US3629638A - Plasma display device with internal-external electrode structure - Google Patents

Plasma display device with internal-external electrode structure Download PDF

Info

Publication number
US3629638A
US3629638A US3629638DA US3629638A US 3629638 A US3629638 A US 3629638A US 3629638D A US3629638D A US 3629638DA US 3629638 A US3629638 A US 3629638A
Authority
US
Grant status
Grant
Patent type
Prior art keywords
gas
member
electrode
cells
internal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
Inventor
Harry Veron
Richard Allan Carey Sr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WALTER E HELLER WESTERN Inc
Sperry Corp
Babcock Display Products Inc
Original Assignee
Sperry Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Images

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00Gas-filled discharge tubes with solid cathode
    • H01J17/38Cold-cathode tubes
    • H01J17/48Cold-cathode tubes with more than one cathode or anode, e.g. sequence-discharge tube, counting tube, dekatron
    • H01J17/49Display panels, e.g. with crossed electrodes, e.g. making use of direct current
    • H01J17/492Display panels, e.g. with crossed electrodes, e.g. making use of direct current with crossed electrodes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00Gas-filled discharge tubes with solid cathode
    • H01J17/38Cold-cathode tubes
    • H01J17/48Cold-cathode tubes with more than one cathode or anode, e.g. sequence-discharge tube, counting tube, dekatron
    • H01J17/49Display panels, e.g. with crossed electrodes, e.g. making use of direct current
    • H01J17/491Display panels, e.g. with crossed electrodes, e.g. making use of direct current with electrodes arranged side by side and substantially in the same plane, e.g. for displaying alphanumeric characters

Abstract

A gas discharge panel display device comprising a planar dielectric member having a plurality of gas cell forming holes arrayed therein and disposed intermediate a pair of exterior planar dielectric members. An electrode configuration for firing the gas cells includes an external electrode structure positioned on the outer surface of one of the exterior members operating in conjunction with an internal electrode arrangement positioned on the remote surface of the intermediate member, holes being formed in the internal electrode structure in overlaying relation with and conforming to the shape of the gas cells.

Description

United States atent [72] inventors Harry Veron .5VV 99TT mm BUM 3355 33 mr r m mama lrll muu SCC'J 8006 5776 9999 I111 8244 00 74 3507 8794 4906 15 2333 Framingham;

Richard Allan Carey, Sr., Marlboro, both of Mass.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-Saxfield Chatmon, Jr. Attorney-S. C. Yeaton [2]] Appl. No.

eels

FPA

ABSTRACT: A gas discharge panel di a planar dielectric memberhavin ing holes arrayed therein and di exterior planar dielectric members. An electrode con tion for firing the gas cells includes an external ele structure positioned on the outer surface of one of the exterior members operating in conjunction with an internal electrode arrangement positioned on the remote surface of the intermediate member, holes being formed in the internal electrode structure in overlaying relation with and conformi shape of the gas cells.

A name.

T M WU Hm U nu W ES n" C mm WD m m BOMB m m m DWF m Y an em A .m mm e P a n 0 MUS m NS l at SEm C G AT .M

PE4 U IF U H mm m U U. r 15 5 UNITED STATES PATENTS 6/1935 Lebedenko et al.

@l il PATENTED UECZI ran FlG.l.

FIG.2.

ATTORNEY PLASMA DISPLAY DEVICE WITH INTERNAL- EXTERNAL ELECTRODE STRUCTURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to visual display panels of the type comprising a matrix of AC-excited excited gas discharge cells disposed between parallel plane electrode structures.

Operation of such devices is based on ionization of the gas in selected cells to provide a visual presentation of alphanumeric or other information which is to be displayed. This is accomplished by energizing an appropriate electrode or plurality of electrodes on each side of the gas cells in a manner to establish an ionizing potential difference across discrete cells such that a light pattern representative of the information to be displayed is produced.

