NASA CASE NO.

PRINT FIG. __m

BIOEIC_

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The invention disclosed in this document resulted from research in aeronautical and

space activities performed under programs of the National Aeronautics and Space

Administration. The invention is owned by NASA and is, therefore, available for

licensing in accordance with the NASA Patent Licensing Regulation (14 Code of

Federal Regulations 1245.2).

To encourage commercial utilization of NASA-owned inventions, it is NASA policy to

grant licenses to commercial concerns. Although NASA encourages nonexclusive

licensing to promote competition and achieve the widest possible utilization, NASA

will provide the necessary incentive to the licensee to achieve early practical

application of the invention.

Address inquiries and all applications for license for this invention to NASA Patent

Counsel, Langley Research Center, Code 143, Hampton, Virginia 23681-0001.

Serial No." 08/286,031

08/04/94 LaRC

(NASA-Case-LAR-14860-1) TACTILE

DISPLAY DEVICE USING AN

ELECTRORHEOLOGICAL FLUID Patent

Application (NASA. Lang|ey

Research Center) 17 p

N95-14112

Unc las

G3/33 0029857
LAR-14860-1 AWARDS ABSTRACT 

TACTILE DISPLAY DEVICE USING AN ELECTRORHEOLOGICAL FLUID 

The present invention relates generally to a device for displaying and refreshing 

a full page of tactile output representative of a computer screen or other data storage 

medium. Specifically, the invention relates to a tactile display device wherein an 

individual tactile dot is raised due to a build-up of electrorheological fluid in a dot 

actuator chamber. 

A voltage is selectively produced uniformly across an electrorheological fluid 

flowing between a common ground electrode and a plurality of conductive dot 

electrodes, thereby producing an increase in the fluid's viscosity to the extent that fluid 

flow between the two electrodes is restricted. The flow restriction produces a build-up 

of electrorheological fluid in a corresponding dot actuator chamber. The resulting 

pressure increase in the chamber displaces an elastic diaphragm fixed to a display 

surface to form a lump which can be perceived by the reader as one dot in a Braille 

character cell. A flow regulation system provides a continually pressurized flow system 

and provides for free flow of the electrorheological fluid through the plurality of dot 

actuator chambers when they are not activated. 

In an alternate embodiment, the elastic diaphragm drives a plurality of springloaded pins provided with positive stops to maintain consistent displacements of the 

pins in their actuated and nonactuated positions. 

The invention offers several advantages: (i) It allows for the use of printed 

circuit techniques. (ii) It avoids pressurizing and unpressurizing the fluid flow system 

for each cycle of dot actuation. (iii) It minimizes the number of electrodes required to 

be driven. (iv) It minimizes the high-voltage requirement. 

Inventor: H. Douglas Garner 

Home Address: 2 Sir Francis Wyatt Place 

Newport News, Virginia 23606 

Employer: NASA Langley Research Center 

Initial Evaluator: Vernie H. Knight, Jr. 

Serial No. 08/286,031 

Filed: AU~US~ 4, 1994 
LAR 14860-1 -1 - PATENT APPLICATION

TACTILE DISPLAY DEVICE USING AN ELECTRORHEOLOGICAL FLUID

Oriqin of the Invention

5 The invention described herein was made by an employee of the United

States Government and may be manufactured and used by the government for

governmental purposes without the payment of any royalties thereon or

therefor.

10 Technical Field

This invention relates generally to a device for displaying and refreshing

a full page of tactile output representative of a computer screen or other data

storage medium. More particularly, the present invention relates to a device

15 utilizing an electrorheological fluid to interact with a display for transmitting

information that may be tactually felt by the user. Specifically, the present

invention relates to a tactile display device which is adaptable to printed circuit

techniques, wherein an individual tactile dot is raised due to a build-up of

electrorheological fluid in a dot actuator chamber resulting from a voltage

20 applied across an electrorheological fluid flowing between a common ground

electrode and an individual conductive dot electrode corresponding to an

individual tactile dot.

