Method and apparatus for controlling formation of two-color balls for a twisting ball display

• US 5,976,428 A
• Filed: 01/09/1998
• Issued: 11/02/1999
• Est. Priority Date: 01/09/1998
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Richley, Edward A.
• Primary Examiner(s): Vargot, Mathieu D.
• Application Number:
  US09/004,959
• Time in Patent Office: 662 Days
• Field of Search: 264/5, 264/8, 264/9, 264/10, 264/12, 264/13, 425/6, 425/8
• US Class Current: 264/10
• CPC Class Codes: B01J 2/04 in a gaseous medium if combined with suspending the material in a gas, e.g. fluidised beds B01J2/16
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167

Abstract

An apparatus for fabricating bichromal balls includes a means for fabricating droplets from electrically conductive hardenable liquids. The liquids have different colors. A forward end of the hardenable liquids becomes unstable and breaks up into the droplets. Each droplet includes hemispheres of different colors. An RF signal generator produces electrical pulses which increase the instability of the forward end of the hardenable liquids. A capacitance in the conductive liquids causes current to flow from the signal generator to the hardenable liquids. A diameter of the droplets is reduced to form substantially spherical balls. Each of the balls includes hemispheres of different colors. The bichromal balls are collected.

Claims

1. An apparatus for fabricating bichromal balls, comprising:

means for fabricating droplets from electrically conductive hardenable liquids having different colors and flowing along the fabricating means, a forward end of the droplets forming ligaments from the hardenable liquids, the ligaments being unstable at an edge region of the fabricating means and breaking up into the droplets, each droplet including hemispheres of different colors;

an RF signal generator for producing electrical pulses at the edge region of the means for fabricating the droplets, for increasing the instability of a distal end of the ligaments, a capacitance in the conductive liquids causing current to flow from the signal generator to the hardenable liquids, thereby increasing the instability by producing Joule heat in at least a part of the ligament;

means for heating the droplets for reducing a diameter of the droplets and forming substantially spherical balls, each of the balls comprising hemispheres of different colors; and

means for collecting the bichromal balls.

2. The apparatus for fabricating bichromal balls according to claim 1, wherein the RF signal generator causes the ligaments to form a front glob, a neck behind the front glob, and a back glob behind the neck, the neck being narrower than the front glob and the back glob being wider than the neck, the front glob and a part of the neck eventually forming the droplet.

3. The apparatus for fabricating bichromal balls according to claim 2, wherein the electrical pulses produce the Joule heat in the hardenable liquids for increasing the instability of the distal end of the ligaments.

4. The apparatus for fabricating bichromal balls according to claim 3, wherein the Joule heat produced by the RF generator boils away at least a part of the neck.

5. The apparatus for fabricating bichromal balls according to claim 3, wherein the RF signal generator produces the electrical pulses at regular time intervals, the droplets being fabricated at the regular time intervals such that the neck associated with each of the droplets is exposed to the electrical pulses during one of the respective regular time intervals.

14. The apparatus for fabricating bichromal balls according to claim 1, wherein the means for fabricating includes a disc.

15. The apparatus for fabricating bichromal balls according to claim 14, including means wherein the disc spins, thereby causing the forward end of the ligaments to be unstable at the edge region of the disc from centrifugal force.

16. The apparatus for fabricating bichromal balls according to claim 1, further including:

at least one electrical conductor for transmitting the electrical pulses from the RF signal generator to the edge region of the disc.

6. An apparatus for fabricating bichromal balls from a slurry, having a first part and a second part and including a polymer capable of forming a hardenable material and an electrically conductive carrier fluid, a first colored pigment added to the first part of the slurry and a second colored pigment added to the second part of the slurry, the slurry being less viscous than the polymer, comprising:

a spindle;

a separator member attached to the spindle through a rotatable connector, the separator member having a first surface and a second surface located opposite the first surface and an edge region in contact with both the first and second surfaces;

means for flowing the first and second parts of the slurry over the first and second surfaces, respectively, toward the edge region so that the first and second parts of the slurry arrive at the edge at substantially the same flow rate and form a reservoir of the parts of the slurry outboard of the edge region, the reservoir including side-by-side regions of the first and second parts of the slurry;

