GB1595894A - Display devices - Google Patents

Description

(54) IMPROVEMENTS IN DISPLAY DEVICES (71) We, CLARKE & SMITH INDUSTRIES LIMITED, a British Company of Melbourne House, MeIbourne Road, Wallington, Surrey, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to tactile display devices and is concerned with electromechanical devices whereby braille characters can be displayed and erased.

Braille was devised to enable the blind to read alpha-numeric characters and is in the form of a code, usually a six-unit code, for each cell representing a character or symbol.

Thus with a six-unit code in each cell there is a matrix of two columns with three in a column.

By employing a six-unit code 64 characters can be catered for which include the 26 Ietters of the alphabet, the numbers 0 and 1 to 9 and various symbols such as full stops, commas, etc. For special purposes. a braille code of four units and sometimes of seven units is employed.

Hitherto braille has been provided in what is known as hard copy, i.e. on stiff paper, by embossing the paper to raise different patterns of dots in different cells representing different characters or symbols.

Of recent times it has been proposed to extend the application of braille for enlarging job-opportunities for the blind by providing electro-mechanical apparatus whereby alphanumeric characters and associated symbols can be set up for reading and erased as required and it is an object of the present invention to provide improved apparatus of this kind.

In patent specification No. 1,483,698 there is claimed "A device comprising an array of key buttons, which can be individually raised and lowered relative to a reference plane to produce a touchable shape, outline or character and a plurality of operating means, each for raising and lowering the respective key button relative to the reference plane, each operating means comprising electromagnetic means energisable selectively to raise or lower the respective key button and mechanical locking means arranged to resist depression of the respective key button on deenergisation of the electromagnetic means." It is an object of the present invention to provide electro-mechanical apparatus suitable for setting-up and erasing alphanumeric characters and other symbols in braille, in which separate electro-magnetic means are employed to raise respective "key buttons" or plungers but in which the unlatching and lowering thereof does not employ individual electro-magnetic means but a simple mechanical device common to all "key buttons" or plungers.

According to the present invention there is provided electro-mechanical apparatus suitable for setting-up and erasing alpha-numeric characters and other symbols in braille, comprising; an array of substantially parallel solenoid windings each with a plunger therein, each plunger having ferro-magnetic material along all or part of its lengths so that it can be moved longitudinally from an inoperative position to an operative position upon energisation of its associated winding for setting up a character, the apparatus further comprising latching means associated with the plungers respectively for latching each plunger independently in its operative position upon energisation of its associated winding and for retaining the plunger in its. operative position when the winding is no longer energised, each latching means comprising a rolling member which is retained in an unlatching position by the plunger in its inoperative position and which rolling member is movable to a latching position when the plunger is moved to its operative position upon energisation of its solenoid winding, the apparatus also com- prising an unlatching member common to the several rolling members and upon which the rolling members sit and which is; slidable laterally to the plungers to roll. rolling members out from latching positions to unlatching positions to permit Patched plungers to return to their inoperative positions and erase characters which have been set up.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows in plan part of a braille display plate, Fig. 2 shows in cross-section part of one embodiment of the invention for use with the display plate of Fig. 1, and Fig. 3 is a diagram of an elementary circuit for controlling the energisation of solenoids in a row of devices according to Fig. 2.

Referring to Fig. 1, this shows part of a braille display-plate 10 which contains a row of 48 braille cells of which three are shown at 11, 12 and 13 each cell containing a matrix of six dot-positions 14 to 19 in two columns of three each as shown. Beneath the display plate 10 there is provided for each cell, electro-mechanical apparatus whereby different patterns of braille dots can be raised through the display plate to be read and whereby they can be retracted for erasure.

The electro-mechanical apparatus for each cell comprises an array of six solenoid windings of which two are shown schematically at 20 and 21 in Fig. 2 for cell 11 of Fig. 1 and associated with the dot positions 16 and 19.

The solenoids are arranged parallel to and closely adjacent one another. Each winding has a ferro-magnetic plunger therein such as the plungers 22 and 23, each plunger having an inoperative position in which the plunger 22 is shown and, upon energisation of its associated winding, an operative position in which the plunger 23 is shown.

For each plunger there are provided independent latching means whereby the plunger can be latched in its operative position. In addition unlatching means are provided common to all plungers.