25

30

Backqround Art

Many persons with vision impairments use Braille to communicate and

could benefit from improved, refreshable Braille displays. Electronic encoding

and storage of data are now an established capability for Braille information,

as is the distribution system for recorded media or electronic media. With the

advent of personal computers and large CD-ROM database libraries
LAR 14860-1 -2- PATENT APPLICATION

containing millions of print characters, the blind need Braille displays that allow

them complete access to the information displayed on a computer monitor or

located on some data storage medium. Advanced Braille technology will offer

the potential for dramatic improvements in telecommunications access for

5 persons with sensory impairments, including access to databases, electronic

mail systems, bulletin board systems and mail order systems. Miniature

actuators for a low cost, high density, refreshable Braille display to enable

persons with severe visual impairments to read out printed material recorded

in computer memory or in another data storage medium are needed.

10 Numerous devices currently exist which convert stored data into a

tactile representation. Braille characters may be displayed, a few at a time, on

an array of "Braille cells." Each cell consists of a group of pins which may be

individually raised from the surface of the device to form the particular Braille

character desired. Each pin of each character must be independently actuated

15 by a magnetic (see U.S. Pat. Nos. 4,194,190 and 4,571,190), piezoelectric

(see U.S. Pat. Nos. 4,044,350; 4,283,178; 4,473,356; 4,758,165 and

4,879,698), pneumatic (see U.S. Pat. No. 3,659,354) or electromechanical

(see U.S. Pat. Nos. 4,033,053; 4,898,536 and 4,191,945) device controlled by

inputs from a data storage medium. Each of these devices requires a large

20 number of actuation devices and a relatively large device for displaying the

entire page. Such devices would be expensive and bulky.

U.S. Pat. No. 4,266,936 discloses a portable Braille display unit which

presents an entire page of Braille characters by means of spring actuated pins

controlled by bimetallic latches. An immediate tactile display is provided which

25 may be read out and then refreshed to read out the next group of characters.

Although this device is lighter in weight and smaller in size than the previous

art, each cell involves a rather complex mechanism and an assembly of cells

representing a line of text becomes quite expensive.

The Braille characters may also be embossed on paper by a special

30 Braille printer (see U.S. Pat. Nos. 3,924,019 and 4,183,683.) The Braille
LAR 14860-1 -3- PATENT APPLICATION

printers are necessarily quite bulky and expensive and require the reader to

wait for the material to be printed out before it can be read.

U.S. Pat. No. 4,687,444 discloses a position detecting mouse with a

Braille display located on its upper surface. The mouse scans a single Braille

5 cell through the text as the reader progresses but does not allow for the

presentation of a complete page of text at one time.

Thus, key limitations for full-page, refreshable Braille displays are the

cost and size of the mechanism. Solution of this problem must focus on the

actuator method to temporarily produce raised dots, approximately 6000 or

10 more per page. This new actuator method must allow sufficiently dense

packing while having low power requirements and low cost. A page size of 11

by 11 inches, the page layout of the Perkins Brailler, is regarded by many as

the most desirable page size. In addition, a display of 25 lines of 40

characters each has become the standard within the industry.

15 Recently, Joerg Fricke, in his U.S. Pat. No. 5,222,895 issued June 29,

1993, disclosed an input/output device which employs an electrorheological

fluid to drive tactile display elements. Electrorheological fluids experience a

substantial increase in viscosity when subjected to a strong electrostatic field.

