Display apparatus

A display apparatus has an interchangeable cassette including a first static image-bearing slatted panel and at least two further movable image-bearing slatted panels, movable relative to the static panel and interleaved therewith. The panels form part of the cassette in which any of the panels can be selectively removed and replaced. Additionally, the display apparatus includes a frame for receiving the cassette. The frame includes a drive system for selectively moving the movable panels to enable the slats on each of the movable panels to move from a position behind the slats of the static panel, to a position in front of the slats of the static panel, thereby enabling an image on the panels to be viewed.

BACKGROUND OF THE INVENTION 
This invention relates to a display apparatus. In particular, it relates to 
a display apparatus capable of sequentially displaying a plurality of 
static images, such as advertising images. 
Display apparatus of this type is extensively used in advertising, 
especially at the point of sale or on billboards for example. A typical 
prior art example of an advertising medium capable of presenting more than 
one image sequentially comprises an array of elongate elements which are 
triangular in cross-section. Parts of the whole image are provided on each 
of the elongate faces so that when one set of these face outward a viewer 
can see an entire image disposed across all the faces. After a time 
period, each of the element rotates about its longitudinal axis to bring 
another face forward to view a second image. Such a system therefore 
enables three different images to be viewed, each for a predetermined 
period of time. 
Such devices are, however, bulky and have a large depth because of the 
depth required by the triangular section pieces. Also, since 
advertisements are changed and updated regularly, it can be difficult to 
change an advertisement since this requires altering the image on each of 
the three faces on each of the triangular pieces. This can be very time 
consuming where a large number of triangular pieces are provided to form 
each image. For example, twenty separate triangular pieces may be laid 
continuously to form a single image. 
Attempts have been made to reduce the complexity of such devices and to 
overcome the complexity of rotating members by using planar sheets. 
Examples of these are shown in U.S. Pat. Nos. 2,141,393, 3,403,465, 
3,421,240 and 3,659,367. Each of these relates to a changeable display 
structure comprising a plurality of slatted sheets which are interleaved 
such that relative sliding movement causes images to be selectively 
exposed to view. Often, as in U.S. Pat. Nos. 2,141,398 and 3,659,367 these 
devices are intended for manual manipulation and are therefore of limited 
use. Attempts to drive the sheets, by means such as motors, have often 
tended to complicate their structure, as in U.S. Pat. No. 3,421,240. Also, 
in prior art devices it has generally been difficult or time consuming to 
change messages. Training, and therefore skilled personnel, is often 
required to change the messages displayed. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an improved display means 
which enables the messages displayed to be easily and simply changed by 
unskilled personnel in a short amount of time. 
According to the present invention there is provided a display apparatus 
comprising an interchangeable cassette including a first static 
image-bearing slatted panel, at least two further image-bearing slatted 
panels, each movable relative to the first slatted panel and interleaved 
therewith, the three or more slatted sheets forming part of a cassette in 
which any of the sheets can be selectively removed and replaced, and a 
frame for receiving the cassette comprising a drive means having means for 
selectively moving the sheets other than the first one to enable the slats 
on each of the movable sheets to move from a position behind the slats of 
the first sheet, to a position in front of the slats of the first sheet, 
to thereby enable the image on the sheet to be viewed. 
Preferably the frame includes the drive means on a rear portion thereof. A 
front frame portion may be provided which can detachably connect to the 
cassette to detachably secure the cassette within the frame. The cassette 
may alternatively or in addition be located by one or more pins and 
cooperating locating holes and sockets on the frame and cassette. 
Preferably, the drive means comprises a plurality of pins driven by means 
such as solenoids and the moveable sneers comprise holes and slots, the 
holes in one sheet being in register with the slots of other sheets such 
that each pin can enter a hole in one sheet only to move only that sheet, 
the pin moving within the slots of the other sheets so that these sheets 
are not moved by that pin. 
The drive means may also be operated and controlled remotely. The device 
may be used as a trilingual (or more) directional sign for example. 
According to the present invention there is further provided a removable 
cassette for a display apparatus, comprising a front panel, a rear panel, 
a static image-bearing slatted panel and at least one image-bearing 
slatted panel, movable with respect to the static panel and interleaved 
therewith, the image-bearing panels being sandwiched between the front and 
rear panels.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the Figures, a display apparatus comprises a frame having a 
rear panel and a front panel. A removable exchangeable cassette can be 
placed within the frame, which cassette comprises means for displaying a 
respective series of images. These may be advertising images and the 
apparatus may be placed at a point of sale for example. 