In Fig. 2 each independent latching means comprises a rolling member in the form of a steel ball such as the balls 24 and 25. Normally each latching ball sits in a pocket such as the pockets 26 and 27 and ball 24 being shown in this position. When a winding such as the winding 21 is energised the plunger23 moves upwardly into its operative position shown whereby a gap 28 is created between the lower end of the plunger 23 and an unlatching plate 29 on which the lower end of the plunger 23 and an unlatching plate 29 on which the lower end of the plunger sits i.e.

when the plunger is in its inoperative position as shown for the plunger 22. As the gap 28 is created, magnetic flux from the plunger 23 attracts the ball 25 into the gap 28 whereby the plunger is latched in its operative position to be held there when the energising currentin the winding 21 is removed.

The unlatching plate 29 is common to all the plungers and to unlatch all plungers which are in their operative positions and permit them to return to their inoperative positions the unlatching plate 29 is made laterally slidable as indicated by the arrow 44. When the plate 29 is so moved all balls, such as the ball 25, which are in latching positions are rolled to one side back into their pockets such as 24 whereby their associated plungers are unlatched and can return to their inoperative positions as shown for the plunger 22.

In an alternative arrangement the rolling members are moved into latching positions by using the force of gravity. To enable this, the unlatching plate is inclined at some suitable angle to the horizontal so that when the plungers are moved to their operative positions by energising their windings, the rolling members can roll on the plate into latching positions. The unlatching plate is laterally slidable as before to roll rolling members out from latching positions to permit latched plungers to return to their inoperative positions.

Referring now to the structure of Fig. 2 in more detail, the windings shown schematically at 20 and 21 are on formers 30 and 31 which extend between two frame members 32 and 33 of non-magnetic material. The member 33 includes the pockets such as 26 and 27 in which the latching balls are normally located.

Apertures such as 34 and 35 are provided in the member 32 through which the plungers extend and contact the lower ends of dotpins such as 36 and 37 which project into apertures such as those indicated at 16 and 19 in the braille display-plate 10. The dot-pins are spring loaded by springs such as those shown at 38 and 39 whereby they are normally retracted downwardly as shown for the dot-pin 36 and urge their associated plungers such as 22 into their inoperative positions.

Each dot-pin has a domed upper end as shown whereby when a dot-pin is urged upwardly by energisation of its associated winding the domed upper end in projecting above the display-plate 10 as shown for the dot-pin 27 simulates a braille dot.

It will be appreciated that when a ball is in its latching position, as shown for the ball 25, and the energising current is removed from its associated winding, the effect of the spring, such as 39, is to urge the plunger into firm contact with the latching ball which makes the latch secure and ensures the rolling action of the ball when the unlatching plate is slid to its unlatching position. Furthermore, to ensure that a ball, such as 25, when in its latching position is centralised with the end of its associated plunger the stroke of the plunger 23 is made long enough to ensure that the ball, held on the end of the plunger by magnetic attraction, enters the mouth of the former 30.When the energising current is removed the magnetic retentivity of the steel ball ensures that the ball remains in its central position as shown for the ball 25 when the plunger is urged back by the return spring 39 to its final operative and latched position.

The unlatching plate is preferably so springloaded as to be normally urged to the right in Fig. 2 into a normal or rest position ready for its unlatching function. It can be arranged to slide the unlatching plate manually when erasure is required or alternatively or in addition it can be actuated by a solenoid (not shown).

In one example of the embodiment shown in Figs. 1 and 2, the pitch of the dot-locations 14 and 19 is 0.1" and the cell pitch is 0.25".

The plungers are 0.041" in diameter and 0.66" long and of cold-drawn, soft iron. The latching balls are of 0.8 mm diameter and of noncorrodable steel. The formers for the windings are of extruded brass tube of 0.056" diameter and 0.807" long. The wall thickness of the brass tube is 0.010" which ensures a rigid assembly and good magnetic coupling between the windings and their associated plungers. With such an arrangement a pulse of energising current of about 10 m.s. has been found sufficient for reliable operation. Thus to set up a braille character in any one cell, the windings for that cell are selected and windings appropriate to the character to be set up in braille are then selected and windings appropriate to the character to be set up in braille are then selected and energised.