Fricke's device has several advantages over the earlier art, including smaller

20 size display elements and a reduced number of moving parts. These

advantages result in a page-sized display produced at a lower cost than what

was previously possible. The half-cylindrical electrode geometry disclosed in

Fricke's device, however, will inhibit the use of printed circuit techniques in the

manufacturing process. These techniques lend themselves much better to

25 manufacturing flat surfaces. Use of the half-cylindrical electrode configuration

to apply voltage across the electrorheological fluid also induces a voltage

gradient across the electrorheological fluid rather than a desired uniform

voltage, therefore requiring higher voltage supply to the electrodes which

reduces the efficiency of the device. Also, the electrical drive circuitry

30 disclosed in Fricke is required to control voltage to either two or four
5

10

LAR 14860-1 -4- PATENT APPLICATION

electrodes for each dot. With 6000 or moretactile dots required for a single

page of Braille characters, the number of electrodes required to be driven for a

single dot is an important cost consideration. In addition, Fricke's device

requires multiple voltage supplies rather than a single voltage supply. Lastly,

Fricke's device appears to require the flow system to be pressurized and

unpressurized for each cycle of dot actuation. It would be advantageous to

have a device which allows for the use of printed circuit techniques, avoids

pressurizing and unpressurizing the fluid flow system, minimizes the number of

electrodes required to be driven, and minimizes the high voltage requirement.

Statement of Invention

Accordingly, one object of the invention is to provide a full-page tactile

display device at a minimum expense.

15 Another object is to provide a full-page tactile display device with

minimum complexity.

Another object is to provide a tactile display device which can be

adapted to manufacture by batch production techniques such as printed circuit,

photo-etching, and injection molding methods.

20 A further object of the invention is to utilize the characteristics of

electrorheological fluids to implement large arrays of electrically actuated

Braille character cells.

Another object is to provide a tactile display device having an efficient

method of applying voltage to the electrorheological fluid.

25 Another object is to provide a tactile display device which avoids

unwanted pressure build-up of the electrorheological fluid.

Another object of the invention is to provide a tactile display device

which minimizes the high voltage requirement.

Another object is to provide a tactile display device which minimizes the

30 number of high-voltage supplies.
LAR 14860-1 -5- PATENT APPLICATION

Another object is to provide a tactile display device which minimizes the

number of electrodes which are required to be driven.

Still another object is to provide a tactile display device which avoids

pressurizing and unpressurizing the entire electrorheological fluid flow system

5 for each cycle of tactile dot actuation.

Yet another object of the invention is to provide a tactile display device

which provides consistent up and down positions among the plurality of tactile

dots.

Additional objects and advantages of the present invention are apparent

10 from the drawings and specification which follow.

Summary of the Invention

According to the present invention, the foregoing and other objects and

15 advantages are attained by providing a tactile display device which utilizes an

electrorheological fluid to activate a plurality of tactile dots representative of

electrical signal inputs, wherein voltages are selectively supplied across an

electrorheological fluid flowing between a single common ground electrode

and a plurality of conductive dot electrodes. The common ground electrode is

20 mounted on the lower surface of an upper nonconductive plate. The

conductive dot electrodes are mounted on the upper surface of a lower

nonconductive plate which is positioned beneath and in close proximity to the

common ground electrode. The upper nonconductive plate has a plurality of

through holes extending from its upper to lower surfaces. The holes form dot

25 actuator chambers. Each dot actuator chamber has one corresponding

conductive dot electrode. The voltage across the electrorheological fluid

between the common ground electrode and a conductive dot electrode

produces an increase in the fluid's viscosity to the extent that fluid flow

between the two electrodes is restricted, thereby causing the fluid to build up

30 in the corresponding dot actuator chamber. An elastic diaphragm defines the
LAR 14860-1 -6- PATENT APPLICATION

upper end of each dot actuator chamber and interacts with the chambers to

convert the build-up of electrorheological fluid in the chambers into the tactile

display. The flow of the electrorheological fluid is controlled such that the

overall flow system is continually pressurized and unwanted pressure build-up

5 in the dot actuator chambers is prevented.

