US3564325A

US3564325A - Display device including a point image

Info

Publication number: US3564325A
Application number: US820216A
Authority: US
Inventors: Richard Arthur Bonnette; Norman Lee Lindburg
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1969-04-29
Filing date: 1969-04-29
Publication date: 1971-02-16
Anticipated expiration: 1988-02-16
Also published as: BE748177A; DE2021077A1; GB1295538A; ES378037A1; NL7006197A; SE362164B; CH523565A; FR2046549A5

Abstract

A display device of the type comprising a plurality of light sources so arranged that when various combinations of the sources are selectively energized, various luminous first symbols are produced. A luminous ''''poing'''' second symbol is also provided comprising a pair of intersecting filaments forming a letter X and having a size substantially smaller than the first symbols.

Description

[56} References Cited UNITED STATES PATENTS 3,358,176 12/1967 Rosenberg et al. 313/1095 3,416,020 12/1968 Carley.......................... 313/1095 Primary Examiner-Roy Lake Assistant ExaminerDavid OReilly Attorney-G. H. Bruestle New Providence, and Norman Lee Lindburg, Berkeley Heights, NJ.

[21] Appl. No. 820,216

Apr. 29, I969 [45] Patented Feb. 16, 1971 [731' Assignee RCA Corporation a corporation of Delaware 6 Claims, 3 Drawing Figs.

United States Patent [72] Inventors Richard Arthur Bonnette [22] Filed [54] DISPLAY DEVICE INCLUDING A POINT IMAGE ABSTRACT: A display device of the type comprising a plurality of light sources so arranged that when various combinations of the sources are selectively energized, various luminous first symbols are produced. A luminous point second symbol is also provided comprising a pair of intersecting filaments forming a letter X and having a size substantially smaller than the first symbols.

PATENTED FEB] a 19m mv avrans Richard A. Bonnette and Norman L. Lmdburg BY 772% DISPLAY DEVICE INCLUDING A POINT IMAGE BACKGROUND OF THE INVENTION This invention relates to display devices of the type comprising a plurality of light sources so s arranged that when various combinations of the sources are selectively energized, various luminous symbols are produced.

It is desired, in certain instances, that the display devices be capable of providing a point symbol, e.g., a decimal point or period. The means heretofore used for providing such a point symbol, e.g., a tiny incandescent bulb within the display device, are undesirably expensive.

SUMMARY OF THE INVENTION A display tube including a pair of crossed filaments providing, when energized, a luminous image having a point appearance when viewed at a normal viewing distance.

DESCRIPTION OFTHE DRAWING FIG. 1 is a section view of the novel display device showing the light sources thereof;

FIG. 2 is a partial section of the device shown in FIG. 1; and

FIG. 3 is a section view, partly broken away, of the device showing the rear connections to the light sources thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION With reference to the drawing, adisplay device is shown which comprises a transparent glass envelope 12 of a type well known in the electron tube arts. The envelope 12 includes a stem 14 having a plurality, e.g.,' nine, through leads 16. Mounted on the leads within the envelope isa thin, fiat substrate 26 of, for example, an alumina ceramic having a dark and dullsurface to minimize light reflection.

Extending through the substrate 26, in bonded relation therewith, are a plurality of support elements or posts 28. Mounted between pairs of posts 28 on the front" side, as viewed in FIG. 1, of the substrate 26 are a plurality of elongated light sources 30.

In this embodiment, the sources 30 comprise seven

filaments

33, 34, 35, 36, 37, 38, and 39 ofa wire ofa refractory metal wound into coils. The seven light sources are arranged to form adjacent rectangular arrays 42 and 44' of light sources, with one of the sources 38 common to both arrays. By selectively energizing various ones of the light sources, that is, by applying a voltage between the pairs of posts 28 between which the selected sources are mounted, various luminous images or symbols, numerals, in the instant embodiment, are obtained. For example, an image of the numeral 2 is obtained by lighting the

light sources

37, 35, 38, 34, and 39, each light source providing an elongated element or segment of the composite image.

