the device and those required to actuate the pin. Thus neither the bias spring nor the SMA wire is required to support the forces applied by the user.