The electrorheological fluid is stored in a fluid source from which it is

pumped into a plurality of parallel supply manifolds. Each supply manifold

supplies fluid to a plurality of dot actuator chambers on both of its sides by way

of flow restricting orifices. The fluid then flows out of each dot actuator

10 chamber by way of an exhaust orifice, positioned through the common ground

electrode. The exhaust orifice has a larger flow area than the inlet orifice so

that unwanted pressure is not built up in the dot actuator chamber. The fluid

then flows through a valving region created by the clearance between the

common ground electrode and each conductive dot electrode. The relative

15 placement of the common ground electrode to the conductive dot electrodes is

such that the necessary voltage across the electrorheological fluid is reduced

and sufficient clearance is provided for the electrorheological fluid to flow out

of the dot actuator chamber, thereby preventing unwanted pressure build-up in

the dot actuator chamber. Based on an electrical signal input, a voltage is

20 selectively supplied to a conductive dot electrode, thereby producing a voltage

across the electrorheological fluid between the common ground electrode and

the conductive dot electrode. The voltage across the fluid increases the

viscosity of the fluid to the extent that fluid flow between the two electrodes is

restricted. The resulting pressure increase in an individual dot actuator

25 chamber displaces the elastic diaphragm fixed to the display surface to form a

lump which can be perceived by the reader as one dot in a Braille character

cell. The device can also be used to produce arrangements of tactile dots

other than Braille characters, such as graphics displays.

The conductive dot electrodes can be fabricated on the lower

30 nonconductive plate by automated printed circuit manufacturing techniques.
LAR 14860-1 -7- PATENT APPLICATION

The device can be adapted to simultaneously display tactile dots

representative of a full page of Braille characters stored on a medium such as

a tape cassette or to display tactile dots representative of non-Braille data

appearing on a computer monitor or contained on another data storage

5 medium.

In an alternate embodiment, an uppermost plate is positioned above

and mounted on the elastic diaphragm. The uppermost plate has a plurality of

through holes extending from its uppermost to lowermost surfaces, wherein the

hole dimensions increase from the top to the base in three stepped lengths.

10 These holes guide a plurality of spring-loaded pins positioned over each dot

actuator chamber. A base segment of each pin has a larger dimension than

the upper segment. A spring extends externally and circumferentially from the

upper surface of the pin's base to the location on the pin corresponding to the

uppermost shoulder in the stepped hole. Displacement of the portion of the

15 elastic diaphragm above a particular dot actuator chamber pushes the pin

upward, against the force of the spring contacting the uppermost shoulder,

until the upper surface of the pin's base contacts the lowest shoulder in the

stepped hole. The pin then protrudes from the top surface of the uppermost

plate and is perceived tactually by the reader. This positive-stop configuration

20 maintains consistent displacements of the pins in both their actuated and

nonactuated positions. This configuration also avoids the possibility of

diaphragm separation from the attached plate, isolates the reader from any

diaphragm leakage, and isolates the reader from the high voltages required to

activate the electrorheological fluid.

25

Brief Description of the Drawin.qs

30

A more complete appreciation of the invention and the many of the

attendant advantages thereof will be readily obtained as the same becomes

better understood by reference to the following detailed description when
5

10

LAR 14860-1 -8- PATENT APPLICATION

considered in connection with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of a single

dot actuator, looking lengthwise along an electrorheological fluid supply

manifold.

FIG. 2 is a layout of six dot-actuators arranged to form one Braille cell.

FIG. 3 is a cross-sectional diagram of the device shown in FIG. 2 taken

along lines II1-111.

FIG. 4 is a layout of a complete page of Braille character cells with the

associated fluid flow regulation system required to energize it, and a block

diagram representing suitable electronic circuitry for electrical signal input and

voltage supply.

FIG. 5 is a diagram showing further detail of suitable electronic logic.

FIG. 6 is a view similar to FIG. 1, but showing a second embodiment.

15 Detailed Description of the Invention

FIG. 1 is a cross-sectional view of a single tactile dot actuator. An

elastic diaphragm 2 is fixed to the upper surface of a nonconductive plate 4.