2. Description of the Prior Art Generally in panel display devices of the type described herein, a two-dimensional array of cells is formed intermediate two electrode planes each including a plurality of lineal parallel electrode elements with the electrodes in one plane orthogonally oriented relative to those in the other plane. The electrodes have typically been positioned either immediately adjacent the gas, forming an internal electrode structure or, alternatively, have been spaced from the gas by respective insulating or dielectric layers to form an electrode structure which is external to the gas cells. In both of these configurations the lighted discharge cells must be viewed through a semitransparent electrode overlaying the cells, resulting in an undesirable diminution of the visible light. Moreover, with the internal structure, wherein both electrodes are in contact with the gas, the likelihood of deleterious electrode sputtering increases. This contaminates the gas fill thereby degrading electrical performance of the device and, in extreme cases, can cause shorting between the electrodes due to the accumulation of sputtered material therebetween. An external electrode configuration substantially reduces the sputtering problem attendant to internal electrodes but usually requires considerably higher power input to achieve a desired light output, namely, a light level suitable for easy viewing under ordinary ambient room lighting conditions.

SUMMARY OF THE INVENTION The above-mentioned disadvantages of prior art gas discharge panel display devices are overcome or significantly reduced with the present invention by the provision of a unique electrode configuration comprising a combination of internal and external electrodes disposed respectively on opposite sides of an ionizable gaseous medium. More specifically, in a flexible symbol format embodiment of the present invention, a planar dielectric member, having a matrix of holes extending therethrough forming the gas cells, is positioned between a pair of exterior planar dielectric members and sealed together therewith at the edges to form a unitary gastight apparatus. A tube connected to the apparatus and scalable at the external end provides for evacuating air and other impurities preparatory to filling with a selected gas at a desired pressure. A set of linear electrodes is affixed to the outer surface of one of the exterior dielectric members in superposed relation to respective rows of the gas discharge cells of the intermediate layer. These constitute the external electrodes. Another set of linear electrodes, arranged in columns, is similarly positioned relative to the gas cells adjacent the interior surface of the other exterior planar member to form the internal electrodes. In each internal electrode holes are formed in overlaying relation and conforming to the shape of the gas cells. This construction provides for sharply defined lighting at each cell and enhances the brightness of the display inasmuch as it is viewed looking directly into the discharge without theprzesenceof an intervening-electrode. Application of ionizingQpotentials to individual orthogonally disposed electrodes or various combinations thereof in the manner to'be described hereinafter thereby enables virtually; any symbol or even a scene to be presented assuming that a sufficient number of gas cells is provided to achieve the necessary resolution.

In a fixed format embodiment of the invention the gas cells are formed in the shape of elongated rectangles arranged relative to one another in a standard alphanumeric symbol generating configuration. In this instance, the internal and external electrodes have the same location relative to the dielectric layers of the composite structure as previously described for the flexible symbol format. The external electrodes have the same shape as the gas cells and are mounted in superimposed relation thereto. The intemal electrodes, on the other hand, are conveniently formed by a single conductive member having a plurality of holes extending therethrough with a shape matching and overlaying the gas cell holes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an exploded perspective view of a flexible format embodiment of the invention,

FIG. 2 is an exploded perspective view of a fixed format embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a gas discharge display device constructed in accordance with the principles of the present invention comprises exterior dielectric members 10 and 11 disposed on opposite sides of interior dielectric member 12. The dielectric members are thin plates, preferably constructed of a material such as glass or quartz and are typically only about 5 to 10 thousandths of an inch thick to minimize the overall thickness of the display panel, but these dimensions are not critical. Interior member 12 has a plurality of holes 13 extending through it which can be formed, for example, by ultrasonic drilling or chemical etching in accordance with conventional techniques well known in the art. While only a small number of holes are depicted in the drawing it will be appreciated that several thousand, perhaps even tens of thousands, of such holes could be provided if needed. External electrodes [4 are disposed on the outer surface of exterior member 10 so as to extend across respective horizontal rows of holes in interior member 12. In a similar manner, internal electrodes 16 are disposed on interior member I2 on the surface thereof remote from the external electrodes. As indicated, the internal electrodes extend in a direction orthogonal to the external electrodes and have holes in them in overlaying relation to the holes in the interior dielectric member. All the electrode elements are preferably constructed of chrome or aluminum.