When using an arrangement as shown in Figs. 1 and 2 it has been found that a compact array of windings and plungers can lead to erratic operation by the effect of stray magnetic field from one winding linking with the plungers of adjacent windings. Two different ways of preventing such erratic operation have been successfully applied. In one of these a single-turn wrapping of high-permeability foil such as mu-metal is provided around each winding. The foil can be of about 0.005" in thickness whereby the cross-sectional area of the mu-metal is about the same as the cross-sectional area of the plunger In the other method each cell has four bars of highpermeability, soft iron located between the windings as shown in dotted lines in Fig. 1 at 40 and extending between the members 32 and 33.

It will be appreciated that the invention enables an electromechanical tactile braille display to be provided in a form sufficiently compact as to conform with the standard size of a braille cell.

The manner in which the solenoids of each cell are energized to provide braille display will depend upon the application concerned.

Referring now to Fig. 3 this is a diagram of an elementary circuit for controlling the solenoids in a row of the devices shown in Fig. 2. Normally there will be 48 in a row but for convenience in the drawing only three are shown at 11, 12 and 13 corresponding to 11, 12 and 13 in Fig. 1.

In Fig. 3 the positive pole of a battery 41 is connected through six spring loaded pushbutton switches into a selector switch 43.

Initially the selector switch 32 is so set as to connect the switches 42 to the six solenoid windings shown of the device 11. Thus a pattern of the windings in the device 11 can be energised from the battery 41 by transient depression of a corresponding pattern of the push-buttons 42 whereby a corresponding tactile display is set up and latched. The selector switch 43 is then operated to disconnect the push-button switches from the windings of the device 11 and to connect them to the windings of the device 12. The pushbuttons 42 are again transiently depressed in a required pattern to set up a corresponding tactile display with the device 12. This process is repeated for all 48 devices.

When all 48 devices have been set-up and read operation of a common unlatching member (not shown) erases the displays on all 48 devices simultaneously.

Although mechanical, manually-operated push-button and selector switches can be used as described, electronic switches will normally be employed.

WHAT WE CLAIM IS 1. Electromechanical apparatus suitable for setting-up and erasing alpha-numeric characters and other symbols in braille, comprising, an array of substantially parallel solenoid windings each with a plunger therein, each plunger having ferro-magnetic material along all or part of its length, so that it can be moved longitudinally from an inoperative position to an operative position upon energisation of its associated winding for setting up a character, the apparatus further comprising latching means associated with the plungers respectively for latching each plunger independently in its operative position upon energisation of its associated winding and for retaining the plunger in its operative position when the winding is no longer energised, each latching means comprising a rolling member which is retained in an unlatching position by the plunger in its inoperative position and which rolling member is movable to a latching position when the plunger is moved to its operative position upon energisation of its solenoid winding, the apparatus also comprising an unlatching member common to the several rolling members and upon which the rolling members sit and which is slidable laterally to the plungers to roll rolling members out from latching positions to unlatching positions to permit latched plungers to return to their inoperative positions and erase characters which have been set up.

2. Electromechanical apparatus as claim ed in claim 1, in which the plungers have springs which urge them against the rolling

