Display indicator and reed switch

The present invention relates to a display device with a movable element. The movable element is driven between ON and OFF positions by switching the polarity of a first high remanence magnetic core. A reed switch is located in the flux path of the switchable magnetic core and of a second magnetic core such that the reed switch assumes open and closed states. The reed switch is connected so that one state turns on or exposes a light source and the other state turns off or masks the light source.

This invention relates to a display element designed to provide a bright or 
dark appearance either as a single element or as a pixel in an array, 
using a reed switch, and also relates to a reed switch control 
arrangement. 
The display elements with which the invention is concerned have a movable 
element movable relative to a stationary element between ON and OFF 
positions and in these positions to provide a bright area or a dark area, 
respectively, visible in the viewing direction. A permanent magnet is 
provided movable with the movable element. A switchable magnetic core is 
provided on the stationary element located and adapted in one and the 
other polarity to cooperate with the permanent magnet to move the movable 
element to ON and OFF position, respectively. Preferably the core is of a 
high remanence material surrounded by an energizing winding which may be 
pulsed by an energizing current to switch the core polarity in an interval 
much less than the interval for the movable element to move between ON and 
OFF position. 
Display devices as described above are well known to those skilled in the 
art and patents thereto include: 
U.S. Pat. No. 4,860,470 to John Browne, dated Aug. 29, 1989, Assigned to 
NEI Canada Limited 
U.S. Pat. No. 4,744,163 to John Browne et al, dated Jul. 17, 1988, Assigned 
to NEI Canada Limited 
U.S. Pat. No. 4,566,210 to Donald Winrow et al, dated Jan. 28, 1986, 
Assigned to NEI Canada Limited 
U.S. Pat. No. 4,426,799 to Donald Winrow dated Jan. 24, 1984, Assigned to 
NEI Canada Limited 
In some aspects this invention is particularly concerned with display 
elements as above defined where the display of the bright area in the 
viewing direction in the ON position is augmented by a luminous source 
such as a light emitting diode (`LED`) or an optic fibre and where such 
source must be turned off or masked from the viewer in the OFF position. 
An example of such display element using an optic fibre is 
U.S. Pat. No. 4,833,806 to Jacques L. Gars, dated May 30, 1989, Assigned to 
Societe D'Etudes Pour Le Devoloppment 
It is useful to note that such light-augmented element is particularly 
useful with `writable` highway signs which are adapted to be read from 
some distance. Such signs will be formed of an array of display elements 
acting as pixels individually selectively switchable to display light or 
dark areas collectively providing information to the motorist. With such 
signs it is frequently desirable that the luminous source be focussed to a 
beam about the viewing direction narrower than the viewing cone of the 
element as a whole to attract the driver's attention so that he, then, 
looks at the display as a whole, obtaining the information it displays 
from the collective effect of both its bright areas and dark areas with 
the bright areas augmented by the luminous sources in each pixel. 
It is an object of one aspect of the invention to provide a display element 
with electromagnetic drive where a reed switch (having open and closed 
states) is arranged to be switched by the stationary member core: 
(a) to a state to illuminate or expose the light source to the viewer; or 
(b) to a state to turn off or mask the light source from the viewer. 
Thus the display element which is light-augmented in its ON position, 
defines a viewing cone centered about a viewing direction which viewing 
cone may have an apex angle larger than 90.degree. and where within the 
cone there is a smaller focussed light beam cone when the element is ON 
with an apex angle of about 15.degree. within the viewing cone. 
It is an object of the invention in the aspect discussed in the previous 
paragraph to provide a reed switch located to be influenced by both the 
stationary element switchable core (sometimes referred to as the `first 
core`) and by a high remanence second core. The first and second cores are 
approximately parallel and located and adapted so that when both cores 
have similar polarity the collective return flux of the two cores causes 
the switch to assume one state and when the two cores have opposite 
polarities causes the switch to assume the other state. The switch is 
connected so that one state turns on or exposes the light source and the 
other state turns off or masks the light source. There is thus provided a 
light augmented display element with ON and OFF states where the control 
of the light augmentator is more convenient than with prior arrangements. 
For example in U.S. Pat. No. 4,833,806 the masking of the light source 
(there an optic fibre) requires either 180.degree. rotation of the disk or 
the presence of a special masking addition to the disk. The 180.degree. 
rotation reduces the strength of the magnetic drive while the masking 
addition adds to the cost of the disk. In comparison the reed switch 
controlled by the switchable core provides a easy control for switching on 
and off a light source such as an incandescent lamp or LED. In the case of 
a glass fibre, the reed switch may be connected to operate a shutter in 
the optic path, which includes the fibre, or, if the fibre has an 
individual light source may switch on and off that source like the lamp or 
LED in the previous example. 