When assembled, exterior member 10 is brought into contact with interior member 12 while exterior member 11 is held against internal electrodes 16 and the dielectric members are then sealed around their edges as by an epoxy or encapsulating material to form a gastight unitary structure. A tube (not shown) can be coupled through the side of the structure into its interior region for the purpose of out-gassing and filling with an ionizable gas such as neon at a pressure of about 300 Torr whereby individual gas cells are formed by the holes in the interior member. Successful operation has been achieved with a device of this type wherein the electrodes are on the order of 1,000 Angstroms thick and 0.030 inches wide with the holes in both the internal electrodes and the interior dielectric member approximately 0.020 inches in diameter and spaced 0.062 inches center to center.

In operation of the device a selected gas cell is illuminated by applying an AC signal of sufficient amplitude to the appropriate internal and external electrodes such that an ionizing discharge is established in the cell to cause visible radiation to be emitted therefrom. For instance, application of potential to electrodes 14a and 16a uniquely establishes a potential difference across cell 13a. Other cells can be ignited by energizing differentelectrode-combinations and obviously a plurality. of cells can be energized simultaneously if desired.

in the case where a cell is ignited by directly applying a potential of sufficient amplitude to ionize the gas, that is, a potential greater than the firing potential, the discharge commences immediately upon application of the signal and likewise terminates upon removal of the excitation. Alternatively, firing can be accomplished by continuously applying to all of the electrodes a sustaining signal which by itself is incapable of ionizing the gas, that is, a sustaining signal at an amplitude slightly less than the ionizing potential and typically at a frequency in the kilohertz range, 300 kilohertz being suitable for the specific device described herein. In this instance an individual cell is fired by applying a writing pulse to the related electrodes in a manner such that the writing signal is decoupled from all the other electrodes but adds to the sustaining signal at the selected electrodes as the sustaining signal crosses from the negative to the positive portion of its cycle thereby raising the instantaneous excitation across the selected cell to a level above the ionizing potential. Thereafter the discharge continues until an erase pulse is provided in a similar manner as the sustaining signal crosses from the positive to the negative portion of its cycle to reduce the applied potential below the ionizing cutoff level.

The internal-external electrode combination provided by the invention provides several advantages such as reduced sputtering, greater efficiency (ratio of light output to power input) and brighter output as explained hereinbefore. It will now be apparent that the latter feature is realized because the gas discharge is viewed as from position 17 by looking directly through glass member 11 without obstruction by any of the electrode members. Regarding the other advantages, it is believed that these obtain from the unique electrode structure which not only enhances the electric field configuration within the individual gas cells but also substantially reduces sputter inducing conduction currents by allowing only a predominant displacement current to flow.

Other refinements known in the art can also be used in the display panel constructed according to the principles of the present invention. For example, an opaque insulating member could be used in place of glass interior member 12 or the walls thereof between the respective cells can be coated with an opaque material to minimize optical coupling between the cells.

The fixed symbol format embodiment of the invention illustrated in FIG. 2 is arranged, constructed and assembled in essentially the same way as described with reference to the flexible format embodiment of H0. 1. Here again the illuminated symbols are viewed by looking through electrical insulator 21 directly into the discharge cells 22 extending through the middle insulator member 22. in this embodiment, however, the discharge cells have a rectangular shape and are configured in a conventional alphanumeric pattern whereby various letters and numbers can be displayed by igniting the appropriate cells. The internal electrode 24 is preferably, but not necessarily, a single metallic member having holes therethrough overlaying and matching the shape of the discharge cell holes in member 23. The external electrodes 26, which are formed by conventional masking and evaporation techniques, consist of individual metallic members positioned on the surface of insulating member 27 distal the internal electrode. The external electrodes have a shape and size conforming to the respective I overlaying holes in insulator 23 and internal electrode 24 and are positioned in superposed relation thereto on member 27.

