Electromechanical braille cell and method of operating same

An electromechanical braille cell is disclosed wherein each cell includes six braille indicia formed by the free ends of six rods protruding through six openings in braille reading surface. The six rods are raised and lowered by six piezoelectric reeds. Applying an operating potential to a respective reed causes the reed to bend about a fulcrum at the supported root end of the reed causing the free end to deflect in such a manner as to cause the indicia rod to be raised and to protrude through an opening in the reading surface of the braille cell. Simultaneous energization of one or more of the six reeds defines a given braille character sensed by the braille reader. Modulating the voltage applied to a given reed serves to vibrate the respective rod for sensing by the braille reader for indicating information, such as upper case, to the reader in addition to the braille character information represented by merely elevating a pattern of rods above the braille reading surface.

BACKGROUND OF THE INVENTION 
The present invention relates in general to electromechanical braille cells 
and, more particularly, to an improved method of operating same. 
DESCRIPTION OF THE PRIOR ART 
Heretofore, electromechanical braille cells have utilized six piezoelectric 
reeds which bend in response to the application of an electric voltage 
thereacross for urging the tip of sensing rods through an array of six 
openings in a braille cell reading surface. The protruding tips of the 
sensing rods are sensed by the finger of the operator to define a braille 
character. One such prior art arrangement is disclosed in U.S. Pat. No. 
4,283,178 issued Aug. 11, 1981 and assigned to the same assignee as the 
present invention. 
One of the problems with the standard braille cell and code is that with 
only six rods it was not possible to include the English alphabet and also 
indicate other information such as upper and lower case with a single 
setting of the six rods. Upper case was indicated by using two cells. The 
first cell was set to indicate the case. 
Others have proposed to add two additional rods to the standard six rod 
cell for indicating upper and lower case and other information. However, 
this adds substantial complexity to the standard six rod electromechanical 
braille cell. 
It would be desirable if additional information, such as case, could be 
imparted to the reader by a single setting of the standard six rod 
electromechanical braille cell. 
SUMMARY OF THE PRESENT INVENTION 
The principal object of the present invention is the provision of an 
improved six rod electromechanical braille cell and method of operating 
same so as to give additional information to the reader. 
In one feature of the present invention, additional information, such as 
upper or lower case, for a single setting (character) of the standard six 
element braille cell is imparted to the reader by vibrating one or more of 
the six elements (rods) of the braille cell, whereby the standard six 
element braille cell may be used without having to add additional elements 
to the cell.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 and 2, there is shown a prior art standard 
electromechanical braille cell 11. The braille cell 11 includes a vertical 
base plate 12 as of ABS plastic material formed by injection molding and 
having upper and lower horizontal flange portions 13 and 14 with a 
recessed central web portion 15 extending vertically therebetween. The web 
portion 15 is notched from the inside edge to provide six generally 
rectangular openings 16 to receive the root portions of six piezoelectric 
reeds 17. The piezoelectric reeds are captured in an interference fit at a 
restricted neck portion 18 at the entrance to each of the rectangular 
openings 16. The neck portions 18 define fulcrum points about which the 
piezoelectric reeds 17 bend in response to an applied operating voltage. A 
top plate 19 is secured to the base plate 12 via the intermediary of 
screws, not shown. The top plate 19 is recessed at 21 and 39 to receive 
stringers, not shown, for mounting the individual braille cells 11 
transversely of the stringers. 
A sensing plate portion 22 of the top plate 19 includes an upper sensing 
surface 23 which is apertured by means of six vertically directed bores 24 
which slideably receive therewithin a narrow neck portion 25 of a sensing 
rod 26. The upper end of the sensing rod 26 is rounded. That portion of 
the rod which protrudes above the surface 23 is sensed by the finger of 
the operator to determine the pattern being displayed on the individual 
braille cell 11. 
The lower extremity of the sensing rod 26 (see FIG. 5) is counterbored at 
27 to slideably receive therewithin in a telescoping manner a rod extender 
insert 28. The insert 28 includes a dowel portion 29 which slides within 
the counterbore 27 in the main body of the rod 26. The dowel portion makes 
a tight interference fit with the internal walls of the bore 27 so that by 
adjusting the degree of penetration of the dowel 29, the axial length of 
the composite rod structure 26 is determined. 
The sensing rods 26 rest at their lower extremity upon the free end 
portions of the respective piezoelectric reeds 17. The reeds 17 are 
cantilevered about the fulcrum support 18 with the free end portions 
thereof supporting their respective sensing rods 26. The reeds 17 are 
arranged in a stair step fashion in pairs. The uppermost reed of each pair 
is apertured to allow passage therethrough of the sensing rod resting upon 
the lowermost reed of each pair. The aperture is conveniently formed by a 
notch which notches out one of the corners of the respective reed. Such a 
notched corner is shown at 31 in FIG. 3. The sensing rod 26 associated 
with the uppermost reed of each stair step pair rests upon the corner of 
the reed at the free end of the reed 17. The sensing rods 26 associated 
with the successively lower pairs or steps of the stack of reeds 17 pass 
by the ends of the reeds above that pair in the stack of reeds 17. 
Referring now to FIG. 4, the piezoelectric reeds 17 each comprise a 
sandwich structure of piezoelectric material in which two layers of 
electrically polarized piezoelectric material 32 and 33 sandwich 
therebetween a leaf of conductive material 34, as of brass. The outer 
surfaces of the piezoelectric layers 32 and 33 are covered with a thin 
layer of electrically conductive material 35 as of gold or nickel. In a 
typical example, the reeds are approximately 1/4 inch wide, 2 inches in 
length and the brass leaf 34 has a thickness as of 0.001 to 0.002 inch and 
piezoelectric layers 32 and 33 have thicknesses as of 0.007 to 0.008 inch. 