The reed switch controlled by the switchable core may be used for other 
purposes than control of the light source or light path. For example the 
reed-switched line may be used to signal the magnetic core state back to a 
scanner or control. The controlled reed switch could be used for other 
purposes, such as driving a slave display, of the same or different type. 
In drawings which illustrates a preferred embodiment of the invention: 
FIG. 1 is a perspective view of a display element in accord with the 
invention; 
FIG. 2 is an exploded view of the device of FIG. 1, 
FIG. 3 is a side view, partly in section, of the device of FIG. 1, in ON 
position, 
FIG. 4 is a side view, partly in section, of the device of FIG. 3 in the 
OFF position, 
FIG. 5 is a schematic view of an array erected over a highway, 
FIG. 6 is a partial view of the front of the array of FIG. 5, 
FIG. 7 shows a circuit including the reed switch and an LED bank, 
FIG. 8 and 9 schematically indicate the magnetic fields with the reed 
switch off and on respectively, 
FIG. 10 schematically indicates the magnetic fields where the switchable 
core is combined with two reed switches,

In the drawings it is proposed to describe the more conventional portions 
followed by the less conventional. The display element shown in FIGS. 1-4 
may be either a single status element or part of an array of the type 
shown in FIG. 6. 
FIG. 1 shows a base plate 12 supporting opposed standards 14A, 14B slotted 
at the outer end of the standard to mount the shaft 16 of a display disk 
18. 
The display disk 18 has a circular frame 20 which mounts a circle of 
resilient plastic material 22 as shown. The resilient plastic material 22 
is brightly colored on one side 22A to be displayed in the viewing 
direction in the ON position (FIG. 3) where it contrasts with the 
background. The resilient plastic material 22 is dark on the other side 
22B to match the background, (and the rim of the disk) so that the area to 
the viewer is bright in the ON position and is dark in the OFF position. 
(The resilient plastic 22 is omitted in FIG. 2). 
The display disk is pivotted to rotate on shaft 16 between stop 24 mounted 
on standard 14B, which stops the rotation of the disk at the ON position 
FIG. 3 (displaying the bright face of the disk in the viewing direction V) 
and the pillar 26 to be described hereafter used stops the disk in the OFF 
position (FIG. 4). It will be noted that in the OFF position the viewer 
sees the dark edge of the disk and the dark background of the element 
where the bright disk side was in ON position. 
Rotatable with the disk 18 on shaft 16 is a cylindrical permanent magnet 28 
magnetized along a diameter as shown in FIGS. 3 and 4. 
Core 30 of preferably high remanence magnetic material preferably of 
extended straight form is mounted on standard 14B to project therefrom in 
the viewing direction and to provide its outer pole 32 in the vicinity of 
the locus of permanent magnet 28. The core pole 32 is positioned relative 
to the magnetic axis of the permanent magnet 28 and the stops 24 and 26 to 
cause the disk to alternate between ON and OFF positions on each switch of 
polarity of pole 32. Energizing coil 34 surrounds core to provide from a 
source not shown, the energizing current to switch the core polarity. 
Preferably the core 30 is of the `hard` or high remanence type so that the 
switching of the core may be performed by a very short pulse of energizing 
current in an interval much shorter than required for the element to 
mechanically move between ON and OFF position. 
The magnetic torque to complete the mechanical movement and to hold the 
element in place afterward is provided by the remanent flux of the 
magnetic core, 30. The switched polarities of pole 32 are indicated as N`, 
S`. 
The element switched as described may be used alone or as part of the array 
of FIG. 6 as so far described operates in accord with design and operating 
principles well known before this development. 
In accordance with the invention the bright side of the disk is augmented 
in the disk's ON position by the presence of a light source `on` or 
illuminated in the ON position and `off` in the OFF position under the 
control of a reed switch to be described. 
In the preferred embodiment the disk is provided with a round aperture 40 
displaced from the disk axis and a bank of seven LED's 42 is provided to 
shine through the aperture 40 in the ON position of the disk. The LED bank 
is supported on the outer end of pillar 26. The LEDs are preferably 
provided with focussing lenses so that their rays shine principally in a 
cone of 15.degree. apex centred on viewing direction V. In FIG. 2 there is 
indicated in dotted form a cylindrical side wall or shroud which is 
preferably provided above the LED bank to limit side radiation or 
reflection. The side wall is not shown in the remaining Figures to allow 
better display of the remaining elements. 
A reed switch 44 well known to those skilled in the art is supported on the 
base parallel and adjacent to the switchable core 30. The reed switch is 
designed to be closed when there is a sufficient flux field with a 
component along the longitudinal axis of the reed switch and open when 
such field is insufficient. This reed switch is normally open. A normally 
closed reed switch could be used although, in the preferred operating 
arrangement it might render the circuit more complex. 
