U.S. patent number 3,812,490 [Application Number 05/290,187] was granted by the patent office on 1974-05-21 for flexible membrane display panel for generating characters visible in ambient light.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to George W. Goodrich.
United States Patent |
3,812,490 |
Goodrich |
May 21, 1974 |
FLEXIBLE MEMBRANE DISPLAY PANEL FOR GENERATING CHARACTERS VISIBLE
IN AMBIENT LIGHT
Abstract
A digitally addressed magnetically actuated ambient light
display panel is disclosed which incorporates a thin flexible
magnetic membrane suspended between a ferromagnetic member and a
transparent window in a fluid of a contrasting color. A plurality
of small electromagnetic elements are disposed along the face of
the ferromagnetic member adjacent to the magnetic membrane, which
are capable of selectively magnetizing the ferromagnetic member at
discrete locations. The magnetized ferromagnetic member attracts or
repels the magnetic membrane in accordance with the magnetic
polarity induced in the ferromagnetic member by the electromagnetic
elements. Repelling the membrane against the face of the window at
predetermined locations displaces the fluid between the membrane
and the window and permits the contrasting color of the flexible
membrane to become visible. A selectively repelled membrane
generates characters or patterns visible under ambient light
conditions.
Inventors: |
Goodrich; George W. (Bloomfield
Hills, MI) |
Assignee: |
The Bendix Corporation
(Southfield, MI)
|
Family
ID: |
23114899 |
Appl.
No.: |
05/290,187 |
Filed: |
September 18, 1972 |
Current U.S.
Class: |
345/84; 359/291;
G9B/5.233 |
Current CPC
Class: |
G09G
3/16 (20130101); G08B 5/22 (20130101); G09F
9/372 (20130101); G09F 9/375 (20130101); G09G
3/3486 (20130101); G11B 5/62 (20130101); G02B
26/004 (20130101) |
Current International
Class: |
G09F
9/37 (20060101); G09G 3/16 (20060101); G09G
3/34 (20060101); G11B 5/62 (20060101); G02B
26/02 (20060101); G08B 5/22 (20060101); G02f
001/34 () |
Field of
Search: |
;340/324R,324M,378R,336,334 ;350/161,267,266,269,278,280
;40/28C,130 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Caldwell; John W.
Assistant Examiner: Curtis; Marshall M.
Attorney, Agent or Firm: Bell; John S.
Claims
1. A character generating ambient light display panel
comprising:
an enclosure having at least one transparent window;
an opaque colored fluid filling said enclosure;
a flexible membrane, having a color contrasting to the color of
said fluid and porous to said fluid, said membrane supported in
said enclosure proximate to and spaced from said transparent
window; and
means disposed in said enclosure for selectively deflecting said
membrane at a plurality of predeterminable locations indicative of
at least one character to contact said transparent window, thereby
displacing said fluid from between said transparent window and said
membrane at said predetermined locations, permitting the
contrasting color of said membrane and therefore said at least one
character to be visible through said
2. The display panel of claim 1 wherein said flexible membrane
further includes a plurality of isolated permanent magnet particles
at least
3. The display panel of claim 2 wherein said means for selectively
deflecting said membrane is a plurality of electromagnetic
elements
4. The display panel of claim 3 wherein said plurality of
electromagnetic elements are equally spaced along orthogonal axes
forming rows and columns
5. The display panel of claim 4 wherein said magnetic elements
comprise at least two electrically isolated superimposed
electromagnets, one of said two electromagnets being associated
with one of said rows, and the second
6. The display panel of claim 5 wherein said means for selectively
deflecting said membrane further includes a ferromagnetic member
having a planar surface, the planar surface of said ferromagnetic
member being located proximate the surface of said flexible
membrane opposite said window and said electromagnetic elements
being disposed along the planar
7. The display panel of claim 6 wherein said ferromagnetic member
has a square hysteresis loop, and wherein the combined magnetic
fields of two of said electromagnets comprising said
electromagnetic elements is required
8. The display panel of claim 7 wherein said ferromagnetic member
is a part
9. The display panel of claim 3 wherein said electromagnetic
elements are arranged in at least seven electrically isolated
linear segments forming a
10. The display panel of claim 9 wherein said means for deflecting
said membrane further comprises ferromagnetic member having a
substantially planar surface, said planar surface located proximate
the surface of said membrane and said electromagnetic elements are
disposed along said planar
11. The display panel of claim 3 wherein said electromagnetic
elements are
12. The display panel of claim 11 wherein a plurality of character
forming serially arranged electromagnetic elements are overlayed
one on top of the
13. The display panel of claim 12 wherein said means for
selectively deflecting said flexible membrane further includes a
ferrite member having a substantially planar surface and said
electromagnetic elements are
14. A magnetically actuated ambient light display panel
comprising:
an enclosure having at least one transparent window;
an opaque colored liquid filling said enclosure;
a magnetically responsive flexible membrane having a color
contrasting to the color of said fluid and porous to said fluid,
said membrane supported in said enclosure a short distance from
said transparent window; and
means disposed in said enclosure proximate said membrane for
generating localized magnetic fields at a plurality of
predeterminable locations indicative of at least one character,
said localized magnetic field operative to deflect said membrane to
contact said transparent window whereby the contrasting color of
said membrane and therefore said at least
15. The display panel of claim 14 wherein said magnetically
responsive deflectible membrane includes a plurality of isolated
permanent magnetic particles systematically polarized normal to the
plane of said membrane.