An interchangeable cassette comprises a rear panel 50 (FIG. 2), three or 
more image bearing panels (of which four are shown in FIGS. 3 to 6) and a 
front panel 23 (FIG. 1) bearing a window 22 through which respective 
images of the image panels may be seen. 
The image bearing panels comprise a first static panel shown in FIG. 3. 
This panel 1 is formed from a thin sheet of a material such as a plastic, 
paper or board material which is cut to form a plurality of parallel slats 
2. An image is formed across the slats so that when viewed from the front 
the image appears to be complete. In FIG. 1, the image is a large 0 
(zero). More typically, the image would of course be advertising or other 
material. The shaded area of the image plates shows the area of the plate 
viewed through the window of the front plate. In this example, twenty 
slatted portions are provided. Six through-holes 3 are formed in the upper 
and lower parts of the sheet, which act as locating holes for fitting over 
pins on the back panel of the cassette. A plurality of slots 4 are also 
provided at each end of the sheet. The number of slots is dependent on the 
number of images which are to be portrayed by the cassette. In the example 
shown, four images are portrayed and therefore three slots are provided at 
each end. If more than three are to be portrayed, say n images, then n-1 
slots will need to be provided at each end of sheet 1. Alternatively, only 
two or more movable sheets may be provided. 
FIGS. 4 to 6 show second, third and fourth sheets, respectively forming 
part of the cassette bearing images 1, 2 and 3, respectively. These are 
movable sheets which slide relative to static sheet 1 to present their 
respective images in front of the image shown by sheet 1. Each of the 
movable sheets has a plurality (for example twenty) of slatted portions 
7.sub.1, 7.sub.2, 7.sub.3. These are each formed by making a plurality of 
cuts 9 parallel to the sides of the sheets and further cuts 10, 11 from 
the top and bottom of each cut 9. Each movable panel comprises through 
holes 14, 14, 15, 15, 8, 8 at each edge for receiving a driving pin to 
move the respective sheet back and forth with respect to static sheet 1. 
One or two slots 16 are also provided at each end of each panel, the slots 
of one panel being positioned so that when the sheets are laid over one 
another a slot from one sheet lays substantially over the whole of a 
second panel and vice-versa so that the pin which is received in, say, 
hole 14 of the first panel moves within the slot 16 of the second and 
third panels so that when this pin is actuated only the first panel 5 and 
not the other panels move. Similar holes and slots are formed in the other 
respective side of each panel. 
Clearly, if more or less than three movable panels are provided then there 
will need to be an increased or decreased number of slots in each panel to 
accommodate the additional or lesser number of pins necessary. 
Further locating slots 18 are provided towards the top and bottom of each 
of the movable panels through which the locating pins which locate into 
holes 3 in sheet 1 can protrude. The slots also limit lateral movement, 
ensuring that the slats remain engaged and do not separate through 
over-travel. Clearly, in the movable panels these must be slots rather 
than holes since the panels are movable and space must therefore be 
allowed for relative movement of the panel and pin. An additional cassette 
location hole is shown at 19 in each of FIGS. 1 to 6. In the front, rear 
and static image panels this is a hole while in the movable panels it is 
of course a slot 
FIG. 7 shows schematically the interconnection of static panel 1 and the 
movable panels. In this figure, a number of adjacent slats of each panel 
are shown. As is shown in the figure, the slats of layer 0 lie at such an 
angle to each other that the slats of layers 1, 2 and 3 can lie between 
adjacent slats of layer 0. Layer 1, 2 and 3 are then slidably moved back 
and forth with respect to layer 0 to bring the image on, respectively, 
layer 1, layer 2 or layer 3 in front of the image of layer 1 to display 
that image. Layer 1 is mounted underlying layer 0, layer 2 underlies layer 
1 and layer 3 underlies layer 2. Clearly, if an additional movable panel 
is to be provided, then the slat angles will need to be greater to 
accommodate the extra depth required between adjacent slats. Alternative, 
less movable panels will need a smaller angle. More than three movable 
panels may be provided, but the angles of the slats start to become so 
large that the image becomes distorted. To minimize this effect, the 
panels are of a thin material in proportion to the size of the graphics 
being displayed. Also, distortion effects may be overcome by increasing 
the slat width, thus reducing the layering angle effect. 