In operation of the device, a numeral 7, for example, can be presented by connecting the energizing AC potentials across the common internal electrode 24 and external electrodes 26a, 26b and 260. For this embodiment, presentation of various symbols by means of signals of sufficient amplitude to ionize the gas in selected cells without the use of a sustaining signal is preferred. Further, it should be noted that the excitation can be applied by means of short bursts of AC energy; for instance, 4 or 5 cycles of a 300 kilocycle signal at a repetition rate of say one kilocycle to I00 kilocycles. Operation in this manner rovides for dimming control simpl5 by varying the duty cyc e of the applied energy bursts, the l 0 ilocycle rate providing a display approximately times brighter than the one kilocycle repetition rate.

Finally, regarding the construction of the fixed format embodiment, it has been found that suitable operation can be achieved by replacing the middle insulator member 23 with a metal shim having the discharge cells formed in it. This construction increases the brightness but tends to consume more power.

While the invention has been described in its preferred embodiments, it is to be understood that the words that have been used are words of description rather than limitation and that changes may be made within the purview of the appended claims without departing from the true scope and spirit of the invention in its broader aspects.

We claim:

1. A gas discharge display apparatus having a plurality of discrete gas cells for displaying symbols in accordance with the selective ionization of gas in the respective cells in response to ionizing potentials applied thereacross, comprismg a substantially planar rear wall insulator member and a substantially planar translucent front wall insulator member sealed together about their edges in spaced apart relation to form a hermetically sealed enclosure for an ionizable gas contained therein,

an additional planar insulator member positioned between the front and rear wall insulator members in contacting relation with the rear wall interior surface and having a plurality of holes extending therethrough forming the individual gas cells,

internal electrode means positioned between and in contacting relation with the interior surface of the front insulator member and adjacent surface of the additional insulator member, said internal electrode means having through holes spatially superposed with the gas cell forming holes in said additional insulator member to enable direct viewing of ionized gas in said cells through the front translucent insulator member, and

external electrode means including a plurality of electrode elements each formed on the exterior surface of the rear insulator member in spatially superposed relation with at least one of the gas cells, said electrode elements thereby being separated from the gas by said rear insulator member whereby sputter material emitted from said internal electrode means and deposited on the walls of the gas cells is precluded from establishing a shorting path between said internal and external electrodes.

2. The apparatus of claim 1 wherein said electrode elements and said holes are in the shape of elongated rectanglesarranged in an alphanumeric format.

3. The apparatus of claim 1 wherein said internal electrode means comprises a plurality of metallic members, each such member extending across a plurality of said gas cells; and the external electrode elements extend in a direction orthogonal to said internal metallic members.

4. The apparatus of claim 3 wherein the holes in said additional insulator member are arrayed in a two-dimensional matrix and said additional member is sealed' around its edge together with said pair of insulating members to form said enclosure.

* i i i

Claims (4)

1. A gas discharge display apparatus having a plurality of discrete gas cells for displaying symbols in accordance with the selective ionization of gas in the respective cells in response to ionizing potentials applied thereacross, comprising a substantially planar rear wall insulator member and a substantially planar translucent front wall insulator member sealed together about their edges in spaced apart relation to form a hermetically sealed enclosure for an ionizable gas contained therein, an additional planar insulator member positioned between the front and rear wall insulator members in contacting relation with the rear wall interior surface and having a plurality of holes extending therethrough forming the individual gas cells, internal electrode means positioned between and in contacting relation with the interior surface of the front insulator member and adjacent surface of the additional insulator member, said internal electrode means having through holes spatially superposed with the gas cell forming holes in said additional insulator member to enable direct viewing of ionized gas in said cells through the front translucent insulator member, and external electrode means including a plurality of electrode elements each formed on the exterior surface of the rear insuLator member in spatially superposed relation with at least one of the gas cells, said electrode elements thereby being separated from the gas by said rear insulator member whereby sputter material emitted from said internal electrode means and deposited on the walls of the gas cells is precluded from establishing a shorting path between said internal and external electrodes.
2. The apparatus of claim 1 wherein said electrode elements and said holes are in the shape of elongated rectangles arranged in an alphanumeric format.
3. The apparatus of claim 1 wherein said internal electrode means comprises a plurality of metallic members, each such member extending across a plurality of said gas cells; and the external electrode elements extend in a direction orthogonal to said internal metallic members.
4. The apparatus of claim 3 wherein the holes in said additional insulator member are arrayed in a two-dimensional matrix and said additional member is sealed around its edge together with said pair of insulating members to form said enclosure.
US3629638A 1970-01-15 1970-01-15 Plasma display device with internal-external electrode structure Expired - Lifetime US3629638A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US312670 true 1970-01-15 1970-01-15