The various posts 28, as shown in FIGS. 2 and 3, are connected, on the back" side of the substrate 26, to different ones of the leads I6, whereby energizing voltages can be selectively applied to individual ones of the various light sources.

To limit the number of leads 16 required for the device 10, one end of each of the filaments is electrically connected to a common lead 16. Likewise, to limit the number of posts 28, as well as to reduce the gaps between the filaments 33 and 34, and between the

filaments

35 and 36, an end of each

filament

33 and 34, and 35 and 36 is mounted on common posts 28.

Display devices of the type to the extent so far described are generally known, see, for example, U.S. Pat. No. 3,416,020, issued Dec. I0, 1968, to J. A. Carley.

For the purpose of providing the display device 10 with a decimal point image, two

filaments

52 and 54 are provided mounted between pairs of

support posts

56 and 58, and 60 and 62, respectively, at the bottom right of the two arrays of light sources 30. Each

filament

52 and 54 comprises a coil of refractory metal wire, the

filaments

52 and 54 being of substantially equal length, and the

filaments

52 and 54 crossing one another at substantially the midpoints thereof, thus forming the letter X. Preferably, the letter X is substantially smaller in size than the combined size of the two arrays 42 and 44 of light sources 30, and each

filament

52 and 54 is shorter in length than any of the light sources 30.

The filaments are preferably uncoated, for greater lighting efficiency, and the filaments are spaced apart in a direction normal to the face of the substrate 26 to prevent shorting together of the filaments.

Preferably, the two

filaments

52 and 54 are electrically connected. For example, in the instant embodiment, the filaments are connected in series by bending and welding together the two

posts

56 and 62 on the back side of the substrate 26. The other two

posts

58 and 60 are connected to different ones of the leads 16.

Altemately, although not shown, the two

filaments

52 and 54 can be connected in series by means of a connector extending between the

posts

56 and 62 on either side of the substrate, the connector being a separate strip of metal or, on the front side of the substrate, an intermediate length of a continuous coil forming the two

filaments

52 and 54.

When energized, the

intersecting filaments

52 and 54 provide a luminous letter X. At a viewing distance, dependent upon the size of the display device, the light from the branches of the X merge into a point or dot of light. The point appearance is the result of several factors, as follows. Each

post

56, 58, 60, and 62 is made of a heat conductive material, e.g., an alloy comprising 17 percent cobalt, 29 percent nickel, and 54 percent iron, by weight, having the trade name Kovar," and serves as a heat sink for the filament mounted thereon. Thus, the filaments are luminous along central portions of the lengths thereof and have nonluminous end portions. The brightly luminous central portions of the filaments cross one another, thus providing a single particularly bright spot. The trailing-off of brightness of the filaments towards the

posts

56, 58, 60, and 62, is at an equal rate for all four branches of the letter X image owing to the symmetry of the image. This contributes to the creation of acircular appearing image.

Additionally, the luminous X is substantially shorter in height than the numerals provided by the light sources 30. In the usual operation of the device 10, each numeral includes at least one longitudinally extending light source 30 from each array 42 and 44, each numeral produced thus having a height equal to the combined height of the arrays. In the instant embodiment, the luminous height of the X is about one-tenth of the luminous height of the numerals, the luminous X having a height of about 60 mils, and the luminous height of the numerals being about 600 mils. At a viewing distance of about 3 to 4 feet, the X appears as a point source of light. Preferably, the height of the luminous X is less than one-quarter of the h one-fourth of the height of the luminous numerals.