The sheets forming the image panels are preferably of a flexible material, 
and may for example be paper encapsulated in a plastic (e.g. 
polypropylene) layer. Polypropylene has a low co-efficient of friction, 
this aids the sliding movement of the panels. Other plastic materials may 
be used. This may, e.g., be heat shrunk onto the paper. The sheets may be, 
for example about 200-250 .mu.m in thickness. The sheets are therefore too 
thin to have inherent mechanical stability. The stability of the slatted 
material is achieved in the present invention by the sandwiching effect 
between the front and back panels of the cassette, enabling the moving 
panels to slide and preventing them from twisting and becoming disengaged. 
The front and back panels are therefore of a rigid or relatively rigid 
material. 
To ensure that the slats do not stick or become disengaged when slid 
backwards and forwards, a degree of overlap is required as shown at 20. 
The slats of layers 1, 2 and 3 overlap the respective slats of layer 0 by 
around 5% of their width. Although this does mean that 5% of the image 
displayed by panel 1 will be obscured, in practice this is insignificant 
and the overall image quality is not unduly visibly deteriorated. Also, it 
is desirable to displace the movable panels by different amounts. Thus, 
layer 7 is displaced by, say, 5% of its slat width less than layers 2 and 
3 from its obscured to its visible position. This is shown at 21 which 
shows the maximum position to which the two panels move. For example, 
Layer 1 may move by 18 mm each stroke, while layers 2 and 3 move by 19 mm. 
FIG. 8 shows schematically the sequence in which the panels are moved. The 
figure shows two adjacent interleaved slats of 4 panels. At a first point 
in time the slats of the movable layers 1, 2 and 3 are obscured behind the 
slats of static layer 0. Thus, the image on layer 0 is viewed. 
Movable panel 1 then moves in front of layer 0. Layer 2 is then moved 
behind layer 1 (step 3). After layer 1 has been viewed for a predetermined 
time it is retracted (step 4) revealing layer 2. Layer 3 is then moved 
behind layer 2 (step 5). After layer 2 has been viewed for a selected 
time, it is retracted (step 6), revealing layer 3. Finally, again after a 
selected time internal layer 3 is retracted and step 1 is reached again. 
The cycle then repeats. 
It is found desirable to move layers into position while the image on the 
previous layer is still being viewed to ensure the smoothest possible 
changeover and to even out the distribution of power consumption. This 
reduces the load on the solenoid or other drive-motors caused by excessive 
power at start-up. 
Preferably, the timing is programmable so that the time for which the image 
on layers 0, 1, 2 and 3 are viewed may differ between each panel. This 
could be useful if one of the panels bears a message containing a lot of 
text for example which takes more time to read and to absorb than the 
other images. Also by making a very quick transition between two or more 
of the images, a degree of animation can be achieved. This has the 
advantage of attracting a potential viewer, as sensations of movement are 
sensed by central or peripheral vision, drawing the viewer to the display. 
FIG. 1 shows the front panel 23 of the cassette which incorporates the 
image panels. The front panel comprises window 22 through which the 
respective images can be viewed. The window may be of optically polished 
glass, or a transparent plastic material for example. The frame may be of 
polycarbonate. The front panel 23 also includes slots 24 at each side, 
corresponding with the slots such as 16 and through which the driving pins 
may move. Frame 23 may also include a peripheral locating flange 25 for 
locating the image panels, as does rear panel 50. 
Thus, in use, an interchangeable cassette comprises a rear panel, the four 
interleaved slatted flexible layer 0 to 3 and a front panel. The front and 
rear panels are spaced apart by pins such as 51 extending from the rear 
panel, through holes or slots 18 in the flexible panels and into 
corresponding blind holes 52 in the front panel. 
As shown in FIG. 9, the display cassette (including the rear panel 50, the 
flexible, slatted image display panels and the front window frame 23) are 
sandwiched in use between a rear drive panel 30 and a front frame portion 
31. Driving pins such as pins 32,33 on the drive unit 30 locate into holes 
14, 15 and 8 and through the slots on the remaining panels of the cassette 
to enable the driven panels to be so driven. The cassette is also located 
by location pins protruding from rear drive and 30 through hole 19. Thus, 
it is an easy matter to remove and replace a cassette. The front and back 
panels may be hinged together so that the front hingeably opens to insert 
or remove a cassette. Other configurations may be used. 
FIG. 10(a) shows a drive mechanism. 