Publications (1)

Publication Number Publication Date
US3629638A true US3629638A (en) 1971-12-21

Family

ID=21704292

Family Applications (1)

Application Number Title Priority Date Filing Date
US3629638A Expired - Lifetime US3629638A (en) 1970-01-15 1970-01-15 Plasma display device with internal-external electrode structure

Country Status (6)

Country Link
US (1) US3629638A (en)
CA (1) CA933571A (en)
DE (1) DE2101935A1 (en)
FR (1) FR2075537A5 (en)
GB (1) GB1331250A (en)
NL (1) NL7100323A (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866084A (en) * 1971-06-22 1975-02-11 Mitsubishi Electric Corp Plasma display panel device
JPS5068773A (en) * 1973-10-22 1975-06-09
US4147959A (en) * 1977-05-25 1979-04-03 Beckman Instruments, Inc. Display section for multilayer gas-discharge display panel
US4887003A (en) * 1988-05-10 1989-12-12 Parker William P Screen printable luminous panel display device
US4956577A (en) * 1988-05-10 1990-09-11 Parker William P Interactive luminous panel display device
US5019750A (en) * 1990-01-16 1991-05-28 Gte Products Corporation Radio-frequency driven display
US5126632A (en) * 1988-05-10 1992-06-30 Parker William P Luminous panel display device
US5198723A (en) * 1988-05-10 1993-03-30 Parker William P Luminous panel display device
WO2003041035A2 (en) * 2001-11-02 2003-05-15 Electro Plasma, Inc. Low voltage high efficiency illuminated display having capacitive coupled electrodes

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2004577A (en) * 1931-10-15 1935-06-11 Iris Licht G M B H Process and apparatus for the production of luminous signs in electric gas dischargetubes
US2848638A (en) * 1953-06-09 1958-08-19 Edwin W Smith Multi-display tube
US3264074A (en) * 1962-04-04 1966-08-02 Lear Siegler Inc Thin film electron emissive electrode
US3497751A (en) * 1967-09-25 1970-02-24 Burroughs Corp Transparent electrode and device using the same
US3509407A (en) * 1967-09-15 1970-04-28 Burroughs Corp Display panel

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2004577A (en) * 1931-10-15 1935-06-11 Iris Licht G M B H Process and apparatus for the production of luminous signs in electric gas dischargetubes
US2848638A (en) * 1953-06-09 1958-08-19 Edwin W Smith Multi-display tube
US3264074A (en) * 1962-04-04 1966-08-02 Lear Siegler Inc Thin film electron emissive electrode
US3509407A (en) * 1967-09-15 1970-04-28 Burroughs Corp Display panel
US3497751A (en) * 1967-09-25 1970-02-24 Burroughs Corp Transparent electrode and device using the same