The elastic diaphragm can be made of any elastic material which is chemically

20 resistant to electrorheological fluids, and the nonconductive plate 4 can be

made of any insulating material which is chemically resistant to

electrorheological fluids. A common ground electrode 6 is fixed to the lower

surface of the nonconductive plate 4 and is common to the plurality of tactile

dot actuators. This electrode can be a sheet of conductive material that is

25 chemically resistant to the electrorheological fluid. Holes corresponding to the

individual dots and extending through the nonconductive plate 4, from its

upper surface to its lower surface, form individual dot actuator chambers 10.

Electrorheological fluid flows into the dot actuator chamber 10 from the

supply manifold 12 by way of the flow-restricting orifice 14. The supply

30 manifolds 12 run parallel to one another internal to and across the
LAR 14860-1 -9- PATENT APPLICATION

nonconductive plate 4. The electrorheological fluid flows out of the dot

actuator chamber 10 by way of the exhaust orifice 16 located through the

common ground electrode 6. A lower nonconductive plate 20 is positioned

beneath and in close proximity to the common ground electrode 6. The lower

5 nonconductive plate 20 can be made of any nonconductive material which is

chemically resistant to the electrorheological fluid. A conductive dot electrode

8 is fixed to the nonconductive plate 20 such that a flat-surface of the electrode

is fixed to the upper surface of the nonconductive plate 20, at a position

corresponding to each dot actuator chamber. The electrorheological fluid

10 continues to flow from the exhaust orifice 16 through the valving region 18

formed by the clearance between the common ground electrode 6 and the

conductive dot electrode 8. When voltage is applied between a conductive dot

electrode 8 and the common ground electrode 6, the viscosity of the

electrorheological fluid between the two electrodes is increased to the extent

15 that fluid flow between the two electrodes is restricted, causing a pressure to

be built up in the dot actuator chamber 10. This pressure increase deflects the

elastic diaphragm 2 such that a lump is formed which is perceived by the

reader as one dot in a Braille character. The voltage which is required across

the electrorheological fluid is reduced as the distance separating the

20 electrodes 6 and 8 is reduced. The only limitation on the minimization of the

distance between the electrodes 6 and 8 is the necessity of sufficient flow area

between the electrodes to allow the electrorheological fluid to flow out of the

dot actuator chambers 10 with minimum restriction, so that little pressure is

built up in a particular dot actuator chamber 10 when its corresponding dot is

25 meant to be in its unpressurized state. Source entry passageways 22 formed

by holes in the nonconductive plate 20 allow continual free flow of the

electrorheological fluid through the lower nonconductive plate 20 to a fluid

source, such as a sump, from which the electrorheological fluid is pumped

back into the supply manifolds 12.

30 FIG. 2 is a layout of six dot-actuators arranged to form one Braille
LAR 14860-1 -10- PATENT APPLICATION

character cell 24, along with a portion of adjacent cells 26. Each supply

manifold 12 supplies electrorheological fluid to the interfacing dot actuator

chambers 10 located on each of its sides.

FIG. 3 is a cross-sectional diagram of the section of the device shown in

5 Fig. 2 along lines II1-111.Tactile dots 28 are in their pressurized states. Tactile

dot 30 is in its unpressurized state.

FIG. 4 is a layout of a complete display of Braille character cells with the

associated fluid flow regulation system required to energize it, and suitable

electronic logic required to supply voltage to the conductive dot electrodes.

10 The electrorheological fluid is stored in sump 32. The electrorheological fluid

is pumped by a low-pressure fluid pump 34 through a filter 36 and pressure

regulator 38 into the supply manifolds. The use of a filter 36 is standard in

hydraulic systems. The pressure regulator 38 maintains a continual pressure

throughout the system during the pressurizing and unpressurizing of the

15 plurality of tactile dots. By controlling the pattern of voltages applied to the

conductive dot electrodes, the pattern of dots perceived by the reader may be

arranged to represent any character desired. Suitable electronic logic is used

to read signal inputs 40 from a data storage medium in the form ofASCII or

other code, convert it 42 into Braille code if necessary, and latch it into high20 voltage drivers 44 attached to each individual dot actuator on the page to

produce a full-page Braille display corresponding to the text received from the

data storage medium.