The conductive layer 35 has a thickness, as of 50 micro inches. Such reeds 
are commercially available from NGK of Nagoya, Japan as model MT-114H 
bimorphous elements. 
The reeds utilized herein are electrically polarized for parallel operation 
at the factory by the application of a high voltage across conductive 
layers 35. A polarization mark 36 indicates the positive terminal during 
the polarizing process. 
The operating potentials are applied to the respective reeds 17 by means of 
a circuit schematically indicated in FIG. 4. More particularly, a source 
of relatively high voltage, as of +160 volts is applied to terminal 37 
which is connected to the upper layer 35 of the bimorphous piezoelectric 
reed 17. The central leaf 34 is connected to one terminal of a double 
pole-double throw switch 38 which is preferably a transistor switch. The 
lower face electrode 35 of the reed 17 is connected to ground. The switch 
38 selectively couples the central leaf 34 either to the high positive 
potential or to ground potential which either places the full 160 volts 
across the lower piezoelectric layer 33, or across the upper piezoelectric 
layer 32 as determined by the position of switch 38. 
When positive potential is applied across the upper piezoelectric layer 32, 
it deflects the reed upwardly about the fulcrum 18 and conversely when the 
positive potential is applied across the lower piezoelectric layer 33, it 
deflects the reed 17 downwardly about the fulcrum 18. The bending moment 
selectively applied to the reed causes the sensing rod 26 associated with 
that reed to be either fully elevated as determined by the shoulder of the 
rod being stopped by the marginal edge of the respective bore 24 in the 
sensing plate 19 or conversely when the bending moment is downward, the 
reed deflects downward and gravity operating on the respective sensing rod 
26 causes the rod to be fully retracted so that the degree to which the 
sensing rod protrudes, if any, from the sensing surface 23 is greatly 
reduced relative to the amount of protrusion when the rod is fully 
elevated. The operator senses the pattern of protruding rods 26 to define 
a given braille character. 
In the schematic diagram of FIG. 4, the switch 38 is closed to the grounded 
terminal for elevating the sensing rod 26. The switch 38 is closed to 
ground by means of an electrical solenoid 41 magnetically operating on a 
magnetically permeable core member 42 mechanically coupled via rod 43 to 
the switch 38. Current is fed to the solenoid 41 from a battery 44 via the 
intermediary of a switch 45 and an interrupter 46. A compression spring 47 
is coupled to the core member 42 and spring biases the switch 38 to the 
high voltage terminal 37 for holding the sensing rod 26 in the normally 
retracted position. 
To raise the sensing rod 26 for indicating to the reader one element of a 
braille character, the switch 45 is closed thus energizing the solenoid 41 
and pulling the core 42 and switch actuating rod 43 against the spring 
bias of spring 47. In this manner, switch 38 is closed to the ground 
position, placing the positive voltage across the upper piezoelectric 
layer 32, for raising the sensing rod 26. 
To indicate additional information, such as the case of the braille 
character being displayed, the interrupter 46 on one or more of the cell 
elements is energized via an input to the interrupter at 48. This will 
interrupt the current to the solenoid at a desired repetition rate and 
produce vibration of the respective sensing rod 26. The braille reader 
senses the vibration and thus receives the additional information, such as 
upper or lower case of the braille character being read by the reader. 
This additional information is imparted to the braille reader without 
having to use a second braille cell and without having to add additional 
sensing rods 26 to the standard six rod electromechanical braille cell 11. 
Although the embodiment of FIG. 4 is depicted using a mechanical switch 38, 
an alternative preferred embodiment would use a transistor switch in its 
place. Such a transistor switch is readily electronically modulated in a 
conventional manner to produce vibration of the sensing rod 26. 
Also, vibration of all of the sensing rods of a braille character need not 
be employed to indicate the additional information. As an alternative, one 
or more of the sensing rods 26 could be vibrated to input the additional 
information. 
Electrical connection is made to the root ends of the respective reeds by 
means of a printed circuit board, mating with the recessed web 15 not 
shown and leads which connect the circuit on the printed circuit board to 
the respective terminals of each of the respective reeds 17 in a manner as 
indicated in FIG. 4. 
In a typical example, the sensing rod 26 is made of ABS plastic, has a 
diameter of 0.082 inch and a length for the neck portion 25 of 0.328 inch. 
The rods are conveniently made by injection molding and their length from 
the shoulder to the base varies from 0.095 inch to 0.845 inch. 
An advantage to the manner in which the electrical potentials are applied 
to the reeds 117 as shown in FIG. 4 is that the piezoelectric layers 32 
and 33 are permanently electrically polarized in the same sense as that of 
the applied operating electric field. More particularly, the electric 
vector of layer 32 is perpendicular to and directed toward the plane of 
the central leaf 34, whereas the permanent electric polarization vector of 
the lower piezoelectric layer 33 is normal to the leaf 34 and directed 
away from the leaf. The applied voltage for actuation of the reed 17 is 
thus always applied in the direction of the electric field polarization of 
the layers 32 and 33. In this manner, depolarization of the reeds with 
usage does not occur. 
The inner ends of the respective top plates 19 are recessed at 39 for 
mounting to a stringer, not shown, extending laterally of the individual 
electromechanical braille cells 11. The recessed portion 39 includes a 
vertical bore 41 to receive a screw passing into a tapped bore in the 
stringer. Similarly, a tapped bore 42 is provided in the centrally 
recessed portion 21 of the top plate to receive a screw passing through 
the central stringer and threadably mating with the threads of the bore 
42. 
By cantilevering the reeds 17, the braille cells 11 may be arranged in a 
pair of rows, as shown in FIG. 6, thereby providing two relatively closely 
spaced lines of braille text.