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866084A (en) * 1971-06-22 1975-02-11 Mitsubishi Electric Corp Plasma display panel device
JPS5068773A (en) * 1973-10-22 1975-06-09
JPS564008B2 (en) * 1973-10-22 1981-01-28
US4147959A (en) * 1977-05-25 1979-04-03 Beckman Instruments, Inc. Display section for multilayer gas-discharge display panel
US4887003A (en) * 1988-05-10 1989-12-12 Parker William P Screen printable luminous panel display device
US4956577A (en) * 1988-05-10 1990-09-11 Parker William P Interactive luminous panel display device
US5198723A (en) * 1988-05-10 1993-03-30 Parker William P Luminous panel display device
US5126632A (en) * 1988-05-10 1992-06-30 Parker William P Luminous panel display device
US5019750A (en) * 1990-01-16 1991-05-28 Gte Products Corporation Radio-frequency driven display
WO2003041035A2 (en) * 2001-11-02 2003-05-15 Electro Plasma, Inc. Low voltage high efficiency illuminated display having capacitive coupled electrodes
WO2003041035A3 (en) * 2001-11-02 2003-12-24 Electro Plasma Inc Low voltage high efficiency illuminated display having capacitive coupled electrodes
US20040100180A1 (en) * 2001-11-02 2004-05-27 Byrum Bernard W. Low voltage high efficiency illuminated display having capacitive coupled electrodes
US6836072B2 (en) 2001-11-02 2004-12-28 Electro Plasma, Inc. Low voltage high efficiency illuminated display having capacitive coupled electrodes

Also Published As

Publication number Publication date Type
FR2075537A5 (en) 1971-10-08 application
NL7100323A (en) 1971-07-19 application
GB1331250A (en) 1973-09-26 application
CA933571A (en) 1973-09-11 grant
DE2101935A1 (en) 1971-07-22 application
CA933571A1 (en) grant

Similar Documents

Publication Publication Date Title
US3327154A (en) Ionizable gas display device with segmented electrode pattern
US3374380A (en) Apparatus for suppression of ion feedback in electron multipliers
US6515433B1 (en) Gas discharge fluorescent device
US7049748B2 (en) Display device employing gas discharge tubes arranged in parallel between front and rear substrates to comprise a display screen, each tube having a light emitting section as part of the display screen and a cleaning section connected to the light emitting section but displaced from the display screen
US3646384A (en) One-sided plasma display panel
US3418509A (en) Electrical discharge character indicator tube
US4887003A (en) Screen printable luminous panel display device
US3051868A (en) Ionization vacuum gauges
US4341980A (en) Flat display device
US2460175A (en) Ionic vacuum pump
US5281898A (en) Display device
US5198723A (en) Luminous panel display device
US3327153A (en) Compact glow discharge device having improved connection means for supplying electrical energy
US5962975A (en) Flat-panel display having magnetic elements
US2643297A (en) Gas discharge transmission arrangement
US3821588A (en) Display panel having flat side edges to permit butting together plural panels
US3231776A (en) Display device
US5777436A (en) Gas discharge flat-panel display and method for making the same
US3870917A (en) Discharge device including channel type electron multiplier having ion adsorptive layer
WO1992002947A1 (en) Thin configuration flat form vacuum-sealed envelope
US3644925A (en) Gaseous discharge display panel with auxiliary excitation cells
US4130777A (en) Scanning means and method for a plasma-sac-type gas-discharge image display panel
US3652891A (en) Plasma display panel having display and counter conductors on one plate
DE2742555A1 (en) Image reproducing device with flat electron gun - has electron extracting electrodes, electron beam deflection system and imaging screen
US3509408A (en) Display panel with separate signal and sustainer electrodes

Legal Events

Date Code Title Description
AS Assignment

Owner name: BECKMAN INDUSTRIAL CORPORATION A CORP OF DE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:EMERSON ELECTRIC CO., A CORP OF MO;REEL/FRAME:004328/0659

Effective date: 19840425

Owner name: EMERSON ELECTRIC CO., A MO CORP.

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BECKMAN INSTRUMENTS, INC.;REEL/FRAME:004319/0695

Effective date: 19840301

AS Assignment

Owner name: DIXON DEVELOPMENT, INC., A CA CORP.

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BECKMAN INDUSTRIAL CORPORATION;REEL/FRAME:004337/0564

Effective date: 19840928

Owner name: WALTER E HELLER WESTERN INCORPORATED

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:DIXON DEVELOPMENT, INC. A CORP. OF CA.;REEL/FRAME:004337/0572

Effective date: 19840928

AS Assignment

Owner name: BABCOCK DISPLAY PRODUCTS,INC.

Free format text: CHANGE OF NAME;ASSIGNOR:DIXION DEVELOPMENT,INC.;REEL/FRAME:004372/0199

Effective date: 19841002