This invention relates to an improved information display apparatus, and more particularly to an improved design of an electromechanical dot-matrix display system. In the applicants British Patent No. 024124 there is described and claimed an information display apparatus for displaying changeable characters or images, comprising a frame in which are mounted a plurality of elements movable relative to the frame, each element having at least two contrasting display areas and an array activating means, characterised by micro-processor means for controlling said array of activating means, the array of activating means comprising an array of selectively energised electromagnets and an array of sensing elements corresponding to the activating means to detect the state of the display elements in advance of actuation to correct errors arising in the display, the frame of elements being traversed by the array of activating means and the frame of elements and the array of activating means being movable relative to one another such that selective energisation of the activating means

moves one or more of the movable elements to create a changeable display of information.

In this known display system a carriage is traversed along a track extending the length of the display in adjacent proximity to a matrix of flags (pixels) mounted along the length of the display. The flags are supported on a welded steel mesh so that the vertical mesh members form the spindles on which the flags can rotate while the horizontal mesh members provide the separation means to keep the rows of flags apart. The flags comprise two mouldings which interlock together. The two mouldings are of contrasting colours so that during operation of the display, information is presented in dot matrix form. The flags are rotated by the selective energisation of a column of electro-magnets mounted on the carriage.

This known system can be improved by providing a more accurate flatness to the mesh frame support for the flags and an improved assembly, assisting volume production.

One problem which has arisen with the known system is the stray of magnetic flux from one electromagnet, actuating a particular flag to an adjacent flag located immediately above and/or below that which it is intended to be actuated.

Another disadvantage is the circuit used to connect the carriage to the power supply, in that energy is wasted in carrying the wires along with the carriage when traversing the display frame. An aim of the improved display system is to overcome or mitigate the above described problems and disadvantage.

According to a first aspect of the present invention there is provided a display apparatus comprising a carriage adapted to be traversed along a track, extending the length of the display, in adjacent

proximity to a matrix of pixels rotatable on a supporting mesh framework, the carriage carrying an array of electromagnets which are selectively energised to actuate the pixels, wherein the electromagnets are staggered in an upright column and include castellated plates which prevent the magnetic flux from an energised electromagnet from actuating adjacent pixels of the matrix.

Preferably, the castellated plates are made from stainless steel. Conveniently, the pixels are rectangular flags which are made in two parts which are mated to rotate on the mesh framework, the opposite sides of each flag having contrasting colours.

According to a second aspect of the invention there is provided a display apparatus comprising a carriage adapted to be traversed along a track, extending the length of the display, in adjacent proximity to a matrix of pixel rotatable on a supporting mesh framework, the carriage carrying an array of electromagnets which are selectively energised to actuate the pixels, wherein the mesh framework is made up of a plurality of cross members held in a spaced relationship by a plurality of rods engaging the cross members.

Conveniently the cross members are moulded plastics rectangular strips with spaced holes for receiving steel rods.

According to a third aspect of the invention there is provided a display apparatus comprising a carriage adapted to be traversed along a track, extending the length of the display in adjacent proximity to a matrix of pixels rotatable on a supporting mesh framework, the carriage carrying an array of electromagnets which are selectively energised to actuate the pixels, wherein the carriage carries a motor and power supply to engage a drive belt to traverse the carriage to and fro along the length of the display track.

Conveniently the power supply has an electrical connection on the carriage which docks and forms an electrical connection with a power supply to re-charge the power supply unit on the carriage. ⁵ in the preferred construction the docking is achieved by a jack plug engaging and forming an electrical connection with an electrical socket.

Embodiments of the present invention will now be described, by way of example only, with reference to the ° accompanying drawings, in which:

Fig. 1 is a fragmentary front elevational view of the electromagnets and castellated shielding plates;

Fig. 2 is a cross-section taken along the line II- II of Fig. 1;

Fig. 3 is a fragmentary elevation of an improved supporting mesh frame;

Fig. 4 is a plan of the mesh frame shown in Fig. 3; Fig. 5 is a diagrammatic rear elevation of the improved carriage; and Fig. 6 is a side view of Fig. 5.

The display apparatus includes an array of staggered electromagnets 1 which are arranged vertically on a carriage generally indicated at 2 (see Figs. 5 and 6) . In between the carriage 2 and a mesh frame 3 are a 5 pair of stainless steel metal shields 4 which have a castellated form, the electromagnets 1 being located in the recesses formed by the castellations.

The mesh frame 3 supports rotatable pixels in the form of flags 5 which have two contrasting coloured 0 faces. As the carriage traverses along the tracks 6 the electromagnets are selectively energised to rotate a respective row of flags 5 to display one or other of its contrasting faces.

It has hitherto been the experience that stray 5 magnetic flux from an energised electromagnet can often

actuate a flag immediately above and/or below that which it is intended to be actuated. To overcome this the pair of castellated shields 4 are located between the electromagnets 1 and the flags 5 as shown in Fig. 2. Located behind the shields 4 is a strip of soft foam 7 to control the rotation of the actuated flag.

Turning now to the improved supporting mesh frame shown in Figs. 3 and 4, the frame, generally indicated at 8 comprises a plurality of moulded rectangular plastics strips 9 which have a series of spaced holes 10. The strips 9 are joined by a series of metal rods 11 which fit with a friction fit in the holes 10 to form a mesh support for the flags 5, one of which is shown, to rotate about the rod 11. An improved carriage 2 is shown in Figs. 5 and 6 which is mounted to traverse along the tracks 6 by wheels 12 mounted one at each corner of the carriage. The carriage is driven from a power supply in the form of a rechargeable battery pack 13 mounted on the rear of the carriage 2.

The power from the battery 13 drives a motor 14 which in turn drives a toothed pulley 15 around which is threaded an endless toothed belt 16. The belt is maintained in driving contact with the pulley 15 by control pulleys 17, see the scrap view at the top of Fig. 5. By mounting the power supply on the carriage this eliminates the need for power supply cables to be attached from a fixed supply to the carriage which uses up energy to transport the cable back and forth along the display.

A further improvements to the carriage drive is to provide a jack plug 18 connected to a fixed power supply (not shown) which plug engages a socket 19 connected with the rechargeable battery pack 13 so that when the carriage 2 reaches the end of the track 6 it docks with the jack plug 18 and the power pack 13 is recharged.

Communication can be effected by means of an infrared link 22 comprising an infrared receiver/transmitter mounted on the carriage and a similar infrared transmitter/receiver mounted on the apparatus main frame so that communication is made between the carriage and the main frame whenever the carriage happens to be located along the display.

Various other modifications may be made to the invention, for example, the free ends of the electromagnet armatures may be angled as shown in Fig. 2 to provide a reduced air gap 20 between the flag 5 and armature 21 of the electromagnet to increase the effective power exerted by the electromagnet.