16. The display panel of claim 14 wherein said means for generating
localized magnetic fields comprise:
a ferrite member having a square hysteresis loop, and at least one
substantially planar surface, said one substantially planar surface
located proximate the surface of said membrane;
a plurality of equally spaced rows of equally spaced and serially
connected electromagnets disposed along the one substantially
planar surface of said ferrite member; and
a plurality of equally spaced columns of equally spaced and
serially connected electromagnets disposed along the one plane
surface of said ferrite member, one of said serially connected
electromagnets of said equally spaced columns being coincident with
one of said serially connected electromagnets of said equally
spaced rows at each intersections
17. The display panel of claim 16 wherein said rows and said
columns of serially connected electromagnets are electrically
isolated, and wherein the combined magnetic fields generated by a
coincident row electromagnet and a coincident column electromagnet
is required to change the magnetic polarity of said ferrite member
at the intersection of a row and a column.
Description
BACKGROUND OF THE INVENTION
This invention relates to the field of ambient light display
panels, and in particular, to digitally addressed
electromagnetically activated ambient light display panels. The
invention is similar with liquid crystal displays because both
types of displays possess the desirable property of visibility
under conditions of both intense and weak ambient illumination.
The use of display panels to display information in remote
locations is increasing rapidly. Display panels may be categorized
by the method in which the information is communicated to the
recipient. Luminous display panels communicate information to the
recipient by the self-generation of light. Luminous displays may
have luminous characters on a black background, or black characters
on a luminous background. Typical examples of luminous displays are
cathode ray tubes, light emitting diode panels and plasma panels.
The primary deficiency of luminous panels is the tendency of the
information displayed to be lost or washed out under intense
ambient lumination. The second category of display panels is the
class of ambient light panels in which the information written on
the display panel and transmitted to the recipient by means of
reflected ambient light. Ambient light display panels are not
self-luminous and are advantageous because the visibility of the
displayed image increases with increasing ambient illumination
conditions. Ambient light display panels have practical application
in a variety of displays where ambient illumination may vary from
intense daylight to subdued conditions such as those found in a
home, an office, an aircraft, or automotive vehicle.
Various types of ambient light display panels are in existence.
Recent developments in liquid crystals have resulted in ambient
light displays which have the desirable property of visibility
under conditions of both intense and weak ambient lumination.
However, the inventive display panel offers several distinct
advantages over presently existing liquid crystal displays. First,
the inventive display panel diffusely reflects ambient light
arriving from all directions, thus the display will not disappear
at any angle of illumination or viewing. Second, the inventive
display panel operates over a wide range of temperatures. Third,
the inventive display panel is easy to digitally address on a
point-for-point basis.
Magnetically activated ambient light display panels of various
types are in existence, however none of the known systems are
capable of meeting today's needs of high density information
transfer. The existing magnetically activated display panels may be
classified as simple on-off systems or character generating
systems. U.S. Pat. No. 3,162,849 describes an on-off display panel
in which a disc, upon which the desired message is printed, is
suspended in a colored liquid a short distance from a transparent
window. An electrically activated solenoid moves the disc against
the transparent window, displacing the liquid, and rendering the
printed message visible. This method is distinguished from the
present invention in several ways: (1) it is basically an on-off
device not readily capable of digital addressing or character
formation; (2) the movable member is rigid, not flexible and
therefore unable to display different patterns within a given area;
(3) the movable member is made from magnetically susceptible
material (soft iron) not from permanent magnetic material having a
fixed magnetic polarity; (4) the display does not have a memory in
the absence of power; and (5) the display requires the continuous
application of electrical power in the off state.