FIG. 5 is a diagram showing further detail of suitable electronic logic.

The driving circuitry can be powered by a single high-voltage supply 46 for the

25 plurality of tactile dots, a high-voltage transistor 48 for each tactile dot which is

positioned between the common ground electrode and each conductive dot

electrode, a base resistor 50 between the output from a multichannel circuit

latch 52 and transistor 48, and a collector resistor 54 between the high-voltage

supply 46 and each conductive dot electrode. This is standard electronic

30 "switch" circuitry for controlling voltage between off and on which is known to
LAR 14860-1 -11- PATENT APPLICATION

those skilled in the art. Other suitable electronic logic and further details of the

disclosed electronic circuitry will be known to those skilled in the art.

FIG. 6 is a second embodiment. An uppermost plate 56, which has a

plurality of holes extending from its upper surface to its lower surface, is

5 positioned above and mounted on elastic diaphragm 2 in order to support and

guide a plurality of spring-loaded pins 58 which are positioned above each dot

actuator diaphragm. When actuated, the pin 58 extends above the upper

surface of the uppermost plate 56 to be detected by the reader. The

engagement of spring 60, extending circumferentially around an exterior

10 portion of pin 54, with shoulder 62 provides a downward force to the pin to

ensure that it returns to its unactuated position once pressure is removed from

the diaphragm 2. A positive stop, wherein the larger diameter portion 64 of the

pin 58 engages the shoulder 66 of the uppermost plate 56, allows for

consistent displacement among the individual tactile dots to aid the reader's

15 detection of raised versus flat dots. This embodiment also avoids the

possibility of diaphragm separation from the plate 4, provides the reader a

measure of isolation from any leakage which might occur from the diaphragm

2, and isolates the reader from the high voltages required to activate the

electrorheological fluid.

20 Obviously, numerous additional modifications and variations of the

present invention are possible in light of above teachings. It is therefore to be

understood that within the scope of the appended claims, the invention may be

practiced otherwise than is specifically described herein.

What is claimed is:
LAR 14860-1 PATENT APPLICATION

TACTILE DISPLAY DEVICE USING AN ELECTRORHEOLOGICAL FLUID

Abstract of the Disclosure

5 A tactile display device utilizes an electrorheological fluid to activate a

plurality of tactile dots. A voltage is selectively produced uniformly across an

electrorheological fluid flowing between a common ground electrode and a

plurality of conductive dot electrodes, thereby producing an increase in the

fluid's viscosity to the extent that fluid flow between the two electrodes is

10 restricted. The flow restriction produces a build-up of electrorheological fluid

in a corresponding dot actuator chamber. The resulting pressure increase in

the chamber displaces an elastic diaphragm fixed to a display surface to form

a lump which can be perceived by the reader as one dot in a Braille character

cell. A flow regulation system provides a continually pressurized flow system

15 and provides for free flow of the electrorheological fluid through the plurality of

dot actuator chambers when they are not activated. The device is adaptable to

printed circuit techniques and can simultaneously display tactile dots

representative of a full page of Braille characters stored on a medium such as

a tape cassette or to display tactile dots representative of non-Braille data

20 appearing on a computer monitor or contained on another data storage

medium. In an alternate embodiment, the elastic diaphragm drives a plurality

of spring-loaded pins provided with positive stops to maintain consistent

displacements of the pins in both their actuated and nonactuated positions.

25
12.

FIG. 1

FIG, 2

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2.7_-. Lg 2Z

FIG. 3
32,

FIG. 4

Individual Latches and

High Voltage Drivers

Code Converter

Signal Inputs

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dZ

Latch

FIG. 5
FIG. 6