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US 5,685,721 AGranted
Refreshable braille-cell display implemented with shape memory alloys
AssigneeAmerican Research Corporation of Virginia
InventorLawrence H. Decker
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AssigneeAmerican Research Corporation of Virginia
InventorLawrence H. Decker
Estimating the term…
A refreshable braille cell display uses a single moving part per tactile element. Tactile elements, formed from stainless steel tubing, are assembled in densely arranged modules. Lower ends of the tactile elements extend beneath the modules and are in contact with a pressurized medium. Shape memory alloy actuators are positioned in the tactile elements, isolated from any motion or flow in the pressurized medium. When a pressurized medium is delivered through a port in a tactile element, the actuator extends upward, thereby forcing the upper portion of the tactile element through a hole in the user contact surface. In that state the tactile element indicates information. When the tactile element is activated, current flows from an electrical contact at the lower end of the tactile element, through the actuator, and into the outer tube of the tactile element. The actuator heats, due to electrical resistance, contracts and exerts a downward force on the pressure medium. The upper portion of the tactile element is drawn below the user contact surface, indicating the absence of information. Distributed pulse width modulation allows instantaneous power requirements to be minimized, and only low safe voltages are needed to operate the array. By applying a bias force to all actuators via a common reservoir of either pneumatic or hydraulic pressure, the design is simplified, and reliability is increased. When integrated with a computer, the refreshable tactile array of elements gives users access to full computer generated screens of text and graphical information in real time.
A tactile element apparatus for use in a refreshable braille display device comprising a first hollow tube section having a top end, a bottom end, an inner diameter, an outer diameter and a port positioned in the first tube section near the bottom end, a second tube section extending partially inside the first tube section and extending outward from the top end of the first tube section, the second tube section having a first portion having an upper end, a lower end and a diameter slightly less than the inner diameter of the first tube section such that the first portion of the second tube section slidably fits in the first tube section, a second portion extending from the upper end of the first portion and having a diameter larger than the inner diameter of the first tube section, and a third portion extending upward from the second portion, the third portion gradually decreasing in inner diameter, a third tube section positioned in the bottom end of the first tube section, the third tube section having a long section and a short section, the short section extending downward from the bottom end of the first tube section, a nonconductive bushing surrounding the long section of the third tube section, the bushing covered third tube section forcibly fitted in the bottom end of the first tube section, an electrical contact connected to the short section of the third tube section, and an actuator extending the length of the element, the actuator having a first end fastened inside the third portion of the second tube section and a second end fastened inside the third tube section.
A full page refreshable braille display apparatus comprising multiple tactile elements, multiple modules, each module having an upper surface and a lower surface, and each module carrying a predetermined number of tactile elements, a row container for holding the multiple modules in a configuration that allows the tactile elements to represent braille cells in standard placement, the container having a plate with multiple slots for holding multiple modules, the modules fitting down inside the slots, and a ledge positioned under the plate such that lower surfaces of the modules rest on the ledge, the ledge further having a sealing means for providing a pressurized area beneath the ledge, a main printed circuit board positioned beneath the lower surfaces of the sealed modules, the printed circuit board having column connections connected in series for receiving plug contacts positioned on the tactile elements, a pressure medium distributed in the pressurized area positioned between the lower surfaces of the modules and the printed circuit board, a means for delivering the pressure medium to the pressurized area, a rigid backing plate positioned underneath the printed circuit board, an airtight extension extending from the row container and surrounding the pressurized area, a user contact surface positioned across a top surface of the container above upper surfaces of the modules, the user contact surface having an upperside, an underside, spacers extending from the underside for applying pressure against the upper surfaces of the modules to force the lower surfaces of the modules against the sealing means of the ledge, and a pattern of holes extending through the user surface, the pattern corresponding to positions of tactile elements in the modules beneath the upper surface, a row driver device positioned on the main printed circuit board and connected to the modules, a column driving device positioned on the main printed circuit board and connected to the modules, a controller connected to the row driving device and the column driving device for controlling activation of individual tactile elements, and connecting means for connecting the backing plate, circuit board, row container and user contact surface into an airtight assembly.
A method for providing a refreshable braille display by applying a bias force to multiple tactile elements via a common reservoir of pressure comprising the steps of extending a lower end of a tactile element in a pressurized area, delivering pressure medium into the pressurized area, exerting pressure on the tactile elements through ports in the lower ends of a tactile elements, causing actuators in the tactile elements to expand, extending upper sections of the tactile elements through holes in a user surface, activating individual tactile elements, applying a current from an electrical contact through the actuator of the activated tactile elements to an outer tube section of the activated tactile elements, heating the actuators in the activated tactile elements through electrical resistance, decreasing lengths of the actuators in the activated tactile elements, exerting a downward force on the pressure medium, and pulling the upper sections of the activated tactile elements beneath the user contact surface.
Dependencies are inferred from the claim text.