Another type of magnetically activated ambient light display panel,
which is disclosed in U.S. Pat. Nos. 3,444,551 and 3,469,258,
include a plurality of cylindrical or spherical members which are
rotated by small electromagnets located proximate to each member.
The individual members have contrasting colors on their opposite
sides, and the direction of the field of the electromagnets
determines which side of the rotatable member and therefore which
color is presented to the observer. These displays come in various
sizes and number of rotatable members, and may be digitally
addressed. However, they are structurally complex, containing a
relatively large number of individual moving parts, and therefore
are difficult to manufacture and maintain.
Still another type of magnetically actuated ambient light display,
described in U.S. Pat. No. 3,292,171, uses a magnetic tape and
magnetically susceptible particles suspended in a transparent
fluid. The information to be displayed is magnetically written on
the tape and the transparent fluid containing magnetically
susceptible particles of a contrasting color is circulated across
the tape. The particles separate from the fluid and form images on
the tape corresponding to the information written thereupon. This
and other concepts based upon magnetic particles suspended in a
fluid face various difficulties and have not found wide
acceptance.
SUMMARY OF THE INVENTION
The present invention is a digitally addressed magnetically
activated ambient light display panel. The inventive display panel
includes a ferromagnetic member which can be selectively magnetized
to form local magnetic fields. Spaced apart from the ferromagnetic
member is a transparent window and interposed between the window
and the ferromagnetic member is a thin magnetized flexible membrane
suspended in a colored fluid. When the ferromagnetic member is
locally magnetized to a predetermined polarity, the magnetic fields
repel the flexible membrane against the window. The membrane
displaces the fluid between the window and the membrane permitting
the contrasting color of the membrane to be visible. Reversing the
local magnetic field in the ferromagnetic member attracts the
flexible membrane away from the window and the colored fluid once
more fills the space between the membrane and the window obscurring
the membrane from visibility. Thus the selective attracting and
repelling of the membrane at predetermined points over the face of
the ferromagnetic member causes the display panel to display
characters visible under ambient light conditions. The advantages
of the inventive display panel are compact size, low power
consumption, and memory in the absence of power. Additionally, a
wide range of contrasting colors including highly visible
fluorescent figures can be used in the inventive display panel. The
inventive display is basically binary although gray scales may be
introduced by combining multiple active cells into each resolution
element. A further advantage of the inventive display is that it
may be extended to incorporate variable colors by associating two
or three cells, each carrying a primary color within each
resolution element thus permitting the generation of images or
characters of different color. This technique of color imaging is
similar to the color printing techniques used in magazines and
newspapers as well as that used in the present day color
television. Another advantage of the disclosed display panel is the
fact that it can be produced at reasonable costs and includes no
parts which are inordinately difficult to manufacture using
standard manufacturing techniques. Further, the system contains a
limited number of discrete parts or members, this is in contrast to
the other prior art magnetically activated ambient light display
panels which comprise a large number of individual components.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the inventive ambient light panel
with a section cut away to show the component parts
FIG. 2 is an exaggerated cross sectional view of the inventive
display panel.
FIG. 3 is an enlarged plan view of one of the preferred
configurations of the electromagnetic coils.
FIG. 4 is an enlarged view of an alternate preferred configuration
of the electromagnetic coils.
FIG. 5 is an enlarged view showing an alternate coil configuration
to form block arabic numerals.
FIG. 6 is an enlarged view showing a stylized numeral 2 using the
inventive display panel.
FIG. 7 is a perspective view showing two electromagnetic coils
superimposed .