Preferably, the electrical impedance of each of the first light sources 30 and the combined impedance of the two

filaments

52 and 54 are substantially equal. An advantage of this is that it allows the use of a somewhat more simple and inexpensive power supply and switching circuit means than is possible where the impedances of the various light sources differ. In the instant embodiment, all the various filaments are formed from a wire of an alloy comprising 3 percent rhenium, balance tungsten, by weight, the wire having a diameter of 0.4 mil, and the wire being wound into a coil having an outer diameter of 2.0 mils. The

filaments

33, 34, 35, and 36 have a length of 3 l 2 mils, the filament coils containing about 577 turns to the inch. The

filaments

37, 38, and 39 have a length of 286 mils, the filament coils containing about 630 turns to the inch. Each

filament

52 and 54 has a length of 103 mils, the filament coils containing about 1,100 turns to the inch. The various light sources 30 and the decimal point image formed by the intersecting filaments 52 and 54' are each operated at a voltage of 4.5 volts and a current of 25 milliamps.

A further advantage of the point" source of the instant invention is that it utilizes rectilinear filaments which need not be bent into special shapes. Also, the heat sinking of the ends of the filaments allows the use of somewhat longer filaments without increasing the luminous size of the X. The longer filaments, especially in small size display devices, are desirable as being easier to handle in the assembly of the devices.

The point image provided by the intersecting filaments 52 and'54 is not limited to use in display devices of the type having filamentary light sources 30, but can be used in devices wherein the elongated light sources comprise electroluminescent, gas discharge electrodes, or the like. Examples of display devices in which point" light sources of the present invention can be used are shown, for example, in US. Pat. Nos. 3,341,916, issued Sept. 19, 1967, to L. E. Greene, and 3,l60,88 l, issued Jul. 12, 1966, to S. Kuchinsky.

We claim:

1. A display device comprising:

a plurality of first light sources arranged to provide, when energized, a luminous first image; and

means for providing, when energized, a luminous point image;

said means comprising a plurality of support means and a pair of filaments, the ends of said filaments being mounte d on said support means, and said filaments crossing one another intermediate the ends thereof, the luminous image produced by said filaments being substantially shorter in height than said luminous first image. 2. A display device as in claim l'wherein said filaments cross at substantially the midpoints thereof.

3. A display device as in claim 2 wherein said filaments are of substantially equal length. a

4. A display device as in claim 1 wherein said filaments are electrically connected, and the electrical impedance of each ofsaid first sources is substantially equal to the combined electrical impedance of said filaments.

5. In a display device, means for producing a luminous representation of a point comprising:

a pair of spaced apart, rectilinear electrical resistance filaments, said filaments crossing one another at substantially the midpoints thereof and being substantially of equal length;

a plurality of elements serving as combination terminal support and heat sink means for said filaments, a different one of said elements being connected to each of the four ends of said filaments; and

said elements being adapted to maintain end portions of said filaments nonluminous when the central portions of said filaments are luminous.

6. In a display device as in claim 5, a plurality of elongated first light sources arranged to provide, when energized, a luminous first image and'the incandescent central portions of said filaments being substantially shorter in length than said light sources.

Claims

1. A display device comprising: a plurality of first light sources arranged to provide, when energized, a luminous first image; and means for providing, when energized, a luminous point image; said means comprising a plurality of support means and a pair of filaments, the ends of said filaments being mounted on said support means, and said filaments crossing one another intermediate the ends thereof, the luminous image produced by said filaments being substantially shorter in height than said luminous first image.

2. A display device as in claim 1 wherein said filaments cross at substantially the midpoints thereof.

3. A display device as in claim 2 wherein said filaments are of substantially equal length.

4. A display device as in claim 1 wherein said filaments are electrically connected, and the electrical impedance of each of said first sources is substantially equal to the combined electrical impedance of said filaments.

5. In a display device, means for producing a luminous representation of a point comprising: a pair of spaced apart, rectilinear electrical resistance filaments, said filaments crossing one another at substantially the midpoints thereof and being substantially of equal length; a plurality of elements serving as combination terminal support and heat sink means for said filaments, a different one of said elements being connected to each of the four ends of said filaments; and said elements being adapted to maintain end portions of said filaments nonluminous when the central portions of said filaments are luminous.

6. In a display device as in claim 5, a plurality of elongated first light sources arranged to provide, when energized, a luminous first image and the incandescent central portions of said filaments being substantially shorter in length than said light sources.