A second longitudinally extending core 46 is located parallel to the 
longitudinal axis reed switch 44 about equally spaced from the reed switch 
as core 30 and on the opposite side therefrom. The second core has 
preferably approximately the same remanance as core 30. 
The second core is not switched but has a permanent polarization as shown. 
The reed switch 44 is connected in series with the bank of LEDs as 
schematically shown in FIG. 7 but the LEDs could be connected in parallel 
with each other as determined by the supply voltage. With the circuit of 
FIG. 7, a resistor 43 is provided in series with the LED's to limit 
current to the LED's. When the reed switch is closed and open, the LED's 
are on and off respectively. The mode of operation of the reed switch is 
as demonstrated in FIGS. 8 and 9. 
In FIG. 9 switchable core 30 has been switched to make pole 32, south (S') 
drive the display element to ON position as shown in FIG. 3. The polarity 
of the second core 46 is chosen so that with the switchable core 30 in ON 
magnetization both cores have the same polarity as shown in FIG. 9. As 
shown schematically in FIG. 9 some of the return flux of the two cores is 
combined along the length of the reed switch and the location and 
remanence of the cores is chosen so that the combined flux along such 
length closes the reed switch illuminating the LED bank which augments the 
bright side of the disk to a viewer in the viewing direction. 
When it is desired that the disk be in OFF orientation the first core 30 is 
switched to make pole 32 north N' (FIG. 8). Since the first and second 
cores are now of opposite polarity each core acts as a preferred path for 
a high proportion of the other's return flux. The magnetic parameters and 
the reed switch are selected so that the flux along the reed switch is 
insufficient to close it so that it opens, extinguishing the LED bank. 
Thus the viewer on the highway sees a dark area of the disk (where the 
bright area would be in `ON` state), being the dark background, the edge 
of the disk and the `off` LED's, a dark pixel in the array shown 
schematically in FIG. 6. 
In highway applications the LED's will customarily be provided with lenses, 
focussing the bright in a beam preferably 15.degree. on the highway at a 
described distance from the sign. On the other hand the viewing angle for 
the bright disk sides and the counterpart dark pixels will be much wider 
usually &gt;90.degree.. Thus with the array showing `S` as indicated in the 
5.times.7 pixel array of FIG. 6, the LED's of the ON pixels rivet the 
motorist's attention at an early stage of his approach so he is alerted to 
read the message of the array created by the joint effect of the bright 
disk sides and the LED's in contrast to the dark pixels. 
The light source may alternatively be incandescent or optic fibres. The 
incandescent light may be switched on and off by the reed switch just as 
are the LED's. The light supply of the optic fibre for each pixel may also 
be switched on and off if there is a separate light for each pixel fibre. 
If there is one light for all fibres in the array the reed switch would be 
connected to operate a shutter to interrupt the corresponding optic fibre 
path. 
The first and second cores are shown oppositely disposed relative to the 
reed switch. Magnetic parameters can be selected so that these cores may 
be nearer to each other say at the corners (with the reed switch) of a 
equilateral triangle. Obviously the second core must be located far enough 
from the locus of the permanent magnet so that the second core does not 
affect the magnet's drive. 
The first and second cores may be different distances from the reed switch 
(and of different remanence) as long as their locations are selected so 
that the flux places the reed switch in a state determined by the polarity 
of the first core. 
The first and second cores need not be precisely parallel but compactness 
and ease of calculation of parameters will usually be improved if the two 
cores are approximately parallel. 
The reed switch need not be precisely parallel to the two cores but the 
usual mode of operation of the reed switch requires that the cores provide 
return flux paths with a substantial component in the direction of the 
longitudinal axis of the reed switch. 
The reed switch may if desired be of the type which opens for flux values 
above a pre-determined value and closes below such value. However, this 
will complicate the switching control for the light source in the 
arrangement of the preferred embodiment. 
The reed switch may be used for other functions than the switching of the 
illumination. For example the reed switch, controlled as above described 
may be used to signal the magnetic status of the first core to a control 
or supervisory device. 
FIG. 10 shows that more than one reed switch may be controlled by the same 
switchable core 30. A normally open reed switch 44 is located on each side 
of the switchable core. Two permanent polarity cores 46 (`second` and 
`third` cores) are located each on the opposite side of a reed switch from 
the switchable core. The two permanent polarity cores are polarized in 
opposite directions as shown. At any time the combination of the return 
flux of the switchable core with the respective second and third cores 
will produce closed and an open state reed switches. These states will be 
reversed when the switchable core 30 is switched to the opposite polarity.