DETAILED DESCRIPTION
Referring to FIG. 1, a perspective view of a preferred embodiment
of the ambient light display panel 10 is shown with sections cut
away to show the major component parts. The display panel comprises
a transparent window 12 supported a short distance from a
ferromagnetic base 14 by a thin rim 16 approximately .01
centimeters thick. The assembly is sealed to form a fluid tight
chamber between the window 12 and the base 14. Internally supported
between the window 12 and the base 14 is a permanently magnetized,
semipermeable flexible membrane 18 suspended in a fluid 20 having
color which contrasts with the color of the membrane 18. The space
between window 12 and membrane 18 is filled with the fluid 20 so
that when the flexible membrane is attracted away from the window
12, the color of the fluid is visible. The internal face of the
ferromagnetic member is overlayed with a plurality of serially
connected electromagnetic elements 22 in rows and columns. The
magnetic elements 22 are capable of locally magnetizing the
ferromagnetic base 14 in small discrete areas surrounding each
magnetic element 22. Connectors 24 and 26 are provided to
distribute electrical signals to the individual rows and columns of
electromagnets.
FIG. 2 is a partial cross section of the display panel in which the
size of the individual electromagnets and the spacing between
window 12 and ferromagnetic base 14 have been exaggerated for
illustrative purposes. The flexible membrane 18 is made from a
stainproof material, such as vinyl or neoprene rubber, and is much
thinner than the center-to-center distance between adjacent
electromagnetic elements 22. For adequate flexibility the thickness
of the membrane should be less than about 1/50 the center-to-center
spacing between adjacent electromagnetic elements. The color of the
flexible membrane is contrasting to the color of the fluid 20
between the ferromagnetic base and the window.
The individual electromagnetic elements 22 of the rows and columns
may be superimposed electrically isolated electromagnet coils 28
and 30, as shown. The distance "W" represents the physical
center-to-center spacing between adjacent rows and columns and
defines the size of a resolution element. In the simplest case a
column may be formed by a plurality of series connected single turn
coils 28 as shown in FIG. 3 and a row formed by a similar plurality
of series connected single turn coils 30. At each intersection of a
row and column the serially connected electromagnetic coils 28 and
30 are superimposed forming an electromagnetic element 22, as shown
in FIG. 7. An alternate configuration of the electromagnetic
element is shown in FIG. 4. In this configuration, crossed parallel
conductors 202 and 204 form the columns and rows respectively. The
electromagnetic elements 22 are the rectangular section formed at
the intersection of electrically connected pairs of adjacent
conductors as shown. The electromagnetic elements may be formed on
the ferromagnetic base 14 by well-known vacuum deposition or
printed circuit techniques. Other well-known methods for forming
electromagnetic elements are equally applicable. If the
ferromagnetic base is electrically conductive, the elements may be
deposited on a thin layer of insulating material separating them
from the base.
The material of the ferromagnetic base is selected to have a square
hysteresis loop so that it operates similar to the ferromagnetic
materials widely used magnetic memories. The electrical current
flowing through the rows and columns of coils is controlled so that
the magnetic field generated by each individual coil element 28 or
30 is less than that required to cause reversal of the direction of
the magnetization of the ferromagnetic base in the immediate
vicinity of the coil. It is only when the magnetic fields generated
by magnet elements 22 consisting of a column electromagnetic coil
element 28 and its associated new electromagnetic coil element 30,
combine that a reversal of magnetization in the ferromagnetic base
14 occurs in the immediate vicinity of the electromagnetic element
22.
The flexible membrane is made magnetic by impregnating the membrane
with particles of permanent magnet material or by any other
suitable method of attaching permanent magnet particles to the
membrane. After or during attachment, the particles are magnetized
in a direction generally perpendicular to the plane of the
membrane. However, the polarity of the magnetization of the
membrane over each electromagnetic elements 22 is opposite the
polarity in the interstitial spaces between the elements. The
reason for the polarity pattern of the membrane is more clearly
understood by referring to FIG. 2. Consider the electromagnet
elements 22, wherein the magnet fields of the coils 28 and 30
combine to produce the flux pattern shown by the arrows. The
direction of the flux lines immediately above the electromagnetic
elements 22 are in a direction going from the base 14 towards the
window 12 while in the space between the electromagnetic elements
22, the flux lines flow in the opposite direction. For high
efficiency, it is desirable to have the magnetization of the
permanent magnet particles in the membrane aligned with the
magnetic field generated by the electromagnet elements and the
field imparted to the ferromagnetic base. This alternating magnetic
polarity may be accomplished in practice by magnetizing the
membrane in a fixture configured like the ferromagnetic base with
electromagnetic elements arranged in the identical pattern. The
magnetizing fixture is desired to provide the much higher magnetic
field needed to magnetically orient the permanent magnetic
particles in the flexible membrane. The alternating magnetic
polarity of the membrane may also be accomplished in the inventive
display panel by having the electromagnet elements 22 themselves
generate the required higher magnetic field to magnetize the
particles after the panel has been assembled.