Driving is achieved by respective pins 32, 33, 34, 132, 133, 134 which act 
upon holes 14, 15 and 8 in lines 1, 2 and 3 to move these layers 
sidewardly. Each pair of pins acts upon a particular layer to move this 
layer relatively to the other layer. Each associated pair of pins, e.g. 32 
and 132 is powered by a drive means connected to two magnetically latched 
solenoids 38 and 39. Other types of drive means may of course be used. Pin 
32 is connected by a rod to solenoid 38 and pin 132 is connected by a rod 
to solenoid 39. The drives from the solenoid are linked to thereby connect 
pins 32 and 132 together to thereby shift the pins together. The mechanism 
of the solenoids is described further below. When solenoid 33 drives rod 
37 to the left in the figure then 32 moves its respective flexible image 
layer leftwardly. Rod 40 is also drawn to the left and thereby pin 132 
also moves leftwardly. When solenoid 39 is actuated it drives rod 40 and 
thereby pin 132 to the right and brings with it rod 37 and pine 32. 
Similarly, pins 33, 133 and pins 34, 134 are driven by respective solenoid 
pairs at different times determined by a timing circuit to move the other 
layers. Timing circuits are well known and will not be described further. 
In an alternative embodiment, the solenoids may be remote from the 
apparatus and connected by, for example, a cable. 
Each of the rods such as 37 and 40 are guided by a plurality of rollers 41. 
The movement of the respective pins is limited by springs 42 and plates 43 
to ensure that their movement stops before the end of a rod hits the end 
of the solenoid, to reduce noise and avoid the clunk that would otherwise 
occur as the rod hits the back of the solenoid at speed. Furthermore, 
dampers are preferably provided (as shown in FIG. 10(c) and in more detail 
in FIG. 11). Additionally, a protrusion 44 on each one of the respective 
rods is connected to a fixed point 45 by a spring 46. Thus, the spring 
connected to each of an opposing pair of rods, such as rods 37 and 40 
oppose one another. These springs act as counterbalances when the cassette 
is used in portrait mode to counter gravitational forces. 
FIG. 10(c) shows a side view of FIG. 10(a) to illustrate the driving 
mechanism in a little more detail and FIG. 10(b) shows a front view. 
Referring to FIG. 10(b) an embodiment is shown in which a front panel of 
the apparatus 31 is connected to back panel 30 by a hinge 50. A cassette 
53 is shown in dashed lines as partially emerging from the frame. In order 
to assist in detaching the cassette when the assembly is opened, a 
cassette detaching member 151 as shown in FIG. 10(a) is at a portion which 
extends under the cassette assembly and an enlarged end portion, having 
apertures to accommodate the driving pins and which rests underneath the 
top part of the assembly 31 at a position where this extends beyond the 
extent of the cassette. The member is hinged 151 and biased so that as top 
part 31 is lifted upwards member 151 moves from its base position shown in 
solid lines in FIG. 10(b) to its upper position shown in dashed lines. 
This in turn pushes upon the cassette 53 and causes it to disengage from 
the pins and to be pushed up a sufficient distance so that it can easily 
be manually removed. Member 151 also therefore acts to protect the driving 
pins when a cassette is removed. A mechanism 151 is preferably present at 
each end of the assembly to protect both sets of pins. 
FIG. 11 shows an enlarged part of FIG. 10(c). The magnetically latched 
solenoid assembly for each rod comprises a solenoid 160 and a permanent 
magnetic 161. The rod 40 extends through permanent magnetic 161 and coil 
160. The situation shown in FIG. 11 is when the right hand solenoid is 
energized to move rod 40 to the right. Since the other solenoid 38 is 
deenergised, the rod on this side is pulled to the right by a combination 
of the magnetic field of permanent magnetic 161 and the force of solenoid 
39, together with the various spring forces. Thus, the stop 43 associated 
with solenoid 38 is abutted against permanent magnetic 161 in the figure 
and the spring 42 is not seen since this is surrounded by stop 43. The 
rods 37 and 40 are connected through a damper 43. This damps the ends of 
the movement to ensure that the movements, although swift, are smooth and 
that there is not a sudden jolt at the end of each rods movement. These 
dampers are similar to those which might be used on, for example, motor 
drives of video cassette players. Essentially, an oil damped cam 162 is 
constrained to move between two transverse limiting rods 163 and 164, the 
cam being acted upon by the ends of rods 37 and 40 and transmitting motion 
between them. The rods are spaced apart to give the required stroke for 
each image plate, e.g. 18 or 19 mm. A separate damper is used for each 
pair of associated rods. FIG. 11 shows, mounted underneath the solenoids 
and damper assembly, a printed circuit board 165 bearing the circuitry for 
the system. 
It will be appreciated that the mechanism may either be used horizontally 
(landscape mode), as shown, or may be used vertically (portrait mode) so 
that the rods and pins move in a generally vertical direction. The springs 
46 then act as counterbalances. 
