Education and demonstration – Communication aids for the handicapped – Tactile reading aid
Patent
1986-01-24
1987-05-12
Grieb, William H.
Education and demonstration
Communication aids for the handicapped
Tactile reading aid
G09B 2100
Patent
active
046646329
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to tactile reading devices of the type having a reading surface provided with openings for a number of tactile rods mounted for reciprocal axial sliding between a protruding position and a retracted position with respect to said surface, each of which rods are movable between said positions via one end of an elongated actuating element of which the other end is fixed, said element being capable of moving to a certain extent by bending deformation perpendicularly to its longitudinal axis between two outermost positions by the application of an operating force thereto.
In known devices of this type, piezo-electric elements are used for actuating the sensing rods. A typical example of the prior art is illustrated in U.S. Pat. No. 4,283,178, in which the piezo-electric elements are arranged perpendicularly to the tactile rods and deform by bending axially to the tactile rods. One important disadvantage with this type of design resides in the fact that the pressure applied to the protruding sensing rods by the finger of the reader, has to be compensated by applying more electrical power to the piezo-electric elements than what would be necessary just for keeping the sensing rods in the protruding position. Understandably, it is necessary for the reader to apply a minimum of pressure with his fingers on the sensing rods in order to determine the character represented by the pattern of the protruding sensing rods.
In another known device, illustrated in French Patent No. 2 399 555, every tactile rod is controlled by means of two piezo-electric elements extending in parallel to the axis of the tactile rod and disposed on either side of said axis, their free ends being connected to the tactile rod by means of connecting bars. According to this disposition, the electric power is applied to the piezo-electric elements only in short pulses for switching the sensing rod from the protruding position to the retracted position, or vice-versa. Thus, the piezo-electric elements must have a mechanical stiffness which is sufficient to ensure the necessary "reading pressure" when the protruding rods are touched by the reader's fingers. However, if, by accident, too great a force is applied on the ends of the protruding tactile rods, these could be returned to the retracted position and cause malfunctioning of the device, seeing that there are no means for indicating to the controlling electronic circuits whether a sensing rod is in a protruding position or in a retracted position.
It is the object of the present invention to overcome the above disadvantages of the known devices by proposing a tactile reading device in which the inward movement of the sensing rods under the pressure applied by the reader's finger is positively limited without the need for applying extra operating power to the actuating elements in order to counteract the reading pressure.
A tactile reading device according to the invention is characterized by the fact that direction of curvature deformation of the actuating element is substantially perpendicular to the direction of displacement of the sensing rod, and that displacement transmitting means are provided between said actuating element and the sensing rod, said displacement transmitting means having a substantially neutral point close to that of the end position of the actuating element in which the sensing rod is protruding. An abutment may be provided to prevent the actuating element from bending beyond said end position.
When piezo-electric actuating elements are used, the invention permits a considerable reduction of the volume of the elements insofar as the electric power to be stored inside said elements during operation is considerably reduced compared to what was needed in the previously known devices. By way of example, the piezo-electric elements used in the device according to U.S. Pat. No. 4,283,178 have a volume of about 140 mm.sup.3, whereas in a device according to the present invention, the piezo-electric elements may have a volume less than 25 mm.sup.3.
REFERENCES:
patent: 4266936 (1981-05-01), Rose et al.
patent: 4283178 (1981-08-01), Tetzlaff
patent: 4305067 (1981-12-01), Tretiakoff et al.
patent: 4379697 (1983-04-01), Linvill
patent: 4473356 (1984-09-01), Fernando et al.
Tretiakoff Andree
Tretiakoff Oleg
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