means for propelling the first and second parts of the slurry from a forward tip of the reservoir as a plurality of ligaments having side-by-side portions of different colors, a forward end of the ligaments being unstable and breaking up into droplets, each droplet including hemispheres of differently colored slurries;

an RF signal generator for producing electrical pulses at the tip of the edge region, the pulses enhancing the break-up of the ligament into the droplets by increasing the instability of the forward end of the ligament, a capacitance in the electrically conductive carrier fluid causing current from the electrical pulses to flow from the signal generator through the tip of the edge region and to the carrier fluid, thereby increasing the instability by producing Joule heat in at least a part of the ligament;

means for removing the carrier fluid from the droplets via heat to form substantially spherical balls, each of the balls comprising hemispheres of different colors and having a diameter less than a diameter of the droplet from which it is formed; and

means for collecting the bichromal balls.

7. The apparatus for fabricating bichromal balls according to claim 6, further comprising:

a first electrical conductor for carrying the pulses from the RF signal generator, through the spindle and to the rotatable connector, the first electrical conductor being electrically insulated from the spindle; and

a second electrical conductor for carrying the pulses from the rotatable connector, through the separator member, and to the tip, of the, edge region, the second electrical conductor being electrically insulated from the separator member.

8. The apparatus for fabricating bichromal balls according to claim 6, wherein:

the means for propelling forms the ligaments to include a narrow portion behind the forward end and a wide portion behind the narrow portion; and

the RF signal generator-produces an RF signal for producing the Joule heat for boiling-away at least a part of the narrow portion.

9. The apparatus for fabricating bichromal balls according to claim 8, wherein the RF signal generator produces the electrical signals at regular time intervals after the forward ends of the ligaments are dispensed from the tip of the edge region, the streams forming subsequent ligaments having a forward end, followed by a narrow portion and a wide portion, the subsequent ligaments being formed approximately at the regular time intervals, and each narrow portion being present at the tip of the edge region when the RF signal produces the heat.

17. The apparatus for fabricating bichromal balls according to claim 6, wherein:

the separator member includes a circular plate;

, the means for propelling includes centrifugal force created from spinning the circular plate.

18. The apparatus for fabricating bichromal balls according to claim 6, wherein the means for removing supplies enough of the heat to boil away the carrier fluid.

10. A method for fabricating bichromal balls, comprising:

spinning a separator member on a spindle;

flowing first and second slurries over opposite surfaces of the separator member and toward an edge thereof so that the slurries arrive at the edge at substantially the same flow rate, the first and second slurries having different colors and being electrically conductive;

forming a reservoir of the first and second slurries outboard of the edge, the reservoir including side-by-side regions of the first and second slurries;

propelling the first and second slurries out of the reservoir as a plurality of ligaments having side-by-side portions of different colors;

generating an electrical pulse at a tip of the reservoir at the edge region for facilitating the forward end of each ligament to become unstable and to break-up into a droplet, a capacitance in the ligament created by the electrically conductive slurries causing a current to flow at the tip, thereby increasing the instability by producing Joule heat in at least a part of the ligament; and

removing fluid from the droplet via heat and forming a substantially spherical ball having hemispheres of different colors and a diameter less than a diameter of the droplet.

11. The method for fabricating bichromal balls according to claim 10 wherein:

the propelling step includes;

forming the forward end of the streams into a first glob, the first glob extending past the tip of the reservoir;

forming the streams behind the first glob into a neck, the neck being narrower than the first glob and being located approximately at the tip of the reservoir; and

forming the streams behind the neck into a second glob, the second glob being wider than the neck and approximately the same size as the first glob, the first glob, the neck and the second glob being formed at regular time intervals; and

the generating step includes;

generating the electrical pulse at the tip of the reservoir at the regular time intervals and when the neck is at the tip of the reservoir.

12. The method for fabricating bichromal balls according to claim 11, the generating step including:

producing the electrical pulse in an RF signal generator; and

passing the electrical pulse from the RF signal generator, through the spindle and the separator member to the tip of the reservoir.

13. The method for fabricating bichromal balls according to claim 12, wherein:

the generating step includes;

producing the Joule heat at the tip of the reservoir for boiling away the neck; and

the method further includes the step;

collecting the bichromal-balls.

19. The method for fabricating bichromal balls according to claim 13 wherein the removing step includes:

applying the heat to boil-away the fluid.