For illustrative purposes the direction of current flowing through
electromagnetic coils designed 32 and 34 in FIG. 2 is opposite to
the direction of current flowing through the remaining
electromagnetic coils designated as 28 and 30 respectively. Coils
32 and 34 produce a magnetic field in which the magnetic flux lines
flow in the opposite directions as shown. The magnetization pattern
of the membrane remains fixed while the direction of the
magnetization of the ferromagnetic base is changed to either
attract or repel the magnetized membrane.
The operation of the display panel is described with reference to
FIG. 2. Initially the display panel is in the erased condition
which is achieved by electrically energizing all the rows and
columns of electromagnetic elements so that the magnetic polarity
of the ferromagnetic material is aligned with the polarity of the
magnetic field in the membrane. This causes the flexible membrane
18 to be attracted to the ferromagnetic base 14 away from the
window 12. Since the membrane is porous, the fluid flows through
the membrane and fills the space between the membrane 18 and the
window 12 occluding the visibility of the membrane. The strength of
the magnetic field generated by the electromagnetic elements 22 is
sufficient to establish the polarity over the entire surface of the
ferromagnetic base 14, therefore the membrane will remain attracted
to the base even after the erase signal to the electromagnetic coil
elements 22 is terminated.
As previously described, applying an electrical signal to either a
row or column alone will not produce a magnetic field of adequate
strength along the row or column to cause a reversal of the
polarity of the ferromagnetic base in the immediate vicinity of the
individual electromagnetic elements. It is only when an electrical
signal is simultaneously applied to a given row and a given column
that a polarity reversal can take place, and this polarity reversal
will only take place at the intersection of the given row and the
given column, where the magnetic fields of the row electromagnetic
coil 30 and the column electromagnetic coil 28 combine.
The magnetic field in the ferromagnetic base is then selectively
reversed at predeterminable points by digitally addressing the rows
and columns of electromagnetic elements in a sequential manner well
known in the art. The electrical polarity of the addressing signals
are opposite the polarity of the erase signals and cause the
magnetic polarity of the ferromagnetic base to be reversed at the
addressed locations. The reversed magnetic polarity repels the
flexible membrane, causing it to press against the window as
illustrated in FIG. 2 showing the membrane repelled above
electromagnetic elements 32 and 34. As stated previously, the
electrical current flowing through elements 32 and 34 are opposite
the current flowing through the remaining elements shown. The fluid
20 is displaced from between the membrane 18 and window 12
permitting the contrasting color of the membrane to be visible.
Only a small physical displacement is required to yield a high
contrast between the attracted and repelled section of the flexible
membrane. Displacements as small as .005 centimeters are capable of
providing adequate contrast for visual perception. The opacity of
the fluid 20 is selected to maximize the contrast between the
attracted and repelled positions of the membrane.
The inventive display panel is also adaptive to the alphanumerical
type of display shown in FIGS. 5 and 6. FIG. 5 illustrates one of
many possible arrangements for the well known seven nonoverlapping
bar system that adequately depicts the arabic numerals. The
illustrated dovetailed configured windings enclose small regions of
magnetic fields of alternating polarity having adequate attractive
and repelling forces to deflect the membrane as required. The
alphanumerical display panel illustrated in FIG. 5 does not require
a ferromagnetic material having a square hysteresis loop because
the magnetic polarity of the ferromagnetic base is switched by a
single electromagnet winding as compared to the digitally addressed
panel discussed above.
FIG. 6 shows an electromagnetic element pattern for generating a
stylized numeral, in particular, the numeral 2. It is possible to
envision several overlays, i.e., one for each numeral or character
desired, stacked together and affixed over the ferromagnetic base.
Each overlay carries its own winding, photoetched or vacuum
evaporated on an insulating film. The stylized display panel is
limited to the number of characters that may be overlayed, and if
many characters are desired, the digitally addressed system may be
more appropriate.
Although the invention is shown embodied in a preferred
configuration with several alternate methods of electromagnet
element construction to form the desired character, the invention
is not limited to the embodiments illustrated and changes can be
made in materials and configuration without departing from the
spirit of the invention.
* * * * *