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. plunger is urged back by the return spring 39 to its final operative and latched position. The unlatching plate is preferably so springloaded as to be normally urged to the right in Fig. 2 into a normal or rest position ready for its unlatching function. It can be arranged to slide the unlatching plate manually when erasure is required or alternatively or in addition it can be actuated by a solenoid (not shown). In one example of the embodiment shown in Figs. 1 and 2, the pitch of the dot-locations 14 and 19 is 0.1" and the cell pitch is 0.25". The plungers are 0.041" in diameter and 0.66" long and of cold-drawn, soft iron. The latching balls are of 0.8 mm diameter and of noncorrodable steel. The formers for the windings are of extruded brass tube of 0.056" diameter and 0.807" long. The wall thickness of the brass tube is 0.010" which ensures a rigid assembly and good magnetic coupling between the windings and their associated plungers. With such an arrangement a pulse of energising current of about 10 m.s. has been found sufficient for reliable operation. Thus to set up a braille character in any one cell, the windings for that cell are selected and windings appropriate to the character to be set up in braille are then selected and windings appropriate to the character to be set up in braille are then selected and energised. When using an arrangement as shown in Figs. 1 and 2 it has been found that a compact array of windings and plungers can lead to erratic operation by the effect of stray magnetic field from one winding linking with the plungers of adjacent windings. Two different ways of preventing such erratic operation have been successfully applied. In one of these a single-turn wrapping of high-permeability foil such as mu-metal is provided around each winding. The foil can be of about 0.005" in thickness whereby the cross-sectional area of the mu-metal is about the same as the cross-sectional area of the plunger In the other method each cell has four bars of highpermeability, soft iron located between the windings as shown in dotted lines in Fig. 1 at 40 and extending between the members 32 and 33. It will be appreciated that the invention enables an electromechanical tactile braille display to be provided in a form sufficiently compact as to conform with the standard size of a braille cell. The manner in which the solenoids of each cell are energized to provide braille display will depend upon the application concerned. Referring now to Fig. 3 this is a diagram of an elementary circuit for controlling the solenoids in a row of the devices shown in Fig. 2. Normally there will be 48 in a row but for convenience in the drawing only three are shown at 11, 12 and 13 corresponding to 11, 12 and 13 in Fig. 1. In Fig. 3 the positive pole of a battery 41 is connected through six spring loaded pushbutton switches into a selector switch 43. Initially the selector switch 32 is so set as to connect the switches 42 to the six solenoid windings shown of the device 11. Thus a pattern of the windings in the device 11 can be energised from the battery 41 by transient depression of a corresponding pattern of the push-buttons 42 whereby a corresponding tactile display is set up and latched. The selector switch 43 is then operated to disconnect the push-button switches from the windings of the device 11 and to connect them to the windings of the device 12. The pushbuttons 42 are again transiently depressed in a required pattern to set up a corresponding tactile display with the device 12. This process is repeated for all 48 devices. When all 48 devices have been set-up and read operation of a common unlatching member (not shown) erases the displays on all 48 devices simultaneously. Although mechanical, manually-operated push-button and selector switches can be used as described, electronic switches will normally be employed. WHAT WE CLAIM IS

1. Electromechanical apparatus suitable for setting-up and erasing alpha-numeric characters and other symbols in braille, comprising, an array of substantially parallel solenoid windings each with a plunger therein, each plunger having ferro-magnetic material along all or part of its length, so that it can be moved longitudinally from an inoperative position to an operative position upon energisation of its associated winding for setting up a character, the apparatus further comprising latching means associated with the plungers respectively for latching each plunger independently in its operative position upon energisation of its associated winding and for retaining the plunger in its operative position when the winding is no longer energised, each latching means comprising a rolling member which is retained in an unlatching position by the plunger in its inoperative position and which rolling member is movable to a latching position when the plunger is moved to its operative position upon energisation of its solenoid winding, the apparatus also comprising an unlatching member common to the several rolling members and upon which the rolling members sit and which is slidable laterally to the plungers to roll rolling members out from latching positions to unlatching positions to permit latched plungers to return to their inoperative positions and erase characters which have been set up.

2. Electromechanical apparatus as claim ed in claim 1, in which the plungers have springs which urge them against the rolling

members when the plungers are latched, and serve to restore the plungers to their inoperative positions when they are unlatched

3. Electromechanical apparatus as claimed in claim 2, in which the unlatching member is spring loaded to restore it to a first position following an unlatching operation in which it is moved to one side from the first position.

4. Electromechanical apparatus as claimed in claim 1, 2 or 3, in which the unlatching member is inclined at such an angle to the horizontal that the rolling members can be rolled into latching positions by the force of gravity to latch plungers in their operative positions.

5. Electromechanical apparatus as claimed in any of claims 1 to 4, in which each rolling member is made of ferro-magnetic material responsive to magnetic flux from the plunger with which it is associated so that upon energisation of the winding the rolling member is urged into a latching position by magnetic attraction.

6. Electromechanical apparatus as claimed in any of claims 1 to 5, in which symbols in braille are set up by means of a tactile display comprising a number of dot-pins which have a domed upper end to simulate a braille dot and are arranged to be moved by the plunger to project through holes in a plate when the plungers are in their operative positions and to have the tops of the domed ends flush with the plate when the plungers are in their inoperative positions.

7. Electromechanical apparatus as claimed in any of claims 1 to 6, in which the solenoid windings each have a high-permeability foil wrapped around them to reduce substantially the amount of magnetic flux from one winding linking with the plunger of another winding.

8. Electromechanical apparatus as claimed in any of claims 1 to 7, in which bars of high-permeability metal are arranged between and substantially parallel to the solenoid windings to reduce substantially the amount of magnetic flux from one winding linking with the plunger of another winding.

9. Electromechanical apparatus substantially as herein before described with reference to the accompanying drawings.