A secondary display may be driven through an electronic signal between the 
master display and the secondary, slave, display. Thus, a secondary slave 
display may be driven in an alternating sequence so that two, or indeed 
more, displays may be placed adjacent to each other, back to back or at 
right angles for example to provide a series of images displayed side by 
side or adjacently. 
The solenoids are actuated by a programmable controller timer, typically a 
programmable integrated circuit, such as a microprocessor, which can 
actuate each solenoid independently to control the time at which each 
panel is moved backwards and then forwards. In one embodiment, the timing 
may be actuated by two adjacent micro switches or other switching devices. 
These are shown at 166 in FIG. 10(a). A combination of different timing 
selections can be made corresponding to which micro switches is actuated. 
Each layer of the cassette, except one layer (typically the static image 
layer), is then provided with two holes or slots in register with the 
switches through which the microswitches can protrude. The remaining layer 
(e.g. the static layer) is used to `program` the microswitch circuit by 
either having one, two or no holes 167 (FIG. 3). If two holes are present 
in this layer then no microswitch is set. If one hole is present then a 
respective corresponding microswitch is set and if two holes are present 
then both microswitches are set. Timing programs can be pre-programmed 
which are different for each combination. Thus, a cassette can be 
pre-programmed to be associated with a certain timing program. A second 
cassette might be associated with a different timing program and insertion 
of that cassette automatically sets up the timing program. This has a 
significant advantage that each cassette automatically sets up its own 
timing program and no additional user input or programming is required. 
Alternative methods of achieving this will be apparent. More combinations 
may be achieved by providing more switching and hole/slots. 
FIGS. 12 and 13 illustrate the various time periods above graphically. 
Layer 1 for instance is exposed for its image to be viewed over time 
period T.sub.1. The solid marks indicate when the various solenoids 
(Solenoid 1 . . . Solenoid 6) driving the panels are actuated. Layer 2 is 
exposed during period T.sub.2 and layer 3 is exposed during period T.sub.3 
and during period T.sub.4 the static layer 0 is exposed. 
In FIG. 12, four different timing routines are shown, set by the cassette 
as described above. The example shown in FIG. 13 is one of these timing 
routines. In mode A no timing holes are provided in layer 0. The units of 
FIG. 12 are seconds. 
The hollow marks of FIG. 3 indicate when the solenoids of an optional slave 
display are actuated, to enable more than one changeable display to be 
used and minimise power dissipation. 
Advantageously, window panel 23 is provided with a finger portion 7 on its 
underside, as shown in FIG. 7. This portion is elongate and has one end 75 
fixed to (or integral with the panel 23. The remainder of the finger tends 
to hang from the panel, as shown in FIG. 9. Finger 71 includes a hinge 
portion 76 between its ends and a downwardly extending portion 77 at its 
distal end. 
Finger 71 acts to ensure that all the panels can have a fixed parking 
portion from where the display cycle starts, or for use during transit of 
the cassette. For this purpose, additional slots 73 are provided in the 
respective display panels 5 and 6, and additional holes 72 and 79 are 
provided respectively in rear cassette panel 50 and static display panel. 
The hole in the static display panel is laterally extended as shown. When 
the panels are interconnected, the distal end of finger 71 drops and 
protrusion 77 locates within slots or holes 72, 73 and 79, each of which 
has a laterally extended portion 80 for receiving protrusion 76. This sets 
the respective positions of the panels and precludes relative movement. It 
is therefore of particular benefit if the cassette is used vertically 
(i.e. in a `portrait` disposition). When the cassette is attached to a 
frame, and the drive means are actuated a pin 81 connected to the rear 
frame or drive pushes protrusion 77, and thereby finger 71 into an upward 
position, thereby pushing protrusion 76 out of slots/holes 72, 73, and 79 
to free it therefrom. Lateral movement of panels 5 and 6 is then enabled 
since pin 81 can slide in slots 73 and 74. When pin 81 is retracted, 
finger 71 drops resiliently into its `locking` position, thus locking the 
panel in a parked position. The finger remains in this position when a 
cassette is removed for transit. In addition, a further microswitch may be 
actuated by finger 151 (FIG. 10(b)) when a cassette is removed, which 
energises the solenoids to move all the panels into the park position. 
FIG. 14 also indicates an extrusion 200 joining the edges of the front and 
back panels of a cassette, and illustrates the image layers sandwiched 
between them. 
Alternatively, the unit may be controlled remotely in order to provide a 
means of selecting a desired message or advertisement for example during a 
given period of time.